SE537538C2

SE537538C2 - Wire heat treated steel wire for high strength spring use, preferred steel wire for high strength spring use and methods for making these threads

Info

Publication number: SE537538C2
Application number: SE1250810A
Authority: SE
Inventors: Masayuki Hashimura; Tetsushi Chida
Original assignee: Nippon Steel Corp
Priority date: 2010-07-06
Filing date: 2011-07-05
Publication date: 2015-06-09
Also published as: US20120291927A1; JP4980496B2; WO2012005373A1; CN102482747B; SE1250810A1; CN102482747A; JPWO2012005373A1; KR20120040728A

Abstract

Sammandrag Dragen varmebehandlad staltrad fOr hoghallfasthetsfjaderanvandning tillhandahallen innehallande, i mass % C: 0,67 % till mindre an 0,9 %, Si: 2,0 till 3, %, Mn: 0,5 till 1,2 %, Cr: 1,3 till 2,5 %, N: 0,003 till 0,007 %, och Al: 0,0005 % till 0,003 %, med ett innehall av Si och Cr som uppfyller fOljande uttryck: 0,3 °AsSi-Cr1 ,2 %, och med en balans av jarn och oundvikliga fOroreningar, P: 0,025 % eller mindre, och S: 0,025 % eller mindre, dessutom med ett innehall av oupplOsta sfariska karbider med en cirkelekvivalent diameter pa mindre an 0,2 pm, dartill med ett innehall av en metallstruktur, atminstone restaustenit i volymsmatt pa Over 6 % till 15 %, med ett tidigare austenit kornstorleksnummer #10 eller mer, och med ett innehall av oupplOsta sfariska karbider med en cirkelekvivalent diameter pa mindre an 0,2 pm. Summary Drawn heat-treated stable row for high-strength spring use provided containing, in mass% C: 0.67% to less than 0.9%, Si: 2.0 to 3%, Mn: 0.5 to 1.2%, Cr: 1 , 3 to 2.5%, N: 0.003 to 0.007%, and Al: 0.0005% to 0.003%, with a content of Si and Cr satisfying the following terms: 0.3 ° As Si-Cr1, 2%, and with a balance of iron and unavoidable impurities, P: 0,025% or less, and S: 0,025% or less, in addition with a content of undissolved spherical carbides with a circle equivalent diameter of less than 0,2 μm, in addition with a content of a metal structure, at least residual austenite in volume mats of Over 6% to 15%, with a previous austenite particle size number # 10 or more, and with an undissolved content of spherical carbides with a circle equivalent diameter of less than 0.2 μm.

Description

Dragen varmebehandlad staltrad for hoghailfasthetsfjaderanvandning, fordragen staltrad for hoghallfasthetsfraderanvandning samt forfaranden for framstallning av dessa tradar BESKRIVNING Teknikomrade Drawn heat-treated steel row for high-strength spring use, preferred steel row for high-strength spring use and procedures for manufacturing these trades DESCRIPTION Technical area

[0001] Foreliggande uppfinningen avser dragen varmebehandlad staltrad, for hOghallfasthetsfjaderanvandning, vilken kan anvandas som material fOr hOghallfasthetsfjadrar, tillverkade genom kallindning, och till fOrdragen staltrad. The present invention relates to drawn heat-treated steel wire, for high-strength spring use, which can be used as a material for high-strength springs, made by cold winding, and to the preferred steel wire.

Teknikens standpunkt The state of the art

[0002] Fjadrar vilka anvands for motorfordonsmotorer, kopplingar, etc. behOver erbjuda mer avancerad prestanda och hOgre hallbarhet fOr att klara av utvecklingen mot lattare vikt och hogre prestanda hos motorfordon. Av den anledningen behbver fjadrarnas material, det vill saga, dragen varmebehandlad staltrad for hoghallfasthetsfjaderanvandning, aven ha hog materialhallfasthet. Vanligen vid tillverkning av sadana sma, heighallfasthetsfjadrar, är materialet has den dragna varmebehandlade staltraden for hoghallfasthetsfjaderanvandning, seghardat fOr att ge hogre materialstyrka, hos den dragna varmebehandlade staltraden fOr hOghallfasthetsfjaderanvandning, darefter kallindat for att erhalla en spiralfjaderform. Dessutom utfOrs spanningsavlastande glOcIgning eller annan varmebehandling och nitrering fOr att erhalla en fardig spiralfjader. Av den anledningen behover dragen varmebehandlad staltrad, fOr hOghallfasthetsfjaderanvandning, inte bara ha hog hallfasthet, utan ocksa tillrackligt hog bearbetningsfOrmaga sa aft den inte bryts vid kallindning och for att dampa mjukning tillfajd av glodgning, nitrering och annan varmebehandling ufford efter lindning, det vill saga, aft ha motstand mot varmerelaterad avmjukning. Springs used for motor vehicle engines, clutches, etc. need to offer more advanced performance and higher durability to cope with the trend towards lighter weight and higher performance of motor vehicles. For this reason, the material of the springs, that is to say, drawn heat-treated steel line for high-half-spring use, also needs to have a high material-half strength. Usually in the manufacture of such small, high-strength springs, the material has the drawn heat-treated steel line for high-strength spring use, toughened to give higher material strength, in the drawn heat-treated steel line for high-strength spring use, which then forms a coil spring. In addition, stress-relieving glazing or other heat treatment and nitriding is performed to obtain a finished coil spring. For this reason, the drawn heat-treated steel line, for high-strength spring use, not only needs to have high half-strength, but also sufficiently high machining ability so that it is not broken during cold winding and to steam softening by annealing, nitriding and other heat treatment, after sawing, aft have resistance to heat-related softening.

[0003] En fjacler behover ha goda utmattningsegenskaper, darfOr anvands dragen varmebehandlad staltrad avsedd for hoghallfasthetsfjaderanvandning, t material, vilket vidare nitreras eller kulbombas for aft Oka hardheten hos fjaderns ytskikt. Hallbarheten hos en fjader omfattar utmattningsegenskaper och en eftergivningsegenskap. Utmattningsegenskaperna paverkas av ythardheten. 1 Eftergivningsegenskapen (egenskapen hos fjadern resulterande i plastisk deformation i belastningsriktningen under anvandning) paverkas mycket av, inte bara av ythardheten, utan ocksa hardheten hos grundmaterialet i fjadern. Av den anledningen, ar ythardheten efter nitrering och motstand mot varmerelaterad avmjukning p insidan, dar kvave inte är introducerat genom nitrering, viktiga hos staltraden, far hoghallfasthetsfjaderanvandning. A fjacler needs to have good fatigue properties, therefore the drawn heat-treated steel row intended for high-strength spring use is used, t material, which is further nitrided or ball-bombed to increase the hardness of the surface layer of the spring. The durability of a spring includes fatigue properties and a resilience property. The fatigue properties are affected by the surface hardness. 1 The resilience property (the property of the spring resulting in plastic deformation in the load direction during use) is greatly affected, not only by the surface hardness, but also the hardness of the base material in the spring. For this reason, the surface hardness after nitriding and resistance to heat-related softening on the inside, where nitrogen is not introduced by nitriding, are important in the stable line, for high-strength spring use.

[0004]Dessutom, vid fjadertillverkning genom kallindning, kan anlapning i olja, induktionshardningsbehandling etc., dar snabb varmning och snabb kylning ar 10 anvandas vid tillverkning av materialet hos den dragna varmebehandlade staltra'den, for haghallfasthetsfjaderanyandning. Av den anledningen, kan den dragna varmebehandlade staltraden far hoghallfasthetsfjaderanvandning minskas i tidigare austenit kornstorlek, sa att en fjader med utmarkta frakturegenskaper kan erhallas. Men om dragen varmebehandlad staltrad far hoghallfasthetsfjaderanvandning Mr hagre hallfasthet, vid kallindning, kan brott uppsta och fjaderformen kan eventuellt inte bildas. In addition, in the case of spring production by cold winding, oiling, induction hardening treatment, etc., where rapid heating and rapid cooling are used in the manufacture of the material of the drawn heat-treated steel wire, can be used for spring strength spring use. For this reason, the drawn heat-treated steel row can be reduced to a high austenite grain size, so that a spring with excellent fracture properties can be obtained. However, if the drawn heat-treated stable row has high half-strength spring use Mr hagre half-strength, in cold winding, fractures can occur and the spring shape may not be formed.

[0005]Frir att hantera problemet foreslog nagra av uppfinnarna att karbiderna bar styras, vilket gar den tidigare austeniten finare, pa detta satt kan bade styrka och 20 kallindningsfOrmaga (PLT 1) hos dragen varmebehandlad staltrad, for hoghallfasthetsfjaderanvandning uppnas. Vidare fareslog uppfinnama styrning av restaustenit och kvarvarande karbider, farfining av tidigare austenit, far att uppna bade styrka och kallindningsformaga (PLT 2 till PLT 4), hos dragen varmebehandlad staltrad, for haghallfasthetsfjaderanyandning. I synnerhet undertrycks startpunkterna 25 far brott orsakade av bildandet av grova oxider och karbider, och distributionen av fina karbider av cementit vilka kravs for att sakra att styrkan blir uniform i syfte att dampa farsamring av utmattningsegenskaperna och bearbetbarheten av den dragna varmebehandlade staltraden for haghallfasthetsfjaderanvandning. To deal with the problem, some of the inventors suggested that the carbides should be controlled, which makes the previous austenite finer, in this way both the strength and cold winding capacity (PLT 1) of the drawn heat-treated steel row can be achieved, for high-strength spring use. Furthermore, the inventors endangered the control of residual austenite and residual carbides, the dyeing of previous austenite, the ability to achieve both strength and cold winding shape (PLT 2 to PLT 4), in the drawn heat-treated steel row, for pasture spring spring breathing. In particular, the starting points are suppressed for fractures caused by the formation of coarse oxides and carbides, and the distribution of fine carbides of cementite which are required to ensure that the strength becomes uniform in order to vaporize the fatigue properties and machinability of the drawn heat treated stable line for pasture spring use.

[0006]PLT 2 fokuserar pa det faktum att omraden av giest fordelade sfariska karbider, med en cirkelekvivalent diameter cm 2 pm eller mer, i omraden med gles fardelning av fina sfariska karbider (i synnerhet, cementit), paverkar de dynamiska egenskaperna och definierar det omeadet. 2 PLT 2 focuses on the fact that the areas of sparsely distributed spherical carbides, with a circle equivalent diameter cm 2 μm or more, in the areas of sparse distribution of fine spherical carbides (in particular, cementite), affect the dynamic properties and define it. omeadet. 2

[0007]PLT 3 och PLT 4 noterar effekten av uffallning av fina karbider pa grund av tillsatsen av legeringsamnet V, och begransar kvave (N) innehallet for att undertrycka oupplOsta sfariska karbider. Det viii saga, de anvander effekten av utfallning av karbider, nitrider, och kolnitrider av V for att mOjliggora tillgodogorande av hardning av staltraden, vid anlOpningstemperaturen eller hardning av ytskiktet vid nitrering. Dessutom, har de ocksa effekten att dampa forgrovning av austenitkornstorleken, pa grund av bildandet av utfallning. Effekten av tillsats av V är anmarkningsvard. Trots detta, bildas oupplbsta sfariska karbider eller nitrider latt, sá aven om kvave (NJ) undertrycks, behOver styrning av utfallningen goras exakt. PLT 3 and PLT 4 note the effect of precipitation of fine carbides due to the addition of the alloying substance V, and limit the nitrogen (N) content to suppress undissolved spherical carbides. Legend has it that they use the effect of precipitation of carbides, nitrides, and carbon nitrides of V to enable the hardening of the steel bar to cure, at the annealing temperature or the hardening of the surface layer during nitriding. In addition, they also have the effect of vaporizing the coarseness of the austenite grain size, due to the formation of precipitate. The effect of the addition of V is remark value. Despite this, undissolved spherical carbides or nitrides are easily formed, so even if nitrogen (NJ) is suppressed, precipitation control needs to be done precisely.

[0008]DartOr jamfOr PLT 4 kvantitativt oupplOsta sfariska karbider och utfallda karbider och definierar mangden fOr att fa sa mycket utfallda V karbider som mojligt, vika inverkar pa den slutliga fjaderprestandan. I synnerhet fOreslar PLT 4 att vaga fallningen av V karbider i den elektrolytiska lesningen, vid konstant potential, och 15 jamfora mangden med mangden V som passerar genom filtret (mangden av utfalld V). DartOr compares PLT 4 quantitatively undissolved spherical carbides and precipitated carbides and defines the amount to obtain as much precipitated V carbides as possible, which affects the final spring performance. In particular, PLT 4 proposes to vague the precipitation of V carbides in the electrolytic reading, at constant potential, and compares the amount with the amount V passing through the filter (the amount of precipitated V).

Referenslista Patentlitteratur Reference list Patent literature

[0009]PLT 1: Japansk patentpublikation (A) No. 2002-180198 PLT 2: Japansk patentpublikation (A) No. 2006-183137 PLT 3: Japansk patentpublikation (A) No. 2006-342400 PLT 4: Internationell publikation W02007/114491 Sammanfattning av uppfinningen 25 Tekniskt problem PLT 1: Japanese Patent Publication (A) No. 2002-180198 PLT 2: Japanese Patent Publication (A) No. 2006-183137 PLT 3: Japanese Patent Publication (A) No. 2006-342400 PLT 4: International Publication WO2007 / 114491 Summary of the Invention Technical Problem

[0010]Under senare ar har ythardning genom nitrering blivit ett konventionellt forfarande, for att Oka hallbarheten hos hoghallfasthetsfjadrar. Vidare har Okning av nitreringsdjupet och forkortning av nitreringstiden, genom Okning av behandlingstemperaturen, studerats. Av den anledningen behever dragen 3 varmebehandlad staltrad, fOr hoghallfasthetsfjader, ytterligare fOrbattrat motstand mot varmerelaterad avmjukning. In recent years, surface hardening by nitriding has become a conventional method, in order to increase the durability of high-strength springs. Furthermore, increasing the nitriding depth and shortening the nitriding time, by increasing the treatment temperature, have been studied. For this reason, the features 3 heat-treated steel row, for high-strength springs, need further improved resistance to heat-related softening.

Det vill saga nar det eftersOks ytterligare battre kallindningsfOrmaga an till och medkonventionelldragenvarmebehandladstaltrad,for 5 hOghallfasthetsfjaderanvandning, utmarkt motstand mot varmerelaterad avmjukning aven efter uppehallstid pa 1 timme vid 500 °C, minimal internmjukning, och storm hardhet hos det yttersta ytlagret. That is to say, when looking for even better cold-winding properties than even conventional heat-treated steel, for high-strength spring application, excellent resistance to heat-related softening even after a residence time of 1 hour at 500 ° C, minimal internal softening and extreme hardness of the surface.

[0011]Ovanstaende konventionella dragna varmebehandiade staltrad, for hOghallfasthetsfjaderanvandning, sakrar en viss grad av uniform spridning av fina karbider for fOrbattrade utmattningsegenskaper och bearbetningsformaga. Men fOr att fOrbattra motstand mot varmerelaterad avmjukning, ar ytterligare spridning nodvandig. I synnerhet har tillsatsen av V, fOreslagen PLT 3 och PLT 4, i hog grad effekten att harda staltraden vid anlOpningstemperaturen, harda ytskiktet vid 16nitrering, och fOrfining av austeniten. ErneHeald, ar styrningen av kvaveinnehallet (N) inte enkel. Som ett resultat falls grova karbider, nitrider, och kolnitrider ut och orsakar forsamring av utmattningshallbarheten. The above conventional drawn heat-treated steel row, for high-strength spring use, ensures a certain degree of uniform dispersion of fine carbides for improved fatigue properties and machining ability. But in order to improve resistance to heat-related softening, further spreading is necessary. In particular, the addition of V, proposed PLT 3 and PLT 4, has to a large extent the effect of hardening the steel row at the annealing temperature, hardening the surface layer at nitriding, and refining the austenite. ErneHeald, the control of the nitrogen content (N) is not simple. As a result, coarse carbides, nitrides, and carbon nitrides fall out, causing fatigue durability to deteriorate.

[0012]PLT 3 tillsatter Nb och Ti, med effekten att fanga Overskottskvave (N), som mal. Aven om tillsats Ors ar styrning av lamplig mangd N fortfarande inte enkel. 20 [0013]PLT 4 tar prov pa kvarvarande oupplOsta sfariska karbider, erhallna som ett resultat, och jamfor med de upplosta karbiderna. DariOr styr PLT4 inte proaktivt uniform spridning av fina karbider. PLT 3 adds Nb and Ti, with the effect of capturing Excess Nitrogen (N), as a mill. Even if additives Ors control of appropriate amount N is still not easy. PLT 4 takes samples of remaining undissolved spherical carbides, obtained as a result, and compares with the dissolved carbides. DariOr PLT4 does not proactively control the uniform distribution of fine carbides.

Pa grund av det som namnts ovan, har fOreliggande uppfinning som syfte aft halla tillsatsen av V och andra legeringsamnen till ett minimum, det vill saga, utan aft 25 precist styra N-innehallet, utveckla dragen varmebehandlad staltrad for hoghallfasthetsfjaderanvandning, vilken har utmarkt strackgrans och hardhet och utmarkt bearbetningsfOrmaga och vilken har Overlagsen ythardhet och innerhardhet aven after nitrering. In view of the above, the present invention has for its object to keep the addition of V and other alloying substances to a minimum, that is to say, without precisely controlling the N content, to develop drawn heat-treated stable line for high-strength spring use, which has excellent tensile strength and hardness and excellent machining ability and which has superior surface hardness and inner hardness even after nitriding.

[0014]Vidare, som beskrivet i PLT 3 och PLT 4, for aft erhalla utmarkt 30 strackgrans och hardhet och utmarkt bearbetningsformaga, skall storleken pa de oupplOsta sfariska karbiderna i stalet vara Refl. Effektiv storlek ar foretradesvis 0,1 pm eller mindre. Om storleken ar Over 1 pm, gar bidraget till hallfasthet och 4 bearbetningsfOrmaga farlorat och en farsamring av deformationsegenskaperna erhalls endast. Av den anledningen, blir narvarodensiteten av oupplasta sfariska karbider med en cirkelekvivalent diameter am 0,2 pm eller mer en viktig indikator. Darfor har fareliggande uppfinning som syfte att inte tillata fOrekomsten av oupplasta sfariska karbider med en cirkelekvivalent diameter am 0,2 pm eller mer, vid forbattring av staltrad far hog hallfasthetsfjaderanvandning. Furthermore, as described in PLT 3 and PLT 4, in order to obtain excellent tensile strength and hardness and excellent machining ability, the size of the undissolved spherical carbides in the steel should be Refl. Effective size is preferably 0.1 μm or less. If the size is Over 1 pm, the contribution to hall strength and 4 processing capacity is lost and only a combination of the deformation properties is obtained. For that reason, the grain density of unplastic spherical carbides with a circle equivalent diameter of 0.2 μm or more becomes an important indicator. Therefore, it is an object of the present invention not to permit the occurrence of unloaded spherical carbides having a circle equivalent diameter of 0.2 .mu.m or more, when improving the shape of the rigid spring half-spring spring.

LOsning pa problemet Solution to the problem

[0015]Uppfinnarna bedrev intensiv forskning for aft lasa ovanstaende problem och erholl som eft resultat foljande upptackter: (a)De upptackte aft genom att noggrant styra innehallet av C, Si, Mn, och Cr i staltraden, far att dampa bildandet av sfariska karbider och genom att tillgodogara sig restaustenit, aven utan tillsats av legeringsamnen sa som V, har dragen varmebehandlad staltrad for haghailfasthetsfjaderanvandning farbattrad hallfasthet och kallindningsformaga jamfort med konventioneli staltrad. The inventors conducted intensive research to solve the above problems and obtained as a result the following discoveries: (a) They discovered again by carefully controlling the content of C, Si, Mn, and Cr in the stable line, to vaporize the formation of spherical carbides and by assimilating residual austenite, even without the addition of alloying elements such as V, the drawn heat-treated steel line for haghail strength spring use has improved half-strength and cold-winding shape compared to conventional steel wire.

[0016](b)Det upptacktes ocksa att genom tillsats av bade Cr och Si i lampliga mangder till staltraden, dampas bildandet av oupplasta sfariska karbider och mjukningen vid gleidgning eller nitrering efter lindning, och dessutom kan hagre hardhet hos det nitrerade lagret uppnas, Det viii saga, far att aka styrkan i utmattningsegenskaperna, är tillsats av Cr effektiv, men Cr är ett amne vilket latt lamnar kvar oupplasta sfariska karbider, vilka har en negativ effekt pa kallindningsformagan. Av den anledningen behavde mangden tillsatt Cr begransas. Uppfinningarna noterade ocksa att Si dampar tillvaxten av oupplOsta sfariska karbider och bildandet av cementit. Uppfinnama upptackte att om Si tillsatts tillsammans med Okad tillsats av Cr, sa kan hallfastheten for dragen varmebehandlad staltrad Oka. Kvantitativt ãr det tillrackligt att tillsatta en star mangd av bade Si och Cr, eftersom farhallandet mellan dem styr skillnaden i mangd tillsatt Si och mangd tillsatt Cr, det viii saga, (Si-Cr) %. (B) It was also discovered that by adding both Cr and Si in appropriate amounts to the steel row, the formation of unplastic spherical carbides and the softening on sliding or nitriding after winding is vaporized, and in addition, better hardness of the nitrated layer can be achieved. viii saga, in order to increase the strength of the fatigue properties, the addition of Cr is effective, but Cr is a substance which leaves uncharged spherical carbides, which have a negative effect on the cold winding shape. For that reason, the amount of added Cr behaved limited. The inventions also noted that Si vaporizes the growth of undissolved spherical carbides and the formation of cementite. The inventors discovered that if Si was added together with Okad addition of Cr, then the half-strength of the drawn heat-treated staldrad Oka. Quantitatively, it is sufficient to add a large amount of both Si and Cr, since the ratio between them controls the difference in the amount of added Si and the amount of added Cr, the viii saga, (Si-Cr)%.

[0017](c)Vidare upptacktes att genom att varma gaten till 1250 °C eller mer, är det majligt att Ora Cr och andra legeringsamnen i stalmaterialet uniformt spridda och dampa bildningen av grova oupplasta sfariska karbider och dessutom Ora fina karbider uniformt spridda. (C) It was further discovered that by heating the gate to 1250 ° C or more, it is possible for Ora Cr and other alloying elements in the steel material to be uniformly dispersed and to vaporize the formation of coarse unplastic spherical carbides and also Ora fine carbides uniformly dispersed.

OupplOsta sfariska karbider är narvarande i stalrnaterialet direkt efter gjutning och blir orsaken till, inte bara dalig lindningsformaga, utan ocksa' till brott vid valsning och dragning. Av den anledningen är det effektivt att Oka varmningstemperaturen vid vane steg och konstant dampa oupplOsta sfariska karbider, fOr att fOrhindra en negativ effekt i gOten efter gjutning, valstradsvalsning, patentering, slackning, och dragning. Undissolved spherical carbides are present in the steel material immediately after casting and become the cause, not only of poor winding, but also of breakage during rolling and drawing. For this reason, it is effective to increase the heating temperature at usual steps and constantly vaporize undissolved spherical carbides, in order to prevent a negative effect in the cast after casting, wire rod rolling, patenting, slackening, and drawing.

[0018](d)Vidare upptacktes aft tillsatsen av V har en skadlig effekt p'a. de mekaniska egenskaperna och utmattningsstyrkan hos staltraden, for 10 fjaderanvandning. (D) Furthermore, it was discovered that the addition of V has a detrimental effect on p'a. the mechanical properties and fatigue strength of the stable row, for spring use.

Det vill saga fran direkt efter gjutning till dess att det bearbetas till en fjader, varms stalmaterial upprepade ganger. Vanligtvis, är de oupplOsta sfariska karbiderna huvudsakligen cementit (Fe3C). Men genom upprepad varmning inkluderar de oupplOsta sfariska karbider ofta Cr, V etc. Det har fOrstatts att det inte bara är sA aft Cr, V och andra legeringsamnen konsumeras slOsaktigt, utan att det aven är mOjligt att fersamra de mekaniska egenskaperna efter nitrering (yth'ardhet, inre hardhet, etc.) Vidare som fOrklarats ovan, vid tillsats av V, an styrning av kvaveinnehall (N) inte latt. Som ett resultat, bildar grova karbider, nitrider och kolnitrider, utfallningar och orsakar forsamrad utmattningsstyrka. It wants to sag from immediately after casting until it is processed into a spring, hot steel material repeatedly. Usually, the undissolved spherical carbides are mainly cementite (Fe3C). However, by repeated heating, the undissolved spherical carbides often include Cr, V, etc. It has been understood that not only is Cr, V and other alloying substances consumed in a waste manner, but it is also possible to combine the mechanical properties after nitration (surface). hardness, internal hardness, etc.) Furthermore, as explained above, when adding V, the control of nitrogen content (N) is not easy. As a result, coarse carbides, nitrides and carbon nitrides form precipitates and cause accumulated fatigue strength.

[0019]Av dessa fakta upptackte uppfinnarna att det är mojligt att dampa forgrovning av oupplOsta sfariska karbider, genom att inte tillsatta V, eller genom aft tillsatta en extremt liten mangd, och vidare, som fOrklarat ovan, styra mangden Cr I jamvikt med mangden Si. From these facts the inventors discovered that it is possible to vaporize the coarsening of undissolved spherical carbides, by not adding V, or by adding an extremely small amount, and further, as explained above, controlling the amount Cr I in equilibrium with the amount Si .

[0020]Har betyder "oupplOsta sfariska karbider" oupplOsta karbider med ett forhallande mellan den maximala storleken (langsta storlek) och den minimala storleken (kortaste storlek) (sidoforhallande) av 2 eller mindre. Egentligen ar "karbider" och "sfariska karbider" ocksa oupplosta. Hy aft understryka kallas dessa ocksa "oupplosta karbider" respektive "oupplosta sfariska karbider trots att de är synonyma. Trots att de är synonyma är respektive ocksa kallade "oupplOsta karbider och "oupplosta sfariska karbider", for att betona. Has means "undissolved spherical carbides" undissolved carbides with a ratio between the maximum size (longest size) and the minimum size (shortest size) (side ratio) of 2 or less. In fact, "carbides" and "spherical carbides" are also undissolved. These are also called "undissolved carbides" and "undissolved spherical carbides" even though they are synonymous. Although they are synonymous, they are also called "undissolved carbides" and "undissolved spherical carbides", respectively, to emphasize.

FOreliggande uppfinning gjordes utifran dessa upptackter. Kontentan av uppfinningen är som foljer: 6 The present invention was made on the basis of these discoveries. The content of the invention is as follows: 6

[0021] (1) FOrdragen staltrad for hOghallfasthetsfjaderanvandning, kannetecknad av innehall i mass av, C: 0,67 % fill 0,9 %, Si: 2,0 till 3,5 %, Mn: 0,5 till 1,2 %, Cr: 1,3 till 2,5 %, N: 0,003 till 0,007 %, och Al: 0,0005 % till 0,003 varvid Si och Cr uppfyller faljande uttryck: 0,3 %5Si-Cr5.1,2 %, med balans av jarn och oundvikliga ftworeningar, varvid P och S som fororeningar innefattande P: 0,025 % eller mindre och S: 0,025 % eller mindre, och vidare, varvid en cirkelekvivalent diameter for oupplOsta sfariska karbider är om mindre an 0,2 pm. (2)FOrdragen staltrad for hOghallfasthetsfjaderanvandning, sasom framlagd i (1), dartill kannetecknad av innehall i mass %, av en eller flera av, 0,03 till 0,10 %, Nb: 0,015 % eller mindre, Mo: 0,05 till 0,30 %, 0,05 till 0,30 %, Mg: 0,002 % eller mindre, Ca: 0,002 `)/0 eller mindre, och Zr: 0,003 % eller mindre, vid innehall av V uppfylls 1,4 %.5.Cri-V52,6 % och 0,70 %5Mn-FV51,3 %, och, 30 vid innehall av Mo och W, uppfylls 0,05 %5Mo+W.Q,5 %. (3) Dragen varmebehandlad staltrad fOr hoghallfasthetsfjaderanvandning, kannetecknad innehall i mass % av, 7 C: 0,67 % till 0,9 %, Si: 2,0 till 3,5 %, Mn: 0,5 till 1,2 %, Cr: 1,3 till 2,5 %, N: 0,003 till 0,007 %, och Al: 0,0005 % till 0,003 %, varvid Si och Cr uppfyller fOljande uttryck: 0,3 %5_Si-Cr51,2 %, och med balans av jam och oundvikliga fOroreningar, 10 med P och S som fororeningar innefattande P: 0,025 % eller mindre och S: 0,025 % eller mindre, och vidare, med en metallstruktur innefattande minst restaustenit av ett volymsmatt pa Over 6 % till 15 %, med ett tidigare austenit kornstorleksnummer #10 eller mer, och vidare varvid en cirkelekvivalent diameter for oupplOsta sfariska karbider ar mindre an 0,2 pm. 20 (4) Dragen varmebehandlad staltrad for htighallfasthetsfjaderanvandning, enligt(3), kannetecknad av innehall i mass %, av en eller flera av, V: 0,03 till 0,10 %, Nb: 0,015 % eller mindre Mo: 0,05 till 0,30 %, W: 0,05 till 0,30 % Mg: 0,002 % eller mindre, Ca: 0,002 % eller mindre, och Zr: 0,003 % eller mindre, vid innehall av V 30 uppfylls 1,4 %5Cr+V52,6 % och 0,70 %5Mn+V.5.1 ,3 %, och, vid innehall av Mo och W, uppfylls 0,05 % 5..Mo+W50,5 %. 8 (5)Dragen varmebehandlad staltrad for hogh611fasthetsfjaderanvandning, enligt (3) eller (4), kannetecknad av att den dragna varmebehandlade staltraden, for hOghallfasthetsfjaderanvandning, har en draghallfasthet 2100 till 2400 MPa. (6)Dragen varmebehandlad staltrad fOr hOghallfasthetsfjaderanvandning, enligt nagot av (3) till (5), kannetecknad av att den dragna varmebehandlade staltraden, for hoghallfasthetsfjaderanvandning, har en strackgrans 1600 till 1980 MPa. (7)Dragen varmebehandlad staltrad for hOghallfasthetsfjaderanvandning, enligt 10 nagon av (3) till (6), kannetecknad av att den dragna varmebehandlade staltrklen, for hOghallfasthetsfjaderanvandning, har ythardhet HV750 eller mer enligt Vickersskalan, och inre hArdhet HV570 eller mer enligt Vickersskalan, efter varsam nitrering vid 500 °C i 1 timme. 15 (8) ProduktionsfOrfarandefOrfOrdragenstaltradIf& hOghallfasthetsfjaderanvandning kannetecknad av att en gOt innehallande i mass %, C: 0,67 % till 0,9 %, Si: 2,0 till 3,5 °A), Mn: 0,5 till 1,2 %, Cr: 1,3 till 2,5 %, N: 0,003 till 0,007 %, och Al: 0,0005 % till 0,003 %, med Si och Cr som uppfyller fOljande uttryck: 0,3 %5Si-Cr51,2 %, med balans av jarn och oundvikliga fOroreningar, med P och S som fororeningar innefattande P: 0,025 % eller mindre och S: 0,025 % eller mindre, varvid geiten varms till 1250°C eller mer, darefter varmvalsas gOten for tillverkande av ett valsamne och varmning av valsamnet till 1200°C eller 30 mer, med efterfOljande varmvalsning for tillverkande av en fardragen staltrad. (9)ProduktionsfOrfarandeforfOrdragenstaltra'dfor htigh6lIfasthetsfjaderanvandning, enligt (8), kannetecknad av att gOten dessutom innehaller, i mass %, en eller flera av 9 0,03 till 0,10 %, NO: 0,015 % eller mindre Mo: 0,05 till 0,30 %, 0,05 till 0,30 % Mg: 0,002 % eller mindre, Ca: 0,002 % eller mindre, och Zr: 0,003 % eller mindre, vid innehall av V uppfylls 1,4 %.5.Cr+V5.2,6 °A) och 0,70 %.5..Mn+W.1,3 %, och, 10 vid innehall av Mo och W, uppfylls 0,05 To 5M0+VV50, ProduktionsfOrfarandefOrtrdragenstaltradfOr hOghallfasthetsfjaderanvandning, kannetecknad vidare av varmning av fOrdragen staltrad enligt (8) eller (9), till 900 'C eller mer, varefter den patenteras vid 600 °C eller mindre. [121] (1) Preferred form line for high strength spring application, can be characterized by content in mass of, C: 0.67% fill 0.9%, Si: 2.0 to 3.5%, Mn: 0.5 to 1.2 %, Cr: 1.3 to 2.5%, N: 0.003 to 0.007%, and Al: 0.0005% to 0.003 with Si and Cr having the following expression: 0.3% 5Si-Cr5.1,2%, with balance of iron and unavoidable impurities, wherein P and S are impurities comprising P: 0.025% or less and S: 0.025% or less, and further, wherein a circle equivalent diameter for undissolved spherical carbides is less than 0.2 μm. (2) Preferred formulations for high-strength spring use, as set forth in (1), therefor can be drawn by content in mass%, of one or more of, 0.03 to 0.10%, Nb: 0.015% or less, Mo: 0.05 to 0.30%, 0.05 to 0.30%, Mg: 0.002% or less, Ca: 0.002 `) / 0 or less, and Zr: 0.003% or less, when V is 1.4%. 5.Cri-V52.6% and 0.70% 5Mn-FV51.3%, and, when containing Mo and W, 0.05% 5Mo + WQ, 5% is satisfied. (3) Drawn heat-treated stable row for high-strength spring use, can be drawn content in mass% of .7 C: 0.67% to 0.9%, Si: 2.0 to 3.5%, Mn: 0.5 to 1.2% , Cr: 1.3 to 2.5%, N: 0.003 to 0.007%, and Al: 0.0005% to 0.003%, Si and Cr having the following expression: 0.3% 5_Si-Cr51.2%, and with balance of jam and unavoidable impurities, with P and S as impurities comprising P: 0.025% or less and S: 0.025% or less, and further, with a metal structure comprising at least residual austenite of a volume mat of Over 6% to 15%, with a previous austenite particle size number # 10 or more, and further wherein a circle equivalent diameter for undissolved spherical carbides is less than 0.2 μm. (4) Drawn heat-treated steel line for high-strength spring use, according to (3), can be characterized by content in mass%, of one or more of, V: 0.03 to 0.10%, Nb: 0.015% or less Mo: 0.05 to 0.30%, W: 0.05 to 0.30% Mg: 0.002% or less, Ca: 0.002% or less, and Zr: 0.003% or less, when V is content, 1.4% 5Cr + V52.6% and 0.70% 5Mn + V.5.1, 3%, and, when containing Mo and W, 0.05% 5..Mo + W50.5% is satisfied. 8 (5) Drawn heat-treated steel line for high-strength spring use, according to (3) or (4), characterized in that the drawn heat-treated steel line, for high-strength spring use, has a tensile strength 2100 to 2400 MPa. (6) Drawn heat-treated steel line for high-strength spring use, according to any one of (3) to (5), characterized in that the drawn heat-treated steel line, for high-strength spring use, has a yield strength of 1600 to 1980 MPa. (7) Drawn heat-treated steel line for high-strength spring use, according to any one of (3) to (6), characterized in that the drawn heat-treated steel line, for high-strength spring use, has a surface hardness of HV750 or more according to the Vickers scale, and internal hardness or more gentle nitration at 500 ° C for 1 hour. (8) Production Procedure for Prefabricated Structural and High Strength Spring Use Can be characterized in that a good content in mass%, C: 0.67% to 0.9%, Si: 2.0 to 3.5 ° A), Mn: 0.5 to 1.2 %, Cr: 1.3 to 2.5%, N: 0.003 to 0.007%, and Al: 0.0005% to 0.003%, with Si and Cr satisfying the following expression: 0.3% 5Si-Cr51.2% , with a balance of iron and unavoidable impurities, with P and S as impurities comprising P: 0,025% or less and S: 0,025% or less, the goat being heated to 1250 ° C or more, then the goat is hot-rolled to produce a rolling stock and heating of the rolling stock to 1200 ° C or 30 more, with subsequent hot rolling for the manufacture of a lined steel line. (9) Production process for the preferred structure spring strength application according to (8), characterized in that the goth also contains, in mass%, one or more of 9 0,03 to 0,10%, NO: 0,015% or less Mo: 0,05 to 0.30%, 0.05 to 0.30% Mg: 0.002% or less, Ca: 0.002% or less, and Zr: 0.003% or less, when content of V is 1.4% .5.Cr + V5 .2,6 ° A) and 0,70% .5..Mn + W,1,3%, and, 10 for Mo and W content, 0,05 To 5M0 + VV50, Production ProcedureContracted for high-strength spring application, can be further illustrated by heating the Treatments shaped according to (8) or (9), to 900 ° C or more, after which it is patented at 600 ° C or less.

ProduktionsforfarandeforvarmebehandladstaltradfOr hOghallfasthetsfjaderanvandning, kannetecknat av dragning av den fOrdragna staltraden vilken tillverkats genom produktionstrfarandet for trdragen staltrad, enligt (8) till (10), varmning av traden i en takt av 10°C! sek eller mer upp till temperaturen A3, bibehallande av temperaturen A3 eller mer i 1 minut till 5 minuter, darefter kylning i en takt av 50°Cisek eller mer ner till 100°C eller mindre. 25 (12) Produktionsforfarande fOr produktion av varmebehandlad staltrad for hOghallfasthetsfjaderanvandning, enligt (11), kannetecknad av vidare bibehallning och anlopning vid 400 till 500°C115 minuter eller mindre. Production process Pre-heat treated steel wire for high strength spring application, characterized by drawing the preferred steel wire which has been produced by the production process of the wire steel wire, according to (8) to (10), heating the wire at a rate of 10 ° C! sec or more up to temperature A3, maintaining the temperature A3 or more for 1 minute to 5 minutes, then cooling at a rate of 50 ° Cisek or more down to 100 ° C or less. (12) Production process for the production of heat-treated stable line for high-strength spring use, according to (11), characterized by further maintenance and tempering at 400 to 500 ° C115 minutes or less.

FOrdelaktiga effekter av uppfinningen Beneficial effects of the invention

[0022]Enligt treliggande uppfinning, i synnerhet, kan dragen varmebehandlad staltrad, fOr hOghallfasthetsfjaderanvandning, med en hog ytskiktshardhet och en innerhardhet, och dessutom hOghallfasthetsfjader med utmarkt hallbarhet, erhallas, pa grund av den utmarkta kallindningsformagan och motstandet mot avmjukning, aven vid nitrering vid 500 °C i 1 tinnnne. Bidraget till industrin ar extremt start. According to the three-pronged invention, in particular, the drawn heat-treated stable line, for high-strength spring application, with a high surface layer hardness and an inner hardness, and also high-strength spring with excellent durability, can be obtained due to the excellent cold winding shape and resistance to resistance. 500 ° C for 1 hour. The contribution to industry is an extreme start.

Kort beskrivning av ritningarna Brief description of the drawings

[0023]FIG. 1 är ett mikrofoto av metallstrukturen som visar ett exempel pa sfariska karbider, i den dragna varmebehandlade staltraden, for hOghallfasthetsfjaderanvandning, i den fOreliggande uppfinningen. Vid spetsarna pa pilarna i figuren ses oupplOsta sfariska karbider. FIG. 1 is a photomicrograph of the metal structure showing an example of spherical carbides, in the drawn heat treated steel row, for high strength spring application, in the present invention. Undissolved spherical carbides are seen at the tips of the arrows in the figure.

FIG. 2 visar en vy av formen av en stans for skapandet av ett spar i ett teststycke. FIG. 2 shows a view of the shape of a punch for creating a groove in a test piece.

FIG. 3 visar en vy av stegen for att skapa ett spar i ett provstycke. FIG. 3 shows a view of the steps for creating a groove in a specimen.

FIG. 4 visar en vy av en oversikt Over ett bajprov av sparet. FIG. 4 shows a view of an overview of a poop sample of the spar.

FIG. 5 ar en vy som visar ett fOrfarande fOr matning av sparets bojningsvinkel. FIG. 5 is a view showing a procedure for feeding the bending angle of the spar.

Beskrivning av utforningsformer Description of embodiments

[0024]Allmant, tillverkas en valstrad fOr fjader enligt foljande: Sjalvfallet är tillverkningen av fjadrar inte begransat till det beskrivna forfarandet. Detta beskriver endast ett exempel. Generally, a rolled spring roll is manufactured as follows: Of course, the manufacture of springs is not limited to the described process. This describes only one example.

G6t gjord av stal innehallande fOrutbestamd kemisk sammansattning, valsas for att erhalla ett valsamne. Darefter valsas valsamnet for att tillverka staltrad av fOrbestamd diameter. Staltraden som tillverkas i detta steg kallas "fOrdragen staltrad". Staltraden vilken tillverkas med valsning patenteras och dras for att erhalla en annu finare staltrad, varefter arbetsspanningen I ytlagret avlagsnas och efterfOljande kallindningsfOrmaga erhalls genom varmebehandling (seghardning), som tillverkas efter valsning, patenteras och dras fOr att erhalla annu finare staltrad, darefter avlagsnas arbetsspanningen vid ytskiktet och kallindningsbearbetningsfOrmaga erhalls genom varmebehandling (seghardning). Staltraden som tillverkas vid detta steg kallas "dragen varmebehandlad staltrad". Made of steel containing a predetermined chemical composition, rolled to obtain a rolling stock. The roll is then rolled to produce a stall of predetermined diameter. The stable line manufactured in this step is called the "Preferred stable line". The steel row which is manufactured by rolling is patented and drawn to obtain an even finer steel row, after which the working stress in the surface layer is removed and subsequent cold winding capacity is obtained by heat treatment (toughening), which is produced after rolling, patented and drawn to obtain even finer steel. the surface layer and cold winding processing ability are obtained by heat treatment (toughening). The stalt line manufactured at this stage is called the "drawn heat-treated stalt line".

[0025]Darefter bearbetas fjadern genom kallindning fOr fOrbattrad styrka och nitrering for fOrbattrad ythardhet. PA sá satt är en "fjader" tillverkad som en slutgiltig prod ukt. 11 Forst kommer den kemiska sammansattningen av den dragna varmebehandlade staltraden, far haghallfasthetsfjaderanvandning, i den fdreliggande uppfinningen och dess material, det vill saga fOrdragen staltrad, fOr hOghallfasthetsfjaderanvandning, att forklaras. Har betyder "%" i den kemiska 5 sammansattningen mass %, om inte annat anges. Thereafter, the spring is machined by cold winding for improved strength and nitriding for improved surface hardness. PA sá satt is a "feather" manufactured as a final product. First, the chemical composition of the drawn heat-treated steel row, for high-strength spring use, in the present invention and its material, that is, the preferred steel spring, for high-strength spring use, will be explained. Has "%" in the chemical composition means mass%, unless otherwise indicated.

[0026]C: 0,67 % till mindre an 0,9 % C ar ett viktigt amne vilket har star effekt pa styrkan hos stalmaterialet och C bidrar ocksa till bildandet av restaustenit. I fOreliggande uppfinning har den lagre gransen for mangden C satts till 0,67 % eller mer for att erhalla tillracklig styrka. FOr att Oka styrkan, utgors mangden C av 0,70 % eller mer, fOretradesvis 0,75 % eller mer. C: 0.67% to less than 0.9% C is an important substance which has a strong effect on the strength of the steel material and C also contributes to the formation of residual austenite. In the present invention, the lower limit of the amount C has been set to 0.67% or more to obtain sufficient strength. To increase the strength, the amount C is 0.70% or more, preferably 0.75% or more.

Daremot am mangden C blir 0,9 % eller mer, resulterar det i overdriven samutfallning, att en star mangd grov cementit utfalls och att segheten avtar 15 anmarkningsvart. Vidare cm mangden C ar Overdriven bildas grova sfariska karbider och ringlingsfOrmagan blir nedsatt. Darfor är den Ovre gransen for mangden C satt till mindre an 0,9 %. Med syftet att dampa bildandet av sfariska karbider ar den Ovre gransen fOr mangden C fOretradesvis 0,85 %, mer fOredraget 0,80 %. On the other hand, if the amount C is 0.9% or more, it results in excessive co-precipitation, that a large amount of coarse cementite precipitates and that the toughness decreases remarkably black. Furthermore, the amount of C is Excessive, coarse spherical carbides are formed and the curvature is reduced. Therefore, the upper limit of the amount C is set to less than 0.9%. In order to vaporize the formation of spherical carbides, the upper limit for the amount C is preferably 0.85%, more preferably 0.80%.

[0027]Si: 2,0 till 3,5 % Si ar ett viktigt amne for att fOrbattra matstandet mot varmerelaterad avmjukning hos stalet och eftergivningsegenskaperna has fjadern. FOr att erhalla dessa effekter, behdver 2,0 % eller mer Si tillsattas. Vidare ar Si effektiv fOr sfaroidisering och fOrfining av cementiten. Far att dampa bildandet av grova sfariska karbider, tillsatts fOretradesvis 2,1 % eller mer av Si. FOr att Oka den innerhardheten, efter nitrering och andra behandlingar, for att Ora ytskiktet hardare, tillsatts fOretradesvis 2,2 % eller mer av Si. Vidare fran balansen med Cr, ar Si mer fOrdelaktigt satt till 2,3 % eller mer. Si satts ibland till 3,0 % eller mer. Si: 2.0 to 3.5% Si is an important substance for improving the food condition against heat-related softening of the steel and the resilience properties have the spring. To obtain these effects, 2.0% or more Si is needed. Furthermore, Si is effective for spheroidization and refinement of the cementite. To vaporize the formation of coarse spherical carbides, 2.1% or more of Si is preferably added. To increase the inner hardness, after nitriding and other treatments, to make the surface layer harder, 2.2% or more of Si was preferably added. Furthermore, from the balance sheet with Cr, Si is more advantageously set at 2.3% or more. Si is sometimes set to 3.0% or more.

Daremot, vid Overdriven tillsattning av Si hardnar staltraden och blir sprOd, darmed utgors Ovre gransen av Si till 3,5 % eller mindre. Med syfte att fOrhindra fersprodning, satts den Ovre gransen feretradesvis till 3,4 %, mer fOredraget 3,3 % eller mindre. On the other hand, with the excessive addition of Si, the steel line hardens and becomes spreading, thus the Upper limit of Si is 3.5% or less. In order to prevent fresh sprouting, the upper limit was set at 3.4%, more preferably 3.3% or less.

[0028]Mn: 0,5 till 1,2% 12 Mn ar ett amne som ar viktigt far att Oka slackningsformagan och far att stabilt sakra mangden restaustenit. I den foreliggande uppfinningen, har Mn tillsats i 0,5 % eller mer, mer foredraget 0,65 % eller mer, annu mer foredraget 0,70 % eller mer, far att Oka strackgransen hos stalet samt far att sakra restaustenit. Mn: 0.5 to 1.2% 12 Mn is a substance that is important for increasing the slackening ability and for stably securing the amount of residual austenite. In the present invention, Mn has been added in 0.5% or more, more preferably 0.65% or more, even more preferably 0.70% or more, to increase the yield strength of the steel and to secure residual austenite.

Daremot, vid Overdriven tillsattning av Mn akar mangden restaustenit. Vid bearbetning, bildas bearbetningsinducerad martensit och kallindningsfOrmagan farsamras. Far att forhindra farsprodning pa grund av Overdriven tillsats av Mn, ar den Owe gransen far Mn satt till 1,2 % eller mindre, foretradesvis 1,1 % eller mindre, mer faredraget 1,0 % eller mindre. On the other hand, in the case of excessive addition of Mn, the amount of residual austenite increases. During machining, machining-induced martensite is formed and the cold-winding forearm collapses. In order to prevent farrowing due to excessive addition of Mn, the Owe limit for Mn is set at 1.2% or less, preferably 1.1% or less, more dangerously 1.0% or less.

[0029]Cr: 1,3 till 2,5% Cr är ett amne vilket ar effektivt for att farbattra slackningssfOrmagan och motstandet mot varmerelaterad avmjukning. Far att erhalla dessa effekter, behaver 1,3 % eller mer Cr tillsattas. Vid nitrering, ar det majligt att gOra det hardade skiktet, som erhallits genom nitrering, tjockare genom tillsats av Cr. Darfar tillsatt 15 foretradesvis mer an 1,5 % av Cr, for att astadkomma hardning genom nitrering och mjukningsmotstand vid nitreringstemperaturen. Mer fardelaktigt tillsatts 1,7 % eller mer av Cr. Cr: 1.3 to 2.5% Cr is a substance which is effective in improving the slackening ability and the resistance to heat-related softening. To obtain these effects, 1.3% or more Cr needs to be added. When nitriding, it is possible to make the hardened layer obtained by nitriding thicker by adding Cr. More than 1.5% of Cr is preferably added, to provide curing by nitration and softening resistance at the nitration temperature. More dangerously, 1.7% or more of Cr.

Daremot, om mangden Cr ar Overdriven, blir tillverkningskostnaden hogre. lnte bara det utan upplosning av karbider farsamras, oupplOsta sfariska karbider blir tier, och lindningsfOrmagan blir forsamrad, sa den Ovre gransen far Cr satts till 2,5 % eller mindre. Vidare, om mangden Cr ar stor, ar mangden Cr faretradesvis undertryckt till 2 % eller mindre, far att dampa bildandet av grova cementiter. Vidare, for att erhalla bade hallfasthet och formbarhet utgors den byre gransen for mangden Cr till 1,8 % eller mindre. On the other hand, if the quantity Cr is Exaggerated, the manufacturing cost will be higher. Not only that, without the dissolution of carbides, it dissolves, undissolved spherical carbides become tier, and the winding capacity becomes condensed, so the Upper border may be set at 2.5% or less. Furthermore, if the amount of Cr is large, the amount of Cr is dangerously suppressed to 2% or less, causing the formation of coarse cementites to evaporate. Furthermore, in order to obtain both hall strength and formability, the maximum limit for the amount of Cr is set at 1.8% or less.

[0030]N: 0,003 till 0,007 % N ar ett amne, vilket bildar nitrider med Al etc. inkluderade som fbrorening stalet, i den fareliggande uppfinningen. For att anvanda fina nitrider och forfina restaustenit, ska 0,003 % eller mer av N inkluderas. Daremot, om mangden N ar Overdriven,fargrovasnitridernaochkallindningsformaganoch 30 utmattningsegenskaperna avtar. Daft- ar den Owe gransen far mangden N gjord 0,007 % eller mindre. Vidare med hansyn taget till formagan till varmebehandling etc., ar faretredesvis mangden N 0,005 % eller mindre. 13 N: 0.003 to 0.007% N is a substance which forms nitrides with Al etc. included as the purification steel, in the present invention. To use fine nitrides and fine residual austenite, 0.003% or more of N should be included. On the other hand, if the amount N is exaggerated, the color rough nitrides and cold winding shape and fatigue properties decrease. Daft- ar den Owe gransen gets the amount N made 0.007% or less. Furthermore, taking into account the conditions for heat treatment, etc., the amount N is dangerously 0.0000% or less. 13

[0031]P: 0,025 % eller mindre P ar en fOrorening. P fbrorsakar att stalet hardnar, bildar segregationer, och orsakar forsprOdning, sa den (hire gransen av P ar sett till 0,025 % eller mindre. 5 Vidare orsakar P, som segregerat vid tidigare austenitkorngranserna, segheten och motstandet mot fOrdrOjda frakturer etc. att avta, sa den Owe gransen fOr mangden P ar foretradesvis sett till 0,015 % eller mindre. Dessutom, ar mangden P foretradesvis begransad till mindre an 0,010 %, nar strackgransen hos staltraden overskrider 2150 MPa. P: 0.025% or less P is a contaminant. P causes the steel to harden, form segregations, and cause proliferation, it said (hire limit of P is seen to be 0.025% or less. 5 Furthermore, P, as segregated at previous austenite grain boundaries, causes toughness and resistance to delayed fractures, etc. to decrease, said the Owe limit for the amount of P is preferably set at 0.015% or less.In addition, the amount of P is preferably limited to less than 0.010% when the yield strength of the steel line exceeds 2150 MPa.

[0032]S: 0,025 % eller mindre S ar ocks6 en trorening. Om S ar narvarande i stal, orsakar den att stSlet bli sprOtt, se den byre gransen fOr mangden S ar sett till 0,025 % eller mindre. For aft dampa effekten av S, ar tillsats av Mn effektiv. Trots det ar MnS en inneslutning. I synnerhet i hOghallfasthets star, blir MnS ibland bOrjan till brott. DarfOr for att dampa 15 forekomsten av frakturer, har den ovre gransen for mangden av S fOretradesvis setts till 0,015 % eller mindre. Vidare, ar mangden S foretradesvis begransad till mindre an 0,01 %, nar strackgransen, hos den dragna varmehenadlade staltraden, for hOghallfasthetsfjaderanvandning, kommer att Overstiga 2150 MPa. S: 0.025% or less S is also a panty liner. If S is present in steel, it causes the steel to crack, see the upper limit for the amount of S seen at 0.025% or less. To dampen the effect of S, the addition of Mn is effective. Nevertheless, MnS is an inclusion. Especially in the star of high-strength, MnS sometimes becomes the beginning of crime. Therefore, in order to vaporize the incidence of fractures, the upper limit of the amount of S has preferably been set at 0.015% or less. Furthermore, the amount S is preferably limited to less than 0.01%, when the yield strength of the drawn heat-treated steel row, for high-strength spring use, will exceed 2150 MPa.

[0033]Al: 0,0005 till 0,003 % Al ar ett deoxiderande amne. Det Overkar bildandet av oxider. Om det bildas h6rda oxider avtar utmattningshallbarheten. I synnerhet om Al tillsatts i Overflode blir utmattningshallfastheten skiftande och stabiliteten fOrsamrad, i hOghallfasthetsfjadrar. Om mangden Al Overskrider 0,003 %, blir fOrekomsten av brott till fOljd av inneslutningar stOrre, sa mangden Al ar begransad till 0,003 % eller mindre i den dragna varmebehandlade st6ltrken fOr hOgh611fasthetsfjaderanvandning, i fbreliggande uppfinning. Det byre gransvardet av mangden Al al fOretradesvis 0,0028 %, mer fOredraget 0,0025 %. Al: 0.0005 to 0.003% Al is a deoxidizing agent. It interferes with the formation of oxides. If hard oxides are formed, the fatigue durability decreases. Especially if Al is added in Overflode, the fatigue strength varies and the stability is impaired, in high strength springs. If the amount of Al exceeds 0.003%, the incidence of fractures due to inclusions becomes larger, so the amount of Al is limited to 0.003% or less in the drawn heat-treated steel for high-strength spring use, in the present invention. The greater the spruce value of the quantity Al al is preferably 0.0028%, the more preferred 0.0025%.

[0034]Daremot, om mangden Al blir mindre an 0,0005 %, bildas latt kiselbaserade hArda oxider. Av den anledningen ar mangden Al sett till 0,0005 % eller mer. Den lagre gransen fOr mangden Al ar foretradesvis 0,0007 %, mer foredraget 0,0008 %, annu mer fOredraget 0,001 % eller mer. 14 [0034] On the other hand, if the amount of Al becomes less than 0.0005%, silicon-based hard oxides are easily formed. For that reason, the amount of Al is 0.0005% or more. The lower limit for the amount of Al is preferably 0.0007%, more preferably 0.0008%, even more preferably 0.001% or more. 14

[0035]Harnast kommer, standpunkten for fOreliggande uppfinning, det vill saga, farhallandet mellan Si och Cr, att forklaras. Det ar redan kant aft bade Si och Cr ar viktiga fOr Okad styrka i fjaderstal. Most recently, the standpoint of the present invention, that is, the relationship between Si and Cr, will be explained. It is already possible that both Si and Cr are important for increased strength in spring numbers.

Trots detta orsakar Overdriven tillsats problem. Despite this, Excessive additive causes problems.

[0036]0,3% 5Si-Cr?1,2 % Om mangden av Si Overstiger den fOreskrivna mangden, blir fOrspradningen extrem och bearbetningsfermagan vid lindning fOrsamras. Inte bara det utan 10 avkalning i Overgangsprocessen blir uppseendevackande. Av den anledningen blir ytskiktshardheten lagre och hallbarheten avtar, i den slutgiltiga fjaderprodukten. Vidare bildas avkalade delar slumpmassigt, vilket Or aft varaktigheten hos hallfastheten, hos den tillverka fjadern, fOrsamras. Nar mangden Si ar mindre an den foreskrivna mangden, avtar hallfastheten. Vidare ar eftergivningsegenskapen atillracklig. Det Ors acksa tydligt i hardheten efter nitrering. Tillracklig hardhet kan varken sakras vid ytskiktet eller inuti. 0.3% 5Si-Cr? 1.2% If the amount of Si exceeds the prescribed amount, the propagation becomes extreme and the processing capacity during winding is reduced. Not only that but 10 decalcification in the Transition process becomes startling. For this reason, the surface layer hardness becomes lower and the durability decreases, in the final spring product. Furthermore, stripped parts are formed randomly, which is affected by the duration of the half-strength, of the manufactured spring. When the quantity Si is less than the prescribed quantity, the half-strength decreases. Furthermore, the forgiveness property is insufficient. It ors accuse clearly in the hardness after nitriding. Sufficient hardness can not be ensured either at the surface layer or inside.

[0037]Tratts detta, ar fOrhallandet mellan Si och Cr, i cementiten, stalet viktigt. Det vill saga, Si ar ett amne vilket destabiliserar cementit. Om en star mangd Cr tillsatts eller andra amnen vilka stabiliserar cementit vid varmning, far det effekten att bildandet av en fast lasning av cementit framjas. Darfor blir mangden av oupplOst sfarisk karbider star-re och bearbetningsfarmagan minskar anmarkningsvart, am mangden Si ar liten, oavsett om star mangd Cr tillsatts. Uppfinnarna upptackte att det ar majligt att anvanda skillnaden mellan Si-innehallet (mass %) och Cr-innehallet (mass %) i stalet, det vill saga, Si-Cr mangden, som en mattstack. Det vill saga, nar vardet av Si-Cr ar mindre an 0,3 %, blir mangden av Cr relativt star och oupplOsta sfariska karbider kvarstar latt. Da'remot, am Si-Cr ar Over 1,2 % blir Si fOrhallandevis overflOdig, viket iatt orsakar fOrspredning, avkalning eller andra problem. Daric5r skall vardet av Si-Cr sattas till 0,3 till 1,2 %. Given this, the ratio of Si to Cr, in the cementite, steel is important. That is to say, Si is a substance which destabilizes cementite. If a large amount of Cr is added or other substances which stabilize cementite on heating, it has the effect that the formation of a solid load of cementite is promoted. Therefore, the amount of undissolved spherical carbides becomes larger and the processing capacity decreases remarkably, while the amount of Si is small, regardless of whether a large amount of Cr is added. The inventors discovered that it is possible to use the difference between the Si content (mass%) and the Cr content (mass%) in the steel, that is to say, the Si-Cr amount, as a carpet stack. That is, when the value of Si-Cr is less than 0.3%, the amount of Cr becomes relatively rigid and undissolved spherical carbides remain light. On the other hand, if Si-Cr is over 1.2%, Si becomes relatively superfluous, which causes spreading, decalcification or other problems. Daric5r the value of Si-Cr should be set to 0.3 to 1.2%.

[0038]Med avsikt att dampa bildandet av karbider, mOjliggar en stor mangd Si-Cr att oupplOsta karbider undertrycks, men industriellt, am Si forekommer i fOr star mangd, blir tjockleken av det hardade lagret genom nitrering latt tunt. Av den anledningen ar foretradesvis Si-Cr 50,9 %, mer foredraget Si-Cr 50,75 %, med tanke p5 beteendet has oupplosta sfariska karbider och det hardade lagret, bildat genom nitrering. Vidare med avsikt att, minska mangden Cr och minska den kvarvarande fOrekomsten av oupplosta sfarisk karbider, jamfOrelsevis, ar den ogre gransen fordelaktig 0,35 %5Si-Cr, mer fOrdelaktigt 0,4 %5 Si-Cr. In order to vaporize the formation of carbides, a large amount of Si-Cr allows undissolved carbides to be suppressed, but industrially, if Si is present in too large an amount, the thickness of the hardened layer by nitriding becomes slightly thin. For this reason, Si-Cr is preferably 50.9%, more preferably Si-Cr is 50.75%, in view of the behavior having undissolved spherical carbides and the hardened layer formed by nitration. Furthermore, with the intention of reducing the amount of Cr and reducing the residual occurrence of undissolved spherical carbides, respectively, the lower limit is advantageously 0.35% 5Si-Cr, more advantageously 0.4% Si-Cr.

[0039]Harnast kommer den selektivt tillsatta kemiska sammansattningen att forklaras, Most recently, the selectively added chemical composition will be explained.

[0040]V: 0,03 till 0,10 % V ar ett amne vilket bildar nitrider, karbider, och kolnitrider. Fina V nitrider, karbider, och kolnitrider med en cirkelekvivalent diameter av mindre an 0,2 pm ar 10 effektiva RN- farfining av restaustenit. Vidare kan dessa aven anvandas fOr hardning av ytskiktet genom nitrering. Daremot, ar det nOcIvandigt att precist styra utfallningen, da oupplOsta karbider och nitrider iatt bildas, aven om kvave (N) undertrycks. Av den anledningen, enligt fOreliggande uppfinning, ar V inte avsiktligt tillsatt. FOr att erhalla s5dan effekt kan en fin mangd V tillsattas. For att erhalla effekten, skall V tillsattas i 0,03 % eller mer, foretradesvis 0,035 % eller mer, mer fOrdelaktigt 0,04 % eller mer. V: 0.03 to 0.10% V is a substance which forms nitrides, carbides, and carbon nitrides. Fine V nitrides, carbides, and carbon nitrides with a circle equivalent diameter of less than 0.2 microns are effective RN staining of residual austenite. Furthermore, these can also be used for hardening the surface layer by nitriding. On the other hand, it is necessary to precisely control the precipitation, as undissolved carbides and nitrides are still formed, even if nitrogen (N) is suppressed. For that reason, according to the present invention, V is not intentionally added. To obtain such an effect, a fine amount of V can be added. To obtain the effect, V should be added in 0.03% or more, preferably 0.035% or more, more advantageously 0.04% or more.

[0041]Daremot, am V tillsats till mer an 0,10 %, bildas grova sfariska karbider och kallindningsfOrmagan och fjader utmattningsegenskaperna forsamras. DarfOr skall V innehaIlet sattas till 0,1 % eller mindre. Vidare genom att tillsatta V, fore dragning, bildas latt en underkyld struktur som orsakar sprickor och brott vid dragning. Av den anledningen ar den owe gransen far mangden V fOretradesvis satt till 0,09 `)/0 eller mindre, mer fOredraget 0,08 % eller mindre, mest fOredraget 0,05 % eller mindre. I synnerhet, i fallet vid tillsats av en liten mangd Nb, ar mangden av tillsats av V foretradesvis satt till 0,05 % eller mindre. Vidare, ar V ett amne vilket kraftigt paverkar bildandet av kvarvarande austenit p5 samma satt som Mn, sa mangden av V maste styras noggrant tillsammans med mangden Mn, On the other hand, with the addition of more than 0.10%, coarse spherical carbides are formed and the cold winding force and spring fatigue properties are compromised. Therefore, the V content must be set to 0.1% or less. Furthermore, by adding V, pre-drawing, an subcooled structure is easily formed which causes cracks and fractures during drawing. For this reason, the upper limit is that the quantity V is preferably set at 0.09 `) / 0 or less, more preferably 0.08% or less, most preferably 0.05% or less. In particular, in the case of the addition of a small amount of Nb, the amount of addition of V is preferably set to 0.05% or less. Furthermore, V is a substance which strongly affects the formation of residual austenite in the same way as Mn, so the amount of V must be carefully controlled together with the amount Mn,

[0042]Nb: 0,015 % eller mindre Nb ar ett amne vilket bildar nitrider, karbider och kolnitrider i st51. Dessa utfallningar anvands ibland fOr att styra austenit kornstorleken etc. Men samtidigt ger Overdriven tillsats minskad duktilitet och resulterar att sprickor lattare bildas under 16 valsning och varmformning. Av den anledningen skall Overdriven tillsats av Nb undvikas. Nb: 0.015% or less Nb is a substance which forms nitrides, carbides and carbon nitrides in st51. These precipitates are sometimes used to control the austenite grain size, etc. But at the same time, the excessive addition gives reduced ductility and results in cracks forming more easily during rolling and hot forming. For this reason, Excessive addition of Nb should be avoided.

[00043]Nb tillatts med syftet att styra mangden N. Utfallningarna inte anvands direkt fOr att styra kvaliteten. Ventilfjadrar och andra fjadrar tillverkas genom slackning, anlopning, darefter kallindning, men vid den tidpunkten, hindrar upplost kvave fargdeformationen och minskar spanningsgransen. Av den anledningen ar kallindningsfOrmagan fOrsamrad. DarfOr blir effekten genom tillsats av Nb och bilning av nitrider vid hog temperatur, att upplOst kvave stalmatrisen minskar och aft kallindningsformagan forbattras. Nb was allowed for the purpose of controlling the quantity N. The precipitates are not used directly to control the quality. Valve springs and other springs are manufactured by slackening, tempering, then cold winding, but at that time, dissolved suffocating color deformation prevents and reduces the stress limit. For this reason, the cold winding stock is mixed. Therefore, the effect is by adding Nb and forming nitrides at high temperature, that the dissolved nitrogen matrix decreases and the cold winding capacity is improved.

[0044]Vidare, ar tillsats av en liten mangd Nb ocksa effektiv for att dampa V och andra oupplosta sfariska karbider inblandade som oundvikliga fororeningar. V ar ett amne vilket ar effektivt for att fOrbattra motstandet mot varmerelaterad avmjukning vid nitrering och det yt-narmsta lagrets hardhet. Men orn mangden tillsatt V blir stOrre, äí V-nitrider, V karbider, och V kolnitrider ofta inte tillrackligt lbsta, aven vid patentering, slackning och andra varmningar, som Ors for att fa en austenitfas, fOr tillverkning av dragen varmebehandlad staltrad for heighallfasthetsfjaderanvandning OupplOsta sfariska karbider av V vaxer fran karnorna av det V-baserade nitriderna, bildade vid tiden av normal hog temperatur. Som ett resultat, kvarstar oupplOsta sfariska karbider och lindningsformagan forsamras. Av den anledningen, ar det nOdvandigt att dampa mangden tillsatt V, nar oupplOsta sfariska karbider undertrycks. I den fOreliggande uppfinningen var V inte ett nodvandigt amne. Furthermore, the addition of a small amount of Nb is also effective in vaporizing V and other undissolved spherical carbides involved as unavoidable impurities. Is a substance which is effective in improving the resistance to heat-related softening during nitriding and the hardness of the outermost layer. However, if the amount of added V becomes larger, V-nitrides, V-carbides, and V-carbon nitrides are often not sufficiently low, even in patenting, slackening and other heatings, as Ors to obtain an austenite phase, for the manufacture of drawn heat-treated steel for high-strength spring use. spherical carbides of V wax from the nuclei of the V-based nitrides, formed at the time of normal high temperature. As a result, undissolved spherical carbides remain and the winding shape accumulates. For this reason, it is necessary to vaporize the amount of added V when undissolved spherical carbides are suppressed. In the present invention, V was not a necessary substance.

[0045]Som motsats till detta, bildar Nb-nitrider vid hOgre temperatur an V. Av den anledningen undertrycker Nb bildandet av V nitrider i staltillverkningsfarfarandet. Det viii saga, Nb bildar nitrider i hegtemperatur regionen, dar V upplOses och inte bildar nitrider, Vidare vid hog temperatur dar V nitrider bildas konsumerar Nb kvave, sa att bildandet av V nitrider fOrsvaras, aven vid kylning. Av den anledningen ar tillsats av en liten mangd Nb synnerligen effektiv for att dampa oupplOsta sfariska karbider och sakra lindningsfOrmagan vid tillsats av star mangd V. In contrast, Nb nitrides form at a higher temperature than V. For this reason, Nb suppresses the formation of V nitrides in the steelmaking process. The viii saga, Nb forms nitrides in the high temperature region, where V dissolves and does not form nitrides, Furthermore, at high temperatures where V nitrides are formed, Nb consumes nitrogen, so that the formation of V nitrides is justified, even on cooling. For this reason, the addition of a small amount of Nb is particularly effective in vaporizing undissolved spherical carbides and securing the winding capacity when adding a large amount of V.

[0046]Om mangden tillsatt Nb ar stOrre an 0,015 %, blir varmduktiliteten fOrsamrad och defekter och andra problem vid valsning framtrader lattare. Av den 17 anledningen, är mangden tillsatt Nb satt till 0,015 % eller mindre, tretradesvis 0,010 % eller mindre, mer fOredraget 0,005 % eller mindre, mest fOredraget mindre an 0,001 %. If the amount of Nb added is greater than 0.015%, the hot ductility is impaired and defects and other problems during rolling appear more easily. For this reason, the amount of Nb added is set to 0.015% or less, three times 0.010% or less, more preferred 0.005% or less, most preferred less than 0.001%.

Daremot, syns effekten av Nb vid styrning av mangden N i fjaderstalet frail 0,0005 %, s6 vid tillsatts av Nb, ar 0,0005 % eller mer att foredra. Vidare nar V etc. tillsatts, er tillsats av en liten mangd Nb mer effektivt. Ett interval! om 0,003 till 0,012 ar att foredra. Vidare, ar ett intervall om 0,005 till 0,009 % mer fOrdelaktigt. Effekten uppnas aven vid 0,005 till 0,001 %. On the other hand, the effect of Nb when controlling the amount of N in the spring number frail 0.0005%, s6 when adding Nb, is 0.0005% or more is preferred. Furthermore, when V etc. is added, your addition of a small amount of Nb is more efficient. An interval! about 0.003 to 0.012 are preferred. Furthermore, a range of 0.005 to 0.009% is more advantageous. The effect is also achieved at 0.005 to 0.001%.

[0047]1,4 % 5_Cr+V 2,6% I den fOreliggande uppfinningen, ar V inte avsiktligt tillsatt. Men, som fOrklarats ovan, har tillsats av en liten mangd V effekt pA fOrfiningen av den tidigare austeniten och bildandet av restaustenit. Genom att noggrant styra summan av mangden tillsatt Cr och V med avseende p V, ar det mOjligt att Oka hallfastheten for att Ora 15 ytskiktshardheten efter nitrering och den innerhardheten lamplig for hoghallfasthetsfjadrar. 1.4% 5_Cr + V 2.6% In the present invention, V is not intentionally added. However, as explained above, the addition of a small amount of V effect on the refinement of the former austenite and the formation of residual austenite. By carefully controlling the sum of the amount of Cr and V added with respect to V, it is possible to increase the hall strength to increase the surface layer hardness after nitriding and that the inner hardness is suitable for high half-strength springs.

[0048]Cr och V är bada amnen som forhindrar mjukning vid varmning genom glOcigning eller nitrering etc. utfOrd efter fjaderlindning, det viii saga delvis sa kallat varmerelaterat motstand mot avmjukning. I synnerhet nitrering orsakar, nitrider att falla ut vid den nitrerade delen av ytskiktet fOr att darigenom fOrbattra yth6rdheten och Oka nitreringseffekten. Vidare aven vid insidan, dar nitrering inte sprider sig, dampas sonderfall av karbider. Daremot ar Cr och V !Ada amnen som underlattar bildandet av oupplOsta sfariska karbider. Cr upplOses i cementiten for att Oka 25 bestandigheten, sa aft upplOsningen av cementit dampas varmningssteget for upplosning av cementit (varmning vid tiden for patentering och varmning vid tiden fOr slackning), kvarstar ofta som oupplOsta sfariska karbider. Vidare, har V ocks6 en upplOsningsternperatur for utfallningarna, som ar hogre an A3 punkten fOr stal, sa V kvarstar !Alt som oupplOsta sfariska karbider. Cr and V are both substances which prevent softening on heating by glowcigning or nitriding etc. performed after spring winding, the viii saga partly so-called heat-related resistance to softening. In particular, nitriding causes nitrides to precipitate at the nitrided part of the surface layer, thereby improving the surface hardness and increasing the nitriding effect. Furthermore, even at the inside, where nitriding does not spread, carbide probes are steamed. On the other hand, Cr and V! Ada are the substances that facilitate the formation of undissolved spherical carbides. Cr is dissolved in the cementite to increase the resistance, so that the dissolution of the cementite vaporizes the heating step for dissolving the cementite (heating at the time of patenting and heating at the time of slackening), often remaining as undissolved spherical carbides. Furthermore, V also6 has a dissolution temperature for the precipitates, which is higher than the A3 point for steel, so V remains! All as undissolved spherical carbides.

[0049]Om det totala innehallet av Cr och V, det vill saga, CNN, ar mindre an 1,4 %, avtar yth6rdheten av heighallfasthetsfjadern under HV750 och den innerhallfastheten avtar under HV570. Av den anledningen, ar Cr+V fOretradesvis 1,4 % eller mer. Vidare, ar 1,5 % eller mer att foredra. Daremot, lamnar Overdriven tillsats 18 Cr+V, av mer an 2,6 %, stora mangder oupplOsta sthriska karbider, vilket leder till att lindningsfOrmagan fOrsamras. DartOr, ar 2,6 % satt till den Ovre gransen. Vidare, ar Cr+V fOretradesvis 2 % eller mindre, mer fOredraget 1,8 % eller mindre. (0050]0,7% 5.Mn+V% Mn och V ar amnen vilka forbattrar slackningsfOrmagan och vilka dessutom har en stor effekt pa bildandet av restaustenit. Om mangden Mn ar stOrre an den fereskrivna mangden, akar mangden av restaustenit. DarfOr, har summan av bade Mn och V, vilka fOrekommer som oundvikliga fOroreningar, en direkt paverkan pa 10 austenits beteende, Det ar inte bara bearbetningsfOrmagan som paverkas, utan aven strackgransen paverkas kraftigt. Tillracklig hallbarhet kan inte sakras. [00511Av den anledningen, ar det totala innehallet av Mn och V, det viii saga Mn+V, saft till 0,7 till 1,3 % i den fOreliggande uppfinningen. For att sakra ett 15 volymsmatt pa Over 6 % av restaustenit, maste den lagre gransen fOr Mn+V sattas till 0,7 % eller mer. (0052]Som fOljd orsakar transformationsinducerad plasticitet att segheten fOrbaftras och mitijliggor att kallindningsformagan sakras. Daremot maste den ovre gransen av Mn+V sattas till 1,3 % eller mindre, for aft Ora restaustenit volymsmaft 15 % eller mindre. Pa grund av detta ar bildandet av bearbetningsinducerade martensit, som en foljd av slagmarken vid kallindning, undertryckt och lokal forsprOdning kan fOrhindras. (0053]Mo: 0,05 till 0,30 °A Mo ar ett amne vilket fOrbattrar slackningsfOrmagan. Vidare ar Mo ocksa extremt effektiv fOr att forbaftra motstandet mot varmerelaterad avmjukning. I synnerhet i den fOreliggande uppfinningen kan 0,05 % eller mer av Mo tillsattas, for aft ytterligare ferbattra motstandet mot varmerelaterad avmjukning. Vidare ar Mo ett amne vilket bildar Mo-baserade karbider stalet. Temperaturen vid vilken de Mo- baserade karbiderna faller ut ar lagre an temperaturen vid vilken V-karbider etc. faller ut. Av den anledningen ar tillsats av en lamplig mangd Mo ocksa effektiv for aft dannpa fOrgrovning av karbider. Tillsats av 0,10 % eller mer av Ma ar att fOredra. Daremot orn mangden tillsatt Mo ar mer an 0,30 %, bildas latt en underkyld struktur, 19 vid varmvalsning, och patentering fare dragning etc. Darfor for att dampa bildandet av en underkyld struktur, orsakande sprickbildning eller tradbrott vid dragning, ar den byre gransen av mangden Mo satt till 0,30 % eller mindre, foretradesvis 0,25 % eller mindre. Vidare om mangden Mo ar stor, vid patentering, blir tiden fram till slutet pa perlitovergangen langre, sa mangden Mo safts feretradesvis till 0,20 ')/0 eller mindre. If the total content of Cr and V, i.e. CNN, is less than 1.4%, the surface hardness of the high-strength spring decreases below HV750 and the inner-half strength decreases below HV570. For that reason, Cr + V is preferably 1.4% or more. Furthermore, 1.5% or more is preferable. On the other hand, Excessive additive leaves 18 Cr + V, of more than 2.6%, large amounts of undissolved steric carbides, which leads to a reduction in the winding capacity. DartOr, 2.6% is set to the Upper border. Furthermore, Cr + V is preferably 2% or less, more preferably 1.8% or less. 0.7% 5.Mn + V% Mn and V are the substances which improve the leaching capacity and which also have a large effect on the formation of residual austenite. If the amount Mn is greater than the prescribed amount, the amount of residual austenite increases. has the sum of both Mn and V, which occur as unavoidable contaminants, a direct effect on the behavior of 10 austenite, It is not only the working capacity that is affected, but also the yield strength is strongly affected. Adequate durability can not be ensured. [00511Therefore, it is the total. the content of Mn and V, the viii saga Mn + V, juice to 0.7 to 1.3% in the present invention To ensure a volume mat of Over 6% of residual austenite, the lower limit for Mn + V must be set to 00% or more. As a result, transformation-induced plasticity causes the toughness to improve and mitigates the cold winding shape, however, the upper limit of Mn + V must be set to 1.3% or less, for aft Ora residual austenitic volume of 15%. el laughs less. Due to this, the formation of processing-induced martensite, as a result of the impact field during cold winding, is suppressed and local propagation can be prevented. Mo: 0.05 to 0.30 ° A Mo is a substance which improves the quenching capacity. Furthermore, Mo is also extremely effective in improving the resistance to heat-related softening. In particular in the present invention, 0.05% or more of Mo is added to further improve the resistance to heat-related softening.More is a substance which forms Mo-based carbides steel.The temperature at which the Mo-based carbides precipitate is lower than the temperature at which V-carbides etc. precipitate. This is because the addition of a suitable amount of Mo is also effective in producing carbide coarsening. Addition of 0.10% or more of Ma is preferable. However, when the amount of Mo is added is more than 0.30%, a supercooled structure is easily formed. , 19 for hot rolling, and patenting for drawing, etc. Therefore, in order to vaporize the formation of a supercooled structure, causing cracking or breaking of wire during drawing, the maximum limit of the amount Mo is set to 0.30% or less, f 0.25% or less. Furthermore, if the amount of Mo is large, in the case of patenting, the time until the end of the perlite transition becomes longer, so the amount of Mo is preferably reduced to 0.20 ') / 0 or less.

Dessutom fOr att forkorta patenteringstiden och stabilt stoppa perlitovergangen ar 0,15 % eller mindre att foredra. In addition, to shorten the patenting time and stably stop the perlite transition, 0.15% or less is preferable.

[0054]W: 0,05 till 0,30 % W i likhet med Mo är ett amne vilket ar effektivt fOr att fOrbattra slackningsfOrmagan och motstandet mot varmerelaterad avmjukninng och ar ett arnne vilket utfalls i stalet som karbider, I synnerhet i den foreliggande uppfinningen tillsatts 0,05 % eller mer W for att forbattra motstandet mot varmerelaterad avmjukning. In particular, W: 0.05 to 0.30% W, like Mo, is a substance which is effective in improving the slackening ability and the resistance to heat-related softening and is a substance which precipitates in the steel as carbides, In particular in the present invention added 0.05% or more W to improve the resistance to heat-related softening.

[0055]Daremot orn W tillsants i OverflOd bildas en underkyld struktur vilken orsakar sprickbildning eller tradbrott vid dragning, sa mangden W maste saftas till 0,30 % eller mindre. On the other hand, when W is present in OverflOd, a supercooled structure is formed which causes cracking or fractures during drawing, so that the amount W must be juiceed to 0.30% or less.

[0056]Dessutom med tanke pa enkelheten vid varmebehandling etc. ar mangden W fOretradesvis 0,1 till 0,2 %, mer fOredraget 0,13 till 0,18 %. In addition, in view of the simplicity of heat treatment, etc., the amount W is preferably 0.1 to 0.2%, more preferably 0.13 to 0.18%.

[0057]0,05 % .5_Mo-i-VV?_ 0,5 % Mo och W ar amnen vilka ar effektiva for att fOrbattra motstandet mot 25 varmerelaterad avmjukning. Om !pada tillsants i kombination med varandra dampas tillvaxten av karbider och motstandet mot varmerelaterad avmjukning kan anmarkningsvart fOrbattras jamfart med vid tillsats av enbart Mo eller W. I synnerhet fOr att fOrbattra motstandet mot varmerelaterad avmjukning vid varmning till 500 "C maste Mo+W sattas till 0,05 % eller mer, fOretradesvis 0,15 % eller mer. 0.05% .5_Mo-i-VV? _ 0.5% Mo and W are the substances which are effective in improving the resistance to heat-related softening. If added in combination with each other, the growth of carbides is vaporized and the resistance to heat-related softening can be remarkably improved with the addition of only Mo or W. In particular, to improve the resistance to heat-related softening when heated to 500 ° C, the Mo + must be set. to 0.05% or more, preferably 0.15% or more.

Daremot om Mo+W ar over 0,5 %, vid varmvalsning och patentering fibre dragning etc., bildas en sá kallad underkyld struktur av martensit, bainit, etc. For att dampa bildandet av en underkyld struktur som orsakar sprickor och tradbratt vid dragning, ar den Ovre gransen av MO+W satt till 0,5 % eller mindre, foretradesvis 0,35 % eller mindre. On the other hand, if Mo + W is above 0.5%, in hot rolling and patenting fiber drawing, etc., a so-called subcooled structure of martensite, bainite, etc. is formed to vaporize the formation of a subcooled structure which causes cracks and wire steepness in drawing. the Upper limit of MO + W is set to 0.5% or less, preferably 0.35% or less.

[0058]Harnast kommer Mg, Ca, och Zr att fOrklaras. Most recently, Mg, Ca, and Zr will be explained.

Mg: 0,002 % eller mindre Mg bildar oxider i smalt stal vid hOgre temperatur an temperaturen for bildandet av MnS. Vid tidpunkten for bildandet av MnS, ar den redan narvarande i det smalta stalet. Darfor kan Mg anvandas som karna for utfallning av MnS. Detta har tillfaljd att fOrdelningen av MnS kan styras. Vidare ar Mg-baserade oxider trotts alit tint fordelade i fOrdelningsantal i det smalta stalet, p sa satt att MnS som bildas runt karnor av de Mg-baserade oxiderna ar tint fOrdelade i stalet, jamfOrt med Si- och 10 Al-baserade oxider vilka ofta framtrader i konventionellt stal. Dail& varierar MnS fOrdelningen beroende pa narvaron av M, aven om S innehallet ar det samma. Tillsats av dessa grir MnS korsstorleken finare. Genom att Ora MnS fint fardelad ar det mOjligt att betrakta MnS som harmles vad galler MnS som utgangspunkt fOr utmattning. Tillracklig effekt uppnis vid sma mangder. FOretradesvis skall Mg 0,0002 % eller mer, mer faredraget 0,0005 % eller mer, tillsattas. Mg: 0.002% or less Mg forms oxides in narrow steel at a higher temperature than the temperature for the formation of MnS. At the time of the formation of MnS, it is already present in the narrow steel. Therefore, Mg can be used as the vessels for precipitation of MnS. This has coincided with the fact that the distribution of MnS can be controlled. Furthermore, Mg-based oxides are nevertheless thinly distributed in the number of distributions in the narrow steel, so that MnS formed around nuclei of the Mg-based oxides is thinly distributed in the steel, compared with Si- and Al-based oxides which are often appears in conventional steel. Dail & varies the MnS distribution depending on the presence of M, although the S content is the same. Addition of these grins MnS cross size finer. By ora MnS finely divided, it is possible to consider MnS as harmed what applies MnS as a starting point for exhaustion. Sufficient effect is achieved with small amounts. Preferably Mg 0.0002% or more, more preferably 0.0005% or more, should be added.

[0059]Med tillsats av mer an 0,001 %, ar det dock svart for Mg att kvarsta I det smalta stalet, det ar en effekt av oxid kompositionen och mangden framtradande oxider som utgor utgangspunkter for utmattning blir stOrre, sa 0,002 % Mg ar den Ovre gransen. DarfOr, sattes den Ovre gransen av mangden tillsatt Mg till 0,002 °/0, fOretradesvis 0,0015 % eller mindre. Vidare nar det galler fjaderstal jamfert med annat stal for konstruktionsanvandning, ar mangden av tillsatt S undertryckt, med tanke pa utbytet etc., ar 0,001 % eller mindre att foredra. Vidare, vid anvandning for hOghallfasthetsventilfjader, ar inneslutningskansligheten hog, sa Mg har effekten av 25 att fOrbattra korrosionsmotstandet och motstandet for att skjuta upp frakturforebyggande valsnings sprickor pa grund av effekten av fbrdelningen av MnS etc. Tillsatts av sa sma mangder som mOjligt I det extremt snava intervallet 0,0002 till 0,001 ar att fOredra. With the addition of more than 0.001%, however, it is black for Mg to remain in the molten steel, there is an effect of the oxide composition and the amount of emerging oxides which form the basis for fatigue becomes larger, so 0.002% Mg is the Upper the border. Therefore, the upper limit of the amount of added Mg was set to 0.002 ° / 0, preferably 0.0015% or less. Furthermore, when it comes to spring steel compared to other steel for construction use, the amount of added S is suppressed, considering the yield, etc., is 0.001% or less is preferable. Furthermore, when used for high strength valve springs, the containment probability is high, so Mg has the effect of improving the corrosion resistance and the resistance to postpone fracture prevention rolling cracks due to the effect of the distribution of MnS etc. Added by so many small amounts. the range 0.0002 to 0.001 is preferred.

[0060]Ca: 0,002 % eller mindre Ca ar eft oxid- och sulfidbildande amne. I fjaderstal Or Ca, sa att MnS blir sfarisk och darigenom dampas utstrackningen av MnS, som tjanar som initierande stallen fOr utmattning och andra frakturer, vilket gor MnS harmlos. Effekten liknar effekten av Mg. Tillsats av 0,0002 % eller mer ar att foredra. Vidare ar inte bara 21 utbytet daligt, aven om mer an 0,002 % tillsatts, utan oxider och CaS och andra sulfider bildas dessutom och problem vid tillverkning och forsamring av fjaderutmattningshallbarhetsegenskaperna faljer, sá mangden sattes till 0,002 % eller mindre. Med tanke pa mangden tillsatt, di inneslutningskansligheten ar hog vid anvandning for hOghallfasthetsventil, ar den fOrdelaktiga mangden foretradesvis 0,0015 % eller mindre, mer fOredraget 0,001 %. Ca: 0.002% or less Ca is after oxide and sulfide-forming substance. In spring figures Or Ca, said that MnS becomes spherical and thereby vaporizes the extent of MnS, which serves as the initiating place for fatigue and other fractures, which makes MnS harmless. The effect is similar to the effect of Mg. Addition of 0.0002% or more is preferable. Furthermore, not only is the yield poor, although more than 0.002% is added, but oxides and CaS and other sulfides are also formed and problems in manufacturing and assembling the spring fatigue durability properties fall, so the amount was set to 0.002% or less. In view of the amount added, in which the probability of containment is high when used for high-strength valve, the advantageous amount is preferably 0.0015% or less, more preferably 0.001%.

[0061]Zr: 0,003 % eller mindre Zr ar ett oxid-, sulfid-, och nitridbildande arnne. I fjaderstal ar oxiderna fint 10 fOrdelade, och pa samma salt som med Mg bildar de karnor fOr uffallning av MnS, och kan pa sa sail Ora MnS fint fOrdelad. Till fOljd av detta ar det mOjligt att fOrbattra utmattningshallbarheten och vidare Oka duktiliteten for att darigenom fOrbattra lindningsfOrmagan. FOretradesvis tillsatts 0,0002 % eller mer. Vidare aven am mer an 0,003 % tillsatts ar inte bara utbytet lagt, utan oxider och ZrN, ZrS, och andra nitrider 15 och sulfider bildas och problem vid produktion eller nedbrytning av fjader hallbarhetsegenskaperna folanieds, sa mangden ar satt till 0,003 % eller mindre. Tillsatt mangd ar fOretradesvis 0,0025 % eller mindre. Dessutom har Zr effekten att fOrbattra lindningsformagan genom styrning av sulfiderna, sa tillsatsen ar fOrdelaktig fOr hOghallfasthetsventilfjadrar, men Mr att minimera effekten av inneslutningar, ar undertryckning till 0,0015 % eller mindre att fOredra. Zr: 0.003% or less Zr is an oxide, sulfide, and nitride-forming moiety. In spring numbers, the oxides are finely distributed, and on the same salt as with Mg they form nuclei for precipitation of MnS, and can then sail Ora MnS finely distributed. As a result, it is possible to improve the fatigue durability and further increase the ductility in order to thereby improve the winding capacity. Preferably 0.0002% or more is added. Furthermore, even if more than 0.003% is added, not only the yield is added, but oxides and ZrN, ZrS, and other nitrides and sulfides are formed and problems in the production or degradation of the spring durability properties are folanied, so the amount is set to 0.003% or less. The amount added is preferably 0.0025% or less. In addition, Zr has the effect of improving the winding capacity by controlling the sulphides, so the additive is advantageous for high strength valve springs, but Mr to minimize the effect of inclusions, suppression to 0.0015% or less is preferable.

[0062]Noter att ovan frivilligt tillsatta kemiska sammansattningar, om den innehaller sma mangder, inte fOrsamrar effekten hos staltradens som innefattar den kemiska grundsammansattningen i fOreliggande uppfinning. Notes that the above voluntarily added chemical compositions, if containing small amounts, do not detract from the effect of the stable radical comprising the basic chemical composition of the present invention.

[0063]Harnastkommermetallstrukturenhosstaltraden,fOr hOghallfasthetsfjaderanvandning i den fOreliggande uppfinningen, att fOrklaras. The metal structure of the housing structure, for high-strength spring use in the present invention, is to be explained.

[0064]OupplOsta sfariska karbider OupplOsta sfariska karbider utgOr en viktig roll nar det galler att sdkra hallfastheten hos staltraden for hOghallfasthetsfjaderanvandning. Daremot orsakar narvaron av oupplOsta sfariska karbider att lindningsfOrmagan forsamras. Vidare orsakar grova karbider dessutom att utmattningsegenskaperna forsamras. Darr& ar det nOdvandigt att dampa oupplOsta sfariska karbider vid lindning och after slutgiltig 22 nitrering skapa en uniform spridning av fina karbider fOr att lOsa problemet fOreliggande uppfinning. Undissolved spherical carbides Undissolved spherical carbides play an important role in ensuring the half-strength of the stable line for high-strength spring use. On the other hand, the presence of undissolved spherical carbides causes the winding stomach to constrict. Furthermore, coarse carbides also cause the fatigue properties to deteriorate. It is necessary to vaporize undissolved spherical carbides on winding and after final nitriding to create a uniform distribution of fine carbides to solve the problem of the present invention.

[0065]Staltraden fOr hOghallfasthetsfjaderanvandning i foreliggande uppfinningen har en Lang storlek av oupplosta sfariska karbider av 0,2 pm eller mindre som undertryckts vid fOrgrovning. De oupplOsta sfariska karbiderna ar redan narvarande efter valstrads valsning Wet vill saga fOrdragen staltrad). The stable line for high-strength spring use in the present invention has a long size of undissolved spherical carbides of 0.2 μm or less which is suppressed during roughening. The undissolved spherical carbides are already present after the rolling of the wire rod Wet wants to say the treaties are shaped).

Oupplosta sfariska karbider ar svara att f att Overga i losning i den senare varmebehandlingen (patentering, bildande av bearbetningsvarme vid dragning, och 10 seghardning, till exempel). !bland vaxer de snarare under dessa varmebehandlingssteg och forgrovas. Det vill saga ibland agerar oupplosta sfariska karbider i fOrdragen staltrad karnor for fOrgrovning av sig sjalva. Undissolved spherical carbides are responsible for dissolving in the latter heat treatment (patenting, formation of processing heat by drawing, and toughening, for example). among other things, they wax during these heat treatment steps and become coarse. It is to say that sometimes undissolved spherical carbides act in the Treaty shaped nuclei for the self-aggravation.

Av den anledningen ar det viktigt att i sa star utstrackning som mOjligt minska oupplOsta sfariska karbider vilka ar narvarande i den fordragna staltraden for aft 15 begransa fagrovningen av oupplbsta sfariska karbider hos staltraden after varmebehandling (varmebehandlad staltrad). Pa grund av det ovanstaende har definitionen "oupplosta sfariska karbider" en viktig mening inte bara fOr fordragen staltrad fOr hoghallfasthetsfjaderanvandning enligt foreliggande uppfinning, utan ocksa for dragen varmebehandlad staltrad for hOghallfasthetsfjaderanvandning. For this reason, it is important to reduce as far as possible undissolved spherical carbides which are present in the preferred steel row to even test the dissolution of undissolved spherical carbides in the steel row after heat treatment (heat treated steel row). In view of the above, the definition "undissolved spherical carbides" has an important meaning not only for the preferred high strength spring use castings of the present invention, but also for the heat treated high tensile springs used.

[0066]Styrkan i staltraden fOr hoghallfasthetsfjaderanvandning I fOreliggande uppfinning Okar genom tillsatts av C, fillsats av Mn och Cr, vidare tillsats av Mo, W, och andra s6 kallade legeringsamnen. Nar stora mangder C och i synnerhet Cr och andra legeringsamnen, vilka bildar nitrider, karbider, och kolnitrider, tillsatts kvarstar 25 sfariska cementitkarbider och legeringsbaserade karbider Iatt I stalet. Sfarisk cementitkarbid och legeringsbaserade karbider ar oupplosta sfariska karbider som inte loses upp i stalet under varmning vid varmvalsning. The Strength in the Stable Row for High Resilience Spring Use In the present invention, Oker is further increased by the addition of C, the fill of Mn and Cr, the further addition of Mo, W, and other so-called alloying elements. When large amounts of C and in particular Cr and other alloying substances, which form nitrides, carbides, and carbon nitrides, are added, spherical cementite carbides and alloy-based carbides remain in the steel. Spherical cementite carbide and alloy-based carbides are undissolved spherical carbides that do not dissolve in the steel during heating during hot rolling.

[0067]Notera att i foreliggande uppfinning kommer bade sfariska legeringsbaserade karbider och sfariska cementitkarbider att refereras till som sfariska karbider. I stalet finns nalformade karbider motsvarande nalformsstrukturen hos anlOpt martensit, men dessa nalformade karbider inkluderas inte i de sfariska karbiderna i den fOreliggande uppfinningen. Nalformade karbider finns inte narvarande direkt efter slackning utan faller ut under valsningsforfarandet. Den 23 anlopta martensitstrukturen är en struktur lamplig for att uppna bade styrka och seghet och bearbetningsfOrmaga. Nalform ar I viss mening den ideala formen fOr karbider. Note that in the present invention, both spherical alloy-based carbides and spherical cementite carbides will be referred to as spherical carbides. In the steel there are nal-shaped carbides corresponding to the nal-shaped structure of tempered martensite, but these nal-shaped carbides are not included in the spherical carbides in the present invention. Squeegee-shaped carbides are not present immediately after slackening but fall out during the rolling process. The 23 tempered martensite structure is a structure suitable for achieving both strength and toughness and machining ability. Nalform is in a sense the ideal form for carbides.

[0068]Strangt draget kan bearbetningsformagan ocksa fOrsamras om karbider med en del andel av 2 eller mer (nalformade karbider) forgrovas. Men i sjalva verket blir nalformade karbider fOrgrovade nar anlOpningstemperaturen ar hog eller nar bibehallningstiden vid anitipning ar extremt lang. Effekten hos prestandan ar aft styrkan och hardheten blir otillracklig. Problem uppstar i andra omraden an med oupplOsta sfariska karbider. FOrgrovade nalformade karbider bildas inte i den 2100 MPa eller sa starka staltraden, innefattad i den fOreliggande uppfinningen. Darfor omfattas inte nal-formade karbider i den fareliggande uppfinningen. Som farklarats ovan ar de utfallda karbiderna normalt oupplOsta, men i fOreliggande uppfinning har termen "oupplast" lagts till. Detta betonar bara deras oupplosta karaktar. I den foreliggande uppfinningen ar "oupplOsta sfariska karbider" och "sfariska karbider" synonyma. Strictly speaking, the machining mold can also be assembled if carbides with a proportion of 2 or more (nal-shaped carbides) are coarse. But in fact, needle-shaped carbides become coarse when the annealing temperature is high or when the retention time during annealing is extremely long. The effect of the performance is because the strength and hardness become insufficient. Problems arise in other areas with undissolved spherical carbides. Coarse-grained nal-shaped carbides are not formed in the 2100 MPa or so strong steel row, included in the present invention. Therefore, nal-shaped carbides are not included in the present invention. As explained above, the precipitated carbides are normally undissolved, but in the present invention the term "unresolved" has been added. This only emphasizes their unresolved character. In the present invention, "undissolved spherical carbides" and "spherical carbides" are synonymous.

[0069]Oupplostasfariskakarbiderkanobserverasmed svekelektronmikroskop (SEM) genom !adoring av ett prov erhallet fran fOrdragen staltrad eller dragen varmebehandlad staltrad, for hoghallfasthetsfjaderanvandning, till spegelglans och etsning av provet genom pikral- eller elektrolytisketsning. Vidare kan sfariska karbider observeras genom modellfOrfarande med transmissionselektronmikroskopi (TEM). Unresolved carbide carbide can be observed with a microscope microscope (SEM) by adhering a sample obtained from a preferred stable or drawn heat-treated stable, for high-strength spring application, to mirror gloss and etching the sample by picral or electrolytic etching. Furthermore, spherical carbides can be observed by model procedure by transmission electron microscopy (TEM).

[0070]Figur 1 visar ett exempel av en strukturell SEM-bild av ett pray efter elektrolytisketsning. I den strukturella bilden I figur 1 observeras att stalets matris har tva typer av strukturer, det vill saga, nalformade strukturer och sfariska strukturer. Bland dessa ar de nalformade strukturerna anlopt martensit bildad genom seghardning. Daremot ar de sfariska strukturerna karbider 1 som har fatt sin sfariska 30 form genom att de inte har lOsts upp i stalet genom att dessutom gOras sfariska genom seghardning genom anlOpning i olja eller induktionshardningsbehandling (oupplOsta sfariska karbider) pa grund av varmning genom varmvalsning. Sfariska karbider kan observeras vid framre anden av pilen i figur 1. 24 Figure 1 shows an example of a structural SEM image of a pray after electrolytic sketching. In the structural picture In Figure 1 it is observed that the matrix of the steel has two types of structures, that is to say saga, squeegee-shaped structures and spherical structures. Among these are the needle-shaped structures of annealed martensite formed by toughening. On the other hand, the spherical structures are carbides 1 which have taken their spherical shape in that they have not been dissolved in the steel by additionally being made spherical by toughening by annealing in oil or induction hardening treatment (undissolved spherical carbides) due to heating by hot rolling. Spherical carbides can be observed at the front of the arrow in Figure 1. 24

[0071]OupplOsta sfariska karbider med en cirkelekvivalent diameter av mindre an 0,2 pm I foreliggande uppfinning paverkar oupplOsta sfariska karbider egenskaperna has den dragna varmebehandlade staltraden for hOghallfasthetsfjaderanvandning och styrs daft- i storlek enligt foljande: Notera att jamfort med tidigare kand teknik är finare sfariska karbider dessutom definierade for att uppna hrigre prestanda och bearbetningsform6ga, i foreliggande uppfinning. Sfariska karbider men en cirkelekvivalent diameter av mindre an 0,2 pm ar extremt effektiva fOr aft sakerstalla styrkan och motstand mot varmerelaterad avmjukning hos stAlet. Undissolved spherical carbides with a circle equivalent diameter of less than 0.2 .mu.m In the present invention, undissolved spherical carbides affect the properties of the drawn heat-treated steel row for high-strength spring application and are controlled in size as follows: Note that compared to prior art. Spherical carbides are further defined to achieve higher performance and machining ability in the present invention. Spherical carbides with a circle equivalent diameter of less than 0.2 .mu.m are extremely effective in maintaining the strength and resistance to heat-related softening of the steel.

[0072]Daremot bidrar sfariska karbider med en cirkelekvivalent diameter om 0,2 pm eller mer inte till att frirbattra styrkan och motstAnd mot varmerelaterad avmjukning och graden av kallindningsfbrmaga. Av den anledningen ar foreliggande uppfinning kannetecknad av att inte tillata bildandet av sfariska karbider med en cirkelekvivalent diameter om 0,2 pm eller mer. In contrast, spherical carbides with a circle equivalent diameter of 0.2 μm or more do not contribute to improving the strength and resistance to heat-related softening and the degree of cold winding capacity. For this reason, the present invention is characterized by not allowing the formation of spherical carbides with a circle equivalent diameter of 0.2 μm or more.

Frirdragen staltrad och dragen varmebehandlad staltrad, I fOreliggande uppfinning, är kannetecknade av aft oupplOsta sfariska karbider har en cirkelekvivalent diameter av mindre an 0,2 pm. Till Mel av defta ar det mrijligt aft sakra styrka och samtidigt sakra bearbetningsformaga. The free-drawn stable row and the drawn heat-treated stable row, in the present invention, are characterized by unresolved spherical carbides having a circle equivalent diameter of less than 0.2 microns. For Mel av defta, it is possible to have secure strength and at the same time secure machining ability.

Sam forklarats ovan maste frirdragen staltrad patenteras, dras och varmas, seghardas, eller pA annat satt varmebehandlas, s6 att oupplOsta sfariska karbider kan vaxa och fOrgrovas. Av den anledningen ar den cirkelekvivalenta diametern hos oupplrista sfariska karbider i fOrdragen staltra'd foretradesvis gjord mindre an 0,2 pm. As explained above, the freewheels must be patented, drawn and heated, toughened, or otherwise heat-treated, so that undissolved spherical carbides can grow and be buried. For this reason, the circle equivalent diameter of undisturbed spherical carbides in the preferred steel wire is preferably made less than 0.2 microns.

Fran resultaten av uppfinnarnas experiment har den cirkelekvivalenta diametern av oupplOsta sfariska karbider, hos frirdragen staltrad, bekraftats kunna minskas till 0,18 pm eller mindre. Vidare ar det ocksa bekraftat att om valsamnets tillverkningstemperatur satts till 1250 °C eller mer, kan diametern griras 0,15 pm eller mindre. From the results of the inventors' experiments, the circle equivalent diameter of undissolved spherical carbides, in the free-drawn shape, has been confirmed to be able to be reduced to 0.18 μm or less. Furthermore, it is also confirmed that if the manufacturing temperature of the roll is set to 1250 ° C or more, the diameter can be set to 0.15 μm or less.

[0073]Har kommer fOrfarandet kir matning av den cirkelekvivalenta diametern och densiteten, av foreliggande sfariska karbider, att frirklaras. Ett prov som har tags fra'n staltraden, for hOghallfasthetsfjaderanvandning, poleras och etsas elektrolytiskt. Notera att det observerade omradet ar slumpmassigt utvalt nara mitten av radien hos den varme behandlade valstraden (staltrklen), det vill saga, den s6 kallade "1/2R- deien", fOr att undanroja speciella fOrh6 Ilanden sa' som avkolning och segregation i mitten. Vidare ar matarean 300 pm2 eller mer. Vid elektrolytisketsning är ytan av provet korroderat genom elektrolys i en elektrolytisklasning (en blandning av acetylaceton 10 mass %, tetametylammoniumklorid 1 mass %, och en jamvikt av 5 metylalkohol) dar provet anvands som anod och platina som katod och dar en strOmgenerator med en lagre potential anvands. Potentalen blir konstant vid en potential som är lamplig fOr provet i intervallet -50 till -200 mV vs SCE. Det är att foredra att potentialen blir konstant vid -100 mV vs SCE, Mr st6ltrAden i den foreliggande uppfinningen. Here, the process of feeding the circle equivalent diameter and density of the present spherical carbides will be explained. A sample that has tags from the stable line, for high-strength spring application, is polished and electrolytically etched. Note that the observed area is randomly selected near the center of the radius of the heat-treated rolling bar (steel bar), that is to say, the so-called "1 / 2R-dough", to eliminate special conditions such as decarburization and segregation in the middle. . Furthermore, the feed area is 300 pm2 or more. In electrolytic sketching, the surface of the sample is corroded by electrolysis in an electrolytic cluster (a mixture of acetylacetone 10 mass%, tetamethylammonium chloride 1 mass%, and an equilibrium of 5 methyl alcohol) where the sample is used as anode and platinum as cathode and has a current potential generator. used. The potential becomes constant at a potential that is suitable for the sample in the range -50 to -200 mV vs SCE. It is preferred that the potential be constant at -100 mV vs SCE, Mr st6ltrAden in the present invention.

[0074]Mangden anvand strOmstyrka kan bestammas av den totala ytarean av provet x 0,133 [c/cm2]. Notera att inte bara den polerade ytan utan ocks6 ytan av provet inbaddat i harts laggs till den totala ytarean av provet. The amount of current used can be determined by the total surface area of the sample x 0.133 [c / cm 2]. Note that not only the polished surface but also the surface of the sample embedded in resin is added to the total surface area of the sample.

StrOmmen sl6s pe och provet bibehalls i 10 sekunder sedan slas strOmmen av och provet rengOrs. The power is turned off and the sample is maintained for 10 seconds then the power is turned off and the sample is cleaned.

[0075]Efter det observeras provet med SEM och en strukturellbild av de sfariska karbiderna tags. I SEM:en fdrefaller strukturen av de sfariska karbiderna relativt vit, och har en andel (del andel) av stOrsta storlek (Ong storlek) och en minsta storlek (kort storlek) av 2 eller minde, sfariska karbider. FOrstoringen av bilden tagen med SEM är X1000 eller mer, varvid X5000 till X20000 att fOredra. Som matningspositioner valdes 10 fait siumpmassigt ut vid en tjocklek av omkring 0,5 till 1 mm fran ytan av valstrAden, de segregerade mittendelarna undviks. SEMstrukturbilden behandlades med bildbehandling fOr att mate den minsta storleken (kort storlek) och den storsta storleken (15ngstorlek) av de sfariska karbiderna observerade i matomradet och den cirkelekvivalenta diametern beraknas. Den cirkelekvivalenta diametern ar diametern nar arean, beraknad genom bildbehandling, hos en oupplOst karbid i ett omrade \Mare konverterad till en cirkel med samma area. After that, the sample is observed with SEM and a structural image of the spherical carbides is tagged. In the SEM, the structure of the spherical carbides is relatively white, and has a proportion (partial proportion) of largest size (Ong size) and a minimum size (short size) of 2 or smaller, spherical carbides. The magnification of the image taken with SEM is X1000 or more, with X5000 to X20000 to be preferred. As feed positions, the solids were selected at a thickness of about 0.5 to 1 mm from the surface of the roll wire, the segregated center portions being avoided. The SEM structure image was processed with image processing to feed the smallest size (short size) and largest size (size) of the spherical carbides observed in the feed area and the circle equivalent diameter is calculated. The circle equivalent diameter is the diameter near the area, calculated by image processing, of an undissolved carbide in an area \ Mare converted to a circle with the same area.

Vidare är det ocks5 mojligt att mata densiteten av narvarande sfariska karbider med 30 en cirkelekvivalent diameter av 0,2 pm eller mer observerade I matomr6det. Furthermore, it is also possible to feed the density of present spherical carbides with a circle equivalent diameter of 0.2 μm or more observed in the food area.

[0076]Metalstrukturhosfordragenstaltradfor hoghallfasthetsfjaderanvandning och dragen varmebehandlad stark 26 Metal strukturen hos dragen varmebehandlad staltrad for hoghallfasthetsfjaderanvandning, enligt fOreliggande uppfinning, innefattar volymsmatt Over 6 % till 15 % av restaustenit och en balans av anlOpt martensit. Fina inneslutningar ar tillatna. De "fina inneslutningarna" är oxider och sulfider. Oxiderna ar deoxidationsprodukter av Al och Si etc., varvid sulfiderna motsvara MnS, CaS, etc. The metal structure of the drawn high-strength spring application and drawn heat-treated strong 26 The metal structure of the drawn heat-treated steel line for high-strength spring use, according to the present invention, comprises volume mat Over 6% to 15% of residual austenite and a balance of anlOpt martensite. Fine inclusions are allowed. The "fine inclusions" are oxides and sulfides. The oxides are deoxidation products of Al and Si etc., the sulfides corresponding to MnS, CaS, etc.

Vidare innehaller jamvikten av den anlOpta martensitstrukturen ocksa oupplosta sfariska karbider i sma mangder. Furthermore, the balance of the annealed martensite structure also contains undissolved spherical carbides in small amounts.

[0077]Den tidigare austenit kornstorleken i strukturen ar #10 eller mer, varvid den cirkelekvivalenta diametern av de sfariska karbiderna ar mindre an 0,2 pm. The previous austenite grain size in the structure is # 10 or more, with the circle equivalent diameter of the spherical carbides being less than 0.2 μm.

Vidare utgor perlitstrukturen 90 % eller mer, fOretradesvis 95 % eller mer, mer foredraget 98 % eller mer, av metall strukturen hos fOrdragen staltrad, fOr hoghallfasthetsfjaderanvandning, enligt fOreliggande uppfinning. En signifikant 100 % perlitstruktur al ideal. Furthermore, the perlite structure constitutes 90% or more, preferably 95% or more, more preferably 98% or more, of the metal structure of the preferred steel row, for high strength spring use, according to the present invention. A significant 100% perlite structure is ideal.

[0078]Tidigare austenit kornstorleksnummer: #10 eller mer Strukturenhosdragenvarmebehandladstaltradfor hOghallfasthetsfiaderanvandning i den fOreliggande uppfinningen innefattas huvudsakligen av anlopt martensit. Tidigare austenit kornstorlek har stor effekt pa 20 egenskaperna. Det vill saga utmattningsegenskaperna och formbarheten forbattras till fOljd av trfining av den tidigare austenit kornstorleken som en effekt av kornstorleksminskning. I den fOreliggande uppfinningen ar den tidigare austenit kornstorleken gjord #10, for att uppna tillrackliga utmattningsegenskaper och form ba rhet. Previous austenite grain size number: # 10 or more The structure which has been heat treated for high strength fiber use in the present invention is comprised mainly of tempered martensite. Previous austenite grain size has a large effect on the 20 properties. That is, the fatigue properties and formability are improved due to the refinement of the previous austenite grain size as an effect of grain size reduction. In the present invention, the former austenite grain size is made # 10, in order to achieve sufficient fatigue properties and formability.

[0079]Forfining av tidigare austenit ar synnerligen effektivt for att frirbattra egenskapernahosdragenvarmebehandladstaltradfOr haghallfasthetsfjaderanvandning. Det tidigare austenit kornstorleksnumret ar fOretradesvis gjord #11, mer fOredraget #12. FOr att fOrfina kornstorleken av tidigare austenit, ar det effektivt att minska varmningstemperaturen vid slackning. Notera att "tidigare austenit kornstorleksnummer" ar baserat pa JIS G 0551. Om slackning utfors genom minskning av varmningstemperaturen och fOrkortning av tiden kan den tidigare austenit kornstorleken fOrfinas, men orimligt lag temperatur och kort behandlingstid Okar inte bara mangden oupplosta sfariska karbider, utan resulterar 27 ibland ocksa i otillrackllg austenit omvandling i sig och slackning I tv6 faser. Motsatt minskas ibland formbarheten och utmattningsegenskaperna. Av den anledningen ar vanligtvis #13,5 den ovre gransen. Refining of prior austenite is particularly effective in improving the properties of the heat treated steel for high strength spring use. The previous austenitic grain size number is preferably made # 11, more preferred # 12. To refine the grain size of previous austenite, it is effective to reduce the heating temperature during slackening. Note that "previous austenite grain size number" is based on JIS G 0551. If slackening is performed by reducing the heating temperature and shortening the time, the previous austenite grain size can be refined, but unreasonably low temperature and short treatment time not only increases the amount of undissolved spherical carbides, but results 27 sometimes also in unsatisfactory austenite transformation per se and slackening in tv6 phases. Conversely, the formability and fatigue properties are sometimes reduced. For that reason, # 13.5 is usually the upper limit.

[0080]Restaustenit: Over 6 % till 15 % (volymenhet) Mikrostrukturenhosdragenvarmebehandladstaltradfor hoghjIlfasthetsfjaderanvandning innefattar efter seghardning, anlopt martensit, restaustenit, och en liten volymsfraktion av inneslutningar (har är de beskrivna utfallningarna ocksj inkluderade i inneslutningarna). Restaustenit ar effektiv for att 10 forbattra kallindningsfOrmagan. Volymenheten av restaustenit ar gjord 6 %, faretradesvis 7 % eller mer, mer fOredraget 8 % eller mer, fOr att sakra kallindningsfOrmagan, I fOreliggande uppfinning. Residual austenite: Over 6% to 15% (unit by volume) The microstructure which is heat treated for high strength spring application includes after toughening, tempered martensite, residual austenite, and a small volume fraction of inclusions (the precipitates described are also included). Residual austenite is effective in improving cold winding capacity. The volume unit of residual austenite is made 6%, preferably 7% or more, more preferably 8% or more, to secure the cold winding capacity, in the present invention.

[0081]Daremot om restaustenit Overskrider volymsm5ftet 15 %, orsakar 15 martensit, vilken bildats till foljd av arbetsinducerad omvandling, aft kallindningsegenskaperna avtar. DarfOr är volymsmattet av restaustenit satt till 15 % eller mindre, fOretradesvis 14 % eller mindre, mer foredraget 12 % eller mindre. On the other hand, if residual austenite exceeds the volume content by 15%, martensite, which is formed as a result of work-induced conversion, causes the cold winding properties to decrease. Therefore, the volume mat of residual austenite is set at 15% or less, preferably 14% or less, more preferably 12% or less.

Volymsmattetavrestaustenitkanbestammasmed rontgendiffraktionsfOrfaranden och magnetiska matfOrlaranden. De magnetiska matfOrfarandena mOjliggor enkel matning av volymsmattet restaustenit, sá det Jr det foredragna matfOrlarandet. Har ar volymsm5ttet matt, men de erhallna uppgifterna ar de samma som mattet pa arean. The volume mat of the most austenitic can be determined by X-ray diffraction procedures and magnetic food explanations. The magnetic food methods allow easy feeding of the volume food residual austenite, so it is the preferred food method. The volume measurement is matt, but the data obtained are the same as the matt on the area.

[0082]Noter att restaustenit ar mjukare an anlOpt martensit, vilket minskar strackgransen. Vidare ar den omvandlingsinducerade plasticiteten anvand for att forbattra formbarheten, vilket bidrar anmarkningsvart till att fOrbattra kallformbarheten. Daremot kvarstar ofta restaustenit i de segregerade delarna, tidigare austenit korgranser, och omraden klamda av hangkornen, s6 att martensit vilken bildas genom arbetsinducerad fasomvandling (arbetsinducerad martensit) blir utOngspunkten for brott. Vidare, om restaustenit okar, avtar anlOpt martensit proportionellt. Note that residual austenite is softer than annealed martensite, which reduces the yield strength. Furthermore, the transformation-induced plasticity is used to improve the formability, which contributes remarkably to improve the cold formability. On the other hand, residual austenite often remains in the segregated parts, former austenite basket boundaries, and areas clamped by the hanging grains, so that martensite which is formed by work-induced phase transformation (work-induced martensite) becomes the starting point for crime. Furthermore, if residual austenite increases, anlOpt martensite decreases proportionally.

[0083]Av den anledningen har tidigare minskning i styrka och kallindningsfOrm6ga, till fOljd av restaustenit, betraktats som ett problem. Men i 28 hOghallfasthets staltradar pa Over 2000 MPa, blir mangden tillsatt C, Si, Mn, Cr, etc. storm vilket gor nyttjande av restaustenit extremt effektivt fOr att fOrbattra kallindningsfOrmagan. Vidare har fly hOg prestanda fjaderbearbetningsteknologi gjort det mOjligt att dampa fOrsamringen av formbarhetsegenskaperna aven om delar med hOg hardhet bildas lokalt pa grund av bildandet av bearbetningsinducerade martensit vid formning av fjadern. For this reason, previous decrease in strength and cold winding ability, due to residual austenite, has been considered a problem. But in 28 high-strength steel radar of over 2000 MPa, the amount is added C, Si, Mn, Cr, etc. storm which makes the use of residual austenite extremely effective to improve cold winding capacity. Furthermore, flight high performance spring machining technology has made it possible to vaporize the deterioration of the formability properties even if parts with high hardness are formed locally due to the formation of machining induced martensite in forming the spring.

[0084]Harnast kommer de mekaniska egenskaperna hos dragen varmebehandlad staltrad for hOghallfasthetsfjaderanvandning att fOrklaras. Most recently, the mechanical properties of the drawn heat-treated steel row for high-strength spring use will be explained.

FOr att minska storleken och fOr att Ora fjadern lattare är det effektivt att gora den mer hallfast. Vidare kravs att fjadern har Overlagsen utmattningshallfasthet. I den fOreliggande uppfinningen tillverkas h6ghallfasthetsfjader genom bOjning av materialet hos dragen varmebehandlad staltrad, for hOghallfasthetsfjaderanvandning, till Onskad form darefter nitreras, kulbombas, eller pa annat satt hardas ytan. Vid nitrering an fjadern varmd till 500 °C eller sa, vilket gor att fjadern ibland är mer uppmjukad an materialet hos dragen varmebehandlad staltrad, for hoghallfasthetsfjaderanvandning To reduce the size and to make the Ora spring lighter, it is effective to make it more hall-fixed. Furthermore, it is required that the spring has Overlagsen fatigue resistance. In the present invention, high-strength spring is manufactured by bending the material of the drawn heat-treated steel row, for high-strength spring application, to the desired shape, then nitriding, ball-bombing, or otherwise hardening the surface. When nitriding the spring heated to 500 ° C or so, which means that the spring is sometimes softer than the material of the drawn heat-treated stable row, for high-strength spring use

[0085]Darfor är det nOdvandigt att sakerstalla strackgransema for material hos dragen varmebehandlad trad, for hOghallfasthetsfjaderanyandning, for att Oka hallfastheten hos fjadern och forbattra utmattningsegenskaparna. Vidare kravs kallindningsfOrmaga fOr att dragen varmebehandlad staltrad, fOr h6ghallfasthetsfjaderanvandning, skall kunna bearbetas till Onskad form, sa den Ovre gransen for strackgransen maste begransas. Therefore, it is necessary to set the tensile limits for materials of the drawn heat-treated wire, for high-strength spring respiration, in order to increase the half-strength of the spring and improve the fatigue properties. Furthermore, cold-winding capacity is required in order for the drawn heat-treated steel row, for high-strength spring use, to be able to be processed into the desired shape, so the upper limit for the stretch limit must be limited.

[0086]Strackgrans: 2100 till 2400 MPa Om fOrdragen varmebehandlad staltrad, for hoghillfasthetsfjaderanvandning, hardad vid ytan genom nitrering etc., har stor strackgrans ar det mOjligt att fOrbattra utmattningsegenskaperna och eftergivningsegenskapen hos fjadern. I den 30 foreliggande uppfinningen är strackgransen hos dragen varmebehandlad staltrad fOr hoghallfasthetsfjaderanyandning gjord 2100 MPa eller mer, fOr att fOrbattra fjaderns utmattningsegenskaper och eftergivningsegenskap. Stretch limit: 2100 to 2400 MPa If the Preferred heat-treated stable line, for high-hill spring application, hardened at the surface by nitriding, etc., has a large tensile limit, it is possible to improve the fatigue properties and the resilience property of the spring. In the present invention, the tensile strength of the drawn heat-treated stable row for high-strength spring use is made 2100 MPa or more, to improve the fatigue properties and resilience properties of the spring.

Vidare desto stOrre strackgrans dragen varmebehandlad staltrad for hoghallfasthetsfjaderanvandning har, desto battre utmattningsegenskaper far fjadern, 29 sa dragen varmebehandlad staltrad for hoghallfasthetsfjaderanvandning har en strackgrans pa fOretradesvis 2200 MPa eller mer, mer fOredraget 2250 MPa eller mer. Furthermore, the larger the straight-line drawn heat-treated steel line for high-strength spring use has, the better the fatigue properties of the spring, 29 so the drawn heat-treated steel line for high-strength spring use has a straight line of preferably 2200 MPa or more, more for 2250 MPa or more.

[0087]Daremot orn dragen varmebehandlad staltrad fOr hOghallfasthetsfjaderanvandning har for stor strackgrans avtar kallindningsformagan sá strackgransen satts till 2400 MPa eller mindre. [0087] On the other hand, if the drawn heat-treated steel row for high-strength spring use has too large a stretch limit, the cold-winding shape decreases so that the stretch limit is set to 2400 MPa or less.

[0088]Strackgrans (am strackgrans inte kan observeras, pavisar 0,2 % provspanning): 1600 till 1980 MPa den fOreliggande uppfinningen betyder strackgransen eller strackpunkten av dragen varmebehandlad staltrad, fOr hOghallfasthetsfjaderanvandning, den hogsta strackgransen nar en strackpunkt ses pa spanningsitOjningskurvan i ett en-axligt draghallfasthetstest och 0,2 % pavisar spanning nar ingen strackpunkt syns. FOr att sakra styrkan och eftergivningsmotstandet hos fjadern, vilken elastiskt deformeras genom upprepad spanning, ar Okad strackgrans att fOredra. FOr att Oka strackgransen hos fjadern ar det att fOredra att Oka strackgransen hos materialet det vill saga dragen varmebehandlad staltrad, fOr hOghallfasthetsfjaderanvandning. Strain boundary (if tensile strength cannot be observed, indicates 0.2% test stress): 1600 to 1980 MPa the present invention means the tensile strength or tensile point of drawn heat-treated steel line, For high-strength spring use, the highest tensile strength when a tensile point is seen on the stress curve -axial tensile strength test and 0.2% shows tension when no tensile point is visible. In order to ensure the strength and resilience of the spring, which is elastically deformed by repeated tensioning, increased tensile strength is preferred. In order to increase the yield strength of the spring, it is preferable to increase the yield strength of the material that is to say drawn heat-treated steel row, for high-strength spring use.

[0089]Daremot, am dragen varmebehandlad staltrad fOr hOghallfasthetsljaderanvandning far stor strack grans blir kallindningsformagan ibland kirsamrad. DarfOr har dragen varmebehandlad staltrad for hOghallfasthetsfjaderanvandning foretradesvis en strackgrans pa 1600 MPa eller mer, for att sakra fjaderns styrka och eftergivningsegenskap. [0089] On the other hand, with the drawn heat-treated steel line for high-strength ladder use, there is a great deal of scrutiny, and the cold-winding shape is sometimes cherry-picked. For this purpose, the heat-treated steel line for high-strength spring use preferably has a tensile strength of 1600 MPa or more, in order to ensure the strength and resilience of the spring.

[0090]For att ge ytterligare hOgre hallbarhet ar 1700 MPa eller mer att fOredra. To provide further higher durability, 1700 MPa or more is preferable.

Daremot om strackgransen Overskrider 1980 MPa, ar kallindningsformagan ibland forsamrad sa strackgransen ar fOretradesvis satt till 1980 MPa eller mindre. Notera att det ar att fOredra att minska volymsmattet av restaustenit for att Oka 30 strackgransen hos materialet med samrna strackgrans direkt efter snabb seghardningavdragenvarmebehandladstaltradfOr hOghallfasthetsfjaderanvandning. On the other hand, if the yield strength exceeds 1980 MPa, the cold winding capacity is sometimes reduced, so the yield strength is preferably set at 1980 MPa or less. Note that it is preferable to reduce the volume mat of residual austenite in order to increase the yield strength of the material by combining the yield strength directly after rapid toughening of the heat-treated treatment plant for high-strength spring application.

[0091]Vickers hardhet efter nitrering genom bibehallning vid 500 °C i 1 timme: Ytskiktshardhet HV?.750, innerhardhet HVa570 En hOghallfasthetsfjader fOrbattras i ytskiktshdrdhet vid nitrering, varvid insidan uppmjukas. Till exempel vid iatt gasnitrering vid 500 °C var det svart att 5 dampa uppmjukning av insidan av dragen varmebehandlad staltrad, fOr hOghallfasthetsfjaderanvandning, cm den konventionella varmningstemperaturen blir 500 'C. Dragen varmebehandlad staltrad fOr hOghallfasthetsfjaderanvandning, i den fOreliggande uppfinningen, har utmarkt motstand mot varmerelaterad avmjukning och mOjliggOrsakerstallandeavfjadernsutmattningsegenskaperoch 10 eftergivningsegenskapen efter varmning vid 500 °C. Vickers hardness after nitration by maintaining at 500 ° C for 1 hour: Surface hardness HV? .750, inner hardness HVa570 A high-strength spring is improved in surface layer hardness during nitration, whereby the inside is softened. For example, in the case of gas nitriding at 500 ° C, it was black to evaporate the softening of the inside of the drawn heat-treated steel row, for high-strength spring application, when the conventional heating temperature becomes 500 ° C. The drawn heat-treated stable line for high-strength spring use, in the present invention, has excellent resistance to heat-related softening and enables the cause of the spring fatigue properties and the resilience property after heating at 500 ° C.

I den fOreliggande uppfinningen ar ytskiktshardheten och den innerhardheten efter mjuk gasnitrering definierad. In the present invention, the surface hardness and the inner hardness after soft gas nitriding are defined.

[0092]Ytskiktshardheten satts till mikro Vickershdrdheten vid ett djup av 50 till 100 pm fran ytskiktet med Vickershardheten 750 eller mer. Om Vickershardheten ar 750 eller mer, blir ytskiktshardheten otillracklig och utmattningshallbarhet blir dessutom forsamrad, vilket gor att kvarvarande spanning efter kulbombningen inte minskas tillrackligt. FOretradesvis är ytskiktshardheten 780 eller mer. The surface layer hardness is added to the micro Vickers hardness at a depth of 50 to 100 μm from the surface layer with the Vickers hardness 750 or more. If the Vickers hardness is 750 or more, the surface layer hardness becomes insufficient and fatigue durability is also impaired, which means that the residual stress after the ball bombing is not sufficiently reduced. Preferably, the surface layer hardness is 780 or more.

[0093]Daremot mats innerhardhet Vickershardheten ibland vid slackning, nar temperaturen vid ytskiktet pa staltraden ar hOgre an inuti, vilket gor att matning av den innerhardheten foretradesvis Ors vid en position av 500 m djup fran ytan. For aft sakerstalla eftergivningshallfasthetsegenskaperna och eftergivningsegenskapen, skall Vickershardheten efter varmebehandling bibehallande traden vid 500 °C 1 1 timme vara 570 eller mer. Vidare, ar 575 eller mer fOredraget. On the other hand, the inner hardness is sometimes measured. The Vickers hardness is sometimes measured during slackening, when the temperature at the surface layer of the steel row is higher than inside, which means that feeding of the inner hardness is preferably Ors at a position 500 m deep from the surface. In order to ensure the yield strength and yield properties, the Vickers hardness after heat treatment maintaining the range at 500 ° C for 1 hour shall be 570 or more. Furthermore, 575 or more are the Lecture.

Notera aft, den ovre gransen for Vickershardheten efter bibehallning vid 500 °C 1 1 timme for varmebehandling ar inte sarskilt definierat, men for aft fOrsakra aft Vickershardheten fore varmebehandling inte Overskrids, satts den vanligtvis till 783 eller mindre. Note that the upper limit of Vickers hardness after maintenance at 500 ° C for 1 hour for heat treatment is not specifically defined, but for causes of Vickers hardness before heat treatment not being exceeded, it is usually set to 783 or less.

[0094]Vidare ar ytskiktet hos dragen varmebehandlad staltrad fer hoghallfasthetsfjaderanvandningsomanvandssommaterialfor heighdlifasthetsfjadrar, hardat med kulbombning, nitrering, etc. Daremot ar Vickershardheten vid en position av 500 pm djup fran ytan av hOghallfasthetsfjadern 31 (innerhardhet) paverkad av varmning vid nitrering. Darr& kommer den innerhardheten att variera beroende p6 nitrerings temperatur vid verklig produktion av en fjader. Furthermore, the surface layer of the drawn heat-treated steel row for high-strength spring use is used as material for high-strength springs, hardened by ball bombardment, nitriding, etc. The inner hardness will vary depending on the nitriding temperature during actual production of a spring.

[0095]Notera att nar dragen varmebehandlad staltrad fOr hOgh511fasthetsfjaderanvandning, i den treliggande uppfinningen, anvands som ett material for produktion av hOghallfasthetsfjader, är den kallindad och nitrerad. Av den anledningen, avtar restaustenit nAgot, vid ett djup av 500 pm fran ytan av hoghallfasthetsfjadern, jamfort med materialet for dragen varmebehandlad staitrad fOr hog hallfasthetsfjaderanvandning. Note that when drawn heat-treated stable wire for high-strength spring use, in the three-pronged invention, is used as a material for producing high-strength spring, it is cold-wound and nitrided. For this reason, residual austenite decreases somewhat, at a depth of 500 μm from the surface of the high-strength spring, compared with the material for the drawn heat-treated steel for high-strength spring use.

Men den kemiska sammansattningen sfariska karbider och tidigare austenit kristallkornstorlek trutsatts vara lite paverkad av kallindning och nitrering. Dartr är den kemiska sammansattningen sfariska karbider och tidigare austenit kristallkornstorlek hos hogh611fasthets stal, tillverkad anvandande dragen 15 varmebehandlad staltrad for hOghallfasthetsfjaderanvandning, i den framlagda uppfinningen, som eft material är samma kemiska komposition, sfariska karbider, och tidigare austenit kristall kornstorlek av dragen varmebehandlad staltrad fOr hoghallfasthetsfjaderanvandning, i treliggande uppfinning. However, the chemical composition of spherical carbides and former austenite crystal grain size has been found to be slightly affected by cold winding and nitriding. There, the chemical composition is spherical carbides and former austenite crystal grain size of high strength steel, made using drawn heat treated steel row for high strength spring use, in the present invention, which by material is the same chemical composition, spherical austenite carbide crystalline, high-strength spring use, in a three-pronged invention.

[0096]Harnast kommer trfarandet for produktion av dragen varmebehandlad staltrtel for hOghAllfasthetsfjaderanvandning, treliggande uppfinning, att forklaras. En stalgOt anpassad enligt trutbestamd kemisk sammansattning valsas for att producera eft st6Ivalsamne av minskad storlek. Vidare varms valsamnet upp varefter det varmvalsas for all erhalla fordragen staltrad fOr 25 hOgh61Ifasthetsfjaderanvandning. Den fOrdragna st6ltraden for hOghallfasthetsfjaderanvandning patenteras, formas och dessutom glifidges den for att gore den hArda ytan mjuk. Darefter dras, slacks och antps staltraden far att producera dragen varmebehandlad staltrad fOr hOghallfasthetsfiaderanvandning. "Patenteringere innebar varmebehandling fOr att Ora strukturen av stAlet efter varmvalsning ferrit och perlit och Ors for mjukning av staltraden fore dragning. Efter dragning genomfors antpning i olja, induktionshardningsbehandling, och seghardning for att justera staltradens struktur och egenskaper. 32 Most recently, the process for producing the drawn heat-treated steel frame for high-strength spring application, the present invention, will be explained. A steel grade adapted according to the chemical composition of the trout is rolled to produce a steel roll of reduced size. Furthermore, the roll assembly is heated, after which it is hot-rolled for all obtained contracts designed for 25 high-strength spring application. The preferred steel wire for high strength spring application is patented, shaped and also slipped to make the hard surface soft. Thereafter, the draft line is drawn, slacks and antps to produce the drawn heat-treated steel line for high-strength fiader application. "Patenting involved heat treatment to lubricate the structure of the steel after hot rolling ferrite and perlite and ors for softening the steel wire pre-coating. After drawing, antifouling in oil, induction hardening treatment, and toughening are carried out to adjust the steel wire structure and properties. 32

[0097]FOrfarandet kir aft fOrhindra forgrovning av sfAriska karbider är viktigt vid produktion av fordragen staltrad for hoghallfasthetsfjaderanvandning, i den fOreliggande uppfinningen. The method of preventing spheronization of spherical carbides is important in the production of the preferred designs for high strength spring use in the present invention.

[0098]I synnerhet nar innehallet av C och Cr Ai- Mgt, i den foreliggande uppfinningen, är det extremt viktigt att varma geten eller valsamnet tillrAckligt fore valsning i det stadiet och ferenkla utfallning inne i stalet och aft upplOsa de interna grova karbiderna (legeringskarbider och cementiter) och Ora materialet homogent. For att fOrhindra bildandet av grova karbider, maste grova karbider vilka bildas gOten eller valsamnet, upplosas i st8let. Vidare, ar det nOcIvAndigt att skapa uniform spridning stalet. Av den anledningen Ar Cikad varmningstemperatur att fOredra. In particular, when the content of C and Cr Ai-Mgt, in the present invention, it is extremely important to heat the goat or rolling stock sufficiently for pre-rolling at that stage and to simplify precipitation inside the steel and to dissolve the internal coarse carbides (alloy carbides). and cementites) and the Ora material is homogeneous. In order to prevent the formation of coarse carbides, coarse carbides which are formed by the goth or whey must be dissolved in the steel. Furthermore, it is nOcIvAndigt to create uniform spreading steel. For this reason, Cikad heating temperature is preferred.

[0099]Darr& Ar gOten eller valsamnet gjord foist efter gjutning vid en varmningstemperatur av 1250 'C eller mer. Till fOljd av det är det mOjligt att Ora de 15 oupplosta sfariska karbiderna tillrackligt upplOsta. Av den anledningen, varmningstemperaturen och varmningstiden otillrAcklig vid vArmningen efter efterfOljande valsning, patentering och slAckning, s8 oupplOsta sfAriska karbider kvarstar iatt, men for att mojliggeira tillrAcklig upplOsning fran borjan, kan dimensionerna hos de oupplOsta sfariska karbiderna styras till mindre An 0,2 pm. 20 GOtens varmningstemperatur skall vara 1270 °C eller mer. [0099] Darr & Ar gOten or the roll made foist after casting at a heating temperature of 1250 ° C or more. As a result, it is possible to dissolve the 15 undissolved spherical carbides sufficiently. For this reason, the heating temperature and the heating time are insufficient during the heating after subsequent rolling, patenting and quenching, so undissolved spherical carbides remain overnight, but in order to allow sufficient dissolution from the beginning, the dimensions of the vessels may be insoluble. The heating temperature of the GO should be 1270 ° C or more.

[0100]Darefter Ar valsAmnet, vilket tillverkats genom valsning av gOten, vidare varmvalsat (valstrAd är valsad) for att tillverka fordragen stAltr 'Ad for hOghallfasthetsfjaderanvAndning. Vid denna tid Ar varmningstemperaturen av valsamnet satt till 1200 °C eller mer. FOretradesvis ska varmningstemperaturen av valsAmnet sattas till 1250 °C eller mer. Thereafter, the roll blank, which has been manufactured by rolling the cast iron, is further hot-rolled (the roll is rolled) to make the preferred steel for high-strength spring use. At this time, the heating temperature of the roll is set to 1200 ° C or more. Preferably, the heating temperature of the roll blank should be set to 1250 ° C or more.

Efter stAlet utvunnits fran varmningsugnen, sjunker temperaturen och utfallningar tilltar. Av den anledningen är det att fOredra att varmvalsning avslutas inom 5 minuter, efter det at stAlet utvunnits fran varmningsugnen. Genom ovan 30 varmning av got och valsAmne, Ai- de grova karbiderna i stalet homogent spridna och upplasta och karbiderna kan uniformt fint fallas ut vid den senare utfallningen. After the steel has been extracted from the heating furnace, the temperature drops and precipitation increases. For this reason, it is preferable that hot rolling be completed within 5 minutes, after the steel has been extracted from the heating furnace. By heating the casting and rolling stock above, the coarse carbides in the steel are homogeneously spread and loaded and the carbides can be precipitated out uniformly in the latter precipitation.

Notera att vid valsning av goten till staltrad, utan att fOrst Ora ett valsamne, skall varmningstemperaturen fore valsning av gOten sAttas till 1250 °C eller mer; foretradesvis 1270 °C eller mer. 33 Note that when rolling the gutter into a stable row, without first making a rolling stock, the heating temperature before rolling the goth must be set to 1250 ° C or more; preferably 1270 ° C or more. 33

[0101]I ovanstaende forfarande ar det nOdvandigt att Ora storleken mindre fOr att undvika fOrgrovning for att dampa fOrgrovning av oupplOsta sfariska karbider has staltraden efter varmebehandling aven am de oupplosta sfariska karbiderna, vilka ar narvarande fore dragning Wet vill saga, efter vaistrads valsning), reduceras kraftigt eller am till exempel oupplOsta karbider ar narvarande. In the above procedure, it is necessary to reduce the size in order to avoid coarseness in order to vapor coagulation of undissolved spherical carbides has the stable line after heat treatment of the undissolved spherical carbides, which are presently preferred Wet will say, after vaistra greatly reduced or if, for example, undissolved carbides are present.

DariOr ar det viktigt att Ora gotvarmningstemperaturen och valsamnesvarmningstemperaturen tillrackligt hog i valsningssteget far varmning fore dragning for att upplOsa karbider. Till fOljd av det kan storleken pa de sfariska karbiderna hallas liten. Valsningen av fjaderstal till en storlek av materialet fore dragning am cirka 4) 10 mm, slutfOrs flera minuter efter utvinning av valsamnet fran varmningsugnen. Av den anledningen, ar det viktigt att varma till 1200 °C eller mer nar effekten av valsamnets varmningstemperatur ar stor. Varmning till 1250 °C eller mer ar att foredra. Varmning till 1270 °C eller mer ar mer fOredraget. Therefore, it is important that the well warming temperature and the rolling stock heating temperature be sufficiently high in the rolling step to obtain a heating preference to dissolve carbides. As a result, the size of the spherical carbides can be kept small. The rolling of spring figures to a size of the material preference of about 4) 10 mm, is completed several minutes after extraction of the roll stock from the heating furnace. For this reason, it is important to heat to 1200 ° C or more when the effect of the rolling stock's heating temperature is large. Heating to 1250 ° C or more is preferred. Heating to 1270 ° C or more is more preferred.

[0102]Efter valsning tags trad upp i en spole och luftkyls enligt konventionellt fOrfarande. Av denna anledning innefattar vanligtvis mikrostrukturen av fordragen staltrad (staltrad efter valsning av valstrad), ferrit och perlit eller perlit med en hog perlitstruktur fraktion, eftersom mangden C ar hog. OupplOsta sfariska karbider ar narvarande i grundmaterialet. After rolling tags appeared in a spool and air cooler according to conventional method. For this reason, the microstructure of the preferred staltra (staltra after rolling of rolling) usually comprises ferrite and perlite or perlite with a high perlite structure fraction, since the amount C is high. Undissolved spherical carbides are present in the base material.

[0103]Oupplesta sfariska karbider kan observeras genom att ett polerat och etsat detektionsprov observeras med SEM. OupplOsta karbider kan klart sarskiljdas fran laminarcementit innesluten I perlitstrukturen has grundmaterialet eftersom de ar sfariska. Naturligtvis kan storleken ocksa matas. Unread spherical carbides can be observed by observing a polished and etched detection sample by SEM. Undissolved carbides can be clearly distinguished from laminar cementite contained in the perlite structure because the base material is spherical. Of course, the size can also be fed.

Pa grund av ovan namnda steg ar fordragen staltrad fOr fjaderanvandning (valsad valstrad) observerad. Due to the steps mentioned above, the treaties designed for spring use (rolled rolled) are observed.

[0104]Efter varmvalsning patenteras fOrdragen staltrad for fjaderanvandning. After hot rolling, the preferred steel row is patented for spring use.

Varmningstemperaturen vid patenteringen kan sattas till 900 °C eller mer fOr att underlatta upplesning av karbider. En hogre temperatur av 930 °C eller mer är att fOredra. Vidare ar 900 eller mer att foredra. Darefter kan traden patenteras vid 600 °C eller mindre. I fordragen staltrad for fjaderanvandning, i enlighet med foreliggande uppfinning, ar fOrfarandena for patentering och dragning inte begransade. Om 34 konventionell patentering och dragningsforfarande for staltrad, kan samma behandling som vanligt utforas. The heating temperature during patenting can be set to 900 ° C or more to facilitate carbide reading. A higher temperature of 930 ° C or more is preferred. Furthermore, 900 or more are preferred. The trade can then be patented at 600 ° C or less. In the treaties established for spring use, in accordance with the present invention, the procedures for patenting and drawing are not limited. If 34 conventional patenting and drawing process for staltrad, the same treatment as usual can be performed.

Nar dragning av tad diametern och fordrad precision utesluts, kan patenteringssteget fc5re dragning uteslutas. I detta fall kan upplOsning av de 5 oupplOsta sfariska karbiderna framjas genom att varmningstemperaturen, i den senare fOrklarade slackning, Ors hog (till exempel, 970 °C eller mer). When drawing the tad diameter and required precision are excluded, the patenting step prior to drawing can be excluded. In this case, dissolution of the undissolved spherical carbides can be promoted by the heating temperature, in the later explained slacking, Ors hog (for example, 970 ° C or more).

[0105]Slackningen efter dragning utfOrs genom varmning till en temperatur av A3 punkten eller mer. For att framja upplOsning av karbider, ar det att fbredra att Oka 10 varmningstemperatumn vid slackningen. Vid slackningen satts varmningstakten tretradesvis till 10 °C/ sek eller mer och bibehallningstiden vid temperaturen fOr A3- punketen eller mer ar fOretradesvis till 1 min till 5 min, for att dampa tillvaxten av karbider. For att dampa korntillvaxt av austenit, ar det att fOredra att forkorta bibehallningstiden. For att framja slackningen och martensit transformation Ors kylningstakten fOretradesvis 50 °C/sek till 100 C. The slackening after drawing is carried out by heating to a temperature of A3 point or more. To promote the dissolution of carbides, it is advisable to increase the heating temperature at slackening. Upon slackening, the heating rate was set three times to 10 ° C / sec or more and the retention time at the temperature of the A3 point or more is preferably to 1 min to 5 min, to vaporize the growth of carbides. In order to dampen the grain growth of austenite, it is advisable to shorten the retention time. To promote slackening and martensite transformation, the cooling rate should preferably be 50 ° C / sec to 100 ° C.

[0106]Kylmedlet vid slackningsforfarandet satts fOretradesvis till 100 °C eller mindre, mer fOredraget en lag temperatur om 80 °C eller mindre, fOr att exakt styra mangden restaustenit. Ors kylvatsketemperaturen 40 °C eller mer i den foreliggande 20 uppfinningen. Valet av kylmedel ar inte sarskilt begransat sa lange som det ar en olja, eft vattenlOsligt slackningsmedel eller annat kylmedel som framjar slackning. Vidare kan kyltiden kortas pa samma satt som vid antOpning i olja och induktionshardningsbehandling. Det är att foredra att undvika fOrlangd bibehallningstid vid lag temperatur for att kraftig minska restaustenit och sanka kylmedelstemperaturen till 30 °C eller mindre. Det vill saga det är att foredra att slackningen avslutas inom 5 minuter. The refrigerant in the quenching process is preferably set to 100 ° C or less, more preferably a low temperature of 80 ° C or less, to accurately control the amount of residual austenite. The coolant temperature is 40 ° C or more in the present invention. The choice of coolant is not particularly limited as long as it is an oil, after water-soluble quencher or other coolant that promotes quenching. Furthermore, the cooling time can be shortened in the same way as for oil opening and induction hardening treatment. It is preferable to avoid prolonged retention time at low temperature to greatly reduce residual austenite and lower the refrigerant temperature to 30 ° C or less. That is to say, it is preferable that the slacking is completed within 5 minutes.

[0107]Efter slackning utfOrs anlopning. Anboning undertrycker tillvaxten av karbider, sá det ar att feredra att varmningstakten ar 10 °C/sek eller mer och att bibehallningstiden Jr 15 minuter eller mindre. Bibehallningstemperaturen varierar pa grund av den kemiska sammansattningen och malet fOr hallfastheten, men materialet ar vanligtvis bibehallet vid 400 till 500 'C. [0107] After slackening, tempering is performed. Fertilization suppresses the growth of carbides, so it is preferable that the heating rate is 10 ° C / sec or more and that the retention time is 15 minutes or less. The retention temperature varies due to the chemical composition and the target for the half strength, but the material is usually maintained at 400 to 500 ° C.

[0108]Fordragen staltrad for hOghallfasthetsfjaderanvandning ar kallindad fOr att bearbetas till onskade fjaderform, befriad fran spanning och nitrerad och kulbombning fOr att tillverka fjadern. The designs designed for high strength spring use are cold wound to be processed into the desired spring shape, freed from stress and nitrided and ball bombing to manufacture the spring.

[0109]Den kallindade staltraden ateruppvarms genom spanningsavlastande glocigning, nitrering, etc. Vid denna tidpunkt är insidan uppmjukad vilket medfOr att prestandan hos fjadem avtar. I synnerhet i fOreliggande uppfinningen ar tillracklig hardhet bevarad aven om nitrering utfOrs vid en hog temperatur av omkring 500 'C. Som ett resultat ar det mbjligt att Ora mikro Vickershardheten vid ett djup av 500 pm fan ytskiktet av hoghallfasthetsfjadrar HV575 eller mer, for fOrdragen staltrad fOr hOghallfasthetsfjaderanvandning. Notera att mikro Vickeshardheten mats vid ett djup av 500 pm fran ytskiktet av fjadem fOr att utvardera Vickershardhet hos grundmaterialet som inte paverkats av nitrering och kulbombning vid hardning. 15 Exempel The cold-wound steel row is reheated by stress-relieving glocigning, nitriding, etc. At this time, the inside is softened, which means that the performance of the spring decreases. In particular, in the present invention, sufficient hardness is preserved even if nitration is carried out at a high temperature of about 500 ° C. As a result, it is possible to increase the micro Vickers hardness at a depth of 500 microns from the surface layer of high-strength springs HV575 or more, for the designs designed for high-strength spring application. Note that the micro Vickers hardness is fed at a depth of 500 μm from the surface layer of spring to evaluate Vickers hardness of the base material which is not affected by nitriding and ball bombing during curing. Example

[0110]Stal med den kemiska sammansattningen som visas i tabell 1-1 till 1-4 smarts i en 10 kg vakuumsmaltugn och gjuts fOr att erhalla got eller valsamne. Dessa vakuum smalta material varmpressades upp till 08 mm. Darefter varmdes materialen som ar varmpressande upp till 8 mm, vid 1270 "Cx4 timmar. Vidare forfinas en del av provet i en 250 ton omvandlare, kontinuerligt gjutna fOr att fOrbereda goten, sedan varmda vid 1270 °Cx4 timmar eller mer, sedan gjord till valsamnen med tvarsnitt 160mmx160 mm. Vidare valsas dessa for att erhalla 1)8 mm valsad valstrad. Varmningstemperaturen av valsamnet fore valsning sattes till 1200 °C eller mer. 25 [0111]En diameter av 8 mm av fOrdragen staltrad (valsad valstrad) Ors foretradesvis till en enkelt dragen struktur genom patentering fare dragning. Varmningstemperaturen vid patentering ar fOretradesvis 900 °C eller mer sa tillracklig upplrisning av karbider etc. astadkoms. Patentering utfors genom varmning vid 930 °C darefter matas provet in i en strommande badd vid 600 °C. Efter patentering ar staltraden dragen far att erhalla en 4 mm diameter dragen valstrad. Pa detta saft genom varmning av griten vid hOr temperatur varefter temperaturen i valsningsfOrfarande, patentering, och slackning Ors sá hog som mOjligt ar det mojligt att dampa tillvaxt av oupplrista sfariska karbider och halla dimensionerna nere till 0,2 pm eller mindre. 36 Steel with the chemical composition shown in Tables 1-1 to 1-4 is smeared in a 10 kg vacuum malting furnace and cast to obtain a cast or roll blank. These vacuum narrow materials were hot pressed up to 08 mm. Thereafter, the materials which are hot pressed up to 8 mm were heated at 1270 ° Cx4 hours. Furthermore, a portion of the sample is refined in a 250 ton converter, continuously cast to prepare the cast, then heated at 1270 ° Cx4 hours or more, then made into roll rolls. with a cross-section of 160 mmx160 mm. These are further rolled to obtain 1) 8 mm of rolled wire. The heating temperature of the roll blank for rolling was set to 1200 ° C or more. [0111] A diameter of 8 mm of the preferred steel wire (rolled wire) is preferably The heating temperature at patenting is preferably 900 ° C or more so sufficient raising of carbides etc. is achieved.Patenting is performed by heating at 930 ° C then the sample is fed into a flowing bath at 600 ° C. patenting, the steel wire drawn is allowed to obtain a 4 mm diameter drawn wire rod, on this juice by heating the grit at a high temperature after which the temperature in the rolling process e, patenting, and slackening As high as possible, it is possible to vaporize the growth of undisturbed spherical carbides and keep the dimensions down to 0.2 μm or less. 36

[0112]FOr att anpassa strackgransen hos den patenterade och dragna staltraden, seghardas staltraden fOr att tillverka fordragen staltrad for fjaderanvandning. Notera att det prov som brast under dragning inte var seghardat. 5 Seghardning gjordes genom varmning av dragen staltrad vid en varmningstakt av 10 °C/sek eller mer vid 950 'C eller 1100 °C (temperatur vid A3 punkt eller mer), bibehallning vid varmningstemperaturens topp under 4 minuter till 5 minuter, sedan placeras stalet i en rumstempererad vattentank sa att kylningstakten blir 50 'Ci sek eller mer och nedkylningen Ors till 100 °C eller mindre. In order to adapt the stretch limit of the patented and drawn staltraden, the staltraden is hardened to manufacture the preferred staltrad for spring use. Note that the sample that broke during drawing was not toughened. Tough curing was done by heating the drawn stable at a heating rate of 10 ° C / sec or more at 950 ° C or 1100 ° C (temperature at A3 point or more), maintaining at the top of the heating temperature for 4 minutes to 5 minutes, then placing the steel in a room temperature water tank said that the cooling rate will be 50 ° C in sec or more and the cooling Ors to 100 ° C or less.

[0113]Resultaten av utvarderingen visar tillstandet av tradbrott, tidigare austenit kornstorleksnummer, restaustenitmangd (vol%), cirkelekvivalentdiameter och densitet av narvaro av karbider, strackgrans, provspanning 0,2 %, sparbOjningsvinkel, medelutmatningsstyrkan, Vickershardheten efter varsam 15 gasnitrering. The results of the evaluation show the state of wire breakage, previous austenite grain size number, residual austenite quantity (vol%), circle equivalent diameter and density of carbide presence, yield strength, sample stress 0.2%, saving bending angle, average discharge strength, Vickers hardness strength.

Malvardena som skulle uppnas sattes enligt foljande med hanvisning till konventionell staltrad for hOghallfasthetsfjaderanvandning. The malvardena to be achieved were set as follows with male reference to conventional stable line for high strength spring application.

Tidigare austenit kornstorleksnummer: 10 grader eller mer Mangd restaustenit (vol %): 20 % eller mindre Cirkel ekvivalent diameter av sfariska karbider 0,2 pm eller mindre Strackgrans: 2100 MPa eller mer 0,2 % provspanning 1800 MPa eller mer UtbytesfOrhallande: 75 % till 95 % Sparets bOjningsvinkel: 28 grader eller mer Genomsnittlig utmattningshallfasthet (Nakamura typ av roterande bojningshallfasthet): 900 MPa eller mer Internhardhet via Vickershardhet efter gasnitrering: 590 HV eller mer Nitrerad skikthardhet via Vickershardhet efter 30 gasnitrering: 750 HV eller mer Notera att bade styrka och bearbetningsfOrmaga (lindningsfOrmaga) maste uppnas i staltraden, enligt foreliggande uppfinning, for om utbytesfarhallandet är alltfOr hog, fOrsamras bearbetningsfOrmagan. Darr& är den Owe gransen for utbytesfOrhallandet fOretradesvis 90 %, mer att foredraget 88 % eller mindre. 37 Previous austenite grain size number: 10 degrees or more Amount of residual austenite (vol%): 20% or less Circle equivalent diameter of spherical carbides 0.2 μm or less Straightening: 2100 MPa or more 0.2% test stress 1800 MPa or more Yield ratio: 75% to 95% Spare bending angle: 28 degrees or more Average fatigue strength (Nakamura type of rotary bending strength): 900 MPa or more Internal hardness via Vickers hardness after gas nitriding: 590 HV or more Nitrated layer hardness via Vickers hardness after 30 gas nitriding After 30 gas nitriding: 750 HV or more and machining capacity (winding capacity) must be obtained in the stable line, according to the present invention, because if the exchange ratio is too high, the processing capacity is compromised. Therefore, the Owe limit for the exchange ratio is preferably 90%, more that the lecture 88% or less. 37

[0114]Ett prov taget fran den erhallna dragna varmebehandlade staltraden fOr fiaderanvandning, utvarderad far tidigare austenit kornstorlek, volymsandel av restaustenit, och karbider, darefter utsaft provet for eft dragprov, bajningsprov av 5 sparet, och mikro Vickers hardhetsprov. Notera att utmattningsegenskaperna utvarderades genom simulerande behandling och produktion av fjadern (nedan, refererad till som "fiaderproduktion och behandling") innefattande gasnitrering, simulerande nitrering utfard pa en fjader efter bearbetning (500 °C, 60 minuter), kulbombning (diameter av skuren tad 0,6 mm, 20 minuter), och avstressningsbehandling vid lang temperatur (180 00, 20 minuter). A sample taken from the obtained heat-treated steel-treated steel row for fiader use, evaluated for previous austenite grain size, volume fraction of residual austenite, and carbides, then the sample for tensile test, bending test of the spar, and micro Vickers hardness test. Note that the fatigue properties were evaluated by simulating treatment and production of the spring (hereinafter, referred to as "feather production and treatment") including gas nitriding, simulating nitriding on a spring after processing (500 ° C, 60 minutes), ball bombing (diameter of cut tad 0 , 6 mm, 20 minutes), and long-term de-stressing treatment (180 00, 20 minutes).

[0115]Tidigare austenit kornstorleksnummer uppmattes baserade pa JIS G 0551. Karbidernas cirkelekvivalenta diameter och densitet mattes genom att ett elektroniskt etsat prov anvands for att erhalla en SEM strukturellavbildning, och 15 genom att bilden analyseras. Vidare mats volymsmattet av restaustenit med det magnetiska matfOrfarandet. Previous austenite grain size numbers were measured based on JIS G 0551. The circle equivalent density and density of the carbides were measured by using an electronically etched sample to obtain a SEM structural image, and by analyzing the image. Furthermore, the volume mat of residual austenite is fed by the magnetic feeding method.

[0116] Utmattningsprovet ar ett Nakamura typ av roterande bajningsutmattningsprov (utmattningsprov bojning genom tva-punkter skids vikt och svarvning av motorn aft tillampa tryck- och dragspanning till ytan av traden). Den hagsta belastningskraften sattes till den genomsniftliga utmattningshallfastheten far 10 prover, uppvisande en livslangd av 7 cykler eller mer med en sannolikhet av 50 % eller mer. Bajningsprovet vid sparet är ett test for att utvardera kallindningsformagan och utfOrs enligt fOljande. The fatigue test is a Nakamura type of rotary bending fatigue test (fatigue test bending through two-point skid weight and turning the motor to apply compressive and tensile stress to the surface of the wire). The maximum loading force was added to the average fatigue strength for 10 samples, having a life of 7 cycles or more with a probability of 50% or more. The bending test at the spar is a test for evaluating the cold winding shape and is performed as follows.

[0117]En stans 2 med en vinkel av spetsen som visas i figur 2 pa 10 anvandes for att astadkomma ett spar (hack) av eft maximalt djup av 30 pm i ett provstycke. Notera aft som visas i figur 3 astadkommes sparet 4 vid en ratvinkel i farhallande till langsgaende riktingen i mitten av provstycket 3 i den langsgaende riktningen. Darefter som visas i figur 4 fran den motsatta sidan av hacket 4, anvandes en stans 5 far att applicera en last P av en hOgsta draghallfasthetsspanning genom an lastanvandningsanordning 6 och provstycket deformerades genom trepunktsbOjning. Notera att krakningsradien r av spetsen av 38 lastanyandningsanordning 6 gjordes 4,0 mm, varvid skillnaden L mellan forstarkningar gjordes L.--.2r-F3D. Dar D ar diametern pa provstycket. A punch 2 with an angle of the tip shown in Figure 2 on 10 was used to provide a notch (notch) of a maximum depth of 30 μm in a specimen. Note that as shown in Figure 3, the notch 4 is provided at a steering angle in the longitudinal to longitudinal direction in the middle of the test piece 3 in the longitudinal direction. Then, as shown in Fig. 4 from the opposite side of the notch 4, a punch 5 was used to apply a load P of a highest tensile strength stress through a load applying device 6 and the specimen was deformed by three-point bending. Note that the cracking radius r of the tip of 38 load breathing device 6 was made 4.0 mm, the difference L between reinforcements being made L .--. 2r-F3D. Where D is the diameter of the specimen.

[0118]Bojningsdeformeringen tillampades till dess aft delen med sparet brats. The bending deformation was applied to the aft part with the spar brats.

Bajningsvinkeln vid tiden far brottet (sparbajningsvinkel) mattes sa som visas figur 5. Notera att efter att provstycket brutits sander placerades de brutna delarna tillsammans for att mata sparets bajningsvinkel G. I den foreliggande uppfinningen har ett prov med en sparbajningsvinkel pa 28' eller mer bedornts ha utmarkt kallindningsfOrmaga. The bending angle at the time the fracture (saving bending angle) is measured as shown in Figure 5. Note that after the specimen was broken, the broken parts were placed together to feed the saving bending angle G. In the present invention, a sample having a saving bending angle of 28 'or more is damaged. have excellent cold-winding ability.

[0119]Mikro Vickershardhet efter nitrering utvarderades vid ett djup av 500 pm eller mer fran ytskiktet eftersom den innerhardhet definierades som "nitrerad skikthardher av mikro Vickers hardhet vid ett djup av 50 pm fran ytskiktet. Matningsvikten var 10 gram. Micro Vickers hardness after nitriding was evaluated at a depth of 500 μm or more from the surface layer because the inner hardness was defined as "nitrated layer hardness of micro Vickers hardness at a depth of 50 μm from the surface layer. The feed weight was 10 grams.

[0120]Resultatet av dessa tester visas i tabellema 1-5 till 1-8. Notera att i tabellerna 1-5 till 1-8 innefattar metallstrukturen restaustenit (y) samt anlapt martensit samt vissa inneslutningar. Vidare var jam och oundvikliga faroreningar jamvikten av de kemiska sammansattningarna. The results of these tests are shown in Tables 1-5 to 1-8. Note that in Tables 1-5 to 1-8, the metal structure includes residual austenite (y) and annealed martensite as well as certain inclusions. Furthermore, jams and unavoidable hazardous impurities were the weight of the chemical compositions.

FOrdragen staltrad (staltrad efter valsning valstrad) utvarderades endast utifran den cirkelekvivalenta diametern av oupplasta sfarisk karbider. Detta beror pa att det har sker fare varmebehandlingen, och att det da inte ar sa mycket mening med bilderna, trots att mekaniska egenskaper eller austenit kornstorlek etc. mats. Preferred stable row (stable row after rolling rolled) was evaluated only on the basis of the circle equivalent diameter of unplastic spherical carbides. This is due to the fact that the heat treatment takes place, and that the images do not make much sense, even though mechanical properties or austenite grain size etc. are fed.

[0121]Exemplen 1 till 47, i fareliggande uppfinning, visar alla kallindningsfOrmaga, det vill saga, sparets bajningsvinkel, av en god 28° eller mer och ar en utmarkt indikation pa fjaderhallfasthet, det vill saga, Nakamura typ av roterande bajningsutmattningsstyrka (harifran och frarnat enkelt refererad till som "utmattningshallfasthetern och en utmarkt indikation pa eftergivningsegenskapen och motstand mot varmerelaterad avmjukning, det vill saga, nitridskikthardheten. Examples 1 to 47, in the present invention, show all the cold winding capacity, i.e., the bending angle of the spare, of a good 28 ° or more and are an excellent indication of spring half strength, i.e., Nakamura type of rotary bending fatigue strength (from here and there). simply referred to as the "fatigue strength" and an excellent indication of the resilience and resistance to heat-related softening, that is, the nitride layer hardness.

[0122]Jamfarande exempel 48 och 49 ar exempel dar mangden tillsatt C ligger utanfOr intervallet i patentkraven. Om mangden C tillsatts Over foreskriven mangd (jamfarande exempel 48), blir de oupplasta sfariska karbiderna strirre och 39 forsamring av kallindningsformagan och sparets bOjningsvinkel indikeras. Daremot om C foreligger I mindre mangd an fOreskriven mangd (jamfOrande exempel 49), fOrsamras seghardningsegenskapen vilket gör att tillracklig hallfasthet inte kan sakras. I synnerhet blir den innerhdrdheten efter nitrering och fjader hallfastheten 5 (Nakamura typ av roterande bOjningsutmattningshallfasthet) och eftergivningsegenskapen (intern hardhet efter nitrering) lagre. Further examples 48 and 49 are examples where the amount of added C is outside the range of the claims. If the quantity C is added Above the prescribed quantity (cf. Example 48), the unloaded spherical carbides become stiffer and 39 accumulation of the cold winding shape and the bending angle of the spar are indicated. On the other hand, if C is present in a smaller amount than the prescribed amount (comparative example 49), the toughening property is impaired, which means that sufficient half-strength cannot be ensured. In particular, the inner hardness after nitriding and spring spring strength (Nakamura type of rotary bending fatigue strength) and the resilience property (internal hardness after nitriding) become lower.

[0123]JamfOrande exempel 50 och 51 ar exempel dar mangden tillsaft Si ligger utanfor intervallet I patentkraven. Om mangden Si Overskrider fOreskriven 10 mangd fOrsprOdas matrisen och bearbetningsfOrmagan forsamras, det viii saga, sparets bOjningsvinkel ar lag. Daremot om Si fOrekommer i mindre mangd an fOreskriven, fersamras seghardningsegenskaperna, vilket gor att tillracklig hallfasthet inte kan sakras, efter varmning genonn nitrering. I synnerhet blir den innerhardheten efter nitrering och det nitrerade skiktets hardhet lag. Comparative Examples 50 and 51 are examples where the amount of Si added is outside the range of the claims. If the quantity Si Exceeds the prescribed quantity 10, the matrix is propagated and the working capacity is collected, that is to say, the bending angle of the savings is law. On the other hand, if Si occurs to a lesser extent than prescribed, the toughening properties merge, which means that sufficient half-strength cannot be ensured after heating by nitration. In particular, the inner hardness after nitriding and the hardness of the nitrated layer become law.

[0124]JamfOrande exempel 52 och 53 ar exempel dar mangden tillsatt Mn ligger utanfOr det foreskrivna intervallet i patentkraven. Om Mn foreligger i storm mangd an i det foreskrivna intervallet, blir restaustenit grovre, strackgransen avtar, ochutmattningshallfastheten(Nakamuratypavroterande bOjningsutnnattningshallfasthet) ar underordnad. Daremot nar Mn foreligger i mindre mangd an den ftireskrivna mangden, avtar restaustenit fOr mycket och bearbetningsfbrmagan forsamras, vilket har till fOljd att sparets bOjningsvinkel avtar. Comparative Examples 52 and 53 are examples where the amount of added Mn is outside the prescribed range in the claims. If Mn is present in a large amount in the prescribed interval, the residual austenite becomes coarser, the yield strength decreases, and the fatigue strength (Nakamura-type rotating bending fatigue strength) is subordinate. On the other hand, when Mn is present in a smaller quantity than the prescribed quantity, the residual austenite decreases too much and the working capacity is reduced, which has the consequence that the bending angle of the spare decreases.

[0125]JamfOrande exempel 54 och 55 ar exempel dar mangden av tillsatt Cr ligger utanfor intervallet i patentkraven. Om mangden Cr Overskrider det fOrskrivna intervallet, stabiliseras cementit och aven vid varmning av gOten eller valsamnet till hog temperatur, seghardning etc., Okar oupplOsta karbider och fjaderns bearbetningsformaga reduceras kraftigt. Av denna anledning avtar sparets bOjningsvinkel. Daremot om Cr foreligger i mindre mangd an den fOreskrivna mangden, mjukas stalet upp vid varmebehandling vid nitrering etc. och det s8 kallade motstandet mot varmerelaterad avmjukning blir otillrackligt vilket gor att det nitrerade skiktets hardhet avtar. Comparative Examples 54 and 55 are examples where the amount of Cr added is outside the range of the claims. If the amount Cr exceeds the prescribed interval, cementite and even when heating the goth or rolling stock to high temperature, toughening, etc., increase undissolved carbides and the working capacity of the spring is greatly reduced. For this reason, the bending angle of the spar decreases. On the other hand, if Cr is present in a smaller amount than the prescribed amount, the steel softens during heat treatment during nitration, etc., and the so-called resistance to heat-related softening becomes insufficient, which causes the hardness of the nitrated layer to decrease.

[0126]JamfOrande exempel 56, 57, och 58 ar exempel dar mangden tillsatt Mo, W, and Mo+W ar stOrre an intervallet patentkraven. Om mangden Mo och W overskrider de foreskrivna mangderna, bildas en underkyld struktur av martensit, bainit etc., vid valsning och kylning och efter patentering och annan varmebehandling vilket har till MO att traden bryts vid transport eller vid dragningsforfarandet, och att matningstestet inte kan utfaras. Comparative Examples 56, 57, and 58 are examples where the amount of Mo, W, and Mo + W added is greater than the range of claims. If the quantities Mo and W exceed the prescribed quantities, a supercooled structure of martensite, bainite etc. is formed, during rolling and cooling and after patenting and other heat treatment which has to MO that the wire is broken during transport or during the drawing process, and that the feed test cannot be performed .

[0127]JamfOrande exempel 59 ar ett exempel pa Overdriven tillsats av V. V är ett amne som bildar karbider i stalet. Overdriven tillsats orsakar oupplOsta karbider 10 att bildas runt V, bearbetningsfOrm6gan fOrsamras och sparets bOjningsvinkel avtar. (0128]JamfOrande exempel 60 och 61 an fall dar mangden N an Overdriven jamfOrt med intervallet i patentkraven. Den Overdrivna mangden N fOrhOjer temperaturen fOr bildandet av nitrider och kolnitrider av V, Nb, etc. och fOrorsakar 15 fOrgrovning av karbider och andra fallningar som anvander dessa som karnor. Vidare loses nitrider, kolnitrider och karbider upp ofullstandigt och en stor mangd grova oupplosta sfariska karbider kvarstar nar upprepad varmning, sasom i fOreliggande uppfinning anvands. Som ett resultat av detta ar bearbetningsfOrmagan fOrsamrad. Della ar ett exempel dar sparets bOjningsvinkel avtar, Comparative Example 59 is an example of Excessive addition of V. V is a substance which forms carbides in the steel. Excessive addition causes undissolved carbides 10 to form around the V, the machining ability is impaired and the bending angle of the spare decreases. Comparative Examples 60 and 61 show the amount N of Excessive compared to the range of claims. The Excessive amount N increases the temperature for the formation of nitrides and carbon nitrides of V, Nb, etc. and causes the coarse formation of carbides and other precipitates such as In addition, nitrides, carbon nitrides and carbides dissolve incompletely and a large amount of coarse undissolved spherical carbides remain after repeated heating, as is used in the present invention.As a result, the working capacity is compromised. ,

[0129]JamfOrande exempel 62 och 63 ar exempel dar mangden tillsatt Nb ligger utanfOr intervallet I patentkraven. Om Nb Overstiger den fOreskrivna mangden, ar den varma formbarheten anmarkningsvart fOrsamrad, ett flertal ytbristningar intraffade hos det valsade materiaiet, tradbratt intraffade under dragning, och eft matningstest kunde inte utfOras, Comparative Examples 62 and 63 are examples where the amount of Nb added is outside the range of the claims. If Nb exceeds the prescribed quantity, the hot formability is remarkably black, a number of surface cracks occurred in the rolled material, occurred sharply during drawing, and after feeding tests could not be performed,

[0130]JamfOrande exempel 64 ar dot fall dar summan av mangden tillsatt Mn och V ar mer an intervallet enligt i foreliggande uppfinning. Mangden av restaustenit staltraden blir da storre an det fOreskrivna vardet. I bOjningstestet av sparet avtar 30 hardheten hos delen med sparet till ft* av stress framkallad fasomvandling och bearbetningsfermagan avtar. Detta an ett exempel dar sparets bOjningsvinkel avtar. Upprepande oss sjalva ar V inte tillsatt i den framlagda uppfinning, men ibland ingar V som en oundviklig fOrorening vilket gor att V inte kan fOrklaras ovidkommande. 41 Comparative Example 64 is the case where the sum of the amounts added Mn and V is more than the range according to the present invention. The amount of residual austenite staltraden then becomes greater than the prescribed cairn. In the bending test of the spar, the hardness of the part decreases with the spar to ft * of stress-induced phase transformation and the machining capacity decreases. This is an example where the bending angle of the savings decreases. Repeating ourselves, V is not added in the present invention, but sometimes V is included as an inevitable contaminant, which means that V cannot be declared irrelevant. 41

[0131]JamfOrande exempel 65 ar det fall dar summan av mangderna tillsatt Mn och V ar lagre an intervallet enligt foreliggande uppfinning. Mangden restaustenit ar mindre an det optimala intervallet, vilket gOr att bearbetningsfOrmagan det vill saga sparets bojningsvinkel avtar. Comparative Example 65 is the case where the sum of the amounts added Mn and V is lower than the range of the present invention. The amount of residual austenite is less than the optimal range, which means that the working capacity of the saving bend angle decreases.

[0132]Jamforande exempel 66 ar det fall dar summan av mangderna tillsatt Cr och V ar stOrre an innehallet fOrklarat i framlagd uppfinning. Oupplosta sfariska karbider kvarstar i Overdriven mangd och bearbetningsfOrmagan, det vill saga, sparets bOjningsvinkel avtar. Comparative Example 66 is the case where the sum of the amounts of Cr added and V is greater than the content explained in the present invention. Undissolved spherical carbides remain in Excessive quantity and machining capacity, that is, the bending angle of the spar decreases.

[0133]JamfOrande exempel 67 ar det fall dar summan av mangden tillsatt Cr och V ar mindre an intervallet forklarat i fOreliggande uppfinning. Bearbetningsformagan ar utmarkt, men den innerhardheten efter nitrering och det nitrerade skiktets hardhet ar otillracklig och fjaderns prestanda ar otillracklig. Comparative Example 67 is the case where the sum of the amount of Cr and V added is less than the range explained in the present invention. The machining ability is excellent, but the inner hardness after nitriding and the hardness of the nitrided layer are insufficient and the performance of the spring is insufficient.

[0134]JamfOrande exempel 68 till 70 ar fall dar skillnaden mellan mangden Si och mangden Cr ([Si %]-[Cr %]) skiljer sig fran innehallet I patentkraven och mangden Cr ar storre an mangden Si. Om mangden Cr ar Overdriven i fOrhallande till mangden Si, kvarstar oupplOsta sfariska karbider och bearbetningsformagan ar nedsatt, det vill saga sparets bOjningsvinkel avtar. Comparative Examples 68 to 70 are cases where the difference between the amount of Si and the amount of Cr ([Si%] - [Cr%]) differs from the content of the claims and the amount of Cr is greater than the amount of Si. If the amount Cr is Exaggerated in relation to the amount Si, undissolved spherical carbides remain and the working capacity is reduced, ie the bending angle of the saving decreases.

[0135]Pa samma satt ar jamfbrande exempel 71 och 72 fall dar skillnaden i mangden Si och mangden Cr ([Si °/0]-[Cr %]) är stOrre an den ovre gransen for intervallet i patentkraven. Mangden Si ar mycket Overdriven i fOrhallande till mangden Cr. I dessa fall vaxer ytskiktets avkolade skikt hos det valsade materialet kraftigt och kan inte avlagsnas I tillracklig utstrackning genom ytskiktsrakning i liten mangd. Av denna anledning var utmattningshallfastheten (Nakamura typ av roterande bOjningsutmattningshàllfasthet) ovidkommande. In the same way, comparative examples 71 and 72 are cases where the difference between the amount Si and the amount Cr ([Si ° / 0] - [Cr%]) is greater than the upper limit of the range in the claims. The quantity Si is very Exaggerated in relation to the quantity Cr. In these cases, the charred layer of the rolled material of the rolled material grows strongly and cannot be removed to a sufficient extent by surface shaving in a small amount. For this reason, the fatigue strength (Nakamura type of rotary flexural fatigue strength) was irrelevant.

[0138]JamfOrande exemplen 73 och 74 ar respektive exempel 1 och exempel 23 av uppfinningen, dar stalet valsas vid valsamnets varmningstemperatur 1100 °C. I bOrjan av valsningen kvarstar oupplosta sfariska karbider. Effekterna kvarstar sá bearbetningsfOrmagan fOrsamras slutligen, det vill saga sparets bOjningsvinkel avtar. 42 Comparative Examples 73 and 74 are Example 1 and Example 23, respectively, of the invention, in which the steel is rolled at the heating temperature of the rolling stock 1100 ° C. At the beginning of the rolling, undissolved spherical carbides remain. The effects remain so that the working capacity is finally concentrated, that is to say the bending angle of the saving decreases. 42

[0137]Exemplen 101 till 109 ar exempel av uppfinningen av fardragna staltrAdar av exempel 1 till 5 och 20 till 23 av uppfinningen. JamfOrande exempel 110 och 111 ar exempel 101 och 106 av uppfinningen, dar valsamnets varmningstemperatur Ors 1100 °C. Examples 101 to 109 are examples of the invention of drawn stalls of Examples 1 to 5 and 20 to 23 of the invention. Comparative Examples 110 and 111 are Examples 101 and 106 of the invention, where the heating temperature of the roll is 1100 ° C.

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[0139] Tabell 1-2Kemiska sammans&ttningar (mass %) ... Table 1-2 Chemical compositions (mass%) ...

(DT,: 2 . 4 .3.3:1: 2 2 4 ", ; ,7,1 0 . 7,31, ,-,s 0 , r. r.' r. 21,-; , c:n =:. 2 ,-....,- 1-% I T-7-: ; 0 . 0 0 2: 1 ';; L,1 6; ...3.36; 43 0 , 0032 0 . 0040 . . 733 ---4- ,-77"-- ;C; . 03 i; 0 3 09 ; ---3----1------3-34: ; 0 3...0,;.:33, 30 , 0,- 35 , 09 -,...!..,-; Q • 0090 . 0 .0 . J :33 -- y, 3-. ,- 3 043003 3 0 . 0,3C:3. "4003. (DT,: 2. 4 .3.3: 1: 2 2 4 ",;, 7,1 0. 7,31,, -, s 0, rr 'r. 21, -;, c: n = :. 2 , -...., - 1-% I T-7-:; 0. 0 0 2: 1 ';; L, 1 6; ... 3.36; 43 0, 0032 0. 0040.. 733 - -4-, -77 "-; C;. 03 i; 0 3 09; --- 3 ---- 1 ------ 3-34:; 0 3 ... 0,;.: 33, 30, 0, - 35, 09 -, ...! .., -; Q • 0090. 0 .0. J: 33 - y, 3-., - 3 043003 3 0. 0,3C: 3. "4003.

U . 0002 ,."--',..11 -30 . 136 Zr 3. , 79_4._ 31. "74 0, 84 D. 5,3 D 0.331 - .... 3: - 1 ; 3 %- 3 4;- ; 1 ; :f --------------, 0 , 5. 0 .28 0 , 11j ...1: .27 0 .333 C, 0 , ., ' 1 2 : Inv . ,-.•'. 2 ,,". r; :: ;:',r.)r-;rt. ,,, c) 1( c: 0 , Q02,33 313. 003:32 0. 03.33.S 0, 00335 :3 G00 11 ._9; . 0011 5 „ 0012 0 . 0 p r; .: --____„ :0 .'7.: .1 n v . ex , ., 0 ,0 -L 0 - ..........._ 7. 00 0 . 0. 0 0 , 1 3 _ 3.,, .12 013 0 , 34 3'3 -'- 0 , 1 5.; - ;3 r " 3 ;0 , 0 0;34 ,c3.. :000? ' , 0091 ,... „;,0 0 r..,,l, „ - %"- 1 , 632 3.. ,,.,.2 ._004.%3 $I Inv . ex , 0 . C.) ;3332 ,1. 1 , 41 3 0 . 0034 U . El 0 . 93 0 , 9-333 0 . 6,, " 0 . 8'3_ '-4 - 0 : 59 4_33. 0 . T-'""""---",-i _ ;...1 , 44% ,1 , 73 %1 . 543 0. 0. 53 D . "13 3 ,;7,3, 3:3,-. Inv 3,..3J 223 ---1 0013;3 0 . 004._ Ce; „ 11 10 . :iI - 0 . 0 0 0 1 .,-; 2 . 86 -÷ 19 3c , ;r., 230 , 000 ,'.-1---',. . "-- 3 0 .0004 i 0 . 090:3 l'r30 n=3 : " . ' ..- __;) . D 0336_ -•''-' 10 . 13 %2 . 57; i-._'; 33, 92;3 03 '.' .". 0. ; : 3 '... 37'j ;Inv , 7.. 29 2 , 31 o. 5 3 -1 0 . 76 0 , 6,L1L. 1ri.f.,..'•.:',' 30 .331 333. 0073 -.....__ 0046 0 . 0 ::: 4 : i.) 3 0 . 0 r.323. 3 0 . 0022 3_ LI.1.30133. r.L::: 1:-: . o:-.;37 c.; . r; 032 ) . 003f, 0 , 0032 i'2 . 09 30 , 09 , 30_, 0 %J__ ;- 3004 0-2 1 i L.09 3:0 , 04 0 . C,1___L:4; 0 . 009 .I . 000 _0 . 1. 11,3 , ex , i).: 0: 3 3 0 , 434;6 % 3 C;...,: 33. 0034... 2 , 0 0 _1. 91 2.3. 80 7.53 0 .3- ,3%,: ;,,,,,' %O...., , , -, - • 43. 0002 ;-; D .132 D .7-2 37 % Inv. es. ) .5043 -3---'4 00 :.: .224.3 r„:..)..32_31,3 0 , 004:3 0 . 0034 -----1----------' 31 . 006 1 .0::).,-, . oILL2_,. - 10i 4 0,32 c..: .1: 33 10 .14 O. 0009 Cr-v. ex:. ex . .33; ",,,., ,... 2 .1..3.3 . 09 --- ---- 51,03? C4 0 .3:3001 3 0 . 5002 o.00cr.:L 0 , 0002 ("3. 0009 ..; . 0,0:.-, 7, ---"k 641. 1 .1 --- 0. ", 4 '3 7. 7252 2,39 1 0, 26 c:.-,,,,, 0 , :33002 ,0c:o4 .:3.',1 0 „ .5., 0 .39 7. 0 , 72 :- 4,, 0 . 00:33 , o 012 33.51 31.91 30 ,? 31 .69'3 0. 7,9 „ ;:. 2 .37 0.;.;.-S;,4 0 . :.-; 0:;::0 , 00 67 1, :3.3 3 0 , 0029 C3.3,4 3) .1730 ,3,0002 0 . 0004 %3n ,..; . !....);..1.2.1V. 4.- _ x.3 e, 2.44 0 . 73 ' 0 . 00 0.3 0 . 0033S 0.3.3043 1,37 „ .., 10.", 30" , 0 0 .., i 0.00532 0 ,:)05:: '0 , 0 :3 .Q.0 - i- .. C'• . 1 0 n14 , ,7 3,3.4 .3 U ,:93-- 7,743 0.0n,22 7. -_.bun:.: . 0.7.33,; „ .._. 0,003 :, 33 -,0.52 4,2 . D 3 ,----------------- ....,_... 0000210"r331,54 ,4,, 0.7051 0.77 • , 1 „. -1 4 j.., 7.-..7.7 , r/. 0.73 2,t 0.36 3 0.0079 ; 0 03339 1.333 2 . 23 0 , 76') , 009 0 01.r.:,,,::-, :, 3_ ,,E, 9 1C. ,.-„; 0 2 ',:„: 0 . 1.'r 0 5 :i CI ,0 0 „ 006 0 .11 9, . "19,3--%,- -0.6 31.74 - 3._1 „ 92i i1.933, 0 54 0. 48 D. 4 :: 3 .1_ 1 0,24 0 . 0.27 A ,E, -1- r; ... ,, „ ex ., c;7 E., 2 .:.,, 0 . 8 0j: 0 , 00%,,,333; 0.,33; f,.. 3,, 33 "7 30. 0;32:;.; , 00335, 70 030 . o ;3.0 ,1,-; ;;.. E;3003"30 . 0003 ,1,3 .301 ;330 . 99 -t - . 73J. TIV , e x . "7 7 2.8.-; 7;0; , 0 8 .,., 8 „ 0053 :,;3a, 3 D . 005 , 0033 30. 07 0 . 003 :31.30 z o . 17c: . 0 .'),::.., F1:,,,,'8 .0 0 :-: 3 3 S.30.630.34 Tabell 1-3 0 *Ztr ri 0 - :- , '4,› --:-- ,:,... >21,0 . U. 0002,. "- ', .. 11 -30. 136 Zr 3., 79_4._ 31." 74 0, 84 D. 5,3 D 0.331 - .... 3: - 1; 3% - 3 4; -; 1; : f --------------, 0, 5. 0 .28 0, 11j ... 1: .27 0 .333 C, 0,., '1 2: Inv. , -. • '. 2 ,, ". R; ::;: ', r.) R-; rt. ,,, c) 1 (c: 0, Q02,33 313. 003: 32 0. 03.33.S 0, 00335: 3 G00 11 ._9;. 0011 5 „0012 0. 0 pr;.: --____„: 0 .'7 .: .1 nv. Ex,., 0, 0 -L 0 - ....... ...._ 7. 00 0. 0. 0 0, 1 3 _ 3. ,, .12 013 0, 34 3'3 -'- 0, 1 5 .; -; 3 r "3; 0, 0 0; 34, c3 ..: 000? ', 0091, ... „;, 0 0 r .. ,, l,„ -% "- 1, 632 3 .. ,,.,. 2 ._004.% 3 $ I Inv. Ex, 0. C.); 3332, 1. 1, 41 3 0. 0034 U. El 0. 93 0, 9-333 0. 6 ,, "0. 8'3_ '-4 - 0: 59 4_33. 0. T - '"" "" --- ", - i _; ... 1, 44%, 1, 73% 1. 543 0. 0. 53 D." 13 3,; 7,3, 3: 3 , -. Inv 3, .. 3J 223 --- 1 0013; 3 0. 004._ Ce; „11 10. : iI - 0. 0 0 0 1., -; 2. 86 - ÷ 19 3c,; r., 230, 000, '.- 1 ---' ,. . "- 3 0 .0004 i 0. 090: 3 l'r30 n = 3:". '..- __;). D 0336_ - • '' - '10. 13% 2. 57; in-._'; 33, 92; 3 03 '.' . ". 0.;: 3 '... 37'j; Inv, 7 .. 29 2, 31 o. 5 3 -1 0. 76 0, 6, L1L. 1ri.f., ..' •. : ',' 30 .331 333. 0073 -.....__ 0046 0. 0 ::: 4: i.) 3 0. 0 r.323. 3 0. 0022 3_ LI.1.30133. RL ::: 1: -:. O: - .; 37 c .;. R; 032). 003f, 0, 0032 i'2. 09 30, 09, 30_, 0% J__; - 3004 0-2 1 i L.09 3: 0, 04 0. C, 1 ___ L: 4; 0. 009 .I. 000 _0. 1. 11,3, ex, i) .: 0: 3 3 0, 434; 6% 3 C; ... ,: 33. 0034 ... 2, 0 0 _1. 91 2.3. 80 7.53 0 .3-, 3% ,:; ,,,,, ''% O ....,,, -, - • 43. 0002; -; D .132 D .7-2 37% Inv. Es.) .5043 -3 --- '4 00:.: .224.3 r „: ..) .. 32_31,3 0, 004: 3 0. 0034 ----- 1 ---------- '31. 006 1 .0 ::)., -,. OILL2_ ,. - 10i 4 0,32 c ..: .1: 33 10 .14 O. 0009 Cr-v. Ex :. ex .33; ",,,.,, ... 2 .1..3.3. 09 --- ---- 51.03? C4 0 .3: 3001 3 0. 5002 o.00cr.:L 0, 0002 ("3. 0009 ..;. 0,0: .-, 7, ---" k 641. 1 .1 --- 0. ", 4 '3 7. 7252 2,39 1 0, 26 c: .- ,,,,, 0,: 33002, 0c: o4.: 3. ', 1 0 „.5., 0 .39 7. 0, 72: - 4, , 0. 00:33, o 012 33.51 31.91 30,? 31 .69'3 0. 7,9 „;:. 2 .37 0.;.; .- S;, 4 0.: .-; 0: ; :: 0, 00 67 1,: 3.3 3 0, 0029 C3.3,4 3) .1730, 3,0002 0. 0004% 3n, ..;.! ....); .. 1.2.1V . 4.- _ x.3 e, 2.44 0. 73 '0. 00 0.3 0. 0033S 0.3.3043 1,37 „.., 10.", 30 ", 0 0 .., i 0.00532 0, :) 05 :: '0, 0: 3 .Q.0 - i- .. C' •. 1 0 n14,, 7 3,3.4 .3 U,: 93-- 7,743 0.0n, 22 7. -_. Bun :.:. 0.7.33 ,; „.._. 0,003:, 33 -, 0.52 4,2. D 3, ----------------- ...., _... 0000210 "r331,54, 4 ,, 0.7051 0.77 •, 1„. -1 4 j .., 7 .- .. 7.7, r /. 0.73 2, t 0.36 3 0.0079; 0 03339 1.333 2. 23 0, 76 '), 009 0 01.r.:,,,::-,:, 3_ ,, E, 9 1C. , .- „; 0 2 ',: „: 0. 1.'r 0 5: i CI, 0 0 „006 0 .11 9,. "19,3 -%, - -0.6 31.74 - 3._1„ 92i i1.933, 0 54 0. 48 D. 4 :: 3 .1_ 1 0,24 0. 0.27 A, E, -1- r ; ... ,, „ex., C; 7 E., 2.:. ,, 0. 8 0j: 0, 00% ,,, 333; 0., 33; f, .. 3 ,, 33" 7 30. 0; 32:;.; , 00335, 70 030. o; 3.0, 1, -; ;; .. E; 3003 "30. 0003, 1,3 .301; 330. 99 -t -. 73J. TIV, e x." 7 7 2.8.-; 7; 0; , 0 8.,., 8 „0053:,; 3a, 3 D. 005, 0033 30. 07 0. 003: 31.30 z o. 17c:. 0. '), :: .., F1: ,,,,' 8 .0 0: -: 3 3 S.30.630.34 Table 1-3 0 * Ztr ri 0 -: -, '4, ›- : -,:, ...> 21.0.

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N C. , . ,--;•,-, .:',-,0.1 0 0 .,-;0 ; ,, ..N•-■". r--,',I. I C. C. 0 0 I'.-•• .-N' :0.1,-, 0 0 ,, 0 t C. 0 t 0 C. i',: 0 t 01 Cr; r.:0 --N ' < -:•N 0 :):4 I:1■1:■•-■ 0 :„ • 1 t CC : t :_, ,-, ,.. , -• 1:-..1 c iC: 1..-4 09 C. . C>1 61:-.1 t. 0 , • ,---? k i C: 61-4--1 0 _. cc., , -•■• ,-) C c 0 t 1. :411, 4_,.21 1.2.`C211 :-:::.,:.-:, .--“. 0 t• 0.:; c • i. ..... 1C.4.C.,C-2. ..---,C.-, C.-2: :1 4 c t ".7.1;0 1.--: 0.>0:1-, ... ,:-‘,.---, ■ -----;-.---.---; ,---;:-.- --icc. — • .---; i,---; .,r•• ::: • -.----. ,, , . ...1.•---,,---• ,; r... .........+ ....... 0,.....: -;:N I' ,...... ---....-.1 1 0(:•-:,-N t ..-., ,::Nt•-• • C. 01 • 0 ....-, CC1.---.. N C.,. , -; •, -,.: ', -, 0.1 0 0., -; 0; ,, ..N • - ■ ". R -, ', I. I CC 0 0 I' .- ••.-N ': 0.1, -, 0 0 ,, 0 t C. 0 t 0 C. i ',: 0 t 01 Cr; r.:0 --N' <-: • N 0 :): 4 I: 1 ■ 1: ■ • - ■ 0: „• 1 t CC: t: _,, -,, .., - • 1: - .. 1 c iC: 1 ..- 4 09 C.. C> 1 61: -. 1 t. 0, •, ---? Ki C: 61-4 --1 0 _. Cc.,, - • ■ •, -) C c 0 t 1.: 411, 4 _ ,. 21 1.2.`C211: - :::.,: .- :, .-- “ . 0 t • 0.:; C • i. ..... 1C.4.C., C-2. ..---, C.-, C.-2:: 1 4 ct ".7.1 ; 0 1 .--: 0.> 0: 1-, ...,: - ', .---, ■ -----; -. --- .---; , ---;: -.- --icc. - • .---; in,---; ., r •• ::: • -.----. ,,,. ... 1. • --- ,, --- •,; r ... ......... + ....... 0, .....: - ;: NI ', ...... ---....-. 1 1 0 (: • -:, - N t ..-.,, :: Nt • - • • C. 01 • 0 ....-, CC1 .--- ..

C - t 41,40:.1-, .1-:1: 0...0•-, 1..1 ,- L..- t C..-; :,--..............--.: u:,s; -::.5") C":.0: ;1:i , ' C--:;N.,..r)--a', ..;cr).X.CC;:-.-:,CC, ----; ; ••:-.')C.,0000 CP :V • 0'; .. r.,.. . C - t 41,40: .1-, .1-: 1: 0 ... 0 • -, 1..1, - L ..- t C ..-; :, --..............-- .: u:, s; - ::. 5 ") C":. 0:; 1: i, 'C - :; N., .. r) - a', ..; cr) .X.CC;: -.- :, CC, ----; ; ••: -. ') C., 0000 CP: V • 0'; .. r., ...

C C -.---: 0 0 • --: -z.,c.c:o .---,.---; 0: '..> to 'ic.-_, ,,---, 0 i,---;1 C:.; C: ' o IT: •••'• I•-; 0 0. :7:.: 0 CC) .- 0 0 0 :-N,-:■-■:'. ,I, C 0 0 0 . C C -.---: 0 0 • -: -z., C.c: o .---, .---; 0: '..> to' ic.-_, ,, ---, 0 i, ---; 1 C:.; C: 'o IT: •••' • I • -; 0 0.: 7:.: 0 CC) .- 0 0 0: -N, -: ■ - ■: '. , I, C 0 0 0.

C.C:,o 0 0 ,-. C.: o ti.0:: 0 'to , • --.-", ' 'N.--:,---, 0 0 C., o.toc. 0 C. 0 0 t 0-. .".:, .c. tC.., . • :' : t-N .0.,. , ,--_-• t ',.. :r:1.1:1 t 1--.`1, t ; - ; , ,...,.- ,..] . . ,-,-,.-,, c 'KC:C 0. r'. .C.::: r--cc, . C.C:, o 0 0, -. C .: o ti.0 :: 0 'to, • --.- ",' 'N .--:, ---, 0 0 C., o.toc. 0 C. 0 0 t 0-. . ".:, .c. tC ..,. •: ': t-N .0.,. ,, --_- • t ', ..: r: 1.1: 1 t 1 -. `1, t; -; ,, ..., .-, ..]. . , -, -, .- ,, c 'KC: C 0. r'. .C. ::: r - cc,.

-C-: :-.::C-,' C.:0 , 0 . c--0 ,,,-,, . 0 cc, . c-0 , , r.r - .. .....c... 1cr-, . c, . -C-:: -. :: C-, 'C.:0, 0. c - 0 ,,, - ,,. 0 cc,. c-0,, r.r - .. ..... c ... 1cr-,. c,.

C-0 ...---1.--, c, . :.-.1.---! 1 0 00 ',.,' . .--.•c.--000 1,--- Q.-.• '-' c.-. C-0 ...--- 1 .--, c,. : .-. 1 .---! 1 0 00 ',.,'. .--. • c .-- 000 1, --- Q .-. • '-' c.-.

C, ...._, c.'', 0 -.--- i.flrs;,CC; .--,- -, :-_,c•El:.-..-, (1,,-.).1":.C: '• :.1..,•-_-_,c..,.cl, -.7.• c_ ., • -_-, ,---::0 11--4 .. C, ...._, c. '', 0 -.--- i.flrs;, CC; .--, - -,: -_, c • El:.-..-, (1 ,, -.). 1 ":. C: '•: .1 .., • -_-_, c ..,. cl, -.7. • c_., • -_-,, --- :: 0 11--4 ..

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Lr, ‘.1.1. 0 o C. c,', ,E--., C..: • .1, "--;-• c:•,• .7., , % ...„. :-,0". -•-_-, 1 c.;--_-: O.cl: .• C..•.-_, .. i. C.1: c. :-..• -1, :I: . -_-, EDI ::, — c. Lr, ‘.1.1. 0 o C. c, ',, E--., C ..: • .1, "-; - • c: •, • .7.,,% ...„.: -, 0 ". - • -_-, 1 c.; --_-: O.cl:. • C .. •.-_, .. i. C.1: c.: - .. • -1,: I: . -_-, EDI ::, - c.

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[0141]Tabell 1-4Kemiska sammansAttningar (mass %) 0.76 2.4P.074' 0.00 ,14",0.4". E% •0,0034, 0047 2 . Ei% 02.5;'0,0253. 10, 0,78 2 1 3. 4 L 0 0 LL, 0.023 ,pc)• ; 2 4:3:3 6. P,:337, e .- x J3% 2 360 ', 00330,-- -3 3 1,0 , .30%313.06016,03:12 0.000:3. 1)0'1 ri 00%3%3 0.00 03 0,000,6 0.0,301, '3022: 0 0,: 0.56 % 0,27 -7-77 ,. 5S, . 0,00:16 U 0C x 023_0,0042 %. 0013 0.00 3.4 3 0..60341_0,-10 0,00 0.12 13.003,S0,03 %0„003,_0,1510,".:.6 6.0044 5,r.)70.11.0,opo, 0,00330e, i0.00€ 0,13 %n. c)co4 0.44 % 0.2S 0,23 1 0,31 % 1.&80.56 1 0,27 ) 48 HArdhet nitrerat skikt itnn j W - Inre hirdhet after nitrering (Hy) Nakamuratyp av roterande bojning (HPa) Spirbiijning grader (grader) Utbytesforhallande (%) 0,2 % provapanning - " Draghillfaathet (MPa) Restauetenit (vol %) .(3:1 Tidigare aue e itkornator lek (74) Proximal sfarisk karbiddiameter rn Tradbrott etc. ingen abnormitst] lackningstemperatur Patenteringatemperatur ) Valeamnestemperatur -t Bra for alla inv, ex Hirdhet ho s nitrerat skikt (lW) Inre hArdhet after nitrarcing (HIT) Nakamuratyp av roterande bojning (mPa) SpArbojning grader (grader) UtbytesforhAllande (%) 0,2 % provepAnning aghAllfasthet (MPa) Restaustentit (vol %) Tidigare austenitkornstorisk Maximal sfarisk k bid-diameter M N M M (x... CC. M - , 7-• H 7-) N -■, C) 0 • C- C)Cr; CC , M CCN N CC-CC C7,1 Tradbrott etc. Table 1-4Chemical Compositions (Mass%) 0.76 2.4P.074 '0.00, 14 ", 0.4". E% • 0.0034, 0047 2. Ei% 02.5; '0.0253. 10, 0.78 2 1 3. 4 L 0 0 LL, 0.023, pc) •; 2 4: 3: 3 6. P,: 337, e .- x J3% 2 360 ', 00330, - -3 3 1,0, .30% 313.06016,03: 12 0.000: 3. 1) 0'1 ri 00% 3% 3 0.00 03 0.000.6 0.0.301, '3022: 0 0 ,: 0.56% 0.27 -7-77,. 5S,. 0.00: 16 U 0C x 023_0.0042%. 0013 0.00 3.4 3 0..60341_0, -10 0,00 0.12 13.003, S0,03% 0 „003, _0,1510,".:. 6 6.0044 5, r.) 70.11.0, opo, 0,00330e, i0.00 € 0.13% n. c) co4 0.44% 0.2S 0.23 1 0.31% 1. & 80.56 1 0.27) 48 HAARD hardness nitrated layer itnn j W - Inner hardness after nitriding (Hy) Nakamura type of rotating bend (HPa) Spirbiijning degrees (degrees) Yield ratio (%) 0.2% test pan - "Draghill fatness (MPa) Restauetenite (vol%). (3: 1 Previous aue e itcornator lek (74) Proximal spherical carbide diameter rn Tradbrott etc. no abnormitst] lacquering temperature Patenting temperature) Valeamnestemperature -t Good for all inv, ex Hardness ho s nitrated layer (lW) Inner hardness after nitrarcing (HIT) Nakamura type of rotating bending (mPa) Saving bending degrees (degrees) Yield ratio (%) 0% 2% sample aghHallfastness (MPa) Residual austenite (vol%) Previous austenitic grain history Maximum spherical k bite diameter MNMM (x ... CC. M -, 7- • H 7-) N - ■, C) 0 • C- C) Cr; CC, M CCN N CC-CC C7.1 Tradbrott etc.

[Bra ingen abnormitet] glAckningstemperatur (CC) rI Patenteringstemperatur E-1(°C) ValsAmnestemperatur (°C) Bra for alla inv., ex., (1, M M•M "N, ; N C., C 07: M M M . [Good no abnormality] Glucing temperature (CC) rI Patent temperature E-1 (° C) Roller Subject temperature (° C) Good for all inv., Ex., (1, MM • M "N,; N C., C 07: MMM .

M M :N CC iN C., N:C , C. M X M , X X X 11`. , >■.> 111 H H H :H „ >7› H H CC CC _ X X X .`.4 X M H H H 49 Hardhet nitrerat skikt (Fv) -------------------- Dire hirdhet after nitrring (KV) CV 01 0: 0: s. 4.... -, , 0 C — ,-, .., c c.c. 0, ,-,,c, .4. M M: N CC iN C., N: C, C. M X M, X X X 11`. ,> ■.> 111 HHH: H „> 7› HH CC CC _ XXX .`.4 XMHHH 49 Hardness nitrated layer (Fv) -------------------- Dire hirdhet after nitrring (KV) CV 01 0: 0: s. 4 .... -,, 0 C -, -, .., c cc 0,, - ,, c, .4.

, N . , N.

, N IS,N CC.Cc. , N IS, N CC.Cc.

CS., WCI-, CI, ' M c; CI., N CII .anuratyp av roterande bajning(MPa) ,,, .-c ,,, : , ...: , 1 Sparbojning grader (grader) Dtbytesfe,rhAllande (%) : 0,2 ss provmingsapanning , :-. 4.- n : ,-- i.:. ) :. 1 :-_, t 1 N ■ , r, c‘.0 , N-0 ,0: ,,4' 1 C 4 ,c, 04 c Draghillfasthet(ME,a) CC :-., ,-; N N [ • - -; W M ,I,/ --,.., ,, ,, c-,, CC , , .-I ,,-, N :.:,.; , -, C, Cc, cn C.■ :: C -• M W ,.) CI 1. CS., WCI-, CI, 'M c; CI., N CII .anura type of rotating bending (MPa) ,,,.-C ,,,:, ...:, 1 Sparbojning degrees (degrees) Dtbytesfe, rhAllande (%): 0,2 ss test opening,: - . 4.- n:, - i.:. ):. 1: -_, t 1 N ■, r, c‘.0, N-0, 0: ,, 4 '1 C 4, c, 04 c Draghillfastthet (ME, a) CC: -.,, -; N N [• - -; W M, I, / -, .., ,, ,, c- ,, CC,,.-I ,, -, N:.:,.; , -, C, Cc, cn C. ■ :: C - • M W,.) CI 1.

N U.: - N ; 4 N N ; 4 , c‘. cc. N U .: - N; 4 N N; 4, c ‘. cc.

N , ., W : ,--: . c, , c, N ; ,--,, ,,.-_, ::: , ,\, cn c. N CI , cn c, ",X,..,, w .N IN: " N --; , -:. ,,o .N1, M;',", ,I.;N .,, N c , , c: c , • c: Restauenit(vol%) idigare anatenitkornato lek()'#) Maximal sfarisk karbid- diameter (•) adbrott etc. N,., W:, -:. c,, c, N; , - ,, ,,.-_, :::,, \, cn c. N CI, cn c, ", X, .. ,, w .N IN:" N -; , - :. ,, o .N1, M; ', ",, I.; N. ,, N c,, c: c, • c: Restauenit (vol%) idigare anatenitkornato lek ()' #) Maximum spherical carbide diameter ( •) adbrott etc.

[Bra = ingen abnormitet] 0 14 al , 00 E4 P .83 00 PIA Aal . [Good = no abnormality] 0 14 al .00 E4 P .83 00 PIA Aal.

El .....4444. k Slackningstemperatur (°C) rc, .1, ..c. , , 1 c, c.: N 1 "C" 4 CC,: 04 F,,,,,,, , 4, Patenteringstemperatur (0o ) Valsamnestemperatur 1 o (44) C-4, N ('C) c-1: 0., .4_, Cc . El ..... 4444. k Slacking temperature (° C) rc, .1, ..c. ,, 1 c, c .: N 1 "C" 4 CC,: 04 F ,,,,,,,, 4, Patent temperature (0o) Roll sample temperature 1 o (44) C-4, N ('C) c- 1: 0., .4_, Cc.

. N Q. :",1 '1 , ,, C N' ............ (sC) . . a ., r: cr, 1 ,-, Cr.,,4 :0 . . N Q.: ", 1 '1, ,, C N' ............ (sC).. A., R: cr, 1, -, Cr. ,, 4: 0.

. . ,,C, . c,),c.c, '('Cs.c . q ::: , LC = o 0 i . c ::. 0.7■ CX Z. . . ,, C,. c,), c.c, '(' Cs.c. q :::, LC = o 0 i. c ::. 0.7 ■ CX Z.

..... C.,.: : D 0 5 0 Tabell 1- 8 Ln Hardhet nitrerat skikt (W) , Intre hirdhet efter nitrering (fly) kamuratyp av roterande jning Sparbojning grader (grader) : . ..... C.,.:: D 0 5 0 Table 1- 8 Ln Hardness nitrided layer (W), Internal hardness after nitriding (fly) kamura type of rotating jning Saving bending degrees (degrees):.

Uthyteafarhal/ande (%) - "provspanning raghallfesthet(MPa) --- Restaustennit(%) .-- , : Tidigare austenitkornetor- lek(y#) Maximal sfarisk karbiddia, meter ci. _ Tradbrott etc. Uthyteafarfar / ande (%) - "test voltage raghallfasthet (MPa) --- Restaustennit (%) .--,: Previous Austenite grain size (y #) Maximum spherical carbiddia, meters ci. _ Tradbrott etc.

(Bra - ingen abnormiteti i c)1 4 Q C, 7) ,I) C., 00) - C. (Good - no abnormality in c) 1 4 Q C, 7), I) C., 00) - C.

:Slackningstemperatur CC) Pate tingetemperatur CC) , Valeamnestemperatur (C) CC ),.: X W - :4 (1) - ,- ›: :::: ::. . , . tl: , ,i ... : Slackningstemperatur CC) Pate tingetemperature CC), Valeamnestemperature (C) CC),.: X W -: 4 (1) -, - ›: :::: ::. . ,. tl:,, i ...

: -, ,., X ; -. 51 Industrie!! tillampbarhet [01461FOreliggande uppfinning kan anvandas for produktion av staltrad for hOghallfasthetsfjaderanvandning. FlOghallfasthetsfjaderrnaterialet kan anvandas inom manga industriella omraden utgaende ifran bilindustrin. : -,,., X; -. 51 Industry !! Applicability The present invention can be used for the production of steel wire for high strength spring application. The flight strength spring material can be used in many industrial areas based on the automotive industry.

Lista Over hanvisningsbeteckningar List of male designation designations

[0147]1 sfariska karbider 2 stans 10 3 provstycke 4 spar inmatare 6 stativ anvant fOr last P last L distans mellan stOd 0 sparets bOjningsvinkel 52 1 spherical carbides 2 punch 10 3 test piece 4 spare feeder 6 stand used for load P load L distance between supports 0 bending angle of the spare 52

Claims

Patentkrav 1. Fordragen staltrad f6r hOghallfastighetsfjaderanvandning, kannetecknad av den innehaller i mass %, C: 0,67 (:)/0 till 0,9 (:)/0, Si: 2,0 till 3,5 %, Mn: 0,5 till 1,2 %, Cr: 1,3 till 2,5 %, N: 0,003 till 0,007 %, och Al: 0,0005 % till 0,003 %, varvid Si och Cr uppfyller foljande uttryck: 0,3 (YoSi-Cr1,2 %, och vidare, valfritt innehaller en eller flera av 22. 0,03 till 0,10%, Nb: 0,015 % eller mindre, Mo: 0,05 till 0,30 `)/0, 23. 0,05 till 0,30 %, Mg: 0,002 (:)/0 eller nnindre, Ca: 0,002 % eller mindre, och Zr: 0,003 (:)/0 eller mindre, vid innehall av V uppfylls 1,4 (:)0Cr+VQ,6 (:)/0 och 0,70 (Yoa/ln+V1,3 (:)/0, och, vid innehall av Mo och W, uppfylls 0,0(Yoa/lo-FW0,5 %, och med balans av jam n och oundvikliga f6roreningar, varvid P och S som fororeningar innefattande P: 0,025 (:)/0 eller mindre och S: 0,0(:)/0 eller mindre, och, vid are, varvid en cirkelekvivalent diameter for oupplosta sfariska karbider är mindre an 0,2 pm. 2. Dragen varmebehandlad staltrad f6r hoghallfastighetsfjaderanvandning, kannetecknad av den innehaller i mass %, 53 C: 0,67 `)/0 till 0,9 %, Si: 2,0 till 3,5 %, Mn: 0,5 till 1,2 %, Cr: 1,3 till 2,%, N: 0,003 till 0,007 (:)/0, och Al: 0,0005 (:)/0 till 0,003 %, varvid Si och Cr uppfyller fOljande uttryck: 0,3 `)/0Si-Cr1,2 %, och vidare, valfritt innehaller en eller flera av 22. 0,03 till 0,10%, Nb: 0,015 % eller mindre Mo: 0,05 till 0,30 %, 23. 0,05 till 0,(:)/0 Mg: 0,002 % eller mindre, Ca: 0,002 % eller mindre, och Zr: 0,003 `)/0 eller mindre, vid innehall av V uppfylls 1,4 `)/0Cr+W2,6 `)/0 och 0,70 (Yoa/In+W ,3 `)/0, och, vid innehall av Mo och W, uppfylls 0,05 (:)/0(:)/0, med balans av jam och oundvikliga fororeningar, med P och S som fororeningar innefattande P: 0,025 (:)/0 eller mindre och S: 0,025 (:)/0 eller mindre, och vidare, med en metallstruktur innefattande minst restaustenit av ett volymsmatt pa over 6 % till 15%, med ett tidigare austenit kornstorleksnummer #10 eller mer, och med ett innehall med oupplosta sfariska karbider med en cirkelekvivalent diameter om mindre an 0,2 pm. 3. Dragen varmebehandlad staltrad for hoghallfastighetsfjaderanvandning, enligt patentkrav 2, kannetecknad av att den dragna varmebehandlade staltraden f6r hoghallfastighetsfjaderanvandning har en draghallfastighet av 2100 till 2400 MPa. 54 4. Dragen varmebehandlad staltrad for hoghallfastighetsfjaderanvandning, enligt patentkrav 3, kannetecknad av att den dragna varmebehandlade staltraden f6r hOghallfastighetsfjaderanvandning har en strackgrans av 1600 till 1980 MPa. 5. Dragen varmebehandlad staltrad f6r hoghallfastighetsfjaderanvandning, enligt patentkrav 2, kannetecknad av att den dragna varmebehandlade staltraden fOr hoghallfastighetsfjaderanvandning har en ythardhet HV750 eller mer enligt Vickersskalan, och inre hardhet HV570 eller mer enligt Vickersskalan, efter varsam nitrering vid 500°C i 1h. 6. Produktionsforfarande f6r f6rdragen staltrad f6r hoghallfastighetsfjaderanvandning kannetecknat av en got innehallande i mass %, C: 0,67 % till 0,9 °/0, Si: 2,0 till 3,5 %, Mn: 0,5 till 1,2 %, Cr: 1,3 till 2,5 %, N: 0,003 till 0,007 °A, och Al: 0,0005 °A) till 0,003 %, med Si och Cr som uppfyller foljande uttryck: 0,3 (:)0Si-Cr1,2 %, och vidare, valfritt innehallande en eller flera av 22. 0,03 till 0,10%, Nb: 0,015 % eller mindre Mo: 0,05 till 0,30 %, 23. 0,05 till 0,30 °A) Mg: 0,002 % eller mindre, Ca: 0,002 % eller mindre, och Zr: 0,003 °A) eller mindre, vid innehall av V uppfylls 1,4 °A4Cr+W2,6 och 0,70 °44Mn+V1,3 %, och, vid innehall av Mo och W, uppfylls 0,05 °A) ailo-FW0,5 %, med balans av jam och oundvikliga fororeningar, 5 nned P och S sonn fororeningarna innefattande P: 0,025 % eller mindre och S: 0,025 (:)/0 eller mindre, och, varvid goten varms till 1250°C eller mer, darefter varmvalsas goten for tillverkande av ett valsamne och varmning av valsamnet till 1200°C eller mer, med efterfoljande varmvalsning f6r tillverkande av en f6rdragen staltrad. 7. Produktionsforfarande for fordragen staltrad for hoghallfastighetsfjaderanvandning kannetecknat vidare av varmning av fordragen staltrad enligt patentkrav 6 till 900 °C eller mer, varefter den patenteras vid 600 °C eller mindre. 8. Produktionsforfarande for varmebehandlad staltrad for hoghallfastighetsfjaderanvandning kannetecknat av dragning av den fordragna staltraden vilken tillverkats genom produktionsforfarandet for fordragen staltrad enligt patentkrav 6, varmning av staltraden i en takt av 10°C/ sek eller mer upp till temperaturen A3, bibehallande av temperaturen A3 eller mer i 1 nninut till 5 minuter, darefter kylning i en takt av 50 °C/sek eller mer, ner till 100°C eller mindre. 9. Produktionsforfarandeforvarmebehandladstaltradfor hOghallfastighetsfjaderanvandning kannetecknat av dragning av den fOrdragna staltraden vilken tillverkas genom produktionsforfarandet fOr fordragen staltrad enligt patentkrav 7, varmning av staltraden i en takt av 10 °C/sek eller mer upp till temperaturen A3, bibehallande av staltraden vid temperaturen A3 eller mer, i 1 minut till 5 minuter, darefter kylning av staltraden i en takt av 50 °C/sek eller mer ner till 100 °C eller mindre. 10. Produktionsforfarande for produktion av varmebehandlad staltrad for hoghallfastighetsfjaderanvandning enligt patentkrav 8 kannetecknat av vidare bibehallande och anlopning vid 400 till 500 °C i 15 minuter eller mindre. 56 11. Produktionsforfarande for produktion av varmebehandlad staltrad for hoghallfastighetsfjaderanvandning enligt patentkrav 9 kannetecknat av vidare bibehallande och anlopning vid 400 till 500 °C i 15 minuter eller mindre. 57 VC, Pr Lx, s$ n A ,‘t‘' - - ---° € ,..,Claims 1. Contracts designed for high-rise property spring use, can be characterized by it containing in mass%, C: 0.67 (:) / 0 to 0.9 (:) / 0, Si: 2.0 to 3.5%, Mn: 0 .5 to 1.2%, Cr: 1.3 to 2.5%, N: 0.003 to 0.007%, and Al: 0.0005% to 0.003%, Si and Cr having the following expression: 0.3 (YoSi -Cr1.2%, and further, optionally contains one or more of 22. 0.03 to 0.10%, Nb: 0.015% or less, Mo: 0.05 to 0.30 `) / 0, 23. 0 .05 to 0.30%, Mg: 0.002 (:) / 0 or lower, Ca: 0.002% or less, and Zr: 0.003 (:) / 0 or less, when V is satisfied 1.4 (:) 0Cr + VQ, 6 (:) / 0 and 0.70 (Yoa / ln + V1.3 (:) / 0, and, when containing Mo and W, 0.0 (Yoa / lo-FW0.5% is satisfied, and with balance of iron n and unavoidable impurities, wherein P and S as impurities comprising P: 0.025 (:) / 0 or less and S: 0.0 (:) / 0 or less, and, in the case of are, wherein a circle equivalent diameter for undissolved spherical carbides is less than 0.2 pm 2. Drawn heat-treated stable row for hoghallf spring use, can be characterized by it contains in mass%, 53 C: 0.67 `) / 0 to 0.9%, Si: 2.0 to 3.5%, Mn: 0.5 to 1.2%, Cr: 1.3 to 2%, N: 0.003 to 0.007 (:) / 0, and Al: 0.0005 (:) / 0 to 0.003%, Si and Cr satisfying the following expression: 0.3 ') / OSi- Cr1.2%, and further, optionally contains one or more of 22. 0.03 to 0.10%, Nb: 0.015% or less Mo: 0.05 to 0.30%, 23. 0.05 to 0, (:) / 0 Mg: 0,002% or less, Ca: 0,002% or less, and Zr: 0,003 `) / 0 or less, if the content of V is 1,4`) / 0Cr + W2,6 `) / 0 and 0.70 (Yoa / In + W, 3 `) / 0, and, when containing Mo and W, 0.05 (:) / 0 (:) / 0 is met, with a balance of jam and unavoidable impurities, with P and S as impurities comprising P: 0.025 (:) / 0 or less and S: 0.025 (:) / 0 or less, and further, with a metal structure comprising at least residual austenite of a volume mat of over 6% to 15%, with a former austenite grain size number # 10 or more, and with a content of undissolved spherical carbides with a circle equivalent diameter of less than 0.2 μm. Drawn heat-treated stable line for high-hall property spring use, according to claim 2, characterized in that the drawn heat-treated steel line for high-hall spring spring use has a drawn hall property of 2100 to 2400 MPa. 54 4. Drawn heat-treated steel row for high hall property spring use, according to claim 3, characterized in that the drawn heat-treated steel row for high-hall spring spring use has a yield strength of 1600 to 1980 MPa. Drawn heat-treated stable line for high-hall property spring use, according to claim 2, characterized in that the drawn heat-treated steel line for high-hall property spring use has a surface hardness HV750 or more according to the Vickers scale, and internal hardness HV570 or more according to Vickerscalan. 6. Production process for preferred shaped rigs for high hall property spring use may be characterized by a good containing in mass%, C: 0.67% to 0.9 ° / 0, Si: 2.0 to 3.5%, Mn: 0.5 to 1, 2%, Cr: 1.3 to 2.5%, N: 0.003 to 0.007 ° A, and Al: 0.0005 ° A) to 0.003%, with Si and Cr having the following expression: 0.3 (:) OSi-Cr1.2%, and further, optionally containing one or more of 22. 0.03 to 0.10%, Nb: 0.015% or less Mo: 0.05 to 0.30%, 23. 0.05 to 0.30 ° A) Mg: 0.002% or less, Ca: 0.002% or less, and Zr: 0.003 ° A) or less, when content of V is satisfied 1.4 ° A4Cr + W2.6 and 0.70 ° 44Mn + V1.3%, and, when containing Mo and W, 0.05 ° A) ailo-FW0,5% is met, with a balance of jam and unavoidable impurities, below the P and S son impurities comprising P: 0.025% or less and S: 0,025 (:) / 0 or less, and, whereby the cast is heated to 1250 ° C or more, then the cast is hot rolled to produce a roll and heat the roll to 1200 ° C or more , with subsequent hot rolling for the production of a preferred steel row. The production method of the preferred stable row for high hall property spring use further characterized by heating the preferred stable row according to claim 6 to 900 ° C or more, after which it is patented at 600 ° C or less. Production process for heat-treated stable line for high-hall spring spring use characterized by drawing the preferred steel line which is manufactured by the production method for preferred steel line according to claim 6, heating the steel line at a rate of 10 ° C / sec or more up to temperature A3, maintaining temperature A3 or more for 1 minute to 5 minutes, then cooling at a rate of 50 ° C / sec or more, down to 100 ° C or less. Production process pre-heat treated stall line for high hall spring spring use characterized by drawing the preferred steel line which is manufactured by the production method for the preferred steel line according to claim 7, heating the steel line at a rate of 10 ° C / sec or more up to temperature A3, maintaining the temperature A3, for 1 minute to 5 minutes, then cooling the stable line at a rate of 50 ° C / sec or more down to 100 ° C or less. A production process for the production of heat-treated stable line for high-hall property spring use according to claim 8, characterized by further maintaining and tempering at 400 to 500 ° C for 15 minutes or less. A production process for the production of heat-treated stable row for high hall property spring use according to claim 9, characterized by further maintaining and tempering at 400 to 500 ° C for 15 minutes or less. 57 VC, Pr Lx, s $ n A, ‘t‘ ’- - --- ° €, ..,

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