CN102796943A - Thin strip steel for thin-wall oil drum and manufacturing method of thin strip steel - Google Patents
Thin strip steel for thin-wall oil drum and manufacturing method of thin strip steel Download PDFInfo
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Abstract
The invention discloses a thin strip steel for a thin-wall oil drum and a manufacturing method of the thin strip steel. Double-roll thin strip continuous production is adopted; a dry ice spray mode is adopted after a cast strip is discharged from a crystallization roll; uniform enhanced cooling is performed on the cast strip; the cast strip is quickly cooled to be below 1,280 DEG C; the cooling rate is 200-300 DEG C/s; in such a cooling mode, separation of coarse BN (Boron Nitride) can be promoted and low-melting-point phase B2O3 and fine AlN (Aluminum Nitride) separation are prevented to fulfill the aims of uniformizing austenite crystal grains and reducing the yield ratio; and then austenite is recrystallized and rolled on line, and the strip steel which is subjected to hot rolling is cooled through anti-oxidation quick cooling, wherein the cooling rate is 80-200 DEG C/s and the coiling temperature is 500-600 DEG C. Through the invention, the thin strip steel for the thin-wall oil drum with low yield ratio and superior impact performance can be obtained. According to the thin strip steel for the thin-wall oil drum produced by the method, the hot thin strip steel can be directly used in place of a cold one, a cold rolling step is removed, and the production cost is greatly reduced.
Description
Technical field
The present invention relates to continuous casting process, particularly a kind of thin-walled oil drum is with strip steel and method of manufacture thereof.
Background technology
In the traditional process Iron and Steel Production; Tin (Sn) is typical residual element or harmful element in the steel; To remove very difficulty and be very expensive of Sn in the steelmaking process fully,, can't thoroughly eliminate basically in case contain Sn in the steel; Can only reduce the content of Sn through the dilution molten steel, these all cause the rising of steel products cost.
In recent years; Because the continuous recycle of steel scrap causes the content of the residual element such as Sn in the steel to raise gradually, the Sn in the steel is prone to segregation element; Be enriched in crystal boundary easily and cause defective generations such as crackle; Therefore in traditional technology the content of Sn element by strictness control, ordinary construction with steel in, the content of Sn is all had clear and definite requirement: Sn (wt%)≤0.005%.
Therefore, if can accomplish " turning harm into good ", will produce active influence to whole metallurgical boundary to residual element such as Sn in the steel (particularly steel scrap); Can realize effective utilization of existing steel scrap or low-quality ore resources inferior (high tin ore) is promoted the recycle of steel, reduce production costs, realize the iron and steel industry Sustainable development.
Traditional strip mostly is to be produced through multi-pass continuous rolling by the strand of the thick 70-200mm of reaching; Traditional hot roll process flow process is: continuous casting+strand reheat insulation+roughing+finish rolling+cool off+batch, promptly at first obtaining thickness through continuous casting is the strand about 200mm, to strand carry out reheat and the insulation after; Carry out roughing and finish rolling again; Obtain thickness generally greater than the steel band of 2mm, at last steel band is carried out the laminar flow cooling and batch, accomplish whole hot rolling production process.If produce thickness less than the 1.5mm steel band of (containing), then difficulty is relatively large, will carry out follow-up cold rolling and annealing to hot rolled strip usually and accomplish.And technical process is long, energy consumption is high, unit equipment is many, the capital construction cost high, causes production cost higher.
The continuous casting and rolling technique of sheet bar flow process is: continuous casting+strand insulation soaking+hot continuous rolling+cool off+batch.The key distinction of this technology and traditional technology is: the slab thickness of sheet bar process is attenuate greatly; Be 50-90mm; Because strand is thin; As long as strand is through 1 ~ 2 passage roughing (when slab thickness is 70-90mm) or need not pass through roughing (when slab thickness is 50mm), and the continuously cast bloom of traditional technology will be through multi-pass be rolling repeatedly, just can be thinned to required specification before the finish rolling; And the strand of sheet bar process is without cooling, directly gets into soaking pit and carries out the soaking insulation, mends temperature perhaps on a small quantity, so sheet bar process shortened technical process greatly, reduced energy consumption, reduced investment, thereby reduced production cost.But CSP since faster cooling rate can cause steel strength to improve; Yield tensile ratio improves, thereby increases rolling load, makes that the thickness specification that can produce hot-rolled product economically also can not be too thin; Yi Ban Wei ≧ 1.5mm; See patent CN200610123458.1, CN200610035800.2 and CN200710031548.2, and these patents all do not relate to element B and Sn.Solve CSP organize thinner and inhomogeneous, the higher problem of yield tensile ratio as one very important problem be suggested.
The technical process shorter than CSP is sheet-band continuous casting and rolling technology; Strip continuous casting technology is a cutting edge technology in metallurgy and the investigation of materials field; Its Iron And Steel Industry that appears as brings a revolution, and it has changed the production process that tradition is controlled steel band in the metal working industry, and will cast continuously, rolling even thermal treatment etc. integrates; Make the strip base of production approach steel band with regard to disposable formation through the online hot rolling of a time; Simplified production process greatly, shortened the production cycle, its processing line length is only about 50m; The also corresponding minimizing of facility investment, product cost significantly reduces, and is a kind of hot rolled thin strip production technique of low-carbon environment-friendly.Twin-roll thin strip continuous casting technology is a kind of principal mode of thin strap continuous casting technology, also is a kind of thin strap continuous casting technology of unique in the world realization industrialization.
The typical technical process of twin-roll thin strip continuous casting is: the molten steel in the big bag through big bag long nozzle, tundish and flow distribution device cast directly over one relatively rotate by two and refrigerative crystallization roller and lateral seal surround fast molten bath in; Molten steel solidifies in the peripheral surface of crystallization roller rotation and forms solidified shell and growth gradually; And then in two crystallization roller gap cracks minimum place (nip point) forms the thick steel band of 1-5mm; Steel band is sent into the strip that is rolled into 0.7-2.5mm in the milling train via guide plate guiding pinch roll; Through the apparatus for supercooling cooling, behind the shear arrangement crop, send into reeling machine at last and batch rolling subsequently.
Adopt thin strap continuous casting to produce the thin-walled oil drum and use steel, because thinner thickness, for the thin size hot-rolled product of thickness less than 1.5mm (containing), thin strap continuous casting technology has stronger manufacturing and cost advantage.The thin-walled oil drum is very big with the consumption of strip steel in worldwide; The hot-rolled sheet state directly product specification characteristic thickness of the supply of material is 1.25mm and 1.5mm; The product specification characteristic thickness of the cold-reduced sheet and the supply of material of cold rolling hot dip galvanizing state is 1.0mm, 1.2mm and 1.5mm; Because product thickness is thinner; Therefore adopt traditional hot continuous rolling process production cost higher, the domestic manufacturer that can stablize the hot-rolled sheet supply of material at present mainly contains Baosteel, Wuhan Iron and Steel Plant and Taiyuan Iron and Steel Co. etc., and a lot of producers are because the capabilities limits of traditional hot-rolling line; The producer of original available hot-rolled sheet supply of material transfers the employing Cold Rolled Sheet Steel to or the cold rolling hot dip galvanizing tole replaces the supply of material, and this has also increased the production cost of thin-walled oil drum with steel.
Hot rolled strip requires very high to strip surface quality when perhaps " with hot Dai Leng " product uses as thin size hot-rolled plate.The thickness of general requirement belt steel surface oxide debris is got over Bao Yuehao; This just need be in the Cast Strip generation of each follow-up stage controlled oxidation iron sheet; In typical process; All adopt the Cast Strip oxidation of confined chamber device preventing at the crystallization roller until the milling train inlet, in the confined chamber device, add hydrogen and in patent US20060182989, control oxygen content, all can control the scale thickness on surface, Cast Strip less than 5% like patent US6920912.But milling train to batch this section course of conveying how the seldom relevant patent of thickness of controlled oxidation skin relate to; Especially adopting laminar flow cooling or spray cooling that the band steel is carried out in the refrigerative process; Pyritous band steel contacts with water coolant, and the scale thickness on surface, Cast Strip increases very fast.Simultaneously, pyritous band steel contacts also with water coolant can bring a lot of problems: one of which, can form water spots (rust staining) at belt steel surface, and influence surface quality; Its two, the water coolant of laminar flow cooling or spray cooling usefulness causes the local inhomogeneous cooling of belt steel surface even easily, causes the inhomogeneous of band steel interior microscopic tissue, thereby causes the inhomogeneous of band rigidity ability, influences quality product; Its three, the local inhomogeneous cooling of belt steel surface is even, can cause the deterioration of plate shape, influences strip shape quality.
But thin strap continuous casting is owing to the fast solidification technology characteristic of itself, the steel grade ubiquity structure refinement of production, the problem that unit elongation is on the low side, yield tensile ratio is higher, formability is bad; Simultaneously the Cast Strip austenite crystal has obvious ununiformity, and the finished product that can cause being obtained behind the austenite phase transformation are organized also inhomogeneous, thereby cause performance of products unstable.Therefore adopt the thin strap continuous casting production line to produce the product with good formability of some automobile industries, petrochemical industry, oil drum manufacturing needs, have certain difficulty.When thin size hot-rolled band steel uses with product made from steel as the thin-walled oil drum; Require steel grade on mechanical property, to have strong preferably plasticity coupling; Have higher unit elongation (unit elongation reaches more than 24%), and on use characteristics, have good punching performance (press depth reaches 9-12mm).In the face of high like this performance requriements; Have certain challenge to adopting thin strap continuous casting to produce this steel grade, therefore, when adopting thin strap continuous casting to produce the thin-walled oil drum with the strip steel; Indiscriminately imitate traditional one-tenth division technique and be and to produce qualified thin-walled oil drum with steel, need on composition and technology, breakthrough be arranged.
Summary of the invention
The object of the present invention is to provide a kind of thin-walled oil drum with strip steel and method of manufacture thereof,, after thin strap continuous casting band steel goes out the crystallization roller, adopt sprinkling dry ice (solid-state CO to band steel both sides through in containing the soft steel composition of Sn, adding micronutrient boron
2) mode the band steel is carried out rapid and uniform cooling, the effect that improves cooling uniformity and cooling intensity and reach anti-oxidation, even austenite crystal tissue, reduction rolling temperature; Adopt the online recrystallize of austenite rolling simultaneously, the online recrystallize of austenite after the realization Cast Strip hot rolling; Adopt anti-oxidation method for rapid cooling can reduce the belt steel surface scale thickness then, improve the belt steel temperature homogeneity, improve strip surface quality.Thin strap continuous casting is when producing this type of steel grade; Can solve the problem that tissue odds is even in the thin strap continuous casting technological process, unit elongation is on the low side, yield tensile ratio is higher, formability is bad; Satisfy request for utilizations such as bending and molding, impact briquetting, thereby satisfy the request for utilization of cold rolling base-material and " with hot Dai Leng " product.
For achieving the above object, technical scheme of the present invention is:
A kind of thin-walled oil drum is used the strip steel, and its chemical component weight per-cent is: C:0.04-0.12%, Si:0.2-0.4%; Mn:0.4-1.0%, P :≤0.055%, S :≤0.008%; N:0.004-0.010%, Al:0.01-0.06%, Sn:0.005-0.04%; B:0.001-0.006%, all the other are Fe and unavoidable impurities.
In chemical composition design of the present invention:
C:C is a strengthening element most economical, the most basic in the steel, improves the intensity of steel through solution strengthening and precipitation strength.C separates out the requisite element of cementite in the austenitic transformation process, so the height of C content determines the intensity rank of steel, the intensity rank that promptly higher C content is corresponding higher to a great extent.But because the gap solid solution of C and plasticity and the toughness of separating out steel have bigger harm, and too high C content is unfavorable to welding property, so C content can not be too high, and the intensity of steel remedies through suitable interpolation alloying element.So the C content range that the present invention adopts is 0.04-0.12%.
Si:Si plays the solution strengthening effect in steel, and adds Si in the steel and can improve purity of steel and deoxidation, but the Si too high levels can cause weldability and welding heat influence area toughness to worsen.So the Si content range that the present invention adopts is 0.2-0.4%.
Mn:Mn is one of the most cheap alloying element of price; It can improve the hardening capacity of steel; In steel, has sizable solid solubility; Through the intensity of solution strengthening raising steel, harmless basically to the plasticity and the toughness of steel simultaneously, be the topmost strengthening element of intensity that improves steel under the C content situation reducing.But the Mn too high levels can cause weldability and welding heat influence area toughness to worsen.So the Mn content range that the present invention adopts is 0.4-1.0%.
P:P can significantly improve the corrosion resistance nature of steel, and can improve intensity.But high-load P increases the cold shortness of steel easily at grain boundary segregation, and welding property is degenerated, and reduces plasticity, and cold-bending property is degenerated.In thin strap continuous casting technology, solidify and the rate of cooling of Cast Strip are exceedingly fast, and can effectively suppress the segregation of P, thereby can effectively avoid the inferior position of P, give full play to the advantage of P, and oil drum is objectively also requiring steel grade to have certain erosion resistance with steel.So in the present invention, adopt P content higher when producing the thin-walled oil drum with steel than traditional technology, suitably relax the content of P element; Cancellation dephosphorization operation in actually operating, does not need painstakingly to carry out the dephosphorization operation in the steel making working procedure; Do not need extra interpolation phosphorus, the scope of P content≤0.055% yet.
S: S is a harmful element in the steel under normal conditions, makes steel produce red brittleness, reduces the ductility and the toughness of steel, when rolling, causes crackle.S also can reduce welding property and erosion resistance.So in the present invention, S also controls as impurity element, its content range is≤and 0.008%.
Al:Al is the element that adds for deoxidation in the steel, and the Al that adds 0.01-0.06% content helps improving the toughness and tenacity of steel.
N: similar with the C element, the N element can improve the intensity of steel through the gap solid solution, and the present invention will utilize N in the steel with the precipitated phase of B effect generation BN, and needing has certain N content in the steel.But the gap solid solution of N has bigger harm to the plasticity and the toughness of steel, and the existence of free N can improve the yield tensile ratio of steel, so N content can not be too high.The N content range that the present invention adopts is 0.004-0.010%.
The Sn:Sn element is acknowledged as the harmful element in the steel, because Sn is prone to segregation element, a spot of Sn will be in the crystal boundary enrichment, and causing is that defective such as crackle takes place, and therefore the content of Sn element is controlled by strictness in traditional technology.Thin strap continuous casting is owing to rapid solidification, and element reduces in interdendritic segregation greatly, can improve the solid solution capacity of element greatly, and therefore under the thin strap continuous casting processing condition, the scope of Sn element can enlarge, and therefore can reduce steel-making cost greatly.Fig. 3 is the relation of Sn element and mean heat flux.Visible by Fig. 3, when the Sn add-on less than 0.04% the time, little to the influence of heat flow density, promptly to the not influence of thin strip solidification process.Fig. 3 is the relation of Sn content and surfaceness.Produce because the crackle on surface, Cast Strip all is the fold place of the surface irregularity in the Cast Strip usually, a situation arises to characterize surface crack with surfaceness.If roughness is big, then the probability of crackle generation is high.Can know by Fig. 4, the increase of Sn content, the surface quality that under the rapid solidification condition, does not have the Cast Strip exerts an adverse impact.Result by Fig. 3 and Fig. 4 can know that Sn does not produce detrimentally affect to solidifying with surface quality of Cast Strip.The content range of Sn is at 0.005-0.04%.
The remarkable effect of B:B in steel is that the boron of denier just can make the hardening capacity of steel be multiplied; Thereby B can preferentially separate out thick BN particle in high temperature austenite suppresses separating out of tiny AlN; Weaken the pinning effect of tiny AlN to crystal boundary; Improve the energy for growth of crystal grain, thus the alligatoring austenite crystal; The B of some solid solution simultaneously gathers partially at austenite grain boundary and has suppressed the ferritic forming core, has reduced ferritic nucleation rate, thereby reaches the effect that reduces yield tensile ratio, improves processability; B can effectively prevent crystal boundary lower melting point B mutually with the combination of N in addition
2O
3Appearance.
B vivaciously is prone to segregation element, gathers partially at crystal boundary easily, and when traditional technology production contained the B steel, the very strictness of the general control of B content was generally about 0.001-0.003%; And in thin strap continuous casting technology, solidify with rate of cooling comparatively fast, and can effectively suppress the segregation of B, the more B content of solid solution, so the content of B can suitably relax; Can also generate thick BN particle through reasonable technique control, suppress tiny AlN and separate out, play the effect of fixed nitrogen, solve the inferior position that band steel yield tensile ratio is higher, formability is bad that thin strap continuous casting is produced.So in the present invention, adopt the B content higher than traditional technology, scope is 0.001-0.006%.
A kind of thin-walled oil drum of the present invention is with the method for manufacture of strip steel, and it comprises the steps:
A) smelt
Smelt according to following chemical ingredients, the molten steel chemical ingredients is: C:0.04-0.12%, Si:0.2-0.4%; Mn:0.4-1.0%, P :≤0.055%, S :≤0.008%; N:0.004-0.010%, Al:0.01-0.06%, Sn:0.005-0.04%; B:0.001-0.006%, all the other are Fe and unavoidable impurities;
B) casting
Adopt twin-roll thin strip continuous casting, continuous casting of molten steel is formed the thick Cast Strip of 1.5-3mm, crystallization roller diameter 500-1500mm, casting rate 60-150m/min;
C) secondary cooling
After thin-belt continuous casting was taken the crystallization roller out of, the Cast Strip temperature was at 1420-1480 ℃, and width is provided with two device for cooling along the Cast Strip in the both sides of Cast Strip, and beginning to cool down of two device for cooling a little is arranged on from nip point 250-750mm, whole two cold but segment length 200-500mm; The Cast Strip goes out to adopt the mode of spraying dry ice that rapid and uniform is carried out in the Cast Strip to the both sides, Cast Strip immediately behind the crystallization roller to be cooled to below 1280 ℃ rate of cooling 200-300 ℃/s;
D) online hot rolling
The cooled Cast Strip of secondary goes out confined chamber after pinch roll will be delivered to the band steel that is rolled into 0.7-2.5mm thickness in the milling train with steel, and rolling temperature 1050-1200 ℃, draft is 20-50%;
E) the band steel rolls postcooling
Band steel after the online hot rolling is rolled postcooling adopt anti-oxidation quick refrigerative mode, dry ice is injected directly on belt steel surface, with the cooling of accelerated band steel, rate of cooling 80-200 ℃/s;
F) strip coiling
Cooled hot rolled strip directly batches rolling, coiling temperature 500-600 ℃ behind the second-rate head of crop shears excision.
Further; Above-mentioned secondary cooling is carried out in the confined chamber under the Cast Strip; The reinforcement method of cooling that adopts injects directly on the surface, Cast Strip with dry ice, and wherein dry ice and rare gas element or nitrogen mixed volume ratio are 5:1 ~ 10:1, and is directly that dry ice blasting is surperficial in the Cast Strip with the pressure of 0.5-5MPa.
Again, hot rolling draft 30-50%.The thickness of steel band is 1.2-2.0mm after the hot rolling.1050-1150 ℃ of hot rolling temperature.
Have, the anti-oxidation quick refrigerative mode of the present invention injects directly on belt steel surface with dry ice again, and wherein dry ice and rare gas element or compressed nitrogen mixed volume ratio are 5:1 ~ 10:1, with the pressure of 0.2-3MPa directly with dry ice blasting at belt steel surface.
In addition, batch two reeling machine forms that adopt.
In method of manufacture of the present invention,
The secondary cooling, after thin-belt continuous casting was taken the crystallization roller out of, the Cast Strip temperature was at 1420-1480 ℃, and width is provided with two device for cooling along the Cast Strip in the both sides of Cast Strip, is used to adopt sprinkling dry ice (solid-state CO to the both sides, Cast Strip immediately behind the band
2) mode rapid and uniform carried out in the Cast Strip be cooled to below 1280 ℃, can significantly improve the cooling uniformity and the cooling intensity of band steel, promote separating out of BN in the steel.
Above-mentioned secondary cooling is carried out in the confined chamber under the Cast Strip, adopts and strengthens method of cooling with dry ice (solid-state CO
2) inject directly on the surface, Cast Strip, to quicken the cooling of Cast Strip, played reduction Cast Strip action of temperature on the one hand, solid-state on the other hand dry ice is sprayed onto hot surface, Cast Strip and can gasifies, and forms highdensity vaporific gas, carbonic acid gas (CO on the surface, Cast Strip
2) belong to a kind of inert atmosphere, can be coated on the surface, Cast Strip, play the anti-oxidation effect in Cast Strip, thereby effectively controlled the growth of Cast Strip surface scale.
The theoretical basis of the BN precipitated phase that the Cast Strip secondary cooling of the present invention's design relates to:
Boron and nitrogen, aluminium and the nitrogen thermodynamical equilibrium equation in γ-Fe is following in the steel:
BN=B+N；Log[B][N]＝-13970/T+5.24 (1)
AlN=Al+N；Log[Al][N]=-6770/T+1.03 (2)
As shown in Figure 2, in the steel BN begin separate out temperature about 1280 ℃, separating out of BN tended to balance in the time of 980 ℃, and this moment separating out just of AlN just begin (AlN separates out temperature about 980 ℃), say that from thermodynamics separating out of BN will have precedence over AlN.Therefore the present invention is through the reasonable technique control means, and promotion B combines with N's, generates thick BN particle, thereby even austenite crystal tissue suppresses tiny AlN and separates out.
Usually; Do not adopt any cooling provision under the thin strap continuous casting in the confined chamber, under the casting situation for a long time, the envrionment temperature of confined chamber is up to more than 800 ℃; The load-bearing under secular high temperature of the confined chamber underframe of steelwork and confined chamber wall is on active service; Can deform, influence the intensity and the precision of whole mechanical framework structure, the danger such as cracking at underframe welding junction place also take place easily.A lot of work are being done by therefore a lot of producers aspect the cooling of confined chamber; Light factory thin strap continuous casting such as Nippon Steel adopts the form of water wall to reach cooling purpose with regard to having reported time confined chamber wall; Concrete scheme is that the confined chamber wall adopts the welding of two block plates down, middle logical recirculated water; The Castrip of U.S. Nucor (seeing patent US5960856A) adopts the form of " water-cooled pillow " to reach cooling purpose; Concrete scheme is from the near slightly place of band steel the water-cooled pillow to be set, and the inside lead to recirculated water, and form (confined chamber) just as in big room is provided with a hot room of septulum (water-cooled is rested the head on and surrounded); The band steel passes the hot room of septulum that the water-cooled pillow surrounds; Temperature is absorbed, and at band steel refrigerative simultaneously, plays the temperature drop effect to big room (confined chamber).The present invention sprays dry ice at the confined chamber inner high voltage, adopts " distillation " physical property of dry ice self, can absorb great amount of heat, when the band steel is realized cool quickly, the temperature of confined chamber is also played the effect of effective cooling; Effective reduction of confined chamber temperature is played cooling effect to the underframe (generally being steelwork) and the confined chamber wall of whole confined chamber, can effectively prevent the distortion of confined chamber underframe.
Online hot rolling, the cooled Cast Strip of secondary go out confined chamber after pinch roll will be delivered to the band steel that is rolled into 0.7-2.5mm thickness in the milling train with steel, and 1050-1200 ℃ of controlled rolling temperature, purpose are austenite generation perfect recrystallization after the assurance hot rolling.Control hot rolling draft is 20-50%, and the hot rolling draught increases can promote austenite recrystallization.
Realize relatively low rolling temperature 1050-1200 ℃ through secondary cooling apparatus, relatively low rolling temperature, for rolling be favourable; Rolling temperature is low more, helps the control of rolling strip shape quality more, in conventional strip technological process; Temperature before the milling train is often up to more than 1200 ℃, even more than 1250 ℃, the band steel of this moment is very soft; Can't apply bigger rolling load, be difficult to effectively rolling.Under the prerequisite that guarantees the online recrystallize of austenite, preferably, rolling temperature 1050-1150 ℃.
The band steel rolls postcooling, and the band steel after the online hot rolling is rolled postcooling, and cooling adopts anti-oxidation quick refrigerative mode with dry ice (solid-state CO
2) inject directly on belt steel surface, to quicken the cooling of steel band, played the effect that reduces belt steel temperature on the one hand, on the other hand CO
2Belong to a kind of inert atmosphere, its proportion is bigger than oxygen, can be coated on belt steel surface, plays the anti-oxidation effect of band steel, thereby has effectively controlled the growth of hot rolled strip surface scale.The problem that this kind type of cooling can avoid traditional laminar flow cooling zone evenly descends the belt steel surface temperature, improves the belt steel temperature homogeneity, thereby reaches the effect of homogenizing interior microscopic tissue; Cooling simultaneously evenly can improve the strip shape quality of band steel; Reduce the scale thickness of belt steel surface, the follow-up pickling when being convenient to do cold rolling base-material.
The present invention adopts high-speed gas to wrap dry ice (CO
2) the injection belt steel surface is used for brokenly phosphorus and strengthens cooling, because dry ice can become CO after touching hot band steel meeting rapid absorption heat
2Gas does not influence strip surface quality and composition so can not embed belt steel surface; In addition, because the quick heat-absorbing action of dry ice can have been played quick cooling effect to band; The more important thing is, become atmospheric carbon dioxide (CO after the dry ice volatilization
2), completely cut off and oxygen (O
2) contact, the restriction strip surface oxide debris further generate.
Strip coiling, cooled hot rolled strip directly batches rolling behind the second-rate head of crop shears excision.The coiling temperature of control hot rolling band is 500-600 ℃, so that the hot rolling band has the tissue signature of bainite.Reeling machine adopts two forms of batching, and guarantees the continuous production of band steel.
The present invention adds the B element in containing the soft steel of Sn, through rational two cold patterns, after thin strap continuous casting band steel goes out the crystallization roller, adopt high pressure to spray dry ice (solid-state CO to band steel both sides
2) mode the band steel is carried out rapid and uniform cooling, the effect that improves cooling uniformity and cooling intensity and reach anti-oxidation, even austenite crystal tissue, reduction rolling temperature; Band steel after rolling adopts anti-oxidation Cooling Mode can reduce the belt steel surface scale thickness, improves the belt steel temperature homogeneity, improves strip surface quality.Thin strap continuous casting can solve the problem that tissue odds is even in the thin strap continuous casting technological process, unit elongation is on the low side, yield tensile ratio is higher, formability is bad, thereby satisfy request for utilizations such as bending and molding, impact briquetting when producing this type of steel grade.
Utilize strip continuous casting technology to produce boracic (B) thin-walled oil drum and use steel, still be not reported up to now, it is following to conclude advantage:
(1) saved slab heating, multi-pass complex process such as hot rolling repeatedly, the online hot rolling of a time is directly carried out in thin Cast Strip, production cost significantly reduces.
(2) Cast Strip thickness itself is thinner, and through the online expected product thickness that is hot-rolled down to, the production of thin slab product need not passed through cold rolling, directly " with hot Dai Leng "; On the other hand, because thinner thickness, when being used for cold rolling base-material, can reduce the passage of follow-up cold rolling attenuate greatly, save production cost greatly.
(3) utilize the steel scrap that contains Sn, the Sn in the steel is accomplished " turning harm into good ", realize effective utilization of existing steel scrap or low-quality ore resources inferior (high tin ore) is promoted the recycle of steel, reduce production costs, realize the iron and steel industry Sustainable development.Add the B element, can solve even, the higher problem of yield tensile ratio of tissue odds in the thin strap continuous casting technological process, thereby satisfy the request for utilization of cold rolling base-material; Be easy to bending, impact briquetting simultaneously.
(4) alloying element taking place and separate out, tends to during the slab reheat dissolve insufficient alloying element utilization ratio that reduces owing to alloying element returns in the traditional technology slab process of cooling.In the thin strap continuous casting technology, the direct hot rolling in high temperature Cast Strip, the alloying element that is added mainly exists with the solid solution attitude, can improve the alloy utilization ratio.
Major advantage of the present invention:
1. adopt thin strap continuous casting explained hereafter thin-walled oil drum use the strip steel, carry out after the hot rolling directly that supply market uses, reach the purpose of the thin size hot-rolled plate supply of material and satisfy that cold rolling base-material requires and " cold with the torrid zone " purpose, can significantly improve the cost performance of strip material.
2. the present invention adopts the boron that adds trace, reaches effective reduction band steel yield tensile ratio, improves the effect of band steel processability, and production cost is obviously cheap than tradition and thin slab production technique.The further simultaneously volume of comprehensive utilization that improves harmful residual element P in the steel, the dephosphorization operation in the cancellation steel-making makes production cost obviously cheap than tradition and thin slab production technique.
3. utilize the steel scrap that contains Sn, the Sn in the steel is accomplished " turning harm into good ", realize effective utilization of existing steel scrap or low-quality ore resources inferior (high tin ore) is promoted the recycle of steel, reduce production costs, realize the iron and steel industry Sustainable development.
4. adopt secondary cooling apparatus to realize relatively low rolling temperature, help online hot rolling, help the control of rolling strip shape quality; Utilize the physics heat-absorbing action of dry ice " distillation " in addition, play effective reduction confined chamber temperature and the effect that prevents the distortion of confined chamber steel structure frame.The iron scale thickness that the anti-oxidation quick cooling in back effectively reduces the hot rolled strip surface is rolled in employing, can improve plate surface quality greatly.
5. the state space of production line has been widened in processing parameter control flexibly rationally, can satisfy the production needs of variant prodn specification.
The difference of the present invention and prior art and improvements:
Mention a kind of method and device of casting black metal strip among the patent EP0830223A1/CN1180325A/US5960856A/DE69700737D; After the band steel solidifies two rollers; The a pair of contactless heat absorber of steel refrigerative that is used to be with is set, is used for the latent heat of solidification that discharges after the absorption band steel solidifies fully.This patent is compared with the present invention; The key distinction is on the cooling intensity, and the method that the present invention adopts high pressure to spray dry ice directly contacts with the strip and forces cooling; Can realize the cooling intensity that 200 ℃/s is above; The cooling performance that is higher than contactless heat absorber far away effectively reduces rolling temperature, helps the raising of rolling strip shape quality.
Patent CN1472019A discloses a kind of method for continuous casting sheet band and device, in crystallization roller exit, high temperature Cast Strip broad ways blowing gas is realized cooling to the Cast Strip.Though this patent can play cooling effect to the Cast Strip; But adopt the gas cooling mode, the span of control of rate of cooling has certain limitation, and this patent adopts high pressure to spray the method for dry ice; Directly contact with the strip and force cooling; Can realize the cooling intensity that 200 ℃/s is above, effectively reduce rolling temperature, help the raising of rolling strip shape quality.
Patent JP-A-5-277654 through the transmission of heat by contact of driven roll and Cast Strip, reaches the cooling effect to the band steel at the driven roll that crystallization roller outlet lower end 300-400mm has increased a pair of external diameter Φ 200mm.The present invention is different fully with the means that this method adopts, and the present invention is through the band steel directly being carried out the method that high pressure sprays dry ice, taking away the band heat of steel.The main drawback of patent JP-A-5-277654 is that cooling intensity is limited, secondly is the speeds match problem of crystallization roller and pony roll, if mate badly, be prone to give a discount in the Cast Strip, and production operation is inconvenient, controls dumb.
Description of drawings
Fig. 1 arranges synoptic diagram for production technique of the present invention.
Fig. 2 is the thermomechanical curve synoptic diagram that BN, AlN separate out.
Fig. 3 is the synoptic diagram that concerns of Sn content and mean heat flux.
Fig. 4 is the synoptic diagram that concerns of Sn content and Cast Strip surfaceness.
Embodiment
Referring to Fig. 1; Technological process of the present invention: molten steel is through big bag 1; Through big bag long nozzle 2, tundish 3 and flow distribution device 4 cast directly over one relatively rotate by two and refrigerative crystallization roller 5a, 5b and side seal board device 6a, 6b surround fast molten bath 7 in; Molten steel solidifies in the peripheral surface of crystallization roller 5a, 5b rotation, and then the formation solidified shell and the thick Cast Strip 11 of the formation 1.5-3mm of minimum place (nip point) in two crystallization roller gap cracks subsequently of growing gradually.Dry ice (solid-state CO is sprayed to 11 both sides, Cast Strip through two device for cooling 8 in confined chamber 10 after going out to be with immediately in the Cast Strip
2), control its rate of cooling, Cast Strip 11 rapid and uniform are cooled to below 1280 ℃.Through swing guide 9, pinch roll 12 hot rolls 13 is delivered in the Cast Strip then, form the hot rolled strip of 0.7-2.5mm after the hot rolling, anti-oxidation quickly cooling device 14 after rolling again is with dry ice (solid-state CO
2) inject directly on belt steel surface; With the cooling of accelerated band steel, controlled chilling speed is after rollgang 15 to shear arrangement 16 crops; Crop is fallen in the flying shear hole 18 along flying shear guide plate 17, and the hot rolled strip behind the crop gets into reeling machine 19,19 ' and batches.After coil of strip taken off from reeling machine, naturally cool to room temperature.
Need not lead to the protection of inert gas Cast Strip in addition in the confined chamber 10 at above-mentioned secondary cooling place, directly utilize and spray the CO that dry ice evaporates
2Gas is realized the protection against oxidation to the Cast Strip.Gas collector 20 is set, to be used for collecting too much high-density CO 2 gas on confined chamber 10.
Embodiment of the invention chemical ingredients is as shown in table 1.Performance behind processing parameter and the hot rolling band cool to room temperature is seen table 2.Comparative Examples 1 is not added the B element in the thin strap continuous casting technology composition; The thin-walled oil drum that Comparative Examples 2 is produced for the traditional hot roll process is used the strip steel, does not add the B element in the composition.
In sum; The thin-walled oil drum that utilizes the thin strap continuous casting Technology to make by steel grades scope of design provided by the invention is used the strip steel, and ys reaches more than the 275MPa, and tensile strength reaches more than the 345MPa; Unit elongation reaches more than 24%; Yield tensile ratio is lower than 0.8, and press depth is more than 10.0mm, and the cold working buckling performance is qualified.Obtain the thin-walled oil drum through the present invention and use the strip steel, can effectively solve the problem that the ubiquitous tissue odds of steel grade is even, yield tensile ratio is higher, formability is bad that thin strap continuous casting is produced, satisfy the thin-walled oil drum with the molded request for utilization of steel drift.
The chemical ingredients (wt.%) of table 1 embodiment steel
The processing parameter and the product performance of table 2 embodiment steel
Claims (8)
1. a thin-walled oil drum is used the strip steel, and its chemical component weight per-cent is: C:0.04-0.12%, Si:0.2-0.4%; Mn:0.4-1.0%, P :≤0.055%, S :≤0.008%; N:0.004-0.010%, Al:0.01-0.06%, Sn:0.005-0.04%; B:0.001-0.006%, all the other are Fe and unavoidable impurities.
2. a thin-walled oil drum is with the method for manufacture of strip steel, and it comprises the steps:
A) smelt
Smelt according to following chemical ingredients, the molten steel chemical ingredients is: C:0.04-0.12%, Si:0.2-0.4%; Mn:0.4-1.0%, P :≤0.055%, S :≤0.008%; N:0.004-0.010%, Al:0.01-0.06%, Sn:0.005-0.04%; B:0.001-0.006%, all the other are Fe and unavoidable impurities;
B) casting
Adopt twin-roll thin strip continuous casting, continuous casting of molten steel is formed the thick Cast Strip of 1.5-3mm, crystallization roller diameter 500-1500mm, casting rate 60-150m/min;
C) secondary cooling
After thin-belt continuous casting was taken the crystallization roller out of, the Cast Strip temperature was at 1420-1480 ℃, and width is provided with two device for cooling along the Cast Strip in the both sides of Cast Strip, and beginning to cool down of two device for cooling a little is arranged on from nip point 250-750mm, whole two cold but segment length 200-500mm; The Cast Strip goes out to adopt the mode of spraying dry ice that rapid and uniform is carried out in the Cast Strip to the both sides, Cast Strip immediately behind the crystallization roller to be cooled to below 1280 ℃ rate of cooling 200-300 ℃/s;
D) online hot rolling
The cooled Cast Strip of secondary goes out confined chamber after pinch roll will be delivered to the band steel that is rolled into 0.7-2.5mm thickness in the milling train with steel, and rolling temperature 1050-1200 ℃, draft is 20-50%;
E) the band steel rolls postcooling
Band steel after the online hot rolling is rolled postcooling adopt anti-oxidation quick refrigerative mode, dry ice is injected directly on belt steel surface, with the cooling of accelerated band steel, rate of cooling 80-200 ℃/s;
F) strip coiling
Cooled hot rolled strip directly batches rolling, coiling temperature 500-600 ℃ behind the second-rate head of crop shears excision.
3. thin-walled oil drum as claimed in claim 2 is with the method for manufacture of strip steel; It is characterized in that; Described secondary cooling is carried out in the confined chamber under the Cast Strip; The reinforcement method of cooling that adopts injects directly on the surface, Cast Strip with dry ice, and wherein dry ice is 5:1 ~ 10:1 with rare gas element or nitrogen mixed volume ratio, and is directly that dry ice blasting is surperficial in the Cast Strip with the pressure of 0.5-5MPa.
4. thin-walled oil drum as claimed in claim 2 is characterized in that with the method for manufacture of strip steel, hot rolling draft 30-50%.
5. thin-walled oil drum as claimed in claim 2 is characterized in that with the method for manufacture of strip steel the thickness of band steel is 1.2-2.0mm after the hot rolling.
6. thin-walled oil drum as claimed in claim 2 is characterized in that with the method for manufacture of strip steel, 1050-1150 ℃ of hot rolling temperature.
7. thin-walled oil drum as claimed in claim 2 is with the method for manufacture of strip steel; It is characterized in that; Anti-oxidation quick refrigerative mode; Dry ice is injected directly on belt steel surface, and wherein dry ice and rare gas element or compressed nitrogen mixed volume ratio are 5:1 ~ 10:1, with the pressure of 0.2-3MPa directly with dry ice blasting at belt steel surface.
8. thin-walled oil drum as claimed in claim 2 is characterized in that with the method for manufacture of strip steel, batches two reeling machine forms that adopt.
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| CN201210317224.6A CN102796943B (en) | 2012-08-31 | 2012-08-31 | Thin strip steel for thin-wall oil drum and manufacturing method of thin strip steel |
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| CN201210317224.6A CN102796943B (en) | 2012-08-31 | 2012-08-31 | Thin strip steel for thin-wall oil drum and manufacturing method of thin strip steel |
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| CN102796943B CN102796943B (en) | 2014-07-23 |
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| CN104607473A (en) * | 2014-12-30 | 2015-05-13 | 山东钢铁股份有限公司 | Rolled workpiece cooling device and method |
| CN105014025A (en) * | 2015-07-23 | 2015-11-04 | 烟台万隆真空冶金股份有限公司 | Production method for copper-nickel-tin alloy strip |
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| CN112404127A (en) * | 2020-11-20 | 2021-02-26 | 广东宝盛兴实业有限公司 | Cold rolling mill and cold rolling process for steel strip |
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| CN104607473A (en) * | 2014-12-30 | 2015-05-13 | 山东钢铁股份有限公司 | Rolled workpiece cooling device and method |
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| CN109844153B (en) * | 2016-10-06 | 2021-02-02 | 杰富意钢铁株式会社 | Steel for crude oil tanker and crude oil tanker |
| CN107245645A (en) * | 2017-05-26 | 2017-10-13 | 宝钢集团新疆八钢铁有限公司 | A kind of system of selection of thin-walled sauce bucket cold-rolled steel sheet and cold-rolled steel sheet |
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| CN112522566A (en) * | 2019-09-19 | 2021-03-19 | 宝山钢铁股份有限公司 | Thin-specification patterned steel plate/strip and manufacturing method thereof |
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| WO2021052317A1 (en) * | 2019-09-19 | 2021-03-25 | 宝山钢铁股份有限公司 | Hot-rolled steel plate/strip for sulfuric acid dew point corrosion resistance and manufacturing method therefor |
| CN112404127A (en) * | 2020-11-20 | 2021-02-26 | 广东宝盛兴实业有限公司 | Cold rolling mill and cold rolling process for steel strip |
| CN114669613A (en) * | 2022-04-19 | 2022-06-28 | 安徽工业大学 | Flexible roller contact type thin belt combined cooling method |
| CN114669613B (en) * | 2022-04-19 | 2023-06-20 | 安徽工业大学 | Flexible roller contact type Bao Daizu cooling method |
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