CN100567547C - High-tension heavy steel plate and manufacture method thereof - Google Patents
High-tension heavy steel plate and manufacture method thereof Download PDFInfo
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Abstract
A kind of high-tension heavy steel plate, it is characterized in that, % contains in quality: C:0.02～0.20%, Si:0.2～0.5%, Mn:1～1.8%, Cu and/or Ni: add up to 0.2～1%, surplus is Fe and unavoidable impurities, and, ferrite divides rate: more than the 80 volume %, retained austenite divides rate: more than the 1 volume %, and the amount of the C in the described retained austenite is 0.80～1.10 quality %.
Description
Technical field
The present invention relates to the employed Plate Steel of large structure and the manufacture method thereof of boats and ships etc., particularly relate to intensity and be 490MPa above, be lower than the Plate Steel more than 590MPa (hereinafter referred to as the 490MPa level), the thick about 5mm.
Background technology
If boats and ships collide or boats and ships hit a submerged reef each other, the hull opening that can rupture then, the infiltration sinking, meeting such as lade and fuel outflow and cause pollution of the sea in the ship in addition is so become a social concern.Therefore, proposed variously to collide each other or boats and ships when hitting a submerged reef, can absorb striking energy that hull is subjected to and the hull steel plate that prevents the drawback that destruction caused of hull at boats and ships.
Can excellent hull steel plate as this shock absorption, a kind of steel plate of proposition in patent documentation 1, this steel plate contain 1.0～20% retained austenite (residual γ) in area occupation ratio in the table nexine more than 1/8 of thickness of slab at least.It is known that residual the steel plate of austenite (γ) is arranged is TRIP (Transformation Induced Plasticity, phase change induction plasticity) steel plate, if the TRIP steel plate is implemented machining deformation, then residual γ brings out under stress and becomes martensite mutually, can access from the unit elongation of the excellence of γ with from martensitic high strength.
In above-mentioned patent documentation 1, absorb can (EA) to record and narrate as striking energy and be with the relation of the mechanical characteristics of steel, the unit elongation characteristic of steel plate [unit elongation (E1) fully] is long-pending big more with intensity row (YP, TS), and striking energy absorbs and can (EA) improve more.
But, based on the absorption of complete unit elongation (E1) can evaluation, may not be associated with the evaluation of the security of hull structure, in order to estimate the tensile deformation of the ship hull plate that is supported by stiffening bar under the incomparable long span of distance between the punctuate in tension test, consideration need be estimated (with reference to patent documentation 2) by being considered to the homogeneous unit elongation (the same unit elongation) high with the unit elongation characteristic degree of correlation of ship hull plate.
The TRIP steel plate that is suitable for as building structure etc., the applicant has taken the lead in proposing the technology (with reference to patent documentation 3 and patent documentation 4) of last homogeneous unit elongation rate of the high-tension heavy steel plate of raising 590MPa level.At patent documentation 3,,, make in addition to generate residual γ in the steel, thereby improve the homogeneous unit elongation to guarantee high strength of parent by making structure of steel based on bainite.In patent documentation 4, by with structure of steel as the low temperature phase change bainite to guarantee strength of parent, island martensite body and residual γ are generated, thereby improve the homogeneous unit elongation.
Therefore as above-mentioned patent documentation 3 and patent documentation 4 and do not require the intensity that exceeds necessary limit but with in the steel plate, is that the requirement from the design decides necessary yielding stress at hull, and according to the position of using, the strength grade of steel plate is changed.On the other hand,, only can access about about 15% homogeneous unit elongation, require the further improvement of homogeneous unit elongation in order to adapt to boats and ships according to above-mentioned patent documentation 3 and patent documentation 4 described methods.In addition as the high-tension heavy steel plate of above-mentioned patent documentation 3 and patent documentation 4 described 590MPa levels, also require the tenacity excellent of the heat affected zone (hereinafter referred to as HAZ) when the welding with steel plate for hull.
[patent documentation 1] spy opens flat 11-246934 communique
[patent documentation 2] spy opens the 2001-262272 communique
[patent documentation 3] spy opens the 2002-266048 communique
[patent documentation 4] spy opens the 2003-160835 communique
Summary of the invention
The present invention does in view of such situation, and its purpose is to provide a kind of Plate Steel that is specially adapted to the high intensity level with 490MPa level of boats and ships, the excellent Plate Steel of a kind of homogeneous unit elongation (the same unit elongation).In addition, its purpose also is to provide the also Plate Steel of excellence of weldability (HAZ toughness).Another object of the present invention is in addition, the manufacture method of this Plate Steel is provided.
The so-called of the present invention this high-tensile steel that can solve above-mentioned problem is following this steel, and it contains:
C:0.02～0.20% (the meaning of quality %.Below relevant chemical ingredients all identical),
Si：0.2～0.5％、
Mn：1～1.8％、
Cu and/or Ni: add up to 0.2～1%,
Surplus is Fe and unavoidable impurities, and,
Ferrite divides rate: more than the 80 volume %,
Retained austenite divides rate: more than the 1 volume %, and the amount of the C in the described retained austenite is 0.80～1.10 quality %.
In addition, Plate Steel of the present invention, also contain as other elements:
Ti：0.005～0.025％、
N：0.0015～0.010％、
B:0.0005～0.003%, and the content of above-mentioned Ti, N, B satisfies following formula (1).Wherein in the following formula (1) [] expression element content.
0≤[N]-0.292×[Ti]≤(14/10.8)×([B]-0.0003)…(1)
Described C is preferably 0.02～0.10%.
Plate Steel of the present invention can also contain at least a kind that selects the group who constitutes from following I～III as other elements.
I group:
Among following (a)～(c) at least a kind
(a) Cr:0.5% following (not containing 0%)
(b) Mo:0.2% following (not containing 0%)
(c) more than a kind of selection from the group that V, Nb, Zr, Hf and Ta constitute: add up to and (do not contain 0%) below 0.05%
II group: Al:1% following (not containing 0%)
III group: more than a kind of selection from the group that Mg, Ca, Sr, Ba, Ce and La constitute.
High-tensile steel of the present invention can adopt following manufacturing to make, this method for making comprises first operation that above ferrite of 80 volume % and the above retained austenite of 1 volume % are generated, with second operation in the scope that the amount of the C in the described retained austenite is controlled at 0.80～1.10 quality %, as described second operation, be the temperature range arbitrarily between 500～300 ℃ to be carried out Xu Leng 50～3600 seconds, perhaps kept 50～3600 seconds with the temperature arbitrarily between 500～300 ℃ with the average cooling rate below 1 ℃/second.
According to the present invention,,, can significantly improve the homogeneous unit elongation of Plate Steel so the TRIP effect that residual γ brings is positively brought into play because the amount of the C among the residual γ (C γ R) is suitably controlled.According to the present invention, the one-tenth of suitably having adjusted steel plate is grouped in addition, can improve HAZ toughness even therefore weld also.Plate Steel of the present invention has the high intensity levels of the 490MPa level that is particularly suitable for boats and ships, therefore the former material that for example is used for hull, even just in case crash or when hitting a submerged reef accident, also can prevent hull fracture opening, perhaps make area of fracture than significantly reducing in the past.
Description of drawings
Fig. 1 is the figure that medelling ground shows the thermal process when making Plate Steel of the present invention.
Fig. 2 is the C amount of expression among the residual γ and the graphic representation of the relation of homogeneous unit elongation.
Embodiment
Present inventors are in order to provide the 490MPa level TRIP Plate Steel of homogeneous unit elongation excellence, and the 590MPa level TRIP Plate Steel so that aforesaid patent documentation 3 and patent documentation 4 are recorded and narrated has carried out research with keen determination.Consequently, in order merely directly to use the disclosed residual γ generation method of these patent documentations, and make it to be reduced to the intensity rank that is suitable for boats and ships, even parent phase still can't be obtained ideal homogeneous unit elongation (specifically more than 18%) as soft ferritic structure, but present inventors have got the problem place clear by a large amount of infrastest.
So what present inventors further studied repeatedly found that, (a) by suitably controlling the C amount among the residual γ, can significantly improve the homogeneous unit elongation of 490MPa level TRIP Plate Steel, (b) in order suitably to control the C amount among the residual γ, need be with among the composition in the steel, especially Si is reduced to below 0.5%, and as adding Cu and/or Ni by composition, and after hot rolling according to adjusting cooling conditions in 500～300 ℃ the temperature range closely with the relation of hold-time, thereby finished the present invention.
So in the present invention, the C among the residual γ is measured the scope that is controlled at 0.80～1.10 quality %, the homogeneous unit elongation is just brought up to more than 18%.By the C among the residual γ of suitable control amount,, also can positively bring into play the TRIP effect that residual γ brings even be in the Plate Steel of 490MPa level at intensity rank.The employing accompanying drawing is explained.
Fig. 2 is based on the result of embodiment described later, represents the graphic representation of C amount and the relation of homogeneous unit elongation among the residual γ.Among the figure, the 0th, the No.1 in table 3～table 4～6,13,16～25,35,37～42,44 result, ■ is the No.10,11,14,32,33,34 in table 3～table 4,36 result.Also have in Fig. 2, composition and ferrite branch rate and residual γ branch rate satisfy the example of the scope of the present invention's regulation in the just steel of drafting.
As indicated in Fig. 2,, can significantly improve the homogeneous unit elongation of Plate Steel by the amount of the C among the residual γ is controlled at above-mentioned scope.
In addition, demonstrate, even the cooling conditions after the controlled rolling and generate the residual γ (being more than the 1 volume % specifically) of specified amount, the homogeneous unit elongation that still can't obtain wishing as patent documentation 3 and patent documentation 4.If this compare also and can show with the No.3,6,10,11 of table 3～table 4 among the embodiment described later.These all are that residual γ amount is the example of 5 area %, by composition in the control steel C amount (C γ R) among the residual γ is changed, even but residual γ amount satisfies the scope of the present invention's regulation, and C γ R breaks away from the No.10 and 11 of the scope of the present invention's regulation, and its homogeneous unit elongation all reduces (with reference to following table 4).Below just the present invention be elaborated.
At first, the chemical ingredients for Plate Steel of the present invention describes.Plate Steel of the present invention contains C, Si, Mn and Cu and/or Ni as fundamental element.The content of these elements is as follows.
C：0.02～0.20％
C is used to guarantee the needed element of intensity, particularly, ferrite and residual γ contain for being generated, but the HAZ toughness when improving welding, C is preferably few.Ferrite can generate in a large number but the C amount is lower than at 0.02% o'clock, and the residual γ of specified amount can't generate, so can not improve the homogeneous unit elongation.Therefore C more than 0.02%, is preferably more than 0.03%.On the other hand, if the C amount surpasses 0.20%, then ferritic generation tails off, and the homogeneous unit elongation reduces.Ferrite divides the rate step-down in addition, the toughness deterioration of mother metal.Therefore C is below 0.20%, is preferably below 0.15%, more preferably below 0.12%.HAZ toughness when particularly welding for further raising, C is preferably below 0.10%, more preferably below 0.08%.
Si：0.2～0.5％
Si is when 500～300 ℃ temperature field maintenance, suppresses to decompose to cementite from γ, thereby guarantees the residual γ of specified amount and the important element of the amount of the C among the residual γ.Si is the element that improves the tensile strength of mother metal by solution strengthening in addition.But the Si amount is lower than the decomposition that can not suppress γ at 0.2% o'clock fully, can not fully make to improve the useful residual γ generation in homogeneous unit elongation aspect.Therefore Si is more than 0.2%, is preferably more than 0.25%, more preferably more than 0.30%.On the other hand, Si surpasses 0.5% residual γ and still can generate, but if excessively contain Si, then the C quantitative change among the residual γ of Sheng Chenging gets too much, so the homogeneous unit elongation reduces.In addition, ferrite embrittlement and base metal tenacity deterioration.In addition, the HAZ toughness deterioration after the welding.Therefore Si is below 0.5%.
Mn：1～1.8％
Mn is when 500～300 ℃ temperature field maintenance, suppresses the element of the decomposition of residual γ, and has the effect of the C multiviscosisty that makes among the residual γ.Mn is the element that improves hardenability in addition, also is to be used to guarantee element important on the intensity.But the Mn amount is lower than 1% o'clock intensity becomes not enough, and the C quantitative change of multiviscosisty is few in residual γ, can not improve the homogeneous unit elongation fully.Therefore Mn is more than 1%, is preferably more than 1.2%, more preferably more than 1.3%, more preferably more than 1.4%.On the other hand, if Mn amount surpasses 1.8%, then hardenability becomes excessively so that ferrite is difficult to generate, and it is too high that intensity becomes.In addition, if ferrite divides the rate step-down, also variation of homogeneous unit elongation then.Therefore Mn below 1.8%, is preferably below 1.6%.
Cu and/or Ni: add up to 0.2～1%
Cu is the same with Si and Mn with Ni, is when 500～300 ℃ temperature field maintenance, suppresses the γ decomposition and forms cementite, makes effective element in the residual γ generation.In addition, Cu and Ni make multiviscosisty among the residual γ and the element that improves the homogeneous unit elongation.In addition, Cu and Ni also have effect as the substitute element of Si in the present invention.As described above, the heavy addition of Si can cause the reduction of base metal tenacity, even if also weldability brings detrimentally affect, but according to the present invention, by adding Cu and/or the Ni that has same purpose with Si, still can guarantee the residual γ that expects fully to improve the homogeneous unit elongation even reduce the Si amount.Cu and Ni are contained, and base metal tenacity can be not impaired yet.
Cu and Ni can distinguish separately use or and usefulness, but the total amount of these elements is lower than at 0.2% o'clock, shown in the embodiment, promptly allow to guarantee the residual γ of specified amount as described later, but the C quantitative change among the residual γ is few, still can not fully improve the homogeneous unit elongation.Therefore the total amount of these elements is more than 0.2%, is preferably more than 0.3%, more preferably more than 0.4%.On the other hand, if the total amount of Cu and Ni surpasses 1%, then ferrite is difficult to generate because hardenability becomes very good, thereby can not improve the homogeneous unit elongation.Therefore the total amount of Cu and Ni is below 1%, is preferably below 0.9%, more preferably below 0.8%.
Plate Steel of the present invention contains above-mentioned element, and surplus is Fe and unavoidable impurities.As unavoidable impurities, for example can enumerate P, S and N etc.
P and S are the elements that makes the ferrite embrittlement, and be preferably the least possible.P is preferably below 0.05%, more preferably below 0.04%, more preferably below 0.03%.S is preferably below 0.05%, more preferably below 0.03%, more preferably below 0.02%.
N then is to cause dysgenic element to base metal tenacity and HAZ toughness if exist with solid solution condition, and is preferably the least possible.N is preferably below 0.01%, more preferably below 0.008%, more preferably below 0.005%.
In addition, the form of other of Plate Steel of the present invention also has as other elements and contains Ti, N, B.When Plate Steel of the present invention contained these elements with the state that satisfies certain relational expression, its weldability (HAZ toughness) was more excellent.The content of these elements is as follows.
Ti：0.005～0.025％
Ti combines with N in the Plate Steel and forms the element of TiN, and this TiN is bringing into play the effect (pinning effect) that stops thickization of crystal grain when welding is heated, thereby improves HAZ toughness.But Ti is lower than at 0.005% o'clock, and the growing amount of TiN is few, can not improve HAZ toughness.Therefore Ti is more than 0.005%, is preferably more than 0.007%, more preferably more than 0.008%.On the other hand, if excessively contain Ti, thickization of TiN then, the tough property improvement effect of HAZ can't be brought into play.Therefore Ti is below 0.025%, is preferably below 0.02%, more preferably below 0.018%.
N：0.0015～0.010％
N combines with above-mentioned Ti and forms the element of TiN, and is the same with above-mentioned Ti, is to improve effective element on the HAZ toughness.But N is lower than at 0.0015% o'clock, and the TiN growing amount is few, can not improve HAZ toughness.Therefore N is more than 0.0015%, is preferably more than 0.002%, more preferably more than 0.003%.On the other hand, if excessively contain N, thickization of TiN then, the tough property improvement effect of HAZ can't be brought into play.Therefore N is below 0.010%, is preferably below 0.08%, more preferably below 0.05%.
B：0.0005～0.003％
B suppresses the element that grain boundary ferrite [be called as crystal boundary type ferrite (allotriomorphic ferrite) or just analyse ferrite] generates, and HAZ toughness is improved.The grain boundary ferrite generation can not be suppressed but B is lower than at 0.0005% o'clock, HAZ toughness can not be improved.Therefore B is more than 0.0005%, is preferably more than 0.0008%, more preferably more than 0.0010%.On the other hand, B is excessively contained, it also is saturated suppressing the effect that grain boundary ferrite generates, and excessive in addition B and N etc. combine and form boride, make HAZ toughness deterioration on the contrary.Therefore B is below 0.003%, is preferably below 0.0028%, more preferably below 0.0025%.
The content of above-mentioned Ti, N, B need satisfy following formula (1).Also has the content of [] expression element in the following formula (1).
0≤[N]-0.292×[Ti]≤(14/10.8)×([B]-0.0003)…(1)
If the atomic molar ratio of N and Ti satisfies the relation of 0≤[N]-0.292 * [Ti], then N combines with Ti and is combined into TiN, or is present in the steel as free N.At this moment make the existence of N more excessive, then can make the TiN miniaturization, thereby improve HAZ toughness than the stoichiometry ratio of mixture of Ti.
In addition, if the content of B and N and Ti satisfies by the relation shown in [N]-0.292 * [Ti]≤(14/10.8) * ([B]-0.0003), then in Plate Steel, have the above B of 0.0003 quality % (3ppm) that needs, can suppress the grain boundary ferrite generation as free B.Also have, the 14th, the nucleidic mass of N (nitrogen), the 10.8th, the nucleidic mass of B (boron).
Plate Steel of the present invention can also contain following (a)～(c) at least a kind and the element more than a kind selected as other elements from the group that Al, Mg, Ca, Sr, Ba, Ce and La constituted.
At least a among following (a) and (b), (c): (a) Cr:0.5% following (not containing 0%), (b) Mo:0.2% following (not containing 0%), (c) from the group that V, Nb, Zr, Hf and Ta constitute, select more than a kind: add up to below 0.05% and (do not contain 0%)
Cr, Mo, V, Nb, Zr, Hf and Ta all are the elements that form carbide in steel, act on improving bringing into play effectively on the intensity by separating out intensity.But, then, therefore on the contrary effect of the present invention is caused detrimentally affect owing to can hinder residual γ generation if carbide excessively generates.
Therefore Cr is below 0.5%, is preferably below 0.4%, more preferably below 0.3%.In order to bring into play above-mentioned effect, preferably contain more than 0.02%, more preferably more than 0.05%.
Mo is below 0.2%, is preferably below 0.15%, more preferably below 0.1%.In order to bring into play above-mentioned effect, preferably contain more than 0.02%, more preferably more than 0.04%.
V, Nb, Zr, Hf and Ta add up to below 0.05%, are preferably below 0.04%.In order to bring into play above-mentioned effect, preferably contain more than 0.01%, more preferably more than 0.02%.
Element shown in above-mentioned (a)～(c) can contain separately respectively (for example only contain Cr, only contain Mo, only contain V), also can make up and contain optional element (for example Cr and Mo, Cr and V).
Al:1% following (not containing 0%)
Al suppresses γ to be decomposed to form cementite, the element that works in the residual γ generation that makes specified amount.But if the Al amount surpasses 1%, then solid solution Al increases, the ferrite embrittlement, and the homogeneous unit elongation reduces.Therefore Al is below 1%, is preferably below 0.5%, more preferably below 0.3%.In order to bring into play above-mentioned effect, preferably contain more than 0.02%, more preferably more than 0.025%.
Contain the element of from the group that Mg, Ca, Sr, Ba, Ce and La constitute, selecting more than a kind, add up to below 0.01% and (do not contain 0%)
Mg, Ca, Sr, Ba, Ce and La are the elements that forms fine oxide compound in Plate Steel, and this oxide compound helps to prevent thickization of organizing of HAZ portion when welding is heated, thereby improve HAZ toughness.Add up to surpass 0.01% but these elements are contained, it also is saturated that HAZ toughness improves effect, and oxide amount becomes in addition too much can become the tensile strength that makes mother metal and the reason of toughness deterioration.Therefore above-mentioned element is preferably and adds up to below 0.01%, more preferably below 0.005%, more preferably below 0.003%.In order to bring into play above-mentioned effect, preferably make it to contain more than 0.0005%.
Above-mentioned Mg, Ca, Sr, Ba, Ce and La can contain separately respectively, perhaps also with optional element more than 2 kinds.
Next the tissue for Plate Steel of the present invention describes.Plate Steel of the present invention, containing ferrite branch rate as the parent phase tissue is more than the 80 volume %, containing residual γ as second phase constitution is more than the 1 volume %.
In Plate Steel of the present invention, in order to ensure the tensile strength of 490MPa level, its tissue is based on ferrite.Ferrite is soft, is the high tissue of plasticity-, also helps the raising of homogeneous unit elongation.In order to bring into play such effect, ferrite branch rate is more than the 80 volume %.Ferrite branch rate is preferably more than the 83 volume %, more preferably more than the 86 volume %.But if ferrite excessively generates, tissue becomes single-phaseization of ferrite, and then residual γ does not generate, and the homogeneous unit elongation reduces, so is limited to 99 volume % on it.Be limited to 97 volume % on preferred, be limited to 95 volume % on preferred.
The tissue of Plate Steel of the present invention, generating mutually as second has residual γ.Residual γ is subjected to stress and becomes martensite mutually, utilizes this TRIP effect to make good homogeneous unit elongation performance.In order to bring into play such effect, residual γ branch rate is necessary for more than the 1 volume %.Residual γ branch rate is preferably more than the 2 volume %, more preferably more than the 2.5 volume %.But if residual γ branch rate becomes excessive, the C quantitative change among the then residual γ is few, can make residual γ instabilityization as described later, can not obtain the TRIP effect.Therefore residual γ branch rate is preferably below the 20 volume %, more preferably below the 15 volume %, more preferably below the 10 volume %.
In addition in the present invention, the amount of the C among the residual γ is that 0.80～1.10 quality % is very important.What embodiment confirmed as described later, based on ferrite,, can not improve the homogeneous unit elongation fully as the second residual γ that only generates mutually specified amount.C amount among the residual γ has confidential relation with the stability (the TRIP effect that the generation of residual γ brings) of residual γ, in the present invention in the Plate Steel as the 490MPa level of object, C amount among the residual γ is controlled in above-mentioned scope, and residual γ takes place can bring into play best homogeneous unit elongation when phase transformation is brought out in processing in the front of crest point.That is, when the C amount among the residual γ was lower than 0.80 quality %, it is unstable that residual γ becomes, and residual γ processing takes place easily brings out phase transformation, can not improve the homogeneous unit elongation.Therefore the C amount among the residual γ is more than the 0.80 quality %, is preferably more than the 0.85 quality %, more preferably more than the 0.90 quality %.On the other hand, surpass 1.10 quality % as if the amount of the C among the residual γ, the excessive stabilization of then residual γ, therefore residual γ is difficult to take place to process bring out phase transformation, can not obtain the TRIP effect.Therefore the amount of the C among the residual γ on be limited to 1.10 quality %, be limited to 1.05 quality % on preferred, be limited to 1.00 quality % on preferred.
Plate Steel of the present invention has the above ferrite branch rate of at least 80 volume % and the above residual γ branch rate of 1 volume % gets final product, and also can contain tissue in addition.For example also can generate bainite, martensite and perlite etc.Remaining organizes ratio for example to get final product below 19 volume %, is preferably especially below the 15 volume %.
C amount among the ratio of the tissue of Plate Steel and the residual γ is measured according to the method described in the project of embodiment described later and is got final product.Also have, for the ratio of the tissue of Plate Steel, by microscopic examination measure area occupation ratio be considered to equate with volume fraction.
Plate Steel of the present invention, for example intensity is the 490MPa level, can be applicable to the former material as the large structure that requires the high homogeneous unit elongation and the boats and ships of weldability etc.
The manufacture method of Plate Steel of the present invention can adopt method manufacturing as follows.Promptly, comprise first operation that above ferrite of 80 volume % and the above retained austenite of 1 volume % are generated, with second operation in the scope that the amount of the C in the described retained austenite is controlled at 0.80～1.10 quality %, in described second operation, (a) with the average cooling rate that (does not contain 0 ℃/second) below 1 ℃/second the temperature range arbitrarily between 500～300 ℃ was carried out Xu Leng 50～3600 seconds, perhaps (b) got final product with the temperature arbitrarily between 500～300 ℃ in lasting 50～3600 seconds.
Specifically, after being heated to the single-phase temperature field of γ, the steel that just will have an above-mentioned chemical ingredients carries out hot rolling, when it is cooled off, with the average cooling rate below 2 ℃/second the temperature field arbitrarily between 850～620 ℃ is cooled off, thereby ferrite is generated, Xu Lenghou, be chilled to temperature range arbitrarily between 500～300 ℃ with average cooling rate more than 10 ℃/second, thereby residual γ is generated, behind the chilling, (a) temperature range arbitrarily between 500～300 ℃ is carried out the Xu Leng of specified time with the average cooling rate below 1 ℃/second, perhaps (b) keeps the specified time with the temperature arbitrarily between 500～300 ℃, can in residual γ, make the C multiviscosisty thus, can improve the homogeneous unit elongation of Plate Steel.With reference to accompanying drawing these operations are illustrated.
Fig. 1 is the figure that medelling ground shows the thermal process when making Plate Steel of the present invention.In Fig. 1, adopt water cooling equipment and heat treatment furnace, with the condition shown in the following table 2 rolled stock is handled.Promptly, with average cooling rate R1 (℃/second) with the rolled stock that obtains from Xu Leng begin temperature T 1 (℃) Xu Lengzhi Xu Leng finish temperature T 2 (℃), with average cooling rate R2 (℃/second) from T2 be chilled to Xu Leng begin temperature T 3 (℃), with average cooling rate R3 (℃/second) finish from T3 Xu Leng (comprise with temperature T 3 and keep the homothermic situations) to Xu Leng temperature T 4 (℃).Also have, begin temperature T 1 to Xu Leng from Xu Leng and finish time that temperature T 2 spent, begin time that temperature T 3 to Xu Leng end temperature T 4 are spent as t2 (second) from Xu Leng as t1 (second).
At first, the steel that will have an above-mentioned chemical ingredients is heated to the single-phase temperature field of γ and carries out austenitizing.The single-phase temperature field of so-called γ is about 910～1300 ℃.
After being heated to the single-phase temperature field of γ, following ordinary method and carry out hot rolling.The hot rolled outlet temperature is about 900～800 ℃, and final thickness of slab is to get final product about 5～50mm.
After the hot rolling, with the average cooling rate below 2 ℃/second to the T1～T2 of temperature range arbitrarily between 850～620 ℃ (℃) carry out the Xu Leng of 20 seconds above (t1).This operation is even more important on the ferritic structure of parent phase guaranteeing, surpasses 850 ℃ if Xu Leng begins temperature, and then ferritic growing amount tails off, if the Xu Leng end temp is lower than 620 ℃, then austenite can become perlite and bainite mutually, and ferritic growing amount tails off, and does not generate residual γ.
In addition, if the residence time t1 in the said temperature scope is lower than 20 seconds, then ferritic growing amount tails off.
Above-mentioned temperature range T1～T2 (℃) average cooling rate R1 (℃/second) get final product below 2 ℃/second, be preferably below 1 ℃/second.Average cooling rate R1 also can be 0 ℃/second.In the condition b of the table 2 of embodiment described later, be to keep 30 constant temperature in second (T1=T2) for example with 750 ℃.
After Xu Leng or constant temperature keep, avoid perlite and bainitic transformation, and meanwhile with the average cooling rate more than 10 ℃/second (R2) from temperature T 2 be chilled to temperature T arbitrarily 3 between 500～300 ℃ (℃).Thus, can make not to be phase-changed into ferritic austenite and to become residual γ and generate, and can prevent that the residual γ that generates is phase-changed into perlite and bainite.Average cooling rate R2 is preferably more than 15 ℃/second, more preferably more than 20 ℃/second.
Be chilled to after the temperature T 3, with the average cooling rate below 1 ℃/second (R3) to the T3～T4 of temperature range arbitrarily between 500～300 ℃ (℃) carry out Xu Leng and continue 50～3600 seconds, perhaps carrying out constant temperature with the temperature arbitrarily (T3) between 500～300 ℃ keeps 50～3600 seconds (t2) (at this moment R3 is 0 ℃/second, T3=T4).If Xu Leng begins temperature T 3 or constant temperature keeps beginning temperature T 3 to surpass 500 ℃, pearlitic transformation can take place and residual γ is generated in then residual γ.In addition, even the Xu Leng end temp is lower than 300 ℃, residual γ is generated.
This operation is of crucial importance for the C amount of guaranteeing residual γ.Particularly keep, can begin to obtain above-mentioned C amount (with reference to embodiment described later) by Xu Leng or the constant temperature that continues the specified time (t2) at this temperature field.Also have, in the method that aforesaid patent documentation 3 and patent documentation 4 are recorded and narrated, owing to do not comprise this operation, so think the C γ R that can not obtain to wish.
This temperature range T3～T4 (℃) average cooling rate R3 is above 1 ℃/second down, when perhaps the residence time t2 under this temperature field was lower than 50 seconds, C was insufficient to the multiviscosisty of residual γ, can not improve the homogeneous unit elongation of Plate Steel.Therefore, average cooling rate R3 is below 1 ℃/second, is preferably below 0.5 ℃/second.Average cooling rate R3 also can be 0 ℃/second.Speed of cooling is under 0 ℃/second the situation, carries out constant temperature with temperature T 3 and keeps T3=T4.For example in the condition d of the table 2 of embodiment described later, kept 1800 seconds with 400 ℃ of constant temperature.
In addition, residence time t2 is more than 50 seconds, is preferably more than 100 seconds, more preferably more than 300 seconds.But if residence time t2 surpasses 3600 seconds, then C excessively multiviscosisty in residual γ, residual γ stabilization, the homogeneous unit elongation reduces.Therefore residence time t2 is below 3600 seconds, is preferably below 3000 seconds, more preferably below 2000 seconds.
After 500～300 ℃ temperature fields carry out Xu Leng or constant temperature maintenance, carry out air cooling according to conventional methods and get final product.
[embodiment]
Illustrate in greater detail the present invention by the following examples, but following embodiment does not limit character of the present invention, the scope of stating aim before and after can meeting can suitably change enforcement, and these include in technology art scope of the present invention.
[embodiment 1]
The one-tenth that will be obtained by the melting of small size vacuum smelting furnace is grouped into the steel (surplus is by Fe and unavoidable impurities) that is presented in the following table 1 with 1100 ℃ of heating 30 minutes, carries out hot rolling after becoming austenite one phase.Finishing temperature is 800 ℃, and final thickness of slab is 12.5mm.
Use water cooling equipment and heat treatment furnace, the hot rolling material that obtains is cooled off with the condition shown in the following table 2.T1～T4, t1～t2, R1～R3 and the numbering of attaching on aforesaid Fig. 1 are corresponding in the table 2.
After being cooled to Xu Leng end temperature T 4, air cooling is made Plate Steel (thickness of slab 12.5mm) to room temperature.
By following main points, measure its tissue [the C amount among ferrite branch rate, residual γ branch rate, the residual γ] and mother metal characteristic [yield-point (YP), tensile strength (TS), homogeneous unit elongation (EU), toughness] for the Plate Steel that obtains.Measurement result is presented in following table 3 and the table 4.
[tissue]
In the present embodiment, (a) amount of the C among ferrite branch rate, (b) residual γ branch rate, (c) residual γ is measured at thickness of slab 1/4 position of Plate Steel.But the look-out station of tissue is not limited thereto, and for example also can confirm to generate at thickness of slab 1/2 position and the identical tissue in thickness of slab 1/4 position.
(a) ferrite divides rate
Thickness of slab 1/4 position of mirror ultrafinish Plate Steel is carried out etch (corrosion back) with the test film that forms thus with 3% nital, takes 10 visuals field with opticmicroscope with 400 times.The zone of axle shape such as white is a ferrite in each photo, other zone is second phase and traces designs, (micromedia system " Image-pro ") analyzes it with image analysis software, measures ferritic area occupation ratio, calculates the mean value in 10 visuals field.This ferrite area occupation ratio is a ferrite branch rate.
Also have, the error that the area of the line during for fear of tracing causes, ferrite area occupation ratio utilization following formula calculates.
Ferrite area occupation ratio=[by ferritic area/(total area of the line of the area-tracing of field of view) of the line encirclement that traces designs] * 100
(b) residual γ divides rate (V γ R)
The test film that thickness of slab 1/4 position of Plate Steel has been carried out mirror ultrafinish carries out X-ray diffraction, try to achieve theoretical strength by the peak strength of α-Fe (200) face and γ-Fe (200) face than by calculating according to vertical wave spy (liebert) method, and try to achieve residual γ branch rate.The X-ray diffraction device uses electric system of science " RAD-RU300 ", and target is Co, and the target output rating is 40kV, 200mA.
(c) amount of the C among the residual γ (C γ R)
Has carried out on the test film of mirror ultrafinish at thickness of slab 1/4 position at Plate Steel, as reference material coating Si, the peak of decision Si and residual γ (γ R), with these peak values according to D.J.Dysonetal., Journal of The Iron and Steel Institute, (1970), p469～474 steps of being put down in writing, the lattice parameter a0 of mensuration γ R.The peak value that uses is (111), (200), (220), (311).
The utilization following formula is measured (C γ R) by the C that lattice parameter a0 tries to achieve among the residual γ.
CγR＝(a0-3.578-0.00095×[Mn]+0.0002×[Ni]-0.0006×[Cr]-0.022×[N]-0.0056×[A1]+0.0004×[Co]-0.0015×[Cu]-0.0031×[Mo]-0.0051×[Nb]-0.0039×[Ti]-0.0018×[V]-0.0018×[W])/0.033
[mother metal characteristic]
(a) tension test
Employing is measured yield-point (YP), tensile strength (TS), homogeneous unit elongation (EU) from thickness of slab 1/4 position of Plate Steel, by No. 14 test films (the parallel portion diameter is 10mm) of JIS Z2201 defined based on " the metal material stretching test method " of JIS Z2241 regulation.Trial speed during tension test is 0.5mm/ second.TS is that 490MPa situation above, that be lower than 590MPa is qualified, and UE is that the situation more than 18.0% is qualified.The so-called UE meaning is the stretching of crest point.In addition, the amount of the C among the residual γ is presented among Fig. 2 with the relation of homogeneous unit elongation.
(b) shock test
Employing is from thickness of slab 1/4 position of Plate Steel, by the V nick-break test sheet of JIS Z2202 defined, carries out pendulum impact test based on " the metallic substance impact test method " of JIS Z2242 regulation, measures-40 ℃ of absorption energy (vE-40) down thus.VE-40 is that the above situation of 100J is qualified.
[table 1]
[table 2]
| Condition | T1 [℃] | R1 [℃/sec] | t1 [sec] | T2 [℃] | R2 [℃/sec] | T3 [℃] | R3 [℃/sec] | t2 [sec] | T4 [℃] |
| a | 750 | 1.0 | 30 | 720 | 20 | 400 | 0.0 | 900 | 400 |
| b | 750 | 0 | 30 | 750 | 20 | 400 | 0.0 | 900 | 400 |
| c | 750 | 10 | 30 | 720 | 20 | 400 | 0.0 | 200 | 400 |
| d | 750 | 1.0 | 30 | 720 | 20 | 400 | 0.0 | 1800 | 400 |
| e | 600 | 0 | 30 | 600 | 20 | 400 | 0.0 | 900 | 400 |
| f | 750 | 1.0 | 5 | 745 | 20 | 400 | 0.0 | 900 | 400 |
| g | 750 | 1.0 | 5 | 745 | 20 | 250 | 0.0 | 900 | 250 |
| h | 750 | 1.0 | 200 | 550 | 20 | 400 | 0.0 | 900 | 400 |
| i | 750 | 1.0 | 30 | 720 | 5 | 400 | 0.0 | 900 | 400 |
| j | 750 | 1.0 | 30 | 720 | 20 | 600 | 0.0 | 200 | 600 |
| k | 750 | 1.0 | 30 | 720 | 20 | 250 | 0.0 | 200 | 250 |
| l | 750 | 1.0 | 30 | 750 | 20 | 400 | 0.5 | 300 | 250 |
| m | 750 | 1.0 | 30 | 720 | 20 | 450 | 2.0 | 75 | 300 |
| n | 750 | 1.0 | 30 | 720 | 20 | 400 | 0.0 | 10 | 400 |
| o | 750 | 1.0 | 30 | 720 | 20 | 400 | 0.0 | 5400 | 400 |
[table 3]
[table 4]
Can carry out following investigation by table 3～table 4.No.1～6, No.13, No.16～25, No.35, No.37～42, No.44 all are the examples that satisfy regulation prerequisite of the present invention, because the one-tenth of Plate Steel is grouped into and tissue has been carried out suitably control, so can access the Plate Steel of the 490MPa level of homogeneous unit elongation excellence.
On the other hand, No.7 is the few example of C, though there is ferrite to generate, residual γ growing amount is few, and the homogeneous unit elongation is low.No.8 is the many examples of C, because ferritic generation is few, so the homogeneous unit elongation is low, base metal tenacity is also low.No.9 is the few example of Si, does not generate residual γ.Therefore the homogeneous unit elongation is low.No.10 is the many examples of Si, and the C quantitative change among the residual γ is many, homogeneous unit elongation step-down.Base metal tenacity is also poor in addition.No.11 is the few example of Mn, and the C amount among the residual γ is few, and the homogeneous unit elongation is low.No.12 is the many examples of Mn, because ferrite divides rate little, so that intensity becomes is too high, the homogeneous unit elongation is also low.No.14 is the example that does not contain Cu and Ni, and the C amount among the residual γ is few, and the homogeneous unit elongation is low.No.15 is the many examples of content of Cu and Ni, and ferrite divides rate little, and the homogeneous unit elongation is low.No.36 is the poor example of Cu and Ni, and the C amount among the residual γ is few, and the homogeneous unit elongation is low.
No.26～34, No.43 all are the disengaging examples by recommended range of the present invention of creating conditions, ferrite divides rate low (No.26 and 27, No.43), perhaps do not generate residual γ (No.26,28～31), or the C among residual γ amount can not be controlled in the scope of the present invention's regulation (No.32～34, No.43), so the homogeneous unit elongation is low.
[embodiment 2]
The one-tenth that will be obtained by the melting of small size vacuum smelting furnace is grouped into the steel (surplus is by Fe and unavoidable impurities) that is presented in following table 5 or the table 6 with 1100 ℃ of heating 30 minutes, carries out hot rolling after becoming austenite one phase.Finishing temperature is 800 ℃, and final thickness of slab is 12.5mm.In following table 5 or table 6, utilization following formula (1) is grouped into the value of calculating " [N]-0.292 * [Ti] " and the value of " (14/10.8) * ([B]-0.0003) " according to the one-tenth of steel, and shows this value in the lump.
Use water cooling equipment and heat treatment furnace, the hot rolling material that obtains is cooled off with the condition shown in the following table 7.T1～T4, t1～t2, R1～R3 and the numbering of attaching on aforesaid Fig. 1 are corresponding in the table 7.
After being cooled to Xu Leng end temperature T 4, air cooling is made Plate Steel (thickness of slab 12.5mm) to room temperature.
According to the main points identical, measure its tissue [the C amount among ferrite branch rate, residual γ branch rate, the residual γ] and mother metal characteristic [yield-point (YP), tensile strength (TS), homogeneous unit elongation (EU), toughness] for the Plate Steel that obtains with embodiment 1.In addition, measure HAZ toughness by following main points.Measurement result is presented in following table 8～table 11.
[HAZ toughness]
Heat affected zone (HAZ portion) when welding in order to simulate cools off after 5 seconds continuously with 1350 ℃ of above-mentioned Plate Steels of heating.At this moment from the lasting cooling of 800 ℃ to 500 ℃ temperature field 40 seconds, carry out air cooling thereafter.Cut out the V nick-break test sheet of JIS Z2202 defined behind the air cooling, carry out pendulum impact test, measure-20 ℃ of absorption energy (vE-20) down thus based on " the metallic substance impact test method " of JISZ2242 regulation.VE-20 is that the above situation of 100J is qualified.
[table 5]
[table 6]
[table 7]
| Condition | T1 [℃] | R1 [℃/sec] | t1 [sec] | T2 [℃] | R2 [℃/sec] | T3 [℃] | R3 [℃/sec] | t2 [sec] | T4 [℃] |
| a | 750 | 1.0 | 30 | 720 | 20 | 400 | 0.0 | 900 | 400 |
| b | 750 | 0 | 30 | 750 | 20 | 400 | 0.0 | 900 | 400 |
| c | 750 | 1.0 | 30 | 720 | 20 | 400 | 0.0 | 200 | 400 |
| d | 750 | 1.0 | 30 | 720 | 20 | 400 | 0.0 | 1800 | 400 |
| e | 600 | 0 | 30 | 600 | 20 | 400 | 0.0 | 900 | 400 |
| f | 750 | 1.0 | 5 | 745 | 20 | 400 | 0.0 | 900 | 400 |
| g | 750 | 1.0 | 5 | 745 | 20 | 250 | 0.0 | 900 | 250 |
| h | 750 | 1.0 | 200 | 550 | 20 | 400 | 0.0 | 900 | 400 |
| i | 750 | 1.0 | 30 | 720 | 5 | 400 | 0.0 | 900 | 400 |
| j | 750 | 1.0 | 30 | 720 | 20 | 600 | 0.0 | 200 | 600 |
| k | 750 | 1.0 | 30 | 720 | 20 | 250 | 0.0 | 200 | 250 |
| l | 750 | 1.0 | 30 | 750 | 20 | 400 | 0.5 | 300 | 250 |
| m | 750 | 1.0 | 30 | 720 | 20 | 450 | 2.0 | 75 | 300 |
| n | 750 | 1.0 | 30 | 720 | 20 | 400 | 0.0 | 10 | 400 |
| o | 750 | 1.0 | 30 | 720 | 20 | 400 | 0.0 | 5400 | 400 |
[table 8]
[table 9]
[table 10]
[table 11]
Can carry out following investigation by table 8～table 11.No.1～5, No.7, No.13, No.16～23, No.29～30, No.40, No.42～46, No.48～51, No.53 all are the examples that satisfy the prerequisite of the present invention's regulation, because the one-tenth of Plate Steel is grouped into and tissue has been carried out suitably control, so can access the also Plate Steel of excellent 490MPa level of homogeneous unit elongation height, HAZ toughness.
On the other hand, No.6 is the few example of C, though there is ferrite to generate, residual γ growing amount is few, and the homogeneous unit elongation is low.No.8 is the many examples of C, because ferritic generation is few, so that intensity becomes is too high.The homogeneous unit elongation is low in addition, and base metal tenacity and HAZ toughness are also low.No.9 is the few example of Si, does not generate residual γ.Therefore the homogeneous unit elongation is low.No.10 is the many examples of Si, homogeneous unit elongation step-down.Base metal tenacity and HAZ toughness are also poor in addition.No.11 is the few example of Mn, and the C amount among the residual γ is few, and the homogeneous unit elongation is low.No.12 is the many examples of Mn, because ferrite divides rate little, so that intensity becomes is too high, the homogeneous unit elongation is also low.No.14 is the example that does not contain Cu and Ni, and the C amount among the residual γ is few, and the homogeneous unit elongation is low.No.15 be Cu and-example that the content of Ni is many, ferrite divides rate little, it is too high that intensity becomes, the homogeneous unit elongation is low.No.24～28 all are examples that the content of Ti, B, N breaks away from specialized range of the present invention, and HAZ toughness is low.No.41 is the poor example of Cu and Ni, and the C amount among the residual γ is few, and the homogeneous unit elongation is low.No.47 is that the content of Ti, B, N does not satisfy the example of above-mentioned formula (1), HAZ toughness deterioration.
No.31～39 and No.52 all are the disengaging examples by recommended range of the present invention of creating conditions, ferrite divides rate low (No.31 and 32, No.52), perhaps do not generate residual γ (No.31,33～36), or the C among residual γ amount can not be controlled in the scope of the present invention's regulation (No.37～39, No.52), so the homogeneous unit elongation is low.
Claims (4)
1. high-tension heavy steel plate is characterized in that % contains in quality:
C：0.02～0.20％、
Si：0.2～0.5％、
Mn：1～1.8％、
Cu and/or Ni: add up to 0.2～1%,
Surplus is Fe and unavoidable impurities, and,
Ferrite divides rate: more than the 80 volume %,
Retained austenite divides rate: more than the 1 volume %, and the amount of the C in the described retained austenite is 0.80～1.10 quality %.
2. high-tension heavy steel plate according to claim 1 is characterized in that % also contains in quality:
Ti：0.005～0.025％、
N：0.0015～0.010％、
B：0.0005～0.003％，
And the content of described Ti, N, B satisfies following formula (1),
0≤[N]-0.292×[Ti]≤(14/10.8)×([B]-0.0003)…(1)
In the following formula (1), the content of [] expression element.
3. high-tension heavy steel plate according to claim 2 is characterized in that described C counts 0.02～0.10% with quality %.
4. according to each described high-tension heavy steel plate in the claim 1～3, it is characterized in that, also contain from by at least a kind that selects following I～III was constituted the group in quality %,
I group:
Among following (a)～(c) at least a kind,
(a) Cr:0.5% is following but do not contain 0%
(b) Mo:0.2% is following but do not contain 0%
(c) from the group that V, Nb, Zr, Hf and Ta constitute, select more than a kind: add up to below 0.05% but do not contain 0%,
II group: Al:1% is following but do not contain 0%,
III group: from the group that Mg, Ca, Sr, Ba, Ce and La constitute, select more than a kind, add up to below 0.01% but do not contain 0%.
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| CN108677084B (en) * | 2018-04-08 | 2020-11-03 | 敬业钢铁有限公司 | Production method of low-inclusion clean steel |
| WO2020105406A1 (en) * | 2018-11-21 | 2020-05-28 | Ｊｆｅスチール株式会社 | Steel sheet for cans and method for manufacturing same |
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