CN100374586C - High-strength hot-rolled steel sheet excellent in shape fixability and method of producing the same - Google Patents
High-strength hot-rolled steel sheet excellent in shape fixability and method of producing the same Download PDFInfo
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Abstract
A high-strength hot-rolled steel sheet excellent in shape fixability having ferrite or bainite as the phase of the largest volume percentage, satisfying all of the following at least at 1/2 sheet thickness: a mean value of X-ray random intensity ratio in the orientation component group of {100}<011> to {223}<110> to X-ray random diffraction intensity ratio of at least 2.5; a mean value of X-ray random intensity ratio in the three crystal orientation components of {554}<225>, {111}<112>, and {111}<110> to X-ray random diffraction intensity ratio of 3.5 or less; an X-ray intensity ratio to X-ray random diffraction intensity ratio at {100}<011> of at least the X-ray random intensity to X-ray random diffraction intensity ratio at {211}<011>; and an X-ray random intensity ratio to X-ray random intensity ratio diffraction intensity ratio at {100}<011> of at least 2.5, having at least one of an r-value of the rolling direction and an r-value of a direction perpendicular to the rolling direction of not more than 0.7, having an anisotropy DeltauEl of uniform elongation of not more than 4%, having an anisotropy DeltaLE1 of local elongation of at least 2%, and having an DeltauEl of not more than the DeltaLE1.
Description
Technical field
The present invention relates to a kind of have good shape can fixed high-strength hot-rolled steel sheet and production method thereof, described have good shape and can be used for trolley part etc. by fixed high-strength hot-rolled steel sheet, and can alleviate the weight of trolley part effectively.
Background technology
In order to suppress the discharging of carbon dioxide in the automobile, utilize high-strength steel sheet to alleviate the weight of body of a motor car.In addition, in order to guarantee passenger's safety, body of a motor car is not only utilized soft steel sheet, but also utilize high-strength steel sheet.In addition, in order in the future to alleviate the weight of body of a motor car, new requirement proposed to the intensity usage level that improves high-strength steel sheet is very fast.
Yet, when high-strength steel sheet is applied flexural deformation, because high strength, so shape " resilience " phenomenon after processing tends to depart from the shape of forming jig, and return towards the direction of first being processed shape, and sidewall planar " wall warpage " phenomenon since during processing as crooked-crooked result's recovery of elasticity and final surface that forms again with curvature.
Therefore, in conventional body of a motor car, used steel mainly is limited to the high-strength steel sheet that intensity is lower than 440MPa.Concerning body of a motor car, be necessary to adopt intensity to alleviate the weight of vehicle body greater than the high-strength steel sheet of 490MPa.Even now, but there are not resilience and wall warpage seldom and the good high-strength steel sheet of shape stationarity yet.
Much less, but improve high-strength steel sheet or the shape stationarity of soft steel sheet after processing that intensity is lower than 440MPa, all very important to the accuracy of shape that improves automobile, household electrical appliance and other products.
Some contrivers in WO 00/106791, disclose a kind of its 100} plane with but the ratio on 111} plane is at least 1 ferrite steel sheet being used to improve the shape stationarity, but this patent documentation does not describe reducing the wall warpage.Therefore, also undeclared in this patent documentation 100}＜011 〉～223}＜110〉and in the direction component group with respect to X ray at random the diffracted intensity ratio the X ray strength ratio and 100}＜011〉in the direction component with respect to the X ray X ray strength ratio of diffracted intensity ratio at random.
In addition, some contrivers conduct in the uncensored patent gazette of Japan (spy opens) No.2001-64750 is used to reduce the technology of springback capacity, disclose a kind of Cold Rolled Sheet Steel, { the X ray strength ratio of 100} planar reflection is controlled at 3 or bigger wherein will to be parallel to the steel sheet planar.Yet this Cold Rolled Sheet Steel is characterised in that in the outmost surface of steel sheet thickness specifies the X ray strength ratio, therefore is and the diverse steel sheet of the present invention.
In addition, some contrivers in Japan uncensored patent gazette (spy opens) No.2002-363965 and Japanese patent application No.2002-286838 (Japanese uncensored patent gazette (spy opens) No.2004-124123), disclose a kind of have good shape can fixed low yield ratio, high strength steel sheet and production method thereof.
Compare with these inventions, the present invention has studied working condition, but thereby realized more superior shape stationarity, but and obtained the two working condition of shape stationarity and workability thus.
That is to say that the inventor finds that for above-mentioned purpose, control texture and control ductile anisotropy are very important, and as the result that the present invention studies, have found to satisfy the optimum control condition of these requirements.
Summary of the invention
If improve the crooked steel-sheet intensity for the treatment of that is used for trolley part, then springback capacity increases along with the rising of steel sheet intensity, and shape defect occurs, so the use of high-strength steel sheet is being restricted at present.
In addition, good compacting formability and high striking energy absorbability are the key propertys that high-strength steel sheet is used for trolley part etc.
The present invention has fundamentally solved this problem, and provide a kind of have good shape can fixed high-strength hot-rolled steel sheet and production method thereof.
According to general knowledge, as the means that are used to reduce springback capacity and suppress the fixed in shape defective, known reduction steel-sheet yield-point is important.In addition, in order to reduce yield-point, must use steel sheet with low tensile strength.
Yet this is not unique basic solution that is used to improve the steel sheet flexible, reduces springback capacity and minimizing fixed in shape defective.
Therefore, the contriver notices the influence of steel sheet texture to flexible, and sets about the studying in great detail and exploring of role and influence about it, so that improve flexible and fundamentally solve the problem that the fixed in shape defective occurs.As a result, they found a kind of have good shape can fixed steel sheet.
That is to say, the contriver finds, by control 100}＜011 〉～223}＜110〉and in the direction component group with respect to the X ray X ray strength ratio of diffracted intensity at random, especially 100}＜011〉direction component and 111}＜112〉and 111}＜110〉on the direction component with respect to the X ray X ray strength ratio of diffracted intensity at random, and by making r value on the rolling direction and low as far as possible perpendicular in the r value on the direction of rolling direction at least one, and be at least 2% by the anisotropy that makes local elongation, significantly improved flexible.
Yet, bigger if the anisotropy of local elongation becomes, elongation flange formability (the elongated flange formability) variation of expection, but and be difficult to not only obtain the shape stationarity but also obtain formability.Therefore, the contriver has carried out the research of concentrating, and found that, but realizes that simultaneously texture control and carbide control can improve the shape stationarity.
In addition, because heterogeneous steel is effectively for keeping good compacting formability and high impact absorbability, so the contriver has found to be used for most preferably condition of hot rolled from texture control and microstructure control angle.
In addition, do not limit cutting be used to the to be shaped direction of blank of various parts the yield that improves steel is had great role.For this reason, the anisotropic minimizing of ductile anisotropy, especially uniform elongation has great importance.
The contriver found through experiments, temperature by control steel sheet finishing hot rolled starting temperature and end, can make 100}＜011〉direction component is as main direction component development, but and guarantee above-mentioned shape stationarity and formability thus, and reduce the anisotropy of uniform elongation simultaneously.
The present invention is based on above-mentioned discovery, and have following main points:
(1) a kind of have good shape can fixed high-strength hot-rolled steel sheet, wherein ferrite or bainite are the phases of percentage by volume maximum,
At least satisfy all following conditions at 1/2 place of thickness of slab:
(i) 100}＜011 〉～223}＜110〉mean value of X ray random strength ratio of orientation group is 2.5 or bigger,
(ii) 554}＜225 〉, 111}＜112 〉, 111}＜110〉mean value of X ray random strength ratio in three orientation is 3.5 or littler,
(iii) 100}＜011〉the X ray random strength than greater than 211}＜011〉and X ray random strength ratio,
(iv) 100}＜011〉X ray random strength ratio be 2.5 or bigger,
In the r value on the rolling direction be 0.7 or littler perpendicular in the r value on the direction of rolling direction at least one,
The anisotropy Δ uE1 of uniform elongation is 4% or littler,
The anisotropy Δ LE1 of local elongation is 2% or bigger, and
Δ uE1 equals Δ LE1 or less than Δ LE1,
Herein,
ΔuE1＝{|uE1(L)-uE1(45°)|+|uE1(C)-uE1(45°)|}/2
ΔLE1＝{|LE1(L)-LE1(45°)|+|LE1(C)-LE1(45°)|}/2
UE1 (L): the uniform elongation on rolling direction
UE1 (C): uniform elongation in a lateral direction
UE1 (45 °): the uniform elongation on 45 ° of directions
LE1 (L): the local elongation on rolling direction
LE1 (C): local elongation in a lateral direction
LE1 (45 °): the local elongation on 45 ° of directions
(2) as (1) described have good shape can fixed high-strength hot-rolled steel sheet, it is characterized in that diameter is that the occupation rate (occupancy rate) of 0.2 μ m or bigger iron carbide is 0.3% or littler.
(3) as (1) described have good shape can fixed high-strength hot-rolled steel sheet, it is characterized in that aging index AI is 8MPa or bigger.
(4) as (1) described have good shape can fixed high-strength hot-rolled steel sheet, it is characterized in that % meter by weight contains:
C：0.01-0.2％，
Si：0.001-2.5％，
Mn：0.01-2.5％，
P：≤0.2％
S：≤0.03％，
Al：0.01-2％
N :≤0.01%, and
O：≤0.01％
All the other are Fe and unavoidable impurities.
(5) as (4) described have good shape can fixed high-strength hot-rolled steel sheet, it is characterized in that also contain at least a or multiple among Nb, Ti and the V, its total amount % is by weight counted 0.001-0.8%.
(6) as (4) or (5) described have good shape can fixed high-strength hot-rolled steel sheet, it is characterized in that, also contain at least a or multiple in the following element, % meter by weight,
B：≤0.01％，
Mo：≤1％，
Cr：≤1％，
Cu：≤2％，
Ni：≤1％，
Sn：≤0.2％，
Co：≤2％，
Ca：0.0005-0.005％，
Rem：0.001-0.05％，
Mg：0.0001-0.05％，
Ta：0.0001-0.05％。
(7) as (1) described have good shape can fixed high-strength hot-rolled steel sheet, it is characterized in that the % meter contains by weight
C：0.02-0.3％，
Total amount % is by weight counted at least a or multiple in the following column element of 0.1-3.5%:
Mn：0.05-3％，
Ni：≤3％，
Cr：≤3％，
Cu：≤3％，
Mo：≤1％，
Co :≤3%, and
Sn：≤0.2％
Total amount % is by weight counted at least a among the Si of 0.02-3% and the Al or whole two kinds:
Si :≤3% and
Al：≤3％
All the other are Fe and unavoidable impurities, and have heterogeneous structure, and wherein ferrite or bainite are the phases of percentage by volume maximum, and martensitic percentage by volume is 1-25%.
(8) as (7) described have good shape can fixed high-strength hot-rolled steel sheet, it is characterized in that % meter by weight contains at least a or multiple among Nb, Ti and the V, its total amount % is by weight counted 0.001-0.8%.
(9) as (7) or (8) described have good shape can fixed high-strength hot-rolled steel sheet, it is characterized in that, also contain at least a or multiple in the column element down, % meter by weight,
P：≤0.2％，
B：≤0.01％
Ca:0.0005-0.005%, and
Rem：0.001-0.02％。
(10) as (4) or (5) described have good shape can fixed high-strength hot-rolled steel sheet, wherein steel sheet is through plating.
(11) as (7) or (8) described have good shape can fixed high-strength hot-rolled steel sheet, wherein steel sheet is through plating.
(12) a kind of production have good shape can fixed high-strength hot-rolled steel-sheet method, may further comprise the steps:
After being cast as the strand that has as composition as described in (4) or (5), directly this strand is carried out hot rolling, perhaps in a single day this strand is cooled off and then be heated to 1000-1300 ℃ temperature range after this strand is carried out hot rolling, wherein at Ar
3～(Ar
3+ 150) overall compression ratio under ℃ the temperature (roll and prolong ratio, reduction ratio) is 25% or bigger, (1)～(4) that establish an equation under the temperature T FE when temperature T FS when the finishing hot rolling begins and finishing hot rolling finish satisfies simultaneously, and
Will be through the cooling of hot rolled steel sheet, then
In the subcritical temperature T
0With batch described critical temperature T under 400～700 ℃ the temperature
0Shown in decision of steel-sheet chemical ingredients and equation (5) below,
TFE≥Ar
3 (1)
TFE≥800℃ (1’)
TFS≤1100℃ (2)
20℃≤TFS-TFE≤120℃ (4)
T
0＝-650.4×{C％/(1.82×C％-0.001)}+B (5)
Wherein B is obtained by the composition of steel of representing with weight %
B＝-50.6×Mneq+894.3
Mneq＝Mn％+0.24×Ni％+0.13×Si％+0.38×Mo％+0.55×Cr％
+0.16×Cu％-0.50×Al％-0.45×CoA+0.90×V％
Ar
3＝901-325×C％+33×Si％+287×P％+40×Al％
-92×(Mn％+Mo％+Cu％)-46(Cr％+Ni％)
(13) having good shape as (12) described production can fixed high-strength hot-rolled steel-sheet method, it is characterized in that, will be at Ar
3～(Ar
3+ 150) carrying out frictional coefficient at least one mill train of hot rolled in ℃ the temperature range is controlled to be and is not more than 0.2.
(14) a kind of production have good shape can fixed high-strength hot-rolled steel-sheet method, it is characterized in that, to by as (12) described production have the skin-pass that hot rolled steel sheet that good shape can fixed high-strength hot-rolled steel-sheet method be produced applies 0.1-5%.
(15) a kind of production have good shape can fixed high-strength hot-rolled steel-sheet method, may further comprise the steps,
After being cast as the strand that has as composition as described in (7) or (8), directly this strand is carried out hot rolling, perhaps in a single day this strand is cooled off and then be heated to 1000-1300 ℃ temperature range after this strand is carried out hot rolling, wherein at Ar
3～(Ar
3+ 150) overall compression ratio under ℃ the temperature is 25% or bigger, and the temperature T FS when the finishing hot rolling begins, the temperature T FE when the finishing hot rolling finishes and the residual strain Δ ε that calculates satisfy following relationship formula (1)～(4) simultaneously, and
Will be through the cooling of hot rolled steel sheet, then
In the subcritical temperature T
0Be not higher than under 400 ℃ the temperature and batch described critical temperature T
0By the chemical ingredients of steel plate determine and below relational expression (5) shown in:
TFE≥Ar
3℃ (1)
TFS≤1100℃ (2)
Δε≥(TFS-TFE)/375 (3)
20℃≤(TFS-TFE)≤120℃ (4)
T
0＝-650.4×{C％/(1.82×C％-0.001)}+B (5)
Wherein B is obtained by the composition of steel of representing with weight %
B＝-50.6×Mneq+894.3
Mneq＝Mn％+0.24×Ni％+0.13×Si％+0.38×Mo％+0.55×Cr％
+0.16×Cu％-0.50×Al％-0.45×C0％+0.90×V％
Herein,
Ar
3＝901-325×C％+33×Si％+287×P％+40×Al％
-92×(Mn％+Mo％+Cu％)-46(Cr％+Ni％)
The Δ ε equivalent strain ε i given from each pallet (stand) place in rolling n finish rolling stage wherein the time ti between i=1～n, each pallet wherein the rolling temperature Ti of i=1～n-1, time tn, each pallet from last pallet to the cooling beginning wherein i=1～n and constant R=1.987 try to achieve, wherein ti, tn are unit with the second, Ti is a unit with K (Kelvin)
α＝Δε1+Δε2+...+Δεn
Herein, Δ ε i=ε i * exp{-(ti
*/ τ n)
2/3}
τi＝8.46×10
-9×exp{43800/R/Ti}
ti
＊＝τn×{ti/τi+t(i+1)/τ(i+1)+...+tn/τn}。
(16) having good shape as (15) described production can fixed high-strength hot-rolled steel-sheet method, it is characterized in that, will be at Ar
3～(Ar
3+ 150) carrying out frictional coefficient at least one mill train of hot rolled in ℃ the temperature range is controlled to be and is not more than 0.2.
(17) a kind of production have good shape can fixed high-strength hot-rolled steel-sheet method, it is characterized in that, to by as (15) described production have the skin-pass that hot rolled steel sheet that good shape can fixed high-strength hot-rolled steel-sheet method be produced applies 0.1-5%.
Embodiment
Below, will describe content of the present invention in detail.
In the steel sheet plane at 1/2 thickness of slab place 100}＜011 〉～223}＜110〉and the group X ray with The mean value of machine strength ratio:
When in steel sheet mid-depth position the steel sheet plane being implemented X-ray diffraction and obtain strength ratio with respect to each direction component of randomized specimen, 100}＜011 〉～223}＜110〉mean value of direction component group must be at least 2.5.If this mean value is less than 2.5 or littler, but shape stationarity variation then.
Be included in main direction component in the direction component group and be 100}＜011,116}＜110 〉, 114}＜110 〉, 113}＜110 〉, 112}＜110 〉, 335}＜110〉and 223}＜110 〉.
Can obtain in these direction components with respect to the X ray X ray random strength ratio of diffracted intensity at random according to three-dimensional texture, described three-dimensional texture is calculated by vector method or Series Expansion Method, described vector method is based on { 110} pole graph, described Series Expansion Method utilize pole graph { 110}, { 100}, { 211} and { a plurality of (it is desirable to 3 or more) pole graph among the 310}.
For example, for by in the above-mentioned crystal orientation component that calculates of one method of back with respect to X ray at random the X ray random strength of diffracted intensity compare, can under the situation that does not add modification, use in the three-dimensional texture intensity at (001) [1-10], (116) [1-10], (114) [1-10], (113) [1-10], (112) [1-10], (335) [1-10] and (223) [1-10] of φ 2=45 ° cross-section.
The direction component group 100}＜011 〉～223}＜110〉and mean value be the arithmetical mean ratio of all above-mentioned direction components.In the time can not obtaining the intensity of all these direction components, can with direction component 100}＜011 〉, 116}＜110 〉, 114}[110], 112}＜110〉and 223}＜110〉and the arithmetical av of intensity replace.
In addition, preferential direction component group 100}＜011 〉～223}＜111〉and in respect to X ray at random the mean value of the X ray random strength ratio of diffracted intensity be 4.0 or bigger.
Three crystal orientation components in steel sheet plane, 1/2 thickness of slab place 554}＜225 〉, 111}＜112〉and 111}＜110〉and the mean value of X ray random strength ratio:
Three crystal orientation components in the steel sheet plane at 1/2 thickness of slab place 554}＜225 〉, 111}＜112〉and 111}＜110〉and in respect to X ray at random the mean value of the X ray random strength ratio of diffracted intensity should be 3.5 or littler.If this mean value is 3.5 or bigger, though then the direction component group 100}＜011 〉～223}＜110〉and in intensity suitable, but also be difficult to obtain good shape stationarity.
Can calculate according to the three-dimensional texture that calculates according to the method described above 554}＜225 〉, 111}＜112〉and 111}＜110〉and locate with respect to the X ray X ray random strength ratio of diffracted intensity at random.
In addition, preferred 554}＜225 〉, 111}＜112〉and 111}＜110〉and locate with respect to X ray at random the arithmetical av of the X ray random strength ratio of diffracted intensity be 2.5 or littler.
In steel sheet plane, 1/2 thickness of slab place 100}＜011〉with 211}＜011〉X ray located with The machine strength ratio:
In steel sheet plane, 1/2 thickness of slab place, and 100}＜011〉locate with respect to X ray at random the X ray random strength ratio of diffracted intensity must be at least 211}＜011〉and locate with respect to the X ray X ray random strength ratio of diffracted intensity at random.If 211}＜011〉and locate with respect to X ray at random diffracted intensity the X ray random strength than greater than 100}＜011〉and locate with respect to the X ray X ray random strength ratio of diffracted intensity at random, then the anisotropy of uniform elongation becomes bigger and the formability variation.
Should be noted that mentioned herein to 100}＜011〉and 211}＜011〉as bearing range with effect same, allow be with the perpendicular direction (horizontal direction) of rolling direction as rotation ± 12 °, more preferably ± 16 °.
But needn't know when X ray intensity is for bending machining in the above-mentioned crystal orientation component the shape stationarity or for the anisotropy important reasons very of elongation, but can estimate that the slip behavior of xln has certain contact during flexural deformation.
The sample that is used for X-ray diffraction (mensuration) is prepared by following method: by mechanical mill etc. steel sheet is reduced to predetermined steel sheet thickness; Eliminate strain and make the plane at steel-sheet 1/2 thickness place become measurement plane simultaneously by methods such as chemical grinding, electrolytic polishings then.
When in having segregation line, defective etc. in the steel-sheet mid-depth layer and measuring, going wrong, can be by adjusting sample according to the method described above so that the suitable plane in the 3/8-5/8 of thickness of slab scope becomes measurement plane measures.
Very natural, if the qualification of X ray intensity is not only satisfactory near 1/2 thickness of slab the time, and also also satisfactory at thickness as much as possible (especially from outermost layer to 1/4 thickness of slab), but then the shape stationarity can become better.
Should be pointed out that by hkl}＜uvw〉the crystal orientation representation in components of expression: steel sheet planar normal direction and＜hkl〉parallel, and rolling direction and＜uvw parallel.
The r value (rL) of rolling direction and perpendicular to the r value (rC) of the direction of rolling direction:
Above-mentioned two r values are all very important in the present invention.That is to say that the contriver studies the present invention, the result recognizes: even the X ray intensity of above-mentioned crystal orientation component is suitable, obtain good shape stationarity surely but also differ.
In above-mentioned X ray intensity, must make among rL and the rC at least one is 0.7 or littler, more preferably is 0.55 or littler.
Under the situation of the lower limit that does not limit rL and rC especially, can obtain effect of the present invention.The r value is assessed by the tension test of having used No. 5 tension test sheets of JIS (Japanese Industrial Standards).
Tension strain is generally 15%, but when uniform elongation less than 15% the time, should be in the uniform elongation scope assess by the strain near 15% as far as possible.
It is different and different to should be noted that bending direction is looked the parts of processing, therefore be not particularly limited, but preferred main vertically or along the direction bending steel sheet of the direction that approaches vertical little r value.
Yet usually, known texture is relevant with the r value, but in the present invention, with the relevant qualification of the X ray strength ratio of diffracted intensity and the limiting meaning relevant with the r value are different at random with respect to X ray in the crystal orientation component.Do not satisfy this two kinds of qualifications simultaneously, but just can not obtain good shape stationarity.
Prolong the anisotropy of (exhibition) property:
When the press forming steel sheet, the steel-sheet uniform elongation-be that the n value has great importance.Especially, in being mainly used in the high-strength steel sheet that punching stretch is shaped, when uniform elongation (n value) when having anisotropy, must be carefully according to the selected direction of downcutting blank of parts, thus make productivity low and make the decline of steel-sheet yield.
In addition, in some cases, can not make steel sheet form desirable shape.
In the steel sheet of tensile strength,, can know that then it has shown the good formability that is independent of direction if the anisotropy Δ uE1 of uniform elongation is 4% or littler greater than about 400MPa (resulting maximum strength in tensile strength).
When the strict especially formability of needs, preferred anisotropy Δ uE1 is not more than 3%.
The lower limit of the anisotropy Δ uE1 of uniform elongation does not limit especially, but from the formability viewpoint, most preferably is 0%.
In addition, if the anisotropy Δ LE1 of local elongation less than 2%, but therefore shape stationarity variation then makes the following of Δ LE1 be limited to 2%.The upper limit of Δ LE1 is not set especially, if but Δ LE1 is too big, and then formability descends, so the upper limit is preferably 12%.
Yet, even satisfy above-mentioned condition, but when Δ uE1＞Δ LE1, still can not obtain good formability and shape stationarity simultaneously, therefore make Δ uE1 be not more than Δ LE1.
Should be noted that the elongation that utilizes direction (L direction), vertical direction (C direction) and the 45 ° directions parallel with rolling direction is defined as follows the anisotropy of uniform elongation and local elongation:
ΔuE1＝{|uE1(L)-uE1(45°)|+|uE1(C)-uE1(45°)|}/2
ΔLE1＝{|LE1(L)-LE1(45°)|+|LE1(C)-LE1(45°)|}/2。
Microstructure:
In the trolley part of reality, but not only problem in the parts by stating shape stationarity that bending causes.Sometimes be subjected to extending flange, reaming crimp/deburring or other processing at other position of same parts, therefore, can find much to require punching stretch to be shaped, to draw/twist or the situation of the compacting formability that other is good.
Therefore, but except during being used to control the bending machining of texture, improving the shape stationarity, also must improve the hole extendability and the compacting formability of steel sheet self.
From this viewpoint, the steel-sheet microstructure should be to have the phase microstructure as the percentage by volume maximum of the ferrite or the bainite of high hole extendability.Yet from the texture viewpoint, the bainite that generates by low-temperature transformation makes that mutually the development of texture is stronger, therefore preferably makes bainite become principal phase.
Should be noted that said bainite can comprise or can not comprise the iron carbide particle herein in microstructure.In addition, make the remarkable variation of ductility at transformation ferrite post-treatment and that have high inside dislocation desity (through the ferrite of processing), and be not suitable for component processing, therefore have any different with ferrite of the present invention.
In addition, the contriver finds, the feature of steel plate of the present invention comprises having 1% martensite in the steel sheet at least to reduce yield ratio, and most preferably at least one among rL and the rC is not more than 0.7, to be used for satisfying the raising to the punching stretch formability.
At this moment, if martensitic percentage by volume surpasses 25%, steel-sheet intensity is improved surpass required degree, and the ratio of martensite that is connected in the network is increased, therefore thereby the remarkable variation of steel-sheet formability is with 25% maximum value that is decided to be the martensite percentage by volume.
In addition, be to realize reducing by martensite the effect of yield ratio, when maximum volume is percentile when being ferrite mutually, preferred martensitic fraction values is at least 3%; And when maximum volume is percentile when being bainite mutually, preferred martensitic fraction values is at least 5%.
In addition, when the percentile phase of maximum volume is not ferrite or bainite, thereby the intensity of steel improves above required degree formability variation, perhaps unwanted carbide precipitation makes it can not guarantee the martensite of necessary amounts, thereby the remarkable variation of steel-sheet formability, so percentile ferrite or the bainite of being limited to mutually of maximum volume.
In addition, even when being cooled to room temperature, contain the residual austenite of not finishing transformation, to effect of the present invention also without any big influence.Yet, if the percentage by volume by discovery residual austenites such as reflection x-ray methods increases, then yield ratio raises, so the percentage by volume of residual austenite preferably is not more than the twice of martensite percentage by volume, more preferably no more than martensitic percentage by volume.
In addition, making the diameter of elongation flange formability remarkable variation is that the occupation rate of 0.2 μ m or bigger iron carbide is preferably limited to 0.3% or littler.The occupation rate of iron carbide also can be replaced by the iron carbide area percentage that draws by picture processing in amplifying 500 times light micrograph at least.In addition, the lattice that also can find out on photo to be painted is counted among the n by 0.2 μ m or the bigger shared lattice of the iron carbide m that counts, and with m/n as occupation rate.
Aging index AI:
The ageing Index A I of expression steel sheet is preferably 8MPa at least.If AI is less than 8MPa, but then the shape stationarity descends, therefore 8MPa is decided to be lower limit.But the reason of shape stationarity variation it be unclear that when AI descends, but AI is relevant with the activity bit dislocation density in the steel sheet, therefore can think that the difference of activity bit dislocation density has certain influence to distortion.
The upper limit of AI is not particularly limited, if but AI greater than 100MPa, tension strain then occurs, thereby easily significantly damage the steel-sheet outward appearance, so AI is preferably and is not more than 100MPa.
Should be understood that, aging index is to measure like this: No. 5 tension test sheets of JIS that use L direction or C direction, and with the difference of deformation stress and yielding stress as aging index AI, described deformation stress is the deformation stress when applying 10% prestrain, in a single day described yielding stress is for removing the timeliness that carried out 1 hour the load back under 100 ℃, and then the yielding stress when carrying out tension test (when surrender taking place stretch, lower yielding stress).
Below, preferred chemical ingredients of the present invention will be described.The unit of should be pointed out that is quality %.
At first, explanation is had ferrite wherein or bainite be the percentage by volume maximum phase microstructure and have good shape can fixed high-strength hot-rolled steel-sheet chemical ingredients.Should be noted that in above-mentioned steel sheet, the hole extendability is also good.
C：
The following of C is limited to 0.01%, because be lower than under 0.01% situation at C, is difficult to guarantee steel-sheet intensity when keeping high formability.On the other hand, if C content is higher than 0.2%, then form the austenite phase or martensitic phase and the coarse grain carbide that reduce the hole extendability easily, weldability also descends in addition, therefore will be defined as 0.2% on the C content.
Si：
Si is the effective element that is used to improve the steel sheet physical strength, if but Si content is higher than 2.5%, and then therefore formability variation or surface spots occurs is decided to be the upper limit with 2.5%.On the other hand, in the steel of reality, be difficult to make Si content, therefore be decided to be lower limit 0.001% less than 0.001%.
Mn：
Mn is the effective element that is used to improve the steel sheet physical strength, if but Mn content surpasses 2.5%, and then therefore the formability variation is decided to be the upper limit with 2.5%.On the other hand, in the steel of reality, be difficult to make Mn to be lower than 0.01%, therefore be decided to be lower limit 0.01%.
In addition, except that Mn, when fully adding the Ti that is used to suppress the hot tearing that caused by S and other element, wish to add a certain amount of Mn, addition is counted Mn/S 〉=20 by quality %.
P，S：
The addition of P and S is not more than 0.2% and 0.03%.This is in order to prevent in hot rolling or formability variation or crack when cold rolling.
Al：
The Al of interpolation at least 0.01% is to be used for deoxidation.Yet, if the amount of Al is too big, can becomes second nature and reduce and the surface property variation, therefore will be defined as 2.0% on the Al.
N，O：
These elements are impurity.For preventing the formability variation, the amount of N and O is decided to be respectively is not higher than 0.01% and be not higher than 0.01%.
Ti，Nb，V：
These elements are by improve the element of material quality such as mechanism such as precipitation strength, texture control, saccharoid reinforcements.As required, preferably above-mentioned one or more elements are added to become to add up at least 0.001%.
Yet, even add the excessive unusual effect that also do not have.On the contrary, can make formability and surface property variation, therefore the total amount upper limit with above-mentioned one or more elements is set at 0.8%.
B：
B is effective for strengthening the grain boundary and improving steel strength, if but the addition of B surpasses 0.01%, then not only effect is saturated, and steel-sheet intensity is raise above required degree, thereby cause the parts formability to descend, therefore will be defined as 0.01% on the B.Yet, for realizing the additive effect of B, preferred interpolation at least 0.002%.
Mo，Cr，Cu，Ni，Sn，Co：
These elements have the effect that improves physical strength or improve material quality, therefore preferably as required every kind of element are added at least 0.001%.Yet, add excessive meeting and make the formability variation, therefore the upper limit with Mo, Cr, Cu, Ni, Sn and Co is decided to be 1%, 1%, 2%, 1%, 0.2% and 2% respectively.
Ca, Rem (rare earth element):
Therefore suitably these elements are the effective elements that are used to control inclusion, add and can improve hot formability, excessively can aggravate thermal embrittlement on the contrary but add, so as required the amount of Ca and Rem are decided to be 0.0005%-0.005% and 0.001%-0.05%.Herein, " rare earth element " is meant Y, Sr and lanthanon, and industrial be the mixture of above-mentioned element.
In addition, add the Mg of 0.0001%-0.05% and the Ta of 0.001%-0.05% and also have equal effect.
Here, in all cases, lower limit all be expressed as the performance Control and Inclusion Removal effect and add minimum.Surpass maximum value, inclusion can be grown too much on the contrary, and the others of therefore extending flange formability and hole extendability all reduce.It rationally is favourable adding for cost as mishmetal (mixture).
Below, with explanation have ferrite wherein or bainite be the percentage by volume maximum phase microstructural heterogeneous structure and comprise percentage by volume be the martensite of 1-25% and have good shape can fixed high-strength hot-rolled steel-sheet chemical ingredients.
Should be noted that above-mentioned steel sheet is a kind of low yielding ratio steel sheet.
C：
C is the most important element of decision steel strength.Contained martensite percentage by volume tends to increase along with the rising of C concentration in the steel sheet in the steel sheet., when adding C amount is lower than 0.02%, will be difficult to obtain hard martensite herein, and therefore be decided to be institute and add the lower limit that C measures 0.02%.
In addition, surpass 0.3% if institute adds C amount, then not only steel-sheet intensity is elevated to greater than required degree, and as the remarkable variation of weldability of the key character of automobile steel material, is defined as 0.3% on therefore will adding C amount,
Mn, Ni, Cr, Cu, Mo, Co and Sn:
Adding Mn, Ni, Cr, Cu, Mo, Co and Sn all is in order to regulate the microstructure of steel.Especially, when when the weldability viewpoint limits the addition of C, adding these an amount of elements is effective to the hardenability of regulating steel effectively.
In addition, although these elements do not reach the content range of Al and Si, have and suppress the effect that cementite produces, and can control martensitic percentage by volume effectively.In addition, these elements have by strengthening the function of matrix ferrite or the bainite anti-dynamic deformation under being lifted at a high speed with sosoloid with Al and Si.
Yet when one or more the total addition level in these elements is lower than 0.1% or Mn content when being lower than 0.05%, required martensite percentage by volume will no longer can be guaranteed, make the intensity step-down of steel, and may not effectively alleviate the weight of body of a motor car again, therefore, the following of Mn content is defined as 0.05%, the following of total addition level of one or more elements in the above-mentioned element is defined as 0.1%.
On the other hand, when above-mentioned total addition level surpasses 3.5%, when any content among Mn, Ni, Cr, Cu and the Co surpasses 3%, when Mo content surpasses 1% or when Sn content surpasses 0.2%, matrix ferrite or bainite sclerosis reduce the formability of steel, toughness reduces and steel product cost increases thereby the capital makes, therefore, to be defined as 3.5% on the above-mentioned total addition level, to be defined as 3% on Mn, Ni, Cr, Cu and the Co content, to be defined as 1% on the Mo content, and will be defined as 0.2% on the Sn content.
Al，Si：
Al and Si are ferritic stabilizers, and play by increasing the ferrite percentage by volume and improve the effect of steel formability.In addition, Al and Si suppress the generation of cementite, therefore can suppress bainite or comprise the generation of other phase of carbide, and can cause martensitic generation effectively.
As the interpolation element with these functions, except Al and Si, that can mention has P or Cu, Cr, a Mo etc.Suitably add these elements and also can produce similar effects.
Yet, when the total amount of Al and Si is lower than 0.05%,, and can not obtain suitable martensite percentage by volume to the inhibition effect deficiency of cementite generation, therefore Al and the following of Si one of them or the two total amount are defined as 0.05%.
In addition, when a kind of or whole two kinds total amount among Al and the Si surpasses 3%, can make matrix ferrite or bainite hardening or become fragile, make the formability of steel to reduce, toughness reduces and steel product cost is increased, therefore but chemical treatment properties and the remarkable variation of other surface treatment characteristics are defined as 3% with on a kind of or whole two kinds among Al and the Si.
Nb，Ti，V：
These elements are by improving material quality such as mechanism such as fixed carbon and nitrogen, precipitation strength, texture control, saccharoid reinforcements.As required, preferably the total amount of one or more above-mentioned elements is added at least 0.001%.In addition,, but can when hot rolling, easily form the texture favourable, therefore preferably initiatively utilize this point the shape stationarity by interpolation Nb or Ti.Yet, add excessive meeting and make the formability variation, therefore will be defined as 0.8% on added one or more element total amounts.
P：
P is to improving steel strength and as mentioned above to guaranteeing that martensite all is effectively, if but addition surpasses 0.2%, then can make the stress corrosion dehiscence resistant variation or make fatigue characteristic and the toughness variation, therefore will on be defined as 0.2%.Yet in order to realize additive effect, the amount of preferred inclusion is 0.005% or more.
B：
B is effectively for strengthening the grain boundary and improving steel strength, if but the amount of B surpasses 0.01%, then not only effect is saturated, and steel-sheet intensity is brought up to greater than required degree, thereby the parts formability is descended, therefore will on be defined as 0.01%.Yet for realizing additive effect, preferred content is at least 0.0005%.
Ca，Rem：
These elements improve elongation flange formability by the formation of control sulfide, therefore preferably add 0.0005% or more and 0.001% or more as required respectively.Even it is excessive to add, do not have significant effect yet and cost uprised, therefore will add Ca and Rem on be defined as 0.005% and 0.02%.
N：
As C, N is to causing that martensitic generation is effectively, but tends to make the toughness and the ductility variation of steel simultaneously, therefore preferably makes the amount of N be not more than 0.01%.
O：
O forms oxide compound, and makes hole extendability variation as inclusion, and described hole extendability represented by the elongation flange formability of the formability of steel especially steel or fatigue strength or toughness, therefore preferably the amount of O is controlled to be and is not more than 0.01%.
Below production method of the present invention will be described.
Slab reheat temperature:
The steel of adjusting to predetermined composition is cast, in a single day directly hot rolling then perhaps is being cooled to Ar
3Carry out hot rolling after transition temperature or lower and then the heating.When at this moment the reheat temperature is lower than 1000 ℃, will be difficult to guarantee the finishing hot rolling terminal temperature be scheduled to therefore the following of reheat temperature is defined as 1000 ℃.
In addition, when adding temperature above 1300 ℃ again, the industrial scale during because of heating causes the yield variation, and production cost is increased, and therefore will be defined as 1300 ℃ on the reheat temperature.
Even the slab local midway or all heating in hot rolling through heating do not have any influence to feature of the present invention yet.
Hot-rolled condition:
By hot rolling and subsequently cold rolling steel sheet is controlled to predetermined microstructure and texture.The steel sheet texture that finally obtains has very big change owing to the hot-rolled temperature district is different.If hot rolling terminal temperature TFE is lower than Ar
3℃, then the anisotropy Δ uE1 of uniform elongation surpasses 4%, the remarkable variation of formability, therefore
TFE≥Ar
3(℃) (1)
TFE generally is that the final rolling pallet in carrying out hot rolling records later, but also can utilize the temperature that obtains by calculating when needing.
In addition, the upper limit of hot rolling terminal temperature does not limit especially, but when surpassing (Ar
3+ 180) in the time of ℃, surface property descends owing to produce zone of oxidation at the surface of thin steel sheet place, therefore (Ar
3+ 180) ℃ or lower be preferred.
When seeking stricter surface property, preferably TFE is decided to be (Ar
3+ 150) ℃ or lower.
Yet, production have ferrite wherein or bainite be the percentage by volume maximum phase microstructure and have good shape can fixed high-strength hot-rolled steel-sheet method in, no matter steel-sheet chemical ingredients, when TFE is lower than 800 ℃, calendering load when hot rolling can become too high, steel-sheet ductility anisotropy becomes bigger simultaneously, therefore
TFE≥800℃ (1’)
In addition, when finishing hot rolling starting temperature TFS was higher than 1100 ℃, the steel-sheet surface property significantly descended, therefore
TFS≤1100℃ (2)
In addition, when the difference between TFS and the TFE is 120 ℃ or when higher, but the development of texture be not enough to obtain good shape stationarity and low anisotropy, can make operation be difficult to carry out and make this difference be not more than 20 ℃, therefore,
20℃≤(TFS-TFE)≤120℃ (4)
Here, production have comprise percentage by volume be the martensitic microstructure of 1-25% and have good shape can fixed high-strength hot-rolled steel-sheet method in, the relational expression (3) below the residual strain Δ ε when finish rolling finishes, finishing hot rolling starting temperature TFS that calculates and finishing hot rolling terminal temperature TFE should satisfy.If do not satisfy this relational expression, but then during hot rolling, can not form the texture favourable to the shape stationarity:
Δε≥(TFS-TFE)/375 (3)
Should be noted that Δ ε is by (((i=1～n) and constant R=1.987 try to achieve the time ti (second) between i=1～n), (process) pallet for i=1～n-1), rolling temperature Ti (K) from last pallet to the time tn (second) that begins to cool down, each pallet at the given equivalent strain ε i in each pallet place in rolling n finish rolling stage.
ε＝Δε1+Δε2+...+Δεn
In the formula, Δ ε i=ε i * exp{-(ti
*/ τ n)
2/3}
τi＝8.46×10
-9×exp{43800/R/Ti}
ti
＊＝τn×{ti/τi+t(i+1)/τ(i+1)+...+tn/τn}
In addition, in the hot rolling of this method, at Ar
3～(Ar
3+ 150) compression ratio in ℃ the temperature range also has a significant impact the formation of final steel-sheet texture.When the compression ratio in this temperature range less than 25% the time, texture evolution is insufficient, thereby but the steel sheet that finally obtains does not have good shape stationarity, therefore will be at Ar
3～(Ar
3+ 150) the following of compression ratio in ℃ the temperature range is defined as 25%.
Compression ratio is high more, and then desirable texture evolution is many more, therefore preferably compression ratio is decided to be at least 50%.In addition, more preferably compression ratio is 75% or bigger.
The upper limit of compression ratio limits especially, but compresses 99% or manyly can bring big load to system, and does not produce any special effect, therefore preferably will on be defined as less than 99%.
Herein,
Ar
3＝901-325×C％+33×Si％+287×P％+40×Al％
-92×(Mn％+Mo％+Cu％)-46×(Cr％+Ni％)。
Even under household condition in this temperature range, carry out hot rolling, but final steel-sheet shape stationarity is also very high, but when but needs further improved the shape stationarity, the frictional coefficient at least one mill train of hot rolled that then will implement in this temperature range was controlled to be and is not more than 0.2.
If frictional coefficient greater than 0.2, does not then have special difference with common hot rolling, therefore will be defined as 0.2 on the frictional coefficient.
On the other hand, frictional coefficient is low more, and then difficult more formation in the surface sheared texture, and but the shape stationarity is good more, so the lower limit of frictional coefficient limits especially, if but frictional coefficient less than 0.05, then be difficult to guarantee operational stability, therefore preferably frictional coefficient be decided to be at least 0.05.
In addition, be used for deoxidation layer before hot rolling processing, inject high pressure water, to spray fine particles etc. be effectively for improving final steel-sheet surface property, is preferred therefore.
With regard to the cooling after the hot rolling, the control coiling temperature is most important, but preferably makes average cooling rate be at least 15 ℃/seconds.Preferably after hot rolling, begin to cool down rapidly.In addition, air cooling has during cooling also prevented final steel-sheet characteristic variation.
For the austenite texture that will form like this forwards on the final hot rolled steel sheet, critical temperature T must be higher than
0(℃) temperature under batch steel sheet, this critical temperature T
0(℃) represent by following relational expression (5).Therefore, with the T that is defined as on the coiling temperature by the one-tenth branch decision of steel
0(℃).
This T
0Temperature is defined as austenite and has the temperature of identical free energy with the bainite identical with the austenite composition on thermodynamics, and can be calculated simply by following relational expression (5), considers the influence of the composition except that C simultaneously.
Other composition except that composition of the present invention is because to T
0Temperature Influence is little, so ignore herein.
When cooling is the T that is determined by the steel chemical ingredients being higher than
0Finish under the temperature and when batching steel sheet at this moment, even satisfied above-mentioned hot-rolled condition, desirable texture can not fully development on the steel sheet that finally obtains, but and steel-sheet shape stationarity do not uprise yet.
T
0＝-650.4×{C％/(1.82×C％-0.001)}+B (5)
In the formula, B is tried to achieve by the composition of steel of representing with quality %,
B＝-50.6×Mneq+894.3
Mneq＝Mn％+0.24×Ni％+0.13×Si％+0.38×Mo％+0.55×Cr％
+0.16×Cu％-0.50×Al％-0.45×Co％+0.90×V％
When production has can the be fixed high-strength hot-rolled steel sheet of good shape-microstructure of this steel plate has ferrite or the bainite as the phase of percentage by volume maximum, if coiling temperature is above 700 ℃, then guarantee on the length that whole batching coiling temperature becomes difficult, thereby become the reason that material quality changes.In addition, when comprising carbide forming element such as Ti, Nb and/or V, these carbide are in the growth of place, grain boundary, thereby have significantly weakened ultimate deformation ability (ultimatedeformability).Therefore, will be defined as 700 ℃ on the coiling temperature.
On the other hand,, then will in steel sheet, produce austenite in a large number mutually or martensitic phase, and the ultimate deformation ability will descend, so the following of coiling temperature will be defined as 400 ℃ if coiling temperature is lower than 400 ℃.
In addition, when production has can the be fixed high-strength hot-rolled steel sheet of good shape-microstructure of this steel plate comprises that percentage by volume is the martensite of 1-25%, if coiling temperature surpasses 400 ℃, then do not form martensitic phase.Therefore will be defined as 400 ℃ on the coiling temperature.From this viewpoint, the upper limit of coiling temperature preferably is decided to be 350 ℃, more preferably is decided to be 300 ℃.
Should be noted that if coiling temperature is lower than room temperature, then not only need excessive fund input, and can not get significant effect, the therefore preferred following room temperature that is defined as coiling temperature.
Skin-pass:
Before shipment, the steel sheet of the present invention with aforesaid method production is applied skin-pass and make that the steel-sheet shape is good.At this moment, if the skin-pass compression ratio less than 0.1%, therefore then effect is very little, the following of skin-pass compression ratio is defined as 0.1%.
In addition,, must transform common skin milll in order to implement to surpass 5% skin-pass, thus generation shortcoming economically, and the remarkable variation of steel-sheet formability, therefore will be defined as 5% on the skin-pass compression ratio.
In addition, defined yield ratio is the breaking tenacity (MPa) that obtains in No. 5 tension tests of common JIS and yield strength (0.2% yield strength)-be the ratio of yield ratio (YS/TS * 100) among the present invention, and from the formability viewpoint, preferably this ratio is not more than 70%.In addition,, but then can improve the shape stationarity, therefore wish that yield ratio is not more than 65% if yield ratio is not more than 65%.
Plating:
The type and the method for plating are not particularly limited.Can obtain effect of the present invention by any methods such as plating, melt plating, evaporation platings.
Steel sheet of the present invention can be used for bending, and can be used for combined shaping, described combined shaping mainly comprise such as crooked, punching stretch is shaped, draw/twist (restriction) etc.
[example]
(example 1)
This relates to have good shape can fixed high-strength hot-rolled steel-sheet embodiment, and the microstructure of this steel plate has as the ferrite of the percentile phase of maximum volume or bainite.
The steel A-K that table 1 is listed is heated to 1100-1270 ℃ and carry out hot rolling under the listed hot-rolled condition of table 2, so that obtain the thick steel sheet of 2.5mm.In the assessment result of table 3 to the hot rolled steel sheet of all kinds shown in the table 4.
Table 1
| The steel type | C | Si | Mn | P | S | Al | Ti | Nb | V | Mo | Cr |
| A | 0.03 | 0.06 | 0.30 | 0.009 | 0.004 | 0.042 | |||||
| B | 0.04 | 0.32 | 0.54 | 0.012 | 0.005 | 0.045 | 0.13 | ||||
| C | 0.06 | 0.83 | 1.32 | 0.010 | 0.006 | 0.036 | 0.11 | 0.033 | |||
| D | 0.05 | 0.02 | 0.78 | 0.016 | 0.007 | 0.039 | 0.010 | ||||
| E | 0.04 | 0.03 | 0.82 | 0.011 | 0.005 | 0.028 | 0.13 | 0.021 | 0.01 | ||
| F | 0.06 | 0.25 | 1.22 | 0.021 | 0.005 | 0.043 | 0.210 | 0.030 | 0.05 | ||
| G | 0.07 | 0.11 | 0.98 | 0.013 | 0.006 | 0.036 | 0.18 | 0.040 | |||
| H | 0.08 | 0.68 | 1.36 | 0.014 | 0.008 | 0.042 | 0.35 | 0.02 | |||
| I | 0.09 | 0.62 | 1.10 | 0.009 | 0.004 | 0.031 | 0.025 | ||||
| J | 0.1 | 0.55 | 1.39 | 0.012 | 0.002 | 0.040 | |||||
| K | 0.26 | 0.65 | 3.57 | 0.006 | 0.004 | 0.035 | 0.06 | 0.043 |
| The steel type | Cu | Ni | Co | B | N | 0 | Sn | Ca/Rem | Distinguish |
| A | 0.0020 | 0.002 | 0.02 | Steel of the present invention | |||||
| B | 0.0021 | 0.0019 | 0.004 | Steel of the present invention | |||||
| C | 0.0038 | 0.003 | Ca0.003 | Steel of the present invention | |||||
| D | 0.07 | 0.0022 | 0003 | Steel of the present invention | |||||
| E | 0.0030 | 0.002 | Steel of the present invention | ||||||
| F | 0.0023 | 0.002 | Steel of the present invention | ||||||
| G | 0.2 | 0.1 | 0.0018 | 0.001 | Steel of the present invention | ||||
| H | 0.0031 | 0.003 | Ca：0.002 | Steel of the present invention | |||||
| I | 0.0020 | 0.002 | Steel of the present invention | ||||||
| J | 0.0026 | 0.001 | Steel of the present invention | ||||||
| K | 0.0021 | 0.002 | La0.0025 | Comparative steel |
Underscoring shows that numerical value is outside scope of the present invention.
Table 2
| No. | Steel | Ar 3 ℃ | Ar 3+150 ℃ | Compression ratio * 1 | TFS ℃ | TFE ℃ | TFS-TFE ℃ | Hot-rolling lubricating | T 0 ℃ | CT ℃ | Skin-pass compression ratio % | Type |
| 1 | A | 870 | 1020 | Good | 955 | 883 | 72 | Not | 516 | 483 | 0.8 | Example of the present invention |
| 2 | B | 854 | 1004 | Good | 1020 | 970 | 50 | Be | 504 | 495 | 0.5 | Example of the present invention |
| 3 | C | 792 | 942 | Good | 1015 | 920 | 95 | Not | 462 | 450 | 0.8 | Example of the present invention |
| 4 | C | 792 | 942 | Good | 1000 | 892 | 108 | Be | 462 | 455 | 0.8 | Example of the present invention |
| 5 | C | 792 | 942 | Good | 880 | 773 | 107 | Not | 462 | 438 | 0.8 | Comparative example |
| 6 | C | 792 | 942 | Difference | 1107 | 989 | 118 | Be | 462 | 530 | 0.8 | Comparative example |
| 7 | C | 792 | 942 | Good | 1050 | 855 | 195 | Not | 462 | 455 | 0.8 | Comparative example |
| 8 | C | 792 | 942 | Difference | 1010 | 938 | 72 | Not | 462 | 450 | 0.8 | Comparative example |
| 9 | C | 792 | 942 | Good | 930 | 880 | 50 | Not | 462 | 580 | 0.8 | Comparative example |
| 10 | C | 792 | 942 | Good | 1017 | 888 | 129 | Not | 462 | ＜200 | 0.8 | Comparative example |
| 11 | C | 792 | 942 | Difference | 980 | 890 | 90 | Not | 462 | 150 | 0.8 | Comparative example |
| 12 | D | 826 | 976 | Good | 990 | 905 | 85 | Not | 493 | 480 | 1.2 | Example of the present invention |
| 13 | D | 826 | 976 | Good | 890 | 803 | 87 | Not | 493 | 467 | 0.8 | Comparative example |
| 14 | E | 818 | 968 | Good | 975 | 875 | 100 | Not | 491 | 425 | 0.8 | Example of the present invention |
| 15 | E | 818 | 968 | Good | 905 | 730 | 175 | Be | 491 | 400 | 0.8 | Comparative example |
| 16 | F | 783 | 933 | Good | 985 | 878 | 107 | Be | 470 | 400 | 0.8 | Example of the present invention |
| 17 | G | 774 | 924 | Good | 955 | 860 | 95 | Not | 482 | 478 | 0.8 | Example of the present invention |
| 18 | H | 778 | 928 | Good | 935 | 846 | 89 | Not | 461 | 458 | 1.1 | Example of the present invention |
| 19 | I | 795 | 945 | Good | 920 | 863 | 57 | Not | 476 | 465 | 0.8 | Example of the present invention |
| 20 | J | 761 | 811 | Good | 950 | 880 | 70 | Be | 461 | 449 | 0.8 | Example of the present invention |
| 21 | K | 513 | 663 | Difference | 905 | 823 | 82 | Not | 352 | 325 | 0.8 | Comparative example |
Underscoring shows that numerical value is outside scope of the present invention;
*1: at Ar
3℃～(Ar
3+ 150) overall compression ratio is shown " good " at least 25% information slip 0 in ℃ the temperature range, and other information slip is shown " poor ".
Table 3
| No. | Sample | Maximum volume percentage phase | Maximal phase percentage by volume % | The accounting example % of the coarse grained carbon Chemistry and Physics Institute | Steel-sheet r value | The anisotropy of elongation | ΔLEL- ΔuE1 | AI(MPa) | Type | ||
| rL | rC | ΔuEl | ΔLE1 | ||||||||
| 1 | A | Ferrite | 96 | ＜0.1 | 0.51 | 0.64 | 1.3 | 5.4 | 4.1 | 23 | Example of the present invention |
| 2 | B | Ferrite | 85 | ＜0.1 | 0.53 | 0.62 | 1.0 | 4.8 | 3.8 | 35 | Example of the present invention |
| 3 | C | Bainite | 78 | ＜0.1 | 0.51 | 0.61 | 0.8 | 4.5 | 3.7 | 30 | Example of the present invention |
| 4 | C | Ferrite | 98 | ＜0.1 | 0.58 | 0.66 | 2.4 | 3.8 | 1.4 | 18 | Example of the present invention |
| 5 | C | Ferrite | 96 | ＜0.1 | 0.43 | 0.56 | 5.3 | 4.8 | -0.5 | 42 | Comparative example |
| 6 | C | Ferrite | 95 | 0.2 | 0.86 | 0.92 | 2.4 | 0.8 | -1.6 | 25 | Comparative example |
| 7 | C | Ferrite | 89 | ＜0.1 | 0.73 | 0.77 | 3.8 | 3.5 | -0.3 | 30 | Comparative example |
| 8 | C | Ferrite | 97 | 0.8 | 0.78 | 0.93 | -0.5 | 1.2 | 1.7 | 18 | Comparative example |
| 9 | C | Ferrite | 67 | ＜0.1 | 0.82 | 0.86 | 1.8 | 1.3 | -0.5 | 12 | Comparative example |
| 10 | C | Ferrite | 89 | ＜0.1 | 0.85 | 0.72 | 5.2 | 4.3 | -0.9 | 0 | Comparative example |
| 11 | C | Ferrite | 78 | ＜0.1 | 0.73 | 0.78 | 2.3 | 1.7 | -0.6 | 28 | Comparative example |
| 12 | D | Ferrite | 72 | ＜0.1 | 0.58 | 0.66 | 1.8 | 3.8 | 2.0 | 43 | Example of the present invention |
| 13 | D | Ferrite | 68 | ＜0.1 | 0.51 | 0.63 | 4.6 | 4.2 | -0.4 | 29 | Comparative example |
| 14 | E | Ferrite | 73 | 0.12 | 0.55 | 0.68 | 2.9 | 4.3 | 1.4 | 25 | Example of the present invention |
| 15 | E | The ferrite of processing | 78 | ＜0.1 | 0.56 | 0.73 | -2.3 | -1.2 | 1.1 | # | Comparative example |
| 16 | F | Ferrite | 71 | ＜0.1 | 0.57 | 0.61 | 2.3 | 4.3 | 3.3 | 35 | Example of the present invention |
| 17 | G | Ferrite | 68 | ＜0.1 | 0.58 | 0.66 | 2.6 | 4.9 | 2.3 | 27 | Example of the present invention |
| 18 | H | Ferrite | 77 | ＜0.1 | 0.51 | 0.61 | 2.5 | 5.8 | 3.3 | 38 | Example of the present invention |
| 19 | I | Bainite | 72 | ＜0.1 | 0.58 | 0.66 | 1.6 | 4.6 | 3.0 | 24 | Example of the present invention |
| 20 | J | Ferrite | 89 | ＜0.1 | 0.55 | 0.68 | 3.9 | 4.2 | 0.3 | 40 | Example of the present invention |
| 21 | K | Ferrite | 77 | ＜0.1 | 0.60 | 0.78 | 3.8 | 1.9 | -1.9 | 87 | Comparative example |
Underscoring shows that numerical value is outside scope of the present invention;
#: the expression uniform elongation is less than 10% and can not measure.
Table 4 (continuous table 3)
| No. | Sample | 100}＜011 〉-223}＜110〉the X ray average intensity of orientation group | 554}＜225 〉, 111}＜112 〉, 111}＜110〉the X ray average intensity | 100}＜011〉and X ray intensity (A) | 211}＜011〉and X ray intensity (B) | (A)-(B) | Hole ratio * 2 | But the shape stationarity is estimated * 3 | Type |
| 1 | A | 6.66 | 2.85 | 7.02 | 4.98 | 2.04 | Good | Good | Example of the present invention |
| 2 | B | 7.28 | 1.03 | 13.20 | 5.03 | 8.17 | Good | Good | Example of the present invention |
| 3 | C | 6.88 | 1.99 | 8.69 | 5.77 | 2.92 | Good | Good | Example of the present invention |
| 4 | C | 6.35 | 1.56 | 6.55 | 6.43 | 0.12 | Good | Good | Example of the present invention |
| 5 | C | 6.27 | 2.09 | 4.33 | 7.43 | -3.10 | Good | Good | Comparative example |
| 6 | C | 2.23 | 2.42 | 2.67 | 1.89 | 0.78 | Good | Difference | Comparative example |
| 7 | C | 5.43 | 1.38 | 4.35 | 6.92 | -2.57 | Good | Difference | Comparative example |
| 8 | C | 1.78 | 3.00 | 1.89 | 2.37 | -0.48 | Good | Difference | Comparative example |
| 9 | C | 1.96 | 1.03 | 2.23 | 2.02 | 0.21 | Difference | Difference | Comparative example |
| 10 | C | 4.36 | 1.56 | 3.89 | 6.35 | -2.46 | Difference | Good | Comparative example |
| 11 | C | 2.04 | 1.56 | 2.45 | 2.31 | 0.14 | Good | Difference | Comparative example |
| 12 | D | 5.10 | 2.09 | 6.02 | 4.31 | 1.71 | Good | Good | Example of the present invention |
| 13 | D | 4.62 | 2.44 | 4.22 | 5.22 | -1.00 | Good | Difference | Comparative example |
| 14 | E | 5.67 | 2.27 | 7.35 | 4.89 | 2.46 | Good | Good | Example of the present invention |
| 15 | E | 4.99 | 5.90 | 7.67 | 2.89 | 4.78 | Difference | Difference | Comparative example |
| 16 | F | 6.23 | 1.73 | 6.99 | 5.22 | 1.77 | Good | Good | Example of the present invention |
| 17 | G | 6.54 | 1.24 | 8.35 | 5.09 | 3.26 | Good | Good | Example of the present invention |
| 18 | H | 5.50 | 2.31 | 6.99 | 4.38 | 2.61 | Good | Good | Example of the present invention |
| 19 | I | 7.38 | 2.67 | 9.23 | 4.99 | 4.24 | Good | Good | Example of the present invention |
| 20 | J | 4.93 | 2.39 | 5.87 | 5.23 | 0.64 | Good | Good | Example of the present invention |
| 21 | K | 2.29 | 3.02 | 2.58 | 2.00 | 0.58 | Difference | Difference | Comparative example |
Underscoring shows that numerical value is outside scope of the present invention;
2
*: information slip satisfied, λ/TS 〉=0.15 is shown " good ", and other information slip is shown " poor ";
3
*: it is satisfied that 0≤1000/ ρ≤(0.012 * TS-4.5) information slip is shown " good ", and the information slip that does not satisfy above-mentioned condition is shown " poor ".
Utilize 270mm length * 50mm wide * but the band sample of thickness of slab estimates the shape stationarity, described sample is wide by the drift of 78mm, the drift of R5mm is takeed on, the punch die of R5mm is takeed on and various fold inhibition pressure forms hat-shaped, the amount of camber of measuring wall portion then is with as radius-of-curvature ρ (mm), and obtains 1000/ ρ reciprocal.1000/ ρ is more little, but the shape stationarity is good more.
Usually, if known steel-sheet intensity raises, but shape stationarity variation then.The contriver makes some physical units.As can be known from the results, 1000/ ρ that suppresses to record by aforesaid method under the pressure when the fold at 70KN is 0 (mm
-1) or bigger, and become (0.012 * TS-4.5) (mm
-1) or than steel-sheet tensile strength TS[MPa] hour, but can obtain good shape stationarity.
Therefore, with 0≤1000/ ρ≤(0.012 * TS-4.5) be evaluated as be used for good shape can fixed condition.
Increase if fold suppresses pressure, then 1000/ ρ trends towards reducing.Yet, no matter select any fold to suppress pressure, the steel-sheet shape is can fixed superiority order all constant.Therefore, but 70KN fold suppresses the evaluation of pressure also represents steel-sheet shape stationarity.
Be the hole of 10mm, be the diameter in 60 ° tapered punch hole with the initial apertures expansion and when allowing crackle to run through steel sheet with drift angle by central heart punching press one diameter at the test film of 100mm
d(mm) estimate the hole extendability with the hole rate of spread (following relational expression) of the diameter 10mm of initial apertures:
λ＝{(d-10)/10}×100(％)
When steel sheet intensity raises, the general variation of the hole rate of spread.
Therefore, with the indication of (hole rate of spread λ [%])/(steel-sheet tensile strength TS[MPa]) as the hole extendability, and with 0.15 or bigger numerical Evaluation be good hole extendability.
Utilize No. 5 tension test sheets of JIS to measure r value, ductility anisotropy and AI.In addition, come the measured X ray with as the steel-sheet typical value by the preparation sample, said sample is parallel to the steel sheet plane in the position of steel sheet thickness 7/16.In table 2, the hot-rolled condition of NO.5～11, NO.13 and NO.15 is all outside the scope of the invention, therefore the ductile anisotropy is big, but the shape stationarity is also not enough in some cases, elongation flange formability is also not enough, but therefore can not get having the shape stationarity, low anisotropy and the high-strength steel sheet of hole extendability.
The composition of NO.21 and hot-rolled condition all outside the scope of the invention, but so its can not be satisfactory on shape stationarity and hole extendability.
When by within the scope of the present invention steel sheet of the hot-rolled condition production chemical ingredients in the scope of the invention, but known good ductility anisotropy and hole extendability and the good shape stationarity of obtaining.
(example 2)
This relates to have good shape can embodiment of fixed high-strength hot-rolled steel-sheet, and described steel sheet has heterogeneous structure, and wherein ferrite or bainite are the phase of percentage by volume maximum, and comprise that percentage by volume is the martensite of 1-25%.
Chemical ingredients is heated to 1100-1270 ℃ at the steel A-L shown in the table 5, and under the hot-rolled condition shown in the table 6, carries out hot rolling, so that obtain the thick hot rolled steel sheet of 2.5mm.Various types of measurements and evaluation result are shown in table 6 and the table 7 (continuous table 6).
Utilize 270mm length * 50mm wide * but the band sample of thickness of slab estimates the shape stationarity, described sample is wide by the drift of 78mm, the drift of R5mm is takeed on, the punch die of R5mm is takeed on and various fold inhibition pressure forms hat-shaped, the amount of warpage of measuring wall portion then is with as radius-of-curvature ρ (mm), and obtains 1000/ ρ reciprocal.1000/ ρ is more little, but the shape stationarity is good more.
Usually, if known steel-sheet intensity raises, but shape stationarity variation then.The contriver makes some physical units.As can be known from the results, 1000/ ρ that suppresses to record by aforesaid method under the pressure when the fold at 70kN is 0 (mm
-1) or bigger, and become (0.012 * TS-0.45) (mm
-1) or than steel-sheet tensile strength TS[MPa] hour, but can obtain good shape stationarity.
Therefore, with 0≤1000/ ρ≤(0.012 * TS-4.5) be evaluated as be used for good shape can fixed condition.
Increase if fold suppresses pressure, then 1000/ ρ trends towards reducing.Yet, no matter select any fold to suppress pressure, the steel-sheet shape is can fixed superiority order all constant.Therefore, but 70KN fold suppresses the evaluation of pressure also represents steel-sheet shape stationarity.
Utilize No. 5 tension test sheets of JIS to measure r value, ductility anisotropy and YR.In addition, to represent numerical value as steel-sheet, said sample is parallel to the steel sheet plane in the position of steel sheet thickness 7/16 by preparation sample measurement X ray.
In table 6 and table 7, No.2,5,7,9-11,13,15,17,18 and the hot-rolled condition of 21-23 and composition all outside the scope of the invention, so the ductile anisotropy is big, but the shape stationarity is also not enough in some cases, and do not satisfy YR yet, but therefore can not get having the high-strength steel sheet of shape stationarity and less anisotropy.
When with the steel sheet of the hot-rolled condition production chemical ingredients in the scope of the invention in the scope of the invention that illustrates in addition, but known good ductility anisotropy, shape stationarity and the YR of obtaining.
Table 5
| Code name | Chemical ingredients (quality %) | ||||||||||||
| C | Si | Al | Si+Al | Mn | Ni | Cr | Cu | Mo | W | Co | Sn | ＊1 | |
| A | 0.03 | 0.02 | 0.040 | 0.060 | 1.10 | 1.10 | |||||||
| B | 0.06 | 1.2 | 0.048 | 1.258 | 1.05 | 0.1 | 1.15 | ||||||
| C | 0.06 | 1.10 | 0.032 | 1.132 | 0.98 | 0.3 | 1.28 | ||||||
| D | 0.08 | 0.01 | 0.300 | 0.310 | 1.50 | 0.4 | 1.90 | ||||||
| E | 0.08 | 1.35 | 0.030 | 1.380 | 0.72 | 0.1 | 0.2 | 1.02 | |||||
| F | 0.11 | 0.09 | 0.045 | 0.135 | 1.80 | 0.3 | 2.10 | ||||||
| G | 0.07 | 1.25 | 0.035 | 1.285 | 0.75 | 0.75 | |||||||
| H | 0.10 | 0.04 | 0.041 | 0.081 | 1.92 | 1.92 | |||||||
| I | 0.11 | 0.29 | 0.520 | 0.810 | 2.54 | 2.54 | |||||||
| J | 0.13 | 1.05 | 0.032 | 1.082 | 2.32 | 0.5 | 2.82 | ||||||
| K | 0.005 | 0.09 | 0.041 | 0.131 | 0.B2 | 0.02 | 0.84 | ||||||
| L | 0.05 | 1.02 | 0.038 | 1.058 | 0.03 | 0.03 | |||||||
| Code name | Continuous chemical ingredients (quality %) | Annotate | |||||||||
| Nb | Ti | ★2 | V | P | S | N | B | Ca | Rem | ||
| A | 0.030 | 0.03 | 0.009 | 0.004 | 0.003 | Steel of the present invention | |||||
| B | 0.012 | 0.005 | 0.002 | 0.0008 | Steel of the present invention | ||||||
| C | 0.020 | 0.020 | 0.04 | 0.010 | 0.002 | 0.003 | Steel of the present invention | ||||
| D | 0.012 | 0.003 | 0.003 | 0.001 | Steel of the present invention | ||||||
| E | 0.021 | 0.021 | 0.010 | 0.006 | 0.003 | 0.002 | Steel of the present invention | ||||
| F | 0.009 | 0.001 | 0.002 | Steel of the present invention | |||||||
| G | 0.018 | 0.082 | 0.1 | 0.005 | 0.003 | 0.003 | Steel of the present invention | ||||
| H | 0.015 | 0.092 | 0.107 | 0.012 | 0.001 | 0.003 | 0.0018 | Steel of the present invention | |||
| I | 0.012 | 0.011 | 0.023 | 0.01 | 0.011 | 0.002 | 0.002 | 0.001 | Steel of the present invention | ||
| J | 0.020 | 0.02 | Steel of the present invention | ||||||||
| K | 0.029 | 0.029 | 0.022 | 0.006 | 0.003 | 0.001 | Comparative steel | ||||
| L | Comparative steel | ||||||||||
Underscoring shows that numerical value is outside scope of the present invention;
＊1：Mn+Ni+Cr+Cu+Mo+W+Co+Sn；
＊2：Nb+Ti。
Table 6
| No. | Steel | Ar 3℃ | Ar 3+150 ℃ | Compression ratio * 1 | TFS℃ | TFE℃ | TFS- TFE℃ | (TFS- TFE)/375 | Δε | Hot-rolling lubricating | T 0℃ | CT℃ | Skin-pass compression ratio (%) | Type |
| 1 | A | 795 | 945 | Good | 940 | 870 | 70 | 0.19 | 0.42 | Have | 476 | ＜200 | 0.5 | Example of the present invention |
| 2 | A | 795 | 945 | Good | 960 | 880 | 80 | 0.21 | 0.17 | Have | 476 | ＜200 | 0.8 | Comparative example |
| 3 | B | 830 | 980 | Good | 1020 | 900 | 120 | 0.32 | 0.41 | Have | 474 | 300 | 0.8 | Example of the present invention |
| 4 | C | 818 | 968 | Good | 940 | 870 | 70 | 0.19 | 0.41 | Do not have | 474 | 250 | 0.8 | Example of the present invention |
| 5 | C | 818 | 968 | Good | 975 | 850 | 125 | 0.33 | 0.16 | Do not have | 474 | ＜200 | 0.8 | Comparative example |
| 6 | D | 753 | 903 | Good | 930 | 865 | 65 | 0.17 | 0.37 | Have | 476 | ＜200 | 0.5 | Example of the present invention |
| 7 | D | 753 | 903 | Good | 890 | 830 | 60 | 0.16 | 0.39 | Do not have | 476 | 550 | 0.8 | Comparative example |
| 8 | E | 834 | 984 | Good | 940 | 880 | 60 | 0.16 | 0.39 | Do not have | 488 | 250 | 0.8 | Example of the present invention |
| 9 | E | 834 | 984 | Difference | 945 | 860 | 86 | 0.23 | 0.25 | Do not have | 488 | 250 | 0.8 | Comparative example |
| 10 | E | 834 | 984 | Good | 875 | 760 | 115 | 0.31 | 0.35 | Do not have | 488 | 300 | 1.2 | Comparative example |
| 11 | E | 834 | 984 | Good | 1150 | 860 | 290 | 0.77 | 0.35 | Do not have | 488 | 300 | 1.2 | Comparative example |
| 12 | F | 679 | 829 | Good | 875 | 805 | 70 | 0.19 | 0.33 | Have | 439 | 250 | 0.8 | Example of the present invention |
| 13 | F | 679 | 829 | Difference | 960 | 870 | 90 | 0.24 | 0.21 | Do not have | 439 | 250 | 1.2 | Comparative example |
| 14 | G | 853 | 1003 | Good | 980 | 900 | 80 | 0.21 | 0.28 | Have | 489 | ＜200 | 1.2 | Example of the present invention |
| 15 | G | 853 | 1003 | Good | 890 | 820 | 70 | 0.19 | 0.28 | Have | 489 | ＜200 | 1.0 | Comparative example |
| 16 | H | 698 | 848 | Good | 880 | 800 | 80 | 0.21 | 0.28 | Do not have | 439 | ＜200 | 0.5 | Example of the present invention |
| 17 | H | 698 | 848 | Difference | 925 | 810 | 115 | 0.31 | 0.35 | Do not have | 439 | 600 | 0.5 | Comparative example |
| 18 | H | 698 | 858 | Good | 930 | 800 | 130 | 0.35 | 0.42 | Have | 439 | ＜200 | 0.5 | Comparative example |
| 19 | I | 665 | 815 | Good | 840 | 790 | 50 | 0.13 | 0.35 | Have | 418 | ＜200 | 0.8 | Example of the present invention |
| 20 | J | 661 | B11 | Good | 840 | 800 | 40 | 0.11 | 0.2 | Do not have | 399 | 250 | 1.0 | Example of the present invention |
| 21 | J | 661 | 811 | Difference | 870 | 790 | 80 | 0.21 | 0.23 | Do not have | 399 | 510 | 1.0 | Comparative example |
| 22 | K | 835 | 985 | Good | 1135 | 875 | 260 | 0.69 | 0.45 | Do not have | 452 | 250 | 1.0 | Comparative example |
| 23 | L | 916 | 1066 | Good | 1040 | 890 | 150 | 0.40 | 0.32 | Do not have | 524 | 300 | 1.0 | Comparative example |
Underscoring shows that numerical value is outside scope of the present invention;
*1: at Ar
3℃～(Ar
3+ 150) overall compression ratio in ℃ scope is expressed as " good ", and other information slip is shown " poor ".
Table 7 (continuous table 6)
| No. | Steel | The percent by volume maximum value | The martensite percent by volume | Steel sheet r value | The anisotropy of elongation | ΔLE1- ΔuE1 | 100}＜011 〉-223}＜110〉the X ray average intensity of orientation group | 554}＜225 〉, 111}＜112 〉, 111}＜110〉x ray average intensity | 100}＜011〉and X penetrate intensity (A) | 211}＜011〉and X ray intensity (B) | (A}-(B) | YR％ | But the shape stationarity is estimated * 2 | Type | ||
| rL | rC | ΔuE1 | ΔLE1 | |||||||||||||
| 1 | A | Ferrite | 4.4 | 0.56 | 0.62 | 1.3 | 4.5 | 3.2 | 6.49 | 2.95 | 6.82 | 5.92 | 0.90 | 59％ | Good | Example of the present invention |
| 2 | A | Ferrite | 4.5 | 0.62 | 0.78 | 4.1 | 2.3 | -1.8 | 4.88 | 0.83 | 3.89 | 5.62 | -1.73 | 62％ | Good | Comparative example |
| 3 | B | Ferrite | 7.5 | 0.59 | 0.63 | 1.8 | 5.3 | 3.5 | 5.38 | 1.67 | 6.12 | 4.36 | 1.76 | 56％ | Good | Example of the present invention |
| 4 | C | Ferrite | 7.8 | 0.60 | 0.65 | 0.9 | 5.5 | 4.6 | 5.45 | 1.96 | 5.95 | 4.59 | 1.36 | 61％ | Good | Example of the present invention |
| 5 | C | Ferrite | 8.3 | 0.89 | 0.96 | 2.9 | 1.9 | -1.0 | 2.78 | 1.98 | 2.15 | 3.65 | -1.50 | 60％ | Difference | Comparative example |
| 6 | D | Ferrite | 6.5 | 0.63 | 0.63 | 1.2 | 4.2 | 3.0 | 6.49 | 2.85 | 7.37 | 5.68 | 1.69 | 65％ | Good | Example of the present invention |
| 7 | D | The cable body | 0 | 0.77 | 1.00 | 2.2 | 1.5 | -0.7 | 1.95 | 1.22 | 2.13 | 1.23 | 0.90 | 85％ | Difference | Comparative example |
| 8 | E | The cable body | 4.9 | 0.59 | 0.66 | 1.3 | 4.3 | 3.0 | 5.05 | 2.92 | 6.55 | 4.92 | 1.63 | 63％ | Good | Example of the present invention |
| 9 | E | The cable body | 6.3 | 0.82 | 0.96 | 1.3 | 1.1 | -0.2 | 2.35 | 0.89 | 2.05 | 2.55 | -0.50 | 63％ | Difference | Comparative example |
| 10 | E | Bainite | 8.4 | 0.63 | 0.75 | 5.3 | 4.6 | -0.7 | 4.59 | 4.52 | 5.13 | 4.00 | 1.13 | 64％ | Good | Comparative example |
| 11 | E | Ferrite | 6.3 | 0.65 | 0.73 | 4.8 | 3.2 | -1.6 | 6.33 | 1.82 | 4.95 | 7.33 | -2.38 | 65％ | Good | Comparative example |
| 12 | F | Ferrite | 7.5 | 0.55 | 0.62 | 1.1 | 4.5 | 3.4 | 7.08 | 1.23 | 8.30 | 6.58 | 1.72 | 62％ | Good | Example of the present invention |
| 13 | F | Ferrite | 7.6 | 0.88 | 0.92 | 1.9 | 1.5 | -0.4 | 1.78 | 1.75 | 2.15 | 1.50 | 0.65 | 59％ | Difference | Comparative example |
| 14 | G | The cable body | 5.8 | 0.59 | 0.63 | 1.2 | 4.6 | 3.4 | 3.71 | 2.85 | 4.92 | 3.02 | 1.90 | 60％ | Good | Example of the present invention |
| 15 | G | Ferrite | 9.8 | 0.65 | 0.75 | 4.7 | 6.5 | 1.8 | 4.14 | 4.56 | 4.79 | 3.85 | 0.94 | 69％ | Good | Comparative example |
| 16 | H | Bainite | 10.2 | 0.66 | 0.66 | 2.1 | 5.3 | 3.2 | 6.88 | 1.81 | 7.99 | 4.99 | 3.00 | 59％ | Good | Example of the present invention |
| 17 | H | Ferrite | 0.2 | 0.78 | 1.09 | 1.9 | 1.3 | -0.6 | 1.95 | 2.23 | 1.35 | 2.25 | -0.90 | 89％ | Difference | Comparative example |
| 18 | H | Ferrite | 11.8 | 0.61 | 0.82 | 1.7 | 1.1 | -0.6 | 6.64 | 1.53 | 5.12 | 7.85 | -2.73 | 63％ | Difference | Comparative example |
| 19 | I | Bainite | 12.5 | 0.53 | 0.53 | 1.4 | 4.9 | 3.5 | 6.37 | 2.78 | 6.93 | 5.55 | 1.38 | 62％ | Good | Example of the present invention |
| 20 | J | Bainite | 15.3 | 0.56 | 0.59 | 0.0 | 5.1 | 5.1 | 6.51 | 2.65 | 6.99 | 5.88 | 1.11 | 68％ | Good | Example of the present invention |
| 21 | J | Bainite | 0 | 1.00 | 0.99 | 2.5 | 1.5 | -1.0 | 2.12 | 2.23 | 2.29 | 2.00 | 0.29 | 92％ | Difference | Comparative example |
| 22 | K | Ferrite | 0 | 0.59 | 0.77 | 5.6 | 3.2 | -2.4 | 4.58 | 1.89 | 3.87 | 5.21 | -1.34 | 75％ | Good | Comparative example |
| 23 | L | Ferrite | 0 | 0.89 | 1.02 | 6.2 | 1.9 | -4.3 | 1.38 | 2.36 | 1.36 | 1.47 | -0.11 | 78％ | Difference | Comparative example |
Underscoring shows that numerical value is outside scope of the present invention;
*1: satisfied 0≤1000/ ρ≤(0.012 * TS-4.5) information slip is shown " good ".The information slip that does not satisfy the above-mentioned relation formula is shown " poor ".
[industrial applicibility]
As mentioned above, according to the present invention, but can provide without resilience, have good shape stationarity, have a sheet metal without anisotropic compacting formability simultaneously, even so that pass by to be difficult to use the parts of high-strength steel sheet also can use high-strength steel sheet owing to the problem of shape difference, simultaneously can not only realize automotive safety but also alleviate vehicle weight, and can be to satisfying environment and social desirability-for example reduce CO2Very large contribution is made in the automatic production of discharging. Therefore, the present invention is a kind of in the industrial invention that high value is arranged.
Claims (17)
- One kind have good shape can fixed high-strength hot-rolled steel sheet, wherein ferrite or bainite are the phases of percentage by volume maximum,At least satisfy all following conditions at 1/2 place of thickness of slab:(1) 100}＜011 〉～223}＜110〉mean value of X ray random strength ratio of orientation group is 2.5 or bigger,(2) 554}＜225 〉, 111}＜112 〉, 111}＜110〉mean value of X ray random strength ratio in three orientation is 3.5 or littler,(3) 100}＜011〉the X ray random strength than greater than 211}＜011〉and X ray random strength ratio,(4) 100}＜011〉X ray random strength ratio be 2.5 or bigger,In the r value on the rolling direction be 0.7 or littler perpendicular in the r value on the direction of rolling direction at least one,The anisotropy Δ uE1 of uniform elongation is 4% or littler,The anisotropy Δ LE1 of local elongation is 2% or bigger, andΔ uE1 equals Δ LE1 or less than Δ LE1,Herein:ΔuE1＝{| uE1(L)-uE1(45°)|+| uE1(C)-uE1(45°)|}/2ΔLE1＝{| LE1(L)-LE1(45°)|+| LE1(C)-LE1(45°)|}/2UE1 (L): the uniform elongation on rolling directionUE1 (C): uniform elongation in a lateral directionUE1 (45 °): the uniform elongation on 45 ° of directionsLE1 (L): the local elongation on rolling directionLE1 (C): local elongation in a lateral directionLE1 (45 °): the local elongation on 45 ° of directions.
- According to claim 1 described have good shape can fixed high-strength hot-rolled steel sheet, it is characterized in that diameter is that the occupation rate of 0.2 μ m or bigger iron carbide is 0.3% or littler.
- According to claim 1 described have good shape can fixed high-strength hot-rolled steel sheet, it is characterized in that aging index AI is 8MPa or bigger.
- According to claim 1 described have good shape can fixed high-strength hot-rolled steel sheet, it is characterized in that % meter by weight contains following ingredients:C：0.01-0.2％，Si：0.001-2.5％，Mn：0.01-2.5％，P：≤0.2％，S：≤0.03％，Al：0.01-2％，N :≤0.01%, andO：≤0.01％All the other are Fe and unavoidable impurities.
- According to claim 4 described have good shape can fixed high-strength hot-rolled steel sheet, it is characterized in that the composition of this steel plate also comprises at least a or multiple among Nb, Ti and the V, its total amount % is by weight counted 0.001-0.8%.
- According to claim 4 or 5 described have good shape can fixed high-strength hot-rolled steel sheet, it is characterized in that, also contain at least a or multiple in the column element down, % meter by weight,B：≤0.01％，Mo：≤1％，Cr：≤1％，Cu：≤2％，Ni：≤1％，Sn：≤0.2％，Co：≤2％，Ca：0.0005-0.005％，Rem：0.001-0.05％，Mg：0.0001-0.05％，Ta：0.0001-0.05％。
- According to claim 1 described have good shape can fixed high-strength hot-rolled steel sheet, it is characterized in that % meter by weight contains following ingredients:C：0.02-0.3％，Total amount % is by weight counted at least a or multiple in the following column element of 0.1-3.5%:Mn：0.05-3％，Ni：≤3％，Cr：≤3％，Cu：≤3％，Mo：≤1％，Co :≤3%, andSn：≤0.2％，Total amount % is by weight counted at least a among the Si of 0.02-3% and the Al or whole two kinds:Si :≤3%, andAl：≤3％All the other are Fe and unavoidable impurities, and have heterogeneous structure, and wherein ferrite or bainite are the phases of percentage by volume maximum, and martensitic percentage by volume is 1-25%.
- According to claim 7 described have good shape can fixed high-strength hot-rolled steel sheet, it is characterized in that % meter by weight, the composition of this steel plate comprise at least a or multiple among Nb, Ti and the V, its total amount % by weight is 0.001-0.8%.
- According to claim 7 or 8 described have good shape can fixed high-strength hot-rolled steel sheet, it is characterized in that, also contain at least a or multiple in the column element down, % meter by weight,P：≤0.2％，B：≤0.01％，Ca:0.0005-0.005%, andRem：0.001-0.02％。
- According to claim 4 or 5 described have good shape can fixed high-strength hot-rolled steel sheet, it is characterized in that steel sheet is through plating.
- 11. according to claim 7 or 8 described have good shape can fixed high-strength hot-rolled steel sheet, wherein steel sheet is through plating.
- 12. a production has good shape can fixed high-strength hot-rolled steel-sheet method, may further comprise the steps,After casting the strand that has as composition as described in claim 4 or 5, directly this strand is carried out hot rolling, perhaps in a single day this strand is cooled off and then be heated to 1000-1300 ℃ temperature range after this strand is carried out hot rolling, wherein at Ar 3～(Ar 3+ 150) overall compression ratio under ℃ the temperature is 25% or bigger, and the temperature T FE when temperature T FS when the finishing hot rolling begins and finishing hot rolling finish satisfies following relationship formula (1)～(4) simultaneously, andWill be through the cooling of hot rolled steel sheet, thenIn the subcritical temperature T 0With batch described critical temperature T under 400～700 ℃ the temperature 0Shown in decision of steel-sheet chemical ingredients and equation (5) below,TFE≥Ar 3 (1)TFE≥800℃ (1’)TFS ≤ 1100 (2)20℃≤TFS-TFE ≤ 120 (4)T 0＝-650.4×{C％/(1.82×C％-0.001)}+B (5)Wherein B is obtained by the composition of steel of representing with weight %B＝-50.6×Mneq+894.3Mneq＝Mn％+0.24×Ni％+0.13×Si％+0.38×Mo％+0.55×Cr％+0.16×Cu％-0.50×Al％-0.45×Co％+0.90×V％Ar 3＝901-325×C％+33×Si％+287×P％+40×Al％-92×(Mn％+Mo％+Cu％)-46(Cr％+Ni％)
- 13. having good shape according to the described production of claim 12 can fixed high-strength hot-rolled steel-sheet method, it is characterized in that, will be at Ar 3～(Ar 3+ 150) carrying out frictional coefficient at least one mill train of hot rolled in ℃ the temperature range is controlled to be and is not more than 0.2.
- 14. a production has good shape can fixed high-strength hot-rolled steel-sheet method, it is characterized in that, apply the skin-pass of 0.1-5% have hot rolled steel sheet that good shape can fixed high-strength hot-rolled steel-sheet method be produced by production as claimed in claim 12.
- 15. a production has good shape can fixed high-strength hot-rolled steel-sheet method, may further comprise the steps,After casting the strand that has as composition as described in claim 7 or 8, directly this strand is carried out hot rolling, perhaps in a single day this strand is cooled off and then be heated to 1000-1300 ℃ temperature range after this strand is carried out hot rolling, wherein at Ar 3～(Ar 3+ 150) overall compression ratio under ℃ the temperature is 25% or bigger, and the temperature T FS when the finishing hot rolling begins, the temperature T FE when the finishing hot rolling finishes and the residual strain Δ ε that calculates satisfy following relationship formula (1)～(4) simultaneously, andWill be through the cooling of hot rolled steel sheet, thenIn the subcritical temperature T 0Be not higher than under 400 ℃ the temperature and batch described critical temperature T 0By the chemical ingredients of steel plate determine and below relational expression (5) shown in:TFE≥Ar 3℃ (1)TFS≤1100℃ (2)Δε≥(TFS-TFE)/375 (3)20℃≤(TFS-TFE)≤120℃ (4)T 0＝-650.4×{C％/(1.82×C％-0.001)}+B (5)Wherein B is obtained by the composition of steel of representing with weight %B＝-50.6×Mneq+894.3Mneq＝Mn％+0.24×Ni％+0.13×Si％+0.38×Mo％+0.55×Cr％+0.16×Cu％-0.50×Al％-0.45×Co％+0.90×V％Herein,Ar 3＝901-325×C％+33×Si％+287×P％+40×Al％-92×(Mn％+Mo％+Cu％)-46(Cr％+Ni％)The Δ ε equivalent strain ε i given from each pallet place in rolling n finish rolling stage wherein the time ti between i=1～n, the pallet wherein the rolling temperature Ti of i=1～n-1, time tn, each pallet from last pallet to the cooling beginning wherein i=1～n and constant R=1.987 try to achieve, wherein ti, tn are unit with the second, Ti is unit with Kε＝Δε1+Δε2+...+ΔεnHerein, Δ ε i=ε i * exp{-(ti */ τ n) 2/3}τi＝8.46×10 -9×exp{43800/R/Ti}ti *＝τn×{ti/τi+t(i+1)/τ(i+1)+...+tn/τn}。
- 16. having good shape according to the described production of claim 15 can fixed high-strength hot-rolled steel-sheet method, it is characterized in that, will be at Ar 3～(Ar 3+ 150) carrying out frictional coefficient at least one mill train of hot rolled in ℃ the temperature range is controlled to be and is not more than 0.2.
- 17. a production has good shape can fixed high-strength hot-rolled steel-sheet method, it is characterized in that, apply the skin-pass of 0.1-5% have hot rolled steel sheet that good shape can fixed high-strength hot-rolled steel-sheet method be produced by production as claimed in claim 15.
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| JP182675/2003 | 2003-06-26 | ||
| JP2003182675A JP4276482B2 (en) | 2003-06-26 | 2003-06-26 | High-strength hot-rolled steel sheet with excellent ultimate deformability and shape freezing property and its manufacturing method |
| JP092280/2004 | 2004-03-26 |
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| CN1809646A CN1809646A (en) | 2006-07-26 |
| CN100374586C true CN100374586C (en) | 2008-03-12 |
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Also Published As
| Publication number | Publication date |
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| CN1809646A (en) | 2006-07-26 |
| JP2005015854A (en) | 2005-01-20 |
| JP4276482B2 (en) | 2009-06-10 |
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