CN100494449C - High strength cold rolled steel sheet having excellent shape freezability, and method for manufacturing the same - Google Patents
High strength cold rolled steel sheet having excellent shape freezability, and method for manufacturing the same Download PDFInfo
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- CN100494449C CN100494449C CNB2005800329215A CN200580032921A CN100494449C CN 100494449 C CN100494449 C CN 100494449C CN B2005800329215 A CNB2005800329215 A CN B2005800329215A CN 200580032921 A CN200580032921 A CN 200580032921A CN 100494449 C CN100494449 C CN 100494449C
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/02—Hardening by precipitation
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
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Abstract
A high-strength isotropic cold-rolled steel sheet having excellent shape-fixability, and a method for manufacturing the same are disclosed. The steel sheet is made using a low-carbon steel comprising a little amounts of Ti to have an r of 1.3 or less, r approaching 1, and a low in-plane anisotropy index (Dr) of 0.15 or less, ensuring excellent shape-fixability so as to be suitable for automotive outer panels which are essentially subjected to deformation in a stretching mode.
Description
Technical field
The present invention relates to be suitable for the high strength cold rolled steel plate of making automobile-used outer panels.More particularly, the present invention relates to a kind of high strength cold rolled steel plate, its r
90Be less than or equal to 1.3, average plastic strain ratio r
mNear 1, (in-plane) anisotropic index Δ r is low in its face, is less than or equal to 0.15, so just provides good shape freezability (shape-fixability), so that steel plate isotropically viscous deformation in the impact briquetting process; The invention still further relates to the manufacture method of this steel plate.
Background technology
For being used for the steel plate of car body, requiring to use cold-rolled steel sheet to carry out drawing and workpiece, defect do not occur, and can after drawing, make the automobile-used parts of desired shape efficiently with less anisotropy.Concrete is that for automobile-used outer panels, it must possess shock-resistance and shape freezability.
With regard to shock-resistance, use the steel plate of baking hardening usually, its intensity improves after japanning.In addition, in order to improve shape freezability, described panel must homogeneous deformation on its in-plane, and stands lower load in stamping process.
For automobile-used wainscot,, therefore be preferably and be provided at the cold-rolled steel sheet that has high stretch and plastic strain ratio in the described panel process of processing because described plate is out of shape under the deep draw pattern usually.
On the other hand, for automobile-used outer panels,, therefore be preferably and be provided at homogeneous deformation and the low cold-rolled steel sheet of twin shaft yield strength on the in-plane because described panel is out of shape under stretch mode usually.Use and thisly have excellent shape freezability so that its uniform plastic deformation and cold-rolled steel sheet with low twin shaft yield strength on in-plane can advantageously be made the automobile-used outer panels with complicated shape.
Stretchiness is one of mechanical property of material, when described material is applied drawing force, and its percent change on length of disruptive Materials Measurement to described prolongation and not.Therefore, the high stretch of steel plate can be out of shape on big degree ground described steel plate.
Plastic strain ratio " r " is the defined value of ratio of the strain on strain and the thickness direction on the width.The high-ductility strain ratio is meant, suppose that steel plate has the constant strain amount on width, when coming that by the predetermined deformation amount on the certain orientation steel plate applied drawing force, steel plate with high-ductility strain ratio has a low strain on thickness direction, therefore described steel plate need not constriction (necking) and just can process, even have big deflection.Described plastics strain ratio is because the anisotropy of steel plate produces, and therefore presents the different value that depends on tension direction.
For the value of measurement, average plastic strain ratio r is arranged according to the intensity of variation of the plastic strain ratio of tension direction
mWith intra-face anisotropy index Δ r, they are calculated by following equation (1) and (2) respectively:
r
m＝(r
0+2r
45+r
90)/4 (1)
Δr＝(r
0+r
45+r
90)/2 (2)
In the formula, r
0, r
45And r
90Be respectively that relative plate mill roll direction becomes the plastic strain ratio on 0,45 and 90 tension directions of spending.
The high-ductility strain ratio causes twin shaft yield strength height, thereby is difficult to be processed into the outer panels with complicated shape.Fig. 1 has shown the notional result based on Taylor polycrystal model, and the influence of plastix strain comparison steel plate yield strength track has been described, described steel plate comprises two different main crystalline structure (texture).Under the situation of matter continuously (IF) steel plate, can find from Fig. 1, even steel plate is in the yield strength and average plastic strain ratio r of roll direction with high-ductility strain ratio
mIsotropic steel plate of=1 is identical, and described IF steel plate also has high twin shaft yield strength.
Therefore, in order to reduce twin shaft yield strength, r
mBetter be reduced near 1.
In addition, in order to reduce Δ r, must reduce the difference between the plastic strain ratio of all directions when on all directions, steel plate being applied tension force.
In other words, low Δ r is meant that in stamping process strained is distributed on the in-plane of steel plate evenly, and this helps steel formability, and make its distortion under stretch mode evenly.Like this, in the automobile-used outer panels course of processing that mainly under stretch mode, deforms, r
mNear 1 and the low steel plate of Δ r improved shape freezability.
The technology of the automobile-used steel formability of improvement that other is known hereinafter has been described.
Open communique No. equals into the disclosed technology that is used to improve automobile-used steel plate deformed among the 9-296226 according to Japanese Patent, Ti or Nb are added in the ultralow carbon cold-rolled steel plate as independent component or mixture, sosoloid C and N are deposited as carbide and nitride, improve stretchiness and plastic strain ratio, improved plasticity thus.
In addition, put down into 6-158176, put down into 8-109416, put down into 11-40531, equal into the technology of disclosed improvement plasticity among 4-95392 and the 2002-3951 according to the open communique No. of Japanese Patent, the intra-face anisotropy that reduces described steel plate reduces the defective in stamping process, as planar disfigurement.According to above-mentioned routine techniques, the in-plane anisotropy of described ultralow carbon cold-rolled steel plate reduces by the grain refining of using quenching apparatus to carry out the hot rolling structure immediately after finish rolling.
But there is following problem in above-mentioned routine techniques: have higher r owing to added the ultra low-carbon steel of Ti and/or Nb
mWith Δ r, it demonstrates serious intra-face anisotropy, and demonstrates twin shaft yield strength height with respect to the distortion under the stretch mode, is disadvantageous with regard to shape freezability therefore, even it has good deformability under the deep draw pattern.In addition, according to described routine techniques, because the carbon that only adds below 0.005% or 0.005% improves the deep draw ability usually, so be difficult to obtain high strength.
Simultaneously, DE 3843732, DE 3803064 and U.S. Patent No. 5139580 disclose the method that a kind of manufacturing has the high strength cold rolled steel plate of isotropy plasticity, it controls carbide and microlite structure in course of hot rolling, and anneal by adding Ti, Nb, V etc., in soft steel, form carbide.
But there is following problem in this routine techniques: these technology are to use intermittence, and annealing device carries out, and described arts demand long time period has so just reduced the productive rate of unit time.In addition, the open communique No. of Japanese Patent puts down into 10-130780 and discloses the technology of being used continuous annealing apparatus manufacturing high strength isotropy steel by the soft steel that adds Ti or Nb.The purpose of this technology is to use the low steel plate of close relation manufacturing Δ r of the total degree of drawing of recrystallization and Δ r of the steel plate of described adding Ti or Nb.
In other words,, be equal to or less than 0.1 steel plate, when manufacturing has the automobile-used parts of circle or dihedral post, reduce the formation of pin hole (ear), do not consider by with r though can form Δ r according to this routine techniques
mBe reduced near 1 and guarantee to have good shape freezability.
Simultaneously, for the general steel plate as automobile-used outer panels, it need be equal to or less than the ageing index (AI) of 30MPa.In this respect, because routine techniques is to be used to make formed steel plate to have circle or dihedral post, therefore do not consider ageing index.
Simultaneously, U.S. Patent No. 6162308 discloses a kind of technology of being used continuous annealing apparatus manufacturing high strength isotropy steel plate by the soft steel that adds Ti and/or Nb.Because the purpose of this routine techniques is to make not aged mild steel plate (it does not need to carry out overaging), therefore must outside adding Ti and Nb, add at least a among maximum 0.15% Cu, V and the Ni again.In addition, because the Δ r of described conventional steel plate is 0.15-0.28, be disadvantageous with regard to isotropy therefore.
Summary of the invention
Technical problem
The present invention is used to overcome the above problems, and the object of the present invention is to provide a kind of high-intensity isotropy cold-rolled steel sheet, and it uses the soft steel manufacturing that comprises a small amount of Ti, makes its r
90Be equal to or less than 1.3, r
mNear 1, Δ r is equal to or less than 0.15, guarantees to have good shape freezability, makes it be suitable for steel plate as the automobile-used outer panels of making the distortion carry out stretch mode basically; The method of making above-mentioned steel plate also is provided.
Technical scheme
One aspect of the present invention provides the high strength cold rolled steel plate with excellent shape freezability, has reached the above purpose and other purpose.Described steel plate comprises the Mn, 0.1% or Si still less, 0.03% or P still less, 0.03% or S still less, 0.08% or Sol A l still less (Sol.Al), 0.01% or N still less of Ti, 0.1-1% of C, the 0.005-0.06% of 0.01-0.05%, and the Fe of surplus and other unavoidable impurities, in weight %; Wherein, the composition of Ti and N satisfies following relational expression: Ti/N〉5; The composition of Ti and C satisfies following relational expression: (48/12) C-Ti
*0.03%[wherein, Ti
*=Ti-(48/14) N], and the ageing index of described steel plate (AI) is 30MPa or littler.
Be that described steel plate comprises the C of 0.015-0.035% better.
Be that described steel plate comprises the Ti of 0.01-0.04% better.
Be relational expression (48/12) C-Ti better
*Be 0.06-0.11%.
The present invention provides a kind of manufacturing to have the method for the high strength cold rolled steel plate of excellent shape freezability on the other hand, said method comprising the steps of: at Ar
3Temperature or higher temperature finish rolling steel, hot-rolled steel sheet is provided, described ladle contains the Mn, 0.1% or Si still less, 0.03% or P still less, 0.03% or S still less, 0.08% or Sol A l still less, 0.01% or N still less of Ti, 0.1-1% of C, the 0.005-0.06% of 0.01-0.05%, and the Fe of surplus and other unavoidable impurities, in weight %; Wherein, the composition of Ti and N satisfies following relational expression: Ti/N〉5; The composition of Ti and C satisfies following relational expression: (48/12) C-Ti
*0.03%[wherein, Ti
*=Ti-(48/14) N], and the ageing index of described steel plate (AI) is 30MPa or lower; , then the steel plate coiled is rolled up the hot-rolled steel sheet rapid quenching with 50 ℃/second or faster speed 650 ℃ or lower temperature; The steel plate of opposing connection rolling carries out acidleach, follows the cold rolling described steel plate of rate of reduction (reduction rate) with 50-80%; Be heated to recrystallization temperature to Ar
3Temperature after, cold-rolled steel sheet is annealed; With 3 ℃/second or faster speed described annealed steel plate is cooled to 600-700 ℃ for the first time, then described refrigerative steel plate is cooled to once more 100-500 ℃ temperature with 30 ℃/second or faster speed; Under 200-500 ℃ temperature that the refrigerative steel plate is aging in 10 minutes, and with 0.5% or higher rate of reduction steel plate is carried out temper rolling (skinpass rolling).
Be that described steel plate comprises the C of 0.015-0.035% better.
Be that described steel plate comprises the Ti of 0.01-0.04% better.
Be relational expression (48/12) C-Ti better
*Be 0.06-0.11%.
Be to carry out in 1 second that the rapid quenching of hot-rolled steel sheet is finished in finish rolling better.
Be that the annealing of described steel plate is being carried out below 5 minutes or 5 minutes under 760-820 ℃ better.
Be that described steel plate is annealed with 3 ℃/second or faster speed heating better.
Advantageous effects
Apparent from the above description, the invention provides high-intensity isotropy cold-rolled steel sheet, its r
90Be equal to or less than 1.3, r
mNear 1, and Δ r is low, is equal to or less than 0.15, guarantees to have good shape freezability, makes it be suitable for steel plate as the automobile-used outer panels of making the distortion carry out stretch mode basically; The method of making above-mentioned steel plate also is provided.When forming automobile-used parts, steel plate of the present invention can easily be processed into complicated automobile-used parts under stretch mode.
The accompanying drawing summary
Can be expressly understood the present invention above-mentioned and other purpose, feature and other advantage more by detailed description below in conjunction with accompanying drawing:
Fig. 1 is the figure that concerns between explanation plastic strain ratio and the yield strength track;
Fig. 2 is the figure of the variation of continuous annealing process and the microstructure that causes because of this continuous annealing process in explanation one embodiment of the present invention;
Fig. 3 is the figure that the part of the main crystalline structure that forms in steel is described;
Fig. 4 is the figure of explanation crystalline structure to the influence of r value;
The crystalline orientation figure of steel A of the present invention after carrying out continuous annealing that Fig. 5 is to use EBSD equipment to make;
Fig. 6 is the optical microscopy map of steel A of the present invention after continuous annealing;
Fig. 7 has shown that steel A of the present invention is measured by orientation distribution function ψ after continuous annealing
2The cross section of=45 ° of resulting steel A of the present invention.
Preferred forms of the present invention
Describe preferred implementation in detail below with reference to accompanying drawing.
The present inventor finds in theory, as the r of steel
mBe reduced near 1 o'clock, the twin shaft yield strength of steel also reduces, and so just provides good shape freezability to steel.Then, the inventor is by carrying out various researchs continuously, the technology that provides soft steel that a kind of use comprises a small amount of Ti to make cold-rolled steel sheet makes it the ageing index that has good shape freezability, isotropic structure and be equal to or less than 30MPa, makes this steel plate be suitable for use as automobile-used outer panels.
Found that, by the amount of Ti, N and C in the adjustment steel plate, make it have the predetermined composition relation, and adjust the condition of making steel plate, specifically is hot-rolled condition and annealing conditions, can make high strength cold rolled steel plate by continuous annealing apparatus, its r
90Be equal to or less than 1.3, r
mNear 1, and Δ r is low, is equal to or less than 0.15, and ageing index is 30MPa.
At first, the reasons are as follows of the composition of steel plate of the present invention and this scope is described in detail, and hereinafter " weight % " simple table is shown " % ".
Carbon is a kind of matter sosoloid element in the steel, and to the intensity of cold rolling and annealing process light plate and the influence that crystalline structure has highly significant, the form with iron carbide exists simultaneously.Carbon content is preferably 0.01-0.05%.When carbon content less than 0.01% the time, the intensity of described steel plate reduces, and Δ r excessively increases.
Therefore, require carbon content be 0.01% or more than.In addition, because C and Fe coupling form iron carbide in steel, C can stably be present in the steel.In the present invention,, must have the C of appropriate amount, make C in steel, be deposited as iron carbide for fear of aged at room temperature.Because excessive C causes the intensity of steel to significantly improve, ductility lowers, and makes the cold rolling performance degradation of steel, thus carbon content on be limited to below 0.05% or 0.05%.
Be that carbon content is 0.015-0.035% better.When steel heats during in continuous annealing, C and Ti coupling are deposited as TiC in steel.Sedimentary TiC provides the PH effect to steel, and it causes the intensity of steel to increase.In addition, the normal direction (ND) that helps reducing Δ r plays the effect that enlarges the crystal grain rate of recovery and recrystallization speed, it have be parallel to＜111 crystalline orientation (＜111〉//ND), make to have crystallization direction＜111 //crystal grain of ND partly reduces.Simultaneously, the C of trace at high temperature is deposited as Ti
4C
2S
2, it is thicker than TiC, and therefore the development to the crystalline orientation of recrystallization particle not have to influence substantially.
In the present invention, Ti is one of most important element except that C.Ti and N and C coupling form TiN, and the effect that suppresses AlN formation is provided.The AlN settling that forms in course of hot rolling causes the hot rolling construction stretch, has improved the anisotropy of steel plate shape thus.Like this, Ti plays by suppressing that AlN forms and depositing Ti C reduces the effect of the crystal grain part with strong anisotropy orientation, therefore has by PH to reduce Δ r and improve the effect of steel strength.
But because Ti is expensive element, from manufacturing originally, it is favourable adding the least possiblely in the steel.Therefore, in the present invention, consider manufacturing cost and can not make to add the obtained deleterious of Ti that Ti is preferably 0.005-0.06%.Be that Ti is 0.01-0.04% better.Simultaneously, be deposited as TiC in order to make Ti in annealing process, and suppress the formation of AlN, must add Ti in steel, the ratio (Ti/N) that makes Ti and N is greater than 5, i.e. Ti/N〉5.
In addition, because the C that must have appropriate amount, so that the C of described appropriate amount is deposited as iron carbide, to suppress aged at room temperature, Ti content better satisfies following relational expression (at C and N):
(48/12) C-Ti
*0.03%, wherein, Ti
*=Ti-(48/14) N.
At this, Ti
*Refer to effective Ti content, it is to form the required Ti amount of TiC, has wherein got rid of the Ti amount (being to form in order to suppress AlN in course of hot rolling) that must be used to form TiN.Be C and effective Ti (Ti better
*) ratio, i.e. (48/12) C-Ti
*Be 0.06-0.11%.
Mn is used for the effective element that sosoloid is strengthened in the steel, and and steel in S be deposited as MnS together, suppress the high-temperature embrittlement that causes because of S in level and smooth cracking (slip breakage) and the course of hot rolling thus.In experiment of the present invention, when Mn content less than 0.1% the time, can not improve intensity, and S can not deposit by Mn, be difficult to guarantee the plasticity of steel like this.On the contrary, when Mn content greater than 1% the time, then superfluous because of adding the advantageous effects that Mn causes.
Si plays the effect of sosoloid strengthening element in the steel, and better adds below 0.1% or 0.1%, has suitable stretchiness to guarantee steel.
Higher P content is highly beneficial to improving steel strength.But excessive P has increased the possibility of steel embrittlement, and this causes the level and smooth rimose possibility of course of hot rolling plate of moderate thickness height.In addition, when adding excessive P in steel, P is diffused into crystal grain (gain) border easily, and is isolated in wherein after annealing, causes secondary processing embrittlement in the forming technology process thus.Therefore, P content must limit.In the present invention, because the PH effect that produces by TiC can make steel reach required intensity, P content better is limited in below 0.03% or 0.03%.
Nitrogen and sulphur are the inevitable elements of introducing in the steel process for making in the steel, therefore importantly make the content of N and S low as far as possible.But, for the final content that reduces nitrogen and sulphur, the problem that exists a steel refining cost to improve.In this, require the content of N and S to be reduced in the acceptable scope of operational condition, in the present invention, S content better is restricted to below 0.03% or 0.03%.In addition, because therefore N at high temperature forms TiN, and can change the effective Ti content that is used for coupling C, higher N content can cause reducing the problem of effective Ti content.Therefore, in the present invention, N content better is restricted to below 0.01% or 0.01%.
Sol A l is effective as the deoxygenated element of fusion steel.But because there is negative influence in excessive Sol A l to the plasticity of steel, so the content of Sol A l better is limited to below 0.08% or 0.08%.
Below describe the method that the present invention makes high tensile steel plate in detail.
As for the raw material of hot-rolled steel sheet, can use by the formed steel of continuous casting with above composition, need not to form ingot iron.Perhaps, can use heating steel ingot afterwards once more with above-mentioned composition.At this moment, when using described steel ingot to form steel plate, require steel ingot is heated to more than 1200 ℃ or 1200 ℃ once more, make the Ti that in the steel ingot process of cooling, forms
4C
2S
2Be dissolved in once more in the steel, as sosoloid.
In the present invention, carry out hot rolling, form hot-rolled steel sheet according to ordinary process, and require finish rolling for the last time at Ar
3Or finish under the above temperature.If the hot rolled outlet temperature reduces, then the surface of hot-rolled steel sheet and edge will hot rollings under the temperature of two phase region, make crystal grain become thicker, and the heterogeneity that becomes causes surface imperfection occurring at the stamping process light plate.
After finish rolling, steel plate is gone up with 50 ℃/second or faster speed rapid quenching to roll bending temperature or higher temperature, to form close grain in hot-rolled steel sheet at runoff table (ROT).If steel plate quenches with the speed less than 50 ℃/second, then crystal grain can chap.
In addition, described steel plate is more preferably after finish rolling is finished and quenches in 1 second, to form thinner crystal grain.The rapid quenching of steel plate can use the high-density water cooler that is installed in the ROT front to carry out.After with steel plate quenching, steel plate more fortunately under 650 ℃ or the following temperature around volume.Surpass 650 ℃ around the volume temperature and can make the chap of TiC settling, the time-delay answer effect and the recrystallization speed of subgrain (having strong anisotropy orientation in annealing process) are died down, improve the ratio of crystal grain thus with strong anisotropy orientation.
The steel plate of described coiled volume carries out acidleach by ordinary process, better carries out cold rolling with the rate of reduction of 50-80% then.If cold rolling rate of reduction less than 50%, then can not be carried out recrystallization fully in annealing process, so just reduced ductility, if cold rolling rate of reduction greater than 80%, then the intra-face anisotropy of steel plate improves.
Among the present invention, annealing is meant continuous annealing shown in Figure 2, in recrystallization temperature or higher temperature and less than Ac
3Or carry out under the lower temperature.If annealing temperature surpasses Ac
3, then described steel plate is annealed in the two-phase coexistent zone of α and γ, promotes to have the crystal grain recrystallization of strong anisotropy orientation and grow up, and makes crystal grain thicker.Because thicker crystal grain can cause intensity and ductility variation simultaneously, so annealing temperature better is limited in Ac
3Or following temperature.
On the other hand, be starkly lower than recrystallization temperature as if annealing temperature, then the ductility variation.Therefore, annealing temperature is more preferably and is 760-820 ℃.In addition, kept 5 minutes under the above annealing temperature of steel plate.Steel plate keeps the longer time can cause r under above-mentioned annealing temperature
90 increases, and the grain growth with strong anisotropic crystalline orientation.
In addition, cold-rolled steel sheet better is heated to annealing temperature with 3 ℃/second or above speed.Rate of heating can cause the annealing cycle elongated less than 3 ℃/second, may make grain coarsening.
Afterwards, institute's annealed steel plate is cooled off for the first time, temperature to 600-700 ℃, this temperature is carbon high temperature of solid solubility in Fe matrix, carry out the secondary cooling then immediately, to 100-500 ℃ temperature, this temperature is carbon low temperature of solid solubility in Fe matrix, makes iron carbide be deposited on grain boundary and at the interface.First cooling is better carried out with 3 ℃/second or above speed.And secondary cooling is better carried out with 30 ℃/second or above speed.
If the secondary speed of cooling is less than 30 ℃/second, so oversaturated C can stop iron carbide fully to deposit, and causes the ductility variation thus, and causes aged at room temperature.After the secondary cooling, steel plate is heated to 200-500 ℃ once more, and overaging afterwards grows up sedimentary iron carbide below 10 minutes or 10 minutes.If carry out overaging being lower than under 200 ℃ the temperature, iron carbide can not fully be grown up so, makes a part of C be dissolved into sosoloid once more, makes the ductility variation and causes aged at room temperature; And if carry out overaging being higher than under 500 ℃ the temperature, the solubleness of the C in the Fe matrix can increase, and makes the ductility variation like this, and causes aged at room temperature.
Then, better with 0.5% or above rate of reduction steel plate is carried out temper rolling.
Pattern of the present invention
The present invention provide following examples in order more to be expressly understood.The data that should be understood that the concrete technology, condition, ratio and the record that are used to illustrate the principle of the invention and embodiment are exemplary, therefore can not be used to limit the scope of the invention.
Fusing and continuous casting have composition shown in Figure 1 adding after the soft steel of Ti, steel is heated to 1200 ℃ once more, and in 870-890 ℃ of following hot finishing to 2.5 (doubly).Then, after through the time opening of quenching shown in the table 2, the hot rolled steel passes through the high-density water cooler with 60 ℃/second speed, quenches; And shown in the table 2 under the volume temperature coiled volume.After the surface oxide layer on the steel plate of removing the coiled volume, steel plate is with the cold rolling one-tenth 0.75 of 70% rate of reduction (doubly).
Then, cold-rolled steel sheet is heat-treated on the continuous annealing streamline.In heat treatment process, steel plate is heated to the highest 780-800 ℃ temperature.After the heating steel plate 1 minute, steel plate is cooled to 700 ℃ for the first time with 5 ℃/second speed under this temperature, is cooled to 100 ℃ with 60 ℃/second speed secondary then.Described steel plate is heated to 300-350 ℃ once more, and wore out 3 minutes, and carry out temper rolling with rate of reduction 1-1.3%.After institute's annealed steel plate is processed into the EN10002-1 test sample, steel plate after the annealing that makes by above-mentioned technology is carried out tension test.
Table 1
Following table 2 has shown makes the condition with cold-rolled steel sheet of forming shown in the table 1, and the result of uniaxial test.In table 2, FDT represents the outlet temperature of finish rolling, and CT represents that ST represents annealing temperature around the volume temperature, and YP represents yield strength, and TS represents tensile strength, and E1 represents total extensibility, r
90Represent that relative plate mill roll direction is the plastic strain ratio on 90 directions of spending, anisotropic index in the Δ r presentation surface, AI represents ageing index.AI use the stress of fluidity that applies before the heating steel plate after 7.5% prestrain with 100 ℃ down the difference of the stress of fluidity after the heating steel plate 1 hour calculate.
Table 2
In the table 2, steel plate A-H of the present invention satisfies composition of the present invention and creates conditions.As seen in Table 2, these samples have and are equal to or less than 1.3 r
90, and Δ r is equal to or less than 0.15, and anisotropic index in low twin shaft yield strength and the bottom surface is provided like this.
Simultaneously, comparative steel I-L is different from the present invention, relative nitrogen content, and its Ti content is low.In other words, because Ti/N is less than of the present invention 5, the Δ r of these comparative steel is equal to or greater than 0.15.Concrete is, in the creating conditions of comparative steel I and J, the quenching time opening after finish rolling is than length of the present invention.
In comparative steel M and N, the Ti/N ratio within the scope of the invention, and r
90, Δ r and ageing index all not within the scope of the invention.For comparative steel M, think owing to around rolling up temperature than height of the present invention, in hot-rolled steel sheet, TiC is deposited because of sosoloid C, and chap, the deposition of TiC is not enough in annealing process, makes to have high r
90Increase with the development of the crystalline orientation of Δ r ({ 554}＜225 〉), cause like this obtaining the isotropy steel.For comparative steel M and N, think because Ti content can not satisfy relational expression (48/12) C-Ti
*=0.6, the ageing index height of described steel.
In addition, for comparative steel 0, quench the time opening not within the scope of the invention.Compare with the quenching time opening that shortens, the structure chap of hot-rolled steel sheet, the nucleation number of sites that is used for iron carbide in the cold-rolled process after annealing reduces.Therefore, the aged at room temperature index height of comparative steel 0, Δ r is equal to or greater than 0.15.
Fig. 3 has shown the orientation distribution function ψ of the major portion that crystalline structure forms in the relative steel
2=45 °.Fig. 4 has shown use Taylor polycrystal theory, calculates crystalline structure for the anisotropic Theoretical Calculation result in the plastic strain ratio of the major portion of crystalline structure shown in Figure 3.
Apparent from Fig. 4, there is different influences in the crystalline structure of the crystalline structure of alpha fibers (RD//＜110 〉) and gamma fiber (ND//＜111 〉) to plastic strain ratio.For the crystalline structure of alpha fibers (RD//＜110 〉), plastic strain ratio is low usually, and r
45Be maximum, and for comprise gamma fiber (ND//＜111 〉) 554}＜225〉and crystalline structure, r
45It is Schwellenwert.Therefore, the incompatible isotropy steel that provide of suitable groups that need above-mentioned crystalline structure as can be known.
Fig. 5 is to use the crystalline orientation figure (COM) of the steel A of the present invention that electronics backscattering diffraction (EBSD) equipment that is installed to field emission scanning electron microscope (FE-SEM) obtains.When the color on the counter-rotating utmost point figure more shown in Figure 5, can find that the crystalline structure of alpha fibers in the steel of the present invention (RD//＜110 〉) and gamma fiber (ND//＜111 〉) fully develops.Fig. 6 has shown the result who analyzes crystal grain and iron carbide by opticmicroscope.Can find that from Fig. 6 iron carbide mainly is formed on granule boundary.Fig. 7 has shown orientation distribution function (ODF) ψ based on the data that correction data obtained of utmost point figure
2=45 °, above-mentioned utmost point figure provides by the X-ray diffraction of microcrystalline texture development among the steel A of the present invention.
Can find that from Fig. 7 the crystalline structure of alpha fibers (RD//＜110 〉) and gamma fiber (ND//＜111 〉) fully develops.According to these test-results, the crystalline structure of (ND//＜111 〉) fully develops as can be known because alpha fibers (RD//＜110 〉) and gamma fiber in the steel of the present invention, and steel of the present invention have good isotropy.
The embodiment and the accompanying drawing that should be understood that description are used for illustrative purposes, and the present invention is only limited by following claims.And those skilled in the art can carry out various modifications, interpolation and replacement as can be known under the condition that does not deviate from the described scope of the invention of appended claims and spirit.
Claims (9)
1. high strength cold rolled steel plate with excellent shape freezability, it comprises, in weight %, the Mn of the C of 0.015-0.035%, the Ti of 0.005-0.06%, 0.1-1%, 0.1% or Si still less, 0.03% or P still less, 0.03% or S still less, 0.08% or solubility in acid Al still less, 0.01% or N still less, and the Fe of surplus and other unavoidable impurities; Wherein, the composition of Ti and N satisfies following relational expression: Ti/N〉5; The composition of Ti and C satisfies following relational expression: (48/12) C-Ti
*0.03%, Ti wherein
*=Ti-(48/14) N, the ageing index of described steel plate is 30MPa or lower.
2. the described cold-rolled steel sheet of claim 1 is characterized in that, described steel plate comprises the Ti of 0.01-0.04%.
3. claim 1 or 2 described cold-rolled steel sheets is characterized in that, relational expression (48/12) C-Ti
*Be 0.06-0.11%.
4. a manufacturing has the method for the high strength cold rolled steel plate of excellent shape freezability, said method comprising the steps of:
At Ar
3Temperature or higher temperature finish rolling steel, hot-rolled steel sheet is provided, described ladle contains, in weight %, the Mn of the C of 0.015-0.035%, the Ti of 0.005-0.06%, 0.1-1%, 0.1% or Si still less, 0.03% or P still less, 0.03% or S still less, 0.08% or solubility in acid Al still less, 0.01% or N still less, and the Fe of surplus and other unavoidable impurities; Wherein, the composition of Ti and N satisfies following relational expression: Ti/N〉5; The composition of Ti and C satisfies following relational expression: (48/12) C-Ti
*0.03%, Ti wherein
*=Ti-(48/14) N, the ageing index of described steel is 30MPa or lower;
, then the steel plate coiled is rolled up the hot-rolled steel sheet rapid quenching with 50 ℃/second or faster speed 650 ℃ or lower temperature;
The steel plate of opposing connection rolling carries out acidleach, then with the cold rolling described steel plate of the rate of compression of 50-80%;
Be heated to recrystallization temperature-Ar
3Temperature after, cold-rolled steel sheet is annealed;
With 3 ℃/second or faster speed described annealed steel plate is cooled to 600-700 ℃ for the first time, then described refrigerative steel plate is cooled to once more 100-500 ℃ temperature with 30 ℃/second or faster speed;
In 10 minutes under 200-500 ℃ temperature with the overaging of refrigerative steel plate; And
With 0.5% or higher rate of reduction steel plate is carried out temper rolling.
5. the described method of claim 4 is characterized in that, described ladle contains the Ti of 0.01-0.04%.
6. claim 4 or 5 described methods is characterized in that, relational expression (48/12) C-Ti
*Be 0.06-0.11%.
7. the described method of claim 4 is characterized in that, carries out in 1 second that the rapid quenching of described hot-rolled steel sheet is finished in finish rolling.
8. the described method of claim 4 is characterized in that, the annealing of described steel plate is being carried out below 5 minutes under 760-820 ℃ the temperature.
9. claim 4 or 8 described methods is characterized in that, described steel plate is annealed with 3 ℃/second or faster speed heating.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR1020040077814A KR20060028909A (en) | 2004-09-30 | 2004-09-30 | High strength cold rolled steel sheet with excellent shape freezing property and manufacturing method thereof |
| KR1020040077814 | 2004-09-30 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN101031666A CN101031666A (en) | 2007-09-05 |
| CN100494449C true CN100494449C (en) | 2009-06-03 |
Family
ID=36740656
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB2005800329215A Expired - Fee Related CN100494449C (en) | 2004-09-30 | 2005-09-30 | High strength cold rolled steel sheet having excellent shape freezability, and method for manufacturing the same |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US20070289679A1 (en) |
| EP (1) | EP1805339A4 (en) |
| JP (1) | JP2008514820A (en) |
| KR (1) | KR20060028909A (en) |
| CN (1) | CN100494449C (en) |
| WO (1) | WO2006080670A1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2013060619A (en) * | 2011-09-12 | 2013-04-04 | Jfe Steel Corp | Thin steel sheet excellent in workability and method for producing the same |
| JP5862254B2 (en) * | 2011-12-08 | 2016-02-16 | Ｊｆｅスチール株式会社 | Hot-rolled steel sheet for cold rolling material and manufacturing method thereof |
| CN104254633B (en) * | 2012-04-26 | 2016-10-12 | 杰富意钢铁株式会社 | There is good ductility, stretch flangeability, the high tensile hot rolled steel sheet of uniform in material and manufacture method thereof |
| KR101594670B1 (en) * | 2014-05-13 | 2016-02-17 | 주식회사 포스코 | Cold-rolled steel sheet and galvanized steel sheet having excellent ductility and method for manufacturing thereof |
| KR101676194B1 (en) * | 2015-11-13 | 2016-11-15 | 주식회사 포스코 | High Strength Blackplate Having Excellent Flangeability And Method For Manufacturing The Same |
| CN105441802B (en) * | 2015-12-01 | 2017-05-24 | 攀钢集团西昌钢钒有限公司 | Titanium-containing acid pickling plate and preparation method thereof |
| KR101786318B1 (en) * | 2016-03-28 | 2017-10-18 | 주식회사 포스코 | Cold-rolled steel sheet and plated steel sheet having excellent yield strength and ductility and method for manufacturing thereof |
| JP7343788B2 (en) * | 2020-03-26 | 2023-09-13 | 日本製鉄株式会社 | Heat treatment simulation method, heat treatment simulation device, and program |
| CN113122690B (en) * | 2021-04-16 | 2022-03-22 | 攀钢集团攀枝花钢铁研究院有限公司 | Low-delta r-value micro-carbon steel cold-rolled steel plate and preparation method thereof |
| CN115627424B (en) * | 2022-11-07 | 2023-08-18 | 鞍钢股份有限公司 | 1.5 GPa-grade high-plasticity cold-rolled DH steel and preparation method thereof |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR800000710B1 (en) * | 1979-09-15 | 1980-07-23 | 히라이도미 사부로오 | High strength cold rolled steel sheet having bake-hardening properties |
| JPS57169022A (en) * | 1981-04-11 | 1982-10-18 | Sumitomo Metal Ind Ltd | Production of cold rolled mild steel plate by continuous annealing |
| DE3803064C2 (en) * | 1988-01-29 | 1995-04-20 | Preussag Stahl Ag | Cold rolled sheet or strip and process for its manufacture |
| JPH04500541A (en) * | 1989-05-09 | 1992-01-30 | シュタールヴェルケ パイネ・ザルツギッター アクチエンゲゼルシャフト | Method for producing hot strip material that does not buckle and aging-resistant cold strip material that is plated |
| CA2037316C (en) * | 1990-03-02 | 1997-10-28 | Shunichi Hashimoto | Cold-rolled steel sheets or hot-dip galvanized cold-rolled steel sheets for deep drawing |
| JP2814818B2 (en) * | 1992-01-22 | 1998-10-27 | 日本鋼管株式会社 | Manufacturing method of cold-rolled steel sheet for deep drawing with excellent material stability |
| DE19622164C1 (en) * | 1996-06-01 | 1997-05-07 | Thyssen Stahl Ag | Cold rolled steel sheet with good drawing properties |
| JP3546287B2 (en) * | 1997-10-15 | 2004-07-21 | Ｊｆｅスチール株式会社 | High-strength hot-rolled steel sheet excellent in workability and method for producing the same |
| JP4157279B2 (en) * | 1998-07-27 | 2008-10-01 | 新日本製鐵株式会社 | Ferritic steel sheet with excellent shape freezing properties |
| TW550296B (en) * | 2000-02-29 | 2003-09-01 | Kawasaki Steel Co | High tensile cold-rolled steel sheet having excellent strain aging hardening properties and manufacturing method thereof |
-
2004
- 2004-09-30 KR KR1020040077814A patent/KR20060028909A/en not_active Ceased
-
2005
- 2005-09-30 US US11/664,182 patent/US20070289679A1/en not_active Abandoned
- 2005-09-30 WO PCT/KR2005/003239 patent/WO2006080670A1/en active Application Filing
- 2005-09-30 EP EP05856408A patent/EP1805339A4/en not_active Withdrawn
- 2005-09-30 JP JP2007534514A patent/JP2008514820A/en not_active Withdrawn
- 2005-09-30 CN CNB2005800329215A patent/CN100494449C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| EP1805339A4 (en) | 2009-03-25 |
| CN101031666A (en) | 2007-09-05 |
| US20070289679A1 (en) | 2007-12-20 |
| JP2008514820A (en) | 2008-05-08 |
| EP1805339A1 (en) | 2007-07-11 |
| WO2006080670A1 (en) | 2006-08-03 |
| KR20060028909A (en) | 2006-04-04 |
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