CN109536837B - high-N-content ultrafine-grain 1200 MPa-grade cold-rolled dual-phase steel and production process thereof - Google Patents
high-N-content ultrafine-grain 1200 MPa-grade cold-rolled dual-phase steel and production process thereof Download PDFInfo
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Abstract
The invention discloses high-N-content ultrafine-grained 1200 MPa-grade cold-rolled dual-phase steel and a production process thereof, belongs to the technical field of automobile steel, and solves the problems that the existing cold-rolled dual-phase steel cannot simultaneously meet ultrahigh strength, high plasticity, low yield ratio and low cost. The steel comprises the following components in percentage by mass: c: 0.14% -0.17%, Si: 0.20-0.30%, Mn: 1.5-2.0%, P is less than or equal to 0.015%, S is less than or equal to 0.010%, V: 0.10-0.15%, Cr: 0.03% -0.04%, Als: 0.02-0.03%, N: 0.012-0.018 wt% of Fe, C/N not more than 12 wt%, N/V not more than 0.15 wt% and Fe and inevitable impurity for the rest. The high N content ultrafine grain 1200MPa grade cold rolled dual phase steel is suitable for automobile steel.
Description
Technical Field
The invention belongs to the technical field of automobile steel, and particularly relates to high-N-content ultrafine-grained 1200 MPa-grade cold-rolled dual-phase steel and a production process thereof.
Background
Advanced high-strength steel is the fastest growing material in the automobile industry at present, and light weight and high safety are important development directions in the automobile industry, so that the automobile steel is required to have mechanical properties of high strength, high plasticity and high product of strength and elongation after fracture. In this field, dual phase steels are the most widely used materials. According to the prediction of Goldman Sachs Japan, the global automobile yield reaches 1.07 hundred million vehicles by 2020, and the annual consumption of dual-phase steel in global automobiles reaches 1400 million tons. However, as the strength is continuously improved, the plasticity of the material is increasingly poor, and particularly, the high-strength steel above 1180MPa has general damage resistance, which is one of the main factors limiting the further development of the high-strength steel.
The microstructure of dual phase steel is mainly martensite and ferrite, wherein martensite is considered as a hard phase to have strength, and ferrite is considered as a soft phase to have ductility. How to improve the strength and have higher plasticity is a problem which needs to be solved urgently by the current dual-phase steel.
The patent (CN108193139A) discloses 1180MPa grade cold-rolled high-strength dual-phase steel for automobiles and a production method thereof, and the chemical components of the steel are as follows: 0.10 to 0.13 percent of C, 0.45 to 0.68 percent of Si, 2.25 to 2.55 percent of Mn, less than or equal to 0.02 percent of P, less than or equal to 0.008 percent of S, 0.10 to 0.14 percent of Ti, 0.40 to 0.65 percent of Cr, 0.17 to 0.21 percent of Mo, less than or equal to 0.0050 percent of N, 0.025 to 0.060 percent of Als, and the balance of Fe and inevitable impurities. Through the addition of alloy elements such as Ti, Cr, Mo and the like and the control of a continuous annealing process, the dual-phase steel with the yield strength of 800-900 MPa and the tensile strength of more than 1200MPa is produced, the yield ratio is high, the elongation is low, the forming performance is poor, and the cost is increased due to the addition of excessive alloy elements. The prior art can not simultaneously meet the requirements of low cost, ultrahigh strength (tensile strength is more than or equal to 1200MPa), low yield ratio (yield ratio is less than or equal to 0.5) and high elongation (A)50Not less than 15 percent).
Disclosure of Invention
In view of the above analysis, the invention aims to provide the high-N-content ultrafine-grained 1200 MPa-grade cold-rolled dual-phase steel and the production process thereof, and the problems that the existing cold-rolled dual-phase steel cannot simultaneously meet the requirements of ultrahigh strength, high plasticity, low yield ratio and low cost are fundamentally solved by optimizing alloy components and adjusting continuous annealing process parameters.
The purpose of the invention is mainly realized by the following technical scheme:
a high-N-content ultrafine-grained 1200 MPa-grade cold-rolled dual-phase steel comprises the following components in percentage by mass: c: 0.14% -0.17%, Si: 0.20-0.30%, Mn: 1.5-2.0%, P is less than or equal to 0.015%, S is less than or equal to 0.010%, V: 0.10-0.15%, Cr: 0.03% -0.04%, Als: 0.02-0.03%, N: 0.012-0.018 wt% of Fe, C/N not more than 12 wt%, N/V not more than 0.15 wt% and Fe and inevitable impurity for the rest.
Further, the components by mass percent are as follows: c: 0.15% -0.16%, Si: 0.25-0.28%, Mn: 1.76-1.89%, P is less than or equal to 0.005%, S is less than or equal to 0.004%, V: 0.11-0.136%, Cr: 0.034% -0.038%, Als: 0.022-0.024%, N: 0.013-0.017 percent, wherein C/N is less than or equal to 12, N/V is less than or equal to 0.15, and the balance of Fe and inevitable impurities.
Further, the volume fraction of ferrite in the steel is 50-65%, and the volume fraction of martensite is 35-50%.
Further, the grain size of ferrite of the steel is less than or equal to 1.6 μm.
A production process of high-N content ultrafine grain 1200MPa cold-rolled dual-phase steel is characterized by comprising the following steps:
s1, heating a steel billet and carrying out soaking treatment;
s2, removing phosphorus by using high-pressure water, carrying out hot rolling, cooling to 450-550 ℃ at a cooling speed of 12-13 ℃/s by adopting a post-rolling front-stage cooling process after rolling is finished, and coiling;
s3, carrying out cold rolling on the hot rolled plate after acid pickling;
and S4, continuous annealing.
Further, in step S1, the temperature of the soaking section is 1220 to 1250 ℃, and the soaking time is 120 min.
Further, in step S2, the initial rolling temperature of hot rolling is 1150-1200 ℃, and the final rolling temperature is higher than 900 ℃.
Further, in step S3, the cold rolling reduction is controlled to be 60 to 70%.
Further, in step S4, the continuous annealing is performed by controlling the soaking temperature to be 740-770 ℃, the slow cooling temperature to be 670-700 ℃ and the overaging temperature to be 280-330 ℃.
Furthermore, the produced cold-rolled dual-phase steel has the thickness of 1.0-2.0 mm, the yield strength of the material is more than or equal to 600MPa, the tensile strength is more than or equal to 1200MPa, and the elongation A50Not less than 15 percent and the yield ratio not more than 0.5.
Compared with the prior art, the invention has the following beneficial effects:
1) the invention adopts vanadium-nitrogen microalloying technology, and V is separated out in austenite during hot rolling, so that austenite grains can be refined; ferrite grains are obviously refined in the hot rolling and cooling process; in the continuous annealing process, V is dispersed and precipitated in ferrite, the effect of selectively strengthening the ferrite is achieved, and the influence of the martensite content on the strength and the ductility of the dual-phase steel is reduced. The N energy and the V in the steel are combined to form second phase particle precipitation, the nitrogen increasing energy in the steel controls the precipitation of the V in austenite, the distribution of the V which plays a role in fine grain strengthening and precipitation strengthening is changed, a process route of the fine grain strengthening of the V can be played, the fine grain strengthening replaces part of the precipitation strengthening, and the plasticity of a matrix is improved under the condition of unchanged strength. Yield strength is not lower than 600MPa, tensile strength is not lower than 1200MPa, and elongation A50Not less than 15 percent, and the yield ratio is less than or equal to 0.5, and simultaneously meets the requirements of ultrahigh strength, high plasticity, low yield ratio and low cost.
2) The steel adopts vanadium-nitrogen microalloying technology, selectively strengthens ferrite through vanadium, reduces the relevance of tensile strength and martensite content, reduces the sensitivity of alloy to critical annealing temperature, obtains an ultra-fine grain structure below 1.6 mu m, and obtains ultra-high strength and high plasticity cold-rolled dual-phase steel.
3) The cold-rolled dual-phase steel is finally rolled at the temperature of over 900 ℃, the load on a rolling mill is small, and the service life of the rolling mill can be effectively ensured.
4) The increase of nitrogen promotes the separation of V, can effectively reduce the using amount of vanadium, saves vanadium resources and reduces cost.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims thereof.
Detailed Description
A high N content ultra fine grain 1200MPa grade cold rolled dual phase steel and its production process will be described in further detail with reference to specific examples, which are provided for comparison and explanation purposes only and the present invention is not limited to these examples.
The high-N-content ultrafine-grained 1200 MPa-grade cold-rolled dual-phase steel is characterized by comprising the following chemical components in percentage by mass: c: 0.14% -0.17%, Si: 0.20-0.30%, Mn: 1.5-2.0%, P is less than or equal to 0.015%, S is less than or equal to 0.010%, V: 0.10-0.15%, Cr: 0.03% -0.04%, Als: 0.02-0.03%, N: 0.012-0.018 wt% of Fe, C/N not more than 12 wt%, N/V not more than 0.15 wt% and Fe and inevitable impurity for the rest.
By adopting a vanadium-nitrogen microalloying mode, the using amount of vanadium can be effectively reduced, vanadium resources are saved, the production cost is reduced, the sensitivity of the alloy to the critical annealing temperature is reduced, an ultrafine grain structure below 1.6 mu m is obtained, ferrite is selectively strengthened by vanadium, the relevance of the tensile strength and the martensite content is reduced, and the cold-rolled dual-phase steel with ultrahigh strength and high plasticity is obtained.
Specifically, in the high-N content ultrafine grain 1200MPa grade cold-rolled dual-phase steel, the action and the proportion of each element are as follows:
c is the most important solid solution strengthening element in the dual-phase steel and is the guarantee of high strength of the material, when the carbon content is too low, the austenite content is low when the dual-phase steel is heated in the same critical region (ferrite and austenite), which is not beneficial to obtaining high strength, but the carbon content is too high, which is not beneficial to the welding performance of the material, so the C content needs to be controlled in a proper range. Although the carbon content is reduced in the present invention, the range of V is set to 0.14% to 0.17% in order to promote the precipitation of V.
Si is also an important solid solution strengthening element, on one hand, the strength of the material can be improved, on the other hand, Si can effectively promote the enrichment of C element to austenite, the hardenability of austenite is improved, and meanwhile, a ferrite phase is purified, the elongation is improved, but excessive Si element can bring adverse effects on the welding performance and the surface quality. Therefore, in order to achieve the strength, weldability, and surface quality at the same time, the range is defined as 0.20% to 0.30%.
Mn is an alloy element which plays a main role in the micro-alloying steel phase transformation strengthening and solid solution strengthening mechanism, and can also improve the stability of austenite and enable the C curve to move to the right, thereby obviously reducing the critical cooling rate of martensite. However, since the weldability of steel deteriorates due to an excessively high Mn content, the range is defined as 1.5% to 2.0%.
P is an impurity element in steel, and the lower the content of P is, the better the performance of the dual-phase steel is, so that the P is limited to be less than or equal to 0.015 percent.
S is an unavoidable harmful element in steel, and forms MnS inclusions to reduce toughness and weldability of the steel, so that its content is reduced as much as possible to be controlled to be less than 0.010%.
Als is a deoxidizer in steel, and when the content of Als is less than 0.02%, the effect cannot be exhibited, but the content of Al cannot be too high, and it can combine with the content of N to form AlN, and the range of 0.02% to 0.03% is determined from the results of many tests.
Cr can remarkably retard the transformation of pearlite and bainite and improve the hardenability of austenite, so that enough martensite guaranteed strength is obtained, and the dual-phase steel is beneficial to production, but the cost is increased due to excessive addition of Cr, and the range of Cr is regulated to be 0.03-0.04% through repeated tests.
V is a key microalloying element in the cold-rolled dual-phase steel. During hot rolling, V is separated out from austenite, so that austenite grains can be refined; meanwhile, the interface energy of the particles and ferrite is small, and ferrite grains are obviously refined in the hot rolling cooling process. In the continuous annealing process, V is dispersed and precipitated in ferrite, the effect of selectively strengthening the ferrite is achieved, and the influence of the martensite content on the strength and the ductility of the dual-phase steel is reduced. When the vanadium content is less than 0.10%, the minimum strength requirement required in the present invention cannot be satisfied. Meanwhile, the upper limit should be controlled to be 0.15% for cost.
N is a key microalloying element in the cold-rolled dual-phase steel. N energy and V in steel are combined to form second phase particles to be separated out, nitrogen increasing energy in the steel controls the separation of V in austenite, the distribution of V which plays a role in fine-grain strengthening and precipitation strengthening is changed, a process route of the fine-grain strengthening effect of V can be played, fine-grain strengthening is used for replacing part of the precipitation strengthening effect, the plasticity of a matrix is improved under the condition that the strength is not changed, the separation of V is promoted by the increase of nitrogen, and therefore the using amount of V is reduced, and the cost is reduced. However, too high an N content increases the age brittleness of the steel. Therefore, in combination with the content of V, the content of N should be controlled to be 0.012-0.018%.
In addition, the N and V contents need to satisfy that N/V is less than or equal to 0.15, and the N and C contents need to satisfy that C/N is less than or equal to 12, which are important control factors in the invention, mainly because when the N content is less, the residual V can be combined with C to be separated out, so that the strength of the steel is reduced, the N content is too high, the V can not completely fix nitrogen, and the aging brittleness of the steel is increased.
In order to further improve the comprehensive performance of the high-N content ultrafine grain 1200MPa grade cold-rolled dual-phase steel, the composition of the steel can be further adjusted. Illustratively, the composition may be, in weight percent: c: 0.15% -0.16%, Si: 0.25-0.28%, Mn: 1.76-1.89%, P is less than or equal to 0.005%, S is less than or equal to 0.004%, V: 0.11-0.136%, Cr: 0.034% -0.038%, Als: 0.022-0.024%, N: 0.013-0.017 percent, wherein C/N is less than or equal to 12, N/V is less than or equal to 0.15, and the balance of Fe and inevitable impurities.
The volume fraction of ferrite in the steel is 50-65%, the volume fraction of martensite is 35-50%, and the grain size of ferrite is less than 1.6 μm.
The microstructure of the dual-phase steel in the present invention is mainly ferrite and martensite, the martensite is a hard phase, and the ferrite is a soft phase. The vanadium-nitrogen microalloying is adopted, after the vanadium-nitrogen microalloying is adopted, V is separated out in austenite by increasing N during hot rolling, austenite grains are refined, the interfacial energy of the grains and ferrite is small, and ferrite grains are obviously refined in the hot rolling cooling process. In the continuous annealing process, a large amount of V is dispersed and precipitated in the ferrite to play a role in selectively strengthening the ferrite, the influence of the martensite content on the strength of the dual-phase steel can be reduced, and the aim of improving the plasticity on the basis of not reducing the strength is fulfilled by reducing the martensite content and increasing the ferrite content.
A production process of high-N content ultrafine grain 1200MPa cold-rolled dual-phase steel mainly comprises the following steps:
s1, heating a steel billet: heating the steel billet, setting the temperature of a soaking section to be 1220-1250 ℃, and soaking for 120 min;
s2, hot rolling: removing phosphorus by using high-pressure water, carrying out hot rolling, controlling the initial rolling temperature to be 1150-1200 ℃, controlling the final rolling temperature to be higher than 900 ℃, adopting a post-rolling front-stage cooling process after rolling, cooling to 450-550 ℃ at a cooling rate of 12-13 ℃/s, and coiling;
s3, cold rolling: carrying out acid pickling on the hot rolled plate, and then carrying out cold rolling, wherein the cold rolling reduction is controlled to be 60-70%;
s4, continuous annealing: controlling the soaking temperature to be 740-770 ℃, keeping the soaking temperature for 120s, slowly cooling the steel plate to be 670-700 ℃, overaging the steel plate to be 280-330 ℃ and keeping the overaging temperature for 600 s.
The ultrahigh-strength cold-rolled dual-phase steel has the advantages of hot rolling and continuous annealing procedures:
hot rolling: the heating temperature of the billet is 1220-1250 ℃, the initial rolling temperature of rough rolling is 1150-1200 ℃, and the finish rolling temperature is higher than 900 ℃; the controlled rolling in the austenite recrystallization region has lower requirements on the rolling force of the rolling mill and small load, and is beneficial to protecting the rolling mill.
Continuous annealing: the soaking temperature is 740-770 ℃, the slow cooling temperature is 670-700 ℃, and the overaging temperature is 280-330 ℃; the soaking temperature is relatively wide, the sensitivity of the alloy to the critical annealing temperature is reduced after vanadium-nitrogen microalloying treatment is mainly adopted, and the ferrite is selectively strengthened through vanadium, so that the relevance of the tensile strength and the martensite content is reduced, and the plasticity of the cold-rolled dual-phase steel is improved on the premise of ensuring that the strength is not reduced.
The cold-rolled dual-phase steel has the thickness specification of 1.0-2.0 mm, the yield strength of the steel material is more than or equal to 600MPa, the tensile strength of the steel material is more than or equal to 1200MPa, and the elongation percentage A of the steel material50Not less than 15 percent, and the yield ratio not more than 0.5, and simultaneously meets the requirements of ultrahigh strength, high plasticity, low yield ratio and low cost.
The cold-rolled dual-phase steels of examples 1 to 5 and comparative examples 1 to 4 were produced industrially, and the chemical compositions of the cold-rolled dual-phase steels in the examples and comparative examples are shown in table 1. The thicknesses of examples 1 to 5 were 1.8mm, 1.6mm, 1.4mm, 1.2mm and 1.0mm, respectively, and the thicknesses of comparative examples 1 to 4 were 1.2mm, respectively, and the production processes are shown in Table 2.
TABLE 1 chemical composition (wt%) of examples and comparative cold-rolled dual-phase steel
| Type (B) | C | Si | Mn | P | S | Cr | Als | V | N | C/N | N/V |
| Example 1 | 0.17 | 0.29 | 1.89 | 0.005 | 0.004 | 0.038 | 0.022 | 0.149 | 0.017 | 10.00 | 0.114 |
| Example 2 | 0.16 | 0.21 | 1.56 | 0.005 | 0.004 | 0.032 | 0.022 | 0.105 | 0.014 | 11.43 | 0.133 |
| Example 3 | 0.15 | 0.25 | 1.76 | 0.003 | 0.003 | 0.034 | 0.023 | 0.136 | 0.014 | 10.71 | 0.103 |
| Example 4 | 0.14 | 0.28 | 1.92 | 0.004 | 0.003 | 0.039 | 0.024 | 0.147 | 0.018 | 7.78 | 0.122 |
| Example 5 | 0.14 | 0.22 | 1.52 | 0.005 | 0.003 | 0.031 | 0.023 | 0.110 | 0.013 | 10.77 | 0.118 |
| Comparative example 1 | 0.11 | 0.27 | 1.81 | 0.005 | 0.003 | 0.027 | 0.012 | 0.12 | 0.013 | 8.46 | 0.108 |
| Comparative example 2 | 0.18 | 0.26 | 1.64 | 0.005 | 0.003 | 0.026 | 0.016 | 0.11 | 0.005 | 36 | 0.045 |
| Comparative example 3 | 0.17 | 0.23 | 1.63 | 0.004 | 0.003 | 0.027 | 0.016 | 0.08 | 0.012 | 14.17 | 0.150 |
| Comparative example 4 | 0.18 | 0.27 | 1.55 | 0.005 | 0.003 | 0.029 | 0.011 | 0.11 | 0.025 | 7.2 | 0.227 |
As can be seen from Table 1, the chemical compositions of the 5 test steels produced according to the present invention all meet the requirements of the present invention, wherein C/N, N/V also meets the requirements of the present invention; the C content in comparative example 1 does not satisfy the requirements of the present invention, the C content, N content and C/N ratio in comparative example 2 do not satisfy the requirements of the present invention, the V content and C/N ratio in comparative example 3 do not satisfy the requirements of the present invention, and the C content and N/V ratio in comparative example 4 do not satisfy the requirements of the present invention.
TABLE 2 Process parameters of the examples and comparative examples Cold-rolled Dual-phase steels
In examples 3-1 to 3-4, the heating temperatures were 740 ℃, 750 ℃, 760 ℃, 770 ℃, and the slow cooling temperatures were 670 ℃, 680 ℃, 690 ℃, and 700 ℃, respectively, and the same process parameters were used, and it is understood from table 3 that the martensite content decreased from 47.7% to 39.7% with the decrease in temperature, which resulted in a large change, but the tensile strength was decreased by only 25 MPa. The steel adopts the vanadium-nitrogen microalloy technology, so that a large amount of V is separated out in ferrite, the ferrite is selectively strengthened, the problem of strength reduction caused by the reduction of martensite content is solved, and the relevance of tensile strength and martensite content is reduced; and the yield strength and the ferrite grain size fluctuation are small, so that the vanadium-nitrogen microalloy technology is adopted in the steel, the sensitivity of the alloy to the critical annealing temperature is reduced, and the ultrafine grain structure below 1.6 mu m is obtained.
TABLE 3 mechanical properties, texture content and grain size of cold-rolled dual-phase steels of examples and comparative examples
As shown in Table 3, the cold-rolled dual-phase steel has the tensile strength of 1220-1285 MPa, the yield strength of 605-630 MPa and the elongation A5015.8 to 18.4%, a yield ratio of 0.484 to 0.496, a martensite content of 37.3 to 48.9, and a ferrite grain size of 1.40 to 1.58 μm. The yield strength of the cold-rolled dual-phase steel produced by the comparative examples 1, 2 and 3 is lower than 600MPa, the tensile strength is lower than 1200MPa, and the elongation rate of the comparative example 4 cannot meet the requirement.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.
Claims (8)
1. The high-N-content ultrafine-grained 1200 MPa-grade cold-rolled dual-phase steel is characterized by comprising the following components in percentage by mass: c: 0.14% -0.17%, Si: 0.25-0.28%, Mn: 1.5-2.0%, P is less than or equal to 0.015%, S is less than or equal to 0.010%, V: 0.10-0.15%, Cr: 0.03% -0.04%, Als: 0.02-0.03%, N: 0.012-0.018 wt% of Fe and inevitable impurities, wherein C/N is less than or equal to 12 and N/V is less than or equal to 0.15; the volume fraction of ferrite of the steel is 50-65%, the volume fraction of martensite is 35-50%, and the grain size of the ferrite of the steel is less than or equal to 1.6 mu m; the tensile strength is more than or equal to 1200 MPa.
2. The high-N content ultrafine grained 1200MPa cold rolled dual phase steel according to claim 1, characterized by comprising, in mass percent: c: 0.15% -0.16%, Si: 0.25-0.28%, Mn: 1.76-1.89%, P is less than or equal to 0.005%, S is less than or equal to 0.004%, V: 0.11-0.136%, Cr: 0.034% -0.038%, Als: 0.022-0.024%, N: 0.013-0.017 percent, wherein C/N is less than or equal to 12, N/V is less than or equal to 0.15, and the balance of Fe and inevitable impurities.
3. The process for producing high N content ultra-fine grained 1200MPa grade cold rolled dual phase steel according to claim 1 or 2, characterized by comprising the following steps:
s1, heating a steel billet and carrying out soaking treatment;
s2, removing phosphorus by using high-pressure water, carrying out hot rolling, cooling to 450-550 ℃ at a cooling speed of 12-13 ℃/s by adopting a post-rolling front-stage cooling process after rolling is finished, and coiling;
s3, carrying out cold rolling on the hot rolled plate after acid pickling;
and S4, continuous annealing.
4. The production process of the high-N content ultrafine grained 1200MPa cold rolled dual-phase steel according to the claim 3, characterized in that in the step S1, the temperature of the soaking section is 1220-1250 ℃, and the soaking time is 120 min.
5. The process for producing the ultra-fine grain 1200MPa grade cold rolled dual phase steel with high N content as claimed in claim 3, wherein in the step S2, the hot rolling start temperature is 1150-1200 ℃, and the finish rolling temperature is higher than 900 ℃.
6. The process for producing the high-N content ultrafine grained 1200MPa cold rolled dual phase steel according to claim 3, wherein in step S3, the cold rolling reduction is controlled to be 60-70%.
7. The production process of the high-N content ultrafine grained 1200MPa grade cold rolled dual phase steel according to the claim 3, characterized in that in the step S4, the continuous annealing is performed by controlling the soaking temperature to 740-770 ℃, the slow cooling temperature to 670-700 ℃ and the overaging temperature to 280-330 ℃.
8. The process for producing high N content ultra-fine grain 1200MPa grade cold rolled dual phase steel according to any one of claims 3-7, characterized in that the produced cold rolled dual phase steel has a thickness of 1.0-2.0 mm, a yield strength of the material of not less than 600MPa, and an elongation A50Not less than 15 percent and the yield ratio not more than 0.5.
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| JP2009024227A (en) * | 2007-07-20 | 2009-02-05 | Nippon Steel Corp | Dual-phase steel sheet superior in formability, and manufacturing method therefor |
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| CN101768695B (en) * | 2010-01-21 | 2011-11-16 | 北京科技大学 | Preparation method of Ti microalloyed ultra-fine grained cold rolling dual-phase steel of 1,000MPa level |
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| CN105925912B (en) * | 2016-07-11 | 2018-01-26 | 攀钢集团攀枝花钢铁研究院有限公司 | Tensile strength 780MPa levels cold-rolled biphase steel containing vanadium and preparation method thereof |
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| JP2009024227A (en) * | 2007-07-20 | 2009-02-05 | Nippon Steel Corp | Dual-phase steel sheet superior in formability, and manufacturing method therefor |
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