CN114606449B - DP980 cold-rolled dual-phase steel with high strength and elongation product and low yield ratio and production method thereof - Google Patents
DP980 cold-rolled dual-phase steel with high strength and elongation product and low yield ratio and production method thereof Download PDFInfo
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- 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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
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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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
- C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
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- 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
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
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- C21D2211/005—Ferrite
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/008—Martensite
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Abstract
The invention discloses a high-strength-product low-yield-ratio DP980 cold-rolled dual-phase steel and a production method thereof. Through reasonable technological parameter regulation and control of the two-phase zone quenching and tempering process and the introduction of a slow cooling section in the two-phase zone quenching and tempering process, the finally produced cold-rolled dual-phase steel has the tensile strength of 1023MPa-1071MPa, the total elongation of 14.5% -16.9% and the yield ratio of 0.56-0.58, thereby not only meeting the strength requirement of DP980 dual-phase steel which is more popular in the market, but also greatly improving the plasticity, improving the strength and the plastic product, and enabling the strength and plastic product to reach 15.5 Gpa-17.3 Gpa% which is higher than that of DP dual-phase steel (12.5 Gpa-980.4 Gpa%) produced by the two-phase zone direct quenching and tempering process and other comparison processes. In addition, DP980 incorporating the quench section also has a lower yield ratio, i.e., more excellent formability.
Description
Technical Field
The invention belongs to the field of high-strength metallurgical steel plate production, and particularly relates to DP980 cold-rolled dual-phase steel with high strength and elongation products and a production method thereof.
Background
The dual-phase steel is one of the most widely used lightweight materials in the automotive industry, which are different from other advanced high-strength steels, due to the low alloy cost, excellent strength and plastic fit, continuous yield and low yield ratio, high initial work hardening rate, superior formability and weldability. Currently, the automobile body in white mainly uses the dual-phase steel with the tensile strength of 590MPa and 780MPa, and with the continuous upgrading of the automobile light weight trend, the dual-phase steel with the tensile strength of 980MPa and above is becoming more and more popular due to higher strength and relatively considerable plasticity. Generally, there are three heat treatment processes for producing dual-phase steel, one is controlled rolling and cooling, one is conventional quenching and tempering process, and the other is continuous annealing production process. The strength-plastic product of the DP980 cold-rolled dual-phase steel under the processes is generally below 15GPa percent, so that the strength-plastic product and yield ratio of the dual-phase steel are improved, the comprehensive performance threshold of the dual-phase steel can be fully improved, the formability can be improved, and the requirements of different customers on the dual-phase steel can be met. Therefore, the production process of the dual-phase steel is improved, and the strength and the plastic strength are improved and the yield ratio is reduced under the condition of meeting the requirement of strength, so that the dual-phase steel is the target of the invention.
China patent published in 2021, 4 and 27: a low-cost and easily-produced cold-rolled dual-phase steel with 980 MPa-level tensile strength comprises the following components of C0.0800.095%, si 0.40.6%, mn 2.1.3%, als 0.060.08%, cr 0.20.4%, nb 0.03.05%, ti 0.01.02%, ca 0.0015.0040%, P less than or equal to 0.012%, S less than or equal to 0.005%, N less than or equal to 0.005% and the balance Fe. The method has the advantages of no addition of expensive Mo and V, low alloy content and easy rolling. However, the yield ratio is high, which is unfavorable for the subsequent forming; and the product of strength and plasticity is not more than 15GPa, and the comprehensive performance is improved.
Disclosure of Invention
The invention aims to provide the DP980 cold-rolled dual-phase steel with high strength and elongation products and low yield ratio and the production method thereof, and the DP980 cold-rolled dual-phase steel with high strength and elongation products and low yield ratio obtained by the production method has the strength and elongation products of 15.5 Gpa.about.17.3 Gpa.about.and is easy to produce and good in formability.
The production method of the invention introduces slow cooling before quenching, carries out sectional quenching, and utilizes the slow cooling to separate out tiny ferrite with extremely low dislocation density, thereby obviously improving the plasticity of the cold-rolled dual-phase steel under the condition of unobvious strength reduction so as to improve the strong plastic product.
The high-strength-product low-yield-ratio DP980 cold-rolled dual-phase steel provided by the invention comprises the following chemical components in percentage by mass: 0.11 to 0.14 percent of C, 0.10 to 0.15 percent of Si, 2.22 to 2.24 percent of Mn, less than or equal to 0.014 percent of P, less than or equal to 0.003 percent of S, 0.13 to 0.16 percent of Mo, 0.27 to 0.31 percent of Cr, 0.17 to 0.21 percent of Al, 0.03 to 0.05 percent of Ti, and the balance of Fe and unavoidable impurities. Wherein, elements such as C, mn, cr, mo and the like can improve the hardenability and the tensile strength of the steel; the elongation is improved by adopting Si element, and meanwhile, partial Si element is replaced by Al element, so that the problems of oxidation, galvanization and welding caused by excessive Si element are solved.
The invention provides a production method of DP980 cold-rolled dual-phase steel with high strength-plastic product and low yield ratio, which comprises the following steps: smelting, continuous casting, hot rolling, pickling and cold rolling, sectional quenching and tempering, wherein the sectional quenching process comprises the following steps: placing the cold-rolled sheet sample into a tube furnace for soaking treatment, then slowly cooling, and carrying out oil quenching after slow cooling; the slow cooling mode is as follows: after soaking, the power supply of the tube furnace is turned off, ventilation is carried out for slow cooling, the slow cooling termination temperature is 657-662 ℃, and the slow cooling speed is 0.3-0.5 ℃/s.
Further, the continuous casting process adopts a dynamic soft reduction and electromagnetic stirring device, and the thickness of a casting blank is 265mm.
Further, the hot rolling includes heating, rough rolling, finish rolling, laminar cooling, and coiling.
Further, the heating: heating the casting blank to 1160-1210 ℃ and the furnace time is 3-3.3h.
Further, the heating: the cast slab was heated to 1200 ℃ for 3.2 hours in the furnace.
Further, DP980 cold-rolled dual-phase steel with high tensile strength (1023 MPa-1071 MPa), high product of plastic (15.5 Gpa. Cndot. 17.3 Gpa. Cndot.), and low yield ratio (0.56-0.58) is obtained by adjusting heat treatment process parameters.
Further, the rough rolling: and performing rough rolling for 15-20 times until the thickness is 20-30mm.
Further, the rough rolling: the casting blank is subjected to 15-pass rough rolling and rolled to 25mm.
Further, the finish rolling: after rough rolling, performing 8-10 times of finish rolling to 4-6mm, wherein the initial rolling temperature of the finish rolling is 950-1050 ℃ and the final rolling temperature is 840-900 ℃.
Further, the finish rolling: after rough rolling, 8 passes of finish rolling are carried out, the finish rolling is carried out until the thickness reaches 5mm, the initial rolling temperature of the finish rolling is 1020 ℃, and the final rolling temperature is 860 ℃.
Further, the coiling: the coiling temperature is 590-620 ℃, and air cooling is performed after coiling.
Further, after finish rolling, laminar cooling and winding were performed at a winding temperature of 600 ℃, and after winding, air cooling was performed.
Further, the pickling cold rolling: the cold rolling reduction rate in the pickling cold rolling process is 70-75%.
Further, the cold rolled slab was subjected to pickling cold rolling, and the cold rolling reduction was 70%.
Further, the process of the sectional quenching is as follows: putting the obtained cold-rolled sheet into a 796-806 ℃ tubular furnace for soaking treatment, closing a power supply of the tubular furnace after soaking, ventilating for slow cooling, and immediately performing oil quenching after slow cooling; the slow cooling mode is as follows: and after soaking, closing the power supply of the tube furnace, and ventilating for slow cooling.
Further, the obtained cold-rolled sheet is put into a tube furnace at 796-803 ℃ for soaking treatment.
Further, tempering the plate subjected to the sectional quenching at 238-242 ℃ for 220-260 s.
The invention also provides the high-strength product and low-yield ratio DP980 cold-rolled dual-phase steel produced by the production method, wherein the high-strength product and low-yield ratio DP980 cold-rolled dual-phase steel comprises the following chemical components in percentage by mass: 0.11 to 0.14 percent of C, 0.10 to 0.15 percent of Si, 2.22 to 2.24 percent of Mn, less than or equal to 0.014 percent of P, less than or equal to 0.003 percent of S, 0.13 to 0.16 percent of Mo, 0.27 to 0.31 percent of Cr, 0.17 to 0.21 percent of Al, 0.03 to 0.05 percent of Ti and the balance of Fe; the microstructure of the DP980 cold-rolled dual-phase steel is that raised martensite is distributed on a ferrite matrix in an island shape, the volume fraction of the martensite is 28-34%, and the volume fraction of the ferrite is 66-72%; the tensile strength of the high-strength-product low-yield-ratio DP980 cold-rolled dual-phase steel is 1023MPa-1071MPa, the total elongation is 14.5% -16.9%, the strength-product is 15.5 Gpa-17.3 Gpa-and the yield ratio is 0.56-0.58.
The main technical innovation points of the invention are as follows:
1. the DP980 cold-rolled dual-phase steel obtained by the invention has high tensile strength (1023 MPa-1071 MPa), high product of strength and elongation (15.5 Gpa. Cndot. 17.3 Gpa. Cndot.), and low yield ratio (0.56-0.58).
2. According to the invention, slow cooling is introduced in the traditional quenching and tempering process, the ratio of the recrystallized ferrite to the oriented ferrite is increased, the plasticity of the DP980 cold-rolled dual-phase steel is obviously improved under the condition of small influence on tensile strength, so that the strength and plastic product is improved, in addition, the yield ratio is reduced, and the low yield ratio is beneficial to the formation of the dual-phase steel.
3. The invention has simple heat treatment process and low alloy composition.
Drawings
FIG. 1 is a chart showing the scanning metallographic structure of the DP980 cold-rolled dual-phase steel with high product of plastic and low yield ratio prepared in example 1.
FIG. 2 is a scanning metallographic structure diagram of DP980 cold-rolled dual-phase steel prepared in comparative example 1.
FIG. 3 is a graph showing tensile mechanical properties of the high product and low yield ratio DP980 cold-rolled dual-phase steel prepared in example 1 and the DP980 cold-rolled dual-phase steel prepared in comparative example 1, respectively.
Detailed Description
Specific implementations of the invention are further described below with reference to the drawings and examples, but the implementations and protection of the invention are not limited thereto. It should be noted that the following processes, if not specifically described in detail, can be realized or understood by those skilled in the art with reference to the prior art. The reagents or apparatus used were not manufacturer-specific and were considered conventional products commercially available.
Example 1:
the DP980 cold-rolled dual-phase steel with high strength and elongation product and low yield ratio comprises the following components in percentage by mass: 0.13% of C, 0.14% of Si, 2.24% of Mn, 0.014% of P, 0.002% of S, 0.15% of Mo, 0.29% of Cr, 0.19% of Al, 0.04% of Ti and the balance of Fe. The manufacturing process is as follows:
(1) Molten steel with the mass percentage of C0.13%, si 0.14%, mn 2.24%, P0.014%, S0.002%, mo 0.15%, cr 0.29%, al 0.19% and Ti 0.04% is smelted and continuously cast into billets, and casting blanks are obtained;
(2) Heating a casting blank to 1200 ℃, preserving heat for 3.2h, carrying out hot rolling, carrying out 15-pass rough rolling, carrying out rolling to 25mm, carrying out 8-pass finish rolling after rough rolling, carrying out rolling to 5mm, wherein the initial rolling temperature of the finish rolling is 1020 ℃, and the controlled finishing temperature of the finish rolling is 860 ℃;
(3) Performing laminar cooling and coiling after finish rolling, controlling the coiling temperature to be 600 ℃, and performing air cooling after coiling;
(4) Pickling the air-cooled plate blank, wherein the pickling solution comprises the following components in parts by volume: 3 parts of hydrochloric acid with the volume percentage concentration of 38%, 1 part of nitric acid with the volume percentage concentration of 65%, and 1 part of hydrofluoric acid with the volume percentage concentration of 40%;
(5) Cold rolling, wherein the accumulated cold rolling reduction rate is controlled to be 70%, and a cold-rolled sheet is obtained;
(6) Soaking the obtained cold-rolled sheet in a tube furnace, controlling the soaking temperature to be 806 ℃, and soaking time to be 310s, closing a power supply of the tube furnace after soaking is finished, and ventilating for slow cooling;
(7) Slowly cooling to 657 ℃ at a slow cooling speed of 0.4 ℃/s;
(8) Carrying out oil quenching;
(9) Tempering the plate subjected to the sectional quenching, wherein the tempering temperature is 238 ℃, and the tempering time is 220s, so that the high-strength product and low-yield-ratio DP980 cold-rolled dual-phase steel is obtained.
FIG. 1 is a chart showing a scanning metallographic structure of a DP980 cold-rolled dual-phase steel with high yield and low yield ratio, prepared in example 1, wherein the martensite with the raised shape and the shiny edge rings is uniformly distributed on a ferrite matrix in an island shape, the volume fraction of the martensite is 28%, and the volume fraction of the ferrite is 72%.
Example 2:
the DP980 cold-rolled dual-phase steel with high strength and elongation product and low yield ratio comprises the following components in percentage by mass: 0.13% of C, 0.14% of Si, 2.24% of Mn, 0.014% of P, 0.002% of S, 0.15% of Mo, 0.29% of Cr, 0.19% of Al, 0.04% of Ti and the balance of Fe. The manufacturing process is as follows:
(1) Molten steel with the mass percentage of C0.13%, si 0.14%, mn 2.24%, P0.014%, S0.002%, mo 0.15%, cr 0.29%, al 0.19% and Ti 0.04% is smelted and continuously cast into billets, and casting blanks are obtained;
(2) Heating a casting blank to 1200 ℃, preserving heat for 3.2h, carrying out hot rolling, carrying out 15-pass rough rolling, carrying out rolling to 25mm, carrying out 8-pass finish rolling after rough rolling, carrying out rolling to 5mm, wherein the initial rolling temperature of the finish rolling is 1020 ℃, and the controlled finishing temperature of the finish rolling is 860 ℃;
(3) Performing laminar cooling and coiling after finish rolling, controlling the coiling temperature to be 600 ℃, and performing air cooling after coiling;
(4) Pickling the air-cooled plate blank, wherein the pickling solution comprises the following components in parts by volume: 3 parts of hydrochloric acid with the volume percentage concentration of 38%, 1 part of nitric acid with the volume percentage concentration of 65%, and 1 part of hydrofluoric acid with the volume percentage concentration of 40%;
(5) Cold rolling, wherein the accumulated cold rolling reduction rate is controlled to be 70%, and a cold-rolled sheet is obtained;
(6) Soaking the obtained cold-rolled sheet in a tube furnace, controlling the soaking temperature to be 796 ℃ and the soaking time to be 305 seconds, closing a power supply of the tube furnace after soaking, and ventilating for slow cooling;
(7) Slowly cooling to 660 ℃ at a slow cooling speed of 0.3 ℃/s;
(8) Carrying out oil quenching;
(9) And tempering the plate subjected to the sectional quenching at the tempering temperature of 240 ℃ for 240s to obtain the DP980 cold-rolled dual-phase steel with high strength and elongation products and low yield ratio.
The high-strength product and low-yield ratio DP980 cold-rolled dual-phase steel prepared in example 2 has a martensite volume fraction of 34% and a ferrite volume fraction of 66%.
Example 3:
the DP980 cold-rolled dual-phase steel with high strength and elongation product and low yield ratio comprises the following components in percentage by mass: 0.13% of C, 0.14% of Si, 2.24% of Mn, 0.014% of P, 0.002% of S, 0.15% of Mo, 0.29% of Cr, 0.19% of Al, 0.04% of Ti and the balance of Fe. The manufacturing process is as follows:
(1) Molten steel with the mass percentage of C0.13%, si 0.14%, mn 2.24%, P0.014%, S0.002%, mo 0.15%, cr 0.29%, al 0.19% and Ti 0.04% is smelted and continuously cast into billets, and casting blanks are obtained;
(2) Heating a casting blank to 1200 ℃, preserving heat for 3.2h, carrying out hot rolling, carrying out 15-pass rough rolling, carrying out rolling to 25mm, carrying out 8-pass finish rolling after rough rolling, carrying out rolling to 5mm, wherein the initial rolling temperature of the finish rolling is 1020 ℃, and the controlled finishing temperature of the finish rolling is 860 ℃;
(3) Performing laminar cooling and coiling after finish rolling, controlling the coiling temperature to be 600 ℃, and performing air cooling after coiling;
(4) Pickling the air-cooled plate blank, wherein the pickling solution comprises the following components in parts by volume: 3 parts of hydrochloric acid with the volume percentage concentration of 38%, 1 part of nitric acid with the volume percentage concentration of 65%, and 1 part of hydrofluoric acid with the volume percentage concentration of 40%;
(5) Cold rolling, wherein the accumulated cold rolling reduction rate is controlled to be 70%, and a cold-rolled sheet is obtained;
(6) Soaking the obtained cold-rolled sheet in a tube furnace, controlling the soaking temperature to be 800 ℃, soaking time to be 290s, closing a power supply of the tube furnace after soaking, and ventilating for slow cooling;
(7) Slowly cooling to 662 ℃ at a slow cooling speed of 0.5 ℃/s;
(8) Carrying out oil quenching;
(9) And tempering the plate subjected to the sectional quenching at 242 ℃ for 260 seconds to obtain the DP980 cold-rolled dual-phase steel with high strength and elongation products and low yield ratio.
The high-strength product and low-yield ratio DP980 cold-rolled dual-phase steel prepared in example 3 has a martensite volume fraction of 32% and a ferrite volume fraction of 68%.
Example 4:
the DP980 cold-rolled dual-phase steel with high strength and elongation product and low yield ratio comprises the following components in percentage by mass: 0.13% of C, 0.14% of Si, 2.24% of Mn, 0.014% of P, 0.002% of S, 0.15% of Mo, 0.29% of Cr, 0.19% of Al, 0.04% of Ti and the balance of Fe. The manufacturing process is as follows:
(1) Molten steel with the mass percentage of C0.13%, si 0.14%, mn 2.24%, P0.014%, S0.002%, mo 0.15%, cr 0.29%, al 0.19% and Ti 0.04% is smelted and continuously cast into billets, and casting blanks are obtained;
(2) Heating a casting blank to 1200 ℃, preserving heat for 3.2h, carrying out hot rolling, carrying out 15-pass rough rolling, carrying out rolling to 25mm, carrying out 8-pass finish rolling after rough rolling, carrying out rolling to 5mm, wherein the initial rolling temperature of the finish rolling is 1020 ℃, and the controlled finishing temperature of the finish rolling is 860 ℃;
(3) Performing laminar cooling and coiling after finish rolling, controlling the coiling temperature to be 600 ℃, and performing air cooling after coiling;
(4) Pickling the air-cooled plate blank, wherein the pickling solution comprises the following components in parts by volume: 3 parts of hydrochloric acid with the volume percentage concentration of 38%, 1 part of nitric acid with the volume percentage concentration of 65%, and 1 part of hydrofluoric acid with the volume percentage concentration of 40%;
(5) Cold rolling, wherein the accumulated cold rolling reduction rate is controlled to be 70%, and a cold-rolled sheet is obtained;
(6) Soaking the obtained cold-rolled sheet in a tube furnace, controlling the soaking temperature to be 802 ℃ and the soaking time to be 304s, closing a power supply of the tube furnace after soaking, and ventilating for slow cooling;
(7) Slowly cooling to 659 ℃ at a slow cooling speed of 0.4 ℃/s;
(8) Carrying out oil quenching;
(9) And tempering the plate subjected to the sectional quenching at 241 ℃ for 250s to obtain the DP980 cold-rolled dual-phase steel with high strength and elongation products and low yield ratio.
The high-strength product and low-yield ratio DP980 cold-rolled dual-phase steel prepared in example 4 has a martensite volume fraction of 30% and a ferrite volume fraction of 70%.
Comparative example 1:
the DP980 cold-rolled dual-phase steel with high strength and elongation product and low yield ratio comprises the following components in percentage by mass: 0.13% of C, 0.14% of Si, 2.24% of Mn, 0.014% of P, 0.002% of S, 0.15% of Mo, 0.29% of Cr, 0.19% of Al, 0.04% of Ti and the balance of Fe. The manufacturing process is as follows:
(1) Molten steel with the mass percentage of C0.13%, si 0.14%, mn 2.24%, P0.014%, S0.002%, mo 0.15%, cr 0.29%, al 0.19% and Ti 0.04% is smelted and continuously cast into billets, and casting blanks are obtained;
(2) Heating a casting blank to 1200 ℃, preserving heat for 3.2h, carrying out hot rolling, carrying out 15-pass rough rolling, carrying out rolling to 25mm, carrying out 8-pass finish rolling after rough rolling, carrying out rolling to 5mm, wherein the initial rolling temperature of the finish rolling is 1020 ℃, and the controlled finishing temperature of the finish rolling is 860 ℃;
(3) Performing laminar cooling and coiling after finish rolling, controlling the coiling temperature to be 600 ℃, and performing air cooling after coiling;
(4) Pickling the air-cooled plate blank, wherein the pickling solution comprises the following components in parts by volume: 3 parts of hydrochloric acid with the volume percentage concentration of 38%, 1 part of nitric acid with the volume percentage concentration of 65%, and 1 part of hydrofluoric acid with the volume percentage concentration of 40%;
(5) Cold rolling, wherein the accumulated cold rolling reduction rate is controlled to be 70%, and a cold-rolled sheet is obtained;
(6) Soaking the obtained cold-rolled sheet in a tube furnace, wherein the soaking temperature is controlled to be 806 ℃, and the soaking time is controlled to be 310s;
(7) Carrying out oil quenching;
(8) And tempering the quenched plate at 238 ℃ for 220s to obtain the DP980 cold-rolled dual-phase steel.
Fig. 2 is a view showing a scanned metallographic structure of the DP980 cold-rolled dual-phase steel prepared in comparative example 1, and it is apparent from fig. 2 that martensite having a bright border in a relief form is distributed on a ferrite substrate, but the dispersion of the martensite distribution is not uniform as that of example 1, and the ferrite rolling characteristics are remarkable, the volume fraction of martensite in the structure is 41%, and the volume fraction of ferrite is 59%.
Fig. 3 is a graph showing the tensile mechanical properties of the high-strength product, low-yield-ratio DP980 cold-rolled dual-phase steel prepared in example 1 and the DP980 cold-rolled dual-phase steel prepared in comparative example 1, and it can be seen from fig. 3 that the high-strength product, low-yield-ratio DP980 cold-rolled dual-phase steel prepared in example 1 has significantly improved plasticity when the tensile strength is equivalent to that of the DP980 cold-rolled dual-phase steel prepared in comparative example 1, thereby improving the strength-plastic product threshold of the DP980 dual-phase steel.
Wherein comparative example 1 was consistent with example 1, except that no quench section was introduced, the ingredients and other processes were identical. In addition, the DP980 finished plate produced by the continuous annealing process of the same components in the factory and the patent CN111455285B, CN110564928A, CN107058869B, CN110004361a are used as a comparison, and the comparison of the mechanical properties is shown in table 1.
Table 1 comparison of mechanical Properties of various Cold rolled DP980 steels
As can be seen from the table 1, comparing the examples 1-4 with the comparative example 1, it is obvious that under the requirement of 980MPa tensile strength, the average product of high strength and plastic of the DP980 cold-rolled dual-phase steel with low yield ratio prepared in the examples 1-4 reaches 16.4 GPa%, compared with the product of high strength and plastic of the DP980 cold-rolled dual-phase steel prepared in the comparative example 1 without introducing a slow cooling section, the product of high strength and plastic is 12.9 GPa%, and after introducing the slow cooling section, the product of high strength and plastic is obviously improved; in addition, the yield ratio was also lower after introduction of slow cooling, compared to comparative example 1, which is advantageous for the formation of the material. Examples 1-4 also have greater advantages in yield ratio and product strength over the same component DP980 finished board (industrial continuous finished board) using the industrial continuous process. The yield strength product was higher and the yield ratio was lower for examples 1-4 compared to the proprietary CN111455285B and CN110004361a in the tables. The yield ratios were comparable with the products of the strengths of examples 1-4 being higher than that of CN 110564928A. In comparison with the patent CN107058869B (patent name "method for manufacturing cold rolled DP980 dual phase steel with ultra low yield ratio"), although the yield ratio of the patent CN107058869B is slightly lower, the tensile strength and the product of strength and elongation of examples 1 to 4 are more advantageous.
The foregoing examples are illustrative of the present invention and are not intended to be limiting, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principles of the invention are intended to be equivalent to the present invention.
Claims (2)
1. The production method of the DP980 cold-rolled dual-phase steel with high strength and elongation and low yield ratio is characterized by comprising the following steps: smelting, continuous casting, hot rolling, pickling cold rolling, sectional quenching and tempering to finally obtain the DP980 cold-rolled dual-phase steel with high strength and elongation and low yield ratio, wherein the sectional quenching process comprises the following steps: placing the cold-rolled sheet sample into a tube furnace for soaking treatment, then slowly cooling, and carrying out oil quenching after slow cooling; the slow cooling mode is as follows: after soaking, turning off the power supply of the tube furnace, and ventilating for slow cooling, wherein the slow cooling termination temperature is 657-662 ℃, and the slow cooling speed is 0.3-0.5 ℃/s; the hot rolling comprises heating, rough rolling, finish rolling, laminar cooling and coiling; the heating: heating the casting blank to 1160-1210 ℃ and the furnace time is 3-3.3h; the rough rolling: rough rolling for 15-20 times until the thickness is 20-30mm; the finish rolling: after rough rolling, performing 8-10 times of finish rolling to 4-6mm, wherein the initial rolling temperature of the finish rolling is 950-1050 ℃ and the final rolling temperature is 840-900 ℃; the coiling: the coiling temperature is 590-620 ℃, and air cooling is performed after coiling; the pickling cold rolling: the cold rolling reduction rate is 70% -75% in the pickling cold rolling process; the process of the sectional quenching is as follows: placing the cold-rolled sheet sample into a 796-806 ℃ tubular furnace for soaking treatment, and performing slow cooling after 290-310s of furnace time, and performing oil quenching after slow cooling; the slow cooling mode is as follows: after soaking, closing the power supply of the tube furnace, and ventilating for slow cooling; the tempering: tempering temperature is 238-242 ℃ and tempering time is 220-260 s; the high-strength-plastic product and low-yield-ratio DP980 cold-rolled dual-phase steel comprises the following chemical components in percentage by mass: 0.11 to 0.14 percent of C, 0.10 to 0.15 percent of Si, 2.22 to 2.24 percent of Mn, less than or equal to 0.014 percent of P, less than or equal to 0.003 percent of S, 0.13 to 0.16 percent of Mo, 0.27 to 0.31 percent of Cr, 0.17 to 0.21 percent of Al, 0.03 to 0.05 percent of Ti and the balance of Fe.
2. The DP980 cold-rolled dual-phase steel with high strength and elongation products and low yield ratio produced by the production method as claimed in claim 1, which is characterized in that microstructure of the DP980 cold-rolled dual-phase steel is that raised martensite is distributed on a ferrite matrix in an island shape, the volume fraction of the martensite is 28% -34%, and the volume fraction of the ferrite is 66% -72%; the tensile strength of the high-strength-product low-yield-ratio DP980 cold-rolled dual-phase steel is 1023MPa-1071MPa, the total elongation is 14.5% -16.9%, the strength-product is 15.5 Gpa-17.3 Gpa-and the yield ratio is 0.56-0.58.
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| US5843246A (en) * | 1996-01-16 | 1998-12-01 | Allegheny Ludlum Corporation | Process for producing dual phase ferritic stainless steel strip |
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