600MPa-grade cold-rolled dual-phase steel and regulation and control method thereof

Abstract

The invention relates to the technical field of steel, and provides 600MPa-grade cold-rolled dual-phase steel and a regulation and control method thereof. The 600MPa-grade cold-rolled dual-phase steel is prepared from the following components in percentage by weight: 0.12 percent to 0.18 percent of C, 0.25 percent to 0.35 percent of Si, 1.4 percent to 1.6 percent of Mn, 0.005 percent to 0.012 percent of B, 0.005 percent to 0.015 percent of Nb, less than or equal to 0.008 percent of S, less than or equal to 0.025 percent of P, less than or equal to 0.006 percent of N and the balance of Fe and other inevitable impurities. According to the technical scheme, the problems that the volume fraction of martensite of 600MPa-grade cold-rolled dual-phase steel is difficult to control and the total elongation at break is low in the related technology are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of steel materials, and in particular to a 600MPa grade cold-rolled dual-phase steel and a control method thereof. Background Art

[0002] In recent years, with the rapid development of the automotive industry, the demand for high-strength, high-ductility, and lightweight steel has continued to grow. Cold-rolled duplex steel, due to its excellent mechanical properties, has become an ideal material for automotive structural components. Duplex steel is primarily composed of ferrite and martensite, with ferrite providing good ductility and toughness, and martensite imparting high strength.

[0003] However, traditional 600MPa grade cold-rolled duplex steel still faces the following problems in practical applications: First, its process usually relies on the addition of precious alloying elements such as Cr and Mo to stabilize the supercooled austenite and inhibit the pearlite and bainite phase transformation to ensure the formation of martensite. This not only increases production costs, but also makes the regulation process of the martensite volume fraction complex and unstable, resulting in large fluctuations in the mechanical properties of the final product. Secondly, due to the insufficient synergy between martensite and ferrite in traditional duplex steel, its total elongation at fracture is relatively low, which makes it difficult to meet the automotive industry's requirements for high plasticity of materials. Especially in the absence of Cr and Mo, the toughness of the material is further reduced, limiting its application in complex formed parts. In addition, the use of alloying elements such as Cr and Mo also exacerbates the carbon emission problem in the steelmaking process, which is not in line with the current development trend of green manufacturing.

[0004] Therefore, the development of a 600MPa grade cold-rolled dual-phase steel that does not rely on precious alloying elements such as Cr and Mo, can accurately control the volume fraction of martensite, improve the total elongation at break, and has relatively low cost has important industrial application value and market prospects. Summary of the Invention

[0005] The present invention provides a 600MPa grade cold-rolled dual-phase steel and a control method thereof, which solves the problems in the related art of difficult to control martensite volume fraction and low total elongation at break of 600MPa grade cold-rolled dual-phase steel.

[0006] The technical solutions of the present invention are as follows: The present invention provides a 600MPa grade cold-rolled dual-phase steel, which is composed of the following components in percentage by weight: C 0.12%~0.18%, Si 0.25%~0.35%, Mn 1.4%~1.6%, B 0.005%~0.012%, Nb 0.005%~0.015%, S≤0.008%, P≤0.025%, N≤0.006%, the balance is Fe and other inevitable impurities.

[0007] The 600MPa-grade cold-rolled dual-phase steel of the present invention is composed of multiple elements including C, Si, Mn, B, Nb, S, P, and N. Mn reduces the starting temperature (Ar3 temperature) for the transformation of austenite to ferrite and expands the austenite region; Si inhibits cementite precipitation and promotes carbon partitioning; C provides a driving force for carbon partitioning; and the contents of S, P, and N are strictly controlled to reduce the adverse effects of these impurity elements on steel properties. The coordinated effects of the various components improve the quality and performance stability of the 600MPa-grade cold-rolled dual-phase steel.

[0008] As a further technical solution, the weight percentages of the B, Nb and Mn satisfy the following relationship: 15.8≤Mn / 5(B+Nb)≤19.8.

[0009] As a further technical solution, the weight ratio of B to Nb is 1:1.

[0010] In the 600 MPa grade cold-rolled dual-phase steel of the present invention, by regulating the content ratio of B, Nb, and Mn, when the weight percentages of B, Nb, and Mn satisfy 15.8≤Mn / 5(B+Nb)≤19.8, and the weight ratio of B to Nb is 1:1, the total elongation at break of the 600 MPa grade cold-rolled dual-phase steel can be further improved, and its total elongation at break A80 can reach 22.0% to 22.5%.

[0011] As a further technical solution, the microstructure of the 600 MPa grade cold-rolled dual-phase steel is ferrite and martensite.

[0012] The 600MPa grade cold-rolled dual-phase steel of the present invention has ferrite and martensite as two phases that work synergistically. Ferrite as a soft phase ensures formability and energy absorption properties, while martensite as a hard phase provides high-strength support.

[0013] As a further technical solution, the volume fraction of martensite is 22%~28%.

[0014] The present invention provides a method for regulating and controlling 600MPa grade cold-rolled dual-phase steel, which is used to regulate the 600MPa grade cold-rolled dual-phase steel, comprising the following steps: S1, molten steel is smelted and continuously cast to form slabs; S2, rough rolling, finish rolling, and cooling the slab to obtain a hot-rolled plate; S3. Cold rolling and annealing the hot-rolled plate to obtain the 600 MPa grade cold-rolled dual-phase steel.

[0015] As a further technical solution, in step S2, during the rough rolling, the temperature is 1020~1080℃, for example, it can be 1020℃, 1040℃, 1050℃, 1060℃, 1070℃, 1080℃, preferably 1020℃, 1050℃, 1080℃, and more preferably 1050℃; during the finish rolling, the temperature is 810~860℃, for example, it can be 810℃, 820℃, 830℃, 840℃, 850℃, 860℃, preferably 810℃, 850℃, 860℃, and more preferably 850℃.

[0016] As a further technical solution, after the rough rolling, the austenite grain size is 45-50 μm.

[0017] The 600MPa grade cold-rolled dual-phase steel of the present invention has rough rolling and finish rolling stages as austenite state regulation stages, realizing dynamic recrystallization control. In the rough rolling stage, the temperature is 1020-1080°C, and austenite grain refinement is realized by complete dynamic recrystallization, so that the austenite grain size is ≤50μm, specifically 45-50μm; in the finish rolling stage, the temperature is 810-860°C, and high-density dislocations are introduced by sub-dynamic recrystallization.

[0018] As a further technical solution, in step S2, the cooling is divided into a first stage cooling, a second stage cooling and a third stage cooling; During the first cooling stage, the temperature is cooled to 700-750°C at a cooling rate of 6-15°C / s; During the second cooling stage, the temperature is cooled to 650-672°C at a cooling rate of 6-9°C / s; During the third cooling stage, the temperature is cooled to 450-480° C. at a cooling zone rate of 32-40° C. / s.

[0019] In the 600MPa grade cold-rolled dual-phase steel of the present invention, a cooling process is performed after finish rolling, wherein the stage from 860°C to 650°C is the ferrite phase transformation zone. Air cooling is used in this stage, and the temperature is first cooled to 700°C to 750°C at a cooling rate of 6°C / s, and then cooled to 650°C to 672°C at a cooling rate of 6°C / s to 9°C / s. During this process, the austenite is slowly cooled in the high-temperature zone, and the ferrite preferentially nucleates and grows at the austenite grain boundaries. The stability of the high-carbon austenite is enhanced, and its premature decomposition into pearlite or bainite during subsequent cooling can be avoided. The cooling rate is strictly controlled in the first two staged coolings to achieve a proeutectoid ferrite phase transformation, and the carbon content of the retained austenite is increased to 0.25% to 0.35% through the carbon partitioning effect. The 650°C to 450°C range is the metastable austenite retention zone. Rapid cooling at a cooling zone rate of 32-40°C / s suppresses carbide precipitation (carbon supersaturation ≥ 90%), resulting in a metastable austenite structure with a high dislocation density. The hot-rolled microstructure is characterized by a polygonal structure, an average ferrite grain size of 3-5μm, a high dislocation density, and a carbon supersaturation of 30-40% metastable austenite, providing the nucleation driving force for cold rolling and annealing, resulting in a fluctuating composition. By combining a "slow first, then slow, then fast" cooling rate, the duplex steel maintains total elongation at break while also exhibiting excellent mechanical properties.

[0020] As a further technical solution, the cooling rate during the first cooling stage is less than the cooling rate during the second cooling stage.

[0021] In the 600 MPa grade cold-rolled dual-phase steel of the present invention, when the cooling rate in the first cooling stage is less than the cooling rate in the second cooling stage, the tensile strength of the 600 MPa grade cold-rolled dual-phase steel can be further improved, so that the tensile strength can be increased to 638 MPa.

[0022] As a further technical solution, during the cold rolling, the compression ratio is 48% to 55%, for example, it can be 48%, 49%, 50%, 52%, 55%, preferably 48%, 50%, 55%, and more preferably 50%.

[0023] In the 600MPa-grade cold-rolled dual-phase steel of the present invention, a compression ratio of 48% to 55% is adopted. The relatively low deformation can reduce the elongation of ferrite grains along the rolling direction, retain the nearly equiaxed crystal morphology (grain aspect ratio ≤ 1.5), and avoid the formation of banded structure caused by high compression ratios (compression ratio > 60%). Moderate deformation introduces dislocation density to form uniformly distributed subgrain boundaries (size 0.5 to 1.0 μm), providing low-energy interfaces for austenite nucleation during subsequent annealing, while avoiding abnormal grain growth caused by excessive defects. In addition, the low compression ratio can reduce the mechanical crushing of MA islands (untransformed austenite + martensite), retaining their original size (2 to 5 μm), and ensuring the activity of MA islands as austenite nucleation cores during annealing.

[0024] As a further technical solution, during the annealing, after annealing at 700-735° C. for 110-150 seconds, the material is cooled to room temperature at a cooling rate of 55-60° C. / s.

[0025] In the 600MPa-grade cold-rolled dual-phase steel of the present invention, a dynamic annealing process is adopted, and the annealing temperature is 700-735°C. During this stage, the deformation-induced subgrain boundaries can serve as fast carbon diffusion channels, accelerating the carbon partitioning rate from ferrite to austenite, so that the carbon concentration in the carbon-rich region of the austenite reaches 0.25%-0.35% (critical value ≥0.20%), significantly improving the ability to maintain the metastable state below the martensite transformation starting temperature. Subsequently, rapid cooling at a cooling rate of 55-60°C / s, combined with a low compression ratio process, increases the martensite transformation driving force of the carbon-rich austenite, expands the martensite transformation temperature window, promotes continuous shear phase transformation, and ultimately effectively controls the volume fraction of martensite.

[0026] The control method for producing 600MPa-grade cold-rolled dual-phase steel employs a three-in-one process system: controlled rolling and controlled cooling carbon partitioning, genetic microstructural manipulation, and dynamic annealing optimization. This method achieves precise control of the martensite volume fraction in the absence of Cr / Mo, resulting in a stable martensite volume fraction between 22% and 28%, a tensile strength of 620MPa or higher, and a total elongation at break of 17.5% or higher. This method offers superior overall performance compared to conventional Cr-Mo-based cold-rolled ferrite-martensite dual-phase steel (reducing costs by 18%). Based on an annual production capacity of 300,000 tons of cold-rolled ferrite-martensite dual-phase steel, this method can save over 120 million yuan in alloy costs and reduce steelmaking carbon emissions by 15% (CO2 emissions per ton of steel) to 1.2 tons. This provides a promising solution for the steel industry to address the "dual carbon" goals and the cost reduction needs of the automotive industry.

[0027] The working principle and beneficial effects of the present invention are: Unlike conventional processes that rely on adding precious alloying elements like Cr and Mo to stabilize supercooled austenite and inhibit pearlite and bainite transformations to ensure martensite formation during subsequent annealing, thereby regulating the martensite volume fraction, the present invention introduces boron, niobium, and manganese into the 600MPa-grade cold-rolled dual-phase steel. The combined use of boron, niobium, and manganese stabilizes supercooled austenite, inhibits phase transformations that are detrimental to martensite formation, and creates a uniform internal structure within the 600MPa-grade cold-rolled dual-phase steel. This solves the problem of difficult-to-control martensite volume fraction in the absence of Cr / Mo and reduces production costs. Furthermore, the combined use of boron, niobium, and manganese improves the toughness of the 600MPa-grade cold-rolled dual-phase steel, achieving a total elongation at break (A80) exceeding 17.5%. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0029] Example 1 A method for regulating and controlling 600 MPa grade cold-rolled dual-phase steel comprises the following steps: S1, molten steel is smelted and continuously cast to form slabs; S2, rough rolling the slab at 1020°C (austenite grain size 45 μm), finish rolling at 810°C, cooling to 700°C at a cooling rate of 6°C / s, then cooling to 650°C at a cooling rate of 6°C / s, and then cooling to 450°C at a cooling rate of 32°C / s, and coiling to obtain a hot-rolled plate; S3, cold rolling the hot-rolled plate to control the reduction ratio to 48%, annealing at 700°C for 150s, and then cooling to room temperature at a cooling rate of 55°C / s to obtain 600MPa grade cold-rolled dual-phase steel; Among them, the microstructure of 600MPa grade cold-rolled dual-phase steel is ferrite with a volume fraction of 78% and martensite with a volume fraction of 22%. The target component composition is: C 0.15%, Si 0.3%, Mn 1.4%, B 0.005%, Nb 0.005%, S 0.005%, P 0.02%, N 0.005%, and the balance is Fe and other inevitable impurities.

[0030] Example 2 A method for regulating and controlling 600 MPa grade cold-rolled dual-phase steel comprises the following steps: S1, molten steel is smelted and continuously cast to form slabs; S2, rough rolling the slab at 1050°C (austenite grain size 48 μm), finish rolling at 850°C, cooling to 700°C at a cooling rate of 6°C / s, cooling to 650°C at a cooling rate of 6°C / s, and then cooling to 450°C at a cooling rate of 32°C / s, and coiling to obtain a hot-rolled plate; S3, cold rolling the hot-rolled plate with a reduction ratio of 50%, annealing at 720°C for 130s, and then cooling to room temperature at a cooling rate of 58°C / s to obtain a 600MPa grade cold-rolled dual-phase steel; Among them, the microstructure of 600MPa grade cold-rolled dual-phase steel is ferrite with a volume fraction of 76% and martensite with a volume fraction of 24%. The target component composition is: C 0.18%, Si 0.35%, Mn 1.588%, B 0.006%, Nb 0.006%, S 0.006%, P 0.018%, N 0.004%, and the balance is Fe and other inevitable impurities.

[0031] Example 3 A method for regulating and controlling 600 MPa grade cold-rolled dual-phase steel comprises the following steps: S1, molten steel is smelted and continuously cast to form slabs; S2, rough rolling the slab at 1080°C (austenite grain size is 50 μm), finish rolling at 860°C, cooling to 700°C at a cooling rate of 6°C / s, cooling to 650°C at a cooling rate of 6°C / s, and then cooling to 450°C at a cooling rate of 32°C / s, and coiling to obtain a hot-rolled plate; S3, cold rolling the hot-rolled plate to control the reduction ratio to 55%, annealing at 735°C for 110s, and then cooling to room temperature at a cooling rate of 60°C / s to obtain 600MPa grade cold-rolled dual-phase steel; Among them, the microstructure of 600MPa grade cold-rolled dual-phase steel is ferrite with a volume fraction of 72% and martensite with a volume fraction of 28%. The target component composition is: C 0.12%, Si 0.25%, Mn 1.6%, B 0.012%, Nb 0.015%, S 0.008%, P 0.025%, N 0.006%, and the balance is Fe and other inevitable impurities.

[0032] Example 4 The only difference between this embodiment and Example 2 is that in this embodiment, the microstructure of the 600 MPa grade cold-rolled dual-phase steel is ferrite with a volume fraction of 77% and martensite with a volume fraction of 23%, and the target component composition includes 1.576% by weight of Mn, 0.012% by weight of B, and 0.012% by weight of Nb.

[0033] Example 5 The only difference between this embodiment and Example 2 is that in this embodiment, the microstructure of the 600 MPa grade cold-rolled dual-phase steel is ferrite with a volume fraction of 75% and martensite with a volume fraction of 25%, and the target component composition includes 1.58% by weight of Mn, 0.01% by weight of B, and 0.01% by weight of Nb.

[0034] Example 6 The only difference between this embodiment and Example 2 is that in this embodiment, the microstructure of the 600 MPa grade cold-rolled dual-phase steel is ferrite with a volume fraction of 74% and martensite with a volume fraction of 26%, and the target component composition includes 1.584% by weight of Mn, 0.008% by weight of B, and 0.008% by weight of Nb.

[0035] Example 7 The difference between this embodiment and embodiment 6 is that, in this embodiment, step S2 is different, specifically: S2, rough rolling the slab at 1050°C (austenite grain size 48 μm), finish rolling at 850°C, cooling to 700°C at a cooling rate of 6°C / s, then cooling to 672°C at a cooling rate of 6°C / s, and then cooling to 480°C at a cooling rate of 32°C / s, and coiling to obtain a hot-rolled plate; Finally, the microstructure of the 600 MPa grade cold-rolled dual-phase steel is ferrite with a volume fraction of 73% and martensite with a volume fraction of 27%.

[0036] Example 8 The difference between this embodiment and embodiment 6 is that, in this embodiment, step S2 is different, specifically: S2, rough rolling the slab at 1050°C (austenite grain size 48 μm), finish rolling at 850°C, cooling to 730°C at a cooling rate of 8°C / s, cooling to 650°C at a cooling rate of 8°C / s, and then cooling to 450°C at a cooling rate of 35°C / s, and coiling to obtain a hot-rolled plate; Finally, the microstructure of the 600 MPa grade cold-rolled dual-phase steel is ferrite with a volume fraction of 76% and martensite with a volume fraction of 24%.

[0037] Example 9 The difference between this embodiment and embodiment 6 is that, in this embodiment, step S2 is different, specifically: S2, rough rolling the slab at 1050°C (austenite grain size is 48 μm), finish rolling at 850°C, cooling to 750°C at a cooling rate of 15°C / s, cooling to 660°C at a cooling rate of 9°C / s, cooling to 460°C at a cooling rate of 40°C / s, and coiling to obtain a hot-rolled plate; Finally, the microstructure of the 600 MPa grade cold-rolled dual-phase steel is ferrite with a volume fraction of 78% and martensite with a volume fraction of 22%.

[0038] Example 10 The only difference between this embodiment and embodiment 8 is that in step S2 of this embodiment, after cooling to 730°C at a cooling rate of 10°C / s, cooling to 650°C at a cooling rate of 8°C / s, cooling to 450°C at a cooling rate of 35°C / s, and coiling to obtain a hot-rolled plate; Finally, the microstructure of the 600 MPa grade cold-rolled dual-phase steel is ferrite with a volume fraction of 74% and martensite with a volume fraction of 26%.

[0039] Example 11 The only difference between this embodiment and embodiment 8 is that in step S2 of this embodiment, after cooling to 730°C at a cooling rate of 6°C / s, cooling to 650°C at a cooling rate of 8°C / s, cooling to 450°C at a cooling rate of 35°C / s, and coiling to obtain a hot-rolled plate; Finally, the microstructure of the 600 MPa grade cold-rolled dual-phase steel is ferrite with a volume fraction of 75% and martensite with a volume fraction of 25%.

[0040] Comparative Example 1 The only difference between this comparative example and Example 1 is that in this comparative example, the target component composition of the 600 MPa-grade cold-rolled dual-phase steel includes 1.4% by weight of Mn and 0.01% by weight of B, and no Nb is contained. Furthermore, the microstructure of the 600 MPa-grade cold-rolled dual-phase steel has a volume fraction of ferrite of 81% and a volume fraction of martensite of 19%.

[0041] Comparative Example 2 The only difference between this comparative example and Example 1 is that in this comparative example, the target component composition of the 600 MPa grade cold-rolled dual-phase steel includes 1.4% by weight of Mn and 0.01% by weight of Nb, and no B is contained. Furthermore, the microstructure of the 600 MPa grade cold-rolled dual-phase steel has a volume fraction of ferrite of 80% and a volume fraction of martensite of 20%.

[0042] Comparative Example 3 The only difference between this comparative example and Example 1 is that in this comparative example, the target component composition of the 600 MPa-grade cold-rolled dual-phase steel includes 1.41% by weight of Mn, and contains no B or Nb. Furthermore, the microstructure of the 600 MPa-grade cold-rolled dual-phase steel includes 87% by volume of ferrite and 13% by volume of martensite.

[0043] Comparative Example 4 The only difference between this comparative example and Example 1 is that in this comparative example, the target component composition of the 600 MPa grade cold-rolled dual-phase steel includes 0.705% by weight of B and 0.705% by weight of Nb, and no Mn is contained. Furthermore, the microstructure of the 600 MPa grade cold-rolled dual-phase steel has a volume fraction of ferrite of 85% and a volume fraction of martensite of 15%.

[0044] Comparative Example 5 The only difference between this comparative example and Example 1 is that in this comparative example, the target component composition of the 600 MPa-grade cold-rolled dual-phase steel includes 1.0% by weight of Cr and 0.41% by weight of Mo, and no Mn, B, or Nb is contained. Furthermore, the microstructure of the 600 MPa-grade cold-rolled dual-phase steel has a volume fraction of ferrite of 81% and a volume fraction of martensite of 19%.

[0045] Experimental Example 1 The 600 MPa grade cold-rolled dual-phase steels prepared in Examples 1 to 6 and Comparative Examples 1 to 5 were tested for total elongation at break according to the test method in GB / T 228.1-2021 "Tensile testing of metallic materials - Part 1: Room temperature test methods". The test results are shown in Table 1: Table 1 Total elongation at break test results

[0046] As can be seen from Table 1, compared with Comparative Examples 1 to 5, the total elongation at break of the 600 MPa-grade cold-rolled dual-phase steels prepared in Examples 1 to 6 is improved, indicating that the combined use of B, Nb, and Mn in the 600 MPa-grade cold-rolled dual-phase steel of the present invention can effectively improve the total elongation at break of the 600 MPa-grade cold-rolled dual-phase steel, such that the total elongation at break A80 is ≥17.5%.

[0047] Experimental Example 2 The 600 MPa grade cold-rolled dual-phase steel prepared in Examples 6 to 11 was tested for tensile strength and yield strength according to the test method in GB / T 228.1-2021 "Tensile testing of metallic materials - Part 1: Room temperature test methods". The test results are shown in Table 2: Table 2 Tensile strength and yield strength test results

[0048] As can be seen in Table 2, Examples 6-11 exhibited yield strengths ≥378 MPa and tensile strengths ≥620 MPa, indicating that a staged cooling process after finish rolling, with a cooling rate of 6-15°C / s in the first stage, 6-9°C / s in the second stage, and 32-40°C / s in the third stage, resulted in 600 MPa-grade cold-rolled dual-phase steels exhibiting excellent mechanical properties. The tensile strength of the 600 MPa-grade cold-rolled dual-phase steel produced in Example 11 was significantly improved compared to Examples 6-10, indicating that the tensile strength of 600 MPa-grade cold-rolled dual-phase steel can be further improved when the cooling rate in the first stage is less than the cooling rate in the second stage.

[0049] In addition, from the volume fraction of martensite in the microstructure of the 600 MPa grade cold-rolled dual-phase steels prepared in Examples 1 to 11 and Comparative Examples 1 to 5, it can be seen that the control method of the 600 MPa grade cold-rolled dual-phase steel of the present invention can accurately control the volume fraction of martensite in the microstructure of the 600 MPa grade cold-rolled dual-phase steel to be precisely controlled within a range of 22% to 28%.

[0050] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A 600MPa grade cold-rolled dual-phase steel, characterized in that: It is composed of the following components in percentage by weight: C 0.12%~0.18%, Si 0.25%~0.35%, Mn 1.4%~1.6%, B 0.005%~0.012%, Nb 0.005%~0.015%, S≤0.008%, P≤0.025%, N≤0.006%, the balance is Fe and other inevitable impurities.

2. The 600MPa grade cold-rolled dual-phase steel according to claim 1, characterized in that: The weight percentages of the B, Nb, and Mn satisfy the following relationship: 15.8≤Mn / 5(B+Nb)≤19.

8.

3. The 600MPa grade cold-rolled dual-phase steel according to claim 1, characterized in that: The microstructure of the 600MPa grade cold-rolled dual-phase steel is ferrite and martensite.

4. The 600MPa grade cold-rolled dual-phase steel according to claim 3, characterized in that: The volume fraction of martensite is 22% to 28%.

5. A method for regulating and controlling 600 MPa grade cold-rolled dual-phase steel, for regulating and controlling the 600 MPa grade cold-rolled dual-phase steel according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1, molten steel is smelted and continuously cast to form slabs; S2, rough rolling, finish rolling, and cooling the slab to obtain a hot-rolled plate; S3. Cold rolling and annealing the hot-rolled plate to obtain the 600 MPa grade cold-rolled dual-phase steel.

6. The control method for 600MPa grade cold-rolled dual-phase steel according to claim 5, characterized in that: In step S2, during the rough rolling, the temperature is 1020-1080°C; during the finish rolling, the temperature is 810-860°C.

7. The control method for 600MPa grade cold-rolled dual-phase steel according to claim 5, characterized in that: In step S2, the cooling is divided into a first cooling stage, a second cooling stage and a third cooling stage; During the first cooling stage, the temperature is cooled to 700-750°C at a cooling rate of 6-15°C / s; During the second cooling stage, the temperature is cooled to 650-672°C at a cooling rate of 6-9°C / s; During the third cooling stage, the temperature is cooled to 450-480° C. at a cooling rate of 32-40° C. / s.

8. The control method for 600MPa grade cold-rolled dual-phase steel according to claim 7, characterized in that: The cooling rate during the first stage of cooling is less than the cooling rate during the second stage of cooling.

9. The control method for 600MPa grade cold-rolled dual-phase steel according to claim 5, characterized in that: During the cold rolling, the compression ratio is 48% to 55%.

10. The control method for 600MPa grade cold-rolled dual-phase steel according to claim 5, characterized in that: During the annealing, the material is annealed at 700-735° C. for 110-150 seconds, and then cooled to room temperature at a cooling rate of 55-60° C. / s.

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