A method for producing DP590 dual-phase steel based on a traditional hot-dip galvanizing production line

Abstract

The present application relates to a method for producing DP590 dual-phase steel based on a traditional hot-dip galvanizing production line, and belongs to the technical field of steel manufacturing. The method comprises: obtaining molten steel with a set chemical composition, wherein the set chemical composition comprises: replacing precious alloys with a small amount of Ti; sequentially performing continuous casting, hot rolling and coiling on the molten steel to obtain a hot-rolled coil; sequentially performing pickling and cold rolling on the hot-rolled coil to obtain a chilled coil; sequentially performing annealing and galvanizing on the chilled coil to obtain a hot-dip coil; wherein the annealing comprises: two-stage heating and two-stage cooling; performing skin-finishing treatment on the hot-dip coil to obtain DP590 dual-phase steel.

Description

Technical Field

[0001] The present application relates to the technical field of steel manufacturing, and in particular to a method for producing DP590 dual-phase steel based on a traditional hot-dip galvanizing production line. Background Art

[0002] With the continuous development and progress of the domestic automobile industry, consumers have put forward higher requirements for the corrosion resistance of automobiles. From outer coverings to white bodies, a large number of parts have switched from the original continuous annealing plates to galvanized plates. DP590 duplex steel is a good choice for body structural parts because of its low yield strength ratio and high work hardening index. Therefore, in recent years, the market demand for hot-dip galvanized DP590 duplex steel has been increasing. In order to meet the demand, steel mills have transferred DP590 duplex steel to traditional hot-dip galvanizing production lines with weak equipment capacity. However, due to the low operating speed of traditional hot-dip galvanizing production lines, the strength of DP590 duplex steel produced by the composition and process of the original continuous annealing production line is generally insufficient. To solve this problem, a large amount of alloy elements will be added to the matrix to improve the hardenability and meet the strength requirements. The addition of a large number of alloy elements will not only greatly increase the manufacturing cost, but also increase the difficulty of recycling steel after the end of its life cycle, which is not conducive to the long-term continued progress of the domestic automobile manufacturing industry.

[0003] Therefore, based on the traditional hot-dip galvanizing production line with low equipment capacity and low speed operation, it is necessary to develop a DP590 duplex steel with low alloy element addition. Summary of the invention

[0004] The present application provides a method for producing DP590 dual-phase steel based on a traditional hot-dip galvanizing production line to solve the following technical problem: how to reduce the cost of producing DP590 dual-phase steel by a traditional hot-dip galvanizing production line.

[0005] The present application embodiment provides a method for producing DP590 dual-phase steel based on a conventional hot-dip galvanizing production line, the method comprising:

[0006] A molten steel having a set chemical composition is obtained, wherein the set chemical composition includes: replacing a precious alloy with a small amount of Ti;

[0007] The molten steel is sequentially continuously cast, hot rolled and coiled to obtain a hot rolled coil;

[0008] The hot-rolled coil is pickled and cold-rolled in sequence to obtain a chilled coil;

[0009] The cold hardened coil is sequentially annealed and galvanized to obtain a hot dipped coil; wherein the annealing includes: two stages of heating and two stages of cooling;

[0010] The hot dip coil is subjected to skin pass treatment to obtain DP590 dual-phase steel.

[0011] Optionally, the set chemical composition includes, by mass fraction: C: 0.08% to 0.14%, Mn: 1.7% to 2%, Si: 0.05% to 0.25%, Al: 0.02% to 0.05%, P≤0.03%, S≤0.005%, Ti: 0.01% to 0.03%, and matrix element Fe.

[0012] Optionally, the set chemical composition includes, by mass fraction: C: 0.11% to 0.12%, Mn: 1.9% to 2%, Si: 0.1% to 0.2%, Al: 0.02% to 0.04%, P≤0.02%, S≤0.003%, Ti: 0.01% to 0.03%, and matrix element Fe.

[0013] Optionally, the two-stage heating includes a first-stage heating and a second-stage heating; the two-stage cooling includes a first-stage cooling and a second-stage cooling.

[0014] Optionally, the terminal temperature of the first stage of heating is 650°C to 690°C, and the heating rate of the first stage of heating is 5°C / s to 8°C / s.

[0015] Optionally, the terminal temperature of the second stage heating is 760°C to 800°C, and the heating rate of the second stage heating is 1°C / s to 3°C / s.

[0016] Optionally, the terminal temperature of the first stage of cooling is 660°C to 700°C, and the cooling rate of the first stage of cooling is 7°C / s to 9°C / s.

[0017] Optionally, the terminal temperature of the second stage cooling is 440°C to 480°C, and the cooling rate of the second stage cooling is 8°C / s to 11°C / s.

[0018] Optionally, the total reduction rate of the cold rolling is 65% to 75%.

[0019] Optionally, the finishing elongation of the finishing treatment is 0.6% to 0.8%.

[0020] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0021] The embodiment of the present application provides a method for producing DP590 dual-phase steel based on a traditional hot-dip galvanizing production line, the method comprising: obtaining molten steel with a set chemical composition, the set chemical composition comprising: replacing precious alloys with a small amount of Ti; sequentially continuous casting, hot rolling and coiling the molten steel to obtain a hot-rolled coil; sequentially pickling and cold rolling the hot-rolled coil to obtain a chilled coil; sequentially annealing and galvanizing the chilled coil to obtain a hot-dip coil; wherein the annealing comprises: two-stage heating and two-stage cooling; and performing skin-finishing treatment on the hot-dip coil to obtain DP590 dual-phase steel. By reducing the amount of precious alloy added, only a small amount of Ti is added to obtain fine grains and a certain strength, which reduces the alloy cost and reduces the production cost of the existing hot-dip galvanized DP590 dual-phase steel. In addition, by optimizing the production steps such as hot rolling, cold rolling, annealing and galvanizing to adapt to the traditional hot-dip galvanizing production line running at a low speed, the efficient production of DP590 dual-phase steel is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0024] Figure 1 A schematic flow chart of a method for producing DP590 dual-phase steel based on a traditional hot-dip galvanizing production line provided in an embodiment of the present application. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0026] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a rigid limitation on the scope of the present application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within the range; for example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range; in addition, whenever a numerical range is indicated in this document, it is meant to include any cited numbers (fractions or integers) within the indicated range.

[0027] In this document, the terms including "including" and "including" mean "including but not limited to". Relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. "And / or" describes the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone; where A and B can be singular or plural. "At least one" means one or more, and "plurality" means two or more; "at least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items; for example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple. "Parts" such as parts by weight and parts by mass indicate the proportional relationship between the components. In the proportional relationship involved in this article, the parameters that need to be described by proportion should be understood as the first term of the proportional formula in the order of description, and the proportional numbers should be understood as the second term of the proportional formula. For example, if the weight ratio of substance A, substance B and substance C is 1:2:3, then substance A, substance B and substance C should correspond to the proportional numbers in the proportional formula in the order of description, that is, the weight of substance A: the weight of substance B: the weight of substance C = 1:2:3.

[0028] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this article can be purchased from the market or prepared by existing methods.

[0029] Figure 1 A schematic flow chart of a method for producing DP590 dual-phase steel based on a conventional hot-dip galvanizing production line provided in an embodiment of the present application;

[0030] like Figure 1 As shown, the embodiment of the present application provides a method for producing DP590 dual-phase steel based on a traditional hot-dip galvanizing production line, comprising:

[0031] S1. Obtaining molten steel with a set chemical composition, wherein the set chemical composition includes: replacing precious alloys with a small amount of Ti;

[0032] The key to this chemical composition is to reduce production costs by replacing precious alloys with a small amount of Ti. At the same time, the chemical composition must ensure that the required dual-phase microstructure can be formed during subsequent processing.

[0033] In some embodiments, the set chemical composition includes, by mass fraction: C: 0.08% to 0.14%, Mn: 1.7% to 2%, Si: 0.05% to 0.25%, Al: 0.02% to 0.05%, P≤0.03%, S≤0.005%, Ti: 0.01% to 0.03%, and matrix element Fe.

[0034] In some embodiments, the set chemical composition includes, by mass fraction: C: 0.11% to 0.12%, Mn: 1.9% to 2%, Si: 0.1% to 0.2%, Al: 0.02% to 0.04%, P≤0.02%, S≤0.003%, Ti: 0.01% to 0.03%, and matrix element Fe.

[0035] The positive effect of limiting the mass fraction of C to 0.08% to 0.14% is that C is a solid solution strengthening element of steel, which can enable DP590 dual-phase steel to obtain sufficient tensile strength. When the mass fraction of C is higher than 0.14%, the carbon equivalent of the steel will increase, affecting the welding quality of the material and causing a decrease in the elongation after fracture; when the mass fraction of C is lower than 0.08%, the martensitic structure strength and content obtained after the strip steel leaves the zinc pot are insufficient, and the tensile strength is insufficient. Within the above range, suitable mechanical properties and welding properties can be obtained at the same time. Exemplarily, the mass fraction of C can be 0.08%, 0.09%, 0.10%, 0.11%, 0.12%, 0.13%, 0.14%, etc.

[0036] The positive effect of limiting the mass fraction of Mn to 1.7% to 2% is: ensuring the tensile strength of the strip. Mn is dissolved in the grains to improve the strength. When the mass fraction of Mn is lower than 1.7%, the tensile strength of the matrix is ​​insufficient. For example, the mass fraction of Mn can be 1.7%, 1.75%, 1.8%, 1.85%, 1.9%, 1.95%, 2%, etc.

[0037] The positive effect of limiting the mass fraction of Si to 0.05% to 0.25% is to improve the stability of the ferrite structure and ensure the plasticity of the strip. When the mass fraction of Si is higher than 0.25%, red rust will be generated, affecting the surface quality of the hot-dip galvanized finished product. For example, the mass fraction of Si can be 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, etc.

[0038] The positive effect of limiting the mass fraction of Al to 0.02% to 0.05% is that Al is used for deoxidation in molten steel, and a small amount of Al is present in the embodiments of the present application. The mass fraction of Al above 0.05% will increase the viscosity of the molten steel and make continuous casting production difficult. For example, the mass fraction of Al can be 0.02%, 0.025%, 0.03%, 0.035%, 0.04%, 0.045%, 0.05%, etc.

[0039] The positive effect of limiting the mass fraction of P to ≤ 0.03% is that in order to control costs, the refining process does not need to have too strict requirements on S, but the upper limit still needs to be controlled. If the mass fraction of P is higher than 0.03%, the strip will become cold and brittle. For example, the mass fraction of P can be 0.005%, 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, etc.

[0040] The positive effect of limiting the mass fraction of S to ≤ 0.005% is that in order to control costs, the refining process does not need to make too strict requirements on the S element, but the upper limit still needs to be controlled. When the mass fraction of S is higher than 0.005%, the strip will be hot brittle, and inclusions with Ti will be generated, which will reduce the plasticity and strength of the strip. For example, the mass fraction of S can be 0.001%, 0.002%, 0.003%, 0.004%, 0.005%, etc.

[0041] The positive effect of limiting the mass fraction of Ti to 0.01% to 0.03% is that Ti can precipitate and strengthen in steel, making the grains of steel finer, thereby improving strength and plasticity. If the mass fraction of Ti is lower than 0.01%, it will react preferentially with N, S, etc., and will not have a strengthening effect; if the mass fraction of Ti is higher than 0.03%, the cost will be higher, the strength surplus will be larger, and waste will occur. For example, the mass fraction of Ti can be 0.01%, 0.015%, 0.02%, 0.025%, 0.03%, etc.

[0042] Preferably, the mass fraction of C is 0.11% to 0.12%, the mass fraction of Mn is 1.9% to 2%, the mass fraction of Si is 0.1% to 0.2%, the mass fraction of Al is 0.02% to 0.04%, the mass fraction of P is ≤0.02%, and the mass fraction of S is

[0043] ≤0.003%, the mass fraction of Ti is 0.01%~0.03%.

[0044] More preferably, the mass fraction of C is 0.115%, the mass fraction of Mn is 1.95%, the mass fraction of Si is 0.15%, the mass fraction of Al is 0.03%, the mass fraction of P is 0.013%, the mass fraction of S is 0.0027%, and the mass fraction of Ti is 0.025%.

[0045] Fe is a matrix element. The specific content / content range of Fe can be obtained by the upper and lower limit formula of the component, that is:

[0046] The sum of the percentages of the contents of each component in a composition should be equal to 100%, and the content ranges of several components should meet the following conditions: the upper limit value of a component + the lower limit value of other components ≤ 100; the lower limit value of a component + the upper limit value of other components ≥ 100.

[0047] In the embodiment of the present application, based on the DP590 dual-phase steel produced by the traditional hot-dip galvanizing production line, the amount of precious alloy added is reduced in the chemical composition design, and only a small amount of Ti is added to obtain fine grains and obtain a certain strength. The alloy cost is reduced, and the production cost of the existing hot-dip galvanized DP590 dual-phase steel is reduced.

[0048] S2, sequentially performing continuous casting, hot rolling and coiling on the molten steel to obtain a hot rolled coil;

[0049] Continuous casting: Ensure that the molten steel is properly cooled and solidified during the continuous casting process to form a uniform ingot.

[0050] Hot rolling: Through the hot rolling process, the ingot is further deformed and the grains are refined, while the plasticity and toughness of the material are improved.

[0051] Coiling: Coiling the hot rolled steel into coils for subsequent processing and handling.

[0052] S3, pickling and cold rolling the hot rolled coil in sequence to obtain a chilled coil;

[0053] Pickling: Removes scale and impurities from the surface of hot-rolled coils to provide a clean surface for subsequent cold rolling.

[0054] Cold rolling: During the cold rolling process, the thickness and mechanical properties of the material are adjusted by controlling the reduction rate.

[0055] In some embodiments, the total reduction ratio of the cold rolling is 65% to 75%.

[0056] This control range not only helps to refine the grains of the material, thereby improving its strength and toughness; it also improves the surface quality of the material and reduces defects and cracks; in addition, through plastic deformation during cold rolling, the yield strength and tensile strength of the material can be increased. For example, the total reduction rate of cold rolling can be 65%, 67%, 69%, 71%, 73%, 75%, etc.

[0057] S4, sequentially annealing and galvanizing the chilled coil to obtain a hot dipped coil; wherein the annealing includes: two stages of heating and two stages of cooling;

[0058] The chilled coil is then annealed. This annealing process consists of two stages of heating and two stages of cooling, aimed at forming the desired dual-phase microstructure. The first stage of heating and cooling: the chilled coil is heated to a certain temperature and then cooled to introduce a short TRIP effect (i.e., the induced plasticity effect of the transformation of retained austenite to martensite). The second stage of heating and cooling: the steel is reheated to another temperature and then cooled. This process helps to complete the martensitic phase transformation and refine the grains.

[0059] In some embodiments, the two-stage heating includes a first-stage heating and a second-stage heating; the two-stage cooling includes a first-stage cooling and a second-stage cooling.

[0060] In some embodiments, the terminal temperature of the first stage heating is 650° C. to 690° C., and the heating rate of the first stage heating is 5° C. / s to 8° C. / s.

[0061] In the embodiment of the present application, the purpose of the first stage of heating is to eliminate cold deformation, recrystallize the strip steel, and obtain equiaxed grains of appropriate size. The end temperature is 650℃~690℃. This temperature range ensures that the cold deformation structure in the strip steel is fully eliminated and avoids excessive grain growth. If the end temperature is lower than 650℃, the work hardening will not be fully eliminated, and the elongation after fracture of the final product will decrease; if the end temperature is higher than 690℃, the grain of the structure will grow excessively, and the tensile strength of the final product will decrease. Exemplarily, the end temperature of the first stage of heating can be 650℃, 660℃, 670℃, 680℃, 690℃, etc. The heating rate of 5℃ / s~8℃ / s helps to uniformly heat the strip steel and avoid local overheating or overcooling. Exemplarily, the heating rate of the first stage of heating can be 5℃ / s, 5.5℃ / s, 6℃ / s, 6.5℃ / s, 7℃ / s, 7.5℃ / s, 8℃ / s, etc.

[0062] In some embodiments, the terminal temperature of the second stage heating is 760° C. to 800° C., and the heating rate of the second stage heating is 1° C. / s to 3° C. / s.

[0063] The purpose of the second stage of heating is to regulate the appropriate austenite ratio to ensure that sufficient martensite can be obtained after cooling, thereby improving the tensile strength. The terminal temperature is 760℃~800℃. This temperature range ensures the formation of austenite and avoids excessive austenitization. If the terminal temperature is lower than 760℃, sufficient austenite cannot be obtained, and sufficient martensite cannot be obtained after cooling, and the tensile strength is insufficient; if the terminal temperature is higher than 800℃, excessive austenitization will result, resulting in excessive tensile strength and insufficient elongation after fracture of the final product. Exemplarily, the terminal temperature of the second stage of heating can be 760℃, 770℃, 780℃, 790℃, 800℃, etc. The heating rate of 1℃ / s~3℃ / s helps to homogenize austenite and reduce component segregation in the organization. Exemplarily, the heating rate of the second stage of heating can be 1℃ / s, 1.5℃ / s, 2℃ / s, 2.5℃ / s, 3℃ / s, etc.

[0064] In some embodiments, the terminal temperature of the first stage cooling is 660° C. to 700° C., and the cooling rate of the first stage cooling is 7° C. / s to 9° C. / s.

[0065] The purpose of the first stage of cooling is to adjust the appropriate ferrite ratio to balance the tensile strength and elongation after fracture. The terminal temperature is 660℃~700℃. This temperature range ensures the formation of ferrite and avoids the insufficient tensile strength caused by excessive ferrite. If the terminal temperature is lower than 660℃, more ferrite will be obtained, and the tensile strength of the final product will be insufficient; if the terminal temperature is higher than 700℃, the ferrite ratio will be reduced, the tensile strength of the final product will increase, and the elongation after fracture will be insufficient. Exemplarily, the terminal temperature of the first stage of cooling can be 660℃, 670℃, 680℃, 690℃, 700℃, etc. A cooling rate of 7℃ / s~9℃ / s helps to obtain an ideal ferrite ratio and morphology. Exemplarily, the cooling rate of the first stage of cooling can be 7℃ / s, 7.5℃ / s, 8℃ / s, 8.5℃ / s, 9℃ / s, etc.

[0066] In some embodiments, the terminal temperature of the second stage cooling is 440° C. to 480° C., and the cooling rate of the second stage cooling is 8° C. / s to 11° C. / s.

[0067] The purpose of the second stage of cooling is to ensure that the strip can complete hot-dip galvanizing smoothly and avoid poor galvanizing and de-galvanizing. The end temperature is 440℃~480℃. This temperature range ensures that the strip has an appropriate temperature before galvanizing, thereby ensuring the uniformity and adhesion of the galvanized layer. Exemplarily, the end temperature of the second stage of cooling can be 440℃, 450℃, 460℃, 470℃, 480℃, etc. The cooling rate of 8℃ / s~11℃ / s helps the strip to maintain a stable temperature during the galvanizing process and avoid quality problems during the hot-dip galvanizing process. Exemplarily, the cooling rate of the second stage of cooling can be 8℃ / s, 8.5℃ / s, 9℃ / s, 9.5℃ / s, 10℃ / s, 10.5℃ / s, 11℃ / s, etc.

[0068] After annealing, the steel is galvanized to form hot-dip coils. The galvanized layer not only improves the corrosion resistance of the steel, but also provides it with an aesthetic appearance.

[0069] S5. Perform skin-pass treatment on the hot-dip galvanized coil to obtain DP590 dual-phase steel.

[0070] In some embodiments, the finishing elongation of the finishing treatment is 0.6% to 0.8%.

[0071] The skin finishing process improves the surface quality and mechanical properties of the steel strip by slightly plastically deforming it. Skin finishing elongation refers to the degree of plastic deformation of the steel strip during the skin finishing process, usually expressed as a percentage of the length of the steel strip. Skin finishing can eliminate minor defects on the surface of the steel strip, such as scratches, scale, etc., thereby improving its surface finish and gloss. Within this specific skin finishing elongation range, the surface of the steel strip can be effectively improved, making it smoother. Skin finishing can also release the residual stress inside the steel strip through slight plastic deformation and improve its mechanical properties. At a skin finishing elongation of 0.6% to 0.8%, the roughness and yield strength of the steel strip can be guaranteed. A skin finishing elongation lower than 0.6% will result in insufficient yield strength and roughness of the steel strip, and a skin finishing elongation higher than 0.8% will cause the yield strength and roughness of the steel strip to exceed the upper limit. For example, the skin finishing elongation can be 0.6%, 0.65%, 0.7%, 0.75%, 0.8%, etc.

[0072] In summary, the embodiment of the present application innovatively provides a method for producing DP590 dual-phase steel based on a traditional hot-dip galvanizing production line, which has the following advantages:

[0073] 1. Low cost: The production cost of DP590 duplex steel is significantly reduced by optimizing the chemical composition design and production steps.

[0074] 2. High efficiency: The traditional hot-dip galvanizing production line is combined with the method of the embodiment of the present application to achieve efficient production of DP590 duplex steel.

[0075] 3. Excellent performance: Despite the reduced cost, the produced DP590 duplex steel still maintains excellent mechanical properties and surface quality.

[0076] Therefore, the method for producing DP590 dual-phase steel based on a traditional hot-dip galvanizing production line provided in the embodiment of the present application achieves a combination of low cost, high efficiency and excellent performance of DP590 dual-phase steel by precisely controlling the chemical composition and optimizing the production steps, providing new ideas and technical support for the sustainable development of the steel industry.

[0077] The present application is further described below in conjunction with specific embodiments. The experimental methods in the following embodiments that do not specify specific conditions are usually measured in accordance with national standards / industry standards; if there are no corresponding national standards / industry standards, they are measured in accordance with common international standards, conventional conditions, or conditions recommended by the manufacturer.

[0078] The method for producing DP590 dual-phase steel based on a traditional hot-dip galvanizing production line provided in the embodiment of the present application includes:

[0079] A molten steel having a set chemical composition is obtained, wherein the set chemical composition includes: replacing a precious alloy with a small amount of Ti;

[0080] The molten steel is sequentially continuously cast, hot rolled and coiled to obtain a hot rolled coil;

[0081] The hot-rolled coil is pickled and cold-rolled in sequence to obtain a chilled coil;

[0082] The cold hardened coil is sequentially annealed and galvanized to obtain a hot dipped coil; wherein the annealing includes: two stages of heating and two stages of cooling;

[0083] The hot dip coil is subjected to skin pass treatment to obtain DP590 dual phase steel. Specific process parameters are shown in the following embodiment.

[0084] Example 1

[0085] The specification of the cold-rolled steel coil in this embodiment is 1.2×1257mm, and the chemical composition of the steel coil is calculated by mass fraction: C: 0.107%, Mn: 1.91%, Si: 0.113%, Al: 0.032%, P: 0.014%, S: 0.0029%, Ti: 0.021%, the total reduction rate of cold rolling is 66%, the end temperature of the first stage heating is 676°C, and the heating rate is 5.5°C / s. The end temperature of the second stage heating is 782°C, and the heating rate is 2.7°C / s. The end temperature of the first stage cooling is 685°C, and the cooling rate is 7.9°C / s. The end temperature of the second stage cooling is 454°C, and the cooling rate is 8.7°C / s, and the skin-clearing elongation is 0.64%.

[0086] Mechanical properties: tensile strength 624MPa, yield strength 389MPa, elongation 27% at gauge length 80mm.

[0087] Example 2

[0088] The specification of the cold-rolled steel coil in this embodiment is 1.8×1007mm, and the chemical composition of the steel coil is calculated by mass fraction: C: 0.137%, Mn: 1.98%, Si: 0.224%, Al: 0.042%, P: 0.015%, S: 0.0031%, Ti: 0.018%, the total reduction rate of cold rolling is 69%, the end temperature of the first stage heating is 682°C, and the heating rate is 6.8°C / s. The end temperature of the second stage heating is 795°C, and the heating rate is 2.9°C / s. The end temperature of the first stage cooling is 691°C, and the cooling rate is 8.1°C / s. The end temperature of the second stage cooling is 447°C, and the cooling rate is 10.2°C / s, and the skin-clearing elongation is 0.71%.

[0089] Mechanical properties: tensile strength 669MPa, yield strength 401MPa, elongation 26% at gauge length 80mm.

[0090] Example 3

[0091] The specification of the cold-rolled steel coil in this embodiment is 0.9×1103mm, and the chemical composition of the steel coil is calculated by mass fraction: C: 0.094%, Mn: 1.75%, Si: 0.167%, Al: 0.037%, P: 0.017%, S: 0.0024%, Ti: 0.024%, the total reduction rate of cold rolling is 68%, the end temperature of the first stage heating is 664°C, and the heating rate is 6.1°C / s. The end temperature of the second stage heating is 771°C, and the heating rate is 2.2°C / s. The end temperature of the first stage cooling is 668°C, and the cooling rate is 7.7°C / s. The end temperature of the second stage cooling is 459°C, and the cooling rate is 9.3°C / s, and the skin-clearing elongation is 0.65%.

[0092] Mechanical properties: tensile strength 607MPa, yield strength 379MPa, elongation 29% at gauge length 80mm.

[0093] It can be seen from the examples that the chemical composition of Examples 1 to 3 reduces the amount of precious alloys added and adds a small amount of Ti. Combined with the corresponding production process of the examples of the present application, the prepared hot-dip galvanized DP590 dual-phase steel still maintains excellent performance.

[0094] One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0095] The embodiment of the present invention reduces the amount of alloy elements added, which is beneficial to the recycling of steel and environmental protection.

[0096] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. It will be apparent to those skilled in the art that various modifications to these embodiments are possible, and the general principles defined in the present application can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown in the present application, but will conform to the widest range consistent with the principles and novel features applied for by the present application.

Claims

1. A method for producing DP590 dual-phase steel based on a conventional hot-dip galvanizing production line, the method comprising: A molten steel having a set chemical composition is obtained, wherein the set chemical composition includes: replacing a precious alloy with a small amount of Ti; The molten steel is sequentially continuously cast, hot rolled and coiled to obtain a hot rolled coil; The hot-rolled coil is pickled and cold-rolled in sequence to obtain a chilled coil; The cold hardened coil is sequentially annealed and galvanized to obtain a hot dipped coil; wherein the annealing includes: two stages of heating and two stages of cooling; The hot dip coil is subjected to skin pass treatment to obtain DP590 dual-phase steel.

2. The method according to claim 1, characterized in that In terms of mass fraction, the set chemical composition includes: C: 0.08% to 0.14%, Mn: 1.7% to 2%, Si: 0.05% to 0.25%, Al: 0.02% to 0.05%, P≤0.03%, S≤0.005%, Ti: 0.01% to 0.03%, and matrix element Fe.

3. The method according to claim 1, characterized in that In terms of mass fraction, the set chemical composition includes: C: 0.11% to 0.12%, Mn: 1.9% to 2%, Si: 0.1% to 0.2%, Al: 0.02% to 0.04%, P≤0.02%, S≤0.003%, Ti: 0.01% to 0.03%, and matrix element Fe.

4. The method according to claim 1, characterized in that: The two-stage heating includes a first-stage heating and a second-stage heating; the two-stage cooling includes a first-stage cooling and a second-stage cooling.

5. The method according to claim 1 or 4, characterized in that: The terminal temperature of the first stage heating is 650° C. to 690° C., and the heating rate of the first stage heating is 5° C. / s to 8° C. / s.

6. The method according to claim 1 or 4, characterized in that: The terminal temperature of the second stage heating is 760° C. to 800° C., and the heating rate of the second stage heating is 1° C. / s to 3° C. / s.

7. The method according to claim 1 or 4, characterized in that: The terminal temperature of the first stage cooling is 660° C. to 700° C., and the cooling rate of the first stage cooling is 7° C. / s to 9° C. / s.

8. The method according to claim 1 or 4, characterized in that: The terminal temperature of the second stage cooling is 440°C to 480°C, and the cooling rate of the second stage cooling is 8°C / s to 11°C / s.

9. The method according to claim 1, characterized in that: The total reduction ratio of the cold rolling is 65% to 75%.

10. The method according to claim 1, characterized in that The finishing elongation of the finishing treatment is 0.6% to 0.8%.

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