Multi-scale TiC particle reinforced large-thickness abrasion-resistant steel and preparation method thereof

Abstract

The invention relates to the technical field of metallurgical materials, in particular to multi-scale TiC particle reinforced large-thickness abrasion-resistant steel and a preparation method thereof, the particle size of TiC particles in the steel is D, the weight percentage of the TiC particles with the particle size being larger than or equal to 30 nm and smaller than 100 nm is 40-55%, the weight percentage of the TiC particles with the particle size being larger than or equal to 100 nm and smaller than 500 nm is 25-35%, and the weight percentage of the TiC particles with the particle size being larger than or equal to 500 nm and smaller than or equal to 2 microns is 15-25%. The steel has excellent strength, toughness, wear resistance and corrosion resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metallurgical materials, in particular to a multi-scale TiC particle reinforced large-thickness wear-resistant steel material and a preparation method thereof. BACKGROUND

[0002] Wear-resistant steel is a functional steel widely used in harsh working conditions such as mining machinery, ocean equipment, and conveying equipment. Its main performance requirements are high strength, high hardness, and good wear resistance. However, in many practical application scenarios such as ocean platforms, mortar pipelines, and ore dressing equipment, the material not only bears mechanical wear but also is exposed to corrosive media (such as salt mist, slurry, and chloride solution), forming a "corrosion-wear" combined effect, which makes traditional wear-resistant steel face serious problems of short service life and severe surface damage.

[0003] Traditional C-Si-Mn martensitic wear-resistant steel exhibits good wear resistance in dry wear environments, but in order to obtain high hardness, it usually adopts a high carbon content, which leads to the problem of accelerated electrochemical corrosion in corrosive environments containing salt and weak acid, especially the formation of corrosion pits, which accelerates the wear process. In addition, this type of steel generally has weak work hardening capacity, poor toughness, and insufficient crack resistance, which cannot meet the increasingly complex industrial application requirements.

[0004] In recent years, researchers have attempted to introduce micro-alloying elements (such as Ti, Nb, and V) and corrosion-resistant elements (such as Sn, Cu, and Ni) into steel to improve the microstructure and service performance. Among them, Ti element can react with C in situ to form high-hardness TiC particles in steel, significantly improving the wear resistance of the material. However, the size control and distribution uniformity of TiC particles in the existing technology during heat treatment still have deficiencies, and problems such as oversize or aggregation easily occur, limiting the further development of its strengthening effect.

[0005] On the other hand, Sn element as a typical corrosion-resistant alloying element has good electrochemical stability, and its micro-alloying can to some extent inhibit the chloride-induced local corrosion and pitting behavior, but existing applications are mostly concentrated in the field of low-strength steel or stainless steel, and its synergistic effect with the strengthening mechanism in multi-phase microstructure high-strength wear-resistant steel has not been fully developed.

[0006] Therefore, there is an urgent need to provide a steel material with excellent strength, toughness, wear resistance, and corrosion resistance and a preparation method thereof. SUMMARY

[0007] The present application aims to solve the technical problem of providing a steel material with excellent strength, toughness, wear resistance, and corrosion resistance and a preparation method thereof.

[0008] To achieve the above object, the present application provides a multi-scale TiC particle reinforced large-thickness erosion-resistant steel material, wherein, The TiC particle size in the steel material is D, wherein, The weight percentage of TiC particles with 30 nm≤D<100 nm is 40-55%, The weight percentage of TiC particles with 100 nm≤D<500 nm is 25-35%, The weight percentage of TiC particles with 500 nm≤D≤2 μm is 15-25%.

[0009] The present application provides a preparation method of the above multi-scale TiC particle reinforced large-thickness erosion-resistant steel material, wherein the method comprises: melting and casting, homogenization treatment, rolling, and heat treatment; The homogenization treatment conditions include 1150-1250 °C × 2.5-3.5 h; The final rolling temperature is 900-920 °C, and the temperature is cooled to 20-30 °C at a speed of 0.1-0.3 °C / s after rolling.

[0010] The present application has the following beneficial effects: (1) The introduction of nano, sub-nano, and micron-sized TiC particles in the wear-resistant steel realizes multi-scale dispersion strengthening on the martensite-ferrite matrix, significantly improving the hardness and erosion resistance.

[0011] (2) By reasonably controlling the synergistic content of Cr and Mo, the PSI index is >1.3, which ensures that the central region obtains the same strengthening structure as the surface layer, effectively solving the problem of uneven organization of thick plates.

[0012] (3) By Sn micro-alloying to control the electrochemical stability, the pitting corrosion propagation is significantly inhibited, the corrosion resistance is improved, and the CDWI≤1.4 is controlled, showing excellent combined service ability.

[0013] (4) The present application uses conventional continuous casting, controlled rolling, and heat treatment process, which has low equipment investment cost, wide composition and organization control window, is suitable for batch industrial production, can be used in marine engineering, mining transportation, coastal equipment, and salt mud erosion scenes, and has significant engineering popularization value and industrialization prospect. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 SEM image of the steel material obtained in Example 1 of the present application; Figure 2 TEM image of the steel material obtained in Example 1 of the present application; Figure 3 SEM image of the steel material obtained in Comparative Example 5 of the present application. DETAILED DESCRIPTION

[0015] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0016] In the existing technology, the existing alloy composition and preparation process make it difficult to produce steel with excellent strength, toughness, wear resistance and corrosion resistance, making it difficult to apply the steel to various high-corrosion and wear conditions such as marine engineering, mining machinery, mortar transportation, etc.

[0017] In the present invention, the inventors found that simply introducing microalloying elements (such as Ti, Nb, V) and corrosion-resistant elements (such as Sn, Cu, Ni) into steel to improve the microstructure and service performance is still difficult to achieve excellent strength, toughness, wear resistance and corrosion resistance.

[0018] To achieve this goal, the inventors optimized the composition of wear-resistant steel components. The inventors found that the synergistic mechanism of optimizing chemical composition design, heat treatment process and microstructure regulation can significantly improve the wear resistance, corrosion resistance and comprehensive mechanical properties of steel.

[0019] The first aspect of the present invention provides a multi-scale TiC particle reinforced large thickness wear-resistant steel, wherein: The particle size of TiC particles in the steel is D, wherein: The weight percentage of TiC particles with a size of 30nm≤D<100nm is 40-55%, The weight percentage of TiC particles with a size of 100nm≤D<500nm is 25-35%, The weight percentage of TiC particles with a size of 500 nm ≤ D ≤ 2 μm is 15-25%.

[0020] In the present invention, the TiC particles are formed into a multi-peak particle size distribution by controlling the solidification cooling rate, rolling finishing temperature, cooling rate and heat treatment insulation system, and are evenly distributed within the grains and grain boundaries to achieve multi-scale dispersion strengthening.

[0021] In the present invention, nano-scale, sub-nano-scale and micron-scale TiC particles of specific sizes and contents are distributed within the grains and in the grain boundary regions, respectively, to achieve a multi-scale dispersion-strengthened structure.

[0022] According to the application, the pearlite suppression index PSI of a 2mm steel plate centered at the thickness direction 1 / 2 of the steel material is greater than 1.3, the PSI is defined by the following formula: PSI=C+0.35Mn+0.8Cr+1.5Mo, wherein each element represents the content of the respective element in weight percentage.

[0023] In the application, the core refers to the center in the thickness direction 1 / 2, i.e. the center in the thickness direction of the steel material.

[0024] In the application, by reasonably regulating the synergistic content of Cr and Mo, the PSI index is greater than 1.3, so that the core region obtains the same strengthening structure as the surface layer, and the uneven problem of the thick plate structure is effectively solved.

[0025] According to the application, the components and weight percentages in the steel material are as follows: The content of C is 0.18-0.22%; The content of Si is 0.8-1.2%; The content of Mn is 1.6-2.0%; The content of Cr is 0.3-0.6%; The content of Mo is 0.1-0.3%; The content of Ti is 0.25-0.35%; The content of Sn is 0.05-0.1%; The content of Al is 0.15-0.25%; The content of B is 0.001-0.003%; The content of S is ≤0.10%; The content of P is ≤0.02%; The content of other impurity elements is ≤0.03% individually; The total content of other impurity elements is ≤0.1%; The balance is Fe.

[0026] In the application, Cr and Mo are added in combination to improve the hardenability and suppress the pearlite structure in the core of the thick plate; Sn element improves the corrosion resistance by increasing the electrode potential, especially inhibiting the expansion of pitting induced by chloride ions; B element can significantly refine the grains and improve the toughness of the material; Al, as a strong deoxidizing agent, can also form AlN particles with the unavoidable N element in the steel, realizing grain refinement and dislocation pinning, which helps to improve the impact toughness in the thickness direction of the steel plate.

[0027] According to the application, the volume content of the martensite phase of the steel material is 75-85%, and the volume content of the ferrite phase is 15-25%.

[0028] According to the application, the steel material has a thickness of 60-120 mm, a tensile strength of 1200-1320 MPa at 1 / 4 of the thickness direction, an elongation after fracture of 16-18%, and a surface hardness of 400-440 HV.

[0029] In the application, the 1 / 4 of the thickness direction of the steel material refers to the 1 / 4 and 3 / 4 of the same thickness direction as the center to take the standard piece for tensile strength test, both of which have excellent performance of tensile strength of 1200-1320 MPa.

[0030] According to the application, in the combined environment of 3.5% NaCl solution and abrasive particle erosion, the corrosion and wear synergistic index CDWI of the steel material is ≤1.4.

[0031] In the application, the electrochemical stability is regulated by Sn micro-alloying to significantly inhibit the propagation of pitting corrosion and improve corrosion resistance, while controlling CDWI ≤1.4, showing excellent combined service capability.

[0032] The second aspect of the application provides a preparation method of the above-mentioned multi-scale TiC particle reinforced large-thickness wear-resistant and corrosion-resistant steel material, wherein the method comprises: melting and casting, homogenization treatment, rolling, and heat treatment; The homogenization treatment conditions include: 1150-1250°C × 2.5-3.5h; The final rolling temperature is 900-920°C, and the cooling rate after rolling is 0.1-0.3°C / s to 20-30°C.

[0033] In the application, the melting and casting conditions can be according to the conventional melting and casting conditions in the art.

[0034] Specifically, the refining temperature is 1600-1650°C, the casting temperature is 1550-1600°C, and the casting speed is 0.8-1.2 m / min.

[0035] According to the application, the heat treatment conditions include heating the rolled and cooled plate to 840-880°C, and the relationship between the holding time T and the thickness L of the steel plate after rolling is T=3L, the unit of T is min, and the unit of L is mm, and the water cooling temperature after holding is 20-30°C.

[0036] Test method Tensile test: the standard GB / T 228.1-2020 "Metallic materials-Tensile test-Part 1: Method of test at room temperature" is used to test the tensile strength and elongation after fracture of the steel material, and the sample preparation and test conditions meet the requirements of the standard.

[0037] The surface Brinell hardness test is tested according to the standard GB / T 231.1-2021 "Metallic Materials - Brinell Hardness Test - Part 1: Test Method", and the Brinell hardness of the steel surface is measured.

[0038] The abrasion resistance is tested in combination with ASTM G65-16 (2021) "Standard Test Method for Measuring Abrasion Using the Dry Sand / Rubber Wheel Apparatus" and T / CSCP 0035.8-2017 "Laboratory Corrosion Testing of Low Alloy Structural Steel - Part 8: Laboratory Uniform Corrosion Immersion Test Method for Low Alloy Structural Steel", and the abrasion resistance of the steel is comprehensively evaluated.

[0039] The technical solutions of the present application will be described in further detail below in combination with the drawings and examples. Obviously, the examples described herein are only some of the examples of the present application and are not intended to limit the present application. Based on the examples in the present application, all other examples implemented by those of ordinary skill in the art without making creative improvements fall within the protection scope of the present application.

[0040] Example 1 The chemical composition of the steel (in percentage by weight) is as follows: C: 0.22%, Si: 1.2%, Mn: 2.0%, Cr: 0.6%, Mo: 0.3%, Ti: 0.35%, Sn: 0.10%, Al: 0.20%, B: 0.003%, S≤0.005%, P≤0.003%, and the rest is Fe, and the content of other impurity elements is ≤0.03% individually and ≤0.1% in total. The above chemical composition is proportioned and charged into a converter for smelting and then subjected to secondary refining to form a continuous casting slab. The slab is heated to 1200℃ for homogenization treatment, and then is rolled into a 120mm thick steel plate by using a controlled rolling process, with the finish rolling temperature controlled at 910℃, and then cooled to room temperature at a cooling rate of 0.3℃ / s, and then heated to 880℃ in the furnace, and then water-cooled to room temperature after holding for 360 minutes, to finally obtain a martensite + ferrite dual-phase composite structure.

[0041] The volume content of the martensite phase is 85%, and the volume content of the ferrite phase is 15%; during thermal deformation and controlled cooling, Ti and C react in situ to form multi-scale TiC particles, which have a three-peak distribution in particle size, with nanoscale (30~100nm) accounting for 55%, submicron scale (100~500nm) accounting for 25%, and micron scale (0.5~2μm) accounting for 20%, and are uniformly distributed in the grain and grain boundary regions to construct a multi-scale strengthening network; PSI=1.85, effectively inhibiting the transformation of the center pearlite.

[0042] The steel A1 is prepared.

[0043] The 120mm-thick steel plate has a tensile strength of 1263MPa, an elongation after fracture of 19.6%, and a surface hardness of 433HV, and the comprehensive performance meets the use requirements of high-corrosion and high-wear working conditions.

[0044] Example 2 The steel material has the following chemical components (in percentage by weight): C: 0.20%, Si: 1.0%, Mn: 1.8%, Cr: 0.4%, Mo: 0.20%, Ti: 0.30%, Sn: 0.10%, Al: 0.20%, B: 0.003%, S≤0.005%, P≤0.003%, and the rest is Fe and inevitable impurities. The above chemical components are proportioned and ingredients, smelted in a converter, and subjected to secondary refining to form a continuous casting slab. The slab is heated to 1200℃ for homogenization treatment, and then rolled into an 80mm-thick steel plate by using a controlled rolling process, with the finish rolling temperature controlled at 910℃. After rolling, the steel plate is cooled to room temperature at a cooling rate of 0.2℃ / s, and then heated to 860℃ in the furnace, and then water-cooled to room temperature after holding for 240 minutes. Finally, a dual-phase composite structure of martensite + ferrite is obtained.

[0045] The volume content of the martensite phase is 80%, and the volume content of the ferrite phase is 20%. During thermal deformation and controlled cooling, Ti and C react in situ to form multi-scale TiC particles, which have a three-peak distribution in particle size, with 50% of nano-scale (30-100nm), 30% of sub-micron scale (100-500nm), and 20% of micron scale (0.5-2μm) particles, which are uniformly distributed in the grain and grain boundary regions, and construct a multi-scale strengthening network. The PSI is 1.45, which effectively inhibits the transformation of the center pearlite.

[0046] The steel material A2 is prepared.

[0047] The 80mm-thick steel plate has a tensile strength of 1257MPa, an elongation after fracture of 18.9%, and a surface hardness of 427HV, and the comprehensive performance meets the use requirements of high-corrosion and high-wear working conditions.

[0048] Example 3 The chemical composition of the steel material (in percentage by weight) is as follows: C: 0.18%, Si: 0.8%, Mn: 1.6%, Cr: 0.4%, Mo: 0.20%, Ti: 0.30%, Sn: 0.10%, Al: 0.20%, B: 0.003%, S≤0.005%, P≤0.003%, and the balance being Fe and inevitable impurities. The above chemical composition is proportioned and prepared, smelted in a converter, and then subjected to secondary refining to form a continuous casting slab. The slab is heated to 1200°C for homogenization treatment, and then rolled into a 60mm-thick steel plate by using a controlled rolling process, with the finish rolling temperature being controlled at 910°C. After rolling, the steel plate is cooled to room temperature at a cooling rate of 0.1°C / s, and then heated to 840°C in the furnace, and then water-cooled to room temperature after holding for 180 minutes, so as to finally obtain a dual-phase composite structure of martensite and ferrite.

[0049] The volume content of the martensite phase is 75%, and the volume content of the ferrite phase is 25%. During thermal deformation and controlled cooling, Ti and C react in situ to form multi-scale TiC particles, which have a three-peak distribution in particle size, with the nano-scale (30-100nm) accounting for 40%, the sub-micron scale (100-500nm) accounting for 35%, and the micron scale (0.5-2μm) accounting for 25%. The multi-scale TiC particles are uniformly distributed in the grain and the grain boundary region, and construct a multi-scale strengthening network. The PSI is 1.36, and the transformation of the center portion of the pearlite is effectively inhibited.

[0050] The steel material A3 is prepared.

[0051] After performance testing, the tensile strength of the 60mm-thick steel plate is 1262MPa, the elongation after fracture is 18.5%, and the surface hardness is 431HV. The comprehensive performance meets the use requirements of high corrosion and wear conditions.

[0052] Comparative Example 1 The steel material is prepared according to the method of Example 1, except that no Ti element is added, and no multi-scale TiC particles are formed to provide precipitation strengthening effect. Finally, a dual-phase structure of martensite and ferrite is obtained, in which the volume content of the martensite phase is 70%, and the volume content of the ferrite phase is 30%. No nano-scale TiC particles are observed.

[0053] Due to the lack of TiC particle dispersion strengthening, the matrix strengthening effect is significantly reduced.

[0054] The steel material DA1 is prepared.

[0055] After performance testing, the tensile strength of the 120mm-thick steel plate is 1018MPa, the elongation after fracture is 15.3%, and the surface hardness is 368HV. The comprehensive performance does not meet the requirements of the present application.

[0056] Comparative Example 2 The steel material is prepared according to the method of Example 1, except that the Ti content is 0.1%, and no multi-scale TiC particles are formed to provide precipitation strengthening effect. Finally, a dual-phase structure of martensite and ferrite is obtained, in which the volume content of the martensite phase is 75%, and the volume content of the ferrite phase is 25%. The nano-scale (30-100 nm) accounts for 15%, the sub-micron scale (100-500 nm) accounts for 10%, the micron scale (0.5-2 μm) accounts for 20%, and the size greater than 2 μm accounts for 55%. Since the Ti content is only 0.1%, a multi-scale TiC three-peak particle distribution cannot be formed, resulting in insufficient precipitation strengthening effect.

[0057] The steel material DA2 is prepared.

[0058] Through performance testing, the tensile strength of the 120 mm thick steel plate is 1098 MPa, the elongation after fracture is 15.7%, and the surface hardness is 387 HV, which does not meet the comprehensive performance requirements of the present application.

[0059] Comparative Example 3 The steel material is prepared according to the method of Example 1, except that Sn element is not added, and the volume content of the martensite phase is 80%, and the volume content of the ferrite phase is 20%. The nano-scale (30-100 nm) accounts for 35%, the sub-micron scale (100-500 nm) accounts for 35%, and the micron scale (0.5-2 μm) accounts for 30%.

[0060] The steel material DA3 is prepared.

[0061] Since Sn is not introduced, the effect of Sn element on improving electrode potential is lacking, and the pitting sensitivity of the steel material in the corrosion environment is significantly increased, and the interface instability causes the plasticity to decrease significantly.

[0062] Through performance testing, the tensile strength of the 120 mm thick steel plate is 1157 MPa, the elongation after fracture is 12.4%, and the surface hardness is 398 HV, which does not meet the comprehensive performance requirements of the present application.

[0063] Comparative Example 4 The steel material is prepared according to the method of Example 1, except that the Cr content is 0.2% and the Mo content is 0.1%. The PSI decreases to 1.05. The nano-scale (30-100 nm) accounts for 30%, the sub-micron scale (100-500 nm) accounts for 30%, and the micron scale (0.5-2 μm) accounts for 20%. The volume content of the martensite phase is 55%, the volume content of the ferrite phase is 20%, and the pearlite content is 25%.

[0064] The steel material DA4 is prepared.

[0065] Pearlite is generated in the core, and the ductility, strength and hardness decrease significantly.

[0066] The 120mm thick steel plate has a tensile strength of 944MPa, an elongation of 10.4%, and a surface hardness of 374HV, which do not meet the comprehensive performance requirements of the present application.

[0067] Comparative Example 5 The steel material was prepared according to the method of Example 1, except that the rolled and cooled steel material was heated to 800℃.

[0068] The steel material DA5 was prepared.

[0069] Due to the decrease of the quenching temperature, the ferrite structure increases, and the proportion of the martensite decreases, and the volume content of the martensite phase is 60%, and the volume content of the ferrite phase is 40%. Due to the heating temperature being lower than the critical range of austenitization, the austenite transformation amount is insufficient, the proportion of the martensite phase formed is only 60%, the structure is soft, and the strength and hardness decrease. The proportion of the nanoscale (30-100nm) is 20%, the proportion of the submicron (100-500nm) is 20%, the proportion of the micron (0.5-2um) is 25%, and the proportion of the particles with a size greater than 2um is 35%. The 120mm thick steel plate has a tensile strength of 956MPa, an elongation of 18.4%, and a surface hardness of 364HV, which do not meet the comprehensive performance requirements of the present application.

[0070] Corrosion and wear experiments were conducted on A1-A3, DA1-DA5 and conventional C-Si-Mn steel, and the experimental results are shown in Table 1 Table 1 Through the comparison of the examples and the comparative examples, it can be seen that the steel material provided by the present application has excellent strength, toughness, wear resistance and corrosion resistance.

[0071] The SEM image of the steel material obtained in Example 1 of the present application is shown in the accompanying drawings. Figure 1 The TEM image of the steel material obtained in Example 1 of the present application is shown in the accompanying drawings.

[0072] The SEM image of the steel material obtained in Comparative Example 5 of the present application is shown in the accompanying drawings. Figure 2 The TEM image of the steel material obtained in Comparative Example 5 of the present application is shown in the accompanying drawings.

[0073] The SEM image of the steel material obtained in Comparative Example 5 of the present application is shown in the accompanying drawings. Figure 3 The TEM image of the steel material obtained in Comparative Example 5 of the present application is shown in the accompanying drawings.

[0074] The above merely describes preferred embodiments of the present application, but the protection scope of the present application is not limited thereto, and any skilled person in the art, according to the technical scheme and inventive concept of the present application, makes equivalent replacement or change within the technical range disclosed by the present application, should be covered within the protection scope of the present application.

Claims

1. A multi-scale TiC particle reinforced thick wear-resistant steel, characterized in that: The particle size of TiC particles in the steel is D, wherein: The weight percentage of TiC particles with a size of 30nm≤D<100nm is 40-55%, The weight percentage of TiC particles with a size of 100nm≤D<500nm is 25-35%, The weight percentage of TiC particles with a size of 500 nm ≤ D ≤ 2 μm is 15-25%.

2. The steel material according to claim 1, characterized in that A 2 mm steel plate is taken with 1 / 2 of the thickness of the steel as the center, and the pearlite suppression index PSI of the steel plate is greater than 1.

3. The PSI is defined by the following formula: PSI=C+0.35Mn+0.8Cr+1.5Mo, wherein each element represents its own element content in weight percentage.

3. The steel material according to claim 1, characterized in that The components and weight percentages in the steel are as follows: C content is 0.18-0.22%; Si content is 0.8-1.2%; Mn content is 1.6-2.0%; Cr content is 0.3-0.6%; Mo content is 0.1-0.3%; Ti content is 0.25-0.35%; Sn content is 0.05-0.1%; Al content is 0.15-0.25%; B content is 0.001-0.003%; S content ≤ 0.10%; P content ≤ 0.02%; The individual content of other impurity elements is ≤0.03%; The total content of other impurity elements is ≤0.1%; The balance is Fe.

4. The steel material according to claim 1, characterized in that The volume content of the martensite phase of the steel is 75-85%, and the volume content of the ferrite phase is 15-25%.

5. The steel material according to claim 1, characterized in that The thickness of the steel is 60-120 mm, the tensile strength at 1 / 4 of the thickness direction of the steel is 1200-1320 MPa, the elongation after fracture is 16-18%, and the surface hardness is 400-440 HV.

6. The steel material according to claim 1, characterized in that In the combined environment of 3.5% NaCl solution and abrasive erosion, the corrosion wear synergy index CDWI of the steel is ≤1.

4.

7. A method for preparing the multi-scale TiC particle reinforced thick wear-resistant steel according to any one of claims 1 to 6, characterized in that: The method comprises: Casting, homogenization, rolling, heat treatment; The homogenization treatment conditions include: 1150-1250°C × 2.5-3.5h; The final rolling temperature is 900-920°C, and after rolling, it is cooled to 20-30°C at a rate of 0.1-0.3°C / s.

8. The method according to claim 7, characterized in that The heat treatment conditions include: heating the steel cooled after rolling to 840-880°C, the relationship between the holding time T and the thickness L of the steel plate after rolling is: T=3L, the unit of T is min, the unit of L is mm, and water cooling to 20-30°C after holding.

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