A process for reducing shrinkage cavities and porosity in the core of Fe-12Mn-8.5Al-0.8C low-density steel

Abstract

The invention relates to a process for reducing shrinkage cavities and porosity in the core of Fe-12Mn-8.5Al-0.8C low-density steel. The process comprises the steps of vacuum induction furnace smelting, high-temperature homogenization treatment, two rapid forging and drawing, stress relief annealing and the like, which effectively reduces the metallurgical defects of Fe-12Mn-8.5Al-0.8C low-density steel, improves the comprehensive mechanical properties of the material, and enables Fe-12Mn-8.5Al-0.8C low-density steel to play a more important role in the application of lightweight automobiles.

Description

Technical Field

[0001] The invention belongs to the technical field of iron and steel metallurgy, and particularly relates to a process for reducing shrinkage cavities and porosity in the core of Fe-12Mn-8.5Al-0.8C low-density steel. Background Art

[0002] The number of cars in my country is increasing year by year. Pollutants such as carbon monoxide, nitrogen monoxide, and hydrocarbons emitted by automobile exhaust have caused PM2.5 in the atmosphere to exceed the standard, seriously affecting the quality of the air environment. Studies have shown that for every 10% reduction in the weight of a car, its fuel consumption can be reduced by 1% to 8%, and exhaust emissions can be reduced by 5% to 1%; and for every 1L reduction in fuel consumption, 2.45Kg of carbon dioxide will be reduced. Due to the need for energy conservation and environmental protection, lightweighting of cars has become a trend in the development of the world's automobiles. Studies have shown that the density of steel only needs to be reduced by 10% to maintain or even significantly improve the superiority and competitiveness of steel in the automotive industry.

[0003] From the perspective of material selection, there are currently two main ways to reduce the weight of automobiles: one is to use lightweight materials, such as low-density aluminum and aluminum alloys, magnesium and magnesium alloys, engineering plastics, etc., but such lightweight materials have very low strength, which seriously limits their application in stress-bearing and load-bearing parts of automobiles. The second is to use ultra-high-strength steel to replace traditional steel, reduce the thickness of steel plates to reduce the weight of the vehicle body, but high-strength steel plates are prone to rebound after forming, and the rebound amount is much greater than that of traditional low-carbon steel plates, and the material properties are more complex and difficult to control. In the 1930s, Ton and Korter first proposed the concept of low-density steel. They added manganese and aluminum elements with low relative molecular mass to iron to form Fe-Mn-Al low-density steel, and made a phase diagram after quenching. In 1958, Ham and Cairns developed a low-cost Fe-34Mn-10Al-0.71C austenitic low-density steel with a tensile strength of 750MPa. Cr-Ni stainless steel requires the addition of a large amount of metals such as chromium and nickel. At that time, 95.1% of the world's chromium was in South Africa and Zimbabwe. Chromium became an extremely scarce element. The addition of chromium and nickel caused the production cost of stainless steel to be very high. The newly developed austenitic low-density steel has excellent corrosion resistance and oxidation resistance. Low-density steel not only has cost advantages, but also has the development potential of low density. Ham et al. proposed to use cheap Fe-Mn-Al low-density steel to replace expensive Cr-Ni stainless steel, which became a hot topic in the automotive and steel industries in the 1950s. Since the 1990s, environmental pollution has attracted much attention, and the requirements for energy saving and lightweight in various fields have become increasingly higher. A research and development idea with development potential for lightweighting is to develop a steel grade that combines low density and high strength and toughness - low-density steel (low-density steel), so low-density steel has become a hot research topic in various countries. Some scholars pointed out that by adding a certain amount of lightweight elements such as aluminum, manganese, silicon and carbon to steel, a new type of steel with low density and high strength and toughness can be obtained on the basis of optimizing the alloy composition and heat treatment process. In this way, the weight of the car itself can be effectively reduced without sacrificing the strength and rigidity of the car structure. According to relevant research, in Fe-Mn-Al-C low-density steel, when the Al content is 2.5%-1.0%, the density of the steel is less than 7.5g / cm 3 , the weight reduction is 4.5%; when the Al content is 1.0%-10.0%, the density of the steel can be less than 7.2g / cm 3 , the weight reduction can be greater than 8.3%; when the Al content is 10.0%-15.0%, the density of the steel can be less than 1.5g / cm 3 , weight loss can reach 17.2%.

[0004] Patent document CN104928519A discloses a 800MPa grade high ductility low-density steel and its manufacturing method. The method uses smelting, casting, hot rolling, pickling, cold rolling and continuous annealing processes to prepare a steel plate with a tensile strength of >800MPa and a post-fracture elongation of >25%. However, the method improves the comprehensive mechanical properties of low-density steel by means of rolling deformation, and the low-density steel prepared by the method is complex, which increases the production cost of low-density steel and affects the use of low-density steel in lightweighting. Patent document CN104174109A discloses a low-density Fe-Mn-Al-C cold-rolled automotive steel plate and its preparation method. The method requires forging, hot rolling and other processes to improve the performance of the steel plate. Its preparation process is complex and will be severely restricted in lightweight applications.

[0005] The existing Fe-12Mn-8.5Al-0.8C low-density steel is prone to composition segregation and metallurgical defects such as core shrinkage and shrinkage during the metallurgical process due to the high content of alloy elements, which seriously affects the comprehensive mechanical properties of the material. Summary of the invention

[0006] In order to overcome the shortcomings of the existing methods, the present invention provides a process for reducing shrinkage cavities and shrinkage in the core of Fe-12Mn-8.5Al-0.8C low-density steel and improving its mechanical properties. The Fe-12Mn-8.5Al-0.8C low-density steel used in the present invention has good strength and plasticity, which makes its application range more extensive. The process effectively reduces the metallurgical defects of Fe-12Mn-8.5Al-0.8C low-density steel through high-temperature homogenization treatment, two rapid forging and drawing, and stress relief annealing, improves the comprehensive mechanical properties of the material, and makes Fe-12Mn-8.5Al-0.8C low-density steel play a more important role in the application of lightweight automobiles.

[0007] The technical solution adopted by the present invention is as follows: a process for reducing shrinkage and porosity of the core of Fe-12Mn-8.5Al-0.8C low-density steel, the process comprising the following steps:

[0008] a. Vacuum induction furnace smelting:

[0009] The alloy raw materials, except for the rare earth element components, are loaded into the crucible of the vacuum induction furnace according to the component ratio, and the crucible of the vacuum induction furnace is evacuated; then, the alloy raw materials are completely melted by electricity, and the rare earth element components are added to the molten steel in the molten steel refining stage, and the composition of the Fe-12Mn-8.5Al-0.8C low-density steel is tested and fine-tuned before steel is tapped, and the steel can be cast after the component test is qualified, and an ingot of a certain diameter is obtained;

[0010] b. High temperature homogenization treatment:

[0011] The ingot with a certain diameter obtained by melting in a vacuum induction furnace is used as the base ingot, and then subjected to high-temperature homogenization treatment and heat preservation;

[0012] c. Two times of rough drawing and lengthening:

[0013] The ingot that has completed the high-temperature homogenization treatment is kept at a predetermined temperature for a predetermined time, and is taken out of the furnace after the temperature of the ingot is uniform; the entire ingot is subjected to the first roughening by a press, and the first elongation is performed immediately after the first roughening is completed;

[0014] The ingot that has completed the first roughing and drawing is returned to the furnace for a predetermined time at the same predetermined temperature, and after the temperature of the ingot is uniform, it is taken out of the furnace for a second roughing and drawing, and the whole ingot is roughed for the second time by a press, and the second roughing and drawing is immediately performed after the second roughing is completed, and then the ingot is rounded to a certain diameter specification; after the second roughing and drawing is completed, it is slowly cooled to room temperature;

[0015] d. Stress relief annealing treatment:

[0016] The ingot after two roughing and drawing processes is subjected to stress relief annealing treatment.

[0017] Furthermore, the steel casting temperature is 150011100°C; the steel is cast into an ingot with a diameter of 200 mm1250 mm; and the vacuum induction furnace crucible is evacuated to 100 1300 Pa.

[0018] Furthermore, the steel casting temperature is 1550° C., and the steel is cast into an ingot with a diameter of 230 mm; and the crucible of the vacuum induction furnace is evacuated to 100 Pa.

[0019] Furthermore, the high temperature homogenization treatment temperature is 1200 11300°C, and the holding time is 10 115h.

[0020] Furthermore, the high temperature homogenization treatment temperature is 1250° C. and the holding time is 15 h.

[0021] Furthermore, the ingot after high temperature homogenization treatment is cooled, and then peeled and refined into an ingot with a diameter of 2001230mm.

[0022] Furthermore, the ingot after the high temperature homogenization treatment is cooled, and then peeled and refined into an ingot with a diameter of 200 mm.

[0023] Furthermore, the ingot that has completed the homogenization treatment is kept at 1100-11150°C for 1-12 hours; the ingot that has completed the first roughening and drawing is returned to the furnace and kept at 1100-11150°C for 1-12 hours.

[0024] Furthermore, during the first roughing and drawing process and the second roughing and drawing process, the roughing reduction rate is controlled at 20%-150%, the drawing reduction rate is controlled at 10%-120%, and the ingot temperature is controlled to be ≥1050°C.

[0025] Furthermore, after the roughening is completed, the steel is immediately stretched and then rounded to an ingot with a diameter of 180-1200 mm.

[0026] Furthermore, the stress relief annealing treatment is carried out in a regenerative walking beam heating furnace, the heating temperature of the regenerative walking beam heating furnace is set to 500-1550°C, and the holding time is 3-15h.

[0027] Furthermore, the ingot after the two roughening and drawing processes is subjected to stress relief annealing treatment, and the surface temperature and the core temperature of the ingot after the two roughening and drawing processes are controlled within ±5°C.

[0028] The present invention has the following beneficial effects: the process designed by the present invention strictly controls the process parameters of high-temperature homogenization treatment, drawing and stress relief annealing treatment of Fe-12Mn-8.5Al-0.8C low-density steel, and finally makes the tensile strength of Fe-12Mn-8.5Al-0.8C low-density steel ≥800MPa, the yield strength ≥500MPa, and the elongation after fracture ≥30%, so that the Fe-12Mn-8.5Al-0.8C low-density steel has good comprehensive mechanical properties; at the same time, the core of the ingot after the process treatment has no visually visible defects such as shrinkage cavities, shrinkage, bubbles, cracks or inclusions, and the structure is uniform and the quality is good.

[0029] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 The macrostructure diagram of Fe-12Mn-8.5Al-0.8C low-density steel after high-temperature homogenization treatment, secondary drawing and stress relief annealing treatment is shown in the embodiment of the present invention;

[0032] Figure 2The macrostructure diagram of the low-density cast steel prepared in the comparative example of the present invention after smelting, casting and heat treatment is shown. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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 creative work are within the scope of protection of the present invention.

[0034] The present invention relates to a process for reducing shrinkage cavities and porosity in the core of Fe-12Mn-8.5Al-0.8C low-density steel, the process comprising the following steps:

[0035] a. Vacuum induction furnace smelting:

[0036] The alloy raw materials, except for the rare earth element components, are loaded into the crucible of the vacuum induction furnace according to the component ratio, and the crucible of the vacuum induction furnace is evacuated; then, the alloy raw materials are completely melted by electricity, and the rare earth element components are added to the molten steel in the molten steel refining stage, and the composition of the Fe-12Mn-8.5Al-0.8C low-density steel is tested and fine-tuned before tapping, and the steel can be tapped and cast after the component test is qualified, and an ingot of a certain diameter is obtained;

[0037] b. High temperature homogenization treatment:

[0038] The ingot with a certain diameter obtained by melting in a vacuum induction furnace is used as the base ingot, and then subjected to high-temperature homogenization treatment and heat preservation;

[0039] c. Two times of rough drawing and lengthening:

[0040] The ingot that has completed the high-temperature homogenization treatment is kept at a predetermined temperature for a predetermined time, and is taken out of the furnace after the temperature of the ingot is uniform; the entire ingot is subjected to the first roughening by a press, and the first elongation is performed immediately after the first roughening is completed;

[0041] The ingot that has completed the first roughing and drawing is returned to the furnace for a predetermined time at the same predetermined temperature, and after the temperature of the ingot is uniform, it is taken out of the furnace for a second roughing and drawing, and the whole ingot is roughed for the second time by a press, and the second roughing and drawing is immediately performed after the second roughing is completed, and then the ingot is rounded to a certain diameter specification; after the second roughing and drawing is completed, it is slowly cooled to room temperature;

[0042] d. Stress relief annealing treatment:

[0043] The ingot after two roughing and drawing processes is subjected to stress relief annealing treatment.

[0044] In the above process, the alloy raw materials are melted and refined by using a vacuum induction furnace. Under vacuum conditions, there is no air and slag pollution, the metal is not easy to volatilize and oxidize, and the chemical composition of Fe-12Mn-8.5Al-0.8C low-density steel can be accurately controlled and adjusted. At the same time, vacuum smelting also creates good degassing conditions. At the same time, there is a certain amount of electromagnetic stirring in the molten pool, which can promote the uniformity of molten steel composition and temperature, so that inclusions in the steel float up, thereby obtaining high-quality Fe-12Mn-8.5Al-0.8C low-density steel ingots. In this process, if the steel tapping casting temperature is too low, it is easy to cause nozzle blockage and casting interruption; defects such as blisters, slag inclusions, and cracks are easy to occur on the surface of the ingot; non-metallic inclusions are not easy to float up, affecting the intrinsic quality of the billet. The hazards of too high steel tapping casting temperature: accelerated erosion of refractory materials, easy to cause uncontrolled casting flow, and reduce casting safety; increased non-metallic inclusions, affecting the intrinsic quality of the slab; developed columnar crystals in the billet; aggravated center segregation, and easy to produce centerline cracks.

[0045] In the above process, high temperature homogenization treatment is a heat treatment process in which the Fe-12Mn-8.5Al-0.8C low-density steel ingot is heated to a temperature below the solidus line for a long time and then slowly cooled to eliminate dendrite segregation and chemical composition inhomogeneity. Due to the fast cooling rate under industrial production conditions, the structure of the Fe-12Mn-8.5Al-0.8C low-density steel ingot after condensation is in a non-equilibrium state to varying degrees, which is mainly manifested in the generation of dendrite segregation. Due to the existence of segregation, the components of each part of the ingot differ greatly, thereby causing differences in the phase change process, which will lead to extremely uneven structure and performance of large ingots. At the same time, a large organizational stress is generated, and the banded structure formed by segregation will cause the mechanical properties of low-density steel to deteriorate seriously. The purpose of homogenization treatment is to eliminate the dendrite segregation and regional segregation generated in the ingot during the solidification process, and to dissolve the coarse primary phase into the matrix, so that the composition and structure of the Fe-12Mn-8.5Al-0.8C low-density steel are homogenized, and the strength and toughness of the material are improved. When the high temperature homogenization treatment temperature is lower than 1200℃, it cannot achieve the effect of eliminating dendrite segregation and uniform chemical composition; when the high temperature homogenization treatment temperature is higher than 1300℃, it will accelerate the coarsening of grains and reduce the mechanical properties of the material.

[0046] In the above process, two quick forging and pulling operations can increase the equivalent strain of the core of the ingot, increase the shrinkage cavity and shrinkage welding rate, and reduce the influence of the central shrinkage cavity and shrinkage on the ingot quality.

[0047] In the above process, stress relief annealing treatment can eliminate the residual stress of the ingot during the forging process, improve the dimensional stability of the ingot, prevent deformation and cracking of the workpiece, refine the grains and eliminate overheating defects.

[0048] The above process will be described in detail below through specific examples.

[0049] Example

[0050] A process for reducing shrinkage cavities and porosity in the core of Fe-12Mn-8.5Al-0.8C low-density steel, the process comprising the following steps:

[0051] a. Except for the rare earth element component (Ce), the alloy raw materials are loaded into the crucible of a vacuum induction furnace according to the component ratio shown in Table 1, and the vacuum is evacuated to 100 Pa; then, the alloy raw materials are completely melted by power, and the rare earth element component is added to the molten steel during the molten steel refining stage. Before tapping, the composition of the Fe-12Mn-8.5Al-0.8C low-density steel is tested and fine-tuned. After the component test is qualified, the steel can be tapped. The tapping casting temperature is 1550° C., and the ingot with a diameter of 230 mm is cast. The main components and contents of the ingot are shown in Table 1.

[0052] Table 1 Composition and content of Fe-12Mn-8.5Al-0.8C low-density steel (mass percentage / %)

[0053] element Mn Al C O N H P S Ce Fe content 12.0 8.5 0.8 0.002 0.003 0.0001 0.008 0.002 0.002 margin

[0054] b. The ingot with a diameter of 230 mm obtained by smelting in a vacuum induction furnace is used as the base ingot for high-temperature homogenization treatment. The high-temperature homogenization treatment temperature is 1250°C and the holding time is 15 hours. After that, the ingot after the high-temperature homogenization treatment is cooled, and then the skin is peeled and refined into an ingot with a diameter of 200 mm;

[0055] c. Keep the ingot after high temperature homogenization treatment at 1150℃ for 2h, and take it out of the furnace for the first upsetting after the temperature of the ingot is uniform. Use a 10t press to perform the first upsetting of the whole ingot, and immediately perform the first upsetting after the first upsetting is completed. The first upsetting reduction rate is between 20% and 150%, and the first upsetting reduction rate is between 10% and 120%. During the first upsetting and first upsetting, ensure that the ingot temperature is ≥1050℃;

[0056] The ingot that has completed the first upsetting and drawing is returned to the furnace and kept at 1150℃ for 1h. After the ingot temperature is uniform, it is taken out of the furnace for the second upsetting and drawing. The whole ingot is subjected to the second upsetting and roughening by a 10t press. The second upsetting and drawing are immediately carried out. The second upsetting and roughening reduction ratio is between 20% and 150%, and the second drawing and drawing reduction ratio is between 10% and 120%. Then the ingot is rounded to a diameter of 200mm. During the second upsetting and roughening and drawing process, the ingot temperature is ensured to be ≥1050℃. After the second upsetting and drawing, it is slowly cooled to room temperature.

[0057] d. The ingots after two roughing and drawing processes are subjected to stress relief annealing. The stress relief annealing is carried out in a regenerative step heating furnace. The temperature of the regenerative step heating furnace should be well controlled with a small temperature error. The heating temperature is set to 500°C, and the surface temperature and core temperature of the ingot are controlled within ±5°C. The insulation time is 3h.

[0058] Figure 1 This is a macrostructure diagram of the Fe-12Mn-8.5Al-0.8C low-density steel after high-temperature homogenization, secondary drawing and stress relief annealing. Figure 1 It can be seen that there are no visible shrinkage holes, shrinkage cavities, bubbles, cracks or inclusions in the core of the ingot, and the structure is uniform and the quality is good.

[0059] According to tests, the tensile strength of the Fe-12Mn-8.5Al-0.8C low-density steel in the above embodiment is 812 MPa, the yield strength is 198 MPa, and the elongation after fracture is 37%.

[0060] The present invention strictly controls the process parameters of high-temperature homogenization treatment, drawing and stress relief annealing treatment of Fe-12Mn-8.5Al-0.8C low-density steel through experiments, and finally makes the tensile strength of Fe-12Mn-8.5Al-0.8C low-density steel ≥800MPa, the yield strength ≥500MPa, and the elongation after fracture ≥30%, so that the Fe-12Mn-8.5Al-0.8C low-density steel has good comprehensive mechanical properties.

[0061] Comparative Example

[0062] a. Ingredients: high-purity pig iron rods, electrolytic manganese, ferrosilicon blocks, ferrotitanium blocks, ferrovanadium blocks, ferroniobium blocks, pure aluminum particles, and carburizer are used as raw materials and the ingredients are prepared according to the requirements of the Fe-Mn-Al-C series low-density cast steel;

[0063] b. Modeling: Use water glass sand to model, use carbon dioxide to harden the sand mold, then paint the inner wall of the sand mold, dry it and wait for pouring;

[0064] c. Melting: Melting the ingredients in a medium frequency induction furnace at normal pressure and temperature of 1500-1100°C to obtain alloy steel liquid;

[0065] d. Pouring: Increase the power of the medium frequency induction furnace again, raise the temperature to 1550-1150℃ and then tap the steel; after deoxidation and slag removal, pour the alloy steel liquid into the sand mold and air cool to obtain the casting;

[0066] e. Heat treatment: The heat treatment of castings is carried out in a muffle furnace. First, solution treatment is carried out at a temperature of 700-1300°C for 10min-5h. Water is used as the quenching medium, and the initial temperature of the quenching medium is 10-50°C. Aging treatment is carried out within 5h after quenching at a temperature of 300-100°C for 1-10h. Air cooling is then performed to obtain low-density cast steel.

[0067] Figure 2 The macroscopic structure diagram of the low-density cast steel prepared in the comparative example of the present invention after smelting, casting and heat treatment is shown; Figure 2 It can be seen that the low-density cast steel obtained by the preparation method of the comparative example has shrinkage cavities and shrinkage defects.

[0068] After testing, the low-density cast steel prepared in the above comparative example finally has a tensile strength of 735 MPa, a yield strength of 103 MPa, and an elongation after fracture of 35.31%, which are all lower than the tensile strength, yield strength and elongation after fracture of the Fe-12Mn-8.5Al-0.8C low-density steel prepared by the process method of the present invention.

[0069] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A process for reducing shrinkage and porosity in the core of Fe-12Mn-8.5Al-0.8C low-density steel, the process comprising the following steps: a. Vacuum induction furnace smelting: The alloy raw materials, except for the rare earth element components, are loaded into the crucible of the vacuum induction furnace according to the component ratio, and the crucible of the vacuum induction furnace is evacuated; then, the alloy raw materials are completely melted by electricity, and the rare earth element components are added to the molten steel in the molten steel refining stage, and the composition of the Fe-12Mn-8.5Al-0.8C low-density steel is tested and fine-tuned before steel is tapped, and the steel can be cast after the component test is qualified, and an ingot of a certain diameter is obtained; Among them, the steel casting temperature is 1500-1600℃; b. High temperature homogenization treatment: The ingot with a certain diameter obtained by melting in a vacuum induction furnace is used as the base ingot, and then subjected to high-temperature homogenization treatment and heat preservation; Among them, the high temperature homogenization treatment temperature is 1200-1300°C, and the insulation time is 10-15h; c. Two times of pier roughing and lengthening: The ingot that has completed the high-temperature homogenization treatment is kept at a predetermined temperature for a predetermined time, and is taken out of the furnace after the temperature of the ingot is uniform; the entire ingot is subjected to the first roughening by a press, and the first elongation is performed immediately after the first roughening is completed; The ingot that has completed the first roughing and drawing is returned to the furnace, kept at the same predetermined temperature for the same predetermined time, and after the temperature of the ingot is uniform, it is taken out of the furnace for the second roughing and drawing. The whole ingot after the temperature is uniform is roughed for the second time by a press. After the second roughing is completed, the second drawing is immediately carried out, and then it is rounded to a certain diameter specification; after the second roughing and drawing is completed, it is slowly cooled to room temperature; The ingot after homogenization treatment is kept at 1100-1150°C for 1-2 hours; the ingot after the first roughening and drawing is returned to the furnace and kept at 1100-1150°C for 1-2 hours; During the first roughing and drawing process and the second roughing and drawing process, the roughing reduction rate is controlled at 20% to 50%, the drawing reduction rate is controlled at 10% to 20%, and the ingot temperature is controlled to be ≥1050℃; d. Stress relief annealing treatment: The ingot after two times of roughening and drawing is subjected to stress relief annealing treatment; Among them, the stress relief annealing treatment is carried out in a regenerative walking beam heating furnace. The heating temperature of the regenerative walking beam heating furnace is set to 500-550°C, and the insulation time is 3-5h. The surface temperature and core temperature of the ingot after two roughening and drawing processes are controlled within ±5°C.

2. The process according to claim 1, wherein Cast into an ingot with a diameter of 200mm to 250mm; the crucible of the vacuum induction furnace is evacuated to 100 to 300Pa.

3. The process according to claim 2, wherein: The steel casting temperature is 1550°C, and the steel is cast into an ingot with a diameter of 230 mm; the crucible of the vacuum induction furnace is evacuated to 100 Pa.

4. The process according to claim 1, wherein: The high temperature homogenization treatment temperature is 1250°C and the holding time is 15h.

5. The process according to claim 1 or 4, wherein: The ingot after high temperature homogenization treatment is cooled, and then peeled and trimmed into an ingot with a diameter of 200 to 230 mm.

6. The process according to claim 5, wherein: The ingot after high temperature homogenization treatment is cooled, and then peeled and trimmed into an ingot with a diameter of 200 mm.

7. The process according to claim 1, wherein: After the roughening is completed, it is immediately stretched and then rounded to an ingot with a diameter of 180-200mm.

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