Preparation method of high-performance bainite-martensite complex-phase die steel

Abstract

The invention relates to the field of preparation of high-performance die steel, in particular to a preparation method of high-performance bainite-martensite complex-phase die steel, which comprises the following steps: S1, putting required alloy components into a vacuum furnace in proportion for smelting to obtain uniformly distributed molten iron; s2, molten iron is injected into the prefabricated casting mold through a hot chamber die-casting process, and an original steel billet is obtained; s3, carrying out temperature-controlled slow-cooling precipitation regulation and control treatment on the steel billet, and then carrying out high-temperature homogenization; and S4, afterwards, isothermal quenching salt bath treatment, structure stabilizing treatment, low-temperature aging curing treatment, subzero treatment, multi-stage tempering and isostatic pressing heat treatment are sequentially conducted. The process has the advantages that process control is highly accurate, internal defects are few, strength, toughness and wear resistance are synergistically improved, and a new solution is provided for manufacturing of high-performance die steel and high-end dies.

Description

Technical Field

[0001] The present invention relates to the field of high-performance mold steel preparation, and in particular to a method for preparing high-performance Bema duplex mold steel. Background Art

[0002] As the manufacturing industry transforms towards high-precision and high-efficiency production, higher requirements are placed on the performance of mold steel. Traditional mold steel often finds it difficult to strike a balance between high hardness, high wear resistance and good toughness, resulting in problems such as thermal fatigue, fracture and wear during use, which seriously affects production efficiency and mold life. In recent years, the Bema complex phase structure has attracted widespread attention because it can improve hardness and strength while maintaining moderate toughness. This structure achieves a synergistic improvement in high strength and high toughness by forming a multiphase composite system in the matrix. However, the existing preparation technology of the Bema complex phase mold steel still has deficiencies in terms of phase structure control, phase uniform distribution and interface bonding strength. It is prone to problems such as uneven organization, performance fluctuations and poor thermal stability, and cannot fully meet the needs of modern manufacturing for high-performance mold steel. Therefore, the development of a mold steel and its preparation method that can achieve uniform distribution of the Bema complex phase structure and ensure high strength, excellent toughness and excellent wear-resistant thermal stability has important theoretical significance and broad engineering application prospects.

[0003] In view of this, the present invention provides a method for preparing high-performance Bema duplex die steel. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing high-performance Bema duplex die steel in response to the deficiencies of the prior art.

[0005] In order to solve the above technical problems, the following technical solutions are adopted:

[0006] A method for preparing high-performance Bema complex phase die steel comprises the following steps:

[0007] S1. The desired alloy components are placed in a vacuum furnace for smelting according to the proportion to obtain a uniform distribution of molten iron;

[0008] S2. The molten iron is injected into the prefabricated mold through the hot chamber die casting process to obtain the original billet;

[0009] S3. The billet is subjected to temperature control and slow cooling precipitation control treatment and then subjected to high temperature homogenization;

[0010] S4. Then, isothermal quenching salt bath treatment, microstructure stabilization treatment, low-temperature aging solidification treatment, cryogenic treatment, multi-stage tempering and isostatic pressing heat treatment are carried out in sequence.

[0011] A further improvement based on the above technical solution is that the specific process of S1 is as follows: the alloy components required for the mold steel are placed in a vacuum furnace according to the proportion, and the vacuum degree of the vacuum furnace used is controlled at 10 -3 Pa below, ensure the uniform distribution of alloy components, reduce the internal impurity content to a minimum, heat the vacuum furnace to 1550-1600 ℃ to start melting and smelting, and use electromagnetic stirring to promote the full mixing of alloy components, reduce the content of non-metallic inclusions in the molten iron, and obtain uniformly distributed molten iron.

[0012] A further improvement based on the technical solution is that in S1, the alloy components used are: C: 0.31wt%, Si: 0.82wt%, S: 0.002wt%, P: 0.007wt%, Mn: 0.28, Ni: 0.95wt%, Cr: 10.84wt%, Mo: 1.61wt%, V: 0.62wt%, Cu: 0.04wt%, W: 0.26wt%, Ti: 0.01wt%, Co: 0.02wt%, Nb: 0.04wt%, N: 0.09wt%, and the balance is Fe.

[0013] A further improvement based on the technical solution is that the specific process of S2 is as follows: when the smelting is completed and the furnace temperature naturally drops to 1200-1300°C, the molten iron is quickly poured into the preheated ladle; then, the molten iron is injected into the prefabricated mold through the hot chamber die-casting process, and the mold is fully filled with the help of the automatic flow of the feed port on the pressure chamber, thereby obtaining an original steel billet with a smooth surface and dense structure.

[0014] A further improvement based on the above technical solution is that the specific process of S3 is as follows: after the steel billet solidifies, the steel billet is slowly cooled to 600°C by adopting a temperature-controlled slow cooling precipitation control method to avoid the formation and aggregation of coarse carbides and improve the uniformity of the structure;

[0015] After the steel billet solidifies, it is subjected to high temperature homogenization treatment, kept at 1300-1400°C for 45 minutes, and degassing treatment is carried out simultaneously. The degassing treatment requires the vacuum degree to be maintained at 10 -2 Pa ensures the purity of the material while eliminating element segregation and optimizing grain distribution.

[0016] A further improvement based on the technical solution is that, in S4, the specific process of the austempering salt bath treatment is as follows: the homogenized steel is placed in a salt bath furnace for austempering salt bath treatment, kept at a temperature of 200-230°C for 2 hours, and then naturally cooled to room temperature to generate high-strength bainite; wherein the salt bath furnace has a power of 4.5KW, the inner tank is made of 310S stainless steel, and the molten salt medium is high-purity sodium chloride.

[0017] A further improvement based on the technical solution is that in S4, the specific process of the structure stabilization treatment is as follows: the steel is placed at a temperature of 350°C and kept warm for 1 hour for structure stabilization treatment, and then naturally cooled to room temperature to induce the metastable austenite to transform into lath martensite.

[0018] A further improvement based on the technical solution is that in S4, the specific process of the low-temperature aging curing treatment is as follows: the steel is placed at a temperature of 150°C and kept warm for 40 minutes. After the insulation is completed, it is taken out and placed in 60-65°C warm water for hot water bath curing treatment, and the steel is taken out after cooling to the water temperature.

[0019] A further improvement based on the above technical solution is that, in S4, the specific process of the cryogenic treatment is as follows: the solidified steel is cryogenically treated for a holding time of 12 hours to transform part of the retained austenite into high-strength martensite and promote the precipitation of fine carbides;

[0020] The cryogenic treatment is a gas method, in which the solidified steel is placed in a liquid nitrogen environment, and the latent heat of liquid nitrogen vaporization and the heat absorption of low-temperature nitrogen are used for cooling.

[0021] A further improvement based on the above technical solution is that, in S4, the specific process of the multi-stage tempering and isostatic pressing heat treatment is as follows:

[0022] The first tempering treatment is carried out immediately after cryogenic treatment, with the temperature kept at 500℃ for 2 hours to eliminate the residual stress inside the material and make the mold steel achieve a better balance between strength and plasticity;

[0023] Then the second tempering treatment was carried out at a temperature of 550℃ for 2h, followed by air cooling to improve the stability of the microstructure;

[0024] Finally, the steel after secondary tempering is subjected to isostatic pressing heat treatment at 400-450°C and 100MPa to eliminate internal stress and microcracks and promote grain refinement and structural homogenization.

[0025] The above technical solution has the following beneficial effects:

[0026] The present invention is a method for preparing high-performance Bema complex phase mold steel. During the low-temperature aging solidification and deep cryogenic treatment stages, the retained austenite is further transformed into high-strength martensite, and the uniform precipitation of fine carbides is promoted, thereby significantly improving wear resistance and thermal stability. Multi-stage tempering and isostatic pressing heat treatment eliminate internal residual stress and microcracks, optimize grain refinement and structural uniformity, and ensure the long-term stability and reliability of mold steel under high temperature, high pressure and complex working conditions. The process of the present invention not only has the advantages of highly precise process control and few internal defects, but also achieves a synergistic improvement in strength, toughness and wear resistance, providing a new solution for high-performance mold steel and high-end mold manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be further described below in conjunction with the accompanying drawings:

[0028] Figure 1 It is a structural schematic diagram of the microstructure of the mold steel of the present invention. DETAILED DESCRIPTION

[0029] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is described in detail below with reference to the accompanying drawings and examples. However, it should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the scope of the present invention. In addition, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessary confusion of the present invention.

[0030] Example 1

[0031] See Figure 1 A method for preparing high-performance Bema complex phase die steel comprises the following steps:

[0032] S1. The desired alloy components are placed in a vacuum furnace for smelting according to the proportion to obtain a uniform distribution of molten iron;

[0033] S2. The molten iron is injected into the prefabricated mold through the hot chamber die casting process to obtain the original billet;

[0034] S3. The billet is subjected to temperature control and slow cooling precipitation control treatment and then subjected to high temperature homogenization;

[0035] S4. Then, isothermal quenching salt bath treatment, microstructure stabilization treatment, low-temperature aging solidification treatment, cryogenic treatment, multi-stage tempering and isostatic pressing heat treatment are carried out in sequence.

[0036] As a further explanation of this embodiment, the specific process of S1 is as follows: the alloy components required for the mold steel are placed in a vacuum furnace according to the proportion, and the vacuum degree of the vacuum furnace used is controlled at 10 -3Pa below, ensure the uniform distribution of alloy components, reduce the internal impurity content to a minimum, heat the vacuum furnace to 1550-1600 ℃ to start melting and smelting, and use electromagnetic stirring to promote the full mixing of alloy components, reduce the content of non-metallic inclusions in the molten iron, and obtain uniformly distributed molten iron.

[0037] As a further illustration of this embodiment, in the S1, the alloy components used are: C: 0.31wt%, Si: 0.82wt%, S: 0.002wt%, P: 0.007wt%, Mn: 0.28, Ni: 0.95wt%, Cr: 10.84wt%, Mo: 1.61wt%, V: 0.62wt%, Cu: 0.04wt%, W: 0.26wt%, Ti: 0.01wt%, Co: 0.02wt%, Nb: 0.04wt%, N: 0.09wt%, and the balance is Fe.

[0038] As a further illustration of this embodiment, the specific process of S2 is as follows: when the smelting is completed and the furnace temperature naturally drops to 1200-1300°C, the molten iron is quickly poured into the preheated ladle; then, the molten iron is injected into the prefabricated mold through the hot chamber die-casting process, and the mold is fully filled with the help of the automatic flow of the upper feed port of the pressure chamber, thereby obtaining an original steel billet with a smooth surface and dense structure.

[0039] As a further illustration of this embodiment, the specific process of S3 is as follows: after the steel billet solidifies, the steel billet is slowly cooled to 600° C. using a temperature-controlled slow cooling precipitation control method to avoid the formation and aggregation of coarse carbides and improve the uniformity of the structure;

[0040] After the steel billet solidifies, it is subjected to high temperature homogenization treatment, kept at 1300-1400°C for 45 minutes, and degassing treatment is carried out simultaneously. The degassing treatment requires the vacuum degree to be maintained at 10 -2 Pa ensures the purity of the material while eliminating element segregation and optimizing grain distribution.

[0041] As a further illustration of this embodiment, in S4, the specific process of the austempering salt bath treatment is as follows: the homogenized steel is placed in a salt bath furnace for austempering salt bath treatment, kept at a temperature of 200-230°C for 2 hours, and then naturally cooled to room temperature to generate high-strength bainite, thereby forming a unique complex phase structure and improving the comprehensive mechanical properties of the steel; wherein the salt bath furnace has a power of 4.5KW, the inner tank is made of 310S stainless steel, and the molten salt medium is high-purity sodium chloride.

[0042] As a further illustration of this embodiment, in S4, the specific process of the structure stabilization treatment is as follows: the steel is placed at a temperature of 350°C and kept warm for 1 hour for structure stabilization treatment, and then naturally cooled to room temperature to induce metastable austenite to transform into lath martensite, thereby enhancing the wear resistance and impact toughness of the matrix.

[0043] As a further illustration of this embodiment, in S4, the specific process of the low-temperature aging curing treatment is as follows: the steel is placed at a temperature of 150°C and kept warm for 40 minutes. After the insulation is completed, it is taken out and placed in 60-65°C warm water for hot water bath curing treatment. The steel is taken out after cooling to the water temperature. This process further promotes the homogenization of the surface microstructure and the refinement of the grains, while maintaining the original surface finish, thereby achieving the purpose of improving the surface hardness and overall fatigue resistance.

[0044] As a further illustration of this embodiment, in S4, the specific process of the cryogenic treatment is as follows: the solidified steel is cryogenically treated with a holding time of 12 hours to transform part of the residual austenite into high-strength martensite, and promote the precipitation of fine carbides to improve the wear resistance and thermal stability of the steel.

[0045] The cryogenic treatment is a gas method, in which the solidified steel is placed in a liquid nitrogen environment, and the latent heat of liquid nitrogen vaporization and the heat absorption of low-temperature nitrogen are used for cooling.

[0046] As a further illustration of this embodiment, in S4, the specific process of the multi-stage tempering and isostatic pressing heat treatment is as follows:

[0047] The first tempering treatment is carried out immediately after cryogenic treatment, with the temperature kept at 500℃ for 2 hours to eliminate the residual stress inside the material and make the mold steel achieve a better balance between strength and plasticity;

[0048] Then the second tempering treatment was carried out at a temperature of 550℃ for 2h, followed by air cooling to improve the stability of the microstructure;

[0049] Finally, the steel after secondary tempering is subjected to isostatic pressing heat treatment at 400-450°C and 100MPa to eliminate internal stress and microcracks and promote grain refinement and structural homogenization.

[0050] The preparation principle of the present invention is: to achieve high performance of the Bema duplex die steel through a precisely designed multi-step heat treatment and tissue control process. First, vacuum smelting and electromagnetic stirring technology are used to ensure the uniform distribution of each alloy component and reduce the content of internal impurities and non-metallic inclusions, so as to obtain pure, uniform molten iron; the hot chamber die-casting process is used to produce the original steel billet with a smooth surface and dense structure. Subsequently, the precipitation of dispersed carbides is induced by temperature-controlled slow cooling technology, which effectively improves the matrix strength and avoids the aggregation of coarse carbides, thereby improving the uniformity of the Bema duplex structure. High-temperature homogenization treatment is carried out at 1300-1400°C, which not only eliminates element segregation and optimizes the grain structure, but also prepares for subsequent heat treatment.

[0051] Based on the initial heat treatment, the present invention further utilizes a staged austempering process: First, austempering is performed in a salt bath furnace to partially transform austenite into bainite, enhancing the material's initial strength. Next, at 350°C, the metastable austenite is induced to transform into lath martensite, forming a unique Bema duplex structure, further enhancing overall strength. Low-temperature aging and hot water bath curing are then used to eliminate subsurface microcracks in the mold steel and reduce microstress, significantly improving fatigue resistance. Liquid nitrogen cryogenic treatment further promotes the transformation of retained austenite and utilizes the secondary precipitation effect of carbides to ensure a uniform distribution of fine carbides, enhancing wear resistance and thermal stability. Finally, multi-stage tempering and isostatic pressing heat treatment eliminate internal residual stresses and microcracks, further refine the grain size, and improve the material's strength-ductility balance and microstructural stability. This ensures that the Bema duplex mold steel maintains high mechanical properties and long-term stability under high temperature, high pressure, and harsh operating conditions.

[0052] Example 2, namely comparative example 1.

[0053] Preparation of mold steel using traditional heat treatment process:

[0054] (1) The alloy components required for the mold steel are placed in a vacuum furnace in proportion to ensure uniform distribution of the alloy components and reduce the internal impurity content to a minimum. The vacuum furnace is heated to 1550-1600℃ to start melting and smelting. At the same time, electromagnetic stirring technology is used to promote the full mixing of the alloy components and reduce the content of non-metallic inclusions in the molten iron.

[0055] (2) When the smelting is completed and the furnace temperature naturally drops to 1200-1300℃, the molten iron is quickly poured into the preheated ladle. Subsequently, the molten iron is injected into the prefabricated mold through the hot chamber die casting process. With the help of the automatic flow of the feed port on the die chamber, the mold is fully filled, thus obtaining a raw steel billet with a smooth surface and dense structure.

[0056] (3) After the steel billet solidifies, it is taken out for high-temperature homogenization treatment and kept at 1300-1400 °C for 45 min. Degassing treatment is carried out simultaneously to ensure the purity of the material while eliminating element segregation and optimizing grain distribution.

[0057] (4) The steel is heated to 1080°C for quenching to increase the martensite content inside the matrix and enhance the hardness and strength of the material.

[0058] (5) After quenching, the steel is treated with a low-temperature aging process. The steel is placed at 150°C for 40 minutes. After the insulation is completed, it is taken out and placed in a hot water bath at 60-65°C for curing. Wait until the steel cools to the water temperature before taking it out.

[0059] (6) After low-temperature aging treatment, tempering treatment is carried out immediately at a temperature of 500°C for 2 hours to eliminate the residual stress inside the steel and achieve a better strength-plastic balance for the mold steel.

[0060] (7) The tempered steel is subjected to isostatic pressing heat treatment at 400-450°C and 100 MPa to eliminate stress and microcracks inside the steel and promote grain refinement and structural homogenization.

[0061] Example 3, i.e. comparative example 2.

[0062] Only controlled temperature slow cooling process is used to prepare mold steel:

[0063] (1) The alloy components required for the mold steel are placed in a vacuum furnace in proportion to ensure uniform distribution of the alloy components and minimize the internal impurity content. The vacuum furnace is heated to 1550-1600°C to start melting and smelting. At the same time, electromagnetic stirring technology is used to promote the full mixing of the alloy components and reduce the content of non-metallic inclusions in the molten iron.

[0064] (2) When the smelting is completed and the furnace temperature naturally drops to 1200-1300℃, the molten iron is quickly poured into the preheated ladle. Subsequently, the molten iron is injected into the prefabricated mold through the hot chamber die casting process. With the help of the automatic flow of the feed port on the die casting chamber, the mold is fully filled, thereby obtaining a raw steel billet with a smooth surface and dense structure;

[0065] (3) After the billet solidifies, the temperature-controlled slow cooling precipitation control method is adopted to slowly cool the billet to 600 °C to avoid the formation and aggregation of coarse carbides and improve the uniformity of the structure.

[0066] (4) After the billet solidifies, it is taken out for high-temperature homogenization treatment, kept at 1300-1400℃ for 45 minutes, and degassing is carried out simultaneously to ensure the purity of the material while eliminating element segregation and optimizing grain distribution;

[0067] (5) The steel is heated and placed at 1080°C for quenching to increase the martensite content inside the matrix and enhance the hardness and strength of the material;

[0068] (6) After quenching, the steel is treated with a low-temperature aging process. The steel is placed at 150°C for 40 minutes. After the insulation is completed, it is taken out and placed in a hot water bath at 60-65°C for curing. Wait for the steel to cool to the water temperature before taking it out;

[0069] (7) Tempering treatment is performed immediately after low-temperature aging treatment, with the temperature kept at 500°C for 2 hours to eliminate the residual stress inside the steel and achieve a better balance between strength and plasticity of the mold steel;

[0070] (8) The tempered steel is subjected to isostatic pressing heat treatment at 400-450°C and 100 MPa to eliminate stress and microcracks inside the steel and promote grain refinement and structural homogenization.

[0071] Example 4, i.e. Comparative Example 3:

[0072] Tool steels prepared using only multi-stage quenching process:

[0073] (1) The alloy components required for the mold steel are placed in a vacuum furnace in proportion to ensure uniform distribution of the alloy components and minimize the internal impurity content. The vacuum furnace is heated to 1550-1600°C to start melting and smelting. At the same time, electromagnetic stirring technology is used to promote the full mixing of the alloy components and reduce the content of non-metallic inclusions in the molten steel.

[0074] (2) When the smelting is completed and the furnace temperature naturally drops to 1200-1300℃, the molten steel is quickly poured into the preheated ladle. Subsequently, the molten iron is injected into the prefabricated mold through the hot chamber die casting process. With the help of the automatic flow of the feed port on the die casting chamber, the mold is fully filled, thereby obtaining a raw steel billet with a smooth surface and dense structure;

[0075] (3) After the billet solidifies, it is taken out for high-temperature homogenization treatment, kept at 1300-1400℃ for 45 minutes, and degassing is carried out simultaneously to ensure the purity of the material while eliminating element segregation and optimizing grain distribution;

[0076] (4) The homogenized steel is placed in a salt bath furnace for isothermal quenching at 200-230°C for 2 hours, and then naturally cooled to room temperature to form a unique complex phase structure and improve the comprehensive mechanical properties of the material;

[0077] (5) The steel is placed at 350 °C and kept warm for 1 h for microstructure stabilization, and then naturally cooled to room temperature to induce the transformation of metastable austenite into lath martensite, thereby enhancing the wear resistance and impact toughness of the matrix.

[0078] (6) After isothermal quenching, the steel is treated with a low-temperature aging process. The steel is placed at 150°C for 40 minutes. After the insulation is completed, it is taken out and placed in a hot water bath at 60-65°C for curing. Wait for the steel to cool to the water temperature before taking it out;

[0079] (7) Tempering treatment is performed immediately after low-temperature aging treatment, with the temperature kept at 500°C for 2 hours to eliminate the residual stress inside the steel and achieve a better balance between strength and plasticity of the mold steel;

[0080] (8) The tempered steel is subjected to isostatic pressing heat treatment at 400-450°C and 100 MPa to eliminate stress and microcracks inside the steel and promote grain refinement and structural homogenization.

[0081] Example 5, i.e. Comparative Example 4:

[0082] Only mold steel prepared by cryogenic treatment process:

[0083] (1) The alloy components required for the mold steel are placed in a vacuum furnace in proportion to ensure uniform distribution of the alloy components and minimize the internal impurity content. The vacuum furnace is heated to 1550-1600°C to start melting and smelting. At the same time, electromagnetic stirring technology is used to promote the full mixing of the alloy components and reduce the content of non-metallic inclusions in the molten iron.

[0084] (2) When the smelting is completed and the furnace temperature naturally drops to 1200-1300℃, the molten iron is quickly poured into the preheated ladle. Subsequently, the molten iron is injected into the prefabricated mold through the hot chamber die casting process. With the help of the automatic flow of the feed port on the die casting chamber, the mold is fully filled, thereby obtaining a raw steel billet with a smooth surface and dense structure;

[0085] (3) After the steel billet solidifies, it is taken out for high-temperature homogenization treatment, kept at 1300-1400°C for 45 minutes, and degassing treatment is carried out simultaneously to ensure the purity of the steel while eliminating element segregation and optimizing grain distribution;

[0086] (4) The steel is quenched at 1080°C to increase the martensite content inside the matrix and enhance the hardness and strength of the material;

[0087] (5) After quenching, the steel is treated with a low-temperature aging process. Place the steel at 150°C for 40 minutes. After the insulation is completed, take it out and place it in a hot water bath at 60-65°C for curing. Wait for the steel to cool to the water temperature before taking it out.

[0088] (6) After low-temperature aging curing, tempering treatment is immediately carried out at a temperature of 500°C for 2 hours to eliminate the residual stress inside the steel and achieve a better strength-plastic balance for the mold steel;

[0089] (7) The solidified steel is cryogenically treated for 12 hours to transform part of the retained austenite into high-strength martensite and promote the precipitation of fine carbides, thereby improving the wear resistance and thermal stability of the steel.

[0090] (8) The tempered steel is subjected to isostatic pressing heat treatment at 400-450°C and 100 MPa to eliminate stress and microcracks inside the steel and promote grain refinement and structural homogenization.

[0091] Example 6, i.e. Comparative Example 5:

[0092] Tool steels prepared using only multiple tempering processes:

[0093] (1) The alloy components required for the mold steel are placed in a vacuum furnace in proportion to ensure uniform distribution of the alloy components and minimize the internal impurity content. The vacuum furnace is heated to 1550-1600°C to start melting and smelting. At the same time, electromagnetic stirring technology is used to promote the full mixing of the alloy components and reduce the content of non-metallic inclusions in the molten iron.

[0094] (2) When the smelting is completed and the furnace temperature naturally drops to 1200-1300℃, the molten iron is quickly poured into the preheated ladle. Subsequently, the molten iron is injected into the prefabricated mold through the hot chamber die casting process. With the help of the automatic flow of the feed port on the die casting chamber, the mold is fully filled, thereby obtaining a raw steel billet with a smooth surface and dense structure;

[0095] (3) After the steel billet solidifies, it is taken out for high-temperature homogenization treatment, kept at 1300-1400℃ for 45 minutes, and degassing is carried out simultaneously to ensure the purity of the steel while eliminating element segregation and optimizing grain distribution;

[0096] (4) The steel is quenched at 1080°C to increase the martensite content inside the matrix and enhance the hardness and strength of the material;

[0097] (5) After quenching, the steel is treated with a low-temperature aging process. The steel is kept at 150°C for 40 minutes. After the insulation is completed, it is taken out and placed in a hot water bath at 60-65°C for curing. Wait for the steel to cool to the water temperature before taking it out;

[0098] (6) After low-temperature aging treatment, tempering treatment is immediately carried out at a temperature of 500°C for 2 hours to eliminate the residual stress inside the steel and achieve a better strength-plastic balance for the mold steel;

[0099] (7) After the low-temperature aging treatment, the first tempering treatment is carried out immediately at a temperature of 500 ° C for 2 hours to eliminate the residual stress inside the steel and achieve a better strength-plastic balance for the mold steel;

[0100] (8) Perform a second tempering treatment at 550 °C for 2 h, followed by air cooling to improve the stability of the microstructure;

[0101] (9) The steel after secondary tempering is subjected to isostatic pressing heat treatment at 400-450℃ and 100MPa to eliminate stress and microcracks inside the steel and promote grain refinement and structural homogenization.

[0102] Example 7, i.e. Comparative Example 6:

[0103] Die steel produced using only controlled slow cooling and multi-stage quenching processes:

[0104] (1) The alloy components required for the mold steel are placed in a vacuum furnace in proportion to ensure uniform distribution of the alloy components and minimize the internal impurity content. The vacuum furnace is heated to 1550-1600°C to start melting and smelting. At the same time, electromagnetic stirring technology is used to promote the full mixing of the alloy components and reduce the content of non-metallic inclusions in the molten iron.

[0105] (2) When the smelting is completed and the furnace temperature naturally drops to 1200-1300℃, the molten iron is quickly poured into the preheated ladle. Subsequently, the molten iron is injected into the prefabricated mold through the hot chamber die casting process. With the help of the automatic flow of the feed port on the die casting chamber, the mold is fully filled, thereby obtaining a raw steel billet with a smooth surface and dense structure;

[0106] (3) After the billet solidifies, the temperature-controlled slow cooling precipitation control method is adopted to slowly cool the billet to 600 ° C to avoid the formation and aggregation of coarse carbides and enhance the uniformity of the structure;

[0107] (4) After the steel billet solidifies, it is taken out for high-temperature homogenization treatment, kept at 1300-1400℃ for 45 minutes, and degassing is carried out simultaneously to ensure the purity of the steel while eliminating element segregation and optimizing grain distribution;

[0108] (5) The homogenized steel is placed in a salt bath furnace for isothermal quenching at 200-230°C for 2 hours, and then naturally cooled to room temperature to form a unique complex phase structure and improve the comprehensive mechanical properties of the steel.

[0109] (6) The steel is placed at 350 °C and kept warm for 1 h for microstructure stabilization, and then naturally cooled to room temperature to induce the transformation of metastable austenite into lath martensite, thereby enhancing the wear resistance and impact toughness of the matrix.

[0110] (7) After quenching, the steel is treated with a low-temperature aging process. Place the steel at 150°C and keep it warm for 40 minutes. After the insulation is completed, take it out and put it into a hot water bath at 60-65°C for curing. Wait for the steel to cool to the water temperature before taking it out;

[0111] (8) After low-temperature aging treatment, tempering treatment is immediately carried out at a temperature of 500°C for 2 hours to eliminate the residual stress inside the steel and achieve a better strength-plastic balance for the mold steel;

[0112] (9) The tempered steel is subjected to isostatic pressing heat treatment at 400-450°C and 100 MPa to eliminate stress and microcracks inside the steel and promote grain refinement and structural homogenization.

[0113] Example 8, i.e. Comparative Example 7:

[0114] Die steel prepared only using controlled temperature slow cooling and cryogenic treatment processes:

[0115] (1) The alloy components required for the mold steel are placed in a vacuum furnace in proportion to ensure uniform distribution of the alloy components and minimize the internal impurity content. The vacuum furnace is heated to 1550-1600°C to start melting and smelting. At the same time, electromagnetic stirring technology is used to promote the full mixing of the alloy components and reduce the content of non-metallic inclusions in the molten iron.

[0116] (2) When the smelting is completed and the furnace temperature naturally drops to 1200-1300℃, the molten iron is quickly poured into the preheated ladle. Subsequently, the molten iron is injected into the prefabricated mold through the hot chamber die casting process. With the help of the automatic flow of the feed port on the die casting chamber, the mold is fully filled, thereby obtaining a raw steel billet with a smooth surface and dense structure;

[0117] (3) After the billet solidifies, the temperature-controlled slow cooling precipitation control method is adopted to slowly cool the billet to 600 °C to avoid the formation and aggregation of coarse carbides and enhance the uniformity of the structure.

[0118] (4) After the steel billet solidifies, it is taken out for high-temperature homogenization treatment, kept at 1300-1400℃ for 45 minutes, and degassing is carried out simultaneously to ensure the purity of the steel while eliminating element segregation and optimizing grain distribution;

[0119] (5) The steel is quenched at 1080°C to increase the martensite content inside the matrix and enhance the hardness and strength of the material;

[0120] (6) After quenching, the steel is treated with a low-temperature aging process. Place the steel at 150°C and keep it warm for 40 minutes. After the insulation is completed, take it out and put it into a hot water bath at 60-65°C for curing. Wait for the steel to cool to the water temperature before taking it out;

[0121] (7) The solidified steel is cryogenically treated for 12 hours to transform part of the retained austenite into high-strength martensite and promote the precipitation of fine carbides, thereby improving the wear resistance and thermal stability of the steel.

[0122] (8) Tempering treatment is performed immediately after cryogenic treatment at a temperature of 500°C for 2 hours to eliminate the residual stress inside the steel and achieve a better balance between strength and plasticity of the mold steel;

[0123] (9) The tempered steel is subjected to isostatic pressing heat treatment at 400-450°C and 100 MPa to eliminate stress and microcracks inside the steel and promote grain refinement and structural homogenization.

[0124] Example 9, i.e. Comparative Example 8:

[0125] Die steel produced using only controlled temperature slow cooling and multiple tempering processes:

[0126] (1) The alloy components required for the mold steel are placed in a vacuum furnace in proportion to ensure uniform distribution of the alloy components and minimize the internal impurity content. The vacuum furnace is heated to 1550-1600°C to start melting and smelting. At the same time, electromagnetic stirring technology is used to promote the full mixing of the alloy components and reduce the content of non-metallic inclusions in the molten iron.

[0127] (2) When the smelting is completed and the furnace temperature naturally drops to 1200-1300℃, the molten iron is quickly poured into the preheated ladle. Subsequently, the molten iron is injected into the prefabricated mold through the hot chamber die casting process. With the help of the automatic flow of the feed port on the die casting chamber, the mold is fully filled, thereby obtaining a raw steel billet with a smooth surface and dense structure;

[0128] (3) After the billet solidifies, the temperature-controlled slow cooling precipitation control method is adopted to slowly cool the billet to 600 °C to avoid the formation and aggregation of coarse carbides and enhance the uniformity of the structure.

[0129] (4) After the steel billet solidifies, it is taken out for high-temperature homogenization treatment, kept at 1300-1400℃ for 45 minutes, and degassing is carried out simultaneously to ensure the purity of the steel while eliminating element segregation and optimizing grain distribution;

[0130] (5) The steel is heated and placed at 1080°C for quenching to increase the martensite content inside the matrix and enhance the hardness and strength of the material;

[0131] (6) After quenching, the steel is treated with a low-temperature aging process. Place the steel at 150°C and keep it warm for 40 minutes. After the insulation is completed, take it out and put it into a hot water bath at 60-65°C for curing. Wait for the steel to cool to the water temperature before taking it out;

[0132] (7) After the low-temperature aging treatment, the first tempering treatment is carried out immediately at a temperature of 500 ° C for 2 hours to eliminate the residual stress inside the steel and achieve a better strength-plastic balance for the mold steel;

[0133] (8) Perform a second tempering treatment at 550 °C for 2 h, followed by air cooling to improve the stability of the microstructure;

[0134] (9) The tempered steel is subjected to isostatic pressing heat treatment at 400-450°C and 100 MPa to eliminate stress and microcracks inside the steel and promote grain refinement and structural homogenization.

[0135] Example 10, i.e. Comparative Example 9:

[0136] Die steel produced using only multiple quenching and cryogenic treatment processes:

[0137] (1) The alloy components required for the mold steel are placed in a vacuum furnace in proportion to ensure uniform distribution of the alloy components and minimize the internal impurity content. The vacuum furnace is heated to 1550-1600°C to start melting and smelting. At the same time, electromagnetic stirring technology is used to promote the full mixing of the alloy components and reduce the content of non-metallic inclusions in the molten iron.

[0138] (2) When the smelting is completed and the furnace temperature naturally drops to 1200-1300℃, the molten iron is quickly poured into the preheated ladle. Subsequently, the molten iron is injected into the prefabricated mold through the hot chamber die casting process. With the help of the automatic flow of the feed port on the die casting chamber, the mold is fully filled, thereby obtaining a raw steel billet with a smooth surface and dense structure;

[0139] (3) After the steel billet solidifies, it is taken out for high-temperature homogenization treatment, kept at 1300-1400℃ for 45 minutes, and degassing is carried out simultaneously to ensure the purity of the steel while eliminating element segregation and optimizing grain distribution;

[0140] (4) The homogenized steel is placed in a salt bath furnace for isothermal quenching at 200-230°C for 2 hours, and then naturally cooled to room temperature to form a unique complex phase structure and improve the comprehensive mechanical properties of the steel.

[0141] (5) The steel is heated to 350 °C and kept at this temperature for 1 h for microstructure stabilization. It is then naturally cooled to room temperature to induce the transformation of metastable austenite into lath martensite, thereby enhancing the wear resistance and impact toughness of the matrix.

[0142] (6) After quenching, the steel is treated with a low-temperature aging process. Place the steel at 150°C and keep it warm for 40 minutes. After the insulation is completed, take it out and put it into a hot water bath at 60-65°C for curing. Wait for the steel to cool to the water temperature before taking it out;

[0143] (7) After low-temperature aging treatment, tempering treatment is immediately carried out at a temperature of 500°C for 2 hours to eliminate the residual stress inside the steel and achieve a better strength-plastic balance for the mold steel;

[0144] (8) The solidified steel is cryogenically treated for 12 hours to transform part of the retained austenite into high-strength martensite and promote the precipitation of fine carbides, thereby improving the wear resistance and thermal stability of the steel.

[0145] (9) The tempered steel is subjected to isostatic pressing heat treatment at 400-450°C and 100 MPa to eliminate stress and microcracks inside the steel and promote grain refinement and structural homogenization.

[0146] Example 11, i.e. Comparative Example 10:

[0147] Tool steels produced using only multiple quenching and multiple tempering processes:

[0148] (1) The alloy components required for the mold steel are placed in a vacuum furnace in proportion to ensure uniform distribution of the alloy components and minimize the internal impurity content. The vacuum furnace is heated to 1550-1600°C to start melting and smelting. At the same time, electromagnetic stirring technology is used to promote the full mixing of the alloy components and reduce the content of non-metallic inclusions in the molten iron.

[0149] (2) When the smelting is completed and the furnace temperature naturally drops to 1200-1300℃, the molten iron is quickly poured into the preheated ladle. Subsequently, the molten iron is injected into the prefabricated mold through the hot chamber die casting process. With the help of the automatic flow of the feed port on the die casting chamber, the mold is fully filled, thereby obtaining a raw steel billet with a smooth surface and dense structure;

[0150] (3) After the steel billet solidifies, it is taken out for high-temperature homogenization treatment, kept at 1300-1400℃ for 45 minutes, and degassing is carried out simultaneously to ensure the purity of the steel while eliminating element segregation and optimizing grain distribution;

[0151] (4) The homogenized steel is placed in a salt bath furnace for isothermal quenching at 200-230°C for 2 hours, and then naturally cooled to room temperature to form a unique complex phase structure and improve the comprehensive mechanical properties of the steel.

[0152] (5) The steel is placed at 350 °C and kept warm for 1 h for microstructure stabilization, and then naturally cooled to room temperature to induce the transformation of metastable austenite into lath martensite, thereby enhancing the wear resistance and impact toughness of the matrix.

[0153] (6) After quenching, the steel is treated with a low-temperature aging process. The steel is kept at 150°C for 40 minutes. After the insulation is completed, it is taken out and placed in a hot water bath at 60-65°C for curing. Wait for the steel to cool to the water temperature before taking it out;

[0154] (7) After the low-temperature aging treatment, the first tempering treatment is immediately carried out at a temperature of 500°C for 2 hours to eliminate the residual stress inside the steel and achieve a better strength-plastic balance for the mold steel;

[0155] (8) Perform a second tempering treatment at 550 °C for 2 h, followed by air cooling to improve the stability of the microstructure;

[0156] (9) The tempered material is subjected to isostatic pressing heat treatment at 400-450°C and 100 MPa to eliminate stress and microcracks inside the material and promote grain refinement and structural homogenization.

[0157] Example 12, i.e. Comparative Example 11:

[0158] Tool steels prepared using only cryogenic treatment and multiple tempering processes:

[0159] (1) The alloy components required for the mold steel are placed in a vacuum furnace in proportion to ensure uniform distribution of the alloy components and minimize the internal impurity content. The vacuum furnace is heated to 1550-1600°C to start melting and smelting. At the same time, electromagnetic stirring technology is used to promote the full mixing of the alloy components and reduce the content of non-metallic inclusions in the molten iron.

[0160] (2) When the smelting is completed and the furnace temperature naturally drops to 1200-1300℃, the molten iron is quickly poured into the preheated ladle. Subsequently, the molten iron is injected into the prefabricated mold through the hot chamber die casting process. With the help of the automatic flow of the feed port on the die casting chamber, the mold is fully filled, thereby obtaining a raw steel billet with a smooth surface and dense structure;

[0161] (3) After the billet solidifies, it is taken out for high-temperature homogenization treatment, kept at 1300-1400℃ for 45 minutes, and degassing is carried out simultaneously to ensure the purity of the material while eliminating element segregation and optimizing grain distribution;

[0162] (4) The steel is placed at 1080°C for quenching to increase the martensite content inside the matrix and enhance the hardness and strength of the steel;

[0163] (5) After quenching, the steel is treated with a low-temperature aging process. The steel is kept at 150°C for 40 minutes. After the insulation is completed, it is taken out and placed in a hot water bath at 60-65°C for curing. Wait for the steel to cool to the water temperature before taking it out;

[0164] (6) The solidified steel is cryogenically treated for 12 hours to transform part of the retained austenite into high-strength martensite and promote the precipitation of fine carbides, thereby improving the wear resistance and thermal stability of the steel.

[0165] (7) After cryogenic treatment, the first tempering treatment is carried out immediately at a temperature of 500 ° C for 2 hours to eliminate the residual stress inside the material and achieve a better balance between strength and plasticity of the mold steel;

[0166] (8) Perform a second tempering treatment at 550 °C for 2 h, followed by air cooling to improve the stability of the microstructure;

[0167] (9) The tempered steel is subjected to isostatic pressing heat treatment at 400-450°C and 100 MPa to eliminate stress and microcracks inside the steel and promote grain refinement and structural homogenization.

[0168] Example 13, i.e. Comparative Example 12:

[0169] Die steels produced using only controlled slow cooling, multi-stage quenching and cryogenic treatment processes:

[0170] (1) The alloy components required for the mold steel are placed in a vacuum furnace in proportion to ensure uniform distribution of the alloy components and minimize the internal impurity content. The vacuum furnace is heated to 1550-1600°C to start melting and smelting. At the same time, electromagnetic stirring technology is used to promote the full mixing of the alloy components and reduce the content of non-metallic inclusions in the molten steel.

[0171] (2) When the smelting is completed and the furnace temperature naturally drops to 1200-1300℃, the molten steel is quickly poured into the preheated ladle. Subsequently, the molten iron is injected into the prefabricated mold through the hot chamber die casting process. With the help of the automatic flow of the feed port on the die casting chamber, the mold is fully filled, thereby obtaining a raw steel billet with a smooth surface and dense structure;

[0172] (3) After the billet solidifies, the temperature-controlled slow cooling precipitation control method is adopted to slowly cool the billet to 600 ° C to avoid the formation and aggregation of coarse carbides and enhance the uniformity of the structure;

[0173] (4) After the steel billet solidifies, it is taken out for high-temperature homogenization treatment, kept at 1300-1400℃ for 45 minutes, and degassing is carried out simultaneously to ensure the purity of the steel while eliminating element segregation and optimizing grain distribution;

[0174] (5) The homogenized steel is placed in a salt bath furnace for isothermal quenching salt bath treatment at 200-230°C for 2 hours, and then naturally cooled to room temperature to form a unique complex phase structure and improve the comprehensive mechanical properties of the steel;

[0175] (6) The steel is placed at 350 °C and kept warm for 1 h for microstructure stabilization, and then naturally cooled to room temperature to induce the transformation of metastable austenite into lath martensite, thereby enhancing the wear resistance and impact toughness of the matrix.

[0176] (7) After quenching, the steel is treated with a low-temperature aging process. The steel is kept at 150°C for 40 minutes. After the insulation is completed, it is taken out and placed in a hot water bath at 60-65°C for curing. Wait for the steel to cool to the water temperature before taking it out;

[0177] (8) The solidified steel is cryogenically treated for 12 hours to transform part of the retained austenite into high-strength martensite and promote the precipitation of fine carbides, thereby improving the wear resistance and thermal stability of the steel.

[0178] (9) Tempering treatment is performed immediately after cryogenic treatment at a temperature of 500°C for 2 hours to eliminate the residual stress inside the material and achieve a better balance between strength and plasticity of the mold steel;

[0179] (10) The tempered steel is subjected to isostatic pressing heat treatment at 400-450°C and 100 MPa to eliminate stress and microcracks inside the steel and promote grain refinement and structural homogenization.

[0180] Example 14, i.e. Comparative Example 13:

[0181] Die steel produced using only controlled slow cooling, multi-stage quenching and multiple tempering processes:

[0182] (1) The alloy components required for the mold steel are placed in a vacuum furnace in proportion to ensure uniform distribution of the alloy components and minimize the internal impurity content. The vacuum furnace is heated to 1550-1600°C to start melting and smelting. At the same time, electromagnetic stirring technology is used to promote the full mixing of the alloy components and reduce the content of non-metallic inclusions in the molten iron.

[0183] (2) When the smelting is completed and the furnace temperature naturally drops to 1200-1300℃, the molten iron is poured into the preheated ladle. Subsequently, the molten iron is injected into the prefabricated mold through the hot chamber die casting process. With the help of the automatic flow of the feed port on the die casting chamber, the mold is fully filled, thereby obtaining a raw steel billet with a smooth surface and dense structure;

[0184] (3) After the billet solidifies, the temperature-controlled slow cooling precipitation control method is adopted to slowly cool the billet to 600 ° C to avoid the formation and aggregation of coarse carbides and enhance the uniformity of the structure;

[0185] (4) After the steel billet solidifies, it is taken out for high-temperature homogenization treatment, kept at 1300-1400℃ for 45 minutes, and degassing is carried out simultaneously to ensure the purity of the steel while eliminating element segregation and optimizing grain distribution;

[0186] (5) The homogenized steel is placed in a salt bath furnace for isothermal quenching at 200-230°C for 2 hours, and then naturally cooled to room temperature to form a unique complex phase structure and improve the comprehensive mechanical properties of the steel.

[0187] (6) The steel is placed at 350°C for 1 hour to stabilize the structure, and then naturally cooled to room temperature to induce the transformation of metastable austenite into lath martensite, thereby enhancing the wear resistance and impact resistance of the matrix;

[0188] (7) After quenching, the steel is treated with a low-temperature aging process. The steel is kept at 150°C for 40 minutes. After the insulation is completed, it is taken out and placed in a hot water bath at 60-65°C for curing. Wait for the steel to cool to the water temperature before taking it out;

[0189] (8) After the low-temperature aging treatment, the first tempering treatment is carried out immediately at a temperature of 500 ° C for 2 hours to eliminate the residual stress inside the steel and achieve a better strength-plastic balance for the mold steel;

[0190] (9) Perform a second tempering treatment at 550 °C for 2 h, followed by air cooling to improve the stability of the microstructure;

[0191] (10) The tempered steel is subjected to isostatic pressing heat treatment at 400-450°C and 100 MPa to eliminate stress and microcracks inside the steel and promote grain refinement and structural homogenization.

[0192] Example 15, i.e. Comparative Example 14:

[0193] Die steel produced using only controlled slow cooling, cryogenic treatment and multiple tempering processes:

[0194] (1) The alloy components required for the mold steel are placed in a vacuum furnace in proportion to ensure uniform distribution of the alloy components and minimize the internal impurity content. The vacuum furnace is heated to 1550-1600°C to start melting and smelting. At the same time, electromagnetic stirring technology is used to promote the full mixing of the alloy components and reduce the content of non-metallic inclusions in the molten iron.

[0195] (2) When the smelting is completed and the furnace temperature naturally drops to 1200-1300℃, the molten iron is quickly poured into the preheated ladle. Subsequently, the molten iron is injected into the prefabricated mold through the hot chamber die casting process. With the help of the automatic flow of the feed port on the die casting chamber, the mold is fully filled, thereby obtaining a raw steel billet with a smooth surface and dense structure;

[0196] (3) After the billet solidifies, the temperature-controlled slow cooling precipitation control method is adopted to slowly cool the billet to 600 ° C to avoid the formation and aggregation of coarse carbides and enhance the uniformity of the structure;

[0197] (4) After the steel billet solidifies, it is taken out for high-temperature homogenization treatment, kept at 1300-1400℃ for 45 minutes, and degassing is carried out simultaneously to ensure the purity of the steel while eliminating element segregation and optimizing grain distribution;

[0198] (5) The steel is quenched at 1080°C to increase the martensite content inside the matrix and enhance the hardness and strength of the material;

[0199] (6) After quenching, the steel is treated with a low-temperature aging process. The steel is placed at 150°C for 40 minutes. After the insulation is completed, it is taken out and placed in a hot water bath at 60-65°C for curing. The steel is taken out after cooling to the water temperature. In this process, the surface microstructure is further homogenized and the grains are refined, while the original surface finish is maintained, thereby achieving the purpose of improving the surface hardness and overall fatigue resistance.

[0200] (7) The solidified steel is cryogenically treated for 12 hours to transform part of the retained austenite into high-strength martensite and promote the precipitation of fine carbides, thereby improving the wear resistance and thermal stability of the steel.

[0201] (8) After cryogenic treatment, the first tempering treatment is carried out immediately at a temperature of 500 ° C for 2 hours to eliminate the residual stress inside the steel and achieve a better strength-plastic balance of the mold steel;

[0202] (9) Perform a second tempering treatment at 550 °C for 2 h, followed by air cooling to improve the stability of the microstructure;

[0203] (10) The steel after secondary tempering is subjected to isostatic pressing heat treatment at 400-450°C and 100 MPa to eliminate stress and microcracks inside the steel and promote grain refinement and structural homogenization.

[0204] Example 16, i.e. Comparative Example 15:

[0205] Only mold steels produced using multi-stage quenching, cryogenic treatment and multiple tempering processes:

[0206] (1) The alloy components required for the mold steel are placed in a vacuum furnace in proportion to ensure uniform distribution of the alloy components and minimize the internal impurity content. The vacuum furnace is heated to 1550-1600°C to start melting and smelting. At the same time, electromagnetic stirring technology is used to promote the full mixing of the alloy components and reduce the content of non-metallic inclusions in the molten iron.

[0207] (2) When the smelting is completed and the furnace temperature naturally drops to 1200-1300℃, the molten iron is quickly poured into the preheated ladle. Subsequently, the molten iron is injected into the prefabricated mold through the hot chamber die casting process. With the help of the automatic flow of the feed port on the die casting chamber, the mold is fully filled, thereby obtaining a raw steel billet with a smooth surface and dense structure;

[0208] (3) After the steel billet solidifies, it is taken out for high-temperature homogenization treatment, kept at 1300-1400℃ for 45 minutes, and degassing is carried out simultaneously to ensure the purity of the steel while eliminating element segregation and optimizing grain distribution;

[0209] (4) The homogenized steel is placed in a salt bath furnace for isothermal quenching salt bath treatment at 200-23°C for 2 hours, and then naturally cooled to room temperature to form a unique complex phase structure and improve the comprehensive mechanical properties of the steel;

[0210] (5) The steel is placed at 350 °C and kept warm for 1 h for microstructure stabilization, and then naturally cooled to room temperature to induce the transformation of metastable austenite into lath martensite, thereby enhancing the wear resistance and impact toughness of the matrix.

[0211] (6) After quenching, the steel is treated with a low-temperature aging process. Place the steel at 150°C and keep it warm for 40 minutes. After the insulation is completed, take it out and put it into a hot water bath at 60-65°C for curing. Wait for the steel to cool to the water temperature before taking it out;

[0212] (7) The solidified steel is subjected to cryogenic treatment with a holding time of 12 hours to transform part of the retained austenite into high-strength martensite and promote the precipitation of fine carbides, thereby improving the wear resistance and thermal stability of the material;

[0213] (8) After cryogenic treatment, the first tempering treatment is carried out immediately at a temperature of 500 ° C for 2 hours to eliminate the residual stress inside the material and achieve a better balance between strength and plasticity of the mold steel;

[0214] (9) Perform a second tempering treatment at 550 °C for 2 h, followed by air cooling to improve the stability of the microstructure;

[0215] (10) The material after secondary tempering treatment is subjected to isostatic pressing heat treatment at 400-450°C and 100 MPa to eliminate stress and microcracks inside the material and promote grain refinement and structural homogenization.

[0216] Performance testing:

[0217] Tensile properties were tested in accordance with the national testing standard GB / T228.1-2010. Impact properties were tested in accordance with the national testing standard GBT229-2007. Wear resistance testing was conducted on a high-temperature rotary wear tester at a temperature of 400°C, a load of 60 N, a rotation speed of 60 r / min, and a test time of 20 min. Sample dimensions were 28 mm (diameter) × 5 mm (height), and the surface roughness was 300 nm to 400 nm. The test results are shown in Table 1.

[0218] Table 1. Comparison of mechanical properties and wear resistance of mold steels with different heat treatment processes

[0219]

[0220]

[0221] In the table: YS is yield strength, UTS is tensile strength, εf is elongation, ak is impact toughness, and WV is volume wear.

[0222] It can be seen from the data in Table 1 that with the continuous addition of temperature-controlled slow cooling, multi-stage quenching, cryogenic treatment and multiple tempering treatment processes, the yield strength, tensile strength, elongation, impact toughness and volume wear of mold steel have all increased to varying degrees.

[0223] Depend on Figure 1 It can be seen that after temperature-controlled slow cooling, multi-stage quenching, deep cryogenic treatment and multiple tempering treatments, the microstructure of the mold steel is uniform, contains more bainite and martensite, and the grain refinement is high and evenly distributed.

[0224] The present invention discloses a high-performance Bema complex phase die steel and a preparation method thereof. The core of the invention is to utilize the principle of multi-stage heat treatment and precise organization control to construct a composite bainite-martensite microstructure with high strength, high toughness and high wear resistance. First, by smelting in a vacuum environment and adopting electromagnetic stirring technology, it is ensured that the alloy components are fully mixed and evenly distributed, and internal impurities and non-metallic inclusions are effectively reduced. Subsequently, a hot chamber die-casting process is used to prepare an original steel billet with a smooth surface and dense structure, and the temperature-controlled slow cooling technology is used to slowly cool the steel billet during the solidification process, thereby suppressing the formation of coarse carbides and ensuring grain refinement and uniform precipitation. High-temperature homogenization degassing treatment is then used to eliminate element segregation and further optimize the internal grain structure. After salt bath isothermal quenching and organization stabilization treatment, part of the austenite is transformed into bainite, and then further heat treatment is used to induce the metastable austenite to transform into martensite, forming a unique Bema complex phase structure. Low-temperature aging and hot-water bath curing processes maintain a smooth surface while further balancing the microstructure and eliminating subsurface microcracks. Cryogenic treatment promotes the uniform precipitation of fine carbides, comprehensively improving wear resistance and thermal stability. Finally, multi-stage tempering and isostatic pressing eliminate internal stresses and microcracks, refine the grain size, and ensure overall stable performance. This preparation method fully demonstrates the synergistic advantages of each stage of the heat treatment process, providing a solid theoretical and process foundation for achieving high-performance mold steel and its products.

[0225] The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications based on the present invention to solve substantially the same technical problems and achieve substantially the same technical effects are included within the scope of protection of the present invention.

Claims

1. A method for preparing high-performance Bema duplex die steel, characterized by: The following steps are involved: S1. The desired alloy components are placed in a vacuum furnace for smelting according to the proportion to obtain a uniform distribution of molten iron; S2. The molten iron is injected into the prefabricated mold through the hot chamber die casting process to obtain the original billet; S3. The billet is subjected to temperature control and slow cooling precipitation control treatment and then subjected to high temperature homogenization; S4. Then, isothermal quenching salt bath treatment, microstructure stabilization treatment, low-temperature aging solidification treatment, cryogenic treatment, multi-stage tempering and isostatic pressing heat treatment are carried out in sequence.

2. The method for preparing a high-performance Bema duplex die steel according to claim 1, characterized in that: The specific process of S1 is as follows: put the alloy components required for the mold steel into the vacuum furnace according to the proportion, and the vacuum degree of the vacuum furnace used should be controlled at 10 -3 Pa below, ensure the uniform distribution of alloy components, reduce the internal impurity content to a minimum, heat the vacuum furnace to 1550-1600 ℃ to start melting and smelting, and use electromagnetic stirring to promote the full mixing of alloy components, reduce the content of non-metallic inclusions in the molten iron, and obtain uniformly distributed molten iron.

3. The method for preparing a high-performance Bema duplex die steel according to claim 2, characterized in that: In the S1, the alloy components used are: C: 0.31wt%, Si: 0.82wt%, S: 0.002wt%, P: 0.007wt%, Mn: 0.28, Ni: 0.95wt%, Cr: 10.84wt%, Mo: 1.61wt%, V: 0.62wt%, Cu: 0.04wt%, W: 0.26wt%, Ti: 0.01wt%, Co: 0.02wt%, Nb: 0.04wt%, N: 0.09wt%, and the balance is Fe.

4. The method for preparing a high-performance Bema duplex die steel according to claim 1, characterized in that: The specific process of S2 is as follows: when smelting is completed and the furnace temperature naturally drops to 1200-1300℃, the molten iron is quickly poured into the preheated ladle; then, the molten iron is injected into the prefabricated mold through the hot chamber die casting process, and the mold is fully filled with the help of the automatic flow of the upper feed port of the die casting chamber, thereby obtaining an original steel billet with a smooth surface and dense structure.

5. The method for preparing a high-performance Bema duplex die steel according to claim 1, characterized in that: The specific process of S3 is as follows: after the steel billet solidifies, the steel billet is slowly cooled to 600° C. by adopting a temperature-controlled slow cooling precipitation control method to avoid the formation and aggregation of coarse carbides and improve the uniformity of the structure; After the steel billet solidifies, it is subjected to high temperature homogenization treatment, kept at 1300-1400°C for 45 minutes, and degassing treatment is carried out simultaneously. The degassing treatment requires the vacuum degree to be maintained at 10 -2 Pa ensures the purity of the material while eliminating element segregation and optimizing grain distribution.

6. The method for preparing high-performance Bema duplex die steel according to claim 1, characterized in that: In S4, the specific process of the austempering salt bath treatment is as follows: placing the homogenized steel in a salt bath furnace for austempering salt bath treatment, keeping the temperature at 200-230°C for 2 hours, and then naturally cooling to room temperature to generate high-strength bainite; wherein the salt bath furnace has a power of 4.5KW, the inner tank is made of 310S stainless steel, and the molten salt medium is high-purity sodium chloride.

7. The method for preparing high-performance Bema duplex die steel according to claim 1, characterized in that: In S4, the specific process of the structure stabilization treatment is as follows: the steel is placed at 350° C. and kept warm for 1 hour for structure stabilization treatment, and then naturally cooled to room temperature to induce the metastable austenite to transform into lath martensite.

8. The method for preparing high-performance Bema duplex die steel according to claim 1, characterized in that: In S4, the specific process of the low-temperature aging curing treatment is as follows: the steel is placed at 150°C for 40 minutes, after which it is taken out and placed in 60-65°C warm water for hot water bath curing treatment, and the steel is taken out after cooling to the water temperature.

9. The method for preparing high-performance Bema duplex die steel according to claim 1, characterized in that: In S4, the specific process of the cryogenic treatment is as follows: the solidified steel is cryogenically treated for 12 hours to transform part of the retained austenite into high-strength martensite and promote the precipitation of fine carbides; The cryogenic treatment is a gas method, in which the solidified steel is placed in a liquid nitrogen environment, and the latent heat of liquid nitrogen vaporization and the heat absorption of low-temperature nitrogen are used for cooling.

10. The method for preparing high-performance Bema duplex die steel according to claim 1, characterized in that: In S4, the specific process of the multi-stage tempering and isostatic pressing heat treatment is as follows: The first tempering treatment is carried out immediately after cryogenic treatment, with the temperature kept at 500℃ for 2 hours to eliminate the residual stress inside the material and make the mold steel achieve a better balance between strength and plasticity; Then the second tempering treatment was carried out at a temperature of 550℃ for 2h, followed by air cooling to improve the stability of the microstructure; Finally, the steel after secondary tempering is subjected to isostatic pressing heat treatment at 400-450°C and 100MPa to eliminate internal stress and microcracks and promote grain refinement and structural homogenization.

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