Magnesium-modified high-performance hot-work die steel and method of manufacturing the same

Abstract

This invention discloses a high-performance H13 mold steel modified with magnesium and its manufacturing method, belonging to the field of special steel metallurgical technology. The chemical composition of the steel, by mass percentage, is: C: 0.36~0.42%, Si: 0.80~1.20%, P: ≤0.025%, S: ≤0.003%, Mn: 0.25~0.60%, Cr: 4.90~5.30%, Mo: 1.10~1.50%, V: 0.80~1.0%, Mg: 0.0020~0.0035%, with the balance being Fe and unavoidable impurities. The manufacturing method includes: smelting → magnesium modification treatment → casting → rolling → spheroidizing annealing → quenching and tempering treatment. This invention, by precisely controlling the amount and timing of magnesium addition, transforms large-sized Al2O3 inclusions in the steel into fine and dispersed MgO·Al2O3 spinels. Simultaneously, magnesium agglomerates at grain boundaries, suppressing alloy element segregation, refining liquid carbides, and improving their distribution. Compared with the prior art, the steel of the present invention has an average inclusion diameter of ≤3.0μm, an average carbide size of ≤10μm, a banded segregation rating of ≤2.5, a tensile strength of ≥1780MPa, an impact energy of ≥150J, and significantly improved wear resistance and thermal fatigue performance, making it suitable for the manufacture of high-end hot work dies.

Description

Technical Field

[0001] This invention belongs to the field of special steel metallurgical technology, specifically relating to a high-performance H13 hot work die steel with magnesium modification treatment and its manufacturing method. By adding trace amounts of magnesium, the inclusions and carbides in the steel are synergistically controlled, significantly improving the mechanical properties and service life of the steel. Background Technology

[0002] H13 steel (4Cr5MoSiV1) is a widely used hot work die steel with excellent hot strength, toughness, and resistance to thermal fatigue. It is widely used in aluminum alloy die casting molds, hot forging dies, and extrusion dies. However, in conventional industrial production, especially in continuous casting processes, traditional H13 steel is prone to the formation of large-sized inclusions and liquid carbides, which affect its mechanical properties and service life.

[0003] Studies have shown that the liquid carbides in H13 steel mainly include MC type (V-rich), M2C type (Mo-Cr-rich), and M7C3 type (Cr-rich). These carbides precipitate directly from the liquid phase during solidification, with a size of 50-100 μm, and are mostly distributed between dendrites and grain boundaries, becoming crack initiation sites and severely deteriorating the toughness and fatigue performance of the steel. Simultaneously, Al2O3 inclusions in the steel tend to aggregate to form cluster structures, leading to nozzle blockage and anisotropy in the steel.

[0004] To improve the microstructure and properties of H13 steel, the industry has explored various methods, including alloy composition optimization, heat treatment process improvement, and rare earth treatment. In recent years, magnesium treatment has attracted attention due to its excellent deoxidation, desulfurization, and inclusion modification effects. Magnesium has a strong affinity for oxygen and sulfur, which can modify irregular clusters of Al2O3 inclusions in steel into fine, dispersed MgO·Al2O3 spinel or MgO particles. Simultaneously, the segregation of magnesium at grain boundaries can suppress the segregation of alloying elements and hinder the preferential growth of carbides at grain boundaries, thereby refining the carbides and improving their distribution.

[0005] However, while existing magnesium processing technologies have made some progress, they still have significant limitations and are difficult to adapt to the needs of large-scale industrial production, especially in continuous casting processes. For example: Existing technology CN120575091A discloses a vacuum induction furnace smelting process for magnesium microalloying of H13 hot work die steel, which discloses a method for magnesium microalloying of H13 steel. It uses thermodynamic calculations to determine that the Mg content is 0.0008wt%~0.0019wt%, which can convert Al2O3 into MgAl2O4 spinel and refine carbides and solidification structure, relying on special smelting equipment such as a vacuum induction furnace. Existing technology CN106834931A discloses a hot work die steel resistant to thermal fatigue and its preparation method, which discloses a hot work die steel resistant to thermal fatigue with a Mg content ranging from 0.0005wt%~0.003wt%, using a special composite process of medium frequency induction melting + electroslag remelting. The aforementioned patents require high-purity processes such as vacuum induction or electroslag remelting, which suffer from problems such as closed production processes, extremely low efficiency, lengthy processes, high manufacturing costs, and long production cycles. They are only suitable for small-batch trial production in the laboratory and cannot be adapted to conventional electric furnace + ladle refining + continuous casting industrial production lines. At the same time, the Mg content they determine can only be stably effective in a vacuum low-oxygen activity environment. In industrial continuous casting conditions with higher oxygen activity and larger steel volume, magnesium is easily oxidized and burned off, resulting in drastic fluctuations in yield. It is difficult to stably achieve the effects of inclusion modification and carbide refinement, and therefore they do not meet the conditions for industrial promotion.

[0006] The existing technology CN121575296A discloses a method for manufacturing high-quality electric arc furnace hot work die steel, specifically a method for manufacturing H13 steel using an electric arc furnace process. This method involves intermittent feeding of magnesium-cored wire after vacuum degassing (VD) to improve carbide formation. However, this process uses die casting to produce large ingots, resulting in slow solidification and cooling. Problems such as dendrite segregation and coarse-grained carbides remain prominent, requiring a large forging ratio for improvement. This leads to low yield and poor production flexibility. The technology only discloses the magnesium-cored wire and intermittent feeding operation, without mentioning the addition of Mg or specifying a clear Mg content control range. Furthermore, the Mg content in the magnesium-cored wire is extremely low. It also lacks a post-feeding soft argon blowing and static homogenization process, making it impossible to achieve a stable and uniform magnesium yield. Additionally, it fails to match the key parameters required for continuous casting, such as superheat, electromagnetic stirring, and casting speed, thus failing to address problems such as well-developed columnar crystals, inclusion aggregation, and severe banded segregation in continuously cast billets, making it difficult to achieve stable and uniform microstructure control.

[0007] Therefore, existing technologies still suffer from problems such as the inability to quantify and determine the amount of magnesium added, unstable magnesium yield, and unclear magnesium modification mechanism. Furthermore, there is a lack of systematic continuous casting magnesium modification schemes for H13 steel. Therefore, developing an industrially feasible continuous casting method for producing magnesium-modified H13 steel that enables synergistic control of inclusions and carbides, and the resulting steel, has significant theoretical and engineering application value. Summary of the Invention

[0008] The purpose of this invention is to provide a high-performance H13 hot work die steel with magnesium modification and its manufacturing method. By precisely controlling the amount and timing of magnesium addition, the invention achieves synergistic regulation of inclusions and carbides in H13 steel produced by continuous casting, significantly refining the size of inclusions and carbides, improving their distribution morphology, and enhancing the comprehensive mechanical properties and service life of the steel. This invention, through precise control of the amount and timing of magnesium addition, transforms large-sized Al2O3 inclusions in the steel prepared by continuous casting into fine and dispersed MgO·Al2O3 spinels. Simultaneously, magnesium agglomerates at grain boundaries, inhibiting the segregation of alloying elements, refining liquid carbides, and improving their distribution. Compared with existing technologies, the steel of this invention has an average inclusion diameter ≤3.0μm, an average carbide size ≤10μm, a banded segregation rating ≤2.5, a tensile strength ≥1780MPa, an impact energy ≥150J, and significantly improved wear resistance and thermal fatigue performance, making it suitable for high-end hot work die manufacturing.

[0009] The technical solution adopted by the present invention to achieve the above objectives is as follows.

[0010] A method for manufacturing a high-performance hot work die steel with magnesium modification includes the following steps: smelting, magnesium modification treatment, continuous casting, rolling, spheroidizing annealing, and quenching and tempering treatment; wherein the chemical composition of the high-performance hot work die steel, by mass percentage, includes: C: 0.36~0.42%, Si: 0.80~1.20%, P: ≤0.025%, S: ≤0.003%, Mn: 0.25~0.60%, Cr: 4.90~5.30%, Mo: 1.10~1.50%, V: 0.80~1.0%, Mg: 0.0020~0.0035%, with the balance being Fe and unavoidable impurities; The magnesium modification treatment step involves feeding magnesium cored wire using a wire feeding method, with the amount of magnesium added being 0.03~0.05% of the mass of the molten steel, and the target magnesium content being controlled at 0.0020~0.0035%.

[0011] By adopting the aforementioned technical solution: Currently, conventional methods for improving the performance of H13 mold steel in the industry mostly rely on increasing alloy content, using special processes such as vacuum induction, electroslag remelting, or casting large steel ingots, which result in high production costs and difficulties in promotion. The core idea of ​​this invention is to achieve controllable regulation of inclusion type, size, and distribution without relying on high-cost processes and high alloying. This is achieved by precisely controlling the Mg content and combining it with magnesium modification treatment to ensure Mg yield. At the same time, by combining precise smelting and continuous casting processes for coordinated control, harmful Al2O3 cluster inclusions are transformed into fine and dispersed MgO·Al2O3 spinel inclusions, thereby optimizing the morphology and distribution of carbides, reducing banded segregation, and ultimately significantly improving the steel's strength, toughness, wear resistance, and thermal fatigue resistance in the most economical way on conventional industrial continuous casting production lines, significantly reducing process costs, and possessing excellent performance.

[0012] Preferably, the magnesium content is controlled at 0.0020~0.0025%, which results in the best refinement effect of inclusions and carbides. When the magnesium content is below 0.0020%, the modification effect is not obvious, and when the magnesium content is above 0.0025%, large-sized MgO inclusions are easily formed, which deteriorates the steel performance.

[0013] Preferably, the method specifically includes the following steps: (1) Smelting: The smelting process is carried out using an electric arc furnace (EAF) + ladle refining furnace (LF) + vacuum degassing (VD). Preferably, the tapping temperature of the electric arc furnace is 1640~1680℃; Preferred method: LF refining involves adjusting the composition to control the slag basicity (CaO / SiO2) at 3.5~4.5, and the FeO content in the slag at ≤1.0%. Preferably, the VD vacuum treatment is performed with a vacuum degree of ≤67Pa, a holding time of 15~25min, and a temperature of 1560~1580℃ after vacuum breaking. (2) Magnesium modification treatment: Magnesium modification treatment is carried out after VD void breaking and before continuous casting; magnesium cored wire is added by feeding method, with a feeding speed of 2.5~3.5m / s, more preferably 2.5~3.0m / s, preferably intermittent feeding, completed in 2~3 times, with the interval between each feeding controlled at 15~30 s; by adopting the above scheme, the Mg recovery rate can be ensured to be about 30%; Preferably, after feeding the wire, the wire is gently blown with argon gas and stirred for 5-10 minutes. More preferably, after the gentle blowing, the wire is allowed to stand for 10-15 minutes to allow the inclusions to float to the surface, which promotes the uniform distribution of magnesium in the molten steel and the modification of the inclusions, so that the inclusions are evenly distributed and avoid agglomeration. Preferably, the target magnesium content is controlled at 0.0020~0.0025%; Preferably, the magnesium-coated wire has a Mg content of 20-30% and a core wire diameter of 10-13 mm; more preferably, the magnesium-coated wire has a specific composition comprising magnesium, silicon, and iron with mass fractions of 20-30%, 20-30%, and 40-60%, respectively. (3) Continuous casting: Protective casting is used to prevent secondary oxidation of molten steel; Preferably, the tundish superheat is 25~35℃; the crystallizer electromagnetic stirring is 300~400A current and 2.5~3.5Hz frequency; and the pulling speed is 0.55~0.85m / min. Preferably, secondary cooling is used, employing a weak cooling system with a specific water flow rate of 0.20~0.25L / kg; (4) Heating and rolling; Preferably, the billet heating temperature is 1180~1220℃, and the holding time is ≥2h; the initial rolling temperature is 1120~1150℃. Preferably, the final rolling temperature is ≥950℃; the material is then piled up and cooled slowly to room temperature after rolling. (5) Spheroidizing annealing; Preferably, the annealing temperature is 830~860℃, and the holding time is 4~6h; after furnace cooling to 750℃, the temperature is isotherm is 2~3h, and then furnace cooling is 500℃ or lower before unloading; the hardness after annealing is ≤235HBW. (6) Conditioning and tempering treatment; Preferably, the quenching process involves austenitizing at 1020~1060℃, with a holding time of 1.5 min / mm, and can be performed by oil quenching or gas quenching. Preferably, tempering: tempering twice at 550~600℃, holding for 2~3 hours each time, followed by air cooling.

[0014] Preferably, the steel prepared by the method has an average inclusion diameter ≤3.0μm and a density ≥20 inclusions / mm². 2 More preferably, the inclusions have an average diameter of 2.62~2.85μm and a density of 24~35 inclusions / mm². 2 The inclusions are mainly MgO·Al2O3 spinel and MgO, with MgO·Al2O3 accounting for ≥50%. The inclusions are significantly refined, more uniformly distributed, and local aggregation is reduced.

[0015] Preferably, the average size of the liquid carbides in the steel prepared by the method is ≤10μm, the average size of the MC-type liquid carbides is ≤10μm, and the proportion of carbides ≤5μm is ≥70%, the carbide morphology is granular or blocky, and the distribution is more uniform.

[0016] Preferably, the steel prepared by the method has a banded segregation rating of ≤2.5 (according to NADCA #207 standard).

[0017] Preferably, the steel prepared by the method has a tensile strength of 1780-1880 MPa; a yield strength of 1550-1650 MPa; an elongation after fracture (elongation) of 11-13%; an impact energy (Akv, 20℃) of 155-185 J; and high-temperature tensile properties (600℃): tensile strength retention rate ≥85%.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) Significant refinement and dispersion of inclusions: After magnesium modification, the inclusions in the steel changed from large-sized (3.08~4.38μm) CaO-Al2O3-SiO2, Al2O3, etc. in the original process to fine and dispersed (2.62~2.85μm) MgO·Al2O3 spinel, MgO, and composite inclusions. The inclusion density increased from 14~26 inclusions / mm 2 Increased to 24~35 pieces / mm 2The similar area percentages indicate that the inclusions are more evenly distributed, reducing local aggregation.

[0019] (2) Carbide size significantly reduced and morphology improved: After magnesium modification, the size of liquid carbides in the billet decreased from 50-100 μm in the original process to 5-10 μm, and the size of MC-type carbides in the bar decreased from 10-20 μm to 3-8 μm. Moreover, the morphology of carbides changed from network and elongated to granular and blocky, and the distribution became more uniform. The evolution of carbide types is consistent with the results of thermodynamic calculations (Thermo-Calc).

[0020] (3) Significant reduction in banded segregation: After magnesium modification, the alternating light and dark bands after rod corrosion are significantly reduced, the distribution of alloying elements is more uniform, and the banded segregation rating is reduced from 3.0~4.0 in the original process to 1.5~2.5 (according to NADCA #207 standard).

[0021] (4) Significantly improved mechanical properties: Tensile strength (Rm): increased from 1650-1750MPa in the original process to 1780-1880MPa; Yield strength (Rp0.2): increased from 1400-1500MPa to 1550-1650MPa; Elongation after fracture (A): increased from 8-10% to 11-13%; Impact energy (Akv, 20℃): increased from 80-100J to 155-185J; High temperature tensile properties (600℃): Tensile strength retention rate ≥85%.

[0022] (5) Improved wear resistance and thermal fatigue performance: After magnesium modification, the wear resistance of the material is improved by about 30% due to the refinement and uniform distribution of carbides (wear test, load 100N, time 30min); the thermal fatigue crack initiation life is extended by about 50% (thermal fatigue test, cycle temperature 20→700℃).

[0023] In summary, this invention, through creative process improvements and precise control of magnesium addition, achieves magnesium modification of continuously cast H13 steel to refine inclusions and carbides, reduce segregation, and comprehensively optimize the microstructure of hot work die steel. This significantly improves its mechanical properties, high-temperature stability, wear resistance, and thermal fatigue resistance, extending the service life of the dies and demonstrating broad market application prospects. Furthermore, the preparation method provided by this invention is suitable for matching traditional industrial lines and is applicable to large-scale industrial production. Attached Figure Description

[0024] Figure 1 The inclusions in the comparative sample billet were large-sized (4~6μm) irregular Al2O3 clusters. Figure 2 Example 1: The inclusions in the cast billet are fine (1~3μm) near-spherical MgO·Al2O3 spinel inclusions, which are evenly distributed; Figure 3 The comparative example showed an inclusion density of 15 inclusions / mm², an average diameter of 3.25 μm, and a maximum size of 12.5 μm. Figure 4 Example 2: Inclusion density 24 inclusions / mm², average diameter 2.62 μm, maximum size 7.8 μm; Figure 5 The carbides in the core of the comparative billet are long strip-shaped and network-shaped MC-type carbides with a size of 50-100 μm. Energy dispersive spectroscopy shows that they are rich in V and contain small amounts of Mo and Cr. Figure 6 Example 3: The carbides in the core of the cast billet are granular and blocky MC-type carbides with a size of 5-10 μm and uniform distribution. Detailed Implementation

[0025] To better clarify and understand the objectives, process solutions, and advantages of this invention, the technical solutions and implementation methods of this invention will be further described clearly, completely, and in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the embodiments described in this invention are implemented under the premise of the technical solutions of this invention, providing detailed implementation methods and specific operating procedures, but are only some embodiments of this invention, not all embodiments. The specific implementation methods described are limited to illustrating and explaining this invention and do not limit this invention. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0026] Unless otherwise specified, the experimental methods and conditions used in the embodiments of this invention are conventional methods and conditions. The materials, reagents, instruments, and equipment used in the embodiments, unless otherwise specified, are all conventional substances or equipment known to those skilled in the art and can be obtained commercially or prepared by conventional methods. The reaction conditions described in the invention's content can all achieve the stated reactions and obtain the desired products. Due to space limitations, some embodiments are listed below to further illustrate the advantages of the technical solution of this invention.

[0027] Example 1: (1) Smelting H13 steel was smelted in a 60t electric arc furnace at a tapping temperature of 1660℃, and the molten steel was fed into an LF furnace. The LF refining process adjusted the composition to the target range: C 0.38%, Si 0.95%, Mn 0.38%, Cr 5.20%, Mo 1.25%, V 0.92%, slag basicity 4.0, and FeO content in the slag 0.8%. Vacuum treatment (VD) was performed for 25 minutes at a vacuum level of 60 Pa, and the temperature after vacuum breaking was 1570℃.

[0028] (2) Magnesium modification treatment After VD breaks the void, magnesium-coated wire (Mg content 25%, core wire diameter 12mm) is added using a wire feeding method at a feeding speed of 3.0m / s and an addition amount of 0.035% (based on the mass of molten steel). After wire feeding, argon gas is gently blown for 8 minutes and then allowed to stand for 12 minutes.

[0029] (3) Continuous casting The tundish superheat is 30℃, the crystallizer electromagnetic stirring current is 350A and the frequency is 3.0Hz, the casting speed is 0.50m / min, and the specific water content is 0.22L / kg. The billet cross-section is 200mm×200mm.

[0030] (4) Heating and rolling The billet is heated to 1200℃ and held for 3 hours. The initial rolling temperature is 1130℃ and the final rolling temperature is 970℃. It is rolled into Φ60mm bars and then cooled in a stack.

[0031] (5) Spheroidizing annealing Hold at 830℃ for 5 hours, furnace cool to 750℃ isothermal for 2.5 hours, then furnace cool to below 500℃ before removing from the furnace. The hardness after annealing is 215HBW.

[0032] (6) Conditioning Austenitizing at 1040℃ (holding for 90 min), oil quenching; tempering twice at 580℃, holding for 2.5 h each time, followed by air cooling.

[0033] (7) Test Results Chemical composition: Mg content 0.0021%; Inclusions: average diameter 2.68 μm, density 26 inclusions / mm 2 The maximum size is 7.2 μm, and the main type is MgO·Al2O3, accounting for 65%; Carbides: mainly MC type carbides with a size of 4-7 μm and uniform distribution; Band segregation rating (according to NADCA #207 standard): 1.5; Mechanical properties: The mechanical properties of the material were tested according to GB / T 228.1 and GB / T 228.2 (the same below). Tensile strength Rm 1850MPa, yield strength Rp0.2 1620MPa, elongation after fracture A 12.5%, impact energy Akv 178J (20℃), high temperature tensile properties 600℃ tensile strength 1580MPa, tensile strength retention ≥85%; Abrasion resistance: The abrasion resistance of the material was determined according to ASTM G133-22, with a wear mass loss of 4.2 mg (load 100 N, 30 min).

[0034] Example 2 The experiment was essentially the same as in Example 1, except that the amount of magnesium-coated wire added was adjusted to 0.04%, with a target magnesium content of 0.0026%. Test results: Mg content 0.0027%, average inclusion diameter 2.95 μm, density 22 inclusions / mm². 2 The MC carbide size is 5-9 μm, and the mechanical properties are shown in Table 1. They are slightly lower than those in Example 1 but still better than the original process.

[0035] Example 3 The experiment was essentially the same as in Example 1, except that the amount of magnesium-coated wire added was adjusted to 0.05%, with a target magnesium content of 0.0035%. Test results: Mg content 0.0034%, average inclusion diameter 2.85 μm, density 24 inclusions / mm². 2 However, there are a small number of large-sized (5-8 μm) MgO inclusions and MC carbides with a size of 4-8 μm. The mechanical properties are shown in Table 1 and are comparable to those of Example 1, but the impact energy is slightly reduced (158 J).

[0036] Comparative example: No magnesium modification treatment was performed; the remaining processes were the same as in Example 1. Test results: Mg content 0.0003%, average inclusion diameter 3.82 μm, density 14 inclusions / mm². 2 It contains a large number of large-sized (8-12μm) Al2O3 clusters; MC carbides are 15-30μm in size, some of which are distributed in a network; banded segregation is rated 4.0; mechanical properties: Rm 1680MPa, Rp0.2 1450MPa, A 9.5%, Akv 92J.

[0037]

[0038] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications may be made without departing from the technical solutions described in the claims.

Claims

1. A method for manufacturing a high-performance hot work die steel with magnesium modification treatment, characterized in that, The process includes the following steps: smelting, magnesium modification treatment, continuous casting, rolling, spheroidizing annealing, and quenching and tempering treatment; wherein, the chemical composition of the high-performance hot work die steel, by mass percentage, includes: C: 0.36~0.42%, Si: 0.80~1.20%, P: ≤0.025%, S: ≤0.003%, Mn: 0.25~0.60%, Cr: 4.90~5.30%, Mo: 1.10~1.50%, V: 0.80~1.0%, Mg: 0.0020~0.0035%, with the balance being Fe and unavoidable impurities; The magnesium modification treatment step involves feeding magnesium cored wire using a wire feeding method, with the amount of magnesium added being 0.03~0.05% of the mass of the molten steel, and the target magnesium content being controlled at 0.0020~0.0035%.

2. The method according to claim 1, characterized in that, The magnesium content is controlled between 0.0020 and 0.0025%.

3. The method according to claim 1, characterized in that, The method yields steel with inclusions having an average diameter ≤3.0μm and a density ≥20 inclusions / mm². 2 The inclusions are mainly MgO·Al2O3 spinel and MgO, with MgO·Al2O3 accounting for ≥50%.

4. The method according to claim 1, characterized in that, The average size of the MC-type liquid carbides in the steel obtained by the method is ≤10μm, and the proportion of carbides ≤5μm is ≥70%, and the carbide morphology is granular and / or blocky.

5. The method according to claim 1, characterized in that, The banded segregation rating of the steel obtained by the method is ≤2.

5.

6. The method according to claim 1, characterized in that, In the magnesium modification process, magnesium cored wire is added using a feeding method at a speed of 2.5-3.5 m / s; the magnesium cored wire contains 20-30% Mg. And / or, use intermittent feeding, which is completed in 2 to 3 times, with the interval between each feeding controlled at 15 to 30 seconds; And / or, after the magnesium modification treatment, the mixture is stirred with soft-blown argon gas for 5-10 minutes and then allowed to stand for 10-15 minutes to promote the floating and uniform distribution of inclusions.

7. The method according to claim 1, characterized in that, In the continuous casting process, the superheat of the tundish is controlled at 25~35℃, the electromagnetic stirring current of the crystallizer is 300~400A, the frequency is 2.5~3.5Hz, and the casting speed is 0.55~0.85m / min.

8. The method according to claim 1, characterized in that, In the spheroidizing annealing step, the annealing temperature is 830-860℃, the holding temperature is 4-6h, the furnace is cooled to 750℃ and then isothermal for 2-3h, and then furnace cooled to below 500℃ before being removed from the furnace.

9. The method according to claim 1, characterized in that, In the tempering process, the quenching temperature is 1020~1060℃, and the tempering temperature is 550~600℃. The tempering is repeated twice, and each time the temperature is maintained for 2~3 hours.

10. A high-performance hot work die steel with magnesium modification prepared by the method according to any one of claims 1-8.

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