Hot work die steel and method for producing the same

Abstract

The present application relates to a kind of high toughness high thermal conductivity hot work die steel and its production method, belong to die steel production technical field.The present application is based on H11 steel and H13 steel, fine-tune chemical composition, reduce the content of silicon element and slightly improve Cr element content to ensure the oxidation resistance while improving thermal conductivity, by adding a small amount of Nb element content further refine grain, by adding trace rare earth Ce element to modify inclusion.The method is obtained by vacuum induction melting, vacuum consumable melting, high temperature homogenization and forging, ultra-fine and spheroidizing annealing and quenching and tempering treatment high thermal conductivity, inclusion number density≤1 / mm 2 ;And transverse V-shaped notch Charpy impact energy is improved to about 45J hot work die steel.The thermal conductivity and impact toughness of existing die steel cannot meet the service life requirement of body integration die casting die.

Description

Technical Field

[0001] This invention relates to a hot work die steel and its production method, belonging to the field of die steel production technology. Background Technology

[0002] Hot work dies play a crucial role in the production of alloy products such as magnesium, aluminum, and zinc. During operation, they are subjected to complex alternating loads, with the cavity in direct contact with high-temperature metal, repeatedly undergoing rapid cooling and heating, resulting in extremely harsh working conditions. Currently, commonly used hot work die steels both domestically and internationally include H11 (1.2343 steel), H13 (1.2344 steel, 8407 steel), and DIEVAR steel (8418 steel). DIEVAR steel, based on H13, has reduced V and Si content and increased Mo content, giving it higher impact toughness and thermal conductivity.

[0003] Chinese patent CN110923584A discloses a long-life die-casting mold steel and its heat treatment process. This invention discloses a long-life die-casting mold steel comprising the following components by mass percentage: C: 0.33%–0.41%, Si: not more than 0.5%, Mn: not more than 0.5%, Cr: 4.8%–5.5%, Mo: 2.0%–2.4%, V: 0.3%–0.8%, Ni: not more than 0.40%, with the balance being Fe and unavoidable impurities. The mold steel described in this invention possesses excellent thermal conductivity, toughness, and ductility, and exhibits minimal deformation under heat, significantly extending its service life. However, the hot-work mold steel disclosed in this invention has an impact energy of only 15 J and a thermal conductivity of approximately 30 W / (m·K) at 100℃.

[0004] Chinese patent CN103334061A discloses a high thermal conductivity large-section die-casting mold steel and its preparation and heat treatment method. This invention relates to a high thermal conductivity large-section die-casting mold steel and its preparation and heat treatment method. The steel is characterized by the following mass percentage composition of its main alloying elements: C 0.30–0.45%, Mn 0.20–0.30%, Si 0.10–0.30%, Cr 2.00–3.50%, Ni 2.00–6.00%, W 2.50–4.00%, Mo 1.00–1.50%, V 0.35–0.65%, P < 0.025%, S < 0.025%, and Fe as the balance. The steel preparation process is as follows: batching, smelting, and casting; followed by electroslag remelting and annealing; high-temperature homogenization treatment; multi-directional forging; ultra-fine refining treatment; and finally quenching and tempering heat treatment. Its thermal conductivity, hardenability, high-temperature strength, and resistance to hot cracking are all far superior to H13 steel. The thermal conductivity of the hot work die steel described herein is better than that of H13 steel, with a thermal conductivity of approximately 35.5 W / (m·K) at 100℃. Its V-notch impact resistance can reach 24 J, approaching the level of DIEVAR steel.

[0005] The rapid development of the new energy vehicle industry and the ability of integrated die casting to significantly reduce production costs have led to increasingly stringent requirements from major OEMs regarding mold lifespan. This places higher demands on the performance of hot-work die steels. Experience shows that the number of times a die-casting mold can be used is directly related to the material's impact toughness and thermal conductivity. This is because the hot-cold cycle during die casting generates thermal stress. High thermal conductivity can quickly dissipate heat, reducing temperature differences and thermal stress, while high impact toughness reduces the probability of thermal crack initiation. However, the thermal conductivity and impact toughness of existing die steels are insufficient to meet the harsh service environment of integrated die casting molds. Summary of the Invention

[0006] The technical problem to be solved by this invention is that the thermal conductivity and impact toughness of existing mold steels cannot meet the harsh service environment of integrated body die-casting molds.

[0007] The technical solution adopted by this invention to solve its technical problem is: hot work die steel, with the following chemical composition by mass percentage: C 0.34%~0.38%, Mn 0.20%~0.40%, Si 0.05%~0.2%, Cr 5.50%~6.00%, Mo 1.40%~1.70%, V 0.65%~0.75%, Nb 0.005%~0.015%, Ce 0.01%~0.08%, Ni ≤0.10%, Cu ≤0.060%, S ≤0.0015%, P ≤0.010%, and the residual gas content is: H ≤1ppm, O ≤10ppm, N ≤30ppm, and the five harmful elements: Pb+Sn+As+Sb+Bi≤0.01%, with the remainder being Fe and unavoidable impurities.

[0008] Furthermore, the raw materials used are: ultra-low sulfur pure iron, with pure iron requiring S≤0.0010% and P≤0.008%; high-purity graphite blocks with carbon content≥99.9%; industrial pure silicon 99.99%; metallic manganese 99.9%, metallic chromium 99.9%, molybdenum bars 99.9%, metallic niobium 99.9%, ferrovanadium and metallic cerium.

[0009] The production method of hot work die steel includes the following steps: S1. Vacuum induction melting, including loading the raw materials of the above components into the furnace, melting them completely, refining them, sampling and adjusting the composition, and casting them to obtain induction ingots; S2. Vacuum consumable melting: The induction casting ingot is made into an electrode rod, which is then subjected to arc ignition, normal melting, filling melting and ingot cooling to obtain a consumable ingot. S3. High-temperature homogenization and forging: The consumable ingot is homogenized at high temperature and then forged to obtain a forged ingot; S4. Ultrafine and spheroidizing annealing: The forging ingot is subjected to ultrafine and spheroidizing annealing treatment to obtain the forging annealed ingot; S5. Quenching and tempering treatment: The forged annealed ingot is subjected to high-temperature quenching and multiple low-temperature tempering treatments to obtain a quenched and tempered ingot.

[0010] Furthermore, in the furnace loading stage of step S1, 2 / 3 of the high-purity graphite blocks are loaded into the furnace along with the furnace. Except for metallic chromium, metallic manganese, industrial pure silicon, metallic niobium, ferrovanadium and metallic cerium, the remaining raw materials are also loaded into the furnace along with the furnace. In the sampling and composition adjustment stage of step S1, high-purity manganese, industrial pure silicon, metallic niobium, ferrovanadium and metallic cerium are added to adjust the composition to the target value.

[0011] Furthermore, in the full melting stage of step S1, the temperature is raised to 1600-1620℃, 0.5-1.5 kg of high-purity graphite blocks are added for deoxidation, and after stirring for 20-25 minutes, high-purity chromium is added, and the sample is taken to ensure that N ≤ 0.0015%; In the refining stage of step S1, the temperature is controlled at 1560℃±10℃, the stirring is carried out at industrial frequency for ≥30min, the refining time is controlled at ≥60min, argon is purged at 2800~4500Pa, and high-purity graphite blocks are added according to the designed C content. Furthermore, during the pouring process in step S1, it must be ensured that the pouring height is greater than 2 / 3 of the riser height.

[0012] Furthermore, in step S2, during the arc ignition stage of vacuum self-consumption, the arc ignition current is 2200–13800A; the arc ignition voltage is 20–24V. In the normal smelting stage of step S2, the melting rate is controlled at 4.7 to 6 kg / min, with an allowable fluctuation range of ±15%, and the droplet count is adjusted from 1.0 to 6.0 / s, with an allowable fluctuation range of ±2. In the filling and melting stage of step S2, the filling weight is set to 300-350 kg, and the remaining 50-80 kg filling parameters are controlled by melting rate + dripping rate. The feeding melting rate is 5-2 kg / min, and the filling time is controlled to be 80-120 minutes.

[0013] Furthermore, in step S3, the high-temperature homogenization adopts a three-stage heating process: first, it is held at 600-660℃ for ≥2h, then heated to 850℃±20℃ at a heating rate of ≤30℃ / h and held for ≥3h, and then heated to 1260℃±10℃ and held for ≥16h.

[0014] Furthermore, after the high-temperature homogenization and heat preservation, the consumable ingot is taken out for forging. The initial forging temperature is ≥1050℃, the final forging temperature is ≥850℃, the number of upsetting and drawing is ≥3, and the forging ratio is greater than or equal to 8 to obtain a forging module. After forging, the forging module is kept at 850℃±10℃ for ≥10h for softening annealing.

[0015] Furthermore, in step S4, the ultrafine refining process will employ a two-stage heating process. First, the forging module will be heated to 840℃±20℃ at a rate of ≤100℃ / h and held for ≥2h. Then, it will be heated to 1000℃±10℃ at a rate of ≤100℃ / h and held for ≥5h. After the holding period, it will be water-cooled for ≥30min to cool to at least the core temperature ≤300℃. After air-cooling to ≤200℃, it can be placed in a furnace at 840℃±10℃ for spheroidizing annealing. It will be held at 850℃±10℃ for ≥8h, and then cooled to 600℃ at a rate of 10℃ / h before being removed from the furnace and air-cooled.

[0016] Furthermore, in step S5, the tempering process is divided into high-temperature quenching and multiple tempering. The high-temperature quenching involves heating the required module blank at 980℃~1020℃ until it is thoroughly heated and held for ≥30min, followed by oil quenching, and then performing multiple temperings at 560℃~630℃, with each tempering lasting ≥2h.

[0017] The beneficial effects of this invention are: (1) This invention uses a vacuum induction + vacuum self-consumption production process for production, and selects high-quality metal raw materials for smelting, which greatly improves its purity. The addition of Ce also modifies the inclusions and reduces their size. This results in the final product having S ≤0.0015%, P ≤0.010%, five harmful elements (Pb, Sn, As, Sb, Bi) ≤0.01%, H ≤1ppm, O≤10ppm, N ≤30ppm, and inclusion rating according to GB / T 10561~2023 national standard, reaching AT0, AH0, BT≤1, BH≤0.5, CT0, CH0, DT≤1, DH≤0.5, and DS0 grades. ASPEX fully automatic inclusion analysis results show that its inclusion number density is ≤1 inclusion / mm 2 .

[0018] (2) This steel grade has reduced the Si content and achieved an ultra-low inclusion level through ultra-high cleanliness, resulting in high thermal conductivity. Its thermal conductivity at 25℃, 200℃, 400℃ and 600℃ is as high as 38.4 W / (m·K), 42.7 W / (m·K), 42.5 W / (m·K) and 36.7 W / (m·K), respectively. The reduction of Si content will weaken the oxidation resistance of the material. Therefore, the Cr content in this steel is increased to 5.50% to 6.00% to improve the oxidation resistance. The increase of Cr content has almost no effect on thermal conductivity.

[0019] (3) A small amount of Nb element was added to this steel to form fine and dispersed carbides. Together with the fine and dispersed carbides formed by V, the grain size was refined. Combined with the characteristics of high purity and low inclusions, the impact toughness of this steel was improved. At a hardness of 44 to 46 HRC in the tempered state, according to the current national standard GB / T 229 to 2020, the Charpy impact energy of the transverse V-notch was increased from about 30 J to about 45 J compared with H11 steel. Detailed Implementation

[0020] The present invention will be further described below with reference to embodiments and comparative examples.

[0021] Hot work die steel, by chemical composition by mass percentage: C 0.34%–0.38%, Mn 0.20%–0.40%, Si 0.05%–0.2%, Cr 5.50%–6.00%, Mo 1.40%–1.70%, V 0.65%–0.75%, Nb 0.005%–0.015%, Ce 0.01%–0.08%, Ni ≤0.10%, Cu ≤0.060%, S ≤0.0015%, P ≤0.010%, and residual gas content: H ≤1ppm, O ≤10ppm, N ≤30ppm, five harmful elements: Pb+Sn+As+Sb+Bi≤0.01%, the remainder being Fe and unavoidable impurities. Those skilled in the art should understand that this steel grade is based on H11 and H13 steels, with fine-tuned chemical composition. The silicon content is reduced while the chromium content is slightly increased to ensure oxidation resistance and improve thermal conductivity. A small amount of nitrogen (Nb) is added to further refine the grain size, and trace amounts of rare earth element (Ce) are added to modify inclusions. Furthermore, the production process is optimized to further reduce the inclusion content in the steel. The reduced Si content, increased purity, and decreased inclusion content improve the thermal conductivity of the steel grade. The refined grain size and reduced inclusion content enhance the impact toughness of the steel grade, resulting in products with better microstructure and mechanical properties, better suited to extremely harsh service environments.

[0022] Preferably, the raw materials used are: ultra-low sulfur pure iron, with pure iron requirements of S≤0.0010% and P≤0.008%; high-purity graphite blocks with carbon content ≥99.9%; industrial pure silicon 99.99%; metallic manganese 99.9%, metallic chromium 99.9%, molybdenum bars 99.9%, metallic niobium 99.9%, ferrovanadium and metallic cerium.

[0023] The production method of hot work die steel includes the following steps: S1. Vacuum induction melting, including loading the raw materials of the above components into the furnace, melting them completely, refining them, sampling and adjusting the composition, and casting them to obtain induction ingots; S2. Vacuum consumable melting: The induction casting ingot is made into an electrode rod, which is then subjected to arc ignition, normal melting, filling melting and ingot cooling to obtain a consumable ingot. S3. High-temperature homogenization and forging: The consumable ingot is homogenized at high temperature and then forged to obtain a forged ingot; S4. Ultrafine and spheroidizing annealing: The forging ingot is subjected to ultrafine and spheroidizing annealing treatment to obtain the forging annealed ingot; S5. Tempering treatment: The forged annealed ingot undergoes high-temperature quenching and multiple low-temperature tempering processes to obtain a tempered ingot. Those skilled in the art should know that this invention employs a vacuum induction + vacuum self-consumption production process, selecting high-quality metal raw materials for smelting, which greatly improves its purity. The addition of Ce also modifies inclusions and reduces their size.

[0024] Preferably, in the furnace loading stage of step S1, 2 / 3 of the high-purity graphite blocks are loaded into the furnace along with the furnace. Except for metallic chromium, metallic manganese, industrial pure silicon, metallic niobium, ferrovanadium and metallic cerium, the remaining raw materials are loaded into the furnace along with the furnace. In the sampling and composition adjustment stage of step S1, high-purity manganese, industrial pure silicon, metallic niobium, ferrovanadium and metallic cerium are added to adjust the composition to the target value.

[0025] Preferably, in the full melting stage of step S1, the temperature is raised to 1600-1620℃, 0.5-1.5 kg of high-purity graphite blocks are added for deoxidation, and after stirring for 20-25 minutes, high-purity chromium is added, and the sample is taken to ensure that N ≤ 0.0015%; In the refining stage of step S1, the temperature is controlled at 1560℃±10℃, the stirring is carried out at industrial frequency for ≥30min, the refining time is controlled at ≥60min, argon is purged at 2800~4500Pa, and high-purity graphite blocks are added according to the designed C content. Furthermore, during the pouring process in step S1, it must be ensured that the pouring height is greater than 2 / 3 of the riser height. Those skilled in the art should know that adding raw materials in stages allows for precise control of the composition and improves purity. First, the basic raw material (pure iron) is added, and oxygen, nitrogen, hydrogen, and other gases, as well as low-melting-point impurities, are thoroughly removed under vacuum. Then, alloying elements are added, which prevents impurities from being encapsulated by the alloying elements or forming difficult-to-remove compounds, thus improving the purity of the molten steel.

[0026] Preferably, in step S2, during the arc initiation stage of vacuum self-consumption, the arc initiation current is 2200–13800A; and the arc initiation voltage is 20–24V. In the normal smelting stage of step S2, the melting rate is controlled at 4.7 to 6 kg / min, with an allowable fluctuation range of ±15%, and the droplet count is adjusted from 1.0 to 6.0 / s, with an allowable fluctuation range of ±2. In the filling and melting stage of step S2, the filling weight is set to 300-350 kg, and the remaining 50-80 kg filling parameters are controlled by melting rate + dripping rate. The feeding melting rate is 5-2 kg / min, and the filling time is controlled to be 80-120 minutes.

[0027] Preferably, in step S3, the high-temperature homogenization adopts a three-stage heating process: first, the temperature is held at 600-660℃ for ≥2h, then the temperature is raised to 850℃±20℃ at a heating rate of ≤30℃ / h and held for ≥3h, and then the temperature is raised to 1260℃±10℃ and held for ≥16h.

[0028] Preferably, after the high-temperature homogenization and heat preservation is completed, the consumable ingot is taken out for forging, with an initial forging temperature ≥1050℃, a final forging temperature ≥850℃, upsetting and drawing times ≥3 times, and a forging ratio ≥8, to obtain a forging module; after forging, the forging module is kept at 850℃±10℃ for ≥10h for softening annealing.

[0029] Preferably, in step S4, the ultrafine refining process adopts a two-stage heating method. First, the forging module is heated to 840℃±20℃ at ≤100℃ / h and held for ≥2h. Then, it is heated to 1000℃±10℃ at ≤100℃ / h and held for ≥5h. After the holding period, it is water-cooled for ≥30min to cool to at least the core temperature ≤300℃. After air-cooling to ≤200℃, it can be put into a furnace at 840℃±10℃ for spheroidizing annealing. It is held at 850℃±10℃ for ≥8h, and then cooled to 600℃ at 10℃ / h before being taken out of the furnace and air-cooled.

[0030] Preferably, in step S5, the tempering process is divided into high-temperature quenching and multiple tempering. The high-temperature quenching involves heating the required module blank at 980℃~1020℃ until it is thoroughly heated and held at that temperature for ≥30 minutes, followed by oil quenching, and then performing multiple temperings at 560℃~630℃, with each tempering lasting ≥2 hours.

[0031] Example 1 The actual composition of the hot work die steel of this invention, in mass percentage, is shown in Table 1:

[0032] The production method of hot work die steel is as follows: S1. Vacuum induction melting: Vacuum induction melting is divided into several stages, including furnace loading, full melting, refining, sampling and composition adjustment, and casting, to obtain induction ingots. The weight of each raw material is determined according to the component content of the hot work die steel. To ensure that the levels of pollutants and residual elements meet the target requirements, the raw materials used are: ultra-low sulfur pure iron, with S≤0.0010% and P≤0.008%; high-purity graphite blocks with a carbon content ≥99.9%; industrial pure silicon 99.99%; metallic manganese 99.9%; metallic chromium 99.9%; molybdenum bars 99.9%; metallic niobium 99.9%; ferrovanadium; and metallic cerium. During the furnace charging stage, 2 / 3 of the furnace is filled with high-purity graphite blocks. Except for metallic chromium, high-purity manganese, industrial-grade silicon, metallic niobium, ferrovanadium, and metallic cerium, all other furnace materials are added. During the full melting stage, the temperature is raised to 1610℃, and 0.8 kg of high-purity graphite is added for deoxidation. After stirring for 22 minutes, high-purity chromium is added, and sampling ensures N ≤ 0.0015%. During the refining stage, the temperature is controlled at 1560℃ ± 10℃, with stirring at industrial frequency for 40 minutes. The refining time is 65 minutes, ensuring the carbon-oxygen reaction is essentially complete during refining. Argon is purged at 3300 Pa, and high-purity graphite blocks are added according to the designed C content. During the sampling and composition adjustment stage, high-purity manganese, industrial-grade silicon, metallic niobium, ferrovanadium, and metallic cerium are added to adjust the composition to the target value.

[0033] S2. Vacuum self-consumable melting: The induction ingot obtained in step S1 is first softened and annealed, then the riser of the induction ingot is cut off and the end is flattened. The surface is then machined or polished to make an electrode rod for vacuum consumable melting. Vacuum consumable melting consists of several stages, including arc initiation, normal melting, filling melting, and ingot cooling, to obtain the consumable ingot.

[0034] During the arc ignition stage, the arc ignition current is 2200–13800A and the arc ignition voltage is 20–24V. During the normal melting stage, the melting rate is controlled at 5.1–6 kg / min and the number of molten droplets is 1.0–6.0 / s. During the filling melting stage, the filling weight is set at 300–350 kg, and the remaining 50–80 kg of filling parameters are controlled by melting rate and molten droplets. The shrinkage melting rate is 5–2 kg / min and the filling time is 95 minutes.

[0035] S3. High-temperature homogenization and forging: The consumable ingot obtained in step S2 is subjected to high-temperature homogenization and then forged to obtain a forged ingot.

[0036] The high-temperature homogenization process employs a three-stage heating method: first, the temperature is held at 620℃ for 2 hours; then, the temperature is increased to 850℃±20℃ at a rate of 25℃ / h and held for 3 hours; finally, the temperature is increased to 1260℃±10℃ and held for 18 hours. After the high-temperature homogenization holding period, the consumable ingot is removed for forging. The initial forging temperature is ≥1050℃, the final forging temperature is ≥850℃, the upsetting and drawing process is repeated 3 times, and the forging ratio is 8.5, resulting in a forging module. After forging, the forging module is held at 850℃ for 12 hours for softening annealing.

[0037] S4. Ultrafine and spheroidizing annealing: The forging ingot from step S3 is subjected to ultrafine and spheroidizing annealing to obtain a forging annealed ingot.

[0038] The ultrafine refining process employs a two-stage heating method. First, the forging module is heated to 850℃±20℃ at a rate of 80℃ / h and held for 2 hours. Then, it is heated to 1020℃±10℃ at a rate of 100℃ / h and held for 5 hours. After the holding period, it is water-cooled for 35 minutes to cool to at least ≤300℃. After air-cooling to 190℃, it is placed in a furnace at 850℃±10℃ for spheroidizing annealing. It is held at 850℃±10℃ for 10 hours and then cooled to 600℃ at a rate of 10℃ / h before being removed from the furnace and air-cooled.

[0039] S5. Quenching and tempering treatment: The forged annealed ingot is subjected to quenching and tempering treatment of high temperature quenching and multiple low temperature tempering to obtain quenched and tempered ingot.

[0040] The tempering process is divided into high-temperature quenching and multiple tempering. The high-temperature quenching involves oil quenching the required module blank at 1000℃±5℃ for 30 minutes, followed by the first tempering at 590℃ for 2 hours and air cooling, the second tempering at 600℃ for 2 hours and air cooling, and the third tempering at 600℃ for 2 hours and air cooling, to achieve a high-toughness, high-thermal-conductivity hot work die steel with a target hardness of 45HRC.

[0041] Example 2 The actual composition of the hot work die steel of this invention, in mass percentage, is shown in Table 2:

[0042] Hot work die steel is produced as follows: S1. Vacuum induction melting: Vacuum induction melting is divided into several stages, including furnace loading, full melting, refining, sampling and composition adjustment, and casting, to obtain induction ingots. The weight of each raw material is determined according to the component content of the hot work die steel. To ensure that the levels of pollutants and residual elements meet the target requirements, the raw materials used are: ultra-low sulfur pure iron, with S≤0.0010% and P≤0.008%; high-purity graphite blocks with a carbon content ≥99.9%; industrial pure silicon 99.99%; metallic manganese 99.9%; metallic chromium 99.9%; molybdenum bars 99.9%; metallic niobium 99.9%; ferrovanadium; and metallic cerium. During the furnace charging stage, 2 / 3 of the furnace is filled with high-purity graphite blocks. Except for metallic chromium, high-purity manganese, industrial-grade silicon, metallic niobium, ferrovanadium, and metallic cerium, all other furnace materials are added. During the full melting stage, the temperature is raised to 1610℃, and 1.0 kg of high-purity graphite is added for deoxidation. After stirring for 24 minutes, high-purity chromium is added, and sampling ensures N ≤ 0.0015%. During the refining stage, the temperature is controlled at 1560℃ ± 10℃, with stirring at industrial frequency for 44 minutes. The refining time is 72 minutes, ensuring the carbon-oxygen reaction is essentially complete during refining. Argon is purged at 3600 Pa, and high-purity graphite blocks are added according to the designed C content. During the sampling and composition adjustment stage, high-purity manganese, industrial-grade silicon, metallic niobium, ferrovanadium, and metallic cerium are added to adjust the composition to the target value.

[0043] S2. Vacuum self-consumable melting: The induction ingot obtained in step S1 is first softened and annealed, then the riser of the induction ingot is cut off and the end is flattened. The surface is then machined or polished to make an electrode rod for vacuum consumable melting. Vacuum consumable melting consists of several stages, including arc initiation, normal melting, filling melting, and ingot cooling, to obtain the consumable ingot.

[0044] During the arc ignition stage, the arc ignition current is 2200–13800A and the arc ignition voltage is 20–24V. During the normal melting stage, the melting rate is controlled at 5.1–6 kg / min and the number of molten droplets is 1.0–6.0 / s. During the filling melting stage, the filling weight is set at 300–350 kg, and the remaining 50–80 kg of filling parameters are controlled by melting rate and molten droplets. The shrinkage melting rate is 5–2 kg / min and the filling time is 104 minutes.

[0045] S3. High-temperature homogenization and forging: The consumable ingot obtained in step S2 is subjected to high-temperature homogenization and then forged to obtain a forged ingot.

[0046] The high-temperature homogenization process employs a three-stage heating method: first, the temperature is held at 630℃ for 2 hours; then, the temperature is increased to 850℃±20℃ at a rate of 25℃ / h and held for 4 hours; finally, the temperature is increased to 1260℃±10℃ and held for 19 hours. After the high-temperature homogenization holding period, the consumable ingot is removed for forging. The initial forging temperature is ≥1050℃, the final forging temperature is ≥850℃, the upsetting and drawing process is repeated 3 times, and the forging ratio is 8.6, resulting in a forging module. After forging, the forging module is held at 850℃ for 12 hours for softening annealing.

[0047] S4 Ultrafine and Spheroidizing Annealing: The forging ingot from step S3 is subjected to ultrafine and spheroidizing annealing treatment to obtain a forging annealed ingot.

[0048] The ultrafine refining process employs a two-stage heating method. First, the forging module is heated to 850℃±20℃ at a rate of 80℃ / h and held for 2 hours. Then, it is heated to 1020℃±10℃ at a rate of 100℃ / h and held for 6 hours. After the holding period, it is water-cooled for 36 minutes to cool to at least ≤300℃. After air-cooling to 190℃, it is placed in a furnace at 850℃±10℃ for spheroidizing annealing. It is held at 850℃±10℃ for 12 hours and then cooled to 600℃ at a rate of 10℃ / h before being removed from the furnace and air-cooled.

[0049] S5. Quenching and tempering treatment: The forged annealed ingot is subjected to quenching and tempering treatment of high temperature quenching and multiple low temperature tempering to obtain quenched and tempered ingot.

[0050] The tempering process is divided into high-temperature quenching and multiple tempering. The high-temperature quenching involves oil quenching the required module blank at 1000℃±5℃ for 30 minutes, followed by the first tempering at 590℃ for 2 hours and air cooling, the second tempering at 605℃ for 2 hours and air cooling, and the third tempering at 600℃ for 2 hours and air cooling, to achieve a high-toughness, high-thermal-conductivity hot work die steel with a target hardness of 45HRC.

[0051] Example 3 The actual composition of the hot work die steel of this invention, in mass percentage, is shown in Table 3:

[0052] The production method of hot work die steel is as follows: S1. Vacuum induction melting: Vacuum induction melting is divided into several stages, including furnace charging, full melting, refining, sampling and composition adjustment, and casting, to obtain induction ingots. The weight of each raw material is determined according to the component content of the hot work die steel. To ensure that the levels of pollutants and residual elements meet the target requirements, the raw materials used are: ultra-low sulfur pure iron with S≤0.0010% and P≤0.008%; high-purity graphite blocks with a carbon content ≥99.9%; industrial pure silicon 99.99%; 99.9% metal; 99.9% metallic chromium; 99.9% molybdenum bars; 99.9% metallic niobium; ferrovanadium; and cerium. During the furnace charging stage, 2 / 3 of the high-purity graphite blocks are charged into the furnace, excluding metallic chromium, high-purity manganese, industrial pure silicon, metallic niobium, ferrovanadium, and cerium. In addition, all other furnace materials are charged into the furnace. During the full melting stage, the temperature is raised to 1620℃, and 0.8 kg of high-purity graphite is added for deoxidation. After stirring for 21 minutes, high-purity chromium is added, and sampling is conducted to ensure that N ≤ 0.0015%. During the refining stage, the temperature is controlled at 1560℃ ± 10℃, and the furnace is stirred at industrial frequency for 46 minutes. The refining time is 64 minutes. During the refining process, the carbon-oxygen reaction is ensured to be basically completed. Argon is purged at 3500 Pa, and high-purity graphite blocks are added according to the designed C content. During the sampling and composition adjustment stage, high-purity manganese, industrial-grade silicon, metallic niobium, ferrovanadium, and metallic cerium are added to adjust the composition to the target value.

[0053] S2. Vacuum self-consumable melting: The induction ingot obtained in step S1 is first softened and annealed, then the riser of the induction ingot is cut off and the end is flattened. The surface is then machined or polished to make an electrode rod for vacuum consumable melting. Vacuum consumable melting consists of several stages, including arc initiation, normal melting, filling melting, and ingot cooling, to obtain the consumable ingot.

[0054] During the arc ignition stage, the arc ignition current is 2200–13800A and the arc ignition voltage is 20–24V. During the normal melting stage, the melting rate is controlled at 5.1–6 kg / min and the number of molten droplets is 1.0–6.0 / s. During the filling melting stage, the filling weight is set at 300–350 kg, and the remaining 50–80 kg of filling parameters are controlled by melting rate and molten droplets. The shrinkage melting rate is 5–2 kg / min and the filling time is 109 minutes.

[0055] S3. High-temperature homogenization and forging: The consumable ingot obtained in step S2 is subjected to high-temperature homogenization and then forged to obtain a forged ingot.

[0056] The high-temperature homogenization process employs a three-stage heating method: first, the temperature is held at 620℃ for 2 hours; then, the temperature is increased to 850℃±20℃ at a rate of 25℃ / h and held for 3 hours; finally, the temperature is increased to 1260℃±10℃ and held for 18 hours. After the high-temperature homogenization holding period, the consumable ingot is removed for forging. The initial forging temperature is ≥1050℃, the final forging temperature is ≥850℃, the upsetting and drawing process is repeated 3 times, and the forging ratio is 8.5, resulting in a forging module. After forging, the forging module is held at 850℃ for 12 hours for softening annealing.

[0057] S4. Ultrafine and spheroidizing annealing: The forging ingot from step S3 is subjected to ultrafine and spheroidizing annealing to obtain a forging annealed ingot.

[0058] The ultrafine refining process employs a two-stage heating method. First, the forging module is heated to 850℃±20℃ at a rate of 80℃ / h and held for 2 hours. Then, it is heated to 1020℃±10℃ at a rate of 100℃ / h and held for 6 hours. After the holding period, it is water-cooled for 35 minutes to cool to at least ≤300℃. After air-cooling to 195℃, it is placed in a furnace at 850℃±10℃ for spheroidizing annealing. It is held at 850℃±10℃ for 12 hours and then cooled to 600℃ at a rate of 10℃ / h before being removed from the furnace and air-cooled.

[0059] S5. Quenching and tempering treatment: The forged annealed ingot is subjected to quenching and tempering treatment of high temperature quenching and multiple low temperature tempering to obtain quenched and tempered ingot.

[0060] The tempering process is divided into high-temperature quenching and multiple tempering. The high-temperature quenching involves oil quenching the required module blank at 1000℃±5℃ for 35 minutes, followed by the first tempering at 590℃ for 2 hours and air cooling, the second tempering at 600℃ for 2 hours and air cooling, and the third tempering at 600℃ for 2 hours and air cooling, to achieve a high-toughness, high-thermal-conductivity hot work die steel with a target hardness of 45HRC.

[0061] Comparative Example 1 Comparative Example 1 is an H11 steel produced using conventional EBT (electric furnace) + LF + VD + VAR (vacuum arc remelting) processes. The specific composition is shown in Table 4.

[0062] The specific steps include: S1. Electric furnace + LF + VD smelting: In the electric furnace stage: 800 kg of lime is placed at the bottom of the furnace before charging. Charging is then performed, followed by power-on melting. The carbon content (C) in the electric furnace charge is greater than 1.00%, and the tapping temperature is 1660–1690℃. In the LF furnace stage: Temperature is measured before entering the LF furnace, requiring an initial temperature ≥1540℃. 100–200 kg / furnace of refining slag and 700–800 kg of lime are added, with the prepared alloy added in the order of Fe–Si, high chromium, and low chromium. Carbon powder is used for diffusion deoxidation and slag formation. When the temperature reaches ≥1650℃, a complete analysis (including Al) is performed, followed by stirring and then slag decanting (S must be controlled ≤0.005% before slag decanting). After slag decanting, the slag is placed in the ladle, and 700–800 kg of lime, 100–200 kg of refining slag, and ≥20 kg of carbon powder are added. When the temperature reaches ≥1650℃, an additional 200 kg of quicklime, 80 kg of refining slag, and ≥10 kg of carbon powder are added. At a temperature of 1640–1660℃, Al is fed to 0.04%, and sponge zirconium is added at a rate of 10 kg / furnace. With S ≤ 0.002% and a temperature of 1680–1720℃, slag is removed using a ladle. After a slag thickness of 60–100 mm, the ladle is switched to vacuum degassing (VD). During VD: Ar is blown at a high flow rate of ≥150 L / min under an ultimate vacuum of ≤67 Pa for ≥35 min; approximately 1–2 min before breaking the vacuum, the Ar flow rate is adjusted to 20–40 L / min. Static Ar blowing time is ≥20 min to ensure the molten steel is not exposed to air and absorbs nitrogen. The ladle pouring temperature is 1525–1535℃. During the pouring stage: a pouring car is used, and the nozzle height is controlled to ≤50 mm. The resulting ingot is then obtained.

[0063] S2. Vacuum self-consumable melting: The ingot obtained in step S1 is first softened and annealed, then the riser is cut off and the end is flattened. The surface is then machined or polished to make an electrode rod for vacuum consumable melting. Vacuum consumable melting consists of several stages, including arc initiation, normal melting, filling melting, and ingot cooling, to obtain the consumable ingot.

[0064] During the arc ignition stage, the arc ignition current is 2200–13800A and the arc ignition voltage is 20–24V. During the normal melting stage, the melting rate is controlled at 5.1–6 kg / min and the number of molten droplets is 1.0–6.0 / s. During the filling melting stage, the filling weight is set at 300–350 kg, and the remaining 50–80 kg of filling parameters are controlled by melting rate and molten droplets. The shrinkage melting rate is 5–2 kg / min and the filling time is 105 minutes.

[0065] S3. High-temperature homogenization and forging: The vacuum consumable ingot obtained in step S2 is homogenized at high temperature and then forged to obtain a forged ingot.

[0066] The high-temperature homogenization process employs a three-stage heating method: first, the temperature is held at 620℃ for 4 hours; then, the temperature is increased to 850℃±20℃ at a rate of 25℃ / h and held for 6 hours; finally, the temperature is increased to 1260℃±10℃ and held for 18 hours. After the high-temperature homogenization holding period, the consumable ingot is removed for forging. The initial forging temperature is ≥1050℃, the final forging temperature is ≥850℃, the upsetting and drawing process is repeated 3 times, and the forging ratio is 8.3 to obtain the forging module. After forging, the forging module is held at 850℃ for 12 hours for softening annealing.

[0067] S4. Ultrafine and spheroidizing annealing: The forging ingot from step S3 is subjected to ultrafine and spheroidizing annealing to obtain a forging annealed ingot.

[0068] The ultrafine refining process employs a two-stage heating method. First, the forging module is heated to 850℃±20℃ at a rate of 80℃ / h and held for 7 hours. Then, it is heated to 1020℃±10℃ at a rate of 100℃ / h and held for 10 hours. After the holding period, it is water-cooled for 34 minutes to cool to at least ≤300℃ at the core. After air-cooling to 194℃, it is placed in a furnace at 850℃±10℃ for spheroidizing annealing. It is held at 850℃±10℃ for 12 hours and then cooled to 500℃ at a rate of 10℃ / h before being removed from the furnace and air-cooled.

[0069] S5. Quenching and tempering treatment: The forged annealed ingot is subjected to quenching and tempering treatment of high temperature quenching and multiple low temperature tempering to obtain quenched and tempered ingot.

[0070] The tempering process is divided into high-temperature quenching and multiple tempering. The high-temperature quenching involves placing the required module blank at 1000℃±5℃ for 30 minutes for oil quenching, followed by a first tempering at 590℃ for 2 hours and air cooling, a second tempering at 600℃ for 2 hours and air cooling, and a third tempering at 600℃ for 2 hours and air cooling, to achieve the target hardness of 45HRC for H11 hot work die steel.

[0071] Comparative Example 2 Comparative Example 2 is an H13 steel produced using conventional EBT (electric furnace) + LF + VD + ESR (electroslag remelting) processes. The specific composition is shown in Table 5.

[0072] The specific steps include: S1. Electric furnace + LF + VD smelting: In the electric furnace stage: 800 kg of lime is placed at the bottom of the furnace before charging, then the furnace is charged and energized for melting. The electric furnace charge has a carbon content > 1.00%, an oxidation endpoint carbon content ≤ 0.06%, a phosphorus content ≤ 0.005%, and a tapping temperature of 1660–1690℃. In the LF furnace stage: Temperature is measured before entering the LF furnace, requiring an inlet temperature ≥ 1540℃. 100–200 kg / furnace of refining slag and 700–800 kg of lime are added, with the prepared alloy added in the order of Fe–Si, high chromium, and low chromium. Carbon powder is used for diffusion deoxidation and slag formation. When the temperature reaches ≥ 1650℃, a sample is taken for complete analysis (including Al), stirred, and then decanted (S must be controlled ≤ 0.005% before decanting). After decanting, the slag is placed in the ladle, and 700–800 kg of lime, 100–200 kg of refining slag, and ≥ 20 kg of carbon powder are added. When the temperature reaches ≥1650℃, add 200 kg of quicklime, 80 kg of refining slag, and ≥10 kg of carbon powder. At 1640~1660℃, feed Al to 0.04%, and add sponge zirconium at 10 kg / furnace. At S≤0.002% and 1680~1720℃, remove slag using a ladle. With a slag thickness of 60~100mm, proceed to VD (vacuum treatment). VD stage: Under an ultimate vacuum of ≤67Pa, blow Ar at a high flow rate of ≥150L / min for ≥35min; approximately 1~2min before breaking the vacuum, adjust the Ar flow rate to 20~40L / min. Static Ar blowing time ≥20min to ensure the molten steel is not exposed to air and absorbs nitrogen. Ladle pouring temperature: 1525~1535℃. Pouring stage: Use a pouring car during pouring, controlling the nozzle height to ≤50mm. Obtain electroslag remelting electrode rods.

[0073] S2. Electroslag remelting: This specifically includes electrode rod annealing, surface cleaning and trimming, and electroslag remelting. The result is an electroslag remelted ingot.

[0074] During the electrode rod annealing process, the electrode rod is heated to 850-870℃ at a rate of ≤100℃ / h and held for ≥12h, then cooled to 300℃ at a rate of ≤50℃ / h before being removed from the furnace. The electrode rod is then surface-machined and the riser end is cut off. A dummy electrode is welded to the tail of the electrode rod, and remelting is initiated from the riser end (end A). Ar is used throughout the process, with a flow rate of 60-180 L / min. The slag system is CaF2:Al2O3 = 70:30 (%), using pre-melted slag. The slag material is weighed strictly according to the process and baked at 700-800℃ for ≥6 hours before use. After the protective atmosphere electroslag furnace is closed, Ar gas is introduced to purge the air from the furnace. Power is only supplied after the oxygen concentration meter detects that the O2 in the furnace atmosphere is ≤1000ppm. Oxygen concentration is continuously monitored for up to 2 hours after power supply, and the Ar gas flow rate is selected to maintain O2 ≤800ppm. Then, maintain the Ar gas flow rate at which O2 ≤ 800 ppm is maintained until remelting is complete. The electroslag remelting feeding stage employs a two-stage method of melting rate control + power control, with a final weight of ≥ 100 kg.

[0075] S3. High-temperature homogenization and forging: The electroslag remelted ingot obtained in step S2 is subjected to high-temperature homogenization and then forged to obtain a forged ingot.

[0076] The high-temperature homogenization process employs a three-stage heating method: first, the temperature is held at 620℃ for 2 hours; then, the temperature is increased to 860℃±20℃ at a rate of 25℃ / h and held for 4 hours; finally, the temperature is increased to 1260℃±10℃ and held for 18 hours. After the high-temperature homogenization holding period, the consumable ingot is removed for forging. The initial forging temperature is ≥1050℃, the final forging temperature is ≥850℃, the upsetting and drawing process is repeated 3 times, and the forging ratio is 8.5 to obtain the forging module. After forging, the forging module is held at 860℃ for 12 hours for softening annealing.

[0077] S4. Ultrafine and spheroidizing annealing: The forging ingot from step S3 is subjected to ultrafine and spheroidizing annealing to obtain a forging annealed ingot.

[0078] The ultrafine refining process employs a two-stage heating method. First, the forging module is heated to 840℃±20℃ at a rate of 80℃ / h and held for 7 hours. Then, it is heated to 1020℃±10℃ at a rate of 100℃ / h and held for 10 hours. After the holding period, it is water-cooled for 35 minutes to cool to at least ≤300℃. After air-cooling to 192℃, it is placed in a furnace at 860℃±10℃ for spheroidizing annealing. It is held at 860℃±10℃ for 12 hours and then cooled to 500℃ at a rate of 10℃ / h before being removed from the furnace and air-cooled.

[0079] S5. Quenching and tempering treatment: The forged annealed ingot is subjected to quenching and tempering treatment of high temperature quenching and multiple low temperature tempering to obtain quenched and tempered ingot.

[0080] The tempering process is divided into high-temperature quenching and multiple tempering. The high-temperature quenching involves oil quenching the required module blank at 1020℃±5℃ for 30 minutes, followed by a first tempering at 590℃ for 2 hours and air cooling, a second tempering at 610℃ for 2 hours and air cooling, and a third tempering at 600℃ for 2 hours and air cooling, to achieve the target hardness of 45HRC for H13 hot work die steel.

[0081] The physical properties of the mold steels prepared in Examples 1-3 and Comparative Examples 1-2 were tested for inclusion rating, and the data in Table 6 are as follows:

[0082] Based on the analysis in Table 6, the hot work die steels prepared in Examples 1-3 of the present invention have higher purity than the die steels prepared in Comparative Examples 1-2. Furthermore, the die steels prepared in the present invention reach the following grades: AT0, AH0, BT≤1, BH≤0.5, CT0, CH0, DT≤1, DH≤0.5, and DS0.

[0083] The physical property tests of inclusion number density were performed on the mold steels obtained in Examples 1-3 and Comparative Examples 1-2 using ASPEX fully automated inclusion analysis, and the data are shown in Table 7.

[0084] Analysis based on Table 7 shows that the hot work die steels obtained in Examples 1-3 of the present invention have higher purity than the die steels obtained in Comparative Examples 1-2, and the inclusion density of the die steels obtained by the present invention is ≤1 inclusion / mm². 2 .

[0085] The physical properties of the mold steels prepared in Examples 1-3 and Comparative Examples 1-2, including their coefficient of thermal expansion and thermal conductivity, were tested, and the data are shown in Table 8.

[0086] Based on the analysis in Table 8, under the same coefficient of thermal expansion, the hot work die steels prepared in Examples 1-3 of the present invention have better thermal conductivity than the die steels prepared in Comparative Examples 1-2, indicating that the die steels prepared in the present invention have good thermal conductivity.

[0087] The physical properties of the die steels prepared in Examples 1-3 and Comparative Examples 1-2 were tested for Rockwell hardness and V-notch Charpy impact energy, and the data are shown in Table 9:

[0088] Based on the analysis in Table 9, at the same Rockwell hardness, the hot work die steels prepared in Examples 1-3 of the present invention have better V-notch Charpy impact energy compared with the die steels prepared in Comparative Examples 1-2, indicating that the die steels prepared in the present invention have good toughness and ductility.

Claims

1. Hot work die steel, characterized in that: Based on the mass percentage of chemical composition: C 0.34%–0.38%, Mn 0.20%–0.40%, Si 0.05%–0.2%, Cr 5.50%–6.00%, Mo 1.40%–1.70%, V 0.65%–0.75%, Nb 0.005%–0.015%, Ce 0.01%–0.08%, Ni ≤0.10%, Cu ≤0.060%, S ≤0.0015%, P ≤0.010%, and the residual gas content is: H ≤1ppm, O ≤10ppm, N ≤30ppm, the five harmful elements: Pb+Sn+As+Sb+Bi≤0.01%, the remainder is Fe and unavoidable impurities.

2. The hot work die steel according to claim 1, characterized in that: The raw materials used include: ultra-low sulfur pure iron, with pure iron requirements of S≤0.0010% and P≤0.008%; high-purity graphite blocks with carbon content ≥99.9%; industrial pure silicon 99.99%; metallic manganese 99.9%, metallic chromium 99.9%, molybdenum bars 99.9%, metallic niobium 99.9%, ferrovanadium and metallic cerium.

3. A method for producing hot work die steel, characterized in that... Includes the following steps: S1. Vacuum induction melting, including loading the raw materials of the above components into the furnace, melting them completely, refining them, sampling and adjusting the composition, and casting them to obtain induction ingots; S2. Vacuum consumable melting: The induction casting ingot is made into an electrode rod, which is then subjected to arc ignition, normal melting, filling melting and ingot cooling to obtain a consumable ingot. S3. High-temperature homogenization and forging: The consumable ingot is homogenized at high temperature and then forged to obtain a forged ingot; S4. Ultrafine and spheroidizing annealing: The forging ingot is subjected to ultrafine and spheroidizing annealing treatment to obtain the forging annealed ingot; S5. Quenching and tempering treatment: The forged annealed ingot is subjected to high-temperature quenching and multiple low-temperature tempering treatments to obtain a quenched and tempered ingot.

4. The method for producing hot work die steel according to claim 3, characterized in that: In the furnace loading stage of step S1, 2 / 3 of the high-purity graphite blocks are loaded into the furnace. Except for metallic chromium, metallic manganese, industrial pure silicon, metallic niobium, ferrovanadium and metallic cerium, the remaining raw materials are loaded into the furnace. In the sampling and composition adjustment stage of step S1, high-purity manganese, industrial pure silicon, metallic niobium, ferrovanadium and metallic cerium are added to adjust the composition to the target value.

5. The method for producing hot work die steel according to claim 4, characterized in that: In the full melting stage of step S1, the temperature is raised to 1600-1620℃, 0.5-1.5 kg of high-purity graphite blocks are added for deoxidation, and after stirring for 20-25 minutes, high-purity chromium is added. Samples are taken to ensure that N ≤ 0.0015%. In the refining stage of step S1, the temperature is controlled at 1560℃±10℃, the stirring is carried out at industrial frequency for ≥30min, the refining time is controlled at ≥60min, argon is purged at 2800~4500Pa, and high-purity graphite blocks are added according to the designed C content. Furthermore, during the pouring process in step S1, it must be ensured that the pouring height is greater than 2 / 3 of the riser height.

6. The method for producing hot work die steel according to claim 3, characterized in that: In step S2, during the arc initiation stage of vacuum self-consumption, the arc initiation current is 2200–13800A; the arc initiation voltage is 20–24V. In the normal smelting stage of step S2, the melting rate is controlled at 4.7 to 6 kg / min, with an allowable fluctuation range of ±15%, and the droplet count is adjusted from 1.0 to 6.0 / s, with an allowable fluctuation range of ±2. In the filling and melting stage of step S2, the filling weight is set to 300-350 kg, and the remaining 50-80 kg filling parameters are controlled by melting rate + dripping rate. The feeding melting rate is 5-2 kg / min, and the filling time is controlled to be 80-120 minutes.

7. The method for producing hot work die steel according to claim 3, characterized in that: In step S3, the high-temperature homogenization adopts a three-stage heating process: first, it is held at 600-660℃ for ≥2h, then heated to 850℃±20℃ at a heating rate of ≤30℃ / h and held for ≥3h, and then heated to 1260℃±10℃ and held for ≥16h.

8. The method for producing hot work die steel according to claim 7, characterized in that: After the high-temperature homogenization and heat preservation is completed, the consumable ingot is taken out for forging. The initial forging temperature is ≥1050℃, the final forging temperature is ≥850℃, the number of upsetting and drawing is ≥3, and the forging ratio is greater than or equal to 8 to obtain the forging module. After the forging is completed, the forging module is kept at 850℃±10℃ for ≥10h for softening annealing.

9. The method for producing hot work die steel according to claim 3, characterized in that: In step S4, the ultrafine refining process will employ a two-stage heating method. First, the forging module will be heated to 840℃±20℃ at a rate of ≤100℃ / h and held for ≥2h. Then, it will be heated to 1000℃±10℃ at a rate of ≤100℃ / h and held for ≥5h. After the holding period, it will be water-cooled for ≥30min to cool to at least the core temperature ≤300℃. After air-cooling to ≤200℃, it can be placed in a furnace at 840℃±10℃ for spheroidizing annealing. It will be held at 850℃±10℃ for ≥8h, and then cooled to 600℃ at a rate of 10℃ / h before being removed from the furnace and air-cooled.

10. The method for producing hot work die steel according to claim 3, characterized in that: In step S5, the tempering process is divided into high-temperature quenching and multiple tempering. The high-temperature quenching involves heating the required module blank at 980℃~1020℃ until it is thoroughly heated and held for ≥30min, followed by oil quenching, and then multiple temperings at 560℃~630℃, with each tempering time ≥2h.

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