Vacuum differential temperature heat treatment method for large-scale die-casting mold

Abstract

The application discloses a large-scale die-casting die vacuum differential temperature heat treatment method, which comprises the following steps: stress relief annealing treatment is performed on the large-scale die-casting die; a temperature measuring thermocouple is arranged on the surface and the core of the large-scale die-casting die before loading into a furnace; the large-scale die-casting die is heated in a vacuum furnace; a certain temperature difference is formed between the surface and the core of the die by controlling the heating process, so that the surface of the large-scale die-casting die is fully austenitized, and the core of the large-scale die-casting die is austenitized at a lower temperature; the large-scale die-casting die is cooled and quenched, then is taken out of the furnace and air-cooled until the surface temperature reaches a specified temperature, and then is immediately loaded into the furnace for several times of tempering, so that the hardness is adjusted to 44-46HRC. The large-scale die-casting die vacuum differential temperature heat treatment method improves the heat fatigue resistance and high-temperature stability of the die surface, strengthens the toughness of the core of the die, reduces the internal stress formed in the quenching process, eliminates the overall cracking risk of the die, reduces the heat treatment deformation of the die, and prolongs the service life of the die.

Description

Technical Field

[0001] This invention relates to the field of heat treatment technology for hot work molds, and more particularly to a vacuum differential temperature heat treatment method for large die-casting molds. Background Technology

[0002] Large die-casting molds are core equipment in die-casting production. They operate under complex conditions of high temperature, high pressure, alternating thermal shock, and mechanical impact for extended periods, placing extremely high demands on the mold's surface thermal fatigue resistance, high-temperature stability, overall toughness, and crack resistance. Currently, the industry's conventional heat treatment process for hot-work die-casting molds such as H11, 4Cr5Mo1V, and 4Cr5Mo2V mostly employs an overall isothermal heating process. During heating, the entire mold is held at the normal austenitizing temperature range for an extended period to achieve full austenitization.

[0003] Existing conventional heat treatment processes have significant technical drawbacks in the processing of large die-casting molds: Large molds have a large overall volume and uneven wall thickness, making it impossible to achieve differentiated austenitization control between the mold surface and core using conventional isothermal heating methods. While conventional heating achieves normal austenitization temperatures for both the mold surface and core through prolonged holding within the normal austenitization temperature range, the mold surface achieves better microstructure and properties during quenching due to its rapid cooling rate. However, the core cools slowly, and under conditions of full austenitization, the slow cooling process at the core leads to the precipitation of carbides along grain boundaries, resulting in a significant reduction in core toughness. Furthermore, the high core temperature angle causes a large temperature difference between the core and surface during quenching, leading to substantial internal stress. After heat treatment, molds generally exhibit low core toughness and high overall internal stress, resulting in a high risk of cracking during both heat treatment and actual die-casting operations. This significantly shortens mold lifespan, increases mold replacement costs and downtime costs in die-casting production, and severely restricts the large-scale and stable production of large precision die-casting products. Summary of the Invention

[0004] In view of the aforementioned deficiencies in the prior art, the technical problem to be solved by the present invention is the insufficient core toughness and high internal stress during quenching and cooling of existing large die-casting molds using conventional heat treatment processes. The present invention provides a vacuum differential temperature heat treatment method for large die-casting molds. Through a synergistic process design of vacuum differential temperature gradient heating, high-pressure quenching, and multiple precise tempering processes, it simultaneously improves the mold surface's resistance to thermal fatigue and high-temperature stability, strengthens the core toughness of the mold, reduces internal stress formed during quenching, eliminates the risk of overall mold cracking, reduces mold heat treatment deformation, extends mold service life, and reduces die-casting production costs.

[0005] To achieve the above objectives, the present invention provides a vacuum differential temperature heat treatment method for large die-casting molds, comprising the following steps:

[0006] S1, stress-relieving annealing treatment for large die-casting molds;

[0007] S2, Before vacuum heat treatment of large die-casting molds, place thermocouples on the surface and core of the large die-casting molds.

[0008] S3, the large die-casting mold is placed in a vacuum furnace and heated. By controlling the heating process, a certain temperature difference is achieved between the surface and core of the mold, so that the surface of the large die-casting mold is fully austenitized while the core of the large die-casting mold is austenitized at a lower temperature.

[0009] S4. Large die-casting molds are cooled and quenched using a pressure of not less than 8 Bar. The quenching process is completed when the core temperature of the large die-casting mold reaches below 150°C. The mold is then removed from the furnace and air-cooled.

[0010] S5. After the large die-casting mold is quenched, it is air-cooled until the surface temperature reaches the specified temperature, and then immediately put into the furnace for tempering. Several tempering cycles are used to adjust the hardness of the large die-casting mold to 44-46HRC.

[0011] Furthermore, S1, stress-relief annealing is performed on the large die-casting mold, specifically including placing the large die-casting mold in a heating furnace and heating it to 650°C, holding it at that temperature, and then air-cooling or furnace-cooling it to room temperature. The holding time is calculated based on the effective thickness of the large die-casting mold, with 60 minutes of holding time per 25mm.

[0012] Furthermore, S2, before vacuum heat treatment of the large die-casting mold, thermocouples are placed on the surface and core of the large die-casting mold. Specifically, the thermocouples are placed in the process holes or water channel holes of the large die-casting mold and fixed. The entrance of the hole is sealed with refractory mud or insulation cotton. The temperature measuring point of the surface thermocouple is 15-20mm away from the surface, and the temperature measuring point of the core thermocouple is placed at the centroid of the entire mold.

[0013] Furthermore, the large die-casting mold is placed in a vacuum furnace for heating. Specifically, the furnace temperature is first raised to 650°C and held at that temperature. When the core temperature reaches 5-10°C lower than the set furnace temperature, the holding period ends.

[0014] Next, raise the furnace temperature to 850℃ and hold it there. When the core temperature is 5-10℃ lower than the set furnace temperature, end the holding period.

[0015] Raise the furnace temperature to 950-970℃ and hold it there. When the core temperature is 10℃ lower than the set furnace temperature, hold it there for another 60 minutes and then stop holding.

[0016] Raise the furnace temperature to the final austenitizing temperature of 1010-1040℃ and hold it at that temperature. When the surface temperature reaches 5℃ lower than the set furnace temperature, stop holding and begin quenching.

[0017] Furthermore, the large die-casting mold is placed in a vacuum furnace and heated, specifically as follows:

[0018] a. Raise the furnace temperature to 650℃ at a heating rate of 3-4℃ / min and hold it at that temperature. Stop holding the temperature when the core temperature is 5-10℃ lower than the set furnace temperature.

[0019] b. Raise the furnace temperature to 850℃ at a heating rate of 3-4℃ / min and hold it at that temperature. Stop holding the temperature when the core temperature is 5-10℃ lower than the set furnace temperature.

[0020] c. Raise the furnace temperature to 950-970℃ at a heating rate of 5-10℃ / min and hold it at that temperature. When the core temperature reaches 10℃ lower than the set furnace temperature, hold it for another 60 minutes to end the holding period.

[0021] d. Raise the furnace temperature to the final austenitizing temperature of 1010-1040℃ at a heating rate of 10-15℃ / min and hold it at that temperature. When the surface temperature reaches 5℃ lower than the set furnace temperature, stop holding and start quenching.

[0022] Furthermore, in S4, the mold is cooled and quenched using a pressure of not less than 8 Bar, so that the surface of the mold is cooled to 330-350°C at a cooling rate of not less than 28°C / min, and the surface cooling rate is controlled at 9-12°C / min until the core temperature reaches 150°C, at which point the mold is removed from the furnace and air-cooled.

[0023] Furthermore, after the mold is quenched, it is air-cooled until the surface temperature reaches 50-60℃, and then immediately put into the furnace for tempering. Four tempering cycles are used to adjust the mold hardness to 44-46HRC.

[0024] Furthermore, stress-relief annealing of large die-casting molds also includes cleaning the oxide layer, oil, iron filings and / or other impurities from the surface of the large die-casting molds.

[0025] Furthermore, the power of the vacuum furnace is set to 800-1000KW.

[0026] Furthermore, it is applicable to various mainstream large hot work die casting mold steels such as H11, 4Cr5Mo1V, and 4Cr5Mo2V.

[0027] This invention provides a vacuum differential temperature heat treatment method for large die-casting molds, which has the following technical effects:

[0028] 1. Rapid and complete austenitization, resulting in extremely high high-temperature stability and thermal fatigue resistance of the mold surface: After the mold is heated uniformly at a lower austenitizing temperature, the temperature is rapidly increased to heat the mold surface to the normal austenitizing temperature of the material. This process can increase the austenite nucleation rate, resulting in finer austenite grains. In the subsequent rapid cooling process, finer martensite structure can be obtained, resulting in higher thermal stability, toughness and thermal fatigue resistance.

[0029] 2. The mold core is kept at a low austenitizing temperature, and the core can obtain higher toughness after quenching: The mold core is kept in a low austenitizing temperature range throughout the heating process. During quenching and cooling, the core position can ensure that sufficient martensite structure is obtained and the precipitation of intergranular carbides can be effectively alleviated. The toughness of the material is more than twice that of conventional heat treatment process, which greatly reduces the risk of cracking of large die casting molds in heat treatment and die casting process.

[0030] 3. Less internal stress during heat treatment and less deformation during mold heat treatment: Due to the relatively low temperature in the core of the mold, the temperature difference between the inside and outside of the mold is smaller during quenching and cooling, resulting in less internal stress. The deformation of the mold is reduced from 0.3% in the industry to less than 0.15%.

[0031] 4. Wide adaptability and strong practicality: It is specifically adapted to a variety of mainstream large hot work die casting mold steels such as H11, 4Cr5Mo1V, and 4Cr5Mo2V. It has strong process versatility and can be widely used in the heat treatment processing of various large precision die casting molds, effectively extending the service life of the molds and reducing the mold procurement, maintenance, and downtime production costs of enterprises. It has extremely high industrial promotion value.

[0032] The following will further explain the concept, specific structure, and technical effects of the present invention in order to fully understand the purpose, features, and effects of the present invention. Detailed Implementation

[0033] To make the technical problems, solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0034] In the following description, specific details, such as particular internal procedures and techniques, are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will appreciate that the invention may be practiced in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of the invention with unnecessary detail.

[0035] This invention provides a vacuum differential temperature heat treatment method for large die-casting molds, comprising the following steps:

[0036] S1, stress-relief annealing treatment of large die-casting molds; specifically, this includes placing the large die-casting mold in a heating furnace and heating it to 650°C, holding it at that temperature, and then air-cooling or furnace-cooling it to room temperature. The holding time is calculated based on the effective thickness of the large die-casting mold, with 60 minutes of holding time per 25mm. After stress-relief annealing treatment of large die-casting molds, it also includes cleaning the oxide layer, oil stains, iron filings and / or other impurities from the surface of the large die-casting mold.

[0037] S2. Before vacuum heat treatment of large die-casting molds, place thermocouples on the surface and core of the molds. Specifically, place and fix the thermocouples in the process holes or water channels of the large die-casting molds. Seal the entrances of the holes with refractory clay or insulation cotton. The temperature measuring point of the surface thermocouple should be 15-20mm away from the surface, and the temperature measuring point of the core thermocouple should be placed at the centroid of the entire mold. Specifically, both the surface and core thermocouples need to be inserted into the process holes or water channels, but to the same depth. Large molds will have process holes drilled near the centroid for temperature measurement. Therefore, the core thermocouple is placed in the process holes or water channels of the mold (at the centroid of the entire mold).

[0038] S3. The large die-casting mold is placed in a vacuum furnace for heating. Specifically, the furnace temperature is first raised to 650℃ and held until the core temperature is 5-10℃ lower than the set furnace temperature. Then, the furnace temperature is raised to 850℃ and held until the core temperature is 5-10℃ lower than the set furnace temperature. Next, the furnace temperature is raised to 950-970℃ and held until the core temperature is 10℃ lower than the set furnace temperature, then held for another 60 minutes. Finally, the furnace temperature is raised to the final austenitizing temperature of 1010-1040℃ and held until the surface temperature is 5℃ lower than the set furnace temperature, at which point the holding period ends and quenching begins. By controlling the heating process, a certain temperature difference is created between the mold surface and the core, allowing the surface of the large die-casting mold to be fully austenitized while the core of the large die-casting mold is austenitized at a lower temperature.

[0039] Specifically:

[0040] a. Raise the furnace temperature to 650℃ at a heating rate of 3-4℃ / min and hold it at that temperature. Stop holding the temperature when the core temperature is 5-10℃ lower than the set furnace temperature.

[0041] b. Raise the furnace temperature to 850℃ at a heating rate of 3-4℃ / min and hold it at that temperature. Stop holding the temperature when the core temperature is 5-10℃ lower than the set furnace temperature.

[0042] c. Raise the furnace temperature to 950-970℃ at a heating rate of 5-10℃ / min and hold it at that temperature. When the core temperature reaches 10℃ lower than the set furnace temperature, hold it for another 60 minutes to end the holding period.

[0043] d. Raise the furnace temperature to the final austenitizing temperature of 1010-1040℃ at a heating rate of 10-15℃ / min and hold it at that temperature. When the surface temperature reaches 5℃ lower than the set furnace temperature, stop holding and start quenching.

[0044] S4. Large die-casting molds are cooled and quenched using a pressure of not less than 8 Bar. The quenching is completed when the core temperature of the large die-casting mold reaches below 150°C, and the mold is then air-cooled. Specifically, the mold is cooled and quenched using a pressure of not less than 8 Bar, so that the surface of the mold is cooled to 330-350°C at a cooling rate of not less than 28°C / min. The surface cooling rate is controlled at 9-12°C / min, and the quenching is completed when the core temperature reaches 150°C, and the mold is then air-cooled.

[0045] S5. After quenching, the large die-casting mold is air-cooled until the surface temperature reaches the specified temperature, and then immediately placed in the furnace for tempering. Several tempering cycles are used to adjust the hardness of the large die-casting mold to 44-46 HRC. Specifically, after quenching, the mold is air-cooled until the surface temperature reaches 50-60℃, and then immediately placed in the furnace for tempering. Four tempering cycles are used to adjust the mold hardness to 44-46 HRC.

[0046] The power of the vacuum furnace is set to 800-1000KW.

[0047] The following example illustrates a vacuum differential temperature heat treatment method for large die-casting molds provided by this invention.

[0048] This invention provides a vacuum differential temperature heat treatment process for a large die-casting mold. The mold is made of H11 and has dimensions of 2000*680*560mm. The process specifically includes the following steps:

[0049] 1. Stress relief treatment of mold

[0050] First, a low-temperature stress-relief annealing treatment is performed to remove forging stress and residual stress from machining inside the mold. The stress-relief process is as follows: the furnace temperature is raised to 670℃ at a heating rate of 3.5℃ / min and held for 1360 minutes before being removed from the furnace and air-cooled. After the stress-relief treatment, the mold is naturally air-cooled to room temperature. All impurities, such as oxide layer, oil, and iron filings, are cleaned from the mold surface to ensure that the mold surface is clean and free of defects. This prevents impurities from affecting the subsequent vacuum heat treatment effect and also eliminates heat treatment deformation and crack defects caused by residual stress.

[0051] 2. Arrangement of furnace loading and thermocouples

[0052] After stress relief treatment, the mold is placed stably on the vacuum furnace tooling support to ensure uniform stress distribution and orderly placement, preventing deformation during heating. Based on the mold's dimensions, wall thickness, and structural characteristics, surface thermocouples (15-20mm deep) are placed on the typical working and forming surfaces of the mold. Core thermocouples are placed in the mold's centroid region to ensure real-time and accurate acquisition of surface and core temperature data.

[0053] 3. Vacuum gradient differential temperature heating and austenitization

[0054] Place the mold in a vacuum furnace. The vacuum furnace must have sufficient power (800-1000KW) to ensure the smooth completion of the following steps. Set the heating process according to the mold size. The specific steps are as follows:

[0055] a. Raise the furnace temperature to 650℃ at a heating rate of 3.5℃ / min and hold it at that temperature. Stop holding the temperature when the core temperature is 10℃ lower than the set furnace temperature.

[0056] b. Raise the furnace temperature to 850℃ at a heating rate of 3.5℃ / min and hold. Stop holding when the core temperature is 5℃ lower than the set furnace temperature.

[0057] c. Raise the furnace temperature to 950℃ at a heating rate of 6℃ / min and hold it at that temperature. When the core temperature reaches 10℃ lower than the set furnace temperature, hold it for another 60 minutes to end the holding period. Ensure that the mold is kept at a temperature lower than the normal austenitizing temperature so that the core of the mold can achieve austenitization under sub-temperature conditions.

[0058] d. Raise the furnace temperature to the final austenitizing temperature of 1020℃ at a heating rate of 15℃ / min and hold it at that temperature. When the surface temperature reaches 5℃ lower than the set furnace temperature, stop holding and start quenching. This step aims to rapidly austenitize the mold surface at the normal austenitizing temperature, while keeping the mold core in a sub-temperature austenitizing state, so that the mold surface can obtain high temperature resistance and the core can obtain high toughness in the next step.

[0059] 4. High-pressure rapid quenching and cooling

[0060] After the austenitizing process is completed, the high-pressure gas quenching system is immediately started, using high-purity nitrogen as the cooling medium. The quenching cooling pressure is controlled to be no less than 8 Bar, so that the mold surface is cooled to 350°C at a cooling rate of no less than 28°C / min. This allows the austenite structure on the mold surface to be fully transformed into a fine and uniform martensite structure. After that, the cooling rate of the mold surface is controlled to be 9-12°C / min, and the mold core is cooled to below 150°C before being removed from the furnace and air-cooled. When the mold surface temperature reaches 50-60°C, it is immediately put into the furnace for tempering.

[0061] 5. Four tempering processes and hardness control

[0062] A four-stage tempering process is employed to fully transform the mold's microstructure and release residual quenching stress within the mold. In this step, the main purpose of tempering is to adjust hardness, remove heat treatment stress, and promote the complete transformation of the quenched structure into a tempered structure. After three tempering cycles, hardness adjustment and microstructure transformation are essentially complete. The fourth tempering cycle primarily removes the stress regenerated during the third microstructure transformation. At this point, the objectives of tempering are essentially achieved. The specific steps are as follows:

[0063] First tempering process: Heat to 250℃ at a rate of 1.5℃ / min and hold for 120 minutes, then heat to 540℃ at a rate of 1.5℃ / min and hold for 1360 minutes, then air cool to room temperature.

[0064] Second tempering process: Heat to 250℃ at a rate of 1.5℃ / min and hold for 120 minutes, then heat to 580℃ at a rate of 1.5℃ / min and hold for 1360 minutes before air cooling.

[0065] The third tempering process: heat to 250℃ at a rate of 1.5℃ / min and hold for 120 minutes, then heat to 560℃ at a rate of 1.5℃ / min and hold for 1360 minutes before air cooling.

[0066] The fourth tempering process: heat to 250℃ at a rate of 1.5℃ / min and hold for 120 minutes, then heat to 550℃ at a rate of 1.5℃ / min and hold for 1360 minutes before air cooling.

[0067] 6. After the mold is tempered, the hardness of the mold is tested and found to be 44-46 HRC. The surface microstructure of the mold is fine and uniform, without heat treatment defects such as intergranular carbide precipitation. The notched impact energy of the surface sample is 25 J, and the notched impact energy of the core sample is 16 J, which is much higher than the 6-8 J level of conventional treatment.

[0068] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A vacuum differential temperature heat treatment method for large die-casting molds, characterized in that, Includes the following steps: S1, stress-relieving annealing treatment for large die-casting molds; S2, Before vacuum heat treatment of large die-casting molds, place thermocouples on the surface and core of the large die-casting molds. S3, the large die-casting mold is placed in a vacuum furnace and heated. By controlling the heating process, a certain temperature difference is achieved between the surface and core of the mold, so that the surface of the large die-casting mold is fully austenitized while the core of the large die-casting mold is austenitized at a lower temperature. S4. Large die-casting molds are cooled and quenched using a pressure of not less than 8 Bar. The quenching process is completed when the core temperature of the large die-casting mold reaches below 150°C. The mold is then removed from the furnace and air-cooled. S5. After the large die-casting mold is quenched, it is air-cooled until the surface temperature reaches the specified temperature, and then immediately put into the furnace for tempering. Several tempering cycles are used to adjust the hardness of the large die-casting mold to 44-46HRC.

2. The vacuum differential temperature heat treatment method for a large die-casting mold as described in claim 1, characterized in that, S1, stress-relief annealing treatment for large die-casting molds, specifically includes placing the large die-casting mold in a heating furnace and heating it to 650°C, holding it at that temperature, and then air-cooling or furnace-cooling it to room temperature. The holding time is calculated based on the effective thickness of the large die-casting mold, with 60 minutes of holding time per 25mm.

3. The vacuum differential temperature heat treatment method for a large die-casting mold as described in claim 1, characterized in that, S2. Before vacuum heat treatment of large die-casting molds, place thermocouples on the surface and core of the large die-casting molds. Specifically, place the thermocouples in the process holes or water channels of the large die-casting molds and fix them. Seal the entrance of the holes with refractory mud or insulation cotton. The temperature measuring point of the surface thermocouple is 15-20mm away from the surface, and the temperature measuring point of the core thermocouple is placed at the centroid of the entire mold.

4. The vacuum differential temperature heat treatment method for a large die-casting mold as described in claim 1, characterized in that, The large die-casting mold is placed in a vacuum furnace for heating. Specifically, the furnace temperature is first raised to 650°C and held at that temperature. When the core temperature reaches 5-10°C lower than the set furnace temperature, the holding time is ended. Next, raise the furnace temperature to 850℃ and hold it there. When the core temperature is 5-10℃ lower than the set furnace temperature, end the holding period. Then raise the furnace temperature to 950-970℃ and hold it there. When the core temperature is 10℃ lower than the set furnace temperature, hold it there for another 60 minutes and then end the holding process. Raise the furnace temperature to the final austenitizing temperature of 1010-1040℃ and hold it at that temperature. When the surface temperature reaches 5℃ lower than the set furnace temperature, stop holding and begin quenching.

5. The vacuum differential temperature heat treatment method for a large die-casting mold as described in claim 4, characterized in that, The large die-casting mold is placed in a vacuum furnace and heated, specifically as follows: a. Raise the furnace temperature to 650℃ at a heating rate of 3-4℃ / min and hold it at that temperature. Stop holding the temperature when the core temperature is 5-10℃ lower than the set furnace temperature. b. Raise the furnace temperature to 850℃ at a heating rate of 3-4℃ / min and hold it at that temperature. Stop holding the temperature when the core temperature is 5-10℃ lower than the set furnace temperature. c. Raise the furnace temperature to 950-970℃ at a heating rate of 5-10℃ / min and hold it at that temperature. When the core temperature reaches 10℃ lower than the set furnace temperature, hold it for another 60 minutes to end the holding period. d. Raise the furnace temperature to the final austenitizing temperature of 1010-1040℃ at a heating rate of 10-15℃ / min and hold it at that temperature. When the surface temperature reaches 5℃ lower than the set furnace temperature, stop holding and start quenching.

6. The vacuum differential temperature heat treatment method for a large die-casting mold as described in claim 5, characterized in that, S4. The mold is cooled and quenched using a pressure of not less than 8 Bar, so that the surface of the mold is cooled to 330-350°C at a cooling rate of not less than 28°C / min. The surface cooling rate is controlled at 9-12°C / min until the core temperature reaches 150°C, at which point the mold is removed from the furnace and air-cooled.

7. The vacuum differential temperature heat treatment method for a large die-casting mold as described in claim 6, characterized in that, After the mold is quenched, it is air-cooled until the surface temperature reaches 50-60℃, and then immediately put into the furnace for tempering. The mold hardness is adjusted to 44-46HRC by tempering four times.

8. The vacuum differential temperature heat treatment method for a large die-casting mold as described in claim 2, characterized in that, Stress-relief annealing of large die-casting molds also includes cleaning the oxide layer, oil, iron filings and / or other impurities from the surface of the large die-casting molds.

9. The vacuum differential temperature heat treatment method for a large die-casting mold as described in claim 1, characterized in that, The power of the vacuum furnace is set to 800-1000KW.

10. The vacuum differential temperature heat treatment method for a large die-casting mold as described in claim 1, characterized in that, It is suitable for various mainstream large hot work die casting mold steels such as H11, 4Cr5Mo1V, and 4Cr5Mo2V.