Many units that use quenching injection molds also use this steel to make injection molds. This steel has good strength, toughness, and heat resistance balance, and its machinability is also very good. The hardness before heat treatment is between HRC25-HRC28. If the process is appropriate and the product shape is reasonable during processing and use, the service life of the die-casting mold can generally reach 100,000 molds or more.

　　First, let's talk about the procurement process. Generally, you should purchase from a Hitachi Metals specialty store and request to purchase electroslag remelting vacuum-melted steel. This type of steel has better performance than ordinary vacuum-melted special steel of the same grade because of its good homogeneity and it is not easy to deform. The price difference between the two is about RMB 20 yuan/KG. The specialty store will provide a steel quality guarantee letter. If conditions permit, the heat treatment of the material should also be undertaken by the specialty store, and three tempering services should be requested (heat treatment price and transportation costs are included in the purchase price).

　　Secondly, let's talk about design. Our current design ideas are basically the same as Japan's, that is, the cavity of the die-casting mold is basically manufactured using an embedded method, which can save special steel. However, it is necessary to calculate the rigidity balance point during design to avoid insufficient mold rigidity due to saving special steel, resulting in a significant decrease in mold life. When designing, priority should be given to the design of the cooling system and the reliability of the slider to ensure the service life of the mold. Secondly, perform mold flow analysis and select the appropriate flow direction and inlet scheme. When designing the cavity, try to avoid stress concentration in the relatively weak parts during die casting.

　　Next, let's talk about the processing process. In the processing process, the first step is rough machining and semi-finishing. In this process, attention should be paid to the accumulation of internal stress during processing. Especially in the later stages of processing, the workpiece should not be severely dropped or struck to avoid internal stress causing potential cracks.

　　Then send it for heat treatment. In the vacuum furnace, there should be a relatively gentle heating process. When it reaches 500-550℃, there is a heat preservation process; generally 1.5 times the first heating time. Then enter the second stage of heating. When it reaches 750-800℃, there should be a heat preservation time twice the second stage of heating to ensure better elimination of internal stress during processing. Next, when the third stage is heated to 1000-1050℃, there should be a heat preservation time twice the third stage of heating to ensure that the temperature of the processed steel is uniform throughout. After quenching, air cool to room temperature, and then perform the first tempering. Of course, oil cooling will appropriately increase the service life. When oil cooling, the quenched parts should be cooled in continuously flowing quenching oil to ensure uniform hardness.

　　Tempering is performed after secondary heating to 600℃ for heat preservation, the time depends on the size and thickness of the workpiece. The entire process is generally 24 hours or more. After being taken out of the furnace, oil cool to room temperature. At this time, the hardness of the material should be between HRC46-HRC52.

　　Next is semi-finishing and finishing. After completion, perform the second tempering. At this time, the hardness of the material should be between HRC44-HRC50.

　　Welding is not allowed in the die-casting mold cavity, because even after preheating, welding with the same material, and heat preservation after welding, the service life of this part is less than one-third of the normal service life. Sometimes, due to design changes, cavity welding is unavoidable. After annealing and requenching and tempering, even so, its life is often half of the normal life.

　　Slider. Generally, the slider should use a material different from the cavity body material, and the hardness is different from the cavity body material to ensure that only the worn part is replaced during use. If copper-based graphite friction plates can be used, it is even better. This technology has been rapidly popularized because the slider and cavity are generally not damaged, and only the friction plates need to be replaced.

　　Mold trial. Many factories do not connect cooling water to the mold for the sake of convenience during mold trial, which is absolutely not allowed. Not connecting cooling water during mold trial will directly lead to a serious reduction in the service life of the die-casting mold. Even if cracks are not visible at the time, cavity cracks will inevitably appear prematurely during normal use.

　　During mold trial, it must be noted that when the mold temperature is not reached, the pressure can only be gradually increased. The injection pressure can only be in place when the mold temperature is uniformly reached.

　　The temperature of the aluminum or zinc liquid should be in accordance with the specified parameters. Arbitrarily increasing the liquid temperature will also damage the mold.

　　In-service tempering. Generally, after 5000 molds (including the number of mold trials) are used for a new mold, the cavity should be removed for tempering to eliminate internal stress. Then use it normally until about 15000 molds before tempering again. If cracks appear on the surface of the cavity, do not temper it.

　　Mold maintenance. When the mold is put into storage after use, the oil and water should be drained, anti-rust oil should be applied inside the cavity, high-temperature lubricating oil should be applied to the sliding parts, and the cooling system and cavity should be sealed to prevent rust.

　　With the rapid development of the mold industry, many new technologies have also been used in mold making. For example, vacuum spraying ceramic materials on the cavity part opposite the inlet can greatly improve the life of this part, maintain the accuracy of the cavity shape and size, and make the overall life of the mold more consistent. As far as I know, there are two types of coatings: 0.01 mm and 0.001 mm, and there is also overall cavity spraying. If this technology is adopted, ordinary hot-work die steel can achieve the effect of high-grade hot-work die steel. You may try it before promoting it.