In manufacturing practice, it is often found that some steel mills produce hot stamping die steel with serious chemical composition deviation, and the heat treatment process of hot stamping die steel is designed without reasonable forging and spheroidal annealing. The installation process is broken. Because the correct cooling method is also critical in the design of the heat treatment process of die steel.

Hot forging die steel heat treatment calculation method

1、the quenching process will produce a large amount of thermal stress and tissue stress, must be promptly relieved by tempering, otherwise it is easy to cause mold deformation and cracking, tempering as slowly as possible when heating. Hot stamping steel generally requires tempering 3 times, tempering temperature is determined by the hardness measured in the previous process. Usually 550~600℃ is appropriate. Hardening time is at least 2 hours.

2、Oil cooling, air cooling and 500-550℃ heat bath cooling can be used. Fast cooling rate will lead to large thermal stress and large deformation. However, if the cooling rate is too slow, carbide will be deposited in the grain boundaries, which will limit the strength of the material, so it is generally recommended to use 500-550℃ grading or high pressure gas quenching in vacuum furnace. The shape of complex mold can not be cooled to room temperature and then hardened, generally cooled to about 80 ℃, immediately into the 100-150 ℃ heating furnace, holding time calculated by 1 hour / 100mm, so the core can complete the tissue transformation, and then hardened again.

In particular, the heat treatment process of hot work mold steel is as follows.

1、need to first heat treatment of hot stamping steel die and die frame sold in the current market, prepared in the steel mill, and annealed heat treatment to ensure its good machinability, and then no annealing. . However, they were later modified by the manufacturer, destroying the previous performance, and therefore had to be returned for annealing.

2、after heat treatment of hot stamping die steel, if carburizing or nitrogen-carbon seepage, can make the hot stamping die steel further hardened, but the temperature should be set lower, also can extend the normal service life. Dead.

3、the carbon content of the die steel is increased accordingly, the strength of the steel will improve, for hot work die steel, heat resistance, heat resistance and wear resistance will have a greater degree of improvement, but this will relatively lead to its rigidity decline.

Hot work die steel The non-metallic impurities in the die steel will lead to cracks inside the die steel. The vacuum degassing melting process is used to reduce the H, O and inclusions in the steel. Electroslag remelting smelting process can further improve the purity of steel, in addition, the use of multiple slag systems allows inclusions in steel to be removed by adsorption. In addition, an iron process is applied. It can dilute the residual Ni and Cu in the steel, but the mold made with high Cu content is easy to break, and the finished product with high Ni content has poor surface quality. (Chongqing Meida)