H13 steel is a kind of hot working die steel widely used abroad. In recent years, H13 steel has been widely used to manufacture hot working dies for aluminum profiles in China. The hot extrusion die of aluminum profile is subjected to high temperature (4500c-5200c), high pressure and severe friction of aluminum material in the production process. The failure of the die is mainly due to wear and thermal fatigue, as well as improper heat treatment, resulting in early failure such as fracture, soft, collapse, lack and other factors. At present, there is still a certain gap between the average service life of domestic dies and the international advanced level. The backwardness of heat treatment technology and surface treatment technology is the main reason for low die life. After cryogenic treatment, the microstructure of H13 alloy steel changes as follows:
1) Some or all of retained austenite is transformed into martensite
2) The microstructure of retained austenite is relatively stable, and its microstructure is refined, so it is strengthened and contributes to toughness
3) The toughness of the material is improved and the impact toughness is high
The test workpiece is aluminum profile extrusion die. The workpiece was processed by machine, but no fine processing was carried out. According to the conventional heat treatment process of die, quenching at 1040 ° C, tempering at 580 ° C (twice), nitriding.