About the cooling rate of cryogenic treatment, generally put the mold into liquid nitrogen cooling. According to foreign reports, the use of slow cooling is better than direct liquid nitrogen. Some experiments show that the cooling rate will affect the organizational transformation of cryogenic treatment, the better way is to use a program controlled temperature control box to control the cooling rate.

The orthogonal experiment was used to study the cryogenic treatment of cemented carbide YT15. It was found that the cryogenic temperature had the greatest influence on the performance of the die and mold, followed by the cooling rate.Steel bonded hard alloy after quenching and tempering of the organization are very different,after quenching structure of the steel bonded hard alloy has a lot of residual austenite,martensite is over saturated; as fully austenitic tempering, usually below 1% residues after tempering, and after tempering after hardening, martensite alloy greatly reduced; residual austenite the volume of martensite and alloy of martensitic precipitated from austenite and carbide has great influence on residual after cryogenic treatment of steel bonded cemented carbide,influence the effect of cryogenic treatment.

Many reports about the effect of Tempering on hardness and lifetime of hard alloy after cryogenic treatment, mainly concentrated in the cryogenic treatment after tempering time, a short time is that one is that insulation can be hard alloy materials long time better insulation effect. According to the different time of cryogenic, cryogenic treatment of YG20 cemented carbide hardness are improved to varying degrees, the short time of 2 ~ 4H to reach the peak, Vivtorinox 1689HV30 and 1666HV30 respectively to the hardness values from the 1610HV30 prior to treatment, increased respectively 4.91% and 3.48%.

Cryogenic treatment technology to improve the performance of cemented carbide.Cryogenic treatment can significantly improve the hard alloy wear resistance and long service life,it has been a consensus, but the cryogenic treatment on residual mechanical properties of hard alloy should impact stress there are different views, many studies suggest that the residual stress in the surface strengthening is the main reason of crystal structure transformation and Co high temperature stress; quenching also has great effect on improving the performance of cemented carbide, the interaction between heat treatment and cryogenic treatment are few researchers involved. It is still in the initial stage of industrialization and application of cryogenic treatment of cemented carbide tools. Therefore, in view of the hard alloy types and composition of diversity and complexity, and cryogenic treatment on P, K, M of different grades of cemented carbide was optimized to improve the performance of cemented carbide,there is no technological specification of hard alloy cryogenic technology, development of cryogenic equipment must be advanced, in-depth exploration of the mechanism of cryogenic treatment that is the direction of research and development. It can be concluded that the deep cryogenic technology of cemented carbide has a very broad prospect for improving the technical level of China's mold industry and the comprehensive competitiveness of the manufacturing industry.

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