1. Cryogenic treatment should be carried out immediately after the workpiece is quenched and cooled to room temperature, so as to avoid the thermal stabilization of austenite caused by too long residence time at room temperature
2. Cold treatment temperature is generally -60 ~ -80oC, the higher the content of steel carbon and alloy elements (mass fraction), the lower the Mf, the lower the cryogenic treatment temperature
Second, the cooling method
1. Workpieces should not be placed directly in thermal insulation cooling liquid (such as alcohol and dry ice mixture), but should be placed in air-cooled low temperature box
2. For workpieces with complex shapes and large sizes, the temperature should be reduced from room temperature to processing temperature with the equipment to prevent the workpiece from cracking
3. Holding time
1. The transformation of martensite is mainly in the continuous cooling process. After the single piece cold treatment reaches the temperature, the transformation can be released
2. When the furnace load is large, in order to ensure that the core of the workpiece reaches the cold treatment temperature, it should be kept at the cold treatment temperature for 1 ~ 3h
4. Temperature rise
1. After the cold treatment, the workpiece is taken out of the cold treatment equipment, returned to room temperature in the air, and the surface of the workpiece is wiped in time to prevent frost and coated with anti-rust oil
2. Tempering can not be done before reaching room temperature. After reaching room temperature, it should be tempered in time to prevent cracking
Five, low temperature tempering
The workpiece after cold treatment should be tempered at 160 ~ 180oC for 2h
Cryogenic treatment mainly uses liquid fluorine as the coolant (-196 degrees Celsius), and uses the rapid cooling method of latent heat of vaporization to cool the quenched mold to below -120 degrees Celsius for a period of time.
Nuoruida (Tianjin) science and Technology Co., Ltd. is committed to research, development, and sales of liquid nitrogen cryogenic equipment. Using European technology, we provide a variety of equipment. The main equipment is liquid nitrogen Cryogenic treatment equipment, cryogenic furnace, sub-zero processing equipment, low temperature cold assembly equipment, cryogenic freezing equipment, and so on.
