1. Direct quenching+low temperature tempering

After carbonitriding, it is directly quenched at the carburizing temperature (820-860 ℃), and then tempered at a low temperature of 160-200 ℃ × 2～3h。 This process is simple and suitable for medium and low carbon steels and low alloy steels. Satisfactory surface and central structures can be obtained. Oil quenching (or water quenching) is generally selected.

2. Stepped quenching+low temperature tempering

After carbonitriding, directly step quenching in 110~200 ℃ hot oil or alkali bath at 820~860 ℃ for 1~15min, then air cooling, and 160~200 ℃ low temperature tempering. This process is suitable for alloy steel parts with strict size requirements due to its small deformation.

3. Secondary heating and quenching+low temperature tempering

After carbonitriding, air cooling or slow cooling in the cooling pit, and then reheating and quenching+low temperature tempering heat treatment. It is applicable to the workpieces that need to be machined or should not be directly quenched due to various reasons after the penetration.

4. Direct quenching, cold treatment+low temperature tempering

After carbonitriding, it is directly quenched from the carburizing temperature, and then cold treated at - 80~- 70 ℃, followed by low temperature tempering to reduce the residual austenite in the surface layer, improve the hardness and stabilize the size. It is applicable to alloy steels containing more chromium and nickel, such as 12CrNiA, 20Cr2Ni4A, 18CrNiWA, etc.

5. Slow cooling, high temperature tempering, reheating quenching+low temperature tempering

After carbonitriding, air cooling or slow cooling in cooling pit shall be carried out, and then high temperature tempering heat treatment shall be carried out (it shall be carried out in green iron chips or protective atmosphere) to reduce residual austenite, and then reheating quenching+low temperature tempering shall be carried out. It is applicable to alloy steel containing more chromium and nickel, as well as machined parts after carbonitriding.