9SiCr steel circular die nitriding quenching composite heat treatment

9SiCr steel circular die is a commonly used hand tool with a large consumption, and the main form of failure is wear. The technical requirements are 62-65HRC, and its conventional heat treatment is salt bath heating and quenching at 870°C, tempering at 180°C and bluing treatment. Normally, in order to improve the hardness and wear resistance of cutting tools, chemical heat treatment process can be used, but the chemical heat treatment temperature is generally above 400°C. Therefore, after heat treatment of 9SiCr steel round die, a surface treatment process must be selected to improve the surface hardness and wear resistance. It is very difficult to keep the hardness of the matrix unchanged while maintaining abrasion resistance. After research, it is found that the use of high-frequency induction heating equipment for heat treatment can solve this problem. The following is a brief introduction.

1) Composite heat treatment process. Nitriding-quenching-cold treatment-tempering at 180℃. The nitriding process is 550℃×12h; the quenching heating temperature is 870℃ and oil quenching; the cold treatment process is -80℃×3h.

2) Conclusion. Through several heat treatment process tests, the following conclusions are drawn.

①The hardness value of 9SiCr steel after quenching + cold treatment + low temperature tempering process is higher than that of quenching + tempering treatment.

②The hardness of the hardened area of 9SiCr steel after combined nitriding and quenching treatment is higher than that of quenching + cold treatment + tempering and quenching + tempering.

③ The combined nitriding and quenching treatment of 9SiCr steel can form a thicker hardened layer on the surface of the workpiece, with a hardness of ≥857HV at 0.2-0.6mm, and can improve the tempering resistance of the hardened area.