Abstract：Abstract: 25Cr3Mo3NiNbZr steel has excellent high temperature strength and good low temperature toughness. It is a potential long-life pressure vessel steel that can meet the material performance requirements of increasingly stringent service conditions. By studying the effects of quenching temperature and tempering temperature on the microstructure and mechanical properties of 25Cr3Mo3NiNbZr steel, the best toughness matching was obtained. The results show that with the quenching temperature increasing from 950 °C to 1050 °C, the amount of coarse M6C carbides in 25Cr3Mo3NiNbZr steel continues to increase, and the content of MC carbides remains basically unchanged. MC carbide has high temperature stability and can suppress quenched grain growth at 1050 °C. After tempering, 25Cr3Mo3NiNbZr steel is tempered sorbite. With the increase of tempering temperature, the carbide type changes from M3C to M2C, and M6C type carbides are precipitated at 650-700 °C. Nano-scale M2C carbides are at 550 °C. A large amount of precipitation is the main reason for the secondary hardening peak strength of 25Cr3Mo3NiNbZr steel.
2019, Vol. 38 