25Cr3Mo3NiNbZr钢组织及力学性能研究

Microstructure and properties of 25Cr3Mo3NiNbZr

25Cr3Mo3NiNbZr钢具有优异的高温强度以及良好的低温韧性,是潜在的长寿命压力容器用钢,能够满足日益严苛的服役工况对材料性能的需求。为了获得材料强韧性最佳匹配,研究了淬火温度和回火温度对25Cr3Mo3NiNbZr钢组织及力学性能的影响,结果表明:随着淬火温度由950℃提高到1 050℃,25Cr3Mo3NiNbZr钢中粗大的M6C类碳化物回溶量持续增加,MC类碳化物质量分数基本保持不变。MC碳化物具有高温稳定性,可抑制1050℃淬火晶粒长大。25Cr3Mo3NiNbZr钢回火后组织为回火索氏体,随着回火温度的升高,碳化物类型由M3C转变为M2C,在650~700℃析出M6C类型碳化物,纳米级M2C碳化物在550℃大量析出,是25Cr3Mo3NiNbZr钢产生二次硬化峰值强度的主要原因。

25Cr3Mo3 NiNbZr 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. In order to obtain the best match of material strength and toughness,the influence of quenching temperature and tempering temperature on the microstructure and mechanical properties of 25Cr3Mo3 NiNbZr steel was studied.The results show that with the quenching temperature increasing from 950 ℃ to 1 050 ℃,the amount of coarse M6C carbides in 25Cr3Mo3 NiNbZr steel continues to increase,and the content of MC carbides remains basically unchanged.MC carbide has high temperature stability and can inhibit the growth of quenching grains at 1 050 ℃. After tempering,25Cr3Mo3 NiNbZr steel is tempered sorbite. With the increase of tempering temperature,the carbide type changes from M3C to M2C,M6C type carbide was precipitated at 650-700 ℃,and nano-grade M2C carbide was precipitated in large quantities at 550 ℃,which was the main reason for the peak strength of secondary hardening of 25Cr3Mo3 NiNbZr steel.