Q460FRW耐火钢的组织稳定性

采用Thermo-Calc热力学软件计算Q460FRW耐火钢的平衡态析出相。利用金相显微镜、扫描电子显微镜、透射电子显微镜观察和分析Q460FRW耐火钢600℃保温处理前后的基体与析出相演变。结果表明:600℃下的平衡态析出相由M7C3,M23C6(M=Fe,Cr,Mo,Mn)和MX(M=Nb,Ti;X=C,N)构成。热机械控制工艺下,组织主要由粒状贝氏体和针状铁素体构成。600℃保温处理后,粒状贝氏体中的M/A组元逐渐分解,针状铁素体逐渐转变为块状铁素体。随600℃下保温时间的延长,富Cr/Mn的M7C3相尺寸持续增加,富Nb/Ti的MX相尺寸在小幅度增加后保持稳定,未发现M23C6型析出相。在保温过程中,Mo主要以固溶态存在,其对耐火性能的作用主要为固溶强化。

Microstructural stability of Q460FRW fire-resistant steel

The precipitates in Q460FRW fire-resistant steel under equilibrium state were calculated using Thermo-Calc thermodynamic software.The evolutions of matrix and precipitates in this steel before and after high temperature exposure at 600℃were experimentally observed and analyzed using optical microscopy(OM),scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The results show that the precipitates under equilibrium state at 600℃are carbides including M 23 C 6,M 7C 3(M=Fe,Cr,Mo,Mn)and MX(M=Nb,Ti;X=C,N).The matrix of this steel at TMCP(thermo-mechanical control process)state consists of granular ferrite and acicular ferrite.After soaking at 600℃,M/A constitutes decompose gradually,while the acicular ferrite is transformed into bulk ferrite.Besides,longer exposure time brings about larger size of M 7C 3 particles,while the size of MX particles increases after short time heating and keeps constant with longer exposing time.During the heating process,no M 23 C 6 particles are found,while most of Mo addition contributes to solid-solution strengthening effect.