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利用光学显微镜、透射电镜等分别对模拟火灾状态下耐火钢的显微组织、M-A岛的变化进行分析,研究了高温下钢中析出相情况。结果表明,试验耐火钢的组织是由铁素体、少量粒状贝氏体和M-A岛组成的混合组织;在高温状态下,试验耐火钢的强度和显微硬度有所下降,但大部分M-A岛都表现出较好的稳定性;Nb和Ti的碳氮化物在基体或晶界析出所形成的第二相质点,以析出强化的方式来提高钢的高温强度。
The changes of microstructure and M-A island of refractory steel under simulated fire condition were analyzed respectively by optical microscope and transmission electron microscope. The precipitated phase in steel at high temperature was studied. The results show that the microstructure of the test refractory steel is a mixed microstructure composed of ferrite, a small amount of granular bainite and MA islands. At high temperature, the strength and the microhardness of the refractory steel are decreased. However, most of the MA islands All showed good stability. The second phase particles formed by the precipitation of carbonitride of Nb and Ti in the matrix or grain boundary enhanced the high temperature strength of steel by precipitation strengthening.