Fracture mechanism of T23/12Cr1 MoV dissimilar steel welding in high- temperature reheater operated for 8 000 hours in the 1 900 t/h boiler was researched by means of macro-morphology analysis of crack characteristics, hardness test and metallographic examination.The results show that the martensitic organization become hardened in the weld and the heat affected zone without preheating and heat treatment after weld, and the grain boundaries became weakening because of grain coarsening in coarse grain zone.On the condition of higher temperature, welding residual stresses and high steam pressure of pipes, the stress concentration in the interfacial of welded joint and coarse grain zone was accelerated.With the increasing of apphed stress plasticity, the crack between the grain boundary of coarse grain zone and welded point was emerged.The reheated cracks are the main reason for the welding failure of T23/12Cr1 MoV dissimilar steel in high-temperature reheater.%通过裂纹宏观形貌、硬度试验、裂纹微观形态等分析,研究了1 900t/h锅炉高温再热器T23/12CrlMOV异种钢安装焊缝运行8000h断裂失效机理.结果表明:取消焊前预热及焊后热处理,将造成焊缝及热影响区产生淬硬马氏体组织,粗晶区晶粒严重粗化,晶界弱化;在高温运行温度下,焊接残余应力及管内蒸汽运行压力下,在焊缝与粗晶区界面处产生应力集中,随着外加应力塑性增加,在焊缝与粗晶区界面粗晶界产生裂纹.再热裂纹是造成高温再热器T23/12CrlMoV异种钢焊缝断裂失效的主要原因.
展开▼
