退火保温时间对T91耐热钢TIG接头显微组织及相变影响

Microstructure and Phase Transformation of TIG Welded Joint of T91 Heat Resistant Steel under Different Anneal Holding Time

采用金相、硬度、扫描电子显微分析(SEM)、能谱分析(EDS)及X射线衍射分析(XRD)试验方法,对760℃下不同保温时间退火处理前后T91耐热钢TIG接头显微组织及相变进行研究。研究发现,在760℃下经不同保温时间的退火处理后,T91耐热钢TIG接头焊缝区显微组织结构由板条马氏体向片状或针片状马氏体转变,孪生现象及高的碳当量是促进结构转变的主要原因。经退火保温6 h处理后,相对均匀细小的第二相粒子弥散分布在晶界、马氏体针状界及马氏体内部,故第二相强化效果明显,焊缝区硬度较高。

Metallographic, hard, scanning electron microscope(SEM) analyses, energy dispersive spectrometer(EDS)analyses and X-ray diffractometer(XRD) analyses test methods were applied to study the microstructure and phase transformation of tungsten inert-gas arc welding(TIG) joint of T91 heat resistant steel under different anneal holding time at 760℃. The test results show that the microstructure in the weld zone transforms from lath martensite to plate martensite or acicular martensite under different anneal holding time at 760℃ of TIG welded joint of T91 heat resistant steel, and transformation of microstructure is caused by twin phenomenon and high carbon equivalent. When the anneal holding time is 6 hours, relatively uniform and fine second phase particles are dispersed in grain boundaries, martensite acicular boundaries and interior of martensite, so the second phase has obvious strengthening effect. The hardness of weld zone is higher.