焊接热循环对X80管线钢粗晶区韧性和组织的影响

利用焊接热模拟技术、光学金相、透射电子显微镜和示波冲击韧度试验、断裂韧度试验研究了焊接热循环对X80管线钢粗晶区韧性和组织的影响。试验结果表明，在六种热循环参数下，X80管线钢模拟粗晶区具有不同的显微组织，当焊接热循环参数较小时，以下贝氏体和板条马氏体为主，随着热循环参数的增大，以粒状贝氏体为主，且其中的M—A岛的形态由细短条状转变成大长条状或大块状，分布由晶界转向晶内，同时数量增多，韧性恶化。

Influence of welding thermal cycle on toughness and microstructure in grain-coarsening region of X80 pipeline steel

The influence of welding thermal cycle on toughness and microstructure in grain-coarsening region in the heat affected zone (HAZ) of X 80 pipeline steel was investigated by weld thermal simulation technique, metallography, transmission electron microscopy (TEM), the instrumented Charpy impact toughness test and fracture toughness test. The results showed that there were different microstructures in the simulated grain-coarsening region of X80 pipeline steel under six different welding thermal cycle conditions. When the thermal cycling parameters were small,the microstructure of grain-coarsening region was primarily lower bainite and lath martensite, and when the thermal cycling parameters increased,it was mainly granular bainite. The structural morphology of M-A islands changed from thin and short bars to large long bars or large piece-like,and distributed in the grains instead of on the grain boundary. At the same time,the number of the M-A islands increased and the toughness got worse.