用热模拟试验机研究了18Ni钢焊接接头半熔化区的韧性,测定了18Ni钢热塑性曲线.文章认为半熔化区韧性较低的原因是由于热循环温度高于1300℃或试样从高温缓慢冷却到700℃时,晶粒明显粗大化以及脆性相和杂质元素在晶界偏聚,致使晶界性能变坏试样呈沿晶断裂. The thermal simulator was used to study the ductility of 18Ni steel welded joints in the semi-melt zone, and the thermoplastic curve of 18Ni steel was measured.The reason of the low ductility of the semi-melt zone is that the thermal cycling temperature is higher than 1300 ℃ or the sample slowly cooling from high temperature When the temperature was 700 ℃, the grains were obviously coarsening and the brittle phase and the impurity elements segregated at the grain boundaries, resulting in the deterioration of the grain boundary. The samples were intergranular fracture.