铁素体/奥氏体异种钢焊接接头的微观组织及其力学性能

Microstructure and Mechanical Properties of Ferritic/Martensitic Dissimilar Steel Welded Joint

采用钨极氩弧焊(TIG)对铁素体钢501B和奥氏体钢316LN进行了焊接,对焊接接头的微观组织和力学性能进行了检测分析。结果表明:铁素体侧热影响区出现了粗大的组织,而奥氏体侧热影响区的晶粒只发生了轻微长大。熔合区形成了晶粒细小的等轴晶,焊核区的中心部分形成了垂直于焊接方向的柱状晶。合金元素在两侧熔合区均发生了一定程度的扩散。焊接接头硬度分布不均,波动较大,且存在硬度陡降的薄弱区。室温拉伸结果显示,试样断裂在316LN母材处,断口为韧性断裂。高温拉伸试样断裂在焊缝区,断裂形式为脆性断裂和韧性断裂相结合的混合断裂。

The welding of ferritic steel 501 B and austenitic steel 316 LN was carried out by using tungsten inert gas arc welding, and the microstructure and mechanical properties of welded joint were tested and analyzed.The results show that coarse grains appear in the heat affected zone（HAZ） of ferritic steel and slight grain growth is detected in the HAZ of austenite steel. Fine equiaxed grains are formed in fusion zone, and columnar grains perpendicular to the welding orientation are formed in the center of weld nugget zone. Alloy elements in both sides of fusion zone have a certain degree of diffusion.Micro-hardness presents an uneven distribution and an abrupt decrease. The results of tensile properties at room temperature show that the fracture is in 316 LN base metal, which is ductile fracture. And the tensile fracture at high temperature is in the weld zone, which is a combination of brittle fracture and ductile fracture.