高强钢激光复合焊接T型接头组织分析

Microstructure of T-joint of Laser Hybrid Welding for High Strength Steel

采用15kW高功率激光复合焊接船用低合金高强钢T型接头构件。测定了接头截面的显微硬度,通过光学显微镜、扫描电镜和透射电镜分析了焊缝微观组织。结果表明:焊接接头没有气孔、裂纹等缺陷;焊缝和热影响区显微硬度均高于母材,焊缝显微硬度最高为290HV;焊缝组织主要为细条状的粒状贝氏体和少量的M-A组元。贝氏体铁素体为细条状的铁素体,晶粒细小,晶界密度高。Cu、Ti等微合金元素形成的碳化物沉淀强化相分布于贝氏体铁素体内。细条状的粒状贝氏体组织的晶粒细化及其微合金碳化物(Cu,Ti)xCy的沉淀强化使得焊缝强度高于母材。

T joint in shipbuilding was manufactured by 15 kW advanced high power laser hybrid welding technology. The microhardness of cross section of T joint was measured. The microstructure was also analyzed by optical microscopy, scanning electron microscopy and transmission electron microscopy. The results show that without crack and porosity, the weld metal consists of granular bainite and a little MA constituent. The microhardness of both weld metal and heat affected zone is larger than that of base metal. The microhardness of weld metal is up to 290 HV. The acicular bainitic ferrite possesses high density of grain boundary. The micro-alloying carbide （Cu, Ti）xCy nucleates and precipitates in austenite before the carbide transforms into bainitic ferrite.