激光束偏移量对异种金属焊接接头组织和性能的影响

Effects of laser beam offset on the microstructure and mechanical properties of dissimilar welded joint

采用不同激光束偏移量对EH36船用结构钢和304不锈钢进行了异种合金焊接,并测试和分析了焊缝的显微组织及力学性能。结果表明:在偏移量为0 mm和0.1 mm时,两侧母材金属熔化均匀,接头成形良好;激光焊接的热源直径较小,对偏移量非常敏感,不推荐采用大于热源直径的偏移量;正偏移时,随着偏移量增大,焊缝显微组织中奥氏体组分减少,分布于晶界和亚晶界的铁素体增多;负偏移时,随着偏移量减小,焊缝组织逐渐转变为马氏体;在最优的工艺参数下,焊缝抗拉强度高达570 MPa,断裂发生在EH36侧的热影响区处,但焊缝会出现硬度提高和伸长率降低的问题。

304 stainless steel and EH36 marine structural steel were dissimilar welded by laser beam and the effects of beam offset on the microstructures and mechanical properties of welds were investigated in details. The results showed that high quality joints with similar amount side fusion could be obtained by the offset values of 0 mm and 0.1 mm. Owning to the laser beam diameter was relatively small and susceptive to offset, the offset values greater than the diameter of heat source were no recommended. With increasing laser beam offset, the fraction of austenite was reduced and the amount of ferrite was increased which located at the grain boundaries and subgrain boundaries, when offset values were positive. With decreasing laser beam offset, the microstructures of weld was characterized of martensite,when offset values were negative. When the optimized offset parameter was employed, ultimate tensile strength of the weld was as high as 570 MPa and the cracking occured at HAZ but the hardness of weld increased seriously.