Invar合金激光-MIG复合多层焊接焊缝形貌及显微组织

摘要

借助激光-MIG复合焊技术，采用Invar M93焊丝对厚度为19.05mm的Invar合金板材进行多层对接焊实验。分析了工艺参数对焊缝熔深、熔宽及深宽比等宏观形貌参数的影响，并研究 Invar 合金复合焊接头不同区域的显微组织特点及形成原因。结果表明：从打底层到盖面层焊缝的平均深宽比由2.6减小到0.86，热影响区宽度明显增加，焊缝形貌由钉头状转变为高脚杯状。焊缝中心区域形成纵向分布的狭长奥氏体柱状树枝晶，两侧为斜向生长的奥氏体胞状树枝晶。从打底层到盖面层，焊缝中不同区域的晶粒度均逐渐增大。另外，相邻焊缝边界亦存在热影响区，出现联生结晶现象。%Invar alloy plates with thickness of 19.05mm were welded with Invar M93 filler wire bylaser-MIG hybrid welding. The effects of welding parametersonweld appearance including beam penetration, weld witch and depth-to-witch ratio were analyzed. The features and the forming mechanism of the microstructure on different regions of the weld were investigated.The results show thatthe weld depth-to-witch ratio gradually decreases from 2.6 to 0.86 in averageand the witch of HAZ obviously increasesfrom back weld to cover weld, leading to the weld appearance changing from nail-head shape to goblet shape. NarrowAustenticcolumnar dendritecrystalsin longitudinal direction and oblique diagonal cellular dendrite crystal are formed in weld center and off-centered area, respectively. The grain size in different regions of the weldincreaseslayer-by-layer. In addition, HAZ is also found at the boundary of adjacent weld layers, where appears epitaxial solidification.