Invar合金激光-MIG復合多層焊接焊縫形貌及顯微組織

Invar合金激光-MIG復合多層焊接焊縫形貌及顯微組織Weld appearance and microstructure of Invar alloys hybrid multi-layer welded joints using laser-MIG

借助激光-MIG復合焊技術，采用Invar M93焊絲對厚度為19.05 mm的Invar合金板材進行多層對接焊實驗。分析了工藝參數對焊縫熔深、熔寬及深寬比等宏觀形貌參數的影響，并研究Invar合金復合焊接頭不同區域的顯微組織特點及形成原因。結果表明:從打底層到蓋面層焊縫的平均深寬比由2.6減小到0.86，熱影響區寬度明顯增加，焊縫形貌由釘頭狀轉變為高腳杯狀。焊縫中心區域形成縱向分布的狹長奧氏體柱狀樹枝晶，兩側為斜向生長的奧氏體胞狀樹枝晶。從打底層到蓋面層，焊縫中不同區域的晶粒度均逐漸增大。另外，相鄰焊縫邊界亦存在熱影響區，出現聯生結晶現象。

Invar alloy plates with thickness of 19.05 mm were welded with Invar M93 filler wire by laser-MIG hybrid welding. The effects of welding parameters on weld 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 that the weld depth-to-witch ratio gradually decreases from 2.6 to 0.86 in average and the witch of HAZ obviously increases from back weld to cover weld, leading to the weld appearance changing from nail-head shape to goblet shape. Narrow Austentic columnar dendrite crystals in 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 weld increases layer-by-layer. In addition, HAZ is also found at the boundary of adjacent weld layers, where appears epitaxial solidification.

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