焊接热输入对镁合金与镀铜钢冷金属过渡焊接接头性能和缺陷影响

利用冷金属过渡焊(CMT)对镁合金和镀铜钢异种金属进行焊接,填充材料选择AZ31镁合金焊丝,对焊接接头的显微组织进行检测,分析焊接接头的性能和缺陷。实验结果表明:Cu元素对镁合金在钢表面的润湿铺展起到良好的促进作用,焊接热输入影响Cu元素对镁/钢表面的润湿铺展效果。焊接接头产生富铜区,易产生裂纹,降低了焊接接头强度。经过拉伸测试,在焊接热输入为212. 2 J/mm时,焊接接头强度达到最大值3. 99 k N,但在焊接热输入达到254. 6 J/mm时,焊接强度反而降低,这是由于钎焊区生成了大量的中间层脆性化合物。焊接接头组织中检测到气孔、夹渣和裂纹等焊接缺陷的存在,这与母材表面的氧化膜和焊缝内应力有关。

The study of welding heat input on microstructure and properties of CMT welded joints of magnesium alloy and copper plated steel

Cold metal transfer (CMT) was used to weld magnesium alloy and different metals of copper plated steel. AZ31 magnesium alloy welding wire was selected as filler material. The microstructure and the properties of welded joints was detected and the defects of welded joints were analyzed. The experiment result shows that Cu element plays a good role in promoting wetting and spreading of magnesium alloy on steel surface, and welding heat input affects wetting and spreading effect of Cu element on magnesium/steel surface. By tensile test, when the welding heat input is 212.2j /mm, the welding joint strength reaches the maximum value of 3.99KN. However, when the welding heat input reaches 254.6j /mm, the welding strength decreases instead, which is due to a large number of intermediate brittle compounds generated in the brazing area. Defects such as slag inclusion and cracks were detected in the weld joint structure, which was related to the oxide film on the base material surface and the stress in the weld.