厚板5083铝合金MIG焊工艺与性能研究

Research on MIG welding process and performance of thickplate 5083 aluminum alloy

针对25 mm船用5083厚板铝合金MIG焊,焊接难度大,接头性能不达标,出现未熔合、未焊透、大量气孔的问题.经过对焊接接头宏观断口,力学性能,宏观金相等进行分析.研究通过焊前打磨并预热至150℃,打底焊焊接电流提高到170~180 A,层间焊接电流提高到210~230 A,坡口增大至90°,增加焊接道数至27~28道,对称施焊,采用高纯度保护气体等措施改进工艺.通过改进工艺,经过无损检测、拉伸、弯曲、金相发现焊接接头缺陷大大减少,焊接接头拉伸性能提高57.6%,展现出良好的性能,符合生产标准.实验结果发现焊接接头强度下降,是因为在焊接过程中,焊接接头受热循环影响,热影响区形变强化减弱.焊缝中心焊接热输入导致熔池Mg元素烧损,焊缝组织β强化相减少,出现焊接接头软化现象.

This research is aimed at MIG welding of 25 mm marine 5083 thick plate aluminum alloy.The welding is difficult,the joint performance is not up to standard,and there are problems of incomplete fusion,incomplete penetration and a large number of pores.After analyzing the macroscopic fracture,mechanical properties and macroscopic metallurgy of the welded joint,we study the effects on improving the process of measures such as grinding and preheating to 150℃ before welding,carrying out symmetrical welding,using high-purity shielding gas,and increasing the welding current of backing welding to 170~180 A,the welding current between layers to 210~230 A,the groove to 90°,and the number of welding passes to 27~28.After the improvement of the process,through non-destructive testing,stretching,bending,and metallography,it is found that the defects of the welded joints are greatly reduced,and the tensile properties of the welded joints are increased by 57.6%,showing good performance and meeting production standards.According to the experimental results,it is found that the strength of the welded joint decreases because the welded joint is affected by the thermal cycle during the welding process,and the deformation strengthening of the heat-affected zone is weakened.The welding heat input in the center of the weld leads to the burning of the Mg element in the molten pool,the reduction of the β-strengthening phase of the weld structure,and the softening of the weld joint.