镁钢无匙孔搅拌摩擦点焊工艺参数对接头扩散程度的影响

Influence of friction stir keyholeless spot welding process parameters on the diffusion degree of AZ31B Mg-steel

对DP600镀锌钢板和AZ31B镁合金板进行无匙孔搅拌摩擦搭接点焊试验,利用正交试验确定影响因素主次和最优试验方案,在最优焊接工艺下接头的拉伸载荷达到10.1 kN.通过分析接头宏观、微观形貌及界面元素分布,探讨不同工艺参数对接头元素扩散程度的影响,结果表明,搅拌区镁钢存在"弯钩"状的机械互锁结构,形成牢固的机械连接;扩散区镁钢发生了元素扩散,最优工艺参数下扩散层厚度为8μm;在一定的范围内,增大搅拌头转速、轴肩下压量和搅拌针伸出量,可以促进元素之间的扩散,提高接头连接性能.

Friction stir keyholeless spot welding(FSKSW)is an efficient manufacturing method for joining dissimilar alloys,which can dramatically offer high mechanical joint strength.Lap joints between AZ31B Mg and galvanized steel DP600 were made by FSKSW,in which the orthogonal tests were used to determine main influencing factors and the optimal scheme.Under the optimal process,the tensile load of the joint reaches 10.1 kN.Based on the analysis of the macro-micro morphology and the distribution of the interface elements,the effects of different process parameters on the diffusion degree of the elements were discussed.The results show that:(1)there is mechanical interlocking structure of hook shape in the stirring area,forming solid mechanical connection;(2)in the diffusion region,there is element diffusion occurring in the interface of Mg-steel with the diffusion layer thickness being 8 pm;(3)in a certain range,increasing the rotation speed of the tool,the vertical descent of the shoulder and the extended length of the pin can promote the elements diffusion in the interface and improve the connection performance.