铝合金电阻点焊中电极点蚀对焊接质量的影响

采用有限元和物理模拟方法,考察了铝合金AA5182电阻点焊过程中电极点蚀对焊接质量的影响。结果表明:当电极尖端点蚀面积增加时,电极与试件界面上的实际接触面积基本不变,而试件与试件界面上的接触面积显著增加,电流密度大大减小,形成熔核的厚度和直径都减小。物理模拟试验所得熔核的形状和尺寸与有限元法预测结果符合很好。物理模拟和数值模拟都表明,点蚀孔直径为5.0mm时,只能形成厚度十分有限的环状熔核。研究揭示:电极尖端点蚀导致被连接试件之间的接触面积增大是其影响焊接质量的主要原因之一。

EFFECT OF ELECTRODE PITTING ON WELDING QUALITY IN RESISTANCE SPOT WELDING OF ALUMINIUM ALLOYS

The effect of electrode pitting on the welding qualityin resistance spot welding (RSW) of aluminum alloy AA5182 isinvestigated using both finite element analysis and physicalmodeling methods. Results show that with the increasing of thepitted area at the electrode tip, the actual contact area at elec-trode/sheet interface does not change so much, while the con-tact area at sheet/sheet interface is increased significantly,therefore, the current density at the sheet/sheat interface is re-duced greatly, and the thickness and diameter of the nuggetformed are both decreased. Dimensions and shapes of the nug-gets from physical modeling are in very good coincidence withnumerical predictions. Only a donut shape nugget with verylimited thickness is formed when the diameter of the pittinghole is 5.0 mm. These results reveal that the increasing of con-tact area at sheet/sheet interface by the increasing pitting holediameter at the electrode tip is one of the major causes for worseand worse welding quality durin RSW of aluminum alloys.