Experimental and theoretical investigations to the effects of zinc coatings and splash on electrode cap wear

Abstract

The zinc used in coated steels causes alloying of spot welding electrode tips. This leads to tip deformation which causes substandard welds to be produced. The presence of expulsion during a weld is also an indication of poor welds and is another factor of reduced electrode life. A series of spot welds have been carried out on sheets of uncoated and sheets of galvanised steel using an industrial spot welding machine using the same welding parameters. The electrode force was varied in the experiments to show how force settings have an effect on electrode cap life. Peel tests were performed on the welds to measure weld nugget diameters and the results were plotted to generate weld growth curves and weldability lobes. SEM results and Vickers micro-hardness tests are also presented which show the alloying effects of zinc on the electrode caps. SORPAS ® has been used to simulate weld growth curves and to predict when splash will occur.