Investigation of Electrode Cap Life Made of New Cu–Cr–Zr Copper Alloys with Scandium Addition Dedicated for Resistance Spot Welding of Galvanized Steel Sheets

This study presents results on developing new copper alloys for electrode caps used in resistance spot welding (RSW) of galvanized steel sheets. Two copper alloys-CuCr0.7Zr0.05 and CuCr0.3Ni0.1Zr0.05-were modified with scandium (Sc) additions of 0.01 and 0.05 wt. %. Within this article, the influence of scandium content on Vickers hardness (HV) and electrical conductivity during alloy aging was investigated. In addition, the electrode life of the produced electrodes was subjected to detailed analysis. The results demonstrated that Sc modification enables an increase in hardness with only a minimal decrease in electrical conductivity. Moreover, Sc-modified electrodes exhibited a significantly reduced diffusion layer thickness in the electrode material, which led to lower degradation of the working face geometry and reduced material loss compared with commercial Cu-Cr-Zr electrodes. Mechanical testing showed that spot joints produced with the new electrodes exceed the minimum shear-tension strength requirements even after 500 welds. These results confirm that the proposed alloying approach extends electrode cap life and improves spot weld quality, supporting its application in industrial RSW.