Research on zinc diffusion in the resistance spot welding process of galvanised steels using Cu-Sc and Cu-Zr alloy electrodes

Resistance spot welding of galvanized steels is of critical importance in the welding industry, particularly within the automotive sector, where it is extensively utilized in car body manufacturing. During the welding process, cap electrodes experience significant degradation due to elevated temperatures, zinc diffusion, and mechanical stresses. The predominant mechanisms contributing to electrode degradation include the formation of brass layers induced by zinc diffusion, resulting in the deterioration of mechanical and electrical properties, which ultimately compromises the quality of weld joints. The objective of the presented research is to assess the properties of electrodes fabricated from copper alloy with scandium additions (Cu-Sc). Such electrodes demonstrate enhanced thermal, electrical, and mechanical resistance, potentially leading to improved performance during the welding of galvanized steel. Experimental investigations revealed that the incorporation of scandium into copper alloys substantially increases material hardness and significantly reduces the depth of the zinc diffusion layer. Conducted studies resulted in the extended electrode lifespan and enhanced weld joint quality, which could translate into reduced production costs and improved welding process efficiency.