Optimization of Welding Parameters for Small-Scale Resistance Spot Welding of Zirconium Alloys

This paper presents the results of optimization of parameters for resistance spot welding of parts made of E110 zirconium alloy with a thickness of 0.25 + 0.25 mm. Its purpose was to determine the influence of welding current profiles on nugget metal structure and mechanical properties of welds. The highest tensile strength comparable with base metal (380...440 MPa) was observed when the ratio of integral heat input to current pulse duration was about two. Formation of martensitic structure and coarsening of nugget metal was observed with larger ratios. A proper fusion zone was not formed with lower ratios. Annealing of welded joints at a pressure of ~ 10–4 Pa and a temperature of 580 °C for one hour was necessary to reduce residual stresses and transformation of metastable martensitic phase to a more stable state. This reduced microhardness of nugget metal by 30...35% and increased tensile strength of welds. It was also possible to increase tensile strength and reduce dispersion of its values by increasing duration of current down slope after formation of a nugget. An increase in duration from 1 to 14 ms caused rise in tensile strength by ~ 18% and dispersion of its values by ~ 3%.