Study on the influence of tool rotational speeds/welding traverse speeds on the quality and surface formation of 6mm copper friction stir welding

Abstract

Abstract This paper describes a study on the formation and process parameters of friction stir welding joints on 6mm thick copper plates. Numerous experiments were conducted at lower rotational speeds and moderate welding traverse speeds to obtain optimal process parameters for high-quality friction stir welding joints with good surface formation and no internal defects. Simultaneously, considering the thickness tolerance fluctuations in the large-scale engineering application of Copper FSW, tests were conducted with pin lengths and shoulder plunge depths less than the plate thickness. Additionally, a unique modular stirring tool was designed by ourselves to reduce costs in large-scale engineering applications. The experimental results demonstrate that under the parameters of a rotational speed of 275r/min and a traverse speed of 120mm/min, welding joints with both surface and internal integrity can be achieved, with the joint strength level exceeding 80% of the base material. The mechanical weak point of the joint is located in the TMAZ region just below the pin as revealed by SEM testing, which shows both plastic and brittle fractures. EDS results indicate no inclusions or second-phase precipitates at the surface and port locations.