The objective of the work was to develop a technology for the friction stir welding (FSW) of copper elements of thicknesses exceeding 15 mm and possible to use in the production of current conductor rails. The length of the conductor rail element joining line amounts to approximately 100 mm. The first stage involved FSP tests, i.e. tests of copper plasticisation, using the FSW method and creating the compact weld structure on plates having thicknesses between 8 and 20 mm. The next stage consisted in friction stir welding of copper elements. The investigation involved testing copper plasticisation conditions while using the FSW process, the development of a welding tool as well as the development of conditions for proper welding of sheets/plates having thicknesses of up to 20 mm. It was observed that properly formed welds require the use of a relatively low tool rotation rate and good cooling of element-fixing tooling.