The article presents results of the FEM simulation involving friction stir welding (FSW) of check valve ball elements. The tests involved the obtainment of temperature fields, information about stresses and displacements during the process and about residual stresses and strains following the cooling of elements welded. The knowledge obtained concerning process thermal conditions and that concerning the field of stresses and strains was used to design clamps of a station intended for welding check valve ball elements.