The heat-transfer mechanism initiating the friction welding process is examined and a transient two-dimensional heat-conduction model for the welding of two dissimilar cylindrical metal bars is introduced. The bar materials consist of copper and steel. To relate the theoretical predictions with the resulting welds, experiments are conducted under different welding conditions by means of which metallurgical and microprobe analysis of the weld cross-sections are carried out. This provides a visualization of the melted zones and of the diffusion depths. A statistical analysis is carried out for the affecting parameters on the mechanical properties of the resulting welds. The factors affecting the weld include the speed of rotation, the weld duration (burn-off time), and the friction load, whilst the mechanical properties include the tensile strength, the yield strength, the ultimate yield strength and the micro hardness of the weld cross-sections. (C) 1998 Elsevier Science S.A. All rights reserved.