Contains the papers presented at the fourth International Seminar "Numerical Analysis of Weldability" held in September 1997 at Schloss Seggau near Graz, Austria. Topics covered include: melt pool phenomena, solidification, modelling tools and computer programs, microstructural modelling in weld metal and heat affected zone, heat flow, friction welding, modelling special welding processes, and residual stresses and distortion.