The present paper describes the new methodology used for the development of the crackfree welding processes. The presented approach is based on the accurate experimental observations on binary Al-Si alloys, which clearly demonstrate that the crack initiation is a result of the accumulation of macroscopic tensile strain in a microscopic intergranular liquid film of segregates at the final stage of the weld metal solidification. The numerical model takes into account the effects of strain accumulation as well as the influence of thermo-dynamical and thermo-mechanical properties of the welded material. The new approach provides a clear phenomenological interrelation between the cracking susceptibility, parameters of the welding process and properties of the base and filler material. It is successfully applied for development of technological means for elimination of the solidification cracking during welding of aluminium alloys AA6056, such as a multi-beam welding.