Hot cracking phenomena in welds are still a major issue to choose suitable welding conditions. Solidification cracking in welds depends on microstructure morphology, thermal and mechanical loadings. It is still difficult to discriminate the influence of the different phenomena because they are all connected. To investigate solidification cracking, numerical modelling that integrates most of these phenomena is developed in this paper. Thermal and mechanical fields are computed with a finite element model at the process scale. The thermal field is combined with a cellular automata (CA) to predict microstruc-ture at a meso scale. Based, on this prediction, the intergranular network is extracted. Finally, the pressure in the intergranular fluid network is computed during solidification. The fluid flow model along grain boundaries predicts an eventual nucleation of pore/void in the remaining liquid by investigating the maximum pressure drop in the solidifying microstructure. The numerical model is able to describe some hot cracking phenomena observed during experimental tests.