The article illustrates melting processes in fixed meshes, based on mixture continuity equations, momentum equations and energy equations for both liquid and solid phases by introducing scalar of liquid fraction and applying source-based method. The model was applied to laser processing of AISI 304 stainless steel. The effects of heat conduction, Marangoni flow and thermal buoyancy on melting process and shape of molten pool were analyzed and physical fundament of laser processing were evidenced. Compared to the experimental outcome, the proposed model and numerical techniques are validated.