Analysis of surface tension driven flow and solidification behavior in laser linear welding of stainless steel

摘要： A transient three-dimensional thermal-?uid-metallurgy model was proposed to study the surface tension driven ?ow and welding metallurgical behavior during laser linear welding of 304 stainless steel. Numerical simulation and experimental method were both used to investigate the thermal behavior, surface tension driven ?ow, driving mechanism and solidi?cation characteristics. The temperature related driving force was qualitatively analyzed, and surface tension and surface shear stress were quantitatively studied. Numerical method and dimensional analysis were also carried out to understand the importance of di?erent driving forces, respectively. The metallurgical model was sequentially coupled to the thermal-?uid model to calculate four solidi?cation parameters. Temperature gradient was observed to be much larger at the front of the melt pool due to the e?ect of thermal conductivity, and decreased from center to the periphery. Both the surface tension and surface tension driven ?ow were found smaller in the central area. The maximum shear stress may reach 2500 N/m2 and pushed an intense outward convection. The solidi?cation parameters were used to predict the solidi?ed morphology, and the prediction was well validated by experimental results. The obtained basic conclusions in this work demonstrated that this study of thermal-?uid-metallurgical behavior could provide an improved understanding of the surface tension driven ?ow and solidi?cation behavior inside the melt pool of welding and additive manufacturing process.