アルミニウムのレーザ溶接におけるポロシティ生成挙動の数値シミュレーションと最適溶接条件の策定

The present paper deals with the behavior of porosity under an influence of convection in the weld pool during laser welding of aluminum by means of a numerical simulation developed by the authors. The simulation system based on the finite element method can calculate and represent the formation of “key-hole” and bubbles called porosities, together with the flowing behavior of porosities under convection in the weld pool during entire process from the onset of melting until the completion of solidification. Porosities appeared behind the keyhole where the flow under a compressive force dominantly affects the formation of them. The upward flow behind the keyhole was composed of two modes such as a circulating flow and a flow along the solid/liquid interface. The optimized welding condition to produce sound joints with no porosity was derived from these two distinct flows.