Effect Of Laser Incidence Angle On Welding Performance And Molten Pool Flow Of 304 Stainless Steel Laser Deep Penetration Welding

Laser deep penetration welding is a high energy density heat source welding technology,which has the advantages of fast welding speed,high precision and strong controllability,and has been widely used in automobile manufacturing,aerospace and electronic manufacturing and other fields.However,due to the complex flow behavior of the molten pool during the welding process,it will affect the forming,strength and other properties of the welded joint,so it is of great significance to study the influence of the molten pool flow behavior on the performance of the welded joint.In laser deep penetration welding,the laser incidence angle will directly affect the shape of the keyhole of the molten pool,and different inclination methods have a certain impact on the flow of the molten pool.In this paper,the effects of different inclined laser deep penetration welding methods on the macromorphology,microstructure and mechanical properties of SUS 304 stainless steel were studied by laser deep penetration welding experiment combined with "semi-sandwich" direct observation of molten pool flow experiment,and the influence mechanism of laser incidence angle on the welding performance and molten pool flow behavior of laser deep penetration welding 304 stainless steel was studied by laser incidence angle as a variable,and the fracture morphology and porosity defects of weld stretched parts were analyzed,and the influence mechanism of laser incidence angle on the welding performance and molten pool flow behavior of laser deep penetration welding 304 stainless steel was revealed by combining the experimental study of direct observation of molten pool flow.Based on the experimental research and analysis of laser deep penetration whiteboard welding plus butt welding and direct observation of molten pool flow,the results show that the laser incidence angle has little effect on the macromorphology,microstructure and microhardness of SUS 304 stainless steel laser deep penetration welding joint.In terms of the mechanical properties of the weld,the laser incidence angle has different effects on different positions of the weld,and the influence on the upper part is small,and the tensile strength and elongation of the weld are enhanced compared with the substrate.The influence on the middle is secondary,and the generation of solidification cracks is mainly concentrated in the middle of the weld;The influence on the lower part is the largest,the bottom stretch of the weld has more porous defects,and the tensile strength and elongation of the weld under the negative laser incidence angle are greater than the positive laser incidence angle.The laser incidence angle has a great influence on the flow of the molten pool,the stability of the molten pool and the weld defect,the shape of the keyhole under the positive laser incidence angle makes the bottom prone to eddy current,which is not conducive to the discharge of bubbles,the stability of the molten pool is poor,and the probability of the formation of weld porosity defects shows that the positive laser incidence angle is higher than the negative laser incidence angle.