Study On The Spatter Formation Mechanism,Controlling Method And Joint Performance Of Laser Welding Of 304 Stainless Steel Sheet

304 stainless steel has gotten more and more widely used due to its good appearance and excellent strength corrosion resistance.High quality weld can be acquired more efficiently by fiber laser welding for its unique advantages,such as high power density and high efficiency.Therefore,the fiber laser welding of 304 stainless steel has been studied intensively.From the previous experiments,it can be found that spatter formed on the back of weld and underfilling of the joint are the mainly defects in the laser welding of 304 stainless steel thin plate,which will will seriously affect the appearance and corrosion resistance of metal surface.Especially in the welding of stainless steel pipe,spatter occurred on the back of weld is difficult to clean,which greatly limits its range of application.Therefore,it is of great importance to study the formation mechanism of backsplash in laser welding of thin plate stainless steel and allocate appropriate technological parameters to reduce or even avoid splashing.With the matching of laser power and welding speed,different spatter quantity and spectrum were obtained in the fiber laser welding of 2mm 304 stainless steel when the energy input was kept the same.And the joint forming and surface corrosion resistance of the weld were studied.The results show that with the increase of welding speed,the weld width of the under surface is increasing while the upper surface is decreasing with the increase of welding speed;the number and size of the back metal spatter significantly increased,the eruption of metal vapor from back outlet of keyhole,as well as the oscillation of concave molten pool,was the main reason for large size spatters;the intensity of plasma characteristic spectrum gradually increases while the electron temperature decreases;the weld and splash will reduce the corrosion resistance of the surface,some small and deep corrosion pore will produce around the spatters,and the size is closely related to the splash.As for the welding process of the welding speed of 5m/min and 6m/min,the change of the weld formation and the back metal spatter amount get realized by changing the incident laser direction and the defocusing amount.The test results showed that increasing the defocusing amount,or inclination along traveling direction,is helpful to suppress spatters and improve joint forming of laser tailored welding of thin blank at high speed.Reverse incident of laser has little effect on the back width when the defocusing amount decreases,and will create strong interference in the molten pool which will increase the back splash.In this paper,the model of the interaction of molten pool flow and metal vapor under different welding speed and laser power is put forward from weld joint forming and forming conditions of all kinds of metal spatter on the back weld.The mechanism of spatter formation of thin plate laser welding is analyzed,and the action mechanism of defocusing amount and incident laser angle on the flow of molten pool is analyzed.