Experimental Study On The Suppression Pores Stainless Steel Butt Joint During Laser Welding

The 304 stainless steel has good toughness and corrosion resistance,and its welding performance is also very high quality.It is widely used in Pharmaceutical containers,Chemical energy,Shipbuilding,Aerospace industry,Instrumentation machinery and other fields.Laser welding has the advantages of high efficiency,high welding precision,many kinds of welding materials,and few restrictions on working environment,welding blowhole defects will be occurred easily during the laser welding.The defects of welding porosity are prone to occur during the laser welding.This paper studies the test of laser welding porosity,and put forwards solution of the suppression method.This paper mainly study the following content:(1)Based on the laser deep-melt welding stainless steel butt joint test,the welding morphology and pore distribution under different process parameters were studied,and the influence of different process parameters on the welding pores was revealed.It was found that the laser power increased moderately,the weld surface morphology could be improved,and the formation of pores could be effectively inhibited.With the increase of welding speed,the interaction time between laser and metal decreases,and the weld width decreases.In the laser beam swing welding,the porosity of the circular beam scanning track and the 8-beam scanning track is less.Increasing the butt gap properly will reduce the porosity,among which the weld gap is controlled at 0.1 mm,and the most obvious effect is to restrain the porosity.(2)It is found that with the increase of laser power,the depth width ratio of the weld pool increases,so the welding stability increases and the porosity can be restrained effectively.With the decrease of welding speed,the contact time between laser beam and material becomes longer,the heat input is increased,and the formation of porosity is reduced.With the increase of defocusing amount,the penetration becomes smaller,the width and shallowness of the weld are obtained,and the porosity of the weld is increased.It is found that the porosity can be restrained by increasing the gap properly.(3)Through the comparison between the laser deep penetration welding mode and the heat conduction welding mode of 304 stainless steel,it is found that the welding quality and porosity inhibition of the deep penetration welding are better than that of the heat conduction welding,and the welding speed is faster and the welding efficiency is higher.The weld of deep penetration welding is deeper,and the quality and strength of weld are higher than that of heat conduction welding.Through the study of the influence of increasing laser power on the two welding modes,it is found that the porosity of deep penetration welding is more obvious than that of heat conduction welding.Compared with the results of welding speed test,it is found that with the increase of welding speed,the porosity of deep penetration welding decreases more smoothly,while with the increase of welding speed,the porosity of heat conduction welding increases.It is found that the change of gas porosity in heat conduction welding is not as obvious as that in deep penetration welding.When the welding gap of the two welding modes is 0.1 mm,the porosity is less,and the existence of a certain butt gap will reduce the porosity.To sum up,the main suppression methods of laser welding are welding mode,process parameters and beam swing.(4)Through the test of the microstructure and tensile strength of the stainless steel welded joint,the hardness of the weld is slightly higher than that of the base metal,and the microstructure grain of the weld becomes finer.It is found that the smaller the grain size is,the greater the microhardness is.When the porosity content of weld is less,the yield strength and tensile property of weld joint are better.