A Study Of Gas Coupled Activating TIG Welding With Filler Metal For Stainless Steel

This topic is in the GPCA-TIG welding laboratory developed the excellent active welding method based on introduction of filler metal,welding filler wire to build the platform,the activity of GPCA-TIG SUS304 austenitic stainless steel welding wire,in addition,the high speed photography platform with active filler wire welding process combining the welding process real-time image acquisition,exploration wire the activity of welding process characteristics,in-depth study of the wire melting transition behavior.This is of great significance for the application of GPCA-TIG active welding method and the study of its mechanism.First,a wire feeding fixture for wire filling GPCA-TIG welding gun is designed and made,and the automatic TIG welding machine is used to m ake the GPCA-TIG welding method possible.Then preliminary test welding is carried out to determine some basic parameters of the later process test.The results of test welding surface,welding wire filling in GPCA-TIG process,the wire feeding direction on the surface of weld forming has a great impact,rear wire,welding wire melting is extremely uneven and inadequate,bead can easily be scratched by wire;pre wire,weld uniform and beautiful.The oxygen flow rate is within 4L/min.In order to ensure the stability of the welding process,the arc arc length is determined to be 4mm.Then,using SUS304 as a test of stainless steel plate,the filler wire GPCA-TIG welding test,the control variable method,the effect of the welding current,welding speed and wire feeding speed,influence of inner and outer layer of gas species and flow rate of 304 austenitic stainless steel wire GPCA-TIG welding weld.The test results show that when the welding current is within 140~180A,the weld penetration will increase with the increase of current,and the weld penetration will start to decrease rapidly when the current increases in GPCA-TIG.The optimum current value of the test is 180 A.The weld penetration gradually decreases with the increase of the welding speed.The bes t welding speed is 40mm/min feeding speed,which has great influence on weld penetration and penetration.With the increase of wire feeding speed,the penetration depth of weld decreases and the remaining height increases.Only when the internal and external gases are adjusted to the appropriate proportion can a narrow and deep weld be obtained.The optimum inner protective gas flow rate is 10L/min,and the outer oxygen flow rate is 1L/min.When the amount of nitrogen is introduced in the outer layer of gas in 1L/min,the weld penetration is slightly reduced,and the flow rate of nitrogen continues to increase,and the weld penetration begins to decrease significantly.With the TIG welding process,a single channel can be welded through the 304 stainless ste el plate with a thickness of 8mm,and the TIG welding depth of the same parameters is only about 2.3mm.The arc voltage of filler wire GPCA-TIG welding is slightly higher than that of filler wire TIG welding.The arc does not shrink obviously.Arc shrinkag e is not the main reason for the increase of penetration depth of GPCA-TIG welding.Subsequently,the typical samples in filler wire GPCA-TIG welding test were selected for ferrite content analysis,nitrogen and oxygen analysis,OM/SEM observation,tensile test,low temperature impact and corrosion resistance.The microstructure and properties of filler wire GPCA-TIG welding specimen were systematically studied.There is a thin layer of oxide layer on the surface of the GPCA-TIG welding seam,with a thickness of about 11.65~19.25 m.The microstructure of GPCA-TIG welding is mainly composed of austenite and skeleton ferrite.When only oxygen is introduced in the outer layer,the microstructure of TIG welding seam is coarse-grained than that of the filler metal.The weld microstructure is refined when nitrogen and oxygen mixed gas is introduced into the outer layer.The tensile strength and yield strength of filler wire GPCA-TIG weld are slightly lower than those of filler TIG weld only when oxygen is added into the outer gas path,while the yield strength of the outer layer is higher than that of the filler wire TIG welding 38 MPa,and the tensile strength is slightly increased.The outer gas path only oxygen,numerical low temperature impact toughness of GPCA-TIG weld filler wire was significantly lower than that of TIG filling wire weld,but can still reach the 83%;and the outer layer into the gas mixture of oxygen and nitrogen,the toughness is improved obviously,the impact toughness is slightly stronger than TIG filling wire welding.The electrochemical corrosion resistance of filler wire GPCA-TIG weld is slightly lower than that of filler wire TIG when oxygen is added to the outer gas path.When the nitrogen and oxygen mixture is introduced into the outer layer,the electrochemical corrosion resistance of the filler wire GPCA-TIG weld is increased slightly,which is slightly higher than that of the filler wire TIG weld.Finally,a high-speed photography platform is set up to collect real-time images in the welding process,and further study the melting and transition behavior of welding wire and the influence on weld formation of filler wire GPCA-TIG welding.The test results of surface,GPCA-TIG filling wire welding mainly has two forms: droplet droplet transition and bypass transition,droplet transfer,melting unit time less the amount of the filler metal,the arc energy is mainly used for melting in the parent material,180 A,parameters 60 mm,8mm test plate can be directly welded through;bypass transition when the weld is uniform in appearance,but this mode may wire melting excessive consumption of arc energy is larger,and the interference on melt flow is relatively large,the penetration is only about 6.21 mm.