Molten Wire Tungsten Inert Gas Welding Process

Although traditional Tungsten Inert Gas(TIG)welding process is stable and can produce good welding quality,the welding efficiency of it is low.Compared with TIG welding,efficiency of traditional Metal Inert Gas(MIG)welding is higher,but MIG welding process is not stable and produce spatter.The Molten Wire Tungsten Inert Gas welding process was put forward in this thesis,which was based on the advantages and disadvantages of the traditional TIG and MIG welding processes.Its working principle is as follows: the wire and the work-piece are connected to the anode of the power supply simultaneously,and the tungsten electrode is connected to the cathode of the power supply.When the welding starts,arcs are produced between the tungsten electrode and the wire,and between the tungsten electrode and the work-piece.The arc between the tungsten electrode and the work-piece melts the work-piece,and the arc between the tungsten electrode and the wire melts the wire.Thus,this process can improve the welding efficiency.The molten wire TIG welding system was designed and stable welding process was realized.ER50-6 wire was surfaced on Q235 steel plate to investigate influences of the welding process parameters on the welding process stability and the weld appearance of the molten wire TIG welding process.Microstructures and mechanical properties of the butt welding joint were analyzed and the welding spatter rate was calculated with sound process parameters.The welding spatter rate,microstructures and mechanical properties of the joint were compared with MIG and TIG butt joints with sound process parameters.304 stainless steel wire was surfaced on Q235 steel plate to investigate the welding fusion ratio of the molten wire TIG welding process with sound process parameters,and was compared with the fusion ratio of MIG welding process.Sound process parameters of the molten wire TIG butt welding were chosen as: the welding current 150 A,arc voltage 20 V,welding speed 210 mm/min,distance of tungsten electrode to work-piece 6~8mm.The MIG welding torch and the TIG welding torch were both protected,and the gas flow rate were both 10 ~ 12 L/min.Microstructures in the seam welded with the molten wire TIG process were pearlite and ferrite,which grew up as columnar crystal with perpendicular to the fusion boundary,and small amount of cementite.Upper part of the welding beam was of isometric crystal,which was relatively small.Hardness of the seam welded with the molten wire TIG process was 200-230 HV,lower than that with the MIG and TIG processes.Joint tensile strength was 500 MPa,a little higher than that with the MIG welding process,the same as that with TIG welding process.Welding seam impact absorbing energy was 27.5 J,higher than that with MIG and TIG welding processes.The cold bent angle of the joint was up to 180 °,with the same as that with MIG and TIG welding processes.Spatter rate ot the molten wire TIG process was only 0.057%,close to that of the TIG welding process,much lower than that of the MIG welding process,2.984%.The molten wire TIG process was very stable.The fusion ratio of the molten wire TIG welding was 17.34%,much lower than that of the MIG welding process,23.532%.