Research On Molten Wire Tungsten Inert Gas Welding Process Of Ta2 Titanium Alloy

Titanium alloy has the advantages of low density,high specific strength and strong corrosion resistance,so it has been used widely in the industries.Traditional titanium alloy welding methods cannot solve the controdiction between efficient and high quality production and low cost control.A new welding method with low cost,high efficiency and high quality,molten wire tungsten inert gas welding process,was investigated for its feasibility and craftability.in the field of titanium alloy welding in this thesis.In this thesis,the feasibility of the molten wire tungsten inert gas welding process in titanium alloy welding was first investigated by orthogonal experiments.By changing the welding current,welding speed,the angle between the wire feeding torch and the platform,and the angle between the TIG welding torch and the platform,the influence of different process parameters on the remaining height coefficient and wetting angle was analyzed.Then,a 5mm thick TA2 titanium alloy one-side welding with back formation process test was conducted to investigated the influence of welding process parameters on the stability of the welding process and the formation of the weld seam.The microstructure and mechanical properties of the butt joint under the optimized process parameters were analyzed.The results show that the molten wire tungsten inert gas welding process can be used in welding of titanium alloys,and the welding current is the main factor affecting the residual height coefficient and wetting angle of the surfacing joint.The molten wire tungsten inert gas welding process can realize 5mm thick TA2 titanium alloy one-side welding with back formation The optimized process parameters are: 70° V-shaped groove,welding current 230 A,welding speed 155 mm / min.The wire speed is 6.0m / min,the tungsten electrode is 9-10 mm away from the workpiece,the angle between the wire feeding torch and TIG torch and the workpiece are 30° and 75°,respectively,and the gas flow is 15 L / min and 10 L / min.The morphology,microstructure and mechanical properties of the welded joints obtained after optimization were analyzed.The results show that with the optimized welding parameters,the welded joints are well formed without spatters,unfused,non-penetration and other defects.The microstructure in the center of the weld is an irregular sawtooth ? and a small amount of acicular martensite.The grains are relatively coarse and are typical as-cast structures.The highest hardness in the joint is 147.2HV at the center of the weld.The average tensile strength of the welded joint is 393.21 MPa,which is 90.1% of the base metal.The fracture location is in the heat-affected zone.The tensile fracture is cup-shaped,and the fracture mode is ductile fracture.The joint has good toughness,and the cold bending angle can reach 180° at room temperature without cracks.