Study On Laser-Arc Hybrid Welding Process Of Titanium Alloy T-shaped Structure

Titanium alloy has lots of excellent characteristics, such as low density, high strength, excellent mechanical properties, high-temperature resistance, corrosion resistance, etc. It is widely used in various fields like aerospace, marine engineering, petrochemical, biomedical, nuclear power, metallurgy, vehicles. TIG welding, A-TIG welding, laser welding, vacuum electron beam welding, laser-arc hybrid welding are common processes used in titanium alloy T-shaped structure welding. As a new efficient welding method, laser-arc welding combines the advantages of TIG welding and high energy beam welding, achieves a good application in welding steel and non-ferrous metal. Laser-TIG hybrid welding shows great advantages in titanium alloy T-shaped structure penetration welding, such as good weld bead performance, high production efficiency and energy saving.In this paper, Laser-TIG and TIG-Laser hybrid welding mode were utilized in TC4 titanium alloy T-shaped structure penetration welding process. Compared the characteristics of both modes and observed influences on weld performance by changing the process parameters. Advantages and disadvantages of two modes are summarized in the titanium T-shaped structure penetration welding; In laser-TIG hybrid welding mode, an effective way was obtained by regulating the process parameters to improve the weld performance. And laser-TIG efficient welding process is used in the practical application of titanium alloy T-shaped structure penetration welding.The results show that, Laser-TIG hybrid welding process can achieve efficient connection in titanium alloy T-shaped structure penetration welding. TIG-Laser hybrid welding mode possess centralized heat source, strong penetration, severe oxidation after cold filler wire, weld joints can be protected well without filler wire, but severely undercut; Laser-TIG hybrid welding mode has relatively scattered heat source, poor penetration, but the welding process is stable. It's easy to obtain protection intact, forming excellent welding joints, and cold filler wire can effectively solve undercuts and other defects. Mechanical properties test results show that the tensile strength of welded joints can be as high as more than 98% of the base material, totally meet the performance requirements.Changing T-shaped structure jig from free formed to enforce formed, available welding parameters range increases. Continue to improve optimization of process parameters on the basis of parameters obtained in free formed, we get process parameters for different combinations of thicknesses T-shaped structural member, and produced different thickness of welded joints. Micro structure comparison found that free formed welded joints has messy irregular grains while enforce formed welded joints has regular grains, coarse grains growing perpendicular to the panel, which reflects the cooling trend of the weld pool. Under different stress levels, fatigue life of titanium hybrid welding T-joints are different. Undercuts and other defects will seriously reduce the fatigue life of the weld, while the excellent welding joints' fatigue life may also be higher than the base metal. Machine processing of the weld surface can improve the fatigue life of welded joints.