Process and mechanism of low power laser-double arc welding of titanium alloy plate

Single tungsten inert gas welding (STIG), double tungsten inert gas welding (DTIG), laser-single TIG arc hybrid welding (L-STIG) and laser-double TIG arc hybrid welding (L-DTIG) were used to weld TA2 titanium alloy butt joints with 6 mm thickness , and one-side welding with back formation were achieved. The results show that the arc energy of L-DTIG hybrid welding is more concentrated, and the welding speed can reach 680 mm/min. The heat input of L-DTIG hybrid welding is 605.5 J/mm, which is only 35.5% of DTIG and 59.0% of L-STIG. The grain size of L-DTIG weld zone is fine, and the microhardness can reach 229.5 HV. Tensile specimens fracture at the base material and the joint strength is better than that of the base material. After the addition of laser, the arc plasma central conductive zone of L-DTIG shrinks by 51.0% and 45.5% in the xOy and yOz planes, respectively, and the arc root shrinks by 75.0%. The measured arc pressure of the L-DTIG composite welding heat source on the workpiece was 3 465 Pa, which was 4.17 and 2.25 times higher than that of DTIG and L-STIG composite welding, respectively. The higher arc shrinkage ratio and arc pressure can significantly improve the welding efficiency and reduce the welding heat input.