Investigation of Effective Gas Shielding Method for a Wide-area in Vertical-position Laser Welding of Titanium

Abstract

A ring-type nozzle was proposed to apply gas shielding of wide area in vertical-position laser welding of pure titanium. Argon shielding gas was supplied to the center from the circumference of ring-type nozzle, and the nozzle diameter of open-side was varied to distinguish the appearance of oxidation phenomena for pure titanium. Laser irradiation experiments and computer fluid dynamics analysis results made it clear that a small velocity of argon gas inside the ring-type nozzle was important to reduce the oxidation. A large total flow rate and low supplying speed of argon gas were effective to increase the concentration of argon gas inside the ring-type nozzle. Therefore, 25 mm thickness filter consisted of ceramic fibers was installed on the inner of newly designed ring-type nozzle, and the oxidation of pure titanium could be successfully avoided for the open-area of 150 mm diameter even in vertical-position laser welding.