Fundamental Study for the Relationship between Melt Flow and Spatter in High-Power Laser Welding of Pure Titanium

Abstract

The objectives of this study is to clarify the rerationship between melt flow and spatters ejected from a molten pool during 10 kW laser welding of a pure titanium plate. Three-dimensional X-ray transmission in-situobservation of the weld molten pool with tungsten carbide tracers revealed that the melt flowed mainly along the bottom of the molten pool from the keyhole tip to the rear part and then from the rear to the front near the surface of the molten pool, while the melt in front of a keyhole flowed upwards along the keyhole wall at a velocity of less than 0.6m/s and then was accelerated to 2.1m/s at the height of about 2 mm above the keyhole inlet. One-way upward melt flows were continuously piled up at the tip of the elongated melt, resulting in spattering as droplets from the molten pool. Moreover, about 80% of spatters were generated from 50-100mm/s to 300 mm/s, the ratio and the size of spatters occurring from the rear part of a keyhole increased from 20% to 80% and became smaller than 1 mm