Phenomena of welding with high-power fiber laser

Abstract

This study was performed with the objective of obtaining a fundamental knowledge of welding phenomena and mechanisms in producing deep and narrow weld beads in Type 304 stainless steel with a high-power fiber laser beam. Welding penetrations and defects were classified in weld beads made with the laser of about 115 and 360 Pm in beam diameter at the power of 6 kW. A focused high-power fiber laser beam could produce deeply penetrated weld beads with narrow widths, and the weld penetrations and bead widths were extremely deeper and narrower, respectively, at higher laser power density with the smaller beam diameter. Molten pool and keyhole behavior, bubble/porosity generation and melt flows, resulting in characteristic weld beads and defects, were observed during welding through high-speed video camera and the X-ray transmission real-time imaging apparatus. Consequently the formation situations and mechanisms of porosity, sound weld beads and underfilled weld beads were interpreted in terms of bubbles formation from a keyhole tip at low welding speeds, the formation of a long molten pool at moderate speeds and the production of spattering and a narrow, short molten pool at high welding speeds, respectively.This study was performed with the objective of obtaining a fundamental knowledge of welding phenomena and mechanisms in producing deep and narrow weld beads in Type 304 stainless steel with a high-power fiber laser beam. Welding penetrations and defects were classified in weld beads made with the laser of about 115 and 360 Pm in beam diameter at the power of 6 kW. A focused high-power fiber laser beam could produce deeply penetrated weld beads with narrow widths, and the weld penetrations and bead widths were extremely deeper and narrower, respectively, at higher laser power density with the smaller beam diameter. Molten pool and keyhole behavior, bubble/porosity generation and melt flows, resulting in characteristic weld beads and defects, were observed during welding through high-speed video camera and the X-ray transmission real-time imaging apparatus. Consequently the formation situations and mechanisms of porosity, sound weld beads and underfilled weld beads were interpreted in terms of bubbles forma...