Abstract
High-power lasers are very effective in welding of plates thicker than 10 mm due to the keyhole mode. High-power intensity generates a vapor-filled cavity which provides substantial penetration depth. Due to the narrow and deep weld geometry, there is susceptibility to high hardness and weld defects. Imperfections occur due to keyhole instability. A 16-kW disk laser was used for single-pass welding of 12- to 15-mm thick plates in a butt joint configuration. Root humping was the main imperfection and persisted within a wide range of process parameters. Added arc source to the laser beam process may cause increased root humping and sagging due to accelerated melt flow. Humping was mitigated by balancing certain arc and other process parameters. It was also found that lower welding speeds (< 1.2 m/min) combined with lower laser beam power (< 13 kW) can be more positive for suppression of humping. Machined edges provided more consistent root quality and integrity compared with plasma cut welded specimens. Higher heat input (> 0.80 kJ/mm) welds provided hardness level below 325 HV. The welded joints had good Charpy toughness at − 50 °C (> 50 J) and high tensile strength.
Highlights
Laser beam welding (LBW) and laser-arc hybrid welding (LAHW) are promising joining methods for a wide variety of industries with extensive range of plate thicknesses from 0.7 up to 50 mm [1]
A gas metal arc welding (GMAW) torch was tilted by max. of 60° to the welding surface to eliminate impingement with a laser beam at closer distances
The weld macrographs for the 12-mm thick plate are shown in Fig. 4 for the plasma cut sidewalls with sequentially adjusted process parameters
Summary
Laser beam welding (LBW) and laser-arc hybrid welding (LAHW) are promising joining methods for a wide variety of industries with extensive range of plate thicknesses from 0.7 up to 50 mm [1]. When compared with LBW, LAHW is a more advanced process due to the added arc Single-pass welding of thick steel sections may be highly relevant for structural applications. Full penetration single-pass welding technique causes specific and serious welding imperfections such as root humping or sagging related to melt dropout. This is a challenge when no backing is allowed. It was found that 1030-μm wavelength lasers have very narrow process window due to higher absorption coefficient and subsequent melt overheat in welding of carbon steels.
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