Abstract
Vacuum laser beam welding enables deeper penetration depth and welding stability than atmospheric pressure laser welding. However, contaminated coupling glass caused by welding fumes in the vacuum space reduces laser transmittance, leading to inconsistent penetration depth. Therefore, a well-designed protective system is indispensable. Before designing the protective system, the contamination phenomenon was quantified and represented by a contamination index, based on the coupling glass transmittance. The contamination index and penetration depth behavior were determined to be inversely proportional. A cylindrical protective system with a shielding gas supply was proposed and tested. The shielding gas jet provides pressure-driven contaminant suppression and gas momentum-driven contaminant dispersion. The influence of the shielding gas flow rate and gas nozzle diameter on the performance of the protective system was evaluated. When the shielding gas flow was 2.0 L/min or higher, the pressure-driven contaminant suppression dominated for all nozzle diameters. When the shielding gas flow was 1.0 L/min or lower, gas momentum-driven contaminant dispersion was observed. A correlation between the gas nozzle diameter and the contamination index was determined. It was confirmed that contamination can be controlled by selecting the proper gas flow rate and supply nozzle diameter.
Highlights
Laser beam welding (LBW) employs a high-energy-density power source, and it can achieve relatively deep penetration depths with less heat input than other welding processes [1]
vacuum laser beam welding (VLBW) enables deep penetration depth and welding stability under relatively low laser power, which is hard to achieve in atmospheric pressure laser welding [4]
The laser transmission region on the coupling glass turned an opaque gray color, and its surrounding area became a brown color on the coupling glass turned anindex opaque color, and its surrounding became a brown color
Summary
Laser beam welding (LBW) employs a high-energy-density power source, and it can achieve relatively deep penetration depths with less heat input than other welding processes [1]. During LBW, deeper penetration depth is enabled by the high energy-per-unit length and/or the high energy density of the laser beam. Many trials have been conducted to achieve both deep penetration and weld quality, and the vacuum laser beam welding (VLBW) method has been proposed as one of the promising methods. VLBW enables deep penetration depth and welding stability under relatively low laser power, which is hard to achieve in atmospheric pressure laser welding [4].
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