Lasers in Manufacturing Conference 2015 Influence of Ambient Pressure on Spatter Formation during Laser Welding of Copper

Due to its high electrical and thermal conductivity, copper has a wide range of applications. Many of those require an efficient and reliable welding process most preferably using a remote laser technique. However, the low absorptivity of copper at the wavelength of 1 μm together with its high heat conductivity makes remote laser welding of copper a challenging task. Welding speeds below 10 m/min are required to obtain penetration depths of several millimeters in copper when using laser sources with average powers below about 8 kW. Such welds suffer from numerous defects such as melt ejections and pores. As these weld defects degrade both, the mechanical and electrical properties of the weld seam, it is important to reduce or even avoid such weld defects especially for industrial applications. For the present paper the influence of the ambient pressure on defect formation was investigated. High-speed X-ray imaging of the welding process was used to analyze keyhole stability. It was seen that spatter formation was strongly reduced for reduced ambient pressure. Simultaneously, the penetration depth was decreased of up to 40% using identical laser parameters. It was seen that changing the ambient pressure directly correlates with a change of both, the shape and the stability of the keyhole.