Forced deep-penetration welding with low-power second-harmonic assistance of cw copper welding with 1 μm wavelength

Laser welding of copper is a challenging process and therefore not yet well established in industrial applications. Due to the low absorptivity at wavelengths of 1 μm and above and the very high heat conductivity, the start of the process is particularly critical and often results in an incomplete welding or even in damaged optics caused by the reflected laser light. Thanks to the significantly higher absorption, green laser light is the obvious choice to improve the initiation of the process.The present paper discusses the results of cw-welding experiments with different copper alloys using a diffraction-limited and frequency-doubled disk laser with 70 W of output power in combination with a second disk laser of high-brightness radiation at the fundamental wavelength of 1.03 μm and a maximum output power of 5 kW.