Laser power modulation at the threshold from heat-conduction to deep-penetration welding

Abstract

While the cw mode laser welding is commonly used for larger structural welds, pulsed welding is mainly used for smaller components, as it allows precise matching of the pulse properties with the desired melting and solidification conditions.In this paper the investigations focus on an alternative approach with a sinusoidal modulation of the cw laser power at the deep-penetration threshold. Thereby the lower laser power levels lead to heat-conduction welding whereas the higher levels result in deep-penetration welding. An interesting welding process is generated where the variation of modulation parameters such as frequency or amplitude leads to significant changes in welding depth and welding efficiency.Experiments were performed with a 5 kW disk laser on AlMgSi1. The process is monitored using a high-speed camera and a coaxial measurement of back-reflected laser radiation.The experiments clearly show that the resulting changes are caused by opening and closing mechanisms of the capillary. Both, the time constant of the power modulation and the energy input determine the characteristics of the process.While the cw mode laser welding is commonly used for larger structural welds, pulsed welding is mainly used for smaller components, as it allows precise matching of the pulse properties with the desired melting and solidification conditions.In this paper the investigations focus on an alternative approach with a sinusoidal modulation of the cw laser power at the deep-penetration threshold. Thereby the lower laser power levels lead to heat-conduction welding whereas the higher levels result in deep-penetration welding. An interesting welding process is generated where the variation of modulation parameters such as frequency or amplitude leads to significant changes in welding depth and welding efficiency.Experiments were performed with a 5 kW disk laser on AlMgSi1. The process is monitored using a high-speed camera and a coaxial measurement of back-reflected laser radiation.The experiments clearly show that the resulting changes are caused by opening and closing mechanisms of the capillary. Both, the time ...