Process control by real-time pulse shaping in laser beam welding of different material combinations

Joining of metallic material combinations with limited solubility is a challenging task. Because of low solubility, such material combinations lead to the formation of intermetallic compounds (IMC) during common weld bath. IMC then lead to increased hardness and brittleness. Generally, these properties are undesirable and the aim is to reduce intermetallics to a minimum. In this contribution, a process control by real-time pulse shaping is realized, whereby the power is adjusted in each individual pulse. The material-specific emissions are continuously detected by photodiodes and used as control variable. By equipping the photodiodes with band-pass filters, the wavelength can be selected in a material-dependent manner. The control loop including data processing and pulse shaping as well as the connection to the power supply of the laser beam source is realized by a novel system in less than 10 µs. This enables laser welding of different metals with a nearly constant penetration depth at the boundary layer and, therefore, the limitation of IMC.