Product Code: ICAL06_1708

Set of a High Power Diode Laser in Order to Enhance Wettability Conditions and Process Speed in a Controlled Short Arc Brazing Process of Zinc Coated Steels
Authors:
J. Wilden, TU Ilmenau; Ilmenau Germany
Jean Pierre Bergmann, TU Ilmenau; Ilmenau Germany
Presented at ICALEO 2006

Joining of zinc coated steels represents a continuously changing challenge for welding specialist as the low boiling point of zinc leads to evaporation of the zinc coating in the seam as well as in the HAZ. Due to these conditions post treatment of the surface has to be performed in order to guarantee sufficient corrosion resistance. Brazing with CuSi3 alloys represents one way in order to reduce zinc evaporation, which nevertheless occurs as the working temperature of Cu-based braze materials is higher than the boiling point of zinc. In further investigations of the authors the successful set of zinc as filler wire for laser brazing was investigated. Due to the lower working temperatures, which are comparable to the melting temperature of the zinc coating no damaging of the coating could be achieved. Contemporarily new developments in short arc technology were carried out in Europe. The conventional short arc doesn't allow brazing with zinc wires, as eruption like evaporation occurs in the arc. Thanks to the electronic control of the short arc (for example cold Arc of EWM Hightech welding, Germany), the drop formation and the metal transfer, the heat input can be controlled very precisely, so that processing of filler material can be performed easily for thin sheets (till 1,0-1,5 mm) and at low processing speed, below 0,3-0,4 m/min. In this paper investigations regarding the set of high power diode laser in front of the GMA-torch in order to pre-warm the steel sheets are reported. A "coldArc" device of EWM (Germany), which allows a controlled short arc and the control of the heat input was used. As laser source a fibre coupled high power diode laser was set, with a maximum output of 3 kW. The strategy results in a better wettability and in an increase till 1 m/min (approx. 900 W laser power) due to the preheating effect of the sheets through a very low laser power. The influence of the process conditions on the process stability will be cleared. Especially the distance between the torch and the heating source as well as the heat management coldArc-Laser represent a main topic of the paper. Mechanical properties of overlap as well as edge welds will be reported. The effect of the strategy on the joining of steel and aluminium represents a further topic of the investigation, which will be withdrawn with basic investigation. In conclusion the economical benefit of this strategy will be pointed out.