Product Code: ICAL07_1003

Laser Brazing of High Strength Steels
Authors:
A. Wirth, BIAS; Germany
C. Thomy, BIAS; Hambergen Germany
H. Laukant, University of Bayreuth; Germany
Frank Vollertsen, BIAS; Germany
U. Glatzel, University of Bayreuth; Germany
Presented at ICALEO 2007

The development of high strength steels demands for joining methods for these new materials. As welding may be difficult for some of these new steels due to a detrimental effect of weld metal and HAZ on the mechanical properties of the joint, brazing of these steels could be a better solution. Therefore, in this paper, laser brazing of high-strength steels is regarded. Besides the brazeability of high strength steels such as TRIP800, the possibility of brazing these steels to automotive steels (DC05) with or without zinc coatings is discussed. Tests were made with different filler materials of different working temperature to determine the effect on the brazed joints and, in special, on the formation of a heat affected zone. The heat affected zones of these joints were analysed and the change of hardness in the HAZ compared to the base material was measured. It was established that the hardness of the steels is increased within the HAZ for all steels considered. These results are correlated with the strength of the joint and cracking behaviour. This behaviour was experimentally verified by static fracture tests. So the influence of the HAZ on the strength of the joint is better understandable. As high strength TRIP-steels induce a lattice transformation on the formed base material, the effect of the HAZ on the formed material is also analysed by high-resolution scanning electron microscopy. The results will contribute to an improved understanding of the brazeability of high-strength steels.