Product Code: ICAL05_P550

A New Joining Strategy in Order to Join Zinc Coated Steels with Minimized Damaging of the Coating
Authors:
Jean Pierre Bergmann, Technical University Ilmenau; Ilmenau Germany
Johannes Wilden, Technische UniversitIlmenau; Ilmenau Germany
Markus Dolles, Technical University of Ilmenau; Ilmenau Germany
Sebastian Reich, Tecnical University of Ilmenau; Ilmenau Germany
Presented at ICALEO 2005

Metallic components undergo during complete lifetime complex loading conditions, which are a combination of mechanical, environmental as well as corrosive loading. The developments within the ULSAB-project allowed the enhancement of mechanical properties of low alloyed and unalloyed steels, as for example for DP- and CP steel sorts. The corrosion resistance of high strength steels and of deep drawing steel can be only enhanced through coating technology, as for example through hot dipping in zinc or elctrolitic zinc coating. Thermal joining of zinc coated steeel sheets presents some difficulties, as the boiling temperature of zinc (907?C) is lower than the steel melting point. As a result of the eruptionlike evaporation of zinc, pores in the weld seam are present after solidification and the zinc coating near the weldment is spoilt and has to be reestablished. Furthermore the degassing of zinc influences negatively process conditions, as for example arc turbulences when MSG welding and wear of the electrons when resistance spot welding is performed. Even if solutions were developed, brazing of zinc coated steels with CuSi-alloys is nowadays mostly set when joining zinc coated steels. Nevertheless the high melting point of these filler materials (over 900?C) requires very restricted process strategies and damaging of the zinc coating near the brazing seam can?t be avoided.
ZnAl-alloy filler wires, on the contrary, allow to achieve low joining temperatures similar to the melting point of zinc in the region between 400-500?C and offer new possibilities in order to join zinc coated steels without damaging of the zinc layer. In this paper investigations regarding the set of different ZnAl-alloys (Zn till ZnAl15) for soldering zinc coated steels are reported. Investigations were performed with Nd:YAG, with a diode laser and confirm the suitability of these alloys for joining these steels. Mechanical behaviour is reported as well, as a further confirm of the successfully set of Zn-Alloys for soldering applications.