Product Code: ICAL06_506

Laser Brazing Phenomena of Galvanized Steel and Pit Formation Mechanism
Authors:
Masami Mizutani, Joining and Welding Research Institute; Osaka Japan
Seiji Katayama, Joining and Welding Research Institute; Osaka Japan
Seita Kimura, Joining and Welding Research Institute, Osaka University; Osaka Japan
Shinsuke Takemura, NISSAN MOTOR CO.; Kanagawa Japan
Presented at ICALEO 2006

Laser brazing technology for Zn-coated steels with a copper alloy wire receives considerable attention due to its many advantages such as good mechanical properties, good alloyability with zinc, improved gap tolerance, and so on in automotive industries. However, defects such as pits or porosity are sometimes found in laser-brazed beads, and their formation mechanism is not elucidated. YAG laser brazing was carried out on galvanized steel sheets using a copper alloy wire to evaluate the effects of the conditions such as the distance between a laser beam axis and a wire target, brazing volume, traveling speed, brazing directions and defocused distance on the pits or porosity formation. The conditions for the formation and prevention of their defects were confirmed. Laser brazing phenomena and pit formation mechanism were elucidated by observing droplet transfer from a copper alloy wire, molten pool behavior, evaporation of zinc, and bubble formation and flow with a high-speed video and an X-ray transmission real-time observation method.