Combined Welding-Brazing Process for Joining AluminumSteel-Tailored Blanks with High Power Laser Sources

The use of high power laser sources (CO₂) enables the joining of aluminum and zinc-coated steel sheets in butt configuration, using a combined welding-brazing process. Comparable to conventional thermal joining technologies, like resistance spot welding, intermetallic phases are formed in the contact zone leading to a decrease of the mechanical properties of the joint. With locally restricted energy input and high joining speeds the formation of these phases can be minimized to a none critical level. For the characterization of the seam morphology optical, X-ray and electron microscopy examinations have been carried out, demonstrating a phase layer thickness of about 2 μm. In mechanical tests, fracture stresses of 144 N/mm² have been achieved.