| Abstract Scope |
The use of dual phase zinc coated steels is quite common in current automotive designs. However, the formation of spatter and porosity can be an issue using gas metal arc welding, and can lead to formation of liquation cracks in resistance spot welds. In addition, the use of high power laser welding can still produce softening in the heat affected zone. This presentation will compare two approaches to brazing these steels using ERCuSi-A copper based filler metal. The first utilizes a defocused laser to promote wetting using the filler metal. This provides very high joint surface quality and welding speeds of 2.5 m/min, and is particularly effective for fillet welds on a flare joint. The decrease of wire feed speed tends to increase iron content of the braze metal, which can promote weld metal precipitate formation. In comparison, hybrid laser arc weld brazing using copper based filler metal is demonstrated as a method for lap joint fillet welding, where the laser and arc interact to mitigate the influence of the zinc coating. Hybrid laser brazing is shown to enable increasing speeds from 0.75 to 1.5 m/min versus conventional gas metal arc brazing, while comparable joint strength is achieved. This appears to result from enhanced wetting when the laser leads the weld pool formed by the arc. |