Influence of laser parameters on laser brazed DX56 to DX56 galvanized steel joint

Abstract

Galvanized steel finds application in the automobile industry for their excellent corrosion resistance. Joining of these steel is challenging with conventional fusion joining process such as Metal arc weld (MAW) and Tungsten inert gas weld (TIG) due to excessive zinc evaporation at the joint area and also formation brittle intermetallics at the interface. In order to minimize the problems laser brazing was tried out. In the present study, the amount of zinc loss, intermetallic formation and corrosion properties of the joint area has been evaluated. Galvanized steel (DX56) of 1.5 mm thickness was laser brazed with 1.5 mm diameter solid Cu-Al filler wire. During laser brazing 3 m/min wire feed rate and 3 m/min laser scan speed were kept constant with varying laser power of 4.2, 3.8, 3.4 kW. The Microstructure of laser brazed joint reveals cast structure in the fusion zone and intermetallics formation at the steel interface. Intermetallic thickness decreasing with decreasing heat input. It was found that increase in wetting length improves the joint mechanical and electro-chemical properties.