Laser braze welding using hot (88%-aluminum,12%-silicon) filler material to join steel with aluminum Available to Purchase

New anti-pollution and energy-saving regulations will require the automobile industry to reduce the rate of fuel consumption per vehicle. Part of the solution could be to make car bodies lighter, which can be achieved by introducing some aluminum parts in place of steel. Laser braze welding is an appropriate method for realizing such structures. The main problem in thermal joining processes is the formation of intermetallic phases, which are detrimental to the mechanical performance of the joint. Laser brazing localizes the fusion and inhibits the development of brittle phases. Another problem encountered in brazing is poor wetting of the liquid material on the sheet-joint surface. This problem is often solved by the use of a brazing chemical flux or by working in a controlled atmosphere or vacuum. In an industrial context, however, such techniques are very difficult to implement. This paper presents the results of joining a 6016 aluminum alloy with hot dip galvanized low carbon steel using an aluminum-based filler material. This study demonstrates that the use of a chemical flux is not necessary. In order to improve the mechanical performance of the joint, the use of a hot wire, rather than a chemical brazing flux, appears a good solution. Optical and scanning electron microscopy was employed to characterize the joints. The temperature of the wire, just before illumination by the laser beam, was measured with a pyrometric device. It was found that preheating the wire has a strong influence on the mechanical properties of the joints.