Product Code: ICAL05_2005

Laser Braze Welding Using Hot (88%-Al,12%-Si) Filler Material to Join Steel with Aluminum
Authors:
Alexandre Mathieu, LTm-IUT Le Creusot; Le Creusot France
Jean-claude Viala, LMI; Villeurbanne France
Simone MatteLTm; Le Creusot France
Dominique Grevey, LTm; Le Creusot France
Presented at ICALEO 2005

New anti-pollution and energy saving laws impose reduction of fuel consumption for vehicles of the automobile industry. Reducing the weight of vehicle by introducing Aluminum parts into a steel car-body can be a solution for this reduction. Laser braze welding represent an adequate process than can be used to realize this kind of new structure.
The main problem of thermal joining processes is the formation of intermetallic phases, which are detrimental for the mechanical performance of the joint. Laser-brazing allows a localized fusion involving a limitation of the brittle-phases propagation. Another problem generally encountered when using the brazing technique is the bad wetting of the liquid material on the sheet-join surface. This problem is frequently solved by using a brazing chemical flux or by working under controlled atmosphere or vacuum. In an industrial context, these techniques are very complex to implement.
This paper presents the results of the joining of a 6016 aluminum alloy with low-carbon steel using aluminum-basis alloy filler materials. The study shows that the use of a brazing chemical flux is not necessary. In order to increase the joint mechanical performance, the use of a hot wire appears to be a good solution instead of using a chemical brazing flux.
Simultaneously, observations by optical and scanning electronic microscopy were employed to characterize the joints. The temperature of the wire, just before the laser beam irradiation, was measured by the mean of a pyrometric device. It was found that the wire pre-heating has a strong influence on the mechanical properties of the obtained joints.