Development of technologies for flux-free brazing using brazing material application by means of ultrasonic welding

Brazing can be utilised as a joining technology for mixed joints. Material-locking joints executed by means of brazing are mostly affected by an oxide coat which is extremely distinct, for example, in the case of steels and aluminium. Fluxes are utilised in order to eliminate the oxide coats. These must be removed after the brazing since they may lead to corrosion on the components.

Ultrasonic brazing material application offers a new process for mixed joints with the aim of flux-free brazing. The aims of the investigations were to develop the process and to prove its applicability by means of brazing tests.

Ultrasonic metal welding should be utilised in order to join the brazing material and the workpiece with each other. The oxide coat is mechanically removed from the region to be wetted which is protected from repeated oxidation by the brazing material. The zone between the brazing material and the base material is thus activated and covered at the same time.

Thereafter, the sheets to which the brazing material has been applied can be brazed in identical, similar and dissimilar joints. The suitability of various heat sources was investigated for this purpose. Conductive resistance heating has proven to be suitable. Thus, resistance brazing can be used for the execution of mixed joints with few brittle phases. The figures show one example.