Bead on plate laser brazing of dual phase steel with two copper based consumables

Abstract

High strength steels with good formability properties have been developed in recent years, especially for the automotive industry. Joining these metals is however increasingly difficult as the fusion joining processes destroy the carefully constructed microstructure of the steels, resulting in less favourable mechanical properties in and around the joint. A possible solution to this problem is the use of joining processes that require less heat input; laser brazing is one such process. In this work, the brazability of a dual phase steel sheet has been investigated by means of bead on plate brazes produced with two consumables, CuSi3 and CuAl8. Two brazability diagrams are reported and high speed video images are used to explain the differences in operating conditions for these two consumables. Temperature measurements in the steel provide an indication about the temperatures reached during the joining process, which in turn explain the changes observed in the hardness of the steel.