Dissimilar Metal Joining of Aluminum to Steel by MIG Arc Brazing Using Flux Cored Wire

Dissimilar metal joining of aluminum to steel, which is difficult due to the formation of the brittle intermetallic compound at the interface of the welded joint, by DC pulsed MIG arc brazing in a lap joint with the flux cored Al-Si filler wire has been investigated for the application of the weight saving of automobiles. The major compound formed at the interface between steel and weld metal was determined to be Al7.4Fe2Si as the Al-Fe-Si ternary compound. The composition control of weld metal can suppress the growth of the intermetallic compound layer less than the thickness of 2.5 μm. In this condition, the transverse tensile strength of the welded joint was about 80 MPa, 70% of that of Al base metal due to the fracture at HAZ on the aluminum side. The mechanism of the suppressed growth of the intermetallic compound layer during MIG arc brazing has been discussed.