Fusion-brazing joining between 5A02 aluminium alloy and Q235 steel by Nd:YAG laser-pulsed MIG hybrid welding

A special type brazing flux was successfully developed. Using this special type brazing flux, 5A02 aluminium sheet could be joined to Q235 steel sheet by large spot Nd:YAG laserpulsedMIG hybrid welding.Weld appearance and mechanical properties and component of the joints as well as the function of each composition of the brazing flux were analyzed.The results indicated that a good fusion-brazing weld could be obtained by using KAlF₄+Sn+Zn brazing flux on the Q235 steel sheet, and the process was stable.The tensile strength of the joint could reach 167.3 MPa, about 83.6% of the aluminium base metal, which is equivalent to the fusion joint by conventional arc welding.The fracture of the joints was within the heat-affected zone on the aluminium side, and the heat-affected zone is intenerated appreciably.The fracture morphology mainly was ductile with somewhat brittle.The shear strength of the joint was up to 106.3 MPa.The SEM test results showed that an intermetallic compounds layer was found in the joint, but the thickness of the layer was only about 3.27 μm.The EDS test results showed that around the brazing interface Al and Fe atoms diffused sufficiently with each other.