a hekeda131@126.com, b qiurf1221@163.com KEYWORD: Aluminum alloy; Mild steel; Resistance spot welding ABSTRACT: Aluminum alloy A6061 and mild steel Q235 sheets were welded by resistance spot welding. The interfacial microstructure was observed and the feature and distribution of the interfacial reactant were analyzed and the effects of welding current on the nugget size and tensile shear strength of the joint were investigated. The results indicate that both the tensile shear strength and nugget diameter of the joint increase with the increasing of welding current in some degree. When welding current exceeds a certain range, the nugget diameter of the joint tends towards stability and the tensile shear strength decreases. The joint with the maximum tensile shear load of 1.5 kN is obtained at the condition of 12 kA welding current. The interfacial reaction layer thickness decreased from central joints region to surrounding area.
Joining steel to aluminum alloy by resistance spot welding with a rivet A new joining method, termed resistance spot welding with a rivet, was tried to weld steel to aluminum alloy. Scanning electron microscopy studies of the interfacial microstructures revealed the presence of an FeAl reaction layer at the rivet/aluminum alloy interface, and of FeAl 3 at the steel/ aluminum alloy interface. A tensile shear load of a maximum of 3.85 kN was obtained at a welding current of 21 kA. The results reveal that resistance spot welding with a rivet is an effective method for joining steel and aluminum alloy.
Commercially pure titanium and stainless steel sheets were welded using resistance spot welding with interlayer of Nb. The interfacial microstructure was observed, the effects of welding current on nugget diameter and tensile shear load were investigated deeply. The results show that the interfacial reaction products were consisted of Nb and FeNb eutectic structure. The joint with the maximum tensile shear load of 5.61kN was obtained at the condition of 10 kA. It reveals that it is effective to weld titanium and stainless steel using resistance spot welding with an interlayer of Nb.
Pure aluminum was welded by friction welding in this study. Friction welding of pure aluminum was performed in the fixed upset pressure and friction pressure respectively. The tensile strength of joints was measured. According to the studies performed, pure aluminum welding effect of welding parameters on the tensile strength, friction pressure and upset pressure are the 3.5kN, the maximum tensile load of the welded joint, joint strength, 29.1kN. Parameter influence on deformation of joints, pressure and friction presses increase, such that the displacement increases, excessive wear and flanging on the adverse effects on material properties. The results have revealed a successful joint. Therefore pure aluminum in friction pressure is 2kN, upset pressure is 2kN, friction is 2.5s, can get sound joint.
Magnesium alloys were welded by friction welding. The mechanical properties of the joint were investigated; the effects of welding parameters on flanging amount, wear amount and tensile shear load of the joints were discussed. The results show that the joint strength increases with the increase of friction force and decreases with the increase of upset force. As a result, we could obtain high quality weld joint when friction pressure is 2 kN, and upset pressure is 2 kN.
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