High frequency pulsed MIG welding and repairing of 6005A-T6 aluminum alloy by new technology

Welding and repairing was carried out on the butt joint of 6005 A-T6 aluminum alloy（ 6 mm plate） for rail vehicle with the rapid thermal start-up technology（ RTS）,and the microstructures and properties of the welded joint were studied. The test results show that,compared with the traditional welding and repairing process,the RTS with 80 ℃ before welding can significantly reduce the porosity defect that produces in the conventional welding and repairing. The welding residual stress in the weld toe of the heating（ starting） zone decreases by about 10%,while the residual stress in the weld toe of the other zone decreases by about 5%. In the junction zone of new and original weld metal,the phenomenon of grain coarsening is not obvious,and its microstructure is better than that of the conventional welding and repairing. The strength coefficient of the welded joint by RTS is 0. 6,and when the bending angle is 180°,the bending specimen has no crack and the joint has good plasticity. After once welding and repairing,the fatigue strength of the welded joint is 77. 4 MPa,which is about 17% higher than that of the conventional one.