| Activating flux TIG Welding is a new welding method evolved on the basis of the TIG welding,it can improve the defects of traditional TIG welding such as shallow penetration and low deposition efficiency. But A-TIG Welding of Aluminum alloy prone to hot crack. To solve this problem, this paper analyzes the welding crack and studied the technological performance of A-TIG for Aluminum alloy. Based on the analysis of welding crack, found the cause of the crack and the method of reduce welding crack. Several kinds of activating flux were screened out as the basal component for the multi-component formulation coated in center zone which can reduce welding crack and significantly increase the penetration with good surface performance by means of deposit surfacing welding experiment. With this multi-component formulation welding procedure tests were scheduled, and a set of optimal welding process parameters were achieved. And the effect of welding parameters such as welding current quantity on microstructure and joint performance has been studied. In order to improve the performance of joint, a set of optimal heat treatment process parameters were achieved by heat treatment tests.The experimental results the main cause of the crack is: Mg and Si elements in activating fluxes come into weld line by metal flow in the molten pool, and generate low melting eutectic with Cu and Fe elements. Crack produced in the process of weld solidification, in the tensile stress function.In order to solve the problem of the hot crack of aluminum alloy, mainly from the adjustment of active ingredients. A multi-component flux named MX7 which can reduce welding crack and significantly increase the penetration with good surface performance have been achieved by reducing content of SiO2 and MgO, improve the content of Cr2O3 and AlN. The effect of welding parameters such as welding current, welding velocity and coating quantity on weld penetration and width has been studied. And achieved a set of optimal welding process parameters. Optimal parameters: current 200~240A, welding speed 40~60mm/min, coating quantity near 2 mg/cm2.The effect of welding parameters such as welding current quantity on microstructure and joint performance has been studied. An increase of the welding current resulted in grain size increase in weld zone, decreased slightly microhardness of Aluminum alloy weld joints and increase the UTS value. When the welding current is 200 a joint maximum tensile strength of 212.4 MPa, welding joint is given priority to with quasi cleavage fracture. For joint composition and phase analysis, found that the joint distribution of each element of uniform, mainly for Mg2 Si phase.Post-weld artificial aging of weld joint was performed in different solution temperature and aging temperature after being A-TIG welded. The results showed that the microhardness of WZ could become more uniform and the joint high tensile strength when the parameter 530℃×1h+180℃×6h. Joint average tensile strength of 262.7 Mpa, increased by 28.8% before heat treatment and achieve 90.6% of the parent metal tensile strength. Solid solution and aging by produce β″phase and β′phase rather than change the joint morphology and size of crystal grain to influence the joint performance. |
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