Research On The Welding Procedure And Microstructure And Mechanical Property Of Tubular Aluminum Busbar

This project investigated the welding technology of the aluminum busbar; comprehensive measured the tensile strength and Vickers hardness of aluminum busbar welding joint; researched the influence of the welding current on the tensile strength ; analyzed the micromorphology of the fracture of aluminum busbar and welding joint by scanning electron microscope; have a deep research on the metallurgical structure of welding joint and the formation mechanism of the welding defect, received some important results which are as follows:1. If the selection of welding material,parameters and bevel are reasonable,we can get the welding joint which is zero defect and whose mechanical property is good by semiautomatic MIG welding;2. HAZ of aluminum busbar became softened on the effect of welding heat input. If there is no defect in the welding joint,the fracture of tensile sample located in HAZ;and through vickers hardness curve,we find that the hardness of HAZ is the lowest,the hardness of weld is the highest;3. The main reason for the incomplete fusion is that the welding current is too samll. With the increase of the welding current, tensile strength of the tensile sample become small on the premise that the material is complete penetration and the welding parameter is fixed except the welding current;4. The position of the fracture of aluminum busbar and the value of tensile strength have a direct relation with the defect of welding joint.If there is defect existing in weld,such as incomplete fusion,tensile sample will fracture at the surface of the incomplete fusion;5. Solidification structure of aluminum busbar change from columnar crystal to equiaxed grain.The composition and the microstructure in fusion zone of aluminum busbar have big inhomogeneity,and this is because that the both sides of the fusion zone have different crystallization and phase transformation;6.The fracture of tensile samples of the welding joint of 1A90 ,1A93 and base metal belong to dimples-quasi-cleavage fracture.We can see tearing ridge on the fracture of welding joints of 1A90,and there are impurities inside the base metal whose size is about 100μm;7. Porosity and nonfusion appeared easily during the aluminum welding, the emergence of porosity have a direct relation with hydrogen which is dissolved in molten pool, the main reason of nonfusion is that the current is too small.