| The aluminum alloy 5A05 contains magnesium as major alloying element and small amounts of copper, manganese, iron, silicon and zinc. This alloy is commonly used for welding parts working in liquid condition due to its good resistance to corrosion. However, the mechanical properties of joints are low. If the yield strength of the weld metal can be improved by some means it will be useful in increasing load.Metal transfer is an important phenomenon in Metal Inert Gas arc welding (MIG) with longitudinal alternating magnetic field. It is of great significance to observe the metal transfer modes under different excitatory currents and frequencies. However, it is very difficult to view the metal transfer process directly during welding, for the strong interference from the arc light. To obtain the relationship between the metal transfer modes and the different magnetic fields, a high-speed video camera was used to acquire the images of globules. Different metal transfer modes in the condition of different magnetic fields and welding parameters were studied. The experiment shows clear images of droplet transfer and how the longitudinal magnetic fields influence the metal transfer and the globule shape.The influence of different magnetic fields during MIG arc welding in 5A05 Al-alloy was studied. It was found that the structures of alloy could not be refined under any magnetic fields, the proper magnetic field conditions could largely reduce the grain size, and however, the improper magnetic field conditions would make the grain bigger than that without magnetic field. With application of magnetic field, on the hand, the convection becomes large and the grains were refined; on the other hand, the under cooling was decreased and the grain was coarsened. The solidification structure was the result of the restriction by these two actions. At the same time, the macrostructures was also determined by the other two actions, which were nucleation and growth. It was also found that the grain size was tended to enlarge when the frequency or the magnetic density was too big.Experience shows that the introduced magnetic field can give an effective intervention to the transition of droplet, flowing of molten bath metal, crystalline and nucleation of molten bath and the process of crystalline growth. The magnetic field promotes the refining degree of primary crystallization structure, decreases the chemistry non-homogeneity. The technique resulted in fine equaixed grains in weld metal and optimum parameters of electromagnetic stirring were suggested based on the extent of refinement. Fine-grained weld metal exhibited better yield strength and significant improvement in percent elongation.The paper compared different arc forms under pulsed and steady MIG arc welding and studied how the external magnetic field affected the shape of arc. In addition, the movement of charged particles in longitudinal magnetic field was analyzed, and the mechanism of arc rotation was studied. In reversed longitudinal magnetic field, the profile of arc forms bell shape when the direct of rotation is clockwise in helix while the arc shape is cone shape when it rotates in counter clockwise. Compared with the arc shape with external field, the arc without longitudinal field forms cone shape.By using the large-scale finite element analysis software-ANSYS based on equivalent thermal enthalpy finite element theory, the temperature field in the influence of magnetic stirring was simulated. The result of simulation in accordance with double-peak heat source.
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