GAS-METAL-ARC WELDING OF ALUMINIUM AND ITS ALLOYS

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It is well known that aluminium and its alloys are very difficult to obtain no porosity, deep penetration and good mechanical properties of the weld metals, when they are arc-welded using an argon atomosphere. An argon-nitorogen mixture gas-metal-arc welding was tried to aluminium and Al-Mg alloy 5083, and the aplicability was examined. The results are as follows.(1) Aluminium plates were welded with aluminium and aluminium-zinc alloy electrode wires using argon-nitrogen gas mixture shielding. The effects of the nitrogen percent in shielding gas and the zinc content of electrode wire on the bead appearance, penetration, porosity, microstructure, hardness and tensile properties of weld metal were examined. Some amount of nitrogen gas addition to the argon shielding gas brought a good bead appearance, deep penetration and less porosity in the weld metal. Zinc addition to the electrode wire decreased the porosity of weld metal. The nitrogen and zinc addition resulted in AlN phase and zinc … More solid solution in the weld metal. The Vickers hardness increased with the nitrogen and zinc addition. The tensile strength of weld metal was equal or higher than those of base metal, but the elongation of weld metal was equal or less than that of base metal and decreased with the nitrogen and zinc addition.(2) Al-Mg alloy 5083 plates were welded with Al-Mg alloy 5183 electrode wire using argon-nitrogen gas mixture shielding. The effects of the nitrogen percent in shielding gas on the bead appearance. penetration depth, porosity, microstructure, hardness and tensile properties of weld metal were examined. Some amount of nitrogen gas addition to the argon shielding gas brought a good bead appearance, deep penetration and no porosity in the weld metal. The nitrogen addition produced fine AlN phase in the weld metal. More than 20% addition of nitrogen into the shielding gas made weld metals having equal or higher hardness than that of the base material. The yield stress and tensile strength of weld metal were close to those base material, but the elongation of weld metal was less than that of base material. Less