Aluminum and aluminum alloys have low density, lightweight, high strength and high thermal conductivity, good low-temperature toughness and corrosion resistance, have been increasingly widely used in key fields such as automobiles, high-speed railways, ships, aerospace and so on. The main welding methods of aluminum are manual TIG welding (non-molten inert gas welding), automatic TIG welding and MIG welding (molten inert gas welding). When select aluminum and its alloy welding wires, we must consider the requirements of the weld composition, as well as its mechanical properties, corrosion resistance, structural rigidity, color and crack resistance, etc. The intergranular crack tendency in the heat-affected zone can be greatly reduced by choosing a filling metal whose melting temperature is lower than that of the base metal. Usually, a base metal can be welded by a variety of aluminum alloy welding materials, such as 5083 welding available 5356,5183,5556 and other welding wires, but each wire may result in a joint that is optimal performance in a specified term. 5000 series wires containing more than 3% magnesium should not be used in structures with temperatures above 65 ° C because these alloys are sensitive to stress corrosion cracks. At present, most of the commonly used aluminum alloy welding wire is similar to the matrix metal composition of the standard grade welding wire. The following tips should be paid attention to when choosing aluminum alloy welding wire:

(1) Crack sensitivity of weld joints

The intergranular crack tendency in the heat-affected zone can be greatly reduced when the melting temperature of the filling metal is lower than that of the base metal. So make the alloy content higher than that of base metal wire as filler meta, if use filler metal 6061 containing 0.6% silicon, crack sensitivity is large, but use the 4043 wire containing 5% silicon, of which melting temperature is lower than the base metal in the process of cooling has better plastic to eliminate the shrinkage stress of crack, so the crack resistance is good. We also should avoid the crack-sensitive weld metal composition, for example, there should not be combined with magnesium and copper in the aluminum alloy weld so 5000 series welding wire can also be used for welding 2000 base metal.

(2) Strength of the joints

The strength of the welded joint varies with the alloying element content of the welding wire. In other words, the welded joint strength of non-heat treated alloy increases in the order of 1000 series, 4000 series and 5000 series, and the welded joint strength increases in the order of 5554, 5654, 5356, 5183 and 5556 with the increase of the content of Mg and Mn in 5000 series. Although aluminum-silicon welding wire has higher crack resistance poor plasticity, the workpiece that needs plastic deformation processing after welding should avoid the use of silicon welding wire.

(3) The workability of the joint (Plasticity)

In particular, the welded joints that need bending are greatly affected by plasticity. For base materials (5154, 5056, 5082, 5182, 5083, 5086) containing more than 3% magnesium, avoid using silicon-containing wires (4043, 4047) because of the decrease in ductility due to the large amount of Mg2Si.

(4) Color difference after anodic oxidation treatment

In order to improve the corrosion resistance of the welding joints, the anodic oxidation treatment is necessary, if the composition of the weld metal is significantly different from that of the base metal, or the casting structure of the weld metal is different from that of the calendering structure of the base metal, the color difference will occur after the anodic oxidation process. For example, the welding seam of 4000 series welding wire containing silicon is gray-black after anodic oxidation treatment, and the base metal of 2000, 5000 and 6000 series is silvery white. When choosing the welding wire, the composition and the welded tissue formed must be considered.