Tips on MIG welding aluminium

 Material thickness that can be welded with MIG process on aluminium are 14 Ga. and heavier. How heavy depends on the output capacity of the welder being used. To MIG weld aluminium thinner than 14 Ga. (.074") either specialised pulsed MIG or AC TIG welding equipment may be necessary.
 The removal of lubricants from the aluminium base material may be necessary. This is best done with solvents. Consult with your local welding distributor for their recommendation.
 Oxide removal should be done after degreasing. This should be done with a stainless wire brush and can be done with a hand wire brush or with a cup wire brush. If a power-wire brush is used the RPM'S and pressures are kept low to reduce smearing the surface of the material, which could entrap oxides and impurities under the surface. Always use a wire brush that is used on aluminium only, to keep from contaminating the base material.
 Contact your local welding distributor or aluminium filler metal representative for recommendations on wire alloys that fit your application. Know the alloy of your base aluminium and what conditions the finished part will be subjected to. The 2 most readily available aluminium filler wires are ER4043 and ER5356.

Techniques
 
 Hook spool gun to the positive stud on the power supply. For MIG welding aluminium, you need to use a 10 to 15 degree push travel angle (tip and nozzle pointed in the direction of travel). Remember that pulling or using a drag angle will produce porous, dirty welds because of lack of gas coverage.
 Spray transfer is the desired mode of metal transfer for welding aluminium. The spray transfer is a very smooth transfer of molten metal droplets from the end of the electrode to the molten pool. The droplets crossing the arc are smaller in diameter than the electrode. There is no short-circuiting in spray transfer. With spray transfer the deposition rate and efficiency is relatively high. The arc is very smooth, stable, and stiff and the weld bead has a nice appearance and a good wash into the sides. In the spray transfer, a large amount of heat is involved which creates a large weld pool with good penetration that can be difficult to control and cannot be used on materials thinner than 14 Ga. This transfer will produce a hissing sound, and no spatter.
The short arc transfer on aluminium produces poor cleaning action, poor tie in at the edges of the weld, and large amounts of spatter and smoke. Maintain a tip to work distance, and have the contact tip recessed approximately 1/8" inside the nozzle if possible.
 The reflective heat and weld puddle that is present when MIG welding aluminium is very hot. Holding the tip closer than this could lead to the wire burning back to the contact tip and other feeding problems.
The most common shielding gas for MIG welding aluminium is 100% argon. Flow rates of 20 to 30 CFH (cubic feet per hour) are acceptable. C25 or argon Co2 mixes is not acceptable.
Avoid large weave beads on aluminium. If larger fillet welds are needed, multiple pass straight beads will provide better appearance and have less chance of cold lapping, burn through, and other weld defects.
It will be necessary to increase torch travel speed as the base material becomes heated during the weld.
The skill level of the operator, joint types, fit up, and positions, as well as the welding power supply will all have great influence on the weldability of the aluminium and your success.

 Common problems/troubleshooting

Burn-through (melt through) caused by overheating the base material
1. Increase travel speed. Make shorter welds.
2. Move around on part, spreading out the heat.
3. Use thicker material or change joint design or welding process to ACКроссовки Lifestyle