Mig welding (initials for "metal inert gas") uses a continuous wire electrode and a cover gas, which flows continuously from a torch. Aluminum requires some changes for those used to welding steel; it is a much softer metal, so the continuous wire must be wider. Aluminum is also a better conductor of heat, so it requires more control over the electrode power supply.
Steps
Method 1 of 2: Choose the Equipment and Materials
Step 1. Use stronger machines for thicker metals
A 115V welder can weld aluminum up to 3mm thick with adequate preheating, while a 220V machine can weld up to 6mm thick. Purchase a machine with an output power greater than 200 amps if it is to be used daily.
Step 2. Choose the appropriate cover gas
Aluminum requires argon as a shielding gas, unlike steel for which a mixture of argon and carbon dioxide (CO2) is usually used. The gas change should not require changing the pipes as well, but sometimes it is necessary to change the regulators that are designed for use with CO2.
Step 3. Use aluminum electrodes
The thickness of the electrodes is particularly important with aluminum, and the possibilities are less. Thinner wire is harder to slide, while thicker wire requires more power to melt. Electrodes for aluminum should be less than a millimeter in diameter. One of the best choices is 4043 aluminum; a harder alloy such as 5356 aluminum is easier to slide, but requires more power.
Method 2 of 2: The Correct Technique
Step 1. Get an aluminum electrode kit
These kits are easily found on the market, and will allow you to slide the thin aluminum wire thanks to the following features:
- Larger holes on the contacts. Aluminum expands more than steel when heated. This means that at the exit the wire will need a larger hole than the one used for steel. However, the wire should be small enough to ensure good electrical contact.
- U-pulleys. Aluminum spools should be mounted on pulleys that do not damage the wire. Pulleys of this type will not spoil the softer wire, while for steel V-pulleys are used, specially designed to trim the wire.
- Non-metallic sheaths, which will reduce friction on the wire as it flows.
Step 2. Keep the welder cable as straight as possible to allow the wire to flow properly
The softer wire tends to twist more if the cable is bent.
Advice
- The aluminum alloys that are the easiest to weld are also the weakest. Many alloys, on the other hand, cannot be welded.
- Temper the piece after welding, to increase its resistance.
- An aluminum weld will rarely be as strong as the starting material.
Warnings
- Wear full protective clothing when balancing, which also covers your arms, legs, and hands. Sparks and splinters are a constant danger.
- Always wear a welder's mask. You never have to look at the arc light, even with the mask.
