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MIG welders are versatile systems designed to handle a wide variety of projects, including welding aluminum. However, when welding aluminum, there are a few important factors that the welder needs to keep in mind, as there are certain differences from welding steel. Read on for tips on how to MIG weld aluminum.
First of all, before starting welding, make sure that you’ve got all the protective gear on you. As welding is a dangerous process, it’s very important to have proper protection. It should include a welding helmet, jacket, gloves, boots, and other.
Aluminum Thickness
First of all, when welding thinner sheets of aluminum, make sure that the MIG welder is not using too much power. Otherwise, it can burn through the metal. The minimum thickness you should attempt to weld is 14 gauge. For thinner aluminum, you will need to use the welder’s pulse setting. And for very thin aluminum it’s best to use a TIG welder.
Get a Spool Gun
Also, keep in mind that the MIG aluminum wire is much softer than steel. Because of this, it won’t be able to effectively feed through the system and it will keep on getting jammed inside the cable liner. To avoid wasting a lot of time on this, you can get a spool gun. It attaches to the MIG gun and through it, the wire is fed right to the torch.
Pre-Welding Cleaning
Before starting the welding process, clean the aluminum surface. Remove any lubricants if necessary using solvents. Also, remove oxides from the surface or otherwise the joints won’t weld well together. Use a wire brush that is for aluminum use only.
Choose the Right Equipment
Make sure that the welder has adequate power. For thicker aluminum, you will need a more powerful machine. For example, a 115 volts system will be able to weld material up to ⅛” thickness, while 230 volt machine can weld up to ¼”.
Choose the Right Gas
Steel welding typically uses the combination of argon and carbon dioxide. For welding aluminum, on the other hand, you should use pure argon as the shielding gas. When working on thicker aluminum, helium is sometimes added, which gives deeper penetration into the metal.
Use Aluminum Electrodes
With aluminum, it’s especially important to choose the right electrode thickness. Look for electrodes that are 0.035 inches in diameter. A good choice is the 4045 aluminum electrode. Some other alloys, like the 5536 might be easier to feed, but for it to melt more current will be required.
Travel Speed
If you’re not moving fast enough, the weld can burn through and cause the weld puddle to fall right through the work piece. Generally, you can use the same voltage settings as for the mild steel welding but move at double the travel speed.
Transfer Spray
This mode creates a smooth transfer of the molten metal droplets into the weld puddle. With spray transfer technique there’s no short circuit transfer process involved as with MIG welding steel. For spray transfer, you need to boost the welder’s voltage and it will produce a large amount of heat to create a large weld pool. So that can be difficult to control, especially when working on thinner materials.
Should You Push or Pull?
You should weld in the forehand direction so that the shielding gas can sufficiently cover the weld puddle. So you should push the torch instead of pulling it. Pulling the torch won’t provide enough gas coverage and will result in porous, dirty welds.
Try to maintain the distance from the torch to the work piece. The torch movement should be straight and steady to keep the impurities outside of the weld puddle.
As for the travel angle, keep the torch at a 10 to 15 degree angle. As we have mentioned above, keep the tip and nozzle of the torch pointed in the direction of travel.
Other Tips
If you’re getting dirty welds, make sure that the metal is properly cleaned, that you’re using proper shielding gas and wire type. Also, make sure that you’re using a push and not drag technique.
If you’re burning through aluminum, try to increase travel speed, but at the same time make shorter welds. Also, the aluminum might be too thin and you might need to switch to AC TIG.
