MIG Welding Aluminium
Aluminium is a versatile and relatively soft metal that requires the addition of alloy(s) to increase its strength. The properties of aluminium vary greatly from steel, meaning welding aluminium alloys can present some challenges including:
- Distortion
- Sensitivity to heat input
When using specialist equipment and procedures, MIG welding aluminium¹ becomes an efficient and cost effective fabrication option.
Read our considerations for optimal aluminium MIG welding below.
Considerations
Thickness
Generally, we MIG weld aluminium 3mm thick or greater. Anything thinner would normally be TIG welded, which gives less heat distortion and a finer weld in most circumstances.
Often, we don’t recommend welding aluminium less than 2mm thick, however there are items which fall below this threshold. And in those circumstances, our tradesmen use Fronius Pulsed MIG welders and AC TIG welders.
We do offer fabrication services for light gauge aluminium, however the cost increases due to the specialist equipment, processes and additional time and skill required to fabricate thinner aluminium.
Cleaning
Aluminium must be clean and free of any lubricants and oxide to ensure integrity and success of the weld.
Gas
Aluminium is non-ferrous, therefore requires a 100 percent argon shielding gas, and we recommend flow rates of 0.566337 to 0.849505 cubic metres per hour.
Process
Spray transfer for thicknesses of 2mm and thicker provides a smooth transfer of molten metal droplets from the end of the electrode to the molten pool. Droplets crossing the arc are smaller in diameter than the electrode, and with no short-circuiting in spray transfer, the deposition rate and efficiency are relatively high. Reason being spray transfer requires a high amount of heat creating a large weld pool with good penetration that can be hard to control.
Welding Techniques
- 10 to 15 degree push travel angle with the tip and nozzle pointed in the direction of travel. Pulling or using a drag angle will produce dirty porous welds due to lack of gas coverage.
- Maintain proper tip-to-work distance and recess the contact tip approximately 3.175mm inside the nozzle
- The reflective heat and weld puddle are very hot. Holding the tip closer than suggested can cause the wire burning back to the contact tip and other feeding problems.
- Avoid large weave beads. If larger fillet welds are required, multiple pass straight beads will provide a more aesthetic look and have less chance of cold lapping, burn-through or other weld defects.
- Increase torch travel speed as the base material becomes heated during the weld.
To sum it all up
MIG welding aluminium is an effective and efficient fabrication method, when specialist equipment and techniques are utilised. Contact the team at Alumac today for advice on your aluminium fabrication project. We’re conveniently located in southern Sydney and offer concept to completion aluminium fabrication services.
References millerwelds.com/resources/article-library/gmaw-mig-aluminum-welding-hints