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Beginners’ Guide: How to weld aluminium - Part One (MIG)


 

Need to weld aluminium but not sure where to start? You’re not the first. That’s why we’ve put together two articles to help you get started, part one and two.

Part one outlines how to weld aluminium using a MIG welder and part two looks at how to weld aluminium using a TIG welder.

Understanding aluminium

Aluminium is no ordinary metal. Not only is it much softer than other metals but also it is a better conductor of heat. This means welding aluminium requires a few changes on the part of the aluminium welder, especially if you’re used to welding metals like steel.

In these two articles, we’ll look at how to use MIG and TIG welding for aluminium, starting with the easiest welding process – MIG welding.

MIG Welding aluminium

Metal Inert Gas (or MIG) welding is an arc welding process. It uses a constant consumable wire feed as the welding electrode along with shielding gas to protect the weld puddle from those atmospheric gases that can weaken the weld.

The process for MIG welding is simple. The wire electrode comes on a spool and sits inside the MIG welder. This wire is fed through a gun when the trigger is pulled.

However, for aluminium, consider the following matters:


  1. Power

For thicker metal, you need a more powerful welding machine. A 115-volt MIG welder can handle aluminium up to 3 mm thick with sufficient preheating, and a 230-volt MIG welder can weld aluminum up to 6 mm thick. As with all welding machines, you also need to consider how frequently you’ll be welding. If you intend welding aluminium daily, look for a machine with an output of more than 200 amps.


  1. Shielding Gas

The correct shielding gas is critical. Whereas steel can use a blend of Argon and CO2, aluminium needs a shielding gas of pure argon, or Argon gas with a small percentage of helium. The good news is you shouldn’t need any new hoses, though you will probably need to replace regulators. 

 

  1. Wire and Gun selection

One of the most important differences when welding aluminium is the wire used. Aluminium MIG wire is softer than the wires used on other metals such as as mild steel and is designed to fuse at a temperature appropriate to the aluminium melting point. Selecting the wrong metal will lead to poor weld quality. View here a range of aluminium wire suitable for MIG welding and see here a range of MIG welders appropriate for aluminium wire.

Because aluminium wire is softer than other wires, it  will not feed through most ordinary MIG Guns. You therefore need to look at investing in a Spool Gun which are designed specifically for wleding with aluminium wire. Make sure that if you plan to MIG weld aluminium, your machine is spool gun ready before you purchase it. 

 Spool guns like this Uni-Mig 200amp gun can deliver professional results on aluminium

 

For high-end welding and a professional result on thin aluminium sheets when welding equipment such as boat trailers, a push-pull Gun may also be an option. A push-pull system is general only suitable for higher end welders. It utilises dual motors: an assist motor that pushes the electrode from the feeder, and a primary motor that is located in the gun that pulls the electrode. This will offer you the best of both worlds when welding aluminium. It can accomodate any type of aluminium wire, and it offers the feeding performance of a spool gun.


  1. Technique

Make sure you feed the electrodes using an aluminium feeding kit, as this will allow you to feed the softer wire. These kits feature larger holes on the contact tips, since aluminium expands more than steel when it’s heated. At the same time, the holes still need to be small enough to provide good electrical contact.

The aluminium feeders should also use drive rolls that won’t shave the softer aluminium wire. And non-metallic liners will also reduce as the wire goes through the feeder.

Once you’re ready to go, aim to keep the gun cable as straight as possible so the wire feeds correctly. The most important thing to be aware of is that the softer aluminium wire is more prone to kinks during feeding.


Making your decision

Remember, MIG welding is one of the easiest ways, if not the easiest, to learn how to weld. So it’s a great place to start if you’re welding aluminium for the first time.  

Now you can either read Part 2 where we look at how to weld aluminium using TIG welding, or if you want to get started with MIG welding, check out  here our wide range of aluminium MIG welders.