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TIG Aluminium welding – a ‘how to’ guide

29 Apr , 2014  

By Kym Morgan

29 Apr 2014

ALUMINIUM WELDING is to the welding industry what Luis Suarez is to the Liverpool Football Club.

It can be difficult to work with but it’s extremely important.

Aluminium is one of the most widely used metals in the modern world and any serious welder is probably going to need to master it at some point.

Don’t agree? Have a think about aluminium’s role in automotives and construction and for a start.

In automotives, aluminium is used in car, truck and bus engines block, transmission housing and body panels. In construction, it’s used in sheet products for roofing and wall cladding and in castings for builders.

Then there’s aluminium’s role in packaging, and the electrical sector. You get my drift!

So, rather than avoid aluminium welding it’s time to embrace it, master it and massively increase your welding skill set in the process.

This Blog is dedicated to the art of TIG Aluminium welding, which I believe is the best process for working with aluminium but in a subsequent blog I’ll cover off on MIG aluminium welding. I recommend steering clear of Stick aluminium welding. Getting precise enough welds for aluminium using the Stick/Arc process is a massive ask and I don’t recommend it.

Ok, so TIG aluminium welding. let’s get into it.

Prepare for your project

As with every welding process, preparation is key. Remember the old saying, if you’re given hours to chop down a tree, spend the first seven hours sharpening your axe.

Make sure you’ve got the tools you need

  • A TIG welding machine

Given we’re talk about TIG aluminium welding this an obvious one. More specifically, you should consider investing in a TIG inverter welder with AC (alternating current) function if you’re seeking to achieve high quality aluminium welds. The reason AC welders are more effective on aluminium, and magnesium, is because of the properties of these metals.

Aluminium forms an oxide layer when exposed to air and this layer has a far higher melting temperature than the base metal itself – 1982C, compared to 648C.

If not removed properly, this oxide layer will inhibit proper weld fusion and affect its quality.

A TIG welder with an alternating current basically erases this oxide layer from the surface, so that the integrity of the weld is not compromised when the base metal melts. eWelders.com.au sells a big range of TIG welders with AC/DC function starting at $1199. A big investment, but extremely cheap compared to our competitors.

Way out of your price range? Don’t despair. It is possible to aluminium weld with a TIG inverter that only has DC function which start fromjust  $249 in price here. The key will be cleaning away the oxide layer manually before you start your weld. We will cover off on this a little lower in this article.

  • Aluminum filler rod.

The aluminium Filler Rod will bond your two pieces of aluminium together, as we will explain later. These can be purchased inexpensively at eWelders here.

  • A canister of Argon Gas 

You will use this as your shielding gas. Pure argon is an economic alternative. For added stability you can  use argon with 3% helium.

  • Safety equipment

Obviously you’ll need to protect yourself when carrying out aluminium welding. Click here for our article on welding safety and preparation but in the meantime make sure you cover off these basics.

  • A pair of flame resisted insulated welding gloves
  • An auto darkening welding helmet (Lens should be 9-13 uv rated)
  • A professional leather welding jacket or a thick 100% cotton long sleeve shirt (failure to wear long sleeves can result in burns on your arms)
  • A fire extinguisher

Prepare the aluminium

Ok, now that you’ve got the equipment you need its time to get ready to weld.

First of all, you should clean your aluminium. As I mentioned earlier, if you are using a TIG inverter which only has DC function, it is crucial that you do this in order to remove the oxide layer that will have formed on your aluminium. This layer has a far higher melting temperature than the base metal and, if not removed, will compromise your weld. To clean your aluminium sheet:

  • Spray it with acetone.
  • Rinse it in water, and and allow it to dry.
  • Then scrub the aluminum with a a stainless steel brush.

Prepare your filler rod

To complete your cleaning preparation your should clean the filler rod you intend to use. a dirty filler rod can contaminate the weld so use an abrasive cleaning pad to clean the rod before you start.

Practice run

Before you start have a few practice runs. There’s no need to light the torch for this if you’re trying to save on metal.

 The steps

  • Hold the torch similar to how you would hold a pencil and tilt it back very slightly at about 10-15 degree angle.
  • Hold the tip of the tungsten about 6mm from the metal. If you hold it much further than this the arc will spread too wide and the weld will become too difficult to control.
  • Practice running the torch along where you plan to weld trying to keep that 6mm gap between the tungsten and the metal. Make sure to practice with your gloves on so you get a feel for how it be once your arc is lit

The filler rod

  • Make sure to hold the filler rod at about 90 degrees to the torch tip. You will lead the the weld with the filler rod but you don’t want it to come into contact with the the torch tip because this will contaminate the weld

A few final bits of preparation!

Preheat the aluminium

Aluminium is much more cooperative if it has been preheated to about 175C. Failure to do this can lead to a weak, shallow weld. To preheat your aluminium weld you can set your oven to 175C and put it in there. Don’t worry about the sheet melting while it’s in the oven. Remember, aluminium has a melting temperature of 648C.

Alternatively, use a gas torch to heat the heat sink that the aluminium sheet is clamped to. This will distribute the heat throughout the aluminium.

Fit your aluminium sheets together as tightly as possible

TIG welders don’t like it when the metals are not fitted together nice and tightly prior to welding. It can result in a weak weld. Fill your sheets before you clamp them to avoid this.

Set your welder to the appropriate settings

  • Aim to set your amperage to about 1amp per 25mm in thickness of your aluminium. This may seem low but that is the nature of aluminium welding.
  • You can set the amperage slightly higher than your estimated need and then ease it back once under way.

Lets weld!

  • Use the diametre of your nozzle to gauge the distance between the nozzle and your tungsten electrode. If you’re using a 6mm nozzle, your tungsten should extend no further than 6mm from your nozzle.
  • Tap the electrode tip against the aluminium sheet and then pull it away about 3mm. At this point you can strike your arc.
  • Melt the work piece until you have a nice sized puddle, the size of this puddle needs to be consistent as you move along your weld.
  • As you move along the weld add just enough filler rod to fill the joint and create the the fusion. Continue this along the length of the weld.
  • Remember, the heat will increase as you weld so gradually lower the amperage.
  • Very slowly push the puddle created by the torch into the joint, adding filler as you go.

 

Congratulations, you’re done!

Don’t be disheartened if you’re first attempts at TIG aluminium welding is a raging success. You’re taking on a more advanced leve welding skill here and it will take a few attempts to master.