Aluminium Welding (MIG and TIG)

Can you weld aluminium? Yes you can, but if you ask any welder which materials are most challenging they’ll probably mention this one. Fortunately, applying a few tips, tricks and guidelines makes aluminium welding even easier to master. So what does the R-Tech Welding Equipment team suggest? Read on to find out…

 But first, a few words on the challenge of working with aluminium. Not surprisingly, it’s aluminium’s inherent characteristics that create the biggest test for welders.

Why is welding aluminium difficult?

Aluminium is a good thermal conductor that disperses heat quickly, which can easily lead to unwanted workpiece distortion or cracking. Furthermore, aluminium is renowned for its vulnerability to ‘blow through’ – where the metal just melts away under an over-powerful arc. Aluminium also oxidises very quickly when exposed to the atmosphere. This gives aluminium its renowned ability to resist corrosion, but it also means your aluminium workpiece will need thorough cleaning before you strike an arc and weld. And, as R-Tech’s Mike Gadsby explains, ‘the colour of aluminium can even make it hard to see if it’s ready to weld, particularly with the TIG process.’

What welder do you use for aluminium?

Almost exclusively, it will be a MIG or TIG machine. You’ll find a couple of machine suggestions later, but now let’s move on to that guidance. Let’s start with MIG welding aluminium.

MIG welding aluminium

 Can you use a MIG welder on aluminium?

Absolutely! So here’s some useful advice for MIG welding aluminium. Naturally, it’s a high-level summary. For more detail, research further or seek advice from reliable sources such as Mike and his R-Tech colleagues. There isn’t much they haven’t seen regarding MIG welding aluminium. Mike adds: ‘MIG welding aluminium may not be the easiest process to set up, or the most accurate. But it’s a fast, valuable addition to any MIG welder’s skills.’

• When choosing electrode tips for MIG welding aluminium, make sure they’re specifically designed (Al-marked) for this versatile material.
• Make sure your welding machine and wire-feed mechanism is correct for aluminium welding. This includes fitting a Teflon liner and U-groove rollers. Or by using a dedicated aluminium spool gun  to minimise the length of electrode wire being driven. It might also involve – normally only for intensive professional use – using a push-pull MIG torch for super-precise wire delivery. However, do be aware that not all MIG welding machines work with a dedicated aluminium spool gun – look at R-Tech’s MIG 180, MIG181 Easy-Set and MTS 251 TFT to see some machines that do. By the way, although the R-Tech MTS 450 doesn’t take a spool gun, it has a very good four-roller wire-feed system that can be fitted with U-grooved rollers that grip aluminium wire firmly.
• Moving from the welding machine cabinet to the MIG torch, do make sure that your torch is in good condition. If you’re planning lots of aluminium MIG welding, you might consider a larger-sized torch. Why? Because the greater heat generated by welding aluminium can overwhelm a low-capacity torch. With aluminium, it’s always good to have power in hand…
• Now think back to how aluminium oxidises, and the different thermal properties of aluminium and those oxides. It’s vital to clean your aluminium workpieces thoroughly before welding. Use a stainless-steel wire brush that’s only used on aluminium, brush in one direction only, and be careful not to work the oxide layer into the material. If the aluminium’s surface is oily, use a good degreaser.
• As with all MIG welding, make sure to choose the correct wire for the grade of material (in this case aluminium) that you’re welding.
• Due to its thermal properties, aluminium is very prone to distortion. Minimise the risks by tack welding or clamping the joint to prevent movement or distortion as you weld.
• If you’re welding particularly thin aluminium, consider using a brass or copper backing plate behind your work. It helps avoid the blow through that aluminium is so susceptible to. Welding with a fast travel speed is another way to prevent blow through – and distortion.
• Stop and start as little as you can. To avoid porosity or voids when MIG welding aluminium, weld in one pass wherever possible. Because aluminium’s notoriously cold to start with, it needs to get up to temperature and stay there – hence the importance of that single pass if you want to avoid undesirable cold-lapping. 

What gas do you use for MIG welding aluminium?

Typically, it’s pure argon run at a gas-flow rate of around 14–16 LPM.

TIG welding aluminium

As with the MIG process, remembering and applying a few basic guidelines makes a difference when TIG welding aluminium. Again, choosing the correct TIG welding machine is vital. You’ll need an AC/DC machine with sufficient power to weld the thicknesses of aluminium you’re working with. Machines such as R-Tech’s AC/DC TIG161 and 170EXT exhibit the characteristics of a good TIG machine.

• So the first advice for TIG welding aluminium is to make sure you use a suitable machine.
• Again, as for MIG (or any welding process), make sure to clean your material thoroughly before welding. If it’s dirty or oxidised, use a dedicated stainless-steel wire brush. And if it’s oily, degrease it thoroughly.
• When TIG welding aluminium, torch set-up is critical. Make sure the torch has a suitable duty cycle for the amperage you’re using. Generally, avoid using very lightweight, light-duty, TIG torches on aluminium – you risk burning the torch out.
• As you start welding, be sure to allow the weld puddle to pool before you introduce the filler rod. If you don’t, the rod is likely to stick to the workpiece.
• The quality and condition of torch consumables is also critical when TIG welding aluminium. If in any doubt about optimum combinations of gas cup, tungsten type and electrode diameter, seek advice from your TIG welding machine’s supplier. It all comes down to your specific project and what you’re trying to achieve.
• For best results, match your TIG filler rod to the grade of aluminium that you’re working with. Typical grades include 4043A (5% Si) and 5356 (5% Mg). Make sure to match the rod thickness to the specific welding task too. And remember to wipe your filler rod clean to remove any oily residue.
• Because aluminium is such a sensitive material, learn how to use a foot pedal when TIG welding – or a TIG torch with a variable amperage control. Both aid precise, controlled TIG welding of aluminium.
• Additionally, remember to set your AC frequency and balance to suit the aluminium you’re working with. R-Tech’s Ben Steger says:

‘In my experience, the frequency sweet spot with aluminium is usually around 80–120 Hz. And remember to set your AC balance to a suitable value for the work; start with 30–35% for clean aluminium, then gradually increase the percentage on dirtier material so the arc lifts the oxide off.’

What welder do I need for aluminium?

As mentioned above, the following is a small selection of R-Tech machines that work really well with aluminium:

MIG welders

R-Tech 180 Amp Portable Inverter MIG Welder (240v)
R-Tech MIG181 EASY-SET 180 Amp Portable Inverter MIG Welder (240v)
R-Tech MIG251 EASY-SET 250A MIG welder
R-Tech MTS251 TFT 3-in-1 MIG-TIG-ARC Welder

TIG welders

R-Tech TIG161 Inverter TIG Welder AC/DC
R-Tech TIG201 Inverter TIG Welder AC/DC
R-Tech TIG171TFT EASY-SET
R-Tech TIG211TFT EASY-SET
R-Tech TIG261TFT EASY-SET
R-Tech TIG325TFT EASY-SET
R-Tech TIG401TFT EASY-SET

Get more advice on welding aluminium

Of course, having the right machine is just the start. As with all welding processes, MIG or TIG welding aluminium benefits from consistent application of helpful tips such as those above. Add some well-chosen accessories, quality consumables and loads of practice and you’ll be well on your way to mastering ‘ally’ welding.

Whether you’re a professional welder or an amateur who’s curious about how to weld aluminium at home, or how to TIG weld aluminium pipe, reliable advice and information at your level makes all the difference.

Talk aluminium welding with the team

Remember that the R-Tech team is here for you. Yes, they’d love to sell you the right MIG welder or some ‘Al-capable’ MIG tips. But they also like sharing valuable advice based on decades of experience – or simply talking aluminium welding for a few minutes…