Welding Aluminum

Welding aluminum can be a challenging task, even for experienced and highly-skilled welders. The trick with welding aluminum is getting a good weld without the components breaking, warping or cracking.

While this page is not intended to be an exhaustive tutorial, it will hopefully steer you in the right direction if you decide to tackle this operation.

Your first consideration when welding aluminum is the equipment you’ll need. While almost any of the popular welding methods will work on aluminum, most knowledgable welders recommend using a TIG welder for this task.

While the top-of-the-line TIG units have a variety of features that facilitate the welding of aluminum, you can still get a good end product with a less expensive welder. If you have a high-end TIG unit available then of course take advantage of it, but don’t feel like you need to run out and spend $5000 on a welder unless it’s an investment that’s you get a good return on in the future.

Other equipment you’ll need are a good quality welding helmet and gloves, vise grips or clamps, a dedicated cleaning brush for stainless steel only, and a heavy long-sleeved work shirt to protect your skin from the UV radiation Stick welding aluminum plate in factoryproduced by TIG welding (ignore this last item and expect some serious sun burns and blisters).

You’ll also need a tank of argon gas, and an aluminum welding rod that’s matched to the alloy you’ll be welding. You can find a good chart for this at http://www.tinmantech.com

Once you’ve completed your shopping list of equipment, you’re ready to try your first aluminum weld. Expect a lot of mistakes at first, and it’s better to find some scraps to practice on before you attempt anything that’s going to matter.

Step 1 – The first step at this point is to make sure the aluminum to be welded is clean. This is one of the most critical elements when welding aluminum, and you’ll waste a lot of time and material if you ignore it. And don’t go by appearances – even a brand new piece of aluminum is “dirty” and full of contaminants that will make getting a good weld difficult if not impossible.

You can give your aluminum workpieces a good cleaning by first rinsing it in acetone (but avoid spray-type brake cleaners as they can result in poison gas when heated). Then rinse the piece in water to remove any residue. Next scrub the piece thoroughly with a stainless steel brush or a 3M Scotchbrite pad. And be aware that if the aluminum is going to sit for more than 8 hours before welding, you’ll need to clean it again.

Step 2 – to avoid warping, clamp your workpiece down on some sort of heatsink. Copper works well for this. Be aware that aluminum is a metal that has a high heat transfer rate, and if you don’t bleed off some of that heat, it can cause the entire piece to shrink or warp. Bad news.

Step 3 – Preheat your work before attempting a weld. There is some debate about this in welding circles, but in general, preheating the aluminum can help avoid cracking in the weld. But be careful here – avoid preheating aluminum above 250 degrees F, and use some sort of temperature guage to measure the temperature. You can heat the workarea with a torch, or inside an oven if you have one.

Step 4 – use a separate separate gun liner on your welding gun when welding aluminum. If the welding current is going to exceed 200 amps you’ll want to use a water-cooled gun to curtail excessive heat buildup that can cause wire-feeding difficulties. And change gun liners often to help avoid wire feeding problems due to aluminum oxide buildup.

Step 5 – and lastly, fit the workpieces together as snugly as possible before welding. Try not to leave any gaps if you can. The heat from a TIG welder is very focused, and if there’s a gap between the pieces, the metal will pool on one side or the other, making it hard to bridge the gap with filler. You’ll save yourself a lot of time and effort if you grind or file the two workpieces to ensure a tight fit before welding.


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