How To TIG Weld Aluminum

Today we’re going to give a crash course in TIG welding aluminum and hopefully we can help you pick up some tips along the way. TIG welding aluminum it’s something that a lot of beginners have problems with when starting out. We’ve seen welders returned because the user thought it wasn’t working correctly when it was an incorrect setting or technique issue. I’m going to try and show you the proper technique when you’re welding aluminum and some tips for beginners.

On the front here of the Eastwood TIG 200 AC/DC there’s a power amperage setting. This knob Is adjusted where when you’re welding with the switch on the trigger. Otherwise you’re going to be using the pedal to vary your amperage. Below the amperage knob we have our pre-flow adjustment. The pre-flow setting is the amount of time the welder will put out shielding gas before it initiates an arc.  This means that when you hit that pedal there will be a delay before the arc starts. Next to that knob is what we call our clearance effect setting and I’m going to talk about that in depth a little more but that’s only used for the AC side when you’re welding aluminum or any other metal that requires AC. The last knob on the TIG 200 is our post flow. This setting allows you to determine the amount of time that the welder continues to flow shielding gas over the weld. This will keep the weld from getting “shocked” with the impurities in the air as it is changing from a liquid to solid state. Today we’re going to be welding on the AC side, so we will flip the AC/DC switch to the AC setting. It is helpful to learn what all the common types of aluminum are and how they react when welding. When your welding on old or used aluminum, it is going to be dirty and it could be a lower quality aluminum depending on the use and age.

Clearance effect or AC Balance is one of the most important settings when welding aluminum. When you’re welding aluminum on AC your welder is bouncing between electrode positive and electrode negative. If you think of it like a sine wave when it’s going up and down your welder is alternating-current going from electrode positive electrode negative.

So why is the alternating current important? Let’s show you on some aluminum samples. Aluminum is always in a state of corrosion on the surface and this creates an oxide coating that will contaminate the weld. Electrode positive is going to clean the metal and burn off that corrosion or oxide that’s on the surface. When you’re welding you will see the arc dance around as it’s cleaning until the metal is clean and the arc stabilizes. The alternating between electrode positive and negative happens FAST and all sort of seems to happen in one process as you weld. When it goes to the electrode negative side it’s putting the heat into the piece so you can weld. You can see on this sample piece there’s a white halo around the weld. That halo is our cleaning area and it should go out around the actual weld seem to keep from any contaminants entering the weld puddle.

The Clearance Effect or AC Balance control goes from positive six to negative six. I’ve found that the “sweet spot” for most jobs are right around negative three. The more negative that you go with the clearance effect, the more penetration you’re going to get but the smaller your cleaning area is going to be. This means you need to have a good flow of shielding gas, your metal needs to be clean, and your technique needs to be good as well. Sometimes when repairing used parts, the aluminum is dirty from years of abuse or the type of aluminum is a lower grade and you may need to go further towards the positive side to get the extra cleaning effect. I may go to negative one for a project and what that’s going to do is enlarge your cleaning area, but the weld penetration will be reduced. This setting is about getting just the right amount of cleaning while still getting the proper penetration and may take some test passes to get your machine dialed in.

You can see the first weld on this sample piece I maxed out the machine on negative six Clearance Effect. The cleaned area with the white halo is tiny and barely surrounding the weld puddle. Any change in torch angle or stray contaminant would harm this weld so the room for error is minimal. Next, I jumped up the scale and you can see the cleaning band gets larger around the outside of the weld. You can see the sweet spot is right around negative three or four. You can see the closer I got to zero or positive side the larger the cleaning area and weld puddle gets. We’re getting a clean weld, but the weld puddle and heat is dramatically increasing as well. It may not be an issue on this sample but if you’re welding something that’s real crucial that you can’t touch the edge or something next to just can’t get hot then that’s where you’re going to want to stick more towards the negative side as much as you can. If you want some additional help with keeping the heat and weld puddle small you can keep the machine more towards the negative side and spend more time with prepping the part. You can preheat the aluminum in an oven or with a torch to bake out contaminates in the pores. You can also be diligent with cleaning the part. You can start with a sander or stainless wire brush to clean the surface and then follow up with acetone. The last beads are on the plus side. That means it’s hanging on that positive side for longer. What it’s doing is putting a lot of the heat into the electrode itself instead of the work piece. This means it’s cleaning a large area, but if you allow it to go too long on this setting it will overheat the tungsten and the tip could even melt or fall off and contaminate the weld. In most home garages and welding projects there isn’t much of a reason that you should be using the positive side of the Clearance Effect.

In my opinion proper cleaning of the work piece is probably the number one problem that beginners have with TIG welding aluminum. Think of welding aluminum as if you’re in an operating room. That’s how clean you should strive to get your parts prepped to if possible. The cleaner the aluminum is the better it will weld. This piece here is a brand-new piece of aluminum from the metal yard. This has a protective coating on it that keeps it from oxidizing quickly when in storage. It may look clean, but once you start welding you will find contaminates floating in your weld. If the metal is clean or new to begin with you can take a can of acetone or our Low-Voc Pre and a scuff pad or stainless wire brush and scuff the part up. The aluminum should have a dull, brushed look once that coating has been removed. Once the part is wiped off and the acetone or PRE evaporates you’re ready to weld.

For Modern Inverter welders we suggest using a hybrid tungsten like a “purple band” E3 tungsten. This will allow you to weld on any type of material without changing tungsten like older transformer TIG welders. When sharpening your tungsten, we suggest grinding the tip to a sharp point and then putting a small flat on the end. If you want to change the shape of your arc you can put a larger flat on the tip or change the angle of your grind.

Now that the welder is on I want to mention that we suggest using 100% Argon for shielding gas on 99% of your TIG welding jobs. This is true for most any material whether it’s aluminum, stainless steel, or mild steel. I also like to crank my shielding gas flow up higher for aluminum to help with gas coverage when welding.

For this weld I have it set at about 130 amps max. Most of the time I’ll be welding a little under that but that’s about the spot that gives me the range of motion in the pedal that I like. This range of motion is important as it allows me to change things on the fly and if I need to get a little more amperage out of the machine to the heat an area I can and then I can back off at the end of the work piece.

I’m going to start by initiating an arc and you can see it’s cleaning by that little white halo you see, and the arc is dancing around like we were talking about. Once I have some heat into the metal and it’s cleaned sufficiently I can slowly give the pedal more pressure which ramps up the amperage and heat. You will see the weld puddle start to open and shimmer where the aluminum has become a liquid. You will then start to see a little opening at the front of the puddle and you want to add your filler rod to the front leading edge where it “opens up”. Be careful not to hang your filler rod in the next to the tungsten for too long as it could cause the filler rod to start to melt just from the heat coming off the weld.

After putting your first dab of filler rod into the puddle you can move about half the distance of the weld and add another dab of filler. Continue to repeat this process as you go, making sure that you are allowing the cleaning action to keep working as you move. The hotter the workpiece becomes the quicker you will need to move, or you will have to back off of the amperage to compensate. As near the end of the weld seam I like to slowly back off the pedal and add one last dab of filler rod to the end of the puddle and continue to back off of the pedal, moving the torch to the bottom edge of the puddle until you are fully off the pedal. Make sure you leave the torch hovering over the weld to allow shielding gas to cover the weld puddle until it stops completely.

If you pull your torch away instantly you take that shielding gas from the weld and it is “shocked” and could cause a pit or crack in the end of the weld. The pit or crack could spread and fail over time. You can see in the top weld above there is a crater in the center of the last bit of weld and small cracks coming from the crater. This is what you will typically see if shielding gas was pulled from the weld too quickly.

We hope these tips and tricks will help you jump start your learning curve on TIG welding aluminum.

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