How To TIG Weld Aluminum
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TIG welding can seem like a complicated procedure for those new to welding or familiar with other welding methods. TIG welding aluminum can seem even more challenging, but with the proper settings and practices in place, it is a great skill to learn.
As with any welding procedure, there are certain adjustments that will need to be made to your welder, especially if you have recently or only welded mild or stainless steel. Workpiece preparation and tungsten choice will also significantly impact your final product.
I Have A TIG Welder; How Do I Start?
First and foremost, you will want to ensure your welder can weld in AC or alternating current. In AC welding, the polarity of the arc changes rapidly from straight to reverse polarity. This is helpful when welding aluminum because the insulating surface oxide layer forms rapidly on aluminum. That layer melts at a higher temperature than the base metal and can make it difficult to melt the base metal.
The alternating current does two different jobs. The reverse polarity breaks the surface oxidation layer, while the straight polarity melts the base metal. This happens hundreds of times a second and makes a distinct buzzing sound when welding.
With your welder set to AC, the next step will be to select your voltage. While there is no perfect answer for your particular setting, a good rule of thumb is 1 amp for every thousandth of material thickness.
For example, working on a ⅛” thick piece of aluminum, setting your amps to 125 will be a good start, and you can fine-tune from there.
Pure Argon is the preferred shielding gas for TIG welding, and the flow rate on your regulator will be measured in cfh or cubic feet per hour. This setting will be based on what cup size you are using. A good rule of thumb is to set your cfh to 2.5x your cup size.
For example, if you are using a number 5 cup, you want your argon flow around 12.5 cfh.
This approximation can be changed based on personal preference and the area in which you are working. There are some other fine adjustments that can be made depending on the capabilities of your welder, which will be focused on later in this article.
My Machine Is Set Up; What’s Next?
We touched briefly on aluminum’s insulating oxide layer and why it makes welding aluminum difficult. Because of this, preparing and cleaning the metal to be welded must be done carefully and only with particular objects. The best tool to use is a stainless steel brush.
Avoid using the brush to clean oil, grease or paint from surfaces. To avoid contamination, the stainless brush must only be used on other aluminum surfaces. Acetone is also an excellent solution for cleaning your workpiece. It is good practice to wipe away any residual oxidation or debris from your metal after cleaning with a brush.
Other chemicals, such as brake cleaner, can be used, but you must take extreme caution to use non-chlorinated brake cleaner only. The chemical tetrachloroethylene found in chlorinated brake cleaners makes phosgene gas when exposed to extreme temperatures and can prove fatal. For this reason, it is best to stick with acetone.
With your welder correctly set up and your metal prepared, it is time to choose your tungsten and address a few other finite adjustments on your machine.
There are many choices for tungsten when TIG welding, and every welder generally has their own preference. When starting the Ceriated 2%, gray or the Lanthanated 2%, blue are excellent choices. They can be used on AC or DC and work well with inverter machines.
The thickness of your workpiece will determine the tungsten diameter. Depending on which welder you are using, you may notice a few other adjustments we still need to cover, both pertinent to TIG welding aluminum.
- The first is balance. Balance refers to the negative and positive current percentages alternating between the electrode and your workpiece. A good starting point is 30% AC and 70% DC. This balance will clean the aluminum well and still allow for excellent penetration. This setting will keep the tungsten relatively cool and prevent you from constantly balling the end.
- The second adjustment is frequency. This will be measured in Hz; a good starting point is between 100 and 120 Hz. Adjusting the frequency will change the arc cone’s shape and the arc force’s strength. The increasing frequency will narrow the cone and increase the force.
These settings are more for those experienced in TIG welding, but the above suggestions should get you going. This summarizes what it takes to get started, and everybody’s situation or preferences will differ. Once you are comfortable setting up the machine, you can tweak certain adjustments to your liking.
Ready, Set, Weld!
Now that you are all set, it’s finally time to weld. Attach your ground clamp to your workpiece and ensure you have the proper safety equipment. A quality welding hood is an excellent investment, make sure it is turned on and has functioning batteries. The arc will produce extreme heat, so you should always wear the proper gloves for handling materials, filler rods and torch. Make sure to get your puddle formed quickly. Moving the torch smoothly and feeding wire quickly will produce a nice strong and good-looking weld.