Beginners Guide to TIG Welding Aluminum
TIG welding can be a difficult task for people that are new to welding. If you’re interested in this article, most likely you’re trying your hand at Aluminum for the first time. Aluminum is a great material that can be used in many applications, but it comes with a specific set of rules and challenges. In the next few paragraphs, we will go over some rules and guidelines to follow to help you on your way to Aluminum welding success.
A little information about Aluminum:
Before attempting to weld Aluminum, it is important to know a little bit about what makes it different from Steel. Aluminum has an oxide layer on top of it that melts at around 3762 degrees fahrenheit. Aluminum melts at around 1221 degrees fahrenheit. Think about that for a moment… The oxide that sits on top of every piece of Aluminum melts at a temperature nearly three times as the base metal. This is why we TIG weld Aluminum with Alternating Current (AC).
What is Alternating Current (AC)?
Alternating current bounces from DCEP (Direct Current Electrode Positive) to DCEN (Direct Current Electrode Negative) hundreds of times per second. When on the DCEP side of the wave, the current is cleaning the oxides off the top of the Aluminum. This is very important, because when on the DCEN side of the wave, the current is penetrating into the metal. This is the process that allows us to break through the oxides that melt much higher than the base material, in order to weld Aluminum.
As it is with any TIG welding process, it is important to clean your material before welding. TIG is a very clean process and will not deal with dirty material like stick welding or flux core welding will. It is also essential to use a dedicated Stainless Steel brush that is ONLY used to clean Aluminum. If you use a brush that was used on Steel or other material, it will contaminate your workpiece and cause you problems later on during welding.
Here’s where it gets a little tricky (if you’re accustomed to welding steel). Some machines have “AC Frequency Control”. This allows you to tell the machine how long to spend on DCEP and DCEN side of the wave. A good starting point is to put your machine to 70% negative. This means your machine will spend 70% of its cycle on the negative, or penetration, side of the sine wave and 30% on the DCEP (cleaning) side. You will notice a small oxide layer forming around the weldment. Those are the oxides burning off. Aluminum is a heat sink. It takes approximately 1 amp of power for every .001” of material thickness. This means if you are welding on ⅛” thick Aluminum your amps should be set around 125 amps. If you have a remote amperage control, such as a foot pedal or hand amperage control, you might set it around 150 amps so you have some room to go up or down as needed.
When you strike your arc, hold the arc stationary until you see a mirrored pool form. Once that pool forms you can start to add filler metal. Aluminum is a heat sink and will hold heat as you weld, so you need to be cognisant of your amps as you’re welding. Aluminum is extremely sensitive to “hot short cracking” which is a crack that will form down the center of your weldment. There are two ways to make sure this doesn’t happen to you:
- Always use filler metal.
- When you reach the end of your weldment, build up the crater with an extra dab or two.
Now you know the basics. For more information on welding Aluminum or to get help, join the Everlast Facebook group to interact with other operators using Everlast equipment.