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Filler Metal: ER 4043 or ER 5356 for most applications
Gas: Argon or Argon/Helium Mix
You can weld aluminum with TIG or MIG, but if you are to weld aluminum with MIG you must switch to a Spool Gun set up. For this post we will be talking strictly about TIG welding on Aluminum.
The settings on most TIG welders will allow you to manipulate the arc for all different scenarios, for this post we will keep it simple. When welding Aluminum switch your polarity to AC (Alternating Current. See post AC/DC Welding).
For aluminum you your amperage will very depending on thickness, keep in mind that aluminum has high thermal conductivity. This means the heat distributes quickly throughout the work piece.
Now this will take some time to figure out exactly what works best for you as switching different cups out either a number #5 or #7 will often change the arc profile.
Personally i like using a gas lens with a #7 cup and 1/8" Tungsten. Although this is not i deal in all situations and you may need to use a #5 to get a tighter more precise arc.
When it comes to your tungsten, you want it to have a slight shiny ball at the end. To achieve this i have had varying results. Best practice is to sharpen your tungsten to a point and then sand the tip to basically create a platform for the tungsten to ball up on.
The best Tungsten's used for Aluminum welding are 2% Lanthanated or 2% Ceriated.
Get The Tungsten Balled Tip:
On your first Arc strike after sharpening your tungsten i have found that having very little stick out and striking an arc and forming a puddle on some scrap copper helps get a clean Balled Tungsten Tip.
This step is critical when it comes to welding aluminum. Because this metal creates an oxide layer on its surface you must wire brush wherever your welding with a copper wire brush.
As your wire brushing the aluminum you will see that the color starts to change from shiny to a more dull look, and you will sometimes feel a difference in the way it brushes once this aluminum oxide layer is removed.
After your done wire brushing take your Denatured Alcohol and clean off all the oxide and aluminum dust, also at this time clean your filler rods to avoid any contamination on them.
Once you have your machine set up on AC, your Grounded to the work piece, argon gas is on, your weld joint has been prepped and cleaned, you have balled up your tungsten and got the proper cup size and gas lens for the application, than you can flipped down your hood and strike the arc.
If you want more help please check out my other posts or ask me a question!
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