100% helium required for aluminum
Please don't give the man false information. I am glad you said that though because now I can properly inform him on shielding gas for use with aluminum.
First off Helium isn't required. Lets get that out of the way.
Helium is usually used to get a hotter burn. The thermal conductivity is about double that of the other gas that is great for alum. (Argon) This allows you to have greater penetration, wider spread, weld thicker pieces.....This is good but it also allows for burn through especially when new to welding.
Helium also produces a burned looking bead. Which can be removed with a wire brush ect.
Helium is also more expensive, less dense, and requires a higher flow rate than argon. You will find yourself going through it faster, until you learn you can go faster with the gun.
Now Argon is great for welding thinner types of metal. Its produces a narrow spread, its a little more pourus, and the beads are generically brighter and shinier.
Keep that in mind when doing production work.
Any type of structural aluminum should be done with helium or a 75/25 mix of helium and argon.
You can mix these two gasses no problem, the more work you do you will realize which mixture works the best for you.
Remember argon is cheaper, if you are not doing alum chassis, certified alum roll bars/cages...then you probably dont need helium, and/or you can adjust the amount of helium in you mix to help if you weld thicker materials.
I prefer argon as its cheaper I get more for my money, it produces a cleaner brighter weld, and I don't have to switch the bottle if I want to weld some steel pretty quick. Welding steel with a pure argon mix isn't recommended but can be done if you need to do something quick where strength isn't a concern. If you have ever tried welding steel with helium you get erratic patterns and its almost impossible.
I do a lot of side work on custom cars, intake piping, catch cans, radiators, inter coolers, reservoirs ect. Helium is not needed, I have a smaller bottle, that I can go out and fill with 100% helium if I do a certified cage, but because of the price I have only done one before.
