Tig Welding Aluminum

It's been awhile since I welded aluminum but if I remember correctly I would stick the whole tungsten out about 1/2" and switch the polarity to DC-positive and hold the torch vertical over a half inch thick piece of copper or bronze. And slowly ramp up the amps creating the ball on the end of the tungsten. You then have to slowly ramp down to prevent a crater or hole from forming on the tungsten ball, otherwise your arc will sometimes go directions you didn't want it to. Don't forget to switch back to AC.

I dont recommend grinding tungsten that has been dipped into the weld puddle. Instead hold the tungsten off the edge of a steel table at a slight angle and use a bronze hammer or whatever you got and break the contaminated tip off. An instructor from Miller taught me these things. If you do want to grind the tungsten use a grinding wheel that is only intended for aluminum. Use a separte wheel for other metals.

Use the largest gas lens you can find. It has wire mesh inside that allows the gas to flow better over the weld and also use Argon + Hydrogen for cleaner welds.

Also the key to good uniform welds is being relaxed. Resting your arm on a some thing that is propped up to keep your hand steady. This goes for your other hand that has the welding rod too.

Make sure your aluminum is preheated enough before starting the weld puddle. If you don't you get booger welds. Watch the joining aluminum pieces become wet looking and then apply some rod to form a puddle. Add the rod every second or two depending on your speed. And also remember to breathe. I use to hold my breath when I first began welding.

Adjust the tungsten so it is sticking about 1/8"- 3/16". When I was welding aluminum housings I would pull the tungsten out further and notice alittle more penetration of the welds.
imp:

I found the hardest part of aluminum welding was to keep everything CLEAN,CLEAN,CLEAN.
I clean the weld area with MEK or acetone to remove any oils and finger prints,then use a stainless steel brush or stainless steel wool to remove oxidation JUST BEFORE welding and then use the stainless steel wool to clean the filler rod to remove any oxidation from the rod. Aluminum can oxidize in MINUTES so clean just before welding. Most sanding disks and grinder wheels have resins that bond the abrasive together and will contaminate the weld area so avoid grinding the area clean. Carbon steel wire brushes and steel wool will contaminate the weld also.I always break off the contaminated tungsten but one of my teachers told me grinding the tungsten was OK! GO figure?
I use a 30 year old miller 250E-HF with no special controls like the new electronic ones have and once get it set to the amperage I want and everything CLEANED, welding Aluminum isn't really any harder than steel .
And remember the old welder's trick to pretty welds: go over any ugly welds with the torch and run a" line of fusion" to smoothen out the weld area to make it more appealing looking:thumbup:

The tungsten itself becomes oxidized after putting down a certain amount of weld beads. You'll notice the tungsten becoming light grey or off white. This means it's time to change the tungsten. The strength of the arc will deminish from the oxidation on the tungsten tip. Allowing the tungsten to stick out too far or removing the tungsten from the completed weld before post purge cooling of the weld will decrease the effectiveness of the tungsten which will have to be reground and balled up using DC-Positive as mentioned on my previous post.

The oxidation on the aluminum requires alot more heat than the aluminum itself because aluminum oxide on the surface melts at 3,700 F while the base material melts at around 1,200 F so that is why it is critical to remove the oxidation before welding. Also degreasers work best to prepare the weld, but make sure the degreaser doesn't contain hydrocarbons. Cleaning aluminum can be done simply with soap and water. I've done this many times with great success. Etching soultion is also an option for cleaning the material. Before beginning to weld use a stainless steel brush and brush ONLY in one direction. DO NOT brush heavly on the area to be welded or you could add contaminates to the weld.

And again I'd like to remind that a GAS LENS is critical for the cleanist welds possible regardless of the material being welded. The standard is a collet body but the gas lens body consists of a series of coarse and fine screens inside the collet body which gives better shielding of argon on the weld and provides optimum laminar gas flow to allow your welds to look their best. The gas lens also allows the tungsten to be extended out further for improved weld joint access.