tig on aluminum..what the heck am I doing wrong?

Regarding arc starting, it is important to point out the relative difficulty, especially in the circumstances experienced by James.

With helium, arc initiation is easier than what James is currently experiencing with the oxidation layer being impossible to break through using pure argon.

Helium usually exhibits less arc stability.

Arc initiation with helium may be harder in DC, but rarely presents difficulty with AC.

guys ... Am I mising something?

at school we learn /practice on aluminum (TIG) with pure argon, also miller has a nice TIG chart which list different materials tungsten, gas flow , filler configuration and such, and it does reccomend pure argon for alu. as well.

The key word being school. It is unlikely that a school would invest the money to add helium/helium mixed gas where argon gets the job done. Just a guess but one could probably TIG weld with any of the inert gases, but you probably won't find Xenon at your local welding supplier because it is not as practical as Argon. IIRC, TIG was originally called Heliarc as in helium.

Shawn

I will try handling a TIG torch this weekend. I go back to teaching next Monday.

I think I will have a REALY good safety lecture on the first night

I have a consultation with the Seattle Hand Surgery group on Thursday to discuss reconstructive surgery. I am perfectly willing to sacrifice some toes to have my fingertips back. I will know more then.

I believe it has too much copper. The only aluminum/copper alloy that is weldable is 2219, and you need

Airbus supposedly has figured out how to laser weld 2024, but it can't be TIG welded without cracking.

Same here. I use a higher helium mix for copper. Pure helium for really thick copper. I have 2 TIGs at school with argon/helium mixers to demonstrate the benefits of helium mixed with argon.

Don't forget to check your GRINDING WEEL (been there, done that...).

Let's save Ernie's bruised fingers. A google search gives the following link:

"To put some order in the above we should first understand the structure of hardenable Aluminum Alloys. In very simple terms, Aluminum Alloys of Type 2xxx include about 5% of copper which confers special properties to the material.

It all depends on a property called solubility, that is the capacity of an element of being dissolved into another in what is called solid solution. The favorable situation arises when at room temperature the solubility is limited, while it is larger at a more elevated temperature (less than the melting point). When this situation arises, at the higher temperature the atoms of the less abundant element take definite positions in crystals, which are the building blocks of the alloy, but at room temperature, say after cooling from melting, they group in disorganized lumps.

With some elements, like copper in aluminum, a strange effect appears. While heating at a certain temperature, below the melting point, all of the copper present enters into uniform solution, like sugar in water (except that we are talking here of Solid Solution).

A property called diffusion provides the driving force for displacing copper atoms into the matrix (the mass) of aluminum, so that the density of copper atoms, given sufficient time, is homogeneous or equal in each and every point.

When the material is cooled back to room temperature one of two different things may happen. If cooling is slow, copper atoms driven by the reduced solubility at lower temperature, will again group themselves in lumps, useless for providing improved properties.

But if cooling takes place immediately, by quenching the material into water, the copper atoms have no time to diffuse back, so they remain in a so called supersaturated solution at room temperature, which is a not so stable condition. Then just by themselves, in about four days, they precipitate out of solution in tiny particles or "phases", in a microstructure which exhibits much higher mechanical properties (strength and hardness). This process is called natural aging. A similar process called artificial aging, is produced much more quickly by heating at about 120 to 180 oC (250 to 360 oF). That is why the complete process is called solutioning and precipitation hardening.

Welding-aluminum of these types, will not only hurt the mechanical properties, but also the corrosion resistance, practically destroying the properties that made them useful: therefore they are considered non-weldable, except by resistance welding. "

Make sure there isn't a breeze blowing the shielding gas away. Even a light breeze you can barely feel can cause troubles.

Maybe.

Why then do we see this recurring theme of "What am I doing wrong with aluminum welding?"? This theme comes back to this list approximately every three months. Eventually, it may even make it to the FAQ.

Everybody that comes to this list with the same lamentations, are following the pure argon approach and noticing a need for high current, poor starts, sooty welds, and generally uncooperative material. This was my experience as well. Sure, you could spend all day brushing the aluminum, or have the acetylene torch on standby to keep the aluminum hot enough to enable welding with argon. After losing the heat treat on the aluminum, losing corners, features, edges, and patience, helium comes as a welcome relief.

After the use of helium is recommended, voila, no more complaints. The difference is so stark, that people don't ask questions after experiencing the ease and success of welding with helium. They just put the grief of argon with aluminum behind them.

This is why it is so easy to recommend helium, because it works, plain and simple.

Also, the "heliarc" process was developed within the context of aircraft aluminum welding. Helium was likely incorporated as part of the trade name because of the exceptional success when using it for this purpose.

It is difficult to ascertain why welding aluminum in a school setting works, and why it doesn't work out so well in real life. Perhaps it has something to do with material type in school, or preparation. It might even be related to technique.

In real life, aluminum welding is rarely ideal. Using helium does make it a lot more pleasant. It doesn't' require as much cleaning, as is the case with argon, and keeps the weldor welding.

Again, the difference is so stark that I doubt anyone would come back to this list, and recommend avoiding helium altogether because of the needless expense.

Ground position is also an important factor, which is largely ignored in steel welding applications. Steel welding is far less sensitive to ground positioning. Since most people get their start with steel, it is a hurdle to develop sensitivity to this issue. With aluminum, the effect of ground position is very noticeable. Most people do not brush the location where the ground clamp is attached, or make a clamp that maximizes contact. If you get sooty black marks at the ground clamp, you have a poor ground. Grounding directly to the work is advisable, and even in the vicinity of the weld, or in a directional relationship to the area requiring the most heat yields the best results. In some types of work, you can actually use the grounding clamp to better direct heat and penetration, or to avoid making holes in thinner sections.

Using helium with aluminum is analogous to back-gassing with stainless. If you want your weldors to be occupied with grinding, brushing, cleaning and so forth -instead- of welding, keep on using argon with aluminum, and don't do any back gassing on stainless. Your suppliers will love you for buying all the grinding supplies.

Ok...I don't mind buying another bottle. If I use a mix as Ernie suggested, what percentage of Helium/Argon do I request?

Earllier this summer, i was welding great on new pieces of 1/8 scrap aluminum...but if there is something that can make a significant difference in weld quality and ease, I'm all over it.

Thanks

Oh..and..if I went with a mix instead of Argon..can I use that for steel as well??

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Reverse tha if you are working a lot of copper. so 75% helium, 25% argon.

I use a bottle of each and a simple mixing "Y" with back-check valves. I guess at the mix and it works fine.

snip

It will work for everything.

I had to order the mix. The local guys didn't have it in stock so it'll be in next Wednesday. Can't wait to try it. Ordered the 75% Argon/25% Helium mix.

Thanks guys

Run 100% helium and it's possible to DCEN aluminum for much greater penetration and a lesser HAZ than AC welding aluminum.

Even without cleaning action it's not as hard as conventional aluminum welding wisdom would stipulate.

(Not recommended for welding thin stock however.)

Dennis van Dam

I'm hearing rumors that there is a helium shortage on the horizon. Apparently the main world supply for it is some natural gas wells in east Texas that have about 2% helium in them. They are beginning to play out, and by 2011 or so, supplies will really tighten up. So by all means, substitute with Argon or CO2 wherever and whenever you can. We should certainly stop filling party balloons with the precious gas.-Jitney

Ah yes, the helium shortage story again. Talk to people who work with helium, and they will tell you that there's been shortages almost as long as there have been oil shortages.

The other story you can look forward to is the helium plant breaking down. It goes something like this: there are only a few cryogenic machines that refine helium, every time one breaks down, they have to custom machine parts for it.

The excess helium is on the same tanker as the rarefied crude.

Get it yet? It's just more BS suppliers use to jack the price.

Yes, do make parsimonious use of the gas, by all means. Take power away from the tyrannical barons of helium.

Dont worry too much. The US government maintains and we taxpayers fund the Stratigic Helium Reserve.

"I mean, when's the last time you heard of a college where the Young Republicans staged a "Sit In" to close down the Humanities building? On the flip side, how many sit in's were staged to close the ROTC building back in the '60's? Liberals stage protests, do civil disobedience, etc. Conservatives talk politely and try to work out a solution to problems through discourse until they believe that talking won't work... they they go home and open the gun cabinets. Pray things never get to the point where the conservatives decide that "civil disobedience" is the next step, because that's a very short route to "voting from the rooftops" Jeffrey Swartz, Misc.Survivalism