Using Helium for Aluminum Wheel Repair (jakeru's #19)

[jakeru]

I got a new welding toy to play with... a bottle of Helium! (Old 155cf Argon, meet your new pal: 330cf Helium!)


I found the tank on craigslist as basically an empty tank for $100, and it came with a balloon filling gauge/regulator. I then got the tank filled (exchanged) from my local welding supply for another $120 out the door.

I was hoping to be able to mix the helium and argon with a "Y", but I measured one of my regulators puts out 30 psi and another puts out 50 psi, (so I think that might not work too well.)

This aluminum wheel will be my first experiment (and also a paid welding job) where I will try the Helium. The outer wheel lip was previously repaired with bondo/body filler, which cracked out when a tire was being mounted, a poor repair solution. I hammered and ground it all out (and I even found an extra "hidden pocket" of the stuff! Tapping with a hammer, the filler sounds dull compared to the sharp metallic ring of aluminum), and prepped it down to fresh aluminum surfaces with a flap wheel.
Before prep:

After prep:


For the Helium test, I set up everything up for welding just as I would if I were using Argon: 3/32" 1.5% lanthanated tungsten (sharpened with blunted tip), 20%EP (AC mode), and footpedal for current control (with full machine output of 200 amps current at wide pedal down.) And I used a #6 stubby gas lens with 15 cfh gas flow.

First thing I noticed when starting the pre-flow, was the floating ball in the regulator floats up and down with some more "springiness" in Helium than it does with Argon. And the sound of the Helium coming out of the torch even sounds different (quieter) than argon.

The arc through Helium was definitely harder to start than it was through Argon. (I was thinking, it was good that I was using a lanthanated electrode and not pure or zirconiated, which tend to be even more difficult to start!) I was really amazed how I had an instant puddle on the cold aluminum wheel, even with very light current. The footpedal position that what would have just "etched" the surface with cleaning action on Argon, actually left a 3/16-1/4" wide swath of melted metal surface on Helium! So with Helium, it wasn't possible to just "etch" the surface, it was melted aluminum surface, or nothing at all. (Crazy stuff!) I don't think I ever floored the machine; it felt like I did most of the welding at 20%-40% pedal depression. I have a feeling I would have been running double the current or more if I was using Argon and may have perhaps floored it, at least at the start.

Anyhow, I was getting some black "smut" on the outer edges of my weld area I haven't figured out yet, but I think it's because the lightweight Helium shielding gas is doing a 180 degree turn out of the cup and floating upwards. I'll have to try pumping up the cfh and see if it cleans up the dirtiness next time. Amazingly, it wasn't anything that posed any problems welding over - I was able to melt through it effortlessly with a new puddle. It did just look a little bit like hell. (No problem on this application, all the surface will be getting ground off anyway.) The surface of the puddle however looked bright and shiny under the arc - no oxides floating on the surface were noted.

After some grinding (because I got a little filler rod feeding happy on the first pass ), I did a second welding pass to further fill in and 'touch up' any low spots. I also noted that the aluminum deposited in the first pass I ground down, was totally solid and free of porosity and inclusions (a good thing!). And after the second weld pass I'll say, it's ready to go back to my wheel repair customer for them to further work over. (They will further grind/smooth, straighten as needed, and paint.)


I think I'd like to do some more scientific back to back tests of He vs Ar... I need to work out a way to mix them in various ratios, I'm thinking.

[Wrenchtamer]

I'm glad to see you are finally getting to experiment with helium, Jake. I know you have been itching to try it for a while. A few months ago at my old shop, they ordered up two huge bottles of helium to fill balloons for a promotion they were having. In my typical "I'll ask for forgiveness later" manor, I was able to requisition said bottle of helium and give it a go. My experience was similar. Very quick puddle formation, difficult arc start, and lot of sooty ickyness deposits. This was unmixed helium as well. From what I can gather using pure helium just kind of naturally looks dirtier than with argon.

I work at a different shop now, (not related) and we do custom builds and restorations that sell for upwards of a quarter mil on the high end, low 120s on the low end. I order a lot of custom fabbed parts and on some of them I have noticed that there is an identical black residue left in some of the nooks and crannies of the parts. I believe cleaning the parts after welding is how the make the helium work look so good. I would like to try a mix. I bet it would be a lot cleaner and soften the arc starts. Keep us updated.

[dgarnier]

you can use balloon helium? I was told you need ultra pure helium and its $$$

[jakeru]

Wrenchtamer - That's interesting about you noticing the black smut also after experimenting with TIG welding helium. I have a few ideas what could be causing it at this point, and hope to get to the bottom of it eventually.

One thing I did with the helium was, I filled a small balloon with it. I found it pretty eye opening how readily that Helium balloon wanted to float (and how fast it would rise when I let it go!)

I wonder what ratio I'd need to mix (He%/Ar%) to get a gas that would have "neutral buoyancy" in air? (Neither sink nor float?) If anyone is inclined in calculating such Chemistry related things, your help would be appreciated. (I remember kind of glossing over things like "moles" and such being discussed in my high school chemistry classes, and I didn't take any chemistry in college.) I also wonder if welding with this "neutral buoyancy" shielding gas mix, may be able to use an even lower flow rate (for good shielding) than pure argon. IE: gas stays where you flow it, rather than floating away OR sinking.

FYI, I didn't spring for the "ultra high purity / lab testing" Helium tank. My welding supply manager recommended against it, due to an extra $40 per bottle and he claimed it wouldn't be necessary. I've also ready differing opinions about whether its helpful or necessary for welding. Although it's good to know he did have it, (and even right there in stock!)

I determined last night that both of my regulators/flowmeters actually have about the same outlet pressure, of ~50 psi. (The false, 30psi read I took on one the other day was because I had it hooked up to a nearly empty argon bottle, which must have only had only about that much pressure in it!) Time for an argon bottle refill. (And do you want to know something I really like about my local welding supplier? ...open on Saturdays! )

bigjoe - I've e-mailed Jody about the He/Ar mixing, regulator outlet pressures, and check valves. He agrees that the check valves probably aren't necessary if the two regulators have the same outlet pressures. (They do seem like nice things to have though, because in case one tank gets empty, the check valve will prevent the other gas from potentially leaking out and into the other tank. I did just have my flowmeter/regulators taken apart last night, and will need to do some pondering on how this might happen.)

--Edit---
I just took a crack at the "neutral buoyancy" He/Ar mix calculation. I found some simple, "pounds per cubic foot" density numbers in the He/Ar MSDS datasheets (http://www.centralwelding.com/MSDS-P...ld%201,2,3.pdf)
Ar = .103 lbs/cuft (at 21.1C / 70F)
He = .0103 lbs/cuft (at 21.2C / 70F)

...and I also found a density from Wikipedia for air (http://en.wikipedia.org/wiki/Density_of_air) for a similar temperature/pressure
1.2041 Kg/cubic meter (at 20C / 71F)
= .079825 lbs/cuft

Then it's just solving "X" for the equation,
Helium + Argon = .0705169 lbs/cubic
x*.0103 + (1-x)*.103 = .075169
and I got x = .3, or 30%.

So, the mixture of Helium and Argon that would in theory give neutral buoyancy in air (and would possibly neither rise nor fall after exiting the TIG torch cup) would be 30% Helium / 70% argon.

[DaveO]

Seems like the 30% He / 70% Ar mix would result in neutral buoyancy in a balloon or similar contained space... but witrhout containment, don't those weights suggest the argon
would displace the air, and the helium would rise quickly?

[jakeru]

Dave, I think there may be forces at play that keep mixed gasses mixed and not let them separate out immediately (at least to some degree.)

If the components in air separated out very quickly/readily, wouldn't we only get to breathe the densest contents (IE: argon) down at sea level? Anyhow, my neutral buoyancy theory should be something that I might be able to test. Here is something I just noticed - ck worldwide's guide to shielding gas flows recommendation chart, says 30% or less Helium (/Argon) mixes can use the same flow rate as for pure Argon:
http://www.ckworldwide.com/tech-3.pdf
(Kind of interesting they picked 30% as the cutoff point...)

I'm excited because I'm up and running with not only a fresh argon bottle, but I also now have a "Y" setup. I've tried it so far, just flowing gas out of the torch (haven't done any arc tests yet), and so far so good. Both floating balls respond instantly when the gas solenoid opens, and adjusting one of the gas flows does not impact the flowrate of the other - perfect. I incorporated 1/4" NPT fittings into the "Y" connection, so I may be able to add checkvalves on later if desired. I put a standard outlet fitting (5/8-18 flare I believe) on the outlet of the "Y", so I can connect the same hose that connects direct to a regulator to the outlet of the "Y" (or back the other direction) as needed. (This was easier said than done... I had to weld two brass fittings together to make it happen!) Good stuff.



Edit: I just did some quick tests on various He/Ar mixes, run back to back. 0% He, 33% He, 66% He, 100% He, then repeated the sequence again, and a few other things. Just small 1" long beads run on 1/16" flat stock with 1/16" filler rod. I found something interesting only on the pure (100%) He, the glow of the arc was actually red in the middle, just off the tungsten. Around the red glowing zone, it had the normal green glow. On all other mixes, the arc didn't have the red glow at all, it was only the usual green. (This is though my auto-darkening lens, of course.) Pretty cool.

I did all my test with 20% EP (minimum AC Balance my machine goes to), and it seems the 33%-66% He mixes could be useful in reducing the ethed zone while still providing some necessary cleaning. The 100% He had oxides in the puddle and a "crazed" cathodic etch pattern in the surfaces around the weld bead. I used 15 total cfh for most of the tests, but I did try boosting the cfh with heavy He concentrations to improve cleaning (I think I boosted it to 20cfh, which didn't seem to do much; maybe I need to boost to something crazier, like 30cfh.) This is with a #5, non-gas lens cup. I wasn't finding any evidence of smut or soot (of any kind) on any of these tests. I'm really glad I have the ability to vary the mix, and didn't get a pre-mixed bottle, this is cool. Oh yeah back to back going from He mixes back to pure argon, definite increase in the amount of foot pedal depression to get a puddle. I was using a 1/16" tungsten.

There is a definite difference in noise of the He vs the Ar (as well as any major change in the relative mix) coming out of the TIG torch cup. In fact, after I vary the mix, I can hear it when the new gas mix starts making its way out of the TIG torch. (Doesn't take long for the new mix to get to the cup, about 2 seconds with my setup, I'd say.) Different noise the gases make "whistling" or "hissing" out of the cup, (or through the orifices in the collet body, perhaps.)

[everlastsupport]

Hey Jake,

Any finished pictures after grind and polish? Or did you hand it off and say "there ya go".

[Cippee]

After 80% helium or so you lose arc stability. You can weld 100% helium they do it when they tig weld thick copper but it isn't alot of fun. After all it is heliarc.

[Legacyartist247]

I guess it takes a trained eye to notice the difference between Helium, & argon...... Ive used both & simple cant tell any difference... Either way your welds look good, & it looks like you got good penetration.....*****

[bigjoeinkg]

Check out "weldingtipsandtricks.com" for setting up a "Y" mix for Ar & He. Make sure to use check valves in each line between the regulator and the "Y". He needs a higher flow rate.