Welding gas question

Lizer

Lizer

Mad Scientist
For Mig I’ve always used 75/25 Argon CO2.

I want to buy a bigger tank and a guy has a large tank locally for sale completely full with trigon, which is 89% Argon, 8.5% CO2 and 2.5% 02.

What are the advantages or disadvantage of this blend for Mig?

And secondly, when I need to exchange my tank, do you think I’d be able to do it for a 72/25 if I wanted to? Not sure if there’s some industry standard around that or if it’s supplier specific.
 
The 89% argon value is to high. You could mid weld with it but, you'll sacrifice tensile strength so, it's not recommended.

As far as using the tank for an exchange, that shouldn't be a problem.
 
im not sure if its a local law here or not but dont you have to get the tank recertified every 5 years otherwise its illegal for a supplier to fill it? if so keep that in mind when buying the tank. it may be older, need a recert which will add to the cost of the tank. its been years since i had one done but i remember it being around $150 back then. im sure it hasn't gotten cheaper
 
Here Praxair exchanges the tank. They told me to buy a used one and the age didn’t matter.
 
yeah we do a tank exchange here as well but you still have to pay $150 every 5 years to cover a cert test even if its not on your actual tank. just sayin...read the fine print to make sure of any extra charges like that
 
Never heard of a tri-mix containing O2 being used for MIG. Tri mix is usually used for stainless but with a small amount of CO2 not O2. Blends with more Argon are OK for sheet, although not used as much. Argon gives a shallower bead, with less penetration, so on heavy materials with the MIG it's not the best choice. TIG is a different story. 100% CO2 is sometimes used, it penetrates deep but it is miserable to use on sheet. And the welds are very very hard due to the carburizing effect of the shielding gas.
75/25 is a compromise and works well for all around MIG welding. 80/20 is sometimes sold as well.
Keep in mind if you buy a tank from an individual, you may have issues getting re-fills at your gas supplier. Local ones to me, AirGas and Arcet will only exchange their tanks now. YMMV.
 
Praxair are the ones who told me to go buy my own used tank. They also swapped out my tank I brought with me from Iowa when I needed to fill it. So between Iowa and MI over the last 14 years I’ve never experienced the issues described above with the tanks.
 
With O2 in the tri-mix--that shielding/ionization gas is not the best for short-arc welding with MIG for low carbon steel with decent results. You might be able to fudge it and do a lot of grinding clean-up afterward. It may be used for metal-cored wire with MIG for steel welding 1/8" and up. I don't recognize that mixture here where I live. I will ask my friend who works at an air separation plant tomorrow. You may not have the power on your welder use it well--but worth a try if you get the cylinder for lost-cost considering the cost of the gas inside may have no value to you.

For short-arc transfer welding on low carbon steel gauge thickness to 3/16" or so, any mixture 75AR/25CO2 to 95AR/5CO2 is typically good. It makes no difference for strength with ER70S-3 or 6 in anything worth mentioning. ER70S-2 is still sold and used for cold-wire TIG in the 1# spools in 0.030" but it is not commonly available in many places.

You can buy and legally possess "customer" cylinders. They will not have any stamping on the valve ring or on the cylinder stating "Property of:........." See that don't buy it used--the refiller will seize it and return it to whoever it is owned by. They might be in competition--they still do this and get a "finder's fee". You should be able to buy this cylinder--get it filled with any AR/CO2 mix you want or that they sell even if the hydrotest date is not current. The time on the manifold for refilling these gases is the real expense. Larger is always less money. Was a bit shocked to get some Helium/AR mixtures the other day for well over $300/cylinder--maybe 225 cubic feet. AR has gone up some but Helium.........................................some are paying close to $500/cylinder depending on how much helium.

The last hydrotest (req. every 5-10 years) is stamped on the cylinder in month and year. That used to be an Interstate Commerce Commision requirement for transport and perhaps it still is along with OSHA. What you do is just turn in your cylinder empty and exchange for another customer owned one ready to go and such. I done it this way for 30 years and at least 4 different welding distributors wherever I ended up living. Before that--used to pay to have my cylinders tested and returned to me--then it was $35 and a very long wait. No point in that for me now. Just make sure the one they give you back is indeed a customer owned one. Or, when you go back to have it filled--they will charge you a monthly demurrage charge of perhaps $5/month you have had it. Many cylinders in use today date to before WWII. One of the CO2 rental cylinders delivered the other day was 1931 as the first hydrotest date stamped in it. I've seen them to 1918.

Try to find an independent welding supply distributor chain with his own air/separation plant--or refill contract with the large companies--hard now but is a better option if such exist in your area. They tend to treat individuals better. Most people are stuck with whatever supplier is near them and they know this.
 
The guy is asking $300 for the cylinder (it’s one of the bigger ones) and it’s completely full.

Right now I have a small cylinder, I think it’s a 42 or something weird like that, but as you said it’s expensive to fill and not much cheaper than bigger cylinders. I go through 2 of these cylinders a year on average.
 
Keep looking. You should be able to find a 125 cu. ft. ( about 4' high ) filled for $260 - $300.
Refill (exchange) will be around $55-$65 dollars.
 
MJM said:
Keep looking. You should be able to find a 125 cu. ft. ( about 4' high ) filled for $260 - $300.
Refill (exchange) will be around $55-$65 dollars.
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That is the size tank I have. I paid $145 for a full tank last year from a small independent near me. Charged me $56 to fill it last week
I have more problems with recertification on my oxy/acy tanks than I do with my welding tanks.
 
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It might be an interesting thing to try, here's a Linde brochure talking it up:


I wonder of the little bit of oxygen helps consume some of the fumes, I imagine the chemistry inside the little gas-shielding cloud is interesting to say the least. But I wouldn't want to pay that much just to test something out of curiosity.
 
crashtech said:
I'm voting hard no on that in the absence of any real world experience with O2 containing shielding gases. Unless you have welded with it before, stick with 75/25.
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I actually talked to a friend of mine who's a professional welder a few days ago and he told me the tri mixes are pretty good and will give a better puddle, but they're more expensive so most people just stick with a regular CO2/O2. He said I'd probably really like the tri mix.
 
I don't think trimix is allowed for OE certification and it isn't recommended by I-CAR as far as I know. So that's why I pushed back on it. But if there isn't any collision repair on modern vehicles going on at your place, it might not be a concern.
 
crashtech said:
I don't think trimix is allowed for OE certification and it isn't recommended by I-CAR as far as I know. So that's why I pushed back on it. But if there isn't any collision repair on modern vehicles going on at your place, it might not be a concern.
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Lol. Are you mistaking me for talented?
 
Still wouldn't use it for carbon steel Lizer. This got me curious and I went back through some welding textbooks I had from my I-Car days. From what I can tell the mix you listed above is used with MIG spray transfer on low alloy steels (4130, 4140 etc.) and some stainless. Personally I think for $300 you could purchase a large tank of the proper gas, and have money left for a refill or even two.
 
Well the guy never responded back to me anyway so probably a lost cause at this point. I’ll just keep an eye out for 75/25 tanks.
 
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