Very basic welding gas questions. Don't laugh

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I keep reading a 75/25 mix is good for mig welding.My question is do I need two bottles or is the gas mixed in one bottle?I always thought it was one bottle but I have seen pictures of people with two bottles on their cart so it is confusing me.I am guessing a 75 argon 25 CO2 mix in one bottle is what I need for my mm211.Also, I plan on welding aluminum with a spoolmate 150.  Will I need a separate bottle with different gas? if so, what gas?
Reply:Yes, one bottle with the mix.
Reply:okay. ill bite. 75/25 is a good place to start for non-flux wire. Gas is premixed and comes in one cylinder. You have the choice of different size cylinders from your welding supply.
Reply:No such thing as a stupid question. Just stupid mistakes for not asking...We were all n00bs once.The MIG gas mix is often referred to as 'C25'.Be wary of The Numbers: Figures don't lie,. but liars can figure.Welders:2008 Lincoln 140 GMAW&FCAW2012 HF 165 'toy' GTAW&SMAW1970's Cobbled together O/A
Reply:Argon for aluminum.An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.
Reply:You'll need a separate bottle of Argon that you'll need for aluminum welding.Ed Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:Yes you can purchase "C25" (75%-25% mixed in the bottle) n different sized bottles.  Initially the larger bottle costs more to buy outright, but the refill price for the gas works out to be much cheaper than for smaller bottles.
Reply:Would it be ok to just go pure Argon then if I only have one bottle?Or do you have to have the mix to weld regular steel with mig?
Reply:Now you tell me, DAM ! I was wondering why the supplier looked at me funny when I asked for 75 bottles of argon and 25 of CO2. Seriously, some questions are funny, BUT it's a question. It's better to ask the question then make a serious mistake by not asking as stated. So. keep asking !! Others will definitely benefit from questions.
Reply:To MIG weld steel you can use pure CO2 or a mix of Argon and CO2.  75/25 is a common mix. Mixtures with less than 25% CO2 are used (sometimes with O2) for MIG using spray transfer.The two bottles you see could be one of 75/25 for steel and another Argon bottle for aluminum.  Or the second one could be a tri-mix gas for welding stainless steel. Or just a spare."USMCPOP" First-born son: KIA  Iraq 1/26/05Syncrowave 250 w/ Coolmate 3Dialarc 250, Idealarc 250SP-175 +Firepower TIG 160S (gave the TA 161 STL to the son)Lincwelder AC180C (1952)Victor & Smith O/A torchesMiller spot welder
Reply:Originally Posted by OldendumTo MIG weld steel you can use pure CO2 or a mix of Argon and CO2.  75/25 is a common mix. Mixtures with less than 25% CO2 are used (sometimes with O2) for MIG using spray transfer.
Reply:CO2 is a reactive gas, and is considered necessary for steel MIGging.  Stainless requires a different gas helium, argon, and CO2. Aluminum Needs an inert gas.An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.
Reply:Originally Posted by travr6Can you use pure argon for mug welding steel?My boss has a Hobart mig welder with pure argon. I have welded with it before and it does ok. I take it that pure argon for welding steel with mig is not normal?
Reply:Originally Posted by Willie BBy the way, most of us don't mug weld, lots of us drink from a mug while welding.
Reply:Originally Posted by Willie BCO2 is a reactive gas, and is considered necessary for steel MIGging.  Stainless requires a different gas helium, argon, and CO2. Aluminum Needs an inert gas.
Reply:Originally Posted by travr6So if you had to weld steel and had to use either pure argon or pure co2, the co2 would be the better option?Looks like I will be needing two bottles then.Pure argon for aluminum with the spool gun and c25 mix for mig. Is that the best set up?I can actually mig weld fairly well. I have just never set a welder up before. I have used mainly stick for the past 10 years.
Reply:Originally Posted by Willie BBy the way, most of us don't mug weld, lots of us drink from a mug while welding.
Reply:Originally Posted by CGT80100% argon is not specified for MIG welding steel, but some do it and say it works. Argon costs more than CO2, so the 75/25 mix should be less than 100% argon.Tri mix is for stainless. I tried that for welding steel and did not like the results.CO2 should produce a hotter weld, but it splatters more and the bead doesn't wet out as nicely, IIRC. CO2 is the lest expensive gas.75/25 Is a great all purpose gas for welding steel and I like to run ER70s-6 for wire. It is the most common.You got it: one bottle of 100% argon for aluminum MIG/Spoolgun and one bottle of 75/25 for mild steel MIG and you will be covered for many projects.My favorite size bottle is an 80 cubic foot. It is pretty easy to move around and I can pick it up and put it in a truck without killing my back. My brother has a 248 cuft bottle for his mig and it is a bear for me to handle. My bottle costs $30 or so to fill and his is around 60 bucks, but he gets 3x the gas for only 2x the price. There is a volume discount, so to speak.Did you just get the new Miller 211 inverter? I just unpacked mine today and need to go out and play with it. It is soooo much easier to move than my old Miller 135!
Reply:Use 85/15 for production welding w/ MIG .......cheaper than 75/25 , less spatter to clean up , easier to run spray transfer mode too
Reply:Originally Posted by SmoothOperatorUse 85/15 for production welding w/ MIG .......cheaper than 75/25 , less spatter to clean up , easier to run spray transfer mode too
Reply:For what it is worth, I toyed with playing with various mixtures, where I would self-mix.  In other words, have a Ar tank, and a CO2 tank, and mix to what I wanted.There were a couple of concerns.  First, a complete and accurate mix is somewhat non-trivial, over a moderate range of flows and temperatures.  The commercially available mixers are not cheap, but I determined that I could make a turbulent flow mixer which would work at flow rates of 5 to 50 CFH.  My day job is as a scientist, and have a background in aerodynamics, of which a significant part is turbulent flow.  Second, it turns out that my welder is programmed for CO2 and C25, and does a pretty good job with each.  I have not tried it with tri mixes with stainless, nor have I done any Al welding.So I back-burnered my project, but the bottom line for me was that I now have several tanks, including Ar, C25, CO2 and a couple of spares for each.  So while I decided I could mix, I chose to go with the more conventional approach.A final point, at my LWS, Ar is cheaper than C25.  Go figure.  Make that at the two LWS houses I use, Ar is cheaper than C25.
Reply:I started out with straight CO2 when I got my welder almost 20 years ago and it works fine...especially if you aren't welding new steel all the time.  I did get a fair amount of spatter though with my Hobart Betamig 250 but it doesn't seem to be near as bad with my new (to me) Millermatic 250.  We do have a Lincoln 140 (?) at work set up with C25 that welds very nice, but it doesn't seem to penetrate like it seems it should.  I did check into swapping out my CO2 bottle a few years back and found that C25 cost 3x as much.  I didn't think it was worth the additional expenses.
Reply:Originally Posted by Iain PMy big mig welder at work has cup holders for my coffee mug built in. Does that make it a mug welder?
Reply:I set up with stainless gas and wire on a MM252. I had bad information that anything would work for back purging, MIG was a fail with stainless. The part time fabricator at the pellet mill tried with a MM252. That wasn't working well. He couldn't do anything with it on 1/8" sheet, but was a success with SMAW & a Trailblazer. I tried a stick with surprising success. For reasons I don't understand, back purging seems unnecessary with stick.Aluminum MIG is not always the best choice. I'm a TIG lover.An optimist is usually wrong, and when the unexpected happens is unprepared. A pessimist is usually right, when wrong, is delighted, and well prepared.
Reply:Originally Posted by Willie BI set up with stainless gas and wire on a MM252. I had bad information that anything would work for back purging, MIG was a fail with stainless. The part time fabricator at the pellet mill tried with a MM252. That wasn't working well. He couldn't do anything with it on 1/8" sheet, but was a success with SMAW & a Trailblazer. I tried a stick with surprising success. For reasons I don't understand, back purging seems unnecessary with stick.Aluminum MIG is not always the best choice. I'm a TIG lover.