MIG cover gas...argon and carbon dioxide mix

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Does anyone know the percentages of argon and carbon dioxide when used as the typical cover gas for MIG?  What I am trying to determine is the weight of the mixture compared to air....is it lighter or heavier than standard atmosphere air.  Will it displace air if used in a confined space?  Thanks for any help on this.
Reply:75 argon /25 CO2 is common. Argon is heavier than air.Everlast PA160-STH... and that's about it!
Reply:Typical mix is 75/25 or 80/20 argon CO2 and yes it's heavier than air and would cause issues in a confined space assuming the space is small enough and you use enough shielding gas. Anytime you go into some sort of confined space to weld you need to take proper precautions, not just because of shielding gases..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Thanks.
Reply:You can use any Argon and CO2 mix from about 85% to 90% Argon all the way to 100% CO2.I run 2 tanks one for CO2 and one for Argon, usually run about an 80% CO2 to argon mix, because I am cheap and it lays down really good welds at a real fast pace.See: http://weldingweb.com/vbb/showthread.php...wn-welding-gasLast edited by mad welder 4; 09-15-2013 at 01:21 PM.old Miller spectrum 625 Lincoln SP-135 T, CO2+0.025 wireMiller model 250 and WP-18V torchCraftsman 100amp AC/DC and WP-17V torchCentury 115-004 HF arc stabilizerHome made 4 transformer spot welderHome made alternator welder
Reply:Molecular mass of air is ~29, molecular mass of argon is 40, CO2 is, 44.  75/25 should be right at 41Experience is something you get right after you need it
Reply:Originally Posted by Fred sMolecular mass of air is ~29, molecular mass of argon is 40, CO2 is, 44.  75/25 should be right at 41
Reply:Quote Originally Posted by Fred s View PostMolecular mass of air is ~29, molecular mass of argon is 40, CO2 is, 44. 75/25 should be right at 41
Reply:Originally Posted by mad welder 4You can use any Argon and CO2 mix from about 85% to 90% Argon all the way to 100% CO2.I run 2 tanks one for CO2 and one for Argon, usually run about an 80% CO2 to argon mix, because I am cheap and it lays down really good welds at a real fast pace.See: http://weldingweb.com/vbb/showthread.php...wn-welding-gas
Reply:Originally Posted by gnm109I like to use straight CO2 for GMAW. I got started using it and it's perfect for my hobby welding fabrication projects.  With liberal use of welding gel, the spatter is easily controlled and the extra penetration that it provides is very nice. Obviously, Ar-CO2 would make a prettier weld, but it's twice the price of the straight CO2 so CO2 is the gas of choice for me for my MM252. I learned about it from a machinist friend of mine who also does repair welds on farm equipment from time to time and he uses for most of his heavy work with a vintage MM200.
Reply:Originally Posted by mad welder 4That is why I run about an 80% CO2 mix, a little bit of argon makes the welds look a lot nicer and cuts down on the spatter.If I used a traditional 75% argon mix I would be burning almost $20 a day worth of argon.I am pretty sure CO2 is a lot cheaper than argon. My 15lb CO2 bottle only costs $20 to fill, the argon bottle also costs about $20 also per fill and it only holds about 2 or 3 pounds of argon.
Reply:Yes C25 is only marginally cheaper than pure argon.But you cant weld aluminum or stainless with C25.Having spare bottles must be nice. I would like to have a second argon and CO2 bottle for swap outs. If the gas company is open I can just swap out the argon (during bankers hours) and my CO2 gets refilled, not swapped out, so I have to drop it off at the fire supply place during bankers hours and have it filled which takes between 15 min and 4hrs.My belief is the scrap yard will provide... In the last year I have been looking for and found,,,, a 40cu.ft helium bottle, two small 8 or 10 cubic foot oxygen bottles and a small matching acetylene bottle so far. So when the scrap yard produces an argon or CO2 bottle that's when I will get it, some day...old Miller spectrum 625 Lincoln SP-135 T, CO2+0.025 wireMiller model 250 and WP-18V torchCraftsman 100amp AC/DC and WP-17V torchCentury 115-004 HF arc stabilizerHome made 4 transformer spot welderHome made alternator welder
Reply:Can't help it, I work in the gas industryExperience is something you get right after you need it
Reply:Originally Posted by Fred sCan't help it, I work in the gas industry
Reply:Originally Posted by mad welder 4Yes C25 is only marginally cheaper than pure argon.But you cant weld aluminum or stainless with C25.Having spare bottles must be nice. I would like to have a second argon and CO2 bottle for swap outs. If the gas company is open I can just swap out the argon (during bankers hours) and my CO2 gets refilled, not swapped out, so I have to drop it off at the fire supply place during bankers hours and have it filled which takes between 15 min and 4hrs.My belief is the scrap yard will provide... In the last year I have been looking for and found,,,, a 40cu.ft helium bottle, two small 8 or 10 cubic foot oxygen bottles and a small matching acetylene bottle so far. So when the scrap yard produces an argon or CO2 bottle that's when I will get it, some day...
Reply:Originally Posted by gnm109That's an interesting way to obtain a cylinder. I have often looked for items like that but have never yet seen a gas cylinder in a scrap yard. Assuming you could find one, the LWS would look for the last date for hydrostatic testing. If the cylinder were out of date, you would have to pay for a hydrostatic test in order to be able to exchange it.If I were you, I'd find a way to get your own CO2 cylinder. Where I am, I doubt that I could get a refill of any type of cylinder the same week since the filling plant is remote to the office of the LWS. That would be a terrible inconvenience to me since I live in a rural area some 30 miles from the LWS and it would entail two trips at $3.99 a gallon of fuel to get there. That would be 4 gallons of gas in my truck for one trip ($16.00) and two trips ($32.00). My other car, the Ford Escort usually gets 30 mpg but I don't like to carry cylinders in it since I would have to fold the rear seat down and it's not safe to have a cylinder pointing at the back of your head in a small car. LOL. My son is just starting to weld his own items with the Lincoln SP175 plus that I gave him when I bought the MM252. He recently purchased his own 20# CO2 cylinder. It was something like $150 out the door but he can exchange it for a refill for $25 without a wait. I've always owned my tanks, or at least the right to exchange tanks with no leasing fee. I never understood the leasing deals. They used to call it a 99 year lease, meaning that the ownership of the cylinder remained with the LWS and you could freely exchange the cylinder. In any case, it's always better to own your tanks. I know that our friends in the UK and other areas can't buy them due to government regulations. They are forced to pay exorbitant leasing and rental fees which is a real shame.