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Thread: Straight co2

  1. #1
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    Straight co2

    Hello!

    What are the advantages and disadvantages of mig welding with straight co2 vs 75/25? I don't think I would ever be welding the very thin gauges like 20-24 (probably never even 18 gauge).

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    Re: Straight co2

    Outside of being cheaper to run CO2 I don't know of any. It's a lot more violent of an arc, and a lot more spatter.

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    Re: Straight co2

    CO2 gets downright COLD as it exits the tank, so it has a greater cooling effect on the MIG gun. Better duty cycle and/or higher amps for shorter periods.
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    Re: Straight co2

    I use it exclusively. Some modern machines like my Multimatic 200 have programming specifically for CO2 to help with the spatter, although honestly spatter has never been an issue for me with CO2. I use it in the MM200 with solid wire, and I use it in Suitcase 12RC's running off of either XMT304's or TB325's with ESAB 7100 Ultra Dual-Shield wire.

    CO2 generally gives you more penetration as well as being cheaper to run. Because it's a liquid changing to a gas as it exits the tank, you get more runtime per tank volume than you'd expect. So since most LWS's won't allow you to own much larger than an 80cf tank, you get more bang for your buck with CO2 when talking customer-owned tanks. The tiny tanks of mixed gases like 75/25 are positively highway robbery-priced for what you get, and if you get a large enough tank to get better pricing, now you're paying an annual tank lease at $70+ per year.

    I haven't bought or run any 75/25 for what must be nearly a decade.

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    Re: Straight co2

    Quote Originally Posted by cbourbeau32 View Post
    Hello!

    What are the advantages and disadvantages of mig welding with straight co2 vs 75/25? I don't think I would ever be welding the very thin gauges like 20-24 (probably never even 18 gauge).
    CO2 is cheaper and generally runs hotter than C25, meaning more penetration. CO2 can produce more spatter. Lots of folks say/think that C25 produces better looking welds with less clean up, which may be important if you are doing auto body work. I am with Tbone, I don't see much difference for the stuff I do. That being said, I am running 90/10 exclusively now, because I need the high concentration of argon for spray/pulse MIG with my new welder.
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    Re: Straight co2

    If you doing a lot of welding and cost is a factor then CO2.
    If doing little or cost not a factor then 75/25 has a smother weld.

    There are other factors to type of wire you are using.

    In my shop I had CO2 and could mix gas too. But cost was a factor as all my work was Quoted.
    A bottle of CO2 will last almost 3 times longer and cost less too.

    Dave

    Quote Originally Posted by cbourbeau32 View Post
    Hello!

    What are the advantages and disadvantages of mig welding with straight co2 vs 75/25? I don't think I would ever be welding the very thin gauges like 20-24 (probably never even 18 gauge).

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    Re: Straight co2

    The other thing to consider is that some machines weld great with straight CO2 and others don't. My Hobart Handler 190 was an example of a machine set up from the factory to run well with straight CO2. Machines with adjustable inductance settings can usually be tweaked to run pretty well with straight CO2.
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    Re: Straight co2

    1 pound (liquid Co2) equals roughly 8.5Cuft of gas. So, a 20# tank of Co2 has about 175 Cuft of gas in it. unless you have a regulator for Co2 already, you will need a CGA320-CGA580 adapter, and make sure you have the nylon washers!. Pure Co2 runs cooler than mixed gases, a good start is to add about 3 volts to your settings

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    Re: Straight co2

    It cost me $19 to fill the 200 size tank with CO2 and the same size in 75/25 is $78. That as well as the CO2 lasting about 4 times as long makes it a no brainer for me. If you are having excess spatter issues then you aren't keeping your nozzle close enough to the weld. I build a lot of furniture that has to be perfect and if it was a problem then I would change but it just doesn't.

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    Re: Straight co2

    Quote Originally Posted by Bob View Post
    It cost me $19 to fill the 200 size tank with CO2 and the same size in 75/25 is $78. That as well as the CO2 lasting about 4 times as long makes it a no brainer for me. If you are having excess spatter issues then you aren't keeping your nozzle close enough to the weld. I build a lot of furniture that has to be perfect and if it was a problem then I would change but it just doesn't.
    Bob, what welder do you use?

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    Re: Straight co2

    I happen to recall, as a CO2 source you can use a CO2-bottle that pub-owners use to pressurize the beer-pump.
    That would be the cheapest method.
    Do not know about separate fittings to connect and legal issues eventually.

    oldwelderman

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    Re: Straight co2

    One other thing with CO2,

    If you weld in a cold winter shop issues can arise.

    More than a few times running straight CO2, I had to get out my heat gun/ hair dryer and mount it next to the regulator because the blasted thing was freezing and cutting off flow.
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    Re: Straight co2

    Quote Originally Posted by 455dan View Post
    One other thing with CO2,

    If you weld in a cold winter shop issues can arise.

    More than a few times running straight CO2, I had to get out my heat gun/ hair dryer and mount it next to the regulator because the blasted thing was freezing and cutting off flow.

    Speaking of freezing CO2, I saw this image the other day - for a regulator/heater combination.



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    Last edited by Jack Ryan; 01-30-2022 at 07:03 PM.

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    Re: Straight co2

    Quote Originally Posted by cbourbeau32 View Post
    Bob, what welder do you use?
    I use a Miller Shopmaster 300 with an S52 feeder unit attached to it and I also have a Millermatic 251 and use CO2 on both. I also use it occasionally on a Miller suitcase rig on my Trailblazer 301.

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    Re: Straight co2

    Quote Originally Posted by tbone550 View Post
    So since most LWS's won't allow you to own much larger than an 80cf tank
    This is something that is entirely dictated by location. There are many places where LWSs will sell you any size bottle you want. I only point it out because it may not be true for the OP, or many other people reading this. I have 330 bottles that I own and refills are around $75. I'm sure Co2 would be a bit cheaper, but I'm not using enough that it makes any difference to me.
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    Re: Straight co2

    If cold inside the shop the regulator ice will form. But you need to use a lot of gas.

    Dave

    Quote Originally Posted by Jack Ryan View Post
    Speaking of freezing CO2, I saw this image the other day - for a regulator/heater combination.



    Jack

  22. #17
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    Re: Straight co2

    Forgot to mention one thing...some people find Co2 a little harder to dial in compared to mixed gas.
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  23. #18
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    Re: Straight co2

    CO2 is different and most charts are for mix gas.
    I like mix gas but I do not like the cost and some types of flux core wire is only rated for CO2.

    I think come down to how must welding you plan to do.
    My self I could use 60 pounds of co2 a week. This would be almost 530 cf of mix gas a week.

    Dave

    Quote Originally Posted by G-ManBart View Post
    Forgot to mention one thing...some people find Co2 a little harder to dial in compared to mixed gas.

  24. #19
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    Re: Straight co2

    Quote Originally Posted by oldwelderman View Post
    I happen to recall, as a CO2 source you can use a CO2-bottle that pub-owners use to pressurize the beer-pump.
    That would be the cheapest method.
    Do not know about separate fittings to connect and legal issues eventually.

    oldwelderman
    It is the same bottle.

    It's not really cheaper buying from a beverage supplier then a welding gas supplier. The gas and the cylinder are the same thing.

    benefit of having a bottle of CO2 on your welding machine is that you can use it on a Beer tap if needed.Name:  CO2-Beer-Cooler-2-scaled-768x558.jpg
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  26. #20
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    Re: Straight co2

    The higher the C02 content, the higher energy the gas. It will also affect the shape and depth of the weld kernel. C02 weld pool will freeze faster than a mixed gas pool.
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  27. #21
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    Re: Straight co2

    Here in Japan, CO2 is very common in the average job shop. Running 25/75 costs around 6x more. I run a heated regulator that plugs into the standard 100v outlet, and never have issues with icing.

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  29. #22
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    Re: Straight co2

    I run straight CO2 with dual shield due to cost, an E size C02 bottle has more gas than a g size c25 while also being half the price of an E size C25

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