Shielding Gas

[tomstin]

Take me to school on shielding gas for welding. I'm on the edge of purchasing my first mig welder to repair floor pans on a project of mine. Now, its been years, should I say decades, since I picked up a welder and that was stick. As I understand, for the thin body panels MIG, fine wire with shielding gas is my low cost alternative.

Given I don't plan on doing this regularly, I'm looking to learn a new skill and move forward on this project, I'm not interested in spending a fortune. I'm willing to stick my toe in the water and if I decide to jump in later and upgrade to TIG, that's a whole different story.

So, when it comes to shielding gas, what's the lowest entry cost? Researching it appears I can rent a bottle? Can I transport the bottles laying down in the trunk (like I did with scuba tanks)? Argon or Argon mix seems to be recommended, but CO2 is an alternative.

Thanks for the insight!

 

[doojus]

Not sure how in depth you want to go with this, but I'll try to answer some of your questions:

1) You want 75%Argon / 25% CO2 (C25) for what you're doing with MIG
2) If you want to TIG mild steel you need 100% Argon
3) If you want to MIG aluminum you need 100% Argon
4) There is no media inside the shielding gas tanks and the gas does not liquify, so you can transport them any way you like and use them immediately after up righting them
5) You could use 100% CO2 but the beads will look like **** and you'll need an extra adapter

 

[koditten]

The gas will be one of the smaller investments. Depending on the size of a tank, it last a long time. I use the largest, portable tanks and can get 2 years on a can. I do a lot of welding.

 

[ilovevocs]

You can run straight CO2 to mig steel. It burns hotter but is dirtier and requires a bit more clean-up than C25. You may likely never have a practical need to use C02 but wouldn't hurt to do a little google searching on the applications / opnions floating around on the web as it relates to co2 and argon for mig welding steel.

Conversely the lower the Co2, the higher the argon, lower penetration but cleaner weld. Some people prefer to use 90% argon 10% CO2 for some applications.

Not that you need to concern yourself with this at this juncture but its something to continue to learn about as you gain skill with your tool.

To start off you need a bottle of c25 and use the baseline settings listed on your welder. For patch panels use .025 wire; ER70S-6.

 

[Professur]

I did the entire floor and firewall of a rotted out pickup truck with straight CO2. Since it's stored liquid and not compressed gas, it's a small bottle that last a long time. You're not going to be running beads putting in floor pans, so forget worrying about appearance. Tack, tack, tack, tack ... clean and seal. You'll need a welder with some decent amount of adjustibility. On-off-high-low isn't gonna cut it. Definitely want the thin .023 solid wire ... and don't buy it at horrible freight. Pay for the good stuff.

 

[zkling]

Call around to your local shops and see what their policy is on rent or purchase a 125 cubic foot 75 25 tank. Say it just as that. They will know what you want. Some places will not let individuals own tanks above 80cf, others will. You need to figure out what your local place is willing to do, this can be a very regional thing. A 125cf is a good mix between fill cost per volume and easy transportation/storage for the average home guy.

If you want to get into tig later, you'll need a bottle of straight argon. Skip the straight Co2, it's roughly between self shielded wire and 75/25 end result wise for the smaller machines.

 

[MoonRise]

The 'standard' shielding gas for short-circuit transfer mode GMAW on steel (aka MIG in 'low' power mode, as opposed to 'high power' spray mode transfer) is C25 aka 25% CO2+75% argon.

Relatively 'clean' welds, and pretty much all the 'small' MIG machine parameter charts/recommendations list the settings/parameters for/with C25 gas.

As to the cylinder (aka 'bottle'), get the biggest one you can buy/store/handle. The cost for the actual gas is usually the smallest part of the refill fee/cost. The rest is all the handling, etc.

ex: (using made-up but semi-realistic numbers) refilling a 40 ft3 C25 cylinder may be about $35 and refilling an 80 ft3 cylinder may be about $50. Twice the amount of gas for less than twice the cost there. Even bigger cylinders usually give an even lower $/ft3 ratio. YMMV.

summary: Get the biggest cylinder of C25 you can.

 

[dr_clyde]

I did the entire floor and firewall of a rotted out pickup truck with straight CO2. Since it's stored liquid and not compressed gas, it's a small bottle that last a long time. You're not going to be running beads putting in floor pans, so forget worrying about appearance. Tack, tack, tack, tack ... clean and seal. You'll need a welder with some decent amount of adjustibility. On-off-high-low isn't gonna cut it. Definitely want the thin .023 solid wire ... and don't buy it at horrible freight. Pay for the good stuff.

If you get a liquid co2 setup, make sure you have a regulator designed for it. Co2 sold for welding comes as a gas, not a liquid, unless you're buying bulk. Co2 for food service is a liquid. Using a gas reg on a liquid setup is a good way to damage regs. Not saying it won't work, just not recommended.

I'd get a cylinder on 75% argon 25% co2 to start.

 

[Professur]

If you get a liquid co2 setup, make sure you have a regulator designed for it. Co2 sold for welding comes as a gas, not a liquid, unless you're buying bulk. Co2 for food service is a liquid. Using a gas reg on a liquid setup is a good way to damage regs. Not saying it won't work, just not recommended.

I'd get a cylinder on 75% argon 25% co2 to start.

Yup. The regulator I have is good for both. The dedicated CO2 ones have a long brass neck to let the CO2 warm up before it gets up to the works. The adapter to use the generic welder regulator is ... a long brass tube with fittings on either end matching bottle and regulator. Keep your draw under control or you risk freezing it. Welding in cold temps isn't advised. When I'm going to pull a lot, I keep a wet rag on that tube and watch it for ice.

 

[gungatim]

If you get a liquid co2 setup, make sure you have a regulator designed for it. Co2 sold for welding comes as a gas, not a liquid, unless you're buying bulk. Co2 for food service is a liquid. Using a gas reg on a liquid setup is a good way to damage regs. Not saying it won't work, just not recommended.

I'd get a cylinder on 75% argon 25% co2 to start.

co2 is liquid under pressure. when you release pressure it turns to gas. never heard of a "liquid CO2 setup" or vice versa. all CO2 I have ever purchased, is liquid. Please explain. We filled Food and beverage CO2 tanks right alongside Mig tanks all the time...

 

[gungatim]

or do you mean liquid withdrawl dip tube for filling smaller tanks?

 

[dr_clyde]

I had inquired about this to the welding supply. All pure Co2 is indeed liquid in the cylinders, but they have their own regulators that are designed for it. Using a regulator that is designed for mixed gas which is vapor only will damage the reg.

 

[gungatim]

I had inquired about this to the welding supply. All pure Co2 is indeed liquid in the cylinders, but they have their own regulators that are designed for it. Using a regulator that is designed for mixed gas which is vapor only will damage the reg.

Regulators for argon/mix are different from CO2, they will not thread on the tank, all gasses have specific fittings to prevent using the wrong regulators. As for liquid regulators, I still have no clue what you mean, all mig's use gas, liquid withdrawl is for filling paintball tanks, or from larger tanks to smaller, not for welding. A regulator is a spring and a diaphragm, it does not work on liquid, and liquid CO2 will freeze up, which is why, on paintball guns, we use special expansion chambers to ensure no liquid gets in the gun. There is no welding regulator I am aware of for liquid co2, so if I am missing something, please clarify....

 

[Jagmandave]

To sum up:

120V Mig welder, a "brand" name is preferred but not necessary.

Mig Mix gas, the bigger bottles are a lot harder to transport in a car, a "knee high" bottle will last you a long time, as long as you remember to shut it off after use.

.023 wire for sheet metal

Good to go!

 

[Professur]

If I may. CO2 is liquid in the bottle ... with a small space above the liquid filled with gaseous CO2. When you hold the bottle upright and open the valve, the gaseous CO2 flows out, lowering the pressure of the gas filled space above the liquid, allowing more of the liquid to vapourize. So long as the debit of gas from that space doesn't exceed the rate the liquid CO2 vapourizes .. all is good. Draw too much too fast, some liquid can boil up and out the spout, destroying your regulator. Hold the bottle upside down ... goodbye regulator. Weather is too cold and the liquid CO2 doesn't vapourize quick enough ... same thing.

The CO2 going through the regulator IS gas, vapour from the headspace above the liquid in the bottle.
Found this nifty little pamphlet. http://catalogs.praxairdirect.com/i/27114-safety-precautions-for-carbon-dioxide/29
And here's a pretty good entry level tutorial on the difference between compressed CO2 gas and liquid CO2 and how it's all processed. http://www.powermag.com/capturing-co2-gas-compression-vs-liquefaction/

All good?

A similar process applies to acetylene. The difference being that instead of the acetylene being liquid, it's a gas dissolved in a liquid. The standard rule of 7 being applied. You draw no more than 1/7th the volume dissolved per period of time .. otherwise you end up with the solvent (acetone) in your regulators and hoses. Ends badly, don't do it.

 

[trackwelder]

Get a bottle of 75/25 for your project. If you decide to try TIG later on just swap your bottle for argon. Most welding supply stores have no problem swapping different high pressure gas for another.

 

[aggierailroad]

The 'standard' shielding gas for short-circuit transfer mode GMAW on steel (aka MIG in 'low' power mode, as opposed to 'high power' spray mode transfer) is C25 aka 25% CO2+75% argon.

Relatively 'clean' welds, and pretty much all the 'small' MIG machine parameter charts/recommendations list the settings/parameters for/with C25 gas.

As to the cylinder (aka 'bottle'), get the biggest one you can buy/store/handle. The cost for the actual gas is usually the smallest part of the refill fee/cost. The rest is all the handling, etc.

ex: (using made-up but semi-realistic numbers) refilling a 40 ft3 C25 cylinder may be about $35 and refilling an 80 ft3 cylinder may be about $50. Twice the amount of gas for less than twice the cost there. Even bigger cylinders usually give an even lower $/ft3 ratio. YMMV.

summary: Get the biggest cylinder of C25 you can.

Very astute advice. Tell us more about your setup (or planned setup) before we can recommend a gas. Short Arc MIG? TIG, etc. Most planned welding type? (low carbon steel such as A36?). What thicknesses do you think you'll average.

You can really save a lot more time by slightly upgrading your gas to a proper mix. This usually nets more money in your pocket by saving on grinding, both consumable and your time.

Short answer, C25 will get you pretty far in a <30 amp MIG setup with ER70S-2,6, etc. wire. I bought a small 80ft bottle and haven't replaced it in nearly two years with light use.

 

[dr_clyde]

If I may. CO2 is liquid in the bottle ... with a small space above the liquid filled with gaseous CO2. When you hold the bottle upright and open the valve, the gaseous CO2 flows out, lowering the pressure of the gas filled space above the liquid, allowing more of the liquid to vapourize. So long as the debit of gas from that space doesn't exceed the rate the liquid CO2 vapourizes .. all is good. Draw too much too fast, some liquid can boil up and out the spout, destroying your regulator. Hold the bottle upside down ... goodbye regulator. Weather is too cold and the liquid CO2 doesn't vapourize quick enough ... same thing.

The CO2 going through the regulator IS gas, vapour from the headspace above the liquid in the bottle.
Found this nifty little pamphlet. http://catalogs.praxairdirect.com/i/27114-safety-precautions-for-carbon-dioxide/29
And here's a pretty good entry level tutorial on the difference between compressed CO2 gas and liquid CO2 and how it's all processed. http://www.powermag.com/capturing-co2-gas-compression-vs-liquefaction/

All good?

A similar process applies to acetylene. The difference being that instead of the acetylene being liquid, it's a gas dissolved in a liquid. The standard rule of 7 being applied. You draw no more than 1/7th the volume dissolved per period of time .. otherwise you end up with the solvent (acetone) in your regulators and hoses. Ends badly, don't do it.

This is pretty much all I was trying to say. The regulators are different for different gases, and I can pretty much garauntee the one that came with your welder is designed for mixed high pressure gas. It won't work with the little 20# beverage style Co2 cylinder. That's all I'm trying to say.

 

[Professur]

Yep... but given the benefits of choosing CO2 and the minimal cost of a dedicated CO2 regulator, it's tough to worry after getting C25 on the weekend. Restaurant supply work weekends and often they've got night service too. A bar that needs supply doesn't make any money with it's kegs down.

http://www.alibaba.com/showroom/welding-regulator-co2.html

 

[koditten]

Let's look at the original post.

He wants to weld floor panel in the car. That means you want the least amount of sparks going where you do not want them.

Don't waste time with saving a buck by using carbon dioxide. Welding gas is not that rare that you can't make it thru a weekend. Just get some proper gas and go from there.

Report back after the job is done with pics. Be aware, the paint used on into body's burns real good. I won't do it without a second person watching with a water bottle. Inside a car is worse. Please use caution.

 

[dr_clyde]

75/25 is the best gas for general purpose short arc mig. I was merely discussing something that was posted about co2.

 

[gungatim]

This is pretty much all I was trying to say. The regulators are different for different gases, and I can pretty much garauntee the one that came with your welder is designed for mixed high pressure gas. It won't work with the little 20# beverage style Co2 cylinder. That's all I'm trying to say.

agree on the regulators for MIG come for pressure, but disagree on the small 20# cylinders...None of my beverage cylinders are liquid withdrawal. it's been a few years since I worked at a large well known cola company, but we filled them all day long and they were not liquid withdrawal. I've got a 20# and 2 of the larger 80# ones. All regular CO2, except one, which I took in to have a dip tube added to fill paintball cylinders when I had it re-tested.

Not saying they are not out there, as lots of people fill their own paintball cylinders, but they are not normal in the US (at least they weren't 15 yrs. ago). in the UK it may be more common.

BTW, if it is a liquid withdrawal cylinder it should be marked: "Liquid withdrawal CO2 cylinders can be identified by a vertical stripe down its side or via an orange ring attached under the cylinder valve with the letters “DP” embossed into it."

 

[tomstin]

All, thanks for all the insight! Someone asked for more information on my "plan".

Right now I'm looking at Hobart Handler 140 Wire-Feed MIG Welder — 115 Volt
http://www.northerntool.com/shop/tools/product_200471413_200471413

Seems to be a middle of the road, entry level MIG machine both in capability and price.

The floor pans seem to be pretty thin material, appears to be 21 gauge (roughly .8mm) from what I can tell.

Also appears to be mild steel.

I've cut out the rusted sections, cleaned off the undercoat and using a sanding disk on the grinder, cleaned the edges.

 

[Professur]

Hobart's a solid choice for this job. Can't do much better for the money. Keep your extension cords fat and short.

 

[Showkey]

For the same money I would consider this:

http://www.eastwood.com/mig-welders-175-amp-mig-welder-w-spool-gun.html

220v, Spool gun, long warranty

 

[R.Anderson]

Not sure how in depth you want to go with this, but I'll try to answer some of your questions:

1) You want 75%Argon / 25% CO2 (C25) for what you're doing with MIG
2) If you want to TIG mild steel you need 100% Argon
3) If you want to MIG aluminum you need 100% Argon
4) There is no media inside the shielding gas tanks and the gas does not liquify, so you can transport them any way you like and use them immediately after up righting them
5) You could use 100% CO2 but the beads will look like **** and you'll need an extra adapter

If your weld looks like **** using CO2 you are doing something wrong. I use CO2 with my MIG setup and get great looking welds very little spatter along the weld and darn near all can be cleaned off with a wire brush, only con for me is weld splatter builds up in the nozzle faster than 75/25.

 

[BigMike782]

CO2 cyls can be vapor withdrawal or liquid withdrawal and both are CGA320
Liquid could be used for freezing pipes or making dry ice. Liquid will not ruin a regulator but will freeze it in short order and stop flow. Vapor will freeze a regulator also if you draw it fast enough.