Multi gas

[Bradley fish]

hi, got a job comeing up that I have dragged my old mig out for and need gas. I was wondering because I don't use my mig anywhere near as my TIG could I get away with useing one gas for both mild and stainless. For Tig I use argon due to mainly welding stainless but also "works" for mild.

Cheers

 

[hotrodder]

Pure argon is the right gas for welding everything with TIG. Argon/CO2 mixes will trash the tungsten immediately as CO2 has an oxidising effect. There are a few 'special' mixes for TIG but they're all relatively spendy (argon + a little hydrogen for stainless for example), mostly about increasing productivity and totally different to MIG mixes for carbon and stainless steels

Pure argon doesn't work properly with MIG on mild or stainless steels. Some CO2 is needed for reasons to do with arc stability, weld shape/wetting and fusion (CO2 adds energy to the weldpool). A little O2 is also often added to further improve wetting. Very roughly thicker carbon steel = more CO2 ideally. Stainless on the other hand is more sensitive to CO2 and more than 2.5% has detrimental effects

See http://www.mig-welding.co.uk/gas-composition.htm and http://www.mig-welding.co.uk/stainless.htm At the end of the day it comes down to the type/quality of the work your doing... something like argoshield light is used by some people for both carbon and stainless, the stainless welds will need cleaning up and depending on the service environment may be fine (say, a car exhaust) or may end up 'less stainless' than they're supposed to be if the corrosion resistance is properly tested- say, marine stuff in brackish water

 

[Ed.]

If I read your post right, you are hoping to use straight argon for MIG welding stainless and mild steel.

As Hotrodder has said above "Pure argon doesn't work properly with MIG on mild or stainless steels", having said that my 12m x 10m garage shed/carport and a few large stainless boat anchors were MIG welded using pure Argon, would I recommend it ...No! you can get away with it although it depends on what you are trying to weld, and if you are really desperate, provided you have a largish decent MIG machine and you need to set it using more volts than you would need with an Argon mix, as well as knowing how to weld properly which is the most important thing. The beads will not look nice, be taller and more irregular as the arc is not stable and you probably wont get the proper penetration compare to using an Argon mix but technically it can be done, although It really is not worth the effort and I would not do it again.

Cheers

Ed.

 

[Bradley fish]

If I read your post right, you are hoping to use straight argon for MIG welding stainless and mild steel.

As Hotrodder has said above "Pure argon doesn't work properly with MIG on mild or stainless steels", having said that my 12m x 10m garage shed/carport and a few large stainless boat anchors were MIG welded using pure Argon, would I recommend it ...No! you can get away with it although it depends on what you are trying to weld, and if you are really desperate, provided you have a largish decent MIG machine and you need to set it using more volts than you would need with an Argon mix, as well as knowing how to weld properly which is the most important thing. The beads will not look nice, be taller and more irregular as the arc is not stable and you probably wont get the proper penetration compare to using an Argon mix but technically it can be done, although It really is not worth the effort and I would not do it again.

Cheers

Ed.

I think I have just complicated things with talking about TIG. I want a gas that I can use for mild and stainless for MIG. From what I gather argon co2 sounds the best. Would 10% co2 be too much ?

 

[Bill Edwards]

Probably, unless you want to weld fairly thick stuff - it may be too much for stainless of any thickness anyway, I don't know on that point.

Look at the Volkzone offer from BOC where you get a 20l bottle of argoshield light which is 95% argon and is ideal for up to about 4mm mild steel. If you're working on much thicker stuff then it may not be ideal, you don't say what you typically weld but it certainly works well for most hobby folk.

 

[Ed.]

Yes, it would be too much, if there is too much CO2, the carbon migrates to the molten stainless when the Carbon and the O2 disassociates in the arc, and that makes the weld more brittle and the surface not very nice, so if you are after an all in one gas, I don't think they exist. When doing TIG you can use straight Argon on Mild, Stainless and Aluminium, but not using MIG as it is a different process. Depending on what the stainless job you want to weld, you might be able to get away with MIG using a a 95%Ag, 3%CO2 2%O2, which is great for mild steel but not so good for stainless, although it will weld it.

You might be able to get a bottle of the more exotic mixes but as I haven't tried them I can't tell you if it would work or not and they are pretty expensive in which case it still might be cheaper to get 1 bottle of Argon for the TIG and another bottle of Argon mix for the MIG. Try to look up Arcal 12 which might be a possibility as well.

I have attached some info which might explain the gasses better.

Cheers

Ed.

 

[Bradley fish]

Think I will just bite the bullet and get a light argon co2 gas for mild as that is mainly what I use the mig for and like you say it will "do" stainless.
Just would have been nice to get a gas which does both at a good quality but oh well.
Welding about 1.5 - 3 mm.

Cheers guys

 

[Bradley fish]

Just had a look at where I get my gas from and the only mix they do is argon co2 15%
http://issuu.com/unitedwlding/docs/albee_rental_free_cylinder_united_welding_pdf?e=2530737/2228013

So I take it that if 5% is too much 15% is going to be way to much

But saying that I have just looked at the old clarke disposable bottle I have and it is a 86% argon 14% CO2

This is starting to give me headache now with all these gases :S
Wish all welding was as simple as stick

 

[Ed.]

Those other gas mixes should be available in the larger sized bottles but they are much more expensive, if you only need to do a small stainless job then it might be cheaper or less hassle to just pay someone else to do it for you and just stick to the mild steel welding. It really depends on how much welding you need to do to justify the cost of the bottle rental and the gas. I am in a similar position, I have to get some Argon for the TIG and also a Argon mix for the MIG, as I do 99% MIG welding, it is hard to justify the Argon cost even if it is convenient to have both when I need them for those quick odd jobs. I am going to buy the cylinders outright either an "E" size for the MIG and maybe a "G" or "E" size for the Argon which will save on the rental, 2 years rental pays for the cylinder costs.

Cheers

Ed.

 

[dannyp]

if it's work just get the right gas for the job, if you really don't want to do it right just sub it out

 

[backpurge]

The industry accepted maximum CO2 content for MIG welding stainless is 2.5%, anything more is going to be a compromise

 

[Richard.]

2.5%CO2 is the required mix for stainless and 5% plus for steel
I totally get that it's not practical at home to have 2 cylinder types for one process.
I've ran stainless in 5% before and it does work even though not recommended
95Ar 5Co2 would be as good you'll get for both processes. If you find yourself doing more stainless than steel I would advise you to invest in the 2.5% optimum mix