Rent free gas for stainless mig - 2% CO₂ in Argon or 2% O₂ in Argon?

[Jelly_Sheffield]

I am looking for a rent free option for gas to MIG weld stainless steel.

Ideally I would just pop into BOC and get a cylinder of Specshield 2% O₂ or Stainshield Light, but they only do size W, and I won't possibly use enough of a £210 or £450 fill to justify renting the cylinder.

Ostensibly, Adams Gas and Hobbyweld both offer 2% CO₂ in Argon, which some sources say is an acceptable substitute for the Specshield... However I am ******** if I can find a stockist from either supplier who actually carry it.



It has occurred to me to get a 10L cylinder of Argon, and rig up a manifold to blend it with Oxygen by partial pressure to get 2%.... But that's actually quite difficult to execute well in an intermittent flow application, and would necessitate buying multiple additional regulators which totally throws away any cost saving.

 

[hotponyshoes]

Sgs will mix on request through a dealer.
Others might do the same?

 

[hotponyshoes]

It's easy enough to make a gas mixer but as you say, you then need at least 1 extra regulator. I ended up using extra flow gauges on mine as well.
A bit of a faff setting it up and you ideally want 2-stage regs on the bottles as well or you'll be constantly adjusting it.
Does mean you can vary the gas mix to suit the material/weld if you do it that way though.

 

[hotponyshoes]

Another option is mix in the bottle by partial pressure but you'll need a suitably accurate gauge(s), hoses & adaptors and a bottle to refill (that you obviously own yourself)

Dive centers might do you a mix but you'll then need to buy a (in date) dive bottle then still need to faff about with another adaptor to connect a regulator

 

[Jelly_Sheffield]

Sgs will mix on request through a dealer.
Others might do the same?

Useful to know, I will have to ring round the local distributors to find out:
1) how many of them actually know they sell welding gas at all,
2) how many of those are willing to ring SGS to request a special order.

It might be easier working backwards by ringing SGS and asking them to point me to the distributor local to me who actually moves significant volumes of gas, and is engaged.

It's easy enough to make a gas mixer but as you say, you then need at least 1 extra regulator. I ended up using extra flow gauges on mine as well.
A bit of a faff setting it up and you ideally want 2-stage regs on the bottles as well or you'll be constantly adjusting it.
Does mean you can vary the gas mix to suit the material/weld if you do it that way though.

In principle I really like the idea...

But by the time I buy two additional two-stage regs and the relevant bits of tube, I had might as well just get the Stainshield and be done with it.

I suppose it's sort of buy-once cry-once, but still works out to be a lot of money for Argon-Oxygen, if I wanted to add CO₂ or He... That's another £245 per gas.

Maybe I need to ring some old colleagues to see if I can scrounge up some 8500 series regs from laboratory closures.

Another option is mix in the bottle by partial pressure but you'll need a suitably accurate gauge(s), hoses & adaptors and a bottle to refill (that you obviously own yourself)

Absolutely not doing any bottle mixing with O₂ especially not when it would be oxygen in first!

I am sure it's fine, but the one time it isn't for some reason, it really won't be.

Dive centers might do you a mix but you'll then need to buy a (in date) dive bottle then still need to faff about with another adaptor to connect a regulator

Dive centers could be an option, but I seem to remember that their use of argon is confined to filling dry suits in cold water, and even then it's niche...

I have a mate with two steel dive tanks going spare, and it's only about £60 a tank to get them recertified... Worth a conversation at least.

 

[hotponyshoes]

Try an actual welding supplier rather than a car parts place that also sells welding gas..

My mixing setup didn't actually cost a lot.
I had rent free oxygen anyway plus a regular source of medical oxygen and the bottle regulator.

If you already have the argon then it might actually be cheaper to get a rent free oxygen than get a rent free bottle of mix as you would only need a small bottle (depending how much you need)

It was just a hassle setting everything up and it was all wall mounted so when I got a bottle of 2% for some mobile stainless welding I didn't use it again.

 

[minimutly]

Well since this is a welding forum, and I don't know the answer, why not just go straight argon?

 

[tom2207]

a dive shop may sell you a partial fill of oxy , but thats about as far as they will go , they probably wont top off a bottle they didnt fill , or want to analyse a bottle for you that they didnt blend especially if its not nitrox ,,,

 

[hotponyshoes]

Well since this is a welding forum, and I don't know the answer, why not just go straight argon?

The 2% or so of mix breaks down the surface tension of the weld puddle and helps it flow a lot better.
It's a noticeable/decent difference.

If you try welding stainless with pure argon you'll find it doesn't come out anything like a weld on steel. Switch to a mix and you can weld it just like you would steel.

 

[hotponyshoes]

Absolutely not doing any bottle mixing with O₂ especially not when it would be oxygen in first!

I am sure it's fine, but the one time it isn't for some reason, it really won't be.

Why not try carbon dioxide as the mix gas then? 2.5%?
You'll need an accurate set of scales and some maths..

 

[hotponyshoes]

Most dive centers routinely supply mix gases. Tri-mix is not uncommon.

Argon is quite common in drysuits. I'd imagine most of the inland (quarry) diving places have it.

You'll need a dive bottle that is 'O2 Clean' if you want them to put oxygen in it.

Check they can/will mix before buying a bottle!

They'll probably expect to see "not breathing gas" or something painted clearly on the bottle.

 

[hotponyshoes]

a dive shop may sell you a partial fill of oxy , but thats about as far as they will go , they probably wont top off a bottle they didnt fill , or want to analyse a bottle for you that they didnt blend especially if its not nitrox ,,,

I analyse my mix with a purge monitor.
Although a some of the purge monitors display 100% inert what most of them actually do is measure the amount of oxygen and just show 100% when the oxygen reading is 0%.

Handheld analysers are also available for diving mixes. You might pick one of those up used cheaper than a purge monitor?

 

[tom2207]

I analyse my mix with a purge monitor.
Although a some of the purge monitors display 100% inert what most of them actually do is measure the amount of oxygen and just show 100% when the oxygen reading is 0%.

Handheld analysers are also available for diving mixes. You might pick one of those up used cheaper than a purge monitor?

Ive a tri mix analyser , I did dive tri mix for a while , hence the gas blending certs , I prefer to mix my own gasses ,,, then went to twin 3ltr and an off board set up . But I built a gas mixing station for a friend of mine a few years ago ,,, we wouldnt even let you take a cylinder out of your car let alone plug it in , strictly empty bottle policy here unless we supplied it and then we would top off but thats it.

 

[Jelly_Sheffield]

Try an actual welding supplier rather than a car parts place that also sells welding gas..

Easier said than done, I can't see one in their network within 50 miles of me... There's some engineering merchants with trade counters, but I'd need an account with them first.

I emailed SGS to ask them if they could offer either:

98% Ar, 2% O₂
or
85% He, 13.5% Ar, 1.5% CO₂

And asked if they could "advise of a local distributor who could fulfill special gas mix requests".

I didn't explicitly say "your distribution network in my area is pants and barely acknowledges your existence" but I assume they must know that.

My mixing setup didn't actually cost a lot.
I had rent free oxygen anyway plus a regular source of medical oxygen and the bottle regulator.

If you already have the argon then it might actually be cheaper to get a rent free oxygen than get a rent free bottle of mix as you would only need a small bottle (depending how much you need)

It was just a hassle setting everything up and it was all wall mounted so when I got a bottle of 2% for some mobile stainless welding I didn't use it again.

I don't already have argon, but I do have plenty of oxygen (I use gas welding when other people would tig).

From an execution point of view I have found it's a lot easier* to accurately mix gasses with regulators that read out (accurate) discharge pressure rather than trying to do it by flow rate, and I wouldn't want to swap the gauge on my good oxygen reg over.

I suppose I could just put pressure gauges on the mixer manifold itself actually.


*Ok, easier is relative... If you know the correct partial pressures for each gas, you just set the regulators and it will be right immediately.

In practice that does mean you need a spreadsheet or script set up to use the van-der-Waals equation to solve for the relevant partial pressures, given the desired v/v or w/w concentrations, the discharge pressure of the mixer, and the temperature that day as input criteria.

I appreciate that if you don't already have that, then writing something to solve a system of cubic equations is not what everyone would call easy.

 

[AlexBrown_1]

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This is who I use, I always find him a lot cheaper than any other option but I just get bog standard welding gas.

 

[hotponyshoes]

Easier said than done, I can't see one in their network within 50 miles of me... There's some engineering merchants with trade counters, but I'd need an account with them first.

I emailed SGS to ask them if they could offer either:

98% Ar, 2% O₂
or
85% He, 13.5% Ar, 1.5% CO₂

And asked if they could "advise of a local distributor who could fulfill special gas mix requests".

I didn't explicitly say "your distribution network in my area is pants and barely acknowledges your existence" but I assume they must know that.


I don't already have argon, but I do have plenty of oxygen (I use gas welding when other people would tig).

From an execution point of view I have found it's a lot easier* to accurately mix gasses with regulators that read out (accurate) discharge pressure rather than trying to do it by flow rate, and I wouldn't want to swap the gauge on my good oxygen reg over.

I suppose I could just put pressure gauges on the mixer manifold itself actually.


*Ok, easier is relative... If you know the correct partial pressures for each gas, you just set the regulators and it will be right immediately.

In practice that does mean you need a spreadsheet or script set up to use the van-der-Waals equation to solve for the relevant partial pressures, given the desired v/v or w/w concentrations, the discharge pressure of the mixer, and the temperature that day as input criteria.

I appreciate that if you don't already have that, then writing something to solve a system of cubic equations is not what everyone would call easy.

My setup was just 2 pea shooter type flow gauges feeding into the mixer. The 2% one was a lower scale medical thing. 0lpm-1lpm or something
I then had a 3rd on the outlet end to set the actual flow and provide a bit of back pressure. You do need a chart for the various mixes that relates to the inlet gauges but, in my case, that was just for 2% and 2.5% at a couple of different flow rates.

I've never done anything with it that needs a wps or any form of gas testing but it looked ok on the analyser.

Most of the pipes and fittings are the same as you would need for back purging, nothing particularly special

 

[Turbo]

Some info here.

https://www.mig-welding.co.uk/forum/threads/argoshield-for-stainless-mig.37316/

I suggest you contact the owner of SGS direct, he's a member on here.

 

[Jelly_Sheffield]

Some info here.

https://www.mig-welding.co.uk/forum/threads/argoshield-for-stainless-mig.37316/

I suggest you contact the owner of SGS direct, he's a member on here.

I emailed SGS to ask them if they could offer either:

98% Ar, 2% O₂
or
85% He, 13.5% Ar, 1.5% CO₂

They emailed back already.

They can't do either mixture, but recommended contacting https://progasesuk.com/ in Bootle to see if they could help.

Progases also appear to do dissolved acetylene rent free which is interesting news.

Edit: emailed Pro-Gasses to find out what they can offer