Custom gas mix

[shenion]

In the discussion over the best mix, us Americans have the solution

This should be interesting:

Could not resist at under $60; there is another one on "buy now" for $825.

I have an argon tank and CO2 tank already. I'll need to get 2 regulators capable of supplying 50psi and some hoses.

 

[malcolm]

Good buy! It'll be interesting to see what happens when you increase the percentage of CO2 - fancy doing a write up?

 

[shenion]

Yes, found they retail for $1495 new, so $60 is a steal.

I think I'll find a piece of 1mm steel. Draw a grid and do some welds with Ar/Co2 of 0/100, 75/25, 80/20, 90/10, 95/5 and 100/0 mixes. Then post some pics of the results.

 

[shenion]

Ok, here's some first tests:

Did not have time to really play with things. Current should have been higher.

I did not change the wire speed, as the amount of CO2 was increased, the wire speed should have been decreased as the current drops with CO2.

The 75/25 looks like it will be the best for general use.

Notes:

1. Pure argon weld is actually taller than it is wide.
2. Notice all the "spatter" around the pure agron. AFAIK this is pitting caused by stray arcing.
3. Penetration looks to be almost the same. The difference is how tall the welds are.
4. Pure argon is probably the loudest arc. Definitely more current; most blue.
5. Pure Co2 has a quiet buzz. Arc is yellow.
6. top pure CO2 had wire speed decreased a bit.
7. No weave on welds, all pull, attempted to keep torch speed same.
8. As I rotate the gas mix, the sound coming from the gun changes. Does not sound like flow is changing, must be the different density gas.

I have real work to do now . Later, I want to find some 2mm sheet, draw a grid and do some real tests. Want to compare settings, I.e how wire speed needs to be changed for optimal results. Then cut sheet to see weld profile.

It seems to work ok. Funny, I nearly spent as much on fittings/adapters as I did for the unit (female-->male female-->hose barb X 3). I still have a kludge on the last fitting for the plastic tube run to the welder. I have no good supply for metric pipe fittings locally. Will stop by weldings supply. Should have some US thread --> plastic tube adapter.

 

[malcolm]

Thanks for posting back on this one. I had the same thing with pure argon - pointy triangular welds with that weird bubbling beside them. Must be stray arc, but I didn't notice it happening while welding. You can see the lack of smoothing on the sides of the argon only weld in the second photo.

For the great CO2 debate - I didn't notice any real difference in penetration when I changed from pure argon to 5% CO2. Though maybe 5% makes no difference. Big difference was smoother, more rounded welds.

Notice a few blobs of spatter around the pure CO2 welds. I got the same with CO2, and also notices the arc stability dropped off - like welding dirty or rusty steel.

It's interesting that your photos don't show a lot of difference between a tiny bit of CO2 in the mix and quite a lot of CO2 in the mix. Maybe the Brits and Americans are both right in the "correct" mixes.

 

[shenion]

You can barely see the pitting by eye, the camera flash must enhance it.

I have done some real smooth CO2 work. Even on highest setting the current is less. With the wire speed slower it works well with little spatter.

Higher argon mixes increase current and weld faster.

The "correct" mix varies. I notice there are several argoshield. Heavy has more CO2.

Yes, the penetration is a farce. Adding CO2 makes for a flatter weld.

As is, the comparisons are not completely valid. Current was too low and wire and torch speed need to be adjusted for the mix.

I will probably use 50/50 just to save cost on argon and still get very good results.

Thin metal shoud be interesting. Want to try full penetration and see the difference in difficulty blowing through. 100% argon seemed to cut through, while 100% CO2 caused the wider weld to sag.

 

[shenion]

Hmm, it has a slow leak on the argon side.

Opened it up, huge diaphragm with about 6 tubes coming in/out.

It also has "Reworked 1987" penciled on the diaphragm, so this is probably at least 25 years old.

The internal connections are 1/4" plastic tubing that is real hard. Probably cause of leak. Will see about getting new tubing.

It works though

 

[shenion]

Ok, final results for thin metal are posted here: http://shdesigns.org/Welding/gasmix.html

Malcom, feel free to add a link on your pages that compares gasses.

 

[Drains]

Shenion, just read up your results. Very interesting, particularly your impressions re 100%co2, and the best mix at 75%/25%.

Thanks for going to the trouble of letting us know your results - it was a good test. That mixer was a lucky find!

Si.

 

[malcolm]

That's an excellent write up. Great info and insight there so I've linked it from the gas page.

One additional thing that would be really interesting is to find out how little CO2 you need to put in to get the same sort of results as the 25% CO2 mix. My guess is we won't be able to tell the difference between 5% and 25%.

Well spotted on the copper "slag" I'd kind of noticed that appearing on the sides of my CO2 only welds, and to a lesser extent on the surface of the mix welds, but hadn't really thought about it before.

 

[shenion]

That's an excellent write up. Great info and insight there so I've linked it from the gas page.

These forums have been great, I have learned a lot in a short time. Just trying to give back.

One additional thing that would be really interesting is to find out how little CO2 you need to put in to get the same sort of results as the 25% CO2 mix. My guess is we won't be able to tell the difference between 5% and 25%.

The overview picture has 95, 90, and 80%. The 100% Argon is actually undercut; looks like put down from a toothpaste tube.

95% makes the weld near semicircular; 90 and 80 have slightly lower profiles. 90 and 80% are acceptable, with some tuning of wire speed and torch spped these would do excellent welds.

Well spotted on the copper "slag" I'd kind of noticed that appearing on the sides of my CO2 only welds, and to a lesser extent on the surface of the mix welds, but hadn't really thought about it before.

Took me a while to realize what it was. I have seen the dimple at the end of welds look gold colored. It wasn't until these tests that I saw the cladding puddle up.

I would bet that the cooling effect of argon creates a skin on the weld pool; preventing the copper from coming to the surface.

 

[weldequip]

The major gas companies have spent millions on R&D doing just the same, to come up with the perfect shielding gas for each application. Great that you have done such a comparison yourself Shenion, and thank's for taking the time & trouble of posting your opinions.
I have had a long running argument with a lot of my counter trade customers (and on the forum) over the CO2 v Argon/Co2 mixtures. The plain fact is that the gases recommended by the gas manufacturers are the gases required for the task, anything else is an 'also ran'. People use CO2 because of budget restraints, pure & simple. It will 'stick' metal together, but if you want ideal welding properties you have to go with the experts & use the tried & tested stuff.
weldequip

 

[shenion]

Yes, CO2 will produce a less than ideal weld. I would never use it if I was welding a tube frame. Really for mild steel, any Ar/Co2 mix will do well. For a tube frame, you would likely be using a custom alloy with specific requirements.

These tri-mix gasses are fine, but over-engineered for general use. Ed Craig (weldreality.com) is big on how these tri-mix gases are nothing more than marketing hype to sell more expensive gases. The addition of O2 is needed for some metals, not all.

In reality there are too many variables to just say the gas is enough. Often the need for O2 in the gas is negated by additives in the wire. I have found the type of wire has significant effects. My switching to a wire with better oxidizers helped. Probably the same as adding O2 to the mix. Funny, I came up with the same as Lorenzo uses on his big projects. 75/25 and wire with oxidizers (but not dual shield).

Specialty metals, high-nickel allows, stainless etc, need specific gas mixes and wire to suit.

My experience and others here is the gas suppliers will sell you what they want. Those on the front lines are completely ignorant (hence them selling me pure argon when I asked for a mix for general mild steel.).

I would not go to the gas suppliers for recommendation. I would go by those who use welding in production. You don't see Miller or Lincon mention tri-mix until you get to speciatly metals.

Really, it depends on needs. The crap steel used in old car frames and bodies is easy. The wire used is probably a better grade steel. The gas is not real important.

Once you get into specialty metals (i.e the exotic alloys in some new cars) then it is a whole different story. The gas is the least of the issues. The almost frame-less design (unibody) requires welds that exactly match the tensile strength if the original. At this point, the gas is the least of the worries and a minuscule part of the costs.

 

[weldequip]

Once you get into specialty metals (i.e the exotic alloys in some new cars) then it is a whole different story. The gas is the least of the issues. The almost frame-less design (unibody) requires welds that exactly match the tensile strength if the original. At this point, the gas is the least of the worries and a minuscule part of the costs.

Well I agree with most of what you have said but I'm afraid the above is bulls***! When you get to critical welding operations the gas is also critical & play's a fundamental part.
weldequip

 

[shenion]

Well I agree with most of what you have said but I'm afraid the above is bulls***! When you get to critical welding operations the gas is also critical & play's a fundamental part.
weldequip

Critical and fundimental, yes. But the wire, weld process and equipment need to be there first to use the gas.

You have said these take 10-20k investment in equipment (mig brazing thread). At this point paying for an more exotic gas is not an issue.

My point was not that the gas was unimportant but in these cases the cost was not an issue.