"Bad" welding gas?

[American Locomotive]

So we've been working on a project at my buddy's house. He has a little Lincoln 140A MIG with 75/25 gas. It's served him well, and really hasn't had any problems.

We've noticed that when welding, we're no longer getting the familiar slightly "sweet" ozone smell. Instead, we've been getting this absolutely vile and putrid smell. I don't even know how to describe it. It's vaguely reminiscent of the smell you get when you pick up a set of keys or wash out an empty can of food with warm water - except about 30x more intense.

The parts were just wire brushed with a grinder, no brake cleaner or anything else was used. Various different parts were welded and the smell remained the same every time.

Any ideas? Could the welding gas be contaminated? I did notice the welds were getting covered in brown soot way more than usual. Flow meter was set to around 20 cfh.

 

[danielbuck]

Did you just have the bottle filled/exchanged? It's entirely possible that the bottle was filled with the incorrect gas. I've never had this happen to me, but I've heard of it happening before.

As for the smell, I have no idea, but that might be an indication of incorrect gas.

 

[American Locomotive]

The bottle hasn't been exchanged recently. Maybe I'll have him take the gun/tip apart and clean it out.

 

[cooljoe57]

Was it new or used material?

 

[American Locomotive]

New and used, but it was all descaled and cleaned.

 

[MattT]

Did you check the gas is coming out of the gun nozzle? Could have sprung a leak somewhere.

I guess the other thing has he just put a new spool of wire on the machine?

 

[BillK]

Are you sure the material isnt galvanized ? Thats almost what it sounds like.

 

[Jack84]

Has the bottle been sitting for a while?
Mixing it up might help.


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[bdbecker]

My guess is there is some sort of contamination in the base material. I recently repurposed some t-iron garage door opener track and it smelled terrible when cutting and welding. I had some new angle iron that I was also using on the same project, no unusual smell.

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Has the bottle been sitting for a while?
Mixing it up might help.

Old wives tale... gas doesn't separate under pressure in a cylinder.

 

[Bopbop]

I have heard of gas going bad over time from sitting. Usually from what I have been told is the weld quality will be poor. I would think that there is something on or in the metal that is causing the smell

 

[Jack84]

My guess is there is some sort of contamination in the base material. I recently repurposed some t-iron garage door opener track and it smelled terrible when cutting and welding. I had some new angle iron that I was also using on the same project, no unusual smell.



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Old wives tale... gas doesn't separate under pressure in a cylinder.

Think I heard it on the welding tips and tricks podcast. I’ll look into it some more.

 

[bdbecker]

Think I heard it on the welding tips and tricks podcast. I’ll look into it some more.

Please let me know what you find - I'd be curious to hear what Jody has to say about it.

My apologies if my comment came across as rude - that was not my intention. To be fair, my comment also isn't technically correct from a physics standpoint. Under a certain set of very strict conditions, the gasses could theoretically separate in the container. However, a weld gas bottle in a shop does not meet that set of strict conditions and it is highly unlikely that separation would ever occur or be the cause of the issue.

https://en.wikipedia.org/wiki/Kinetic_theory_of_gases
https://en.wikipedia.org/wiki/Brownian_motion

 

[Jack84]

"Bad" welding gas?

Please let me know what you find - I'd be curious to hear what Jody has to say about it.

My apologies if my comment came across as rude - that was not my intention. To be fair, my comment also isn't technically correct from a physics standpoint. Under a certain set of very strict conditions, the gasses could theoretically separate in the container. However, a weld gas bottle in a shop does not meet that set of strict conditions and it is highly unlikely that separation would ever occur or be the cause of the issue.

https://en.wikipedia.org/wiki/Kinetic_theory_of_gases
https://en.wikipedia.org/wiki/Brownian_motion

Episode 55, around the 65 min mark.


No problem, I didn’t it was rude. More to the point.

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[bdbecker]

Re: "Bad" welding gas?

Episode 55, around the 65 min mark...

Thanks for tracking that down! (Looks like I've got a new podcast to listen to as well!)

I have a tremendous amount of respect for Jody and what he does and I also agree with the sentiment that what happens in the scientific world doesn't always match up to what happens in reality. I don't agree with how he uses that to justify why he thinks weld gas will separate over time. I say that because, outside of a controlled lab setting, it has been my experience that the discrepancy between theory and reality typically only occurs when you attempt to do something that should work in theory but doesn't in reality, not the other way around.

 

[MattT]

To be fair, my comment also isn't technically correct from a physics standpoint. Under a certain set of very strict conditions, the gasses could theoretically separate in the container.

You're ignoring temperature. CO2 will liquify under pressure at relatively high temperatures, and it is the dead of winter. And I know for a fact it's possible to "freeze" Xenon out of Argon because I've done it. Also accidentally liquified the Argon carrier too which turned the lamps into minature bombs when they warmed up

Not saying temperature is reducing the CO2 content of the mix but I reckon it's possible. Definitely isn't removing all the CO2 or the OP would be complaining about the wire melting back to the tip. Yeah I've BTDT too

 

[bdbecker]

You're ignoring temperature. CO2 will liquify under pressure at relatively high temperatures, and it is the dead of winter...

I think you meant to say that CO2 will liquefy at low temps, but I get your point. Temperature is a factor, but so is pressure, specifically partial pressure when dealing with mixed gasses in a cylinder. Even though your gauge may read 2000psi, the pressure of the CO2 in that mix is only 500psi because CO2 is only 25% of the gas in the cylinder. For CO2 to convert between liquid and gas at 500psi, the temperature must drop to 31F.

http://www.energy.psu.edu/tools/CO2-EOS/index.php
https://www.quora.com/At-what-pressure-does-CO2-liquefy

Circling back to the welding world, if in fact some of the CO2 had liquefied and affected the mix of gas, it would only help it in the right direction (up to about C10 equivalent).

 

[MattT]

I think you meant to say that CO2 will liquefy at low temps, but I get your point. Temperature is a factor, but so is pressure, specifically partial pressure when dealing with mixed gasses in a cylinder. Even though your gauge may read 2000psi, the pressure of the CO2 in that mix is only 500psi because CO2 is only 25% of the gas in the cylinder. For CO2 to convert between liquid and gas at 500psi, the temperature must drop to 31F.

I meant relative to what most other gases liquify at, not room temperature. Beyond that it looks like we're in agreement. It does appear that CO2 might liquify at unheated northern shop temperatures.

Regards the gas mix ratio do you know what < C10 would do?

Or I guess the other possibility is that the cylinder was used earlier at < C25. Then when the remaining contents warmed up it became > C25. Any idea what effect that would have?

 

[American Locomotive]

The only thing that would happen is I'd have a higher argon concentration, and my weld would burn a little colder.

 

[bdbecker]

You need C20 to get into spray transfer. We run C10 in the shop bulk mixer because we do pulsed MIG (a version of spray transfer) the majority of the time. Spray transfer is nice because it doesn't spatter like short circuit, but the lower CO2 content means you need to need more power to achieve the same penetration.

That is a very interesting point you bring up about welding in the cold when the CO2 may have been in a liquid state, causing the ratio to be off once the bottle warms up again. I hadn't considered that before, but it seems plausible.

 

[American Locomotive]

It was like at least 60 in the garage.

 

[TLGriff]

Your mention of brake cleaner in the same sentence as welding makes a reminder worthwhile that using brake cleaner with any high source of heat such as welding, can be a fatal mistake. Gases such as hydrogen chloride and even phosgene can be produced in the process.

Tom

 

[Steve from Socal]

There are no welding gasses that would cause a bad smell as described on their own. The odor sounds like a coating, zink, cad etc burning and out gassing. The brown soot is also a clue there is an impurity in the weld. Can you sand the weld area to confirm clean metal?

Steve

 

[American Locomotive]

Your mention of brake cleaner in the same sentence as welding makes a reminder worthwhile that using brake cleaner with any high source of heat such as welding, can be a fatal mistake. Gases such as hydrogen chloride and even phosgene can be produced in the process.
Tom

Yup, that's why we avoided using it. Although the brake cleaner we do have is non-chlorinated anyways.

There are no welding gasses that would cause a bad smell as described on their own. The odor sounds like a coating, zink, cad etc burning and out gassing. The brown soot is also a clue there is an impurity in the weld. Can you sand the weld area to confirm clean metal?

Steve

The metal was ground down to bare steel prior to welding.

 

[Steve from Socal]

Is the wire contaminated?

Steve