CO2/Argon 5%, 10%, 15% ?? When? Why?

OK - now we get onto territory I have more knowledge on.

Thanks to @cbrasher for mentioning the regulator. The calibration of regulators does depend on the gas density. So yes - you do get regulators that are calibrated for Helium, Argon, Oxygen .. whatever. This is OK so long as always, the proper gas is in it's own color coded cylinder.

Of course, it's a darned pain if you have gas mixes. You can have a lookup scaling factor to let you use a regulator for one gas, adjusted for another, or a mix. Here is where one can get out the old high school notes about partial pressures.

I forgot some gases are sold by weight. Of course they are, especially those that are liquid under pressure, like butane.
It gets complicated with stuff like acetylene, which is shipped dissolved in acetone.

I did not know CO2 has a liquid phase. I know that I needed compressed air filtered completely free of CO2 to stop it turning solid and blocking dewars when used for cooling IR cameras, and I watch frozen CO2 turning from solid straight into gas without going through being a liquid (dry ice). Maybe CO2 can be liquid at high enough pressure - I don't know.

The volume of gas you have is escaping into standard atmospheric pressure - is that about 14.5 pounds/sq inch.
The way to figure how much gas you have to use is then the volume of the cylinder x the pressure in it when "full", divided by standard atmospheric pressure.
Volume available = (Volume of cylinder x pressure)/(standard atmospheric pressure).

Definitely there is more to using CO2 than just the (attractive) lower cost. As @General Zod has mentioned, the character of the arc, the behavior of the weld pool, and the penetration of the weld are changed. Of course, I am just setting out on welding stuff. Clearly I cannot simply buy and try set of gas bottles in all combinations of weld mixes. I had to get the real solid information.
 
graham-xrf said:
Thanks to @cbrasher for mentioning the regulator. The calibration of regulators does depend on the gas density. So yes - you do get regulators that are calibrated for Helium, Argon, Oxygen .. whatever. This is OK so long as always, the proper gas is in it's own color coded cylinder.
Click to expand...

Just so we don't confuse the folks in the States who read this....there is no color code system in place for gas in the U.S.
 
I recently switched from straight C02 to 75/25 CO2 argon mix. Now my welder is the machine that it was meant to be. I wish that I didn't wait so long to do it.

The lure of dirt cheap CO2 and no strings attached on the bottle was just too irresistible. I have a friend that works for the 2nd largest soft drink company in the world and a full bottle costed me $15.
 
The short and curlies are:

Use straight argon for TIG, "argo-shield 5" (5% CO2) for MIG. Those two cover everything your welder is capable of.

I started out MIGing with straight CO2. Once I discovered the joys of the argon mixes and hobby suppliers popped up (I had a deal with the village pub for CO2 bottles), I swore I'd never go back. Smoother, more control, less messy, instantly better welds. You need that 5% of the slightly reactive CO2 with the argon, which is why a straight argon cylinder won't do both processes.

You can MIG with straight CO2 or straight argon, but there's no gain to be had at hobbyist level and you won't get the best results. The mixes have been developed and are used the world over for good reason. For how much gas you're likely to use, there's not even much of a financial incentive.
 
You guys ever, "stir" your tanks?
I saw a video Jodie did where he lays the CO2-Argon tank on it's side and rolls the tank to mix the 2 gasses.
Like most of you, my tanks sit on the cart for months on end. I have never stirred my tanks.
Just curious.
 
No, I'd not heard of that, but I can see why you'd do it now you mention it. I've not welded in ages, I'll do a run, "stir" and do another run and report back next time I do. Will be interesting.
 
Gases do not settle in the long-term. At first they can, such as if Argon is introduced into a small confined space in our atmosphere, but due to entropy and the mean-particle velocity (which can be calculated), they will be homogeneously blended. For if they did settle, our atmosphere would have different layers of Oxygen/nitrogen/Argon/etc/etc. Someone would have to "stir the Earth" to make it into "air" constantly.
 
General Zod said:
Gases do not settle in the long-term.
Click to expand...
This was my initial reaction but then it occurred to me that, at high pressure CO2 Ar mixtures might have a liquid phase
that would indeed settle. A quick google turned up actual data. At room temperature 25% CO2 in argon does not form
a liquid phase at any pressure so no need to stir your tanks. However, if you are welding in the arctic (-40C) a liquid will
form above 2000psi or so.
 
All of my mix gas bottles have a valve with "DT" on the stem. Some call that a dip tube, some a siphon and others an inductor tube. As I've read, it draws from two different parts of the tank (Co2 near the bottom) to help draw them out in the correct proportion. Look at a 100% argon bottle and it won't have that "DT" stamped on the stem.
 
You must log in or register to reply here.
Back
Top