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Tue, 31 Aug 2021 15:57:11 GMT
I often read about building a little box to contain your gas, like if your welding Ti or whatever.  or how He rises and Argon sinks.I bet argon rises too since it's so damn hot.   just as a hot air baloon rises.I would imagin that as it comes out of the hot torch it has heated and expanded way past the point were it sinks.and it's immediately diluted.I'm not saying that what everyone says about containing your shielding is all wrong... but I figure it is probably exaggerated statement to think that your gass is actually flowing up or down in a predictable manner.   I think the "box" mostly decreases drafts and increases the local concentration of your sheilding gas.any science to prove either theory?
Reply:Air is about 80% Nitrogen which has an atomic weight of 14 while Argon has a weight of 40. The gas law says that    P V= n R T    where P is pressure, V is volume, n is moles, R is the gas constant and T is the Absolute temperature (starting at Absolute zero so about 273* more than the number on the centigrade scale). You can see that Argon is closer to three times as heavy as nitrogen (and therefore air) at normal temperature, so it would have to expand nearly three times while hot to have the same density as cold Nitrogen.  Using the formula above, this is true only when it's temperature is above about 800* K  but the gas will cool way below that level almost immediately to fairly close to ambient temperature. Thus it will be much denser than air and will sink. Also remember  that the nozzle directs it downward at first, which will counteract the first tendency to rise while still in the arc.Helium has a weight of 2 so clearly will rise quickly.
Reply:Originally Posted by dsergisonI often read about building a little box to contain your gas, like if your welding Ti or whatever.  or how He rises and Argon sinks.I bet argon rises too since it's so damn hot.   just as a hot air baloon rises.I would imagin that as it comes out of the hot torch it has heated and expanded way past the point were it sinks.and it's immediately diluted.I'm not saying that what everyone says about containing your shielding is all wrong... but I figure it is probably exaggerated statement to think that your gass is actually flowing up or down in a predictable manner.   I think the "box" mostly decreases drafts and increases the local concentration of your sheilding gas.any science to prove either theory?
Reply:well yeah thats a little harsh but of course this is the internet and you can only assume I havent if I ask a question like that.  random thoughts on sheilding gas andI've been there, done that (physics & chemistry).  15 years ago.yes I'm familiar with PV=NRTI was, however, not aware (was lazy, didn't look, didnt remember) that argon was THAT MUCH HEAVIER.   I  figured %25 - %50 heavier not %285 heavier.   nor that He (which now that I look is a 4 not a 2) was %350 lighter.I do thank you for re-aquainting me with Avagrado.Last edited by dsergison; 07-15-2008 at 02:31 PM.
Reply:Maybe this is going to sound a little harsh, but I think that you should take some basic Chemisty and Physics classes at your local CC. You would be shocked at how the stuff you learn in there applies to welding and everyday life....
Reply:not harsh at all. When trying to reinvent the wheel, do some quick research.
Reply:It's only been about 30 years since I took my last chemistry class and needless to say I couldn't remember absolute zero and can't really recall how Kelvin relates to degrees in C or F. It would be different if I actually used them for anything, lol. Thanks for the refresher.The difference between art and craft is the quality of the workmanship. I am an artist.
Reply:Originally Posted by dsergisonI often read about building a little box to contain your gas, like if your welding Ti or whatever.  or how He rises and Argon sinks.I bet argon rises too since it's so damn hot.   just as a hot air baloon rises.I would imagin that as it comes out of the hot torch it has heated and expanded way past the point were it sinks.and it's immediately diluted.I'm not saying that what everyone says about containing your shielding is all wrong... but I figure it is probably exaggerated statement to think that your gass is actually flowing up or down in a predictable manner.   I think the "box" mostly decreases drafts and increases the local concentration of your sheilding gas.any science to prove either theory?
Reply:there's a difference between what i meant by "immediately"  and what you thought guys I meant.I mean,  so your argon flows out of your cup then it travels kinda like a garden hose stream untill it hits your parts.  then it kinda bounces/slides off about like you would think a soft stream of water would.   now the difference between what I am saying and what you are saying is that you say the argon will go down and "puddle" in a container below.I'm saying it's not.  I think it's so diluted and hot at that point that it's rising with all the convection currents.now if you build up a little open top shoebox and put a supply of argon into it you've made an area of little disturbance with a lot of argon in it.so, to test this:why dont we fill a little shoebox.  turn the argon off and weld without.    see how long the shield holds up.then for another test put a candle in a box about 6" below your work and weld up a something above it.Last edited by dsergison; 07-17-2008 at 10:40 AM.
Reply:I think part of the difference in your theory is for the box to work well it needs to be flooded with argon to displace the air first, like backpurging pipe. If you try and fill the box with the torch it will take a while for the gas to displace the air and you will get dilution and posibly some rise in the warm argon.You should have no problem welding in a box of argon with the torch gas off as long as you don't "slop" (think of it like a full tub of water) the gas out as you weld.BTW it would be kind of hard to keep a candle lit in a box of full of argon before you even start to weld. I doubt an unlit candle will prove much.  I understand your idea however, and it might work if you used the candle to show how fast the air filled box filled with argon from just the torch. When the candle goes out there's no air left below the flame so you could assume its almost all argon.
Reply:Oxygen level to support a candle flame, about 19%.See old thread.  http://weldingweb.com/vbb/showthread.php...ghlight=candle
Reply:The problem with that is that if a small  amount of air is mixed with the argon, it will react with the metal. Argon is a gas, not a liquid or a viscous material which will stick to the metal or even to itself and thereby exclude the oxygen. A better test would be to find a colored gas with lower density than argon, such as Chlorine which is greenish-yellow and has a wt. of about 35. Fill a flask with the chlorine, then run argon into it and watch as the argon settles in the bottom and the chlorine sits on top with a fairly distinct layer. Chlorine is much too reactive to try this while having the arc on; it would react with most metals and even with plain carbon, so some other gas would be needed if that part were added. Perhaps nitrogen mixed with a higher nitrogen oxide to give a brown color to the mix, and copper as the metal welded. I'll think about this some more and maybe have a better idea later.
Reply:are you recommending that someone play with Chlorine gas in an open box? I would highly discourage this type of experiment.
Reply:BTW it would be kind of hard to keep a candle lit in a box of full of argon before you even start to weld.i meant two distinclty different experiments.  one, see ho long argon sits in a box while you weld not introducing any more.two. see if welding above an open box of air will get enough argon to settle into it over a period of time to extinguish tha flame.it would sure be neat to be able to see gases
Reply:are you recommending that someone play with Chlorine gas in an open box? I would highly discourage this type of experiment

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