Impure Argon is a Waste of Time.
Bad gas sucks! I’m not talking about the type naturally produced after consuming too many legumes. I’m talking about the type that you get by the cylinder-full at the welding supply store.
A few nights ago while welding on a project, one of my two argon cylinders was running low. The tank pressure was all the way down to zero, and it was only a matter of time before the argon completely ran out in the middle of a weld.
When argon runs out in the middle of a weld, the sudden loss of shielding gas around the weld puddle means impurities can enter the molten metal. This means porosity, or metal filled with air pockets. The only way to fix porosity is to grind out all the porous metal and re-do the bad part of the weld.
Changing the argon cylinder before the argon completely runs out saves the hassle of fixing a porous weld. Changing the argon cylinder too soon wastes argon, since there’s still usable argon inside the near-empty cylinder. I figured I'd pushed my luck far enough and used up all the argon I dared. Making sure the cylinder valve was tightly closed, I cautiously loosened the regulator from the cylinder threads, and set it aside. I then found the safety cap and tightened it in place over the valve. Next, I unhooked the safety chain and lifted the cylinder out of its place on my welding cart.
Installing the new cylinder was done in the reverse order of removal. The cylinder was chained in place, the safety cap was removed, and after checking to make sure there weren’t any obstructions in the valve threads, the regulator was tightened in place. Now, I’d be able to weld for several more hours without worrying about the argon running out mid-weld.
I cracked the cylinder valve open, and re-adjusted the regulator for the flow I needed. Now, to start my weld. I got the TIG torch in position, flipped down my welding hood, and stepped on the foot pedal. Things got ugly.
Instead of a nice, smooth arc and an equally smooth puddle, the arc was jumpy and seemed to be cloaked in a miniature storm around the tungsten electrode. The puddle formed, but it was just as jumpy as the arc. Something was wrong.
I stopped welding, flipped up my welding hood, and double-checked the regulator. A quick tap on the foot pedal got the gas flowing again, and I could see that the regulator was indeed delivering the proper pressure. I could hear the gas flowing out of the torch nozzle.
Was the base metal dirty? Wire brushing took away the sooty deposit where the jumpy weld had been. I didn’t see any oil on the metal, and the metal was bare and free from paint, rust, and mill scale.
Was the tungsten contaminated? I removed the tungsten from the torch and ground a new point.
After I’d re-assembled the torch with the freshly-ground tungsten, it was time to give it another go.
I moved to a different spot on the metal and tried again. Same result. Crap!
My suspicion all along had been that I’d gotten yet another cylinder of contaminated argon at the welding supply store. This bad bottle made the third or fourth time. I go through maybe a dozen bottles a year. Finding three or four contaminated cylinders out of a dozen is a sign of a major screw-up by the supplier.
To validate my suspicion, I put the regulator back onto the near-empty cylinder. Voila! The arc and the weld puddle were as calm and as smooth as could be.
Fortunately, I was able to weld the rest of the evening on the near-empty bottle. Under the welding hood, I was fuming. What’s so hard about properly re-filling an argon cylinder? Honestly, re-filling an argon cylinder might be tough, but that's part of what I pay the welding supply store to do. I pay them to do it because I don't have the equipment or training to do it myself.
I’m sure the welding supply store will give me another full cylinder to replace the contaminated one, but that’s not the chief point of irritation. The chief point of irritation is the time lost carting the bulky cylinder back and forth, and the energy expended telling the store employees that yes, I’ve got another bad cylinder of argon that needs to be replaced free of charge. Will my contaiminated cylinder be replace with another cylinder of contaminated argon?
I’m a pretty loyal customer, but it’s time to try somewhere else. On the way to the office today, I stopped in at a competitor’s store, and they said they’d refill my cylinders there. This was a huge relief. I was afraid they wouldn’t refill them at all since I purchased them elsewhere. I’ll be stopping in at the new store tomorrow with an empty cylinder.
As for the second cylinder of contaminated argon, I have to pay my original supplier a visit. I already know what I’ll say:
“This cylinder of argon is bad. The arc is jumpy and the weld is full of porosity.” Then, handing the clerk a section of square tube with a tab welded on, I’ll continue: “Here’s a sample weld that I did with good gas. I want you to see it so you can understand that I know what I’m doing.”
We’ll see how it goes. Once again, bad gas sucks.