TIG gas supply - switch or no?

[Mr Fro]

Hey everyone!

I've been fiddling around getting the bits and bobs for having a bash at basic TIG stuff.

I bought one of the larger 2.2L disposable bottles as it should work out a bit less uneconomical than the little bottles but doing the calculations it'll still only last 15-20 mins or so before I run out.

Seeing as I've only got a basic torch, I thought I'd pop a foot operated gas switch between the regulator and dinse connector to save me some argon (and save me fiddling about closing, opening and setting the flow at the bottle) as I'm bound to knacker the tip or something a good few times before I get my eye in.

If I set the flow at 10-15lpm and allow a few seconds pre and post do you think I'll be alright with this sort of set up?

Oh, and while I'm at it, I've got some sheet stainless to practice on. It's probably ~1.5mm or so and fairly clean. What should I do for prep? Quick run over with a sanding disc and a wipe down with acetone or is that last bit overkill?

Cheers,
Fro

 

[optima21]

with TIG, you need to have the metal as clean as possible, so acetone isn't overkill, you're just reducing your risk of having impurities in the weld, but many people will weld sucessfully without going to those extremes. also you may find that with TIG you can get away with 5lpm of argon, so that would give you more welding time.

 

[Mr Fro]

So I had a do at TIG the other night. I had to turn it down to 25-30 amps to prevent warping and I ate through the gas bottle in about 10 mins at ~10lpm but all in all, I think I made a reasonable fist of things. :-)
Like an idiot, I bought an 8 metre torch package so the flipping cable ran pretty much to the end of the garage and back and I didn't weigh the gas bottle before using it. Beginner error!
It's a shame you can't use the same gas for TIG and MIG as I don't have a massive amount of space at the moment but I feel a BOC order coming on nonetheless. ;-)

 

[hotrodder]

Turn the gas flow down. 10 lpm is overkill, as said 5 lpm (sometimes even a little less) is often adequate for TIG and you'll rarely need more than 7 lpm. Less is usually more for example if having shielding problems when welding an outside corner turning the gas flow up is more likely to make things worse. Check out http://www.mig-welding.co.uk/tig-tutorial.htm too.

All welds shrink & stainless distorts more than mild steel from localised heating as it has a higher coefficient of thermal expansion coupled with poor thermal conductivity. Turning the amperage down and welding more slowly typically makes things worse and also effects weld quality

The whole cleaning thing with TIG is waaaaaay overdone on the internet. Outside of aerospace or the like there's no nead to religously degrease stuff unless the metal is covered in oils/greases/sticky tape residue etc. Hot rolled mild steel needs more attention with TIG than it would if using MMA, stainless sheet on the other hand is virtually always cold finished so there's no mill scale that needs removing mechanically

 

[eSCHEn]

When I was trying to stick two stanley blades together I had the amps down to 4 (lowest on machine) and had to drop the gas really low (2 - 2.5lpm) or else it kept blowing the arc out!

 

[Mr Fro]

Cheers Hotrodder. I had a good read of the tutorials before I got cracking and they gave me a great starting point!

I buzzed a sanding disc over the sheet before I started (It had about 4 years of grime on it from sitting in the corner of the garage). I was going to play about with speed and current but ran out of gas. I think turning the flow down would work fine as I measured the flow a few mins before I ran out and it was giving 3lpm - I couldn't see any significant difference in the welds.

I'm curious; All I read tells me that TIG is really gas hungry vs MIG. However, the flow rate is much lower with TIG and if one can flow the gas on demand then surely it's gas sparing compared to MIG or am I missing something?

 

[eSCHEn]

It's more that TIG is much slower than MIG so for every metre of weld bead in TIG you use more gas as it takes longer to produce it than MIG.

 

[hotrodder]

The lower travel speeds is a big part of it but IMO the whole 'gas hungry' deal is more of a beginner/learning thing than anything or at least exagerated when learning due to even lower travel speeds and a LOT more stop/starts using extra gas... initial surge (assuming a single stage reg) and post flow time soon add up if stopping every few inches

FWIW http://www.mig-welding.co.uk/forum/threads/argon-consumption.52101/#post-602176

 

[eSCHEn]

I've been TIGing for a year now and the speed I travel now is much much faster. A large part of that is simply me getting more skill and muscle memory but also deliberately running hotter on more amps and going fast so as to minimise warping.

The gas went quick when I was slow and lasted longer when I sped up. I still feel tacking up is like pouring money out my pocket with all the stop start though lol.