Problems tig welding carbon steel tubing

[longcut]

To start, I'm a novice, but here it goes.
I'm having problems with welds becoming contaminated while welding exhaust tubing.
1. joint clean & sanded
2. argon at about 30 psi
3. cup is about half in in dia.
For some reason the "stack of dimes" is impossible to get. It will go ok for a while, then I'll see the puddle dance (get pin holes). Sometimes the puddle looks like it is heating up way too much and looks like I'm gas welding.
Sheet & metal bar stock seems to do ok which makes me think that the dom tubing is poor quality.
Any help would be appreciated.

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[Toysrme]

To start, I'm a novice, but here it goes.
I'm having problems with welds becoming contaminated while welding exhaust tubing.

For some reason the "stack of dimes" is impossible to get. It will go ok for a while, then I'll see the puddle dance (get pin holes). Sometimes the puddle looks like it is heating up way too much and looks like I'm gas welding.

what kind of pipe is it? what kind of filler is it? how are you welding dipping or walking the cup? how many amps? how many cf/h of argon, what kind of electrode stickout? what kind of electrode?

2. argon at about 30 psi

we are welding. not using an oxy-fuel torch. we do not measure gas flow rate in psi. We do it volume / time (typicall cf/h or l/m) if you're using 30psi then you're using 29-30psi too much. If you don't have a correct flow meter, forget it until you get one, or get alot more experiance.

3. cup is about half in in dia.

is it a cup or a gas lens? cups suck, use a gas lens for pipe to give you better coverage and more stickout to do merges.

1. joint clean & sanded

Cleaned with what? Sanded with what?






sounds to me like you're contaminating the welds from being FAR in excess of what gas coverage you need (8-12cf/h on a medium gas lens, 15-20cf/h for a normal mid sized cup) im sure you're contaminating your filler and electrodes. and using far too much heat and too low a travel speed.


Post some pictures.

[longcut]

I've been meaning to look into a gas lens...I'm going to start with backing down on the Argon and pushing the tungsten back and buy a lens.
I think the tunsten was sticking out about .250+.
Speed looks to be another factor because it does appear to be heating up to much.
Cleaning I use fresh (medium) scotchbrite. Is that sufficient? It's new tubing so it doesn't take much to come up "brite". I have used acetone because the tube is mandrel bent and they tend to be shipped with residue left inside.
Tubing is carbon steel (I'm guessing 1117) .031 wall
Tungsten 3/32 2% thoriated
Filler - same diameter, but I'd have to check type/number
Thanks again

[mxtras]

It's possible the heat is attracting the lubricant from the bending to the seam. Do you notice this occurs more in one clock position on the tube or is it random?

Could it be the angle of the torch relative to the work/filler?

Just tossing out some first impressions here...

Scott

[tauntdesigns]

I'm have not welded much but, I have a couple of ?'s

I had heard that you need 1amp per .001" of material to melt plain carbon steel...
So I'm thinking you need to set machine to 32amps for your tubing
but
your filler is .093" and machine would need to be set to 93amps which would be too hot for the tubing.

Is that right? .....If it is, does the OP need to use smaller filler?

Thinking out loud,
Jack

[Toysrme]

I'm have not welded much but, I have a couple of ?'s

I had heard that you need 1amp per .001" of material to melt plain carbon steel...
So I'm thinking you need to set machine to 32amps for your tubing
but
your filler is .093" and machine would need to be set to 93amps which would be too hot for the tubing.

Is that right? .....If it is, does the OP need to use smaller filler?

Thinking out loud,
Jack

The rule you're trying to say are all related to stick welding hehe.
Forget mild steels, its most common to one pass schedule-10 (0.109") 1.5" T304 stainless tubing at just 30-40 amps with a 3/32 electrode and no gap. Or two-pass it at 25-35 amps. If you use a proper root gap opening and weld it you can one pass it at 30 amps.










longcut, scotch brite won't do anything in an very constructive amount of time. use a stainless wire brush.

I will almost gaurentee you that you're drawing large amounts of atmosphere into your shielding gas from the turbulence of the pipe, and your high argon rate. which is contaminating your work, your filler and your electrode. a 1/2" gas lens will let you have > 1/4" stickout in the right circomstances, but a regular lens wil only give you about a 1/8" stickout. so you can't be shielding your welds very well from the atmosphere. and don't hit your filler or workpiece to your tungsten.
if you do that I bet it goes away.






You're using 0.031" wall thickness? Why? If it was free I wouldn't use it for an exhaust. Most definately not an exhaust that would ever see forced induction. Use 16-gauge (0.065"), Schedule-10 (0.109"), or Schedule-40 (0.145") If you just want to practice with what you have start with 15 amps.
http://www.acestainless.com/
http://store.racing-solutions.org/

[tauntdesigns]

I'll have to give my buddy a hard time for telling me that...

He had told me 1amp per .001 for steel, 50% less for stainless, and 50% more for alum.

My bad,
Jack