AC TIG question

[SS.]

My question is when we weld on AC I notice a chaulk like dust all over the tig cup, is this normal or am I doing something wrong?
We have a SYNC 250DX, running 1/8" pure tungsten, 100% Argon, 20 to 40 cfm trying different gas flow to see if it produce a ifferent outcome.

Thanks
Sal

[turboglenn]

I only get this when i run low on or out of gas. Make sure that your bottle is full, regulator set properly (between 13 and 20 cfh will sufice for most jobs) Also make sure your collet bodiy is in good shape and that none of the holes are obstructed.

If all of these check out you might try using a gas lense to help with the flow. Now, on your welds on AC aluminum work you should see a white area around the bead, this is from the cleaning action that occurs when the arc is in it's positive state, the actual heat input is all done in the negative state, thus why DC TIG is mostly done on DCEN (the torch being in the negative state at all times) DCEP will still weld but with less penetration, and is good for really thin stuff ( i mean REALLY THIN)

Try those and report back!

[SS.]

Turbo thanks for the tips. I checked the tank and it is more than half full, I tried a new collet body and new tungsten and cup, just trying to rule out any and possible problems. Yes I get the cleaning marks on outside of the bead. The weld bead looks good but still get the powder like on the cup. Could it be a bottle of bad gas causing it?
Thanks Again
sal

[davedarragh]

I only get this when i run low on or out of gas. Make sure that your bottle is full, regulator set properly (between 13 and 20 cfh will sufice for most jobs) Also make sure your collet bodiy is in good shape and that none of the holes are obstructed.

If all of these check out you might try using a gas lense to help with the flow. Now, on your welds on AC aluminum work you should see a white area around the bead, this is from the cleaning action that occurs when the arc is in it's positive state, the actual heat input is all done in the negative state, thus why DC TIG is mostly done on DCEN (the torch being in the negative state at all times) DCEP will still weld but with less penetration, and is good for really thin stuff ( i mean REALLY THIN)

Try those and report back!

Turbo: TIG welding in DCEP (DCRP) will blow a hole in 1/8 mild steel! Where'd you ever here DC+ has "less penetration?" It's EXACTLY the opposite. DC- has less penetration. You'll burn tungstens up galore, and melt your work in DC+.

AC has no polarity, because AC is current. It alternates, and that's where you get your "cleaning," and "penetration" values. DC Current travels in a straight line.

Dave

[Wicked one]

Turbo: TIG welding in DCEP (DCRP) will blow a hole in 1/8 mild steel! Where'd you ever here DC+ has "less penetration?" It's EXACTLY the opposite. DC- has less penetration. You'll burn tungstens up galore, and melt your work in DC+.

AC has no polarity, because AC is current. It alternates, and that's where you get your "cleaning," and "penetration" values. DC Current travels in a straight line.

Dave

It does not have less penetration it will however produce a very narrow bead which put's all the heat in a narrow area. You will also have a very dirty weld. We used to weld very thin aluminum with DCEP with a miller aerowave was designed to weld aluminum that way with high freq ,which in my opinion was the best aluminum welding machine I 've ever used and miller stopped making it. You could run a bead on the edge of a 3/32 piece of aluminum, it was awesome.

[ASKANDY]

DC electrode POS will give less penetration AND burn up tungsten if not sized properly to handle the current flowing up to the tungsten.

DC EN gives penetration to the work piece.

This is why tuning up your balance on AC to a higher number (which is adding more electrode NEG) gives MORE penetration and less cleaning.

Andy

[davedarragh]

DC electrode POS will give less penetration AND burn up tungsten if not sized properly to handle the current flowing up to the tungsten.

DC EN gives penetration to the work piece.

This is why tuning up your balance on AC to a higher number (which is adding more electrode NEG) gives MORE penetration and less cleaning.

Andy

Andy: You worded it correctly, I did not. In GTAW, when in DCEP mode, cleaning action takes place on the work surface by impact of gas ions. 70% of the heat is developed at the positive tungsten electrode, so in order to obtain the same heat on the work piece, the current must be increased by 2.3. This necessitates using an electrode 4 times the diameter normally used in DCEN. The impracticallity of this is obvious.

DCEN put's 70% of the heat in the work, and although it provides little to no cleaning, used with ferrous metals, it isn't really an issue. Gas ions flow FROM the work TO the elecrode, and electrons flow FROM the electrode TO the work.

I just know from machine setting errors (leaving it on DCEP), I've "blown" holes in 1/8" flat stock, and ruined a few tungstens.

Thanks for clarifying this.

Dave