TIG arc start & cleanliness etc?

[julianf]

I picked up my new (2nd hand, but looks as new) chinease tig last night (Rehmann).

In my eagerness to test it when i got back late, i hooked it up to a bit of mild steel plate and tried to get an arc without gas. The steel was clean some weeks ago, but had thin patchy surface rust on it.


Results were -
Arc started, beaded the tip within seconds, as if id touched.
Try 2, with same beaded tip - could not get an arc, just thin 'lightening' style bridges.
Tried this for a while. Tried to scratch start, which was probably successful once, but again, spitting like my SIP mig.

Gave up, went to bed, before i burnt holes in my (only) suit...

Ive used TIG machines before, but only for a limited time, and only expensive units at fabricators. So im not skilled, but have a few hours experience.


Were my problems last night -

a) lack of gas
b) lack of experience
c) metal needed to be cleaner
d) tools (welder 2nd hand, but looks as if its virtually unused)

 

[edd]

a.
Once you have "a" sorted you will then have problems with b & c!

Ed

 

[julianf]

Right -

Reground electrode
Connected up gas (about 5lpm)
Found a bit of stainless - even gave it a clean.

Arc initiates fine now, but the electrode burns back like mig wire thats not feeding. I have the amps set to minimum, but im thinking that shoud not make a difference. Im not touching the work, and, besides, the electrode is burning back into the shroud, where i couldnt touch anyhow.

The electrode is one that i got with the machine. Its got a red band on its end.

I realise i did not expressly purge the gas lines, but i did mess about for a while getting the flow rate sorted, so id imagine they were full of gas, but possibly not?


edit: another regrind. turned up the gas and the post flow. pulsed the torch several times to initiate post flow, and hopefully purge. tried again, and same thing - arc initiates, but instantly burns away the electrode.

 

[julianf]

Wonderful!!!

Who would have thought that a change of polarity would make so much difference.

(well, not me, obviously!)

: )

 

[Jan]

Sorted! Nice.

 

[Brad93]

electrode with a red band is 2% thoriated tungsten. Ideal for DCEN welding on m/s and stainless. Gas flow probably could be higher for the stainless 6-7lpm i use.

 

[BrokenBiker]

with the torch connected to positive the tungsten is seeing about 2/3 of the heat, which will cause problems with the tungsten

 

[zardoz]

Wonderful!!!

Who would have thought that a change of polarity would make so much difference.

(well, not me, obviously!)

: )

I have had it happen myself, with a new machine and too eager to have a go before bedtime (exactly like yourself) Makes a fierce if short display as the tungsten vaporizes and the ceramic blackens up, does it not ?