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Soot on arc start

Posted: Sat Oct 22, 2016 1:10 am
by PaterNovem
Very new to welding, TIG welding in particular. When doing my bead practice, every now and then I get a black soot ring when I start the arc. Seems to do it on my first arc on a cold piece but sometimes later. I thought maybe my argon hadn't gotten to the nozzle by the time the arc started so I set a 2 second gas purge to start.

Everlast 200DX, pure argon, 3/32 2% Lanthanated electrode. 4043 rod, just running practice beads on some 1/8" scrap. I clean with a SS brush prior to starring.


Thoughts on what I am doing?

Re: Soot on arc start

Posted: Sat Oct 22, 2016 11:04 am
by zank
Pretty common for me to see that. As long as it's on the border of the cleaning zone and not in the puddle and/or bead, you are ok.

Re: Soot on arc start

Posted: Sat Oct 22, 2016 3:30 pm
by Otto Nobedder
As Mike said, this is not actually a problem; The soot should brush away easily.

One possible cause is, after ending the previous bead you moved your torch quickly enough to get air to the tungsten before your post flow allowed it to cool, so you're starting with a little oxidation on the end of the tungsten. The other likely cause you would be very aware of if you'd done it... having dipped or brushed the tungsten in the puddle or with the filler.

Steve S

Re: Soot on arc start

Posted: Sat Oct 22, 2016 7:55 pm
by Welsh Weldlord
Hi
As Mike and ottoman stated nothing to worry about but don't forget that post purge is just as important as pre purge on the start of your weld, if your 4043 rod is still hot when you remove from the weld area covered by argon it is prone to oxidation, then when you start your next weld it is already contaminated, I know it can be hard to do or easy to forget but when you lift off the pedal or release the switch wait for the post flow to stop while keeping the rod in the purge zone. If you ever start welding aluminium oil coolers or intercoolers or cast aluminium you will be cleaning and regrinding tungstens and wiping tig rods every run of welds you do, so if you do get the occasional blemish while practicing learn from it and move on enjoying all the experiences that come with all types welding and from the looks of the photos your doing great!