Testing out on 2" schedule 160 TIG (70S-2) for root and hot pass, and ER 309 all the way out

by Radu P. Laurentiu
(Wheaton, IL)

X - Ray Test in two weeks, kinda nervous... 5/1/2010

My problem for the last couple of months has been getting a root suck back on my TIG root pass. I grind down my landing to a feather edge, and try to put a 1/8" root gap, and still get suck back...

Just the other day I switched to a smaller TIG torch cup, and got the cup real deep into the groove, for the first time ever I had a decent root pass with TIG, still a small suck back, but not the Grand Canyon type like I had before...

Does the Tungsten selection make a difference when welding for X - ray quality weld test, on carbon steel 6G??

A book said to use Zirconium / Thoriated...??

All I'm trying to do is pass this test, real confident in the 6010 / 7018 test, just the suck back on the TIG is been killing me.

My instructor at school said that if you get a suck back on the root pass, you can turn up the heat on the hot pass and push it out some, I was surprised and somewhat confused by that answer...??? Is it true??

Well those are pretty much it,

Thank you,

Radu P. Laurentiu


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Radu,

I have found that the key to preventing suck back is using as little side to side motion as possible. That might be why the small cup worked better...because the tungsten doesnt not move as much. If you must walk the cup, dont wiggle much ,,,just enough to progress the weld.

forget zirconiated electrodes. you will probably be required to use either 2% thor, ceriated, or lanthanated. not much difference in the final weld just subtle things.

I tested once and walking the cup was prohibited.
just a straight forward and then backward method was mandated....yes mandated. I thought they were whack but it worked great....pushed the root thru even at 6 o clock.

thanks,

jody