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Up Topic Welding Industry / General Welding Discussion / tig root pass
- - By short stack (**) Date 06-22-2008 22:38
wanted to see if i could get some advice on putting a root pass on some 2 pipe i have to make a 2 stainless test next week
i really appriciate it!!
Parent - - By tighand430 (***) Date 06-23-2008 00:17
1/8 gap with 1/8 rod, run your machine at about 65-75 amps and run over the wire. Ought to give you a root that lools like a machine did it.
Parent - By ericpratt (*) Date 06-23-2008 02:12
be careful with a 1/8 gap could close up on ya and might give you a little trouble
Parent - By sqiggy (**) Date 06-23-2008 02:14
Lot depends on who's looking at it.
Find out before you even tack it up what the QC man wants to see. If he wants a root just above the pipe, I'd go with a 3/16 gap with 1/8 rod. Run your wire just inside your joint and feed it all the way up to about 3 o'clock and 9 o'clock By the time you get up both sides, It'll close up on ya, you will probably have to go with some 3/32 wire. Coming up the to the top, just lay your wire in the bevel and run over it. It will just fall right in there. Don't forget to purge it throughout the root pass and hot pass.
Who are you testing for??
Parent - - By swsweld (****) Date 06-23-2008 02:18
Knife edge on the root edge. Make sure you have a good purge with vent at top. Not too much CFM argon. Feather tacks sharp for good tie ins. Cut wire ends off every time after welding. Cut wire on 45 degrees. Sharp tungsten, prefer gas lens. Last quarter cut argon back slightly.
Parent - - By ZCat (***) Date 06-23-2008 04:39
cut wire on 45 degrees??? what does that does?
Parent - By swsweld (****) Date 06-24-2008 02:51
It makes the start a little friendlier. Occasionally the wire will ball up on you when fire up. Cutting the end on an angle and putting the sharp side of the wire near the tungsten reduces the chance of wire balling up. It's aggravating when you fire up, wire balls up and you have to jab it in before you get a keyhole. Not a big tip but a tip nonetheless.
Parent - - By zach benefield (*) Date 06-23-2008 02:25
dont forget to purge it
Parent - - By chris2698 (****) Date 06-23-2008 03:06
I prefer to run 1/8th gap and a 3/32 rod but I was welding sch 10 pipe to and purge it
Parent - - By sqiggy (**) Date 06-24-2008 04:12
Ain't nuthin wrong with that.
But on sch 40 and up, I like a gap that I can feed a 1/8 wire on the inside. Just about all the QC's I've tested for don't want the botton flush. They like to see a little meat on that bottom side.
Parent - - By chris2698 (****) Date 06-24-2008 11:07
yeah if it was thicker I'd probally want a little wider gap to
Parent - - By short stack (**) Date 06-24-2008 23:47
2''160 wall on carbon pipe  with stainless rods after tacking do u  stick ur rod from the top inside the pipe or???
Parent - By sqiggy (**) Date 06-25-2008 15:39
On 2", I only put 2 tacks. Top and bottom. Put your purge line in on one end and tape it up real good where it won't fall out. I like to use the big gas lens on the end of my purge line. On the other end, cover completely with maskin tape. Then using my tig wire, punch a few holes in the tape. This will allow excess gas to escape. Then tape up your tacked test piece, running the tape from top tack to bottom tack, both sides. Then start the purge. Peel back enough of tape to start from the bottom and go up to 3 o'clock. Just lay your tig wire just inside the bevel and just run over the wire but make sure you are tying in on each side of the bevels. Then do the same thing on the other side, going up to 9 o'clock. By now, your gap will close up, maybe a loose 3/32. You can use 1/8 wire, just lay it in the bevel and run over the wire or go to a 3/32 wire and feed it. Either way, it should fall right in there. Just remove enough of the tape to weld from one point to the next. Once you get the root in, leave purge on and hot pass. Once you get the hot pass in, you can remove the purge and the rest of the tape on the ends. The reason for the purge, the root on your stainless will what we call "sugar on ya". This will end your test pruddy quick.  
Parent - - By short stack (**) Date 06-24-2008 23:29
Parent - - By ericpratt (*) Date 06-24-2008 23:32
if its carbon you dont have to purge it of course.
Parent - - By Shane Feder (****) Date 06-25-2008 01:29
Hi guys,
I think the company must be taking advantage of QW 423.1 from ASME IX where you can substitute carbon pipe for stainless pipe for welder qualification. It is much too expensive to be throwing away pieces of Sch 160 stainless steel.
They will still be using s/s filler so purge will be required.
Parent - By pipewelder_1999 (****) Date 06-25-2008 02:49
The SS filler metal is not even required for the GTAW portion. Basically all that needs to be certified for if one already has GTAW Carbon is the SMAW portion using F5 material.
Parent - By sqiggy (**) Date 06-25-2008 15:42
But he will be using stainless on carbon, so yes, he will have to purge.
Parent - By sqiggy (**) Date 06-25-2008 15:46
Oh, I almost forgot, when you go to tack up your test, you WILL need to purge that as well. If there's another welder there testing, get him to help you set it up.
Up Topic Welding Industry / General Welding Discussion / tig root pass

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