[cameronccc]

New here and have a few questions. First off I've been welding pipe for a few years, mostly downhill 60/70/8010 and some 7018. well the test is tig.. I've been tig welding for years just not on pipe! the test is 2" sch 160 tig all the way. Well at first I thought the root would be the problem but that's not the case. The root looks good every time, like I've been doing it my whole life. But here's my problem, after the root, the hot pass,filler and caps just don't look good. There a dull grey color and it just doesn't look right to me. Seems like the should shine like the root does. I understand that heat does this but im doing my best to let it cool after every pass! Another thing im noticing is the root turns that grey color after ive been welding also. IS that normal for the root or should it stay the same color?

Some info
2" sch 80 (don't have 160)
knife edge
3/32-1/8 gap
1/8 filler

Root is 115 amps
Hot pass is 125 amps
Cap is 130 amps

Lincoln square wave 275 or Lincoln sa200
CK flex head 17
jumbo gas lense
number 8 cup
15-20 on the flow meter
scratch start

if any one has a picture of what there root looks like after a complete weld that would be great.

[Coldman]

Welcome to the forum Cameron.

I only ever do 2" sched160 for test coupons which then get the works done to them ndt, dt. Always 100% tig.
My settings are:
Root: 125a
Hot Pass: 130A
Fill Pass: 150A
Cap: 150A

Prep: 30* bevel, knife edge, 3/32" gap. 3/32" wire. 3/32" tungsten with plenty of stick out, 11Lmin argon, No.8 cup.

I found an old practice piece in misfits drum, root pass only so the inside probably sucks. When I get a chance later I will cut it up for a pic on the inside. Here is the pic on the outside.

50R.jpg (65.65 KiB) Viewed 1187 times

There is always grey scaling on the inside after the complete weld due to all the heat that's gone in, don't let that worry you. A No.26 torch is best for this weld, a 17 gets hot in your hand and can't be doing it any good.

Cheers.

[cameronccc]

Thanks for the info. Like I said my root is great, nice on the inside and nice color on the outside. Really just looking for info as why my other passes look so dull. And for the torch I like the 17 with the super flex cable, its light weight and fits me good. It does get hot but the only time I feel the heat is the root because I free hand it. The other passes I walk the cup so my had is at the bottom of the handle.

[Braehill]

Cameron,
I don't know if it's good, bad or indifferent but mine always turn grey after the root is done also. A lot of heat goes into a schedule 160 weld so it's bound to turn grey from oxidation.

Len

[cameronccc]

Ya but what about my fillers and cap being grey? seems like they should shine! ill try to post some pictures tomorrow.

[Rick_H]

All I have is sch 80 pics...

[cameronccc]

ill go weld one out and get pictures

[cameronccc]

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[cameronccc]

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[cameronccc]

sorry the pictures are all out of order and sideways. root went in good, tacks were kind of heavy but good enough. hot pass and fill did ok and the cap needs to be tightened up. all these pictures were from the left side, that's my hard side. so the other side of the pipe not pictured looks a tad bit better.

Lincoln square wave 275
ck flex head 17
3/32 ck red tungsten
root was 110 amps
hot pass was 115
fill and cap at 120
#6 jumbo cup

after every side I welded I let it cool enough were I could touch it. switched from a 8 to a 6 cup and seemed to like it more. liked it so much I never took it off! welded the whole thing with it..

[Markus]

That root is sweet! How you guys get that much reinforcement to root? Especially at 6 o'clock.

About those cap passes. Isn't root weld usually little smaller than rest of the passes.... Less heat brought. You already mention about cooling between passes. But think it this way

When you start welding your pipe is only 20 ºC or so. Root pass done and carbon steel have now sucked really much heat energy and conducted it to large area. Then you let it cool down to touch. Let's say that pipe is 40 or 50 ºC as you start your hot pass or cap, if you will. Now you already have 20 ºC difference compared to root pass. You put the same heat to the to pipe as in root for example, but total heat is difference and it can easily affect to color of the weld. In other words weld cooling time is longer and it reacts with air in higher temperatures.

Does it matter at all in this case? No, as already stated here. That color is just oxides and impurities reacting with oxygen in higher temperature. Specially I wouldn't worry as long as it can be brushed clean with ease.

[cameronccc]

the root goes in easy for me. 3/32 gap, 1/8 wire and I just go back and forth over the wire never letting the tungsten get outside the gap.

ive always ran my root with a loose gap where the wire would fall through, seen someone post about the 3/32 gap and 1/8 wire. I thought it sounded crazy! but it works so good!!!

[cameronccc]

yall tear it apart!