2" sch 80 tig root 7018 cap 6g test help

[Boilermech]

I am 35 years old and done some stick and mig welding over 10 years ago back when I done paint and body. I have been an operator at a coal fired power plant for the last 4 years and I transfered to a boiler mechanic at the first of the year at the same plant. They want me to get my state license here in Oklahoma (steam card) so I can take all their tests and be a welder for them. The bad news is I never done any tig welding before. So I started going to a night welding school to learn how. The school started around the first of the year and is now almost over and I am still having trouble with the root pass. I can do the hot pass and the cap but I need help with the root. I know practice makes perfect. At first I was doing it with a tight 3/32 gap, 3/32 wire and around 75 amps with the keyhole dip technique. The problem I was having was not getting in far enough. After practicing every day I am now using a loose 1/8 gap, 1/8 filler rod and 90 amps. With the lay wire technique. But I have just gone the complete opposite. Now I have way to much root inside. I am using a feather edge with 37 1/2 bevel. I will try to post pics. Any info on gap and amps or technique would help. Thanks.






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[performance]

Are you allowed to walk the cup?

Several suggestions here.
1) Stick with the 3/32.
2) Use a 3/32 root gap.
3) Use 3/32 tungsten
4) Go down to 65 amps, and SLOW down. IT isn't a race. I've done it with barely more than 50 amps.
5) Keep your tungsten almost in the puddle...no more than a pennies thickness above the puddle..
6) Use the force of the arc to "push" the metal in...including using it to push the metal to the sides.
7) Forget about lay wire, because you need more wire than it provides to correctly fill.
8) Start at the bottom and work around to the top, and IF you are using the foot pedal back off the heat once you reach 90 degrees around...the heat will be traveling up and you won't need as much.

I can't stress too much that I THINK the issue is that you are using too many amps and going too fast, in both scenarios.

[Boilermech]

I am using a 3/32 tungsten. When I go slower with a 3/32 gap and 3/32 filler rod it gets all crusty inside and looks kind of concave and not even flush. That is with the dip technique. And I am not to good at walking the cup on the root. I can walk it good on the cap but this test requires stick for the cap. I will try it again with your suggestions tomorrow and post updates. Thank you for all the input.

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[Rambozo]

I would agree with everything Mark says, and add the following:
Depending on the WPS go with a 1/16" land for 2" pipe.
For me, 2" is right on the border for 1/16" tungsten or 3/32", either will work fine, but you can get in tight with 1/16" and still have some wiggle room to adjust position. I find it easier to see with as well. Try both and see what works best for you.
Looks like you're jumping right into 6G. Get to where you can nail 1G, 2G, and 5G first. If you have problem areas, practice that angle with plate, as you will get a lot more time at the problem angle. With pipe it changes too fast so it's a lot harder to figure out what you're doing wrong, more so with smaller pipe like 2".
Try to keep a consistent rhythm of torch motion and filler rod. If you find you're feeding rod faster in some places, you know something is wrong. The pipe is the same all the way around, your weld needs to be the same all the way around.

[performance]

Rambozo, he's having trouble getting the root through...I don't think a land will help him get it through any better. It may be different on 2 inch than the 6 inch I am used to working with.

Boilermech,
Do you have any pictures of the "colder" root pass? What's the issue? Suck back?

[Boilermech]

Suck back on the bottom and my instructor told me that I am moving way to slow. I sit in one spot to long trying to tie in the edges. It also looks crusty on the sides of the root inside the pipe. Instructor says thats because I sit in one spot to long. He was actually very happy on this root pass that I just done because it made it in at least. I started at ground zero 4 months ago just walking the cup with no filler rod making hundreds of beads. Then moved to plate then pipe at 1g then 2g then 5g. Now I am on 6g. And its kicking my butt. Here are some pics of the outside. I will try to get some pics of my other lower amperage roots later today. Thanks for any input. Positive or negative is great. Thanks again.




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[performance]

For starters, I don't know how you are being trained, but that looks like a second or third pass. The root pass should be paper thin and JUST wide enough to bridge the gap. The top looks gray. You may not have enough gas flow as well.

IF it is thin, then the hot pass, IF you have any suck back will partially remelt the bottom pass and push it out in the next couple of passes if you use enough filler. If you don't, it will suck back on the hot pass.

[Boilermech]

My instructor is around 55 or so and he's been welding pipe for several years. He can do the root pass then the hot pass then the 7018 cap and be done. Thats how he teaching me to do it. I only know how to do it the way Im taught. There are no filler passes. I will try a 3/32 gap and 3/32 rod after work and post pics of the results.
Picture of my walking the cup on 6" pipe cap. Remember only been tig welding 4 months.

[performance]

I guess that 2 inch is probably about 1/4" wall thickness?
That would be about right in total "layers", but maybe not in total passes, as you have two caps side by side there.

The undercutting you are getting on the side, is either too hot, or you aren't pausing long enough on the sides.
I am surprised that they aren't telling you to run stringers.

The way I figure it is that you should figure up the wall thickness, say on 6" pipe, it's 3/8 of an inch. If I were to run a root pass with say a 3/32 6010
then run a hot pass with a 3/32 7018, and then it would take two or three filler passes side by side then the cap passes..

A pass should not deposit any more metal than the rod is thick in diameter (the steel part, not counting the flux) if done correctly.

The root pass will deposit way less, and may only end up a 1/16" thick if it's done with TIG.


So if it's a quarter inch thick, then with a 3/32 TIG root pass, and a 3/32 7018 Hot pass, that's 6/32, or 3/16" but consider part of that thickness is inside the pipe by about 1/16" if it's a FULL 3/32 inch... and maybe less sticking above if its thin as it should be. The cap of 1/8" 7018" would barely make the top pass flat, even if its two wide.

[Boilermech]

On my 2" sch 80 test the root and hot pass will be tig but the cap will be 7018 stringers. The pipe is 1/4" thick wall. I was just practicing walking the cup on that picture of 6" pipe.
So if I do a root pass and one hot pass on the 2" with tig then cap with 3/32 7018 it shouldn't fill the bevel all the way out?
Sorry if I am asking dumb questions I am just trying to learn as much as I can from as many welders as I can. Because I've only been shown by one guy and I know everyone welds different.

[zoama]

Here are some videos on the subject from a man who I consider to be an expert welder and teacher...
http://www.youtube.com/watch?v=bBXjRS4e6PA
http://www.youtube.com/watch?v=H9X30P6rrLQ
http://www.youtube.com/watch?v=RPlMCAibE8c
There are lots of pipe welding videos on youtube from others.

[performance]

I'd rather put in an extra pass, rather than worry about having something trapped under the metal.

Feel free to give me a call...Just call in at ext 204 later this evening when you are working on it at home, and maybe I can help.

[Boilermech]

How about this one? I used 3/32 gap but one side opened up to almost a 1/8th and the other side closed up on me to a tight 3/32 gap. I used 3/32 ER70S-6 with 3/32 tungsten. Amp settings was 85 on the right side then turned it down to 80 when using my left hand. Because I figured the pipe was already pretty hot. Argon set at 10 L/min whatever that is equal to in cfh (my welder came with this funky gauge for the gas). Anyway I will try another later and get a better fitup. Let me know what you all think. The last pic is how they were looking before now so you can see my excitement.
I am just excited to see the root all the way in finally :-)

[zoama]

LPM is about half of CFH

[DVA]

How about this one? I used 3/32 gap but one side opened up to almost a 1/8th and the other side closed up on me to a tight 3/32 gap. I used 3/32 ER70S-6 with 3/32 tungsten. Amp settings was 85 on the right side then turned it down to 80 when using my left hand. Because I figured the pipe was already pretty hot. Argon set at 10 L/min whatever that is equal to in cfh (my welder came with this funky gauge for the gas). Anyway I will try another later and get a better fitup. Let me know what you all think. The last pic is how they were looking before now so you can see my excitement.
I am just excited to see the root all the way in finally :-)

You are lucky to be working for a utility that will train you to weld. Every outage at my plant we send a lot of welders packing and too many times before the welds are even radiographed.

Do you need to pass a radiograph? If not, what type of inspection is performed on the weld?

As for the weld, you still have IF (incomplete fusion). This will be rejected by an inspector if they are required to inspect the weld prior to using the 7018 for the rest of the weld. From what I see in the weld you need to slow down and make sure that you are keeping the puddle completely wetted and melting the puddle into both sides of the pipe. It looks from the freeze lines that you are not moving the puddle from side to side as you move around the pipe. You should be pushing the puddle from side to side as you work around to ensure that the metal is flowing and tying into the pipe. From the look of the IF you have, there is most likely some cold lap also as you are feeding too much filler and not tying in to the pipe well. If you need to pass a radiograph this will all show up. If ultra sound or phased array ultra sound are used this will show up.
Looks like the root is getting better from the first post of the thread. The large buggers would be rejected from your first post on this thread. As for the fourth photo this is incomplete penetration and looks like you lost shielding gas here as it looks like some porosity exists.

[Boilermech]

LPM is about half of CFH

Ok thanks. At welding school they only show cfh. So i could probably turn that down a little since i only use 15 cfh at school. Thanks

[DVA]

Attached is a picture of a 2" Heavy Walled pipe I was practicing on a few months ago. Have not had that much time to practice pipe welding. On the bottom you can see that I was fighting gravity and not evenly depositing the material from side to side. But look at the top how the metal is wetted into both sides of the pipe.

[performance]

It looks to me as if the metal is cooking...Try welding at a lower amp like we talked about 65-70...what could it hurt? Move the torch from side to side, washing in the metal on the sides. Don't pause in the center, but on the sides. The reason it ended up loose on one side and tight on on the other is that you didn't use enough tacks or spacing rods and welded up on one side and it pulled the other apart.

What I see is that it is still too hot, and you are pushing too much filler in trying to close up the key hole. The key hole should be barely visible, and not really a keyhole when you add the filler.

[Boilermech]

You are lucky to be working for a utility that will train you to weld. Every outage at my plant we send a lot of welders packing and too many times before the welds are even radiographed.

Do you need to pass a radiograph? If not, what type of inspection is performed on the weld?

As for the weld, you still have IF (incomplete fusion). This will be rejected by an inspector if they are required to inspect the weld prior to using the 7018 for the rest of the weld. From what I see in the weld you need to slow down and make sure that you are keeping the puddle completely wetted and melting the puddle into both sides of the pipe. It looks from the freeze lines that you are not moving the puddle from side to side as you move around the pipe. You should be pushing the puddle from side to side as you work around to ensure that the metal is flowing and tying into the pipe. From the look of the IF you have, there is most likely some cold lap also as you are feeding too much filler and not tying in to the pipe well. If you need to pass a radiograph this will all show up. If ultra sound or phased array ultra sound are used this will show up.
Looks like the root is getting better from the first post of the thread. The large buggers would be rejected from your first post on this thread. As for the fourth photo this is incomplete penetration and looks like you lost shielding gas here as it looks like some porosity exists.

I work for a great power company here in Oklahoma. We are a coal fired power plant producing 960 MW of power. I am a mechanic there. The first test I have to do is steam card bend test. I get to cut the pipe and grind down both sides smooth then they put it on the bend machine. The inspector will visually check each pass. After I pass that test then I have to try to pass 10 company tests that are all different sizes and materials including enconel. Those are plant tests that are x-ray. The only one I am working on right now is the state test (bend test). We have a contracting company that works for us and they let go welders all the time during outages.

[Boilermech]

Here is my last try on the root pass for tonight. Please criticize, thanks.




Thanks again everyone for any and all help.
Forgot to mention this is a tight 3/32 gap, 3/32 70S6, 3/32 tungsten, lay wire technique, 90 amps and 8 lpm gas.