any pipe fitter/welders

[Jorville]

I want to Tig weld the open root on cast steel caps on a schedule 40 pipe. The second weld I am wondering if it should be a 7018, or would another Tig weld be OK. The pipe is schedule 40 black steel, 2 and a 1/2 inch, a couple on two inch pipe and four on inch and a half pipe.

Another welder said to Tig it all, I am thinking the cover passes should be 7018. I think this weld can be done in two passes. What are you guys thoughts on this?

 

[Shield Arc]

I don't see any reason not to Tig weld all the way.

 

[Arc weld]

What are you using them for? 7018 would be faster if you can roll them but I'm not sure if you could do TIG in 2 passes.

 

[Tractor Seabee]

Arc Weld is right. I fitted for a lot of SS process pipe welding. Tigged, always three passes on pipe above 2". What is the end use? Pressure, structural, appearance? Two passes of Tig for appearance you can fill flush (no bead). SMAW is a lot faster from the bottom up on mild steel. We could blow and go SMAW welding with 6010 root and 2 passes 7014. We did OA welding on up to 3" in one pass; hot work but 2-3 times as many welds as SMAW per hour.

Been away from the trade 20 years now so maybe things have changed. Back then Tig on mild steel was unheard of. Left the trade as automatic Tig pipe pipe welding was on the upswing. That was a slow process with keeping track of the settings and doing a lot of coupons for certified work. Tig pipe welders on process work and high tech clean room work were real primadonnas.

Ron

 

[Jorville]

I don't see any reason not to Tig weld all the way.

I was thinking because the butt weld fittings are cast steel it might be better to use 7018, than to use mild steel filler all the way.

 

[Jorville]

This piping is on a hot water heating manifold. It will all be welded on the bench, so I could lay two pieces of angle down and roll the pipe and weld. I am not sure on two passes either, that pipe is not very thick. Two passes with tig most likely would not fill with a cover, but I thought a 7018 might fill it with a slight cover.???????

 

[Jorville]

Arc Weld is right. I fitted for a lot of SS process pipe welding. Tigged, always three passes on pipe above 2". What is the end use? Pressure, structural, appearance? Two passes of Tig for appearance you can fill flush (no bead). SMAW is a lot faster from the bottom up on mild steel. We could blow and go SMAW welding with 6010 root and 2 passes 7014. We did OA welding on up to 3" in one pass; hot work but 2-3 times as many welds as SMAW per hour.

Been away from the trade 20 years now so maybe things have changed. Back then Tig on mild steel was unheard of. Left the trade as automatic Tig pipe pipe welding was on the upswing. That was a slow process with keeping track of the settings and doing a lot of coupons for certified work. Tig pipe welders on process work and high tech clean room work were real primadonnas.

Ron

The end use of this job is a new hot water heating system in my boiler room. What is there now is a 1970's design that I put in, in 1983. I since added two rooms and want to heat them so I need to re-plumb my boiler room. I am using 2016 design and ideas. So there will be a little pressure 12 psi cold and a few more pounds when the water is hot. I would like it to look nice, even though I will probably insulate the piping. All the piping will be welded on the bench so it can be rolled.

I have not done pipe in 30 or more years, did O/A on small pipe and arc on the larger stuff. I did not do a lot of it. I know on SS there need to be an argon purge. Do you think a purge needs to be done on mild steel?

 

[Shield Arc]

Back then Tig on mild steel was unheard of.

Ron talking to different welders who work in the local Navy ship yards. All pipe welding is done with Tig. The welders who work on the submarines amaze me when they have to stick the filler rod through the pipe to weld on the opposite side of the pipe.

 

[chuck172]

I want to Tig weld the open root on cast steel caps on a schedule 40 pipe. The second weld I am wondering if it should be a 7018, or would another Tig weld be OK. The pipe is schedule 40 black steel, 2 and a 1/2 inch, a couple on two inch pipe and four on inch and a half pipe.

Another welder said to Tig it all, I am thinking the cover passes should be 7018. I think this weld can be done in two passes. What are you guys thoughts on this?

What's with the cast steel caps? Must it be cast? Why not reg. mild steel caps. That's your problem, the cast steel.

 

[Jorville]

Shield Arc, There is a u-Tube video on that, and you are right, it takes skill. I personally don't do enough welding now to be at my best.

It had to be a little past three AM on the west coast when you posted this, don't you sleep? Or do you have the same problem that I do.
Have a great day, always enjoy your posts.

 

[Shield Arc]

I guess it comes from having to be in Seattle by 6:00 AM every day. I've always got up early!:thumbdown::thumbdown:

 

[Jorville]

What's with the cast steel caps? Must it be cast? Why not reg. mild steel caps. That's your problem, the cast steel.

The caps look to be cast steel, there are also reducing couplings, they look to be cast steel, maybe they are not. Is there a way to tell what they are without doing a grind test on them? Maybe I can ask the company that I bought them from what they are made of. Maybe they are mild steel, hope so.

 

[Mysfyt]

The end use of this job is a new hot water heating system in my boiler room. What is there now is a 1970's design that I put in, in 1983. I since added two rooms and want to heat them so I need to re-plumb my boiler room. I am using 2016 design and ideas. So there will be a little pressure 12 psi cold and a few more pounds when the water is hot. I would like it to look nice, even though I will probably insulate the piping. All the piping will be welded on the bench so it can be rolled.



I have not done pipe in 30 or more years, did O/A on small pipe and arc on the larger stuff. I did not do a lot of it. I know on SS there need to be an argon purge. Do you think a purge needs to be done on mild steel?

I purge everything when practical. Especially where pressure and leakage is a concern.

 

[chuck172]

I doubt they are cast. All you need to do is 6010 root, hot pass, fill it out with 7018. Really, I'd just use 6010. That's all you need.

 

[Tractor Seabee]

Steel butt weld fittings fittings are forged steel not cast. I assumed the OP was really using those type. Shield Arc; there is a big difference in the various venues for pipe welding. Navy marine work is even more technical than commercial ship work. Navy, nuclear, high tech process piping, power piping, are all 100% tested and cost is not a big factor. Highly competitive commercial/industrial work which the OPs project is based on price hence labor cost is precious.

Ron

 

[nybirdman]

40+years as a union pipefitter/certified nuclear welder.I would Tig the first pass and hot pass with Tig and 7018 out.You could Tig all the way if you chose.Maybe four or five passes.No need to purge on carbon steel.

 

[Arc weld]

I realize this is for your own system but I see a potential problem. You're asking questions about purging mild steel and thinking the caps are cast steel. Are you using seamless pipe suitable for welding a pressure sytem? This is a pressurized boiler system so I have to ask, are you a certified pressure welder? I believe anything over 7 psi requires a pressure ticket(s). 12 psi cold is certainly going to be higher when heated. If something went wrong you could be in a lot of trouble. Not trying to discourage you, just asking. If you roll the welds, get some wheels to roll the pipe. Trying to roll it on a piece of angle iron isn't going to roll smooth enough.

 

[Shield Arc]

If you roll the welds, get some wheels to roll the pipe. Trying to roll it on a piece of angle iron isn't going to roll smooth enough.

Or get one of these. This thing makes my welds look good! :cool2:

 

[Arc weld]

Or get one of these. This thing makes my welds look good! :cool2:

Yes, especially for TIG.

 

[Shield Arc]

Yes, especially for TIG.

Oh yeah!