MIG welding pipe

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I'm a pipe welder with 23 yrs experience with TIG and Stick. My boss has a job coming up which involves welding 26" heavy wall pipe. We're talking something like 2" wall thickness. And has to be 100% x-ray. Normally we would TIG the root pass and then Stick weld the rest. A lot of welding! We are considering using the Pipe Worx 400 machine on this project to speed things up. I have run MIG quite a bit but never on pipe. Any suggestions on using this machine for that type of job. Should we use pure CO2 for gas or a mix? We can't have any lack of fusion anywhere in the joint. Thanks.
Reply:Originally Posted by Welder DeanI'm a pipe welder with 23 yrs experience with TIG and Stick. My boss has a job coming up which involves welding 26" heavy wall pipe. We're talking something like 2" wall thickness. And has to be 100% x-ray. Normally we would TIG the root pass and then Stick weld the rest. A lot of welding! We are considering using the Pipe Worx 400 machine on this project to speed things up. I have run MIG quite a bit but never on pipe. Any suggestions on using this machine for that type of job. Should we use pure CO2 for gas or a mix? We can't have any lack of fusion anywhere in the joint. Thanks.
Reply:Here is how I would accomplish that job.  Please adjust to your equipment and shop practices.  These assume SA-53B or SA-106B pipe.Option 1:TIG root ER70S-6Flux Core E71T-1 with 100% CO2 all the way out.  0.052 wire or thicker would make short work of the bevel.Option 2 (if you can roll the pipe):TIG root ER70S-6Sub Arc ER70S-6 with an active flux (Lincolnweld 760 or better) all the way out.  3/32" wire for first pass and up to 1/8" if it's not too much of a pain.  Alternatively, weld one hot pass on top of the TIG root then go with 1/8" all the way out.
Reply:We run our roots in with that same exact machine then we fill and cap with flux core.. we use a 75/25 mix. Are you going to be doing the whole pipe Mig?Last edited by justinT; 01-01-2012 at 01:38 PM.
Reply:Since this is xray are you certified to weld using the possible new process? Is it needed?
Reply:I've run thousands of 100% xray round seams on pipe with mig and fluxcore. First thing: yes, make sure that you are certified and have a weld procedure that you can follow. IF not, that may  bite you in the butt soon enough.  Second, I would do what you're most comfortable with. I would mig the root and flux the rest. IF you're a little hesitant with the mig run tig. Mig root beads on carbon pipe burn in wonderfully and leave a perfect root with little practice. For the rest of the passes, I run a short maybe six inch weld and stop. Grind my starts and stops and feather it back to make sure there is no porosity or bad spots. Flux sometimes traps spots on your stop if you're not careful. I NEVER burn over slag and obviously stagger your stops and starts. Now, this is all assumming that you have a positioner to roll your pipe around. If not, just use an all position flux to your liking and go to town. If you guys do pipe often, you really need a positioner. GAS: i always use good old 75/25 and never have a problem. Low splatter and smooth welds. THats some pretty thick walled pipe. Have fun!!
Reply:Originally Posted by freshintulsaMig root beads on carbon pipe burn in wonderfully and leave a perfect root with little practice.
Reply:Downhill root beads always. IF i can roll the pipe in a positioner, I will run the fill/cap with flux "downhill". Its not really downhill, but when you roll the pipe, roll it away from you while you are on top of the pipe. It lets the weld lay flatter and looks very slick. When going uphill you tend to either run smaller stringer beads or weaves, which still look good when done right, but aren't as appealing visually to me. HOpe that helps, Doug.
Reply:Originally Posted by freshintulsaDownhill root beads always.
Reply:Tig root with 0.45 GMAW-P (pulse) is also and option. I do crap loads of x-ray welds with pulse. Just one of a bunch of options available.CERTIFICATIONS:7018M- H.V.O10718M- H.V.O11018M- H.V.O9N10- H.V.O71T-1-HYM- H.O.V100S1 PULSE ARC 0,035- H.O.V100S1 PULSE ARC 0.045- H.O.VER70S-3 PULSE ARC 0.035 H.O.VER70S-3 PULSE ARC 0.045 H.O.VER5554- H.O.V
Reply:Fergenbush, assuming you can make all of the welds in 1G wouldn't it be more beneficial to run it with MIG instead of fluxcore?  Saves on cleanup time, higher deposition rates and no risk of slag inclusions.David, unless someone else can correct me I believe metalcore can only be run in the flat position.  I'm not sure if you were suggesting that it can be ran in all positions, but to the best of my knowledge it can't.  Just too much metal flowing around there.Have we all gone mad?
Reply:Originally Posted by sn0border88Fergenbush, assuming you can make all of the welds in 1G wouldn't it be more beneficial to run it with MIG instead of fluxcore?  Saves on cleanup time, higher deposition rates and no risk of slag inclusions.David, unless someone else can correct me I believe metalcore can only be run in the flat position.  I'm not sure if you were suggesting that it can be ran in all positions, but to the best of my knowledge it can't.  Just too much metal flowing around there.
Reply:There are some metal cored wires that can be run out of position with pulsed MIG spray arc or short circuit transfer.Welder Dean,Your pipeworx machine has Miller's RMD process built in.  You can use this with solid wire or metal cored wire to put in the bead on your 26" heavy wall pipe. .035" SW is really easy to run with 75/25 and the RMD process.  If you have a lot of these joints to make, then an 0.045" wire might be faster, but will need just a little more practice.  Then I'd suggest switching to 0.045" fluxcore that runs with 75/25 gas.  You can run an 0.052" wire also, but this will take a little more skill.  In my experience the mixed gas wire s are better for pipewelding for 2 reasons; less spatter, and the 100% CO2 wires tend to dig in more than I like.There are a few folks who've suggested solid wire is faster than fluxcored wires.  If you can roll the joint and use spray arc, this is probably true.  But if you have to weld this in position, then deposition rates should be better with fluxcore.  Fluxcore typically doesn't suffer from cold lap, which can happen with solid wire if the welder isn't careful.  The time spent on cleanup should be minimal with a skilled welder and a good procedure.  Good fluxcored wire is virtually self peeling when used correctly.  At worst, drag a chipping hammer over the bead to release the slag. Originally Posted by sn0border88Fergenbush, assuming you can make all of the welds in 1G wouldn't it be more beneficial to run it with MIG instead of fluxcore?  Saves on cleanup time, higher deposition rates and no risk of slag inclusions.David, unless someone else can correct me I believe metalcore can only be run in the flat position.  I'm not sure if you were suggesting that it can be ran in all positions, but to the best of my knowledge it can't.  Just too much metal flowing around there.
Reply:Originally Posted by A_DAB_will_doThere are a few folks who've suggested solid wire is faster than fluxcored wires.  If you can roll the joint and use spray arc, this is probably true.  But if you have to weld this in position, then deposition rates should be better with fluxcore.  Fluxcore typically doesn't suffer from cold lap, which can happen with solid wire if the welder isn't careful.  The time spent on cleanup should be minimal with a skilled welder and a good procedure.  Good fluxcored wire is virtually self peeling when used correctly.  At worst, drag a chipping hammer over the bead to release the slag.
Reply:I work in a refinery and we MIG weld carbon steel pipe and some chrome alloys. I don't have the skill, but I have been around it some. I general we don't MIG outdoors. It's done indoors in the shop mainly, but we do do it outdoors in an enclosure. The roots go in downhill. Cold lap can be an issue and it won't typically show up in an x-ray, so use a bend test to qualify your procedure. Typically failures occur on the transition from vertical to horizontal, so the coupons are cut out at 1:30, 4:30, 7:30, and 10:30. I assume they are prepared to some ASTM standard. I believe we use .045" ER70S-6 and 75/25. Most of the time we only do the root and the hot pass with MIG. It's filled and capped with SMAW 7018 or sub arc in the shop if it's in a positioner. All our work is short circuit. We don't have a qualified spray or pulse procedure. Hope this helps,Gus
Reply:we used to do x ray heavy pipe with flux core. root fill and cap.was pretty fast compared to stick.all done out of position.you can get some thick flux core wires if you have the volts to melt it!get the heat right and it peals it's self.If your going to tig the root then you might have to tig the hot pass before you will be able to run flux core. tig root alone will probably be to thin to take a FC hot pass.let us know how it works out for youG
Reply:I definitely came to the right place. Thanks for all the replies. Will print out and let the boss read. We have until May to come up with a procedure for this and get a few welders certified for it. From what I am reading, it sounds like flux core is the way to go. Also, something I did not mention in my original post, I believe this pipe has some chrome in it and will have to be pre-heated to 400 or 500 F. I'm not sure how much chrome. This is high pressure steam line at a power house. Most of the time we run either ER 80 or ER 90 TIG rod and then 8018 or 9018 stick. Depending on the pipe specs. Also, this pipe will have to be welded in position, no rolling of pipe.
Reply:For the gmaw pipe guys, what's the joint prep like? Knife edged like TIG or do you use a land? Gap? I've never seen gmaw being used for pipe yet, but that's just because we don't have weld procedure for the process. I work with some guys who have used it at other sites.
Reply:Originally Posted by SR20steveFor the gmaw pipe guys, what's the joint prep like? Knife edged like TIG or do you use a land? Gap? I've never seen gmaw being used for pipe yet, but that's just because we don't have weld procedure for the process. I work with some guys who have used it at other sites.
Reply:Originally Posted by A_DAB_will_doThen I'd suggest switching to 0.045" fluxcore that runs with 75/25 gas.
Reply:Best check with your Owner (end user) and make sure GMAW is allowed per the Contract.  Sounds like fairly high pressure and high temp, and it sounds like you may be into the P-91/92 materials.  Not everybody is excited about using GMAW roots on this service.  You will almost certainly be in for pretty involved pre-and post weld HT.
Reply:last shop I worked at migged the root ran dual sheild for hot/cap big 052 wire. All on a positioner