fcaw for open root pipe

By - Date 03-26-2006 02:40

George,
FCAW isn't really designed for open butt root welds, but it is quite possible to achieve such if certain precautions are adhered to. Striclty form my personal recommendations, I will give my suggestions.

First of all, the joint configuration is the most important factor to be considered. If you are using an 0.045" diameter electrode, I would recommend a feather edged land while using a 37.5 degree bevel on each side of the joint. I would recommend a 1/16" root opening. If you are using a 316L FCAW wire, the parameters should be around 24-26 volts and around 160-180 amps if you are welding in the flat position. A good shielding gas would be a 75%Ar/25%O2 mixture. A bead technique, not a weave technique, would be advisable for best penetration. Gringing to a smooth metal surface would be a good idea to eliminate any possible flux contamination and is advisable before starting any subsiquent pass.

By georgechian Date 03-26-2006 05:04

Thanks a lot, Chuck
Is there a special fcaw wire for 5G or 6G downhand? which company makes it? does it work well like solid wire on 5G which has enough inside reinforcement?

By aevald

Date 03-26-2006 14:06

Hello George, you,ve sparked my curiousity here a bit. A couple of questions as to the application of the stainless FCAW here. As Chuck stated, typically SS FCAW would not be used for any type of full pen application, x-ray or not. I could see possibly using a tig or GMAW root and a hot pass in conjunction with an Argon purge and then switching to the FCAW for the fill and cap, yet the multiple process scenario would present some complicating time issues, etc. Since the FCAW will generate slag, the open root scenario would present some sort of slag cleanup issues on the internal bore of the pipe unless it were large enough to allow internal access to the root area for cleanup, I'm not quite sure that it would work without contamination issues as well and if you tried to use a purge would it need to be of the same gas makeup as the shielding gas? As I said you've sparked my curiousity. Additional information would be appreciated. Regards, aevald

By georgechian Date 03-26-2006 16:46

Thanks for your info. Nothing special. I just think that the welding tech itself still need to get devolping and progressing. If FCAW could do everything from root to cap just changing wire and machine setting, that would be great! Regards, george

By - Date 03-26-2006 14:47

Without trying to offend some people and make this a "sales forum", I will try to answer your concerns. Usually the flux from a FCAW will rise to the face (top) of a weld, including a root pass. Like has been said by all of us, FCAW is usually not used on a root pass if x-ray quality welds are required, but it certainly has been done. The smaller the root opening, the greater chance of the flux rising to the surface. Too wide of a root opening and the greater chance of burn-through, and flux contamination. Both Avesta and Kobe produce wires that can be used in out-of-position welding. I'm not going to say which wire I prefer because I've been criticized by some for trying to make this forum into a sales forum (whatever that meant). Let me say that I work for Avesta Welding and have seen fabricators use the Avesta wire on open butt welds successfully. The things that made is successful was to use the smaller root opening and rapid travel speed. You will not be depositing lot of metal, but FCAW isn't the 1st choice for open butt welding. Again, this is strictly my opinion and experience. It may not work for everyone.

Chuck

By georgechian Date 03-26-2006 17:04

Thanks again, Chuck, I will try it.

By pipehead (***)

Date 03-28-2006 03:10

As Chuck said FCAW is not highly recommended on open root applications But it can be done. Altough I have not run it on stainless we did a job on a power house running E71-T1 esab open root on six inch pipe it just required alot of purging and alot higher flow through the gun we ran about 45CFH. it was all full x-ray but out of the first 26 welds we had 5 rejects and after the 40th weld the engineers changed to SMAW root&hot pass and FCAW fill and cap.

Well good luck let us know how it goes

By TimGary (****)

Date 03-28-2006 12:37

Hi Chuck,

I love reading your posts as I always learn something...
I'm curious about the sheilding gas you specified, 75% Ar / 25% O2.
Was that a typo, or is it correct?

Thanks,
Tim

By Lawrence (*****)

Date 03-28-2006 15:43

Tim

Most of the SS FCAW can now be run on both 75/25 or 100% CO2. The flux apparently takes on some of the shielding duties.

The Mix is advertized to provide less spatter and the CO2 requires a couple more volts...

We have recently been doing some trials with the stuff and I can see very little difference in overall performance between the two gasses as far as finished profiles and spatter if a little attention to parameters is taken.

By jwright650 (*****)

Date 03-28-2006 15:46

Lawrence,
I think the 25%O2 (oxygen) was what Tim was asking about. I'm not familiar enough with all of those gas mixes to comment.
John Wright

By Lawrence (*****)

Date 03-28-2006 17:05

Ooooh

I see now.

I bet a cup of coffee that the 25% O2 is a typo

By automation Date 04-07-2006 14:52

For me It must be a typing mistake. I have never heard such a shielding gas composition for SS.

By - Date 04-07-2006 16:42

Tim,
I'm very sorry...25% CO2, not O2. Big typo mistake..