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Up Topic Welding Industry / Technical Discussions / pipe weld on SS321
- - By zambrota (**) Date 11-10-2010 22:21
Does anybody have experience welding 321 stainless steel butt weld on Ø800mm pipe 24mm wall thickness. It's single V prep 70° included angle, 1.6mm root face, no root gap, welding process is FCAW and 1.2mm flux core wire E347. Is full penetration achievable? Welding is possible only from one side. Do I still need Argon back purge or not? Your input would be much appreciated.

Thanks
Parent - - By GIOVANILOPES (*) Date 11-11-2010 23:27
Use ceramic baking...
Parent - - By zambrota (**) Date 11-12-2010 08:52
What do you mean by that? Access is only from one side and full penetration is required.
Parent - - By Shane Feder (****) Date 11-12-2010 14:54
zambrota,
I strongly suggest you re-evaluate the process you are intending to use.
You will not - and i repeat WILL NOT get a code compliant weld using FCAW for an open root weld (no matter how good your welders are).
I have no experiece with ceramic backing on s/s so cannot comment.
Regards,
Shane
Parent - - By Shane Feder (****) Date 11-12-2010 15:04
zambrota,
Just re-read your post and the alarm bells went off in my head.
Whether or not you need purge is the least of your problems.
24 mm thick (nearly 1") 321 s/s is a serious weld and you do not have a WPS ?.
Or, are you asking advice on the forum as per recommendations to qualify a WPS ?
GTAW is the only way to put a code compliant root run in a s/s pipe - regardless of diameter.
Regards,
Shane
Parent - By ssbn727 (*****) Date 11-12-2010 16:16
FWIW, I agree Shane. ;)

Respectfully,
Henry
Parent - - By Lawrence (*****) Date 11-12-2010 17:20
Code compliant open root first pass welds are put into stainless steels every day with

Lincoln STT  (surface tension transfer)

Miller  RMD  (regulated metal deposition)

Fronius CMT (Cold Metal Transfer)

However those processes are not very adaptable to field work.

Zambrotal;

I agree with Shane that FCAW is a process choice that is not likely to work out for you on open root butt joints on pipe of any diameter or thickness.

To what standard are you complying with these pipe welds.???
Parent - - By zambrota (**) Date 11-14-2010 22:08
Thanks Lawrence & Shane,

Just to clarify: I need to qualify welding procedure as per API Spec 6A standard. Please note that root gap = 0. What would you recommend?

Thanks
Parent - - By MBSims (****) Date 11-15-2010 01:22
I would recommend proposing a GTAW root with 1.5-2.4 mm root opening with argon purge, GTAW hot pass, then switch to FCAW.
Parent - By Daon (*) Date 11-15-2010 06:59
I agree however we are also keeping the purge for at least 10 mm of fill.
- - By zambrota (**) Date 11-15-2010 07:51
Is possible to make full penetration weld without root opening using feather joint?

Thanks
Parent - By js55 (*****) Date 11-15-2010 15:17
Its possible but not easy. We did it all the time with GTAW in roll outs. In position, lots of luck. You will most likely have concavity on the bottom. You're timing on travel speed will have to be perfect or gravity will not be your friend.
I would NOT recommend it.
- - By zambrota (**) Date 11-16-2010 08:55
Would GMAW be an acceptable alternative or not?
Parent - By fschweighardt (***) Date 11-16-2010 13:03
That zero root opening is going to kill you, If you open it up, it becomes a fairly easy GTAW root pass.
Parent - By js55 (*****) Date 11-16-2010 13:26
Of course its acceptable.
Parent - By fschweighardt (***) Date 11-17-2010 03:26
define acceptable
- - By zambrota (**) Date 11-17-2010 21:35
Doest it mean, that GTAW is the only welding process you propose for root run on pipe welds? What about site work? Is it economical solution on big size jobs?
Parent - - By js55 (*****) Date 11-18-2010 14:35
The non acceptability of GMAW for 321 cannot be argued from a mechanical, chemical, or metallurgical standpoint. Once the wire is melted it does not remember if it was on a spool or a stick. If you semi auto GTAW you will be using the same wire as GMAW. But the concern here may be the existence of drawing compound for the wire which would need to be cleansed for semi auto GTAW. However, it may be unnacceptable based upon customer specification, or if you insist on using 321 filler you will lose Ti across the arc, and therefore stabilization, in which case GTAW would be your only choice. This is why 347 has become the filler of choice.
Parent - - By Lawrence (*****) Date 11-18-2010 15:38
MC grade wire (certified clean) can be purchased in rolls or straight lenghts, so no problem there.

What is the original posters reasoning to use 321 filler rather than the traditionally accepted 347 ??  I would like to know.

But the notion of running wire fed semi-auto GTAW for "on site" operations could be a problem unless you are willing to invest in some very high level equipment and are prepared to make your on site conditons ammenable to that kind of GTAW.

but if the original poster is talking about manual GTAW or Semi-auto GMAWP (operator hand held operations) I think you are going to have real problems getting consistancy with a zero gap butt joint configuration.  I think it could be done with some consistancy by utilizing more automated processes, which by their nature are going to be problematic in the field (but maybe not impossible)
Parent - By js55 (*****) Date 11-18-2010 16:51
I agree Lawrence. I would not do zero gap in the field.  I would not do semi auto GTAW in the field.
I suspect 321 as base metal is cheaper here in the states. The US tends to use 321 the europeans tend not to. Everyones tends to use 347 filler. In some instances 321 filler isn't even available.
Up Topic Welding Industry / Technical Discussions / pipe weld on SS321

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