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Up Topic Welding Industry / Technical Discussions / 316 SS vs 347 SS tig wire
- - By Pipeslayer (**) Date 06-30-2008 15:50
I've not had alot of experience with 347 tig wire, is 316 a suitable subistute? What are the pro's and con's?
Parent - - By jon20013 (*****) Date 06-30-2008 15:55
One of my hero's, the late Chuck Meadows explained it to me in very simple terms; 347 is really just a stabilized 308... so, based on that simple analogy, you could compare 347 to 308 very nicely.  347 withstands higher temperatures better than 308 but for welding purposes, you wouldn't know the difference.  316 is a higher alloy and has it's place.  What's the application?  I believe generally speaking, you'll probably pay more for the 316 and if it's required, by all means use it, if not, don't worry about the 347, you'll like it.

I'm sure js55 could and maybe will provide a more in-depth discussion on the technical aspects but above is somewhat of a "users" recommendation.
Parent - - By Pipeslayer (**) Date 06-30-2008 16:19
So I really should'nt worry about the 347. This is in a customer spec. We have a procedure for 316 and we would like to use that in lieu of 347.
Parent - - By jon20013 (*****) Date 06-30-2008 16:38
If it's a requirement of your customer's spec., I would most definately recommend using the 347.  Since 347 and 316 are the same F. No. and A. No. under ASME Rules, I'd just ask your customer if it would be acceptable to use 347 rod with your 316 welding procedure to keep from having to qualify a new one.  If I were your customer and you asked me the answer would most definately be "yes" you may.

Don't muck around asking to change the rod, the have 347 specified for some reason.
Parent - - By js55 (*****) Date 06-30-2008 17:00
If I may add my two cents worth. 347 is stabilized with Cb which makes it is much more crack sensitive than 316. For the same reason that Alloy 20Cb, Alloy 625, and 15-5 PH can be crack sensitive. Cb/Nb is pushed along the solidification front and finally settles towards the terminal stages of solidification, which means that it has a tendency to be depleted within the grains and of high concentration at the grain boundaries which are then crack sensitive.
Parent - - By Pipeslayer (**) Date 06-30-2008 17:08
some powers that be want to solar flux but this sounds like a purge setup.
Parent - - By jon20013 (*****) Date 06-30-2008 17:11
It is.

EDIT: Flux used in lieu of purge.  Can't speak whether its good or not, I always purge.
Parent - - By Pipeslayer (**) Date 06-30-2008 17:37 Edited 06-30-2008 17:40
The application is 2"-36" Sch 10 SS 312 material. These wleds are on chemical and product line in a fiber plant. Most of the material is imported SS from germany. My inspection of the pipe revealed some of the most truely round SS pipe I ever seen.
Parent - By 803056 (*****) Date 06-30-2008 18:35
It isn't often that I've experienced problems with materials supplied from Germany.

The one time I did, it was because the equipment specification was so poorly written it was a wonder the client got a functional piece of equipment at all. After delivery, the client wanted to add all sorts of additional requirements that were not part of the original purchase requirements.

Best regards - Al
Parent - - By js55 (*****) Date 06-30-2008 19:24
Well, that actually changes everything. 312 has a nominal tensile strength of 100ksi, whereas 316 and 347 come in around 75ksi. And is this high temp (you mention 347), since 312 is loaded with ferrite (it is actually a duplex alloy) and will form sigma rather readily depending upon how high temp. If your base metal is 312 I'd recommend 312 filler.
Parent - - By Pipeslayer (**) Date 06-30-2008 19:40
I'm not sure how much lead way we can get with the engineer on a deviation. My concern is quality, weldabilty and profitabilty. I don't want  what looks to be a great job to turn into a inspection nightmare. I really just want whats right and best for all. I have to look out for my company and our welders.I've just begun my research for this project. Is there a down side to using 316 or 347 in this particular application???
Parent - - By js55 (*****) Date 06-30-2008 20:03
If the engineer says 316 or 347, you use 316 or 347. But a 25ksi RT TS min spec difference is significant.  I'd at least bring the subject up. If anything he'll tell you his rationale.
Current costs would have to be researched. The down side to 347 is cracks. As far as quality is concerned you can achieve excellent quality with either of the two. 316 and 347 both have a long history in nukies. 312 will have the lowest crack tendency and the highest strength.
Parent - - By jon20013 (*****) Date 07-01-2008 01:01
Pipeslayer, are you sure it's TYPE 312, or is it Specification, like A312 or SA312?  If it's an A or SA312 it would be an austenitic, isn't that correct js55?
Parent - - By Pipeslayer (**) Date 07-01-2008 11:17
I've to visit the job site today and recheck our material and fab area. I do think that you are correct and SA312 was what it was it was ashrink wrapped. I should have a BOM and shipping list when I return. I hope to resolve everything today as I've only had 2 brief trips to the site. We've got X-ray issues on another site but thats a whole other story.
Parent - - By jon20013 (*****) Date 07-01-2008 11:55
My hunch is you'll find it marked SA-312, Type 304... just a guess, lol
Parent - - By js55 (*****) Date 07-01-2008 13:13
jon,
I think you're right on this one. That would make much more sense wouldn't it?
Wish I'd thought of that. :)
312 is unusual enough and to weld it with 316 or 347 doesn't make sense for most services it would be intended for(requiring a little higher strength). I would think.
Parent - By ssbn727 (*****) Date 07-04-2008 12:16
If it's from Germany, do not assume that it's a 304 SS just because it's stamped SA312 or A312 either because, they do use alot of 316Ti over there especially with the pipe dimensions given... Especially schedule 10!!! I welded a whole bunch of the 316Ti schedule 10 from Germany, and it too had some of the most consistent rounded circumferences I've ever encountered with that schedule SS pipe... 316lSi is a good choice for filler instead of 347 for reasons that Jeff stated... For higher service temps, it's better to use a 318 filler(low carbon version is even better!!!) provided that it is indeed a 316Ti pipe you're using as opposed to a 304.

Respectfully,
Henry 
Up Topic Welding Industry / Technical Discussions / 316 SS vs 347 SS tig wire

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