Not logged inAmerican Welding Society Forum
Forum AWS Website Help Search Login
Up Topic Welding Industry / Technical Discussions / Heat Treating Stainless Steel
- - By Richard V. Roch (**) Date 03-23-2007 12:04
I am in the process of having to qualify a welding procedure to ASME Section IX, using GMAW/FCAW, ER309L and E309LT-1 wire for a carbon to Stainless (304L) joint. I will need to heat treat this joint due to the vessel (carbon steel) requirements. What effect will a 1150 deg. F heat treat have on the 304L material? Any help would be greatly appreciated.
Thanks again
Parent - - By jon20013 (*****) Date 03-23-2007 12:21
Richard, it depends on the amount of time held at that temperature.  In my admitted small knowledge on this subject I wouldn't expect too many problems.  You are somewhat at risk of sensitizing the materials but in my opinion the risk is probably relatively small as you will likely only be holding for an hour?  The temperature of 1100F is far enough below the danger zone (again in my limited knowledge of this topic) to worry about.  Look for responses from Chuck Meadows or js55 for better answers.
Parent - - By Richard V. Roch (**) Date 03-23-2007 12:37
Thank you hope to hear from the other gentlemen as well. Have a great weekend Jon.
Parent - - By js55 (*****) Date 03-23-2007 15:02
You really have two choices. You can take the Sensitization hit and weld it straight up. 309 is a good choice. Sensitization being really the only problem I can foresee. Did tons of these with SS O-lets on carbon headers. Or, you can butter the carbon with nickel, heat treat that, and then 'as weld' your SS.
However, why butter? Quite frankly I have never understood a concern for sensitization of a SS when you are attaching it to carbon. Who cares if the corrosion resistant chrome has now become a carbide. It will still be better than the carbon steel it is attached to.
But, if you are concerned the only other choice is to contact the design engineer and inquire as to his choice of materials. I always found that there was no real metallurgical justification. Usually just habit inherited from prior specifications.

PS: I ain't heard from Chuck in a while. Must be on the road.
Parent - - By chuck meadows (***) Date 03-23-2007 15:21
My Dad was admitted to the hospital down in Galveston and had to spend time down there. Plus, I was on vacation this week and tried to get in a little bass fishing. But, come Monday things will be back to the abnormal normality.
Parent - - By G.S.Crisi (****) Date 03-23-2007 16:10
Chuck,
we, the frequentors of this site, don't know each other personally, but over the years of exchanging ideas and experience in welding, have become friends, havn't we?
I'm very sorry about your father and hope him a prompt recovery. I'll remember him in my prays today. You see, I believe that religion and science are not opposite nor incompatible, as others do, and so I consider myself a religious person.
As for Richard's question, I remember that L type stainless steels, more expensive to produce than plain ones, were developed exactly to solve the problem of welding difficulties due to sensitization. Therefore, in my opinion, Richard can have pleasent dreams.
Giovanni S. Crisi
Sao Paulo - Brazil
Parent - - By chuck meadows (***) Date 03-23-2007 16:19
Giovanni,
  Thank you for remembering my father in your prayers. He was having bleeding in his lungs, he's 86 yr. old, but the Doctors assured us that the bleeding has been taken care of. Medication should help him in his recovery. My father is a very strong Christian, so he is not worried. Again, thank you for your concerns.

Best Regards,
Chuck
Parent - - By jon20013 (*****) Date 03-23-2007 16:47
Chuck, my thoughts are with you and hoping also for a recovery for you father.  You're very lucky to have had him around so many years... mine passed at a rather young 72... which of course I used to think was ancient!!!  In any case, you know you have many people who care for you and we all wish you the best.
Parent - - By chuck meadows (***) Date 03-23-2007 17:16
Thanks, Bro. and to any others that take a moment to remember him in their prayers.
Parent - By billvanderhoof (****) Date 03-24-2007 01:57
Count on me for a prayer for your dad also.
Bill
Parent - By DaveBoyer (*****) Date 03-24-2007 03:32
Chuck, sorry to hear of Your Father's problem, hope He recovers quickly.
Parent - By CWI555 (*****) Date 03-24-2007 01:28
My prayers are with you and family. Everthing else is full stop in light of something like that.
Parent - - By chuck meadows (***) Date 03-23-2007 15:09
Richard,
  As Jon noted, it is all dependent on time at temperature, but I do not anticipate any problems since you are using a low carbon grade of stainless and a low carbon filler. This scenario is done every day without any problems. I would suggest you proceed with confidence. By the way, the low carbon grade delays the onset of sensitization and I cannot imagine you being in a heat treatment process long enough to worry about sigma. So, go for it....
Parent - - By Richard V. Roch (**) Date 03-23-2007 18:15
Thanks all for your comments, and Chuck my prayers for your father and your whole family, a speedy recovery.
Thank you
Parent - - By chuck meadows (***) Date 03-25-2007 00:47
Bill, Jon, Jeff, Giovanni, Dave, Gerald, Richard, and anyone I forgot to mention....Thank you very much, and God bless you, too. It's guys like y'all that make this Forum so special...
Parent - By jon20013 (*****) Date 03-25-2007 10:52
Chuck, without guys like you, this Forum would be left with a gaping hole... I've been through what you're going through, and my thoughts are with ya dude!
Parent - By GRoberts (***) Date 03-25-2007 04:01
Richard,
The problem with using 309L with PWHT, is that since it is designed to weld carbon steel to stainless without cracking (among other things), it normally comes with a fairly high FN.  When doing PWHT, this can turn into sigma.  I've seen bend tests fail for this reason.  If you work with your filler metal manufacturer, they can hold the FN down quite a bit, or Inconel is your other choice and is the more highly recommended chioce for welding with PWHT.
Parent - - By chuck meadows (***) Date 03-25-2007 13:45
Richard,
  Using a 1150F PWHT for an hour or two is unlikely to form sigma. It would take a much higher temperature and longer times at temperature for sigma to form.
Parent - - By js55 (*****) Date 03-26-2007 13:48
This is very interesting. At first blush I would tend to agree with Chuck on the unlikelyhood of Sigma forming in a diluted 309 at a CS PWHT. However, I suppose it is possible, though never experienced it myself.
The other possibility is a very highly diluted 309 (reducing localized alloy content)forming a local martensitic phase that intitiates fracture under fiber elongation.
Greg,
Were you able to perform micros to determine the cause of failure?
Parent - - By chuck meadows (***) Date 03-26-2007 14:50
I guess anything is possible, but this is doubtful. Also, a martensitic structure is also unlikely due to the reduced carbon content of the diluted metals.
Parent - - By js55 (*****) Date 03-26-2007 15:16
Morninin Chuck,
I really have no disagreement with you. I am curious however as to whether or not Greg was able to perform any micro's to determine cause of failure.
Sometimes new revelations come out of phenomena that ain't supposed to happen.
And even if Sigma is formed, how much would it take to cause fracture. Even though ferrite may be high for 309 it is still much lower than it is in Duplex, for example, of which some Sigma is tolerated, if you take the time to look for the stuff, and threshold specifications have been developed for volume fraction. Though impacts are a more common evaluation.
I don't know that .5 volume % Sigma in 309 is possible given those parameters, and I don't know that .5 volume % Sigma would lead to fiber elongation failure in a predominantly austenitic microstructure.
Very interesting.
Parent - By chuck meadows (***) Date 03-26-2007 16:00
As we know, small amounts of sigma, usually less than 5% volume, is relatively innocuous because the phase tends to be rather discontinuous in the microstructure. In this case, the amount of sigma that can form is always less than the ferrite content because the sigma phase has a higher chromium content than the ferrite it grows in. In the austenitic grades, a relatively high ferrite content is required to promote sigma phase embrittlement. Naturally, the actual level is a function of the weld metal composition, but it usually must exceed 15FN. It is unusual for a 309L, with a ferrite content of approximately 12FN, to encounter sigma embrittlement when PWHT'ed at 1150F in 2 hours or less. Very unusual.. 
Parent - - By GRoberts (***) Date 03-29-2007 01:00
I guess I wasn't specifically thinking about the time since it wasn't mentioned in original question.  The PWHT on the test in question was 1250 for 6 hours.  I didn't have an oppertunity to perform metallography, but do know that the same test was sucessfull with 308 filler metal which had less ferrite.  Whatever the embrittlement mechanism though, the bend tests failed with only 5 degrees of bend in them.  Pretty brittle.  I can say that I have also seen tests pass with 1125F for 4 hours.  Personally, I just don't like to PWHT 309 if I can help it because personally, I don't know where the line is  between 1125F and 1250F &/or 4 vs 6 hours.  So whether or not a specific amount of time at 1150F will produce embrittlement I can't say, but it would be something to be catious about. 
Parent - - By js55 (*****) Date 03-29-2007 13:24
5 deg? WOW!!  You can almost bend glass that much. No doubt something went terribly wrong on that one. But still-and Chuck could certainly shed some light here as far as time temp curves for Sigma of 309-I don't think Sigma even with those parameters could create a condition of embrittlment so extensive that you witness brittle fracture at 5deg. Sigma will favor the ferrite side of the dual phase structure, or the grain boundaries. I'm not sure that Sigma could be extensive enough to create a fracture that soon. Seems to me the network of ductile austenite would take the brunt of the deformation for at least that long.
But I have to admit, without Sigma I am at a loss as to what the mechanism would be. 309 to CS is done by the ton every day with PWHT regimes with no problems. Its even perfomed regularly under Nuke regimes where time at temp requirements are imposed on PWHT for WPS's.
I can certainly understand your assumption.
Parent - - By chuck meadows (***) Date 03-30-2007 13:07
I cannot imagine a 309L welded structure fracturing at only 5 degrees. Even a severely sigmatized weldment, I would think, would go past 5 degrees. The 309L, containing no moly, can still have a somewhat high rate of formation of sigma with the potential of larger volume fractions, but it would have to be a a sigma temperature for quite some time. The most rapid temperature for the "moly-less" austenitics is in the range of 800-900C. I would never dispute what Greg is telling us, but just find it very unusual as to the circumstances. Like you said Jeff, 309L is welded every day, MANY times a day, with no problems from the required PWHT. As was said earlier, relatively high ferrite contents are required to promote sigma (usually more than 15FN), but higher temperatures and holding rates will allow sigma to start forming in less time. A continuous network of sigma will more adversly affect the ductility and impact toughness than a discontinuous network, but to have so much sigma that a fracture at 5 degrees is mystifying to me. Another metallurgical mystery, I guess. 
Parent - By jon20013 (*****) Date 03-30-2007 13:19 Edited 03-30-2007 13:53
Chuck, js55, I fully agree.  I've a great respect for Greg so I can't quite come to questioning his statements in my mind... still, this seems absolutely unusual to say the least.  I am preparing to enter a major job in which we'll deposit 309L / 308L strip clad onto a very thick section and then form it into elbow shapes.  Our forming temperatures will be around 1750F and then air cooled, and quenched and tempered afterwards.  I've done one helluva lot of research and have mixed input from a variety of experts.  Sensitization has been ruled as a non-issue by my customer so I'm not anticipating any *major* metallurgical problems... Greg's experience sounds like a question for Dr. Kotecki....
Parent - - By js55 (*****) Date 03-30-2007 13:32
Chuck,
I would agree that I think Greg's experience is certainly valid, not meaning to talk about you Greg like you aren't here, this one is a real mystery.
It seems it can't be Sigma while at the same time Sigme seems the only explanation. If tons and tons of this stuff wasn't welded every single day you might think there was something new going on. But given the extensive history of this stuff its doubtful.
I for one think that maybe the welder didn't hold his tongue right. I've seen this effect my own welds.
Parent - - By chuck meadows (***) Date 03-30-2007 14:02
Jeff and Jon,
  I'm not in my office and do not have Sec. IX handy, but do you guys know the P number for 17-4 PH (UNS 17400)? I seem to remember that there is no P#, but I cannot remember.
Parent - - By jon20013 (*****) Date 03-30-2007 16:04
Chuck, you are correct, 17-4PH has not been assigned a P-No.
Parent - - By chuck meadows (***) Date 03-30-2007 16:30
Thanks Bro.
  Now, is it safe to assume that the recommended filler metal E/ER 630 does not have an A#?
Parent - - By jon20013 (*****) Date 03-30-2007 17:20
That would sound correct however you are far more knowledgable than myself on that!~ ;-)  I did a quick check of A-Numbers in IX but didn't find one where the chemistries matched up... lol!
Parent - - By chuck meadows (***) Date 03-30-2007 18:33
Thanks Bro, I was working off of my fading memory. You know what they say about the memory being the 1st thing to go...I'm getting a little worried what the 2nd is...
Parent - By ssbn727 (*****) Date 03-31-2007 10:09
That's alright Chuck!

I'm still trying to remember what the third was!!!!! Hmmm?????
Btw, what comes after???? Ohh never mind - Get it?????

Respectfully,
Henry
Parent - - By GRoberts (***) Date 03-31-2007 06:52
Since I didn't get a chance to evalute the weld microstructure, we will probably never know, but I do know a lot of 309 filler is designed with a lot of ferrite for crack resistance when welding carbon to stainless.  15FN or higher is not that uncommon with 309.

http://www.select-arc.com/pdfs/cert_of_conf/309L-AP-CO2.pdf

If you have a good relationship with a filler metal manufacturer, you could probably get them to make some lower ferrite 309.  I was working on that recently until I moved on to different work.
Parent - - By chuck meadows (***) Date 03-31-2007 13:03 Edited 03-31-2007 13:18
I have a pretty good relationship with a filler metal manufacturer, and we certainly listen to customer requirements regarding ferrite levels for 309/309L. The much discussed 15FN is normally considered the "starting point" for the continuous network of sigma. A 15FN filler metal would need more time at temperature for sigma than a 18, 19, or 20FN, for example. That's why a Duplex can experience sigma in just a couple of minutes at temperature. 15FN and below can experience discontinuous networks of ferrite but time at temperature is the deciding factor between a continuous and discontinuous network. The 309L-AP flux core certification you presented with a 23FN is somewhat normal for an all-position FCW wire, but electrodes (SMAW) are "normally" not above 15FN. We know why the FN is higher in the FCW wire, though.

Typical ferrite levels of Avesta 309L wire:
309L SMAW--15FN
309L GMAW--10FN
309L GTAW--10FN
309L FCAW--19FN  (309LT1-1  --20FN)

In essence, there is a big difference in different manufacturers levels of ferrite for a 309 series of wires.
All wire was calculated to WRC-92    
Parent - - By js55 (*****) Date 04-02-2007 14:24
I'd like to ask a question here(or a corretion of my perspective), and not intending just to be argumentative. But I believe the idea that 309 is designed with high ferrite to minimizing cracking is incorrect. The cracking phenomena that 309 is intended to prevent is martensitic embrittlement due to dilution. The amount of ferrite is essentially just a 'fallout' from the chemistry necessary in the alloy to prevent martensitic formation due to lean alloy content. This is an entirely different phenomena than the accomodating of junk residuals (for example S and P), which is the primary effect of maintaining ferrite levels that prevents hot cracking. And this is very effective at ferrite levels far less than what we see with 309. In fact, this very discussion of the possibility of Sigma argues for the detrimental effect of high ferrite (where 3% to 6% is generally considered plenty) as opposed to its purposeful addition.
Isn't this correct?
Little help here Chuck.
Parent - - By chuck meadows (***) Date 04-02-2007 16:59
I agree that 309L is used for more than just resisting cracking. I'm not real sure that a 309L is specifically used to prevent the formation of mrtensite. Higher carbon contents contribute to a martensitic structure, also. Usually a low carbon filler is required when martensite is available. Then again, a PWHT is soften the martensite. Anyway, a lower ferrite content filler metal (like a 308 or 316) than a 309 (FN up to about 18) can be used if cracking is the only issue. But, I agree with what you said totally.
Parent - - By js55 (*****) Date 04-02-2007 17:17
Hello Chuck,
thanks,
And I guess what I meant by 309 preventing martensite has to do with alloying elements ability to form martensite even in low carbon steels. This is actually what Grade 91 is all about. A high alloy with low carbon and martensitic microstructure. They used the high carbon X20's in europe and they were crack sensitive. P91 comes along with low carbon and a martensitic microstructure, still crack sensitive but not as bad a X20.
My opinion is that if 300 series SS's are diluted enough you fall out of the room temp austenite range and the alloy content can form martensite even with low carbon. The punched alloy content of 309 allows higher dilution before this happens.
Parent - - By chuck meadows (***) Date 04-02-2007 19:05
Sorry, I was thinking along the lines of the martensitic grades of SS. I guess that's why I said the low carbon 309 was essential. But still, I think the 309L has attributes other than just for crack resistance. Jeff, how do we get started on one subject and end up on something totally different??  LOL (joking)
Parent - By js55 (*****) Date 04-02-2007 19:37
Well, all conversations to a certain extent evolve. But it doesn't help when you have a tendency to emphasize only what little you know as oppsoed to the general jist of the post.  Ha!!!
Speaking only for myself of course.
Up Topic Welding Industry / Technical Discussions / Heat Treating Stainless Steel

Powered by mwForum 2.29.2 © 1999-2013 Markus Wichitill