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REGRUMBLE (Structural) (OP)
8 Oct 09 13:42
We are fabricating a vessel from 1 1/4" SA516-70 and our Sub arc proceure uses a Lincoln EM12K electrode which our customer claims is not suitable for PWHT. They did not give a reason. Does anyone know why this electrode is not suitable or which type of sub arc wire would be more suitable. The procedure must meet the same tensile, elongation and impacts as the parent metal. I have contacted Lincoln about this and they are not very helpful.  
Helpful Member!  vesselfab (Mechanical)
8 Oct 09 14:34
the client is correct.

we use EM14K (Lincoln LA71) with 880M (lincoln)

you should not have any problem with impacts as long as the temperature does not go to low and you you keep you preheats high and interpass temps low.
DVWE (Petroleum)
8 Oct 09 16:32
It depends on the flux you use with the wire.  Typical wire flux classification for this electrode is F7A6-EM12K.  The "A" stands for "as welded" and is not tested with PWHT per SFA-5.17

You want a classification with "P" in the designation which stands for "post-weld heat treatment", and is tested per SFA-5.17 with PWHT.  For example F7P4-EM14K.

That is probably why your client is not accepting it.
REGRUMBLE (Structural) (OP)
9 Oct 09 6:37
Thank you vesselfab. It looks like the LA71 with 880M or 888 flux will be the answer. To DVWE the client will not accept any procedure with the EM12 class. It did not matter which flux we suggested. We had to change to EM11 or EM14 but I do not know why?
vesselfab (Mechanical)
9 Oct 09 7:58
typical tensiles after PWHT are too low
JStephen (Mechanical)
9 Oct 09 9:03
It seems this would be addressed in the weld procedures- do you have qualified weld procedures with that electrode that meet the tensile requirements, with PWHT?
DVWE (Petroleum)
9 Oct 09 10:25
Regrumble,

I doubt there is a classification with a P in it using EM12K.  That's the only reason why.  JStephen brings up a good point, did you qualify this procedure with PWHT?
DG72 (Mechanical)
9 Oct 09 23:24
As long as you successfully qualify the wire/flux combination per ASME section IX, it is legal per ASME.  The problem is, the welding consumable mfg's do not "certify" the wire/flux combination in the PWHT'd condition.  This shouldn't matter, since ASME doesn't require this certification, but many welding engineers have gone above and beyond ASME code, and allow only wire/flux combinations that are certified by the mfg in the heat treated condition .
vesselfab (Mechanical)
10 Oct 09 0:34
might be legal and barely squeak by the pqr.

that's why the users and engineering companies want to approve weld procedures.

would you really want to risk your company's reputation and safety of user's personel with welds that may not be up to tensile after pwht?

lincoln may know best and that is why they put the A classification on the wire.
DVWE (Petroleum)
10 Oct 09 22:42
I agree with vesselfab.  The only way this might be acceptable is if the fabricator agrees to test every flux lot and wire lot combination which would be used in production.
petronik (Mechanical)
11 Oct 09 7:31
we are using the filler EH12K for this type of welding.(thichness 25~60mm with PWHT). you can find our WPS and welding process specification in attached.
i hope this document can help you.  
DVWE (Petroleum)
11 Oct 09 10:53
petronik,

Your WPS is incorrect.  QW-404, Electrode/Flux (Class) should be the classification of the electrode/flux when combined.  for example, you should have something like F7P4-EH12K listed there.  

"Basic" means the type of flux.  There are basic and active type fluxes available.  Basic, which I believe also means neutral does not add significant alloying elements to the final weld deposit, whereas Active fluxes will add alloying elements.
vesselfab (Mechanical)
11 Oct 09 10:54
do you have a pqr to go with that

would like to see the tensile results
petronik (Mechanical)
11 Oct 09 11:32
yes we have PQR.
Ultimated tensile strenght for 8 specimens were:73428~79232(PSI)
DG72 (Mechanical)
11 Oct 09 14:27
Vesselfab, I usually agree with your posts.  In this case, let me explain our position.  A few years back, our WPS was rejected by our client on the basis that the wire/flux combination wasn't certified by the mfg in the PWHT condition.  This came as a shock to us since we had easily qualified this combination for the PWHT condition for decades with no difficulties. (Pior to this, we were not aware that it wasn't certified; still, it was legal since we successfully qualified the WPS per ASME Sec IX).

We were told that there were some reasons unrelated to S&T heat exchanger applications that were the basis for the mfg not certifying the combination in the PWHT condition.  I wish I could remember the reason, but it didn't have anything to do with our industry.

Since then, we have switched to a wire/flux combination that is certified by the mfg (btw, we had better results with our original combination than we did with the "certified" combination).

I am not a welding engineer--just my thoughts.
DVWE (Petroleum)
11 Oct 09 16:48
There's nothing wrong with using a wire/flux combo which is designated as "A" or as welded in a PWHT situation as long as the wire has been tested (per lot) with PWHT.  When a "P" is present, obviously the manufacturer tests each lot.  All a PQR will tell you is that particular lot of wire or wire/flux will pass tensile requirements.  If a fabricator is willing to do the testing, then what's the issue?  To further note, testing per SFA-5.17 is different than a typical PQR test, as the SFA spec calls for an all weld metal tensile coupon.  
Helpful Member!  SJones (Petroleum)
11 Oct 09 20:40
A good discussion touching on the quality assurance aspects of welding, specifically: does a PQR with one batch of consumables really support production welding with any other batch of the same consumable?  It encapsulates the way consumables are specified, manufactured, purchased and tested: does one accept a certificate of conformity (EN 10204 Test Report Type 2.2)from an SFA-5.01 Schedule G level of testing or should it be an inspection report Type 3.1 for a Schedule J or K level of testing with a highly restricted lot classification, for example?  I would say that the answer depends on what is to be fabricated, the service it will see, and the level of testing that will occur during manufacture.

 

Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
 

stanweld (Materials)
12 Oct 09 8:59
It's amazing that all those thousands of vessels welded with Lincoln's L61 wire and 860 flux and post weld heat treated with welding procedures qualified with multiple hours of PWHT have not failed. Having said that, the carbon equivalents of welds deposited with that flux/filler composition have decreased appreciably since the mid 1980's.   

vesselfab (Mechanical)
12 Oct 09 11:42
hey

I agree with the fact that thousands have been pwht with this wire and flux and have not failed.

it's a testament to the old 4:1 safety factor

But I just play by the rules that the big boys set up

For me, just a meager little fabricator, it's easier to go by rules and certs set up by Lincoln and use the different flux/wire combo that is just fractionally higher priced than it is to argue with a customer.

Our business is to make cutomers happy with a good product delivered on time with high quality.  Not to argue over a weld procedure that can be fixed easily with a new flux/wire combination.

Sorry guys....it's just easier to comply sometimes.
REGRUMBLE (Structural) (OP)
12 Oct 09 13:54
I want to thank all of the contribtors this has been very informative. I have since found out that our client (Flour) did not even look at our procedure (which was qualified and has been used many tiems with PWHT)they just will not accept any with the EM12K as a matter of policy. But as Vesselfab indicated we are also just a little fabricator and are trying to keep the client happy so if I have to do another new proceudre then that is what we do.  
brimstoner (Materials)
13 Feb 10 18:55
Usually better to stay with a 'certified' combination if it gives the customer a headache.  Unless you will be using many tens of thousands of pounds, the extra pennies per pound should not matter much.  

Also, you will typically qualify a WPS using no thicker than 1.5".  This might buy you 8" in production, but at 8" it will require longer PWHT, lowering the strength of the production work.  If I put myself in the owner's place, I would be wary of borderline acceptable test results on PQRs and how valid they might be for a given design.  Remember, they are representative of given heats of plate, wire, flux, a given welder, etc. (the weather?)

I have done a bit of SAW welding, and found the AWS wire/flux classification system a bit clumsy.  

 
jte (Mechanical)
16 Feb 10 12:06
Regarding the "have not failed" statements... Those of you making that statement - have you tracked the vessels or have you simply not been notified? More often than not (read 0.1%) when I'm dealing with some type of issue with a vessel we do not notify the original manufacturer. Even if it was a fab shop foul up.

I'm no welding expert so I'll stay out of that arena...

jt

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