EM12K procedure
EM12K procedure
(OP)
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.





RE: EM12K procedure
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.
RE: EM12K procedure
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.
RE: EM12K procedure
RE: EM12K procedure
RE: EM12K procedure
RE: EM12K procedure
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?
RE: EM12K procedure
RE: EM12K procedure
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.
RE: EM12K procedure
RE: EM12K procedure
i hope this document can help you.
RE: EM12K procedure
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.
RE: EM12K procedure
would like to see the tensile results
RE: EM12K procedure
Ultimated tensile strenght for 8 specimens were:73428~79232(PSI)
RE: EM12K procedure
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.
RE: EM12K procedure
RE: EM12K procedure
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: EM12K procedure
RE: EM12K procedure
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.
RE: EM12K procedure
RE: EM12K procedure
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.
RE: EM12K procedure
I'm no welding expert so I'll stay out of that arena...
jt