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Up Topic Welding Industry / Technical Discussions / Welding T22 with 8018B3
- - By whip (*) Date 10-23-2008 03:49
Anybody's view's on Welding 2 1/4 Chromium 9018 with 1 1/4 8018B3 electrodes It looks to me like you get the chromium content to match but not the tensile strength?? They also told me they can not preheat the 2 1/4 tubes because they are to old and corroded. Everywhere else there has been old and corroded tubes they do. These people are self insured, They own the RT Co literally. Their WPS "which they wrote" back's up the process all but the "forget the preheat" step. "The Welding Engineer has they said" studyed the failures Metallurgically and says this is the way to now do it. I most Certainly dont know everything but it goes aginst everything I have seen in my short 36 yrs inthe field. But I do want to give this the benefit of doubt, I know I just could be wrong.There could be in this particular case sound reasoning in this process. I would like to hear some other view's and thoughts on this Welding procedure.

                                                                                                                                                WHIP
Parent - - By js55 (*****) Date 10-23-2008 12:45
First of all, there is no E8018B3. There is an E8018B3L. And the L (low carbon) is what is responsible for it being 80 instead of 90. The electrode was developed for the express purpose of welding those alloys when PWHT is impossible or highly impractical. The L would also be integral to minimizing preheat. But you need to make sure they comply with the code.
Parent - By whip (*) Date 10-24-2008 03:43
js55, Thank you for the follow up . I did not add the "L" I should have my mistake. Please if you dont mind elaborate on the integral to minimizing preheat. There is no PWHT these are .220 Boiler Tubes.   T-22 alloy welded with 8018B3L  no preheat???      I hear you! Complying with the code is why I am no longer there. And It's good to hear from someone that stands on the same ground that I do.

                                                                                                                                                             Whip.
Parent - - By 3.2 Inspector (***) Date 10-24-2008 16:24
Are you sure its not: 803056  ?

3.2
Parent - - By jrw159 (*****) Date 10-24-2008 18:21
Nope, 803056 is a form of AL that is "moore" forgiving and easier to work with than most, but only up to a point. :-)

jrw159
Parent - - By js55 (*****) Date 10-24-2008 20:16
Don't think I'd wanna use aluminum on boiler tubes.  :)
Parent - - By 3.2 Inspector (***) Date 10-24-2008 22:15
Seeing the way that some boiler tubes are welded, I am sure they could use some "Moore Al" during welding :)

3.2
Parent - By jrw159 (*****) Date 10-25-2008 01:10
Nice reply. I can sure agree, I have learned "moore" from this "alloy" than I could repay.

jrw159
Parent - - By jrw159 (*****) Date 10-25-2008 01:08
VVRRRRROOOOOMMMNNN!!!>>>>>>.................

What the he** was that?  LOL
Parent - By whip (*) Date 10-25-2008 05:07
I was hopeing somebody would have come across this procedure. As I was merely trying to understand and learn something that might have some merit to an otherwise seemingly wrong approach of joining two alloys with the wroung filler metal, and no preheat that is required for that alloy. Proposing to someone this question in a fashion that gives this coal-corrosion, high temperature enviroment the benifit of the doubt at their procedure. The WPS was written by their Welding Engineer "Qualified" I was told? {However their WPS does require preheating}  Anyone who has ever been on a coal fired unit shutdown knows the terrible condition of the old tubes that you have to weld back to. Normally you do everything you can from prep to fit to preheat to try to get a good weld with what you have to work with. Its been going on for years with great success. But with Utility Companys trying to get more and more out of a unit could there just maybe be something to this.

                                                                                                                                              WHIP
Parent - - By MBSims (****) Date 10-25-2008 15:05
Per your info the electrode was E8018-B3L, which is the low carbon version of 2.25Cr-1Mo electrodes.  The E8018-B3L has a maximum of 0.05% carbon and an 80,000 psi specified minimum tensile strength.  The E9018-B3 has a specified carbon content of 0.05% to 0.12%. and a specified minimum tensile strength of 90,000 psi.  In contrast, the SA213-T22 tube material has a specified carbon content of 0.05% to 0.15% and a specified minimum tensile strength of 60,000 psi.

So, the minimum tensile strength of an E8018-B3L is still much greater than the T22 tube and there would not be a strength concern.  The low carbon electrodes are a good choice where postweld heat treatment will not be performed because their lower carbon content reduces the hardenability of the weld deposit and potential for cracking.

Not performing the preheat presents several issues.  Metallurgically, there should not be a problem with the microstucture in the heat affected zone of a tube weld.  Preheat is intended to slow the cooling rate to minimize the potential for martensite formation.  However, in a thin-wall (less than ~3/8"), small diameter (less than ~4" OD) T22 tube with 0.15% maximum carbon content, the cooling rate is not rapid enough for martensite formation and it is not usually a problem.  I've examined the HAZ microstructure in new T22 tubes that were overlayed with nickel alloys while water was pumped through the tube.  This would represent a worst-case cooling rate, but the actual HAZ looked fine with no martensite.  However, when welding on old tube it is good practice to preheat the tube to drive off any moisture that is present on the surface or in any corrosion products.  The other issue is Code compliance.  Per Table PW-39 in ASME Section I, for a circumferential butt weld in a P-No. 5A tube to be exempt from postweld heat treatment the following conditions must be met:

(1) a maximum specified chromium content of 3.0%
(2) a maximum thickness of 5/8 in.
(3) a maximum specified carbon content of not more than 0.15%
(4) a minimum preheat of 300°F

So, I'll agree it may be metallurgically acceptable, but from a workmanship and Code compliance standpoint it is not acceptable.
Parent - - By whip (*) Date 10-26-2008 00:14
Thank you very much for a helpful professional answer. That helps me understand this in the way that I needed to. Now I need to learn how and where to find the answer to that kind of a problem by myself.

                                                                                                         Thank you WHIP.
Parent - By rodofgod (**) Date 11-03-2008 22:32
Hi All!

Just like to agree with WHIP!

An excellent answer!

Regards
Up Topic Welding Industry / Technical Discussions / Welding T22 with 8018B3

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