Re: [MW:15727] RE: 15720] PQR - WPS - PWHT P91 to CS

Direct welding not accepted due to
1. PWHt of P91 will cross lower critical temp of CS (727)
2. Service temp
Pandithan

On 10/21/12, pgoswami <pgoswami@quickclic.net> wrote:
> Hi Zakaria,
>
> Dissimilar welds between Grade-91 to other lower alloyed steels e.g grade
> 11 and grade 22 are quite common. However a straight change from Grade-91
> to
> Carbon steel is a Bad Design, unless the margins provided by the OEM takes
> care of the service induced damages.
>
> A straight service induced damages could be a few as mentioned:-
>
> *
>
> Grade-91 steel operates at very high operating temperature regime
> (550-560 Deg C), which is is not safe for P1 material. P1 materials in the
> vicinity of the weld is likely to get exposed to spheroidization (on
> exposure to this temperature range) and may result in failures by creep
> *
>
> Thus welding of a intermediate or transition spool piece such as
> Grade-22 steel would be a better design.
>
> Grade-91 to Grade-22 could be welded in a few ways, see the following
> tables
> for welding materials selection and subsequent PWHT.
>
> You may qualify a WPS /PQR , however that does not always mean that the
> good
> engineering design basis is maintained.
>
> Also please see below the comments on your queries.
>
> Thanks
>
>
>
> Pradip Goswami,P.Eng.IWE
>
> Welding & Metallurgical Specialist
>
> Ontario, Canada.
>
> Email-pgoswami@sympatico.ca <blocked::mailto:Email-pgoswami@sympatico.ca> ,
>
> pgoswami@quickclic.net <blocked::mailto:pgoswami@quickclic.net>
>
> Dissimilar Welding Filler Metal Selection-
>
>
>
>
> Recommended PWHT Temperatures (0F) for Dissimilar Welds
>
>
>
> _____
>
> From: materials-welding@googlegroups.com
> [mailto:materials-welding@googlegroups.com] On Behalf Of Zakaria ghrab
> Sent: Saturday, October 20, 2012 6:29 AM
> To: materials-welding@googlegroups.com
> Subject: [MW:15720] PQR - WPS - PWHT P91 to CS
>
>
> Dear experts,
>
> Need your support.
>
> We performed one PQR P91 grade ( P number 15E) to Carbon steel (P number 1)
> welded GTAW/SMAW ER90S-B9 / E9015-B9, 11mm thickness, PWHT @ 740°C - 40
> minutes.
>
> PQR and related WPS already approved by our client. but the Owner
> consulting
> agency sent to us some comments :
>
> 1- No possible to weld P91 directly to CS shall add transition material P11
> grade : We answer that it's design issue and i requested some explain /
> calculation from design. -- This is a good and conservative design. If
> accepted one may have to weld the transition pieces, i.e involving welds
> between P91-P4 & P4-P1 base metal.The PWHT may be controlled to the better
> extent such that the P1 base metal would not get over tempered.
>
> 2- Should use filler metal compatible with lower grade material : i answer
> that can make choice of filler metal between to material grades (included)
> so we can weld with lower, heigher or iontermediate filler metal when
> mechanical properties is ok and don't have ebjection from project spec.
> --If
> you're welding in the above sequence recommendation would be :
>
> *
>
> P91-P4 -welds use -E/ER 8016/18 electrde/ filler metal
> *
>
> P4--P1 -welds use -E/ER 8016/18 electrode/ filler metal
>
>
> 3- this is the main issue : PWHT @ 740 °c is heigher than lower critical
> temperature for CS so we must perform PWHT in intermediate Temperature : in
> this case if will do like this WPS will not supported by Prepared PQR;
> --740Deg Cis quite high a temeprature for P1 steel , which could cause over
> tempeating of this steel
>
> PQR approved by Client and weld already done, i propose to perform hardness
> test, PMI and metallographic replic in production ( just one weld) to
> confirm.
>
>
> Need your support .
>
>
>
> Regards.
>
>
>
>
>
> --
>
> زكرياء غراب
> GHRAB Zakaria
>
>
>
> --
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The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.