Dear Mr Rana,
I had come across requirements of stabilising anneal, in various specifications:-
MOBIL ENGINEERING GUIDE :-EGE 55-B-2 — 1990, MATERIALS APPLICATION NAPHTHA PRETREATERS
7. MATERIAL CONSIDERATIONS DURING FABRICATION
7.1 To minimize the possibility of intergranular corrosion, stabilized grades (Type 321 or Type 347) of austenitic stainless steel shall be used in welded construction. Stabilized austenitic stainless steels especially Type 321 piping, may become sensitized after several years of service at temperatures over425ºC (800ºF). To prevent intergranular stress corrosion cracking in the heat-affected zones (HAZ) of welds,a stabilizing anneal heat treatment should be performed after welding. This treatment consists of heating to a range of 870ºC to 900ºC (1600ºF to 1650ºF) and holding for four hours, followed by rapid cooling.
NACE have a guiding document on Stabilizing Anneal.
NACE –RP-0170-2004-Protection of Austenitic Stainless Steels and other Austenitic Alloys from Polythionic SCC During Shutdown of Refinery Equipment.
· Clause 1.2.3:- Austenitic S.S and other austenitic alloys are susceptible materials that can crack in the presence of polythionic acid in sensitized conditions.
· 2.2- Austenitic S.S can be sensitized due to their carbon content, thus becoming susceptible to polythionic acid (PTA) SCC. The sensitization resistance may be enhanced through a stabilizing heat treatment, preferably by steel manufacturers.
· Such heat treatments are performed at 843ºC to 900ºC (1550ºF to 1650ºF) for 2 to 4 hrs for forming Ti or Nb carbides.
· The stabilizing heat treatment should be performed after the material has been solution annealed.
· Weld and HAZ of welded stabilized materials that have not received a post fabrication thermal stabilization can be subject to PTA SCC due to dissolution of carbides. Hence post fabrication r thermal stabilization may be performed on welded joints to improve the resistance of the HAZ to sensitization and PTA SCC.
ASME Sec-II, Requirements:-
· ASTM/ASME provide an option of stabilizing anneal as supplementary requirements to many product requirements (SA-213-2007, S2 , SA-312-2007, S6). The HT cycle has to be mutually agreed upon.
The attached NACE paper provides good information on the effects of Stabilizing anneal.
This requirement is more of a service requirement, typically for refining environment, where Polythionic Acid (PTA) SCC is expected to occur. Polythionic Acid (PTA) SCC typically occurs during refinery equipment shutdowns, when ingress of moisture causes formation of the above acids and resultant SCC of susceptible materials.
Thanks.
Pradip Goswami,P.Eng
Senior Engineer/Specialist(Welding-Metallurgy)
Engineering & Training Services Division
ONTARIO POWER GENERATION Inc.
PO Box-2000, RR-55(South)
Nanticoke, Ontario,N0A1L0
Tel:-(519) 587-2201, Ext 3107--in Nanticoke
(416) 231-4111, Ext 5925--in Kipling,Toronto
Fax: (519) 587-6814
From: jignesh.r@thyssenkrupp.com
To: materials-welding@googlegroups.com
CC: jignesh_rana@indiatimes.com
Date: Wed, 10 Feb 2010 09:03:15 +0530
Subject: RE: [MW:4273] Requirement of stabilized PWHT in the case of ER 347
Dear Hrishi,
In normal condition, weld joints doesn’t call for stabilizing heat treatment for stabilized grades like 321/321H/ 347/347H.
I come to know, some refinery applications wherein process licensors like Axen specifies, stabilizing heat treatment @ 900 DegC for 4 Hrs (Rate of cooling, depends on manufacturer), where the operating temp is 425- 850 deg C. The requirements of stabilizing heat treatment are applicable to raw materials only. However, the same cycle may be continued for weld also, after consultation with process licensor.
It has been observed that stabilizing properties are improved by heating @ 900 Deg C. It is worth to note that there is no test to check the whether, material is stabilized or not ?
Regards,
Jignesh R Rana
Chief Engineer - INSP. & EXP.
UHDE India Ltd.
P Please don't print this e-mail unless you really need to
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of K.M Hrishikesan
Sent: 09 February, 2010 5:24 PM
To: materials-welding@googlegroups.com
Subject: [MW:4259] Requirement of stabilized PWHT in the case of ER 347
Hi friends
Is PWHT mandatory in the case of depositing stabilized weld metal using ER 347 for welding SA 312 TP 321 pipings?
If so what will be the cycle?
The typical application is heater coil.
Regards
Hrishi
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