Mr Hegde,
Stabilizing anneal relatively low temperature annealing process , (with respect to solution anneal) but of longer duration, which causes the formation of Ti (in 321H s.s) or Nb carbides (in 347 s.s). Typical cycle would involve 870-900 deg C, 2-4 hours.Generally both of these S.S grades are stabilized, contains more "C" than L grades and have every possibility of forming Cr-carbides during fabrication, causing sensitization. This is fixed primarily with stabilizing anneal.
Many of the high temperature components in refinery, such as heaters tubes, piping and other components experience polythionic acid SCC problem and stabilizing anneal is one of the accepted practices to mitigate this right from the design and fabrication stage. ASME SA-213, 312 covers stabilizing anneal as a supplementary require.
IGC Practice-E is very common test with any austenitic S.S. While this test is designed to reveal the effects of intergranular corrosion ,the effects of Polyphonic SCC is not detected by this test. ASTM G-35 is the standard for polythionic acid SCC test. You may ask this test at the mill, however it will increase fabrication cost and other stringencies.
I had replied to the similar query in the forum, which is attached for your info. Plus the extract from API-571 would tell you the backgounr behind such requirements from user's perspectives.
Thanks
Pradip Goswami,P.Eng.
Welding & Metallurgical Engineer/Specialist
Ontario Power Generation Inc.
Email-pgoswami@sympatico.ca,
From: pgoswami [mailto:pgoswami@quickclic.net]
Sent: Tuesday, August 03, 2010 6:56 AM
To: GOSWAMI Pradip -THERMAL
Subject: FW: [MW:6282] Satbalising (Treatment of SA321H
Pradip Goswami,P.Eng.
Welding & Metallurgical Engineer/Specialist
Ontario Power Generation Inc.
Email-pgoswami@sympatico.ca,
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Bathula Raghuram (Mumbai - PIPING)
Sent: Tuesday, August 03, 2010 3:18 AM
To: 'materials-welding@googlegroups.com'
Subject: RE: [MW:6282] Satbalising (Treatment of SA321H
Carbon in case of 321 will be dissolved in any way during solution annealing, hence generally not recommended for 321 grade (practically no C left to form CrC). Ti or Nb have stronger affinity to form carbides than Cr.
In my opinion even in case of 321 H this is generally recommended if service temperatures are low (above 1200 °F will take care of stabilization during operation) or fluid is corrosive (refer NACE RP 0170 for polythionic acid SSC) and not necessarily in all cases.
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Sayee Raghunathan
Sent: Tuesday, August 03, 2010 11:33 AM
To: materials-welding@googlegroups.com
Subject: RE: [MW:6278] Satbalising (Treatment of SA321H
Hegde Sahib
i)What is the significance of stabilizing treatment at 950-980C with soaking for 2 hrs and cool in air even after solution annealing at 1050C followed by water quenching? Why Stabilizing treatment is necessary for H grade Ss and not in L grade SS ?
The ASM Handbook states that 'the stabilising anneal.. consists of holding at 845-900°C for up to 5h, depending on section thickness', but does not give methods of cooling or cooling rates. The Metals Handbook suggests a stabilising treatment of 2-4h at 870-900°C followed by rapid cooling to precipitate all possible carbon as Ti or Nb carbides and subsequently prevent Cr carbide precipitation. This is especially needed for H grades of stainless steels.
ii) Is there any affect on properties if we do not go for Stabilizing treatment
Yes, in effect with no stabilised treatment, you would expect that Cr carbides are formed (rather than Ti or Nb carbides) thereby reducing the corrosion resistance (primarily).
iii)What will be the microstructure of Stabilized 321H steel as against only Solution annealed
See above, you will have Cr carbides in the grain boundaries, leading to depletion of Cr in a narrow band around grain boundaries. Hence the requirement for IGC practice E.
Rgds
Sayee
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of PB HEGDE
Sent: 03 August 2010 05:07
To: materials-welding@googlegroups.com
Subject: RE: [MW:6271] Satbalising (Treatment of SA321H
Dear Friends
My query was particularly for H grade 321 i.e. 321 H
i)What is the significance of stabilizing treatment at 950-980C with soaking for 2 hrs and cool in air even after solution annealing at 1050C followed by water quenching? Why Stabilizing treatment is necessary for H grade Ss and not in L grade SS ?
ii) Is there any affect on properties if we do not go for Stabilizing treatment
iii)What will be the microstructure of Stabilized 321H steel as against only Solution annealed
Regards
Hegde p.B.
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Shashank Vagal
Sent: Monday, August 02, 2010 11:46 PM
To: materials-welding@googlegroups.com
Subject: Re: [MW:6262] Satbalising (Treatment of SA321H
I am confused-
Sir |
--
To post to this group, send email to materials-welding@googlegroups.com
To unsubscribe from this group, send email to materials-welding-unsubscribe@googlegroups.com
For more options, visit this group's bolg at http://materials-welding.blogspot.com/
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.
THIS MESSAGE IS ONLY INTENDED FOR THE USE OF THE INTENDED RECIPIENT(S) AND MAY CONTAIN INFORMATION THAT IS PRIVILEGED, PROPRIETARY AND/OR CONFIDENTIAL. If you are not the intended recipient, you are hereby notified that any review, retransmission, dissemination, distribution, copying, conversion to hard copy or other use of this communication is strictly prohibited. If you are not the intended recipient and have received this message in error, please notify me by return e-mail and delete this message from your system. Ontario Power Generation Inc.
No comments:
Post a Comment