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[MW:10944] RE: 10937] Heat Treatment of P91 Pipe

By Materials & Welding

Hello Sandy,

Some insights on your query on P-91 steel.

9Cr-1Mo-V alloy is a deep hardening steel and forms almost 100% martensite on cooling.Critical cooling rate to obtain 100% Martensite is about 0.2ºC/sec (0.36ºF/sec).See the  Continuous Cooling Temperature (CCT) diagram for Grade 91.

By air cooling ( still or forced) or by quenching and tempering (as agreed between client and manufacturer)  from the austenitizing   temperature to room temperature, ideally  this alloy  would transform almost completely to Martensite .

As per ASME, Sec-IIA, SA 335,P-91, the pipes are to be supplied as:-

  • Normalized ( [1040–1080deg C)] and Tempered  [730–800 deg C)
  • Quenched and tempered (Temperature as above).This applies for typically 3" and above.
See under Table-2, SA 335 for details. For the section thickness specified below normalizing and tempering would be applicable.

Hope this would clarify your query.
 
Thanks.


Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist & Consultant
Ontario,Canada.
Email-pgoswami@sympatico.ca,
pgoswami@quickclic.net


                                                CCT Diagram of Grade 91 Steel


-----Original Message-----
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Saurabh Makker
Sent: Tuesday, May 03, 2011 11:16 PM
To: materials-welding@googlegroups.com
Subject: [MW:10937] Heat Treatment of P91 Pipe

Dear All,
I like a little knowledge about P91 seamless pipe heat treatment. As per standard its says Normalizing ans tempering. Please guide about that what should be cooling media and cooling rate on both the condition when the job thickness is 38 & 30 mm.
Regards--
Sandy
UAE

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