Hi Govindaraju,
This temperature corresponds to the Martensite finish temperature for this steel.Grade-91 is thorough hardening steel and produces martesite on air cooling. The best room temperature mechanical properties (tensile, impact and hardness) for this steel and the best high temperature creep properties are achieved when this steel is in fully tempered martensitic condition, i.e tempered @ 740-780 Deg C, following welding
Cooling to this temperature ,80c-110C immediately following welding but prior to PWHT is strongly advisable.
Thanks.
Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of GOVINDARAJU RAJU
Sent: Tuesday, October 23, 2012 4:43 AM
To: materials-welding@googlegroups.com
Subject: [MW:15748] Reagrdin p91 intermediate cooling
Dear sir
I am doing qc engineer in power plant construction.I have doubt regarding P91 welding.After completion of welding, we are doing intermediate cooling at 80c-110C.What is the need of intemediate cooling?
Rgds
V.GOVINDARAJU
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