Re: [MW:17615] PHWT for P91

a) Heat treatment time should be followed as prescribed.

b) The answer is in metallurgy. You need a certain type of micro structure to be developed as there is a strong structure-property co-relation

for P 91 steels and other creep resistant ferritic steels.

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From: Binoy Soman <binoy.spp@DAELIM.CO.KR>
To: "materials-welding@googlegroups.com" <materials-welding@googlegroups.com>
Sent: Tuesday, May 7, 2013 11:38 AM
Subject: [MW:17614] PHWT for P91

 

Dear experts,

 

Kindly explain following queries

(a)   PWHT holding time for P91 mentioned in B 31.1 is 1 hr/25 mm; minimum 30 minutes. Does it mean that if the thickness is 6/10/12.5 mm the holding time is 30 minutes & for 15 ,20,30,40 mm the holding time is 36  48,72,96 minutes respectively.

(b)    I got some special heating curves for P 91 from our group. But Kindly explain about the reference /standard used for preparation of this heat curve ( eg- why the preheat maintenance is 4 hours & again free cooling).

I raised these doubts earlier in [MW:17585], but I didn't receive any response. Please give your comments.

 

 

S.Binoy

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