Hi
During PWHT when steel is heated below the A1 transformation temperature i.e 723 degree C, dislocation takes place,carbon is released from nucleated areas which allows the structure to deform plastically and relieve its internal stresses. There is no phase transformation below A1. It reduces hardness, tensile strength and increases toughness.
However crossing A1 temp. may result in very large / coarse grains, softer structure and poor toughness.
Hope this clarifies this issue.
Regards
Prem Nautiyal
Cell:9820313278
Mumbai.
On Tue, 09 Mar 2010 14:01:24 +0530 wrote
>
Remaining austenite, larger grain size
Dr. G. Dilintas
I&F Regional Technical Manager
Bureau Veritas Piraeus - Greece
Tel: +30 210 40 63 113/4
Fax: +30 210 40 63 118
"Girish Shejale"
"Girish Shejale"
Sent by: materials-welding@googlegroups.com
08/03/2010 09:20
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RE: [MW:4484] Why maximum PWHT temp shall be at least 20 °C less than tempering temp.
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What kind of microstructural transformations are expected here?
Regards,
Girish Shejale
-----Original Message-----
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com]On Behalf Of george.dilintas@gr.bureauveritas.com
Sent: Monday, March 08, 2010 10:26 AM
To: materials-welding
Subject: Re: [MW:4473] Why maximum PWHT temp shall be at least 20 °C less than tempering temp.
The pwht temperature must be lower than the lower transformation temperature in order to avoid microstructure alterations.
From: "Pradip Patil" [pradipp@godrej.com]
Sent: 08/03/2010 11:40 ZE5B
To:
Subject: [MW:4472] Why maximum PWHT temp shall be at least 20°C less than tempering temp.
Dear Sir,
Why maximum PWHT temp for CS and Low alloy steel materials shall be at least 20°C less than tempering temp?
With Regards,
Pradip Patil.
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PREM S NAUTIYAL
CELL : 9820313278
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