Mr Bagchi,
Thanks for your feedback. Such transformation would occur only when the the "Lower Critical Temperature" is exceed in course of post weld heat treatment. Usually the rule of thumb rule(say for C-Mn Steel )is :-
- Lower Critical Temperature
 |
- Tempering Temperature
 |
- Stress Relieving Temperature
-600-640 Deg C
There should not be major surprises, if these rules are followed.
Best Regards.
Pradip Goswami, P.Eng,IWE
Welding & Metallurgical Specialist
Ontario, Canada
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Shomenath Bagchi
Sent: Monday, July 01, 2013 7:48 AM
To: materials-welding@googlegroups.com
Subject: Re: [MW:18063] RE: 18041] metallurgy of weld joint PWHT
Transformation to retained austenite is possible, but is a relatively rare case.
--
From: pgoswami <pgoswami@quickclic.net>
To: materials-welding@googlegroups.com
Cc: smv.monody@gmail.com
Sent: Monday, July 1, 2013 9:19 AM
Subject: RE: [MW:18056] RE: 18041] metallurgy of weld joint PWHT
--Sandeep,The issue is back to very basics of welding metallurgy. Please see the attached documents. The types of PWHT are many, however stress relieving is by far the most common PWHT adopted in BPV, Piping fabrication or any weld repair .What is stress relief and its' effects are nicely described in these documents.Stress relief does cause any metallurgical transformation. Metallurgical transformation during PWHT will add to stresses.If the metallurgical transformations are occurring during so called stress relief then PWHT is totally out of control.Thanks.Pradip Goswami, P.Eng,IWEWelding & Metallurgical SpecialistOntario, Canada
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Ramin Kondori
Sent: Sunday, June 30, 2013 8:54 AM
To: materials-welding@googlegroups.com
Subject: Re: [MW:18054] RE: 18041] metallurgy of weld joint PWHT--Dear Sandeep:
Cooling after welding is quite fast and when temp drops below Martensite Finish (Mf), it retards the transformation of austenite to some extent. SR is very similar to tempering and will help transformation of Retained Austenite (RA) and improves dimensional stability and soft spot issues.Of course this RA comes out in Alloys with more than 0.3% Carbon content but it may happen in low carbon grades too. Read the following article, you will get the idea.Regards
On Sun, Jun 30, 2013 at 4:35 PM, sandeep monody <smv.monody@gmail.com> wrote:
Dear Ramon Kondori Sir.
Earlier I was believing the same what you wrote in the reply.
Regarding the 3rd point u mentioned needs more clarification.,because no microstructure changes during pwht as pwht temperature is below the lower critical temperature of the metal but brittleness/hardness changes.
Please clarify your 3rd point
Sandeep.M.V
--
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