RE: [MW:15282] SDSS - PWHT reg

What is meant by SDSS?  I am guessing that the SS is stainless steel but SD.  I recommend against using non-standard acronyms.

 

John A. Henning

Welding & Materials

 

From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Siva
Sent: Tuesday, September 11, 2012 3:06 AM
To: materials-welding@googlegroups.com
Subject: Re: [MW:15272] SDSS - PWHT reg

 

PWHT is not necessary to reduce hardness due to rapid cooling. the heat treatment when is performed is usually a solution annealing at approx 1050°c but this is done to dissolve the carbides (sensitization of SS) that reduce the corrosion resistance.
The effects of post-weld heat treatment (PWHT) on thermal fatigue resistance and hardness were evaluated by thermal fatigue and hardness testing, respectively. The weld metal microstructure was investigated by utilizing optical microscopy, scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM). Results showed that, by increasing the PWHT temperature, hardness decreased but there was a simultaneous improvement in weldment thermal fatigue resistance. During tempering, carbide, such as (Fe, Cr)₂₃C₆, precipitated in the weld metals and molybdenum appeared to promote (Fe, Cr, Mo)₂₃C₆ formation. The precipitates of (Fe, Cr, Mo)₂₃C₆ revealed a face-centered cubic (FCC) structure with fine grains distributed in the microstructure, thereby effectively increasing thermal fatigue resistance. However, by adding nickel, the A_C1 temperature decreased, causing a negative effect on thermal fatigue resistance.

PWHT is not necessary to reduce hardness due to rapid cooling. the heat treatment when is performed is usually a solution annealing at approx 1050°c but this is done to dissolve the carbides (sensitization of SS) that reduce the corrosion resistance.

Regards,

Sivalingam

On Tue, Sep 11, 2012 at 9:40 AM, Sundaram Sundaram <nss2410@gmail.com> wrote:

Dear Experts,

                          Please give detailed metallurgical input on SDSS ,why PWHT cannot be carried out on SDSS,if carried out what will be the metallurgical changes.

 

with thanks,

N.S.S

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Regards,
G.Sivalingam., BE.,
Quality Control Inspector - Welding,
SAS Project, Abu Dhabi, UAE.

 

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