[MW:14165] RE: 14154] PWHT OF P 91 ALLOY STEEL MATERIAL.

-----Original Message-----
From: John Henning
Sent: 27/04/2012, 6:42 pm
To: materials-welding@googlegroups.com
Subject: [MW:14158] RE: 14154] PWHT OF P 91 ALLOY STEEL MATERIAL.


Stress corrosion cracking has been noted in as welded 91 material when
it has been wetted. The concern is that the welds may have dew
formation, or in some way be exposed to water. 91 in the as welded
condition should be held indoors in temperature and/ humidity controlled
conditions. An alternative is to keep in indoor storage but with the
welded material maintained at a temperature above the expected dew point
(by electric resistance pads most likely). The seven day thing is bit
arbitrary and my personal take is that it is just to make sure that PWHT
is performed in a timely manner. My experience with large amounts of
welded 91 is that there has been no cracking even after extended time (a
couple of months) in the as welded condition but we hold all as welded
91 in climate controlled conditions. I have not seen any empirical
evidence that 7 days, 14 days, or 30 days makes any difference provided
storage conditions are appropriate.



Note that function of the preheating and post heating you are doing is
to prevent hydrogen assisted cracking. The preheat and post heat allow
hydrogen to diffuse out of the material. Entirely different worry than
SCC in the presence of water.



Also note that any water; pure or otherwise has been demonstrated to
allow SCC in as welded 91 and it only needs be a film of water.



John A. Henning

Welding & Materials



From: materials-welding@googlegroups.com
[mailto:materials-welding@googlegroups.com] On Behalf Of manoj john
Sent: Thursday, April 26, 2012 3:24 AM
To: materials-welding@googlegroups.com
Subject: [MW:14154] PWHT OF P 91 ALLOY STEEL MATERIAL.



Dear All,



We are going to do P91 piping fabrication, as per client
specification the stroage time after welding is limited to maximum 7
days for PWHT. Is there any problem if it delays 10 days when we are
following preheating procedure for welding as mentioned below:



Preheat at 200 degree C. Min. 300 degree C. Max.

Inter pass temperature 250 to 300 degree C.

Cooling 20 to 80 degree C. after wleding

Post heating (extended heating) after cooling 300 degree C.

for four hours or 400 degree C. for three hours.



Thanks in advance for your response.\



Manoj.



--
To post to this group, send email to materials-welding@googlegroups.com
To unsubscribe from this group, send email to
materials-welding+unsubscribe@googlegroups.com
For more options, visit this group's bolg at
http://materials-welding.blogspot.com/
The views expressed/exchnaged in this group are members personel views
and meant for educational purposes only, Users must take their own
decisions w.r.t. applicable code/standard/contract documents.


______________________________________________________________________
The information in this email is confidential, and is intended solely for the addressee(s). If you are not the intended recipient of this email please let us know by reply and then delete it from your system; you should not copy this message or disclose its contents to anyone. The internet can not guarantee the integrity of this message. HAMON (and its subsidiaries) shall (will) not therefore be liable for the message if modified.
______________________________________________________________________

--
To post to this group, send email to materials-welding@googlegroups.com
To unsubscribe from this group, send email to materials-welding+unsubscribe@googlegroups.com
For more options, visit this group's bolg at http://materials-welding.blogspot.com/
The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.

--
To post to this group, send email to materials-welding@googlegroups.com
To unsubscribe from this group, send email to materials-welding+unsubscribe@googlegroups.com
For more options, visit this group's bolg at http://materials-welding.blogspot.com/
The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.