what were the storage conditions. If pipe is being kept dry there should be no problem. The concern with delay is the possibility of SCC if the the as welded material gets wet. Wet in this case means any water including dew formation. Been a lot of discussion on this issue in the past. In 30 years of experience I have not seen any evidence of as welded cracking as long as there was controlled storage.
Sent: Thursday, February 25, 2016 10:58 PM
To: materials-welding@googlegroups.com
Subject: [MW:24374] RE: 24373] Time between Hydrogen Bake Out and PWHT
Hi Mac,
One week without PWHT on 3.5” think Grade -91 Steel is too long. In spite of hydrogen bake out one may get cracking. Did any one check the hardness of weld and HAZ by any means (just for curiosity??).
Also prior to the DHT the welds should be cooled to Mf temperature which is generally the ambient temperature. In absence of it full martens tic transformation won’t happen causing poor creep strength in these steels. DHT may be adopted before the PWHT, however not advised to delay PWHT so long.
It’s worth looking at.
Thanks.
Pradip Goswami, P.Eng,IWE
Independent Welding & Metallurgical Engineering Specialist & Consultant.
Ontario,Canada.
ca.linkedin.com/pub/pradip-goswami/5/985/299
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com]
Sent: Thursday, February 25, 2016 3:47 PM
To: Materials & Welding
Subject: [MW:24373] Time between Hydrogen Bake Out and PWHT
Dear Sirs,
We welded a 15E Pipe material (16 inch - 87mm thickness).
Our procedure will be preheated with 205 deg centigrade then welding and will be
( hydrogen ) bakeout and perform PAUT, If accepted in PAUT, immediately followed
by PWHT and will perform MT.
Process is B31.1
The joint has been accepted by PAUT, my query is, how long should be acceptable if there is a delay in performing PWHT?
Right now it is almost 1 week that the welded joint is not yet PWHT.
Need your advice.
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