Tuesday, August 17, 2010

Re: [MW:6548] RE: 6522] Normalising requirment in code

Dear Pradip,
Thanks for you reply
In that case does NACE MR0175/NACE MR0103/NACE RP0472 either of them specify normalising requirment?I mean holding time and holding period?

Regards
Sachin

On Tue, 17 Aug 2010 08:58:08 +0530 wrote
>
Hello Sachin,
See below the extract from ASME Sec-VIII,DIV-1 on the
requirements of post forming heat treatments. Yes the code mandates only stress
relieving as post forming heat treatment due to the fact that
C.S/LAS can accommodate deformation strains, thus it's safe to perform
post forming heat treatmentswell below the lower critical (AC1)
temperature.
Unless forming is done above upper critical temperature (AC3)
re-normalizing is not required. Some of the rationale as per my thoughts
are as follows:-



C.S and some LAS do not have appreciable changes in mechanical
properties following forming below AC1 temperature under normal service
environments.

If the servicemedia is such so as to
cause environmental cracking such as SCC, then it would be dictated by process
specific specifications such as NACE or appropriate API guidelines or specific
requirements from process licensors.

Normalizing causes changes of phases during heating and
cooling. The resultant change of microstructure changes mechanical and other
properties

Normalizing is done in the mill under due care. Unless shops are
well equipped, re-normalize following formingmay destroy material
properties.
I hope
this clarifies your query.

Thanks


Pradip Goswami,P.Eng.
Welding & Metallurgical
Engineer/Specialist

Ontario Power Generation Inc.
Email-pgoswami@sympatico.ca,
pgoswami@quickclic.net


UCS-79 FORMING SHELL SECTIONS
AND HEADS- Vessel shell sections, heads,
and other pressure boundary parts of carbon and low alloy steel plates
fabricated by cold forming shall be heat treated subsequently(see UCS-56) when
the resulting extreme fiber elongation is more
than 5% from the as-rolled condition. For
P-No.1 Group Nos. 1 and 2 materials the extreme fiber elongation may be as great as 40% when none of the
following conditions
exist:
(1) The vessel will contain lethal substances either liquid or
gaseous (see UW-2).
(2) The material is not exempt from impact testing by the rules of this Division or impact testing is required
by the material specification.
(3) The thickness of the part before cold forming exceeds 5⁄8 in. (16
mm).
(4) The
reduction by cold forming from the as-rolled
thickness is more than 10% at any location where the extreme fiber
elongation exceeds 5%.
(5) The
temperature of the material during forming
is in the range of 250°F to 900°F (120°C to 480°C).
>


From: materials-welding@googlegroups.com
[mailto:materials-welding@googlegroups.com] On Behalf Of sachin
sankhe
>Sent: Monday, August 16, 2010 11:22 AM
>To:
materials-welding@googlegroups.com
>Subject: [MW:6522] Normalising
requirment in code
>
>
Hi,
>
>Why ASME sec VIII div.1 is silent of heat treatment above
lower transformation temp.I mean normalising is not mentioned any where.
>As
per ASME sec VIII div.1 if due to cold forming fibre elongation is more that 5%
then it gives reference of UCS-56,where it mention only stress releiving.
>In
which code I can find Normalising requirment(Temp, Holding time,loading
temp)
>I am aware that temp of normalising is about 910 Deg.c & holding
time is 1mm/min.But I need reference of code.
>
>Regards
>Sachin
>




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