PWHT of Alloy 800HT#304H

[Bathula Raghuram (Mumbai - PIPING)]

Welded joint between 304H#UNS N08811 in a vessel constructed in accordance with ASME sec VIII div1 , where the design temp exceeds 540  ⁰C, to meet the requirements of UNF56(e)(1), do we need to PWHT this weld?

[pjo...@technip.com]

Is this a hypothetical case or a real case of material selection?

I personally feel that the application of 304H above 1000F (540 C) is not
advisable. The main reason being graphite precipitation at higher
temperature + very low Creep resistance of SS material (above 900F/480 C).

In this context, if the use of 304H is only for non-pressure part like,
anchor bolts or external support/structural part, etc. the dsigner may go
for the same heat treatment as specified in UNF 56 (e)(1). But if the use
of 304H is for pressure part, as per my personal opinion, it may be a case
of wrong selection of material. The case should be referred to process
licensor for their opinion. It may be avoided by changing the material to
either NF or other well-known HT creep-resistant material. (the luid and
operating conditions may govern)

I hope this may be useful. The case is typical and sounds interesting.
Please share the final outcome.

Best regards,

Prasad Joshi

"Bathula Raghuram
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[MW:436] PWHT of Alloy 800HT#304H

20/12/07 03:07 PM


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Welded joint between 304H#UNS N08811 in a vessel constructed in accordance
with ASME sec VIII div1 , where the design temp exceeds 540 0C, to meet
the requirements of UNF56(e)(1), do we need to PWHT this weld?

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[Bathula Raghuram (Mumbai - PIPING)]

it just hypothetical, i was going thro the para UNF56, and had in back of my mind, what will happen in case something like comes in, any way thank you for your clarification!

but i have seen a column like this few years back in a bid (thou i was not involved in this at that time) where top section has been made of Austenitic in an 800H vessel, becuase opearting temp are lesser in top section)

[pjo...@technip.com]

Even though, hypothetical case, it was good to brush up the code
requirements. Thanks for sharing such ideas.

for the case you mentioned, if the design temperature is lower, Austenitic
stainless steel may be used along with NF alloys. In such situation, you
may avoid application of UNF 56/e (complicated HT requirement).

But in my opinion, rather than using 304H (which is rather economical), one
can choose stabilized grades like, 321/347/316Ti where carbon is in the
form of carbides rather than in austenitic form.

Of course, I am not expert of material selection, other members may
contribute to this topic.

Thanks and regards,

Prasad Joshi
e-mail: pjo...@technip.com
Phone: +971-(0)2-611-6643

"Bathula Raghuram
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PIPING\)" To
<R.Bathula@ticb.c <material...@googlegroups.com
om> >
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[MW:439] RE: 437] Re: PWHT of Alloy
800HT#304H
22/12/07 08:06 AM

Best regards,

Prasad Joshi

20/12/07 03:07 PM

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