Hi,
Pls.refer Sec.VIII,Div.1 - UHA 44 and Table UHA-44. You should calculate the strain % as per UHA44 and if you cannot calculate,then UHA44(b) shall be applied and follow as below.
According to Table UHA-44,If strain Percentage exceed 20% (for Design Temp - 580 to 675) and 10% for design temp. more than 675 degree celsius ,Head shall be heat treated (heating at the temperatures given in Table UHA-44 for 20 min/in. (20 min/25 mm) of thickness or 10 min, whichever is greater, followed by rapid cooling:)
Pls. find below the extraction.
UHA-44 REQUIREMENTS FOR
POSTFABRICATION HEAT TREATMENT DUE TO STRAINING
UHA-44(a) to general rules for forming given in UHA-40. UHA-44(a)(1) cold formed areas of pressure-retaining components manufactured
of austenitic alloys shall be solution annealed by
heating at the temperatures given in Table UHA-44 for 20
min/in. (20 min/25 mm) of thickness or 10 min, whichever
is greater, followed by rapid cooling: (a) the finishing-forming temperature is below theminimum heat-treating temperature given in Table UHA- 44; and (b) the design metal temperature and the formingstrains exceed the limits shown in Table UHA-44. UHA-44(a)(2) Forming strains shall be calculated asfollows:
(b) spherical or dished heads formed from plate:% strain = 75t/Rf(1-Rf/Ro)R f p mean radius after formingR o p original radius (equal to infinity for a flat plate)
p nominal thickness of the plate, pipe, or tube beforeforming
UHA-44(b) When forming strains cannot be calculatedas shown in (a) above, the Manufacturer shall have the responsibility to determine the maximum forming strain. In such instances, the forming limits for flares, swages, or upsets in Table UHA-44 shall apply.
Thanks & Regards,. (Karthik)
Karthikeyan.S
QA/QC Manager
Getabec Energy Co.,Ltd.
379,Moo6,Soi8,Nikhomphatana,
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Thailand.
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Hand Phone: 0066 892512282 --- On Tue, 9/13/11, asad azmi <azmias...@gmail.com> wrote: |
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Austenitic stainless steels that meet the chemical composition requirements specified in Paragraph 2.5.2 are acceptable at a hardness of 22 HRC maximum in the solution-annealed and quenched or solution-annealed and thermally stabilized condition, provided they are free of cold work intended to enhance their mechanical properties.
As you can see from above , both NACE documents talk about the similar requirements
Forming of heads ( cold or hot ) is very well known to all increase the mechanical properties of austenitic stainless steels including hardness and induce residual tensile stress. Any increase in hardness value and residual tensile stress due to forming accelerates SCC significantly.
As these forming strains can not be removed by any form stress relieving between 450-650 Deg C( sensitization range), austenitic S.S have no choice but to be fully solution annealed or subjected to thermal stabilization anneal.
Hence from designers stand point solution anneal is considered to be a "safe approach rather then being sorry". ASME SecVIII, DIV-1 does not readily call for solution anneal of austenitic stainless steels in all conditions except that there are something written in fine prints in UHA-6 & UHA-105 which directs to solution annealing to ensure the best properties of this alloy.
Thanks.
I suggest you have a look on ASME BPVC Section VIII - Div 1 Part UHA and more particularly UHA-44.
From: Krishnnaa26 <krishna....@gmail.com>
To: material...@googlegroups.com
Date: 16/01/2014 05:09
Subject: Re: [MW:19870] Requirement of Solution Annealing for SS DIshed head after forming
Sent by: material...@googlegroups.com
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