Thank you very much for the detailed and informative reply, as usual. However, I like to share my views further to this.
The important requirement for Austenitic stainless steel - " shall be free from cold working intended to enhance mechanical properties " requires further discussions.
Can dished end forming be considered as cold working intended to enhance the mechanical property? If so, then even shell rolling also falls in same category.
According to my opinion, Material like A 666, 1/2 H, 1/4H, 3/4H etc. may fall in this requirement. ( Cold worked austenitic stainless steel materials). Pl share your views.
From practical point of view, during fabrication process (forming, welding and pressure testing etc.) certain amount of residual stresses will develop and it is not possible to make the vessel completely free from residual stresses.
Hence I understand that, a sealing limit on residual stresses, based on field and laboratory data been suggested for different materials. This sealing limit is in turn reflected as Hardness values for different materials.
Let's consider hypothetical case, dished end with hardness less than 22 HRC - then why to go for Solution Annealing ?
Further, as per ASM Handbook Vol. 4 (Heat treatment of steel), Austenitic stainless steel may be stress relieved at @ 900 deg C. However, the material, design conditions, fabrication procedure involved etc. needs to be considered before final call. If stress relief is warranted then due regard to metallurgical changes and effect on remaining life of the equipment shall be considered.
Further, solution annealing (water quenching or fast cooling in other medium) reintroduce high residual stresses. (Ref. ASM hand book vol. 4)
Back up supportive are all fine, but when manufactures / inspector has to take a final call on this, code requirements has to be followed.
As far as the code requirements are concerned neither upstream nor downstream code for sour services clearly indicates- Thermal treatment (solution annealing) is required for austenitic stainless steel material, after cold working. It restrict the residual stresses and in turn the hardness values for austenitic steels. If it exceeds 22 HRC then further decision has to be taken.
Even for carbon and low alloy steel the limit is restricted upto 5 % fiber elongation. For the hypothetical case of formed end with fiber elongation < 5 % and meeting the hardness requirement, thermal treatment to relieve residual stresses is not required as per specification.
Thanks.
With Best Regards,
Jignesh R Rana
Manager - Materials Technology, QA/QC & Standards
Linde Engineering India Pvt. Ltd.
'Linde House'
Opp: VUDA Office, VIP Road, Karelibaug,Vadodara - 390018, India.
Tel.: +91 265 3056789, Fax: +91 265 2335213 , Mobile: +91 90999 86019
jignesh.rana@linde-le.com, www.linde-india.com
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From: "pgoswami" <pgoswami@quickclic.net>
To: <materials-welding@googlegroups.com>
Date: 18-09-2011 09:38
Subject: [MW:12476] Requirement of Solution Annealing for SS DIshed head after forming
Sent by: materials-welding@googlegroups.com
Hi Mr Azmi,
In addition to the excellent explanations provided by Mr Rana, I would like to add a few more points.
Austenitic stainless steels are very well known for stress corrosion cracking in certain types of operating medias. Sour service have two guiding documents for up stream and downstream industries(see below), where the emphasis is primarily on avoiding " sulfide stress cracking". Sour media could include significant level of chlorides, which harms austenitic stainless steels significantly
MR 0175/ISO-15156 Table-A.2 have environmental and material limitations for Austenitic S.S 316L (UNS S31603) as follows:-
- Maximum recommended temperature -149 deg C
- Partial pressure H2S Max-1.5 psi
- Max chloride concentration -1000 ppm.
- be in the solution-annealed and quenched, or annealed and thermally stabilized heat-treatment condition;
- be free of cold work intended to enhance their mechanical properties; and
- have a maximum hardness of 22 HRC
- 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.
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.
Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist & Consultant
Ontario,Canada.
Email-pgoswami@sympatico.ca,
pgoswami@quickclic.net
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of jignesh.rana@Linde-LE.com
Sent: Wednesday, September 14, 2011 3:07 AM
To: materials-welding@googlegroups.com
Subject: Re: [MW:12449] Requirement of Solution Annealing for SS DIshed head after forming
Dear Mr. Asad,
I like to share my views on the topic with respect to the various applicable code.
1.0 ASME Section VIII Div. 1 - Since the material is SA 240 316L,(and assumed that is being cold worked) , requirements of post fabrication heat treatment due to straining as per
UHA- 44 will not be applicable and therefore solution annealing is not required. Please note that any of- L Grades" is not included in table UHA- 44.
2.0 Considering Sour Services-----
NACE MR 0103 - Austenitic stainless steel shall be supplied with 22 HRC hardness max. in solution annealed and quenched or sol. annealed and thermally stabilized conditions.
As per this clause thermal treatment is not required (if fiber elongation exceeds 5 %), which is case for carbon and low alloy steel as per clause no. 2.1.7 of NACE MR 0103.
However, considering good practice, ensure hardness of formed dished end below 22 HRC.
With Best Regards,
Jignesh R Rana
Manager - Materials Technology, QA/QC & Standards
Linde Engineering India Pvt. Ltd.
'Linde House'
Opp: VUDA Office, VIP Road, Karelibaug,Vadodara - 390018, India.
Tel.: +91 265 3056789, Fax: +91 265 2335213 , Mobile: +91 90999 86019
jignesh.rana@linde-le.com, www.linde-india.com
This e-mail is confidential. If you are not the intended recipient, please notify us immediately. You should not disclose its contents to any other person nor use it for any purposes.
From: asad azmi <azmiasadayub@gmail.com>
To: materials-welding@googlegroups.com
Date: 13-09-11 16:55
Subject: [MW:12442] Requirement of Solution Annealing for SS DIshed head after forming
Sent by: materials-welding@googlegroups.com
Dear All,
Greetings.
SS Vessel is being fabricated as per construction code - ASME SEC VIII DIV 1
SERVICE : SOUR Service
Material of Construction for Dished Head - SA 240 316L, 20 mm Thickness.
I believe stresses will be induced in the material during forming and as a result , Sulfide Stress Cracking (SSC) failure may occur during operation.
Whether Solution Annealing of SS Dished Head is required after forming?
Please give reference of any International Standard.
Thanks & Regards
Asad Azmi
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