SIST EN ISO 17781:2017
(Main)Petroleum, petrochemical and natural gas industries - Test methods for quality control of microstructure of austenitic/ferritic (duplex) stainless steel (ISO 17781:2017)
Petroleum, petrochemical and natural gas industries - Test methods for quality control of microstructure of austenitic/ferritic (duplex) stainless steel (ISO 17781:2017)
This document specifies quality control testing methods and test conditions for the characterization
of microstructure in relation to relevant properties in ferritic/austenitic (duplex) stainless steel
components supplied in the solution annealed condition and fabrication welds in the as welded
condition.
This document supplements the relevant product and fabrication standards with respect to destructive
testing methods including sampling of test specimens, test conditions and test acceptance criteria to
show freedom from deleterious intermetallic phases and precipitates in duplex stainless steels. In
addition, this document specifies the documentation of testing and test results by the testing laboratory.
NOTE 1 This document is based upon experience with duplex stainless steels in offshore oil and gas industry
applications including topside and subsea hydrocarbon service, sea water service, as well as structural use.
NOTE 2 The austenite spacing is relevant to the susceptibility of duplex stainless steels to hydrogen-induced
stress cracking (HISC) in subsea applications where cathodic protection is applied. This falls outside the scope of
this document. Reference is made to DNV/GL RP-F112[4].
Erdöl-, petrochemische und Erdgasindustrie - Werkstofftestanforderungen für nichtrostenden Duplexstahl (ISO 17781:2017)
Industries du pétrole, de la pétrochimie et du gaz naturel - Méthodes d'essai de contrôle de la qualité de la microstructure des aciers inoxydables (duplex) austénitiques/ferritiques (ISO 17781:2017)
ISO 17781:2017 spécifie les méthodes et les conditions d'essai de contrôle de la qualité pour caractériser la microstructure par rapport aux propriétés pertinentes des composants en acier inoxydable ferritique/austénitique (duplex) fournis à l'état recuit et les soudures de fabrication à l'état brut de soudage.
ISO 17781:2017 complète les normes de fabrication du produit concerné par rapport aux méthodes d'essais destructifs, y compris le prélèvement des éprouvettes, les conditions d'essai et les critères d'acceptation des essais, pour démontrer l'absence de phases intermétalliques préjudiciables et de précipités dans les aciers inoxydables duplex. De plus, le présent document précise la documentation des essais et des résultats des essais par le laboratoire d'essai.
NOTE 1 Le présent document se fonde sur l'expérience acquise avec des aciers inoxydables duplex dans des applications de plates-formes d'extraction en mer de pétrole et de gaz, y compris dans le cadre d'un fonctionnement en milieu hydrocarbure sous-marin ou en surface ou en service dans l'eau de mer ou pour une utilisation structurelle.
NOTE 2 L'espacement austénitique est pertinent pour la sensibilité des aciers inoxydables duplex à la fissuration par contrainte induite par l'hydrogène (HISC) dans les applications sous-marines en présence d'une protection cathodique. Cela ne relève pas du domaine d'application du présent document. Cela relève du domaine d'application du DNV/GL RP-F112[4].
Petrokemična industrija ter industrija za predelavo nafte in zemeljskega plina - Preskusne metode za kontrolo kakovosti mikrostrukture avstenitno-feritnega (dupleksnega) nerjavnega jekla (ISO 17781:2017)
Ta dokument določa preskusne metode za kontrolo kakovosti in preskusne pogoje za karakterizacijo mikrostrukture glede na ustrezne lastnosti komponent iz avstenitno-feritnega (dupleksnega) nerjavnega jekla, ki so dobavljene v žarjenem stanju, in proizvodnih zvarov v varjenem stanju.
Ta dokument dopolnjuje ustrezne standarde proizvodov in izdelave v zvezi s porušitvenimi preskusnimi metodami, vključno z vzorčenjem, preskusnimi pogoji in merili sprejemljivosti preskusa, za dokazovanje neprisotnosti zdravju škodljivih intermetalnih faz in izločkov v dupleksnih nerjavnih jeklih. Dokument poleg tega določa dokumentacijo za preskušanje in rezultate preskusa iz laboratorija za preskušanje.
OPOMBA 1: Ta dokument temelji na izkušnjah z dupleksnimi nerjavnimi jekli, ki se uporabljajo v industriji za predelavo nafte in zemeljskega plina, med drugim v sistemih za rokovanje z ogljikovodiki, sistemih za rokovanje z morsko vodo in uporabo v strukturah na palubi in pod morsko gladino.
OPOMBA 2: Avstenitni razmak je pomemben za določanje občutljivosti dupleksnega nerjavnega jekla na inducirano vodikovo napetostno pokanje (HISC) pri uporabi pod vodo, kjer se uporablja katodna zaščita. Slednje ne spada na področje uporabe tega dokumenta. Dokument se sklicuje na dokument DNV/GL RP-F112[4].
General Information
Buy Standard
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 17781:2017
01-november-2017
3HWURNHPLþQDLQGXVWULMDWHULQGXVWULMD]DSUHGHODYRQDIWHLQ]HPHOMVNHJDSOLQD
3UHVNXVQHPHWRGH]DNRQWURORNDNRYRVWLPLNURVWUXNWXUHDYVWHQLWQRIHULWQHJD
GXSOHNVQHJD QHUMDYQHJDMHNOD ,62
Petroleum, petrochemical and natural gas industries - Test methods for quality control of
microstructure of austenitic/ferritic (duplex) stainless steel (ISO 17781:2017)
Erdöl-, petrochemische und Erdgasindustrie - Werkstofftestanforderungen für
nichtrostenden Duplexstahl (ISO 17781:2017)
Industries du pétrole, de la pétrochimie et du gaz naturel - Méthodes d'essai de contrôle
de la qualité de la microstructure des aciers inoxydables (duplex)
austénitiques/ferritiques (ISO 17781:2017)
Ta slovenski standard je istoveten z: EN ISO 17781:2017
ICS:
75.180.01 Oprema za industrijo nafte in Equipment for petroleum and
zemeljskega plina na splošno natural gas industries in
general
77.140.20 Visokokakovostna jekla Stainless steels
SIST EN ISO 17781:2017 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 17781:2017
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SIST EN ISO 17781:2017
EN ISO 17781
EUROPEAN STANDARD
NORME EUROPÉENNE
August 2017
EUROPÄISCHE NORM
ICS 75.180.01
English Version
Petroleum, petrochemical and natural gas industries - Test
methods for quality control of microstructure of
ferritic/austenitic (duplex) stainless steels (ISO
17781:2017)
Industries du pétrole, de la pétrochimie et du gaz Erdöl-, petrochemische und Erdgasindustrie -
naturel - Méthodes d'essai de contrôle de la qualité de Prüfverfahren für die Qualitätslenkung von
la microstructure des aciers inoxydables (duplex) Microstrukturen von austenitisch/ferritisch
austénitiques/ferritiques (ISO 17781:2017) nichtrostendem Duplexstahl (ISO 17781:2017)
This European Standard was approved by CEN on 1 July 2017.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2017 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 17781:2017 E
worldwide for CEN national Members.
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SIST EN ISO 17781:2017
EN ISO 17781:2017 (E)
Contents Page
European foreword . 3
2
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SIST EN ISO 17781:2017
EN ISO 17781:2017 (E)
European foreword
This document (EN ISO 17781:2017) has been prepared by Technical Committee ISO/TC 67 “Materials,
equipment and offshore structures for petroleum, petrochemical and natural gas industries” in
collaboration with Technical Committee CEN/TC 12 “Materials, equipment and offshore structures for
petroleum, petrochemical and natural gas industries” the secretariat of which is held by NEN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by February 2018, and conflicting national standards
shall be withdrawn at the latest by February 2018.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
Endorsement notice
The text of ISO 17781:2017 has been approved by CEN as EN ISO 17781:2017 without any modification.
3
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SIST EN ISO 17781:2017
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SIST EN ISO 17781:2017
INTERNATIONAL ISO
STANDARD 17781
First edition
2017-07
Petroleum, petrochemical and
natural gas industries — Test
methods for quality control of
microstructure of ferritic/austenitic
(duplex) stainless steels
Industries du pétrole, de la pétrochimie et du gaz naturel — Méthodes
d’essai de contrôle de la qualité de la microstructure des aciers
inoxydables (duplex) austénitiques/ferritiques
Reference number
ISO 17781:2017(E)
©
ISO 2017
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SIST EN ISO 17781:2017
ISO 17781:2017(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
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Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2017 – All rights reserved
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SIST EN ISO 17781:2017
ISO 17781:2017(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and abbreviated terms . 2
3.1 Terms and definitions . 2
3.2 Abbreviated terms . 3
4 Sampling of test specimens . 4
4.1 General . 4
4.2 Casting test blocks. 6
4.3 Welds in the as welded condition . 6
5 Test methods . 7
5.1 General . 7
5.2 Microstructural examination . 7
5.2.1 General. 7
5.2.2 Preparation of specimen . 7
5.2.3 Etching of specimens . . 7
5.2.4 Microstructural evaluation of test specimens . 8
5.3 Ferrite content measurement .10
5.3.1 Test standard and conditions .10
5.3.2 Acceptance criteria .11
5.3.3 Reporting .11
5.4 Charpy V-notch impact toughness test .11
5.4.1 Test standard and conditions .11
5.4.2 Acceptance criteria .11
5.4.3 Reporting .12
5.5 Corrosion test .12
5.5.1 Test standard and conditions .12
5.5.2 Preparation of test specimens .13
5.5.3 Acceptance criteria .13
5.5.4 Reporting .13
Annex A (informative) Chemical compositions of duplex stainless steels .14
Annex B (informative) Preparation and etching for microstructural examination .16
Bibliography .18
© ISO 2017 – All rights reserved iii
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SIST EN ISO 17781:2017
ISO 17781:2017(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO’s adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: w w w . i s o .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 67, Materials, equipment and offshore
structures for petroleum, petrochemical and natural gas industries.
iv © ISO 2017 – All rights reserved
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SIST EN ISO 17781:2017
ISO 17781:2017(E)
Introduction
The aim of this document is to establish common test methods for quality control of microstructure of
ferritic/austenitic (duplex) stainless steels for the oil and gas industry, enabling the manufacturers to
apply the same test procedures for their clients.
Duplex stainless steels have a dual phase microstructure consisting of ferrite and austenite. Ideally,
these phases are present in equal proportions; although in alloys which are commercially available, the
ferrite phase volume fraction can vary between 35 % and 65 % for products in the solution annealed
condition. They are characterized by high-chromium (19 % to 33 %) and low-nickel contents compared
with austenitic stainless steels.
Duplex stainless steels are prone to precipitation of intermetallic phases, carbides and/or nitrides
possibly causing embrittlement and reduced corrosion resistance. The formation of intermetallic
phases such as Sigma, σ, and Chi, χ, occurs depending on exposure time in the approximate temperature
range 590 °C to 1 000 °C (1 094 °F to 1 832 °F) and decomposition of ferrite to Alpha Prime occurs in the
range 300 °C to 540 °C (572 °F to 1 004 °F).
The microstructure of components or fabrication welds is affected by amongst others the thermal-
mechanical history associated with hot working, solution annealing and with subsequent forming
and welding. The destructive test methods with acceptance criteria specified herein are considered
relevant to verify that exposure time at above stated temperature ranges have been within acceptable
limits and to ensure that desired corrosion resistance and mechanical properties are obtained in final
products.
© ISO 2017 – All rights reserved v
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SIST EN ISO 17781:2017
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SIST EN ISO 17781:2017
INTERNATIONAL STANDARD ISO 17781:2017(E)
Petroleum, petrochemical and natural gas industries —
Test methods for quality control of microstructure of
ferritic/austenitic (duplex) stainless steels
1 Scope
This document specifies quality control testing methods and test conditions for the characterization
of microstructure in relation to relevant properties in ferritic/austenitic (duplex) stainless steel
components supplied in the solution annealed condition and fabrication welds in the as welded
condition.
This document supplements the relevant product and fabrication standards with respect to destructive
testing methods including sampling of test specimens, test conditions and test acceptance criteria to
show freedom from deleterious intermetallic phases and precipitates in duplex stainless steels. In
addition, this document specifies the documentation of testing and test results by the testing laboratory.
NOTE 1 This document is based upon experience with duplex stainless steels in offshore oil and gas industry
applications including topside and subsea hydrocarbon service, sea water service, as well as structural use.
NOTE 2 The austenite spacing is relevant to the susceptibility of duplex stainless steels to hydrogen-induced
stress cracking (HISC) in subsea applications where cathodic protection is applied. This falls outside the scope of
[4]
this document. Reference is made to DNV/GL RP-F112 .
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 148-1, Metallic materials — Charpy pendulum impact test — Part 1: Test method
1)
ISO 15614-1 , Specification and qualification of welding procedures for metallic materials — Welding
procedure test — Part 1: Arc and gas welding of steels and arc welding of nickel and nickel alloys)
ASTM A 370, Standard test methods and definitions for mechanical testing of steel products
ASTM A 1058, Standard test methods and definitions for mechanical testing of steel products — Metric
ASTM A 1084, Standard test method for detecting detrimental phases in lean duplex austenitic/ferritic
stainless steels
ASTM E 3, Standard practice for preparation of metallographic specimens
ASTM E 562, Standard test method for determining volume fraction by systematic manual point count
ASTM E 1245, Standard practice for determining the inclusion or second-phase constituent content of
metals by automatic image analysis
ASTM G 48, Standard test methods for pitting and crevice corrosion resistance of stainless steels and
related alloys by use of ferric chloride solution
1) For the purpose of this document, the following documents are considered equivalent: ASME Boiler and
[2]
pressure vessel code, section IX Welding and brazing qualifications .
© ISO 2017 – All rights reserved 1
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SIST EN ISO 17781:2017
ISO 17781:2017(E)
3 Terms, definitions and abbreviated terms
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
NOTE For limitations in chemical composition of each specific material grade of duplex stainless steel,
reference is made to the appropriate product standards or UNS number. For nominal chemical composition of
duplex stainless steels and grouping of different types, used within this document, reference is made to Annex A.
3.1 Terms and definitions
3.1.1
centreline intermetallic stringer
group of intermetallic phases (3.1.4) aligned within the mid-thickness area due to alloy segregation
Note 1 to entry: They can be observed as both continuous and discontinuous precipitates.
3.1.2
fabrication
building of structures or equipment by cutting, bending, and assembling processes such as welding,
riveting, threaded fasteners or other joining methods
3.1.3
ferritic/austenitic (duplex) steel
stainless steel (3.1.8) with a high-chromium mass fraction (19 % to 33 %) with or without molybdenum
additions up to 5 %, and a nickel mass fraction intermediate to those of ferritic and austenitic
stainless steels
3.1.4
intermetallic phase
solid-state compounds, containing two or more metallic elements, whose ordered structure differs
from that of its constituents
Note 1 to entry: In duplex stainless steel, the most relevant phases are identified as σ-phase, χ-phase and R-phase.
3.1.5
lot
finite quantity of products from the same heat (or melt), same manufacturing process steps and same
heat treatment load
Note 1 to entry: For continuous and semi-continuous furnaces, the lot definition should comply with the
applicable product standards.
3.1.6
non-metallic precipitate
solid-state compounds, containing two or more elements, whose ordered structure differs from that of
its constituents
Note 1 to entry: In duplex stainless steel, the relevant non-metallic precipitates are chromium carbides and
nitrides.
2 © ISO 2017 – All rights reserved
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SIST EN ISO 17781:2017
ISO 17781:2017(E)
3.1.7
pitting resistance equivalent number
PREN
number indicating the resistance of stainless steel (3.1.8) to pitting corrosion related to chemical
composition and derived from one of the equations PREN = % Cr + 3,3 % Mo + 16 % N or PREN = % Cr +
3,3 × % (Mo + 0,5W) + 16 × % N (mass fraction)
Note 1 to entry: All PREN limits are absolute limits based upon the heat analysis. The calculated value is not to be
rounded.
3.1.8
stainless steel
steel with at least 10,5 % mass fraction or more chromium, possibly with other elements added to
secure special properties
3.1.9
type 20Cr duplex Group A
ferritic/austenitic stainless steel (3.1.8) alloys with 24,0 ≤ PREN < 28,0
3.1.10
type 20Cr duplex Group B
ferritic/austenitic stainless steel (3.1.8) alloys with 28,0 ≤ PREN < 30,0
3.1.11
type 22Cr duplex
ferritic/austenitic stainless steel (3.1.8) alloys with 30,0 ≤ PREN < 40,0 and Cr ≥ 19 % (mass fraction)
3.1.12
type 25Cr duplex
ferritic/austenitic stainless steel (3.1.8) alloys with 40,0 ≤ PREN < 48,0
3.1.13
type 27Cr duplex
ferritic/austenitic stainless steel (3.1.8) alloys with 48,0 ≤ PREN ≤ 55,0 and Cr ≤ 33,0 % (mass fraction)
3.2 Abbreviated terms
For the purposes of this document, the following abbreviated terms are used.
ASTM American society for testing and materials
CVN Charpy V-notch
HIP hot isostatically-pressed
NA not applicable
OD outside diameter
PREN pitting resistance equivalent number
QL quality level
T ruling section thickness
UNS unified numbering system
© ISO 2017 – All rights reserved 3
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SIST EN ISO 17781:2017
ISO 17781:2017(E)
4 Sampling of test specimens
4.1 General
The test samples shall be made from a sacrificial product or from a prolongation/extension of a
product in the final solution annealed condition with location of test specimens as defined in Table 1
representing the thickest product within the lot. Alternatively, a representative test block may be used
when agreed with the purchaser.
4 © ISO 2017 – All rights reserved
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SIST EN ISO 17781:2017
ISO 17781:2017(E)
Table 1 — Sampling of test specimens dependent of product
Product
a
Product Test sample Test method Test direction Thickness location
dimension
Plates, and Prolongation of All CVN Transverse Mid-thickness
seamless tubes, the product
b
Corrosion, Transverse Full thickness
pipes and fit-
Microstructure
tings
Welded pipes Prolongation or All CVN Transverse Mid-thickness
and fittings welded exten-
c b
Corrosion , Transverse Full thickness
sion piece
Microstructure
Bars and long Prolongation OD or section CVN Longitudinal Mid-thickness
solid forgings thickness
b
Corrosion, Transverse Surface to centre
without weld <50 mm (2 in)
Microstructure
end
OD or section CVN Longitudinal 1/4 thickness
thickness
b
Corrosion, Transverse Surface to centre
≥50 mm (2 in)
Microstructure
d
Flanges and Sacrificial prod- All CVN Both longitudinal Mid-thickness
other hollow uct or prolonga- and tangential to weld end
contour shaped tion at weld end centre bore
forgings with
b
Corrosion, Longitudinal or Full thickness
weld end includ-
Microstructure tangential weld end
ing tees
HIP products Sacrificial prod- All CVN Any direction Mid-thickness
with weld end uct or prolonga- weld end
tion at weld end
b
Corrosion, Any direction Full thickness
with greatest
Microstructure weld end
wall thickness
HIP products Sacrificial prod- Section thick- CVN Any direction Mid-thickness
without weld uct or prolon- ness <50 mm
b
Corrosion, Any direction Surface to centre
b
end gation at cross (2 in)
Microstructure
section with
Section thick- CVN Any direction 1/4 thickness
greatest wall
ness ≥50 mm
b
thickness
Corrosion, Any direction Surface to centre
(2 in)
Microstructure
Castings Sacrificial Test block CVN Any direction Mid-thickness
product or test thickness Corrosion,
block (see 4.2) <50 mm (2 in) Microstructure
Test block CVN Any direction Within hatched
thickness Corrosion, area (see Figure 1)
≥50 mm (2 in) Microstructure
a
For definition of test directions, reference is made to ASTM A 370/ASTM A 1058.
b
For products with large sections, the corrosion test specimen shall be taken transverse to the longitudinal axis with
dimensions of approximately 6 mm × 25 mm (1⁄4 in × 1 in) by thickness. For very large sections, the thickness dimension of
the specimen can be cut so that one-half to two-thirds of the product thickness is tested.
c
For welded products, the test specimens for corrosion testing and microstructure examination shall include weld
metal and the heat affected zone of parent metal. For products with wall thickness exceeding 25 mm, more than one (1)
specimen can be taken to cover full thickness. In such a case, all specimens shall fulfil the specified criteria.
d
When flange body thickness <50 mm (2 in) or weld end OD ≤100 mm (4 in), test specimens may be taken from the
flange body mid-thickness in tangential direction.
For all products, the mid-length of the test specimens shall be located one T or minimum 50 mm to any
second surface provided this is feasible within the size of the test sample/sacrificial product.
CVN testing is required when the wall thickness is ≥6 mm, wherever geometry permits.
For all products, the notch axis of CVN test specimens shall be positioned perpendicular to the closest
outer surface.
© ISO 2017 – All rights reserved 5
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SIST EN ISO 17781:2017
ISO 17781:2017(E)
For welded products, two (2) sets of three (3) CVN impact toughness test specimens shall be taken from
mid-thickness of the component, one (1) with notch located in base material and the other notched in
the weld metal.
For forgings, HIP products and fittings, dimensioned sketches shall be established showing type, size
and orientation of test specimens to be taken from a prolongation of product or a sacrificial product.
4.2 Casting test blocks
Test blocks shall be integral or gated with the casting(s) they represent and shall accompany the
castings through all heat treatment operations. During any heat treatment of products, which the test
block represents, the test blocks shall be tack welded onto the casting and shall accompany the castings
through all heat treatment operations. Alternatively, a sacrificial product may be used as a test sample.
The thickness of the test block shall be equal to the thickest section of the casting(s) represented. For
flanged components, the largest flange thickness should be used as the ruling section.
Dimensions of test blocks and location of test specimens within the test blocks are shown in Figure 1 for
integral and gated test blocks, respectively. All test specimens shall be taken within the cross hatched
area. When the thickness T of the test block is ≤50 mm, the longitudinal axis of test specimens shall be
located in the centre of the test block.
Figure 1 — Int
...
SLOVENSKI STANDARD
oSIST prEN ISO 17781:2016
01-julij-2016
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3UHVNXVQHPHWRGH]DNRQWURORNDNRYRVWLPLNURVWUXNWXUHDYVWHQLWQRIHULWQHJD
GXSOHNVQHJD QHUMDYQHJDMHNOD ,62',6
Petroleum, petrochemical and natural gas industries - Test methods for quality control of
microstructure of austenitic/ferritic (duplex) stainless steel (ISO/DIS 17781:2016)
Erdöl-, petrochemische und Erdgasindustrie - Werkstofftestanforderungen für
nichtrostenden Duplexstahl (ISO/DIS 17781:2016)
Industries du pétrole, de la pétrochimie et du gaz naturel - Méthodes d'essai de contrôle
de la qualité de la microstructure des aciers inoxydables (duplex)
austénitiques/ferritiques (ISO/DIS 17781:2016)
Ta slovenski standard je istoveten z: prEN ISO 17781
ICS:
75.180.01 Oprema za industrijo nafte in Equipment for petroleum and
zemeljskega plina na splošno natural gas industries in
general
77.140.20 Visokokakovostna jekla Stainless steels
oSIST prEN ISO 17781:2016 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
oSIST prEN ISO 17781:2016
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oSIST prEN ISO 17781:2016
DRAFT INTERNATIONAL STANDARD
ISO/DIS 17781.2
ISO/TC 67 Secretariat: NEN
Voting begins on: Voting terminates on:
2016-05-17 2016-07-11
Petroleum, petrochemical and natural gas industries —
Test methods for quality control of microstructure of
ferritic/ austenitic (duplex) stainless steels
Industries du pétrole, de la pétrochimie et du gaz naturel — Méthodes d’essai de contrôle de la qualité de la
microstructure des aciers inoxydables (duplex) austénitiques/ferritiques
ICS: 75.180.01
ISO/CEN PARALLEL PROCESSING
This draft has been developed within the International Organization for
Standardization (ISO), and processed under the ISO lead mode of collaboration
as defined in the Vienna Agreement.
This draft is hereby submitted to the ISO member bodies and to the CEN member
bodies for a parallel five month enquiry.
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
To expedite distribution, this document is circulated as received from the
IN ADDITION TO THEIR EVALUATION AS
committee secretariat. ISO Central Secretariat work of editing and text
BEING ACCEPTABLE FOR INDUSTRIAL,
composition will be undertaken at publication stage.
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 17781.2:2016(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
©
PROVIDE SUPPORTING DOCUMENTATION. ISO 2016
---------------------- Page: 3 ----------------------
oSIST prEN ISO 17781:2016
ISO/DIS 17781.2:2016(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2016, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2016 – All rights reserved
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oSIST prEN ISO 17781:2016
ISO/DIS 17781.2:2016(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and abbreviations . 2
3.1 Terms and definitions . 2
3.2 Abbreviations . 3
4 Sampling of test specimens . 3
4.1 General . 3
4.2 Casting test blocks. 5
4.3 Welds in the as welded condition . 5
5 Test methods . 6
5.1 General . 6
5.2 Microstructural examination . 6
5.2.1 General. 6
5.2.2 Preparation of specimen . 6
5.2.3 Etching of specimens . . 6
5.2.4 Microstructural evaluation of test specimens . 7
5.3 Ferrite content measurement . 8
5.3.1 Test standard and conditions . 8
5.3.2 Acceptance criteria . 8
5.3.3 Reporting . 9
5.4 Charpy V-notch impact toughness test . 9
5.4.1 Test standard and conditions . 9
5.4.2 Acceptance criteria . 9
5.4.3 Reporting .10
5.5 Corrosion test .10
5.5.1 Test standard and conditions .10
5.5.2 Preparation of test specimens .11
5.5.3 Acceptance criteria .11
5.5.4 Reporting .11
Annex A (informative) Chemical compositions of duplex stainless steels .12
Annex B (informative) Preparation and etching for microstructural examination .14
Bibliography .16
© ISO 2016 – All rights reserved iii
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oSIST prEN ISO 17781:2016
ISO/DIS 17781.2:2016(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2. www.iso.org/directives
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received. www.iso.org/patents
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 67, Materials, equipment and offshore structures
for petroleum, petrochemical and natural gas industries.
iv © ISO 2016 – All rights reserved
---------------------- Page: 6 ----------------------
oSIST prEN ISO 17781:2016
ISO/DIS 17781.2:2016(E)
Introduction
The aim of this International Standard is to establish common test methods for quality control of
microstructure of ferritic/austenitic (duplex) stainless steels for the oil and gas industry, enabling the
manufacturers to apply the same test procedures for their clients.
Duplex stainless steels have a dual phase microstructure consisting of ferrite and austenite. Ideally,
these phases are present in equal proportions although in commercial alloys the ferrite phase volume
fraction may vary between 35 % and 65 % for products in the solution annealed condition. They are
characterized by high chromium (19 % to 33 %) and low nickel contents compared with austenitic
stainless steels.
Some duplex stainless steels are prone to precipitation of intermetallic phases and nitrides possibly
causing embrittlement and reduced corrosion resistance. The formation of intermetallic phases such
as Sigma and Chi occurs depending on exposure time in the approximate temperature range 590 °C to
1000 °C (1 094 °F to 1 832 °F) and decomposition of ferrite to Alpha Prime occurs in the range 300 °C
to 540 °C (572 °F to 1 004 °F).
The microstructure of components or fabrication welds is affected by amongst others the thermal-
mechanical history associated with hot working, solution annealing and with subsequent forming
and welding. The destructive test methods with acceptance criteria specified herein are considered
relevant to verify that exposure time at above stated temperature ranges have been within acceptable
limits and to ensure that desired corrosion resistance and mechanical properties are obtained in final
products.
© ISO 2016 – All rights reserved v
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oSIST prEN ISO 17781:2016
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oSIST prEN ISO 17781:2016
DRAFT INTERNATIONAL STANDARD ISO/DIS 17781.2:2016(E)
Petroleum, petrochemical and natural gas industries —
Test methods for quality control of microstructure of
ferritic/ austenitic (duplex) stainless steels
1 Scope
This International Standard specifies quality control testing methods and test conditions for the
characterization of microstructure in relation to relevant properties in ferritic/austenitic (duplex)
stainless steel components supplied in the solution annealed condition and fabrication welds in the as
welded condition.
This International Standard supplements the relevant product and fabrication standards with
respect to destructive testing methods including sampling of test specimens, test conditions and test
acceptance criteria to show freedom from deleterious intermetallic phases and precipitates in duplex
stainless steels. In addition this International Standard specifies how testing and test results shall be
documented by the testing laboratory.
NOTE 1 This International Standard is based upon experience with duplex stainless steels in offshore oil
and gas industry applications including topside and subsea hydrocarbon service, sea water service as well as
structural use.
NOTE 2 The austenite spacing is relevant to the susceptibility of duplex stainless steels to hydrogen induced
stress cracking (HISC) in subsea applications where cathodic protection is applied. This falls outside the scope of
this International Standard. Reference is made to DNV/GL RP-F112 [6].
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
1)
)
ISO 148-1 , Metallic materials — Charpy pendulum impact test — Part 1: Test method
2)
ISO 15614-1 , Specification and qualification of welding procedures for metallic materials — Welding
)
procedure test — Part 1: Arc and gas welding of steels and arc welding of nickel and nickel alloys
ASTM A 1084, Standard test method for detecting detrimental phases in lean duplex austenitic/ferritic
stainless steels
ASTM E 3, Standard practice for preparation of metallographic specimens
ASTM E 562, Standard test method for determining volume fraction by systematic manual point count
ASTM E 1245, Standard practice for determining the inclusion or second-phase constituent content of
metals by automatic image analysis
ASTM G 48, Standard test methods for pitting and crevice corrosion resistance of stainless steels and
related alloys by use of ferric chloride solution
)
1) For the purpose of this International Standard, the following documents are considered equivalent:—
ASTM A 370, Standard test methods and definitions for mechanical testing of steel products— ASTM A 1058,
Standard test methods and definitions for mechanical testing of steel products – Metric
)
2) For the purpose of this International Standard, the following documents are considered equivalent:—
ASME Boiler and pressure vessel code, section IX Welding and brazing qualifications
© ISO 2016 – All rights reserved 1
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oSIST prEN ISO 17781:2016
ISO/DIS 17781.2:2016(E)
3 Terms, definitions and abbreviations
For limitations in chemical composition of each specific material grade of duplex stainless steel
reference is made to the appropriate product standards or UNS number. For nominal chemical
composition of duplex stainless steels and grouping of different types, used within this International
Standard, reference is made to Annex A.
For the purposes of this document, the following terms and definitions shall apply.
3.1 Terms and definitions
3.1.1
centreline intermetallic stringer
group of intermetallic phases aligned within the mid-thickness area due to alloy segregation
Note 1 to entry: They can be observed as both continuous and discontinuous precipitates.
3.1.2
fabrication
building of structures or equipment by cutting, bending, and assembling processes such as welding,
riveting, threaded fasteners or other joining methods
3.1.3
ferritic/austenitic (duplex) steel
stainless steel with a high chromium mass fraction (19 % to 33 %) with or without molybdenum additions
up to 5 %, and a nickel mass fraction intermediate to those of ferritic and austenitic stainless steels
3.1.4
intermetallic phase
solid-state compounds, containing two or more metallic elements, whose ordered structure differs
from that of its constituents
Note 1 to entry: In duplex stainless steel the relevant phases are identified as σ-phase, χ-phase and R-phase.
3.1.5
pitting resistance equivalent number
PREN
number indicating the resistance of stainless steel to pitting corrosion related to chemical composition
and derived from one of the equations PREN = % Cr + 3,3 % Mo + 16 % N or PREN = % Cr + 3,3 × % (Mo
+ 0,5W) + 16 × % N (mass fraction)
Note 1 to entry: All PREN limits are absolute limits based upon the heat analysis. The calculated value is not to be
rounded.
3.1.6
precipitate
solid-state compounds, containing two or more elements, whose ordered structure differs from that of
its constituents
Note 1 to entry: In duplex stainless steel the relevant precipitates are chromium carbides and nitrides.
3.1.7
stainless steel
steel with at least 10,5 % mass fraction or more chromium, possibly with other elements added to
secure special properties
3.1.8
type 20Cr duplex Group A
ferritic/austenitic stainless steel alloys with 24,0 ≤ PREN < 28,0
2 © ISO 2016 – All rights reserved
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oSIST prEN ISO 17781:2016
ISO/DIS 17781.2:2016(E)
3.1.9
type 20Cr duplex Group B
ferritic/austenitic stainless steel alloys with 28,0 ≤ PREN < 30,0
3.1.10
type 22Cr duplex
ferritic/austenitic stainless steel alloys with 30,0 ≤ PREN < 40,0 and Cr ≥ 19 % (mass fraction)
3.1.11
type 25Cr duplex
ferritic/austenitic stainless steel alloys with 40,0 ≤ PREN < 48,0
3.1.12
type 27Cr duplex
ferritic/austenitic stainless steel alloys with 48,0 ≤ PREN ≤ 55,0 and Cr ≤ 33,0 % (mass fraction)
3.2 Abbreviations
For the purposes of this document, the following abbreviations are used:
ASTM American Society for Testing and Materials
CVN Charpy V-notch
HIP hot isostatically-pressed
NA not applicable
OD outside diameter
PREN pitting resistance equivalent number
QL quality level
UNS unified numbering system
4 Sampling of test specimens
4.1 General
The test samples shall be made from a sacrificial product or from a prolongation/extension of a
product in the final solution annealed condition with location of test specimens as defined in Table 1
representing the thickest product within the lot.
Table 1 — Sampling of test specimens dependent of product
Product dimen-
a
Product Test sample Test method Test direction Thickness location
sion
Plates, and seam- Prolongation of All CVN Transverse Mid-thickness
less tubes, pipes the product
b
Corrosion Micro- Transverse Full thickness
and fittings
structure
Welded pipes and Prolongation or All CVN Transverse Mid-thickness
fittings welded extension
c b
Corrosion Micro- Transverse Full thickness
piece
structure
© ISO 2016 – All rights reserved 3
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oSIST prEN ISO 17781:2016
ISO/DIS 17781.2:2016(E)
Table 1 (continued)
Product dimen-
a
Product Test sample Test method Test direction Thickness location
sion
Bars and long Prolongation OD or sec - CVN Longitudinal Mid-thickness
solid forgings tion thickness
b
Corrosion Micro- Transverse Surface to centre
without weld end < 50 mm (2 in)
structure
OD or sec - CVN Longitudinal 1/4 thickness
tion thickness
b
Corrosion Micro- Transverse Surface to centre
≥ 50 mm (2 in)
structure
d
Flanges and other Sacrificial prod- All CVN Both longitudinal Mid-thickness weld
hollow contour uct or prolonga- and tangential to end
shaped forgings tion at weld end centre bore
with weld end in-
b
Corrosion Micro- Longitudinal or Full thickness weld
cluding tees
structure tangential end
HIP products with Sacrificial prod- All CVN Any direction Mid-thickness weld
weld end uct or prolonga- end
tion at weld end
b
Corrosion Micro- Any direction Full thickness weld
with greatest wall
structure end
thickness
HIP products Sacrificial prod- Section thickness CVN Any direction Mid-thickness
b
without weld end uct or prolonga- < 50 mm (2 in)
b
Corrosion Micro- Any direction Surface to centre
tion at cross sec-
structure
tion with greatest
Section thickness CVN Any direction 1/4 thickness
wall thickness
≥ 50 mm (2 in)
b
Corrosion Micro- Any direction Surface to centre
structure
Castings Sacrificial prod- Test block thick- C V N Any direction Mid-thickness
uct or test block, ness < 50 mm Corrosion Micro-
see 4.2. (2 in) structure
Test block thick- C V N Any direction Within hatched area,
ness ≥ 50 mm Corrosion Micro- see Figure 1
(2 in) structure
a
For definition of test directions reference is made to ASTM A 370/ASTM A 1058.
b
For products with heavy sections, the corrosion test specimen shall be taken transverse to the longitudinal
axis with dimensions of approximately 6 mm by 25 mm (1⁄4 in by 1 in) by thickness. For very heavy sections, the
thickness dimension of the specimen can be cut so that one half to two thirds of the product thickness is tested.
For convenience, the specimen can be cut in pieces of 50 mm (2 in).
c
For welded products the test specimens for corrosion testing and microstructure examination shall include
weld metal and the heat affected zone of parent metal. For products with wall thickness exceeding 25 mm more
than one (1) specimen can be taken to cover full thickness. In such a case all specimens shall fulfil the specified
criteria.
d
When flange body thickness < 50 mm (2 in) or weld end OD ≤ 100 mm (4 in), test specimens may be taken
from the flange body mid-thickness in tangential direction.
For all products, the mid-length of test specimens shall be equal to the product wall thickness
or minimum 50 mm to any second surface provided this is feasible within the size of the test
sample/sacrificial product.
CVN testing is required when the wall thickness is ≥ 6 mm, wherever geometry permits.
For all products, the notch axis of CVN test specimens shall be positioned perpendicular to the closest
outer surface.
For welded products, two (2) sets of three (3) CVN impact toughness test specimens shall be taken from
mid-thickness of the component, one (1) with notch located in base material and the other notched in
the weld metal.
4 © ISO 2016 – All rights reserved
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oSIST prEN ISO 17781:2016
ISO/DIS 17781.2:2016(E)
For forgings, HIP products and fittings, dimensioned sketches shall be established showing type, size
and orientation of test specimens to be taken from a prolongation of product or a sacrificial product.
4.2 Casting test blocks
Test blocks shall be integral or gated with the casting(s) they represent and shall accompany the
castings through all heat treatment operations. During any heat treatment of products, which the test
block represents, the test blocks shall be tack welded onto the casting and shall accompany the castings
through all heat treatment operations. Alternatively, a sacrificial product may be used as a test sample.
The thickness of the test block shall be equal to the thickest product of the casting represented. For
flanged components, the largest flange thickness should be used as the ruling section.
Dimensions of test blocks and location of test specimens within the test blocks are shown in Figure 1 for
integral and gated test blocks, respectively. All test specimens shall be taken within the cross hatched
area. When the thickness T of the test block is ≤ 50 mm the longitudinal axis of test specimens shall be
located in the centre of the test block.
Figure 1 — Integral and gated test block for castings
4.3 Welds in the as welded condition
Test specimens for weld procedure qualification shall be taken in accordance with the requirements of
ISO 15614-1 or applicable design code.
The test specimens for microstructural examination shall comprise a cross section of the weld metal,
heat affected zones and base metal of parts connected in full thickness.
The ferrite content shall be determined in the weld metal root and the last bead of the weld cap 2 mm
(0,08 in) below the surface. For welds with thickness less than 5 mm (0,2 in) the ferrite content shall be
determined through the full thickness.
In total three sets of CVN test specimens shall be taken from the following positions from the weld
cap area:
— weld metal;
— fusion line;
— fusion line + 2 mm (0,08 in).
© ISO 2016 – All rights reserved 5
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oSIST prEN ISO 17781:2016
ISO/DIS 17781.2:2016(E)
When the weld thickness exceeds 25 mm (1,0 in), two (2) additional sets of specimens shall be taken
from the weld root area 2 mm from the internal surface, one (1) from the weld metal and one (1) from
the fusion line +2 mm (0,08 in).
The corrosion test specimen shall include the external and internal surface and a cross sectional surface
including the weld zones in full wall thickness. The test specimens shall have a dimension of full wall
thickness by 25 mm (1,0 in) along the weld and 50 mm (2,0 in) across the weld. For products with great
wall thickness, e.g. exceeding 25 mm (1,0 in), more than one (1) specimen can be taken to cover full
thickness. In such a case all specimens shall fulfil the specified criteria.
5 Test methods
5.1 General
Laboratory test methods for evaluation of the microstructure of duplex stainless steel are as follows:
a) microstructural examination;
— check for presence of intermetallic phases and precipitates;
— determine ferrite content.
b) CVN impact toughness testing;
c) ferric chloride corrosion test.
There are several parameters of the material microstructure that can influence the test results and the
use of all three test methods, as far as practical, is necessary to demonstrate acceptable quality.
Note This standard specifies how test results should be documented by the test house. Material certification
reporting requirements are outside the scope of this standard.
5.2 Microstructural examination
5.2.1 General
Microstructural examinations shall be carried out by trained and experienced technicians.
5.2.2 Preparation of specimen
Metallographic preparation of duplex stainless steels shall be in accordance with ASTM E 3 and shall be
polished to a metallographic finish suitable for light optical examination at minimum 400 X (200 X for
casting) after etching.
With mechanical polishing, an 1 μm diamond final polish or equivalent shall be used as minimum.
Preferably, a final oxide polish (e.g. colloidal silica/alumina) should be used.
Electro polishing may be used as an alternative to mechanical polishing.
The use of conductive mounts can affect the subsequent etching. Samples should consequently be
mounted into a resin (thermo-setting or cold-setting).
5.2.3 Etching of specimens
Electrolytic etching shall be performed after final polishing using one (1) of the following options:
1) Combination of two (2) solutions in sequence with examination in between:
i) 10 % oxalic acid solution or V2A etchant
...
SLOVENSKI STANDARD
oSIST prEN ISO 17781:2015
01-marec-2015
3HWURNHPLþQDLQGXVWULMDWHULQGXVWULMD]DSUHGHODYRQDIWHLQ]HPHOMVNHJDSOLQD
3UHVNXVQHPHWRGH]DNRQWURORNDNRYRVWLPLNURVWUXNWXUHDYVWHQLWQRIHULWQHJD
GXSOHNVQHJD QHUMDYQHJDMHNOD ,62',6
Petroleum, petrochemical and natural gas industries - Test methods for quality control of
microstructure of austenitic/ferritic (duplex) stainless steel (ISO/DIS 17781:2015)
Erdöl-, petrochemische und Erdgasindustrie - Werkstofftestanforderungen für
nichtrostenden Duplexstahl (ISO/DIS 17781:2015)
Industries du pétrole, de la pétrochimie et du gaz naturel - Méthodes d'essai de contrôle
de la qualité de la microstructure des aciers inoxydables (duplex)
austénitiques/ferritiques (ISO/DIS 17781:2015)
Ta slovenski standard je istoveten z: prEN ISO 17781
ICS:
75.180.01 Oprema za industrijo nafte in Equipment for petroleum and
zemeljskega plina na splošno natural gas industries in
general
oSIST prEN ISO 17781:2015 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
oSIST prEN ISO 17781:2015
---------------------- Page: 2 ----------------------
oSIST prEN ISO 17781:2015
DRAFT INTERNATIONAL STANDARD
ISO/DIS 17781
ISO/TC 67 Secretariat: NEN
Voting begins on: Voting terminates on:
2014-11-10 2015-02-10
Petroleum, petrochemical and natural gas industries —
Test methods for quality control of microstructure of
austenitic/ferritic (duplex) stainless steel
Industries du pétrole, de la pétrochimie et du gaz naturel — Exigences de test pour les matériaux en acier
duplex inoxydable
ICS: 75.180.01
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 17781:2014(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
©
PROVIDE SUPPORTING DOCUMENTATION. ISO 2014
---------------------- Page: 3 ----------------------
oSIST prEN ISO 17781:2015
ISO/DIS 17781:2014(E)
Copyright notice
This ISO document is a Draft International Standard and is copyright-protected by ISO. Except as
permitted under the applicable laws of the user’s country, neither this ISO draft nor any extract
from it may be reproduced, stored in a retrieval system or transmitted in any form or by any means,
electronic, photocopying, recording or otherwise, without prior written permission being secured.
Requests for permission to reproduce should be addressed to either ISO at the address below or ISO’s
member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Reproduction may be subject to royalty payments or a licensing agreement.
Violators may be prosecuted.
ii © ISO 2014 – All rights reserved
---------------------- Page: 4 ----------------------
oSIST prEN ISO 17781:2015
Contents Page
Foreword . vii
Introduction . viii
1 Scope .1
2 Normative references .1
3 Terms, definitions and abbreviated terms .2
3.1 Terms and definitions .2
3.2 Abbreviated terms .3
4 Test methods .3
4.1 Microstructural examination .3
4.1.1 General .3
4.1.2 Preparation of specimen .3
4.1.3 Etching of specimens .4
4.1.4 Microstructural evaluation of specimens for intermetallic phases, and precipitations .5
4.2 Ferrite content measurement .8
4.2.1 Test standard and conditions .8
4.2.2 Acceptance criteria .8
4.2.3 Reporting .8
4.3 Charpy V-notch impact toughness test .9
4.3.1 Test standard and conditions .9
4.3.2 Acceptance criteria . 10
4.3.3 Reporting . 10
4.4 Corrosion test . 10
4.4.1 Test standard and conditions . 10
4.4.2 Preparation of test specimens . 11
4.4.3 Acceptance criteria . 11
4.4.4 Reporting . 11
5 Sampling of test specimens . 12
5.1 General . 12
5.2 Plates, seamless tubes and pipes, and wrought fittings . 12
5.3 Solution annealed welded pipes and fittings . 12
5.4 Bars . 12
5.5 Forgings . 13
5.5.1 General . 13
5.5.2 Branched forgings . 13
5.5.3 Flanges and other contour shaped forgings . 13
5.6 Hot isostatically-pressed (HIP) products . 13
5.7 Castings . 13
5.8 Welds in as welded condition . 14
6 Ferritescope measurements on product . 14
Annex A (informative) Chemical compositions of duplex stainless steels . 17
Bibliography . 18
6 © ISO 2014 – All rights reserved
---------------------- Page: 5 ----------------------
oSIST prEN ISO 17781:2015
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 17781 was prepared by Technical Committee ISO/TC 67, Materials, equipment and offshore structures
for petroleum, petrochemical and natural gas industries.
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oSIST prEN ISO 17781:2015
Introduction
Duplex stainless steels have a two phase microstructure consisting of austenite and ferrite. Ideally these
phases are present in equal proportions although in commercial alloys the ferrite phase volume fraction may
vary between 35 % and 60 % for products in the solution annealed condition. Duplex stainless steels have
roughly twice the strength of austenitic stainless steels with the same PREN value. Their resistance to
localised corrosion (i.e. pitting and crevice corrosion) is similar, but the resistance of the duplex grades to
chloride stress corrosion cracking is generally higher. They are characterized by high chromium
(19 % to 33 %) and low nickel contents compared to austenitic stainless steels.
Duplex stainless steels are more prone than austenitic steels to precipitation of nitrides and intermetallic
phases causing embrittlement and reduced corrosion resistance. The formation of intermetallic phases such
as Sigma and Chi occurs in the temperature range 590 °C to 950 °C (1 100 °F to 1 750 °F) and reformation of
ferrite occurs in the range 340 °C to 520 °C (650 °F to 975 °F). Exposure at these temperatures should
therefore be avoided. In normal heat treatment and welding operations the risk of embrittlement is low.
However, certain risks exist and consequently the thermal treatments required for manufacture and
fabrication, as well as the operation conditions, must take the reaction kinetics of phase formation into account
[4], [ 5]
to ensure that desired corrosion resistance and mechanical properties are obtained .
The mechanical properties, corrosion performance and hydrogen embrittlement properties of duplex stainless
steels require the control of the microstructure through application of appropriate manufacturing routes. The
microstructure of fabricated equipments is sensitive to the thermal-mechanical history associated with hot
working, solution annealing and with subsequent fabrication and welding.
Quality control testing should be specified to verify that components in these steel stainless grades are
manufactured, heat treated and fabricated within acceptable parameters and possess the required properties
for the relevant stainless steel grades.
This standard defines quality control testing methods, test conditions for the characterization of microstructure
in relation to relevant properties of ferritic/austenitic stainless steels and specifies corresponding
recommended acceptance criteria. The aim is to facilitate common testing requirements among the end users
enabling the manufacturers to apply the same test procedures for their clients.
This standard may be used to supplement other product related standards and specifications. As such the
standard should be applicable to a range of industrial users.
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oSIST prEN ISO 17781:2015
ISO/DIS 17781:2014(E)
Petroleum, petrochemical and natural gas industries — Test
methods for quality control of microstructure of
austenitic/ferritic (duplex) stainless steels
1 Scope
This ISO standard provides quality control testing methods, conditions and specifies acceptance criteria to be
used for the characterization of microstructure in relation to relevant properties in wrought, cast, hot
isostatically pressed and welded austenitic/ferritic (duplex) stainless steel components in the solution
annealed condition and fabrication welds. The standard considers “lean“, “standard“, “super“ and “hyper“
duplex grades.
The standard is based upon experience with duplex stainless steels in offshore oil and gas industry
applications including topside and subsea hydrocarbon service, sea water service as well as structural use.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 148-1, Metallic materials — Charpy pendulum impact test — Part 1: Test method
ISO 8249, Welding — Determination of ferrite number (FN) in austenitic and duplex ferritic-austenitic
Cr-Ni stainless steel weld metals
ISO 17025, General requirements for the competence of testing and calibration laboratories
ASTM A370, Standard test methods and definitions for mechanical testing of steel products
ASTM A1084, Standard test method for detecting detrimental phases in lean duplex austenitic/ferritic stainless
steels
ASTM E562, Standard test method for determining volume fraction by systematic manual point count
ASTM E1245, Standard practice for determining the inclusion or second-phase constituent content of metals
by automatic image analysis
ASTM G48, Standard test methods for pitting and crevice corrosion resistance of stainless steels and related
alloys by use of ferric chloride solution
AWS A4.2 Standard procedures for calibrating magnetic instruments to measure the delta ferrite content of
austenitic and duplex austenitic-ferritic stainless steel weld metal
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oSIST prEN ISO 17781:2015
3 Terms, definitions and abbreviated terms
For the purposes of this document, the following terms and definitions apply.
3.1 Terms and definitions
3.1.1
type 20Cr duplex Group A (lean duplex)
ferritic/austenitic stainless steel alloys with 24 ≤ PREN < 28
3.1.2
type 20Cr duplex Group B (lean duplex)
ferritic/austenitic stainless steel alloys with 28 ≤ PREN ≤ 30
3.1.3
type 22Cr duplex (standard duplex)
ferritic/austenitic stainless steel alloys with 30 < PREN < 40 and Cr ≥ 19,5 % (mass fraction)
3.1.4
type 25Cr duplex (super duplex)
ferritic/austenitic stainless steel alloys with 40 ≤ PREN < 48
3.1.5
type 27Cr duplex (hyper duplex)
ferritic/austenitic stainless steel alloys with 48 ≤ PREN ≤ 55
3.1.6
pitting resistance equivalent number
PREN
index, developed to reflect and predict the pitting resistance of a stainless steel, based upon the proportions of
Cr, Mo, W and N in the chemical composition of the alloy
Note 1 to entry: For the purposes of this part of this International Standard, all PREN limits specified in this
International Standard shall be considered absolute limits, as defined in ASTM E29. With the absolute method, an
observed value or a calculated value is not to be rounded, but is to be compared directly with the specified limiting value.
Conformance or non-conformance with the specification is based on this comparison.
Note 2 to entry: The PREN calculation is based on actual composition, not nominal composition. Nominal composition
is used for general classification only.
PREN W 3,3 W 0,5 W 16 W
Mo W
Cr N
where
W is the mass fraction of chromium in the alloy, expressed as a percentage of the total composition;
Cr
W is the mass fraction of molybdenum in the alloy ,expressed as a percentage of the total composition;
Mo
W is the mass fraction of tungsten in the alloy, expressed as a percentage of the total composition;
W
W is the mass fraction of nitrogen in the alloy, expressed as a percentage of the total composition.
N
Note 3 to entry: There are several variations of the PREN. All were developed to reflect and predict the pitting
resistance of Fe/Ni/Cr/Mo corrosion resistant stainless steels in the presence of dissolved chlorides and oxygen. e.g. in
sea water. Though useful, these indices are not directly indicative of corrosion resistance in H S-containing oil field
2
environments.
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oSIST prEN ISO 17781:2015
3.2 Abbreviated terms
HAZ heat affected zone
HIP hot isostatically-pressed
PREN pitting resistance equivalent number
RT room temperature
UNS unified numbering system
4 Test methods
Compliance with the chemical and mechanical requirements for the applicable product specification does not
necessarily indicate the absence of detrimental phases in the product or weldments made in duplex stainless
steel grades. Therefore additional testing is specified to verify that the manufacturing process and the final
quality heat treatment process are carried out under conditions that develop the required material properties
and expected formability and weldability of the product.
NOTE The presence of intermetallic phases such as Sigma and Chi laves, and nitride and carbide precipitates are
readily detected in all tests listed above when present in a certain amount. The test methods, conditions and acceptance
criteria established and presented within this standard are based upon experience with the use of type 22 and 25Cr duplex
grades in the oil and gas industry over the last 20 – 30 years.
Laboratory test methods for evaluation of the microstructure of duplex SS are as follows:
a) microstructural examination;
check for presence of intermetallic phases and precipitates;
ferrite content counting.
b) Charpy V-notch impact toughness testing;
c) Ferric chloride corrosion test; ASTM G48 Method A or ASTM A1084 (type 20Cr duplex).
There are several parameters of the material microstructure that can influence the test results and the use of
all three test methods as far as practical is necessary to demonstrate acceptable quality.
NOTE Preparation of metallographic specimens and subsequent etching procedures, Charpy V-notch impact
toughness testing and corrosion testing require the use of hazardous equipment, consumables and chemicals. Personnel
should be adequately trained. Facilities and procedures shall follow the relevant safety guidelines in place at the
laboratory.
4.1 Microstructural examination
4.1.1 General
Microstructural examinations should be carried out at an appropriately equipped test house, by trained and
experienced technicians and in accordance with established procedures in line with requirements of
ISO 17025 and the requirements specified by this ISO standard.
4.1.2 Preparation of specimen
Duplex stainless steels can be prepared according to standard metallographic methods (grinding and
polishing; manual or automated). The surface to be examined shall be free from any artefacts that may
interfere with the interpretation of the microstructure.
NOTE Guidance to metallographic preparation of stainless steels may be found in ASTM E3.
With mechanical polishing, a 1 μm diamond final polish or equivalent should be considered a minimum.
Preferably, a final oxide polish (e.g. colloidal silica/alumina) should be used.
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oSIST prEN ISO 17781:2015
Electro polishing may be used as an alternative to mechanical polishing.
4.1.3 Etching of specimens
There are several suitable methods for etching duplex stainless steels for metallographic examination, and it
is recommended to examine ASTM E407 for additional details.
NOTE 1 Identification and evaluation of non-metallic inclusions, cracks, pores etc. is best performed in the as-polished
condition. Metallographic samples should consequently be examined in a microscope prior to etching.
Performing the etching immediately after final polishing is recommended.
Examples of suitable etching methods are given in Table 1. These methods are generally applicable for all
commercially available duplex stainless steel alloys. Application recommendations are based on the ability to
reveal phases of interest, achieved contrast between constituents, consistency and ease of use. Exact
parameters are typically best established by trial and error, and may depend on factors such as cathode
material and area, geometry of the electrochemical cell, and specimen surface area and alloying content.
NOTE 2 The electrolytic etching techniques described are performed as direct current electrolysis with the specimen as
anode. Cathode material may be e.g. stainless steel or platinum. Electrical connection to the sample surface can be made
e.g. by touching it with a platinum (or other noble material) wire. Electrolytic etching generally provides more reproducible
and consistent results than chemical and colour etching alternatives. Uneven etching of the specimen surface is however
often encountered, generally with heavier etching near edges.
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oSIST prEN ISO 17781:2015
a
Table 1 — Examples of suitable etching methods for duplex stainless steels
ASTM E407
Method Composition Application of etching
Etchant No.
Electrolytic etching. Typically at 5 – 6 V for 5 – 60 s.
Lower voltages at longer times may also be used. Excellent for
10 g oxalic acid delineating microstructure.
10 % oxalic 13
100 ml H O Recommended for detecting nitride precipitates. May over-etch
2
intermetallic precipitates quite rapidly.
Poor contrast between austenite and ferrite phases.
Electrolytic etching. Typically at 1.5 – 3.0 V for 5 – 10 s.
Colours ferrite and intermetallic phases.
20 g NaOH Recommended for ferrite measurements and the detection of
b
20 % NaOH 220
intermetallic precipitates. Considered not applicable for
100 ml H2O
detection of nitrides.
Other solutions containing varying content of NaOH or KOH
may also be used with similar results.
5 ml HNO Etching performed at room temperature and up to 50 °C.
3
50 ml HCl Recommended etchant for detecting intermetallic phases and
V2A etchant 104 mod
nitride precipitates.
50 ml H O
2
To be used fresh and never be stored.
Combination of two above methods in sequence:
This combination has proven advantageous for achieving good
a) 10 % oxalic acid solution or V2A etchant; contrast between austenite and ferrite, and for the detection of
any intermetallic phases and chromium nitride precipitates.
b) 20 – 40 % NaOH/KOH solution.
Electrolytic etching. Typically at 1.0 – 2.0 V for 10 – 120 s
(with SS cathode).
60 ml HNO
3
60 % HNO 219 Highly sensitive to voltage and cathode material.
3
40 ml H O
2
Good for delineating microstructure. Reveals intermetallic
phases and nitride precipitates. Darkens ferrite slightly.
Use fresh.
Various modifications of etchant composition may be used.
10 g K Fe(CN)
3 6
At 20 °C: Reveals carbides after short times. May reveal
Murakami’s 98 10 g KOH
intermetallic phases (vaguely) after approx. 3 minutes.
100 ml H O
2
At 75 –100 °C: May reveal intermetallic phases clearly.
Etches/colours ferrite. Considered not applicable for detection
of nitrides.
Colour etching. Use fresh.
Immerse at room temperature until sample colouration is
0.5 – 1 g K SO observed.
2 5
Beraha’s 212 20 ml HCl HCl content may be varied depending in corrosion resistance of
alloy.
100 ml H O
2
Differentiates between austenite and ferrite.
Considered not applicable for detection of nitrides.
a
These recommendations only cover a limited selection of etchants. Numerous other etching procedures suitable for duplex stainless
steels may be found in published literature or acquired from other sources.
b
Other concentrations of NaOH or KOH solution may be used with same result. The conditions for etching should be adjusted and
qualified to verify acceptable results.
4.1.4 Microstructural evaluation of specimens for intermetallic phases, and precipitations
The microstructure shall be examined by optical microscopy at a magnification sufficient to observe the
presence of any intermetallic phases and/or nitride/carbide precipitates. The examination shall be carried out
over a range of magnifications across the full test specimen. For subsequent zooming in at locations with
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oSIST prEN ISO 17781:2015
(possible) intermetallic phases or precipitates or with the highest concentration of these, a higher
magnification is required. The assessment of the microstructure shall be made with a magnification
of 400 to 500 X.
The presence of intermetallic phases and/or nitride/carbide precipitates shall be noted and recorded with
micrographs representative of the location(s) with the highest concentration of intermetallic phases and the
locations with the highest concentration of nitride/carbide precipitates. If intermetallic phases and
nitride/carbide precipitates are not detected, a representative micrograph at or near mid wall thickness shall
be recorded. Micrographs should include a scale bar.
Products may contain centreline segregations aligned in stringers. Measurement of these should be
performed according to the concept of stringer length a through thickness cross-section transverse to the
rolling direction. The measurement should be performed at 200 X magnification and the sum of stringer
lengths in each measured field of view should be summed up and reported as a mean value. The following
two rules shall be used to divide stringers from each other.
if the length of the gap between two parts (particles or set of particles in a row) of a possible stringer
configuration is less than the length of one of the parts then this gap shall be considered a part of the
stringer. Otherwise the two parts should be considered as two separate stringers.
if a continuous gap is observed between two possibly parallel stringer configurations then each of them
should be considered as individual stringers.
The measurement principle is shown in Figure 1 and the measurement should be performed in the centre and
along the whole length of the micro sample (at least 15 mm).
Figure 1 — Assessment principle of centreline stringers in rolled products transverse
to rolling direction
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oSIST prEN ISO 17781:2015
The length of the accumluated stringers shall be calculated using the following Formula (1):
n
D fi
2
i 1
SI 0,5 mm/mm (1)
2
D
S n
4
where
SI is the stringer index;
D is the diameter, field of vision in mm;
S is the diameter, field of vision in scale divisions;
n is the total scanned fields;
n
fi is the sum of stringer lengths over n fields.
i 1
4.1.4.1 Acceptance criteria
The following acceptance criteria for intermetallic phases and precipitates are recommended for use.
a) intermetallic phases.
The microstructure shall be examined and assessed at 400 to 500 X magnificatio
...
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