Corrosion of metals and alloys - Stress corrosion testing - Part 10: Reverse U-bend method (ISO 7539-10:2020)

This document specifies procedures for designing, preparing and using reversed U-bend (RUB) test
specimens for investigating the susceptibility of the metal to stress corrosion cracking. The term
“metal” as used in this document includes alloys.

Korrosion der Metalle und Legierungen - Prüfung der Spannungsrisskorrosion - Teil 10: Vorbereitung und Anwendung von reversierten Bügelproben (ISO 7539-10:2020)

Dieses Dokument legt die Verfahrensweisen für die Planung, Vorbereitung und Anwendung von reversierten  Bügelproben (RUB Proben; en: Reversed U bend) bei Prüfungen zur Ermittlung der Anfälligkeit von Metallen gegenüber Spannungsrisskorrosion fest. Der in diesem Dokument verwendete Begriff „Metall“ umfasst Legierungen.

Corrosion des métaux et alliages - Essais de corrosion sous contrainte - Partie 10: Méthode d'essai par cintrage en U inversé (ISO 7539-10:2020)

Le présent document spécifie les modes opératoires de conception, de préparation et d'utilisation d'éprouvettes d'essai cintrées en U invers (RUB, aussi dénommées « selles de cheval ») permettant d'étudier la sensibilité du métal à la corrosion fissurante sous contrainte. Pour les besoins du présent document, le terme « métal » inclut également les alliages.

Korozija kovin in zlitin - Ugotavljanje pokanja zaradi napetostne korozije - 10. del: Reverzna metoda "U-upognjenci" (ISO 7539-10:2020)

General Information

Status
Published
Public Enquiry End Date
09-Oct-2019
Publication Date
16-Jun-2020
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
08-Jun-2020
Due Date
13-Aug-2020
Completion Date
17-Jun-2020

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SLOVENSKI STANDARD
SIST EN ISO 7539-10:2020
01-julij-2020
Nadomešča:
SIST EN ISO 7539-10:2015

Korozija kovin in zlitin - Ugotavljanje pokanja zaradi napetostne korozije - 10. del:

Reverzna metoda "U-upognjenci" (ISO 7539-10:2020)

Corrosion of metals and alloys - Stress corrosion testing - Part 10: Reverse U-bend

method (ISO 7539-10:2020)

Korrosion der Metalle und Legierungen - Prüfung der Spannungsrisskorrosion - Teil 10:

Vorbereitung und Anwendung von reversierten Bügelproben (ISO 7539-10:2020)

Corrosion des métaux et alliages - Essais de corrosion sous contrainte - Partie 10:

Méthode d'essai par cintrage en U inversé (ISO 7539-10:2020)
Ta slovenski standard je istoveten z: EN ISO 7539-10:2020
ICS:
77.060 Korozija kovin Corrosion of metals
SIST EN ISO 7539-10:2020 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN ISO 7539-10:2020
---------------------- Page: 2 ----------------------
SIST EN ISO 7539-10:2020
EN ISO 7539-10
EUROPEAN STANDARD
NORME EUROPÉENNE
May 2020
EUROPÄISCHE NORM
ICS 77.060 Supersedes EN ISO 7539-10:2014
English Version
Corrosion of metals and alloys - Stress corrosion testing -
Part 10: Reverse U-bend method (ISO 7539-10:2020)

Corrosion des métaux et alliages - Essais de corrosion Korrosion der Metalle und Legierungen - Prüfung der

sous contrainte - Partie 10: Méthode d'essai par Spannungsrisskorrosion - Teil 10: Vorbereitung und

cintrage en U inversé (ISO 7539-10:2020) Anwendung von reversierten Bügelproben (ISO 7539-

10:2020)
This European Standard was approved by CEN on 10 May 2020.

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, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,

Poland, Portugal, Republic of North Macedonia, 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: Rue de la Science 23, B-1040 Brussels

© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 7539-10:2020 E

worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST EN ISO 7539-10:2020
EN ISO 7539-10:2020 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

---------------------- Page: 4 ----------------------
SIST EN ISO 7539-10:2020
EN ISO 7539-10:2020 (E)
European foreword

This document (EN ISO 7539-10:2020) has been prepared by Technical Committee ISO/TC 156

"Corrosion of metals and alloys" in collaboration with Technical Committee CEN/TC 262 “Metallic and

other inorganic coatings, including for corrosion protection and corrosion testing of metals and alloys”

the secretariat of which is held by BSI.

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 November 2020, and conflicting national standards

shall be withdrawn at the latest by November 2020.

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.

This document supersedes EN ISO 7539-10:2014.

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, France, Germany, Greece, Hungary, Iceland,

Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of

North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the

United Kingdom.
Endorsement notice

The text of ISO 7539-10:2020 has been approved by CEN as EN ISO 7539-10:2020 without any

modification.
---------------------- Page: 5 ----------------------
SIST EN ISO 7539-10:2020
---------------------- Page: 6 ----------------------
SIST EN ISO 7539-10:2020
INTERNATIONAL ISO
STANDARD 7539-10
Second edition
2020-05
Corrosion of metals and alloys —
Stress corrosion testing —
Part 10:
Reverse U-bend method
Corrosion des métaux et alliages — Essais de corrosion sous
contrainte —
Partie 10: Méthode d'essai par cintrage en U inversé
Reference number
ISO 7539-10:2020(E)
ISO 2020
---------------------- Page: 7 ----------------------
SIST EN ISO 7539-10:2020
ISO 7539-10:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
---------------------- Page: 8 ----------------------
SIST EN ISO 7539-10:2020
ISO 7539-10:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Principle ........................................................................................................................................................................................................................ 1

5 Specimens .................................................................................................................................................................................................................... 2

5.1 General ........................................................................................................................................................................................................... 2

5.2 Preparation of RUB specimens .................................................................................................................................................. 2

5.2.1 Tubing and piping ........................................................................................................................................................... 2

5.2.2 Other products ................................................................................................................................................................... 2

5.2.3 Reverse U-bending process .................................................................................................................................... 3

5.3 Fastening RUB specimens with a loading bolt ............................................................................................................. 3

6 Experimental procedure .............................................................................................................................................................................. 3

7 Post-exposure evaluation ............................................................................................................................................................................ 4

8 Test report ................................................................................................................................................................................................................... 5

Annex A (informative) Preparation of non-pre-strained half tube RUB specimens ............................................6

Annex B (informative) Preparation of RUB specimens with a gauge section .............................................................9

Bibliography .............................................................................................................................................................................................................................15

© ISO 2020 – All rights reserved iii
---------------------- Page: 9 ----------------------
SIST EN ISO 7539-10:2020
ISO 7539-10:2020(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 of 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 www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 156, Corrosion of metals and alloys, in

collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/

TC 262 Metallic and other inorganic coatings, including for corrosion protection and corrosion testing of

metals and alloys, in accordance with the Agreement on technical cooperation between ISO and CEN

(Vienna Agreement).

This second edition cancels and replaces the first edition (ISO 7539-10:2013), which has been technically

revised. The main changes compared with the previous edition are as follows:

— the specimen preparation, i.e. how RUB specimens are machined, bent and fastened, has been

revised in Clause 5 and Annexes A and B;

— the experimental procedure of how specimens are tested in a multiple immersion test with different

periods or in a serial immersion test has been revised in Clause 6;

— the post-exposure evaluation of how specimens are observed has been revised in Clause 7;

— information has been added for the test report in Clause 8;
— Figures A.1, A.2 and B.3 and Table B.1 have been revised;

— new Figures A.3 and B.4 have been added to illustrate the RUB specimen before and after fastening.

A list of all parts in the ISO 7539 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2020 – All rights reserved
---------------------- Page: 10 ----------------------
SIST EN ISO 7539-10:2020
INTERNATIONAL STANDARD ISO 7539-10:2020(E)
Corrosion of metals and alloys — Stress corrosion
testing —
Part 10:
Reverse U-bend method

WARNING — This document can involve hazardous materials, operations and equipment. It is

the responsibility of the user of this document to consult and establish appropriate safety and

health practices and to determine the applicability of regulatory limitations prior to use.

1 Scope

This document specifies procedures for designing, preparing and using reversed U-bend (RUB) test

specimens for investigating the susceptibility of the metal to stress corrosion cracking. The term

“metal” as used in this document includes alloys.
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 7539-1, Corrosion of metals and alloys — Stress corrosion testing — Part 1: General guidance on testing

procedures

ISO 8407, Corrosion of metals and alloys — Removal of corrosion products from corrosion test specimens

3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 7539-1 apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
4 Principle

The RUB test is a particularly severe test for assessing susceptibility to stress corrosion cracking.

The test is intended primarily for application to metals with high corrosion resistance, such as Ni-

based alloys, with the advantage, compared to methods such as the conventional U-bend test, of

having significantly less stress relaxation. It is used primarily as a screening test for tubing, piping,

plate, bar and other products including welded materials. It may also be used as an acceptance test for

performance in service subject to agreement between the parties.

The principle of the test is to introduce very severe stresses in a high corrosion resistance metal, with

minimum relaxation, in order to enhance the likelihood of inducing stress corrosion cracking.

The test involves exposing a piece of metal of a semi-circular section bent back on itself (i.e. reversed

bent) into a U-shape to the corroding medium and holding it in a manner that ensures that there are

initial tensile stresses in excess of the yield strength over a large proportion of the inner surface. The

© ISO 2020 – All rights reserved 1
---------------------- Page: 11 ----------------------
SIST EN ISO 7539-10:2020
ISO 7539-10:2020(E)

test is accelerated by the presence of complex bi-axial stresses that may or may not exist in service. In

the act of forming specimens, varying amounts of cold work may be introduced, and this deformation

can influence the stress corrosion cracking tendency as compared to that of the material in the original

condition.

The test is normally performed in a laboratory by exposing the specimens to simulated service

conditions.

A further objective of the test is to compare and evaluate the influence of different material parameters.

The principal advantages of the test are its simplicity and its ability to provide a rapid screening. If

conventional U-bend or C-ring specimens are used for screening tests in a high temperature solution of

573 K or higher, marked stress relaxation occurs and a long testing time is needed for the evaluation.

However, the stress relaxation in RUB specimens is smaller than that in conventional U-bend and C-ring

specimens, due to the bi-axial stresses in RUB specimens. Therefore, screening tests can be done within

a relatively short time through the use of RUB specimens.

A disadvantage is that the stress state is complicated and is difficult to quantify with accuracy. If an

accurate stress state is desired, an alternative method should be used.

Wide variations in test results can be obtained for a given metal and environment even when testing

nominally identical specimens and the replication of tests is frequently necessary.

If specimens are prepared from tubing of different dimensions or are subjected to different stressing

procedures, test results can be even more variable.
5 Specimens
5.1 General

RUB specimens are prepared from pieces of production tubing, piping and other hollow cylindrical

products cut into half longitudinally or from a plate, bar or other products formed into a semi-circular

shape along the axial direction. The specimens should be cut by sawing or other such methods that do

not affect the material properties. Then they should be shaped into their dimensions by machining. The

side face of the specimens should be deburred and then finished by sequentially coarse-to-fine grinding

using abrasive papers or cloths to a su
...

SLOVENSKI STANDARD
oSIST prEN ISO 7539-10:2019
01-oktober-2019

Korozija kovin in zlitin - Ugotavljanje pokanja zaradi napetostne korozije - 10. del:

Reverzna metoda "U-upognjenci" (ISO/DIS 7539-10:2019)

Corrosion of metals and alloys - Stress corrosion testing - Part 10: Reverse U-bend

method (ISO/DIS 7539-10:2019)

Korrosion der Metalle und Legierungen - Prüfung der Spannungsrisskorrosion - Teil 10:

Vorbereitung und Anwendung von reversierten Bügelproben (ISO/DIS 7539-10:2019)

Corrosion des métaux et alliages - Essais de corrosion sous contrainte - Partie 10:

Méthode d'essai par cintrage en U inversé (ISO/DIS 7539-10:2019)
Ta slovenski standard je istoveten z: prEN ISO 7539-10
ICS:
77.060 Korozija kovin Corrosion of metals
oSIST prEN ISO 7539-10:2019 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
oSIST prEN ISO 7539-10:2019
---------------------- Page: 2 ----------------------
oSIST prEN ISO 7539-10:2019
DRAFT INTERNATIONAL STANDARD
ISO/DIS 7539-10
ISO/TC 156 Secretariat: SAC
Voting begins on: Voting terminates on:
2019-07-22 2019-10-14
Corrosion of metals and alloys — Stress corrosion
testing —
Part 10:
Reverse U-bend method
Corrosion des métaux et alliages — Essais de corrosion sous contrainte —
Partie 10: Méthode d'essai par cintrage en U inversé
ICS: 77.060
THIS DOCUMENT IS A DRAFT CIRCULATED
This document is circulated as received from the committee secretariat.
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
ISO/CEN PARALLEL PROCESSING
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 7539-10:2019(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 2019
---------------------- Page: 3 ----------------------
oSIST prEN ISO 7539-10:2019
ISO/DIS 7539-10:2019(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2019

All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved
---------------------- Page: 4 ----------------------
oSIST prEN ISO 7539-10:2019
ISO/DIS 7539-10:2019(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative reference ......................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Principle ........................................................................................................................................................................................................................ 1

5 Specimens .................................................................................................................................................................................................................... 2

5.1 General ........................................................................................................................................................................................................... 2

5.2 Preparation of RUB specimens .................................................................................................................................................. 2

5.3 Fastening RUB specimens with a loading bolt ............................................................................................................. 3

6 Experimental procedure .............................................................................................................................................................................. 3

7 Post-exposure evaluation ............................................................................................................................................................................ 4

8 Test report ................................................................................................................................................................................................................... 5

Annex A (informative) Preparation of non-pre-strained half tube RUB specimens ............................................6

Annex B (informative) Preparation of RUB specimens with a gauge section .............................................................9

© ISO 2019 – All rights reserved iii
---------------------- Page: 5 ----------------------
oSIST prEN ISO 7539-10:2019
ISO/DIS 7539-10:2019(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 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: www .iso .org/iso/foreword .html.

The committee responsible for this document is ISO/TC 156, Corrosion of metals and alloys.

ISO 7539 consists of the following parts, under the general title Corrosion of metals and alloys — Stress

Corrosion testing:
— Part 1: General guidance on testing procedures
— Part 2: Preparation and use of bent-beam specimens
— Part 3: Preparation and use of U-bend specimens

— Part 4: Method for the preparation and use of uniaxially loaded tension specimens

— Part 5: Preparation and use of C-ring specimens

— Part 6: Preparation and use of pre-cracked specimens for tests under constant load or constant

displacement
— Part 7: Method for slow strain rate testing
— Part 8: Preparation and use of specimens to evaluate weldments

— Part9: Preparation and use of pre-cracked specimens for tests under rising load or rising

displacement
— Part 10: Reverse U-bend test method

— Part 11: Guidelines for testing the resistance of metals and alloys to hydrogen embrittlement and

hydrogen-assisted cracking
iv © ISO 2019 – All rights reserved
---------------------- Page: 6 ----------------------
oSIST prEN ISO 7539-10:2019
DRAFT INTERNATIONAL STANDARD ISO/DIS 7539-10:2019(E)
Corrosion of metals and alloys — Stress corrosion
testing —
Part 10:
Reverse U-bend method

WARNING — This International Standard may involve hazardous materials, operations, and

equipment. It is the responsibility of whoever uses this standard to consult and establish

appropriate safety and health practices and determine the applicability of regulatory limitations

prior to use.
1 Scope

This part of ISO 7539 covers procedures for designing, preparing and using reversed U-bend (RUB)

test specimens for investigating the susceptibility of the metal to stress corrosion cracking. The term

“metal” as used in this standard includes alloys.
2 Normative reference

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies. Members

of IEC and ISO maintain registers of currently valid International Standards.

ISO 7539-1, Corrosion of metals and alloys — Stress corrosion testing — Part 1: General guidance on testing

procedures

ISO 8407, Corrosion of metals and alloys — Removal of corrosion products from corrosion test specimens

ISO 3366, Coated abrasives — Abrasive rolls
ISO 21948, Coated abrasives — Plain sheets
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 7539-1 apply.

4 Principle

The RUB test is a particularly severe test for assessing susceptibility to stress corrosion cracking. The

test is intended primarily for application to metals with high corrosion resistance, such as Ni-based

alloys, with the advantage compared to methods such as the conventional U-bend test of having

significantly less stress relaxation. It is used primarily as a screening test for tubing, piping, plate,

bar and other products including welded materials. It may also be used as an acceptance test for

performance in service subject to agreement between the parties.

The principle of the test is to introduce very severe stresses in a high corrosion resistance metal, with

minimum relaxation, in order to enhance the likelihood of inducing stress corrosion cracking.

The test consists of exposing to the corroding medium a piece of metal of semi-circular section bent

back on itself (i.e. reversed bent) into a U-shape and held in a manner which ensures that there are

initial tensile stresses in excess of the yield strength over a large proportion of the inner surface. The

© ISO 2019 – All rights reserved 1
---------------------- Page: 7 ----------------------
oSIST prEN ISO 7539-10:2019
ISO/DIS 7539-10:2019(E)

test is accelerated by the presence of complex bi-axial stresses that may or may not exist in service. In

the act of forming specimens, varying amounts of cold work may be introduced and this deformation

may influence the stress corrosion cracking tendency as compared to that of the material in the original

condition.

The test is normally performed in the laboratory by exposing the specimens to simulated service

conditions.

A further objective of the test is to compare and evaluate the influence of different material parameters.

The principal advantages of the test are its simplicity and its ability to provide rapid screening: if

conventional U-bend or C-ring specimens are used for screening tests in high temperature solution as

573 K or higher, marked stress relaxation occurs and a long testing time is needed for the evaluation.

However, the stress relaxation in RUB specimens is smaller than that in conventional U-bend and C-ring

specimens, due to the bi-axial stresses in RUB specimens. Therefore, screening tests can be done within

a relatively short time through the use of RUB specimens.

A disadvantage is that the stress state is complicated and is difficult to quantify with accuracy. If an

accurate stress state is desired an alternative method should be used.

Wide variations in test results may be obtained for a given metal and environment even when testing

nominally identical specimens and the replication of tests is frequently necessary.

If specimens are prepared from tubing of different dimensions or are subjected to different stressing

procedures test results may be even more variable.
5 Specimens
5.1 General

RUB specimens are prepared from pieces of production tubing, piping and other hollow cylindrical

products cut into half longitudinally or from plate, bar or other products formed into a semi-circular

shape along the axial direction. The specimens should be cut by sawing or other such methods that do

not affect material properties, and then they should be shaped into their dimensions by machining. The

side face of the specimens should be deburred and then finished by sequentially coarse-to-fine grinding

using abrasive papers or cloths to a surface finish such as P600 (ISO 3366 or ISO 21948) without

increasing the temperature of the specimens.

Two-stage stressing consisting of bending and fastening with a loading bolt should be performed for RUB

specimens. Elastic-stress relief should be avoided during fastening RUB specimens with a loading bolt.

5.2 Preparation of RUB specimens
5.2.1 Tubing and piping

A variety of tube dimensions and specimen size s can be employed. The tube is cut to selected specimen

lengths and then sectioned axially to produce specimens with a semi-circular section.

The tubing shall retain its original surface finish.

If heat treatment is added, final heat treatment shall be performed before the reverse U-bending process

(and pre-straining if this is adopted).
5.2.2 Other products

A variety of bar stock, plate and other forged or rolled material or welded material can be employed.

These materials shall be machined into a plate after final heat treatment and pressed into a semi-

circular shape between inner and other formers. The surface of the specimens shall be finished by

sequentially coarse-to-fine grinding using abrasive papers or clothes up to a surface finish such as

2 © ISO 2019 – All rights reserved
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oSIST prEN ISO 7539-10:2019
ISO/DIS 7539-10:2019(E)
P600 (ISO 3366 or ISO 21948) without increasing the
...

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