EN ISO 7539-1:1995
(Main)Corrosion of metals and alloys - Stress corrosion testing - Part 1: General guidance on testing procedures (ISO 7539-1:1987)
Corrosion of metals and alloys - Stress corrosion testing - Part 1: General guidance on testing procedures (ISO 7539-1:1987)
Descsribes the general considerations which apply when designing and conducting tests to assess susceptibility of metals to stress corrosion. Particular methods of test are not treated in detail in this document. These are specified in the additional parts of ISO 7539.
Korrosion der Metalle und Legierungen - Prüfung der Spannungsrißkorrosion - Teil 1: Allgemeine Richtlinien für Prüfverfahren (ISO 7539-1:1987)
Dieser Teil von ISO 7539 beschreibt die allgemeinen Betrachtungen für die Planung und Durchführung von Prüfungen zur Beurteilung der Anfälligkeit von Metallen für Spannungsrißkorrosion. Anmerkung: Die einzelnen Verfahren sind in diesem Dokument nicht im Detail behandelt. Diese sind Gegenstand der weiteren Teile von ISO 7539.
Corrosion des métaux et alliages - Essais de corrosion sous contrainte - Partie 1: Guide général des méthodes d'essai (ISO 7539-1:1987)
La présente partie de l'ISO 7539 expose les considérations générales qui s'appliquent à la mise au point et à la réalisation des essais servant à évaluer la sensibilité à la corrosion sous contrainte.
NOTE -- Aucune méthode particulière n'est traitée en détail dans ce document. Voir pour cela les parties appropriées de l'ISO 7539.
Korozija kovin in zlitin – Ugotavljanje pokanja zaradi napetostne korozije - 1. del: Splošna navodila za postopke preskušanja (ISO 7539-1:1987)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
01-oktober-1999
Korozija kovin in zlitin – Ugotavljanje pokanja zaradi napetostne korozije - 1. del:
Splošna navodila za postopke preskušanja (ISO 7539-1:1987)
Corrosion of metals and alloys - Stress corrosion testing - Part 1: General guidance on
testing procedures (ISO 7539-1:1987)
Korrosion der Metalle und Legierungen - Prüfung der Spannungsrißkorrosion - Teil 1:
Allgemeine Richtlinien für Prüfverfahren (ISO 7539-1:1987)
Corrosion des métaux et alliages - Essais de corrosion sous contrainte - Partie 1: Guide
général des méthodes d'essai (ISO 7539-1:1987)
Ta slovenski standard je istoveten z: EN ISO 7539-1:1995
ICS:
77.060 Korozija kovin Corrosion of metals
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
ISO
INTERNATIONAL STANDARD
First edition
1987-08- 15
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION
ORGANISATION INTERNATIONALE DE NORMALISATION
MEXflYHAPOAHAR OPTAHM3A~MR fl0 CTAHAAPTM3A~MM
Corrosion of metals and alloys - Stress corrosion
testing -
Part 1 :
General guidance on testing procedures
Essais de corrosion sous contrainte -
Corrosion des m&aux et alliages -
Partie 1: Guide g&&al des mhthodes d’essai
Reference number
ISO 7539-1 : 1987 (E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of
national Standards bodies (ISO member bedies). The work of preparing International
Standards is normally carried out through ISO technical committees. Esch 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, govern-
mental and non-governmental, in liaison with ISO, also take part in the work.
Draft International Standards adopted by the technical committees are circulated to
the member bodies for approval before their acceptance as International Standards by
the ISO Council. They are approved in accordance with ISO procedures requiring at
least 75 % approval by the member bodies voting.
International Standard ISO 7539-1 was prepared by Technical Committee ISO/TC 156,
Corrosion of metals and alloys.
Users should note that all International Standards undergo revision from time to time
and that any reference made herein to any other International Standard implies its
latest edition, unless otherwise stated.
0 International Organkation for Standardization, 1987 l
Printed in Switzerland
INTERNATIONAL STANDARD ISO 7539-1: 1987 (E)
Corrosion of metals and alloys - Stress corrosion
testing -
Part 1 : .
General guidance on testing procedures
2.2 threshold stress (for stress corrosion) : The stress
0 lntroduction
above which stress corrosion Cracks initiate and grow, for the
specified test conditions.
This part of ISO 7539 gives general guidance on the selection,
use and interpretation of the significance of various test pro-
cedures that have been developed for the assessment of the
2.3 threshold stress intensity factor (for stress
resistance of metals and alloys to stress corrosion. These test
corrosion) : The stress intensity factor above which stress cor-
procedures are described in a series of additional Parts as
rosion Cracks will initiate, under conditions of high constraint to
follows :
plastic deformation, i.e. under plane strain predominant condi-
tions.
Part 2 : Preparation and use of bent-beam specimens.
2.4 test environment : Either a Service environment, or an
Part 3 : Preparation and use of U-bend specimens.
environment produced in the laboratory, to which the test
specimen is exposed and which is maintained constant or
Part 4 : Preparation and use of uniaxially loaded tension
varied in an agreed manner. In the case of stress corrosion the
specimens.
environment is often quite specific (see clause 6).
Part 5 : Preparation and use of C-ring specimens.
2.5 Start of test : The time when the stress is applied or
Part 6 : Preparation and use of pre-cracked specimens.
when the specimen is exposed to the test environment,
whichever occurs later.
Part 7 : Slow strain rate testing.
2.6 Crack initiation time : The period from the statt of a
test to the time when a Crack is detectable by the means
employed.
1 Scope and field of application
2.7 time to failure : The period elapsing between the Start
This part of ISO 7539 describes the general considerations
of a test and the occurrence of failure, the criterion of failure
which apply when designing and conducting tests to assess
being the first appearance of cracking or the total Separation of
susceptibility of metals to stress corrosion.
the test piece, or some agreed intermediate condition.
NOTE - Particular methods of test are not treated in detail in this
document. These are described in the additional Parts of ISO 7539.
2.8 slow strain rate test : A test involving controlled
extension or bending of the test specimen at a strain rate
usually in the region 10 -3 to IO-7 s -1. The strain is increased
either continuously or in Steps, but not cyclically.
2 Definitions
2.9 average Crack velocity : The maximum depth of
2.1 stress corrosion : Synergistic attack on a metal caused
crack(s) due to stress corrosion, divided by the test time.
by the simultaneous action of a corrosive environment and
nominally static tensile stress which usually results in the for-
mation of Cracks. This process frequently results in a significant 2.10 orientation : The direction of applied tensile stress of a
reduction of the load-bearing properties of metallic structures. test specimen with respect to some specified direction in the
product from which it was prepared, e.g. the rolling direction in
the plate.
NOTE - See stress corrosion cracking (3.1).
Iso 7539-1: 1987 (El
3.5 In the following clauses attention is drawn particularly to
3 Background
the fact that the stress corrosion process tan be extremely sen-
sitive to small changes in exposure or test conditions. The user
3.1 From the definition of stress corrosion (2.1) it is apparent of materials is responsible for selecting the conditions under
that stress corrosion cracking is a particular case of stress
which stress corrosion tests are performed and the fact that
corrosion and in some circumstances attack may not result in some tests are described in this International Standard does not
the formation of Cracks. Although it is generally agreed that
imply that these tests are the most appropriate ones for any
cracking is the usual result, other manifestations such as given Situation. The justification for describing these tests in a
intergranular corrosion or elongated fissures, which are Standard is that they are in widespread use and have been pro-
enhanced by the presence of stress, have also to be recog-
ven as valid for specific or common equipment-environment
nized. Systems. However, the responsibility for interpretation of the
test results remains with the user of materials and it is in no way
diminished by the’existence of this Standard.
Whilst recognizing that these differentes exist, for the purpose
of this document, which is concerned with test methods, the
terms “stress corrosion” and “stress corrosion cracking” tan
3.6 In addition to specific Parts of this International Standard
be regarded as being synonymous as is usually the case in
to cover the most widely used methods, it is considered that
corrosion literature.
this more general document, concerned with the selection of
test details and the interpretation of results, is required. In
preparing this Part, use has been made of an earlier review of
As far as this International Standard is concerned, all
the subject, updated where appropriate.
phenonema involving metal dissolution or the action of
hydrogen introduced into the metal as the result of
simultaneous effects of a corrosive environment and a tensile
4 Selection of test method
stress are included except for embrittlement by liquid metal and
exfoliation corrosion.
4.1 Before embarking on a Programme of stress corrosion
testing, a decision has to be made regarding which type of test
NOTE - A distinction should be made between local dissolution due
is appropriate. Such a decision depends largely upon the pur-
to deteriorations and those phenomena caused by hydrogen. The two
pose of the test and the information required. Whilst some
types of phenomena may be superimposed but cannot be confused
tests attempt to reproduce Service conditions as closely as
with a phenomenon directly imputable to deliberate hydrogen loading.
possible and are of value to the plant engineer, others may be
designed to study a mechanistic aspect of failure; In the
former, for example restrictions of material, space, time, etc.,
3.2 There exists a wide diversity of methods used for assess-
may mean the use of a relatively simple test procedure whereas
ing the stress corrosion properties of metals. Esch has its own
in other circumstances more sophisticated testing techniques
particular advantage in certain situations.
may be essential. Thus, studies of Crack propagation rates may
involve the use of pre-cracked specimens, although these may
be inappropriate when considering, for example, the effects of
3.3 Itis important to realize that the word “test” has a special
surface finish. Although a number of sophisticated techniques
meaning in the context of stress corrosion resistance or suscep-
are available, the adoption of a simple test may prove of great
tibility. Whether or not a stress corrosion process occurs in a
value in some circumstances when more elaborate techniques
given case depends on both the exposure conditions and the
cannot be used.
propetties of the material. The word “susceptibility” to stress
corrosion does not describe a material property or quality that
tan be located on a universally applicable scale, since the Order
4.2 When selecting a test method of the pass/fail type, it is
of merit of a given set of alloys may vary with exposure con-
important to realize that this should not be so severe that it
ditions.
leads to the condemnation of a material that would prove
adequate for a particular Service condition, nor should it be so
trifling as to encourage the use of a material in circumstances
3.4 Ideally, in Order to establish the risk of stress corrosion in
where rapid failure would ensue.
a given application, it is necessary to carry out Simulation >
testing under all likely Service exposure conditions. In practice
4.3 The aim of stress corrosion testing is usually to provide
this is difficult, if not impossible, and rarely achieved, but a
information more quickly than tan be obtained from Service ex-
number of “Standard tests” have been found as a result of
perience, but at the same time predictive of Service behaviour.
experience to provide reasonable guidance on likely Service
Among the most common approaches employed to achieve
behaviour for given specific applications. However, these
this are the use of higher stress, slow continuous straining, pre-
laboratory “Standard tests” are only appropriate to Service ton-
cracked specimens, higher concentration of species in test en-
ditions where experience has shown an appropriate relation-
vironment than in Service environment, increased temperature,
ship, however empirical, to exist. The fact that a given alloy
and electrochemical Stimulation. lt is important however, that
Passes or does not pass a test previously found useful in rela-
these methods be controlled in such a way that the details of
tion to another alloy may or may not be significant and a test
the failure mechanism are not changed.
that discriminates correctly between alloys used for a given
application will not necessarily provide safe guidance if the
exposure conditions are different. The use of a Standard test
4.4 If it is too difficult to reproduce the Service conditions
beyond the Point for which there is experience therefore
exactly, it may be useful to analyse the stress corrosion process
requires Validation.
in Order to determine as far as possible the main factors
ISO 75394 : 1987 (E)
5.2.5 Constant total strain tensile tests are sometimes pre-
operating at different stages. The stress corrosion test then
ferred to bend tests, thus simplifying both the application and
selected may involve only one step of the corrosion
calculation of the stress. However, the former require more
mechanism.
massive restraining frames than bend test specimens of similar
Cross-section.
5 Stressing Systems
5.2.6 The use of restraining frames may be avoided by
employing internally stressed specimens containing residual
5.1 General
Stresses as the result of inhomogeneous deformation. The lat-
ter may be introduced by plastic bending, e.g. by producing a
Methods of loading test pieces, whether initially plain, notched
bulge in sheet or plate material, or by welding, but such tests
or pre-cracked, tan be conveniently grouped according to
involve Problems in systematic Variation of the initial stress,
whether they invoive
which usually achieves maximum values in the region of the
yield stress. Moreover, elastic spring-back, in introducing
a) a constant total strain (see 5.2);
residual Stresses by bulging plate or partially flattening tube,
may Cause Problems and where welding is involved the struc-
b) a constant load (see 5.3); tural modifications may raise difficulties, unless the test is
simulative of a practical Situation.
c) an applied slow strain rate (see 5.4).
5.2.7 Constant total strain specimens are sometimes loaded
In the case of pre-cracked specimens, threshold conditions are
by being placed initially into conventional testing machines or
defined in terms of a stress intensity value Klscc and tests may
similar devices and then, whilst being maintained in their strain-
also be conducted under constant strain intensity conditions.
ed condition, having a restraining frame attached. When the
load applied by the testing machine is removed, the specimen
Knowledge of the limitations of the various methods is at least
remains stressed
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.