1、BRITISH STANDARD BS EN ISO 7539-4:1995 Incorporating Amendment No.1 Corrosion of metals and alloys Stress corrosion testing Part4: Preparation and use of uniaxially loaded tension specimens The European Standard EN ISO7539-4:1995 has the status of a BritishStandardBSENISO7539-4:1995 This BritishStan
2、dard, having been prepared under the directionof the Iron and Steel Standards Policy Committee andthe Non-ferrous Metals Standards Policy Committee, waspublished under the authorityof the Board of BSIandcomes into effect on 31 July1990 BSI04-2000 The following BSI references relate to the work on th
3、is standard: Committee reference ISM/NFM/8 Draft for comment88/36941DC ISBN 0 580 18794 2 Committees responsible for this BritishStandard The preparation of this BritishStandard was entrusted by the Iron and Steel Standards Policy Committee (ISM/-) and Non-ferrous Metals Standards Policy Committee (
4、NFM/-) to Technical Committee ISM/NFM/8, upon which the following bodies were represented: Aluminium Federation British Gas plc British Steel Industry Department of Trade and Industry (National Physical Laboratory) Department of Transport (Transport and Road Research Laboratory) Electricity Supply I
5、ndustry in England and Wales Institution of Corrosion Science and Technology Institution of Structural Engineers Society of Chemical Industry UnitedKingdom Atomic Energy Authority Welding Institute Amendments issued since publication Amd. No. Date Comments 8713 October 1995 Indicated by a sideline i
6、n the marginBSENISO7539-4:1995 BSI 04-2000 i Contents Page Committees responsible Inside front cover National foreword ii Foreword 2 Text of EN ISO 7539-4 3 Publications referred to Inside back coverBSENISO7539-4:1995 ii BSI 04-2000 National foreword This Part of BS EN ISO7539 has been prepared unde
7、r the direction of the Engineering Sector Board. It is identical with ISO7539-4:1989 Corrosion of metals and alloys Stress corrosion testing Part4: Preparation and use of uniaxially loaded tensions specimens, published by the International Organization for Standardization (ISO). BS EN ISO7539 compri
8、ses the following parts: Part1: General guidance on testing procedures; Part2: Preparation and use of bent-beam specimens; Part3: Preparation and use of U-bend specimens; Part4: Preparation and use of uniaxially loaded tension specimens; Part5: Preparation and use of C-ring specimens; Part6: Prepara
9、tion and use of pre-cracked specimens; Part7: Slow strain rate testing. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer im
10、munity from legal obligations. Cross-references International Standard Corresponding BritishStandard ISO6892:1994 BS EN10002 Tensile testing of metallic materials Part1:1990 Method of test ISO7539-1:1987 BS EN ISO7539 Corrosion of metals and alloys Stress corrosion testing Part1:1995 Guide to testin
11、g procedures (Identical) ISO7539-6:1989 Part6:1995 Preparation and use of pre-cracked specimens (Identical) Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, theEN ISO title page, pages2 to6, an inside back cover and a back cover. This standard has been upd
12、ated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO7539-4 May1995 ICS77.060 Descriptors: Metals, alloys, tests, corrosion tests, stress corrosion tests Eng
13、lish version Corrosion of metals and alloys Stress corrosion testing Part4: Preparation and use of uniaxially loaded tension specimens (ISO7539-4:1989) Corrosion des mtaux et alliages Essais de corrosion sous contrainte Partie4: Prparation et utilisation des prouvettes pour essais en traction uniaxi
14、ale (ISO7539-4:1989) Korrosion der Metalle und Legierungen Prfung der Spannungsrikorrosion Teil4: Vorbereitung und Anwendung von einachsig belasteten Zugproben (ISO7539-4:1989) This European Standard was approved by CEN on1995-04-08. CEN members are bound to comply with the CEN/CENELEC Internal Regu
15、lations 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 Central Secretariat or to any CEN member. This E
16、uropean 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 Central Secretariat has the same status as the official versions. CEN members are the n
17、ational standards bodies of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and UnitedKingdom. CEN European Committee for Standardization Comit Europen de Normalisation Europisches Komitee fr
18、Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 1995 All rights of reproduction and communication in any form and by any means reserved in all countries to CEN and its members. Ref. No. EN ISO7539-4:1995 EENISO7539-4:1995 BSI 04-2000 2 Foreword This European Standard has been taken
19、over by the Technical Committee CEN/TC262, Protection of metallic materials against corrosion, from the work of ISO/TC156, Corrosion of metals and alloys, of the International Organization for Standardization (ISO). This European Standard shall be given the status of a national standard, either by p
20、ublication of an identical text or by endorsement, at the latest by November1995, and conflicting national standards shall be withdrawn at the latest by November1995. According to the CEN/CENELEC Internal Regulations, the following countries are bound to implement this European Standard: Austria, Be
21、lgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, UnitedKingdom. Contents Page Foreword 2 1 Scope 3 2 Normative references 3 3 Definitions 3 4 Principle 3 5 Specimens 3 6 Procedure 4 7 Assessment of resul
22、ts 5 8 Test report 6ENISO7539-4:1995 BSI 04-2000 3 1 Scope 1.1 This part of ISO7539 covers procedures for designing, preparing and using uniaxially loaded tension test specimens for investigating the susceptibility of a metal to stress corrosion. The term “metal” as used in this part of ISO7539 incl
23、udes alloys. 1.2 Tension test specimens are adaptable for testing a wide variety of product forms, including plate, rod, wire, sheet and tubes, as well as parts joined by welding, riveting, or other methods. Notched specimens may also be used(see5.1.3). 1.3 Uniaxially loaded tensile specimens may be
24、 stressed quantitatively with equipment for application of either a constant load, a constant strain or an increasing load or strain. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this part of ISO7539. At the time of
25、 publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this part of ISO7539 are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registe
26、rs of currently valid International Standards. ISO6892:1984, Metallic materials Tensile testing. ISO7539-1:1987, Corrosion of metals and alloys Stress corrosion testing Part1: General guidance on testing procedures. ISO7539-6:1989, Corrosion of metals and alloys Stress corrosion testing Part6: Prepa
27、ration and use of pre-cracked specimens. 3 Definitions For the purposes of this part of ISO7539, the definitions given in ISO7539-1 are applicable. 4 Principle 4.1 The test consists in subjecting a specimen to constant load, constant strain or increasing load or strain with a view to determining str
28、ess corrosion susceptibility by reference to one or more of the parameters enumerated in clause7. 4.2 Corrosive environments may cause a deterioration of the properties of stressed materials beyond those observed with the same combination of environment and material when the latter is not subjected
29、to stress. This enhanced deterioration may be expressed in a number of different ways for the purpose of assessing stress corrosion susceptibility. 4.3 The commonest form of deterioration due to stress corrosion involves the initiation and growth of cracks, one or more of which may eventually lead t
30、o total failure of a specimen if the test is conducted for an appropriate time. In the absence of total failure, the mechanical properties of the specimens will be impaired by an amount depending upon the extent of crack development or the growth of pits or fissures. 4.4 Wide variations in test resu
31、lts 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 to different sizes or orientations or are subjected to different stressing pressures, test results may be even more va
32、riable. 5 Specimens 5.1 General 5.1.1 Specimens of constant cross-section may be circular, square, rectangular, annular or, in special cases, of other forms. 5.1.2 Specimens having tapered gauge lengths may be employed for the purpose of obtaining a range of initial stresses. 5.1.3 Tension specimens
33、 containing a machined notch or in which a mechanical pre-crack has been started may also be used. In the case of notched specimens, a triaxial stress state is present in the vicinity of the notch. In addition, the axial stress at the root of the notch will be greater than the nominal stress derived
34、 using the minimum cross-sectional area at the root of the notch. The maximum stress at the notch can be calculated from the product of this nominal stress and the stress concentration factor K Tfor the specific notch. Pre-cracked specimens are dealt with separately in ISO7539-6. 5.1.4 Finished prod
35、ucts may be tested in the manufactured condition by agreement between the parties. 5.1.5 The proportionality of machined specimens used for tensile testing in general is less important in stress corrosion testing, but for purposes of comparison it is desirable to use specimens as used for tensile te
36、sts complying with ISO6892.ENISO7539-4:1995 4 BSI 04-2000 5.1.6 To minimize stress concentration, whereby crack initiation may be facilitated, machined specimens should incorporate a transition radius between the gripped end and the parallel length, if these are of different dimensions. The value of
37、 this transition radius is at least as important in stress corrosion testing as in tensile testing in general and, unless otherwise specified, should conform to the requirements of the appropriate International Standard. Crack initiation may also be facilitated at sharp corners in specimens having s
38、uch cross-sections as square or rectangular if such corners are not appropriately rounded. 5.1.7 The gripped ends may be of any shape to suit the holders of the testing machine. Problems may arise unless the gripped portion of the specimen is isolated from the corrosive test environment(see6.3). 5.1
39、.8 A wide range of sizes of specimens is possible, depending primarily upon the dimensions of the product to be tested. Because the expression of the results from stress corrosion tests can be markedly influenced by the cross-sectional area of the specimen, this factor should be given careful consid
40、eration with regard to the object of the investigation. 5.1.9 The number of constant load test machines can be minimized by testing chains of specimens. These may be connected by loading links which are designed to prevent unloading on the failure of specimens. 5.1.10 Small cross-section specimens m
41、ay be used because they a) are directly related to product form; b) permit greater convenience in testing; c) usually give test results more quickly; d) usually have a greater sensitivity to the presence of small stress corrosion cracks. On the other hand, small cross-section specimens are more diff
42、icult to machine and their performance is more likely to be influenced by extraneous stress concentrations resulting from non-axial loading, corrosion pits or other forms of attack, for example general corrosion. In the case of machined specimens, dimensions greater than10mm in gauge length and3,0mm
43、 in section are preferred. 5.2 Preparation of specimens 5.2.1 The pronounced effect of surface conditions on the time required to initiate stress corrosion cracking in certain combinations of metal and environment is well established. Of particular importance is the avoidance of stress concentration
44、s, machining damage and chemical contamination. Unless it is desired to evaluate the as-supplied or as-fabricated surface, the final preparation usually preferred is a mechanical process followed by degreasing. Stress intensification at surface irregularities is usually more important in the initiat
45、ion of stress corrosion cracks in high strength alloys than in lower strength, ductile alloys, but a surface quality of14m root mean square or better should always be the aim. 5.2.2 Care should be taken to avoid over-heating or excessive pressure during the final preparation, which may otherwise ind
46、uce residual stresses or metallurgical changes in the surface. Post-preparation heat treatment, chemical polishing or electro-polishing may be appropriate to overcome such effects in some cases. Care should also be taken to minimize contamination of the surface by polishing residues. 5.2.3 It should
47、 not be assumed that electropolishing will invariably give the correct results, i.e.devoid of the problems mentioned above deriving from mechanical preparation of surfaces. 5.2.4 If the final surface preparation involves a chemical treatment, care must be taken to ensure that the conditions used do
48、not result in selective phase attack on the metal or leave a deposit of undesirable residues on the surface. 5.2.5 Chemical or electrochemical treatments that generate hydrogen must not be used on materials that are susceptible to hydrogen-induced damage. 5.2.6 Where it is necessary to mark the spec
49、imen for purposes of identification, the methods given in ISO7539-1 should be followed. 6 Procedure 6.1 The environmental testing conditions selected depend upon the purpose of the test but, ideally, should be the same as those prevailing for the intended use of the alloy or comparable to the anticipated service condition. In practice, a number of standard environments are used for ranking purposes, but the results obtained require cautious interpretation in relation to the anticipated service conditions.ENISO7539-4:1995 BSI 04-2000 5 6.
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