BS EN 16602-70-36:2014 BSI Standards Publication Space product assurance — Material selection for controlling stress-corrosion cracking BS EN 16602-70-36:2014 BRITISH STANDARD National foreword This British Standard is the UK implementation of EN 16602-70-36:2014 It supersedes BS EN 14101:2001 which is withdrawn The UK participation in its preparation was entrusted to Technical Committee ACE/68, Space systems and operations A list of organizations represented on this committee can be obtained on request to its secretary This publication does not purport to include all the necessary provisions of a contract Users are responsible for its correct application © The British Standards Institution 2014 Published by BSI Standards Limited 2014 ISBN 978 580 84600 ICS 49.140 Compliance with a British Standard cannot confer immunity from legal obligations This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 November 2014 Amendments/corrigenda issued since publication Date Text affected EN 16602-70-36 EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM October 2014 ICS 49.025.01; 49.140 Supersedes EN 14101:2001 English version Space product assurance - Material selection for controlling stress-corrosion cracking Assurance produit des projets spatiaux - Sélection des matériaux en vue d'éviter leur fissuration par corrosion sous contrainte Raumfahrtproduktsicherung - Kriterien für die Werkstoffwahl zur Vermeidung von Spannungsrisskorrosion This European Standard was approved by CEN on 11 April 2014 CEN and CENELEC 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 and CENELEC 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 and CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions CEN and CENELEC members are the national standards bodies and national electrotechnical committees 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, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels © 2014 CEN/CENELEC All rights of exploitation in any form and by any means reserved worldwide for CEN national Members and for CENELEC Members Ref No EN 16602-70-36:2014 E BS EN 16602-70-36:2014 EN 16602-70-36:2014 (E) Table of contents Foreword Scope Normative references Terms, definitions and abbreviated terms 3.1 Terms from other standards 3.2 Terms specific to the present standard .8 3.3 Abbreviated terms Principles 4.1 Stress corrosion 4.2 Evaluation of metal alloys Requirements 10 5.1 5.2 Stress corrosion cracking resistance evaluation of metal alloys 10 5.1.1 Overview 10 5.1.2 Requirements for case 10 5.1.3 Requirements for Case 11 Materials selection criteria 11 5.2.1 General .11 5.2.2 High SCC resistance alloys 11 5.2.3 Moderate SCC resistance alloys 12 5.2.4 Low SCC resistance alloys 12 5.2.5 Unlisted materials .13 5.3 Design and assembly .13 5.4 Customer’s approval .13 Annex A (normative) Request for SCC resistance evaluation - DRD 23 A.1 A.2 DRD identification 23 A.1.1 Requirement identification and source document 23 A.1.2 Purpose and objective .23 Expected response 23 A.2.1 Scope and content 23 BS EN 16602-70-36:2014 EN 16602-70-36:2014 (E) A.2.2 Special remarks 23 Annex B (normative) SCC resistance test specifications and procedures (Work Proposal) - DRD 24 B.1 B.2 DRD identification 24 B.1.1 Requirement identification and source document 24 B.1.2 Purpose and objective .24 Expected response 24 B.2.1 Scope and content 24 B.2.2 Special remarks 24 Annex C (normative) Stress-corrosion evaluation form (SCEF) - DRD 25 C.1 C.2 DRD identification 25 C.1.1 Requirement identification and source document 25 C.1.2 Purpose and objective .25 Expected response 25 C.2.1 Scope and content 25 C.2.2 Special remarks 29 Annex D (informative) Grain orientation 31 D.1 Introduction .31 D.2 Anisotropy of grain orientation 31 Annex E (informative) SCC resistance of alloys 35 E.1 Stress corrosion susceptibility 35 E.2 Metal alloys 36 E.2.1 Aluminium 36 E.2.2 Steel 36 E.2.3 Nickel 36 E.2.4 Copper 36 Annex F (informative) Stress sources 38 F.1 Introduction .38 F.2 Stress sources 38 Bibliography 39 Figures Figure C-1 : Example of a Stress-corrosion evaluation form 29 Figure D-1 : Grain orientations in standard wrought forms 32 BS EN 16602-70-36:2014 EN 16602-70-36:2014 (E) Figure D-2 : Examples of tensile stresses in short transverse direction applied during assembly 33 Figure D-3 : Examples of tensile stresses in short transverse direction resulting from assembly 34 Figure E-1 : Typical residual stress distributions in 7075 Aluminium alloys 37 Tables Table 5-1: Alloys with high resistance to stresscorrosion cracking 14 Table 5-2: Alloys with moderate resistance to stresscorrosion cracking 18 Table 5-3: Alloys with low resistance to stresscorrosion cracking 20 Table F-1 : Sources of stress 38 BS EN 16602-70-36:2014 EN 16602-70-36:2014 (E) Foreword This document (EN 16602-70-36:2014) has been prepared by Technical Committee CEN/CLC/TC “Space”, the secretariat of which is held by DIN This standard (EN 16602-70-36:2014) originates from ECSS-Q-ST-70-36C 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 April 2015, and conflicting national standards shall be withdrawn at the latest by April 2015 Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights This document supersedes EN 14101:2001 This document has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association This document has been developed to cover specifically space systems and has therefore precedence over any EN covering the same scope but with a wider domain of applicability (e.g : aerospace) 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, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom BS EN 16602-70-36:2014 EN 16602-70-36:2014 (E) Scope This Standard covers the following processes of the general materials, mechanicals parts and processes (MMPP) flow of ECSS-Q-ST-70: • The selection of metal alloys for which preference is given to approved data sources (Table 5-1 to Table 5-3) • The criticality analysis to determine if a stress corrosion cracking (SCC) evaluation is necessary This Standard sets forth the criteria to be used in the selection of materials for spacecraft and associated equipment and facilities so that failure resulting from stress-corrosion is prevented It is intended to provide general criteria to be used in stress-corrosion cracking control, which begins during design thanks to a methodological material selection This document does not intend to include all factors and criteria necessary for the total control of stresscorrosion cracking in all alloys The criteria established in this Standard are only applicable to designs for service involving exposure conditions similar to testing conditions As regards weldments, this Standard is applicable to aluminium alloys, selected stainless steels in the 300 series and alloys listed in Table 5-1 This Standard is not applicable to listed materials whose behaviour differs at elevated temperature and in specific chemical This standard may be tailored for the specific characteristic and constrains of a space project in conformance with ECSS-S-ST-00 BS EN 16602-70-36:2014 EN 16602-70-36:2014 (E) Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this ECSS Standard For dated references, subsequent amendments to, or revision of any of these publications not apply, However, parties to agreements based on this ECSS Standard are encouraged to investigate the possibility of applying the more recent editions of the normative documents indicated below For undated references, the latest edition of the publication referred to applies EN reference Reference in text Title EN 16601-00-01 ECSS-S-ST-00-01 ECSS system - Glossary of terms EN 16602-70 ECSS-Q-ST-70 Space product assurance - Materials, mechanical parts and processes EN 16602-70-37 ECSS-Q-ST-70-37 Space product assurance - Determination of the susceptibility of metals to stress-corrosion cracking NASA-MSFC-SPEC 522B (July 1987) Design criteria for controlling stress-corrosion cracking BS EN 16602-70-36:2014 EN 16602-70-36:2014 (E) Terms, definitions and abbreviated terms 3.1 Terms from other standards For the purpose of this Standard, the terms and definitions from ECSS-ST-00-01 and ECSS-Q-ST-70 apply 3.2 Terms specific to the present standard 3.2.1 stress-corrosion combined action of sustained tensile stress and corrosion that can lead to the premature failure of materials 3.3 Abbreviated terms For the purpose of this Standard, the abbreviated terms from ECSS-S-ST-00-01 and the following apply: Abbreviation Meaning SCC stress-corrosion cracking SCEF stress-corrosion evaluation form BS EN 16602-70-36:2014 EN 16602-70-36:2014 (E) b a a a If more pertinent, the basic function of the assembly shall be listed in replacement of the basic function of the part Effect of failure The possible effects of the failure of the part or assembly on the overall function or mission of the major assembly involved shall be listed Evaluation of stresscorrosion susceptibility The SCEF shall contain the rationale underlying the material selection and a short explanation as to why no stress-corrosion problem is expected Remarks The SCEF shall contain any additional information or explanatory notes not included in the preceding sections NOTE Relevant laboratory reports can be referenced BS EN 16602-70-36:2014 EN 16602-70-36:2014 (E) C.2.2 Special remarks C.2.2.1 Stress-corrosion evaluation form Originator (Name, Organization, Address): Used on system/subsystem: Project: Declared material list identification Use and location Number of identical parts Manufacturer Material Heat treatment Size and form Sustained tensile stresses - magnitude and direction: a Process residual b Assembly c Design, static Special processing 10 Weldments: a Alloy form, temper of parent metal b Filler alloy (if none, indicate) c Welding process d Weld bead removed: Yes ( ) No ( ) e Post–weld thermal treatment f Post–weld stress relief 11 Environment 12 Protective finish 13 Function of part 14 Effect of failure 15 Evaluation of stress–corrosion susceptibility 16 Remarks Figure C-1: Example of a Stress-corrosion evaluation form BS EN 16602-70-36:2014 EN 16602-70-36:2014 (E) C.2.2.2 a Annexes Annexes may be supplied with the stress-corrosion evaluation form NOTE For example: Construction drawings for intended use or laboratory stresscorrosion test report, as per clause xx.xx of Standard_Reference BS EN 16602-70-36:2014 EN 16602-70-36:2014 (E) Annex D (informative) Grain orientation D.1 Introduction Rolling, extrusion and forging are the most common processing operations employed in the production of standard forms of wrought metal All of these produce a flow of metal in a predominant direction so that when viewed microscopically, is the metal neither isotropic nor homogeneous As a result, the properties of the metal vary according to the direction in which they are measured The extent of directional variation depends on the property of interest D.2 Anisotropy of grain orientation The anisotropy of grain orientation, produced by rolling and extruding, is illustrated in Figure D-1 Taking the rolled plate as an example, it is conventional to describe the direction of rolling as the longitudinal direction, the direction perpendicular to the longitudinal axis and in the plane of the plate as the long transverse direction, and the direction through the thickness of the plate as the short transverse direction BS EN 16602-70-36:2014 EN 16602-70-36:2014 (E) Figure D-1: Grain orientations in standard wrought forms For certain shapes, it is not possible to distinguish both a long and a short transverse direction on the basis of the simple rules for identifying those directions in a plate NOTE As an example, consider the thick tee illustrated in Figure D-2, where a region with both long and short transverse orientations has been identified on the basis of experience with that particular shape and a knowledge of the forming method BS EN 16602-70-36:2014 EN 16602-70-36:2014 (E) Figure D-2: Examples of tensile stresses in short transverse direction applied during assembly Forgings also require special consideration when identifying the short transverse direction In a forging operation, the flow of metal is influenced and constrained by the shape of the die cavity For complex shapes, there may be several regions where a short transverse direction exists The direction perpendicular to the parting plane of the dies is always short transverse, as illustrated in Figure D-3 BS EN 16602-70-36:2014 EN 16602-70-36:2014 (E) Figure D-3: Examples of tensile stresses in short transverse direction resulting from assembly The resistance of metals, particularly alloys of aluminium, to stresscorrosion cracking is always less when tension is applied in a transverse direction It is least for the short transverse direction Figure D-2 and Figure D-3 were drawn to illustrate undesirable situations in which tensile stresses due to assembly have been applied in the short transverse direction BS EN 16602-70-36:2014 EN 16602-70-36:2014 (E) Annex E (informative) SCC resistance of alloys E.1 Stress corrosion susceptibility The stresscorrosion susceptibility of alloys included in this document was determined at ambient temperature: • by means of laboratory tests in which specimens were either sprayed with salt water or periodically immersed (every xx days/mn/sec) and withdrawn; • by exposing specimens in sea coast or mild industrial environments; • Example of mild industrial environment; • by subjecting fabricated hardware to service conditions NOTE For example: Example of service condition for a given hardware NOTE Use of the criteria established herein should therefore be limited to designs for service involving similar exposure conditions Weldments present specific problems, as described in Document_Reference, in designing for resistance to SCC In addition to the susceptibility of the parent metals, it is also necessary to consider the filler metal and the microstructural effects of heat introduced by the welding operations and subsequent heat treatments, such as Subsequent_Heat_Treatment_Example Because of the additional variables to be considered (Additional_Variables_List), susceptibility data are not as extensive for weldments as for alloys in mill form In designing for stress-corrosion resistance, it is important to realize that stresses are additive and that threshold stresses for susceptibility are often low There have been a number of stress-corrosion failures for which design stresses were intermittent and of short duration, and only of minor significance in contributing to failure Stress-corrosion cracking in those cases occurred because a combination of residual and assembly stresses not even anticipated in design Unfortunately, for most service environments, accurate threshold stresses are difficult to assess In addition to stresses resulting from operational, transportation and storage loads that are anticipated during design, assembly and residual stresses also contribute to stress-corrosion failure BS EN 16602-70-36:2014 EN 16602-70-36:2014 (E) E.2 Metal alloys E.2.1 Aluminium Many aluminium alloys exhibit excellent resistance to stresscorrosion cracking in all standard tempers The highstrength alloys, however, which are of primary interest in aerospace applications, is approached cautiously Some are resistant only in the longitudinal grain direction, and the resistance of others varies with the specific temper Because metallurgical processing of aluminium alloys usually results in a pronounced elongation of grains, the variation of susceptibility with grain orientation is more extensive than for other metals Also, because conventional processing methods are designed to optimise strength, residual stresses - especially in thick sections - are usually greater in aluminium products than in wrought forms of other metals For this reason, wrought, heattreatable aluminium products specified for use in the fabrication of hardware should be mechanically stress relieved (the TX5X or TX5XX temper designations) whenever possible Both the residual stress distribution and the grain orientation are carefully considered, as specified in clause 5.3, in designing a part to be machined from wrought aluminium Machining does not only alter the stress distribution but, as indicated in Figure D-2, it can also result in the exposure of a short transverse region on the surface of the finished part which is subjected to tension in service E.2.2 Steel Carbon and lowalloy steels with ultimate tensile strengths below 225 MPa (180 ksi) are generally resistant to stresscorrosion cracking Austenitic stainless steels of the 300 series are generally resistant Martensitic stainless steels of the 400 series are more or less susceptible, depending on composition and heat treatment Precipitationhardening stainless steels vary in susceptibility from extremely high to extremely low, depending on composition and heat treatment The susceptibility of these steels is particularly sensitive to heat treatment, and special vigilance is required to avoid problems due to stresscorrosion cracking E.2.3 Nickel As a class, alloys with high nickel content are resistant to stresscorrosion cracking E.2.4 Copper Natural atmospheres containing the pollutants sulphur dioxide, oxides of nitrogen, and ammonia are reported to cause stresscorrosion cracking of some copper alloys Chlorides present in marine atmospheres may cause stresscorrosion problems, but to a lesser extent than the previously listed pollutants, which indicates that industrial areas are probably more aggressive than marine sites to copperbase alloys Many copper alloys containing over 20 % zinc are susceptible to stresscorrosion cracking even in the presence of alloying additions that normally impart resistance to stress-corrosion BS EN 16602-70-36:2014 EN 16602-70-36:2014 (E) Figure E-1: Typical residual stress distributions in 7075 Aluminium alloys BS EN 16602-70-36:2014 EN 16602-70-36:2014 (E) Annex F (informative) Stress sources F.1 Introduction In addition to stresses resulting from operational, transportation and storage loads that are anticipated during design, assembly and residual stresses also contribute to stress-corrosion, and in many cases are the major contributors to stresscorrosion failure F.2 Stress sources Table F-1: Sources of stress Stress type Assembly Residual1 Source • improper tolerances during fitup (Figure D-3 and Figure E-1) • overtorquing • press fits • highinterference fasteners • welding • machining • forming • heat-treating Transportation Storage Operational Some typical residualstress distributions through plate and rod are illustrated in Figure D-1 to provide an indication of the magnitudes of stress which can be developed as the result of conventional heat treating and forming operations BS EN 16602-70-36:2014 EN 16602-70-36:2014 (E) Bibliography EN reference Reference in text Title EN 16601-00 ECSS-S-ST-00 ECSS system – Description, implementation and general requirements EN 16602-70-36:2014 (E) This page deliberately left blank This page deliberately left blank NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW British Standards Institution (BSI) BSI is the national body responsible for preparing British 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