Def Stan 03-04

Transcript

M ini nis stry tr y of of Def Defence nce Defence Standard 03-4 I ssue 6 Publi ublicati cation on Date 12 August ugust 20 201 11  Th  T he Pre Pr e-Tre -Tr eatment and Pr otecti tectio on of of Stee Steel I tem tems of  Spec Specified Ma M axi xim mum T ens nsiile Stre Str ength ngth E xce xceedi ding ng 1450M Pa DEF STAN STAN 03-4 Issu e 6 Contents Foreword...........................................................................................................................................................iv 0 Introduction........................................................................................................................................v 1 Sco pe ............................................................................................... ..................................................................................................................................................2 ...................................................2 2 Warnin Warn ing g ........................................................................... ..............................................................................................................................................2 ...................................................................2 3 Nor mat ive iv e Refer ences.......................................................................................................................2 enc es.......................................................................................................................2 4 Defi niti ni ti ons on s ....................................................................................... ..........................................................................................................................................3 ...................................................3 4.2 Baking.................................................................................................................................................3 4.3 Categor Categ oris is ati on of Steels ................................................................................................... ...................................................................................................................3 ................3 4.4 Desi gn Auth Au th orit or it y ........................................................................... ...............................................................................................................................4 ....................................................4 4.5 Heat Treatm ent Times Tim es ........................................................................... .......................................................................................................................4 ............................................4 4.6 Hydro Hyd rogen gen Embri Emb ri tt lem ent ............................................................................................... ..................................................................................................................4 ...................4 4.7 Pro ces s Contr Con trol ol Schedu Sch edule................................................................................................................4 le................................................................................................................4 4.8 Physi Phy si cal Prepar ati on ...................................................................................... .........................................................................................................................4 ...................................4 4.9 Str ess Reli ef................................................................................................ ef .......................................................................................................................................4 .......................................4 5 Info rmat ion to be Supp lied li ed by the th e Purc haser................ haser...................... ........... ........... ............ ........... ........... ............ ........... ........... ............ ........... ........5 ...5 6 Pro ces s Contr Con trol ol ...................................................................................... .................................................................................................................................5 ...........................................5 7 Recomm endati ons for Design and Manufac tur e.......... e................ ............ ........... ........... ........... ........... ............ ........... ........... ............ ............ .........5 ...5 7.1 Desi gn Consi Con sider derati ati ons on s ...................................................................................... .....................................................................................................................5 ...............................5 7.1.1 Choic Cho ic e of Steel ................................................................................................ ..................................................................................................................................5 ..................................5 7.1.2 7.1.2 Avo idan ce of Stres s Conc entr atio ns ........... ................. ............ ............ ........... ........... ............ ........... ........... ............ ........... ........... ............ ............ ............ ........5 ..5 7.1.3 Pro tec ti ve Treatment Treat ment ............................................................................................ .........................................................................................................................5 .............................5 7.2 Type Typ e Test ing in g .......................................................................................... ......................................................................................................................................6 ............................................6 7.3 Manuf act ure ur e .................................................................................................. .......................................................................................................................................6 .....................................6 7.3.1 Machin Mach in ing in g and Grind Gri ndin in g ................................................................................................... ...................................................................................................................6 ................6 7.3.2 Chemic Chem ic al Machi ning ni ng .................................................................................... ..........................................................................................................................6 ......................................6 7.3.3 Col d Formi For ming ng .............................................................................. .....................................................................................................................................6 .......................................................6 7.3.4 Sur fac e Rol li ng ......................................................................................... ..................................................................................................................................6 .........................................6 7.3.5 Pro tec ti on Dur ing in g Manuf act ure.............................................................................. ur e........................................................................................................7 ..........................7 7.3.6 Etc h Ins pecti pec ti on .............................................................................................. ..................................................................................................................................7 ....................................7 8 Physi Phy si cal Preparati Prep arati on .......................................................................................... .........................................................................................................................7 ...............................7 8.1 Str ess Reli ef................................................................................................ ef .......................................................................................................................................7 .......................................7 8.1.1 General ....................................................................................... ...............................................................................................................................................7 ........................................................7 8.1.2 Stan dard dar d Proced Pro cedur ure e ............................................................................................... ..........................................................................................................................7 ...........................7 8.1.3 Str ess Reli ef of Items Item s ........................................................................................... ........................................................................................................................8 .............................8 8.1.3. 8.1.3.1 1 Items not given a Treatment Treatment to Intro Intro duce Benefic Benefic ial Compr Compr essive Stresses Stresses into the Surface.8 8.1.3. 8.1.3.2 2 Items given a Treatment Treatment to Intro Intro duce Benefici Benefici al Compressi ve Stresses into the Surface.......8 Surface.......8 8.1.3.3 Sprin Spr ings gs ............................................................................................. ...............................................................................................................................................8 ..................................................8 8.2 Mechani Mech ani cal Prepar ati on ........................................................................................ ....................................................................................................................8 ............................8 8.2.1.1 Sho t Peenin g ............................................................................ .....................................................................................................................................8 .........................................................8 ii DEF STAN 03-4 Issu e 6 8.2.1.2 Surfac e Rolli ng ..................................................................................................................................8 8.2.1.3 Abrasive Bl ast ing ..............................................................................................................................8 9 Cleani ng .............................................................................................................................................8 9.2 Category 1451 – 1800 MPa Steels....................................................................................................9 9.3 Category 1801 MPa and Greater Steels ..........................................................................................9 10 Protec ti ve Treatments .......................................................................................................................9 10.1 Precaut ion s App licabl e to all Treatments ......................................................................................9 10.2 Cadmium Electrod eposi ti on (Def Stan 03-19)..............................................................................10 10.2.1 Prepar ation ......................................................................................................................................10 10.2.2 Choic e of Electrol yte ......................................................................................................................10 10.2.3 Bak ing ..............................................................................................................................................10 10.2.4 Protecti on Agai nst Vapour Corro sion ..........................................................................................10 10.3 Physi cal Vapour Depositi on of Alum iniu m, Cadmium and Titanium Nitri de (Def Stan 03-28 parts 1, 2 and 3)...............................................................................................................................10 10.4 Zinc Electrod eposit ion (Def Stan 03-20)......................................................................................10 10.5 Hard Chromiu m Electrod epos ition (Def Stan 03-14) ...................................................................10 10.5.1 Prepar ation ......................................................................................................................................10 10.5.2 Baking .............................................................................................................................................11 10.5.3 Post -Electr odepo sition Grind ing ...................................................................................................11 10.6 Nick el Elect rod eposition for Engineerin g Purpo ses (Def Stan 03-27).......................................11 10.7 Electrol ess Nick el Coatin g of Metals (BS EN ISO 4527) .............................................................11 10.8 Silv er Electrod eposit ion (Def Stan 03-9).......................................................................................11 10.9 Gold Electrod eposition (Def Stan 03-17) ......................................................................................11 10.10 Sprayed Coati ngs of Alumi nium and Zinc (BS EN ISO 2063).....................................................11 10.11 Phosphate Treatm ent (Def Stan 03-11).........................................................................................11 10.12 Paint Appl ied to Unc oated Steel ....................................................................................................12 10.13 Proc esses Permit ted but not Recomm ended ..............................................................................12 10.13.1 Tin Electr odeposi ti on (BS 1872)....................................................................................................12 10.13.2 10.14 Copp er Electr odeposi ti on .............................................................................................................12 Proces ses not Permi tt ed ................................................................................................................13 10.14.1 Tin-Zinc Alloy Elect rod eposition ...................................................................................................13 10.14.2 Sheradizin g (BS 4921) ....................................................................................................................13 10.14.3 Hot Dip Galvanizin g ........................................................................................................................13 10.15 Re-Proc essing and Re-Furb is hment .............................................................................................13 11 Inspecti on and Testing ...................................................................................................................13  Annex A Method for Determining Oxidi zable Materi al in Sulf uric Ac id ....................................................15  A.1 Methodol ogy ....................................................................................................................................15 Tables Table 1 Tensil e Strength Criteria ................................................................................................................4 Table 2 Baking Treatments to be Given to Items aft er Prot ective Processi ng ....................................13 ii i DEF STAN 03-4 Issu e 6 Foreword  AMENDMENT RECORD Amd No Date Text Affected Signature and Date REVISION NOTE  This standard is raised to Issue 6 to update its content. HISTORICAL RECORD  This standard supersedes the following: Def Stan 03-4 / Issue 1 dated 23 November 1971 Def Stan 03-4 / Issue 2 dated 31 March 1977 Def Stan 03-4 / Issue 3 dated 1 February 1991 Def Stan 03-4 / Issue 4 dated 2 J anuary 1998 Def Stan 03-5 / Issue 5 dated 13 October 2006 a) This standard provides requirements for the pre-treatment and protection of steel items of specified maximum tensile strength exceeding 1450 MPa. b) This standard has been produced on behalf of the Defence Material Standardization Committee (DMSC) by the Corrosion Prevention and Metallic Materials Standards Production Group (E3). c) This standard has been agreed by the authorities concerned with its use and is intended to be used whenever relevant in all future designs, contracts, orders etc. and whenever practicable by amendment to those already in existence. If any difficulty arises which prevents application of the Defence Standard, UK Defence Standardization (DStan) shall be informed so that a remedy may be sought. d) Any enquiries regarding this standard in relation to an invitation to tender or a contract in which it is incorporated are to be addressed to the responsible technical or supervising authority named in the invitation to tender or contract. e) Compliance with this Defence Standard shall not in itself relieve any person from any legal obligations imposed upon them. f) This standard has been devised solely for the use of the Ministry of Defence (MOD) and its contractors in the execution of contracts for the MOD. To the extent permitted by law, the MOD hereby excludes all liability whatsoever and howsoever arising (including, but without limitation, liability resulting from negligence) for any loss or damage however caused when the standard is used for any other purpose. iv DEF STAN 03-4 Issu e 6 0 Introduction 0.1  This Standard sets out the special treatments and precautions that are to be observed when protective and other surface treatments are applied to items, including springs, made from steel of specified maximum tensile strength exceeding 1450 MPa. The requirements of this S tandard qualify those in process specifications and override the latter where there is conflict. The Standard also gives advice on design, manufacture, and preparation of items prior to cleaning and protection. 0.2  Though this Standard refers to the use of cadmium, it should be noted that in accordance with MOD Policy and UK E nvironmental (Control of Hazardous Substances) No.2 Regulation1993, cadmium is only to be used where specific agreement has been given by the MOD. Every effort must be made to define alternative coatings (see Def Stan 03-36) and cadmium is only to be used where its use is permitted by regulation and no other acceptable alternative is available. 0.3 Similarly there is increasing concern regarding the use of hexavalent chromium chemicals with more and more legislation being introduced to limit its use. Although this standard refers to the use of chromium electroplating, for instance, users should make every effort to identify alternatives (see Def Stan 03-38). NOTE In the case of hexavalent chromium it is the coating process itself where the hazard exists not the end product; i.e. chromium electroplate is non-toxic. This is contrary to cadmium for instance where potential hazards exist during processing, use and disposal. v DEF STAN 03-4 Issu e 6 Standards for Defence - The Pre-Treatment and Protection of  Steel Items of Maximum Tensile Strength Exceeding 1450MPa 1 Scope  This Standard sets out the special treatments and precautions that are to be observed when protective and other surface treatments are applied to items, including springs, made from steel of specified maximum tensile strength exceeding 1450 MPa. The requirements of this Standard qualify those in process specifications and override the latter where there is conflict. The Standard also gives advice on design, manufacture, and preparation of items prior to cleaning and protection. 2 Warning  The Ministry of Defence (MOD), like its contractors, is subject to both United Kingdom and European laws regarding Health and Safety at Work. All Defence Standards either directly or indirectly invoke the use of  processes and procedures that could be injurious to health if adequate precautions are not taken. Defence Standards or their use in no way absolves users from complying with statutory and legal requirements relating to Health and Safety at Work. 3 Normative References 3.1  The publications shown below are referred to in the text of this standard. Publications are grouped and listed in alpha-numeric order. 3.2 Reference in this Standard to any normative references means in any Invitation to Tender or contract the edition and all amendments current at the date of such tender or contract unless a specific edition is indicated. 3.3 In consideration of clause 3.2 above, users shall be fully aware of the issue and amendment status of  all normative references, particularly when forming part of an Invitation to Tender or contract. Responsibility for the correct application of standards rests with users. 3.4 DStan can advise regarding where normative references documents are obtained from. Requests for such information can be made to the DStan Helpdesk. How to contact the helpdesk is shown on the outside rear cover of Def Stans. Title BS EN ISO 2063 BS BS BS BS BS BS BS BS BS 2 EN ISO 4527 EN ISO 6507-1 EN 2828 EN 2829 EN 2830 EN 2831 EN 2832 1872 4921 Designation Thermal Spraying. Metallic and Other Inorganic Coatings. Zinc, Aluminium and their Alloys Metallic Coatings. Autocatalytic (Electroless) Nickel-Phosphorous Alloy Coatings Metallic Materials: Vickers Hardness Test: Test Method Adhesion Tests for Metallic Coatings by Burnishing Adhesion Tests for Metallic Coatings by Shot Peening Adhesion Tests for Metallic Coatings by Shearing Action Hydrogen Embrittlement of Steels: Test by Slow Bending Hydrogen Embrittlement of Steels: Notched Specimen Test Specification for Electroplated Coatings of Tin Specification for Sherardized Coatings on Iron and Steel DEF STAN 03-4 Issu e 6 Title Designation BS 7195 BS M37 BS 2X33 BS 2X34 Def Stan 00-970 Def Stan 03-2 Def Stan 03-9 Def Stan 03-11 Def Stan 03-14 Def Stan 03-17 Def Stan 03-19 Def Stan 03-20 Def Stan 03-21 Def Stan 03-27 Def Stan 03-28 Def Stan 03-30 Def Stan 03-31 Def Stan 03-36 Def Stan 03-38 Def Stan 80-54 Def Stan 80-161 Def Stan 80-206 Def Stan 80-207 Def Stab 80-208 Def Stan 91-70 ASTM F519 4 Guide for the Prevention of Corrosion of Metals Caused by Vapours from Organic Coatings Method for the Etch Inspection of Metallic Materials and Components Specification for Two Component Epoxy Primer for Aerospace Purposes Specification for Air Drying, Two Component, Polyurethane Finish for Aerospace Purposes Design and Airworthiness Requirements for Service Aircraft Cleaning and Preparation of Metal Surfaces Electro-Deposition of Silver Phosphate Treatment of Iron and Steel Electro-Deposition of Chromium for Engineering Purposes Electro-Deposition of Gold Electro-Deposition of Cadmium Electro-Deposition of Zinc Mechanical Methods for the Inducement of Compressive Surface Residual Stresses Electro-Deposition of Nickel for Engineering Purposes Physical Vapour Deposition of Metals Treatments for the Protection of Metal Parts of Service Stores and Equipment Against Corrosion A Guide to the use of Chromium Plating for Engineering Purposes Guidance to the Use of Cadmium Alternatives in the Protective Coating of Defence Equipment Guidance to the Use of Alternatives to Hard Chromium Plating and Chromium Conversion Coatings for the Protective Coating of Defence Equipment Paint, Finishing, General Service, Fuel Resistant, Gloss Paint, Finishing, Spraying, Epoxy, Multi Pack Paint, Priming, Zinc Phosphate, Non-Aircraft Use, Low VOC, Single or Multi Pack Paint, Priming, Zinc Chromate, Non-Aircraft Use, Low VOC, Single or Multi Pack Paint, Finishing, Polyurethane Multi Pack, Matt IRR, Chemical Agent Resistant, Non-Aircraft Use, Low VOC Cutting Fluid, Soluble, Biostable. J oint Service Designation Mechanical Hydrogen Embrittlement Evaluation of Plating/Coating Processes and Service Environments Definitions 4.1 For the purpose of this Standard the following definitions apply: 4.2 Baking A low temperature heat treatment given after processing to reduce or eliminate the danger of hydrogen embrittlement by expelling absorbed hydrogen and/or diffusing it throughout the item. 4.3 Categoris ation of Steels 4.3.1  Throughout this S tandard the tensile strength figures refer to specified maximum tensile strength. Steels shall be categorised according to specified maximum tensile strength in accordance with Table 1. Where the steel specification specifies only the minimum tensile strength the equivalent maximum tensile strength category shall be determined from Table 1. 3 DEF STAN 03-4 Issu e 6 Table 1 Tensi le Strength Criteria Spec if ied Mini mum Ten si le St ren gth MPa Sp ec if ied Max im um Tens il e St ren gt h MPa * up to 1000 * up to 1100 * from 1001 to 1400 * from 1101 to 1450 from 1401 to 1800 from 1401 to 1800 1801 and greater 1801 and greater * Included for comparison purposes 4.3.2 If no maximum or minimum tensile strength figure is specified for the steel, hardness values of  425HV, 440HV and 560HV (as determined in accordance with BS EN ISO 6507-1) shall be regarded as equivalent to 1400, 1450 and 1800 MPa respectively. Steels which have been wholly or partly surface hardened shall be considered as being in the category appropriate to the hardness of the surface layer. 4.4 Design Autho rity  The approved firm, establishment or branch responsible for the detailed des ign of materiel to approved specifications and authorised to sign a certificate of design or to certify sealed drawings. 4.5 Heat Treatment Times  The appropriate heat treatment time commences when the items have reached the specified temperature. 4.6 Hydrogen Embrittl ement A loss of ductility, load carrying ability or cracking (usually initiating as sub-microscopic cracks) of a metal or alloy due to the presence of Hydrogen in or on the material. The hydrogen can be introduced during fabrication, cleaning, pickling, phosphating, electro-plating and auto-catalytic processes. 4.7 Process Contr ol Sched ul e  The document which specifies / defines: (a) The sequence of manufacturing operations and processes. (b) The control parameters and their tolerances for each individual process within the total sequence. 4.8 Physi cal Preparation Physical preparation is concerned with the reduction of deleterious internal and surface stresses, and / or the introduction by mechanical means of beneficial compressive stresses in the surface 4.9 Stress Relief  A low temperature heat treatment given before processing to reduce stresses in the surface of the item, not necessarily causing the relief of deeper internal stresses. 4 DEF STAN 03-4 Issu e 6 5 Information to be Suppl ied by th e Purc haser   The following information shall be given on the drawing, contract or order: (a) The specification and category of the steel (see 4.3), or other information from which the category can be established. (b) Instructions concerning stress relief (see 8.1). These instructions shall take into account the highest temperature to which the part may be heated and the prior physical preparation. (c) 6 The number of this Defence Standard and the section(s) / clauses(s) applicable. Process Contro l 6.1 A Process Control Schedule suitable of achieving the requirements of this Standard shall be prepared by the processing contractor(s) prior to the commencement of production. 6.2 Details of the coating process, including all preparatory treatments and after treatments, processing, the pH range, operating temperature, chemical composition, method of agitation, any galvanic or electrolytic initiation, pre and post-plating heat treatments, tests and all other processes and treatments shall be included in the Process Control Schedule. 6.3 7 All stages in the complete Schedule shall follow each other without delay. Recommendatio ns for Design and Manufact ure 7.1 7.1.1 Design Consi deratio ns Choice of Steel 7.1.1.1 Designers should avoid selecting steels of unnecessarily high strength. The susceptibility of high strength steels to hydrogen embrittlement is affected by the type of  steel and the steelmaking process, therefore advice should be sought. 7.1.1.2 In order that effective stress relief and de-embrittlement by baking can be given to the item, steels which give the required strength with a tempering temperature greater than 300ºC should be chosen in preference to those requiring tempering at a lower temperature. 7.1.1.3 Designers should seek authoritative advice and recommendations concerning the implementation of the applicable parts of this Standard, particularly when steels of tensile strength 1800 MPa and greater are selected. 7.1.2  Av oidanc e of Stress Concentrati ons 7.1.2.1 Notches, sharp radii and sudden changes of section should be avoided as they lead to the development of stress concentrations which promote failure both under sustained load and by fatigue. 7.1.2.2 Stresses produced by press and shrink fits and tapers, or otherwise introduced during assembly, should be kept to a minimum. 7.1.3 Protecti ve Treatment  The choice of protective treatment is normally made by the designer from Def Stan 03-30 or from the appropriate master design manual for the item in question, e.g. the design requirements laid down for aircraft (Def Stan 00-970) etc. Hydrogen embrittlement can be avoided by using non-electrolytic processes, e.g. wide tolerance items may be metal sprayed with Aluminium or Zinc (BS EN ISO 2063) and close tolerance items may be coated with cadmium by ion vapour deposition (Def Stan 03-28 Part 2). Whenever possible processes known either not to embrittle or to produce the lowest hydrogen absorption shall be used. 5 DEF STAN 03-4 Issu e 6 7.2 Type Testing 7.2.1 Methods whereby aqueous protective treatments can be applied without some risk of harmful effects, e.g. embrittlement or poor adhesion, are not yet established with certainty. Much laboratory work remains in progress, and of necessity this Standard contains a high proportion of descriptive and advisory matter. Many of the special requirements and recommendations are directed to the avoidance of hydrogen embrittlement and of the harmful effect on the surface treatments and heat treatments on fatigue properties. 7.2.2  The behaviour of standard laboratory test specimens is not always a reliable guide to the behaviour of actual items, and it is strongly recommended that production items should be type tested on the protected condition under the type of stress and in the kind of environment the items will meet in service. 7.2.3 For the detection of hydrogen embrittlement, sustained load tests e.g. BS EN 2832 or ASTM F519, or slow bend tests e.g. BS EN 2831 are recommended. 7.2.4 For the assessment of adhesion, testing by burnishing (e.g. BS EN 2828), shot peening (e.g. BS EN 2829), or shearing (e.g. BS EN 2830) may be used. 7.3 7.3.1 Manufacture Machi ning and Grindi ng 7.3.1.1  The final mechanical shaping of fully heat-treated items should be carried out in a way designed to avoid introducing tensile stresses or thermal abuse into the surface. Tool and work-piece should be held rigid and machining or grinding should be light with copious cooling of the work-piece. An appropriate grade of  abrasive wheel shall be selected for use and the wheel regularly dressed to prevent its use in a glazed condition. 7.3.1.2 Cutting oils and coolants can introduce hydrogen into the steel. The risk is least with mineral oils with the next in order of preference being water-oil-emulsions. If soluble oils are used, they should be of the non-activated type such as ZX-9 (Def  Stan 91-70) and should be used with an oil content of not less than 15%. Sulfurized oils and fully activated oils should be avoided, but if their use is essential the time of contact of the item with the oil should be kept to a minimum and should not be longer than 30 minutes at room temperature. Any type of emulsion (water-in-oil, or oil-in-water) used should be removed as soon as possible after machining and replaced by a temporary protective. 7.3.1.3 All components of a critical nature shall be thoroughly inspected after all grinding operations by a suitable etch inspection method, e.g. BS M37, which will identify grinding damage. Such inspection techniques must be defined in the Process Control Schedule. NOTE Etch inspection which makes use of acid solutions may introduce hydrogen into the surface. It must therefore precede any scheduled de-embrittling treatment and in any case be followed by de-embrittlement. 7.3.2 Chemical Machi ning Chemical contouring and electro-chemical machining offer attractive ways of shaping very strong steel items but may only be used subject to agreement by the Design Authority. Methods known to be non-embrittling are available. 7.3.3 Cold Forming Heat-treated items, other than springs, shall not be cold formed or straightened without the concurrence of  the Design Authority. 7.3.4 Surface Rollin g  Threads and other areas containing unavoidable sharp radii should, after final heat-treatment, be subject to surface rolling or other treatment likely to impart compressive surface stresses (see clause 8). Stress relief  (see clause 8) before rolling is an advantage. 6 DEF STAN 03-4 Issu e 6 7.3.5 Protecti on During Manufacture Up to the time at which the final protective coating is applied, items shall be protected with a temporary protective or a non-aggressive oil. 7.3.6 Etch Inspecti on If items are given an etching treatment in an acid solution, e.g. nital etching, to reveal damage to the surface caused by abusive grinding or machining, then this treatment shall be given at this stage, i.e. prior to stress relief; any hydrogen embrittlement caused by the etching treatment will be eliminated by the stress relieving providing it is carried out immediately after etching. 8 Physic al Preparation 8.1 Stress Relief  8.1.1 General  The relief of internal and deleterious surface stresses, by a suitable heat treatment, aids resistance to sustained load and fatigue failure. As a rule, internal stresses developed during quenching are relieved at temperatures of 400ºC and above, and surface stresses developed during mechanical finishing operations can be reduced by heating at temperatures of 200ºC and above. The relief of beneficial surface compressive stresses introduced during production should however be avoided (see 8.1.3). Stress relief shall be applied before cleaning according to clause 9, although items may, if necessary, be degreased before heating. Items, e.g. springs manufactured to certain British Standard Aircraft Series specifications, which have been stress relieved as a mandatory requirement for the manufacturing specification, do not require further stress relief before cleaning. The stress relief treatment can be omitted for maraging steels which have been aged after final machining. 8.1.2 Standard Procedure  The standard stress relief consists of heating the items to the highest temperature possible within the limit imposed by the tempering or ageing temperature or by any susceptibility of the steel to temper brittleness.  The period at temperature shall be as follows:• for category 1451 – 1800 MPa, not be less than 18 hours at 200 - 230ºC • for category 1801 MPa and over, not be less than 24 hours at 200 - 230ºC followed by cooling in still air. NOTE 1 Suitable combinations of a shorter time at appropriate higher temperatures may be used if they have been shown not to be detrimental. NOTE 2 At the discretion of the Design Authority, case hardened items which are not to be electroplated on the hardened area may, however, be stress relieved at only 130ºC for 6 hours, as a higher temperature may unacceptably reduce the hardness of the case. NO TE 3 If the tempering temperature of the steel is less than 50°C above the temperature ranges stated above, the heat treatment may be undertaken at a temperature that is at least 50°C below the tempering temperature. 7 DEF STAN 03-4 Issu e 6 8.1.3 Stress Relief of Items  The application of stress relief should be considered in relation to the methods of mechanical preparation of  items, described in 8.2. 8.1.3.1 Items not given a Treatment to Introduce Beneficial Compressive Stresses into the Surface.  The standard treatment (see 8.1.2) shall be applied to all items. 8.1.3.2 Items given a Treatment to Introd uce Benefici al Compress ive Stresses into the Surface. Standard stress relief prior to these mechanical treatments is recommended and if given shall not be repeated after the mechanical treatment. If no prior stress relief is given, then items given one of the mechanical treatments all over shall not be stress relieved after treatment and items given one of the mechanical treatments over only part of the surface shall be stress relieved after treatment by the standard procedure (8.1.2). 8.1.3.3 Springs Notwithstanding the above, shot peened or dry blasted springs may be stress relieved at a temperature recommended by the manufacturer but not exceeding 230ºC. 8.2 Mechani cal Preparation  The introduction of compressive stresses into the surface is strongly recommended, either all over or upon selected areas. These stresses will be balanced by tensile stresses of varying intensity elsewhere in the item, and design and mechanical preparation should be such that these tensile stresses can do no harm. 8.2.1 8.2.1.1  The following treatments introduce compressive stresses into surfaces: Shot Peening  The advantage of this process is that it can be controlled and that the beneficial effects persist after the surface has been ground smooth under controlled conditions. The intensity of peening shall produce on an Almen A test specimen an arc height of not less than 0.3 mm when measured by the method described in Def Stan 03-21. If necessary the peened surface of the item may be ground smooth by the removal of the minimum possible amount of metal from the surface, and in any case not more than 0.1 mm, measurement being made from the asperities of the peened surface. 8.2.1.2 Surf ace Roll ing  This may be carried out after heat treatment, e.g. of bolts. 8.2.1.3 Abrasi ve Blast ing Methods D1 and D2 of Def Stan 03-2 may be of value in some instances (grit blasting which is used for descaling and other purposes is also used prior to metal spraying as metal spraying processes can reduce fatigue properties). 9 9.1 Cleaning Prior to protective treatment, items shall be cleaned by one or more of the following methods. The steps selected in the cleaning sequence shall follow one another without interruption other than any necessary washing, and be followed immediately by the protective treatment. The Method numbers refer to the particular methods in Annex J of Def Stan 03-2 to be used to produce a chemically clean surface receptive to subsequent processing, e.g. for maraging steels the final preparation for plating shall be dry grit blasting with virgin aluminium oxide. Special cleaning procedures may also be required for steels, other than maraging steels, prior to particular processes, e.g. as in 10.5.1.2 prior to chromium electrodeposition etc. 8 DEF STAN 03-4 Issu e 6 9.2 9.2.1 Categor y 1451 – 1800 MPa Steels Degreasing in an organic solvent (Method A1 or A2). 9.2.2 Degreasing in an aqueous alkaline solution (Method B1) with applied anodic direct current if desired. Neither cathodic nor alternating current treatments shall be used. 9.2.3 Alkaline de-rusting (Method K1). 9.2.4 Abrasive cleaning (Process D). This Process, especially grit blasting (Method D1) leaves the surface very susceptible to corrosion, and further processing shall be given without delay. 9.2.5 Anodic pickling in sulphuric acid solution (Process H) must be carefully controlled. Additionally, parts shall be connected and the current switched on before the parts are immersed in the solution, and after treatment the items shall be withdrawn rapidly before the current is finally switched off, and washed immediately. The sulphuric acid used to make up the solution shall at no time contain more than 11 ppm oxidizable material calculated as sulphur dioxide, determined by the method described in  Annex A (this precaution is necessary because reduced sulphur, phosphorus, and arsenic compounds in the acid promote hydrogen absorption during washing). 9.2.6 Where electrolytic de-rusting to Def Stan 03-2 (Process K) is required, an alkaline electrolyte and anodic current shall be used. A sea-water electrolyte and cathodic current or alternating current shall not be used (unlikely because heavily rusted very strong steel items would normally be rejected for poor surface condition and poor fatigue properties). 9.3 Categor y 1801 MPa and Greater Steels 9.3.1 Degreasing in an organic solvent as in 9.2.1. 9.3.2 Alkaline treatments as in 9.2.2, 9.2.3 or 9.2.6. 9.3.3 Abrasive cleaning as in 9.2.4. 10 10.1 Protectiv e Treatments Precautions Applic able to all Treatments 10.1.1 Protective treatment shall follow without delay the last stage of cleaning. Surfaces shall be clean, free from rust and cleaning products. 10.1.2 Items other than close-coiled springs shall not be mechanically stressed during treatment, e.g. by  jigs, clips etc. Close-coiled springs should be extended only sufficiently to allow adequate coverage of the springs and the constraint should be removed immediately after post treatment washing. Electrodeposited or phosphated springs shall not be unnecessarily flexed before baking for the removal of hydrogen embrittlement. 10.1.3 Wherever practicable treatment shall start as soon as the item enters the treatment solution.  Treatment baths shall be at full operating temperature and large items should be warmed before treatment, e.g. by immersion in hot water if it is not appropriate to heat them in the processing solution. 10.1.4 Baking treatments shall be started as soon as possible and preferably within 3 hours of the completion of the electroplating or phosphate treatment. NOTE In certain applications the Design Authority may require baking to commence within one hour on completion of processing. 10.1.5 If after baking a protective process has been applied to only part of the surface, the untreated surface shall then be coated with a temporary protective. 9 DEF STAN 03-4 Issu e 6 10.2 10.2.1 Cadmiu m Electro deposi tio n (Def Stan 03-19) Preparation Items shall be prepared and cleaned as described earlier in clauses 7, 8 and 9. Subject to 10.2.2 and 10.2.3 below, the requirements of Def Stan 03-19 shall be followed. 10.2.2 Choice of Electrol yte  The electrolyte shall not contain brightening agents. The proportions of the constituents of a normal cyanide electrolyte may influence hydrogen embrittlement. Acid electrolytes may cause less embrittlement than standard cyanide electrolytes, but may have rather poor throwing power. Proprietary cyanide electrolytes containing oxidising agents such as nitrate and pertitanate also cause less embrittlement but need careful control. Electrolytes maintained in a high state of purity may cause less embrittlement. A cadmium strike at a high current density (100 A/m²) may be beneficial in reducing the risk of embrittlement. 10.2.2.1  The Design Authority may require non-embrittling characteristics of the process to be demonstrated prior to production use and monitored thereafter. A suitable hydrogen embrittlement test is the sustained load notched tensile test, described in ASTM F519 or BS EN 2832 or the slow bend test described in BS EN 2831. 10.2.3 Baking Electrodeposited items shall be baked according to the requirements of Table 2 prior to passivation. 10.2.4 Protecti on Agains t Vapour Corros ion For protection of unpainted cadmium against corrosion by organic vapours (see BS 7195) a tin flash may be applied over fully baked, unpassivated, cadmium electroplate. Further baking is neither required nor, because of the melting point of cadmium-tin alloy (176ºC), is it permitted. The process is unsuitable for items subject to temperatures exceeding 160ºC in service. 10.3 Physic al Vapour Deposi tio n of Alu mini um, Cadmium and Titanium Nitri de (Def Stan 03-28 parts 1, 2 and 3)  This process does not cause hydrogen embrittlement and is the preferred method of coating cadmium. Items shall be treated in accordance with the relevant part of Def Stan 03-28. 10.4 Zinc Electrodepos iti on (Def Stan 03-20) During zinc electrodeposition the problems of hydrogen absorption from a cyanide solution are broadly the same as those from cadmium electroplating, and similar advice and requirements apply (see 10.2.1, 10.2.2 and 10.2.3). 10.5 Hard Chromiu m Electrodepo sit ion (Def Stan 03-14)  This process is applied to working items many of which are subject to fatigue as well as to sustained load. It has however, a very deleterious effect on fatigue properties unless special measures are taken. Mechanical preparation of shot–peening which improves fatigue properties also improves sustained load properties. Designers should consult Def Stan 03-31 before using this process. 10.5.1 Prep aration Items shall be prepared and cleaned as described in clauses 7, 8 and 9. It is strongly recommended that items made in steel subject to fatigue in service shall be prepared by shot-peening in accordance with 8.2. 10.5.1.1 Items shall be further cleaned as specified in Def Stan 03-14. Although anodic pickling is not generally allowed by 9.3 for category 1800 MPa and greater steels, it may be used on both categories when followed by chromium electroplating and baking. 10 DEF STAN 03-4 Issu e 6 10.5.1.2 Any prior nickel electrodeposition, e.g. such as a nickel strike, shall be carried out in accordance with clause 10.6. and 10.7, and preparation for subsequent chromium electroplating shall be in accordance with Def Stan 03-14. 10.5.2 Baking Electrodeposited items shall be baked according to the requirements of Table 2. 10.5.3 Post-Electrod eposit ion Grindin g A fluorescent penetrant inspection method which is capable of identifying cracks caused by abusive grinding shall be used. 10.6 Nickel Electr odeposition for Engineering Purposes (Def Stan 03-27 )  The general requirements of Def Stan 03-27 apply but copper undercoats are not permitted. Items shall be prepared and cleaned as described in clauses 7, 8 and 9. Steels may be anodically pickled as in 9.2.5. Heavy electroplating has a deleterious effect on fatigue properties and it is strongly recommended that items subject to fatigue in service shall be prepared as in 10.5.1 and electrodeposited by the low stress sulfamate process. Electrodeposited items shall be baked according to the requirements of Table 2. 10.7 Electrol ess Nickel Coating of Metals (BS EN ISO 4527) Items shall be treated in accordance with the requirements of clause 10.6. The process also has a deleterious effect on fatigue properties. NOTE The hardness of the electoless-nickel deposit will depend significantly on the post-deposition, heat treatment temperature and the phosphorus content. 10.8 Silver Electrod eposit ion (Def Stan 03-9) Items shall be prepared and cleaned as described in clauses 7, 8 and 9. The general requirements of Def  Stan 03-9 shall apply except that copper or brass undercoats are not permitted. Electrodeposited items shall be baked according to the requirements of Table 2. 10.9 Gold Electrodepos iti on (Def Stan 03-17)  The items shall first be electroplated with nickel and / or silver according to clauses 10.6 and 10.8 including the appropriate baking treatment. Copper electrodeposition is not permitted. The items shall be prepared and cleaned as described in clauses 7, 8 and 9. Any electrolytic cleaning shall be anodic. The items after gold electroplating shall be baked according to the requirements of Table 2. 10.10 Sprayed Coatings of Alum iniu m and Zinc (BS EN ISO 2063) Providing tolerances and thicknesses allow and the requirements of BS EN ISO 2063, particularly those relating to adhesion, are met, the steel may be metal sprayed. For improved corrosion protection metal spraying should be followed by a full paint scheme; over zinc, an etch primer shall be used but over aluminium, an etch primer is optional. No baking is required for hydrogen de-embrittlement after metal spraying. 10.11 Phos phate Treatment (Def Stan 03-11)  The general requirements of Def Stan 03-11 shall apply. In order to reduce hydrogen absorption, the phosphate treatment process shall be of the accelerated, but copper-free, type working at a pointage not exceeding 30. Items shall be prepared and cleaned as described in clauses 7, 8 and 9. Phosphate items shall be baked according to the requirements of Table 2. 11 DEF STAN 03-4 Issu e 6 10.12 Paint Appl ied to Uncoated Steel 10.12.1 Items shall be prepared and cleaned as described in clauses 7, 8 and 9. Prior to painting, mild abrasive cleaning shall be carried out (Method D2 of Def Stan 03-2 is preferred) but care shall be taken that the abraded surface is free from abrasive, dust and rust when the paint is applied. 10.12.2  The priming coat shall be a full anti-corrosion primer and shall be selected from one of the following paint schemes. BS 2X33 Def Stan 80-54 Def Stan 80-161 Def Stan 80-206 Def Stan 80-207 Def Stan 80-208 NOTE Primer BS 2X33 is usually used with finish to BS 2X34 10.12.3 E tch priming may only be used for direct application to bare steels in either category at the discretion of the Design Authority. Many paint schemes which include etch primers afford corrosion protection of a high order. However, the etch primer introduces hydrogen into the base steel and a baking treatment to remove embrittling effects will be required after etch priming. The present state of knowledge on temperatures and duration of baking and their effects on hydrogen embrittlement and corrosion resistance properties is incomplete but a recommended baking treatment is given in Table 2. 10.13 Pr ocesses Permitted but not Recommended 10.13.1 Tin Elect rodepos iti on (BS 1872) 10.13.1.1  This process is not recommended for direct application to either category of steel because of the danger of inter-granular penetration of the tin into the steel occurring at temperatures below the melting point of tin (232ºC) during the 190-220ºC baking treatment required to remove embrittlement. NOTE Should the use of tin electroplating be necessary a flash coating (5µm) of nickel will reduce the chance of  inter-granular penetration. 10.13.1.2 If this process is used, organic agents shall not be added to the electrolyte and the items shall be prepared and cleaned as described in clauses 7, 8 and 9. Electroplated items shall be baked according to the requirements of Table 2; the lower end of the baking range, 190ºC, is recommended. 10.13.1.3 If tin electroplating is applied to baked cadmium plated surfaces for protection against vapour corrosion see 10.2.4. 10.13.2 Copper Electrodeposition Copper electroplating may only be used at the discretion of the Design Authority. It is not normally permitted for any purpose as it can introduce irreversible embrittlement effects and may reduce fatigue properties. 12 DEF STAN 03-4 Issu e 6 10.14 Process es not Permitt ed 10.14.1 Tin-Zinc Alloy Electrodeposition  This process is prohibited because of the danger of inter-granular penetration of this alloy into the steel occurring at temperatures below its melting point of 200ºC during the 190-220ºC baking treatment required to remove embrittlement. 10.14.2 Sheradizin g (BS 4921)  This process shall not be used as it may adversely affect the properties of the item. 10.14.3 Hot Dip Galvaniz in g  This process shall not be used as it may adversely affect the properties of the item. 10.15 Re-Processi ng and Re-Furbishm ent 10.15.1 Items may only be stripped and re-coated at the discretion of the Design Authority. 10.15.2  The method of stripping shall be appropriate to the coating to be removed. Anodic electrolytic processed may be used but cathodic process shall not be used. Acid solutions should be avoided. 10.15.3 After stripping and before re-coating, items shall be baked according to the re-coating requirements of Table 2. After re-coating, the items shall be given the full baking treatment appropriate to the coating process. 11 Inspectio n and Testi ng See clauses 6 and 7.2 along with the individual standards referred to in clause 10. 13 DEF STAN 03-4 Issu e 6 Table 2 Baking Treatments to be Given to Items after Prot ective Processi ng Standard Clause Process Specification Protective Treatment Baking Treatment at temperatures in °C and times generally in hours (h) Category 1451 to 1800 MPa 10.2 Def Stan 03-19 Cadmium Electrodeposition MPa 1451-1500 1501-1600 1601-1700 1701-1800 10.3 Def Stan 03-28 (part 2) Def Stan 03-20 Def Stan 03-14 Cadmium Vacuum Ion Vapour deposition Zinc Electrodeposition Chromium Electrodeposition None None 190°-220° for 24h minimum 190°-220° for 24h minimum 10.6 Def Stan 03-27 10.7 BS EN ISO 4527 Nickel Electro-deposition (heavy) Electroless Nickel As for Cadmium Electro-deposition (Above) Peened items and unpeened items not subject to fatigue As for Cadmium Electro-deposition (Above) Unpeened items subject to fatigue 1450 – 1800 MPa: 400-480°C for 1h minimum As for Cadmium Electro-deposition (Above) 10.8 Def Stan 03-9 Silver Electro-deposition As for Cadmium Electro-deposition (Above) 10.9 Def Stan 03-17 Gold Electro-deposition As for Cadmium Electro-deposition (Above) 10.10 BS EN ISO 2063 Def Stan 03-11 Sprayed Metal None 10.4 10.5 10.11 10.12 10.13.1 Phosphate  Treatment Paint applied to bare steel where etch primer is used BS 1872 Tin Electrodeposition After stripping and before all processing by wet methods  Treatment 190°-220° 16h minimum 190°-220° 18h minimum 190°-220° 20h minimum 190°-220° 22h minimum Category 1801 MPa and Greater  190°-220° for 24h minimum As for Cadmium Electro-deposition (Above) 130°-200° 4h minimum 190°-200° 45 – 75 minutes 190°-230°C 190°-220° for 24h minimum 190°-220° for 24h minimum 190°-220° for 24h minimum 190°-220° for 24h minimum None 170°-200° for 6h minimum 190°-200° for 45 – 75 minutes 18h minimum 190°-230° 24h minimum 10.15 Not less than190° for not less than 6h Not less than 190° for not less than 18h Note 1: Case Hardened items – At the discretion of the Design Authority, case hardened items not electrodeposited over the hardened area may be baked at not less than 130° for not less than 6h Note 2: hard Drawn Springs – For springs made from hard drawn wire or strip, the duration of baking at 190° - 230° may be reduced to not less than 8h 14 DEF STAN 03-4 Issu e 6  Annex A Metho d fo r Determin ing Oxidi zable Material in Sulfu ric Acid  A.1 Meth od ol og y Add 15 ml of concentrated sulphuric acid to 60 ml of distilled water, cool, and to the mixture add 0.10 ml of  0.02 molar solution of potassium permanganate solution (3.3 g/l). The pink colour shall persist for 5 minutes indicating a presence of not more than 11 ppm oxidizable substances calculated as sulphur dioxide. 15 ©Crown Copyright 2011 Copying Only as Agreed with DStan Defence Standards are published by and obtainable from: Defence Equipment and Support UK Defence Standardization Kentigern House 65 Brown Street GLASGOW G2 8EX DStan Helpdesk  Tel : 0141 224 2531/2 Fax 0141 224 2503 Internet e-mail [email protected] File Reference  The DStan file reference relating to work on this standard is D/DStan/313/4/2 Contract Requirements When Defence Standards are incorporated into contracts users are responsible for their correct application and for complying with contractual and statutory requirements. Compliance with a Defence Standard does not in itself confer immunity from legal obligations. Revision of Defence Standards Defence Standards are revised as necessary by up issue or amendment. It is important that users of Defence Standards should ascertain that they are in possession of the latest issue or amendment. Information on all Defence Standards can be found on the DStan web site www.dstan.mod.uk updated weekly and supplemented regularly by Standards in Defence News (SID News). Any person who, when making use of a Defence Standard encounters an inaccuracy or ambiguity is requested to notify the Directorate of Standardization (DStan) without delay in order that the matter may be investigated and appropriate action taken. Sponsors and authors shall refer to Def Stan 00-00 part 2 before proceeding with any standards work.