BS 7371-1-2009 金属紧固件涂层.一般要求和选择指南规范

raising standards worldwide™ NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BSI British Standards Coatings on metal fasteners – Part 1: Specification for general requirements and selection guidelines BS 7371-1:2009 BS 7371-1:2009 BRITISH STANDARD Publishing and copyright information The BSI copyright notice displayed in this document indicates when the document was last issued. © BSI 2009 ISBN 978 0 580 55382 0 ICS 21.060.01, 25.220.01 The following BSI references relate to the work on this standard: Committee reference FME/9 Draft for comment 08/30133813 DC Publication history First published January 1992 Second (present) edition, August 2009 Amendments issued since publication Date Text affected ????? www.bzfxw.com ???? www.bzfxw.com BRITISH STANDARD © BSI 2009 • i BS 7371-1:2009 Contents Foreword iii 1 Scope 1 2 Normative references 1 3 Terms and definitions 1 4 Selection of coatings 1 5 Preparation before coating 2 6 Hydrogen embrittlement 2 7 Thickness and coating weight 3 8 Sampling for inspection 3 9 Delivery conditions 4 10 Information to be supplied to the coater and designation 4 Annexes Annex A (informative) Selection guidelines 5 Annex B (informative) Avoidance of hydrogen embrittlement 9 Annex C (informative) Surface areas of bolts, screws and nuts 10 Annex D (informative) Delivery conditions 14 Bibliography 15 List of figures Figure C.1 – Constituent surface areas of a bolt or screw 11 List of tables Table A.1 – Protective value and service condition number 5 Table A.2 – Coating selection 6 Table A.3 – Coating recommendations for parallel threads 8 Table C.1 – Surface areas of screws and bolts 11 Table C.2 – Surface areas of nuts for electroplated coatings 12 Table C.3 – Surface areas of nuts for non-electroplated coatings 12 Summary of pages This document comprises a front cover, an inside front cover, pages i to iv, pages 1 to 16, an inside back cover and a back cover. www.bzfxw.com BS 7371-1:2009 ii • © BSI 2009 BRITISH STANDARD This page deliberately left blank ????? www.bzfxw.com ???? www.bzfxw.com BRITISH STANDARD © BSI 2009 • iii BS 7371-1:2009 Foreword Publishing information This part of BS 7371 is published by BSI and came into effect on 31 August 2009. It was prepared by Subcommittee FME/9/1, Mechanical properties of fasteners, under the authority of Technical Committee FME/9, Fasteners. A list of organizations represented on this committee can be obtained on request to its secretary. Supersession This part of BS 7371 supersedes BS 7371-1:1991, which is withdrawn. Relationship with other publications Other published Parts of BS 7371 are as follows: • BS 7371-2, Coatings on metal fasteners – Part 2: Specification for torque/clamping force relationship; • BS 7371-3, Coatings on metal fasteners – Part 3: Specifications for electroplated zinc; 1) • BS 7371-4, Coating on metal fasteners – Part 4: Specification for electroplated nickel, nickel/chromium and copper/nickel/ chromium coatings; • BS 7371-6, Coatings on metal fasteners – Part 6: Specification for hot dipped galvanized coatings; • BS 7371-7, Coatings on metal fasteners – Part 7: Specification for mechanically applied zinc and zinc based coatings; • BS 7371-8, Coatings on metal fasteners – Part 8: Specification for sherardized coatings; • BS 7371-9, Coatings on metal fasteners – Part 9: Specification for phosphate or phosphate and oil coatings; • BS 7371-10, Coatings on metal fastenings – Part 10: Specification for organic coatings; • BS 7371-11, Coatings on metal fasteners – Part 11: Specification for zinc flake non-electrolytically applied cured coatings; 2) • BS 7371-12, Coatings on metal fasteners – Part 12: Requirements for imperial fasteners. The Parts of BS 7371 listed describe coatings for: a) corrosion protection; b) appearance; c) electrical conductivity; d) controlled lubricity; e) identification; and f) avoidance of hydrogen embrittlement. Attention is drawn to Clause 4 and Annex A which provides advice on the suitability and limitations of the coatings for these purposes. 1) Being reviewed, replaced by BS EN ISO 4042 but remains current. 2) Obsolescent, replaced by BS EN ISO 10683 but remains current. www.bzfxw.com BS 7371-1:2009 iv • © BSI 2009 BRITISH STANDARD Information about this document This is a full revision of the standard, and introduces the following principal changes: • Change to Figure C.1. • Exclusion of cadmium. • General revision. Product certification/inspection/testing. Users of this British Standard are advised to consider the desirability of third-party certification/ inspection/testing of product conformity with this British Standard. Users seeking assistance in identifying appropriate conformity assessment bodies or schemes may ask BSI to forward their enquiries to the relevant association. Presentational conventions The provisions of this standard are presented in roman (i.e. upright) type. Its requirements are expressed in sentences in which the principal auxiliary verb is “shall”. Commentary, explanation and general informative material is presented in smaller italic type, and does not constitute a normative element. Contractual and legal considerations This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard cannot confer immunity from legal obligations. The attention of the user of this Part of BS 7371 is drawn to the restrictions placed on the use and supply of hexavalent chromium-containing substances by ECC Directive 2000/53/EC on End of Life Vehicles [1] and amendment of Annex II by Commission Decision June 2002 [Document No. C(2002) 2238] [2], and Non-Use on Motor Vehicles marketed after July 2007. Attention is drawn to The Waste Electrical and Electronic Equipment (WEEE) Directive (2002/96/EC) [3], which came into force on 31 December 2006. Attention is drawn to the restrictions placed on the marketing and use of cadmium and its compounds by in the Environmental Protection (Controls on Injurious Substances) (No. 4) Regulations 1992 [4]. Cadmium has thus been excluded from this Specification. ????? www.bzfxw.com ???? www.bzfxw.com BRITISH STANDARD © BSI 2009 • 1 BS 7371-1:2009 1 Scope This Part of BS 7371 specifies general requirements that apply to coatings covered by all other Parts of BS 7371, including: a) preparations before coating; b) hydrogen embrittlement avoidance; c) sampling for inspection; d) thickness testing; e) area tables for metric parallel threaded fasteners (area tables for imperial fasteners can be found in BS 7371-12); and f) selection of coatings (including the opportunity to select non-hexavalent chromium-containing coatings). Specific requirements are given in each Part of BS 7371. 2 Normative references The following references are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. BS 6041:1981+A1:1981, Method of sampling of electrodeposited metallic coatings and related finishes: procedures for inspection by attributes 3 Terms and definitions 3.1 significant surfaces areas visible on a part when assembled 3.2 batch average thickness average thickness of the coating on all components of a batch 3.3 production run batches of parts processed continuously without any changes in coating techniques or constituents within a single working day 4 Selection of coatings The coating shall be selected with regard to: a) corrosion resistance; b) appearance; c) shape and size; d) embrittlement; e) conductivity; f) lubricity; g) application limitations; h) colour (if applicable); and i) whether hexavalent chromium can be tolerated. NOTE Annex A provides guidance on suitable coatings for specific components. www.bzfxw.com BS 7371-1:2009 2 • © BSI 2009 BRITISH STANDARD 5 Preparation before coating Prior to coating, fastener parts shall be free of oil, grease, scale, oxides and other foreign matter. NOTE 1 The cleaning process should not induce hydrogen embrittlement (see Clause 6). NOTE 2 It is essential that the cleaning process is not detrimental to the substrate. 6 Hydrogen embrittlement 6.1 Cleaning processes Fastener parts heat-treated or cold-worked to a surface hardness of 320 HV to 390 HV, and also property classes3) 9.8, 10.9, and 10.9, shall be cleaned with an inhibited acid, alkaline or mechanical process. NOTE 1 The time during which parts are immersed in inhibited acid cleaning agents increases the risk of the introduction of potential hydrogen embrittlement. Immersion time in the inhibited acid should therefore be of minimum duration. Cathodic cleaning processes should be avoided. Special cleaning processes using non-acidic methods such as dry honing, abrasive blasting or alkali derusting shall be used to clean parts which have been heat-treated or cold-worked to a surface hardness greater than 390 HV or property class 12.9 and above. NOTE 2 Hydrogen embrittlement might cause premature failure of parts which are heat-treated or cold-worked to a surface hardness of 320 HV and above when subjected to stress. The property classes affected include 9.8 and above. Although baking after coating will minimize the risk of failure, the process can never be guaranteed to be completely effective. Annex B includes a more detailed explanation. 6.2 Coating processes Fastener parts shall be coated in accordance with the appropriate Parts of BS 7371. NOTE The risk of hydrogen-embrittlement failure of parts with a surface hardness greater than 390 HV, and also property class 12.9 and above, cannot be precluded unless coating processes are used which do not involve electrolysis from aqueous solutions. Only high-efficiency, non-cyanide type electroplating solutions or alternative non-embrittling coatings should be used (see Annex B). 6.3 De-embrittlement processes NOTE 1 Although property class 8.8 might marginally exceed 320 HV surface hardness, it is not neccessary to take these precautions provided that the surface hardness of this particular property class does not exceed 350 HV. Except for those parts described in Note 1, parts heat-treated or cold-worked to a surface hardness greater than 320 HV (and also property classes 9.8 and above which have been electroplated) shall be de-embrittled by baking. Parts shall not be heated to a temperature above that at which they were originally tempered. 3) Property classes are designated in BS EN ISO 898-1. ????? www.bzfxw.com ???? www.bzfxw.com BRITISH STANDARD © BSI 2009 • 3 BS 7371-1:2009 The baking process specified shall apply to the parts within the scope of this standard with the exception of: a) parts tempered below 180 °C; b) parts susceptible to hydrogen embrittlement; c) parts with coatings adversely affected by a temperature of 180 °C to 210 °C; and d) parts adversely affected by a temperature of 180 °C to 210 °C. The heating process shall commence within 1 h after the completion of electroplating. Except for those parts listed in a) to d), parts shall be heated to achieve a temperature of 180 °C to 210 °C within 4 h (maximum) after the completion of electroplating and shall be maintained at this temperature for the appropriate time as given in 1) to 6) below. These times shall be treated as minimum times at temperature. 1) Bolts and screws of property classes 9.8, 10.9 and 10.9 4 h. 2) Bolts and screws of property class 12.9 (see 6.1) 6 h. 3) Spring steel parts hardness range 400 HV to 500 HV 8 h. 4) Spring steel parts hardness range 500 HV to 600 HV 12 h. 5) Case-hardened tapping screws 2 h. 6) Case-hardened thread rolling screws 6 h. NOTE 2 It should not be assumed that the specified baking process will completely remove hydrogen embrittlement in all cases. Other conditions of duration and temperature can be used if they have been shown to be effective for the parts listed in a) to d). Parts which have been tempered at temperatures below 180 °C need baking at a lower temperature. Generally, parts baked at lower temperatures require longer times at that temperature. Some types of steel are more susceptible to hydrogen embrittlement than others and the baking times given might be inadequate in some circumstances. Certain coatings, e.g. tin, and the physical properties of some parts might be adversely affected by a temperature of 180 °C to 210 °C. In such cases, lower temperatures and longer times will be required. 7 Thickness and coating weight Thickness and coating weight shall be evaluated using the appropriate methods specified in each Part of BS 7371, which include: a) local thickness; b) batch average thickness; and c) mass per unit area. NOTE To assist in calculations, areas of standard metric bolts, screws and nuts are defined in Annex C. 8 Sampling for inspection Sampling for thickness measurement shall be in accordance with BS 6041:1981+A1. Sampling for corrosion testing or torque/clamping force measurement shall be in accordance with BS 6041:1981+A1, Table 3. www.bzfxw.com BS 7371-1:2009 4 • © BSI 2009 BRITISH STANDARD 9 Delivery conditions All requirements of the coating specifications shall be conformed to at the time of delivery of the fasteners or accessories to the location specified by the purchaser (see Annex D). NOTE The purchaser should state the location in the enquiry or order. 10 Information to be supplied to the coater and designation The following information shall be supplied to the coater. a) The number of this British Standard, i.e. BS 7371-1:2009. b) The Part of BS 7371 appropriate to the coating required. c) The coating grade or thickness as applicable. d) The requirement for lubrication, if applicable. e) The requirement, if any, for stress relieving before coating, and the stress relieving conditions. f) Special requirements, e.g. additional protection for storage (see Clause 9 and Annex D). g) The requirements of subsequent operations such as the application of adhesives. The coating shall be specified using at least the following designation (see footnote A) to Table A.2): “Coating in accordance with BS 7371-X:20XX: Grade ”. The lubricated condition shall be designated by the letter “L” after the grade identification (see Annex A). EXAMPLE An electroplated zinc coating of grade Zn8C with added lubrication is designated thus: BS 7371-3:2009: Grade Zn8CL. ????? www.bzfxw.com ???? www.bzfxw.com BRITISH STANDARD © BSI 2009 • 5 BS 7371-1:2009 Annex A (informative) Selection guidelines A.1 Guidelines on the selection of coatings A.1.1 Protective value and service condition number The protective value and service life of a coating will vary according to the type of coating, its thickness, the use of a chromate conversion treatment (or other coating where appropriate), and so on. For the purpose of this standard, degrees of severity are defined in Table A.1 and equated to a service condition number. A.1.2 Coating selection Coatings should be selected using the data in Table A.2 and Table A.3 in accordance with the criteria defined in Clause 4 and in conjunction with the appropriate Part of BS 7371. NOTE Increased thicknesses may be specified to extend resistance to rust provided that thread dimensions before plating are adjusted. All coatings except phosphate and oil coatings will not substantially deteriorate when stored in a good storage environment for a period of 3 months. Table A.1 Protective value and service condition number Designation number and service condition Description and application examples 0 Very mild Exposure to indoor atmospheres and not subject to condensation, wear or abrasion Example: a product with temporary protective coating for storage 1 Mild Exposure to indoor atmospheres with rare condensation and subject to minimum wear or abrasion Example: domestic furniture screws 2 Moderate Exposure mostly to dry indoor atmospheres but subject to occasional condensation, wear or abrasion Examples: fasteners for motor vehicle interiors, industrial machinery 3 Severe Exposure to condensation, perspiration, infrequent wetting by rain, and cleaners Examples: fasteners for window fittings, washing machines, bicycles 4 Very severe Exposure to harsh conditions or subject to frequent exposure to moisture, cleaners and saline solutions, plus likely damage by denting, scratching or abrasive wear Examples: plumbing, motor vehicle underbody fasteners NOTE For exceptionally severe service conditions for outdoor use (for example, electrical transmission towers, buildings and bridges, etc.) where very long service is required, consider hot dip galvanizing to BS 7371–6 or mechanical galvanizing to BS 7371-7 or sheradizing to BS 7371-8. For the extra thread tolerances required, see ISO 965-5:1998, thread tolerance 6AZ. www.bzfxw.com BS 7371-1:2009 6 • © BSI 2009 BRITISH STANDARD Table A.2 Coating selection Coating Grade A) Embrittlement B) Galvanic C) Conductive D) Lubricity E) Appearance and chromium content F) Service condition number Electroplated zinc G) Zn5A ✗ ✗ ✗ — Silver6+ 1 Zn5B ✗ ✗ ✗ — Silver6+ 1 Zn5C ✗ ✗ ✗ — Yellow6+ 2 Zn5D ✗ ✗ ✗ — Olive drab6+ 3 Zn5V ✗ ✗ ✗ — Silver-blue3+ 1 Zn5W ✗ ✗ ✗ — Silver-irid.3+ 1 ZN8A ✗ ✗ ✗ — Silver6+ 1 Zn8B ✗ ✗ ✗ — Silver6+ 1 Zn8C ✗ ✗ ✗ — Yellow6+ 2 Zn8D ✗ ✗ ✗ — Olive drab6+ 3 Zn8V ✗ ✗ ✗ — Silver-blue3+ 1 Zn8W ✗ ✗ ✗ — Silver-irid.3+ 1 Zn12A ✗ ✗ ✗ — Silver6+ 1 Zn12B ✗ ✗ ✗ — Silver6+ 2 Zn12C ✗ ✗ ✗ — Yellow6+ 3 Zn12D ✗ ✗ ✗ — Olive drab6+ 4 Zn12V ✗ ✗ ✗ — Silver-blue3+ 1 Zn12W ✗ ✗ ✗ — Silver-irid.3+ 2 Mechanically plated zinc G) Zn5AM — ✗ ✗ ✗ Silver6+ 1 Zn5BM — ✗ ✗ ✗ Silver6+ 1 Zn5CM — ✗ ✗ ✗ Yellow6+ 2 Zn5DM — ✗ ✗ ✗ Olive drab6+ 3 Zn5VM — ✗ ✗ ✗ Silver-blue3+ 1 Zn5WM — ✗ ✗ ✗ Silver-irid.3+ 1 Zn8AM — ✗ ✗ ✗ Silver6+ 1 Zn8BM — ✗ ✗ ✗ Silver6+ 1 Zn8CM — ✗ ✗ ✗ Yellow6+ 2 Zn8DM — ✗ ✗ ✗ Olive drab6+ 3 Zn8VM — ✗ ✗ ✗ Silver-blue3+ 1 Zn8WM — ✗ ✗ ✗ Silver-irid.3+ 1 ????? www.bzfxw.com ???? www.bzfxw.com BRITISH STANDARD © BSI 2009 • 7 BS 7371-1:2009 Table A.2 Coating selection (continued) Coating Grade A) Embrittlement B) Galvanic C) Conductive D) Lubricity E) Appearance and chromium content F) Service condition number Zn12AM — ✗ ✗ ✗ Silver6+ 1 Zn12BM — ✗ ✗ ✗ Silver6+ 2 Zn12CM — ✗ ✗ ✗ Yellow6+ 3 Zn12DM — ✗ ✗ ✗ Olive drab6+ 4 Zn12VM — ✗ ✗ ✗ Silver-blue3+ 1 Zn12WM — ✗ ✗ ✗ Silver-irid.3+ 2 Organic OA — — — ✗ Coloured H) 1 OB — — — ✗ Coloured 2 OC — — — ✗ Coloured 3 OD — — — ✗ Coloured 4 Zinc flake A — ✗ ✗ ✗ Silver greyc 3 B — ✗ ✗ ✗ Silver greyc 4 Hot dip galvanized — — ✗ ✗ ✗ Silver/grey 4 NOTE 1 The use of cadmium is severely restricted, cadmium has been removed from this table. NOTE 2 For exceptionally severe service conditions for outdoor use (for example, electrical transmission towers, buildings and bridges, etc.) where very long service is required, consider hot dip galvanizing to BS 7371-6 or mechanical galvanizing to BS 7371-7 or sheradizing to BS 7371-8. For the extra thread tolerances required, see BS ISO 965-5:1998, thread tolerance 6AZ. A) The designation can be extended to include requirements such as lubricity, colour, etc., in accordance with the appropriate Part of BS 7371 applicable to the specific coating. B) ✗ indicates the potential for embrittlement of parts during the coating process, see Clause 6. C) ✗ indicates that the method of protection is galvanic. D) ✗ indicates an ability to form part of an electrically conductive assembly at voltages of 12 V and greater with little resistance. E) ✗ indicates that lubricity is, or can be,