1、| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD BS 7371 : Part 9 : 1996 I
2、CS 21.060; 25.220 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Coatings on metal fasteners Part 9. Specification for phosphate or phosphate and oil coatingsThis British Standard, having been prepared under the direction of the Engineering Sector Board, was published under t
3、he authority of the Standards Board and comes into effect on 15 October 1996 BSI 1996 The following BSI references relate to the work on this standard: Committee reference FME/9 Draft for comment 95/702198 DC ISBN 0 580 26245 6 BS 7371 : Part 9 : 1996 Amendments issued since publication Amd. No. Dat
4、e Text affected Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee FME/9, Bolts, nuts and accessories, upon which the following bodies were represented: BEAMA Ltd. British Constructional Steelwork Association Ltd. British In
5、dustrial Fasteners Federation British Steel Industry British Steel Industry (Wire Section) Gauge and Tool Makers Association National Association of Fastener Stockholders Society of Motor Manufacturers and Traders Ltd. Washer Manufacturers Association of Great Britain The following bodies were also
6、represented in the drafting of the standard, through subcommittees and panels: British Turned-parts Manufacturers Association Institute of Metal Finishing Metal Finishing Association National Centre of Tribology Stainless Steel Fabricators Association of Great BritainBS 7371 : Part 9 : 1996 BSI 1996
7、 i Contents Page Committees responsible Inside front cover Foreword ii Specification Introduction 1 Scope 1 2 References 2 3 Definitions 2 4 Applications and type of coating 2 5 Coating 2 6 Gauging after coating for threaded fastener components 3 7 Information to be documented and supplied to the co
8、ater 3 8 Identification 3 Annex A (informative) Determination of coating mass per unit area 4 Table 1 Classification of coating and coating mass per unit area 2 List of references Inside back coverii BSI 1996 BS 7371 : Part 9 : 1996 Foreword This British Standard has been prepared by Technical Commi
9、ttee FME/9 to provide Part of a series of standards on requirements for coatings on metal fasteners. WARNING. This British Standard calls for the use of substances and/or procedures that may be injurious to health if adequate precautions are not taken. It refers only to technical suitability and doe
10、s not absolve the user from legal obligations relating to health and safety at any stage. Compliance with a British Standard does not of itself confer immunity from legal obligations. BSI 1996 1 BS 7371 : Part 9 : 1996 1) All other Parts of BS 7371 should be read in conjunction with this Part. Speci
11、fication Introduction BS 7371 deals with the performance and selection of coatings on metal fasteners and accessories. This Part of BS 7371 specifies the requirements for phosphate or phosphate and oil coatings. Other published Parts of BS 7371 are as follows: BS 7371 : Part 1 : 1991 Specification f
12、or general requirements and selection guidelines 1) BS 7371 : Part 2 : 1993 Specification for torque/clamping force relationship BS 7371 : Part 3 : 1993 Specification for electroplated zinc and cadmium coatings BS 7371 : Part 4 : 1994 Specification for electroplated nickel, nickel/chromium and coppe
13、r/nickel/chromium coatings BS 7371 : Part 7 : 1993 Specification for mechanically applied zinc coatings BS 7371 : Part 10 : 1994 Specification for organic coatings BS 7371 : Part 11 : 1993 Specification for zinc flake non-electrolytically applied cured coatings Further Parts of the series to incorpo
14、rate the following are in preparation: Specification for electroplated tin and tin/lead coatings Specification for electroplated coatings for special purposes Specification for mechanically applied coatings for special purposes Phosphate coatings covered by this Part of BS 7371 are for use on fasten
15、ers and accessories where the following apply: a) a relatively low corrosion resistance can be accepted; b) a low cost coating with lubricative properties is required, to give a controlled torque/clamping force relationship; c) the risk of hydrogen embrittlement of high tensile steel fasteners is ac
16、ceptable, or is minimized by suitable processing (see BS 7371 : Part 1 : 1991 and 5.4 of this standard); d) an even overall coverage is required; e) a coating is required as an undercoat to assist adhesion and/or corrosion resistance of an organic type coating (see BS 7371 : Part 10 : 1994). The sha
17、pe of certain parts may create difficulties in the application of these coatings and reference to the coater is recommended to enquire whether a difficulty exists or whether it can be overcome by the use of specialized processing methods. Typical difficulties arise when bulk processing the following
18、: 1) parts with flat surfaces that may stick together during processing, e.g. flat washers; 2) parts with shapes that induce nesting; 3) parts with recesses which may retain excessive lubricant. The coatings specified in this standard are suitable for application to metal components such as the foll
19、owing: i) parallel threaded fasteners and accessories; ii) screws that cut or form their own threads, e.g. self-tapping screws (see for example BS 4174 : 1972); iii) woodscrews (see for example BS 1210 : 1963); iv) springs and spring components; v) pipe nuts and connectors with parallel or tapered t
20、hreads. When these coatings are applied to non-ferrous fasteners the corrosion resistance requirements do not apply. NOTE. The coating processes covered by this standard may induce hydrogen embrittlement in certain ferrous fasteners. Attention is drawn to the appropriate requirements of BS 7371 : Pa
21、rt 1 : 1991. 1 Scope This Part of BS 7371 specifies requirements for phosphate or phosphate and oil coatings on metal fasteners and accessories, applied by immersion or spraying. NOTE 1. Phosphate coatings are primarily intended for application to ferrous, zinc or zinc alloy fasteners. NOTE 2. Phosp
22、hate coatings can be used as an undercoat to improve the corrosion resistance and adhesion of a subsequently applied top coat (e.g. organic coating). NOTE 3. Phosphate coatings can be used to impart a controlled torque/clamping force relationship to a threaded fastener (see BS 7371 : Part 2 : 1993).
23、 This Part of BS 7371 should be read in conjuction with the requirements for phosphate and phosphate and oil coatings of BS 7371 : Part 1 General requirements and selection guidelines. This Part of BS 7371 also specifies requirements for the following: a) the minimum coating mass per unit area; b) a
24、ssessment of the corrosion resistance of unused coated parts when subjected to neutral salt spray testing (see for example BS 7479 : 1991).2 BSI 1996 BS 7371 : Part 9 : 1996 2) See BS EN 20898 : Part 1 : 1992 for property classes. 2 References 2.1 Normative references This Part of BS 7371 incorporat
25、es, by dated or undated reference, provisions from other publications. These normative references are made at the appropriate places in the text and the cited publications are listed on the inside back cover. For dated references, only the edition cited applies; any subsequent amendments to or revis
26、ions of the cited publication apply to this Part of BS 7371 only when incorporated in the reference by amendment or revision. For undated references, the latest edition of the cited publication applies, together with any amendments. 2.2 Informative references This Part of BS 7371 refers to other pub
27、lications that provide information or guidance. Editions of these publications current at the time of issue of this standard are listed on the inside back cover, but reference should be made to the latest editions. 3 Definitions For the purposes of this Part of BS 7371, the definitions given in BS 7
28、371 : Part 1 : 1991 apply. 4 Applications and type of coating 4.1 Cleaning and pretreatment Parts, fasteners and accessories shall be cleaned and pretreated in accordance with clauses 4 and 5 of BS 7371 : Part 1 : 1991. NOTE. Precautions appropriate for the avoidance of hydrogen embrittlement of hig
29、h tensile parts should be observed. 4.2 Type of coating The coating shall be matt grey and crystalline in appearance and consist primarily of manganese or zinc phosphate. 4.3 Application The coating shall be applied to the fastener by either immersion in or spraying with the appropriate solution of
30、manganese or zinc phosphate. 5 Coating 5.1 Surface condition When supplied unoiled the coating shall be dry and of crystalline appearance. NOTE. The appearance may vary slightly according to the surface condition of the substrate, even on the same fastener. Phosphate coatings shall be supplied oiled
31、 unless otherwise requested (see clause 8). NOTE. The oiled coating is dark grey to black and may be visibly oily. The torque/clamping force performance of a phosphate and oiled coating shall be in accordance with BS 7371 : Part 2 : 1993. 5.2 Classification of coating Phosphate coatings shall be cla
32、ssified as shown in table 1. 5.3 Minimum coating mass per unit area The minimum coating mass per unit area shall be as shown in table 1. NOTE. A suitable method for the determination of coating mass per unit area is given in annex A. Table 1. Classification of coating and coating mass per unit area
33、Classification Coating type Minimum coating mass per unit area g/m 2 Type 1 1) Manganese phosphate 8 Type 2 2) Zinc phosphate 3) 10 1) Oiled type 1 coatings are usually used to impart corrosion resistance coupled with a controlled torque/clamping force relationship to a threaded fastener. 2) Type 2
34、coatings may be used as an undercoat for organic coatings (see BS 7371 : Part 10 : 1994). 3) Other metal phosphates may be incorporated in the coating, e.g. calcium or iron. 5.4 De-embrittlement process Fasteners heat treated or cold worked to a surface hardness greater than 320 HV or of property cl
35、ass 9.8 2) and above which are phosphate coated shall be heat treated within 1 h of the completion of the phosphating process to reduce the risk of embrittlement failure. The heat treatment process shall consist of baking the fastener for min. 1 h at a temperature of between 130 C and 200 C. Fastene
36、rs shall not be baked at temperatures greater than that at which they were finally tempered during any heat treatment process carried out prior to the phosphating treatment. NOTE 1. High tensile fasteners with a surface hardness below 390 HV need not have this baking treatment if they are not used u
37、ntil at least 48 h after the completion of the phosphating treatment. NOTE 2. Although the surface hardness of fasteners of property class 8.8 may marginally exceed 320 HV it is not a requirement of this standard that they should be heat treated subsequent to any phosphating process provided that th
38、e surface hardness is not in excess of 350 HV. NOTE 3. Where any subsequent hardening heat treatment of a phosphate coated fastener is likely to increase the surface hardness above 320 HV, the phosphate coating should be removed prior to the hardening heat treatment process in order to reduce the ri
39、sk of any resulting embrittlement. BSI 1996 3 BS 7371 : Part 9 : 1996 3) Marking BS 7371 : Part 9 : 1996 on or in relation to a product represents a manufacturers declaration of conformity, i.e. a claim by or on behalf of the manufacturer that the product meets the requirements of the standard. The
40、accuracy of the claim is solely the claimants responsibility. Such a declaration is not to be confused with third party certification of conformity, which may also be desirable. 5.5 Corrosion resistance of oiled coated ferrous parts NOTE. There is no requirement in this standard for the corrosion re
41、sistance of unoiled phosphate coatings or for coatings applied to non-ferrous fasteners and parts. Unless otherwise agreed, representative samples from a batch of phosphate and oiled coated fasteners shall be selected in accordance with clause 7 of BS 7371 : Part 1 : 1991 and shall be tested for res
42、istance to salt spray in accordance with BS 7479 : 1991. The time for base metal corrosion varies according to the make and type of oil used but shall be a minimum of 24 h. Other corrosion requirements shall be agreed between the purchaser and supplier. 6 Gauging after coating for threaded fastener
43、components After coating, the finished threaded fastener component shall conform to the following. a) A coated externally threaded fastener component shall assemble into a similarly threaded nut with thread of tolerance class 6H in accordance with Part 2 of BS 3643 : 1981. b) A coated internally thr
44、eaded fastener component shall assemble onto a similarly threaded bolt with thread of tolerance class 6g in accordance with Part 2 of BS 3643 : 1981. NOTE. Phosphate coatings are unlikely to cause thread interference when applied to standard threads of pitch 0.45 and above. 7 Information to be docum
45、ented and supplied to the coater The following information to be supplied by the purchaser shall be fully documented. Both the definitive requirements specified throughout the standard and the following documented items shall be satisfied before a claim of compliance with the standard can be made an
46、d verified: a) the number and date of this British Standard, i.e. BS 7371 : Part 9 : 1996; b) the coating classification (see table 1); c) the oil or subsequent treatment; d) the hardness and property class of the component to be coated; e) if lubrication of the coating is required in accordance wit
47、h BS 7371 : Part 2 : 1993; f) any additional information regarding limitations of the process to be used; g) the requirement of any subsequent coating (e.g. organic coating). 8 Identification The coating shall be identified by the number and date of this British Standard, i.e. BS 7371 : Part 9 : 199
48、6 3) together with the coating designation in accordance with table 1. All phosphate coatings shall be supplied oiled unless otherwise specified by the purchaser. Examples: An oiled manganese phosphate coating is identified as BS 7371 : Part 9 : 1996 Type 1. An unoiled zinc phosphate coating is iden
49、tified as BS 7371 : Part 9 : 1996 Type 2 unoiled.BS 7371 : Part 9 : 1996 4 BSI 1996 Annex Annex A (informative) Determination of coating mass per unit area A.1 Determination of coating mass Degrease the group of components in an organic solvent and dry thoroughly. Determine the coating mass per unit area of phosphate using the method given in BS 5411 : Part 14 : 1982. A.2 Calculation of coating mass per unit area Calculate the coating mass per unit area in g/m 2 from the following formula: Coating mass per unit area = mass of stripped coating (in g)3 10 4 surface area (in c
