BS 5338-1976 Code of practice for zinc alloy pressure die casting for engineering《工程用锌合金压模铸件实用规程》.pdf

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1、BRITISH STANDARD BS 5338:1976 Code of practice for Zinc alloy pressure die casting for engineering (formerly CP 3001) UDC 621.74.043.2:669.55BS5338:1976 This British Standard, having been prepared under the directionof the Non-ferrous Metals Standards Committee,waspublished underthe authorityof the

2、Executive Board on 30 June 1976 BSI 10-1999 First published as CP 3001 March 1955 First revision as BS 5338 June1976 The following BSI references relate to the work on this standard: Committee reference CP/NFE/8 Draft for comment 74/43204 DC ISBN 0 580 09432 4 Cooperating organizations The Non-ferro

3、us Metals Standards Committee, under whose supervision this British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: Aluminium Federation Association of Bronze and Brass Founders British Electrical and Allied Ma

4、nufacturers Association British Lead Manufacturers Association BNF Metals Technology Centre British Non-ferrous Metals Technology Centre Copper Development Association Department of Trade Electric Cable Makers Confederation Institute of British Foundrymen Institution of Mechanical Engineers* Institu

5、tion of Mining and Metallurgy Institution of Production Engineers Institution of Structural Engineers Lead Development Association Light Metal Founders Association London Metal Exchange Magnesium Industry Council Ministry of Defence* National Brassfoundry Association Non-ferrous Metal Stockists Post

6、 Office Royal Institute of British Architects Society of Motor Manufacturers and Traders Ltd.* Tin Research Institute Zinc Development Association* Individual manufacturer The organizations marked with an asterisk in the above list, together with the following, were directly represented on the commi

7、ttees entrusted with the preparation of this British Standard: Zinc Alloy Die Casters Association Amendments issued since publication Amd. No. Date of issue CommentsBS5338:1976 BSI 10-1999 i Contents Page Cooperating organizations Inside front cover Foreword iii Section 1. General 1 Scope 1 2 Refere

8、nces 1 3 Definitions 1 4 Consultation on design 2 Section 2. Materials 5 British Standards 2 6 Certification 2 Section 3. Basic design factors 7 General requirements 2 8 Advantages and limitations of zinc alloy die castings 2 9 Choice of alloy 2 10 Finishing 3 11 Mechanical properties 3 12 Dimension

9、al changes 3 Section 4. Component design 13 General aims 3 14 Section thickness 4 15 Ribs 4 16 Uniformity of sections 4 17 Undercuts 4 18 Fillets 4 19 Exterior corners 4 20 Bosses 4 21 Studs 4 22 Threads 4 23 Inserts 4 24 Lettering 5 25 Textured surfaces 5 26 Dimensions 5 27 Draft angle 5 28 Cored h

10、oles 5 Section 5. Working practice 29 Pressure die casting machines 5 30 Cleanliness of working 6 31 Metal temperature 6 32 Die temperature 6 33 Reclaimed metal 6 Section 6. Inspection 34 Inspection requirement 6 35 Ingot 6 36 Identification of castings 6 37 Provision of samples for inspection 6 38

11、Freedom from defects 7 39 Tests for compliance 7 40 Determination of minimum weight 7BS5338:1976 ii BSI 10-1999 Page Appendix A Properties of the zinc die casting alloys 8 Appendix B Dimensional changes of zinc alloy die castings on ageing 10 Appendix C Stress and energy unit conversions 11 Figure 1

12、 Stress and time to produce given amounts of strain (alloy A) at 20 C 9 Figure 2 Stress and time to produce given amounts of strain (alloy B) at 20 C 9 Figure 3 Diagrammatic part-section of hot chamber system used for the zinc alloys 12 Figure 4 Diagrammatic description of a horizontal cold-chamber

13、pressure die casting system 13 Table 1 Mechanical properties of zinc alloy diecastings at 20 C to 21 C 8 Table 2 Effect of temperature variation on mechanical properties 9 Table 3 Mechanical and physical properties of zinc alloy die castings 10 Publications referred to Inside back coverBS5338:1976 B

14、SI 10-1999 iii Foreword This code of practice was first published in 1955 asCP3001 and in accordance with current practice has been renumbered asBS5338. The revision ofBS1004 “Zinc alloys for die casting and zinc alloy die castings” in1972made it timely also to revise the code, which makes frequent

15、reference toBS1004. Accordingly the Zinc Alloy Die Casters Association submitted a draft revision to BSI for submission to a joint committee of BSI and the Institution of Mechanical Engineers. The present document drafted in metric terms is issued with their amendments and approval. As zinc alloy di

16、e castings are increasingly used for engineering components subject to stress, the new edition refers to the recently developed techniques for the control of pressure die casting machines by instrumentation, to ensure that they are working properly and consistently; and to the behaviour of the die c

17、astings when subjected to continuous stress. For the majority of engineering applications zinc alloys toBS1004 are completely satisfactory, but when subjected to continuous stress at temperatures appreciably above those of normal atmospheres they may not be suitable because of their tendency to cree

18、p. Zinc alloy die castings will perform satisfactorily in service only if they are free from contamination by certain elements harmful to their mechanical properties and corrosion resistance. It is therefore essential that these elements and, in particular, lead, tin, cadmium and indium should not b

19、e present in higher proportions than those indicated inBS1004. When supplies of die castings are required in accordance with this code of practice, it is desirable that both the enquiry and the order should state “Castings to be in accordance with the recommendations of the British Standard Code of

20、practiceBS5338”. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This do

21、cument comprises a front cover, an inside front cover, pages i to iv, pages 1 to 14, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.iv blankBS

22、5338:1976 BSI 10-1999 1 Section 1. General 1 Scope This code is concerned with the practice to be adopted in the design and manufacture of pressure die castings in compliance with the requirements ofBS1004. 2 References The titles of the British Standards referred to in this code are listed on the i

23、nside back cover. 3 Definitions For the purposes of this code of practice the following definitions apply. 3.1 pressure die casting a method of casting components by injecting molten metal into a split metal die where it solidifies under the applied pressure (see section 4); also a casting produced

24、on a pressure die casting machine 3.2 hot chamber pressure die casting machine a machine incorporating a self-replenishing pump immersed in the molten metal (seeFigure 3) 3.3 cold chamber pressure die casting machine a machine in which a metered quantity of metal is poured into a transfer chamber fo

25、r injection into the die (seeFigure 4) 3.4 injection cylinder the chamber that, in conjunction with the plunger, enables molten metal to be forced into the die 3.5 plunger the piston that, operating in a cylinder, forces molten metal into the die 3.6 die cavity the impression in the die in the shape

26、 of the required component 3.7 parting line the intersection with the die cavity of the surface or surfaces at which the die members abut 3.8 ejector pins rods bearing on the spray to release it from the die (seeFigure 3 andFigure 4) 3.9 draft angle or taper the angle on the surfaces of the die to f

27、acilitate ejection 3.10 runner a channel in the die through which molten metal fills the die cavity. This term is also applied to the metal that solidifies in this channel 3.11 gate that part of the die through which the metal enters the die cavity from the runner 3.12 sprue the metal attached to th

28、e runner that solidifies in the sprue bush (seeFigure 3) on a hot chamber machine 3.13 slug the residual metal from the injection cylinder of a cold-chamber machine that is attached to the runner. Sometimes termed “biscuit” 3.14 vent provision in the die to permit the escape of air from the die cavi

29、ty or overflow 3.15 overflow a recess with entry from the die cavity that assists in the production of sound castings 3.16 spray a casting or castings, complete with sprue or slug resulting from a single casting operation or “shot” 3.17 inserts shaped pieces, commonly of metal, that are inserted int

30、o prepared locations in the die and become part of the cast component 3.18 core an element of the die forming a recess in the casting 3.19 quenching the rapid cooling of a casting by immersion in waterBS5338:1976 2 BSI 10-1999 4 Consultation on design There should be early and continuous co-operatio

31、n between the die caster and the purchaser to ensure the satisfactory design and production of the component. Section 2. Materials 5 British Standards Compliance with the following British Standards is implied when the recommendations given in this code of practice are adopted: BS 1004, BS 3436, BS

32、3630. 6 Certification It is recommended that die castings should be produced under the certification scheme forBS1004 of the British Standards Institution. Only such castings may bear the certification mark as evidence of their compliance with the requirements ofBS1004. This mark shall, whenever pra

33、cticable, be applied to castings by die casters who hold a licence from BSI. Section 3. Basic design factors 7 General requirements Common requirements for components for engineering and allied uses are strength, structural soundness and dimensional accuracy. In addition, pressure tightness is somet

34、imes specified. When considering strength and structural soundness, it is necessary to take account of the stresses that may be involved in installation and that may well exceed those that are met in service. Allowance may have to be made for the removal of components for periodic inspection. These

35、matters may concern not only the general strength of the component but particularly the strength of screw threads, small bosses etc. 8 Advantages and limitations of zinc alloy die castings The pressure die casting of zinc alloy is a highly efficient method of production, particularly where quantity

36、requirements are large. The employment of precisely machined and highly finished steel dies permits complex shapes to be cast with great dimensional accuracy and with wall thicknesses that may be as little as0.5mm over relatively extensive areas. The as-cast surface is smooth enough to allow electro

37、deposited, organic and other finishes to be applied with a minimum of surface pretreatment. The designer of stressed components should take into account the continuous load, the amount of permissible distortion and the service temperature at which the component will operate (seeAppendix A). Due to a

38、geing effects the mechanical properties given inAppendix A may not be achieved before five weeks after casting. Zinc alloy die castings are unsuitable as components to be subjected to temperatures above150 C in service. Zinc alloys undergo a reduction in impact strength, though not of tensile streng

39、th, at subnormal temperatures (seeAppendix A) and, when required for use at low temperatures, it is necessary that components that may suffer shock loading should be designed with this in mind. The use of steel inserts at locations of likely high stress has proved satisfactory under extreme service

40、conditions. 9 Choice of alloy Alloy A toBS1004 is almost invariably selected for engineering applications. It has the advantage over alloy B of greater dimensional stability and better response to a stabilizing anneal where extremely close tolerances are specified. It is also rather more resistant t

41、o corrosion than alloy B; it is more ductile and retains its high impact strength during prolonged service at100 C. Alloy B is sometimes preferred, as for example in zip fastener sliders and gear wheels, on account of its slightly greater strength and hardness and also castability for thin section w

42、ork.BS5338:1976 BSI 10-1999 3 10 Finishing Resistance of zinc alloys to atmospheric corrosion is good and only abnormal conditions demand protective measures. Thus, excessively damp locations call for a chromate treatment (see Ministry of Defence, Defence Specification DEF130 “Chromate passivation o

43、f cadmium and zinc surfaces” 1) ) and installations exposed to very severe conditions, such as damp interior walls, require the added protection of a suitable paint after chromating. Normally where paint coatings are desired it is necessary to employ a preparatory phosphate treatment, a chromate tre

44、atment or an etch primer. When required for special resistance to contact with chemicals or for electrical insulation, plastics coatings may be applied either by dipping heated die castings into a fluidized bed of plastics particles or by electrostatically coating die castings with plastics particle

45、s that coalesce on stoving. The maximum temperature permissible is dependent on time at temperature. The following table offers a guide to the interrelationship between the two. Electroplated coatings are used mainly for decoration. The most usual practice is to electroplate with copper, followed by

46、 nickel and chromium (seeBS1224). Bright zinc plating is used to improve the appearance of some die castings. Alternative coatings, e.g. of noble metals, stainless iron etc., have been developed. When increased resistance to wear is desirable, a hard chromium deposit may be used. Resistance to wear

47、may also be increased by an anodizing process that coats the zinc alloy surface with a mixture of zinc ammonium phosphate and zinc chromate. This coating also has excellent resistance to neutral salt solutions and hot detergent solutions. 11 Mechanical properties When a component previously made in

48、another material is being redesigned as a zinc alloy die casting, the designer should give adequate consideration to the probable differences in mechanical properties, in order that the full economies of the process can be realized. Appendix A gives details of the mechanical and physical properties

49、of zinc die casting alloys. 12 Dimensional changes Zinc alloy die castings undergo very small dimensional changes on ageing, the magnitude of which depends on whether the castings are quenched or air cooled. A small shrinkage, which commences immediately after casting and proceeds at a diminishing rate over a period of years, may be of importance where certain dimensions are highly critical. A stabilizing treatment (seeAppendix B) accelerates these changes, particularly in respect of alloy A. The magnitude of the dimensional changes and details of the s