Copper Alloy Spring Materials

Copper Development Association

Copper Alloy Spring Materials

CDA Publication TN12, 1973

Copper Alloy Spring MaterialsCDA Publication TN12

Edited by A K Woollaston, 1973

AcknowledgementsThis publication is based on information sheets prepared by the Spring Materials Working Group set up bythe Mechanical Engineering Industry Committee of the Copper Development Association. The gratitude ofthe Association is recorded to all members for their co-operation and assistance. The Group reviewed theinformation available on the properties of the copper-base materials required for the design of copper alloysprings, and made additions and revisions to the original sheets published early in 1969.

The following organisations were represented on the Working Group:

Member companies of the British Non-Ferrous Metals Federation

The City University, Industrial Liaison Centre

International Nickel Limited

The Spring Research Association


Copper Development AssociationCopper Development Association is a non-trading organisation sponsored by the copper producers andfabricators to encourage the use of copper and copper alloys and to promote their correct and efficientapplication. Its services, which include the provision of technical advice and information, are available tothose interested in the utilisation of copper in all its aspects. The Association also provides a link betweenresearch and user industries and maintains close contact with other copper development associationsthroughout the world.

Website: www.cda.org.uk

Email: [email protected]

Copyright: All information in this document is the copyright of Copper Development Association

Disclaimer: Whilst this document has been prepared with care, Copper Development Association can giveno warranty regarding the contents and shall not be liable for any direct, indirect or consequential lossarising out of its use

1ContentsIntroduction .................................................................................................................................................2

Purchasing specification..............................................................................................................................2

Properties .....................................................................................................................................................2

Corrosion resistance ....................................................................................................................................2

Shear strength..............................................................................................................................................2

Availability ...................................................................................................................................................2

Shear elastic limit.........................................................................................................................................3

Modulus of rigidity ......................................................................................................................................3

Elongation ....................................................................................................................................................3

Fatigue, springback and bend test data .....................................................................................................3

Temper and hardness ..................................................................................................................................3

Definitions and conversion factors .............................................................................................................4

Bend ratio.....................................................................................................................................................4

Determination of approximate bend ratio and bend radius ....................................................................5

5% Phosphor Bronze (Copper-Tin-Phosphorus) ...................................................................................12

7% Phosphor Bronze (Copper-Tin-Phosphorus) ...................................................................................13

Nickel Silver (Copper-Nickel-Zinc)..........................................................................................................14

70/30 Brass .................................................................................................................................................16

2/1 and Common Brass .............................................................................................................................17

Copper-Beryllium......................................................................................................................................18

Nickel Copper NA 18.................................................................................................................................19

Nickel Copper NA 13.................................................................................................................................19

TablesTable A Bibliography 7

Table B Designations and compositions of copper alloy spring materials.8

Table C - Physical properties of copper and copper alloy spring materials 8

Table D Mechanical properties of copper and copper alloy spring materials.. 9

2IntroductionThe purpose of this technical note is to set out basic data on the copper alloys used in the formof strip and wire for springs, in order to assist the designer and user to prepare designs ofoptimum efficiency and economy. The note is based on information sheets prepared by theSpring Materials Working Group set up by the Mechanical Engineering Industry Committee ofthe Copper Development Association see Acknowledgements on inside front cover.

Purchasing specificationIt is recommended that material should be ordered to the relevant British Standard Specificationwhere applicable or to a specification agreed between the customer and the manufacturer. Thistechnical note is not intended to form the basis of a purchasing specification, but is primarilyintended for the use of designers.

PropertiesIn general, the values of mechanical properties quoted in Table D are the British Standardminima for each material and condition unless otherwise stated, or when a range is given. Inparticular, the physical properties are for material in the annealed condition, with the exceptionof the copper-beryllium alloy. In this case, the physical properties are typical for material inprecipitation hardened conditions.

Corrosion resistanceResistance to corrosion is important in most spring applications since corrosive attack mayincrease contact resistance and lead eventually to mechanical failure.

Copper alloys exhibit excellent resistance to atmospheric corrosion and in this respect are muchsuperior to carbon and low alloy steels. For instance, tests have shown that the resistance toattack in industrial atmospheres of copper alloys is up to ten times that of mild steel.

There are some differences in corrosion resistance between various copper alloys used forsprings and, in order to determine the most suitable material for a specific environment andapplication, reference should be made to the supplier or the Copper Development Association.

Shear strengthShear strength values for the brasses quoted in Table D are based on one-half and two-thirds ofthe tensile strength in the transverse and longitudinal rolling directions respectively. Shearstrength values for all other alloys are based on two-thirds of the tensile strength in thelongitudinal direction.

AvailabilityThe appearance of a particular alloy in Table B in strip form only, does not necessarily implythat the wire form is not available. Reference should be made to the relevant British Standardfor details of wire properties.

3Shear elastic limitThe values quoted for elastic limit in shear in Table D are based on 45% of the tensile strength,but some variations are likely due to both wiremaking and springmaking practices. Forinstance, the elastic limit of coil wound compression springs can be increased by amanufacturing process known as "prestressing" which is carried out whenever possible. In suchcases, a spring manufacturer should be consulted regarding optimum design stresses since thesedepend on both wire size and spring configuration.

Modulus of rigidityThe modulus of rigidity values quoted in Table C are based on 37.5% of the modulus ofelasticity for each material unless practical test results are available.

ElongationThe elongation values in Table D are quoted as a guide to formability. These values are quotedover the same hardness range for all phosphor bronzes to show the variation in formabilitybetween the different alloys.

Fatigue, springback and bend test dataFatigue, springback and bend test data are included in Table D where available.

Temper and hardnessIn general, temper of strip is measured by hardness, and temper of wire by tensile strength. Thetemper designations are contained in BS1420:1965 "Glossary of terms applicable to wroughtproducts in copper, zinc and their alloys", of which the following are typical examples andcommonly used in this technical note:

H Half hardH HardEH Extra hardSH Spring hardESH Extra spring hardW(H) Material which has been solution heat treated and subsequently cold

worked to hard temperW(H)P Material which has been solution heat treated, cold worked to hard

temper, fabricated and then precipitation heat treatedW(H)M Mill hardened material which has been solution heat treated, cold

worked to hard temper, and supplied in a precipitation-heat-treatedcondition for subsequent fabrication. No post fabrication heattreatment is required.

In addition, nickel silver strip may be assigned a temper grade ranging from 1 (hardest) to 5(softest). Vickers hardness (HV) values are used throughout this technical note. Tables forother hardness scales are contained in BS860:1967 "Tables for comparison of hardness scales".

4An alternative method of specifying the temper of strip material is by the amount of cold rollingapplied. This latter method is used in American (ASTM) specifications and this technical notecontains graphs indicating the approximate relationship between the two methods. It should beemphasised that the curves relating hardness with degree of cold working are typical formaterial of normal grain size (ie about 0.040 mm) and some variation will occur withdifferences in processing and grain size.

The ASTM temper designations for flat products are tabulated as follows:

Designation Percentage ReductionAnnealed 0Hard hard 20.7Hard 37.1Extra hard 50.15Spring hard 60.5Extra spring hard 68.65

Definitions and conversion factorsThe information contained in this technical note is given in Systme International d'Units (SI)units. The following table lists the factors for converting these SI units into Imperial units:

To convertFrom to

Multiply by

MS/m %IACS 1.724

ohm/m ohm in 39.37W/m C Btu ft/ft2hF 0.578N/mm2 lbf/in2 145.0per C per F 0.556N/mm2 tonf/in2 0.065

Bend ratio

Bend ratio (tR

) is defined as the ratio of minimum inside forming radius (t) to thickness of

material (R), eg bend ratio 2 defines inside radius of bend as twice material thickness.

5Determination of approximate bend ratio and bend radius

Example 1 - 5 % phosphor bronze strip (185HV) 0.040 in thick to be bent through 90 at 45to rolling direction.

1. Select experimental point (A) on relevant graph based on thickness and direction of rolling

2. Join origin (O) through point (A) and continue to edge of chart (B)

3. Typical obtainable bend ratios (BR) can be seen above line (OAB)

4. Actual minimum bend raduis E (in) can be obtained by drawing horizontal line (EAF)through point A.

Example 1 5% phosphor bronze 185HV 0.040 in 45o rolling direction

6Example 2 - 5 % phosphor bronze strip (210HV) 1.5mm thick to be bent through 90 at 90 torolling direction.

1. 1.5 mm does not conform to experimental thickness point

2. Take nearest experimental thickness point, ie 0.064 in (G)

3. Join origin (O) through (G) and continue to edge of chart (H)

4. Typical obtainable bend ratios (BR) can be seen above line (OGH)

5. Actual minimum bend radius,J (mm), can be obtained by drawing horizontal line throughintersection of vertical 1.5 mm thickness line (LK) and (OGH).

Example 2 - 5% phoshor bronze strip (210HV) 1.5 mm 90 rolling direction

7Table A - Bibliography

Spring designElastic stresses and deflections of helical compression springs of round wire,Engineering Sciences Data Unit item No 65005.

Notes on design of helical compression springs of round wire, EngineeringSciences Data Unit item No 65006.

Springs: materials/design/manufacture 1968, Spring Research Association, HenryStreet, Sheffield S3 7EQ

Gross, S C, Calculations and design of metal springs. Chapman & Hall, London,1966.

Wahl. A M, Mechanical springs. 2nd ed McGraw Hill, London, 1963.

British StandardsBS1726: Guide to the design and specification of coil springs. Part 1: 1964Helical compression springs.

BS2870:1698 Rolled copper and copper alloys. Sheet, strip and foil. (Metricunits.)

BS2873:1969 Copper and copper alloys. Wire. (Metric units).

BS3073:1968 Nickel and nickel alloys. Strip. (Metric and inch units.)

BS3075:1968 Nickel and nickel alloys. Wire. (Metric and inch units.)


No 71 The nickel silvers - design data and applications.

TN 10 Compositions and properties of copper and copper alloys (Superseded in2004 by Publication 120).

Mechanical and physical propertiesGohn, G R, Guerard, J and Herbert, G J. The mechanical properties of somenickel silver alloy strips. Proc ASTM, 1954, 54, 229.

Copper and copper alloy data. Conseil International pour le Developpement duCuivre (CIDEC), 100 rue du Rhone, Geneva.

12

5% Phosphor Bronze (Copper-Tin-Phosphorus)

13

7% Phosphor Bronze (Copper-Tin-Phosphorus)

14

Nickel Silver (Copper-Nickel-Zinc)

15

18% Nickel Silver NS107 (Copper-Nickel-Zinc)

16

70/30 Brass

17

2/1 and Common Brass

18

Copper-Beryllium

19

Nickel Copper NA 18

Nickel Copper NA 13

Copper Development Association5 Grovelands Business CentreBoundary WayHemel HempsteadHP2 7TE

Website: www.cda.org.ukEmail: [email protected]

ContentsTables

IntroductionPurchasing specificationPropertiesCorrosion resistanceShear strengthAvailabilityShear elastic limitModulus of rigidityElongationFatigue, springback and bend test dataTemper and hardnessDefinitions and conversion factorsBend ratioDetermination of approximate bend ratio and bend radius5% Phosphor Bronze (Copper-Tin-Phosphorus)7% Phosphor Bronze (Copper-Tin-Phosphorus)Nickel Silver (Copper-Nickel-Zinc)70/30 Brass2/1 and Common BrassCopper-BerylliumNickel Copper NA 18Nickel Copper NA 13

Documents

Copper Alloy Spring Materials