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Spring Materials


Introduction

Solid springs made from elastomers are not covered on this page.   This page covers materials used for making metal springs which mainly include helical compression, tensile, and torsion springs.  Leaf springs and disc spring materials properties may be identified in the more general notes.  The notes also concentrate more on the carbon steel and alloy steel grades rather than the non-ferrous grades.  Future updates will include more comprehensive information

A wide range of materials are available for the manufacture of metal springs including

  • Carbon steels
  • Alloy steels
  • Corrosion resisting steels
  • Corrosion resisting steels
  • Phosphor bronze
  • Spring brass
  • Beryllium copper
  • Nickel alloy steels
  • Titanium alloy steels

Springs are manufactured by hot or cold working processes.   The process depends on the section of the material, the spring index (C= D/d) and the properties required.

Pre-hardened wire should not be used if D/d < 4 or if d >6mm>



Reference Standard Notes

BS EN 10270-1:2001 ..Steel wire for mechanical springs. Patented cold drawn unalloyed spring steel wire
BS EN 10270-2:2001 ..Steel wire for mechanical springs. Oil hardened and tempered spring steel wire
BS EN 10270-3:2001 ..Steel wire for mechanical springs. Stainless spring steel wire


BS EN 10270-1:2001 ..Steel wire for mechanical springs. Patented cold drawn unalloyed spring steel wire
Wire designated within this standard is allocated one of a number of grades.

  • SL Grade is low tensile strength on static duties
  • SM Grade is medium tensile strength on static duties
  • SH Grade is high tensile strength on static duties
  • DM Grade is medium tensile strength on dynamic duties
  • DH Grade is high tensile strength on dynamic duties

A typical wire designation would be "Spring wire BS EN 10270-1-SH -3,60 ph.
Spring wire grade SH with a nominal diameter of 3,6mm phosphated.
The grade would have a tensile strength (according to the standard) Rm = 1700-1970MPa


BS EN 10270-2:2001 ..Steel wire for mechanical springs. Oil hardened and tempered spring steel wire
Wire designated within this standard is allocated one of nine grades.

  • Low Tensile grades - FDC (Static)... TDC(Medium Fatigue)...VDC (High Fatigue)
  • Medium tensile tensile grades- FDCrV (Static)... TDCrV(Medium Fatigue)...VDCrV (High Fatigue)
  • High tensile tensile grades- FDSiCr (Static)... TDSiCr(Medium Fatigue)...VDSiCr (High Fatigue)

The FD,FDCrV, and FDSiCr (Static) Grades have a size range of 0,5 to 17,00mm
The TDC,FDCrV, and TDSiCr (Medium Fatigue) Grades have a size range of 0,5 to 10,00mm
The VDC,VDCrV, and VDSiCr (High Fatigue) Grades have a size range of 0,5 to 10,00mm

A typical wire designation would be "Spring wire BS EN 10270-2-VDC -3,60 ".
Spring wire grade VDC with a nominal diameter of 3,6mm .
The grade would have a tensile strength (according to the standard) Rm = 1550-1650MPa


BS EN 10270-3:2001 ..Steel wire for mechanical springs. Stainless spring steel wire
This standard includes information on three steel grades 1,4310 ( with a normal tensile strength (NS) and a high tensile strength (HS)) , 1,4401, and 1,4568.

A typical designation according to this standard would be "Spring Wire BS EN 10270-2 - 1.4310 - NS -3,60 Ni coated
Steel designation number 1,4310 with nominal strength level. Nominal dia 3,6mm . Nickel coated
This steel has a nominal tensile Rm = 1500 MPa


Spring Material

Music Wire

This is the most widely used of all spring materials for small springs because it is the toughest.   It has the highest strength tensile and can withstand higher stresses under repeated loading conditions than any other spring material.  It can be obtained in diameters from 0,12 to 3mm.  It has a usable temperature range from 0 to 120oC

Oil-tempered Wire.  Music wire will contract under heat, and can be plated.

This is a general purpose spring material used for spings where the cost of music wire is prohibitive and for sizes outside the range of music wire.  This material is not suitable for shock or impact loading.  This material is available in diameters from 3 to 12mm.   The temperature range for this material is 0 to 180 oC..Will not generally change dimensions under heat.   Can be plated.   Also available in square and rectangular sections.

Hard-drawn wire

This is the cheapest general purpose spring steel and is should only be used where life, accuracy and deflection are not too important.  This material is available in sizes 0,8mm to 12mm.  It has an operating range 0 to 120oC

Chrome Vanadium wire

This is the most popular alloy spring steel for improved stress, fatigue, long endurance life conditions as compared to high carbon steel materials.  This material is also suitable for impact and shock loading conditions.  Is available in annealed and tempered sizes from 0,8mm to 12mm.  It can be used for temperatures up to 220 oC.   Will not generally change dimensions under heat. Can be plated.

Chrome-silicon wire

This an excellent spring material for highly-stressed springs requiring long life and/or shock loading resistance.  It is available in diameters 0,8mm to 12mmm and can be used from temperatures up to 250oC.   Will not generally change dimensions under heat. Can be plated.

Martensitic Stainless steel wire

This is a corrosion, resisting steel which is unsuitable for sub-zero conditions.

Austentic Stainless steel wire

A good corrosion, acid, heat resisting steel with good strength and moderate temperatures.  Has low stress relaxation.

Spring Brass

This is a low cost material which is convenient to form.  It is a high conductivity material.  This material has poor mechanical properties.  This metal is frequently used in electrical components because of its good electrical properties and resistance to corrosion.

Phosphor Bronze

Popular alloy .Withstands repeated flexures.  This metal is frequently used in electrical components because of its good electrical properties and resistance to corrosion.   Suitable to use in sub-zero temperatures.   They are much more costly than the more common stocks and cannot be plated.   Generally will not change dimensions under heat.

Beryllium Copper

High elastic and fatigue strength.  Hardenable.  They are much more costly than the more common stocks and cannot be plated.   Generally will not change dimensions under heat.

Nickel base alloys

These alloys are corrosion resistant.  They can withstand a wide temperature fluctuation.   The materials are suitable to use in precise instruments because of their non-magnetic characteristic. They also poses a high electrical resistance and should not be used as an electrical conductors.

Titanium

Used mainly in aerospace industry because of its extremely light weight and high strength.  This material is very expensive,  It is dangerous to work as titanium wire will shatter explosively under stress if its surface is scored.  Size range 0,8 to 12mm.   Generally will not change dimensions under heat.   Cannot be plated.


Spring Material Strength Values

Important Note..It is important to note that it is best to obtain springs from specialists suppliers who can provide the correct material for the specific application.  If springs are being designed for specific applications then strength values should be obtained from the relevant standards as identified above.  Care should be taken to include for fatigue and adverse operating conditions.   The notes on this page are for rough spring designs.

The material structure , the manufacturing process, and the heat treatment all have an influence on the strength of the spring material.  The strength of spring materials vary significantly with the wire size such that the strength of a selected spring material cannot be determined without knowing the wire size.  The standards identified all list the material strengths against the wire sizes.

The tensile strength versus the wire diameter is almost a straight line when plotted on log-log paper .   The equation for this line is..

Sut = A / dm

The table below provides some typical values for the above variables..

MaterialDiameter Range(mm)Exponent mA (MPa)
Music Wire0,1 to 6,50,1452211
Oil-Tempered 0,5 to 120,1871855
Hard Drawn0,7 to 120,1901783
Chrome_Vanadium0,8 to 120,1682005
Chrome_Silicon1,6 to 100,1081975
302-Stainless0,3 to 2,5,0,1461867
302-Stainless2,5 to 50,2632065
302-Stainless5 to 100,4782911
Phos-Bros0,1 to 0,601000
Phos-Bros0,6 to 2,00,028913
Phos-Bros2,0 to 7,50,064932


In calculating the spring parameters the torsional yield strength (S ys ) is used.   The relationship between the torsional yield strength and the ultimate strength Sut can be approximated with a range as follows.

0,35 Sut =< S ys =< 0,52 Sut


Music wire and hard drawn steel wire have an approximate relationship S ys = 0,45 Sut
Valve spring, CR_Va, CR-Si, Hardened and Tempered Carbon steel wires have an approximate relationship S ys >= 0,50 Sut
Many Non-ferrous materials have an approximate relationship S ys >= 0,35 Sut



Modulus Of Rigitity values

Typical Values for The modulus of Rigidity for different Spring materials are listed below

Material Modulus of Rigitity = G
-(x 10 3 N/mm 2 )
Carbon Steel78,6
316 Stainless68,9
Brass 34,5
Phos Bros41,4
Monel65,5
Iconel72,4
Berylium copper50,0


Links to Spring Design
  1. How to make springs ...A very informative website on springs and how to design and make them
  2. Midwest springs ...Site contains table of spring materials with properties - Imperial units though
  3. Bauer Springs ...some notes on materials to be used for disc springs
  4. Copper Developments Association ...Informatation on Copper based alloys for spring design


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Last Updated 21/02/2008