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ASTM A228 (SWP-A, K08500) Music Wire

ASTM A228 music wire is a carbon (non-alloy) steel formulated for primary forming into wrought products. Cited properties are appropriate for the cold worked (strain hardened) condition. ASTM A228 is the defining standard for this material. K08500 is the UNS number.

It has the highest tensile strength among wrought carbon or non-alloy steels. In addition, it has a fairly low ductility and a moderately low thermal conductivity.

The graph bars on the material properties cards below compare ASTM A228 music wire to: wrought carbon or non-alloy steels (top), all iron alloys (middle), and the entire database (bottom). A full bar means this is the highest value in the relevant set. A half-full bar means it's 50% of the highest, and so on.

Mechanical Properties

Brinell Hardness


Elastic (Young's, Tensile) Modulus

190 GPa 27 x 106 psi

Elongation at Break

12 %

Fatigue Strength

1280 MPa 190 x 103 psi

Poisson's Ratio


Shear Modulus

72 GPa 10 x 106 psi

Shear Strength

1470 MPa 210 x 103 psi

Tensile Strength: Ultimate (UTS)

2450 MPa 360 x 103 psi

Tensile Strength: Yield (Proof)

2050 MPa 300 x 103 psi

Thermal Properties

Latent Heat of Fusion

250 J/g

Maximum Temperature: Mechanical

400 °C 750 °F

Melting Completion (Liquidus)

1450 °C 2650 °F

Melting Onset (Solidus)

1410 °C 2570 °F

Specific Heat Capacity

470 J/kg-K 0.11 BTU/lb-°F

Thermal Conductivity

49 W/m-K 28 BTU/h-ft-°F

Thermal Expansion

12 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

7.1 % IACS

Electrical Conductivity: Equal Weight (Specific)

8.2 % IACS

Otherwise Unclassified Properties

Base Metal Price

1.8 % relative


7.8 g/cm3 490 lb/ft3

Embodied Carbon

1.4 kg CO2/kg material

Embodied Energy

19 MJ/kg 8.0 x 103 BTU/lb

Embodied Water

45 L/kg 5.4 gal/lb

Common Calculations

Resilience: Ultimate (Unit Rupture Work)

280 MJ/m3

Stiffness to Weight: Axial

13 points

Stiffness to Weight: Bending

24 points

Strength to Weight: Axial

87 points

Strength to Weight: Bending

52 points

Thermal Diffusivity

13 mm2/s

Thermal Shock Resistance

79 points

Alloy Composition

Iron (Fe)Fe 98 to 99
Carbon (C)C 0.7 to 1.0
Manganese (Mn)Mn 0.2 to 0.6
Silicon (Si)Si 0.1 to 0.3
Sulfur (S)S 0 to 0.030
Phosphorus (P)P 0 to 0.025

All values are % weight. Ranges represent what is permitted under applicable standards.

Followup Questions

Similar Alloys

Further Reading

ASTM A228: Standard Specification for Steel Wire, Music Spring Quality

ASM Specialty Handbook: Carbon and Alloy Steels, J. R. Davis (editor), 1996

Ferrous Materials: Steel and Cast Iron, Hans Berns and Werner Theisen, 2008

Steels: Processing, Structure, and Performance, 2nd ed., George Krauss, 2015