Music Wire vs Piano Wire (ASTM A228): Properties and Limits
Music wire and piano wire are two names for the same cold-drawn, high-carbon spring wire. In the US it is specified as ASTM A228; JIS uses SWP grades. This guide explains its properties, practical limits, and how it compares with other spring wire standards.
Why it dominates
- Strength: tensile strength is very high and rises as diameter falls (thinner is stronger) — among the highest of common spring materials; take the values for your diameter from the standard or the mill certificate
- Fatigue: excellent, thanks to fine drawn microstructure and good surface
- Cost: the cheapest per unit of stored energy
- Availability: widely available from mills and stockists, including in Taiwan, across a broad range of fine to medium diameters; confirm your diameter and lot before ordering
Its three limits
- Corrosion. Unprotected music wire rusts in humid air, and rust pits are fatigue crack starters. Plating (zinc, nickel) or oiling is mandatory for anything beyond dry indoor service.
- Temperature. Above roughly 120°C properties fade; by 150°C relaxation becomes significant. Choose chrome silicon or stainless for hot environments.
- Hydrogen embrittlement risk when plated. Electroplating high-strength music wire requires baking within hours — see plating springs.
Specifying it
Write "ASTM A228" or "JIS G 3522 SWP-B" plus the finish. Grades matter little for most work: A228 is a single tight spec; JIS distinguishes SWP-A/SWP-B/SWP-V (valve-spring cleanliness). For fatigue-critical uses in clean environments, SWP-V or Cr-Si buys certified cleanliness.
Music wire is the default answer to "material?" — but it is not automatically the right call. Our engineers check the environment and duty on every RFQ before confirming it.
Frequently Asked Questions
Is music wire the same as piano wire?
Yes — the names are interchangeable. The material is cold-drawn, high-carbon (≈0.8% C) steel wire with tightly controlled surface quality.
Why is thinner music wire stronger?
Cold drawing work-hardens the steel; thinner wire has undergone more reduction, so tensile strength rises as diameter falls. Standards tabulate strength by diameter for this reason.
Can music wire springs be used in salt environments with plating?
Poorly. Zinc plating delays rust but marine environments defeat it. Move to stainless 316 or consider the corrosion comparison in our materials guide.