This high quality high-carbon spring wire is the most common and readily available today. You might say that music wire will give you the biggest bang for your buck. This material is widely used for helical compression, extension and torsion springs in a wide range of applications, especially in the finer wire diameters. Known for its high tensile strength, high elastic limit, music wire can withstand high stresses under repeated loadings, and will continue to perform well under many normal cyclic applications.

Music wire is manufactured by a hard-drawn process, ideally to a “patented” specification. Today, in the North American market, the sizing is specified in decimal inch, available from .005” to .283”. Local distributors stock material manufactured in primarily in Canada, the United States, Korea and Japan.

The common specification standard used in everyday practice is ASTM A 228 (from the American Society for Testing and Materials).

A few interesting design considerations for music wire:

1. Maximum working temperature is 250 °F (120 °C) to ensure optimal performance – at this temperature the spring will lose approximately 5 percent of its load.
2. This material is used for cold-coiled springs only.
3. Do not attempt to weld this material.
4. Springs made from this material can successfully undergo a number of plating processes, both Electro- and Nonelectro-mechanical, such as Bright Zinc, Dichromate (various colours), Cadmium, Tin, Tin-Lead, Nickel, Copper, Black Oxide, or Zinc Phosphate. E-coating, Powder Coating, Painting, and Vinyl Dip finishes are also available to this material.
5. Can be ordered in preplated finish such as zinc, galvanized or Bezinal. This is especially beneficial to springs or wire forms that will not plate successfully due to tangling, nesting or distortion during the mechanical plating process.
6. Can be ordered in round, flat, square, as well as special shapes.
7. Maximum stress levels must be taking into account when designing a spring. “Setting” , “fatiguing” , or “breakage “ can occur when springs are worked passed their optimum levels/range.
8. Very limited corrosion resistance.
9. Shot-peening process can be used on music wire springs to improve fatigue life.

KEY MECHANICAL PROPERTIES of MUSIC WIRE:

Elastic Limit – Percent of tensile strength: in tension, 65 to 75 percent; in torsion, 45 to 50 percent.

Hardness, Rockwell – 42 to 46 °C.

Electrical Conductivity – Percent of copper, 8 to 12 percent.

Bending Properties – All diameters should be capable of being bent around an arbour equal to the wire diameter without breaking or cracking the surface.

Weight – per cubic inch, 0.284 (0.129 kg); per cubic centermeter 7.85 g.

HEAT TREATMENT

Referred to as “stress relieving”, “baking” or “stress equalizing” by spring makers, this operation should be done shortly after cold coiling or forming to remove residual coiling or bending stresses and to settle the molecule structure (or the resetting of the memory). At Springs & Things Inc. all springs and wire forms are stressed relieved by default, anywhere from 400 °F (200 °C) to 550 °F (290 °C). Normal tempering time is 30 minutes.

Interestingly, a usually desirable outcome arises from the stress relieving process known as “secondary hardness.” A spring will gain 2 to 3 points of Rockwell C hardness, resulting in an increase in the tensile strength and elastic limit.

CHEMICAL COMPOSITION OF MUSIC WIRE ASTM A 228 (% – percent)