This specification deals with the highest quality of round carbon steel spring wire, uniform in quality and temper, intended especially for the manufacture of valve springs and other springs requiring high-fatigue properties. The steel wire shall be subjected to continuous casting, hardening, and tempering to produce the desired mechanical properties. The steel shall conform to the chemical requirements for carbon, manganese, phosphorus, sulfur, and silicon. Mechanical properties shall be determined by the tension test, wrap test, twist test, and special surface inspection. The material as represented by tension test specimens shall conform to the tensile requirements for tensile strength and reduction of area. Metallurgical characterization of steel shall include decarburization, surface condition, and microstructure.