Kobe Steel, Ltd.

Takeshi Inoue

Koichi Sakamoto

Tomoko Sugimura

Atsuhiko Yoshida

Sei Kimura

Yoshio Fukuzaki

High cleanliness spring steel useful in manufacturing a spring with SiO-based inclusions being extremely controlled and excellent in fatigue properties is provided. High cleanliness spring steel which is steel containing;

High cleanliness spring steel and high cleanliness spring excellent in fatigue properties

High cleanliness spring steel useful in manufacturing a spring with SiO-based inclusions being extremely controlled and excellent in fatigue properties is provided.

An object of this invention is to provide a steel for high-cleanliness spring which is useful for the production of a spring excellent in fatigue characteristics in high Si steels. The steel for high-cleanliness spring with excellent fatigue characteristics according to the invention contains: in terms of mass %, C: 1.2% or less (excluding 0%); Si: 1.8% to 4%; Mn: 0.1% to 2.0%; and total Al: 0.01% or less (excluding 0%), with the remainder being iron and inevitable impurities, in which the Si amount and a solute (SIMS) Ca amount in the steel satisfy a relationship of the following expression (1):Si&#xd7;10&#x2266;solute (SIMS) Ca&#x2266;Si&#xd7;5&#xd7;10&#x2003;&#x2003;(1)(in which each of the solute (SIMS) Ca and Si represents the amount thereof (mass %) in the steel).

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Kobe, Japan

Takeshi Inoue