Kabushiki Kaisha Kobe Seiko Sho (kobe Steel, Ltd.)

Kobe Steel, Ltd.

Yoshio Fukuzaki

Koichi Sakamoto

Tomoko Sugimura

Atsuhiko Yoshida

Sumie Suda

Takeshi Kuroda

Yoshinori Yamamoto

Takeshi Inoue

Masaki Nitta

Daisuke Ogura

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).

Steel for high-cleanliness spring with excellent fatigue characteristics and high-cleanliness spring

The present invention relates to a high-cleanliness steel having a high fatigue strength and high cold workability, and a method of making the high-cleanliness steel. The method adds a Li&#x2014;Si alloy having a Li content between 20 and 40% and/or LiCOas a Li-containing substance to a molten steel. The Li-containing substance is added to the molten steel after the completion of a series of steps of a ladle refining process including composition adjustment, temperature adjustment and slag refining. The high-cleanliness steel has a total-Li content between 0.020 and 20 ppm by mass and contains 1.0 or below oxide inclusion particle having a major diameter of 20 &#x3bc;m or above at a maximum in 50 g of the steel wire. The steel contains an oxide inclusion that has a CaO content between 15 and 55%, SiOcontent between 20 and 70%, an AlOcontent of 35% or below, a MgO content of 20% or below and a LiO content between 0.5 and 20%. The high-cleanliness steel has improved fatigue characteristics and improved cold workability.

Method for producing high cleanness steel excellent in fatigue strength or cold workability

Method for producing high cleanliness steel excellent in fatigue strength or cold workability

A spring steel containing SiO,, Al,O,, CaO, and MgO as oxide type inclusions, which have an average composition (by weight) of 35%&lE;SiO,&lE;75%, 5%&lE;Al,O,&lE;30%, 10%&lE;CaO&lE;50%, and MgO&lE;5% (excluding 0%). This spring steel is superior in fatigue properties.

Spring steel superior in fatigue properties

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Kobe, Japan

Yoshio Fukuzaki