Kabushiki Kaisha Kobe Seiko Sho

Kobe Steel, Ltd.

Nhk Spring Co., Ltd.

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

Suncall Corporation

Shinko Wire Company, Ltd.

Sumie Suda

Nobuhiko Ibaraki

Koichi Sakamoto

Tomoko Sugimura

Atsuhiko Yoshida

Noritoshi Takamura

Nao Yoshihara

Yoshio Fukuzaki

Koji Harada

Tadayoshi Fujiwara

Tetsuo Jinbo

Shigetsugu Yoshida

Satoru Tendo

Naoki Terakado

Atushi Inada

Satoru Tendoh

A steel wire has tempered martensite, comprises, as essential components, by mass, C: 0.53 to 0.68%; Si: 1.2 to 2.5%; Mn: 0.2 to 1.5%; Cr: 1.4 to 2.5%; Al: 0.05% or less; further comprises, as a selective component, Ni: 0.4% or less; V: 0.4% or less; Mo: 0.05 to 0.5%; or Nb: 0.05 to 0.5%; and further comprises remainder essentially consisting of Fe and inevitable impurities, wherein the grain size number of prior austenite is 11.0 or larger, and the proof stress ratio (&#x3c3;/&#x3c3;), namely, a ratio of 0.2% proof stress (&#x3c3;) to tensile strength (&#x3c3;) is 0.85 or lower. Satisfying the above requirements makes it possible to produce a steel wire for high-strength spring excellent both in workability (cold workability), and in sag resistance and fatigue properties.

Steel wire for high strength spring excellent in workability and high strength

Disclosed is a hard-drawn spring which exhibits fatigue strength and sag resistance equal or superior to springs produced using an oil-tempered wire. The hard-drawn spring is produced using a steel wire containing 0.5 to 0.7 mass % of C, 1.0 to 1.95 mass % of Si, 0.5 to 1.5 mass % of Mn and 0.5 to 1.5 mass % of Cr, with the balance being Fe and inevitable impurities. In the steel wire, the number of carbides having circle-equivalent diameters of 0.1 &#x3bc;m or more is 5 particles/100 &#x3bc;mor less.

Spring produced by a process comprising coiling a hard drawn steel wire excellent in fatigue strength and resistance to setting

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

The spring steel according to the present invention is a spring steel excellent in sag resistance and fatigue property containing: C: 0.5 to 0.8% by mass (hereinafter, referred to as %), Si: 1.2 to 2.5%, Mn: 0.2 to 1.5%, Cr: 1.0 to 4.0%, V: 0.5% or less (including 0%), P: 0.02% or less (excluding 0%), S: 0.02% or less (excluding 0%), Al: 0.05% or less (excluding 0%), and Fe and inevitable impurities as the balance, wherein the Si content and the Cr content satisfy the following formula (1):0.8&#xd7;[Si]+[Cr]&#x2267;2.6&#x2003;&#x2003;(1)(wherein, [Si] and [Cr] respectively represent the Si content (%) and the Cr content (%)). The spring steel is useful in improving both sag resistance and fatigue property.

Spring steel excellent in sag resistance and fatigue property

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

Steel wire for hard drawn spring excellent in fatigue strength and resistance to settling, and hard drawn spring and method of making thereof

Disclosed herein is an ultra clean spring steel which contains inclusions easily elongated and broken into fine particles by hot rolling and which is easily adaptive to cold rolling and yields springs excelling in fatigue characteristics. The spring steel is characterized in that the wire contains oxide inclusions with a sulfur concentration no more than 10 mass % such that no less than 70% (in terms of numbers) of such inclusions, which exist in the outer layer outside one quarter of the diameter of the wire and have a width no smaller than 3 &#x3bc;m, satisfies the formula (1) below,CaO+AlO+SiO+MnO+MgO&#x3e;80 (mass %) . &#x2003;&#x2003;(1)

Ultra clean spring steel

Disclosed is a steel wire rod for hard-drawn springs capable of exhibiting fatigue strength and sag resistance equivalent to or higher than springs made of an oil-tempered wire. The steel wire rod contains carbon in a range from 0.5 to less than 0.7 mass %, silicon in a range from 1.4 to 2.5 mass %, manganese in a range from 0.5 to 1.5 mass %, chromium in a range from 0.05 to 2.0 mass %, and vanadium in a range from 0.05 to 0.40 mass %, and has an area ratio Rp with respect to pearlite which satisfies the mathematical expression (1):(area %)&#x2267;55&#xd7;[]+61&#x2003;&#x2003;(1)where [C] denotes the content (mass %) of carbon.

Steel wire rod for hard drawn spring, drawn wire rod for hard drawn spring and hard drawn spring, and method for producing hard drawn spring

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Kobe, Japan

Sumie Suda