Nhk Spring Co., Ltd.

Kabushiki Kaisha Kobe Seiko Sho

Shinko Wire Company, Ltd.

Satoru Tendo

Noritoshi Takamura

Nobuhiko Ibaraki

Sumie Suda

Tadayoshi Fujiwara

Naoki Terakado

Tetsuo Jinbo

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

A coil spring reduces Hertzian stress on a first turn and bending stress on a coil end. A coil endis shifted in a diametral outer or inner direction of a coil spring relative to the first turn, to form a vertical gap between the coil endand the first turnin a free state without load on the coil spring. Due to the gap, the coil spring including the coil endand first turncan be entirely processed by shot peening as well as the remaining portion. The first turnreceives a combination of torsional stress and Hertzian stress (contact stress). Since the coil endthat receives high Hertzian stress is shifted in a diametral outer or inner direction of the coil spring relative to the first turn, a contact point on the first turnis shifted in the diametral outer or inner direction to reduce the torsional stress on the first turn. The shift and gap formed between the coil endand the first turnare effective to prevent excessive bending stress and breakage of the coil endwhen the coil endand first turnare repeatedly engaged and disengaged in the gap.

Coil spring

Growing community of inventors

Nagano, Japan

Satoru Tendo