Honda Giken Kogyo Kabushiki Kaisha

Nippon Steel Corporation

Chuo Hatsujo Kabushiki Kaisha

Masato Yanase

Masayuki Hashimura

Ikuo Ochiai

Toshio Ozone

Takashi Otowa

Taisuke Nishimura

Hiroshi Yarita

Masaaki Mikura

The present invention provides, at low cost, a valve spring steel having a tensile strength as high as 210 to 240 kgf/mm.sup.2 after oil tempering. The high strength spring steel comprises, based on weight, 0.65 to 0.85% of C, 1.90 to 2.40% of Si, 0.50 to 1.00% of Mn, 0.70 to 1.30% of Cr, 0.10 to 0.30% of Mo, 0.20 to 0.50% of V, 0.01 to 0.04% of Nb and the balance Fe and unavoidable impurities and is subjected to heating at temperature of 1,050 to 1,250.degree. C. and then to rolling so that carbides in the steel have a size of up to 0.15 .mu.m in terms of equivalent circle. A valve spring having a tensile strength as high as 210 to 240 kgf/mm.sup.2 after oil tempering and stabilized quality can be produced while the material cost is greatly reduced by decreasing costly alloying components as much as possible.

High strength spring steel and process for producing same

Growing community of inventors

Muroran, Japan

Masato Yanase