Daido Tokushuko Kabushiki Kaisha

Honda Giken Kogyo Kabushiki Kaisha

Daido Machinery Corporation

Unitika Ltd.

Yukio Ito

Tsutomu Saka

Tomohito Iikubo

Tadashi Akazawa

Takao Noguchi

Tadaya Ishibashi

Tadahiro Mori

A spring steel of medium strength and sufficient corrosion resistance prepared by simple procedures, and therefore, at a low cost, is provided. The spring steel has the alloy composition of: C 0.3-0.6%, Si 1.0-2.0%, Mn 0.1% to less than 0.5%, Cr 0.4-1.0%, V 0.1-0.3%, Ni more than 0.5% to 1.2%, Cu 0.1-0.3% and the balance of Fe, wherein S being at highest 0.005%, and [O], at highest 0.0015%. Addition of Ca 0.001-0.005% is preferable. In order to ensure clearly improved fatigue limit under corrosive environment to the conventional steel, SUP7, specific contents of S, Ni, Cr, Cu and V are chosen in the range set forth above. For the purpose of obtaining such a low hardness after normalizing at which annealing prior to processing is unnecessary contents of C, Si, Mn, Cr and Ni are further chosen in the above ranges.

Corrosion-resistant spring steel

A lubricant to be sprayed onto the surface of a steel material for forming a lubricant coat on the surface of the steel material to be forged. The lubricant comprises a particulate lubricant composed of thermally melting resin mixed with inorganic lubricant. The particulate lubricant is applied onto the surface of a steel material to be forged. Before or after applying the particulate lubricant onto the surface of the steel material, the surface of the steel material is heated. Consequently, the thermally melting resin melts and coheres with the inorganic lubricant over the surface of the steel material, resulting in the formation of a uniformly thick lubricant coat over the steel material. The lubricant coat prevents the steel material from being burnt in a forging device even during hot forging. The lubricant coat is fit for the forging of hard to work steel material. The lubricant coat also contributes to the decrease in forging cost, without deteriorating the forging environment.

Forging lubricant and a method for forming a lubricant coat on the

A method for forming a lubricant coat on a surface of steel slug to be forged and a forging device provided with a lubricant coat forming system. The method makes possible the forging of hard to work material, such as stainless steel. Highly durable parts can be manufactured easily. The durability of the metal molds of the forging device is increased, thereby decreasing the cost for the manufacture of the parts. In the method, the uniformly thick lubricant coat can be formed easily even on the transformed end surfaces of the material being worked, providing effective lubrication. The lubricant coat forming member can replace the oil lubrication of the related-art forging device of the inline type, in which the cut end surfaces of the material are not lubricated, without modifying the structure of the related-art forging device especially. The forging device of this invention continuously forges the material, lengthening the interval for replacing metal molds and decreasing the cost for the manufacture of the parts.

Method for forming a lubricant coat on the surface of a material to be

A high-strength steel for valve springs, consisting of 0.50-0.70 wt. % of carbon, 1.50-2.50 wt. % of silicon, 0.50-1.20 wt. % of manganese, 1.50-2.50 wt. % of nickel, 0.50-1.00 wt. % of chromium, 0.20-0.50 wt. % of molybdenum, 0.15-0.25 wt. % of vanadium, and the balance being iron and inevitably included inclusions. Also disclosed is a process for producing such a high-strength steel, which includes a step of minimizing oxygen in a melt of the steel, so as to reduce the oxygen content of the steel to 15 ppm or less, and a step of adding calcium to the melt and thereby controlling the form of the inclusions. The process may further includes a step of minimizing titanium and nitrogen in the melt, so as to reduce the titanium and nitrogen content of the steel to 50 ppm or less, and 60 ppm or less, respectively.

Process for producing steel for valve springs

A high-strength steel for valve springs, consisting of 0.50-0.70 wt. % of carbon, 1.50-2.50 wt. % of silicon, 0.50-1.20 wt. % of manganese, 1.50-2.50 wt. % of nickel, 0.50-1.00 wt. % of chromium, 0.20.0.50 wt. % of molybdenum, 0.15-0.25 wt. % of vanadium, and the balance being iron and inevitably included inclusions. Also disclosed is a process for producing such a high-strength steel, which includes a step of minimizing oxygen in a melt of the steel, so as to reduce the oxygen content of the steel to 15 ppm or less, and a step of adding calcium to the melt and thereby controlling the form of the inclusions. The process may further include a step of minimizing titanium and nitrogen in the melt, so as to reduce the titanium and nitrogen content of the steel to 50 ppm or less, and 60 ppm or less, respectively.

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Yokkaichi, Japan

Yukio Ito