Daido Tokushuko Kabushiki Kaisha

Hideaki Inaba

Kenji Isokawa

Shigeru Takeda

Shuzi Sakakibara

Hisashi Ohta

Masaaki Takagi

Toshio Yanagiya

A high-strength spring steel has a high fatigue limit and is characterized by restricting the number of oxide particle inclusion having a diameter of not less than 10 .mu.m in steel to not more than 12 particles/100 mm.sup.2.

High-strength spring steels and method of producing the same

An improved steel for cold forging for machine structural use, particularly, case hardening steel, contents of Al, N and Nb are selected to satisfy a specific corelation therebetween, and the amounts of O and S are controlled. The steel is resistant to cracking at the cold forging, and growth of austenite crystals to coarse grains during carburizing or carbonitriding is prevented. Disclosed are preferable structure of the steel and rolling conditions to obtain the structure, and conditions for continuous casting of the steel.

Steel for cold forging and method of making

A steel refining method of the type in which the steel is refined through an interfacial reaction between the molten steel in a vessel and a slag on the molten steel. The method simultaneously employs both of blowing of an inert gas into the molten steel from the bottom of the vessel to stir the molten steel by bubbling and blowing an inert gas from the upper side of the vessel into the zone on which the movement of the slag is dull. Consequently, the stirring effect on the molten steel is enhanced to promote the refining reaction. The inert gas can contain a desulfurization agent.

Growing community of inventors

Chita, Japan

Hideaki Inaba