A high-carbon steel sheet is used for automobile drive-line components, such as chains, gears and clutches. When an automobile drive-line component is manufactured, cold-working as shaping and quenching and tempering are performed of the high-carbon steel sheet. Weight reduction of automobile is currently in progress, and for drive-line components, weight reduction by strength enhancement is also considered. For example, to achieve strength enhancement of parts such as drive-line components undergone quenching and tempering, adding carbide-forming elements represented by Ti, Nb, Mo or increasing the content of C is effective.
Patent Literature 1 describes a method of manufacturing a mechanical structural steel intended for achieving both high hardness and high toughness, Patent Document 2 describes a method of manufacturing a rough-formed bearing intended for omission of spheroidizing, or the like, and Patent Literatures 3 and 4 describe methods of a manufacturing high-carbon steel sheet intended for improvement of punching property. Patent Literature 5 describes a medium-carbon steel sheet intended for improvement of cold workability and quenching stability, Patent Literature 6 describes a steel material for bearing element part intended for improvement of machinability, Patent Literature 7 describes a method of manufacturing a tool steel intended for omission of normalizing, and Patent Literature 8 describes a method of manufacturing a high-carbon steel sheet intended for improvement of formability.
On the other hand, the high-carbon steel sheet is required to have a good fatigue property, for example, a rolling contact fatigue property after quenching and tempering. However, the conventional manufacturing methods described in Patent Literatures 1 to 8 cannot achieve a sufficient fatigue property.
USPTO Backgrounds
USPTO Backgrounds