Abstract: A nitriding treatment method of a steel member, in which a nitriding treatment step is performed in which the steel member is subjected to a nitriding treatment in a nitriding gas atmosphere having a nitriding potential with which a ?? phase or ? phase iron nitride compound layer is generated on a surface of the steel member, and then, a passing step is performed in which the steel member is made to pass through an atmosphere at 425° C. to 600° C. where the iron nitride compound layer does not grow over five minutes or more, the iron nitride compound layer has the ?? phase uppermost surface layer, and the ?? phase is made to precipitate in the iron nitride compound layer by the proportion of 40% or more.

Abstract: A continuous nitriding treatment furnace includes a nitriding chamber, a heater, a first nitriding zone, and a second nitriding zone lower in atmosphere gas temperature than the first nitriding zone by 25° C. to 150° C., the continuous nitriding treatment furnace being configured such that an atmosphere gas in the first nitriding zone flows into the second nitriding zone and being configured to execute a nitriding treatment that forms an iron nitride compound layer composed of an ? phase or of the ? phase and a ?? phase on a surface of the steel member in the first nitriding zone and precipitates the ?? phase in the iron nitride compound layer in the second nitriding zone.

Abstract: A continuous nitriding treatment furnace includes a nitriding chamber, a heater, a first nitriding zone, and a second nitriding zone lower in atmosphere gas temperature than the first nitriding zone by 25° C. to 150° C., the continuous nitriding treatment furnace being configured such that an atmosphere gas in the first nitriding zone flows into the second nitriding zone and being configured to execute a nitriding treatment that forms an iron nitride compound layer composed of an ? phase or of the ? phase and a ?? phase on a surface of the steel member in the first nitriding zone and precipitates the ?? phase in the iron nitride compound layer in the second nitriding zone.

Abstract: A nitriding treatment method of a steel member, in which a nitriding treatment step is performed in which the steel member is subjected to a nitriding treatment in a nitriding gas atmosphere having a nitriding potential with which a ?? phase or ? phase iron nitride compound layer is generated on a surface of the steel member, and then, a passing step is performed in which the steel member is made to pass through an atmosphere at 425° C. to 600° C. where the iron nitride compound layer does not grow over five minutes or more, the iron nitride compound layer has the ?? phase uppermost surface layer, and the ?? phase is made to precipitate in the iron nitride compound layer by the proportion of 40% or more.