A transverse field induction heating apparatus for the inductive heating of sheet metal in a rolling mill includes an upper inductor and a lower inductor. The upper inductor includes two adjacently positioned upper partial induction loops which are series-connected and fed an electrical current in opposite directions. The lower inductor includes two adjacently positioned lower partial induction loops which are series-connected and fed an electrical current in opposite directions. The electrical current in both partial induction loops is oriented in an opposing direction. Each of the upper and lower partial induction loop is structured to be moved individually perpendicular to a sheet axis and includes a rounded head positioned adjacent to each other such that the rounded head is shaped as a hammer head.

A method for treating a part made of ferrous metal includes a nitriding operation forming on the part a combination layer having a thickness of between 5 and 30 μm, and a diffusion region, arranged beneath and in contact with the combination layer, having a thickness of between 100 μm and 500 μm. The method also includes an operation of quenching the part by high-frequency induction, over an induction depth that is greater than or equal to 0.5 mm, thereby hardening the part. The resulting part has a surface hardness greater than or equal to 50 HRC, a hardness of the combination layer greater than or equal to 400 HV0.05, and a hardness of the part greater than or equal to 500 HV0.05 at a depth of 500 μm. The high-frequency induction quenching operation is performed without the application of a protective film on the part prior to the induction quenching operation.

A method of induction hardening a bearing ring includes positioning first and second inductors at a start zone on the bearing ring and a preheat inductor in an end zone on the bearing ring spaced one hundred eighty degrees from the start zone. A first traversing element moves the first inductor circumferentially from the start zone toward the end zone along a first half of the bearing ring circumference while the first inductor heats the bearing ring, and a second traversing element moves the second inductor circumferentially from the start zone toward the end zone along a second half of the bearing ring circumference while the second inductor heats the bearing ring. A third traversing element moves the preheat inductor circumferentially within the end zone so as to traverse a portion of each half of the bearing ring circumference while the preheat inductor heats the end zone.

A method of induction hardening a bearing ring includes positioning first and second inductors at a start zone on the bearing ring and a preheat inductor in an end zone on the bearing ring spaced one hundred eighty degrees from the start zone. A first traversing element moves the first inductor circumferentially from the start zone toward the end zone along a first half of the bearing ring circumference while the first inductor heats the bearing ring, and a second traversing element moves the second inductor circumferentially from the start zone toward the end zone along a second half of the bearing ring circumference while the second inductor heats the bearing ring. A third traversing element moves the preheat inductor circumferentially within the end zone so as to traverse a portion of each half of the bearing ring circumference while the preheat inductor heats the end zone.

A method of manufacturing a hypoid gear includes face hobbing a gear blank and forming a green hypoid gear with gear teeth, heat treating the green hypoid gear to form a heat treated hypoid gear with heat treated gear teeth, and hard hobbing the heat treated gear teeth to form a hard finished hypoid gear. Critical non-tooth features on the heat treated hypoid gear are hard finished. Also, the critical non-tooth features on the heat treated hypoid gear can be hard finished prior to hard hobbing the heat treated gear teeth. The heat treating includes at least one of carburizing and induction hardening the green hypoid gear, a surface of the heat treated gear teeth has a hardness greater than or equal to 58 HRC, and the hard hobbing removes heat distortion from the heat treated gear teeth.

A method of manufacturing a hypoid gear includes face hobbing a gear blank and forming a green hypoid gear with gear teeth, heat treating the green hypoid gear to form a heat treated hypoid gear with heat treated gear teeth, and hard hobbing the heat treated gear teeth to form a hard finished hypoid gear. Critical non-tooth features on the heat treated hypoid gear are hard finished. Also, the critical non-tooth features on the heat treated hypoid gear can be hard finished prior to hard hobbing the heat treated gear teeth. The heat treating includes at least one of carburizing and induction hardening the green hypoid gear, a surface of the heat treated gear teeth has a hardness greater than or equal to 58 HRC, and the hard hobbing removes heat distortion from the heat treated gear teeth.

An example bushing of a hydraulic hammer tool includes a bulk region and an inner region. The inner region has a relatively greater hardness than the bulk region. The inner region may also be compressively stressed, while the bulk region may have tensile stress. The stress and/or hardness profile of the bushing may enhance its resistance to wear and galling defects when a hammer of the hydraulic hammer tool is held in alignment by the bushing. The bulk region of the bushing may be relatively soft, resulting in the bushing having a relatively high level of toughness. The bushing may be formed using medium to high carbon steel by rough forming the bushing, hardening the bushing, tempering the bushing, induction hardening the inner region of the bushing, and then quenching the inner region.

The present invention provides a nitriding treatment method for forming a compound layer of ε phase (Fe.sub.2-3N) and γ′ phase (Fe.sub.4N) iron nitride excellent in wear durability in a steel material, from which a sliding member is formed, by short treatment, with a high thermal efficiency, with a reduced amount of used nitriding gas, and with a low environmental load. The nitriding treatment method of the present invention includes heating a sliding member made of a steel material at a temperature of 600° C. to 700° C. for a time of 1 to 25 minutes under an atmosphere of nitriding gas through high frequency induction heating or resistive heating, to form a compound layer of ε phase (Fe.sub.2-3N) and γ′ phase (Fe.sub.4N) iron nitride, the compound layer having a nitrogen content of higher than 4.5%, in a surface layer portion of the sliding member.

An orifice-type quenching nozzle for an induction hardening system includes a body having a plurality of nozzle orifices configured to apply a quenching fluid onto a to-be-quenched workpiece. The nozzle orifices are arranged on at least one surface of the body in rows and in columns, and the plurality of nozzle orifices are positioned such that each nozzle orifice is located a same distance from each directly adjacent nozzle orifice.

An orifice-type quenching nozzle for an induction hardening system includes a body having a plurality of nozzle orifices configured to apply a quenching fluid onto a to-be-quenched workpiece. The nozzle orifices are arranged on at least one surface of the body in rows and in columns, and the plurality of nozzle orifices are positioned such that each nozzle orifice is located a same distance from each directly adjacent nozzle orifice.