In this steel component, the concentration of C in a surface layer is 0.85 mass % or more to 1.2 mass % or less, which is higher than the concentration of C in a starting material steel, the surface layer has a volume ratio of a retained-austenite structure higher than 0% and lower than 10%, the remainder of the surface layer is a martensitic structure, the area fraction of grain boundary carbides in the surface layer is lower than 2%, a layer inside the surface layer is higher than the surface layer in a volume ratio of a retained-austenite structure, and in the layer inside the surface layer, the remainder is a martensitic structure.

In this steel component, the concentration of C in a surface layer is 0.85 mass % or more to 1.2 mass % or less, which is higher than the concentration of C in a starting material steel, the surface layer has a volume ratio of a retained-austenite structure higher than 0% and lower than 10%, the remainder of the surface layer is a martensitic structure, the area fraction of grain boundary carbides in the surface layer is lower than 2%, a layer inside the surface layer is higher than the surface layer in a volume ratio of a retained-austenite structure, and in the layer inside the surface layer, the remainder is a martensitic structure.

Steel according to one embodiment of the present invention has predetermined chemical components, wherein in a region where a distance r from the center of a cross-section perpendicular to the length direction satisfies 0.7Rr0.9R, structures include ferrite and bainite, the average fraction of the ferrite is in the range of 40 to 70% in terms of area ratio, the total average fraction of the structures other than the ferrite and the bainite is 0% or more and 3% or less on average, and the balance includes bainite; and the standard deviation of a ferrite fraction in the region is 4% or less.

Steel according to one embodiment of the present invention has predetermined chemical components, wherein in a region where a distance r from the center of a cross-section perpendicular to the length direction satisfies 0.7Rr0.9R, structures include ferrite and bainite, the average fraction of the ferrite is in the range of 40 to 70% in terms of area ratio, the total average fraction of the structures other than the ferrite and the bainite is 0% or more and 3% or less on average, and the balance includes bainite; and the standard deviation of a ferrite fraction in the region is 4% or less.

Provided is a heat treatment apparatus capable of more reliably conveying a workpiece along a desired conveyance path by a simple configuration. A heat treatment apparatus 1 includes a heating chamber 7, a cooling chamber 8 disposed adjacent to the heating chamber 7, a conveyance tray 2 to support the workpiece 100, and a first conveyance mechanism 3 to convey the conveyance tray 2 along a conveyance path B1 from the outside of the heating chamber 7 to the outside of the cooling chamber 8 through the heating chamber 7 and the cooling chamber 8.

Provided is a heat treatment apparatus capable of more reliably conveying a workpiece along a desired conveyance path by a simple configuration. A heat treatment apparatus 1 includes a heating chamber 7, a cooling chamber 8 disposed adjacent to the heating chamber 7, a conveyance tray 2 to support the workpiece 100, and a first conveyance mechanism 3 to convey the conveyance tray 2 along a conveyance path B1 from the outside of the heating chamber 7 to the outside of the cooling chamber 8 through the heating chamber 7 and the cooling chamber 8.

A method for producing a workpiece having a toothing or profiling, including the steps: a) Soft machining the workpiece, in which the toothing or profiling is produced; b) Hardening the toothing or profiling; c) Hard fine machining the toothing or profiling, wherein the toothing or profiling is machined with a first tool that is a grinding worm, a grinding wheel or a honing wheel, wherein the tool has a base body with a first elastic modulus; d) Reinforcement of at least a section of the workpiece by a shot blasting process; and, following step d): e) Repeated hard fine machining of the toothing or profiling, wherein the toothing or profiling is machined with a second tool that is a grinding worm, a grinding wheel, a set of grinding wheels or a honing wheel. The second tool has a base body with a second elastic modulus which is at most 33% of the first elastic modulus. The second tool has a base body made of a plastic or rubber.

An induction coil with inner and outer coil segments joined together by a transition segment is arranged so that the outer coil segment generally inductively heat treats an annular outer region of a workpiece positioned under the coil, the inner coil segment generally inductively heat treats an annular inner region of the workpiece, and the transition segment traverses at least a portion of the width of the overall annular region of the workpiece to be heat treated. Relative arrangement of inner, outer and transition coil segments provides for controlled induction heat treatment across the overall annular region such as the gear teeth region of an intersecting axes or non-intersecting and non-parallel axes gear.

An induction coil with inner and outer coil segments joined together by a transition segment is arranged so that the outer coil segment generally inductively heat treats an annular outer region of a workpiece positioned under the coil, the inner coil segment generally inductively heat treats an annular inner region of the workpiece, and the transition segment traverses at least a portion of the width of the overall annular region of the workpiece to be heat treated. Relative arrangement of inner, outer and transition coil segments provides for controlled induction heat treatment across the overall annular region such as the gear teeth region of an intersecting axes or non-intersecting and non-parallel axes gear.

An induction heating device for heating a metal article includes a support plate with an upper surface for receiving the metal article, and a plurality of induction coils, which are arranged concentrically around an axis and are provided at an underside of the support plate. Each induction coil is connected to and selectively powered by a generator, and at least one temperature probe is disposable on the metal article during heating in order to monitor and control the heating of the article.