A workpiece conveyance jig, which is formed of a threaded shaft made of a ceramic, includes an inner member, which is formed of a solid shaft having a constant diameter, and is configured to receive a rotational driving force, and an outer member, which has a hollow shaft-like shape, has a helical protrusion, and is mounted on an outer periphery of the inner member so as to be rotatable integrally with the inner member. The outer member includes a plurality of cylindrical bodies arranged in a row in an axial direction of the workpiece conveyance jig, and has a convex and concave fitting portion formed between two adjacent ones of the plurality of cylindrical bodies, which is configured to engage the two adjacent cylindrical bodies with each other in a direction of rotation of the inner member.

A workpiece conveyance jig, which is formed of a threaded shaft made of a ceramic, includes an inner member, which is formed of a solid shaft having a constant diameter, and is configured to receive a rotational driving force, and an outer member, which has a hollow shaft-like shape, has a helical protrusion, and is mounted on an outer periphery of the inner member so as to be rotatable integrally with the inner member. The outer member includes a plurality of cylindrical bodies arranged in a row in an axial direction of the workpiece conveyance jig, and has a convex and concave fitting portion formed between two adjacent ones of the plurality of cylindrical bodies, which is configured to engage the two adjacent cylindrical bodies with each other in a direction of rotation of the inner member.

When a rod-shaped workpiece (W) having an outer peripheral surface with a circular cross section is inductively heated to a quenching temperature while being conveyed at a predetermined velocity along an axial direction of the rod-shaped workpiece (W), the rod-shaped workpiece (W) being currently conveyed is heated to a predetermined temperature equal to or lower than the quenching temperature by a first heating coil (2A), which is electrically connected to a first high-frequency power supply (3) and has a constant output. Then, the rod-shaped workpiece (W) being currently conveyed is heated so as to be maintained at the quenching temperature by a second heating coil (2B), which is electrically connected to a second high-frequency power supply (4) and has a constant output.

When a rod-shaped workpiece (W) having an outer peripheral surface with a circular cross section is inductively heated to a quenching temperature while being conveyed at a predetermined velocity along an axial direction of the rod-shaped workpiece (W), the rod-shaped workpiece (W) being currently conveyed is heated to a predetermined temperature equal to or lower than the quenching temperature by a first heating coil (2A), which is electrically connected to a first high-frequency power supply (3) and has a constant output. Then, the rod-shaped workpiece (W) being currently conveyed is heated so as to be maintained at the quenching temperature by a second heating coil (2B), which is electrically connected to a second high-frequency power supply (4) and has a constant output.

Provided is an induction heating apparatus including a conveying device, which is configured to convey a rotatable workpiece along a linear guiding conveyance path, and a heating coil, which is configured to inductively heat the workpiece being conveyed along the guiding conveyance path. The conveying device includes a first shaft member and a second shaft member, which are arranged in parallel so as to be separated from each other, and a rotary mechanism, which is configured to rotationally drive at least one of the first shaft member and the second shaft member about an axis thereof. The second shaft member is formed of a threaded shaft having a helical convex portion formed along an outer periphery of the second shaft member. The guiding conveyance path is formed by a groove bottom surface of a helical groove defined on the second shaft member by the helical convex portion.

Provided is an induction heating apparatus including a conveying device, which is configured to convey a rotatable workpiece along a linear guiding conveyance path, and a heating coil, which is configured to inductively heat the workpiece being conveyed along the guiding conveyance path. The conveying device includes a first shaft member and a second shaft member, which are arranged in parallel so as to be separated from each other, and a rotary mechanism, which is configured to rotationally drive at least one of the first shaft member and the second shaft member about an axis thereof. The second shaft member is formed of a threaded shaft having a helical convex portion formed along an outer periphery of the second shaft member. The guiding conveyance path is formed by a groove bottom surface of a helical groove defined on the second shaft member by the helical convex portion.

Provided is a heat treatment apparatus (1), including: a conveying device (10), which is configured to convey a rod-shaped workpiece (W) at a predetermined velocity along an axial direction of the workpiece (W); and a heating device (2) including a heating coil (3) configured to inductively heat the workpiece (W) being conveyed to a quenching temperature, wherein the heating coil (3) includes a first heating section (3A) and a second heating section (3B), which are coupled to each other in series along the axial direction of the workpiece (W), and is electrically connected to a single high-frequency power supply (4), and wherein a coil pitch (D2) of the second heating section (3B) arranged relatively on a front side in a conveying direction for the workpiece (W) is larger than a coil pitch (D1) of the first heating section (3A) arranged relatively on a rear side in the conveying direction.

Provided is a heat treatment apparatus (1), including: a conveying device (10), which is configured to convey a rod-shaped workpiece (W) at a predetermined velocity along an axial direction of the workpiece (W); and a heating device (2) including a heating coil (3) configured to inductively heat the workpiece (W) being conveyed to a quenching temperature, wherein the heating coil (3) includes a first heating section (3A) and a second heating section (3B), which are coupled to each other in series along the axial direction of the workpiece (W), and is electrically connected to a single high-frequency power supply (4), and wherein a coil pitch (D2) of the second heating section (3B) arranged relatively on a front side in a conveying direction for the workpiece (W) is larger than a coil pitch (D1) of the first heating section (3A) arranged relatively on a rear side in the conveying direction.

A bearing part according the present invention includes, as the chemical composition, by mass %, C: 0.95% to 1.10%, Si: 0.10% to 0.70%, Mn: 0.20% to 1.20%, Cr: 0.90% to 1.60%, Al: 0.010% to 0.100%, N: 0.003% to 0.030%, P: 0.025% or less, S: 0.025% or less, O: 0.0010% or less, and optionally Mo: 0.25% or less, B: 0.0050% or less, Cu: 1.0% or less, Ni: 3.0% or less, and Ca: 0.0015% or less, and a remainder including Fe and impurities; metallographic structure includes a retained austenite, a spherical cementite and a martensite; an amount of the retained austenite is 15% to 25%, by volume %; an average grain size of prior-austenite is 8.0 m or less; and a number density of a void having a circle equivalent diameter of 0.02 m to 3.0 m is 2000 mm.sup.2 or less in the metallographic structure.

A bearing part according the present invention includes, as the chemical composition, by mass %, C: 0.95% to 1.10%, Si: 0.10% to 0.70%, Mn: 0.20% to 1.20%, Cr: 0.90% to 1.60%, Al: 0.010% to 0.100%, N: 0.003% to 0.030%, P: 0.025% or less, S: 0.025% or less, O: 0.0010% or less, and optionally Mo: 0.25% or less, B: 0.0050% or less, Cu: 1.0% or less, Ni: 3.0% or less, and Ca: 0.0015% or less, and a remainder including Fe and impurities; metallographic structure includes a retained austenite, a spherical cementite and a martensite; an amount of the retained austenite is 15% to 25%, by volume %; an average grain size of prior-austenite is 8.0 m or less; and a number density of a void having a circle equivalent diameter of 0.02 m to 3.0 m is 2000 mm.sup.2 or less in the metallographic structure.