Patent ID: 11421727

Abstract:
A carburized shaft part having a predetermined composition, a C content at a surface layer part of a mass % of 0.60 to 1.00%, at least one hole at an outer circumferential surface, a total volume ratio of martensite and retained austenite of 97% or more at a structure at a position of a 1 mm depth from the outer circumferential surface in an axial direction of the hole and a position of a 20 μm depth from the surface of the hole, a maximum retained austenite volume ratio (R1) of 10.0 to 30.0% at a position of a 1 mm depth from the outer circumferential surface in the axial direction of the hole and a range up to a 200 μm depth from the surface of the hole, and a retained austenite reduction ratio of 20% or more found from R1 and the retained austenite volume ratio (R2) at a position of a 1 mm depth from the outer circumferential surface in the axial direction of the hole and a position of a 20 μm depth from the surface of the hole by the formula (A): Δγ=(R1−R)/R1×100.