Machine element and method for manufacturing thereof

摘要

A hub ring and/or an outer ring constituting a bearing device for a wheel, which is formed of a steel which contains 0.45 to 0.70 mass % of C and at least one of V, Nb and Ti in a total amount of 0.3 mass % or less, wherein a micro structure of a part being not surface-hardening-treated contains a ferrite in 15 to 30 area % and contains a particulate ferrite.