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.

An inner ring or and outer ring for a roller bearing includes: 0.30-0.45 wt. % carbon, 0.1-0.7 wt. % silicon, 0.6-0.9 wt. % manganese, 0.9-1.2 wt. % chromium, 0.15-0.7 wt. % molybdenum, 0-2.0 wt. % nickel, 0-0.02 wt. % phosphorus, and 0 -0.02 wt. % sulfur, the balance being iron and unavoidable impurities. The microstructure of the steel composition contains bainite, and a carbonitrided case layer is provided on a surface of the inner ring or outer ring.

A link component (150) with an oil hole (150E) is attached to a crankshaft (106) of an internal combustion engine (E), and the oil hole (150E) allows communication from an outside to the crankshaft (106) side. The oil hole (150E) has an inclined surface (150F) along an opening rim on the crankshaft (106) side. A surface other than the oil hole (150E) has a carbon concentration of 0.5 wt % or more. The inclined surface (150F) has a carbon concentration within a range of 0.7 wt % or more and 0.9 wt % or less. Production cost is suppressed, and at the same time, damage is prevented by increasing resistance of the oil-hole part on which stress is liable to concentrate.

A fastening structure (105) includes a pair of fastening members (105A) joined to each other, which is coupled with a bolt. The fastening member (105) is made of steel. A surface other than joint surfaces (Sa) has a Rockwell hardness of 50 HRC or more. The joint surfaces (Sa) have a Rockwell hardness of 30 HRC or more and less than 50 HRC. The joint surfaces (Sa) have an arithmetic mean roughness (Ra) of 0.2 μm or more and 0.5 μm or less. Production cost is suppressed, and at the same time, bending fatigue strength is secured and secondary damage due to abrasion powder generated by fretting is prevented.

A rolling-sliding member that is high in hardness and continues to have a passivation film reliably even after being subjected to a process that does not require any processing for removal of scale, etc., as well as a rolling bearing using the same and a method for manufacturing the rolling-sliding member.

It is possible to provide an iron-based sintered sliding material excellent in the sliding performance. Provided is an iron-based sintered sliding material including, a base containing, by mass, 3 to 15% of S, 0.2 to 6% in a total amount of at least one selected from the group consisting of Cr, Ca, V, Ti, and Mg, and a remainder of Fe and inevitable impurities, sulfide particles containing at least one selected from the group consisting of Cr, Ca, V, Ti, and Mg being dispersed in the base, and pores.

A bearing steel according to an embodiment of the present disclosure includes, as a chemical composition: 0.51 to 0.56 wt % of carbon (C); 0.30 to 0.55 wt % of silicon (Si); 0.60 to 0.90 wt % of manganese (Mn); 0.025 wt % or less (excluding 0 wt %) of phosphorus (P); 0.008 wt % or less (excluding 0 wt %) of sulfur (S); 0.01 to 0.20 wt % of chromium (Cr); 0.08 wt % or less (excluding 0 wt %) of molybdenum (Mo); 0.25 wt % or less (excluding 0 wt %) of nickel (Ni); 0.01 to 0.20 wt % of vanadium (V); 0.20 wt % or less (excluding 0 wt %) of copper (Cu); 0.003 wt % or less (excluding 0 wt %) of titanium (Ti); 0.01 to 0.05 wt % of aluminum (Al); 0.0015 wt % or less (excluding 0 wt %) of oxygen (O); 0.001 wt % or less (excluding 0 wt %) of calcium (Ca); and iron (Fe) and unavoidable impurities as a remainder.

There is provided a hot rolled steel according to one aspect of the invention including, as a predetermined chemical composition: Bi: 0.0001 mass % to 0.0050 mass %, in which 90 area % or more of a metallographic structure is configured with a ferrite and a pearlite, and an average number density of Mn sulfides measured on a cross section parallel to a rolling direction having an aspect ratio of more than 10 and 30 or less which is extended along the rolling direction, is 50 pieces/mm.sup.2 to 200 pieces/mm.sup.2.

A method for manufacturing a bearing ring of a rolling bearing includes a series of steps of cutting out an annular member from a material, forming a surface-hardened layer on the annular member, quenching and tempering the annular member, and polishing inner and outer diameter surfaces of the annular member. The method includes, after the quenching, rapidly cooling the ring member such that the ring member has a surface temperature of 50° C. or lower to form a bearing ring intermediate member, and after the tempering, polishing inner and outer diameter surfaces of the bearing ring intermediate member.

A sintered bearing bush material for a sliding bearing may include: 0.5 to 1.7 percentage by weight carbon; 0.2 to 1.2 percentage by weight manganese; 0.2 to 1.2 percentage by weight sulphur; 1.2 to 2.4 percentage by weight nickel; 1.0 to 2.1 percentage by weight molybdenum; 3.0 to 7.0 percentage by weight copper; 0.2 to 1.2 percentage by weight tin; 0 to 0.8 percentage by weight phosphorus; and a residual component.