The invention relates to a carburizing bearing steel and a preparation method thereof. The carburizing bearing steel of the invention comprises: 0.18˜0.24 wt % of C, 0.4˜0.6 wt % of Cr, 0.20˜0.40 wt % of Si, 0.40˜0.70 wt % of Mn, 1.6˜2.2 wt % of Ni, 0.15˜0.35 wt % of Mo, 0.001˜0.01 wt % of S, 0.001˜0.015 wt % of P, 0˜0.20 wt % of Nb, 0˜0.20 wt % of V and the remaining is iron, wherein the contents of Nb and V are not 0 at the same time. In the invention, an appropriate amount of Nb and V is added in combination with other elements so as to refine the grain size, inhibit the generation of large granular carbides in the steel during carburization and improve the uniformity of the microstructure of steel materials, thus further enhancing the contact fatigue life of the carburizing bearing steel.

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.

A bearing component such as a bearing ring includes a metallic base body and at least one alloy steel coating on the base body, the coating being applied to the base body by deposition welding. The base body is preferably non-alloy steel or cast iron, and the alloy includes at least one carbide-forming transition metal such as niobium, tantalum, zirconium, titanium, hafnium, tungsten, molybdenum, vanadium, or manganese. The coating can form a raceway of the bearing component or a structural element such as a flange. Also a method of forming such a bearing component is provided.

The invention relates to a carburizing bearing steel and a preparation method thereof. The carburizing bearing steel of the invention comprises: 0.18˜0.24 wt % of C, 0.4˜0.6 wt % of Cr, 0.20˜0.40 wt % of Si, 0.40˜0.70 wt % of Mn, 1.6˜2.2 wt % of Ni, 0.15˜0.35 wt % of Mo, 0.001˜0.01 wt % of S, 0.001˜0.015 wt % of P, 0˜0.20 wt % of Nb, 0˜0.20 wt % of V and the remaining is iron, wherein the contents of Nb and V are not 0 at the same time. In the invention, an appropriate amount of Nb and V is added in combination with other elements so as to refine the grain size, inhibit the generation of large granular carbides in the steel during carburization and improve the uniformity of the microstructure of steel materials, thus further enhancing the contact fatigue life of the carburizing bearing steel.

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.

A steel material for a torsionally stressed component, such as a driveshaft, having a minimum tensile strength of 800 MPs, and the microstructure consists of more than 50 vol. % of bainite, having an alloy with the following composition in wt. %: C: 0.02 to 0.3; Si: up to 0.7; Mn: 1.0 to 3.0; P: max. 0.02; S: max. 0.01; N: max. 0.01; Al: up to 0.1; Cu: up to 0.2; Cr: up to 3.0; Ni: up to 0.3; Mo: up to 0.5; Ti: up to 0.2; V: up to 0.2; Nb: up to 0.1; B: up to 0.01; where 0.02≤Nb+V+Ti≤0.25, residual iron, and smelting impurities. The steel material is inexpensive and has good torsional fatigue strength when used for a torsionally stressed component. The invention also relates to a method for producing a component made of the material and to such a component.

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 sliding member includes a back-metal layer and a sliding layer made of a copper alloy. The back-metal layer is made of a hypoeutectoid steel including 0.07 to 0.35 mass % of carbon, and has a structure including a ferrite phase and pearlite. The back-metal layer includes a pore existing region including a plurality of closed pores that are not open to a bonding surface when viewing a cross-section perpendicular to a sliding surface. The closed pores have an average size of 5 to 15 μm. The pore existing region extends from the bonding surface toward an inner portion of the back-metal layer, and has a thickness of 10 to 60 μm. A ratio V2/V1 of a total volume V2 of the closed pores to a volume V1 of the pore existing region is 0.05 to 0.1.

The present invention provides a steel material which is excellent in both of the strength (particularly, fatigue strength) and the manufacturability (particularly, bending straightening properties), and thus can be used as an automobile component such as a crankshaft by being formed into a product shape, being subjected to a high strength treatment such as a nitrocarburizing treatment, and then being subjected to the bending straightening.

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.