A cooling system includes a refrigerant compressor and a first operating medium, which includes a mixture of refrigerant and lubrication oil. An oil separator reduces the percentage of the refrigerant in the operating medium so that a second lubrication oil enriched operating medium is provided by the oil separator, the provided second operating medium having at least in a second operating state a viscosity ratio of K>1.

A cooling system includes a refrigerant compressor and a first operating medium, which provides a mixture of refrigerant and lubrication oil. An oil separator reduces the percentage of the refrigerant in the operating medium to a value between 25% by weight and 80% by weight.

An outer ring, an inner ring, and a ball each serving as a bearing part is made of a steel containing 0.95 mass % or more and 1.10 mass % or less of carbon, 0.05 mass % or more and less than 0.3 mass % of silicon, 0.10 mass % or more and 0.50 mass % or less of manganese, and 1.30 mass % or more and 2.00 mass % or less of chromium, with the rest made up of iron and an impurity. A surface layer region defined as a region extending to a depth of not more than 20 m from an outer ring raceway surface, an inner ring raceway surface, and a ball rolling surface, which are each a surface where the bearing part is in rolling contact with another part, has an average nitrogen concentration of 0.2 mass % or more and 0.7 mass % or less. Five or more carbides with a diameter of 0.5 m or less are present per 100 m.sup.2 in the surface layer region.

A steel alloy for a bearing, the alloy having a composition having from 0.04 to 0.1 wt. % carbon, from 10.5 to 13 wt. % chromium, from 1.5 to 3.75 wt. % molybdenum, from 0.3 to 1.2 wt. % vanadium, from 0.3 to 2.0 wt .% nickel, from 6 to 9 wt. % cobalt, from 0.05 to 0.4 wt. % silicon, from 0.2 to 0.8 wt. % manganese, from 0.02 to 0.06 wt. % niobium, from 0 to 2.5 wt. % copper, from 0 to 0.1 wt. % aluminium, from 0 to 250 ppm nitrogen, from 0 to 30 ppm boron, and the balance iron, together with any unavoidable impurities.

The present invention relates to a bearing assembly that provides a magnetic sensor; a shaft; and a bearing. One of the shaft and the bearing is provided with a surface having a bearing steel and including a magnetic pattern disposed thereon for indicating a rotation of the shaft relative to the bearing. The magnetic pattern is provided by the microstructure of the surface; and the sensor is arranged to sense the pattern and output a signal indicative of a rotation of the shaft relative to the bearing.

Provided is a steel for carbonitrided bearing which excels in hardenability and also excels in toughness, wear resistance, and surface-originated flaking life after quenching and tempering. A steel for carbonitrided bearing of the present embodiment has a chemical composition containing, in mass %, C: 0.22 to 0.45%, Si: not more than 0.50%, Mn: 0.40 to 1.50%, P: not more than 0.015%, S: not more than 0.005%, Cr: 0.30 to 2.0%, Mo: 0.10 to 0.35%, V: 0.20 to 0.40%, Al: 0.005 to 0.10%, N: not more than 0.030%, and O: not more than 0.0015%, with the balance being Fe and impurities, and satisfying Formulae (1) and (2).

1.20<0.4Cr+0.4Mo+4.5V<2.60(1)

2.7C+0.4Si+Mn+0.8Cr+Mo+V>2.20(2)

Provided is a carbonitrided bearing part which has high hardenability and toughness, and is excellent in wear resistance and surface-originated flaking life. A carbonitrided bearing part of the present embodiment has a chemical composition containing, in mass %, C: 0.15 to 0.45%, Si: not more than 0.50%, Mn: 0.40 to 1.50%, P: not more than 0.015%, S: not more than 0.005%, Cr: 0.30 to 2.0%, Mo: 0.10 to 0.35%, V: 0.20 to 0.40%, Al: 0.005 to 0.10%, N: not more than 0.030%, and O: not more than 0.0015%, with the balance being Fe and impurities, and satisfying Formulae (1) and (2). At surface, C concentration is 0.7 to 1.2%, N concentration is 0.15 to 0.6%, and Rockwell hardness HRC is 58 to 65.

1.20<0.4Cr+0.4Mo+4.5V<2.60(1)

2.7C+0.4Si+Mn+0.8Cr+Mo+V>2.20(2)

A bearing constituent member includes a base material including steel and a carbonitrided layer that is a surface layer on the steel, the steel including 0.3 to 0.45 mass % of carbon, 0.5 mass % or lower of silicon, 0.4 to 1.5 mass % of manganese, 0.3 to 2 mass % of chromium, 0.1 to 0.35 mass % of molybdenum, 0.2 to 0.4 mass % of vanadium, and a remainder of iron and unavoidable impurities. Surface Vickers hardness at a position at a depth of 50 m from a surface of a rolling sliding surface is 700 to 800, internal hardness is 550 to 690 in terms of Vickers hardness, and an amount of residual austenite in a range from the surface to a depth of 10 m is at least 30 vol %.

A method for surface hardening at least one part of a surface of a metal component is provided. The steps include a) enriching the at least one part of a surface of a metal component with at least one of carbon and nitrogen, and b) induction hardening the at least one part of the surface of the metal component.

A ball joint includes an outer ring having a spherical inner surface and an inner ring having a spherical outer surface in contact with the spherical inner surface of the outer ring. The outer ring is formed from a nickel-based material, the inner surface of the outer ring includes a carbonitrided layer, and the inner ring is formed from a cobalt-based or nickel-based material.