Abstract: An outer ring, an inner ring, and a ball, each of which is a bearing part, are made of a quench-hardened steel containing not less than 0.90 mass % and not more than 1.05 mass % of carbon, not less than 0.15 mass % and not more than 0.35 mass % of silicon, not less than 0.01 mass % and not more than 0.50 mass % of manganese, and not less than 1.30 mass % and not more than 1.65 mass % of chromium with the rest consisting of an impurity. A contact surface thereof with another part has a nitrogen concentration of not less than 0.25 mass %. A remaining austenite amount in the contact surface is not less than 6 volume % and not more than 12 volume %.

Abstract: A seal lip portion 9 includes a lip main body (9a) and a projecting section (16) protruding from a peripheral edge of the lip main body (9a) and slidingly engageable with an inner ring (1), and this projecting section (16) is made of a highly frictionally wearable material which allows the projecting section (16), when frictionally worn, to establish a non-contact or a light contact to such an extend as to result in a contact pressure that can be regarded as zero. A fitting section (13) fitted into a seal mounting groove (2b) in a seal member main body (8) is held in a drag-rotation preventive structure that prevents circumferential movement due to a drag-rotation relative to an outer ring (2).

Abstract: An outer ring, an inner ring, and a ball, each of which is a bearing part, are made of a quench-hardened steel containing not less than 0.90 mass % and not more than 1.05 mass % of carbon, not less than 0.15 mass % and not more than 0.35 mass % of silicon, not less than 0.01 mass % and not more than 0.50 mass % of manganese, and not less than 1.30 mass % and not more than 1.65 mass % of chromium with the rest consisting of an impurity. A contact surface thereof with another part has a nitrogen concentration of not less than 0.25 mass %. A remaining austenite amount in the contact surface is not less than 6 volume % and not more than 12 volume %.