A rolling bearing is a tapered roller bearing, a cylindrical roller bearing, or a deep groove ball bearing including an inner ring, an outer ring, and a rolling element, each of the inner ring, the outer ring, and the rolling element being composed of a steel, the rolling bearing having a quench-hardened layer in at least one of an inner ring raceway surface of the inner ring, an outer ring raceway surface of the outer ring, and a rolling contact surface of the rolling element. A ratio of a total area of a plurality of martensite crystal grains in the quench-hardened layer is more than or equal to 70%. The plurality of martensite crystal grains are classified into a first group and a second group. An average grain size of the martensite crystal grains belonging to the first group is less than or equal to 0.97 μm.

An example bushing of a hydraulic hammer tool includes a bulk region and an inner region. The inner region has a relatively greater hardness than the bulk region. The inner region may also be compressively stressed, while the bulk region may have tensile stress. The stress and/or hardness profile of the bushing may enhance its resistance to wear and galling defects when a hammer of the hydraulic hammer tool is held in alignment by the bushing. The bulk region of the bushing may be relatively soft, resulting in the bushing having a relatively high level of toughness. The bushing may be formed using medium to high carbon steel by rough forming the bushing, hardening the bushing, tempering the bushing, induction hardening the inner region of the bushing, and then quenching the inner region.

The invention relates to a method for the inductive surface layer hardening of a surface which runs around an annular component and has an initial zone, an end zone and two intermediate zones extending between the initial zone and the end zone. The initial zone is brought to hardening temperature by an inductor and quenched by a spray. Subsequently, an inductor arrangement is moved in each case along the intermediate zone to the end zone. Each inductor arrangement includes a leading inductor for preheating the region covered by it, a trailing inductor for finish-heating the preheated region and a spray for quenching the finish-heated region. After the inductor arrangements are located at a certain distance from the initial zone, the leading inductor of at least one of the inductor arrangements is moved in the direction of the end zone at an increased feed rate compared to the trailing inductor. The leading inductor thus reaches the end zone by a time interval earlier, whose duration is equal to the duration required by the trailing inductor to overcome the distance previously resulted between said trailing inductor and the leading inductor. In the meantime, the end zone is preheated by the leading inductor that reached it. When one of the trailing inductors of the inductor arrangements has arrived in the end zone, it heats the end zone to the finished hardening temperature.

A bearing unit having a stationary radially outer ring, a radially inner ring rotatable about a central rotation axis (X) of the bearing unit is provided with at least one raceway and, in an end portion thereof, with at least two circular sector segments, at least one row of rolling elements interposed between the radially outer ring and the radially inner ring, and a concentric collar for clamping the radially inner ring on a rotating shaft, where an induction-hardening heat treatment is applied to a portion of the radially inner ring that overlaps with at least a portion of the at least one raceway.

A method of manufacturing a wheel hub bearing unit includes providing a bearing ring having at least one raceway surface, the bearing ring preferably being a bearing outer ring which is preferably formed of a steel having a carbon content of between about 0.55% by weight and 0.60% by weight. The bearing ring is carbonitrided within a furnace having an enclosed atmosphere containing ammonia gas. The bearing ring is then tempered by heating the ring to at least five hundred degrees Celsius (500° F.). Next, the induction hardening the at least one raceway surface of the ring is induction hardened, preferably by means of special inductor coil. Finally, the raceway surface(s) of the ring is machined to desired final dimensions and surface finish.

A bearing unit having a stationary radially outer ring provided with a raceway, a radially inner ring rotatable about a central rotation axis (X) of the bearing unit and provided with a raceway, a row of rolling elements interposed between the radially outer ring and the radially inner ring, at least one sealing device mounted by means of interference on the radially outer ring and in sliding contact with the radially inner ring, wherein both the radially outer ring and the radially inner ring are made of low carbon steel with a minimum percentage by weight of carbon equal to 0.42%, and a central portion of the radially outer ring situated along the raceway and a central portion of the radially inner ring situated along the raceway are heat treated by means of induction hardening.

An automotive shaft includes a journal having a crest-to-crest contact surface area defined by and between undercut regions of the shaft, an entirety of the crest-to-crest contact surface area being laser hardened to a depth no greater than 1 mm to form a layer that does not contain unhardened portions.

A bearing unit having a stationary radially outer ring provided with a raceway, a radially inner ring rotatable about a central rotation axis (X) of the bearing unit and provided with a raceway, a row of rolling elements interposed between the radially outer ring and the radially inner ring, at least one sealing device mounted by means of interference on the radially outer ring and in sliding contact with the radially inner ring, wherein both the radially outer ring and the radially inner ring are made of low carbon steel with a minimum percentage by weight of carbon equal to 0.42%, and a central portion of the radially outer ring situated along the raceway and a central portion of the radially inner ring situated along the raceway are heat treated by means of induction hardening.

Provided is a steering function-equipped hub unit including: a hub unit body including a hub bearing; a unit support member configured to be provided to a chassis frame component, the unit support member supporting the hub unit body such that the hub unit body is rotatable about a turning axis extending in a vertical direction; and a steering actuator configured to rotationally drive the hub unit body about the turning axis, wherein the hub bearing includes an outer race integrally provided with turning shaft parts protruding upward and downward in the vertical direction on an outer peripheral surface of the outer race, each of the turning shaft parts having an axis coinciding with the turning axis, and the hub unit body is rotatably supported by the unit support member through the turning shaft parts.

A member for guiding an element mobile in oscillation or rotation is presented. The member has a body made of a hardened metallic material, provided with a bore for assembling the mobile element, having cavities that are distributed discontinuously in the bore and capable of acting as grease reserves, and having optional grease supply. In the bore are defined a bearing surface outside of the cavities and the grease supply, and a non-bearing surface in the cavities and the grease supply. The bore includes at least one zone with: cavities having a depth of between 2 and 5 mm, and a quantity of grease in the cavities per bearing surface of between 0.05 and 0.3 g/cm.sup.2. A mechanical system having such a member and a method for manufacturing such a member is also contemplated.