JP2009236232A - Roller bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a roller bearing not only suppressing a decrease in hardness of a part under a high-temperature environment and improving durability under an environment where a foreign material enters, but also achieving dry-run performance. <P>SOLUTION: An outer ring 11 and an inner ring 12 of a three-point contact ball bearing 1 are constituted of steel containing 0.11 to 0.15% of carbon, 0.1 to 0.25% of silicon, 0.15 to 0.35% of manganese, 3.2 to 3.6% of nickel, 4 to 4.25% of chromium, 4 to 4.5% of molybdenum, and 1.13 to 1.33% of vanadium with the rest consisting of iron and impurities. Nitrogen-enriched layers 11B, 12B having a nitrogen concentration of at least 0.05 mass% are formed on a region including rolling surfaces 11A, 12A, and the total of a carbon concentration and the nitrogen concentration in the nitrogen-enriched layers 11B, 12B is at least 0.55 mass% and not more than 1.9 mass%. A DLC coating layer 11E is arranged on a region including an outer ring contact surface 11D. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rolling bearing, and more particularly to a rolling bearing in which the occurrence of seizure is suppressed.

  In recent years, with the progress of high performance and high efficiency of a mechanical device in which a rolling bearing is used, the rolling bearing tends to be required to have high durability under a severe use environment. Specifically, in a rolling bearing used in a foreign matter mixed environment where hard foreign matter enters inside, the rolling bearing is damaged early (with an operation time shorter than the calculated life of the bearing) due to the biting of the foreign matter. There is a case. Further, seizure may occur in a rolling bearing used in an environment where lubrication is insufficient. In particular, seizure is likely to occur between a cage constituting the rolling bearing and a race member such as an inner ring or an outer ring that guides the cage. Furthermore, when the rolling bearing is used in a high temperature environment, for example, a high temperature environment exceeding 200 ° C., the hardness of parts such as race members and rolling elements constituting the rolling bearing is lowered, and the durability may be lowered.

  On the other hand, when parts such as race members and rolling elements are made of steel, the strength at high temperature is improved by adding 4% by mass or more of chromium to the steel to improve the temper softening resistance of the steel. The durability of the rolling bearing in a high temperature environment can be improved. In addition, when the bearing part is made of steel having a carbon content of 0.15% by mass or less, in order to improve the durability in a foreign matter mixed environment, for example, carburizing treatment is performed on the bearing part in addition to the surface layer portion. After forming a region (carburized layer) having a higher carbon concentration than that in the region, a process for forming a nitrogen-enriched layer having a higher nitrogen concentration in the surface layer portion than in other regions, such as nitriding, is performed. Measures can be adopted.

  Here, in a bearing component made of steel having a high chromium content, for example, steel containing 4% by mass or more of chromium, a chemically stable oxide film is formed on the surface layer portion. Therefore, even if a normal nitriding treatment is performed, there is a problem that nitrogen does not enter the surface layer portion and a nitrogen-enriched layer is not formed. On the other hand, a countermeasure for forming a nitrogen-enriched layer by performing plasma nitriding has been proposed (see, for example, Patent Document 1). With respect to the control of the plasma nitriding treatment, for example, a method based on spectroscopic analysis of glow discharge and a method based on the current density of the current flowing through the workpiece have been proposed (see, for example, Patent Documents 2 and 3). ). As a result, a nitrogen-enriched layer can be formed on the surface layer portion of the bearing part made of steel containing 4% by mass or more of chromium.

In order to improve seizure resistance, a countermeasure has been proposed in which balls, which are rolling elements, are immersed in an organic phosphorus compound to form a reaction film on the surface (see, for example, Patent Document 4).
Japanese Patent Laid-Open No. 2-57675 JP-A-7-118826 Japanese Patent Laid-Open No. 9-3646 JP-A-9-133130

  However, even when a nitrogen-enriched layer is formed on the surface layer of a bearing part made of steel containing 4 mass% or more of chromium using the plasma nitriding treatment as described above, the characteristics of the part are not sufficiently improved. There is a case. That is, when stress is repeatedly applied to the components as described above, peeling or fracture may occur at an early stage (decrease in fatigue strength). Further, when an impact stress is applied to the above-described component, breakage may easily occur (decrease in toughness). In other words, in bearing parts made of steel containing 4% by mass or more of chromium, merely forming a nitrogen-enriched layer increases the hardness of the surface layer portion, but it is not always sufficient particularly in terms of fatigue strength and toughness. There is a problem in that it may not be possible to obtain proper characteristics.

  Also, the environment in which rolling bearings are used is becoming increasingly severe. For example, in rolling bearings used for jet engines such as aircraft, not only is the hardness reduction of parts under a high temperature environment and improvement of durability in a foreign matter mixed environment, but also the durability against lubrication when temporarily blocked. Improvement of seizure property (so-called dry run performance improvement) is required. In order to improve the dry run performance, it is particularly necessary to effectively suppress seizure between the raceway member and the cage. Therefore, it cannot be said that conventional countermeasures including the countermeasures disclosed in Patent Documents 1 to 4 are sufficient.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a rolling bearing that can achieve not only suppression of hardness reduction of parts under a high temperature environment and improvement of durability in a foreign matter mixed environment but also improvement of dry run performance.

  The rolling bearing according to the present invention has carbon of 0.11% by mass to 0.15% by mass, silicon of 0.1% by mass to 0.25% by mass, and 0.15% by mass to 0.35%. Manganese of not more than mass%, nickel of not less than 3.2 mass% and not more than 3.6 mass%, chromium of not less than 4 mass% and not more than 4.25 mass%, and molybdenum of not less than 4 mass% and not more than 4.5 mass% 1,3 to 1.33% by mass of vanadium, the balance is made of steel consisting of iron and impurities, and the region including the surface has a nitrogen concentration of 0.05% by mass or more. An enriched layer is formed, and the total value of the carbon concentration and the nitrogen concentration in the nitrogen-enriched layer is 0.55% by mass or more and 1.9% by mass or less; A plurality of rolling elements arranged on an annular track, and the rolling elements are kept on the track. And a cage for. The track member includes a track member contact surface that contacts the cage. On the other hand, the cage includes a cage contact surface that contacts the raceway member. And the seizure prevention layer which consists of a material different from the material which comprises a track member is arrange | positioned in the area | region containing at least any one of a track member contact surface and a cage contact surface.

  The present inventor has made a detailed study on the cause of a decrease in fatigue strength and toughness when a nitrogen-enriched layer is formed on a bearing part made of steel containing 4% by mass or more of chromium. As a result, it was found that the fatigue strength and toughness of the parts are reduced due to the following phenomenon.

That is, when a nitrogen-enriched layer is formed on a bearing part made of steel containing 4% by mass or more of chromium by plasma nitriding as described above, the amount of nitrogen in the surface layer portion is the solid solubility limit ( It exceeds the solid solubility limit including nitrogen contained in the precipitate. Therefore, iron nitrides (Fe ₃ N, Fe ₄ N, etc.) that precipitate along the grain boundaries are formed in the steel constituting the part. An iron nitride formed with a length of not less than 2 μm and a length of not less than 7.5 μm (hereinafter referred to as having an aspect ratio of not less than 2 and a length of not less than 7.5 μm along the grain boundary) The formed iron nitride is referred to as grain boundary precipitate), which may be the starting point of peeling and fracture.

  More specifically, when stress is repeatedly applied to a part on which grain boundary precipitates are formed, the grain boundary precipitates may become a stress concentration source, and cracks may occur. And since this crack progresses and it leads to peeling and a fracture | rupture, the fatigue strength of components falls. In addition, when an impact stress is applied to the part on which the grain boundary precipitate is formed, the grain boundary precipitate promotes the generation and progress of cracks, and thus the toughness may be reduced. That is, as a result of an excessive amount of nitrogen entering the surface layer portion of the component such as the race member and the rolling element, a grain boundary precipitate is formed, which may cause a decrease in fatigue strength and toughness of the component.

  On the other hand, in the race member constituting the rolling bearing of the present invention, a nitrogen enriched layer having a nitrogen concentration of 0.05% by mass or more is formed in a region including the surface of the race member made of steel having an appropriate component composition. In addition, the formation of grain boundary precipitates can be suppressed by setting the total value of the carbon concentration and the nitrogen concentration in the nitrogen-enriched layer within an appropriate range. As a result, according to the race member constituting the rolling bearing of the present invention, it is made of steel containing 4% by mass or more of chromium, so that a decrease in hardness in a high temperature environment is suppressed, and a nitrogen enriched layer is formed on the surface layer portion. Can be provided, and a raceway member in which fatigue strength and toughness are sufficiently secured can be provided. The reason why the component ranges of steel constituting the raceway member and the nitrogen and carbon concentrations in the nitrogen-enriched layer are limited to the above ranges will be described below.

Carbon: 0.11 mass% or more and 0.15 mass% or less In the steel which comprises a track member, if carbon is less than 0.11 mass%, the problem of the manufacturing cost rise of steel may generate | occur | produce. On the other hand, when carbon exceeds 0.15 mass%, problems such as an increase in core hardness and a decrease in toughness may occur. Therefore, carbon needs to be 0.11 mass% or more and 0.15 mass% or less.

Silicon: 0.1 mass% or more and 0.25 mass% or less In the steel which comprises a track member, if silicon is less than 0.1 mass%, the problem of the manufacturing cost rise of steel may generate | occur | produce. On the other hand, when silicon exceeds 0.25 mass%, the problem that the hardness of a raw material will rise and cold workability will fall may generate | occur | produce. Therefore, silicon needs to be 0.1 mass% or more and 0.25 mass% or less.

Manganese: 0.15% by mass or more and 0.35% by mass or less In the steel constituting the race member, if manganese is less than 0.15% by mass, there may be a problem of an increase in steel manufacturing cost. On the other hand, when manganese exceeds 0.35 mass%, the problem that the hardness of a raw material will rise and cold workability will fall may generate | occur | produce. Therefore, manganese needs to be 0.15 mass% or more and 0.35 mass% or less.

Nickel: 3.2 mass% or more and 3.6 mass% or less In the steel constituting the raceway member, if nickel is less than 3.2 mass%, there may be a problem that the effect of improving corrosion resistance, hardness and toughness is reduced. . On the other hand, when nickel exceeds 3.6 mass%, the problem of an increase in the amount of retained austenite may occur. Therefore, nickel needs to be 3.2 mass% or more and 3.6 mass% or less.

Chromium: 4% by mass or more and 4.25% by mass or less In the steel constituting the race member, when chromium is less than 4% by mass, there may be a problem that the temper softening resistance is lowered. On the other hand, when chromium exceeds 4.25 mass%, the problem that the solid solution of carbide is inhibited when quenching is performed may occur. Therefore, chromium needs to be 4 mass% or more and 4.25 mass% or less.

Molybdenum: 4% by mass or more and 4.5% by mass or less In the steel constituting the raceway member, when molybdenum is less than 4% by mass, there may be a problem that the temper softening resistance is lowered. On the other hand, when molybdenum exceeds 4.5 mass%, the problem that the manufacturing cost of steel rises may generate | occur | produce. Therefore, molybdenum needs to be 4 mass% or more and 4.5 mass% or less.

Vanadium: 1.13 mass% or more and 1.33 mass% or less In the steel constituting the raceway member, if vanadium is less than 1.13 mass%, the effect of reducing the temper softening resistance and refining the microstructure by adding vanadium is effective. The problem of fewer may occur. On the other hand, when vanadium exceeds 1.33 mass%, the problem that the manufacturing cost of steel rises may generate | occur | produce. Therefore, vanadium needs to be 1.13 mass% or more and 1.33 mass% or less.

Nitrogen concentration in the nitrogen-enriched layer: 0.05% by mass or more In the raceway member made of the above steel, in order to provide sufficient hardness to the surface layer portion and ensure wear resistance, the nitrogen concentration in the region including the surface It is necessary to form a nitrogen-enriched layer with 0.05% by mass or more. In order to further improve the wear resistance and the like, the nitrogen concentration on the surface of the race member is preferably 0.15% by mass or more.

Total value of nitrogen concentration and carbon concentration in the nitrogen-enriched layer: 0.55% by mass or more and 1.9% by mass or less In the raceway member made of the above steel, sufficient hardness is given to the surface layer part to provide wear resistance and the like. In order to secure it, it is important to manage not only the nitrogen concentration but also the carbon concentration. And, if the total value of the nitrogen concentration and the carbon concentration in the nitrogen-enriched layer is less than 0.55 mass, it is difficult to impart sufficient hardness to the surface layer portion to ensure wear resistance and the like. Found out. Therefore, the total value of the nitrogen concentration and the carbon concentration in the nitrogen-enriched layer needs to be 0.55% by mass or more. Further, in order to make it easy to provide sufficient hardness to the surface layer portion to ensure wear resistance and the like, the total value of the nitrogen concentration and the carbon concentration in the nitrogen-enriched layer is 0.7% by mass or more. It is preferable that

  On the other hand, in the raceway member made of the steel, when the nitrogen concentration in the surface layer portion increases, grain boundary precipitates are easily formed, and when the carbon concentration increases, the tendency becomes stronger. And this inventor discovered that it will become difficult to suppress formation of a grain-boundary precipitate when the total value of the nitrogen concentration and carbon concentration in a nitrogen enriched layer exceeds 1.9 mass%. Therefore, the total value of the nitrogen concentration and the carbon concentration in the nitrogen-enriched layer needs to be 1.9% by mass or less. Moreover, in order to further suppress the formation of grain boundary precipitates, the total value of the nitrogen concentration and the carbon concentration in the nitrogen-enriched layer is preferably 1.7% by mass or less. The carbon concentration and nitrogen concentration refer to concentrations in the substrate (matrix) that is a region other than carbides such as iron and chromium.

  Furthermore, in the rolling bearing of the present invention, an anti-seizure layer made of a material different from the material constituting the race member is disposed in the region including at least one of the race member contact surface and the cage contact surface. Yes. As described above, in order to achieve improvement in seizure resistance of the rolling bearing, particularly improvement in dry run performance, it is necessary to effectively suppress seizure between the raceway member and the cage. On the other hand, as described above, the raceway member according to the present invention is made of steel, and the cage is usually made of a metal material such as steel. Thus, when the raceway member and the cage are made of the same material, seizure tends to occur in an environment where lubrication is insufficient. On the other hand, the seizure resistance of the rolling bearing is provided by arranging an anti-seizure layer made of a material different from the material constituting the race member in a region including at least one of the race member contact surface and the cage contact surface. Improvement, in particular, dry run performance can be achieved. In addition, in the manufacturing process of the track member, when the nitrogen-enriched layer is formed not only in the region (rolling surface) of the surface of the track member that contacts the rolling element but also on the track member contact surface, the track member is held. There may be a case where seizure occurs between the containers. In order to avoid the formation of the nitrogen-enriched layer on the raceway member contact surface in the nitriding treatment for forming the nitrogen-enriched layer, a film for preventing nitridation on the raceway member contact surface before performing the nitriding treatment Etc., a complicated process is required in which nitriding is performed and then the film is removed. Therefore, in the rolling bearing of the present invention based on the formation of the nitrogen-enriched layer on the raceway member, the above troublesome process in the manufacturing process can be avoided by forming the seizure prevention layer.

  As described above, in the rolling bearing of the present invention, the raceway member is made of steel containing 4% by mass or more of chromium, so that a decrease in the hardness of the component in a high temperature environment is suppressed. In addition, by forming a nitrogen-enriched layer with an appropriate range of the total value of carbon concentration and nitrogen concentration on the surface layer of a raceway member made of steel having an appropriate component composition, the durability of parts in a foreign matter-contaminated environment Improves. Furthermore, by arranging the anti-seize layer in a region including at least one of the raceway member contact surface and the cage contact surface, improvement in seizure resistance, particularly improvement in dry run performance is achieved. As a result, according to the rolling bearing of the present invention, it is possible to provide a rolling bearing capable of achieving not only the suppression of the hardness reduction of components under a high temperature environment and the improvement of durability in a foreign matter mixed environment but also the improvement of dry run performance. Can do.

  Here, as a material constituting the seizure prevention layer, for example, ceramics such as DLC (Diamond Like Carbon), alumina, silicon nitride, silicon carbide, zirconia, polyimide resin, PTFE (Poly Tetra Fluoro Ethylene), PFA (PFA) Perfluoro Alkoxyl Alkane), FEP (Fluorinated Ethylene Propylene Copolymer), ETFE (Ethylene Tetra Fluoro Ethylene), PVdF (Poly Vinylene Fluorine E) Etc. can be adopted.

  In the rolling bearing, the seizure prevention layer may be made of DLC. Since DLC has high hardness and a dynamic friction coefficient with steel is smaller than steel, it is suitable as a material constituting the seizure prevention layer.

  In the rolling bearing, the anti-seizure layer can be made of a low dynamic friction coefficient resin. Low dynamic friction coefficient resins such as polyimide resins, PTFE, PFA, FEP, ETFE, PVdF, and other fluororesins, PEEK, PPS, phenolic resins, etc. However, since the occurrence of seizure is suppressed when the seizure prevention layer wears, it is suitable as a material constituting the seizure prevention layer.

  In the rolling bearing, preferably, the low dynamic friction coefficient resin has a porous structure, so that the lubricant can be impregnated. Thereby, during the operation of the bearing, even when the lubricant is impregnated in the low dynamic friction coefficient resin and the lubrication is insufficient, the lubrication is ensured by the impregnated lubricant and the occurrence of seizure is suppressed. . Here, phenol resin etc. are employable as low dynamic friction coefficient resin which has a porous structure.

  In the rolling bearing, preferably, the nitrogen-enriched layer has a thickness of 0.05 mm or more. In the race member, the strength of the surface and the region immediately below the surface, specifically, the region within a distance of 0.05 mm or less from the surface is often important. Therefore, by setting the thickness of the nitrogen-enriched layer to 0.05 mm or more, it becomes possible to give sufficient strength to the race member. In order to further increase the strength of the raceway member, the thickness of the nitrogen-enriched layer is preferably 0.10 mm or more.

  In the rolling bearing, preferably, the nitrogen-enriched layer has a hardness of 800 HV or more. By setting the hardness of the nitrogen-enriched layer formed on the surface layer portion to 800 HV or higher, it is possible to ensure the strength of the race member more reliably.

  Preferably, in the rolling bearing, when the nitrogen-enriched layer is observed with a microscope, the number of iron nitrides having an aspect ratio of 2 or more and a length of 7.5 μm or more is 1 or less in a square region 5 field of view having a side of 150 μm. It is.

  As described above, grain boundary precipitates, which are iron nitrides having an aspect ratio of 2 or more and a length of 7.5 μm or more, may reduce the characteristics such as fatigue strength and toughness of the parts. And when the inventor investigated the relationship between the fatigue strength and the number density of the grain boundary precipitates for the parts made of steel having the above component composition, when the nitrogen-enriched layer was observed with a microscope, the grain boundary precipitates It is found that the fatigue strength of the component is reduced when it is present at a number density of more than 1 in 5 fields of a square area of 150 μm on a side. Therefore, when the nitrogen-enriched layer is observed with a microscope, the fatigue strength of the raceway member can be improved by the number of grain boundary precipitates being one or less in a 5 visual field in a square region having a side of 150 μm. In order to further improve the fatigue strength of the raceway member, the number of the grain boundary precipitates is preferably 1 or less in the field of view of the square region 60 having a side of 150 μm.

  In the rolling bearing, preferably, the rolling element is made of ceramics. Thereby, since the raceway member and rolling element which mutually contact become a dissimilar material, seizure resistance improves. Moreover, the durability of the rolling element in a foreign matter mixed environment is improved by adopting a ceramic having a higher hardness than steel as the material of the rolling element. Moreover, since the rolling elements are made of ceramics, a decrease in hardness of the rolling elements in a high temperature environment is suppressed. Here, as the ceramic constituting the rolling element, for example, silicon nitride, sialon, alumina, zirconia, or the like can be employed.

  In the rolling bearing, the rolling element may be made of steel. As steel constituting the rolling elements, for example, AISI standards M50, M50NiL, etc. can be adopted. When the rolling element is made of M50NiL, it is preferable that the rolling element is formed with a nitrogen-enriched layer having the same configuration as that of the race member. Further, when the rolling element is made of M50, it has basically the same configuration as the raceway member, and the total value of the carbon concentration and the nitrogen concentration is 0.82 mass% or more and 1.9 mass% or less. A nitrogen enriched layer is preferably formed.

  The rolling bearing may be used as a bearing that rotatably supports a rotating member that is a main shaft or a member that rotates by receiving the rotation of the main shaft with respect to a member adjacent to the rotating member within the gas turbine engine. Good. For bearings that support rotating members (the main shaft or members that rotate in response to the rotation of the main shaft) inside the gas turbine engine, it is possible to reduce the hardness of parts under high-temperature environments, improve durability in the presence of foreign matter, and dry-run performance. Improvement is required. For this reason, the rolling bearing of the present invention that can achieve not only the suppression of hardness reduction of parts under a high temperature environment and the improvement of durability in an environment where foreign matter is mixed, but also the improvement of dry run performance is provided with a rotating member inside the gas turbine engine. It is suitable as a bearing to support.

  The concentration of nitrogen and carbon in the nitrogen-enriched layer can be investigated by, for example, EPMA (Electron Probe Micro Analysis). The number density of the iron nitride (grain boundary precipitates) can be investigated, for example, as follows. That is, the part is first cut in a cross section perpendicular to the surface, and the cross section is polished. Thereafter, the cross section is corroded with an appropriate corrosive solution, and then the nitrogen-enriched layer is observed with a scanning electron microscope (SEM) or an optical microscope to take a photograph. Then, a square visual field having a side of 150 μm whose surface is defined as one side of the visual field is analyzed by an image analyzer, and the number of grain boundary precipitates is investigated. This is performed randomly in five or more visual fields, and the number of grain boundary precipitates per five visual fields is calculated.

  As is apparent from the above description, according to the rolling bearing of the present invention, it is possible to achieve not only the suppression of the hardness reduction of parts under a high temperature environment and the improvement of the durability in a foreign matter mixed environment but also the improvement of the dry run performance. A rolling bearing can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
FIG. 1 is a schematic view showing a configuration of a turbofan engine which is a gas turbine engine to which the rolling bearing of the present invention can be applied. With reference to FIG. 1, the structure of the turbofan engine in the present embodiment will be described.

  With reference to FIG. 1, a turbofan engine 70 includes a compression unit 71, a combustion unit 72, and a turbine unit 73. The turbofan engine 70 is disposed so as to surround the outer peripheral surface of the low-pressure main shaft 74 and the low-pressure main shaft 74 disposed from the compression section 71 through the combustion section 72 to the turbine section 73. 77.

  The compression unit 71 is connected to the low pressure main shaft 74 and surrounds the fan 75 having a plurality of fan blades 75A formed so as to protrude radially outward from the low pressure main shaft 74, and the combustion unit 72. A fan nacelle 76 extending toward the end and a compressor 81 arranged on the combustion portion 72 side when viewed from the fan 75 are included. The compressor 81 includes a low-pressure compressor 81A and a high-pressure compressor 81B disposed on the combustion unit 72 side when viewed from the low-pressure compressor 81A. The low pressure compressor 81A has a plurality of compressor blades 88 connected to the low pressure main shaft 74, projecting radially outward from the low pressure main shaft 74 side, and arranged side by side in a direction approaching the combustion unit 72 from the fan 75 side. Yes. The high pressure compressor 81B has a plurality of compressor blades 88 connected to the high pressure main shaft 77, projecting radially outward from the high pressure main shaft 77 side, and arranged side by side in a direction approaching the combustion unit 72 from the fan 75 side. is doing. Further, a core cowl 78 is disposed so as to surround the outer peripheral side of the low-pressure compressor 81A. The annular space between the core cowl 78 and the fan nacelle 76 constitutes a bypass channel 79.

  The combustion section 72 is connected to the high-pressure compressor 81B of the compression section 71, and includes a combustion chamber 82 having a fuel supply member and an ignition member (not shown). The turbine unit 73 includes a turbine 83 having a high-pressure turbine 83B and a low-pressure turbine 83A disposed on the opposite side of the combustion unit 72 when viewed from the high-pressure turbine 83B. Further, a turbine nozzle 84 for discharging the combustion gas in the turbine 83 to the outside is disposed on the opposite side of the low pressure turbine 83A from the high pressure turbine 83B. The low-pressure turbine 83A is connected to the low-pressure main shaft 74, has a plurality of turbine blades 87 that protrude radially outward from the low-pressure main shaft 74 side and are arranged side by side in a direction approaching the turbine nozzle 84 from the combustion chamber 82 side. ing. The high-pressure turbine 83B is connected to the high-pressure main shaft 77, protrudes radially outward from the high-pressure main shaft 77 side, and has a plurality of turbine blades 87 arranged side by side in a direction approaching the turbine nozzle 84 from the combustion chamber 82 side. Have.

  The low-pressure main shaft 74 and the high-pressure main shaft 77 as rotating members that are the main shaft or a member that rotates by receiving the rotation of the main shaft are members that are disposed adjacent to the low-pressure main shaft 74 and the high-pressure main shaft 77 by the rolling bearing 89. On the other hand, it is supported rotatably. That is, the rolling bearing 89 includes a low-pressure main shaft 74 or a high-pressure main shaft 77 as a rotating member that is a member that rotates in response to the rotation of the main shaft or the main shaft inside the turbofan engine 70 that is a gas turbine engine. Alternatively, it is rotatably supported with respect to a member adjacent to the high-pressure main shaft 77.

  Next, the operation of the turbofan engine 70 in the present embodiment will be described. Referring to FIG. 1, air on the side opposite to the combustion portion 72 as viewed from the fan 75, that is, on the front side of the turbofan engine 70 is surrounded by the fan nacelle 76 by the fan 75 rotating around the axis of the low-pressure main shaft 74. (Arrow α). A part of the taken-in air flows in the direction along the arrow β and is discharged to the outside through the bypass channel 79 as an air jet. This air jet becomes part of the thrust generated by the turbofan engine 70.

  On the other hand, the remaining portion of the air taken into the space surrounded by the fan nacelle 76 flows into the compressor 81 along the arrow γ. The air that has flowed into the compressor 81 is compressed by flowing inside the low-pressure compressor 81A having a plurality of compressor blades 88 rotating around the low-pressure main shaft 74 toward the high-pressure compressor 81B, and flows into the high-pressure compressor 81B. . Further, the air that has flowed into the high-pressure compressor 81B is further compressed by flowing toward the combustion chamber 82 through the inside of the high-pressure compressor 81B having a plurality of compressor blades 88 that rotate about the axis of the high-pressure main shaft 77, and enters the combustion chamber 82. Inflow (arrow δ).

  The air compressed in the compressor 81 and flowing into the combustion chamber 82 is mixed with fuel supplied into the combustion chamber by a fuel supply member (not shown) and then ignited by an ignition member (not shown). Thereby, combustion gas is generated in the combustion chamber 82. This combustion gas flows out of the combustion chamber 82 and flows into the turbine 83 (arrow ε).

  The combustion gas flowing into the turbine 83 collides with the turbine blade 87 connected to the high-pressure main shaft 77 in the high-pressure turbine 83B, thereby rotating the high-pressure main shaft 77 around the axis. As a result, the high-pressure compressor 81B having the compressor blade 88 connected to the high-pressure main shaft 77 is driven. Further, the combustion gas that has passed through the high-pressure turbine 83B collides with the turbine blade 87 connected to the low-pressure main shaft 74 in the low-pressure turbine 83A, thereby rotating the low-pressure main shaft 74 around the axis. As a result, the low pressure compressor 81A having the compressor blade 88 connected to the low pressure main shaft 74 and the fan 75 having the fan blade 75A connected to the low pressure main shaft 74 are driven.

  The combustion gas that has passed through the low-pressure turbine 83A is discharged from the turbine nozzle 84 to the outside. This jet of exhausted combustion gas becomes part of the thrust generated by the turbofan engine 70.

  Here, in the turbofan engine 70, a rolling bearing 89 that rotatably supports the low-pressure main shaft 74 or the high-pressure main shaft 77 with respect to a member adjacent to the low-pressure main shaft 74 or the high-pressure main shaft 77 is generated in the turbofan engine 70. It is used under high temperature environment due to the influence of heat. Further, hard foreign matters such as metal powder and carbon powder may enter the rolling bearing 89. For this reason, the rolling bearing 89 is required to suppress a decrease in the hardness of components in a high temperature environment and to improve durability in a foreign matter mixed environment. Further, when the turbofan engine 70 is installed in an aircraft, even if the lubrication of the rolling bearing 89 is temporarily interrupted for some reason, the low-pressure spindle 74 or the high-pressure spindle is not seized until the lubrication is recovered. The rolling bearing 89 is required to have a dry run performance that continues to support the bearing 77 in a rotatable manner.

  On the other hand, when the rolling bearing 89 is a rolling bearing according to the first embodiment described below, the above requirement can be satisfied.

  FIG. 2 is a schematic cross-sectional view showing a configuration of a three-point contact ball bearing as a rolling bearing in the first embodiment. FIG. 3 is a schematic partial cross-sectional view showing an enlarged main part of FIG. A three-point contact ball bearing as a rolling bearing in the first embodiment will be described with reference to FIGS.

  Referring to FIG. 2, a three-point contact ball bearing 1 includes an annular outer ring 11 that is a race member, an annular inner ring 12 that is a race member disposed inside the outer ring 11, and an outer ring 11 and an inner ring 12. And a plurality of balls 13 as rolling elements that are disposed between and held by an annular retainer 14. An outer ring rolling surface 11 </ b> A is formed on the inner circumferential surface of the outer ring 11, and an inner ring rolling surface 12 </ b> A is formed on the outer circumferential surface of the inner ring 12. And the outer ring | wheel 11 and the inner ring | wheel 12 are arrange | positioned so that 12A of inner ring | wheel rolling surfaces and 11A of outer ring | wheels may mutually oppose. The inner ring 12 includes a first inner ring 121 and a second inner ring 122, and has a structure divided at the axially central portion. A first inner ring rolling surface 121A and a second inner ring rolling surface 122A are formed on the outer peripheral surfaces of the first inner ring 121 and the second inner ring 122, respectively. The first inner ring rolling surface 121A and the second inner ring rolling surface 122A constitute an inner ring rolling surface 12A. Further, the plurality of balls 13 can contact and hold the first inner ring rolling surface 121A, the second inner ring rolling surface 122A, and the outer ring rolling surface 11A on the ball rolling surface 13A that is the outer peripheral surface. By being arranged at a predetermined pitch in the circumferential direction by the vessel 14, it is held so as to roll on an annular track. With the above configuration, the outer ring 11 and the inner ring 12 of the three-point contact ball bearing 1 can rotate relative to each other.

  Here, the outer ring 11 and the inner ring 12 that are raceway members are 0.11% by mass or more and 0.15% by mass or less of carbon, 0.1% by mass or more and 0.25% by mass or less of silicon, and 0.15% by mass. % To 0.35 mass% manganese, 3.2 mass% to 3.6 mass% nickel, 4 mass% to 4.25 mass% chromium, 4 mass% to 4.5 mass% % Of molybdenum and 1.13 mass% or more and 1.33 mass% or less of vanadium, and the balance is made of steel consisting of iron and impurities. Then, referring to FIG. 2, the outer ring nitrogen enrichment in which the nitrogen concentration is 0.05 mass% or more in the region including outer ring rolling surface 11 </ b> A and inner ring rolling surface 12 </ b> A which are the surfaces of outer ring 11 and inner ring 12. Layer 11B and inner ring nitrogen-enriched layer 12B are formed. Furthermore, the total value of the carbon concentration and the nitrogen concentration in the outer ring nitrogen-enriched layer 11B and the inner ring nitrogen-enriched layer 12B is 0.55 mass% or more and 1.9 mass% or less. Here, the impurities include inevitable impurities such as those derived from steel raw materials or those mixed in the manufacturing process.

  Further, referring to FIG. 3, outer ring 11 that is a raceway member includes an outer ring contact surface 11 </ b> D (cage guide surface) as a raceway member contact surface that comes into contact with cage 14. The cage 14 includes a cage contact surface 14 </ b> D that contacts the outer ring 11. That is, the cage 14 of the three-point contact ball bearing 1 is guided by the outer ring 11. A DLC coating layer 11E as an anti-seizure layer made of DLC is disposed in a region including the outer ring contact surface 11D.

Further, the balls 13 that are rolling elements are made of ceramics. More specifically, in the present embodiment, the balls 13 are made of a sintered body containing silicon nitride as a main component and the remaining impurities. Incidentally, the sintered body, aluminum oxide _{(Al 2 O} 3), may contain a sintering aid such as yttrium oxide _(Y 2 _{O 3).}

  Here, the balls 13 may be made of steel having the same composition as the outer ring 11 and the inner ring 12. In this case, it is preferable that the ball 13 is further formed with a nitrogen-enriched layer having the same configuration as the outer ring 11 and the inner ring 12. The ball 13 may be made of AISI standard M50. In this case, a nitrogen-enriched layer having basically the same structure as the outer ring 11 and the inner ring 12 and having a total value of carbon concentration and nitrogen concentration of 0.82% by mass or more and 1.9% by mass or less. Preferably it is formed.

  In the outer ring 11 and the inner ring 12 that are race members of the three-point contact ball bearing 1 in the present embodiment, the outer ring rolling surface 11A and the inner ring rolling formed on the surface are made of steel having the appropriate component composition described above. An outer ring nitrogen-enriched layer 11B and an inner ring nitrogen-enriched layer 12B having a nitrogen concentration of 0.05% by mass or more are formed in a region including the surface 12A. Then, the total value of the carbon concentration and the nitrogen concentration in the outer ring nitrogen-enriched layer 11B and the inner ring nitrogen-enriched layer 12B is set to an appropriate range of 0.55 mass% or more and 1.9 mass% or less. Sufficient hardness is imparted to the part, and formation of grain boundary precipitates is suppressed. As a result, the outer ring 11 and the inner ring 12 that are the race members in the present embodiment are made of steel containing 4% by mass or more of chromium, a nitrogen-enriched layer is formed in the surface layer portion, and fatigue strength and It is a part with sufficient toughness.

  Furthermore, in the three-point contact ball bearing 1 in the present embodiment, a DLC coating layer 11E is disposed in a region including the outer ring contact surface 11D. Thereby, the three-point contact ball bearing 1 is a rolling bearing in which improvement in seizure resistance, particularly improvement in dry run performance is achieved.

  In the three-point contact ball bearing 1 according to the present embodiment, the balls 13 that are rolling elements are made of ceramics. Thereby, since the outer ring | wheel 11 and the inner ring | wheel 12, and the ball | bowl 13 which mutually contact become a dissimilar material, seizure resistance improves. As a result, durability under an environment where lubrication is insufficient, for example, improvement in dry run performance is achieved. Moreover, the durability of the ball 13 in a foreign matter mixed environment is improved by using ceramics having a higher hardness than steel as the material of the ball 13. Furthermore, since the balls 13 are made of ceramics, a decrease in the hardness of the balls 13 in a high temperature environment is suppressed. In addition, since the ball 13 is made of ceramics, the ball 13 is lighter than the ball 13 made of steel, and the centrifugal force acting on the ball 13 is reduced. It is suitable as a rolling bearing that supports a member that rotates at high speed.

  In addition, the ball 13 is made of steel such as AISI standards M50NiL and M50, and when the nitrogen-enriched layer is formed, the ball 13 contains a sufficient amount of chromium as in the outer ring 11 and the inner ring 12. While being made of steel, a nitrogen-enriched layer is formed in the surface layer portion, and the component has sufficiently secured fatigue strength and toughness. As a result, a decrease in the hardness of the ball 13 in a high temperature environment is suppressed, and the durability of the ball 13 in a foreign matter mixed environment is improved.

  As described above, in the three-point contact ball bearing 1 according to the present embodiment, the outer ring 11 and the inner ring 12 that are race members are made of steel containing 4% by mass or more of chromium, so that Hardness reduction is suppressed. Further, the outer ring nitrogen in which the total value of the carbon concentration and the nitrogen concentration is within an appropriate range in the region including the outer ring rolling surface 11A and the inner ring rolling surface 12A of the outer ring 11 and the inner ring 12 made of steel having an appropriate component composition. By forming the enriched layer 11B and the inner ring nitrogen-enriched layer 12B, the durability of the component in a foreign matter mixed environment is improved. Furthermore, since the DLC coating layer 11E is disposed in a region including the outer ring contact surface 11D, improvement in dry run performance is achieved. As a result, the three-point contact ball bearing 1 is a rolling bearing that achieves not only the suppression of the hardness reduction of parts under a high temperature environment and the improvement of durability in a foreign matter mixed environment, but also the improvement of dry run performance.

  Furthermore, the thickness of the outer ring nitrogen-enriched layer 11B and the inner ring nitrogen-enriched layer 12B formed on the outer ring 11 and the inner ring 12 is preferably 0.05 mm or more. Thereby, sufficient strength is imparted to the outer ring 11, the inner ring 12 and the ball 13.

  Furthermore, the outer ring nitrogen-enriched layer 11B and the inner ring nitrogen-enriched layer 12B preferably have a hardness of 800 HV or more. As a result, the strength of the outer ring 11 and the inner ring 12 can be more reliably ensured.

  Further, when the outer ring nitrogen-enriched layer 11B and the inner ring nitrogen-enriched layer 12B are observed with a microscope, the number of iron nitrides having an aspect ratio of 2 or more and a length of 7.5 μm or more is within 5 fields of a square region having a side of 150 μm. The number is preferably 1 or less. Thereby, the fatigue strength of the outer ring 11 and the inner ring 12 can be improved.

  Next, a method for manufacturing the rolling bearing in the embodiment of the present invention will be described. FIG. 4 is a flowchart showing an outline of a method of manufacturing the rolling bearing in the first embodiment.

  Referring to FIG. 4, the rolling bearing manufacturing method according to the present embodiment includes a raceway member manufacturing process including steps (S10) to (S120), and a cage manufacturing process including steps (S210) to (S230). And an assembling process implemented as a process (S300).

  First, the race member manufacturing process will be described. In the steel member preparation step implemented as the step (S10), 0.11% by mass to 0.15% by mass of carbon, 0.1% by mass to 0.25% by mass of silicon, and 0.15% by mass. % To 0.35 mass% manganese, 3.2 mass% to 3.6 mass% nickel, 4 mass% to 4.25 mass% chromium, 4 mass% to 4.5 mass% % Of molybdenum and 1.13 mass% or more and 1.33 mass% or less of vanadium, made of steel consisting of the remaining iron and impurities, and a steel member molded into the approximate shape of the raceway member is prepared. . Specifically, for example, an outer ring as a race member is formed by using a steel bar, steel wire, or the like containing the above components as a raw material, and performing processing such as cutting, forging, and turning on the steel bar, steel wire, etc. 11, steel members formed into a schematic shape such as the inner ring 12 are prepared.

  Next, a heat treatment step is performed on the above-described steel member prepared in step (S10) to perform a heat treatment including a quenching treatment and a nitriding treatment. The heat treatment process includes a carburization process performed as the process (S20), a quenching process performed as the process (S30), a first tempering process performed as the process (S40), and a first process performed as the process (S50). As a 1st subzero process, the 2nd tempering process implemented as process (S60), 2nd subzero process implemented as process (S70), 3rd tempering process implemented as process (S80), and process (S90) It includes a plasma nitriding step to be performed and a diffusion step to be performed as step (S100). Details of this heat treatment step will be described later.

  Next, a finishing process in which a finishing process or the like is performed on the steel member that has been subjected to the heat treatment process is performed as a process (S110). Specifically, for example, polishing is performed on the outer ring rolling surface 11A, the inner ring rolling surface 12A, and the like of the steel member on which the heat treatment process has been performed. In addition, it is preferable that the finishing process is also performed on the region where the DLC coating layer 11E is to be formed in the step (S120) described later.

  Next, as a step (S120), a seizure prevention layer forming step is performed. Specifically, the DLC coating layer 11E is formed on the steel member to be the outer ring 11 among the steel members on which the step (S110) has been performed. The DLC coating layer 11E can be formed by a method such as a plasma CVD (Chemical Vapor Deposition) method, a PVD (Physical Vapor Deposition) method, or the like. Thereby, the track member in the present embodiment is completed, and the track member manufacturing process in the present embodiment is completed.

  Next, details of the above-described heat treatment step will be described. FIG. 5 is a diagram for explaining the details of the heat treatment step included in the raceway member manufacturing step in the present embodiment. In FIG. 5, the horizontal direction indicates time, and the time elapses toward the right. In FIG. 5, the vertical direction indicates the temperature, and the higher the temperature, the higher the temperature.

Referring to FIG. 5, in the heat treatment step in the present embodiment, first, a carburizing step in which a steel member as a workpiece is carburized is performed. Specifically, for example, a steel member is heated to a temperature T ₁ that is a temperature equal to or higher than the A ₁ transformation point in a carburizing gas atmosphere containing carbon monoxide and hydrogen, and is held for a time t _1. Carbon enters the surface layer of the member. Thereby, a carburized layer having a high carbon concentration is formed in the region including the surface of the steel member as compared with the internal region which is a region other than the region including the surface.

Next, referring to FIG. 5, a quenching process is performed in which the carburized steel member is quenched. Specifically, the steel member is quenched and hardened by being cooled from a temperature T ₁ which is a temperature equal to or higher than the A ₁ transformation point to a temperature equal to or lower than the M _S point.

Here, the point A ₁ in the case of heating the steel refers to a point that the structure of the steel corresponds to the temperature to start the transformation from ferrite to austenite. Further, the M _s point means a point corresponding to a temperature at which martensite formation starts when the austenitized steel is cooled.

Next, the 1st tempering process which performs a tempering process is implemented with respect to the steel member in which the quenching process was implemented. Specifically, referring to FIG. 5, for example, after a steel member is heated to a temperature T ₂ that is a temperature lower than the A ₁ transformation point in a reduced-pressure atmosphere (in a vacuum) and held for a time t ₂ , Tempering is performed by cooling. Thereby, the residual stress due to the quenching treatment of the steel member is relaxed, and the effect of suppressing the strain due to the heat treatment can be obtained.

Next, the 1st subzero process which performs a subzero process is implemented with respect to the steel member in which the 1st tempering process was implemented. Specifically, with reference to FIG. 5, the steel member, for example liquid nitrogen is sprayed is cooled to a temperature T ₃ at a temperature of less than 0 ° C., is sub-zero treatment by being held for a time t ₃ The Thereby, the residual austenite produced | generated by the hardening process of the steel member transforms into a martensite, and effects, such as stabilization of the structure of steel, are acquired.

Next, the 2nd tempering process which performs a tempering process is implemented with respect to the steel member in which the 1st subzero process was implemented. Specifically, referring to FIG. 5, for example, a steel member is heated to a temperature T ₄ that is a temperature below the A ₁ transformation point in a vacuum, held for a time t ₄ , and then cooled. Tempered. Thereby, the residual stress due to the sub-zero treatment of the steel member is relaxed, and effects such as suppression of strain can be obtained.

Next, a second subzero process is performed in which the subzero process is performed again on the steel member that has been subjected to the second tempering process. Specifically, with reference to FIG. 5, the steel member, for example liquid nitrogen is sprayed is cooled to a temperature T ₅ at a temperature of less than 0 ° C., is sub-zero treatment by being held for a time t ₅ The Thereby, the residual austenite produced | generated by the hardening process of the steel member further transforms into a martensite, and the effect that the structure | tissue of steel is stabilized more is acquired.

Next, the 3rd tempering process which performs a tempering process again is implemented with respect to the steel member in which the 2nd subzero process was implemented. Specifically, with reference to FIG. 5, as in the second tempering step, the steel members are heated to a temperature T ₆ is a temperature lower than the A ₁ transformation point in a vacuum, held for a time t ₆ And then tempering by cooling. Here, the temperatures T ₆ and t ₆ can be the same conditions as the temperatures T ₄ and t _{4 in} the second tempering step. As a result, the residual stress that can be generated by the sub-zero treatment of the steel member in the second sub-zero process is relaxed, and effects such as suppression of strain can be obtained.

Next, a plasma nitriding step for performing a plasma nitriding process is performed on the steel member on which the third tempering step has been performed. Specifically, referring to FIG. 5, for example, selected from the group consisting of nitrogen (N ₂ ), hydrogen (H ₂ ), methane (CH ₄ ), and argon (Ar) so that the pressure is 50 Pa or more and 5000 Pa or less. A steel member is inserted into a plasma nitriding furnace into which at least one of the above is introduced and heated to a temperature T ₇ under conditions of a discharge voltage of 50 V to 1000 V and a discharge current of 0.001 A to 100 A. after being held for a time t _7, the steel member is treated plasma nitriding by being cooled. Thereby, nitrogen penetrate | invades into the surface layer part of a steel member, a nitrogen enriched layer is formed, and the intensity | strength of the said surface layer part improves. Here, the temperature T ₇ can be, for example, 300 ° C. or more and 550 ° C. or less, and the time t ₇ can be 1 hour or more and 80 hours or less. The heat treatment conditions such as the temperature T ₇ and the time t ₇ take into account the allowance in the finishing process performed in the finishing process, and the grain boundary precipitate layer (grain boundary precipitate is formed in the plasma nitriding process). The thickness of the layer) can be determined to be equal to or less than the thickness that can be removed in the finishing process.

When the steel constituting the steel member is AMS standard 6278 (AISI standard M50NiL), the pressure in the plasma nitriding step is 50 Pa to 1000 Pa, the discharge voltage is 50 V to 600 V, and the discharge current is 0.001 A to 300 A. The temperature T ₇ is preferably 350 ° C. or higher and 450 ° C. or lower, and the time t ₇ is preferably 1 hour or longer and 50 hours or shorter.

Next, the diffusion process which performs a diffusion process is implemented with respect to the steel member in which the plasma nitriding process was implemented. Specifically, with reference to FIG. 5, for example, is heated to a temperature T ₈ in vacuo, the steel member is diffusion process by being held between the time t _8. Here, the temperature T ₈ can be 300 ° C. or higher and 480 ° C. or lower, preferably 300 ° C. or higher and 430 ° C. or lower, and the time t ₈ can be 50 hours or longer and 300 hours or shorter. Thereby, nitrogen which penetrate | invaded steel can be made to reach | attain a desired area | region, suppressing that the hardness increase of the surface layer part by nitrided layer formation is canceled. And by carrying out this diffusion process, even if the depth of penetration of nitrogen in the plasma nitriding process is limited to a range in which the grain boundary precipitate layer can be removed in the finishing process, the nitrogen that has entered the steel is desired. It is possible to reach even the area. Through the above steps, the heat treatment step in this embodiment is completed.

  As described above, according to the heat treatment method in the present embodiment, the surface layer portion of steel containing 4% by mass or more of chromium is nitrided to form a high hardness nitrogen-enriched layer, and grain boundary precipitates Can be suppressed.

  In addition, according to the raceway member manufacturing step in the above embodiment, it is made of steel containing 4% by mass or more of chromium, and the surface layer portion is nitrided to form a high hardness nitrogen-enriched layer, and the grain boundary Track members (outer rings 11, 21, inner rings 12, 22, etc.) in which the generation of precipitates is suppressed can be manufactured. As a result, as described above, the nitrogen concentration is 0.05 mass in the region including the surface (outer ring rolling surface 11A, inner ring rolling surface 12A, etc.) of the raceway members (outer ring 11, inner ring 12, etc.) in the present embodiment. %, A total value of carbon concentration and nitrogen concentration is 0.55 mass% or more and 1.9 mass% or less, and a nitrogen enriched layer having a thickness of 0.05 mm or more and a hardness of 800 HV or more is formed. When the layer is cut in a cross section perpendicular to the surface and the cross section is observed with five fields of view of a 150 μm side square including the surface at random using an optical microscope or SEM, the number of detected grain boundary precipitates is one. It can be as follows. Here, the carbon concentration and the nitrogen concentration in the nitrogen-enriched layer are controlled, for example, by adjusting the processing time of plasma nitriding performed in the plasma nitriding step and the processing time of diffusion processing performed in the diffusing step. Can do.

  On the other hand, referring to FIG. 4, in the cage manufacturing process, first, as a step (S <b> 210), a molded member preparation process is performed in which a molded member having a molded shape of the cage is prepared. Specifically, for example, a steel material made of SAE standard 4340 is prepared, and a formed member is prepared by performing processing such as cutting.

  Next, as a step (S220), a heat treatment step is performed in which heat treatment is performed on the molded member. Specifically, an appropriate hardness is imparted to the molded member by performing a quenching process and a tempering process on the prepared molded member made of SAE4340.

  Next, a finishing process is performed as a process (S230). Specifically, for example, finishing is performed on the molded member that has been subjected to the heat treatment step. Through the above steps, the cage manufacturing step in the present embodiment is completed.

  And with reference to FIG. 4, the assembly process in which the completed components are combined and a rolling bearing is assembled is implemented as a process (S300). Specifically, for example, the outer ring 11, the inner ring 12 and the cage 14 produced by the above-described steps and the ball 13 which are separately prepared are combined, and the three-point contact ball bearing 1 is assembled. Thereby, the rolling bearing in the present embodiment is completed.

  Here, when the ball 13 is made of ceramics, the ball 13 can be manufactured as follows. First, ceramics employed as a material constituting the balls 13, for example, silicon nitride powder is prepared. Next, a sintering aid is added to the prepared ceramic powder and mixed. Further, a mixture of the ceramic powder and the sintering aid is formed into a general shape of the balls 13. Specifically, the mixture of the ceramic powder and the sintering aid is subjected to molding using a technique such as press molding, casting molding, extrusion molding, rolling granulation, etc. A molded body formed into 13 schematic shapes is produced. Further, the molded body is sintered. Specifically, the molded body is sintered using a pressure sintering method such as HIP (Hot Isostatic Press) or GPS (Gas Pressure Sintering). As a result, a sintered body having the approximate shape of the ball 13 is obtained. Next, the balls 13 as rolling elements are completed by polishing the surface (rolling surface) of the obtained sintered body.

  Moreover, when the ball 13 is made of the same steel as the outer ring 11 and the inner ring 12, the ball 13 can be manufactured by the same steps as the above steps (S10) to (S90). In addition, when formation of a nitrogen enriched layer is unnecessary, process (S70) and (S80) can be skipped. Further, when the ball 13 is made of, for example, AISI standard M50, the ball 13 can be similarly manufactured except that the carburizing step in the heat treatment step is omitted.

(Embodiment 2)
Next, Embodiment 2 which is another embodiment of the present invention will be described. FIG. 6 is a schematic cross-sectional view showing a configuration of a cylindrical roller bearing as a rolling bearing in the second embodiment. FIG. 7 is a schematic partial cross-sectional view showing an enlarged main part of FIG.

  Referring to FIGS. 6 and 7, cylindrical roller bearing 2 in the second embodiment has basically the same configuration as the three-point contact ball bearing 1 in the first embodiment, and has the same operational effects. . That is, the cylindrical roller bearing 2 is disposed between the annular outer ring 21, the annular inner ring 22 disposed inside the outer ring 21, and the outer ring 21 and the inner ring 22, and is held by the annular cage 24. A plurality of rollers 23 as rolling elements are provided. The roller 23 has a cylindrical shape. An outer ring rolling surface 21 </ b> A is formed on the inner circumferential surface of the outer ring 21, and an inner ring rolling surface 22 </ b> A is formed on the outer circumferential surface of the inner ring 22. The outer ring 21 and the inner ring 22 are arranged so that the inner ring rolling surface 22A and the outer ring rolling surface 21A face each other. Further, the plurality of rollers 23 come into contact with the inner ring rolling surface 22A and the outer ring rolling surface 21A on the roller rolling surface 23A, which is the outer circumferential surface, and are arranged at a predetermined pitch in the circumferential direction by the cage 24. It is held on an annular track so as to be freely rollable. With the above configuration, the outer ring 21 and the inner ring 22 of the cylindrical roller bearing 2 can rotate relative to each other.

  Here, referring to FIG. 7, outer ring 21 and inner ring 22 of cylindrical roller bearing 2 in the present embodiment are replaced with outer ring 11 and inner ring 12 of three-point contact ball bearing 1 in the first embodiment, and roller 23 is It corresponds to the ball 13 and has the same configuration and has the same effect. That is, the outer ring 21 and the inner ring 22 are made of the same steel as the outer ring 11 and the inner ring 12. In the regions including the outer ring rolling surface 21A and the inner ring rolling surface 22A, which are the surfaces of the outer ring 21 and the inner ring 22, the outer ring nitrogen-enriched layer 21B and the inner ring nitrogen rich whose nitrogen concentration is 0.05% by mass or more, respectively. An insulating layer 22B is formed. The total value of the carbon concentration and the nitrogen concentration in the outer ring nitrogen-enriched layer 21B and the inner ring nitrogen-enriched layer 22B is 0.55 mass% or more and 1.9 mass% or less. The outer ring 21 and the cage 24 have an outer ring contact surface 21D and a cage contact surface 24D corresponding to the outer ring contact surface 11D and the cage contact surface 14D. That is, the cage 24 of the cylindrical roller bearing 2 is guided by the outer ring 21.

  However, the cylindrical roller bearing 2 in the second embodiment is different from the three-point contact ball bearing 1 in the first embodiment in the structure of the seizure prevention layer. Specifically, referring to FIG. 7, a resin ring 21 </ b> E made of a phenol resin or the like that has a porous structure and can be impregnated with a lubricant is disposed in a region including outer ring contact surface 21 </ b> D of cylindrical roller bearing 2. Has been. As the lubricant, for example, MIL-PRF-23699 can be employed.

  In the cylindrical roller bearing 2 according to the second embodiment, the resin ring 21E is employed as the seizure prevention layer, so that the dynamic friction coefficient between the outer ring 21 and the cage 24 is reduced, and provisional lubrication is temporarily insufficient. Even if the resin ring 21E is worn, the occurrence of seizure is suppressed. Further, when the lubrication is insufficient, the lubrication is ensured by the lubricant impregnated in the resin ring 21E during the operation of the bearing, and the occurrence of seizure is further suppressed. Further, by adopting the resin ring 21E instead of the coating layer, in the manufacturing process of the rolling bearing, no complicated coating process is required. For example, the resin ring 21E is fitted into the outer ring 21, thereby preventing the seizure prevention layer. Can be formed.

  Next, the manufacturing method of the cylindrical roller bearing 2 in Embodiment 2 is demonstrated. The cylindrical roller bearing 2 can be manufactured basically in the same manner as the three-point contact ball bearing 1 in the first embodiment. However, due to the difference in the structure of the seizure prevention layer, the manufacturing method is partially different.

  That is, referring to FIG. 4, in the method for manufacturing cylindrical roller bearing 2, in step (S <b> 10), the groove portion for fitting resin ring 21 </ b> E into the region where resin ring 21 </ b> E of outer ring 21 is to be disposed is the inner peripheral surface. Formed along. Then, after the steps (S20) to (S110) are performed as in the case of the first embodiment, the resin ring 21E separately prepared is fitted into the groove portion in the step (S120). Other steps are performed in the same manner as in the first embodiment. Thereby, the cylindrical roller bearing 2 in Embodiment 2 can be completed, without performing the complicated coating process of a procedure.

  When the anti-seizure layer is formed by fitting the resin ring as described above, the resin ring may be fitted to the outer peripheral surface of the cage, but in this case, the resin ring is not operated during the operation of the rolling bearing. Centrifugal force acts in a direction that makes it easy to come off the cage. Therefore, when the raceway member contact surface becomes the inner peripheral surface of the outer ring (that is, when the cage is an outer ring guide), the resin ring is preferably fitted into the inner peripheral surface of the outer ring as described above. On the other hand, when the raceway member contact surface becomes the outer peripheral surface of the inner ring (that is, when the cage is an inner ring guide), the resin ring is preferably fitted into the inner peripheral surface of the cage.

(Embodiment 3)
Next, Embodiment 3 which is still another embodiment of the present invention will be described. FIG. 8 is a schematic cross-sectional view showing a configuration of a cylindrical roller bearing as a rolling bearing in the third embodiment. FIG. 9 is a schematic partial cross-sectional view showing an enlarged main part of FIG.

  8 and 9, the cylindrical roller bearing 3 in the third embodiment has basically the same configuration as the three-point contact ball bearing 1 and the cylindrical roller bearing 2 in the first and second embodiments. The same effect is obtained. That is, the cylindrical roller bearing 3 corresponds to the outer ring 31 corresponding to the outer rings 11 and 21, the inner ring 32 corresponding to the inner rings 12 and 22, the ball 13 and the roller 23, and contacts the outer ring 31 and the inner ring 32 on the roller rolling surface 33A. A retainer 34 corresponding to the roller 33 and the retainers 14 and 24 is provided. Further, the outer ring 31 and the inner ring 32 are arranged in a region including the outer ring rolling surface 31A and the inner ring rolling surface 32A, respectively, in the outer ring nitrogen enriched layer 31B and the inner ring nitrogen enriched layer 12B corresponding to the outer ring nitrogen enriched layers 11B and 21B. , 22B corresponding to the inner ring nitrogen-enriched layer 32B.

  However, the cylindrical roller bearing 3 in the third embodiment is different from the rolling bearing in the first and second embodiments in the configuration of the raceway member contact surface, the cage contact surface, and the seizure prevention layer. That is, referring to FIG. 9, inner ring 32 and cage 34 of cylindrical roller bearing 3 have inner ring contact surface 32D and cage contact surface 34D that are in contact with each other. That is, the cage 34 of the cylindrical roller bearing 3 is guided by the inner ring 32. And the resin coating layer 34E as a seizure prevention layer is arrange | positioned in the area | region containing retainer contact surface 34D. Thereby, the occurrence of seizure between the cage contact surface 34D and the inner ring contact surface 32D is suppressed.

  Next, the manufacturing method of the cylindrical roller bearing 3 in Embodiment 3 is demonstrated. FIG. 10 is a flowchart showing an outline of a method of manufacturing a rolling bearing in the third embodiment. Referring to FIGS. 10 and 4, the method for manufacturing cylindrical roller bearing 3 in the third embodiment is basically the same as the method for manufacturing three-point contact ball bearing 1 in the first embodiment. However, due to the difference in the configuration of the raceway member contact surface, the cage contact surface, and the seizure prevention layer, the method of manufacturing the rolling bearing in the third embodiment is partially different from that in the first embodiment. ing.

  That is, in the raceway member manufacturing step of the manufacturing method of the cylindrical roller bearing 3 in the third embodiment, the steps (S10) to (S110) are performed as in the case of the first embodiment, and the step (S120) is omitted. . On the other hand, in the cage manufacturing process, steps (S210) to (S230) are performed as in the case of the first embodiment. Thereafter, in the third embodiment, a seizure prevention layer forming step is further performed as a step (S240). Specifically, the resin coating layer 34E is formed on the inner peripheral surface of the molded member for which the finishing process has been completed. The resin coating layer 34E can be formed by a method such as compression molding, extrusion molding, injection molding, or powder coating. Thereby, the cage in the present embodiment is completed, and the cage manufacturing process in the present embodiment is completed.

  Then, as in the case of the first embodiment, the assembly step is performed as the step (S300), whereby the cylindrical roller bearing 3 in the third embodiment is completed.

  In the above embodiment, a three-point contact ball bearing and a cylindrical roller bearing have been described as examples of the rolling bearing of the present invention. However, the rolling bearing of the present invention is not limited to this, for example, a deep groove ball bearing or an angular ball. It may be a bearing, a thrust needle roller bearing, a self-aligning ball bearing, a self-aligning roller bearing, or the like. Moreover, in the said embodiment, although the case where the seizure prevention layer was formed in one among the track member contact surface and cage contact surface which contact each other was demonstrated, you may form in both.

  Further, in the claims, specification and abstract of the present application, the expression that the raceway member includes a raceway member contact surface that contacts the cage, and the cage includes a cage contact surface that contacts the raceway member. Although adopted, this means that the rolling bearings are arranged in a state where they can contact each other during operation.

  Embodiment 1 of the present invention will be described below. A sample having the same structure as the race member constituting the rolling bearing of the present invention was actually produced using the heat treatment method in the above embodiment, and generation of grain boundary precipitates in the surface layer portion was suppressed. A confirmation experiment was conducted. The experimental procedure is as follows.

  First, 0.11% by mass to 0.15% by mass of carbon, 0.1% by mass to 0.25% by mass of silicon, 0.15% by mass to 0.35% by mass of manganese, 3.2 mass% or more and 3.6 mass% or less nickel, 4 mass% or more and 4.25 mass% or less chromium, 4 mass% or more and 4.5 mass% or less molybdenum, and 1.13 mass% or more A steel material of AMS standard 6278 (AISI standard M50NiL), which contains 1.33 mass% or less of vanadium and is composed of the remaining iron and impurities, is prepared and processed to have an outer diameter of 40 mm, an inner diameter of 30 mm, and a thickness. A test piece of t16 mm was produced.

Next, a heat treatment step using the steel heat treatment method described with reference to FIG. 5 in the above embodiment was performed on the test piece. Here, T ₁ , t ₁ , T ₂ , t ₂ , T ₃ , t ₃ , T ₄ , t ₄ , T ₅ , t ₅ , T ₆ and t ₆ are the test pieces after the third tempering step. The hardness was determined to be 58 to 65 HRC, T ₇ was 430 ° C., t ₇ was 10 hours, T ₈ was 430 ° C., and t ₈ was 160 hours. In the plasma nitriding step, as the treatment temperature _{T 7} during plasma nitridation is 430 ° C., the discharge voltage 200V or 450V or less controlled the discharge current at 5A below the range of 1A. Further, in the plasma nitriding process, gas is introduced into the furnace at a ratio of nitrogen (N ₂ ): hydrogen (H ₂ ) = 1: 1 so that the pressure in the furnace during plasma nitriding is 267 Pa or more and 400 Pa or less. did.

  Furthermore, in the diffusion step, the diffusion treatment is performed so that the test piece is heated in an atmosphere furnace adjusted to a nitrogen atmosphere, and the sum of the carbon concentration and the nitrogen concentration on the surface of the test piece is 1.9% by mass or less. It was implemented. As described above, a test piece on which the same heat treatment step as in the above embodiment was performed was used as a sample of an example of the present invention (Example A).

On the other hand, the heat treatment process which abbreviate | omitted the diffusion process was implemented from the heat treatment method of the steel demonstrated based on FIG. 5 in the said embodiment with respect to the test piece which consists of AMS specification 6278 similarly produced. Here, T ₁ , t ₁ , T ₂ , t ₂ , T ₃ , t ₃ , T ₄ , t ₄ , T ₅ , t ₅ , T ₆ and t ₆ are the test pieces after the third tempering step. The hardness was determined to be 58 to 65 HRC, T ₇ was 480 ° C., and t ₇ was 30 hours. In the plasma nitriding step, the discharge voltage was controlled in the range of 200 V to 450 V and the discharge current in the range of 1 A to 5 A so that the processing temperature T ₇ during plasma nitriding was 480 ° C. Further, in the plasma nitriding step, nitrogen (N ₂ ): hydrogen (H ₂ ): methane (CH ₄ ) = 79: 80: 1 is set so that the pressure in the furnace during plasma nitriding is 267 Pa or more and 400 Pa or less. Gas was introduced into the furnace at a rate. The test piece subjected to the above heat treatment method was used as a sample of a comparative example of the present invention (Comparative Example A).

  And the sample of Example A and Comparative Example A produced as described above was cut in a cross section perpendicular to the surface, and the cross section was polished. Further, after the polished cross section was corroded with a corrosive liquid, five fields of view of a square having a side of 150 μm including the surface were randomly observed.

  Next, experimental results will be described. FIG. 11 is an optical micrograph of the microstructure near the surface of Example A. FIG. 12 is a diagram showing the hardness distribution in the vicinity of the surface of Example A. FIG. 13 is a graph showing the distribution of carbon and nitrogen concentrations in the vicinity of the surface of Example A. FIG. 14 is an optical micrograph of the microstructure in the vicinity of the surface of Comparative Example A. FIG. 15 is a diagram showing a hardness distribution in the vicinity of the surface of Comparative Example A. FIG. 16 is a graph showing the distribution of carbon and nitrogen concentrations in the vicinity of the surface of Comparative Example A. 11 and 14, the upper part of the photograph corresponds to the surface side of the sample. 12 and 15, the horizontal axis indicates the depth (distance) from the surface, and the vertical axis indicates the hardness (unit is Vickers hardness). In FIGS. 13 and 16, the horizontal axis indicates the depth (distance) from the surface, the vertical axis indicates the concentration of carbon and nitrogen, the thin line indicates the carbon concentration, and the thick line indicates the nitrogen concentration.

  Referring to FIG. 11, in the surface layer portion of the sample of Example A of the present invention, grain boundary precipitates (iron nitride formed with an aspect ratio of 2 or more and a length of 7.5 μm or more) It is not observed and has a good microstructure. 12 and 13, the region within 0.05 mm in depth from the surface of the sample of Example A has a sufficient hardness of 950 HV or more, and a sufficient amount of nitrogen has entered. is doing. Therefore, by performing finishing such as polishing on the surface of the steel member subjected to the same heat treatment as in Example A, the nitrogen concentration is 0.05% by mass or more, and the total value of the carbon concentration and the nitrogen concentration is 0. When a nitrogen-enriched layer having a thickness of 0.05 mm or more and 1.9 mass% or less, a thickness of 0.05 mm or more, and a hardness of 800 HV or more is formed, and the nitrogen-enriched layer is observed with a microscope, One or less machine parts can be manufactured within 5 fields of view of a square area of 150 μm per side.

  On the other hand, referring to FIG. 14, a large number of grain boundary precipitates 90 are observed in the surface layer portion of the sample of Comparative Example A, which is outside the scope of the present invention. Further, referring to FIGS. 15 and 16, a region within a depth of 0.05 mm from the surface of the sample of Comparative Example A has a sufficient hardness of 950 HV or more, as in Example A, A sufficient amount of nitrogen has penetrated. Therefore, even when a finishing process such as polishing is performed on the surface of the steel member that has been subjected to the same heat treatment as in Comparative Example A, a high-hardness surface layer portion is formed, but grain boundary precipitates remain in the surface layer portion. Machine parts to be obtained. Such a bearing component cannot be said to have sufficient fatigue strength and toughness as described above.

  As mentioned above, according to the manufacturing method of the raceway member which adopted the heat treatment method in the above-mentioned embodiment, it is made of steel containing 4% by mass or more of chromium, and a nitrogen-enriched layer is formed in the surface layer part, and It was confirmed that it was possible to produce a race member with sufficient fatigue strength and toughness.

  Embodiment 2 of the present invention will be described below. An experiment was conducted to investigate an appropriate heating temperature range in the diffusion step of the heat treatment method described in the above embodiment. The experimental procedure is as follows.

  First, 0.11% by mass to 0.15% by mass of carbon, 0.1% by mass to 0.25% by mass of silicon, 0.15% by mass to 0.35% by mass of manganese, 3.2 mass% or more and 3.6 mass% or less nickel, 4 mass% or more and 4.25 mass% or less chromium, 4 mass% or more and 4.5 mass% or less molybdenum, and 1.13 mass% or more A steel material of AMS standard 6278 (AISI standard M50NiL), which contains 1.33 mass% or less of vanadium and is composed of the remaining iron and impurities, is prepared and processed to have an outer diameter of 40 mm, an inner diameter of 30 mm, and a thickness. A test piece of t16 mm was produced.

  Next, among the heat treatment steps using the steel heat treatment method described with reference to FIG. 5 in the above embodiment for the test piece, the steps from the carburization step to the third tempering step are the examples of the first embodiment. It carried out like the case of A. And the process similar to a diffusion process was implemented by hold | maintaining the said test piece at the temperature of 430 degreeC-570 degreeC for various time, and the hardness of the carburized layer was measured. More specifically, the hardness was measured at 9 points in a region where the distance from the surface of the test piece was 0.2 mm or more and 0.4 mm or less, and the minimum hardness was calculated. Furthermore, the measurement result was analyzed based on the reaction kinetics, and the relationship between the heat treatment time (diffusion time) at each heating temperature in the diffusion step and the hardness of the carburized layer was calculated.

On the other hand, after carrying out the same test piece from the carburizing step to the third tempering step in the same manner as in Example A of Example 1, the plasma nitriding step and the diffusion step were actually carried out, Experiments were also conducted to confirm the hardness distribution. In the plasma nitriding step, the discharge voltage is controlled in the range of 200 V to 450 V, the discharge current is controlled in the range of 1 A to 5 A and maintained for 1 hour so that the processing temperature T ₇ during plasma nitridation is 480 ° C. Nitriding was performed. Furthermore, in the plasma nitriding step, gas was introduced into the furnace at a ratio of nitrogen (N ₂ ): hydrogen (H ₂ ) = 1: 1 so that the pressure in the furnace during plasma nitriding was 267 Pa or more and 400 Pa or less. . Further, a diffusion step of holding at 480 ° C. for 50 hours was performed on the test piece for which the plasma nitriding step was completed. And the hardness distribution in the surface layer part of the test piece before and behind implementing a diffusion process was measured.

  Next, the results of the experiment will be described. FIG. 17 is a diagram (Abami plot) showing the relationship between the heat treatment time (diffusion time) at each heating temperature in the diffusion step and the hardness of the carburized layer, obtained as a result of the analysis based on the reaction kinetics. In FIG. 17, the horizontal axis indicates the heat treatment time (diffusion time), and the vertical axis indicates the hardness of the carburized layer. Moreover, FIG. 18 is a figure which shows the hardness distribution of the surface layer part of the test piece which performed the spreading | diffusion process hold | maintained at 480 degreeC for the test piece before performing a diffusion process for 50 hours. In FIG. 18, the horizontal axis indicates the depth (distance) from the surface, and the vertical axis indicates the hardness. Moreover, in FIG. 18, the rhombus indicates the hardness of the test piece before the diffusion step, and the square indicates the hardness of the test piece after the diffusion step held at 480 ° C. for 50 hours.

  Referring to FIG. 17, the hardness of the carburized layer of the test piece decreases in a shorter time as the diffusion temperature becomes higher, but when the diffusion temperature reaches 480 ° C., the hardness decreases even when the diffusion treatment is performed for 200 hours. The width becomes 50 HV or less, and the influence of the decrease in the hardness of the base material (the hardness in the region of the carburized layer where there is no influence of nitrogen intrusion due to plasma nitriding) on the hardness of the surface layer portion is reduced. Further, when the diffusion temperature is 460 ° C., even when the diffusion treatment is performed for 200 hours, the decrease in hardness is 30 HV or less, and the influence of the decrease in the hardness of the base material on the hardness of the surface layer is further reduced. Further, when the diffusion temperature is 430 ° C., even when the diffusion treatment is performed for 200 hours, the decrease in hardness becomes 10 HV or less, and the decrease in the hardness of the base material hardly affects the hardness of the surface layer portion.

  On the other hand, referring to FIG. 18, when the diffusion step of holding at 480 ° C. for 50 hours is performed, the actual decrease in the hardness of the base material is almost the same as the analysis result of FIG. 17, and the analysis result of FIG. Is considered to be consistent with the actual heat treatment results.

  From the above experimental results, the heating temperature (diffusion temperature) in the diffusion step is a viewpoint that allows nitrogen that has entered the steel to reach a desired region while suppressing the influence of the decrease in the hardness of the base material on the hardness of the surface layer portion. Therefore, it is necessary to set the temperature to 480 ° C. or lower, and preferably 460 ° C. or lower. Furthermore, by setting the heating temperature to 430 ° C. or lower, the diffusion step can be carried out with almost no influence on the hardness of the surface layer portion due to the decrease in the hardness of the base material. In addition, from the viewpoint of suppressing the influence of the decrease in the hardness of the base material on the hardness of the surface layer portion, it is preferable to lower the heating temperature in the diffusion step, but the nitrogen that has entered the steel reaches the desired region. Therefore, the heating temperature is preferably set to 300 ° C. or higher in order to avoid the time required for the operation from exceeding the allowable limit in the actual production process.

  Embodiment 3 of the present invention will be described below. Using the heat treatment method described in the above embodiment, a nitrogen-enriched layer was formed in a region including the rolling surface, and an experiment was conducted to confirm the improvement in durability of the rolling bearing by the nitrogen-enriched layer. The experimental procedure is as follows.

  First, a method for producing a test bearing will be described. A JIS in which an AISI standard M50NiL is adopted as a material and a nitrogen-enriched layer is formed on the rolling surface by carrying out the steps (S10) to (S110) in FIG. 4 in the same manner as in the first embodiment. Standard 6206 model inner rings, outer rings and balls were produced. And the said inner ring | wheel, the outer ring | wheel, and the ball were assembled to the bearing (Example). On the other hand, for comparison, in the same process, by omitting steps (S90) and (S100), inner rings, outer rings and balls that do not form a nitrogen-enriched layer on the rolling surface are also produced. The bearing was assembled (comparative example).

Next, test conditions will be described. The test bearings of the above examples and comparative examples were lubricated with a lubricating oil in which a load of 6.9 kN was applied in the radial direction, and 0.4 g of powder of 45 μm to 105 μm particle size made of alumina was added per liter. Rotating at a rotational speed of 2000 rpm in a foreign matter mixed environment. And the time until peeling occurred on the rolling surface was recorded as the lifetime. This test was performed on nine test bearings, and the results were statistically processed to calculate a life value (L ₁₀ life) at which the cumulative failure probability was 10%. Then, the _{L 10} life was evaluated by the ratio of _{L 10} life of Comparative Example.

Next, test results will be described. Figure 19 is a diagram showing the investigation results of the L ₁₀ life in the third embodiment. 19, the vertical axis represents the ratio of L ₁₀ life for Comparative Example.

  Referring to FIG. 19, even when the same material is used, the lifetime in a foreign matter mixed environment is about 30 times longer by forming a nitrogen-enriched layer. From this, it was confirmed that the durability of the rolling bearing can be significantly improved by forming the nitrogen-enriched layer using the same heat treatment method as in the first embodiment.

  The embodiments and examples disclosed herein are illustrative in all respects and should not be construed as being restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The rolling bearing of the present invention can be particularly advantageously applied to a rolling bearing that is required to have improved durability under severe conditions.

It is the schematic which shows the structure of a turbofan engine. 3 is a schematic cross-sectional view showing a configuration of a three-point contact ball bearing in the first embodiment. FIG. FIG. 3 is a schematic partial cross-sectional view showing an enlarged main part of FIG. 2. 3 is a flowchart showing an outline of a method of manufacturing a rolling bearing in the first embodiment. It is a figure for demonstrating the detail of the heat processing process included in a track member preparation process. FIG. 5 is a schematic cross-sectional view showing a configuration of a cylindrical roller bearing in a second embodiment. It is a schematic fragmentary sectional view which expands and shows the principal part of FIG. FIG. 6 is a schematic cross-sectional view showing a configuration of a cylindrical roller bearing in a third embodiment. It is a general | schematic fragmentary sectional view which expands and shows the principal part of FIG. 10 is a flowchart showing an outline of a method of manufacturing a rolling bearing in a third embodiment. 2 is an optical micrograph of the microstructure near the surface of Example A. FIG. It is a figure which shows the hardness distribution in the surface vicinity of Example A. FIG. 4 is a graph showing the distribution of carbon and nitrogen concentrations in the vicinity of the surface of Example A. 4 is an optical micrograph of a microstructure in the vicinity of the surface of Comparative Example A. 6 is a diagram showing a hardness distribution in the vicinity of the surface of Comparative Example A. FIG. 6 is a graph showing the distribution of carbon and nitrogen concentrations in the vicinity of the surface of Comparative Example A. FIG. It is a figure (Abami plot) which shows the relationship between the heat processing time (diffusion time) in each heating temperature of a spreading | diffusion process, and the hardness of a carburized layer. It is a figure which shows the hardness distribution of the surface layer part of the test piece which performed the spreading | diffusion process hold | maintained at 480 degreeC for the test piece before performing a spreading | diffusion process for 50 hours. Is a diagram showing the investigation results of the L ₁₀ life in the third embodiment.

Explanation of symbols

  1 3-point contact ball bearing, 2, 3 cylindrical roller bearing, 11, 21, 31 outer ring, 11A, 21A, 31A outer ring rolling surface, 11B, 21B, 31B outer ring nitrogen-enriched layer, 11D, 21D outer ring contact surface, 11E DLC coating layer, 12, 22, 32 inner ring, 12A, 22A, 32A inner ring rolling surface, 12B, 22B, 32B inner ring nitrogen-enriched layer, 13 balls, 13A ball rolling surface, 14, 24, 34 cage, 14D 24D, 34D Cage contact surface, 21E Resin ring, 23, 33 Roller, 23A, 33A Roller rolling surface, 32D Inner ring contact surface, 34E Resin coating layer, 70 Turbofan engine, 71 Compression unit, 72 Combustion unit, 73 Turbine, 74 Low pressure spindle, 75 fan, 75A fan blade, 76 fan nacelle, 77 High pressure spindle, 78 Core cowl 79 Bypass channel, 81 Compressor, 81A Low pressure compressor, 81B High pressure compressor, 82 Combustion chamber, 83 Turbine, 83A Low pressure turbine, 83B High pressure turbine, 84 Turbine nozzle, 87 Turbine blade, 88 Compressor blade, 89 Rolling bearing, 90 grains Boundary precipitate, 121 1st inner ring, 121A 1st inner ring rolling surface, 122 2nd inner ring, 122A 2nd inner ring rolling surface.

Claims (9)

2. 0.11% by mass to 0.15% by mass of carbon, 0.1% by mass to 0.25% by mass of silicon, 0.15% by mass to 0.35% by mass of manganese, 2 mass% or more and 3.6 mass% or less nickel, 4 mass% or more and 4.25 mass% or less chromium, 4 mass% or more and 4.5 mass% or less molybdenum, 1.13 mass% or more 1. It contains 33% by mass or less of vanadium, and is composed of steel consisting of the balance iron and impurities, and in the region including the surface, a nitrogen enriched layer having a nitrogen concentration of 0.05% by mass or more is formed. The total value of the carbon concentration and the nitrogen concentration in the nitrogen enriched layer is 0.55% by mass or more and 1.9% by mass or less, and the race member,
A plurality of rolling elements in contact with the raceway member and disposed on an annular raceway;
A holder for holding the rolling element on the track,
The track member includes a track member contact surface that contacts the cage,
The cage includes a cage contact surface that contacts the raceway member,
A rolling bearing in which an anti-seizure layer made of a material different from the material constituting the raceway member is arranged in a region including at least one of the raceway member contact surface and the cage contact surface.   The rolling bearing according to claim 1, wherein the seizure prevention layer is made of DLC.   The rolling bearing according to claim 1, wherein the seizure prevention layer is made of a low dynamic friction coefficient resin.   The rolling bearing according to claim 3, wherein the low dynamic friction coefficient resin has a porous structure so that a lubricant can be impregnated therein.   The rolling bearing according to any one of claims 1 to 4, wherein the nitrogen-enriched layer has a thickness of 0.05 mm or more.   The rolling bearing according to claim 1, wherein the nitrogen-enriched layer has a hardness of 800 HV or more.   When the nitrogen-enriched layer is observed with a microscope, the number of iron nitrides having an aspect ratio of 2 or more and a length of 7.5 μm or more is 1 or less in 5 fields of a square region having a side of 150 μm. The rolling bearing according to any one of 6.   The rolling bearing according to claim 1, wherein the rolling element is made of ceramics.   The inside of a gas turbine engine WHEREIN: The rotating member which is a member which rotates in response to rotation of a main shaft or the said main shaft is rotatably supported with respect to the member adjacent to the said rotating member. Rolling bearing according to item.