JP5597976B2 - Bearing constituent member, method for manufacturing the same, and rolling bearing provided with the bearing constituent member - Google Patents

Description

  The present invention relates to a bearing component, a method for manufacturing the same, and a rolling bearing provided with the bearing component.

For example, when a rolling bearing is used under conditions where foreign matter is mixed, foreign matter is pressed against the inner and outer rings and rolling elements that are bearing components, and indentations are formed on the raceway surfaces of the inner and outer rings and the surface of the rolling elements. There is. A surface damage portion such as an indentation generated by such a foreign matter becomes a starting point of fatigue peeling due to stress concentration, and is one of the causes of reducing the life of the rolling bearing.
Therefore, there is a demand for an improvement in the life of the rolling bearing under the foreign matter mixing condition.

In order to improve the life of a rolling bearing, it has been proposed to obtain a bearing constituent member by subjecting a shaped material having a predetermined shape to carbonitriding from a steel material made of SUJ2 which is bearing steel.
Further, for example, an element formed in a predetermined shape from a steel material containing 3.2 mass% or more and less than 5.0 mass% chromium, less than 1.0 mass% molybdenum, less than 0.5 mass% vanadium, or the like. By heating the shape material in a carburizing atmosphere having a carbon potential of 1.2 to 1.5 at 850 to 930 ° C. and quenching, the shape material is subjected to carburizing treatment and then tempered. The average particle diameter of the carbide particles in the surface layer of the bearing component of the rolling bearing is 0.5 μm or less, the area ratio of the carbide particles is 9 to 30%, and the Rockwell C hardness is 63 (Vickers hardness). As described above, it has been proposed that the amount of retained austenite in the surface layer portion is 30 to 50% by volume (see Patent Document 1).

JP 2006-176863 A

  However, the bearing component obtained by using the steel material made of SUJ2 has a large amount of retained austenite inside, so that the retained austenite changes to martensite with time and the volume expands. , Dimensional changes are likely to occur, and there is a drawback that dimensional stability over time is low.

Further, since the bearing component described in Patent Document 1 has a large amount of retained austenite in the surface layer portion, the life of the rolling bearing can be extended. Since the amount of site is reduced, the yield stress is low, and there is a drawback that a sufficient static load capacity cannot be secured.
For this reason, the rolling bearing provided with the bearing component described in Patent Document 1 has a long life. However, when the bearing receives an excessive static load during use or a large impact during rotation at an extremely low rotational speed. When a load is applied, permanent deformation occurs at the contact portion between the raceway surfaces of the inner and outer rings and the rolling elements, and smooth rotation is hindered when the static load or impact load exceeds a limit load.

  In addition to this, the bearing constituent member described in Patent Document 1 has a large amount of retained austenite in the same manner as the bearing constituent member obtained by using the steel material made of SUJ2. There is a disadvantage that the property is low.

  The present invention has been made in view of such circumstances, and a bearing configuration capable of extending the life of a rolling bearing and ensuring sufficient static load capacity and sufficient dimensional stability. It aims at providing a member and its manufacturing method. Another object of the present invention is to provide a rolling bearing that has a long life and exhibits sufficient static load capacity and sufficient dimensional stability.

The bearing component of the present invention comprises 0.7 to 0.9 mass% carbon, 3.2 to 5.0 mass% chromium, and 0.05 mass% or more and less than 0.5 mass% vanadium. A bearing constituent member having a raceway portion obtained from a steel material and polished and having a carbon content in a surface layer in a range from the surface of the raceway portion to 10 μm is 1.1 to 1. .6 mass%, Vickers hardness at a depth of 50 μm from the surface of the track portion is 740 to 900, and the amount of retained austenite at a depth of 10 μm from the surface of the track portion is 20 The surface content in the surface layer in the range of ~ 55% by volume and in the range of 10 μm from the surface of the track part is 0.1 to 1.0% by mass, and the surface in the range of 10 μm from the surface of the track part The layer has a particle size of 0. The particles having a particle size 0.2~2μm consisting of particles and / or vanadium carbonitrides of ~2μm and having at least, Bonito particles having a particle size 0.2~2μm consisting vanadium nitride on the surface layer good beauty when both particle size 0.2~2μm of particles consisting of vanadium carbonitrides are present, particles and vanadium carbonitride particle size 0.2~2μm consisting of vanadium nitride in the surface layer The total area ratio with the particles having a particle diameter of 0.2 to 2 μm is 1 to 10%, and the surface layer is made of vanadium nitride particles having a particle diameter of 0.2 to 2 μm and vanadium carbonitride. When any one of particles having a particle size of 0.2 to 2 μm is present, particles having a particle size of 0.2 to 2 μm made of vanadium nitride and particles having a particle size of 0.2 to 2 μm made of vanadium carbonitride Said surface of Ri area ratio of 1-10% der particles present in the layer, the content of carbon in the surface layer ranging from the surface of the non-abrasive portion existing in a portion other than the track portion to 10μm is 0.7 .0 is the mass%, and the Vickers hardness at the position of a depth of 50μm from the surface of the non-abrasive portion is characterized by 700 to 800 der Rukoto (also referred to as "bearing part 1"). The surface layer in the range from the surface to 10 μm is defined as the range between the surface and a position at a depth of 10 μm from the surface.

According to the bearing component 1 configured as described above, the Vickers hardness at a depth of 50 μm from the surface is 740 to 900 (Rockwell C hardness is 62 to 67), and 10 μm from the surface. Since the amount of retained austenite at the depth position is 20 to 55% by volume, stress concentration on the surface damaged portion such as the indentation can be reduced. Moreover, the bearing component 1 has a surface layer in the range from the surface of the raceway portion to 10 μm, a particle having a particle diameter of 0.2 to 2 μm made of vanadium nitride and / or a particle diameter made of vanadium carbonitride. the particles of 0.2~2μm and having at least, and the particle size 0.2 consisting of particles and vanadium carbonitride particle size 0.2~2μm consisting vanadium nitride on the surface layer When both 2 μm particles are present , the total of particles having a particle diameter of 0.2 to 2 μm made of vanadium nitride and particles having a particle diameter of 0.2 to 2 μm made of vanadium carbonitride in the surface layer. The area ratio is 1 to 10%, and either one of particles having a particle diameter of 0.2 to 2 μm made of vanadium nitride and particles having a particle diameter of 0.2 to 2 μm made of vanadium carbonitride exists in the surface layer. If you are, Bana Area ratio of 1-10% der particles present in said surface layer of the particle size 0.2~2μm of particles consisting of particles and vanadium carbonitride particle size 0.2~2μm consisting um nitride Ri, the content of carbon in the surface layer ranging from the surface of the non-abrasive portion existing in a portion other than the track portion to 10μm is 0.7 to 1.0% by mass because, not reduce the amount of retained austenite However, high yield stress can be obtained.
Therefore, according to the bearing component 1 of the present invention, sufficient static load capacity can be obtained by high yield stress while ensuring a long life of the rolling bearing by relaxing stress concentration on the surface damage portion such as the indentation. Can be secured.
Further, the carbon content in the surface layer in the range from the surface of the non-polished part existing in the part other than the track part to 10 μm is 0.7 to 1.0 mass%, and the depth is 50 μm from this surface. Since the Vickers hardness at the position is 700 to 800, it is possible to suppress the occurrence of excessive carburized structure in the non-polished part.
Therefore, the bearing component 1 having such a configuration can be easily applied to an external load in addition to obtaining the operational effect of the on-axis component 1. For example, when used as an outer ring of a rolling bearing, the rolling component 1 The rolling fatigue life of the bearing can be improved, and sufficient strength can be given to the rolling bearing.

The steel material comprises 0.7 to 0.9 mass% carbon, 0.05 to 0.70 mass% silicon, 0.05 to 0.7 mass% manganese, and 3.2 to 5.0. It is a steel material containing 0.1% by mass of chromium, 0.1% to 1.0% by mass of molybdenum, and 0.05% by mass or more and less than 0.5% by mass of vanadium, with the balance being iron and inevitable impurities. It is preferable.
In this case, the amount of coarse eutectic carbide that precipitates during steelmaking in the bearing component member is reduced, fatigue failure in the bearing is suppressed, and sufficient hardness after quenching and after carbonitriding and tempering. Secured.

Method of manufacturing a bearing part of the present invention, in one aspect, 3. A processing step of processing a steel material containing 2 to 5.0% by mass of chromium and 0.05% by mass or more and less than 0.5% by mass of vanadium into a predetermined shape to obtain a shaped material,
Carburizing by heating the base material at 850 to 900 ° C. in a carbonitriding atmosphere having a carbon potential of 0.9 to 1.3 and an ammonia gas concentration of 2 to 5% by volume with respect to the base material. Carburizing and nitriding process to obtain nitriding and intermediate material,
The intermediate material after the carbonitriding treatment is subjected to a tempering treatment process in which the intermediate material is tempered by heating at 160 ° C. or higher, and the intermediate material after the tempering treatment is subjected to a finishing process. The content of carbon in the surface layer in the range from the surface to 10 μm is 1.1 to 1.6% by mass, and the Vickers hardness at a depth of 50 μm from the surface is 740 to 900 (Rockwell C hardness) 62 to 67), the amount of retained austenite at a depth of 10 μm from the surface is 20 to 55% by volume, and the nitrogen content in the surface layer in the range from the surface to 10 μm is 0.1 to 1 The surface layer in the range of 0.0 mass% and from the surface to 10 μm has a particle diameter of 0.2 to 2 μm made of vanadium nitride and / or a particle diameter of 0.2 to 2 μm made of vanadium carbonitride. Of have particles, and both of the surface layer grain size particles of 0.2~2μm consisting vanadium nitride and vanadium carbonitride of nitride particle size 0.2~2μm particles When present , the total area ratio of particles having a particle diameter of 0.2 to 2 μm made of vanadium nitride and particles having a particle diameter of 0.2 to 2 μm made of vanadium carbonitride in the surface layer is 1 to 10 %, And any one of particles having a particle diameter of 0.2 to 2 μm made of vanadium nitride and particles having a particle diameter of 0.2 to 2 μm made of vanadium carbonitride is present in the surface layer, vanadium A bearing having an area ratio of 1 to 10% of particles existing in the surface layer among particles having a particle size of 0.2 to 2 μm made of nitride and particles having a particle size of 0.2 to 2 μm made of vanadium carbonitride Includes finishing process to obtain components It is characterized by a door (also referred to as a "manufacturing method 1").

In the production method 1 in which such a configuration is adopted, a shaped material obtained from a steel material containing 3.2 to 5.0 mass% chromium and 0.05 mass% or more and less than 0.5 mass% vanadium. On the other hand, in a carbonitriding atmosphere with a carbon potential of 0.9 to 1.3 and an ammonia gas concentration of 2 to 5% by volume, the carbon steel is heated at 850 to 900 ° C. and quenched and subjected to a carbonitriding process. And since the tempering process which heats the said intermediate raw material to 160 degreeC or more is performed with respect to the intermediate raw material after a carbonitriding process, content of carbon in the surface layer of the range from the surface of the obtained bearing structural member to 10 micrometers 1.1 to 1.6% by mass, Vickers hardness at a depth of 50 μm from the surface is 740 to 900 (Rockwell C hardness is 62 to 67), and at a depth of 10 μm from the surface Retained austenite 20 to 55% by volume, the nitrogen content in the surface layer in the range from the surface to 10 μm is 0.1 to 1.0% by mass, and the particle size made of vanadium nitride in the surface layer in the range from the surface to 10 μm the presence of particles and / or particle size 0.2 to 2 .mu.m particles consisting of vanadium carbonitrides of 0.2 to 2 .mu.m, and your particles having a particle size 0.2 to 2 .mu.m consisting vanadium nitride on the surface layer good beauty when both particle size 0.2~2μm of particles consisting of vanadium carbonitrides are present, particles and vanadium carbonitride particle size 0.2~2μm consisting of vanadium nitride in the surface layer 1 to 10% of the total area ratio with particles having a particle size of 0.2 to 2 μm, and particles having a particle size of 0.2 to 2 μm made of vanadium nitride and vanadium carbonitride on the surface layer Of 0.2-2 μm particles When any one of them is present, particles present in the surface layer among particles having a particle size of 0.2 to 2 μm made of vanadium nitride and particles having a particle size of 0.2 to 2 μm made of vanadium carbonitride the area ratio of the can 1-10% and to Rukoto. Therefore, according to the manufacturing method 1, the bearing structural member 1 which has the above-mentioned outstanding effect can be obtained.

Moreover, the manufacturing method of the bearing structural member of this invention is a manufacturing method of the said bearing structural member 1 on the other side, Comprising: 0.7-0.9 mass% carbon, 3.2-5.0 A raceway member having a grinding allowance at least at a portion where a raceway surface is formed by processing a steel material containing chromium of 0.05% by mass and vanadium of 0.05% by mass or more and less than 0.5% by mass into a predetermined shape. Processing steps to obtain a shaped material,
Carburizing by heating the raw material at 850 to 900 ° C. for 4 hours or more in a carbonitriding atmosphere with a carbon potential of 0.9 to 1.3 and an ammonia gas concentration of 2 to 5% by volume. Carburizing and nitriding process to obtain nitriding and intermediate material,
A tempering process for subjecting the intermediate material after the carbonitriding treatment to a tempering process in which the intermediate material is heated at 160 ° C. or higher ; and
The portion of the intermediate material that forms the raceway surface after the tempering treatment is subjected to polishing finishing to form the raceway portion, and the carbon content in the surface layer in the range from the surface of the raceway portion to 10 μm The amount is 1.1 mass% or more and less than 1.6 mass%, the Vickers hardness at a depth of 50 μm from this surface is 740 to 900, and the residual at a depth of 10 μm from the surface The amount of austenite is 20 to 55% by volume, the content of nitrogen in the surface layer in the range from the surface to 10 μm is 0.1 to 1.0% by mass, and the surface layer in the range from the surface to 10 μm has a particle diameter 0.2~2μm consisting of particles and / or vanadium carbonitrides particle size 0.2~2μm consisting of vanadium nitrides, and consists of vanadium nitride on the surface layer grain If both particles having a particle size 0.2~2μm consisting of particles and vanadium carbonitride of 0.2~2μm is present, particle size 0.2 consisting of vanadium nitride in the surface layer The total area ratio of the 2 μm particles and the vanadium carbonitride particles having a particle diameter of 0.2 to 2 μm is 1 to 10%, and the surface layer has a particle diameter of 0.2 to 2 μm made of vanadium nitride. When either one of particles and particles of vanadium carbonitride having a particle size of 0.2 to 2 μm is present, particles of vanadium nitride having a particle size of 0.2 to 2 μm and particles of vanadium carbonitride Surface area in the range from 1 to 10% of particles present in the surface layer among particles having a diameter of 0.2 to 2 [mu] m to a surface of 10 [mu] m from the surface of the non-polishing part existing in the part other than the track part The carbon content in the layer is 0.7 It is characterized by including a finishing step of obtaining a raceway member having a Vickers hardness of 700 to 800 at a position of 50 μm deep from this surface and having a Vickers hardness of 700 to 800 (“Manufacturing method 2”) Also called) .

  According to the production method 2 that employs such a configuration, the shaped material obtained by processing the steel material into a predetermined shape has a carbon potential of 0.9 to 1.3 and an ammonia gas concentration of 2 to 5% by volume. By heating at 850 to 900 ° C. for 4 hours or more in a carbonitriding atmosphere of the above, the carbonitriding treatment is performed on the raw material, so that the race member as the bearing component 2 that exhibits the above-described excellent effects can be obtained. it can.

  A rolling bearing according to the present invention is a rolling bearing having an inner ring having a raceway portion on an outer peripheral surface, an outer ring having a raceway portion on an inner peripheral surface, and a plurality of rolling elements disposed between both raceway portions of the inner and outer rings. A bearing is characterized in that at least one of the inner ring, the outer ring and the rolling element is made of the above-described bearing component.

  In the rolling bearing of the present invention, at least one of the inner ring, the outer ring and the rolling element is composed of the above-described bearing constituent member, so that it has a long life and exhibits a sufficient static load capacity and a sufficient dimensional stability.

  According to the bearing component and the manufacturing method thereof of the present invention, it is possible to extend the life of the rolling bearing and to obtain an excellent effect that a sufficient static load capacity and a sufficient dimensional stability can be ensured. Played. Moreover, according to the rolling bearing of this invention, there exists an outstanding effect that it is long life, and shows sufficient static load capacity and sufficient dimensional stability.

It is a schematic explanatory drawing which shows the ball bearing as a rolling bearing which has an inner ring | wheel, an outer ring | wheel, and a ball which is an example of the bearing structural member which concerns on one Embodiment of this invention. It is process drawing which shows the manufacturing method of the inner / outer ring which is an example of the bearing structural member which concerns on one Embodiment of this invention. It is a diagram which shows the heat processing conditions at the time of manufacture of the inner / outer ring of Example 1. It is a diagram which shows the heat processing conditions at the time of manufacture of the inner / outer ring of Example 2 and Example 4. It is a diagram which shows the heat processing conditions at the time of manufacture of the inner / outer ring of Example 3. It is a diagram which shows the heat processing conditions at the time of manufacture of the inner and outer rings of Comparative Example 1 and Comparative Example 9 and at the time of manufacturing rolling elements of ball bearings using the inner and outer rings. It is a diagram which shows the heat processing conditions at the time of manufacture of the inner / outer ring of the comparative example 2. It is a diagram which shows the heat processing conditions at the time of manufacture of the rolling element of the ball bearing using the inner and outer rings of Examples 1-3 and Comparative Examples 2-7 at the time of manufacture of the inner and outer rings of Comparative Example 3. It is a diagram which shows the heat processing conditions at the time of manufacture of the inner and outer ring | wheel of the comparative example 4. It is a diagram which shows the heat processing conditions at the time of manufacture of the inner / outer ring of the comparative example 5. It is a diagram which shows the heat processing conditions at the time of manufacture of the inner / outer ring of the comparative example 6. It is a diagram which shows the heat processing conditions at the time of manufacture of the inner and outer ring | wheel of the comparative example 7. (A) is a drawing substitute photograph showing carbon mapping on the surface of the inner ring of Example 1, (B) is a drawing substitute photograph showing mapping of nitrogen on the surface of the inner ring of Example 1, and (C) is 3 is a drawing-substituting photograph showing mapping of vanadium on the inner ring surface of Example 1. FIG. FIG. 4 is a schematic diagram schematically showing a measuring means for a raceway indentation depth in Test Example 1. In Test Example 2, it is a graph which shows the relationship between test time and a cumulative failure probability. In Test Example 3, it is a graph showing the relationship between aging time and dimensional change rate. It is a diagram which shows the heat processing conditions in Example 5. FIG. It is a diagram which shows the heat processing conditions in Example 6. FIG. It is a diagram which shows the heat processing conditions in Example 7. FIG. It is a diagram which shows the heat processing conditions in the comparative example 8. It is a diagram which shows the heat processing conditions in the comparative example 10. It is a diagram which shows the heat processing conditions in the comparative example 11. It is a diagram which shows the heat processing conditions in the comparative example 12. It is a drawing substitute photograph which shows the result of having observed the surface (polishing part) of the track part of the track member of Example 4 with the electron microscope. It is a drawing substitute photograph which shows the result of having observed the surface of the track part of the track member of Example 4 [polishing part (in the figure, A)] and the surface of the non-polishing part (in the figure, B) with an electron microscope. It is a drawing substitute photograph which shows the result of having observed the surface of the track part of the track member of the comparative example 12 [the grinding | polishing part (C in the figure)] and the surface of a non-polishing part (D in the figure) with the electron microscope.

[Bearing components and rolling bearings]
Hereinafter, a bearing constituent member according to an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic explanatory view showing a ball bearing as a rolling bearing having an inner ring, an outer ring and balls, which is an example of a bearing constituent member according to an embodiment of the present invention.

  The ball bearing 10 includes an inner ring 1 having a raceway portion 1a on an outer peripheral surface, an outer ring 2 having a raceway portion 2a on an inner peripheral surface, and a plurality of raceways disposed between both raceway portions 1a and 2a of the inner and outer rings 1 and 2. A ball 3 as a rolling element and a cage 4 that holds a plurality of balls 3 at predetermined intervals in the circumferential direction are provided.

The surfaces of the raceway portion 1a, the end surface 1b, the shoulder surface 1c, and the inner peripheral surface 1d of the inner ring 1 are polished portions that are polished. On the other hand, the chamfer 1e on the inner peripheral side of the inner ring 1 having an R-shaped cross section connected to the end surface 1b and the inner peripheral surface 1d of the inner ring 1, and the chamfer on the outer peripheral side of the inner ring 1 having a linear cross section connected to the end surface 1b and the shoulder surface 1c. 1f is configured as a non-polishing portion that has not been polished.
The surfaces of the raceway portion 2a, the end surface 2b, the shoulder surface 2c, and the outer peripheral surface 2d of the outer ring 2 are polished portions that are polished. On the other hand, a chamfer 2e on the outer peripheral side of the outer ring 2 having a R-shaped cross section connected to the end surface 2b and the outer peripheral surface 2d of the outer ring 2, and a chamfer 2f on the inner peripheral side of the outer ring 2 having a linear cross section connected to the end surface 2b and the shoulder surface 2c. Is configured as a non-polishing part that has not been polished.

The hardness at a depth of 50 μm from the surface of each of the polishing part and the ball 3 including the raceway parts 1a and 2a of the inner and outer rings 1 and 2 is determined when the ball bearing 10 is used in the lubricating oil mixed with foreign matter. From the viewpoint of reducing the size of the indentation generated when the foreign matter is bitten, the Vickers hardness is 740 (Rockwell C hardness 62) or more, and from the viewpoint of preventing embrittlement, the Vickers hardness 900 (Lock Well C hardness 67) or less.
Further, in the present specification, the Vickers hardness means a value measured by applying a Vickers indenter to a position at a depth of 50 μm from the surface after cutting the inner ring in the depth direction from the surface. Furthermore, in this specification, Rockwell C hardness means the value calculated | required by converting the measured Vickers hardness.

The amount of retained austenite (surface layer retained austenite amount) at a depth of 10 μm from the surface of each of the polishing portion and the ball 3 including the raceway portions 1a and 2a of the inner and outer rings 1 and 2 is around the surface damaged portion such as indentation. From the viewpoint of relaxing the stress concentration, it is 20% by volume or more, and from the viewpoint of obtaining a sufficient surface hardness, it is 55% by volume or less.
Further, the inner part of each of the polishing parts including the raceway parts 1a and 2a of the inner and outer rings 1 and 2 and the ball 3 (a region deeper than the carbonitriding layer formed on the surface, for example, in the case of a bearing of model number 6206, The amount of retained austenite (internal retained austenite amount) at a depth of 5 mm or more is 15% by volume or less from the viewpoint of obtaining good dimensional stability. The lower limit of the amount of internal retained austenite can be set as appropriate, and can be, for example, 3% by volume or more. Thereby, dimensional stability can be improved.
In the present specification, “dimensional stability” refers to stability against dimensional change over time.

There are particles made of vanadium nitride and / or particles made of vanadium carbonitride in the surface layer in the range of 10 μm from the surface of each of the polishing portion and the ball 3 including the raceway portions 1a and 2a of the inner and outer rings 1 and 2a. doing. The particle size of the particles is preferably 0.2 μm or more from the viewpoint of improving yield stress by dispersion strengthening by the Orowan mechanism, and preferably 2 μm or less from the viewpoint of inducing coarsening of the particles by Ostwald growth. Note that the surface layer in the range from the surface of the polishing portion to 10 μm also includes particles having a particle size of less than 0.2 μm.
Further, cementite, M ₇ C ₃ type carbide, and M ₂₃ C ₆ type carbide are deposited on the surfaces of the polishing portion including the raceway portions 1a and 2a of the inner and outer rings 1 and 2 and the balls 3 respectively.

  Particles having a particle diameter of 0.2 to 2 μm and / or vanadium charcoal made of the vanadium nitride in the surface layer in a range of 10 μm from the surface of each of the polishing part and the ball 3 including the raceway parts 1a and 2a of the inner and outer rings 1 and 2 The area ratio of particles having a particle diameter of 0.2 to 2 μm made of nitride is 1% or more from the viewpoint of improving yield stress by dispersion strengthening by the Orowan mechanism and ensuring sufficient static load capacity. Vickers hardness as a bearing component (Vickers hardness at a depth of 50 μm from the surface) 740 to 900 (Rockwell) by suppressing excessive nitrogen intrusion and ensuring the required amount of carbon C hardness of 62 to 67) is obtained, and from the viewpoint of extending the life and securing a sufficient static load capacity, it is 10% or less. In the present specification, the area ratio of the particles means the particle size of 0.2 to 2 μm composed of vanadium nitride and vanadium carbonitride in the surface layer in the range from the surface to 10 μm. The area ratio of the particles combined with 2 to 2 μm particles.

  The carbon content in the polishing layer including the raceway portions 1a and 2a of the inner and outer rings 1 and 2 and the surface layer in the range of 10 μm from the surface of each ball 3 is the effect of mitigating stress concentration on the surface damaged portion such as the indentation. From the viewpoint of securing a certain amount of retained austenite and high surface hardness, it is 1.1% by mass or more, and is a coarse precipitate of carbide in the surface layer (for example, a precipitate having a particle size exceeding 10 μm). From the viewpoint of further improving the life by reducing the abundance, it is 1.6% by mass or less.

  The nitrogen content in the polishing layer including the raceway portions 1a and 2a of the inner and outer rings 1 and 2 and the surface layer in the range from the surface of each ball 3 to 10 μm is sufficient to improve the yield stress by dispersion strengthening by the Orowan mechanism. From the viewpoint of securing a sufficient static load capacity and obtaining sufficient crushing strength, it is 0.1% by mass or more, and by suppressing the ingress of excessive nitrogen into the steel material, the required amount of carbon is secured. Vickers hardness (Vickers hardness at a depth of 50 μm from the surface) 740 to 900 (Rockwell C hardness 62 to 67) is obtained as a bearing component member, and the service life is extended and sufficient static From the viewpoint of securing load capacity and preventing embrittlement due to excessive nitriding, the content is 1.0% by mass or less.

  In one embodiment, the surface layer in the range from the surface of the polishing portion including the raceways 1a and 2a to 10 μm may have particles (nitride particles) made of nitride having a particle size of 500 nm or less. The area ratio of the precipitate containing nitride in the surface layer may be 5 to 20%. In this case, generation of excess carburized structure is suppressed, and sufficient crushing strength can be obtained.

  In one embodiment, the area ratio of precipitates including nitride in the surface layer in the range from the surface of the polishing portion including the track portions 1a and 2a to 10 μm suppresses the occurrence of excessive carburized structure in the non-polishing portion. From the viewpoint of obtaining sufficient crushing strength, 5% or more is preferable, and from the viewpoint of preventing embrittlement due to excessive nitriding, 20% or less is preferable.

  Further, in one embodiment, from the surface of the non-polished portion including the chamfer 1e on the inner circumference side of the inner ring, the chamfer 1f on the outer circumference side of the inner ring, the chamfer 2e on the outer circumference side of the outer ring, and the chamfer 2f on the inner circumference side of the outer ring. The content of carbon in the surface layer in the range of up to 10 μm is 0.7% by mass or more from the viewpoint of obtaining hardness for securing static strength as a bearing, and generation of an excessive carburized structure in the non-polished part. Is 1.0% by mass or less from the viewpoint of obtaining sufficient crushing strength.

  Further, in one embodiment, from the surface of the non-polished portion including the chamfer 1e on the inner circumference side of the inner ring, the chamfer 1f on the outer circumference side of the inner ring, the chamfer 2e on the outer circumference side of the outer ring, and the chamfer 2f on the inner circumference side of the outer ring. The Vickers hardness at a position having a depth of 50 μm is 700 or more from the viewpoint of obtaining sufficient strength as a ball bearing, and is 800 or less from the viewpoint of ensuring sufficient toughness.

[Production method of bearing components]
Below, the manufacturing method of the bearing structural member which concerns on one Embodiment of this invention is demonstrated. FIG. 2 is a process diagram of a method for manufacturing an inner and outer ring that is an example of a bearing component according to an embodiment of the present invention.

  First, an outer ring made of a steel material containing 0.7 to 0.9% by mass of carbon, 3.2 to 5.0% by mass of chromium, and 0.05% by mass or more and less than 0.5% by mass of vanadium. The annular material 23 [see FIG. 2 (a)] is processed into a predetermined shape by cutting or the like, and a portion having a raceway surface 21a, an end surface 21b, a shoulder surface 21c, and an outer peripheral surface 21d has a polishing allowance. In addition, a chamfer 21e on the outer peripheral side of the outer ring having an R shape that is not polished and connected to the end surface 21b and the outer peripheral surface 21d, and a chamfer 21f on the inner peripheral side of the outer ring having a linear shape that is not polished and connected to the end surface 21b and the shoulder surface 21c. The outer ring shaped member 24 having the following is obtained (pre-processing step) [see FIG. 2 (b)]. Further, the inner ring annular material 13 made of the same steel material as the outer ring annular material 23 (see FIG. 2 (f)) is processed into a predetermined shape by cutting or the like, and the raceway surface 11a, the end surface 11b, the shoulder surface 11c, and Each of the portions forming the inner peripheral surface 11d has a grinding allowance, and is provided with a chamfer 11e on the inner peripheral side of the inner ring having an R shape that is not polished and connected to the end surface 11b and the inner peripheral surface 11d, and an end surface 11b and a shoulder surface 11c. An inner ring shaped member 14 having a chamfer 11f on the outer peripheral side of the inner ring that is connected and not polished is obtained (pre-processing step) [see FIG. 2 (g)].

  As said steel materials, 0.7-0.9 mass% carbon, 0.05-0.70 mass% silicon, 0.05-0.7 mass% manganese, 3.2-5. A steel material containing 0% by mass of chromium, 0.1-1.0% by mass of molybdenum, 0.05% by mass or more and less than 0.5% by mass of vanadium, with the balance being iron and inevitable impurities is used. be able to.

According to such a steel material, the amount of coarse eutectic carbides precipitated during steel making on the surfaces of the inner and outer rings can be reduced, and fatigue fracture at the bearing can be suppressed, and after quenching and after carbonitriding and tempering. In this case, sufficient hardness can be ensured.
In addition, according to the steel material, in order to improve the life of the rolling bearing, the amount of retained austenite at a depth of 10 μm from the polished surface of each of the inner and outer rings is 55% by volume. Even if it exists, while ensuring sufficient hardness, dimensional stability can be improved.
In general, when a steel material made of SUJ2 which is a bearing steel is used as the steel material, the dimensional stability tends to deteriorate when the amount of internal retained austenite exceeds 5% by volume. However, when a steel material containing 3.2 to 5.0 mass% chromium and 0.05 mass% or more and less than 0.5 mass% vanadium is used, the inside (on the surface) of the inner and outer ring raceways. The amount of retained austenite (internally retained austenite amount) in a region deeper than the carburized hard layer to be formed, for example, in the case of a bearing of model number 6206, at a depth of 1.5 mm or more from the surface) is 15% by volume or less. By doing so, good dimensional stability can be obtained.

In the steel material, carbon is an element for increasing the hardness of the steel material and obtaining the internal hardness for securing the strength when performing the carbonitriding process of the next step. In addition, before carbonitriding, which will be described later, carbon is left in a large amount of undissolved carbides in the steel material, and after it is carbonitrided, it remains in a fine and large amount, thereby reducing the rolling fatigue life. It is an element that makes it possible to improve.
The content of carbon contained in the steel material is 0.7% by mass or more from the viewpoint of sufficiently leaving undissolved carbides in the steel material, and sufficient workability before carbonitriding is obtained. From the viewpoint of suppressing the formation of coarse eutectic carbides that are likely to be the starting point of fatigue failure during steel production, the content is 0.9% by mass or less.

Further, in the steel material, chromium generates a large amount of undissolved carbides that act as precipitation nuclei during the carbonitriding process before the carbonitriding process, and fine carbides (M ₇ C ₃ type carbide, M ₂₃ C ₆ type carbide), fine carbonitride [M ₇ (C, N) ₃ type carbonitride, M ₂₃ (C, N) ₆ type carbonitride] and fine nitride ( CrN, VN) is an element for improving the rolling fatigue life of the bearing constituent member by precipitating. Chromium promotes the nitriding reaction in the outermost surface layer of the steel material by promoting the formation of carbonitrides and nitrides in the steel material, and suppresses the carburizing reaction (suppresses the occurrence of excessive carburized structure).
From the viewpoint of obtaining the above effect, the content of chromium contained in the steel material is 3.2% by mass or more, and the viewpoint and cost of easily suppressing the formation of eutectic carbide that becomes the starting point of fatigue fracture. From a viewpoint of reducing, it is 5.0 mass% or less.

In the steel material, vanadium is an element that has a very strong affinity for carbon, and is an element that forms carbide. In addition, since vanadium carbide produced from carbon and vanadium has a higher solid solution temperature than molybdenum carbide, in the carbonitriding temperature range in the production of the bearing component of the present invention, Most of the vanadium carbide that was present in the steel was not dissolved, but was present in the steel as undissolved vanadium carbide. Such insoluble vanadium carbide serves as a precipitation nucleus for carbide (VC), carbonitride [V (C, N)], nitride [(Cr, V) N], etc. during carbonitriding, This contributes to the refinement of precipitates such as carbides, carbonitrides and nitrides, and can improve the hardness and rolling fatigue life of steel materials. In addition, vanadium should promote the nitriding reaction in the outermost surface layer of the steel material and promote the carburization reaction (suppression of excessive carburization structure) by promoting the formation of carbonitrides and nitrides more than chromium in the steel material. Can do.
From the viewpoint of obtaining the above effect, the content of vanadium contained in the steel material is 0.05% by mass or more, and by suppressing the production of vanadium carbide, a sufficient amount of solute carbon is secured, and the residual From the viewpoint of sufficiently securing the amount of austenite, it is less than 0.5% by mass.

In the steel material, silicon is an element necessary for deoxidation during refining of steel. In addition, silicon is an element having an effect of suppressing coarse growth of carbide because it has a property of being hardly dissolved in carbide.
From the viewpoint of obtaining the above effect, the content of silicon contained in the steel material is 0.05% by mass or more, and from the viewpoint of sufficiently obtaining workability before carbonitriding, it is 0.70% by mass or less.

In the steel material, manganese is an element that stabilizes austenite in the steel material. Manganese is an element that can easily increase the amount of retained austenite by increasing the amount contained in the steel material.
From the viewpoint of obtaining the above effects, the manganese content in the steel material is 0.05% by mass or more, increasing the amount of undissolved carbide in the steel material, precipitating the carbide, and hardening the steel material. From the viewpoints of improving the rolling fatigue life and obtaining sufficient hot workability and machinability, the content is 0.7% by mass or less, and preferably 0.50% by mass or less.

In the steel material, molybdenum is an element having a stronger affinity for carbon than chromium, and is an element involved in the formation of carbides and carbonitrides. Molybdenum is an element that increases the solid solution temperature of carbides and carbonitrides at the temperature of carbonitriding when manufacturing the bearing component of the present invention, and increases undissolved carbides and carbonitrides. . Therefore, molybdenum is an important element for increasing the amount of fine carbides and carbonitrides in the surface carbonitriding layer after carbonitriding and increasing the hardness of the steel material. Molybdenum improves the hardenability of the steel material and increases the amount of retained austenite in the steel material. Furthermore, molybdenum is an element that efficiently precipitates carbide (M ₂₃ C ₆ type carbide) and carbonitride [M ₂₃ (C, N) ₆ type carbonitride].
From the viewpoint of obtaining the above effect, the content of molybdenum contained in the steel material is 0.10% by mass or more, and the viewpoint of reducing cost and the viewpoint of suppressing the generation of coarse eutectic carbide that becomes the starting point of fatigue fracture. To 1.0% by mass or less.

Next, the outer ring shaped material 24 and the inner ring shaped material 14 obtained are heat treated, and the hardness of the surfaces of the outer ring shaped material 24 and the inner ring shaped material 14 is, for example, It hardens | cures so that it may become Vickers hardness (Hv) 700 or more [refer FIG.2 (c) and (d), FIG.2 (h) and (d)].
In the heat treatment step, first, the raw material is heated at 850 to 900 ° C. in a carbonitriding atmosphere having a carbon potential of 0.9 to 1.3 and an ammonia gas concentration of 2 to 5% by volume. Hold and then quench (carbonitriding process) [see FIG. 2 (c) and FIG. 2 (h)].

  The carbon potential in the carbonitriding atmosphere is 0.9 or more from the viewpoint of forming a carburized layer having a sufficient carburized depth and providing a sufficient hardened layer, and the vanadium nitride or vanadium in the outer ring 2 and the inner ring 1 respectively. While making the area ratio of the precipitate containing carbonitride into the above-mentioned range and suppressing generation | occurrence | production of an excessive carburized structure | tissue, it is 1.3 or less.

  The ammonia gas concentration in the carbonitriding atmosphere is 2% by volume or more from the viewpoint of suppressing the occurrence of excessive carburized structure, and 5% by volume or less from the viewpoint of preventing embrittlement due to excessive nitriding.

The heating and holding temperature in the carbonitriding atmosphere is 850 ° C. or higher from the viewpoint of forming a sufficient hardened layer, and suppresses the excessive carbon intrusion into the bearing constituent member and suppresses the occurrence of excessive carburized structure. From the viewpoint of suppressing the precipitation of coarse carbides, the temperature is 900 ° C. or lower.
The heating and holding time is 4 hours or more from the viewpoint of obtaining a carburized depth sufficient for strengthening the surface layer.

  The rapid cooling is performed by oil cooling in an oil bath of cooling oil. The oil bath temperature of the cooling oil may usually be 60 to 180 ° C.

Next, a tempering process is performed in which the intermediate material after the carbonitriding process is heated and held at a temperature of 160 ° C. or higher (see FIGS. 2D and 2I) (tempering process step).
The heating and holding temperature in the tempering treatment is 160 ° C. or higher from the viewpoint of recovering the toughness of martensite after the quenching treatment, and 250 ° C. or lower from the viewpoint of suppressing decomposition of the retained austenite.

After that, the outer ring shaped member 24 (intermediate material) after the tempering treatment is subjected to polishing on the portions forming the raceway surface 21a, end surface 21b, shoulder surface 21c, and outer peripheral surface 21d, and the raceway surface 21a. Is finished to a predetermined accuracy [see FIG. 2 (e)].
In this way, the desired outer ring 21 can be obtained. Here, the raceway surface 21a, the end surface 21b, the shoulder surface 21c, and the outer peripheral surface 21d are configured as a polishing portion. Among the outer ring 21, a chamfer 21e on the outer peripheral side of the outer ring and a chamfer 21f on the inner peripheral side of the outer ring are defined. It is configured as a non-polished non-polished part.
Similarly, the raceway surface 11a, the end surface 11b, the shoulder surface 11c, and the inner peripheral surface 11d of the inner ring shaped member 14 (intermediate material) after the heat treatment are polished and the raceway surface 11a is also polished. Superfinishing is performed to achieve a predetermined accuracy [see FIG. 2 (j)].
In this way, the desired inner ring 11 can be obtained. In the inner ring 11, the raceway surface 11 a, the end surface 11 b, the shoulder surface 11 c, and the inner peripheral surface 11 d are configured as a polishing portion, and among the inner ring 11, the chamfer 11 e on the inner peripheral side of the inner ring and the chamfer on the outer peripheral side of the inner ring. 11f is configured as a non-polished non-polished part.

[Modification]
In the ball bearing 10 as the rolling bearing shown in FIG. 1, at least one of the inner ring, the outer ring, and the ball may be a bearing component according to an embodiment of the present invention.
The ball bearing 10 may include an outer ring 21 (for example, see FIG. 2 (e)) as an outer ring as a bearing constituent member according to an embodiment of the present invention, and an inner ring different from the present invention. Alternatively, as an inner ring, an inner ring 11 (see, for example, FIG. 2 (j)) as a bearing component according to an embodiment of the present invention may be provided, while an outer ring different from the present invention may be provided.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in more detail, this invention is not limited only to this Example.

[Examples 1 to 3 and Comparative Examples 1 to 7]
Each of the two types of steel materials A and B having the composition shown in Table 1 is processed into a predetermined shape, and each of the inner and outer rings of a ball bearing (model No. 6206) has a grinding allowance at a portion forming the raceway surface. The material was manufactured. Steel material B of Table 1 is JIS SUJ2 which is a bearing rope. The diameter of the rolling element was 9.525 mm.

  Next, the obtained shaped material is subjected to heat treatment under the heat treatment conditions shown in FIGS. 3 to 12, and a polishing process is performed on a portion forming the raceway surface of the obtained intermediate material after the heat treatment. 1 to 3 and Comparative Examples 1 to 7 were combined. Specifically, in the combinations of the inner and outer rings of Examples 1 to 3 and Comparative Examples 1 to 7, the inner ring and the outer ring are the same as shown in Tables 3 and 5 in each Example and Comparative Example. It was made to be a combination of inner and outer rings obtained by heat-treating the steel material under the same heat treatment conditions.

The heat treatment condition shown in FIG. 3 is that the raw material was heated at 860 ° C. for 7 hours in a carbonitriding atmosphere having a carbon potential of 1.1 and an ammonia gas concentration of 2% by volume, and then oil-cooled to 80 ° C. Then, it is heated (tempering treatment) at 180 ° C. for 2 hours.
The heat treatment condition shown in FIG. 4 is that the raw material was heated at 860 ° C. for 7 hours in a carbonitriding atmosphere having a carbon potential of 1.2 and an ammonia gas concentration of 5% by volume, and then oil-cooled to 80 ° C. Then, it is heated (tempering treatment) at 180 ° C. for 2 hours.
The heat treatment condition shown in FIG. 5 is that the raw material was heated at 860 ° C. for 7 hours in a carbonitriding atmosphere having a carbon potential of 1.0 and an ammonia gas concentration of 2% by volume, and then oil-cooled to 80 ° C. Then, it is heated (tempering treatment) at 180 ° C. for 2 hours.
The heat treatment conditions shown in FIG. 6 are as follows: the raw material was heated in an atmosphere having a carbon potential of 0.8 at 830 ° C. for 0.5 hours, quenched, then cooled to 80 ° C., and then oil cooled. , Heated at 180 ° C. for 2 hours (tempering treatment).
The heat treatment conditions shown in FIG. 7 are as follows: the raw material was heated in a carburizing atmosphere with a carbon potential of 1.2 at 850 ° C. for 5 hours, then oil-cooled to 80 ° C., and then heated at 160 ° C. for 2 hours [ (Tempering treatment).
The heat treatment condition shown in FIG. 8 is that the raw material was heated at 850 ° C. for 4 hours in a carbonitriding atmosphere having a carbon potential of 1.2 and an ammonia gas concentration of 2% by volume, and then oil-cooled to 80 ° C. Thereafter, heating (tempering treatment) is performed at 160 ° C. for 2 hours.
The heat treatment conditions shown in FIG. 9 are as follows: the raw material was heated in an atmosphere having a carbon potential of 0.8 at 900 ° C. for 0.5 hours, quenched, then cooled to 80 ° C., and then oil cooled. , Heated at 180 ° C. for 2 hours (tempering treatment).
The heat treatment condition shown in FIG. 10 is that the shaped material is heated in a carburizing atmosphere having a carbon potential of 1.2 at 900 ° C. for 7 hours, then oil-cooled to 80 ° C., and then heated at 160 ° C. for 2 hours [ (Tempering treatment).
The heat treatment conditions shown in FIG. 11 are as follows: the raw material was heated at 860 ° C. for 7 hours in a carbonitriding atmosphere having a carbon potential of 1.2 and an ammonia gas concentration of 1% by volume, and then oil-cooled to 80 ° C. Then, it is heated (tempering treatment) at 180 ° C. for 2 hours.
The heat treatment conditions shown in FIG. 12 are as follows: the raw material was heated at 860 ° C. for 7 hours in a carbonitriding atmosphere having a carbon potential of 1.2 and an ammonia gas concentration of 15% by volume, and then oil-cooled to 80 ° C. Then, it is heated (tempering treatment) at 180 ° C. for 2 hours.

[Test Example 1]
For the inner rings of Examples 1 to 3 and Comparative Examples 1 to 7, Vickers hardness (Rockwell C hardness) at a depth of 50 μm from the surface (polishing part) of the track part, depth of 10 μm from the surface The amount of retained austenite on the surface layer at a position of 2 mm, the amount of internal retained austenite at a depth of 2 mm from the surface, the carbon content in the surface layer in the range of 10 μm from the surface, the surface in the range of 10 μm from the surface The nitrogen content in the layer, the precipitate morphology, and the vanadium-based precipitates in the surface layer in the range from the surface to 10 μm (particles composed of vanadium carbonitride having a particle size of 0.2-2 μm and vanadium nitride) The area ratio of 0.2-2 μm particles) was examined.

  In order to measure the hardness of the substantial surface layer, the Vickers hardness at a depth of 50 μm from the surface is 50 μm from the surface after cutting the inner ring in the depth direction from the surface of the track portion. The measurement was performed by applying a Vickers indenter to the depth position. The Rockwell C hardness was determined by converting the measured Vickers hardness. The amount of retained austenite on the surface layer at a depth of 10 μm from the surface is obtained by electrolytic polishing up to a depth of 10 μm from the surface of the inner ring raceway and measuring the amount of retained austenite on the surface subjected to charge polishing. It was. The amount of internal retained austenite at a depth of 2 mm from the surface was determined by electropolishing the surface of the inner ring raceway to a depth of 2 mm and measuring the amount of retained austenite on the surface subjected to charge polishing. . The carbon content in the range from the surface to 10 μm and the nitrogen content in the range from the surface to 10 μm are respectively in the range from the surface to 10 μm after cutting the inner ring in the depth direction from the surface of the track portion. It calculated | required by measuring each content.

  The precipitate form was evaluated by observing a range from the surface to 10 μm after cutting the inner ring in the depth direction from the surface of the track portion. Area ratio of vanadium-based precipitates (particles having a particle diameter of 0.2 to 2 μm made of vanadium carbonitride and particles having a particle diameter of 0.2 to 2 μm made of vanadium nitride) in the surface layer ranging from the surface to 10 μm After measuring the inner ring in the depth direction from the surface, it was measured in a range from the surface to 10 μm.

The area ratio of the precipitate form and the vanadium-based precipitate (particles having a particle diameter of 0.2 to 2 μm made of vanadium carbonitride and particles having a particle diameter of 0.2 to ² μm made of vanadium nitride) was 800 μm ^2. In the measurement visual field of FIG. 13, carbon was used using a field emission electron probe microanalyzer under the conditions of acceleration voltage: 15.0 kV, irradiation current: 2.016 × 10 ⁻⁷ A, and scan magnification: 3000 times [FIG. )], Nitrogen [FIG. 13B] and vanadium [FIG. 13C] were mapped, and the area ratio was calculated by an image processing apparatus. The results of mapping carbon, nitrogen, and vanadium on the inner ring surface of Example 1 (range from the surface to 10 μm) are shown in FIGS. In FIG. 13, the scale bar indicates 5 μm.

  From the results shown in FIGS. 13A to 13C, in the range from the surface of the raceway portion of the inner ring of Example 1 to 10 μm, the yield stress can be improved by dispersion strengthening by the Orowan mechanism 0.2 μm or more. It can be seen that particles composed of vanadium-based precipitates (vanadium carbonitride and vanadium nitride) having a particle size of 2 μm or less that can induce coarsening of particles by Ostwald growth can be confirmed. Further, from the results shown in FIGS. 13A to 13C, it can be seen that there are also particles made of vanadium-based precipitates having a particle diameter of less than 0.2 μm.

  Similarly, for the inner rings of Examples 2-3 and Comparative Examples 6 and 7, vanadium-based precipitates (particle diameter of vanadium carbonitride in the surface layer in the range from the surface to 10 μm from the surface of the precipitates. As a result of evaluating the area ratio of 0.2 to 2 μm particles and vanadium nitride particles having a particle size of 0.2 to 2 μm, the surface of each inner ring of Examples 2-3 and Comparative Examples 6 and 7 (from the surface) In the range up to 10 μm), there are particles having a particle diameter of 0.2 to 2 μm composed of vanadium-based precipitates (vanadium nitride and vanadium carbonitride), and each of Examples 2-3 and Comparative Examples 6 and 7 Particle size and particle size of vanadium-based precipitates (vanadium nitride and vanadium carbonitride) on the surface of the inner ring raceway (in the range from the surface to 10 μm) Jo did those much different particles consisting of vanadium-based precipitates in the inner ring of the first embodiment. However, the particle diameters of vanadium-based precipitates (vanadium nitride and vanadium carbonitride) precipitated on the surface (range from the surface to 10 μm) of the inner ring raceways of Examples 2-3 and Comparative Examples 6 and 7 The amount (area ratio) of particles of 0.2 to 2 μm was different from that in Example 1.

  Moreover, each ball bearing of Examples 1-3 and Comparative Examples 1-7 was assembled using the combination of the inner and outer rings of Examples 1-3 and Comparative Examples 1-7, respectively. In each of the ball bearings of Examples 1 to 3 and Comparative Examples 2 to 7, a rolling element obtained by subjecting the steel material B to heat treatment under the heat treatment conditions shown in FIG. 8 was used. On the other hand, in Comparative Example 1, a rolling element obtained by subjecting the steel material B to heat treatment under the heat treatment conditions shown in FIG.

Rated capacity ratio of each ball bearing of Examples 1 to 3, Comparative Examples 1 to 7 is 1.3C _0. For each of the ball bearings of Examples 1 to 3 and Comparative Examples 1 to 7, the life in a lubricating oil mixed with foreign matter (life in foreign matter oil), which is one index of life, was examined. Further, for each of the ball bearings of Examples 1 to 3 and Comparative Examples 1 to 7, the race ring indentation depth and dimensional stability, which are one index of the static load capacity, were examined.

The life in foreign oil was tested under the conditions shown in Table 2. The foreign oil life was evaluated according to the following criteria.
〔Judgment criteria〕
○: Eight or more times the L10 life of the ball bearing of Comparative Example 1.
X: Less than 8 times the L10 life of the ball bearing of Comparative Example 1.

Further, as shown in FIG. 14, the race ring indentation depth is such that the inner rings of the ball bearings of Examples 1 to 3 and Comparative Examples 1 to 7 are fitted to the shaft so that the axis is horizontal, and one ball is placed on the inner ring raceway. A load of 14.7 kN is applied to the outer peripheral surface of the outermost ring in the vertical direction of the outer ring, which is located at the uppermost position in the vertical direction of the single ball, and the maximum load is applied to the raceway of the ball bearing. The depth of the indentation in the portion where the sag occurred was evaluated by measuring with a three-dimensional shape measuring instrument. The bearing ring indentation depth is a sum of the indentation depth generated in the inner ring and the indentation depth generated in the outer ring. The track ring indentation depth was evaluated according to the following criteria.
〔Judgment criteria〕
○: Indentation depth is 0.635 μm or less ×: Indentation depth is greater than 0.635 μm Note that “0.635 μm” is a smooth rotation in a ball bearing when the rolling element diameter is 9.525 mm. This is the amount of permanent deformation that is the limit that does not hinder. This value is equal to the inner ring, the outer ring, and the rolling element when the deformation due to the indentation is within the allowable limit of deformation due to the indentation in the entire rolling bearing determined by the rolling element diameter (9.525 mm) × 1/10000. Assuming that it occurs (1/3 of the whole), the combined value of the indentation depth of the inner ring and the indentation depth of the outer ring is 2/3 of the allowable limit of deformation due to the indentation in the entire rolling bearing. It is a value obtained by setting 2/3 of the allowable limit of deformation due to indentation in the entire rolling bearing as an allowable value.

A shaft (outer diameter 30 mm, length 50 mm) was press-fitted into the new inner rings of Examples 1 to 3 and Comparative Examples 1 to 7, and held at 150 ° C. for 1000 hours in a thermostatic bath. In addition, the tensile stress at the time of shaft press-fitting is 100 to 150 MPa. Thereafter, the shaft was removed from each inner ring, and the inner diameters of six points on the inner diameter surface of each inner ring (two points spaced in the axial direction at three locations spaced equally in the circumferential direction) were measured. As a control, the inner diameters of the six points before the shaft press-fitting were measured. Thereafter, the rate of change in dimension after the passage of time with respect to the dimension after the passage of time with respect to the dimension of the six points on the inner ring inner diameter surface before being heated and held [dimensional change rate (%)] was calculated. Note that the dimensional change rate is (the dimension of the inner diameter after the passage of each time−the dimension of the inner diameter before the shaft press-fitting) / the dimension of the inner diameter before the shaft press-fitting.
The dimensional change rate was evaluated according to the following criteria.
○: Dimensional change rate is less than 0.11% ×: Dimensional change rate is 0.11% or more

  Table 3 shows the types of steel materials used for the inner and outer rings of Examples 1 to 3, heat treatment conditions, the types of steel materials constituting the rolling elements used for assembling the ball bearings of Examples 1 to 3, and heat treatment conditions. Table 4 shows the types and heat treatment conditions of the steel materials used for the inner and outer rings of Comparative Examples 1 to 7, and the types and heat treatment conditions of the steel materials constituting the rolling elements used for assembling the ball bearings of Comparative Examples 1 to 7. For the combinations of the inner and outer rings of Examples 1 to 3 and Comparative Examples 2 to 7, the rolling elements obtained by applying heat treatment under the heat treatment conditions shown in FIG. . For the combination of the inner and outer rings of Comparative Example 1, steel members B were used as the rolling elements, and the rolling elements obtained by heat treatment under the heat treatment conditions shown in FIG. 6 were used.

Vickers hardness (Rockwell C hardness) at a position of 50 μm depth from the surface of the raceway portion of the inner ring of Examples 1 to 3 and Comparative Examples 1 to 7, surface layer at a position of 10 μm depth from the surface Part retained austenite, internal retained austenite at a depth of 2 mm from the surface, carbon content in the surface layer in the range from the surface to 10 μm, nitrogen content in the surface layer in the range from the surface to 10 μm , Precipitate form, area ratio of vanadium-based precipitates in the surface layer in the range from the surface to 10 μm, Examples 1-3, life in foreign oil in ball bearings of Comparative Examples 1-7, Examples 1-3, comparison Table 5 (Examples 1 to 3) and Table 6 (Comparison) show the indentation depth of the ball bearings of Examples 1 to 7 and the dimensional stability of the inner rings of Examples 1 to 3 and Comparative Examples 1 to 7. Examples 1-7). In the table, “Vickers hardness (Rockwell C hardness)” indicates the Vickers hardness (or Rockwell C hardness) at a depth of 50 μm from the surface of the track portion, and “surface portion retained austenite amount” “(Volume%)” indicates the amount of retained austenite on the surface layer at a depth of 10 μm from the surface of the track portion, and “carbon content (mass%)” and “nitrogen content (mass%)” are respectively The carbon content and the nitrogen content in the surface layer in the range from the surface of the track part to 10 μm are shown, and the “area ratio (%) of vanadium-based precipitate” is the surface layer in the range from the surface of the track part to 10 μm. 2 shows the area ratio of a combination of particles having a particle diameter of 0.2 to 2 μm made of vanadium nitride and particles having a particle diameter of 0.2 to 2 μm made of vanadium carbonitride. Further, the “internal residual austenite amount (volume%)” is the surface of the track portion, which is a region deeper than the carbonitrided layer formed from the surfaces of the inner and outer rings of Examples 1 to 3 and Comparative Examples 3, 6, and 7. The amount of retained austenite in a region deeper than 1.5 mm, and the amount of internal retained austenite at a depth of 2 mm from the surface of the track portion.
“Internal residual austenite amount (volume%)” also indicates the internal residual austenite amount at a depth of 2 mm from the surface of the raceway portion of the inner ring in Comparative Examples 1, 2, 4, and 5. The depth of 2 mm from the surface is a region deeper than the carburized layer formed from the surfaces of the inner rings of Comparative Examples 2 and 5.

  From the results shown in Table 5, the life in foreign oil of the ball bearings of Examples 1 to 3 is 8 times or more the L10 life of the ball bearing of Comparative Example 1. Therefore, according to the inner and outer rings of Examples 1 to 3, it can be seen that the life of the rolling bearing can be extended.

  Moreover, from the results shown in Table 5, the raceway indentation depth of the ball bearings of Examples 1 to 3 is a limit that does not hinder smooth rotation of the ball bearing when the rolling element diameter is 9.525 mm. The amount of permanent deformation is 0.635 μm or less. Therefore, according to the inner and outer rings and rolling elements of Examples 1 to 3, it can be seen that a sufficient static load capacity can be ensured.

  Furthermore, from the results shown in Table 5, the dimensional change rate of the inner ring of Examples 1 to 3 after 1000 hours from the press-fitting of the shaft is less than 0.11% (0.05 to 0.06%). It can be seen that the inner rings of Examples 1 to 3 are superior in dimensional stability to the inner ring of Comparative Example 1.

  On the other hand, from the results shown in Table 6, the life in foreign oil of the ball bearings of Comparative Examples 2 to 4 is less than 8 times (1 to 3 times) the L10 life of the ball bearing of Comparative Example 1. It can be seen that the life in foreign oil is shorter than the ball bearings of Examples 1 to 3. Moreover, the raceway indentation depth of the ball bearings of Comparative Examples 1 to 4 is larger than 0.635 μm (0.82 to 1.0 μm), and is a permanent deformation that is a limit that does not hinder smooth rotation in the ball bearing. It turns out that it is more than quantity. Furthermore, the dimensional change rate of the inner ring of Comparative Examples 1 to 4 is 0.11 to 0.20%, which indicates that the dimensional stability is low.

Furthermore, from the results shown in Table 6, the life in foreign oil of the ball bearings of Comparative Examples 5 and 6 is at least 8 times the L10 life of the ball bearing of Comparative Example 1 [each 10 times (Comparative Example 5) and 12 times (Comparative Example 6)], and it can be seen that the ball bearings of Examples 1 to 3 have almost the same life as the foreign oil.
However, the bearing ring indentation depths of the ball bearings of Comparative Examples 5 and 6 are larger than 0.635 μm [1.4 μm (Comparative Example 5) and 1.6 μm (Comparative Example 6), respectively]. It can be seen that the amount of deformation is not less than the permanent deformation amount that does not hinder smooth rotation. Furthermore, the dimensional change rate of the inner ring of Comparative Example 5 is 0.15%, respectively, indicating that the dimensional stability is low.
In addition, the dimensional change rate of the inner ring of Comparative Example 6 is 0.06%, which indicates that the inner ring of Examples 1 to 3 is substantially equivalent.

Furthermore, from the results shown in Table 6, it can be seen that the dimensional change rate of the inner ring of Comparative Example 7 is 0.05%, which is substantially equivalent to the inner rings of Examples 1 to 3.
However, the life in foreign oil of the ball bearing of Comparative Example 7 is less than 8 times (3 times) the L10 life of the ball bearing of Comparative Example 1, and in foreign oil compared to the ball bearings of Examples 1 to 3. Life is shortened. Moreover, the raceway indentation depth of the ball bearing of Comparative Example 7 is greater than 0.635 μm (2.0 μm) and is equal to or greater than the permanent deformation amount, which is a limit that does not hinder smooth rotation of the ball bearing.

  Therefore, from these results, the steel material A was used, and the inner and outer rings had Vickers hardness at a depth of 50 μm from the surface within a range of 740 to 900 (Rockwell C hardness 62 to 67), from the surface. The amount of retained austenite at a depth of 10 μm is in the range of 20 to 55% by volume, the carbon content in the surface layer in the range from the surface to 10 μm is in the range of 1.1 to 1.6% by mass, from the surface The nitrogen content in the surface layer in the range up to 10 μm is in the range of 0.1 to 1.0% by mass, and the particle size is 0.2 to 2 μm made of vanadium-based precipitate in the surface layer in the range from the surface to 10 μm. When the area ratio of the particles is in the range of 1 to 10% (Examples 1 to 3), the life of the rolling bearing can be extended, and sufficient static load capacity and sufficient dimensional stability are ensured. What can be done It can be seen.

  In contrast, in the inner and outer rings, the Vickers hardness (Rockwell C hardness) at a depth of 50 μm from the surface, the amount of retained austenite at a depth of 10 μm from the surface, and the range from the surface to 10 μm. Any of particles having a particle size of 0.2 to 2 μm comprising a carbon content in the surface layer, a nitrogen content in the surface layer in the range from the surface to 10 μm, and a vanadium-based precipitate in the surface layer in the range from the surface to 10 μm Is not included in the range, it can be seen that any of the life, static load capacity and dimensional stability of the rolling bearing is insufficient.

[Test Example 2]
Using the new ball bearing of Example 1, the time until the surface damage occurred on the component (test time) was measured under the conditions shown in Table 2, and the relationship between the test time and the cumulative failure probability was examined. Further, the operation was performed in the same manner as described above except that the ball bearings of Comparative Examples 1 and 3 were used, and the relationship between the test time and the cumulative failure probability was examined. A graph showing the relationship between the test time and the cumulative failure probability is shown in FIG. In the drawing, the solid line (black circle) indicates the ball bearing of Example 1, the one-dot broken line (white square) indicates the ball bearing of Comparative Example 1, and the two-dot broken line (white triangle) indicates the ball bearing of Comparative Example 3.

  From the results shown in FIG. 15, it can be seen that the ball bearing of Example 1 has a life approximately 7 to 10 times longer than the ball bearings of Comparative Examples 1 and 3.

[Test Example 3]
A shaft (outer diameter 30 mm, length 50 mm) was press-fitted into the inner ring of the component of Example 1, and held at 150 ° C. for a predetermined aging time in a thermostatic bath. In addition, the tensile stress at the time of shaft press-fitting is 100 to 150 MPa. After 50 hours, 100 hours, 200 hours, 500 hours, 1000 hours, and 2000 hours, 6 points on the inner diameter surface of each inner ring (spaces are spaced in three axial directions at equal intervals in the circumferential direction). 2 points) were measured. As a control, the inner diameters of the six points before the shaft press-fitting were measured. Thereafter, the dimensional change rate [dimensional change rate (%)] after the elapse of time with respect to the 6 points of the inner ring inner surface before being heated and held was calculated in the same manner as in Test Example 1. Further, for the inner rings of Comparative Examples 1 and 3, the dimensional change rate was calculated in the same manner as described above. A graph showing the relationship between the aging time and the dimensional change rate is shown in FIG. In the figure, the solid line (black circle) indicates the inner ring of Example 1, the one-dot broken line (white square) indicates the inner ring of Comparative Example 1, and the two-dot broken line (white triangle) indicates the inner ring of Comparative Example 3.

  From the results shown in FIG. 16, the inner ring of Example 1 has a smaller dimensional change over time than the inner rings of Comparative Examples 1 and 3, and has a low dimensional change rate over a long period of time. It can be seen that it has dimensional stability.

[Examples 4-7 and Comparative Examples 8-12]
Using two types of steel materials C and D having the composition shown in Table 7, each was processed into a predetermined shape, and nine types of raw materials for manufacturing the outer ring and the inner ring of the ball bearing of model number 6206 were manufactured. In addition, the steel material D of Table 7 is JIS SUJ2 which is bearing steel.

Next, the obtained shape material is subjected to heat treatment under the heat treatment conditions shown in FIGS. 4, 17 to 20, 6, 21 to 23, and the raceway surface of the obtained intermediate material after the heat treatment, An unpolished cross-section R shape that connects the end surface and the inner peripheral surface (in the case of the inner ring) by polishing the end surface, shoulder surface, inner peripheral surface (in the case of the inner ring), and outer peripheral surface (in the case of the outer ring). Examples 4 to 6 are track members each having a chamfer having an unpolished cross-section R shape connected to an end surface and an outer peripheral surface (in the case of an outer ring), and an unpolished cross-section linear chamfer connecting to an end surface and a shoulder surface. 7 and Comparative Examples 8 to 12 were produced.
The heat treatment conditions shown in FIG. 17 are: the raw material was heated at 860 ° C. for 7 hours in a carbonitriding atmosphere having a carbon potential of 1.2 and an ammonia gas concentration of 5% by volume, and then oil-cooled to 80 ° C. Next, it is maintained at −75 ° C. for 1 hour (sub-zero treatment), and then heated at 180 ° C. for 2 hours (tempering treatment).
The heat treatment conditions shown in FIG. 18 are as follows: the raw material was heated at 860 ° C. for 5.5 hours in a carbonitriding atmosphere having a carbon potential of 1.2 and an ammonia gas concentration of 2% by volume, and then oil-cooled to 80 ° C. After that, it is heated (tempering treatment) at 180 ° C. for 2 hours.
The heat treatment conditions shown in FIG. 19 are as follows: the raw material was heated at 860 ° C. for 9 hours in a carbonitriding atmosphere having a carbon potential of 1.2 and an ammonia gas concentration of 2% by volume, and then oil-cooled to 80 ° C. Then, it is heated (tempering treatment) at 180 ° C. for 2 hours.
The heat treatment conditions shown in FIG. 20 are as follows: the raw material was heated at 850 ° C. for 4 hours in a carbonitriding atmosphere having a carbon potential of 1.2 and an ammonia gas concentration of 5% by volume, and then oil-cooled to 80 ° C. Then, it is heated (tempering treatment) at 180 ° C. for 2 hours.
The heat treatment condition shown in FIG. 21 is that the shaped material is heated at 850 ° C. for 5 hours in a carburizing atmosphere having a carbon potential of 1.2, then oil-cooled to 80 ° C., and then heated at 180 ° C. for 2 hours [ (Tempering treatment).
The heat treatment conditions shown in FIG. 22 are as follows: the raw material was heated in an atmosphere having a carbon potential of 1.0 at 900 ° C. for 0.5 hours, quenched, then cooled to 80 ° C., and then oil cooled. , Heated at 180 ° C. for 2 hours (tempering treatment).
The heat treatment conditions shown in FIG. 23 are as follows: the raw material was heated in a carburizing atmosphere with a carbon potential of 1.2 at 930 ° C. for 7 hours, followed by heating at 900 ° C. for 0.5 hour, and then 80 Oil-cooled to ℃ and then heated (tempering treatment) at 180 ℃ for 2 hours.

  Table 8 shows the types of steel materials used in the production of the inner and outer rings of Examples 4 to 7 and Comparative Examples 8 to 12 and heat treatment conditions.

  Table 9 shows the heat treatment quality of the outer ring raceway surface (polishing portion) of Examples 4 to 7, and Table 10 shows the heat treatment quality of the non-polishing portion of the outer ring of Examples 4 to 7. Furthermore, Table 11 shows the heat treatment quality of the surface (polishing portion) of the raceway portion of the outer ring of Comparative Examples 8 to 12, and Table 12 shows the heat treatment quality of the non-polished portion of the outer ring of Comparative Examples 8 to 12.

As heat treatment quality of the surface (polishing part) of the track part in Table 9 and Table 11, Vickers hardness at a depth of 50 μm from the surface (polishing part) of the track part (in the table, “Vickers hardness”), Surface layer retained austenite amount at a depth of 10 μm from the surface (in the table, “surface layer retained austenite amount”), and internal retained austenite amount at a depth of 2 mm from the surface (in the table, “internal retained austenite” Amount ”), carbon content in the surface layer in the range from the surface to 10 μm (in the table,“ carbon content ”), nitrogen content in the surface layer in the range from the surface to 10 μm (in the table,“ nitrogen content ”) ), Precipitate form, vanadium-based precipitates in the surface layer in the range from the surface to 10 μm (particles having a particle diameter of 0.2 to 2 μm made of vanadium carbonitride and particles having a particle diameter of 0.2 to 2 μm made of vanadium nitride) μm particles) area ratio (in the table, “area ratio of vanadium-based precipitates”) and area ratio of precipitates containing nitride in the surface layer in the range from the surface to 10 μm (in the table, “including nitrides”) The area ratio of the precipitates ”) is shown.
Further, as the heat treatment quality of the non-polished part in Table 10 and Table 12, the Vickers hardness at a depth of 50 μm from the surface of the non-polished part (in the table, “Vickers hardness”), the range from the surface to 10 μm The carbon content in the surface layer (in the table, “carbon content”), the nitrogen content in the surface layer in the range from the surface to 10 μm (in the table, “nitrogen content”), and the surface in the range from the surface to 10 μm The presence or absence of coarse carbon compound particles having a particle size of 10 μm or more in the layer (in the table, “coarse carbon compound particles having a particle size of 10 μm or more”) is shown.

  Furthermore, a drawing-substituting photograph showing the result of observation of the surface (polished part) of the raceway part of the outer ring of Example 4 with an electron microscope is shown in FIG. Further, FIG. 25 is a drawing-substituting photograph showing the results of observation of the surface of the raceway portion of the outer ring of Example 4 (the polishing portion (A in the figure)) and the surface of the non-polishing portion (B in the drawing) with an electron microscope. Show. As a control, a drawing-substituting photograph showing the results of observing the surface of the raceway portion of the outer ring of Comparative Example 12 [the polishing portion (C in the figure)] and the surface of the non-polishing portion (D in the drawing) with an electron microscope. It shows in FIG.

From the results shown in Table 9 and Table 10, the outer ring of Example 4 obtained by subjecting the shaped material obtained from the steel material C to carbonitriding is the surface of the track portion (polishing portion) in the polishing portion. To 50 μm depth Vickers hardness is 810, surface layer portion retained austenite content at a depth of 10 μm from the surface is 43 vol%, carbon content in the surface layer in the range from the surface to 10 μm Is 1.4% by mass, the nitrogen content in the surface layer in the range from the surface to 10 μm is 0.4% by mass, and the area ratio of the precipitate containing nitride in the surface layer in the range from the surface to 10 μm is 13%. It can be seen that the amount of internal retained austenite at a depth of 2 mm from the surface is 15% by volume, and the area ratio of vanadium-based precipitates in the surface layer in the range from the surface to 10 μm is 5%.
Further, in the non-polished part, the Vickers at a position of 50 μm depth from the surface of the non-polished part is 735, the carbon content in the surface layer in the range from the surface to 10 μm is 0.8% by mass, and from the surface to 10 μm. It can be seen that the nitrogen content in the surface layer in the range is 1.0% by mass.
Furthermore, the results shown in FIG. 24 indicate that nitride particles having a particle size of 500 nm or less exist on the surface (polishing portion) of the raceway portion of the outer ring of Example 1. Further, as shown in FIG. 25, the non-polished portion of the outer ring of Example 1 did not have coarse carbon compound particles having a particle size of 10 μm or more in the surface layer in the range from the surface to 10 μm (B in the figure). reference).

Further, from the results shown in Table 9 and Table 10, the outer ring of Example 5 obtained by subjecting the shaped material obtained from the steel material C to carbonitriding treatment and then sub-zero treatment, The Vickers hardness at a depth of 50 μm from the surface of the track portion (polishing portion) is 880, the amount of retained austenite at the depth of 10 μm from the surface is 22% by volume, and 2 mm from the surface. The amount of internal retained austenite at the depth position is 5% by volume, the carbon content in the surface layer in the range from the surface to 10 μm is 1.4% by mass, and the nitrogen content in the surface layer in the range from the surface to 10 μm. Of the vanadium-based precipitate in the surface layer in the range of 10 μm from the surface is 6%, and the precipitate containing nitride in the surface layer in the range of 10 μm from the surface is It can be seen that the product ratio is 12%.
In the non-polishing part, the Vickers hardness at a position of 50 μm depth from the surface of the non-polishing part is 800, and the carbon content in the surface layer in the range from the surface to 10 μm is 0.8% by mass,
It can be seen that the nitrogen content in the surface layer in the range from the surface to 10 μm is 1.3% by mass, and there are no coarse carbon compound particles having a particle size of 10 μm or more in the surface layer in the range from the surface to 10 μm.

In Example 4, the outer ring of Example 6 obtained by performing the same operation except that the ammonia gas concentration in the carbonitriding atmosphere was set to 2% by volume and heated for 5.5 hours was the raceway portion in the polishing portion. Vickers hardness at a position of 50 μm depth from the surface (polishing part) of 780, surface volume part retained austenite at a position of 10 μm depth from the surface is 45% by volume, depth of 2 mm from the surface The amount of internal retained austenite at the position is 10% by volume, the carbon content in the surface layer in the range from the surface to 10 μm is 1.2% by mass, and the nitrogen content in the surface layer in the range from the surface to 10 μm is 0. 2% by mass of the vanadium-based precipitate area ratio in the surface layer in the range of 10 μm from the surface, 3% of the precipitate containing nitride in the surface layer in the range of 10 μm from the surface It can be seen that the product ratio is 8%.
Further, in the non-polished part, the Vickers hardness at a depth of 50 μm from the surface of the non-polished part is 720, the carbon content in the surface layer in the range from the surface to 10 μm is 0.8% by mass, the surface It can be seen that the nitrogen content in the surface layer in the range from 1 to 10 μm is 1.1 mass%, and there is no coarse carbon compound particle having a particle size of 10 μm or more in the surface layer in the range from the surface to 10 μm.

Similarly, in Example 4, the outer ring of Example 7 obtained by performing the same operation except that the ammonia gas concentration in the carbonitriding atmosphere was set to 2% by volume and heated for 9 hours, Vickers hardness at a depth of 50 μm from the surface of the part (polishing part), 755, surface austenite retained austenite at a depth of 10 μm from the surface, 49% by volume, depth of 2 mm from the surface The amount of internal retained austenite at the position of 14% by volume, the carbon content in the surface layer in the range from the surface to 10 μm is 1.6% by mass, and the nitrogen content in the surface layer in the range from the surface to 10 μm is 0%. .3 mass%, the area ratio of vanadium-based precipitates in the surface layer in the range from the surface to 10 μm is 4%, precipitation containing nitride in the surface layer in the range from the surface to 10 μm It can be seen that the area ratio is 17%.
Further, in the non-polished part, the Vickers hardness at a depth of 50 μm from the surface of the non-polished part is 730, the carbon content in the surface layer in the range from the surface to 10 μm is 0.8% by mass, It can be seen that the nitrogen content in the surface layer in the range from 1 to 10 μm is 1.4% by mass, and there is no coarse carbon compound particle having a particle size of 10 μm or more in the surface layer in the range from the surface to 10 μm.

As in the outer ring of Example 4 shown in FIG. 24, nitride particles having a particle size of 500 nm or less were present on the surface (polishing part) of the outer ring raceway of each of Examples 5 to 7. .
The surfaces of the outer races of the outer rings of Examples 5 to 7 (polishing portions) are particles made of nitride having a particle size of 500 nm or less in a surface layer in a range from the polished surface to 10 μm. And the area ratio of the precipitate containing nitride in the surface layer in the range from the surface to 10 μm is 5 to 20%, so that the surface hardness is improved and in the lubricating oil mixed with foreign matter Even if it is used in the above, stress concentration around the indentation generated when a foreign object is bitten can be reduced.
From these results, it is suggested that by forming the carbonitriding layer in the non-polished part as in the outer rings of Examples 5 to 7, the occurrence of excessive carburized structure is suppressed in the non-polished part.

  On the other hand, from the results shown in Tables 11 and 12, the outer ring of Comparative Example 12 obtained by carburizing the raw material obtained from Steel C has nitrogen (N) on the surface of the non-polished part. It turns out that it is not included. Further, from the results shown in FIG. 26, since the coarse carbon compound particles having a particle size of 10 μm or more are present in the non-polished portion (see C in the figure) of the outer ring of Comparative Example 12, an excessive carburized structure is present. You can see that it has occurred.

[Test Example 4]
Next, a life test and a crushing strength test in foreign oil were performed on the outer rings and the inner rings of Examples 4 to 7 and Comparative Examples 8 to 12, respectively. When conducting a life test in foreign oil, a pair of outer and inner rings manufactured as the same Examples and Comparative Examples of Examples 4 to 7 and Comparative Examples 8 to 12, respectively, and a high carbon chromium bearing rope (JIS SUJ2) were used. After the carbonitriding treatment, a ball bearing of model No. 6206 was assembled by combining with the balls manufactured by quenching and tempering treatment, and the obtained ball bearing was subjected to a foreign oil life test. The test conditions for the foreign oil life test are the same as in Table 2. Table 13 shows the test conditions for the crushing strength test. In the crushing strength test, the first location in the circumferential direction of the 6206 outer ring and the second location where the first location in the circumferential direction was moved in the circumferential direction at 180 ° C. were measured in the radial direction with an Amsler tester. The first part and the second part are moved close to each other at a speed of 0.5 mm / min along a direction perpendicular to the axis of the 6206 outer ring connecting the first part and the second part. This is a test to evaluate the radial load when the 6206 outer ring is deformed, broken, and broken. The crushing strength ratio is a ratio of the load when the 6206 outer ring of each example and comparative example breaks to the load when the 6206 outer ring of comparative example 9 breaks. These results are shown in Table 14.

  From the results shown in Table 14, the ball bearings including the outer ring and the inner ring of Examples 4 to 7 in which the steel material C having the composition of Table 7 is used are the outer ring and the inner ring of Comparative Examples 8 to 10 in which the steel material D is used. It can be seen that the life in foreign oil is longer and the crushing strength of the outer ring is higher than that of the ball bearing provided with.

On the other hand, from the results shown in Table 14, the ball provided with the outer ring of Comparative Example 12 in which carburizing treatment was performed on the shaped material obtained from the same steel material C as the steel material used for the outer rings of Examples 4 to 7. It turns out that the crushing strength of the outer ring is lower than that of the ball bearing having the outer ring of Comparative Examples 8 to 10 in which the steel material D is used. On the other hand, the ball bearing provided with the outer ring and the inner ring of Examples 4 to 7 obtained by subjecting the shaped material obtained from the steel material C to carbonitriding has a life in a foreign oil and the collapse of the outer ring. It can be seen that both strengths are improved.
As described above, in Comparative Examples 10 and 12, coarse carbon compound particles having a particle size of 10 μm or more exist in the non-polished portion existing in the portion excluding the track portion, and an excessive carburized structure such as free carbide is generated. It has been found that the excessive carburized structure decreases the crushing strength of the rolling bearing by becoming the starting point of stress concentration. And in Examples 4-7, by performing a carbonitriding process on predetermined | prescribed conditions with respect to predetermined | prescribed steel materials, forming the long life structure | tissue (carburized structure | tissue) with few precipitates in the track | orbit part of a rolling bearing. However, in the non-polished part, coarse carbon compound particles having a particle size of 10 μm or more are not generated, the occurrence of excessive carburized structures such as free carbide is suppressed, the reduction in crushing strength is suppressed, and a high rolling fatigue life is achieved. I was able to.

  Therefore, from these results, as in Examples 4 to 7, according to the race member obtained by carbonitriding the shaped material obtained from the steel material C having the composition shown in Table 7, the non-polished part This suggests that an excessively carburized structure is not formed, and that a rolling bearing having excellent life in foreign oil and excellent crushing strength can be obtained.

    1,11 inner ring, 1a, 11a raceway part, 2,21 outer ring, 2a, 21a raceway part, 10 ball bearing

Claims (5)

It is obtained from a steel material containing 0.7 to 0.9% by mass of carbon, 3.2 to 5.0% by mass of chromium, and 0.05% by mass or more and less than 0.5% by mass of vanadium, and polished. A bearing component having a finished raceway ,
The carbon content in the surface layer in the range from the surface of the track portion to 10 μm is 1.1 to 1.6% by mass,
Vickers hardness at a position of a depth of 50 μm from the surface of the track portion is 740 to 900,
The amount of retained austenite at a depth of 10 μm from the surface of the track portion is 20 to 55% by volume,
The nitrogen content in the surface layer in the range from the surface of the track part to 10 μm is 0.1 to 1.0% by mass,
In the surface layer in the range from the surface of the track portion to 10 μm, at least particles having a particle diameter of 0.2 to 2 μm made of vanadium nitride and / or particles having a particle diameter of 0.2 to 2 μm made of vanadium carbonitride are contained. It has, and by both the particle size 0.2~2μm of particles consisting of particles and vanadium carbonitride particle size 0.2~2μm consisting vanadium nitride to the surface layer is present If there are, the total area ratio of the particles having a particle size 0.2~2μm consisting of particles and vanadium carbonitride particle size 0.2~2μm consisting of vanadium nitride in the surface layer is 1-10% When any one of particles having a particle diameter of 0.2 to 2 μm made of vanadium nitride and particles having a particle diameter of 0.2 to 2 μm made of vanadium carbonitride is present on the surface layer, vanadium nitride is used. Particle size 0.2 Area ratio of particles present in said surface layer is 1-10% der of the 2μm particles and vanadium carbonitride particle size 0.2~2μm of particles consisting of is,
The carbon content in the surface layer in the range from the surface of the non-polishing part existing in the part other than the track part to 10 μm is 0.7 to 1.0% by mass, and 50 μm from the surface of the non-polishing part. bearing part of Vickers hardness at the position of depth characterized by 700 to 800 der Rukoto.   The steel material is 0.7 to 0.9% by mass of carbon, 0.05 to 0.70% by mass of silicon, 0.05 to 0.7% by mass of manganese, and 3.2 to 5.0. It is a steel material containing 0.1% by mass of chromium, 0.1% to 1.0% by mass of molybdenum, and 0.05% by mass or more and less than 0.5% by mass of vanadium, with the balance being iron and inevitable impurities. The bearing component according to claim 1. 3 . A pre-processing step of obtaining a base material by processing a steel material containing 2 to 5.0% by mass of chromium and 0.05% by mass or more and less than 0.5% by mass of vanadium into a predetermined shape;
Carburizing by heating the base material at 850 to 900 ° C. in a carbonitriding atmosphere having a carbon potential of 0.9 to 1.3 and an ammonia gas concentration of 2 to 5% by volume with respect to the base material. Carburizing and nitriding process to obtain nitriding and intermediate material,
The intermediate material after the carbonitriding treatment is subjected to a tempering treatment process in which the intermediate material is tempered by heating at 160 ° C. or higher, and the intermediate material after the tempering treatment is subjected to a finishing process. The carbon content in the surface layer in the range from the surface to 10 μm is 1.1 to 1.6% by mass, the Vickers hardness at a depth of 50 μm from the surface is 740 to 900, and 10 μm from the surface. The amount of retained austenite at the position of the depth is 20 to 55% by volume, the nitrogen content in the surface layer in the range from the surface to 10 μm is 0.1 to 1.0% by mass, and from the surface to 10 μm the surface layer in the range of, have a particle diameter 0.2~2μm consisting of particles and / or vanadium carbonitrides particle size 0.2~2μm consisting of vanadium nitride, and said surface When both particle size 0.2~2μm particles and vanadium carbonitride of nitride particle size 0.2~2μm of particles consisting of vanadium nitrides are present in vanadium nitride in the surface layer The total area ratio of the particles having a particle diameter of 0.2 to 2 μm made of a product and the particles having a particle diameter of 0.2 to 2 μm made of vanadium carbonitride is 1 to 10%, and the surface layer is made of vanadium nitride. When any one of particles having a particle size of 0.2 to 2 μm and particles having a particle size of 0.2 to 2 μm made of vanadium carbonitride is present, the particle size of 0.2 to 2 μm made of vanadium nitride Including a finishing step of obtaining a bearing component having an area ratio of 1 to 10% of particles present in the surface layer among particles having a particle diameter of 0.2 to 2 μm made of particles and vanadium carbonitride. Manufacture of bearing components Law. A method of manufacturing a bearing part according to 請 Motomeko 1,
A steel material containing 0.7 to 0.9 mass% carbon, 3.2 to 5.0 mass% chromium, and 0.05 mass% or more and less than 0.5 mass% vanadium is formed into a predetermined shape. Processing to obtain a track member shape material having a grinding allowance in at least a portion forming the raceway surface,
Carburizing by heating the raw material at 850 to 900 ° C. for 4 hours or more in a carbonitriding atmosphere with a carbon potential of 0.9 to 1.3 and an ammonia gas concentration of 2 to 5% by volume. Carburizing and nitriding process to obtain nitriding and intermediate material,
A tempering process for subjecting the intermediate material after the carbonitriding treatment to a tempering process in which the intermediate material is heated at 160 ° C. or higher ; and
The portion of the intermediate material that forms the raceway surface after the tempering treatment is subjected to polishing finishing to form the raceway portion, and the carbon content in the surface layer in the range from the surface of the raceway portion to 10 μm The amount is 1.1 mass% or more and less than 1.6 mass%, the Vickers hardness at a depth of 50 μm from this surface is 740 to 900, and the residual at a depth of 10 μm from the surface The amount of austenite is 20 to 55% by volume, the content of nitrogen in the surface layer in the range from the surface to 10 μm is 0.1 to 1.0% by mass, and the surface layer in the range from the surface to 10 μm has a particle diameter 0.2~2μm consisting of particles and / or vanadium carbonitrides particle size 0.2~2μm consisting of vanadium nitrides, and consists of vanadium nitride on the surface layer grain If both particles having a particle size 0.2~2μm consisting of particles and vanadium carbonitride of 0.2~2μm is present, particle size 0.2 consisting of vanadium nitride in the surface layer The total area ratio of the 2 μm particles and the vanadium carbonitride particles having a particle diameter of 0.2 to 2 μm is 1 to 10%, and the surface layer has a particle diameter of 0.2 to 2 μm made of vanadium nitride. When either one of particles and particles of vanadium carbonitride having a particle size of 0.2 to 2 μm is present, particles of vanadium nitride having a particle size of 0.2 to 2 μm and particles of vanadium carbonitride Surface area in the range from 1 to 10% of particles present in the surface layer among particles having a diameter of 0.2 to 2 [mu] m to a surface of 10 [mu] m from the surface of the non-polishing part existing in the part other than the track part The carbon content in the layer is 0.7 A method for producing a bearing component, comprising: a finishing process for obtaining a raceway member having a Vickers hardness of 700 to 800 at a position of 50 μm depth from the surface of the bearing member. . A rolling bearing having an outer ring having a raceway portion on an inner peripheral surface, an inner ring having a raceway portion on an outer peripheral surface, and a plurality of rolling elements arranged between both raceway portions of the inner and outer rings,
A rolling bearing, wherein at least one of the outer ring and the inner ring is made of the bearing constituent member according to claim 1 or 2 .