JP2022096585A - Rolling component, bearing, and manufacturing methods of these - Google Patents

Abstract

To provide a rolling component, a bearing, and manufacturing methods of these capable of suppressing peeling caused by a fiber flow, and both of inclusion origin type pealing and surface origin type peeling.SOLUTION: A rolling component has a surface. A fiber flow FF is included in the rolling component. An angle α formed by the surface and the fiber flow FF is equal to or larger than 15°. In a region within a depth of 100 μm from the surface, a maximum compression residual stress is equal to or higher than 700 MPa. A residual austenite amount on the surface is 11% or more and 28% or less.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to rolling parts, bearings and methods of manufacturing them, and in particular to rolling parts, bearings and methods of manufacturing them, the components of which include fiber flow.

In order to extend the life of the bearing, for example, in Japanese Patent Application Laid-Open No. 2019-95044 (Patent Document 1), the angle between the fiber flow and the raceway surface is 15 ° or more, and the compressive residual stress on the surface is 700 MPa or more. , Rolling parts that make up bearings have been proposed. According to JP-A-2019-095044, a sufficient compressive residual stress is imparted to the surface of a rolling component by subjecting it to plastic working such as burnishing. As a result, the gap between the non-metal inclusions in the rolling component and the base material of the rolling component is reduced, and crack growth is suppressed. Therefore, peeling of the surface of the bearing starting from the non-metal inclusions is suppressed, and the life of the bearing is extended.

On the other hand, the peeling of the bearing surface starts from the indentation generated on the surface due to the biting of foreign matter mixed in the lubricating oil, in addition to the inclusion-based peeling starting from the non-metal inclusions as described above. There is surface-based peeling. Surface-based peeling may occur in a shorter time than inclusion-based peeling. In order to prevent the occurrence of surface-origin type peeling, it is conceivable to design the bearing so that foreign matter does not enter the inside of the bearing by adding, for example, a seal. In addition, in order to prevent the occurrence of surface-origin type peeling, for example, Japanese Patent Application Laid-Open No. 2016-108596 (Patent Document 2) proposes a technique for increasing the amount of residual austenite on the surface by a special heat treatment. This is because if the amount of retained austenite is increased, the shape of the indentation on the surface due to the foreign matter is deformed, and the stress concentration around the indentation is relaxed.

JP-A-2019-095044 Japanese Unexamined Patent Publication No. 2016-108596

Hub bearings used in automobiles have a structure of double-row angular contact ball bearings. Therefore, in the hub bearing, the fiber flow tends to have a large angle with respect to the raceway surface. Hub bearings may need to be subjected to residual stress to prevent shortening of life due to fiber flow. However, if residual stress is applied by burnishing as in JP-A-2019-095044, the amount of residual austenite decreases. If the amount of retained austenite is reduced, stress concentration around the indentation on the surface due to foreign matter is induced, and surface-origin type peeling is likely to occur. In both JP-A-2019-095044 and JP-A-2016-108596, the fiber flow has a large angle with respect to the raceway surface, compressive residual stress is applied to the surface, and surface-origin type peeling due to intrusion of foreign matter is suppressed. The configuration made has not been considered.

This disclosure has been made in view of the above issues. An object of the present invention is to provide rolling parts, bearings and methods for manufacturing them, which can suppress both peeling caused by fiber flow, inclusion-based peeling and surface-based peeling.

Rolling components according to the present disclosure have a surface. Rolling components include fiber flow. The angle between the surface and the fiber flow is 15 ° or more. The maximum compressive residual stress is 700 MPa or more in a region within 100 μm in depth from the surface. The amount of retained austenite on the surface is 11% or more and 28% or less.

Bearings according to the present disclosure include an outer ring, a rolling element, and an inner ring. The rolling element is arranged on the inner peripheral surface of the outer ring. The inner ring is arranged on the inner peripheral side of the rolling element. At least one of the outer ring, the rolling element and the inner ring is the rolling component. The surface of the rolling component is either the raceway surface of the outer ring, the raceway surface of the inner ring, or the rolling surface of the rolling element.

In the method of manufacturing a rolling component having a surface according to the present disclosure, a member having a surface to be machined and containing a fiber flow is prepared. The surface to be machined is polished. After being polished, the surface to be machined is subjected to plastic working. The angle between the surface and the fiber flow is 15 ° or more. It is formed so that the maximum compressive residual stress is 700 MPa or more in a region within 100 μm in depth from the surface. The amount of retained austenite on the surface is 11% or more and 28% or less. Burnishing is performed in the process of performing the plastic working.

The bearing in the method of manufacturing a bearing according to the present disclosure includes an outer ring, a rolling element, and an inner ring. The rolling element is arranged on the inner peripheral surface of the outer ring. The inner ring is arranged on the inner peripheral side of the rolling element. At least one of the outer ring, the rolling element and the inner ring is the rolling component. The surface of the rolling component is either the raceway surface of the outer ring, the raceway surface of the inner ring, or the rolling surface of the rolling element.

According to the present disclosure, rolling parts, bearings, and methods for manufacturing them can be obtained, in which peeling due to fiber flow, inclusion-based peeling, and surface-based peeling can be suppressed.

It is a schematic sectional drawing which shows the partial structure of the hub bearing which concerns on this embodiment. It is a schematic cross-sectional view of the region II surrounded by the dotted line in FIG. It is a schematic sectional drawing which shows the gap between the base material of a rolling part, and the non-metal inclusions present in the base material. It is a schematic diagram which shows the 1st process of the manufacturing method of a rolling part. It is a schematic diagram which shows the 2nd process of the manufacturing method of a rolling part. It is a schematic diagram which shows the 3rd process of the manufacturing method of a rolling part. It is a schematic diagram which shows the 4th process of the manufacturing method of a rolling part. It is a schematic diagram which shows the 5th process of the manufacturing method of a rolling part. It is a graph which shows the residual austenite amount of the surface layer of the rolling part made by SUJ2 before and after the burnishing process. It is a graph which shows the residual austenite amount of the surface layer of the rolling part made by SCM445H before and after the burnishing process. It is a graph which shows the residual austenite amount of the surface layer of the rolling part made by SUJ3 which carburized nitriding treatment performed before and after the burnishing process. It is a graph which shows the relationship between the depth from the surface of the rolling component, and the residual stress before and after the carburizing and nitriding treatment of SUJ3.

Hereinafter, the present embodiment will be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing a partial structure of a hub bearing according to the present embodiment. With reference to FIG. 1, the bearing according to the present embodiment is a hub bearing 10 for an automobile. The hub bearing 10 is for a driven wheel. The hub bearing 10 mainly includes two rows of rolling elements 1, a plurality of rolling elements 1 included in each row, an inner ring 2, an outer ring 3, a hub ring 4, and a cage 5. The rolling element 1 has a rolling surface 1a. The inner ring 2 has a raceway surface 2a. The outer ring 3 has a double row (two rows in FIG. 1) of raceway surfaces 3a. The outer ring 3 is connected to a knuckle (not shown) by a bolt (not shown). The hub wheel 4 has a raceway surface 4a. The plurality of rolling elements 1 in two rows are sandwiched between the raceway surface 2a, the raceway surface 3a, and the raceway surface 4a, and are held by the cage 5. A high load is applied to the raceway surfaces 2a, 3a, 4a from the rolling element 1. Therefore, a surface hardened layer is formed on the raceway surfaces 2a, 3a, 4a by induction hardening or the like. The hub wheel 4 has a non-cut portion. A seal 6 is arranged to close the gap between the outer ring 3 and the inner ring 2 and the hub ring 4.

The hub wheel 4 functions as a part of the inner ring of the hub bearing 10. In other words, both the inner ring 2 and the hub ring 4 are inner rings arranged on the inner peripheral side of the rolling element 1 in the hub bearing 10. Note that only a part of the hub wheel 4 in FIG. 1 is arranged on the inner peripheral side of the rolling element 1 and the other part is arranged on the outside of the rolling element 1, but the hub ring 4 in this case is a rolling element here. It is assumed that it is arranged on the inner peripheral side of 1. The hub bearing 4 is separately crimped so as to tighten the inner ring 2 provided on the hub bearing 10. Specifically, the crimping portion 4b is formed on the hub ring 4, and the inner ring 2 is crimped by the crimping portion 4b. A swing crimping method is used for the above crimping process. The hub ring 4 has a stepped wall 4s. The inner ring 2 is coupled to the hub ring 4 in a state of being pressed against the step wall 4s.

A hub bolt 11 is arranged on the hub wheel 4. The hub wheel 4 is connected to a tire (not shown) and rotatably supported. In FIG. 1, a hole through which the hub bolt 11 penetrates is provided in the wheel mounting flange 4c. In order to reduce the weight, a structure may be adopted in which the wheel mounting flange 4c is used as an arm for each hub bolt. The hub wheel 4 has a surface 4d on the inboard side of the wheel mounting flange 4c and a surface 4d on the outer side of the central portion, and these are non-cut surfaces, so that the manufacturing cost is reduced.

The vehicle body load of the automobile reaches the wheels via the outer ring 3 → the rolling element 1 → the inner ring 2 and the hub wheel 4, and balances with the reaction force from the ground.

As described above, the hub bearing 10 includes a rolling element 1 as a rolling component, an inner ring 2 and a hub ring 4 as an inner ring, and an outer ring 3. In other words, at least one of the rolling element 1, the inner ring 2, the outer ring 3 and the hub ring 4 is the above-mentioned rolling component. FIG. 2 is a schematic cross-sectional view of region II surrounded by a dotted line in FIG. FIG. 2A shows a state in which the fiber flow FF is formed on the inner ring 2. With reference to FIG. 2A, for example, the rolling surface 1a of the rolling element 1 and the raceway surface 2a of the inner ring 2 come into contact with each other. Each rolling component, such as the rolling surface 1a and the raceway surface 2a, has a surface that is in contact with the other rolling component. Although not shown in FIG. 2, the rolling surface 1a of the rolling element 1 and the raceway surface 3a of the outer ring 3 also come into contact with each other. That is, the outer ring 3 which is a rolling component also has a raceway surface 3a which is a surface in contact with the rolling element 1 which is another rolling component. The rolling surface 1a of the rolling element 1 and the raceway surface 4a of the hub ring 4 also come into contact with each other. That is, the hub wheel 4, which is a rolling component, also has a raceway surface 4a, which is a surface that comes into contact with the rolling element 1, which is another rolling component.

As shown in FIG. 2A, for example, the inner ring 2 which is a rolling component contains a fiber flow FF in its structure. The angle α formed by the raceway surface 2a, which is the surface of the inner ring 2, and the fiber flow FF included in the inner ring 2 is 15 ° or more. In FIG. 2A, the inner ring 2 may be replaced with the hub ring 4, and the raceway surface 2a may be replaced with the raceway ring 4a.

FIG. 2B shows a state in which the fiber flow FF is formed on the rolling element 1. With reference to FIG. 2B, the fiber flow FF may be included on the side of the rolling element 1. Also in this case, the angle α formed by the rolling surface 1a, which is the surface of the rolling element 1, and the fiber flow FF included in the rolling element 1 is 15 ° or more.

The maximum in the rolling surface 1a of the rolling element 1, the raceway surface 2a of the inner ring 2, the raceway surface 3a of the outer ring 3, the raceway surface 4a of the hub ring 4, and the region where the depth in the vertical direction from the surface is within 100 μm. The maximum compressive residual stress, which is the compressive residual stress, is 700 MPa or more. Further, the rolling surface 1a and the raceway surfaces 2a, 3a, 4a have a retained austenite amount of 11% or more and 28% or less. Here, the amount of retained austenite in the surface layer including the rolling surface 1a and the raceway surfaces 2a, 3a, 4a is shown. The surface layer is not limited to the exposed rolling surface 1a and the raceway surfaces 2a, 3a, 4a, but is extremely shallow in the rolling parts adjacent to the exposed rolling surface 1a and the raceway surfaces 2a, 3a, 4a. Means an area.

FIG. 3 is a schematic cross-sectional view showing a gap between a base material of a rolling component and a non-metal inclusions present in the base material. In particular, FIG. 3 (A) shows the mode of the non-metal inclusions arranged so as to be exposed on the surface of the base metal, and FIG. 3 (B) shows the mode of the non-metal inclusions inside away from the surface of the base metal. Shows. With reference to FIGS. 3A and 3B, in the rolling parts such as the inner ring 2, the non-metal inclusions 41 existing on the surface side (upper side of FIG. 3A) such as the raceway surface 2a The gap 42 with the base material constituting the inner ring 2 is smaller than the gap 42 between the non-metal inclusions 41 existing on the inner side away from the raceway surface 2a of the inner ring 2 and the base material constituting the inner ring 2. .. This also applies to the rolling element 1, the outer ring 3, and the hub wheel 4. As shown in FIG. 3A, there may be no gap between the non-metal inclusions 41 and the base metal on the surface side such as the raceway surface 2a.

The material constituting the rolling element 1, the inner ring 2, the outer ring 3 and the hub ring 4 may be steel. Needless to say, the steel contains iron (Fe) as a main component and may contain unavoidable impurities in addition to the above elements. Inevitable impurities include phosphorus (P), sulfur (S), nitrogen (N), oxygen (O), aluminum (Al) and the like. The amount of each of these unavoidable impurity elements is 0.1% by mass or less. The rolling elements 1, inner ring 2, outer ring 3 and hub ring 4 may be formed of a steel material having an oxygen content of, for example, 5 ppm or more.

The steel is, for example, JIS standard S53C, which is an example of a material for bearings. S53C contains 0.5% by mass or more and 0.56% by mass or less of carbon, 0.15% by mass or more and 0.35% by mass or less of silicon, and 0.6% by mass or more and 0.9% by mass or less of manganese. .. Further, S53C contains 0.03% by mass or less of phosphorus, 0.035% by mass or less of sulfur, 0.2% by mass or less of chromium, and 0.02% by mass or less of nickel.

Next, a rolling component having the above configuration and a method for manufacturing the hub bearing 10 including the rolling component will be described with reference to FIGS. 4 to 9. The following FIGS. 4 to 9 show the manufacturing process of the inner ring 2 as an example. However, the manufacturing process of the inner ring 2 is also related to the manufacturing process of the rolling element 1, the outer ring 3 arranged on the outer peripheral surface of the rolling element 1, and the hub ring 4 including the portion arranged on the inner peripheral surface of the rolling element 1. Is similar to.

FIG. 4 is a schematic view showing a first step of a method for manufacturing a rolling component. With reference to FIG. 4, first, a steel material 101 for forming any of the rolling elements 1, the inner ring 2, the outer ring 3, and the hub ring 4, which are rolling components, is prepared. The material of the steel material 101 is as described above. The steel material 101 includes, for example, a fiber flow FF extending in the left-right direction in the figure. The rolling component forming region 103 is cut from the steel material 101 by the cutting tool 102.

FIG. 5 is a schematic view showing a second step of a method for manufacturing a rolling component. With reference to FIG. 5, a member having a cavity 104 in the center is formed to form the inner ring 2.

FIG. 6 is a schematic view showing a third step of a method for manufacturing a rolling component. With reference to FIG. 6, the outer peripheral surface of the inner ring 2 is subjected to generally known processing such as grinding and heat treatment such as quenching. As a result, as shown in the figure, a member including the fiber flow FF and having an outer peripheral surface, that is, a work surface 2B inclined with respect to the extending direction of the fiber flow FF is formed. The surface to be machined 2B is formed so that the angle formed with the fiber flow FF is 15 ° or more.

FIG. 7 is a schematic view showing a fourth step of a method for manufacturing a rolling component. With reference to FIG. 7, the surface to be machined 2B of the inner ring 2 is polished. Here, for example, it is preferable that polishing is performed by an inner ring grinding machine.

After the polishing process shown in FIG. 7, the surface to be machined 2B is subjected to plastic working. As a result, the machined surface 2B becomes the raceway surface 2a of the inner ring.

FIG. 8 is a schematic view showing a fifth step of a method for manufacturing a rolling component. In particular, FIG. 8 shows an example of the above plastic working. With reference to FIG. 8, in the step of performing plastic working, it is preferable that, for example, burnishing is performed. In the burnishing process, a pressing portion CC such as a hard ball made of ceramic or a protrusion-shaped portion made of diamond is used as a tool. In FIG. 8, a spherical pressing portion CC is shown as an example. The pressing portion CC rotates on the workpiece surface 2B while rotating the pressing portion CC in the direction of the arrow R1 in the drawing and rotating the inner ring 2 in the circumferential direction of the arrow R2 about the virtual axis L penetrating the cavity 104. Press with the force indicated by the arrow F. This pressing is performed so that the burnishing tool 25 to which the pressing portion CC is attached applies the force of the arrow F to the pressing portion CC. Further, the burnishing tool 25 feeds the pressing portion CC on the surface to be machined 2B so as to move in the direction of the arrow M. As a result, the minute uneven shape and the like existing on the surface to be machined 2B are flattened.

Before the step of performing plastic working, the member may be subjected to carburizing and nitriding treatment. In the carburizing nitriding treatment, for example, a gas having an atmosphere of 850 ° C. or higher and 960 ° C. or lower, in which carbon having a volume ratio of 1.0% and ammonia having a volume ratio of 7% are mixed with an endothermic modified gas (Rx gas). Made in the furnace. The rolling parts obtained as described above have the same properties as the rolling parts shown in FIGS. 2 (A) and 2 (B) above.

Next, the action and effect of this embodiment will be described.
The rolling parts (rolling element 1, inner ring 2, outer ring 3, hub ring 4) according to the present disclosure have a surface. Rolling components include fiber flow FF. The angle between the surface and the fiber flow FF is 15 ° or more. The maximum compressive residual stress is 700 MPa or more in a region within 100 μm in depth from the surface. The amount of retained austenite on the surface is 11% or more and 28% or less. Here, the region within 100 μm in depth from the surface includes the surface.

The rolling component has a maximum compressive residual stress of 700 MPa or more in a region such as the raceway surface 2a of the inner ring 2 which is the surface and a region having a depth of 100 μm or less. As a result, the gap between the non-metal inclusions exposed on the surface of the raceway surface and the base material around the non-metal inclusions is narrowed or filled so as to disappear.

That is, in particular, as shown in FIG. 3, due to plastic working, the gap 42 between the non-metal inclusions 41 on the surface side such as the raceway surface 2a and the base material is formed between the non-metal inclusions 41 on the inner side of the rolling component and the mother. It is smaller than the gap 42 with the material. Therefore, the cause of premature breakage of rolling parts due to cracks is reduced (or disappears). As a result, the expansion of cracks (inclusion-origin type peeling) starting from the gap 42 between the non-metal inclusions 41 and the base metal on the rolling surface 1a and the raceway surfaces 2a, 3a, 4a can be suppressed, and the length of the bearing can be suppressed. The life can be extended.

Further, from the viewpoint of suppressing peeling due to an opening crack, the angle formed by the fiber flow FF and the rolling surface 1a and the raceway surfaces 2a, 3a, 4a is preferably 15 ° or less as described above. It is said that. From the viewpoint of using a clean steel material, it is considered preferable that the oxygen content of the rolling parts is 5 ppm or less. However, in the present embodiment, even if the angle is 15 ° or more, the plastic working can suppress the occurrence of peeling due to the opening crack, and the life of the bearing can be extended. can. Further, in the present embodiment, the oxygen content of the rolling element 1, the inner ring 2, the outer ring 3 and the hub ring 4 may be 5 ppm or more. Even if the oxygen content is 5 ppm or more, the plastic working can suppress the occurrence of peeling due to the opening crack, and the life of the bearing can be extended.

Further, by setting the residual austenite amount on the surface of the rolling component to 11% or more, indentation is generated on the surface, and when the rolling element 1 rolls and contacts on the indentation, the indentation shape is deformed and stress is concentrated. Can be relaxed. This is because retained austenite is softer than martensite, which is the main structure constituting the material of the rolling parts after quenching, and is more easily deformed than martensite. Therefore, it is possible to suppress surface-origin type peeling starting from indentations generated on the surface due to foreign matter or the like. However, in order to obtain this effect, the amount of retained austenite must be 11% or more. However, if the amount of retained austenite on the surface of the rolling component is more than 28%, the dimensional stability of the rolling component is lowered. Therefore, by setting the residual austenite amount to 28% or less, it is possible to suppress a decrease in dimensional stability and a shortening of the life due to surface-origin type peeling due to foreign matter contamination or the like. The amount of retained austenite can be measured by cutting out a part of the surface of the bearing component, electrolytically polishing the surface, and using an X-ray diffractometer. Further, the maximum compressive residual stress can be measured by cutting out a part of the surface of the bearing component, electrolytically polishing the surface, and using an X-ray diffractometer, similarly to the amount of residual austenite.

Bearings according to the present disclosure include an outer ring 3, a rolling element 1, and an inner ring 2 (the inner ring 2 includes both with and without the hub ring 4 described below). The rolling element 1 is arranged on the raceway surface 3a, which is the inner peripheral surface of the outer ring 3. The inner ring 2 is arranged on the inner peripheral side of the rolling element 1. At least one of the rolling element 1, the inner ring 2, and the outer ring 3 is the rolling component. The surface of the rolling component is either the raceway surface 3a of the outer ring 3, the raceway surface 2a of the inner ring 2 (which may include the raceway ring 4a), or the rolling surface 1a of the rolling element 1. As a result, the bearing has the effect of improving the life by suppressing the occurrence of peeling as described above.

The bearing is used as a hub bearing for an automobile, and the hub bearing for an automobile may further include a hub wheel 4 as at least a part of the inner ring 2. In this case, the inner ring 2 includes, for example, both the inner ring 2 and the hub ring 4 in FIG. When plastic working such as burnishing is applied to rolling parts constituting automobile bearings, the residual austenite in the surface layer is subjected to work-induced transformation, and the amount of residual austenite in the surface layer is reduced. When the amount of retained austenite in the surface layer is small, the surface layer becomes sensitive to foreign substances, and surface origin peeling is likely to occur.

Further, since the hub bearing for an automobile has a structure of a double-row angular contact ball bearing, the hub bearing for an automobile may be infiltrated with muddy water while the automobile is running. Therefore, hub bearings for automobiles are required to have high durability against foreign substances.

In general, hub bearings tend to have a large fiber flow angle with respect to the raceway surface. However, the hub bearing 10 for automobiles according to the present disclosure has a maximum compressive residual stress of 700 MPa or more in a region within 100 μm in depth from the surface as described above, so that even if the angle between the surface and the fiber flow FF is 15 ° or more. Even if it becomes large, the life can be extended against peeling starting from the non-metal inclusions 41. Further, the hub bearing 10 for an automobile includes rolling parts having a residual austenite amount of 11% or more and 28% or less. For this reason, even if the angle between the surface and the fiber flow FF is as large as 15 ° or more and the conditions are such that peeling due to an opening crack is likely to occur, surface-based peeling is suppressed and foreign matter is introduced while the vehicle is running. Even if it penetrates, the life of the bearing can be extended.

The manufacturing method according to the present disclosure is a manufacturing method of a rolling component having a surface. The manufacturing method has a surface to be machined 2B, and a member including a fiber flow FF is prepared. The surface to be machined 2B is polished. After the polishing process is applied, the workpiece surface 2B is subjected to plastic working. The angle formed by the surface (rolling surface 1a and raceway surface 2a, 3a, 4a) and the fiber flow FF is 15 ° or more. It is formed so that the maximum compressive residual stress is 700 MPa or more in a region within 100 μm in depth from the surface. The amount of retained austenite on the surface is 11% or more and 28% or less. Burnishing is performed in the process of plastic working.

Since it has the above configuration, according to the manufacturing method of the present embodiment, inclusion-based peeling and surface-based peeling can be suppressed even under conditions where peeling is easy, and the life of the bearing can be extended.

In the above-mentioned method for manufacturing a rolling component, a step of carburizing and nitriding the member may be further provided before the step of performing plastic working. The carburizing nitriding treatment can increase the amount of retained austenite on the surface (surface layer) of the rolling component. Specifically, for example, the amount of retained austenite on the surface can be 11% or more and 28% or less. As a result, the stress concentration around the indentation due to the biting of foreign matter is alleviated, and the surface-origin type peeling is suppressed, so that the life of the bearing can be extended.

The bearing according to the manufacturing method according to the present disclosure includes an outer ring 3, a rolling element 1, and an inner ring 2 (the inner ring 2 includes both the case where the hub ring 4 described below is provided and the case where the bearing is not present). .. The rolling element 1 is arranged on the raceway surface 3a, which is the inner peripheral surface of the outer ring 3. The inner ring 2 is arranged on the inner peripheral side of the rolling element 1. At least one of the rolling element 1, the inner ring 2 and the outer ring 3 is the rolling component. The surface of the rolling component is either the raceway surface 3a of the outer ring 3, the raceway surface 2a of the inner ring 2 (which may include the raceway ring 4a), or the rolling surface 1a of the rolling element 1. The bearing obtained by the manufacturing method has the effect of improving the life by suppressing the occurrence of peeling as described above. The bearing according to the manufacturing method is used as an automobile hub bearing, and the automobile hub bearing may further include a hub wheel 4 as at least a part of the inner ring 2.

The results of an investigation into how the amount of retained austenite in the surface layer of rolling parts changes due to plastic working (burnishing) are shown below. FIG. 9 is a graph showing the amount of retained austenite in the surface layer of the rolling component made of SUJ2 before and after the burnishing process. FIG. 10 is a graph showing the amount of retained austenite in the surface layer of the rolling component made of SCM445H before and after the burnishing process. In each of the graphs of FIGS. 9 and 10, the horizontal axis indicates the depth from the surface of the rolling component (unit: μm), and the vertical axis indicates the amount of retained austenite (unit:%) at the depth. Here, the amount of retained austenite indicates the volume ratio of retained austenite to the entire depth region.

With reference to FIG. 9, in the rolling parts made of SUJ2, if the amount of residual austenite in the surface layer before the burnishing process (“without burnishing” in the graph) is about 12% or more and 14% or less, after the burnishing process. (“With vanishing” in the graph), the amount of residual austenite in the surface layer in the same sample is approximately 6% or more and 8% or less. On the other hand, referring to FIG. 10, in the rolling parts made of SCM445, if the amount of residual austenite in the surface layer before the burnishing process is about 5% or more and 7% or less, the same sample after the burnishing process is used. The amount of retained austenite in the surface layer is approximately 3% or more and 5% or less. From this, it can be seen that if the amount of retained austenite in the surface layer is less than 10% before the burnishing process, almost no residual austenite remains in the surface layer after the burnishing process.

The results of investigating the relationship between the depth from the surface and the amount of retained austenite in a rolling component having a larger amount of retained austenite than a normal product obtained by quenching SUJ2 are shown below. FIG. 11 is a graph showing the amount of residual austenite in the surface layer of the rolling component made of SUJ3 which has been carburized and nitrided before and after the burnishing process. In the graph of FIG. 11, the horizontal axis indicates the depth from the surface of the rolling component (unit: μm), and the vertical axis indicates the amount of retained austenite (unit:%) at the depth.

With reference to FIG. 11, by carburizing and nitriding SUJ3, the rolling parts of the bearing made of SUJ3, which has a larger amount of retained austenite than the normal hardened product made of SUJ2, have the residual austenite on the surface after the burnishing process. It was confirmed that the amount was 11% or more and 28% or less.

Specifically, SUJ3 here is a kind of high carbon chromium bearing steel having a higher ratio of manganese than SUJ2, for example. Further, in the above carburizing nitriding treatment, an atmosphere of 850 ° C. or higher and 960 ° C. or lower, in which carbon having a volume ratio of 1.0% and ammonia having a volume ratio of 7% are mixed with an endothermic modified gas (Rx gas). Made in a gas furnace. In particular, in FIG. 11, the amount of retained austenite on the surface after the burnishing process is 15% or more and 23% or less. In the SUJ3 after the carburizing and nitriding treatment of FIG. 11, the amount of residual austenite in the region within a depth of about 50 μm from the surface was about 30% (22% or more and 33% or less) in the initial state before the burnishing process. rice field.

FIG. 12 is a graph showing the relationship between the depth from the surface of the rolling component and the residual stress before and after the carburizing and nitriding treatment of SUJ3. In the graph of FIG. 12, the horizontal axis indicates the depth from the surface of the rolling component (unit: μm), and the vertical axis indicates the residual stress (unit: MPa) at the depth. Here, the residual stress indicates the average value of the residual stress with respect to the entire depth region.

By performing the carburizing nitriding treatment on SUJ3 in the same manner as in Example 2 with reference to FIG. 12, the maximum compressive residual stress may be 700 MPa or more in the region within 100 μm in depth from the surface after the burnishing process. It could be confirmed.

The features described in the above-described embodiments (each example included in the above examples) may be applied so as to be appropriately combined within a technically consistent range.

The embodiments and examples disclosed this time should be considered to be exemplary and not restrictive in all respects. The scope of the present invention is shown by the scope of claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

1 Rolling element, 1a Rolling surface, 2 Inner ring, 2a, 3a, 4a Track surface, 2B Processed surface, 3 Outer ring, 4 Hub wheel, 4b Clamping part, 4c Wheel mounting flange, 4d surface, 4s step wall, 5 Cage, 6 seals, 11 hub bolts, 25 burnishing tools, 41 non-metal inclusions, 42 gaps, 101 steel, 102 cutting tools, 103 rolling component forming areas, 104 cavities, CC presses, FF fiber flow.

Claims (7)

A rolling component with a surface
The rolling components include fiber flow and
The angle between the surface and the fiber flow is 15 ° or more.
The maximum compressive residual stress is 700 MPa or more in a region within 100 μm in depth from the surface.
A rolling component having an amount of retained austenite on the surface of 11% or more and 28% or less. The rolling component according to claim 1, which is formed of a steel material having an oxygen content of 5 ppm or more. With the outer ring
A rolling element arranged on the inner peripheral surface of the outer ring and
A bearing provided with an inner ring arranged on the inner peripheral side of the rolling element.
At least one of the outer ring, the rolling element, and the inner ring is the rolling component according to claim 1 or 2.
A bearing whose surface in the rolling component is any one of the raceway surface of the outer ring, the raceway surface of the inner ring, and the rolling surface of the rolling element. Used as a hub bearing for automobiles
The bearing according to claim 3, wherein the automobile hub bearing further includes a hub ring as at least a part of the inner ring. A method for manufacturing rolling parts that have a surface.
The process of preparing a member that has a surface to be machined and contains fiber flow,
The process of polishing the surface to be processed and
A step of plastic working the surface to be machined is provided after the step of performing the polishing process.
The angle between the surface and the fiber flow is 15 ° or more.
It is formed so that the maximum compressive residual stress is 700 MPa or more in a region within 100 μm in depth from the surface.
The amount of retained austenite on the surface is 11% or more and 28% or less.
A method for manufacturing rolling parts, in which vanishing is performed in the process of performing plastic working. The method for manufacturing a rolling component according to claim 5, further comprising a step of carburizing and nitriding the member before the step of performing the plastic working. With the outer ring
A rolling element arranged on the inner peripheral surface of the outer ring and
It is a method of manufacturing a bearing including an inner ring arranged on the inner peripheral side of the rolling element.
At least one of the outer ring, the rolling element, and the inner ring is the rolling component according to claim 5 or 6.
A method for manufacturing a bearing, wherein the surface of the rolling component is any one of a raceway surface of the outer ring, a raceway surface of the inner ring, and a rolling surface of the rolling element.

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