Manufacturing method of bearing race

Abstract

To provide a manufacturing method of a bearing ring in which deformation due to a heat treatment is suppressed.SOLUTION: A manufacturing method of a bearing ring includes an annular member arrangement step of arranging a plurality of annular members 1 to be a bearing ring on a basket 10, a basket arrangement step of arranging the basket 10 inside a heating furnace 20, and a heat treatment step of heat-treating the plurality of annular members 1 arranged on the basket 10. In the annular member arranging step, the plurality of annular members 1 are arranged on the basket 10 so as not to contact each other. In the heat treatment step, the plurality of annular members 1 are quenched by performing heating and cooling while maintaining the arrangement of the plurality of annular members 1 on the basket 10.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a bearing ring. [Background technology]

[0002] The bearing ring, which is an annular member, is required to have a desired mechanical strength as a function of the ring. In order to impart mechanical strength to the bearing ring, the manufacturing process of the bearing ring involves carrying out heat treatment including quenching on the annular member formed from bearing steel (SUJ2), for example.

[0003] For example, Patent Document 1 discloses a continuous heat treatment furnace that performs heat treatment such as carburizing and sintering on an object to be heated. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2009-228116 A Summary of the Invention [Problem to be solved by the invention]

[0005] Bearing raceways have low rigidity against elliptical deformation, and circular blanks cut from materials can become elliptical due to the effects of heat and phase transformation during hardening. Elliptical deformation is a phenomenon in which circular steel parts become distorted into an elliptical shape.

[0006] The oval deformation of the bearing raceway is evaluated by measuring the roundness of the raceway surface of the bearing raceway after hardening. The oval deformation caused by this heat treatment is removed by a subsequent grinding process, but if the oval deformation of the bearing raceway is large and the roundness is poor, the amount of grinding must be increased, which increases the cost of the manufacturing process of the bearing raceway.

[0007] When heat treating the annular members that will become bearing races, for example, continuous or batch heat treatment can be used. The continuous type is a mass production method in which the annular members are placed on a belt conveyer or the like and heated as they pass through a furnace. The batch type is a method in which the annular members are placed in a basket and the basket is placed in a fixed furnace (batch heating furnace) for heat treatment (heating and cooling). A batch heating furnace has the advantage that the temperature and time can be freely adjusted each time depending on the type of bearing rolling element, heating conditions, etc.

[0008] However, when an annular member is heat-treated using a batch-type heating furnace, the annular member is subject to elliptical deformation and deterioration in roundness, which has been a problem for some time. However, the cause of this elliptical deformation and deterioration in roundness has not been clear.

[0009] The present invention has been made in view of the above circumstances, and has an object to provide a method for manufacturing a bearing race that can suppress deformation due to heat treatment. [Means for solving the problem]

[0010] The above object of the present invention can be achieved by the following configuration. (1) A method for manufacturing a bearing ring, comprising the steps of: an annular member arrangement step of arranging a plurality of annular members that will become bearing races on a basket; a basket placement step of placing the basket inside a heating furnace; a heat treatment step of heat treating the plurality of annular members arranged on the basket; Including, In the annular member arrangement step, the plurality of annular members are arranged on the basket so as not to come into contact with each other; In the heat treatment step, the plurality of annular members are quenched by performing heating and cooling while maintaining the arrangement of the plurality of annular members on the basket. A method for manufacturing a bearing ring. (2) During the quenching in the heat treatment step, the basket is immersed in a cooling liquid stored in a liquid tank, and the cooling liquid is caused to flow in an up-down direction to contact the plurality of annular members, thereby cooling the plurality of annular members. A method for manufacturing the bearing raceway according to (1). (3) The plurality of annular members are set at predetermined positions on the basket by a positioning member. A method for manufacturing a bearing race according to (1) or (2). (4) The heating furnace is a batch type heating furnace. A method for manufacturing a bearing race according to any one of (1) to (3). (5) In the annular member arranging step, the plurality of annular members are arranged in a staggered pattern. A method for manufacturing a bearing race according to any one of (1) to (4). (6) In the heat treatment step, the plurality of annular members are carburized. A method for manufacturing a bearing race according to any one of (1) to (5). (7) In the heat treatment step, the plurality of annular members are subjected to a nitriding treatment. A method for manufacturing a bearing race according to any one of (1) to (5). (8) In the heat treatment step, the plurality of annular members are subjected to carbonitriding treatment. A method for manufacturing a bearing race according to any one of (1) to (5). (9) In the heat treatment step, the plurality of annular members are deep-quenched. A method for manufacturing a bearing race according to any one of (1) to (5). (10) In the heat treatment step, after the quenching is performed on the plurality of annular members, the plurality of annular members are further subjected to tempering. A method for manufacturing a bearing race according to any one of (1) to (9). (11) The method further comprises a grinding step of grinding the annular member after the heat treatment step. A method for manufacturing a bearing race according to any one of (1) to (10). Effect of the Invention

[0011] According to the method for manufacturing a bearing race of the present invention, it is possible to suppress deformation of the annular member due to heat treatment. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a diagram showing a state in which a plurality of annular members are arranged on a basket in the embodiment (Example 1). [Diagram 2] FIG. 13 is a diagram showing a state in which a plurality of annular members are arranged on a basket in a comparative example. [Diagram 3] FIG. 2 is a schematic cross-sectional view of a heating furnace. [Figure 4] FIG. [Diagram 5] FIG. 13 is a diagram showing a state in which a plurality of annular members are arranged on a basket in an embodiment (Example 2). [Figure 6] 1(a) to (c) are diagrams showing the results of measuring the roundness of a plurality of annular members after carbonitriding treatment, where (a) to (c) are the results of measuring the roundness of a comparative example, example 1, and example 2, respectively. [Figure 7] 1(a) to (c) are diagrams showing the results of measuring the roundness of a plurality of annular members after secondary quenching, where (a) to (c) are the results of measuring the roundness of a comparative example, an example 1, and an example 2, respectively. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, a method for manufacturing a bearing race according to an embodiment of the present invention will be described. In the following description, the bearing race will also be simply referred to as a "race".

[0014] The method for manufacturing the raceway includes an annular member preparation step of preparing an annular member 1 to become the raceway, an annular member arrangement step of arranging a plurality of annular members 1 on a basket 10, a basket arrangement step of arranging the basket 10 inside a heating furnace 20, a heat treatment step of heat treating the plurality of annular members 1 arranged on the basket 10, and, after the heat treatment step, a grinding step of grinding the annular members 1.

[0015] (Annular member preparation process) In the process of preparing the annular member 1 that will become the race (inner or outer ring), the annular member 1 is prepared as a material that will become the race. Case-hardened steel is preferable as the material for the annular member 1, so that a surface hardened layer can be easily formed by carburizing, nitriding, carbonitriding, etc. Also, in order to improve hardenability, it is also preferable to add Cr, Mn, etc. to the annular member 1 as an alloy component.

[0016] (Annular member placement process) After preparing the annular members 1, a plurality of the annular members 1 are arranged on a basket 10 in an annular member arrangement step, as shown in Fig. 1. The basket 10 has a flat bottom surface 11 and a flange portion 13 standing up from the peripheral edge of the bottom surface 11. Therefore, the basket 10 has a tray-like shape without an upper surface.

[0017] Although not shown, the bottom surface 11 and the flange portion 13 of the basket 10 are mesh-like, which prevents the annular member 1 from falling out of the basket 10 and allows efficient heat treatment (heating and cooling) of the annular member 1.

[0018] In the present invention, a plurality of annular members 1 are arranged on the bottom surface 11 of the basket 10 so as not to come into contact with each other. That is, the minimum horizontal distance L between adjacent annular members 1 is set to be greater than 0 (L>0).

[0019] 1, the multiple annular members 1 are preferably arranged in a staggered pattern. Positioning members may be used to accurately place the multiple annular members 1 at predetermined positions on the basket 10. By adopting a staggered pattern, it is possible to arrange more annular members 1 on the basket 10 while ensuring a gap between adjacent annular members 1.

[0020] The arrangement of the multiple annular members 1 is not limited to a staggered pattern, and may be, for example, a grid pattern (grid pattern), as long as a gap between adjacent annular members 1 can be secured (L>0).

[0021] When arranging multiple annular members 1 on the basket 10 so that there are gaps between them, the multiple annular members 1 may be positioned by using a jig that is separate from or integrated with the basket 10, or the multiple annular members 1 may be positioned by providing protrusions and recesses or the like on the basket 10, and the positioning method is not particularly limited.

[0022] As shown in FIG. 2, in the conventional technology, a plurality of annular members 1 were packed tightly on a basket 10. Packing adjacent annular members 1 tightly so that they are in contact with each other is normal in terms of productivity. In other words, when a plurality of annular members 1 are packed tightly, the number of races that can be produced at one time can be increased, and the arrangement work is also very easy. In such a conventional technology, elliptical deformation occurs in the annular member 1 after heat treatment, but the machining allowance is increased to ensure the roundness of the annular member 1 in the subsequent grinding process. Therefore, in the past, there was no tendency to be very concerned about the elliptical deformation of the annular member 1. However, in reality, it took a lot of time and cost to ensure the roundness of the annular member 1 in the grinding process.

[0023] The inventors of the present application noticed that when the annular member 1 is heat-treated using a batch-type heating furnace, the annular member 1 undergoes elliptical deformation and the roundness deteriorates in the above-mentioned conventional method, and discovered that this elliptical deformation and the deterioration of the roundness are caused by the fact that adjacent annular members 1 are heat-treated (especially during cooling during quenching) while in contact with each other. Therefore, they came up with the idea of ​​arranging multiple annular members 1 so that they do not come into contact with each other, as described above.

[0024] (Basket placement process) Next, a basket arrangement step for arranging the basket 10, on whose bottom surface 11 a plurality of annular members 1 are arranged, inside the heating furnace 20 will be described.

[0025] 3, the heating furnace 20 is a batch-type heating furnace, and includes a loading section 30 into which the basket 10 is loaded, a heating section 40 for heating the plurality of annular members 1, a cooling section 50 for cooling the plurality of annular members 1, and a transport section 60 for transporting the basket 10 between the loading section 30 and the heating section 40 and between the loading section 30 and the cooling section 50. Note that in FIG. 3, the circulation device 55 provided in the cooling section 50 is omitted from illustration. The circulation device 55 will be described later with reference to FIG. 4.

[0026] The loading section 30, the heating section 40, the cooling section 50 and the transport section 60 each have a plurality of rollers 31, 41, 51, 61 for moving the basket 10, and a base 33, 43, 53, 63 for supporting the rollers 31, 41, 51, 61, respectively.

[0027] An openable and closable first door 71 is provided between the loading section 30 and the transport section 60, and an openable and closable second door 73 is provided between the transport section 60 and the heating section 40.

[0028] The heating section 40 includes a burner 45 for heating the inside of the heating section 40 and a fan 47 for stirring the atmosphere inside the heating section 40 .

[0029] The base 53 of the cooling section 50 and the base 63 of the transport section 60 are connected to each other and can be moved vertically together by a cylinder 65 provided above.

[0030] The cooling unit 50 is a liquid tank in which a cooling liquid is stored, and in this example, it is an oil tank in which cooling oil O is stored. The cooling liquid is not limited to cooling oil, and may be water, an aqueous solution, or the like. The height of the liquid level of the cooling oil O is set so that all of the multiple baskets 10 arranged in the cooling unit 50 are immersed in the cooling oil O.

[0031] 4, the cooling unit 50 includes a circulation device 55 that circulates the cooling oil in the oil tank. Fig. 4 is a diagram of the cooling unit 50 in Fig. 3 as viewed from the left and right. The circulation device 55 is arranged on both sides of the base 53 and includes a pair of screws 56 that generate a flow of cooling oil O in the vertical direction, and a pair of guide members 57 that surround the pair of screws 56 from the outside and guide the flow of cooling liquid by the pair of screws 56.

[0032] Therefore, when a downward flow of cooling oil O is generated near the pair of screws 56, the cooling oil O passes upward through the basket 10 placed on the base 53 (see the dashed arrow in FIG. 4). On the other hand, when an upward flow of cooling oil O is generated near the pair of screws 56, the cooling oil O passes downward through the basket 10 placed on the base 53.

[0033] When arranging the baskets 10 inside such a heating furnace 20, first, a plurality of baskets 10, each accommodating a plurality of annular members 1, are stacked vertically on the base 33 (rollers 31) of the loading section 30. In the illustrated example, ten stacked baskets 10 are arranged in two rows on the base 33.

[0034] Next, the first door 71 is opened, the basket 10 is moved onto the base 63 of the transport section 60, and the first door 71 is closed. Then, the second door 73 is opened, the basket 10 is moved onto the base 43 of the heating section 40, and the second door 73 is closed. In this manner, the multiple baskets 10, each accommodating a multiple annular members 1, are disposed in the heating section 40.

[0035] (Heat treatment process) In the heat treatment process for heat-treating the plurality of annular members 1 housed in each basket 10, a heat treatment of quenching (heating and cooling) is performed, followed by a heat treatment of tempering (heating and cooling).

[0036] It is preferable to form a surface-hardened layer on the annular member 1 by carburizing, nitriding, or carbonitriding. This is because, when elliptical deformation is suppressed as in the case of the annular member 1 of this embodiment, the surface-hardened layer can be ground uniformly in the circumferential direction, so that a hardened layer with little unevenness can be formed on the surface of the annular member 1. The carburizing, nitriding, or carbonitriding is performed by holding the annular member 1 in a carbon or nitrogen gas atmosphere at 900 to 1000°C for several to several tens of hours. This allows the desired surface-hardened layer to be obtained.

[0037] The plurality of annular members 1 arranged in the heating section 40 are subjected to quenching (heating). It is preferable to subject the plurality of annular members 1 to deep quenching. The deep quenching conditions are oil cooling at a quenching temperature of 800 to 850°C.

[0038] Next, the cylinder 65 is driven to raise the base 53 of the cooling section 50 and the integrated base 63, and position them at the same height as the base 33 of the loading section 30 and the base 43 of the heating section 40. Then, after the quenching (heating) of the multiple annular members 1 is completed, the second door 73 is opened, and the basket 10 is moved to the base 53 of the cooling section 50. Then, the base 53 of the cooling section 50 is lowered so that all the baskets 10 are immersed in the cooling oil O.

[0039] As described above, the pair of screws 56 causes the cooling oil O to pass upward or downward through the mesh basket 10 placed on the base 53. Note that quenching (cooling) is performed by stirring the cooling oil O at 60 to 100°C.

[0040] Here, the heating furnace 20 is a batch-type heating furnace and has the above-mentioned configuration, so that quenching (heating) and quenching (cooling) are performed while maintaining the arrangement of the multiple annular members 1 on the basket 10. That is, the multiple annular members 1 are arranged on the basket 10 in a staggered pattern so as not to come into contact with each other as shown in Fig. 1, and move between the loading section 30, the heating section 40, the cooling section 50, and the transport section 60 while maintaining this arrangement (without the multiple annular members 1 moving).

[0041] Therefore, even when the multiple annular members 1 are quenched (cooled) in the cooling section 50, the multiple annular members 1 are arranged on the basket 10 so as not to come into contact with each other. As a result, the cooling oil O flows vertically between the adjacent annular members 1, so that the cooling of the annular members 1 is uniform. On the other hand, when the cooling oil O flows horizontally (both sides, one side), the cooling is different due to the difference in the flow rate of the cooling oil depending on the location where the annular members 1 are arranged, and all the annular members in the same basket are not cooled uniformly, and the deformation of the annular members 1 becomes large. When the cooling oil O flows vertically as in this embodiment, there is no problem in that only a part of the annular member 1 is cooled and the other parts are not cooled, and the entire annular member 1 is cooled uniformly.

[0042] The inventors of the present application have discovered that whether or not the annular members 1 can be uniformly cooled during this quenching (cooling) is related to the elliptical deformation (deterioration of roundness) of the annular members after heat treatment. In other words, they have discovered that the cause of the elliptical deformation of the annular members 1 after heat treatment is uneven cooling, in which the parts where the annular members 1 are in contact with each other are not sufficiently cooled during quenching (cooling), while the parts where the annular members 1 are not in contact with each other are cooled. They then came up with a configuration in which multiple annular members 1 are arranged on a basket 10 so that they do not come into contact with each other, in order to cool the annular members 1 uniformly.

[0043] The above-described arrangement of the multiple annular members 1 is particularly suitable when quenching (heating) and quenching (cooling) are performed while maintaining the arrangement of the multiple annular members 1 on the basket 10, i.e., when using a batch-type heating furnace 20. In the batch-type heating furnace 20, the arrangement of the multiple annular members 1 on the basket 10 is maintained from the annular member arrangement step before the annular members 1 are carried into the heating furnace 20, through the basket arrangement step and the heat treatment step, so the arrangement of the multiple annular members 1 during the annular member arrangement step is very important.

[0044] In contrast, in a continuous heating furnace, the arrangement of the multiple annular members 1 may differ between quenching (heating) and quenching (cooling). That is, during quenching (cooling), the multiple annular members 1 are individually placed in an oil tank that stores cooling oil. In this case, the arrangement of the multiple annular members 1 is not maintained. In such a case, even if the multiple annular members 1 are arranged so as not to come into contact with each other and quenched (heated), the annular members 1 may come into contact with each other during quenching (cooling), causing elliptical deformation of the annular members 1.

[0045] After quenching (cooling), the basket 10 is again moved to the base 33 of the carry-in section 30, and then moved to a tempering furnace (not shown), where tempering (heating and cooling) is performed on the multiple annular members 1. The tempering is performed at 150 to 300°C for 1 to 2 hours.

[0046] (Grinding process) After the heat treatment step, a grinding step is performed to grind the annular member 1. In the grinding step, the inner and outer diameter surfaces of the annular member 1 are ground to produce a bearing ring. According to the manufacturing method of the present application, elliptical deformation of the annular member 1 due to heat treatment is suppressed and the circularity of the annular member 1 is good, so that the amount of grinding required in the grinding step can be reduced, and the number of grinding steps can be reduced.

[0047] The bearing race completed by the above method can then be assembled with rolling elements and a cage to form a bearing.

[0048] (Example) Next, the effect of the arrangement of the multiple annular members 1 on the basket 10 on the elliptical deformation (roundness) of the annular members 1 after heat treatment was examined.

[0049] In Example 1, as shown in Fig. 1, a plurality of annular members 1 are housed in a basket 10 so as not to come into contact with one another. The number of annular members 1 arranged in one basket 10 is 42, and 16 of these baskets 10 are stacked in two rows as shown in Fig. 3, and heat treatment is performed. Therefore, 1344 (42 x 16 x 2) annular members 1 are heat treated simultaneously.

[0050] In Example 2, as shown in Fig. 5, a plurality of annular members 1 are housed in a basket 10 so as not to come into contact with one another. In Example 2, the number of annular members 1 arranged on the basket 10 is reduced in order to further increase the distance between adjacent annular members 1, as compared to Example 1. The number of annular members 1 arranged on one basket 10 is nine, and 12 of these baskets 10 are stacked in two rows as shown in Fig. 3, and heat treatment is performed. Therefore, 216 (9 x 12 x 2) annular members 1 are heat treated simultaneously.

[0051] In the comparative example (L=0), a plurality of annular members 1 are packed tightly on a basket 10 as shown in Fig. 2. The number of annular members 1 arranged in one basket 10 is 54, and these baskets 10 are stacked in 12 stages, which are arranged in two rows as shown in Fig. 3, and subjected to heat treatment. Therefore, 1296 (54 x 12 x 2) annular members 1 are heat treated at the same time.

[0052] The material of the annular member 1 used in Example 1, Example 2, and Comparative Example is steel with a carbon concentration of 0.4 wt%, to which appropriate amounts of alloy elements such as Cr and Mn are added in order to ensure hardenability in oil cooling. This steel was used as the material, and formed into a predetermined size by machining, and various effects were evaluated. It was confirmed that when annular members made from the above material were quenched under the heat treatment conditions described in this application, all of the annular members 1 and all of the heat treatment conditions were sufficiently hardened.

[0053] The outer diameter of the annular member 1 was about φ75 mm. In the heat treatment process, the annular member 1 was subjected to carbonitriding treatment for 3.5 hours in a batch-type heating furnace, and then secondary heating, quenching in oil at about 100°C (secondary quenching), and tempering treatment were performed. The roundness of multiple annular members 1 that had been subjected to this heat treatment was measured.

[0054] The results of measuring the roundness of a number of annular members 1 after carbonitriding are shown in Figures 6(a) to (c). In Figures 6(a) to (c), the horizontal axis represents the roundness (μm) and the vertical axis represents the number of annular members 1 having a roundness within the corresponding range. Figures 6(a) to (c) show the results of measuring the roundness of the comparative example, example 1, and example 2, respectively. The results of Figures 6(a) to (c) are summarized in Table 1 below.

[0055] [Table 1]

[0056] In the comparative example, among the multiple annular members 1, the maximum circularity was 200 μm, the minimum circularity was 20 μm, and the average circularity was 85 μm. In the example 1, among the multiple annular members 1, the maximum circularity was 160 μm, the minimum circularity was 10 μm, and the average circularity was 58 μm. In the example 2, the maximum circularity was 120 μm, the minimum circularity was 10 μm, and the average circularity was 43 μm. Thus, it can be seen that the circularity of the examples 1 and 2 is better than that of the comparative example. In particular, the circularity of the example 2, in which the gap between the adjacent annular members 1 is set large, is even better than that of the example 1.

[0057] The results of measuring the roundness of a number of annular members 1 after secondary quenching are shown in Figures 7(a) to (c). In Figures 7(a) to (c), the horizontal axis represents the roundness (μm) and the vertical axis represents the number of annular members 1 having a roundness within the corresponding range. Figures 7(a) to (c) show the results of measuring the roundness of the comparative example, example 1, and example 2, respectively. The results of Figures 7(a) to (c) are summarized in Table 2 below.

[0058] [Table 2]

[0059] In the comparative example, the maximum circularity of the multiple annular members 1 was 260 μm, the minimum circularity was 20 μm, and the average circularity was 108 μm. In the first example, the maximum circularity was 220 μm, the minimum circularity was 10 μm, and the average circularity was 68 μm. In the second example, the maximum circularity was 140 μm, the minimum circularity was 10 μm, and the average circularity was 52 μm. As in the roundness measurement after carbonitriding, the roundness of the first and second examples was better than that of the comparative example in the roundness measurement after secondary quenching. In particular, the second example, in which the gap between adjacent annular members 1 was set large, had a better roundness than the first example.

[0060] As described above, it has become clear that elliptical deformation can be suppressed when the annular members 1 are heat treated while being arranged at a fixed interval. In Examples 1 and 2, since the annular members 1 after heat treatment are suppressed in elliptical deformation and have good roundness, the amount of grinding can be reduced in the grinding process after heat treatment, resulting in a significant cost reduction effect. [Explanation of symbols]

[0061] 1 Annular member 10. Basket 11 Bottom 13 Flange 20 Heating furnace (batch type heating furnace) 30 Loading section 31 Roller 33 Foundation 40 Heating section 41 Roller 43 Foundation 45 Burner 47 Fans 50 Cooling section 51 Roller 53 Foundation 55 Circulation device 56 Screw 57 Guide member 60 Conveyor 61 Roller 63 Foundation 65 cylinders 71 First Door 73 Second Door O Cooling oil (cooling liquid)

Claims

1. A method for manufacturing a bearing ring, comprising the steps of: an annular member arrangement step of arranging a plurality of annular members that will become bearing races on a basket such that the central axes of the annular members face in the vertical direction; a basket placement step of placing the basket inside a heating furnace; a heat treatment step of heat treating the plurality of annular members arranged on the basket; Including, In the annular member arrangement step, the plurality of annular members are arranged on the basket so as not to come into contact with each other; In the heat treatment step, the plurality of annular members are quenched by performing heating and cooling while maintaining the arrangement of the plurality of annular members on the basket; During the quenching in the heat treatment step, the basket is immersed in a cooling liquid stored in a liquid tank, and the cooling liquid is caused to flow in an up-down direction to contact the plurality of annular members, thereby cooling the plurality of annular members; The cooling liquid passes through the mesh-like basket in the vertical direction, flows through the central hole of the annular member in the vertical direction, and flows between adjacent annular members in the vertical direction. A method for manufacturing a bearing ring.

2. The method for manufacturing a bearing race according to claim 1 , wherein the plurality of annular members are set at predetermined positions in the basket by a positioning member.

3. The heating furnace is a batch type heating furnace. A method for manufacturing a bearing ring according to claim 1 or 2.

4. In the annular member arranging step, the plurality of annular members are arranged in a staggered pattern. A method for manufacturing a bearing ring according to any one of claims 1 to 3.

5. In the heat treatment step, the plurality of annular members are carburized. A method for manufacturing a bearing ring according to any one of claims 1 to 4.

6. In the heat treatment step, the plurality of annular members are subjected to a nitriding treatment. A method for manufacturing a bearing ring according to any one of claims 1 to 4.

7. In the heat treatment step, the plurality of annular members are subjected to carbonitriding treatment. A method for manufacturing a bearing ring according to any one of claims 1 to 4.

8. In the heat treatment step, the plurality of annular members are deep-quenched. A method for manufacturing a bearing ring according to any one of claims 1 to 4.

9. In the heat treatment step, after the quenching is performed on the plurality of annular members, the plurality of annular members are further subjected to tempering. A method for manufacturing a bearing ring according to any one of claims 1 to 8.

10. The method further includes a grinding step of grinding the annular member after the heat treatment step. A method for manufacturing a bearing ring according to any one of claims 1 to 9.

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