JP7759545B2 - Annular member and method for manufacturing the same - Google Patents

Description

The present invention relates to an annular member and a method for manufacturing an annular member.

Steel components used in automotive parts and other applications are required to have high resistance to wear and fatigue. For this reason, these components are carburized and quenched. Carburizing and quenching improves the wear resistance and fatigue resistance of the surface. However, quenching generates thermal stress due to temperature changes and stress associated with volume changes due to phase transformation, causing distortion within the component. This distortion manifests as deformation and dimensional changes after quenching. If post-processing is performed to correct this, it will increase costs and construction time. Therefore, reducing heat treatment distortion is a challenge.

JP 2010-174289 A discloses a method for preventing distortion during heat treatment by providing heat transfer coefficient reduction means in areas of the component to be quenched where cooling is likely to proceed, and/or heat transfer coefficient acceleration means in areas of the component to be quenched where cooling is delayed, in order to prevent deformation due to distortion during heat treatment.

JP 2019-143211 A discloses a method for manufacturing an annular gear having a through hole for fixing a shaft, which prevents large differences in inner diameter depending on the position in the axial direction. This manufacturing method includes a suppression step of applying a carburization inhibitor to an annular gear material made of steel and having a through hole, and a carburization-hardening step of applying the carburization inhibitor to the gear material applied in the suppression step. The gear material includes a cylindrical portion having a pair of end faces, an inner peripheral surface, and an outer peripheral surface, and a plurality of teeth provided on the outer peripheral surface of the cylindrical portion. In the suppression step, a carburization inhibitor is applied to the pair of end faces.

JP 2010-174289 A Japanese Patent Application Laid-Open No. 2019-143211

When the roundness of sleeves used in automotive parts deteriorates due to deformation during heat treatment, it becomes impossible to pass a shaft or other part through the sleeve, which can be a problem. JP 2019-143211 A discloses a method for preventing large differences in inner diameter depending on the axial position, but does not mention how to prevent the roundness from deteriorating.

An object of the present invention is to provide a method for manufacturing an annular member in which deterioration of roundness is suppressed. Another object of the present invention is to provide an annular member in which deterioration of roundness is suppressed.

A method for manufacturing an annular member according to one embodiment of the present invention is a method for manufacturing an annular member by carburizing and quenching an annular raw material, in which the raw material has a first portion with a constant inner diameter and a second portion including a portion with an inner diameter smaller than the inner diameter of the first portion, and carburizing and quenching are performed by providing a non-carburized portion on at least one of a portion of the inner surface of the first portion and a portion of the outer surface of the second portion.

An annular member according to one embodiment of the present invention is an annular member having carburized layers on its inner and outer peripheral surfaces, and is equipped with a first portion having a constant inner diameter and a second portion including a portion whose inner diameter is smaller than the inner diameter of the first portion. At least one of a portion of the inner peripheral surface of the first portion and a portion of the outer peripheral surface of the second portion has a non-carburized portion where the carburized layer is not formed.

The present invention provides an annular component with reduced deterioration in roundness.

FIG. 1 is a cross-sectional view that schematically shows the configuration of a toothed annular member, which is an example of an annular member. FIG. 2 is a diagram showing the change in shape of the toothed annular member before and after carburizing and quenching, obtained by heat treatment simulation, at a deformation magnification of 70 times. FIG. 3A is a graph showing the amount of displacement of the outer radius of the toothed portion, the amount of displacement of the outer radius of the toothless portion, and the change in ellipticity γ over time during hardening when carburizing is performed. FIG. 3B is a graph showing the amount of displacement of the outer radius of the toothed portion, the amount of displacement of the outer radius of the toothless portion, and the change in ellipticity γ over time during hardening when carburizing is not performed. FIG. 4 is a diagram showing the change in shape of the toothed annular member before and after the temperature change, obtained by an analysis in which a temperature rise is applied to the inner periphery of the toothless portion, with the amount of deformation emphasized. FIG. 5 is a diagram showing a pattern in which a non-carburized portion is provided on a part of the surface of the toothed annular member. FIG. 6 is a cross-sectional view schematically showing the configuration of a stepped annular member, which is another example of the annular member. FIG. 7 is a graph showing the change in the outer radius of the thick-walled portion during hardening, the change in the outer radius of the thin-walled portion, and the ellipticity γ over time when carburizing is performed. FIG. 8 is a cross-sectional view schematically showing the configuration of an example of an annular material used in the method for manufacturing an annular member according to the first embodiment of the present invention. FIG. 9 is a cross-sectional view schematically showing the configuration of an example of an annular material used in the method for manufacturing an annular member according to the second embodiment of the present invention. FIG. 10 is a diagram showing the dimensions of the members used in analysis example 1. FIG. 11 is a diagram showing the history of heat treatments used in the analysis example. FIG. 12 is a diagram showing the heat transfer coefficient during quenching used in the analysis example. FIG. 13 is a schematic diagram showing a case where a non-carburized portion is provided on the outer peripheral surface of a toothed portion (pattern A) and a case where a non-carburized portion is provided on the inner peripheral surface of a toothless portion (pattern B). FIG. 14 is a graph showing the relationship between the ratio of the non-carburized portion to the circumference and the ellipticity. FIG. 15 is a diagram showing dimensions of members used in analysis example 2. FIG. 16 is a graph showing the relationship between the ratio of the non-carburized portion to the circumference and the ellipticity.

During quenching, components undergo thermal contraction due to cooling and volume expansion due to phase transformation. When a component is immersed in oil during quenching, cooling proceeds faster near the surface and slower in the interior. As a result, the volume change that occurs within the component varies depending on the location and is affected by the shape.

The inventors conducted a heat treatment simulation analysis of the deformation that occurs when carburizing and quenching an annular material, and obtained the following findings. Detailed conditions for the heat treatment simulation are described below.

[Analysis of toothed annular members]
1 is a cross-sectional view showing a schematic configuration of a toothed annular member 10, which is an example of an annular member. The toothed annular member 10 has a toothless portion 11 having no teeth on its inner circumferential surface, and a toothed portion 12 having a plurality of teeth on its inner circumferential surface.

Figure 2 shows the change in shape of the toothed annular member 10 before and after carburizing and quenching, obtained through a heat treatment simulation, at a deformation magnification of 70 times. When carburizing and quenching is performed, the toothed annular member 10 deforms into an elliptical shape with the toothed portion 12 as its major axis.

To investigate the cause of this deformation, an analysis was conducted on the toothed annular member 10 when it was quenched without being carburized. As a result, no oval deformation occurred. This suggests that the cause of the oval deformation of the toothed annular member 10 is related to carburization.

Here, the ellipticity γ is introduced as an index for evaluating the elliptical deformation. The ellipticity γ is given by the following equation, where a is the outer diameter at the center of the toothed portion 12 and b is the outer diameter at the center of the toothless portion 11.
γ=(1-a/b)×100 (%)

A positive value for the ellipticity γ means that the toothed annular member 10 is elliptical, with its major axis aligned in the direction of the toothless portion 11. A negative value for the ellipticity γ means that the toothed annular member 10 is elliptical, with its major axis aligned in the direction of the toothed portion 12.

Figures 3A and 3B are graphs showing the change in the outer radius (mm) of the toothed portion 12 and the outer radius (mm) of the toothless portion 11 during hardening, and the ellipticity γ (%) over time, for cases where carburizing was performed (Figure 3A) and not (Figure 3B). The horizontal axis represents the elapsed time (s) from the start of hardening (start of cooling). The change in the outer radius of the toothed portion 12 and the toothless portion 11 is based on the outer radius of the toothed portion 12 and the toothless portion 11 before heating (20°C). The temporary large decrease in ellipticity γ immediately after the start of hardening is due to the difference in the timing at which rapid cooling begins between the toothed portion 12 and the toothless portion 11, resulting in a temporary large temperature difference.

When carburizing was performed (Figure 3A), the ellipticity γ decreased approximately 200 seconds after the start of quenching, and the final ellipticity γ became a negative value. On the other hand, when carburizing was not performed (Figure 3B), this trend was not observed, and the ellipticity became close to 0 approximately 30 seconds after the start of quenching. Since this time corresponds to the occurrence of phase transformation in the carburized area, it is thought that the phase transformation in the carburized area is the cause of the elliptical deformation.

Carburizing creates a gradient in carbon concentration, with a high carbon concentration on the surface and a low carbon concentration in the interior. This difference in carbon concentration also results in differences in the structure after quenching. Table 1 shows the carbon concentration and structure of each part of the toothed annular member 10 obtained through heat treatment simulation. In Table 1, the "Non-carburized part" column shows the carbon concentration and structure of the central part in the thickness direction of the toothed annular member 10, which is an area that is hardly affected by carburizing. The "Carburized part of toothed part" and "Carburized part of toothless part" columns show the carbon concentration and structure of the outermost layer on the inner surface of the toothed part 12 and toothless part 11, respectively. The "F," "P," "B," "M," and "A" in the structure represent ferrite, pearlite, bainite, martensite, and austenite, respectively.

As shown in Table 1, the carburized portion of the toothed portion 12 has a higher carbon concentration than the carburized portion of the toothless portion 11. Focusing on the structure, the carburized portion of the toothed portion 12 contains less martensite and more austenite than the carburized portion of the toothless portion 11. Therefore, the carburized portion of the toothed portion 12 has a higher density and a smaller amount of volumetric expansion than the carburized portion of the toothless portion 11. It is believed that this difference in volumetric expansion causes the toothed annular member 10 to deform into an ellipse with its major axis aligned with the direction of the toothed portion 12.

To confirm this mechanism, an analysis was conducted in which a temperature rise was applied to the portion corresponding to the inner circumference of the toothless portion 11 to a degree that would not cause a phase transformation. This simulated a situation in which a temperature rise causes different amounts of volumetric expansion between the toothed portion 12 and the toothless portion 11 on the inner circumference of the toothed annular member 10. Here, the toothed portion 12, which does not experience a temperature rise, has a high density and a small amount of volumetric expansion, while the toothless portion 11, which does experience a temperature rise, has a low density and a large amount of volumetric expansion.

Figure 4 shows the change in shape of the toothed annular member 10 before and after applying a temperature change, as obtained through this analysis, with the amount of deformation emphasized. As shown in Figure 4, the difference in volume change due to the temperature increase also caused the toothed annular member 10 to deform into an ellipse with the toothed portion 12 as the major axis. This shows that the difference in the amount of volumetric expansion between the toothed portion 12 and the non-toothed portion 11 causes the elliptical deformation.

The inventors came up with the idea that oval deformation of a component can be reduced by providing carburized and non-carburized regions (non-carburized regions) rather than carburizing the entire surface of the component. The carburized and non-carburized regions differ in carbon concentration and the structure that develops during quenching, resulting in a difference in the amount of volumetric expansion that occurs during quenching. In the analysis example shown in Table 1, the carburized regions have a lower density and therefore a larger volume than the non-carburized regions. The non-carburized regions have a higher density and a smaller volume. These regions are mutually constrained within the same component, causing deformation. It is believed that providing non-carburized regions in appropriate regions can suppress oval deformation and make the final shape closer to a perfect circle.

Let's consider the effect of providing a non-carburized portion on part of the surface. Figure 5 shows patterns for providing a non-carburized portion on part of the surface of the toothed annular member 10. Specifically, Figure 5 shows cases where a non-carburized portion is provided on the entire outer surface of the toothed portion 12 (pattern A), the entire inner surface of the toothless portion 11 (pattern B), the entire outer surface of the toothless portion 11 (pattern C), and the entire inner surface of the toothed portion 12 (pattern D).

A heat treatment simulation was performed using these data to determine the ellipticity γ after carburizing and quenching. The non-carburized areas were set by not changing the carbon concentration in the relevant areas. In this analysis, heat transfer coefficients obtained from two types of quenching oil with different properties (referred to as "hot oil" and "cold oil") were used. The results are shown in Table 2.

As shown in Table 2, regardless of the type of quenching oil, there was a tendency for the outer diameter to increase in areas where the inner surface was made non-carburized, and for the outer diameter to decrease in areas where the outer surface was made non-carburized. Specifically, in pattern A, where the outer surface of the toothed portion 12 was made non-carburized, the ellipticity γ increased as the outer diameter a of the toothed portion 12 decreased. Similarly, in pattern B, the ellipticity γ increased as the outer diameter b of the toothless portion 11 increased; in pattern C, the ellipticity γ decreased as the outer diameter b of the toothless portion 11 decreased; and in pattern D, the ellipticity γ decreased as the outer diameter a of the toothed portion 12 increased.

As mentioned above, if no non-carburized portion is provided, the toothed annular member 10 will deform into an ellipse with its major axis aligned with the direction of the toothed portion 12. Therefore, by providing a non-carburized portion of an appropriate size on at least one of a portion of the outer peripheral surface of the toothed portion 12 and a portion of the inner peripheral surface of the toothless portion 11, it is believed that the deformation can be counteracted and the elliptical deformation can be reduced.

[Analysis of stepped annular members]
6 is a cross-sectional view schematically illustrating the configuration of a stepped annular member 20, which is another example of an annular member. The stepped annular member 20 has a thin-walled portion 21 and a thick-walled portion 22 having an inner diameter smaller than that of the thin-walled portion 21.

As with the toothed annular member 10, a heat treatment simulation was performed on the stepped annular member 20 to determine the ellipticity γ after carburizing and quenching. In calculating the ellipticity γ of the stepped annular member 20, the outer diameter at the center of the thick-walled portion 22 was set to a, and the outer diameter at the center of the thin-walled portion 21 was set to b.

Figure 7 is a graph showing the change over time in the displacement (mm) of the outer radius of the thick-walled portion 22, the displacement (mm) of the outer radius of the thin-walled portion 21, and the ellipticity γ (%) during hardening when carburizing was performed. As with the toothed annular member 10 (Figure 3A), the final ellipticity γ of the stepped annular member 20 also became a negative value. Furthermore, although not shown, no elliptical deformation occurred when carburizing was not performed. From this, it is believed that the cause of elliptical deformation in the stepped annular member 20 is also related to carburizing.

As with the toothed annular member 10, a heat treatment simulation was performed on the stepped annular member 20 by varying the arrangement of the non-carburized portions, and the ellipticity γ after carburizing and quenching was determined. Specifically, a heat treatment simulation was performed with the entire outer surface of the thick-walled portion 22 (pattern A), the entire inner surface of the thin-walled portion 21 (pattern B), the entire outer surface of the thin-walled portion 21 (pattern C), and the entire inner surface of the thick-walled portion 22 (pattern D) as non-carburized portions, and the ellipticity γ after carburizing and quenching was determined. The results are shown in Table 3.

As with the toothed annular member 10 (Table 2), the stepped annular member 20 also showed a tendency for the outer diameter to increase in areas where the inner circumferential surface was non-carburized, and for the outer diameter to decrease in areas where the outer circumferential surface was non-carburized.

For this reason, it is believed that in the stepped annular member 20, as in the toothed annular member 10, deformation can be counteracted and elliptical deformation reduced by providing an appropriately sized non-carburized portion on at least one of a portion of the outer peripheral surface of the thick-walled portion 22 and a portion of the inner peripheral surface of the thin-walled portion 21.

The present invention was completed based on the above findings. Below, an embodiment of the present invention will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are designated by the same reference numerals, and their description will not be repeated. The dimensional ratios between the components shown in each drawing do not necessarily represent the actual dimensional ratios.

[First embodiment]
The method for manufacturing an annular member according to the first embodiment of the present invention is a method for manufacturing an annular member by carburizing and quenching an annular material.

Figure 8 is a cross-sectional view showing a schematic configuration of material 30, an example of an annular material used in the manufacturing method of an annular member according to this embodiment. Material 30 has a first portion 31 having a constant inner diameter and a second portion 32 including a portion whose inner diameter is smaller than the inner diameter of first portion 31.

The inner circumferential surface of the second portion 32 is formed with a plurality of teeth that protrude a predetermined height from the inner circumferential surface of the first portion 31. That is, in this embodiment, these tooth portions correspond to "portions whose inner diameter is smaller than the inner diameter of the first portion 31." Note that in the example of Figure 8, the inner diameter of the portions between the teeth of the second portion 32 is the same as the inner diameter of the first portion 31, but these do not have to be the same. Note that the inner diameter of the portions between the teeth of the second portion 32 is preferably equal to or smaller than the inner diameter of the first portion 31. That is, it is preferable that the inner diameter of the second portion 32 throughout is equal to or smaller than the inner diameter of the first portion 31.

Although not limited to this, it is preferable that the material 30 have a constant outer diameter.

The material of the base material 30 may be, for example, steel. While not limited to this, carbon steel for mechanical structures specified in JIS G 4051 and alloy steel for mechanical structures specified in JIS G 4053 are suitable.

In this embodiment, a non-carburized portion is provided on a portion 31a of the inner surface of the first portion 31 or a portion 32a of the outer surface of the second portion 32, and then carburized and quenched. Non-carburized portions may also be provided on both the portion 31a of the inner surface of the first portion 31 and the portion 32a of the outer surface of the second portion 32.

More specifically, carburization is performed with a carburization inhibitor or jig placed on at least one of a portion 31a of the inner surface of the first portion 31 and a portion 32a of the outer surface of the second portion 32, and then quenching is performed. The carburization inhibitor may be applied to the area where the non-carburized portion is to be formed, or a sheet-like material may be attached. The carburization inhibitor is not limited to this, but for example, a carburization inhibitor whose main component is a boric acid compound can be used.

When a non-carburized portion is provided on part 31a of the inner peripheral surface of first portion 31, the area of the non-carburized portion is preferably 1/8 or less of the area of the inner peripheral surface of first portion 31. In this case, the area of the non-carburized portion is more preferably 1/16 or less of the area of the inner peripheral surface of first portion 31. In this case, even a small non-carburized portion will be effective, but the lower limit of the area of the non-carburized portion is preferably 1/128 of the area of the inner peripheral surface of first portion 31, and more preferably 1/64 of the area of the inner peripheral surface of first portion 31.

When a non-carburized portion is provided on part 32a of the outer peripheral surface of second portion 32, the area of the non-carburized portion is preferably 1/8 or less of the area of the outer peripheral surface of second portion 32. In this case, the area of the non-carburized portion is more preferably 1/16 or less of the area of the outer peripheral surface of second portion 32. In this case, even a small amount of non-carburized portion will be effective, but the lower limit of the area of the non-carburized portion is preferably 1/128 of the area of the outer peripheral surface of second portion 32, and more preferably 1/64 of the area of the outer peripheral surface of second portion 32.

When non-carburized portions are provided on both the portion 31a of the inner surface of the first portion 31 and the portion 32a of the outer surface of the second portion 32, it is preferable to set the ratio (area of the non-carburized portion on the portion 31a of the inner surface of the first portion 31) / (area of the inner surface of the first portion 31) + (area of the non-carburized portion on the portion 32a of the outer surface of the second portion 32) / (area of the outer surface of the second portion 32) to 1/8 or less. It is more preferable to set the ratio (area of the non-carburized portion on the portion 31a of the inner surface of the first portion 31) / (area of the inner surface of the first portion 31) + (area of the non-carburized portion on the portion 32a of the outer surface of the second portion 32) / (area of the outer surface of the second portion 32) to 1/16 or less. The lower limit of (area of the non-carburized portion provided on part 31a of the inner surface of first portion 31)/(area of the inner surface of first portion 31) + (area of the non-carburized portion provided on part 32a of the outer surface of second portion 32)/(area of the outer surface of second portion 32) is preferably 1/128, and more preferably 1/64.

Through the above steps, an annular member is manufactured. Carburized quenching forms a carburized layer on the inner and outer peripheral surfaces, excluding non-carburized portions. In other words, the annular member according to this embodiment is an annular member having carburized layers on the inner and outer peripheral surfaces, and comprises a first portion 31 with a constant inner diameter and a second portion 32 including a portion whose inner diameter is smaller than the inner diameter of the first portion 31. At least one of a portion 31a of the inner peripheral surface of the first portion 31 and a portion 32a of the outer peripheral surface of the second portion 32 has a non-carburized portion where no carburized layer is formed.

This embodiment produces an annular component with reduced deterioration in roundness.

Second Embodiment
In the method for manufacturing an annular member according to the second embodiment of the present invention, a material having a different shape from the material used in the method for manufacturing an annular member according to the first embodiment is used.

Figure 9 is a cross-sectional view schematically illustrating the configuration of material 40, an example of an annular material used in the manufacturing method for an annular member according to this embodiment. Similar to material 30, material 40 has a first portion 41 having a constant inner diameter and a second portion 42 including a portion whose inner diameter is smaller than the inner diameter of first portion 41. In this embodiment, the inner diameter of second portion 42 is smaller than the inner diameter of first portion 41 throughout. It is preferable that the inner diameter of second portion 42 is constant.

In this embodiment, a non-carburized portion is provided on a portion 41a of the inner surface of the first portion 41 or a portion 42a of the outer surface of the second portion 42, and then carburized and quenched. Non-carburized portions may also be provided on both the portion 41a of the inner surface of the first portion 41 and the portion 42a of the outer surface of the second portion 42. The preferred area of the non-carburized portion is the same as in the first embodiment.

The annular member is manufactured through the above process. In this embodiment, too, carburized quenching forms a carburized layer on the inner and outer peripheral surfaces, excluding non-carburized portions. That is, the annular member according to this embodiment is an annular member having carburized layers on the inner and outer peripheral surfaces, and comprises a first portion 41 having a constant inner diameter and a second portion 42 including a portion whose inner diameter is smaller than the inner diameter of the first portion 41. At least one of a portion 41a of the inner peripheral surface of the first portion 41 and a portion 42a of the outer peripheral surface of the second portion 42 has a non-carburized portion where no carburized layer is formed.

This embodiment also produces an annular member with reduced deterioration in roundness.

[Analysis example 1]
A heat treatment simulation was used to analyze a steel annular component, simulating carburizing and quenching, to determine its shape after carburizing and quenching. Figure 10 shows the dimensions of the component used in the analysis. This component is cylindrical, with an outer diameter of 120 mm, an inner diameter of 105 mm, and a thickness of 7.5 mm. It has a toothed portion with 2.5 mm-high teeth and a toothless portion with no teeth on the inner circumferential surface. Due to the symmetry of the component's shape, the analysis was performed on a quarter-scale model shown in Figure 10. The component was assumed to be made of SCr2. Experimental values were used for the mechanical properties, and calculated values derived from the chemical composition shown in Table 4 were used for the thermal properties.

Figure 11 shows the heat treatment history used in the analysis. The heat treatment consists of austenitizing, carburizing, quenching (oil cooling), and air cooling. Figure 12 shows the heat transfer coefficient during quenching. Here, heat transfer coefficients obtained from two types of quenching oil with different properties (referred to as "hot oil" and "cold oil") were used. The non-carburized areas were set by not changing the carbon concentration in the relevant areas during the carburizing process.

Figure 13 is a schematic diagram showing the case where a non-carburized portion is provided on the outer peripheral surface of the toothed portion (Pattern A), and the case where a non-carburized portion is provided on the inner peripheral surface of the toothless portion (Pattern B). The ratio l1/L1, the ratio of the circumferential length l1 of the non-carburized portion to the outer peripheral surface L1 of the part, and the ratio l2/L2, the ratio of the circumferential length l2 of the non-carburized portion to the inner peripheral surface L2 of the part (calculated from the inner diameter of the toothless portion) (hereinafter, l1/L1 and l2/L2 are collectively referred to as the "ratio of the non-carburized portion to the circumference") were varied from 0 (no non-carburized portion) to 1/2.

The elliptical deformation was evaluated by calculating the ellipticity γ using the displacement of point P1 in the x direction and the displacement of point P2 in the y direction in Figure 10.

Figure 14 is a graph showing the relationship between the ratio of the non-carburized portion to the circumference and the ellipticity γ. When no non-carburized portion is provided (when the ratio of the non-carburized portion to the circumference is 0), the ellipticity γ is a negative value, indicating elliptical deformation with the toothed portion as the major axis. When a non-carburized portion is provided, the ellipticity γ increases as the ratio of the non-carburized portion to the circumference increases, regardless of the type of quenching oil, and in both Pattern A and Pattern B. When the ratio of the non-carburized portion to the circumference is 1/16 or less (when the area of the non-carburized portion on the outer surface of the toothed portion is 1/8 or less of the area of the outer surface of the toothed portion, or when the area of the non-carburized portion on the inner surface of the toothless portion is 1/8 or less of the area of the inner surface of the toothless portion), the absolute value of the ellipticity γ is smaller than when no non-carburized portion is provided, resulting in a shape closer to a perfect circle.

[Analysis example 2]
A heat treatment simulation was performed on the annular member shown in Fig. 15. Conditions other than the member dimensions and shape were the same as those in Analysis Example 1. The annular member in Fig. 15 has thick-walled portions and thin-walled portions instead of the toothed portions and non-toothed portions of the annular member in Fig. 10.

Figure 16 is a graph showing the relationship between the proportion of the non-carburized portion to the circumference and the ellipticity γ for the component in Figure 15. Even in this case, when the proportion of the non-carburized portion to the circumference is 1/16 or less (when the area of the non-carburized portion on the outer surface of the thick portion is 1/8 or less of the area of the outer surface of the thick portion, or when the area of the non-carburized portion on the inner surface of the thin portion is 1/8 or less of the area of the inner surface of the thin portion), the absolute value of the ellipticity γ is smaller than when no non-carburized portion is provided, resulting in a shape that is closer to a perfect circle.

The above describes an embodiment of the present invention, but the above-described embodiment is merely an example for implementing the present invention. Therefore, the present invention is not limited to the above-described embodiment, and it is possible to appropriately modify the above-described embodiment and implement it without departing from the spirit of the present invention.

10: Toothed annular member 11: Toothless portion 12: Toothed portion 20: Stepped annular member 21: Thin portion 22: Thick portion 30, 40: Material 31, 41: First portion 32, 42: Second portion

Claims (8)

A method for manufacturing an annular member by carburizing and quenching an annular material, comprising:
the blank has a first portion having a constant inner diameter and a second portion including a portion having an inner diameter smaller than the inner diameter of the first portion,
a non-carburized portion is provided on one of a part of the inner peripheral surface of the first portion and a part of the outer peripheral surface of the second portion, and the non-carburized portion is carburized and quenched;
when the non-carburized portion is provided on a part of the inner circumferential surface of the first portion, the area of the non-carburized portion is ⅛ or less of the area of the inner circumferential surface of the first portion,
A method for manufacturing an annular member, wherein when the non-carburized portion is provided on part of the outer peripheral surface of the second portion, the area of the non-carburized portion is 1/8 or less of the area of the outer peripheral surface of the second portion. The method for manufacturing the annular member according to claim 1,
A method for manufacturing an annular member, wherein the second portion has an inner diameter that is equal to or smaller than the inner diameter of the first portion throughout. A method for manufacturing an annular member according to claim 1 or 2,
The method for manufacturing an annular member, wherein a plurality of teeth are formed on an inner peripheral surface of the second portion. A method for manufacturing an annular member according to claim 1 or 2,
The second portion has an inner diameter that is smaller than the inner diameter of the first portion throughout the entire length. An annular member having a carburized layer on an inner peripheral surface and an outer peripheral surface,
a first portion having a constant inner diameter;
a second portion including a portion having an inner diameter smaller than the inner diameter of the first portion,
a non-carburized portion where the carburized layer is not formed on one of a part of the inner circumferential surface of the first portion and a part of the outer circumferential surface of the second portion;
when the non-carburized portion is present on a part of the inner circumferential surface of the first portion, the area of the non-carburized portion is ⅛ or less of the area of the inner circumferential surface of the first portion,
an annular member, wherein when the non-carburized portion is present on part of the outer peripheral surface of the second portion, the area of the non-carburized portion is 1/8 or less of the area of the outer peripheral surface of the second portion. 6. The annular member according to claim 5,
The second portion has an inner diameter that is equal to or smaller than the inner diameter of the first portion throughout the annular member. 7. The annular member according to claim 5 or 6,
An annular member having a plurality of teeth formed on an inner circumferential surface of the second portion. 7. The annular member according to claim 5 or 6,
The second portion has an inner diameter that is smaller than the inner diameter of the first portion throughout the annular member.