Annular member and method for manufacturing the same

Abstract

To provide a manufacturing method of an annular member in which deterioration of roundness is suppressed.SOLUTION: Provided is a manufacturing method of an annular member by which an annular member is manufactured by carburizing and quenching an annular material 30. The material 30 has: a first part 31 with a constant inner diameter; and a second part 32 including a portion with an inner diameter smaller than that of the first part 31. A non-carburizing part is provided on at least one of one part 31a of an inner peripheral surface of the first part 31 and one part 32a of an outer peripheral surface of the second part 32, and is subjected to carburizing and quenching.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to an annular member and a method for manufacturing an annular member. [Background technology]

[0002] 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, which causes 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.

[0003] Japanese Patent Application Laid-Open Publication No. 2010-174289 discloses a method for hardening a material to be hardened to prevent distortion due to heat treatment, in which a heat transfer coefficient reducing means is provided in areas of the material to be hardened where cooling is likely to proceed, and / or a heat transfer coefficient promoting means is provided in areas of the material to be hardened where cooling is delayed, in order to prevent deformation due to heat treatment distortion.

[0004] Japanese Patent Application Laid-Open Publication No. 2019-143211 discloses a method for manufacturing an annular gear having a through hole for fixing a shaft, which method prevents large differences in inner diameter depending on the position in the axial direction. This manufacturing method includes a suppression step of providing a carburization inhibitor on an annular gear blank made of steel and having a through hole, and a carburization-quenching step of subjecting the gear blank provided with the carburization inhibitor in the suppression step. The gear blank 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, the carburization inhibitor is provided on the pair of end faces. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-174289 [Patent Document 2] Japanese Patent Application Publication No. 2019-143211 Summary of the Invention [Problem to be solved by the invention]

[0006] In sleeves used in automobile parts, if the roundness deteriorates due to deformation during heat treatment, it becomes impossible to pass a shaft or the like through the sleeve, which becomes 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.

[0007] 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. [Means for solving the problem]

[0008] 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, wherein the raw material has 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, and the raw material is carburized and quenched 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.

[0009] 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 provided 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, and has a non-carburized portion where the carburized layer is not formed on 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. [Effects of the Invention]

[0010] According to the present invention, an annular member in which deterioration of roundness is suppressed can be obtained. [Brief explanation of the drawings]

[0011] [Figure 1] 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. [Figure 2] FIG. 2 is a diagram showing the change in shape of the toothed annular member before and after carburizing and quenching at a deformation magnification of 70 times, obtained by heat treatment simulation. [Figure 3A] 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. [Figure 3B] 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 no carburizing is performed. [Figure 4] FIG. 4 is a diagram showing the change in shape of the toothed annular member before and after applying a temperature change, obtained by an analysis in which a temperature rise is applied to the inner circumference of the toothless portion, with the amount of deformation emphasized. [Figure 5] 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. [Figure 6] FIG. 6 is a cross-sectional view that schematically shows the configuration of a stepped annular member, which is another example of the annular member. [Figure 7] FIG. 7 is a graph showing the amount of displacement of the outer radius of the thick-walled portion during quenching, the amount of displacement of the outer radius of the thin-walled portion, and the change in ellipticity γ over time when carburizing is performed. [Figure 8] FIG. 8 is a cross-sectional view that schematically shows 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. [Figure 9] 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. [Figure 10] FIG. 10 is a diagram showing the dimensions of the members used in analysis example 1. [Figure 11] FIG. 11 is a diagram showing the history of heat treatments used in the analysis example. [Figure 12] FIG. 12 is a diagram showing the heat transfer coefficient during quenching used in the analysis example. [Figure 13] 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). [Figure 14] FIG. 14 is a graph showing the relationship between the ratio of the non-carburized portion to the circumference and the ellipticity. [Figure 15] FIG. 15 is a diagram showing the dimensions of the members used in the second analysis example. [Figure 16] FIG. 16 is a graph showing the relationship between the ratio of the non-carburized portion to the circumference and the ellipticity. DETAILED DESCRIPTION OF THE INVENTION

[0012] During quenching, components undergo thermal contraction due to cooling and volume expansion due to phase transformation. When components are immersed in oil during quenching, cooling proceeds quickly near the surface and slows down in the interior. Therefore, the volume change that occurs within the component varies depending on the location and is affected by the shape.

[0013] The present inventors have conducted a heat treatment simulation analysis of the deformation that occurs when an annular material is carburized and quenched, and have found the following: The detailed conditions of the heat treatment simulation will be described later.

[0014] [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 multiple teeth on its inner circumferential surface.

[0015] 2 is a diagram obtained by heat treatment simulation, showing the change in shape of the toothed annular member 10 before and after carburizing and quenching at a deformation magnification of 70. 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.

[0016] 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. From this, it is believed that the cause of the oval deformation of the toothed annular member 10 is related to carburizing.

[0017] 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 (%)

[0018] A positive value of the ellipticity γ means that the toothed annular member 10 has an elliptical shape with its major axis aligned with the direction of the toothless portion 11. A negative value of the ellipticity γ means that the toothed annular member 10 has an elliptical shape with its major axis aligned with the direction of the toothed portion 12.

[0019] 3A and 3B are graphs showing the change in the outer radius (mm) of the toothed portion 12 and the toothless portion 11, and the ellipticity γ (%) over time during hardening, for the case where carburizing was performed (FIG. 3A) and the case where no carburizing was performed (FIG. 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 ellipticity γ temporarily decreases significantly immediately after the start of hardening because the timing at which rapid cooling begins is different between the toothed portion 12 and the toothless portion 11, temporarily increasing the temperature difference.

[0020] When carburizing was performed (Fig. 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 (Fig. 3B), this trend was not observed, and the ellipticity became close to 0 approximately 30 seconds after the start of quenching. This time corresponds to the occurrence of phase transformation in the carburized area, and it is thought that this phase transformation in the carburized area is the cause of the elliptical deformation.

[0021] 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 by heat treatment simulation. In Table 1, the "Non-Carburized Area" column shows the carbon concentration and structure of the central part of the toothed annular member 10 in the thickness direction, which is an area that is hardly affected by carburizing. The "Carburized Area of ​​Toothed Area" and "Carburized Area of ​​Missing Tooth Area" columns show the carbon concentration and structure of the outermost layer on the inner surface of the toothed area 12 and the missing tooth area 11, respectively. The "F," "P," "B," "M," and "A" in the structure represent ferrite, pearlite, bainite, martensite, and austenite, respectively.

[0022] [Table 1]

[0023] 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. In terms of structure, the carburized portion of the toothed portion 12 contains less martensite and more austenite than the carburized portion of the toothless portion 11. As a result, 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.

[0024] To confirm this mechanism, an analysis was conducted in which a temperature rise was applied to the part 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 the toothed portion 12 and the toothless portion 11 on the inner circumference of the toothed annular member 10 would have different amounts of volumetric expansion due to a temperature rise. 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.

[0025] Figure 4 is a diagram obtained by this analysis, showing the change in shape of the toothed annular member 10 before and after applying a temperature change, 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 volume expansion between the toothed portion 12 and the non-toothed portion 11 causes the elliptical deformation.

[0026] 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 differences in the amount of volumetric expansion that occurs during quenching. In the analysis example shown in Table 1, the carburized region has a lower density and therefore a larger volume than the non-carburized region. The non-carburized region has a higher density and a smaller volume. These regions are mutually constrained within the same component, resulting in deformation. By providing non-carburized regions in appropriate areas, oval deformation can be suppressed, and the final shape can be closer to a perfect circle.

[0027] Let us consider the effect of providing a non-carburized portion on a portion of the surface. Fig. 5 shows patterns for providing a non-carburized portion on a portion of the surface of the toothed annular member 10. Specifically, Fig. 5 shows cases in which a non-carburized portion is provided on the entire outer peripheral surface of the toothed portion 12 (pattern A), the entire inner peripheral surface of the toothless portion 11 (pattern B), the entire outer peripheral surface of the toothless portion 11 (pattern C), and the entire inner peripheral surface of the toothed portion 12 (pattern D).

[0028] Using these, a heat treatment simulation was performed 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.

[0029] [Table 2]

[0030] As shown in Table 2, regardless of the type of quenching oil, there was a tendency for the outer diameter to increase in regions where the inner peripheral surface was made non-carburized, and for the outer peripheral surface to decrease. Specifically, in pattern A, where the outer peripheral surface of the toothed portion 12 was made non-carburized, the outer diameter a of the toothed portion 12 decreased, resulting in an increase in ellipticity γ. Similarly, in pattern B, the outer diameter b of the toothless portion 11 increased, resulting in an increase in ellipticity γ. In pattern C, the outer diameter b of the toothless portion 11 decreased, resulting in a decrease in ellipticity γ. In pattern D, the outer diameter a of the toothed portion 12 increased, resulting in a decrease in ellipticity γ.

[0031] As described 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 circumferential surface of the toothed portion 12 and a portion of the inner circumferential surface of the non-toothed portion 11, it is thought that the deformation can be counteracted and the elliptical deformation can be reduced.

[0032] [Analysis of stepped annular members] 6 is a cross-sectional view schematically showing 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.

[0033] As with the toothed annular member 10, a heat treatment simulation was performed to determine the ellipticity γ after carburizing and quenching for the stepped annular member 20. 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.

[0034] 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 the elliptical deformation of the stepped annular member 20 is also related to carburizing.

[0035] As with the toothed annular member 10, heat treatment simulations were also performed on the stepped annular member 20 by changing the arrangement of the non-carburized portions, and the ellipticity γ after carburizing and quenching was determined. Specifically, heat treatment simulations were performed on the entire outer peripheral surface of the thick-walled portion 22 (pattern A), the entire inner peripheral surface of the thin-walled portion 21 (pattern B), the entire outer peripheral surface of the thin-walled portion 21 (pattern C), and the entire inner peripheral 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.

[0036] [Table 3]

[0037] As in the case of the toothed annular member 10 (Table 2), the stepped annular member 20 also showed a tendency for the outer diameter to be larger in the region where the inner surface was made non-carburized, and for the outer diameter to be smaller in the region where the outer surface was made non-carburized.

[0038] For this reason, it is believed that in the stepped annular member 20, as in the case of the toothed annular member 10, the deformation can be counteracted and the elliptical deformation can be reduced by providing a non-carburized portion of an appropriate size on at least one of a part of the outer surface of the thick-walled portion 22 and a part of the inner surface of the thin-walled portion 21.

[0039] The present invention has been completed based on the above findings. Hereinafter, embodiments 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.

[0040] [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.

[0041] 8 is a cross-sectional view schematically illustrating the configuration of a blank 30, which is an example of an annular blank used in the method for manufacturing an annular member according to this embodiment. Blank 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.

[0042] 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, the toothed portions correspond to "portions whose inner diameter is smaller than the inner diameter of the first portion 31." Note that, in the example of FIG. 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 is equal to or smaller than the inner diameter of the first portion 31 throughout the entire second portion 32.

[0043] Although not limited to this, it is preferable that the material 30 has a constant outer diameter.

[0044] The material of the blank 30 is, for example, steel, but is not limited to this, and carbon steel material for machine structures of JIS G 4051 and alloy steel material for machine structures of JIS G 4053 are preferably used.

[0045] In this embodiment, a non-carburized portion is provided on a portion 31 a of the inner peripheral surface of the first portion 31 or a portion 32 a of the outer peripheral surface of the second portion 32, and then carburized and quenched. A non-carburized portion may be provided on both the portion 31 a of the inner peripheral surface of the first portion 31 and the portion 32 a of the outer peripheral surface of the second portion 32.

[0046] More specifically, carburization is performed with a carburization inhibitor or a jig placed on at least one of a portion 31a of the inner circumferential surface of the first portion 31 and a portion 32a of the outer circumferential surface of the second portion 32, and then quenching is performed. The carburization inhibitor may be applied to the area where a non-carburized portion is to be provided, or a sheet-like material may be attached. The carburization inhibitor is not limited to this, but for example, a carburization inhibitor containing a boric acid compound as its main component can be used.

[0047] 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 if the non-carburized portion is small, the effect can be obtained, 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.

[0048] 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.

[0049] When non-carburized portions are provided on both the portion 31a of the inner peripheral surface of the first portion 31 and the portion 32a of the outer peripheral surface of the second portion 32, it is preferable to set the ratio (area of ​​the non-carburized portion provided on the portion 31a of the inner peripheral surface of the first portion 31) / (area of ​​the inner peripheral surface of the first portion 31) + (area of ​​the non-carburized portion provided on the portion 32a of the outer peripheral surface of the second portion 32) / (area of ​​the outer peripheral 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 provided on the portion 31a of the inner peripheral surface of the first portion 31) / (area of ​​the inner peripheral surface of the first portion 31) + (area of ​​the non-carburized portion provided on the portion 32a of the outer peripheral surface of the second portion 32) / (area of ​​the outer peripheral surface of the second portion 32) to 1 / 16 or less. The lower limit of (area of ​​the non-carburized portion provided on a 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 provided on a portion 32a of the outer surface of the second portion 32) / (area of ​​the outer surface of the second portion 32) is preferably 1 / 128, and more preferably 1 / 64.

[0050] The annular member is manufactured through the above steps. Carburizing and quenching forms a carburized layer on the inner and outer peripheral surfaces, excluding the 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 includes 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 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.

[0051] According to this embodiment, an annular member in which deterioration of roundness is suppressed can be obtained.

[0052] [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.

[0053] 9 is a cross-sectional view schematically illustrating the configuration of a material 40, which is an example of an annular material used in the manufacturing method of an annular member according to this embodiment. Similar to the material 30, the 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 the first portion 41. In this embodiment, the inner diameter of the second portion 42 is smaller than the inner diameter of the first portion 41 throughout. It is preferable that the inner diameter of the second portion 42 is constant.

[0054] In this embodiment as well, a non-carburized portion is provided on a portion 41a of the inner peripheral surface of the first portion 41 or a portion 42a of the outer peripheral surface of the second portion 42, and carburized and quenched. A non-carburized portion may be provided on both the portion 41a of the inner peripheral surface of the first portion 41 and the portion 42a of the outer peripheral surface of the second portion 42. The preferred area of ​​the non-carburized portion is the same as in the first embodiment.

[0055] The annular member is manufactured through the above steps. In this embodiment, too, carburized layers are formed on the inner and outer peripheral surfaces, excluding the non-carburized portions, by carburizing and quenching. That is, the annular member according to this embodiment is an annular member having carburized layers on the inner and outer peripheral surfaces, and includes 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 41 a of the inner peripheral surface of the first portion 41 and a portion 42 a of the outer peripheral surface of the second portion 42 has a non-carburized portion where no carburized layer is formed.

[0056] According to this embodiment as well, an annular member in which deterioration of roundness is suppressed can be obtained.

[0057] [Analysis example 1] Assuming a steel annular component as the target, an analysis was conducted simulating carburizing and quenching using a heat treatment simulation to determine the 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, and has a toothed section with teeth 2.5 mm high and a toothless section with no teeth on the inner surface. Due to the symmetry of the component's shape, the analysis was conducted on only a 1 / 4 scale model as shown in Figure 10. Assuming that the component was 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.

[0058] [Table 4]

[0059] Figure 11 shows the heat treatment history used in the analysis. The heat treatment consisted of austenitizing, carburizing, quenching (oil quenching), and air cooling. Figure 12 shows the heat transfer coefficient during quenching. Here, the heat transfer coefficients used were obtained from two types of quenching oil with different properties (referred to as "hot oil" and "cold oil"). The non-carburized areas were set by not changing the carbon concentration in the relevant areas during the carburizing process.

[0060] 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 circumferential length l1 of the non-carburized portion to the outer peripheral surface L1 of the part, and the ratio l2 / L2, 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.

[0061] The elliptical deformation was evaluated by finding the ellipticity γ using the displacement of point P1 in the x direction and the displacement of point P2 in the y direction in FIG.

[0062] 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.

[0063] [Analysis example 2] A heat treatment simulation was performed on the annular member shown in Figure 15. Conditions other than the member dimensions and shape were the same as in Analysis Example 1. The annular member in Figure 15 has thick-walled and thin-walled portions instead of the toothed and non-toothed portions of the annular member in Figure 10.

[0064] Figure 16 is a graph showing the relationship between the ratio of the non-carburized portion to the circumference and the ellipticity γ for the member shown in Figure 15. Even in this case, 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 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 there is no non-carburized portion, resulting in a shape that is close to a perfect circle.

[0065] Although the embodiments of the present invention have been described above, the above-described embodiments are merely examples for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiments, and the above-described embodiments can be appropriately modified and carried out without departing from the spirit of the present invention. [Explanation of symbols]

[0066] 10 Toothed annular member 11 Missing tooth area 12 Toothed part 20 Stepped annular member 21 Thin-walled section 22 Thick wall part 30,40 Material 31,41 Part 1 32,42 Part 2

Claims

1. 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.

2. 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.

3. 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.

4. 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.

5. 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. 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. 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.

8. 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.

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