Manufacturing method of sintered component

Abstract

To improve the dimensional accuracy of a sintered component.SOLUTION: A manufacturing method of a sprocket 1 includes a material forming step of obtaining a material comprising a metallic powder and a binder, a forming step of injection-molding the material to obtain a formed body S1 having an inner hole h, a degreasing step of degreasing the formed body S1 to obtain a degreased body S2 portion, and a sintering step of sintering the degreased body S2 to obtain a sintered body S3. In particular, a runner portion 120 having a plurality of spoke portions 121 extending radially from the central portion of the inner hole h in the molded body S1 is formed. Then, the sintered body S3 is formed in a state where the runner portions 120 are attached.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a method for manufacturing sintered parts.

Background Art

[0002] Conventionally, a method for manufacturing sintered parts using metal injection molding (MIM) has been known (see Patent Document 1). In this method, a sintered part is manufactured through a process of manufacturing a molded body by metal injection molding, a process of degreasing the molded body, and a process of sintering the degreased body to obtain a sintered body.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the conventional method for manufacturing sintered parts, there is a risk of deterioration in dimensional accuracy. That is, generally, in metal injection molding, when injecting a molded body having an inner hole in an annular (ring-shaped) shape, the gate, which is the injection port of the raw material to be injected, is installed on the outer peripheral surface or end surface of the product, avoiding the inner peripheral surface of the inner hole. Depending on the position where the gate is installed, the orientation due to the filling pressure of the raw material during injection, the variation in molding density, the molding residual stress, etc. affect the dimensional accuracy of the product and become factors for reducing the dimensional accuracy. In general, in the method for manufacturing a sintered part by metal powder injection molding, in the degreased body from which the binder has been removed by the degreasing process, there is an internal space of 30 to 40% by volume. However, when the degreased body undergoes the sintering process, the internal space decreases to 5% or less, and a metal part having characteristics equivalent to those of the melted material is obtained. At this time, in the sintering process, the dimensions of the degreased body shrink by about 15 to 20% as the linear shrinkage rate of the dimensions, and the deformation accompanying the shrinkage becomes a factor in reducing the dimensional accuracy of the sintered body. In particular, for a ring-shaped sintered part having an inner hole, the roundness of the inner hole decreases due to the deformation accompanying the shrinkage, and the decrease in the roundness of the inner hole affects all other dimensions. Therefore, additional processing for improving the dimensional accuracy is required, or depending on the shape, the additional processing itself may not be practical, and the manufacturing by metal powder injection molding may be postponed. An object of the present invention is to improve the dimensional accuracy of sintered parts.

Means for Solving the Problems

[0005] In order to solve the above problems, a method for manufacturing a sintered part according to a first invention includes a step of obtaining a raw material including a metal powder and a binder, a step of molding the raw material by injection molding to obtain a molded body having an inner hole, a step of degreasing the molded body to obtain a degreased body, and a step of sintering the degreased body to obtain a sintered body (hereinafter referred to as the "sintering step"). In the molded body, a runner portion is formed. The runner portion has a plurality of spoke portions extending radially from the center portion of the inner hole, and the sintered body is formed in a state where the runner portion is attached. In the method for manufacturing a sintered part according to the first invention, a runner portion is formed in the molded body. In particular, the runner portion has a plurality of spoke portions extending radially from the center portion of the inner hole. As a result, in the step of obtaining the molded body, it is possible to equalize the filling pressure of the raw material. As a result, it is possible to improve the dimensional accuracy of the sintered part. Also, the debinding process is carried out with the runner part attached to the molded body. As a result, in the debinding process, it is possible to suppress deformation due to the self-weight of the molded body and residual stress during molding by the runner part, and it is possible to suppress a decrease in the roundness of the inner hole. Furthermore, the sintering process is carried out with the runner part attached to the debound body. As a result, in the sintering process, it is possible to suppress deformation accompanying the shrinkage of the debound body by the runner part, and it is possible to suppress a decrease in the roundness of the inner hole. As a result, it is possible to improve the dimensional accuracy of the sintered part. Here, as the sintered part, for example, the sprocket 1 described later is applicable. As the inner hole, for example, the inner hole h described later is applicable. As the molded body, for example, the molded body S1 described later is applicable. As the debound body, for example, the debound body S2 described later is applicable. As the sintered body, for example, the sintered body S3 described later is applicable. As the spoke part, for example, the spoke part 121 described later is applicable. As the runner part, for example, the runner part 120 described later is applicable.

[0006] The method for manufacturing a sintered part according to the second invention is the method for manufacturing a sintered part according to the first invention, wherein, on the inner peripheral surface of the inner hole, recesses corresponding to the respective spoke parts are provided, and inside the recesses, gate parts corresponding to the respective spoke parts are connected. In the method for manufacturing a sintered part according to the second invention, in the molded body, the gate parts corresponding to the respective spokes are connected inside the recesses provided on the inner peripheral surface of the inner hole. As a result, in the sintered part from which the runner part has been removed, it is possible to suppress a situation where the mark of the gate part interferes with the inner diameter dimension of the inner hole. Here, as the recess, for example, the recess r described later is applicable.

[0007] The method for manufacturing a sintered part according to the third invention is the method for manufacturing a sintered part according to the first or second invention, wherein, in each spoke part, ribs extending along the central axis of the inner hole are formed, and in the step of obtaining the sintered body, the tips of the ribs serve as the grounding surface against the jig. In the method for manufacturing a sintered part according to the third invention, in the sintering step, the tip of the rib provided on each spoke portion of the degreased body serves as the grounding surface against the jig. As a result, in the sintering step, it becomes possible to disperse the load of the entire degreased body including the runner portion, and it becomes possible to suppress the occurrence of variations in shrinkage resistance in the inner hole. As a result, it becomes possible to further improve the dimensional accuracy of the sintered part. Here, as the rib, for example, the rib 121a described later corresponds.

Effects of the Invention

[0008] According to the method for manufacturing a sintered part according to the present invention, it becomes possible to improve the dimensional accuracy of the sintered part.

Brief Description of the Drawings

[0009]

Figure 1

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Figure 9

Modes for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The manufacturing method of the sintered part according to the present invention can be applied to the manufacture of sintered parts having an inner hole (inner diameter), such as gears, sprockets, rings, etc. In the present embodiment, an example of applying the manufacturing method of the sintered part according to the present invention to the manufacture of the sprocket 1 will be described.

[0011] (Configuration of Sprocket 1) First, the configuration of the sprocket 1 will be described. FIG. 1 is a perspective view showing the front side of the sprocket 1. FIG. 2 is a perspective view showing the back side of the sprocket 1. As shown in FIGS. 1 and 2, the sprocket 1 includes an annular (ring-shaped) wheel portion 10 and a plurality of tooth ribs (teeth) 20 provided at equal intervals on the outer peripheral surface of the wheel portion 10. Further, a boss (not shown) is provided on the front end surface of the wheel portion 10. And an inner hole (axial hole) h is provided in the wheel portion 10 (and the boss) along the central axis. The sprocket 1 is composed of an iron-based sintered material obtained by sintering a raw material powder mainly composed of iron powder.

[0012] (Manufacturing Method of Sprocket 1) Next, the manufacturing method of the sprocket 1 will be described. FIG. 3 is a flowchart showing the manufacturing method of the sprocket 1. FIG. 4 is a perspective view showing the front side of the green compact S1. FIG. 5 is a perspective view showing the back side of the green compact S1. FIG. 6 is a rear view of the green compact S1. FIG. 7 is a side view of the green compact S1. FIG. 8 is a cross-sectional view of the green compact S1. The sprocket 1 is manufactured by metal injection molding (MIM). As shown in FIG. 3, in the manufacturing method of the sprocket 1, first, a raw material generation step is performed. In the raw material generation step, raw materials are generated. Specifically, in the raw material generation step, first, a metal powder and a binder are kneaded to generate a compound. Next, the generated compound is granulated to generate pellet-shaped raw materials. At this time, as the metal powder, Fe powder, a mixed powder of Fe powder, Fe-based alloy powder (including SUS), Ti powder, Ti alloy powder, etc. can be used. As the binder, a thermoplastic resin, wax, or the like can be used.

[0013] Next, a molding step is performed. In the molding step, a molded body S1 is produced by injection molding. Specifically, in the molding step, an injection molding machine is used to inject and fill the raw material into a metal mold (not shown) to mold the molded body S1. At this time, a cavity for forming the part that will become the product and passages (specifically, a sprue, a runner, and a gate) for feeding the raw material injected from the nozzle of the injection molding machine into the cavity are formed inside the mold. Then, in the molding process, the raw material injected from the nozzle of the injection molding machine passes through each passage in the order of the sprue, runner, and gate, and is fed into the cavity. At this time, in this embodiment, the raw material is fed into the cavity via a spoke-shaped runner (runner portion 120 described later). This makes it possible to equalize the filling pressure of the raw material in the molding process, and improve the dimensional accuracy of the sprocket 1 (product). In this embodiment, the runner system is a cold runner system. As a result, as shown in Figs. 4 to 8, a product part 100, a sprue part 110, a runner part 120, and a gate part 130 are formed in the molded body S1 (degreased body S2, sintered body S3). The product part 100 is a part of the mold molded by the cavity (a part made of raw material solidified in the cavity), and is a part of the molded body S1 that becomes a product. The sprue part 110 is a part of the mold molded by the sprue (a part made of raw material solidified in the sprue), and is a part of the molded body S1 that does not remain in the product. The runner part 120 is a part of the mold molded by the runner (a part made of raw material solidified in the runner), and is a part of the molded body S1 that does not remain in the product. The gate part 130 is a part of the mold molded by the gate (a part made of raw material solidified in the gate), and is a part of the molded body S1 that does not remain in the product. Here, in this embodiment, the runner system is a cold runner system. However, the runner system may also be a hot runner system. As shown in FIGS. 4 to 8, in the molded body S1, the product portion 100 is formed in an annular (ring-shaped) shape having an inner hole h. In particular, in this embodiment, a spoke-shaped runner portion 120 is formed in the molded body S1. The runner portion 120 has a plurality (three or more) of spoke portions 121 that extend radially from the central portion of the inner hole h. In this embodiment, nine spoke portions 121 are provided in the runner portion 120. Here, the number of the spoke portions 121 can be appropriately set according to the use and shape of the product as long as it is three or more. At this time, if the number of the spoke portions 121 is less than three, the effect of equalizing the filling pressure of the raw material during injection molding becomes small, and the effect of preventing deformation of the degreased body S2 during sintering described later becomes small. On the other hand, the more the number of the spoke portions 121 increases, the greater the effect of equalizing the filling pressure and the greater the effect of preventing deformation of the degreased body S2 during sintering. However, if the number of the spoke portions 121 exceeds 15, the number of the recesses r provided on the inner peripheral surface of the inner hole h increases, and the reduction in the effective area of the inner diameter dimension becomes excessive. Therefore, the number of the spoke portions 121 is preferably in the range of 3 to 15. The plurality of spoke portions 121 are provided at equal angular intervals in the circumferential direction of the inner hole h. Each spoke portion 121 is formed in a cylindrical shape, a columnar shape with a trapezoidal cross-section, a columnar shape with a semi-circular cross-section, or the like. The plurality of spoke portions 121 are connected to each other at the central portion of the inner hole h. At this time, the base ends of the respective spoke portions 121 are connected to the base ends of the other spoke portions 121 at the central portion of the inner hole h. A gate portion 130 is formed at the tip of each spoke portion 121. The outer diameter of the gate portion 130 is smaller than the outer diameter of the spoke portion 121. And the tip of each spoke portion 121 is connected to the inner circumferential surface of the inner hole S1 via the gate portion 130. Here, recesses r corresponding to the respective spoke portions 121 (each gate portion 130) are provided on the inner circumferential surface of the inner hole h. And each gate portion 130 is connected to the inside of the recess r corresponding to the gate portion 130. That is, the tip of each spoke portion 121 is connected to the inside of the recess r corresponding to the spoke portion 121 via the gate portion 130. Thereby, in the sprocket 1 (product) from which the runner portion 120 has been removed, it is possible to suppress a situation where the mark of the gate portion 130 interferes with the inner diameter dimension of the inner hole h. Each spoke portion 121 is provided with a rib 121a. Each rib 121a is formed in a cylindrical shape. Each rib 121a extends along the central axis of the inner hole h. And each rib 121a extends to a position where the tip surface of the rib 121a reaches the end surface on the other side of the product portion 100 (in this embodiment, the side opposite to the boss). That is, each rib 121a extends to a position where the tip surface of the rib 121a is arranged on substantially the same plane as the end surface on the other side of the product portion 100 (in this embodiment, the side opposite to the boss). Thereby, it becomes possible to use the tip surface of each rib 121a and the end surface on the other side of the product portion 100 (in this embodiment, the side opposite to the boss) as a grounding surface for a sintering jig described later. Or, each rib 121a extends to a position where the tip surface of the rib 121a protrudes downward with respect to the end surface on the other side of the product portion 100 (in this embodiment, the side opposite to the boss). Thereby, it becomes possible to use the tip surface of each rib 121a as a grounding surface for a sintering jig. The sprue part 110 is formed in a cylindrical shape, a columnar shape with a trapezoidal cross-section, a columnar shape with a semi-circular cross-section, or the like. The sprue part 110 is arranged substantially coaxially with respect to the central axis of the inner hole h. And the sprue part 110 is connected to the central part of the runner part 120 (the part where the plurality of spoke parts 121 are connected to each other, the central part of the inner hole h). In the molding process, the sprue part 110 may be removed from the molded body S1. At this time, the runner part 120 and the gate part 130 are not removed and are maintained in a state of being connected to the molded body S1.

[0014] Next, a debinding process is performed. In the debinding process, the molded body S1 is heated to remove the binder from the molded body S1 and create a debound body S2. Specifically, in the debinding process, the molded body S1 is placed on a sintering jig (setter). Then, the molded body S1 placed on the sintering jig is heated (debounded) under a predetermined atmosphere and predetermined temperature conditions using a debinding furnace, and the binder contained in the molded body S1 is vaporized and evaporated to form a debound body S2. At this time, as the predetermined atmosphere, for example, a vacuum atmosphere, a reduced-pressure atmosphere, a nitrogen atmosphere, an AR atmosphere, or the like can be used. Also, as the predetermined temperature conditions, for example, it can be within the range of 100 to 800 °C. In particular, in this embodiment, the debinding process is performed while the runner part 120 and the gate part 130 are connected to the molded body S1. As a result, in the debinding process, it becomes possible to suppress deformation of the molded body S1 due to its own weight and residual stress during molding by the runner part 120, it becomes possible to suppress a decrease in the roundness of the inner hole h, and it becomes possible to suppress deformation at all locations including the outer diameter.

[0015] Next, a sintering process is performed. In the sintering process, the debound body S2 is sintered to form a sintered body S3. Specifically, in the sintering process, the debound body S2 placed on the sintering jig is heated (sintered) under a predetermined atmosphere and predetermined temperature conditions using a sintering furnace to form a sintered body S3. At this time, as the predetermined atmosphere, for example, a vacuum atmosphere, a reduced-pressure atmosphere, a nitrogen atmosphere, an AR atmosphere, etc. can be used. Further, as the predetermined temperature condition, for example, it can be within the range of 1200 to 1400 °C. In particular, in the present embodiment, in the degreased body S2, the sintering process is carried out with the runner portion 120 and the gate portion 130 connected. As a result, in the sintering process, it becomes possible to suppress the deformation accompanying the shrinkage of the degreased body S2 by the runner portion 120, it becomes possible to suppress the decrease in the roundness of the inner hole h, and it becomes possible to improve the dimensional accuracy of the sprocket 1 (product). Further, in the sintering process, the tip surface of the rib 121a provided on each spoke portion 121 of the degreased body S2 becomes the grounding surface with respect to the sintering jig. As a result, in the sintering process, it becomes possible to disperse the load of the runner portion 120, it becomes possible to suppress the occurrence of variations in shrinkage resistance in the inner hole h, and it becomes possible to further improve the dimensional accuracy of the sprocket 1 (product). Here, also in the sintered body S3, the state in which the runner portion 120 and the gate portion 130 are connected is maintained.

[0016] Next, a post-processing step is carried out. In the post-processing step, the sprue portion 110, the runner portion 120, and the gate portion 130 are removed from the sintered body S3. At this time, since the sprue portion 110, the runner portion 120, and the gate portion 130 after sintering can be removed by lightly tapping, it becomes possible to simplify and reduce the cost of the post-processing step as compared with the case of removing the film gate by cutting. Also, in the post-processing step, if necessary, heat treatment, sizing, machining, plating, etc. are performed on the sintered body S3 from which the sprue portion 110, the runner portion 120, and the gate portion 130 have been removed. And through the post-processing step, the sprocket 1 (product) is completed.

[0017] (Example) Next, an example of the present invention will be described. FIG. 9 is a diagram showing the results of measuring the roundness, deformation tendency, and flatness of the teeth of the sprockets according to Example 1 and Comparative Examples 1 and 2. One type of sprocket (Example 1) was manufactured as an embodiment of the present invention. Two types of sprockets (Comparative Examples 1 and 2) were manufactured as comparative examples. The roundness and tooth flatness of the sprockets according to Example 1 and Comparative Examples 1 and 2 were then measured. In this case, the roundness was measured by using a caliper to measure the diameter of the inner hole (inner hole h) while changing the position around the entire circumference of the inner hole h, and the difference between the maximum and minimum values ​​of the measured diameter was taken as the roundness. In addition, the flatness of the teeth was measured by using a height gauge to measure the height of the step with one point as the reference point for each tooth trace (tooth trace 20), and the difference between the maximum and minimum values ​​was taken as the flatness. The sprocket according to Example 1 was manufactured according to the above-mentioned manufacturing method of the sprocket 1. Specifically, after the sintering process was carried out for the sprocket according to Example 1, the runner portion 120 and the gate portion 130 were removed from the product portion 100 of the sintered body S3. 5,000 sprockets according to Example 1 were manufactured. For the sprocket of Comparative Example 1, the runner portion 120 and gate portion 130 were removed from the product portion 100 of the compact S1 in the molding process (before the degreasing process was carried out). In addition, in the degreasing process and sintering process, the end face on the boss side of the compact S1 (degreased body S2) was used as the contact surface with the sintering jig. Other conditions, such as the raw materials, degreasing conditions, and sintering conditions, were the same as those in Example 1. 50 sprockets were manufactured as the sprockets of Comparative Example 1. The sprocket according to Comparative Example 2 was manufactured according to the manufacturing method of the sprocket 1 described above. However, the runner portion 120 was configured so that the ribs 121a were not provided. Specifically, for the sprocket according to Comparative Example 2, after the sintering process was carried out, the runner portion 120 (without the ribs 121a) and the gate portion 130 were removed from the product portion 100 of the sintered body S3. Other conditions, such as the raw materials, degreasing conditions, and sintering conditions, were the same as those in Example 1. 50 sprockets were manufactured as the sprockets according to Comparative Example 2. Here, for Example 1 and Comparative Examples 1 and 2, a mixed powder of Fe powder and Ni powder was used as the metal powder contained in the raw material. Also, for Example 1 and Comparative Examples 1 and 2, a mixture of PP (polypropylene), PE (polyethylene), and PW.St (paraffin wax stearic acid) was used as the binder contained in the raw material. Further, for Example 1 and Comparative Examples 1 and 2, in the debinding process, debinding was carried out with a debinding atmosphere = vacuum atmosphere, a debinding temperature = 700 °C, and a debinding time = 10 [h]. Furthermore, for Example 1 and Comparative Examples 1 and 2, in the sintering process, sintering was carried out with a sintering atmosphere = reduced-pressure nitrogen atmosphere, a sintering temperature = 1250 °C, and a sintering time = 2 [h]. For each of the sprockets according to Example 1 and Comparative Examples 1 and 2, the roundness and the flatness of the teeth were measured. As a result, as shown in Fig. 9, for the sprocket according to Example 1, the roundness was 0.03 - 0.06 (average 0.04). On the other hand, for the sprocket according to Comparative Example 1, the roundness was 0.3 - 0.5 (average 0.4). Also, for the sprocket according to Comparative Example 2, the roundness was 0.05 - 0.12 (average 0.08). Thus, it was confirmed that for the sprockets according to Example 1 and Comparative Example 2, compared with the sprocket according to Comparative Example 1, the roundness was significantly improved and the deformation was small. In particular, for the sprocket according to Example 1, compared with the sprocket according to Comparative Example 2, the roundness was improved and the deformation was small. Also, for the sprocket according to Example 1, the flatness of the teeth was 0.03 - 0.04 (average 0.03). On the other hand, for the sprocket according to Comparative Example 1, the flatness of the teeth was 0.13 - 0.21 (average 0.15). On the other hand, for the sprocket according to Comparative Example 2, the flatness of the teeth was 0.03 - 0.15 (average 0.11). Thus, it was confirmed that for the sprockets according to Example 1 and Comparative Example 2, compared with the sprocket according to Comparative Example 1, the flatness of the teeth was improved and the deformation was small. In particular, for the sprocket according to Example 1, compared with the sprocket according to Comparative Example 2, the flatness of the teeth was improved and the deformation was small.

[0018] (Operation of the present invention) The manufacturing method of the sprocket 1 according to the present invention includes a raw material generation step of obtaining a raw material containing a metal powder and a binder, a molding step of molding the raw material by injection molding to obtain a molded body S1 having an inner hole h, a debinding step of debinding the molded body S1 to obtain a debound body S2, and a sintering step of sintering the debound body S2 to obtain a sintered body S3. Further, in the molded body S1, a runner portion 120 is formed. In particular, the runner portion 120 has a plurality of spoke portions 121 extending radially from the center portion of the inner hole h. Then, the sintered body S3 is formed with the runner portion 120 attached thereto. That is, in the manufacturing method of the sprocket 1 according to the present invention, in the molded body S1, a runner portion 120 is formed. In particular, the runner portion 120 has a plurality of spoke portions 121 extending radially from the center portion of the inner hole h. Thereby, in the molding step, it becomes possible to equalize the filling pressure of the raw material, and it becomes possible to improve the dimensional accuracy of the sprocket 1. Further, the sintered body S3 is formed with the runner portion 120 attached to the molded body S1. Thereby, in the sintering step, it becomes possible to suppress the deformation accompanying the shrinkage of the debound body S2 by the runner portion 120, it becomes possible to suppress the decrease in the roundness of the inner hole h, and it becomes possible to improve the dimensional accuracy of the sprocket 1.

[0019] Further, in the manufacturing method of the sprocket 1 according to the present invention, recesses r corresponding to the respective spoke portions 121 are provided on the inner peripheral surface of the inner hole h. And inside the recess r, a gate portion 130 corresponding to each spoke portion 121 is connected. That is, in the manufacturing method of the sprocket 1 according to the present invention, in the molded body S1, the gate portion 130 corresponding to each spoke portion 121 is connected inside the recess r provided in the inner hole h. Thereby, in the sprocket 1 from which the runner portion 120 is removed, it becomes possible to suppress a situation where the mark of the gate portion 130 interferes with the inner diameter dimension of the inner hole h. Here,

[0020] Furthermore, in the method for manufacturing the sprocket 1 according to the present invention, in each spoke portion 121, a rib 121a extending along the central axis of the inner hole h is formed. And in the sintering process, the tip of the rib 121a serves as the grounding surface against the sintering jig. That is, in the method for manufacturing the sprocket 1 according to the present invention, in the sintering process, the tip of the rib 121a provided in each spoke portion 121 of the degreased body S2 serves as the grounding surface against the sintering jig. As a result, in the sintering process, it becomes possible to disperse the load of the entire degreased body S2 including the runner portion 120, and it becomes possible to suppress a situation where variations in shrinkage resistance occur in the inner hole h. Therefore, it becomes possible to further improve the dimensional accuracy of the sprocket 1.

Explanation of Reference Numerals

[0021] 1 Sprocket 10 Wheel portion 20 Tooth ridge 100 Product portion 110 Sprue portion 120 Runner portion 121 Spoke portion 121a Rib 130 Gate portion h Inner hole S1 Green body S2 Degreased body S3 Sintered body

Claims

1. A step of obtaining a raw material containing a metal powder and a binder; A step of molding the raw material by injection molding to obtain a molded body having an inner hole; A step of degreasing the molded body to obtain a degreased body; A step of sintering the degreased body to obtain a sintered body, including: In the molded body, a runner portion is formed; The runner portion has a plurality of spoke portions extending radially from the center portion of the inner hole; A method for manufacturing a sintered part, characterized in that the sintered body is formed with the runner portion attached.

2. On the inner peripheral surface of the inner hole, recesses corresponding to the respective spoke portions are provided; The method for manufacturing a sintered part according to claim 1, characterized in that a gate portion corresponding to each spoke portion is connected inside the recess.

3. In each spoke portion, a rib extending along the central axis of the inner hole is formed; The method for manufacturing a sintered part according to claim 1 or 2, characterized in that in the step of obtaining the sintered body, the tip of the rib serves as a grounding surface for the jig.

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