Metal powder forming method

Abstract

In this metal powder forming method, a rolling tool (3) is pressed against an end surface (2) positioned at an end of a metal workpiece (1) that rotates about a rotation axis (O), the end being in a direction parallel to the rotation axis (O), thereby forming a rolling surface on which a protruding part is formed. Thereafter, the protruding part formed on the rolling surface of the rotating workpiece (1) is cut by a cutting tool (4) to form a metal powder.

Description

Metal powder forming method

[0001] The present invention relates to a metal powder forming method.

[0002] Patent Literature 1 discloses a method for forming metal powder from a rotating cylindrical metal workpiece. This method includes forming a plurality of minute protrusions on the peripheral surface of the workpiece by rolling and then cutting the formed protrusions with a cutting tool. This method allows for the formation of metal powder particles having a desired size or aspect ratio, and the formed metal powder particles can be used for metal 3D printing, etc.

[0003] WO 2023 / 148980

[0004] In the method disclosed in Patent Document 1, the peripheral surface of the workpiece is cut, so the outer diameter of the workpiece gradually decreases as the process progresses. During the rolling process, a rolling tool must be pressed against the peripheral surface of the workpiece with a high load. However, if the rigidity of the workpiece decreases as the outer diameter decreases, the workpiece may bend due to the high load during the rolling process. In this case, the processing accuracy of the rolling and cutting processes decreases, and the desired metal powder particles cannot be obtained. As a result, the rolling and cutting processes can only be performed up to an outer diameter where bending does not occur, and the workpiece cannot be used up completely. As a result, the raw material yield of the workpiece is low and the production cost of metal powder particles increases.

[0005] An object of the present invention is to provide a method for forming metal powder that can reduce the manufacturing cost of metal powder.

[0006] In a method for forming metal powder according to one aspect of the present invention, a rolling tool is pressed against an end face of a workpiece rotating around a rotation axis in a direction parallel to the rotation axis to form a rolled surface with convex portions formed thereon, and then the convex portions formed on the rolled surface of the rotating workpiece are cut with a cutting tool to form metal powder.

[0007] According to one aspect of the present invention, the manufacturing cost of metal powder can be reduced.

[0008] Fig. 1 is a schematic front view showing a metal powder forming apparatus that performs a metal powder forming method according to a first embodiment. Fig. 2 is a schematic plan view showing the metal powder forming apparatus shown in Fig. 1. Fig. 3 is a schematic front view showing rolling marks and cutting trajectories formed on a workpiece. Fig. 4 is a side view of a rotary cutting tool. Fig. 5 is a schematic front view showing a metal powder forming apparatus that performs a metal powder forming method according to a second embodiment. Fig. 6 is a schematic side view showing the metal powder forming apparatus shown in Fig. 5. Fig. 7 is a schematic front view showing rolling marks and a straight edge of a cutting tool. Fig. 8 is a schematic side view showing a metal powder forming apparatus that performs a metal powder forming method according to a third embodiment.

[0009] Hereinafter, a metal powder forming method according to an embodiment will be described with reference to the drawings.

[0010] 1 to 4, a metal powder forming method according to a first embodiment will be described. In the metal powder forming method according to this embodiment, a metal workpiece 1 is rotated about a rotation axis O, an end face 2 of the workpiece 1 in the direction of the rotation axis O is rolled to form a rolled surface, and the rolled surface is then cut to form metal powder. The workpiece 1 is a cylindrical hollow member with a hollow portion 2a formed along a central axis extending in the longitudinal direction of the member.

[0011] The base end of the workpiece 1 is fixed to a chuck of a lathe (not shown). The workpiece 1 is fixed so that its central axis coincides with the rotation axis O, and the workpiece 1 is rotated around the rotation axis O by the lathe. Rolling and cutting are performed on an end face 2 located at the end of the workpiece 1 in the direction of the rotation axis O, i.e., the end face 2 intersecting with the rotation axis O. In this embodiment, the end face 2 is an annular surface surrounding the rotation axis O and perpendicular to the rotation axis O.

[0012] The metal powder forming apparatus for realizing the metal powder forming method includes a rolling tool 3 and a cutting tool 4. The rolling tool 3 and the cutting tool 4 are arranged to face each other with a rotation axis O therebetween, for example.

[0013] The rolling tool 3 is a tool that transfers a predetermined rolling pattern to the end face 2 by being pressed against the end face 2, and is composed of a cylindrical rolling roller 3a. When the workpiece 1 is viewed from the end face 2 side, the rolling roller 3a is provided at s (the right side in Figure 1, the upper side in Figure 2) with respect to the rotation axis O. A plurality of linear protrusions that form the rolling pattern are formed in parallel on the circumferential surface of the rolling roller 3a. The plurality of linear protrusions are not parallel to the rotation axis O3 of the rolling roller 3a. The particle size of the metal powder formed from the workpiece 1 is several tens of micrometers, and the pitch and height of the plurality of linear protrusions are approximately several tens of micrometers. The particle size of the metal powder is controlled by the formation pitch of the rolling pattern formed on the circumferential surface of the rolling roller 3a.

[0014] The rolling roller 3a pressed against the workpiece 1 rotates around a rotation axis O3 as the workpiece 1 rotates. The rotation axis O3 coincides with the radial direction of the end face 2 in the front view shown in FIG. 1 and is perpendicular to the rotation axis O in the plan view shown in FIG. 2. To transfer the rolling pattern to the end face 2, the rolling roller 3a is pressed against the end face 2 with a high load. This high load acts in a direction parallel to the rotation axis O, i.e., in the direction of the central axis of the workpiece 1, and the workpiece 1 is firmly supported by the lathe, preventing the workpiece 1 from bending. Therefore, a highly accurate rolled surface can be stably formed. By transferring the rolling pattern of the rolling roller 3a to the end face 2, a rolled surface with fine convex portions is formed on the end face 2. In this embodiment, the rolling pattern is parallel linear convex portions, so the convex portions on the rolled surface are multiple parallel ridge-like convex portions X (see FIG. 3).

[0015] The height of the convex portions on the rolling surface affects the particle size of the metal powder formed. The height of the convex portions is controlled based on the pressure load on the end face 2 of the rolling roller 3a (load control of the rolling roller 3a). The height of the convex portions may also be controlled based on the depth of pressure on the end face 2 of the rolling roller 3a (position control of the rolling roller 3a). Whether load control or position control is used, the rolling roller 3a is fed in a direction parallel to the rotation axis O by a predetermined feed amount during rolling. As the rolling surface is cut by the cutting tool 4, the end face 2 gradually decreases. In other words, the length of the workpiece 1 in the direction of the rotation axis O gradually decreases. The rolling roller 3a is fed in a direction parallel to the rotation axis O as the length of the workpiece 1 in the direction of the rotation axis O decreases.

[0016] The cutting tool 4 is a tool for cutting the convex portions formed on the rolling surface. When the workpiece 1 is viewed from the end face 2 side, the cutting tool 4 is provided on the other side of the rotation axis O (the left side in FIG. 1 , the bottom side in FIG. 2 ). As shown in FIG. 4 , the cutting tool 4 of this embodiment is a rotary cutting tool 4a having a cutting blade with multiple comb teeth 4b. The particle size of the metal powder formed is controlled by the pitch of the comb teeth 4b. The rotation axis O4 of the rotary cutting tool 4a is parallel to the rolling surface, i.e., perpendicular to the rotation axis O in the plan view shown in FIG. 2 . Furthermore, the rotation axis O4 coincides with the radial direction of the end face 2 in the front view shown in FIG. 1 . In the front view shown in FIG. 1 , the rotation axis O4 exists on an extension of the rotation axis O3. However, the rotation axis O4 does not have to be on an extension of the rotation axis O3. The extension of the rotation axis O4 and the extension of the rotation axis O3 may intersect at a predetermined angle at the rotation axis O. The rotary cutting tool 4a may rotate so as to follow the rotating rolling surface on the cutting surface, or may rotate in the opposite direction. The rotary cutting tool 4a shown in Figure 4 is an example. The length of the rotary cutting tool 4a and the pitch of the comb teeth 4b are set according to the width of the rolling surface and the desired particle size of the metal powder.

[0017] The cutting tool 4 cuts the rolled surface with a depth of cut equal to or less than the height of the convex portions formed on the rolled surface. When cutting the rolled surface, the cutting tool 4 is fed in a direction parallel to the rotation axis O by a predetermined feed amount (depth of cut). As the rolled surface is cut, the length of the workpiece 1 in the direction of the rotation axis O gradually decreases. The cutting tool 4 is fed in a direction parallel to the rotation axis O as the length of the workpiece 1 in the direction of the rotation axis O decreases. In addition, since the cutting tool 4 in this embodiment is a rotary cutting tool 4a having a comb tooth 4b, its cutting loci form multiple parallel cutting loci Y (see FIG. 3 ). Furthermore, because the rolled surface (end face 2) to be cut is rotating and the comb tooth 4b is arranged spirally around the rotation axis O4, the cutting loci Y are oblique to the rotation axis O4.

[0018] Next, with reference to Figure 3, the relationship between the multiple parallel ridge-like convex portions X formed on the rolled surface and the cutting path Y of the rotary cutting tool 4a will be described. As shown in Figure 3, as the workpiece 1 rotates, the rolling roller 3a performs rolling on the end face 2, forming convex portions, in this embodiment multiple parallel ridge-like convex portions X, on the rolled surface. This rolled surface is fed to a cutting position using the rotary cutting tool 4a as the workpiece 1 rotates. At the cutting position, the rotary cutting tool 4a is positioned so that the cutting path Y of the rotary cutting tool 4a intersects with the ridge-like convex portions X. The parallel ridge-like convex portions X are cut by the multiple comb teeth 4b of the rotary cutting tool 4a so that they intersect, thereby forming a metal powder having a desired particle size and aspect ratio.

[0019] The cut rolling surface, i.e., the cutting surface, is returned to the rolling position as the workpiece 1 rotates. Although the cutting surface does not return to a completely flat surface, the rolling process by the rolling roller 3a reprocesses it into a rolling surface suitable for obtaining the desired metal powder. In this way, by utilizing the rotation of the annular end face 2 of the workpiece 1, the rolling process and the cutting of the resulting rolled surface are performed in parallel and continuously. This results in extremely high metal powder production efficiency. Furthermore, since the workpiece 1 is a hollow member, the end face 2 on which the rolling and cutting processes are performed is an annular surface. Therefore, there is no interference between the rolling roller 3a and the rotary cutting tool 4a, and rolling and cutting can be performed on the entire radial extent of the end face 2, resulting in a high yield of metal powder formation. The entire workpiece 1 can be processed into metal powder except for the vicinity of the base end held by the lathe chuck.

[0020] Second Embodiment A metal powder forming method according to a second embodiment will be described with reference to Figures 5 to 7. The metal powder forming method and metal powder forming apparatus of this embodiment have many points in common with the method and apparatus of the first embodiment. Below, methods and configurations that differ from those of the first embodiment will be described.

[0021] In this embodiment, the rolling tool 3 includes a rolling roller 3a (hereinafter referred to as the "first rolling roller 3a") and a second rolling roller 3b. The cutting tool 4 is a non-rotary cutting tool 4c, rather than the rotary cutting tool 4a as in the first embodiment. The non-rotary cutting tool 4c has a straight blade 4d. In the metal powder forming method of this embodiment, while rotating a metal workpiece 1 around a rotation axis O, the workpiece 1 is rolled with the first rolling roller 3a to form a first rolled surface, and then the first rolled surface is further rolled with the second rolling roller 3b to form a second rolled surface. The second rolled surface is then cut to form the metal powder.

[0022] The first and second rolling rollers 3a, 3b are arranged on the opposite side of the rotation axis O from the cutting tool 4. The first rolling roller 3a is arranged at a position rotated upstream in the rotation direction by a central angle of 45° about the rotation axis O relative to the rolling roller 3a of the first embodiment. On the other hand, the second rolling roller 3b is arranged at a position rotated downstream in the rotation direction by a central angle of 45° relative to the rolling roller of the first embodiment. Therefore, the rotation axis O3a of the first rolling roller 3a and the rotation axis O3b of the second rolling roller 3b are perpendicular to each other at the rotation axis O. Furthermore, the rotation axes O3a and O3b are also perpendicular to the rotation axis O at their intersection.

[0023] Similar to the rolling roller 3a of the first embodiment, multiple parallel linear convex portions are formed on the circumferential surface of each of the rolling rollers 3a and 3b. However, the inclination directions of the rolling rollers 3a and 3b are different. Therefore, the convex portions formed on the first rolling surface rolled by the first rolling roller 3a are multiple parallel ridge-like convex portions X1 (see FIG. 7). On the second rolling surface rolled by the second rolling roller 3b, ridge-like convex portions X2 with different inclination directions are formed, resulting in multiple square pyramidal convex portions X1+X2 (see FIG. 7) arranged in a matrix.

[0024] The second rolling surface can also be formed using a single rolling roller having a rolling pattern for rolling multiple square pyramidal protrusions X1+X2 arranged in a matrix. However, when forming metal powder having a particle size of several tens of micrometers, the rolling pattern becomes very dense. It is not easy to manufacture a rolling roller having a dense rolling pattern. Therefore, in this embodiment, in order to accurately form metal powder having a particle size of several tens of micrometers, the second rolling surface is formed using two rolling rollers 3a and 3b.

[0025] The first and second rolling rollers 3 a, 3 b are pressed against the end face 2 with a high load. However, because this high load acts in a direction parallel to the rotation axis O, the workpiece 1 does not bend. Therefore, high-precision first and second rolling surfaces can be stably formed. As in the first embodiment, the height of the convex portions on the first and second rolling surfaces is controlled based on the pressing load of the first and second rolling rollers 3 a, 3 b against the end face 2 (load control of the first and second rolling rollers 3 a, 3 b). Of course, the height of the convex portions may also be controlled based on the pressing depth of the first and second rolling rollers 3 a, 3 b against the end face 2 (position control of the first and second rolling rollers 3 a, 3 b).

[0026] As the workpiece 1 rotates, the second rolling surface is fed to a cutting position using the non-rotary cutting tool 4c. At the cutting position, the straight blade 4d of the non-rotary cutting tool 4c cuts the second rolling surface with a cutting depth equal to or less than the height of the quadrangular pyramidal convex portion X1+X2 formed on the second rolling surface. The straight blade 4d comes into contact with the second rolling surface parallel to the surface and cuts the second rolling surface. This removes the quadrangular pyramidal convex portion X1+X2, resulting in metal powder having the desired particle size and aspect ratio. In this embodiment, the straight blade 4d is arranged along a straight line extending radially from the end face 2. However, the straight blade 4d may also be arranged at an angle relative to the straight line.

[0027] In this embodiment, the rotation of the annular end face 2 of the workpiece 1 is utilized to perform the first and second rolling processes and the cutting of the second rolled surface formed thereby in parallel and continuously. This results in extremely high metal powder production efficiency. Furthermore, because the workpiece 1 is a hollow member, there is no interference between the rolling rollers 3a, 3b and the non-rotating cutting tool 4c. Since the rolling and cutting processes can be performed using the entire end face 2, the yield of metal powder formation is high. The entire workpiece 1 can be processed into metal powder except for the vicinity of the base end held by the lathe chuck.

[0028] Third Embodiment A metal powder forming method according to a third embodiment will be described with reference to FIG. 8 . The metal powder forming apparatus of this embodiment has a configuration similar to that of the first embodiment described above. The workpiece 1a of this embodiment is the same as that of the first embodiment in that the workpiece 1a is rotated around the rotation axis O, but differs from the first embodiment in that it is a cylindrical solid member. Furthermore, while the end face 2 of the first embodiment was a surface perpendicular to the rotation axis O, the end face 2b of this embodiment is an inclined surface inclined at an acute angle with respect to the rotation axis O. More specifically, the end face 2b is a conical surface, and the apex of the conical surface coincides with the rotation axis O.

[0029] The rolling roller 3a serving as the rolling tool 3 is substantially the same as that in the first embodiment, but its rotation axis O3 is also inclined relative to the rotation axis O in accordance with the inclination of the end face 2b. One end of the rolling roller 3a is located at the apex of the end face 2b, which is a conical surface. The width of the circumferential surface of the rolling roller 3a (the length in the direction of the rotation axis O3) is longer than the length of the generatrix of the end face 2b, which is a conical surface. In other words, the rolling roller 3a can form a rolling surface over the entire end face 2b.

[0030] Meanwhile, the rotary cutting tool 4a serving as the cutting tool 4 is also substantially the same as in the first embodiment, but its rotation axis O4 is also inclined relative to the rotation axis O in accordance with the inclination of the end face 2b. The tip of the cutting portion of the rotary cutting tool 4a intersects with the rotation axis O. In other words, the tip of the cutting portion of the rotary cutting tool 4a reaches the apex of the end face 2b, which is a conical surface. The base end of the cutting portion of the rotary cutting tool 4a is also located outside the base of the conical surface. Therefore, the rotary cutting tool 4a can also cut the entire end face 2b. Note that, as in the first and second embodiments, the rolling roller 3a and the cutting tool 4 are sequentially fed in a direction parallel to the rotation axis O.

[0031] By making the end surface 2b, which is subjected to rolling and cutting, an inclined surface, a wide processing area can be secured, thereby improving the efficiency of metal powder formation. Furthermore, by making the end surface 2b an inclined surface, even when a solid member is used as the workpiece 1, it is possible to position the rolling roller 3a and cutting tool 4 close to the rotation axis O without interfering with each other, as shown in Fig. 8. For example, in the case of a workpiece that is a cylindrical solid member having an end surface perpendicular to the rotation axis O, it is difficult to position the rolling roller 3a and cutting tool 4 at the center of the end surface, i.e., near the rotation axis of the workpiece, without interfering with each other, and an unprocessed portion is left near the rotation axis.

[0032] In this manner, in this embodiment, since the end face 2b of the workpiece 1 is machined, it is possible to prevent the workpiece 1 from warping. Note that in this embodiment, a hollow member may be used as the workpiece 1 instead of a solid member. Even in this case, a wide machining area can be secured by the inclined end face 2b to be machined, thereby improving the efficiency of forming metal powder.

[0033] As described above, according to the metal powder forming methods of the first to third embodiments, a rolling tool 3 is pressed against the end face 2b located at the end of the rotating workpiece 1 in the direction of the rotation axis O, thereby forming a rolling surface (second rolling surface) with a convex portion formed thereon. The convex portion formed on the rolling surface of the rotating workpiece 1 is then cut with the cutting tool 4 to form metal powder. Because the end faces 2, 2b intersecting with the rotation axis O at the end of the direction of the rotation axis O become the processed surface, the high load during rolling can be borne in the direction of the rotation axis O of the workpiece 1, thereby suppressing deflection of the workpiece 1. This allows for accurate metal powder formation. Furthermore, even if metal powder formation continues, the workpiece 1 can be used as much as possible. This improves the efficiency of metal powder production, thereby reducing metal powder production costs.

[0034] In the metal powder forming methods according to the first to third embodiments, the rolling process using the rolling tool 3 and the cutting process using the cutting tool 4 can be performed in parallel as the workpiece 1 rotates. This improves the efficiency of metal powder production.

[0035] In the metal powder forming method according to the third embodiment, the end surface 2b is an inclined surface that is inclined with respect to the rotation axis O. Since a wide processing area can be secured, the production efficiency of the metal powder can be improved.

[0036] In the metal powder forming methods according to the first and second embodiments, the workpiece 1 is a hollow member having a hollow portion formed along the rotation axis O. In this case, the end face 2 is an annular surface surrounding the rotation axis O, and the rolling surface is formed on the annular surface. In this way, metal powder can be formed over the entire area of ​​the end face 2 without causing interference between the rolling tool 3 and the cutting tool 4, thereby improving material yield.

[0037] In the metal powder forming methods according to the first to third embodiments, the rolling tool 3 is composed of rolling rollers 3a and 3b that rotate as they are pressed against the end face 2, and the rolling surface is formed by feeding the rolling rollers 3a and 3b in a direction parallel to the rotation axis O. The feeding of the rolling rollers 3a and 3b in a direction parallel to the rotation axis O directly feeds the rolling tool 3 as the workpiece 1 decreases. This allows the movement of the rolling tool 3 to be efficiently controlled.

[0038] In the metal powder forming methods according to the first to third embodiments, the height of the convex portions formed on the rolling processing surface is controlled based on the pressing load on the end faces 2, 2b of the rolling tool 3. By controlling the height of the convex portions, the particle size of the formed metal powder can be made uniform. Alternatively, the height of the convex portions can be controlled based on the pressing depth on the end faces 2, 2b of the rolling tool 3. This makes it possible to make the particle size of the metal powder uniform.

[0039] In the metal powder forming methods according to the first to third embodiments, the cutting tool 4 cuts the rolled surface (second rolled surface) with a cutting depth equal to or less than the height of the convex portion while being fed in a direction parallel to the rotation axis O. The feed of the cutting tool 4 in a direction parallel to the rotation axis O directly corresponds to the feed of the cutting tool 4 as the workpiece 1 is reduced. This allows the movement of the cutting tool 4 to be efficiently controlled.

[0040] In the metal powder forming method according to the first embodiment, the cutting tool 4 is configured as a rotary cutting tool 4a having a plurality of comb teeth 4b. The convex portions are a plurality of parallel ridge-like convex portions X formed on the rolling surface. The rotary cutting tool 4a cuts the ridge-like convex portions X so that the cutting trajectory Y of the comb teeth 4b intersects with the ridge-like convex portions X. By cutting the ridge-like convex portions X with the comb teeth 4b, it is possible to control the shape, such as the particle size, of the metal powder. This makes it possible to form metal powder of uniform quality.

[0041] In the metal powder forming method according to the second embodiment, the cutting tool 4 is a non-rotating cutting tool 4c having a straight blade 4d, and the straight blade 4d is brought into contact with the second rolling surface in parallel to cut the second rolling surface. By cutting the convex portions formed on the second rolling surface with the straight blade 4d parallel to the second rolling surface, it is possible to control the shape of the metal powder, such as its particle size. This makes it possible to form metal powder of uniform quality.

[0042] In the metal powder forming method according to the third embodiment, the workpiece 1 is a solid member, the end face 2b of the workpiece 1 is an inclined surface inclined at an acute angle with respect to the rotation axis O, and the cutting portion of the cutting tool 4 intersects with the rotation axis O. As described above, because the end face 2b is an inclined surface, a wide processing area can be secured, improving the efficiency of metal powder production. In this case, even if the workpiece 1 is a solid member, the rolling tool 3 and the cutting tool 4 can be positioned near the rotation axis O without interfering with each other. Therefore, even if the workpiece 1 is a solid member, it is possible to form metal powder by using as much of the workpiece 1 as possible, improving yield.

[0043] Although the present embodiment has been described above, the description and drawings forming a part of this embodiment should not be understood as limiting this embodiment. Various alternative embodiments, examples, and operation techniques will become apparent to those skilled in the art from this embodiment.

[0044] For example, in the third embodiment described above, a hollow workpiece 1 may be used. In this case, it is possible to more easily avoid interference between the rolling tool 3 and the cutting tool 4. Furthermore, in the first to third embodiments, the positions of the rolling tool 3 and the cutting tool 4 are fixed, and the workpiece 1 is rotated. However, the workpiece 1 may be fixed and not rotated, and the positions of the rolling tool 3 and the cutting tool 4 may be rotated about a rotation axis O that coincides with the central axis of the workpiece 1. That is, the workpiece 1 may be rotated relative to the rolling tool 3 and the cutting tool 4 about the rotation axis O. Furthermore, the rolling tool 3 may be configured with a coating to improve transfer performance. It is desirable that the cutting tool 4 have a small R-surface (curved surface) at the cutting edge to suppress plastic deformation of the convex portion during cutting.

[0045] 1, 1a Workpiece 2, 2b End face 2a Hollow portion 3 Rolling tool 3a Rolling roller (first rolling roller) 3b Second rolling roller 4 Cutting tool 4a Rotary cutting tool 4b Gang blade 4c Non-rotary cutting tool 4d Straight blade O Rotation axis X, X1 Ridge-shaped convex portion X2 Ridge-shaped convex portion Y Cutting locus

Claims

1. A method for forming metal powder, comprising: forming a forged surface having a convex portion by pressing a forging tool against an end face located at an end portion in a direction parallel to the rotation axis in a metal workpiece rotating about a rotation axis; and forming metal powder by cutting the convex portion formed on the forged surface of the rotating workpiece with a cutting tool.

2. The method for forming metal powder according to claim 1, wherein the forging process by the forging tool and the cutting process by the cutting tool are performed in parallel as the workpiece rotates.

3. The method for forming metal powder according to claim 1 or 2, wherein the end face is an inclined surface inclined with respect to the rotation axis.

4. The method for forming metal powder according to any one of claims 1 to 3, wherein the workpiece is a hollow member having a hollow portion formed along the rotation axis, the end face is an annular surface surrounding the rotation axis, and the forged surface is formed on the annular surface.

5. The forging tool is composed of a forging roller that rotates as it presses against the end face, and the forging roller forms the forged surface while being fed in a direction parallel to the rotation axis. The method for forming metal powder according to any one of claims 1 to 4.

6. The method for forming metal powder according to any one of claims 1 to 5, wherein the formation height of the convex portion is controlled based on the pressing load of the forging tool against the end face.

7. The method for forming metal powder according to any one of claims 1 to 5, wherein the formation height of the convex portion is controlled based on the pressing depth of the forging tool against the end face.

8. The method for forming metal powder according to any one of claims 1 to 7, wherein the cutting tool cuts the forged surface with a cutting amount not exceeding the height of the convex portion while being fed in a direction parallel to the rotation axis.

9. The cutting tool is composed of a rotary cutting tool having a plurality of comb-shaped cutting edges, the convex portion is a plurality of parallel ridge-shaped convex portions formed on the forged surface, and the rotary cutting tool cuts the ridge-shaped convex portions such that the cutting trajectory of the comb-shaped cutting edges intersects the ridge-shaped convex portions. The method for forming metal powder according to any one of claims 1 to 8.

10. The cutting tool is a non-rotary cutting tool having a straight cutting edge, and the straight cutting edge is brought into contact with the forged surface in parallel to cut the forged surface. The method for forming metal powder according to any one of claims 1 to 8.

11. The workpiece is a solid member extending along the rotation axis, the end face is an inclined surface inclined with respect to the rotation axis, and the cutting portion of the cutting tool intersects the rotation axis. The method for forming metal powder according to any one of claims 1 to 10.

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