Metal powder forming method

Abstract

A metal powder forming method for forming a metal powder by cutting the surface of a metal workpiece, said method comprising: a first rolling step for supporting the workpiece with three or more rollers including at least a first roller having an uneven outer circumferential surface and a second roller having a smooth outer circumferential surface, and forming a plurality of protrusions in the workpiece via the first roller; a cutting step for forming a metal powder by cutting the plurality of protrusions of the workpiece at cutting depths of less than the respective heights of the plurality of protrusions, via a cutting tool; and a second rolling step for smoothing the rough surface of the workpiece after the cutting, via the second roller.

Description

Method for forming metal powder

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

[0002] Patent Document 1 discloses a method for forming metal powder by forming a plurality of fine convex portions on the circumferential surface of a rotating metal cylinder with a rolling tool and then cutting the formed convex portions with a cutting tool.

[0003] International Publication No. 2023 / 148980

[0004] By the way, unevenness remains on the cutting surface after cutting the convex portions, and cracks may occur in the convex portions formed in the next rolling process. When cutting convex portions having cracks, there is a risk that the aspect ratio of the formed metal powder decreases.

[0005] An object of the present invention is to provide a method for forming metal powder capable of suppressing a decrease in the aspect ratio of the metal powder after cutting.

[0006] The method for forming metal powder according to one aspect of the present invention forms metal powder by cutting the surface of a workpiece made of metal. In this method, the workpiece is supported by three or more rollers including at least a first roller having unevenness on its outer peripheral surface and a second roller having a smooth outer peripheral surface. The method includes a first rolling step of forming a plurality of convex portions on the workpiece with the first roller, a cutting step of cutting the plurality of convex portions of the workpiece with a cutting depth less than the height of each of the plurality of convex portions with a cutting tool to form metal powder, and a second rolling step of smoothing the rough surface of the workpiece after cutting with the second roller.

[0007] According to the above method for forming metal powder, it is possible to smooth the unevenness remaining on the rough surface of the workpiece after cutting, so that cracks are suppressed from occurring in the convex portions formed in the subsequent rolling process, and a decrease in the aspect ratio of the metal powder after cutting can be suppressed.

[0008] Figure 1 is a schematic side view of an apparatus for performing a metal powder formation method according to an embodiment. Figure 2 is a schematic perspective view showing the metal powder formation method. Figure 3 is a schematic side view showing the metal powder formation method. Figure 4A is a schematic perspective view showing the shape of the outer surface of the workpiece after the first rolling process and the cutting process. Figure 4B is a schematic perspective view showing the shape of the rough surface of the workpiece after cutting. Figure 4C is a schematic perspective view showing the second rolling process and the shape of the outer surface of the workpiece after the second rolling process.

[0009] The average aspect ratio or average particle size of the metal powder M1 formed by the metal powder formation method according to the embodiment was measured using a particle image analyzer (product name: Morphologi 4, manufactured by Malvern Panalogical). More specifically, several thousand to tens of thousands of particulate metal powder M1 particles were dispersed on a glass plate using a powder dispersion unit, photographed with an objective lens of a predetermined magnification, and the average aspect ratio or average particle size was calculated using image analysis software. The magnification of the objective lens can be appropriately set according to the shape of the metal powder M1, etc. The aspect ratio is the ratio of the major axis diameter to the minor axis diameter of the powder or particle in an image taken from a predetermined direction. The particle size is the equivalent circle diameter of the particle. The equivalent circle diameter is the diameter of a circle having an area equal to the projected area of ​​the photographed particle. In the following description, the average aspect ratio and average particle size of the metal powder M1 will be simply referred to as aspect ratio and particle size, respectively.

[0010] In the metal powder formation method according to this embodiment, a metal powder M1 having a particle size of, for example, 1 μm to 500 μm can be formed. The metal powder M1 can also be used as a molding material in a metal 3D printer (not shown). In that case, the particle size of the metal powder M1 is, for example, 1 μm to 100 μm. The mode diameter of the metal powder M1 may also be 25 μm to 75 μm. The mode diameter is the particle size or range of particle size that is most frequently present in the measurement sample. The metal powder M1 can be used, for example, as a powder material supplied to the powder bed in a powder bed type 3D printer. The metal powder M1 may also be used in other types of metal 3D printers. For example, it may be used as a powder material mixed with a thermoplastic resin in a fused deposition modeling (FDM) 3D printer.

[0011] The closer the aspect ratio of the metal powder M1 is to 1, the closer its shape is to a sphere. In other words, a closer aspect ratio of the metal powder M1 is to 1 improves its fluidity. When the fluidity of the metal powder M1 is improved, it can be spread more densely and uniformly in the powder bed of the powder bed type 3D printing described above, thus improving the quality of the 3D printed product. In addition to 3D printing as described above, the metal powder M1 can also be used as a raw material for metal injection molding and thermal spraying. In these cases as well, if the fluidity of the metal powder M1 is good, the supply of the metal powder M1 inside the injection molding machine or thermal spraying machine can be carried out smoothly.

[0012] The metal powder formation method according to the embodiment will be described below with reference to the drawings. Furthermore, components having the same function as those already described will be denoted by the same reference numerals and their descriptions will be omitted.

[0013] The metal powder formation method according to this embodiment is a method for forming metal powder M1 by cutting the surface of a metal workpiece 1, and comprises a first rolling step, a cutting step, and a second rolling step. The metal powder M1 is composed of a large number of metal particles.

[0014] As illustrated in Figure 1-3, the apparatus for performing the metal powder forming method according to the embodiment comprises three or more rollers 10, including at least first rollers 10A and 10B and a second roller 10C. The rollers 10 support the workpiece 1 during the first rolling process, the cutting process, and the second rolling process. During the above processes, the rollers 10 apply a predetermined pressing load toward the central axis A1 in the radial direction of the workpiece 1. Also, as illustrated in Figure 1, when the above processes are not being performed, the rollers 10 are positioned in a retracted position on the radially outer side of the workpiece 1.

[0015] As illustrated in Figure 1-3, the apparatus for performing the metal powder formation method according to the embodiment includes a first rolling roller 10A and a second rolling roller 10B, which are first rollers 10A and 10B for performing the first rolling process. The first rolling roller 10A and the second rolling roller 10B are provided with irregularities 11 and 12 on their outer surfaces, respectively. Furthermore, as illustrated in Figure 1-3, the apparatus also includes a third rolling roller 10C, which is a second roller 10C for performing the second rolling process. The third rolling roller 10C has a smooth outer surface.

[0016] The workpiece 1 is a metal component that serves as the material for the metal powder M1, and is composed of, for example, aluminum, aluminum alloy, copper, copper alloy, etc. In the example shown in Figure 1-3, the workpiece 1 extends with the first axis A1 as its central axis and has a substantially circular shape in a cross section perpendicular to the first axis A1. Therefore, the workpiece 1 as a whole has a cylindrical shape. However, the shape of the workpiece 1 is not limited to this, and for example, a part of the workpiece 1 may have a smaller radial dimension than other parts. Also, the workpiece 1 may have shapes such as an elliptical prism or a polygonal prism.

[0017] The workpiece 1 has a first surface P1 in the state before the first rolling process and the cutting process are performed. The first surface P1 has an axisymmetric shape around the first axis A1. In the example shown in Figures 1 and 2, the first surface P1 constitutes the outer circumferential surface of the workpiece 1. That is, the first surface P1 has the shape of a cylindrical surface with the first axis A1 as its central axis.

[0018] The first rolling process is a process of forming a plurality of protrusions 30 on the first surface P1 of the workpiece 1. Rolling is a type of plastic deformation process. In the following description, the outer circumferential surface of the workpiece 1 on which the plurality of protrusions 30 have been formed by rolling will be referred to as the second surface P2. In the first rolling process, the workpiece 1 is plastically deformed by pressing the first rolling roller 10A and the second rolling roller 10B against the first surface P1, thereby forming a plurality of protrusions 30 (see Figure 2). The plurality of protrusions 30 are formed in a state where they are aligned in at least one direction. The material of the first rolling roller 10A and the second rolling roller 10B should have a higher hardness than the workpiece 1. For example, the first rolling roller 10A and the second rolling roller 10B are made of cemented carbide. In addition, a sliding film may be formed on the surfaces of the first rolling roller 10A and the second rolling roller 10B. The sliding film may be, for example, a DLC (Diamond-Like Carbon) coating. Furthermore, the sliding film may be formed by known film formation methods such as PVD (Physical Vapor Deposition) or CVD (Chemical Vapor Deposition).

[0019] In the first rolling process, a first rolling roller 10A and a second rolling roller 10B, which are molds having a rolling pattern, are pressed against the workpiece 1 to plastically deform the first surface P1 of the workpiece 1 and form a rolling pattern. The first surface P1 of the workpiece 1 is plastically deformed without being cut away, and a plurality of protrusions 30 are formed on the second surface P2 after the rolling process. On the other hand, in the cutting process, the plurality of protrusions 30 formed by the rolling process are cut away with a cutting tool 20. When the plurality of protrusions 30 are cut away, metal powder M1 is obtained as cutting dust. In the following description, the outer surface of the workpiece 1 after the plurality of protrusions 30 have been cut away will be referred to as the rough surface P3.

[0020] As illustrated in Figure 1-3, in this embodiment, a first rolling roller 10A is positioned below the workpiece 1, a second rolling roller 10B is positioned on one side of the workpiece 1 in the left-right direction, a third rolling roller 10C is positioned on the other side, and a cutting tool 20 is positioned above the workpiece 1. The cutting tool 20 in this embodiment is a cutting tool. The arrangement of the workpiece 1, the first rolling roller 10A, the second rolling roller 10B, the third rolling roller 10C, and the cutting tool 20 is not limited to the illustrated example and can be appropriately set according to the processing apparatus for carrying out the metal powder forming method according to this embodiment, as well as the shape, dimensions, etc. of the workpiece 1.

[0021] As illustrated in Figure 1-3, the first rolling roller 10A is rotatable around the second axis A2 and has a disc shape when viewed in the axial direction parallel to the second axis A2. The second rolling roller 10B is rotatable around the third axis A3 and has a disc shape when viewed in the axial direction parallel to the third axis A3. The second axis A2 and the third axis A3 extend parallel to the first axis A1, but are not limited to this. The second axis A2 or the third axis A3 may extend in a direction inclined with respect to the first axis A1. In Figure 1, A2' and A3' indicate the positions of the second axis and the third axis when the first rolling roller 10A and the second rolling roller 10B are positioned in the retracted position described above. The first rolling roller 10A is configured to move back and forth along a trajectory parallel to the radial direction with respect to the central axis A1 of the workpiece 1 (see Figure 1). The second rolling roller 10B is configured to swing along an arc-shaped trajectory relative to the workpiece 1, for example (see Figure 1).

[0022] A rolling pattern 11 with irregularities is formed on the outer circumferential surface of the first rolling roller 10A. The rolling pattern 11 is composed of a plurality of protrusions. Each of these protrusions extends in a direction intersecting the second axis A2 when viewed radially from the first rolling roller 10A and is arranged parallel to one another. The rolling pattern 12 with irregularities formed on the outer circumferential surface of the second rolling roller 10B is formed by extending a plurality of protrusions in a direction intersecting the extending direction of the protrusions on the first rolling roller 10A. The first rolling roller 10A and the second rolling roller 10B form a number of protrusions 30 on the outer circumferential surface (second surface P2) of the workpiece 1 in the rotational and axial directions of the workpiece 1 (see Figure 2).

[0023] In this embodiment, the rolling apparatus includes a first rolling roller 10A and a second rolling roller 10B. Multiple protrusions 30 are formed by pressing the first rolling roller 10A against the surface (outer surface) of the workpiece 1 rotating around a central axis A1 to form multiple first grooves extending in one direction, and pressing the second rolling roller 10B against the outer surface of the workpiece 1 rotating around a central axis A1 to form multiple second grooves. In this case, the multiple second grooves extend in a direction intersecting the multiple first grooves, and the multiple protrusions 30 are arranged in the direction in which the first grooves and second grooves extend, respectively. That is, the first rolling roller 10A and the second rolling roller 10B form a diagonal rolling pattern consisting of multiple protrusions 30 on the outer surface of the workpiece 1. Alternatively, a single first roller having a diagonal rolling pattern may form the diagonal rolling pattern consisting of multiple protrusions 30 on the outer surface of the workpiece 1. In this case, the roller 10 may include two or more second rollers with smooth outer surfaces. Furthermore, the cutting tool 20 is equipped with a cutting blade 21 at its tip. The cutting blade 21 is a flat blade extending in a direction parallel to the first axis A1. In this embodiment, in the direction parallel to the first axis A1, the width of the cutting blade 21 of the cutting tool 20 and the widths of the first rolling roller 10A and the second rolling roller 10B are approximately equal.

[0024] In the rolling process according to this embodiment, one end of the workpiece 1 is fixed to the chuck of an NC (numerically controlled) lathe, and the rolling process is performed while the workpiece 1 rotates around the first axis A1. In the first rolling process, the first rolling roller 10A is pressed with a predetermined load against the first surface P1 of the workpiece 1 that is rotating around the first axis A1. As a result, as shown in Figure 4, a part of the first surface P1 is crushed and another part is raised in a shape corresponding to the rolling pattern of the first rolling roller 10A, forming a plurality of parallel ridges.

[0025] The outer circumferential surface of the workpiece 1, on which ridges have been formed by the first rolling roller 10A, is immediately subjected to rolling by the second rolling roller 10B, which creates ridges that intersect with the existing ridges. Since ridges have already been formed, the ridges formed by the rolling pattern of the second rolling roller 10B are intermittently crushed, and as shown in Figure 4A, convex portions 30 are formed on the second surface P2 after rolling. In this embodiment, the convex portions 30 have the shape of a square pyramid with a rhombus-shaped base and a rounded apex. In a diagonal rolling pattern, these square pyramidal convex portions 30 with rhombus-shaped bases are continuously arranged in a two-dimensional manner on the outer circumferential surface of the workpiece 1. The two pairs of opposite sides of the rhombus are parallel to each other. Therefore, the first rolling roller 10A and the second rolling roller 10B, each having parallel ridges as their rolling patterns, are suitable for forming a diagonal rolling pattern in which rhombuses are arranged.

[0026] Next, the cutting process will be described. The multiple protrusions 30 that have been formed are cut by a cutting tool 20. In the cutting process, as shown in Figure 1-4A, the protrusions 30 are cut by moving the cutting tool 20 relative to the workpiece 1 in the direction of rotation of the workpiece 1, i.e., in the circumferential direction. In this embodiment, the cutting tool 20 is fixed, and the protrusions 30 are cut in the cutting direction C1 as the workpiece 1 is rotated (see Figure 4A). That is, the direction of rotation of the workpiece 1 coincides with the cutting direction C1. Alternatively, the first rolling roller 10A, the second rolling roller 10B, the third rolling roller 10C, and the cutting tool 20 may be moved relative to the workpiece 1 in the axial direction. In this case, by adjusting the axial movement speed to match the axial pitch described above, cutting can be performed while continuously rolling the above-described rolling pattern in the axial direction on the circumferential surface of the workpiece 1.

[0027] In order to obtain a large amount of metal powder M1 by cutting the protrusions 30, the cutting depth is set to less than the height of the protrusions 30 described above. As a result, grooves 40 are formed on the rough surface P3 of the workpiece 1 after cutting, due to the remaining irregularities 11 that were not cut (see Figure 4B). In addition, in the first rolling process, two rolling patterns are formed by the first rolling roller 10A and the second rolling roller 10B, respectively, so it is difficult for the height (depth) of the protrusions 30 in each direction to be perfectly the same. Therefore, even when the cutting depth is set to the height of the protrusions 30 (i.e., when cutting is performed targeting the bottom portion of the protrusions 30), grooves 40 may be formed on the rough surface P3 of the workpiece 1 after cutting, due to the remaining irregularities 11 that were not cut (see Figure 4B).

[0028] In the second rolling process, the third rolling roller 10C is pressed against the workpiece 1 as a die having a rolling pattern, thereby plastically deforming the rough surface P3 of the workpiece 1 and forming the rolling pattern. The third rolling roller 10C is rotatable about the fourth axis A4 and has a disc shape when viewed in the axial direction parallel to the fourth axis A4. The fourth axis A4 extends parallel to the first axis A1, but is not limited to this. The fourth axis A4 may extend in a direction inclined with respect to the first axis A1. In Figure 1, A4' indicates the position of the fourth axis when the third rolling roller 10C is positioned in the retracted position described above. The third rolling roller 10C is configured to swing along an arc-shaped trajectory relative to the workpiece 1, for example (see Figure 1).

[0029] As illustrated in Figure 2, the outer surface of the third rolling roller 10C has a smooth shape. That is, the rolling pattern 13 is formed with a smooth shape in the circumferential and axial directions. The grooves 40 on the rough surface P3, which is the outer surface of the workpiece 1 after cutting, are crushed in the rolling direction C2 by the third rolling roller 10C, and the rough surface P3 is formed into an outer surface (fourth surface P4) with a smooth shape in the rotational and axial directions of the workpiece 1 (see Figure 4C).

[0030] The workpiece 1, which has a smooth shape obtained by the second rolling process, may be subjected to the first rolling process again, and metal powder M1 may be obtained by the cutting process. That is, the cycle in which the cutting process is performed after the first rolling process, the second rolling process is performed after the cutting process, and the first rolling process is performed after the second rolling process may be repeatedly carried out.

[0031] The third rolling roller 10C, which performs the second rolling process, may be configured to apply a greater pressing load to the workpiece 1 than the first rolling roller 10A and the second rolling roller 10B. This allows for a smoother formation of the rough surface P3 of the workpiece 1 during the second rolling process.

[0032] The first rolling roller 10A, the second rolling roller 10B, and the third rolling roller 10C may support the workpiece 1 in such a way that they cancel each other out toward the central axis A1 in the radial direction of the workpiece 1. This suppresses unevenness in the pressing load and suppresses deflection of the workpiece 1. As a result, cutting accuracy is improved and powder quality is improved. Consequently, the workpiece 1 can be processed to a smaller diameter, and material yield is improved.

[0033] As illustrated in Figure 1-3, in this embodiment, three rollers 10 are provided by two first rollers, a first rolling roller 10A, a second rolling roller 10B, and one second roller, a third rolling roller 10C. As illustrated in Figure 1, the contact points between the first rolling roller 10A, the second rolling roller 10B, and the third rolling roller 10C and the workpiece 1 may be located at positions with a rotational angle of 120° in the circumferential direction when viewed from the central axis A1 of the workpiece 1. That is, the angles α, β, and γ around the central axis A1 in Figure 1 may each be set to 120°. This makes it possible to more appropriately cancel out the bias in the pressing loads of the first rolling roller 10A, the second rolling roller 10B, and the third rolling roller 10C.

[0034] As illustrated in Figure 1-3, in this embodiment, the third rolling roller 10C contacts the workpiece 1 after the cutting tool 20 and before the first rolling roller 10A and the second rolling roller 10B in the rotational direction of the workpiece 1. That is, after the cutting process, the processes are carried out in the order of the second rolling process and the first rolling process. In other words, the cutting process is performed after the first rolling process, the second rolling process is performed after the cutting process, and the first rolling process is performed after the second rolling process. Therefore, in the rotational direction of the workpiece 1, the third rolling roller 10C is not positioned between the first rolling roller 10A, the second rolling roller 10B and the cutting tool 20. Also, in the rotational direction of the workpiece 1, the first rolling roller 10A and the second rolling roller 10B are not positioned between the cutting tool 20 and the third rolling roller 10C. As a result, the irregularities 11 remaining on the rough surface P3 of the workpiece 1 after cutting can be smoothed out without destroying the rolling pattern formed in the first rolling process, thereby forming a smooth fourth surface P4.

[0035] As illustrated in Figure 3, the heating means 50 sets the surface temperature of the third rolling roller 10C higher than the surface temperatures of the first rolling roller 10A and the second rolling roller 10B. This further promotes the smooth formation of the rough surface P3 of the workpiece 1. The heating means 50 is, for example, a halogen heater.

[0036] In the above configuration, the surface temperature of the second roller 10C is set to, for example, 250°C or higher. This allows for greater deformation of the rough surface P3 of the workpiece 1 during the second rolling process, further smoothing out the remaining irregularities 11 on the rough surface P3, and forming a smooth fourth surface P4. In the embodiment, the surface temperature of the second roller 10C is, for example, 250°C or higher and less than 500°C.

[0037] (1) The metal powder forming method according to the embodiment forms metal powder M1 by cutting the surface of a metal workpiece 1. In this method, the workpiece 1 is supported by three or more rollers 10, which include at least first rollers 10A and 10B having irregularities 11 on their outer surfaces and a second roller 10C having a smooth outer surface. This method includes a first rolling step in which the first rollers 10A and 10B form a plurality of protrusions 30 on the workpiece 1; a cutting step in which a cutting tool 20 cuts the plurality of protrusions 30 on the workpiece 1 with a cutting depth less than the height of each of the plurality of protrusions 30 to form metal powder M1; and a second rolling step in which the second roller 10C smooths the rough surface P3 of the workpiece 1 after cutting. The second roller 10C can crush the irregularities 11 remaining on the rough surface P3 of the workpiece 1 after cutting, and a smooth fourth surface P4 can be formed. This suppresses the occurrence of cracks in the shape of the protrusions 30 formed in the subsequent first rolling process, and suppresses the decrease in the aspect ratio of the metal powder M1 after cutting.

[0038] (2) In this embodiment, the second roller 10C has a greater pressing load on the workpiece 1 than the first rollers 10A and 10B. As a result, the irregularities 11 remaining on the rough surface P3 of the workpiece 1 after cutting can be more effectively flattened, and a smooth fourth surface P4 can be formed.

[0039] (3) Furthermore, in this embodiment, the first rollers 10A, 10B and the second roller 10C support the workpiece 1 such that they cancel each other out toward the central axis A1 in the radial direction of the workpiece 1. This suppresses unevenness in the pressing load and suppresses deflection of the workpiece 1. As a result, cutting accuracy is improved and powder quality is improved. Consequently, the workpiece 1 can be cut to a smaller diameter, and material yield is improved.

[0040] (4) In this embodiment, three rollers 10 are provided, and the contact points between the first rollers 10A, 10B and the second roller 10C and the workpiece 1 are located at positions with a rotational angle of 120° in the circumferential direction when viewed from the central axis A1 of the workpiece 1. This makes it possible to more appropriately cancel out the unevenness of the pressing load by the first rollers 10A, 10B and the second roller 10C.

[0041] (5) Furthermore, in this embodiment, the second roller 10C contacts the workpiece 1 after the cutting tool 20 and before the first roller 10A in the rotational direction of the workpiece 1. This makes it possible to flatten the irregularities 11 remaining on the rough surface P3 of the workpiece 1 after cutting without crushing the rolled pattern formed in the first rolling process, thereby forming a smooth fourth surface P4.

[0042] (6) In this embodiment, the surface temperature of the second roller 10C is higher than the surface temperature of the first roller 10A. This allows the second rolling process to be carried out with a relatively high surface temperature of the second roller 10C. As a result, in the second rolling process, the irregularities 11 remaining on the rough surface P3 of the workpiece 1 after cutting can be further smoothed out, and a smooth fourth surface P4 can be formed.

[0043] (7) Furthermore, in this embodiment, the surface temperature of the second roller 10C is 250°C or higher. As a result, in the second rolling process, the irregularities 11 remaining on the rough surface P3 of the workpiece 1 after cutting can be further smoothed out, and a smooth fourth surface P4 can be formed.

[0044] (8) In another embodiment, the apparatus is equipped with two first rollers 10A and 10B, and the plurality of protrusions 30 are formed by a plurality of first grooves extending in one direction, which are formed by pressing the first rolling roller 10A against the surface of the workpiece 1 rotating around the central axis A1, and a plurality of second grooves extending in a direction intersecting the plurality of first grooves, which are formed by pressing the second rolling roller 10B against the surface of the workpiece 1 rotating around the central axis A1. As a result, a diagonal rolling pattern can be formed on the outer surface of the workpiece 1 while appropriately offsetting the bias of the pressing load by the first rollers 10A and 10B and the second roller 10C.

[0045] (9) Further, in the embodiment, there is a mechanism for advancing and retreating one of the rollers 10 along a trajectory parallel to the radial direction with respect to the central axis A1 of the workpiece 1, and a mechanism for swinging two of the rollers 10 along an arc-shaped trajectory with respect to the workpiece 1. Thereby, when replacing the workpiece 1, the roller 10 can be retracted and swung with respect to the workpiece 1 and arranged at the retracted position (see FIG. 1). Therefore, the take-out path and the input path of the workpiece 1 are secured, and the take-out and input operations of the workpiece 1 are facilitated.

[0046] As described above, the embodiments of the present invention have been described. However, the description and drawings forming a part of this disclosure should not be understood as limiting the present invention. Various alternative embodiments, examples, and operation techniques will be apparent to those skilled in the art from this disclosure.

[0047] This application claims priority based on Japanese Application No. 2025-009012 filed on January 22, 2025, and the entire contents of the application are incorporated herein by reference.

[0048] 1 Workpiece 10 Roller 10A First forging roller (first roller) 10B Second forging roller (first roller) 10C Third forging roller (second roller) 11 Forging pattern (concave and convex) 12 Forging pattern (concave and convex) 20 Cutting tool 30 Convex portion A1 First axis (central axis) M1 Metal powder P3 Rough surface

Claims

1. A method for forming metal powder by cutting the surface of a metal workpiece, comprising: supporting the workpiece with three or more rollers, each including at least a first roller having an uneven outer surface and a second roller having a smooth outer surface; a first rolling step of forming a plurality of protrusions on the workpiece with the first roller; a cutting step of cutting the plurality of protrusions on the workpiece with a cutting tool to a cutting depth less than the height of each of the protrusions, thereby forming metal powder; and a second rolling step of smoothing the rough surface of the workpiece after cutting with the second roller.

2. The metal powder forming method according to claim 1, wherein the second roller applies a greater pressing load to the workpiece than the first roller.

3. The metal powder forming method according to claim 1 or 2, wherein the first roller and the second roller support the workpiece such that they cancel each other out toward the central axis in the radial direction of the workpiece.

4. The metal powder forming method according to claim 1, or claim 3, which references claim 1, wherein three rollers are provided, and the contact points between the first roller and the second roller and the workpiece are respectively located at a rotational angle of 120° in the circumferential direction when viewed from the central axis of the workpiece.

5. The metal powder forming method according to claim 1 or 2, wherein the second roller contacts the workpiece after the cutting tool and before the first roller in the rotational direction of the workpiece.

6. The metal powder forming method according to claim 1 or 2, wherein the surface temperature of the second roller is higher than the surface temperature of the first roller.

7. The metal powder forming method according to claim 6, wherein the surface temperature of the second roller is 250°C or higher.

8. The metal powder forming method according to claim 4, comprising two first rollers, wherein the plurality of protrusions are formed by a plurality of first grooves extending in one direction, formed by pressing one of the first rollers against the surface of the workpiece rotating around the central axis, and a plurality of second grooves extending in a direction intersecting the plurality of first grooves, formed by pressing the other of the first rollers against the surface of the workpiece rotating around the central axis.

9. The metal powder forming method according to claim 4, comprising: a mechanism for moving one roller back and forth along a trajectory parallel to the radial direction with respect to the central axis of the workpiece; and a mechanism for swinging two rollers along an arc-shaped trajectory with respect to the workpiece.

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