Method for manufacturing metal powder

Abstract

To provide a highly productive method for manufacturing metal powder. [Solution] The process includes a plastic deformation step P1 in which ultrasonic vibrations are applied to the surface of a metal workpiece 1 to form a plurality of protrusions 11 aligned in one direction, and a cutting step P2 in which a cutting tool 3 is used to cut the plurality of protrusions 11 to generate metal powder 4.

Description

Technical Field

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[0007] According to the present invention, it is possible to provide a method for producing metal powder with high productivity. [Brief explanation of the drawing]

[0008] [Figure 1] This is a process diagram showing a method for producing metal powder according to one embodiment of the present invention. [Figure 2] This is a schematic diagram showing the processing state in the plastic deformation process and cutting process according to one embodiment of the present invention. [Figure 3] This is a view from arrow III in Figure 2. [Figure 4] This is a schematic diagram showing the machining state in a cutting process according to one embodiment of the present invention. [Figure 5] This is a schematic diagram showing the machining state in a cutting process according to one embodiment of the present invention. [Modes for carrying out the invention]

[0009] The following describes embodiments for carrying out the present invention with reference to the drawings. The method for producing metal powder in this embodiment involves cutting the surface of a workpiece made of a metal material and recovering the fine cutting powder generated by the cutting as a metal powder product. The material of the target metal powder is not particularly limited as long as it is a metal. For example, aluminum, aluminum alloys, copper, copper alloys, iron, stainless steel, titanium, titanium alloys, nickel, nickel alloys, cobalt alloys, etc., can be used as examples. The particle size of the fine metal powder produced in this embodiment is not particularly limited. For example, it is a metal powder with an average particle size of several tens of micrometers to about 500 micrometers.

[0010] The applications of the fine metal powder manufactured in this embodiment are not particularly limited. For example, it can be used as metal powder for metal 3D printing or as metal powder mixed into resin pellets. When the metal powder manufactured in this embodiment is used as metal for metal 3D printing, it can be used, for example, as metal powder for powder bed 3D printing. When the metal powder manufactured in this embodiment is used as metal for metal 3D printing, it can also be used in 3D printing methods called Fused Deposition Modeling (FDM) or Fused Filament Fabrication (FFF), which involve mixing metal powder into resin filaments to form a laminate. Furthermore, when the metal powder manufactured in this embodiment is used as metal powder mixed into resin pellets, resin pellets containing the metal powder can be formed, and these pellets can be used for injection molding.

[0011] Furthermore, injection-molded parts and laminates 3D printed using the fused deposition modeling (FDM) or filament filament melting (FFF) methods described above can be degreased and fired to obtain metal parts from which the resin has been removed. For these applications, it is preferable that the particle aspect ratio (the ratio of the long axis to the short axis of the particle) is close to 1, i.e., that the particle is spherical.

[0012] Figure 1 is a process diagram showing a method for manufacturing metal powder according to one embodiment of the present invention. As shown in Figure 1, the method for manufacturing metal powder according to the present invention involves preparing a metal workpiece 1, forming a plurality of convex portions 11 aligned in one direction on the surface of the workpiece 1 while applying ultrasonic vibration (plastic deformation process P1), cutting the plurality of convex portions 11 formed on the surface of the workpiece 1 using a cutting tool 3 to generate metal powder 4 (cutting process P2), and recovering the generated metal powder 4 as a product (powder recovery process P3). After the cutting process P2 is completed and the plurality of convex portions 11 have been cut off the workpiece 1, the plastic deformation process P1 and the cutting process P2 are performed on the cut surface of the workpiece 1 as needed.

[0013] Figure 2 is a schematic diagram showing the processing state in the plastic deformation process P1 and cutting process P2 according to one embodiment of the present invention, and Figure 3 is a view from arrow III in Figure 2. The workpiece 1 in this embodiment shown in Figures 2 and 3 extends with the first axis A1 as its central axis and is circular or substantially circular in cross-section perpendicular to the first axis A1, so the workpiece 1 as a whole is cylindrical. However, the shape of the workpiece 1 is not limited to this, and for example, a part of the workpiece 1 may include a part that has a smaller radial dimension than other parts. Also, the workpiece 1 may be elliptical, polygonal, or the like. In the plastic deformation process P1 and cutting process P2 of this embodiment, one end 12 of the workpiece 1 is fixed to the chuck of an NC lathe and rotated around the first axis A1 in the direction of arrow H, and rolling and cutting processes are continuously performed on the other end 13 of the workpiece 1 while feeding the workpiece 1 in the direction of the first axis A1.

[0014] In this embodiment, the workpiece 1 has a first surface S1 before the plastic deformation process P1 and the cutting process P2 are performed. The first surface S1 has an axisymmetric shape around the first axis A1. In the examples shown in Figures 2 and 3, the first surface S1 is formed on the outer circumferential surface of the workpiece 1. That is, the first surface S1 has the shape of a cylindrical surface with the first axis A1 as its central axis.

[0015] The plastic deformation process P1 of this embodiment is a process of forming a plurality of protrusions 11 on the first surface S1 of the workpiece 1 by performing plastic deformation, for example, as shown in Figure 4. In the following description, the surface of the workpiece 1 on which the plurality of protrusions 11 have been formed by plastic deformation will be referred to as the second surface S2. In the plastic deformation process P1, the workpiece 1 is plastically deformed by pressing the plastic deformation tool 2 against the first surface S1, thereby forming a plurality of protrusions 11. The plurality of protrusions 11 are formed in a state where they are aligned in at least one direction. The material of the plastic deformation tool 2 only needs to have a higher hardness than the workpiece 1. For example, the plastic deformation tool 2 may be made of cemented carbide. In addition, a sliding film (not shown) may be formed on the processing die of the plastic deformation tool 2. The sliding film may be, for example, a DLC (Diamond Like Carbon) coating. In addition, the sliding film may be formed by known film formation methods such as PVD (Physical Vapor Deposition) or CVD (Chemical Vapor Deposition). A "processing die" refers to a portion of a plastic deformation tool that has a predetermined shape and is formed on its surface to plastically deform the surface of a workpiece into a desired shape.

[0016] Plastic deformation is a process in which a workpiece 1 is pressed with a predetermined pressure using a die, causing the first surface S1 of the workpiece 1 to undergo plastic flow and deform plastically without removing any material from the base material. Below, we will describe a case in which the first surface S1 is plastically deformed by rolling as an example of plastic deformation to form a plurality of protrusions 11. However, the present invention is not limited to this. For example, the plurality of protrusions 11 may be formed by press working. Furthermore, the rolling process described below is an example of a plastic deformation process P1, but the present invention is not limited to this. For example, the plastic deformation process P1 may be a press working process.

[0017] In this embodiment, a knurling tool 21 can be used as the plastic working tool 2. The knurling tool 21 is one form of a rolling tool. In this embodiment, a cutting tool 31 can be used as the cutting tool 3. In the example shown in Figures 2 and 3, the knurling tool 21 is placed on one radial side of the workpiece 1, and two cutting tools 31 are placed opposite each other on the other side. Note that the arrangement relationship between the workpiece 1, the knurling tool 21, and the cutting tools 31 is not limited to the illustrated example and can be appropriately set according to the shape and dimensions of the processing apparatus for manufacturing metal powder according to the embodiment. For example, one cutting tool 31 may be placed on one radial side of the workpiece 1, and the knurling tool 21 may be placed on the other side.

[0018] The knurling tool 21 of this embodiment includes a first knurling tool 21a and a second knurling tool 21b, as shown in Figure 2. In the illustrated example, the first knurling tool 21a is rotatable around the second axis A2 and is a roller-type tool with a disc shape when viewed in the axial direction of the second axis A2. The second knurling tool 21b is rotatable around the third axis A3 and is a roller-type tool with a disc shape when viewed in the axial direction of the third axis A3. The first knurling tool 21a rotates in the direction of arrow I in accordance with the rotation of the workpiece 1, and the second knurling tool 21b rotates in the direction of arrow J. Although the second axis A2 and third axis A3 illustrated in the figure extend parallel to the first axis A1, the present invention is not limited to this. For example, the second axis A2 or the third axis A3 may extend in a direction inclined with respect to the first axis A1.

[0019] A processing die 22 is formed on the outer peripheral surface of the first knurling tool 21a. The processing die 22 is composed of a plurality of rib portions. In the example shown in FIG. 3, each of the plurality of rib portions extends in a direction intersecting the second axis A2 in a radial view of the first knurling tool 21a and is arranged parallel to each other. Further, a processing die (not shown) formed on the outer peripheral surface of the second knurling tool 21b is configured by extending a plurality of rib portions not shown in a direction intersecting the extending direction of the rib portions of the first knurling tool 21a. In the swaging process of the present embodiment, by pressing the knurling tool 21 against the first surface S1 of the workpiece 1 rotating around the first axis A1 with a predetermined pressing load, a plurality of convex portions 11 having a so-called diamond pattern in which the first surface S1 bulges into a shape corresponding to the processing die 22 of the knurling tool 21 are formed.

[0020] The knurling tool 21 illustrated in FIGS. 2 and 3 includes a first knurling tool 21a and a second knurling tool 21b which are two roller-type tools, but the present invention is not limited thereto. For example, the knurling tool 21 may include only one roller-type tool. In that case, a plurality of concave portions having shapes such as a square pyramid shape and a hemisphere shape may be formed on the outer peripheral surface of the one roller-type tool.

[0021] The cutting process P2 is a process of cutting the plurality of convex portions 11 formed by the plastic working process P1 with the cutting tool 3. When the plurality of convex portions 11 are cut, metal powder 4 as cutting powder is obtained. In the following description, the surface of the workpiece 1 after the plurality of convex portions 11 are cut is also referred to as the third surface S3.

[0022] The tool bit 31 of the present embodiment includes a cutting edge 32. The cutting edge 32 has a flat edge shape extending in a direction parallel to the first axis A1. As shown in FIG. 3, in the direction parallel to the first axis A1, the width of the cutting edge 32 of the tool bit 31 and the width of the knurling tool 21 may be substantially equal.

[0023] In the plastic deformation process P1 of this embodiment, rolling is performed while inputting ultrasonic vibrations to the first surface S1 of the workpiece 1 using an ultrasonic input device 5. As shown in Figure 2, the ultrasonic input device 5 of this embodiment includes an oscillator 51 that generates and adjusts high-frequency power, an ultrasonic transducer 52 that converts the high-frequency power from the oscillator 51 into ultrasonic vibrations, and a horn 53 that amplifies the ultrasonic waves from the ultrasonic transducer 52. The horn 53 is positioned in contact with the surface of the workpiece 1 and inputs ultrasonic waves of a predetermined frequency to the workpiece 1.

[0024] In this embodiment, the horn 53 is positioned facing the knurling tool 21 on the workpiece 1. As a result, the direction of the ultrasonic vibration input from the horn 53 coincides with the direction of the rolling process by the knurling tool 21, further improving the formability of the rolling process.

[0025] Furthermore, the horn 53 in this embodiment is positioned 90 degrees out of phase with the position of the cutting tool 31. In other words, the positional relationship between the horn 53 and the cutting tool 31 is set so that the direction of vibration of the workpiece 1 caused by the horn 53 and the tangential direction of the cutting tool 31 with respect to the surface of the workpiece 1 are in the same direction. As a result, even if the workpiece 1 is subjected to ultrasonic vibration, the amount of cutting by the cutting tool 31 can be kept constant.

[0026] In the metal powder manufacturing method of this embodiment, the diameter of the workpiece 1 gradually decreases by performing the cutting process P2. However, the energy of the ultrasonic vibration may be controlled to a small amount by adjusting the high-frequency power of the oscillator 51 as the diameter of the workpiece 1 decreases. This makes it possible to maintain a constant height for the protrusions 11 made by the knurling tool 21, and to maintain a constant particle size for the generated metal powder.

[0027] Furthermore, in the embodiment shown in Figure 2, ultrasonic vibrations are input to the workpiece 1 by bringing the horn 53 into contact with the surface of the workpiece 1. However, the present invention is not limited to this, and ultrasonic vibrations may also be input to the knurling tool 2, i.e., the knurling tool 21, by bringing the horn 53 into contact with the knurling tool 21. Alternatively, ultrasonic vibrations may be input to both the workpiece 1 and the knurling tool 21.

[0028] Next, I will explain the mechanism of action. As shown in Figure 2, in the plastic deformation process P1 and cutting process P2 of this embodiment, one end 12 of the workpiece 1 is fixed to the chuck of the NC lathe, the workpiece 1 is rotated in the direction of arrow H around the first axis A1, and while the workpiece 1 is fed in the direction of the first axis A1, ultrasonic vibrations are also applied to the workpiece 1, and rolling and cutting processes are continuously performed on the other end 13 of the workpiece 1.

[0029] As a result, the first surface S1 of the workpiece 1 becomes a second surface S2 with multiple protrusions 11 made up of a diagonal pattern, and then some or all of the protrusions 11 of the second surface S2 are cut away to become a third surface S3. Metal powder 4 is generated at this time. Furthermore, if the rotation of the workpiece 1 is continued, the third surface S3 of the workpiece 1 becomes a second surface S2 with multiple protrusions 11 made up of a diagonal pattern, and then some or all of the protrusions 11 of the second surface S2 are cut away to become a third surface S3 again.

[0030] Furthermore, when performing the rolling process, the pitch of the multiple protrusions 11 can be adjusted by adjusting the pitch of the protrusions of the first knurling tool 21a or the second knurling tool 21b. In addition, the height H1 of each of the multiple protrusions 11 in the radial direction of the workpiece 1 (see Figure 4) can be controlled by the pressing load of the knurling tool 21 during the rolling process. For example, when performing the rolling process, the height H1 of the protrusions 11 can be made lower by reducing the pressing load of the knurling tool 21. Note that height H1 refers to the distance between the top 11a and the first surface S1 in an axial view parallel to the first axis A1 in Figure 4.

[0031] Furthermore, when performing cutting, the cutting tool 31 shown in Figure 4 may be used to cut in the direction of arrow K with a predetermined depth of cut D. At this time, the movement of the cutting tool 31 in a direction perpendicular to the cutting direction may be restricted. In the example shown in the figure, the depth of cut D refers to the distance in the radial direction of the workpiece 1 between the top 11a of the protrusion 11 and the point P of the cutting blade 32 that is closest to the first axis A1. The depth of cut D may also be less than or equal to the height H1 of each of the multiple protrusions 11 in the radial direction of the workpiece 1. By cutting the cutting tool 31 into the second surface S2 having multiple protrusions 11, at least a portion of the multiple protrusions 11 is cut by the cutting blade 32, as illustrated in Figure 5, and metal powder 4 is generated as cutting chips.

[0032] In particular, the metal powder manufacturing method of this embodiment includes a plastic deformation step P1 in which a plurality of convex portions 11 aligned in one direction are formed on the surface of a metal workpiece 1 while applying ultrasonic vibrations, and a cutting step P2 in which the plurality of convex portions 11 are cut using a cutting tool 3 to generate metal powder 4. As a result, the formability during plastic deformation is improved by applying ultrasonic vibrations. Consequently, metal powder 4 can be produced with fewer plastic deformation steps, resulting in higher productivity.

[0033] Furthermore, in the metal powder manufacturing method of this embodiment, the tangential direction of the cutting tool 3 to the surface of the workpiece 1 is the same as the direction of vibration of the workpiece 1 due to the input of ultrasonic vibrations. Therefore, the amount of cutting can be maintained at a predetermined amount even with respect to the vibrating workpiece 1, and as a result, the particle size of the generated metal powder 4 can be maintained at a predetermined value.

[0034] Furthermore, in the metal powder manufacturing method of this embodiment, as the diameter of the workpiece 1 decreases due to the cutting step P2, the energy of the ultrasonic vibration is controlled to be smaller, so that the height of the protrusions 11 formed in the plastic deformation step P1 can be maintained at a predetermined value, and as a result, the particle size of the generated metal powder 4 can be maintained at a predetermined value.

[0035] Furthermore, in the metal powder manufacturing method of this embodiment, the plastic deformation tool 2 is a rolling tool 21, and the plastic deformation step P1 is a rolling step in which the plurality of protrusions 11 are formed on the surface of the workpiece 1 using the rolling tool 21. Therefore, the formability during plastic deformation is improved by inputting ultrasonic vibrations. As a result, metal powder 4 can be produced with fewer rolling steps, and productivity is increased.

[0036] Furthermore, in the metal powder manufacturing method of this embodiment, the surface of the workpiece 1 has an axisymmetric shape around a predetermined axis, the first axis A1, and the cutting process P2 is performed while the workpiece 1 is rotated around the predetermined axis, the first axis A1, so that the rolling process and the cutting process can be performed continuously in accordance with the rotation of the workpiece 1.

[0037] Furthermore, in the metal powder manufacturing method of this embodiment, a cutting tool 31 having a cutting blade 32 parallel to the predetermined axis, the first axis A1, is used as the cutting tool 3, and cutting is performed with a depth of cut D that is less than or equal to the height H1 of the protrusion 11. As a result, the formability during plastic deformation is improved by the input of ultrasonic vibrations. Consequently, metal powder 4 can be produced with fewer plastic deformation steps, resulting in higher productivity.

[0038] Furthermore, in the metal powder manufacturing method of this embodiment, the direction of vibration of the workpiece 1 due to the input of ultrasonic vibration is the same as the direction in which the rolling tool 21 is pressed against the workpiece 1. Therefore, the input of ultrasonic vibration has an even greater influence on the formability during plastic deformation, resulting in improved formability. As a result, metal powder 4 can be produced with fewer plastic deformation steps, increasing productivity. [Explanation of Symbols]

[0039] 1…Work material 11…Convex part 12... One end 13...the other end 2…Plastic processing tools 21, 21a, 21b... Knurling tools (rolling tools) 22…Processing mold 3…Cutting tools 31...bytes 32…Cutting blade 4...Metal powder 5. Ultrasonic input device 51…Oscillator 52… Ultrasonic transducer 53... Horn P1…Plastic working process P2…Cutting process P3... Powder recovery process H1...Height of the protrusion

Claims

1. A plastic deformation process that forms multiple convex portions aligned in one direction on the surface of a metal workpiece while applying ultrasonic vibrations, A method for producing metal powder, comprising a cutting step of cutting the plurality of protrusions using a cutting tool to produce metal powder.

2. The method for producing metal powder according to claim 1, wherein the tangential direction of the cutting tool with respect to the surface of the workpiece is the same as the direction of vibration of the workpiece due to the input of ultrasonic vibrations.

3. A method for producing metal powder according to claim 1 or 2, wherein the energy of the ultrasonic vibration is controlled to decrease as the diameter of the workpiece decreases due to the cutting process.

4. The method for producing metal powder according to claim 1 or 2, wherein the plastic deformation step is a rolling step in which a plurality of protrusions are formed on the surface of the workpiece using a rolling tool.

5. The surface of the workpiece has an axisymmetric shape around a predetermined axis, The method for producing metal powder according to claim 4, wherein the cutting process is performed while the rolling process is carried out while the workpiece is rotated around the predetermined axis.

6. A method for producing metal powder according to claim 5, wherein a cutting tool having a cutting blade parallel to the predetermined axis is used as the cutting tool, and the cutting is performed with a depth of cut less than or equal to the height of the protrusion.

7. The method for producing metal powder according to claim 4, wherein the direction of vibration of the workpiece due to the input of the ultrasonic vibration is the same as the direction in which the rolling tool is pressed against the workpiece.

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