Cutting tool

Abstract

The cutting tool is a cutting tool comprising a substrate and a diamond layer covering the substrate. The cutting tool comprises a rake face and a flank face. The flank face is continuous with the rake face. The ridge line between the rake face and the flank face constitutes a cutting edge. The diamond layer has a flank face covering portion. The flank face covering portion constitutes the flank face. The thickness of the flank face covering portion is 10 μm or more and 25 μm or less. In a cross section perpendicular to the tangent of the cutting edge, the radius of curvature of the cutting edge is less than a value obtained by multiplying the thickness of the flank face covering portion by 0.3. The rake face includes a first portion. The first portion is constituted by the flank face covering portion. The first portion is continuous with the flank face. The maximum height roughness of the first portion is less than 2 μm.

Description

Technical Field

[0001] The present disclosure relates to a cutting tool.

Background Art

[0002] Japanese Unexamined Patent Application Publication No. 2015-085462 (Patent Document 1) discloses a hard film-coated cutting tool in which a diamond film is coated on a tool body having a cutting edge formed at an intersection ridge line portion between a flank face and a rake face. In the hard film-coated cutting tool, the film thickness of the diamond film on the flank face side is 8 μm or more and 30 μm or less. When the rounding of the cutting edge tip is approximated by an arc of a radius, the radius is 0.1 times or more and 0.8 times or less the film thickness of the diamond film on the flank face side.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] The cutting tool according to the present disclosure is a cutting tool including a base material and a diamond layer covering the base material. The cutting tool includes a rake face and a flank face. The flank face is continuous with the rake face. The ridge line between the rake face and the flank face constitutes a cutting edge. The diamond layer has a flank face covering portion. The flank face covering portion constitutes the flank face. The thickness of the flank face covering portion is 10 μm or more and 25 μm or less. In a cross section perpendicular to the tangent line of the cutting edge, the radius of curvature of the cutting edge is less than a value obtained by multiplying the thickness of the flank face covering portion by 0.3. The rake face includes a first portion. The first portion is constituted by the flank face covering portion. The first portion is continuous with the flank face. The maximum height roughness of the first portion is less than 2 μm.

Brief Description of the Drawings

[0005]

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DETAILED DESCRIPTION OF THE INVENTION

[0006] [PROBLEMS TO BE SOLVED BY THE PRESENT DISCLOSURE] When the cutting edge of a cutting tool is covered with a diamond layer, the wear resistance of the tool improves as the thickness of the diamond layer increases. As the radius of curvature of the cutting edge decreases, the sharpness of the cutting edge improves. Thereby, damage to the cutting tool can be suppressed. However, even when the thickness of the diamond layer is large and the radius of curvature of the cutting edge is small, chip adhesion may occur on the cutting edge due to the surface state of the diamond layer. As a result, when a constituent cutting edge is formed, damage to the tool tends to progress. As described above, it has been difficult to improve the tool life in a cutting tool having a diamond layer.

[0007] An object of the present disclosure is to provide a cutting tool capable of improving tool life. [Effects of the Present Disclosure] According to the present disclosure, a cutting tool capable of improving tool life can be provided.

[0008] [Outline of Embodiment] First, an outline of an embodiment of the present disclosure will be described.

[0009] (1) The cutting tool according to the present disclosure is a cutting tool having a base material and a diamond layer covering the base material. The cutting tool has a rake face and a flank face. The flank face is continuous with the rake face. The ridge line between the rake face and the flank face constitutes a cutting edge. The diamond layer has a flank face covering portion. The flank face covering portion constitutes the flank face. The thickness of the flank face covering portion is 10 μm or more and 25 μm or less. In a cross section perpendicular to the tangent line of the cutting edge, the radius of curvature of the cutting edge is less than a value obtained by multiplying the thickness of the flank face covering portion by 0.3. The rake face has a first portion. The first portion is constituted by the flank face covering portion. The first portion is continuous with the flank face. The maximum height roughness of the first portion is less than 2 μm.

[0010] According to the cutting tool of the present disclosure, it is possible to suppress a part of the first portion from protruding excessively. For this reason, it is possible to suppress the occurrence of chip adhesion starting from the excessively protruding portion. As a result, the tool life can be improved.

[0011] (2) According to the cutting tool according to (1) above, the rake face may have a first rake face portion and a second rake face portion. The first rake face portion may be separated from the flank face. The second rake face portion may be provided between the first rake face portion and the flank face. The second rake face portion may be continuous with each of the first rake face portion and the flank face. The second rake face portion may be inclined with respect to the first rake face portion in a direction from the first rake face portion toward the flank face. Thereby, the angle formed by the rake face and the flank face can be increased. For this reason, the strength of the cutting edge can be improved.

[0012] (3) According to the cutting tool according to (2) above, the inclination angle of the second rake face with respect to the first rake face may be 3° or more and 50° or less. By the inclination angle of the second rake face being 3° or more, it is possible to suppress an excessive decrease in the strength of the cutting edge. By the second angle θ2 being 50° or less, it is possible to suppress an excessive decrease in the sharpness of the cutting edge.

[0013] (4) According to the cutting tool according to (2) above, the thickness of the flank face covering portion may be 15 μm or more and 20 μm or less. Thereby, the wear resistance of the cutting tool can be improved.

[0014] (5) According to the cutting tool according to any one of (1) to (4) above, in a cross section perpendicular to the tangent line of the cutting edge, the radius of curvature of the cutting edge may be less than the value obtained by multiplying the thickness of the flank face covering portion by 0.1. Thereby, the sharpness of the cutting edge can be improved.

[0015] (6) According to the cutting tool according to any one of (1) to (5) above, the base material may be composed of a cemented carbide containing tungsten carbide particles. The average particle diameter of the tungsten carbide particles may be 2 μm or less. Thereby, it is possible to suppress the diamond layer from peeling off from the base material. As a result, the tool life can be further improved.

[0016] (7) According to the cutting tool according to any one of (1) to (6) above, the clearance angle of the flank face may be 15° or more and 35° or less.

[0017] (8) According to the cutting tool according to any one of (1) to (7) above, the maximum height roughness of the first portion may be less than 1.5 μm.

[0018] [Details of Embodiment] Hereinafter, details of an embodiment of the present disclosure (hereinafter also referred to as this embodiment) will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

[0019] (First Embodiment) <Configuration of Cutting Tool> First, the configuration of the cutting tool according to the first embodiment will be described.

[0020] FIG. 1 is a schematic plan view showing a cutting tool according to the first embodiment. The cutting tool 100 according to the first embodiment has a tip portion 6, a body portion 7, and a shank portion 8. The cutting tool 100 is, for example, a ball end mill. The cutting tool 100 is, for example, a rotary cutting tool that rotates about an axis X as a rotation axis.

[0021] FIG. 2 is an enlarged schematic plan view showing region II of FIG. 1. FIG. 3 is an enlarged schematic side view showing the configuration of the cutting tool 100 according to the first embodiment. The enlarged schematic side view shown in FIG. 3 is an enlarged schematic side view seen along the arrow A in FIG. 2.

[0022] As shown in FIGS. 2 and 3, the cutting tool 100 has a rake face 1 and a flank face 2. The rake face 1 is continuous with the flank face 2. The ridge line between the rake face 1 and the flank face 2 constitutes a cutting edge 3. As shown in FIG. 2, when viewed perpendicular to the rake face 1, the tangent line of the cutting edge 3 is a first virtual straight line 91.

[0023] FIG. 4 is a schematic cross-sectional view taken along line IV-IV of FIG. 2. The cross-section shown in FIG. 4 is a cross-section perpendicular to the first virtual straight line 91 (see FIG. 2). As shown in FIG. 4, the cutting tool 100 has a substrate 4 and a diamond layer 5.

[0024] The substrate 4 has a first face 41 and a second face 42. The first face 41 constitutes, for example, a part of the rake face 1. The second face 42 is continuous with the first face 41. The second face 42 is substantially parallel to the flank face 2.

[0025] The diamond layer 5 covers at least a part of the base material 4. Specifically, the diamond layer 5 covers the second surface 42. The diamond layer 5 constitutes the flank 2. The portion of the diamond layer 5 that constitutes the flank 2 is defined as the flank covering portion 52. The first surface 41 is exposed from the diamond layer 5, for example.

[0026] The diamond layer 5 contains diamond crystals, for example. The diamond layer 5 is composed of, for example, polycrystalline diamond. The diamond layer 5 may contain components other than diamond (for example, amorphous components). The diamond layer 5 does not necessarily contain diamond crystals. The diamond layer 5 may be composed of, for example, DLC (Diamond Like Carbon).

[0027] The rake face 1 is planar, for example. The rake face 1 is composed of the flank covering portion 52 and the base material 4. The portion of the rake face 1 constituted by the flank covering portion 52 is defined as the first portion 16. The first portion 16 is continuous with the flank 2. From another perspective, the ridge line between the first portion 16 and the flank 2 constitutes the cutting edge 3. The portion of the rake face 1 constituted by the base material 4 is defined as the second portion 17. In other words, the rake face 1 has the first portion 16 and the second portion 17. The second portion 17 is substantially parallel to the first portion 16.

[0028] The thickness H of the flank covering portion 52 is 10 μm or more and 25 μm or less. The thickness H is the thickness of the flank covering portion 52 in the direction perpendicular to the flank 2. The thickness H may be, for example, 15 μm or more and 20 μm or less, or 15 μm or more and 17 μm or less. The thickness H may be, for example, 12 μm or more, or 14 μm or more. The thickness H may be, for example, 22 μm or less, or 18 μm or less.

[0029] <Maximum height roughness> As an index for quantifying surface roughness, there is the maximum height roughness defined as Rz (hereinafter also referred to as the maximum height roughness Rz or Rz). The maximum height roughness Rz is a surface property parameter defined in JIS (Japanese Industrial Standards) B0601:2013.

[0030] The Rz of the first part 16 is less than 2 μm. The Rz of the first part 16 may be, for example, 1.8 μm or less, 1.5 μm or less, or 1.2 μm or less. Rz may be, for example, 0.01 μm or more, or 0.5 μm or more.

[0031] Rz is measured, for example, using a laser microscope (「OPTELICS HYBRID」 (trademark) manufactured by Lasertech). For example, five different measurement regions within the first part 16 are set. Each of the five measurement regions is a linear region. The position of each of the five measurement regions is an arbitrary position within the first part 16. The average value of Rz measured at each of the five measurement regions is taken as the Rz of the first part 16. In other words, the value obtained by dividing the total value of Rz of the five measurement regions by 5 is taken as the Rz of the first part 16. The measurement pitch is, for example, 0.1 μm. The measurement range is, for example, 10 μm.

[0032] <Radius of curvature and second inclination angle> FIG. 5 is an enlarged cross-sectional schematic view showing the region V of FIG. 4. As shown in FIG. 5, in a cross-section perpendicular to the first virtual straight line 91, the shape of the cutting edge 3 may be substantially arc-shaped. In a cross-section perpendicular to the first virtual straight line 91, the radius of curvature R of the cutting edge 3 is less than the value obtained by multiplying the thickness H (see FIG. 4) of the flank covering portion 52 by 0.3. The radius of curvature R may be, for example, less than the value obtained by multiplying the thickness H by 0.2, less than the value obtained by multiplying the thickness H by 0.1, or less than the value obtained by multiplying the thickness H by 0.08. The radius of curvature R is, for example, greater than the value obtained by multiplying the thickness H by 0.001. The radius of curvature R is, for example, 0.5 μm or more and 7 μm or less.

[0033] As shown in FIGS. 4 and 5, in a cross section perpendicular to the first virtual straight line 91, a straight line that is perpendicular to the rake face 1 and in contact with the cutting edge 3 is defined as the second virtual straight line 92. In a cross section perpendicular to the first virtual straight line 91, the flank face 2 is inclined with respect to the second virtual straight line 92 in a direction from the cutting edge 3 toward the rake face 1. From another perspective, the flank face 2 is inclined with respect to the second virtual straight line 92 in a direction from the front end 58 toward the rear end 59. In a cross section perpendicular to the first virtual straight line 91, the inclination angle of the flank face 2 with respect to the second virtual straight line 92 (the first angle θ1) is, for example, 15° or more and 35° or less. The first angle θ1 may be, for example, 17° or more, or may be 19° or more. The first angle θ1 may be, for example, 33° or less, or may be 30° or less. The first angle θ1 is the relief angle of the flank face 2.

[0034] The radius of curvature R and the first angle θ1 are measured, for example, using a non-contact surface property measuring device “PF-60” manufactured by Mitaka Kohki Co., Ltd. For example, in the rake face 1 and the flank face 2, five different measurement regions are set. Each of the five measurement regions extends substantially perpendicular to the tangent line of the cutting edge 3 (see the first virtual straight line 91, FIG. 2) and is a linear region that intersects the cutting edge 3. The position of each of the five measurement regions is set to an arbitrary position within the first portion 16. The measurement pitch is, for example, 0.1 μm. The measurement range is, for example, 200 μm.

[0035] In each of the five measurement regions, curves indicating the shapes of the flank face 2, the cutting edge 3, and the rake face 1 are obtained. Based on the five obtained curves, the radius of curvature of the cutting edge 3 in each of the five measurement regions is measured. The average value of the radii of curvature of the cutting edge 3 in the five measurement regions is defined as the radius of curvature R of the cutting edge 3 in the cutting tool 100. In other words, the value obtained by dividing the total value of the radii of curvature of the cutting edge 3 in the five measurement regions by 5 is defined as the radius of curvature R of the cutting edge 3 in the cutting tool 100.

[0036] Similarly, based on the five acquired curves, the inclination angle of the flank face 2 with respect to the second virtual straight line 92 in each of the five measurement regions is measured. The average value of the inclination angles of the flank face 2 with respect to the second virtual straight line 92 in the five measurement regions is taken as the first angle θ1. In other words, the value obtained by dividing the total value of the inclination angles of the flank face 2 with respect to the second virtual straight line 92 in the five measurement regions by 5 is taken as the first angle θ1.

[0037] <Material constituting the base material> The base material 4 is made of, for example, a cemented carbide containing tungsten carbide (WC) particles. The cemented carbide constituting the base material 4 contains, for example, tungsten carbide particles and a binder such as cobalt.

[0038] The average particle size of the WC particles contained in the cemented carbide constituting the base material 4 is, for example, 2 μm or less. The average particle size of the WC particles contained in the cemented carbide constituting the base material 4 may be, for example, 1.5 μm or less, or may be 1 μm or less. The average particle size of the WC particles contained in the cemented carbide constituting the base material 4 may be, for example, 0.01 μm or more, or may be 0.1 μm or more.

[0039] In this specification, the average particle size of the above WC particles is the average value of the equivalent circle diameters of the WC particles. The average value of the equivalent circle diameters of the WC particles means the arithmetic average based on the number of the equivalent circle diameters of the WC particles measured on the surface or cross-section of the cemented carbide. The average value of the equivalent circle diameters of the tungsten carbide particles is measured by the following procedure.

[0040] Specifically, an arbitrary surface or an arbitrary cross-section of the cemented carbide is mirror-finished. Examples of the mirror-finishing method include a method of polishing with diamond paste, a method using a Focused Ion Beam (FIB) apparatus, a method using a Cross-section Polisher (CP) apparatus, and a method combining these.

[0041] The machined surface of the cemented carbide is photographed with a scanning electron microscope ("S-3400N" manufactured by Hitachi High-Technologies Corporation). Prepare three such photographed images. The photographing areas of each of the three images are different. The photographing location can be set arbitrarily. The photographing condition is a backscattered electron image. The observation magnification is 5000 times. The acceleration voltage is 10 kV.

[0042] The three photographed backscattered electron images are imported into a computer using image analysis software (ImageJ, version 1.51j8: https: / / imagej.nih.gov / ij / ). Binarization processing is performed on the three photographed backscattered electron images. The binarization processing is executed under the conditions preset in the above image analysis software by pressing the display "Make Binary" on the computer screen after importing the image. In the image after binarization processing, tungsten carbide particles and the parts other than tungsten carbide particles can be distinguished by the shade of color. For example, in the image after binarization processing, tungsten carbide particles are shown as black regions, and the parts other than tungsten carbide particles are shown as white regions.

[0043] In each of the three images after binarization processing obtained, a rectangular measurement field of 25.3 μm in length × 17.6 μm in width is set. Using the above image analysis software, for each of all tungsten carbide particles (black regions) in the three measurement fields, the equivalent circle diameter (Heywood diameter: equivalent diameter of an equal-area circle) is measured. The arithmetic mean value based on the number of equivalent circle diameters of all tungsten carbide particles in the three measurement fields is calculated. In this specification, the arithmetic mean value corresponds to the average value of the equivalent circle diameters of WC particles.

[0044] As far as the applicant has measured, as long as the measurement is made on the same sample, even if the above measurement is performed multiple times by changing the selected location of the measurement field, it has been confirmed that the variation in the measurement results is small and it does not become arbitrary even if the measurement field is set arbitrarily.

[0045] <Method for manufacturing a cutting tool> Next, a method for manufacturing the cutting tool 100 according to the first embodiment will be described.

[0046] FIG. 6 is a flowchart schematically showing a method for manufacturing a cutting tool according to the first embodiment. As shown in FIG. 6, the method for manufacturing the cutting tool 100 includes a step of forming a diamond layer on a substrate (S10), a step of sharpening a cutting edge by laser processing a rake face (S20), and a step of smoothing the rake face using ion etching (S30).

[0047] First, the step of forming a diamond layer on the substrate (S10) is performed. Specifically, for example, using HFCVD (Hot Filament Chemical Vapor Deposition) or the like, a diamond layer 5 is formed on the substrate 4. As a result, each of the first surface 41 and the second surface 42 of the substrate 4 is covered with the diamond layer 5.

[0048] Next, the step of sharpening the cutting edge by laser processing the rake face (S20) is performed. FIG. 7 is a schematic cross-sectional view showing the step of sharpening the cutting edge by laser processing the rake face (S20). As shown in FIG. 7, at least a part of the diamond layer 5 constituting the rake face 1 is removed using laser processing. Specifically, a laser 81 is irradiated toward the cutting tool 100. The irradiation direction of the laser 81 is the direction along the arrow B. The irradiation direction of the laser 81 is, for example, substantially parallel to the rake face 1. From another perspective, the irradiation direction of the laser 81 is, for example, substantially parallel to the first surface 41.

[0049] A laser processing region 82 is formed centering on the focal point F of the laser 81. The laser processing region 82 is a region where the energy of the laser 81 is concentrated. The portion of the cutting tool 100 within the laser processing region 82 is removed. By scanning the laser 81, the diamond layer 5 constituting the rake face 1 is removed within a predetermined range. As a result, the cutting edge 3 can be sharpened. In other words, the radius of curvature R of the cutting edge 3 can be reduced.

[0050] When the irradiation direction of the laser 81 is perpendicular to the rake face 1, most of the irradiated laser 81 hits the cutting tool 100. In this case, the area of the diamond layer 5 that generates heat due to the irradiation of the laser 81 becomes large. Therefore, the surface roughness of the diamond layer 5 is likely to deteriorate due to heat generation. Specifically, for example, the surface roughness of the diamond layer 5 deteriorates due to an oxidation reaction occurring in the heated diamond layer 5.

[0051] According to the manufacturing method of the cutting tool 100 according to the first embodiment, the irradiation direction of the laser 81 is substantially parallel to the rake face 1. For this reason, a part of the laser 81 passes through the focal point F without hitting the cutting tool 100. As a result, the area of the diamond layer 5 that generates heat due to the irradiation of the laser 81 can be reduced. As a result, deterioration of the surface roughness of the diamond layer 5 can be suppressed. By suppressing the deterioration of the surface roughness of the diamond layer 5, the processing time in the step (S30) of smoothing the rake face using ion etching described later can be shortened.

[0052] Next, a step (S30) of smoothing the rake face using ion etching is performed. Ion etching is performed so that each of the rake face 1 and the flank face 2 is etched. The rake face 1 is smoothed. Specifically, the maximum height roughness of the first portion 16 is reduced. The processing time in ion etching is, for example, 0.3 hours. By setting the processing time in ion etching to about 0.3 hours, it is possible to suppress the thickness H (see FIG. 4) of the flank face covering portion 52 from becoming excessively small. Thus, the cutting tool 100 according to the first embodiment shown in FIGS. 1 to 4 is manufactured.

[0053] (Second Embodiment) <Configuration of Cutting Tool> Next, the configuration of the cutting tool 100 according to the second embodiment will be described. The cutting tool 100 according to the second embodiment is different from the cutting tool 100 according to the first embodiment mainly in that the rake face 1 has a first rake face portion 11 and a second rake face portion 12, and in other respects, it is substantially the same as the cutting tool 100 according to the first embodiment. Hereinafter, the description will focus on the differences from the cutting tool 100 according to the first embodiment.

[0054] FIG. 8 is a schematic cross-sectional view showing the configuration of the cutting tool 100 according to the second embodiment. The cross-section shown in FIG. 8 corresponds to the cross-section shown in FIG. 4. As shown in FIG. 8, the diamond layer 5 may cover the first surface 41 of the base material 4. The portion of the diamond layer 5 covering the first surface 41 is defined as a rake face covering portion 51. From another perspective, the diamond layer 5 has a rake face covering portion 51 and a flank face covering portion 52.

[0055] The rake face 1 may have a first rake face portion 11 and a second rake face portion 12. The first rake face portion 11 is constituted by, for example, the diamond layer 5. The first rake face portion 11 is spaced apart from the flank face 2. The first rake face portion 11 is substantially parallel to the first surface 41.

[0056] The second rake face portion 12 is provided between the first rake face portion 11 and the flank face 2. The second rake face portion 12 is continuous with each of the first rake face portion 11 and the flank face 2. The ridge line between the second rake face portion 12 and the flank face 2 constitutes the cutting edge 3.

[0057] The second rake face portion 12 is inclined with respect to the first rake face portion 11 in a direction from the first rake face portion 11 toward the flank face 2. Specifically, in a direction perpendicular to the rake face 1, the second rake face portion 12 is inclined in a direction from the first rake face portion 11 toward the flank face 2. When the rake face 1 has the first rake face portion 11 and the second rake face portion 12, the direction perpendicular to the rake face 1 is defined as the direction perpendicular to the first rake face portion 11.

[0058] The inclination angle of the second rake face 12 with respect to the first rake face 11 is the second angle θ2. In a cross-section perpendicular to the tangent line of the cutting edge 3, the second angle θ2 is the angle formed by the extension line 93 of the first rake face 11 and the second rake face 12. The second angle θ2 is, for example, 3° or more and 50° or less. The second angle θ2 may be, for example, 3° or more and 40° or less. The second angle θ2 may be, for example, 5° or more, or 10° or more. The second angle θ2 may be, for example, 35° or less, or 30° or less, or 20° or less.

[0059] The second rake face 12 is composed of a first portion 16, a second portion 17, and a third portion 18. The first portion 16 is provided between the flank face 2 and the second portion 17. The second portion 17 is a portion of the second rake face 12 composed of the base material 4. The second portion 17 is continuous with the first portion 16. The second portion 17 is spaced apart from the flank face 2. The second portion 17 is provided between the first portion 16 and the third portion 18.

[0060] The third portion 18 is a portion of the second rake face 12 composed of the rake face covering portion 51. The third portion 18 is provided between the second portion 17 and the first rake face 11. The third portion 18 is continuous with each of the second portion 17 and the first rake face 11. The third portion 18 is spaced apart from the first portion 16.

[0061] As shown in FIG. 9, the width W of the second rake face 12 in the direction perpendicular to the tangent line of the cutting edge 3 (see FIG. 2) is, for example, 0.01 mm or more and 0.2 mm or less. In the base material 4, the second portion 17 is continuous with each of the first surface 41 and the second surface 42. The second portion 17 is provided between the first surface 41 and the second surface 42. The second portion 17 is inclined in the direction from the first rake face 11 toward the flank face 2 with respect to the first surface 41. The second surface 42 is spaced apart from the first surface 41.

[0062] <Method for manufacturing a cutting tool> Next, a method for manufacturing the cutting tool 100 according to the second embodiment will be described. FIG. 9 is a schematic cross-sectional view showing a step (S20) of sharpening the cutting edge by laser processing the rake face in the method for manufacturing the cutting tool 100 according to the second embodiment. As shown in FIG. 9, in the method for manufacturing the cutting tool 100 according to the second embodiment, the irradiation direction (arrow B) of the laser 81 is inclined with respect to the rake face 1. From another perspective, the irradiation direction of the laser 81 is inclined substantially with respect to, for example, the first face 41. The inclination angle of the irradiation direction of the laser 81 with respect to the rake face 1 is the second angle θ2 (see FIG. 8). From another perspective, the irradiation direction of the laser 81 is substantially parallel to the second rake face portion 12 (see FIG. 8). Thereby, while reducing the radius of curvature R of the cutting edge 3, the second rake face portion 12 is formed.

[0063] <Use state> Next, the use state of the cutting tool 100 according to the present disclosure will be described.

[0064] FIG. 10 is a partial cross-sectional schematic view showing the use state of the cutting tool 100 according to the present disclosure. As shown in FIG. 10, a workpiece 90 is prepared. The workpiece 90 is made of, for example, cemented carbide. Specifically, the workpiece 90 is made of, for example, cemented carbide. The workpiece 90 may be made of, for example, ceramics such as alumina, silicon carbide, silicon, and CFRP (Carbon Fiber Reinforced Plastics). While the cutting tool 100 rotates about the axis X, the cutting edge 3 contacts the workpiece 90. Thereby, the workpiece 90 is cut.

[0065] Next, the operation and effect of the cutting tool 100 according to the present disclosure will be described. For example, when the workpiece is made of a hard and brittle material such as cemented carbide, it is necessary to cut hard ceramic particles using a cutting tool. In this case, a cutting tool having a high-hardness diamond layer is usually used. When the cutting edge of the cutting tool is covered with the diamond layer, as the thickness of the diamond layer increases, the cutting edge becomes rounded. In this case, as the sharpness of the cutting edge decreases, the tool is more likely to be damaged. On the other hand, when the thickness of the diamond layer is excessively thin, the wear resistance of the tool becomes excessively low. Even when both a sufficient thickness of the diamond layer and a high sharpness of the cutting edge are achieved by processing the diamond layer, chip adhesion may occur at the cutting edge due to the surface state of the diamond layer. In this case, when the configured cutting edge is formed, the tool is more likely to be damaged. In particular, when the workpiece is made of cemented carbide, the tungsten carbide particles contained in the cemented carbide are likely to adhere to the cutting edge. As described above, it has been difficult to improve the tool life of a cutting tool having a diamond layer.

[0066] According to the cutting tool 100 according to the present disclosure, the diamond layer 5 has a flank covering portion 52. The flank covering portion 52 constitutes the flank 2. The rake face 1 has a first portion 16. The first portion 16 is constituted by the flank covering portion 52. The maximum height roughness of the first portion 16 is less than 2 μm. In this way, it is suppressed that a part of the first portion 16 protrudes excessively. When the workpiece 90 is cut using the cutting tool 100, the chip is likely to come into contact with the first portion 16. Therefore, it is possible to suppress the occurrence of chip adhesion starting from an excessively protruding portion. As a result, the tool life can be improved.

[0067] According to the cutting tool 100 according to the present disclosure, the thickness of the flank covering portion 52 is 10 μm or more and 25 μm or less. By the thickness of the flank covering portion 52 being 10 μm or more, the wear resistance of the cutting tool 100 can be sufficiently improved.

[0068] According to the cutting tool 100 according to the present disclosure, in a cross section perpendicular to the tangent of the cutting edge 3, the radius of curvature R of the cutting edge 3 is less than the value obtained by multiplying the thickness of the flank face covering portion 52 by 0.3. As a result, the sharpness of the cutting edge 3 can be sufficiently improved. As a result, it is possible to make it difficult for the tool to be damaged.

[0069] According to the cutting tool 100 according to the second embodiment, the rake face 1 has a first rake face portion 11 and a second rake face portion 12. The second rake face portion 12 is inclined with respect to the first rake face portion 11 in a direction from the first rake face portion 11 toward the flank face 2. As a result, the angle formed by the rake face 1 and the flank face 2 can be increased. Therefore, the strength of the cutting edge 3 can be improved.

[0070] According to the cutting tool 100 according to the second embodiment, the inclination angle (second angle θ2) of the second rake face portion 12 with respect to the first rake face portion 11 is 3° or more and 50° or less. When the second angle θ2 is 3° or more, it is possible to suppress the angle formed by the second rake face portion 12 and the flank face 2 from becoming excessively small. As a result, it is possible to suppress the strength of the cutting edge 3 from being excessively reduced. When the second angle θ2 is 50° or less, it is possible to suppress the angle formed by the second rake face portion 12 and the flank face 2 from becoming excessively large. As a result, it is possible to suppress the sharpness of the cutting edge 3 from being excessively reduced.

[0071] According to the cutting tool 100 according to the present disclosure, the base material 4 is made of a cemented carbide containing tungsten carbide particles. The average particle size of the tungsten carbide particles is 2 μm or less. As the average particle size of the tungsten carbide particles becomes smaller, the adhesion between the base material 4 and the diamond layer 5 is improved. Therefore, when the average particle size of the tungsten carbide particles is 2 μm or less, the adhesion between the base material 4 and the diamond layer 5 can be improved. As a result, it is possible to suppress the diamond layer 5 from peeling off from the base material 4. As a result, the tool life can be further improved.

[0072] In the above description, the configuration where the cutting tool 100 is a ball end mill has been described. However, the cutting tool 100 according to the present disclosure is not limited to a ball end mill. For example, the cutting tool 100 may be a radius end mill or the like. The cutting tool 100 may also be a turning tool such as a cutting insert.

Example

[0073] (Sample preparation) First, cutting tools 100 according to Samples 1 to 22 were prepared. Samples 1, 3, 4, 8 to 18, and 22 are examples. Samples 2, 5 to 7, and 19 to 21 are comparative examples. Cutting tools 100 according to Samples 1 to 22 were manufactured in accordance with the manufacturing method of the cutting tool 100 according to the present disclosure described above. Specifically, the cutting tool 100 was manufactured using the conditions shown in Table 1 below.

[0074]

Table 1

[0075] Table 1 shows the manufacturing conditions of the cutting tool 100 and the parameters of the cutting tool 100 in Samples 1 to 22. As shown in Table 1, in Samples 1 to 18, 21, and 22, the step (S20) of sharpening the cutting edge by laser processing the rake face was performed. In Samples 1 to 7, the irradiation direction of the laser 81 was parallel to the rake face 1. In Samples 8 to 18 and 22, the irradiation direction of the laser 81 was inclined with respect to the rake face 1. From another perspective, the cutting tools 100 according to Samples 8 to 18 and 22 had a second rake face portion 12. In Sample 21, the irradiation direction of the laser 81 was perpendicular to the rake face 1. In Samples 19 and 20, the step (S20) of sharpening the cutting edge by laser processing the rake face was not performed.

[0076] In Samples 1 to 6, 8 to 19, 21, and 22, the processing time of the ion etching in the step (S30) of smoothing the scooping surface using ion etching was set to 0.3 hours. In Samples 7 and 20, the step (S30) of smoothing the scooping surface using ion etching was not performed.

[0077] In Samples 1 to 7 and 19 to 21, the second angle θ2 was 0°. In other words, in Samples 1 to 7 and 19 to 21, the scooping surface 1 was planar (see FIG. 4). In Samples 8 to 18 and 22, the second angle θ2 was set to be 3° or more and 55° or less. In other words, in Samples 8 to 18 and 22, the scooping surface 1 had a first scooping surface portion 11 and a second scooping surface portion 12 (see FIG. 7).

[0078] In the samples according to the examples (Samples 1, 3, 4, 8 to 18, and 22), the thickness H was 10.1 μm or more and 24.8 μm or less. The value (R / H) obtained by dividing the radius of curvature R by the thickness H was 0.076 or more and 0.272 or less. In other words, the radius of curvature R was not less than the value obtained by multiplying the thickness H by 0.076 and not more than the value obtained by multiplying the thickness H by 0.272. The Rz of the first portion 16 was 0.08 μm or more and 1.92 μm or less.

[0079] In Samples 2, 19, and 20, the value (R / H) obtained by dividing the radius of curvature R by the thickness H was 0.3 or more. In Sample 5, the thickness H of the flank surface covering portion 52 was less than 10 μm. In Sample 6, the thickness H was greater than 25 μm. In Samples 7 and 19 to 21, the Rz of the first portion 16 was 2 μm or more.

[0080] In Samples 1 to 22, the average particle size of the tungsten carbide particles contained in the cemented carbide constituting the base material 4 was 0.5 μm or less and 3 μm or less. In Samples 11 to 18, the average particle size of the tungsten carbide particles was 0.5 μm or more and 2 μm or less. In Samples 1 to 22, the first angle θ1 was 15° or more and 40° or less. In Samples 1 to 22, the radius of the tip portion 6 was 0.5 mm.

[0081] (Evaluation Method) Next, an evaluation of the tool life of the cutting tool 100 according to Samples 1 to 22 was performed. Specifically, using the cutting tool 100 according to Samples 1 to 22, machining was performed on the workpiece 90 to form a hemispherical hole having a diameter of 10 mm and a depth of 5 mm. The workpiece 90 was made of cemented carbide. In the machining, the rotational speed of the cutting tool 100 was set to 30000 rpm. The table feed speed was set to 200 m / min. The cutting depth in the direction parallel to the axis X (axial cutting depth ap) was set to 0.04 mm. The cutting depth in the direction perpendicular to the axis X (radial cutting depth ae) was set to 0.2 mm. The volume of the workpiece 90 that could be cut by the cutting tool 100 until it was damaged (machined volume) was measured.

[0082] (Evaluation Results)

[0083] [Table 2]

[0084] Table 2 shows the evaluation results for Samples 1 to 22. As shown in Table 2, in the samples according to the comparative examples (Samples 2, 5 to 7, and 19 to 21), the machined volume was 679.9 mm 3 or less. In the samples according to the examples (Samples 1, 3, 4, 8 to 18, and 22), the machined volume was 1046 mm 3 or more.

[0085] From the above results, it was confirmed that the cutting tool 100 according to the example has an improved tool life compared to the cutting tool 100 according to the comparative example.

[0086] The embodiments and examples disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims are included.

Explanation of Signs

[0087] 1 rake face, 2 flank face, 3 cutting edge, 4 base material, 5 diamond layer, 6 tip portion, 7 body portion, 8 shank portion, 11 first rake face portion, 12 second rake face portion, 16 first portion, 17 second portion, 18 third portion, 41 first face, 42 second face, 51 rake face coating portion, 52 flank face coating portion, 58 front end, 59 rear end, 81 laser, 82 laser processing region, 90 workpiece, 91 first virtual straight line, 92 second virtual straight line, 100 cutting tool, A, B arrows, F focus, H thickness, R radius of curvature, W width, X axis line, θ1 first angle, θ2 second angle.

Claims

1. A cutting tool comprising a substrate and a diamond layer coating the substrate, wherein the cutting tool includes a rake face and a flank face continuous with the rake face, a ridge line between the rake face and the flank face constitutes a cutting edge, the diamond layer has a flank face covering portion that constitutes the flank face, the thickness of the flank face covering portion is 10 μm or more and 25 μm or less, in a cross section perpendicular to the tangent line of the cutting edge when viewed perpendicular to the rake face, the radius of curvature of the cutting edge is not less than a value obtained by multiplying the thickness of the flank face covering portion by 0.076 and less than a value obtained by multiplying the thickness of the flank face covering portion by 0.3, the rake face includes a first portion constituted by the flank face covering portion and continuous with the flank face, the maximum height roughness of the first portion is less than 2 μm, an angle formed by the rake face and the flank face is 53° or more and 130° or less. A cutting tool.

2. The rake face has a first rake face portion spaced apart from the flank face, and a second rake face portion provided between the first rake face portion and the flank face and continuous with each of the first rake face portion and the flank face, wherein the second rake face portion is inclined with respect to the first rake face portion in a direction from the first rake face portion toward the flank face. The cutting tool according to claim 1.

3. The inclination angle of the second rake face portion with respect to the first rake face portion is 3° or more and 50° or less. The cutting tool according to claim 2.

4. The thickness of the flank face covering portion is 15 μm or more and 20 μm or less. The cutting tool according to any one of claims 1 to 3.

5. In a cross section perpendicular to the tangent line of the cutting edge, the radius of curvature of the cutting edge is less than a value obtained by multiplying the thickness of the flank face covering portion by 0.

1. The cutting tool according to any one of claims 1 to 3.

6. The substrate is made of a cemented carbide containing tungsten carbide particles, and the average particle size of the tungsten carbide particles is 2 μm or less. The cutting tool according to any one of claims 1 to 3.

7. The relief angle of the flank face is 15° or more and 35° or less. The cutting tool according to any one of claims 1 to 3.

8. The maximum height roughness of the first portion is less than 1.5 μm. The cutting tool according to any one of claims 1 to 3.

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