Cutting tool

Abstract

This cutting tool has a body portion and a cutting edge layer. The body portion is rod-shaped. The cutting edge layer is provided at the front end of the body portion. The cutting edge layer forms a cutting edge. The body portion is formed of cemented carbide containing tungsten carbide and cobalt. The cutting edge layer is formed of polycrystalline diamond. In the cemented carbide, the percentage of a value obtained by dividing the weight of the tungsten carbide by the weight of the entire cemented carbide is 90.0-95.0%. In the cemented carbide, the percentage of a value obtained by dividing the weight of the cobalt by the weight of the entire cemented carbide is 4.0-9.0%.

Description

cutting tools

[0001] The present disclosure relates to cutting tools.

[0002] Japanese Utility Model Publication No. 59-183301 (Patent Document 1) discloses a boring tool in which a composite cutting edge tip is brazed into a tip seat provided at the tip of a cylindrical tool body.

[0003] Japanese Utility Model Publication No. 59-183301

[0004] The cutting tool according to the present disclosure includes a main body and a cutting edge layer. The main body is rod-shaped. The cutting edge layer is provided at the front end of the main body. The cutting edge layer forms a cutting edge. The main body is formed of a cemented carbide containing tungsten carbide and cobalt. The cutting edge layer is formed of polycrystalline diamond. In the cemented carbide, the weight of tungsten carbide divided by the total weight of the cemented carbide is a percentage of 90.0% or more and 95.0% or less. In the cemented carbide, the weight of cobalt divided by the total weight of the cemented carbide is a percentage of 4.0% or more and 9.0% or less.

[0005] FIG. 1 is a schematic plan view showing the configuration of a cutting tool according to this embodiment. FIG. 2 is an enlarged schematic view showing region II in FIG. 1 . FIG. 3 is a schematic side view showing the configuration of a cutting tool according to this embodiment. FIG. 4 is a schematic front view showing the configuration of a cutting tool according to this embodiment. FIG. 5 is a schematic cross-sectional view taken along line V-V in FIG. 1 . FIG. 6 is a schematic cross-sectional view taken along line VI-VI in FIG. 2 . FIG. 7 is a schematic view showing the configuration of a cutting tool viewed along the extension direction of a first cutting edge portion. FIG. 8 is a schematic view showing the configuration of a cutting tool viewed along the extension direction of a second cutting edge portion. FIG. 9 is a partial cross-sectional schematic view illustrating the use of a cutting tool according to this embodiment. FIG. 10 is an enlarged schematic view showing the cutting of a workpiece using a cutting tool according to this embodiment.

[0006] [Problem to be Solved by the Present Disclosure] When cutting a workpiece using a cutting tool, the body of the cutting tool may vibrate, which may increase the surface roughness of the machined surface of the workpiece.

[0007] An object of the present disclosure is to provide a cutting tool that can reduce the surface roughness of the machined surface of a workpiece.

[0008] Effect of the Present Disclosure According to the present disclosure, it is possible to provide a cutting tool that can reduce the surface roughness of the machined surface of a workpiece.

[0009] [Outline of the embodiment] First, an outline of the embodiment of the present disclosure will be described.

[0010] (1) A cutting tool according to the present disclosure has a main body and a cutting edge layer. The main body is rod-shaped. The cutting edge layer is provided at the front end of the main body. The cutting edge layer forms a cutting edge. The main body is formed of a cemented carbide containing tungsten carbide and cobalt. The cutting edge layer is formed of polycrystalline diamond. In the cemented carbide, the weight of tungsten carbide divided by the total weight of the cemented carbide is a percentage of 90.0% or more and 95.0% or less. In the cemented carbide, the weight of cobalt divided by the total weight of the cemented carbide is a percentage of 4.0% or more and 9.0% or less. Therefore, vibration of the cutting tool can be suppressed when machining a workpiece. This can reduce the surface roughness of the machined surface of the workpiece.

[0011] (2) According to the cutting tool of (1) above, the percentage of the weight of cobalt in the cemented carbide divided by the weight of the entire cemented carbide may be 5.0% or more and 8.0% or less. This effectively prevents an excessive decrease in the transverse rupture strength of the main body, thereby effectively preventing breakage of the main body.

[0012] (3) In the cutting tool according to (1) or (2) above, the polycrystalline diamond may contain a plurality of diamond particles. In the polycrystalline diamond, the weight of the binder that binds the plurality of diamond particles divided by the total weight of the polycrystalline diamond may be 10.0% or less, or 0%. This improves the wear resistance of the cutting edge layer.

[0013] (4) In the cutting tool according to (3) above, the weight of the binder in the polycrystalline diamond may be 1.0% or less or 0% by weight, which can effectively improve the wear resistance of the cutting edge layer.

[0014] (5) In the cutting tool according to any one of (1) to (4) above, the diameter of the main body may be 6 mm or less, thereby enabling inner diameter machining even when the inner diameter of the workpiece is relatively small.

[0015] (6) The cutting tool according to any one of (1) to (5) above may have a brazing filler metal. The brazing filler metal may join the cutting edge layer and the main body. The brazing filler metal may contain silver, copper, or titanium. This can improve the rigidity of the entire cutting tool.

[0016] (7) According to the cutting tool of any one of (1) to (6) above, the cutting edge may have a corner cutting edge portion, a first cutting edge portion, and a second cutting edge portion. The corner cutting edge portion may have a first end point and a second end point. The second end point may be opposite to the first end point. The first cutting edge portion may be connected to the corner cutting edge portion at the first end point. The first cutting edge portion may be provided relative to the corner cutting edge portion in a direction from the front end to the rear end along the axis of the main body. The second cutting edge portion may be connected to the corner cutting edge portion at the second end point. The second cutting edge portion may be provided relative to the corner cutting edge portion in a direction from the corner cutting edge portion toward the axis. The cutting edge layer may have a first flank surface. When viewed along the direction in which the first cutting edge portion extends, the first flank surface may be inclined in a direction from the first cutting edge portion toward the axis with respect to an imaginary line that is perpendicular to an imaginary plane including the corner cutting edge portion and the first cutting edge portion and intersects with the first cutting edge portion, and the angle between the imaginary line and the first flank surface may be 7° or more and 13° or less.When viewed perpendicular to the imaginary plane, the first cutting edge portion may be inclined in a direction from the first end point toward the axis with the first end point as a fulcrum, and the angle between the axis and the first cutting edge portion may be 2° or more and 4° or less.

[0017] This makes it possible to effectively reduce the surface roughness of the machined surface of the workpiece while suppressing a decrease in the strength of the cutting edge.

[0018] (8) According to the cutting tool of (7) above, the cutting edge layer may have a second flank. The second flank may be continuous with the first flank. The second flank may be located on the opposite side of the first cutting edge portion from the first flank. When viewed along the direction in which the first cutting edge portion extends, the second flank may be inclined with respect to an imaginary line in a direction from the first cutting edge portion toward the axis, and the angle between the imaginary line and the second flank may be 20° or more. The width of the first flank in the direction in which the imaginary line extends may be 0.4 mm or less. This makes it possible to prevent contact between the cutting edge layer and the workpiece when performing internal machining on a workpiece with a small internal diameter.

[0019] [Details of the embodiment] Hereinafter, details of the embodiment of the present disclosure (hereinafter also referred to as the present embodiment) will be described with reference to the drawings. Note that the same or corresponding parts in the following drawings are designated by the same reference numerals, and the description thereof will not be repeated.

[0020] <Configuration of Cutting Tool> First, the configuration of the cutting tool 100 according to this embodiment will be described.

[0021] FIG. 1 is a schematic plan view showing the configuration of a cutting tool 100 according to this embodiment. The cutting tool 100 is a turning tool that turns a rotating workpiece (not shown) by bringing a cutting edge 10 into contact with the workpiece. Specifically, the cutting tool 100 is, for example, a boring tool. In other words, the cutting tool 100 is used, for example, for enlarging the inner diameter of the workpiece. More specifically, the cutting tool 100 is used, for example, for enlarging the inner diameter of the workpiece and for machining with a relatively small depth of cut.

[0022] As shown in FIG. 1 , the cutting tool 100 has a main body 3 and a cutting edge layer 4. The main body 3 is rod-shaped. The main body 3 extends along an axis X. The main body 3 has a front end 1 and a rear end 2. The front end 1 is a portion that faces a workpiece. The rear end 2 is a portion that faces a machine tool (not shown) that supports the cutting tool 100.

[0023] The main body 3 extends in a direction from the front end 1 to the rear end 2 along the axis X. In this specification, the direction from the front end 1 to the rear end 2 along the axis X is also referred to as a first direction 101. The length L1 of the main body 3 in the first direction 101 is, for example, 30 mm or more. The main body 3 is made of a cemented carbide alloy. The cemented carbide alloy is a sintered body whose main component is tungsten carbide particles. The specific composition of the cemented carbide alloy that forms the main body 3 will be described later.

[0024] The cutting edge layer 4 is provided on the front end 1 of the main body 3. The cutting edge layer 4 forms a cutting edge 10. The cutting edge layer 4 is made of polycrystalline diamond. The specific composition of the polycrystalline diamond that forms the cutting edge layer 4 will be described later.

[0025] <Composition of Cemented Carbide> The cemented carbide forming the main body 3 contains tungsten carbide (WC) and cobalt (Co). The cemented carbide contains a hard phase and a binder phase. The hard phase is substantially composed of WC particles. The binder phase bonds the WC particles together. The binder phase contains Co and the like. In this specification, the percentage obtained by dividing the weight of a component contained in a substance by the weight of the entire substance is referred to as the content of that component in the substance.

[0026] The WC content (WC content) in the cemented carbide forming the main body 3 is 90.0% or more and 95.0% or less. The WC content may be, for example, 91.0% or more, or 93.0% or more. The WC content may be, for example, 94.7% or less, or 94.3% or less.

[0027] The Co content (Co content) in the cemented carbide forming the main body 3 is 4.0% or more and 9.0% or less. The Co content may be, for example, 5.0% or more and 8.0% or less, or 5.0% or more and 7.0% or less. The Co content may be, for example, 4.3% or more, or 4.7% or more. The Co content may be, for example, 8.5% or less, 7.5% or less, or 6.5% or less.

[0028] The sum of the WC content and the Co content may be, for example, 98% or more, or 99% or more. The sum of the WC content and the Co content may be 100% or less. From another perspective, the cemented carbide forming the main body 3 may contain components other than WC and Co. The binder phase may contain, for example, TiC (titanium carbide), TaC (tantalum carbide), NbC (niobium carbide), etc. The cemented carbide forming the main body 3 may contain inevitable impurities.

[0029] <Composition of Polycrystalline Diamond> The polycrystalline diamond forming the cutting edge layer 4 contains a plurality of diamond particles. The polycrystalline diamond forming the cutting edge layer 4 may be polycrystalline sintered diamond (PCD: Poly-Crystalline Diamond) or binderless polycrystalline diamond (hereinafter also referred to as BLPCD).

[0030] PCD is composed of, for example, a binder and multiple diamond particles. BLPCD is polycrystalline diamond in which multiple diamond particles are bonded together without a binder. In other words, BLPCD does not contain a binder. The binder is composed of Co. The binder may contain inevitable impurities such as TiC in addition to Co. The polycrystalline diamond forming the cutting edge layer 4 may be nano-polycrystalline diamond. Nano-polycrystalline diamond refers to polycrystalline diamond in which the particle size of the multiple diamond particles is on the order of nanometers.

[0031] The content of binder (binder content) in the polycrystalline diamond forming the cutting edge layer 4 is, for example, 0%. When the polycrystalline diamond is BLPCD, the binder content is 0%. From another perspective, the polycrystalline diamond may be composed of a plurality of diamond grains and inevitable impurities.

[0032] The binder content may be 10.0% or less. The binder content may be, for example, 0.01% or more, or 0.1% or more. The binder content may be, for example, 5.0% or less, 1.0% or less, or 0.5% or less.

[0033] The WC content, Co content, and binder content can be measured using an energy dispersive X-ray spectroscopy (EDX) attached to a field emission scanning electron microscope (FE-SEM) by the following measurement method. For example, a Gemini 450 manufactured by ZEISS and an Ultim Max manufactured by Oxford Instruments can be used as the FE-SEM and EDX.

[0034] When measuring the WC content and Co content, first, the main body 3 is embedded in resin. The main body 3 is cut to expose a cross section of the main body 3. Next, this exposed cross section is polished to prepare a polished surface for observation. Five arbitrary locations (five fields) on this polished surface for observation are observed at 3000x magnification using EDX for elemental analysis. This allows the content (weight %) of each element to be determined. The composition of the cemented carbide forming the main body 3 can be identified by calculating the average value of the values ​​for each element in the five fields. The WC content and Co content can be determined using the identified cemented carbide composition. A thermosetting resin or the like can be used as the resin for embedding the main body 3.

[0035] A conventionally known method can be used to polish the cross section of the main body 3. For example, a smoothed polished surface for observation can be obtained by subjecting the cross section of the main body 3 to ion milling using argon ions. The conditions for the ion milling using Ar ions are, for example, as follows: Acceleration voltage: 6 kV Irradiation angle: 0° to 5° from a plane parallel to the cross section of the main body 3 Irradiation time: 6 hours

[0036] Similarly, when measuring the binder content, the composition of the polycrystalline diamond forming the cutting edge layer 4 can be identified by using the above-mentioned measurement method on the cutting edge layer 4. The binder content can be determined using the identified composition of the polycrystalline diamond. Specifically, the Co content in the polycrystalline diamond can be taken as the binder content.

[0037] <More specific configuration of cutting tool> Figure 2 is an enlarged schematic view showing region II in Figure 1. Figure 3 is a schematic side view showing the configuration of cutting tool 100 according to this embodiment. As shown in Figures 2 and 3, main body 3 has a seat surface 31, a side wall surface 32, an outer circumferential surface 33, and a front end surface 34.

[0038] The bearing surface 31 is, for example, flat. The side wall surface 32 is continuous with the bearing surface 31. The side wall surface 32 is, for example, perpendicular to the bearing surface 31. The bearing surface 31 and the side wall surface 32 form a recess 39. The cutting edge layer 4 is arranged in the recess 39.

[0039] The outer peripheral surface 33 has a flat surface portion 36 and a curved surface portion 37. The flat surface portion 36 is flat. The flat surface portion 36 is, for example, parallel to the seating surface 31. The flat surface portion 36 is continuous with the side wall surface 32. The curved surface portion 37 is continuous with each of the seating surface 31 and the side wall surface 32.

[0040] The front end surface 34 is located at the front end 1 of the main body 3. The front end surface 34 is continuous with the seat surface 31, the side wall surface 32, the flat surface portion 36, and the curved surface portion 37.

[0041] As shown in FIG. 2 , the cutting edge 10 has a corner cutting edge portion 8, a first cutting edge portion 6, and a second cutting edge portion 7. The corner cutting edge portion 8 is provided in a direction opposite to the first direction 101 with respect to the main body portion 3. The corner cutting edge portion 8 has a first end point 81 and a second end point 82. The second end point 82 of the corner cutting edge portion 8 is opposite to the first end point 81. The first end point 81 is located in the first direction 101 with respect to the second end point 82. The first cutting edge portion 6 is continuous with the corner cutting edge portion 8 at the first end point 81. The first cutting edge portion 6 is provided in the first direction 101 with respect to the corner cutting edge portion 8.

[0042] In FIG. 2 , a dashed line indicates an imaginary plane 95. The imaginary plane 95 includes the first cutting edge portion 6 and the corner cutting edge portion 8. From another perspective, the first cutting edge portion 6 and the corner cutting edge portion 8 are, for example, substantially coplanar. The imaginary plane 95 may include the axis X. FIG. 2 shows the configuration of the cutting tool 100 viewed perpendicularly to the imaginary plane 95. When viewed perpendicularly to the imaginary plane 95, the direction from the first end point 81 toward the axis X is defined as a second direction 102. The second direction 102 is perpendicular to the axis X. The imaginary plane 95 extends, for example, along each of the first direction 101 and the second direction 102.

[0043] 2, the corner cutting edge portion 8 has a curved shape when viewed perpendicularly to the imaginary plane 95. When viewed perpendicularly to the imaginary plane 95, the corner cutting edge portion 8 may have, for example, an arc shape. When viewed perpendicularly to the imaginary plane 95, the radius of curvature of the corner cutting edge portion 8 is, for example, 0.05 mm or more and 0.5 mm or less.

[0044] As shown in Fig. 2, the first cutting edge portion 6 is, for example, linear. When viewed perpendicularly to the imaginary plane 95, the first cutting edge portion 6 is inclined in the second direction 102 with respect to the axis X, with the first end point 81 as a fulcrum. From another perspective, when viewed perpendicularly to the imaginary plane 95, the distance between the first cutting edge portion 6 and the axis X decreases with increasing distance from the first end point 81. The first imaginary straight line 91 shown in Fig. 2 is a straight line parallel to the axis X.

[0045] When viewed perpendicularly to the imaginary plane 95, the inclination angle of the first cutting edge portion 6 with respect to the axis X is defined as a first angle θ1. The first angle θ1 is, for example, 2° or greater and 4° or less. The first angle θ1 may be, for example, 2.3° or greater, or 2.7° or greater. The first angle θ1 may be, for example, 3.7° or less, or 3.3° or less.

[0046] The first cutting edge portion 6 is provided in a direction opposite to the second direction 102 with respect to the outer peripheral surface 33 of the main body 3. In the second direction 102, the first cutting edge portion 6 is provided between the outer peripheral surface 33 and the first end point 81.

[0047] The second cutting edge portion 7 is provided in the second direction 102 relative to the corner cutting edge portion 8. From another perspective, the second cutting edge portion 7 is provided in a direction from the corner cutting edge portion 8 toward the axis X. The second cutting edge portion 7 is continuous with the corner cutting edge portion 8 at the second end point 82. From another perspective, in the cutting edge 10, the corner cutting edge portion 8 is located between the first cutting edge portion 6 and the second cutting edge portion 7.

[0048] The second cutting edge portion 7 is, for example, linear. When viewed perpendicularly to the imaginary plane 95, the second cutting edge portion 7 is inclined in the first direction 101 with respect to the second imaginary straight line 92, with the second end point 82 as a fulcrum. When viewed perpendicularly to the imaginary plane 95, the second imaginary straight line 92 is a straight line perpendicular to the axis X.

[0049] When viewed perpendicularly to the imaginary plane 95, the inclination angle of the second cutting edge portion 7 with respect to the second imaginary line 92 is set to a second angle θ2. The second angle θ2 is, for example, 3°. The second angle θ2 may be, for example, 2° or greater and 4° or less.

[0050] When viewed perpendicularly to the imaginary plane 95, the front end surface 34 of the main body 3 may be substantially parallel to the second cutting edge portion 7. The front end surface 34 is located in a first direction 101 relative to the second cutting edge portion 7. In the first direction 101, the second cutting edge portion 7 is located between the front end surface 34 and the second end point 82.

[0051] As shown in FIG. 2 , the cutting edge layer 4 has a rake face 11 and a curved surface 18. The rake face 11 is continuous with the cutting edge 10. Specifically, the rake face 11 is continuous with each of the corner cutting edge portion 8, the first cutting edge portion 6, and the second cutting edge portion 7. The rake face 11 is, for example, flat. The rake face 11 extends, for example, along an imaginary plane 95. The curved surface 18 is continuous with the rake face 11. When viewed perpendicular to the imaginary plane 95, the curved surface 18 is, for example, arc-shaped.

[0052] 3 , the cutting edge layer 4 has a bottom surface 41, a first flank surface 12, a second flank surface 19, and a corner flank surface 13. The bottom surface 41 is located opposite the rake face 11. A direction perpendicular to the imaginary plane 95 and extending from the rake face 11 toward the bottom surface 41 is defined as a third direction 103.

[0053] The first flank 12 is continuous with the first cutting edge portion 6. The first cutting edge portion 6 is formed by the ridge line between the first flank 12 and the rake face 11. The first flank 12 is provided in a third direction 103 with respect to the rake face 11. The second flank 19 is continuous with each of the first flank 12 and the bottom surface 41. The second flank 19 is provided in the third direction 103 with respect to the first flank 12. From another perspective, the second flank 19 is opposite the first cutting edge portion 6 with respect to the first flank 12. In the third direction 103, the second flank 19 is provided between the first flank 12 and the bottom surface 41.

[0054] The corner flank 13 is continuous with the corner cutting edge portion 8. The corner cutting edge portion 8 is formed by the ridge line between the corner flank 13 and the rake face 11. The corner flank 13 is continuous with each of the first flank 12 and the second flank 19. The curved surface 18 is continuous with each of the rake face 11, the first flank 12, the second flank 19, and the bottom surface 41.

[0055] As shown in Figure 3, the front end surface 34 has a first front end surface portion 21 and a second front end surface portion 22. The first front end surface portion 21 is continuous with the planar portion 36. When viewed in the second direction 102, the first front end surface portion 21 extends along the third direction 103. The second front end surface portion 22 is provided in the third direction 103 relative to the first front end surface portion 21. When viewed in the second direction 102, the second front end surface portion 22 is inclined in the first direction 101 relative to the first front end surface portion 21. Note that Figure 3 shows the configuration of the cutting tool 100 when viewed in the second direction 102.

[0056] Fig. 4 is a schematic front view showing the configuration of the cutting tool 100 according to this embodiment. Fig. 4 shows the configuration of the cutting tool 100 as viewed in a first direction 101. As shown in Fig. 4, the cutting edge layer 4 has a third flank 14 and a side surface 42. The third flank 14 is continuous with the corner flank 13, the bottom surface 41, and the second cutting edge portion 7.

[0057] The third flank 14 is provided in a third direction 103 relative to the second cutting edge portion 7. The second cutting edge portion 7 is formed by a ridge between the third flank 14 and the rake face 11 (see FIGS. 2 and 3). The side surface 42 is continuous with each of the third flank 14, the bottom surface 41, and the rake face 11 (see FIGS. 2 and 3).

[0058] As shown in FIG. 4 , when viewed along the axis X, the second cutting edge portion 7 may be parallel to the second direction 102. When viewed along the axis X, the corner cutting edge portion 8 may be linear. When viewed along the axis X, the corner cutting edge portion 8 may be parallel to the second direction 102. The bottom surface 41 may be parallel to an imaginary plane 95, for example. When viewed along the axis X, the curved surface portion 37 of the main body portion 3 is, for example, arc-shaped. The flat surface portion 36 of the main body portion 3 is, for example, parallel to the second direction 102. The second front end surface portion 22 is continuous with the first front end surface portion 21.

[0059] Fig. 5 is a schematic cross-sectional view taken along line V-V in Fig. 1. The cross section shown in Fig. 5 is a cross section perpendicular to the axis X. As shown in Fig. 5, the outer shape of the main body 3 is, for example, cylindrical. In this specification, a cylindrical shape refers to a shape that includes an arc with a central angle of 180° or more at the outer edge of the cross-sectional shape. Specifically, for example, a cylindrical shape includes a case where the cross-sectional shape is circular and a case where the outer edge of the cross-sectional shape is formed by an arc and a straight line with a central angle of 180° or more.

[0060] The axis X passes through the center of the main body 3. Specifically, in a cross section perpendicular to the axis X, the axis X is located at the center of a circle that includes an arc along the curved surface 37, for example. The diameter D1 of the main body 3 is, for example, 6 mm or less. When the main body 3 is cylindrical, the diameter D1 is the longest linear distance between two different points on the curved surface 37 in the cross section perpendicular to the axis X. In other words, the diameter D1 is the maximum diameter of the main body 3.

[0061] The diameter D1 may be, for example, 5 mm or less, 4 mm or less, or 3 mm or less. The diameter D1 may be, for example, 1 mm or more, or 2 mm or more. The value obtained by dividing the length L1 of the main body 3 in the first direction 101 (see FIG. 1 ) by the diameter D1 is, for example, 3 or more.

[0062] Fig. 6 is a schematic cross-sectional view taken along line VI-VI in Fig. 2. The cross section shown in Fig. 6 is perpendicular to the axis X and intersects with each of the main body portion 3 and the cutting edge layer 4. As shown in Fig. 6, the cutting tool has a brazing filler metal 5.

[0063] The brazing filler metal 5 joins the cutting edge layer 4 and the main body portion 3. The brazing filler metal 5 is located between the cutting edge layer 4 and the main body portion 3. The brazing filler metal 5 contains, for example, silver, copper, and titanium. The brazing filler metal 5 has a first portion 51 and a second portion 52.

[0064] In the third direction 103, the first portion 51 is provided between the bottom surface 41 of the cutting edge layer 4 and the seating surface 31 of the main body 3. The first portion 51 is in contact with both the bottom surface 41 and the seating surface 31. The first portion 51 extends along both the second direction 102 and the first direction 101 (see FIG. 2 ). In a cross section perpendicular to the axis X and intersecting both the main body 3 and the cutting edge layer 4, the seating surface 31 is covered by the first portion 51.

[0065] The second portion 52 is continuous with the first portion 51. The second portion 52 is provided between the side surface 42 of the cutting edge layer 4 and the side wall surface 32 of the main body portion 3. The second portion 52 is in contact with the side surface 42 of the cutting edge layer 4 and the side wall surface 32 of the main body portion 3. The second portion 52 extends along each of the third direction 103 and the first direction 101. In a cross section that is perpendicular to the axis X and intersects with each of the main body portion 3 and the cutting edge layer 4, the side surface 42 is covered by the second portion 52.

[0066] FIG. 7 is a schematic diagram showing the configuration of the cutting tool 100 as viewed along the extension direction of the first cutting edge portion 6. FIG. 7 shows the configuration of the cutting tool 100 as viewed along the arrow A shown in FIG. 2. Arrow A is the direction from the first end point 81 toward the rear end 2 (see FIG. 2) along the extension direction of the first cutting edge portion 6. FIG. 7 also shows a third imaginary straight line 93. The third imaginary straight line 93 is perpendicular to the imaginary plane 95. The third imaginary straight line 93 intersects with the first cutting edge portion 6. From another perspective, when viewed along the extension direction of the first cutting edge portion 6, the third imaginary straight line 93 passes through the first end point 81.

[0067] 7, when viewed along the direction in which the first cutting edge portion 6 extends, the first flank surface 12 is inclined in the second direction 102 with respect to the third imaginary straight line 93. From another perspective, the first flank surface 12 is parallel to the imaginary plane 95 and is inclined in the direction from the first cutting edge portion 6 (see FIG. 2) toward the axis X (see FIG. 2).

[0068] When viewed along the direction in which the first cutting edge portion 6 extends, the angle formed by the third virtual line 93 and the first flank 12 is defined as a third angle θ3. The third angle θ3 is, for example, 7° or greater and 13° or less. The third angle θ3 may be, for example, 9° or greater, or 11° or greater. The third angle θ3 may be, for example, 12.5° or less, or 12° or less.

[0069] 7, when viewed along the direction in which the first cutting edge portion 6 extends, the second flank surface 19 is inclined in the second direction 102 with respect to the third imaginary straight line 93. From another perspective, when viewed along the direction in which the first cutting edge portion 6 extends, the second flank surface 19 is inclined with respect to the third imaginary straight line 93 in a direction that is parallel to the imaginary plane 95 and extends from the first cutting edge portion 6 (see FIG. 2) toward the axis X (see FIG. 2).

[0070] When viewed along the direction in which the first cutting edge portion 6 extends, the angle between the third virtual line 93 and the second flank 19 is set to a fourth angle θ4. The fourth angle θ4 is greater than the third angle θ3. From another perspective, when viewed along the direction in which the first cutting edge portion 6 extends, the second flank 19 is inclined in the second direction 102 with respect to the first flank 12.

[0071] The fourth angle θ4 is, for example, equal to or greater than 20°. The fourth angle θ4 may be, for example, equal to or greater than 25°, or may be equal to or greater than 30°. The fourth angle θ4 may be, for example, equal to or less than 50°, or may be equal to or less than 45°.

[0072] The width H of the first flank surface 12 in the direction in which the third imaginary straight line 93 extends is 0.4 mm or less. The direction in which the third imaginary straight line 93 extends is the same as the third direction 103. The width H may be, for example, 0.35 mm or less, or 0.3 mm or less. The width H may be, for example, 0.1 mm or more, or 0.15 mm or more.

[0073] FIG. 8 is a schematic diagram showing the configuration of the cutting tool 100 as viewed along the extension direction of the second cutting edge portion 7. FIG. 8 shows the configuration of the cutting tool 100 as viewed along the arrow B shown in FIG. 2. Arrow B is the direction from the second end point 82 toward the axis X (see FIG. 2) along the extension direction of the second cutting edge portion 7. FIG. 8 also shows a fourth imaginary line 94. The fourth imaginary line 94 is perpendicular to an imaginary plane 95. The fourth imaginary line 94 intersects with the second cutting edge portion 7. From another perspective, when viewed along the extension direction of the second cutting edge portion 7, the fourth imaginary line 94 passes through the second end point 82.

[0074] 8 , when viewed along the direction in which the second cutting edge portion 7 extends, the third flank surface 14 is inclined in the first direction 101 with respect to the fourth imaginary straight line 94. When viewed along the direction in which the second cutting edge portion 7 extends, the angle formed between the fourth imaginary straight line 94 and the third flank surface 14 is defined as a fifth angle θ5. The fifth angle θ5 is, for example, equal to or greater than 7° and equal to or less than 13°.

[0075] <State of Use of Cutting Tool> Next, an example of a state of use of the cutting tool 100 according to this embodiment will be described. Fig. 9 is a partial cross-sectional schematic view illustrating a state of use of the cutting tool 100 according to this embodiment. As shown in Fig. 9, the cutting tool 100 is attached to a machine tool 200. Specifically, the cutting tool 100 is supported by the machine tool 200 by the portion of the main body 3 including the rear end 2 being gripped by the machine tool 200.

[0076] The length of the part of cutting tool 100 that protrudes from machine tool 200 in first direction 101 is defined as protrusion amount L2. Protrusion amount L2 is, for example, 12 mm or more.

[0077] A workpiece 99 is prepared. The workpiece 99 is made of, for example, a cemented carbide alloy. An inner peripheral surface 97 of the workpiece 99 is the surface to be cut using the cutting tool 100. The inner diameter D2 of the inner peripheral surface 97 is, for example, 7 mm or less. The value (L / D) obtained by dividing the protrusion amount L2 by the inner diameter D2 is, for example, 3 or more.

[0078] When machining the workpiece 99, the workpiece 99 rotates around the central axis C of the inner peripheral surface 97. The rotation direction of the workpiece 99 is, for example, clockwise when viewed in a first direction 101. In a second direction 102, the axis X of the cutting tool 100 is located between the central axis C and the inner peripheral surface 97. The cutting tool 100 is moved along the arrow F. The arrow F is the opposite direction to the first direction 101. As a result, the cutting edge 10 comes into contact with the workpiece 99 while the workpiece 99 is rotating.

[0079] FIG. 10 is an enlarged schematic diagram showing a state in which a workpiece 99 is being cut using a cutting tool 100 according to this embodiment. As shown in FIG. 10 , the workpiece 99 is cut using the corner cutting edge portion 8. As a result, a machined surface 98 is formed. The cutting depth ap of the cutting tool 100 is, for example, 0.1 mm or less. The first cutting edge portion 6 comes into contact with the machined surface 98. As a result, the workpiece 99 is cut using the corner cutting edge portion 8, while the machined surface 98 is finished using the first cutting edge portion 6. In this manner, the inner diameter D2 of the workpiece 99 is enlarged.

[0080] Next, the effects of the cutting tool 100 according to this embodiment will be described. When cutting a workpiece, the surface roughness of the machined surface of the workpiece may become excessively large. In this case, for example, the machined surface is polished after the cutting process. This increases the time required to machine the workpiece. For this reason, when cutting a workpiece, it is necessary to reduce the surface roughness of the machined surface. In particular, when the workpiece is a mold made of cemented carbide, it is necessary to reduce the surface roughness of the machined surface after the cutting process.

[0081] The cutting tool 100 according to this embodiment has a main body 3 and a cutting edge layer 4. The cutting edge layer 4 forms a cutting edge 10. The main body 3 is formed of a cemented carbide containing WC and Co. The cemented carbide forming the main body 3 has a WC content of 90.0% or more and 95.0% or less. The cemented carbide forming the main body 3 has a Co content of 4.0% or more and 9.0% or less.

[0082] By setting the Co content to 9.0% or less and the WC content to 90.0% or more, the rigidity of the main body 3 can be improved. Therefore, vibration of the cutting tool 100 can be suppressed when machining a workpiece. This allows the machined surface of the workpiece to be smooth. Specifically, the surface roughness of the machined surface of the workpiece can be reduced.

[0083] According to the cutting tool 100 of this embodiment, the Co content is 4.0% or more, which can prevent an excessive decrease in the transverse rupture strength of the main body 3. Therefore, even when a relatively high load is applied to the cutting tool 100 when machining the workpiece 99, breakage of the main body 3 can be prevented.

[0084] When a cutting tool with a cutting edge made of polycrystalline diamond is used to machine a workpiece, such as a mold made of cemented carbide, the portion of the cutting tool near the cutting edge may be excessively worn due to the relatively high hardness of the cemented carbide. In this case, the shape of the cutting edge may be distorted. Therefore, it may be difficult to machine the workpiece for a relatively long time.

[0085] According to the cutting tool 100 of this embodiment, the content of binder in the polycrystalline diamond forming the cutting edge layer 4 is 10.0% or less, or 0%. This improves the hardness of the cutting edge layer 4. This improves the wear resistance of the cutting edge layer 4. This prevents wear of the cutting edge layer 4 even when the workpiece is made of a relatively hard material such as cemented carbide. This allows the workpiece to be machined for a relatively long time.

[0086] With the shift to electric vehicles, the demand for small-diameter screws is increasing. This has led to a need for small-diameter internal machining using cutting processes in mold manufacturing. In small-diameter internal machining, the diameter of the cutting tool is small, making it difficult to simultaneously suppress vibrations of the cutting tool and prevent breakage of the cutting tool.

[0087] According to the cutting tool 100 of this embodiment, the diameter D1 of the main body 3 is 6 mm or less. This allows for internal machining even when the internal diameter of the workpiece is relatively small. Furthermore, according to the cutting tool 100 of this embodiment, even when the diameter D1 of the main body 3 is relatively small, as described above, it is possible to sufficiently suppress vibration of the cutting tool 100 and prevent breakage of the main body 3.

[0088] The cutting tool 100 according to this embodiment includes a brazing filler metal 5. The brazing filler metal 5 joins the main body 3 and the cutting edge layer 4. The brazing filler metal 5 contains silver, copper, and titanium. This improves the strength of the brazing filler metal 5. This improves the rigidity of the entire cutting tool 100. This reduces vibrations of the cutting tool 100 when machining a workpiece. This effectively reduces the surface roughness of the machined surface of the workpiece.

[0089] According to the cutting tool 100 of this embodiment, when viewed perpendicularly to the imaginary plane 95, the first cutting edge portion 6 is inclined in the second direction 102 with respect to the axis X, with the first end point 81 as a fulcrum. At the first end point 81, the first cutting edge portion 6 is connected to the corner cutting edge portion 8. When viewed perpendicularly to the imaginary plane 95, the angle (first angle θ1) between the axis X and the first cutting edge portion 6 is 2° or more and 4° or less. By setting the first angle θ1 to 4° or less, excessive reduction in the strength of the cutting edge 10 can be suppressed. By setting the first angle θ1 to 2° or more, the first cutting edge portion 6 can be used to perform finish machining on the machined surface of the workpiece. As a result, the surface roughness of the machined surface of the workpiece can be effectively reduced.

[0090] According to the cutting tool 100 of this embodiment, the cutting edge layer 4 has a first flank 12. The first flank 12 is continuous with the first cutting edge portion 6. When viewed along the extension direction of the first cutting edge portion 6, the angle (third angle θ3) formed between the first flank 12 and an imaginary line perpendicular to the imaginary plane 95 is 7° or more and 13° or less. When the third angle θ3 is 7° or more, excessive friction between the first flank 12 and the workpiece can be suppressed. When the third angle θ3 is 13° or less, excessive reduction in the strength of the cutting edge 10 can be suppressed.

[0091] According to the cutting tool 100 of this embodiment, the cutting edge layer 4 has a second flank 19. The second flank 19 is continuous with the first flank 12. When viewed along the first cutting edge portion 6, the angle between the second flank 19 and an imaginary line perpendicular to the imaginary plane 95 is 20° or greater. The width of the first flank 12 in the direction of extension of the imaginary line perpendicular to the imaginary plane 95 is 0.4 mm or less. Therefore, when performing internal diameter machining on a workpiece with a small inner diameter, contact between the cutting edge layer 4 and the workpiece can be prevented. Specifically, for example, when performing internal diameter machining on a workpiece with an inner diameter of 6 mm or less, contact between the cutting edge layer 4 and the workpiece can be prevented.

[0092] Although the above description has been given of a configuration in which the main body 3 is cylindrical, the configuration of the cutting tool 100 according to the present disclosure is not limited to the above configuration. Specifically, the main body 3 may be prismatic. From another perspective, the outer peripheral surface 33 may be polygonal in a cross section perpendicular to the axis X. When the main body 3 is prismatic, the diameter D1 of the main body 3 is the diameter of a circumscribed circle of the outer peripheral surface 33 in a cross section perpendicular to the axis X.

[0093] Although the above description has been given of a configuration in which the main body portion 3 and the cutting edge layer 4 are joined by the brazing filler metal 5, the cutting tool 100 according to the present disclosure does not need to have the brazing filler metal 5. Specifically, the cutting tool 100 may be a throw-away cutting tool. The main body portion 3 and the cutting edge layer 4 may be fastened together by, for example, a screw.

[0094] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples.

[0095] <Sample Preparation> First, the influence of the composition of the main body 3 on the surface roughness of the machined surface of a workpiece was investigated. Cutting tools 100 according to Samples 1-1 to 1-5 were prepared. The cutting tools 100 according to Samples 1-1 to 1-3 were examples. The cutting tools 100 according to Samples 1-4 and 1-5 were comparative examples.

[0096] In manufacturing the cutting tools 100 according to Samples 1-1 to 1-5, first, polycrystalline diamond was prepared. The thickness of the polycrystalline diamond was 0.65 mm. The shape of the polycrystalline diamond was a sector with a central angle of 60° and a radius of 3 mm.

[0097] The polycrystalline diamond and the main body 3 were joined together with a brazing material 5. The polycrystalline diamond was processed using laser processing to form a cutting edge layer 4. In this manner, cutting tools 100 according to samples 1-1 to 1-5 were prepared.

[0098]

[0099] Table 1 shows the configuration of the cutting tool 100 according to Samples 1-1 to 1-5. As shown in Table 1, in Samples 1-1 to 1-3, the WC content was 92% or more and 94% or less. The Co content was 5% or more and 8% or less. In Samples 1-4 and 1-5, the WC content was 89% or less. In Sample 1-4, the Co content was 12%. In Sample 1-5, the Co content was 6%.

[0100] In Samples 1-1 to 1-5, the cutting edge layer 4 was formed of nano-polycrystalline diamond. The binder content of the polycrystalline diamond forming the cutting edge layer 4 was 0%. The diameter of the main body 3 was 3.5 mm. The first angle θ1 was 3°. The clearance angle (third angle θ3) was 10°.

[0101] <Evaluation Method> The following cutting evaluations were performed using the cutting tools 100 according to Samples 1-1 to 1-5. Specifically, the cutting tools 100 were attached to the turret of an NC (Numerical Control) lathe. A cylindrical workpiece was fixed to the chuck of the NC lathe. The workpiece was subjected to turning under the following cutting conditions. Note that, hereinafter, HRA refers to the Rockwell hardness A scale.

[0102] <Cutting conditions> Workpiece: cemented carbide (hardness: HRA 88.0, outer diameter: 30 mm, inner diameter: 5 mm, total length: 18 mm) Cutting speed (Vc): 10 m / min Cutting depth (ap): 0.025 mm Feed per revolution (f): 0.04 mm / revolution Overhang: 20 mm Cutting oil: None (DRY machining) In the above turning process, the surface roughness (maximum height roughness Rz and arithmetic mean roughness Ra) of the machined surface of the workpiece was measured when the cutting distance reached 5.6 m. Rz and Ra were measured using a surface roughness measuring instrument in accordance with JIS (Japanese Industrial Standards) B 0601:2001. It is understood that the smaller the Rz and Ra values, the smoother the sample can finish the machined surface of the workpiece.

[0103] <Evaluation results>

[0104]

[0105] Table 2 shows the evaluation results for Samples 1-1 to 1-5. As shown in Table 2, in Samples 1-1 to 1-3, the Rz of the processed surface was 1.832 μm or less. The Ra of the processed surface was 0.337 μm or less. In Samples 1-4 and 1-5, the Rz of the processed surface was 2.258 μm or more. The Ra of the processed surface was 0.431 μm or more.

[0106] From the above, it was confirmed that the cutting tool 100 according to the example can reduce the surface roughness of the machined surface of the workpiece, compared to the cutting tool 100 according to the comparative example. It is believed that the cutting tool 100 according to the example suppresses vibration of the cutting tool 100 during cutting due to the improved rigidity of the main body 3. It is believed that this is why the machined surface of the workpiece can be finished smoothly.

[0107] <Sample Preparation> Next, the surface roughness of the machined surface was investigated when the diameter D1 of the main body 3 was 2.5 mm. Cutting tools 100 according to Samples 2-1 to 2-5 were prepared. The cutting tools 100 according to Samples 2-1 to 2-3 were examples. The cutting tools 100 according to Samples 2-4 and 2-5 were comparative examples. The manufacturing method for the cutting tools 100 according to Samples 2-1 to 2-5 was substantially the same as the manufacturing method for the cutting tools 100 according to Samples 1-1 to 1-5 described above.

[0108]

[0109] Table 3 shows the configuration of the cutting tool 100 according to Samples 2-1 to 2-5. As shown in Table 3, in Samples 2-1 to 2-3, the WC content was 92% or more and 94% or less. The Co content was 5% or more and 8% or less. In Samples 2-4 and 2-5, the WC content was 89% or less. In Sample 2-4, the Co content was 12%. In Sample 2-5, the Co content was 6%.

[0110] In Samples 2-1 to 2-5, the cutting edge layer 4 was formed of nano-polycrystalline diamond. The binder content of the polycrystalline diamond forming the cutting edge layer 4 was 0%. The diameter of the main body 3 was 2.5 mm. The first angle θ1 was 3°. The clearance angle (third angle θ3) was 10°.

[0111] <Evaluation Method> The following cutting evaluations were performed using the cutting tools 100 according to Samples 2-1 to 2-5. Specifically, the cutting tools 100 were attached to the turret of an NC lathe. A cylindrical workpiece was fixed to the chuck of the NC lathe. The workpiece was subjected to turning under the following cutting conditions.

[0112] <Cutting conditions> Workpiece: cemented carbide (hardness: HRA 88.0, outer diameter: 30 mm, inner diameter: 5 mm, total length: 13 mm) Cutting speed (Vc): 10 m / min Cutting depth (ap): 0.025 mm Feed per revolution (f): 0.04 mm / revolution Overhang: 15 mm Cutting oil: none (dry machining) In the above turning process, the surface roughness (Rz and Ra) of the machined surface of the workpiece was measured when the cutting distance reached 5.6 m. Rz and Ra were measured using a surface roughness measuring instrument in accordance with JIS B 0601:2001.

[0113] <Evaluation results>

[0114]

[0115] Table 4 shows the evaluation results for Samples 2-1 to 2-5. As shown in Table 4, for Samples 2-1 to 2-3, the Rz of the processed surface was 2.02 μm or less. The Ra of the processed surface was 0.407 μm or less. For Samples 2-4 and 2-5, the Rz of the processed surface was 2.785 μm or more. The Ra of the processed surface was 0.591 μm or more.

[0116] From the above, it was confirmed that the cutting tool 100 according to the example can reduce the surface roughness of the machined surface of the workpiece, compared to the cutting tool 100 according to the comparative example. It is believed that the cutting tool 100 according to the example suppresses vibration of the cutting tool 100 during cutting due to the improved rigidity of the main body 3. It is believed that this is why the machined surface of the workpiece can be finished smoothly.

[0117] <Sample Preparation> Next, the effect of the composition of the main body portion 3 on the transverse rupture strength of the main body portion was investigated. Cutting tools 100 according to Samples 3-1 to 3-3 were prepared. The cutting tools 100 according to Samples 3-1 and 3-2 were examples. The cutting tool 100 according to Sample 3-3 was a comparative example. The manufacturing method for the cutting tools 100 according to Samples 3-1 to 3-3 was substantially the same as the manufacturing method for the cutting tools 100 according to Samples 1-1 to 1-5 described above.

[0118]

[0119] Table 5 shows the configurations of cutting tools 100 according to Samples 3-1 to 3-3. As shown in Table 5, in Samples 3-1 and 3-2, the WC content was 92% or more and 94% or less. The Co content was 5% or more and 8% or less. In Sample 3-3, the WC content was 99%. The Co content was 0.7%.

[0120] In Samples 3-1 to 3-3, the cutting edge layer 4 was formed of nano-polycrystalline diamond. The binder content of the polycrystalline diamond forming the cutting edge layer 4 was 0%. The diameter of the main body 3 was 2.5 mm. The first angle θ1 was 3°. The clearance angle (third angle θ3) was 10°.

[0121] <Evaluation Method> The following cutting evaluation was performed using the cutting tools 100 according to Samples 3-1 to 3-3. Specifically, the cutting tools 100 were attached to the turret of an NC lathe. A cylindrical workpiece was fixed to the chuck of the NC lathe. The workpiece was subjected to turning under the following cutting conditions.

[0122] <Cutting conditions> Workpiece: cemented carbide (hardness: HRA 88.0, outer diameter: 30 mm, inner diameter: 5 mm, total length: 25 mm) Cutting speed (Vc): 10 m / min Cutting depth (ap): 0.05 mm Feed per revolution (f): 0.1 mm / revolution Overhang: 27 mm Cutting oil: none (dry machining) In the above turning process, the surface roughness (Rz and Ra) of the machined surface of the workpiece was measured when the cutting distance reached 1 km. Rz and Ra were measured using a surface roughness measuring instrument in accordance with JIS B 0601:2001.

[0123] When the cutting distance reached 1 km, the flank wear width (maximum flank wear width) was measured at the cutting edge portion corresponding to the position where the depth of cut of the workpiece was maximum. The position where the depth of cut of the workpiece was maximum was the position on the cutting edge 10 where the distance between the axis X and the cutting edge 10 in the second direction 102 was maximum. The flank wear width was the width in the third direction 103 of the flank portion where wear was confirmed. It is understood that the smaller the maximum flank wear width, the higher the wear resistance of the cutting edge portion corresponding to the position where the depth of cut of the workpiece was maximum.

[0124] <Evaluation results>

[0125]

[0126] Table 6 shows the evaluation results for Samples 3-1 to 3-3. As shown in Table 6, in Samples 3-1 and 3-2, the maximum flank wear width was 14.65 μm or less. The Rz of the machined surface was 4.012 μm or less. The Ra of the machined surface was 0.941 μm or less. In Sample 3-3, the main body 3 broke during the cutting process, so the above-mentioned turning process was discontinued. Therefore, in Sample 3-3, the maximum flank wear width, the Rz of the machined surface, and the Ra of the machined surface could not be measured. On the other hand, no breakage of the main body 3 was confirmed in Samples 3-1 and 3-2.

[0127] From the above, it was confirmed that the cutting tool 100 according to the example can prevent breakage of the main body 3 compared to the cutting tool 100 according to the comparative example. From another perspective, it was confirmed that the cutting tool 100 according to the example can suppress an excessive decrease in the transverse rupture strength of the main body 3. When the Co content is 0.7% or less, the transverse rupture strength of the main body 3 decreases excessively, and therefore it is considered that the cutting tool is not suitable for the above-mentioned turning process.

[0128] <Sample Preparation> Next, the influence of the first angle θ1 on the surface roughness of the machined surface and the influence of the third angle θ3 on the maximum flank wear width were investigated. Cutting tools 100 according to Samples 4-1 to 4-4 were prepared. The cutting tools 100 according to Samples 4-1 to 4-4 were examples. The manufacturing method for the cutting tools 100 according to Samples 4-1 to 4-4 was substantially the same as the manufacturing method for the cutting tools 100 according to Samples 1-1 to 1-5 described above.

[0129]

[0130] Table 7 shows the configuration of the cutting tool 100 according to Samples 4-1 to 4-4. As shown in Table 7, in Samples 4-1 to 4-3, the first angle θ1 was 3°. The clearance angle (third angle θ3) was 7° or greater and 13° or less. In Sample 4-4, the first angle θ1 was 5°. The clearance angle (third angle θ3) was 10°.

[0131] In Samples 4-1 to 4-4, the WC content was 92%. The Co content was 8%. In Samples 4-1 to 4-4, the cutting edge layer 4 was formed of nano-polycrystalline diamond. The binder content of the polycrystalline diamond forming the cutting edge layer 4 was 0%. The diameter of the main body 3 was 3.5 mm.

[0132] <Evaluation Method> The following cutting evaluation was performed using the cutting tools 100 according to Samples 4-1 to 4-4. Specifically, the cutting tools 100 were attached to the turret of an NC lathe. A cylindrical workpiece was fixed to the chuck of the NC lathe. The workpiece was subjected to turning under the following cutting conditions.

[0133] <Cutting conditions> Workpiece: cemented carbide (hardness: HRA 88.0, outer diameter: 30 mm, inner diameter: 5 mm, total length: 18 mm) Cutting speed (Vc): 10 m / min Depth of cut (ap): 0.025 mm Feed per revolution (f): 0.04 mm / revolution Overhang: 20 mm Cutting oil: None (DRY machining) In the above turning process, the surface roughness (Rz and Ra) of the machined surface of the workpiece was measured when the cutting distance reached 1 km. Rz and Ra were measured using a surface roughness measuring instrument in accordance with JIS B 0601:2001. When the cutting distance reached 1 km, the maximum flank wear width was measured.

[0134] <Evaluation results>

[0135]

[0136] Table 8 shows the evaluation results for Samples 4-1 to 4-4. As shown in Table 8, for Samples 4-1 to 4-3, the Rz of the machined surface was 2.017 μm or less. The Ra of the machined surface was 0.372 μm or less. For Sample 4-4, the Rz of the machined surface was 2.322 μm. The Ra of the machined surface was 0.469 μm. For Samples 4-1 to 4-4, the maximum flank wear width was 14.7 μm or more and 23.2 μm or less.

[0137] From the above, it was confirmed that the samples (Samples 4-1 to 4-3) in which the first angle θ1 was 3° could reduce the surface roughness of the machined surface of the workpiece, compared to the sample (Sample 4-4) in which the first angle θ1 was 5°. It is believed that the cutting tools 100 of Samples 4-1 to 4-3 were able to smoothly machine the machined surface of the workpiece because the length of the first cutting edge portion 6 that contacts the workpiece was long. It was also confirmed that the larger the third angle θ3, the smaller the maximum flank wear width.

[0138] <Sample Preparation> Next, the influence of the binder content of the polycrystalline diamond forming the cutting edge layer 4 on the maximum flank wear width and the surface roughness of the machined surface was investigated. Cutting tools 100 according to Samples 5-1 to 5-3 were prepared. The cutting tools 100 according to Samples 5-1 to 5-3 were examples.

[0139] The manufacturing method for cutting tool 100 according to Sample 5-1 was substantially the same as the manufacturing method for cutting tool 100 according to Samples 1-1 to 1-5 described above. The manufacturing method for cutting tool 100 according to Samples 5-2 and 5-3 was substantially the same as the manufacturing method for cutting tool 100 according to Samples 1-1 to 1-5 described above, except for the method for processing the polycrystalline diamond. Specifically, in Samples 5-2 and 5-3, cutting edge layer 4 was formed by processing polycrystalline diamond using a grinding process.

[0140]

[0141] Table 9 shows the configurations of cutting tools 100 according to Samples 5-1 to 5-3. As shown in Table 9, Sample 5-1 had a binder content of 0%. Sample 5-2 had a binder content of 10%. Sample 5-3 had a binder content of 15%. In Sample 5-1, the cutting edge layer 4 was formed of nano-polycrystalline diamond. In Samples 5-2 and 5-3, the cutting edge layer 4 was formed of polycrystalline diamond.

[0142] In Samples 5-1 to 5-3, the WC content was 92%. The Co content was 8%. The diameter of the main body 3 was 3.5 mm. The first angle θ1 was 3°. The clearance angle (third angle θ3) was 10°.

[0143] <Evaluation Method> The following cutting evaluation was performed using the cutting tools 100 according to Samples 5-1 to 5-3. Specifically, the cutting tools 100 were attached to the turret of an NC lathe. A cylindrical workpiece was fixed to the chuck of the NC lathe. The workpiece was subjected to turning under the following cutting conditions.

[0144] <Cutting conditions> Workpiece: cemented carbide (hardness: HRA 88.0, outer diameter: 30 mm, inner diameter: 5 mm, total length: 18 mm) Cutting speed (Vc): 10 m / min Depth of cut (ap): 0.025 mm Feed per revolution (f): 0.04 mm / revolution Overhang: 20 mm Cutting oil: None (DRY machining) In the above turning process, the surface roughness (Rz and Ra) of the machined surface of the workpiece was measured when the cutting distance reached 16.8 m. Rz and Ra were measured using a surface roughness measuring instrument in accordance with JIS B 0601:2001. When the cutting distance reached 16.8 m, the maximum flank wear width was measured.

[0145] <Evaluation results>

[0146]

[0147] Table 10 shows the evaluation results for Samples 5-1 to 5-3. As shown in Table 10, the maximum flank wear width was 22.86 μm or less for Samples 5-1 and 5-2. The maximum flank wear width was 171.8 μm for Sample 5-3.

[0148] In Samples 5-1 and 5-2, the Rz of the machined surface was 3.886 μm or less. The Ra of the machined surface was 0.646 μm or less. In Sample 5-3, the Rz of the machined surface was 15.662 μm. The Ra of the machined surface was 2.448 μm.

[0149] From the above, it was confirmed that, compared to the sample (Sample 5-3) with a binder content of 15%, the samples (Samples 5-1 and 5-2) with a binder content of 10% or less can improve the wear resistance of the cutting edge layer 4 and reduce the surface roughness of the machined surface of the workpiece. In Samples 5-1 and 5-2, the wear resistance of the cutting edge layer 4 is thought to have been improved by improving the hardness of the cutting edge layer 4. This is thought to have reduced the maximum flank wear width. Therefore, compared to the cutting tool 100 of Sample 5-3, the cutting tools 100 of Samples 5-1 and 5-2 enable long-term cutting.

[0150] In each of Examples 1 to 5, the composition of the hard phase in the cemented carbide forming the main body 3 was examined by X-ray diffraction, and it was found that the hard phase in all samples was substantially composed of WC particles.

[0151] The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not the above description, and is intended to include meanings equivalent to the claims and all modifications within the scope thereof.

[0152] 1 Front end, 2 Rear end, 3 Main body portion, 4 Cutting edge layer, 5 Brazing material, 6 First cutting edge portion, 7 Second cutting edge portion, 8 Corner cutting edge portion, 10 Cutting edge, 11 Rake face, 12 First flank face, 13 Corner flank face, 14 Third flank face, 18 Curved surface, 19 Second flank face, 21 First front end surface portion, 22 Second front end surface portion, 31 Bearing surface, 32 Side wall surface, 33 Outer peripheral surface, 34 Front end surface, 36 Flat portion, 37 Curved portion, 39 Depression, 41 Bottom surface, 42 Side surface, 51 First portion, 52 Second portion, 81 First end point, 82 Second end point, 91 First virtual straight line, 92 Second virtual straight line, 93 Third virtual straight line, 94 Fourth virtual straight line, 95 Virtual plane, 97 Inner peripheral surface, 98 Machining surface, 99 Workpiece, 100 cutting tool, 101 first direction, 102 second direction, 103 third direction, 200 machine tool, A, B, F arrows, C central axis, D1 diameter, D2 inner diameter, H width, L1 length, L2 protrusion amount, X axis, ap cutting amount, θ1 first angle, θ2 second angle, θ3 third angle, θ4 fourth angle, θ5 fifth angle.

Claims

1. A cutting tool comprising: a rod-shaped main body; and a cutting edge layer provided at the front end of the main body and forming a cutting edge, wherein the main body is formed from a cemented carbide containing tungsten carbide and cobalt, and the cutting edge layer is formed from polycrystalline diamond, and wherein, in the cemented carbide, the weight of the tungsten carbide divided by the total weight of the cemented carbide is a percentage of 90.0% or more and 95.0% or less, and the weight of the cobalt divided by the total weight of the cemented carbide is a percentage of 4.0% or more and 9.0% or less.

2. The cutting tool according to claim 1, wherein the percentage of the weight of the cobalt in the cemented carbide divided by the total weight of the cemented carbide is 5.0% or more and 8.0% or less.

3. A cutting tool according to claim 1 or claim 2, wherein the polycrystalline diamond comprises a plurality of diamond particles, and the weight of the binder that binds the plurality of diamond particles in the polycrystalline diamond divided by the total weight of the polycrystalline diamond is 10.0% or less or 0%.

4. A cutting tool according to claim 3, wherein in said polycrystalline diamond, the percentage of the weight of said binder divided by the total weight of said polycrystalline diamond is 1.0% or less or 0%.

5. A cutting tool according to any one of claims 1 to 4, wherein the diameter of the main body is 6 mm or less.

6. A cutting tool according to any one of claims 1 to 5, further comprising a brazing material joining the cutting edge layer and the main body portion, the brazing material including each of silver, copper, and titanium.

7. The cutting edge has: a corner cutting edge portion having a first end point and a second end point opposite the first end point; a first cutting edge portion connected to the corner cutting edge portion at the first end point and disposed relative to the corner cutting edge portion in a direction from the front end to the rear end along the axis of the body portion; and a second cutting edge portion connected to the corner cutting edge portion at the second end point and disposed relative to the corner cutting edge portion in a direction from the corner cutting edge portion toward the axis, the cutting edge layer has a first flank surface connected to the first cutting edge portion, and when viewed along the extension direction of the first cutting edge portion, the first flank surface is perpendicular to an imaginary plane including the corner cutting edge portion and the first cutting edge portion and is inclined in a direction from the first cutting edge portion toward the axis with respect to an imaginary line intersecting the first cutting edge portion, and the angle formed by the imaginary line and the first flank surface is 7° or more and 13° or less, 7. The cutting tool according to claim 1, wherein, when viewed perpendicularly to the imaginary plane, the first cutting edge portion is inclined with respect to the axis line in a direction from the first end point toward the axis line, with the first end point as a fulcrum, and an angle formed between the axis line and the first cutting edge portion is equal to or greater than 2° and equal to or less than 4°.

8. A cutting tool according to claim 7, wherein the cutting edge layer has a second flank surface that is continuous with the first flank surface and is located on the opposite side of the first cutting edge portion from the first flank surface, and when viewed along the direction in which the first cutting edge portion extends, the second flank surface is inclined with respect to the imaginary straight line in a direction from the first cutting edge portion toward the axis, the angle formed by the imaginary straight line and the second flank surface is 20° or more, and the width of the first flank surface in the direction in which the imaginary straight line extends is 0.4 mm or less.

Images