Turning tool

Abstract

The turning tool is a turning tool used for turning, and includes a holder portion and a cutting edge portion fixed to the holder portion, the cutting edge portion being made of synthetic single crystal diamond, the cutting edge portion including a rake face, a flank face, and a cutting edge disposed at an intersection where the rake face and the flank face intersect, and has a nose R with a curvature radius of 0.1 mm or more and 1.2 mm or less, and the nose R is such that the direction of the intersection between the rake face and a bisecting section of its apex angle is equal to or greater than the curvature radius of the synthetic single crystal diamond. <110> Within ±10° from the direction and <100> At least one of the conditions is met: the angle is within ±10° from the direction.

Description

Technical Field

[0001] The present disclosure relates to a turning tool. This application claims priority based on Japanese Patent Application No. 2018-147806, a Japanese patent application filed on August 6, 2018. All the descriptions described in the Japanese patent application are incorporated herein by reference.

Background Art

[0002] Conventionally, cutting tools using single-crystal diamond at least for the cutting edge (hereinafter, also referred to as "single-crystal diamond cutting tools") have been used for the processing of non-ferrous metals, mirror finishing and precision machining of plastics, etc. When single-crystal diamond is used for the cutting edge of a cutting tool, characteristics such as the wear resistance and chipping resistance of the cutting tool vary greatly depending on which crystal plane and crystal orientation of the single-crystal diamond are used for the rake face and flank face of the cutting tool, as disclosed in, for example, International Publication No. 2014 / 003110 (Patent Document 1).

[0003] Therefore, a single-crystal diamond cutting tool is manufactured after selecting a more appropriate crystal plane and crystal orientation of the single-crystal diamond according to the user's requirements, usage conditions, etc. For example, the single-crystal diamond cutting tool of Patent Document 1 is manufactured such that the rake face of the cutting edge is composed of the (100) plane of single-crystal diamond and the cutting edge tip is in the <100> direction.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] A turning tool according to one aspect of the present disclosure is a turning tool used for turning. The turning tool includes a holder portion and a cutting edge portion fixed to the holder portion. The cutting edge portion is made of a synthetic single crystal diamond. The cutting edge portion includes a rake face, a flank face, and a cutting edge disposed at an intersection where the rake face and the flank face intersect, and has a nose R with a curvature radius of 0.1 mm or more and 1.2 mm or less. For the nose R, at least one of the conditions that the intersection direction between the bisecting cross-section of its apex angle and the rake face is within ±10° from the <110> direction of the synthetic single crystal diamond and within ±10° from the <100> direction is satisfied.

Brief Description of the Drawings

[0006]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0007] [Problems to be Solved by the Present Disclosure] The above single-crystal diamond cutting tool is hardly used for machining automotive parts in the non-ferrous metal processing market. When machining under severe conditions such as high-speed cutting, high-feed, and deep cutting depths, which are commonly used in automotive parts, using a single-crystal diamond cutting tool results in frequent chipping and easy wear. Therefore, it is required to endow the single-crystal diamond cutting tool with excellent wear resistance so that machining under severe conditions becomes possible. Furthermore, there is a strong demand for smoothly finishing the surface of machined parts such as automotive parts.

[0008] In view of the above circumstances, an object of the present disclosure is to provide a turning tool having wear resistance and capable of smoothly finishing the machined surface of a workpiece.

[0009] [Effects of the Present Disclosure] According to the above, it is possible to provide a turning tool having wear resistance and capable of smoothly finishing the machined surface of a workpiece.

[0010] [Description of Embodiments of the Present Disclosure] First, the embodiments of the present disclosure will be listed and described.

[0011] [1] A turning tool according to an aspect of the present disclosure is a turning tool used for turning, and the turning tool includes a holder portion and a cutting edge portion fixed to the holder portion. The cutting edge portion is made of synthetic single-crystal diamond. The cutting edge portion includes a rake face, a flank face, and a cutting edge disposed at an intersection where the rake face and the flank face intersect, and has a nose R with a curvature radius of 0.1 mm or more and 1.2 mm or less. The nose R satisfies at least one of the conditions that the direction of the intersection line between the bisecting cross-section of its apex angle and the rake face is within ±10° from the <110> direction and within ±10° from the <100> direction of the synthetic single-crystal diamond. A turning tool having such characteristics has wear resistance and can smoothly finish the machined surface of a workpiece.

[0012] [2] The above intersection line direction is preferably within ±5° from the <110> direction of the above synthetic single crystal diamond. Thereby, the turning tool has higher wear resistance and can finish the machined surface of the workpiece smoothly.

[0013] [3] The above intersection line direction is preferably within ±5° from the <100> direction of the above synthetic single crystal diamond. Thereby, the turning tool has higher wear resistance and can finish the machined surface of the workpiece smoothly.

[0014] [4] The above synthetic single crystal diamond preferably contains 1 ppm or more and 100 ppm or less of nitrogen atoms. Thereby, the turning tool can also be excellent in defect resistance.

[0015] [5] The above tip angle is preferably 55° or more and 90° or less. Thereby, the turning tool has a better balance between cutting resistance and cutting edge strength, so that wear resistance and defect resistance can be improved.

[0016] [6] The above turning is preferably performed under the condition that the relief angle is 7° or more and 15° or less. Thereby, the turning tool can finish the machined surface of the workpiece more smoothly.

[0017] [7] The above turning is preferably performed under the condition that the feed f is 0.01 mm / rev or more and less than 0.7 mm / rev. Thereby, the turning tool can finish the machined surface of the workpiece more smoothly.

[0018] [8] The above synthetic single crystal diamond is preferably CVD single crystal diamond. Thereby, the turning tool has more sufficient wear resistance and can finish the machined surface of the workpiece smoothly.

[0019] [Details of Embodiments of the Present Disclosure] Hereinafter, the embodiments of the present disclosure (hereinafter also referred to as "the present embodiment") will be described in more detail, but the present embodiment is not limited thereto. Hereinafter, the description will be made with reference to the drawings.

[0020] Here, in this specification, the notation in the form of "A to B" means the upper and lower limits of the range (i.e., A or more and B or less). When there is no unit description for A and there is a unit description only for B, the units of A and B are the same. When representing a compound or the like by a chemical formula in this specification, when the atomic ratio is not particularly limited, it includes all conventionally known atomic ratios and is not necessarily limited only to those within the stoichiometric range. In this specification, "mechanical strength" means mechanical strength including various properties such as wear resistance, defect resistance, and bending strength.

[0021] Furthermore, in this specification, "nose R" refers to the part that comes into contact with the chip of the workpiece by directly participating in cutting at the cutting edge portion. Specifically, it refers to the portion of the cutting edge 3 included in the virtual semi-circle (solid line) shown in FIG. 1. The radius of this virtual semi-circle is such that the virtual line (broken line) obtained by extending two opposing ridge lines forming the intersection of the rake face and the flank face of the cutting edge 3 intersects at an intersection point o, and has a predetermined distance d from the intersection point o towards the ridge line.

[0022] The "radius of curvature" of the nose R refers to the reciprocal of the "curvature" of the curved surface of the nose R. Specifically, the curved surface of the nose R is given, for example, as an arc included in the virtual circle of the broken line shown in FIG. 1. In this case, the radius r of the virtual circle of the broken line is referred to as the "radius of curvature" of the nose R, and the reciprocal (1 / r) is referred to as the "curvature" of the curved surface of the nose R. Here, in FIG. 1, the radius of curvature (the radius of the virtual circle of the broken line) r of the nose R and the distance d from the intersection point o towards the ridge line are the same in magnitude (d = r).

[0023] The "apex angle" of the nose R refers to the angle α formed by the two virtual lines (broken lines) described above in FIG. 1. The virtual cross-section that bisects the angle α of the "apex angle" is referred to as the "bisecting cross-section" of the apex angle of the nose R. Furthermore, the "flank angle" refers to the angle formed by the workpiece and the flank face at the cutting edge portion.

[0024] In addition, the "intersection line direction" between the bisecting cross-section of the apex angle of the nose R and the rake face means, when the rake face has a curved surface at the cutting edge portion 3, the surface on the base metal side or the upper surface of the base metal at the cutting edge portion 3 is regarded as the rake face, and it means the intersection line direction between this assumed rake face and the bisecting cross-section of the apex angle of the nose R.

[0025] In this specification, "synthetic single crystal diamond" refers to artificially manufactured diamonds such as single crystal diamonds manufactured by the high pressure high temperature synthesis (HPHT) method and single crystal diamonds manufactured by the chemical vapor deposition (CVD) method, which are different from natural diamonds. In particular, "CVD single crystal diamond" refers to a single crystal diamond produced by epitaxially growing a single crystal of diamond on a single crystal substrate of diamond using the CVD method. The <110> direction of this CVD single crystal diamond means the equivalent four crystal orientations including [01-1] of the CVD single crystal diamond, specifically, the crystal orientations consisting of [01-1], [0-1-1], [0-11], and

[0011] of the CVD single crystal diamond. The <100> direction of the CVD single crystal diamond means the equivalent four crystal orientations including

[0010] of the CVD single crystal diamond, specifically, the crystal orientations consisting of

[0010] , [00-1], [0-10], and

[0001] of the CVD single crystal diamond. Here, the "-" represented when expressing the crystal orientation is originally represented above the number and is read as "bar". For example, [01-1] is read as "zero·one·one·bar".

[0026] ≪Turning Tool≫ The turning tool according to this embodiment is a turning tool used for turning. The turning tool includes a holder part and a cutting edge part fixed to the holder part. The cutting edge part is made of synthetic single crystal diamond. Further, the cutting edge part includes a rake face, a flank face, and a cutting edge disposed at an intersection where the rake face and the flank face intersect, and has a nose R with a curvature radius of 0.1 mm or more and 1.2 mm or less. The nose R satisfies at least one of the conditions that the direction of the intersection line between the bisecting cross-section of the apex angle thereof and the rake face is within ±10° from the <110> direction of the synthetic single crystal diamond and within ±10° from the <100> direction. The turning tool having such characteristics has wear resistance and can finish the machined surface of the workpiece smoothly.

[0027] The turning is preferably performed under the condition that the feed f is 0.01 mm / rev or more and less than 0.7 mm / rev. Further, the synthetic single crystal diamond is preferably CVD single crystal diamond. Thereby, the turning tool has more sufficient wear resistance and can finish the machined surface of the workpiece smoothly.

[0028] Hereinafter, regarding the turning tool according to this embodiment, for convenience of explanation, first, a form in which the direction of the intersection line between the bisecting cross-section of the apex angle of the nose R and the rake face is within ±10° from the <110> direction of the synthetic single crystal diamond will be described as the turning tool according to the first embodiment. Next, a form in which the direction of the intersection line between the bisecting cross-section of the apex angle of the nose R and the rake face is within ±10° from the <100> direction of the synthetic single crystal diamond will be described as the turning tool according to the second embodiment.

[0029] Furthermore, in the following description, an aspect in which the turning by the turning tool is performed under the condition that the feed f is 0.01 mm / rev or more and less than 0.7 mm / rev and the synthetic single crystal diamond is CVD single crystal diamond will be exemplified.

[0030] <First Embodiment> The turning tool according to the first embodiment is a turning tool used for turning. The above turning is preferably performed under the condition that the feed f is not less than 0.01 mm / rev and less than 0.7 mm / rev. The feed f is determined by the relationship with the radius of curvature of the cutting edge portion (nose R) of the turning tool used for turning. Therefore, when the turning tool according to the first embodiment is used for turning under the condition that the feed f is within the above range, it has particularly excellent wear resistance and can finish the machined surface of the workpiece smoothly. In this embodiment, using the turning tool for turning under the condition that the feed f is less than 0.01 mm / rev is not realistic because the machining time becomes extremely long. In this embodiment, using the turning tool for turning under the condition that the feed f is not less than 0.7 mm / rev tends to cause the cutting edge to be easily damaged and makes it difficult to finish the machined surface of the workpiece smoothly.

[0031] As shown in FIG. 2, the turning tool 1 includes a holder portion 10 and a cutting edge portion 3 fixed to the holder portion 10. The material of the holder portion 10 should not be particularly limited, but it is preferably made of, for example, steel, cemented carbide, etc. The shape of the holder portion 10 should not be particularly limited as long as it can be used for turning, but it can be, for example, a shape including a corner for accommodating the alloy 2 shown in FIG. 3. The corner of the holder portion 10 is formed by partially recessing a part of the upper surface of the holder portion 10. The cutting edge portion 3 is fixed to this corner of the holder portion 10 via the alloy 2. Specifically, when the alloy 2 has a hole, the cutting edge portion 3 is fixed to the holder portion 10 via the alloy 2 by using a method of clamping the hole (lever lock method) or a method of screwing the hole (screw-on method). When the alloy 2 has no hole, the cutting edge portion 3 is fixed to the holder portion 10 via the alloy 2 by using clamping means such as a method of pressing and gripping the upper surface of the alloy 2 (clamp-on method). The material of the alloy 2 should not be particularly limited, but it is preferably made of, for example, cemented carbide, etc.

[0032] (Cutting edge portion) The cutting edge portion 3 is made of synthetic single crystal diamond. Specifically, in the first embodiment, the cutting edge portion 3 is made of CVD single crystal diamond. The CVD single crystal diamond will be described later. As shown in FIG. 3, the cutting edge portion 3 includes a rake face 4, a flank face 5, and a cutting edge 6 disposed at an intersection where the rake face 4 and the flank face 5 intersect, and has a nose R with a radius of curvature of 0.1 mm or more and 1.2 mm or less. The rake face 4 and the flank face 5 are formed by grinding or polishing the CVD single crystal diamond. The cutting edge 6 corresponds to a ridge line as an intersection where the rake face 4 and the flank face 5 intersect. A chamfer 8 with unequal widths may be disposed at the intersection where the rake face 4 and the flank face 5 intersect. In this case, the cutting edge 6 is formed at a ridge line at a position where the flank face 5 and the chamfer 8 intersect. The chamfer 8 can also be formed by grinding or polishing the CVD single crystal diamond. The rake face 4 of the cutting edge portion 3 is preferably the (100) face of the CVD single crystal diamond.

[0033] (CVD single crystal diamond) As described above, in the first embodiment, the cutting edge portion 3 is made of CVD single crystal diamond. The CVD single crystal diamond can be produced by epitaxially growing a single crystal of diamond on a single crystal substrate of diamond using the CVD method as described later. The synthetic single crystal diamond preferably contains 1 ppm or more and 100 ppm or less of nitrogen atoms. Specifically, in the first embodiment, the CVD single crystal diamond preferably contains 1 ppm or more and 100 ppm or less of nitrogen atoms. When the CVD single crystal diamond contains nitrogen atoms within the above range, an effect of suppressing the propagation of chipping can be obtained even when a strong stress is applied to a specific portion of the cutting edge 6, so that the mechanical strength such as toughness and hardness can be improved. Thereby, the turning tool can also be excellent in chipping resistance. The nitrogen atoms exist as impurity elements in the CVD single crystal diamond. Here, the impurity element refers to an element (foreign element) other than carbon, which is the main constituent element of the single crystal diamond.

[0034] When the nitrogen atom content in CVD single crystal diamond is less than 1 ppm, the effect of suppressing the propagation of chipping cannot be sufficiently obtained, and there is a tendency that the chipping resistance cannot be improved. When the nitrogen atom content in CVD single crystal diamond exceeds 100 ppm, crystal defects increase, and when a strong stress is applied to a specific part of the cutting edge 6, a large defect tends to occur in the cutting edge 6. The nitrogen atom content in CVD single crystal diamond is preferably 20 ppm or more and 80 ppm or less.

[0035] CVD single crystal diamond may contain impurity elements other than nitrogen atoms. CVD single crystal diamond may contain, for example, silicon, boron, hydrogen, etc. as impurity elements other than nitrogen atoms. In CVD single crystal diamond, the impurity elements other than nitrogen atoms may contain 0.01 ppm or more and 3 ppm or less of each element alone for silicon and boron, may contain 1 ppm or more and 100 ppm or less of hydrogen alone, and may contain 1 ppm or more and 100 ppm or less in total of these elements.

[0036] The contents of nitrogen atoms and other impurity elements in CVD single crystal diamond can be measured by secondary ion mass spectrometry (SIMS).

[0037] (Nose R) The cutting edge portion has a nose R with a radius of curvature of 0.1 mm or more and 1.2 mm or less as described above. Since the radius of curvature of the nose R is 0.1 mm or more and 1.2 mm or less, the balance between the cutting resistance and the cutting edge strength is improved, and thus the machined surface of the workpiece can be finished smoothly. When the radius of curvature of the nose R is less than 0.1 mm, the cutting edge 6 becomes excessively acute, so that it tends to be difficult to finish the machined surface smoothly. When the radius of curvature of the nose R exceeds 1.2 mm, the cutting resistance increases, so that the cutting edge 6 tends to be easily damaged. The radius of curvature of the nose R is preferably 0.2 mm or more and 0.8 mm or less. The radius of curvature of the nose R can be measured by magnifying and projecting it onto a screen using a projector used in tool inspection or the like.

[0038] The direction of the intersection line between the bisecting plane of the apex angle of the nose R and the rake face 4 is within ±10° from the <110> direction of the synthetic single crystal diamond. In particular, the direction of the intersection line between the bisecting plane of the apex angle of the nose R and the rake face 4 is preferably within ±5° from the <110> direction of the synthetic single crystal diamond. That is, in the first embodiment, the direction of the intersection line between the bisecting plane of the apex angle of the nose R and the rake face 4 can be within ±10° from the <110> direction of the CVD single crystal diamond, and in particular, the direction of the intersection line between the bisecting plane of the apex angle of the nose R and the rake face 4 is preferably within ±5° from the <110> direction of the CVD single crystal diamond. Furthermore, the apex angle of the nose R is preferably 55° or more and 90° or less. The apex angle of the nose R can be 35° or more and 90° or less.

[0039] Here, in the turning tool according to the present disclosure using CVD single crystal diamond, when the (110) plane perpendicular to the <110> direction contacts the workpiece, that is, becomes the surface that wears during cutting, the <100> direction that becomes the wear direction within the (110) plane is known to be the easy wear direction. For this reason, when the intersection direction between the bisecting cross-section of the apex angle of the nose R and the rake face 4 is within ±10°, preferably within ±5° from the <110> direction of the CVD single crystal diamond, by performing cutting under severe conditions with a large depth of cut (ap) of the workpiece, the portion of the cutting edge 6 corresponding to the position where the depth of cut of the workpiece is maximum tends to wear significantly.

[0040] On the other hand, in this case, at the front cutting edge boundary portion of the cutting edge 6 which is the boundary contacting the workpiece, by positioning the <100> direction of the CVD single crystal diamond, within the (100) plane perpendicular to this <100> direction, the <100> direction which becomes a direction having relatively high wear resistance with respect to the above-mentioned easy wear direction (hereinafter, also referred to as "wear-resistant direction") can be arranged. In particular, in the above case, the off angle which is the angle at which the <100> direction of the CVD single crystal diamond of the cutting edge 6 and the orientation of the CVD single crystal diamond at the front cutting edge boundary portion of the cutting edge 6 intersect does not become large. Further, when the apex angle of the nose R is 55° or more and 90° or less, the <100> direction within the (100) plane of the CVD single crystal diamond can be positioned at the front cutting edge boundary portion of the cutting edge 6 with the off angle made smaller. Thereby, the effect that the front cutting edge boundary portion of the cutting edge 6 is relatively less likely to wear with respect to the above-mentioned easy wear direction can be obtained.

[0041] At the part of the cutting edge 6 corresponding to the position where the depth of cut of the workpiece is maximum, the <100> direction (easy wear direction) within the (110) plane of the CVD single crystal diamond is arranged, and at the front cutting edge boundary part, the <100> direction (wear-resistant direction) within the (100) plane of the CVD single crystal diamond is arranged, then the following effects can be obtained. That is, as the turning process progresses, the cutting edge 6 wears at the part corresponding to the position where the depth of cut of the workpiece is maximum, while almost no wear occurs at the front cutting edge boundary part. That is, as the turning process progresses, the chip amount decreases at the part of the cutting edge 6 corresponding to the position where the depth of cut of the workpiece is maximum, but the chip amount hardly changes at the front cutting edge boundary part.

[0042] Stated from the perspective of the machined surface of the workpiece, the difference in the chip amount cut at the position where the depth of cut of the workpiece is maximum and the position of the workpiece corresponding to the front cutting edge boundary part of the cutting edge 6 becomes smaller as the turning process progresses. Thereby, the surface roughness (Ra) of the machined surface of the workpiece becomes smaller. Thus, the turning tool of the present embodiment can finish the machined surface of the workpiece smoothly.

[0043] Furthermore, since the <100> direction within the (100) plane of the CVD single crystal diamond is located at the front cutting edge boundary part of the cutting edge 6, the flank wear width is difficult to expand. Therefore, the wear resistance evaluated by the expansion of the flank wear width at the front cutting edge boundary part is good. Thus, the turning tool of the present embodiment can be excellent in wear resistance.

[0044] Here, the above-mentioned turning process is preferably executed under the condition that the relief angle is 7° or more and 15° or less. By executing the turning process under the condition that the relief angle is within the above range, even when the cutting edge 6 wears, the contact between the workpiece and the flank can be reduced as much as possible, and the cutting edge strength can be ensured. Thus, the wear resistance and chipping resistance provided by the turning tool of the present embodiment can be fully exerted. Note that the above-mentioned turning process can be executed under the condition that the relief angle is 7° or more and 20° or less. Further, for reference, FIG. 4 shows the use state of the turning tool 1 turning the workpiece Z.

[0045] The crystal orientation of the CVD single crystal diamond in the direction of the intersection line between the bisecting cross-section of the apex angle of the nose R and the rake face 4 can be obtained, for example, by using the Laue camera method utilizing X-ray diffraction.

[0046] (Function) From the above, the turning tool according to the first embodiment has wear resistance and can finish the machined surface of the workpiece smoothly. In particular, it is suitable for cutting under severe conditions where the depth of cut (ap) is large.

[0047] <Second Embodiment> Hereinafter, the turning tool according to the second embodiment will be described. In the following, the points different from the turning tool according to the first embodiment will be mainly described, and the repeated descriptions will not be repeated.

[0048] In the turning tool according to the second embodiment, for the nose R, the direction of the intersection line between the bisecting cross-section of its apex angle and the rake face 4 is within ±10° from the <100> direction of the synthetic single crystal diamond. In particular, it is preferably within ±5° from the <100> direction of the synthetic single crystal diamond. That is, in the second embodiment, for the nose R, the direction of the intersection line between the bisecting cross-section of its apex angle and the rake face 4 can be within ±10° from the <100> direction of the CVD single crystal diamond, and in particular, it is preferably within ±5° from the <100> direction of the CVD single crystal diamond. The apex angle of the nose R is preferably 55° or more and 90° or less, similar to the turning tool according to the first embodiment. Also in the turning using the turning tool according to the second embodiment, it is preferably executed under the condition that the clearance angle is 7° or more and 15° or less, similar to the first embodiment. Also in the second embodiment, the apex angle of the nose R can be 35° or more and 90° or less, and the clearance angle in turning can be executed under the condition of 7° or more and 20° or less.

[0049] The <100> direction of the CVD single crystal diamond is the wear-resistant direction as described above. That is, when the (100) plane perpendicular to the <100> direction of the CVD single crystal diamond becomes the surface in contact with the workpiece (the wear surface during cutting), it is known that the <100> direction within the (100) plane becomes the wear-resistant direction. Therefore, when the intersection direction between the bisecting cross-section of the nose R apex angle and the rake face 4 is within ±10°, preferably within ±5°, from the <100> direction of the CVD single crystal diamond, the portion of the cutting edge 6 corresponding to the position where the depth of cut of the workpiece is maximum is less likely to experience wear.

[0050] In this case, in the cutting process with a small depth of cut (ap), it is also possible to position the leading cutting edge boundary portion, which is the boundary in contact with the workpiece, in an orientation close to the <100> direction (wear-resistant direction) of the CVD single crystal diamond. Thereby, the turning tool of the present embodiment can have wear resistance. Furthermore, in the cutting process with a small depth of cut (ap), it is possible to reduce the surface roughness (Ra) of the machined surface of the workpiece. Thus, the turning tool of the present embodiment can finish the machined surface of the workpiece smoothly.

[0051] (Function) From the above, the turning tool according to the second embodiment has wear resistance and can finish the machined surface of the workpiece smoothly. In particular, it is suitable for cutting processes under conditions of a small depth of cut (ap).

[0052] <Manufacturing method of turning tool (cutting edge part)> The turning tool according to the present embodiment can be manufactured by appropriately using conventionally known methods. Therefore, the manufacturing method of the above turning tool should not be particularly limited. However, regarding the manufacturing of the cutting edge part made of CVD single crystal diamond in the above turning tool, for example, it is preferable to use the following method.

[0053] That is, as a method for manufacturing the cutting edge portion, a first step of preparing a single crystal substrate made of diamond, a second step of forming a conductive layer on the surface of the single crystal substrate by ion implantation into the single crystal substrate, a third step of epitaxially growing a growth layer made of diamond on the conductive layer, a fourth step of separating the growth layer from the single crystal substrate, and a fifth step of obtaining a cutting edge portion made of CVD single crystal diamond by grinding or polishing the separated growth layer can be mentioned.

[0054] (First step) First, in the first step, a single crystal substrate made of diamond is prepared. A conventionally known single crystal substrate made of diamond can be used. For example, a single crystal substrate (type: Ib) made of diamond having a flat plate shape and manufactured by a high temperature and high pressure synthesis method can be used to prepare the single crystal substrate.

[0055] The single crystal substrate is a flat plate having a surface composed of the (100) plane of single crystal diamond and side surfaces composed of the (001) plane and the (011) plane perpendicular to the surface. The single crystal substrate preferably has a thickness variation of 10% or less as the flat plate. Further, the surface of the single crystal substrate preferably has a surface roughness (Ra) of 30 nm or less. The shape of the surface (upper surface) of the single crystal substrate may be, for example, a rectangular shape such as a square or a rectangle, or a polygon other than a rectangular shape such as a hexagon or an octagon.

[0056] Furthermore, it is preferable that etching is performed on the surface of the single crystal substrate. For example, the surface of the single crystal substrate is etched by reactive ion etching (RIE: Reactive Ion Etching) using oxygen (O2) gas and carbon tetrafluoride (CF4) gas. The etching method should not be limited to the above RIE, and for example, sputtering with a gas mainly composed of argon (Ar) gas may be used.

[0057] (Second step) In the second step, a conductive layer is formed on the surface of the single-crystal substrate by ion implantation into the single-crystal substrate. Specifically, carbon (C) ions are implanted toward the surface of the single-crystal substrate etched as described above. Thereby, a conductive layer can be formed in a region including the surface of the single-crystal substrate. The implanted ions should not be limited to carbon ions, and may be nitrogen ions, silicon ions, phosphorus ions, or sulfur ions.

[0058] (The third step) In the third step, an epitaxial growth layer made of diamond is epitaxially grown on the conductive layer. Specifically, a single-crystal substrate with the conductive layer formed thereon is placed in a CVD furnace in which an atmosphere is formed by introducing hydrogen (H2) gas, methane (CH4) gas, and nitrogen (N2) gas, and microwave plasma CVD is performed in the CVD furnace. Thereby, single-crystal diamond can be epitaxially grown through the conductive layer, and thus a growth layer made of diamond can be formed on the conductive layer. The method for forming the growth layer should not be limited to the microwave plasma CVD method, and for example, a thermal filament CVD method, a DC plasma method, etc. can be used. In the atmosphere in the CVD furnace, the content of nitrogen atoms in the CVD single-crystal diamond can be determined by adjusting the amount of nitrogen (N2) gas.

[0059] Furthermore, regarding the atmosphere in the CVD furnace, a gas containing other hydrocarbons such as ethane gas can be used instead of methane gas. The surface of the single-crystal substrate for forming the growth layer is preferably a (100) plane, and more preferably a plane having an off-angle of 0.5° or more and 0.7° or less with respect to the (100) plane.

[0060] (The fourth step) In the fourth step, the growth layer is separated from the single-crystal substrate. Specifically, the single-crystal substrate and the growth layer can be separated by performing electrochemical etching on the conductive layer in the single-crystal substrate. Thereby, a CVD single-crystal diamond (growth layer) can be obtained. The method for separating the growth layer should not be limited to the above-described electrochemical etching, and for example, slicing using a laser may be used.

[0061] (Step 5) In the fifth step, a cutting edge portion made of CVD single-crystal diamond is obtained by grinding or polishing the separated growth layer. Specifically, by performing conventionally known grinding or polishing on the CVD single-crystal diamond (growth layer), a cutting edge portion including a rake face, a flank face, and a cutting edge disposed at an intersection where the rake face and the flank face intersect can be obtained. At this time, with respect to the cutting edge portion, grinding or polishing is performed so as to have a nose radius R with a curvature radius of 0.1 mm or more and 1.2 mm or less. In addition, the direction of the intersection line between the bisecting cross-section of the apex angle of the nose R and the rake face satisfies at least one of the conditions of within ±10° from the <110> direction of the CVD single-crystal diamond and within ±10° from the <100> direction.

[0062] As described above, a cutting edge portion made of CVD single-crystal diamond in the present embodiment can be manufactured. The turning tool according to the present embodiment can be manufactured by fixing the above-described cutting edge portion to the corner of the holder portion via a base metal using, for example, known clamping means.

[0063] (Supplementary Note) The above description includes the embodiments described in the supplementary notes below. (Supplementary Note 1) A turning tool used for turning under the condition that the feed f is 0.01 mm / rev or more and less than 0.7 mm / rev, The turning tool includes a holder portion and a cutting edge portion fixed to the holder portion, The cutting edge portion is made of CVD single-crystal diamond, The cutting edge portion includes a rake face, a flank face, and a cutting edge disposed at an intersection where the rake face and the flank face intersect, and has a nose R with a radius of curvature of 0.1 mm or more and 1.2 mm or less. The nose R is a turning tool in which the direction of the intersection line between the bisecting cross-section of its apex angle and the rake face is within ±10° from the <110> direction or within ±10° from the <100> direction of the CVD single-crystal diamond. (Appendix 2) The turning tool according to Appendix 1, wherein the intersection line direction is within ±5° from the <110> direction of the CVD single-crystal diamond. (Appendix 3) The turning tool according to Appendix 1, wherein the intersection line direction is within ±5° from the <100> direction of the CVD single-crystal diamond. (Appendix 4) The turning tool according to any one of Appendices 1 to 3, wherein the CVD single-crystal diamond contains 1 ppm or more and 100 ppm or less of nitrogen atoms. (Appendix 5) The turning tool according to any one of Appendices 1 to 4, wherein the apex angle is 55° or more and 90° or less. (Appendix 6) The turning tool according to any one of Appendices 1 to 5, wherein the turning is performed under the condition that the flank angle is 7° or more and 15° or less.

Example

[0064] Hereinafter, the present disclosure will be described in more detail with reference to examples, but the present disclosure is not limited thereto.

[0065] ≪Example 1≫ <Fabrication of a cutting edge portion made of CVD single-crystal diamond> By using the manufacturing method of the cutting edge portion described above, a cutting edge portion made of CVD single-crystal diamond was manufactured. In Example 1, a total of 26 cutting edge portions of Samples 1-1 to 1-21 and Samples 1-A to 1-E shown in Table 1 were fabricated to correspond to the cutting tests described later.

[0066] First, 26 single-crystal substrates with a thickness of 0.7 mm and a distance (width) between the sides of 5 mm were prepared. The surfaces of these single-crystal substrates were etched by RIE to a depth region of 0.3 μm from the surface (first step).

[0067] Next, carbon ions were implanted with an energy of 3 MeV and a dose of 3.0×10 16 ions / cm 2 to form a conductive layer on the surface of the above single-crystal substrate (second step). Further, microwave plasma CVD method was performed to epitaxially grow a growth layer made of diamond with a thickness of 0.7 mm on the conductive layer of the above single-crystal substrate (third step). At this time, hydrogen gas, methane gas and nitrogen gas were used as the atmosphere in the CVD furnace, the concentration of methane gas with respect to hydrogen gas was set to 10% by volume, and the concentration of nitrogen gas with respect to methane gas was set to 1% by volume. Further, the pressure in the CVD furnace was set to 10 kPa and the substrate temperature was set to 900 °C.

[0068] Next, by performing electrochemical etching on the conductive layer in the above single-crystal substrate, the growth layer (CVD single-crystal diamond) was separated from the single-crystal substrate (fourth step). When the nitrogen atom content in the above growth layer (CVD single-crystal diamond) was measured by SIMS, it was 50 ppm. Further, using the above-mentioned Laue camera method, the crystal plane and crystal direction of the above growth layer (CVD single-crystal diamond) were specified.

[0069] Finally, by appropriately grinding and polishing the above growth layer (CVD single-crystal diamond), a cutting edge portion including a rake face, a flank face, and a cutting edge disposed at an intersection where the rake face and the flank face intersect was obtained (fifth step). When performing the above grinding and polishing, for the cutting edge portions of Samples 1-1 to 1-21 and Samples 1-A to 1-E, the radius of curvature of the nose R was made as shown in Table 1. At the same time, the angle at which the intersection direction of the bisecting cross-section of the apex angle of the nose R and the rake face intersects with the <110> direction of the CVD single-crystal diamond in the above cutting edge portion was made as shown in the "off angle" in Table 1.

[0070] That is, in Table 1, the column of "off angle" shows the angle at which the intersection direction of the bisecting cross-section of the apex angle of the nose R and the rake face intersects with the <110> direction of the CVD single-crystal diamond. Further, in Table 1, the unit of the "radius of curvature" of the nose R is mm. At the cutting edge portions of Samples 1-1 to 1-21 and Samples 1-A to 1-E, the apex angle of the nose R was set to 60°.

[0071] <Manufacture of Turning Tool> The above cutting edge portion was fixed to the holder portion (material: cemented carbide) by a screw-on method via a base alloy. Thus, turning tools for Samples 1-1 to 1-21 and Samples 1-A to 1-E were manufactured. The turning tools for Samples 1-1 to 1-21 are examples, and the turning tools for Samples 1-A to 1-E are comparative examples.

[0072] <Cutting Test> The following cutting test was conducted using the turning tools for Samples 1-1 to 1-21 and Samples 1-A to 1-E. Specifically, the above turning tool was attached to the turret of an NC lathe. On the other hand, a cylindrical workpiece was fixed to the chuck of the NC lathe, and turning was performed on this workpiece under the following cutting conditions. In this turning, the relief angle was set to 7°.

[0073] (Cutting Conditions) Workpiece: Aluminum alloy ADC12 (with 4 intermittent grooves) Cutting speed (Vc): 200 m / min Depth of cut (ap): 0.3 mm Feed (f): Changed in the range of 0.005 to 0.7 mm / rev (see Table 1) Cutting oil: 2% by mass of water-soluble emulsion.

[0074] <Evaluation> (Surface Roughness (Ra)) For the turning tools of Specimens 1-1 to 1-21 and Specimens 1-A to 1-E, the surface roughness (Ra) of the workpiece at the time when the cutting distance reached 1 km, 30 km, and 60 km by the above turning process was measured. Regarding this surface roughness (Ra), it was determined in accordance with JIS B 0601:2001 using a surface roughness measuring instrument. The results are shown in the column of "Surface Roughness [Ra]" in Table 1. In the column of "Surface Roughness [Ra]", the description of "-" means that there is no value because cutting could not be completed due to the chipping of the cutting edge. It is understood that the smaller the numerical value shown in the column of "Surface Roughness [Ra]", the more capable the specimen is of finishing the machined surface of the workpiece smoothly.

[0075] (Flank wear width at the cutting edge part corresponding to the position where the depth of cut of the workpiece is maximum) For the turning tools of Specimens 1-1 to 1-21 and Specimens 1-A to 1-E, at the time when the cutting distance reached 1 km, 30 km, and 60 km by the above turning process, the flank wear width at the cutting edge part corresponding to the position where the depth of cut of the workpiece is maximum was measured. The results are shown in the column of "Flank Wear Width (Maximum Depth of Cut)" in Table 1. The unit of the numerical value described in the column of "Flank Wear Width (Maximum Depth of Cut)" is mm. Furthermore, the description of "chipping" in this column means that the above turning process was aborted due to the occurrence of chipping or other defects at the cutting edge part corresponding to the position where the depth of cut of the workpiece is maximum. It is understood that the smaller the numerical value shown in the column of "Flank Wear Width (Maximum Depth of Cut)", the more excellent the wear resistance of the specimen at the cutting edge part corresponding to the position where the depth of cut of the workpiece is maximum.

[0076] (Flank wear width at the front cutting edge boundary) For the turning tools of Specimens 1-1 to 1-21 and Specimens 1-A to 1-E, when the cutting distances reached 1 km, 30 km, and 60 km by the above turning process, the flank wear width at the rake face boundary of the cutting edge was measured. The results are shown in the column of "Flank wear width (rake face boundary)" in Table 1. The unit of the numerical values described in this column of "Flank wear width (rake face boundary)" is mm. Further, the description of "chipping" in this column means that the above turning process was aborted due to chipping or other defects occurring at the rake face boundary of the cutting edge. It is understood that the smaller the numerical value shown in the column of "Flank wear width (rake face boundary)", the more excellent the wear resistance of the specimen at the rake face boundary of the cutting edge.

[0077] (Burr generation distance) For the turning tools of Specimens 1-1 to 1-21 and Specimens 1-A to 1-E, the cutting distance (km) at the time when burrs (height 0.1 mm) occurred during the intermittent part breakage by the above turning process was measured. The results are shown in the column of "Burr generation" in Table 1. The description of "-" in this column of "Burr generation" means that no burrs with a height of 0.1 mm or more occurred when the cutting distance exceeded 60 km. It is understood that the larger the numerical value shown in the column of "Burr generation", the more capable the specimen is of finishing the machined surface of the workpiece smoothly. Further, it is understood that the specimens with "-" described in the column of "Burr generation" can also finish the machined surface of the workpiece smoothly.

[0078]

Table 1

[0079] According to Table 1, it can be seen that the turning tools of Samples 1-1 to 1-21 have smaller values of the surface roughness (Ra) of the workpiece than those of the turning tools of Samples 1-A to 1-E. That is, the turning tools of Samples 1-1 to 1-21 can finish the machined surface of the workpiece smoothly. Furthermore, it is understood from the values of the flank wear width at the cutting edge portion corresponding to the position where the depth of cut of the workpiece is maximum and the flank wear width at the front cutting edge boundary of the turning tools of Samples 1-1 to 1-21 that they have wear resistance enabling turning under severe conditions.

[0080] <<Example 2>> <Fabrication of a cutting edge portion made of CVD single crystal diamond> By using the same method as in Example 1 above, a cutting edge portion made of CVD single crystal diamond was manufactured. In Example 2, a total of 26 cutting edge portions of Samples 2-1 to 2-21 and Samples 2-A to 2-E shown in Table 1 were fabricated to correspond to the cutting tests described later.

[0081] However, in Example 2, in the grinding and polishing processes for obtaining the cutting edge portion from the growth layer (CVD single crystal diamond), regarding the cutting edge portions of Samples 2-1 to 2-21 and Samples 2-A to 2-E, the radius of curvature of the nose R was made as shown in Table 2. Also, the angle at which the intersection direction between the bisecting plane of the apex angle of the nose R and the rake face intersects with the <100> direction of the CVD single crystal diamond in the above cutting edge portion was made as shown in the "off angle" in Table 2.

[0082] That is, in Table 2, in the column of "off angle", the angle at which the intersection direction between the bisecting plane of the apex angle of the nose R and the rake face intersects with the <100> direction of the CVD single crystal diamond is shown. Furthermore, in Table 2, the unit of the "radius of curvature" of the nose R is mm. In the cutting edge portions of Samples 2-1 to 2-21 and Samples 2-A to 2-E, the apex angle of the nose R was 60°.

[0083] <Fabrication of a turning tool> By using the same method as in Example 1 above, turning tools for Samples 2-1 to 2-21 and Samples 2-A to 2-E were produced. The turning tools for Samples 2-1 to 2-21 are examples, and the turning tools for Samples 2-A to 2-E are comparative examples.

[0084] <Cutting test> The same cutting test as in Example 1 was performed on the turning tools for Samples 2-1 to 2-21 and Samples 2-A to 2-E. The evaluation was also the same as in Example 1. The results are shown in Table 2.

[0085]

Table 2

[0086] According to Table 2, it can be seen that the turning tools for Samples 2-1 to 2-21 have smaller values of the surface roughness (Ra) of the work material than the turning tools for Samples 2-A to 2-E. That is, the turning tools for Samples 2-1 to 2-21 can finish the machined surface of the work material smoothly. Furthermore, it is understood from the values of the flank wear width at the cutting edge portion corresponding to the position where the depth of cut of the work material is maximum and the flank wear width at the front cutting edge boundary for the turning tools of Samples 2-1 to 2-21 that they have wear resistance enabling turning under severe conditions.

[0087] ≪Example 3≫ <Manufacture of cutting edge portion made of CVD single crystal diamond> By using the same method as in Example 1 above, a cutting edge portion made of CVD single crystal diamond was manufactured. In Example 3, a total of 8 cutting edge portions for Samples 3-1 to 3-8 were produced to correspond to the cutting test described later.

[0088] However, in Example 3, when performing the microwave plasma CVD method, by adjusting the nitrogen (N2) gas in the atmosphere, the content of nitrogen atoms in the cutting edge portions (CVD single crystal diamond) of Samples 3-1 to 3-8 was made as shown in Table 3. This content of nitrogen atoms was measured by SIMS.

[0089] Also, in the grinding and polishing processes for obtaining the cutting edge portion from the growth layer (CVD single crystal diamond), with respect to the cutting edge portions of Samples 3-1 to 3-2 and Samples 3-5 to 3-6, the intersection direction between the bisecting plane of the nose R apex angle and the rake face was made to coincide with the <110> direction of the CVD single crystal diamond (the off-angle was 0°). With respect to the cutting edge portions of Samples 3-3 to 3-4 and Samples 3-7 to 3-8, the intersection direction between the bisecting plane of the nose R apex angle and the rake face was made to coincide with the <100> direction of the CVD single crystal diamond (the off-angle was 0°). For specifying the crystal direction of the CVD single crystal diamond, the above-mentioned Laue camera method was used. Further, with respect to the cutting edge portions of Samples 3-1 to 3-8, the apex angle of the nose R was set to 60°.

[0090] <Manufacture of Turning Tools> By using the same method as in Example 1 above, turning tools for Samples 3-1 to 3-8 were manufactured.

[0091] <Cutting Test> A cutting test for evaluating the chipping resistance was conducted on the turning tools of Samples 3-1 to 3-8 above. Specifically, the above turning tool was attached to the turret of an NC lathe. On the other hand, a cylindrical work material was fixed to the chuck of the NC lathe, and turning was performed on this work material under the following cutting conditions. In this turning, the relief angle was set to 7°. Thereby, the chipping resistance was evaluated by the evaluation method described later. Here, in Example 3, the evaluation of the chipping resistance described later was also performed on the turning tools of Samples 1-1 and 2-1 described above.

[0092] (Cutting Conditions) Work material: Aluminum alloy A390 (8 intermittent grooves) Cutting speed (Vc): 800 m / min Depth of cut (ap): 0.3 mm Feed (f): 0.3 mm / rev Cutting oil: 2 mass% water-soluble emulsion.

[0093] <Evaluation> (Chipping Resistance) As an evaluation of chipping resistance, the machining distance (unit: km) that allowed the above turning operation to be performed until chipping of 0.02 mm or more occurred was measured at the cutting edge portions of the turning tools of Sample 1-1, Sample 2-1, and Samples 3-1 to 3-8. It is understood that the longer the machining distance of the sample, the better the chipping resistance. The results are shown in Table 3.

[0094]

Table 3

[0095] According to Table 3, it is understood that the turning tools of Sample 1-1, Sample 2-1, and Samples 3-1 to 3-4, in which the nitrogen atom content in the CVD single crystal diamond is 1 ppm or more and 100 ppm or less, exhibit excellent characteristics in terms of chipping resistance compared to the turning tools of Samples 3-5 to 3-8, in which the nitrogen atom content is outside the above range.

[0096] ≪Example 4≫ <Fabrication of a cutting edge portion made of CVD single crystal diamond> By using the same method as in Example 1 above, a cutting edge portion made of CVD single crystal diamond was manufactured. In Example 4, a total of two cutting edge portions of Samples 4-1 to 4-2 were fabricated to correspond to the cutting tests described later.

[0097] However, in Example 4, in the grinding and polishing processes for obtaining the cutting edge portion from the growth layer (CVD single crystal diamond), for the cutting edge portions of Samples 4-1 to 4-2, the tip angles were set as shown in Table 4. In addition, for the cutting edge portions of Samples 4-1 to 4-2, the intersection direction between the bisecting plane of the tip angle of the nose R and the rake face was made to coincide with the <110> direction of the CVD single crystal diamond (the off angle was 0°). The above-mentioned Laue camera method was used to specify the crystal direction of the CVD single crystal diamond.

[0098] <Fabrication of a turning tool> By using the same method as in Example 1 above, turning tools of Samples 4-1 to 4-2 were fabricated.

[0099] <Cutting test> For the turning tools of Specimens 4-1 to 4-2, a cutting test was conducted under the same cutting conditions as in Example 1, except that turning was performed with the relief angles shown in Table 4. Specifically, for Specimens 4-1 to 4-2, the same radius of curvature, feed, off-angle, and cutting conditions as those of Specimen 1-10 were used. However, in the evaluation of the turning tools of Specimens 4-1 to 4-2, only when the cutting distance reached 60 km by the above turning, the surface roughness (Ra), the flank wear width at the flank corresponding to the position where the depth of cut of the work material was maximum, and the flank wear width at the flank of the rake face boundary of the cutting edge were measured. Furthermore, the cutting distance (km) at the time when burrs with a height of 0.1 mm or more occurred was also measured. The results are shown in Table 4.

[0100]

Table 4

[0101] According to Table 4, it can be seen that both of the turning tools of Specimens 4-1 to 4-2 have small values of surface roughness (Ra). That is, the turning tools of Specimens 4-1 to 4-2 can finish the machined surface of the work material smoothly. Furthermore, it is understood from the values of the flank wear width at the flank corresponding to the position where the depth of cut of the work material is maximum and the flank wear width at the flank of the rake face boundary of the turning tools of Specimens 4-1 to 4-2 that they have wear resistance enabling turning under severe conditions.

[0102] As described above, the embodiments and examples of the present disclosure have been explained, but it has also been initially planned to appropriately combine the configurations of the above-described embodiments and examples.

[0103] The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above-described embodiments but by the claims, and it is intended that all meanings equivalent to the claims and all modifications within the scope are included.

Explanation of reference signs

[0104] 1 Turning tool, 2 Alloy, 3 Cutting edge part, 4 Rake face, 5 Relief face, 6 Cutting edge, 8 Chamfer, 10 Holder part, Z Workpiece.

Claims

1. A turning tool used for turning, The turning tool includes a holder portion and a cutting edge portion fixed to the holder portion, The cutting edge portion is made of synthetic single crystal diamond, The cutting edge portion includes a rake face, a flank face, and a cutting edge disposed at an intersection where the rake face and the flank face intersect, and has a nose radius R with a curvature radius of 0.1 mm or more and 0.4 mm or less, The nose radius R satisfies the condition that the direction of the intersection line between the bisecting cross-section of its apex angle and the rake face is within ±10° from the <110> direction of the synthetic single crystal diamond, The apex angle is 55° or more and 90° or less, a turning tool.

2. The turning tool according to claim 1, wherein the direction of the intersection line is within ±5° from the <110> direction of the synthetic single crystal diamond.

3. The turning tool according to claim 1 or claim 2, wherein the synthetic single crystal diamond contains 1 ppm or more and 100 ppm or less of nitrogen atoms.

4. The turning tool according to any one of claims 1 to 3, wherein the turning is performed under the condition that the flank angle is 7° or more and 15° or less.

5. The turning tool according to any one of claims 1 to 4, wherein the turning is performed under the condition that the feed f is 0.01 mm / rev or more and less than 0.7 mm / rev.

6. The turning tool according to any one of claims 1 to 5, wherein the synthetic single crystal diamond is CVD single crystal diamond.

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