WO2024005058A1

WO2024005058A1 - Insert and cutting tool

Info

Publication number: WO2024005058A1
Application number: PCT/JP2023/023936
Authority: WO
Inventors: 太志磯部; 亜寿紗萩原; 佑脩永岡; 真二明日山
Original assignee: 京セラ株式会社
Priority date: 2022-06-28
Filing date: 2023-06-28
Publication date: 2024-01-04

Abstract

An insert according to the present disclosure comprises a cubic boron nitride sintered compact including a plurality of cubic boron nitride particles and a binding phase that bind the plurality of cubic boron nitride particles. In the cross-section of the cubic boron nitride sintered compact, the length of grain boundaries between the binding phase and the plurality of cubic boron nitride particles per unit area of the plurality of cubic boron nitride particles is 3.2 μm-1 or greater.

Description

inserts and cutting tools

Cross-reference of related applications

This application claims priority to Japanese Patent Application No. 2022-103940 filed on June 28, 2022, and the entire disclosure of this earlier application is hereby incorporated by reference.

The present disclosure relates to inserts and cutting tools.

Cubic boron nitride (cBN) has a hardness second only to diamond and is excellent in chemical stability. Therefore, cBN sintered bodies are widely used as cutting tools for machining ferrous metals such as hardened steel, cast iron, or sintered alloys.

Patent No. 6900590

An insert according to one aspect of the present disclosure includes a cubic boron nitride sintered body that includes a plurality of cubic boron nitride particles and a binder phase that binds the plurality of cubic boron nitride particles. In the cross section of the cubic boron nitride sintered body, the length of the grain boundary between the plurality of cubic boron nitride particles and the binder phase per unit area of the plurality of cubic boron nitride particles is 3.2 μm ^- It is ¹ or more.

FIG. 1 is a perspective view showing an example of an insert according to an embodiment. FIG. 2 is a side sectional view showing an example of the insert according to the embodiment. FIG. 3 is a cross-sectional view showing an example of the coating film according to the embodiment. FIG. 4 is a schematic enlarged view of section H shown in FIG. 3. FIG. 5 is a cross-sectional view showing an example of a cBN sintered body constituting the base according to the embodiment. FIG. 6 is a front view showing an example of the cutting tool according to the embodiment. FIG. 7 is a diagram showing the results of image analysis on photographs of each cross section of the cBN sintered body according to the example and photographs of each cross section of the cBN sintered body according to the comparative example. FIG. 8 shows the field of view No. in the cBN sintered body according to the example. 1 is a partially enlarged view of a cross-sectional photograph of No. 1. FIG. FIG. 9 shows the field of view No. in the cBN sintered body according to the comparative example. 1 is a partially enlarged view of a cross-sectional photograph of No. 1. FIG.

Hereinafter, embodiments for implementing the insert and cutting tool according to the present disclosure (hereinafter referred to as "embodiments") will be described in detail with reference to the drawings. This embodiment does not limit inserts and cutting tools according to the present disclosure. Each embodiment can be combined as appropriate within the scope of not contradicting the contents. In each of the following embodiments, the same parts are given the same reference numerals, and redundant explanations will be omitted.

In the embodiments described below, expressions such as "constant," "orthogonal," "perpendicular," or "parallel" may be used, but these expressions strictly refer to "constant," "orthogonal," and "perpendicular." Or, they do not need to be "parallel". That is, each of the above expressions allows deviations in manufacturing accuracy, installation accuracy, etc., for example.

The above-mentioned conventional techniques have room for further improvement in terms of improving wear resistance and chipping resistance.

Therefore, it is expected to realize a technology that can overcome the above-mentioned problems and improve wear resistance and chipping resistance.

<Insert>
First, the specific configuration of the insert 1 according to the embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a perspective view showing an example of an insert 1 according to an embodiment. FIG. 2 is a side sectional view showing an example of the insert 1 according to the embodiment.

As shown in FIG. 1, the insert 1 according to the embodiment is an insert for a cutting tool, and has, for example, a hexahedral shape in which the upper surface and the lower surface (the surface intersecting the Z axis shown in FIG. 1) are parallelograms. have

(Main body part 2)
The insert 1 according to the embodiment includes a main body 2 and a base 10 attached to the main body 2 via a bonding material 40 (see FIG. 2), which will be described later.

The main body portion 2 is made of cemented carbide, for example. The cemented carbide contains W (tungsten), specifically, WC (tungsten carbide). The cemented carbide may contain Ni (nickel) or Co (cobalt). The main body portion 2 may be formed of cermet. The cermet contains, for example, Ti (titanium), specifically TiC (titanium carbide) or TiN (titanium nitride). The cermet may contain Ni or Co.

A seat surface 4 for attaching the base 10 is located at the end of the main body 2. A through hole 5 that vertically passes through the main body 2 is located in the center of the main body 2 . A screw 75 for attaching the insert 1 to a holder 70 (described later) is inserted into the through hole 5 (see FIG. 6).

(Base 10)
The base 10 is attached to the seat surface 4 of the main body 2. Thereby, the base body 10 is integrated with the main body portion 2.

The base 10 has a first surface 6 (here, the top surface) and a second surface 7 (here, the side surface) connected to the first surface 6. In the embodiment, the first surface 6 functions as a "rake surface" that scoops up chips generated by cutting, and the second surface 7 functions as a "relief surface." A cutting blade 8 is located on at least a portion of the ridge line where the first surface 6 and the second surface 7 intersect, and the insert 1 cuts the work material by applying the cutting blade 8 to the work material. do.

The base body 10 is a cubic boron nitride (cBN) sintered body (hereinafter referred to as "cBN sintered body"). cBN has a hardness second only to diamond and has excellent chemical stability. The specific structure of the cBN sintered body constituting the base body 10 will be described later.

As shown in FIG. 2, a substrate 30 made of, for example, cemented carbide or cermet may be located on the lower surface of the base 10. In this case, the base 10 is bonded to the seat surface 4 of the main body 2 via the substrate 30 and the bonding material 40. The bonding material 40 is, for example, a brazing material. The base 10 may be joined to the main body 2 via a bonding material 40 at a portion of the main body 2 other than the seat surface 4 .

In the embodiment, only the base body 10, which is a part of the insert 1, is made of a cBN sintered body, but the entire insert 1 may be made of a cBN sintered body.

(Coating film 20)
The base body 10 may be covered with a coating film 20. The coating film 20 covers the base body 10 for the purpose of improving the wear resistance, heat resistance, etc. of the base body 10, for example. In the example of FIG. 2, the coating film 20 covers the main body portion 2 and the base 10 entirely. However, the present invention is not limited thereto, and the coating film 20 may be located on at least a portion of the surface of the base body 10 . In this case, the heat resistance and abrasion resistance of the base body 10 can be improved. The coating film 20 may be located on the upper surface of the main body part 2. When the coating film 20 is located on the upper surface of the base 10, the first surface 6 (see FIG. 1) has high wear resistance and high heat resistance. When the coating film 20 is located on the side surface of the base 10, the second surface 7 (see FIG. 1) has high wear resistance and heat resistance.

Here, the specific structure of the coating film 20 will be explained with reference to FIG. 3. FIG. 3 is a cross-sectional view showing an example of the coating film 20 according to the embodiment.

As shown in FIG. 3, the coating film 20 includes a hard layer 21. The hard layer 21 is a layer with excellent wear resistance compared to the metal layer 22 described later. Hard layer 21 includes one or more metal nitride layers. The hard layer 21 may be one layer. As shown in FIG. 3, multiple metal nitride layers may be overlapped. The hard layer 21 may include a laminated portion 23 in which a plurality of metal nitride layers are laminated, and a third metal nitride layer 24 located on the laminated portion 23. The structure of such hard layer 21 will be described later.

(Metal layer 22)
Covering film 20 includes metal layer 22 . Metal layer 22 is located between base body 10 and hard layer 21 . Specifically, the metal layer 22 is in contact with the upper surface of the base 10 on one surface (here, the lower surface), and is in contact with the lower surface of the hard layer 21 on the other surface (here, the upper surface).

The metal layer 22 has higher adhesion to the base 10 than the hard layer 21. Examples of metal elements having such characteristics include Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si, and Y. The metal layer 22 contains at least one metal element among the above metal elements. In this way, when the metal layer 22 contains at least one element selected from the group consisting of Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si, and Y, The adhesion between the coating film 10 and the coating film 20 can be improved.

A simple substance of Ti, a simple substance of Zr, a simple substance of V, a simple substance of Cr, and a simple substance of Al are not used as the metal layer 22. This is because all of these have low melting points and low oxidation resistance, making them unsuitable for use in cutting tools. Hf alone, Nb alone, and Ta alone have low adhesion to the substrate 10. However, this does not apply to alloys containing Ti, Zr, V, Cr, Ta, Nb, Hf, or Al. Therefore, the metal layer 22 may be made of a metal other than Ti, Zr, V, Cr, Ta, Nb, Hf, and Al. In this case, the oxidation resistance of the metal layer 22 and the adhesion between the base 10 and the coating film 20 can be improved.

The metal layer 22 may be an Al-Cr alloy layer containing an Al-Cr alloy. Since the metal layer 22 has particularly high adhesion to the base 10, it is highly effective in improving the adhesion between the base 10 and the coating film 20.

When the metal layer 22 is an Al-Cr alloy layer, the content of Al in the metal layer 22 may be greater than the content of Cr in the metal layer 22. For example, the composition ratio (atomic %) of Al and Cr in the metal layer 22 may be 70:30. With such a composition ratio, the adhesion between the base body 10 and the metal layer 22 is higher.

The metal layer 22 may contain components other than the above metal elements (Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si, and Y). However, from the viewpoint of adhesion to the base 10, the metal layer 22 may contain at least 95 atomic % or more of the above metal elements in total. The metal layer 22 may contain the above metal elements in a total amount of 98 atomic % or more. For example, when the metal layer 22 is an Al--Cr alloy layer, the metal layer 22 may contain at least 95 atomic % or more of Al and Cr in total. The metal layer 22 may contain at least 98 atomic % or more of Al and Cr in total. The proportion of metal components in the metal layer 22 can be determined, for example, by analysis using an EDS (energy dispersive X-ray spectrometer).

Since Ti has poor wettability with the substrate 10 according to the embodiment, the metal layer 22 may contain as little Ti as possible from the viewpoint of improving adhesion with the substrate 10. Specifically, the content of Ti in the metal layer 22 may be 15 atomic % or less.

In this way, in the insert 1 according to the embodiment, by providing the metal layer 22 which has higher wettability with the base 10 than the hard layer 21 between the base 10 and the hard layer 21, the base 10 and the coating film can be bonded to each other. 20 can be improved. Since the metal layer 22 has high adhesion to the hard layer 21, peeling of the hard layer 21 from the metal layer 22 is unlikely to occur.

cBN used as the substrate 10 is an insulator, and cBN, which is an insulator, has room for improvement in adhesion with a film formed by PVD (physical vapor deposition). In contrast, in the insert 1 according to the embodiment, by providing the conductive metal layer 22 on the surface of the base 10, the adhesion between the hard layer 21 and the metal layer 22 formed by PVD is high.

(Hard layer 21)
Next, the structure of the hard layer 21 will be explained with reference to FIG. 4. FIG. 4 is a schematic enlarged view of section H shown in FIG. 3.

As shown in FIG. 4, the hard layer 21 has a laminated part 23 located on the metal layer 22 and a third metal nitride layer 24 located on the laminated part 23.

The laminated portion 23 includes a plurality of first metal nitride layers 23a and a plurality of second metal nitride layers 23b. The laminated portion 23 has a structure in which first metal nitride layers 23a and second metal nitride layers 23b are alternately laminated.

The thickness of the first metal nitride layer 23a and the second metal nitride layer 23b may each be 50 nm or less. By forming the first metal nitride layer 23a and the second metal nitride layer 23b thin in this way, the residual stress in the first metal nitride layer 23a and the second metal nitride layer 23b is small. Thereby, for example, peeling or cracking of the first metal nitride layer 23a and the second metal nitride layer 23b becomes less likely to occur, so that the durability of the coating film 20 is high.

The first metal nitride layer 23a is a layer in contact with the metal layer 22, and the second metal nitride layer 23b is formed on the first metal nitride layer 23a.

The first metal nitride layer 23a and the second metal nitride layer 23b may contain the metal contained in the metal layer 22.

For example, assume that the metal layer 22 contains two types of metals (herein referred to as "first metal" and "second metal"). In this case, the first metal nitride layer 23a contains nitrides of the first metal and the third metal. The third metal is a metal that is not included in the metal layer 22. Further, the second metal nitride layer 23b contains nitrides of the first metal and the second metal.

For example, in the embodiment, the metal layer 22 may contain Al and Cr. In this case, the first metal nitride layer 23a may contain Al. Specifically, the first metal nitride layer 23a may be an AlTiN layer containing AlTiN, which is a nitride of Al and Ti. The second metal nitride layer 23b may be an AlCrN layer containing AlCrN, which is a nitride of Al and Cr.

In this way, by positioning the first metal nitride layer 23a containing the metal contained in the metal layer 22 on the metal layer 22, the adhesion between the metal layer 22 and the hard layer 21 is high. This makes it difficult for the hard layer 21 to peel off from the metal layer 22, so the durability of the coating film 20 is high.

The first metal nitride layer 23a, that is, the AlTiN layer, has excellent adhesion with the metal layer 22 described above and, for example, excellent wear resistance. The second metal nitride layer 23b, ie, the AlCrN layer, has excellent heat resistance and oxidation resistance, for example. In this way, the coating film 20 controls the characteristics such as wear resistance and heat resistance of the hard layer 21 by including the first metal nitride layer 23a and the second metal nitride layer 23b having mutually different compositions. be able to. Thereby, the tool life of the insert 1 can be extended. For example, in the hard layer 21 according to the embodiment, mechanical properties such as adhesion with the metal layer 22 and abrasion resistance can be improved while maintaining the excellent heat resistance of AlCrN.

The laminated portion 23 may be formed by, for example, an arc ion plating method (AIP method). The AIP method uses arc discharge in a vacuum atmosphere to evaporate target metals (here, AlTi target and AlCr target), and forms metal nitrides (here, AlTiN and AlCrN) by combining with _N2 gas. This is a method of coating. The metal layer 22 may also be formed by the AIP method.

The third metal nitride layer 24 may be located on the laminated portion 23. Specifically, the third metal nitride layer 24 is in contact with the second metal nitride layer 23b of the laminated portion 23. The third metal nitride layer 24 is, for example, a metal nitride layer (AlTiN layer) containing Ti and Al, like the first metal nitride layer 23a.

The thickness of the third metal nitride layer 24 may be thicker than each of the first metal nitride layer 23a and the second metal nitride layer 23b. Specifically, when the first metal nitride layer 23a and the second metal nitride layer 23b have a thickness of 50 nm or less as described above, the third metal nitride layer 24 may have a thickness of 1 μm or more. For example, the thickness of the third metal nitride layer 24 may be 1.2 μm.

Thereby, for example, when the third metal nitride layer 24 has a low coefficient of friction, the welding resistance of the insert 1 can be improved. For example, when the third metal nitride layer 24 has high hardness, the wear resistance of the insert 1 can be improved. For example, when the oxidation start temperature of the third metal nitride layer 24 is high, the oxidation resistance of the insert 1 can be improved.

The thickness of the third metal nitride layer 24 may be thicker than the thickness of the laminated portion 23. Specifically, in the embodiment, when the thickness of the laminated portion 23 is 0.5 μm or less, the thickness of the third metal nitride layer 24 may be 1 μm or more. For example, when the thickness of the laminated portion 23 is 0.3 μm, the thickness of the third metal nitride layer 24 may be 1.2 μm. By making the third metal nitride layer 24 thicker than the laminated portion 23 in this way, the effect of improving the welding resistance, wear resistance, etc. described above is even higher.

The thickness of the metal layer 22 may be, for example, 0.1 μm or more and less than 0.6 μm. That is, the metal layer 22 may be thicker than each of the first metal nitride layer 23a and the second metal nitride layer 23b, and thinner than the laminated portion 23.

<Structure of cBN sintered body>
Next, the configuration of the cBN sintered body 11 that constitutes the base body 10 according to the embodiment will be explained with reference to FIG. FIG. 5 is a cross-sectional view showing an example of the cBN sintered body 11 that constitutes the base body 10 according to the embodiment.

As shown in FIG. 5, the cBN sintered body 11 constituting the base 10 according to the embodiment includes a plurality of cubic boron nitride (cBN) particles (hereinafter referred to as "cBN particles") 12 and a binder phase 13. including. The cBN particles 12 are particles made of cubic boron nitride (cBN).

The binder phase 13 refers to a portion of the cBN sintered body 11 other than the plurality of cBN particles 12. The bonded phase 13 is located between the plurality of cBN particles 12. The bonded phase 13 binds the plurality of cBN particles 12. That is, in the cBN sintered body 11, a plurality of cBN particles 12 are bonded together via the binder phase 13.

The binder phase 13 is, for example, a carbide containing Ti (TiC), a nitride containing Ti (TiN), a carbonitride containing Ti (TiCN), a boride containing Ti, Al, AlN, and Al. Contains at least one compound selected from _the group consisting of _2O3 . Examples of boride containing Ti include titanium diboride (TiB ₂ ).

Such a binder phase 13 can more firmly bind the plurality of cBN particles 12. Thereby, it is possible to reduce shedding of the cBN particles 12 from the binder phase 13 and/or the occurrence of cracks in the cBN sintered body 11. Thereby, the wear resistance and chipping resistance of the insert 1 including the base body 10 made of the cBN sintered body 11 can be improved.

In the cross section of the cBN sintered body 11 according to the embodiment, the length of the grain boundary between the plurality of cBN particles 12 and the binder phase 13 per unit area of the plurality of cBN particles 12 is 3.2 μm ⁻¹ That's all.

The cross section of the cBN sintered body 11 according to the embodiment is not particularly limited, and is any cross section of the cBN sintered body 11. For example, a photograph of the cross section of the cBN sintered body 11 can be taken using a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

By applying image analysis to a photograph of the cross section of the cBN sintered body 11, it is possible to determine the number of cBN particles 12 and the binder phase per unit area of the plurality of cBN particles 12 in the cross section of the cBN sintered body 11. 13 can be obtained. For image analysis of the photograph of the cross section of the cBN sintered body 11, image processing software such as Image J can be used, for example.

First, by applying image analysis to a photograph of the cross section of the cBN sintered body 11, the area of the cross section of the cBN sintered body 11 (cross-sectional area of the cBN sintered body 11) (μm ² ) and the cBN The content rate (area %) of a plurality of cBN particles 12 in the quality sintered body 11 is obtained. The content rate of the cBN particles 12 in the cBN sintered body 11 is determined by the sum of the area of the cBN particles 12 included in the cross section of the cBN sintered body 11 relative to the area of the cross section of the cBN sintered body 11. The ratio is x100. Next, by multiplying the cross-sectional area of the cBN sintered body 11 by the content ratio of the plurality of cBN particles 12 in the cBN sintered body 11/100, the number of cBN particles in the cross section of the cBN sintered body 11 is calculated. The total area (μm ² ) of the particles 12 is obtained.

By applying image analysis to a photograph of the cross section of the cBN sintered body 11, the length of the grain boundary between the plurality of cBN particles 12 and the binder phase 13 in the cross section of the cBN sintered body 11 can be determined. Obtain the sum (μm).

Next, by dividing the total length of the grain boundaries between the multiple cBN particles 12 and the binder phase 13 by the total area of the multiple cBN particles 12 as described above, The length (μm ⁻¹ ) of grain boundaries between the plurality of cBN particles 12 and the binder phase 13 per unit area of the particles 12 is obtained.

When the length of the grain boundary between the plural cBN particles 12 and the binder phase 13 per unit area of the plural cBN particles 12 is 3.2 μm ⁻¹ or more, the plural cBN particles 12 and the binder phase 13 can be increased. That is, the dispersibility of the plurality of cBN particles 12 in the binder phase 13 can be improved. Thereby, the bonding between the plurality of cBN particles 12 and the binder phase 13 can be improved. That is, the plurality of cBN particles 12 can be more firmly bound (sintered) by the binder phase 13.

In other words, bonding between the plurality of cBN particles 12 can be reduced. As a result, it is possible to reduce shedding of the cBN particles 12 from the binder phase 13 and/or the occurrence of cracks in the cBN sintered body 11, which are thought to occur from the joint portions between the plurality of cBN particles 12. Thereby, the wear resistance and chipping resistance of the insert 1 including the base body 10 made of the cBN sintered body 11 can be improved.

In the cross section of the cBN sintered body 11 according to the embodiment, the length of the grain boundary between the plurality of cBN particles 12 and the binder phase 13 per unit area of the cBN sintered body 11 is 2.2 μm ⁻ It may be ¹ or more.

By applying image analysis to a photograph of the cross section of the cBN sintered body 11, the cross sectional area (μm ² ) of the cBN sintered body 11 and the plurality of cBN particles 12 within the cross section of the cBN sintered body 11 are determined. The total length (μm) of grain boundaries between and the binder phase 13 is obtained. Next, by dividing the sum of the lengths of the grain boundaries between the plurality of cBN particles 12 and the binder phase 13 as described above by the cross-sectional area of the cBN sintered body 11, the cBN sintered body 11 is determined. The length (μm ⁻¹ ) of the grain boundary between the plurality of cBN particles 12 and the binder phase 13 per unit area is obtained.

When the length of the grain boundary between the plurality of cBN particles 12 and the binder phase 13 per unit area of the cBN-based sintered body 11 is 2.2 μm ⁻¹ or more, the plurality of cBN particles 12 and The contact area with phase 13 can be increased. That is, the dispersibility of the plurality of cBN particles 12 in the binder phase 13 can be improved. Thereby, the bonding between the plurality of cBN particles 12 and the binder phase 13 can be improved. That is, the plurality of cBN particles 12 can be more firmly bound (sintered) by the binder phase 13.

In the cross section of the cBN sintered body 11 according to the embodiment, the content of the plurality of cBN particles 12 in the cBN sintered body 11 may be at least 60 area % or more. The content of the plurality of cBN particles 12 in the cBN sintered body 11 may be 65 area % or more. By applying image analysis to a photograph of the cross section of the cBN sintered body 11, the content rate (area %) of the plurality of cBN particles 12 in the cBN sintered body 11 is obtained.

In the cross section of the cBN sintered body 11 according to the embodiment, the content rate of the plurality of cBN particles 12 in the cBN sintered body 11 may be 55 area % or more and 85 area % or less. When the content of the plurality of cBN particles 12 in the cBN sintered body 11 is 55 area% or more, the fracture resistance of the insert 1 including the base body 10 constituted by the cBN sintered body 11 is improved. can be done. When the content of the plurality of cBN particles 12 in the cBN sintered body 11 is 85 area% or less, the wear resistance of the insert 1 including the base body 10 constituted by the cBN sintered body 11 is improved. can be done.

<Method for producing cBN sintered body>
Next, an example of a method for manufacturing the cBN sintered body 11 according to the embodiment will be described. The method for manufacturing the cBN sintered body 11 is not limited to the method shown below.

First, 72 to 82 volume % TiN raw powder, 13 to 23 volume % Al raw material powder, and 1 to 11 volume % Al ₂ O ₃ raw material powder are prepared. An organic solvent is added to each prepared raw material powder. As the organic solvent, acetone or alcohols such as isopropyl alcohol (IPA) can be used. Thereafter, each raw material powder in an organic solvent is ground and mixed in a ball mill for 20 to 24 hours. After pulverizing and mixing each raw material powder, the organic solvent is evaporated to obtain a first mixed powder.

Next, cBN powder having an average particle size of 2.0 to 4.5 μm is added to the obtained first mixed powder. Here, the volume ratio of the first mixed powder and the cBN powder is 22-32%:68-78%. An organic solvent is added to the first mixed powder and cBN powder. As the organic solvent, acetone or alcohols such as IPA can be used. Thereafter, the first mixed powder in the organic solvent and the cBN powder are ground and mixed in a ball mill for 20 to 24 hours. After pulverizing and mixing the first mixed powder and cBN powder, the organic solvent is evaporated to obtain a second mixed powder.

Next, the obtained second mixed powder is heat-treated in a vacuum atmosphere at 650 to 1000° C. for 1 to 4 hours in a vacuum furnace to obtain a third mixed powder.

Next, an organic solvent is added to the obtained third mixed powder. As the organic solvent, acetone or alcohols such as IPA can be used. Thereafter, the third mixed powder in the organic solvent is ground and mixed in a ball mill for 20 to 24 hours. After pulverizing and mixing the third mixed powder, an organic binder is added to the third mixed powder in the organic solvent. As the organic binder, paraffin, acrylic resin, or the like can be used. Thereafter, a fourth mixed powder is obtained by evaporating the organic solvent.

Note that in the process using a ball mill, a dispersant may be added as necessary.

A molded body is obtained by molding this fourth mixed powder into a predetermined shape. For forming, known methods such as uniaxial press or cold isostatic press (CIP) can be used. This molded body is heated at a predetermined temperature within the range of 500 to 1000°C to evaporate and remove the organic binder, thereby obtaining a molded body for firing.

Next, the molded body for firing is placed in an ultra-high pressure heating device and heated at a temperature of 1200 to 1500° C. for 15 to 30 minutes under a pressure of 4 to 6 GPa. As a result, a cBN sintered body 11 according to the embodiment is obtained.

In this way, within the cross section of the cBN sintered body 11, the length of the grain boundary between the plurality of cBN particles 12 and the binder phase 13 per unit area of the plurality of cBN particles 12 is 3.2 μm ^{- 1} or more, the cBN-based sintered body 11 can be obtained. Further, in the cross section of the cBN sintered body 11, the length of the grain boundary between the plurality of cBN particles 12 and the binder phase 13 per unit area of the cBN sintered body 11 is 2.2 μm ⁻¹ or more. Thus, a cBN sintered body 11 can be obtained. Further, the cBN sintered body 11 is arranged so that the content of the plurality of cBN particles 12 in the cBN sintered body 11 is 55 area % or more and 85 area % or less in the cross section of the cBN sintered body 11. can be obtained. An insert 1 including a base body 10 can be obtained using the obtained cBN sintered body 11.

<Cutting tools>
Next, the configuration of the cutting tool 100 including the insert 1 described above will be described with reference to FIG. 6. FIG. 6 is a front view showing an example of the cutting tool 100 according to the embodiment.

As shown in FIG. 6, the cutting tool 100 according to the embodiment includes an insert 1 and a holder 70 for fixing the insert 1.

The holder 70 is a rod-shaped member that extends from a first end (upper end in FIG. 6) to a second end (lower end in FIG. 6). The holder 70 is made of steel or cast iron, for example. In particular, among these materials, steel with high toughness is sometimes used.

The holder 70 has a pocket 73 at the first end. The pocket 73 is a portion to which the insert 1 is attached, and has a seating surface that intersects with the rotational direction of the workpiece, and a restraining side surface that is inclined with respect to the seating surface. The seating surface is provided with a screw hole into which a screw 75 (described later) is screwed.

The insert 1 is located in the pocket 73 of the holder 70 and is attached to the holder 70 by a screw 75. That is, a screw 75 is inserted into the through hole 5 of the insert 1, and the tip of the screw 75 is inserted into a screw hole formed in the seating surface of the pocket 73, so that the screw portions are screwed together. Thereby, the insert 1 is attached to the holder 70 so that the cutting edge portion 3 protrudes outward from the holder 70.

In the embodiment, a cutting tool used for so-called turning is exemplified. Examples of turning processing include inner diameter processing, outer diameter processing, and grooving. The cutting tool is not limited to those used for turning. For example, the insert 1 may be used in a cutting tool used for milling. Cutting tools used for milling include, for example, milling cutters such as flat milling cutters, face milling cutters, side milling cutters, and groove milling cutters, and end mills such as single-flute end mills, multi-flute end mills, tapered-flute end mills, and ball end mills. Examples include.

For example, cutting of a workpiece includes (1) a process of rotating the workpiece, (2) a process of bringing the cutting blade 3 of the insert 1 into contact with the rotating workpiece to cut the workpiece, and , (3) including the step of separating the insert 1 from the workpiece. Note that typical examples of the material of the workpiece include carbon steel, alloy steel, stainless steel, cast iron, and non-ferrous metals.

Examples of the present disclosure will be described below, but the present disclosure is not limited to the following examples.

(Example)
A cBN sintered body according to an example was produced as described below.

First, acetone and a dispersant were added to 77% by volume TiN raw powder, 18% by volume Al raw material powder, and ₅ % by volume _Al2O3 raw material powder, and then each raw material was mixed in acetone for 24 hours in a ball mill. The powder was ground and mixed. After pulverizing and mixing each raw material powder, acetone was evaporated to obtain a first mixed powder.

Next, cBN powder with an average particle size of 3 μm was added to the obtained first mixed powder. The volume ratio of the first mixed powder and cBN powder was 27:73. After adding acetone and a dispersant to the first mixed powder and cBN powder, the first mixed powder and cBN powder were ground and mixed in acetone for 24 hours in a ball mill. After pulverizing and mixing the first mixed powder and cBN powder, acetone was evaporated to obtain a second mixed powder.

Next, the obtained second mixed powder was heat treated in a vacuum atmosphere at a temperature of 800° C. for 2 hours in a vacuum furnace to obtain a third mixed powder.

Next, acetone and a dispersant were added to the obtained third mixed powder, and then the third mixed powder in acetone was ground and mixed in a ball mill for 24 hours. After pulverizing and mixing the obtained third mixed powder, an organic binder was further added to the third mixed powder in acetone. Thereafter, the acetone was evaporated to obtain a fourth mixed powder.

Next, a molded body was obtained by molding the obtained fourth mixed powder using a uniaxial pressure press. The organic binder was evaporated and removed by heating the obtained molded body at a temperature of 800° C., and a molded body for firing was obtained.

Next, the obtained compact for firing was placed in an ultra-high pressure heating device and heated at a temperature of 1350° C. for 20 minutes under a pressure of 5 GPa. As a result, a cBN sintered body according to the example was obtained.

(Comparative example)
A cBN sintered body according to a comparative example was produced as described below.

First, acetone and a dispersant were added to 77% by volume TiN raw powder, 18% by volume Al raw material powder, and ₅ % by volume _Al2O3 raw material powder, and then each raw material was mixed in acetone for 24 hours in a ball mill. The powder was ground and mixed. After pulverizing and mixing each raw material powder, acetone was evaporated to obtain a fifth mixed powder.

Next, cBN powder having an average particle size of 3 μm was added to the obtained fifth mixed powder. The volume ratio of the fifth mixed powder and cBN powder was 27:73. After adding acetone and a dispersant to the fifth mixed powder and cBN powder, the fifth mixed powder and cBN powder were ground and mixed in acetone for 24 hours in a ball mill. After grinding and mixing the fifth mixed powder and cBN powder, an organic binder was further added to the fifth mixed powder and cBN powder in acetone. Thereafter, the acetone was evaporated to obtain a sixth mixed powder.

Next, a molded body was obtained by molding the obtained sixth mixed powder using a uniaxial pressure press. The organic binder was evaporated and removed by heating the obtained molded body at a temperature of 800° C., and a molded body for firing was obtained.

Next, the obtained compact for firing was placed in an ultra-high pressure heating device and heated at a temperature of 1350° C. for 20 minutes under a pressure of 5 GPa. As a result, a cBN sintered body according to a comparative example was obtained.

(Image analysis)
For each of the obtained cBN sintered body according to the example and the cBN sintered body according to the comparative example, a photograph of a cross section of the cBN sintered body was taken using a scanning electron microscope (SEM). Here, the field of view No. in the cBN sintered body according to the example. 1. Field of view No. 2. Field of view No. 3, and field of view no. A photograph of the cross section of 4 was taken. Field of view No. in the cBN sintered body according to the comparative example. 1. Field of view No. 2, and field of view no. I took a photo of the cross section of 3.

Next, by using image processing software Image J, image analysis was performed on the photographs of each cross section of the cBN sintered body according to the example and the photographs of each cross section of the cBN sintered body according to the comparative example. By image analysis of photographs of each cross section of such a cBN sintered body, the cross-sectional area (μm ² ) of the cBN sintered body, the content rate (area %) of cBN particles in the cBN sintered body, and The total length (μm) of the grain boundaries between the cBN particles and the binder phase in the cross section of the cBN sintered body was obtained.

The total area (μm ² ) of cBN particles in the cross section of the cBN sintered body was calculated from the cross-sectional area of the cBN sintered body and the content of cBN particles in the cBN sintered body. From the total length of the grain boundaries between the cBN particles and the binder phase and the total area of the cBN particles, the length of the grain boundaries between the cBN particles and the binder phase per unit area of the cBN particles (μm ^-1 ) was calculated. From the total length of the grain boundaries between the cBN particles and the binder phase and the cross-sectional area of the cBN sintered body 11, the length of the grain boundaries between the cBN particles and the binder phase per unit area of the cBN sintered body is calculated. The length (μm ⁻¹ ) was obtained.

FIG. 7 is a diagram showing the results of image analysis for photographs of each cross section of the cBN sintered body according to the example and the photographs of each cross section of the cBN sintered body according to the comparative example.

As shown in FIG. 7, for each cross section of the cBN sintered body according to the example, the relationship between the cBN particles and the binder phase per unit area of the cBN particles in the cross section of the cBN sintered body according to the example is The grain boundary length was 3.2 μm ⁻¹ or more. For each cross section of the cBN sintered body according to the example, the length of the grain boundary between the cBN particles and the binder phase per unit area of the cBN sintered body in the cross section of the cBN sintered body according to the example. The thickness was 2.2 μm ⁻¹ or more. Regarding each cross section of the cBN sintered body according to the example, the content of cBN particles in the cBN sintered body in the cross section of the cBN sintered body according to the example is 55 area % or more and 85 area % or less. there were.

On the other hand, as shown in FIG. 7, for each cross section of the cBN sintered body according to the comparative example, the ratio of cBN particles and binder phase per unit area of cBN particles in the cross section of the cBN sintered body according to the comparative example is The length of the grain boundaries between the grains was less than 3.2 μm ⁻¹ . For each cross section of the cBN sintered body according to the comparative example, the length of the grain boundary between the cBN particles and the binder phase per unit area of the cBN sintered body in the cross section of the cBN sintered body according to the comparative example. The thickness was less than 2.2 μm ⁻¹ .

FIG. 8 shows the field of view No. in the cBN sintered body according to the example. 1 is a partially enlarged view of a cross-sectional photograph of No. 1. FIG. FIG. 9 shows the field of view No. in the cBN sintered body according to the comparative example. 1 is a partially enlarged view of a cross-sectional photograph of No. 1. FIG.

As shown in FIGS. 8 and 9, the contact area between the cBN particles and the binder phase in the cBN sintered body according to the example is the same as the contact area between the cBN particles and the binder phase in the cBN sintered body according to the comparative example. It was confirmed that the contact area between the In other words, the frequency of bonding between cBN particles in the cBN sintered body according to the example is lower than the frequency of bonding between cBN particles in the cBN sintered body according to the comparative example. I was able to confirm. In other words, it is confirmed that the dispersibility of cBN particles in the binder phase in the cBN sintered body according to the example is higher than the dispersibility of cBN particles in the binder phase in the cBN sintered body according to the comparative example. I was able to do that.

As described above, an insert according to an embodiment (for example, insert 1) includes a plurality of cubic boron nitride particles (for example, a plurality of cBN particles 12) and a bonding phase that binds the plurality of cubic boron nitride particles. A cubic boron nitride sintered body (for example, a cBN sintered body 11) containing a binder phase 13 (for example, a binder phase 13) is provided. In the cross section of the cubic boron nitride sintered body, the length of the grain boundary between the plurality of cubic boron nitride particles and the binder phase per unit area of the plurality of cubic boron nitride particles is 3.2 μm ^- It is ¹ or more.

In the cross section of the cubic boron nitride sintered body, the length of the grain boundary between the binder phase and the plurality of cubic boron nitride particles per unit area of the cubic boron nitride sintered body is 2.2 μm. ^-1 or more.

In the cross section of the cubic boron nitride sintered body, the content of the plurality of cubic boron nitride particles in the cubic boron nitride sintered body is 55 area % or more and 85 area % or less.

Thereby, the dispersibility of the plurality of cBN particles in the binder phase can be improved, and therefore the bonding between the plurality of cBN particles and the binder phase can be improved. Therefore, the wear resistance and chipping resistance of the insert including the base body made of the cBN sintered body can be improved.

The insert 1 according to the embodiment may further include a coating film (for example, the coating film 20) located on the cBN sintered body 11. By having a coating film, wear resistance and heat resistance can be further improved.

In the embodiment described above, an example was shown in which the shape of the top surface and the bottom surface of the cutting tool 100 is a parallelogram, but the shape of the top surface and the bottom surface of the cutting tool 100 may be a rhombus, a square, or the like. The shape of the upper surface and lower surface of the cutting tool 100 may be triangular, pentagonal, hexagonal, or the like.

The shape of the cutting tool 100 may be a positive type or a negative type. The positive type is a type in which the side surface is inclined with respect to a central axis passing through the center of the upper surface and the center of the lower surface of the cutting tool 100, and the negative type is a type in which the side surface is parallel to the central axis.

Additional Note (1): A cross-section of the cubic boron nitride sintered body comprising a plurality of cubic boron nitride particles and a binder phase that binds the plurality of cubic boron nitride particles. In the insert, the length of the grain boundary between the plurality of cubic boron nitride particles and the binder phase per unit area of the plurality of cubic boron nitride particles is 3.2 μm ⁻¹ or more.
Additional Note (2): Within the cross section of the cubic boron nitride sintered body, grains between the plurality of cubic boron nitride particles and the binder phase per unit area of the cubic boron nitride sintered body. The insert according to appendix (1), wherein the field length is 2.2 μm ⁻¹ or more.
Additional Note (3): In the cross section of the cubic boron nitride sintered body, the content of the plurality of cubic boron nitride particles in the cubic boron nitride sintered body is 55 area % or more and 85 area %. The insert according to supplementary note (1) or (2), which is as follows.
Additional Note (4): The binder phase is a group consisting of a carbide containing Ti, a nitride containing Ti, a carbonitride containing Ti, a boride containing Ti, Al, AlN, and Al ₂ O ₃ The insert according to any one of Supplementary Notes (1) to (3), containing at least one compound selected from the above.
Supplementary Note (5): The insert according to any one of Supplementary Notes (1) to (4), further comprising a coating film located on at least a portion of the surface of the cubic boron nitride-based sintered body.
Additional Note (6): The coating film includes a hard phase and a metal layer located between the cubic boron nitride sintered body and the hard phase, and the metal layer includes Ti, Zr, V , Cr, Ta, Nb, Hf, and Al, the insert according to supplementary note (5).
Supplementary Note (7): The metal layer contains at least one element selected from the group consisting of Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si, and Y. ).
Supplementary Note (8): A cutting tool comprising a rod-shaped holder having a pocket at an end, and an insert according to any one of Supplementary Notes (1) to (7) located within the pocket.

Further advantages and/or modifications can be easily deduced by those skilled in the art. Therefore, the broader aspects of the invention are not limited to the specific details and representative embodiments shown and described above. Accordingly, various changes may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

1 insert 2 main body 3 cutting edge 4 seating surface 5 through hole 6 first surface 7 second surface 8 cutting edge 10 base 11 cBN sintered body 12 cBN particles 13 binder phase 20 coating film 21 hard layer 22 metal layer 23 Laminated portion 23a First metal nitride layer 23b Second metal nitride layer 24 Third metal nitride layer 30 Substrate 40 Bonding material 70 Holder 73 Pocket 75 Screw 100 Cutting tool

Claims

A cubic boron nitride sintered body comprising a plurality of cubic boron nitride particles and a binder phase that binds the plurality of cubic boron nitride particles,
In the cross section of the cubic boron nitride sintered body, the length of the grain boundary between the plurality of cubic boron nitride particles and the binder phase per unit area of the plurality of cubic boron nitride particles is: 3.2 μm −1 or more,
insert.
In the cross section of the cubic boron nitride sintered body, the length of the grain boundary between the plurality of cubic boron nitride particles and the binder phase per unit area of the cubic boron nitride sintered body is , 2.2 μm −1 or more,
An insert according to claim 1.
In the cross section of the cubic boron nitride sintered body, the content of the plurality of cubic boron nitride particles in the cubic boron nitride sintered body is 55 area % or more and 85 area % or less,
An insert according to claim 1 or 2.
The binder phase is at least selected from the group consisting of Ti-containing carbide, Ti-containing nitride, Ti-containing carbonitride, Ti-containing boride, Al, AlN , and Al2O3 . Contains a type of compound,
An insert according to any one of claims 1 to 3.
further comprising a coating film located on at least a portion of the surface of the cubic boron nitride sintered body,
An insert according to any one of claims 1 to 4.
The coating film is
hard phase, and
a metal layer located between the cubic boron nitride sintered body and the hard phase;
The metal layer is made of a metal other than Ti, Zr, V, Cr, Ta, Nb, Hf, and Al,
Insert according to claim 5.
The metal layer contains at least one element selected from the group consisting of Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si, and Y.
Insert according to claim 6.
a rod-shaped holder with a pocket at the end;
A cutting tool comprising: an insert according to any one of claims 1 to 7, located within the pocket.