JP5499718B2 - Sintered body and cutting tool using the sintered body - Google Patents

Description

  The present invention relates to a sintered body and a cutting tool using the sintered body, and more particularly to a sintered body containing cubic boron nitride and a cutting tool using the sintered body.

  Cubic boron nitride (hereinafter also referred to as cBN) has the second highest hardness and thermal conductivity after diamond. Furthermore, it has the feature that the reactivity with an iron-type metal is low compared with a diamond. Therefore, the sintered body containing cubic boron nitride is widely used as a tool material in cutting iron-based difficult-to-cut materials because of the advantage of improving the working efficiency.

  For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 53-77811) contains 80 to 40% by volume of cubic boron nitride, and the balance is a carbide of Group 4a, 5a, 6a transition metals in the periodic table. Further, there is disclosed a sintered body for a high-hardness tool characterized by consisting mainly of nitride, boride, silicide or a mixture thereof or a mutual solid solution compound.

  In Patent Document 2 (Japanese Patent Publication No. 52-43846), in a polishing body containing cubic boron nitride crystal and carbide, two lumps are strongly bonded to form a composite, and one of the lumps is More than 70% by volume of cubic boron nitride crystals, each of which is a sintered carbide agglomerate, the other of the agglomerates being bonded to each other with or without a metal binding medium, and the remainder from the material introduced at the time of manufacture There has been disclosed a polishing body comprising the lump.

  Patent Document 3 (Japanese Examined Patent Publication No. 63-20792) discloses an abrasive molded body having cubic boron nitride particles and a mass composed of a second phase bonded to a hard aggregate, In a polished body having a cubic boron nitride content of at least 80% by weight, adjacent cubic boron nitride particles are bonded together to form an alternately grown material, and the second phase is mainly nitrided. An abrasive formed body comprising aluminum halide and aluminum diboride is disclosed.

  The sintered body containing the cubic boron nitride has a low reactivity with the iron-based metal, but reacts to some extent. The sintered body constitutes an element added to an iron-based hard-to-cut material (for example, chromium or nickel added to stainless steel, molybdenum added to hardened steel, chromium, etc.), or a heat-resistant alloy. It is known to react with components (nickel, chromium, cobalt, titanium, etc.). Therefore, in a cutting tool manufactured using the sintered body, the sintered body reacts with the workpiece during cutting. And due to this reaction, the wear of the cutting tool may progress and the tool life may be reached.

  In view of this, research has been conducted on a technique capable of reducing the reactivity with a workpiece while utilizing high hardness in a sintered body having cubic boron nitride.

For example, Patent Document 4 (Japanese Patent Publication No. 61-32275) discloses a powder mainly composed of cubic boron nitride powder and Al ₂ O ₃ , AlN, Si ₃ N ₄ , B ₄ C, and SiC serving as a binder phase. And a method for producing a sintered body for a high-hardness tool produced using metallic Al or Si or a powder made of both of them.

Patent Document 5 (Japanese Patent Publication No. 62-13311) discloses a sintered body for high-hardness tools characterized by containing cubic boron nitride, α-type Si ₃ N ₄ , and β-type Si ₃ N _4. Is disclosed.

  Patent Document 6 (Patent No. 2825701) contains 30 to 85 volume% of cubic boron nitride, and the balance is made of a mixture or compound of silicon nitride, aluminum nitride, and rare earth metal oxide. A cubic boron nitride sintered body is disclosed.

  Patent Document 7 (Japanese Patent Laid-Open No. 2008-121046) discloses a high-hardness high-density cubic crystal in which cubic boron nitride powder and β-sialon powder are mixed and sintered by spark plasma sintering. A boron nitride-based sintered body is disclosed.

  The sintered body includes silicon nitride or sialon having an α-type or β-type crystal structure with low reactivity with iron-based metal, together with cubic boron nitride. These sintered bodies can reduce the reactivity with the workpiece, but the hardness is insufficient.

  Therefore, from the viewpoint of hardness and reactivity with a workpiece, there is a need for a sintered body that can provide a cutting tool having an excellent tool life when used as a cutting tool material.

JP-A-53-77811 Japanese Examined Patent Publication No. 52-43846 Japanese Examined Patent Publication No. 63-20792 Japanese Patent Publication No.61-32275 Japanese Examined Patent Publication No. 62-13311 Japanese Patent No. 2825701 JP 2008-121046 A

  An object of the present invention is to provide a sintered body having low reactivity with a workpiece while maintaining high strength and hardness, and a cutting tool having excellent wear resistance using the sintered body.

  The sintered body of the present invention is a sintered body containing cubic boron nitride, a first compound, and a second compound, and the content of the cubic boron nitride is 35 volume% or more and 93 volume% or less. The first compound is at least one of cubic sialon and cubic silicon nitride, and the second compound is a group consisting of α-sialon, β-sialon, α-type silicon nitride, and β-type silicon nitride. At least one compound selected from the group consisting of

  As a result of intensive studies in view of the above problems, the present inventors have formed a sintered body so as to include cubic boron nitride, the first compound, and the second compound as described above. It has been found that a cutting tool using a sintered body as a material has excellent wear resistance and tool life. This is considered to be because the sintered body of the present invention has low reactivity with the workpiece, has an excellent balance between hardness and toughness, and has high strength. The reason why the sintered body has a high hardness is that the sintered body contains cubic boron nitride having a high hardness. As a reason why the sintered body has low reactivity with the workpiece, it is conceivable that the sintered body contains at least one of sialon and silicon nitride having low reactivity with the workpiece. As a reason that the sintered body has an excellent balance between hardness and toughness, it is considered that the sintered body contains both the first compound and the second compound.

In the sintered body of the present invention, preferably, the volume γ of the first compound and the volume α of the second compound in the sintered body or mixture are as follows:
0.2 ≦ γ / (γ + α) <1
Indicates.

  The cutting tool using the sintered body of the present invention as a material has an excellent tool life. It is considered that the sintered body containing the first compound and the second compound in the above proportions has improved balance between hardness and toughness. This characteristic of the sintered body is considered to improve the tool life of the cutting tool.

  In the sintered body of the present invention, preferably, the sintered body further includes a third compound. The third compound is at least one element selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements and aluminum, and at least one element selected from the group consisting of nitrogen, boron and carbon One or more compounds consisting of

  The cutting tool using the sintered body of the present invention as a material has an excellent tool life. The third compound particles increase the bonding force between the cubic boron nitride particles in the sintered body, between the first compound particles, between the second compound particles, and between these particles. It is thought that the property can be improved. This characteristic of the sintered body is considered to improve the tool life of the cutting tool.

  In the sintered body of the present invention, preferably, the sintered body further includes a fourth compound. The fourth compound is at least one compound selected from the group consisting of a cobalt compound, an aluminum compound, and a tungsten compound.

  The cutting tool using the sintered body of the present invention as a material has an excellent tool life. The fourth compound particles increase the bonding force between the cubic boron nitride particles in the sintered body, between the first compound particles, between the second compound particles, and between these particles. It is thought that the property can be improved. This characteristic of the sintered body is considered to improve the tool life of the cutting tool.

  In the sintered body of the present invention, the cubic boron nitride is preferably particles having an average particle diameter of 0.5 μm or more and 5 μm or less.

  The cutting tool using the sintered body of the present invention as a material has an excellent tool life. A sintered body containing cubic boron nitride particles having an average particle diameter in the above range is considered to have excellent fracture resistance. It is believed that this characteristic of the sintered body leads to an improvement in the tool life of the cutting tool.

  The cutting tool of this invention consists of said sintered compact. A cutting tool using the above sintered body as a material has an excellent tool life.

  According to the sintered body and the cutting tool using the sintered body of the present invention, a cutting tool having an excellent tool life can be obtained.

<Sintered body>
[Embodiment 1]
In one embodiment of the present invention, the sintered body includes cubic boron nitride, a first compound, and a second compound.

  Cubic boron nitride has the second highest hardness and thermal conductivity after diamond. Furthermore, it has the feature that the reactivity with an iron-type metal is low compared with a diamond. Therefore, it is considered that a sintered body having a high hardness can be obtained by producing a sintered body using cubic boron nitride.

  The content of cubic boron nitride is 35% by volume to 93% by volume in 100% by volume of the sintered body. If the content of cubic boron nitride is less than 35% by volume, it is considered that the high hardness characteristic of cubic boron nitride cannot be sufficiently obtained in the sintered body. On the other hand, if the content of cubic boron nitride exceeds 93% by volume, the sintered body is considered to have a high hardness, but the fracture resistance is lowered.

  The cubic boron nitride is preferably particles having an average particle diameter of 0.5 μm or more and 5 μm or less.

  The first compound is at least one of cubic sialon and cubic silicon nitride.

The cubic sialon has a cubic crystal structure among sialons having a structure in which aluminum atoms (Al) and oxygen atoms (O) are dissolved in silicon nitride (Si ₃ N ₄ ). Cubic sialon has higher hardness than α-type and β-type sialon. Therefore, it is considered that the sintered body containing cubic sialon can have high hardness while maintaining the sialon characteristic of low reactivity.

  The cubic sialon used above can be obtained, for example, by treating α-type sialon or β-type sialon by an impact compression method.

  The impact compression method is preferably processed at 1800 ° C. or higher and 3000 ° C. or lower and 40 GPa or higher.

  By processing α-type sialon or β-type sialon by the impact compression method, a mixture of α-type sialon or β-type sialon and cubic sialon can be obtained. Remove the mixed materials by shock treatment and remove only the cubic sialon by centrifugal separation using the difference in specific gravity between α sialon and β sialon and cubic sialon. Can be put out.

  Cubic silicon nitride has higher hardness than α-type silicon nitride and β-type silicon nitride. Therefore, it is considered that a sintered body containing cubic silicon nitride can have high hardness while maintaining the characteristic of silicon nitride that is low reactivity.

  One of cubic sialon and cubic silicon nitride can be used, or both can be used.

  The second compound is at least one compound selected from the group consisting of α-type sialon, β-type sialon, α-type silicon nitride, and β-type silicon nitride. These can use a commercially available thing. The second compound remains in the α-type or β-type sialon or α-type or β-type silicon nitride treated by the shock compression method without being converted into cubic sialon or cubic silicon nitride. It is also possible to use α-type or β-type sialon or α-type or β-type silicon nitride.

  Since the second compound has low reactivity with the workpiece, it is considered that the sintered body containing the second compound can have excellent wear resistance.

  Since a sintered compact contains both the 1st compound and the 2nd compound, it is thought that hardness and toughness are improving with sufficient balance. If the sintered body contains the first compound and does not contain the second compound, it is considered that the toughness of the sintered body is lowered. On the other hand, when the sintered body contains the second compound and does not contain the first compound, it is considered that the hardness is insufficient.

  It is preferable from the viewpoint of the balance between hardness and toughness that the volume γ of the first compound and the volume α of the second compound in the sintered body have the following relationship.

0.2 ≦ γ / (γ + α) <1
The total content of the first compound and the second compound is preferably 2% by volume or more and 65% by volume or less in 100% by volume of the sintered body. When the total content of the first compound and the second compound in the sintered body is within the above range, it is considered that the reaction between the sintered body and the workpiece is suppressed.

[Embodiment 2]
In one embodiment of the present invention, the sintered body includes cubic boron nitride, a first compound, a second compound, and a third compound.

  As the cubic boron nitride, the first compound, and the second compound, those similar to those in Embodiment 1 can be used.

  The third compound is at least one element selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements and aluminum, and at least one type selected from the group consisting of nitrogen, boron and carbon. One or more compounds composed of elements, including solid solutions of the compounds. In the sintered body, the third compound is composed of cubic boron nitride particles, first compound particles, second compound particles, or cubic boron nitride particles and first compound particles, cubic crystals. The type boron nitride particles and the second compound particles, and the first compound particles and the second compound particles are bonded. Therefore, it is considered that the sintered body having the third compound has improved bond strength between particles and has excellent fracture resistance.

  The third compound is a nitride of at least one element selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements and aluminum, borides of the elements, and carbides of the elements. preferable. For example, titanium nitride (TiN), titanium carbonitride (TiCN), and aluminum nitride (AlN) are preferable. These third compounds may be used alone or in combination with different types.

  The total content of the third compound is preferably 10% by volume to 60% by volume in 100% by volume of the sintered body.

[Embodiment 3]
In one embodiment of the present invention, the sintered body includes cubic boron nitride, a first compound, a second compound, and a fourth compound.

  As the cubic boron nitride, the first compound, and the second compound, those similar to those in Embodiment 1 can be used.

  The fourth compound is at least one compound selected from the group consisting of a cobalt compound, an aluminum compound, and a tungsten compound, and includes a solid solution of the compound. In this specification, the cobalt compound includes cobalt, the aluminum compound includes aluminum, and the tungsten compound is used as a concept including tungsten. In the sintered body, the fourth compound is composed of cubic boron nitride particles, cubic sialon particles, cubic silicon nitride particles, or cubic boron nitride particles and cubic sialon. Particles, cubic boron nitride particles and cubic silicon nitride particles, and cubic sialon particles and cubic silicon nitride particles. Therefore, it is considered that the sintered body having the fourth compound has improved bonding strength between particles and has excellent fracture resistance.

As the fourth compound, for example, cobalt aluminum (CoAl) is preferably used.
The total content of the fourth compound is preferably 3% by volume to 30% by volume in 100% by volume of the sintered body.

  In the third embodiment, the third compound described in the second embodiment can be contained together with the fourth compound.

< Reference Examples 1-6, Comparative Examples 1-2>
(Preparation of cubic sialon)
β type sialon particles were filled in a stainless steel container and treated at a pressure of about 40 GPa and a temperature of 2000 ° C. to 2500 ° C. by an impact compression method by explosion of explosives. After the treatment by the impact compression method, the stainless steel container and the mixed member were dissolved in acid, and the powder was recovered. When the collected powder was analyzed by X-ray diffraction, cubic sialon and β-sialon were contained.

  The collected powder was separated into cubic sialon particles and β-sialon particles using a centrifugal separation method.

(Production of sintered body)
Next, the raw material powder is cubic boron nitride particles, cubic sialon particles, β-sialon particles and α-type so that the sintered body has the sintered body composition (volume%) shown in Table 1. Ball mill mixing of the sialon particles was performed using a cemented carbide pot and balls. Next, the mixed powder was filled in a cemented carbide container, and sintered at 1400 ° C. for 20 minutes while applying a pressure of 5 GPa to obtain sintered bodies shown in Table 1.

  The composition ratio of the sintered body is identified by cutting out the sintered body and using a scanning electron microscope (cross-section polisher (CP processing) with a cross-section polisher (CP processing). This was observed by FE-SEM). In the backscattered electron image obtained by SEM observation, shading occurs depending on the atomic number of each composition. The composition of each color portion was identified by energy dispersive X-ray fluorescence analysis (EDX). And the content of each composition was identified by carrying out image analysis of the image. Alternatively, the sintered body may be cut out, a sample may be cut out by focused ion beam processing (FIB), and the content of the composition may be identified by image analysis using a high-angle scattering dark field method with a transmission electron microscope. Even in the high-angle scattering dark field method of a transmission electron microscope, light and shade are produced in the image due to the density difference of each composition. The composition of each color portion can be identified by elemental analysis by energy dispersive X-ray fluorescence analysis (EDX) or electron diffraction.

(Performance evaluation 1)
The obtained sintered body was processed into an ISO model SNGN120408-shaped cutting chip, a cutting test was performed under the following conditions, and a processing time until the tool life was evaluated. The tool life was determined as a defect.
Work material: SCM415 Carburized and hardened steel (HRc62) With 4 U-grooves in the axial direction External diameter cutting speed: 170 m / min
Cutting depth: 0.15 mm
Feed amount: 0.1mm / rev
Coolant: None The results are shown in Table 1.

(Evaluation result 1)
Reference Examples 1 to 4 and 6 are 50% by volume of cubic boron nitride (average particle size 1 μm), 47.5 to 10% by volume of cubic sialon, and 2.5 to 2.5 of α-type or β-type sialon. It was a sintered body containing 40% by volume. In Reference Examples 1 to 4 and 6, the effect of improving the tool life was remarkable as compared with Comparative Examples 1 and 2 that did not contain either cubic sialon particles or α-type or β-type sialon.

Reference Example 5 was a sintered body containing 50% by volume of cubic boron nitride (average particle size 1 μm), 5% by volume of cubic sialon, and 45% by volume of β-sialon. The tool life of Reference Example 5 was better than Comparative Example 2 that did not contain cubic sialon, but was shorter than Reference Examples 1 to 4. This is presumably because the content of the cubic sialon was small and defects occurred due to a decrease in hardness and strength.

  Comparative Examples 1 and 2 were sintered bodies containing 50% by volume of cubic boron nitride (average particle size 1 μm) and 50% by volume of cubic sialon or β-sialon. In Comparative Examples 1 and 2, chipping occurred in the initial stage and the tool life was short.

[ Examples 11 to 13, 16, Reference Examples 7 to 12 , Comparative Examples 3 to 6]
(Preparation of cubic sialon particles)
Cubic sialon particles were prepared in the same manner as in Reference Example 1.

(Preparation of cubic silicon nitride particles)
β-type silicon nitride particles were filled in a stainless steel container and treated at a pressure of about 40 GPa and a temperature of 2000 ° C. to 2500 ° C. by an impact compression method using an explosive explosion. After the treatment by the impact compression method, the stainless steel container was acid-dissolved and the powder was recovered. When the collected powder was analyzed by X-ray diffraction, it contained cubic silicon nitride and β-type silicon nitride. The collected powder was separated into cubic silicon nitride particles and β-type silicon nitride particles using a centrifugal separation method.

(Production of sintered body)
In the same manner as in Reference Example 1, cubic boron nitride particles, cubic silicon nitride particles, which are raw material powders, so that the sintered body has the sintered body composition (volume%) shown in Table 2, Cubic sialon particles, β-type silicon nitride particles, β-type sialon particles, α-type sialon particles, and titanium nitride (TiN) particles and aluminum (Al) particles (TiN: Al mass ratio 4: 1) as other components Were mixed to obtain sintered bodies of Examples 11 to 13, 16, Reference Examples 7 to 12 and Comparative Examples 3 to 6.

(Performance evaluation 2)
Using the sintered bodies of Examples 11 to 13, 16 and Reference Examples 7 to 12 and Comparative Examples 3 to 6, they were processed into ISO type SNGA1204112-shaped cutting tips and subjected to a cutting test under the following conditions. The processing time until the end of life was evaluated. The tool life was determined as missing or worn (when the flank wear amount exceeded 0.2 mm).
Work material: Ni-based heat-resistant alloy (Inconel 718 (registered trademark) manufactured by Special Metal Co., Ltd.) Outer diameter turning Cutting speed: 280 m / min
Cutting depth: 0.2mm
Feed amount: 0.15mm / rev
Coolant: Yes The results are shown in Table 2.

(Evaluation result 2)
Reference Examples 7 to 9 were sintered bodies containing 45 to 60% by volume of cubic boron nitride (average particle size 2 μm) and 55 to 40% by volume in total of the first compound and the second compound. In Reference Examples 7 to 9, there was no chipping during processing, and the tool life was very long as compared with Comparative Example 3 in which the content of cubic boron nitride was 30% by volume.

Examples 11 to 13, 16 and Reference Examples 10 to 12 were obtained by adding 60% by volume of cubic boron nitride (average particle size 0.3, 2 or 7 μm), the first compound, the second compound and the titanium compound ( It was a sintered body containing a Ti compound and an aluminum compound (Al compound) (excluding sialon). In Examples 11 to 13, 16 and Reference Examples 10 to 12 , there was no chipping during processing, and the tool life was very long.

  Comparative Example 3 was a sintered body containing 30% by volume of cubic boron nitride (average particle size 2 μm), 52.5% by volume of cubic sialon, and 17.5% by volume of β-sialon. . Comparative Example 3 was lost in the initial stage of processing.

  Comparative Examples 4 to 6 are cubic volume boron nitride (average particle size 2 μm) of 60% by volume, a second compound, a titanium compound (Ti compound), and an aluminum compound (Al compound) (however, sialon And a sintered body containing 40% by volume. In all cases, the wear resistance was poor and the tool life was short.

<Examples 21 to 23, Reference Examples 13 to 19 , Comparative Examples 7 to 8>
In the same manner as in Reference Example 7, the raw material powder was cubic boron nitride particles, cubic sialon particles, β so that the sintered body had the sintered body composition (volume%) shown in Table 3. Type sialon particles and titanium nitride (TiN) particles and aluminum (Al) particles (TiN: Al mass ratio 4: 1) as other components were mixed, and Examples 21 to 23, Reference Examples 13 to 19 and Comparison The sintered bodies of Examples 7 and 8 were obtained.

(Performance evaluation 3)
The obtained sintered body was processed into a cutting tip having an ISO model number CNGA12041 shape, a cutting test was performed under the following conditions, and a processing time until the tool life was evaluated. The tool life was determined as missing or worn (when the flank wear amount exceeded 0.2 mm).
Work material: Ni-base heat-resistant alloy (Inconel 718 (registered trademark) manufactured by Special Metal Co., Ltd.) Outer diameter turning Cutting speed: 350 m / min
Cutting depth: 0.8mm
Feed amount: 0.2mm / rev
Coolant: Yes Table 3 shows the results.

(Evaluation result 3)
Reference Examples 13 to 15 were sintered bodies containing 60% by volume of cubic boron nitride (average particle size 2 μm), 30 to 10% by volume of cubic sialon, and 10 to 30% by volume of β-sialon. . The tool life of Reference Examples 13 to 15 was improved as compared with Comparative Examples 7 to 8 not containing cubic sialon.

Reference Example 16 was a sintered body containing 60% by volume of cubic boron nitride (average particle size 2 μm), 5% by volume of cubic sialon, and 35% by volume of β-sialon. The tool life of Reference Example 16 was equivalent to Comparative Examples 7 to 8 that did not contain cubic sialon.

  In Examples 21 to 23, cubic boron nitride (average particle size 2 μm) was 60% by volume, the first compound was 15 to 5% by volume, β-sialon was 5 to 15% by volume, and a titanium-based compound (Ti system) Compound) and an aluminum compound (Al compound) (however, excluding sialon) was a sintered body containing 20% by volume in total. The tool life of Examples 21 to 23 was improved as compared with Comparative Examples 7 to 8 not containing cubic sialon.

Reference Example 17 is 60% by volume of cubic boron nitride (average particle size 2 μm), 3% by volume of cubic sialon, 17% by volume of β-sialon, and titanium-based compounds (Ti-based compounds) and aluminum-based It was a sintered body containing 20% by volume in total of compounds (Al compounds) (excluding sialon). The tool life of Reference Example 17 was slightly improved as compared with Comparative Examples 7 to 8 which did not contain cubic sialon.

In Reference Examples 18 and 19 , 60% by volume of cubic boron nitride (average particle size 0.3 or 7 μm), 15% by volume of cubic sialon, 5% by volume of β-sialon, and titanium compound (Ti This was a sintered body containing a total of 20% by volume of the compound (based compound) and the aluminum compound (Al compound) (excluding sialon). The tools of Reference Examples 18 and 19 were defective. This is because if the average particle size of the cubic boron nitride particles is too small, minute cracks generated in the sintered body during the cutting propagate and lead to defects. If the average particle size of the cubic boron nitride particles is too large, This is thought to be due to a decrease in the strength of the body leading to a defect.

  Comparative Examples 7 and 8 are 60% by volume of cubic boron nitride (average particle size 2 μm), 40 or 20% by volume of β-sialon, and Comparative Example 8 is a titanium compound (Ti compound) and an aluminum compound. It was a sintered body containing 20% by volume of (Al-based compound) (excluding sialon) in total. Comparative examples 7 and 8 were missing in the early stage of processing.

< Examples 29 and 30, Reference Examples 20 and 21 , Comparative Examples 9 to 10>
By the same method as in Reference Example 1, the raw material powder was cubic boron nitride particles, cubic silicon nitride particles, so that the sintered body had the sintered body composition (volume%) shown in Table 4. Cubic sialon particles, β-type silicon nitride particles, β-type sialon particles, and cobalt (Co) particles, aluminum (Al) particles, and tungsten carbide (WC) particles (Co: Al: WC mass ratio of 5 as other components) : 4: 1) to obtain sintered bodies of Examples 29 and 30, Reference Examples 20 and 21, and Comparative Examples 9 and 10.

(Performance evaluation 4)
The obtained sintered body was processed into a cutting tip having an ISO model number CNGA12041 shape, a cutting test was performed under the following conditions, and a processing time until the tool life was evaluated. The tool life was determined as missing or worn (when the flank wear amount exceeded 0.2 mm).
Work Material: Maraging Steel Outer Diameter Cutting Speed: 160m / min
Cutting depth: 0.15 mm
Feed amount: 0.12mm / rev
Coolant: Yes The results are shown in Table 4.

(Evaluation result 4)
Reference Example 20 was a sintered body containing 90% by volume of cubic boron nitride (average particle size 2 μm), 7.5% by volume of the first compound, and 2.5% by volume of the second compound. Reference Example 20 had no defects, had a long processing life, and improved the processing life compared to Comparative Example 10 that did not contain the first compound and the second compound.

In Reference Example 21 and Examples 29 and 30 , cubic boron nitride (average particle size 2 μm) was 90% by volume, the first compound was 0.75 to 2.8% by volume, and the second compound was 0.2 to 0. .Sintering containing 3 to 9% by volume of cobalt compound (Co compound), aluminum compound (Al compound) (excluding sialon) and tungsten compound (W compound) It was a body. Reference Example 21 and Examples 29 and 30 had no defects, had a long processing life, and improved the processing life compared to Comparative Example 10 that did not contain the first compound and the second compound.

  Comparative Example 9 was a sintered body containing 96% by volume of cubic boron nitride (average particle size 2 μm), 3% by volume of the first compound, and 1% by volume of the second compound. The comparative example 9 was missing at the initial stage of processing.

Comparative Example 10 is 90% by volume of cubic boron nitride (average particle size 2 μm), cobalt-based compound (Co-based compound), aluminum-based compound (Al-based compound) (except sialon), and tungsten-based compound. It was a sintered body containing 10% by volume of (W-based compound) in total. Comparative Example 10 had a shorter tool life than Examples 29 and 30 and Reference Examples 20 and 21 , which did not contain the first compound and the second compound.

< Examples 32-34, Reference Examples 22 , 23 , and Comparative Example 11>
In the same manner as in Reference Example 20 , the raw material powder was cubic boron nitride particles, cubic sialon particles, β, so that the sintered body had the sintered body composition (volume%) shown in Table 5. Type sialon particles and cobalt (Co) particles, aluminum (Al) particles, and tungsten carbide (WC) particles (Co: Al: WC mass ratio 5: 4: 1) as other components were mixed, and Example 32 To 34, Reference Examples 22 and 23, and Comparative Example 11 were obtained.

(Performance evaluation 5)
The obtained sintered body was processed into a cutting tip having an ISO model number CNGA12041 shape, a cutting test was performed under the following conditions, and a processing time until the tool life was evaluated. The tool life was determined as the machining time until failure.
Work material: Gray cast iron FC300 6 V-grooved round bar Outer diameter turning Cutting speed: 800m / min
Cutting depth: 0.5mm
Feed amount: 0.15mm / rev
Coolant: None The results are shown in Table 5.

(Evaluation result 5)
Reference Example 22 was a sintered body containing 90% by volume of cubic boron nitride (average particle size 2 μm), 7.5% by volume of cubic sialon, and 2.5% by volume of β-sialon. The tool life of Reference Example 22 was slightly improved compared to Comparative Example 11 that did not contain cubic sialon.

In Examples 32-34 and Reference Example 23 , cubic boron nitride (average particle size 2 μm) is 90% by volume, cubic sialon is 2.8-0.4% by volume, and β-sialon is 0.2-0.2%. A sintered body containing 2.6% by volume, and a total of 7% by volume of a cobalt compound (Co compound), an aluminum compound (Al compound) (excluding sialon) and a tungsten compound (W compound). Met. The tool life of Examples 32-34 and Reference Example 23 was improved over Comparative Example 11 that did not contain cubic sialon.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

Claims (3)

A sintered body containing cubic boron nitride, a first compound, a second compound, and a fourth compound,
The cubic boron nitride content is 35% by volume or more and 93% by volume or less,
The volume γ of the first compound and the volume α of the second compound in the sintered body have the following relationship:
0.2 ≦ γ / (γ + α) <1
Indicate
The total content of the first compound and the second compound is 2% by volume or more and 65% by volume or less,
The first compound is at least one of cubic sialon and cubic silicon nitride,
The second compound is at least one compound selected from the group consisting of α-type sialon, β-type sialon, α-type silicon nitride, and β-type silicon nitride,
The cubic boron nitride is a particle having an average particle diameter of 0.5 μm or more and 5 μm or less,
Said fourth compound, cobalt, cobalt aluminum, is at least one selected from aluminum and tungsten emissions by Li Cheng group,
The total content of the fourth compound is a sintered body that is not less than 3% by volume and not more than 30% by volume. The sintered body further includes a third compound,
The third compound includes at least one element selected from the group consisting of Group 4 elements, Group 5 elements, Group 6 elements and aluminum, and at least one type selected from the group consisting of nitrogen, boron and carbon. One or more compounds consisting of elements,
The sintered body according to claim 1, wherein the total content of the third compound in the sintered body is 10% by volume or more and 60% by volume or less.   A cutting tool comprising the sintered body according to claim 1.