JP2007145667A - Cubic boron nitride sintered compact - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a cubic boron nitride sintered compact by which a cutting tool being excellent in wearing resistance and lubricity, having high hardness and being suitable for high speed cutting can be served without film forming and the like. <P>SOLUTION: The cubic boron nitride sintered compact comprises cubic boron nitride and a binding material and is characterized in that carbon contained in the binding material is 0.01-3 mass% to the whole cubic boron nitride sintered compact. It is favorable that the particle diameter of the cubic boron nitride sintered compact is 30 nm or less when carbon is contained as graphite. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a cubic boron nitride sintered body excellent in wear resistance, or a cubic boron nitride sintered body having lubricity in addition to wear resistance.

Cubic boron nitride (cBN) is a material having the second highest hardness after diamond, and is mainly used as a material for metal cutting tools and the like.
In order to improve the wear resistance of the cubic boron nitride, it has been proposed to have a composition in which titanium carbide, titanium nitride, and aluminum have a specific ratio (see Patent Document 1).
However, in recent years, in order to further improve the machining efficiency, the cutting speed has been increased. Under such a high speed, the wear resistance of cubic boron nitride was not sufficient even in the above composition.

  In addition, it has also been proposed to provide a cubic boron nitride sintered body with a film such as titanium nitride or titanium carbide (see Patent Document 2 and Patent Document 3). The problem is that the production efficiency of the cutting tool is reduced.

  On the other hand, lubrication can be imparted to a sintered body used for the cutting edge of a cutting tool by adding a solid lubricant (see Patent Document 4), but adding a solid lubricant inhibits sintering. There is a problem that pores are generated when the sintered body contracts during the sintering process, and the sintered body cannot be densified.

Japanese Patent Laid-Open No. 10-226575 JP 2004-291150 A JP 2001-341006 A JP-A-8-295570

  The present invention provides a cubic boron nitride that is excellent in wear resistance and lubricity, has a high hardness, and can be suitably used for high-speed cutting without requiring film formation. The object is to obtain a sintered body.

The cubic boron nitride sintered body of the present invention has been made to achieve the above object, and has the following configuration.
(1) A cubic boron nitride sintered body made of cubic boron nitride and a binder, wherein the carbon content in the binder is 0.01 with respect to the entire cubic boron nitride sintered body. It is a cubic boron nitride sintered body characterized by being ˜3 mass%.
(2) The cubic boron nitride sintered body according to (1), wherein the carbon content is 0.1 to 1% by mass with respect to the entire cubic boron nitride sintered body.
(3) The binder includes one or more elements selected from the group consisting of Group 4 to 6 elements of the periodic table, Fe, Co, Ni, and Al,
The element is contained in one or more states selected from the group consisting of simple substances, mutual solid solutions, carbides, nitrides, carbonitrides, borides, and oxides. This is a cubic boron nitride sintered body.
(4) The binder contains carbon and one or more nitrides of group 4 elements in the periodic table other than carbon, and the carbon contains a nitride and a mutual solid solution of the group 4 elements in the periodic table. The cubic boron nitride sintered body according to any one of (1) to (3), which is formed.
(5) The cubic boron nitride sintered body according to (3) or (4), wherein the group 4 element in the periodic table other than carbon is Ti and / or Hf.
(6) TiN is contained as a binder, and in the diffraction pattern of the TiN by Cu-Kα X-ray, the 2111 positions of (111) and (200) reflections are 36.10 to 36.60 and 41.90 to respectively. The cubic boron nitride sintered body according to any one of (1) to (5), which is in a range of 42.50.
(7) The cubic boron nitride sintered body according to any one of (1) to (6), wherein the cubic boron nitride has a particle size of 0.2 to 10 μm.
(8) The cubic boron nitride sintered body according to any one of (1) to (7), wherein a cubic boron nitride content in the cubic boron nitride sintered body is 40 to 75% by volume. It is.
(9) The cubic boron nitride sintered body according to any one of (1) to (3), wherein carbon is contained as graphite.
(10) The cubic boron nitride sintered body according to (9), wherein the graphite has a particle size of 30 nm or less.
(11) The cubic boron nitride sintered body according to (9) or (10), wherein the particle size of cubic boron nitride is 0.2 to 10 μm.
(12) The cubic boron nitride sintered body according to any one of the above (9) to (11), wherein the cubic boron nitride content in the cubic boron nitride sintered body is 40 to 95% by volume. It is.

In the present invention, a cubic boron nitride sintered body having improved wear resistance, high slipperiness and high hardness can be obtained by adopting the above-described configuration.
Therefore, the present invention can provide a cubic boron nitride sintered body suitable for a cutting tool that can withstand practical use even at a high cutting speed.

The cubic boron nitride sintered body of the present invention comprises cubic boron nitride and a binder.
(Cubic boron nitride)
The cubic boron nitride is not particularly limited, and various cubic boron nitrides can be used. For example, cubic boron nitride obtained using pyrolytic boron nitride as a raw material and hexagonal boron nitride as a raw material. Examples thereof include cubic boron nitride obtained.
The cubic boron nitride preferably has a particle size of 0.2 to 10 μm, more preferably 0.2 to 6 μm. If the particle size of the cubic boron nitride is too small, the thermal conductivity of the resulting cubic boron nitride sintered body tends to decrease, heat resistance tends to deteriorate, and wear resistance during high-speed cutting may decrease. is there. Also, if the cubic boron nitride particle size is too large, when the obtained cubic boron nitride sintered body is used for a cutting tool or the like, stress tends to concentrate on the cubic boron nitride having a large particle size, and cracks will occur. It tends to be the starting point of occurrence and may shorten the life of cutting tools and the like.

(Binder)
The cubic boron nitride sintered body of the present invention needs to contain 0.01 to 3% by mass of carbon in the binder, based on the entire cubic boron nitride sintered body.
If the carbon content is too low, the technical effect of the present invention cannot be obtained.If the carbon content is too high, the wear resistance of the resulting cubic boron nitride sintered body is improved, Defectability may deteriorate and performance as a cutting tool may be inferior.

The binder of the cubic boron nitride sintered body of the present invention contains carbon, but the composition of the binder other than carbon is not particularly limited, and is generally used as a binder of the cubic boron nitride sintered body. The binder used can be used. Among them, it is preferable to include one or more elements selected from the group consisting of Group 4 to 6 elements of the periodic table, Fe, Co, Ni, and Al.
All of Group 4 to 6 elements of the periodic table, Fe, Co, Ni, and Al have a function of firmly bonding cubic boron nitride particles. Therefore, the composition of the binder includes one or more elements selected from the group consisting of Group 4 to 6 elements of the periodic table, Fe, Co, Ni and Al, so that the cubic boron nitride particles Thus, a cubic boron nitride sintered body excellent in wear resistance in which is firmly bonded can be obtained.

In particular, the raw material of the binder preferably contains a group 4 element of the periodic table and / or a nitride of a group 4 element of the periodic table. The nitrides of group 4 elements (Ti, Zr, Hf) in the periodic table tend to form mutual solid solutions with carbon, and the structure of the binder containing carbon tends to be stable even at high temperatures. Therefore, when the obtained cubic boron nitride sintered body is used for a cutting tool, a cubic boron nitride sintered body having superior wear resistance and lubricity even at a high cutting speed is obtained. Tend to be.
Among the raw materials for the binder, it is more preferable to contain one or more selected from the group consisting of Ti, Hf, TiN, and HfN. When the binder contains one or more selected from the group consisting of Ti, Hf, TiN, and HfN, the binder phase of the cubic boron nitride sintered body in the high temperature range can be stabilized. In addition, when the obtained cubic boron nitride sintered body is used for a cutting tool, a cubic boron nitride sintered body having particularly excellent wear resistance and lubricity even at a high cutting speed can be obtained. Can do.

Among the raw materials for the binder, it is more preferable to contain TiN. In the diffraction pattern of TiN by Cu—KαX rays, the 2θ positions of (111) and (200) reflections are 36.1 to 36, respectively. Most preferably in the range of .60 and 41.90-42.50. When the obtained cubic boron nitride sintered body is used for a cutting tool because the binder contains TiN, the cubic material has excellent wear resistance and lubricity even at a high cutting speed. A sintered boron nitride sintered body can be obtained. Among them, in the diffraction pattern of TiN by Cu—KαX-ray, the 2θ positions of (111) and (200) reflections are preferably in the range of 36.10 to 36.60 and 41.90 to 42.50, respectively. .
In the diffraction pattern of TiN by Cu-Kα X-rays, it is known that the 2θ positions of (111) and (200) reflections are such that carbon is solid-dissolved in TiN, and the shift width varies depending on the solid-solution amount of carbon. ing. When the 2θ positions of (111) and (200) reflections are in the range of 36.10 to 36.60 and 41.90 to 42.50, respectively, in the diffraction pattern of TiN by Cu—KαX-ray, A cubic boron nitride sintered body in which carbon is appropriately solid-solved and particularly excellent in wear resistance can be obtained.

Carbon in the binder of the cubic boron nitride sintered body of the present invention may exist as a mutual solid solution of carbon and other elements, or may exist as graphite.
When the carbon is present as a mutual solid solution with other elements in the binder, the wear resistance of the cubic boron nitride sintered body is improved without going through a separate process for forming a film. Can do.
Further, when the carbon is present as graphite in the binder, a cubic boron nitride sintered body having high lubricity and high hardness can be obtained. The particle size of the graphite is not particularly limited, but is preferably 30 nm or less. If the particle size of the graphite is too large, it may become a starting point for abruptly advancing the wear of the cubic boron nitride sintered body, and the wear resistance of the cubic boron nitride sintered body may deteriorate. In addition, if the particle size of the graphite is too large, stress concentration may occur when the cubic boron nitride sintered body is used for a cutting tool, and cracks are likely to occur in the cubic boron nitride sintered body. There is a case.

Examples of the method of containing carbon in the binder include a method in which a carbon compound or a polymer organic substance is added to the raw material of the binder of the cubic boron nitride sintered body and sintered.
Examples of the carbon compound include graphite, amorphous carbon, fullerene, carbon nanotubes, and carbides of group 4 to 6 elements.
Examples of the polymer organic material include polyethylene, polypropylene, polystyrene, and the like.

(Cubic boron nitride sintered body)
The cubic boron nitride sintered body of the present invention is made of cubic boron nitride and a binder, and contains a specific amount of carbon in the binder.
The carbon content in the binding material needs to be 0.01 to 3% by mass with respect to the entire cubic boron nitride sintered body. From the viewpoint of hardness, it is preferably 0.1 to 1% by mass.
If the carbon content is too small, the wear resistance is not sufficient, and the lubricity is not sufficient. Moreover, when there is too much content of the said carbon, there exists a tendency for the hardness of a cubic boron nitride sintered compact to become low.

In the cubic boron nitride sintered body of the present invention, when the carbon in the binder forms a mutual solid solution with other elements, the ratio of the cubic boron nitride in the cubic boron nitride sintered body is It is preferable that it is 40-75 volume%, and it is more preferable that it is 50-70 volume%. If the proportion of cubic boron nitride is too small, sufficient wear resistance may not be obtained. If the proportion is too large, particles of cubic boron nitride are liable to be lost, and the cubic boron nitride sintered body is cut into a cutting tool. The tool life tends to be shortened when used.
Further, in the cubic boron nitride sintered body of the present invention, when carbon in the binder exists as graphite, the cubic boron nitride is preferably 40 to 95% by volume, and 50 to 95%. More preferably, it is volume%. When the carbon in the binder is present as graphite, if the proportion of cubic boron nitride is too small, sufficient wear resistance may not be obtained, and if it is too large, cubic boron nitride particles are formed. When the cubic boron nitride sintered body is used for a cutting tool, the tool life tends to be shortened.

TiN powder and Al powder were uniformly mixed at a mass ratio of 85:15, and then heat-treated at 1200 ° C. for 20 minutes using a vacuum furnace to obtain a binder A.
A metal powder such as Co, W, Fe, Ni, and Hf and graphite or amorphous carbon with a particle size of 8 μm are added to this binder A to create a mixed powder that is a raw material for some binders. Using a ball mill consisting of a container and cemented carbide balls, uniform mixing was performed to prepare several types of binders.
Further, instead of using the binder A, a plurality of metals and ceramic materials were mixed, carbon nanotubes having a particle diameter of 1 μm were added thereto, and uniformly mixed using a ball mill to prepare several binders.

CBN powders with various particle sizes are added to these binders so that the mixing ratio is 40 to 90% by volume, and uniformly using a ball mill comprising a cemented carbide container and a cemented carbide ball. Mixed. After the obtained mixed powder was filled into a cemented carbide capsule, it was held at a pressure of 6 GPa and a temperature of 1700 ° C. for about 15 minutes using an ultrahigh pressure apparatus, and Examples 1 to 7 and Comparative Examples 2 to 8 A cubic boron nitride sintered body was obtained.
Furthermore, cBN powder is added to the binder A and mixed uniformly by a ball mill. After the resulting mixed powder is filled into a cemented carbide capsule, the pressure is about 6 GPa and the temperature is about 1700 ° C. using an ultrahigh pressure apparatus. The cubic boron nitride sintered body of Comparative Example 1 was obtained by holding for 15 minutes.

Next, the obtained sintered body was analyzed by an X-ray diffractometer (XRD) using Cu—Kα rays, the composition was identified, and the 2θ values of the (111) and (200) peaks of TiN were measured. For those in which the graphite peak was observed by XRD, the average particle diameter was determined from the half width of the peak.
Further, ICP analysis of the sintered body was performed, and the weight ratio of the carbon contained in the sintered pair to the entire sintered body was determined.
These results are shown in Table 1.

  In Table 1, the XRD composition indicates the composition of the cubic boron nitride sintered body analyzed using an X-ray diffractometer, and the graphite particle size indicates that carbon is precipitated as graphite in the cubic boron nitride sintered body. In this case, the particle size of graphite is measured. The element marked as a binder-containing element is an element added to be a binder during the production of a cubic boron nitride sintered body.

The cubic boron nitride sintered body obtained as described above was brazed to a cemented carbide base material to prepare a cutting tool having an ISO model number SNGA120408.
Using these tools prepared from the sintered bodies of Examples 1 to 6 and Comparative Examples 1, 2, 4 to 8, a cutting test for continuously cutting hardened steel at high speed was performed under the following conditions. The results are shown in Table 2.
The cutting test conditions were as follows: cutting speed: V = 200 mm / min, feed: f = 0.1 mm / rev, cutting: d = 0.2 mm, dry cutting, work material: SUJ2.
In Table 2, the tool life is defined as the tool life when the flank wear amount of the tool exceeds 0.1 mm, or when the cutting edge is damaged and the quality of the machined surface changes. The life of a tool using the sintered body of Example 1 is set as 1, and the relative comparison with this is shown.

Moreover, the cutting test which cuts hardened steel continuously at high speed on the following conditions using said tool created from the sintered compact of Example 7, 8 and Comparative Example 3, 9, 10 was implemented. The results are shown in Table 3.
The cutting test conditions were cutting speed: V = 400mm / min, feed: f = 0.12mm / rev, cutting: d = 0.2mm,
Wet cutting, work material: Ductile cast iron FCD450 was used.
In Table 3, the tool life is defined as the tool life when the flank wear amount of the tool exceeds 0.1 mm, or when the cutting edge is damaged and the quality of the machined surface is changed. The life of a tool using the sintered body was expressed as a relative comparison with this as 1.

  From the results of Table 2 and Table 3, it can be seen that the cBN sintered body of the present invention exhibits excellent cutting performance.

The cubic boron nitride sintered body of the present invention is useful as a cutting tool.

Claims (12)

  A cubic boron nitride sintered body made of cubic boron nitride and a binder, wherein the carbon content in the binder is 0.01 to 3 mass with respect to the entire cubic boron nitride sintered body. %. Cubic boron nitride sintered body characterized by being%.   2. The cubic boron nitride sintered body according to claim 1, wherein the content of carbon is 0.1 to 1 mass% with respect to the entire cubic boron nitride sintered body. The binder includes one or more elements selected from the group consisting of Group 4 to 6 elements of the periodic table, Fe, Co, Ni, and Al,
The cubic element according to claim 1 or 2, wherein the element is contained in one or more states selected from the group consisting of simple substances, mutual solid solutions, carbides, nitrides, carbonitrides, borides, and oxides. Boron nitride sintered body.   The binder contains carbon and one or more nitrides of group 4 elements in the periodic table other than carbon, and the carbon forms a mutual solid solution with the nitrides of group 4 elements of the periodic table. The cubic boron nitride sintered body according to any one of claims 1 to 3.   The cubic boron nitride sintered body according to claim 3 or 4, wherein the group 4 element in the periodic table other than carbon is Ti and / or Hf.   TiN is contained as a binder, and in the diffraction pattern of TiN by Cu-Kα X-ray, the 2111 positions of (111) and (200) reflections are 36.10 to 36.60 and 41.90 to 42.50, respectively. The cubic boron nitride sintered body according to any one of claims 1 to 5, wherein the sintered body is in the range of   The cubic boron nitride sintered body according to any one of claims 1 to 6, wherein a particle diameter of the cubic boron nitride is 0.2 to 10 µm.   The cubic boron nitride sintered body according to any one of claims 1 to 7, wherein a cubic boron nitride content in the cubic boron nitride sintered body is 40 to 75% by volume.   The cubic boron nitride sintered body according to any one of claims 1 to 3, wherein carbon is contained as graphite.   The cubic boron nitride sintered body according to claim 9, wherein the particle diameter of graphite is 30 nm or less.   The cubic boron nitride sintered body according to claim 9 or 10, wherein the particle diameter of the cubic boron nitride is 0.2 to 10 µm. The cubic boron nitride sintered body according to any one of claims 9 to 11, wherein a cubic boron nitride content in the cubic boron nitride sintered body is 40 to 95% by volume.