Cubic boron nitride polycrystal, cutting tool, wear-resistant tool, grinding tool, and method of producing cubic boron nitride polycrystal

Abstract

A cubic boron nitride polycrystal includes cubic boron nitride, the cubic boron nitride having an average grain size of not more than 150 nm, a ratio b / a being not more than 0.085 in measurement of Knoop hardness at 23° C.±5° C. under a test load of 4.9 N, the ratio b / a being a ratio between a length a of a longer diagonal line and a length b of a shorter diagonal line of a Knoop indentation.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a cubic boron nitride polycrystal, a cutting tool, a wear-resistant tool, a grinding tool, and a method of producing the cubic boron nitride polycrystal, in particular, a cubic boron nitride polycrystal, a cutting tool, a wear-resistant tool, a grinding tool, and a method of producing the cubic boron nitride polycrystal, which are useful as cutting tool, wear-resistant tool and grinding tool for an iron-based material.

[0003] 2. Description of the Background Art

[0004] Cubic boron nitride (hereinafter, also referred to as “cBN”) has hardness second to diamond and is also excellent in thermal stability and chemical stability. Further, cubic boron nitride is more stable with respect to an iron-based material than diamond, so that a cBN sintered compact has been used as a working tool for the iron-based material.

[0005] However, the cBN sintered compact includes about 10 to 40 volume % of a binde...

Examples

examples

[0084]While the present invention will be described in more detail with reference to Examples, the present invention is not limited thereto.

examples 1 to 5

[0085]Each of cubic boron nitride polycrystals according to Examples 1 to 5 was produced by the following method. First, as a starting material, hexagonal boron nitride powder having a grain size of 0.5 μm (indicated as “Fine-Grain hBN Powder” in the column “Starting Material” in Table 1 below) was prepared (preparing step).

[0086]Next, the hexagonal boron nitride powder prepared as above was introduced into a capsule made of metal having a high melting point, and was held for 20 minutes in temperature and pressure described in Table 1 (column “Synthesis Condition”) using a ultra-high pressure / high-temperature generating device, thereby converting the hexagonal boron nitride powder into cubic boron nitride and wurtzite type boron nitride and sintering them (sintering step). Accordingly, the cubic boron nitride polycrystal was obtained.

[0087]It should be noted that the temperature and pressure in Table 1 satisfy the following condition. P≧0000122T2−0 0531T+65.846.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a cubic boron nitride polycrystal, a cutting tool, a wear-resistant tool, a grinding tool, and a method of producing the cubic boron nitride polycrystal, in particular, a cubic boron nitride polycrystal, a cutting tool, a wear-resistant tool, a grinding tool, and a method of producing the cubic boron nitride polycrystal, which are useful as cutting tool, wear-resistant tool and grinding tool for an iron-based material.

[0003] 2. Description of the Background Art

[0004] Cubic boron nitride (hereinafter, also referred to as “cBN”) has hardness second to diamond and is also excellent in thermal stability and chemical stability. Further, cubic boron nitride is more stable with respect to an iron-based material than diamond, so that a cBN sintered compact has been used as a working tool for the iron-based material.

[0005] However, the cBN sintered compact includes about 10 to 40 volume % of a binde...

Examples

examples

[0084]While the present invention will be described in more detail with reference to Examples, the present invention is not limited thereto.

examples 1 to 5

[0085]Each of cubic boron nitride polycrystals according to Examples 1 to 5 was produced by the following method. First, as a starting material, hexagonal boron nitride powder having a grain size of 0.5 μm (indicated as “Fine-Grain hBN Powder” in the column “Starting Material” in Table 1 below) was prepared (preparing step).

[0086]Next, the hexagonal boron nitride powder prepared as above was introduced into a capsule made of metal having a high melting point, and was held for 20 minutes in temperature and pressure described in Table 1 (column “Synthesis Condition”) using a ultra-high pressure / high-temperature generating device, thereby converting the hexagonal boron nitride powder into cubic boron nitride and wurtzite type boron nitride and sintering them (sintering step). Accordingly, the cubic boron nitride polycrystal was obtained.

[0087]It should be noted that the temperature and pressure in Table 1 satisfy the following condition. P≧0000122T2−0 0531T+65.846.

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