JP5416507B2 - Rotary cutting tool - Google Patents

Description

  The present invention relates to a rotary cutting tool such as a drill, an end mill, a milling cutter, and a fly cutting.

  Conventionally, cemented carbide has been used as a material for rotary cutting tools such as drills (see Patent Document 1), but various diamond materials have been studied due to poor wear resistance and breakage resistance. However, since single crystal diamond (see Patent Document 2) has a different wear amount depending on the crystal orientation (uneven wear), there is a problem in life that the desired number of holes cannot be obtained with the lapse of use time. For example, the amount of wear differs greatly between the (111) plane and the (100) plane. Another problem is that it may break during use, probably due to cleavage.

  On the other hand, sintered diamond may be used as a countermeasure against the above-mentioned uneven wear (see Patent Document 3). Sintered diamond is obtained by sintering diamond particles using a metal binder such as cobalt, and the metal binder exists between the diamond particles. However, since the metal binder portion is softer than the diamond particles, the wear proceeds in a short time. If the binder is reduced, diamond particles may fall off, resulting in a problem that the desired number of holes cannot be obtained.

  In addition, there is a method in which a diamond thin film is coated on the surface of a cemented carbide drill by a CVD method (chemical vapor deposition method) as polycrystalline diamond that does not include a metal binder (see Patent Document 4). However, this diamond has a problem that it has a short wear life because it is a thin film, and has a short wear life because of its small interparticle bonding force.

Japanese Patent Application Laid-Open No. 2004-230481 Japanese Patent Laid-Open No. 2003-127019 JP 2006-198743 A JP-A-8-155947

  It is an object of the present invention to provide a rotary cutting tool that has superior wear resistance and breakage resistance compared to conventional rotary cutting tools that use a single-crystal diamond or a diamond sintered body containing a metal binder. Objective.

  The inventors of the present invention provide a diamond polycrystalline body that does not contain a metal binder such as cobalt as a rotary cutting tool material, and the average particle diameter of the diamond sintered particles constituting the diamond polycrystalline body is larger than 50 nm and 2500 nm. By using a diamond polycrystalline body having a purity of 99% or more and a sintered body particle size of D90 particle size of (average particle size + 0.9 × average particle size) or less, The present invention was completed by finding that a rotary cutting tool having excellent wear resistance and breakage resistance can be obtained.

That is, this invention is a rotary cutting tool as described below.
(1) A diamond polycrystalline body obtained by converting and sintering non-diamond-type carbon from a non-diamond type carbon without addition of a sintering aid or a catalyst under ultrahigh pressure and high temperature, and the diamond sintering constituting the diamond polycrystalline body From polycrystalline diamond in which the average particle size of the particles is greater than 50 nm and less than 2500 nm, the purity is 99% or more, and the diamond D90 particle size is (average particle size + average particle size × 0.9) or less. A rotary cutting tool characterized by comprising:
(2) The rotary cutting tool according to (1), wherein the diamond has a D90 particle size of (average particle size + average particle size × 0.7) or less.
(3) The rotary cutting tool according to (1) or (2), wherein the diamond has a D90 particle size of (average particle size + average particle size × 0.5) or less.
(4) The rotary cutting tool according to any one of (1) to (3), wherein the diamond polycrystal has a hardness of 100 GPa or more.
(5) The rotary cutting tool according to any one of (1) to (4), wherein a rotary tool diameter range formed of the polycrystalline diamond is characterized by Φ0.010 mm to Φ500 mm.

  According to the rotary cutting tool of the present invention, it is possible to obtain a rotary cutting tool having excellent wear resistance and breakage resistance as compared with conventional rotary cutting tools using a single crystal diamond or a diamond sintered body containing a metal binder. Can do. These tool shapes can be applied to drills, end mills, mills and fly cuts.

First, the diamond polycrystal which comprises the rotary cutting tool which concerns on this invention is explained in full detail below.
The material of the rotary cutting tool of the present invention, which is substantially a diamond single phase (purity of 99% or more) that does not contain a metal binder such as cobalt, is a raw material graphite (graphite), glassy carbon, amorphous It can be obtained by converting non-diamond carbon such as carbon into diamond directly under a super-high pressure and high temperature (temperature 1800 to 2600 ° C., pressure 12 to 25 GPa) without a catalyst or a solvent and simultaneously sintering. In the rotary cutting tool made of polycrystalline diamond thus obtained, uneven wear as seen in the rotary cutting tool using single crystal diamond does not occur.

A method for obtaining dense and high-purity polycrystalline diamond by direct conversion sintering by indirect heating at a high pressure and high temperature of 12 GPa or more and 2200 ° C. or more using high-purity graphite as a starting material is disclosed in, for example, the following documents: .
Reference 1: SEI Technical Review 165 (2004) 68 (Kakutani et al.)
Literature 2: JP 2007-22888 A Literature 3: JP 2003-292397 A

When a rotary cutting tool is manufactured with diamond obtained by the method described in each of the above documents and the wear resistance and breakage resistance are examined, the one described in Document 1 has abnormally grown grains about 10 times the average grain size. It is found that the wear of the large particle portion is extremely advanced because of the existence of the coarse diamond converted from the added coarse raw material. As a result, there is a problem that the rotary cutting tool is broken. Therefore, in order to obtain a rotary cutting tool with excellent wear resistance and breakage resistance, it is necessary to eliminate the extremely worn portion, and for that purpose, the particle size distribution of the sintered body particle size is controlled. I found that it was necessary. Therefore, when a rotary cutting tool with a controlled particle size distribution was produced, there were no extremely worn particles, and a tool with excellent wear resistance and breakage resistance could be obtained.
Moreover, because the one described in Document 3 is the same manufacturing method as Document 1, there is abnormal grain growth and there is a problem similar to that described in Document 1.

The above problems are that the average particle size is greater than 50 nm and less than 2500 nm, the purity is 99% or more, and the D90 particle size of the sintered body particle size is (average particle size + 0. 9 × average particle diameter) or less can be used as a polycrystalline diamond, and according to the rotary cutting tool using the polycrystalline diamond, a tool having excellent wear resistance and breakage resistance Can be obtained. This is because abnormal wear is suppressed by setting the D90 particle size of the sintered particles of the polycrystalline diamond to (average particle size + 0.9 × average particle size) or less.
The average particle diameter in the present invention is a number average particle diameter measured by using a TEM (transmission electron microscope).
The average particle size and the D90 particle size can be controlled by controlling the particle size and sintering conditions of the starting material.

In the diamond polycrystal, the case where the numerical value of the average particle diameter and the numerical value of the D90 particle diameter satisfy the above relationship is shown as a specific numerical value as follows.
Example 1: When the average particle size is 60 nm, the D90 particle size is 114 nm or less. Example 2: When the average particle size is 100 nm, the D90 particle size is 190 nm or less. Example 3: When the average particle size is 500 nm, the D90 particle size is 950 nm or less. The D90 particle size is more preferably (average particle size + 0.7 × average particle size) or less, and the D90 particle size is further preferably (average particle size + 0.5 × average particle size) or less.
On the other hand, when the average particle size is 50 nm or less and 2500 nm or more, the hardness is less than 100 GPa, and wear progresses in a short time, so that a tool with excellent wear resistance and breakage resistance cannot be obtained.

  The hardness of the polycrystalline diamond constituting the rotary cutting tool is preferably 100 GPa or more. When the hardness of the polycrystalline diamond is less than 100 GPa, the life of the rotary cutting tool is shortened.

Examples of embodiments of the rotary cutting tool according to the present invention are shown below.
First, the measurement / evaluation method will be described.

<Average particle diameter, D90 particle diameter>
The D50 particle size (average particle size) and D90 particle size of the graphite particles in the raw graphite fired body and the diamond sintered particles in the present invention are photographed at a magnification of 100,000 to 500,000 with a transmission electron microscope. Obtained by performing image analysis based on the image.
The detailed method is shown below.
First, the particle size distribution of the crystal grains constituting the sintered body is measured based on a photographed image taken with a transmission electron microscope. Specifically, individual particles are extracted using image analysis software (for example, ScionImage, manufactured by Scion Corporation), and the extracted particles are binarized to calculate the area (S) of each particle. Then, the particle size (D) of each particle is calculated as the diameter of a circle having the same area (D = 2√ (S / π)).
Next, the particle size distribution obtained above is processed with data analysis software (for example, Origin manufactured by OriginLab, Mathchad manufactured by Parametric Technology, etc.) to calculate D50 particle size and D90 particle size.
In Examples and Comparative Examples described below, H-9000 manufactured by Hitachi, Ltd. was used as a transmission electron microscope.

<Hardness>
In the examples and comparative examples, the hardness was measured using a Knoop indenter with a measurement load of 4.9N.
<Tool shape and machining conditions>
A drill shape was adopted as the tool shape. The tool rotation speed was 100 to 50,000 rotations / minute, and the tool feed speed was 0.2 μm / rotation or more.

[Example 1]
As non-diamond carbon as a raw material for diamond, graphite (graphite) having an average particle diameter of 100 nm and a D90 particle diameter of 180 nm or less (average particle diameter + 0.9 × average particle diameter) was prepared. Using this as a raw material, it was directly converted and sintered into diamond under pressure conditions where diamond was thermodynamically stable. As a result, a polycrystalline diamond having an average particle size of 200 nm and a D90 particle size of 370 nm was obtained. The hardness of the polycrystalline diamond thus obtained was as extremely high as 110 GPa. A rotary cutting tool having a drill diameter of Φ1 mm was produced from the obtained polycrystal. Using this drill, a hole was made in a cemented carbide plate having a thickness of 1 mm, and the wear resistance and breakage resistance were investigated.
The processing conditions were as follows: the number of revolutions was 4000 revolutions / minute, and the feed rate was 2 μm / revolution.
As a comparative material, using a CVD polycrystalline diamond in which a CVD diamond thin film is coated on a cemented carbide (WC-Co), single crystal diamond, sintered diamond (Co binder), cemented carbide substrate (WC-Co). A rotary cutting tool similar to that in Example 1 was prepared, and a drill was drilled into a 1 mm-thick carbide plate using this drill, and the wear resistance and breakage resistance were investigated in the same manner as in Example 1. .
The results are shown in Table 1. As shown in Table 1, it was found that the material of the present invention was superior to the conventional material.
[Comparative example]

The following materials were produced as Examples 2-7.
[Example 2]
As non-diamond carbon used as a raw material for diamond, graphite (graphite) having an average particle diameter of 110 nm and a D90 particle diameter of 175 nm or less (average particle diameter + 0.7 × average particle diameter) was prepared. Using this as a raw material, it was directly converted and sintered into diamond under pressure conditions where diamond was thermodynamically stable. As a result, a polycrystalline diamond having an average particle size of 230 nm and a D90 particle size of 380 nm was obtained.

[Example 3]
As non-diamond carbon used as a raw material for diamond, graphite (graphite) having an average particle size of 95 nm and a D90 particle size of 135 nm or less (average particle size + 0.5 × average particle size) was prepared. Using this as a raw material, it was directly converted and sintered into diamond under pressure conditions where diamond was thermodynamically stable. As a result, a polycrystalline diamond having an average particle size of 180 nm and a D90 particle size of 260 nm was obtained.

[Example 4]
As non-diamond carbon used as a raw material for diamond, graphite (graphite) having an average particle size of 30 nm and a D90 particle size of 40 nm or less (average particle size + 0.5 × average particle size) was prepared. Using this as a raw material, it was directly converted and sintered into diamond under pressure conditions where diamond was thermodynamically stable. As a result, a polycrystalline diamond having an average particle size of 55 nm and a D90 particle size of 80 nm was obtained. The hardness of the polycrystalline diamond thus obtained was as extremely high as 105 GPa.

[Example 5]
As non-diamond carbon used as a raw material for diamond, graphite (graphite) having an average particle size of 30 nm and a D90 particle size of 40 nm or less (average particle size + 0.5 × average particle size) was prepared. Using this as a raw material, it was directly converted and sintered into diamond under a pressure condition in which diamond was thermodynamically stable over a longer time than Example 9. As a result, a polycrystalline diamond having an average particle size of 560 nm and a D90 particle size of 830 nm was obtained. The hardness of the polycrystalline diamond thus obtained was as extremely high as 120 GPa.

[Example 6]
As non-diamond carbon used as a raw material for diamond, graphite (graphite) having an average particle size of 30 nm and a D90 particle size of 40 nm or less (average particle size + 0.5 × average particle size) was prepared. Using this as a raw material, it was directly converted and sintered into diamond under a pressure condition in which diamond was thermodynamically stable over a longer time than Example 9. As a result, a polycrystalline diamond having an average particle diameter of 1100 nm and a D90 particle diameter of 1600 nm was obtained. The hardness of the polycrystalline diamond thus obtained was as extremely high as 112 GPa.

[Example 7]
As non-diamond carbon used as a raw material for diamond, graphite (graphite) having an average particle size of 30 nm and a D90 particle size of 40 nm or less (average particle size + 0.5 × average particle size) was prepared. Using this as a raw material, it was directly converted and sintered into diamond under a pressure condition in which diamond was thermodynamically stable over a longer time than Example 9. As a result, a polycrystalline diamond having an average particle size of 2400 nm and a D90 particle size of 3500 nm was obtained. The hardness of the polycrystalline diamond thus obtained was as extremely high as 102 GPa.
When the diamond polycrystals obtained in Examples 2 to 7 were tested in the same manner as in Example 1, 10 good holes could be formed in the same manner as in Example 1.

Table 2 shows data on the raw materials and diamond polycrystals of Examples 1 to 7.
Table 2 shows numerical values of the average particle diameter, the D90 particle diameter, the coefficient (K), the hardness, and the wear life of the sintered particles of the polycrystalline diamond in the above examples and comparative examples. The coefficient (K) is defined by the following equation (1).
D90 particle size = average particle size + average particle size × K (1)

The following materials were produced as Comparative Examples 1-3.
[Comparative Example 1]
As non-diamond carbon used as a raw material for diamond, graphite (graphite) having an average particle diameter of 100 nm and a D90 particle diameter of about 210 nm (average particle diameter + 1.1 × average particle diameter) was prepared. Using this as a raw material, it was directly converted and sintered into diamond under pressure conditions where diamond was thermodynamically stable. As a result, a polycrystalline diamond having an average particle size of 200 nm and a D90 particle size of 400 nm was obtained. The hardness of the polycrystalline diamond thus obtained was as extremely high as 112 GPa.

[Comparative Example 2]
As non-diamond carbon used as a raw material for diamond, graphite (graphite) having an average particle size of 20 nm and a D90 particle size of about 37 nm (average particle size + 0.9 × average particle size) was prepared. Using this as a raw material, it was directly converted and sintered into diamond under pressure conditions where diamond was thermodynamically stable. As a result, a polycrystalline diamond having an average particle size of 45 nm and a D90 particle size of 80 nm was obtained. The hardness of the polycrystalline diamond thus obtained was 95 GPa and was slightly soft.

[Comparative Example 3]
As non-diamond carbon used as a raw material for diamond, graphite (graphite) having an average particle diameter of 100 nm and a D90 particle diameter of approximately 180 nm (average particle diameter + 0.9 × average particle diameter) was prepared. Using this as a raw material, it was directly converted and sintered into diamond under pressure conditions where diamond was thermodynamically stable for a long time. As a result, a polycrystalline diamond having an average particle diameter of 2700 nm and a D90 particle diameter of 3900 nm was obtained. The hardness of the polycrystalline diamond thus obtained was 91 GPa and was slightly soft.
Table 2 shows data on the raw materials and polycrystalline diamond for Comparative Examples 1-3.
When the diamond polycrystals obtained in Comparative Examples 1 to 3 were tested in the same manner as in Example 1, 10 holes could not be formed satisfactorily.

  Since the polycrystalline diamond in the present invention is superior in wear resistance and breakage resistance compared to the conventional single crystal diamond and the diamond sintered body containing the metal binder, the polycrystalline diamond in the present invention using the polycrystalline diamond is used. The rotary cutting tool can be suitably used as a rotary cutting tool such as a drill, an end mill, a milling cutter, and a fly cutting.

Claims (5)

  A diamond polycrystalline body obtained by converting and sintering non-diamond type carbon under an ultrahigh pressure and high temperature without adding a sintering aid or a catalyst, and an average of the diamond sintered particles constituting the diamond polycrystalline body It is made of polycrystalline diamond having a particle size of greater than 50 nm and less than 2500 nm, a purity of 99% or more, and a diamond D90 particle size of (average particle size + average particle size × 0.9) or less. A featured rotary cutting tool.   The rotary cutting tool according to claim 1, wherein the diamond has a D90 particle size of (average particle size + average particle size x 0.7) or less.   The rotary cutting tool according to claim 1 or 2, wherein the diamond has a D90 particle size of (average particle size + average particle size x 0.5) or less.   The rotary cutting tool according to any one of claims 1 to 3, wherein the diamond polycrystal has a hardness of 100 GPa or more.   The rotary cutting tool according to any one of claims 1 to 4, wherein a diameter range of the rotary tool formed of the polycrystalline diamond is Φ0.010 mm to Φ500 mm.