JPH0116894B2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for manufacturing a high-hardness sintered body, which can be manufactured even at relatively low sintering pressure and temperature,
The obtained high-hardness sintered body can be used to cut particularly hard steel materials at high speeds, and to cut cast iron, cast steel, and mild steel with high efficiency even when it is impossible with conventional tools. It is used as a material for tools and as a wear-resistant material that can withstand long-term wear by being used on contact surfaces and friction surfaces with various materials.

<Conventional technology> Conventional cubic boron nitride (hereinafter referred to as CBN)
Sintered bodies containing and/or wurtzite boron nitride (hereinafter referred to as WBN) are known, and cutting tools or abrasive materials containing these as main components have higher efficiency than those that do not contain them. Recently, its use has been rapidly expanding because it can be cut with abrasion and has wear resistance.

First, we will discuss prior documents that have been disclosed regarding methods for manufacturing sintered bodies containing CBN and/or WBN (hereinafter collectively referred to as high-pressure phase boron nitride).

Japanese Patent Publication No. 39-8948 discloses CBN alone or CBN with 3 to 30% by weight of an additive selected from aluminum oxide, beryllium, tungsten, molybdenum, nickel, copper, chromium, manganese, and titanium. A method for manufacturing a sintered body in which CBN particles are bonded together is described.

Furthermore, JP-A No. 49-44014 describes a sintered body made of WBN and ceramic and a method for producing the same. In some cases, a continuous phase of ceramic is said to be obtained. In addition, metals such as aluminum and nickel can be used as optional components.
It is said that coating with WBN is preferable.

Furthermore, JP-A-50-82689 describes abrasive particles selected from CBN, diamond, and mixtures thereof, and regarding CBN as abrasive particles, aluminum, lead, tin,
It is described that an abrasive molded article is formed by adhering a solvent substance selected from magnesium, lithium, and alloys thereof with a resistant substance such as a boride, nitride, or silicide.

Also, in Japanese Patent Application Laid-open No. 56-77359, CBN4~
One or more ceramic materials selected from the group consisting of nitrides, oxides, borides, and carbides, containing 15 to 60 volume % of high-pressure phase boron nitride consisting of 16 volume % and WBN 96 to 84 volume %. 70-95
Volume % and method for manufacturing a sintered body made of one or more metals selected from nickel, cobalt, chromium, manganese, iron, molybdenum, tungsten, vanadium, aluminum, magnesium, silicon, titanium, zirconium, and hafnium It is stated that the obtained sintered body is characterized by being easy to process after sintering.

Furthermore, in Japanese Patent Publication No. 57-49621, CBN80~
20% by volume, carbides, nitrides, borides, silicides, or mixtures thereof or mutual solid solution compounds of transition metals of groups 4a, 5a, and 6a of the periodic table as the first binder phase, and aluminum, silicon, nickel, cobalt. , iron, or an alloy or compound containing these as a second binder phase, and the first and second binder phases form a continuous binder phase in the sintered body structure. is listed.

<Problems to be Solved by the Invention> However, the methods for producing sintered bodies disclosed in the above-mentioned publications still have the following practical problems.

That is, the method described in Japanese Patent Publication No. 39-8948 is as follows:
In the case of a sintered body made only of CBN, CBN has extremely high strength at high temperatures, so when attempting to sinter it, it must be sintered at an extremely high pressure and temperature of about 90,000 atm.
℃, the load on the ultra-high pressure and high temperature equipment for sintering is extremely large, and the life of the equipment is extremely short, making it practically unprofitable to manufacture it industrially.

Also, a method for manufacturing a sintered body with additives added to CBN is described, but if the additive is metal, metal has low strength at high temperatures, and like cutting tools, it must withstand high temperatures and large stress during use. It is not suitable as an essential material. That is, a preferable sintered body cannot be obtained simply by mixing with CBN and sintering it. Furthermore, when aluminum oxide was used as an additive, or when aluminum oxide was added together with metal, the performance of the sintered body was still insufficient.

The method for manufacturing a sintered body described in JP-A-49-44014 is obtained by adding ceramic to WBN having an extremely large surface area and sintering the mixture. WBN is an excellent material as a raw material for hard sintered tool materials, but it is generally synthesized instantaneously by the impact of an explosive explosion, so there is no crystal growth, and each WBN powder particle is an aggregation of microcrystal grains on the order of tens of nanometers. The strength of the powder grain itself is not stronger than that of a single crystal. If the particles are crushed to a single crystal and used, the problem of particle strength can be solved, but the area of the bonding interface with the added ceramic or metal increases, and the strength of the bonding interface is naturally lower than the strength of the WBN itself. The strength of the sintered body is also lower than when larger single crystals are sintered.
That is, the sintered body described in this publication had a certain limit in strength.

Furthermore, the method for producing a sintered body disclosed in Japanese Patent Application Laid-Open No. 50-82689 has a very wide range of additives as indicated in the claims. However, as a specific example, 19.5% by weight of a mixture of 32% by weight aluminum and 68% by weight silicon nitride was used as an additive.
Only an example in which CBN was added to 80.5% by weight and sintered is shown. In addition, regarding the particles of each component, "preferably 40 microns or less, more preferably 40 microns or less,
There is only a statement that ``the particle size is reduced to 12 microns or less''.Also, according to the claims,
“Abrasive compacts characterized in that they have abrasive particles adhered to one another by a matrix comprising a solvent substance and a refractory substance capable of dissolving them (abrasive particles…in this case CBN) at least to a limited extent” It is understood that the bonding between CBN particles is carried out through a matrix of a solvent substance and a refractory substance. However, there is a certain limit to the hardness of this material.

The invention disclosed in Japanese Unexamined Patent Publication No. 56-77359 is a CBN
It is characterized in that both CBN and WBN are used as starting materials for the sintered body, but CBN contained in the sintered body
The total amount of and WBN is 15-60% by volume, and CBN
Particles or WBN particles or CBN particles and WBN
There are very few bonding points between particles. Therefore, the sintered body has low hardness and is easy to grind.

That is, a method for producing a highly hard sintered body according to the present invention is not disclosed.

The characteristics of the invention disclosed in Japanese Patent Publication No. 57-49621 are as follows:
CBN is more important than the bonds between CBN particles.
and a second bonding phase, which is said to provide excellent properties. The above-mentioned binder phase is very excellent as a binder phase for CBN particles, and the sintered body obtained by this invention is also excellent.
Similar to the invention disclosed in No. 56-77359, it is expected that there will be very little bonding between CBN particles, and therefore the strength of the sintered body will be lower than that of a sintered body that has bonds between CBN particles, and therefore it will be difficult to cut during cutting. Not suitable for cutting with heavy loads or impact.

The method for manufacturing a sintered body according to the above-mentioned prior art and the properties of the obtained sintered body are summarized as follows.

1. Very high pressure and temperature are required to obtain a high-pressure phase boron nitride sintered body with excellent strength, which is economically disadvantageous.

2 When the additive is added with high pressure phase boron nitride,
Although the manufacturing conditions are relatively gentle, the strength of the sintered body is insufficient.

3. When attempting to bond conventional sintered bodies containing CBN and/or WBN and high-pressure phase boron nitride particles, extremely high pressure and temperature are applied to reduce the content of high-pressure phase boron nitride to, for example, 70% by volume. However, simply increasing the amount of high-pressure phase boron nitride added is insufficient to bond the high-pressure phase boron nitride particles together.

Therefore, in order to obtain a sintered body with lower manufacturing cost and higher strength than before, it is necessary to deform the high-pressure phase boron nitride particles at a low sintering pressure of 20,000 atmospheres or more. It is now required to obtain a sintered body as strong as that obtained by sintering under severe conditions that fill the voids.

<Means for Solving the Problems> As a result of examining and considering the problems of the prior art described in the previous section, the inventors have reached the following conclusion.
In other words, in order to improve the strength of a sintered body containing high-pressure phase boron nitride and to moderate the sintering conditions, it is necessary to increase the bonding opportunities between high-pressure phase boron nitride particles. .

In order to increase the bonding opportunities between particles, it is sufficient to simply use fine high-pressure phase boron nitride particles. However, simply using fine high-pressure phase boron nitride particles causes various problems such as those described in JP-A-49-44014.

As a result of various studies, the present inventors have found that a method for manufacturing a sintered body in which the volume ratio of CBN and WBN of high-pressure phase boron nitride in the sintering raw material, types of additives, and particle size are specified, The present invention was completed by confirming that the resulting sintered body had superior properties compared to the manufacturing method of . That is, the method for producing a sintered body of the present invention uses cubic boron nitride having a maximum particle size of 10 to 50 μm and a minimum particle size of 1 μm or less and a continuous particle size distribution therebetween, or the cubic boron nitride and wurtzite type nitride. 65 to 95 volume % of high-pressure phase boron nitride consisting of boron, 4 to 34 volume % of an additive that is at least one of titanium or each of titanium and tantalum carbides, nitrides, and carbonitrides, and Add aluminum to make it 100% by volume and further divide by 0.1~
A high-hardness sintered body in which a mixture containing 5% by volume of boron is obtained and the mixture is sintered at a minimum of 1200°C and 20,000 atmospheres to form a continuous matrix in which high-pressure phase boron nitrides bond together. This is a manufacturing method.

The high-pressure phase boron nitride in the mixture obtained in the method for producing a high-hardness sintered body of the present invention is 70 to 95% by volume.
is preferably cubic boron nitride and the remainder is wurtzite boron nitride, and the additive is a compound of titanium, so that titanium diboride (TiB ₂ ) is formed and the high pressure phase boron nitride is formed. Preferably, a tightly bonded continuous matrix is formed.

The high-hardness sintered body obtained by the production method of the present invention is particularly preferably composed of high-pressure phase boron nitride of 70 to 95% by volume, cubic boron nitride of 5 to 30% by volume of wurtzite boron nitride.

The above-mentioned continuous particle size distribution means that particles with a particle size of 1 μm or more from the maximum particle size are classified into 5 μm increments.
1 out of 100 grains has a grain belonging to that grade, and
It is sufficient if the number of particles 1 μm or smaller is at least 10% of the number of particles 1 μm or larger.

<Function> In the high-hardness sintered body obtained by the production method of the present invention, high-pressure phase boron nitride forms a matrix, and the voids are filled with titanium or carbides, nitrides, and carbonitrides of titanium and tantalum. An additive consisting of at least one of these and aluminum plays a filling role. Titanium compounds have good sinterability, and themselves have excellent heat resistance and thermal conductivity during cutting. That is, in the present invention, the above compound is
It is not only used as a material for bonding high-pressure phase boron nitride with a continuous bonding phase as in the sintered body described in Publication No. 49621, but also as a material for bonding high-pressure phase boron nitride particles with each other as described above. It plays the role of forming a high-pressure phase boron nitride matrix by combining the parts to fill the voids and creating a strong and hard sintered body. In addition, titanium compounds often have an excessive amount of titanium bonded, and in this case, during sintering, the excess titanium reacts with aluminum to form a Ti-Al compound. moreover,
During sintering, titanium reacts with high-pressure boron nitride at the interface to form _TiB2 , and aluminum reacts with the high-pressure boron nitride to form aluminum nitride (AlN). These have a structure in which the high-pressure phase boron nitrides are glued together at points where they are in contact with each other to create a strong bond, and the high-pressure phase boron nitrides are directly bonded to each other to form a three-dimensional matrix. Become. In the present invention, high-pressure phase boron nitride with a wide particle size range is included, so various types of particles are densely packed, with medium particles between large particles and small particles between medium particles. In order to create such a structure, the contact points between the high pressure phase boron nitrides are much greater than when a narrow particle size range of high pressure phase boron nitride is used as the raw material, thus improving the strength of the matrix. Note that AlN produced during sintering is a sintering catalyst for CBN, and in the method of the present invention, high-pressure phase boron nitride is sintered together at extremely low temperature and pressure to create a high-hardness sintered body with a continuous matrix. leading to the formation of

In the present invention, if the amount of high-pressure phase boron nitride is less than 65% by volume, a matrix with sufficient strength cannot be obtained, and if it exceeds 95% by volume, the amount of binder phase is insufficient and It is not possible to obtain a high hardness sintered body.

The reason why the amount of titanium or titanium and tantalum carbides, nitrides, and carbonitrides is limited to 4 to 34% by volume is as follows. That is, the combination of these and aluminum constitutes the remainder of the high-pressure phase boron nitride, and if the high-pressure phase boron nitride accounts for 95% by volume, titanium or carbides, nitrides, and carbonitrides of titanium and tantalum are 4% by volume. % by volume, aluminum requires 1% by volume, and if the high-pressure phase boron nitride occupies 65% by volume, titanium or carbides, nitrides, carbonitrides of titanium and tantalum require 4% by volume.
Ranges from 34% by volume to 31% by volume for aluminum
By setting the content within the range of 1% by volume, the desired high hardness sintered body can be obtained.

Furthermore, the reason why a pressure of 20,000 atmospheres or more is required for sintering is that stable sintering is difficult if it is lower than that, and the reason why a temperature of 1,200 degrees Celsius or more is required is that if it is lower than that, the strength of the sintered body will decrease. This is because it is insufficient.

In carrying out the method of the present invention, it is necessary to pressurize the raw material mixture at a temperature of 1,200° C. or higher and a pressure of 20,000 atmospheres or higher. Note that this sintering can be carried out at a higher temperature and pressure than the above, but the actual temperature and pressure can be determined depending on the conditions of the apparatus itself. That is, there is no particular upper limit to the pressure as the sintering condition, and the sintering can be carried out at a high temperature within a range in which the raw material mixture does not undergo phase transformation from high-pressure phase boron nitride to low-pressure phase boron nitride. Also, by adding boron, it is possible to prevent the hardness of the sintered body from decreasing due to high temperatures.

Further, it is preferable that the proportion of WBN in the high-pressure phase boron nitride is 30% by volume or less. The reason is as follows.

Coarse WBN particles do not have very high strength as grains, and therefore, when determining the strength as grains, it is best to limit the grain size to 5 μm at most. In practice, CBN particles with a maximum dimension of 10 μm or more are ground by grinding the raw powder with a particle size of 10 μm or more.
CBN with a minimum dimension of 1 μm or less from CBN particles
By incorporating it into a sintered body as a CBN raw material with a continuous particle size distribution down to the particles, it can shorten the grinding time,
For the purpose of increasing the content of high-pressure phase BN of 1 μm or less
It is appropriate to add WBN. Then,
Since WBN supplements the content of fine particles of CBN, it is preferable to limit the content to 30% by volume or less of the total amount of high-pressure phase BN. In addition, when CBN is crushed to create a continuous particle size distribution, the fracture surface of the crushed CBN grains is a fresh surface that has not been exposed to the atmosphere since CBN was synthesized, and therefore it is not affected by the atmosphere. It is also preferable in that it is less likely to introduce impurities during sintering because it is not contaminated. Therefore, after pulverization, it is preferable to store the material in vacuum or in an inert gas without exposing it to the atmosphere as much as possible until sintering. Furthermore, if necessary, CBN particle groups having a plurality of particle size distributions may be combined and pulverized to produce a raw material having a continuous particle size distribution. For example, ball mill, stamp mill, edge runner,
Particles having a continuous particle size distribution can be obtained by using a crusher, a vibrating mill, or the like.

<Examples> Next, the present invention will be explained in detail with reference to specific examples and comparative examples.

Example 1 CBN with an average particle size of 15 μm and CBN with an average particle size of 5 μm
A mixture having a ratio of 3:1 was pulverized and mixed in a cemented carbide ball mill for 4 hours. The largest particle of the resulting mixture is 18 μm, and the particles smaller than 1 μm are 23
%, and it was confirmed by underwater sedimentation classification treatment and microscopic observation that particles exceeding 1 μm had a continuous particle size distribution.

Next, 72% by volume of the above CBN mixture, 10% by volume of titanium carbide with a molar ratio of titanium and carbon of 1:0.68, 4% by volume of tantalum carbide with a molar ratio of tantalum and carbon of 1:1, and mol of titanium and nitrogen. The ratio is 1:0.72
Titanium nitride 2.6% by volume and aluminum
11.4% by volume was mixed in a cemented carbide ball mill for 12 hours.

Next, 3.8% by volume of amorphous boron was added to this mixture and mixed.

Furthermore, a cylindrical capsule with an outer diameter of 15 mm, a height of 6 mm, and a thickness of 0.8 mm made of industrially pure titanium with a bottom is first filled with cemented carbide powder containing 10% by weight of cobalt to a depth of 3 mm from the bottom. The mixed powder containing amorphous boron was press-fitted to a thickness of 2 mm and sealed with an industrially pure titanium disc. This sealed capsule was surrounded by salt molded to a density of 98% of the theoretical density, and placed in a belt-type ultra-high pressure device, where it was sintered at a pressure and temperature of 25,000 atm and 1,400°C for 8 minutes. The temperature was gradually raised, held as it was for 20 minutes, and then lowered to room temperature and pressure for 12 minutes, and then taken out.

CBN where the capsule was removed with a grinder
The mixed powder containing the powder and the cemented carbide powder are strongly sintered, and the two are separated into two layers and joined to a thickness of approximately
A disc-shaped sintered body with a diameter of 2.8 mm and a diameter of approximately 12.3 mm was obtained.

The hardness of the sintered body containing CBN was measured using a micro-Vickers hardness tester under a load of 1 kg, and the average of the 5 measurement points was 4350 kg/mm ² . When the sintered body containing CBN was polished with diamond paste and observed under an optical microscope at 1500x magnification, a structure in which CBN was bonded together was observed.

Next, this sintered body containing CBN was immersed in a mixture of hydrofluoric acid with a concentration of 46% and nitric acid with a concentration of 35% in a volume ratio of 1:1. The sintered body after immersion maintained its shape even after chemical treatment.

X-ray diffraction measurements were performed on this CBN-containing sintered body before and after chemical treatment, and the results showed that the peaks of titanium carbonitride, titanium boride, and tantalum carbide disappeared after chemical treatment, indicating that the strong CBN Only the peak and weak aluminum nitride peak were confirmed.

That is, the high-hardness sintered body produced by the method of the present invention contains a continuous matrix bonded with CBN having a continuous particle size distribution before sintering, and titanium carbide, tantalum carbide, tantalum nitride, and aluminum. One thing is clear.

Next, the fact that the high-hardness sintered body manufactured by the present invention is extremely excellent in practical use will be explained by using an example in which the high-hardness sintered body is used as a cutting tool.

That is, the disk-shaped sintered body manufactured in Example 1 was finished with a diamond grindstone so that the diameter of the sintered body was 11 mm, the thickness was 2.5 mm, and the thickness of the sintered body portion containing CBN was approximately 1 mm. Next, cut the circle into 6 equal parts using a diamond cutter along a cutting line that passes through the center of the circle, create a fan-shaped chip with an apex angle of 60°, and solder it to a K20 grade cemented carbide stand with silver solder. It was polished with a whetstone and processed into a throw-away tip called TNG332 with an apex angle of 60°, an inscribed circle dimension of 9.525 mm, a thickness of 4.76 mm, and a cutting edge radius of 0.8 mm.

As the workpiece material for the cutting test, a groove with a rectangular cross section of 20 mm width and 20 mm depth was carved into a piece of SCM415 grade steel with a diameter of 120 mm and a length of 500 mm.
A heat-treated scale 58 was prepared, and the outer periphery was cut using the aforementioned throw-away tip. The cutting conditions were: circumferential speed (hereinafter referred to as V) = 201 m/min, depth of cut (hereinafter referred to as d) = 0.5 mm, feed (hereinafter referred to as f) = 0.2 mm/rev, and continuous cutting was performed for 60 minutes.
Flank wear on the cutting edge stopped at 0.08 mm, and no tendency for chipping or chipping was observed, and it was determined that further cutting could be continued. This type of cutting method is generally called continuous cutting, and with conventional sintered tools containing CBN, it could not be performed at all under the harsh conditions used in this test, as the cutting edge would break quickly.

Comparative example 1 CBN with an average particle size of 3 μm was used without being crushed.
All other treatments were carried out in the same manner as in Example 1, except that amorphous boron was not added and the mixing treatment with other additives was carried out for 3 hours.

The microvitkers hardness of the obtained sintered body is
It is 3400Kg/mm ² which is lower than that of Example 1. this is
This is thought to be due to the lack of bonding between CBNs, but this was also confirmed by observation with an optical microscope.
It was confirmed that the grains were separated from each other by a binder phase. Furthermore, chemical treatment was performed in the same manner as in Example 1.

As a result, the sintered body collapsed, indicating that the CBNs were not bonded to each other.

When the same cutting test as in Example 1 was conducted, the cutting edge broke off after only 2 minutes of cutting, and when the same test was repeated, it broke off after 1 minute and 30 seconds.

Comparative Example 2 All treatments were carried out in the same manner as in Example 1, except that amorphous boron was not added and all additives were replaced with aluminum oxide. Both observation using an optical microscope and observation after chemical treatment confirmed that CBNs were bonded to each other.

When a cutting test similar to that in Example 1 was conducted, the flank wear of the cutting edge reached 0.8 mm after 18 minutes of cutting, and further cutting could not be performed.

From Example 1 and Comparative Example 1, in the present invention
It is clear that CBN has a continuous particle size distribution, and that the types of additives are different from those of Example 1 and Comparative Example 2.
It can be seen that this has a large effect on the bonding between particles.

Comparative Example 3 A high hardness sintered body was obtained in the same manner as in Example 1 except that amorphous boron was not added and the sintering pressure and temperature were 38,000 atm and 1520°C.

The hardness of the obtained sintered body was 4020Kg/ ^mm2 , and the results of optical microscopy and chemical treatment both showed that CBN was bonded to each other.

As a result of conducting a cutting test similar to the cutting test conducted in Example 1 at a lower V = 188 m/min, the flank wear after cutting for 60 minutes became more gradual as the circumferential speed became lower. Nevertheless,
The diameter was 0.08 mm, which is the same as in Example 1, and almost no chipping or chipping was observed.

From Example 1 and Comparative Example 3, it is clear that in the present invention, by adding boron, a sintered body with the same or better cutting performance can be obtained even under milder sintering conditions than Comparative Example 3. be.

Comparative Example 4 A sintered body was obtained in the same manner as in Example 1 except that the CBN used was all granules with an average particle size of 5 μm.

The hardness of the obtained sintered body was 3800 Kg/mm ² .
Both optical microscopy and observation after chemical treatment showed that there was no bonding between CBNs, or if there was, there was only a small amount of bonding.

When the same cutting test as in Example 1 was conducted, the cutting edge broke off after only 8 minutes of cutting, and when the same test was repeated two more times, it broke off after 5 minutes and 10 minutes and 30 seconds.

<Effects of the Invention> The present invention has been achieved by adding a specific amount of boron in addition to the particle size and blending ratio of high-pressure phase boron nitride in the sintering raw material, specific additives and blending ratio, and specific metal and blending ratio. This is a method for manufacturing a high-hardness sintered body in which the sintering conditions (temperature, pressure) are relaxed and high-pressure phase boron nitrides are bonded together to form a continuous matrix.

It is known that a sintered body containing high-pressure phase boron nitride according to the prior art exhibits far superior performance in cutting ferrous materials compared to other conventional tool materials, but the sintered body obtained by the present invention showed even better performance than that. In particular, it is superior to conventional sintered bodies containing high-pressure phase boron nitride in high-speed interrupted cutting of high-hardness hardened steel, heavy cutting of raw materials such as cast steel, cast iron, and type steel, heavy cutting of hardened materials, high-speed cutting of sintered metal, and high-speed cutting of sintered metal. Furthermore, it is also suitable for cutting steel ranging from low carbon to high carbon, which was conventionally considered unsuitable for sintered bodies containing high-pressure phase boron nitride, and in fact did not show good results when cutting. That is, the present invention can be applied to conventional CBN and/or
Manufacture of sintered bodies for tools that can perform cutting under severe conditions that cannot be performed with sintered bodies containing CBN and WBN, especially high-speed interrupted cutting of hardened hardened steel and unheat-treated steel. This is an industrially extremely useful invention.

Claims (1)

[Scope of Claims] 1. Cubic boron nitride having a maximum particle size of 10 to 50 μm and a minimum particle size of 1 μm or less, with a continuous particle size distribution therebetween, or a polymer comprising the cubic boron nitride and wurtzite boron nitride. 65 to 95 volume % of phase pressure boron nitride, 4 to 34 volume % of an additive that is at least one of titanium or a carbide, nitride, or carbonitride of each of titanium and tantalum, and aluminum. A mixture of 100% by volume and further added 0.1 to 5% by volume of boron was obtained,
A method for producing a high-hardness sintered body, in which the mixture is sintered at a minimum of 1200°C and 20,000 atm, so that high-pressure phase boron nitrides bond together to form a continuous matrix. 2. The method for producing a high-hardness sintered body according to claim 1, wherein the high-pressure phase boron nitride comprises 70 to 95 volume % of cubic boron nitride and 5 to 30 volume % of wurtzite boron nitride. 3. The additive is at least one of titanium carbide, nitride, and carbonitride, and during sintering, titanium diboride and aluminum nitride are generated to form a continuous matrix in which high phase pressure boron nitride is firmly bonded. A method for manufacturing a high-hardness sintered body according to claim 1.