JPS61209958A - Sintered body for high hardeness tool and manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] There are two types of high-pressure phase type boron nitride (BN), cubic crystal and wurtzite crystal, and both have a hardness second only to diamond and are extremely useful as materials for grinding and cutting. It is considered promising. It is already widely used for grinding purposes.

For cutting purposes, some sintered bodies made of cubic BN bonded with metals such as Go have been released on a trial basis.

This metal-bonded BN sintered body is a type of cermet, and has a problem in terms of heat resistance. In other words, it is unsuitable for applications where the temperature of the cutting edge increases, such as during high-speed cutting.The present invention uses a metal compound with excellent heat resistance and wear resistance as a bonding body, and is intended to provide high strength. .

The inventors had previously invented a highly hard sintered body for tools made by bonding cubic boron nitride (abbreviated as CBN) with a metal compound with excellent heat resistance and high thermal conductivity, and filed a patent application (51- 15
4570.52-54666). The inventors applied the same idea to CBN to wurtzite BN, which is another high-pressure phase of boron nitride, and as a result of various studies, they arrived at the present invention.

Wurtzite type BN can be synthesized using hexagonal type BN as a raw material using a dynamic ultra-high pressure generation method using shock waves. In this method, C is synthesized using a static ultra-high pressure device.
It has the advantage of being cheaper to manufacture than BN. In this synthesis method using the shock wave method, the duration of pressure and temperature during synthesis is short, so the time for crystal growth is limited, and the grain size of Wurtz-type BN crystals synthesized by this method is generally 10μ.
Japanese Patent Publication No. 50-39444 filed by one of the following inventors discloses a sintered body obtained by using this wurtzite-type BN as a raw material and sintering it under high temperature and high pressure. It has been shown that this wurtzite BN alone is also excellent.

The inventors have determined the characteristics of this wurtzite-type BN sintered body,
As a result of a detailed investigation of the performance, we found that there were many variations between each sintered body.
It was also found that there is room for improvement in both toughness and wear resistance in terms of performance as a tool.

As mentioned above, wurtzite-type BN synthesized using shock waves is an extremely fine powder, and the particle shape is complex and the surface has many irregularities, so it has a large surface area. Therefore, gas is easily adsorbed on the particle surface, and oxides and hydroxides are formed on the particle surface. When sintering using such a fine powder, it is not difficult to let this gas out of the system when the material to be sintered is not sealed, but as in the present invention,
When sintering under ultra-high pressure, it is almost impossible for the generated gas to escape outside the heating system.

Generally, in such cases, it is common knowledge in the powder metallurgy industry to perform degassing treatment in advance, but if the degassing temperature is not high enough (it is not possible, there is a problem. This case is exactly the challenge). That is, when considering the transformation of wurtzite type BN to a low positive phase, there is an upper limit to the heating temperature.

The degassing process of fine powder involves the following stages depending on the temperature. First, at low temperatures, physically adsorbed substances and hygroscopic moisture are removed, and then chemically adsorbed substances and hydroxides are decomposed. At the end, oxide remains. wurtzite type BN
In this case, it is stable up to about 80°C, so it can be heated to this temperature in advance. Therefore, it can be considered that if the gas is degassed and heated in advance, the residual gas components remain in the form of oxides. Conversely, since it is desired that gas components remain in the sintered body as little as possible, it is preferable to remove all water and hydrogen as a preliminary treatment.

However, this thermal degassing treatment cannot remove oxides on the particle surface, and in the case of wurtzite-type BN particles, it is likely that boron oxide (B
The oxide remains in the form of *Os).

Boron oxide has a low melting point (450°C) and becomes glassy at high temperatures. In addition, conventional wurtzite-type BN sintered bodies, which easily absorb moisture in the atmosphere and become hydroxide, are sintered with this B x Os remaining on the surface of the crystal particles.
Variations in properties occur depending on the amount, and this is one of the causes of reduced wear resistance and toughness when used in cutting tools and the like.

The present invention solves this problem and provides a high-performance, stable sintered body for tools. The inventors sintered a mixed powder of wurtzite-type BN and various heat-resistant compound powders and examined the characteristics and performance. As a result, they found that carbides, nitrides, and carbonitrides of group 4a and 5a metals of the periodic table were sintered. It has been found that a high-performance sintered body with stable properties can be obtained when using .

The reason why such a good sintered body can be obtained when carbides, nitrides, and carbonitrides of metals in groups 4a and 5a of the periodic table are used is considered to be as follows.

That is, these compounds of metals in groups 4a and 5a of the periodic table have MCI:! :X, MN+ ±, , M (C, N)
I±8 (M is "+Zr+" of Group 4a of the periodic law
Hf or group 58 metals V, Nb, Ta, X
means the presence of N or C atomic vacancies or a relative excess of atoms. ) has a composition range that is on the M-C, M-N, M-C-N phase diagram. Especially T s of group 4a metals
+ Z r s Hf has a wide range of existence.

For example, taking the nitride expressed in the form of MN, ±8 as an example, the reason why a good sintered body is obtained when MN, ±8 is added is considered to be as follows. That is,
The surface of the wurtzite-type BN powder contains oxides, probably B t Os, that could not be removed by heating and degassing in vacuum, for example.
There are things of the form. This B20. and MN, if M corresponding to the ±8 ku-X) portion reacts, Bias +4M-4MB! +3 MO(1) and no gas is generated. MO and MN have the same crystal structure and form a mutual solid solution. It is believed that there is a reason why a good sintered body can be obtained when a nitride of a group 4a or 5a metal of the periodic table, represented by MN, ±8, is added. This is not limited to nitrides, but also carbides represented by the form MC,+, carbonitrides represented by M(C,N)+±, or the above-mentioned compounds containing two or more metals as M. The same can be said about Also, periodic table 4a,
These compounds of S a group metals can also form solid solutions with carbides and nitrides of Cr, Mo, and W, which are group 68 metals of the periodic table. Such composite carbides, nitrides, and carbonitrides can also be applied to the sintered body of the present invention as long as they have an existence range expressed in the form of (M, M')N, ±wings, for example. The inventors prototyped sintered bodies by mixing wurtzite-type BN and these compound powders with various composition ranges of (, ±X), and investigated the characteristics and performance. ) It was confirmed that a strong and good sintered body can be stably obtained when a compound powder having N or C atom vacancies with a value of 0.97 or less is used.

The sintered body according to the present invention is made of wurtzite type BN with TiN+f:x
The case where a sintered body is created by mixing will be explained in more detail.

- Considering the case where the amount of TiN added is 60χ and 1 oz, the amount of oxygen retained even after preheating of wurtzite BN is probably 1% at most, so in this extreme case, TiN
When calculating the minimum required amount of X of +-1l, TiN
For wurtzite type BN 602 40% x -0,05410χ
In the case of 90χ, x = 0.727.

That is, when the amount of TiN0 is large, it is sufficient to use TiN+-x with a small value of X, and when it is small, it is necessary to use a material with a large value of X. As shown in Figure 1, Ti
The existence region of N is wide, and the lower limit is approximately TiN*, &.

There are various theories regarding the upper limit, and there are also reports of TiN+ and +i. Therefore, in the case of 90%BN-10%TiN, if the amount of oxygen is large, TiN,! : It is necessary to add a mixture of Ti. However, this is not preferable because the amount of TiN as a binder is small (it becomes less), and rather the amount of TiN used as a binder is
The preferable value of (1-X), which should reduce the amount of oxygen in
O) is the range that exists as a phase, and approximately (1-X)≧0
．． It is 6. The Ti-N-0 solid solution phase remaining in the sintered body is B80. It is a stable compound with much higher heat resistance and higher hardness than . Furthermore, as shown in formula 11 above, when 8203 decomposes, TiB1 is produced, but since this is also a high-hardness, heat-resistant compound, it does not degrade the performance of the sintered body. ?
The same is true for nitrides and carbonitrides. Figure 2 shows Ti-
Although this is a phase diagram of the C-B system, there is also some B in TiCt-x.
It has been shown that Bi12 and TiCt-
The compound produced in the reaction is TiB z + Tt B
It is considered that in addition to the +Tt-C-O solid solution, a Ti-C-0-B solid solution may also be formed.

Now, in the sintered body of the present invention, the amount of the above compound powder added to wurtzite-type BN needs to be selected depending on the oxygen content in the raw BN powder and the composition of the compound powder to be added, but the sintered body can also be used as a tool. It is limited in terms of performance when

If the content of wurtzite BN is less than 10% by volume in the sintered body, the hardness of the sintered body will be low, and there will be no noticeable difference in performance from the sintered body that does not contain BN. If the amount is less than 10% by volume in the compact, most of the oxides contained in the wurtzite-type BN powder are decomposed, which is insufficient to fully exhibit the effects of the present invention. A particularly preferable composition range is a wurtzite BN content of 3o to 70% by volume in the sintered body.
% range.

In this limited composition range, by selecting the particle sizes of the raw BN powder and the additive compound powder as described later, the additive compound according to the present invention forms a continuous binder phase in the sintered body, and the surface of the BN particles is Because it is in an enclosed state, raw material B
The oxide on the surface of the N powder is completely decomposed and dissolved into the binder phase compound during sintering, making it possible to obtain a tough sintered body.

The particle size of the wurtzite-type BN powder used in producing the sintered body of the present invention is not particularly limited, but the particle size of BN obtained by the shock wave method is generally a fine powder of lo μ or less.

This BN powder and carbides of metals from group 4a+58 of the periodic table,
Mix compound powders mainly consisting of nitrides and carbonitrides.

The particle size of this compound powder must be finely dispersed between the BN powder particles in order to exhibit the effects of the present invention. Therefore, it is better to use particles with a particle size finer than that of BN powder, and in the present invention, all powders with a particle size of 10 μm or less, preferably 1 μm or less are used. This mixed powder or embossed body is heated and degassed to a temperature of 80θ℃ or less under a vacuum of 10-'mmHg or higher, and is then processed using an ultra-high pressure device. It is a device such as a mold. A graphite cylinder is used as the heating element, and an insulating material such as talc or NaCl is filled in the cylinder to enclose the CBH mixed powder molded body.

A pressure medium such as pyroferrite is placed around the graphite heating element. The pressure and temperature conditions for sintering are preferably within the stable region of high-pressure phase type boron nitride shown in Figure 3 (i.e., the temperature and pressure conditions above line A-A' in Figure 3); is not necessarily known accurately and is only a guideline.

The line B-B' in Figure 3 shows the metastable region of wurtzite BN, and under the pressure and temperature conditions in the area surrounded by line B-B' and A-A'M, wurtzite BN Cubic crystal type BN from the mold
It is known to convert into

In producing the sintered body of the present invention, part or all of the wurtzite BN may be converted into cubic boron nitride by sintering within this region.

When the sintered body of the present invention is used, for example, as a cutting tool, it is sufficient that the hard sintered body layer containing high-pressure phase boron nitride forms the cutting edge part of the tool, and the part that supports this is used during cutting. Another material with high strength that can withstand the stress and heat applied to the tool is used.The material used as the support is a high strength cemented carbide with similar rigidity to the hard sintered layer. ing. In particular, WCC cemented carbide has good thermal conductivity and is optimal as a support for a hard sintered body layer.

This support and the sintered body of the present invention containing high-pressure phase type boron nitride are bonded together during sintering under high pressure and high temperature, in contact with the stamped body of the mixed powder that forms this hard sintered body layer. Cemented carbide can be placed and sintered and joined at the same time. If this hard sintered body forming part is composed only of wurtzite boron nitride powder, it is difficult to obtain a sintered body that is firmly bonded to the cemented carbide support even under high pressure and high temperature.
In the sintered body of the present invention, between the boron nitride particles,
, compound phases mainly consisting of carbides, nitrides, and carbonitrides of group 5a metals are finely dispersed, and these compounds and cemented carbide have a higher chemical affinity than boron nitride at the bonding interface. This results in a strong bond.

The sintered body of the present invention has excellent wear resistance, high hardness and toughness, and is used for tool materials and wire drawing dies for cutting high hardness steel such as hardened steel and high hardness cast iron. .

Examples will be described below.

Example 1 Wurtzite type B made by shock wave method with particle size of 2 microns or less
Nitrogen content 1a, 1% (Ti N
TiN powder having a particle size of 1 micron was added at step 30, s) and mixed in a 48-hour ball mill using acetone as a solvent. As a result of analysis, the oxygen content of the raw material, wurtzite-type BN powder, is 0.
．． It was 7%.

This mixed powder was pressed and molded to have an outer diameter of 10111M and a thickness of 1.5mm. This embossed body was placed in a hollow cylindrical container with a bottom made of iron. Place this in a vacuum furnace at 700°C for 20 minutes.
Degassing treatment was performed under the conditions of 0-'ma+Hg.

This degassed product was placed in a belt device, which is one of the ultra-high pressure devices mainly used for diamond synthesis. Pyroferrite was used as the pressure medium and graphite as the heater.

Raise the pressure to 55Kb and then raise the temperature to 1200℃3
It was held for 0 minutes. After lowering the temperature, the pressure was reduced and the sintered body was taken out.

After grinding the sintered body using a diamond grindstone, it was roughened with diamond paste. When I measured the Vickers hardness of the wrapped surface, it was approximately 4000 g7mta.
Met. When the same surface was examined by X-ray diffraction, weak diffraction lines of TiBz were observed in addition to diffraction lines corresponding to wurtzite BN and a Ti(N,O) solid solution.

Example 2 An embossed body made of the same wurtzite-type BN powder as in Example 1 and a mixed powder of T1No and @ was created. A disk with an outer diameter of ioam and a thickness of 3 mm made of pre-sintered cemented carbide with a WC-6% co composition was placed in the same iron bottomed container as in Example 1, and the stamped body was placed in contact with it. placed.

Thereafter, a sintered body was obtained in the same manner as in Example 1. Wurtzite type B
The sintered body had a layer of about 1 m# thick of the hard sintered body containing N firmly bonded to the cemented carbide disk.

The cross section of the sintered body was observed by breaking it.

When we observed the interface between the hard sintered layer containing wurtzite BN and the cemented carbide using an xvA microanalyzer, we found that
No diffusion of CO in the cemented carbide into the hard sintered body layer was observed.

The sintered body joined to this cemented carbide was brazed to a steel support to create a cutting tool.

This cutting tool was used to cut a heat-treated material of SN0M9 with a hardness of 57 on the Rockwell C scale.

Even after cutting for 40 minutes at a cutting speed of 90 m/min, depth of cut of 0.2a+a+, feed rate of 0.04 mm per rotation, and water-soluble cutting oil, the flank wear width was 0.20 mm, and even longer cutting times were It was possible. On the other hand, JIS is the hardest cemented carbide! When I shaved it using IKOI, it was only 2
Flank wear of 0.20 m+s or more per minute was observed, and further cutting was impossible.

Example 3 Various compounds shown in Table 1 were blended with the wurtzite boron nitride used in Example 2.

Table 1 Thereafter, a sintered body was produced in the same manner as in Example 1.

The pressure and temperature conditions during sintering were as shown in Table 1, and all sintering was performed under these conditions for 30 minutes. All were good sintered bodies, and the hardness measurement results were as shown in Table 1.

[Brief explanation of the drawing]

Figure 1 shows TiN used in the sintered body of the present invention.
- This is for explaining the existence range on the N phase diagram. FIG. 2 is a ternary system phase diagram of Ti-C-H, which is used to explain the state in which the additive compound of the sintered body of the present invention exists in the sintered body. FIG. 3 is for explaining the manufacturing conditions of the sintered body of the present invention, and shows the region where high-pressure phase type boron nitride exists on the P-T phase diagram. Hardness (0C) Procedural amendment December 18, 1985 1. Indication of case Patent application filed on November 30, 1985 2) Name of invention High hardness sintered body for tools and method for manufacturing the same 3. Amendment Relationship with the case of a person who does
Satoshi Kawakami, President, Sumitomo Electric Industries, Ltd.
Department 4, Agent address: 5, Sumitomo Electric Industries, Ltd., 1-1-3 Shimaya, Konohana-ku, Osaka, Japan. lI! Date of official order 11 6. Specification and drawings to be amended 7. Contents of amendment (1) Submit the amended specification as attached. (2) The drawing and Figure 1 will be corrected as shown in the attached sheet. Amended Description 1. Name of the Invention High Hardness Sintered Body for Tools and Method for Manufacturing the Same 2) Claims (1) Wurtzite-type boron nitride powder and Periodic Table No. 48+5
When the 8+ group metal is M, MC,±, of (, ±, l)
The value of is 95% or less of the upper limit of the stable state of the metal carbide.
．． In a sintered body obtained by hot-pressing a mixed powder of a compound powder mainly composed of carbides of 6 or more under high pressure and high temperature, wurtzite-type boron nitride or a part of wurtzite-type boron nitride during sintering. The high-pressure phase boron nitride, which has been completely converted into cubic boron nitride, is contained in the volume of the sintered body in a total amount of 10% or more, and the remainder is a solid solution compound phase in the form of M'(C,O). A high-hardness sintered body for tools, characterized by being mainly composed of. (2) M(C,
A sintered body for a tool with high hardness, characterized in that the solid solution phase of O) forms a continuous binder phase in the sintered body. Mixing a compound powder mainly consisting of a carbide, in which the value of MC, (, ± A method for producing a highly hard sintered body for tools, which is characterized in that this is truly pressed at 1200° C. or higher under pressure and temperature conditions in which wurtzite BN or cubic BN is stable. 3. Detailed description of the invention There are two types of high-pressure phase boron nitride (BN): cubic crystal, wurtz crystal, and monocrystalline crystal. Both have hardness second only to diamond, and are extremely useful as materials for grinding and cutting. It is considered promising. It is already widely used for grinding purposes. For cutting purposes, some sintered bodies made of cubic BN bonded with metals such as Go have been released on a trial basis. This metal-bonded BN sintered body is a type of cermet, and has a problem in terms of heat resistance. That is, it is unsuitable for applications where the temperature of the cutting edge increases, such as during high-speed cutting.The present invention aims to provide a bonded body with heat resistance and strength. The inventors had previously invented a highly hard sintered body for tools made by bonding cubic boron nitride (abbreviated as CBN) with a metal compound with excellent heat resistance and high thermal conductivity, and filed a patent application (patent application). Showa 51
-154570. Patent application 52-54666). The inventors applied the same idea to CBN to wurtzite BN, which is another high-pressure phase of boron nitride, and as a result of various studies, they arrived at the present invention. Wurtzite type BN can be synthesized using hexagonal type BN as a raw material using a dynamic ultra-high pressure generation method using shock waves. In this method, C is synthesized using a static ultra-high pressure device.
It has the advantage of being cheaper to manufacture than BN. In this synthesis method using the shock wave method, the duration of pressure and temperature during synthesis is short, so the time for crystal growth is limited, and the grain size of Wurtz-type BN crystals synthesized by this method is generally 10μ.
There are many of the following. In Japanese Patent Publication No. 50-39444 filed by one of the inventors, it is shown that a sintered body made of wurtzite-type BN as a raw material has higher hardness than CBN single crystal and has excellent heat resistance. . The inventors have determined the characteristics of this wurtzite-type BN sintered body,
As a result of a detailed investigation of the performance, we found that there were many variations between each sintered body.
It was also found that there is room for improvement in both toughness and wear resistance in terms of performance as a tool. As mentioned above, wurtzite-type BN synthesized using shock waves is an extremely fine powder, and the particle shape is complex and the surface has many irregularities, so it has a large surface area. Therefore, gas is easily adsorbed on the particle surface, and oxides and hydroxides are formed on the particle surface. When sintering using such fine powder, it is not difficult to release this gas from the system if the material to be sintered is not sealed. However, as in the present invention,
When sintering under ultra-high pressure, it is almost impossible for the generated gas to escape outside the heating system. - In case of (a), degassing treatment must be carried out in advance.
Although this is common knowledge in the powder metallurgy industry, it becomes a problem if the degassing treatment temperature cannot be made high enough. This is exactly the case in this case; there is an upper limit to the heating temperature when considering the transformation of wurtzite-type BN to a low-pressure phase. The degassing process of fine powder involves the following stages depending on the temperature. First, at low temperatures, physically adsorbed substances and hygroscopic water are removed. Decomposition of chemisorbed substances and hydroxides then occurs. At the end, oxide remains. wurtzite type BN
In this case, it is stable up to about 800°C, so it can be heated to about this temperature in advance. Therefore, it can be considered that if the gas is degassed and heated in advance, the residual gas components remain in the form of oxides. Conversely, since it is desired that gas components remain in the sintered body as little as possible, it is preferable to remove all water and hydrogen as a preliminary treatment. However, this heating and degassing treatment cannot remove oxides on the particle surface. In the case of wurtzite-type BN particles, boron oxide (B
The oxide remains in the form of iO2). Boron oxide has a low melting point (450°C) and becomes glassy at high temperatures. It also easily absorbs moisture from the atmosphere and becomes hydroxide. Conventional wurtzite-type BN sintered bodies are sintered with this B t Os remaining on the surface of the crystal grains, resulting in variations in properties depending on the amount, and when used in cutting tools, etc., this results in poor wear resistance. This was one of the causes of decreased strength and toughness. The present invention solves this problem and provides a high-performance, stable sintered body for tools. The inventors sintered a mixed powder of wurtzite-type BN and various heat-resistant compound powders and examined the characteristics and performance. As a result, they found that when using carbides of Group 4a and 5a metals of the periodic table, the characteristics It has been found that a stable and high-performance sintered body can be obtained. The reason why such a good sintered body can be obtained when a carbide of a metal in group 4a of the periodic table, Sa group, is used is considered to be as follows. That is, these compounds of metals of groups 4a and 5a of the periodic table are shown in the form MC, ±8 (M is Ti of group 4a of the periodic table,
It represents Zr, If or metals of group 5a, V, Nb, Ta, and X means the presence of atomic vacancies of C or a relative excess of atoms. ) has a wide composition range on the M-C phase diagram. In particular, the group 4a metals Ti, Zr, and llf have a wide range of existence. For example, taking the carbide expressed in the form of MC, ±8 as an example, the reason why a good sintered body is obtained when MC1±x is added is considered to be as follows. That is,
On the surface of the ur-nite type BN powder, there is an oxide, probably in the form of B2O3, that could not be removed by heating and degassing in a vacuum.
When M corresponding to free M) reacts, B2O3+ 4 M-IMBZ, + 3 MO(11
Therefore, no gas is generated. Then, MO and MC form a mutual solid solution. It is believed that there is a reason why a good sintered body can be obtained when a carbide of a metal of group 4a of the periodic table, Sa group, represented by M C+±×, is added. In addition, these compounds of metals in groups 4a and 5a of the periodic table are metals in group 68 of the periodic table (r, MO, and W can form solid solutions with carbides and nitrides.Such composite carbides, For example, nitrides and carbonitrides can be applied to the sintered body of the present invention as long as they have an existence range expressed in the form (M. M') C, ±. As a result of investigating the various properties and performance of (1±X) with these compound powders, it was found that the compound powder has C atom vacancies with a value of (1±X) of 0°95 or less, which is the upper limit of the stable state of carbide. It was confirmed that a strong and good sintered body can be stably obtained when using the sintered body of the present invention by mixing wurtzite BN with TiC+±. Let me explain this in more detail.If we consider the cases where the amounts of Tf and C added are 60χ and 10χ, the amount of oxygen that wurtzite-type BN retains even after preheating is probably 1% at most, so in these extreme cases, TiC
Calculating the minimum required amount of X for t-1l, in the case of TiC wurtzite type BN 60χ 40χ
In the case of 0χ, x = 0.757. That is, if the amount of TiC is large, use TiCt-+t with a small value of X, and if the amount of TiC is small, use the true value. You need to use something big. As shown in Figure 1, T
IC exists in a wide range of areas. The lower limit is approximately TiC,,5. The upper limit is T1Co, qa. Therefore 90%BN
- In the case of 10% TiC, if the amount of oxygen is large, it is necessary to add a mixture of TiC and Ti. However, this is not preferable because the amount of TiC0 as a binder decreases, so it is used instead. BN oxygen should be reduced. The preferred value of (1-X) varies depending on the metal element used, but in the case of TiCt-x, the solid solution phase of Ti-C-0 remaining in the viscous material during sintering is B20. It is a stable compound with much higher heat resistance and hardness than . Moreover, as shown in the above-mentioned formula (1), B20. When TtBz decomposes, TtBz is generated, but since this is also a high hardness and heat resistant compound, it does not deteriorate the performance of the sintered body. Figure 2 is a phase diagram of the Ti-C-B system.
It has been shown that some B is dissolved in solid solution in X, and B2
The compound produced by the reaction between 0° and TiCl-x is T.
i B z, Ti B . In addition to Ti-C-0 solid solution, Ti-C-0-B solid solution 4
Now, the amount of the above compound powder added to the wurtzite type BN in the sintered body of the present invention needs to be selected depending on the oxygen content in the raw material BN powder and the composition of the compound powder to be added. However, it is further limited in terms of performance when the sintered body is used as a tool. When the content of wurtzite-type BN is less than 10% by volume in the sintered body, the hardness of the sintered body is low, and the difference in performance from the sintered body that does not contain BN is not significant. Furthermore, if the added compound is less than 1% by volume in the sintered body, most of the oxides contained in the wurtzite-type BN powder are decomposed, which is insufficient to fully exhibit the effects of the present invention. . A particularly preferred composition range is one in which the content of wurtzite BN is 30 to 70% by volume in the sintered body.
% range. In this limited composition range, by selecting the particle sizes of the raw BN powder and the additive compound powder as described later, the additive compound according to the present invention forms a continuous binder phase in the sintered body, and the surface of the BN particles is Because it is in an enclosed state, raw material B
The oxide on the surface of the N powder is completely decomposed and dissolved into the binder phase compound during sintering, making it possible to obtain a tough sintered body. In producing the sintered body of the present invention, the particle size of the wurtzite-type BN powder used is not particularly limited. Generally, the particle size of BN obtained by the shock wave method is a fine powder of 10 μm or less. This BN powder and periodic table 4a. A compound powder mainly composed of carbides of Group 5a metals is mixed. The particle size of this compound powder must be finely dispersed between the BN powder particles in order to exhibit the effects of the present invention. Therefore, it is better to use particles with a particle size finer than that of BN powder, and in the present invention, all powders with a particle size of 10 μm or less, preferably 1 μm or less are used. This mixed powder or embossed body is heated under a vacuum degree of 10-' ma + I (800 g or more).
The material is heated and degassed to a temperature of 0° C. or lower, and then sintered at high pressure and high temperature using an ultra-high pressure device. The ultra-high pressure equipment used is a girdle type, belt type, etc. equipment used for diamond synthesis. A graphite cylinder is used as the heating element, and an insulating material such as talc or NaCj is filled in the cylinder to enclose the CBN mixed powder molded body. The graphite heating element is surrounded by a high-pressure phase type boron nitride containing pyroferrite or other pressurized water in the stable region (i.e., Fig. 3A-A).
It is preferable to perform the test under the temperature and pressure conditions above the line.
This equilibrium line is not always known exactly and cannot be used as a guideline. The line B-B' in Figure 3 shows the metastable region of wurtzite-type BN, and under the pressure and temperature conditions in the area surrounded by the line B-B' and line A-A', It is known that BN converts from BN type to cubic type BN. In producing the sintered body of the present invention, part or all of the wurtzite BN may be converted into cubic boron nitride by sintering within this region. When the sintered body of the present invention is used, for example, as a cutting tool, it is sufficient that the hard sintered body layer containing high-pressure phase boron nitride forms the cutting edge part of the tool, and the part that supports this is used during cutting. Another high strength material may be used to withstand the stress and heat applied to the tool. A suitable material for use as such a support is a high-strength cemented carbide, which has the same rigidity as the hard sintered body layer. In particular, WCC cemented carbide has good thermal conductivity and is optimal as a support for a hard sintered body layer. This support and the sintered body of the present invention containing high-pressure phase type boron nitride are bonded under high pressure and high temperature. This can be achieved by placing a cemented carbide 0 alloy and bonding it at the same time as sintering. If this hard sintered body forming part is composed only of wurtzite boron nitride powder, it is difficult to obtain a sintered body that is firmly bonded to the cemented carbide support even under high pressure and high temperature. In the sintered body, a compound phase mainly composed of carbides of group 48+5a metals of the periodic table is finely dispersed between the boron nitride particles, and even at the bonding interface, these compounds and the cemented carbide are more sensitive than the boron nitride. A strong bond can be obtained due to the high chemical affinity. The sintered body of the present invention has excellent wear resistance, is highly hard and strong, and is used for tool materials and wire drawing dies for cutting high-hardness ropes such as hardened steel and high-hardness cast iron. . Examples will be described below. Attachment Example 1 Wurtzite type B created by shock wave method with particle size of 2 microns or less
Carbon content 14.9% (TiCo
, t), TiC powder with a particle size of 1 micron was added, and mixed in a 50 hour ball mill using acetone as a solvent. As a result of analysis, the oxygen content of the raw material, wurtzite-type BN powder, was 0.
It was 7%. This mixed powder has an outer diameter of 10II111 and a thickness of 1.5mm.
Embossed and molded. This embossed body was placed in a hollow cylindrical container with a bottom made of iron. Place this in a vacuum furnace at 700℃ x 20
Degassing was carried out under conditions of 10-'+mHg. This degassed product was placed in a belt device, which is one of the ultra-high pressure devices mainly used for diamond synthesis. Pyroferrite was used as the pressure medium and graphite as the heater. Raise the pressure to 55Kb and then raise the temperature to 1250℃1
It was held for 5 minutes. After lowering the temperature, the pressure was reduced and the sintered body was taken out. After grinding the sintered body using a diamond grindstone, it was wrapped with diamond paste. The Vickers hardness of the wrapped surface was measured to be approximately 3800 Kg/mm. Also, when the same surface was examined by X-ray diffraction, diffraction lines corresponding to wurtzite BN and Ti(C,O) solid solution were detected. In addition, a weak diffraction line of TiBz was observed.Example 2 An embossed body made of a mixed powder of wurtzite-type BN powder and TiC0,s as in Example 1 was created.An iron bottom as in Example I A disk with an outer diameter of 10 mm and a thickness of 3 mm made of cemented carbide having a WC-6% Co composition that had been sintered in advance was placed in a container, and the embossing body was placed in contact with it. A sintered body was obtained in the same manner. Wurtzite type B
The sintered body was a layer of a hard sintered body containing N that had a thickness of approximately 111 m and was firmly bonded to the cemented carbide disk. A notch was made in the sintered body using a diamond cutting blade, and the cutout was broken to observe the cross section of the sintered body. Wurtzite-type BN using X′a microanalyzer
When the interface between the hard sintered body layer containing the cemented carbide and the cemented carbide was observed, no diffusion of Co in the cemented carbide into the hard sintered body layer was observed. The sintered body joined to this cemented carbide was brazed to a steel support to create a cutting tool. This cutting hide was used to cut a 5KDII heat-treated material with a Rockwell C scale hardness of 60. Even after cutting for 20 minutes at a cutting speed of 100 m/min, depth of cut of 0.2 mm+, and feed rate of 0.1 mm per revolution using water-soluble cutting oil, the flank wear width is 0.18 mm, making it possible to cut for even longer periods of time. Met. - The strength is JIS hard metal carbide! When it was cut using KO, it showed flank wear of 0.20 mm or more in just 30 seconds, and further cutting was impossible. Example 3 Various compounds shown in Table 1 were blended with the wurtzite boron nitride used in Example 2. Table 1 Below, sintered bodies were prepared in the same manner as in Example 1. The pressure and temperature conditions during sintering were as shown in Table 1, and all sintering was carried out under these conditions for 15 minutes. All were good sintered bodies, and the hardness measurement results were as shown in Table 1. 4. Brief explanation of the drawings Figure 1 shows TiC used in the sintered body of the present invention.
- This is for explaining the existence range on the C phase diagram. FIG. 2 is a ternary system phase diagram of Ti-C-B, which is used to explain the state in which the additive compound of the sintered body of the present invention exists in the sintered body. FIG. 3 is for explaining the manufacturing conditions of the sintered body of the present invention, and shows the region where high-pressure phase type boron nitride exists on the P-T phase diagram.

Claims (3)

[Claims] (1) Wurtzite boron nitride powder and Periodic Table 4a and 5a
, when the group metal is M, MC_1±_x of (_1±_
A sintered body obtained by hot-pressing a mixed powder of a compound powder mainly composed of carbides, in which the value of x) is 95% or less of the upper limit of the stable state of the metal carbide and 0.6 or more under high pressure and high temperature. In this case, wurtzite boron nitride or high-pressure phase boron nitride in which part or all of the wurtzite boron nitride is converted into cubic boron nitride during sintering is present in the total amount in the volume of the sintered body. A high hardness sintered body for a tool, characterized in that the content is 10% or more, with the remainder mainly consisting of a solid solution compound phase in the form of M(C,O). (2) M(C,
A sintered body for a tool with high hardness, characterized in that the solid solution phase of O) forms a continuous binder phase in the sintered body. (3) (_1±_x) of MC_1±_x, where M is Wurtz-type boron nitride powder and metals from groups 4a and 5a of the periodic table.
The value of is 95% or less of the upper limit of the stable state of the metal carbide.
．． It is characterized by mixing compound powders mainly consisting of carbides having a molecular weight of 6 or more, and hot pressing the mixture at 1200°C or higher under pressure and temperature conditions where wurtzite-type BN or cubic-type BN is stable. A method for manufacturing a high hardness sintered body for tools.