JP7428982B2 - High-toughness high-pressure phase boron nitride-based solidified body (sintered body) and its manufacturing method - Google Patents

Description

The present invention relates to a sintered body containing cBN (cubic boron nitride), wBN (wurtzite boron nitride), or both, and a method for producing the same.

High-pressure phase boron nitride (cubic boron nitride (cBN) and wurtzite boron nitride (wBN)) has a hardness second only to diamond, and is stable even at red-hot temperatures; Because it has no reactivity with iron even at high temperatures, it is widely used as a cutting tool material that can cut and turn high-hardness steel materials with high efficiency.

cBN is manufactured using low-pressure phase boron nitride (hBN) as a starting material, using a static high-pressure, high-temperature synthesis method using a press, and wBN is manufactured by applying impact pressure to hBN using explosives and the high temperatures generated at that time. It is manufactured by a dynamic high-pressure synthesis method that simultaneously adds The obtained high-pressure phase BN is either powdery or granular, and in order to be used as a cutting tool material, a step of obtaining a solid body (sintered body) by sintering the powdery or granular high-pressure phase BN is required. I need.

Methods for sintering high-pressure phase BN are well known. Known examples include a sintered body hardened with a binder of materials (Japanese Patent Laid-Open No. 54-066909), and a sintered body hardened with a mixture of cBN and wBN together with metals and ceramics (Japanese Patent Laid-open No. 59-064737). There is.

In all of these, powdered or granular high-pressure phase BN is filled into capsules together with a binder and housed in a high-pressure and high-temperature device similar to that used to obtain high-pressure phase cBN from low-pressure phase hBN. It is manufactured by applying ultra-high pressure and high temperature to obtain an integrated sintered body through static high-pressure and high-temperature treatment.

Therefore, a high temperature of over 1000°C, which is necessary for sintering, and a high pressure of 4 GPa or higher, at which the high-pressure phase BN can exist as a thermodynamically stable phase, are simultaneously applied for a certain period of time to the high-pressure phase BN, which is the sintering raw material. High-pressure, high-temperature equipment that requires this has a limited processing volume, and the dimensions and quantity of the sintered material to be processed are limited, making it difficult to improve productivity.

In addition, the high-pressure and high-temperature equipment used for sintering has a short lifespan because high pressure and temperature are repeatedly applied under conditions close to the limits of durability, and the short lifespan of expensive equipment is a factor that increases product costs. It has become one.

As a method to avoid the above-mentioned problems inherent in the static method using high-pressure and high-temperature equipment, especially the limitations on processing size and the cost increase due to the short life of the manufacturing equipment, dynamic high-pressure and Attempts have been made to produce sintered bodies using high temperature processing methods. However, although densification of the starting powder mixture was achieved by high impact pressure, it was not possible to bond the powders together to obtain an integrated sintered body.

The reason for this is that in the dynamic pressurization method that applies explosive shock, the effective pressurization time is very short, microseconds, and the temperature rises momentarily due to adiabatic compression, but as the pressure decreases, the temperature also decreases. Therefore, it is considered that the powder particles were not joined by melting or diffusion.

Japanese Patent Application Publication No. 54-046211 Japanese Patent Application Publication No. 54-066909 Japanese Patent Application Publication No. 59-064737

R. G. McQueen et al. (1970) "The equation of state of solids from shock wave studies" in High-Velocity Impact Phenomena (ed. R. Kinslow) Academic Press, New York, pp. 293-300.

The present invention eliminates the above-mentioned problems associated with high-pressure and high-temperature processes based on conventional static and dynamic methods, especially the limitations on product size, and makes it possible to manufacture high-pressure phase BN sintered bodies of any size and shape. This provides an innovative method to achieve this goal.

In the present invention, the manufacturing process of the sintered body is divided into a first stage and a second stage, and in the first stage, the mixed powder as a starting material is densified by a dynamic pressure method, and in the second stage, the mixed powder is densified in the first stage. The mixed powders are bonded by heat treatment of the mixed powders. By performing pressure treatment and heat treatment in separate processes in this way, it is possible to manufacture large-scale products of high-pressure phase BN sintered bodies and process them in large quantities, eliminating the need for expensive static high-pressure and high-temperature equipment. We decided to make it possible to supply low-cost high-pressure phase BN sintered bodies, including cost reductions.

The product of the present invention is a solidified body in which the starting material is compressed to 90% or more of its theoretical density by impact ultra-high pressure and further heat-treated, and the high-pressure phase (high-density phase) is nitrided at 30 to 90% by mass. Contains boron particles. The boron nitride particles are formed through metal nitrides and metal borides, which are formed by the reaction between nitrogen and boron, which are the constituent components of boron nitride, and the binder-forming metal contained in the starting material. They are bonded and integrated to form a high-toughness, high-pressure phase boron nitride-based solid.

The solidification is achieved by the following method. That is,
(1) A starting material in which high-pressure phase boron nitride particles account for 30 to 90% of the total mass ratio, and the remainder is powder of a binder-forming metal capable of forming borides and/or nitrides, is sealed in an implosion processing container. death,
(2) subjecting the container to impact ultra-high pressure to achieve a density of 90% or more of the total theoretical density;
(3) Next, by holding the heating temperature and heat-treating it, the high-pressure phase boron nitride particle surface and the particle surface newly generated by impact pressure are transformed into metal nitrides and/or metals generated on the spot during the heat treatment. Combine and integrate through borides.

That is, in the present invention, explosive impact or impact pressure of 1 GPa or more is added to the mixed powder of the starting material to form a high-density body, which is heated and maintained at a temperature of 800°C to 1800°C, preferably 1000°C to 1500°C. do. Through this operation, Al, Si, and one or more binder-forming metals selected from the group 4a, 5a, and 6a metals of the periodic table, which are added to and mixed with the high-pressure phase BN powder in the starting material, and/or the preformed High-pressure phase BN powder particles of one or more types of binder-forming metals selected from borides, nitrides, carbides, and oxide ceramics, especially one or more types of metals selected from Al, Si, Ti, Zr, and Hf. A densely integrated sintered body is obtained by promoting diffusion and wetting between the particles, chemical bonding with the high-pressure phase BN powder particles, rearrangement of particles due to the appearance of a melt phase, etc.

In the present invention, the bonding mechanism between high-pressure phase BN and metal, etc., or between metals, etc. is considered to be bonding via a compound caused by diffusion and wetting of solid phase or liquid phase metal between high-pressure phase BN powder particles. In addition, since the explosive impact is applied to the mixed powder of the starting material, cracks inevitably occur in the high-pressure phase BN, which is a highly hard and brittle material, but metal, etc. enters the cracks due to heating, joins, and fills the cracks. Therefore, the high-pressure phase BN particles and the like are bonded over an area larger than the original surface area of the high-pressure phase BN, etc., and high strength can be obtained.

In addition, although high-pressure phase BN has high hardness, it has a brittle property that is easily fractured by impact, but although its hardness is lower than that of high-pressure phase BN, it is bonded by nitride and/or boride, which has high toughness. The high-pressure phase BN sintered body obtained by the heat treatment after compression has higher toughness than a sintered body consisting only of high-pressure phase BN.

Ceramics such as borides, nitrides, carbides, oxides, etc. of preformed binder-forming metal species added to the starting material cannot be expected to bond directly with the high-pressure phase BN powder particles, but the physical properties of the binder phase The effect of contributing to improvement, especially imparting toughness, can be expected.

The reason why the explosive impact or impulsive pressure to be applied to achieve densification of the starting material is specified to be 1 GPa or more is because empirically, it is impossible to compress it to the required density at less than 1 GPa.

The explosion pressure generated by the explosive is calculated from formula 1).
P= ρ ₀ DU _p・・・・・・・・・ 1)
Here, P is the explosion pressure, ρ ₀ is the density of the explosive at the time of filling, D is the explosion velocity, and U _p is the flow velocity of the explosion products.

U _p = D/4 ・・・・・・・・・・・・ 2)
Since it is known that it can be approximated by , Equation 1) can be transformed into the following equation.
P= ρ ₀ D ² /4 ・・・・・・・・・ 3)

The pressure exerted on the metal container by a metal body colliding at high speed can be obtained from the following equation when the metal body and the metal material constituting the implosion processing container are equal.
P= ρ ₀ U _s U _p・・・・・・・・・4)
U _p = U _fs /2 ・・・・・・・・・ 5)
Here U _fs is the collision speed.

Although it is relatively easy to measure the impact velocity U _fs , it is difficult to measure the shock wave velocity U _s . Therefore, for example, if the material of the metal body that collides with the metal container is steel, the relationship between U _s and U _p is known,
U _s = 3.574 + 1.920U _p - 0.068U _p ²・・・・・・・・・・・・ 6)
In the above, the units of U _s and U _p are km/s.

A method for calculating the pressure generated when the metal container and the metal body are made of materials other than steel or when objects of different materials collide can be found in Non-Patent Technical Document 1.

The reason why it is necessary to compress a powder mixture (hereinafter referred to as a mixture) made of cBN etc. and metal etc. by impact according to the present invention to a density exceeding 90% of the total density of the constituent materials is as follows. This is because if the density is lower than that, even if cBN etc. and metal etc. are integrally bonded by heat treatment, the necessary hardness and strength as a high hardness sintered body containing cBN etc. cannot be obtained.

The density in the compressed state is calculated by using the ratio of the total theoretical density of the constituent materials to the density of the compressed and integrated material. In reality, the theoretical density and the actual density of a ceramic material differ slightly because the actual atomic ratio that makes up the ceramic is slightly different from the theoretical atomic ratio, but this does not pose a practical problem, so the calculations include the following: Use the theoretical density of the material.

The solidified body of the present invention can take various shapes and configurations depending on the purpose and use, and accordingly, many embodiments are possible in the application of explosive impact compression. Some examples thereof will be described in detail below with reference to the accompanying drawings.

1 is a cross-sectional view schematically showing an overall arrangement and details of typical parts for explosive impact compression processing of a mixed powder of starting materials contained in a cylindrical metal container in a first embodiment of the invention; FIG. FIG. 2 is a cross-sectional view schematically showing an explosive configuration for carrying out explosive impact compression processing while accommodating the configuration of FIG. 1; FIG. 5 is a vertical cross-sectional view taken along the plane BB in FIG. 4 below, showing an example of a configuration for simultaneously producing large quantities of three-dimensional sintered articles in a second embodiment of the present invention. 4 is a plan cross-sectional view taken along the line AA in FIG. 3. FIG. FIG. 7 is a longitudinal cross-sectional view showing a configuration example for simultaneously mass-producing another three-dimensional sintered body product (lace center) in a third embodiment of the present invention. In the fourth embodiment of the present invention, a vertical cross section taken along the plane BB in FIG. It is a front view. 7 is a plan cross-sectional view taken along the line AA in FIG. 6. FIG. FIG. 7 is a diagram showing a configuration for pressurizing a starting material mixed powder etc. by the impact of a metal plate flying due to explosion pressure in a fifth embodiment of the present invention.

1 and 2 and FIGS. 3 and 4 respectively show high-pressure phase BN-containing mixed powder compacts 11 and 33 as starting materials, and powder compacts 12 and 34 as supporting material raw materials for reinforcing this high-pressure phase BN-containing sintered layer. A layout diagram (Figures 1 and 2) shows how to combine multiple composite molded bodies in parallel and pressurize them in the axial direction of the cylinder, or by stacking the entire body on opposing flat metal plates for impact pressure. The formwork is shown loaded (FIGS. 3 and 4) and the explosives 18 and 45 are placed.

In FIGS. 1 and 2, the powder compacts 11 and 12 are made into various compositions depending on the purpose and are housed in a cylindrical metal container (implosion processing container) 16, and the whole is further loaded into an explosive container 17. The surrounding area is filled with explosives 18. As the mixed powder for forming the reinforcing support material, it is possible to use, for example, powders of WC--Co cemented carbide and various other cermet raw materials. Note that both FIGS. 1 and 2 are shown as cross-sectional views taken along the cylindrical axis of the container.

As shown in the partial detail drawing, both molded bodies 11 and 12 were stacked and housed in a metal implosion container 16 as a set of composite molded bodies, and were simultaneously compressed and sintered to firmly join them. It is extracted as a single piece (composite material). Composite molded bodies can be compressed and sintered individually, but it is especially possible to mass-produce them by arranging multiple bodies side by side in an implosion processing container and processing them at the same time, as shown in Figure 1. .

Note that when housing the composite molded bodies 11 and 12 in a metal container, there is a risk of mutual interference between the composite molded body and the wall of the container 16, and also between adjacent composite molded bodies when processing multiple composite molded bodies at the same time. For the purpose of preventing joining, it is effective to arrange plate-like or layer-like separating materials 20 and 21, respectively. As the material of the separating material, heat-resistant materials that are not sintered in the operation of the present invention can be used, such as graphite, hexagonal boron nitride, and ceramic powder.

Metal stoppers 22 and 23 are placed at both ends of the metal container 16 to seal the contents. Furthermore, cushioning materials 24 and 25 are arranged inside these plugs in order to suppress the influence of the metal plug material on the contents during impact pressurization, but these are the same as the separating materials 20 and 21 described above. It can be made of any material.

The metal container 16 containing the composite molded bodies 11 and 12 is further loaded into an explosive container 17 made of metal, plastic, paper, etc. for implosion processing, and the surrounding area is filled with an explosive 18. All kinds and grades of explosives, such as dynamite, ANFO (ammonium nitrate oil explosive), and compound explosives, are selected and used as appropriate depending on the required pressure. An electric detonator 26 for detonation is connected to the explosive container 17, and a vacuum pipe 27 is connected to exhaust the inside of the implosion processing container.

3 and 4, as another embodiment of the present invention, a large-area flat metal formwork 31 is used, and a large number of cylindrical starting material accommodation holes 32 provided in the formwork are filled with the above-mentioned A configuration example for simultaneously producing a large amount of three-dimensional sintered bodies by filling and holding a starting material 33 and a powder molded body 34 of a supporting material raw material as a stacked composite molded body is shown as a longitudinal cross-sectional view and a plan cross-sectional view, respectively. .

Each composite molded body has pressurizing metal disks 35, 36 with the same diameter as the starting material laminated on its upper and lower surfaces via separation materials 37, 38, and the entire upper and lower surfaces of the formwork 31 are covered with materials to prevent metal-to-metal explosion. It is covered with cushioning material sheets 39 and 40 (made of graphite sheets, for example) that also serve as buffers, and is sandwiched between pressure plates 41 and 42 to form an implosion configuration. The entire bag 43 is placed in an airtight plastic bag 43, and the inside of the bag 43 is sufficiently evacuated via a vacuum pipe 44, and then the pipe 44 is crushed and vacuum-sealed. This is wrapped in explosive 45 and an electric detonator 46 for detonation is attached.

FIG. 5 shows an example of a configuration for manufacturing a lace center as an example of a three-dimensional sintered tool. In a cylindrical implosion processing container 51, a cylindrical part 52 made of a cemented carbide mixed powder and a composite molded body 54 made of a mixed powder containing high-pressure phase BN are placed in a truncated conical part 53 as a lace center material. are held in a mold 55 made of graphite or the like and arranged in series around the axis of the cylindrical container. Both ends of the container are sealed with metal plugs 58 and 59 via rigid cushioning materials 56 and 57 such as alumina.

The method of storing the container 51 in an explosive container (not shown) and imploding in the cylindrical axis direction is the same as in the case of FIG. Although the implosion container has a cylindrical configuration in FIGS. 1, 2, and 5, it can have any shape such as a square, hexagon, or asymmetric shape depending on the object to be compressed.

6 and 7 are diagrams showing configuration examples applicable to the production of a large-area plate-shaped sintered body, and the implosion method and assembly are similar to those in FIGS. 3 and 4, respectively.
A rectangular space cut out in the thickness direction of the metal formwork 61 is filled with a flat plate-shaped starting material 62 and a powder molded body 63 of a support material raw material in an overlapping manner. Further, in the same way as above, pressurizing metal plates 66 and 67 having the same planar dimensions as the starting material are laminated on the upper and lower surfaces of the metal formwork 61 via separation materials 64 and 65, and the upper and lower surfaces of the metal formwork 61 are used to prevent explosions. It is covered with a cushioning material (for example, made of graphite sheet) 68, 69, and impact pressure plates 70, 71 are arranged on the outside.

This structure is stacked in multiple stages (two stages in the figure), the whole is placed in an airtight plastic bag 72, the inside of the bag 72 is sufficiently evacuated via a vacuum pipe 73, and then the pipe 73 is crushed to create a vacuum. Seal. This is sandwiched between explosives 74 and an electric detonator 75 for detonation is attached.

In FIG. 8, a metal plate (flying plate) 83 placed on the bottom surface of the explosive is caused to fly at high speed by the explosion of an explosive 82 housed in a container 81 made of a flexible material such as a paper tube, and a molded powder mixture of starting materials is formed. 84 is made to collide with the metal lid 86 of the metal pedestal 85 containing the metal holder 84 to apply impact pressure. The explosive 82 and the flying plate 83 are supported by a cylinder 87 made of a low-strength material such as paper, and are detonated by an electric detonator 88.
Embodiments of the present invention will be described below with reference to Examples.

A cutting tool material in which a circular high-pressure phase BN sintered body was bonded onto a cemented carbide support material was produced in large quantities using the cylindrical impact pressurization method schematically illustrated in FIG.
The mixed powder of the starting materials was 40% cBN with an average particle size of 5 μm (mass ratio; the same applies hereinafter), 5% wBN with a particle size of 1 μm or less, and titanium carbide TiC1-2 with a particle size of 1 to 2 μm (hereinafter referred to as TiC-Nippon Shinkin Co., Ltd.). ) 28%, titanium nitride TiN-02 (hereinafter referred to as TiN-manufactured by Nippon Shinkinzoku Co., Ltd.) with an average particle size of 2 μm, aluminum powder Super Fine No. 22000 (hereinafter referred to as Al-Daiwa Metal Powder) with a particle size of 44 μm or less 9% (manufactured by Kogyo Co., Ltd.) was weighed out and mixed in a wet ball mill using acetone for 2 hours. After separating the acetone, it was heat-treated in vacuum at 600°C for 2 hours to remove oxygen and other adsorbed gases.

The mixed powder after heat treatment was a weakly bonded mass, so it was crushed in a nitrogen atmosphere and then press-molded in the same nitrogen atmosphere to create a molded product of the mixed powder with an outer diameter of 18.9 mm and a thickness of 1.0 mm. It was made into a disc-shaped pellet. The weight of the molded pellets was 0.9 g on average. This value corresponds to 77% of the theoretical density compared to the pellet mass of 1.169g calculated from the density of the constituent materials.

Separately, as a mixed powder for supporting materials, 95% tungsten carbide powder WC-25 (manufactured by Nippon Shinkinzoku Co., Ltd.) with an average particle size of 2 μm and 5% cobalt powder (manufactured by Freeport Cobalt Oy) with a particle size of 1.0 to 1.5 μm were used. The mixture was mixed in a wet ball mill for 2 hours, dried, and then press-molded to produce a supporting material powder molded body and pellets with an outer diameter of 18.9 mm and a thickness of 3.0 mm.

We prepared 36 sets of cutting tool starting materials made by stacking the above mixed powder pellets and support material pellets, and prepared impact pressure steel pipes (steel pipes for implosion processing) with an outer diameter of 25.0 mm, an inner diameter of 21.0 mm, and a length of 250 mm. Loaded inside. A flexible graphite sheet with a thickness of 1 mm was used as a buffer material to isolate each starting material, and a graphite sheet was also used to isolate the starting material and the steel pipe for implosion processing.

After filling the starting material, both ends of the steel pipe for implosion processing are filled with alumina powder with a grain size of 15 μm as a buffer material, each 10 mm thick, and sealed by press-fitting a steel plug with an outer diameter of 21.1 mm and a thickness of 25 mm. did. However, a copper vacuum pipe with an outer diameter of 10 mm and a wall thickness of 1 mm is brazed through one of the steel plugs, and after the interior of the steel pipe for implosion is sufficiently evacuated, the vacuum pipe is compressed. The crushed cutting tool starting material was vacuum sealed.

Align this steel pipe for implosion with the axial center of a steel pipe explosive container with a length of 300 mm, an outer diameter of 101.6 mm, and an inner diameter of 93.2 mm, align the end of the steel plug on the vacuum pipe side with the end of the explosive container, and fix it. , 1945g of powdered explosive was filled between the implosion steel pipe and the explosive container. The packing density of the explosive was 1.04g/ ^cm3 .

When an electric detonator (26) was placed at the end of the explosive and it was detonated, the explosive exploded at an explosion speed of 2410 m/s. Applying this value to Equation 3) above, the approximate value of the impact pressure force was estimated to be 1.51 GPa.

The outer diameter of the implosion steel pipes recovered after the explosion treatment, excluding the steel plug, had shrunk to an average of 21 mm. The implosion steel pipe containing the contents was heated to 1300°C in a heating furnace, held for 2 hours, slowly cooled for 1 hour, and the contents were removed by turning using a lathe.

The mixed powder pellet (11) containing high-pressure phase BN and the WC-Co supporting material pellet (12) were metallurgically joined, and both appeared to be strong sintered bodies. The Vickers hardness of the surface-polished high-pressure phase BN-containing sintered body was 32.3 GPa. Furthermore, the cemented carbide layer was removed by grinding to form a layer consisting only of the high-pressure phase BN-containing sintered body, and the density was measured by the Archimedes method to find that it was 4.08 g/cm ³ , which was the theoretical density of 4.17 g/cm ³ In comparison, it was 97.8%.

Identification of the high-pressure phase BN-containing sintered layer by X-ray diffraction revealed that in addition to cBN, wBN, TiC, TiN, aluminum nitride (hereinafter referred to as AlN), and titanium diboride (hereinafter referred to as TiB ₂ ), aluminum boride AlB ₂ was also detected. It was recognized that each component particle was firmly bonded by the compound synthesized by heat treatment.

The ratio of the measured density to the theoretical density is not necessarily an appropriate value because the value used as the theoretical density is the value in the raw material state before treatment, and there is a composition change due to a chemical reaction after treatment. However, since it is virtually impossible to know the amounts of each, it is unavoidable that they be determined from the composition before treatment.

The recovered high-pressure phase BN sintered body was bonded to a cemented carbide support material, and both sides of the circular cutting tool material were smoothed by grinding and adjusted to a thickness of 2.5 mm, with an apex angle of 90°. A triangular chip with two sides of 4 mm was cut out, and a cutting test was conducted using a SNGN120404-shaped indexable chip with silver soldering applied to one corner of the pedestal. When SKD61 heat-treated H _RC 61 was prepared as the work material and cut for 30 minutes at a depth of cut of 0.5 mm, feed rate of 0.1 mm/rev, and circumferential speed of 182 m/min, the amount of flank wear was 0.23 mm.

For comparison, a commercially available cBN sintered body with a similar composition was processed into an indexable insert of the same shape and a cutting test was conducted under the same conditions, and the amount of flank wear caused by cutting for the same time was 0.26 mm. It was proved that the performance of the sintered body according to the present invention is comparable to that of a cBN sintered body sintered in a conventional static high-pressure/high-temperature apparatus.

A cutting tool material was manufactured using the planar impact pressure method shown in FIGS. 3 and 4. The mixed powder and the mixed powder molded bodies (pellets) for the supporting material were made of the same materials as those prepared in Example 1, and were molded into a disk shape with a diameter of 18.9 mm. The mixed powder molded body was further press-molded to a thickness of 1.0 mm and a theoretical density ratio of 72%, and this was combined with a cemented carbide molded body for supporting material of the same diameter and a thickness of 4.0 mm and a theoretical density ratio of 73%, as shown in the figure. A number of composite molded bodies with the configuration shown were produced.

A plurality of through holes were provided in the metal formwork, the composite molded body was loaded into these holes, and mild steel plugs for pressurization were placed above and below the through holes. Furthermore, a graphite sheet with a thickness of 0.5 mm is placed on the outside as a separation material made of a material that does not sinter under the explosive bonding working conditions according to the present invention, and the processed composite molded body is joined to a metal plate for pressurization. The impact on the composite molded body during processing was alleviated.

The above elements were placed together in an airtight plastic bag with explosives placed around it. An exhaust pipe was connected to the plastic bag to evacuate the inside.

The metal formwork was made of a rectangular steel plate measuring 224 mm long, 116 mm wide, and 8 mm thick, with through holes 20 mm in diameter arranged in 4 columns x 8 rows at 7 mm intervals. A graphite sheet with a thickness of 0.5 mm is wrapped around the inner wall of each through-hole, and mixed powder pellets of sintered material and pellets for supporting material are stacked and loaded, and the graphite sheets with a thickness of 2 mm are placed above and below through the graphite sheets with a thickness of 0.5 mm. , plugged with a mild steel plug of the same diameter. The top and bottom of the metal formwork in which the starting materials, etc. were charged were covered with graphite sheet separators with the same planar dimensions and a thickness of 1 mm, and mild steel plates for impact pressure with the same planar dimensions and a thickness of 1 mm were placed on the upper and lower surfaces. The whole was sealed in an airtight plastic bag and evacuated via a vacuum pipe.

The upper and lower surfaces of the above assembly were covered with colloidal dynamite 10 mm thick, and detonated from one end with an electric detonator. Since the explosive detonated at 3200 m/s and had a density before detonation of 1.15 g/cm ³ , applying the values to Equation 3, the approximate value of the explosion pressure was equivalent to 2.94 GPa. The above combination after the explosion treatment was heat treated in the same manner as in Example 1, except that the treatment temperature was 1320 ° C. and the material after the impact treatment was not airtight, so it was treated in a vacuum furnace. A sintered body of the tool material bonded to the supporting material of the cemented carbide layer was obtained.

The Vickers hardness of the polished surface of the high-pressure phase BN layer of the obtained sintered body was 31.6 GPa. Next, the cemented carbide layer was removed by polishing to form a layer consisting only of cBN, etc., and the density was measured by the Archimedes method, and it was 3.88 g/cm ³ , which was 93.0% of the theoretical density of 4.17 g/cm ³ . Ta.

When a cutting tool similar to that produced in Example 1 was prepared and a similar cutting test was conducted, the flank wear after 30 minutes of cutting was 0.29 mm, which was found to be sufficiently practical. Furthermore, it was observed that the composition after sintering was the same as in Example 1.

The lace center member shown in FIG. 5 was manufactured from a cBN-containing sintered body. The graphite mold that accommodates the starting material has an outer diameter of 25.5 mm and a length of 30 mm, with a cylindrical portion having a diameter of 20 mm and a length of 13 mm, a truncated conical portion having a length of 14 mm, and a flat tip portion having a diameter of 6 mm. , the inclination angle was 60°, and the truncated cone portion on which the load was applied was made of a cBN-based material, and the cylindrical portion of the support member was made of a WC-based material.

The mixed powder (53) of cBN-based materials is composed of cBN with an average particle size of 10 μm: 50, cBN with an average particle size of 3 μm: 8, TiB ₂ with an average particle size of 5 μm: 15, TiC _0.7 with an average particle size of 3 μm: 13. Al: 9 with a particle size of 44 μm or less and Si: 5 with a particle size of 10 μm or less were mixed in a wet ball mill for 2 hours and vacuum dried at 600° C. for 2 hours. The mixed powder (52) of the material for the cylindrical part of the support material was prepared by mixing 95% by mass of WC powder and 5% by mass of Co powder in a wet ball mill for 2 hours, and vacuum drying at 600° C. for 2 hours.

While protecting the graphite mold with a reinforcing mold, 5.4 g of mixed powder of cBN material was tamped and filled into the truncated conical part of the mold, and then 45 g of WC material was filled to achieve a theoretical density of 71 to 72. %.

The steel pipe for implosion processing had an outer diameter of 30.0 mm, an inner diameter of 26.0 mm, and a length of 250 mm, and six molded products were arranged in series around the axis of the steel pipe. A 9 mm alumina layer was sandwiched between both ends and the tube was sealed with a steel plug, exhaust was evacuated via a vacuum-drawn copper tube, and the inside of the steel tube was vacuum-sealed. The bottom of the cylindrical portion in contact with the alumina layer was partitioned with a 1.6 mm thick mild steel plate via a 0.5 mm graphite sheet.

This implosion steel tube was placed at the center of an explosive tube with an outer diameter of 120 mm and a length of 330 mm, which was housed in a paper tube. The explosive was in powder form, and when detonated from one end, it exploded at an explosion speed of 2,340 m/s. The packing density was 0.92 g/cm ³ , and when the values were applied to equation 3), the estimated explosion pressure corresponded to 1.26 GPa.

The outer diameter of the metal tubes recovered after the explosion treatment, excluding the steel plugs, had shrunk to an average of 25 mm. The metal tube containing the contents was heated to 1350°C in a heating furnace, held for 2 hours, slowly cooled for 1 hour, and the implosion steel tube was removed by lathe turning.

The retrieved sintered product was a dense product with a diameter of approximately 15 mm, a total length of approximately 26 mm, and a theoretical density of approximately 96%, and was able to be used for practical use by lightly modifying the outer periphery with a diamond grindstone.

A flat plate-shaped sintered body was manufactured with the configuration shown in Figure 6. The composition of the mixed powder molded body is cBN: 65, wBN: 10, Al: 5, Hf: 10, Ti: 5, SiC: 5 in mass %, and powders with an average particle size of 10 μm or less are used in each case. there was. This was press-molded to an average thickness of 0.9 mm, width of 39 mm, and length of 79 mm to obtain a mixed powder molded body with a packing density of 75% of the theoretical density. The powder molded body of the supporting material superimposed on the mixed powder molded body had a composition of 95.5% WC-4.5% Co, had a thickness of 4.5 mm, and had a packing density of 70% of the theoretical density.

The metal formwork for impact pressure is 55 mm wide, 90 mm long, and 10 mm thick, and the above mixed powder molded body and WC-Co powder are placed in the cutout part of 40 mm wide and 80 mm long inside. The molded bodies were stacked and stored, and a 2 mm mild steel plate was fitted as a backing plate with graphite sheets of the same size and 0.5 mm thick interposed above and below. Graphite sheets (68) with a thickness of 3 mm and the same dimensions as the formwork were placed above and below this patch plate, and sandwiched between 3.2 mm thick mild steel plates for impact pressure. A graphite sheet with a thickness of 0.5 mm was placed between the metal mold and the mixed powder molded body.

Two sets of assemblies configured as described above were prepared and stacked, and the whole was housed in a plastic bag, which was evacuated via the vacuum pipe (73), and the inside of the bag was vacuum-sealed.

Colloidal dynamite with a thickness of 25 mm was placed on the top and bottom of the above structure, and detonated with an electric detonator from one end. The explosion velocity at that time was 4100 m/sec, the density of the explosive was 1.38 g/cm ³ , and the generated pressure was estimated to be 5.8 GPa from equation 3). The high-pressure phase BN-containing layer and the WC-Co layer were each housed in a mold and collected with their upper and lower surfaces sandwiched between mild steel plates.

The recovered material from the implosion process was heated in this state to 1380°C in a vacuum furnace for 3 hours, allowed to cool, and taken out at below 100°C. When the mild steel plate sandwiching the high-pressure phase BN-containing layer and the WC-Co layer from both sides was removed by grinding, both layers were firmly bonded, and observation of the cut surface revealed slight undulations between the two layers. Ta. As a result of flattening the recovered bonded plate by grinding, the thickness of the high-pressure phase BN-containing layer was 0.6 to 0.7 mm, and the thickness of the cemented carbide layer was 3.0 to 3.5 mm. On the other hand, the planar dimensions were 41 mm in width and 82 mm in length after removing the missing parts on the periphery.

A cutting chip material of a desired shape and size could be cut out from this bonded plate by wire cutting.

The micro-Vickers hardness of the high-pressure phase BN-containing layer was measured at 10 points each at the center and the periphery and fell within the range of 36 to 37 GPa, confirming that there is no problem in practical use.
Furthermore, the presence of cBN, wBN, AlN, HfN, TiB ₂ , TiN, AlB ₂ and SiC was confirmed by X-ray diffraction.

Furthermore, when a triangular chip similar to that in Example 1 was cut out using the method described in paragraph 0054 and a similar cutting test was performed, similar results were obtained. It was found that a similar sintered body could be made.

With the configuration shown in FIG. 8 using a metal flying object, the held mixed powder molded body was subjected to impact pressure treatment to produce a sintered body.
In the figure, the powder explosive had a packing density of 1.08 g/cm ³ and was detonated via an electric detonator. The mixed powder of the starting material (84) has a mass ratio of cBN with an average particle size of 5 μm: 32%, HfC with an average particle size of 6 μm: 29%, ZrN with an average particle size of 1.5 μm: 29%, and Ti with an average particle size of 13 μm. : 6%, Si: 4% with an average particle size of 0.5 μm. 14 g of powdered explosive (82) was packed in a paper cylinder with an inner diameter of 20 mm and a height of 40 mm. A recess with a depth of 8 mm and a diameter of 20 mm is provided in the center of a steel pedestal with a diameter of 30 mm and a height of 13 mm, and a 0.5 mm thick graphite sheet is placed on the inner wall and bottom to accommodate a molded body with a diameter of 18.9 mm inside. It was filled with molded pellets of mixed powder with a thickness of 6 mm. A copper disk with a thickness of 2 mm and a diameter of 20 mm was placed on the bottom of the paper cylindrical container and on the top of the molded body storage cavity to cover it. A paper cylinder was placed between the steel pedestal and the explosive cylinder to support it at a distance of 10mm in height, ensuring the distance that the copper plate would fly in the event of an explosion.

In the above configuration, the powder explosive (82) was detonated by the electric detonator (88), and the copper disk (83) was caused to collide with the copper disk (86) covering the pellet (84) at a speed of 420 m/s. The pressure generated by the collision was calculated using equations 4), 1), and 6), and was estimated to be 7.98 GPa. The part covered by the copper disk (86) had sunk into the recess of the steel pedestal due to the impact pressure.

In that state, it was heated to 1350° C. in a nitrogen atmosphere, held for 2 and a half hours, slowly cooled in a furnace, and taken out, and the sintered mixture was taken out by turning. Approximately 2 mm from the outer periphery of the mixture had a low degree of compression, so it was removed by grinding, and the top and bottom surfaces were also smoothed to obtain a strong sintered body with a diameter of 16 mm and a thickness of 4 mm.

The Vickers hardness of the sintered body was 30 GPa as the average value of 8 measurements. Diffraction lines of cBN, HfC, ZrN, TiB ₂ , TiN, and Si ₃ N ₄ were observed by X-ray diffraction.

A cutting tool similar to that in Example 1 was manufactured, and when cutting SNCM439 steel tempered to H _RC 48 for 30 minutes at a cutting depth of 0.5 mm, feed rate of 0.1 mm/rev, and circumferential speed of 189 m/min, the amount of flank wear was 0.24 mm. Met.

When a cutting test was conducted under the same conditions using a commercially available cBN indexable insert with the same composition and shape for comparison, the amount of flank wear that occurred was 0.23 mm, and the performance of the sintered body according to the present invention was as follows. It has been proven that the cBN sintered body is comparable to that of a cBN sintered body sintered using a conventional static high-pressure apparatus.

The compositions and hardness of sintered bodies prepared by molding mixtures of various compositions shown in Table 1 into pellets with a diameter of 18.9 mm and a thickness of 6 mm using the same pressing method as in Example 5 are shown below. All of the sintered bodies showed cutting performance suitable for practical use in a cutting test conducted in the same manner as in Example 1.

11 High-pressure phase BN-containing mixed powder molding 12 Powder molding of supporting material raw material 16 Metal container/implosion processed container 17 Explosive container 18 Explosive 20 Separation material 21 Separation material 22 Metal plug 23 Metal plug 24 Cushioning material 25 Cushioning material 26 Electric detonator for detonation 27 Vacuum drawing pipe 31 Metal formwork 32 Starting material accommodation hole 33 Starting material powder molded body 34 Supporting material raw powder molded body 35 Metal disc for pressurization 36 Metal disc for pressurization 37 Separation material 38 Separation material 39 Cushioning material sheet 40 Cushioning material sheet 41 Pressure plate 42 Pressure plate 43 Plastic bag 44 Vacuum pipe 45 Explosive 46 Electric detonator 51 Implosion processed container 52 Cylindrical portion 53 truncated conical tip portion 54 Composite molded body 55 Molding mold 56 Rigid cushioning material 57 Rigid cushioning material 61 Metal formwork 62 Flat plate-like starting material 63 Powder molding of support material raw material 64 Separation material 65 Separation material 66 Pressure metal plate 67 Pressure metal plate 68 Explosion prevention and buffering Material 69 Explosion prevention and cushioning material 70 Impact pressure plate 71 Impact pressure plate 72 Plastic bag 73 Vacuum pipe 74 Explosive 75 Electric detonator 81 Container 82 Explosive 83 Metal plate (flying plate)
84 Mixed powder molded body 85 Metal pedestal 86 Metal lid 87 Cylindrical body 88 Electric detonator

Claims (14)

(1) Explosing a starting material consisting of a mixed powder of high-pressure phase boron nitride particles in a mass ratio of 30 to 90% of the total, and the remainder being a powder of a binder-forming metal capable of forming borides and/or nitrides. Enclosed in a shrink container,
(2) subjecting the container to impact ultra-high pressure to make the entire starting material have a density of 90% or more of the theoretical density;
(3) Next, by holding the heating temperature and heat-treating, the high-pressure phase boron nitride particles, including particles with newly generated surfaces due to impact pressure, are mutually bonded to metal nitrides and/or metal nitrides generated in situ during the heat treatment. Or a method for producing a high-toughness high-pressure phase boron nitride solidified body, which is bonded and integrated via a metal boride. 2. The method of claim 1, wherein the starting material further contains one or more preformed binder-forming metal species selected from borides, nitrides, carbides, and oxides. 3. The method according to claim 2 , wherein the binder-forming metal species includes one or more selected from Al, Si, Ti, Zr, and Hf. The method according to claim 1 , wherein the impact ultra-high pressure is 1 GPa or more. 2. The implosion container is axially elongated and cylindrical, and the starting material is radially and axially pressurized by the detonation (explosion) of an explosive disposed along the outer periphery of the container . The method described in. 2. The method of claim 1 , wherein the implosion vessel has a circular or polygonal cross section perpendicular to its axis. The starting material is stored (loaded) in an implosion processing container, sandwiched or enclosed between a pair of opposing flat plates, and the starting material is impact-compressed by detonating an explosive on the back side of one or both of the flat plates. A method for producing a high-pressure phase boron nitride sintered body according to claim 1 . Claim 1 : Starting materials are stored (loaded) in a plurality of implosion processing containers, stacked and sandwiched between a pair of opposing flat plates, and explosives are detonated on the back of the flat plates to shock-compress the starting materials. The method described in. Claim 1 : A pressure-resistant plate-like body is arranged on the axis of the implosion processing container, and the starting material is pressurized by moving the plate-like body in the axial direction at high speed by detonation (explosion) of explosives. The method described in. 2. The method according to claim 1 , wherein the starting material is a (powder) shaped body, the cross-section perpendicular to the axial direction of the shaped body varying along the axis. The method according to claim 1 , wherein the heating temperature is 800°C or more and 1800°C or less. The method according to claim 1 , wherein the heating temperature is 1000°C or more and 1500°C or less. 2. The method of claim 1 , wherein the starting material is placed in a container adjacent to the shaped support stock and the two are bonded together by impact loading from an explosive explosion. 14. The method according to claim 13, wherein the supporting material raw material is a mixed powder compact having a cemented carbide composition.

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