JPH0693995B2 - Diamond abrasive grain manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing diamond abrasive grains by an impact compression method, and more specifically, as an abrasive grain for a grinding wheel or an abrasive grain for polishing work. The present invention relates to a method for inexpensively producing polycrystalline diamond abrasive grains having excellent particle strength.

[Prior Art] Conventionally, this kind of thing is as follows.

Among the known materials, diamond, which has the highest hardness, has been widely used as abrasive grains for grinding wheels, lapping, and polishing grains because of its excellent wear resistance.

In addition to the recent introduction of new industrial materials and the establishment of processing methods for them, even in conventional materials, there are many demands for high-precision and high-efficiency processing, and there are more and more processing fields where diamond processing is inevitable. It tends to increase.

Conventionally, most of diamond abrasive grains have been synthesized by a static ultra-high pressure method using a solvent having a contact action.

The diamond particles synthesized by this method are single crystals, and diamond abrasive grains of various sizes and grades have been synthesized and are commercially available by controlling the type of solvent, synthesis pressure, and temperature conditions during synthesis.

On the other hand, as another diamond synthesis method, there is a dynamic ultrahigh pressure method, that is, a shock compression method using a shock wave.

In this method, generally, a small amount of carbon raw material powder is mixed with metal powder and shock-compressed to synthesize diamond powder.

The metal powder used here has no catalytic action, and has the effect of increasing the impact pressure at the carbon raw material powder part in the mixture and the effect of a refrigerant body that enables rapid cooling after converting to diamond. ing.

Diamond synthesized by this method is a fine polycrystalline powder, which is commercially available and used mainly as abrasive grains for lapping and polishing.

[Problems to be Solved by the Invention] The conventional techniques described above have the following problems.

With the introduction of new materials such as ceramics and composite materials and the enhancement of the functionality of materials, not only the demand for improving the machining efficiency of grinding and polishing, but also the demand for better machined surface properties has increased. There is.

Not only the roughness of the machined surface, but also the degree of damage such as strain and microcracks remaining on the machined surface is of great interest to the surface texture here.

Generally, in the grinding process using a grindstone using diamond abrasive grains, the larger the abrasive grains used, the better the grinding efficiency and life, but the worse the finished surface condition. On the contrary, when fine abrasive grains are used, the finished surface condition is improved, but the machining efficiency is significantly reduced.

The single crystal diamond powder synthesized by the static ultra-high pressure method is easily cleaved into particles having sharp corners due to the cleavage property peculiar to diamond crystals, and also large particles are easily obtained.

Therefore, such single crystal diamond particles are
Exhibits high processing performance as abrasive grains. But,
On the other hand, since sharp corners are constantly formed and bite into the processed material to remove the material, there is a drawback that damage to the processed surface becomes large.

On the other hand, when fine single crystal diamond particles are used, the damage given to the processed surface is small as described above and the finishing surface accuracy is improved, but there is a problem that the processing efficiency is remarkably reduced as compared with the case of large particles. .

In order to solve the problems with such conventional single crystal particles, a method of using agglomerated abrasive grains prepared by once solidifying fine single crystal diamond particles using a metal as a binder, instead of large single crystal particles, and Similarly, there has been proposed a method of using diamond sintered particles made by pulverizing again a sintered body obtained by adding a minute amount of a metal component to fine single crystal diamond particles and performing ultra-high pressure sintering.

As examples of the former, Japanese Patent Publication No. 56-190 and Japanese Patent Laid-Open No. 58-51076 disclose an example of a method of solidifying fine single crystal diamond particles with a metal component such as Cu containing Ti.

Further, as examples of the latter, JP-A-59-152065 and JP-B-60
-54909 and JP-B-61-9245, there are disclosed examples of sintered diamond abrasive grains obtained by using an ultrahigh pressure apparatus.

However, the particle strength of the abrasive grains obtained by the former method is not sufficiently high, and there is a problem that the material removing ability is poor in grinding or polishing a high-strength ceramic material or composite material.

This is probably because this method uses a large amount of metal components and is not a diamond thermodynamically stable production.

On the other hand, the latter sintered abrasive grains, the amount of the metal component contained is small, and since it was sintered under the stable conditions of diamond, it has a sufficiently high particle strength, In the processing of high-strength materials as described above, while exhibiting a grinding efficiency comparable to the case of using single crystal diamond abrasive grains of the same size, it is possible to obtain excellent processed surface properties more than in the case of single crystal abrasive grains. .

However, in order to manufacture the sintered abrasive grains, fine diamond powder once synthesized and purified using an ultra-high pressure apparatus is sintered again using the ultra-high pressure apparatus, and the sintered body is further Since it has to be crushed and classified, and its manufacturing process requires a process twice or more as long as a normal diamond abrasive grain manufacturing process, there has been a problem that its manufacturing cost becomes extremely high.

The diamond powder obtained by subjecting the metal and carbon raw materials to the impact treatment is a polycrystalline powder as described above. However, the duration of impact compression is generally extremely short, 10-6-10-5, and it has been difficult to obtain large-sized polycrystalline diamond particles having a large particle strength during this period by the conventional method. Also,
In the X-ray diffraction of the diamond powder synthesized by the impact compression method which is currently commercially available, the intensity of the diffraction line is low, but the diffraction line indicating the presence of graphite is always around 26.5 ° at the diffraction angle 2θ with respect to the Cu Ka line. appear.

It is considered that such a graphite component is present in the grain boundaries of the fine particles constituting each polycrystalline diamond, and causes the strength of the polycrystalline particles to be reduced.

The present invention has been made in view of the above circumstances, large-sized polycrystalline diamond particles, excellent grinding as abrasive grains, while utilizing the polishing performance, the drawbacks of the conventional manufacturing method as described above It is an object of the present invention to provide an improved diamond abrasive grain and a production method capable of inexpensively producing a polycrystalline diamond powder having an excellent particle strength suitable as an abrasive grain for a grinding wheel or polishing work. .

[Means for Solving the Problem] The present inventors have conventionally studied the synthesis of diamond powder by the impact compression method. In the process,
We also obtained some important findings regarding the type of carbon raw material powder in the starting material, the pressure and temperature conditions used in the synthesis, and the correlation between the characteristics of the synthesized diamond particles.

The present inventors, in order to solve the above problems, based on those findings, aim at the development of a method of synthesizing a polycrystalline diamond abrasive grains having a large grain and excellent grain strength by a simpler device and method. I have earnestly studied.

As a result, first, the starting raw material consisting of the metal and the graphite raw material powder is oriented in a certain crystal axis direction by utilizing the unique crystal habit of the graphite raw material powder particles to prepare the starting raw material. After creating, the sample material for impact treatment of this starting material is adjusted and filled so that the ratio of pores in the sample container, that is, the porosity is 15 to 50%, and the oriented graphite By shock-compressing the starting material at a pressure of 20 GPa or more using a shock wave propagating in the c-axis direction of the raw material powder particles, the conversion rate to diamond can be increased,
It has been found that a large-sized polycrystalline diamond powder having a large particle strength can be obtained, and the present invention has been completed.

That is, the present invention provides a method for producing diamond abrasive grains by shock-compressing a starting material composed of a metal and a graphite raw material powder using a shock wave generated by the explosion of explosives or the collision of a high-velocity projectile. The graphite raw material powder inside is oriented in a certain crystal axis direction, and the shock wave propagating in the c-axis direction of the oriented graphite raw material powder particles causes 20 GPa.
Provided is a method for producing diamond abrasive grains, characterized in that the starting material is shock-compressed under the above pressure.

In this case, the graphite raw material powder may be a graphite raw material powder composed of scaly or plate-like particles having a particle size of 0.1 μm to 1 mm, and the starting raw material is oriented in at least one surface in a certain direction. Thickness of the deposited graphite raw material powder 0.01
A starting material having a structure in which metal plates of mm to 2 mm are stacked in a certain direction and / or a structure in which the metal plates are spirally or concentrically wound can also be used.

[Operation] The effect will be described.

Embodiments of the Invention Embodiments will be described with reference to the drawings.

In the method for producing diamond abrasive grains according to the present invention,
The starting raw material is composed of metal and graphite raw material powder, and the graphite raw material powder particles are oriented in a certain crystal axis direction in the metal component.

As a method for orienting the graphite raw material powder in a certain crystal axis direction, for example, the following method can be used.

1) Using scaly or plate-shaped metal powder, uniformly synthesizing this into graphite raw material powder, and then putting it into a molding die, filling and pressurizing it while giving a small vibration from above and below to orient the graphite raw material powder particles. .

2) Similarly, a flaky or plate-shaped metal powder is used, and this is uniformly mixed with the graphite raw material powder, and then ethanol is further added to form a slurry.

The graphite raw material powder particles are oriented by placing this in a mold for molding, allowing it to stand and drying, and then, after drying, pressure-molding as necessary.

3) A solvent such as ethanol is added to the graphite raw material powder to form a slurry, which is applied to one or both surfaces of a metal plate and dried to orient the graphite raw material powder particles in a certain direction.

Next, a starting material in which graphite raw material powder particles are oriented in a certain direction can be obtained by stacking the metal plates in a certain direction or by winding the metal plates in a spiral and / or concentric manner.

In the method according to the present invention, good crystallinity as the graphite raw material powder, a well-developed powder having a layered structure is suitable, in particular,
When the flaky or tabular graphite raw material powder having a particle size of 0.1 μm to 1 mm is used, the orientation operation of the graphite raw material powder particles in the starting raw material becomes easy, and the orientation rate can be increased, and as a result, It is desirable because the conversion rate to diamond can be increased and a strong and coarse-grained polycrystalline diamond powder can be obtained.

Further, as the graphite raw material powder, carbon having an amorphous and / or turbostratic structure that does not hinder the orientation of the graphite raw material powder particles in the metal component and does not impair the particle strength of the diamond to be synthesized. Graphite raw material powders containing and graphite can be used.

The reason why a powder having good crystallinity and a well-developed layered structure is suitable as the graphite raw material powder for the purpose of obtaining large-sized polycrystalline diamond particles is considered as follows.

The transition from graphite to diamond due to impact compression is not a so-called diffusion type transition in which the constituent atoms of graphite are once disassembled and then rearranged into the structure of diamond, but the constituent atoms of graphite are displaced slightly relative to each other. It is considered to be a non-diffusion type transition that becomes a diamond structure, that is, a martensite type transition.

This is consistent with the fact that in the synthesis of diamond under conditions of low impact temperature, the use of graphite powder having a regular crystal structure as a starting material results in a high conversion rate to diamond. Further, in the method according to the present invention, graphite having good crystallinity is oriented in a certain direction and shock-compressed by the shock wave propagating in the c-axis direction, but this method may further increase the conversion rate to diamond. I found it. A high conversion rate to diamond is a necessary condition for obtaining large diamond particles.

On the other hand, the above-mentioned martensite type transition generally occurs at a very high speed, and particularly in the case of shock compression, the shock wave rises, that is, in the shock wave front, strong uniaxial pressure causes hydrostatic stress. It is considered that extremely fast shear deformation to bring into a state occurs, and the high-speed movement of atoms accompanying this deformation enables a high-speed transition from graphite to diamond.

Therefore, immediately after passing through the shock wave surface, a large number of diamond fine particles having a uniform crystal orientation were generated in the first graphite raw material powder particles, and the sintering reaction between these diamond fine particles took 10-6 hours. Although it is as short as a second, it is considered to occur during impact compression when the thermodynamic stability condition of diamond is satisfied. In the method according to the present invention, a graphite raw material powder particles are used as a starting material, which are oriented in a certain direction, and are transformed within individual graphite raw material powder particles during impact compression,
It is considered that not only between the generated diamond fine particles but also between the diamond particles in a larger unit was sintered, and as a result, large diamond particles were obtained.

On the other hand, the metal component in the starting material has the effect of increasing the pressure generated in the graphite raw material powder particle portion as described above and the effect of immediately quenching the generated diamond immediately after passing the shock wave to prevent the diamond from being converted back into graphite. To have.

As this metal component, a metal that does not react with carbon to form a stable carbide, for example, copper, nickel, cobalt, tin, or the like can be used. However, in terms of cost and the purification step of diamond after synthesis, Considering it, copper is suitable.

Further, in the method according to the present invention, it is possible to use powders of the above metal components, in particular, of these metals, thickness 0.
The method of applying a graphite raw material powder by the method 3) above using a plate of 01 mm to 2 mm improves the orientation of the graphite raw material powder particles, and also has an excellent rapid cooling effect on diamond, which is desirable. Is the way.

The proportion of the graphite raw material powder in the starting raw material is 5 to 60% by volume, preferably 10 to 40% by volume. When the proportion of the graphite raw material powder is less than 5%, the impact pressure required for diamond synthesis can be lowered, and the diamond synthesis is facilitated, but the yield of diamond per one time is significantly reduced, resulting in high manufacturing cost. It is not preferable.

On the other hand, when the graphite raw material powder exceeds 60%, the impact pressure required for diamond synthesis increases,
Not only is it unfavorable in manufacturing, but the quenching effect due to the metal component cannot be expected, and as a result, the quality of the diamond particles and the yield are lowered due to the reverse conversion, which is not preferable.

The porosity in the starting material is 50% or less, preferably 35%.
% Or less. When the porosity is 50% or more, the temperature immediately after passing the shock wave becomes too high and the diamond is converted back into graphite, so the yield of diamond decreases and the strength of the obtained diamond particles also decreases. , Not preferable.

FIG. 1 shows an example of a plane impact compression apparatus that can be used in the method for producing diamond abrasive grains of the present invention.

In the device of this example, the detonator 1 and the sheet explosive from above
2a, 2b, metal plates 3a, 3b, explosive container 5, explosive system consisting of main explosive 4 and drive plate 6, sample part consisting of container holder 8 accommodating sample container 10 for filling starting material and collection of sample container 10 Side Momentum Trap 7 to facilitate
And lower momentum ton wrap 9.

FIG. 2 shows a cross section of the sample container 10, the sample container body.
10a, starting material 11, spacer 10b and screw 10c.

The starting raw material composed of the metal component and the graphite raw material powder prepared by the above-mentioned method is placed at the position of the starting raw material 11 in the sample container 10 shown in FIG. Are filled so that the orientation plane of the sample is vertical, that is, the axial direction of the sample container and the c-axis direction of the graphite raw material particles are parallel to each other, spacers 10b are arranged, and fixed with screws 10c.

This sample container 10 is placed in the container holder 8 shown in FIG. 1, and the side momentum trap 7 is installed on the outer side thereof and the lower momentum trap 9 is installed on the lower side thereof. The side momentum trap 7 mainly absorbs momentum in the lateral direction of the sample container, and the lower momentum trap 9 absorbs each momentum in the downward direction of the sample container to facilitate the recovery of the sample after the impact treatment.

The material of the sample container 10 can be selected from a wide range, but an iron-based material is suitable in terms of cost and strength.

The upper part of Fig. 1 is the explosive constituent part of this shock compression device, and the detonation initiated by the detonator 1 is transmitted to the sheet explosive 2a having the metal plate 3a inside, and the inside metal is detonated by the progress of this detonation. The plate 3a is blown toward the sheet explosive 2b, linearly collides with the sheet explosive 2b, and detonates it. Here, the point detonation changes to the line detonation.

The sheet explosive 2b has a metal plate 3b under it, and the detonation of the sheet explosive 2b causes the lower metal plate 3b to fly downward,
It collides flatly with the lower explosive 4 and detonates it.

Here, the linear detonation changes to a surface detonation.

Then, the lower drive plate 6 is accelerated to a predetermined speed by the detonation of the main explosive 4, collides with the sample container 10, and a shock wave is generated in the sample container 10.

The shock wave here propagates in the axial direction of the sample container, and the graphite raw material powder in the starting material 11 in the sample container 10 is shock-compressed by the shock wave propagating in the c-axis direction.

The pressure and temperature generated in the starting material part due to the passage of the shock wave can be controlled mainly by the amount of explosive used and the porosity in the starting material, and the duration of the pressure can be controlled by the driving plate as shown in FIG. When the thickness of the iron plate is 3.2 mm, the pressure duration is about 1.5 * 10-6 seconds, which is extremely short.

In the method according to the present invention, an impact pressure of 20 GPa or more is required, but when an iron plate is used as the drive plate 6 and stainless steel is used as the sample container 10, 1.1 Km / s or more is required to obtain a pressure of 20 GPa or more. Drive plate speed is required.

FIG. 3 is a longitudinal sectional view showing an embodiment of a cylindrical impact compression device which can be used in the method of the present invention.

In the figure, reference numeral 17 denotes a cylindrical explosive container, which is composed of an outer cylinder 17a, and an upper plate 17b and a lower plate 17c arranged above and below the outer cylinder 17a.

Reference numeral 14 denotes a cylindrical sample container coaxially located at the center of the cylindrical explosive container 17, and 13 also has a driving chamber provided coaxially with the cylindrical explosive container 17 with a space 15 provided outside the cylindrical sample container 14. It is a tube.

An upper plug 16a and a lower plug 16b are provided above and below the cylindrical sample container 14 and the driving tube 13 for the purpose of positioning them.

Reference numeral 11 is a starting material obtained by orienting the graphite raw material powder using the above-mentioned metal plate. Here, the c-axis of the graphite raw material powder is set to be perpendicular to the central axis direction of the cylindrical sample container. Fill.

1 is a detonator and 12 is explosive.

In this device, first, the explosive 12 is placed at the upper end of the detonator 1
The detonation propagates downward, and the
It accelerates so as to narrow 13 in the central axis direction, and collides with the inner cylindrical sample container 14.

Due to this collision, a shock wave traveling in the direction of the central axis of the cylindrical sample container 14 is generated, propagates through the cylindrical sample container 14 to the starting material 11, and the starting material is shock-compressed.

As a result, the graphite raw material powder particles in the starting raw material are shock-compressed by the shock wave propagating in the c-axis direction.

The impact pressure and temperature generated in the starting material can be controlled by the type and amount of explosive used and the porosity in the starting material.

Here, as the material of the cylindrical explosive container 17, metal, paper, wood,
Although plastic can be used, an iron-based material is suitable as the material for the cylindrical sample container 14 and the drive tube 13 in terms of cost and strength.

Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1 A flaky graphite powder showing a sharp diffraction line in X-ray diffraction and having a well-developed layered structure and a particle size of 5 to 30 μm was used as a graphite raw material powder, and 3 g of ethanol was added to 4 g of this powder to prepare a slurry. After applying this to one side of a copper plate having an outer diameter of 11.9 mm and a thickness of 0.1 mm using a brush and drying it, the starting material 11 of the sample container 10 in FIG. 2 has a porosity of 25%. The sheets were laminated one by one while applying pressure to obtain a starting material for this example.

The volume ratio of graphite raw material powder / metal component in this starting material is 25.
It was / 75. Here, a stainless steel container was used as the sample container 10, and the size into which the starting material was placed was 12 mmφ * 5 mm.

Incidentally, coating on a copper plate, after fixing the cross section of the dried graphite raw material powder with a resin, when observed by an optical microscope and a scanning electron microscope, 90% or more of the graphite particles, the plate-shaped surface of the flaky particles The particles were oriented so as to be parallel to the surface of the copper plate, that is, the particles of the graphite raw material powder were aligned and arranged on the copper plate so that the c-axis of the particles was vertical. The above starting material was subjected to impact treatment using the plane impact compression device shown in FIG.

Here, dynamite with an explosion velocity of 7 Km / s was used as the main explosive 4, and a 3.2 mm thick iron plate was used as the drive plate. The impact velocity of the drive plate to the sample container was 2.2 Km / s, and the impact pressure generated in the starting material at this time was 52 GPa as a result of calculation.

After the impact treatment, the sample container is collected, the stainless steel on the outside of the sample is removed by grinding, and the sample is taken out.
After soaking in a 19% solution for a whole day and night to dissolve copper, the precipitate was collected by filtration.

In addition, lead monoxide was added to remove unconverted graphite.
The graphite was air-oxidized at 450 ° C., the lead oxide was removed by acid treatment, filtered, and dried to obtain a pale gray diamond powder.

The diamond conversion rate calculated from the diamond obtained here was 62%.

When the light gray diamond powder was observed by a scanning electron microscope, it was found that the powder was composed of dense particles of 50 to 100 μm.

As a result of X-ray diffraction of this powder, the diffraction intensity of diamond was high, and no diffraction line due to graphite was observed.

Furthermore, the spread of the width of the diffraction line was extremely small.

The crystallite size calculated from the broadening of the diffraction line width is
It was 280 nm.

Next, the particle strength of the diamond powder obtained by this method was evaluated by a planetary ball mill device and a ball mill method using a cemented carbide pot and a ball. Inner volume
Put 1 g of the obtained diamond powder in a 250 cc pot, add 2 cc of distilled water to it, put 40 balls with a diameter of 10 mm, and after crushing operation for 30 minutes at a rotation speed of 360 rpm, After drying, the sample was collected.

Next, the particle size of the post-treated diamond powder removed by the treatment with the mixed cemented carbide component acid was examined by a scanning electron microscope.

As a result, the diamond grain size is 50-100 μm to 45-9
It was only slightly changed to 0 μm.

(Comparative Example 1) The same graphite as in Example 1 was used as a graphite raw material powder, and a slurry was prepared by using ethanol in the same manner as in Example 1, and the slurry was applied to a copper plate having a thickness of 0.1 mm and a width of 5 mm. ,
The strip-shaped copper plate was dried, rolled into a spiral shape, and filled in the sample container 10 of FIG. 2 so that the porosity of the starting material 11 was 25%, which is the same as in Example 1.

The sample container filled with this starting material was shock-compressed by the same apparatus, method and conditions as in Example 1 to collect the sample.

The volume ratio of graphite raw material powder / metal component in this starting material was 25/75, which was the same as in Example 1.

In the case of this comparative example, the graphite raw material powder particles were shock-compressed by the shock wave propagating in the direction perpendicular to the c-axis direction.

Diamond powder was recovered from the recovered sample container by the same method and procedure as in Example 1. The conversion rate to diamond calculated from the amount of diamond powder obtained is 47%.
Met.

Moreover, the obtained diamond powder had a dark gray color.

When the powder was observed with a scanning electron microscope, it was found that the powder consisted of aggregated fine particles of about 0.1 μm and particles with many gaps of 10 μm or less.

Further, in the X-ray diffraction analysis of this diamond powder, in addition to the diffraction line of diamond, the diffraction line of graphite having a low intensity was recognized.

Furthermore, the size of the crystallite of diamond determined from the broadening of the width of the diffraction line was 25 nm.

Example 2 Plate-shaped graphite having a particle size of 50-100 μm was used as a graphite raw material powder, and scaly copper powder having an average particle size of 50 μm was added to this powder.
80% by volume was added, and the mixture was dry mixed for 12 hours using an iron ball mill to obtain a mixed powder of graphite raw material powder and copper powder.

Put this mixed powder in a 12 mmφ mold, tap it well, fill it with a vibrator using a vibration smaller than the vertical direction, and then press it to 12 mm with a porosity of 30%.
A φ * 5 mm molded body was created.

Observation of the fracture surface of this molded body with a scanning electron microscope revealed that 80% or more of the plate-shaped graphite particles in the molded body had the plate-shaped surface oriented perpendicular to the pressing direction.

The mixed powder is filled in the position of the starting material 11 of the sample container 10 of FIG. 2 at the position of the starting material 11 by the same method as the method of forming the above-mentioned molded body so as to have a porosity of 30%, and pressurized to prepare the starting material of this example. did.

Using the same apparatus and method as in Example 1, the sample container filled with this starting material was subjected to impact treatment at a driving plate speed of 2.5 Km / s.

At this time, the impact pressure generated in the starting material was calculated as 60 GP
It was a.

After the impact treatment, the sample container was recovered, and the diamond powder was recovered by the same method and procedure as in Example 1.

The conversion rate to diamond calculated from the amount of the obtained diamond powder was 57%.

As a result of examining this diamond powder by X-ray diffraction and a scanning electron microscope, it was found that the powder mainly consisted of dense particles of 40 to 120 μm and the crystallite size was 230 nm.

Next, the diamond powder obtained by the method of this example
Using 1 g, the particle strength was evaluated by the same method as in Example 1.

The ball mill time was 30 minutes. As a result, the diamond particles changed only slightly from 40-120 μm to 30-100 μm.

Comparative Example 2 The same graphite as in Example 2 was used as a graphite raw material powder, spherical copper powder having an average particle size of 70 μm was added to this powder so as to be 80% by volume, and dry mixing was performed by the same method as in Example 2. A mixed powder of graphite raw material powder and copper powder was obtained.

This mixed powder was pressed and molded at one time without using small vibrations from above and below using the same 12φ mold as in Example 2, and the fracture surface of the molded body was observed. It was randomly oriented.

The mixed powder was mixed with the sample container 10 shown in FIG.
The starting raw material of this comparative example was obtained by filling the starting raw material 11 in the same position as above with the same method as the molding method of the above-mentioned molded body so as to have a porosity of 30%.

The sample container 10 filled with this starting material was subjected to impact treatment in the same manner as in Example 2 to recover the sample container, and then diamond powder was obtained by the same method and procedure as in Example 1.

The diamond powder obtained had a dark gray color, and the conversion rate to diamond calculated from the amount of this recovered diamond was 48%.

Observation of this diamond powder with a scanning electron microscope revealed that, in addition to fine particles, particles of 10 to 50 μm were included although they were not dense.

Using 1 g of this diamond, the particle strength was evaluated by the same method as in Example 1.

The ball mill time was set to 30 minutes, and the change in the particle size of the diamond particles before and after that was examined. As a result, no particles of 10 μm or more could be observed in the sample after the ball mill.

(Example 3) Particle size 0.5 to 1 consisting of 90% hexagonal graphite and the remaining rhombohedral graphite
Flake-shaped graphite of 0 μm was used as a graphite raw material powder, and 1.5 cc of ethanol was added to 1 g of graphite to make a slurry, which was applied to one surface of a copper plate having a thickness of 0.5 mm and a width of 150 mm and dried. .

This copper plate was spirally wound so as to have an outer diameter of 25 mm, and was used as a starting material of this example.

The volume ratio of graphite raw material powder / copper component in this starting material is 15
It was / 85 and the porosity was 28%.

This starting material was subjected to impact treatment using the cylindrical impact compression device shown in FIG.

Here, the cylindrical sample container 14 and the drive tube 13 were made of iron, and the space 15 between them was 15 mm.

Also, as explosive 12, dynamite with an explosion speed of 6.5 Km / s was used. The collision speed of the drive tube 13 to the cylindrical sample container 14 is 1.9K.
m / s, and the impact pressure generated in the starting material at this time was 42 GPa as a result of calculation.

After the impact treatment, the cylindrical sample container integrated with the drive tube was collected, cut with a lathe, and the sample portion was taken out.

The sample taken out was treated by the same method and procedure as in Example 1 to recover diamond.

The diamond obtained here had a gray color, and the conversion rate to diamond determined from the recovered amount was 54%.

Observation of this diamond powder with a scanning electron microscope revealed that it was mainly composed of dense particles of 30 to 70 μm.

In addition, in the X-ray diffraction analysis, no diffraction line other than diamond was recognized, and the size of the crystallite obtained from the broadening of the width of the diffraction line was 250 nm.

Furthermore, 1 g of this diamond powder was used in Example 1
The particle strength of diamond was evaluated by the same method and conditions as above.

As a result, the diameter of diamond particles is 30-70 μm.
It was only slightly decreased to 25-60 μm.

[Effects of the Invention] Since the present invention is configured as described above, it has the effects described below.

As described above, according to the method of the present invention, a large-sized polycrystalline diamond powder having excellent particle strength can be efficiently synthesized by the impact compression method using a simple apparatus.

The polycrystalline diamond powder obtained by this method exhibits excellent processing performance as an abrasive grain for a grinding wheel for processing ceramics, high-strength materials such as composite materials, and high-performance materials and as abrasive grains for polishing work. It is a thing.

[Brief description of drawings]

FIG. 1 is a perspective view of a plane impact compression apparatus applicable to the method for producing diamond abrasive grains of the present invention, and FIG. 2 is an embodiment of a sample container of the plane impact compression apparatus applicable to the method of producing diamond abrasive grains of the present invention. FIG. 3 is a vertical sectional view showing an embodiment of a cylindrical impact compression device applicable to the method for producing diamond abrasive grains of the present invention. 1 ... Detonator, 2a, 2b ... Sheet explosive, 3a, 3b ... Metal plate, 4 ... Main explosive, 5 ... Explosive container, 6 ... Drive plate, 7 ... Side momentum trap, 8 ... Container Holder, 9 ... Lower momentum trap, 10 ... Sample container, 10a ... Sample container body, 10b ... Spacer, 10c ... Screw, 11 ... Starting material, 12 ... Explosive, 13 ... Drive tube, 14 …… Cylindrical sample container, 15 …… space, 16a …… upper plug, 16b …… lower plug, 17 …… cylindrical explosive container, 17a …… outer cylinder, 17b …… upper plate, 17c …… lower plate.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeru Matsui 1-4-5 Marunouchi, Chiyoda-ku, Tokyo Sumitomo Coal Mining Co., Ltd. (72) Inventor Akira Sawaoka 6-36 Mitakedai, Midori-ku, Yokohama-shi, Kanagawa

Claims (3)

[Claims] 1. A method for producing diamond abrasive grains by shock-compressing a starting material consisting of a metal and a graphite raw material powder by using a shock wave generated by the explosion of explosives or the collision of a high-speed flying object. Characterized in that the graphite raw material powder is orientated in a certain crystal axis direction, and the starting material is shock-compressed at a pressure of 20 GPa or more by a shock wave propagating in the c-axis direction of the oriented graphite material powder particles. Abrasive grain manufacturing method. 2. The method for producing diamond abrasive grains according to claim 1, wherein the graphite raw material powder is composed of flake shaped or plate shaped particles having a particle size of 0.1 μm to 1 mm. 3. The starting material has a structure in which metal plates having a thickness of 0.01 mm to 2 mm in which graphite raw material powders oriented in a certain direction are arranged on at least one surface are stacked in a certain direction and / or the metal plates are spiral or concentric. The method for producing diamond abrasive grains according to claim 1, wherein the method has a structure in which the diamond abrasive grains are wound into a roll.