JP2000343438A - Vitrified grinding wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vitrified grinding wheel providing sufficiently high abrasive grain holding force in spite of the fact that abrasive grains are not deteriorated due to heat. SOLUTION: 25 volume arts of CBN abrasive grains (average particle diameter of 3 to 6 μm), 10 volume parts of carbon quality beads (average particle diameter of 200 μm), 45 volume parts of vitrified binder powders, and 20 volume parts of metallic cobalt particles (average particle diameter of 1 μm) are mixed and stirred, the obtained mixed and stirred material is filled into a mold (dimension of a space part of a recessed part is 40 mm×4 mm×7 mm) made of carbon and is held for two minutes at 600 deg.C and pressure of 300 kgf/cm2 by a resistance sintering machine, and current-carrying, heating, pressurizing, and sintering manufacture is done to obtain a vitrified grinding wheel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vitrified grinding wheel and a method for manufacturing the same, and more particularly, to honing, super finishing of a race surface of a bearing, and PCD polishing.
Vitrified grindstones preferably used when performing grinding without dressing, in particular, vitrified grindstones containing carbonaceous spherical particles in the grindstones, among which CBN (cubic boron nitride, hereinafter the same) The present invention relates to a vitrified superabrasive grindstone using superabrasive grains such as abrasive grains and diamond abrasive grains, and a method for producing the same.

[0002]

2. Description of the Related Art Generally, in superfinishing, a grinding wheel is used in a state in which it is in surface contact with a workpiece. Therefore,
In order to stably obtain a high-precision finished surface, it is important that the grindstone structure is uniform and that clogging or crushing due to surface contact does not occur.

Therefore, a vitrified grindstone which contains pores and is less likely to cause clogging or crushing is used. For example, a porous superfinishing wheel having atmospheric pores in Japanese Patent Publication No. 64-2870, a superabrasive superfinishing wheel containing both diamond abrasive grains and CBN abrasive grains in Japanese Patent Publication No. 6-69669,
Japanese Patent Publication No. 7-16880 discloses a super-finishing whetstone in which the particle size distribution of huge pores is controlled.

[0004]

However, the above-mentioned vitrified superfinishing wheel has the following problems.

[0005] (1) Since it is manufactured by firing at a high temperature, the abrasive grains in the manufactured grindstone have deteriorated the function of the abrasive grains due to thermal deterioration. For example, diamond abrasive grains undergo thermal degradation at about 600 ° C. CBN abrasive grains are thermally degraded at about 900 ° C. Furthermore, the finer the abrasive grains, the greater the thermal degradation compared to coarse grains. Therefore, in order to sufficiently exhibit the characteristics of the abrasive grains, it is ideal to manufacture the grindstone by firing at a temperature at which the abrasive grains do not thermally deteriorate.

[0006] However, in order to secure the holding power of the abrasive grains in the grindstone, it is necessary to bake at a high temperature as shown in the following example, which actually causes the deterioration of the abrasive grains. For example, an example of Japanese Patent Publication No. 64-2870 describes that firing is performed at 1240 ° C. In addition, the example of Japanese Patent Publication No. 6-69669 describes that firing is performed at 900 ° C. in a nitrogen atmosphere. In addition, an example of Japanese Patent Publication No. 7-16880 describes that firing is performed at 980 ° C.

(2) The abrasive grains deteriorate due to a chemical reaction between the abrasive grains and the vitrified binder at the time of firing, and their function as abrasive grains is reduced. For example, CBN abrasive grains generate B ₂ O _{3 on the} surface due to heat during firing, chemically react with the vitrified binder, and are firmly held. This leads to abrasive holding power. However, on the other hand, the finer the abrasive grains, the higher the reactivity with the vitrified binder,
It is considered that abrasive grains having a greater degree of reaction with the vitrified binder cause deterioration and reduce their function as abrasive grains.

(3) The structure of the grindstone is limited. For example,
When it is desired to reduce the content of the abrasive grains (for example, 25% by volume or less), the raw material is manufactured by increasing the amount of the pore-forming material contained in the raw grindstone (formed body, hereinafter the same) before firing. The pore-forming material is a combustible material that is contained in a molded body, burns out during firing of the molded body, and forms pores in a grindstone obtained after firing. However, when the amount of the pore-forming material is increased, cracks are generated when the molded body is dried due to a dispersion problem of the pore-forming material in the molded body, and cracks are also generated due to uneven shrinkage of a grindstone obtained after firing. And
It is difficult to lower the abrasive rate without cracking.
Even if a grinding wheel can be manufactured without cracking, the manufacturing cost is high because the finished shape and size of the manufactured grinding wheel are large, and the shrinkage is large. Become.

For this reason, it is conceivable to manufacture a vitrified whetstone using a method such as hot pressing or hot coining used in a method of manufacturing a metal bond whetstone. A vitrified whetstone disclosed in Japanese Patent Publication No. 55-137885 is disclosed. Have been. According to the method of manufacturing a vitrified grindstone using the above-described method, it is difficult to generate pores in the grindstone, and the grindstone contains only 2% by volume or less of pores, but a soluble portion (eluted during wet grinding) The pores are created by including a soluble portion that forms the pores.

However, as described in Japanese Patent Publication No. 64-2870, Japanese Patent Publication No. 6-69669, etc., in super-finishing, the amount of pores, the shape of pores, and the distribution of pores are important. Therefore, even if the method of manufacturing a vitrified grinding wheel using a method such as hot pressing or hot coining is simply applied to a super-finishing wheel, it is difficult to control the amount, shape and distribution of desired pores, and it is not practical. It was not possible to obtain a super-finishing whetstone to obtain.

[0011] As described above, the grindstone can be manufactured by a manufacturing method in which the abrasive grains do not cause thermal deterioration.
Being a grindstone having an abrasive grain holding power equal to or higher than that of a vitrified grindstone whose abrasive grains have been thermally degraded by reaction with a vitrified binder in order to sufficiently secure the holding power of the abrasive grains,
It is considered that a vitrified grindstone that can be manufactured by freely controlling the amount, shape and distribution of pores is ideal.

A first object of the present invention is to provide a vitrified grindstone which exhibits a sufficiently high abrasive grain holding power even though the abrasive grains are not thermally degraded. A second object of the present invention is to provide a vitrified grindstone that can be manufactured by freely controlling the amount, shape and distribution of pores.

[0013] A third object of the present invention is to provide a vitrified whetstone exhibiting a sufficiently high abrasive-grain holding power despite being capable of being manufactured while preventing thermal deterioration of the abrasive. An object of the present invention is to provide a method for manufacturing a vitrified grinding wheel. A fourth object of the present invention is to provide a method for manufacturing a vitrified grinding wheel capable of manufacturing a vitrified grinding wheel by freely controlling the amount, shape and distribution of pores in the vitrified grinding wheel.

[0014]

Means for Solving the Problems The present inventor has conducted various studies on a vitrified grinding wheel, and as a result, when a specific substance is used as a filler of the vitrified grinding wheel, excellent results have been obtained. I do.

That is, according to a first aspect of the present invention, there is provided a sintered body containing at least abrasive grains, carbonaceous spherical particles, and a vitrified binder, and the sintered body has a porosity. 5% by volume or less, and the average particle diameter of the carbonaceous spherical particles is at least half to 50 times the average particle diameter of abrasive grains mainly present in the sintered body. Can be achieved. The action of the carbonaceous spherical particles is as shown in the following (1) to (3).

(1) The carbonaceous spherical particles act as a solid lubricant. In other words, carbonaceous spherical particles are easily evacuated by the irregularities of the work (object to be ground) in the initial stage of processing, and the loose particles act as a solid lubricant to reduce the grinding resistance and improve the sharpness of the grindstone. .

(2) The carbonaceous spherical particles fall off the grindstone during grinding. The space created in the grindstone after the carbonaceous spherical particles fall off acts as air holes. In other words, air holes are obtained in the traces where the carbonaceous spherical particles are cut off and fall off, effectively acting for the removal of cuttings, and the grinding stone is not clogged.

(3) The carbonaceous spherical particles do not reduce the strength of the grindstone structure. That is, the carbonaceous spherical particles in the grindstone of the present invention have a spherical shape and an average particle diameter of not less than half of the abrasive grains, so that the strength of the grindstone itself is not reduced. As a result, the abrasive grains do not fall off abnormally.

The vitrified grinding wheel of the present invention can be operated as follows. The average aspect ratio of the carbonaceous spherical particles can be 1.7 or less. When the content of the carbonaceous spherical particles in the sintered body is 3
５０50% by volume. The abrasive grains may include both cubic boron nitride abrasive grains and diamond abrasive grains, and the average grain size of the diamond abrasive grains may be equal to or less than the average grain size of the cubic boron nitride abrasive grains. . The sintered body can have at least one type of metal particle dispersed in the phase of the vitrified binder.

The metal particles have a standard free energy of formation ΔG of oxide at 700 ° C. of -600 kJ / mol /
0 ₂ or more that is, it does not substantially oxidized,
All configurations having an average particle diameter of 10 μm or less and a coefficient of thermal expansion in the range of 0 to 100 ° C. and 10 to 20 × 10 ⁻⁶ / ° C. can be provided.

According to a second aspect of the present invention, a mixed powder containing at least abrasive particles, 3 to 50% by volume of carbonaceous spherical particles and vitrified binder powder is mixed with 70% by weight.
A pressure sintering step of obtaining a sintered body having a porosity of 5% by volume or less by pressure sintering at 0 ° C. or less, and mainly present in the mixed powder as the carbonaceous spherical particles At least one of the above objects is attained by a method for producing a vitrified grindstone using carbonaceous spherical particles having an average particle diameter of at least half to 50 times the average particle diameter of the abrasive grains and an average aspect ratio of 1.7 or less. Can be achieved.

In the method for producing a vitrified grinding wheel of the present invention, the abrasive grains include both cubic boron nitride abrasive grains and diamond abrasive grains, and the diamond abrasive grains have an average grain size of the cubic boron nitride abrasive grains. Abrasive grains having an average particle size or less can be used. Further, as the mixed powder,
A mixed powder further containing at least one kind of metal particles is used, and as the metal particles, the standard free energy of formation ΔG of the oxide at 700 ° C. is −600 kJ / mol / 0.
₂ or more, the average particle size is 10 μm or less, the coefficient of thermal expansion is 10 to 20 × 10 at 0 to 100 ° C.
^-6 / ° C., using the metal particles having all the configurations that are in the range of ⁻⁶ / ° C., and in the pressure sintering step, under the condition that the metal particles having all of the above configurations are not oxidized, Pressure sintering can be performed. In the present invention, the description of the numerical range includes not only both end values, but also all arbitrary intermediate values included therein.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION First, abrasive grains, carbon-based spherical particles and vitrified binder which can be suitably used in the vitrified grindstone or the method for producing a vitrified grindstone of the present invention will be described.

[Abrasives] As abrasives, general abrasives such as Al ₂ O ₃ -based abrasives and SiC-based abrasives, or Knoop hardness 3000 such as cubic boron nitride abrasives and diamond abrasives.
There are the above superabrasive grains, and at least one selected from these can be used. For example, at least one of the general abrasive grains and at least one of the superabrasive grains can be used in combination. The dimensions of the abrasive grains can be appropriately set according to the use of the grindstone and the like, and those having an average particle diameter of, for example, 0.1 to 200 μm can be used.

Incidentally, the super-abrasive grains are generally abrasive grains having a Knoop hardness of 3000 or more, preferably, abrasive grains having a hardness of at least about the same as cubic boron nitride. There are abrasive grains such as crystalline boron nitride abrasive grains and diamond abrasive grains, and in some cases, a mixture thereof.

[Carbon Spherical Particles] In the present invention, the term “carbonaceous” in the carbonaceous (carbonaceous) spherical particles refers to a material containing 90% by weight or more of carbon, such as graphite (graphite). Is included.

The “spherical shape” of the carbonaceous spherical particles according to the present invention includes not only a perfect spherical shape but also a substantially spherical shape having a major axis and a minor axis. It includes those having a substantially elliptical shape and a circular cross section in the minor axis direction, and those having a substantially elliptical cross section in the major axis direction and the minor axis direction.

The carbonaceous spherical particles preferably have an average aspect ratio of 1.7 or less (more preferably 1.5 or less).
Or less, more preferably 1.3 or less, particularly preferably 1 or less.
To 1.2) are formed into carbonaceous spherical particles. The aspect ratio refers to a ratio L / S between the longest diameter L and the shortest diameter S of the carbonaceous spherical particles.

The carbonaceous spherical particles in the present invention are, for example, solid and have a true specific gravity of 1 or more (for example, 1.3 to 1.3).
1.4). The carbonaceous spherical particles in the present invention may have a coating layer of, for example, metal.

The reason why a spherical particle is particularly selected from the carbonaceous particles is as follows.

Since the carbonaceous particles do not bind firmly to the vitrified matrix (vitrified binder material phase), the carbonaceous particles act as foreign matter in the grindstone and may cause a decrease in the strength of the grindstone. For this reason, spherical particles having a small surface area are suitable.

When the surface area is small, the carbonaceous particles are less likely to contact each other in the grindstone, and the grindstone can contain a large amount of carbonaceous particles. By setting the average particle diameter of the carbonaceous particles to be at least half to 50 times the average particle diameter of the abrasive grains, the surface area of the carbonaceous spherical particles is reduced.

Therefore, the vitrified whetstone of the present invention
Since a large amount of carbonaceous particles can be contained, the lubricating action and pore forming action of the carbonaceous particles can be further increased.

The average particle size of the carbonaceous spherical particles is at least half (0.5 times) to 50 times (preferably 0.7 to 40 times, more preferably 1 to 30 times) the average particle size of the abrasive grains.
Times). When the average particle diameter of the carbonaceous spherical particles is less than half the average particle diameter of the abrasive grains, the strength of the grinding stone tends to decrease due to an increase in the particle surface area of the carbonaceous spherical particles. Small pores are sometimes formed,
The effect of preventing clogging tends to be small.

If the average particle diameter of the carbonaceous spherical particles exceeds 50 times the average particle diameter of the abrasive grains, the average particle diameter of the carbonaceous spherical particles approaches the size of the grinding stone, and the strength of the grinding stone decreases. Tend to. For example, if the average grain size of the abrasive grains is 5μ
m, the average particle size of the carbonaceous spherical particles is 2
Since it exceeds 50 μm, the dimensions of the grinding stone (for example,
Is too large for a grindstone having a thickness of about 1 mm.

It is desirable that the carbonaceous spherical particles are uniformly dispersed in the grindstone. However, when the carbonaceous spherical particles are large, the number of carbonaceous spherical particles tends to be small. Tends to decrease.

[Vitrified Binder] As the vitrified binder, for example, borosilicate glass or crystallized glass may be used. Examples of the crystallized glass include those that precipitate willemite. The thermal expansion coefficient of the vitrified binder should be
It is desirable that the thermal expansion coefficient of the abrasive grains be within a range of ± 2 × 10 ⁻⁶ (1 / K) (room temperature to 500 ° C.).

The preferred composition for the binder is as follows.

SiO ₂ 40 to 70 wt% Al ₂ O ₃ 10 to 20 wt% B ₂ O ₃ 10 to 20 wt% RO 2 to 10 wt% R ₂ O 2 to 10 wt%

In the above, "RO" represents an oxide of one or more metals selected from alkaline earth metals, and "RO"
₂ O "indicates an oxide of one or more metals selected from alkali metals.

The particle size of the powder of the vitrified binder used in the production method of the present invention may be a particle size capable of pressure sintering, and the average particle size may be, for example, 1 to 15 μm. Preferably, it can be 2 to 10 μm.

In the production method of the present invention, when the specific mixed powder or a compact thereof is produced by sintering at a temperature of 700 ° C. or less under pressure, the powder of the vitrified binder is 700
It is necessary to melt at ℃.

[Vitrified Grinding Stone] The sintered body in the vitrified grinding stone of the present invention contains at least abrasive grains, carbonaceous spherical particles, and a vitrified binder, and the vitrified binder is preferably a vitrified binder. It is contained as a binder phase (matrix phase). The sintered body is preferably a sintered body of a mixed powder containing at least abrasive grains, carbonaceous spherical particles, and powder of a vitrified binder. The porosity of the sintered body is 5% by volume or less, preferably 3% by volume or less (more preferably 2% by volume or less). The reason for this is to prevent the strength of the sintered body from being reduced due to the addition of the carbonaceous spherical particles.

The average particle diameter of the carbonaceous spherical particles is at least half to 50 times the average particle diameter of abrasive grains mainly present in the sintered body. When a plurality of types of abrasive grains having different average particle diameters are present in the sintered body, the abrasive grains mainly present in the sintered body are different from the plurality of types of abrasive grains having different average particle diameters. Abrasive grains having the highest content volume ratio among the grains. Abrasive grains having different materials and the same average particle diameter can be regarded as one kind of abrasive grains.

Sintering in the vitrified grinding wheel of the present invention
The body can contain at least one metal particle
You. The metal particles are preferably oxidized at 700 ° C.
The standard free energy of formation ΔG of an object is -600 kJ / mo.
1/0_Two(Preferably -500 kJ / mol / 0_TwoLess than
Above, more preferably -400 kJ / mol / 0_Twothat's all)
, Not substantially oxidized, average grain
The diameter is 10 μm or less (preferably 8 μm or less, more preferably
Or 5 μm or less) and a coefficient of thermal expansion of 0 to 1
10-20 × 10 at 00 ° C^-6/ C range (preferably 1
0-18 × 10 ^-6/ C range, more preferably 10-1
7 × 10^-6/ C range)
Metal particles having the structure described above.

By dispersing the specific metal particles having all of the above structures in the vitrified binder phase in the sintered body, the retraction of the vitrified binder phase during use of the grindstone of the present invention can be freely performed. Can be controlled. In other words, the specific metal particles in the vitrified binder phase are reduced, the regression of the vitrified binder phase is reduced, and a design that emphasizes the reduction in the amount of wear of the grindstone, or conversely, the specific in the vitrified binder phase, By increasing the number of metal particles, it is possible to perform a design in which the regression of the vitrified binder phase is increased and the processing amount of the workpiece is increased.

Examples of the metal particles having all of the above structures include metal particles of Co, Cu, and Ni, and each can be suitably used.

The abrasive grains contained in the sintered body in the grindstone of the present invention include both cubic boron nitride abrasive grains and diamond abrasive grains, and the diamond abrasive grains have an average grain size of the cubic boron nitride abrasive grains. When the average grain size is smaller than the average grain size, a high processing rate is maintained by the lapping effect of fine diamond abrasive grains being released to the processing surface and becoming free abrasive grains, and the grinding effect of cubic boron nitride fixed abrasive grains. At the same time, the effect of improving the surface roughness can be obtained.

Preferably, the average grain size of the diamond abrasive grains is smaller than the average grain size of the cubic boron nitride abrasive grains. Thereby, diamond abrasive grains having a small average particle diameter are easily released, and diamond abrasive grains having a finer particle diameter are more advantageous for improving the surface roughness of the workpiece. The average particle diameter of the diamond abrasive grains is preferably 1/100 to 1 times (more preferably 1/100 to 0.7 times, more preferably 1/10) the average particle diameter of the cubic boron nitride abrasive grains.
0 to 1/2 times).

The content of abrasive grains in the sintered body is preferably 5 to 40% by volume (more preferably 5 to 30% by volume,
The content of the carbonaceous spherical particles is preferably 3 to 50% by volume, and the content of the vitrified binder is preferably 10 to 25% by volume.
85% by volume (more preferably 15 to 80% by volume, still more preferably 20 to 75% by volume).

The sintered body may contain at least one kind of metal particles. When the sintered body contains metal particles, the volume ratio of the vitrified binder to the metal particles in the sintered body is preferably 100: 5 to 10
0: 100 (more preferably 100: 10 to 100: 9
0, more preferably 100: 10 to 100: 80). When the sintered body contains metal particles, the total content of the vitrified binder and the metal particles is preferably 10 to 85% by volume (more preferably 15 to 80% by volume, and still more preferably 20 to 75% by volume). % By volume).

The vitrified grindstone of the present invention only needs to have the above-mentioned specific sintered body, and it is sufficient that at least a portion involved in grinding is the above-mentioned specific sintered body. For example, a vitrified grindstone according to the present invention includes a holder made of metal, ceramics, plastic, or the like in which the specific sintered body is present on the surface.

The vitrified grinding wheel of the present invention is suitable for grinding highly precise parts.

[Method of Manufacturing Vitrified Grinding Wheel] The method of manufacturing a vitrified grinding wheel of the present invention is characterized in that a mixed powder containing at least abrasive grains, carbonaceous spherical particles, and a vitrified binder powder is sintered under pressure to reduce the porosity. It has a pressure sintering step of obtaining a sintered body of 5% by volume or less. In the pressure sintering step, the compact of the mixed powder may be pressure-sintered to obtain a sintered body having a porosity of 5% by volume or less. As the carbonaceous spherical particles, carbonaceous spherical particles having an average particle diameter of at least half to 50 times the average particle diameter of abrasive grains mainly present in the mixed powder are used. The mixed powder or its molded body can contain at least one kind of metal powder.

The average particle diameter of the carbonaceous spherical particles is at least half to 50 times the average particle diameter of abrasive grains mainly present in the mixed powder or its compact. When a plurality of types of abrasive grains having different average particle diameters are present in the mixed powder or the compact thereof, the average particle diameter is different from the abrasive grains mainly present in the mixed powder or the compact thereof. Is the abrasive having the highest content volume ratio among a plurality of types of abrasives. In this case, the abrasive particles having different materials and the same average particle diameter can be regarded as one type of abrasive particles.

In the pressure sintering step in the method for manufacturing a vitrified grindstone of the present invention, the mixed powder or its compact is preferably subjected to pressure sintering at 700 ° C. or lower. By performing pressure sintering at 700 ° C. or less, deterioration of abrasive grains and burning of carbonaceous spherical particles can be sufficiently avoided.

In the pressure sintering step, the pressure at which the mixed powder or its compact is sintered under pressure is such that the porosity of the sintered body obtained by pressure sintering is 5% by volume or less (preferably). Is 3% by volume or less, and more preferably 2% by volume or less. Specifically, the pressure is preferably 5%.
It may be about 0 to 400 kgf / cm ² .

During the sintering, the pressure is applied between the abrasive grains, the vitrified binder powder and the carbonaceous spherical particles (when the metal particles are added to the mixed powder or its compact, the abrasive This is for promoting the contact between the carbon particles and the vitrified binder powder, the carbonaceous spherical particles and the metal particles, and sintering. Therefore, it becomes possible to make the carbonaceous spherical particles and the abrasive grains more contact with each other, and the abrasive grains are pressed around the carbonaceous spherical particles. Therefore, when using the grindstone obtained by the production method of the present invention, a plurality of abrasive grains arranged in a ring are exposed on the grinding surface of the grindstone, and the plurality of grindstones are traced in the trace of the carbonaceous spherical particles coming off. Works effectively as a cutting edge.

As the abrasive grains, in particular, alumina-based abrasive grains having a fine crystal grain size (1 μm or less) (for example, sintered alumina-based abrasive grains produced by using a sol-gel sintering method) and the like are used in the present invention. When applied to the manufacturing method, since the abrasive grains do not grow due to the fact that the temperature can be reduced at the time of pressure sintering, the performance of the alumina-based abrasive grains characterized by minute crushing is sufficiently exhibited. Can be done.

Examples of the method of pressure sintering include hot pressing, hot coining, resistance sintering and plasma discharge sintering, which are heating sintering methods, and vacuum pressure sintering with a pump function added to a hot press. Is preferably used.

Before the pressure sintering step, a molding step of molding the mixed powder to obtain a molded body can be provided. The raw material components to be contained in the mixed powder and the content thereof are appropriately set according to the structure of the vitrified grindstone to be produced.

The mixed powder is contained as a raw material for production.
Preferably, the metal particles are oxides at 700 ° C.
Has a standard free energy of formation ΔG of -600 kJ / mol
/ 0 _Two(Preferably -500 kJ / mol / 0_TwoLess than
Above, more preferably -400 kJ / mol / 0_Twothat's all)
Having an average particle diameter of 10 μm or less (preferably
8 μm or less, more preferably 5 μm or less)
Coefficient of thermal expansion is 10-20 × 10 at 0-100 ° C^-6/ ℃
(Preferably 10 to 18 × 10^-6/ ° C range
More preferably, 10 to 17 × 10^-6/ ° C range)
Metal particles having all of the above structures
You. As metal particles having all the above-mentioned configurations
Is, for example, each metal particles of Co, Cu and Ni,
Each can be suitably used.

In the pressure sintering step in the production method of the present invention, when the mixed powder containing metal particles or a compact thereof is subjected to pressure sintering, preferably, the metal particles (particularly, all of The mixed powder or a compact thereof is subjected to pressure sintering under conditions that do not substantially oxidize the metal particles having the above.

[0064]

EXAMPLES Example 1 Carbonaceous beads of the same quality as those used in Example 2 and below of the present invention were evaluated. Hereinafter, “wt%” is “weight%”.

When the mass loss of the carbonaceous beads was measured at a temperature rising condition of 10 ° C./min, the burning start temperature (the temperature at which the mass of the carbonaceous beads decreased by 10 wt%) was 7
The temperature was 00 ° C, and the burn-out completion temperature (the temperature at which the mass of the carbon beads was reduced by 90 wt%) was 820 ° C. The average particle size of the carbon beads is 50 μm.
m.

Further, the raw material (the carbonaceous beads) was observed with an electron microscope, and ten samples (carbonaceous beads) were selected from an electron microscope photograph to confirm the aspect ratio. The average of the aspect ratio was 1.0.

Example 2 The raw materials shown in Table 1 below were mixed and stirred at the volume ratios shown in the column of Example 2, and the resulting mixed and stirred product was molded into a carbon mold (dimensions of the space of the concave portion 40 mm × 4
mm × 7mm) and pressure 300kgf with resistance sintering machine
/ Cm ² and maintained at 600 ° C. for 2 minutes, and subjected to electric heating and pressure sintering to obtain a vitrified grindstone. The average particle size of the vitrified binder is 3 μm. The average particle size of the vitrified binder used in each of the following Examples and Comparative Examples is also 3 μm.

[0068]

[Table 1]

Comparative Example 1 A vitrified grindstone was obtained in the same manner as in Example 2 except that the raw materials in Table 1 were used at the volume ratio shown in the column of Comparative Example 1.

Comparative Example 2 A vitrified grindstone was obtained in the same manner as in Example 2 except that the raw materials shown in Table 1 were used at the volume ratios shown in the column of Comparative Example 2.

Table 1 shows Example 2 and Comparative Examples 1 to
Particle size A and CBN of carbonaceous beads used in each of No. 2
The particle size ratio A / B with the particle size B of the abrasive grains is also shown. The average particle diameter of the CBN abrasive grains in Table 1 is 3 to 6 μm, but the average particle diameter when calculating the particle diameter ratio A / B is (3 + 6) / 2.
= 4.5 (μm). Hereinafter, when calculating the particle size ratio between the particle size of the carbonaceous beads and the particle size of the CBN abrasive grains, when the average particle size is described as a to b μm, the average particle size is (a + b) / 2 ( μm).

<Evaluation of Three-Point Bending Strength> The three-point bending strength of the vitrified grindstone obtained in each of Example 2 and Comparative Examples 1 and 2 (JIS R1601-1995, the same applies hereinafter).
Was measured. Table 1 also shows the measurement results. Comparative Example 1
Compared to the whetstone of Comparative Example 2, the whetstone of Comparative Example 2 had an excessively large decrease in strength. Therefore, the particle size ratio A / B between the particle size A of the carbonaceous beads and the particle size B of the CBN abrasive grains.
If it is 50 or less, it is considered that it can endure practical use.

Example 3 A vitrified grindstone was obtained in the same manner as in Example 2 except that the raw materials shown in Table 2 below were used at the volume ratio shown in the column of Example 3.

[0074]

[Table 2]

Comparative Example 3 A vitrified grindstone was obtained in the same manner as in Example 2 except that the raw materials shown in Table 2 were used at the volume ratio shown in the column of Comparative Example 3.

Comparative Example 4 A vitrified grindstone was obtained in the same manner as in Example 2 except that the raw materials shown in Table 2 were used at the volume ratio shown in the column of Comparative Example 4.

Table 2 shows Example 3 and Comparative Examples 3 to
Particle size A and CBN of carbonaceous beads used in each of No. 4
The particle size ratio A / B with the particle size B of the abrasive grains is also shown.

<Evaluation of Three-Point Bending Strength> The three-point bending strength of the vitrified grindstones obtained in Example 3 and Comparative Examples 3 and 4 was measured. Table 2 also shows the measurement results. Compared to the grindstone of Comparative Example 3, the grindstone of Comparative Example 4 has an excessively large decrease in strength, but the grindstone of Example 3 has a small decrease in strength due to the addition of carbonaceous beads, and can withstand practical use. Therefore, it is considered that if the particle diameter ratio A / B of the particle diameter A of the carbonaceous beads to the particle diameter B of the CBN abrasive particles is 1/2 or more (half or more), it can be practically used.

[Examples 4A and 4B] A vitrified grindstone was obtained in the same manner as in Example 2 except that the raw materials shown in Table 3 below were used at the volume ratio shown in the column of Example 4A or Example 4B. Table 3 also shows the particle size ratio A / B between the particle size A of the carbonaceous beads and the particle size B of the CBN abrasive grains used in each of Examples 4A and 4B.

[0080]

[Table 3]

[Comparative Examples 5 to 7] The raw materials shown in Table 4 below were mixed and stirred at the volume ratios shown in the respective columns of Comparative Examples 5 to 7, and the resulting mixed and stirred product was press-molded. Firing was performed in an air atmosphere for an hour to obtain a vitrified whetstone.

[0082]

[Table 4]

<Evaluation of Grinding Performance> Example 4A, Example 4
B and the grindstones obtained in each of Comparative Examples 5 to 7 were each processed into a rectangular parallelepiped having a size of 4 mm × 9 mm × 6 mm, and the grinding performance, that is, (a) super-finishing amount, (b) grindstone wear size,
(C) The surface roughness was examined. Table 5 shows the results.
In addition, the numerical value shown as a result of each item in Table 5 is a relative value when the value of Comparative Example 5 is set to 100.

[0084]

[Table 5]

The grindstone of Example 4A has a higher superfinishing amount, a smaller surface roughness and higher performance than the grindstone of Comparative Example 5. Regarding the grinding wheel wear dimension, the grinding wheel of Example 4A is slightly higher than the grinding wheel of Comparative Example 5, but can be said to be equivalent. Also, the grindstone of Example 4A has a larger grindstone wear size than the grindstones of Comparative Examples 6 and 7, but the grindstones of Comparative Examples 6 and 7 have too small a super finish. The grindstone of Example 4B is inferior to the grindstone of Example 4A in superfinishing amount and grindstone wear size as compared with the grindstone of Example 4A, but the surface roughness is improved and the effect of the fine-grained diamond appears. .

The grinding conditions and dressing conditions for evaluating the above-mentioned grinding performance are as follows.

Grinding method Super finish Grinding fluid flow rate 1.4 l / min Work material SUJ-2 (HRC61) Work material peripheral speed 3.3 m / sec Cycle time 10 seconds Grinding wheel surface pressure 2.8 MPa Pre-process surface roughness 3S Wheel frequency 16.7 / sec Wheel amplitude 1.5mm

[Examples 5A and 5B] Vitrified grindstones were obtained in the same manner as in Example 2 except that the raw materials shown in Table 6 below were used in the volume ratios shown in the columns of Examples 5A and 5B.

[0089]

[Table 6]

Comparative Example 8 A vitrified grindstone was obtained in the same manner as in Example 2 except that the raw materials shown in Table 6 were used at the volume ratios shown in the column of Comparative Example 8.

[Comparative Examples 9 to 11] The raw materials shown in Table 7 below were mixed at the volume ratios shown in the respective columns of Comparative Examples 9 to 11 and stirred to obtain mixed and stirred products. Each of the mixed and stirred materials was press-formed so that the abrasive grain ratio occupied 45% by volume of the whetstone volume, and the obtained compact was fired at 900 ° C. for 5 hours in an air atmosphere, and the vitrified products of Comparative Examples 9 to 11 were obtained. I got a whetstone.

[0092]

[Table 7]

<Evaluation of grinding performance> Example 5A, Example 5
B and the grindstones obtained in each of Comparative Examples 8 to 11 were each processed into a square pillar-shaped grindstone having a size of 3 mm × 3 mm × 20 mm, and the grinding performance, that is, (a) allowance, (b) grindstone wear size , (C) surface roughness, and (d) power consumption. Table 8 shows the results. The numerical values shown as the results of each item in Table 8 are relative values when the value of Comparative Example 8 is set to 100.

[0094]

[Table 8]

The grindstone of Example 5A has a larger allowance, smaller surface roughness, lower power consumption, and higher performance than the grindstone of Comparative Example 8. The whetstone of Example 5A is slightly higher than the whetstone of Comparative Example 8, but the whetstone wear size is equivalent.

Comparative Example 9, 10 and 11
As compared with the respective grinding wheels, the wear size is larger, but each grinding wheel of the comparative example has too little allowance.

When the grindstone of Example 5A is compared with the grindstone of Example 5B, the grindstone of Example 5A is superior in terms of machining allowance and grindstone wear size, and the grindstone of Example 5B is lower in surface roughness and power consumption. It is excellent, and the effect of the fine diamond abrasive grains used in the grindstone of Example 5B appears.

The grinding conditions and dressing conditions when the above-mentioned grinding performance was evaluated are as follows.

Grinding method Honing Spindle peripheral speed 0.50 m / sec Spindle reciprocating speed 0.13 m / sec Stroke amount 20 mm Crosshatch angle 30 degrees Grinding liquid Water-free Truing method Hand truing Work material SCM415H (Carburizing and quenching)

[0100]

[Table 9] Spark out: 3 round trips

[0101]

The vitrified grindstone of the present invention has a sintered body containing at least abrasive grains, carbonaceous spherical particles, and a vitrified binder, and the sintered body has a porosity of 5% by volume or less. Since the average particle size of the carbonaceous spherical particles is at least half to 50 times the average particle size of the abrasive grains mainly present in the sintered body, the abrasive grains are thermally degraded. In spite of the absence, a sufficiently high abrasive grain holding force is exhibited, so that a sufficient processing amount can be secured and a reduction in the amount of wear of the grinding stone can be achieved.

Further, since the vitrified grindstone of the present invention has the above-described configuration, the amount, shape and distribution of pores can be freely controlled according to the processing conditions and the required accuracy when processing the workpiece. Can be manufactured.

In the method for producing a vitrified grinding wheel of the present invention, a powder mixture containing at least abrasive grains, 3 to 50% by volume of carbonaceous spherical particles and vitrified binder powder is sintered under pressure at 700 ° C. or less. A pressure sintering step of obtaining a sintered body having a porosity of 5% by volume or less, wherein the carbonaceous spherical particles have an average particle diameter of at least half or more of an average particle diameter of abrasive grains mainly present in the mixed powder; Since carbonaceous spherical particles having an average particle diameter of up to 50 times and an average aspect ratio of 1.7 or less are used, it is possible to prevent the abrasive grains from thermally deteriorating and to manufacture them sufficiently. Vitrified whetstones exhibiting high abrasive grain holding power can be manufactured.

Further, since the method for manufacturing a vitrified grinding wheel of the present invention has the above-described structure, the amount, shape and distribution of pores in the vitrified grinding wheel can be freely controlled to manufacture a vitrified grinding wheel.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) B24D 3/02 310 B24D 3/02 310C (72) Inventor Kenji Ito 3-1-1 Noritakeshinmachi, Nishi-ku, Nagoya-shi, Aichi Prefecture No. 36 Noritake Co., Ltd. F-term (reference) 3C063 AA02 AB01 BB02 BB19 BB20 BC05 BD01 BD02 CC04 FF23

Claims (9)

[Claims] 1. A sintered body containing at least abrasive particles, carbonaceous spherical particles, and a vitrified binder, wherein the sintered body has a porosity of 5% by volume or less, and A vitrified grinding wheel, wherein the average particle diameter of the spherical particles is at least half to 50 times the average particle diameter of abrasive grains mainly present in the sintered body. 2. The vitrified grinding wheel according to claim 1, wherein the carbon-based spherical particles have an average aspect ratio of 1.7 or less. 3. The vitrified grinding wheel according to claim 1, wherein the content of the carbonaceous spherical particles in the sintered body is 3 to 50% by volume. 4. The method according to claim 1, wherein the abrasive grains include both cubic boron nitride abrasive grains and diamond abrasive grains, and the average grain diameter of the diamond abrasive grains is equal to or less than the average grain diameter of the cubic boron nitride abrasive grains. The vitrified whetstone according to any one of claims 1 to 3, which is characterized in that: 5. The vitrified grinding wheel according to claim 1, wherein said sintered body has at least one kind of metal particles dispersed in a phase of a vitrified binder. 6. The metal particles have a standard free energy of formation ΔG of oxide at 700 ° C. of -600 kJ / mol / mol.
0 ₂ or more that is, it does not substantially oxidized,
6. The composition according to claim 5, wherein the average particle diameter is 10 μm or less, and the thermal expansion coefficient is in the range of 10 to 20 × 10 ⁻⁶ / ° C. at 0 to 100 ° C.
The vitrified whetstone described in 1. 7. A powder mixture containing at least abrasive particles, 3 to 50% by volume of carbonaceous spherical particles and vitrified binder powder is sintered under pressure at 700 ° C. or less and has a porosity of 5% by volume or less. A pressure sintering step of obtaining a sintered body, wherein the carbonaceous spherical particles have an average particle diameter of at least half to 50 times the average particle diameter of abrasive grains mainly present in the mixed powder. A method for producing a vitrified grinding wheel, comprising using carbonaceous spherical particles having an average aspect ratio of 1.7 or less. 8. An abrasive grain comprising both cubic boron nitride abrasive grains and diamond abrasive grains as said abrasive grains, wherein said diamond abrasive grains have an average grain size equal to or less than the average grain size of said cubic boron nitride abrasive grains. The method for producing a vitrified grindstone according to claim 7, wherein: As claimed in claim 9, wherein said mixed powder, a mixed powder further contains at least one metal particle, the metal particles, standard free energy ΔG oxide at 700 ° C. is -600kJ / mol / 0 ₂ And the average particle diameter is 10 μm or less, and the thermal expansion coefficient is in the range of 10 to 20 × 10 ⁻⁶ / ° C. at 0 to 100 ° C. The vitrified grinding wheel according to any one of claims 7 to 8, wherein, in the binding step, the mixed powder is sintered under pressure under conditions that do not oxidize the metal particles having all of the above configurations. Production method.