JP2002331462A - Grinding stone for super-finishing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a grinding stone for super-finishing using fine abrasive grain of an average particle size <=45 μm difficult to generate clogging and dulling as compared with a conventional grinding stone. SOLUTION: A granulation operation is performed for a mixture of CBN fine abrasive grain 1 of the average particle size, vitrified binding agent 2 and gas cavity agent of acryl resin having an average particle size of 0.015 mm to form original grain having an average particle size of a range of 0.5 to 0.7 mm (the range which is 30 to 45 times as large as that of the gas cavity agent). The original grain is compressed and molded by pressure of 19.6 MPa, subsequently the original grain is completely dried at >=80 deg.C of a raw formed body. After the drying, the original grain is sintered at a maximum temperature 840 deg.C for sintering cycle 24 hours. The abrasive grain 1 is coupled by the binding agent 2 a unit of, granulation small grinding stone 4 constituted by forming a primary gas cavity 3 in the part of the binding agent 2 is fused each other in a form that a secondary gas cavity 5 is formed. The grinding stone 10 which has an average size of each granulation small grinding tool 4 of the range of 0.2 to 0.35 mm and is formed larger than each secondary gas cavity 5 is prepared.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing particles having an average particle size of 4
The present invention relates to a superfinishing whetstone made of fine abrasive grains of 5 μm or less.

[0002]

2. Description of the Related Art Recent super-finishing whetstones have not only improved finished surface roughness, but also finer abrasive grains from the maintenance and improvement of accuracy, and have high machinability, that is, without clogging and crushing. There is a need for a grindstone with an excellent function of chip discharge.

[0003]

However, as a conventional superfinishing grindstone, a grindstone 20 having a structure as illustrated in FIG. 2 has pores 3, but the abrasive grains 1 and the pores 3 are unevenly distributed. Clogging and crushing are likely to occur partially at a portion where the binder layer 2 occupies a large proportion. Eventually, the entire grinding wheel working surface will be widely clogged and crushed.

According to the present invention, a superfinishing whetstone formed by using "fine abrasive grains having an average particle diameter of 45 μm or less", which is generally used for superfinishing, is superior in the function of discharging chips as compared with the conventional one. That is, it is an object of the present invention to obtain a product without clogging and collapsing.

[0005]

In order to solve the above problems, the present invention provides a fine abrasive having the above average particle diameter, a binder, and an artificial pore agent having an average particle diameter of 0.01 to 0.1 mm. Granulation operation of the mixture with the above, the average granulated particle diameter is 0.2 to 2 m
m and in the range of 5 to 100 times the size of the artificial pore agent, and form the granules in a range of 10 MPa to 50 M.
Compression molding at a pressure of Pa, followed by main drying at a temperature of 80 ° C. or less, and after drying, firing at a maximum temperature of 840 ° C. causes the fine abrasive grains to be bonded with a binder, and a portion of the binder The granulated small whetstones in which the primary pores are formed are fused and bonded together in the form of secondary pores, and the average diameter of each granulated small whetstone is in the range of 0.08 to 1.2 mm. Then, a superfinishing whetstone in which each secondary pore was formed smaller than the average diameter of each granulated small whetstone was produced.

FIG. 1 schematically shows the internal structure of the superfinishing grindstone of the present invention formed as described above. In the figure, those denoted by reference numeral 1 are fine abrasive grains having the above average particle diameter,
2 is a binder, 3 is a primary pore, 4 is a granulated small grindstone, and 5 is a secondary pore.

At this time, the average particle diameter of the artificial pore agent is set to 0.01 to 0.1 mm. If the average pore size is smaller than 0.01 mm, the primary pores 3 formed by disappearance of the artificial pore agent are: This is because the size is not enough to satisfy the sufficient chip discharge function, and if it is more than 0.1 mm, it is difficult to form the granulated small whetstone 4.

The average grain size of the raw granules of the granulated small whetstone 4 is up to 5 to 100 times that of the artificial pore agent and 0.2 to 2 m.
m and in the range of 10 MPa to 5
Compression molding at a pressure of 0 MPa, then 80 ° C.
The main drying is performed below, and after the drying, firing is performed at the maximum temperature of 840 ° C. for the following reasons.

[0009] First, the average particle size of the original particles is 1
If it is larger than 00 times, the secondary pores 5 formed between the small whetstones 4 are too large and small in number for discharging chips, and are liable to be clogged and clogged. If the average grain size of the raw particles is smaller than 5 times that of the artificial pore agent, only a large number of secondary pores 5 which are too small to discharge the chips are formed, which makes it more difficult to discharge the chips. Because it becomes.

On the other hand, when the average grain size of the original grains is 0.2 mm or less, a large difference in performance cannot be exhibited as compared with a normal porous whetstone. This is because the number of the granulated small whetstones 4 or the secondary pores 5 is reduced, and the high cutting ability without clogging and collapsing provided by the present invention cannot be exhibited.

Then, the granulated small whetstone 4 is set to 10 to 50 MPa.
When compression molding at a pressure of less than 10 MPa,
Bonding (fusion) between the granulated small whetstones 4 becomes poor, and 50MP
This is because if it is larger than a, the secondary pores 5 having an appropriate size cannot be generated.

Next, firing under the above-mentioned conditions after the compression molding is performed by first reducing the diameter of the granulated small grinding wheel in the firing wheel to 0.1 mm.
The thickness is preferably in the range of 08 to 1.2 mm, and more preferably 0.8 to 1.2 mm.
Experiments have shown that the one in the range of 1 to 1 mm is good.

On the other hand, since the granulated small whetstone 4 shrinks and changes through the drying and firing steps, in order to finally obtain the granulated small whetstone diameter in the above range, the range of the original granules must be artificial as described above. It is necessary that the pore size is 5 to 100 times that of the pore agent and is in the range of 0.2 to 2 mm.
Drying and baking conditions for reducing and changing the size to a range of ~ 1.2 mm are obtained by compression molding, and then forming the product at 80 ° C.
This was followed by main drying, and after drying, firing at a maximum temperature of 840 ° C.

This condition is obtained from experiments,
When the main drying is performed at 80 ° C. or more, for example, 100 to 120
When dried at ℃, the amount of shrinkage of the formed body is excessive,
Not only does it fall outside the above-mentioned range (0.08 to 1.2 mm), but also the sintering grindstone is specialized in hardness, and the observation between the grindstone structures shows that the pore volume between the granulated small grindstones 4 (2 The secondary pores 5) are reduced, and the grindstone is clogged and easily crushed.

If the firing temperature exceeds 840 ° C., the amount of shrinkage of the grindstone is too large in this case too, and the void volume between the small granulated grindstones decreases, and the grindstone becomes hard. That is, clogging and crushing are likely to occur. If the temperature is lower than 840 ° C. or lower than 830 ° C., the bonding force between the granulated small whetstones 4 becomes weak, the amount of wear of the whetstones increases, and a normal cutting action cannot be obtained.

The superfinishing wheel 1 of the present invention as described above.
0, since the granulated small whetstones 4 located on the processing surface each independently share a cutting action, the machinability is improved, and the secondary pores 5 formed between the granulated small whetstones 4 are used. Since the discharge of the chips during cutting is activated, the occurrence of clogging and crushing is suppressed, and the familiarity of the grindstone with the processed surface is increased.

Further, it is preferable that the granulated small whetstone 4 is dried and hardened by internal heating before the above-mentioned raw particles are compression-molded, so that appropriate strength and flexibility can be obtained. Since it has a shape-retaining property, the secondary pores 5 are formed stably by joining and fusion of the granulated small whetstones 4 without collapsing during compression molding. The reason for curing by internal heating is that a cured state having appropriate flexibility and plasticity is obtained compared to external heating by hot air or the like.
As a method of internal heating, there is heating by far infrared rays or microwaves.

Furthermore, it is preferable to add a softness / plasticity additive during the compression molding of the above-mentioned granules, so that the granules have flexibility and plasticity, and contact deformation Is expected to increase the
Since separation and insulation are not performed, the original particles are continuously joined to each other, and the formation of the secondary pores 5 is facilitated.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (1) Abrasive grains The abrasive grains used in the present invention are not particularly limited in the material thereof, and general abrasive grains such as aluminum oxide or silicon carbide can be used. In the embodiment, as described above, diamond, CBN, and the like, hard abrasive grains generally used for super-finishing wheels are used, and the size thereof is also usually used for super-finishing wheels, and the average particle diameter called micron size is used. Using fine abrasive particles having a particle size of 45 μm or less, preferably, 20 to 25 in which secondary particles are easily formed by an agglomeration action or bulk density is rapidly reduced by an increase in porosity.
μm or less.

(2) Binder As the binder, for example, an inorganic vitrified binder which is generally widely used in the examples described later is used, but an inorganic ceramic bond, an organic resin bond, or various synthetic resins are used. Any of resin bond, metal bond and the like may be applied.

(3) Porous agent The porous agent is burned out when the formed granulated small whetstone is fired, and generates pores (primary pores) in the grindstone structure, so that it is completely burned out. Preferably, for example, polyethylene resin, polystyrene resin,
Alternatively, organic particles such as an acrylic resin may be used.

As described above, the size is set to have an average particle size in the range of 0.01 to 0.1 mm, preferably about 0.01 to 0.06 mm.

(4) Density ratio and particle size ratio of mixed components Density (g / c) of each mixed component of abrasive grains, binder, and pore agent
m ³ ) is 3.52 when the abrasive is diamond, CB
In the case of N, use 3.48. The vitrified binder has a range of 2.0 to 3.0, and the pore agent has a range of 1.0 to 1.2. In order for the mixed powder to be uniformly mixed, the density ratio and the particle size ratio of the mixed components are preferably small, preferably 1: 1.
0 or less, preferably 1: 5 or less. The density ratio of each mixed component in the above case is approximately 1: 3.5.

(5) Granulated small whetstone The small whetstone (granulated small whetstone) formed by granulation has an original grain size in the range of 0.2 to 2 mm as described above, and The size should be 5 to 100 times the size of the artificial pore agent. The reason is as described above.

The granulated small whetstone shrinks and changes after firing, and the degree of the change is, for example, 0.
The change from the range of 2-2 mm to the range of 0.08-1.2 mm is preferable, and the change is preferably within the range of about 0.1-1 mm.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a grindstone of an embodiment will be described. As for the comparative example, only different portions will be described. First, abrasive grains used were CBN having an average particle diameter of 45 μm, the binder was vitrified bond, and the composition was SiO ₂ , Al ₂ O ₃ ,
Using _{B 2 O 3, Na 2 O} , CaO, those MgO, mixing ratio is set to 0.4 parts by weight per unit weight of the abrasive grains.

The artificial pore agent has an average particle size of 0.015 mm
The acrylic resin was used, and the compounding ratio was changed in five steps of 0, 0.1, 0.2, 0.35 and 0.45 parts by weight in each of Examples and Comparative Examples. Comparative Example) 1, 2, 3, 4, and 5.

Each sample composed of the mixed foreign component particles (abrasives, binder, and pore agent) is stirred and mixed in a slurry (slurry) state, cast, dried at a low temperature, dehydrated, and powdered.

Next, a liquid binder composed of dextrin and ethylene glycol is added to the raw powder sample to adjust the humidity. In the embodiment of the present invention, this liquid binder was added to each sample in a range of 0.18 ± 0.03 parts by volume and re-kneaded until a sufficient wet state was obtained. 0.13 ± 0.03 parts by volume per unit weight.

After kneading, for each example, the kneaded sample was passed through a 0.71 mm "sieve opening"
Original granules of granulated small whetstone having an average particle diameter of 0.5 to 0.7 mm are obtained. The original particles are subjected to heat treatment (internal heating) with microwaves for several tens of seconds to harden the surface.

In the comparative example, the kneaded sample was further kneaded for homogenization, and then passed through a 0.3 mm and then a 0.15 mm “mesh opening” to obtain an average particle diameter of 0 mm. A raw grain of 0.02 to 0.1 mm is obtained.

Subsequently, in each of Examples and Comparative Examples, compression molding is performed at a surface pressure of 19.6 MPa using a predetermined square mold.
The formed body is finally dried at 80 ° C. or lower, and the dried sample is fired at a maximum temperature of 840 ° C. for 24 hours in a firing cycle.

After firing, the surface of the grindstone of the example was lapped. Then, when observing the inside with a SEM (scanning electron microscope), as shown in FIG.
Are bonded with the vitrified binder 2 and the granulated small whetstones 4 in the unit where the primary pores 3 are formed in the portion of the vitrified binder 2 are fused to form the secondary pores 5, The average diameter of each granulated small whetstone 4 is 0.2 to 0.1.
Each secondary pore 5 is also in the range of 35 mm and each granulated small whetstone 4
Was found to be smaller than the average diameter of.

The average particle diameter of the granulated small whetstone 4 is 0.2 to
The size in the range of 0.35 mm is a size in the range of 0.08 to 1.2 mm proposed in the present invention. The range of 0.2 to 0.35 mm is also in the range of 13 to 23 times the average particle diameter of the artificial pore agent, and is also in the range of 5 to 100 times proposed in the present invention. .

On the other hand, in the comparative example, after firing, the surface was lap-finished and the inside was observed by SEM (scanning electron microscope). However, the structure as in the example was not found at all, and the structure shown in FIG. As shown in Fig. 7, although pores were observed, grain boundaries were unclear, and a dense and uniform whetstone structure was observed. Such a structure is a structure that easily causes clogging and crushing as described above.

Next, the RH hardness and the structure of the grindstone and the actual cutting test are performed on the grindstones of the embodiment and the comparative example as described above. First, the RH hardness is measured by a Rockwell hardness scale H scale (3.175 mm steel ball indenter, test load 60 kg, indicated value of dial B). The minus RH hardness becomes a minus value when the long hand passes through the set point of 30 and further passes through the zero point and stops, and at this time, the grindstone becomes soft. Table 1 shows the average RH hardness of each sample.

With respect to the grindstone structure, the measured abrasive grain volume content of each sample is shown in Table 1 by concentration. Concentration 100 corresponds to 25% by volume percentage.

Next, in the actual cutting test, the raceway surface of the inner race (material SUJ2, hardness HRc60) of the ball bearing is super-finished using a dedicated machine. Each sample has a cross section of 5 x 5.5 m from the calcination whetstone.
The square stick whetstone of m is cut out and used as a sample for actual cutting.

The super-finishing condition is that the peripheral speed of the workpiece is 327 m / m
in, whetstone swing number 640 cpm, whetstone maximum swing angle ± 15
°, maximum whetstone rocking speed 3.4 m / min, abrasive grains (whetstone)
The maximum inclination angle which gives the shape of the sinusoidal motion trajectory is 36 minutes. The grindstone surface pressure was 2.21 MPa and the processing time was 15 seconds. The processing oil is sulfurized fatty oil. Each grindstone sample is formed so as to have a uniform contact surface with the processed surface before actual cutting.

The super-finishing characteristic value is an average value when 30 pieces are continuously machined, and the grinding wheel wear amount W (μm / PC.), The cutting amount T (μm / PC.) And the cutting amount T (μm / PC.) Per one workpiece, respectively. Determine the finish ratio T / W. Table 1 shows the results of the actual cutting.

[0041]

[Table 1]

As can be seen from Table 1, in the case of the example, the amount of wear W (μm / PC.) Of the grinding wheel was reduced by about 20 to 50%, and the cutting amount T (μm / P
C. ) Is about 10% or more, and is twice or more in the case of a hard grindstone, and is excellent in machinability. As a result, the finishing ratio T / W is more than twice as economical. Finished surface roughness also tends to improve.

Further, the clogged state of the working surface of the grindstone after the actual cutting was also observed, and the results are shown in Table 1 by symbols. Table 1
Indicates a state without clogging, and if there is clogging, the inside of the white circle is painted black depending on the degree of clogging.

As can be seen from Table 1, the example of the present invention has no clogging, the comparative example has a very large clogging in the comparative example 1, and the comparative example 2 has a considerable clogging. Is shown. In Comparative Examples 3, 4, and 5, although clear clogging did not occur, glossy spot-like metal adhesion which can be said to be unique to the CBN porous whetstone was observed, and as a cutting result, the finish ratio was small ( Comparative Example 4,
5) In Comparative Example 3, the "compatibility" described below is low.

The “conformity” is a problem in a grindstone using super-hard abrasive grains. This is because the number of processed pieces (PCS) until the working surface of the grindstone uniformly comes into contact with the processed surface. It is determined by sampling. As can be seen in Table 1, in the example, each of the five
Less than the number of pieces, and a good result of about 1.5 times or more was obtained through the grindstone of the hard or soft state (Examples 4 and 5 and Comparative Examples 4 and 5 having the minus RH hardness) with respect to the comparative example. I have.

[0046]

As described above, the present invention provides a mixture of fine abrasive grains having a desired average particle diameter of 45 μm or less, a binder, and an artificial pore agent having a predetermined average particle diameter. A granulation operation is performed to form raw particles, the raw particles are compression-molded at a predetermined pressure, and then fired, whereby the fine abrasive particles are bonded with a binder, and primary pores are formed in the binder. Granulated small whetstones are fused and bonded together to form secondary pores, each secondary pore is smaller than the average diameter of each granulated small whetstone, and the average of each granulated small whetstone A super-finishing whetstone with a diameter within the specified range has been manufactured, so clogging and crushing are suppressed compared to the conventional type, and therefore super-finishing whetstones are excellent in the function of discharging chips on a wide whetstone working surface. A whetstone is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a structure inside a grindstone of an embodiment.

FIG. 2 is a schematic diagram showing a structure inside a conventional porous grindstone.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hard fine abrasive (CBN) 2 Vitrified binder 3 Primary porosity 4 Granulated small whetstone 5 Secondary porosity

Claims (4)

[Claims] 1. A superfinishing whetstone comprising fine abrasive grains having an average particle diameter of 45 μm or less, wherein said fine abrasive grains are bonded with a binder, and a primary pore is formed in a part of said binder. Small abrasive grains are fused with each other to form secondary pores, the average diameter of each granulated small abrasive stone is in the range of 0.08 to 1.2 mm, and each secondary pore is each granular small abrasive stone. A superfinishing whetstone characterized by being formed smaller than the average diameter of 2. A granulation operation of a mixture of fine abrasive grains having an average particle diameter of 45 μm or less, a binder, and an artificial pore agent having an average particle diameter of 0.01 to 0.1 mm, so that the average particle diameter is reduced. 0.2
２2 mm, and 5-100 of the artificial pore agent.
To form original granules in the range of twice,
A method for producing a superfinishing whetstone, comprising compression-molding at a pressure of Pa, followed by main drying at a temperature of 80 ° C. or lower, followed by drying and firing at a maximum temperature of 840 ° C. 3. The method for producing a superfinishing whetstone according to claim 2, wherein the raw particles are dried and hardened by internal heating before compression molding. 4. The method for producing a superfinishing whetstone according to claim 2, wherein a flexibility and plasticity additive is added during the compression molding of the raw particles.