JPH08155840A - Cohered abrasive grain grinding wheel - Google Patents

Abstract

PURPOSE: To provide a cohered abrasive grain grinding wheel manufacturing method with a simple manufacturing process capable of effecting economical use of a cohered abrasive grain grinding wheel with a large finish ratio and obtaining the precise and minute finished surface without needing a screening process to mixed abrasive grains. CONSTITUTION: Abrasive grains with vitrified bond mixed therein is cohered, and cohered abrasive grains granulated so as to be 0.5mm or less in cohered diameter 4-8 times larger than the abrasive grain diameter are bound to form a cohered abrasive grain grinding wheel. In order to manufacture such a cohered abrasive grain grinding wheel, an aqueous temporary binder is mixed at the mixing time so that the water content is 3-8wt.%, and primary grains are formed by rolling granulation in an agitator. These primary grains are cracked and refined to form secondary grains cohered so as to be 0.5mm or less in cohered diameter 4-8 times larger than the abrasive grain diameter, and the secondary grains are bound and formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an agglomerated abrasive grain grindstone formed by aggregating abrasive grains containing a binder such as vitrified bond and agglomerating the agglomerated abrasive grains.

[0002]

2. Description of the Related Art Generally, abrasive grains are vitrified bonds,
In superfinishing whetstones, honing whetstones, etc., that are formed by blending resin bonds and other binders, individual abrasive grains are uniformly dispersed and filled in the whetstone without being aggregated or aggregated. Technical consideration will be given from both sides.

In particular, when the abrasive grain size is 20 μm or less, it is difficult to make the bond grain size sufficiently smaller than the abrasive grain size, so that irregular agglomerated grains or agglomerates are formed. easy.

Regarding the conventional method for manufacturing a vitrified bond grindstone, two types, a casting method and a compression method, have been known so far. The difference between these manufacturing methods is mainly in the mixing and stirring process of the raw materials, and the former casting method is to perform stirring and mixing in a slurry (slurry) state in which a large amount of raw materials containing abrasive grains and a binder are mixed, and the latter is in a wet state. Of powder. In the casting method, the difference in specific gravity between the abrasive grains, the binder and the other additives is taken into consideration, and stirring and mixing are performed in a sludge state, so that the abrasive grains can be uniformly dispersed relatively easily.

Since such a casting method is difficult in terms of production efficiency and control technology, the present situation is that the following compression method is being adopted.

In the compression method, powder in a wet state is mixed, but since the amount of water is small, irregular grains, agglomerates or agglomerates of abrasive grains are easily generated. In particular, when the abrasive diameter is 20 μm or less, it is difficult to make the vitrified bond particle diameter sufficiently smaller than the abrasive particle diameter,
This tendency is promoted.

Therefore, in order to adjust the size of such irregular mixed abrasive grains, it is necessary to adjust the size of the abrasive grains through the mixing process.
The mixed abrasive grains from three small aggregated aggregated grains to large aggregated grains that are 10 times or more or several tens times the abrasive grain size are made uniform by sieving and I had to adjust the humidity.

In such a sieving process, if the sieve opening (JIS 28801) is less than 180 μm, the mixed powder components are separated, which is inconvenient, and the maximum particle size of the abrasive grains in the sieving process is 250 μm or less, that is, 180 ~
The thickness of about 250 μm is used.

In addition, when manufacturing a metal bond grindstone, the following manufacturing method is adopted in order to eliminate uneven distribution of abrasive grains in the grindstone.

That is, according to the method described in JP-A-5-16074, a mixture fluidized by heating and kneading a mixture of superabrasive grains and metal bond powder, wax and an organic thermoplastic binder such as a thermoplastic resin. Is extruded to an arbitrary size and pelletized. Further, this is heated and fluidized to be molded by an injection molding method or the like, and then degreasing and sintering are performed to manufacture a metal bond grindstone.

Further, in the method described in JP-A-5-16073, a metal bond and a coating layer of an additive are formed on the outer periphery of a superabrasive grain having a relatively large particle diameter, which is coated with a metal, and then this is coated. By mixing with a resin binder and injection-molding in a mold, the resulting grindstone was degreased and sintered to obtain a uniform abrasive grain layer without segregated abrasive grains.

Next, regarding the state of mixing and stirring the fine-grained grindstone, in either case of the casting method and the compression method described above, the stirring tool such as a hook or a leaf (fan) having a large contact surface revolves while revolving. A stirrer of a stirring type is used. The stirring action in this case is stirring, kneading or crushing.

In the compression method, a small amount of liquid is mixed in the powder,
The mixture is wet and highly viscous, but at this time, the mixture in the stirring tank is kneaded from the central portion to the inner wall, and at the same time, it is vertically moved by the twist of the stirring tool described above. At this time, the mixed powder is
The kneading tends to cause uneven agglomeration of abrasive grains. This agglomerate is not sufficiently uniformly crushed, and irregularly-mixed powder containing small particles to large agglomerated particles is produced by stirring. Then, in order to separate and remove the large lump particles formed in this way, the mixed powder,
It was made to pass through a predetermined sieve opening.

[0014]

However, in the above-mentioned conventional agglomerate abrasive wheel, even if the maximum particle size of the abrasive particles is limited to 250 μm or less by the sieving process, the obtained wheel has a sufficient finish grinding ratio. It ’s not very big,
There is a problem that there are many cloggings, and a sufficiently dense and fine finished surface cannot be obtained.

Particularly, in the case of fine grains having an abrasive grain size of 20 μm or less,
There is also a problem that irregular agglomerates or agglomerates are often generated when the raw materials are mixed.

Furthermore, there is a problem that the manufacturing process becomes complicated because a sieving process for mixed abrasive grains of various diameters is required as an essential manufacturing process.

In view of the above, the present invention solves the above-mentioned problems, and makes it possible to use the agglomerated abrasive grain grindstone economically with a large finishing ratio, and to obtain a fine and fine finished surface. That is the issue.

Even when fine particles having a diameter of 20 μm or less are used as the abrasive grains of the agglomerate abrasive wheel, the method for producing an agglomerate abrasive wheel does not produce irregular agglomerates or agglomerations, or mixing is performed. It is an object of the present invention to provide a method for producing an agglomerated abrasive grain grindstone that does not require a sieving process for abrasive grains and has a simple production process.

[0019]

In order to solve the above-mentioned problems, in the present invention, the abrasive grains containing a binder are aggregated to form an aggregate diameter of 0.5 mm or less at 4 to 8 times the abrasive grain size. The agglomerated abrasive grains thus granulated were combined and molded to form an agglomerated abrasive grain grindstone.

Alternatively, the abrasive grains mixed with the vitrified bond binder are aggregated so as to have an aggregate diameter of 0.
This is a vitrified bond agglomerate abrasive wheel formed by combining and shaping agglomerate agglomerates that have been granulated to have a size of 5 mm or less.

In the above-mentioned agglomerated abrasive grain grindstone, abrasive grains containing a binder are agglomerated to form primary particles, and the primary particles are crushed into fine particles to have an aggregate diameter of 0.5 mm or less and an abrasive grain size of 4 ~ 8
It can be manufactured by forming secondary particles which are agglomerated so as to be doubled, and binding and molding the secondary particles.

The details of the above-mentioned manufacturing method are as follows. That is, for example, a water-based temporary binder is added to a mixture of abrasive grains and a binder or other auxiliary agent to obtain a water content of 3 to 8
The primary granulated particles are formed by rolling granulation in a stirrer so as to be 4% to 8 times the abrasive grain size with an aggregate diameter of 0.5 mm or less. It can be produced by forming secondary granulated particles that are finely pulverized and agglomerated into, and bonding and molding the secondary granulated particles.

[0023]

The agglomerate abrasive wheel according to the present invention is formed by aggregating abrasive particles containing a binder in a size within a predetermined range. On the contrary, the larger the original abrasive grain size, the smaller the number of agglomerated abrasive grains, and the agglomerated abrasive grains that can be uniformly dispersed are formed.

A grindstone having such agglomerated abrasive grains has a small grindstone wear amount even if the grindstone coupling degree is relatively soft,
A high cutting amount and a good finished surface roughness can be obtained.

The diameter of the agglomerated abrasive grains which are the secondary particles is
By increasing the water content with an aqueous temporary binder,
The granulation effect increases and becomes larger. In addition, the abrasive grain diameter of 4 ~
In order to agglomerate 8 times, the water content may be set to, for example, 3 to 8% by weight so that the water content is increased by about 25 to 55% in the mixing and stirring by the conventional compression method.

In addition to the above-mentioned granulation conditions, primary granulation particles are formed by rolling granulation in a stirrer, and the primary granulation particles are crushed and finely granulated, and then agglomerated abrasive having a uniform size without unevenness. Grains are obtained.

[0027]

EXAMPLES The abrasive grains used in the present invention are not particularly limited in their material, and include aluminum oxide, silicon carbide,
Cubic boron nitride (CBN), diamond and the like can be exemplified, and a mixed abrasive grain in which two or more kinds of different abrasive grains are mixed can also be adopted.

The agglomerate abrasive grain size of 4 to 8 times the abrasive grain size is, for example, the original abrasive grain size is 30 μm (400 mesh).
In the case of No. 120-240 μm, the original abrasive grain size is 9.5 μm
38 to 76 μm in the case of (1200 mesh), 16 to 32 μ in the case of the original abrasive grain size of 4 μm (3000 mesh)
m. Usually, the smaller the original particle size, the larger the number of agglomerated abrasive grains.

The diameter of such an abrasive grain is JIS-R600.
1 Grain size of abrasives 3 ・ 2 Fine powder, 3 ・ 2 ・ 2 by electrical resistance test method Table 4 Fine particle size distribution, particle size at cumulative height 50% point (dv-50 value). Further, the size of the aggregated particle size was photographed by a scanning electron microscope (SEM) of a sample sampled from the mixed powder of abrasive grains after completion of the mixing.

From the practical range of the agglomerate abrasive grain of the present invention, the original abrasive grain diameter measured in this manner is such that fine abrasive grains of about 60 μm or less have relatively high abrasive stone performance, and especially the original abrasive grain diameter is small. By using fine abrasive grains having an abrasive grain size of 3 μm or less, extremely high grindstone performance can be obtained. It should be noted that such an improvement in performance due to the original abrasive grain size can be seen even when the original abrasive grain exceeding 100 μm is used, and therefore such a large abrasive grain may be adopted depending on the use of the grindstone. Of course.

The agglomerated abrasive grain size in the present invention is 0.5 m.
Adopt m or less. This is because when the maximum grain size is 57 μm (240 mesh), which is the grain size of the fine grain grindstone that is practically used for honing and superfinishing due to the surface contact between the grindstone and the workpiece, the aggregate grain size is 0.5 mm. For larger diameters, the grinding wheel finish ratio (cutting amount / grinding wheel wear amount)
Is smaller, the economy is poor, and the finished surface is rough. However, it is, of course, possible to agglomerate and agglomerate even if the original abrasive grain size is, for example, a coarse grain size of 220 mesh or less that exceeds 100 μm of the sieve opening.

Further, the agglomerated abrasive grain diameter in the present invention is 0.5 mm or less as described above and is 4 to 8 of the original abrasive grain diameter.
Adopt a double range. The reason is that when it exceeds 8 times, the original abrasive grain size becomes considerably small, and in this case, when the aggregated abrasive grain size is relatively small, the cohesive force between the aggregated abrasive grains is strong and the abrasion amount of the grindstone is small. Machinability deteriorates, which is not preferable. If the agglomerated abrasive grain size is made sufficiently large within the above range by more than 8 times, the bonding force between the original abrasive grains will be strong, but the adhesive force between the agglomerated abrasive grains will be weakened. In this case, although the grindstone is crushed or clogged, the abrasion amount of the grindstone is large, the finishing ratio is small, which is not economical and the finished surface is rough, which is not preferable.

As the mixing and stirring conditions for producing such agglomerated abrasive grains, there is no adhesion of the abrasive grain mixing raw material to the inner wall of the stirring tank, and the rolling process is performed under the mixing and dispersing conditions with good dispersibility and reversal motion. Do the grain. Furthermore, by combining crushing or crushing action with such rolling granulation, it is possible to manufacture agglomerated abrasive grains having a uniform diameter. The agglomerated abrasive grains thus obtained have a uniform size, and the sieving step for adjusting the grain size can be omitted, thus improving the productivity.

When it is necessary to control the humidity or dry the mixed raw material, it is preferable to appropriately perform a drying treatment so as not to impair the agglomeration / granulation state.

In the present invention, a water-based temporary binder is mixed in the mixed material so as to be, for example, 3 to 8% by weight, and rolling granulation is carried out by reversing motion on the inner wall surface in the stirrer and repeated stirring by centrifugal force. Secondary particles having a uniform size, which are formed by crushing the primary particles at the same time so that the primary particles are aggregated to have an aggregate diameter of 0.5 mm or less and 4 to 8 times the abrasive particle size. To form.

In order to form such agglomerated abrasive grains (secondary particles), preferable results have been obtained using a stirrer having the following structure and action.

That is, the stirring tool installed in the stirring tank has a main blade that makes a turning motion and a reversing motion, and further has a sword-shaped wing-shaped auxiliary blade that is mounted close to the main blade and rotates. To adopt. Rolling granulation is performed by the rotation of the main blade to form primary granules. At the same time as the rotating movement of the main blade, the auxiliary blade attached close to the main blade is rotated at a high speed to crush and crush the agglomerated particles generated during the primary granulation. Generate secondary particles.

In this manner, the rotating wing-shaped main blade is rotated, and at the same time, the auxiliary blade, which is smaller than the main blade and has the shape of a sword blade, is rotated at high speed. Therefore, the granulation is performed in combination with each other, and in a single step, fine-grained agglomerated abrasive grains (secondary granulated particles) having a uniform size can be obtained.

The agglomerated abrasive grains obtained by the above method are then charged into a predetermined mold for forming a grindstone, taken out from the mold after molding, and dried through a maximum temperature of 1240 ° C., for example. Firing is carried out for 32 hours in the firing cycle to obtain an agglomerated abrasive grain grindstone of the product.

[Examples 1 to 6 and Comparative Examples 1 to 5] 12 parts by weight of a high-melting vitrified bond was mixed with 1 part by weight of white alumina oxide abrasive grains, and an organic auxiliary (ethylene glycol) was used. ) An aqueous temporary binder consisting of 20% by weight and 15% by weight of dextrin was used in Examples 1-2.
˜7.7 wt%, in Comparative Examples 1 to 3, 2.5 to 5.5 wt%, and in Examples 4 to 6 and Comparative Examples 4 and 5, 4.6 to 6.5 wt%. And about Examples 1-6, the main-blade rotation speed is 200 rp with the stirring mixer of the said structure which can be crushed into the secondary granulated primary granulated particles by rolling granulation.
Granulation was conducted under the conditions of m and auxiliary blade rotation speed of 3000 rpm.

Further, in Comparative Examples 1 to 5, the above-mentioned blended raw materials were mixed by a mixing / stirring, crushing and screwing up / down action by a rotation / revolution type mixer with a well-known hook-shaped stirring tool. Then, after the mixing was completed, the particles were classified by passing through a sieve opening of 180 μm.

The raw materials blended in the above are the hardness of the grindstone (RH hardness: Rockwell H scale, indenter 3.17).
RH2 5mm steel ball, test load 60kg, dial B)
Set to 0 and add organic structuring agent (polystyrene) to the hardness of 1.0 ± 0.5
It is added in the range of parts by weight, that is, with the same abrasive grain size,
The same amount of tissue agent was blended.

The agglomerated abrasive grain that has been granulated has a water content of 1.5.
After being dried at a temperature of 80 ° C. or less so as to be ˜3.5 wt%, it was charged into a mold having a predetermined grindstone shape, molded, and then naturally dried. And this is the maximum heating temperature 12
Firing is performed at 40 ° C. for 32 hours in a firing cycle, and the obtained grindstone is finished into a square shape (length 3 mm, width 11 mm),
The following actual cutting test was conducted.

[Actual cutting test] Using a superfinishing machine (manufactured by Seibu Automatic Equipment Co., Ltd.) with processing oil (mineral oil 90%, sulfurized fatty oil 10%), bearing steel (SUJ2, Class 2, 60 on Rockwell C scale) ) Cylindrical outer surface (outer diameter 20 mm, width 12 mm) is the grindstone working surface (circumferential direction width 3 mm, axial direction width 11 mm)
Plunge cut was super finished using.

The main superfinishing conditions at this time are as follows: grindstone vibration frequency 1000 cpm, grindstone amplitude 2 mm, workpiece rotation speed 515
Maximum tilt angle 1 which gives the shape of the sine wave motion locus of the abrasive grain (grinding stone) at rpm and grindstone working surface pressure of 7.3 kgf / cm ^2.
It was once.

The pre-working of the work piece was made uniform by grinding to a surface roughness of 1.5 μm Rz, the superfinishing time was 30 seconds, and each measured amount was an average value for five work piece tests. . In addition, the measurement items are grindstone wear amount Wmm ³ , cutting amount Tmm ³ , finishing ratio T / W, and finished surface roughness Rz μm.
And These results are collectively shown in Table 1 or Table 2.

[0047]

[Table 1]

[0048]

[Table 2]

As is clear from the results shown in Table 1, Examples 1 to 3 have apparently a softer stone coupling degree than Comparative Examples 1 to 3, but the stone abrasion amount W is small and the cutting amount T is small. Therefore, it is understood that the grinding stone has a large finishing ratio T / W and can be processed economically, and the finishing surface is fine and excellent.

The results in Table 2 relate to agglomerate abrasive grains having a grain size of 1200 mesh, and the agglomerate abrasive grain size is 4 of the original abrasive grain size.
When it is less than twice (Comparative Example 4) or more than eight times (Comparative Example 5), T or W increases or decreases in proportion to the cutting amount T or the grindstone wear amount W, so the finishing ratio T / W is small, and The surface was also rough.

On the other hand, Examples 4 to 6 in which G / G ₀ satisfies 4 to 8 have high performance and high economic efficiency.

[0052]

[Effect] As described above, according to the present invention, since abrasive grains are aggregated into a size within a predetermined range and bonded and molded,
The agglomerated abrasive grain stone has an advantage that it can be economically used because it has a large finishing ratio even if the degree of bonding of the stone is soft, and that it can obtain a dense and fine finished surface.

Further, the manufacturing method of the above-mentioned agglomerated abrasive grain grindstone,
A predetermined amount of a temporary binder was added to the abrasive grains containing a binder, and the granulated primary particles were crushed by rolling granulation and then finely granulated and molded. It is a method of manufacturing agglomerate abrasive wheel that does not generate irregular agglomerates or agglomerates even with the use of fine particles, and simplifies the manufacturing process by eliminating the sieving process for mixed abrasive grains. There is.

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[Procedure amendment]

[Submission date] February 22, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0047

[Correction method] Change

[Correction content]

[0047]

[Table 1]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0048

[Correction method] Change

[Correction content]

[0048]

[Table 2]

Claims (3)

[Claims] 1. An agglomerate abrasive formed by agglomerating abrasive particles containing a binder and agglomerating agglomerate particles that are agglomerated so that the agglomerate diameter is 0.5 mm or less at 4 to 8 times the abrasive particle size. Grain whetstone. 2. Abrasive grains containing a vitrified bond binder are aggregated to obtain an aggregate diameter of 0.5 mm at 4 to 8 times the abrasive grain size.
A vitrified bond agglomerate abrasive grain formed by combining and shaping agglomerate agglomerates that have been granulated as described below. 3. Abrasive grains containing a binder are aggregated to form primary particles, and the primary particles are crushed into fine grains so that the aggregate diameter is 4 mm to 8 times the abrasive grain size at 0.5 mm or less. A method for producing an agglomerated fine-grained grindstone, which comprises forming secondary particles agglomerated into particles, and bonding and molding the secondary particles.