JP2002301665A - Grinding wheel and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grinding wheel capable of keeping high bite, high surface roughness and a high grinding rate over a long time and having a long grinding life. SOLUTION: This grinding wheel is characterized by being manufactured by using abrasive grains formed by covering their surfaces with a binding material, and having an uneven coverage for individual abrasive grains and an overall coverage of 85% or more for all the individual abrasive grains. When it is assumed that a coverage for the abrasive grains with the surfaces thereof completely covered with the binding material is 100%, that for those with the surfaces generally covered is 90%, that for those with the surfaces incompletely covered and with part of the surfaces thereof exposed is 50% and that for those with the surfaces almost non-covered is 0%, the grinding wheel is manufactured by using an abrasive coating wherein the abrasive grains having the different coverages coexist and the overall coverage for all the individual abrasive grains is 85% or more. In the grinding wheel, the binding material for covering the abrasive grains belongs to a vitrified group or a resinoid group, and the maximum grain diameter of the binding material is 1/5 or less of the average diameter of the abrasive grains.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grinding wheel, and more particularly to a method of coating abrasive grains with a binder.
The present invention relates to a grinding wheel excellent in grinding life and the like by controlling a covering rate as a total of abrasive grains.

[0002]

BACKGROUND OF THE INVENTION Usually,
The grindstone is manufactured by coating abrasive grains with a binder, press forming and firing. The microstructure of the whetstone manufactured here is
The abrasive grains and the binder form crosslinks, and exhibit a structure in which pores are dispersed therebetween. A grinding stone that has a structure in which the abrasive is uniformly covered with the binder, has less excess binder not involved in cross-linking, and has a structure in which the pores are uniformly dispersed, can maintain a constant sharpness for a long period of time, and has a high grinding ratio. Since the life is long and the abrasive grains fall off uniformly, the surface roughness of the workpiece is good.

[0003] In contrast, when the binder is not uniformly coated on the abrasive grains, the bridging between the abrasive grains and the binder is not uniform, and in some abrasive grains, the bonding strength between the abrasive grains and the binder is high. In addition, with some abrasive grains, the binder hardly adheres, so that the holding and falling off of the abrasive grains during grinding become uneven. In the case of abrasive grains having a weak bonding force, the abrasive grains partially fall off. As a result, the number of cutting edges decreases, and a large force acts on other abrasive grains. Therefore, the grinding ratio is small and the life of the grinding wheel is short.
In addition, there is a disadvantage that the surface roughness becomes coarse due to the large shedding of the abrasive grains, and the dress interval cannot be lengthened. In order to obtain a uniform structure of the grindstone, it is necessary to perform uniform coating when coating the abrasive grains with the binder, and it is difficult to make the structure uniform in subsequent steps.

[0004] However, in order to obtain an abrasive in which the binder is uniformly coated on the abrasive grains (100% coverage), it is necessary to strictly control the coating conditions. For example, when the binder is added to a large amount, a trouble of aggregation between the abrasive grains occurs. It is also conceivable that the mixing takes time, but there is a problem that the cost is increased.

The present invention solves the above-mentioned problems of the prior art, and provides a grinding wheel having a long grinding life, capable of maintaining good sharpness, good surface roughness, and a high grinding ratio for a long period of time. The purpose is to do so.

[0006]

Means for Solving the Problems As a result of investigations, the present invention has been made for the above purpose, and the degree of coating of abrasives with a binder is as follows. The above object is achieved by a grinding wheel produced using abrasive grains having a coverage of 85% or more, preferably 90% or more.

[0007] The coverage of abrasive grains whose surface is coated with a binder is 100% for completely coated abrasive grains, 90% for almost coated abrasive grains, and imperfectly coated and partially When the coverage of the exposed abrasive grains is defined as 50%, and the coverage of the abrasive grains having almost no abrasive grains coated is defined as 0%, the coverage as the sum of the individual abrasive grains is 85% or more. The above object is achieved by a grinding wheel manufactured using abrasive grains.

In the present invention, a vitrified bond and a resinoid bond can be used as the binder, and the maximum particle size thereof is 1/5 or less, more preferably 1/10 or less, of the average particle size of the abrasive grains. As the abrasive grains, alumina-based, silicon carbide-based, CBN-based, diamond-based abrasive grains and the like can be used.

[0009]

Embodiments of the present invention will be described below. As a method for coating the surface of the abrasive grains with the binder, a normal stirring grinder, a powder granulation coating apparatus, or the like can be used. In particular, in order to apply a uniform coating, it is preferable to use a centrifugal rolling granulation coating apparatus that coats the binder while rolling the abrasive grains. In this case, a method in which the surface of the abrasive grains is wetted with a binder in advance and a powder that is a binder is sprayed, or a method in which the binder is dissolved in a solvent and a slurry in which the binder is suspended is sprayed onto the abrasive grains may be employed. it can. However, in order to apply a uniform coating with a coverage of 85% or more and abrasive grains are not aggregated via the binder, a slurry in which the binder is suspended using a rolling granulation coating apparatus or the like. A method of spraying on abrasive grains is more preferred. It is difficult to increase the coverage to 80% or more by a coating process using a usual stirring grinder.

In order to coat the binder uniformly on the abrasive grains, it is necessary that the maximum grain size of the binder material is 1/5 or less as compared with the grain size of the abrasive grains, so that uniform coating can be easily performed. Is preferably 1/10 or less. For example, when abrasive grains having a particle size of # 120 (particle size of 100 to 120 μm) are used, the maximum particle size of the binder is ２０20 μm.
Or less, more preferably 〜１０10 μm or less. When the particle size of the binder is 1/5 or more of the particle size of the abrasive grains, uniform coating becomes difficult. In particular, abrasive grains with a large amount of binder attached,
Abrasive grains to which no binder adheres are mixed, and a grindstone having a uniform structure cannot be manufactured.

Whether or not the abrasive particles are coated with the binder can be confirmed with a scanning electron microscope, an optical microscope or the like. Further, a lump of abrasive grains, which are aggregated with abrasive grains via a binder, and a free bond, which is a binder not covered with the abrasive grains, can be removed by passing through a sieve having an appropriate opening.

In the thus-prepared mixture of the abrasive grains and the binder, the coverage is 85% as the total amount of the entire abrasive grains.
As described above, more preferably, a grinding wheel manufactured using abrasive grains of 90% or more exhibits a uniform structure, and becomes a grinding wheel excellent in grinding performance such as surface roughness, grinding ratio, grinding wheel life and the like. 85% coverage
Below, no remarkable improvement is seen in the grinding performance. The production of the grindstone using the uniformly coated abrasive grains may be performed by a usual method, and the compound can be pressed and fired to produce the grindstone.

As described above, in the fine structure of the grindstone manufactured by using the abrasive grains having a coverage of 85% or more according to the present invention, the crosslinks between the abrasive grains and the binder are formed uniformly, and pores are uniformly dispersed during the formation. Present the organization. Also, the binder is uniformly coated on the abrasive grains,
Since there is little extra binder not involved in cross-linking and the pores are uniformly dispersed, a constant sharpness can be maintained for a long period of time, the grinding ratio is high, the grinding wheel life is long, and the abrasive grains fall off uniformly Therefore, the surface roughness of the processed product is good. FIG. 1 (a) shows a schematic structure of a grindstone manufactured using abrasive grains having a coverage of 85% or more according to the present invention, and FIG. 1 (b) shows a structure manufactured using abrasive grains having a low coverage. 1 shows the structure of a whetstone.

[0014]

The present invention will be specifically described below based on examples and comparative examples.

[Embodiment 1] Hereinafter, the present invention will be described in detail with reference to embodiments and working examples. # 120 C as abrasive
BN abrasive grains were used, and a vitrified bond having an average particle diameter of 6 μm (the maximum particle diameter was 10 μm) was used as a binder. The composition of the vitrified bond is: SiO2: 55 wt%, A
l2O3: 30 wt%, B2O3: 10 wt%, and other components were 5 wt%. A phenol resin as a binder was diluted with ethanol, and a vitrified bond was mixed in the diluted solution to form a slurry. Using a rolling granulation coating apparatus, the abrasive grains were rolled, and the slurry was sprayed to perform coating. The coverage was observed in 10 visual fields using a scanning electron microscope, and the average value was determined. As a result, the coverage was 98%. The bond was 26 parts by weight based on 100 parts by weight of the abrasive grains. FIG. 2 shows a coverage of 100.
%, 90%, 50%, and 0%. The thus-prepared mixture of the abrasive grains and the binder was press-molded into a grindstone shape and baked at 1030 ° C. in a nitrogen atmosphere to produce a straight (100D × 7T × 25H) CBN vitrified grindstone.

[Comparative Example 1] As a method for coating abrasive grains with a binder, a conventional stirring grinder was used, and the abrasive grains were coated with a phenol resin as a binder. Thereafter, a vitrified bond 500 having the same composition as in Example 1 is used.
g was added and stirred and mixed in the same manner to coat the bond. The coverage of the abrasive grains was 65%. In the same manner as in Example 1,
A straight CBN vitrified grindstone was manufactured.

[Working Example] Using the CBN vitrified grindstone obtained in the above embodiment and comparative example, a work material (SU
The surface of J2 quenched 100L × 3.5W) was ground. The grinding conditions are as follows, and the grinding wheel peripheral speed is 1600
m / min, table feed speed 8 m / min, depth of cut 26 μm, wet plunge grinding method. The dress of the whetstone uses SD50M100M as a dresser, speed ratio 0.4, lead 0.1mm / rotation, depth of cut 2μ
m / pass. Grinding ratio (defined as grinding amount (volume) of grinding object / grinding wheel wear amount (volume)) and grinding surface roughness (after grinding a certain amount of grinding object) Table 1 shows the results obtained by examining the surface roughness (Ra) and the grinding resistance (grinding resistance after grinding a fixed amount of the workpiece: current value). The numerical values shown in Table 1 are obtained by relative evaluation of the values of the examples with the comparative example being 1.00.

Example 2 Alumina WA abrasive grains of # 80 were used as abrasive grains, and a phenolic resin-based novolak powder having an average particle diameter of 10 μm (the maximum particle diameter was 15 μm) was used as a binder. A phenol resin was diluted with ethanol as a binder, and a phenol resin diluent was sprayed using a tumbling granulator while rolling the abrasive grains, and then novolak powder was added little by little. This step was repeated to perform coating. As a result of measuring the coverage in the same manner as in Example 1,
The coverage was 87%. The thus-prepared mixture of the abrasive grains and the binder is press-formed into a grindstone shape,
Bake at ℃, cup type (100D × 25T × 25H, 6W)
A resinoid whetstone was prepared.

[Comparative Example 2] As a method of coating a binder on abrasive grains, a liquid phenol resin was coated as a binder on the abrasive grains using an ordinary stirring grinder. After that, novolak powder was added, and the mixture was similarly stirred and mixed to coat the bond. A resinoid grindstone was manufactured in the same manner as in Example 2. The coverage of the abrasive grains was 60%.

[Working Example] The surface of the work material (SUJ2 quenched Φ20) was ground using the alumina-based resinoid grindstones obtained in the above Example 2 and Comparative Example 2. The grinding conditions are as follows, and the grinding wheel peripheral speed is 1200 m / m
in, work material rotation speed 340 rpm, cutting speed 7 mm
/ Min, wet infeed grinding method. The dress of the grindstone uses an impregnated diamond dresser as a dresser, and has a grindstone peripheral speed of 1200 m / min and a lead of 0.1 mm.
1 mm / rotation, cut amount 30 μm / pass, dress amount 1 mm. Table 1 shows the results of examining the grinding ratio, ground surface roughness, and grinding resistance under the above conditions in the same manner as in the above-described processing examples. The numerical values shown in Table 1 indicate that the comparative example is 1.00.
Are relative evaluations of the values of the examples.

[0021]

[Table 1]

Comparative Example 3 Alumina WA abrasive grains of # 80 were used as abrasive grains, and a phenolic resin-based novolak powder having an average particle diameter of 10 μm (the maximum particle diameter was 15 μm) was used as a binder. The phenol resin was diluted with ethanol as a binder.
5 times. Using a tumbling granulator, the phenol resin diluent was sprayed while the abrasive grains were tumbled, and then novolak powder was added little by little. This step was repeated to perform coating. As a result of measuring the coverage in the same manner as in Example 1, the coverage was 100%. When the thus-prepared abrasive grains were blended with the binder, 20% or more of the aggregates of the abrasive grains in which the abrasive grains and the abrasive grains were aggregated via the binder were generated, and many loose binders were also generated. . It is cumbersome, impractical and not applicable to actual production to create a whetstone by post-processing this.

[0023]

As described above, according to the present invention, it is possible to maintain a good sharpness, a good surface roughness and a high grinding ratio over a long period of time, and to provide a grinding wheel having a long grinding life. .

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a coverage and a schematic structure of a grindstone.

FIG. 2 is an observation photograph according to particle coverage.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yuki Nakajima 1333-2, Hara-shi, Ageo-shi, Saitama Mitsui Mining & Smelting Co., Ltd. (72) Inventor Masakazu Sato 11-10 Sayamagahara, Iruma City, Saitama Prefecture Inside Mitsui Grinding Stone Corporation (72) Inventor Katsuhiko Yamashita 11-10 Sayamagahara, Iruma City, Saitama Prefecture Mitsui Grinding Stone Co., Ltd. In-company (72) Inventor Akira Sakai 11-10 Sayamagahara, Iruma-shi, Saitama Mitsui grinding wheel Co., Ltd. F-term (reference) 3C063 AA02 BA37 BB02 BB03 BC03 BC05

Claims (4)

[Claims] An abrasive grain having a surface coated with a binder, wherein the coverage of the individual abrasive grains is not uniform and the total coverage of the individual abrasive grains is 85% or more. A grinding wheel characterized by being manufactured using: 2. The coating rate of an abrasive grain whose surface is completely covered with a binder is 100%, and that of an almost-coated abrasive grain is 90%.
When the coating rate of the abrasive grains whose coating is incomplete and the surface of the abrasive grains is partially exposed is 50%, and the coating rate of the abrasive grains having almost no coated abrasive grains is 0%, these coating rates are different. Abrasive grains are mixed, and the coverage as the sum of individual abrasive grains is 8
A grinding wheel manufactured using 5% or more of abrasive grains. 3. The binder for coating the abrasive grains is a vitrified type or a resinoid type, and the maximum particle size of the binder is 1/5 or less of the average particle size of the abrasive grains. 2. The grinding wheel according to 2. 4. The method for producing a grinding wheel according to claim 1, wherein a slurry in which a binder for coating the abrasive grains is suspended in a solvent is sprayed on the abrasive grains and dried.