JP2002294221A - Method for coating abrasive grain - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abrasive grain for a whetstone which can maintain good cutting sharpness, good surface roughness and a high grinding ratio for a long period of time and has a long grinding life. SOLUTION: The method for coating abrasive grain comprises coating an abrasive grain with a binding material, where a slurry comprising the binding material dispersed in a solvent is sprayed on the abrasive grain and then dried. In the method for coating abrasive grain, the binding material for coating the abrasive grain is preferably a vitrified or a resinoid one and the largest particle size of the binding material is 1/5 or less of the average particle size of the abrasive grain. In the method for coating abrasive grain, an alumina-based, silicon carbide-based, CBN-based or diamond-based abrasive grain is preferably used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coating abrasive grains used in a grinding wheel, and more particularly to a uniform structure in which pores are uniformly dispersed and the bonding force between the abrasive grains and a binder is good. The present invention relates to a method for coating abrasive grains for producing a grinding wheel.

[0002]

BACKGROUND OF THE INVENTION Generally,
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.

The present invention solves the above-mentioned problems of the prior art, and makes it possible to maintain a good sharpness, a good surface roughness and a high grinding ratio over a long period of time, and to produce a grinding wheel having a long grinding life. The purpose of the present invention is to provide abrasive grains for use.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been made for the above purpose, and is a method for coating abrasive grains with a binder, comprising a step of preparing a slurry in which the binder is suspended in a solvent. This is a method for coating abrasive grains, which comprises spraying the abrasive grains and drying them. Further, 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. Is the way. Further, there is provided the abrasive grain coating method as described above, wherein alumina-based, silicon carbide-based, CBN, or diamond is used as the abrasive.

[0006] The degree of coating of the binder on the abrasive grains is defined as follows, and a coating method in which the coating rate is 85% or more has been proposed. The coating rate is 85%, more preferably 9%.
By using 0% or more abrasive grains, good sharpness, good surface roughness, and high grinding ratio can be maintained over a long period of time, and a grinding wheel with a long grinding life can be manufactured. 90% or 100% coverage of abrasive grains whose surface is coated with binder
(100% for completely coated, 90% for almost coated), 50% coverage of incompletely coated and partially exposed abrasive grains, almost abrasive When the coverage of the abrasive grains whose surfaces are not coated is 0%, a method of coating the abrasive grains in which the total coverage of the individual abrasive grains is 85% or more can be provided. In the present invention, a vitrified bond and a resinoid bond can be used as a 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.

[0007]

Embodiments of the present invention will be described below. Examples of a method for coating the surface of the abrasive grains with the binder include a usual stirring grinder, a powder granulation coating apparatus, and the like. 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, there is a method in which the surface of the abrasive grains is wetted with a binder in advance and a powder as 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. However, in order to apply a uniform coating having a coverage of 85% or more and abrasive grains are not agglomerated 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 preferred.

[0008] It is difficult to achieve a coverage of 80% or more in a coating process using a conventional stirring grinder. Also, wet the abrasive surface with a binder in advance,
The method of spraying the powder as a binder can provide a relatively uniform coating, but there are many agglomerates where the abrasive grains are agglomerated through the binder, and there are also many free bonds as the binder that is not coated with the abrasive grains . These abrasive grains and free bonds may be removed by a sieve, but workability is poor in mass production,
Not practical. It is also difficult to increase the coverage and reduce the free bonds. For these reasons, a method has been invented in which a binder is dissolved in a solvent, a slurry in which a binder is suspended is sprayed onto abrasive grains, and the slurry is dried.

Further, in order to coat the abrasive uniformly with the binder, it is necessary that the maximum particle diameter of the binder is 1/5 or less as compared with the particle diameter of the abrasive, 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 is coated with the binder can be confirmed with a scanning electron microscope, an optical microscope, or the like.

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.
Above, there was almost no free bond. A grindstone manufactured using such abrasive grains exhibits a uniform structure and is a grindstone excellent in grinding performance such as surface roughness, grinding ratio, and grinding wheel life. 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. FIG. 2 shows examples of coverages of 100%, 90%, 50%, and 0% as examples of the coverage. FIG. 1 (a) shows an example of a grindstone having a uniform structure manufactured using abrasive grains having a high coverage of 90% or more. Also,
FIG. 1B shows a schematic structure of a grindstone manufactured using a low coverage of about 50%.

[0011]

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

[Example 1] CBN of # 120 as abrasive grains
A vitrified bond having an average particle size of 6 μm (maximum particle size is 10 μm) was used as a binder, using abrasive grains. The composition of the vitrified bond is as follows: SiO 2: 55 wt%, Al 2
O3: 30 wt%, B2O3: 10 wt%, and other components were 5 wt%. A phenol resin as a binder was diluted with ethanol to prepare a 10% diluted solution. Vitrified bond 50 is contained in this diluted liquid (1000 cc).
0 g was mixed 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. 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, an ordinary 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 CBN vitrified grindstone was prepared.

[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, cutting depth 26 μm, wet grinding method. The whetstone dress
SD50M100M was used as a dresser, and the speed ratio was 0.1
4. Lead 0.1mm / rotation, cutting depth 2μm / pa
Performed as ss. 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 as a binder was dissolved in ethanol to prepare a 10% dilution. First, a 15% dilution was sprayed on the abrasive grains while rolling the abrasive grains using a rolling granulator (step 1). Then PV as binder
A was diluted with water using A to prepare a 3% diluted solution. 600 g of novolak was mixed with 1000 cc of PVA diluent, and this slurry was sprayed (step 2). Steps 1 and 2 are performed as 2
The coating was repeated several times. As a result of measuring the coverage in the same manner as in Example 1, the coverage was 92%. The thus-prepared mixture of the abrasive grains and the binder is press-molded into a grindstone shape, baked at 180 ° C., and cup-shaped (100D ×
25T × 25H, 6W) A resinoid grindstone 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 a conventional 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 by using the alumina-based resinoid grindstones obtained in Example 2 and Comparative Example 2 described above. 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.

[0018]

[Table 1]

[0019]

As described above, by using the abrasive grains of the present invention, good sharpness, good surface roughness, and high grinding ratio can be maintained for a long period of time, and a grinding wheel with a long grinding life can be maintained. The bubbles contained are fine and uniform, and have high crushing strength.

[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.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B24D 3/28 B24D 3/28 (72) Inventor Yuki Nakajima 1333-2, Hara-shi, Ageo, Saitama Mitsui Kinzoku Mining Co., Ltd. (72) Inventor Kazutomo Hoshino 1333-2, Hara-shi, Ageo-shi, Saitama Mitsui Mining & Smelting Co., Ltd. (72) Inventor Masakazu Sato 11-10 Sayamagahara, Iruma-shi, Saitama Mitsui grinding stone stock In-company (72) Inventor Katsuhiko Yamashita 11-10 Sayamagahara, Iruma City, Saitama Prefecture Mitsui Grinding Stone Co., Ltd. (72) Inventor Akira Sakai 11-10 Sayamagahara, Iruma City, Saitama Prefecture Mitsui Grinding Stone Co., Ltd. F term (reference) 3C063 AA02 BA37 BB02 BB03 BB04 BC03 BC05 CC01

Claims (3)

[Claims] 1. A method for coating abrasive grains with a binder, comprising:
A method of coating abrasive grains, comprising spraying a slurry in which a binder is suspended in a solvent onto abrasive grains and drying the slurry. 2. The method according to claim 1, wherein the binder covering the abrasive grains is a vitrified or resinoid-based binder, and the maximum grain size of the binder is 1/5 or less of the average grain size of the abrasive grains.
A method for coating abrasive grains according to the above. 3. Alumina, silicon carbide, C
2. The method according to claim 1, wherein BN or diamond is used.
A method for coating abrasive grains according to the above.