JP7450243B2 - Composite abrasive grains and elastic wheels - Google Patents

Description

The present invention relates to composite abrasive grains and elastic grindstones.

A grindstone is widely known as a processing tool for grinding and polishing a workpiece. Among them, an elastic grindstone in which abrasive grains made of alumina (aluminum oxide), silicon carbide, diamond, cubic boron nitride (CBN), etc. are dispersed in a binder with rubber elasticity is used to improve the surface shape of the workpiece. It is known as a sharpening stone that is easy to use.

Since the binding material of an elastic whetstone is flexible, (1) when it comes into contact with the surface of the workpiece, the abrasive grains are pushed into the binding material, making it difficult to grind and polish with the abrasive grains protruding. 2) The binding material absorbs the impact given to the abrasive grains, making it difficult for new cutting edges to occur due to the crushing of the abrasive grains; (3) In order to improve these, if a binding material that is easily worn is used, There are problems such as many abrasive grains falling off without contributing to grinding and polishing. Due to these problems, it has been thought that elastic grinding wheels have lower grinding power and have a shorter lifespan than vitrified grinding wheels and resinoid grinding wheels.

In order to solve the above problems, a method was developed in which multiple abrasive grains are bonded using a resin binder to produce "composite abrasive grains" in the form of agglomerated aggregates, and this is used instead of regular abrasive grains. Ta. By dispersing this composite abrasive grain in a binder having rubber elasticity, it is possible to obtain an elastic whetstone having a grinding force equivalent to that of a pitrified whetstone, a resinoid whetstone, etc. (Patent Document 1).

On the other hand, in recent years, due to the increasing complexity and sophistication of workpieces, there has been an increasing demand for elastic grindstones that have high grinding power, long life, and are capable of suppressing the heat generated during machining.

Special Publication No. 48-8678

The problem to be solved by the present invention is to provide an elastic grindstone that has a high grinding force, has a long life, and can suppress the heat generated during processing.

Each embodiment of the present invention is as follows.
[1] Composite abrasive grains for an elastic grindstone, containing a first binding material containing a thermosetting resin and/or a thermoplastic resin, and ceramic abrasive grains.
[2] The composite abrasive grain of [1], which contains 1 to 6 parts by mass of the ceramic abrasive grains per 1 part by mass of the first bonding material.
[3] The composite abrasive grain of [1] or [2], wherein the first binding material contains a phenolic resin.
[4] The composite abrasive grain according to any one of [1] to [3], having a particle size of 0.1 to 5 mm.
[5] A composite of any one of [1] to [4] and a second binding material containing at least one resin selected from the group consisting of synthetic rubber, natural rubber, thermoplastic resin, and thermosetting resin. An elastic whetstone containing abrasive grains.
[6] The elastic grindstone of [5], which has a rubber hardness of 30 to 95 as measured with a type A durometer in accordance with JIS K6253-3.
[7] The elastic grindstone according to [5] or [6], which contains 0.1 to 6 parts by mass of the composite abrasive grains per 1 part by mass of the second binder.

According to the present invention, it is possible to provide an elastic grindstone that has high grinding power, has a long life, and can suppress heat generated during processing.

It is a plot showing temperature changes of workpieces in Examples and Comparative Examples.

[Composite abrasive]
The composite abrasive grain of the present invention is for an elastic grindstone, and contains a first binding material containing a thermosetting resin and/or a thermoplastic resin, and ceramic abrasive grains.
The elastic grindstone here refers to a grindstone that has rubber elasticity.

In conventional composite abrasive grains, fused alumina (molten aluminum oxide) was mainly used as the abrasive grain. When grinding is performed using an elastic grindstone containing composite abrasive grains using fused alumina abrasive grains, "blindness" in which the tips of the abrasive grains are worn out and flattened tends to occur. If grinding is continued in a state where this eye is closed, the normal grinding resistance will increase, causing problems such as vibration of the tool, burning of the workpiece due to excessive heat generation, and falling off of the abrasive grains.

On the other hand, the ceramic abrasive grains contained in the composite abrasive grains of the present invention are less likely to be crushed, the abrasive grains themselves are less likely to fall off, and high grinding power is maintained. In addition, normal grinding resistance is reduced, and heat generation during machining is suppressed.
With ceramic abrasive grains, when a load is applied to the tip of the abrasive grain during grinding, minute chips occur before the abrasive grains are worn away, and new edges always appear. This is considered to be because the ceramic has a polycrystalline structure in which submicron-sized crystals are gathered. This crystal size is much smaller compared to that of fused alumina. This is considered to have contributed to the above effect.

It is known that in normal machining, when tools made of materials with low thermal conductivity are used, frictional heat during machining cannot be released, and the temperature of the workpiece tends to rise. ing. Most ceramics have relatively low thermal conductivity among materials used for abrasive grains. However, according to experiments conducted by the present inventors, it was found that in a grindstone using composite abrasive grains, by using ceramic abrasive grains, the temperature rise of the workpiece can be suppressed more than when using fused alumina abrasive grains. . Although the reason for this is not clear, one of the reasons is thought to be that in composite abrasive grains, the heat generation suppressing effect due to the reduction in normal grinding resistance becomes dominant as described above.
Hereinafter, the composite abrasive grains of the present invention will be explained in detail for each structure.

(First binding material)
The first bonding material contained in the composite abrasive grain of the present invention contains a thermoplastic resin and/or a thermosetting resin.
Examples of the thermoplastic resin include polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyvinyl acetate, thermoplastic polyurethane, acrylonitrile butadiene styrene (ABS), polymethyl methacrylate, polyethyl methacrylate, polyamide, polyester, polycarbonate, Examples include fluororesin.
Examples of the thermosetting resin include phenol resin, urea resin, epoxy resin, melamine resin, polyurethane, and thermosetting polyimide.

The first bonding material preferably contains a thermosetting resin from the viewpoint of heat resistance and moldability into composite abrasive grains, and includes a phenol resin, a urea resin, an epoxy resin, a melamine resin, and a polyurethane resin. It is more preferable to include one selected from the group consisting of: and it is even more preferable to include a phenol resin from the viewpoints of heat resistance, flame retardance, mechanical properties, oil resistance, chemical resistance, economical efficiency, etc.

The first binder may contain antioxidants, antistatic agents, colorants, fillers, light stabilizers, plasticizers, lubricants, flame retardants, flame retardants, as necessary, within a range that does not impede the effects of the present invention. It may also contain other ingredients such as auxiliaries.
The content of the thermoplastic resin and/or thermosetting resin in the first binding material is preferably 80% by mass or more, and more preferably 90% by mass or more.

(ceramic abrasive)
The composite abrasive grain of the present invention contains ceramic abrasive grain.
In this specification, the term "ceramic" refers to a polycrystalline sintered body obtained by heating and baking inorganic powder or the like.
In this specification, ceramics include those manufactured through a sol-gel method.

Components of the ceramic abrasive grains include alumina, zirconia (zirconium oxide), silicon carbide, silicon nitride, and composite materials thereof.
Among these, as the ceramic abrasive grains, it is preferable to use ceramic abrasive grains containing alumina (preferably α-alumina) as a main component, and use ceramic abrasive grains containing 90% by mass or more of alumina (preferably α-alumina). It is more preferable.
The polycrystal size of the ceramic abrasive grains is preferably 10 μm or less, more preferably 5 μm or less, even more preferably 1 μm or less, and most preferably 0.5 μm or less.

The shape of the ceramic abrasive grains is not particularly limited, and can be selected from those commonly used as ceramic abrasive grains. Among these, shapes with sharp edges are preferable, such as a substantially polyhedron having a dihedral angle that is an acute angle or a substantially polyhedron having a trihedral angle in which all three of its constituent corners are acute angles.
One type of the ceramic abrasive grains may be used alone, or two or more types may be used in combination.

The particle size of the ceramic abrasive grains is preferably 180 to 500 μm, more preferably 200 to 350 μm when the elastic grindstone is used for rough finishing. Further, when the elastic grindstone is used for semi-finishing, it is preferably 40 to 180 μm, more preferably 50 to 100 μm.
By setting the particle size of the ceramic abrasive grains within an appropriate range, a grinding and polishing rate suitable for the processing conditions can be obtained.
The particle size of the ceramic abrasive grains can be classified by a sieving method or the like.

In addition, some ceramic abrasive grains not included in the above particle size range may be included. In that case, the ceramic abrasive grains not falling within the particle size range preferably account for 10% by mass or less, more preferably 5% by mass or less of the total ceramic abrasive grains.

(Ceramic abrasive grain content)
The content of the ceramic abrasive grains in the composite abrasive grains of the present invention is preferably 1 to 6 parts by mass, and preferably 2 to 5 parts by mass, based on 1 part by mass of the first binder. The amount is more preferably 2.5 to 4.5 parts by weight, and most preferably 3 to 4 parts by weight.
When the content of the ceramic abrasive grains is within an appropriate range, the grinding power of the grindstone becomes sufficient, and the occurrence of scratches can be suppressed.

(Structure and shape of composite abrasive grains)
The composite abrasive grain of the present invention preferably has a structure in which a plurality of the ceramic abrasive grains are dispersed using the first bonding material as a matrix. However, some of the ceramic abrasive grains may be in contact with each other.

The particle size of the composite abrasive grains of the present invention is preferably 0.1 to 5 mm.
The particle size of the composite abrasive grains can be classified by a sieving method or the like.
In addition, some composite abrasive grains that are not included in the above particle size range may be included. In that case, it is preferable that the composite abrasive grains not falling within the above particle size range account for 15% by mass or less, more preferably 10% by mass or less of the total composite abrasive grains.

The particle size of the composite abrasive grain of the present invention can be appropriately selected from the above range depending on the use.
For example, in grinding applications, it is more preferable that the particle size of the composite abrasive grains of the present invention is 2 to 5 mm.
Further, in polishing applications, it is more preferable that the particle size of the composite abrasive grains of the present invention is 0.1 to 2 mm.

The composite abrasive grains of the present invention are in the form of blocks. Although its outline is complicated by the presence of the protruding ceramic abrasive grains, it is preferably generally spherical or ellipsoidal in shape as a whole.

(Other abrasive grains)
The composite abrasive grain of the present invention may partially contain other abrasive grains such as fused alumina abrasive grains and diamond abrasive grains in addition to the ceramic abrasive grains.
In that case, the content of the ceramic abrasive grains is preferably 50% by mass or more, more preferably 70% by mass or more of all the abrasive grains.

(Method for manufacturing composite abrasive grains)
The composite abrasive grains of the present invention can be obtained by, for example, mixing raw materials using a stirrer, passing the resulting mixture through a wire gauze to form granules, and granulating the resulting mixture with a granulator. It can be manufactured by heating the body in an electric furnace or the like.

[Elastic grindstone]
The elastic grindstone of the present invention comprises a second binder containing at least one resin selected from the group consisting of synthetic rubber, natural rubber, thermoplastic resin, and thermosetting resin, and the composite abrasive grain of the present invention described above. Contains.
Hereinafter, each configuration of the elastic grindstone of the present invention will be explained in detail.

(Second binding material)
The second binding material contained in the elastic grindstone of the present invention includes at least one resin selected from the group consisting of synthetic rubber, natural rubber, thermoplastic resin, and thermosetting resin.

Examples of the synthetic rubber include styrene-butadiene rubber, butadiene rubber, chloroprene rubber, acrylonitrile-butadiene rubber, isoprene rubber, butyl rubber, ethylene-propylene rubber, acrylic rubber, fluororubber, silicone rubber, and the like.

Examples of the thermoplastic resin include polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyvinyl acetate, thermoplastic polyurethane, acrylonitrile butadiene styrene (ABS), polymethyl methacrylate, polyethyl methacrylate, polyamide, polyester, polycarbonate, Examples include fluororesin.
Examples of the thermosetting resin include phenol resin, urea resin, epoxy resin, melamine resin, polyurethane, and thermosetting polyimide.

From the viewpoint of compatibility with the surface shape of the workpiece, the second bonding material preferably contains natural rubber or synthetic rubber, more preferably contains synthetic rubber, and contains styrene-butadiene rubber or chloroprene rubber. More preferably, it includes styrene-butadiene rubber.
The styrene-butadiene rubber is preferably emulsion polymerized styrene-butadiene rubber.

The second binder may contain an antioxidant, an antistatic agent, a coloring agent, a filler, a light stabilizer, a plasticizer, a lubricant, a flame retardant, a flame retardant, as necessary, within a range that does not impede the effects of the present invention. It may also contain other ingredients such as auxiliaries.
The total content of synthetic rubber, natural rubber, thermoplastic resin, and thermosetting resin in the second binding material is preferably 80% by mass or more, and more preferably 90% by mass or more.

(rubber hardness)
The elastic grindstone of the present invention preferably has a rubber hardness of 30 to 95 as measured with a type A durometer according to JIS K 6253-3.
By keeping the rubber hardness within an appropriate range, both high grinding force and grinding stability can be achieved.

As for the rubber hardness of the elastic grindstone of the present invention, an appropriate hardness can be selected from the above range depending on the use.
For example, in grinding applications, it is more preferable that the rubber hardness is 65 to 95.
Further, in polishing applications, it is more preferable that the rubber hardness is 30 to 65.

(Content of composite abrasive grains)
The content of the composite abrasive grains of the present invention in the elastic grindstone of the present invention is preferably 0.1 to 6 parts by mass, and preferably 1 to 4 parts by mass, based on 1 part by mass of the second binder. The amount is more preferably 1.3 to 3.3 parts by weight, and most preferably 2 to 3 parts by weight.

(Shape and structure of elastic grinding wheel)
The elastic grindstone of the present invention preferably has a structure in which a plurality of composite abrasive grains of the present invention are dispersed using the second bonding material as a matrix. However, a plurality of composite abrasive grains of the present invention may partially contact each other.

The size and shape of the elastic grindstone of the present invention can be appropriately selected depending on the application.
Examples of the shape of the elastic grindstone of the present invention include a cylindrical shape, a substantially cylindrical shape, a conical shape, a cannonball shape, a composite shape of a cylinder and a cone, a composite shape of a cylinder and a substantially conical shape, and a spherical shape.
The elastic grindstone of the present invention is preferably used as a shafted elastic grindstone.

(Other abrasive grains)
In addition to the composite abrasive grains of the present invention, the elastic grindstone of the present invention may partially contain other abrasive grains that are not composite abrasive grains, such as ceramic abrasive grains, fused alumina abrasive grains, and diamond abrasive grains. .
In that case, the content of the composite abrasive grains of the present invention is preferably 90% by mass or more, more preferably 95% by mass or more of all the abrasive grains.

(Manufacturing method of elastic grindstone)
The elastic grindstone of the present invention can be manufactured by, for example, mixing raw materials using a rubber roll machine and molding the mixture using a mold.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples in any way.

[Manufacture of composite abrasive grains]
First, the raw materials shown in Table 1 were mixed using a stirrer (stand mixer manufactured by KitchenAid) and uniformly dispersed to obtain a mixture.
The mixture was passed through a wire mesh (stainless steel sieve (opening: 1 mm) manufactured by Sanpo Co., Ltd.) to obtain a granular mixture.
The granular mixture was subjected to granulation for about 20 minutes using a granulator (parts feeder DMS-45C manufactured by Sinfonia Technology Co., Ltd.) to obtain a composite abrasive grain precursor.
The obtained composite abrasive grain precursor was placed in an electric furnace and heated at 170° C. for 9 hours to obtain composite abrasive grains.
The obtained composite abrasive grains were classified using a stainless steel sieve manufactured by Sanpo Co., Ltd. (openings of 1.4 mm, 1.0 mm, and 0.5 mm), and the particle size distribution was as shown in Table 2.

[Manufacture of elastic grindstone]
Emulsion polymerized styrene-butadiene rubber (JSR1502, manufactured by JSR Corporation) and composite abrasive grains were mixed and uniformly dispersed using a rubber roll machine (pressure kneader DS3-10MWB-S manufactured by Moriyama Co., Ltd.) to obtain a rubber mixture. . The amount of composite abrasive grains blended was 1.5 parts by mass per 1 part by mass of emulsion polymerized styrene-butadiene rubber.
The rubber mixture was packed into a mold and allowed to stand for 30 minutes to obtain an elastic grindstone.
The shape of the obtained elastic grindstone was a cylinder with a diameter of 10 mm and a length of 20 mm.
The rubber hardness of the obtained elastic grindstone was 80 when measured using a type A durometer in accordance with JIS K 6253-3.
The obtained elastic whetstone was fixed to the tip of a shaft (manufactured by Taiyo Seiko Co., Ltd., diameter 3 mm, length 40 mm, material S50C) to obtain an elastic whetstone with a shaft.

[Grinding test]
(Test condition)
Whetstone: Elastic whetstone with shaft (manufactured as above)
Workpiece: 50mm x 50mm x 30mm SUS630
(50mm x 50mm x 10mm SUS630 for heat generation measurement only)
Grinding device: Manufactured by Nakanishi Product name Espart 500
Rotation speed: 30000 revolutions/minute (rpm)
Pressing angle: 15°
Pushing load: Approximately 4.9N (500gf)
Grinding time: 60 seconds Temperature measuring device: Handheld thermometer manufactured by Anritsu Keiki Co., Ltd. Temperature measuring position: Temperature sensor installed 5 mm away from the grinding point in a straight line

(test)
In Examples 1 and 2 and Comparative Example 1, the masses of the workpiece and the shafted elastic grindstone before and after grinding were measured, and the results were as shown in Table 3.
In addition, in Examples 1 and 2 and Comparative Example 1, the temperature of the workpiece relative to the grinding time was measured, and the results were as shown in Table 4 and FIG.

From the above results, it can be seen that the composite grindstone of the present invention has high grinding power, long life, and can suppress the heat generated during machining.

The composite abrasive grains and elastic grindstone of the present invention can be suitably used for various grinding and polishing of workpieces such as aluminum, iron, stainless steel, and titanium.

Claims (7)

a first binding material containing a thermosetting resin and/or a thermoplastic resin;
Containing ceramic abrasive grains made of one or more components selected from the group consisting of alumina, zirconia, silicon carbide, and silicon nitride ,
Containing 1 to 5 parts by mass of the ceramic abrasive grains per 1 part by mass of the first bonding material,
The particle size of the ceramic abrasive grains is 40 to 500 μm (however, ceramic abrasive grains not falling within the particle size range of 40 to 500 μm may be included in an amount of 10% by mass or less of the total ceramic abrasive grains), Composite abrasive grain for elastic grinding wheels. The composite abrasive grain according to claim 1, wherein the first bonding material includes a phenolic resin. The composite abrasive grain according to claim 1 or 2, having a grain size of 0.1 to 5 mm. a second binding material containing at least one resin selected from the group consisting of synthetic rubber, natural rubber, thermoplastic resin, and thermosetting resin; and the composite abrasive grain according to any one of claims 1 to 3. An elastic whetstone containing . The elastic grindstone according to claim 4, wherein the second bonding material includes synthetic rubber or natural rubber. The elastic grindstone according to claim 4 or 5, which has a rubber hardness of 30 to 95 as measured with a type A durometer according to JIS K6253-3. The elastic grindstone according to claim 4, wherein the composite abrasive grains are contained in an amount of 0.1 to 6 parts by mass based on 1 part by mass of the second bonding material.

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