JP7770223B2 - Rotary grinding wheel - Google Patents

Description

The present invention relates to a grinding wheel.

Patent Document 1 discloses a grinding wheel (rotary grinding wheel) that includes a disc-shaped grinding wheel made by binding abrasive grains with a binder, leaving pores, and a hub attached to the grinding wheel's mounting hole, with ventilation holes communicating with the pores at the contact point of the hub with the grinding wheel.

Japanese Patent Application Laid-Open No. 2000-117644

When a grinding wheel is in use, it often becomes hot due to friction with the object being cut or ground, causing sparks. Sparks are not only undesirable from a safety standpoint, but they can also mar the aesthetic appearance of the cut or ground surface of the object and adversely affect the hardness, thermal expansion coefficient, and other properties of the object.

For this reason, it may be possible to use a saw blade, which is less likely to produce sparks, instead of a grindstone, but saw blades take longer to cut than grindstones.

The objective of this invention is to reduce the generation of sparks when using a grinding wheel.

The first invention is a grinding wheel for cutting made of a material containing abrasive grains and a binder, and the material includes microballoons with a flame retardant encapsulated inside.

In this first invention, the material making up the grinding wheel contains microballoons with a flame retardant sealed inside. During use, the microballoons exposed on the peripheral end face or surface of the grinding wheel are destroyed, releasing the flame retardant they contain. As a result, the flame retardant reduces the generation of sparks.

The second invention is the first invention, in which the microballoons are dispersed in the binder.

A specific configuration for a grinding wheel containing microballoons is to incorporate the microballoons into the pores present in the grinding wheel. However, with such a configuration, the amount of microballoons contained in the grinding wheel is limited by the pore content (porosity). In the second invention, the microballoons are dispersed in the binder contained in the grinding wheel, so the amount of microballoons is not limited by the porosity. As a result, the amount of microballoons and flame retardant contained in the grinding wheel can be increased, further reducing the generation of sparks.

A third invention is the second invention, wherein the binder is a thermosetting resin, and the boiling point of the flame retardant is higher than the curing temperature of the thermosetting resin.

Generally, when a thermosetting resin is used as the binder, a baking process is carried out during the manufacturing process of a grinding wheel to harden the thermosetting resin. If microballoons are dispersed in the unhardened thermosetting resin, the flame retardant in the microballoons may burst and evaporate during the baking process. In the third invention, the boiling point of the flame retardant is higher than the hardening temperature of the thermosetting resin, so the baking process can be carried out so that the flame retardant does not rise above its boiling point. In other words, the grinding wheel can be manufactured so that the flame retardant remains in the grinding wheel without completely evaporating. As a result, the generation of sparks can be further reduced.

A fourth invention is any one of the first to third inventions, wherein the binder is a thermosetting resin and the flame retardant does not contain water.

In this fourth invention, the flame retardant does not contain water, so even when a baking process is carried out to harden the thermosetting resin, there is no risk of water evaporating and causing the microballoons to burst. This prevents the flame retardant from leaking out of burst microballoons during the grinding wheel manufacturing process. This means that grinding wheels can be manufactured in such a way that the flame retardant remains reliably within the grinding wheel. As a result, the generation of sparks can be further reduced.

The fifth invention is any one of the first to fourth inventions, in which the content of the microballoons is 5% by volume or more and 50% by volume or less of the material.

In this fifth invention, the microballoon content is 5% or more by volume of the material, ensuring that the flame retardant reduces the generation of sparks. Furthermore, because the microballoon content is 50% or less by volume of the material, the abrasive grains and binder are not too scarce, ensuring that the grinding wheel is endowed with cutting or grinding performance.

The sixth invention is any one of the first to fifth inventions, wherein the microballoons are made of a thermosetting resin. Because thermosetting resins are relatively resistant to high temperatures, the microballoons are less likely to be destroyed even when a firing process is carried out during the manufacturing process of the grinding wheel. Therefore, even if a binder such as phenolic resin, which has a relatively high curing temperature, is used, the grinding wheel can be manufactured without destroying the microballoons, allowing for greater freedom in material selection.

As explained above, the present invention can reduce the generation of sparks when using a grinding wheel.

1 is a cross-sectional view showing a grinding wheel according to an embodiment of the present invention; FIG. 1 is a photograph showing sparks generated by use of a grinding wheel in Example 1. 10 is a photograph showing sparks generated by use of a grinding wheel in Example 2. 10 is a photograph showing sparks generated by use of a grinding wheel in Example 3. 1 is a photograph showing sparks generated by use of a grinding wheel in Comparative Example 1. 10 is a photograph showing sparks generated by use of a grinding wheel in Comparative Example 2. 1 is a photograph showing a cut surface of an SS round bar material cut by a grinding wheel in Example 1. 10 is a photograph showing a cut surface of an SS round bar material cut by a grinding wheel in Example 2. 10 is a photograph showing a cut surface of an SS round bar material cut by a grinding wheel in Example 3. 1 is a photograph showing a cut surface of an SS round bar material cut by a grinding wheel in Comparative Example 1. 1 is a photograph showing a cut surface of an SS round bar material cut by a grinding wheel in Comparative Example 1. 10 is a photograph showing sparks generated by use of a grinding wheel in Example 4. 10 is a photograph showing a cut surface of an SS round bar material cut by a grinding wheel in Example 4.

Embodiments of the present invention are described in detail below with reference to the accompanying drawings. The following description of the preferred embodiment is merely exemplary in nature and is not intended to limit the present invention, its applications, or its uses.

-composition-
1 shows a rotary grinding wheel 1 according to an embodiment of the present invention. This rotary grinding wheel 1 is used to cut rigid objects such as metals. The rotary grinding wheel 1 includes a grinding wheel body 11 and a plastic seat member 12 that is bonded to the grinding wheel body 11.

The grinding wheel body 11 is formed in a circular disk shape with a central hole 11a in the center. The grinding wheel body 11 is formed flat and has a uniform thickness throughout. The outer diameter of the grinding wheel body 11 is, for example, 50 mm to 230 mm, and the thickness is, for example, 5 mm or less. The inner diameter of the central hole 11a is not particularly limited, but is, for example, 15 mm.

The seat member 12 consists of a donut-shaped seat portion 12a glued to one side around the center hole 11a of the grinding wheel body 11, and a bush portion 12b extending axially from the inner peripheral edge of this seat portion 12a and fitted into the inner surface of the center hole 11a.

Figure 2 shows a partially enlarged cross-section of the grinding wheel body 11. The grinding wheel body 11 is composed of a material containing abrasive grains 13, a binder 14 that binds the abrasive grains 13, and a filler 15. The material that composes the grinding wheel body 11 (hereinafter referred to as the "component material") further contains microballoons 17 that contain a flame retardant 16.

From the perspective of imparting high cutting performance to the grinding wheel body 11, the content of abrasive grains 13 is preferably 10% by volume or more of the constituent material, more preferably 20% by volume or more. The content of abrasive grains 13 is preferably not too high so that the constituent material can contain microballoons 17; specifically, it is preferably 50% by volume or less of the constituent material, more preferably 40% by volume or less. Examples of materials for the abrasive grains 13 include alumina abrasives, alumina-zirconia abrasives, and silicon carbide abrasives. The abrasive grains 13 may also be ceramic abrasive grains manufactured by the sol-gel method. The particle size of the abrasive grains 13 is, for example, 0.4 mm or more and 0.6 mm or less.

From the viewpoint of holding the abrasive grains 13 with an appropriate holding force, the content of binder 14 is preferably 10% by volume or more of the constituent material, and more preferably 20% by volume or more. The content of binder 14 is preferably not too high so that the constituent material can contain microballoons 17; specifically, it is preferably 50% by volume or less of the constituent material, and more preferably 40% by volume or less. The binder 14 is made of a thermosetting resin, and examples of thermosetting resins include phenolic resin, polyester resin, epoxy resin, and urethane resin.

Filler 15 does not necessarily have to be included, but it functions as a grinding aid, for example, and is preferably included at least from the perspective of imparting high grinding performance to the grinding wheel body 11. It is more preferable that filler 15 account for 10% or more by volume of the material of the grinding wheel body 11. It is preferable that the filler 15 content is not too high so that microballoons 17 can be incorporated into the constituent material; specifically, it is preferably 40% or less by volume of the constituent material, and more preferably 30% or less by volume. Examples of filler 15 include iron sulfide, potassium sulfate, cryolite, calcium oxide, potassium chloride, potassium cryolite, potassium cryolite, etc.

The microballoons 17 are composed of a thermosetting resin such as gelatin or melamine resin, or other resins or inorganic materials, with a thermosetting resin being preferred. The microballoons 17 are, for example, spherical, with a diameter of, for example, 0.01 mm or more and 0.4 mm or less. The microballoons 17 are dispersed in the binder 14. From the viewpoint of incorporating a large amount of flame retardant into the constituent materials, the content of the microballoons 17 is 5 vol% or more of the material of the grinding wheel body 11, preferably 10 vol% or more, and more preferably 20 vol% or more. From the viewpoint of preventing the content of abrasive grains 13, etc. from becoming too low, the content of the microballoons 17 is 50 vol% or less, preferably 40 vol% or less, and more preferably 30 vol% or less.

The flame retardant 16 is not limited as long as it has flame retardant properties, but examples include phosphate esters, silicone oil, and chlorinated paraffin. The boiling point of the flame retardant 16 is preferably higher than the curing temperature of the thermosetting resin used as the binder 14, and more preferably 10°C or more higher than the curing temperature of the thermosetting resin. The flame retardant 16 does not contain water. The flame retardant 16 may contain aluminum hydroxide, which enhances the cooling effect. The flame retardant 16 preferably reduces the temperature of the object being cut by the grinding wheel 1 by 5°C or more during cutting, compared to when the grinding wheel does not contain the flame retardant 16.

The grinding wheel body 11 may include pores 18, as shown in FIG. 2. If the grinding wheel body 11 includes pores 18, the microballoons 17 are dispersed outside the pores 18.

-Manufacturing method-
The grinding wheel 1 is manufactured as follows: First, the abrasive grains 13, the binder 14, the filler 15, and the microballoons 17 are mixed together. The microballoons 17 are prepared by pre-filling the flame retardant 16 therein.

The mixed materials are then placed in a mold, which is then heated to 40-70°C while under pressure to form the grinding wheel body 11 (molding process). In the firing process that follows this molding process, the heating temperature is set to a temperature above the curing temperature of the thermosetting resin used as the binder and below the boiling point of the flame retardant. For epoxy resin, the temperature is 140°C, and for phenolic resin, the temperature is 180°C.

Finally, the bushing portion 12b of the seat member 12 is fitted into the central hole 11a of the formed grinding wheel body 11, completing the grinding wheel 1.

-effect-
In this embodiment, the constituent material of the grinding wheel body 11 contains microballoons 17 containing flame retardant 16, so that the microballoons 17 exposed on the peripheral end surface are broken during use of the grinding wheel 1, releasing the flame retardant 16. As a result, the flame retardant 16 prevents sparks from being generated.

In addition, in this embodiment, microballoons 17 are dispersed in the binder 14 contained in the grinding wheel body 11. This configuration allows for a higher content of microballoons 17 compared to, for example, a configuration in which the microballoons 17 are contained inside the pores 18. As a result, the content of flame retardant 16 in the grinding wheel body 11 can be increased, further reducing the occurrence of sparks.

Furthermore, in this embodiment, the boiling point of the flame retardant 16 is higher than the curing temperature of the thermosetting resin used as the binder 14, so the firing process can be carried out so that the temperature of the flame retardant 16 does not exceed its boiling point. In other words, the grinding wheel 1 can be manufactured so that the flame retardant 16 remains reliably in the grinding wheel body 11 without completely evaporating the flame retardant 16. As a result, the generation of sparks can be further reduced.

In addition, in this embodiment, the flame retardant 16 does not contain water, so even when a baking process is performed to harden the thermosetting resin used as the binder 14, there is no risk of the water evaporating and causing the microballoons 17 to burst. This prevents the flame retardant 16 from leaking out from burst microballoons 17 during the manufacturing process of the grinding wheel 1. This allows the grinding wheel 1 to be manufactured in such a way that the flame retardant remains reliably within the grinding wheel body 11. As a result, the generation of sparks can be further reduced.

In addition, in this embodiment, the content of microballoons 17 is 5% or more by volume of the material constituting the grinding wheel body 11, so the flame retardant 16 can reliably reduce the generation of sparks. In addition, the content of microballoons 17 is 50% or less by volume of the material constituting the grinding wheel body 11, so the abrasive grains 13 and binder 14 are not too low, ensuring that the grinding wheel 1 is able to reliably impart cutting performance.

In addition, in this embodiment, the microballoons 17 are preferably made of a thermosetting resin. Because thermosetting resins are relatively resistant to high temperatures, the microballoons 17 are less likely to be destroyed even when a baking process is carried out during the manufacturing process of the grinding wheel 1. For example, if the microballoons 17 are made of melamine resin, even when the baking process is carried out at a high temperature of 180°C, not all of the microballoons 17 will be destroyed, and the microballoons 17 will remain reliably in the manufactured grinding wheel body 11. Therefore, even if a phenolic resin, which has a relatively high curing temperature, is used as the binder 13, the grinding wheel 1 can be manufactured without destroying the microballoons 17, allowing for greater freedom in material selection.

However, when microballoons 17 are included in the constituent material of the grinding wheel body 11, the content of abrasive grains 13, binders 14, fillers 15, etc., which affect the cutting performance of the grinding wheel 1, becomes relatively lower than when microballoons 17 are not included. This may result in a decrease in the cutting performance of the grinding wheel 1.

However, according to the present invention, as will be shown in the examples described below, surprisingly, when the constituent material of the grinding wheel body 11 contains microballoons 17, the object can be cut faster than when the constituent material does not contain microballoons 17.

(Modification of the embodiment)
The material constituting the microballoons 17 is not limited to thermosetting resin, but may be, for example, gelatin. In this case, if the baking process is carried out at a relatively low temperature of, for example, 140°C or less, the microballoons 17 will not be destroyed, and the microballoons 17 will remain reliably in the manufactured grinding wheel body 11. In this case, the binder 14 should be one with a relatively low hardening temperature, such as epoxy resin.

(Other embodiments)
The present invention is not limited to the configuration of the above-described embodiment. For example, the grinding wheel 1 according to the present invention is not limited to cutting wheels, but may be a grinding wheel that grinds an object on its surface, such as an offset grinding wheel. The binder 14 is not limited to a thermosetting resin, but may be, for example, a metal.

Below, we will explain Examples 1 to 3 and Comparative Examples 1 and 2, which evaluated the effectiveness of the grinding wheel of the present invention in reducing sparks and the cutting time required to cut an object.

[Example 1]
The materials constituting the grinding wheel body were a mixture of abrasive grains, a thermosetting resin binder, a filler, and microballoons. Ceramic abrasive grains (3M, product name: Cubitron 321) were used as the abrasive grains, epoxy resin (Meiwa Chemical Industry, product name: NWR1502 + Kyoeisha Chemical Industry, product name: Epolite 1600) was used as the thermosetting resin, and potassium cryolite (Venetamia, product name: Kaliflene) was used as the filler. Approximately spherical gelatin microballoons containing a phosphate ester as a flame retardant were used. The contents of the abrasive grains, thermosetting resin, filler, and microballoons in the mixed material were 27 vol%, 24 vol%, 6 vol%, and 27 vol%, respectively. The mixed material contained 16 vol% pores.

The mixed material was then placed in a mold, which was heated to 60°C and molded under pressure. The grinding wheel body was then fired by heating to 140°C, which is lower than the boiling point of the phosphate ester flame retardant. After firing, the grinding wheel body was a disk-shaped body with a diameter of 105 mm and a thickness of 1.6 mm. The bushing of the seat member was fitted into the center hole of the molded grinding wheel body to complete the grinding wheel.

Next, a cutting test was conducted, as shown in Figure 3. The completed grinding wheel was attached to a cutting machine, and the object to be cut, a 13 mm diameter SS round bar, was automatically cut by the cutting machine while applying a load of 1.5 kg. The cut surface of the cut SS round bar was visually inspected. The time required to completely cut one SS round bar was measured.

[Example 2]
In Example 2, a grinding wheel was manufactured in the same manner as in Example 1, except that the flame retardant contained 10 parts by mass of aluminum hydroxide powder per 100 parts by mass of phosphate ester. Also, a cutting test was carried out in the same manner as in Example 1.

[Example 3]
In Example 3, a grinding wheel was manufactured in the same manner as in Example 1, except that silicone oil was used as the flame retardant instead of phosphate ester. Also, a cutting test was carried out in the same manner as in Example 1.

[Comparative Example 1]
In Comparative Example 1, a grinding wheel was manufactured in the same manner as in Example 1, except that an inorganic porous material was used instead of the microballoons containing a flame retardant. A cutting test was also carried out in the same manner as in Example 1.

[Comparative Example 2]
In Comparative Example 2, a commercially available grinding wheel (manufactured by Resibon Japan Co., Ltd., trade name: Resibon Supercut RSC) was attached to the cut-off machine, and a cutting test was carried out in the same manner as in Example 1. The composition of the material constituting the grinding wheel body is shown in Table 1.

Table 1 shows the conditions and results for each example and comparative example.

[result]
3 to 5 show the cutting test results for Examples 1 to 3, respectively, and Figures 6 and 7 show the cutting test results for Comparative Examples 1 and 2, respectively. These photographs show that sparks were generated in each cutting test, but it is clear that the sparks generated in Examples 1 to 3 were reduced compared to the sparks generated in Comparative Examples 1 and 2.

Figures 8-10 show the cut surfaces of the SS round bars cut in the cutting tests of Examples 1-3, respectively, and Figures 11 and 12 show the cut surfaces of the SS round bars cut in the cutting tests of Comparative Examples 1 and 2, respectively. The black areas on each cut surface indicate areas where burns were caused by sparks, and in Comparative Examples 1 and 2, burns are noticeable on the cut surfaces (see Figures 11 and 12). In contrast, in Examples 1-3, burns are not noticeable on the cut surfaces (see Figures 8-10). In particular, in Examples 1 and 2, burns were hardly noticeable on the cut surfaces, resulting in beautiful cut surfaces (see Figures 8 and 9).

Furthermore, Table 1 shows that in Examples 1 to 3, the temperature of the workpiece (SS round bar material) being cut was reduced by at least 28°C compared to Comparative Example 1 due to the inclusion of a flame retardant in the constituent material of the grinding wheel body.

Furthermore, Table 1 shows that Examples 1 to 3, in which sparks were reduced by including a flame retardant in the constituent material of the grinding wheel body, surprisingly had shorter cutting times, i.e., were able to cut faster, than Comparative Examples 1 and 2.

The following describes Example 4, in which the effect of reducing sparks and the cutting time required to cut an object were evaluated by changing the type of microballoons.

[Example 4]
A grinding wheel was manufactured using the materials and configuration shown in Table 2 in the same manner as in Example 1, and a cutting test similar to that in Example 1 was carried out.

[result]
13 shows the state of the cutting test in Example 4. From this photograph, it can be seen that sparks were generated during the cutting test, but it is clear that the sparks generated in Example 4 were reduced compared to the sparks generated in Comparative Examples 1 and 2.

Figure 14 shows the cut surface of the SS round bar material cut in the cutting test of Example 4. It can be seen that in Example 4, there is less noticeable burning on the cut surface compared to Comparative Examples 1 and 2 (see Figure 14).

Furthermore, Table 2 shows that in Example 4, the temperature of the workpiece (SS round bar material) being cut is reduced by at least 28°C compared to Comparative Example 1 because the constituent material of the grinding wheel body contains a flame retardant.

Furthermore, Table 2 shows that Example 4, in which sparks were reduced by including a flame retardant in the constituent material of the grinding wheel body, surprisingly had a shorter cutting time, i.e., was able to cut faster, than Comparative Examples 1 and 2.

Claims (11)

A grinding wheel made of a material containing abrasive grains and a binder,
The material includes microballoons having a flame retardant encapsulated therein;
The grinding wheel , wherein the flame retardant contains a phosphate ester . The grinding wheel according to claim 1,
The grinding wheel, wherein the microballoons are dispersed in the binder. The grinding wheel according to claim 1 or 2,
the binder is a thermosetting resin,
The boiling point of the flame retardant is higher than the curing temperature of the thermosetting resin. The grinding wheel according to any one of claims 1 to 3,
the binder is a thermosetting resin,
The flame retardant does not contain water. The grinding wheel according to any one of claims 1 to 4,
A grinding wheel, wherein the content of the microballoons is 5% by volume or more and 50% by volume or less of the material. The grinding wheel according to any one of claims 1 to 5,
The grinding wheel, wherein the microballoons are made of a thermosetting resin. The grinding wheel according to any one of claims 1 to 6,
The grinding wheel, wherein the microballoons are made of gelatin. The grinding wheel according to any one of claims 1 to 7,
A rotating grinding wheel for cutting. The grinding wheel according to any one of claims 1 to 8,
A grinding wheel having a thickness of 5 mm or less. The grinding wheel according to any one of claims 1 to 9,
the material comprises a filler;
the filler is at least one selected from iron sulfide, potassium sulfate, cryolite, calcium oxide, potassium chloride, and kallic cryolite;
A grinding wheel, wherein the content of the filler is 10% by volume or more and 40% by volume or less of the material. The grinding wheel according to any one of claims 1 to 10,
Contains pores,
The microballoons are dispersed outside the pores.