Rotary grinding wheel

Abstract

To reduce the generation of spark when using a rotary grinding wheel.SOLUTION: A rotary grinding wheel 1 is configured by a material containing abrasive grains 13 and a binder 14. The material includes a microballoon 17 in which a flame retardant 16 is sealed.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a grinding wheel. [Background technology]

[0002] Patent Document 1 discloses a grinding wheel (rotary grinding wheel) that includes a disk-shaped grinding wheel made by solidifying abrasive grains with a binder, leaving pores, and a hub attached to the mounting hole of the grinding wheel, with ventilation holes that communicate with the pores provided at the contact point between the hub and the grinding wheel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-117644 Summary of the Invention [Problem to be solved by the invention]

[0004] During use, grinding wheels often become hot due to friction with the object being cut or ground, generating sparks. Sparks are not only undesirable from a safety standpoint, but also detract from the aesthetic appearance of the cut or ground surface of the object, and can adversely affect the hardness, thermal expansion coefficient, and other properties of the object.

[0005] For this reason, it may be possible to use a saw blade, which is less likely to generate sparks, instead of the grindstone, but the saw blade takes longer to cut than the grindstone.

[0006] An object of the present invention is to reduce the generation of sparks when a grinding wheel is used. [Means for solving the problem]

[0007] A 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 sealed inside.

[0008] In this first invention, the grinding wheel is made of a material containing microballoons filled with a flame retardant, so that when the microballoons exposed on the peripheral end face or surface of the grinding wheel are broken during use, the flame retardant is released, thereby suppressing the generation of sparks.

[0009] A second invention is the first invention, wherein the microballoons are dispersed in the binder.

[0010] One possible configuration for a grinding wheel containing microballoons is to incorporate the microballoons into the pores present in the grinding wheel. However, in 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 in the grinding wheel can be increased, further reducing the generation of sparks.

[0011] 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.

[0012] Generally, when a thermosetting resin is used as a binder, a baking process is performed 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 performed so that the flame retardant does not exceed 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.

[0013] A fourth invention is related to any one of the first to third inventions, wherein the binder is a thermosetting resin, and the flame retardant does not contain water.

[0014] In this fourth invention, the flame retardant does not contain water, so even when a baking process is performed 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 from burst microballoons during the grinding wheel manufacturing process. This allows grinding wheels to be manufactured so that the flame retardant remains reliably within the grinding wheel. As a result, the generation of sparks can be further reduced.

[0015] A fifth invention is any one of the first to fourth inventions, wherein the content of the microballoons is 5% by volume or more and 50% by volume or less of the material.

[0016] In the fifth aspect of the present invention, the content of microballoons is 5% or more by volume of the material, which ensures that the flame retardant reduces the generation of sparks. Also, the content of microballoons is 50% or less by volume of the material, which ensures that the abrasive grains and binder are not too small, ensuring that the grinding wheel has cutting or grinding performance.

[0017] The sixth invention is any one of the first to fifth inventions, wherein the microballoons are made of a thermosetting resin. Thermosetting resins are relatively resistant to high temperatures, so even if a firing process is carried out during the manufacturing process of the grinding wheel, the microballoons are not easily destroyed. Therefore, even if a phenolic resin, which has a relatively high curing temperature, is used as a binder, the grinding wheel can be manufactured without destroying the microballoons, which increases the freedom of material selection. [Effects of the Invention]

[0018] As described above, according to the present invention, it is possible to reduce the generation of sparks when using a grinding wheel. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a cross-sectional view showing a grinding wheel according to an embodiment of the present invention; [Figure 2] FIG. [Figure 3] 1 is a photograph showing sparks generated by use of a grinding wheel in Example 1. [Figure 4] 10 is a photograph showing sparks generated by use of a grinding wheel in Example 2. [Figure 5] 10 is a photograph showing sparks generated by using a grinding wheel in Example 3. [Figure 6] 1 is a photograph showing sparks generated by using a grinding wheel in Comparative Example 1. [Figure 7] 10 is a photograph showing sparks generated by using a grindstone in Comparative Example 2. [Figure 8] 1 is a photograph showing a cut surface of a SS round bar cut by a grindstone in Example 1. [Figure 9] 10 is a photograph showing a cut surface of a SS round bar cut by a grindstone in Example 2. [Figure 10] 10 is a photograph showing a cut surface of a SS round bar cut by a grindstone in Example 3. [Figure 11] 1 is a photograph showing a cut surface of a SS round bar cut by a grindstone in Comparative Example 1. [Figure 12] 1 is a photograph showing a cut surface of a SS round bar cut by a grindstone in Comparative Example 1. [Figure 13] 10 is a photograph showing sparks generated by using a grinding wheel in Example 4. [Figure 14] 10 is a photograph showing a cut surface of a SS round bar cut by a grindstone in Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0020] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the present invention, its applications, or its uses.

[0021] -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.

[0022] The grinding wheel body 11 is formed in a disk shape with a center hole 11a in the center. The grinding wheel body 11 is formed flat with the same thickness throughout. The outer diameter of the grinding wheel body 11 is, for example, 50 mm or more and 230 mm or less, and the thickness is, for example, 5 mm or less. The inner diameter of the center hole 11a is not particularly limited, but is, for example, 15 mm.

[0023] 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.

[0024] 2 shows a partially enlarged cross-section of the grinding wheel body 11. The grinding wheel body 11 is made of a material containing abrasive grains 13, a binder 14 that binds the abrasive grains 13 together, and a filler 15. The material that makes up the grinding wheel body 11 (hereinafter referred to as the "constituent material") further contains microballoons 17 inside which a flame retardant 16 is sealed.

[0025] The content of the abrasive grains 13 is preferably 10% by volume or more of the constituent material, more preferably 20% by volume or more, from the viewpoint of imparting high cutting performance to the grinding wheel body 11. The content of the abrasive grains 13 is preferably not too high so that the constituent material can contain microballoons 17; specifically, the content 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 be ceramic abrasive grains produced by the sol-gel method. The particle diameter of the abrasive grains 13 is, for example, 0.4 mm or more and 0.6 mm or less.

[0026] The content of the binder 14 is preferably 10% by volume or more of the constituent materials, more preferably 20% by volume or more, from the viewpoint of holding the abrasive grains 13 with an appropriate holding force. The content of the binder 14 is preferably not too high so that the constituent materials can contain microballoons 17; specifically, the content is preferably 50% by volume or less of the constituent materials, more preferably 40% by volume or less. The binder 14 is made of a thermosetting resin, examples of which include phenolic resin, polyester resin, epoxy resin, and urethane resin.

[0027] Filler 15 does not necessarily have to be included, but it functions as, for example, a grinding aid, and is preferably included at least from the viewpoint of imparting high grinding performance to grinding wheel body 11. Filler 15 is more preferably included in an amount of 10% by volume or more of the material of grinding wheel body 11. The content of filler 15 is preferably not too high so that microballoons 17 can be included in the constituent material; specifically, it is preferably 40% by volume or less of the constituent material, and more preferably 30% by volume or less. Examples of filler 15 include iron sulfide, potassium sulfate, cryolite, calcium oxide, potassium chloride, potassium cryolite, potassium cryolite, etc.

[0028] The microballoons 17 are made of a thermosetting resin such as gelatin or melamine resin, or other resins or inorganic materials, and are preferably made of a thermosetting resin. 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. The content of the microballoons 17 is 5% by volume or more of the material of the grinding wheel body 11, preferably 10% by volume or more, and more preferably 20% by volume or more, from the viewpoint of including a large amount of flame retardant in the constituent materials. The content of the microballoons 17 is 50% by volume or less, preferably 40% by volume or less, and more preferably 30% by volume or less, from the viewpoint of preventing the content of the abrasive grains 13 and the like from becoming too low.

[0029] The flame retardant 16 is not limited as long as it has flame retardancy, and examples thereof include phosphate ester, 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.

[0030] The grinding wheel body 11 may include pores 18, as shown in Fig. 2. When the grinding wheel body 11 includes pores 18, the microballoons 17 are dispersed outside the pores 18.

[0031] -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.

[0032] Next, the mixed material is placed in a mold, and the mold is heated to 40 to 70°C while applying pressure to form the grinding wheel body 11 (molding process). In the baking process following this molding process, the heating temperature is set to a temperature equal to or higher than the curing temperature of the thermosetting resin used as the binder and lower than the boiling point of the flame retardant. In the case of epoxy resin, the temperature is 140°C, and in the case of phenol resin, the temperature is 180°C.

[0033] Finally, the bushing portion 12b of the seat member 12 is fitted into the central hole 11a of the formed grinding wheel body 11, and the grinding wheel 1 is completed.

[0034] -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 destroyed during use of the grinding wheel 1, releasing the flame retardant 16. As a result, the flame retardant 16 prevents sparks from being generated.

[0035] In this embodiment, microballoons 17 are dispersed in the binder 14 contained in the grinding wheel body 11. This configuration allows the content of microballoons 17 to be higher than in 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 generation of sparks.

[0036] 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 in the grinding wheel body 11 without completely evaporating the flame retardant 16. As a result, the generation of sparks can be further reduced.

[0037] Furthermore, in this embodiment, the flame retardant 16 does not contain water, so even if a baking process is performed to harden the thermosetting resin used as the binder 14, there is no risk of water evaporating and causing the microballoons 17 to burst. This prevents the flame retardant 16 from leaking out of the burst microballoons 17 during the manufacturing process of the grinding wheel 1. This allows the grinding wheel 1 to be manufactured so that the flame retardant remains reliably in the grinding wheel body 11. As a result, the generation of sparks can be further reduced.

[0038] In this embodiment, the content of microballoons 17 is 5% by volume or more of the material constituting the grinding wheel body 11, which reliably achieves the effect of reducing spark generation by the flame retardant 16. Furthermore, the content of microballoons 17 is 50% by volume or less of the material constituting the grinding wheel body 11, which ensures that the abrasive grains 13 and binder 14 are not too small, thereby reliably imparting cutting performance to the grinding wheel 1.

[0039] 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 performed during the manufacturing process of the grinding wheel 1. For example, if the microballoons 17 are made of melamine resin, they will not be destroyed even when baked at a high temperature of 180°C, 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, which increases the flexibility in material selection.

[0040] Incidentally, when the microballoons 17 are contained in the constituent material of the grinding wheel body 11, the content of the abrasive grains 13, binder 14, filler 15, etc., which affect the cutting performance of the grinding wheel 1, becomes relatively lower compared to when the microballoons 17 are not contained. As a result, it was thought that the cutting performance of the grinding wheel 1 would also be reduced.

[0041] However, according to the present invention, as will be shown in the examples described later, it is surprisingly found that 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.

[0042] (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 firing step is carried out at a relatively low temperature, for example, 140°C or less, the microballoons 17 will not be destroyed and 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.

[0043] (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 thermosetting resin, but may be, for example, a metal. [Example]

[0044] Examples 1 to 3 and Comparative Examples 1 and 2, in which the effect of the grindstone according to the present invention in reducing sparks and the cutting time required to cut an object were evaluated, will be described below.

[0045] [Example 1] The materials constituting the grinding wheel body were a mixture of abrasive grains, a thermosetting resin binder, a filler, and microballoons. The abrasive grains were ceramic abrasive grains (3M, product name: Cubitron 321), the thermosetting resin was epoxy resin (Meiwa Chemical Industry, product name: NWR1502 + Kyoeisha Chemical Industry, product name: Epolite 1600), and the filler was potassium cryolite (Venetamia, product name: Kaliflene). The microballoons were roughly spherical and composed of gelatin, with a phosphate ester encapsulated inside as a flame retardant. 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% porosity.

[0046] 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 flame retardant phosphate ester. 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.

[0047] Next, a cutting test was conducted as shown in Figure 3. The completed grinding wheel was attached to a cutting machine, and 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.

[0048] [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. A cutting test was also carried out in the same manner as in Example 1.

[0049] [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.

[0050] [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.

[0051] Comparative Example 2 In Comparative Example 2, a commercially available grinding wheel (manufactured by Nippon Resibon Co., Ltd., trade name: Resibon Supercut RSC) was attached to the cutting machine, and a cutting test was carried out in the same manner as in Example 1. The composition of the constituent materials of the grinding wheel body is shown in Table 1.

[0052] Table 1 shows the conditions and results for each example and comparative example.

[0053] [Table 1]

[0054] [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.

[0055] Figures 8 to 10 show the cut surfaces of the SS round bars cut in the cutting tests of Examples 1 to 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 were noticeable on the cut surfaces (see Figures 11 and 12). In contrast, in Examples 1 to 3, burns were not noticeable on the cut surfaces (see Figures 8 to 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).

[0056] Furthermore, Table 1 shows that in Examples 1 to 3, the temperature of the object (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.

[0057] 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.

[0058] Example 4 will be described below, in which the type of microballoons was changed to evaluate the effect of reducing sparks and the cutting time required to cut an object.

[0059] [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.

[0060] [Table 2]

[0061] [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.

[0062] Fig. 14 shows the cut surface of the SS round bar cut in the cutting test in 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 Fig. 14).

[0063] Furthermore, Table 2 shows that in Example 4, the temperature of the object (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.

[0064] 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

1. 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.

2. The grinding wheel according to claim 1, The grinding wheel, wherein the microballoons are dispersed in the binder.

3. 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.

4. 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.

5. 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.

6. The grinding wheel according to any one of claims 1 to 5, The grinding wheel, wherein the microballoons are made of a thermosetting resin.

7. The grinding wheel according to any one of claims 1 to 6, The grinding wheel, wherein the microballoons are made of gelatin.

8. The grinding wheel according to any one of claims 1 to 7, A rotating grinding wheel for cutting.

9. The grinding wheel according to any one of claims 1 to 8, A grinding wheel having a thickness of 5 mm or less.

10. 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.

11. The grinding wheel according to any one of claims 1 to 10, Contains pores, The microballoons are dispersed outside the pores.

Images