JP6107018B2 - Grinding wheel manufacturing method and grinding wheel - Google Patents

Description

  The present invention relates to a method for manufacturing a grindstone and a grindstone.

  In a vitrified bond grindstone using abrasive grains of cBN or diamond, in order to improve the dispersibility of the abrasive grains, a grindstone containing pores is formed by sintering the coated abrasive grains in which one coating layer is formed after press forming. There is a conventional technique to manufacture (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 9-132771

In the above-mentioned prior art, the distribution density of the abrasive grains can be changed by changing the thickness of the coating layer, but the distribution density of the additive is changed depending on the location, and the distribution density of the pores is made a certain value or less. Is difficult. This is because since the coating layer is a single layer, a structure in which abrasive grains are uniformly dispersed in the coating layer is obtained after molding. Also, the voids are generated based on the space of the gap between the coated abrasive grains during pressure formation, but this space cannot be made smaller than the gap when the coated abrasive grains are filled with the closest packing density. This is why it is difficult to make the value below the value.
The present invention has been made in view of the above circumstances, and provides a method for producing a grindstone and a grindstone capable of setting the distribution location and density of additives to desired values, and further enabling the distribution density of pores to be desired values. With the goal.

In order to solve the above-mentioned problem, the invention according to claim 1 is characterized in that, after forming a first coating layer made of glass, a binder and a plasticizer on the outside of the abrasive grains, the glass on the outside of the first coating layer. And at least one outer coating layer that is deformed with a pressure smaller than that of the first coating layer by making the plasticizer larger than the amount of the plasticizer in the first coating layer. A coating step for forming and producing coated abrasive grains;
After filling the coated abrasive grains into a predetermined shape, a molded product in which gaps are formed between the outer coated layers of the coated abrasive grains that are in contact with each other by pressurizing with a pressure higher than the deformation of the outer coated layer Pressure molding process to manufacture;
A degreasing step of degreasing at a predetermined temperature equal to or higher than a volatilization temperature of the binder and the plasticizer;
It consists of the sintering process which sinters the said molded object by sintering at the temperature more than the softening point of the said glass.

Feature of the invention according to claim 2 is the invention according to claim 1, by adjusting the thickness of the outer coating layer is to adjust the volume ratio of the pores in the grinding stone.

Feature of the invention according to claim 3 is have you to the invention according to claim 1, wherein the outer coating layer is to include hard particles.

A feature of the invention according to claim 4 is that, in the invention according to claim 1, the first coating layer includes cBN grains, and the outer coating layer includes hard particles .

According to the first aspect of the present invention, when the outer coating layer is deformed by applying pressure more than the deformation of the outer coating layer, the outer coating layer is deformed and the gaps between the outer coating layers of the plurality of coated abrasive grains that are in contact with each other. Since the first coating layer is difficult to deform, the first coating layer is in contact with each other, and the outer coating layer is filled in a part of the gaps between the plurality of coated abrasive grains in contact with each other. It becomes a molded product in a heated state. The binder and plasticizer are degreased in the degreasing process, the glass is sintered in the sintering process, and the flowability of the glass is good, so that an abrasive grain holding layer having good adhesion to the abrasive grains can be formed, and the abrasive grain holding power is large. A grindstone can be manufactured.

According to the second aspect of the present invention, the amount of the outer coating layer that moves so as to fill the gap can be controlled by adjusting the thickness of the outer coating layer, and the ratio of filling the gap is set to a desired value. A grindstone having a volume ratio of holes can be manufactured.

According to the invention which concerns on Claim 3, the grindstone which is hard to wear with the hard abrasive of an outer coating layer is realizable.

According to the invention which concerns on Claim 4, the grindstone which is hard to wear with the cBN grain of a 1st coating layer and the hard abrasive grain of an outer coating layer is realizable.

It is a cross-sectional schematic diagram of the coated abrasive grain of 1st Embodiment. It is a schematic diagram of the structure | tissue filled with the coated abrasive grain of 1st Embodiment. It is a schematic diagram of the molding which pressure-molded the coated abrasive grain of 1st Embodiment. It is a schematic diagram of the vitrified bond grindstone of 1st Embodiment. It is a cross-sectional schematic diagram of the coated abrasive grain of 2nd Embodiment. It is a schematic diagram of the molding which pressure-molded the coated abrasive grain of 2nd Embodiment. It is a schematic diagram of the vitrified bond grindstone of 2nd this embodiment. It is a cross-sectional schematic diagram of the coated abrasive grain of 3rd Embodiment. It is a schematic diagram of the vitrified bond grindstone of 3rd Embodiment. It is a schematic diagram of grinding with the vitrified bond grindstone of 3rd Embodiment. It is a cross-sectional schematic diagram of the coated abrasive grain of 4th Embodiment. It is a schematic diagram of the molding which pressure-molded the coated abrasive grain of 4th Embodiment. It is a schematic diagram of the vitrified bond grindstone of 4th this embodiment.

Hereinafter, as an embodiment of the present invention, a vitrified bond grindstone provided with a first coating layer on the outside of a cBN abrasive grain and one outer coating layer (hereinafter referred to as a second coating layer) outside the first coating layer. This will be explained with an example.
As the first embodiment, a case where the second coating layer is deformed with a pressure smaller than that of the first coating layer will be described.
First, the details of the coating process will be described.
In FIG. 1, a first coating layer 2 is a mixture of glass powder having a particle size of several μm or less, a binder such as ammonium polyacrylate and polyethylene glycol as a plasticizer, and cBN abrasive grains 1 (abrasive grains). It is made to adhere to.
Next, the second coating layer 3 having the same constituent material as that of the first coating layer 2 but containing a larger amount of polyethylene glycol as a plasticizer than the amount contained in the first coating layer 2 is used as the first coating layer. The coated abrasive grain 4 is formed by adhering onto 2.
The coated abrasive 4 has the following characteristics. The second coating layer 3 is more plastic than the first coating layer 2, and when a pressure equal to or higher than the pressure at which the second coating layer 3 is plastically deformed is applied to the coated abrasive grains 4, the second coating layer 3 is largely plastically deformed. On the other hand, even if the 1st coating layer 2 does not deform | transform, the deformation amount is small.

Next, the details of the pressure molding process will be described.
When the coated abrasive grains 4 are filled into a mold having a desired shape, the coated abrasive grains 4 come into contact with each other on the outer periphery of the second coating layer 3 as shown in FIG. It will be in the state provided with the predetermined clearance 5 according to.
Next, the molded product 6 is molded by applying pressure through a pressing die (see FIG. 3). The applied pressure may be any pressure that is larger than the lowest pressure at which the second coating layer 3 is plastically deformed, but here, the pressure is further smaller than the lowest pressure at which the first coating layer 2 is plastically deformed. By doing so, as shown in FIG. 3, the molded product 6 has a structure in which the second coating layer 3 is plastically deformed and is in contact with each other on the outer periphery of the first coating layer 2. At this time, the second coating layer 3 in the contact portion flows so as to fill the gap 5, and the volume of the gap 5 is reduced. The degree of this reduction can be controlled by adjusting the thickness of the second coating layer 3. For example, when the shape of the coated abrasive grains 4 is close to a sphere, the volume ratio of the gap when the second coating layer 3 is not provided, that is, when the thickness of the second coating layer 3 is zero, is about 25%. When the thickness of the second coating layer 3 is about 6% of the outer radius of the first coating layer 2, the volume ratio of the gap is 0%. By selecting the thickness of the second coating layer 3 between these two conditions, a molded product 6 having a volume ratio of a desired gap of 25% or less can be manufactured.
The molded product 6 is degreased at a predetermined temperature equal to or higher than the volatilization temperature of the binder and the plasticizer after molding.

  Next, when the molded product 6 is sintered, a vitrified bond grindstone 9 having a bond layer 8 made of glass formed by fusing the first coating layer 2 and the second coating layer 3 as shown in FIG. 4 is obtained. it can. In this vitrified bond grindstone 9, the cBN abrasive grains 1 are dispersed within a predetermined distance determined by the size of the outer radius of the first coating layer 2 in the bond layer 8, and voids formed based on the gap 5 7 has a structure in which a desired ratio is evenly dispersed.

When grinding is performed using the vitrified bond grindstone 9 of the first embodiment, the cBN abrasive grains 1 and the holes 7 are uniformly dispersed with a desired distribution density, so that the same grinding performance is exhibited at any position of the grindstone. it can.

In this embodiment , although the example which mix | blended polyethyleneglycol as a plasticizer was shown, you may use glycerol, propylene glycol, etc. as a plasticizer.
The applied pressure may be larger than the pressure at which the first coating layer is deformed. In this case, both the first coating layer and the second coating layer are deformed, but since the deformation amount of the first coating layer is small, the same effect can be obtained. I can expect.
Although an example of plastic deformation has been shown as the deformation of the second coating layer, deformation by cracking or crushing may be used.
Further, diamond abrasive grains may be used in place of the cBN abrasive grains 1.

<Deformation of this embodiment>
A second embodiment will be described. This realizes a grindstone structure in which a desired material is distributed in a desired place by making the constituent materials of the first coating layer and the second coating layer different.
In FIG. 5, the first coating layer 12 is a mixture of glass powder having a particle size of several μm or less, a binder such as ammonium polyacrylate and polyethylene glycol as a plasticizer, and is attached to the cBN abrasive grains 11. Form.
Next, on the first coating layer 12, a mixed powder of glass powder having a particle size of several μm or less and hard particles having a particle size of several μm or less such as mullite, alumina, titanium oxide, zirconium silicate, the binder, A second coating layer 13 in which a larger amount of the plasticizer than the amount contained in one coating layer 2 is blended is formed.

  Next, after press-molding the coated abrasive grains 14 produced as described above into a predetermined shape, the coated abrasive grains 14 are degreased at a predetermined temperature equal to or higher than the binder volatilization temperature. As shown in FIG. 6, the structure at this time includes a glass powder layer 15 on the outside of the cBN abrasive grain 11, a mixed layer 16 of glass powder and hard particles on the outside, and a gap 5 between the coated abrasive grains 14. It has.

Here, the glass softens and flows during sintering and adheres to the abrasive grains. However, when additive particles such as the above hard particles are mixed, the fluidity of the glass is hindered and the adhesiveness to the abrasive grains decreases. It has been known.
However, in the coated abrasive grains of this embodiment, since the periphery of the cBN abrasive grains 11 is only glass, the glass softened during firing sufficiently flows and adheres to the entire surface of the cBN abrasive grains 11. For this reason, as shown in FIG. 7, the vitrified bond grindstone 19 includes a glass layer 17 in close contact with the entire surface of the cBN abrasive grain 11, and a mixed layer 18 in which additive particles are mixed in the glass at a portion away from the cBN abrasive grain 11. A bond layer is formed, and a structure in which pores 7 are dispersed in the mixed layer 18 is provided.
That is, the vitrified bond grindstone 19 of the present embodiment has two layers, a glass layer 17 having a strong abrasive grain retention because it has good adhesion to the cBN abrasive grains 11, and a mixed layer 18 having a high wear resistance because it contains hard particles. A bond layer comprising the structure is provided.

  When grinding is performed using the vitrified bond grindstone 19 of the second embodiment, a grinding force acts on the cBN abrasive grains 11, but the cBN abrasive grains 11 are unlikely to fall off because the glass adheres closely and the abrasive grain holding power is strong. . In addition, the mixed layer 18 is subjected to an abrasion action by the flow of chips, but wear is small because hard particles are mixed. As a result, the vitrified bond grindstone 19 with little wear can be realized even in high-efficiency grinding.

In the above embodiment, the hard layer is used as the additive for the second coating layer 13 to improve the wear resistance of the mixed layer 18. However, the dressing property of the mixed layer can be improved by adding particles having high friability such as hollow particles. May be better.
Further, diamond abrasive grains may be used in place of the cBN abrasive grains 11.

A third embodiment will be described. As a result of research, when cBN fine powder was added, it was found that there was little decrease in the fluidity of the glass during sintering, and this knowledge was applied.
Since the composition of the first coating layer is the same as that of the second embodiment except for the composition, only the coating process will be described for the manufacturing method.
As schematically shown in FIG. 8, the coated abrasive grains 24 are formed by mixing glass powder, cBN powder, a binder such as ammonium polyacrylate and polyethylene glycol as a plasticizer outside the cBN abrasive grains 21. One covering layer 22 is provided. On the outside of the first coating layer 22, there is provided a second coating layer 23 in which glass, hard particles (additives), the binder, and more plasticizer than the first coating layer 2 is added. .

  When the coated abrasive 24 is used for molding and sintering, the glass powder and cBN powder contained in the first coating layer are distributed in the vicinity of the cBN abrasive grain 21, so that the glass is sufficient during sintering. It flows and adheres to the cBN abrasive grains 21. Therefore, as shown in FIG. 9, the vitrified bond grindstone 27 includes a cBN additive layer 25 in close contact with the entire surface of the cBN abrasive grain 21, and a mixed layer 26 in which additive particles are mixed in the glass at a portion away from the cBN abrasive grain 21. A bond layer is formed, and a structure in which the holes 7 are dispersed in the mixed layer 26 is provided.

When the workpiece W is ground using the vitrified bond grindstone 27 of the third embodiment, as shown in FIG. 10, the ground chips C grow while contacting the cBN-added layer 25 and the mixed layer 26, and the chip After being stored in the pocket 28, the contact between the workpiece W and the vitrified bond grindstone 27 is completed and then discharged. At this time, a grinding force acts on the cBN abrasive grains 21, but the cBN additive layer 25 is in close contact with the cBN abrasive grains 21 and has a strong abrasive retention force, so that the cBN abrasive grains 21 are unlikely to fall off. Further, the mixed layer 26 is subjected to an abrasion action due to the flow of chips, but wear is small because hard particles are mixed. Furthermore, although the cBN added layer 25 is also subjected to an abrasion action by the flow of chips, the wear is small because the cBN fine powder is mixed.
As a result, it is possible to realize the vitrified bond grindstone 27 that is less consumed than in the second embodiment in high-efficiency grinding.

A fourth embodiment will be described. In this method, the coating layer has three layers, thereby improving the adhesiveness of the abrasive grains and realizing the desired abrasive distribution density and the desired pore distribution density.

As shown in FIG. 11, the first coating layer 32 is a mixture of glass powder having a particle size of several μm or less and a binder such as ammonium polyacrylate, and is formed by thinly adhering to the cBN abrasive grains 31. .
Next, on the first coating layer 32, glass powder having a particle size of several μm or less, hard particles having a particle size of several μm or less such as mullite, alumina, titanium oxide, zirconium silicate, the binder, and polyethylene as a plasticizer. The second mixture layer 33 is formed by bonding and drying the glycol mixture.
Further, a third coating in which the constituent material of the second coating layer 33 is the same as that of the second coating layer 33 but the amount of polyethylene glycol, which is a plasticizer, is greater than the amount contained in the second coating layer 33. A layer 34 is deposited on the second coating layer 33 to form coated abrasive grains 35.

The coated abrasive grains 35 have the following characteristics. The third coating layer 34 is more plastic than the second coating layer 33, and when a pressure equal to or higher than the pressure at which the third coating layer 34 is plastically deformed is applied to the coated abrasive grains 35, the third coating layer 34 is greatly plastically deformed. The second covering layer 33 is not deformed or even if it is deformed, the amount of deformation is small. Therefore, as in the second embodiment, when the molded product 36 is molded by pressurization, the third coating layer 34 is plastically deformed and brought into contact with each other on the outer periphery of the second coating layer 33 as shown in FIG. It becomes. At this time, the third coating layer 34 in the contact portion flows into the gap 5 and reduces the volume of the gap 5. The degree of this reduction can be controlled by adjusting the thickness of the third coating layer 34, and a molded product 36 having a desired volume ratio of the gap 5 can be manufactured.
Thereafter, a degreasing treatment is performed at a predetermined temperature equal to or higher than the volatilization temperature of the binder and the plasticizer.

Next, when sintered, a vitrified bond grindstone 39 as shown in FIG. 13 is formed. This vitrified bond grindstone 39 is composed of a thin glass layer 37 in which the glass softened during firing sufficiently flows and is in close contact with the entire surface of the cBN abrasive grains 31, and the second coating layer 33 and the third coating at a portion away from the cBN abrasive grains 31. The layer 34 is fused to form a bond layer 38 in which glass and additive particles are mixed.
Further, the cBN abrasive grains 31 are dispersed in the bond layer 38 at a predetermined distance determined by the size of the outer radius of the first coating layer 32, and the holes 7 generated based on the gap 5 in the bond layer 38. Have a structure in which they are dispersedly arranged at a desired ratio.
That is, since the adhesiveness to the cBN abrasive grains 31 is good, the abrasive grain holding force is strong, but the thickness of the glass layer 37 that is inferior in wear resistance is thinned, and the additive particles are mixed, so the wear resistance is high. The bond layer 38 is brought as close to the cBN abrasive grains 31 as possible to reduce the portion susceptible to wear, and as a result, a vitrified bond grindstone 39 having high wear resistance is realized.

  As shown in the above four embodiments, by producing a vitrified bond grindstone using coated abrasive grains having a plurality of coatings having different compositions on the outside of the abrasive grains, uniform dispersion of abrasive grains and pores can be achieved. The distribution density thereof can be set to a desired value, and further, the vitrified bond grindstone having a desired bond strength can be manufactured by distributing the added particles in a predetermined place.

DESCRIPTION OF SYMBOLS 1, 11, 21: cBN abrasive grain 2, 12, 22: 1st coating layer 3, 13, 23: 2nd coating layer 4, 14, 24: Coated abrasive grain 5: Crevice 6: Molded article 7: Hole 8 : Bond layer 9, 19, 27: Vitrified bond whetstone

Claims (4)

After forming a first coating layer made of glass, a binder, and a plasticizer outside the abrasive grains, the glass, the binder, and the plasticizer are made outside the first coating layer, and the plasticizer is covered with the first coating. A coating process for producing coated abrasive grains by forming at least one outer coating layer that is deformed at a pressure smaller than that of the first coating layer by increasing the amount of the plasticizer in the layer;
After filling the coated abrasive grains into a predetermined shape, a molded product in which gaps are formed between the outer coated layers of the coated abrasive grains that are in contact with each other by pressurizing with a pressure higher than the deformation of the outer coated layer Pressure molding process to manufacture;
A degreasing step of degreasing at a predetermined temperature equal to or higher than a volatilization temperature of the binder and the plasticizer;
Comprising a sintering step of sintering the molded product by sintering at a temperature equal to or higher than the softening point of the glass,
A method for producing a grindstone in which the gap becomes a void between the abrasive grains by the sintering step.   The method for manufacturing a grindstone according to claim 1, wherein a volume ratio of the holes in the grindstone is adjusted by adjusting a thickness of the outer coating layer.   The method for manufacturing a grindstone according to claim 1, wherein the outer coating layer includes hard particles.   The method for manufacturing a grindstone according to claim 1, wherein the first coating layer includes cBN grains, and the outer coating layer includes hard particles.

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