JP2008030157A - Porous abrasive wheel and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a porous abrasive wheel wherein super-abrasive grains are uniformly dispersed into a binding material composing the abrasive wheel and pores contributing to the reduction of abrasive/cutting resistance are appropriately dispersed to prevent cracks from being formed in the inside of the abrasive wheel, and a manufacturing method of the porous abrasive wheel. <P>SOLUTION: The super-abrasive grains 2 are uniformly dispersed into a liquid phenol resin diluted with a solvent to form a mixture, the mixture is calcined without applying pressure to cure the phenol resin to form a cured product. The cured product is crushed, and the crushed grains 1A are pressure-molded with pores formed between grains to make a molded article. Then, the molded article is calcined at the high temperature in an inactive gas or a vacuum, the phenol resin is converted to amorphous carbon, and fine pores 3 are formed in the amorphous carbon by the gas generated accompanying conversion to amorphous carbon to obtain the porous abrasive wheel. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a perforated grindstone used for grinding and cutting, and a method for producing the same.

Conventionally, a resin bond grindstone obtained by mixing phenol resin powder and high-abrasive superabrasive grains such as diamond and cBN, filling the mixture into a molding die, and pressure sintering is known. . Since the resin bond grindstone manufactured by this type of method is fired while being pressure-molded in a state where the phenol resin is softened in a gel state, the grindstone structure becomes a dense structure. This dense-structured grindstone does not have the hollow pores necessary to remove debris generated during grinding / cutting of the workpiece, tends to clog, and has stable machining performance over a long period of time. Difficult to maintain.
Therefore, in order to make a resin bond grindstone in which fine pores are dispersed, various salts such as sodium chloride and sodium sulfate are added as a soluble filler as a pore forming agent together with phenol resin powder and superabrasive grains, or hollow. Means such as adding a hollow filler such as glass beads and further adding granular foamed styrene are used.

  In addition, the resin bond grindstone is elastically deformed due to the presence of the phenolic resin in the binder, so that the contact between the workpiece and the abrasive is eased during grinding and cutting. Compared to the metal bond grindstone and vitrified bond grindstone Thus, there is an advantage that the processing damage to the workpiece is small. Furthermore, since the resin bond grindstone is excellent in the self-generated blade action of the abrasive grains, the resin bond grindstone has a feature that the abrasive grains are not easily crushed compared to the metal bond grindstone.

  However, when using superabrasive grains having an average grain size of 5 μm or less, it is difficult for the resin bond grindstone manufactured by the above method to mix the phenol resin powder and superabrasive grains uniformly, and the superabrasive grains are uniform. It is difficult to stably obtain a dispersed grindstone. The uneven distribution of the fine pores is likely to occur, and it is difficult to appropriately disperse the fine pores having the same size as the superabrasive grains.

  In addition, the resin bond grindstone using fine superabrasive grains having an average particle size of 5 μm or less has a relatively soft phenolic resin, so that the superabrasive grains are buried in the binder during processing, and the workpiece is processed. It becomes easy for the binder to come into contact. Therefore, when fine superabrasive grains are used for the resin bond grindstone, there is a problem that the grinding / cutting resistance is increased and it is difficult to process a stable workpiece.

As a technique for improving the drawbacks of such a resin bond grindstone, Patent Document 1 discloses that a superabrasive grain is dispersed in a phenol resin and sintered in a pressurized state to form a molded body. A grinding wheel in which a phenol resin is converted into amorphous carbon by firing at a high temperature is disclosed.
However, in such a method, since the phenol resin is converted to amorphous carbon while generating gas during high-temperature firing, the grindstone has a high possibility of forming cracks therein, and the molded body is liable to collapse. have.

  As a technique for preventing the occurrence of cracks in a resin bond grindstone, Patent Document 2 discloses a technique in which a solvent such as alcohol is added to a phenol formaldehyde resin to be liquefied, superabrasive grains are mixed, and then the solvent is removed. It is disclosed that pressure baking is performed at a low temperature of about 500C, and then heating is performed at a high temperature of 500C or higher to convert the phenol formaldehyde resin into amorphous carbon, which is pulverized and used as a raw material for a grindstone. And it is also disclosed that the grindstone raw material thus obtained is added to a resin bond raw material such as a phenol resin and fired at a relatively low temperature of about 200 ° C., thereby suppressing thermal distortion caused by the firing and obtaining a high-precision grindstone. Yes.

However, since the grindstone disclosed in Patent Document 2 is fired at a relatively low temperature after the resin bond raw material is added to the grindstone raw material, the pores necessary for removing grinding and cutting waste are sufficient. Further, since the grinding wheel raw material is added to the resin bond raw material, the superabrasive grains may not be uniformly dispersed in the binder.
JP-A-60-232873 JP 2002-274944 A

  The technical problem of the present invention is to uniformly disperse the superabrasive grains in the binder constituting the grindstone and appropriately disperse pores contributing to reduction of grinding / cutting resistance, etc. An object of the present invention is to provide a porous hole grindstone in which no cracks are formed and a method for producing the same.

  The porous abrasive wheel of the present invention for solving the above problems is formed by uniformly dispersing superabrasive grains in a binder made of amorphous carbon and uniformly dispersing fine pores in the binder. There is an intergranular pore, which is a porous stone, wherein the binder in which the superabrasive grains and fine pores are dispersed is a pulverized grain obtained by pulverizing a cured product of a phenol resin in which superabrasive grains are dispersed. The pores in the binder are formed by pressure-molding the desired molded body in a state and then baking it at a high temperature in an inert gas or vacuum to convert the phenol resin into amorphous carbon. However, it is formed by the gas generated in the pulverized particles as the amorphous carbon is formed.

  In a preferred embodiment of the porous hole grindstone according to the present invention, abrasive grains having an average particle diameter of 5 μm or less are used as the superabrasive grains. A filler for adjusting the degree of bonding and / or a pore forming agent for adjusting the amount of fine pores can be added to the phenol resin forming the pulverized particles.

On the other hand, the manufacturing method of the porous hole grindstone of this invention for solving the said subject consists of following process (a)-(d), It is characterized by the above-mentioned.
(A) A step of uniformly dispersing superabrasive grains in a liquid phenolic resin diluted with a solvent to form a mixture.
(B) A step of baking the above-mentioned mixture without pressure to cure the phenol resin to obtain a cured product.
(C) The process which grind | pulverizes the said hardened | cured material and press-molds the grind | pulverized grind | pulverized particle in the state in which an intergranular pore exists, and it is set as a molded object.
(D) A step of firing the molded body at a high temperature in an inert gas or in a vacuum to convert the phenol resin into amorphous carbon and forming fine pores in the amorphous carbon by the gas generated along with the amorphous carbon.

  In preferable embodiment of the manufacturing method of the porous hole grindstone concerning this invention, the said process (b) includes the process of removing a solvent from the said mixture, and the calcination temperature in the said process (d) sets to 700-1200 degreeC. Is done. Moreover, in the said process (a), a thing with an average particle diameter of 5 micrometers or less is used as a superabrasive grain.

In the porous hole grindstone of the present invention having the above-described configuration and its manufacturing method, superabrasive grains are dispersed in a liquid phenolic resin diluted with a solvent, so that superabrasive grains having an average particle diameter of 5 μm or less are used. However, the superabrasive grains can be uniformly dispersed relatively easily.
In addition, pulverized particles obtained by pulverizing a cured product of phenol resin are subjected to pressure molding in the presence of intergranular pores and then baked at high temperature to convert the phenol resin into amorphous carbon. Fine pores due to the generated gas are formed in the pulverized grains, and there are intergranular pores between the pulverized grains, so that part of the generated gas passes through the intergranular pores between the pulverized grains. As a result, no cracks are generated inside the molded porous grindstone. Moreover, the pores in the grindstone are appropriately distributed.
In this way, the superabrasive grains are uniformly dispersed in the grindstone, and a large number of pores are moderately dispersed, so that clogging is difficult to occur at the time of grinding / cutting, processing resistance is reduced, and machining is reduced. There is little fever.

  According to the porous hole grindstone of the present invention and the manufacturing method thereof described above, the superabrasive grains are uniformly dispersed in the binder constituting the grindstone, and the pores contributing to reduction of grinding / cutting resistance are appropriately dispersed. And it can suppress that a crack is formed inside a grindstone in connection with it.

Embodiments of the present invention will be described below in detail with reference to the drawings.
FIG. 1 is an enlarged view of a portion of a porous hole grinding stone according to the present invention. In the porous hole grinding stone, superabrasive grains 2 are uniformly dispersed in a binder 4 that has been converted to amorphous carbon by firing. At the same time, the pulverized particles 1 in which the fine pores 3 are appropriately dispersed are formed in such a state that the interparticle pores 5 exist between the pulverized particles 1. This porous hole grindstone pulverizes a cured product obtained by pressureless firing of a liquid phenolic resin in which superabrasive grains are uniformly dispersed, and press-molds the pulverized grains in an inert gas. Alternatively, it is fired at a high temperature in a vacuum.
As the superabrasive grains 2, diamond abrasive grains are desirable, but cBN abrasive grains and other high-hardness abrasive grains can be used. The diamond abrasive grains and the like are classified into a certain range, and there is no particular limitation on the particle size, but it is effective to use super abrasive grains having an average particle diameter of 5 μm or less.

Next, with reference to FIGS. 2 to 4, the structure of the porous hole grindstone will be described more specifically while explaining the method for manufacturing the porous hole grindstone.
When manufacturing the above-mentioned porous hole grindstone, first, as shown in FIG. 2, a solvent such as alcohol is added to the phenol resin powder that is converted to amorphous carbon to form the above-mentioned binder 4 to obtain a liquefied phenol resin 4A. Then, the liquefied phenol resin 4A was mixed with a superabrasive grain 2, a filler for adjusting the degree of bonding and a pore-forming agent for adjusting the fine pore volume, if necessary, and liquefied. Let it be a mixture in which superabrasive grains 2 and the like are uniformly dispersed in phenol resin 4A.

  As the filler, alumina, silicon carbide, silica, or the like can be used. As the pore forming agent, hollow glass beads, cellulose powder, or the like can be used.

  Next, after removing the solvent from the mixture, the phenol resin was thermally cured by baking without pressure, and the cured product of the thermally cured phenol resin 4B was pulverized and thermally cured as shown in FIG. A pulverized grain 1A in which abrasive grains 2 are dispersed in a phenol resin 4B is obtained. Although the superabrasive grains 2 are uniformly dispersed in the pulverized grains 1A, the fine pores 3 are not yet formed.

The pulverized particles 1A are adjusted in particle size using a sieve or the like, but the particle size is desirably 250 μm or less, and by selecting this particle size, the pulverized particles 1A between the pulverized particles 1 after the pressure forming in the next step The size of the intergranular pores 5 can be set arbitrarily.
Next, the pulverized particles 1A having a selected particle size are filled in a mold having a predetermined shape and subjected to pressure molding to form a molded body 6 as shown in FIG. Bake at high temperature in vacuum. The firing temperature is preferably in the temperature range of 700 to 1200 ° C.
If the firing temperature is lower than 700 ° C., the conversion of the phenol resin into amorphous carbon becomes insufficient, so that the hardness becomes low and unsuitable. If the firing temperature is higher than 1200 ° C., the carbonization of diamond particles proceeds. Therefore, the function of the grinding wheel is greatly impaired.

  By this firing, the phenol resin is converted to amorphous carbon while generating a gas, and at this time, fine pores 3 are formed in each pulverized particle 1A by the generation of the gas. A part of the generated gas is discharged through the intergranular pores 5 formed between the pulverized grains 1, so that no cracks are formed inside the molded body 6. Further, by selecting the highest temperature during firing, the hardness of the amorphous carbon after firing can be selected, and the hardness of the grindstone can be arbitrarily selected.

  Examples of the present invention will be described below in relation to comparative examples, but the present invention is not limited to these examples.

Phenol resin powder (produced by Air Water Velpearl Co., Ltd .: trade name Belpearl), which is liquefied by adding ethyl alcohol as a solvent, diamond abrasive grains classified to an average particle diameter of 2 μm, and silica having an average particle diameter of 0.8 μm Particles were added and mixed to obtain a mixture in which diamond abrasive grains and silica particles were dispersed. In addition, the amount of ethyl alcohol was calculated in advance and added so that the concentration of the solution of this mixture was 60 to 65 wt%.
And after evaporating the alcohol content of the mixture in which the diamond abrasive grains and silica particles are uniformly dispersed, the mixture is baked without pressure in an environment maintained at a temperature of 200 ± 5 ° C. A cured product was obtained.

Next, the cured product was pulverized using a ball mill, and classified using a sieve having an opening of 180 μm, a sieve having an opening of 125 μm, and a sieve having an opening of 90 μm, and adjusted the particle size of the pulverized particles. . The three kinds of pulverized particles thus obtained were each placed in a mold having a diameter of 30 mm, and a molding pressure of 1.5 t / cm ² was applied at room temperature to obtain a molded body having a diameter of 30 mm and a thickness of 5 mm.
The obtained compact was fired by holding it in a nitrogen gas atmosphere with a furnace temperature of 950 ° C. for 3 hours. Specifically, the temperature rising time until reaching the temperature of 950 ° C. was 20 hours, and after maintaining at 950 ° C. for 3 hours, the furnace was gradually cooled until the furnace temperature became 100 ° C. or lower.

  Inside the porous hole grindstone obtained as described above, cracks were not formed regardless of the opening of the sieve, and uniformly dispersed superabrasive grains and pores were formed. Table 1 shows the measurement results of the ratio of the dry weight and volume of the molded body after firing with respect to the sieve opening.

この測定結果によれば、実施例１の有気孔砥石は、乾燥重量と体積の比がフルイ目開きに依存している状態であることがわかる。

According to this measurement result, it can be seen that the porous hole stone of Example 1 is in a state where the ratio of the dry weight to the volume depends on the sieve opening.

The cured product of the phenol resin by pressureless firing obtained in the same manner as in Example 1 was pulverized using a ball mill, and the particle size of the pulverized particles was adjusted using a sieve having an opening of 90 μm. The obtained pulverized grains were put in a predetermined mold, and a molding pressure of 2.0 t / cm ² was applied at room temperature to obtain a ring-shaped molded body having a diameter of 143 mm, a thickness of 5 mm, and a width of 3.5 mm.
This molded body was held at a temperature of 900 ° C. for 3 hours in a vacuum firing furnace and fired. The temperature rising time until reaching the temperature of 900 ° C. was 20 hours, and after maintaining at 900 ° C. for 3 hours, the furnace was gradually cooled until the temperature in the furnace became 100 ° C. or less.

The porous hole grindstone obtained by firing the molded body was cut into a dimension of 32 mm in length, and bonded to an aluminum base using a two-component epoxy adhesive, and then a diameter of 142 mm, a thickness of 3.0 mm, and a width of 2. Molded to a grinding wheel size of 5 mm to obtain a grinding wheel.
This grinding wheel was attached to a horizontal axis super-precision surface grinding machine (HG-130A manufactured by Toshiba Machine Co., Ltd.) and subjected to grinding. As the work material, a silicon wafer having a diameter of 125 mm and a thickness of about 0.5 mm obtained by previously grinding the surface roughness to a center line average roughness Ra of 0.2 μm was used. Grinding by the in-feed method is performed under the conditions of a grinding wheel peripheral speed of 2,920 m / min, a work material rotation speed of 20 rev / min, a grinding wheel feed set amount of 50 μm, and a work table feed speed of 12 μm / min. Carried out. The results of grinding are shown in Table 2 below.

Comparative example

Phenol resin powder (trade name Belpearl manufactured by Air Water Velpearl), diamond abrasive grains classified to an average particle diameter of 2 μm, and silica particles having an average particle diameter of 0.8 μm were mixed in a powder state. The obtained mixture was put into a predetermined mold and fired while applying a molding pressure of 1.5 t / cm ² while maintaining the temperature at 180 ± 5 ° C. A ring-shaped molded body having a diameter of 143 mm, a thickness of 5 mm, and a width of 3.5 mm was obtained.

  The molded body obtained by the above manufacturing method is bonded to an aluminum base using a two-component epoxy adhesive, and then molded into a grinding wheel size of 142 mm in diameter, 3.0 mm in thickness, and 2.5 mm in width. A bond grindstone (grinding grindstone) was obtained. In the same manner as in Example 2, this grinding wheel was attached to a horizontal axis super-precision surface grinder, and grinding by an infeed method was performed. The results of this grinding process are shown in Table 2 together with the results of Example 2.

この実施例２及び比較例２によれば、本発明の有気孔砥石はレジンボンド砥石に比べ、研削量が５０％程度、負荷電流も１０％程度改善されていることから、研削性に優れ、研削抵抗が低い研削砥石であることがわかる。

According to this Example 2 and Comparative Example 2, the porous hole grindstone of the present invention has an excellent grindability because the grinding amount is improved by about 50% and the load current is also about 10% compared to the resin bond grindstone. It turns out that it is a grinding wheel with low grinding resistance.

It is the elements on larger scale of the porous hole grindstone concerning the present invention. It is explanatory drawing which shows the state which mixed the superabrasive grain in the liquefied phenol resin in the manufacturing method of the porous hole grindstone which concerns on this invention. It is explanatory drawing which shows the grinding | pulverization state of the hardened | cured material in the said manufacturing method. It is a perspective view which shows an example of the molded object of the porous hole grindstone which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ground grain 1A Ground grain 2 Superabrasive grain 3 Fine pore 4 Binder 4A Liquefied phenol resin 5 Intergranular pore 6 Molded body

Claims (6)

A porous abrasive wheel in which superabrasive grains are uniformly dispersed in a binder made of amorphous carbon, and fine pores are uniformly dispersed in the binder,
The above-mentioned superabrasive grains and a binder in which fine pores are dispersed are pulverized grains obtained by pulverizing a cured product of a phenol resin in which superabrasive grains are dispersed. After being pressure-molded, it is formed by baking it at a high temperature in an inert gas or vacuum, and converting the phenol resin into an amorphous carbon,
The fine pores in the binder are formed by the gas generated in the pulverized grains accompanying the amorphous carbonization,
A porous hole grindstone characterized by that. The super abrasive grains are abrasive grains having an average particle size of 5 μm or less.
The perforated grindstone according to claim 1. To the phenol resin forming the pulverized grains, a filler for adjusting the degree of bonding and / or a pore forming agent for adjusting the amount of fine pores is added,
The porous hole grindstone according to claim 1 or 2, characterized by things. The manufacturing method of the porous hole grindstone characterized by consisting of following process (a)-(d).
(A) A step of uniformly dispersing superabrasive grains in a liquid phenolic resin diluted with a solvent to form a mixture.
(B) A step of baking the above-mentioned mixture without pressure to cure the phenol resin to obtain a cured product.
(C) The process which grind | pulverizes the said hardened | cured material and press-molds the grind | pulverized grind | pulverized particle in the state in which an intergranular pore exists, and it is set as a molded object.
(D) A step of firing the molded body at a high temperature in an inert gas or in a vacuum to convert the phenol resin into amorphous carbon and forming fine pores in the amorphous carbon by the gas generated along with the amorphous carbon. The step (b) includes a step of removing the solvent from the mixture,
The firing temperature in the step (d) is 700 to 1200 ° C.
The manufacturing method of the porous hole grindstone of Claim 4 characterized by the above-mentioned. In the step (a), the average particle size of the superabrasive grains is 5 μm or less.
The manufacturing method of the porous hole grindstone of Claim 4 or 5 characterized by the above-mentioned.

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