WO2004106001A1

WO2004106001A1 - Vitrified grinding wheel and method of manufacturing the same

Info

Publication number: WO2004106001A1
Application number: PCT/JP2004/007754
Authority: WO
Inventors: Takayuki Yui; Osamu Kubota; Hideo Furukawa; Masatoshi Kishimoto; Naoyuki Ukai
Original assignee: Bosch Corporation; Noritake Co., Limited; Noritake Super Abrasive Co., Ltd.
Priority date: 2003-05-30
Filing date: 2004-05-28
Publication date: 2004-12-09
Also published as: EP1634678A4; BRPI0411190A; KR20060018233A; US20060137256A1; EP1634678A1; KR100881254B1; JPWO2004106001A1; CN1795078A

Abstract

A vitrified grinding wheel having a porosity (desirably 30 to 70 vol.%), a concentration ratio of abrasive grain (desirably 50 to 160), and an abrasive grain size (desirably 10 to 90 μm) based on pre-set grinding efficiency and grinding accuracy, desirably, a grinding accuracy of 0.1 to 1.6 Rz (μm) and a grinding efficiency of 0.1 to 2.0 mm3/(mm·sec), and a method of manufacturing the vitrified grinding wheel.

Description

Vitrified whetstone and method of manufacturing the same

Technical field

The present invention relates to a vitrified whetstone obtained by bonding abrasive grains with a vitrified binder.

And its manufacturing method. In particular, the present invention relates to a method for grinding a small-diameter inner surface of an object to be ground.

Grinding wheel that can provide excellent machining accuracy and grinding accuracy and its manufacturing method

About the law.

Background art

Conventionally, vitrified grinding wheels have been used in a wide range of grinding and polishing operations, including precision grinding, because they can easily adjust the degree of bonding and composition and have water resistance, alkali resistance, and oil resistance.

For example, in the case of small-diameter inner surface grinding in which the inner surface of a small-diameter nozzle such as an engine firing nozzle is ground, the peripheral speed of the grinding wheel is limited and the quill rigidity is also reduced. Therefore, in order to maintain good grinding, it is necessary to make the grinding wheel diameter as large as possible. For this reason, in small-diameter internal grinding, a grindstone having a diameter close to the inner diameter of the workpiece is used. However, in this state of grinding, the chip length becomes longer and clogging is likely to occur. This tendency is particularly remarkable when the grinding efficiency is increased.

Figure 2 shows the relationship between the effective cutting edge distance of the grinding wheel and the chip pocket during internal grinding. Show. As shown in Fig. 2, in order to prevent clogging during grinding and improve machining efficiency, increase the abrasive grain size compared to the standard case (Fig. 2 (A)) One possible method is to increase the cutting edge distance We and the insert pocket P (Fig. 2 (B)). However, in this method, the effective cutting edge interval We is widened, and the machining accuracy (surface roughness) is reduced. On the other hand, in order to improve machining accuracy, it is conceivable to reduce the abrasive grain diameter compared to the standard case (Fig. 2 (A)) to reduce the effective cutting edge interval We and the insert pocket P. (Figure 2 (C)). However, in this method, since the volume of the chip pocket P is small, the chip pocket is immediately filled with the chips of the workpiece. If grinding is continued further in this state, the grinding wheel will be clogged, and it will also cause welding. As described above, since there is a trade-off between the improvement of the processing efficiency of grinding and the improvement of the processing accuracy, it has been conventionally difficult to satisfy both of them at the same time. Conventionally, attempts have been made to achieve both the processing efficiency and the processing accuracy of grinding. For example, a method is conceivable in which the concentration of the abrasive grains, which indicates the ratio of the abrasive grains in the grindstone, is reduced to improve the efficiency and accuracy of the grinding. However, if the concentration of the abrasive grains is reduced, the connectivity between the abrasive grains is reduced, causing problems in the bonding of the abrasive grains, and the dispersibility of the abrasive grains is reduced, so that the abrasive grains are uniformly dispersed in the grindstone. There was a problem that could not be done. For this reason, it was difficult to achieve both grinding efficiency and processing accuracy by the method of reducing the concentration of abrasive grains. Also, a method is known in which a part of cBN cannonball is replaced with an inorganic hollow substance (see Japanese Patent Application Laid-Open No. 62-251707). According to this method, the inorganic hollow material is crushed during grinding, and pores can be formed, so that an effect similar to that of a chip pocket can be expected. For example, by replacing a part of cBN abrasive grains with an inorganic hollow material,

Two

Replacement paper (rules) The whetstone having a concentration of about 100 was poor in particle dispersibility due to the low concentration, and it was difficult to obtain a whetstone in which abrasive grains were uniformly dispersed. Furthermore, since the inorganic hollow material is also held by the vitrified binder, the vitrified binder that should originally hold cBN abrasive grains is caught by the inorganic hollow material. For this reason, when an inorganic hollow material is used, it is necessary to use more vitrified binder than usual, and as a result, there is a disadvantage that the porosity is reduced. Furthermore, if the inorganic hollow material is ruptured during grinding, the vitrified binder used to bind the inorganic hollow material remains in the grindstone, which has the disadvantage of hindering grinding. Was. On the other hand, there is also known a method of forming pores by using an organic pore forming material such as walnut or wood powder in the production of a grindstone. The pore-forming material is contained in the compact before firing and burned out during the firing of the compact to form pores in the grindstone obtained after firing. The use of such a pore-forming material is preferable because it does not have the drawbacks caused by including a filler such as an inorganic hollow body in the grindstone and can reduce only the degree of concentration. However, depending on the type of pore-forming material used, the abrasive grains are non-oxide compared to general abrasives using A-type (alumina-based) general abrasives using WA abrasives (white alumina abrasives). However, since the vitrified binder is used in a large amount, it has a disadvantage that it is easily shrunk. Furthermore, when a conventional pore-forming material is used, it is difficult to uniformly disperse the pores, and it is not suitable for a vitrified cBN grinding wheel that requires a more uniform distribution of abrasive grains than a general grinding wheel. there were. In recent years, even in the case of manufacturing a vitrified whetstone in which the degree of concentration of abrasive grains is less than 200 for the purpose of improving a conventional pore forming material, firing shrinkage is small and pores are reduced. A method of uniformly distributing is known (for example, Japanese Patent Application Laid-Open No. 2000-317840). The grindstone obtained by this method has the advantage that the grinding ratio is high, the grinding burn and welding hardly occur, and the grinding wheel is easy to use, even when the concentration is as small as less than 200. However, even with the above method, when the degree of concentration is further reduced, that is, when a pore forming material having a diameter larger than the average particle diameter of the abrasive grains is used, the space between the abrasive grains is increased. There was a problem that the effective cutting edge interval became large, and as a result, good machining accuracy could not be maintained. Furthermore, in the above method, there was a problem that the uniformity of pores and abrasive grains in the grindstone was insufficient. Therefore, in order to maintain good machining efficiency and machining accuracy even with a grindstone having a further reduced degree of concentration, further improvement of the above method was required. Thus, the present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to maintain a predetermined porosity even when using small-diameter abrasive grains. Another object of the present invention is to provide a vitrified grinding wheel in which pores and abrasive grains are uniformly dispersed. Another object of the present invention is to maintain a predetermined porosity in a grindstone and to uniformly disperse the abrasive grains and pores in the grindstone even when using small-diameter abrasive grains. It is an object of the present invention to provide a method for manufacturing a vitrified whetstone that can be performed. DISCLOSURE OF THE INVENTION In order to solve the above-mentioned problems, the present inventors diligently studied the relationship between the effective cutting edge interval of abrasive grains and the tip pocket volume for the purpose of achieving both the processing efficiency and the processing accuracy of grinding. As a result, the present inventors set the grinding efficiency and machining accuracy in advance, and then, based on the grinding efficiency and machining accuracy, the porosity and the concentration of abrasive grains. We have found a method that can improve both grinding efficiency and machined surface roughness by setting the abrasive grain size, and have completed this effort. That is, the object of the present invention is achieved by the following vitrified grinding wheels.

(1) A vitrified whetstone containing at least a cannonball and a vitrified binder, characterized in that it has a preset porosity based on the processing efficiency and processing accuracy, the concentration of the abrasive, and the abrasive particle size. Vitrified grinding stone.

(2) If the processing accuracy of the grinding is 0. 1~1. 6Rz (ni), pressurized E efficiency of grinding is ^{0. 1~ 2. 0 mm 3 / (} mm-sec) (1) The vitrified whetstone described in 1.

(3) The vitrified whetstone according to (1) or (2), wherein the porosity is 30 to 70% by volume based on the total volume of the whetstone.

(4) The vitrified grinding wheel according to any one of (1) to (3), wherein the porosity includes a forced porosity based on burnout holes formed by burning out the pore-forming material.

(5) The vitrified cannon according to (4), wherein the forced porosity is 5 to 35% by volume based on the total volume of the grindstone.

(6) The vitrified whetstone according to (4) or (5), wherein the pore-forming material has a size of 0.1 to 3 times the average particle size of the abrasive grains.

(7) occupies the volume of all pores, the percentage of pores having 1 three times an average particle diameter of the abrasive grains, one of between 20 and 70 vol. ^_0/0 (1) - (6) The vitrif eyed whetstone described in 1.

(8) The ratio of the pores having a size of 0.1 to 1 times the average particle size of the abrasive grains in the total pore volume is 30 to 70% by volume. (1) Any of (1) to (6) Bites described in crab Refined whetstone.

(9) The vitrified whetstone according to any one of (4) to (8), wherein the pore-forming material is a polymer compound.

(10) The vitrified whetstone according to any one of (1) to (9), wherein the abrasive has an average particle diameter of 10 to 90 μηι.

(11) The vitrified whetstone according to any one of (1) to (10), wherein the degree of concentration of the abrasive grains is 50 to 160.

(12) The vitrified whetstone according to any one of (1) to (11), wherein the cannonball is a cubic boron nitride abrasive.

(13) The ratio of pores having a size of 1 to 3 times the average grain size of the abrasive grains in the volume of all pores, which is a vitrified whetstone containing at least an abrasive grain and a vitrified binder, Vitrified whetstone with 20-70% by volume.

(14) A vitrified grindstone containing at least abrasive grains and a vitrified binder, wherein the proportion of pores having a size of 0.1 to 1 times the average grain size of the abrasive grains in the total pore volume is as follows: Vitrified whetstone with 30-70% by volume.

(15) The vitrified whetstone according to (13) or (14), wherein the abrasive has an average particle diameter of 10 to 90 μπι.

(16) The vitrified whetstone according to any one of (13) to (15), wherein the concentration of the abrasive grains is 50 to: L60. Another object of the present invention is achieved by the following method for manufacturing a vitrified grinding wheel.

(17) A method for producing a vitrified whetstone containing at least an abrasive grain and a vitrified binder, wherein a grinding efficiency and a machining accuracy are set. The above manufacturing method, comprising a step of setting a porosity, a degree of concentration of abrasive grains, and a particle diameter based on processing accuracy.

(18) Processing precision 0. 1 of the grinding: Set L. 6Ι ζ (μΐη), and sets the processing efficiency of cutting the Institute to ^{0. 1~2 Q mm 3 / (mm'sec} ). The production method according to (17).

(19) The production method according to (17) or (18), wherein the porosity is set to 30 to 70% by volume with respect to the entire volume of the grindstone.

(20) The method according to any one of (17) to (19), wherein the porosity includes a forced porosity based on burn-through holes formed by burning out the pore-forming material.

(21 :) The production method according to (20), wherein the forced porosity is set to 5 to 35% by volume based on the total volume of the grindstone.

(22) The production method according to (20) or (21), wherein a pore-forming material having a size of 0.1 to 3 times the average particle size of abrasive grains is used as the pore-forming material.

(23) The production method according to any one of (17) to (22), wherein a polymer compound is used as the pore-forming material.

(24) The method according to any one of (17) to (23), wherein an abrasive having an average particle diameter of 10 to 90 μπι is used as the abrasive.

(25) The method according to any one of (17) to (24), wherein the degree of concentration of the abrasive grains is set to 50 to 160.

(26) The production method according to any one of (17) to (25), wherein cubic boron nitride magnetic particles are used as the abrasive particles. In the present invention, the processing efficiency and the processing accuracy of the grinding are set in advance. For this reason, according to the present invention, the porosity and the degree of concentration of the abrasive grains based on the processing efficiency and the processing accuracy of the grinding are described. And a vitrified grindstone having a grain size and a method for producing the same. MotoTsutomuAkira, for example, even when the machining efficiency of the grinding ^{0. 3 mm 3 / (mm} -sec) or more, providing a grinding wheel having 1. OR z (xm) following good working accuracy can do. In addition, the present invention includes a forced porosity based on burn-through holes of 5 to 35% by volume, even when a small-diameter abrasive having an average particle size of 10 to 90 m is used. The degree of concentration can be maintained at 50 to 160 with a porosity of up to 70% by volume, and a grindstone in which abrasive grains and pores are uniformly dispersed can be provided. As a result, according to the present invention, even if the abrasive grains have a small diameter, they have a uniform cutting edge interval equivalent to that of a large-diameter abrasive grain, and can secure a chip pocket volume. Thus, a vitrified grinding wheel having both grinding efficiency and grinding accuracy, and a method for manufacturing the same can be provided. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic enlarged sectional view of a vitrified grinding wheel of the present invention.

Fig. 2 is a diagram showing the relationship between the effective cutting edge spacing We of the grinding wheel and the tip pocket P during internal grinding.

FIG. 3 is a schematic enlarged sectional view showing the structure of a grindstone manufactured using a conventional burnout material.

FIG. 4 is a schematic enlarged explanatory view showing the structure of a grindstone manufactured without using a burnout material.

FIG. 5 is an explanatory diagram showing the relationship between the grinding efficiency ratio of the grinding wheel of the present invention and the conventional grinding wheel and the effective cutting edge interval.

FIG. 6 is an explanatory diagram for explaining the effective cutting edge interval and the arrangement of abrasive grains according to the present invention. FIG. 7 is a diagram showing the grinding efficiency ratio when the effective cutting edge interval is 0.1 mm in the preferred embodiment and the comparative example of the present invention. Fig. 8 (1) to (3) show the results (in terms of power consumption) of internal grinding with a grinding efficiency of 0.3 mm3 / (mm'sec) using the grinding wheels of Examples 1 to 3 and Comparative Example 2. , Surface roughness and wear). 9 (1) to (3), using the grinding wheel of Examples 1 and 2, grinding processing efficiency 0. 7 mm ³ / (mm'sec) result of the internal grinding in (power consumption, surface (Roughness, wear). BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the vitrified grinding wheel of the present invention and a method for producing the same will be described in more detail.

[Vitrifide whetstone]

The grindstone according to the present invention has a porosity, a degree of concentration of abrasive grains, and an abrasive grain size based on a preset machining efficiency and machining accuracy. The grinding efficiency indicates the amount of grinding per second when the grinding wheel width is lmm, and can usually be expressed in units of mm ³ / (mnrsec). The processing accuracy of grinding can be represented by surface roughness, and is usually represented by ten-point average roughness R 粗 (μιη). For example, in the case of internal grinding, if grinding accuracy of 1 R ζ (μm) or less was to be achieved, the grinding efficiency was conventionally limited to about 0.3 mm ³ / (min * sec) . On the other hand, the grinding wheel of the present invention can achieve a grinding efficiency of 0.3 mm ³ / (mm * sec) or more even with a grinding accuracy of 1 R _Ζ (μm) or less. More specifically, the processing accuracy of grinding is 0.1 to 1.6 Rz (/ xm), preferably 0.2 to 1.0 Rz (m), and more preferably 0.3 to 0.5 Rz. Even when ζ (μηι) is set, the processing efficiency of grinding is 0.1 to 2.0 ram ³ / (mm'sec), and preferably 0.2 to: 1.0 nmi ³ / ( nim'sec),

9

Replacement paper (Rule 2 More preferably, it can be set to 0.3 to 0.7 mm ³ / (mm'sec). Here, in order to explain the relationship between the processing efficiency of the above-mentioned grinding and the effective cutting edge interval We, FIG. 5 shows the relationship between the grinding efficiency ratio and the size of the effective cutting edge interval We. As shown in FIG. 5, for example, the conventional grinding stone has a grinding efficiency ratio of less than 2 when the effective cutting edge interval is 0.1 mm. On the other hand, when the effective cutting edge interval is 0.1 mm, the grinding efficiency ratio of the grinding stone of the present invention can be 2 or more (preferably 2.5 or more, more preferably 3 or more). (Note that Fig. 5 shows an example in which the grinding efficiency ratio is 3 or more when the effective cutting edge interval is 0.1 mm.) In the grindstone of the present invention, abrasive grains having a predetermined size (preferably 10 to 90 μπι) are selected, and unlike the conventional grindstone (see FIG. 2), the abrasive grains are not adjacent to each other as shown in FIG. Maintain a constant effective cutting edge spacing by arranging them evenly as shown in (1). Thus, the grinding wheel of the present invention can achieve a good machining efficiency (grinding efficiency ratio) while maintaining a predetermined grinding accuracy.

As used herein, the term “porosity” refers to the ratio of the volume of pores (space) excluding abrasive grains, binders, and other fillers to the total volume of the grindstone. In the present invention, the porosity is composed of a forced porosity and a natural porosity. Here, the "forced porosity" refers to a burn-through hole formed by firing a molded body containing at least abrasive grains, a vitrified binder, and a pore-forming material in a firing step to burn out the pore-forming material. Means the ratio of the volume to the total pore volume. Further, “natural porosity” means a porosity obtained by subtracting the forcible porosity from the total porosity, and occupies in the compacts in the gaps between the abrasive grains, the vitrified binder and the climate forming material before the firing treatment. Percentage. In the vitrified grinding wheel of the present invention, the porosity is 3 The range is suitably from 0 to 70% by volume, preferably from 40 to 60% by volume, and more preferably from 45 to 55% by volume. If the porosity is 30% by volume or more, the volume of the tip pocket will be insufficient, and there will be no clogging during grinding and welding. Further, in the present invention, since the pore-forming material is burned out in the firing step, a good porosity can be secured as compared with a grindstone not using the pore-forming material, and a porosity of up to 70% by volume can be obtained. it can. Of the above porosity, the forced porosity is suitably in the range of 5 to 35% by volume, preferably 20 to 35% by volume, and More preferably, it is 3 5% by volume. In the vitrified grindstone of the present invention, the forced porosity formed by the pore-forming material mainly contributes to the improvement of the processing efficiency of the grinding. If the forced porosity is 5% by volume or more, the grinding is excellent. Can be done. If the forced porosity is 35% by volume or less, the grinding wheel can be manufactured stably. In the vitrified grinding wheel of the present invention, the size of the forced pores formed by burning out the pore-forming material greatly affects the performance of the grinding wheel. For example, if the size of the forced pores is small, the dispersibility of the abrasive grains and pores in the grindstone increases. Further, since the dispersibility of the abrasive grains and pores is increased, the interval between the cutting blades is stabilized, so that the chip discharging performance is increased, the power consumption during grinding is reduced, and this is advantageous in terms of production efficiency. In addition, since the strength of the grindstone is increased, the abrasion of the grindstone due to grinding is small, and the durability is improved. The vitrified whetstone of the present invention has an average grain size of abrasive grains:! Pores with up to 3 times the size (including forced and natural pores) force 20 to 70 volumes relative to the total pore volume. / ₀ , preferably 30 to 60 volumes. / ₀ , more preferably 30 to 50% by volume. In addition, the vitrified whetstone of the present invention has an average grain diameter of 0. Pores having a size of 1-1 times, 30-70 volumes with respect to the volume of all pores. / _0, good Mashiku 4 0-7 0% by volume, more preferably from Der Rukoto those contained 5 0-7 0 volume ^_0/0. The proportion of pores having a desired size can be adjusted by appropriately setting the size and amount of the pore-forming material used. Further, the ratio of pores having a predetermined size can be determined by slicing a grindstone and analyzing a cross-sectional shape from three-dimensional data obtained by measuring a cross-section with a microscope capable of three-dimensional measurement.

The pore forming material used in the present invention is not particularly limited as long as it can burn out in the firing step. Preferably, the burnout start temperature is equal to or higher than the transition temperature of the vitrified binder described later, and the burnout completion temperature is lower than the maximum temperature within the range of the firing temperature of the vitrified binder. You can do it. For example, as the pore-forming material, the burn-out start temperature is 5 ° C or more (more preferably 10 ° C or more, more preferably 20 ° G or more) higher than the transition point temperature of the vitrified binder. Pores whose completion temperature is at least 5 ° C (more preferably at least 10 ° C, more preferably at least 20 ° C) higher than the maximum temperature within the range of the firing temperature of the grinding wheel raw material containing the vitrifide binder. A forming material can be suitably used. It is preferable that the pore-forming material has such a strength that the material is not crushed when the raw material is stirred during the production of the grinding wheel. As long as the pore-forming material has such a strength that it is not crushed at the time of stirring, any of solid and hollow pore-forming materials can be used. Further, the specific gravity of the pore-forming material is desirably 1 or more (for example, 1 to 2.5, preferably 1 to 1.5). If the specific gravity of the pore-forming material is 1 or more, stirring of the starting material It can be uniformly dispersed in the starting materials without floating during stirring. The size of the pore-forming material is preferably selected according to the desired size of the forced pores. As described above, the smaller the size of the forced pores, the lower the power consumption during grinding and the more advantageous in terms of production efficiency. Also, the smaller the forced pores, the higher the strength of the grindstone, and the less the abrasion of the grindstone due to grinding, and the better the durability. However, if the forced pore diameter is too small, the grinding efficiency will be reduced. From the above viewpoint, it is appropriate that the size of the pore-forming material is 0.1 to 3 times the average particle size of the abrasive grains. In particular, from the viewpoints of power consumption during grinding and durability of the grindstone, the size of the pore-forming material is preferably 0.16 to 1 times the average grain size of the abrasive grains. For example, when using cBN abrasive grains as abrasive grains, when the average grain size of the abrasive grains is 22 to 36 μπι, a pore forming material having a size of about 3.5 to 36 μm is used. Can be used. The shape of the pore-forming material is not particularly limited, but is preferably a true sphere capable of dispersing the abrasive grains in the manufacturing process. The content of the pore-forming material in the starting material is preferably 10 to 50% by volume%, more preferably 15 to 45%, and more preferably 15 to 40%. Is more preferred. When the volume% is 10% or more, the effect of forming burn-through holes is obtained, and when the volume% is 50% or less, it is possible to produce a grinding wheel having appropriate strength and durability. . Specific examples of the pore-forming material include, for example, polymer compounds such as polymethyl acrylate and polymethyl methacrylate, and carbonaceous materials containing 90% by mass or more of carbon. In particular, use of poly (methyl methacrylate) as a pore-forming material Is preferred. <Abrasives>

The grain size of the grain used in the present invention can be appropriately determined in relation to the porosity and the degree of concentration based on the processing efficiency and the processing accuracy of the grinding. For example, within the above-mentioned range of the grinding efficiency and the processing accuracy of the grinding, the average particle size is 10 to 90 μm, preferably 18 to 60 μκι, more preferably 20 to 55 μπι, and most preferably 25 to 45 μπι. It is appropriate to use abrasive grains. If the average grain size is 10 μιη or more, there is no problem of the connectivity between the ffi grains and the working efficiency of grinding is not significantly reduced. When the average grain size of the abrasive grains is 90 / zm or less, a predetermined cutting edge interval can be maintained, and machining accuracy can be improved. The type of abrasive grains is not particularly limited as long as it is within the range of the above average particle size. For example, abrasive grains such as cBN abrasive grains, A-based (alumina-based), and C-based (silicon carbide-based) grains can be used. When grinding high precision parts inside, it is preferable to use cBN abrasive grains. In addition, the type of abrasive grains may be a single type or a mixture of two or more types. When applying cBN abrasive grains as abrasive grains, one or more of general abrasive grains and inorganic hollow materials can be used in combination as a filler if necessary. However, in this case, it is appropriate to adjust the amount of filler used so that the concentration of cBN abrasive grains is 50 to 160. In addition, when diamond abrasive grains are used as abrasive grains, the type of vitrified binder and pore-forming material and the sintering temperature must be controlled in order to suppress the deterioration of the diamond abrasive grains. It is desirable to set conditions appropriately. The degree of concentration of the abrasive grains is suitably from 50 to 160, preferably from 75 to 150, and more preferably from 100 to 125. Here, the “concentration” means the ratio of the abrasive grains in the grinding stone. For example, in the case of diamond abrasive grains, 4.4 ct / cm ³ is 100, and the concentration degree is 25% by volume. Equivalent to. Therefore, the concentration of 200 corresponds to 50% by volume. When using abrasive grains having a different density from diamond abrasive grains, the degree of concentration can be determined according to the above, taking into account the difference in density from diamond abrasive grains. When the abrasive grains are cBN abrasive grains, as in the case of diamond abrasive grains, the degree of concentration 100 corresponds to about 25% by volume, and the degree of concentration 200 corresponds to about 50% by volume. .

In the present invention, by adjusting the concentration to a relatively low range of 50 to 160 and adjusting the porosity to a range of 30 to 70% by volume as described above, a predetermined tip pocket volume can be obtained. Can be maintained or increased, and clogging and welding of the grinding wheel during high-efficiency grinding can be prevented. Vitrifide binder> ''

In the present invention, the vitrified binder can be appropriately selected and used depending on the type of abrasive grains. For example, in the case of manufacturing a vitrified cBN grindstone using cBN abrasive grains as abrasive grains, the vitrified binder may be, for example, borosilicate glass, crystallized glass, or the like. Examples of the crystallized glass include those that precipitate willemite. In order to have sufficient holding power, the coefficient of thermal expansion of the vitrified binder is ± 2 X 10 -6 (1 / K) of the coefficient of thermal expansion of the abrasive grains (room temperature to 500 ° G). Is desirably within the range. When the vitrified binder for superabrasives is used as the vitrified binder, the temperature at which the grinding stone containing the binder is fired is selected according to the type of the vitrified binder for superabrasives used. Since the transition temperature of the vitrified binder for superabrasives is lower than the transition temperature of the vitrified binder for general abrasives, the temperature at which the grindstone raw material containing the vitrified binder for superabrasives is fired is 65500. The temperature is preferably in the range of 100 to 900 ° C, more preferably in the range of 700 to 950 ° C. When the temperature is at least 65 ° C., a grindstone having a certain strength can be obtained even after firing, and when the temperature is at most 100 ° C., deterioration of superabrasive grains does not occur. Preferred compositions of the superabrasive for vitrified bonded material, for _{example, S i 0 2: 4 0~7} 0 mass. /. _{, A 1 2 Os: 1 0~2} 0 wt%, B 2O3: 1 0~2 0 wt%, M ¹ O: 2~1 0 ^{_{wt%, M 2 2 0: 2~1}} 0 be exemplified wt% Can be. Here, M ¹ is one or more metals selected from Al-Li metal and M ² is one or more metals selected from Al-Li metal. The content of the vitrisulfide binder can be appropriately selected, and may be, for example, in the range of 13 to 35% by volume, preferably 18 to 22% by volume, based on the volume of the starting material. The vitrified grindstone of the present invention only needs to have at least a portion related to grinding having the above-described configuration. Therefore, the vitrified grindstone of the present invention also includes, for example, a vitrified grindstone portion containing abrasive grains and a vitrified binder provided on the surface of a ceramic holder that does not contain abrasive grains. When the grindstone of the present invention is a vitrified superabrasive grindstone, if necessary, a usual additive used for a vitrified superabrasive grindstone, for example, a brittle agent, a solid lubricant The agent may be contained in an appropriate amount.

[Method of manufacturing vitrified wheel]

Next, the method for producing a vitrified grinding wheel of the present invention will be described in more detail. The manufacturing method of the present invention includes a step of setting the processing efficiency and the processing accuracy of the grinding, and setting the porosity, the concentration of the abrasive grains, and the abrasive particle diameter based on the processing efficiency and the processing accuracy. As for the processing efficiency, processing accuracy, porosity, degree of concentration of abrasive grains, and abrasive grain size of the grinding, those of the above-mentioned vitrified stone can be used as they are. Further, as the abrasive grains, the vitrifide binder and the pore-forming material used in the manufacturing method of the present invention, the abrasive grains, vitrifide binder and pore-forming material used in the above-mentioned vitrifide grindstone of the present invention are used. Is appropriate. The production method of the present invention can include a firing step of firing a molded article containing at least abrasive grains, a vitrifide binder, and a pore-forming material to burn out the pore-forming material. In the production method of the present invention, in the method for firing a molded body containing at least abrasive grains, a vitrifide binder, and a pore former, the molded body is held at a certain temperature for a certain time and fired to burn out the pore former. The method is preferred. With this method, the pore-forming material burns out before the vitrified binder is melted in the firing step, and the binder ゃ shrinks the firing due to the free movement of the abrasive grains ゃ prevents the distribution of the abrasive grains from being disturbed. Is preferred because The holding time is preferably a time sufficient for the pore forming material contained in the molded body to burn out. The time sufficient for the pore forming material to burn out can be appropriately set according to the shape or size of the grindstone to be manufactured. When the compact is held at the firing temperature of the vitrified binder, it is held at a constant temperature within the firing temperature range. However, within this firing temperature range, a change in the temperature (for example, the temperature with respect to the elapsed time) May rise). The holding temperature at the time of holding for a fixed time during firing is preferably at least the burn-out completion temperature of the pore-forming material (preferably a temperature higher than the burn-through completion temperature by 5 ° C or more, more preferably the burn-through completion temperature). Temperature higher than the temperature by 10 ° C or more). The temperature at which the molded body is fired (the maximum temperature during firing) is a temperature within the range of the firing temperature of the vitrified binder, and may be equal to or higher than the burnout completion temperature of the pore forming material. In the manufacturing method of the present invention, it is preferable that the dimension of the molded body when the molded body is fired is a dimension such that the pore forming material used can be burned out by + minutes. For example, in the case of a rectangular parallelepiped shaped body, the thickness (the length of the rectangular parallelepiped in the thinnest direction) should be 10 mm or less (preferably 5 mm or less, more preferably 3 mm or less). Can be. Further, for example, in the case of a molded article having a cylindrical shape, the edge thickness (thickness of the wall of the cylinder) can be made 10 mm or less (preferably 5 mm or less, more preferably 3 mm or less). In the production method of the present invention, it is appropriate that the atmosphere at the time of firing be an atmosphere in which the pore-forming material sufficiently burns. When the pore-forming material is carbonaceous, for example, an atmosphere containing oxygen can be used. In the production method of the present invention, the step of obtaining the molded body may be provided before the firing step. Preferably, the molded body is obtained by mixing and stirring a starting material containing at least abrasive particles, vitrified binder powder and a pore-forming material, and a primary binder such as a paste, to obtain a mixture in which the above components are uniformly dispersed. The mixture can be obtained by molding under pressure and drying. When producing a vitrified superabrasive grindstone, a suitable amount of a usual additive used in a vitrified superabrasive grindstone, such as an embrittlement agent, a solid lubricant, or a molding aid, may be contained in the starting material, if desired. . The vitrified whetstone obtained by the above manufacturing method can be used as a whetstone of various grinding devices. In particular, even a small-diameter workpiece can exhibit high grinding efficiency and calorie accuracy, so that it can be suitably used for internal grinding. Applications of the grindstone of the present invention include, for example, grinding of an inner surface and a seat surface of an injection nozzle and a pressure adjusting component of a fuel injection device, and inner grinding of an inner ring and an outer ring of a bearing. Examples Hereinafter, the present invention will be described more specifically with reference to Examples.

In addition, the materials, the amounts used, the ratios, the processing contents, the processing procedures, and the like shown in the present embodiment can be appropriately changed without departing from the gist of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the following specific examples.

1. Fabrication of whetstone and its structure The starting materials having the following formulations shown in Examples 1 to 3 and Comparative Examples 1 and 2 were press-molded and fired at 900 for 24 hours in the atmosphere (including 1 hour at 900 ° G.). Holding), and a vitrified whetstone was prepared. In Example 1, when the mass loss was measured at 10 ° C. in the temperature-raising condition, the burning start temperature (10 mass% reduction) of polymethyl methacrylate was 300 ° C., and the burning completion temperature ( (A decrease of 90% by mass) was 500 ° C. In addition, the transition point of the used vitrified binder was 550 ° C, and the specific firing temperature was 850 to 950 ° C.

c BN abrasive grains (average particle size 30 μm (# 600), concentration 160) 5 5.1 volumetric volume polymethylmethacrylate (average particle size 30 μm, true specific gravity 1.2) 1 7.4 volume volume vitrifide binder 2 7.5 volume parts glue 1 4.5 volume parts

c B 麵 grain 40.0 volume part Porosity 40.0 volume part Burn-through hole (forced pore): 10.0 volume part

Natural pores: 30.0 volume

Percentage of pores having a size 1 to 3 times the average particle size of abrasive grains 3 7% by volume Vitrified binder 20.0% by volume

c BN abrasive (average particle size 30 μm (# 600), concentration 160) 1 volume part Polymethyl methacrylate (average particle size 5 m, true specific gravity 1.2) 4 volume part Vitrified binder 27.5 parts by volume Glue 14.5 parts by volume

c B employment grain 40.0 volume part pore 4Ό. 0 volume part Burn-through hole (forced pore): 10.0 volume part

Natural pores: 30.0 volume

Percentage of pores having a size of 0.1 to 1 times the average particle size of the abrasive grains: 67% by volume Vitrified binder 20.0 parts by volume

cBN abrasive grains (average particle diameter 30 m (# 600), concentration 160) 56.5 parts by volume Polymethyl methacrylate (average particle diameter 5 μm, true specific gravity 1.2) 2 1.0 parts by volume Vitrifide binder 2 2 .5 volume parts glue 14.5 volume parts

c B N Abrasive grain 40.0 volume part Pores 0 volume part Burn-through hole (forced pore): 14.0 volume part

Natural pores: 30.0 volume

Vitrifide binder 16.0 parts by volume

<Starting materials of Comparative Example 1 and their blending> c BN abrasive grains (average particle size 30μm (# 600), concentration 160) 55. 1 volume part carbonaceous beads (150μπι) 17.4 volume part vitrifide binder 27.5 volume part paste 14.5 volume Department

c Particles 43.7 volume parts Pores 40.0 volume Burnout holes (forced pores): 10.0 volume parts

Natural pores: 30.0 volume

Vitrified binder 3 parts by volume

cBN abrasive grains (average particle size 30μπι, degree of concentration 180) 69.2 volume part Vitrifide binder 30.8 volume part Glue 14.3 volume part

c ΒAgglomerated particles 45 0 volume parts Pores (natural pores) 35 0 volume parts Vitrified binder 200 0 volume parts A schematic enlarged cross-sectional view of the structure of the grindstones of Example 1, Comparative Examples 1 and 2 obtained after firing is shown in FIG. And Figure 3 and Figure 4 respectively. As shown in FIG. 1, the grindstone of the present invention is a grindstone in which c Β Ν abrasive grains 1 are bonded by vitrified bonding material 3. It has 2 burnout holes (forced pores) and 4 natural pores. Further, as shown in FIG. 3, the grindstone of Comparative Example 1 is a grindstone in which cBN abrasive grains 21 and burn-through holes 22 are bonded by vitrified bonding material 23, and further has pores 24. As shown in FIG. 4, the grindstone of Comparative Example 2 is a grindstone in which cBN abrasive grains 31 are bonded by vitrified binder 32 and, in addition, has pores 33. Comparing the structures of the grindstone of the present invention and the grindstone of the comparative example, the grindstone of Example 1 shown in FIG. 1 has more uniformly dispersed abrasive grains and pores than the grindstones of Comparative Examples 1 and 2. Has a high porosity. In contrast, the grindstone of Comparative Example 1 shown in FIG. 3 has a good porosity but non-uniform abrasive grains. The grindstone of Comparative Example 2 shown in FIG. 4 has non-uniform foundation grains and low porosity. This indicates that the grindstone of the present invention is a grindstone having a good chip pocket size while maintaining a constant effective cutting edge interval.

2. Evaluation of vitrified gemstones (1)

Internal grinding was performed using the grindstones obtained in Example 1 and Comparative Examples 1 and 2, and the relationship between the grinding efficiency ratio and the size of the effective cutting edge interval was examined. Figure 7 shows the results. The work material, processing conditions and dress conditions are as follows. Work Material>

Material S CM4 1 5

Size Diameter Φ3.95 mm

Grinding allowance Φ 0.05 mm

Machine used Internal grinding machine Grinding method Wet oscillating grinding

Wheel speed 22.6 / s

Work material peripheral speed 0.5 / s

Grinding efficiency ratio 1 to 3.2

There is a talented silation

Grinding oil Oily

Dresser φ50 square column rotary

Dress depth φ 1 μm / p a s s

Lead 0.004 mm r e v

According to FIG. 7, in the case of having the same effective cutting edge interval We (0.1 mm), in Example 1, the grinding efficiency ratio could be normally reduced to 3.2. On the other hand, in Comparative Examples 1 and 2, the grinding efficiency ratio was only normal up to 1.9. This shows that the use of the vitrified grindstone of the present invention enables grinding with the same grinding accuracy with a grinding efficiency approximately 1.7 times higher than that of the conventional grindstone.

3. Evaluation of vitrified wheel (2)

Examples 1-3, using a grinding wheel obtained in Comparative Example 2, performs internal grinding in processing efficiency 0. 3m m ³ / grinding (mn sec), was investigated power, surface roughness, wear . Fig. 8 (1) shows the change in power consumption, Fig. 8 (2) shows the measurement result of surface roughness, and Fig. 8 (3) shows the measurement result of wear. In addition, the grindstones obtained in Examples 1 and 2 were subjected to internal grinding at a grinding efficiency of 0.7 mm ³ / (mnr sec), and the power consumption, surface roughness, and wear were examined. The change in power consumption is shown in Fig. 9 (1), the measurement result of surface roughness is shown in Fig. 9 (2), and the measurement result of wear is shown in Fig. 9 (3).

twenty four

^ Replacement paper (Rule 26) However, the grinding wheel of Comparative Example 2 could not be evaluated because welding occurred in the processing immediately after dressing.

The work material, processing condition and dress condition are as follows.

Material SU J -2

Dimension inside diameter Ψ 28.3 mm

Grinding allowance 0.ύ 6 mm

Machine used Internal grinding machine

Grinding method Wet oscillating grinding

Wheel peripheral speed 45 m / s

Workpiece peripheral speed 25 m / s

With oscillation

Grinding oil water-soluble

Dresser φ2 5 prismatic rotary

Dress depth 4 μmZ a s s

Lead 0.030 mm / r e v

(i) Power consumption

As shown in FIG. 8 (1), in the grinding wheel of Comparative Example 2, the power consumption in the initial stage of grinding was extremely high, and welding occurred, and subsequent grinding was impossible. In contrast, as shown in Fig. 8 (1) and Fig. 9 (1), the grinding wheels of Examples 1 to 3 maintain stable power consumption at a low level during grinding, enabling continuous machining without welding. Met.

twenty five

Replacement paper (Rule 26) (ii) Surface roughness

As shown in FIG. 8 (2), the grinding wheel of Examples 1 3, the processing efficiency of grinding 0. In ^{3 mm 3 / (ni m'sec)} , 0. 7 R z (μ m) of the following grinding Processing accuracy was obtained. Further, as shown in FIG. 9 (2), the grinding stones of Examples 1 and 2 obtain a grinding accuracy of 0.8 R zm) or less at a grinding efficiency of 0.7 mm ³ / (mnrsec). I was able to do it.

(iii) Wear

As shown in FIG. 8 (3) and FIG. 9 (3), when comparing Example 1 with Example 2, the diameter of the pore-forming material is small (that is, the forced pores are small). Due to the high strength, there was little wear. Also, as shown in Fig. 8 (3), comparing Example 2 and Example 3 using the pore-forming material of the same diameter, the grinding wheel of Example 2 with a larger amount of binder has higher hardness. Less wear. INDUSTRIAL APPLICABILITY As described above, the vitrified grindstone of the present invention has a porosity, a degree of concentration of abrasive grains, and an abrasive grain diameter based on a preset grinding efficiency and processing accuracy. As a result, with the gantry of the present invention, it is possible to accurately process the roughness of the processed surface while improving the processing efficiency of grinding, which has been conventionally used as an index of a contradictory grindstone. Further, in the method for producing vitrified rubble of the present invention, the grinding efficiency and the processing accuracy are determined in advance, and the porosity, the degree of concentration of the abrasive grains, and the abrasive particle diameter are set based on the grinding efficiency and the processing accuracy. . Thus, according to the manufacturing method of the present invention, the grinding wheel

26

Replacement paper (Norin) The pores and pores can be distributed uniformly, and as a result, it is possible to manufacture a grindstone that achieves both a high grinding efficiency and a high grinding accuracy.

Claims

1. A vitrified whetstone containing at least abrasive grains and a vitrifide binder, having a porosity, a degree of concentration of abrasive grains, and an abrasive grain diameter based on preset grinding efficiency and accuracy. Whetstone.

2. If the processing accuracy of the grinding is 0.1 to 1.6 Rzm),

Efficiency is ^{0. 1~ 2. 0 mm 3} / (mm · sec) Bitorifuaido grindstone according to claim 1 is.

of

3. The vitrified whetstone according to claim 1, wherein the porosity is 30 to 70% by volume based on the total volume of the whetstone.

Enclosure

4. The vitrified grindstone according to any one of claims 1 to 3, wherein the porosity includes a forced porosity based on burnout holes formed by burning out the pore-forming material.

5. The vitrified whetstone according to claim 4, wherein the forced porosity is 5 to 35% by volume based on the total volume of the whetstone.

6. The vitrified whetstone according to claim 4, wherein the pore forming material has a size of 0.1 to 3 times the average particle size of the abrasive grains.

7. The method according to any one of claims 1 to 6, wherein a ratio of pores having a size of 1 to 3 times the average particle size of the abrasive grains in the total pore volume is 20 to 70% by volume. The described vitrif eyed whetstone.

8. The ratio of pores having a size of 0.1 to 1 times the average grain size of the abrasive grains in the total pore volume is 30 to 70% by volume. The vitrified grinding wheel according to item 1.

9. The vitrified whetstone according to any one of claims 4 to 8, wherein the pore-forming material is a polymer compound.

10. The vitrified ffi stone according to any one of claims 1 to 9, wherein the average particle diameter of the cannonball is 10 to 90 m.

11. The vitrified grindstone according to any one of claims 1 to 10, wherein the degree of concentration of the abrasive grains is 50 to 160.

12. The vitrified whetstone according to any one of claims 1 to 11, wherein the foundation grains are cubic boron nitride abrasive grains.

13. A vitrified whetstone containing at least an abrasive grain and a vitrified binder, wherein the proportion of pores having a size of 1 to 3 times the average grain size of the abrasive grains in the total pore volume is 20%. to 7 0 capacity ^_0/0, which is Bitorifuaido grindstone.

14. A vitrified whetstone containing at least abrasive grains and a vitrified binder, wherein the proportion of pores having a size of 0.1 to 1 times the average grain size of the abrasive grains in the volume of all pores is high. Vitrified whetstone that is 30 to 70% by volume.

15. The vitrified grinding stone according to claim 13 or 14, wherein the abrasive has an average particle diameter of 10 to 90 µm.

16. The vitrifite calculus according to any one of claims 13 to 15, wherein the degree of concentration of the abrasive grains is 50 to 160.

17. A method for producing a vitrified grindstone containing at least a grain and a vitrified binder, wherein a grinding efficiency and a machining accuracy are set, and a porosity and a concentration of abrasive grains are determined based on the machining efficiency and the machining accuracy. The above-mentioned manufacturing method, comprising a step of setting a degree and an abrasive grain size.

1-8. 0 machining accuracy of the grinding. 1-1. Set 6 Ι ζ (μ m), and 0 the processing efficiency of the grinding. 1 to 2. 0 mm ³ set / (mm'sec) 18. The production method according to claim 17, wherein

19. The method according to claim 17 or 18, wherein the porosity is set to 30 to 70% by volume based on the total volume of the grindstone.

20. The method according to any one of claims 17 to 19, wherein the porosity includes a forced porosity based on burnout holes formed by burning out the pore-forming material.

21. The production method according to claim 20, wherein the forced porosity is set to 5 to 35% by volume based on the total volume of the grindstone.

22. The method according to claim 20 or 21, wherein the pore-forming material is a pore-forming material having a size of 0.3 to 3 times the average particle size of the abrasive grains.

23. The production method according to any one of claims 17 to 22, wherein a polymer compound is used as the pore-forming material.

24. The production method according to any one of claims 17 to 23, wherein an abrasive having an average particle diameter of 10 to 90 μπι is used as the abrasive.

25. The production method according to any one of claims 17 to 24, wherein the degree of concentration of the abrasive grains is set to 50 to 160.

26. The production method according to any one of claims 17 to 25, wherein cubic boron nitride abrasive grains are used as the grain.