JPH06262528A - Manufacture of porous vitrified grinding wheel - Google Patents

Abstract

PURPOSE:To make sufficient porosity and binding power impartable to a grind ing wheel by burning a ceramic porous body being higher in softening tempera ture than that of a vitrified binder after forming it by mixing it with an abra sive grain and a binding agent in combination. CONSTITUTION:In a manufacturing process of a grinding wheel made up of binding a cubic boron nitride abrasive grain 10 with a virtified binder, at the time of burning, first of all, the vitrified binder is softened, making it come into contact with the grain 10 so as to wrap a ceramic porous particle 16. Since this particle 16 is porous, its surface area is so large that it reacts to the softened vitrified bonder, and both solidly form a vitric body 20. Accordingly, the abrasive grain 10 is locked by this vitric body 20, so sufficient strength is secured while a void 14 of the vitrified binder turns into an integral bubble 22 and it remains in the vitric body 20, whereby the extent of porosity is heightened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a porous vitrified grindstone, and more specifically, by melting an aggregate as a grindstone material with a binder, the proportion of pores forming chip pockets in the grindstone. The present invention relates to a method for manufacturing a porous vitrified grindstone capable of increasing the number of particles.

[0002]

2. Description of the Related Art Conventionally, a porous vitrified grindstone in which cubic boron nitride (hereinafter, referred to as CBN) abrasive grains are bonded using vitrified has been widely used.

Such a vitrified CBN grindstone is
As a conventional technique for increasing the strength of a grindstone using organic particles and burning the grindstone to burn off the organic particles to form pores, a porous vitrified boron nitride grindstone disclosed in Japanese Patent Publication No. 28502/1992 is used. The manufacturing method is listed.

Further, Japanese Patent Publication No. 37-8695 discloses that a glassy hollow sphere is mixed and a grindstone is fired to form pores at arbitrary positions in the grindstone.

[0005]

However, in the conventional technique disclosed in Japanese Patent Publication No. 28502/1992,
When a vitrified CBN grindstone is formed by a method using organic particles, the shape of the grindstone changes because the organic particles forming the pores are completely burned down, or the gripping force of the abrasive grains decreases and the strength of the grindstone decreases. It may decrease. Further, the organic particles in the grindstone are difficult to burn, and if there is a residue, the grindstone has a disadvantage that it cannot obtain a predetermined hardness.

Further, as disclosed in Japanese Patent Publication No. 37-8695, when a grindstone is mixed with glassy hollow spheres, the shell of the hollow spheres is softened, and the gas as the content is thermally expanded. Therefore, the hollow sphere expands. In this case, if the firing conditions are incorrectly set or adjusted, the hollow spheres will burst, the gas inside will be washed away, and the grinding stone will lose its shape.

The present invention has been made in order to solve this kind of problem, and in the method for producing a vitrified CBN grindstone, the production of a porous vitrified grindstone in which sufficient porosity and bonding force are given to the grindstone. The purpose is to provide a method.

[0008]

In order to achieve the above-mentioned object, the present invention provides a method for producing a grindstone in which cubic boron nitride abrasive grains are bonded with a vitrified bond, and the softening temperature of which is higher than that of the vitrified bond. It is characterized in that the highly porous ceramic body is mixed with the abrasive grains and the binder, shaped, and then fired.

Further, in the above method, the ceramic porous body contains an alkali metal compound.

[0010]

In the method for manufacturing the porous vitrified grindstone according to the present invention, the vitrified binder is first softened during firing, and the binder abuts the ceramic porous body so as to wrap it. The porous body has a large surface area because it is porous, and it reacts with the softened vitrified binder to integrally form a new glass body. Therefore, since the abrasive grains are fixed by the glass body, sufficient strength is ensured, and the pores inside the porous body remain as an integrated hole portion inside the glass body to increase the porosity. Let Further, even if the ceramic porous body is lost during firing, the newly produced glass body is produced from the porous body and the vitrified binder, increasing the amount of grinding compared to the original vitrified binder. Since the grain interval is maintained, the grindstone does not shrink and lose its shape. Further, the ceramic porous body lowers the softening temperature, that is, the firing temperature of the grindstone by containing the alkali metal compound, and prevents the abrasive grains from being deteriorated by the firing of the grindstone at a high temperature.

[0011]

The method for producing a porous vitrified grindstone according to the present invention will be described in detail below with reference to the accompanying drawings with reference to the preferred embodiments.

In the method of manufacturing the porous vitrified grindstone according to this embodiment, CBN abrasive grains are used as the abrasive grains, PbO-ZnO-B ₂ O ₃ -based glass ceramics are used as the vitrified binder, and Shirasu is used as the ceramic porous body. To do.

[0013]

[Table 1]

First, as shown in FIG. 1, CBN abrasive grains 10
And the shirasu 12 is arranged at a predetermined position, and the voids 14 formed therebetween are filled with the glass ceramic particles 16. In this case, as shown in Table 1, the CBN abrasive grains 10 are 25% in volume ratio, the shirasu 12 is 25%, the glass ceramic particles 16 are 20%, and the voids 14 are 30%.

[0015]

[Table 2]

[0016]

[Table 3]

Then, it is baked at 930.degree. As shown in Table 2, the glass ceramic particles 16 have a softening temperature of 66.
Since it is 0 ° C. (baking temperature 760 ° C.), it softens first. Therefore, the glass ceramic particles 16 that have been softened and have increased fluidity come into contact with the surfaces of the CBN abrasive grains 10 and the shirasu 12. The shirasu 12 is a volcanic glass having a large number of micropores and has a large surface area. Moreover, PbO, ZnO, B ₂ O _{3 of} the glass ceramic particles 16
The component acts on the shirasu 12 as a flux.
Therefore, although the shirasu 12 has the characteristics shown in Table 3, melting starts when the firing temperature reaches 900 ° C., and at 930 ° C., it reacts with the surrounding glass ceramic particles 16. New glass body 20 (Fig. 2
(See) was formed. As a result, as shown in Table 1, the composition of the grindstone changed. That is, as shown in Table 1, the glass body 20 newly formed as the binder was 27%, and the pores 22 formed inside the glass body 20 were 48%. This is because the softening temperature of the glass ceramic particles 16 is lower than that of the shirasu 12, so the softened glass ceramic particles 16 stick to the surface of the shirasu 12 and contain the bubbles inside the fine pores of the shirasu 12 inside the pores 22, It is considered that this is because air in the voids 14 is taken into the pores 22. Further, only the glass ceramic particles 16 were used as the binder, but since the new glass body 20 was formed by the reaction with the glass 12, the volume of the binder was increased, and the CBN abrasive grains 10 were strongly bonded to the grindstone. The strength of the grindstone is increased and the shape of the grindstone is prevented from being lost due to the disappearance of the shirasu 12.

The vitrified grindstone manufactured as described above exhibits an excellent action when the grinding liquid is hard to reach the grinding surface and the grinding dust is hard to be discharged like the inner surface grinding of the iron-based material. This effect was verified by the experiments described below. As a comparative example, a CBN grindstone containing an alumina-based or silica-based oxide having no pores was used as an aggregate.

The vitrified grindstone 30 and the CB
The N grindstone 32 was formed into a cylindrical body as shown in FIG. 3, and mounted on a grinding machine. Further, the workpiece 34 is iron-based sintered alloy (Rockwell hardness H _R: 55-64) from was used after formed into a ring having an inner circumferential surface 36 as shown in FIG.

The inner peripheral surface 36 of the work 34 thus formed was ground by the above-mentioned grinding machine under the following grinding conditions.

Grinding conditions: Revolution: 8000 rpm Feed rate: 50 mm / min Depth of cut: 0.3 mm When the vitrified grindstone 30 according to this embodiment is used, the surface roughness of the inner peripheral surface 36 of the work 34 is about 2 μmR
_MAX (see Fig. 5), surface roughness is about 5μmR
_The grinding accuracy was clearly superior to the case of the comparative grindstone 30 which was _MAX (see FIG. 6). The reason for this is that in the CBN grindstone 32 of the comparative example, since the grinding dust in the inner surface grinding of the work 34 made of an iron-based material or the like is long and tenacious, the aggregate itself is not finely crushed by the impact during grinding,
Difficulty in forming chip pockets. As a result, it is difficult to discharge grinding debris from the grinding surface, adhere to the CBN grindstone 32, and the work 34 is hit and scratched due to the inclusion of grinding debris. It is considered that grinding burn is likely to occur. On the other hand, in the vitrified grindstone 30 of the present embodiment, since the grindstone 30 is sufficiently formed with pores, the grinding dust is appropriately discharged, and the grinding fluid is sufficiently supplied and the striking is performed. Scratch, work 3
It is considered that highly accurate finish grinding can be performed as shown in FIG. 5 without causing the grinding burn of No. 4 as described above.

As described above, in the method for manufacturing the porous vitrified grindstone according to this embodiment, the grindstone is manufactured from the CBN abrasive grains 10, the glass ceramic particles 16 and the shirasu 12, but the softening temperature of the glass ceramic particles 16 is shirasu 1
Since it is lower than 2, the glass-ceramic particles 16 are first softened to increase the fluidity during firing of the grindstone.
Abuts so as to wrap around. Since the shirasu 12 has a large number of micropores, it has a large surface area and glass ceramic particles 16 having components (PbO, ZnO, B ₂ O ₃ ) that act as a flux and 900 ° C. to 100 ° C.
It reacts at a low temperature of 0 ° C. to generate a new glass body 20.
Since the glass body 20 is formed from the glass ceramic particles 16 and the shirasu 12, the binder is substantially increased. Therefore, even if the shirasu 12 disappears, the shrinkage of the grindstone is slight and the strength of the grindstone is sufficient.
The N abrasive grain 10 is reliably held.

Further, since the bubbles trapped in the fine pores inside the shirasu 12 are formed as one pore 22 by the glass body 20 together with the gas in the void 14, the porosity is substantially increased. . Therefore, when a grinding operation is performed using such a grindstone, since the pores 22 serving as the chip pockets are sufficiently defined, the grinding dust is reliably discharged and the grinding burn can be prevented. Further, the pores 22 can sufficiently supply the grinding liquid to the processed portion during grinding. Further, since the pores 22 are sufficiently defined in the grindstone, heat generation of the dresser during dressing is reduced and wear of the dresser is reduced.

[0024]

[Table 4]

Moreover, as shown in Table 4, the shirasu 12 contains the alkali metal compounds Na ₂ O and K ₂ O.
Since the ZnO and B ₂ O ₃ components act as a flux, the softening and melting temperatures of the shirasu 12, that is, the reaction temperature can be lowered to 900 ° C to 1000 ° C. Therefore, the firing temperature of the grindstone can be suppressed to 900 ° C to 1000 ° C, and when the grindstone is fired at 1000 ° C or higher, CB
There is no possibility that N abrasive grains become boron oxide and impair the original hardness.

[0026]

According to the method for manufacturing a porous vitrified grindstone according to the present invention, the following effects can be obtained.

That is, at the time of firing, the vitrified binder is first softened, and the binder abuts the ceramic porous body so as to wrap it. Since the porous body has a large surface area because it is porous, it reacts with the softened vitrified binder to integrally form a new glass body. Therefore, since the abrasive grains are fixed by the glass body, sufficient strength is ensured, and the pores inside the porous body remain as an integral hole portion inside the glass body to increase the porosity. To raise. Further, even if the ceramic porous body is lost during firing, the newly produced glass body is produced from the porous body and the vitrified binder, and is increased in quantity and strength as compared with the original vitrified binder. Therefore, the whetstone does not shrink and lose its shape. Furthermore, the ceramic porous body contains an alkali metal compound to lower the softening temperature, that is, the firing temperature of the grindstone, and prevents the hardness of the abrasive grains from being impaired by firing at a high temperature.

When the vitrified grindstone manufactured in this manner is used, a high porosity is secured in advance, so that the grinding liquid is sufficiently supplied to the machined surface even when the inner surface of the iron-based material is ground. The grinding dust can be reliably discharged, and highly accurate finish grinding can be performed.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a whetstone before firing in a method for manufacturing a porous vitrified whetstone according to the present invention.

FIG. 2 is a partial cross-sectional view after firing of the grindstone in the method for manufacturing a porous vitrified grindstone according to the present invention.

FIG. 3 is a cross-sectional view showing the shape of a grindstone used in a comparative experiment of a porous vitrified grindstone according to the present invention.

FIG. 4 is a cross-sectional explanatory view of a work in a comparative experiment of the porous vitrified grindstone according to the present invention.

FIG. 5 is a diagram showing a result of grinding a work by a porous vitrified grindstone according to the present invention.

FIG. 6 is a diagram showing a result of grinding a work by a grindstone according to a comparative example with respect to a porous vitrified grindstone according to the present invention.

[Explanation of symbols]

 10 ... CBN abrasive grains 12 ... Shirasu 14 ... Voids 16 ... Glass ceramic particles 20 ... Glass body 22 ... Pores

Claims (2)

[Claims] 1. A method of manufacturing a grindstone in which cubic boron nitride abrasive grains are bonded with a vitrified bond, wherein a ceramic porous body having a softening temperature higher than that of the vitrified bond is mixed with the abrasive grain and the bond. And a method of manufacturing a porous vitrified grindstone, which comprises firing after molding. 2. The method for producing a porous vitrified grindstone according to claim 1, wherein the porous ceramic body contains an alkali metal compound.