JPH08141916A - Vitrified bond grinding wheel with high grinding ratio - Google Patents

Abstract

PURPOSE: To provide a vitrified bond grinding wheel having strong abrasive grain holding power and a high grinding ratio by forming abrasive grains with fine boron oxide abrasive grains formed via the oxidation exothermic reaction of metal fine powder. CONSTITUTION: Cubic boron nitride abrasive grains (CBN) 1 are bonded by a binder to form this vitrified bond grinding wheel T. Mg powder and Mg oxide powder having the prescribed average grain sizes are combined at the prescribed ratio, the slurry thus obtained is covered on the surfaces of the CBN abrasive grains to form covered abrasive grains. The covered abrasive grains are heated by a burner, the Mg powder in the cover layer is exothermically oxidized and finely dispersed and distributed on the surfaces of the abrasive grains to form a B2 O3 pool. The Mg oxide stuck to the surfaces of the B2 O3 pool-formed abrasive grains is eluted and removed by a hydrochloric acid aqueous solution, a vitreous binder 2 and a molding binder are added and mixed to form a fan-shaped molding, and it is degreased and baked in the nitrogen atmosphere to obtain the required grinding wheel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has a strong abrasive grain holding force,
As a result, the present invention relates to a vitrified eye bonded wheel which exhibits a high grinding ratio.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 1 which is a schematic vertical cross-sectional view of a main portion, a vitrifid bond grindstone (hereinafter, simply referred to as a grindstone) T is 20 to 20% in total.
10% to 70% by volume of cubic boron nitride (hereinafter, referred to as CBN) abrasive grains of 50% by volume hardened with 10 to 40% by volume of a vitreous binder 2
It is known that the pores 3 of No. 3 contribute to the reduction of the grinding resistance to the work material P. It is also known that the above-mentioned grindstone is manufactured by mixing CBN abrasive grains and a vitreous binder together with a binder for molding and forming pores, molding them into a predetermined size, degreasing the molded body, and then firing the molded body. ing.

[0003]

On the other hand, in recent years, grinding machines tend to be faster due to the remarkable improvement in performance of grinding machines and the demand for labor saving. When used for high-speed grinding, the abrasive retention by the vitreous binder decreases due to a further temperature rise on the ground surface, and the abrasive particles tend to fall off, resulting in a reduction in the grinding ratio and a relatively short time. At present, the service life is reached in time.

[0004]

Therefore, the present inventors have
From the above viewpoints, as a result of research to solve the problems of the conventional grindstone, fine metal powders such as Mg and Mn, which generate heat by oxidation, are contained in, for example, thermally stable metal oxide powders. Is mixed and dispersed in the mixture, and a binder and a solvent are added to this mixture to form a slurry, and the surface of the CBN abrasive grains is coated with the slurry to a predetermined thickness using, for example, a fluidized bed granulator. When the abrasive grains are burner-heated, for example, in the atmosphere to oxidize the fine metal powder in the coating layer, the heat generated at this time locally oxidizes the heat-generating portion of the CBN abrasive grain surface, and the CBN abrasive grain surface A boron oxide (hereinafter referred to as B ₂ O ₃ ) pool is formed on the entire surface of the metal, and the fine B ₂ O ₃ pool formed by the oxidation exothermic reaction of the fine metal powder is formed on the entire surface. Distributed surface structure When the CBN abrasive grain having the above is used as the abrasive grain of the above-mentioned grindstone, in the resultant grindstone, the B ₂ O ₃ pool is present between the CBN abrasive grain and the vitreous binder on the high temperature heat-ground surface during high speed grinding. As a result, a study result was obtained in that since the reduction of the abrasive holding force of the glass binder was significantly suppressed, a high grinding ratio was exhibited despite high speed grinding.

The present invention has been made based on the above-mentioned research results. In a grindstone in which CBN abrasive grains are bonded by a vitreous binder, the abrasive grains are subjected to an exothermic reaction of oxidation of fine metal powder. It is characterized by a grindstone having a high grinding ratio, which is composed of CBN abrasive grains having a surface structure in which the formed fine B ₂ O ₃ pool is dispersed and distributed over the entire surface.

[0006]

EXAMPLES Next, the grindstone of the present invention will be specifically described by way of examples. First, Mg powder and Mg oxide powder each having an average particle size shown in Table 1 were prepared, and these were also mixed in the proportions shown in Table 1, both of which accounted for the entire proportion, and the acrylic resin as the binder was used. : 1% by weight
And isopropyl alcohol as a solvent: 70% by weight
Were added and mixed to prepare slurries a to e. Then,
The above-mentioned slurries a to e were coated on the surface of each CBN abrasive grain having a particle size shown in Table 2 by using an ordinary fluidized bed granulating apparatus, and were coated with a coating layer in the ratio shown in Table 2 as well. Coated abrasive grains are formed, and the coated abrasive grains are heated by a burner in the air to oxidize Mg powder in the coating layer to form a B ₂ O ₃ pool finely distributed on the surface of the abrasive grains. Then, in the B ₂ O ₃ pool-forming abrasive grains, in a state where Mg oxide adhering to the surface of the abrasive grains was eluted and removed with a hydrochloric acid aqueous solution, SiO ₂ : 60%, Al ₂ O ₃ : 18% by weight.
%, B ₂ O ₃ : 15%, NaO: 3%, others: 1% by weight of polyvinyl alcohol is added as a molding binder, and a glassy binder having the composition of the rest: the rest is added, and the length: 45mm x width: 13mm x thickness: 5
A fan-shaped molded body having a size of mm and a curvature of 100R is formed, and the molded body is subjected to a degreasing treatment at a temperature of 600 ° C. for 1 hour, followed by a nitrogen atmosphere. By baking at a temperature of 1000 ° C. for 5 hours, all of them are vol.%, Abrasive grains: 50%, vitreous binder: 20%, pores: 30%.
Were manufactured respectively. For the purpose of comparison, CBN abrasive grains having the grain sizes shown in Table 2 were used, and the conventional grindstones 1 to 4 were each subjected to the same conditions except that a fine B ₂ O ₃ pool was not formed on the surface thereof. Manufactured.

Next, various grindstones obtained as a result are
Outer diameter: 190 mm × inner diameter: 50.8 mm × thickness: 13 mm with a dimension of 13 mm cylindrical base metal made by adhering to the surface of the work material: SKD-11 (hard Size: H _R C50) Square bar (length: 150 mm x width: 100
mm × thickness: 13 mm), grinding wheel peripheral speed: 1500 m / min, table feed speed: 5 m / min, depth of cut: 5 μm, grinding fluid: JIS W2 Type 2 wet type surface plunge grinding test Surface roughness is JIS standard Ra:
The machining amount of the work material up to 0.6 μm was measured. Further, the grinding ratio was calculated from this measurement result and the amount of wear of the grindstone. Table 2 shows the results.

[0008]

[Table 1]

[0009]

[Table 2]

[0010]

From the results shown in Table 2, the grinding stone of the present invention 1
Nos. 12 to 12 are B ₂ finely distributed on the surface of the abrasive grains.
Even though high-speed grinding is performed by the action of the O ₃ pool, the abrasive grain retention force by the vitreous binder is maintained in a strong state, so that the conventional grindstones 1 to 1 in which the B ₂ O ₃ pool is not formed on the surface of the abrasive grains 1 to It is clear that the machining amount of the work material is significantly larger than that of No. 4, which shows that the service life is extended and the grinding ratio is high. As described above, the grindstone of the present invention exhibits excellent grinding performance for a long period of time, because the decrease in the retention force of the vitreous binder with respect to the CBN abrasive grains is suppressed even under high speed grinding conditions.

[Brief description of drawings]

FIG. 1 is a schematic vertical cross-sectional view of a main part of a conventional grindstone.

Claims (1)

[Claims] 1. A vitrifide bond grindstone in which cubic boron nitride abrasive grains are bonded by a glass binder, wherein the abrasive grains are entirely formed by a fine boron oxide pool formed by an oxidation exothermic reaction of fine metal powder. A vitrifid bond grindstone exhibiting a high grinding ratio, which is composed of cubic boron nitride abrasive grains having a surface structure dispersedly distributed over the entire length.