JP3365175B2 - Vitreous Coated Cubic Boron Nitride Abrasives and Method for Producing Vitrified Bond Grinding Stone Using the Same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vitrified bond grindstone exhibiting a high grinding ratio and therefore exhibiting excellent grinding performance for a remarkably long time, and a vitreous coated cubic boron nitride having excellent formability used therein. It concerns abrasive grains.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 2 which is a schematic longitudinal sectional view of a main portion, a vitrified bond grindstone (hereinafter, simply referred to as a grindstone) T is 20% in total.
˜50% by volume cubic boron nitride (hereinafter referred to as cBN)
The abrasive grains 1 are formed by hardening with a glassy binder 2 of 10 to 40% by volume, and the pores 3 of 10 to 70% by volume existing in the grindstone contribute to the reduction of the grinding resistance to the work material P. It is known. In addition, after the cBN abrasive grains and the powdery material for the vitreous bonding layer are mixed together with the molding binder in the above grindstone and molded into a predetermined size, the molded body is degreased,
It is also known to be manufactured by firing.

[0003]

On the other hand, in recent years, FA in grinding processing has been remarkably changed, and there is also a strong demand for labor saving in grinding processing. Accordingly, a grindstone is strongly required to further improve its grinding ratio. However, the above-mentioned conventional cBN for grinding wheels
Under the present circumstances, the manufacturing method using abrasive grains cannot always satisfy these requirements.

[0004]

Therefore, the present inventors have
From the viewpoint as described above, paying attention to the distribution state of the abrasive grains and pores constituting the grindstone, improving the distribution state of the abrasive grains and the pores, and conducting research to improve the grinding ratio of the grindstone. As a result, they have found that a desired high-performance grindstone can be manufactured by manufacturing the grindstone using the following means. The present invention was obtained based on the above findings, wherein a powdery agent for vitreous bonding layer having an average particle diameter of 1 to 50 µm was added to the cBN abrasive grain surface having an average particle diameter of 40 to 300 µm. 0.05-0.
A glass-coated cBN abrasive grain (hereinafter referred to as a coated abrasive grain) that is 25 times thicker and is coated on the surface to a substantially equal thickness, and is characterized by manufacturing a grindstone using the coated abrasive grain. is there. First, as a method for producing the coated abrasive grains, an average grain size of 4
A powdery material for vitreous bonding layer, which is also used as a raw material, using cBN abrasive grains having a particle size of 0 to 300 μm is as described above.
Finer grains than BN abrasive grains, and an average grain size of 1 to 50
μm, preferably 5 to 30 μm, with a thickness of 0.05 to 0.25 times that of the cBN abrasive grains, and the powder for vitreous bonding layer as shown in FIG. The coated abrasive grains are manufactured by coating the surface of each cBN abrasive grain to a substantially equal thickness and then drying. Next, using the coated abrasive grains, a binder for molding such as polyvinyl alcohol (PVA) is added to the coated abrasive grains to form a predetermined shape, degreasing treatment is performed at a predetermined temperature, and then firing is performed to produce a grindstone. It depends on the manufacturing method. Further, when manufacturing the coated abrasive grains, the drying step is omitted, and after the coated abrasive grains are formed,
This is a method of manufacturing a grindstone in which a molded product is immediately pressure-molded into a predetermined shape, the molded product is degreased, and then fired.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a typical embodiment for carrying out the present invention will be described. A powdery material for vitreous bonding layer and cBN abrasive particles are weighed so as to have a predetermined composition. An inorganic or organic binder is added to and mixed with the powdery material for the vitreous bonding layer to impart tackiness to the powdery material for the vitreous bonding layer.
In addition to the BN abrasive grains, a rolling method is used to coat the surface of the cBN abrasive grains with the powdery material for the vitreous bonding layer and then to dry the coated abrasive grains. As a method for producing the grindstone of the present invention, first, using the coated abrasive grains of the present invention, a binder for molding is added and mixed, and after pressure molding, a predetermined amount for volatilizing the binder and the like added at the time of molding Degreasing at the temperature of (value determined by the binder used), 600 ℃
It is a method for producing the grindstone by firing at a temperature of up to 1200 ° C. Further, in the case of pressure molding, if moldability is ensured, it is not necessary to add a binder for molding, and it may be determined whether or not the binder can be added depending on the dry state of the coated abrasive grains. Further, in order to finely adjust the composition of the grindstone, if necessary, a powdery material for vitreous bonding layer may be added, and none of them fall within the technical scope of the present invention. As another method for producing a grindstone, an inorganic or organic binder is added to and mixed with a powdery material for vitreous bonding layer, which is weighed so as to have a predetermined composition, and is adhered to the powdery material for vitreous bonding layer. And the powdery agent for vitreous bonding layer is added to cBN.
Forming a coated abrasive in which the powdery material for the vitreous bonding layer is coated on the surface of the cBN abrasive by adding to the abrasive by a rolling method or the like, and press-molding the coated abrasive into a predetermined shape, It is a method of producing a grindstone by degreasing and firing at a temperature of 600 ° C to 1200 ° C. It should be noted that, when the coated abrasive grains are pressure-molded, adding a binder as needed does not depart from the gist of the present invention.

When the coated abrasive grains of the present invention formed as described above are pressure-molded into a predetermined shape, the dispersion of the abrasive grains is uniformly distributed by the action of the coated powdery material for the vitreous bonding layer. Not only is it possible to obtain a structurally stable molded body because the pressing force is uniformly dispersed in the molded body, and the grindstone produced by degreasing and firing this molded body Since the abrasive grains are coated with the fused glassy binder, and the individual abrasive grains are bonded through the glassy binder, the retention of the cBN abrasive grains by the glassy binder is further improved. Therefore, it was found that the grinding ratio is improved and the structure is homogenized, so that the grinding ratio is further increased during grinding. Also,
When producing the grindstone of the present invention, the atmosphere in the firing step after the degreasing treatment is preferably a nitrogen gas atmosphere, but may be in the air or an inert gas such as argon gas. The shape of the grindstone is stipulated by JIS, and the pressure at the time of pressure molding depends on the porosity of the grindstone to be produced, and the amount of the mixture of the cBN abrasive grains and the powdery agent for the vitreous bonding layer to be used. And is not particularly limited. The binder used may be one that imparts tackiness to the powdery material for the vitreous bonding layer, and typical examples thereof include water glass as an inorganic binder, PVA and melamine resin as an organic binder. There is no particular limitation on the temperature at which the degreasing treatment is carried out when the grindstone is manufactured, as long as it is determined according to the binder used during molding.

Next, the reason for limiting the numerical values as described above will be explained. (A) Average particle size of cBN abrasive grains The average particle size of cBN abrasive grains is 40 to 300 μm.
If the value is less than 40 μm, agglomeration occurs when coating the powdery material for the vitreous bonding layer, and it becomes difficult to uniformly coat each abrasive grain, and the grindstone manufactured using this abrasive grain has the above-mentioned desired value. Excellent grinding performance cannot be obtained. On the other hand, when the value exceeds 300 μm, the cBN abrasive grains are liable to be chipped or come off, and no remarkable effect is observed.
It was set to 0 to 300 μm.

(B) Average particle diameter of powdery material for vitreous bonding layer This has the function of uniformly coating the cBN abrasive grains and improving the strength of the grindstone manufactured using these abrasive grains. If it is less than 1 μm, the above effects cannot be obtained. On the other hand, if the value exceeds 50 μm, it becomes difficult to uniformly coat with the powdery agent for the vitreous bonding layer.
.About.50 .mu.m, preferably 5 to 30 .mu.m.

(C) Thickness of coating layer of powder for vitreous bonding layer This value is used when the abrasive grains uniformly coated with the cBN abrasive grains are used to form a grindstone having a predetermined shape according to the application.
Since the abrasive grains are coated, the dispersion of the abrasive grains is good when the powder is put into a molding frame, and the cBN abrasive grains do not come into direct contact with each other. Since the layer acts as a lubricating layer, the pressure is almost evenly distributed over the entire surface of the compact. Therefore, the glassy coating cB
When a whetstone is manufactured using N abrasive grains, it has an effect of achieving uniform dispersion of cBN abrasive grains and exhibiting excellent grinding performance, but when the value is less than 0.05 times that of cBN abrasive grains,
The desired effect described above cannot be obtained, while the value is 0.2
If it exceeds 5 times, the strength of the grindstone manufactured from the cBN abrasive grains is lowered, so that the value is 0.05 to 0.2.
It was set to 5 times.

[0010]

EXAMPLE Next, the coated abrasive grain of the present invention was prepared according to an example.
This will be described more specifically. Average grain shown in Table 1 and Table 2
Diameter cBN abrasive grains and the average grain size and the average grain size shown in Table 1 and Table 2.
And Si, Al, B, which are the main constituents of
And oxides of Na and SiO_2,Al₂O_3,B
₂O₃, And Na₂Represented by O, each of which is SiO ₂: 60
Wt%, Al₂O₃: 10% by weight, B₂O_3:18% by weight,
And Na₂O: B containing 5% by weight₂O₃-Al₂O₃-S
iO₂A powdery material for a vitreous tie layer is used as a raw material in this example.
Prepared as a fee. (Example 1) Inorganic powders for vitreous bonding layers listed in Table 1
5% water glass aqueous solution as a binder vitreous bonding layer
10% by weight with respect to the powder powder for use, mixed and
Adhesiveness is imparted to the surface of the powdery agent for vitreous bonding layer,
On the other hand, make the particles relatively coarser than the powder for the vitreous bonding layer.
Also, cBN abrasive grains having the same average grain size as shown in Table 1
On a stainless steel disc that rotates in conjunction with the motor
And rotate the disc at a speed of 60 times / min.
And the powdery agent for vitreous bonding layer with the above-mentioned adhesiveness.
Similarly, the ratio shown in Table 1 was applied to the glassy coating cB.
After forming N abrasive grains, the coated abrasive grains of the present invention are dried by drying.
0 and comparative abrasive grains 1 to 3 were produced. After that, optical microscopy
Using a mirror, measure the particle size of each sample by the biaxial averaging method of the long axis and the short axis.
Measure and use the average value as the average particle size, and display the results.
Shown in 1.

[0011]

[Table 1]

(Example 2) The above-mentioned coated abrasive grains 1 to 10 of the present invention
And 1% by weight of PVA (polyvinyl alcohol) as a molding binder was added to and mixed with the comparative abrasive grains, and the mixture was pressed at a pressure of 1000 kgf / cm ² to form a molded body. After degreasing under the condition of 700 ° C for 2 hours, and by fusion-bonding in nitrogen gas atmosphere under the condition of temperature: 900 ° C for 5 hours, length: 45 mm × width: 13 mm × thickness S: The coated abrasive grains 1 to 10 of the present invention having a size of 5 mm and the curvature of 100 R, and the present invention abrasive stone pieces 1 to 10 and the comparative abrasive stone pieces 1 to 3 using the comparative abrasive grains were manufactured, respectively.

(Conventional Example) Further, for the purpose of comparison, a cBN abrasive grain and a glass having the same average particle size as in the case of forming the coated abrasive grain of the present invention as shown in Table 2 by using an ordinary method are shown. A powder agent for a fine bonding layer was prepared and used as conventional abrasive grains 1-10.
Then, the abrasive grains 1 to 10 and the powdery material for the vitreous bonding layer shown in Table 2 were weighed out so that the same composition as in the production of the grindstone of the present invention was obtained, and PVA was added as a molding binder. Mixed, molded under the same conditions as the manufacturing conditions of the grindstone using the above-described coated abrasive of the present invention, degreased, and then fired, and all have dimensions of length: 45 mm × width: 13 mm × thickness: 5 mm Also, whetstone pieces 1 to 10 using conventional abrasive grains having a curvature of 100 R were manufactured, respectively.

[0014]

[Table 2] Regarding the obtained present invention and conventional grindstone pieces, first, for the purpose of evaluating the structural uniformity, the pore distribution was measured using a mercury porosimeter, and the standard deviation of the pore distribution was calculated from the results, and the results are shown in Table 3. Shown in.

(Embodiment 3) A grindstone piece using the coated abrasive grain of the present invention obtained in the above-mentioned Embodiment 2 and a grindstone piece using the conventional abrasive grain obtained in the conventional example are outer diameter: 190 mm × inner diameter : 50.
8 mm x thickness: 13 mm, a SKD-11 (high-speed steel) tubular base metal is attached with an adhesive to form an assembled grindstone tool, and this is used to cut the work material: SKD-11 ( Hardness: HRC50, Length: 15
(0 mm x width 100 mm x thickness 10 mm) Material Grinding wheel peripheral speed: 1500 m / min, table feed speed: 5 m / min, depth of cut: 30 μm, grinding fluid: JIS-W class 2 equivalent The work amount of the work material and the wear amount of the grindstone until the surface roughness Ra of the work material reaches 0.6 μm (JIS standard) were measured, and the grinding ratio was calculated based on this result. The results are shown in Table 3.

[0016]

[Table 3]

(Example 4) As shown in Table 4, coated abrasive grains were produced under the same conditions using the same material and the same composition as the sample No. 7 of the abrasive grains of the present invention described in Example 1, and the coated abrasive grains were coated. The step of drying the abrasive grains was omitted, pressure molding was performed at a pressure of 1000 kgf / cm ² , a grindstone was manufactured under the same manufacturing conditions as in Example 2, and the pore distribution was measured by a mercury porosimeter in the same manner. Shown in.

[0018]

[Table 4]

[0019]

From the results shown in Tables 3 and 4, in the grindstone using the coated abrasive grains of the present invention, compared with the grindstone using the conventional abrasive grains, the individual abrasive grains constituting the grindstone are The powder for vitreous bonding is a finer particle than that for cBN, so that the cBN abrasive grains are uniformly dispersed during molding, and the powder for vitreous bonding layer is covered during pressure molding. Due to the lubricating action of the agent, the pressure is evenly distributed over the entire grindstone, so that the structure of the grindstone after firing is stable, and the cBN abrasive grains are bonded together through a uniform vitreous binder.
It is clear that the holding power of the N abrasive grains by the vitreous binder is further improved and the homogenization is systematically achieved, so that excellent grinding performance is exhibited over a long period of time, and the results are utilized. This will greatly contribute to the industrial world.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a coated abrasive grain of the present invention.

FIG. 2 is a schematic vertical sectional view of an essential part showing a conventional vitrified bond grindstone.

[Explanation of symbols]

1 abrasive grain 2 Vitreous binder 3 pores T vitrified bond grindstone P Work material

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI C09K 3/14 550 C04B 35/58 103R

Claims (4)

(57) [Claims] 1. A coating layer made of a powdery material for a vitreous bonding layer is formed on the surface of cubic boron nitride abrasive grains having an average particle size of 40 to 300 μm, and the coating layer is made of the cubic boron nitride abrasive grains. A vitreous coated cubic boron nitride abrasive grain characterized by coating the surface of each cubic boron nitride abrasive grain with a thickness of 0.05 to 0.25 times the average grain size. 2. The cubic boron nitride abrasive grain according to claim 1,
2. A mixture of a powdery material for vitreous bonding layer and a binder is added and stirred to coat the powdery material for vitreous bonding layer on the surface of the cubic boron nitride abrasive grains. A method for producing a glassy cubic boron nitride abrasive grain. 3. A molded product obtained by molding the glassy cubic boron nitride abrasive grains according to claim 1 into a predetermined shape by pressure molding is subjected to a degreasing treatment at a predetermined temperature, and then 600 ° C. to 1 ° C.
A method for producing a vitrified bond grindstone using vitreous coated cubic boron nitride abrasive grains, which comprises firing at a temperature between 200 ° C. 4. The cubic boron nitride abrasive grain according to claim 1,
The glass according to claim 1, wherein a predetermined amount of a mixture of a powdery material for vitreous bonding layer and a binder is added and stirred to coat the surface of the cubic boron nitride abrasive grains with the powdery material for vitreous bonding layer. Quality cubic cubic boron nitride abrasive grains are formed, the glassy coated cubic boron nitride abrasive grains are formed into a predetermined shape by pressure molding, and then degreasing treatment is performed at a predetermined temperature, and then 600 ° C. to 1200 ° C. A method for producing a vitrified bond grindstone using vitreous coated cubic boron nitride abrasive grains, characterized by firing at a temperature between ℃.