JPH0829496B2 - Base disk type grinding wheel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a base disk type in which a superabrasive grain layer such as diamond or CBN (cubic boron nitride) or a general abrasive grain layer is bonded to a ground surface. Regarding grinding wheels.

[Prior art]

Conventionally, various grinding wheels have been proposed and put into practical use. As a grinding wheel, there is a base disk type grinding wheel (hereinafter simply referred to as a grinding wheel) in which a super-abrasive grain layer or a general abrasive grain layer is adhered to a metal base disc.

As the super-abrasive grain layer, those in which abrasive grains of diamond or CBN are bonded by vitrified bond are used (for example, Japanese Patent Publication No. 58-34431).

However, as the metal base disk,
Steel, cast iron, α aluminum alloy, etc. are used.

Further, the grinding stone using the above-mentioned superabrasive grains has very little wear, because the abrasive grains themselves are much harder than general abrasive grains. Therefore, there is little dimensional change or variation due to wear, and high-precision grinding is possible. Therefore, it is mainly used for grinding difficult-to-cut materials.

[Problems to be solved]

However, the above conventional grinding wheel for rotary grinding is
Due to the large elongation of the base disk due to the centrifugal force during rotation,
There was a problem that the processing accuracy was lowered. In recent years, it has been strongly desired to improve the machining efficiency and the life of the grindstone, so that the grinding wheel is required to have a higher peripheral speed. Therefore, it is necessary to minimize the elongation of the grinding wheel during rotation.

Further, in the above conventional grinding wheel, the base disk has a large coefficient of thermal expansion. Therefore, the base disk expands due to the heat of grinding or the heat of the bearing device, and the entire grinding wheel including the base disk expands thermally. This causes a decrease in processing accuracy.

Further, the conventional base disc, especially made of steel or cast iron, has a large weight (specific gravity). Therefore, when the grinding wheel is rotated by the grinder, the load on the motor and the load on the grindstone shaft are large, and the amount of heat generated by the motor and the bearing is large. Therefore, these heats are also transferred to the base disk, which causes the thermal expansion of the base disk to be further increased as described above.

The above problem also occurs in a grinding wheel using general abrasive grains.

In recent years, there has been a strong demand for improvement in machining efficiency and life of the grindstone, so that the grinding wheel is required to have a higher peripheral speed. Furthermore, in addition to this, higher and higher processing accuracy is required.

In view of the above-mentioned conventional problems, the present invention intends to provide a base disk-shaped grinding wheel capable of suppressing the expansion (elongation) of the wheel itself due to the rotation of the wheel even at a high peripheral speed and performing highly accurate processing. To do.

[Means for solving problems]

The present invention relates to a grinding wheel for rotary grinding of a base disk type, which is formed by adhering an abrasive grain layer to a base disk, wherein the base disk is made of ceramic fibers or particles in a metal matrix as a base material. Made of a composite material in which is dispersed, and the base disk has a coefficient of thermal expansion of 15 × 10 ^-6 or less and a ratio of density to longitudinal elastic modulus of 3.5 × 10 ^-9 / cm or less. The base disk type grinding wheel is characterized by.

What is most noticeable in the present invention is that the material of the base disk is the above composite material, and the coefficient of thermal expansion and the above ratio are within the above ranges.

In the present invention, the composite material forming the base disk is one in which ceramic fibers or particles are dispersed in a metal matrix (base material), and is called FRM, MMC or the like. Such metal matrix includes aluminum alloy, magnesium alloy, titanium alloy and the like.

Examples of the ceramics include silicon carbide, boron, alumina, silica, carbon, potassium titanate, barium titanate and the like. Among these, the one in which silicon carbide is dispersed in aluminum alloy is
Most preferred.

Next, the above ceramics are preferably contained in the base disk in an amount of 10 to 35% by weight. If it is less than 10%, the elongation during rotation is large, while if it exceeds 35%, it is not preferable because it lacks stability as a product and the material becomes brittle.

Further, it is preferable to use ceramic fibers having a diameter of 1 to 300 μm. Further, it is preferable to use ceramic particles having a particle size of 0.1 to 300 μm.
Outside this range, it is difficult to achieve the object of the present invention.

In the present invention, the base disk has a coefficient of thermal expansion of 15 × 10 ⁻⁶ or less and a density (kg / cm ³ ) / longitudinal elastic modulus (kgf / cm ² ) ratio (N) of 3.5 ×. It should be 10 ^-9 / cm or less. If both of these are not satisfied, thermal expansion of the base disk or elongation due to centrifugal force during rotation becomes large, and the surface roughness, which represents processing accuracy, cannot be 1.0 μRa or less. Here, the unit of surface roughness Ra
Means the center line average roughness defined by JIS B0601.

In addition, an adhesive such as an epoxy resin is used to bond the base disk and the abrasive grain layer.

In the present invention, the abrasive grains include superabrasive grains such as diamond and CBN, and general abrasive grains such as alumina and silicon carbide.

Further, the bonding of the abrasive grains in the abrasive grain layer is performed by vitrified bond, resinoid bond or metal bond.

The present invention is particularly effective for a vitrified bond grinding wheel using superabrasive grains.

[Action and effect]

In the grinding wheel of the present invention, the composite material is used as the material of the base disk. Therefore, the base disc has a lower coefficient of thermal expansion than a conventional metal base disc made of an aluminum alloy or the like. That is, the coefficient of thermal expansion is lower in the composite material in which the fibers or particles of the ceramics are added to the metal than in the case of using only the metal (see Examples).

Further, since the base disc of the present invention is lighter than the conventional base disc, the load on the motor and the grindstone shaft due to the rotation of the grinding wheel is small, and the amount of heat generated by these is small. Therefore, the amount of heat transfer to the base disk is small,
The thermal expansion of the grinding wheel is even less.

The coefficient of thermal expansion of the base disk of the present invention is 15 × 10 5.
^-6 or less, and the ratio (N) is 3.5 × 10 ^-9 / cm.
Therefore, the base disk of the present invention has not only a small thermal expansion but also a small expansion due to centrifugal force during rotation. Therefore,
The base disk type grinding wheel of the present invention is excellent in processing accuracy, and the surface roughness of the processed surface can be 1.0 μRa or less.

Therefore, according to the present invention, it is possible to provide a grinding wheel capable of performing highly accurate processing with a surface roughness of 1.0 μRa or less even under a high peripheral speed.

〔Example〕

A grinding wheel as shown in FIGS. 1 and 2 according to the present invention was produced and ground. Then, the surface roughness of the processed surface was measured. The results are shown in Table 1, FIG. 3 and FIG. These will be described in detail below.

First, as the grinding wheel, as shown in FIGS. 1 and 2, a segment tip 1 (FIG. 1) made of a superabrasive grain layer was prepared and bonded to a base disk 2 as shown in FIG. . An epoxy resin adhesive was used as the adhesive. The base disk 2 has a rotary shaft hole 20 at the center.

Then, the above grinding wheels were prepared in five types (No, 1 to 6) by changing the type of the base disk 2. Also, for comparison, five types of conventional grinding wheels using a base disk were manufactured (No. C1
~ C5).

The segment tip 1 is the same for all the grinding wheels.

That is, the grinding wheel has an outer diameter of 305 mm, a diameter of the hole for the rotating shaft of 76.2 mm, and a thickness of 15 mm. The size of the segment chip is 40mm in length, 15mm in width, and 7mm in thickness.

 The structure of the finished superabrasive layer is as follows.

CBN abrasive grain (# 325/400) ··· 50 volume part, vitrified bond ··· 18 volume part, porosity ····· 32 volume part, and grinding for surface roughness measurement The conditions are as follows.

Grinding wheel peripheral speed: 2700 m / min, table feed speed: 20 m / min, depth of cut: 5 μm / pass, work material: SKH51, work material dimensions: .... Length 300 x width 10 mm, and the material of each base disk is the first
The ones shown in the table were used. Aluminum is JI in this material
S-A6061 was used and JIS-S55C was used for hard steel.

Moreover, SiC is silicon carbide and Al ₂ O ₃ is alumina. The granular SiC used had a particle size of 5 to 40 μm. The fibrous Al ₂ O ₃ used had a diameter of 5 to 20 μm. The SiC whiskers used had a diameter of 5 to 20 μm.

In addition, the addition amount (%) of SiC, etc. in the table is the volume ratio in the base disk.

In the table, the ratio N is a value obtained by dividing the density (kg / cm ³ ) by the longitudinal elastic modulus (kgf / cm ² ).

Table 1 shows the results of surface roughness measurement under the grinding conditions.

As is known from Table 1, comparing the base disks of Examples 1 to 3 with Comparative Example C2, both use the same aluminum alloy, but the base disks of Examples 1 to 3 have thermal expansion coefficients. Is significantly smaller than that of Comparative Example C2 by about half to one third.

Regarding the ratio N, the base disks of Examples 1 to 6 are about half or less of those of Comparative Examples C1 to C5. This ratio N indicates that the lower the value, the smaller the processed surface roughness.

Regarding the thermal expansion, Comparative Example C1 using hard steel was used.
The base disc of Comparative Example C3 or C4 using Super Invar or spheroidal graphite cast iron is lower than those of Examples 2 and 3.

When the relationship between the coefficient of thermal expansion and the ratio N and the surface roughness is considered from Table 1 and FIGS. 3 and 4, the lower the both values, the better the surface roughness obtained. I understand. Also, as is known from the above, the surface roughness is 1.0 μR
In order to make it a or less, the coefficient of thermal expansion is 15 × 10 ⁻⁶ or less,
And it is necessary that the above-mentioned ratio N is 3.5 × 10 ⁻⁹ / cm or less.

Further, since the grinding wheel of Example 1 is lighter than Comparative Example C1, the load on the motor during rotation is small. For example, the motor power in the idle rotation is 0.6 kw for the former and 1.
It is 0kw. In addition, the grinding wheel of Comparative Example C3 has a weight of 1.3 kW.

Thus, the small motor power means that the motor load and the bearing load for the rotation of the grinding wheel are small. Therefore, when the grinding wheel of the present invention is used, heat generation of the motor and heat generation of the bearing are reduced. As a result, the temperature rise of the base disk is suppressed, the elongation of the base disk due to heat is also suppressed, and more precise grinding can be performed.

In addition, therefore, it is possible to further promote the higher peripheral speed of the grinding wheel.

[Brief description of drawings]

1 to 4 show an embodiment, FIG. 1 is a perspective view of the superabrasive grain layer, FIG. 2 is a plan view of a grinding wheel, FIG. 3 and FIG.
The figure is a diagram showing the relationship between the coefficient of thermal expansion or the ratio N and the surface roughness. 1 …… Segment chip, 2 …… Base disk,

Claims (6)

[Claims] 1. A base disk-shaped grinding wheel for rotary grinding, comprising an abrasive grain layer adhered to a base disk, wherein the base disk comprises ceramic fibers or metal fibers in a metal matrix as a base material. The base disk has a coefficient of thermal expansion of 15 × 10 ^-6 or less and a density to longitudinal elastic modulus of 3.5 × 10 ^-9 / cm or less. A base disk type grinding wheel characterized by that. 2. The metal matrix according to claim 1, wherein
A base disk type grinding wheel characterized by being an aluminum alloy, a magnesium alloy or a titanium alloy. 3. The ceramic according to claim 1, wherein the ceramic is one or more of silicon carbide, boron, alumina, silica, carbon, potassium titanate and barium titanate.
A base disk type grinding wheel characterized by being more than one kind. 4. The base disk type grinding wheel according to claim 1, wherein the abrasive grains are superabrasive grains such as diamond and CBN. 5. A base disk type grinding wheel according to claim 1, wherein the abrasive grains are general abrasive grains such as alumina and silicon carbide. 6. The base disk type grinding wheel according to claim 1, wherein the abrasive grains in the abrasive grain layer are bonded by vitrified bond, resinoid bond or metal bond.