JP3132233B2 - Whetstone - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grindstone having an abrasive layer and used for various kinds of grinding and the like, and more particularly to an improvement of a grindstone for improving grinding performance and extending the life of the grindstone. .

[0002]

2. Description of the Related Art As one kind of grindstone used for various grinding processes, there is a grindstone having an abrasive layer composed of a binder phase composed of a binder and abrasive grains dispersed and fixed in the binder phase.
In this case, a resin bond, a vitrified bond, a metal bond, or the like is used as a binder phase, and cubic boron nitride (hereinafter abbreviated as CBN) or polycrystalline cubic other than diamond is used as abrasive grains. Crystalline boron nitride (hereinafter abbreviated as PCBN) is used.

[0003] Here, CBN is composed of a single boron nitride crystal, and has high friability because the crystal has a cleavage boundary. On the other hand, PCBN is obtained by sintering fine particles of CBN together with fine powder of metal, ceramic, or the like, and has a low half-surface hardness and low toughness, and is tough.

Accordingly, when precision grinding of iron-based sintered parts having excellent wear resistance such as a rotor of a trochoid pump is performed, a grinding stone using CBN as abrasive grains (hereinafter referred to as CBN) is used.
It is called a whetstone. When the grinding is performed in step (1), the abrasive grains are appropriately crushed during the grinding, and as a result, sharp abrasive grains are always provided for grinding, so that the grinding performance is improved. Therefore, the grinding speed is increased and the power required for grinding is small. In general, when grinding is performed while the abrasive layer and the work material are in surface contact with each other, burrs are formed at the rear end of the work surface with the grinding. However, when the grinding is performed with a CBN grinding wheel, the grinding performance is high. Therefore, there is an advantage that burrs are reduced.

On the other hand, when grinding is performed with a grindstone using PCBN as abrasive grains (hereinafter, referred to as a PCBN grindstone), the abrasive grains are tough and the life of the grindstone is long, which is advantageous in cost. In addition, when used for double-head grinding, there is an advantage that the parallelism of the work surface formed above and below the work is increased.

[0006]

SUMMARY OF THE INVENTION However, CBN
When a grindstone is used for grinding, the abrasive grains are easily crushed, so that the abrasive grains are quickly consumed. As a result, there is a problem that the life of the grindstone is shortened and dressing and tooling must be frequently performed. On the other hand, in the case of a PCBN grinding wheel, the abrasive grains are tough, but the sharpness of the abrasive grains is lost due to wear caused by grinding, and the grinding performance tends to decrease. As a result, large burrs are formed at the rear end of the work surface as compared with grinding with a CBN grindstone, and since the burrs are difficult to remove even in post-processing such as barrel polishing, the post-processing is troublesome. There's a problem.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is directed to a grindstone having an abrasive layer in which abrasive grains are dispersed and fixed in a binder phase, wherein the abrasive grains are formed of CBN. And P
Possess the CBN, metal bond is used as the binder phase
And the degree of concentration of the abrasive grains is 30 to 70
The particle size of the abrasive grains is CBN: PCBN = 1.3 to
1.5: 1, and the mixing ratio of the abrasive grains is CB
N: PCBN = 60: 40 to 30:70 .

[0008]

In the grinding wheel of the present invention, since the abrasive grains have CBN, the grinding performance of the abrasive grains is high, and the abrasive grains are formed of PCBN.
The abrasive grains have less wear. Where the concentration of abrasive grains
The degree is 30 to 70. This means that if the concentration is less than 30,
The grinding ratio decreases and the grinding efficiency decreases,
If the degree exceeds 70, the abrasive holding power becomes insufficient.
You. The particle size of the abrasive grains is CBN: PCBN = 1.3 to
1.5: 1. This is because the particle size of CBN is PCBN
If it is less than 1.3 times, the influence of PCBN becomes stronger
While the advantages associated with the use of CBN decrease, the particle size of CBN
Exceeds 1.5 times PCBN, PCBN becomes filler
And the grinding action is reduced. Change
In addition, the mixing ratio of the abrasive grains is CBN: PCBN = 60: 40-
30:70. The mixing ratio of CBN is less than 30%.
Large burrs are formed on the edge of the work surface
Post-treatment is troublesome, while the CBN mixture ratio is 60%
Beyond this, abrasive wear is accelerated and the life of the grinding wheel is shortened.
That's because.

[0009]

Embodiments of the present invention will be described below in more detail with reference to the drawings. FIG. 1 is an enlarged view of a grinding wheel cross section showing one embodiment of the grinding wheel according to the present invention. Symbol 1 in the figure
Is a base metal, and the shape of the base metal 1 is not limited.
Any type of base metal conventionally used, such as a wheel type or a full type, may be used.

An abrasive layer 2 is formed on an abrasive layer forming surface 1A of the base metal 1. This abrasive layer 2 contains abrasive particles 4 in a binder phase 3.
In the present embodiment, a metal bond is used for the binder phase 3 and the abrasive grains 4 are CB
N and PCBN are used. Here, it is desirable that the degree of concentration of the abrasive grains 4 be 30 to 70. This is because when the concentration is less than 30, the grinding ratio is reduced and the grinding efficiency is reduced, while when the concentration is more than 70, the abrasive grain holding power becomes insufficient.

The abrasive grains 4 have a particle size of CBN: PCBN.
= 1.3 to 1.5: 1. this is,
If the particle size of CBN is less than 1.3 times that of PCBN, PC
This is because the effect of BN becomes strong and the advantages associated with the use of CBN decrease, while if the particle size of CBN exceeds 1.5 times that of PCBN, PCBN acts only as a filler and the grinding action is reduced.

Further, the mixing ratio of the abrasive grains 4 is CBN: PCB
It is desirable that N = 60: 40 to 30:70. C
When the mixture ratio of BN is less than 30%, large burrs are formed on the periphery of the work surface, and post-processing after grinding becomes troublesome. On the other hand, when the mixture ratio of CBN exceeds 60%, the abrasive grains 4 This is because wear is accelerated and the life of the grinding wheel is shortened.

When grinding is performed with the grinding wheel having the above-described configuration, the CBN in the abrasive grains 4 is appropriately broken and the grinding performance is improved, so that the grinding speed is high and the power is small. In addition, since burrs formed at the rear end of the work surface are reduced as in the case of grinding with a CBN grinding wheel, post-processing after grinding is also facilitated. In addition, since the presence of PCBN in the abrasive grains 4 makes it difficult for the abrasive grains 4 to be worn out during grinding, the life of the grindstone is long and the cost is advantageous.

[0014]

EXPERIMENTAL EXAMPLES The effects of the present invention will be described below with reference to experimental examples. Experimental Example 1 Grinding was performed using grinding wheels of different grinding types, and the current value (spindle current value) consumed by the machine spindle during grinding was calculated.
The change with the amount of wheel drop was measured. The following three types of grinding wheels were used for the experiment. (Comparative Example 1) CBN abrasive grains (abrasive grain size # 140) (Comparative Example 2) CBN (abrasive grain size # 140) + PCBN (abrasive grain size # 140) mixed abrasive grains (grain size ratio: CBN: PCBN =
1: 1) (Invention Example 1) CBN (Abrasive Particle Size # 140) + PCBN (Abrasive Particle Size # 200) Mixed Abrasive Grains (Granularity Ratio CBN: PCBN =
1.43: 1) Note that the outer shape and the binding phase of the grindstone were the same, and grinding was performed under the same grinding conditions.

FIG. 2 shows a change in the spindle current value with a change in the amount of wheel drop by grinding. As can be seen from FIG. 2, the spindle current value was always lowest when the grinding wheel of Inventive Example 1 was used, and the rate of change of the spindle current value with respect to the change in the grinding wheel drop amount was also the smallest. This indicates that the grinding wheel of Inventive Example 1 can maintain high grinding ability for a long time and has high durability.

Experimental Example 2 The three types of grinding wheels used in Experimental Example 1 were compared with PCBN as Comparative Example 3.
Abrasive grains (abrasive grain size # 140) were added, and each of the four types of grindstones was ground under the same conditions as in Experimental Example 1 to compare the size of burrs formed at the rear end of the work surface. . Table 1 shows the results.

[0017]

As can be seen from Table 1, the burrs formed at the rear end of the work surface became smaller in the order of using the grindstones of Comparative Example 1, Invention Example 1, Comparative Example 2, and Comparative Example 3. In addition, while the difference in the burr size between the case of using the grinding stone of Invention Example 1 and the case of using the grinding stone of Comparative Example 2 was 25 μm, the case of using the grinding stone of Comparative Example 1 and the case of Invention Example 1 were compared. The difference in the size of the burr with the case of using the whetstone was only 5 μm. This indicates that the grindstone shown in Inventive Example 1 has a high grinding ability almost equal to that of Comparative Example 1.

[0019]

As described above, by using the grindstone of the present invention, a grindstone having a long life and high grinding performance can be obtained. As a result, the number of times of dressing and tooling is reduced and the power required for grinding is reduced, so that the working efficiency is improved.

[Brief description of the drawings]

FIG. 1 is an enlarged view of a cross section of a grindstone according to a first embodiment of the present invention.

FIG. 2 is a view showing a result of Experimental Example 1 of the present invention, and showing a change in a spindle current value according to a change in a grinding wheel descending amount due to grinding.

[Explanation of symbols]

 1 base metal 1A abrasive layer forming surface 2 abrasive layer 3 bonding phase 4 abrasive

Continued on the front page (72) Inventor Minoru Hoshi 246-1 Egoshi, Kurosuno, Izumi-cho, Iwaki-shi, Fukushima Prefecture Mitsubishi Materials Corporation Iwaki Seisakusho (56) References JP-A-2-218560 (JP, A) JP-A Heisei 6-262527 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B24D 3/00 320 B24D 3/00 330 B24D 3/06

Claims (1)

(57) [Claims] 1. A abrasive grains in the binder phase is a grindstone having abrasive grain layer dispersed fixed, the abrasive grains, possess a cubic boron and polycrystalline cubic boron nitride nitride, said bonding phase Metal bond is used as the
The degree of concentration of the grains is 30 to 70, and the grains of the abrasive grains are
Diameter is cubic boron nitride: polycrystalline cubic boron nitride =
1.3 to 1.5: 1, and the mixing ratio of the abrasive grains
Is cubic boron nitride: polycrystalline cubic boron nitride = 6
A grindstone characterized by the ratio of 0:40 to 30:70 .