JP2000084857A - Super-abrasive grain-vitrified grinding wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the grinding wheel-performance such as the fatigue strength by increasing the filling quantity of abrasive grains while the abrasive grain distribution is uniformly maintained. SOLUTION: Between grinding wheels No.2 and 2C in which the total volume percentage of abrasive grains and aggregates is less than 51 vol.%, there is little difference in the fatigue strength, and the improvement of the performance by the use of vibrating-press molding cannot be observed, while the improvement of the grinding wheel-performance such as the fatgue strength, a grinding ratio, surface roughness by the use of vibrating-press molding is observed between the grinding wheels No.1 and 1C, No.3 and 3C, and No.4 and 4C respectively in each of which the total filling factor is 51 vol.% to 75 vol.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superabrasive vitrified grindstone, and more particularly to a superabrasive vitrified grindstone formed by vibration press molding.

[0002]

2. Description of the Related Art For example, in the grinding of a chill casting such as a camshaft of an engine of an automobile or the like, since the cutting depth is large and the grinding efficiency is high, a high impact action is applied to the grindstone, abrasive grains are dropped, and the grindstone is removed. It tends to wear out quickly. Therefore,
It is effective to increase the number of cutting edges, that is, to increase the filling amount (volume ratio) of superabrasive grains, in order to increase the life of the grindstone, in other words, to obtain a high grinding ratio. To increase the filling amount of superabrasive grains, it is thought that it is necessary to increase the pressing pressure during the formation of the grindstone.However, simply increasing the number of superabrasive grains results in non-uniform dispersion of the superabrasive grains, and the bond There has been a problem that the bonding of the superabrasive grains is partially incomplete and the grasp (holding force) of the superabrasive grains is reduced, and the life of the grindstone is not improved even though the number of the superabrasive grains is increased. In addition, it is possible to manufacture a large-sized grindstone or a deformed whetstone while maintaining a uniform state of superabrasive grains and a binder by filling and molding a grindstone raw material powder into a mold while applying vibration. -79631 and the like.

[0003]

However, even in the vitrified grinding wheel manufactured by using the conventional vibration molding, the volume ratio of the superabrasive grains or the superabrasive grains to the aggregate after firing is 5%.
Because it was 0 vol% or less, the number of cutting edges was essentially small,
The effect of improving the life of the grinding wheel by the vibration molding was not always sufficiently obtained. If the number of cutting edges is small, an excessive force tends to concentrate on the surface during the grinding operation, which promotes the removal of the superabrasive grains. Alternatively, even if the workpiece is not dropped, the grinding surface of the work material is deteriorated, so that frequent dressing operations are required, and as a result, the life of the grinding wheel is shortened.

The present invention has been made in view of the above circumstances, and has as its object the structure (distribution of superabrasive grains).
The purpose of the present invention is to improve the life of the grindstone by increasing the superabrasive grain filling amount, that is, the number of cutting edges, while maintaining the uniform state of.

[0005]

In order to achieve the above object, a first invention is to provide a grindstone raw material powder containing a superabrasive, a vitrified binder, and an optionally mixed aggregate.
A superabrasive vitrified grindstone manufactured by pressing and shaping while applying vibration, and then firing,
The total volume ratio of the superabrasive grains and the aggregate in the fired grindstone or the volume ratio of only the superabrasive grains when the grindstone raw material powder does not contain the aggregate is in a range of 51 vol% to 75 vol%. It is characterized by being within.

A second invention is characterized in that, in the superabrasive vitrified grindstone of the first invention, the aggregate contains an inorganic hollow material.

[0007]

DETAILED DESCRIPTION OF THE INVENTION Here, the abrasive grains are super abrasive grains such as CBN abrasive grains or diamond abrasive grains, and the aggregate is alumina, silicon carbide, boron carbide, alumina-zirconia, mullite,
It is an inorganic particulate material such as sillimanite, or an inorganic hollow material such as a shirasu balloon, an alumina-based balloon, a coal ash balloon, and a glass balloon. The size of the aggregate is preferably about 0.5 to 2 times the particle size of the superabrasive.

[0008] The total volume fraction of the superabrasive grains and the aggregate is preferably 51 vol% to 70 vol%, more preferably 51 vol%.
% To about 65 vol%. Preferably, the volume ratio of the superabrasive is about 51 vol% to 65 vol%, and the volume ratio of the aggregate (ratio to the grindstone) is about 0 vol% to 50 vol%. The volume fraction of the bond or vitrified binder is between 16 vol% and 35 vol%, preferably between 16 vol% and
It is about 26 vol%. On the other hand, if the total volume ratio of super-abrasives and aggregates, or the volume ratio of super-abrasives alone without aggregates, is greater than 75 vol%, the volume ratio of pores will decrease and the work material will be ground. It is not preferable because burning occurs. In some cases, a super-abrasive grain or a mixture of the same and an aggregate may be referred to as an abrasive grain. Is also good.

Hereinafter, embodiments of the present invention will be specifically described. First, using a CBN abrasive having a particle size of 80/100 which does not contain an aggregate and a vitrified binder, a grinding stone No. shown in Table 1 was used. Two types of whetstones 1 and 1C (dimensions: outer diameter 350
mm x thickness 16mm x hole diameter 80mm x abrasive layer thickness 2m
m). The compounding weight ratio (wt%) at this time is as shown in Table 2, and the whetstone No. 1, 1C contains no aggregate.
Density Df, abrasive volume ratio Vg, bond (vitrified binder) volume ratio Vb after firing of the abrasive layer of each grinding wheel
, The pore volume ratio Vp and the aggregate volume ratio Vf are as shown in Table 1. 1C is a press-formed product (comparative product) without applying vibration during molding of the grinding wheel raw material powder.
No. No. 1 is a product obtained by performing vibration press molding in which pressure is applied while applying vibration during the molding of the grinding wheel raw material powder (product of the present invention).
In addition, whetstone No. Total volume ratio V of super-abrasive grains and aggregate of 1
_In this case, _{g + f} (= Vg + Vf) becomes equal to the abrasive grain volume ratio Vg.

[0010]

[Table 1]

[0011]

[Table 2]

Whetstone No. In the case of No. 1, in order to investigate the difference in the effect due to the presence or absence of vibration, the specifications such as the density Df and the abrasive grain volume ratio Vg are the same as those of the grinding wheel No. 1. It was molded to be substantially the same as 1C. The grindstone raw material powder contains a predetermined amount of a temporary adhesive in addition to the CBN superabrasive grains and the vitrified binder, and the conditions for vibration press molding are as follows. (Vibration pressing conditions) Equipment used: Cross vibration powder press (manufactured by Daiichi Co., Ltd.) Molding pressure: 100 kg / cm ² Vibration source air pressure: 0.6 MPa Vibration time: No load 11 seconds Load 7 seconds

Each raw whetstone thus formed is heated at 900 ° C.
For 5 hours. After firing, the propagation speed (m / sec) by ultrasonic waves was measured to examine the mechanical properties of the two types of grinding wheels (CBN wheels). The results shown in Table 3 were obtained. Whetstone No. No. 1 is No. The propagation speed is higher than that of 1C, which indicates that the application of vibration during molding significantly improves the uniformity of the structure (abrasive distribution). FIG. 1 shows a grinding wheel No. 1 obtained by a mercury displacement method. 1
And No. The pore size distribution of 1C was measured.
o. It can be understood that uniform pores are formed in No. 1. Thus, by performing the vibration press molding,
The structure (abrasive grain distribution) becomes uniform, and the grasp (holding force) of the superabrasive grains of the bond is improved.

[0014]

[Table 3]

Using the two types of grinding wheels (CBN wheels), grinding was performed under the following grinding conditions and dressing conditions, and the results of various grinding performances as grinding wheels were examined. FIG. 2 and FIG. Show. (Grinding conditions) Work material: SCM435 (φ60 × t5), hardness HRC4
8 Machine: Cylindrical grinder PA32-50P (manufactured by Mitsubishi Heavy Industries, Ltd.) Grinding method: wet plunge grinding Allowance: φ60 → φ45 Wheel peripheral speed: 80 m / sec Work material peripheral speed: 0.8 m / sec Grinding efficiency: 10 mm ³ / Mm · s Spark out: 20 rev. Grinding oil: SA200HS (× 50) (Dress condition) Dresser: Wheel dresser, SD40Q75MW7,
φ110 × ^U 1.5 dresser peripheral speed: 20m / sec dress lead: 0.075mm / rev of wheel dress ^{cut:. R 2.5μm / pass × 4pass} / cycle × 1
0 cycle

FIG. 2 shows that the grinding wheel No. The vibration press molded product of No. 1 has a grinding ratio about 10% higher than that of a normal molded product without vibration (grinding wheel No. 1C), and has a surface roughness of about 3 μmR.
If y (dot-and-dash line) is the usage limit, the dress interval is about 3
Since it is relatively improved, the life of the grinding wheel can be extended. FIG.
Comparing the number of abrasive grains, the number immediately after dressing is almost the same as that of a normal molded product, but the vibration molded product of the present invention (grinding wheel No. 1) is 3
Even after 0 cuts (after grinding 30 workpieces), as much as 10% can remain, indicating that the abrasive grains are held firmly and firmly.

Next, eight kinds of grinding wheels No. 1 having the properties shown in Table 1 above were used. 1-4C were produced. These compositions are as shown in Table 2. The firing conditions are the same as before. Was cut out 40 mm × 4 mm × 6 mm shape from those of the wheel, the load 13~24kgf from above was added with a period of 5 Hz, the fatigue strength was measured, when the number 10 was repeated ^five times from S-N diagram Fig. 4 shows the result of examining the time strength (strength).
Shown in Both whetstones are manufactured using 80/100 grain size CBN abrasive grains and a vitrified binder.
o. 3C and 3 are aggregates to which WA (white alumina) having the same particle size of about 80 as CBN abrasive grains is added. On the other hand, whetstone N
o. 2C, 3C and 4C are grinding wheels No. As in the case of grinding wheel No. 1C, it was press-molded without applying vibration during the molding of the grinding wheel raw material powder. 2, 3, and 4 are the whetstone Nos. In the same manner as in Example 1, vibration press molding was performed in which pressure was applied while applying vibration during the molding of the grindstone raw material powder. Here, the whetstone No. 2 is
Total volume ratio of superabrasives and aggregate Vg + _f (= Vg + Vf)
Is less than 51 vol%, is outside the scope of the present invention,
On the other hand, whetstone No. Nos. 3 and 4 are products of the present invention because the total volume ratio Vg + _f (= Vg + Vf) of the superabrasive grains and the aggregate is in the range of 51 vol% to 75 vol%.

FIG. 4 shows that the total volume ratio V of the abrasive grains and the aggregate is V
_{g + f} is less than 51 vol%. 2C and 2
Has almost no difference in fatigue strength and no effect of vibration press molding is recognized.
No. Between 1C and 1, 3C and 3, 4C and 4, the fatigue strength is higher when vibration pressing is performed (black bar), and especially, the total volume ratio V _{g + f} is about 65 vol%. No. of whetstone
4 and 4C, the difference is large, and the total volume ratio V _{g + f}
It is considered that the effect of improving the fatigue strength by vibrating press forming is greater as the value of is higher.

FIG. 5 shows a CBN abrasive having a particle size of 80/100:
A raw grindstone obtained by subjecting a grindstone raw material powder of 78 wt%, temporary adhesive: 4 wt%, and vitrified binder to 19 wt% to vibration press molding using a pressing pressure as an adjustment parameter is fired to obtain the same composition and the same content, but abrasive grain volume. Various grinding stones having different ratios Vg (in this case, the same as the total volume ratio of the abrasive grains and the aggregate because they do not contain the aggregate) were produced, and the bending strength of the grinding stone was examined. Up to Vg of about 70 vol%, the higher the grain volume ratio Vg, the higher the bending strength. That is, the bending strength is desirably set so that the total volume ratio of the superabrasive grains and the aggregate in the grindstone after firing is within the range of 75 vol% or less, preferably around 70 vol%.

Next, the results of performance tests performed on a grindstone containing a glass balloon (an example of an inorganic hollow material) as an aggregate will be described. Table 4 shows the CBN with a particle size of 230/270.
Press-forming without vibration (grinding wheel No. 5C) and press-forming while applying vibration (grinding stone No. 5) using abrasive grains, a vitrified binder, and a glass balloon having the same particle size as CBN abrasive grains. Table 5 shows the weight ratio (wt%) of the grindstone after firing in 5). Grinding stone No. "with vibration" In the case of No. 5, the volume ratio Vf of the glass balloon is increased by the increase of the filling ratio due to the vibration, and the total volume ratio Vg + _f (= Vg + Vf) of the abrasive grains and the aggregate is 33 + 26 =
59 vol%. In this case, the pressing pressure at the time of molding cannot be increased so much because the crushing strength of the glass balloon is weak and is considerably low at 50 to 60 kgf / cm ^2. However, the volume ratio Vf of the glass balloon is greatly improved by vibration press molding. At the same time, the shrinkage ratio during firing is small, and a decrease in yield due to deformation is suppressed. On the other hand, the normal molded product No. In 5C, two or three times the pressing pressure is required to obtain the same specifications, which is extremely disadvantageous due to the enlargement of the press machine and the wear of the mold. Further, the possibility of the balloon being crushed increases, and the product yield is significantly reduced.

[0021]

[Table 4]

[0022]

[Table 5]

Next, the manufactured outer diameter of 203 mm ×
13mm thick x 50.8mm hole diameter x 6mm abrasive layer thickness
FIG. 6 shows the results obtained by performing a grinding process under the following grinding conditions using a grindstone (CBN wheel) and examining various grinding performances. (Grinding Conditions) work ^{material: SKH51, HRC61 ± 1, T} 50 × L 10
0 × ^W 10 Machine: surface grinding machine PSG-52DX (manufactured by Okamoto Kosakusho) grinding method: Wet plunge cut wheel peripheral speed: 2000 m / min Table speed: 20 m / min depth of cut: 10 [mu] m / pass grinding efficiency: 3.3 mm ³ / mm · sec Grinding width: 10mm Grinding oil: C-30T (diluted 50 times)

From FIG. 6, it can be seen that the grinding wheel No. 5
(●) indicates the comparison wheel No. Compared with 5C (○), the wear is small and the surface roughness of the ground surface is also excellent. In addition, the surface roughness of the grindstone is fine, indicating that the abrasive grains are less likely to fall off.

The embodiments of the present invention have been described in detail with reference to the drawings. However, these embodiments are merely examples, and the present invention has various modifications and improvements based on the knowledge of those skilled in the art. It can be implemented in embodiments.

[0026]

As described above, according to the superabrasive vitrified grindstone of the present invention, the total volume ratio of the abrasive and the aggregate by vibration press molding, or the volume ratio of only the superabrasive when no aggregate is contained. However, since it can be as high as 51 vol% to 75 vol%, various grinding wheel performances including fatigue strength, grinding ratio, surface roughness and the like are improved. In addition, for a grindstone containing an inorganic hollow material such as a glass balloon, the volume ratio of the inorganic hollow material can be increased without increasing the pressing pressure, and the abrasive grain distribution becomes uniform,
Wheel performance is improved.

[Brief description of the drawings]

FIG. 1 When molded without vibration (Comparative example: Grindstone No. 1
C) and the case of vibration press molding (product of the present invention, grinding wheel No.
It is the figure which compared the pore diameter distribution of each grindstone of 1).

[Fig. 2] Surface roughness, wheel wear and grinding ratio, and wheel unit circumference for each of the whetstones when shaping without vibration (grinding wheel No. 1C) and when vibrating press forming (grinding stone No. 1) It is a figure which compares and shows the result of having investigated the relationship with a contact grinding cross-sectional area.

FIG. 3 shows the results of examining the number of abrasive grains on the surface immediately after dressing and after 30 cuts for each of the whetstones when molded without vibration (grinding wheel No. 1C) and when subjected to vibration press molding (grinding stone No. 1). FIG.

FIG. 4 shows a case of molding without vibration (grinding stone No. 1C, 2
C, 3C, 4C) and the case of vibration press molding (grinding stone No.
It is a figure which compares and shows the result of having investigated the fatigue strength about each grindstone of 1,2,3,4).

FIG. 5 is a diagram showing the results of examining bending strength by preparing various grinding wheels having different grinding wheel volume ratios Vg by adjusting the pressing pressure at the time of vibration press molding.

FIG. 6 shows grinding wheel wear dimensions and work surface roughness of a case where a grinding wheel containing a glass balloon as an aggregate is formed without vibration (grinding wheel No. 5C) and a case where vibration pressing is performed (grinding wheel No. 5). FIG. 4 is a diagram showing a comparison between results obtained by examining a relationship between a grinding wheel surface roughness and a grinding amount.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshihiro Mizuno 3-36 Noritakeshinmachi, Nishi-ku, Nagoya-shi, Aichi F-term in Noritake Co., Ltd. (reference) 3C063 BB01 BB02 BB03 BB04 BB19 BC05 BD01 BD05 CC19 FF22 FF23

Claims (2)

[Claims] 1. A superabrasive manufactured by pressing and shaping a grindstone raw material powder containing a superabrasive grain, a vitrified binder, and an optionally mixed aggregate, followed by firing, followed by firing. A granulated vitrified grindstone, wherein the total volume ratio of the superabrasive grains and the aggregate in the grindstone after firing, or the volume ratio of only the superabrasive grains when the grindstone raw material powder does not include the aggregate, is 51 vol. % -75 vol%, within the range of from 0.5% to 75% by volume. 2. The superabrasive vitrified grindstone according to claim 1, wherein the aggregate contains an inorganic hollow material.