JPH0890423A - Resinoid grinding wheel - Google Patents

Abstract

PURPOSE: To provide the resinoid grinding wheel which prevents cracking as much as possible in a crystallitic sintering aluminum abrasive particle. CONSTITUTION: Large cracking in a crystallitic sintering aluminum abrasive particle 20 by an impact can be prevented because the crystallitic sintering aluminum abrasive particle 20 position on the grinding surface is comparatively elastically held for being covered with an elastic film 28, which has a smaller elastic modulus than that of a resin binder being an adhesive 24, or in other words, which has an easier elastic deformation than the resin bond. It develops a tendency to make thrusting into a material being ground shallow. Thus, crushing of the crystallitic sintering aluminum abrasive particle 20 becomes minute during grinding, wear of a grinding wheel is reduced and grinding ratio is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resinoid grindstone containing microcrystalline sintered aluminous abrasive grains.

[0002]

2. Description of the Related Art Abrasive grains (hereinafter referred to as microcrystalline sintered alumina-based abrasive grains) in which fine crystalline alumina particles having a size of submicron are densely bonded by sintering are known. Examples thereof include microcrystalline sintered aluminous abrasive grains disclosed in US Pat. No. 4,323,364, US Pat. No. 4,314,827, US Pat.

The above-mentioned microcrystalline sintered alumina abrasive grains are prepared, for example, by producing an aqueous sol from microcrystalline hydrated alumina and a mineral acid, and a predetermined amount of zirconia or spinel is produced in the aqueous sol. Magnesia, etc. may be included, but with or without the addition of an effective amount of sub-micron alpha alumina or alpha ferric oxide which functions as a seed or nucleating agent during high temperature firing, and further sheet forming or extrusion. After being molded, it is dried and pulverized to be granulated, and then, for example, it is baked at about 1400 degrees.

The above-mentioned microcrystalline sintered alumina-based abrasive grains are generally high in toughness, and the abrasive grain cutting edge is finely crushed to constantly create a new sharp cutting edge. A grindstone using abrasive grains is characterized in that excellent grinding characteristics or grinding ratio can be obtained.

[0005]

By the way, in conventional grinding wheels, abrasive particles such as fused alumina abrasive grains, co-melted alumina-zirconia abrasive grains, and silicon carbide abrasive grains are used, and the abrasive grains are large during grinding. The cutting blade is regenerated one after another by being crushed. However, although the above-mentioned microcrystalline sintered alumina-based abrasive grains are sintered bodies of fine alumina crystals, they are not limited to a part of their tips when they are subjected to a large impact, and they break off greatly and fall off. In some cases, the characteristics of the abrasive grains may not be exhibited sufficiently, and at the same time, the deformation of the ground surface is large. For example, when it is used as a cutting grindstone, there is a problem that the tip shape of the grindstone collapses.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a resinoid grindstone for preventing cracking of microcrystalline sintered alumina abrasive grains as much as possible. It is in.

[0007]

The object of the present invention to achieve such an object is to provide a resinoid grindstone in which abrasive grains containing microcrystalline sintered aluminous abrasive grains are bonded by resin bond, The microcrystalline sintered alumina-based abrasive grains are covered with an elastic film having a smaller elastic modulus than the resin bond.

[0008]

In this way, the microcrystalline sintered aluminous abrasive grains are coated with an elastic coating having a smaller elastic modulus than the resin bond, that is, an elastic coating that is easier to elastically deform than the resin bond. Since the microcrystalline sintered alumina abrasive grains located on the ground surface are held relatively elastically, large cracks of the microcrystalline sintered alumina abrasive grains can be prevented even when shocked. In addition, the bite into the work material tends to be shallow. Therefore,
During grinding, the microcrystalline sintered aluminous abrasive grains become finely crushed, the wear of the grindstone is reduced, and the cutting ratio is improved.

Here, the resinoid grindstone is preferably a disc-shaped cutting grindstone having a pair of surface layers exposed on both sides and an intermediate layer sandwiched in the thickness direction by the surface layers. The above-mentioned microcrystalline sintered alumina abrasive grains are contained in the abrasive grains in the range of 10 to 100% by volume, and the intermediate layer abrasive grains include the microcrystalline sintered alumina abrasive grains in the surface layer of the abrasive grains. It is contained in the range of 0 to 50% by volume, which is less than the ratio. By doing so, the reduction of the pair of surface layers exposed on both sides is reduced, so that not only the grinding ratio (cutting ratio) is increased, but also the burrs and burns of the cut surface are improved and the shape of the cutting tip is improved. Since it is hard to collapse, oblique cutting is preferably prevented. If the proportion of the microcrystalline sintered alumina abrasive grains in the abrasive grains in the surface layer is less than 10%, the effect of including the microcrystalline sintered alumina abrasive grains cannot be effectively obtained.

Further, preferably, the surface-layer abrasive grains contain the microcrystalline sintered alumina-based abrasive grains in a range of 25 to 70% by volume. If the proportion of the microcrystalline sintered alumina-based abrasive grains in the abrasive grains in the surface layer exceeds 70% by volume, the effect of including the microcrystalline sintered alumina-based abrasive grains is saturated, so that an expensive microcrystalline sintered abrasive grain is used. The cost increases as the amount of alumina-bonded abrasive grains increases. Further, when the proportion of the microcrystalline sintered alumina abrasive grains in the abrasive grains in the surface layer is less than 25% by volume, the effect of including the microcrystalline sintered alumina abrasive grains can be obtained but is efficiently obtained. I will not be able to.

Preferably, the surface abrasive grains contain the microcrystalline sintered aluminous abrasive grains in the range of 30 to 50% by volume. When the proportion of the microcrystalline sintered alumina abrasive grains in the abrasive grains in the surface layer is within the range of 30 to 50% by volume, the effect of including the microcrystalline sintered alumina abrasive grains is substantially remarkable. Obtained and economical.

Preferably, the pair of surface layers are each formed to have a thickness of 1/10 to 1/4 of the thickness of the cutting grindstone. When the thickness of the pair of surface layers is less than 1/10, it becomes difficult to effectively obtain the effect of containing the microcrystalline sintered alumina abrasive grains, and when it exceeds 1/4, the cutting ratio is obtained, The shape of the tip of the cut is likely to collapse, and the inclined cutting tends to occur.

Preferably, the resin bond is a phenolic resin, and the elastic coating is a phenolic resin and is modified with an elasticity imparting agent such as nitrile resin, ABS resin, polyvinyl alcohol, or synthetic rubber. It was done. In this way, since the elastic coating that coats the microcrystalline sintered alumina abrasive grains is the same phenolic resin as the resin bond, mutual adhesiveness with it is preferably obtained, and the strength of the grindstone is impaired. There is no.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view of a cutting wheel 10.
FIG. 2 is an enlarged view of the cut tip portion, and FIG.
FIG. 4 is a diagram for explaining a connective structure of the cutting grindstone 10.

The cutting grindstone 10 is a discoid resinoid grindstone in which abrasive grains are bonded by a phenolic resin, which is a thermosetting resin that functions as a resin bond, and has a pair of surface layers 12 and 14 located on both sides thereof. The intermediate layer 16 is sandwiched between the surface layers 12 and 14 in the thickness direction. This cutting grindstone 10 is, for example, 1000 to 1.
It is formed to have a diameter of about 500 mm and a thickness of about 10 to 15 mm, and is fastened to the rotary shaft of a cutting device (not shown) through the center hole 18.

As shown in FIGS. 2 and 3, the surface layer 1 is
Reference numerals 2 and 14 denote microcrystalline sintered alumina-based abrasive grains 20 in which fine-crystalline alumina particles having a size of about submicron are densely bonded by sintering, and general abrasive grains 22 such as fused alumina abrasive grains. Are mixed and bonded with a binder 24 made of a thermosetting phenolic resin so as to have pores 26 at a predetermined ratio. Further, the intermediate layer 16 is configured to have pores 26 of a predetermined ratio mainly by bonding the general abrasive grains 22 with a phenol resin.

The microcrystalline sintered alumina abrasive grains 20 contained in the surface layers 12 and 14 have a ratio of the microcrystalline sintered alumina abrasive grains 20 to the abrasive grains in the surface layers 12 and 14 of 10 to 10.
It is mixed so as to be within a range of 100% by volume, preferably within a range of 25 to 70% by volume, and more preferably within a range of 30 to 50% by volume. In the intermediate layer 16 as well, the microcrystalline sintered alumina abrasive grains 20 are mixed in the range of 0 to 50% by volume, if necessary.
It is made smaller than the content rates in 2 and 14.

The microcrystalline sintered alumina abrasive grains 20 contained in at least the surface layers 12 and 14 are covered with an elastic coating 28 having a lower elastic modulus than that of the binder 24 made of phenol resin, that is, easily elastically deformed. ing. The elastic coating 28 is, for example, a resin obtained by modifying a phenol resin with an elasticity imparting agent, that is, a part of the elastic coating 28 is replaced with an elasticity imparting agent which is a modifier during the polymerization of the phenol resin so that the elastic coating 28 can be removed from the binder 24. Also has a large elastic deformability. As the elasticity-imparting agent, for example, a thermoplastic resin such as nitrile resin or ABS resin, synthetic rubber, polyvinyl alcohol, etc. are used.

The cutting grindstone 10 is manufactured through the steps shown in FIG. 4, for example. That is, in the elastic film forming step, the microcrystalline sintered alumina-based abrasive grains 20 are charged with, for example, liquid phenol resin into the microcrystalline sintered alumina-based abrasive grains 20 in the mixer, and thereafter, the powdery elastic resin is used. The elastic coating 28 is pre-coated by adding the addition agent-modified phenol resin. In the first kneading step, the surface layer 1
General abrasive particles 22, liquid phenol resin, powder phenol resin prepared at a predetermined ratio for constituting Nos. 2 and 14,
The filler and the microcrystalline sintered aluminous abrasive grain on which the elastic coating is formed are kneaded using a kneader. Further, in the second kneading step, the general abrasive grains 22 prepared at a predetermined ratio for forming the intermediate layer 16, the liquid phenol resin, the powdered phenol resin, and the filler such as iron sulfide powder and ice crystal powder are kneaded with each other. Knead using. In the first charging step, only the amount of the material prepared in the first kneading step for forming the surface layer 12 is charged into the molding die, and then in the second charging step, the second kneading step is prepared. Of the above materials, only an amount for forming the intermediate layer 16 is charged in the molding die, and further, in the third charging step, for forming the surface layer 14 among the materials prepared in the first kneading step. Only the quantity is charged into the mold. Then, after the material charged in the molding die is press-molded in the press-molding step, 180 ° C. in the aging step.
The cutting grindstone 10 is manufactured by being hardened by being heated at a temperature of about ° for a predetermined time and being finished in the finishing step.

Table 1 shows the cutting wheels shown below by the present inventors.
The experimental results of (A), (B), and (C) under the cutting conditions shown below are shown. In Table 1, the cutting ratio (grinding wheel wear amount / cutting area) is shown as a value when the cutting grindstone (A) is 100, and the cutting surface property is expressed in three stages of ○, △, ×. Indicates the highest rating. In addition, cutting wheel
In each of (A), (B), and (C), the ratio of the microcrystalline sintered aluminous abrasive grains to the abrasive grains in the entire grindstone is the same.

Cutting wheel (A) surface layer and intermediate layer: Abrasive grains 43% by volume [25% by volume of the abrasive grains are microcrystalline sintered alumina abrasive grains # 24 (without elastic coating), 75% by volume are # 24 Alundum A Abrasive Grains] Binder (phenol resin + filler) 45% by volume Porosity 12% by volume Cutting stone (B): Surface layer: Abrasive grains 43% by volume [50% by volume of abrasive grains # 2
Microcrystalline Sintered Alumina Abrasive Grains of 4 (without Elastic Coating), 5
0% by volume of # 24 Alundum A abrasive grains] Binder (phenol resin + filler) 45% by volume Porosity 12% by volume Thickness (one side) 1/4 of the total thickness Intermediate layer: Abrasive grains 43% by volume (abrasive grains) 100% by volume of # 2
4 Alundum A abrasive grain) Binder (phenol resin + filler) 45% by volume Porosity 12% by volume Thickness 1/2 of total thickness Cutting stone (C): Surface layer: Abrasive grain 43% by volume [of the abrasive grains 50% by volume is # 2
Microcrystalline Sintered Alumina Abrasive Grains of 4 (with Elastic Coating), 5
0% by volume of # 24 Alundum A abrasive grains] Binder (phenol resin + filler) 45% by volume Porosity 12% by volume Thickness (one side) 1/4 of the total thickness Intermediate layer: Abrasive grains 43% by volume (abrasive grains) 100% by volume of # 2
4 Alundum A abrasive grain) Binder (phenol resin + filler) 45% by volume Porosity 12% by volume Thickness 1/2 of total thickness

Cutting conditions Cutting material: Carbon steel pipe for pressure piping (60.5 mmφ x 5.5 mm)
t) Cutting method: 15 bundles with 2 bundles Cutting efficiency: 6.0 cm ² / sec Grinding wheel peripheral speed: 4800 m / min

[0023]

[Table 1]

As is clear from Table 1, the surface layers 12, 14
In the cutting wheel (B) in which the microcrystalline sintered alumina-based abrasive grains 20 are mixed in a high ratio in (1), the grinding performance of the microcrystalline sintered alumina-based abrasive grains 20 is suitably exhibited and the surface layers 12, 14 are
Wear of the microcrystalline sintered alumina-based abrasive grains 20
A cutting ratio of 1.6 times is obtained as compared with the cutting grindstone (A) in which is uniformly mixed, and burning of the cut surface and generation of burrs are eliminated. Further, since the microcrystalline sintered alumina abrasive grains 20 are mixed in the surface layers 12 and 14 at a high ratio, the shape of the cutting tip is not easily broken, and the oblique cutting is also eliminated.
In addition, the microcrystalline sintered alumina abrasive grains 20 are elastic coatings 28.
The cutting grindstone (C) having the same structure as that of the cutting grindstone (B) except that it is coated with the same as the cutting grindstone (A) in which the microcrystalline sintered alumina abrasive grains 20 are uniformly mixed is A cutting ratio of 1.3 times or more as compared with the cutting grindstone (B) is obtained, and burning, burrs and oblique cutting of the cut surface are eliminated.

Here, if the abrasive grains of the surface layers 12 and 14 contain the microcrystalline sintered alumina abrasive grains 20 within the range of 10 to 100% by volume, a temporary effect can be obtained. If the proportion of the microcrystalline sintered alumina abrasive grains 20 is less than 10%, the effect of including the microcrystalline sintered alumina abrasive grains 20 cannot be substantially obtained. However, preferably, the surface layers 12, 1 are
The abrasive grains of No. 4 contain 2 of the microcrystalline sintered alumina-based abrasive grains 20.
It is contained within the range of 5 to 70% by volume. If the proportion of the microcrystalline sintered alumina-based abrasive grains 20 in the abrasive grains in the surface layers 12 and 14 exceeds 70% by volume, the effect of including the microcrystalline sintered alumina-based abrasive grains 20 is saturated, which is expensive. The cost increases as the number of fine crystalline sintered alumina abrasive grains 20 increases.
Further, when the proportion of the microcrystalline sintered alumina abrasive grains 20 in the abrasive grains in the surface layers 12, 14 is less than 25% by volume, the effect of including the microcrystalline sintered alumina abrasive grains can be obtained. It cannot be obtained efficiently. More preferably, the abrasive grains of the surface layers 12 and 14 include the microcrystalline sintered alumina abrasive grains 20 in the range of 30 to 50% by volume. Surface 1
If the proportion of the microcrystalline sintered alumina abrasive grains 20 in the abrasive grains in 2 and 14 is within the range of 30 to 50% by volume, the effect of including the microcrystalline sintered alumina abrasive grains is substantially. It is remarkably obtained and economical.

The pair of surface layers 12 and 14 are each formed with a thickness of 1/10 to 1/4 of the thickness D of the cutting grindstone 10. When the thickness d of the pair of surface layers 12 and 14 is less than D × 1/10, it becomes difficult to effectively obtain the effect of including the microcrystalline sintered alumina abrasive grains 20.
If it exceeds × 1/4, the cutting ratio can be obtained, but the shape of the cutting tip is likely to collapse, and oblique cutting tends to occur.

As described above, according to the cutting grindstone 10 of this embodiment, the elastic coating 2 in which the microcrystalline sintered alumina abrasive grains 20 have a smaller elastic modulus than the binder 24 which is a resin bond.
8, that is, the fine crystalline sintered alumina abrasive grains 20 located on the ground surface are held relatively elastically because they are covered with the elastic coating 28 that is easier to elastically deform than the resin bond. In addition, large cracks of the microcrystalline sintered alumina-based abrasive grain 20 are prevented against impact, and
The bite into the work material tends to be shallow. Therefore, during grinding, the microcrystalline sintered alumina abrasive grains 20 become finely crushed, wear of the grindstone is reduced, and the cutting ratio is improved.

Further, according to this embodiment, the binder 24, which is a resin bond, is a phenolic resin, and the elastic coating 2
Since 8 is also a phenolic resin which is modified with synthetic rubber, microcrystalline sintered alumina abrasive grains 20
The elastic coating 28 for coating is preferably provided with mutual adhesiveness with the resin bond and does not impair the strength of the grindstone.

Although one embodiment of the present invention has been described above with reference to the drawings, the present invention can be applied to other modes.

For example, in the above embodiment, the cutting grindstone 1
Although 0 has been described, the present invention can be applied to places where the grinding load is large in other types of resinoid grindstones such as a peripheral grinding stone.

In the above embodiment, the binder 24 is made of phenol resin, and the elastic coating 28 is made of phenol resin which is modified by synthetic rubber to give elasticity. Other types of resin such as epoxy resin may be used as the agent 24 and the elastic coating 28. In short, any material may be used as long as it has a property of causing elastic deformation more easily than the binder 24.

The above description is merely one embodiment of the present invention, and the present invention can be variously modified without departing from the gist thereof.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a cutting grindstone according to an embodiment of the present invention.

FIG. 2 is an enlarged view showing a notch tip portion of the embodiment of FIG.

FIG. 3 is a diagram for explaining the connecting structure of the cutting wheel of the embodiment of FIG.

FIG. 4 is a process chart illustrating a manufacturing process of the cutting grindstone of the embodiment of FIG.

[Explanation of symbols]

 10: Cutting grindstone (resinoid grindstone) 12, 14: Surface layer 16: Intermediate layer 20: Microcrystalline sintered alumina abrasive grains 24: Binder 28: Elastic coating

Claims (6)

[Claims] 1. A resinoid grindstone in which abrasive grains containing microcrystalline sintered alumina abrasive grains are bonded with a resin bond, wherein the microcrystalline sintered alumina abrasive grains have a smaller elastic modulus than the resin bond. A resinoid grindstone characterized by being coated with an elastic coating. 2. The resinoid grindstone is a disc-shaped cutting grindstone having a pair of surface layers exposed on both sides and an intermediate layer sandwiched between the surface layers, and the abrasive grains of the surface layer have the microcrystalline property. Sintered alumina-based abrasive grains are included in the range of 10 to 100% by volume, and the microcrystalline sintered alumina-based abrasive grains are contained in the intermediate layer abrasive grains in an amount less than 0% of the surface layer abrasive grains. ~
The resinoid grindstone according to claim 1, wherein the resinoid grindstone is contained within a range of 50% by volume. 3. The resinoid grindstone according to claim 2, wherein the abrasive grains of the surface layer contain the microcrystalline sintered aluminous abrasive grains in the range of 25 to 70% by volume. 4. The resinoid grindstone according to claim 2, wherein the abrasive grains of the surface layer contain the microcrystalline sintered aluminous abrasive grains within a range of 30 to 50% by volume. 5. The resinoid grindstone according to claim 2, wherein the pair of surface layers are each formed to have a thickness of 1/10 to 1/4 of a thickness of the cutting grindstone. 6. The resin bond is a phenolic resin, and the elastic coating is a phenolic resin modified with an elasticity-imparting agent.
Resinoid grindstone.