JPH10175172A - Multi diamond grinding wheel for cutting rare earth magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cut rare earth magnet with good dimensional accuracy and stably over a long period even if the peripheral cutting edge is thin by forming a base plate of a diamond peripheral cutting edge from cemented carbide having a specified Vickers hardness (Hv). SOLUTION: A peripheral cutting edge 6 for cutting rare earth magnets of such a quite new structure where a cutting edge part 2 mainly composed of diamond abrasive grain is further fitted on a base plate 1 is used as a cutting edge of a multi diamond grinding wheel for cutting rare earth magnets. The material quality of the base plate 1 of the peripheral cutting edge 6 is cemented carbide having a Vickers hardness (Hv) ranging from 900 to 2,000. If the Vickers hardness (Hv) is less than 900, in the case of such a recess that cutting and grinding powder of rare earth magnets is caught in the recess part, the grinding wheel base plate is damaged to cause bending or waviness. If the Vickers hardness Hv exceeds 2,000, toughness is poor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-diamond grinding wheel used for multi-cutting a rare earth sintered magnet.

[0002]

2. Description of the Related Art When manufacturing a rare earth magnet product, there are a case where one piece is formed at the stage of press forming, and a case where a large block is formed and cut in a processing step (many pieces). FIG. 3 shows a conceptual diagram thereof. In the case of one-piece (a), if a normal sintered body can be obtained, the burden on the processing step is relatively small, and how to perform press molding and sintering with high productivity is an important point in production. However, when manufacturing a small product or a product with a small thickness in the magnetization direction, it is difficult to obtain a sintered body of normal shape in press molding and sintering, and it becomes a sintered body with large distortion and warpage. Will not be.
On the other hand, in the case of multi-cavity (b), there is no problem as described above, and since the productivity is high in the steps of press molding, sintering, heat treatment and the like, and it is versatile, it has become the mainstream of rare earth magnet production. ing. However, a cutting step is necessary in the subsequent processing, and it is important how efficient and efficient cutting can be performed.

As a cutting blade of a rare earth magnet, an inner peripheral blade of a diamond grindstone in which diamond abrasive grains are adhered to an inner peripheral portion of a thin donut-shaped disk, or a thin disk as shown in FIG. There are two types of diamond grindstone outer peripheral blades having diamond abrasive grains fixed to the outer peripheral portion, but cutting using the outer peripheral blades has recently become the mainstream particularly from the viewpoint of productivity. That is, in the case of the inner peripheral blade, it is a single blade cutting and the productivity is low, whereas in the case of the outer peripheral blade, FIG.
This is because a plurality of outer peripheral blades 6 as shown in (b) are assembled via the spacer 3 and so-called multi-cutting in which a large number of pieces can be taken at once is possible.

[0004] As the binder for the diamond abrasive grains of the outer peripheral blade, there are typically three types: a resin bond as a resin binder, a metal bond as a metal binder, and electrodeposition by plating. Rare earth magnets as hard materials, especially RF
A resin bond is mainly used for cutting the eB-based sintered magnet. This is because the strength (holding force) of resin bond holding diamond abrasive grains is weaker than metal bond,
This is because it has a low strength and a low elastic modulus, so that the hit is soft and the sharpness is excellent. High strength like metal bond,
Bonds with high elastic modulus have excellent abrasive holding power and abrasion resistance, but are more likely to be clogged than resin bonds, and have the disadvantage of increased cutting resistance.However, they are more durable than resin bonds. However, it is also used in the cutting process of R-Fe-B based sintered magnets.

[0005] When cutting a rare-earth magnet using a cutting grindstone and cutting out a large number of products by cutting a block of a certain size as described above, the blade thickness of the cutting grindstone and the object to be cut (rare earth) are required. The relationship between the material yield of magnets and the material yield is very important. Cutting with a thinner blade as possible and with high precision reduces the cutting allowance, increases the number of products obtained, increases the material yield, and improves productivity. It is important to raise it.

[0006]

From the viewpoint of material yield, in order to make the cutting blade thinner, it is naturally necessary to make the wheel base plate thinner. In the case of the outer peripheral blades shown in FIGS. 1 and 2, a steel material is conventionally used as a material of the grindstone base plate 1 mainly from the viewpoint of material cost and mechanical strength. With SK, SKS, SKD, SKT, SK
Alloy tool steel specified as H etc. has been exclusively used. However, when cutting a hard material such as a rare earth magnet with the thin outer peripheral blade 2, the mechanical strength of the conventional plywood of alloy tool steel described above is insufficient, and deformation such as bending occurs at the time of cutting, resulting in loss of dimensional accuracy. I will.

Further, as the grinding wheel base plate 1 is made thinner, the following problems occur. In general, as shown in FIG. 1, a diamond abrasive layer (cutting edge) 2 is protruded from the surface of a grindstone base plate 1 by 0.01 to 0.2 mm, and a gap 4 (hereinafter referred to as an escape) Notation) is provided. The relief 4 serves to eliminate cutting ground powder generated from the object when the cutting wheel is deeply cut into the object. In order to reduce the cutting allowance, that is, the blade thickness 5, it is necessary to make the relief 4 of the grinding wheel base plate 1 as small as possible. One of the problems with the cutting process using a thin grindstone base plate is that the clearance is too small to remove the cutting ground powder, which is caught between the workpiece and the grindstone base plate and damages the grindstone base plate. It is. In particular, when the object to be cut is a rare-earth magnet, it has hardness equal to or higher than that of the alloy tool steel used for the conventional grindstone base plate, and is brittle. If it is caught between the grinding wheel base plate and the object to be cut, the grinding wheel base plate will be damaged. When such a scratch is made on the grindstone base plate, the plastic deformation of the flaw portion causes the stress balance between the front and back of the grindstone base plate to be out of order, and deformation such as bending or undulation occurs in the grindstone base plate. The thinner the grinding wheel base plate, the greater the degree of such bending and undulation due to small scratches. Once the grindstone base plate is deformed by such a scratch, the stress at the time of cutting is applied to further deform the deformed grindstone base plate,
Since the bends and undulations are promoted, the dimensional accuracy of the obtained cut product is largely lost.

In particular, in the case of multi-cutting, since the cutting dimension is determined by the interval between the cutting blades, deformation such as bending or undulation may occur on the base plate, or the amount of deformation may change with time. In addition, the spacing between the cutting blades must be adjusted frequently (adjustment of the spacer thickness) to ensure dimensional accuracy, which may cause a drop in productivity or a failure to obtain the target number. Met. An object of the present invention is to provide a multi-diamond grindstone for cutting rare earth magnets, which solves such problems.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve such a problem, and as a result, the base plate of a diamond outer peripheral blade constituting a multi-diamond grindstone for multi-cutting rare earth magnets has a Vickers hardness (Vickers hardness). 900 in Hv)
By using a multi-diamond grinding wheel for cutting rare earth magnets made of up to 2000 cemented carbides, it is possible to cut rare earth magnets stably over a long period of time with good dimensional accuracy even with a thin outer cutting edge, producing multiple cutting. The inventors have found that the present invention can be performed with high efficiency, and have completed the present invention.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS That is, the present invention provides the following (1) to
The problem is solved by the configuration (5) and the embodiment. (1) A multi-diamond grinding wheel for multi-cutting a rare earth magnet, wherein a base plate of a diamond outer peripheral blade constituting the grinding stone is made of a cemented carbide having a Vickers hardness (Hv) of 900 to 2,000. Multi diamond wheel for cutting. (2) The base plate of the outer peripheral blade has an outer diameter of 200 mm or less and a thickness of 0.1 to 1
The thickness of the abrasive layer as a cutting blade is 0.01 to 0.2 mm on one side and 0.02 on both sides of the thickness of the carbide base plate.
The multi-diamond grinding wheel for cutting rare earth magnets as described above, wherein the grinding wheel is 0.4 mm thick and the relief of the grinding wheel is 0.01 to 0.2 mm. (3) The multi-diamond grinding wheel for cutting rare earth magnets as described above, wherein the multi-diamond grinding wheel is composed of 3 to 200 diamond peripheral blades, 2 to 199 spacers and a shaft portion. (4) The abrasive grains contained in the cutting edge portion of the outer peripheral edge are made of diamond, cBN, or a mixture thereof (hereinafter, these are collectively referred to as diamond abrasive grains), and have an average particle diameter in the range of 50 to 250 μm. In the above, the multi-diamond grinding wheel for cutting a rare earth magnet according to the above, wherein the volume content of the cutting blade portion is in the range of 10 to 50%. (5) The multi-diamond grinding wheel for cutting a rare-earth magnet as described above, wherein the rare-earth magnet is a rare-earth sintered magnet made of an R-Fe-B system (R is at least one of rare-earth elements including Y).

Hereinafter, the present invention will be described in detail. FIG. 1 shows an example of the structure of the diamond wheel of the present invention.
(A) is a top view, (b) is a vertical sectional view taken along line AA, (c) is an enlarged view of an outer peripheral end portion, and FIG. 2 shows an example of a multi-assembly structure using the diamond whetstone of the present invention. Things
(A) is a conceptual diagram, (b) is a sectional view. In the drawing, 1 is a base plate, 2 is an abrasive layer (cutting edge portion), 3 is a spacer, 4 is a relief, 5 is a blade thickness (cutting allowance), and 6 is an outer peripheral blade. The greatest feature of the present invention is that the material of the base plate 1 of the outer peripheral blade 6 is Vickers hardness (H) as a thin cutting blade for multi-cutting a rare earth magnet which is a hard and brittle hard material.
In v), a cemented carbide of 900 to 2000 is to be obtained. Cemented carbide is a material that is so hard and strong that it can be used as a cutting blade by itself. In fact, cutting blades made only of cemented carbide are widely and practically used for cutting wood, stone, fiber, plastic, tobacco filters and the like. In the present invention, an outer blade 6 for cutting a rare-earth magnet having a completely new structure in which a cutting blade portion 2 mainly made of diamond abrasive grains is further mounted on a base plate 1 made of a cemented carbide which should be a cutting tool. It is used as a cutting blade of a multi-diamond grindstone for cutting rare earth magnets.

When cutting a rare earth magnet with a thin outer blade,
Due to its structure, the material of the base plate is very important. As a result of studying various materials that can be a thin grinding wheel base plate that does not bend or undulate even when subjected to a force when cutting compared to conventional alloy tool steel, it was found that a cemented carbide is most suitable. In terms of hardness, ceramics such as alumina are superior, but have poor toughness, especially when the workpiece is a rare-earth magnet, which often breaks due to impact during cutting, and is very dangerous and thin. Not suitable for whetstone base plate. Cemented carbide is WC, TiC, M
Alloy powder obtained by sintering carbide powders of metals belonging to the group IVa, Va, VIa such as oC, NbC, TaC, Cr ₃ C ₂ using Fe _, Co _, Ni _, Mo _, Cu _, Pb _, Sn or their alloys Among them, WC-Co, WC-TiC-Co, and WC-TiC-TaC-Co alloys are typical. As the cemented carbide base plate for rare earth magnet multi-cutting in the present invention, the cemented carbide must have a Vickers hardness (Hv) in the range of 900 to 2,000. Vickers hardness (Hv) of rare earth magnet depends on composition but 400
Vickers hardness (H
If v) is less than 900, as described above, in the case of escape in which the cut and ground powder of the rare earth magnet is caught in the escape portion, the grinding wheel base plate will be damaged, and as a result, bending and undulation will be generated and promoted. Absent. If the Vickers hardness (Hv) exceeds 2,000, the grinding wheel base plate itself will not be damaged even if the cutting ground powder is caught in the escape portion, but the toughness is poor, especially when the workpiece is a rare earth magnet, They are often broken by impact during cutting, which is very dangerous and is not suitable for thin grinding wheel base plates.

When the number of diamond outer peripheral blades used in the multi-diamond grindstone is less than three, the effect of multi-cutting is small, and when the number exceeds 200, the weight of the grindstone is too large to be practically difficult. Number of sheets. Since both ends of the whetstone serve as cutting blades, the number of spacers is 2 to 199. The diamond outer blade and the spacer are used by being incorporated into the shaft portion.

The outer peripheral cutting edge of the present invention is obtained by fixing abrasive grains of diamond powder to the outer peripheral portion of the cemented carbide base plate using a binder. The binder is not limited to resin bond, but may be metal bond, Any method such as a vitrified bond or an electrodeposition bond may be used. In other words, the use of a cemented carbide has a rigidity in the base plate itself, and cutting can be performed with sufficient cutting accuracy maintained even if a metal bond having the largest cutting resistance is used. As described above, the use of a metal bond improves the wear resistance compared to a resin bond, resulting in a longer life of the outer peripheral blade, and can be used for a long time without disassembling the assembled multi-blade This is very effective for multi-cutting of rare earth magnets.

The thickness of the diamond abrasive layer as a cutting blade is 0.01 to 0.2 mm on one side and 0.02 on both sides of the thickness of the base plate.
0.4 mm thick, that is, the relief of the grindstone is 0.01 to 0.2 mm. If the grinding wheel escapes beyond 0.2 mm, the cutting powder will not be caught, but the material yield will decrease. If the thickness is less than 0.01 mm, the base plate is hardly damaged, but the escape is too small, so that cutting powder is clogged and cutting cannot be performed.

The abrasive grains contained in the abrasive layer portion (cutting edge portion) on the outer periphery of the base plate are not limited to diamond, but are cBN abrasive grains (cubic boron nitride), or diamond abrasive grains and cBN abrasive grains.
It may be mixed with abrasive grains. However, the volume content of diamond abrasive grains in the abrasive layer layer is important, and if the volume content of diamond abrasive grains is less than 10%, the diamond abrasive grains contributing to cutting are too small, resulting in poor sharpness. Must be extremely slow, and the cutting efficiency will be reduced. On the other hand, if the content exceeds 50%, the amount of the binder is too small, and the holding force of the diamond abrasive grains is reduced. In the case of a hard workpiece such as a rare-earth magnet, the abrasive grains do not sufficiently contribute to the cutting and fall off. . Accordingly, the volume content of the outer peripheral blade for cutting rare earth magnets in the present invention to the abrasive layer portion of the diamond abrasive grains is limited to 10 to 50%.

Further, as a result of studying the grain size of the abrasive grains, it was found that the average grain size of the diamond abrasive grains was in the range of 50 to 250 μm. When cutting the rare earth magnet, if abrasive grains having an average particle diameter of less than 50 μm are used, the projection of the abrasive grains is poor, so that the grains are easily clogged and the cutting efficiency is reduced. If the average particle size exceeds 250 μm, the cutting efficiency is high, but the cut surface roughness of the rare-earth magnet deteriorates and the thickness of the abrasive grain layer increases even if the base plate is thinned. This is because problems such as the inability to obtain a blade occur.

If the base plate itself is warped or undulated and the dimensional accuracy is not good, the dimensional accuracy of the rare earth magnet after cutting is deteriorated by reflecting the warp and undulation, resulting in a problem that the cutting allowance increases. The warpage and undulation of the base plate are more likely to occur as the base plate becomes thinner and as the diameter increases, and it becomes difficult to manufacture the base plate itself with high accuracy. As for the cemented carbide base plate of the present invention, a precise base plate itself can be manufactured, and as a result of examining the base plate size that can cut rare earth magnets with high dimensional accuracy and stable for a long time, the outer diameter is 200 mm φ or less. And a thickness in the range of 0.1 to 1 mm. In other words, if the outer diameter exceeds 200 mm φ, or if the outer diameter is less than 200 mm φ but the thickness is less than 0.1 mm, large warpage will occur, making it impossible to manufacture cemented carbide with good dimensional accuracy. Become. Further, when the thickness exceeds 1 mm, it is possible to cut the rare earth magnet with high precision even with the conventional base plate made of alloy tool steel, but the cutting allowance becomes too large, which deviates from the improvement of the material yield, which is the gist of the present invention. Out of the range for the reason. Further, when the outer diameter of the base plate exceeds 200 mm, the cost is too high to obtain a thin plate. On the other hand, if the thickness is less than 0.1 mm, it is too thin and breaks.

If the multi-diamond grinding wheel for cutting a rare-earth magnet of the present invention is applied to a rare-earth sintered magnet of the R-Fe-B type (R is at least one of rare-earth elements including Y, the same applies hereinafter), the present invention The effect is remarkable and very useful. These magnets are manufactured as follows. R-Fe
-B-based rare earth sintered magnets are usually 5 to 40% by weight.
R, 50 to 90% Fe, and 0.2 to 8% B. C, Al, Si, Ti, V, Cr, Mn, C to improve magnetic properties and corrosion resistance
In many cases, additional elements such as o, Ni, Cu, Zn, Ga, Zr, Nb, Mo, Ag, Sn, Hf, Ta, and W are added. The amount of these additives is usually 30% by weight or less for Co, and 8% by weight or less for other elements. Addition of more additives causes the magnetic properties to deteriorate. The manufacturing method of the R-Fe-B based rare earth sintered magnet is as follows. The raw metal was weighed, melted and cast, and the resulting alloy was cast with an average particle size of 1 to 1.
Finely pulverized to 20 μm to obtain an R—Fe—B rare earth permanent magnet powder. Then molded in a magnetic field, then at 1000-1200 ° C
After sintering for 0.5 to 5 hours, heat treatment is further performed at 400 to 1000 ° C. to obtain an R—Fe—B rare earth sintered magnet. The effect of the present invention is to perform the multiple cutting of the outer circumference by assembling a plurality of outer circumferences using a diamond abrasive grain outer circumference blade using a cemented carbide having a Vickers hardness (Hv) of 900 to 2000, so that the rare earth magnet can be cut even with a thin outer circumference blade. The object is to stably perform cutting processing with high accuracy for a long period of time, thereby contributing to reduction of cutting cost, improvement of productivity, and improvement of material yield.

[0020]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited thereto. Example 1 and Comparative Example 1 A cemented carbide (WC-90w) having a Vickers hardness (Hv) of 1500
t% / Co-10wt%) was processed into a 115mm φ × 40mm φ × 0.3mm donut-shaped perforated thin disk to obtain a whetstone base plate. Next, diamond abrasive grains were fixed to the outer peripheral portion of the grindstone base plate by a resin bond method using a resin as a binder to produce an outer peripheral cutting blade. That is, the base plate of the cemented carbide is set in a disk-shaped grinding wheel-shaped mold, and a thermosetting phenol resin is used as a binder on the outer periphery thereof, and artificial diamond having an average particle size of 150 μm is 25% by volume content ( 25% abrasive, 75 resin
%), And then molded into a grindstone shape by pressing, and then heat-cured at 180 ° C for 2 hours while being set in a mold, and cooled.
(0.05mm) to obtain a diamond grindstone peripheral edge for rare earth magnets.

As Comparative Example 1, the same shape as in Example 1 was used.
Using an SKD (alloy for tool JIS) grindstone base plate, the diamond abrasive grains were fixed in the same manner as described above to produce a 0.4 mm-thick SKD diamond grindstone outer peripheral blade.

A cutting test was performed using the Nd-Fe-B-based rare earth sintered magnet as an object to be cut using the outer peripheral blades manufactured in Example 1 and Comparative Example 1. Table 1 shows the results. still,
The cutting test was performed under the following conditions. The outer peripheral blades produced in Example 1 and Comparative Example 1 were assembled into a multi at 1.6 mm intervals (the target size of the rare earth magnet after cutting was 1.5 mm), and the number of rotations was increased.
The workpiece was cut at 6000 rpm at a cutting speed of 22 mm / min. 80mmφ × as spacer shape between multiple assembled outer blades
40 mmφ × 1.6 mm was used. In addition, Nd-
Fe-B based rare earth sintered magnets are 50 mm long x 30 mm wide x 15 high
mm, multi-assembly the outer peripheral blade in the length direction, 1.
Many 5mm thick products were taken. At that time, 26 pieces were taken from one block of the magnet in both Example 1 and Comparative Example 1. The thickness of the central portion of each of the rare-earth magnets cut using the outer peripheral blades manufactured in Example 1 and Comparative Example 1 was measured with a micrometer. If it did, the thickness of the spacer was adjusted and multi-correction was performed so as to be within the management width. Furthermore, when the spacer adjustment was performed three or more times at the same position of the outer peripheral blade, it was determined that the outer peripheral blade was not stable, and the outer peripheral blade was replaced with a new one. Under these conditions, 1000 blocks were cut to obtain evaluation results. As is clear from Table 1, the Nd-
By using the multi-diamond grinding wheel of the present invention for multi-cutting of Fe-B based rare earth sintered magnets, dimensional accuracy is stable for a long time even if the blade thickness is thin, and spacer thickness adjustment, replacement of the outer peripheral blade, etc. are completely unnecessary. It was confirmed that productivity was improved.

[0023]

[Table 1]

Example 2, Comparative Example 2, Comparative Example 3 A cemented carbide having a Vickers hardness (Hv) of 1250 (WC-85w
t% / Co-15wt%) was processed into a 125mm φ × 40mm φ × 0.4mm donut-shaped perforated thin disk to obtain a grindstone base plate. Next, an outer peripheral cutting blade having a blade thickness of 0.5 mm (runaway 0.05 mm) was manufactured using a resin bond as a binder in the same manner as in Example 1. The average diameter of the diamond used was 120 μm, and the volume content of the diamond was 20% (abrasive grains 20%, resin 80%).

Further, as Comparative Example 2, a cemented carbide grindstone base plate having a Vickers hardness (Hv) of 800 (125 mm φ ×
40 mmφ × 0.4 mm), diamond abrasive grains were fixed in the same manner as in Example 2, and an outer peripheral cutting blade having a blade thickness of 0.5 mm was manufactured. In addition, as Comparative Example 3, diamond abrasive grains were fixed in the same manner as in Example 2 using an SKD grinding wheel base plate thicker than that of Example 2 (125 mm φ × 40 mm φ × 0.9 mm).
A 1.0mm-thick SKD diamond grinding wheel was manufactured.

Using the outer peripheral blades prepared in Example 2, Comparative Examples 2 and 3, cutting tests were performed using Nd-Fe-B-based rare earth sintered magnets as objects to be cut. Table 2 shows the results. The cutting test was performed under the following conditions. Each of the outer peripheral blades manufactured in Example 2, Comparative Example 2 and Comparative Example 3 was 1.
The workpiece was cut into multiple pieces at 1 mm intervals (the target size of the rare earth magnet after cutting was 1.0 mm) at a rotation speed of 5500 rpm and a cutting speed of 18 mm / min. 80 mmφ × 40 mmφ × 1.1 mm was used as the spacer shape between the multi-assembled outer peripheral blades. The Nd-Fe-B based rare earth sintered magnet, which is the object to be cut, has a length of 50 mm x a width of 30 mm x a height of 20 mm. I took many pieces. At that time, in Comparative Example 3, 24 pieces were taken from one block of the magnet, whereas in Example 2 and Comparative Example 2, 33 pieces were possible because the outer peripheral edge was thin. Example 2, Comparative Example 2
And all the rare earth magnets cut using the outer peripheral blade prepared in Comparative Example 3 were measured with a micrometer for the thickness of the central part, and if the cutting dimension control width was within 1.0 ± 0.05 mm, it was judged as acceptable,
When the dimensions were off, the thickness of the spacer was adjusted as in Example 1. Further, when the spacer adjustment was performed three times or more at the same outer peripheral edge position, it was determined that the outer peripheral edge was not stable, and the outer peripheral edge was replaced with a new one. Table 2 shows the results. As is clear from Table 2, the use of the multi-diamond grindstone of the present invention for the multi-cutting of the Nd-Fe-B based rare earth sintered magnet improves the material yield, and furthermore, the dimensional accuracy is stabilized, and the multi-cutting of the rare earth magnet is performed. It was confirmed that can be performed efficiently.

[0027]

[Table 2]

Example 3, Comparative Example 4 A cemented carbide having a Vickers hardness (Hv) of 1100 (WC-80w
t% / Co-20wt%) was processed into a 100mm φ × 40mm φ × 0.3mm donut-shaped perforated thin disk to obtain a grindstone base plate. Next, diamond abrasive grains were fixed to the outer peripheral portion of the grindstone base plate by a metal bond method using metal as a binder, thereby producing an outer peripheral cutting blade. The manufacturing process is the same as in Example 1, but
A powder having a composition of Cu-70wt% / Sn-30wt% is used as a binder, and a powder obtained by mixing artificial diamond having an average particle diameter of 100 μm and cBN at a weight ratio of 1: 1 as abrasive grains at a volume content of 15%. (Abrasive grains 15%, metal binder 85%). The heating and firing after pressing is 700 ° C ×
Performed for 2 hours and then finished to obtain a diamond grinding wheel outer peripheral blade for rare earth magnets with a blade thickness of 0.4 mm (runaway 0.05 mm).

As Comparative Example 4, the same shape as in Example 3 was used.
Using an SKH (high-speed steel) grindstone base plate, diamond abrasive grains were fixed in the same manner as in Example 3 to produce a 0.4 mm-thick SKH diamond grindstone outer peripheral blade.

Using the outer peripheral blades prepared in Example 3 and Comparative Example 4, a cutting test similar to that in Example 1 was performed using a Nd-Fe-B-based rare earth sintered magnet as a cut object. Table 3 shows the results. The cutting test was performed under the following conditions.
The outer peripheral blades manufactured in Example 3 and Comparative Example 4 were assembled into a multi at 1.3 mm intervals (the target dimensions of the rare earth magnet after cutting were:
The workpiece was cut at a speed of 8000 rpm and a cutting speed of 25 mm / min. A 75 mmφ × 40 mmφ × 1.3 mm spacer was used as the spacer between the multi-assembled outer peripheral blades. The Nd-Fe-B based rare earth sintered magnet to be cut has a length of 50 mm.
Using a width of 30 mm and a height of 10 mm, the outer peripheral blade was multi-assembled in the length direction, and a large number of products with a thickness of 1.2 mm were taken at a time. At that time, in Example 3 and Comparative Example 4, 31 magnets were taken from one block of magnet. The thickness of the central portion of each of the rare-earth magnets cut using the outer peripheral blades prepared in Example 3 and Comparative Example 4 was measured with a micrometer, and the thickness was 1.2 ± 0.
If it was 05 mm, it was determined to be acceptable. If the dimension was out of place, the thickness of the spacer was adjusted and multi-correction was performed so as to be within the management width as in Example 1. Further, when the spacer adjustment was performed three times or more at the same outer peripheral edge position, it was determined that the outer peripheral edge was not stable, and the outer peripheral edge was replaced with a new one. As is clear from Table 3, by using the multi-diamond grindstone of the present invention for the multi-cutting of the Nd-Fe-B-based rare earth sintered magnet, even with a thin metal-bonded blade, it is accurate and stable for a long time. It was confirmed that cutting was possible.

[0031]

[Table 3]

[0032]

According to the present invention, when the rare-earth magnet is multi-cut using the multi-diamond grindstone of the present invention, cutting can be performed over a long period of time while maintaining the cutting accuracy even if the blade thickness is small. Since the cutting allowance can be reduced as much as possible, the material yield can be improved, and its industrial value is extremely high.

[Brief description of the drawings]

FIG. 1 is a diagram showing the structure of a diamond grinding wheel outer peripheral blade,
(A) is a top view, (b) is a vertical sectional view taken along line AA, and (c) is an enlarged view of an outer peripheral end portion A.

FIG. 2 is a view showing a structure of a multi-assembly using an outer peripheral blade;
(A) is a conceptual diagram, (b) is a sectional view.

3A and 3B are conceptual diagrams of a process for manufacturing a rare earth magnet product, in which FIG. 3A is a diagram showing a case of taking one piece, and FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Base plate 2 ... Abrasive grain layer (cutting edge part) 3 ... Spacer 4 ... Relief 5 ... Blade thickness (cutting allowance) 6 ... Peripheral blade 71 ... Rare earth magnet (after press forming) 72 ... Rare earth magnet (after sintering and heat treatment) 73 ... Rare earth magnet (after polishing)

Claims (5)

[Claims] 1. A multi-diamond grindstone for multi-cutting rare earth magnets, wherein a base plate of a diamond outer peripheral blade constituting the grindstone has a Vickers hardness (Hv) of 900 to less.
A multi-diamond grinding wheel for cutting rare-earth magnets, made of 2000 cemented carbide. 2. The base plate of the outer peripheral blade has an outer diameter of 200 mm or less and a thickness of 200 mm or less.
It is a carbide thin plate of 0.1 to 1 mm, and the thickness of the abrasive layer which is the cutting edge is 0.01 to 0.2 mm on one side and 0.02 to 0.4 mm thick on both sides and 0.01 to 0.2 mm thicker than the thickness of the carbide base plate. The multi-diamond grinding wheel for cutting rare earth magnets according to claim 1, which has a diameter of 0.2 mm. 3. The multi-diamond grinding wheel for cutting rare earth magnets according to claim 1, wherein the multi-diamond grinding wheel comprises 3 to 200 diamond outer peripheral blades, 2 to 199 spacers and a shaft portion. 4. The abrasive grains contained in the cutting edge portion of the outer peripheral blade,
4. The method according to claim 1, comprising diamond, cBN or a mixture thereof, having an average particle size in the range of 50 to 250 μm and a volume content in the cutting edge portion in the range of 10 to 50%. A multi-diamond grinding wheel for cutting rare earth magnets as described. 5. The rare-earth magnet cutting device according to claim 1, wherein the rare-earth magnet is a rare-earth sintered magnet made of an R—Fe—B system (R is at least one of rare-earth elements including Y). For multi diamond wheel.