JP2868180B2 - Diamond wheel for cutting rare earth magnets and cutting method of rare earth magnets using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an outer peripheral edge of a diamond grindstone, and more particularly to an outer peripheral edge of a diamond grindstone for cutting a rare earth magnet, which is effective for cutting a rare earth sintered magnet .
The present invention relates to a method for cutting a rare earth magnet .

[0002]

2. Description of the Related Art The cutting blade of various rare earth sintered magnets can be broadly classified into a diamond grindstone inner peripheral blade having diamond abrasive grains adhered to the inner peripheral portion of a thin donut disk as shown in FIG. There are two types of diamond grindstones, in which a thin disk as shown in Fig. 2 is used as a base plate and diamond abrasive grains are adhered to the outer periphery thereof. It is becoming.

[0003]

When cutting a rare earth sintered magnet using a cutting whetstone, for example, when cutting a block of a certain size and cutting out a large number of products, the blade thickness of the cutting whetstone is reduced. The relationship with the material yield of the object to be cut (rare-earth sintered magnet) is a very important cost factor, and cutting is performed with as thin a blade as possible and with high accuracy to reduce the cutting cost and increase the number of products obtained. To increase material yield,
It is important to increase productivity. In order to make a thin cutting blade, it is necessary to make the grindstone base plate thin. With the inner peripheral blade of FIG. 1, a relatively thin cutting blade can be manufactured because the entire outer periphery is tensioned and rotated so that the drum skin is stretched at the time of cutting, and a relatively thin cutting blade can be manufactured. 0.25-0.5m using stainless steel base plate
An inner peripheral blade having a cutting edge of about m can be manufactured. on the other hand,
In the case of the outer peripheral blade shown in FIG. 2, a steel material is conventionally used as a base plate material mainly from the viewpoint of material cost and mechanical strength.
Alloy tool steels defined as K, SKS, SKD, SKT, SKH, etc. have been exclusively used. However, when cutting a hard material such as a rare earth sintered magnet with a thin outer blade, the conventional alloy tool steel base plate described above has insufficient mechanical strength, causing bending and undulation when cutting, resulting in dimensional accuracy. Will be lost. Furthermore, the rare earth sintered magnet of the object to be cut is harder and more brittle than the alloy tool steel used for the conventional grindstone base plate, so when the chips are hardly removed by being caught between the base plate and the cut object, The grinding wheel base plate is damaged, and the life of the base plate is shortened, and bending and undulation of the base plate are promoted, which is a problem. SUMMARY OF THE INVENTION The present invention solves such problems by reducing the deformation, increasing the cutting accuracy, reducing the cutting allowance, and excelling in durability.Diamond grinding wheel outer peripheral blade for cutting rare earth sintered magnets and rare earth magnet using the same Cutting
It seeks to provide a way .

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, the base plate of the outer peripheral cutting blade is formed of a so-called cemented carbide donut-shaped perforated thin plate disk. By using a diamond grindstone peripheral blade containing diamond-based abrasive powder at a volume ratio of 10 to 80% in the cutting edge portion of the outer periphery of the plate, even with a thin peripheral blade, the dimensional accuracy is good and stable over a long period of time. The present inventors have found that cutting of a sintered magnet is possible, established various conditions and completed the present invention, and the gist of the present invention is to use a diamond grinding wheel for cutting a rare earth sintered magnet. A rare earth element characterized in that a base plate to be formed is a doughnut-shaped perforated thin disk made of cemented carbide, and that diamond-based abrasive powder is contained in a cutting blade portion on the outer periphery of the base plate in a volume ratio of 10 to 80%. Magnet cutting tool In Yamondo grindstone peripheral cutting edge. More specifically, 1) the cemented carbide has a Young's modulus of 45,000 to 70
2,000 kgf / mm ² , 2) diamond-based abrasive powder is natural or synthetic industrial diamond powder, cB
N) and a mixture thereof, the average particle size of which is 10 to 500 μm, 3) the base plate of the outer peripheral blade has an outer diameter of 250 mmΦ or less, and is made of a thin plate having a thickness of 0.1 to 1 mm. 4) A diamond wheel for cutting a rare-earth magnet, wherein the rare-earth magnet to be cut is an R-Co-based or R-Fe-B-based (where R is at least one of rare earth elements including Y) rare-earth sintered magnets; The above rare earth magnet cutting
In cutting method of the rare earth magnet Ru with use diamond wheel peripheral cutting edge.

Hereinafter, the present invention will be described in detail. The greatest feature of the present invention is that the cutting blade base plate is used as a thin cutting blade for cutting the outer periphery of a rare earth sintered magnet which is a hard and brittle hard material.
Is a doughnut-shaped perforated thin disk made of cemented carbide , and diamond powder is applied to the cutting edge on the outer periphery of the base plate at a volume ratio of 10 to 10.
80%. When a rare earth magnet is cut with a thin outer blade, the material of the base plate is very important in terms of its structure. As a result of various investigations into materials that can form a thin whetstone base plate that does not bend or undulate even when subjected to force during cutting as compared with conventional alloy tool steel, it was found that cemented carbide is most suitable. In terms of hardness, ceramics such as alumina are superior, but have poor toughness. Particularly when the workpiece is a rare earth sintered magnet, it often breaks due to impact during cutting, which is extremely dangerous. Not suitable for thin whetstone base plate.

Cemented carbides are WC, TiC, MoC, Nb
_{C, Ta C, Cr 3 C} 2 , etc. of the IVa, Va, a carbide powder of a metal belonging to Group VIa Fe, Co, Ni, Mo, Cu
, Pb, Sn or alloys sintered using these alloys. Among them, WC-Co type, WC
-TiC-Co-based and WC-TiC-TaC-Co-based alloys are typical. In the present invention, the composition and components of the cemented carbide base plate for cutting rare earth magnets are not particularly limited, but the cemented carbide must have a Young's modulus in the range of 45,000 to 70,000 kgf / mm ² . If the Young's modulus of the base plate is less than 45000 kgf / mm ² , even if it is a cemented carbide, bending or undulation occurs due to resistance at the time of cutting, and as a result, the base plate cannot be thinned and the advantage of the cemented carbide is lost. Also, since the rigid and brittle but no problem in terms of the bending or undulation exceeds 70000kgf / mm ^2, since a danger becomes easily broken during use 45000～70000Kgf /
It was limited to within the range of mm ^2.

As shown in FIG. 2, the cutting edge portion is formed on the outer peripheral portion of the cemented carbide base plate 3 by diamond-based abrasive powder (abrasive layer 4).
Is fixed using a binder to form an outer peripheral cutting blade, but the binder may be any method such as a metal bond, a resin bond, a vitrified bond, and an electrodeposition bond.
However, the volume ratio of diamond-based abrasive grains in the abrasive layer
If it is less than 10%, the amount of diamond-based abrasive grains contributing to cutting is too small, resulting in poor sharpness, and the cutting speed must be extremely slow, resulting in low cutting efficiency. On the other hand, if it exceeds 80%, on the contrary, the amount of the binder is too small and the holding force of the diamond-based abrasive grains decreases, and on hard cutting objects such as rare-earth sintered magnets, the abrasive grains do not sufficiently contribute to the cutting and break off. Would. Accordingly, the volume ratio of the diamond-based abrasive grains of the outer peripheral blade for cutting the rare earth sintered magnet in the abrasive grain layer portion is preferably in the range of 10% to 80%.

[0008] In addition to the diamond powder for natural or synthetic industrial use, the diamond-based abrasive grains in the abrasive layer portion of the outer peripheral portion of the base plate may be cBN (cubic boron nitride) powder, natural or synthetic industrial diamond powder-cBN powder. It may be a mixture. cBN is the second hardest material after diamond, is more stable to heat than diamond, and has very low reactivity to steel.
It has been confirmed that even when this cBN powder is replaced with part or all of diamond powder, the same performance as that of diamond abrasive grains is obtained as the outer peripheral cutting blade of the rare earth magnet.

Furthermore, as a result of examining the grain size of the abrasive grains in addition to the type of the abrasive grains, it was found that the average grain size of the abrasive grains of the diamond powder, the cBN powder, and a mixture thereof was in the range of 10 to 500 μm. When cutting a rare earth magnet,
If abrasive grains having an average particle size of less than 10 μm are used, the abrasive grains are poorly protruded, so that the grains are easily clogged and the cutting efficiency is reduced. If the average particle size exceeds 500 μm, the cutting efficiency is high, but the cut surface roughness of the rare earth magnet becomes rough, and even if the base plate is thinned, the thickness of the abrasive layer layer becomes thick, resulting in a thin outer blade. This is because such problems as not being possible 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 margin is increased. The warpage or undulation of the base plate is more likely to occur as the base plate becomes thinner and as the diameter becomes larger, and it becomes difficult to manufacture the base plate itself with high accuracy. As for the cemented carbide base plate of the present invention, it is possible to manufacture the base plate with high accuracy, and as a result of examining the base plate size capable of cutting the rare earth magnet with high dimensional accuracy and stably for a long time, the outer diameter is 250 mmφ.
And the thickness was in the range of 0.1 to 1 mm. That is, even if the outer diameter exceeds 250 mmφ and the outer diameter is 250 mmφ or less and the thickness is less than 0.1 mm,
Large warpage occurs, making it impossible to manufacture a cemented carbide base plate with good dimensional accuracy. Further, if the thickness exceeds 1 mm, it is possible to cut the rare earth magnet with high precision even with a conventional base plate made of an alloy tool copper, and the cutting allowance becomes too large and deviates from the gist of the present invention. The reason why the outer diameter is set to 250 mmφ or less is, for example, an adaptation limit when the inner diameter of the base plate (diameter of the center hole) is usually 40 mmφ, and when the inner diameter of the base plate is reduced to 40 mmφ or less depending on the size of the workpiece. And the outer diameter is proportionally 20
It may be as small as ~ 30mm φ.

The diamond cutting wheel for cutting a rare earth magnet according to the present invention is applied particularly to a rare earth sintered magnet of R-Co type or R-Fe-B type (where R is at least one of rare earth elements including Y). If so, the effect of the present invention is remarkably exhibited and is very effective. These magnets are manufactured as follows. R-Co based rare earth sintered magnets are RCo ₅ based, R ₂ C
o Although there are ₁₇ series, etc., most of the
₂ Co ₁₇ system. R ₂ Co ₁₇ rare earth sintered magnets are usually 20 to 28% R, 5 to 30% Fe, 3 to 3% by weight.
10% Cu, 1 to 5 percent of Zr, and the balance Co, firstly dissolved materials were weighed metal, cast, pulverizing the obtained alloy to an average particle size of 1 to 20 [mu] m, R ₂ Co ₁₇ A magnetic powder is obtained. Then molded in a magnetic field, 1100-1250 ℃
Sintering for 0.5-5 hours, then 0-50 ° C above sintering temperature
The solution is solutioned at a low temperature for 0.5 to 5 hours, and is finally aged. The aging treatment is usually carried out at 700 to 950 ° C. for a certain period of time as the first stage aging, followed by continuous cooling or multi-stage aging.

R-Fe-B based rare earth sintered magnets usually have a weight percentage of 5 to 40% R, 50 to 90% Fe, 0.2 to 8%.
B, to improve magnetic properties and corrosion resistance,
C, Al, Si, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, Z
In many cases, additional elements such as r, Nb, Mo, Ag, Sn, Hf, Ta, and W are added. The added amount of these additional elements is 30 for Co.
Usually, the content is not more than 8% by weight in the case of other elements. Addition of more than this will adversely degrade the magnetic properties. The method for producing an R-Fe-B rare earth sintered magnet is as follows. First, a raw metal is weighed, melted and cast, and the obtained alloy is finely pulverized to an average particle size of 1 to 20 μm.
A magnetic powder is obtained. Then molded in a magnetic field, 1000-1200
It is manufactured by sintering at 0.5 to 5 hours at ℃ and further aging at 400 to 1000 ° C.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The operation of the present invention is achieved by forming the base plate of the outer peripheral cutting blade into a donut-shaped perforated thin disk made of cemented carbide and further providing an abrasive layer of diamond powder on the outer peripheral cutting edge portion. Even with a thin outer peripheral blade, the rare-earth magnet can be cut stably with high precision over a long period of time, which can contribute to a reduction in cutting cost and an improvement in material yield.

[0014]

EXAMPLES Hereinafter, embodiments of the present invention will be specifically described with reference to examples and comparative examples, but the present invention is not limited to these. (Example 1, Comparative Example 1) A cemented carbide having a Young's modulus of 58000 kgf / mm ² (composition of WC-90 / Co-10% by weight) is 125 mmφ × 40
The plate was machined into a doughnut-shaped perforated thin disk having a diameter of 0.4 mm and a diameter of 0.4 mm. 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 grindstone-shaped mold, and a thermosetting phenol resin is used as a binder on the outer periphery thereof, and artificial diamond having an average particle diameter of 150 μm is 25% by volume ratio (abrasive particles). twenty five
%, Resin 75%), then form into a whetstone shape by pressing, and leave it in the mold
Heat-cured at 180 ° C for 2 hours, cooled, and blade thickness on lapping machine
Finished to 0.5 mm to make a diamond grindstone peripheral edge for rare earth magnets.

As Comparative Example 1, the same shape as in Example 1 was used.
Using a grinding wheel base plate made of SKD (alloy for tool JIS), fix diamond abrasive grains in the same manner as above, and use a 0.5 mm blade thickness SKD.
A diamond grinding wheel was manufactured.

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. FIG. 3A shows the relationship between the number of cut pieces and the change in dimensions, and FIG. 3B shows the relationship between the number of cut pieces and the cutting accuracy indicated by the parallelism. The cutting test was performed under the following conditions. The two outer peripheral blades of Example 1 and the two outer peripheral blades of Comparative Example 1 were assembled into a multi at 1.5 mm intervals, and the rotation speed was 5000 rpm.
The object was cut at a cutting speed of 12 mm / min. The cut area of the Nd-Fe-B based rare earth sintered magnet to be cut is 40 mm wide × 20 mm high. The thickness of the center of the rare earth magnet and the four corners of the rare-earth magnet cut by two outer blades every 50 sheets from the start of cutting is measured with a micrometer, and the value at the center is cut. It is regarded as the size of the rare earth magnet obtained, and the difference between the maximum value and the minimum value of the five points is defined as the parallelism, that is, the cutting accuracy. The target dimensions of the rare earth magnet after cutting are 1.4 mm in thickness.
It is. As is apparent from FIG. 3, a diamond grindstone for a rare earth magnet, in which a diamond abrasive grain is fixed to the outer periphery using a base plate made of a cemented carbide as an outer cutting blade for an Nd—Fe—B or rare earth sintered magnet. It has been confirmed that the use of No. 1 enables accurate cutting even with a small blade thickness and stable cutting over a long period of time.

(Example 2, Comparative Example 2) Young's modulus 50,000 kgf
/ mm ² cemented carbide (WC-80 / Co-20% by weight)
It was processed into a donut-shaped perforated thin disk disk of 80 mmφ × 40 mmφ × 0.3 mm 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, except that Cu −
Using a powder having a composition of 70 / Sn-30% by weight, a powder obtained by mixing artificial diamond having an average particle diameter of 100 μm and cBN in a weight ratio of 1: 1 as abrasive grains in a volume ratio of 15% (abrasive grains 15%) was used.
%, Metal binder 85%). The heating and sintering after pressing was performed at 700 ° C. for 2 hours, followed by finishing, thereby obtaining a diamond grinding stone outer peripheral blade for a rare earth magnet having a blade thickness of 0.4 mm.

As Comparative Example 2, the same shape as in Example 2 was used.
Using a SKH (high-speed steel) grindstone base plate, the diamond abrasive grains were fixed in the same manner as in Example 2, and the SKH with a 0.4 mm blade thickness was used.
A diamond grinding wheel was manufactured.

A cutting test similar to that of Example 1 was performed using the outer peripheral blades prepared in Example 2 and Comparative Example 2 and using an Sm-Co-based rare earth sintered magnet as an object to be cut. FIG. 4A shows the relationship between the number of cut pieces and the change in dimensions, and FIG. 4B shows the relationship between the number of cut pieces and the cutting accuracy indicated by the parallelism. The cutting test conditions were as follows: the cutting blades were cut into multiple pieces with a 1.0 mm gap between the two cutting blades (the target size of the rare earth magnet after cutting was 0.9 mmt), the number of revolutions was 5,000 rpm, and the cutting speed was 8 mm / min. The cut area of the Sm-Co based rare earth sintered magnet to be cut is 50 mm width x height
10 mm.

(Example 3, Comparative Example 3) Young's modulus 55,000 kgf
/ mm ² of cemented carbide (WC-85 / Co -15% by weight of the composition)
It was processed into a donut-shaped perforated thin disk disk of 150 mmφ × 40 mmφ × 0.5 mm to obtain a grindstone base plate. Next, a natural diamond having an average particle diameter of 50 μm is set on the outer periphery of the grindstone base plate, and the diamond abrasive grains are fixed by an electroplating method using a Ni watt bath. The outer edge was used. The plating thickness was controlled by the time of electroplating, and the volume ratio of diamond abrasive grains in the abrasive grain layer was adjusted to be 40% (abrasive grains 40%, Ni plating 60%).

As Comparative Example 3, the same shape as in Example 3 was used.
Using a SKH (high-speed steel) grindstone base plate, the diamond abrasive grains were fixed in the same manner as in Example 3, and the SKH with a blade thickness of 0.6 mm was used.
A diamond grinding wheel was manufactured.

A cutting test was performed in the same manner as in Example 1 except that the Nd-Fe-B-based rare earth sintered magnet was used as an object to be cut using the outer peripheral blades manufactured in Example 3 and Comparative Example 3. FIG. 5A shows the relationship between the number of cut pieces and the dimension, and FIG. 5B shows the relationship between the number of cut pieces and the cutting accuracy. The cutting test conditions were as follows: the cutting blades were assembled into a multi-piece with the spacing between the two cutting blades at 1.8 mm (the target size of the rare-earth magnet after cutting was 1.7 mm), the rotation speed was 5500 rpm, and the cutting speed was 15 mm / min
The cutting object was cut with. Nd-Fe-B which is the object to be cut
The cut area of the rare earth sintered magnet is 50 mm wide x 30 mm high.

[0023]

By cutting a rare earth magnet using the diamond wheel outer peripheral blade of the present invention, cutting can be performed for a long period of time while maintaining the cutting accuracy even with a small blade thickness, and the cutting margin can be minimized. The material yield can be improved, and its industrial value is extremely high.

[Brief description of the drawings]

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

FIG. 2 is a drawing showing the structure of an outer peripheral blade. (A) is a top view, (b) is a vertical cross-sectional view taken along line BB, and (c) is an enlarged view of an outer peripheral end portion.

FIG. 3 is a drawing showing (a) the relationship between the number of cuts and the cutting dimension and (b) the relationship between the number of cuts and the cutting accuracy in Example 1 and Comparative Example 1.

FIG. 4 is a drawing showing (a) the relationship between the number of cuts and the cutting dimension and (b) the relationship between the number of cuts and the cutting accuracy in Example 2 and Comparative Example 2.

FIG. 5 is a drawing showing (a) the relationship between the number of cuts and the cutting dimension and (b) the relationship between the number of cuts and the cutting accuracy in Example 3 and Comparative Example 3.

[Description of sign]

 1 inner peripheral blade, 2 outer peripheral blade, 3 wheel base plate, 4 abrasive layer, 5 blade thickness or cutting allowance

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification code FI B28D 1/24 B28D 1/24 (56) References JP-A-1-164563 (JP, A) JP-A-62-292366 (JP) JP-A-5-92420 (JP, A) JP-A-6-238563 (JP, A) JP-A-2-251113 (JP, A) JP-A-2-252219 (JP, A) 52-15834 (JP, B1) (58) Fields investigated (Int. Cl. ⁶ , DB name) B24D 5/12 B24D 3/00 310 B24D 3/00 320 B24D 3/00 350 B24D 5/00 B28D 1 / twenty four

Claims (6)

(57) [Claims] 1. A diamond grinding wheel for cutting a rare earth magnet, wherein a base plate constituting the cutting edge is made of a cemented carbide.
Of a donut-shaped perforated thin disk , and a diamond-based abrasive powder in a volume ratio of 10 to 10
An outer peripheral edge of a diamond grindstone for cutting rare earth magnets, characterized by containing 80%. 2. The cemented carbide has a Young's modulus of 45,000 to 700.
2. The outer peripheral edge of the diamond grindstone for cutting rare earth magnets according to claim 1, wherein the outer diameter is 00 kgf / mm ² . 3. The rare earth magnet according to claim 1, wherein the diamond-based abrasive powder comprises natural or synthetic industrial diamond powder, cBN powder, or a mixture thereof, and has an average particle diameter of 10 to 500 μm. Outer edge of diamond wheel for cutting. 4. The base plate of the outer peripheral blade is a thin plate having an outer diameter of 250 mm or less and a thickness of 0.1 to 1 mm.
3. The outer peripheral edge of the diamond grindstone for cutting a rare earth magnet according to any one of 3. 5. The rare earth magnet according to claim 1, wherein said rare earth magnet is R-Co based or R-Fe-
B type (where R is at least one of rare earth elements including Y
The rare-earth sintered magnet according to any one of claims 1 to 4, wherein the diamond grindstone is an outer peripheral blade for cutting a rare-earth magnet. 6. A diamond for cutting a rare earth magnet according to claim 1.
The method for cutting a rare earth magnet Ru using command grindstone peripheral cutting edge.