KR900006532B1 - Making method for permanent magnets - Google Patents

Abstract

Hard magnets are produced by melting an alloy of 8-30 atom.% rare earth metal; 2-28 B; max 50 Co; max 15 Al; balance Fe plus unavoidable impurities, casting into a block and heat-treating at min 250 deg.C to obtain fine crystals which are aligned in a special direction to harden the magnet. Heat treatment is carried out at 500 deg.C or more. The alloy can be atomised due to its property of easily forming fine grains by hot working and each particle contg. several magnetic R2Fe14B grains with R being a rare earth metal. The powder is mixed with an organic binder and hardened in a power metallurgical method. The magnet is produced at l ow cost.

Description

Manufacturing method of permanent magnet

1 is a manufacturing process of the R-Fe-B magnet according to the invention.

2 is an alignment process diagram of a self-alloy by extrusion hot working.

3 is an alignment process diagram of a magnetic alloy by rolling hot working.

4 is an alignment process diagram of a self alloy by stamping hot working.

* Explanation of symbols for the main parts of the drawings

1: hydraulic press 2: die

3: self alloy 4: arrow indicating pressure

5: Arrow indicating direction of magnetization of self alloy

11: Row 12: Self Alloy

13: Arrow indicating the direction of rotation of the roll

14: arrow indicating the direction of movement of the self alloy

15: arrow indicating easy magnetization direction

21: stamp 22: self-alloy

23: base 24: arrow indicating the direction of easy magnetization

25: arrow indicating vertical movement of stamp

26: An arrow indicating the direction of movement of the base plate.

The present invention relates to a rare earth-Fe-based permanent magnet.

At present, the following three methods are practically used to manufacture R-Fe-B magnets.

(1) Sintering method based on powder metallurgy (reference number 1).

(2) A method of preparing a quenched ribbon piece having a thickness of about 30 microns using a molten spin apparatus for producing an amorphous pulse alloy, and producing a magnet from the ribbon piece using a resin bonding technique (reference number 2).

(3) A method of mechanically aligning a ribbon piece prepared by the method (2) using a two-step hot press technique.

Reference number 1; Published on March 15, 1984. Sagawa, S. Fujimura, Endogawa, E. Yamamoto, Y. Matsuura's "Applied Physics in Japan" vol. 55 (6), Volume 2083

Ref. 2: R. Double U. Lee's Applied Physics, published April 15, 1985, vol. 46 (8), page 790

The above-described prior art technique is described below with reference to each reference.

In the sintering method of (1), an alloy ingot is formed by melting and casting, and the ingot is pulverized into a fine powder having a particle diameter of about 3 microns. Next, the magnetic powder is mixed with an adhesive provided as a mold additive and press molded in a magnetic field to obtain a molded body. The molded body is sintered in an argon atmosphere at about 1100 ° C. for 1 hour and then quenched to room temperature. After sintering, the molded body is heat treated at about 600 캜 to increase the intrinsic coercive force.

In the method (2), the quenched ribbon pieces of the R-Fe-B alloy are prepared using a melt spinning apparatus that spins at the optimum substrate speed. The pieces thus obtained are 30 micron-thick ribbons and consist of agglomerates of crystal grains up to 1000 angstroms in diameter. This ribbon piece is vulnerable to burial and magnetically isotropic because its grains are distributed isotropically. The ribbon piece is crushed into particles of a suitable size, the particles are mixed with a resin, and press molded. At this time, the raw material is filled up to 85% by volume under a pressure of about 7ton / cm ² .

In method (3), this rapidly quenched ribbon piece is placed into graphite or other suitable hot die preheated to about 700 ° C. in a vacuum or inert gas atmosphere.

When the temperature of the ribbon piece rises to a predetermined temperature, a single direction of pressure is applied to the ribbon piece. Although the conditions of the temperature of 725 25 degreeC and the pressure of P-1.4 ton / cm <2> are suitable for obtaining sufficient baking, temperature and time are not restrict | limited. At this time, the crystal grains of the magnet are slightly aligned in the press direction but are isotropic as a whole.

Next, a hot pressing step is performed using a large cross section die. The most common press condition is to press for several seconds at a pressure of 0.7 ton / cm 2 at a temperature of 700 ° C. At this time, the thickness of the material is reduced to half of the initial thickness, and self-alignment is performed parallel to the press direction, so that the alloy becomes anisotropic.

This process is referred to as the "two stage hot press process". This process is used to make high density anisotropic R-Fe-B magnets.

Here, it is preferable to make the particle size of the grains of the ribfunn initially prepared by the melt spinning method to be slightly smaller than the grain diameter at which the maximum intrinsic coercive force appears. Because the grains become somewhat coarse during the hot press process, if the grain size of the crystal is slightly smaller than the optimum diameter before the hot fresce process, it will be optimal after the treatment.

Although the R-Fe-B magnets can be made by the techniques of the above and the prior art, these techniques have some disadvantages.

In the sintering method of (1), the alloy must be made into fine powder. However, since the R-Fe-B based alloy reacts very well with oxygen, the R-Fe-B based alloy is oxidized that much easier. Therefore, the oxygen concentration of the sintered compact becomes unavoidably high.

In addition, when molding the powder, an additive such as zinc stearate is required. Although these additives are removed before the sintering process, some of the additive remains in the magnet in the form of carbon. This carbon greatly deteriorates the magnetic performance of R-Fe-B.

Molded articles which are press-molded with the addition of molding additives are called "raw bodies" which are easily broken and very difficult to handle. Therefore, placing the green body in the preferred order in the sintering furnace is a big headache, and this is a big disadvantage.

Due to the above disadvantages, an expensive device is required to manufacture the R-Fe-B-based sintered magnet. In addition, magnets of this type are expensive to manufacture because of their extremely low productivity.

Therefore, the sintering method (1) is not a method that makes good use of the advantages of the low raw material cost of the R-Fe-B-based magnet.

In the methods (2) and (3), a vacuum molten spinning device is used. Currently, this device is unproductive and expensive.

In the method (2), the crystal of the final magnet is isotropic, so the energy is low, and the area of its hysteresis loop is undesirable. Therefore, the magnet produced by the method (2) has a bad temperature coefficient and is disadvantageous in practical use.

The method (3) is unique in that hot work is performed in two steps. However, it is undeniable that this method is very inefficient.

An object of the present invention is to eliminate the disadvantages of the prior art as described above, and to provide a high performance rare earth-Fe-based permanent magnet at a low price.

According to the present invention, the rare earth-Fe-based permanent magnet has an atomic percent of R of 8 to 30, an atomic percent of B of 2 to 28, an atomic percent of Co of 50 or less, an atomic percent of Al of 15 or less, and the balance of Fe And hot-rolling the ingot at a temperature of 500 ° C. or higher to melt the alloy composed of other impurities inevitably included in the manufacturing process, to cast the alloy, to refine the grain of the ingot, and to align the grain axis in a specific direction. It is provided by a process that makes the main alloy magnetically anisotropic by processing.

In addition, according to the present invention, in order to improve the magnetic properties of the final magnet and, in particular, to increase the intrinsic coercivity, the initial raw material has an atomic percentage of R 8 to 25, an atomic percentage of B 2 to 8, and atoms of Co The percentage is 40 or less, the atomic percentage of Al is 15 or less, and the remainder is composed of Fe and other impurities which are inevitably included in the manufacturing process, and is a cast magnetic alloy which is hardened magnetically by heat treatment at a temperature of 250 ° C or higher.

In the case of the resin-bonded magnet, the alloy of the composition is ground using the property of easily producing a hydrogenated compound, the fine powder is mixed with an organic additive, and then cured to obtain a resin-bonded magnet.

In order to obtain a resin-bonded magnet with ordinary fine powder, the crystal grains are easily fined by hot working, and after the fine powder, powders are prepared using the property that each grain of the powder contains a large number of magnetic R ₂ Fe ₁₄ B crystal grains. This powder is mixed with an organic adhesive and then cured to obtain a resin bonding magnet.

As already described, the existing methods for producing the rare earth-Fe-based permanent magnets, that is, the sintering method and the hardening method, each have their own significant determination that the powder is difficult to handle and the productivity is poor. In order to eliminate these disadvantages, the inventors of the present invention have studied the self-hardening in the volume state and oscillated as follows. next; (1) In the composition range of the alloy dried in the present invention, the alloy becomes fine by hot working and becomes anisotropic. (2) The sufficient intrinsic coercive force in the composition range of the alloy according to the present invention is obtained only by heat treatment in the ingot state.

The ingot of (3) (2) is finely divided into powder by hydrogen decreplication, the powder is mixed with an organic adhesive, and the mixture is cured to obtain a resin bonded magnet. (4) Since the ingot after the hot working is composed of many fine grains, the finely divided powder also has a large number of fine grains, and thus a resin bonding magnet is obtained.

In the process of the invention, the hot working to make the ingot anisotropic is only one step, not two steps as in the hardening method described in reference 2.

In addition, since the grains are made fine, the intrinsic coercive force of the workpiece is significantly increased. In addition, there is no need to fine-tune the cast ingot, so the equipment cost is reduced because there is no need to strictly control the atmosphere for sintering. The resin-bonded magnet obtained by the method of the present invention is not isotropic as originally obtained by the conventional quenching method, but it is another advantage of the present invention that an anisotropic resin-bonded magnet is easily obtained. Therefore, the advantage of the high performance and low cost R-Fe-B magnet can be fully utilized.

A similar paper on the magnetization of alloys by volume was presented by Hiroaki Miho et al. (August 1985, Japanese Metal Society Lecture, Lecture No. 544). However, this paper relates to a small sample having a composition of Nd _16.2 Fe _50.7 Co _22.6 V _1.3 B _9.2 extracted with a sample of molten air and exposed to an argon gas spray.

Therefore, in the study of this paper, it is thought that the effect of the crystal grains refined by hardening is obtained by chance because it is a small amount of sample.

We have found through experiments that the grains of Nd ₂ Fe ₁₄ B, the main phase in the composition of this paper, are coarser when cast by conventional casting methods. Although it is possible to produce alloys with anisotropic Nd _16.2 Fe _50.7 Co _22.6 V _1.3 B _9.2 by hot working, it is quite difficult to obtain sufficient intrinsic coercivity with the permanent magnets made from the final body.

In addition, in order to obtain a magnet having a layered intrinsic coercivity even by a conventional casting method, a composition having a low B of the initial material composition, that is, an atomic percentage of R is 8 to 25, and an atomic percentage of B is 2 to 8, It has been found that atomic percentage is less than 50, Al atomic percentage is less than 15, and the balance should be Fe and other unavoidable impurities.

In the prior art it is believed that the typical optimal composition of R-Fe-B based magnets is R ₁₅ Fe ₇₇ B ₈ as shown by reference number 1. This composition is richer in R and B than the composition in which R _11.7 Fe _92.4 B _5.9 has the same atomic percentage as the main phase R ₂ Fe ₁₄ B compound. This is explained by the fact that in order to obtain sufficient intrinsic coercivity, not only the main phase but also the nonmagnetic phase, which is R rich and B rich, are required.

In the composition of the alloy according to the invention, when B is less than in the normal composition, the intrinsic coercive force is superficial. In general, such a low B composition greatly reduces the intrinsic coercive force when the sintering method is performed.

Therefore, this composition range was not considered very much.

However, in the composition range according to the present invention, a high intrinsic coercive force is obtained by a conventional casting method, and inherent coercive force is not sufficient in a composition rich in B, which is the main composition range for the sintering method.

The reason is considered as follows. First, by the sintering method or casting method of the present invention, the intrinsic coercive mechanism of the magnet is essentially in accordance with the nucleation model. This is evidenced by the fact that the initial magnetization curves of the magnets produced by the two methods show a sharp increase, for example as in the initial magnetization curve of SmCo ₅ . This magnet of Hengtae has inherent coercive force according to the single domain structure. That is, if the grains of the R ₂ Fe ₁₄ B compound having large crystal magnetic anisotropy are too large, magnetic walls are generated in the crystal grains, and therefore, the movement of the magnetic walls causes reverse magnetization to be easily reversed, thereby reducing the intrinsic coercivity. On the other hand, if the grains of the R ₂ Fe ₁₄ B compound are smaller than a certain size, the magnetic domain wall disappears from the grains. In this case, the inversion of the magnetic field occurs only by the rotation of the magnetic field, so the intrinsic coercivity decreases.

Therefore, in order to obtain a layered intrinsic coercive force, it is required that the R ₂ Fe ₁₄ B phase has a suitable grain diameter, that is, about 10 microns. When carrying out the sintering method, the diameter of the crystal grains can be suitably adjusted by adjusting the diameter of the powder before sintering. However, using the sintering method, the grain diameter of the R ₂ Fe ₁₄ B compound is determined when the liquid raw material solidifies. Therefore, it is necessary to carefully control the composition and solidification process.

In particular, the composition is important. If B contains more than 8 atomic percent, the grains of the R ₂ Fe ₁₄ B phase in the magnet after casting are much easier to size than 100 microns. In this case, therefore, it is difficult to obtain sufficient intrinsic coercive force in the casting state without using the hardening apparatus as used in Reference 2. In contrast, in the composition range where B is small, the diameter of the crystal grains of the magnet is easily reduced by adjusting the type of mold, the molding temperature and the like.

In either case, however, the grains of the main phase R ₂ Fe ₁₄ B become finer by performing hot working, thus increasing the intrinsic coercive force of the magnet after hot working.

The composition range having sufficient intrinsic coercive force in the cast state, that is, the composition range having less B, may be said to be a composition rich in Fe. In the solidified state, Fe first appears as a first crystal, and then the R ₂ Fe ₁₄ B phase appears by the siphoning reaction. At this time, since the cooling rate is considerably larger than the equilibrium reaction rate, the sample shows that the R ₂ Fe ₁₄ B phase is primary. Since the composition range of B is small, the B-rich phase seen in the magnet of R ₁₅ Fe ₇₇ B ₈ , which is a typical composition suitable for the sintering method, is inevitably too straight so that B Rich images are almost ignored.

The heat treatment in the present invention is to diffuse the primary Fe to reach an equilibrium state. Therefore, the intrinsic coercive force of the final magnet depends greatly on the diffusion of Fe.

Next, the resin bond in this invention is demonstrated.

The resin bonding magnet is actually manufactured by the hardening method of reference numeral 2. However, since the powder obtained by the quenching method is composed of polycrystalline isotropic agglomerates having a diameter of 1000 angstroms or less, the powder is magnetically isotropic. Therefore, anisotropic magnets cannot be obtained and the advantages of inexpensive and high-performance R-Fe-B magnets cannot be exploited by the hardening method. When preparing an R-Fe-B-based magnet, the intrinsic coercive force of the magnet is kept sufficiently high by differentiating with hydrogen decreplication which hardly causes mechanical twist, and thus resin bonding can be realized. The main advantage of this method is that, unlike the reference 2, it is possible to prepare an anisotropic magnet.

Finally, the resin bonding magnet of the present invention will be described.

There are two reasons why a resin-bonded R-Fe-B magnet can be prepared only by a specific differential method.

First, it should be noted that the critical radius of the single domain of the R ₂ Fe ₁₄ B compound is much smaller than the critical radius of SmCo ₅ and the like, so that it is ultra-micron level.

It is extremely difficult to differentiate the raw materials up to such small grain diameters with ordinary mechanical fines. In addition, the powder obtained is so active that it oxidizes and ignites very easily. Therefore, the unique coercive force of the final magnet is very small because of the grain diameter. We have studied the relationship between grain size and final intrinsic coercive force. As a result, the intrinsic coercive force was at most KOe, and it did not increase even when the magnet was surface treated.

Another problem is the torsion caused by mechanical processing. For example, if a magnet having a natural coercive force of 10 KOe in the sintered state is mechanically finely divided, the final powder having a grain diameter of 20 to 30 microns has a coercive force lower than 1 KOe. When mechanically differentiating an SmCo magnet, which is thought to have a similar nucleation model, such a reduction in intrinsic coercivity does not occur, but a powder with sufficient coercivity is easily produced. Due to the above phenomena, the effects of torsion and the like caused by differentiating and processing the R-Fe-B magnets are spread to a great extent. This effect is a significant problem when cutting small magnets, such as for rotor magnets in clock step motors, from sintered magnet masses.

For the same reason as above, that is, the critical radius is small and the effect of mechanical torsion is large, so that the resin bonded magnet cannot be obtained by the normal fine powder. In order to obtain a powder having a sufficient intrinsic coercivity, a powder having a plurality of R ₂ Fe ₁₄ B grains must be prepared as described in reference numeral 2. However, the quenching method of reference 2 has a problem in productivity. In addition, it is practically impossible to prepare this kind of powder by pulverizing the sintered body. Because, during sintering, the grain grows and becomes large to some extent, so it is necessary to finally make the grain diameter smaller than the desired diameter before sintering. However, if the powder size of the powder is considerably small, the oxygen concentration of the powder is extremely high, and the performance of the magnet becomes unsatisfactory.

Thus, after sintering, the permissible grain diameter of the R ₂ Fe ₁₄ B compound is about 10 microns. However, after differentiation, the intrinsic coercive force decreases to almost zero.

The inventors then became interested in miniaturizing the grains by hot working. It is relatively easy to make the R ₂ Fe ₁₄ B compound in the shaped state of approximately constant size grains prepared by sintering. Therefore, by hot working a cast mass containing such grain size R-Fe-B phase, the grains are made finer and aligned, and then finely divided. Since the grain diameter of the powder for the resin-bonded magnet is between 20 and 30 microns, it is possible to include a plurality of R ₂ Fe ₁₄ B grains in the powder in the same manner as above. In this way, a powder having sufficient intrinsic coercivity is obtained. In addition, the final powder thus obtained can be aligned in a magnetic field rather than isotropic as powder obtained by the quenching method of reference number 2, and therefore, an anisotropic magnet is prepared into this type of powder. Of course, if the grains are differentiated by hydrogen decrementation, the intrinsic coercivity remains better.

The reason for selecting the composition of the permanent magnet of the present invention is described below.

For example, one or a compound selected from the rare earth elements Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Td, Dy, Mo, Tm, Yb, and Lu is used. The highest magnetic performance is obtained when selecting Pr. Therefore, for practical use, Pr, Pr-Nd alloy, Ce-Pr-Nd alloy and the like are used.

Sometimes, small amounts of heavy earth additives such as Dy, Tb, Al, Mo, Si, etc. are required to increase the intrinsic coercive force.

The main phase of the R-Fe-B magnet is R ₂ Fe ₁₄ B. If R is less than 8 atomic percent, the above compounds do not appear and a body-centered cubic structure such as α-iron is shown. As a result, high magnetic properties are not obtained. On the other hand, if R is more than 30 atomic percent, the amount of nonmagnetic R-rich phase increases, leading to extremely poor magnetic properties. Thus, a suitable range of R amounts is between 8 and 30 atomic percent. However, a better range of R for cast magnets is between 8 and 25 atomic percent.

B is an essential element to reveal R ₂ Fe ₁₄ B. If B is 2 atomic percent or less, a rhombohedral R-Fe system appears, and as a result, high intrinsic coercive force is not obtained. However, according to the magnet produced by the sintering method of the prior art, if the amount of B is 28 atomic percent or more, the phase in which the nonmagnetic B is enriched increases, and the residual magnetic flux density is significantly reduced. The upper limit of the preferred amount of B for a molded magnet is 8 atomic percent. If B is 8 atomic percent or more, a fine R ₂ Fe ₁₄ B phase is not obtained unless specific cooling is performed, and the intrinsic coercive force is low.

Co is an efficient element for increasing Curie Point, and has the effect of producing R ₂ Fe ₁₄ B by essentially replacing sites of Fe element. However, this R ₂ Fe ₁₄ B compound has a small crystalline anisotropic region, and as the amount of the compound R ₂ Fe ₁₄ B increases, the intrinsic coercive force of the magnet decreases. Therefore, to obtain coercive force of 1 KOe or more deemed sufficient for permanent magnets, Co must be 50 atomic percent or less.

Is referenced 4; It has the effect of increasing the intrinsic coercivity, as described in the 8th International Research Society Bulletin of Rare Earth Magnets, Shang Maokai et al., 1985, P541. Although the same effect appears in the case of cast magnets, this reference number 4 shows only the Al effect in the case of sintered magnets.

However, since Al is a nonmagnetic element, if the amount of Al is large, the residual magnetic flux density decreases, and if the amount of Al is more than 15 atomic percent, the residual magnetic flux density decreases to the light ferrite level. Such a magnet does not realize the high performance purpose as a rare earth magnet. Therefore, the amount of Al is preferably 15 atomic percent or less.

Example 1

Reference is made to FIG. 1, which shows a process for manufacturing a permanent magnet according to the present invention.

First, an alloy of the desired composition is melted in an induction furnace and cast into a die. At this time, in order to give anisotropy to a magnet, various types of hot working are performed to a sample. In this embodiment, the liquid dynamic compacting method, which has a great effect of making the crystal grains fine by quenching rather than the general molding method (see Fig. 5; TSChin et al., J. APPl. Phys. 59 ( 4), 15 February, 1986, P 1297).

The hot working method used in this example is one of (1) extrusion type (FIG. 2), (2) rolling type (FIG. 3), and (3) stamping type, and is performed at a temperature of 1000 DEG C, respectively.

In the extrusion type, a means for applying pressure to the sample from the side of the die is also provided in order to pressurize the sample isostatically. In the rolling and stamping molds, the rolling or stamping speed is controlled to minimize the strain. In either type of method, the easy axis of magnetization of the grains is aligned parallel to the direction in which the alloy is forced.

An alloy of the composition as shown in Table 1 was melted to produce a magnet by the process shown in FIG. In hot working, the temperature is controlled to 1000 ° C., the strain is between 10 ⁻³ and 10 ⁻² per second and the reduction rate is 80%. After hot working, annealing is performed at 1000 ° C. for 24 hours.

TABLE 1

TABLE 2

From Table 2, it can be seen that the residual magnetic flux density increases by any method of extrusion, rolling and stamping-type hot working, and thus the samples are magnetically anisotropic.

Example 2

This embodiment is a general casting method.

First, an alloy having a composition as shown in Table 3 is melted in an induction furnace and cast into a die made of iron. The hot working is then performed at 1000 ° C. using hot pressing, where the strain is adjusted to 10 ⁻³ to 10 ⁻² per second and the reduction rate is 80%. Then, annealing is performed at 1000 ° C. for 24 hours. After annealing, the average grain diameter of the sample is about 15 microns.

In a cast magnet, the surface anisotropic magnet which uses the anisotropy of columnar area | region is obtained by processing a sample to a desired shape, without hot working. In the resin-bonded magnet, the sample was repeatedly finely divided into hydrogen absorption at a pressure of about 10 atm and discharge of hydrogen at a pressure of 10 ⁻⁵ torr in a 18-8 stainless steel vessel at room temperature. Kneaded. Next, the green compact is molded in a magnetic field of 10 KOe applied perpendicularly to the pressing direction.

The properties of this final magnet are shown in Table 4.

TABLE 3

TABLE 4

In the casting mold, (BH) max (maximum energy) and iHc (intrinsic coercive force) are greatly increased by hot working. This is because the grains are aligned by hot working and the area of the BH curve is significantly improved. On the other hand, according to the hardening method of reference number 2, iHc tends to be lowered by hot working. Therefore, it is one of the great advantages of the present invention that the intrinsic coercivity is greatly improved.

Table 5 shows the relationship between strain and magnetic properties. As a representative example, two alloys of the composition as shown in Table 5 are melted in an induction furnace and cast into a die made of iron. It is then hot pressed at various speeds. The results are shown in Table 5. In this case, the temperature is adjusted to 1000 ° C., and the reduction rate is 80%. After hot pressing, the annealing treatment is performed at 1000 ° C. for 24 hours.

As can be seen in Table 3, when the strain is less than 10 ^-4 per second, the intrinsic coercivity decreases extremely. The reason for this is considered to be that the growth of the crystal grains is promoted by heat and the volume becomes large. On the other hand, when the strain rate is too small, productivity decreases and manufacturing cost increases. When the strain is greater than 1 per second, some samples crack because of their composition and such samples cannot be prepared. Thus, the preferred strain is 10 ⁻⁴ to 1 per second, and more preferably 10 ⁻³ to 10 ⁻¹ per second in order to have good magnetic properties.

TABLE 5

As a representative example, three alloys of the compositions shown in Table 6 are melted in an induction furnace and cast into a die made of iron. Then, hot working is carried out by pressing method at various temperatures, and annealing treatment is performed at 1000 ° C. for 24 hours. The relationship between the manufacturing temperature, the intrinsic coercive force, and the C-axis directional ratio is shown in Table 6. The strain is adjusted from 10 ^-3 to 10 ^-2 per second, with a reduction of 80%.

In addition, the C-axis directional ratio represents the ratio (volume percentage) of the easy axis of magnetization of the grains (corresponding to the C-axis of the permanent magnet of the present invention) having the same direction. The larger this empty, the finer anisotropic magnet can be obtained.

As shown in Table 6, if the manufacturing temperature is 500 ℃ or more, the sample is cracked and cannot be manufactured. In order to obtain excellent magnetic properties, the C-axis directional ratio is preferably 80%. In this case, the manufacturing consistency should be between 800 ° C and 1100 ° C. However, if the temperature is 1100 ° C., the intrinsic coercivity is extremely reduced. Thus, more preferred production temperatures are between 800 ° C. and 1050 ° C.

TABLE 6

X: A sample cannot be manufactured. (Triangle | delta): A sample cracks and cannot be measured.

The alloy of the composition shown in Table 7 is melted and cast in the same manner as in Table 6. Next, a hot working in which the reduction rate is varied at a temperature of 1000 ° C., in this case, extrusion is performed. Then annealing for 24 hours at a temperature of 1000 ℃. Table 7 shows the relationship between the reduction ratio, the natural coercive force, and the C-axis directional ratio. In addition, the strain is adjusted from 10 ⁻³ to 10 ⁻² per second. As shown in Table 7, if the C-axis directional ratio is required above 80%, the reduction ratio should be above 60%.

TABLE 7

As described above, according to the present invention, a permanent magnet having sufficient intrinsic coercive force is obtained by performing only hot working without finely injecting ingots as in the usual sintering method.

Moreover, in the present invention, the hot working is only one step and not this step as the hardening method, and has the effect of making the magnet anisotropic as well as increasing the intrinsic coercive force.

Therefore, according to the present invention, the manufacturing process of the permanent magnet is considerably simplified compared with the sintering method or the hardening method in the prior art.

In addition, anisotropic resin-bonded magnets can also be made according to the present invention by subjecting the sample to hydrogen decrementation or fine grinding after hot working.

Claims (5)

In the method for producing a permanent magnet containing a rare earth element containing Y, iron and boron as a main component, the alloy containing the main component is melted and cast, and is subjected to 10 ^-4 to 1 per second at a temperature of 500 ° C or higher. And at least a step of hot working the alloy at a strain rate. The method of manufacturing a permanent magnet according to claim 1, further comprising a heat treatment step at a temperature of 250 ° C. or higher. The method of manufacturing a permanent magnet according to claim 1, further comprising a step of heat-treating the alloy, grinding the alloy, and mixing the final powder with an organic adhesive and pressing the same. The method of manufacturing a permanent magnet according to claim 1, further comprising a heat treatment step at a temperature between 800 ° C and 1050 ° C. The method of manufacturing a permanent magnet according to claim 1, further comprising a heat treatment process having a reduction rate of 60% or more.

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