JP2017135268A - Hybrid magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hybrid magnet in which decrease of coercive force is suppressed while increasing residual magnetic flux density.SOLUTION: In a hybrid magnet containing a first magnet material and a second magnet material, the first magnet material is a R-Fe-B-based alloy, the second magnet material is a Mn-Bi-based alloy, and when the volume ratio of the content of first magnet material and second magnet material is (100-a):(a), (a) is in a range of 5-80.SELECTED DRAWING: None

Description

The present invention relates to a hybrid magnet.

At present, neodymium magnets (Nd ₂ Fe ₁₄ B-based magnets) whose main component is the R—Fe—B-based alloy are the most expensive among rare earth magnets. It is unstable and has the disadvantage that the magnetic properties deteriorate with increasing temperature. Therefore, the maximum use temperature is about 150 ° C. and cannot be used in an environment where the temperature is high.

Therefore, MnBi-based magnets are attracting attention as magnets that do not contain expensive rare earth elements such as Nd and Dy among rare earth metal elements with a high resource procurement risk. This MnBi-based magnet material is well known in the field of magneto-optical recording, and its coercive force does not decrease even at high temperatures. Therefore, it is a promising magnet material as a bulk magnet, but has a drawback of low residual magnetic flux density.

As other promising magnet materials, there are only Co-based magnets (Sm ₂ Co _17- based magnets, SmCo _5- based magnets, FeCrCo-based magnets) and Sm ₂ Fe ₁₇ N _x- based bonded magnets in a temperature environment of 100 ° C. or higher. There is no current situation. Among these, the Co-based magnet is inferior in magnetic properties, is expensive, and has brittleness, so that it has the disadvantage that chipping and cracking are likely to occur. In addition, Sm ₂ Fe ₁₇ N _x has high magnetic characteristics, but has a disadvantage that it causes a disproportionation reaction at about 650 ° C. or more and decomposes into SmN + αFe. Therefore, it is generally impossible to produce a sintered body. Therefore, the Sm ₂ Fe ₁₇ N _x- based magnet is only a bonded magnet as a product, and has a defect that the residual magnetic flux density is lower than that of the Nd ₂ Fe ₁₄ B-based resin bonded magnet.

Further, Patent Document 1 and the like describe a hybrid magnet in which ferrite magnetic powder is mixed with rare earth magnet powder, but the technique of mixing this ferrite has a small saturation magnetization, and a large improvement in residual magnetic flux density cannot be expected. is the current situation.

JP 2003-59706 A

Therefore, a technical problem of the present invention is to provide a hybrid magnet that suppresses a decrease in coercive force while increasing a residual magnetic flux density as compared with an Nd ₂ Fe ₁₄ B resin bonded magnet.

The present invention relates to a hybrid magnet including a first magnet material and a second magnet material, wherein the first magnet material is an R—Fe—B alloy, and the second magnet material is Mn—Bi. It is a system alloy, and when the volume ratio of the content of the first magnet material and the second magnet material is (100-a): a, a is in the range of 5 or more and 80 or less. It is a hybrid magnet.

The reason why the hybrid magnet of the present invention is superior is that the second magnet material occupies the gap of the first magnet material instead of the resin binder, as compared with the Nd ₂ Fe ₁₄ B-based resin bonded magnet. This is because the residual magnetic flux density is improved as compared with the Nd ₂ Fe ₁₄ B resin bond magnet using Nd.

The Mn-Bi alloy, which is the second magnet material, is crystallographically because a hard magnetic alloy called a low temperature phase (LTP) exists as a main constituent phase and has a property of being easily plastically deformed. A magnet having a high relative density can be obtained simply by applying pressure with mechanical stress. Therefore, by combining with an R—Fe—B alloy, a hybrid magnet with improved relative density and improved residual magnetic flux density can be obtained.

In the hybrid magnet according to the present invention, it is preferable that the hybrid magnet further includes a metal binder containing at least one selected from Bi, Al, Cd, Ga, In, Pb, Sn, and Zn as a main component. By using such a metal binder, it becomes easier to plastically deform, the relative density of the magnet can be easily increased in the forming step, and the residual magnetic flux density can be increased.

According to the present invention, while improving the residual magnetic flux density than Nd 2 _Fe 14 _B based resin bonded magnet, it is possible to obtain a hybrid magnet suppressing a decrease in coercive force.

Preferred embodiments of the hybrid magnet according to the present invention will be described, but the present invention is not limited to the following embodiments.

The hybrid magnet according to the present invention is a hybrid magnet including a first magnet material and a second magnet material, wherein the first magnet material is an R—Fe—B alloy, and The magnet material is a Mn—Bi alloy, and the volume ratio of the content of the first magnet material and the second magnet material is (100-a): a, and a is in the range of 5 or more and 80 or less. It is a hybrid magnet characterized by being.

R-Fe-B based alloy that can be used for the first magnetic material in the present embodiment, component composition represented by _{R x Fe 100- (x + y} + z + u) M y B z L u, rare earth R is including Y M is at least one element selected from the elements, M is at least one selected from V, Cr, Mn, Co, Ni, Cu, Zn, Ga, Ge, Al, Si, P, and C, and L is It is at least one selected from Ti, Zr, Mo, Nb, Ta, and W, and x, y, z, and u are atomic percentages of 8% ≦ x ≦ 15%, y ≦ 3.0%, 4% ≦ It satisfies the conditions of z ≦ 8% and u ≦ 1.5%, and is an Nd ₂ Fe ₁₄ B type alloy with a crystal structure.

If x is less than 8%, the Fe phase showing soft magnetism increases as a different phase, which causes a significant decrease in coercive force, which is not preferable.

Increasing x increases the grain boundary phase called R-rich phase and improves the coercive force, but if x exceeds 15%, the main phase R ₂ Fe ₁₄ B phase decreases and the residual magnetic flux density decreases. Therefore, it is not preferable.

M may be added to improve the coercive force. When M is added, y ≦ 3.0% is preferable. If y exceeds 3.0%, an alloy phase having a crystal structure other than the R ₂ Fe ₁₄ B phase or a metal phase of a single element M precipitates as a different phase, which causes a decrease in residual magnetic flux density.

If z is less than 4% or exceeds 8%, it is difficult to form the R ₂ Fe ₁₄ B phase, which is not preferable because the residual magnetic flux density decreases.

L may be added to improve the coercive force. When L is added, u ≦ 1.5% is preferable. Even if u exceeds 1.5%, the addition effect does not change so much and the residual magnetic flux density and coercive force are not affected. However, since L is an expensive element, even if it is added more than necessary, the raw material cost of the magnet material Is preferably 1.5% or less at which the effect of improving the coercive force is saturated.

The average particle size of the R—Fe—B alloy powder is preferably 10 to 200 μm, more preferably 50 to 180 μm. The powder shape is preferably a flat powder, more preferably an anisotropic flat powder having an axis of easy magnetization perpendicular to a flat surface.

The Mn—Bi-based alloy that can be used for the second magnet material in the present embodiment has a component composition represented by Mn _100-w Bi _w , and w is an atomic percentage of 40% ≦ w ≦ 60%. A filling alloy can be used. Since it mainly has a NiAs type hexagonal crystal structure and has a stoichiometric ratio of w = 50%, preferably 45% ≦ w ≦ 55%.

If w is less than 40%, the Mn phase increases and the MnBi low-temperature phase decreases, so the residual magnetic flux density decreases. If w exceeds 60%, the Bi phase increases and the MnBi low-temperature phase decreases, so the residual magnetic flux Since the density decreases, the range of 40% ≦ w ≦ 60% is preferable.

The Mn—Bi alloy is preferably a composite of a low-temperature phase (NiAs type) and a Bi phase.

The average particle size of the Mn—Bi alloy powder is preferably 1 to 200 μm, and more preferably 2 to 10 μm.

In the hybrid magnet according to the present embodiment, when the volume ratio of the content of the R—Fe—B alloy and the Mn—Bi alloy is (100-a): a, a is 5 or more and 80 or less. It is a range. Here, 100 which is the total volume of the first magnet material and the second magnet material does not indicate the apparent volume of the entire hybrid magnet.

If a is less than 5, the second magnet material is insufficient to occupy the gaps of the first magnet material, and the residual magnetic flux density is only slightly improved and does not improve sufficiently. When a exceeds 80, the second magnet material is sufficient to occupy the gap between the first magnet materials, but the first magnet material alone has a lower residual magnetic flux density than the second magnet material. When a is too large, the residual magnetic flux density is lowered. The range of preferable a is 15 or more and 70 or less.

The hybrid magnet in the present embodiment may further include a metal binder whose main component is at least one selected from Bi, Al, Cd, Ga, In, Pb, Sn, and Zn. The metal binder may contain a metal or an alloy of an element different from the element capable of constituting the main component or an oxide as long as it is 10 wt% or less. By using such a metal binder, plastic deformation is facilitated, the relative density of the magnet can be easily increased in the molding process, and the residual magnetic flux density can be further increased.

In addition, since the metal binder has significantly lower moisture permeability and oxygen gas permeability than the resin binder, rust and chipping are suppressed, and long-term reliability is also excellent.

Moreover, 10-200 micrometers is preferable and, as for the average particle diameter of a metal binder, More preferably, it is 20-100 micrometers.

Note that the melting point of the metal binder is preferably a low melting point of 50 ° C. or higher and 400 ° C. or lower, and a Bi—Sn alloy is particularly preferable. Here, even a binary system of Bi—Sn alloy (for example, 58 wt% Bi-42 wt% Sn, melting point: 139 ° C.) is sufficiently useful, but metals that can be included in the Bi—Sn alloy include Hg, Cd, Pb and the like can be mentioned. Further, since the melting point can be lowered, it may be preferable depending on the application. It is known that the metals (Hg, Cd, Pb) that can be contained in these Bi—Sn alloys are toxic and thus have an effect on the human body / environment. Examples include a rose alloy (100 ° C.), an Erhardt alloy (70 ° C.), a wood alloy (about 60 ° C.), and the like. Further, a Bi—Sn—In alloy obtained by adding In to a Bi—Sn alloy (57 wt% Bi—26 wt% In—17 wt% Sn, melting point: 79 ° C.) can lower the melting point while maintaining low toxicity. It is preferable because it is possible. The addition of Sn or the like to the Ga—In alloy can further stabilize the melting point (galistan alloy,> −19 ° C.), but it is very expensive and is actually used when the melting point of the metal binder is too low. This is not preferable because the strength of the metal bonded magnet is lost at the ambient temperature. In general, the melting point of the metal binder is preferably 50 ° C. or higher and 300 ° C. or lower, more preferably 50 ° C. or higher and 150 ° C. or lower.

Here, the metal binder is at least one metal phase interposed between the particles of the magnet material, and the metal phase referred to here may be a single metal or an alloy phase composed of two or more elements. There may be. When two or more kinds of magnet materials are used, they may exist between particles of the same kind of magnet material, or may exist between different kinds of magnet materials. The metal binder may exist in the form of islands or particles between the particles, but it is desirable to form a grain boundary phase along the grain boundaries between the magnet particles in order to effectively contribute to magnetic separation between the particles.

When the volume ratio of the content of the R—Fe—B alloy, the Mn—Bi alloy and the metal binder is (100-a): a: b, b is preferably 0.1 or more and 10 or less. . By setting b to be 0.1 or more and 10 or less, the metal binder is more easily plastically deformed than the second magnet material. Therefore, the relative density of the magnet is further increased as compared with the case where only the second magnet material is mixed. The residual magnetic flux density can be increased easily.

  Next, the suitable manufacturing method of the hybrid magnet which concerns on this embodiment is demonstrated.

  As a manufacturing method of the first magnet material in the present embodiment, a molten alloy melted by using an arc melting method or a high frequency melting method may be used to obtain a ribbon-like alloy by a roll quenching method or a strip casting method, Or an ingot-like alloy. An alloy powder may be obtained from the obtained alloy by a mechanical grinding method or an airflow grinding method. Also, alloy powder may be obtained by grinding the alloy by a method such as HDDR method obtained by removing the hydrogen by heat-treating the ingot in hydrogen, or hot plastic working method by enclosing the alloy in a can An alloy powder may be obtained by pulverizing the alloy whose structure is controlled by the above. Furthermore, it is desirable that the alloy powder obtained by the various methods described above is anisotropic.

As a manufacturing method of the second magnet material in the present embodiment, a molten alloy melted by using an arc melting method, a high frequency melting method, or the like is subjected to a roll quenching method, a strip casting method, an atomizing method (including gas atomizing, disk atomizing, and water atomizing). ) Or an ingot-like alloy. An alloy powder may be obtained from the obtained alloy by a mechanical grinding method such as a ball mill or a disk mill or an airflow grinding method such as a jet mill. Furthermore, it is desirable that the alloy powder obtained by the various methods described above is anisotropic.

  In the present embodiment, the metal binder weighs a predetermined metal in accordance with the component composition, and melts by setting it to a melting point or higher of the metal binder by a heating method such as high-frequency melting, resistance heating, infrared heating, etc. Alloy powder or metal powder is obtained by the method. The average particle size of the powder is 1 mm or less, more preferably 500 μm or less.

  In order to turn the obtained magnet alloy into a magnetic powder, a grinding method such as a brown mill, a pin mill, a vibration mill, a ball mill, or a jet mill can be appropriately used. The average particle size of the powder is 500 μm or less, more preferably 100 μm or less. Furthermore, in order to mix the obtained magnet powder and metal binder, they may be mixed by pulverization simultaneously by the above pulverization method, or a mixer such as a V mixer, a double cone mixer, or a Nauta mixer may be mixed at a temperature from room temperature. It can also be used while adjusting up to 400 ° C. If the temperature at the time of mixing is more than the melting | fusing point vicinity of a metal binder, since the particle | grains of a different magnet powder granulate and a compound with favorable fluidity | liquidity is obtained, it is more preferable.

Further, in a metal bonded hybrid magnet using a metal binder, it is necessary to perform warm forming near or below the melting point (50 ° C. to 400 ° C.) of the metal binder.

As a molding method, there are a method of performing heat treatment after performing compression molding, extrusion molding and injection molding while applying a magnetic field, and a method of making by hot molding such as hot pressing while applying a magnetic field. At that time, it is necessary to suppress the temperature of the heat treatment or hot forming to 400 ° C. or less so that the Mn—Bi-based alloy does not disproportionate. The molding temperature is preferably 50 to 300 ° C., and the molding pressure is preferably 100 MPa to 1200 MPa. In order to prevent oxidation, the atmosphere during the heat treatment or hot forming is vacuum, an inert atmosphere such as Ar, N ₂ , or He, a reducing atmosphere such as H ₂ , or an inert gas and a reducing gas. It is necessary to carry out in a mixed atmosphere.

Examples of the present invention will be described below, but the present invention is not limited to the following examples.

Example 1
For the R—Fe—B-based powder selected as the first magnet material, raw material Nd metal, Fe metal, and Fe—B (ferroboron) alloy are weighed and mixed at a weight ratio of approximately 30:60:10, and are melted at high frequency. The alloy flakes were obtained by a roll quenching method using a Cu metal roll. The alloy flakes were pulverized with a brown mill to obtain an R—Fe—B alloy powder having an average particle size of 100 μm.

For the Mn-Bi alloy powder selected as the second magnet material, the raw material Mn metal and Bi metal are weighed and mixed at a weight ratio of approximately 55:45 so as to have the desired component composition, and arc melting method is used. An alloy ingot was obtained. The alloy ingot was roll-cooled in an Ar gas atmosphere to obtain a ribbon-like alloy powder, and then heat-treated at 350 ° C. for 24 hours in an N ₂ gas atmosphere. This alloy powder was coarsely pulverized by a stamp mill, and pulverized by a ball mill using n-octane as a dispersion medium for 32 hours to obtain a Mn—Bi alloy powder having an average particle size of 10 μm or less and a component composition Mn ₅₀ Bi ₅₀ .

The specific gravity of the first magnet material and the second magnet material was measured and found to be 7.6 g / cm ³ and 8.9 g / cm ³ , and thus weighed so that the volume ratio was 95: 5. After mixing with a V mixer for 4 h, the resulting mixture is filled into a mold, heated to 150 ° C. in a magnetic field of 23 kOe, and molded at a pressure of 1 GPa to produce a 7 × 7 × 7 mm cube-shaped magnet did.
Table 1 shows the volume ratios of the first magnet material, the second magnet material, and the metal binder, and the metal binder.

The obtained magnet was subjected to magnetic hysteresis measurement using a BH tracer (manufactured by Toei Kogyo). Table 1 shows the coercive force HcJ (kOe) and the residual magnetic flux density Br (kG) obtained from the magnetic hysteresis curve.

(Comparative Examples 1-2, Examples 2-5)
About Comparative Example 1 and Comparative Example 2, all except that they are weighed and mixed so that the volume ratio of the first magnet material to the second magnet material is 100: 0 and 0: 100, respectively. It was prepared. For Examples 2 to 5, each was prepared in the same manner as in Example 1 except for weighing and mixing so that the volume ratio of the first magnet material to the second magnet material was 85:15 to 20:80. did. Table 1 shows the coercive force and the residual magnetic flux density for Comparative Examples 1 and 2 and Examples 2 to 5.

(Examples 6 to 12)
Moreover, about Examples 6-12, Bi is used for a metal binder, and ratio of the sum total volume of a 1st magnet material and a 2nd magnet material and the volume of a metal binder is 100: 0.05-100: 12. All were prepared in the same manner as in Example 3 except that they were weighed and mixed. Table 2 shows the coercive force and the residual magnetic flux density for Examples 6 to 12.

(Examples 13 to 19)
In addition, in Examples 13 to 19, all are the same as in Example 9 except that Sn, 50Bi50Al, 50Bi50Ga, 67Bi33In, 58Bi42Sn, 57Bi17Sn26In, and 50Bi50Zn are used as the metal binder (the number immediately before the element name represents weight%). It was prepared. Table 3 shows the coercive force and the residual magnetic flux density for Examples 13 to 19.

As shown in Table 1, when the first magnet material and the second magnet material are mixed, the residual magnetic flux density can be increased while substantially maintaining the coercive force, rather than using the magnets alone. The reason for this is not clear, but the main cause is that the gap between the first magnet materials is occupied by the second magnet material that is easily plastically deformed, so that when the molding pressure is applied, the air gap is reduced, and the residual magnetic flux density. This is probably due to the effect of improving

As shown in Table 2, when the metal binder is added, the residual magnetic flux density can be increased without substantially reducing the coercive force as compared with the case where the metal binder is not added. The reason for this is not clear, but the main reason is that the gap is reduced and the residual magnetic flux density is improved when molding pressure is applied by plastic deformation of the metal binder, which is softer than the second magnet material. It seems to be due to. The effect of increasing the residual magnetic flux density is the volume ratio of 100: 1, and the most effective effect is observed. However, if the amount is too much, the residual magnetic flux density is decreased by relatively decreasing the magnet component. The effect of increasing the coercive force is saturated at a volume ratio of 100: 10, and at 100: 12, the coercive force is not improved and the residual magnetic flux density is decreased. Therefore, addition at a volume ratio of 100: 12 or more is not preferable.

As shown in Table 3, it can be seen that the residual magnetic flux density is improved by adding various metal binders. In comparison of these examples molded at the same molding temperature (150 ° C.), a magnet with improved residual magnetic flux density can be obtained by using a metal binder that liquefies at the molding temperature as in Example 17 and Example 18. This is considered to be due to the action of the liquefied metal binder soaking in between the particles while reducing the friction between the magnet materials during molding and reducing the gap.

Claims (2)

In the hybrid magnet including the first magnet material and the second magnet material, the first magnet material is an R—Fe—B alloy, the second magnet material is an Mn—Bi alloy, A hybrid magnet characterized in that when the volume ratio of the content of one magnet material to the second magnet material is (100-a): a, a is in the range of 5 or more and 80 or less. The hybrid magnet according to claim 1, further comprising a metal binder mainly comprising at least one selected from Bi, Al, Cd, Ga, In, Pb, Sn, and Zn. .