JP2017135267A - Metal bonded hybrid magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnet in which coercive force is improved while suppressing decrease in residual magnetic flux density.SOLUTION: In a metal bonded hybrid magnet containing a first magnet material and a second magnet material, the first magnet material is a Sm-Fe-N-based alloy, the second magnet material is a Mn-Bi-based alloy, and at least one kind selected from Bi, Al, Cd, Ga, In, Pb, Sn, Zn is the chief ingredient of the metal binder and Bi is essential.SELECTED DRAWING: None

Description

The present invention relates to a metal bonded hybrid magnet.

In recent years, MnBi magnets have attracted attention as magnets that do not contain expensive rare earth elements such as Nd and Dy among rare earth metal elements that have a high resource procurement risk. This MnBi magnet material is well known in the field of magneto-optical recording and is a promising magnet material as a bulk magnet. Patent Document 1 discloses a nanocomposite magnet having excellent magnetic properties with a high residual magnetic flux density by mixing nano-sized Fe (iron) metal powder inside an MnBi / Sm2Fe17Nx hybrid magnet. The publication also describes that the coercive force is reduced by adding Fe-based metal powder.

Patent Document 2 discloses a metal bonded magnet formed using a metal binder in an Sm ₂ Fe ₁₇ N _x- based magnet. However, the magnet material is composed of only one kind of Sm ₂ Fe ₁₇ N _x- based magnet. , Zn, Sn, and other metal binders intermixed with the magnet material component elements to form a mixed portion, magnetically separate the particles of the magnet material, and reduce the surface roughness of the particles to reduce the coercive force However, in a metal bonded magnet using an Sm-Fe-N magnet material, a heat treatment near the melting point of the metal binder is required to obtain a sufficient density. There was a problem that the Sm—Fe—N magnet material was decomposed by the influence and the residual magnetic flux density was lowered.

Japanese Patent No. 4968519 Japanese Patent Laid-Open No. 04-338605

  The present invention has been made in view of the above-described problems of the prior art, and an object thereof is to provide a metal bonded hybrid magnet capable of improving coercive force while suppressing a decrease in residual magnetic flux density.

  The present invention provides a metal bonded hybrid magnet including a first magnet material, a second magnet material, and a metal binder, wherein the first magnet material is an Sm-Fe-N alloy, and the second magnet The material is a Mn—Bi alloy, and the metal binder is essentially Bi, and at least one selected from Bi, Al, Cd, Ga, In, Pb, Sn, and Zn is a main component. It is a metal bonded hybrid magnet.

The metal bonded hybrid magnet of the present invention is hard to be plastically deformed, but is mixed with Sm—Fe—N alloy powder having excellent magnetic properties and Mn—Bi alloy powder that is easily plastically deformed. The Mn-Bi alloy powder enters between the particles of the -N alloy powder, and the voids after forming tend to decrease compared to the case of only the Sm-Fe-N alloy powder. Therefore, these hybrid magnets have the effect of improving the residual magnetic flux density.

The metal bonded hybrid magnet of the present invention has a metal binder. Since the metal binder is also easily plastically deformed, the relative density can be increased. However, the Mn-Bi alloy powder and the metal, which are magnetic materials, can be used rather than the combination of the Sm-Fe-N alloy powder and the metal binder alone. By using the binder in combination, the effect of improving the residual magnetic flux density is relatively obtained.

Furthermore, by interposing the metal binder between the particles of the first magnet material and the second magnet material, the protrusion and roughness of the particle surface of the magnet material can be reduced, and magnetic separation between the particles can be achieved. It is considered that the coercive force can be increased.
Furthermore, by making Bi essential for the metal binder, the melting point of the metal binder becomes lower, the softening and liquefaction (melting) of the metal binder occur at a relatively low temperature, and the relative density can be increased even at a low molding temperature. Therefore, the residual magnetic flux density becomes relatively large at the same molding temperature. At the same time, the first magnet material decomposes and deteriorates at high temperatures, and the coercive force decreases even when the temperature is returned to room temperature. The coercive force can be increased more than that using a binder. Therefore, if a low-melting metal binder is used, the residual magnetic flux density can be increased without reducing the coercive force.

  The metal bonded hybrid magnet according to the present invention includes an area ratio a of the first magnet material, an area ratio b of the second magnet material, and an area ratio c of the metal binder in an arbitrary magnet cross section of the metal bonded hybrid magnet. Is expressed as an area ratio a: b: c, it is preferable that 30% ≦ a ≦ 75%, 0% <b ≦ 70%, and 0% <c ≦ 25%.

  Thereby, a metal binder becomes an appropriate amount of interposition on the particle surface of the first magnet material and the particle surface of the second magnet material, and the coercive force can be further increased.

  The metal binder of the present invention preferably contains a Bi—Sn alloy as a main component.

  As a result, the metal binder has a lower melting point, and a high relative density can be obtained even at a low molding temperature. Therefore, the residual magnetic flux density is increased, and decomposition degradation is suppressed at a low molding temperature, thereby further increasing the coercive force. be able to.

Furthermore, the metal binder of the present invention is more preferably a Bi—Sn—In alloy as a main component.
As a result, the metal binder has a lower melting point, and the residual magnetic flux density and coercive force can be further increased.

ADVANTAGE OF THE INVENTION According to this invention, the metal bond hybrid magnet which can improve a coercive force, suppressing the fall of a residual magnetic flux density can be obtained.

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

  The metal bonded hybrid magnet of the present embodiment has a first magnet material, a second magnet material, and a metal binder. .

Component composition of Sm-Fe-N based alloy which can be used for the first magnetic material in the present embodiment is represented by _{R x Fe 100- (x + y} + z + u) M y N z L u, R is a mandatory element of Sm And at least one element selected from Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Mo, Nb, Ta, Ga, Al, and Ca. L is at least one selected from Si and P, and x, y, z, and u are atomic percentages of 3% ≦ x ≦ 15%, y ≦ 3.0%, 5% ≦ z ≦ 15%, It satisfies that u ≦ 1.5%. The first magnet material includes an Sm ₂ Fe ₁₇ N ₃ phase among Sm—Fe—N alloys, and an Sm ₂ Fe ₁₇ N ₃ phase is obtained even when x is less than 3% or more than 15%. I can't. It is preferable that 8% ≦ x ≦ 10%. Although y may be 0%, the addition of a small amount has the effect of making the crystal structure fine and increasing the coercive force. If y is more than 3%, the Sm ₂ Fe ₁₇ N ₃ phase is relatively less, so y ≦ 3% is preferable. If z is less than 5%, the coercive force is lowered, and more than 15% of N atoms are difficult to dissolve in the Sm ₂ Fe ₁₇ N ₃ phase. It is preferable that 13% ≦ z ≦ 15%.

The surface of the first magnet material may be covered with a coating, and if it is a coating with a high concentration of Si or P, it may be difficult to be oxidized. L is at least one selected from Si or P, and it is sufficient that u ≦ 1.5%. The coating can be formed by a surface treatment such as a silane coupling agent, water glass, and phosphoric acid. However, since the treatment cost is high, u may be 0%, that is, L may not be contained. When a film is formed on the surface of the first magnet material, it is easy to be oxidized when u is less than 0.3%, and a secondary phase mainly composed of Fe as a decomposition product is generated to reduce the coercive force, When u exceeds 1.5%, it is difficult to oxidize, but since the residual magnetic flux density decreases because the coating of the nonmagnetic phase increases, more preferably 0.3% ≦ u ≦ 1.5%.

In addition, regarding M in the component composition of the first magnet material, particularly when M is Mo, Nb, or Ta, there may be segregated substances in the particles, or there may be granular segregation of Mo, Nb, or Ta. Absent.

The average particle size of the Sm—Fe—N-based powder is preferably 1 to 200 μm, more preferably 2 to 10 μm. The Sm—Fe—N-based powder has a Curie point of 460 to 650 ° C. and mainly has a Th ₂ Zn ₁₇ type rhombohedral or TbCu ₇ type hexagonal crystal structure.

In the second magnetic material in the present embodiment, the component composition is expressed by Mn _100-w Bi _w , and w satisfies atomic percent 40% ≦ w ≦ 60%. 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 density. Therefore, the range of 40% ≦ w ≦ 60% is preferable. Since it mainly has a NiAs type hexagonal crystal structure and has a stoichiometric ratio of w = 50%, preferably 45% ≦ w ≦ 55%. Among MnBi alloys, a composite of a low-temperature phase (NiAs type) and a Bi phase is preferable.

The average particle size of the second magnet material is preferably 1 to 200 μm, more preferably 2 to 10 μm. The Curie point of the second magnet material powder is 240 to 360 ° C.

The metal binder in the present embodiment is mainly composed of at least one selected from Bi, Al, Cd, Ga, In, Pb, Sn, and Zn with Bi as an essential element, and is 10 wt% or less of the entire metal binder. A metal or alloy of an element different from the element that can constitute the main component may be included, or an oxide may be included. Moreover, 10-500 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. In addition, Bi—Sn—In alloys (In, for example, 57 wt% Bi—26 wt% In—17 wt% Sn, melting point: 79 ° C.) in which Bi is added to Bi—Sn alloys have a low toxicity and a low melting point. Is more preferable. The addition of Sn or the like can lower the melting point of a Ga—In alloy (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 more 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 may be at least one metal phase interposed between particles of the magnet material, and the metal phase referred to here may be a single metal or an alloy composed of two or more elements. It may be a phase. 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. . The grain boundary phase may be composed of only a metal binder, or may be a metal binder formed by diffusing a magnet material in the metal binder.

Moreover, it is preferable to add and mix a metal binder separately from the two types of magnet materials, but a metal phase included as a subphase of the second magnet material may be used as the metal binder. For example, when MnBi-based alloy is used as the second magnet material, if the magnet material is prepared so as to contain the Bi phase as a subphase, a mixed state of the magnet material and the metal binder can be formed in the obtained magnet. In this case, the metal binder may be the same metal as the subphase, a different metal, or an alloy containing these metals. Moreover, even when the metal phase contained as a subphase of the second magnet material is used as a metal binder, a metal binder may be added separately.

  The metal bonded hybrid magnet of the present embodiment shows the relationship between the area ratio a of the first magnet material, the area ratio b of the second magnet material, and the area ratio c of the metal binder in an arbitrary cross section. : C, it is preferable that 30% ≦ a ≦ 75%, 0% <b ≦ 70%, 0% <c ≦ 25%.

  The area ratios a, b, and c represent the occupation areas of the first magnet material, the second magnet material, and the metal binder, respectively, in an arbitrary magnet cross section by a ratio (percent). Note that the sum of the area ratios a, b, and c does not necessarily need to be 100%, and the remainder less than 100% corresponds to voids and other solid contents, and the other solid contents are the first magnet material. Any substance other than the second magnet material and the metal binder may be used.

If the area ratio of the first magnet material is less than 30%, the average saturation magnetization of the entire magnet is excessively decreased, so that the residual magnetic flux density does not increase. This is not preferable, and if it exceeds 75%, the area ratio of the air gap does not decrease. The magnetic flux density is not increased, which is not preferable. More preferably, 45% ≦ a ≦ 60%. If the second magnet material is not mixed, the residual area density is not increased because the area ratio of the air gap does not decrease, and if it exceeds 70%, the average saturation magnetization of the entire magnet is excessively decreased, and the residual magnetic flux density does not increase. Therefore, it is not preferable. More preferably, 10% ≦ b ≦ 50%. If the metal binder is not mixed at all, the gap area ratio is difficult to be reduced, and the residual magnetic flux density is not increased, which is not preferable. If it exceeds 25%, the gap area ratio is reduced but the average saturation magnetization is reduced too much. This is not preferable because the residual magnetic flux density does not increase. More preferably, 2% ≦ c ≦ 10%.

The smaller the void area ratio, the better. The void area ratio of 0% means that the relative density is 100%. The area ratio of the air gap in the metal bonded hybrid magnet of the present invention is desirably less than 35%. The area occupied here can be calculated based on photographic images obtained by observing the polished cross section of the magnet with visual means such as an optical microscope, a metal microscope, or an electron microscope. Can be identified by utilizing the fact that the rate, the reflectance of electrons, etc. differ depending on the material.

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

  The first magnet material and the second magnet material are made into a molten metal by weighing a predetermined metal in accordance with the component composition, and by making it higher than the melting point of the magnet material by a melting method such as arc melting and / or high frequency melting, casting method, strip casting method A magnet alloy or a magnet ribbon can be produced by a solidification method such as a molten metal quenching method or an atomizing method. More preferably, it is a strip casting method in which an anisotropic magnet alloy or magnet ribbon is obtained.

  The metal binder weighs a predetermined metal according to the component composition, melts by heating above the melting point of the metal binder by heating methods such as high-frequency melting, resistance heating, infrared heating, etc., and alloy powder by solidification methods such as atomization and roll quenching Or a metal powder is obtained. 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.

In order to make the obtained magnet powder into a molded body, the magnet powder is filled into a mold, and after magnetic field orientation in a magnetic field of 1 T or more, heated to a predetermined molding temperature and pressurized at a predetermined molding pressure. Can be produced. The molding temperature is preferably 50 to 300 ° C., and the molding pressure is preferably 100 MPa to 1200 MPa.

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

(Comparative Example 1)
Sm metal as a raw material so that the Sm—Fe—N-based powder selected as the first magnet material has the target component composition Sm _9.1 Fe _75.6 Mn _0.1 N _14.3 Si _0.9 , Fe metal and the like were weighed and mixed, and an alloy ingot was obtained by an arc melting method. This alloy ingot was melted in a quartz tube by a high frequency melting method, and alloy flakes were obtained by a strip casting method using a metal roll made of Cu. The alloy flakes were coarsely pulverized by a brown mill and then finely pulverized by a jet mill using N ₂ gas to obtain an Sm—Fe alloy powder having an average particle diameter of 3 μm. The obtained Sm—Fe-based alloy powder was nitrided in a rotary kiln at 350 ° C. in N ₂ gas to obtain an Sm—Fe—N-based alloy powder. The obtained Sm-Fe-N-based alloy powder was treated with a silane coupling agent and modified with a Si oxide coating to obtain an Sm-Fe-N-based alloy powder having a desired component composition.

The raw material Mn metal and Bi metal were weighed and mixed so that the Mn—Bi alloy powder selected as the second magnet material had the target component composition Mn ₅₀ Bi _50, and an alloy ingot was obtained by the arc melting method. 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 with a stamp mill, and pulverized with a ball mill using n-octane as a dispersion medium for 32 hours to obtain an Mn—Bi alloy powder having an average particle size of 10 μm or less.

The first magnet material and the second magnet material were weighed so as to have a weight ratio of 2: 1 and mixed with a V mixer for 4 h, and then the resulting mixture was filled in a mold and 250 ° C. in a magnetic field of 23 kOe. Heated to ° C. and molded at a pressure of 1 GPa to produce a 7 × 7 × 7 mm cubic hybrid magnet. Table 1 shows the component composition of the first magnet material, the component composition of the second magnet material, and the metal binder.

The obtained magnet was subjected to magnetic hysteresis measurement using a BH tracer (manufactured by Toei Kogyo). The coercive force HcJ (kOe) and the residual magnetic flux density Br (kG) were read from the magnetic hysteresis measurement. Moreover, the area ratio was measured from the structure | tissue observation by the reflected electron image of a magnet cross section in SEM (Hitachi High-Tech SU8000 scanning electron microscope). Table 1 shows the area ratio of the first magnet material, the second magnet material, the metal binder and the air gap, and the coercive force and the residual magnetic flux density.

Example 1
Further, as shown in Table 1, in Example 1, the metal binder is Bi, and the ratio of the total weight of the first magnet material and the second magnet material to the weight of the metal binder is 20: 1. A metal bonded hybrid magnet was prepared in the same manner as in Comparative Example 1 except that Bi metal was added to.

(Examples 2 to 15)
In addition, Examples 2 to 15 were produced in the same manner as Example 1 except that the component composition of the first magnet material was different. Table 2 shows the area ratio of the first magnet material, the second magnet material, the metal binder and the gap, and the coercive force and residual magnetic flux density for Examples 2 to 15.

(Examples 16 to 21)
Moreover, about Example 16 to Example 21, the composition of the second magnet material is different, and Bi metal is added so that the area ratio of the first magnet material to the metal binder is 45: 1 to 45: 7. Except for the above, all were produced in the same manner as in Example 1. Table 3 shows the area ratio of the first magnet material, the second magnet material, the metal binder and the air gap, and the coercive force and residual magnetic flux density for Examples 16 to 21.

(Comparative example 2, Examples 22-27)
Further, Comparative Example 2 was produced in the same manner as Example 1 except that the metal binder was Sn and the heating temperature at the time of molding was 400 ° C. Examples 22 to 27 were produced in the same manner as Example 1 except that the metal binder was different. Table 4 shows the area ratio of the first magnet material, the second magnet material, the metal binder and the gap, the coercive force, and the residual magnetic flux density for Comparative Example 2 and Examples 22 to 27.

(Examples 28 to 32, Comparative Example 3)
Further, Examples 28 to 32 and Comparative Example 3 are all the same as in Example 1 except that the weight ratio of the first magnet material to the second magnet material was changed from 1: 2 to 1: 0. It produced similarly. Table 5 shows the area ratio of the first magnet material, the second magnet material, the metal binder and the air gap, and the coercive force and residual magnetic flux density for Examples 28 to 32 and Comparative Example 3.

(Examples 33 to 37)
In addition, Examples 33 to 36 are all the same as Example 1 except that Bi metal is added so that the weight ratio of the first magnet material to the metal binder is 2: 0 to 2: 1. Produced. Further, Example 37 was produced in the same manner as Comparative Example 1 except that Comparative Example 1 and the second magnet material had different component compositions.
Table 6 shows the area ratio of the first magnet material, the second magnet material, the metal binder and the gap, and the coercive force and residual magnetic flux density for Examples 33 to 37.

As shown in Table 1, the coercivity was improved without changing the residual magnetic flux density in the state where the metal binder was mixed because the metal binder was interposed between the particles of the magnet material.

As shown in Table 2, when the element of M was added or replaced in the component composition of the first magnet material, the residual magnetic flux density was reduced, but the coercive force was greatly improved.

As shown in Table 3, when the component composition of the second magnet material is changed, the residual magnetic flux density decreases if the amount of (100-w) atomic% representing the Mn ratio is too much or too little, but the Bi ratio As the amount of Bi increases, the amount of Bi metal used as a metal binder increases, and the area ratio of the metal binder increases, so the coercive force is improved.

As shown in Table 4, the coercive force was improved by changing the type of the metal binder compared to Comparative Example 1 in which the metal binder was “None” and Comparative Example 2 in which Sn was used as the metal binder. In particular, the 58Bi42Sn alloy of Example 25 When the 57Bi17Sn26In alloy of Example 26 was used, the residual magnetic flux density did not decrease while the coercive force was further improved.

As shown in Table 5, even if the area ratio of the metal binder is the same, if the area ratio of the second magnet material is large, the coercive force is improved. On the other hand, the area ratio of the first magnet material is reduced, and the residual magnetic flux is reduced. Density decreased. When the second magnetic material of Comparative Example 3 was not contained, the coercive force was greatly reduced.

  As shown in Table 6, the coercive force was improved when the area ratio of the metal binder was increased, but the residual magnetic flux density was slightly decreased when the area ratio was too large. Further, instead of separately adding Bi of the metal binder as in Example 37, even when it is included as a subphase in the component composition of the second magnet material, the same metal as when Bi of the metal binder is added separately It was found that a metal-bonded hybrid magnet having a binder area ratio and magnetic properties was obtained.

Thus, it was confirmed that the metal bonded hybrid magnet according to the present embodiment has excellent magnetic characteristics such as a coercive force of 4.5 kOe or more and a residual magnetic flux density of 5.0 kG or more.

Claims (4)

In a metal bonded hybrid magnet including a first magnet material, a second magnet material, and a metal binder,
The first magnet material is an Sm—Fe—N alloy,
The second magnet material is a Mn-Bi alloy,
The metal-bonded hybrid magnet characterized in that the metal binder is essentially Bi, and at least one selected from Bi, Al, Cd, Ga, In, Pb, Sn, and Zn is a main component. In an arbitrary magnet cross section of the metal bonded hybrid magnet, the relationship between the area ratio a of the first magnet material, the area ratio b of the second magnet material, and the area ratio c of the metal binder is represented by an area ratio a: b: c. 2. The metal bonded hybrid magnet according to claim 1, wherein 30% ≦ a ≦ 75%, 0% <b ≦ 70%, and 0% <c ≦ 25% are satisfied. The metal bonded hybrid magnet according to claim 1, wherein the metal binder includes a Bi—Sn alloy. The metal-bonded hybrid magnet according to claim 3, wherein the Bi—Sn alloy is a Bi—Sn—In alloy.