CN111418034A

CN111418034A - Permanent magnet, method for manufacturing permanent magnet, and rotary machine

Info

Publication number: CN111418034A
Application number: CN201780097304.6A
Authority: CN
Inventors: 中野善和; 信时英治; 中村泰贵; 辻孝诚; 长谷川治之
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2017-12-05
Filing date: 2017-12-05
Publication date: 2020-07-14
Anticipated expiration: 2037-12-05
Also published as: KR20200079514A; WO2019111328A1; KR102313049B1; JPWO2019111328A1; CN111418034B; JP6359232B1

Abstract

The permanent magnet of the present invention has a tetragonal crystal R₂Fe₁₄B crystal structure. The permanent magnet has a composition formula of (Nd)_1‑x‑yLa_xSm_y)₂Fe₁₄B. Here, x is in the range of 0.01. ltoreq. x.ltoreq.0.16, and y is in the range of 0.01. ltoreq. y.ltoreq.0.16.

Description

Permanent magnet, method for manufacturing permanent magnet, and rotary machine

Technical Field

The present invention relates to an R-T-B permanent magnet, a method for manufacturing the same, and a rotary machine having the same.

Background

In the form of tetragonal crystal R₂T₁₄An R-T-B type permanent magnet in which a heavy rare earth element, Dy, is added is currently known (for example, see patent document 1), and an R-T-B type permanent magnet in which a plurality of rare earth elements including Y and L a are added without fail is also known (for example, see patent document 2).

Patent document 1: japanese laid-open patent publication No. 6-13211

Patent document 2: japanese laid-open patent publication No. 9-115713

Disclosure of Invention

When a permanent magnet is used for an industrial motor, the use temperature environment often exceeds a high temperature of 100 ℃. However, in the conventional permanent magnets disclosed in

patent documents

1 and 2, the coercive force may be significantly reduced with an increase in temperature.

The present invention has been made to solve the above-described problems, and an object thereof is to provide a permanent magnet in which a decrease in coercive force due to a temperature increase is suppressed, a method for manufacturing the permanent magnet, and a rotary machine.

The permanent magnet according to the present invention has a tetragonal crystal R₂Fe₁₄B crystal structure of the formula (Nd)_1-x- _yLa_xSm_y)₂Fe₁₄B, x is more than or equal to 0.01 and less than or equal to 0.16, and y is more than or equal to 0.01 and less than or equal to 0.16.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the permanent magnet of the present invention, the absolute value of the temperature coefficient of the coercivity of the permanent magnet can be reduced. This makes it possible to provide a permanent magnet in which a decrease in coercive force associated with a temperature increase is suppressed. Further, the method for manufacturing a permanent magnet and the rotary machine having a permanent magnet can be provided.

Drawings

Fig. 1 is a flowchart of a method for manufacturing a permanent magnet according to embodiment 1.

Fig. 2 is a diagram for explaining a raw material alloy production step in the method for producing a permanent magnet according to embodiment 1.

Fig. 3 is a diagram illustrating a melting step and a cooling step in the method for manufacturing a permanent magnet according to embodiment 1.

Fig. 4 is a table showing the relationship between the compositional formula and the absolute value of the temperature coefficient of the coercive force in the permanent magnet sample of embodiment 1.

FIG. 5 shows (Nd)_1-x-yLa_xSm_y)₂Fe₁₄B, x and y, and absolute value | α | of the temperature coefficient of coercivity.

FIG. 6 shows a tetragonal Nd₂Fe₁₄Diagram of atomic sites in B.

Fig. 7 is a table showing the stabilization energy of L a at each switching point when the ambient temperature is changed.

Fig. 8 is a table showing the stabilization energy of Sm at each displacement point in the case where the ambient temperature is changed.

Fig. 9 is a schematic sectional view of a rotary machine mounted with the permanent magnets according to embodiment 1, taken in a direction perpendicular to the axial direction of the rotary machine.

FIG. 10 shows (Nd) in embodiment 2_1-x-yLa_xSm_y)₂Fe₁₄B is a table showing the relationship between x/y and the absolute value of the temperature coefficient of coercive force with respect to the effect.

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding portions are denoted by the same reference numerals, and redundant description is omitted.

Embodiment 1.

The R-T-B permanent magnet according to embodiment 1 of the present invention has a square shape as a main generated phaseCrystal form R₂T₁₄And (B) a permanent magnet. Here, R is a rare earth element. T is a transition element. B is boron. Tetragonal R in accordance with embodiment 1₂T₁₄In the permanent magnet of B structure, a structure in which a part of neodymium (Nd) is substituted with lanthanum (L a) and samarium (Sm) is represented by R, and iron (Fe) is represented by t, and thus, in embodiment 1, the composition formula of the permanent magnet is represented by (Nd) and_1-x-yLa_xSm_y)₂Fe₁₄and B represents. First, a method for manufacturing an R-T-B permanent magnet will be described.

Fig. 1 is a flowchart showing a procedure for manufacturing an R-T-B based permanent magnet according to embodiment 1. As shown in FIG. 1, the method for producing an R-T-B permanent magnet includes a raw material alloy production step, a melting step, a cooling step, a pulverization step, a molding step, and a magnetization step.

(Process for producing raw Material alloy)

In the raw material alloy production step, first, raw materials are prepared in weights corresponding to the component ratios of the respective elements of the permanent magnet, and these raw materials are mixed, and Nd, L a, Sm, Fe, and ferroboron (FeB) are used as the raw materials.

Fig. 2 is a structural diagram showing a state in which the mixed raw materials are being melted in the raw material alloy production step of fig. 1. When melting the mixed raw material, the arc 22 is generated from the electrode 21 to the tray 23 in a state where the mixed raw material 24 is placed on the tray 23 made of copper. The mixed raw material 24 is melted on the tray 23 by the arc 22. The melting of the mixed raw material 24 by the arc 22 is performed in a reduced pressure atmosphere containing argon (Ar) which is an inert gas, for example. The raw material alloy may be produced by a method other than melting the mixed raw material 24 by arc.

(melting Process)

After the raw material alloy production step, as shown in fig. 3, in the melting step, the raw material alloy 26 is melted by the high-frequency induction heating coil 25.

(Cooling Process)

Then, the raw material alloy 26 melted in the melting step is cooled in the cooling step. In the cooling step, the raw material alloy 26 is cooled by a liquid quenching method. In the liquid quenching method, the raw material alloy 25 in a molten state is ejected from the nozzle 27 toward the cooling roll 28. When the raw alloy 26 is sprayed to the cooling roll 28, the cooling roll 28 is rotated in advance. Thereby, the raw alloy 26 in a molten state is cooled by the cooling roll 28 to become a ribbon alloy 29. The ribbon alloy 29 can be produced by a method other than the liquid quenching method.

(grinding step)

Then, in the pulverization step, the ribbon alloy 29 is pulverized. Thus, the ribbon alloy 29 becomes a raw material powder having a particle size of 200 μm or less. The ribbon alloy 29 is pulverized using, for example, an agate mortar. In the pulverization of the ribbon alloy 29, a crusher, a jaw crusher, a jet mill, or the like can be used in addition to the mortar. The ribbon alloy 29 is preferably pulverized in an inert gas when the particle size of the raw material powder is particularly reduced. By pulverizing the ribbon alloy 29 in an inert gas, the mixing of oxygen into the raw material powder can be suppressed. When the atmosphere during pulverization does not affect the magnetic properties of the permanent magnet, the ribbon alloy 29 may not be pulverized in an inert gas.

(Molding Process)

Then, a molding step of molding the raw material powder is performed. In the molding step, the raw material powder and the epoxy resin having a heat resistance temperature of 200 ℃ or higher are stirred and mixed. In this case, the volume content ratio of the raw material powder is about 20 vol%. Then, the resin is hardened, thereby molding a bonded magnet. Further, only the raw material powder may be compression molded. Further, the powder obtained by mixing the raw material powder with the organic binder may be compression molded. In the above molding method, molding may be performed by any method while applying a magnetic field.

(sintering Process)

In the case of compression molding only the raw material powder or in the case of compression molding a powder obtained by mixing an organic binder with the raw material powder, the sintering step is performed after the molding step. The sintering step is performed in a vacuum or an inert gas atmosphere in order to suppress oxidation. The sintering step may be performed while applying a magnetic field. In the sintering step, for example, a step of additionally heating the intermediate layer or aging treatment may be performed to improve the magnetic properties, that is, to improve the magnetic field anisotropy or coercive force. In addition, in the sintering step, a step of allowing a compound containing copper or aluminum to penetrate into crystal grain boundaries, which are boundaries between main phases, may be added.

(magnetizing step)

The alloy after the molding step or the sintering step is subjected to cutting, grinding, or surface treatment to form an alloy in the shape of a product. The alloy in the product shape is magnetized by, for example, a capacitor-type magnetization power supply device to become a permanent magnet.

Next, a method for analyzing the composition of the main phase in the R-T-B type permanent magnet will be described. In general, the composition of the permanent magnet can be quantified by using a Wavelength Dispersive X-ray Spectroscopy (WDS) apparatus installed in a scanning electron microscope. However, in the analysis by the WDS device, since the analysis accuracy of the light element is low, it is difficult to quantify B in the R-T-B type permanent magnet. Therefore, the X-Ray Diffraction (XRD) device is used as well. The main phase of formation of the permanent magnet by XRD device is tetragonal R₂Fe₁₄In the WDS device, the composition ratios of elements other than B, that is, the composition ratios of Nd, L a, and Sm constituting R and the composition ratio of Fe constituting T can be obtained, the total composition ratio of the product phase can be obtained from the above 2 results, and in addition, in the XRD device, it is also possible to determine whether or not the element is not contained in the tetragonal crystalR₂Fe₁₄The presence of the B crystal structure was not confirmed as another structure.

Next, a method of evaluating magnetic properties will be described, in which coercivity of a plurality of samples is measured using a pulse-excited B-H tracker, the maximum applied magnetic field achieved by the B-H tracker is 5T or more, the atmosphere at the time of measurement is nitrogen, the coercivity of each sample is measured at each of the 1 st measurement temperature T1 and the 2 nd measurement temperature T2 which are different from each other, the temperature coefficient α [%/c ] of coercivity is a value obtained by dividing the ratio of the difference between coercivity at T1 and coercivity at T2 to the coercivity at T1 by the difference in temperature (T2-T1), and therefore, the smaller the absolute value | α | of the temperature coefficient of coercivity is, the more the decrease in the coercivity of the permanent magnet with respect to the temperature rise is suppressed.

In embodiment 1, a plurality of permanent magnets having different main phase components were produced by the above-described production method as examples 1 to 7 and comparative examples 1 to 8. Each sample was prepared by mixing the components of formula (Nd)_1-x- _yLa_xSm_y)₂Fe₁₄B, x and y are changed. Thus, of each sample (Nd)_1-x-yLa_xSm_y) The combination of x and y in (1) is different for each of examples 1 to 7 and comparative examples 1 to 8. Each sample was produced by mixing a raw material powder and a resin, and then hardening the resin to form a bonded magnet. The shape of each sample was a block shape having a total of 7mm in the longitudinal, lateral and height directions.

The conditions for producing the samples of examples 1 to 7 and comparative examples 1 to 8 are as follows. The temperature at which the raw material alloy 26 is melted in the melting step is set to 1000 to 1500 ℃. In the cooling step, the rotational speed of the cooling roll 28 is set to 10m/s to 40 m/s. In this case, the cooling rate of the raw alloy 26 is 10²℃/s～10⁷DEG C/s. However, the cooling rate of the raw alloy 26 is preferably 10⁴℃/s～10⁷DEG C/s. The spray of the raw alloy 26 from the suction nozzle 27 to the cooling roll 28 is includedAr in a reduced pressure atmosphere.

First, the analysis results of the samples of examples 1 to 7 and comparative examples 1 to 8 will be described. The analysis by the WDS apparatus was performed by irradiating the surface of the ribbon alloy 29 with an electron beam. In the analysis by the WDS apparatus, the acceleration voltage of the electron beam was set to 15kV, the irradiation current of the electron beam was set to 100nA, and the spot diameter was set to 300 μm. Further, the crystal structure analysis by the XRD apparatus was performed in the raw material powder. In the XRD apparatus, Cu was used in the tube sphere. In the analysis by the XRD apparatus, the tube voltage was set to 40kV, the tube current was set to 25mA, and the measurement range 2 θ was set to 20 ° to 70 °.

According to the XRD device, it could not be confirmed that tetragonal R was excluded in the samples of examples 1 to 7 and comparative examples 1 to 8₂Fe₁₄B a crystal phase outside the crystal structure. Thus, it was confirmed that the tetragonal R was formed in each of the samples of examples 1 to 7 and comparative examples 1 to 8₂Fe₁₄B crystal structure. Therefore, the values of x and y in the samples of examples 1 to 7 and comparative examples 1 to 8 were determined by the WDS apparatus. The values of x and y obtained are shown in fig. 4 described later.

Next, the measurement results of the magnetic properties of the samples according to examples 1 to 7 and comparative examples 1 to 8 will be described, in the measurement of the coercive force, the 1 st measurement temperature T1 is set to 23 ℃, the 2 nd measurement temperature T2 is set to 200 ℃. 23 ℃ is set to room temperature, 200 ℃ is a temperature that can be generated as an environment when the motor for automobiles and industrial use is operated, and the temperature coefficient α of the coercive force is calculated using the coercive force at the temperature of 23 ℃ and the coercive force at the temperature of 200 ℃.

FIG. 4 is a table showing the relationship between the compositional formula of the main phase and the absolute value | α | of the temperature coefficient of coercive force in each of the samples according to examples 1 to 7 and comparative examples 1 to 8.

First, Nd is added to a base metal alloy₂Fe₁₄B is added with L a and Sm simultaneously and Nd is relative to base alloy₂Fe₁₄B case where only L a is addedA comparison is made. In this case, regarding (Nd)_1-x-yLa_xSm_y)₂Fe₁₄In the case of samples having the same addition ratio of Nd in B, the absolute value | α | of the temperature coefficient of coercive force was compared, if example 1 and comparative example 3 in which the addition ratio of Nd was 0.980 were compared, example 1 in which L a and Sm were simultaneously added, and comparative example 3 in which only L a was added, and the absolute value | α | of the temperature coefficient of coercive force was small, if example 3 and comparative example 4 in which the addition ratio of Nd was 0.950 were compared, the absolute value | α | of example 3 was small, and similarly, if example 4 and comparative example 5 in which the addition ratio of Nd was 0.906 were compared, the absolute value | α | of example 4 was small, according to the comparison of the above 3 groups, the base alloy Nd was compared with each other₂Fe₁₄The case where L a and Sm are added to B simultaneously with the base alloy Nd₂Fe₁₄In comparison with the case where only L a is added to B, the absolute value | α | of the temperature coefficient of the coercive force is small.

Next, the base metal alloy Nd will be treated₂Fe₁₄B is added with L a and Sm simultaneously and Nd is relative to base alloy₂Fe₁₄B was compared with the case where only Sm was added. In this case, regarding (Nd)_1-x-yLa_xSm_y)₂Fe₁₄In B, samples having the same Nd addition ratio were compared with each other, and the absolute value | α | of the temperature coefficient of coercive force was compared with comparative example 6 in which Sm was added alone, and the absolute value | α | of the temperature coefficient of coercive force was small in example 1 in which both L a and Sm were added, if example 1 and comparative example 6 in which Nd was added at 0.980 were compared, and the absolute value | α | of example 3 was small in example 3 and comparative example 7 in which Nd was added at 0.950, and similarly, the absolute value | α | of example 4 was small in example 4 and comparative example 8 in which Nd was added at 0.906, and according to the comparison of the above 3 groups, the base material alloy was compared with each other₂Fe₁₄The case where L a and Sm are added to B simultaneously with the base alloy Nd₂Fe₁₄In comparison with the case where B is added with Sm alone, the absolute value | α | of the temperature coefficient of coercive force is small.

Comparison of these measurement results shows that Nd is a base metal alloy₂Fe₁₄In the case where B is added to only one of L a and Sm, Nd is added to the base alloy₂Fe₁₄When L a and Sm are added simultaneously to B, the absolute value | α | of the temperature coefficient of the coercive force becomes small.

Next, FIG. 5 pair (Nd) was used_1-x-yLa_xSm_y)₂Fe₁₄The ranges of x and y in B will be described. FIG. 5 shows (Nd)_1-x-yLa_xSm_y)₂Fe₁₄Fig. 5 is a graph showing the relationship between x and y in B and the absolute value | α | of the temperature coefficient of coercivity, where x is y. as shown in fig. 5, the absolute value | α | of the temperature coefficient of coercivity decreases as x increases from 0, where x is 0.086, the absolute value | α | of the temperature coefficient has a minimum value, where x > 0.086, the absolute value | α | of the temperature coefficient increases as x increases, where x > 0.16, the absolute value | α | of the temperature coefficient exceeds the absolute value | α | of the temperature coefficient where x is 0, and where x and y are 0.01 ≦ x ≦ 0.16 and 0.01 ≦ y ≦ 0.16, the absolute value | α | of the temperature coefficient of coercivity is smaller than the absolute value | 8678 a and Sm where Nd are not added₂Fe₁₄Absolute value | α | of the temperature coefficient of the coercive force of B.

As a result of the measurement of the magnetic properties, the absolute value | α | of the temperature coefficient of the coercive force in comparative example 2, where x ═ y ═ 0.186, was larger than that for the base metal alloy Nd₂Fe₁₄The absolute value | α | of the temperature coefficient of the coercive force in comparative example 1 in which L a and Sm were not added B was considered as the cause thereof, with respect to the sample of comparative example 2, according to the crystal structure analysis by XRD device, although tetragonal Nd was detected₂Fe₁₄B, but the peak intensity was lower than that of each of the samples of examples 1 to 7. From this, it is considered that, with respect to the sample of comparative example 2, the base metal alloy Nd was used₂Fe₁₄B is added with L a and Sm in excess, thereby obtaining tetragonal Nd₂Fe₁₄The crystallinity of the B crystal structure is reduced, and therefore high magnetic characteristics cannot be obtained.

Next, using L a and Sm in tetragonal form R in FIGS. 6-8₂Fe₁₄B is a crystal structure in which the atom site is substituted. The replaced sites were determined by band calculation and molecular field approximation by the Heisenberg model to obtain stabilization energy for replacement, and the energy was evaluated by the numerical value.

First, a method of calculating the stabilization energy in L a will be described, and Nd can be used as the stabilization energy₈Fe₅₆B₄Crystal unit of (Nd)₇La₁)Fe₅₆B₄+ Nd and Nd₈(Fe₅₅La₁)B₄The smaller the value of the energy, the more stable the atom substitution at this position, that is, L a is easily substituted at the atomic position with the atomic position having the smallest energy, in this calculation, when L a is substituted with the original atom, the tetragonal R₂Fe₁₄The lattice constant in the B crystal structure does not change according to the difference in atomic radius. FIG. 6 shows a tetragonal Nd crystal used in FIGS. 7 and 8₂Fe₁₄A map of the atomic positions in B (Exhibit: J.F. Herbst et al: PHYSICA L REVIEW B, Vol.29, No.7, pp.4176-4178, 1984).

FIG. 7 is a table showing the stabilization energy of L a at each displacement point when the ambient temperature is changed, and according to FIG. 7, the stable displacement point of L a is an Nd (f) point at a temperature of 1000K or higher and an Fe (c) point at temperatures of 293K and 500 K.in embodiment 1, as described in the description of the manufacturing method, the raw material alloy of the permanent magnet is melted at a temperature of 1000℃ or higher and then rapidly cooled, and therefore, it is considered that the raw material alloy is 1000K or higher, that is, 727℃ or higher, and therefore, in the case of manufacturing the permanent magnet by the above-described manufacturing method, it is considered that L a is also replaced by the (Nd f) point at room temperature, and this is also considered that in the case where the L a-Fe-B alloy is melted by 1073K (800℃) and then cooled by ice water, tetragonal L a is formed₂Fe₁₄B, a study report that L a did not enter the Fe (c) site and entered a site corresponding to the Nd (f) site in FIG. 6 (shown in the figure)YAO Qingrong et al JOURNA L OF RARE EARTHS, Vol.34, No.11, pp.1121-1125, 2016).

Next, a method of calculating the stabilization energy in Sm will be described. (Nd) was determined for Sm₇Sm₁)Fe₅₆B₄+ Nd and Nd₈(Fe₅₅Sm₁)B₄The point where there is no change in lattice constant by substituting atoms is the same as in the case of L a.

FIG. 8 shows the stabilization energy of Sm at each displacement site when the ambient temperature was changed, and from FIG. 8, it is understood that the stable displacement site of Sm was Nd (g) site at any temperature, and that in each of the samples of examples 1 to 7 and comparative examples 1 to 8, L a was replaced by Nd (f) site, Sm was replaced by Nd (g) site, L a was replaced by energy-stable Nd (f) site, and Sm was replaced by energy-stable Nd (g) site₂Fe₁₄B, the permanent magnet to which L a and Sm are added can ensure stability of magnetic characteristics between products.

Next, a rotary machine mounted with a permanent magnet according to embodiment 1 will be described with reference to fig. 9. Fig. 9 is a schematic sectional view of a rotary machine mounted with permanent magnets according to embodiment 1, taken in a direction perpendicular to the axial direction of the rotary machine. In fig. 9, the detail of the hatching and the rotation axis is omitted, taking priority to the clarity of the drawing.

The rotary machine includes a rotor 30 and an annular stator not shown. The structure of the stator is not particularly limited, and may be an existing structure. The rotor 30 is rotatable about a rotation shaft 31. The rotor 30 has a

rotor core

32 and 6 permanent magnets 33. The rotor core 32 is formed by stacking a plurality of disc-shaped electromagnetic steel plates in the axial direction of the rotating shaft 31. The rotor core 32 is provided with 6 magnet insertion holes 34 in the circumferential direction of the rotor 30.

The 6 permanent magnets 33 were manufactured by the above-described manufacturing method. The 6 permanent magnets 33 are inserted into the corresponding magnet insertion holes 34, respectively. The 6 permanent magnets 33 are different in the direction in which the magnetic poles of the permanent magnets 33 on the radially outer side of the rotor 30 are different from those of the adjacent permanent magnets 33Each of which is magnetized. The 6 permanent magnets 33 have a tetragonal crystal R in the main phase of formation₂Fe₁₄B crystal structure of the formula (Nd)_1-x-yLa_xSm_y)₂Fe₁₄B, x and y are each 0.025, for example.

The number of magnetic poles of the rotor 30 may be 2 or more, that is, the number of permanent magnets 33 may be 2 or more. The rotor 30 is a rotor of a magnet-embedded type, but may be a surface magnet type rotor in which permanent magnets are fixed to the outer periphery of the rotor by an adhesive.

When the coercive force of the permanent magnet is reduced at a high temperature, the operation of the rotor 30 becomes unstable. When the permanent magnet 33 according to embodiment 1 is used, the absolute value of the temperature coefficient of the coercive force is small, and therefore, the decrease in the coercive force is suppressed even at high temperatures. Therefore, the operation of the rotor 30 can be stabilized even at high temperatures.

As described above, the permanent magnet according to embodiment 1 has a tetragonal crystal R₂Fe₁₄B crystal structure of the formula (Nd)_1-x-yLa_xSm_y)₂Fe₁₄B, x is more than or equal to 0.01 and less than or equal to 0.16, and y is more than or equal to 0.01 and less than or equal to 0.16. Therefore, a permanent magnet material having a small absolute value of the temperature coefficient of coercive force can be obtained. Therefore, the decrease in the coercive force of the permanent magnet associated with the temperature increase can be suppressed.

Since L a is substituted with Nd (f) site and Sm is substituted with Nd (g) site, the permanent magnet can ensure stable magnetic characteristics between products.

A method for manufacturing a permanent magnet according to embodiment 1 includes: a melting step of melting the raw material alloy 26 for the permanent magnet to bring the raw material alloy 26 into a molten state; and a cooling step of cooling the raw material alloy 26 in a molten state. This makes it possible to easily obtain a permanent magnet that suppresses a decrease in coercive force associated with a temperature increase.

In the method for manufacturing a permanent magnet according to embodiment 1, the cooling rate is set to 10 in the cooling step²～10⁷Thus, the substitution of L a can be maintained atThe state after the Nd (f) site.

In the method for producing a permanent magnet according to embodiment 1, the melting step can replace L a with nd (f) sites by melting the raw material alloy 26 at a temperature of 727 ℃ or higher, that is, 1000k or higher.

The rotary machine further includes a permanent magnet 33, and the permanent magnet 33 has a tetragonal crystal R₂Fe₁₄B crystal structure of the formula (Nd)_1-x-yLa_xSm_y)₂Fe₁₄B, x is more than or equal to 0.01 and less than or equal to 0.16, and y is more than or equal to 0.01 and less than or equal to 0.16. Therefore, a rotary machine that operates stably even at high temperatures can be configured.

Embodiment 2.

Next, a permanent magnet according to embodiment 2 of the present invention will be described with reference to fig. 10. In embodiment 1, x and y are equal values. In embodiment 2, x and y are different.

FIG. 10 shows a formula (Nd) in the composition_1-x-yLa_xSm_y)₂Fe₁₄B is a table showing the relationship between the presence or absence of the effect when the ratio of x to y is x/y and the ratio of the absolute value of the temperature coefficient of the coercive force is C1/C0. X is more than or equal to 0.01 and less than or equal to 0.16, and y is more than or equal to 0.01 and less than or equal to 0.16. C0 is Nd₂Fe₁₄Absolute value of temperature coefficient of coercivity in B. C1 is of component formula (Nd)_1-x-yLa_xSm_y)₂Fe₁₄In the case where C1/C0 is less than 1, the effect of the composite addition of L a and Sm with respect to the temperature coefficient of coercivity is visible, and ○ marks are given to the corresponding columns in fig. 10, and in the case where C1/C0 is not less than 1, the effect of the composite addition of L a and Sm with respect to the temperature coefficient of coercivity is not visible, and × marks are given to the corresponding columns in fig. 10.

As shown in FIG. 10, has a tetragonal crystal of R₂Fe₁₄Component formula (Nd) of B crystal structure_1-x-yLa_xSm_y)₂Fe₁₄A permanent magnet of the magnetic flux density distribution element B,when x and y are in the range of 0.5. ltoreq. x/y. ltoreq.2.0, pass L a and Sm are added to the base alloy Nd₂Fe₁₄The effect of the composite addition of B can reduce the absolute value of the temperature coefficient of the coercive force.

As described above, in the permanent magnet according to embodiment 2, the ratio x/y between x and y is 0.5. ltoreq. x/y. ltoreq.2.0. Thus, a permanent magnet having a small absolute value of the temperature coefficient of coercive force can be obtained.

In the present invention, since expensive heavy rare earth elements such as Gd, Tb, Dy, Ho, Er, Tm, Yb, and L u are not used, a permanent magnet having a small absolute value of the temperature coefficient of coercive force can be produced at low cost.

Description of the reference numerals

26 raw material alloy, 33 permanent magnet.

Claims

1. A permanent magnet having a tetragonal crystal R₂Fe₁₄B, the crystal structure of the crystal is shown,

has the component formula of (Nd)_1-x-yLa_xSm_y)₂Fe₁₄B，

x is more than or equal to 0.01 and less than or equal to 0.16,

y is more than or equal to 0.01 and less than or equal to 0.16.

2. The permanent magnet according to claim 1,

l a is replaced by Nd (f) site,

sm is substituted with Nd (g) sites.

3. The permanent magnet according to claim 1 or 2,

the ratio of x to y, x/y, is 0.5-2.0.

4. A method for producing a permanent magnet according to any one of claims 1 to 3,

the method for manufacturing the permanent magnet comprises the following steps:

a melting step of melting a raw material alloy of the permanent magnet to bring the raw material alloy into a molten state; and

a cooling step of cooling the raw material alloy in the molten state.

5. The method for manufacturing a permanent magnet according to claim 4, wherein,

in the cooling step, the cooling rate was set to 10²～10⁷℃/s。

6. The method for manufacturing a permanent magnet according to claim 4 or 5, wherein,

in the melting step, the temperature at which the raw material alloy is melted is set to 727 ℃ or higher.

7. A rotary machine having the permanent magnet according to any one of claims 1 to 3.