JP6359232B1 - Permanent magnet, method for manufacturing permanent magnet, and rotating machine - Google Patents

Abstract

The permanent magnet of this invention has a tetragonal R2Fe14B crystal structure. This permanent magnet has a composition formula of (Nd1-x-yLaxSmy) 2Fe14B. Here, x is in the range of 0.01 ≦ x ≦ 0.16, and y is in the range of 0.01 ≦ y ≦ 0.16.

Description

  The present invention relates to an RTB-based permanent magnet, a method for manufacturing the permanent magnet, and a rotating machine having the permanent magnet.

R-T-B permanent magnets, whose main phase is tetragonal R ₂ T ₁₄ B intermetallic compounds, are excellent in magnetic properties in that they have a high coercive force, and various high additions including industrial motors. Used for valuable parts. Here, R is a rare earth element, and T is a transition element. Conventionally, an RTB-based permanent magnet added with Dy, which is a heavy rare earth element, is known (see, for example, Patent Document 1). An RTB-based permanent magnet to which a plurality of rare earth elements including Y and La are necessarily added is also known (see, for example, Patent Document 2).

JP-A-6-13211 JP-A-9-115713

  When using a permanent magnet for an industrial motor, the operating temperature environment is often a high temperature exceeding 100 ° C. However, in the conventional permanent magnets disclosed in Patent Documents 1 and 2, the coercive force may be remarkably reduced with an increase in temperature.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a permanent magnet, a method of manufacturing a permanent magnet, and a rotating machine that suppress a decrease in coercive force due to a temperature rise. It is said.

The permanent magnet according to the invention, has a tetragonal R ₂ Fe ₁₄ B crystal structure, a composition formula _{(Nd 1-xy La x Sm} y) is a ₂ Fe ₁₄ B, x is, 0.01 ≦ x ≦ 0 .16, and y is 0.01 ≦ y ≦ 0.16.

  According to the permanent magnet of the present invention, the absolute value of the temperature coefficient of the coercive force of the permanent magnet can be reduced. Thereby, the permanent magnet which suppressed the fall of the coercive force accompanying a temperature rise can be provided. Moreover, the manufacturing method of such a permanent magnet and the rotary machine which has a permanent magnet can be provided.

3 is a flowchart of a method for manufacturing the permanent magnet according to the first embodiment. FIG. 5 is a diagram for explaining a raw material alloy manufacturing step in the method for manufacturing a permanent magnet of the first embodiment. In the manufacturing method of the permanent magnet of Embodiment 1, it is a figure explaining a melting process and a cooling process. 4 is a table showing the relationship between the composition formula and the absolute value of the temperature coefficient of coercive force in the sample of the permanent magnet of the first embodiment. And x and y in _{(Nd 1-xy La x Sm} y) 2 Fe 14 B, the absolute value of the temperature coefficient of coercive force | is a graph showing the relationship between | alpha. It is a diagram showing the atomic sites in tetragonal Nd ₂ Fe ₁₄ B. It is a table | surface which shows the stabilization energy of La in each substitution site at the time of changing environmental temperature. It is a table | surface which shows the stabilization energy of Sm in each substitution site at the time of changing environmental temperature. It is a cross-sectional schematic diagram of the direction perpendicular | vertical to the axial direction of a rotary machine about the rotary machine which mounts the permanent magnet of Embodiment 1. FIG. In the second embodiment, a table showing a relationship between the presence or absence of effects in the ratio of the absolute value of the temperature coefficient of the x / y and a coercive force of _{(Nd 1-xy La x Sm} y) 2 Fe 14 B.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, in each figure, the same or an equivalent part is shown with the same code | symbol, and the overlapping description is abbreviate | omitted.

Embodiment 1 FIG.
The RTB-based permanent magnet according to the first embodiment of the present invention is a permanent magnet having a tetragonal R ₂ T ₁₄ B structure as a main product phase. Here, R is a rare earth element. T is a transition element. B is boron. In the permanent magnet having the tetragonal R ₂ T ₁₄ B structure according to the first embodiment, R is obtained by replacing part of neodymium (Nd) with lanthanum (La) and samarium (Sm), and iron (Fe) is converted to T It is said that. Therefore, in the first embodiment, the permanent magnet composition formula is represented by _{(Nd 1-xy La x Sm} y) 2 Fe 14 B. Here, a method for manufacturing an RTB-based permanent magnet will be described first.

  FIG. 1 is a flowchart showing a procedure for manufacturing an RTB-based permanent magnet according to the first embodiment. As shown in FIG. 1, the manufacturing method of the RTB-based permanent magnet includes a raw material alloy manufacturing process, a melting process, a cooling process, a pulverizing process, a forming process, and a magnetizing process.

(Raw alloy manufacturing process)
When manufacturing an RTB-based permanent magnet, first, a raw material alloy is manufactured in a raw material alloy manufacturing step. In the raw material alloy manufacturing step, first, raw materials having a weight corresponding to the composition ratio of each element of the permanent magnet are prepared, and these raw materials are mixed. Nd, La, Sm, Fe, and ferroboron (FeB) are used as raw materials. Thereby, a mixed raw material in which Nd, La, Sm, Fe, and FeB are mixed is obtained. Next, the mixed raw material is melted. Thereby, a raw material alloy is obtained.

  FIG. 2 is a configuration diagram showing a state when the mixed raw material is melted in the raw material alloy manufacturing step of FIG. When the mixed raw material is melted, an arc 22 is generated from the electrode 21 to the receiving tray 23 in a state where the mixed raw material 24 is disposed in the copper receiving tray 23. The mixed raw material 24 is melted on the tray 23 by the arc 22. The mixed raw material 24 is melted by the arc 22 in, for example, a reduced-pressure atmosphere containing argon (Ar) that is an inert gas. The raw material alloy can also be produced using a method other than the melting of the mixed raw material 24 by arc.

(Melting process)
After the raw material alloy manufacturing step, as shown in FIG. 3, the raw material alloy 26 is melted by the high frequency induction heating coil 25 in the melting step.

(Cooling process)
Thereafter, 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 using a liquid quenching method. In the liquid quenching method, the molten raw material alloy 25 is injected from the nozzle 27 onto the cooling roll 28. When injecting the raw material alloy 26 onto the cooling roll 28, the cooling roll 28 is rotated. Thereby, the raw material alloy 26 in the molten state is cooled by the cooling roll 28 to become a ribbon-shaped alloy 29. The ribbon-like alloy 29 can be produced using a method other than the liquid quenching method.

(Crushing process)
Thereafter, the ribbon-like alloy 29 is pulverized in the pulverization step. Thereby, the ribbon-like alloy 29 becomes a raw material powder having a particle size of about 200 μm or less. The pulverization of the ribbon-like alloy 29 is performed using, for example, an agate mortar. For pulverizing the ribbon-like alloy 29, a stamp mill, a jaw crusher, a jet mill or the like can be used in addition to a mortar. The pulverization of the ribbon-shaped alloy 29 is desirably performed in an inert gas, particularly when the particle size of the raw material powder is reduced. By pulverizing the ribbon-shaped alloy 29 in an inert gas, it is possible to suppress oxygen from being mixed into the raw material powder. If the atmosphere in the pulverization does not affect the magnetic characteristics of the permanent magnet, the ribbon-shaped alloy 29 may not be pulverized in an inert gas.

(Molding process)
Thereafter, a forming step for forming the raw material powder is performed. In the molding step, the raw material powder and an epoxy resin having a heat resistant temperature of 200 ° C. or higher are stirred and mixed. At this time, the volume content ratio of the raw material powder is set to about 20 vol%. Thereafter, the resin is cured to form a bonded magnet. Only the raw material powder may be compression molded. Moreover, you may compression-mold what mixed the organic type binder with the raw material powder. Any of the above-described forming methods may be performed while applying a magnetic field.

(Sintering process)
In the case where only the raw material powder is compression molded, or when the material powder mixed with the organic binder is compression molded, a sintering step is performed after the molding step. The sintering process is performed in a vacuum or an inert gas atmosphere to suppress oxidation. The sintering step may be performed while applying a magnetic field. Moreover, you may add the process of a hot working or an aging process to a sintering process, for example, in order to improve a magnetic characteristic, ie, anisotropy of a magnetic field, or a coercive force improvement. Moreover, you may add the process of making the compound containing copper or aluminum osmose | permeate into the crystal grain boundary which is a boundary between main phases to a sintering process.

(Magnetization process)
The alloy that has undergone the forming process or the sintering process is subjected to cutting, polishing, or surface treatment to form a product-shaped alloy. The product-shaped alloy is magnetized by, for example, a capacitor-type magnetizing power supply device and becomes a permanent magnet.

Next, a method for analyzing the composition of the main phase in the R-T-B system permanent magnet will be described. In general, the composition of a permanent magnet can be quantified by using a wavelength dispersive x-ray spectroscopy (WDS) apparatus attached to a scanning electron microscope. However, in the analysis by the WDS apparatus, since the analysis accuracy of light elements is low, it is difficult to quantify B with an R-T-B system permanent magnet. Therefore, an X-ray diffraction (XRD) apparatus is used in combination. An XRD apparatus confirms that the main product phase of the permanent magnet is a tetragonal R ₂ Fe ₁₄ B crystal structure. Accordingly, it can be confirmed that the main composition of the R-T-B system permanent magnet is R: T: B = 2: 14: 1. In the WDS apparatus, the constituent ratio of elements other than B, that is, the constituent ratio of Nd, La, and Sm that constitute R, and the constituent ratio of Fe that constitutes T can be obtained. From the above two results, the total composition ratio of the generated phase can be obtained. In the XRD apparatus, it can be confirmed whether the element is not included in the tetragonal R ₂ Fe ₁₄ B crystal structure and does not exist as another structure.

  Next, a method for evaluating magnetic characteristics will be described. The magnetic characteristics were evaluated by measuring the coercive force of a plurality of samples using a pulse excitation type BH tracer. The maximum applied magnetic field by the BH tracer is 5T or more. The atmosphere during measurement is nitrogen. The coercive force of each sample was measured at different temperatures of the first measurement temperature T1 and the second measurement temperature T2. The temperature coefficient α [% / ° C.] of the coercive force is obtained by dividing the ratio of the difference between the coercive force at T1 and the coercive force at T2 and the coercive force at T1 by the difference in temperature (T2−T1). Value. Therefore, as the absolute value | α | of the temperature coefficient of the coercive force decreases, the decrease in the coercive force of the permanent magnet with respect to the temperature rise is suppressed.

In the first embodiment, samples of a plurality of permanent magnets having different main phase compositions were manufactured as the samples according to Examples 1 to 7 and Comparative Examples 1 to 8 by the above manufacturing method. Each sample was prepared by changing x and y in the composition formula _{(Nd 1-xy La x Sm} y) 2 Fe 14 B. Thus, the combination of x and y in each sample _{(Nd 1-xy La x Sm} y) is different for each Examples 1 to 7 and Comparative Examples 1-8. Each sample was manufactured in the form of a bonded magnet formed by mixing a raw material powder and a resin and then curing the resin. The shape of each sample is a block shape of 7 mm in length, width, and height.

Moreover, the various conditions in manufacture of each sample by Examples 1-7 and Comparative Examples 1-8 are as follows. The temperature for melting the raw material alloy 26 in the melting step was set to 1000 ° C to 1500 ° C. In the cooling step, the rotation speed of the cooling roll 28 was set to 10 m / s to 40 m / s. In this case, the cooling rate of the raw material alloy 26 is 10 ² ° C / s to 10 ⁷ ° C / s. However, the cooling rate of the raw material alloy 26 is desirably 10 ⁴ ° C / s to 10 ⁷ ° C / s. Moreover, the injection of the raw material alloy 26 from the nozzle 27 to the cooling roll 28 was performed in a reduced pressure atmosphere containing Ar.

  First, the analysis result in each sample by Examples 1-7 and Comparative Examples 1-8 is demonstrated. Analysis by the WDS apparatus was performed by irradiating the surface of the ribbon-shaped alloy 29 with an electron beam. In the analysis using the WDS apparatus, the acceleration voltage of the electron beam was 15 kV, the irradiation current of the electron beam was 100 nA, and the spot diameter was 300 μm. Moreover, the crystal structure analysis by the XRD apparatus was implemented in the raw material powder. In the XRD apparatus, Cu was used for the tube. In the analysis by the XRD apparatus, the tube voltage was 40 kV, the tube current was 25 mA, and the measurement range 2θ was 20 ° to 70 °.

According to the XRD apparatus, no crystal phase other than the tetragonal R ₂ Fe ₁₄ B crystal structure could be confirmed in the samples of Examples 1 to 7 and Comparative Examples 1 to 8. Thus, for each sample according to Examples 1-7 and Comparative Examples 1-8, it was confirmed that a tetragonal R ₂ Fe ₁₄ B crystal structure. Therefore, the value of x and y in each sample by Examples 1-7 and Comparative Examples 1-8 can be calculated | required with a WDS apparatus. The obtained values of x and y are as shown in FIG.

  Next, the measurement result of the magnetic characteristic in each sample by Examples 1-7 and Comparative Examples 1-8 is demonstrated. In the measurement of the coercive force, the first measurement temperature T1 was 23 ° C., and the second measurement temperature T2 was 200 ° C. 23 ° C. is room temperature. 200 ° C. is a temperature that can occur as an environment during motor operation for automobiles and industrial use. The temperature coefficient α of the coercive force was calculated using the coercive force at a temperature of 23 ° C. and the coercive force at a temperature of 200 ° C.

FIG. 4 is a table showing the relationship between the composition formula of the main phase in each sample according to Examples 1 to 7 and Comparative Examples 1 to 8 and the absolute value | α | of the temperature coefficient of the coercive force.
First, compared to the base metal alloy Nd ₂ Fe ₁₄ B, in the case of adding La and Sm simultaneously, against the base material alloy Nd ₂ Fe ₁₄ B, and a case of adding only La. In this case, the addition ratio of Nd in the _{(Nd 1-xy La x Sm} y) 2 Fe 14 B is for the same sample, respectively, the absolute value of the temperature coefficient of coercive force | alpha | Compare. Comparing Example 1 and Comparative Example 3 where Nd addition ratio = 0.980, Example 1 in which La and Sm are added simultaneously is compared with Comparative Example 3 in which only La is added. Thus, the absolute value | α | of the temperature coefficient of the coercive force is small. When Example 3 and Comparative Example 4 where Nd addition ratio = 0.950 are compared, Example 3 has a smaller absolute value | α |. Similarly, when Example 4 and Comparative Example 5 in which the addition ratio of Nd is 0.906 are compared, Example 4 has a smaller absolute value | α |. Comparison According to the three sets of the above comparison, with respect to the base material alloy Nd ₂ Fe ₁₄ B, when added La and Sm simultaneously, against the base material alloy Nd ₂ Fe ₁₄ B, and the case of adding only La Thus, the absolute value | α | of the temperature coefficient of the coercive force is small.

Then compared against the base metal alloy Nd ₂ Fe ₁₄ B, in the case of adding La and Sm simultaneously, against the base material alloy Nd ₂ Fe ₁₄ B, and a case of adding Sm only. In this case, the addition ratio of Nd in the _{(Nd 1-xy La x Sm} y) 2 Fe 14 B is for the same sample, respectively, the absolute value of the temperature coefficient of coercive force | alpha | Compare. Comparing Example 1 and Comparative Example 6 in which Nd addition ratio = 0.980, Example 1 in which La and Sm are added simultaneously is compared with Comparative Example 6 in which only Sm is added. Thus, the absolute value | α | of the temperature coefficient of the coercive force is small. When Example 3 and Comparative Example 7 in which the Nd addition ratio = 0.950 is compared, Example 3 has a smaller absolute value | α |. Similarly, when Example 4 and Comparative Example 8 in which the addition ratio of Nd is 0.906 are compared, Example 4 has a smaller absolute value | α |. Comparison According to the three sets of the above comparison, with respect to the base material alloy Nd ₂ Fe ₁₄ B, when added La and Sm simultaneously, against the base material alloy Nd ₂ Fe ₁₄ B, and the case of adding Sm only Thus, the absolute value | α | of the temperature coefficient of the coercive force is small.

From comparison of these measurement results, La and Sm were compared with respect to the base alloy Nd ₂ Fe ₁₄ B, compared with the case where only one of La and Sm was added to the base alloy Nd ₂ Fe ₁₄ B. It was shown that the absolute value | α | of the temperature coefficient of the coercive force is smaller when both are added simultaneously.

Next, the range of x and y in _{(Nd 1-xy La x Sm} y) 2 Fe 14 B, will be described with reference to FIG. 5, the x and y, the absolute value of the temperature coefficient of the coercive force in the _{(Nd 1-xy La x Sm} y) 2 Fe 14 B | is a graph showing the relationship between | alpha. In FIG. 5, x is equal to y. As shown in FIG. 5, the absolute value | α | of the temperature coefficient of the coercive force decreases as x increases from zero. When x = 0.086, the absolute value | α | of the temperature coefficient has a minimum value. When x> 0.086, the absolute value | α | of the temperature coefficient increases as x increases. When x> 0.16, the absolute value | α | of the temperature coefficient exceeds the absolute value | α | of the temperature coefficient when x = 0. From the above, when x and y are 0.01 ≦ x ≦ 0.16 and 0.01 ≦ y ≦ 0.16, the absolute value of the temperature coefficient of coercive force | α | Is smaller than the absolute value | α | of the temperature coefficient of the coercive force of Nd ₂ Fe ₁₄ B.

As a result of measuring the magnetic characteristics, the absolute value | α | of the temperature coefficient of coercive force in Comparative Example 2 in which x = y = 0.186 is not added to La and Sm with respect to the base alloy Nd ₂ Fe ₁₄ B It is larger than the absolute value | α | The following can be considered as the factor. According to the crystal structure analysis by the XRD apparatus, although the peak related to tetragonal Nd ₂ Fe ₁₄ B was detected for the sample of Comparative Example 2, the peak intensity was lower than that of each sample of Examples 1 to 7. . From this, for the sample of Comparative Example 2, the crystallinity of the tetragonal Nd ₂ Fe ₁₄ B crystal structure decreases due to the excessive addition of La and Sm to the base alloy Nd ₂ Fe ₁₄ B. Therefore, it is considered that high magnetic properties could not be obtained.

Next, the atomic site where La and Sm are substituted in the tetragonal R ₂ Fe ₁₄ B crystal structure will be described with reference to FIGS. The site to be replaced is determined based on the numerical value of the energy obtained by calculating the stabilization energy by the band calculation and the molecular field approximation of the Heisenberg model.

First, the calculation method of the stabilization energy in La is demonstrated. The stabilization energy can be obtained from the energy difference between (Nd ₇ La ₁ ) Fe ₅₆ B ₄ + Nd and Nd ₈ (Fe ₅₅ La ₁ ) B ₄ + Fe using an Nd ₈ Fe ₅₆ B ₄ crystal cell. . The smaller the value, the more stable the energy when an atom is substituted at the site. That is, La is easily replaced with an atomic site having the smallest energy among the atomic sites. In this calculation, when La is replaced with the original atom, the lattice constant in the tetragonal R ₂ Fe ₁₄ B crystal structure does not change with the difference in atomic radius. 6 is a diagram showing atomic sites in tetragonal Nd ₂ Fe ₁₄ B used in FIGS. 7 and 8 (exhibited by JF Herbst et al .: PHYSICAL REVIEW B, Vol. 29, No. 7). , Pp. 4176-4178, 1984).

FIG. 7 is a table showing the stabilization energy of La at each replacement site when the environmental temperature is changed. According to FIG. 7, the stable substitution site of La is an Nd (f) site at a temperature of 1000 K or higher, and an Fe (c) site at temperatures of 293K and 500K. In the first embodiment, as described in the manufacturing method, the permanent magnet raw material alloy is rapidly cooled after being melted at a temperature of 1000 ° C. or higher. Therefore, it is considered that the raw material alloy is maintained in a state of 1000 K or higher, that is, 727 ° C. or higher. Therefore, when a permanent magnet is produced by the above-described manufacturing method, it is considered that La is replaced with an Nd (f) site even at room temperature. This is because when La-Fe-B alloy is melted at 1073 K (800 ° C.) and then cooled with ice water, tetragonal La ₂ Fe ₁₄ B is formed, that is, La is Fe (c) site. A research report (exhibition: YAO Qinglong et al .: JOURNAL OF RARE EARTHS, Vol. 34, No. 11, pp. 1121-1125, 2016) entering the site corresponding to the Nd (f) site in FIG. It is supported by some things.

Next, a method for calculating the stabilization energy in Sm will be described. For Sm, the energy difference between (Nd ₇ Sm ₁ ) Fe ₅₆ B ₄ + Nd and Nd ₈ (Fe ₅₅ Sm ₁ ) B ₄ + Fe is determined. The point that the lattice constant is not changed by the substitution of atoms is the same as in the case of La.

FIG. 8 is a table showing the stabilization energy of Sm at each replacement site when the environmental temperature is changed. According to FIG. 8, it can be seen that the stable substitution site of Sm is an Nd (g) site at any temperature. As described above, in each sample of Examples 1 to 7 and Comparative Examples 1 to 8, La is substituted with the Nd (f) site, and Sm is substituted with the Nd (g) site. La is replaced with an energetically stable Nd (f) site, and Sm is replaced with an energetically stable Nd (g) site. Therefore, in the permanent magnet to which La and Sm are added to the base material alloy Nd ₂ Fe ₁₄ B, the stability of the magnetic characteristics between products can be maintained.

  Next, a rotating machine equipped with the permanent magnet in the first embodiment will be described with reference to FIG. FIG. 9 is a schematic cross-sectional view in the direction perpendicular to the axial direction of the rotating machine of the rotating machine on which the permanent magnets according to Embodiment 1 are mounted. In FIG. 9, priority is given to the clarity of the drawing, and details of hatching and the rotation axis are omitted.

  The rotating machine includes a rotor 30 and an annular stator (not shown). The configuration of the stator is not particularly limited, and may be an existing configuration. The rotor 30 can rotate around the rotation shaft 31. The rotor 30 includes a rotor core 32 and six permanent magnets 33. The rotor core 32 is formed by laminating a plurality of disk-shaped electromagnetic steel plates in the axial direction of the rotary shaft 31. The rotor core 32 is provided with six magnet insertion holes 34 along the circumferential direction of the rotor 30.

The six permanent magnets 33 are manufactured by the manufacturing method described above. Each of the six permanent magnets 33 is inserted into the corresponding magnet insertion hole 34. The six permanent magnets 33 are magnetized such that 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 33. Six permanent magnets 33 has a tetragonal R ₂ Fe ₁₄ B crystalline structure in the main production phase, a composition formula _{(Nd 1-xy La x Sm} y) 2 Fe 14 B, x and y, for example Both are 0.025.

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

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

Thus, the permanent magnet according to the first embodiment, has a tetragonal R ₂ Fe ₁₄ B crystal structure, a composition formula _{(Nd 1-xy La x Sm} y) is a ₂ Fe ₁₄ B, x is 0 .01 ≦ x ≦ 0.16, and y is 0.01 ≦ y ≦ 0.16. Therefore, a permanent magnet material having a small absolute value of the temperature coefficient of coercive force can be obtained. Therefore, it is possible to suppress a decrease in the coercive force of the permanent magnet accompanying the temperature increase.

  Further, La is substituted with an Nd (f) site, and Sm is substituted with an Nd (g) site. Therefore, in the permanent magnet, the stability of the magnetic characteristics between products can be maintained.

  The manufacturing method of the permanent magnet according to the first embodiment includes a melting step of melting the raw material alloy 26 of the permanent magnet to bring the raw material alloy 26 into a molten state, and a cooling step of cooling the molten raw material alloy 26. Thereby, it is possible to easily obtain a permanent magnet in which a decrease in coercive force due to a temperature rise is suppressed.

In the manufacturing method of the permanent magnet in Embodiment 1, the cooling rate is 10 ² to 10 ⁷ ° C / s in the cooling step. As a result, it is possible to maintain a state where La is substituted with the Nd (f) site.

  In the method for manufacturing a permanent magnet in the first embodiment, the temperature at which the raw material alloy 26 is melted in the melting step is 727 ° C. or higher, that is, 1000 K or higher. Thereby, La can be substituted with the Nd (f) site.

Further, the rotating machine has a tetragonal R ₂ Fe ₁₄ B crystal structure, a composition formula _{(Nd 1-xy La x Sm} y) is a ₂ Fe ₁₄ B, x is, 0.01 ≦ x ≦ 0. 16 and y has a permanent magnet 33 satisfying 0.01 ≦ y ≦ 0.16. Therefore, it is possible to configure a rotating machine that operates stably even at high temperatures.

Embodiment 2. FIG.
Next, a permanent magnet according to Embodiment 2 of the present invention will be described with reference to FIG. In the first embodiment, x and y are equal values. In the second embodiment, x and y are different.

10, in the composition formula _{(Nd 1-xy La x Sm} y) 2 Fe 14 B, and the ratio x / y of x and y, and the presence or absence of effects in the ratio C1 / C0 of the absolute value of the temperature coefficient of coercive force It is a table | surface which shows these relationships. x is 0.01 ≦ x ≦ 0.16, and y is 0.01 ≦ y ≦ 0.16. C0 is the absolute value of the temperature coefficient of coercive force in Nd ₂ Fe ₁₄ B. C1 is the absolute value of the temperature coefficient of the coercive force in the composition formula _{(Nd 1-xy La x Sm} y) 2 Fe 14 B (0.01 ≦ x ≦ 0.16,0.01 ≦ y ≦ 0.16) is there. When C1 / C0 is less than 1, the effect of combined addition of La and Sm is seen on the temperature coefficient of the coercive force, and a circle is given in the corresponding column of FIG. In addition, when C1 / C0 is 1 or more, an X mark is given to the corresponding column in FIG. 10 because the effect of combined addition of La and Sm is not observed with respect to the temperature coefficient of coercive force. The sample of the permanent magnet used for the measurement was manufactured by the manufacturing method described in the first embodiment.

As shown in FIG. 10, the tetragonal R ₂ Fe ₁₄ B composition formula having a crystalline structure _{(Nd 1-xy La x Sm} y) 2 permanent magnets of Fe ₁₄ B, in the x and y, 0.5 ≦ x / When in the range of y ≦ 2.0, the absolute value of the temperature coefficient of the coercive force can be reduced by the effect of combined addition of La and Sm to the base material alloy Nd ₂ Fe ₁₄ B.

  Thus, in the permanent magnet according to the second embodiment, the ratio x / y between x and y is 0.5 ≦ x / y ≦ 2.0. Thereby, 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 Lu are not used, a permanent magnet having a small absolute value of the temperature coefficient of coercive force is manufactured at low cost. It is possible.

  26 Raw material alloy, 33 Permanent magnet.

Claims (7)

Having a tetragonal R ₂ Fe ₁₄ B crystal structure,
Composition formula _{(Nd 1-xy La x Sm} y) is a ₂ Fe ₁₄ B,
x is 0.01 ≦ x ≦ 0.16,
y is a permanent magnet satisfying 0.01 ≦ y ≦ 0.16. La is replaced with the Nd (f) site,
The permanent magnet according to claim 1, wherein Sm is substituted with an Nd (g) site.   The permanent magnet according to claim 1, wherein a ratio x / y between x and y is 0.5 ≦ x / y ≦ 2.0. A method for producing a permanent magnet according to any one of claims 1 to 3,
A method of manufacturing a permanent magnet, comprising: 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. The manufacturing method of the permanent magnet of Claim 4 which makes a cooling rate 10 < ² > -10 < ⁷ > degrees C / s in the said cooling process.   The manufacturing method of the permanent magnet of Claim 4 or 5 which sets the temperature which fuse | melts the said raw material alloy to 727 degreeC or more in the said fusion | melting process.   A rotating machine having the permanent magnet according to any one of claims 1 to 3.

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