JP2008078614A - Manufacturing method for isotropic iron-base rare-earth alloy magnet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the Nd-Fe-B-base quench magnet with uniform and fine crystalline structure. <P>SOLUTION: A quench alloy is manufactured by forming and quenching the molten alloy expressed by the composition formula: (Fe<SB>1-m</SB>T<SB>m</SB>)<SB>100-x-y-z</SB>(B<SB>1-p</SB>C<SB>p</SB>)<SB>x</SB>R<SB>y</SB>M<SB>z</SB>, wherein T indicates one or more kinds of elements selected from a group consisting of Co and Ni, R indicates one or more kinds of elements selected from a group consisting of yttrium and rare-earth metal element, M indicates one or more kinds of elements selected from a group consisting of Ti, Zr, Al, Si, V, Mn, Cu, Zn, Ga, Cr, Nb, Mo, Ag, Hf, Ta, W, Pt, Au, Pb, Bi and Sn, and the following relationships of 4≤x≤20, 4≤y≤20, 0.1≤z≤5, 0≤m≤0.8, and 0<p≤0.3 are satisfied. The molten alloy is quenched to manufacture the quench alloy containing the Nd<SB>2</SB>Fe<SB>14</SB>B type compound phase having an average crystalline particle size of 50 nm or less and a volume ratio ranging from not less than 5% to not more than 50%. Thereafter, the quench alloy is subject to the thermal treatment step for keeping its temperature above the crystallization temperature of the Nd<SB>2</SB>Fe<SB>14</SB>B type compound phase in a magnetic field. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a permanent magnet suitably used for various motors and actuators, and particularly to a method for manufacturing an iron-based rare earth alloy magnet.

At present, a hard magnetic phase such as Nd ₂ Fe ₁₄ B phase (hereinafter sometimes referred to as “2-14-1 phase”) and a soft magnetic phase such as iron-based boride and α-Fe are magnetic. Nanocomposite permanent magnets have been developed that have a tissue structure bonded to.

  Nd in the “2-14-1 phase” may be substituted with another rare earth element R, and a part of Fe may be substituted with Co and / or Ni. Furthermore, a part of B in the 2-14-1 phase may be substituted with C (carbon).

  By adding Ti to an alloy having a specific composition, the applicant suppresses the precipitation and growth of the α-Fe phase in the cooling process of the molten alloy, and gives priority to crystal growth of the 2-14-1 phase. I found it to progress. The applicant of the present invention describes a composition and manufacturing method of a nanocomposite magnet having a structure in which a 2-14-1 phase is uniformly dispersed in a fine iron-based boride phase or an α-Fe phase as an effect of added Ti. 1 and Patent Document 2.

Conventionally, single-phase magnets containing an Nd ₂ Fe ₁₄ B type crystal phase, which is a hard magnetic phase, as a main phase and a nonmagnetic phase at the grain boundary of the main phase are widely used. Patent Documents 3 and 4 disclose single-phase magnets.

These isotropic R-Fe-B quenching magnets, such as nanocomposite magnets and single-phase magnets, all have a nanometer-scale crystal grain size, and the molten alloy can be rapidly melted by a superquenching method. It is produced by cooling and solidifying, and then in many cases crystallizing by heat treatment.
Japanese Patent No. 3264664 WO2006 / 064794 Pamphlet JP-A-60-9852 JP-A 64-703 JP-A-61-129802 Japanese Unexamined Patent Publication No. 64-4421 Japanese Patent Laid-Open No. 11-8109

The magnetic properties of the produced magnet depend on its crystal structure. Conventionally, quenching magnets have the effect of improving the residual magnetic flux density _Br by improving the squareness of the magnetic curve by strengthening the exchange coupling between crystal grains when the crystal grain size becomes small (remanence enhancement). It is known that the coercivity may be improved. For this reason, it is desired that an ideal uniform microstructure be realized as the crystal structure of the magnet.

  The crystal structure of the magnet varies greatly depending on the heat treatment conditions (heating rate and holding temperature). For example, when the temperature is raised gently and heat treatment is performed at a low temperature, only crystals that are advantageous in magnetic properties, such as the 2-14-1 phase, can be grown, but the crystal structure is uneven. Become. In addition, when the temperature is increased rapidly and kept at a high temperature for heat treatment, α-Fe phase and the like grow abnormally.

In the conventional manufacturing method, the range of options for the heat treatment conditions is small, and the heat treatment conditions for obtaining good magnetic properties are determined one-to-one with the alloy composition. In other words, once the alloy composition is determined, the heat treatment conditions for obtaining the best magnetic properties with that composition are determined, and the alloy structure that is inevitably obtained is also determined. Therefore, the potential of the high magnetic properties (saturation magnetization I _s , intrinsic retention) is determined. _Even when an alloy having a magnetic force H _cJ ) is found, because the structure is not uniform, good characteristics as a whole cannot often be obtained. That is, since the variation in particle size is large, the residual magnetic flux density _Br and the maximum magnetic energy product (BH) _max are low, and the squareness of the demagnetization curve is often poor.

  In particular, in a nanocomposite magnet containing at least one of an iron-based boride phase and an α-Fe phase as a soft magnetic phase, the magnetic properties are significantly deteriorated as the structure becomes non-uniform.

  The present invention has been made in order to solve the above-mentioned problems, and the object of the present invention is to obtain a magnet whose crystal structure is uniformly refined in an Nd—Fe—B type quenching magnet, thereby providing excellent magnetic properties. It is to provide a magnet.

The method for producing an isotropic iron-based rare earth alloy magnet according to the present invention is represented by the composition formula (Fe _1-m T _m ) _100-xyz (B _1-p C _p ) _x R _y M _z , where T is Co and One or more elements selected from the group consisting of Ni, R is one or more elements selected from the group consisting of yttrium and rare earth metal elements, M is Ti, Zr, Al, Si, V, Mn, Cu, One or more elements selected from the group consisting of Zn, Ga, Cr, Nb, Mo, Ag, Hf, Ta, W, Pt, Au, Pb, Bi, Sn, 4 ≦ x ≦ 20, 4 ≦ a step of producing a molten alloy satisfying the relationship of y ≦ 20, 0.1 ≦ z ≦ 5, 0 ≦ m ≦ 0.8, 0 <p ≦ 0.3, and quenching the molten alloy The Nd ₂ Fe ₁₄ B type compound phase having an average crystal grain size of 50 nm or less is present in a volume ratio of 5% or more and 50% or less of the whole. And a heat treatment step for maintaining the quenching alloy at a temperature higher than the crystallization temperature of the Nd ₂ Fe ₁₄ B type compound phase in a magnetic field.

  In a preferred embodiment, the heat treatment step is performed in a magnetic field of 2T or more.

  In a preferred embodiment, the temperature for holding the quenched alloy in the heat treatment step is 400 ° C. or higher and 800 ° C. or lower.

In a preferred embodiment, in the iron-based rare earth alloy magnet, the average crystal grain size of the Nd ₂ Fe ₁₄ B type compound phase is 10 nm or more and 50 nm or less.

In a preferred embodiment, in the iron-based rare earth alloy magnet, the standard deviation of the crystal grain size of the Nd ₂ Fe ₁₄ B type compound phase is 5 nm or more and 20 nm or less.

In a preferred embodiment, an iron-based boride satisfying the relationship of 10 ≦ x ≦ 16, 6 ≦ y ≦ 10, M containing Ti as an essential element, and having an average crystal grain size of 5 nm to 30 nm by the heat treatment step A nanocomposite structure in which the phase and the Nd ₂ Fe ₁₄ B type compound phase are mixed is formed.

In a preferred embodiment, an α-Fe phase satisfying the relationship of 4 ≦ x ≦ 8, 6 ≦ y ≦ 10, M contains Ti as an essential element, and has an average crystal grain size of 5 nm to 30 nm by the heat treatment step. And a nanocomposite structure in which the Nd ₂ Fe ₁₄ B type compound phase is mixed.

  In the present invention, an isotropic iron-based rare earth alloy magnet having crystal grains uniformly refined can be produced by controlling the structure of the quenched alloy before heat treatment and performing heat treatment in a magnetic field.

The crystallization temperature of the Nd ₂ Fe ₁₄ B phase in the iron-based rare earth alloy magnet targeted by the present invention varies depending on the type of additive element, but is generally in the range of about 400 to 600 ° C. This temperature is sufficiently higher than the Curie point T _c (T _c = about 290 ° C.) of the Nd ₂ Fe ₁₄ B phase. For this reason, even if a magnetic field is applied during the heat treatment step for crystallization, it is considered that the quenched alloy is hardly affected magnetically by the applied magnetic field.

The present inventor applied a heat treatment for crystallization to a quenched alloy containing 5% or more and 50% or less of the entire Nd ₂ Fe ₁₄ B type compound phase having an average crystal grain size of 50 nm or less before heat treatment. As a result, the inventors have found that a uniform and fine crystal structure can be formed as compared with the case where the same heat treatment is performed without applying a magnetic field, and the present invention has been completed.

Although it is well known that the Curie point T _c of the Nd ₂ Fe ₁₄ B phase can be raised by substituting Co for Fe, the inventors have found that the alloy satisfies T _c > heat treatment temperature. It has been confirmed that the effects of the present invention can also be obtained for the system, and the mechanism by which the crystal phase is uniformly refined by application of a magnetic field is unknown at this time.

  Further, as will be described later, it was found that the effect of uniform refinement according to the present invention cannot be obtained even when a magnetic field is applied when the entire quenched alloy before heat treatment is amorphous. That is, it was confirmed that the applied magnetic field hardly contributes to the generation of crystal nuclei, and can affect the heat treatment process for the first time when crystal nuclei or precursors exist before the start of heat treatment.

Thus, in the present invention, by performing heat treatment in a magnetic field on a rapidly solidified alloy containing the Nd ₂ Fe ₁₄ B type compound phase in a predetermined volume ratio before performing the heat treatment for crystallization. The crystal structure can be uniformly refined. Since the magnet produced in the present invention is not an anisotropic magnet but an isotropic magnet, the magnetic field application during the heat treatment is not performed for magnetic anisotropy, and the crystal structure is uniformly refined. Therefore, it is distinguished from the prior art in terms of what it does.

The production method of the present invention is not limited to a single-phase magnet containing only a Nd ₂ Fe ₁₄ B type compound phase as a magnetic phase constituting a magnet, but a nanocomposite in which a hard magnetic phase and a soft magnetic phase are magnetically coupled. The present invention can be widely applied to Nd—Fe—B type quenching magnets including magnets.

<Quenched alloy before heat treatment>
A quenched alloy is produced by forming a molten alloy represented by the composition formula (Fe _1-m T _m ) _100-xyz (B _1-p C _p ) _x R _y M _z and quenching. Here, T is one or more elements selected from the group consisting of Co and Ni, R is one or more elements selected from the group consisting of yttrium and rare earth metal elements, M is Ti, Zr, Al, Si And one or more elements selected from the group consisting of V, Mn, Cu, Zn, Ga, Cr, Nb, Mo, Ag, Hf, Ta, W, Pt, Au, Pb, Bi, and Sn. ≦ x ≦ 20, 4 ≦ y ≦ 20, 0.1 ≦ z ≦ 5, 0 ≦ m ≦ 0.8, 0 <p ≦ 0.3.

  The rapid cooling is preferably performed by a super rapid cooling method. The main ultra-quenching methods in practical use include the melt spinning method and the strip cast method.

In the present invention, the structure of the quenched alloy before the heat treatment is prepared so that the average crystal grain size of the R ₂ Fe ₁₄ B phase, which is a hard magnetic phase, is 50 nm or less and the volume ratio is 5% or more and 50% or less. . In order to produce such a quenched alloy, the cooling rate of the alloy may be 10 ³ to 10 ⁸ K / s (Kelvin / second), preferably 10 ⁴ to 10 ⁷ K / s. The specific quenching conditions differ somewhat depending on the amorphous forming ability of the alloy, but the cooling rate increases as the composition ratio x of (B, C) decreases, and the cooling rate decreases as the composition ratio x increases. It is preferable to do.

The volume ratio of the crystal phase in the quenched alloy is determined by measuring the apparent weight of the quenched alloy at each temperature from room temperature to 1000 ° C. using a thermomagnetic balance. Since the apparent weight greatly decreases at the Curie point of the magnetic phase contained in the alloy, the amount of change is calculated by comparing the value divided by the saturation magnetization of the magnetic phase corresponding to the Curie point. The absence of the nonmagnetic phase can be confirmed by X-ray diffraction. In order to make the average crystal grain size of the R ₂ Fe ₁₄ B phase after heat treatment 50 nm or less, it is necessary to keep the average crystal grain size of the R ₂ Fe ₁₄ B phase in the quenched alloy to 50 nm or less.

The average crystal grain size of the R ₂ Fe ₁₄ B phase in the quenched alloy is preferably 30 nm or less, and more preferably 20 nm or less. Further, when the volume ratio of the R ₂ Fe ₁₄ B phase in the quenched alloy is less than 5%, the absolute number of crystal grains of the R ₂ Fe ₁₄ B phase serving as a crystal nucleus is small, so that the metal structure after heat treatment is naturally coarse. turn into.

When the average grain size of the R ₂ Fe ₁₄ B phase in the quenched alloy exceeds 50%, the standard deviation of the crystal grain size of the R ₂ Fe ₁₄ B phase in the initial quenched structure exceeds 50 nm. The difference in curvature becomes the driving force, and large grains grow more preferentially. In this case, the metal structure after the heat treatment becomes coarse regardless of the presence or absence of a magnetic field. Therefore, the effect of giving magnetic field energy is more remarkable, the volume ratio of the R ₂ Fe ₁₄ B phase in the quenched alloy is 10% or more and 30% or less in order to prevent coarsening of the crystal and to obtain a uniform fine crystal structure. It is more preferable that

When producing a nanocomposite magnet containing an iron-based boride phase as a soft magnetic phase, the above-described composition formula is further limited, and 10 ≦ x ≦ 16 and 6 ≦ y ≦ 10 are satisfied, and M is Ti. Adjust to include as an essential element. Ti exhibits the effect of suppressing the precipitation and coarsening of crystal phases other than the R ₂ Fe ₁₄ B phase during the rapid solidification process. As a result, a nanocomposite structure in which an iron-based boride phase having an average crystal grain size of 5 nm to 30 nm and an Nd ₂ Fe ₁₄ B-type compound phase having an average crystal grain size of 50 nm or less is mixed is formed by a heat treatment process described later. can do.

On the other hand, when producing a nanocomposite magnet containing an α-Fe phase as a soft magnetic phase, the above composition formula is limited, and the relations 4 ≦ x ≦ 8 and 6 ≦ y ≦ 10 are satisfied, and M is Ti. Adjust to include as an essential element. In this case, a nanocomposite structure in which an α-Fe phase having an average crystal grain size of 5 nm or more and 30 nm or less and an Nd ₂ Fe ₁₄ B type compound phase having an average crystal grain size of 50 nm or less is mixed can be formed by the heat treatment step. it can.

In the heat treatment of the present invention, the soft magnetic phase having a relatively high Curie point compared to the hard magnetic phase is more susceptible to the influence of the magnetic field than the hard magnetic phase. Therefore, in the nanocomposite magnet including the soft magnetic phase as the magnetic phase constituting the final magnet, the soft magnetic phase, which has been difficult in the past, becomes a metal structure uniformly dispersed finely, and only the Nd ₂ Fe ₁₄ B type compound phase is obtained. It is considered that the effect of the present invention is more easily achieved than the single-phase magnet containing, and the effect of improving the magnetic properties appears more remarkably.

When a nanocomposite magnet containing an α-Fe phase as a soft magnetic phase is produced by the production method of the present invention, the residual magnetic flux density B _r and the intrinsic coercive force H _cJ are compared with a nanocomposite magnet that has undergone a conventional heat treatment process. in addition to the maximum magnetic energy product (BH) _max are improved effects, effects also obtained of improving the saturation magnetization I _s. This effect is considered to be caused by the fact that the soft magnetic phase having a higher Curie point is more easily affected by the magnetic field than the hard magnetic phase. In the present invention, by volume fraction of alpha-Fe phase is increased, it is estimated that the saturation magnetization I _s is improved. However, the detailed mechanism is unclear at present, as is the effect of uniform miniaturization.

<Heat treatment in magnetic field>
The quenched alloy produced as described above is heat-treated in a magnetic field. The strength of the magnetic field is preferably 0.5T or more and 14T or less, and more preferably 2T or more and 10T or less. When the magnetic field strength is less than 0.5T, the magnetic field energy is too small, and the effect of the present invention is insufficient. On the other hand, in order to generate a magnetic field exceeding 14T, it is inconvenient because necessary facilities and electric power become enormous.

The heat treatment temperature is preferably 400 ° C to 800 ° C, more preferably 550 ° C to 780 ° C. If it is less than 400 ° C., the growth of the R ₂ Fe ₁₄ B phase is difficult to occur, and if it exceeds 800 ° C., crystallization and coarsening of α-Fe are likely to occur. The temperature rising rate is preferably 0.1 to 50 K / s, and more preferably 1 to 10 K / s. The reason is that if it is less than 0.1 K / s, it takes too much processing time, and if it exceeds 50 K / s, abnormal grain growth may occur.

  The application of the magnetic field is preferably started when the heat treatment is started or before it is heated to a temperature sufficiently lower than the crystallization temperature. This is because in order to obtain the effect of the present invention, it is necessary to apply a magnetic field when crystallization and crystal growth of the amorphous portion occur. The application of the magnetic field must be stopped after the crystallization has progressed sufficiently. After the crystallization is substantially completed, application of the magnetic field may be stopped before starting the cooling process. Conversely, the cooling step may be performed during application of the magnetic field.

  Patent Document 5 discloses a heat treatment method in which a heat treatment temperature is low and pulse magnetization is unnecessary by heat-treating all or part of an amorphous R-Fe-B-based quenched alloy in a magnetic field. It is described that it can. However, this method does not define the structure of the quenched alloy before heat treatment (crystal grain size, volume ratio of crystal phase), so it is unclear whether a magnet with a uniform fine structure can be obtained.

  Conventionally, an attempt has been made to produce an anisotropic magnet by heat-treating a quenched alloy in a magnetic field, which is disclosed in Patent Documents 6 and 7 and the like. However, these are all treatments for making the alloy anisotropic. An amorphous alloy is essential or presupposed for the quenched alloy before the heat treatment. Since a large amount of energy is required to generate crystal nuclei from an amorphous state, when nuclei are generated, they grow at once. According to the experiments by the inventors, when the amorphous is heat-treated, the structure after the heat treatment finally obtained regardless of the presence or absence of the magnetic field contains coarse grains, and the magnetic structure has almost no effect due to the magnetic field. I couldn't see it.

<Magnetic structure>
According to the present invention, it is possible to obtain a magnet having an extremely uniform crystal structure in which the average crystal grain size of the R ₂ Fe ₁₄ B phase is 50 nm or less and the standard deviation of the crystal grain size is 5 nm to 20 nm.

In addition, as described above, when the composition range for the nanocomposite magnet is selected, not only the R ₂ Fe ₁₄ B phase but also the soft magnetic phase such as iron-based boride and α-Fe can be obtained by the above heat treatment. A nanocomposite magnet having a uniform and finely dispersed metal structure and exhibiting excellent characteristics can be obtained.

<Example 1>
An alloy having a composition of Nd _9.0 Fe _73.0 B _12.6 C _1.4 Ti _3.0 Nb _1.0 was weighed so that the total amount would be 10 g and put into a quartz crucible of a melt spinning apparatus. The alloy was melted by high frequency heating in an Ar atmosphere at a pressure of 1.33 to 47.92 kPa. After the molten metal temperature reached 1350 ° C., the molten metal surface was pressurized with Ar gas, and the molten metal was injected from the orifice. The injected molten metal was brought into contact with the outer peripheral surface of a pure copper cooling roll rotating at a roll surface speed of 9 m / second at room temperature, rapidly cooled, and solidified into a thin strip. The obtained quenched alloy had a width of 2 mm and a thickness of 40 μm. Further, when the crystal structure of the obtained quenched alloy was observed with a TEM, a crystal phase having an average crystal grain size of 30 nm or less was present in a volume ratio of 20%.

  Next, the rapidly solidified alloy produced by the above method was kept in a 10 T magnetic field in an Ar atmosphere in a heat treatment temperature range of 740 ° C. for 6 minutes, and then cooled to room temperature. The rate of temperature increase in the heat treatment step was about 10 K / s, and the rate of temperature decrease was about 100 K / s. When the crystal structure of the obtained magnet was observed with a transmission electron microscope (TEM), it was a very uniform and fine structure with an average crystal grain size of 50 nm or less and a standard deviation of the crystal grain size of 20 nm. The observation results are shown in FIG.

The obtained magnet is a nanocomposite magnet in which an R ₂ Fe ₁₄ B phase (hard magnetic phase) and an iron-based boride phase (soft magnetic phase) are magnetically coupled, with an average crystal grain size of 50 nm or less, The standard deviation of the particle size was 20 nm.

  Even when the magnetic field applied during the heat treatment was 1 T, the effect of uniform miniaturization was sufficiently achieved. This is considered to be because this example was a nanocomposite magnet containing a soft magnetic phase. In the case of a single-phase magnet, it is considered preferable to apply a magnetic field of 2T or more.

<Comparative example 1>
A magnet was produced in the same manner as in Example 1 except that no magnetic field was applied during the heat treatment. When the crystal structure of the obtained magnet was observed, the average crystal grain size was 100 nm or less, and the standard deviation of the crystal grain size was 50 nm. The observation results are shown in FIG.

<Comparative example 2>
A magnet was produced in the same manner as in Example 1 except that the roll surface speed was 13 m / s in the rapid cooling step and no magnetic field was applied during the heat treatment. When the structure of the obtained quenched alloy was observed, it was 100% amorphous. Further, when the crystal structure of the obtained magnet was observed, the average crystal grain size was 100 nm or less, and the standard deviation of the crystal grain size was 50 nm. The observation results are shown in FIG.

<Comparative Example 3>
A magnet was produced in the same manner as in Example 1 except that the roll surface speed was 13 m / s in the rapid cooling step. That is, the same magnetic field as in Example 1 was applied during the heat treatment. When the structure of the obtained quenched alloy was observed, it was 100% amorphous. Further, when the crystal structure of the obtained magnet was observed, the average crystal grain size was 100 nm or less, and the standard deviation of the crystal grain size was 50 nm. The observation results are shown in FIG.

  FIG. 5 is a graph showing demagnetization curves obtained for the magnets of Example 1 and Comparative Example 1. The magnetic property values measured for these magnets are shown in Table 1 below.

Compared to Comparative Example 1, it can be seen that in Example 1, the residual magnetic flux density B _r , the intrinsic coercive force H _cJ , and the maximum magnetic energy product (BH) _max are all improved. Since the difference was not observed in the saturation magnetization I _s, was confirmed the effect of Le Manet Nsu enhancement due to the metal structure of Example 1 is uniformly fine.

<Example 2>
An alloy having a composition of Nd _7.0 Fe _83.0 B _7.0 C _1.0 Ti _2.0 was weighed so that the total amount became 10 g, and was put into a quartz crucible of a melt spinning apparatus. The alloy was melted by high frequency heating in an Ar atmosphere at a pressure of 1.33 to 47.92 kPa. After the molten metal temperature reached 1350 ° C., the molten metal surface was pressurized with Ar gas, and the molten metal was injected from the orifice. The injected molten metal was contacted with the outer peripheral surface of a pure copper cooling roll rotating at a roll surface speed of 20 m / sec at room temperature, quenched, and solidified into a thin strip. The obtained quenched alloy had a width of 2 mm and a thickness of 30 μm. Further, when the crystal structure of the obtained quenched alloy was observed with a TEM, a crystal phase having an average crystal grain size of 30 nm or less was present in a volume ratio of 40%.

  Next, the rapidly solidified alloy produced by the above-described method was held in a heat treatment temperature range of 700 ° C. for 6 minutes in an Ar atmosphere in an 8T magnetic field, and then cooled to room temperature. The temperature increase rate in the heat treatment step was about 10 ° C./s, and the temperature decrease rate was about 100 ° C./s. When the crystal structure of the obtained magnet was observed by TEM, it was a very uniform and fine structure with an average crystal grain size of 50 nm or less and a standard deviation of crystal grain size of 20 nm.

The obtained magnet was a nanocomposite magnet in which an R ₂ Fe ₁₄ B phase (hard magnetic phase) and an α-Fe phase (soft magnetic phase) were magnetically coupled. It was confirmed that the effect of uniform miniaturization was sufficiently achieved even when the magnetic field applied during the heat treatment was 1T.

<Comparative example 4>
A magnet was produced in the same manner as in Example 2 except that no magnetic field was applied during the heat treatment. When the crystal structure of the obtained magnet was observed, the average crystal grain size was 80 nm or less, and the standard deviation of the crystal grain size was 40 nm.

  FIG. 6 is a graph showing demagnetization curves obtained for the magnets of Example 2 and Comparative Example 4. The magnetic property values measured for these magnets are shown in Table 2 below.

  When producing a nanocomposite magnet containing an α-Fe phase as a soft magnetic phase, in addition to the effect of uniformly and finely dispersing the soft magnetic phase and the hard magnetic phase, the volume fraction of the α-Fe phase that is the soft magnetic phase Therefore, the magnetic characteristics are greatly improved by both effects.

  FIG. 7 is a graph showing the results of XRD measurement performed on the pulverized thin ribbons of Example 2 and Comparative Example 4. According to the obtained XRD pattern, the diffraction peak intensity of the α-Fe phase is higher in Example 2 than in Comparative Example 4. From this, it can be estimated that the volume ratio of the α-Fe phase is improved in the present invention.

  According to the production method of the present invention, an isotropic iron-based rare earth magnet having a finely structured structure and excellent magnetic properties can be obtained and used for various applications.

2 is a transmission electron microscope (TEM) photograph of Example 1. 4 is a TEM photograph of Comparative Example 1. 4 is a TEM photograph of Comparative Example 2. 6 is a TEM photograph of Comparative Example 3. It is a graph which shows a demagnetization curve about the ribbon of Example 1 and Comparative Example 1. It is a graph which shows a demagnetization curve about the ribbon of Example 2 and Comparative Example 4. It is a graph which shows the XRD diffraction pattern of pulverized powder about the ribbon of Example 2 and Comparative Example 4.

Claims (7)

Composition formula is represented by _{(Fe 1-m T m)} 100-xyz (B 1-p C p) x R y M z, T is one or more elements selected from the group consisting of Co and Ni, R is One or more elements selected from the group consisting of yttrium and rare earth metal elements, M is Ti, Zr, Al, Si, V, Mn, Cu, Zn, Ga, Cr, Nb, Mo, Ag, Hf, Ta, One or more elements selected from the group consisting of W, Pt, Au, Pb, Bi, Sn, 4 ≦ x ≦ 20, 4 ≦ y ≦ 20, 0.1 ≦ z ≦ 5, 0 ≦ m ≦ Producing a molten alloy satisfying the relationship of 0.8, 0 <p ≦ 0.3;
A cooling step of rapidly quenching the molten alloy to produce a quenched alloy in which an Nd ₂ Fe ₁₄ B type compound phase having an average crystal grain size of 50 nm or less is present in a volume ratio of 5% or more and 50% or less;
A heat treatment step of maintaining a temperature equal to or higher than a crystallization temperature of the Nd ₂ Fe ₁₄ B type compound phase in a magnetic field with respect to the quenched alloy;
A method for producing an isotropic iron-based rare earth alloy magnet, comprising:   The method for producing an iron-based rare earth alloy magnet according to claim 1, wherein the heat treatment step is performed in a magnetic field of 2 T or more.   The method for producing an iron-based rare earth alloy magnet according to claim 1, wherein the temperature at which the quenched alloy is held in the heat treatment step is 400 ° C or higher and 800 ° C or lower. _{2. The} method for producing an iron-based rare earth alloy magnet according to claim 1, wherein the iron-based rare earth alloy magnet has an average crystal grain size of Nd ₂ Fe ₁₄ B-type compound phase of 10 nm to 50 nm. 5. The method for producing an iron-based rare earth alloy magnet according to claim 4, wherein the iron-based rare earth alloy magnet has a standard deviation of the crystal grain size of the Nd ₂ Fe ₁₄ B type compound phase of 5 nm to 20 nm. 10 ≦ x ≦ 16, 6 ≦ y ≦ 10 is satisfied, M contains Ti as an essential element,
6. The nanocomposite structure in which an iron-based boride phase having an average crystal grain size of 5 nm to 30 nm and the Nd ₂ Fe ₁₄ B-type compound phase are mixed is formed by the heat treatment step. The manufacturing method of the iron-based rare earth alloy magnet of description. 4 ≦ x ≦ 8, 6 ≦ y ≦ 10 is satisfied, M contains Ti as an essential element,
6. The nanocomposite structure in which an α-Fe phase having an average crystal grain size of 5 nm to 30 nm and the Nd ₂ Fe ₁₄ B type compound phase are mixed is formed by the heat treatment step. Of manufacturing iron-based rare earth alloy magnets.