JP2017179396A - Manufacturing method of ferromagnetic alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of an R-T-based ferromagnetic alloy which is used for a raw material alloy of a high performance anisotropic sinter magnet.SOLUTION: There is provided a manufacturing method, including (a) a process for preparing an R1-T1-M-based alloy 10 containing an element M of 3 mol% or more, and having an R1-T1-M-based alloy mainly containing an R1-T1-M compound having a ThMntype structure, a Nd(Fe,Ti)type structure, or a TbCutype structure, or intermediate structure thereof, where M is at least one kind selected from Ti, V, Cr, Mn, Mo, W, Al, and Si, R1 is a rare earth element and T1 is a transition metal element mainly containing iron, and (b) a process for contacting and cooling a R2-T2-based alloy molten metal 20 having molar ratio [T2]/[R2] of T2 to R2 of 9 or more and containing practically no M, where R2 is a rear earth element and T2 is a transition metal element mainly containing iron, with the R1-T1-M-based alloy 10 so as to form an R-T-based ferromagnetic alloy 30 containing an R-T-based ferromagnetic compound phase.SELECTED DRAWING: Figure 1

Description

  The present application relates to a method of manufacturing a ferromagnetic alloy.

  In recent years, there has been a demand for the development of a magnet with a reduced content of rare earth elements. The rare earth element in this specification is at least one element selected from the group consisting of scandium (Sc), yttrium (Y), and lanthanoid. Here, the lanthanoid is a general term for 15 elements from lanthanum to lutetium.

As a ferromagnetic alloy having a relatively small composition ratio of rare earth elements contained, RFe ₁₂ (R is at least one kind of rare earth elements) having a body-centered tetragonal ThMn ₁₂ type crystal structure is known. However, RFe ₁₂ has a problem that the crystal structure is thermally unstable in the binary system.

In order to improve the stability of the crystal structure in RFe ₁₂ , Patent Document 1 discloses that a part of the Fe element is replaced with a structural stabilizing element M (M = Ti, V, Cr, Mn, Mo, W, Al, Si). Patent Document 2 discloses that a part of the R element is replaced with a structural stabilizing element T (T = Zr, Hf, Bi, Sn, In, or Pb selected from one or more elements). Teaching to do. In Patent Document 3, a part of the R element is substituted with at least one selected from Sc, Zr, and Hf, thereby reducing the average atomic radius of the rare earth site, thereby generating a TbCu ₇ type crystal phase. It is described to prompt. Both Patent Literature 1 and Patent Literature 2 teach that the magnetic anisotropy is lowered while the Curie temperature and the saturation magnetization are increased by replacing a part of the Fe element with the Co element. As specific magnetic property values, Non-Patent Document 1 discloses the Co substitution amount dependency of the magnetic moment and the Curie temperature in the case of M = Ti in Patent Document 1.

Further, in Patent Document 4, by selecting Y as a rare earth element, an alloy containing a Y—Fe binary compound having a ThMn ₁₂ type crystal structure can be produced without substitution with the third element M, and this compound is high. It is disclosed that it has saturation magnetization and magnetic anisotropy.

In Patent Document 5, by selecting Y as the rare earth element, it has an intermediate crystal structure between a hexagonal TbCu ₇ type crystal structure and a body-centered tetragonal ThMn ₁₂ type crystal structure, and at least of the occupied sites of the rare earth element Long-period regular substitution does not occur between a part and Fe atom pair (random substitution occurs), and R′—Fe—Co based ferromagnetic compound of space group Immm (R ′ is one or more types) It is disclosed that a rare earth element including at least Y or Gd can be produced.

Further, in Non-Patent Document 3, by using tungsten (W) as a buffer layer using a sputtering method, an NdFe ₁₂ compound having a ThMn ₁₂ type crystal structure can be produced without substitution of M of the third element. It is disclosed that nitriding has high saturation magnetization and magnetic anisotropy.

JP-A 64-76703 JP-A-4-322405 JP-A-6-172936 JP 2014-47366 A Japanese Patent Laying-Open No. 2015-156436

K. H. J. et al. Buschow (Ed.), Handbook of Magnetic Materials Vol. 6 (1991). Hong-Shuo LI and J .; M.M. D. Coey, Chap. 1. S. Sakurada et al. , Journal of Applied Physics 79 p. 4611 (1996). Y. Hirayama et al. , Scripta Materialia. 95 p. 70 (2015).

  In the ferromagnetic alloys described in Patent Document 1 and Non-Patent Document 1, by substituting a part of the Fe element with the structural stabilizing element M, the magnetic moment decreases and the crystal lattice expands, and the saturation magnetic flux density decreases. .

  Further, in the ferromagnetic alloys described in Patent Document 2, Patent Document 3, and Non-Patent Document 2, a part of the rare earth element R is at least one of the elements Zr, Hf, Bi, Sn, In, and Pb smaller than the rare earth element R. Substitution with a seed compensates for the low magnetization disadvantage of the ferromagnetic alloys described in Patent Document 1 and Non-Patent Document 1, but causes a decrease in magnetic anisotropy derived from rare earth elements. In particular, Zr and Hf, which are practical and function as structural stabilization, donate four electrons per atom to the metal bond with the Fe sublattice when forming an alloy. Is weakened.

In the method of Patent Document 4, it is possible to form a Y—Fe compound having excellent magnetic properties. However, when a general casting method such as a book mold is adopted, an α-Fe phase and a Y ₂ Fe ₁₇ phase are mainly used in the formed alloy, and a Y—Fe compound phase (hereinafter referred to as YFe phase) having a ThMn ₁₂ type structure. _An alloy composed mainly of ₁₂ ) cannot be obtained. According to the study by the inventors of the present application, it has been found that in order to increase the ratio of the YFe ₁₂ phase, a technique of mainly heat-treating an alloy produced by a rapid quenching method such as a single roll method is effective. However, since the YFe ₁₂ phase in the alloy obtained by such a technique is magnetically isotropic with fine crystal grains of about several tens of nanometers, the performance of the magnet made using such an alloy is It will be lower. A similar problem occurs even in an alloy manufactured by the method of Patent Document 5.

In the method of Non-Patent Document 3, it is possible to form an NdFe ₁₂ compound phase having excellent magnetic properties by nitriding. However, since it is produced by a thin film method, it is not suitable for applications that require mass production such as magnets used for motor applications.

Thus, the conventional method cannot produce a compound phase having a sufficiently large crystal grain size with a ThMn ₁₂ type crystal structure in a binary system or a ternary system partially substituted with Co element. Thus, a ferromagnetic alloy having a low rare earth composition that exhibits sufficient magnetic properties to add the structural stabilizing elements M and T could not be produced.

  Embodiments of the present invention solve the problem caused by substituting some of the constituent elements with elements other than rare earth elements, and produce a ferromagnetic alloy that is suitably used as a raw material alloy for permanent magnets with sufficient magnetic properties A method can be provided.

In the embodiment, the manufacturing method of the RT ferromagnetic alloy of the present disclosure includes (a) the element M containing 3 mol% or more, a ThMn ₁₂ type structure, an Nd ₃ (Fe, Ti) ₂₉ type structure, or a TbCu _7. R1-T1-M alloy mainly composed of R1-T1-M compound having a mold structure or an intermediate structure thereof, where M is Ti, V, Cr, Mn, Mo, W, Al, And at least one selected from the group consisting of Si, R1 is a rare earth element, T1 is a transition metal element mainly composed of iron, and (b) a step of T2 with respect to R2 R2 is a molten R2-T2 alloy having a molar ratio [T2] / [R2] of 9 or more and substantially free of M, wherein R2 is a rare earth element and T2 is a transition metal element mainly composed of iron. -T2 alloy molten metal is used as the R1-T1-M alloy. The contacted by cooling, R-T-based ferromagnetic compound phase (R is a rare earth element, T is a transition metal element composed mainly of iron) and forming a R-T-based ferromagnetic alloy containing.

In one embodiment, the step (b) includes a step of generating a phase of a TnMn ₁₂ type structure, a TbCu ₇ type structure, or an intermediate structure thereof as the RT ferromagnetic compound phase.

  In one embodiment, the step (b) includes a step of melting at least a part of the surface of the R1-T1-M alloy and solidifying the molten R2-T2 alloy.

  In one embodiment, the step (b) includes a step of performing epitaxial growth from the molten R2-T2 alloy to the R1-T1-M alloy.

  In one embodiment, in the step (b), a part of the element M contained in the R1-T1-M alloy is moved from the R2-T2 alloy to the compound phase.

  In one embodiment, the R1-T1-M alloy is a substrate.

  In one embodiment, the crystal structure of the phase constituting the R1-T1-M alloy is set to be the same as the phase constituting the RT ferromagnetic alloy to be formed.

  In some embodiments, R1 and R2 each contain the same element, and T1 and T2 each contain the same element.

  In certain embodiments, R2 comprises yttrium.

  In one embodiment, an R2-T2 alloy molten metal (R2 is a rare earth element and T2 is a transition metal element mainly composed of iron) is contacted with the RT ferromagnetic alloy and cooled, and the other RT A step (c) of forming an RT-based ferromagnetic alloy including a ferromagnetic compound phase.

  In one embodiment, crystal growth of an RT ferromagnetic compound substantially free of M is advanced by repeating step (c).

  In one embodiment, in step (b), the temperature of the R1-T1-M alloy when the molten R2-T2 alloy is brought into contact with the R1-T1-M alloy is 500 ° C. or higher.

  According to the embodiments of the present invention, it is possible to provide a new method for producing a ferromagnetic alloy having high magnetization and a ferromagnetic alloy.

(A), (b), (c) and (d) is process sectional drawing for demonstrating embodiment of the manufacturing method of the RT ferromagnetic alloy in this indication. (A), (b), (c) and (d) is process sectional drawing for demonstrating embodiment of the manufacturing method of the RT ferromagnetic alloy in this indication. It is a perspective view which shows typically arrangement | positioning of the high frequency coil of the electromagnetic floating mechanism used in the Example of this indication.

  An embodiment of a method for producing an exemplary RT-based ferromagnetic alloy of the present disclosure includes the following steps (a) and (b).

Step (a)
An R1-T1-M alloy is prepared. Here, R1 is a rare earth element, and T1 is a transition metal element mainly composed of iron. This R1-T1-M alloy contains 3 mol% or more of the element M. Here, M is at least one selected from the group consisting of Ti, V, Cr, Mn, Mo, W, Al, and Si. This R1-T1-M alloy is mainly composed of an R1-T1-M compound having a ThMn ₁₂ type structure, an Nd ₃ (Fe, Ti) ₂₉ type structure, a TbCu ₇ type structure, or an intermediate structure thereof. And

Step (b)
The molten R2-T2 alloy is brought into contact with the above R1-T1-M alloy and cooled, and the R-T ferromagnetic compound (crystal) phase (R is a rare earth element, T is a transition metal mainly composed of iron) RT-based ferromagnetic alloy containing (element) is formed. The formation process of this RT ferromagnetic alloy may be called “epitaxial growth”. Here, R2 is a rare earth element, T2 is a transition metal element mainly composed of iron, and the molar ratio [T2] / [R2] of T2 to R2 is 9 or more. The R2-T2 alloy melt is substantially free of M. The compound phase may be single crystal or polycrystalline. Note that the term “epitaxial growth” here refers not only to the case where compounds having the same crystal structure grow while lattice matching, but also includes the case where crystal structures of crystal structures of different space groups grow while lattice matching. As an example of the latter, there is a case where growth is performed while continuously changing the crystal structure from the ThMn ₁₂ phase to the TbCu ₇ phase while maintaining lattice matching.

  In a preferred embodiment, the alloy obtained by adopting such a manufacturing method includes an RT ferromagnetic compound phase having a crystal grain size of 1 μm or more. Further, the content of the stabilizing element M in the RT ferromagnetic compound phase continuously changes in at least a part of the alloy, and the molar ratio of M to (T + M) in the RT compound [M ] / ([T] + [M]) is 0.03 or less.

Hereinafter, as an example of the RT ferromagnetic compound, a Y—Fe based compound having a ThMn ₁₂ type structure (hereinafter referred to as “YFe ₁₂ compound” or “YFe ₁₂ phase”) will be described.

As described above, in order to easily obtain an alloy as described in Patent Document 4, when a rapid quenching method is employed, the YFe ₁₂ phase in the obtained alloy has a crystal grain size as fine as several tens of nm. And since the direction of each crystal grain is random, it is very difficult to produce an anisotropic magnet.

An effective method for producing an anisotropic magnet having high performance includes a method in which individual particles are formed by sintering a powder close to a single crystal in a magnetic field. Such a method is widely applied, for example, as a method for manufacturing a neodymium (Nd) -iron (Fe) -boron (B) magnet. As a raw material alloy for producing a sintered magnet, the size of a ferromagnetic phase serving as a main phase (Nd ₂ Fe ₁₄ B phase in the case of an Nd—Fe—B based magnet) is 1 μm or more, typically 20 μm or more. A raw material alloy having is useful.

However, in order to produce such an alloy, for example, when the book mold method used as a method for producing a general raw material alloy is applied to an alloy having a YFe ₁₂ composition, the magnetic anisotropy is low, not the YFe ₁₂ phase, and permanent. It only becomes a two-phase coexistence state of an α-Fe phase and a Y ₂ Fe ₁₇ phase that are not suitable as a magnet material. This is because the YFE ₁₂ phase exists as an equilibrium phase at YFE binary.

As a method for stably obtaining a Y—Fe-based compound phase having a ThMn ₁₂ structure, as shown in Patent Document 1, it is known that a part of Fe is substituted with a stabilizing element M. However, substitution of the M element causes a significant decrease in magnetization, making it difficult to obtain a raw material alloy for obtaining a permanent magnet having excellent magnetic properties.

In view of the above problems, as a result of intensive studies by the inventor, the element M (M is selected from Ti, V, Cr, Mn, Mo, W, Al, Si, which can stabilize the YFe ₁₂ phase in advance. The above R1-T1 compound containing 3 mol% or more of at least one) and having a ThMn ₁₂ type structure, Nd ₃ (Fe, Ti) ₂₉ type structure, or TbCu ₇ type structure, or an intermediate structure thereof When an R1-T1 based alloy (for example, YFe ₁₁ Ti alloy substrate) is mainly prepared, and a Y-Fe alloy melt containing substantially no M element and having a composition in the vicinity of YFe ₁₂ is dropped thereon, the molten metal is solidified. R1-T1 compound YFE ₁₂ phase M element from partially stabilized been introduced in is formed, that can be M element is aligned with the crystal structure of the YFE ₁₂ phase is grown less YFE ₁₂ phase The It was seen.

YFE alloy thus obtained, the content of M in YFE ₁₂ phase formed continuously changes in at least a portion of the alloy, and, as M YFE ₁₂ phase ( The minimum value of the molar ratio [M] / ([T] + [M]) of T (= Fe) + M) is reduced to 0.03 or less. As a result, the region having a low M content in the YFe ₁₂ phase of the alloy obtained by the embodiment of the manufacturing method of the present invention can have high magnetization. Therefore, an alloy having higher magnetization than that obtained by melting and solidifying a Y-Fe-M alloy containing M element at a concentration sufficient to stabilize the YFe ₁₂ phase can be obtained.

  The thickness of the Y—Fe based ferromagnetic alloy thus obtained is typically 1 μm or more, which is difficult to produce efficiently by the thin film method as shown in Non-Patent Document 3. Can be about 10 μm. Furthermore, since the cooling rate of the molten R2-T2 alloy in the typical embodiment is very low compared to the ultra-quenching method, the crystal grains can be coarsened. For example, a Y—Fe alloy having a large crystal grain of about 10 μm can be suitably used as a raw material alloy for an anisotropic sintered magnet process. In addition, it is also possible to form the powder for bonded magnets by pulverizing the obtained Y—Fe-based alloy and then nitriding as necessary.

  In the present disclosure, the “ferromagnetic alloy” is not limited to an alloy exhibiting ferromagnetism as a whole, and may contain a ferromagnetic phase as a main component.

  Hereinafter, non-limiting exemplary embodiments of the present disclosure will be described with reference to FIGS. 1 and 2.

(A) Step of Preparing Substrate In the present embodiment, first, as shown in FIG. 1A, a substrate 10 of an R1-T1-M alloy is prepared. The R1-T1-M based alloy substrate 10 contains 3 mol% or more of an element M (M is at least one selected from Ti, V, Cr, Mn, Mo, W, Al, Si), and has a ThMn ₁₂ type structure. Or an R1-T1-M compound having an Nd ₃ (Fe, Ti) ₂₉ type structure or a TbCu ₇ type structure or an intermediate structure thereof (R1 is a rare earth element, T is a transition metal mainly composed of iron (Fe)) Element).

The R1-T1-M type alloy substrate 10 is not particularly limited as long as the phase having the crystal structure is a main component, but the phase having the same crystal structure as the phase constituting the target RT type ferromagnetic alloy ( For example, if it is desired to generate a YFe ₁₂ phase, it is preferably composed of a YFe _12-x M _x phase). By doing so, it becomes easy to form a phase having a target crystal structure.

  In addition, by including the same elements as R2 and T2 in R1 and T1, respectively, it becomes easy to obtain the target crystal structure and composition phase. Inclusion of Y in R2 makes it easy to obtain the phase of the target crystal structure.

  A known method can be used as a method for producing the substrate 10 of the R1-T1-M alloy. The substrate 10 may be prepared in advance by dissolution and solidification. Moreover, you may produce by solidifying a molten alloy in the same apparatus, before solidifying the R2-T2 type alloy molten metal performed continuously. Furthermore, instead of solidification of the molten metal, the powder may be produced while scanning the region of local heating / cooling by a method such as three-dimensional additive manufacturing using a 3D printer.

An R1-T1-M-based alloy having a ThMn ₁₂ type structure, an Nd ₃ (Fe, Ti) ₂₉ type structure, or a TbCu ₇ type structure, or an R1- The crystal grain size of the T1-M compound phase preferably has a size of 1 μm or more. The crystal grain size of the R1-T1-M compound phase is more preferably 5 μm or more, and even more preferably 10 μm or more. By using such an alloy mainly having an R1-T1-M compound phase as a substrate for crystal growth, the particle size of a ferromagnetic phase in an R2-T2 alloy obtained by epitaxial growth cannot be realized by the conventional technology. Can be sized. In such crystal growth, each R1-T1-M compound phase functions in the same manner as the “seed crystal”. However, for simplicity, in this specification, an R1-T1-M alloy is referred to as a “seed crystal”. May be called.

  In this embodiment, an R1-T1-M alloy having the form of “substrate” is used, but the embodiment of the present disclosure is not limited to this example. As long as the R2-T2 alloy melt is cooled to function as a seed for realizing epitaxial growth, it may have a form other than the “substrate”, for example, a rod-like, linear, or spherical form. Also, the form of the “substrate” may be various. Irregular patterning such as grooves or steps may be provided on the surface of the “substrate”. Hereinafter, the R1-T1-M alloy substrate may be simply abbreviated as “substrate”.

(B) Step of bringing the R2-T2-M alloy alloy into contact with the R1-T1-M alloy substrate and solidifying the R2-T1-M alloy substrate Next, as shown in FIG. The molten T2 alloy 20 is brought into contact and solidified as shown in FIGS. 1 (c) and 1 (d). FIG. 1 (d) shows an RT ferromagnetic alloy 30 obtained by crystallization.

  The composition of the R2-T2 alloy molten metal 20 is appropriately set so that a desired production phase and alloy structure can be obtained. In order to obtain the RT ferromagnetic alloy 30 used in the high-performance magnet, a composition in which the molar ratio [T2] / [R2] of T2 and R2 is 9 or more and substantially does not contain M is adopted. Is useful.

When the molten R2-T2 alloy 20 contacts the substrate 10, as shown in FIG. 1 (c), a part of the substrate 10 is melted to form a molten layer 12, and then the entire molten part is solidified. It is preferable to do this (FIG. 1 (d)). The necessary M element can be supplied to the R2-T2 alloy melt 20 through such a process. FIG. 1 (d) schematically shows a region 14 in which the M element that has moved into the RT ferromagnetic alloy 30 is distributed. Further, the substrate 10 composed of a phase having the same crystal structure as that of the target RT ferromagnetic alloy 30 (for example, YFe _12-x M _x phase if a YFe ₁₂ phase is to be generated) is used. In this case, the target crystal structure phase is easily formed.

  As shown in FIGS. 2 (a), (b), (c) and (d), an RT ferromagnetic alloy obtained by contacting and solidifying a molten R2-T2 alloy 20 on the surface of the substrate 10; Further, an R2-T2 alloy melt 20 may be brought into contact with 30 to grow a phase having a target crystal structure. By doing so, an RT compound phase having a large particle diameter can be obtained. FIG. 2D shows an RT ferromagnetic alloy 30 whose size is increased in the thickness direction. The RT ferromagnetic alloy 30 mainly contains an RT compound phase having a crystal grain size of 1 μm or more.

  When the temperature of the substrate 10 is low, nucleation occurs without melting a part of the substrate when the R2-T2 alloy melt 20 is cooled, and a fine crystal grain structure is formed. Sometimes. Further, the M element is not sufficiently taken in from the substrate 10, and the target phase may not be obtained. In order to avoid this, the substrate temperature is preferably 500 ° C. or higher. The substrate 10 may be heated to a desired temperature within a range of 500 ° C. or higher and a melting point of the R2-T2 alloy of −100 ° C. or lower. The upper limit of the heating temperature is preferably 900 ° C. or less from the viewpoint of avoiding the complexity of the apparatus. When solidifying in the same apparatus before solidifying the R2-T2 alloy melt 20 to be subsequently performed, the R2-T2 alloy melt 20 is supplied when a desired temperature is reached in the cooling process after solidification. It may solidify.

  As a step of solidifying the molten R2-T2 alloy, a known method can be adopted if an R1-T1-M alloy that functions as a seed for crystal growth can be set. For example, on a substrate of R1-T1-M alloy, a molten R2-T2 alloy is floated by an electromagnetic levitation method using a high frequency coil, and then the R2-T2 alloy melt and R1-T1-M alloy are dropped. May be brought into contact with each other. Among these, a known centrifugal casting method is suitable for mass production. Further, as described above, a method of repeatedly supplying and dissolving / solidifying the powder while scanning the heating / cooling region of the powder by a method such as three-dimensional additive manufacturing is also applicable. If the supplied molten alloy is too much, solidification occurs at a portion other than the portion in contact with the substrate, and it becomes difficult to sufficiently obtain the target RT compound phase. For this reason, it is preferable to use an apparatus capable of crystal growth while controlling the supply amount of the molten R2-T2 alloy.

(C) Characteristics of Alloy In the preferred embodiment, RT-T ferromagnetic alloy 30 obtained in this manner is an RTM having a ThMn ₁₂ type structure, a TbCu ₇ type structure, or an intermediate structure thereof. A compound (R is a rare earth element, T is a transition metal element mainly composed of iron (Fe)), the molar ratio [T] / [R] of T and R is 9 or more, and the RT compound The phase has a crystal grain size of 1 μm or more.

  The element M is supplied from the vicinity of the interface between the R1-T1-M alloy substrate 10 and the R2-T2 alloy melt 20 during the cooling and solidification process of the R2-T2 alloy melt 20. For this reason, the content of the stabilizing element M in the obtained RT compound phase continuously changes in at least a part of the RT ferromagnetic alloy 30. According to an embodiment of the present disclosure, an RT system in which the minimum value of the molar ratio [M] / ([T] + [M]) between M and (T + M) in the RT compound phase is 0.03 or less. A ferromagnetic alloy 30 can be obtained. The minimum value of [M] / ([T] + [M]) is an amount that makes it difficult to obtain the target phase by simply adding M to the RT alloy composition and performing melt casting. As a result of these processes, the molar ratio of M to the entire RT ferromagnetic alloy 30 is smaller than the molar ratio of M in the R1-T1-M alloy substrate 10.

A compound having a ThMn ₁₂ type structure, a TbCu ₇ type structure, or an intermediate structure thereof is a ferromagnetic alloy having a relatively small composition ratio of the rare earth element contained therein, and is suitable as a raw material for a high-performance magnet. Here, “an intermediate structure” means that a part of R in the above structure is replaced with a dumbbell of T, or a void is introduced, resulting in a non-stoichiometric composition (for example, RT1 ₂₋ δ). It shows what is.

  The crystal grain size of the RT phase in the obtained RT ferromagnetic alloy 30 is preferably 1 μm or more, more preferably 5 μm or more, and further preferably 20 μm or more. If the crystal grain size of the RT phase is such a size, single crystal-like powder particles suitable for producing an anisotropic magnet can be obtained by a subsequent pulverization step. In order to increase the crystal grain size of the RT phase in this way, it is preferable that R2 in the molten R2-T2 alloy 20 contains yttrium.

  Of the obtained RT-based ferromagnetic alloy 30, a region other than the target RT compound (including the seed crystal included in the R1-T1-M-based alloy substrate 10) may be used as it is. Good. Further, unnecessary portions may be selectively removed using a known method. An RT ferromagnetic alloy 30 containing a phase having the same crystal structure as an RT compound stabilized with an M element is used as a seed for crystal growth, and an R— with a sufficient thickness of the M element is further reduced. When the T compound phase is formed, the RT ferromagnetic alloy 30 may be used for magnet production without removing the seed.

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

[Example 1]
<Preparation of R1-T1-M alloy>
Y metal, Fe metal, and Ti metal were weighed so as to have an alloy composition of YFe ₁₁ Ti, dissolved in a high-frequency melting furnace, and then solidified on a water-cooled copper hearth. Thereafter, heat treatment was performed at 1100 ° C. for 20 hours to produce an R1-T1-M alloy. As a result of X-ray diffraction, it was confirmed that this R1-T1-M alloy was mainly composed of a Y (Fe, Ti) ₁₂ phase having a ThMn ₁₂ type structure. The obtained R1-T1-M alloy was cut with an outer peripheral cutting machine, and then the processed surface was polished to obtain an R1-T1-M alloy substrate.

<Preparation of R2-T2 alloy>
Y metal and Fe metal were weighed so that the alloy composition would be YFe ₁₂ , melted in a high-frequency melting furnace, and then solidified on a water-cooled copper hearth to produce an R2-T2 alloy. As a result of X-ray diffraction, it was confirmed that this alloy was mainly composed of an α-Fe phase and a Y ₂ Fe ₁₇ phase having a Th ₂ Zn ₁₇ type structure (both not suitable for a permanent magnet).

<Contact and solidification of molten R2-T2 alloy on R1-T1-M alloy>
An R1-T1-M alloy substrate 10 is placed under a vacuum vessel having an electromagnetic levitation mechanism with high frequency coils 100, 200 as shown in FIG. 3, and an R2-T2 alloy 20 ′ is held by a holding mechanism (not shown). Was held directly under the coil. The high frequency coil 100 functions as a floating coil and forms an electromagnetic field that floats the R2-T2 alloy 20 'against gravity. On the other hand, the high frequency coil 200 functions as a stabilizing coil and forms an electromagnetic field that pushes the R2-T2 alloy 20 'downward. Thereafter, vacuuming was performed, and the R1-T1-M alloy substrate 10 was heated to 600 ° C. Then, by applying a high frequency voltage to the coils 100 and 200 of the electromagnetic levitation mechanism, the R2-T2 alloy 20 ′ was melted while floating above the R1-T1-M alloy substrate 10. After the holding mechanism (not shown) is retracted to a position where it does not hinder the fall of the melt of the R2-T2 alloy 20 ′, the voltage application by the coil power supply is stopped and the melt is placed on the R1-T1-M alloy substrate 10. It was dripped. The R2-T2 alloy 20 ′ melt was cooled on the R1-T1-M alloy substrate 10 as it was to obtain an RT ferromagnetic alloy.

<Evaluation of RT ferromagnetic alloy>
As a result of polishing a cross section of the obtained RT-based ferromagnetic alloy and observing with a scanning electron microscope (SEM), the thickness of the RT-based ferromagnetic alloy (corresponding to a portion indicated by reference numeral 30 in FIG. 1) is obtained. Was about 300 μm, and the size of each compound crystal phase produced was sufficiently large, about 10 μm. In addition, a region where a part of the substrate side was re-solidified (crystallized) was also observed, and as a result of analyzing the composition of this region by energy dispersive spectroscopy (EDX), a region where the Ti amount was continuously decreased was confirmed. . It was also confirmed that the minimum value of [M] / ([T] + [M]) in M (= Ti) and T (= Fe) was 0.01 or less.

Furthermore, this area | region was made into the thin piece using the focused ion beam (FIB) process, and the electron beam diffraction was performed using the transmission electron microscope (TEM). As a result, it was confirmed that a compound phase having the same crystal structure as the ThMn ₁₂ type structure constituting the R1-T1-M alloy was formed in the RT ferromagnetic alloy. Even if an alloy having a Y (Fe, Ti) ₁₂ composition with [M] / ([T] + [M]) of 0.01 or less is melted, cast, and heat-treated, the phase of the ThMn ₁₂ type structure remains. It was hardly obtained. However, it was demonstrated that a phase of a ThMn ₁₂ type structure can be generated by dropping and solidifying a molten R2-T2 alloy on an R1-T1-M alloy.

  The method for producing an RT ferromagnetic alloy of the present invention can be suitably used for producing a raw material alloy for a high performance anisotropic sintered magnet, for example.

10 R1-T1-M alloy substrate 20 R2-T2 alloy melt 20 'R2-T2 alloy melt 30 RT ferromagnetic alloy 100 High frequency coil (floating coil)
200 High frequency coil (stabilizing coil)

Claims (11)

A method for producing an RT ferromagnetic alloy,
(A) R1-T1-M compound containing 3 mol% or more of element M and having a ThMn ₁₂ type structure, an Nd ₃ (Fe, Ti) ₂₉ type structure, or a TbCu ₇ type structure, or an intermediate structure thereof R1-T1-M based alloy, wherein M is at least one selected from the group consisting of Ti, V, Cr, Mn, Mo, W, Al, and Si, R1 is a rare earth element, T1 Is a step of preparing an R1-T1-M alloy which is a transition metal element mainly composed of iron;
(B) A molar ratio [T2] / [R2] of T2 to R2 is 9 or more, and is an R2-T2 alloy molten metal that does not substantially contain M, R2 is a rare earth element, and T2 is mainly composed of iron. The R2-T2 alloy molten metal, which is a transition metal element, is brought into contact with the R1-T1-M alloy and cooled, and the R-T ferromagnetic compound phase (R is a rare earth element and T is mainly iron). Forming an RT ferromagnetic alloy containing a transition metal element);
The manufacturing method of the RT ferromagnetic alloy containing this. The step (b) includes the step of generating a phase of a TnMn ₁₂ type structure, a TbCu ₇ type structure, or an intermediate structure thereof as the RT ferromagnetic compound phase. A method for producing a T-based ferromagnetic alloy.   The step (b) includes a step of melting at least a part of the surface of the R1-T1-M alloy and solidifying the R2-T2 alloy melt. A method for producing a magnetic alloy.   4. The R according to claim 1, wherein the step (b) moves a part of the element M contained in the R1-T1-M alloy to the compound phase from the R2-T2 alloy. A method for producing a T-based ferromagnetic alloy.   The method for producing an RT ferromagnetic alloy according to any one of claims 1 to 4, wherein the R1-T1-M alloy is a substrate.   The crystal structure of the phase constituting the R1-T1-M alloy is set to be the same as the phase constituting the RT ferromagnetic alloy to be formed. The manufacturing method of the RT ferromagnetic alloy as described in 1 above. R1 and R2 each contain the same element;
The method for producing an RT ferromagnetic alloy according to any one of claims 1 to 6, wherein T1 and T2 each contain the same element.   The method for producing an RT ferromagnetic alloy according to any one of claims 1 to 7, wherein R2 contains yttrium.   An R2-T2 alloy molten metal (R2 is a rare earth element and T2 is a transition metal element mainly composed of iron) is cooled by contacting the RT alloy with the RT alloy. The manufacturing method of the RT ferromagnetic alloy in any one of Claim 1 to 8 which further includes the process (c) of forming the RT ferromagnetic alloy containing this.   The method for producing an RT ferromagnetic alloy according to claim 9, wherein crystal growth of an RT ferromagnetic compound phase substantially free of M is advanced by repeating step (c).   In the step (b), the temperature of the R1-T1-M alloy when the molten R2-T2 alloy is brought into contact with the R1-T1-M alloy is 500 ° C or higher. The manufacturing method of the RT ferromagnetic alloy in any one.

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