JPH0845718A - Magnetic material and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture rare earth-transition metal-nitrogen base magnetic material having excellent acidproof and temperature characteristics comprising rough particles having large coersive force. CONSTITUTION:This magnetic material is represented by a general formula of RalphaFe(100-alpha-beta-gamma) MbetaNgamma, (provided R: at least one kind out of rare earth elements, M: at least one kind out of Cr, Ti, Zr, Hf, alpha, beta, gamma satisfy the following inequalities in atm%) i.e., 3<=alpha<=20, 1<=beta<=27, 17<=gamma<=25 and the phases thereof are those of rhonbohedral system or hexahedral system crystalline structures using the components of at least said R, Fe, M and N while the mean particle diameter thereof is at least 10mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic material which is most suitable for applications such as small motors and actuators and which has excellent magnetic properties, and particularly excellent coercive force.

[0002]

2. Description of the Related Art Magnetic materials are used in a wide range of fields such as home electric appliances, audio products, automobile parts and peripheral terminals of computers, and their importance as electronic materials is increasing year by year. In particular, recently, there has been a demand for miniaturization and high efficiency of various electric / electronic devices, so that a magnetic material with higher performance is required. In response to such a demand, Sm-Co type (SmCo ₅ type and Sm ₂ Co ₁₇ type),
Demand for rare earth magnetic materials such as Nd-Fe-B system is rapidly increasing, but Sm-Co system has unstable supply of raw material and high raw material cost, and Nd-Fe-B system has high heat resistance and corrosion resistance. There are inferior problems.

On the other hand, as a new rare earth magnetic material, a rare earth-iron-nitrogen magnetic material has been proposed (for example, Japanese Patent Laid-Open No. 2-57663). This material has high magnetization, anisotropic magnetic field, and high Curie point, and is Sm-Co based, Nd-Fe
It is expected as a magnetic material that supplements the drawbacks of the -B type. However, the rare earth-iron-nitrogen-based material disclosed in the above-mentioned publication cannot achieve a high coercive force unless it is finely pulverized to 10 μm or less and used, but when pulverized to 10 μm or less, the surface is oxidized and the coercive force is reduced. However, there was a problem that Further, the temperature change rate β of the coercive force of these materials was −0.45, which was not sufficient for practical physical properties.

As a countermeasure against this, it is considered to improve the coercive force and the stability of the coercive force by including an M component in a rare earth-iron-nitrogen-based material having a rhombohedral crystal structure. Although disclosed in JP-A-3-16102 and JP-A-6-96918, the stability of the coercive force is not radically improved, and the temperature change rate β of the coercive force is hardly improved.

Here, the stability of coercive force is a general term for two characteristics: coercive force does not decrease even if the surface is oxidized (coercive force oxidation resistance) and temperature change rate β. In order to preferably use the above materials in a wider practical range such as high temperature applications exceeding 110 ° C. and flat material applications, it is preferable to use a rare earth-iron-nitrogen-based material with further improved coercive force stability. Is desired.

[0006]

DISCLOSURE OF THE INVENTION According to the present invention, a metal element M is allowed to coexist in a rare earth-iron-nitrogen based material having a rhombohedral or hexagonal crystal structure, and the amount of nitrogen is limited to a highly nitrided region. By doing so, it is an object of the present invention to provide a magnetic material having a rare earth-iron-M-nitrogen composition, which has a high coercive force even with a large particle size of 10 μm or more and solves the above-mentioned problems such as stability of the coercive force. And

[0007]

[Means for Solving the Problems] In order to obtain a rare earth-iron-nitrogen based magnetic material of 10 μm or more having high coercive force and stability of coercive force, a system in which various elements (M) are added to a master alloy is used. As a result of diligent studies, a rare earth (R) -iron (Fe) -M-nitrogen (N) -based magnetic material having a crystal structure and a composition with which the coercive force and the stability of the coercive force are improved, and a microstructure, and a method for producing the same The present invention has been completed and the present invention has been completed.

That is, the present invention is (1) a magnetic material represented by the general formula RαFe _(100- α _- β _- γ ₎ MβNγ (where R is at least one of rare earth elements, M is Cr, Ti, At least one of Zr and Hf, α, β, and γ is atomic% and satisfies the following formula) 3 ≦ α ≦ 20 1 ≦ β ≦ 25 17 ≦ γ ≦ 25 The main phase is at least the above R, Fe, and M. And a magnetic material having a rhombohedral or hexagonal crystal structure containing N as a component and having an average particle size of 10 μm or more, and (2) the above (1) The magnetic material, wherein the nitrogen concentration distribution of the magnetic material has a fine gradation, and (3) 0.01 to 50 of Fe which is a component of the magnetic material described in (1) or (2) above. atom%
A magnetic material characterized by having Co replaced by Co, and (4) a composition in which 50 atomic% or more of R, which is a component of the magnetic material described in (1) to (3) above, is Sm. And (5) M is Cr, which is a component of the magnetic material described in (1) to (4) above.
And (6) heat treating an alloy consisting essentially of R, Fe, and M in the range of 200 to 650 ° C. in an atmosphere containing ammonia gas. The method for producing a magnetic material as described in (1) to (5) above, and (7) an alloy consisting essentially of R-Fe-M in an atmosphere containing at least one of an inert gas and a hydrogen gas, Alternatively, after heat treatment in a range of 600 to 1300 ° C. in a vacuum, nitrogen is introduced by heat treatment in a range of 200 to 650 ° C. in an atmosphere containing ammonia gas. The method for producing a magnetic material as described in (1) above.

The present invention will be described in detail below. As the rare earth element (R), Y, La, Ce, Pr, Nd,
Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, T
It suffices to include at least one of m, Yb and Lu. Therefore, a mixture of two or more kinds of rare earth elements such as misch metal and didymium may be used, but preferable rare earth elements are Y, Ce, Pr, Nd, Sm, Gd, Dy, E
r. More preferably, Y, Ce, Pr, Nd,
It is Sm. In particular, if Sm is contained in an amount of 50 atomic% or more of the entire R component, a material having a significantly high coercive force can be obtained. Furthermore, it is preferable to contain Sm in an amount of 70 atomic% or more.

The rare earth element used here may be of a purity which can be obtained by industrial production, and impurities such as O, H, C, Al, Si, F, Na and M which cannot be avoided in production are inevitable.
It does not matter even if g, Ca, Li, etc. are present. In the magnetic powder of the present invention, the R component is 3
~ 20 atomic% content. When the R component is less than 3 atom%,
The soft magnetic phase containing a large amount of iron component separates beyond the allowable amount even after casting and annealing of the master alloy.Since this kind of soft magnetic phase adversely affects the coercive force of the nitride, it is a practical permanent magnet material. Not preferable. On the other hand, if the R component exceeds 20 atomic%, the residual magnetic flux density decreases, which is not preferable. A particularly preferred range of R is 6 to 12 atom%.

Iron (Fe) is a basic composition of the present magnetic material that is responsible for ferromagnetism, and it is preferable that iron (Fe) is contained in an amount of 30 atomic% or more.
If it is less than 30 atomic%, the magnetization tends to be small.
If the composition range of the iron component is in the range of 50 to 77 atom%,
It becomes a material that balances the coercive force and magnetization of coarse powder,
Particularly preferred. 0.01 to 50 atomic% of Fe is C
O can be substituted, and the introduction of Co raises the Curie point and the magnetization and also improves the oxidation resistance. (In the following, when expressed as "Fe component", "iron component" or expressed as Fe in the formula such as "R-Fe-MN system", 0.01 to 50 atoms of Fe are included. %
Are replaced by Co. ) A particularly preferable range of the Fe substitution amount of Co is 1 to 30 atom%.
Is. When Co exceeds 30 atomic%, the above effect is small and unstable, even if the raw material cost rises.
If it is less than atomic%, the substitution effect is hardly seen.
A particularly preferable range of the Fe substitution amount of Co is 2 to 20 atom%.
Is.

In the present invention, Cr, Ti and Z are further added.
It is necessary to include one of M components selected from r, Hf, and Cr. The effect of adding the M component to the R—Fe—N-based magnetic material is to exhibit a large coercive force in the coarse powder. Among them, Cr is excellent in uniformity of the mother alloy,
In particular, the coercive force is greatly increased by co-adding with Co.

The content of the M component is in the range of 1 to 25 atomic%. If it exceeds 25 atom%, the saturation magnetization is lowered, which is not preferable. It is particularly preferable that the content of the M component is suppressed to 15 atomic% or less. If the content is less than 1 atomic%, the powder particle size is 10
It is not preferable because the coercive force at μm or more is low. In addition to the M component, Mn, Ga, Al, Zn, Sn, Ni, V,
One or more of the elements of Nb, Ta, Mo, W, Pd, C, Si and Ge (M ′ component) may be added, but their content does not exceed the amount of M component. In addition, the total amount with the M component is in the range of 1 to 25 atomic%. Of the M ′ components, Mn is preferable as an element to be co-added in order to enhance the effect of the present invention. (Hereinafter, when referring to the M component or M, the case where the M ′ component is contained therein is also included.) The amount of nitrogen (N) introduced into the above composition is 17 to 25 atom%. It is said that If it exceeds 25 atom%, the magnetization becomes low and the practicality as a magnet material application becomes not so high. 1
If it is less than 7 atomic%, the coercive force of the coarse powder cannot be improved so much (3.5 kOe or less), which is not preferable.

The preferred range of nitrogen content is the desired R-
Fe-M component-R-Fe-M component composition ratio of N-based magnetic material
The optimum nitrogen content depends on the amount ratio of
Since the amount is different, depending on the amount, for example, a rhombohedral structure
Have Sm_10.5Fe_76.1Co _8.9Cr_4.5As the raw material alloy
The optimum nitrogen content is around 17-23 atom%.
It

The optimum amount of nitrogen at this time is the amount of nitrogen for which at least one of the oxidation resistance and magnetic properties of the material is optimum although it varies depending on the purpose, and the magnetic properties are not anisotropic. The absolute value of the temperature change rate of the sex ratio, demagnetization rate, and coercive force is minimum, and the others are maximum. Each composition of the R-Fe-MN magnetic material in the present invention has a rare earth component of 3 to 20 atom%, an iron component of 30 to 79 atom%, an M component of 1 to 25 atom%, and an N of 17 to 25. The range is atomic% and these are satisfied at the same time.

Further, R-Fe-M-N obtained by the present invention
The magnetic material may contain hydrogen (H) in an amount of 0.01 to 10 atom%. Particularly preferred compositions of the R-Fe-M-N based magnetic material of the present invention have the general formula _{RαFe (100- α - β - γ} -
δ ₎ MβNγHδ, α, β, γ, δ are atomic% and 3 ≦ α / (1−δ / 100) ≦ 20 1 ≦ β / (1−δ / 100) ≦ 25 17 ≦ γ / The range is (1-δ / 100) ≤ 25 0.01 ≤ δ ≤ 10. However, α, β, γ, and δ are selected so that the Fe component is 30 atomic% or more, and the above four expressions are simultaneously established.

Further, depending on the manufacturing method, oxygen (O) is 1
It may be contained in an amount of from 10 to 10 atomic%, and in that case, a material having high moldability and magnetic properties of the magnet can be obtained. The magnetic material of the present invention needs to contain a phase having a rhombohedral or hexagonal crystal structure. In the present invention,
These crystal structures are made, and at least R, Fe, M, N
A phase containing a is referred to as a main phase, and a phase having a composition not forming the crystal structure or having another crystal structure is called a subphase. The main phase may contain H and O in addition to R, Fe component, M component and N. However, even if the O component is contained in the main phase, it is about 0.01 to 1 atomic% in a very small amount.

As an example of a preferred main phase crystal structure, T
Examples include rhombohedral crystals having the same crystal structure as h ₂ Zn ₁₇ or the like, or hexagonal crystals having the same crystal structure as Th ₂ Ni ₁₇ , TbCu ₇ , CaZn _5, etc., and at least one of them is included. It is necessary. In this Th ₂
The rhombohedral crystal having the same crystal structure as Zn ₁₇ is most preferable.

For example, RFe as a subphase in the magnetic material
A high-magnetism nitride phase having a tetragonal structure such as a _12-X M _X N _y phase may be contained, but in order to fully exert the effect of the present invention, the volume fraction thereof is the content of the main phase. It is necessary to keep it lower, and it is extremely preferable in practice that the content of the main phase exceeds 75% by volume. The main phase of the R-Fe-M-N-based material is obtained by the intrusion of nitrogen between the lattices of the R-Fe-M alloy, which is the main raw material phase, and the crystal lattice often expands. The structure has almost the same symmetry as the main raw material phase.

The main raw material phase here means at least R,
It is a phase containing Fe and M but not N and forming a rhombohedral or hexagonal crystal structure. (Note that a phase having a composition or crystal structure other than that and not containing N is referred to as an auxiliary material phase.) Among the characteristics of the oxidation resistance performance or the magnetic characteristics, the expansion of the crystal lattice due to the penetration of nitrogen One or more characteristics are improved, and the magnetic material is suitable for practical use. The magnetic properties referred to here are the saturation magnetization (4πIs) of the material and the residual magnetic flux density (B
r), magnetic anisotropy magnetic field (Ha), magnetic anisotropy energy (Ea), magnetic anisotropy ratio, Curie point (Tc), intrinsic coercive force (iHc), squareness ratio (Br / 4πIs), maximum energy At least one of the product [(BH) max], thermal demagnetization rate (α, synonymous with reversible temperature coefficient of magnetization), and temperature change rate of coercive force (β, synonymous with reversible temperature coefficient of coercive force).
However, the magnetic anisotropy ratio is the ratio (a / b) of the magnetization (a) in the difficult magnetization direction and the magnetization (b) in the easy magnetization direction when an external magnetic field of 15 kOe is applied. The smaller the value, the higher the magnetic anisotropy energy.

[0021] For example, rare earth - as the main raw material phase iron -M master alloy, Sm _{10 .5} Fe _85.0 Cr _4.5 with rhombohedral
In the case of selecting, by introducing nitrogen, the crystal magnetic anisotropy changes from in-plane anisotropy to uniaxial anisotropy suitable for a hard magnetic material, and magnetic properties such as magnetic anisotropy energy are obtained. Oxidation resistance is improved. The magnetic material of the present invention is a coarse powder having an average particle size of more than 10 μm, preferably 1
It is 0 to 200 μm. If the average particle size is 10 μm or less, the coercive force is lowered and the magnetic particles are remarkably aggregated, and the magnetic properties originally possessed by the material cannot be sufficiently exhibited, which is not preferable. Here, unless otherwise specified, the average particle diameter means a median diameter obtained based on a volume equivalent diameter distribution curve obtained by a commonly used particle diameter distribution measuring device.

Among the materials of the present invention, S having a rhombohedral crystal
m₂([Fe, Co], Cr)₁₇Material obtained by nitriding mother alloy
Will be described in detail below as an example. Sm₂Fe₁₇Nitrogen
If introduced, Sm₂Fe₁₇S with 3 nitrogens per
m ₂Fe₁₇N₃, Magnetic anisotropy energy, magnetization,
Many magnetic properties such as the Curie temperature are optimized (eg
For example, IEEE Trans. Magn. ,28, 23
26 (1992)). Furthermore, this
The amount of introduced nitrogen is Sm₂Fe₁₇About 5 to 5.5 per
When it is increased, the coercive force in the state of coarse powder becomes maximum.

However, N is Sm ₂ ([Fe, Co], C
r) When the number exceeds ₁₇ per _{17, the} crystal lattice expands because N penetrates into the interstitial lattice and becomes unstable, and finally, the N concentration distribution becomes shaded, or the crystal lattice collapses or collapses. The crossed part occurs. Further, depending on the alloy composition, the amount of nitrogen, the nitriding conditions and the annealing conditions after nitriding, the collapsed or nearly collapsed part of the crystal lattice with a high N concentration around the ferromagnetic phase having a rhombohedral or hexagonal crystal structure. In some cases, a cell-like structure (this structure is hereinafter referred to as a cell structure) that surrounds is generated.

Even in the Sm-Fe-N ternary system, N is Sm ₂ F.
It is known that a similar microstructure occurs when the number exceeds 3 per e ₁₇ and increases to 4 (Journal of Applied Magnetics, Vol. 18, p. 201, 1994). At this time,
When Cr coexists, the coercive force in the high nitriding region greatly increases. For example, coarse powder Sm-Fe-N3 of about 30 μm
In the original system, the maximum value of the coercive force is about 2 kOe as described above, whereas when Cr coexists, the coercive force is 9 to 1
Increase to 2 kOe. Although the role of Cr is unknown, it is considered that the presence of Cr in a portion having a high N concentration or a portion where the crystal lattice is broken or is about to collapse has an effect of suppressing magnetization reversal.

Further, depending on the composition ratio of Cr, Sm
₂ Results of investigating the rising of the magnetic curve and the dependence of the coercive force on the magnetizing magnetic field of the material of the present invention in which the number of N per 4 ([Fe, Co], Cr) ₁₇ is from 4 to 6. , The magnetization reversal mechanism of this material was found to be pinning type. This tendency is similarly observed with and without Co.

Let us consider a case where the vicinity of the surface of the magnetic powder is oxidatively deteriorated to generate a soft magnetic portion which can become a bud of the reverse magnetic domain. Since the domain wall of the nucleation type material easily moves, it grows easily when the reverse magnetic domain occurs and the coercive force deteriorates. As this type of material, the above-mentioned Sm ₂ Fe is used.
₁₇ N ₃ material may be mentioned. On the other hand, the pinning type material is
Even if a reverse magnetic domain occurs near the surface, the domain wall is unlikely to move and maintains a high coercive force. Furthermore, the temperature change rate β of the coercive force may be greatly improved due to the different mechanism of magnetization reversal.

By the way, the existing Sm ₂ Co ₁₇ type material is
The two-phase separation type magnet has a cell type microstructure, but in the manufacturing process thereof, control of solution treatment and aging treatment process is very important. The components of this material are Sm, Co, and Cu as essential components, and in addition to these, Fe, Zr, Ti, Hf, and Ce.
Etc., and after melting these metal elements,
Heat treatment is performed at a high temperature of 900 to 1250 ° C. The Sm ₂ Co _{1 7} alloy having the above components, but are uniformly dissolved at elevated temperatures, such as phase separation at a low temperature of around room temperature, a wide solid solution limit high temperature stable phase is present as a main phase . In order to cool to room temperature while maintaining a stable phase at this high temperature, after solution treatment, quenching is generally carried out in water or oil or by blowing gas. The alloy obtained in this solution heat treatment is subjected to one-step or multi-step aging treatment at a temperature of 400 to 900 ° C., and the concentration of M ″ component such as Cu is increased in the alloy main phase which maintains a uniform composition. A large phase is finely precipitated to adjust a thermodynamically stable two-phase separated structure. This finely precipitated low magnetic phase having a large M component concentration serves as a pinning point, and the existing Sm ₂ Co ₁₇ system material has a pinning type magnetization reversal mechanism. In the solution treatment-aging step described above, precise control of heat treatment temperature, time, and cooling rate is extremely important. For example, the final coercive force depends on whether solution treatment is followed by rapid cooling or slow cooling. It will be completely different.

On the other hand, within the scope of the present invention, the crystal structure of the main raw material phase of the Sm-Fe-Cr alloy, which is the mother alloy, is a rhombohedral crystal having a 2-17 composition at room temperature and is solid even at high temperatures. Since it is almost a line phase with a low melting limit, F
The e component and Cr are uniformly solid-dissolved in the main raw material phase, and Cr and Cr compounds are not finely precipitated in the main raw material phase mainly composed of Fe by solution treatment or aging treatment. Therefore, the aging treatment is not necessary, and the coercive force does not depend on the cooling rate. About 3 per the N Sm ₂ Fe ₁₇ on the main raw material phase (approximately 13.
(6 atomic%), all the nitrogen enters between the crystal lattices to form a uniform microstructure, and the above-mentioned nucleation type magnetic material is obtained. N for Sm
₂ ([Co, Fe], Cr) The introduction of more than 4 (17.4 atom%) per ₁₇ only causes the non-uniform microstructure to be obtained, and the portion with a high nitrogen concentration that can serve as a sufficient pinning point. It occurs in the main phase. This fact indicates that the pinning type microstructure is not induced by the precipitation of Cr and Cr compounds, but the pinning type microstructure is obtained by the fine density of N concentration.

The fine non-uniformity of the N concentration, that is, the period of the density of the N concentration is about 10 to 200 nm.
It is revealed by M observation (Fig. 3 etc.). M '' component such as Cu (M ''; Cu, Zr, Hf, Nb, Ta,
(W, Mo, Ti, V, Cr, Mn) is added to the rare earth-iron-nitrogen-based material for solution treatment and aging treatment, and the M ″ component and M ″ compound are finely precipitated in the main phase for coarse precipitation. An attempt to increase the coercive force of the powder has been concretely exemplified (Japanese Patent Laid-Open No. Hei 4-
(216601, JP-A-6-20813)
However, since the N content of these materials is as low as 13 to 15 atom%, it is not possible to generate the density of the N concentration distribution enough to generate a sufficient pinning point.

Therefore, since the material of the present invention produces a pinning type microstructure due to non-uniformity of N, not to fine precipitation of Cr, the magnetic material is completely different from the magnetic material disclosed in the above-mentioned publication. Hereinafter, the production method of the present invention will be exemplified. (1) Preparation of Master Alloy The magnetic material of the present invention has an R content by introducing excess N.
A microstructure in which pinning points are finely dispersed in a -Fe-M alloy,
For example, when a microstructure having a pinning point at the boundary of the cell structure is adopted, the coercive force value becomes extremely large when M coexists at the pinning point. Therefore, the M component is added at the stage of adjusting the mother alloy.

As a method for producing the R-Fe-M alloy, a)
R, Fe components, M high-frequency melting method of melting metal by high frequency and casting into a mold, (b) arc melting method of charging metal components into a boat such as copper and melting by arc discharge,
C) A super-quenching method in which a high-frequency melt is dropped onto a rotating copper roll to obtain a ribbon-shaped alloy, d) A gas atomization method in which the high-frequency melt is sprayed with gas to obtain an alloy powder, and e) Fe component And / or M powder or Fe-M alloy powder, R and / or M oxide powder, and a reducing agent are reacted at high temperature to reduce R or R and M while R
Or R / D method of diffusing R and M into Fe component and / or Fe-M alloy powder, f) Mechanical alloying method of reacting each metal component and / or alloy while finely pulverizing with a ball mill, etc. The alloy obtained by any of the above methods is heated in a hydrogen atmosphere, and once decomposed into a hydride of R and / or M and an Fe component and / or an M or Fe-M alloy. Any of the HDDR methods of recombining while alloying and alloying may be used.

When the high frequency melting method or the arc melting method is used, a soft magnetic component mainly composed of Fe is likely to precipitate from the molten state when the alloy is solidified, and particularly the coercive force is lowered even after the nitriding step. Therefore, for the purpose of eliminating this soft magnetic component or increasing the rhombohedral or hexagonal crystal structure, an inert gas such as argon or helium, or a gas containing at least one of hydrogen gas or a vacuum is used. It is effective to anneal in the temperature range of 600 ° C to 1300 ° C. The alloy produced by this method has a large crystal grain size, good crystallinity, and high residual magnetic flux density, as compared with the case of using the ultra-quenching method. Therefore, this alloy contains a large amount of homogeneous main raw material phases and is most preferable as a master alloy for obtaining the magnetic material of the present invention. (2) Coarse crushing and classification It is also possible to directly nitride the alloy ingot produced by the above method, but if the crystal grain size is larger than 500 μm, the nitriding time will be longer, and it is better to carry out coarse crushing before nitriding. It is efficient. When the thickness is 200 μm or less, the nitriding efficiency is further improved, which is particularly preferable.

For coarse crushing, a jaw crusher, a hammer,
It is performed by using a stamp mill, a rotor mill, a pin mill, a coffee mill, or the like. Further, even if a crusher such as a ball mill or a jet mill is used, it is possible to prepare an alloy powder suitable for nitriding depending on the conditions. A method in which hydrogen is absorbed by the mother alloy and then crushed by the crusher, or a method in which hydrogen is repeatedly occluded and released may be used.

Further, after coarse pulverization, it is effective to adjust the grain size by using a sieve, a vibration type or a sonic type classifier, a cyclone, etc. for more uniform nitriding.
After coarse pulverization and classification, annealing in an inert gas or hydrogen can remove structural defects, which is effective in some cases. In the above, the preparation method of the powder raw material or the ingot raw material of the rare earth-iron component-M component alloy in the production method of the present invention has been illustrated, but the crystal grain size, pulverized grain size of these raw materials,
The optimum nitriding conditions shown below differ depending on the surface condition. (3) Nitriding / annealing Nitriding is performed by using a gas containing a nitrogen source such as ammonia gas or nitrogen gas obtained in the above (1) or (1) and (2).
By contacting with Fe-M component alloy powder or ingot,
This is a step of introducing nitrogen into the crystal structure.

At this time, coexistence of hydrogen in the nitriding atmosphere gas is preferable because the nitriding efficiency is high and the nitriding can be performed while the crystal structure is stable. In addition, in order to control the reaction, an inert gas such as argon, helium, or neon may coexist. The most preferable nitriding atmosphere is a mixed gas of ammonia and hydrogen. Particularly, if the ammonia partial pressure is controlled in the range of 0.1 to 0.7, the nitriding efficiency is high and the magnetic properties in the entire nitrogen amount range of the present invention are high. The material can be made.

The nitriding reaction can be controlled by the gas composition, heating temperature, heat treatment time, and pressure. Of these, the heating temperature varies depending on the composition of the mother alloy and the nitriding atmosphere, but is 200 to 65
It is desirable to select in the range of 0 ° C. If the temperature is lower than 200 ° C., nitriding does not proceed, and if the temperature exceeds 650 ° C., the main raw material phase decomposes, and it is impossible to perform nitriding while maintaining the rhombohedral or hexagonal crystal structure. In order to increase the nitriding efficiency and the content of the main phase, a more preferable temperature range is 250 to 600.
° C.

After nitriding, it is preferable to anneal in an inert gas and / or hydrogen gas in order to improve magnetic properties. Examples of the nitriding / annealing device include horizontal and vertical tubular furnaces, rotary reaction furnaces, and closed reaction furnaces. It is possible to adjust the magnetic material of the present invention in any of the apparatuses, but it is preferable to use a rotary reactor in order to obtain a powder having a uniform nitrogen composition distribution.

The gas used for the reaction is a gas flow system in which a gas flow of 1 atm or more is sent to the reactor while keeping the gas composition constant, a gas sealing system in which the gas is sealed in a container at a pressure of 0.01 to 70 atm, or Supply them in combination. The manufacturing method of the present magnetic material includes (1) or
It is most preferable to use a step of preparing a master alloy having an R-Fe-M composition by the method illustrated in (1) and (2) and then nitriding it by the method described in (3). In particular, the alloy obtained in (1) or the alloy obtained by pulverizing and classifying the alloy by the method of (2)
Annealing was performed by performing heat treatment at 600 to 1300 ° C. in an atmosphere containing at least one of an inert gas and hydrogen gas, and then performing heat treatment in the range of 200 to 650 ° C. in an atmosphere containing ammonia gas. If nitriding is then carried out, a magnetic material having extremely small deterioration of coercive force due to oxidation can be obtained.

The above is a description of the method for producing the R—Fe—M—N magnetic material of the present invention. In particular, when the magnetic material of the present invention is applied as a practical hard magnetic material, (4)
Regrinding, (5) magnetic field molding, and (6) magnetization may be performed. Among them, the method (4) of introducing the O component in the re-grinding step to obtain a material having higher moldability and magnet characteristics is effective.
The example will be briefly described below. (4) Re-grinding In the re-grinding step, fine powder finer than the above R-Fe-M-N-based material is crushed, or R-Fe-M-N-H-
This is a process performed for the purpose of introducing O and H components into the above-mentioned R—Fe—M—N magnetic material in order to obtain an O-based material.

As the re-grinding method, in addition to the method mentioned in (2), a rotary ball mill, a vibrating ball mill, a planetary ball mill, a wet mill, a jet mill, a cutter mill, a pin mill, an automatic mortar and a combination thereof are used. As a method of adjusting the introduced amount of the O component or the H component within the range of the present invention, a method of controlling the water content or oxygen concentration in the re-grinding atmosphere can be mentioned.

For example, when a dry mill such as a jet mill is used, the amount of water in the milling gas is kept at a predetermined concentration in the range of 1 ppm to 1% and the oxygen concentration is in the range of 0.01 to 5%.
When a wet mill such as a ball mill is used, the amount of water in ethanol or other milling solvent is 0.1 wtppm to 8 wt%.
0 wt%, dissolved oxygen amount 0.1 wtppm ~ 10 wtp
The oxygen amount is controlled in an appropriate range by adjusting the range to pm.

It is also possible to control the amount of oxygen by carrying out the handling operation of the re-ground particles in a glove box controlled to various oxygen partial pressures. The fine powder having a particle size of less than 10 μm by re-grinding is slightly inferior in oxidation resistance performance, but as described later, when used in combination with the coarse powder of 10 μm or more of the present invention, magnetic properties can be improved. Yes, but rather preferred.

The magnetic material of the present invention is
Almost no change in coercive force and no significant decrease in magnetization. Therefore, when the coarse powder of the present invention having a size of 10 μm or more and the fine powder pulverized by the above method are mixed and molded, the packing rate is increased, so that a molded body having high magnetization and maximum energy product can be produced, and a practically preferable magnet. It becomes a material. However, it should be noted that the squareness ratio may decrease depending on the compounding ratio of the coarse powder and the fine powder, that is, the particle size distribution. (5) Magnetic field molding For example, when the magnetic powder obtained in (3) or (3) and (4) is applied to an anisotropic bonded magnet, it is mixed with a thermosetting resin or a metal binder and then in a magnetic field. Compression molding,
After kneading with a thermoplastic resin, injection molding is performed in a magnetic field to perform magnetic field molding.

The magnetic field shaping is preferably 10 kOe in order to sufficiently orient the R-Fe-M-N magnetic material in the magnetic field.
Above, more preferably in a magnetic field of 15 kOe or more. (6) Magnetization Anisotropic bonded magnet material or sintered magnet material obtained in (5),
The isotropic bonded magnet or sintered magnet material obtained by molding the powder obtained in (3) or (3) and (4) together with a resin or a metal binder is usually magnetized in order to improve the magnet performance. Be seen.

The magnetization is, for example, an electromagnet that generates a static magnetic field,
It is performed by a condenser magnetizer that generates a pulsed magnetic field. The magnetic field strength for sufficiently magnetizing is preferably 15 kOe or more, more preferably 30 kOe or more. (7) Addition of M ′ component (3) or M ′ component such as Zn is further added to the magnetic powder obtained in (3) and (4), and heat treatment is performed before or after the step (5). The method of using various magnetic materials as a magnet is an effective method in improving the squareness ratio.

[0046]

The present invention will be described below in detail with reference to examples. The evaluation method is as follows. (1) Magnetic characteristics R-Fe-MN magnetic material or R-Fe which is a coarse powder having an average particle size of about 30 to 36 μm or a fine powder having an average particle size of about 2 μm.
-Copper powder is mixed with N-based magnetic material in an external magnetic field of 15 kOe,
After molding at ² ton / cm ² and pulse-magnetizing in a magnetic field of 80 kOe at room temperature, an intrinsic coercive force (iHc / kOe) and a magnetization (e) at room temperature were measured using a vibrating sample magnetometer (VSM).
mu / g) was measured.

The molded magnet was pulse-magnetized in a magnetic field of 80 kOe at room temperature and then subjected to room temperature intrinsic coercive force (iHc /
kOe), magnetization (kG), and (BH) _max [MGOe] were measured. (2) Nitrogen amount, oxygen amount and hydrogen amount Si ₃ N ₄ (including quantitative amount of SiO ₂ ) was used as a standard sample, and the nitrogen amount was quantified by the inert gas fusion method. (3) Average Particle Size The volume equivalent diameter distribution was measured using a laser diffraction type particle size distribution meter, and the median diameter obtained from the distribution curve was evaluated. (4) Oxidation resistance performance A powder having an average particle size of about 30 to 36 μm or about 2 μm is
The sample was placed in a constant temperature bath at 10 ° C., and the intrinsic coercive force after 200 hours was measured in the same manner as in (1), and the retention rate (%) of the intrinsic coercive force was determined by comparing with the result of (1). The molded magnet was evaluated in the same manner. The higher the retention rate, the higher the oxidation resistance performance. In particular, in this test, since various binders were evaluated without addition, those having a retention rate of more than 90% can be used sufficiently as practical physical properties when used as a bonded magnet, and those having a retention rate of more than 95% are practical. It can be determined that the material is extremely suitable. (5) Temperature characteristic test Using VSM, in the temperature range from room temperature to 150 ° C,
The intrinsic coercive force of the sample prepared in (1) was measured. From the values of the intrinsic coercive force at room temperature and 150 ° C., the decrease rate of the coercive force per 1 ° C. was calculated, and the temperature change rate β of the coercive force [reversible temperature coefficient of the intrinsic coercive force] (% / ° C.) was obtained. A material having a smaller coercive force change rate with temperature is a practically superior material. When applied to a permanent magnet material having a small permeance, such a material generally has a small irreversible temperature coefficient even if the coercive force at room temperature is not so high, and is preferably used for higher temperature applications and flat material applications.

[0048]

Example 1 Sm having a purity of 99.9%, Fe having a purity of 99.9% and Cr having a purity of 99.9% were melt-mixed in a high frequency melting furnace under an argon gas atmosphere, and further, at 1150 ° C. in an argon atmosphere. An alloy having a composition of Sm _10.5 Fe _85.0 Cr _4.5 was prepared by annealing for 20 hours and slowly cooling.

This alloy was crushed with a jaw crusher and then further crushed with a rotor mill in a nitrogen atmosphere, and the particle size was adjusted with a sieve to obtain a powder having an average particle size of about 50 μm. This Sm-Fe-Cr alloy powder was charged into a horizontal tubular furnace, and the ammonia partial pressure was 0.35 at 465 ° C.
1.7 in a mixed gas flow of atm and hydrogen gas of 0.65 atm
After heat treatment for 5 hours and subsequent annealing in an argon stream for 1 hour, the average particle size was adjusted to about 30 μm.

Table 1 shows the composition, magnetic characteristics, oxidation resistance and temperature characteristic test results of the obtained Sm-Fe-Cr-N-based powder. As a result of analysis by the X-ray diffraction method, diffraction lines mainly showing rhombohedral crystals were recognized, and further, diffraction lines were recognized near 2θ = 44 ° (Cu, Kα line).

[0051]

Example 2 An average particle diameter of about 3 was obtained by the same operation as in Example 1 except that the composition of the mother alloy was changed to the composition shown in Table 1.
An R-Fe-Co-Cr-N-based powder of 0 μm was obtained. The results are shown in Table 1. As a result of analysis by the X-ray diffraction method, diffraction lines mainly showing rhombohedral crystals were observed and 2θ
A relatively large diffraction line was recognized around = 44 ° (Cu, Kα line).

Further, the powder of Example 2 was pulverized with a ball mill to an average particle size of about 2 μm. IHc of this material
Was 8.5 kOe. This result shows that in the powder of Example 2, the intrinsic coercive force iHc has no particle size dependency. The evaluation results of the powder having an average particle size of about 2 μm are also shown in Table 1 (Reference Example 1).

[0053]

Examples 3 to 10 By substantially the same operation as in Example 1, except that the composition of the mother alloy was changed to the composition shown in Table 1.
A rare earth-iron component-M component-nitrogen-based powder having an average particle size of about 30 μm was obtained. The results are shown in Table 1.

[0054]

Comparative Example 1 Sm-having the composition shown in Table 1 was prepared in the same manner as in Example 1 except that Cr was not added and the nitriding time was 2 hours.
Fe-N type powder was obtained. IHc of this material is 0.5 kO
It was e. Furthermore, this material is about 2 μm in a ball mill.
Finely ground. Table 1 shows the results.

[0055]

[Comparative Example 2] Nitriding conditions were set to 420 ° C and ammonia partial pressure was set to 0.
S of the composition shown in Table 1 was prepared in the same manner as in Example 1 except that the hydrogen partial pressure was 30 atm, the hydrogen partial pressure was 0.70 atm, and the time was 2.5 hours.
An m-Fe-Cr-N-based powder was obtained. The iHc of this material was 0.35 kOe. Further, this material was finely ground to about 2 μm with a ball mill. Table 1 shows the results.

[0056]

Comparative Example 3 Sm-F having a particle size of about 30 μm obtained in Example 1
The e-Cr-N powder was ² ton / cm ² , 15 kOe.
Magnetic field molding under the conditions
The heat treatment was performed at 0 ° C. for 1 hour. The iHc of the molded body when cooled rapidly was 0.1 kOe or less. The iHc of the powder obtained by pulverizing the compact again to about 30 μm was 0.1 kOe or less. As a result of analyzing the crystal structure of this material by X-ray diffraction, diffraction lines mainly corresponding to α-iron and iron nitride were detected. This did not contain the rhombohedral or hexagonal crystal structure of the present invention.

[0057]

Comparative Example 4 An alloy ingot was obtained by melting and casting in a high frequency induction furnace so that the composition was Sm _11.0 Fe _85.0 Zr _1.0 Mn _3.0 . 1100 this alloy in an argon atmosphere
The solution was subjected to solution treatment at 24 ° C. for 24 hours, and then subjected to aging treatment at 800 ° C. for 1 hour. The solution treatment was gas quenching to room temperature, and the aging treatment was furnace cooling. Further, it was confirmed by XRD that the mother alloy after the solution treatment had almost a single phase of Sm ₂ Fe ₁₇ , but a slight Sm rich phase was present.

The obtained alloy was crushed by using a jaw crusher and a coffee mill in an argon atmosphere, and then 45-1.
The alloy powder obtained by classification to 50 μm was put in an alumina boat and held in a nitriding furnace. The nitriding treatment was performed in 1 atm of pure nitrogen at 500 ° C. for 24 hours. The nitrided alloy was then cooled in the nitriding furnace before being taken out.

The obtained Sm-Fe-M '' component-N-based material had a nitrogen content of 5.0 atom% and a saturation magnetization of 114 emu.
/ G, and the intrinsic coercive force was 0.09 kOe.

[0060]

[Comparative Example 5] Sm _11.0 Fe _65.0 Co _20.0 Ti _1.0 Mn _3.0
The alloy ingot was obtained by melting and casting using a high-frequency melting furnace so that the composition of This was treated in the same manner as in Comparative Example 4 to obtain Sm-Fe-M '' component-N-based material powder.
The nitrogen content of the obtained magnetic powder was 4.6 atomic%, the saturation magnetization was 132 emu / g, and the intrinsic coercive force was 0.08 kOe.

[0061]

Comparative Example 6 Sm _10.0 Ce _2.0 Fe _64.0 Co _20.0 Ti _1.0
An alloy ingot was obtained by melting and casting using a high-frequency melting furnace so that the composition was Mn _3.0 . This was treated in the same manner as in Comparative Example 4 to obtain Sm-Fe-M '' component-N-based material powder. The nitrogen content of the obtained magnetic powder was 7.3 atomic%,
The saturation magnetization was 131 emu / g and the coercive force was 0.1 kOe.

[0062]

[Table 1]

[0063]

As described above, according to the present invention, 1
Rare earth-iron component-M component-nitrogen (-) with a coarse powder of 0 μm or more, high coercive force, and excellent oxidation resistance and temperature characteristics
A hydrogen-oxygen) type magnetic material can be provided.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C22C 38/00 303 D 38/28 C23C 8/24 H01F 1/06

Claims (7)

[Claims] 1. A general formula RαFe _(100- α _- β _- γ ₎ MβN
a magnetic material represented by γ, where R is at least one of rare earth elements, M is Cr, Ti, Zr, Hf
At least one of them, α, β, γ is atomic% and satisfies the following formula) 3 ≦ α ≦ 20 1 ≦ β ≦ 25 17 ≦ γ ≦ 25 The main phase is at least the above R, Fe, M and N. A magnetic material, which is a phase having a rhombohedral or hexagonal crystal structure as a component and has an average particle size of 10 μm or more. 2. The magnetic material according to claim 1, wherein the nitrogen concentration distribution has a fine gradation. 3. The magnetic material according to claim 1, which has a composition in which 0.01 to 50 atomic% of the Fe component is replaced with Co. 4. The magnetic material according to claim 1, wherein 50 atom% or more of the R component is Sm. 5. The magnetic material according to claim 1, wherein the M component is Cr. 6. The alloy according to claim 1, wherein the alloy consisting essentially of R, Fe and M is heat-treated in the range of 200 to 650 ° C. in an atmosphere containing ammonia gas. Manufacturing method of magnetic material. 7. An alloy consisting essentially of R—Fe—M is heat-treated at 600 to 1300 ° C. in an atmosphere containing at least one of an inert gas and hydrogen gas or in vacuum, and then ammonia is added. 20 in an atmosphere containing gas
The method for producing a magnetic material according to any one of claims 1 to 5, wherein the heat treatment is performed in the range of 0 to 650 ° C to introduce nitrogen.