JPH05121221A - Production of rare earth bonded magnet - Google Patents

Abstract

PURPOSE:To provide rare earth bonded magnet which ensures excellent magnetic characteristics and temperature characteristics without using hydrogen. CONSTITUTION:Rare earth metal (R) composed of Nd or Pr or Ce and alloy whose major ingredients are Fe and other metal containing ThMn12 type compound as a major phase are powdered to manufacture alloy powder whose average grain diameter is 200mum. The alloy powder is brought into contact with nitride gas at 200-500 deg.C so as to permit nitrogen to invade, binder is mixed with the nitrogen invaded powder and magnet is manufactured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a rare earth bonded magnet, and more particularly to a method for producing a rare earth bonded magnet having excellent magnetic performance and temperature characteristics.

[0002]

2. Description of the Related Art In recent years, with the demand for high-performance permanent magnets along with the miniaturization of various electronic parts and equipment, Nd
-Fe-B system permanent magnets are widely used because of their high magnetic performance. However, this Nd-Fe-B system permanent magnet has a low Curie point of about 310 ° C and thus has poor temperature characteristics, and is not suitable for use in an atmosphere of 150 ° C or higher. As a countermeasure against this, a part of Fe is replaced with Co, and a part of Nd is replaced with Dy. In the former case, the Curie point is slightly increased, but a small amount of Co replacement is performed. However, there is a problem that the coercive force is greatly reduced. In the latter case, although the coercive force is not reduced, the saturation magnetic flux density is reduced, and Dy is expensive and the cost increase is unavoidable. However, it was difficult to improve the temperature characteristics.

On the other hand, recently, it has been reported that a rare earth metal-iron-nitrogen-hydrogen alloy having a Th ₂ Zn ₁₇ type compound as a main phase can be used as a magnet material (for example, Japanese Patent Laid-Open No. 2-5).
7663). According to this, when Sm is used as a rare earth metal and nitrogen and hydrogen coexist in the alloy, a saturation magnetic flux density equivalent to that of a Nd-Fe-B system permanent magnet and a higher Curie point can be expected. There is.

[0004]

However, according to the above rare earth metal-iron-nitrogen-hydrogen alloy, hydrogen in the alloy is relatively easily released due to changes in temperature and pressure, causing an occlusion phenomenon. In particular, there is a problem in that manufacturability is difficult because hydrogen gas, which has a risk of flammable explosion in the manufacturing process, is apt to become unstable in magnetic performance.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide a method for producing a rare earth bonded magnet which can secure excellent magnetic performance and temperature characteristics without using hydrogen.

[0006]

To achieve the above object, the rare earth bonded magnet material according to the present invention is Nd, P.
Rare earth metal (R) consisting of at least one of r and Ce, Fe and another metal (M) other than R and Fe (M) as main components, and an alloy containing a Th Mn ₁₂ type compound as a main phase are ground and averaged. A first step of obtaining an alloy powder having a particle size of 200 μm or less, a second step of contacting the alloy powder with a nitriding gas at 200 to 500 ° C. to obtain nitrogen by invading nitrogen into the alloy, and A third step of solidifying the nitriding powder with a binder to form a magnet.

The above-mentioned Th Mn ₁₂ type compound is one of various compounds generally found in alloys of rare earth metals and transition metals, and the atomic ratio of rare earth metal to transition metal is approximately 1:12. There are many as the center. However, even with the same type of compounds, SmFe ₁₁ Ti, Sm Fe ₁₀ V ₂
The alloy containing as a main phase has a high coercive force, but has a low saturation magnetic flux density and is not suitable for practical use.

According to the present invention, the saturation magnetic flux density, the crystal magnetic anisotropy, and the Curie point can be sufficiently put into practical use by injecting nitrogen into the rare earth metal-iron alloy having the Th Mn ₁₂ type compound as the main phase. It is an attempt to raise the standard. In this case, for example, if nitrogen is simply introduced into Sm Fe ₁₁ Ti, which is a Th Mn ₁₂ type compound, the crystal magnetic anisotropy becomes in-plane and the magnet material cannot be obtained. However, when any one of Nd, Pr and Ce is used as the rare earth metal,
Uniaxial crystal magnetic anisotropy can be imparted, and other magnetic performance becomes excellent. By the way, N before nitrogen invasion
The saturation magnetic flux density, anisotropic magnetic field and Curie point of the alloy containing d Fe ₁₁ Ti as the main phase are 12.5 kG and 5 kOe, respectively.
, 270 ° C, whereas those of the alloy after nitrogen infiltration are greatly improved to 13.4 kG, 60 kOe, and 460 ° C. In order to adjust the magnetic performance and the cost of raw materials, Nd,
There is no problem in substituting some of Pr and Ce with other rare earth metals. However, even in this case, in order to give the above compound uniaxial crystal magnetic anisotropy, the substitution amount thereof is preferably suppressed to less than 50%.

Regarding the metal element M except R and Fe, it has the effect of stabilizing the Th Mn ₁₂ type compound and further improving the magnetic performance, and Ti, Zr, Hf, V,
Nb, Ta, Cr, Mo, W, Mn, Ni, Pd, Cu
, Ag, Zn, Mg, B, Al, Ga, In, Si, S
At least one of a transition metal such as n, a low melting point metal, or a light metal can be selected. Among these metals, for example, Ti, V, Cr, Si and the like have a great effect on the stabilization of the Th Mn ₁₂ type compound, and Zn, Sn and the like react with a small amount of αFe contained in the alloy to form the compound. It has the effect of suppressing the decrease in coercive force, and also Ti, Zr
, Ta and the like are likely to form nitrides, and thus have a function of increasing coercive force by dispersing and precipitating them in the alloy. When the content of these metals M is less than 1% by weight, the above-mentioned effects are small, and when it exceeds 20%, the saturation magnetic flux density is lowered and it becomes difficult to obtain good magnetic characteristics.
It is desirable to set it as the weight percent. Note that substituting a part of iron with cobalt is effective in raising the Curie point and improving the temperature characteristics.

The present invention is characterized in that nitrogen is infiltrated into the powder alloy to form a nitride powder as described above. To effectively infiltrate this nitrogen, the alloy powder should be 200 μm thick.
It is necessary to do the following. If the particle size of the alloy powder is larger than this, nitrogen does not sufficiently penetrate into the alloy and a uniform nitride compound cannot be obtained. The method of obtaining the alloy powder in the present invention is arbitrary, for example, rare earth metals, iron and other metals are mixed in a predetermined ratio to melt the raw material in a high-frequency induction furnace, the alloy melt is poured into a mold and once alloy ingot After homogenizing at high temperature, the alloy ingot is mechanically crushed with a jaw crusher, the alloy melt is directly injected into the rotating roll surface, the quenching method is used, and the molten alloy is put into gas or liquid. It is possible to employ an atomizing method of spraying at high speed, a mechanical alloying method utilizing mutual diffusion of solid metals instead of melting, and the like. If necessary, a ball mill, an attritor, a jet mill or the like may be used in combination to obtain a powder having a desired size.

According to the present invention, as described above, the alloy powder is
Nitrogen is introduced into the powder alloy by heating it to ~ 500 ° C and contacting it with a nitriding gas. Nitrogen gas, ammonia gas, a mixed gas of nitrogen gas and other reducing gas, etc. is used as this nitriding gas. be able to. In this case, if the temperature is less than 200 ° C, the penetration of nitrogen is not sufficient, and if it exceeds 500 ° C, the Th Mn ₁₂ type compound is decomposed into rare earth nitrides and iron, so the treatment is performed in the range of 200 to 500 ° C. There is a need. It should be noted that pressurizing the atmosphere makes it easier for nitrogen to enter. The content of nitrogen in the final alloy is
If it is less than 0.5, a sufficient anisotropic magnetic field cannot be obtained, and if it exceeds 5%, the Th Mn ₁₂ type crystal structure cannot be maintained and becomes amorphous so that the magnetic performance is generally deteriorated. It is desirable to set it as the weight percent.

Further, the present invention is characterized in that the nitriding powder is hardened with a binder as described above to form a magnet, and the binder is a metal such as Zn, Sn, or Pb, or a heat-resistant epoxy resin or phenol resin. A curable resin or a thermoplastic resin such as a nylon resin can be used. When the above-mentioned metals are used as the binder, in addition to simply functioning as a binder, they partially alloy with each metal constituting the nitriding powder to contribute to an increase in coercive force. If the addition amount of these binders is too small, the binding force will be insufficient, and if the addition amount is too large, the magnetic performance, especially the residual magnetic flux density will be deteriorated. In addition, compression molding can be used to harden the nitriding powder with a binder.
When a resin is used as the binder, injection molding, extrusion molding or the like can also be used. When these moldings are performed by heating, subsequent heat treatment or curing can be omitted.

[0013]

In the rare earth bonded magnet constructed as described above, nitrogen penetrates into the crystal lattice of the Th Mn ₁₂ type compound to increase the saturation magnetic flux density, the crystal magnetic anisotropy and the Curie point, and Since it does not contain hydrogen, performance is stable over a long period of time. Further, since hydrogen is not handled in the manufacturing process, safety is improved.

[0014]

EXAMPLES Examples of the present invention will be described below.

Example 1 Neodymium (Nd) with a purity of 96%, electrolytic iron with a purity of 99.9%,
Then, titanium sponge having a purity of 99% was blended at a predetermined ratio, charged into an alumina crucible, melted in a high frequency induction furnace, and cast into a mold to produce an alloy ingot. In many cases, segregation of the components was observed inside the alloy ingot. Therefore, heat treatment was carried out by holding this in an argon gas atmosphere at 1100 ° C for 24 hours and then rapidly cooling it. Next, this alloy ingot was subjected to a jaw crusher to roughly crush it to a size of several mm, and then further crushed and classified by a stamp mill to obtain an alloy powder having an average particle size of 40 μm. Next, put this alloy powder in a stainless steel small plate and put it in an electric furnace.
Nitrogen powder samples 1 to 4 were obtained by keeping nitrogen atmosphere at 350 ° C. for 4 to 24 hours under nitrogen atmosphere to infiltrate nitrogen, and these were subjected to a magnetic performance and Curie point measurement test described later. For comparison, Nd-Fe-B alloy ingots and Sm-Fe alloy ingots were manufactured, and each ingot was crushed in the same manner as above to obtain an alloy powder. Further, the powder sample 5 was prepared, and the latter was processed in an atmosphere of ammonia gas to prepare the powder sample 6, and the powder sample 5 was also subjected to the magnetic performance and Curie point measurement tests. As a result of analyzing the crystal structure of each powder by an X-ray diffraction method, all of the powder samples 1 to 4 mainly had a Th Mn ₁₂ type crystal structure. Similarly for powder samples 5 and 6,
The structures were Nd ₂ Fe ₁₄ B type and Th ₂ Zn ₁₇ type, respectively.

The Curie point (Tc) was measured by filling each powder sample 1 to 6 in a predetermined holder and using a vibrating sample magnetometer (abbreviated as VSM). The measurement of magnetic performance is
Performed using a DC BH tracer, maximum magnetic flux density 4
πIm is the magnetic flux density in the measured magnetic field of 15 kOe,
An anisotropic magnetic field Ha, which represents the magnitude of crystal magnetic anisotropy, was determined by a drawing method from magnetization curves in two directions parallel and at right angles to the powder orientation in the magnet. In addition, the component analysis
Nd, Sm, Fe, and Ti were measured by ICP emission spectrometry, and N and H were measured by LECO analyzers TC-436 and RH-402, respectively. The results of these tests are shown in Table 1. In the table, the component composition (%) represents the atomic percentage, and the symbol # attached to the sample number represents the comparative example.

[0017]

[Table 1]

As is clear from Table 1, in each of the powder samples 2 to 4 according to the present invention, the maximum magnetic flux density 4πIm, the anisotropic magnetic field Ha and the Curie point Tc were high. On the other hand, it was revealed that the powder sample 1 containing no nitrogen had an anisotropic magnetic field Ha extremely smaller than the others, and was not suitable as a magnet material. Also Nd-Fe-
The Curie point Tc of the B-type powder sample 5 is about 310 ° C.,
It does not reach that of the sample of the present invention. Furthermore, Sm-Fe-
N—H powder samples 6 are powder samples 2 to 4 according to the present invention.
It should be taken into consideration the long-term instability due to the hydrogen content, which shows the magnetic properties equivalent to.

Example 2 As the rare earth metal R, at least one of Nd, Pr and Ce having a purity of 96%, electrolytic iron having a purity of 99.9%, and Ti, V, Cr, Si having a purity of 98% or more as the other metal M. Zr
, W, Cu, Al, Sn, and Zn were mixed in a predetermined ratio to prepare an alloy ingot in the same manner as in Example 1. Next, these alloy ingots were heat-treated, crushed and classified in the same manner as in Example 1 to obtain alloy powders with an average particle size of 10 μm.
Nitrogen was infiltrated by maintaining nitrogen at 350 ° C for 4 hours to obtain a nitride powder. Then, 2% by weight of one-component epoxy resin was mixed with the above-mentioned nitriding powder, and while applying a magnetic field of 15 kOe,
It was compression-molded at a pressure of ton / cm ² and then cured at 150 ° C. in nitrogen gas to produce magnet samples 11 to 25, which were subjected to a magnetic performance measurement test. The magnetic performance measurement test was performed using a DC BH tracer, the residual magnetic flux density Br and the coercive force iHc were determined, and some of the samples were analyzed by X-ray diffraction for the compounds produced.
Table 2 shows the measurement test results of the magnetic performance.

[0020]

[Table 2]

As is clear from Table 2, the magnet samples 13 to 25 according to the present invention have a residual magnetic flux density Br and a coercive force i.
Both Hc showed a high value, and it became clear that a practical permanent magnet could be obtained. Of rare earth metals, Pr or Ce can be used in addition to Nd, and it is effective to use various metal elements M. Among them, Ti, V or Si as M is important for obtaining the alloy of the present invention. It was confirmed that The magnet sample 11 which is a comparative example does not have good magnetic performance, but the result of analysis by X-ray diffraction shows that the Th ₂ Zn ₁₇ type compound occupies the majority, and Th
The presence of the Mn ₁₂ type compound was not recognized, which is considered to be the reason why the magnetic performance was low. On the other hand, the magnet sample 12, which is another comparative example, is inferior in magnetic performance because nitrogen does not penetrate into the alloy.

Example 3 An alloy ingot having a composition of 7.2% Nd-7.4% Ti-balance Fe in atomic percentage was melted, cast and homogenized in the same manner as in Example 1 to produce an alloy ingot. Then, the crushed product with a jaw crusher and a ball mill was classified to obtain average particle sizes of about 300, 200, 100, 40, and 40, respectively.
Alloy powders of 10 μm were obtained, and these alloy powders were kept under a nitrogen gas atmosphere at 5 atmospheres and 400 ° C. for 4 hours, and a predetermined amount of nitrogen was introduced to obtain nitride powders. Next, the powder excluding the 10 μm 2 nitriding powder was further pulverized by a ball mill to obtain powders having an average particle diameter of 10 μm. These powders were hardened with an epoxy resin in the same procedure as in Example 1 to obtain magnet samples 31 to 35, which were subjected to a magnetic performance measurement test. The 10 μm powder was subjected to oxygen analysis using LECO analyzer TC-436. Table 3 shows the magnetic performance of the magnet samples and the measurement results of the component composition analysis values containing oxygen of each powder sample.

[0023]

[Table 3]

As is apparent from Table 3, all of the magnet samples 32 to 35 according to the present invention have magnetic properties sufficiently practical as a magnet. It was also clarified that sufficient magnetic performance could be obtained by pulverizing the nitriding powder again or even with slight oxygen contamination. In addition, in Comparative Example Sample 31, although the nitrogen infiltration treatment time was increased, nitrogen infiltration was not sufficiently performed because the powder particle size was too large, and high magnetic performance was not obtained.

Example 4 An alloy ingot having a composition of 4.0% Pr-2.6% Nd-7.2% Ti-balance Fe in atomic percentage was pulverized to obtain an alloy powder having an average particle size of about 40 μm. Next, this alloy powder is heated to 100 ° C to 6 ° C in a nitrogen gas or ammonia gas stream.
The temperature was maintained at 00 ° C for 1 to 24 hours to allow nitrogen to infiltrate. Next, the obtained powder is crushed with a ball mill so that the average particle size is 5μ.
The powder was pulverized to m 2 and hardened with an epoxy resin by the same procedure as in Example 1 to obtain magnet samples 41 to 48, which were subjected to an analysis test of these nitrogen contents and a measurement test of magnetic properties. The results are shown in Table 4.

[0026]

[Table 4]

As is clear from Table 4, it was revealed that the magnet samples 42 to 47 according to the present invention have excellent magnetic characteristics under various nitrogen infiltration treatment conditions. Further, in the comparative sample 41, since the treatment temperature is low, nitrogen infiltration into the alloy powder is not sufficiently performed, and high magnetic performance cannot be obtained. On the other hand, in Comparative Example sample 48, although the nitrogen penetration amount was large, the processing temperature was too high, so that some decomposition of the Th Mn ₁₂ type compound occurred and the magnetic performance was deteriorated. From the above results, it is suitable that the nitrogen infiltration temperature is in the range of 200 ℃ ~ 500 ℃, and the nitrogen content of the nitriding powder is 0.5 ~ 5 wt%.
It became clear that the range of was suitable.

Example 5 Nd-Ti-N- used for sample No. 13 in Example 2
Fe, Ni nitride powder, Zn, Sn, Pb, In, Al, M
g or their alloy powders were mixed at a ratio of 15% by weight and mixed in a ball mill. These mixed powders were filled in a predetermined mold, and were compacted under a pressure of 6 ton / cm ² while applying a magnetic field of 15 kOe. Subsequently, these molded bodies were loaded into an electric furnace and heat-treated in argon gas at a predetermined temperature for 2 hours to manufacture magnet samples 51 to 59, which were subjected to a magnetic performance measurement test. The results are shown in Table 5. In addition, the numerical value of the mixed metal in Table 5 represents weight% in the case of an alloy.

[0029]

[Table 5]

As is clear from Table 5, the magnet samples 51 to 57 and 59 according to the present invention showed excellent magnetic performance, and particularly the improvement of coercive force was recognized. It should be noted that the heat treatment after magnet molding does not have to be performed as seen in the magnet sample 51, but the coercive force is further improved by adding the heat treatment. However, magnet sample 5 which is a comparative example
When the heat treatment temperature exceeds 500 ° C. as in No. 8, the magnetic performance deteriorates due to the decomposition of the Th Mn ₁₂ type compound in the alloy. In addition, when a metal is used as a binder as in this example, it is suitable for applications requiring heat resistance as well as excellent temperature characteristics of the alloy.

Example 6 Nd-Ti-N- used for sample No. 13 in Example 2
Fe nitride powder was mixed with 5% by weight of zinc and 0.2% by weight of stearic acid, and the mixed powder was hot-pressed at 350 ° C.
It is filled in a mold heated to 10 kOe in a vacuum.
While applying a magnetic field of 1 ton / cm ² for 1 minute, powder compaction was performed to manufacture a magnet sample. The sample density is
It was 7.1 g / cm ³ , and a high density was obtained as compared with the case of room temperature molding due to pressure molding at high temperature. As a result, this magnet sample has a residual magnetic flux density Br = 10.3 (kG) and a coercive force iHc.
= 7.6 (kOe), and it became clear that excellent magnet performance was obtained.

Example 7 Nd-Ti-N- used for sample No. 13 in Example 2
2% by weight of one-component epoxy resin as a binder and 0.2% by weight of oleic acid functioning as a lubricant were mixed with Fe nitride powder. This mixed powder is filled in a predetermined mold,
It was molded at a pressure of 6 ton / cm ² while applying a magnetic field of 15 kOe, and cured at 150 ° C. for 1 hour in nitrogen gas to obtain a magnet sample. As a result of measuring the magnetic performance of the obtained magnet sample, the residual magnetic flux density Br = 8.1 (kG) and the coercive force iH
c = 4.5 (kOe) and excellent magnet performance was obtained.

[0032]

As described in detail above, according to the method for producing a rare earth bonded magnet according to the present invention, Th Mn ₁₂
By injecting nitrogen into a powder alloy containing a type compound as the main phase, it becomes possible to manufacture magnets with excellent magnetic performance and temperature characteristics without the use of hydrogen, and because hydrogen is not used, manufacturing safety is improved. The magnet can be established and the obtained magnet has an effect of stabilizing in the long term.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01F 41/02 G 8019-5E

Claims (5)

[Claims] 1. A rare earth metal (R) consisting of at least one of Nd, Pr and Ce, Fe and a metal (M) other than R and Fe as a main component and a Th Mn ₁₂ type compound as a main phase. The first step of crushing the containing alloy to obtain an alloy powder having an average particle size of 200 μm or less, and
The method is characterized by including a second step of injecting nitrogen into the alloy to obtain a nitriding powder by contacting with a nitriding gas at 500 ° C., and a third step of solidifying the nitriding powder with a binder to form a magnet. Manufacturing method of rare earth bonded magnet. 2. The other metal (M) in the alloy is Ti, Zr.
, Hf, V, Nb, Ta, Cr, Mo, W, Mn, N
i, Pd, Cu, Ag, Zn, Mg, B, Al, Ga,
2. The method for manufacturing a rare earth bonded magnet according to claim 1, wherein the method comprises at least one of In, Si and Sn. 3. Nitrogen is added to the alloy powder at 0.5 in the second step.
The method for producing a rare-earth bonded magnet according to claim 1, wherein the intrusion is about 5% by weight. 4. A Z as a binder in the third step
The method for producing a rare earth bonded magnet according to claim 1, wherein at least one of n, Sn, Pb, In, Al, and Mg is selected. 5. The method for producing a rare earth bonded magnet according to claim 1, wherein a thermosetting resin or a thermoplastic resin is selected as the binder in the third step.