JPH10130796A - Production of fine crystal permanent magnet alloy and isotropic permanent magnet powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably obtain a fine crystal permanent magnet alloy excellent in residual magnetic flux density by rapidly cooling an Nd-Fe-B series ally molten metal with low rate earth concn. having a specified compsn. at a specified roll circumferential speed in an evacuated inert gas atmosphere. SOLUTION: The composition al formula of an alloy is composed of Fe100-x-y Bx Ry , where R denotes one or two kinds among Pr, Nd and Dy, and (x) and (y) satisfy 15<=x<=30at.% and 1<=y<=5at.%. The molten metal of this alloy is rapidly cooled by a melt quenching method using rapid cooling rolls. At this time, the roll curcumferential speed is limited to 2 to 10m/sec. In this way, a fine crystal alloy in which the crystal structure in which Fe3 B type compounds and compound phases having an αFe and Nd2 Fe14 B type crystal structures are coexistent occupies by >=90% and the average grain size is regulated to 10 to 50nm can directly be obtd. from the alloy molten metal. This alloy has the magnetic properties of iHC>=2KOe and Br>=10KG.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to various motors,
Regarding the manufacturing method of microcrystalline permanent magnet alloy which is most suitable for actuator, magnetic circuit for magnetic sensor, magnet roll and speaker, etc., rare earth element content is 5at
% Or less of a specific composition of the R-Fe-B alloy melt is quenched by a liquid quenching method at a roll peripheral speed in a specific reduced pressure inert gas atmosphere, and substantially 90% or more of the Fe ₃ B type compound and α-Fe and a crystal structure in which a compound phase having a Nd ₂ Fe ₁₄ B type crystal structure coexists, and the average crystal grain size of each constituent phase is formed into fine crystals having a diameter of 10 nm to 50 nm, thereby directly from the molten alloy. Thickness 70μm ~ 300μm
The present invention relates to a method for producing a microcrystalline permanent magnet alloy capable of obtaining a permanent magnet alloy having magnetic properties of iHc ≧ 2 kOe and Br ≧ 10 kG, which can be practically used as a thin plate magnet or an alloy powder for a bonded magnet.

[0002]

2. Description of the Related Art Permanent magnets used in stepping motors, power motors, actuators, and the like used in home electric appliances, OA equipment and electrical components, have hitherto been limited to hard ferrite magnets having an excellent performance-to-price ratio. However, there are problems such as low temperature demagnetization characteristics due to a decrease in iHc at low temperatures, low mechanical strength due to the ceramic material, easy occurrence of cracks and chips, and difficulty in obtaining a complicated shape. .

[0003] Today, home appliances, office automation equipment, electrical components, and the like are required to have higher performance and smaller size and lighter weight, and maximize the performance-to-weight ratio of the entire magnetic circuit using permanent magnets. In particular, in the current motor structure, a permanent magnet having a residual magnetic flux density Br of about 5 kG to 7 kG is optimized, but cannot be obtained with a conventional hard ferrite magnet.

[0004] For example, Nd having a main phase of Nd ₂ Fe ₁₄ B
-Fe-B bonded magnets satisfy such magnetic properties, but contain 10 at% to 15 at% of Nd which requires a large number of steps and large-scale facilities for metal separation and purification and reduction reactions. In comparison with hard ferrite magnets, only some models have advanced in terms of performance-price ratio in terms of performance-price ratio. At present, inexpensive permanent magnet materials having Br of 5 kG or more are inexpensive. Not found.

[0005]

On the other hand, Nd-Fe-B
In recent years, magnet materials based on Nd ₄ Fe ₇₇ B ₁₉ (at%) and containing a Fe ₃ B-type compound as a main phase have been proposed (for example, R. Coehoorn et al., J. de Phys.
8, 1988, 669-670). This permanent magnet material is obtained by heat-treating the amorphous ribbon.
It is a metastable permanent magnet material having a crystal texture in which a soft magnetic Fe ₃ B phase and a hard magnetic Nd ₂ Fe ₁₄ B phase are mixed.

[0006] Such a permanent magnet material has a B of about 10 kG.
r and iHc of 2 kOe to 3 kOe, and the content of expensive Nd is as low as about 4 at%.
Although it is less expensive than Nd-Fe-B based bonded magnets with d ₂ Fe ₁₄ B as the main phase, liquid quenching conditions are limited because amorphous alloying of the compounding material is an essential condition. The heat treatment conditions that can be used are narrow and limited, and are not practical for industrial production, and cannot be provided inexpensively as a substitute for hard ferrite magnets.

According to the present invention, a soft magnetic Fe ₃ B phase and a hard magnetic N ₃ are characterized in that the rare earth concentration is as low as 5 at% or less.
A permanent magnet material having a metastable structure having a crystal texture in which d ₂ Fe ₁₄ B phase is mixed is intended to relax the manufacturing conditions to enable stable industrial production.
It is an object of the present invention to provide a method of manufacturing a microcrystalline permanent magnet alloy that has a residual magnetic flux density Br of 10 kG or more and has a performance-to-price ratio comparable to that of a hard ferrite magnet and enables stable mass production of a microcrystalline permanent magnet alloy. .

[0008]

DISCLOSURE OF THE INVENTION The inventors of the present invention aim at a production method capable of stably industrially producing a low rare earth Nd-Fe-B-based permanent magnet material in which a soft magnetic phase and a hard magnetic phase are mixed. As a result of various examinations, when the content of the rare earth element is as small as 5 at% or less, and the molten alloy having a specific composition containing 15 to 30 at% of B is rapidly cooled by a liquid quenching method using a quenching roll, the pressure is reduced to 30 kPa or less. By limiting the peripheral speed of the roll to 2 to 10 m / s in an inert gas atmosphere, substantially 90% or more of Fe ₃ B is directly transferred without passing through a step of crystallizing the amorphous alloy by heat treatment.
Structure in which a compound phase and a compound phase having an α-Fe and Nd ₂ Fe ₁₄ B type crystal structure coexist and have an average crystal grain size of 5
Powder alloy for sintered magnets or powder alloys for bonded magnets consisting of fine crystals of 0 nm or less, or 70 μm to 300 μm in thickness
The inventors have found that a rapidly quenched alloy ribbon (thin plate magnet) of μm can be obtained, and have completed the present invention.

Further, the inventors have found that the average crystal grain size of each constituent phase of the fine crystals directly obtained from the molten alloy is 10 nm to 50 n.
m, the magnetic properties of iHc ≧ 2 kOe and Br ≧ 10 kG can be obtained.
When fine crystals less than m are obtained, the average crystal grain size of each constituent phase becomes 10 nm to 50 nm by performing heat treatment for specific grain growth, iHc ≧ 2 kOe, B
The inventors have found that magnetic characteristics of r ≧ 10 kG can be obtained, and have completed the present invention.

That is, according to the present invention, the composition formula is Fe
_100-xy B _x R _y (where R is one or two of Pr, Nd or Dy) and symbols x and y for limiting the composition range
However, when rapidly quenching a molten alloy satisfying 15 ≦ x ≦ 30 at% and 1 ≦ y ≦ 5 at% by a liquid quenching method using a quenching roll, the roll peripheral speed is set in a reduced pressure inert gas atmosphere of 30 kPa or less. From 2 m / s to 10 m / s,
A crystal structure in which a Fe ₃ B type compound and a compound phase having α-Fe and a Nd ₂ Fe ₁₄ B type crystal structure coexist accounts for 90% or more, and a fine crystal alloy having an average crystal grain size of 10 nm to 50 nm is formed into an alloy melt. From iHc ≧
This is a method for producing a microcrystalline permanent magnet alloy for obtaining a permanent magnet alloy having magnetic properties of 2 kOe and Br ≧ 10 kG.

Further, the present invention provides a method as described above, wherein when a fine crystal alloy having an average crystal grain size of 10 nm or less is directly formed from the molten alloy by the liquid quenching method, the temperature is then raised to 500 ° C. to 700 ° C. Heat treatment for the purpose of grain growth in the region to form a fine crystal alloy having an average crystal grain size of 10 nm to 50 nm, iHc ≧ 2 kOe, Br ≧ 10 k
A method for producing a microcrystalline permanent magnet alloy for obtaining a permanent magnet alloy having the magnetic properties of G is also proposed.

Further, according to the present invention, in the above-mentioned manufacturing method, the obtained fine crystalline permanent magnet alloy has an average powder particle size of 3%.
μm to 500 μm, iHc ≧ 2 kOe, Br
A manufacturing method for obtaining an isotropic permanent magnet alloy powder having magnetic properties of ≧ 7 kG is also proposed.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

Reason for limiting composition Rare earth element R is one or two of Pr, Nd or Dy.
Only when the species is contained in a specific amount, high magnetic properties can be obtained, and other rare earth elements such as Ce and La cannot have properties of iHc of 2 kOe or more, and medium rare earth elements after Sm excluding Tb and Dy, Heavy rare earth elements are not preferable because they cause deterioration of magnetic properties and increase the cost of the magnet.
If R is less than 1 at%, iHc of 2 kOe or more cannot be obtained, and if it exceeds 5 at%, Br of 10 kG or more cannot be obtained, so R is in the range of 1 at% to 5 at%. Preferably, 2 at% to 5 at% is good.

When B is less than 15 at%, precipitation of α-Fe is remarkable in the metal structure after liquid quenching, and precipitation of a compound having an Nd ₂ Fe ₁₄ B type crystal structure which is essential for the development of coercive force is inhibited. Therefore, only iHc of less than 1 kOe is obtained, and if it exceeds 30 at%, the squareness of the demagnetization curve is remarkably reduced, and Br of 10 kOe or more cannot be obtained, so the range is 15 at% to 30 at%. Preferably, 15 at% to 20 at% is good.

Fe accounts for the residual content of the above-mentioned elements, and F
By replacing part of e with Co and Ni, the squareness of the depletion curve is improved, and the maximum energy product (BH) m
ax and heat resistance are improved, and iHc is improved by substitution with Cr.
Si, S, Ni, Cu, Zn, Ga, Ag, Pt, A
By substituting one or two of u and Pb, the squareness of the demagnetization curve is improved, and an effect of increasing Br and (BH) max is obtained.

Reasons for Limiting Manufacturing Conditions The liquid quenching method in the present invention includes a liquid quenching method using a quenching roll and a strip casting method which is an alloy casting method. The alloy melt having the specific composition described above is rapidly cooled by a liquid quenching method in a reduced pressure inert gas atmosphere of 30 kPa or less with a roll peripheral speed of 2 m / s to 10 m / s.
If it is less than 2 m / s, it becomes a metal structure containing coarse α-Fe particles of 100 nm or more, and if it exceeds 10 m / s, it becomes an amorphous metal, which is not preferable, and 90% or more of its crystal structure is Fe ₃ B type compound and α. -Fe and Nd ₂ F
This is because a crystal structure in which a compound phase having an e ₁₄ B-type crystal structure coexists is not obtained. In particular, the average crystal grain size of each constituent phase is iHc ≧ 2 kOe and Br ≧ 10 kG. It is important to obtain an alloy having a diameter of 10 nm to 50 nm.

That is, when the quenching atmosphere exceeds 30 kPa during the quenching treatment of the molten alloy, the atmosphere gas enters between the rotating roll and the molten alloy, and the uniformity of the quenching condition is lost. Metal structure containing
Since the magnetic properties of Hc ≧ 2 kOe and Br ≧ 10 kG cannot be obtained, the alloy quenching atmosphere is set to 30 kPa or less.
Preferably, the pressure is 10 kPa or less. The atmosphere gas is an inert gas for preventing oxidation of the molten alloy, and is preferably in Ar gas.

In the case of the liquid quenching method using a Cu roll,
If the roll peripheral speed exceeds 10 m / sec, the crystal structure contained in the quenched alloy is reduced and the amorphous phase is increased, so that it is necessary to crystallize the amorphous by heat treatment. , Immediately after quenching, to cause grain growth of the crystal structure already precipitated,
An average crystal grain size required to obtain magnetic properties of iHc ≧ 2 kOe and Br ≧ 10 kG becomes a coarser metal structure than 10 nm to 50 nm, and Br of 10 kG or more cannot be obtained.
If the roll peripheral speed is less than 2 m / s, coarse α-Fe precipitates in the quenched alloy, which is not preferable, and the roll peripheral speed is limited to 2 to 10 m / s.

The average crystal grain size of the quenched alloy quenched by the liquid quenching method using the quenching roll under the above-mentioned conditions is iHc
If the average crystal grain size required to obtain magnetic characteristics of ≧ 2 kOe and Br ≧ 10 kG is less than 10 nm, heat treatment for grain growth may be performed, and the heat treatment temperature at which the magnetic characteristics become maximum depends on the composition. However, if the heat treatment temperature is lower than 500 ° C., the grain growth does not occur, so that an average crystal grain size of 10 nm or more cannot be obtained. Deteriorated,
Since the above magnetic properties cannot be obtained, the heat treatment temperature is 500
C. to 700.degree.

In the heat treatment, the atmosphere is preferably an inert gas atmosphere such as Ar gas or N ₂ gas or a vacuum of 1.33 Pa or less to prevent oxidation. The magnetic properties do not depend on the heat treatment time, but if it exceeds 6 hours, Br tends to slightly decrease with the passage of time, so that it is preferably 6 hours or less.

The crystal phase of the microcrystalline permanent magnet alloy according to the present invention is composed of a soft magnetic Fe ₃ B-type compound and α-
Fe and a hard magnetic compound phase having a Nd ₂ Fe ₁₄ B-type crystal structure coexist in the same structure, and each component phase is composed of a fine crystal aggregate having an average crystal grain size in a range of 10 nm to 50 nm. I have. Average crystal grain size of magnet alloy is 50n
m, the squareness of Br and the demagnetization curve deteriorates,
The magnetic properties of Br ≧ 10 kG cannot be obtained.
The average crystal grain size is preferably as small as possible, but if the average crystal grain size is less than 10 nm, iHc is reduced, so the lower limit is set to 10 nm.

In the present invention, by selecting the composition of the molten magnet alloy and the quenching conditions, a powdered magnetic alloy suitable for sintering or bonded magnets, or a thickness of 70 μm to 30 μm can be obtained.
A 0 μm thin plate magnet can be manufactured.

Further, by grinding the microcrystalline permanent magnet alloy according to the present invention to an average particle size of 3 μm to 500 μm, an isotropic permanent magnet alloy powder having magnetic properties of iHc ≧ 2 kOe and Br ≧ 7 kG can be obtained. If the average particle size is less than 3 μm, magnetic properties, particularly Br, are unfavorably reduced, and if it exceeds 500 μm, molding is difficult. Therefore, the average particle size after grinding is limited to 3 μm to 500 μm. The pulverized particle size when used as a powder for a compression-molded bonded magnet is preferably from 20 μm to 300 μm, and is preferably 50 μm or less when used as a powder for an injection-molded bonded magnet.

[0024]

【Example】

Example 1 No. 1 in Table 1. Purity of 99.
5% or more of Fe, Al, Si, S, Ni, Cu, Co,
Cr, Zn, Ga, Ag, Pt, Au, Pb, B, N
d, Pr, and Dy metals were weighed so that the total amount was 30 g, placed in a quartz crucible having an orifice with a diameter of 0.8 mm at the bottom, and placed in an Ar atmosphere maintained at a quenching atmosphere pressure in Table 1. Melted by high frequency heating, melting temperature 1
After the temperature was raised to 300 ° C., the molten metal surface was pressurized with Ar gas, and at room temperature, the molten metal was jetted from a height of 0.7 mm onto the outer peripheral surface of the Cu roll rotating at the roll peripheral speed shown in Table 1 to obtain a width. A quenched alloy ribbon having a thickness of 2 mm to 3 mm and a thickness of 100 μm to 300 μm was produced.

FIG. 1 shows the characteristics of the embodiment No. As shown in the X-ray diffraction pattern in the case of No. 2, the obtained rapidly alloy ribbon was a Fe ₃ B-type compound having soft magnetism,
In addition, it was confirmed that α-Fe and a hard magnetic compound phase having an Nd ₂ Fe ₁₄ B type crystal structure had a metal structure coexisting in the same structure. Also, regarding the crystal grain size,
o. 4, no. 16, No. Except for No. 17, all samples had a fine crystal structure with an average crystal grain size of 10 nm to 50 nm. Table 2 shows the magnet characteristics measured by the VSM.

Example 2 Example No. 1 in Table 1 4, no. 16, No. About 17, since the average crystal grain size was less than 10 nm, the rapidly quenched alloy strip was held at 600 ° C. for 10 minutes in Ar gas,
Heat treatment was performed so that the average crystal grain size became 10 nm or more. Table 2 shows the results of measuring the magnet characteristics using the VSM. In addition, in Example No. 5-No. Al at 17,
Si, S, Ni, Cu, Co, Cr, Zn, Ga, A
g, Pt, Au, and Pb substitute a part of Fe of each constituent phase.

Example 3 2, No. 3, No. 5, no. 6, N
o. 13 using a pulverizer, a pulverized particle size of 25 μm
The powder was pulverized so as to have a particle size of 300 μm and an average powder particle size of 150 μm, thereby producing an isotropic permanent magnet powder. Table 3 shows the magnetic properties of the magnet alloy powder measured by VSM.

Comparative Example 1 In the same manner as in Example 1, 18-No. Using Fe, B, and R having a purity of 99.5% so as to have a composition of 21,
A quenched alloy ribbon was produced under the quenching conditions shown in Table 1. FIG. 1 shows a characteristic X-ray diffraction pattern of Cu-Kα of the obtained sample. As can be seen from the result of the X-ray diffraction pattern, 1
Sample No. 8 was an amorphous alloy that did not exhibit coercive force. In addition, No. The 19 samples had a metal structure in which the α-Fe phase was the main phase. In addition, No. Sample No. 20 has a structure composed of Nd ₂ Fe ₂₃ B ₃ which is a non-magnetic phase and α-Fe. Sample No. 21 was No. 21. As in 19, α-F
e was a metal structure having a main phase. In addition, No. 18 ~
No. Table 2 shows the magnet characteristics measured by the VSM No. 21.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

[Table 3]

[0032]

According to the present invention, the rare earth element content is 5a.
When the alloy melt having a specific composition as small as 15% or less and containing 15 to 30 at% of B is quenched by a liquid quenching method using a quenching roll, the roll peripheral speed is reduced in a reduced pressure inert gas atmosphere of 30 kPa or less. Is limited to 2 to 10 m / s, so that substantially 90% or more of F can be directly reduced without passing through a step of crystallizing the amorphous alloy by heat treatment.
e ₃ B type compound and a compound phase having an alpha-Fe and Nd ₂ Fe ₁₄ B crystal structure becomes crystal structure coexist, iHc ≧ 2 kOe for practical use as a permanent magnet, Br ≧ 10k
The average crystal grain size having magnetic properties of G is 10 nm to 50 n
m, a thin plate magnet having a thickness of 70 μm to 300 μm or a powder alloy for a bonded magnet is obtained.
When a fine crystal of less than nm is obtained, by performing a heat treatment for specific grain growth, the average crystal grain size of each constituent phase becomes 10 nm to 50 nm, iHc ≧ 2 kOe,
The magnetic properties of Br ≧ 10 kG can be obtained, and the process of crystallizing an amorphous alloy by heat treatment, which has been seen in the process of manufacturing a conventional fine crystal type permanent magnet, is not required. Therefore, the manufacturing method is simple and suitable for mass production. Thus, a permanent magnet having excellent magnet properties that cannot be achieved with a hard ferrite magnet can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a graph showing a characteristic X-ray diffraction pattern of Cu-Kα of a sample in an example.

Claims (5)

[Claims] 1. A composition formula is represented by Fe _100-xy B _x R _y (where R is one or two of Pr, Nd or Dy), and symbols x and y for limiting a composition range satisfy the following values. When the molten alloy is quenched by a liquid quenching method using a quenching roll, the roll peripheral speed is set to 2 m / s to 10 m / s in a reduced pressure inert gas atmosphere of 30 kPa or less, and the Fe ₃ B type compound and α -90% or more of a crystal structure in which a compound phase having Fe and a Nd ₂ Fe ₁₄ B type crystal structure coexists;
A method for producing a microcrystalline permanent magnet alloy for obtaining a microcrystalline alloy having an average crystal grain size of 50 nm or less. 15 ≦ x ≦ 30at% 1 ≦ y ≦ 5at% 2. A fine crystal alloy having an average crystal grain size of 10 nm to 50 nm directly from a molten alloy by a liquid quenching method according to claim 1, iHc ≧ 2 kOe, Br ≧ 10 k
A method for producing a microcrystalline permanent magnet alloy for obtaining a magnet alloy having magnetic properties of G. 3. A liquid crystal quenching method according to claim 1, wherein the alloy melt is directly converted into a fine crystal alloy having an average crystal grain size of 10 nm or less, and thereafter, for the purpose of grain growth in a temperature range of 500 ° C. to 700 ° C. The average crystal grain size is 1
0 nm to 50 nm fine crystal alloy, iHc ≧ 2k
A method for producing a microcrystalline permanent magnet alloy for obtaining a magnet alloy having magnetic properties of Oe, Br ≧ 10 kG. 4. The method for producing a microcrystalline permanent magnet alloy according to claim 1, wherein the obtained microcrystalline permanent magnet alloy is a thin plate magnet having a thickness of 70 μm to 300 μm. 5. The isotropic permanent magnet alloy powder according to claim 1, wherein the obtained fine crystalline permanent magnet alloy is pulverized to an average powder particle size of 3 μm to 500 μm to have iHc ≧ 2 kOe and Br ≧ 7 kG magnetic properties. A method for producing the obtained isotropic permanent magnet powder.