JPS6163530A - Production of hard magnetic material - Google Patents

Abstract

PURPOSE:To produce a hard magnetic material having extremely high coercivity, easily, by melting an SrO-Fe2O3 oxide, vitrifying the oxide by quenching with a liquid, and crystallizing the glass by keeping at a specific temperature for a specific time. CONSTITUTION:An SrO-Fe2O3 oxide is melted, and the molten liquid is vitrified by quenching with a liquid at a cooling rate of 10<2>-10<8> deg.C/sec. The glass is crystallized by maintaining at 450-1200 deg.C for 1 musec-200hr to separate fine crystals of SrO.6Fe2O3. A hard magnetic material having extremely high coercivity can be produced by this method. The liquid-quenching of the molten oxide can be carried out effectively e.g. by spraying the molten oxide toward a substrate having relatively high thermal conductivity, or by blasting nonreducing gas against the liquid dripped to a rotary member, etc. The above oxide used as the raw material is preferably composed of about 40-80mol% Fe2O3, about 20-60% SiO, and if necessary, about <=10% Sm2O3, etc. SrO.6F2O3 crystals having an average particle diameter of 90-2,000Angstrom can be precipitated by the above procedure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a hard magnetic material, and more particularly, to a method for producing a hard magnetic material having an extremely high coercive force by a glass crystallization method.

[Conventional technology]

Conventional permanent magnets have a stable magnetic field without supplying electrical energy from outside! The material that generates it is often used in small generators, motors, speakers, measuring instruments, jigs, relays, etc.

Materials for permanent magnets are desired to have high residual magnetic flux density (magnetization 0 strength) and coercive force for the above-mentioned purposes, and various studies are being conducted.

Residual magnetic flux density! Basically, as a means to improve it, the direction of the easy magnetization axis is adjusted by arranging the crystal grains! How to arrange it and
There are two methods of imparting uniaxial magnetocrystalline anisotropy by cooling in a magnetic field.

On the other hand, lattice transformation is a means to increase coercive force.

Precipitation hardening, formation of a regular lattice, etc. increase internal stress and cause domain wall movement! One method is to make it difficult, and the other is to select 7 ferromagnetic materials with large uniaxial magnetocrystalline anisotropy energy.
There is a method of making single magnetic domain fine grains and performing C2 so that the magnetization process is performed only by double-rotation magnetization.

Recently, hexagonal magnetobrambite crystal structure f + Ba0 6Fe203, SrO. 6F
e203, PbO, and 6Fe203 are: ■ have a low specific gravity °, ◎ have a large electrical resistance, θ are chemically stable, and have a composition of Nt.

It is often used as a permanent magnet material along with alnico magnets because it does not contain CoY and can be produced relatively easily and is therefore inexpensive.

One major reason why barium ferrite, such as Ba0.5F', 2o3, etc., can be an excellent permanent magnet material is that
This is because the uniaxial magnetocrystalline anisotropy energy with the C-axis direction as the direction of easy magnetization is large, so the magnetic field strength required for magnetization reversal becomes large, which leads to an increase in coercive force.

Therefore, research has been carried out to obtain high coercive force magnetic materials by turning ferromagnetic materials with -#l magnetocrystalline anisotropy and high sexual energy, such as BaO.6Fe203, into single-domain fine particles and performing the magnetization process only by rotational magnetization. A lot has been done. These are for example C1B, Me e.

J, C1Jeschke: J, Appl, Ph
ys, vol 34 &4<1963>P1271
Ya B, T, 8hirk, W, R, Buesse
m: J, Am, Caram, 8oci, vol.
5344<1970>P]92.

Regarding the glass crystallization method, for example, Koike and Iruto:
Se-y mix vol 18 & 10 <1983>
P2S5, but in this case, B2O3 is used as the glass-forming oxide (Network Forma).
is added.

On the other hand, w, HoMeiklejohn, Q P, Be
an: Phy, Rev.

vol 105 A3 <1957> 1 for B9O4
CO particles with thin oxidation on the surface! It has been described that the M-H loop becomes asymmetric when cooled to 77°K in a magnetic field.

This phenomenon is caused by exchange interaction between the spins of a ferromagnetic material and the spins of an antiferromagnetic material, and is known as exchange anisotropy.

[Problems to be solved by the present invention]

Therefore, the size of ferromagnetic materials such as BaO・6Fe203 with large uniaxial crystal magnetic anisotropy energy! If we control the single-domain fine particle size and coexist with antiferromagnets,
Based on the above-mentioned exchange interaction ζ, it is thought that we can expect the development of a hard magnetic material having a coercive force t greater than that of conventional ferromagnetic single-domain fine particles.

However, in the conventional glass crystallization method for producing ferromagnetic particles, a large amount of B2O3'4r is added as a glass-forming oxide during glass production.
2O3'%: Precipitation of the paramagnetic phase containing 2O3'% was unavoidable. Due to the existence of this paramagnetic phase, it is not possible to control the precipitation phase by crystallization into two phases: a ferromagnetic phase and an antiferromagnetic phase, resulting in the above-mentioned exchange interaction! The problem was that it was not what we expected.

However, Fe without glass-forming oxides such as B2O3
BaO (8ro, pbo) based on 2O3't'
-Fe 203-based oxides and other oxides have a problem in that they are extremely difficult to vitrify.

Therefore, as a result of various experiments and considerations, the present inventors found that Ba0
・6Fe203. SrO・6Fe203 and Pb
o * 6 Among the champions of Fe 203, SrO, which is a ferrimagnetic phase with the largest uniaxial magnetocrystalline anisotropy energy,
6Fe2O3 or even Sm2 as an antiferromagnetic phase
With O3, Fe2O3, etc.! After vitrification using a liquid quenching method, they succeeded in precipitating the crystallization under certain conditions, completing the present invention.

[Object of the present invention]

The purpose of the present invention is to produce a hard magnetic material having the highest coercive force among oxide-based hard magnetic materials. E'P provides.

Another object of the present invention is to eliminate 5rO-Fe without adding 8203'l as a glass-forming oxide during glass production.
203 series oxide glass! Precipitated phase due to crystallization of the glass? The present invention provides a method for producing a hard magnetic material having a ferromagnetic phase or two phases of a ferromagnetic phase and an antiferromagnetic phase without containing a paramagnetic phase.

[Configuration of the present invention]

Invention C: From.

The SrOFe2O3-based oxide is heated and melted to become a liquid, and then this liquid t]02℃/s e c to 108℃/s
Vitrification by rapid cooling using a liquid quenching method at a cooling rate of ee to a total temperature of 450°C to 1200°C]
By holding and crystallizing eC for 200 hours, fine SrO.6Fe203'! a' to precipitate t
The manufacturing method of the hard magnetic material, which is characterized by S rO-Fe 203-8mzOy-based oxide'gm, is made into a liquid by thermal SML, and then this liquid! 102° (7's
The glass is rapidly cooled by a liquid quenching method at a cooling rate of e c to 10' C〆sea, and then vitrified, and the glass is crystallized while maintaining the glass at a temperature of 450° C. to 1200° C.3) to form fine SrO. A method for producing a hard magnetic material is provided, which is characterized in that 6Fe2O3 and Sm2O3.Fe 203 are completely precipitated.

material The oxide which is the starting material will be explained in detail below.

First of all, it is Fa 203, but this oxide form is in the state just before rapid cooling! I mean, it's the stage before that.

For example, in the powder state before melting, pe + FeQ FC3
04r 'Fe3O4, FeCJ! 2 or the same parts thereof may be used. Barefoot,
When these substances are heated and melted in the atmosphere, S and CIA
This is because impurities such as .

Therefore, there is no need for a particularly limited iron source.

Next, with regard to SrO, as with Fe2O3, the n state just before quenching may be SrO, and the previous stages Tesr, SrSO4, 8rCj12. It may also be SrCO3 or the like.

The reason is the same as in the case of Fe203.

Regarding the additive SmOy, it is generally Sm2O3, but 8m2 is said to be the most stable.
In addition to 03, other oxides such as 5r1101.5±2 can be considered, so they are expressed as Namarium oxide\Smxo y.

In addition to Sm oxide, additives include La, Bu, and G.
a.

Oxides of rare earth elements such as Ho and Er are effective.

These starting materials may be in the form of powder, granules, lumps, flakes, slurry, etc., as long as it is possible to maintain the component ratio in an appropriate glass body, which will be described later. It is not limited to the following.

Component ratio In the present invention, can we select seven components that are easy to vitrify without adding any glass-forming oxides? From a practical standpoint, the component ratio is particularly important.

In the present invention, since it is essential to deposit on fine SrO.6Fe203', it is convenient to express the component ratio in moj+%. Therefore, in the present invention, all component ratios are expressed as mo42%.

The appropriate component ratio (component ratio of the glass body, hereinafter the same) in the present invention is as follows.

That is, F e 203 ・・・・・・・・・・・・・・・
・・・・・・・・・ 40~80mof%SrO・・・・
・・・・・・・・・・・・・・・・・・・・・ 20～6
0mon%E3rnxOy・・・・・・・・・・・・
・・・・・・・・・・・・ lOmo! % or less.

The reason for choosing the above component ratio of 7 is as follows.

Fe2O3 is 40 mol! Dividing %, SrO・6F
This is because e203 does not precipitate in the subsequent crystallization heat treatment, and when Fe2O3 exceeds 80 malla, the cooling rate is realistic (at present, it is about 101 mm at most).
This is because vitrification will not occur unless the cooling rate is extremely high (for example, 101" (::/5ee)) exceeding 2°C/+1eO.

SrO is 20-5 for the same reason in combination with Fe2O3.
Q mol! % is desirable.

5inxOy can be understood as a supplement to the above 5rO-Fe203, and l Omol! % or less is desirable. 10
mof%? If it exceeds this, it becomes difficult to vitrify11, and the magnetic properties of the hard magnetic material used as the product are impaired.

Heat melting As a means for hot melting, electrical heating or gas heating in a crucible or melting furnace can be considered, and in the laboratory, there is a method of electrical resistance heating in a platinum crucible. In industrial melting furnace heating, it is difficult to completely prevent contaminants from furnace wall materials (e.g. refractories such as magnesia, alumina, mullite-based refractories, magnesium-chromate, chromium-magnesia, etc.), and the raw materials are oxidized. If you are using this method for reasons such as the fact that induction heating cannot be used because of the nature of the product, there are some ingenuity! It takes.

Therefore, after investigating various means for heating and melting the raw materials without using a container, it was found that very good results could be obtained by using thermal spraying fT:'v.

Thermal spraying methods here include flame spraying using oxygen acetylene, etc., and plasma spraying using plasma jets!
It is a concept that includes

In any case, since the material to be heated (raw material) is already an oxide, thermal spraying can be carried out in air without having to make any particular adjustments to the atmosphere, which is convenient.

The molten state of the oxide is formed by fine droplets (
It may be a liquid (liquid) or a gas (particularly in the case of plasma spraying).

In the case of flame spraying using an oxyacetylene flame, the gas atmosphere may sometimes become reducing, which is not preferable, so it is generally important to maintain a state of excess 02 (oxidizing flame).

In addition, in both the above-mentioned heat-melting process using a heat-resistant container such as a crucible, and in the case of thermal spraying, intermediate treatments such as reheating or pre-heating are necessary because raw materials (0) sizing, mixing, component ratio adjustment, etc. (Q) are used. Processing may be performed.

Rapid Cooling Once heated and melted, the oxide liquid collides with a substrate or a rotating body and is rapidly cooled.

Two important points in the present invention are the constant cooling rate range that can be obtained and the yield of vitrified oxide.

The cooling rate range needs to be within a range that allows vitrification, ie 1O to 10°C 7'sec.

Since no glass-forming substances are added in the present invention, cooling rate is particularly important.

However, by selecting all the component ratios after vitrification (C), vitrification became possible within a practical cooling rate range without adding any glass-forming substances. As for the upper limit of the cooling rate, if possible, the faster the cooling rate is faster than 108° C./sec, the easier the vitrification itself will be, but in reality, it is difficult to implement this on an industrial scale. Therefore, in the present invention, the upper limit of the cooling rate is set to θ°C/sec.

Further, the lower limit of the cooling rate is because vitrification cannot be achieved unless the cooling rate reaches at least 102° C./sec.

In order to facilitate vitrification within the cooling rate range of the present invention and to ensure that fine SrO.6Fe203 is sufficiently precipitated in the subsequent crystallization step, the following component ratio must be selected.

FIG. 1 is a phase diagram of SrO-Fe203-based oxide.

In FIG. 1, the vitrified region (r) is B above the liquidus line.

This is the area surrounded by C and D, and the vitrified area (I
I) is also a region surrounded by F', G, and H on the liquidus line. The existence of these two vitrified regions has been experimentally confirmed.

In the present invention, it is necessary to precipitate SrO.6 Fe 203 represented by a perpendicular line passing through AA, as described repeatedly, but in the prior art described above, SrO.6 Fe 203 is precipitated without undergoing vitrification.
Experiments conducted by the present inventors have revealed that even if an attempt is made to precipitate O.6Fe203k, SrO.5Fe203 having the desired particle size cannot be obtained.

Therefore, as a result of various experiments and considerations Q), the conditions for the precipitation of desirable fine SrO 6Fe203 through vitrification are between points B and D, that is, 2 as In02% of SrO.
It has been found that it is necessary to choose a range between 0 and 60%.

Note that there is also a vitrified region (U), but in this region L
C3SrO.2Fe203 +S rFe03-1 precipitates and SrO.6Fe203 does not precipitate, which is not preferable.

The most desirable condition in the present invention is that 3rOmojL% is 35
-45 range. In this range, the cooling rate does not need to be so high (approximately 102710"°C/5ee), and the desirable fine SrO.6Fe203 is easily precipitated.

The vitrification was confirmed by halo pattern recognition using X-ray diffraction or selected area diffraction image observation using an electron microscope.

Another method is to confirm the paramagnetism of the glass body by measuring the entire Mössbauer effect. This method is extremely effective, especially from the standpoint of requiring magnetic properties in products.

By the way, the glass (glass body, vitrification) in the present invention C2 is completely crystalline (regular atomic arrangement)! I am not referring only to completely amorphous bodies that do not contain any amorphous substances, but states that exhibit paramagnetism magnetically even if they exhibit regularity Z from an X-ray optical perspective, for example, a microcrystalline state! It also includes.

The specific quenching means will be supplemented below.

For example, in the case of flame spraying, high-temperature gas containing molten oxide particles! A thin layered glass body can be obtained by thermal spraying onto a target made of a copper substrate with a thickness of about 5 to 10 nm by narrowing it down as much as possible.

In this case, the target needs to have high thermal conductivity and a certain heat capacity Z.

In experiments conducted by the inventors, the glass body did not adhere to the target, and was easily peeled off even after deposition, which was convenient for subsequent steps.

In addition, target! It was also possible to use a rotating drum to take out glass bodies continuously.

Another method of liquid quenching is to use a high-speed rotating body such as a copper disk or drum to cool the liquid (molten oxide)! High pressure non-reducing gas (air pN2 etc. or Ar, He
There are other methods such as spraying with an inert gas (e.g., inert gas) to obtain a powdered glass body.

crystallization The crystallization process is (1) Furnace mesothermal treatment method (2) Laser irradiation method (3) Infrared irradiation method (4) Resistance bunny fever etc.

(]) is suitable for crystallization with a relatively long retention time, and (
No is suitable for crystallization at high energy density for a short period of time. In (3), it is more difficult to fully converge the beam than in (2), so a high energy density cannot be obtained. (4) is troublesome because the entire glass body must be formed in advance.

Therefore, (1) or (2) will be the mainstream for the time being.

Holding temperature for crystallization is 450”C to 1200℃
The range is preferably from 600°C to 1000°C. The reason is that it takes a very long time to crystallize at temperatures lower than 450'C.IJ, 1200
(J-), this is because crystal grains become coarse.

The heat treatment retention time for crystallization is 1 μscc to 200 μscc.
The hr range is good.

In the case of heating in a furnace, the preferred heating time is 10 min to 1 ohr.

The reason for the limited range is 1μsc even if laser irradiation is used at 1/IY.
This is because if it is less than c, stable crystallization cannot be expected.

- 200 hours when performing thermal treatment in a relatively low temperature furnace
This is because if it exceeds y5-, the crystals tend to become coarser, and energy costs also increase due to heat dissipation outside the furnace.

In the present invention, it is important that the average grain size of the SrO.6Fe203 precipitated in the crystallization treatment 1 is from 90 to 2000.

Preferably, the range is from 150X to 450λ.

The reason for the limitation is as follows.

In other words, unless the average particle size reaches 90X, the precipitated particles are superparamagnetic! This is because it does not exhibit the characteristics of a ferromagnetic material, and if it exceeds 2oooi, it is on the scale of a single magnetic domain structure!
This results in a multi-domain structure.

Domain wall! This is because the effects of the present invention cannot be achieved because of this.

[Operation of the present invention]

First, when at least fine SrO.6Fe203 crystallizes from the glass body, it exhibits an extremely high coercive force Z. The reason for this is that, as mentioned earlier, the uniaxial magnetocrystalline anisotropy energy in the C-axis direction, which is the easy direction of total magnetization, increases, so the magnetic field strength required for magnetization reversal increases, and the fine SrO crystallized from the glass state increases.・6Fe203 has a single domain structure! This makes the coercive force extremely high.

Furthermore, when the additive Sm2O3/Fe2O3 is co-precipitated, it exhibits antiferromagnetism, so SrO/6F
Due to the exchange interaction with e203, SrO 6Fe20
3 each single magnetic domain! Furthermore, it is magnetically bound more firmly, making rotation difficult.

As a result, it has a higher coercive force than barium ferrite.

The present invention will be explained in more detail below using Examples.

[Example 1] 40 moj of SrO using Fe2O3 and SrCO3f!
The mixture was accurately weighed so that %e Fe20Fe203-6O% was obtained, and after thorough mixing, it was heated and melted at 1500° C. for 1 hour in a platinum crucible to remove CO2. The molten sample was poured into an all-platinum plate, cooled, and crushed, which was used as a sample for making →. A small amount of this (7J sample 1 Pt-Rh (30%) wire) was melted on a filament using a heating element, and a high-pressure gas was blown from the top onto a high-speed rotating body (Cu drum) to give a temperature of about 0.5111.
I made one cup of powdered quenched glass.

This glass was crystallized in an electric furnace at a heat treatment temperature of 800° C. and a heat treatment time of 1 hr. Note that the atmosphere is atmospheric.

[Example 2] Component ratio: SrO 40 mo 1%, Fe2O3-57
3 mai 1%.

The same manufacturing method as in Example 1 was followed except that all the reagents were prepared so that Sm2O3w2moj2%.

[Example 3] Component ratio is 5rOx40 mail%, Fe2O3x
56 moi% eSm203 w 4 moj2%
The same manufacturing method as in Example 1 was followed except that the sample was prepared as follows.

[Example 4] Component ratio is 5rO-40mol%s Fe2O3-54
moIt%.

The same manufacturing method as in Example was followed except that all samples were prepared so that Sm2O3w6m was 61%.

[Example 5] Using Fe2O3 and SrCO3f, the component ratio was SrOm 4
0 mai1% e Fe2Q3"" 55 mo1
%, Sm2O3sw4 moJ! % Weigh accurately and mix thoroughly, then add 1 to remove CO2'Ift.
It was melted at 500°C for 1 hour. That molten sample! It was poured into a platinum plate, cooled, and ground to prepare a sample for glass production.

This sample was sprayed onto a rotating α drum with a thickness of approximately 5 cm using a thermal spraying device using a mixed gas of acetylene and oxygen to prepare a thin plate-like rapidly cooled glass sample. The heat treatment method is as in Example 1.
A similar method was followed.

The feature of this quenched glass production method is that a much larger amount of samples can be obtained compared to the method of Example 1, and the produced samples have the same properties as Example 1! It is a point to have.

[Example 6] In Example 3, only the crystallization heat treatment conditions were 'g1000°C.
×α5 hr changed.

[Example 7] In Example 3, only the crystallization heat treatment conditions were changed to 600'CX.
Changed to L6hr.

[Comparative example]

The component ratio is BaOm 40 moJR%* Fe20a-
40mol! %.

Reagent so that B2O3-20mof%! The same method as in Example 1 was followed except for the preparation.

[Comparative Example 2] Component ratio: SrOw 40 mol1%, Fe2O3x
40 no1%.

The general pressure of Example 1 was followed except that the reagents were prepared so that the B2O3""20 m011%.

[Comparative Example 3] Component ratio is BaOm 40 mof%, Fa203=m
60 mai1%.

Weigh accurately and mix thoroughly, then heat at 3500℃ for 1 hour.
r Heated and melted. This molten sample was slowly cooled and crystallized to obtain a sample for magnetization measurement.

This sample was not first vitrified and heat treated to precipitate microcrystals as described above.

The coercive force measured for the above Examples and Comparative Examples and the particle size ya of crystallized SrO.6Fe2O3 are summarized in Table 1.

Table 1: rO-Fe 203-8m203-based crystallized glass (7) Coercive force Hc depends on the grain size of SrO.6Fe203, and takes a certain maximum grain size.

The existence of 8m203 is the coercive force of SrOFe2O3Sm2O3-based crystallized glass! raise. Examples of the highest coercive force obtained with the present invention are Examples 3, 5, and 6.7, 40
S ro + 56 F e 203°45m203
If Q/C1, SrO+ 6F
e203 grain'l 260X+= control shift (800'
CX lhr, IQ 00℃X0.5hr, 60
7000 to 7100 at 0℃ x 1.6 hr heat treatment)
It was 0e.

In addition, the same coercivity was obtained even when the sample was subjected to a very short crystallization heat treatment by laser irradiation.

In any case, the results of the examples of the present invention all have higher coercive force than the comparative examples! It shows.

[Effects of the present invention]

The invention achieves all of the above objectives. In other words, a hard magnetic material with extremely high coercive force can be obtained. Moreover, the present invention is characterized by easy industrialization! have.

[Brief explanation of drawings]

FIG. 1 is a phase diagram of 5rO-Fe203-based oxide.

Claims (8)

[Claims] (1) SrO-Fe_2O_3-based oxide is heated and melted to make it a liquid, and then this liquid is heated at 10^2℃/sec to 1
Vitrification is achieved by rapid cooling using a liquid quenching method at a cooling rate of 0^8°C/sec, and the glass is heated from 450°C to 1200°C for 1
A method for producing a hard magnetic material, characterized in that fine SrO.6Fe_2O_3 is precipitated by crystallization while holding for μsec to 200 hr. (2) The method for producing a hard magnetic material according to claim 1, wherein the liquid quenching method is a thermal spraying method in which molten oxide is thermally sprayed onto a substrate having relatively high thermal conductivity. (3) The method for producing a hard magnetic material according to claim 1, wherein the liquid quenching method is a liquid quenching method in which a liquid dropped onto a rotating body is cooled by spraying a non-reducing gas onto the liquid. (4) The method for producing a hard magnetic material according to claims 1 to 3, wherein the average particle diameter of the precipitated SrO.6Fe_2O_3 is 90 Å to 2000 Å. (5) Heat and melt SrO-Fe_2O_3-SmxOy-based oxide to make it a liquid, and then heat this liquid at 10^2℃/
The glass is rapidly cooled and vitrified by a liquid quenching method at a cooling rate of sec to 10^8 °C/sec, and the glass is heated to 450 °C to 1
By crystallizing at 200℃ for 1μsec to 200hr, fine SrO・6Fe_2O_3 and Sm
A method for producing a hard magnetic material, characterized by precipitating _2O_3 and Fe_2O_3. (6) The method for producing a hard magnetic material according to claim 5, wherein the liquid quenching method is a thermal spraying method in which molten oxide is thermally sprayed onto a substrate having relatively high thermal conductivity. (7) The method for producing a hard magnetic material according to claim 5, wherein the liquid quenching method is a liquid quenching method in which a liquid dropped onto a rotating body is cooled by spraying a non-reducing gas onto the liquid. (8) The method for producing a hard magnetic material according to claims 5 to 7, wherein the average particle diameter of the precipitated SrO.6Fe_2O_3 is 90 Å to 2000 Å.