JPS59146944A - Manufacture of hard ferrite magnet powder - Google Patents

Abstract

PURPOSE:To obtain magnet powder with favorable characteristics for a bonded magnet when magnetoplumbite type hexagonal ferrite magnet powder represented by a specified general formula is manufactured by a flux method, by restricting the kind of a flux and carrying out a pulverizing stage. CONSTITUTION:When magnetoplumbite type hexagonal ferrite magnet powder represented by the formula (where M is one or more among Ba, Sr and Pb, and n=5.0-6.2) is manufactured, compounds as starting material are weighed so as to provide said composition. They are mixed with 1-50wt% in total of one or more kinds of compounded selected among the sulfates, chlorides, bromides, iodides and fluorides of Na, K, Ca, Mg, Ba, Sr and Fe, and the mixture is calcined by heating at a temp. above the m.p. of the flux. The calcined product is pulverized before or after washing and drying. The resulting powder may be annealed at about 400-1,100 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing hard 7 ferrite magnet powder, and more particularly to a method for producing hard 7 ferrite magnet powder suitable for bonded magnets such as rubber magnets and plastic magnets.

Bonded magnets are made by bonding xMi stone powder with a binder such as rubber or plastic, and the magnetic properties are reduced by the amount of binder contained; Because of its good dimensional accuracy and workability, it is suitable for small, thin, and complex-shaped products. It has many advantages and its demand has been increasing in recent years. In the case of bonded magnets, the magnetic properties of the product directly reflect the properties of the magnetic powder used therein, so the magnetic powder itself must have excellent permanent magnetic properties.

It should be noted that in normal manufacturing methods, for example, when taking a ferrite magnet, the final magnet is produced by pressing magnet powder and then sintering it to grow crystal grains. It is not necessarily necessary to exhibit excellent permanent magnetic properties in the original state. Therefore, it is necessary to prepare ferrite magnet powder suitable for bonded magnets.

One method for this purpose is to add sulfates, halides, and other salts of metal elements and then perform calcination to allow the calcination reaction to proceed at a lower temperature than usual, thereby omitting the pulverization process and producing magnetic powder. There is a manufacturing method called the flux method. The present inventors investigated this method and found that the fluxes include Na, K)GaSMgSBa,
Sr.

It has been found that the use of one or more fluxes selected from Fe sulfate, chloride, bromide, iodide, or fluoride provides excellent properties of the magnetic powder. Among these, the use of Napt is particularly economical because the raw material is cheap and the price is low.

However, the flux method is originally characterized in that it does not include a pulverization process. That is, (1) the ideal particle morphology (flat shape) produced by the calcination reaction is maintained; and (2) no mechanical strain is introduced due to pulverization. Nevertheless,
The inventors of the present invention conducted various studies and found that it is better to include a pulverization step even in the case of the flux method to obtain magnet powder with favorable characteristics for use in bonded magnets, thereby completing the present invention. .

The present invention will be explained in detail below. The present invention is based on the general formula M O
e nlPe 203 (where M is one or more metal elements selected from the group of BaXSr and 'pb, n = 5
．． 0 to 6.2), in which Na −, K z OaN is added to the raw material compound weighed so as to have the above composition as a result of the firing reaction. Mg NBa,S
r, Fe sulfate, chloride, bromide, iodide, or fluoride. After mixing 1 to 50 wt% of the total weight of one or more fluxes selected from Fe sulfate, chloride, bromide, iodide, or fluoride, After heating and firing at a high temperature, before washing and drying,
Alternatively, a method for producing hard ferrite magnet powder, which is characterized by carrying out pulverization treatment after washing and drying, and annealing the ferrite magnet powder produced by the above method at a temperature of 400 to 1100 ° C. This is a method for producing ferrite magnet powder, which is characterized by adding ferrite magnet powder.

General formula MOszF0203 (where M is Ba
one or more metal elements selected from the group of Sr and Pb,
? Magnetobrambite hexagonal ferrite represented by L:=5, O~6.2) is well known as a barium ferrite magnet or a strontium ferrite magnet.

In the above general formula, n is stoichiometrically "6", but from the viewpoint of magnetic properties, a range of 5.0 to 6.2 is also good, so this range is also normally used as a permanent magnet. obtain.

The steps and methods used in the prior art are the same as those used in conventional technology, including the point of accurately weighing and adjusting the raw material compounds, such as oxides or carbonates and hydroxides that easily become oxides upon heating, to obtain the desired ferrite composition. Ru. In the method of the present invention, Na, Oa, and Oa are added to this raw material compound.
, Mg , Ba, , 5rsFe sulfate or chloride,
One or more fluxing agents selected from bromides, iodides, and fluorides are mixed in an amount of 1 to 5 owt% by total weight. If the amount of the above-mentioned flux is less than 1%, the effect of the 7 lux method cannot be obtained, and if the amount of the above-mentioned flux exceeds 50%, the generation of gas due to the decomposition of the flux becomes intense during the firing process, resulting in Not only is this highly desirable for industrial production in terms of equipment and work environment, but also the components of the flux remain in the ferrite magnet powder even after washing and drying in subsequent steps, degrading the magnetic properties. Therefore, it is recommended to add a fluxing agent of preferably 3 to 25%, more preferably 5 to 10%.

After mixing these raw materials using a grinder, vibration mill, ball mill, or other suitable mixer,
Firing is carried out at a temperature of 400°C. For example, N as a fluxing agent.
Regarding the case of using a0t, the melting point of NaO4 is 8
Since the temperature is 00'C, firing is possible at a temperature of 800'C or higher, but it is preferable to perform firing at a temperature of 900'C or higher in order to uniformly and completely progress the ferrite formation reaction. Firing temperature is below 1250°C, usually 1100°
C or so is sufficient, but if a particularly high magnetic flux density is required, it is also effective to perform the firing at a temperature exceeding 1250°C. However, temperatures of 1,400°C or higher are not only unnecessary for the ferrite reaction, but are also economically disadvantageous, and furthermore, the flux generates a large amount of decomposed gas, causing pollution and deterioration of the furnace materials. Therefore, it is better to take a walk.

Next, the addition of a pulverization step is a major feature of the method of the present invention. Conventionally, it has been said that one of the advantages of the method for producing ferrite magnet powder using the flux method is that it avoids the pulverization process after firing. However, the present inventors repeated detailed and precise experiments on the method for producing ferrite magnet powder using the flux method, and found that in the case of the method of the present invention, it would be better to add a pulverization process to the method to obtain better results. Ta.

In other words, in the past, when the flux method was used, it was believed that each particle of the heated and fired product obtained in the firing process would fall apart, either in that state or after the process was continued until washing with water. . However, according to the results of studies conducted by the present inventors, even in the ferrite magnet powder produced by the present flux method, each particle could be separated completely independently. Therefore, it has been found that the degree of orientation can be further increased, that is, the squareness of the BH curve can be improved even when oriented in a magnetic field, for example.

Therefore, the greatest significance of the pulverization treatment in the method of the present invention lies in the fact that so-called pulverization is carried out to separate the particles individually, but the advantages of the pulverization treatment do not end there. That is, even when the flux method is used, the ferrite particles produced due to non-uniform raw materials, non-uniform mixing, etc. are not necessarily uniform, and there are large variations in size. Since the coercive force of ferrite is largely dependent on the particle size, this causes variations in the coercive force and deteriorates the magnetic properties. However, by applying appropriate crushing treatment, these defects can be overcome by reducing the angle and r. Can be erased.

When pulverization is added, there is a high probability that relatively large particles will be pulverized first, so if pulverization is continued for an appropriate amount of time, only particles that are too large will be selectively pulverized, reducing the overall particle size distribution. changes in the direction of becoming more uniform. However, if pulverization is carried out for a long time, the probability that even small particles will be pulverized increases, resulting in over-pulverization. Therefore, the pulverization time must be changed depending on the raw material composition, heating and calcination conditions, pulverization method, etc. It is necessary to determine the grinding time by conducting preliminary experiments while considering the above factors.

The pulverization method may be a ball mill, vibration mill, attritor, or any other commonly used pulverization method. It is appropriate to perform water washing and drying after the pulverization process, but if the heated and fired product is relatively powdery. In some cases, this may be done before the pulverization process. Note that washing with water and drying may be performed according to a general method.

As mentioned above, the pulverization treatment in the method of the present invention can be carried out relatively lightly in the ordinary case due to its significance, so that no significant mechanical strain remains in the ferrite particles. However, since there is no mechanical strain, the magnetic properties may be improved if annealing is performed at a temperature of 400 to 1100'c in a step after pulverization. This temperature is 1100°
If it exceeds C, sintering will progress and particles separated into individual particles may be recombined, which is not preferable.
Further, if the temperature is lower than 400°C, there is no effect of annealing.

Usually 500-1000°C1 preferably 700-9o
It is preferable to anneal at a temperature of 0°C, more preferably 700 to 800°C. The annealing time is preferably about 0.25 to 50 JL, preferably about 0.5 to 251 JL, and more preferably about 1 to 10 JL.

Examples of the present invention will be described below.

(Example 1) 5rO03 and FIB203 as raw materials 5rO-5,6
Weighed so as to have a composition ratio of Fe203, and Na07
After adding 5 wt% of the mixture, the mixture was mixed for 5 □ hours using a rice cooker. This was heated and baked at a temperature of 1200'C for 2 hours. Next, the powder was placed in a ball mill at a weight ratio of 1 powder, 2 parts pure water, and 6 balls, and pulverized for 24 hours. Then about 50% of the powder
By washing and drying in a conventional manner using pure water equivalent to twice (by weight), Na04 was removed to obtain Sr ferrite particle powder. When this powder was chemically analyzed, it was confirmed that the NaP content was 08% or less and the OlO content was 1% or less. The average particle size of this powder measured by air permeation method was 2.25μ. Magnetic properties were measured by the following method.

The above Sr ferrite particles were heated at 1oton/c while applying a magnetic field of 80,000θ using a mold with a diameter of 1omm.
m," to obtain a powder compact with a diameter of 10 and a thickness of 8.5 wrn. This powder compact was impregnated with a liquid instant adhesive and solidified. Made 1,
13 HH-3 type) with a maximum applied magnetic field of 15,000
A BH curve of 0e was drawn. The result is the residual magnetic flux density Br
264QG1 had a coercive force rHc 10000e and a maximum energy product (B H) max 1.3 MGOe. (The volume filling rate of the powder was 69%.) In addition, the powder was produced in the same manner as above without being pulverized using a ball mill (however, the resulting powder was pressed with fingers). Although the powder was hard enough to crush, there were some granular particles mixed in, so only the powder that passed through a 200 mesh sieve was used.The average particle size of this powder measured by the air permeation method was 4. It was 33μ.)
The characteristics are Br 2450G, rH'c10500s,
(BH)max O, it was only 9MGOe.

(Example 2) '700,8
Table 1 shows the characteristics of each magnetic powder when annealing was performed for 10 hours at each temperature of QO 1900°C.

Table 1 As shown in Table 1, it can be seen that IHC and (BH)+nax are improved compared to the properties before annealing (Example 1 Nesho).

Note that when the Sr ferrite powder that was not subjected to the pulverization treatment described in the second half of Example 1 was annealed in the same manner, the characteristics were as shown in Table 2.

Table 2 As shown in Table 2, all of the properties are inferior to those obtained by adding the above-mentioned pulverization treatment.

(Example 3) 5rO03 and Fe2O3 as raw materials are 5rO-5,8F
Weigh it so that the composition ratio is θ203, and S r Ot2
- After adding 10 wt% of 6H20, the mixture was mixed for 5 hours using a sieve machine. This was heated and baked at a temperature of 1000°C for 3 hours. Then, 11 parts of the powder, 3 parts of pure water, and 30 parts of the balls were charged into an attritor and pulverized for 10 minutes. after that)
Excess Sr and 01 min were removed by washing and drying using pure water equivalent to approximately 50 times the weight (weight) of the powder, thereby obtaining Sr ferrite particle powder. The average particle size of this powder, measured by air permeation method, was 1°50 μm.

The powder magnetic properties that were investigated by molding the above Sr ferrite particles in the same manner as in Example 1 were as follows: Br2300G, xHc
It was 17500e, (BH)maxl, 2MGOe.

In addition, the average particle diameter of the powder produced in the same manner as above (measured by air permeation method) was 2.02μ, and the magnetic properties were Br 2.
000G, rHc 18000θ, (BH)max
It was only O.8MGOe.

(Example 4) EaOO3197-y, F0203894g, 5rOt
2I6H20208p was mixed for 5 hours in a rice bowl to obtain a raw material powder. This was heated and baked at 1100'C for 1 hour. Next, the powder was put into a ball mill in a weight ratio of 1 powder, 2 parts pure water, and 6 balls, and after pulverizing for 10 hours, it was washed with water and dried in the same manner as in Example 1. Chemical analysis of this powder revealed that the atomic ratio was Sr2.14%, Ba1.32%, Fe3
It was 6.42%, Oto, 04%, and the remainder was 0.

The powder magnetic properties obtained by molding the above 5r-Ba ferrite particles in the same manner as in Example 1 were Br 2200GX I
HC15000e z (BH)maxl, 1MGO
It was e.

In addition, in the above, the magnetic properties of the powder produced in the same manner as above except that the pulverization treatment using a ball mill was not performed are Br.
:L800G, IHC14300e, (BH)ma
It was only x 0.6MGOe.

(Example 5) S r OO3148g, BaO42 dispute 2H20191
g.

, Fe2O3894y were mixed in a sieve machine for 5 hours to obtain a raw material powder. After heating and baking this at 1000°C for 2 hours, it was put into a ball mill at a weight ratio of 1 powder, 2 parts of pure water, and 6 balls, and after pulverizing for 10 hours, it was washed with water and dried in the same manner as in Example 1. The chemical analysis value of this powder is Sr2.5 in atomic ratio.
0%, Ba1.03%, Fe36.6%, Oto, c
6%, and the remainder was 0.

The powder magnetic properties obtained by molding the above 5r-Ba ferrite particles in the same manner as in Example 1 were Br2200GS IH.
C21000e, (EH)maxl, 2MGOe.

In addition, the magnetic properties of the powder produced in the same manner as above except that the pulverization treatment using a ball mill was not performed were Br.
1800 GXIHC21000e, (B H)
It was only max '0.7 MG Os.

(Example 6) 5rO03 and Fe 203 as raw materials SrOe5,
Weigh it so that the composition ratio is 6Fe203, and add Na2
After adding 30 wt% of SO4・:L O1 (20), the mixture was mixed in a sieve machine for 5 hours. This was heated and calcined at 1100°C for 1 hour. Then, in a ball mill, 1 part of powder, 2 parts of pure water,
The balls were added at a weight ratio of 6 and pulverized for 10 hours. Thereafter, Na and SO2 were removed by washing and drying in a conventional manner using pure water equivalent to about 50 times the weight (weight) of the powder to obtain Sr 7-type light particle powder. This powder was molded in the same manner as in Example 1 and the powder magnetic properties were investigated as Br24.
00G, rHc 1800cle, (BH)max
1, 3 M G L, le.

In addition, the magnetic properties of the powder produced in the same manner as above except that the pulverization treatment using a ball mill was not performed were as follows:
1900G, IH (! 1800 Qe, (
B H) m&x O, 7M G Oe.

As detailed above, according to the method of the present invention, it is possible to obtain hard ferrite magnet powder that has excellent permanent magnetic properties as a powder itself. Therefore, as mentioned above, in the case of so-called bonded magnets such as rubber magnets and plastic magnets, the magnetic properties of the product directly reflect the properties of the magnet powder used therein, so the ferrite magnet obtained by the method of the present invention The powder is particularly suitable for producing bonded magnets with excellent magnetic properties.

Substitute entry #1 Ten Hon Takashi

Claims (1)

[Claims] 1. General formula M O@? L Fe 203 (M is one or more metal elements selected from the group of Ba, Sr and Pb, n = 5.0 to 6.2) of magnetobrambite hexagonal crystal In a method for producing ferrite magnet powder, Na1Kz Oa N
After mixing 1 to 50 wt% of the total weight of a fluxing agent of one or more citrons selected from sulfur salts, chlorides, bromides, iodides, or fluorides of Mg SBa % Sr SFe, A method for producing hard ferrite magnet powder, which comprises heating and firing at a temperature equal to or higher than the melting point, and then pulverizing the powder before washing and drying or after washing and drying. 2. A method for producing hard ferrite magnet powder according to claim 1, characterized in that the flux is Na0t. 3. In the method for producing hard ferrite magnet powder according to claim 1 or 2, the hard ferrite is heated and fired at a temperature of not less than the melting point of the flux and not more than 125°C. Method for producing magnetic powder. 4. In the method for producing hard ferrite magnet powder according to claim 3, the heating and firing temperature is 1000 °C.
A method for producing hard ferrite magnet powder, characterized in that the temperature is 120Q' or less. 5. General formula MO*zF0203 (T, M is Ba
. one or more metal elements selected from the group of Sr and Pb,
% == 5, O ~ 6.2) In a method for producing a magnetoblanbite hexagonal ferrite magnet powder expressed by % K, 10 aSMg
N E a N S r , after mixing 1 m or 2 or more types of fluxing agent selected from sulfate, chloride, bromide, iodide, or fluoride of Fe in an amount of 1 to 5 Qwt% by total weight, A method characterized by heating and firing at a temperature equal to or higher than the melting point of the flux, followed by pulverization, water washing, drying or water washing, drying, and pulverization, followed by annealing at a temperature of 400 to 1100°C. A method for producing a doped ferrite magnet powder. 6. The method for producing /'t-doferrite magnet powder according to claim 5, characterized in that the flux is Haot. 2. The method for producing hard ferrite magnet powder according to claim 5 or 6, characterized in that the heating and firing temperature is higher than the melting point of the flux and lower than 1250°C. Method for manufacturing Door Elite magnet powder. 8. In the method for producing 71-doferrite magnet powder according to claim 7, the temperature for heating and firing is 100°C.
A method for producing norh-doferrite magnet powder, characterized in that the temperature is 0°C or more and 1200°C or less. 9. The method for producing hard 7 ferrite magnet powder according to any one of claims 5 to 8, characterized in that the annealing temperature is 600 to 1000"C. Method. 10. In the method for producing nor-1-doferrite magnet powder according to claim 9, the annealing temperature is 700 to 700.
A method for producing a non-ferrite magnet powder characterized by a temperature of 900°C.