JPH0493001A - Bond magnet and its manufacture - Google Patents

Abstract

PURPOSE:To enable rotation in an orientated magnetic field because of no mutual fixing of magnetic power and to obtain high BHmax by forming the remaining part substantially out of rare earth magnet powder with a specified amount of poly organosilsesquioxane containing a phenyl group in the side chain. CONSTITUTION:A bond magnet is prepared from Sm2Co17-based magnetic powder or R-Fe-B-based magnetic powder substantially in the remaining part with a weight ratio of 0.05% to 3.0% of polyorganosilsesquioxane containing a phenyl group in the side chain. It is preferable that the R-Fe-B-based magnetic powder is expressed by a compositional formula RvFewCoxByMz with an average crystal grain size of 0.01mum to 0.5mum. That is, R is a kind or more of rare earth element containing Y, M a kind or more of elements made of Ga, Zn, Si, Al, Nb, Ta, W, Ti, Zr, Hf, Mo, P, C, Cu and Ni and inevitable impurities, where 9<=v<=16, w=100-u-x-y-z, 0<=x<=30, 4<=y<=11, 0<z<5.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a bonded magnet containing rare earth elements.

[Conventional technology]

In the bonded magnet market, ferrite l-based magnetic powder has traditionally been used, but with the demand for downsizing in OA equipment and precision equipment, SmC0-based bonded magnets with a high energy product are now being widely put into practical use ( Tokuko Sho 56-3184.1.
53-32330.53-34640.58-3664
1. ).

R-Fe-B sintered magnets developed in recent years
46008) is widely put into practical use because of its higher residual magnetic flux density and lower price than conventional S m -G o based sintered magnets. However, R-Fe-B alloys do not exhibit the coercive force required for bonded magnets in a pulverized state of 1 μm or more and 1 mm or less. For this reason, we use an ultra-rapid cooling process to
．． R-Fa-B isotropic bonded magnet having fine crystal grains of 5 μm or less (Japanese Patent Application Laid-Open No. 59-211549.60-2
07302) has been developed and put into practical use. In addition, R-Fe-B bonded magnets using ultra-quenching process and warm plastic working can be used as raw materials for anisotropic bonded magnets with high magnetic properties by pulverizing and mixing with resin. It has the following advantages and is currently in the process of research and development. (Unexamined Japanese Patent Application Publication No. 2003-111001) Conventionally, R-Fe-B bonded magnets are Sm-
C.

The Curie point is lower than that of bonded magnets, and it can be used for applications such as automobile motors and servo motors at temperatures of 150 to 200 degrees Celsius.
It has been thought that it is impossible to use it in high-temperature areas. In recent years, the heat-resistant temperature has been improved by adding elements such as Nb.
R-Fe-B magnetic powder has been developed. (
Japanese Patent Application No. 63-250452, Japanese Patent Application No. 63-250452, Japanese Patent Application No. 1999-3039) The magnetic powder made from this alloy system can reduce the irreversible demagnetization rate to about 3% at 200°C, and is promising as a raw material for heat-resistant bonded magnets. .

[Problem that the invention seeks to solve]

The present inventors fabricated bonded magnets from the magnetic powder using liquid epoxy and powder epoxy, and the long-term thermal demagnetization of the magnetic flux (1
70°C x 1000 hours).

When using liquid epoxy (Japanese Patent Application Laid-Open No. 6O-20730
2) High residual magnetic flux density can be obtained due to the elimination of air gaps. However, it became clear that long-term thermal demagnetization was large. Due to the viscosity of the epoxy, it is difficult to uniformly feed magnetic powder into the mold, hardening progresses over time, making it impossible to store large amounts of raw material powder, molded objects are easily chipped and difficult to handle, and the resin hardens. There was a drawback that dimensional accuracy deteriorated due to expansion.

When powdered epoxy is used, storage stability and handling are good, but since the epoxy is a solid, it is impossible to eliminate voids when pressed. For this reason, the residual magnetic flux density is low, oxygen and moisture easily enter, long-term thermal demagnetization is large, and moisture resistance.
It also had the disadvantage of poor corrosion resistance.

The thermally demagnetized bonded magnet is discolored to a blackish color.
It is thought that it underwent high-temperature oxidation. JP-A-62-2300
In 08, by using a silane coupling agent,
It has been shown that the oxidation resistance of magnetic particles and the wettability of magnetic particles and resin can be improved.

However, the improvement in oxidation resistance in this patent is a general discussion, and no specific method for improving oxidation resistance at high temperatures is disclosed. Furthermore, this method has the disadvantage of poor powder feeding performance and poor dimensional accuracy. JP-A-63-152111. JP-A-64-41201 also uses a coupling agent to improve corrosion resistance, but does not mention high temperature oxidation.

JP-A-2-123703 discloses an example in which a silicone ladder polymer is used to improve the high-temperature strength of a bonded magnet. However, this patent does not mention long-term thermal demagnetization of the magnetic flux, and the example of this patent
Bonded magnets that can be used at higher temperatures cannot be obtained.

[Means for solving problems]

An object of the present invention is to provide a bonded magnet that has low long-term thermal demagnetization of magnetic flux, high residual magnetic flux density, and excellent uniform powder feeding, long-term storage stability, and dimensional accuracy. Specifically, the following technical means were used to achieve the objectives listed in (a).

That is, it contains polyorganosilsesquioxane having a phenyl group in its side chain in a weight ratio of 0.05% to 3.0%, and the remainder is substantially Sm2Co17 magnetic powder or R-
The above technical problem was solved by manufacturing a bonded magnet made of Fe-B magnetic powder (R is one or more rare earth elements including Y).

The R-Fe-B magnetic powder is RvFewCoxByMz
(R is one or more rare earth elements including Y, M is Ga, Z
n, Si, Al, Nb, Tap W+ Ti, Zr, H
One or more elements consisting of f, Mo, P, C, Cu, and Ni
]2 and unavoidable impurities, 9≦v≦1-6, w=100
−u−x−y−z, O≦X≦30.4≦y≦11, ○<
2≦5), and the average crystal grain size is 0.01μ
It is desirable that the thickness is not less than m and not more than 0.5 μm.

Less than 70% of the phenyl groups contained in the polyorganosilsesquioxane may be substituted with methyl groups.

Further, the present invention provides a bonded magnet that exhibits little long-term deterioration of magnetic flux and is magnetically anisotropic.

The bonded magnet is made of R-Fe-B magnetic powder (R
can be manufactured by coating the surface with one or more rare earth elements (including Y) and finally subjecting it to a hardening treatment.

In the present invention, the Sm2Co17-based magnetic powder has Sm2Co17 or Sm2 (Co, Fe
)17. As additives, Cu,
The melted ingots 1 to 1 containing mainly columnar crystals containing Zr, Ti, Hf, etc. are solutionized in an inert atmosphere or vacuum, and then rapidly cooled. Thereafter, it is aged at 700 to 800'C for several hours to several tens of hours, and then cooled to room temperature. Thereafter, the ingot 1- is pulverized from several tens of micrometers to 200 micrometers to obtain S m2Co 17-based magnetic powder having magnetic anisotropy.

In the present invention, the R-Fe-B magnetic powder has R2Fe14B or R2(Fe, Co, N1)14 as the main phase.
means magnetic powder having B. Single roll method, double roll method,
By rapidly cooling a molten metal using a molten metal rapid cooling method such as an ultrasonic gas atomization method, it is possible to create an alloy powder in an amorphous state or in a fine crystalline state.

The reason for determining the desirable composition range of the R-Fe-B magnetic powder is as follows. If the amount of R (one or a combination of two or more rare earth elements including Y) is less than 9 at%, sufficient coercive force cannot be obtained. When R exceeds 16 at%, the amount of the main phase decreases, and coarse crystal grains exceeding 0.5 μm are likely to occur, resulting in a decrease in residual magnetic flux density and squareness. Therefore, it was set as 9≦R≦16. Especially when 1o≦R≦14,
It is possible and desirable to achieve high residual magnetic flux density and coercive force at the same time.

When the amount of B is 4 at% or less, Nd, which is the main phase of the water-based magnet,
The 2Fe14B phase is not completely formed, and both the residual magnetic flux density and coercive force are low. Furthermore, when the amount of B exceeds 11 at %, the residual magnetic flux density decreases due to the appearance of phases that are unfavorable in terms of magnetic properties.

Therefore, the amount of B was set to 4≦y≦11. A particularly preferred range for energy product and coercive force is 5≦y≦8.

The Curie point is improved by adding Go, but
The anisotropy constant of the main phase decreases, making it impossible to obtain high coercive force. Therefore, the amount of Co was set to 30 at% or less.

Additional elements include Ga, Zn, Sj, A1. ,Nb,
Tar W+ Ti, Zr, Hf, Mo, pl C, C
The reason for choosing u and Ni is as follows: 3at%
The following Ga, Zn, Si, AI, Nb, Tap W+
Ti, Zr, Hf, Mo+P have an effect on the direction of coercive force. Addition of more than 5 at% significantly reduces coercive force. C mixed into raw materials during the reduction process of rare earths and boron is
If it is 3 at% or less, the coercive force will not be reduced. Cu,N
i improves corrosion resistance without significantly changing magnetic properties.

Ga also has the effect of improving corrosion resistance.

By heat-treating this alloy powder in the range of 550°C to 800°C in an inert gas or vacuum, magnetically isotropic magnetic powder with an average crystal grain size of 0.01 μm or more and 5 μm or less can be produced. can get. Here, magnetic isotropy refers to a phenomenon in which the residual magnetic flux density does not change depending on the measurement direction, and corresponds to the random distribution of easy magnetization directions. If the rapid cooling rate can be appropriately controlled, this heat treatment step can be omitted. By heat-treating alloy powder that is entirely in a substantially amorphous state, it is possible to obtain magnetic powder with less high-temperature demagnetization of magnetic flux. The anisotropic bonded magnetic powder is obtained by plastically deforming the isotropic magnetic powder by 50% or more at a temperature of 600°C or higher and lower than 900°C. As the method of plastic deformation, known hot working methods such as upsetting, rolling, and extrusion can be used. Anisotropic bonded magnet is
Because the easy magnetization directions are aligned, it is possible to achieve a higher residual magnetic flux density than isotropic bonded magnets.

The average grain size varies greatly depending on the composition (particularly the amount of rare earth) and plastic working conditions (heating rate, working temperature, working time, etc.). In the present invention, the average crystal grain size was determined from the number of crystal grains crossing a straight line drawn on a photograph of a fracture surface. The reason for specifying the average crystal grain size is as follows. If the average crystal grain size is less than 0.01 μm, the coercive force required for a heat-resistant bonded magnet cannot be obtained. When the average crystal grain size exceeds 0.5 μm, the coercive force decreases and the absolute value of the temperature coefficient of the coercive force increases, resulting in large thermal demagnetization at high temperatures.

In order to reduce thermal demagnetization at high temperatures in isotropic bonded magnets, the average crystal grain size should be 0.03 μm or more, 0.2
It is more desirable to keep it below pm.

The magnetic powder after heat treatment is an aggregate of the above-mentioned microcrystals, several mm in size.
It has a size of These are usually ground to a size of 10 μm or more, mm or less, to facilitate powder feeding. When the average particle size is less than 10 μm, the residual magnetic flux density decreases because the density decreases. When the average particle size exceeds 1 mm, it is difficult to feed powder into a narrow cavity, but it can be used depending on the application.

The polyorganosilsesquioxane containing a phenyl group in the side chain used in the present invention is obtained by condensing an organosilsesquioxane oligomer by heating, and has the following repeating structure. This resin has a high decomposition temperature of 470°C due to the 5i-0-8j bond and phenyl group, which is the limit temperature for bonded magnets (approximately 200°C).
But it is stable.

C6I(5C6H5C6H5 0-8j -0-8i -0-8i -0-0-8i
-○-8i -○-8i-0C6H5C6H5C6H
5 However, up to 70% of the phenyl groups in the side chains in ``2'' may be substituted with methyl groups. This substitution increases the hardness of the resin by two degrees, which has the advantage of making the magnet less likely to be damaged. The upper limit of the replacement amount is 70%.
If the substitution exceeds 4,000 yen, the oligomer will undergo a condensation reaction at room temperature and become susceptible to change, and the decomposition temperature of the resin after curing will be 400 yen.
This is because the temperature drops from 70°C to 350°C, making it easier to break at high temperatures.

The magnetic powder is kneaded together with an organosilsesquioxane oligomer and a lubricant, and then crushed to become a press molding raw material (compound). By this operation, the organosilsesquioxane oligomer covers substantially the entire surface of the magnetic powder. When liquid epoxy resin is used, it is known that the compound gradually hardens and the magnet density decreases, but the compound of the present invention has excellent long-term storage stability because it does not easily change over an hour. . When the amount of polyorganosilsesquioxane is less than 0.05%, it cannot be used as a bonded magnet because it has no effect of adhering magnetic particles. Moreover, the amount of polyorganosilsesquioxane is 3.
When it exceeds 0%, the residual magnetic flux density decreases so much that it is not practical.

The organosilsesquioxane oligomer only needs to have enough fluidity to uniformly cover the surface of the magnetic particles at the crosstalk temperature. One method is to carry out crosstalk at a temperature in the range of 80°C to 120°C, at which point the organosilsesquioxane oligomer softens. In this method, hardening begins gradually during kneading and the viscosity increases, so the magnetic powder tends to be crushed and the density decreases. Another method is to dissolve the organosilsesquioxane oligomer in an organic solvent (ethanol, 1 to toluene, acetone, impropatol, etc.), mix it with magnetic powder, and evaporate the organic solvent while kneading. . With this method, the surface of the magnetic particles is uniformly coated with the resin, so that long-term thermal demagnetization of the magnetic flux is improved. When manufacturing a compound for anisotropic bonded magnets, it is desirable that the amount of polyorganosilsesquioxane be 1.5% or less in order to suppress adhesion between magnetic particles.

Further, a lubricant is added during kneading to prevent adhesion between magnetic particles, or before press molding, or at both times. As the lubricant, one type or a mixture of two or more types selected from aluminum stearate, zinc stearate, calcium stearate, molten wax, silicone surfactant, and alcohol type lubricant is suitable. It is desirable that the blending ratio to oxane is 1 wt% or more and 10 wt% or less. Calcium stearate may cause blistering due to moisture absorption, so it is used in applications where moisture resistance is not strictly required. Examples of silicone surfactants include dimethylpolysiloxane and compounds of polyalkylene oxide and methylpolysiloxane. Alcohol-based lubricants are lubricants having ○H groups in their side chains, and examples include 0Ctadecyl-3-(3', 5'
-di-tert-butyl-4' -hydroo
xyphenj, 1)propionate, Tet
rakis [methyl, ene-:3- (3'
+5'-di-tert-butyl-4'-hyd
roxyphenil)propionate]met
Hane et al. If the blending ratio of these lubricants to polyorganosilsesquioxane is less than 1 wt%, there is no effect of suppressing adhesion between magnetic particles.

If the blending ratio exceeds 10 wt%, the fracture strength of the bonded magnet after complete hardening will drop significantly, requiring careful handling, which is impractical. A particularly preferable range is 2 wt% or more and 6 wt% or less.

The above compound was press-molded and hardened (1, 80
A bonded magnet can be obtained by holding it at around ℃ for 1 hour). An anisotropic bonded magnet can be obtained by press-molding anisotropic bonded magnetic powder in a magnetic field. Organosilsesquioxane oligomers have smaller dimensional changes upon curing than general resins such as epoxy, and can produce bonded magnets with good dimensional accuracy.

By subjecting the obtained bonded magnet to an impregnation treatment, a bonded magnet with even smaller long-term thermal demagnetization of the magnetic flux can be obtained. As the impregnating substance, organosilsesquioxane oligomer dissolved in an organic solvent, silicone oil, heat-resistant varnish of H class, etc. give good results. In particular, by heating and curing the organosilsesquioxane oligomer, a bonded magnet with low long-term thermal demagnetization of magnetic flux and excellent corrosion resistance can be obtained. Epoxy resin, acrylic impregnating agent, and water glass promote long-term deterioration of magnetic flux, so it is preferable not to use them.

〔Example〕

Example 1 Composition formula N d 1.2.5F ebal, B6.5N
A master alloy was prepared by melting raw materials weighed to b 1.5 (expressed as atomic %, the same applies hereinafter) in an Ar atmosphere using a high-frequency melting furnace. The mother alloy was placed in a transparent quartz nozzle with a hole at the bottom, and then ceramicized on a Cu roll. After the chamber containing the roll was evacuated, Ar gas was introduced to a temperature of 760 Torr. The mother alloy was heated to 760 Torr. After remelting, the molten metal was spouted onto a roll rotating at a circumferential speed of 25 m/sec using an Ar pressure of 250 g/cm2.The molten metal was rapidly cooled and solidified into flakes.

The average thickness was 22 μm, and the coercive force was 0.4 and ○e.

The obtained flakes were held at 650° C. for 1 hour in an Ar'JJ atmosphere and then cooled in a furnace. The average crystal grain size of the obtained flakes was 0.06 μm. This flake was ground to 250 μm or less and fed to a kneader maintained at 50°C. 30 wt% of organosilsesquioxane oligomer (GR-950 manufactured by Showa Denko, hereinafter referred to as oligomer)
The acetone solution was supplied to the mixer, and the acetone was evaporated while being kneaded. The oligomer ratio was changed in several steps from 0.05% to 3.0% by weight. However, as a comparative example, sample 9 was made using liquid epoxy (
oil-based shell epoxy #807) and Himic anhydride (
Hitachi Chemical) was set at 2.5% and kneaded at room temperature without using acetone. A mixture with an oligomer content of 1.5% or less did not aggregate at all even when the temperature was lowered to room temperature. On the other hand, in a mixture with an oligomer content of 265% or more, agglomeration of magnetic powder was observed, and after crushing, the mixture was passed through a 500 μm sieve, and powdered stearic acid amide containing 2 wt % of the oligomer was uniformly mixed to be used as a raw material for a bonded magnet.

This raw material is heated to a diameter of 12.5 mm at a pressure of 7 tons/cm2.
A bonded magnet was produced by molding to a height of 8.3 mm and curing at 200° C. for 1 hour. Table 1 shows the characteristics of the obtained bonded magnet. Energy product (BH) m
ax was measured after magnetization in a magnetic field of 25 kOe. The coercive force jHc of these magnets is all 13.8-14.
It was in the 4kOe range. Thermal demagnetization was carried out by
After magnetization with a pulsed magnetic field of 0 kOe, the temperature was maintained at 170° C. for 1000 hours, and the decrease in magnetic flux was determined by the amount of decrease in magnetic flux when the temperature was returned to room temperature.

Samples 2 to 7 of the invention examples are sample 9 using epoxy resin.
It has a higher energy product (BH) max than that of BH, and is excellent in long-term thermal demagnetization of magnetic flux. Sample 8 has a low energy product because the amount of polyorganosilsesquioxane is too large. Furthermore, in Comparative Example 1, the oligomer layer was too thin, so the adhesive force acting between the magnetic particles was weak, and the magnet collapsed during the experiment.

Example 2 A magnet raw material was prepared in the same manner as Sample 5 except that the phenyl group in the oligomer was replaced with a methyl group. Table 2 shows the results.
Shown below. In the table, polyorganosilsesquioxane D
The decomposition temperature by TA is also shown.

Table 2 =20 Sample 13 is considered to have large thermal demagnetization because the methyl group is easily oxidized.

Example 3 A magnet was produced in the same manner as Sample 12 except that the average particle size was changed. Table 3 shows the average particle size, energy product, and thermal demagnetization.
Shown below.

Table 3 Sample 10 Realizes a bonded magnet with high temperature. Comparative example of imperial prayer and death Example 4 A bonded magnet was produced in the same manner as in Example 6 except that the heat treatment temperature of the quenched flakes was changed and the average crystal grain size was changed. Table 4 shows the energy product and heat resistance temperature. The heat-resistant temperature in this experiment was defined as the temperature at which 5% demagnetization occurred when the temperature was maintained for 1 hour.

Table 4 Example 5 Bonded magnets were prepared in the same manner as Sample 4 and impregnated with various substances. The energy product did not change with impregnation.

Table 5 shows the results of thermal demagnetization.

Table 5 Example 6 A magnet was created in the same manner as Sample 12 except that the composition was changed. The magnetic properties are shown in Table 6. In addition, the average crystal grain size was all within the range of 0.03 to 0.2 μm.

Table 6 Example 7 The composition formula is Nd12. ], FebalCo3B6.5Mx
(M is an additive element), and a magnet was created in the same manner as Sample 7 except that the additive element was changed. Table 7 shows the magnetic properties.
Shown below. In addition, the average crystal grain size is 0.02 to 0.02.
It was within the range of 1 μm.

Table 7 It can be seen that all additives have the effect of increasing the coercive force and decreasing the demagnetization rate.

Example 8 A magnet raw material was prepared in the same manner as Sample 7, except that a lubricant was mixed at the same time when the wires were crossed. The results are shown in Table 8.

Table 8 By controlling the amount of lubricant added to the polyorganosilsesquioxane from 1 wt% to 10%, a bonded magnet raw material with less adhesion between magnetic particles is realized.

Example 9 A magnet raw material was prepared in the same manner as Sample 6 except for the type and amount of the lubricant mixed first. The results are shown in Table 9. however,
Moisture resistance evaluation is 20% in air at 80°C and 90% relative humidity.
Judgment was made based on the presence or absence of rust or swelling when left for 0 hours.

Table 9 Stearic acid-based lubricants are easy to use with no rust, but
Small blisters were observed here and there on the coating film.

Depending on the purpose, it can be used without any problem.

Example 10 Except for changing the magnetic powder to NdXFebalco6B6Gay anisotropic magnetic powder and applying a magnetic field of 15 kOe during compression molding,
A magnet was produced in the same manner as Sample 32. Table 10 characteristics
Shown below.

Table 10 By applying this method to anisotropic bonded magnets, the magnetic particles do not stick to each other, so they can rotate in an orienting magnetic field.
A high (BH)max can be achieved. In addition, since the magnetic powder is coated, good moisture resistance can be achieved at the same time.

Example 11 A magnet was produced in the same manner as Sample 32, except that the magnetic powder was changed to Sm2Co17-based anisotropic magnetic powder and a magnetic field of 15 kOe was applied during compression molding. The characteristics are shown in Table 11.

Table 11 By applying this method to Sm2Co17-based anisotropic bonded magnets, the magnetic particles do not stick to each other, so they can be rotated in an alignment magnetic field and a high (BH)max can be achieved. In addition, since the magnetic powder is coated, good moisture resistance can be achieved at the same time.

〔Effect of the invention〕

As described above, the bonded magnet according to the present invention has low long-term thermal demagnetization of magnetic flux, high residual magnetic flux density, excellent uniformity of powder distribution, long-term storage stability, and dimensional accuracy, and is industrially useful. be.

Claims (6)

[Claims] (1) Contains 0.05% or more and 3.0% or less by weight of polyorganosilsesquioxane containing a phenyl group in the side chain,
A bonded magnet in which the remainder is essentially rare earth magnet powder. (2) The bonded magnet according to claim 1, wherein the rare earth magnet powder is Sm2Co17-based magnetic powder or R-Fe-B-based magnetic powder (R is one or more rare earth elements including Y). (3) R-Fe-B magnetic powder is RvFewCoxByM
z (R is one or more rare earth elements including Y, M is Ga,
Zn, Si, Al, Nb, Ta, W, Ti, Zr, Hf
, one or more elements consisting of Mo, P, C, Cu, and Ni and unavoidable impurities, 9≦v≦16, w=100−u−x
-y-z, 0≦x≦30, 4≦y≦11, 0<z≦5)
It is represented by the composition formula, and the average crystal grain size is 0.01 μm or more.
．． The bonded magnet according to claim 2, wherein the bonded magnet has a diameter of 5 μm or less. (4) The bonded magnet according to claim 1, wherein less than 70% of the phenyl groups contained in the polyorganosilsesquioxane are substituted with methyl groups. (5) The bonded magnet according to claim 1, which is magnetically anisotropic. (6) In a method for manufacturing a bonded magnet in which R-Fe-B magnetic powder (R is one or more rare earth elements including Y) is bonded with a binder, an organosilsesquioxane oligomer containing a phenyl group in the side chain is A method for producing a bonded magnet, which comprises coating the surface of R-Fe-B magnetic powder.