JPH0474425B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a FeBR-based sintered permanent magnet material, and particularly to one having a specific crystal grain size that can improve its temperature characteristics and realize preferable magnetic properties. In the present invention, R represents a rare earth element containing Y. With the recent advances in electronics technology, permanent magnet materials have been developed for use in speakers, motors, magnetic disk drive,
It is widely used in devices such as seismometers, generators, and magnetrons, and is an industrially important material. In addition, alnico, hard ferrite, samarium cobalt (SmCo), etc. are well known as permanent magnet materials and are in practical use. Among these, alnico has a high residual magnetic density (hereinafter abbreviated as Br) but has a low coercive force (hereinafter abbreviated as Hc), and hard ferrite has a high Hc but low Br. As electronics technology advances, electrical components tend to become more highly integrated and smaller.
A magnetic circuit using hard ferrite must be larger in both weight and volume than other components. On the other hand, SmCo magnets have high Br and large
Since it has Hc, it meets the demands for smaller size and higher performance of magnetic circuits, but the samarium used as a raw material is a rare resource, and the supply of cobalt is unstable because the resource is unevenly distributed in specific regions. I am in a situation. Therefore, it has been desired to develop a new permanent magnet material that does not have these problems. However, in order for rare earth magnet materials to be used cheaply and in large quantities in a wide range of fields,
It is necessary that the material does not contain a large amount of expensive cobalt, and that the main component is a light rare earth metal, which is contained in large amounts in ores. As one attempt at such a permanent magnet material, an RFe ₂ compound (where R is at least one kind of rare earth metal) was investigated. Clark (AEClark) found that sputtered amorphous TbFe ₂ has an energy product of 29.5 MGOe at 4.2〓, and when heat-treated at 300-500℃, shows coercive force Hc = 3.4 kOe and maximum energy product (BH) max = 7 MGOe at room temperature. I discovered that.
A similar study was conducted on _SmFe2,77〓
It is reported that it shows 9.2MGOe. However, all of these materials are thin films made by sputtering, and are not magnets used in general speakers or motors. It was also reported that ultra-quenched ribbons of PrFe-based alloys exhibit a high coercive force of Hc = 2.8 kOe. Furthermore, Kuhn et al. (Fe _0.82 B _0.18 ) _0.9 Tb _0.05
We found that when an ultra-quenched amorphous amorphous ribbon with La _0.05 is annealed at 627℃, Hc reaches as high as 9kOe (Br=5kG). However, in this case, the (BH)max is low due to the poor squareness of the magnetization curve (NCKoon
et al., Appl.Phys.Lett.39(10), 1981, paragraphs 840-842). Also, L. Kabacoff et al _.
B _0.2 ) An ultra- _quenched ribbon with a composition of _1-X Pr
It has been reported that some have Hc at kOe level. These ultra-quenched ribbons or sputtered thin films are not practical permanent magnets (bodies) that can be used as such, and practical permanent magnets cannot be obtained from these ribbons or thin films. In other words, the conventional Fe/B/R ultra-quenched ribbon or
Bulk permanent magnets with arbitrary shapes and dimensions cannot be obtained from RFe sputtered thin films. The magnetization curves of Fe・B・R ribbons reported so far have poor squareness, and cannot be considered as practical permanent magnet materials that can compete with conventional magnets. Also,
Both the sputtered thin film and the ultra-quenched ribbon are essentially isotropic, and it is virtually impossible to obtain a practical permanent magnet with magnetic anisotropy from them. Therefore, the basic object of the present invention is to eliminate the drawbacks of the above-mentioned conventional methods and to obtain a new practical permanent magnet material having magnetic properties equivalent to or superior to those of conventional hard ferrite. More specifically, the invention provides:
It is a practical permanent magnet material that has good temperature and magnetic properties above room temperature, can be formed into any shape and practical size, has a highly square magnetization curve, and has magnetic anisotropy. The purpose is to obtain something that can effectively use light rare earth elements, which are abundant in resources. The present inventors have previously discovered that samarium is not necessarily required, and that light rare earths such as Nb, which are abundant resources and have almost no known uses to date, and Fe
A FeBR-based compound permanent magnet containing FeBR as a main component was developed and filed by the same applicant as the present application (patent application filed in 1983).
−145072 (Unexamined Japanese Patent Publication No. 59-46008)). This FeBR-based magnet material has high Br and high energy product (hereinafter abbreviated as (BH)max), and is a brand new industrial permanent magnet material that can replace conventional alnico, hard ferrite, and SmOo-based magnets. . A specific object of the present invention is to provide a range of sintered body crystal grain sizes in order to obtain even better temperature characteristics and magnet materials in this FeBR-based sintered permanent magnet material. The Curie point of this Fe/B/R based magnet material is generally around 300°C, with a maximum of 370°C. This Kyrie point is considerably lower than the Kyrie point of about 800°C of conventional alnico-based or SmCo-based permanent magnet materials. Therefore, the magnetic properties of Fe-B-R permanent magnet materials have greater temperature dependence than conventional alnico-based and SmCo-based magnet materials, and magnetic properties deteriorate at high temperatures. According to the research results of the present invention, etc., the above-mentioned Fe, B,
Since the temperature characteristics of R-based magnet materials deteriorate when used at temperatures above about 100°C, it has been found that it is appropriate to use them within the normal temperature range of about 70°C or below. Therefore, after various experiments, Fe・B・R
We have discovered that replacing a portion of Fe with Co is effective in improving the temperature characteristics of permanent magnet materials. That is, the present invention provides FeBR-based sintered permanent magnet material with an atomic percentage of 8 to 30% R (however, R is Y
one or more rare earth elements including), 2
~28% B, and the remainder substantially Fe, with a portion of said Fe subsumed by up to 50% Co (Co0) of the total composition.
%), and the average crystal grain size of the sintered body is 1
~90 μm and is characterized by magnetic anisotropy. Here, preferably 50% or more of R is one or both of Nd and Pr. The present invention will be explained in detail below. As disclosed in Japanese Patent Application No. 57-145072, the FeBR alloy is a completely new crystalline alloy that exhibits high magnetic properties as a sintered body and has a Curie point of about 300°C to about 370°C. The inventors of the present invention have discovered that by making this FeBR alloy into a sintered body through the processes of melting, casting, pulverization, orientation forming in a magnetic field, and sintering, a permanent magnet with magnetic properties that could not be confirmed with this type of alloy has been achieved. However, in the present invention, it has been found that Fe can exhibit excellent temperature and magnetic properties as a permanent magnet.
Through extensive experiments, it was clarified that the average crystal grain size of the sintered body was replaced with Co and the average grain size of the sintered body was within a certain range. This makes it possible to manufacture the product using the following methods. The FeCoBR alloy has a high magnetocrystalline anisotropy constant Ku as measured by the present inventors, and has a high magnetocrystalline anisotropy constant Ku.
It was found that it has an anisotropic magnetic field Ha comparable to that of the system magnet. According to the theory of single-domain particles, magnetic materials with high Ha have the potential to become high-performance fine particle magnets, such as hard ferrite and SmCo magnets. From this viewpoint, the present inventor created a FeCoBR-based sintered fine particle type magnet material in which the crystal grain size after sintering was changed, and measured the permanent magnet characteristics. As a result, we found that the obtained magnetic properties are closely related to the average grain size after sintering. In general, in single-domain fine-grain magnets, if the particles are large, they will have a domain wall within the particle, so reversal of magnetization easily occurs due to movement of the domain wall, resulting in Hc
is small. On the other hand, when a particle becomes smaller and becomes smaller than a certain size, it no longer has a domain wall within the particle and reversal of magnetization proceeds only by rotation, so Hc increases. The critical dimension for forming a single magnetic domain differs depending on the material, and is said to be about 0.01 μm for iron, 1 μm for hard ferrite, and 4 μm for SmCo. In addition, high values of Hc for each of these materials are obtained near this critical dimension. In the FeCoBR permanent magnet material of the present invention, the average crystal grain size is 1 to 90μ.
Hc1kOe or more can be obtained within the range of m, preferably 1.5
Hc4kOe or more can be obtained in the range of ~50μm. The permanent magnet material of the present invention is obtained as a sintered body. Therefore, the size of crystal grains after sintering the sintered body is a problem. It has been experimentally confirmed that in order to make the Hc of the sintered body 1 kOe or more, the average crystal grain size after sintering needs to be 1 μm or more. In order to obtain a finer sintered body crystal grain size, it is necessary to create a fine powder before sintering. However, the FeCoBR-based fine powder is easily oxidized, the strain applied to the fine particles has a large effect, and when the particle size becomes extremely small, it becomes a superparamagnetic material rather than a ferromagnetic material. is expected to decrease significantly. Moreover, when the crystal grain size becomes larger than 90μm,
The particles are no longer single-domain fine particles, but have domain walls inside the particles, and magnetization reversal occurs easily, resulting in a decrease in Hc. In order to have Hc1kOe or more, it must be 90μm or less. Particularly preferably, the thickness is 1.5 to 50 μm, and a high characteristic Hc of 4 kOe or more can be obtained (see FIG. 2 below). The permanent magnet material of the present invention is made of Fe・B・R alloy.
Temperature characteristics are substantially improved by substituting Co for Fe and containing 50% or less (atomic percentage) of Co in the magnet composition. Furthermore, due to the inclusion of Co, Nd, which is a rare earth element R, is abundant as a resource.
High magnetic properties are achieved by using light rare earth elements such as and Pr. Therefore, the Fe.Co.B.R magnet material of the present invention is advantageous in terms of resources and cost compared to conventional SmCo magnets. Generally, when Co is added to an Fe alloy, the Curie point increases in proportion to the amount added, while in other cases it decreases, and it is difficult to predict the effect of the addition. In the present invention, when a part of Fe is replaced with Co in the Fe/B/R magnet material, the Curie point is the first
As shown in the figure, it was revealed that the Curie point gradually increases as the amount of Co substitution increases.
Even a small amount of Co substitution (for example, 0.1% to 1%) is effective in increasing the Curie point, and as shown in FIG. 1, an alloy having any Curie point of about 300 to about 800 DEG C. can be obtained depending on the amount of Co substitution. Increasing the Kyrie point is effective in improving the temperature characteristics of the magnet, especially the temperature coefficient of Br. When Co is 5% or more, the temperature coefficient of Br is about 0.1%/
℃ or less, and contributes to an increase in Tc at 25% or less without substantially impairing other magnetic properties. When the Co content exceeds 25%, (BH)max gradually decreases, and when it exceeds 35%, a rapid decrease occurs. This is mainly due to the decrease in Hc of the magnet. Co
When the amount reaches 50%, (BH)max decreases to about 4MGOe of hard ferrite. Therefore, Co
The amount is limited to 50%. A Co content of 35% or less is desirable because (BH)max is high and the raw material price is low. Also, since Co has higher corrosion resistance than Fe,
By containing Co, it is also possible to impart corrosion resistance. The rare earth element R used in the permanent magnet material of the present invention includes Y, and is a rare earth element including light rare earths and heavy rare earths, and one or more of them is used. That is, this R includes Nd, Pr, La, Ce, Tb,
Dy, Ho, Er, Eu, Sm, Gd, Pm, Tm, Yb,
Lu and Y are included. As R, light rare earths are preferable, and Nd and Pr are particularly preferable. Also, it is usually sufficient to have one type of R, but in practice, a mixture of two or more types (Mitsushimetal, dididium, etc.) can be used for reasons such as convenience of availability, La,
Ce, Pm, Sm, Eu, Gd, Er, Tm, Yb, Lu,
Y, especially Sm, La, Er, and Tm are other R (Nd, Pr,
(Dy, Ho, Tb), especially Nd, Pr. Note that this R does not have to be a pure rare earth element, and may contain impurities that are unavoidable in manufacturing (other rare earth elements, Ca, Mg,
(Fe, Ti, C, O, etc.) may be included. As B (boron), pure boron or ferroboron can be used, and as impurities Al, Si,
Those containing C or the like can also be used. The permanent magnet material of the present invention has an R of 8 to 30% as described above,
2 to 28% B, 50% or less Co, balance Fe (atomic percentage), coercive force Hc≧1kOe, balance magnetic flux density
It exhibits magnetic properties of Br4kG or higher, and the maximum energy product (BH) max is equal to or higher than that of hard ferrite (about 4MGOe). When R is less than 8 atomic %, Hc becomes lower than 1 kOe. R rises steeply from 8%, and then as R increases, Hc increases, but at 30 atomic%
When the value exceeds 4kG, Br becomes less than the value of hard ferrite, which is about 4kG. B shows a similar tendency, with a 2%
If it is less than 28%, Hc will be lower than 1kOe, and if it exceeds 28%, Br will be lower than 4kG. One or two of Nd and Pr are the main components of R (i.e. 50 atomic% or more in total R), 11 to 24% R, 3 to 27%
The composition of B, 5 to 40% Co, and the balance Fe exhibits a maximum energy product (BH) max≧7MGOe and is within a preferable range. Most preferably, Nd and Pr are the main components of R (same as above), with 12 to 20% R, 4 to 24% B, and 10 to 30%
It has a composition of Co and the balance is Fe, and exhibits a maximum energy product (BH) max ≧ 10 MGOe, with (BH) max reaching a maximum of 33 MGOe or more. The permanent magnet material of the present invention is Fe/Co/B/R based, and has better temperature characteristics than the Fe/B/R based, Br is almost the same, iHc is the same or slightly lower, but the squareness is better. (BH)max is the same or higher. Further, as R, a light rare earth element which is abundant in resources can be used, and it does not necessarily require Sm or need to be made mainly of Sm, so the raw material is abundant and inexpensive, and is extremely useful. Hereinafter, aspects and effects of the present invention will be explained according to Examples. However, the embodiments and descriptions are as follows:
The present invention is not limited to these. Table 1 shows various types of products created by the following steps.
The characteristics of a sintered body made of a Fe(Co)BR compound are shown (things outside the scope of the present invention are also shown with a C symbol for comparison). (1) The alloy is high-frequency melted and cast in a water-cooled copper mold The starting materials are electrolytic iron with a purity of 99.9% as Fe, B
As ferroboron alloy (19.38% B, 5.32%
Al, 0.74%Si, 0.03%C balance Fe), and R with a purity of 99.7% or higher (impurities are mainly other rare earth metals). As Co, electrolytic Co with a purity of 99.9% was used. (2) Grinding: Coarsely pulverize to 35 mesh through using a stamp mill, then finely pulverize (3 to 10 μm) using a ball mill for 3 hours. (3) Orientation and molding in a magnetic field (10kOe) (pressurized at 1.5t/cm ² ). (4) Sintering After sintering in Ar at 1000-1200℃ for 1 hour, let it cool.

[Table] Table 1 mainly shows the cases of Nd and Pr, but Dy, Ho, and Tb can be used alone or in the same manner as Nd and Pr, as well as for other Rs and various combinations of Rs. Other R (11 types such as La) are Nd,
Fe(Co) of the present invention based on Fe(Co)BR compound in combination with one or more of Pr, Dy, Ho, Tb
BR-based crystalline materials exhibit good permanent magnetic properties.
Fe(Co)BR crystalline materials based on Fe(Co)BR compounds exhibit good permanent magnetic properties at appropriate B and R amounts. B in Fe・Co・B・R system
When increasing from 0, Hc increases.
On the other hand, the residual magnetic flux density Br increases monotonically at first, but reaches a peak around 10 at%, and (BH) max reaches 7 to 20 MGOe, reaching a maximum of 33 MGOe or more, making it one of the highest grade permanent magnets currently known. It exhibits high characteristics comparable to SmCo magnets. Further B
As the amount increases, Br decreases monotonically. Hc of at least 1kOe as a permanent magnet material
In order to satisfy this requirement, the amount of B must be at least 2 atomic % or more (preferably 3 atomic % or more). The permanent magnet material of the present invention has a high Br
It is characterized by the fact that it is, and is often used in applications that require high magnetic flux density. In order to make the Br of hard ferrite approximately 4 kG or more, the B content must be 28 atomic % or less.
Note that B3 to 27 atomic % and 4 to 24 atomic % are preferable or optimal ranges for (BH)max7MGOe or more and 10MGOe or more, respectively. Next, the optimum range of the R amount will be considered. As mentioned earlier, the permanent magnet material needs to have an Hc of 1 kOe or more, so the R content must be 8 at % or more. And the higher the amount of R
It has a high Hc and is desirable as a permanent magnet material.
However, although it is good to have a high Hc as the amount of R increases, since R is very easily oxidized, powders of high R alloys are easily flammable and difficult to handle. Therefore, considering mass productivity, the amount of R is 30 atomic%.
The following is desirable. If the amount of R is more than this, the powder becomes easily flammable and mass production becomes very difficult. Furthermore, since R is more expensive than Fe, it is desirable to have as little R as possible. The high permanent magnet properties of the permanent magnet material of the present invention cannot be obtained by conventionally known FeR-based or FeBR-based amorphous ribbons. Next, in the above method (2) pulverization, the pulverization time was changed appropriately so that the average particle size measured with a Fisher sub-sieve sizer was 0.5 to 100 μm. Samples having the respective compositions shown in Table 1 were prepared. Comparative Example In order to obtain a crystal grain size of 100 μm, the sample was held for a long time in an Ar atmosphere at a temperature 5 to 20° C. lower than the sintering temperature after sintering (Table 1, No. C7). The magnetization of the thus obtained samples having the respective compositions shown in Table 1 was examined, and the magnetic properties and average crystal grain size were measured. The results are shown in Table 1. Here, the average crystal grain size is defined by polishing the sample surface, taking a photomicrograph at a magnification of x100 to x1000 using an optical microscope, drawing a circle with a known area, and dividing the circle into eight equal parts by straight lines. The average number of particles on the diameter was counted and calculated. However, particles separated on the boundary (on the circumference) are counted as 1/2 (this method is known as Heyn's method). The part of the hole is omitted from the calculation. In Table 1, those marked with C indicate comparative examples. Furthermore, it can be seen from C7 and C8 that when the crystal grain size is outside the range of the present invention, Hc decreases to 1 kOe or less. Next, we conducted a detailed study on the relationship between the average grain size D and iHco for compositions No. 13 and 16 in Table 1.
The relationship shown in Figure 2 was obtained. From Figure 2, iHc
It can be seen that D peaks around 3 to 10μ, and decreases rapidly when it is smaller than that, and gradually decreases when it is larger. Even if the composition changes within the composition range of the present invention, the relationship between iHc and average grain size D shows the same tendency. This indicates that the FeCoBR magnet is a magnet composed of fine particles that are approximately the same size as a single magnetic domain. From the results in Table 1 and Figure 2, the Br of the FeCoBR magnet is about 4kG or more than that of hard ferrite,
In addition, in order for iHc to be 1 kOe or more, the composition must be within the range of the present invention and the average crystal grain size must be about 1 to about 90 μm.
It is shown that the thickness is 1.5 to 50 μm in order to obtain high characteristics of iHc4kOe or higher. The crystal grain size of the sintered body can be controlled by controlling manufacturing conditions such as crushing, sintering, and heat treatment. As mentioned above, the permanent magnet material consisting of the FeCoBR quaternary magnetic anisotropic sintered body of the present invention includes Fe, Co, B,
Although the presence of impurities unavoidable in the external industrial production of R can be tolerated, the following development is also possible, and the practicality can be further improved. That is, it is also possible to mix C, S, P, Si, etc. into the permanent magnet material of the present invention, thereby making it possible to improve manufacturability and reduce costs. Furthermore, the basic composition FeCoBR includes Al, Ti, Ni, V,
Cr, Mn, Zr, Hf, Nb, Mo, Ge, Ta, W,
By adding one or more of Sn, Bi, and Sb,
High coercive force is possible. In addition, Cu, S, C,
It can contain small amounts of P, Ca, Mg, O, Si, etc.
Ca, Mg, C each 4% or less, Cu, P each 3.5% or less,
S2.0% or less, Si5% or less, total 5% or less is acceptable.
The Br (approx. 4kG) is higher than that of conventional hard ferrite. C is P, Cu, Ca, Mg, from organic molding aids etc.
Si and the like may be mixed in from inexpensive raw materials, and S may be mixed in during the manufacturing process. As described above, the present invention uses rare earth elements (Nd, Pr) which have a specific average crystal grain size, are mainly composed of Fe, and are rich in resources as R and are easily available industrially.
The present invention provides a new type of magnetically anisotropic permanent magnet material that is completely different from conventional permanent magnet materials that can mainly contain In this work, we have realized a magnetically anisotropic permanent magnet with high residual magnetization, high coercive force, and high energy product that even exceeds that of the SmCo system. Its advantages as a permanent magnet material are extremely significant in terms of its main constituent elements when compared with conventional SmCo-based materials. Furthermore, it can be obtained as a practically sufficient bulk permanent magnet material, which cannot be obtained with the proposed amorphous ribbon, and is extremely useful. Also, FeBR
Compared to ternary systems, by replacing a portion of Fe with Co, the temperature characteristics (Curie temperature) have been improved, making it comparable to conventional alnico and SmCo systems. . In addition, the average crystal grain size of this permanent magnet material is 1 to 90 μm.
Regarding the critical significance that these values have on magnetic properties, there are many examples of data (especially Table 1 and Figure 2) that show that there are extremely rapid changes with these values as a field.
It is clearly supported by. And this
The crystal grain size of the Fe(Co)-B-R compound forms a fine structure suitable for a permanent magnet material that exhibits excellent anisotropic magnetic properties.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between the Co content (horizontal axis) and the Curie point (vertical axis) of the permanent magnet example of the present invention, and Figure 2 is a graph showing the relationship between iHc and average grain size of the example of the present invention. The graph showing the relationship between D and Figure 3 is
The graph and FIG.
−x Nd amount in Nd-based examples (atomic %, horizontal axis)
, and a graph showing the relationship between Br (kG) and iHc (kOe).

Claims (1)

[Scope of Claims] 1 8 to 30% R in atomic percentage (wherein R is one or more rare earth elements including Y), 2 to 28
% B, and the remainder substantially Fe, in which part of the Fe is replaced with 50% or less Co (excluding 0%) in the total composition, and the material is sintered. The average crystal grain size of the aggregate is 1 to 90 μm,
A permanent magnetic material characterized by being magnetically anisotropic. 2. The permanent magnet material according to claim 1, wherein 50% or more of R is one or both of Nd and Pr.