JPH052735B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a FeBRM-based sintered permanent material, and particularly to one having a specific crystal grain size that can realize favorable 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 flux 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, but magnetic circuits using alnico and hard ferrite are inevitably larger in weight and volume compared to other components. . On the other hand, SmCo magnets have high Br and large Hc, so they meet the demands for miniaturization and high performance of magnetic circuits, but samarium used as a raw material is a rare resource, and cobalt is a limited resource. Supply is unstable because it is unevenly distributed in several regions. 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 it does not contain 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) reported that sputtered amorphous TbFe ₂ has an energy product of 29.5MGOe at 4.2〓, and when heat treated at 300-500℃, coercive force Hc = 3.4kOe and maximum energy product (BH) max =
7MGOe was found. A similar study
This was also carried out for SmFe ₂ , and it was reported that it showed 9.2 MGOe at 77〓. However, all of these materials are thin films made by sputtering, and are not magnets used in general speakers or motors. In addition, ultra-quenched ribbons of PrFe-based alloys are
It was reported that it exhibited a high coercive force of =2.8kOe. Furthermore, Kuhn et al. (Fe _0.82 B _0.18 ) _0.9 Tb _0.05
We found that when an ultra-quenched 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, pp. 840-842). Also, L. Kabacoff et al _.
B _0.2 ) An ultra-quenched ribbon with a composition of _1-x Pr _x (X = 0 to 0.3 atomic ratio) was prepared, and the
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-based 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. Further, 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 purpose of the present invention is to eliminate the drawbacks of the above-mentioned conventional methods and to create a new practical permanent magnet material that has magnetic properties equivalent to or higher than that of conventional hard ferrite without using rare resources such as Co. It's about getting. More specifically, the present invention provides a practical permanent magnet material that has good 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 object of the present invention is to obtain an element in which light rare earth elements, which are abundant in resources, can be effectively used as R. The present inventors have previously discovered that samarium is not necessarily required, and light rare earths such as Nd, 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). This FeBR-based magnetic 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 SmCo-based magnets. . The basic purpose of the present invention is to provide a range of sintered crystal grain sizes in order to obtain even better magnetic properties in this FeBR-based sintered permanent magnet material, and also to improve the coercive force as necessary. The purpose is also to That is, the permanent magnet material of the present invention is a FeBRM-based sintered permanent magnet material with an atomic percentage of 8 to 30%.
of R (where R is at least one rare earth element including Y), 2 to 28% of B, and one or more of the following specified percentage of additive elements M (however, excluding M0%,
In cases where two or more of the above additive elements are included as M, the total amount of M is less than or equal to the atomic percentage of the one having the maximum value among the additive elements), and the remainder is substantially Fe.
The sintered body has an average crystal grain size of 1 to 90 μm and is characterized by magnetic anisotropy: Ti 4.5% or less, Ni 8.0% or less, Bi 5.0% or less, V 9.5% or less, Nb 12.5% or less, Ta 10.5% or less, Cr 8.5% or less, Mo 9.5% or less, W 9.5% or less, Mn 8.0% or less, Al 9.5% or less, Sb 2.5% or less, Ge 7.0% or less, Sn 3.5% or less, Zr 5.5% or less, and Hf 5.5% or less. Here, R is preferably 50% or more of ND and Pr.
One or two types of 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. Furthermore, in the present invention, excellent magnetic properties as a permanent magnet can be exhibited when the average crystal grain size of the sintered body is within a certain range. There is something
Through extensive experiments, it was clarified that high-performance FeBRM-based sintered permanent magnets can be manufactured stably on an industrial scale. The FeBRM alloy has a high magnetocrystalline anisotropy constant Ku as determined by the inventors' measurements, 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. In general, in single-domain fine-grain magnets, if the particles are large, they will have domain walls within the particles, so reversal of magnetization easily occurs due to the movement of domain walls, resulting in Hc
is small. On the other hand, when the particles become smaller to a certain size or less, the particles no longer have domain walls and reversal of magnetization proceeds only by rotation, so Hc increases. The critical dimension of this 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 FeBRM 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 ~70μm. 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 fine powder of FeBRM alloy is easily oxidized, the effect of strain on the fine particles increases, and when the particle size becomes extremely small, it becomes a superparamagnetic material rather than a ferromagnetic material. is expected to decrease significantly. Further, when the crystal grain size becomes larger than 90 μm, the particles are no longer single-domain fine particles, but have domain walls inside the particles, and magnetization reversal easily occurs, and Hc becomes small. In order to have Hc1kOe or more, it must be 90μm or less. Particularly preferably, the thickness is 1.5 to 70 μm, and a high characteristic Hc of 4 kOe or more can be obtained (see Table 1 below). 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, didymium, etc.) can be used for reasons such as convenience of availability, La,
Ce, Pm, Sm, Eu, Gd, Er, Tm, Yb, Lu,
Y, etc., especially La, Sm, Er, Tm, etc., 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, but may include impurities unavoidable in manufacturing, other rare earth elements, Ca,
It may include Mg, Fe, Ti, C, O, etc. 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, a predetermined % of additive element M, and the remainder Fe (atomic percentage), it exhibits magnetic properties of coercive force Hc ≥ 1 kOe, residual magnetic flux density Br4KG or more, and the maximum energy product (BH) max is hard ferrite (4MGOe). degree) will be equivalent to or higher than that. 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 and the remainder (Fe+M) exhibits a maximum energy product (BH) max≧7MGOe and is within a preferable range. Most preferably, the composition is such that Nd and Pr are the main components of R (same as above), 12 to 20% R, 4 to 28% B, an additive element M of a predetermined % or less, and the balance Fe, and the maximum energy product (BH) Indicates max≧10MGOe, (BH)
The max reaches a maximum of 33MGOe or more. In the magnet material of the present invention, most of M has the effect of increasing iHc. iHc by addition of M
An increase in the magnetic field increases the stability of the magnet and expands its applications. However, since M is a non-magnetic element (excluding Ni), as the amount added increases, Br decreases and (BH)max decreases. (BH)max
Recently, there have been many applications that require a high iHc even if the iHc is a little lower, so alloys containing M are very useful, but they are useful in the range where (BH)max is 4MGOe or more. In order to confirm the effect of each addition of the additive element M on Br, Br was measured by varying the amount added, and the results are shown in FIGS. 1 to 3. Bi, Mn, Ni
Other additive elements M (Ti, Zr, Hf, V, Ta,
The upper limit of the amount of addition (Nb, Cr, W, Mo, Sb, Sn, Ge, Al) can be selected within a range equal to or higher than approximately 4 kG of Br of hard ferrite, as shown in FIGS. 1 to 3. Furthermore, the preferred range from the viewpoint of Br is Br
It can be clearly read from Figures 1 to 3 that the weight is divided into stages of 6.5, 8, 10KG, etc., respectively. From these figures, the upper limit of the amount of the additive element M added is as follows, assuming that it is equivalent to or higher than the hard ferrite level (BH)max of about 4MGOe. Ti 4.5% or less, Ni 8.0% or less, Bi 5.0% or less, V 9.5% or less, Nb 12.5% or less, Ta 10.5% or less, Cr 8.5% or less, Mo 9.5% or less, W 9.5% or less, Mn 8.0% or less, Al 9.5% or less, Sb 2.5% or less, Ge 7.0% or less, Sn 3.5% or less, Zr 5.5% or less, and Hf 5.5% or less. If it contains two or more of the above elements, see Figure 1~
In general, the intermediate value of the specific curve for each additive element shown in FIG. 3 is shown, and the content of each element is within the range of the above percentages, and the total amount is less than the maximum value of the percentages for each element. Generally, as the amount of M added increases, Br decreases, but iHc increases for most M in many aspects, so (BH)max becomes a value equivalent to that without M addition. . Since an increase in coercive force contributes to stabilizing its magnetic properties, it is possible to obtain a permanent magnet that is extremely stable in practice and has a high energy product. When large amounts of Mn and Ni are added, iHc decreases.
Since Ni is a ferromagnetic element, Br does not decrease much. Therefore, the upper limit of Ni is 8% in order to make iHc 1 kOe or more, and from the viewpoint of Hc, Ni is preferably 4.5% or less. Mn addition has a larger effect on Br reduction than Ni, but it is not as drastic. Thus, the upper limit of Mn is preferably 8% from the same viewpoint as Ni, and from the viewpoint of iHc, Mn is preferably 3.5% or less. The vapor pressure of Bi is extremely high and it is virtually impossible to produce an alloy containing more than 5% Bi, so it should be kept at 5% or less. In the case of alloys containing two or more types of M, Br is
In order to satisfy the condition of 4kG or more, it is necessary that the amount of addition of each element mentioned above be less than or equal to the maximum value (%) of the upper limit. The amount of M to be added is most preferably 0.1 to 3%, considering the effect of increasing iHc, decreasing tendency of Br, and influence on (BH)max. Al is preferred. M
The addition of iHc makes the rise of iHc steeper. Generally B,
As the amount of R increases, Br decreases after reaching its maximum value, but
An increase in iHc is obtained in the region of maximum Br. The permanent magnet material of the present invention is Fe-B-R-M system, and does not necessarily need to contain Co, and as R, light rare earths, especially Nd and Pr, which are abundant in resources, can be used, and Sm is not necessarily included. Since it is not necessary or does not require Sm to be the main component, the raw materials are abundant and inexpensive, making it 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. Tables 1 and 2 show the characteristics of sintered bodies made of various Fe, B, and R compounds produced by the following steps (those outside the scope of the present invention are also marked with C for comparison. It is shown). (1) The alloy is high-frequency melted and cast in a water-cooled copper mold.The starting material is pure as Fe (weight ratio, same below)
99.9% electrolytic iron, B as feroboron alloy (19.38% B, 5.32% Al, 0.74% Si, 0.03% C,
The remainder is Fe), R is 99.7% or higher in purity (impurities are mainly other rare earth metals). M is 99% pure Ti, Mo, Bi, Ge, Ni,
Ta, Sb, 98% W, 99.9% Al, Sn, 95%
Hf, and ferrovanadium containing 81.2% V as V, ferronniobium containing 67.6% Nb as Nb, ferrochrome containing 61.9% Cr as Cr, and ferrozirconium containing 75.5% Zr as Zr. . (2) Grinding: Coarsely grind to 35 mesh through using a stamp mill, then finely powder (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. As shown in Table 1, materials based on compounds that do not contain B have a coercive force Hc close to 0 (0 is set because it is too small to be measured with a high Hc measuring instrument).
It will not become a permanent magnet. However, the atomic ratio is 4
%, by adding only 0.64% B by weight, Hc
is as high as 3 kOe (sample C7), and Hc rapidly increases as the amount of B increases. Along with this (BH)
The maximum is 7 to 30MGOe, and the maximum is over 36MGOe, making it the highest grade permanent magnet currently known.
Shows high characteristics comparable to SmCo magnets. Table 1 mainly shows the cases of Nd and Pr, but Dy, Ho, and Tb can also be used alone as well as Nd and Pr.
Other R (11 types such as La) are Nd, Pr, Dy,
The present invention is based on a FeBR compound (or FeBRM compound) in combination with either Ho or Tb.
FeBRM-based crystalline materials exhibit good permanent magnetic properties. The FeBRM-based crystalline material based on this FeBR-based compound exhibits good permanent magnetic properties at appropriate amounts of B and R. As B increases from 0 in the Fe・B・R・M system, Hc increases.
On the other hand, the residual magnetic flux density Br increases monotonically at first, but reaches a peak around 10 atomic %, and as the amount of B is further increased, Br monotonically decreases.

【table】

【table】

【table】

[Table] 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
It is characterized by being Br 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, considering the optimal range of the R content, as mentioned earlier, as a permanent magnet material, Hc is required to be 1 kOe or more, so the R content must be 8 atomic %.
Must be above. The larger the amount of R, the higher the Hc, which 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. In addition, R(Nd, Pr
(50% or more) ranges of 11 to 24 atom% and 12 to 20 atom% (BH)max are 7MGOe or more and 10MGOe, respectively.
This is a preferable or optimal range for achieving the above. 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 Tables 1 and 2 were prepared. Comparative example: In order to obtain a crystal grain size of 100 μm, after sintering, the sample was held in an Ar atmosphere for a long time at a temperature 5 to 20° C. lower than the sintering temperature (Table 1, No. C12). Magnetization of the samples having the compositions shown in Tables 1 and 2 thus obtained was examined, and the magnetic properties and average crystal grain size were measured. The first result is
It is shown in Table 2. Here, the average grain size is determined by polishing the sample surface and using an optical microscope after corrosion.
A microscopic photograph was taken at a magnification of , a circle with a known area was drawn, a straight line was drawn to divide the circle into eight equal parts, and the average number of particles on the straight line 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. Note that C1 to C16 are each outside the scope of the present invention. Furthermore, it can be seen from C12 and C13 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 Hc for compositions No. 6 and 20 in Table 2.
The relationship shown in Figure 4 was obtained. From Figure 4, Hc
It can be seen that D peaks around 3 to 10 μm, 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 Hc and average grain size D shows the same tendency. This indicates that the FeBRM-based magnet is a type magnet consisting of fine particles approximately the same size as a single magnetic domain. The present inventors further obtained an alloy having the same composition as No. 7 in Table 2 by the method (1) described above (casting method), but the average crystal grain size of the cast alloy was 20~20. 80μm
However, only a low Hc value of less than 1 kOe was obtained. From the results in Table 1 and Figure 4, the Br of the FeBRM magnet is approximately 4KG or more than that of hard ferrite,
In addition, in order for Hc to be 1 kOe or more, the composition must be within the range of the present invention and the average grain size must be 1 to 90 μm, and in order to obtain high properties of Hc 4 kOe or more, it must be 2 to 40 μm. It will be done. Figure 5 shows typical examples (1) Fe−8B−15Nd, (2)
Fe−8B−15Nd−1Nb, (3)Fe−8B−15Nd−2Al,
Three types of initial magnetization curves and demagnetization curves (1 to 3) are shown. All exhibit squareness useful as permanent magnet materials. Note that the average crystal grain size was used within a range of 5 to 10 μm. The crystal grain size of the crystalline material can be controlled by controlling manufacturing conditions such as crushing, sintering, and heat treatment. As mentioned above, the permanent magnet material made of the FeBRM quaternary magnetic anisotropic sintered body of the present invention includes Fe, B, R,
Although the presence of impurities that are inevitable in the external industrial production of M can be tolerated, the following development is also possible, and the practicality can be further improved. That is, a part of Fe can also be replaced with Co. In addition, the permanent magnet material of the present invention includes Cu, C, S, P, Ca, Mg, Si, and O.
It is also possible to contain a small amount of the like, making it possible to improve manufacturability and reduce costs. That is, Cu3.5% or less,
S2.5% or less, C4.0% or less, P3.5% or less, Ca, Mg
The content of each element is 4% or less and Si is 5% or less (however, the total amount is less than the maximum value of each element), which is still useful because it contains Br (approximately 4 kG) or more, which is the same as that of hard ferrite. Cu and P may be mixed in from inexpensive raw materials, C may be mixed in from an organic binder, and S may be mixed in during the manufacturing process. As described above, the present invention has a specific average crystal grain size, does not require Co, is mainly composed of Fe, and is mainly composed of rare earth elements (Nd, Pr), which are rich in resources and industrially easy to obtain. The present invention provides a new type of magnetically anisotropic permanent magnet material that is completely different from conventional permanent magnet materials that can be This material has achieved a magnetically anisotropic permanent magnet material 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
Even in contrast to ternary systems, it includes those that can further increase the coercive force by containing a predetermined element M. In addition, the average crystal grain size of this permanent magnet material is 1 to 90 μm.
The critical significance that these values have on magnetic properties is clearly supported by data from many examples (especially Tables 1 and 2, and Figure 4) that show that there are extremely rapid changes with these values as a field. It is being Then, this Fe(Co)-B-R compound (or Fe-
B-RM compound) Crystal grains form a fine structure as a permanent magnet material that exhibits excellent anisotropic magnetic properties.

[Brief explanation of the drawing]

1 to 3 are examples of the present invention (Fe-8B-
Amount of added element M (x%) in 15Nd-xM)
Graph showing the relationship between and residual magnetization Br (kG), 4th
The figure is a graph showing the relationship between Hc and average crystal diameter D for Examples of the present invention, and FIG. 5 shows changes in the demagnetization characteristic curve for Examples with typical compositions of the present invention.

Claims (1)

[Scope of Claims] 1. 8 to 30% R (wherein R is at least one kind of rare earth element including Y), 2 to 28% in atomic percentage
B, one or more of the following additive elements M in the specified percentage (however, excluding M0%, in the case where M includes two or more of the above additive elements, the total amount of M is the maximum value of the said additive elements) Permanent magnet material characterized in that the sintered body has an average crystal grain size of 1 to 90 μm, and is a magnetically anisotropic sintered body: Ti 4.5% or less, Ni 8.0% or less, Bi 5.0% or less, V 9.5% or less, Nb 12.5% or less, Ta 10.5% or less, Cr 8.5% or less, Mo 9.5% or less, W 9.5% or less, Mn 8.0% or less, Al 9.5% or less, Sb 2.5% or less, Ge 7.0% or less, Sn 3.5% or less, Zr 5.5% or less, and Hf 5.5% or less. 2. The permanent magnet material according to claim 1, wherein 50% or more of R is one or both of Nd and Pr.