JPH044383B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing FeBR-based permanent magnet material. Permanent magnetic materials are one of the extremely important electrical components used in a wide range of fields, from various household electrical products to peripheral equipment for large computers. In particular, with the recent demands for smaller size and higher performance of electrical and electronic equipment, permanent magnets are also required to have increasingly higher performance. Current representative permanent magnet materials include alnico ferrite and rare earth/cobalt magnet materials. Although rare earth cobalt magnet material was developed as a permanent magnet material with high residual magnetic flux density and high coercive force, it is very expensive because it contains 50 to 60% by weight of cobalt and uses samarium Sm, which is not contained in rare earth ores. It is. For this reason, its applications are limited, and it is only used in places where it has high added value, especially when it is small due to its magnetic properties. In order for rare earth magnet materials to be used inexpensively and in large quantities in a wide range of fields, it is necessary to use Nd, Pr, and Ce, which do not contain expensive cobalt and are contained in relatively large amounts in ores as rare earth elements. It is necessary that the main component be a light rare earth element such as , La, etc. Attempts are being made to develop permanent magnet materials using such light rare earth elements. As one of them
RFe ₂ -based compounds (where R is at least one rare earth metal) were investigated. Clark (AEClark) created amorphous TbFe ₂ by sputtering and found that it was 4.2〓.
It has an energy product of 29.5MGOe, and further this
When heat treated at 300~500℃, coercive force iHc=
3.4kOe, maximum energy product (BH) max=
7MGOe was found. A similar study
It has also been carried out for SmFe ₂ , and it has been reported that it shows a maximum energy product of 9.2 MGOe at 77〓. In addition, Kuhn (NCKoon) etc. (Fe, B) _0.9
It was discovered that when a ribbon of Tb _0.05 La _0.05 was prepared by the ultra-quenching method and then annealed at around 875〓, the coercive force iHc exceeded 9 kOe. However, in this case, the squareness of the magnetization curve and, of course, the orientation are poor, and as a result, the maximum energy product (BH) max is low (N.
C.Koon et al. App1.Phys.Lett.39(10), 1981, 840-842
Page, IEEE Transaction on Magnetics, vol.
MAG-18, No. 6, 1982, pp. 1448-1450). Furthermore, JJCroat and L. Kabacoff et al. fabricated ribbons with PrFe and NdFe compositions using an ultra-quenching method, and produced 8 kOe at room temperature.
reported a coercive force iHc close to (L. Kabacoff
et al., J.App1.Phys.53(3)1981, pp. 2255-2257, JJ
Croat IEEE Vol.18No.6 1442-1447). These ultra-quenched ribbons or sputtered thin films are not practical permanent magnet materials that can be used as such, and practical permanent magnets cannot be obtained from these ribbons or thin films. That is, it is not possible to obtain a bulk permanent magnet body having arbitrary shapes and dimensions from conventional FeBR-based ultra-quenched ribbons or RFe-based sputtered thin films. The magnetization curves of FeBR ribbons reported so far have poor squareness, and they were not considered to be practical permanent magnet materials that can compete with conventional magnet materials. Furthermore, both the sputtered thin film and the ultra-quenched ribbon are essentially isotropic, and it is virtually impossible to obtain a practical permanent magnet material with magnetic anisotropy from them. As described above, all of the manufacturing methods tried by many researchers to obtain permanent magnet materials of rare earth and iron alloys have been unsuitable for obtaining practical permanent magnet materials. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to eliminate the drawbacks of the above-mentioned conventionally proposed methods for producing permanent magnet materials and to provide a method that can industrially produce a new practical permanent magnet material. Furthermore, the present invention is a practical permanent magnet material that has good magnetic properties above room temperature, can be molded into any shape and size, has a highly square magnetization curve, and has magnetic anisotropy or isotropy. Another object of the present invention is to provide an optimal manufacturing method for obtaining a product that can effectively use light rare earth elements, which are rich in resources, as R. The present inventors previously invented an FeBR-based permanent magnet material that does not necessarily require the use of Sm and Co (Japanese Patent Application No. 145072/1982). This FeBR-based permanent magnet material is
It is based on a new compound different from the conventionally known RCo ₅ and R ₂ Co ₁₇ compounds, and in particular boron (B) is used as an amorphous promoting element in the production of amorphous alloys or in powder metallurgy. It is not added as a sintering accelerating element, but is an essential constituent element of the R-Fe-B compound that is magnetically stable and has a high magnetic anisotropy constant, which constitutes the actual content of this FeBR-based permanent magnet material. It revealed that. (It has also been revealed that a magnetically anisotropic sintered permanent magnet can be obtained by forming an appropriate microstructure based on the above FeBR-based permanent magnet material.) The present inventors have achieved the above object. In order to achieve this, the present invention has been arrived at as a result of further intensive research into methods of manufacturing such permanent magnet materials. That is, according to the present invention, 8 to 8 in atomic percentage
The composition consists of 30% R (where R is at least one rare earth element including Y), 2 to 28% B, and the balance Fe and unavoidable impurities. 0.3～
A FeBR-based permanent magnet material is obtained by molding alloy powder with a particle size of 80 μm and sintering it at 900 to 1200° C. in a reducing or non-oxidizing atmosphere. The present invention will be explained in detail below. The present invention is a method for industrially manufacturing a practical FeBR-based permanent magnet material, and in particular, the FeBR-based permanent magnet material based on a crystalline FeBR compound as described in the earlier application is used as a sintered body with good mass production. It makes it possible to manufacture. In the present invention, the alloy powder composition as a raw material does not necessarily need to contain Co, and as R, light rare earth elements that are abundant in resources can be used, and Sm is not necessarily required or does not need to be mainly composed of Sm. Since there is no raw material, the raw materials are cheap and extremely useful. In the present invention, first, an FeBR-based alloy powder composition having the above composition is prepared. The following explanation will be based on the case of producing a magnetically anisotropic permanent magnet material. In the present invention, boron B is used in an example of Fe, xB, 15Nd as shown in Fig. 1. First, the coercive force iHc required as a permanent magnet material is 1 kOe or more, so in order to satisfy this requirement, boron B must be 2% (hereinafter % is In order to exceed the residual magnetic flux density Br4kG of hard ferrite, it must be 28
Must be less than %. Also, the larger the amount of R
Although iHc is high and it is preferable as a permanent magnet (92−
x) Examples of Fe・8B・xNd are shown in Figure 2.
For iHc to be 1kOe or more, it must be 8% or more. However, since R is very easily oxidized, powders of high R-containing alloys are easily flammable and difficult to handle, so it is desirable that the content be 30% or less. B (boron) used in the present invention includes pure boron or ferroboron, but impurities include Al,
Materials containing Si, C, etc. can also be used. The rare earth element R is a rare earth element that includes Y, light rare earth elements, and heavy rare earth elements, and one or more of them is used. That is, as R, Nd, Pr, La, Ce,
Tb, Dy, Ho, Er, Eu, Sm, Gd, Pm, Tm,
Yb, Lu, and Y are included. Usually, R is a light rare earth element, and Nd, Pr, etc. are particularly preferred. In addition, although it is sufficient to have one type of R, in practice, a mixture of two or more types (Mitsushimetal, didymium, etc.) can be used for convenience of availability, etc. La, Ce, Pm,
Sm, Eu, Gd, Er, Tm, Yb, Lu, Y are other R
(Nd, Pr, Dy, Ho, Tb), especially as a mixture with Nd and Pr. Note that R does not have to be a pure rare earth element, and may contain impurities that are unavoidable during manufacturing (other rare earth elements, Ca,
Those containing Mg, Fe, Ti, C, O, etc.) can also be used. In the present invention, the presence of impurities that are unavoidable during manufacturing can be tolerated in the permanent magnet material. C, S, P, Cu,
It can also contain Ca, Mg, O, Si, etc. within a predetermined limit, contributing to manufacturing convenience and cost reduction. C may be contained as an organic binder, while S, P, Cu, Ca, Mg, O, Si, etc. may be contained from raw materials or manufacturing processes. C4.0
% or less, P3.5% or less, S2.5% or less, Cu3.5% or less,
It is practically preferable that Ca and Mg are each 4% or less, and Si is 5% or less (however, the total of these is less than the maximum value of each component) (in the case of isotropic P, Cu 3.3%).
The following are preferred). In addition, in the state of alloy powder, adsorbed components (moisture, oxygen, etc.) from air during processing are likely to be included, but these can also be removed during sintering. However, care should be taken in processing and storage as necessary. In the present invention, the permanent magnet material has an atomic percentage of 8
~30% R (R is at least one kind of rare earth element including Y), 2~28% B, balance Fe and unavoidable impurities, coercive force iHc is 1 kOe or more,
It exhibits magnetic properties with a residual magnetic flux density Br of 4 kG or more, and the maximum energy product (BH) max is equal to or higher than that of hard ferrite (~4 MGOe) (in the case of magnetic anisotropy). Light rare earths, especially one or two of Nd and Pr, are the main components of R (i.e. 50% or more of the total R)12~
Maximum energy product (BH) at a composition of 24% R, 3-27% B, balance Fe and unavoidable impurities
max is 7MGOe or more, which is a preferable range.
Most preferably, light rare earths (particularly Nd, Pr) are the main components of R (same as above), and the composition is 12 to 20% R, 4 to 24% B, the balance Fe and unavoidable impurities, and the maximum energy product (BH) max indicates 10MGOe or more, reaching a maximum of 33 (BH) max or more. In the present invention, the permanent magnet material is obtained as a sintered body, and the manufacturing method thereof is basically a powder metallurgy method. The density of the sintered body is about 80% or more of the theoretical density, and 95% or more is preferable for magnetic properties.
More preferably, it is 96% or more, reaching a maximum of 99% or more (see each example and FIG. 4). Figure 3 shows a typical example of FeBR magnet material.
The initial magnetization curve 1 of 75Fe/10B/15Nd (anisotropic) and the demagnetization curve 2 of both the first and second inlays are shown. The initial magnetization curve 1 rises rapidly in a low magnetic field and reaches saturation. Demagnetization curve 2 has extremely high squareness. From the shape of the initial magnetization curve 1, it can be seen that the present magnet is a so-called nucleation type permanent magnet whose coercive force is determined by the nucleation of reversal magnetic domains. Moreover, the high squareness of demagnetization curve 2 indicates that this magnet is a typical high performance magnet. For reference, demagnetization curve 3 of a ribbon of an amorphous alloy of 70.5Fe, 15.5B, 7Tb, and 7La is shown as an example of a conventionally known FeBR system, but it shows no squareness at all. The manufacturing method of the present invention makes it possible to exhibit high characteristics of the FeBR-based permanent magnet material, and the manufacturing method will be explained in more detail below. In general, rare earth metals are chemically very active and easily combine with oxygen in the air and easily react with oxygen to create rare earth oxides. It is necessary to carry out in an oxidizing atmosphere. First, an alloy powder having a predetermined alloy composition is prepared. As an example, after weighing and blending the raw materials to a predetermined composition within the above composition range, the ingot is melted in a high frequency induction furnace or the like, and then pulverized. Coercive force (iHc) in the range of powder average particle size 0.3 to 80 μm
It will be more than 1kOe. When the average particle size is smaller than 0.3 μm, oxidation progresses rapidly and it becomes difficult to obtain the desired alloy, which is not preferable for stable production of high-performance products of FeBR-based permanent magnet materials. Also powder particle size 80μ
If it exceeds m, the coercive force iHc becomes less than 1 kOe, which is not preferable in terms of maintaining the performance of the magnetic material. Among powders having a particle size within the above range, two or more powders having different compositions within the composition range of the present invention may be mixed and used in order to adjust the composition or promote densification during sintering. Or a mixture of powders with different FeBR composition ratios, such as B-rich ones, or
mixture of FeBR alloy powder and component elements or their alloys). Although pulverization may be carried out by a conventional pulverization method, it is preferable to carry out the process wet in a solvent, and it is preferable to use an alcohol-based solvent, hexane, trichloroethane, trichloroethylene, xylene, toluene, fluorine-based solvent, paraffin-based solvent, etc. can. The obtained alloy powder having a predetermined particle size is then molded. The pressure during molding is preferably in the range of 0.5 to 8 Ton/cm ² . If the pressure is less than 0.5Ton/cm ² , the molded product will not have sufficient strength and will be extremely difficult to handle in practical use as a permanent magnet material. Moreover, if it exceeds 8Ton/cm ² , the strength of the molded product will increase significantly, making it easier to handle it, but
This is not preferable since it poses a problem when performing continuous molding in terms of the strength of the press punch and die.
However, this molding pressure is not limited. Furthermore, when producing a magnetically anisotropic magnet material, the pressure molding is carried out in a magnetic field, and it is preferable to carry out the pressure molding in a magnetic field of about 7 to 13 kOe.
(In addition, when manufacturing an isotropic permanent magnet material, pressure molding is performed without applying a magnetic field.) A molding binder (auxiliary agent) may be used if necessary. The obtained compact is sintered at a temperature of 900-1200°C, preferably 1000-1180°C. If the sintering temperature is less than 900°C, sufficient density as a permanent magnet material cannot be obtained, and the required magnetic flux density cannot be obtained. Moreover, if the temperature exceeds 1200°C, the sintered body will be deformed, the orientation will be lost, and the magnetic flux density will decrease and the squareness will decrease, which is not preferable. Further, the sintering time may be 5 minutes or more, but if it is too long, there will be a problem in mass productivity, so the preferred sintering time is 30 minutes to 8 hours. Sintering is performed in a reducing or non-oxidizing atmosphere. When an inert gas atmosphere is used as the sintering atmosphere, it may be a constant pressure or pressurized atmosphere, but it is also possible to perform the sintering in a reduced pressure atmosphere or a reduced pressure inert atmosphere as a method of densifying the sintered body. Another method for increasing the sintering density is to conduct the sintering in an atmosphere of H ₂ gas, which is a reducing gas. Through each of the above steps, a magnetically anisotropic (or isotropic) sintered permanent magnet material with high magnetic flux density and excellent magnetic properties can be obtained. An example of the relationship between sintering temperature and magnetic properties is shown in FIG. 4. Although the above description has mainly focused on anisotropic cases, the present invention also includes isotropic cases, in which case the magnetic properties are lower than in anisotropic cases, but compared to conventional isotropic magnetic materials. As a result, products with extremely excellent properties can be obtained. That is, in the case of an isotropic permanent magnet material, an alloy powder composition consisting of 10 to 25% R, 3 to 23% B, and the balance Fe and unavoidable impurities can impart preferable characteristics. In the present invention, "isotropic" means substantially isotropic, and also includes those exhibiting anisotropy that may appear due to pressing or the like. Even in the case of isotropy, as the amount of R increases, iHc
increases, but Br decreases after reaching its maximum value.
Thus, the amount of R that satisfies (BH)max2MGOe or more is 10% or more and 25% or less. Further, as the amount of B increases, iHc increases, but Br decreases after reaching its maximum value. Thus (BH) max2MGOe or more is
B ranges from 3 to 23%. Preferably, light rare earths (particularly Nd, Pr) are the main component of R (at least 50 atomic % of the total R), and 12 to 20% R,
With a composition of 5-18% B, balance Fe (BH)
Shows high magnetic properties exceeding max4MGOe. The most preferable range is light rare earth elements such as Nd and Pr as the main component of R, 12 to 16% R, 6 to 18% B, and the balance Fe.
With a composition of (BH)max of 7MGOe or more, high properties never seen before in an isotropic permanent magnet material can be obtained. Examples of the present invention will be described below. However, the present invention is not limited to the examples.
Each sample was created using the following manufacturing process. (1) The raw material used was 99% or more rare earth (impurities are mainly other rare earth metals, the same applies to raw material purity below weight%). Iron is 99.9% pure
A ferroboron alloy containing 19.4% B as boron and the balance Fe and impurities Al and Si was weighed and blended to obtain a predetermined composition. (2) Magnet raw materials were melted using high-frequency induction. At that time, an aluminum crucible was used as the crucible, and an ingot was made by casting into a water-cooled copper mold. (3) Crush the ingot obtained by melting.
After making it to 35mesh, it is further processed by a ball mill.
Grinding was carried out to obtain particles of 0.3 to 80 μm. (4) Powder is heated in a magnetic field of 7 to 13 kOe at 0.5 to 8 Ton/cm ²
It was molded at a pressure of (However, when manufacturing an isotropic magnet material, it was molded without applying a magnetic field.) (5) The molded body was sintered at a temperature of 900°C to 1200°C. The atmosphere at that time was a reducing gas, an inert gas, or a vacuum. An example of manufacturing a permanent magnet material made of a sintered body obtained by the above process will be shown below. Example 1 An alloy consisting of 72Fe, 8B, and 20Nd in atomic percentage was ground to an average powder particle size of 3.3 μm by the above process to approximately 10 kOe.
^Ar
The sintered density and properties when sintered for 1 hour at each temperature in an atmospheric pressure atmosphere were as follows.

[Table] Example 2 An alloy of 77Fe, 9B, 9Nd, and 5Pr was ground to an average powder particle size of 2.8 μm using the above process and then ground in a magnetic field of 10 kOe.
A molded body is made with a pressure of 1.5Ton/ ^{cm2 and} Ar200Torr.
The sintered density and properties when sintered in an atmosphere at various temperatures for 4 hours were as follows.

[Table] Example 3 77Fe, 7B, 16Pr alloy with average powder particle size of 4.9μ
The sintered density ^and properties of the sintered product ^were as follows: It became like that.

[Table] Example 4 An alloy of 79Fe, 7B, and 14Nd was prepared with an average powder particle size of 5.2μ.
The sintered densities and properties of the sintered materials were as follows when they were pulverized to 1.0 m and molded at a pressure of 1.5 Tons/cm ² in a magnetic field of 10 kOe and sintered for 1 hour at various temperatures in an Ar atmosphere.

[Table] Example 5 Average powder particle size of 68Fe, 17B, and 15Nd alloys
The material was crushed to 1.8μm, molded at a pressure of 2Ton/ ^cm2 in a magnetic field of 10kOe, and sintered for 2 hours at various temperatures in an Ar200Torr atmosphere.The sintered density and properties were as follows. .

[Table] Example 6 An alloy of 77Fe, 8B, and 15Nd was prepared with an average powder particle size of 1.5μ.
The resulting compact was sintered in an Ar atmosphere at various temperatures for 1 hour, and the sintered density and properties were as follows.

[Table] As seen in the above examples, the powder metallurgy sintering method of the present invention can produce magnetically anisotropic or isotropic bulk products with high performance and arbitrary sizes.
It is possible to create FeBR-based permanent magnet materials and, ultimately, final products. It is impossible to provide such high properties and to create an arbitrary shape using conventional manufacturing methods such as sputtering and ultra-quenching. Therefore, the present invention realizes the mass production of FeBR-based products of arbitrary shapes as inexpensive, high-performance permanent magnet materials with good reproducibility, and is industrially very useful.

[Brief explanation of drawings]

Figure 1 is a graph showing changes in B content (x) and magnetic properties Br and iHc of (85-x)Fe・xB・15Nd.
Figure 2 shows the amount of Nd (x) in (92-x)Fe・8B・XNd
Figure 3 is a graph showing the magnetization curve for 75Fe/10B/15Nd. Figure 4 is a graph showing the relationship between sintering temperature and magnetic properties. Figure 5 is a graph showing the relationship between sintering temperature and magnetic properties. It is a graph showing the relationship between the average particle size (μm) of alloy powder and coercive force iHc (kOe).

Claims (1)

[Claims] 1 8-30% R in atomic percentage, 2-28%
An alloy powder with an average particle size of 0.3 to 80 μm is formed with a composition consisting of B, the balance Fe and unavoidable impurities, and is heated to 900 μm to 900 μm in a reducing or non-oxidizing atmosphere.
FeBR characterized by sintering at a temperature of 1200℃
A method for manufacturing permanent magnet materials.