JPH0319296B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to the improvement of permanent magnets, which are one of the extremely important electrical and electronic materials used in a wide range of fields, from various household electrical appliances to peripheral terminals of large computers. −
Regarding R-based permanent magnets. In recent years, with the demand for smaller size and higher efficiency of electrical and electronic equipment, permanent magnets are required to have even higher performance. Current typical permanent magnets are alnico, hard ferrite, and rare earth cobalt magnets. With the recent instability in the raw material situation for cobalt, the demand for alnico magnets containing 20 to 30% cobalt by weight has decreased, and cheap hard ferrite, whose main component is iron oxide, has become the mainstream magnet material. Summer.
On the other hand, rare earth cobalt magnets contain 50 to 65% cobalt by weight and are very expensive because they use Sm, which is not often found in rare earth ores, but they have much higher magnetic properties than other magnets. Therefore, it has come to be used mainly in small, high value-added magnetic circuits. Rare earth cobalt magnets are RCo ₅ , R ₂ Co ₁₇ (R is
It is a permanent magnet based on a binary compound represented by rare earth elements (mainly Sm and Ce).
Part of Co is replaced by small amounts of Cu, Fe, Zr, Ti, V, Hf
It has been attempted to improve the magnetic properties by substituting transition metal elements such as. On the other hand, recently, as a magnetic material that does not contain cobalt,
A sputtered thin film or ultra-quenched ribbon magnetic material containing Fe and R (hereinafter in the present invention, R is used as a symbol representing a rare earth element) as main components has been proposed. For example, the magnetic properties of sputtered thin film amorphous TbFe ₂ , DyFe ₂ , and SmFe ₂ alloys have been reported by Clark: Appl. PhYs.
Lett.vol.23No.11 1December1973 pp. 642-644).
In addition, as a magnetic material for ultra-quenched ribbons, PrFe-based alloys by Croat (JJCroat: Appl.Phys.Lett.37
(12), 15December19801096-1098), and also by Kuhn et al. (Fe _0.82 B _0.18 ) _0.9 Tb _0.05 La _0.05
Alloys (NCKoon et al.: Appl.Phys.Lett.39(10),
(Fe _0.8 B _0.2 ) _1-x Pr _x (x=0-0.3 atomic ratio) alloy by Kabakoff et al. (L. Kabakoff et al.: J.Appl.Phys.53(3),
March 1982, pp. 2255-2257), etc. have been reported. Furthermore, Kloth reported that although light rare earth iron alloys have long been considered attractive candidates for low-cost permanent magnets, attempts to magnetically harden these alloys by powder metallurgy were unsuccessful. They also reported that they found that Pr-Fe and Nd-Fe alloys can be magnetically hardened by melt spinning (ultra-quenching) (JJCroat: J.
Appl.Phys.53(4), April1982, p.3161). In order for magnets using rare earth metals to be used inexpensively and in large quantities in a wide range of fields, it is necessary to use magnets that do not contain expensive cobalt and are rare earth metals.
It would be necessary to have light rare earth elements, which are contained in large amounts in ores, as the main component. On the other hand, as mentioned above, in order to make R-Fe or R-Fe-B alloy useful as a magnetic material, it is said that sputter thinning, ultra-quenching, or amorphous formation is essential. However, it has not been possible to obtain bulk practical permanent magnets having arbitrary shapes and dimensions from these sputtered thin films or ultra-quenched ribbons. The magnetization curves of the Fe-B-R ribbons reported so far have poor squareness and cannot be considered as practical permanent magnets that can compete with conventional magnets. Furthermore, both the sputtered thin film and the ultra-quenched ribbon are essentially isotropic, and it has been virtually impossible to obtain a practical permanent magnet with magnetic anisotropy from them. The basic object of the present invention is to provide a new practical high-performance permanent magnet that should meet such demands. In particular, the present invention provides a practical permanent magnet 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 purpose of the present invention is to obtain a material that can effectively use resource-rich light rare earth elements as R. In order to create such a permanent magnet, the present inventor first developed a method using specific rare earth elements, mainly Nd and Pr, and Fe.
and B in a specific ratio, and is a magnetically anisotropic sintered body. A completely new type of practical high-performance permanent magnet was developed and filed by the same applicant as the present application (Japanese Patent Application No. 145072/1982). This Fe-B-R ternary magnet is based on a new compound different from the conventionally known RCo ₅ and R ₂ Co ₁₇ compounds, and is obtained by forming an appropriate microstructure using powder metallurgy. It is a magnetically anisotropic sintered permanent magnet, especially boron.
(B) is not added as a conventional amorphous promoting element when creating an amorphous alloy or as a sintering promoting element in powder metallurgy, but in this Fe-B-R
It was revealed that it is an essential constituent element of the R-Fe-B compound, which is magnetically stable and has a high magnetic anisotropy constant, which constitutes the substantial content of permanent magnets. The above-mentioned Fe-BR-based magnetically anisotropic sintered permanent magnet does not necessarily need to contain Co, and as a preferable embodiment, Nd and Pr, which are abundant in resources, are used as R.
It is possible to use light rare earths mainly composed of Sm and does not necessarily require Sm or mainly Sm, so the raw material is inexpensive and extremely useful. Moreover, the magnetic properties are better than those of hard ferrite magnets (coercive force iHc≧1kOe, residual magnetic flux density Br≧4kG, maximum energy product (BH) max≧
4MGOe) In a particularly preferred composition range, it can exhibit an extremely high energy product equal to or higher than that of rare earth cobalt magnets. As mentioned above, this Fe-B-R permanent magnet has high cost performance in terms of high magnetic properties based on magnetic anisotropy, arbitrary formability, and the ability to use more abundant materials in terms of resources. -It is extremely useful industrially as a substitute for Co-based magnets, but on the other hand, the Curie point (temperature) of this Fe-BR-based permanent magnet is generally 300°C as disclosed in Japanese Patent Application No. 57-145072. The maximum temperature is 370℃ before and after. This Kyrie point is considerably lower than that of conventional alnico-based or R-Co-based permanent magnets, which is about 800°C. Therefore, the magnetic properties of Fe-BR permanent magnets have greater temperature dependence than conventional alnico-based or R-Co-based magnets, and their magnetic properties deteriorate at high temperatures. According to the results of research conducted by the present inventor, Fe-BR-based sintered magnets deteriorate in temperature characteristics when used at temperatures above about 100°C, so they should be used within the normal temperature range of about 70°C or below. It turned out to be appropriate. As described above, the large temperature dependence of the magnetic properties of permanent magnets, that is, the low Curie point, narrows the range of their use. It was necessary to raise the Kyrie point and improve the temperature characteristics. In addition to the above-mentioned basic object, the present invention further achieves
Another object of the present invention is to improve the temperature characteristics of Fe-BR-based magnetically anisotropic sintered permanent magnets. As a result of various experiments and studies, the inventor has discovered that Fe
-Achieve the above basic objective by replacing Fe with Co in a B-R permanent magnet, and also
It has been found that this method is effective in improving the temperature characteristics of Fe-BR-based permanent magnets, that is, raising the Curie point and reducing the temperature coefficient (temperature-dependent rate of change) of the residual magnetic flux density Br. That is, the permanent magnet of the present invention is as follows. First invention of the present application: Fe-B- consisting of 8 to 30% of at least one of Nd, Pr, Dy, Ho, and Tb as a rare earth element (R), B2 to 28%, and the remainder substantially Fe, in atomic percentage. A permanent magnet characterized in that, in an R-based magnetically anisotropic sintered permanent magnet, a portion of the Fe is replaced with 50% or less (excluding 0%) of Co based on the total composition. Second invention of the present application: At least one of Nd, Pr, Dy, Ho, Tb and La, Ce, Pm, Sm, Eu, Gd, Er, as rare earth elements (R) in atomic percentage
In the Fe-BR-based magnetically anisotropic sintered permanent magnet consisting of a total of 8 to 30% of at least one of Tm, Yb, Lu, and Y, B2 to 28%, and the remainder substantially Fe, the Fe A permanent magnet characterized in that a portion of the total composition is replaced with 50% or less (excluding 0%) of Co. Generally, when Co is added to an Fe alloy, it is recognized that the Curie point (Tc) both increases and decreases as the amount of Co added increases. Therefore, replacing Fe with Co generally produces complex results that are difficult to predict.
For example, when Fe in an RFe ₃ compound is replaced with Co, Tc initially increases as the amount of Co increases, but Fe
It reaches a maximum near R(Fe _0.5 Co _0.5 ) ₃ , which is 1/2 substituted with
After that, it decreases. In addition, in the case of Fe ₂ B alloy, Tc monotonically decreases due to the substitution of Co for Fe. In the substitution of Fe for Co in the Fe-BR system, as shown in FIG. 1, it was revealed that as the amount of Co substitution increased, Tc increased rapidly at first, and then gradually increased. In this Fe-BR-based alloy, a similar tendency is confirmed regardless of the type of R. The amount of Co substitution is small (e.g. 0.1 to 1
atomic%) is also effective in increasing Tc, and as is clear in the system (77-x) Fe-xCo-8B-15Nd illustrated in Figure 1, the temperature can be increased from 400 to 800°C by adjusting x.
Alloys with arbitrary Tc can be obtained. Thus, the present invention provides novel Fe-B-
By substituting a part of Fe in the Fe-B-R magnetic anisotropic sintered permanent magnet based on the R compound with Co, the alloy composition contains 50% or less Co,
Fe-Co based on (Fe, Co)-B-R compound
-BR system magnetically anisotropic sintered permanent magnet is provided. According to the present invention, by containing Co, Fe
- The temperature characteristics of the B-R permanent magnet are improved to substantially the same level as conventional alnico magnets and R-Co magnets, and other advantages are maintained. That is, especially as a rare earth element R, it is abundant in resources.
When using light rare earths such as Nd and Pr, conventional R
-Compared with Co-based magnets, it is advantageous in terms of both resources and cost, and even better magnetic properties can be obtained. In addition, the Co-added Fe-B-R permanent magnet of the present invention has almost the same Br and the same or slightly lower iHc than the Fe-B-R permanent magnet that does not contain Co, but the addition of Co improves the squareness. is improved, so that (BH)max can be made equal to or even higher to a considerable extent. Furthermore, since Co has more corrosion resistance than Fe, it is also possible to impart corrosion resistance by adding Co compared to Fe-BR permanent magnets. Thus, the present invention can provide a novel practical high-performance permanent magnet that is extremely useful industrially. In the present invention, the contents of B and R among the essential elements are basically the same as in the case of Fe--B--R permanent magnets (systems that do not contain Co). That is, (hereinafter % indicates atomic percentage in the alloy), B should be 2% or more to satisfy the coercive force Hc≧1kOe, and B should be 2% or more to make the residual magnetic flux density Br of hard ferrite about 4kG or more.
28% or less. R is required to be 8% or more in order to have a coercive force of 1 kOe or more, and is set to 30% or less because it is easily flammable and difficult to handle and manufacture industrially (and is expensive). The rare earth element R used in the permanent magnet of the present invention includes Y, and is a rare earth element including light rare earths and heavy rare earths, among which one or more predetermined types are 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 mainly composed of Nd and Pr (particularly Nd and Pr) are preferable. Generally, it is sufficient to have one of the specified R (Nd, Pr, Dy, Ho, Tb, etc.), but La, Ce, Pm,
Sm, Eu, Gd, Er, Tm, Yb, Lu, Y, etc. can be used as a mixture with other R, especially Nd, Pr, Dy, Ho, Tb (one or more). In practice, a mixture of two or more types (Mitsushimetal, didymium, etc.) can be used for reasons such as convenience of availability. Sm, La, Er, Tm, Ce, Gd, Y are unfavorable because their iHc is low when used alone; Eu, Pm, Yb,
Lu exists only in trace amounts and is expensive. Therefore, as described above, these rare earth elements can be used as a mixture with other R such as Nd and 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.) within the industrially available range. do not have. 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 remainder essentially consists of Fe and Co, and the amount of Co substitution, which is a feature of the present invention, is desirably selected as appropriate depending on the requirements for magnetic properties, etc., which will be described later. In addition to Fe, Co, B, and R, the permanent magnet of the present invention is C,
The presence of industrially unavoidable impurities such as S, P, Ca, Mg, O, Si, and Al can be tolerated. These impurities are often mixed in from raw materials or manufacturing processes, and the total amount is preferably 5% or less.
Also, Al, Ti, V, Cr, Mn, Zn, Zr, Nb, Mo,
By adding one or more of Ta, W, Sn, Bi, and Sb, it is possible to increase the coercive force, and by adding Ni, it is also possible to improve corrosion resistance. The Fe-Co-B-R permanent magnet of the present invention has at least one of the above-mentioned R, that is, Nd, Pr, Dy, Ho, and Tb, or at least one of these Nd, Pr, Dy, Ho, and Tb. and La, Ce, Pm, Sm, Eu,
A total of 8 to 30% of at least one of Gd, Er, Tm, Yb, Lu, Y, 2 to 28% B, Co50% or less,
The residual Fe exhibits magnetic properties of coercive force iHc ≥ 1kOe and residual magnetic flux density Br ≥ 4kG, and the maximum energy product (BH) max is similar to that of hard ferrite (~4MGOe).
degree) will be equivalent to or higher than that. Furthermore, as R, Nd and Pr are the main components of R (i.e., at least 50% of Nd and Pr in all R), and 12
The composition of ~20%R, 4~24%B, 45% or less Co, and the balance Fe is the maximum energy product (BH) max≧
10MGOe, and especially when Co is less than 35%, the maximum energy product (BH) max is more than 20MGOe,
Reach a maximum of 33MGOe or more. Also, Co contributes to an increase in Tc even when it is less than 5%, and in particular, when it is more than 5%, the temperature coefficient of Br is about 0.1%/℃ or less, and when it is less than 25%, it increases Tc without substantially impairing other magnetic properties. Contribute. The Fe-Co-B-R permanent magnet of the present invention can also be obtained as a magnetically anisotropic sintered body similar to the Fe-B-R permanent magnet filed earlier. Typically, the permanent magnet of the present invention can be obtained by melting the alloy, cooling it (for example, casting), pulverizing the resulting alloy, and then shaping and sintering it in a magnetic field. <Examples> The present invention will be described below with reference to Examples. however,
This example is not intended to limit the invention. Figure 1 shows a representative example of 77Fe−8B−15Nd Fe.
A system in which part of is replaced with Co(x), (77−x)Fe−
The graph shows the change in the Curie point Tc when x of xCo-8B-15Nd is changed from 0 to 77. This sample was produced by the following steps. (1) The alloy is melted by high frequency and cast in a water-cooled copper mold.The starting materials are electrolytic iron with a purity of 99.9% as Fe, and ferroboron alloy as B (19.38% B, 5,32% Al,
0.74%Si, 0.03%C, balance Fe), purity as R
99.7% or more (impurities are mainly other rare earth elements), and electrolytic Co with a purity of 99.9% was used. Purity is expressed in weight%; (2) Grinding, coarsely pulverizing with a stamp mill to a mesh throughput of 35, and then finely pulverizing with a ball mill for 3 hours (3 to 10 μm); (3) Orienting and molding in a magnetic field (10 kOe) (1.5 t) ( ⁴ ) Sintering: 1000-1200°C in Ar for 1 hour, then allowed to cool after sintering. About 0.1 g of a block (polycrystal) was cut out from the sintered body, and its Curie point was measured using VSM as follows. In other words, a magnetic field of 10 kOe is applied to the sample, a temperature change of 4πI is measured in the temperature range from 25℃ to 600℃, and the temperature at which 4πI is almost 0 is defined as the Curie point.
Tc. As the amount of Co substitution for Fe increases in the above system,
Tc increases rapidly, and when Co is 30% or more, Tc is 600
Reaching temperatures above ℃. Generally, in permanent magnet materials, increasing Tc is considered to be the most important factor for reducing temperature changes in magnetic properties. In order to confirm this point, permanent magnet samples shown in Table 1 were prepared using the same process as the samples for Tc measurement, and the temperature characteristics of Br were measured as follows.
That is, the magnetization curve was measured with a BH tracer at each temperature of 25℃, 60℃, and 100℃, and
The temperature change of Br was averaged. Various Fe-B
Table 1 shows the measurement results of the Br temperature coefficients of the -R and Fe-Ce-B-R magnets. From Table 1, it is clear that the temperature change of Br is improved by containing Co in the Fe-BR magnet. Table 1 also lists the magnetic properties of each sample at room temperature. For most compositions, the coercive force iHc decreases due to Co substitution, but (BH)max increases due to the improved squareness of the demagnetization curve. However, when the amount of Co substitution increases, the iHc decreases significantly, so in order to obtain iHc≧1KOe as a permanent magnet material, the amount of Co is set to 50% or less. The reasons for the limitations described above regarding the lower limit and upper limit of B and the lower limit of R can be confirmed from Table 1 (and from FIGS. 3 and 4).

【table】

[Table] Table 1 lists many materials using mainly light rare earth elements such as Nd and Pr as R. Each of them shows high magnetic properties, and the temperature properties are further improved by replacing Fe with Co. has been done. As R,
Mixtures of two or more rare earth elements also prove useful. Furthermore, the obtained sintered bodies (Table 1 No. C2, No. 8, No.
24) was placed in a constant temperature and humidity chamber at 80°C and 90% relative humidity for 200 hours, and weight changes due to oxidation were measured. The rate of weight increase was significantly lower than that of No. C2), and the effect was noticeable depending on the amount of Co added. Next, Fe-Co-B-R in which part of Fe was replaced with Co
57Fe−20Co−8B− is a typical example of sintered magnet.
Figure 2 shows the magnetization curve of 15Nd at room temperature.
The initial magnetization curve 1 rises steeply in a low magnetic field and reaches saturation. The demagnetization curve has extremely high squareness, indicating that the magnet of the present invention is a typical high-performance anisotropic magnet. Judging from the shape of the initial magnetization curve 1, the magnet of the present invention is a so-called nucleation type permanent magnet whose coercive force is determined by the nucleation of reversal magnetic domains. Note that all of the other samples shown in Table 1 (excluding the comparative example) showed magnetization curves similar to those shown in FIG. 2. With a sample manufactured in the same manner as the above-mentioned process,
(82−x)x in the Fe−10Co−8B−xNd system
The relationship between the amount of Nd and Br and iHC was investigated by changing the value from 0 to 40. The results are shown in FIG. moreover,
(75−x)x in the system Fe−10Co−xB−15Nd
The relationship between the amount of B and Br, iHc was investigated by changing the value from 0 to 35, and the results are shown in FIG. The reason for limiting the numerical values of R and B in the present invention is also clear from FIGS. 3 and 4. Furthermore, by the same process, Fe-Co-B-R
In a four-component system, as an example (95-x-y)
The magnetic properties of the Fe-5Co-yB-xNd system were investigated by changing the three components Fe, B, and Nd, and the results are shown in FIG. 5 for (BH)max. The Fe-Co-B-R permanent magnet of the present invention uses an inexpensive R raw material as R, such as a mixture of light rare earths, especially light rare earths centered on Nd and Pr, and heavy rare earths, such as Mitsushimethane and didymium. High magnetic properties are obtained, and the Co content is 45% by weight.
% or less (50% or less in atomic %) is sufficient,
SmCo magnets require Sm and 50 to 65% Co by weight.
Compared to containing Fe-B-R, Sm is not required and Co can be saved, and the temperature characteristics are similar to that of Fe-B-R.
This was a marked improvement compared to other magnets. As detailed above, the present invention provides a novel Fe-Co-
The present invention provides a practical permanent magnet made of a BR-based magnetically anisotropic sintered body, and achieves magnetic properties higher than conventional levels without necessarily using Sm as R or using a large amount of Co. In its embodiment, the present invention further provides a practical high-performance permanent magnet that has a high coercive force and a high energy product superior to conventional magnets, and has temperature characteristics substantially comparable to conventional alnico and R-Co magnets. In a preferred embodiment, it also achieves the highest energy product ever achieved. In addition, as R, Nd, Pr
By using a light rare earth such as as the core of the rare earth, it is a permanent magnet that is excellent in terms of resources, price, and magnetic properties, and has extremely high industrial applicability. Furthermore, when compared with Fe-BR-based magnets, the inclusion of Co provides a sufficiently high Kurie point for practical use, expanding the range of applications and increasing practical value.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between the amount of Co (atomic % on the horizontal axis) and the Kyrie point in the (77-x)Fe-xCo-8B-15Nd system, and Figure 2 is a graph showing the relationship between the amount of Co (atomic % on the horizontal axis) and the Curie point in the (77-x)Fe-xCo-8B-15Nd system.
Magnetization curve of 8B-15Nd magnet at room temperature (initial magnetization curve 1, demagnetization curve 2, vertical axis is magnetization 4πI (kG), horizontal axis is magnetic field H (kOe)), Figure 3 is (82-x) Fe−
Figure 4 is a graph showing the relationship between the amount of Nd (atomic % on the horizontal axis) and iHc, Br in the 10Co-8B-xNd system. The graph showing the relationship between iHc and Br (horizontal axis atomic %) and Figure 5 show the relationship between the composition of the (95-x-y) Fe-yB-xR ternary component and ( BH) A three-component diaphragm showing the relationship with max is shown.

Claims (1)

[Claims] 1 Nd as a rare earth element (R) in atomic percentage;
At least one of Pr, Dy, Ho, Tb 8-30
%, B2~28% and the balance essentially consisting of Fe-
A permanent magnet characterized in that a part of the Fe is replaced with 50% or less (excluding 0%) of Co based on the total composition in a B-R magnetically anisotropic sintered permanent magnet. 2 The rare earth element (R) 12 to 20 in atomic percentage
% (However, more than 50% of the rare earth elements (R) are Nd
and Pr (1 or 2 types), B4 to 24% and the balance substantially consists of Fe, and a part of the Fe is added to the total composition.
The permanent magnet according to claim 1, wherein the permanent magnet is replaced with 45% or less of Co. 3 Nd as a rare earth element (R) in atomic percentage,
At least one of Pr, Dy, Ho, Tb and La,
Ce, Pm, Sm, Eu, Gd, Er, Tm, Yb, Lu,
A total of 8-30% of at least one type of Y, B2-
In an Fe-B-R magnetically anisotropic sintered permanent magnet consisting of 28% Fe and the remainder substantially Fe, a portion of the Fe is 50% or less (excluding 0%) of the total composition.
A permanent magnet characterized by substitution with Co. 4 The rare earth element (R) 12 to 20 in atomic percentage
% (However, more than 50% of the rare earth elements (R) are Nd
and Pr (1 or 2 types), B4 to 24% and the balance substantially consists of Fe, and a part of the Fe is added to the total composition.
4. The permanent magnet according to claim 3, wherein the permanent magnet is replaced with 45% or less of Co.