JP2992808B2 - permanent magnet - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a permanent magnet containing a rare earth element, iron and boron as basic components. 2. Description of the Related Art Permanent magnets are one of important electric and electronic materials used in a wide range of fields, from various home appliances to peripheral terminals of large computers. [0003] With the recent demand for miniaturization and higher efficiency of electric products, permanent magnets are also required to have higher performance. Representative of the permanent magnets currently used are alnico hard ferrites and rare earth-transition metal based magnets. In particular, R-Co which is a rare earth-transition metal based magnet
Many permanent magnets and R-Fe-B permanent magnets have been researched and developed since high magnetic performance can be obtained. Conventionally, as a method of manufacturing these R—Fe—B permanent magnets, there is a method disclosed in the following literature. (1) A method based on sintering based on powder metallurgy. (Reference 1, Reference 2) (2) A quenched thin strip manufacturing apparatus used to manufacture an amorphous alloy, quenched thin flakes having a thickness of about 30 μm, and quenched by melt spinning, in which the flakes are magnetized by a resin bonding method. Resin bonding method using (References 3 and 4) (3) A method of subjecting the quenched flakes used in the method (2) to mechanical orientation treatment by a two-stage hot press method. (Documents 4 and 5) Here, Document 1: JP-A-59-46008; Sagawa, S .; Fujimura,
N. Togawa, H .; Yamamoto, and
Y. Matsuura; Appl, Phys, Vo
1, 55 (6) 15 March 1984, p208
3, Reference 3: JP-A-59-211549; Reference 4: R.I. W. Lee; Appl, Phys, Let
t. Vol, 46 (8 ) 15 April April 1985, p.
790; Reference 5: JP-A-60-100402 Next, the above-mentioned conventional method will be described. First, in the sintering method (1), an alloy ingot is prepared by melting and casting, and the ingot is ground to a particle size of about 3 μm, kneaded with a binder, and press-molded in a magnetic field to form a compact. Is completed. [0007] This compact is heated at 1100 ° C in argon gas.
The coercive force is improved by sintering at a temperature of about 600 ° C. for one hour and then performing a heat treatment at a temperature of about 600 ° C. In the resin bonding method using quenched flakes by the melt spinning method (2), the number of rotations of the quenched ribbon manufacturing apparatus is first optimized to form a polycrystalline aggregate having a diameter of 1000 ° or less. R-Fe-B alloy thickness 30
A μm ribbon-shaped flake is prepared. The crystal axes of the crystal grains in the flakes are isotropically distributed and are magnetically isotropic. If the particles are ground to an appropriate particle size, kneaded with a resin and press-molded, an isotropic magnet is formed. Is obtained. In the production method by the two-stage hot press of (3), the ribbon-shaped quenched flake used in (2) is subjected to a pressure of 1.4 to about 700 ° C. in a vacuum or an inert gas.
Pressed at n / cm2 or less. Next, when the thickness is reduced to the first half by pressing at 700 ° C. at 0.7 ton / cm 2 for several seconds, the alloy becomes anisotropic, and is a dense and anisotropic R-Fe—B magnet. Can be manufactured. [0011] Also, Liquid dynamic co.
Alloys having a coercive force in a bulk state have also been made by the impaction method (hereinafter referred to as the LDC method). (Reference 6) Reference 6: T.I. S. Chin et al. Appl. Ph
ys. 59 (4), 15 February 1986,
[0012] Although the above-mentioned prior art can produce a permanent magnet containing a rare earth element, iron and boron as its basic components, the following problems are involved in these production methods. doing. In the sintering method (1), it is essential to make the alloy into a powder. However, in the case of an R—Fe—B magnet alloy, the powder is very active against oxygen. It is necessary to strictly control the powder used for the above, and expensive equipment such as an inert gas atmosphere is required. In the sintering method, there is a problem that the carbon of the binder has a bad influence on the magnetic performance and a problem that the production efficiency is deteriorated such that it is difficult to handle a green body called a green body. It is hard to say that it is a method that can sufficiently bring out the low cost of raw materials. Further, the methods (2) and (3) require expensive equipment such as a vacuum melt spinning apparatus or a hot press, which has low productivity. In addition, the resin-bonded magnet (2) is isotropic and cannot provide a high energy product, and is disadvantageous in terms of temperature characteristics and use. Furthermore, the method (3) has a very low productivity because of the two-stage hot pressing, and the R-Fe-
It is not possible to sufficiently bring out the low material costs of the B-based magnet. The LDC method also has problems such as expensive equipment and poor production efficiency. The present invention solves the above-mentioned problems of the prior art, and aims at high performance and high performance.
An object of the present invention is to provide a low-cost rare earth-iron permanent magnet . Means for Solving the Problems A permanent magnet according to the present invention comprises: (1) a rare earth element (including Y), iron and boron as basic components, and a cast ingot obtained by casting into a powder process. The magnet has a crystal average particle size of 1 to 100 μm, contains trace amounts of carbon and oxygen , and has a content of 4 % each.
A permanent magnet characterized by being at most 00 ppm and at most 1,000 ppm. (2) When the magnetic energy product BH (max) is 1
It is not less than 8.5 MGOe. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The permanent magnet of the present invention contains a rare earth element, iron and boron as basic components, and its preferred composition is 8 to 30 atomic% of a rare earth element. , Boron 2-28
Atomic%, balance being iron. As rare earth elements, Y, La, Ce, P
r, Nd, Pm, Sm, Eu, Gd, Tb, Dy, H
o, Er, Tm, Yb, and Lu are used.
Pr is preferred. Further , two or more of these rare earth elements may be contained. Further, it may be included manufacturing process unavoidable impurities in addition to the basic components described above, contain a cobalt to improve Curie temperature and the temperature characteristics
Is also good. To improve coercive force, Al, Cr, M
o, W, Nb, Ta, Zr, Hf, 1 kind of such as Ti
Or it may contain two or more. The permanent magnet of the present invention is obtained by casting.
From the ingot of the composition, a powder process, namely grinding,
Manufactured without going through processes such as molding and sintering of crushed materials
Things. For example, as shown in the examples described later,
Heat treatment and hot working
Hot-working and then heat treatment
It is manufactured. Such a permanent magnet of the present invention
Is s content of carbon and oxygen in the magnet husband 400pp
m and 1000 ppm or less. Carbon and
Oxygen content of 400 ppm and 1000 ppm, respectively
Exceeding the range degrades magnetic performance. Such extremely
The low carbon and oxygen concentrations indicate that the magnets
It is manufactured without going through a powder process where oxygen and oxygen are easily mixed.
Is achieved because of In order to obtain a coercive force in a bulk state in the R-Fe-B magnet, the crystal grain size must be appropriate. That is, the average crystal grain size after casting (hereinafter simply referred to as
Exceeding also referred to) is 100 [mu] m "average particle size", be subjected to a hot working after casting, coercivity, since below the 4k0e ferrite magnet becomes difficult to say that practical permanent magnet alloy, the average The particle size must be less than 100 μm. In addition, when the thickness is less than 1 μm, it is difficult to manufacture by a casting method.
It is. The control of the particle size can be performed by changing the conditions such as the cooling rate by adjusting the mold material and the heat capacity of the mold. The heat treatment after casting is necessary for diffusing the Fe phase existing as a primary crystal in the cast alloy to eliminate the magnetically soft phase. Of course, the same heat treatment is performed after hot working. This has the effect of improving its magnetic properties. [0029] To hot working at 500 ° C. or higher, there is an effect of effectively and refining the crystal grains anisotropic reduction by orienting the crystal axes of the crystal grains, greatly magnetic performance Will be improved. In the permanent magnet of the present invention
More preferable are those in Table 4 in Examples described later.
As shown in the column “After hot pressing” and in Table 5,
Energy product (BH) max is 18.5MGOe or more
To achieve. Next, an embodiment of the present invention will be described. EXAMPLES Example 1 Table 1 shows compositions of various rare earth elements, and permanent magnet alloys containing iron and boron as basic components, manufactured by the following steps. Firstly the desired alloy composition was dissolved using a low-frequency melting furnace in an Ar atmosphere, then granulated cast into various molds, was removed 20 minutes after casting alloys. At this time, a rare earth metal having a purity of 95% (impurities were mainly other rare earth metals) was used, a transition metal having a purity of 99.9% or more was used, and boron was a ferroboron alloy. Then, these cast alloys were subjected to a heat treatment at 250 ° C. or more (at 1000 ° C. for 24 hours), cut and ground to obtain permanent magnets. Table 2 shows the magnetic performance and the average particle size when each composition was cast using an iron mold. FIG. 3 and No. 4 shows the relationship between the average grain size (μm) after casting and the coercive force iHc after hot pressing in a sample using the composition of No. 4. [0036] At this time, control of particle size was performed, such as by may grant a water-cooled copper mold, an iron mold, or using various molds such as ceramic molds, vibration to the mold. From these results, it can be seen that a permanent magnet having a high coercive force can be obtained by casting with controlled grain size. The sample No. 10 is flat
This is a comparative example when the average particle size is 150 μm. [Table 1] [Table 2] (Example 2) The composition of the permanent magnet alloy shown in Table 3 was cast using a water-cooled copper mold in the same manner as in Example 1, and then hot-pressed at 1000 ° C to make it anisotropic. Table 4 shows the average particle size and magnetic performance when heat-treated at the casting stage and the average particle size and magnetic performance after hot pressing. In addition, No. 11 and No. 13, No. 1
After hot pressing the sample of No. 4 further at 1000 ° C., 2
Table 5 shows the magnetic properties when the heat treatment was performed for 4 hours. [Table 3] [Table 4] [Table 5] As is apparent from the results, it is understood that the grain size is reduced by the hot working and the magnetic performance is greatly improved, and that the magnetic performance is improved by the heat treatment. Further, in Examples of the present invention, carbon and oxygen contained in the obtained magnet were 400 ppm and 1000 ppm or less, respectively, by employing the casting method. As described above, according to the permanent magnet of the present invention, the coercive force can be obtained in a bulk state without crushing the cast ingot, so that the manufacturing process can be significantly simplified and the cost can be reduced. And a high-performance permanent magnet is provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing a relationship between an average particle size (μm) after casting and a coercive force iHc after hot pressing in Examples.

Continuation of front page    (72) Inventor Tatsuya Shimoda               3-3-5 Yamato, Suwa City, Nagano Prefecture Say               Coepson Corporation                (56) References JP-A-61-238915 (JP, A)                 JP-A-62-205226 (JP, A)

Claims (1)

(57) [Claims] A permanent magnet comprising a rare earth element (including Y), iron and boron as basic components, and a cast ingot obtained by casting without passing through a powder process, wherein the magnet has an average crystal grain size of 1 to 1. A permanent magnet, which is 100 μm , contains trace amounts of carbon and oxygen , respectively , and has a content of 400 ppm or less and 1000 ppm or less, respectively. 2. The permanent magnet according to claim 1, wherein a magnetic energy product BH (max) is 18.5 MGOe or more.