JPH06224018A - Manufacture of r-fe-b-based sintered magnet - Google Patents

Abstract

PURPOSE:To enhance the magnetic characteristics by improving the orientation of molded body during the molding step in a magnetic field in order to manufacture an R-Fe-B-based sintered magnet. CONSTITUTION:Within the manufacturing method of R-Fe-B-based sintered magnet, 8-30 atomic % of R (where R: at least one of rare earth elements including Y) 2-28 atomic % of B, element M not exceeding specific atomic % (where M: combination of one or two of Co not exceeding 50 atomic %, Al, V, Mo, W, Ta, Nb not exceeding 9.5 atomic % Si, Ca, Mg, Ni, Mn, Cr not exceeding 8.0 atomic %, Ti, Zr, Hf not exceeding 4.5 atomic %, Cu, C not exceeding 3.5 atomic % and Zn not exceeding 0.2 atomic %. Furthermore, the total amount of M in the case of including exceeding two kinds of elements including (the value not exceeding the maximum value out of said element M) is to be sintered after the molding step of the residual Fe and the alloy particles comprising the indispesable impurities in the manufacture in pulse magnetic field.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a rare earth-iron-boron system sintered permanent magnet.

[0002]

2. Description of the Related Art In recent years, along with the market trend toward miniaturization and weight reduction of electronic equipment and precision equipment, rare earth magnets have been used in many fields in permanent magnets instead of conventional alnico and ferrite magnets. It was Among rare earth permanent magnets, there is an increasing demand for rare earth-iron-boron-based magnets that can obtain a high energy product, and there is a tendency for higher energy products and higher coercive force to be required than ever. Various attempts have been made to improve the magnetic properties of rare earth-iron-boron magnets, and many inventions based on various additive elements have been disclosed. In addition, many inventions of rare earth-iron-boron magnets by superquenching method, which is an alternative to the conventional powder metallurgy method, have been disclosed. Unlike the powder metallurgy method, the ultra-quenching method
It is not practical because it requires hot plastic working such as upsetting or extrusion to obtain a high energy product, which increases manufacturing costs. Therefore, most of the rare earth-iron-boron based magnets having the energy product of 40 MGOe or more which are currently put to practical use in the market are manufactured by using the powder metallurgy method.

[0003]

By the way, in the method for producing this rare earth-iron-boron system sintered magnet by the powder metallurgy method, an ingot is obtained by melting the rare earth-iron-boron system alloy in a target composition. Has an average particle size of 20 to 500 μm
After roughly pulverizing to a certain degree and further finely pulverizing this to a powder of about 1 to 20 μm, in order to obtain an anisotropic sintered magnet, it is common to perform molding in a magnetic field, and then perform a step of sintering and heat treatment. is there. Then, as one method for producing an anisotropic sintered magnet having high characteristics, it has been studied to improve the degree of orientation after molding in a magnetic field as much as possible. It is possible to increase the applied magnetic field strength in order to improve the degree of orientation in the magnetic field molding, but the magnetic field strength cannot be extremely increased because the amount of heat generated by the coil of the magnetic field generator increases.

Therefore, an object of the present invention is to improve the magnetic properties by improving the degree of orientation of the molded body in the magnetic field molding when manufacturing the rare earth-iron-boron system sintered magnet.

[0005]

According to the present invention, the atomic percentage of R is 8 to 30% (where R is at least one rare earth element containing Y), 2 to 28% of boron B, and a predetermined amount of element or less. M
(Here, M is Co of 50% or less and A of 9.5% or less.
l, V, Mo, W, Ta, Nb, Si of 8.0% or less,
Ca, Mg, Ni, Mn, Cr, Ti of 4.5% or less,
One or a combination of two or more of Zr, Hf, Cu, C of 3.5% or less and Zn of 0.2% or less, which is 2
The total amount of the element M in the case of containing more than one kind is less than or equal to the value of the element M having the maximum value), and the balance Fe and the alloy powder consisting of impurities unavoidable in production are molded in a pulsed magnetic field and then fired. And a rare earth-iron-boron-based sintered magnet manufacturing method. The greatest feature of the present invention is that the powder is molded in a pulsed magnetic field. That is, the orientation degree is improved by applying a large magnetic field using a pulsed magnetic field having a short application time.

The reasons for limiting the component range in the present invention are as follows. The reason why R is set to 8 to 30% is that if it is less than 8%, a coercive force of 1 kOe exceeding hard ferrite cannot be obtained, and if it exceeds 30%, the alloy powder easily burns and mass production becomes extremely difficult. The reason why the content of boron is 2 to 28% is that when the content is 2% or more, the coercive force and the residual magnetic flux density are improved, but when the content exceeds 28%, the residual magnetic flux density of hard ferrite cannot exceed about 4 kG. is there. The balance is Fe and unavoidable impurities, but part of Fe may be replaced with M element. The oxygen content of the sintered magnet obtained by the present invention is preferably in the range of 0.1 to 1.2 wt%. 0.1 wt. %, It is difficult to make it less than 1.2%, and if it exceeds 1.2 wt%, the magnetic properties deteriorate and it becomes impossible to fully enjoy the effect of improving the orientation degree by the pulsed magnetic field.

[0007]

Example As a starting material, a purity of 99.9 wt. % Electrolytic iron, electrolytic cobalt, and boron having a purity of 99 wt. %
Of boron, with R having a purity of 99.7 wt. % Nd, 8% B, 5% Nd in atomic percentage
% Co and the balance Fe were weighed so as to obtain a final sintered body, high-frequency melted, and cast in a water-cooled copper mold to obtain an alloy ingot. The alloy ingot was roughly crushed with a stamp mill and then finely powdered with an average particle diameter of 3 μm by a jet mill.

Next, after filling a molding raw material into a molding space formed by a die and a lower punch, magnetic field strengths 16, 23,
With a pulsed magnetic field of 32 and 43 kOe, so-called transverse magnetic field molding was performed in which the pressing direction and the magnetic field orientation direction were orthogonal to each other. The molding pressure is 1 t / cm ² . The obtained molded body is 108
After sintering at 0 ° C. for 1 hour, it was once held at 920 ° C. for 2 hours, gradually cooled to room temperature, again treated at 680 ° C. for 2 hours and rapidly cooled to room temperature to obtain a sintered magnet. The sintering and heat treatment atmosphere was vacuum. Further, a sintered magnet was obtained in the same manner as above (conventional example) except that the molding in a magnetic field was performed in a conventional static magnetic field (10 kOe, 1 t / cm ² ). Magnetic properties of the obtained magnet (residual magnetic flux density Br, maximum energy product (BH)
max) is shown in Table 1. The amount of oxygen contained in the magnet was 0.55 to 0.65 wt%.

[0009]

[Table 1]

Next, a pulsed magnetic field (23 kOe) during molding
The relationship between the number of applications and the magnetic characteristics was investigated. The results are shown in FIG. 1, and it can be seen that the magnetic characteristics are improved by increasing the number of times the pulsed magnetic field is applied.

[0011]

As described above, according to the present invention, magnetic characteristics can be improved by using a pulsed magnetic field for forming in a magnetic field.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the number of times a pulsed magnetic field is applied and magnetic characteristics.

Claims (2)

[Claims] 1. Atomic percentage of 8 to 30% R (provided that R is at least one rare earth element including Y), 2 to 28% boron B, and a predetermined% or less element M (where M is 50 % Or less Co, 9.5% or less Al, V, Mo, W, Ta, Nb, 8.0% or less Si, Ca, Mg, Ni, Mn, Cr, 4.5% or less Ti, Zr , Hf, 3.5% or less of Cu, C, and 0.2% or less of Zn, and the total amount of the element M in the case of including two or more is the element M. (Less than or equal to the value having the maximum value), the alloy powder containing the balance Fe and impurities unavoidable in production is molded in a pulsed magnetic field and then sintered, and then the rare earth-iron-boron-based firing is performed. A method for manufacturing a magnet. 2. The method for producing a rare earth-iron-boron-based sintered magnet according to claim 1, wherein the forming in the pulsed magnetic field is such that the pressing direction and the magnetic field orientation direction are orthogonal to each other.