KR930002559B1 - Permanent magnet and making method thereof - Google Patents

Abstract

A permanent magnet made from an alloy comprising at least one rare earth element, iron and boron characterised in that the average grain diameter of the crystals of the alloy is not more than 150 mu m, the carbon content and the oxygen content of the alloy being not more than 400 ppm and not more than 1000 ppm respectively.

Description

Permanent magnet and its manufacturing method

1 is a graph showing the relationship between the average particle diameter after the address (μm) and the coercive force (iHc) after a high temperature press in the embodiment.

2 is a process diagram according to an embodiment of the present invention.

The present invention relates to a permanent magnet based on rare earth elements, iron and boron, and a method for producing the same.

Permanent magnets are one of the important electrical and electronic materials used in a wide range of fields, from electrical appliances in general households to peripheral terminals in large computers.

With the recent demand for miniaturization and high efficiency of electrical appliances, permanent magnets are also increasingly required for high performance. Representative permanent magnets currently used are alnico, hard ferrite and rare earth transition metal magnets. In particular, since R-CO permanent magnets and R-Fe-B permanent magnets, which are rare earth transition metal magnets, have high magnetic performance, they have been researched and developed in the past.

Conventionally, the manufacturing method of these R-Fe-B permanent magnets has the method as shown to the following literature.

(1) Methods by sintering based on powder metallurgy (documents 1 and 2).

(2) Resin bonding method using quenching flakes by melt spinning method using quenching flakes having a thickness of about 30 μm in a quenched thin strip manufacturing apparatus used to manufacture amorphous alloy and using the flakes as a magnet in the resin bonding method (Document 3) , Document 4).

(3) The method of performing a mechanical orientation process of the quenching flakes used by the method of (2) mentioned above by the two-step high temperature press method (document 4, document 5).

here

Document 1; Japanese Patent Application Laid-Open No. 59-46008

Document 2; J. Appl, Phys, Vol. 55 (6) (March 15, 1984), page 2083 (M. Sagawa, S.Fujimura, N.Togawa, H.Yamamoto and Y.Matsuura)

Document 3; Japanese Patent Application Laid-Open No. 59-211549

Document 4; App 1, Phys, Lett Vo 1. 46 (8) (April 15, 1985) Page 790 (R.W.Lee)

Document 5; Japanese Patent Application Laid-Open No. 60-100402

Next, the above conventional method will be described.

First, in the sintering method of (1), an alloy ingot is formed by melting and casting, the ingot is pulverized to a particle size of about 3 µm, mixed with a binder, and pressed to form a molded body during storage.

The molded body is sintered for 1 hour at a temperature around 1100 ° C. in argon gas, and then the coercive force is improved by heat treatment at a temperature around 600 ° C.

In the resin bonding method using the quenching flakes by the melt spinning method of (2), the thickness of the R-Fe-B alloy is 30 µm in order to optimize the rotational speed of the quenching thin strip manufacturing apparatus so that it becomes an aggregate of polycrystals having a diameter of 1000 mm or less. Make ribbon flakes. The crystal axes of the crystal grains in the flakes are isotropically distributed, magnetically isotropic, and when they are pulverized to an appropriate particle size, kneaded with a resin and press-molded, an isotropic magnet is obtained.

In the manufacturing method by the two-step high temperature press of (3), the ribbon type quenching flakes used in (2) are pressed at the pressure of 1.4 ton / cm <2> or less in the vacuum or near 70000 degreeC in inert gas. Next, pressing the same thickness at 0.7 ton / cm 2 for several seconds at the same temperature of 700 ° C. makes the alloy anisotropic and an R-Fe-B magnet having anisotropy with high density can be manufactured.

In addition, an alloy having coercive force in the bulk state is also produced by the liquid dynamic cmopaction method (hereinafter referred to as LDC method) (Document 6; J. Appln. Phys. 59 (4) (February 15, 1986) Page 1297 (TSChin et al.).

In the above-described prior art, permanent magnets based on rare earth elements, iron and boron as basic components can be produced, but these manufacturing methods have the following drawbacks.

In the sintering method of (1), it is essential to use an alloy as a powder. However, in the R-Fe-B-based magnetic alloy, the powder is very active against oxygen, so the powder used for the sintering method needs to be managed strictly and inert gas. Expensive facilities such as atmospheres are necessary.

In addition, in the sintering method, there is a problem in that the carbon of the binder adversely affects the magnetic performance, and a problem of worsening the production efficiency that the handling of a molded body called a green body is difficult, resulting in a low raw material cost of the R-Fe-B magnet. It's hard to say it's a good way to get angry.

In addition, the methods of (2) and (3) require a low-productivity, more expensive equipment, such as a vacuum melt spinning apparatus or a hot press.

Furthermore, the resin-bonded magnet of (2) is not isotropic and high energy is not obtained, and it is also disadvantageous in terms of using the temperature characteristic.

In addition, the method of (3) is very poor in productivity due to the two-stage and high temperature press, and it is not possible to sufficiently reduce the raw material cost of the R-Fe-B magnet as in the sintering method.

The LDC method also has problems of expensive equipment and deterioration of production efficiency.

The present invention solves the above-mentioned drawbacks of the prior art, and an object thereof is to provide a high performance and low cost rare earth-iron permanent magnet and a manufacturing method thereof.

The permanent magnet of the present invention is a magnet having a rare earth element (including Y), iron and boron as a basic component, and has a crystal average particle diameter of 150 µm or less and 400 ppm or less of carbon and oxygen, respectively. The permanent magnet is characterized in that less than 1000ppm.

The first method of manufacturing the permanent magnet is a manufacturing method of a magnet having a rare earth element (including Y) and iron and boron as a basic component, so that the average crystal grain size thereof is 150 µm or less. The method of producing a permanent magnet is characterized by casting and subsequent heat treatment at 250 ° C or higher.

A second method of manufacturing the permanent magnet is a method of producing a permanent magnet, wherein the magnet is anisotropically formed by hot working at a temperature of 500 ° C. or higher after casting in the first manufacturing method.

The third method of manufacturing the permanent magnet is a method of manufacturing the permanent magnet, characterized in that heat treatment is performed at 250 ° C. or higher after the hot working in the second manufacturing method.

Preferred compositions of the rare earth element used in the present invention and the permanent magnet based on iron and boron are 8 to 30 atom% of rare earth elements, 2 to 28 atom% of boron, and the rest of iron.

As the rare earth element, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu are used, but Nd and Pr are particularly preferable.

And 2 or more types of these rare earth elements may be contained. In addition to the above basic components, impurities unavoidable in the manufacturing process may be included, and for the improvement of the Curie temperature and the temperature characteristics, the cobalt number, and the coercive force, Al, Cr, Mo, W, Nb, Ta, Zr, Hf , Ti, etc. may be included.

Moreover, in the manufacturing method of this invention, when the content of carbon and oxygen in a magnet exceeds 400 ppm and 1000 ppm, respectively, the magnetic performance will deteriorate, so it was set to 400 ppm or less and 1000 ppm or less.

In the R-Fe-B magnet, the grain size must be appropriate for obtaining the coercive force in the bulk state.

That is, if the average particle diameter after casting exceeds 150 µm, even if hot working is performed after casting, the coercive force is less than 4 KOe of the ferrite magnet and it is hard to say that it is a practical permanent magnet alloy. Therefore, the average particle diameter must be 150 µm or less. These particle size control can be performed by changing the cooling temperature by adjusting the mold material and the heat capacity of the mold.

The heat treatment after casting is necessary to diffuse the Fe phase present as primary in the cast alloy and to remove the magnetic soft phase, and of course, the same heat treatment after hot working has an effect of improving its magnetic properties.

Hot working at a temperature of 500 ° C. or more has the effect of orienting the crystal axes of the crystal grains and anisotropicizing them, and miniaturizing the grains, and greatly improving magnetic performance.

Next, examples of the present invention will be described.

Example 1

Table 1 describes the composition of the various rare earth elements and permanent magnet alloys based on iron and boron made by the following steps.

First, the required composition alloy was melted in an Ar atmosphere using a low frequency melting furnace, cast at 1000 ° C. in various molds, and the cast alloy was taken out after 20 minutes. At this time, a rare earth metal having a purity of 95% (impurity is mainly a rare earth metal) was used, a transition metal having a purity of at least 99.9%, and a boron ferroborn alloy was used.

These cast alloys were subjected to heat treatment at 250 ° C. or higher (24 hours at 1000 ° C.) for cutting and grinding to obtain permanent magnets.

In Table 2, the magnetic performance and average particle diameter in the case of casting using an iron mold in each composition are shown.

1 shows the relationship between the average particle diameter after casting and the coercive force (iHc) after hot pressing in a sample using the compositions of Nos. 3 and 4 in Table 1. FIG. At this time, the control of the particle diameter was performed by applying various molds and vibrations such as water-cooled copper molds, iron molds, ceramic molds, and the like to the molds. From this result, it can be seen that the permanent magnet having a high coercive force is obtained by casting with a controlled particle diameter.

[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 anisotropically formed by hot pressing at 1000 ° C.

The average particle diameter and magnetic performance when the heat treatment in the casting step at this time, and the average particle diameter and magnetic performance after hot pressing are shown in Table 4.

In addition, the magnetic properties of the samples No11, No13, and No14 when the heat treatment at 1000 DEG C for 24 hours after hot pressing are further shown in Table 5.

[Table 3]

[Table 4]

[Table 5]

As a result, it can be seen that the magnetic performance is greatly improved and the magnetic performance is improved by heat treatment as the particle diameter is reduced by hot working.

Moreover, in the Example of this invention, the content of carbon and oxygen in the magnet obtained by employing the casting method were 400 ppm and 1000 ppm or less, respectively.

In addition, referring to Figure 2, a manufacturing process diagram according to the method of the present invention, after casting, hot working by heat treatment, and then processed and coated by the permanent magnet of the present invention is produced.

As described above, according to the permanent magnet of the present invention and the manufacturing method thereof, the coercive force is obtained in the bulk state without crushing the casting ingot, it is possible to significantly simplify the manufacturing process, low cost and high performance permanent magnet alloy Can be manufactured.

Claims (4)

In permanent magnets based on rare earth elements (including Y) and iron and boron, the crystals have an average particle diameter of 150 µm or less, and carbon and oxygen content of 400 ppm or less and 1000 ppm or less, respectively. Permanent magnets. In the method for producing a permanent magnet based on rare earth elements (including Y), iron and boron, casting is performed so that its average grain size is 150 μm or less, and then heat treatment is performed at 250 ° C. or higher. Method of producing a permanent magnet. In the method for producing a permanent magnet based on rare earth elements (including Y) and iron and boron, casting is performed so that the average crystal grain size is 150 µm or less, followed by hot working at a temperature of 500 ° C or higher. Method for producing a permanent magnet, characterized in that the magnetized anisotropic. In the method for producing a permanent magnet based on rare earth elements (including Y) and iron and boron, casting is performed so that the average crystal grain size is 150 µm or less, followed by hot working at a temperature of 500 ° C or higher. After anisotropy, a heat treatment at 250 ° C. or higher is then performed.

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