JPS6320411A - Production of material for permanent magnet - Google Patents

Abstract

PURPOSE:To obtain a raw material for a permanent magnet having high magnetic characteristics by melting specifically composed rare earth/boron/ferrous raw material and casting the melt thereof into a casting mold to cast an ingot, then subjecting the ingot to a heat treatment under specific conditions. CONSTITUTION:The compsn. expressed by the formula I is used for the raw material. In the formula, I, R; >=1 kinds among Nd, Dy and Tb, (a); 8-30atom%, (c); 2-28atom%. This raw material is melted and the melt thereof is cast into the casting mold to produce the ingot; thereafter, the ingot is heat-treated for 10min-10hr in an inert atmosphere or vacuum in a 950-1,120 deg.C range. The compsn. expressed by the formula II is otherwise used for the raw material. In the formula, R; >=1 kinds among Nd, Dy and Tb, X; >=1 kinds among Co, Si and Al, (a); 8-30atom%, (b); 0.1-20atom%, (c); 2-28atom%.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for producing a material for permanent magnets whose main components are rare earth elements, boron, and iron. It is intended to be used in the production of permanent magnets using powder metallurgy methods such as molding, sintering and annealing.

(Prior Art) Permanent magnetic materials are used in a wide range of applications, from various electrical appliances used in ordinary homes to peripheral terminal equipment for computers. In recent years, permanent magnet materials have been used to miniaturize electrical and electronic equipment,
With the demand for higher efficiency, efforts are being made to improve performance.

The typical permanent magnet materials currently used are alnico,
These include hard ferrite and samarium-cobalt magnets, but in recent years permanent magnets containing rare earth elements, boron, and iron as main components have been proposed as new high-performance permanent magnets. (Unexamined Japanese Patent Publication No. 5
Publication No. 9-46008) This magnet is produced by high-frequency melting of raw materials such as iron, boron, and rare earth metals, casting into water-cooled copper molds, etc. to obtain slabs, and then coarsely pulverizing the slabs using a stamp mill, Zic Ruffsha, etc. , further finely pulverized with a disk mill, ball mill, attritor, jet mill, etc. to a powder with an average particle size of 3 to 110 A1, and then molded by a magnetic field press to form a powder with an average particle size of 1000 to 120 A1.
After sintering at 0°C, it is manufactured by annealing at 400-900°C.

(Problems to be Solved by the Invention) The present invention attempts to produce a permanent magnet material having high magnetic properties by a simple method.

(Means for solving the problems) The present invention provides Fe1611-a-c RaBc or Fe1611-a-c RaBc
1O+1-m-b-0RaXbBc (R is Nd, D)
1. At least one type of Tb and X are Co.

At least one kind of Si + Al, a is 8 to 30 atomic percent, b is 0.1 to 20 atomic percent, C is 2 to 28 atomic percent
After melting a raw material with a composition of
10 in an inert atmosphere or vacuum at a temperature range of 20°C.
The purpose is to obtain a raw material for permanent magnets having high magnetic properties by heat treatment for a period of 10 minutes to 10 hours or by rapid cooling after the heat treatment.

The present invention will be explained below.

Water-cooled copper molds are used to manufacture slabs of rare earth, boron, and iron-based permanent magnet alloys, and conventional casting methods include rolling out slabs thinly and then casting them into box-shaped molds like bento boxes. A casting method with a faster solidification rate is used. The reason for increasing the solidification rate of slabs has not been clarified, and the method for stably obtaining sintered magnets with high magnetic properties has not yet been fully elucidated.As a result of various studies, the present inventor has made the following points. revealed.

Cast U-woven fabrics made of permanent magnet materials whose main components are rare earths, boron, and iron vary depending on the amount of boron and the amount of rare earth elements. There are various rare earth elements such as Nd and DV, but Nd is selected as the representative element, and below, iron-boron-N
The d system will be specifically explained.

The cast structure of Fe-B-Nd magnet materials changes depending on the amount of boron (B) and Nd, but usually the main phase is a tetragonal crystal (hereinafter referred to as T phase) consisting of Nd1Fe+4B, and there are other Nd-Fe in which Nd accounts for more than 80%
-B compound (hereinafter referred to as Ndrich phase), an Nd-Fe-B compound containing 5% by weight or more of B (hereinafter referred to as Br1ch phase), and Fe phase. Ndrich phase and Br
The 1ch phase appears as a band-like structure with a certain width in the main TI phase, and the Fe phase is scattered as dendrites or spherical particles within the crystal grains of the main TI phase.

When a slab with a thickness of 20 mm is produced using a normal cast iron mold, the width of the main phase T is about 100 μm,
Ndrich phase and Br1ch phase are localized when the width is 10μ or more, and in component systems with small amounts of Nd and B, Fe
It was found that a large number of phases appeared.

When a slab with a thickness of 5n+ is produced using a water-cooled copper mold, the main phase T is less than 10μ-, the Ndrich phase and Br1ch phase are less than 2μ, and especially the part in contact with the mold is T. , Ndrich phase, and Br1ch phase are all extremely refined. It was also found that only a small amount of Fe phase appears even in a component system with a small amount of Nd or Bfi.

When sintered magnets were produced by crushing these slabs, the magnetic properties of the sintered magnets varied widely and stable properties could not be obtained in the case of ordinary molds. In particular, when the Fe phase is large, the coercive force of the sintered body is almost zero, and although relatively stable magnetic properties were obtained from slabs made with water-cooled copper molds, it was found that the variation in coercive force was quite large. . As a result of these studies, it became clear that the higher the solidification rate of the slab, the more stable the magnetic properties of the sintered magnet.

However, there are many problems in the case of slabs that solidify at a high rate, such as water-cooled copper molds. It became clear that the structure of the part in contact with the mold was refined; It has become clear that when sintered magnets are manufactured by crushing pieces, a mixture of large and small crystal grains results, resulting in variations in magnetism.

Therefore, as a result of intensive study on the metallurgical structure of sintered magnets that can obtain stable magnetic properties and a high maximum energy product (BH) i + ax, which represents the strength of the magnet, we found that the main phase T1
The grain size of the phase is 3 to 30 μm, and the grain size of the Ndrich phase and Br1ch phase is 1 to 20 μm.
It was revealed that the structure was changed so that the ich phase and the Br1ch phase surrounded the main T phase, and the proportion of the Fe phase was 10% or less, preferably 5% or less.

In order to obtain such a structure, it is important to balance the structure of the slab, which is the starting material for the powder.

For this purpose, we have found that heat treating the slab is extremely effective. For example, when a slab manufactured using a water-cooled copper mold is heated in an argon atmosphere or vacuum for 10 minutes to 10 hours in the temperature range of 950°C to 1120°C, the main phase T1 phase changes from 10 to 100.17- as the structure of the slab. The width of the Ndrich phase and the Br1ch phase ranges from 3 to 30μ, and the structure of the entire slab is made uniform. In addition, even in slabs manufactured using normal molds, the Mi texture is made uniform by heat treatment at 950°C to 1120°C, resulting in Ndrich phase and Br.
It was found that the localization of the 1ch phase disappeared, and at the same time, the harmful Fe phase disappeared. It has been found that when sintered magnets are manufactured by making powder from cast slabs that have undergone such heat treatment, the magnetic properties are extremely high and stable, especially the coercive force. The reason for limiting the heat treatment temperature to 950°C to 1120°C is that below 950°C, the diffusion of the elements that make up the Mi weave of the slab is slow (and the desired structure cannot be adjusted), and above 1120°C, the elements that make up the Mi weave of the slab cannot be adjusted. This is because the composition changes, making it difficult to adjust the structure in the same way.The heat treatment time is within the range of 950°C to 1120°C, and stable structure adjustment can be achieved in a low temperature for a long time and a high temperature for a short time. .

Alloy slabs containing rare earth elements are highly susceptible to oxidation, so they must be heat-treated in an inert atmosphere such as argon or helium, or in a vacuum. Furthermore, rapid cooling after heat treatment facilitates pulverization in the subsequent process, makes powder production more effective, and helps prevent oxidation.

Furthermore, depending on the component system, even if the Fe phase is once reduced by heat treatment, it may reappear if the cooling is slow, but rapid cooling is advantageous in that it prevents this. Cooling can be done by gas cooling such as argon gas (and preferably rapid cooling such as water quenching).By performing such heat treatment, it has become possible to manufacture high-performance permanent magnets with stable magnetic properties.

In the above explanation, Nd was mainly selected as the rare earth element in the component system mainly composed of rare earth elements, boron, and iron.
A part of Ndl is replaced with other rare earth elements oy, Tb.

If substituted with Co, Aj! The same effect can be obtained by heat treating the slab when elements such as , Si, etc. are added.

Co, Aj again! , the coercive force increases with the addition of Si,
It also has the effect of improving the temperature characteristics of a magnet.

Here, the reason why the ranges of R, X, and B are specified in the present invention will be explained.

If R (Nd, Dy, Tb) is less than 8 at%, a compound (Nd2Fe, B, main phase) for generating magnetism will not be formed, and if it exceeds 30 at%, it will oxidize and burn easily, and it is expensive. For this reason, it was set to 8 to 30 atχ.

X (Co, St, Al) is added to increase the coercive force, and if it is less than 0.1 atχ, it has no effect, and if it exceeds 20 atχ, the Fe content will decrease and the residual magnetism Br will decrease, so 0.1 ~20atχ.

The range of B is determined by the relationship with Fe and R, but in order to make the coercive force more than IKOe, it needs to be more than 20 at%, and in order to make it have a high magnetic flux density, it needs to be less than 28%. Since it is necessary, it was set to 2 to 28 atχ.

(Examples) Example 1 A cast slab with a thickness of 5 mm containing rare earth elements, boron, and iron as main components was manufactured by melting raw materials in a high-frequency melting furnace. This slab was heat treated at 950°C to 1100°C in an argon atmosphere and water quenched. This slab was coarsely crushed using a di-crusher and then ground into powder having an average particle size of 5 μm using a ball mill. The powder was compacted by a magnetic field press at a pressure of 2t/aj and a magnetic field of 15KG, and after sintering in argon at 1080℃ for 1 hour,
Annealing was performed at ℃ for 1 hour. The residual magnetic flux density Br, coercive force iHc, and maximum energy product (B) s+ax were measured as the magnetic properties of the sintered body. The values are shown in Table 1.

For comparison, the table also shows the case where no heat treatment was performed.

(Effects of the Invention) According to the present invention, it is possible to easily produce a material for a permanent magnet that has high magnetic properties as a sintered permanent magnet and can be used for producing stable products. is useful in industrial soil plowing.

Claims (4)

[Claims] (1) Fe_1_0_0_-_a_-_cR_aB_c
(R is at least one of Nd, Dy, Tb, a is 8-3
0 atomic percent and c is 2 to 28 atomic percent) is melted and cast into a mold to produce a slab. A method for producing a permanent magnet material, which comprises performing heat treatment in a vacuum for 10 minutes to 10 hours. (2) Fe_1_0_0_-_a_-_b_-_cR_
aX_bB_c (R is at least one of Nd, Dy, and Tb
species, X is at least one of Co, Si, Al, a is 8-8
30 atomic percent, b is 0.1 to 20 atomic percent, and c is 2 to 28 atomic percent) is melted and cast into a mold to produce a slab.
A method for producing a permanent magnet material, characterized by heat treatment in an inert atmosphere or vacuum at a temperature range of 50°C to 1120°C for 10 minutes to 10 hours. (3) Fe_1_0_0_-_a_-_cR_aB_c
(R is at least one of Nd, Dy, Tb, a is 8-3
0 atomic percent and c is 2 to 28 atomic percent) is melted and cast into a mold to produce a slab. A method for producing a permanent magnet material, characterized by heat treatment in vacuum for 10 minutes to 10 hours and then rapid cooling. (4) Fe_1_0_0_-_a_-_b_-_cR_
aX_bB_c (R is at least one of Nd, Dy, and Tb
species, X is at least one of Co, Si, Al, a is 8-8
30 atomic percent, b is 0.1 to 20 atomic percent, and c is 2 to 28 atomic percent) is melted and cast into a mold to produce a slab.
A method for producing a material for a permanent magnet, characterized by heat treatment in an inert atmosphere or vacuum for 10 minutes to 10 hours at a temperature range of 50°C to 1120°C, followed by rapid cooling.