KR100366860B1 - Raw material for permanent magnets and production method of the same - Google Patents

Abstract

Provided is a samarium-iron-boron-based permanent magnet material that is easy to manufacture and excellent in magnetic properties, and a method of manufacturing the same.

In the permanent magnet material, samarium and boron diffuse in the surface layer of acicular iron powder obtained by hydrogen reduction of a FeOOH (goethite) acicular crystal. The raw material is FeOOH acicular crystal, alloy of samarium and cobalt, powder of low melting point alloy, melting point of below 700 ℃, boron powder or ferro-boron alloy powder and cobalt powder or cobalt-iron alloy powder as desired. And under a mixed gas atmosphere of nitrogen and heated to a temperature below the melting point of the low-melting alloy of 300 ℃ or more and reducing the FeOOH needle crystal to a needle iron powder, and then heated to a temperature of 1200 ℃ or less above the melting point of the low melting alloy, It is produced by coating and diffusing boron and samarium on the surface layer of acicular iron powder, and then grinding the product.

Description

Raw material for permanent magnets and production method of the same

(Industrial use)

The present invention relates to a samarium-iron boron-based permanent magnet raw material excellent in magnetic properties and a method for producing the same.

(Conventional technology)

Rare earth, iron, and boron permanent magnets are commercially available as permanent magnets having excellent magnetic properties. Japanese Patent Application No. 61-34242 discloses magnetic anisotropic sintered permanent magnets consisting of Fe-B (2-28% by atomic percentage) -R (rare earth element: 8-30% by atomic percentage) and Sm as a rare earth element. Although illustrated, in manufacture, it is necessary to first manufacture the main alloy containing the said component, and then to powder-form and sinter the main alloy, and to cost the powdering of the cast alloy ingot. In addition, there is a problem that the performance is different for each batch. Japanese Patent Publication No. 3-72124 discloses R (but R is at least one of rare earth elements containing Y) 8 atomic%-30 atomic%, B 2 atomic%-28 atomic%, Fe 65 atomic%-82 atomic% In the method for producing an alloy powder for rare earth-iron-boron-based permanent magnets as a main component, a raw material powder consisting of rare earth oxide powder and metal powder and / or alloy powder is subjected to a reduction reaction with metal Ca or CaH ₂ as a reducing agent. Although a method of heating in an inert gas atmosphere and further adding the obtained reaction product in water to remove the reaction by-product is disclosed, since metal Ca or CaH ₂ is used as a reducing agent, it is necessary to remove or dry the reaction by-product. It requires a process. Since the alloy powder for permanent permanent magnets thus obtained is a fine powder having a particle diameter of 1 to 10 µm, it is easily oxidized by oxygen in the air, and when oxygen is included as an impurity, the magnetic properties of the final product deteriorate. Great care must be taken. For this reason, an apparatus or process for metering, mixing, and heat-molding in the state where air is shut off is required, which increases cost. In addition, since it requires a large amount of rare earth, it is inevitably expensive.

(Problem that invention tries to solve)

An object of the present invention is to provide a samarium-iron-boron-based permanent magnet material which is easy to manufacture and excellent in magnetic properties, and a method of manufacturing the same.

(Means to solve the task)

The samarium-iron-boron-based permanent magnet material according to the present invention is characterized in that samarium (Sm) and boron (B) diffuse into the surface layer of acicular iron powder obtained by hydrogen reduction of a FeOOH (goethite) needle peak. Nitrogen diffused to form nitride has more excellent magnetic properties.

The method for producing permanent magnets is a powder of a low melting point alloy having a melting point of 700 ° C. or lower, boron powder or the like of alloy of samarium (Sm) and cobalt (Co) in acicular iron powder obtained by hydrogen reduction of FeOOH (goethite) needle crystal. The ferro-boron alloy powder and cobalt powder or cobalt-iron alloy powder are mixed as desired, and heated to a temperature of 1200 ° C. or lower above the melting point of the low-melting alloy in a mixed gas atmosphere of hydrogen and nitrogen, and samarium is deposited on the surface of the acicular iron powder. And after coating and diffusing boron, the product is pulverized, or a powder of low melting point alloy having a melting point of 700 ° C. or less, boron powder or ferro-alloy of FeOH (goethite) needle crystal and alloy of samarium (Sm) and cobalt (Co). Boron alloy powder and cobalt powder or cobalt-iron alloy powder are mixed as desired, and the melting point of the low melting point alloy is 300 ° C. or higher in a mixed gas atmosphere of hydrogen and nitrogen. The FeOOH acicular crystal was reduced by heating to a needle iron powder, and then heated to a temperature not lower than 1200 ° C. above the process of the low melting point alloy to coat and diffuse boron and samarium on the surface layer of the acicular iron powder, and then crush the product. It is characterized by. In other words, the former hydrogen-reduces FeOOH acicular crystals to form acicular iron, mixes and reheats Sm and boron materials, and diffuses Sm and boron to acicular iron, the latter uses FeOOH acicular crystals, Sm raw materials and boron raw materials. Although it is a method of mixing from the beginning and gradually producing needle iron, spreading Sm and boron, needle iron powder obtained by hydrogen reduction of FeOOH needle crystals is highly active and easily binds to oxygen in the air to form iron oxide, In addition, the latter method is preferred, in which these steps are carried out continuously without contacting air in the same reaction vessel, because they are easily affected by moisture.

Samarium (Sm) is an alloy with cobalt and is used as a powder of low melting point alloy having a melting point of 700 ° C or lower. The melting point of Sm is 1072 ° C and the Co melting point is 1492 ° C. The melting point of the alloy of Sm 64 atomic% and Co 36 atom% is 575 ° C, and the melting point of the alloy of Sm 85 atomic% and Co 15 atomic% is 595 ° C.

It is not necessary to use the lowest melting point alloy, but the lower the melting point is, the better the treatment temperature is, and therefore, the lower the heat energy consumption.

The particle diameter of the acicular iron powder is preferably 10 µm or less in length, for example, 1.0 µm in length and 0.1 µm in width. The FeOOH (geothite) needle crystal having a particle size corresponding to the particle size of the desired acicular iron powder is reduced by heating to a temperature below the melting point of the low melting point alloy, preferably 400 to 500 ° C., in a hydrogen-containing gas atmosphere, and then reduced by hydrogen reduction. Needle iron powder is obtained in the furnace.

It is preferable that a component ratio contains about 0.3-7% of samarium and about 1-10% of boron in atomic percentage. If it is less than this range, the effect of improving magnetic properties is less. On the other hand, even if it is more than this range, improvement of magnetic properties corresponding to an increase in cost cannot be expected. As for content of nitrogen, about 0 to 10% is preferable in atomic percentage.

Although the cobalt component is inevitably contained by using a samarium cobalt alloy as a samarium source, cobalt component may be increased by adding cobalt powder or the powder of a cobalt iron alloy. The content of cobalt is preferably about 1 to 15% in atomic percentage. The rest is needle iron. In the case of using ferro-boron as a boron source, ferrous-boron is included, but iron is included, but there is no problem even if the amount of accompanying ferro-boron is present.

Boron (melting point 2300 ° C.) powder or cobalt (melting point 1492 ° C.) powder is preferably a fine powder having an average particle diameter of about 1 to 10 μm. The alloy of Sm and Co is not necessarily fine because it is treated at its melting point or above.

Since the permanent magnet raw material of the present invention only diffuses Sm to the surface layer of acicular iron powder, the use amount of expensive rare earth is less than that of the conventional rare earth, iron, and boron permanent magnets, which are alloys in which rare earth elements are uniformly mixed with iron. Even if it shows excellent magnetic properties, it is advantageous in cost.

Further, in the case of producing a permanent magnet material in which nitrogen is also diffused, samarium and boron are coated and diffused on the surface layer of acicular iron powder, and then heat-treated under pressurized nitrogen atmosphere. In this case, the pressurized nitrogen atmosphere may be maintained while maintaining the temperature at the same temperature as the diffusion process of samarium and boron, or may be the pressurized nitrogen atmosphere while the temperature is lowered. As for the pressure of nitrogen, 2 kg / cm <2> G or more is preferable.

The permanent magnet raw material manufactured as described above is compression molded in the presence of a magnetic field and heat-sintered to obtain a sintered permanent magnet. Here, the needle iron is vertically oriented by the presence of a magnetic field. Compression molding conditions and heat sintering conditions may be the same as the conventional sintered magnet production conditions.

A bonded permanent magnet is obtained by mixing said permanent magnet raw material and a binder, and carrying out heat compression molding in the presence of a magnetic field. Here, the needle iron is vertically oriented by the presence of a magnetic field. Compression molding conditions are generally used as conditions used for the production of bonded permanent magnets. As the binder, those made of a polymer material such as epoxy resin, polyamide resin, or glassing agent are used. Examples of the glass agent such as MnO, CuO, Bi ₂ O _3, PbO is, open the _{TI 2 O 3, Sb 2 O} 3, Fe 2 O 3 or the like, or a combination thereof.

Furthermore, by adding aluminum phosphate to the pulverized product and heating it at 300 to 500 ° C., if the aluminum phosphate coating layer is provided on the surface of the permanent magnet material of the present invention, it is difficult to be affected by oxygen or moisture in the air, thereby ensuring stability of quality. This is good.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples.

(Examples 1 and 2)

SmCo alloy (melting point 575 ° C), boron powder, and cobalt powder containing 82% by weight of samarium (64 atomic%) in a needle crystal of FeOOH (goethite: Titanium Industry Co., Ltd.) was added to Fe-Co-Sm-B The weight part of the composition is mixed at a ratio which becomes the value shown in Example 1 or Example 2 of Table 1, and it is put into a rotary furnace and mixed gas of 10% by volume of hydrogen and 90% by volume of nitrogen at a rate of 5 l / min. It heated up to 460 degreeC over 2 hours, flowing, and hold | maintained at this temperature for 7 hours.

In the meantime, the FeOOH acicular crystal was reduced to become acicular iron powder (length 0.9 mu m width 0.09 mu m). It heated up to 700 degreeC over 1 hour, flowing the said hydrogen-nitrogen mixed gas continuously, and hold | maintained at this temperature for 7 hours. In the meantime, SmCo alloy (melting point 575 degreeC) melt | dissolved, it adhered to the surface of acicular iron powder together with boron powder and cobalt powder, and it spread to the surface layer of acicular iron powder. It cooled to room temperature over 5 hours, ie, the mass product was obtained, and it grind | pulverized it by the ball mill (using aluminum ball), and obtained permanent magnet raw material. These permanent magnet raw materials are oriented and molded (pressurized to 1.5t / cm 2) in a magnetic field (10KOe), heated and sintered at 1000 to 1200 ° C for 1 hour in an argon atmosphere, and coercive force iHc, Table 1 shows the results of measuring the residual magnetic flux density Br and the maximum energy product (BH) max.

(Example 3)

In the FeOOH (Geothite: Titanium Industry Co., Ltd.) needle crystal, SmCo alloy (melting point 575 ° C.), boron powder, and cobalt powder containing 82% by weight (64 atom%) of samarium were added to Fe-Co-Sm-B. The weight coarseness was mixed at a ratio of the value shown in Example 3 of Table 1, and the mixture was placed in a rotary furnace for 2 hours while flowing 10 vol% hydrogen and 90 vol% nitrogen gas at a rate of 5 l / min. It heated up to 460 degreeC, and hold | maintained at this temperature for 7 hours. In the meantime, the FeOOH needle crystal was reduced to obtain needle iron powder (length 0.9 mu m, width 0.09 mu m). Subsequently, it heated up to 700 degreeC over 1 hour, flowing the said hydrogen-nitrogen mixed gas, and hold | maintained at this temperature for 7 hours. In the meantime, SmCo alloy (melting point 575 degreeC) melt | dissolved, it adhered to the surface of acicular iron powder together with boron powder and cobalt powder, and it spread to the surface layer of acicular iron powder. Here, the discharge of the mixed gas of hydrogen and nitrogen was stopped, and cooled to room temperature over 5 hours while pressurized with a mixed gas of 10% by volume of hydrogen and 90% by volume of nitrogen to the gauge amount, i.e., nitrogen diffused into the bed The surface product of iron obtained the mass product of nitride. This weight part composition is shown in Table 1. This was ground by a ball mill (using aluminum balls) to obtain a permanent magnet raw material. The permanent magnet material is oriented and molded in a magnetic field (10KOe) (pressurized to 1.5t / cm 2), heated in a argon atmosphere at 1000-1200 ° C. for 1 hour, and sintered, and the coercive force iHc, Table 1 shows the results of measuring the residual magnetic flux density Br and the maximum energy product (BH) max.

All of the examples had the necessary conditions as a permanent magnet with coercive force iHc of 3 kOe or more, and exhibited excellent performances with a residual magnetic flux density Br of 10 KG or more and a maximum energy product (BH) max of 50 MGOe or more. Table 2 shows the composition expressed in parts by weight in Table 1 in Table 2, and Table 3 shows the percentages in Weight. Moreover, the values of iHc, Br and (BH) max are the average of two samples.

The increase in cobalt (Example 2) or the diffusion of nitrogen (Example 3) does not change iHc but Br and (BH) max show very high values.

(Effects of the Invention)

Samarium, iron, and boron-based permanent magnet raw materials are obtained, which are easy to manufacture and have a low amount of expensive samarium, and have excellent magnetic properties.

Claims (3)

FeOOH (goethite) acicular crystal is mixed with alloy of samarium (Sm) and cobalt with low melting point powder below 700 ℃, boron powder or ferro-boron alloy powder, cobalt powder or cobalt iron alloy powder, and mixed with hydrogen. And heating to a temperature below the melting point of the low melting point alloy in a mixed gas atmosphere of nitrogen to reduce the FeOOH acicular crystal to form acicular iron powder, and then to a temperature below the melting point of the low melting point alloy above 1200 ° C. A method for producing a samarium-iron-boron-based permanent magnet material, characterized in that the product is ground after coating and diffusing boron and samarium on the surface of acicular iron powder. The method of producing a permanent magnet raw material according to claim 1, wherein the raw material is blended so as to contain 0.3-7% of samarium and 1-10% of boron in atomic percentage. The method for producing a permanent magnet raw material according to claim 1 or 2, wherein the surface layer of acicular iron powder is coated and diffused with samarium and boron, and then heat-treated under a pressurized nitrogen atmosphere.