JP2003031408A - Magnetic powder for rate-earth bonded magnet, its manufacturing method, and bonded magnet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide magnetic powder for a rare-earth isotropic bonded mag netic and its manufacturing method which can maintain a high fluidity of com pound of magnetic powder resin binder even if the filling factor of the magnetic powder in the compound is high, and can form a magnet with satisfactory moldability, and to obtain a bonded magnet which is made of the magnetic powder and has high magnetic performance. SOLUTION: Molten Nd-Fe-B system magnet alloy is chilled by rolling to obtain a ribbon which is crushed into flake powder, and the powder is subjected to a hot-upsetting at 500 to 800 deg.C to obtain a lump which is crushed again into granular powder. In the case of Sm-Fe-N system alloy, molten Sm-Fe system alloy is chilled by rolling to obtain a ribbon which is crushed into flake powder, and the flake powder is subjected to a hot-upsetting under at 500 to 800 deg.C to obtain a lump which is crushed again into granular powder, and the granular powder is subjected to nitriding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnet powder for producing a rare earth bonded magnet, which is a granular magnet powder which can be present in a magnet molded product with a higher filling rate than conventional flaky powder. And a manufacturing method thereof. The present invention also relates to a bonded magnet using this magnet powder.

[0002]

2. Description of the Related Art Isotropic bonded magnets in which rare earth magnet powders are bonded with a resin binder have a large maximum energy product, which is a measure of magnet performance, and have good moldability, so that a desired magnet shape can be easily realized. It is characterized by being widely used as a material for forming small and high-performance parts such as parts for computers and mobile phones. The performance and size of this type of equipment are becoming higher and smaller, and accordingly, the bond magnets used are required to have higher performance and smaller size.

At present, as a magnet powder used as a material for producing a rare earth bonded magnet, a flaky powder obtained by rapidly cooling a melt of a magnet alloy by a roll quenching method to obtain a ribbon and crushing the ribbon is used. The flaky powder provided by the roll quenching method is an advantage that it is a fine crystal and has a large coercive force. As a rare earth magnet used for a bonded magnet, Nd-
The Fe-B system is typical, but the Sm-Fe-N system, which has been developed in recent years, is also effective.

The flaky magnet powder has a thickness of 10 to 30.
This is a flat powder in the range of μm, which has a negative effect on the molding of the bonded magnet and gives a theoretical problem that the filling rate of the magnet powder in the magnet molded product cannot be increased. Even when the bonded magnet is molded by press molding, there is a limit to the filling rate that can be achieved. This limit is
In the case of injection molding, which is even more serious, the maximum amount of magnet powder added to the resin binder must be kept low in order to ensure the fluidity of the resin compound containing the flake powder. In any case, the maximum energy product of the bond resin is at a lower level than that of the sintered magnet.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems in rare earth isotropic bonded magnets, and to improve the fluidity of the compound even if it is added to the compound of the magnet powder-resin binder at a high density. To provide a bonded magnet powder having high magnet performance, which can be processed with good moldability regardless of whether press molding or injection molding is performed, and a manufacturing method thereof. is there. It is, of course, included in the object of the present invention to provide a bonded magnet using this magnet powder.

[0006]

The magnetic powder for a rare earth bonded magnet according to the present invention is obtained by hot upsetting and re-grinding the shape of the powder of the rare earth magnetic alloy or its precursor obtained by the roll quenching method to form flakes. A magnet powder capable of producing a magnet with a high powder packing density, characterized in that the magnet powder is formed into a granular shape.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The rare earth magnet alloy to which the present invention is applied is of a type in which flaky powder is formed by a roll quenching method, and a typical example thereof is Nd-Fe as described above.
-B type magnet alloy. As described above, Sm-
Fe—N based magnet alloys are included.

The method for producing a magnet powder for a rare earth bonded magnet according to the present invention is Nd-Fe-B system in the case of Nd-Fe-B system.
A ribbon obtained by roll-quenching a molten metal of a —Fe—B magnet alloy was crushed to obtain a flake-like powder.
It is characterized in that it is hot upset at a temperature of 0 ° C. to form a lump, and the lump is re-ground to give a granular powder.

In the case of the Sm-Fe-N system, a ribbon obtained by rapidly cooling a molten Sm-Fe system alloy roll is crushed to obtain a flake powder, which is hot upset at a temperature of 500 to 800 ° C. It is characterized in that the lump is made into a lump, and the lump is re-ground to give a granular powder, which is subjected to a nitriding treatment.

The flake powder usually has a thickness of 10 to 10.
Although it is 30 μm, when hot upsetting is performed, the powder sinters into a lump. At this time, the heating temperature is 500
If the temperature is lower than 0 ° C, sintering does not proceed and a lump of magnet metal cannot be obtained. Although the higher the temperature is, the faster the sintering is, the crystal grains may be coarsened and the magnetic characteristics, particularly the coercive force may be lowered, so the upper limit is 800 ° C. Usually 600
~ 650 ° C is suitable.

The crushing of the lumps is preferably carried out using a pin mill after rough crushing. This re-milling gives a granular powder with new fracture surfaces. Granular powders generally have a major axis of 100 to 1000 μm and a minor axis of 30.
˜200 μm. From a practical point of view, such as the filling property in a mold at the time of producing a bonded magnet, a substantially spherical powder having a major axis of 400 μm or less is preferable.

The bonded magnet may be manufactured according to a known technique. According to the present invention, the upper limit (volume%) of the filling rate of the magnet powder to the resin binder can be increased as follows. Press molding (epoxy resin): From conventional 75 to 80% to 80 to 90% Injection molding (nylon resin): From conventional 55 to 60% to 60 to 70%

[0013]

[Example 1 and Comparative Example 1] Nd-Fe-B system weight%, Nd: 27%, Fe: 67%, Co: 5%,
B: A Nd-Fe-B magnet alloy having a composition of 1% was melted, and a quenching flake was obtained by a liquid quenching method using a copper roll rotating at a peripheral speed of 20 m / s. The quenched flakes were crushed into powder having an average particle size of 150 μm. The shape of the flake powder is shown in FIG.

In order to enhance the magnetic properties of the powder, a part of the powder was annealed by heating it at 650 ° C. for 20 minutes in an Ar atmosphere. The magnetic properties of the annealed magnet powder were measured with a vibrating sample magnetometer (VSM) to obtain the following values.
The specific gravity of the magnet powder at this time was 7.6 g / cm ^3, and no demagnetizing field correction was performed. Br: 8.4kG iHc: 10.4kOe [BH] max: 1
4.3 MGOe

200 g of flaky powder (not subjected to annealing treatment) was filled in a mild steel cylindrical container, and a mild steel lid was welded and sealed. 65 by high frequency heating
After raising the temperature to 0 ° C. and maintaining this temperature for 20 minutes, upsetting was performed so that the rolling reduction was 85%. The agglomerated magnet alloy was taken out of the container, the agglomerate was roughly crushed, and then pulverized with a pin mill to obtain granular magnetic powder. The shape of this granular magnet powder is shown in FIG. The average major axis was 350 μm and the minor axis was 70 μm.

The magnetic properties of this granular powder are as follows, and a slight decrease in the magnetic properties due to hot working was observed. Br: 8.0 kG iHc: 9.9 kOe [BH] max: 13.
8MGOe

A mixture of 98% by weight of the above-mentioned granular powder and 2% by weight of an epoxy resin was filled in a mold to obtain 12 tons / cm.
Pressed at a surface pressure of ² . The molded body was heated to 150 ° C. for 1 hour to cure the epoxy resin and obtain a compression molded bonded magnet. For comparison, the above-mentioned flaky powder (which was annealed and not upset) was used as it was, and a compression-molded bond magnet was similarly produced. These two
The magnetic properties of the seed bond magnets were measured and the following values were obtained. Magnet density Br iHc [BH] max Example 6.6 g / cm ³ 7.9 kG 9.8 kOe 12.3 MGOe Comparative example 6.1 g / cm ³ 7.3 kG 10.2 kOe 10.5 MGOe

In the case of following the examples, a slight decrease in magnetic properties was observed due to the processing into granular powder, but in the bonded magnet products, it was confirmed that the magnetic properties, in particular the maximum energy product, were superior to the comparative examples. This shows that it becomes possible to increase the filling rate of the powder when molding the compound of the magnet powder-resin binder, which is more than enough to make up for some deterioration of the magnetic performance of the magnet powder.

[0019]

Example 2 and Comparative Example 2 An Sm-Fe alloy having a composition of Sm: Fe-N system weight% and Sm: 22%, Fe: 78% was melted and rotated at a peripheral speed of 40 m / s. Quenched flakes were obtained by a liquid quenching method using a copper roll. The quenched flakes are crushed to have an average particle size of 150 μm.
Powder. Part of this powder was subjected to an annealing treatment in which was heated to 700 ° C. for 20 minutes in an Ar atmosphere.

200 g of flake powder (not subjected to annealing treatment) was filled in a cylindrical container made of mild steel, and a lid made of mild steel was welded and hermetically sealed. 70 by high frequency heating
After raising the temperature to 0 ° C. and maintaining this temperature for 20 minutes, upsetting was performed so that the rolling reduction was 85%. The agglomerated magnet alloy was taken out of the container, the agglomerate was roughly crushed, and then pulverized with a pin mill to obtain granular magnetic powder. The average major axis of this granular magnet powder was 250 μm, and the average minor axis was 55 μm.

The above flaky powder and granular powder are
Put in an electric furnace, in a hydrogen-ammonia atmosphere, 450 ℃
Was subjected to nitriding treatment to produce Sm-Fe-N based magnet powder. The magnetic properties of two types of magnet powders (Examples using granular powder as a material and Comparative Example using flake-like powder as a material) were measured by VSM, and the following results were obtained. The specific gravity of the magnet powder at this time was 7.7 g / cm ^3, and no demagnetizing field correction was performed. Br iHc [BH] max Example 8.8kG 9.2kOe 15.5MGOe Comparative Example 9.2kG 9.5kOe 16.8MGOe

A mixture of 98% by weight of the above two kinds of powder and 2% by weight of an epoxy resin was filled in a mold and pressed at a surface pressure of 12 ton / cm ² . The molded body was heated to 150 ° C. for 1 hour to cure the epoxy resin and obtain a compression molded bonded magnet. The magnetic properties of these two types of bond magnets are
The following values were obtained by measuring with a tracer. Magnet density Br iHc [BH] max Example 6.7 g / cm ³ 8.7 kG 9.1 kOe 16.4 MGOe Comparative example 6.2 g / cm ³ 8.1 kG 9.3 kOe 14.6 MGOe

[0023]

According to the present invention, the powder of rare earth magnet is
Magnet powder that can be mixed with the resin binder at a high filling rate can be obtained by converting the material into a granular form by hot upsetting and re-grinding, instead of the flake shape obtained by the roll quenching. If a bond resin is produced using this powder, a bond magnet having higher magnetic properties, especially higher maximum energy product than before can be obtained.

[Brief description of drawings]

FIG. 1 is Nd-Fe prepared in an example of the present invention.
-Micrograph showing the shape of flaky powder of B magnet alloy (magnification: 40 times).

FIG. 2 is a photomicrograph (magnification: 40 ×) corresponding to FIG. 1, showing the shape of a granular powder obtained by agglomerating and re-milling the flaky powder of FIG. 1 according to the present invention.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C22C 38/00 303 H01F 41/02 G H01F 41/02 1/06 A F term (reference) 4K017 AA04 BA06 BB12 CA09 DA04 EA03 EC02 FA29 4K018 AA27 AB03 BA18 BB01 BC08 BC19 BD01 GA04 KA46 5E040 AA04 AA19 BB03 CA01 HB07 HB11 HB17 NN18 5E062 CC05 CD05 CE05 CG03

Claims (7)

[Claims] 1. A high powder packing density, characterized in that the powder of the rare earth magnet alloy or its precursor obtained by the roll quenching method is changed from flakes to particles by hot upsetting and re-grinding. Magnet powder for rare earth bonded magnets that can be used to manufacture magnets. 2. The magnet powder according to claim 1, wherein the rare earth magnet alloy is an Nd-Fe-B based magnet alloy. 3. The magnet powder according to claim 1, wherein the rare earth magnet alloy is an Sm-Fe-N-based magnet alloy, and the precursor thereof is an Sm-Fe-based alloy. 4. The size of the granular powder has a major axis of 100 to 1
The magnetic powder according to claim 1, which has a diameter of 000 μm and a minor axis of 30 to 200 μm. 5. A flaky powder is obtained by crushing a ribbon obtained by rapidly cooling a molten metal of Nd-Fe-B magnet alloy into a roll,
A method for producing magnet powder for Nd-Fe-B based bonded magnet, which comprises hot upsetting this at a temperature of 500 to 800 [deg.] C. to form a lump, and re-pulverizing the lump to give a granular powder. 6. A flaky powder is obtained by pulverizing a ribbon obtained by rapidly cooling a molten metal of Sm-Fe alloy into a roll.
Hot upset at a temperature of 00-800 ° C to form a lump,
A method for producing magnet powder for an Sm-Fe-N-based bonded magnet, which comprises subjecting this lump to re-pulverization to give a granular powder and subjecting it to a nitriding treatment. 7. A bonded magnet obtained by molding the compound of the magnet powder according to claim 1 and a resin binder into a magnet shape.