JPH06231923A - Manufacture of rare earth sintered magnet, and its rare earth magnet - Google Patents

Abstract

PURPOSE:To raise the density of a sintered substance by soaking the fine powder of an alloy for a rare earth sintered magnet in hydrophobic solvent, and applying an orientating magnetic field in that condition and pressuring it for molding, and performing the processing for removing the residual hydrophobic solvent in the molded item in specified temperature range, and then, sintering it. CONSTITUTION:The mixture between material powder for an R-Fe-B (R is one kind or two kinds or more out of rare earth elements including Y) and a hydrophobic solvent is wet-molded as it is in condition that powder is oriented, having an orienting magnetic field applied. This is the manufacture of sintering it after applying dehydrophobic solvent processing, which holds it for thirty minutes or more under the condition that the temperature is 100-500 deg.C and the pressure is 10<-1>Torr or under, or applying dehydrophobic solvent processing, which puts the speed of temperature rise within the range from normal temperature to 500 deg.C to 10 deg.C/min. or less under the pressure of 10<-1> Torr or under, to the obtained molded item. Hereby, oxidation or adsorption of water is prevented, and also the density of a sintered substance is improved, and a rare earth sintered magnet having high magnetic property can be obtained.

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 an R--Fe--B system rare earth sintered magnet and the produced rare earth sintered magnet.

[0002]

2. Description of the Related Art Sintered rare earth magnets dissolve raw metal,
The ingot obtained by pouring into a mold is crushed, molded, sintered, heat-treated, and processed by a powder metallurgical technique, such as R-Fe-B rare earth sintered magnet (where R is Y. One or more of rare earth elements including is attracting attention as a high-performance magnet. However, the alloy powder for a rare earth sintered magnet obtained by crushing an ingot is chemically very active, so that it is extremely rapidly oxidized in the atmosphere, resulting in deterioration of magnetic properties. Further, the alloy powder for a rare earth sintered magnet not only generates heat due to abrupt oxidation but also ignites in an extreme case, which is also a problem in terms of safety. Conventionally, as a method of preventing such a rapid oxidation, a process of stabilizing the surface by leaving it in an inert gas such as nitrogen or argon for a long time has been performed, but it takes a long time to perform mass production. There was a problem with sex. Further, the alloy powder for a rare earth sintered magnet has a hygroscopic property, and when left in the atmosphere, it adsorbs moisture in the atmosphere, thereby deteriorating the characteristics of the manufactured rare earth sintered magnet.

[0003]

With respect to this problem, JP-A-61-114505 discloses an R-Fe-B system (where R is Y).
One or more kinds of rare earth elements including) alloy powder and an organic solvent are prepared, the mixture is compressed in a magnetic field, the organic solvent is filtered, and the resulting compact is dried, sintered and heat treated. A method of manufacturing a permanent magnet has been proposed. According to this manufacturing method, since the molding is performed by a wet method, the problems of oxidation and moisture adsorption can be solved. Recently, R-Fe-B system permanent magnets have been extensively studied for obtaining higher magnetic properties, and the present inventor also conducted the study using the wet molding method disclosed in JP-A-61-114505. . As a result, it was found that although the oxygen content was certainly reduced, the density of the sintered body was lower than that of the sintered body obtained by the dry molding method, and therefore the magnetic properties could not be sufficiently improved. Therefore, the present invention provides a rare earth sintered magnet that prevents oxidation and adsorption of moisture, improves the density of the sintered body, and has high magnetic properties, and a method for producing the same.

[0004]

[Means for Solving the Problem] The inventors of the present invention have made various investigations on the cause of the low density of the sintered body by the wet forming method. As a result, the temperature inside the formed body suddenly increases during the temperature rising process up to the sintering temperature. The rare-earth element that contributes to the liquid-phase sintering is unnecessarily consumed by the reaction between the hydrophobic organic liquid (hereinafter referred to as a hydrophobic solvent) that rises in the compact and remains in the compact and R in the compact, that is, the rare-earth element. Therefore, it was speculated that the reason why the increase in density was hindered was that the liquid phase necessary for sintering was not sufficiently generated. Then, in order to solve this problem, the compact is sintered at a temperature of 100 to 500 ° C. and a pressure of 10 ⁻¹ Torr before sintering.
A treatment for holding for 30 minutes or more under the following conditions is performed, or a temperature rising rate in a temperature range from room temperature to 500 ° C is set to 10 ° C / min or less at a pressure of 10 ^-1 Torr or less in a temperature rising process in sintering. I found that it was good. That is, the method for producing a rare earth sintered magnet according to the present invention is applied to a mixture of an R—Fe—B system (R is one or more of rare earth elements including Y) rare earth sintered magnet raw material powder and a hydrophobic solvent. Wet-molding is performed while applying the orientation magnetic field to the powder in an oriented state, and a dehydrophobic solvent treatment in which the obtained compact is kept for 30 minutes or more under conditions of a temperature of 100 to 500 ° C. and a pressure of 10 ⁻¹ Torr or less. Characterized in that it is sintered after being applied, and an R-Fe-B system (R is one or more of rare earth elements including Y) rare earth sintered magnet powder and a hydrophobic solvent are used as an orientation magnetic field. Wet compaction is performed with the powder applied to the compact, and the compact thus obtained is subjected to a pressure of 10 ^-1 Torr or less from room temperature to 500.
It is characterized in that it is sintered after being subjected to a dehydrophobic solvent treatment at a temperature rising rate in the temperature range up to ° C of 10 ° C / min or less.

The present invention will be described in detail below. The rare earth sintered magnet alloy according to the present invention may be an R—Fe—B system, but is preferably an R—Fe (Co) —B—M system.
Is one or more of the rare earth elements including Y 25
~ 35 wt%, B is 0.8-1.2 wt%, M is Al,
Nb, Ti, V, Zr, Mo, W, Ga, Cu, Zn,
5% by weight or less of one or more of Ge and Sn,
The balance is Fe or Fe and Co except for inevitable contaminants.
Consists of. As an alloy system, Nd-Fe-B-Al-N
b, Nd-Fe-Co-B-Al-Nb, Nd-Fe-
B-Al-Ga, Nd-Fe-Co-B-Al-Ga,
Nd-Dy-Fe-B-Al-Nb, Nd-Dy-Fe
-Co-B-Al-Nb, Nd-Dy-Fe-B-Al
-Ga, Nd-Fe-Dy-Co-B-Al-Ga, etc. are exemplified, but not limited thereto.

As the hydrophobic solvent in which the fine powder obtained by crushing these alloys is dipped, n-hexane, toluene, fluorocarbon or the like can be used. In order to immerse the fine powder in the hydrophobic solvent, in the case of wet pulverizing the coarse powder of the rare earth sintered magnet alloy as a raw material by a ball mill or the like, it may be immersed in the hydrophobic solvent in the state of the coarse powder before pulverization,
In the case of dry crushing with a jet mill, it is desirable to immerse the powder in a hydrophobic solvent in an inert or reducing atmosphere immediately after crushing.By doing this, the fine powder is shielded from the atmosphere to prevent oxidation and adsorption of moisture. Can be suppressed. Further, by dissolving the carboxylic acid and / or the amine in these hydrophobic solvents, it is possible to prevent the fine powder from being oxidized by oxygen dissolved in the hydrophobic solvent. It is considered that the carboxylic acid and the amine are adsorbed on the surface of the fine powder in the hydrophobic solvent and prevent the adsorption of oxygen to the fine powder, so that the oxidation of the fine powder can be prevented.

FIG. 1 shows a pressing apparatus suitable for wet-molding the mixture of the fine powder thus obtained and the hydrophobic solvent. An example of wet molding using the press device shown in FIG. 1 will be described below. Filling the mixture of the fine powder and the hydrophobic solvent in the cavity of the mold 1 arranged in the intermittent orientation magnetic field, and applying the orientation magnetic field to orient the fine powder,
When the upper punch 5 is lowered and pressure is applied, the hydrophobic solvent is discharged through the filter 4 placed on the lower punch 2 and through the solvent discharging hole 3 provided in the lower punch 2 to compress the powder,
Molded. An orientation magnetic field may or may not be applied while the mixture of the fine powder and the hydrophobic solvent is compressed, but in order to maintain the orientation of the powder and the clearance between the die 1 and the upper / lower punches 5 and 2. Therefore, in order to prevent the fine powder from blowing out together with the hydrophobic solvent, it is desirable to maintain the state in which the orientation magnetic field is applied until the compression is completed. Although FIG. 1 shows the case where the direction of the orientation magnetic field is perpendicular to the compression direction, the mechanism for generating the orientation magnetic field, that is, the orientation magnetic field coil 6 and the pole piece 7 may be provided so as to be parallel to the compression direction. Absent. The method of generating the orientation magnetic field is not limited to these.

When the molded body thus obtained is left to stand in the air, the hydrophobic solvent evaporates and the surface is dried to form a portion not wet with the hydrophobic solvent, which is gradually oxidized and sintered by rare earth sintering. It deteriorates the characteristics of the magnet. In order to prevent this, it is desirable to store the molded body immediately after molding in a hydrophobic solvent or a gas in a non-oxidizing or reducing atmosphere until it is inserted into a sintering furnace.

Next, the molded body is sintered. When the temperature is continuously raised from room temperature to 950 to 1150 ° C. which is the sintering temperature, the temperature inside the molded body rises rapidly, and the hydrophobic solvent remaining in the molded body is removed. The rare earth element in the compact reacts with each other to generate a rare earth carbide, which hinders the generation of a liquid phase in an amount sufficient for sintering, and a sintered body having a sufficient density cannot be obtained, resulting in deterioration of magnetic properties. In order to prevent this, in the present invention, the temperature is 100 to 5
A dehydrophobic solvent treatment is carried out under the conditions of 00 ° C. and a pressure of 10 ⁻¹ Torr or less for 30 minutes or more. By this treatment, the hydrophobic solvent remaining in the molded body can be sufficiently removed. The holding is not limited to one point as long as it is in the temperature range of 100 to 500 ° C., and may be two or more points. Further, in the present invention, by applying a dehydrophobic solvent treatment at a temperature rising rate from room temperature to 500 ° C. of 10 ° C./min or less, preferably 5 ° C./min or less under a pressure of 10 ⁻¹ or less, a temperature of 100 to
It is possible to obtain the same effect as the treatment of holding for 30 minutes or more under the condition of 500 ° C. and pressure of 10 ⁻¹ Torr or less.

[0010]

EXAMPLES The present invention will be specifically described below with reference to examples, but the contents of the present invention are not limited thereto. (Example 1) As starting materials for rare earth sintered magnets, predetermined amounts of electrolytic iron, ferroboron, and Nd were weighed, melted and cast in a high-frequency melting furnace, and Nd = 31% by weight.
%, B = 1.0%, Al = 0.3%, and the balance Fe was manufactured. This ingot was coarsely pulverized, and then finely pulverized using a jet mill in a nitrogen atmosphere having an oxygen content of 10 ppm. The average particle size of the fine powder was 4.1 μm. The fine powder obtained by crushing was immersed in n-hexane in a nitrogen atmosphere. This was wet-molded using the press shown in FIG. That is, the fine powder dipped in n-hexane is filled in the cavity of the mold 1, and a current is passed through the orientation magnetic field coil 6 to orient the fine powder in n-hexane with an orientation magnetic field strength of 15 kOe. Then, the upper punch 5 was used to apply pressure. Most of the pressurized n-hexane was discharged through the filter 4 through the solvent discharge hole 3 provided in the lower punch 2. After that, the orientation magnetic field current was cut off, the molded body was taken out and immediately immersed in n-hexane. The obtained molded body was taken out from n-hexane and inserted into a sintering furnace at a pressure of 5 × 10 ^-2 Torr from room temperature to 150 ° C at 1.56 ° C.
The temperature is raised at a rate of / min, the temperature is maintained for 1 hour, and the temperature is raised to 500 ° C at a rate of 1.5 ° C / min to remove the hydrophobic solvent in the molded body.
20 ° C from 500 to 1100 ° C at a pressure of 5 × 10 ^-4 Torr
The temperature was raised at / min, the temperature was maintained for 2 hours, and then the furnace was cooled. The obtained sintered body was aged at 900 ° C. for 1 hour and at 600 ° C. for 1 hour, and the oxygen content, carbon content, and magnetic characteristics of the sintered body were measured, and sufficient characteristics were obtained as shown in Table 1. Was given.

Example 2 As starting materials for a rare earth sintered magnet, electrolytic iron, ferroboron and Nd were weighed in predetermined amounts,
By melting and casting in a high-frequency melting furnace, weight% Nd = 31%, B = 1.0%, Al = 0.3%, balance F
An ingot called e was manufactured. This ingot was roughly pulverized, and then finely pulverized by a wet method using n-hexane as a hydrophobic solvent using a ball mill to obtain a mixture of fine powder having a volume ratio of fine powder of 60% and n-hexane.
The average particle size of the fine powder was 4.0 μm. The hydrophobic solvent in which the fine powder was dipped was molded, sintered and heat treated in the same manner as in Example 1, and the oxygen content, carbon content, and
When the magnetic properties were measured, sufficient properties were obtained as shown in Table 1. (Example 3) As starting materials for a rare earth sintered magnet, electrolytic iron, ferroboron, and Nd were weighed in predetermined amounts, melted and cast in a high-frequency melting furnace, and Nd = 31% by weight.
%, B = 1.0%, Al = 0.3%, and the balance Fe was manufactured. This ingot was coarsely pulverized, and then finely pulverized using a jet mill in a nitrogen atmosphere having an oxygen content of 10 ppm. The average particle size of the fine powder was 4.1 μm. The fine powder obtained by grinding was immersed in a nitrogen atmosphere in n-hexane in which 1% by weight of n-hexadecylamine was dissolved in the weight of the fine powder. The hydrophobic solvent in which the fine powder was dipped was molded, sintered and heat treated in the same manner as in Example 1, and the oxygen content, carbon content and magnetic characteristics of the sintered body were measured, and sufficient characteristics were obtained as shown in Table 1. Was given. (Example 4) As starting materials for rare earth sintered magnets, predetermined amounts of electrolytic iron, ferroboron, and Nd were weighed, melted and cast in a high-frequency melting furnace, and Nd = 31% by weight.
%, B = 1.0%, Al = 0.3%, and the balance Fe was manufactured. This ingot was roughly pulverized and then finely pulverized by a wet method using n-hexane having 1% by weight of n-hexadecylamine dissolved in the ball mill as a hydrophobic solvent to obtain a fine powder. A mixture of fine powder having a volume ratio of 60% and n-hexane was obtained.
The average particle size of the fine powder was 4.2 μm. The hydrophobic solvent in which the fine powder was dipped was molded, sintered and heat treated in the same manner as in Example 1, and the oxygen content, carbon content, and
When the magnetic properties were measured, sufficient properties were obtained as shown in Table 1. (Example 5) As starting materials for rare earth sintered magnets, predetermined amounts of electrolytic iron, ferroboron, and Nd were weighed, melted and cast in a high-frequency melting furnace, and Nd = 31% by weight.
%, B = 1.0%, Al = 0.3%, and the balance Fe was manufactured. This ingot was coarsely pulverized, and then finely pulverized using a jet mill in a nitrogen atmosphere having an oxygen content of 10 ppm. A fine powder having an average particle diameter of 3.9 μm obtained by pulverization was immersed in n-hexane in which 1% by weight of stearic acid was dissolved in n-hexane in a nitrogen atmosphere. When the sintered body obtained was molded, sintered and heat-treated in the same manner as in Example 1 and the oxygen content, carbon content and magnetic characteristics were measured, sufficient characteristics were obtained as shown in Table 1. . (Example 6) As starting materials for rare earth sintered magnets, predetermined amounts of electrolytic iron, ferroboron, and Nd were weighed, melted and cast in a high-frequency melting furnace, and Nd = 31% by weight.
%, B = 1.0%, Al = 0.3%, and the balance Fe was manufactured. This ingot was roughly pulverized, and then finely pulverized by a wet method using a ball mill and n-hexane in which 1% by weight of stearic acid was dissolved with respect to the weight of the coarse powder as a hydrophobic solvent. Is 60
% Fine powder and stearic acid dissolved n-hexane mixture was obtained. The average particle size of the fine powder was 4.3 μm. When this was subjected to molding, sintering and heat treatment in the same manner as in Example 1 to measure the oxygen content, carbon content and magnetic characteristics of the sintered body, sufficient characteristics were obtained as shown in Table 1. (Example 7) As starting materials for rare earth sintered magnets, predetermined amounts of electrolytic iron, ferroboron, and Nd were weighed, melted and cast in a high-frequency melting furnace, and Nd = 29% by weight.
%, B = 1.0%, Al = 0.3%, and the balance Fe was manufactured. Using this ingot as a sintered body that was heat-treated by the same steps as in Example 1, the oxygen content, carbon content and magnetic characteristics of the sintered body were measured, and sufficient characteristics were obtained as shown in Table 1. (Example 8) As starting materials for rare earth sintered magnets, predetermined amounts of electrolytic iron, ferroboron, and Nd were weighed, melted and cast in a high-frequency melting furnace, and Nd = 29 by weight%.
%, B = 1.0%, Al = 0.3%, and the balance Fe was manufactured. The ingot was heat-treated in the same process as in Example 2 to obtain a sintered body, and the oxygen content, carbon content, and magnetic characteristics of the sintered body were measured, and sufficient characteristics were obtained as shown in Table 1. (Example 9) As starting materials for rare earth sintered magnets, predetermined amounts of electrolytic iron, ferroboron, and Nd were weighed, melted and cast in a high-frequency melting furnace, and Nd = 29 by weight%.
%, B = 1.0%, Al = 0.3%, and the balance Fe was manufactured. The ingot was heat-treated in the same process as in Example 3 to obtain a sintered body, and the oxygen content, carbon content, and magnetic characteristics of the sintered body were measured, and sufficient characteristics were obtained as shown in Table 1. (Example 10) As starting materials for rare earth sintered magnets, predetermined amounts of electrolytic iron, ferroboron, and Nd were weighed, melted and cast in a high-frequency melting furnace, and Nd = 29 by weight%.
%, B = 1.0%, Al = 0.3%, and the balance Fe was manufactured. This ingot was made into a sintered body that was heat-treated by the same steps as in Example 4, and the oxygen content, carbon content, and magnetic characteristics of the sintered body were measured, and sufficient characteristics were obtained as shown in Table 1. (Example 11) As starting materials for rare earth sintered magnets, predetermined amounts of electrolytic iron, ferroboron, and Nd were weighed, melted and cast in a high-frequency melting furnace, and Nd = 29 by weight%.
%, B = 1.0%, Al = 0.3%, and the balance Fe was manufactured. This ingot was heat-treated in the same process as in Example 5 to obtain a sintered body, and the oxygen content, carbon content and magnetic characteristics of the sintered body were measured, and sufficient characteristics were obtained as shown in Table 1. (Example 12) As starting materials for rare earth sintered magnets, predetermined amounts of electrolytic iron, ferroboron, and Nd were weighed, melted and cast in a high-frequency melting furnace, and Nd = 29 by weight%.
%, B = 1.0%, Al = 0.3%, and the balance Fe was manufactured. This ingot was heat-treated in the same process as in Example 6 to obtain a sintered body, and the oxygen content, carbon content and magnetic characteristics of the sintered body were measured, and sufficient characteristics were obtained as shown in Table 1.

(Comparative Example 1) The same ingot as in Example 1 was crushed in the same manner as in Example 1 and opened in the atmosphere without being recovered in the hydrophobic solvent, and immediately ignited to recover fine powder. I couldn't. (Comparative Example 2) The same ingot as in Example 1 was crushed in the same manner as in Example 1 and recovered in a gas-tight container in nitrogen gas.
The fine powder that has been stabilized in nitrogen gas at atmospheric pressure is molded in the air at an orientation magnetic field strength of 15 kOe and a molding pressure of 1 ton / cm ² , and the obtained molded body is heated from room temperature to 110 at 110 × 10 ⁻⁴ Torr.
The temperature was raised to 0 ° C. at 20 ° C./min, held for 2 hours, and then cooled in the furnace. The obtained sintered body was heat-treated at 900 ° C. for 1 hour and at 600 ° C. for 1 hour, and then the oxygen content, carbon content, and magnetic characteristics of the sintered body were measured. Was higher and the characteristics were lower than those of the examples. (Comparative Example 3) When the same ingot as in Example 7 was crushed in the same manner as in Example and opened in the atmosphere without being recovered in the hydrophobic solvent, it immediately ignited and the fine powder could not be recovered. It was (Comparative Example 4) The same ingot as in Example 7 was crushed in the same manner as in Example 7, and collected in an airtight container in nitrogen gas.
The fine powder that has been stabilized in nitrogen gas at atmospheric pressure is molded in the air at an orientation magnetic field strength of 15 kOe and a molding pressure of 1 ton / cm ² , and the obtained molded body is heated from room temperature at a pressure of 5 × 10 ⁻⁴ Torr. 1
The temperature was raised to 100 ° C. at 20 ° C./min, the temperature was maintained for 2 hours, and the furnace was cooled. The obtained sintered body is heated at 900 ° C for 1 hour and then at 600 ° C for 1 hour.
After heat treatment for a period of time, the oxygen content, carbon content, and magnetic characteristics of the sintered body were measured. As shown in Table 1, the oxygen content was higher than that of Example 5, and the sintered body density and magnetic characteristics were also lower than those of the Examples. Became. (Comparative Example 5) The same ingot as in Example 1 was crushed in the same manner as in Example 1, recovered in n-hexane, and wet-molded.
The obtained molded body is heated from room temperature to 110 at a pressure of 5 × 10 ⁻⁴ Torr.
The temperature was raised to 0 ° C. at 20 ° C./min, held for 2 hours, and then cooled in the furnace. The obtained sintered body was heat-treated at 900 ° C. for 1 hour and at 600 ° C. for 1 hour, and the oxygen content, carbon content, and magnetic properties of the sintered body were measured. Similar to the above, but the carbon content was high and the sintered body density was low, and the magnetic characteristics were lower than those of the examples.

[0013]

[Table 1] ρs: Sintered body density

[0014]

As described in detail above, according to the present invention, fine powder of a rare earth sintered magnet alloy obtained by fine pulverization is immersed in a hydrophobic solvent, and an orienting magnetic field is applied and pressed in that state. By molding and performing a treatment for removing the residual hydrophobic solvent in the molded body from room temperature to 500 ° C., sintering is performed to obtain an oxygen amount of 3000 ppm or less and a sintered body density of 7.45.
It is possible to obtain a sintered body of ~ 7.62 g / cm ³ .

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a pressing apparatus suitable for carrying out a manufacturing method of the present invention.

[Explanation of symbols]

1 ... Mold 2 ... Lower punch 3 ...
Solvent drain hole 4 ... Filter 5 ... Upper punch 6 ...
Coil for orientation magnetic field 7 ... Pole piece

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01F 1/053

Claims (4)

[Claims] 1. An R-Fe-B system (R is one or more of rare earth elements containing Y) rare earth sintered magnet raw material powder and a hydrophobic organic liquid mixture are applied with an orientation magnetic field to form a powder. Wet molding is carried out while being oriented, and the resulting molded body is subjected to a heat treatment of a dehydrophobic organic substance liquid which is held for 30 minutes or more under conditions of a temperature of 100 to 500 ° C. and a pressure of 10 ⁻¹ Torr or less,
A method for producing a rare earth sintered magnet, which is characterized by sintering thereafter. 2. An R-Fe-B system (R is one or more of rare earth elements including Y) rare earth sintered magnet raw material powder and a hydrophobic organic liquid mixture are applied with an orientation magnetic field to form a powder. A dehydrophobic organic substance that is wet-molded in the as-oriented state and has a temperature rise rate of 10 ° C / min or less in the temperature range from room temperature to 500 ° C under a pressure of 10 ^-1 Torr or less A method for producing a rare earth sintered magnet, which comprises subjecting to liquid treatment and then sintering. 3. The method for producing a rare earth sintered magnet according to claim 1, wherein the carboxylic acid and / or amine is dissolved in the hydrophobic organic liquid. 4. The sintered body obtained by the manufacturing method according to claim 1 has an oxygen content of 3000 ppm.
Hereafter, the carbon content is 600 ppm or less, and the sintered body density is 7.45.
~ 7.62g / cm ³ R-Fe-B characterized by
Rare earth sintered magnet.