JPH0786069A - Manufacture of rare earth sintered magnet - Google Patents

Abstract

PURPOSE:To stably manufacture a sintered body of low oxygen and low carbon, by dipping raw material fine powder for an R-Fe-B rare earth sintered magnet in mineral oil or compound oil, and molding and sintering the powder coated with the mineral oil or the compound oil. CONSTITUTION:A specific amount of electrolytic iron, ferro boron and Nd is weighed, which are melted and cast in a high frequency melting furnace. Ingot manufactured by the above process is ground to be rough powder and then pulverized by using a jet mill. The obtained fine powder is dipped in mineral oil whose fractional distillation temperature is 400 deg.C or lower in a nitrogen atmosphere, and turned into a mixture of the fine powder and mineral oil. The mixture is divided into the fine powder and the mineral oil by a centrifugal separator. The powder is oriented in a magnetic field and molded. The temperature of the molded object is raised up to 500 deg.C by a rate of 10 deg.C/min or smaller and at a pressure of 1Torr or lower. After that, the molded body is sintered at a temperature of 950-1150 deg.C and a pressure of 1Torr or lower.

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.

[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 for preventing such a rapid oxidation, a treatment of stabilizing the surface by leaving it in an inert gas such as nitrogen or argon for a long time has been performed.

[0003]

However, these methods have a problem in mass productivity because the processing takes a long time. 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.

[0004]

Means for Solving the Problems As a result of various investigations for solving these problems, the present inventors have found that the alloy powder for rare earth sintered magnets is immersed in mineral oil or synthetic oil and then separated to remove air from the atmosphere. We have come to discover that the alloy powder for rare earth sintered magnets can be stably handled. That is,
By coating the surface of the alloy powder for rare earth sintered magnets with mineral oil or synthetic oil, the adsorption of oxygen and moisture in the atmosphere can be suppressed, and the alloy powder for rare earth sintered magnets can be stably maintained in the atmosphere. It can be handled. Hereinafter, the present invention will be specifically described. The rare earth sintered magnet alloy according to the present invention may be of the R-Fe-B type, but is preferably R-
Fe (Co) -BM system is preferable, R is 25 to 35% by weight of one or more rare earth elements including Y, B is 0.8 to 1.2% by weight, M is Al, Nb. , Ti, V, Z
One or two or more of r, Mo, W, Ga, Cu, Zn, Ge, and Sn are contained in an amount of 5% by weight or less, and the balance is Fe or Fe and Co except for inevitable contaminants. As an alloy system, Nd-Fe-B-Al-Nb, 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-N
b, Nd-Dy-Fe-B-Al-Ga, Nd-Fe-
Dy-Co-B-Al-Ga and the like are exemplified, but the present invention is not limited thereto.

In order to obtain a low-oxygen rare-earth sintered magnet alloy fine powder having an oxygen content of 3000 ppm or less, there are a jet mill in a low-oxygen atmosphere in a dry system, a ball mill, an attritor pulverization in a wet system and the like. Then, in order to immerse the fine powder obtained by crushing in mineral oil or synthetic oil, in the case of dry crushing, after crushing, soak in mineral oil or synthetic oil in a reducing or non-oxidizing atmosphere and wet crush In this case, the raw material coarse powder may be immersed in mineral oil or synthetic oil before crushing. The mineral oil or synthetic oil used here preferably has a maximum distillation point of 400 ° C. or lower. For mineral oils or synthetic oils with the highest fractional boiling points higher than this, sintering will occur because the mineral oils or synthetic oils and the rare earth elements of the compact react to form carbides even if sintered by the method described below during sintering. This is because it may not be possible to sufficiently generate the liquid phase required for the above. Next, as a method for separating the fine powder soaked from the mineral oil or the synthetic oil, natural filtration, vacuum filtration, centrifugal separation and the like can be considered, but any method may be used. This fine powder is pressure-molded in a state of being orientated in a magnetic field as is generally done to obtain a molded body.

The obtained compact is sintered in a sintering furnace, but when heated from room temperature to a temperature of 500 ° C. or more at a temperature rising rate of 20 ° C./min or more under a reduced pressure of 1 Torr or less, In some cases, the residual mineral oil or synthetic oil reacts with the rare earth element of the compact to form a carbide, and the liquid phase required for sintering cannot be sufficiently generated. To prevent this, the following method should be adopted. (1) The temperature rising rate from room temperature to 500 ° C. is 10 ° C./mi
The pressure during this period and during sintering is set to 1 Torr or less. (2) 1 point or 2 in the temperature rising process from room temperature to 500 ° C
The temperature is maintained for 30 min or more at a temperature above the point, and the pressure during this and during sintering is set to 1 Torr or less. (3) The methods of (1) and (2) are used together.

[0007]

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.
An ingot having 0%, B = 1.0%, Al = 0.3% and the balance Fe was manufactured. The ingot was coarsely pulverized, and then finely pulverized by using a jet mill in nitrogen having an oxygen content of 10 ppm. The average particle size of the fine powder was 4.1 μm. The fine powder obtained by pulverization was immersed in a nitrogen atmosphere in a mineral oil having a fractionation point of 200 to 300 ° C. and a kinematic viscosity of 2.0 cSt at room temperature (manufactured by Idemitsu Kosan Co., Ltd., trade name MCOIL P-02). , A mixture of fine powder and mineral oil. The mixture was separated into fine powder and mineral oil by a centrifuge, oriented with an orientation magnetic field strength of 15 kOe, and shaped to obtain a shaped body. This compact was inserted into a sintering furnace and the temperature was raised from room temperature to 500 ° C at 10 ° C / mi.
n, heating at 0.1 Torr, then 11 at the same pressure
The temperature was raised to 00 ° C. at 30 ° C./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 then 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, Nd = 29% by weight, B = 1.0%, Al = 0.3%, balance F
An ingot called e was manufactured. This ingot was roughly crushed, and then the amount of oxygen in the atmosphere was 10 p using a jet mill.
Milled in pm nitrogen. The average particle size of the fine powder is 4.1.
was μm. The fine powder obtained by pulverization has a distillation point in a nitrogen atmosphere of 200 to 300 ° C. and a kinematic viscosity of 2.0 at room temperature.
Mineral oil of cSt (made by Idemitsu Kosan, trade name MC OIL P-
It was immersed in the mineral oil of No. 02) to prepare a mixture of fine powder and mineral oil. The mixture was separated into fine powder and mineral oil by a centrifuge, oriented with an orientation magnetic field strength of 15 kOe, and shaped to obtain a shaped body. Insert this compact into a sintering furnace and remove from room temperature to 500
Up to 10 ° C / min at a pressure of 0.1 Torr, then at the same pressure up to 1100 ° C at 30 ° C / min,
After holding for 2 hours, the furnace was cooled. The obtained sintered body was subjected to the same heat treatment as in Example 1 to measure the amount of oxygen, the amount of carbon and the magnetic properties, and sufficient properties were obtained as shown in Table 1.

Example 3 A rare earth sintered magnet alloy having the same composition as in Example 1 was formed into a compact by the same steps as in Example 1. This compact was inserted into a sintering furnace and the pressure was 0.1 Torr.
At r, the temperature was raised from room temperature to 350 ° C. at 10 ° C./min, held for 3 hours, then raised to 500 ° C. at 10 ° C./min, raised from 500 ° C. to 1100 ° C. at 20 ° C./min, held for 2 hours and cooled in the furnace. . The obtained sintered body was subjected to the same heat treatment as in Example 1 to measure the amount of oxygen, the amount of carbon and the magnetic properties, and sufficient properties were obtained as shown in Table 1. (Example 4) A rare earth sintered magnet alloy having the same composition as in Example 2 was formed into a compact by the same steps as in Example 2. This compact was inserted into a sintering furnace, heated from room temperature to 350 ° C. at 10 ° C./min at a pressure of 0.1 Torr, and held for 3 hours, then 5
The temperature was raised from 00 ° C. to 10 ° C./min, from 500 ° C. to 1100 ° C. at 30 ° C./min, held for 2 hours, and then cooled in the furnace. The obtained sintered body was heat treated in the same manner as in Example 1 to obtain an oxygen content,
When the amount of carbon and the magnetic properties were measured, sufficient properties were obtained as shown in Table 1.

(Example 5) A rare earth sintered magnet alloy having the same composition as in Example 1 was used as a mineral oil having a fractional distillation point of 200 to 400 ° C and a kinematic viscosity of 5.0 cSt at room temperature (manufactured by Idemitsu Kosan Co., Ltd. Using the name MC OIL P-05), a molded product was obtained in the same process as in Example 1. This molded body was heated at a pressure of 0.1 Torr from room temperature to 1100 ° C. at 20 ° C./min, kept at the same pressure for 2 hours, and then cooled in a furnace. The obtained sintered body was subjected to the same heat treatment as in Example 1 and the amount of oxygen, the amount of carbon and the magnetic properties were measured. As shown in Table 1, it was possible to realize an oxygen amount as low as in Example 1. It was (Example 6) An alloy for rare earth sintered magnets having the same composition as in Example 1 was used, with a fractionation point of 300 to 500 ° C and a kinematic viscosity of 3 at room temperature.
1.5 cSt mineral oil (made by Idemitsu Kosan, trade name MC OI
L S-32) was used to obtain a molded product in the same process as in Example 1. This molded body was pressed at a pressure of 0.1 Torr from room temperature to 11
The temperature was raised to 00 ° C. at 20 ° C./min, held at the same pressure for 2 hours, and then cooled in the furnace. The obtained sintered body was subjected to the same heat treatment as in Example 1 to measure the amount of oxygen, the amount of carbon, and the magnetic properties. As shown in Table 1, the amount of oxygen as low as in Examples 1 to 4 was obtained. It was realized.

(Example 7) 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 crushed, and then the amount of oxygen in the atmosphere was 10 p using a jet mill.
Milled in pm nitrogen. The average particle size of the fine powder is 4.0.
was μm. The fine powder obtained by pulverization has a fractionation point of 200 to 300 ° C. in a nitrogen atmosphere and a kinematic viscosity of 2.5 at room temperature.
A synthetic oil of cSt (manufactured by Idemitsu Kosan Co., Ltd., trade name: Daphne Cleaner H) was dipped into a mixture of fine powder and synthetic oil. This mixture was separated into fine powder and synthetic oil by a centrifuge, oriented with an orientation magnetic field strength of 15 kOe, and shaped to obtain a shaped body.
Insert this compact into a sintering furnace and increase the temperature from room temperature to 500 ° C.
The temperature was raised at a temperature of 0.1 ° C./min and a pressure of 0.1 Torr, then the temperature was raised to 1100 ° C. at a rate of 30 ° C./min, and the furnace was cooled after holding for 2 hours. The obtained sintered body was subjected to the same heat treatment as in Example 1 to measure the amount of oxygen, the amount of carbon and the magnetic properties, and sufficient properties were obtained as shown in Table 1.

(Embodiment 8) As starting materials for rare earth sintered magnets, predetermined amounts of electrolytic iron, ferroboron and Nd are weighed,
By melting and casting in a high-frequency melting furnace, Nd = 29% by weight, B = 1.0%, Al = 0.3%, balance F
An ingot called e was manufactured. This ingot was roughly crushed, and then the amount of oxygen in the atmosphere was 10 p using a jet mill.
Milled in pm nitrogen. The average particle size of the fine powder is 3.9.
was μm. The fine powder obtained by pulverization has a fractionation point of 200 to 300 ° C. in a nitrogen atmosphere and a kinematic viscosity of 2.5 at room temperature.
A synthetic oil of cSt (manufactured by Idemitsu Kosan Co., Ltd., trade name: Daphne Cleaner H) was dipped into a mixture of fine powder and synthetic oil. This mixture was separated into fine powder and synthetic oil by a centrifuge, oriented with an orientation magnetic field strength of 15 kOe, and shaped to obtain a shaped body.
Insert this compact into a sintering furnace and increase the temperature from room temperature to 500 ° C.
The temperature was raised at a temperature of 0.1 ° C./min and a pressure of 0.1 Torr, then the temperature was raised to 1100 ° C. at a rate of 30 ° C./min, and the furnace was cooled after holding for 2 hours. The obtained sintered body was subjected to the same heat treatment as in Example 1 to measure the amount of oxygen, the amount of carbon and the magnetic properties, and sufficient properties were obtained as shown in Table 1.

Example 9 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 crushed, and then the amount of oxygen in the atmosphere was 10 p using a jet mill.
Milled in pm nitrogen. The average particle size of the fine powder is 3.8.
was μm. The fine powder obtained by pulverization has a fractionation point of 200 to 300 ° C. in a nitrogen atmosphere and a kinematic viscosity of 2.5 at room temperature.
A synthetic oil of cSt (manufactured by Idemitsu Kosan Co., Ltd., trade name: Daphne Cleaner H) was dipped into a mixture of fine powder and synthetic oil. This mixture was separated into fine powder and synthetic oil by filtration under reduced pressure, oriented with an orientation magnetic field strength of 15 kOe, and shaped to obtain a shaped body. Insert this compact into a sintering furnace and change from room temperature to 500 ° C at 10 ° C.
/ Min, the temperature was raised at a pressure of 0.1 Torr, then the temperature was raised to 1100 ° C at 30 ° C / min at the same pressure, and the furnace was cooled after holding for 2 hours. The obtained sintered body was subjected to the same heat treatment as in Example 1 to measure the amount of oxygen, the amount of carbon and the magnetic properties, and sufficient properties were obtained as shown in Table 1. (Comparative Example 1) A rare earth sintered magnet alloy having the same composition as in Example 1 was pulverized in the same manner as in Example 1, and when the obtained fine powder was taken out into the air, it immediately ignited, The fine powder could not be handled. (Comparative Example 2) A rare earth sintered magnet alloy having the same composition as in Example 1 was pulverized in the same manner as in Example 1, and the fine powder obtained was Ar.
Stabilization was performed for 48 hours in the atmosphere. This fine powder was molded in the same manner as in Example 1, heated from room temperature to 1100 ° C. at a temperature of 20 ° C./min at a pressure of 0.1 Torr, held for 2 hours, and then cooled in a furnace to obtain a sintered body. When this sintered body was subjected to the same heat treatment as in Example 1 and the oxygen content, carbon content and magnetic characteristics were measured, the oxygen content was high and the magnetic characteristics were lower than in Example 1.

[0014]

[Table 1] ──────────────────────────────── ρs oxygen content carbon content Br iHc (BH) max g / cm3 ppm ppm kG kOe MGOe ──────────────────────────────── Example 1 7.59 1890 580 13.2 14.6 41.6 Example 2 7.59 2140 520 13.5 13.7 42.2 Example 3 7.59 1910 560 13.4 14.4 42.1 Example 4 7.59 1880 510 13.8 13.7 43.8 Example 5 7.58 2020 850 13.2 13.5 40.8 Example 6 7.58 1990 890 13.1 13.5 40.6 Example 7 7.59 1860 250 13.2 15.0 41.7 Example 8 7.59 1900 200 13.5 13.8 42.5 Example 9 7.60 1950 230 13.2 14.8 41.6 Comparative Example 2 7.32 5800 480 11.3 5.6 3.5 ρs: sintered body density

[0015]

As described above, by producing a rare earth sintered magnet by the method according to the present invention, a low oxygen and low carbon sintered body can be stably produced.

Claims (4)

[Claims] 1. A raw material fine powder for an R-Fe-B (R is one or more of rare earth elements including Y) -based rare earth sintered magnet is immersed in a mineral oil or a synthetic oil, and then this is immersed. A method for producing a rare earth sintered magnet, characterized in that a powder coated with mineral oil or synthetic oil is obtained after separation, and the powder is molded and sintered. 2. A fractional distillation point of a mineral oil or a synthetic oil in which an R-Fe-B (R is one or more kinds of rare earth elements including Y) -based rare earth sintered magnet raw material fine powder is immersed. 2. The method for producing a rare earth sintered magnet according to claim 1, wherein the maximum value of is less than or equal to 400 ° C. 3. The molded body is heated to 500 ° C. at a pressure of 1 Torr or less and a temperature rising rate of 10 ° C./min or less, and then 95
The method for producing a rare earth sintered magnet according to claim 1 or 2, wherein the sintering is performed at 0 to 1150 ° C and a pressure of 1 Torr or less. 4. The molded body is kept at 500 ° C. or lower at a pressure of 1 Torr.
Hold 1 or 2 or more points below and then 950-115
The method for producing a rare earth sintered magnet according to claim 1, wherein the sintering is performed at 0 ° C. and a pressure of 1 Torr or less.