JPH0314204A - Manufacture of rare earth magnet - Google Patents

Abstract

PURPOSE: To prevent oxidation of magnetic powder and manufacture a sintered area earth magnet excellent in magnetic characteristics, by forming premix by grinding rough particles obtained by grinding an ingot, together with specific titanate binder, drying the premix in a vacuum or an inert atmosphere, pressing and magnetizing the premix in a magnetic field and then performing sintering. CONSTITUTION: Constitutent elements of a rare earth magnet are alloyed and an ingot is formed, which is ground and turned into rough particle having an average diameter of 80-120μm. The rough particles are pulverized together with titanate binder, and premix is obtained. The binder is expressed by a formula (R<1> O)m-Ti(O-X-R<2> )n where (m) is 1-5, (n) is 2 or 3, R<1> is hydrogen or C1 -C10 alkyl, X is phosphate or pyrophosphate or phosphite, and R<2> is C3 -C15 alkyl. The premix is dried in a vacuum or an inert atmosphere. Next it is pressed and magnetized in a magnetic field, and magnetic product having a desired shape is formed. It is sintered by raising a temperatures up to the sintering temperatures. In this case, the temperature is raised at a rate of 0.5-5 deg.C per minute, in the range from about 400 deg.C to about 500 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION It has been a long-standing desire to produce relatively inexpensive, high performance permanent magnets. The performance of such a permanent magnet is, for example, coercive force (Hc) or maximum coercive force, residual magnetization (Br
) or residual magnetism, and Zen large magnetic energy product (BH
)+nax.

In the search for satisfactory permanent magnets, permanent magnets composed of rare earth elements and cobalt elements, most significantly samarium-cobalt magnets, have come to prominence since the 1970s. Due to the unquestionable superiority of these magnets in magnetic performance, rare earth-cobalt magnets account for 20% of today's permanent magnet market. However, rare earth powders are very active in air and can be extremely flammable, so great care must be taken in their manufacture to prevent oxidation. A number of remedies have been taken to overcome the above problems, some of which include the use of antioxidants.

Due to the high prices of samarium and cobalt, which are produced in relatively small quantities, a new series of permanent magnets made from neodymium iron-boron, which is less expensive, has been developed (neodymium is cheaper than samarium and iron is less expensive than cobalt). are also inexpensive). Among them, in 1983, Sumitomo
o Co, a neodymium-iron-boron permanent magnet manufactured by a powder metallurgy method developed by Sagawa (Japan), and Gene
The same magnet manufactured by the rapid solidification method developed by Croat of RAL Motor Co., USA is considered to be a representative example. However, neodymium-iron-boron magnetic powders are much more active in air than samarium-cobalt magnetic powders, so oxidation prevention becomes more important.

In the production of sintered magnets, it is extremely difficult to prevent oxidation because high temperature operations are involved.

One method is to manufacture magnets in vacuum or in an inert atmosphere, and this method is quite effective in preventing oxidation of the magnetic powder. However, completely preventing oxidation in air is very difficult and requires high cost.

In the production of plastic magnets, it has been taught that it is effective to use a phosphate or phosphoric acid aqueous solution containing trace amounts of nylon and silicone oil to prevent oxidation of magnetic powder with an average particle size of several tens to hundreds of micrometers. ing. This method is effective for injection molding plastic materials at about 200-230°C. A typical reference for this is Tsuchi, February 5, 1985.
U.S. Pat. - No disclosure is made regarding the prevention of oxidation of iron-boron magnetic powder.

For example, Elvaoite + Microu + ax, 8 cr
au+ax+Carboulax.

Rare earth magnet manufacturing lubricants such as stearic acid and stearate have been disclosed to be effective in providing some degree of oxidation protection. This typical reference is 1
Japanese Patent Application Publication Section (Sho) 61 published on March 8, 1985
-Specification No. 90401 and C dated June 22, 1976
U.S. Patent No. 3 to I+ aandros et al.
No. 964.939. This method is not applicable to the oxidation prevention of powder metallurgy neodymium-iron-boron magnetic powder due to its weak oxidation prevention ability.

Certain specific dyes, such as direct dyes, acid dyes, alkaline dyes, curable dyes, intermediate dyes (me
diurn dyes), oil dyes and disperse dyes are often used. A typical reference for this is 19
U.S. Patent No. 3 in the name of Smeggill et al., dated July 1, 1975.
, 892,600, but does not disclose oxidation prevention of powder metallurgy neodymium-iron-boron magnetic powder.

Japanese Patent Application Publication No. 60-244004 describes the use of organopolysiloxane as a binder in the production of plastic magnets to improve the mixing and bonding of magnetic powder and plastic components. ing.

Japanese Patent Application Publication No. 60-14406 describes the use of titanate binders in a similar process, but does not discuss oxidation prevention in the manufacture of sintered magnets.

Oxidation of magnetic powder in the production of plastic magnets has been successfully prevented by certain antioxidants;
There is no satisfactory method of preventing oxidation using antioxidants for the manufacture of rare earth magnets using powder metallurgy methods.

Therefore, it would be desirable to provide a method for efficiently and economically preventing oxidation of magnetic powder in powder metallurgy of rare earth neodymium-iron-boron magnets. Of course, this method is also applicable to the production of rare earth-cobalt magnets.

An object of the present invention is to provide a method for preventing oxidation of magnetic powder in the production of sintered magnets.

Another object of the present invention is to provide a method for manufacturing sintered rare earth magnets with excellent magnetic properties.

Yet another object of the present invention is to provide a method for preventing oxidation of neodymium-iron-boron magnetic powder in the production of neodymium-iron-boron magnets.

The present invention provides a method for producing an organic solvent with excellent magnetic performance, comprising: (i) alloying the constituent elements of the rare earth magnet to form an ingot; and (ii) pulverizing the ingot. average particle size 80-12
0 micron coarse particles with temperature; (iii) the coarse particles with the formula: % formula %) [where m is 1 to 5, n is 2 or 3, and R1 is hydrogen or C1-C1°] alkyl, X is phosphate, pyrophosphate or phosphite, and R2 is C3-C. (v) pressing and magnetizing said dried premix in an aligned magnetic field to produce a magnetized product of the desired shape; (vl) controlling the temperature. The sintering temperature (v
i) sintering the magnetized product by sintering the temperature at a rate of 0.5-5°C per minute from about 400°C to about 500°C before reaching the sintering temperature; and a sintering step.

(This specification is condensed into the claims which specifically state and distinctly claim what is considered to be the invention,
It is believed that the invention will be better understood from reading the detailed description and accompanying examples below.

The method of the invention begins with alloying the component elements in the desired organic solvent to obtain an ingot.

The "component element" is an element commonly known for producing rare earth magnets. The present invention is particularly suited to two categories of organic solvents. One of them is classified as a neodymium-iron-F1Z permanent magnet, and has the formula R'-T'
+oo---2B, , where R' is neodymium, praseodymium, dysprosium, terbium or any mixture thereof, preferably neodymium or praseodymium, and T' is iron, cobalt or any mixture thereof , B is boron, is 13 to 20, and y is 5 to 12). Another range of magnets are those classified as samarium-cobalt magnets, with the formula R″T″, where R″ is samarium, praseodymium, or any mixture thereof, preferably samarium, and T″ is cobalt, iron, copper, zinc or any mixture thereof, and 2 is 4,0
~9.5). Alloying of these elements is preferably carried out in an induction furnace by any conventional method.

The obtained alloy ingot was then crushed to an average particle size of 80
Creates coarse particles of ~120 microns. Furthermore, the coarse particles obtained are pulverized, for example, by a ball mill. A titanate binder is added during milling to impart antioxidant capacity to the particles in the subsequent process. The titanate binder used in the present invention has the formula (R'O)m-Ti(0-X-R
2) n (wherein lees is 1-5', n is 2 or 3, R1 is hydrogen or C+-C+O alkyl, X is phosphate, pyrophosphate or phosphite, and R2 is C3-Cl3 alkyl). The milling step is preferably carried out in an organic solvent, including methanol,
Ethanol, isopropyl, toluene, xylene, n-
Hexane or cyclohexane. The milling step continues until the particles have an average particle size of less than about 3 microns.

The resulting mixture is then dried in vacuo or in an inert atmosphere. After drying, the alloy particles become oxidation resistant and can be further processed in an unprotected atmosphere. Further processing steps include powder metallurgy, magnetization and sintering. Since the antioxidant ability is effectively improved by adding a specific antioxidant, the magnetization and magnetic reproducibility can be improved in the present invention.

This is also one of the new aspects of the present invention.

The protected alloy particles are then pressed into a mold by conventional powder metallurgy techniques in an aligned magnetic field to obtain the desired shape of the magnet. The magnet is heated to a sintering temperature and sintered at a sintering temperature to produce the final product. The sintering temperature is typically 1
The temperature is 040-1120°C.

However, the sintering step must include certain slow heating and degassing steps before the temperature is raised to the sintering temperature to remove residual antioxidants. That is, about 40
Preferably, the temperature is increased in steps of 0.5-5°C from 0°C to about 500°C.

The sintered magnet can be further heat treated by conventional methods to impart other desired properties.

Examples are provided below to assist in understanding the invention, but these examples do not limit the scope of the invention. All parts and percentages are by weight unless otherwise noted.

In the examples, the magnetic properties are DCMag of YEW CO,
netic Hysteresis Loop Trac
er (Type 3257).

1 Example Example 1: 100g of (Ndo+9Dyo,+)+5Fe7tBa ingot was ground to ^STM40 mesh and then finely ground in hexane using a ball mill to obtain an average particle size of F,
S, S, S, 3.0±0.211m. Neoalkoxyltri(dioctyl)phosphate titanate 0.33% was added as an antioxidant during milling. The resulting mixture was then dried by heating in a vacuum, and the dried powder was pressed into a cube with a side length of 1 cm in an external magnetic field of 15 kOe in air. The direction of the magnetic field was perpendicular to the direction of the press. The obtained compact was sintered at 1080° C. for 1 hour and then rapidly cooled. Temperature ranges from room temperature to 1080℃
The temperature was then increased by approximately 15°C, but the temperature was increased to 400°C during the degassing stage.
The temperature was slowly increased from 0.degree. C. to 500.degree. C. at a rate of about 3.5.degree. C./min. Next, the green compact was heat treated at 600°C for 1 hour. The magnetic properties of the obtained magnet were as shown by curve A in FIG.

As a comparative experiment, the above method was carried out without the addition of neoalkoxyl tri(dioctyl)phosphate titanate. When this obtained magnet was measured, it was as shown by curve B in FIG.

From FIG. 1, it is clear that the magnet produced by the method of the present invention has excellent properties.

Example 2: (Ndo, asDyo, +□)+5FeyJs ingot was used and neoalkoxyl tri(
Magnets were prepared in the same manner as above using dioctyl) pyrophosphate titanate. The amount of antioxidant was varied in each preparation. The maximum energy product of these products <
(Bll>max), remanence (Br), maximum intrinsic coercivity (iHc) and density (D>) were measured and are shown in Table I.

Amount of topsoil antioxidant (Bll) may Br iHc 0.005 0.10 0.33 0.52 0.85 1.21 1.57 1.94 2.47 2.98 4.05 5.07 24. 5 26.0 28.0 28.8 29.6 30.3 29.3 28.7 27.0 24.0 20.9 35 3.5 10.3 10.8 10.9 11.3 11.4 12 10.9 10.8 10.5 00 9.4 7.8 4.3 13.7 14.7 14.7 15.9 17.0 17.3 17.4 17.3 16.8 15.0 12.8 9.0 2.5 7.46 7.48 51 7.50 7.47 7.48 7.45 7.45 7.44 7.42 7.40 7.38 7.35 Example 3゜(Ndo, gTbo2)+3Fea+Bs ingot 1
00g was ground to ^STM40 mesh, and then finely ground in 78 ethanol using a ball mill to give an average particle size of F, S, S, S,
0.85 g of di(dioctyl)pyrophosphate oxoethylene titanate was added as an antioxidant during the milling. The resulting mixture was then heated in vacuo. Dried, the dried powder was divided into five groups and exposed to the atmosphere for 0.1, 2.3 and 4 hours respectively, then - 15 kOe was applied to a cube with side length 1 cm.
Press molding was carried out in an external magnetic field. The direction of the magnetic field was parallel to the direction of the press. The obtained compact was subjected to the same sintering and heat treatment as in Example 1, and the magnetic properties of the obtained magnet were measured in the same manner as shown in Table 3.

As a comparative experiment, the above method was carried out without adding an antioxidant, and the obtained magnets were measured, and the results were as shown in Table 3.

Table 1 26.6 26.0 26.5 26.5 26.0 10.7 07 10.7 10.7 10.7 12.0 11.9 11.8 11.9 11.9 Table 1 23.5 10.2 23.0 10.1 22.5 10.0 21.0 9.7 12.0 12.0 11.7 11.2 As can be seen from Table ■, the powder prepared by the method of the present invention has 4
Will not deteriorate after exposure to atmosphere for up to an hour. In contrast, without the addition of antioxidants, the magnetization of the resulting magnet decreases with increasing exposure time.

Example 4: A Nd20pe6:l[l+□ ingot was milled in toluene for 40 minutes using a ball mill. In seven experiments, di(dictyl birophosphate oxoethylene titanate) was added as an antioxidant during milling at 0.
0.005.0.21.0.44.0.85.2.2 and 5.0% by weight were added. The resulting mixture was then dried, press-molded, sintered, and heat treated in the same manner as in Example 1. The magnet thus obtained was polished and analyzed for oxygen content using a LECOTC-136 nitrogen-oxygen analyzer, with the results shown in Table 3.

The average particle size of the dry powder was also measured before press molding.

It can be seen that as the amount of antioxidant added increases, the oxygen content decreases considerably. Addition of antioxidants also helps reduce the average particle size of the dried magnetic powder.

Table 1 0 2 , 65
B5500.005 2.
62 78000.21
2.58 B2500.44
2.54 52850
．． 85 2.50
52202.2 2.52
53105.0
2.64 5155 Example 5: Sm(Coo, ++5Feo2tCuo, o6Zro,
o2) Finely mill the t, s ingot in cyclohexane using a ball mill to obtain average particle sizes F, S, S, S 4.
The temperature was set at 5±0.2 pm. di(dioctyl)phosphate ethylene titanate 0.2 as an antioxidant during milling
Weight % added. The resulting mixture was then dried by heating in vacuo, and the dried powder was pressed into a cube with side length ICwl in an external magnetic field of 15 kOe. The direction of the magnetic field was set at right angles to the direction of the press. The obtained green compact was heated at 1150°C for 1 time, including a mild heating step as in the case of Male Side 1.
sintering for 1 hour, followed by 10 hours at 850°C and 1 hour at 700°C.
time, 1 hour at aOO℃, 1 hour at 500℃, further 40
Heat treatment was performed at 0°C for 1 hour. The magnetic properties of the obtained magnet were measured and were as shown by curve A in FIG.

As a comparative experiment, the above method was carried out without adding di(dioctyl)phosphate ethylene titanate, and the characteristics of the obtained magnet were measured, and the characteristics were as shown in curve B in FIG. It has been demonstrated that the addition of the antioxidant of the invention can increase the (BH)max value by 9%.

[Brief explanation of drawings]

1 and 2 are graphs representing the results of an example showing that magnets made by the method of the present invention are superior to prior art magnets. 3

Claims (13)

[Claims] (1) A method for manufacturing a rare earth magnet with excellent magnetic performance, comprising: (i) forming an ingot by alloying the constituent elements of the rare earth magnet; and (ii) crushing the ingot to obtain an average particle size of 80. ~1
(iii) coarsening to 20 microns;
The coarse particles have the formula: (R^1O)m-Ti(O-X-R^2)n [where m
is 1 to 5, n is 2 or 3, R^1 is hydrogen or C_1-C_1_0 alkyl, X is phosphate, pyrophosphate or phosphite, and R^2 is C_3-C_1_5 alkyl (iv) drying said premix in vacuum or in an inert atmosphere; and (v) aligning said dried premix. (vi) sintering the magnetized product by increasing the temperature to a sintering temperature and sintering the product at the sintering temperature; sintering step, about 40 min before reaching said sintering temperature.
a sintering step of increasing the temperature from 0<0>C to about 500<0>C at a rate of 0.5 to 5<0>C per minute. 2. The method of claim 1, wherein the milling step is carried out in an organic solvent selected from the group consisting of methanol, ethanol, isopropyl, toluene, xylene, n-hexane and cyclohexane. (3) The rare earth magnet has the formula: R'_xT'_1_0_0_-_x_-_yB_y [wherein R' is neodymium, praseodymium, dysprosium,
terbium or any mixture thereof; T' is iron, cobalt, or any mixture thereof; B is boron; x is 13 to 20; and y is 5 to 12. 2. The method of claim 1, which is a magnet. (4) The method according to claim 3, wherein said R' is neodymium or praseodymium. (5) The rare earth magnet has the formula: R″T″_z [wherein R″ is samarium, praseodymium, or any mixture thereof, and T″ is cobalt, iron, copper, zinc, or any mixture thereof. and z is 4.0 to 9.5.] The method according to claim 1, wherein the rare earth magnet is: (6) The method according to claim 5, wherein the R'' is samarium. (7) The titanate binder is selected from the group consisting of neoalkoxyl tri(dioctyl) pyrophosphate titanate, neoalkoxyl tri(dioctyl) pyrophosphate titanate, di(dioctyl) pyrophosphate oxoethylene titanate, and di(dioctyl) phosphate ethylene titanate. 2. The method of claim 1, wherein: 8. The method of claim 1, wherein the amount of titanate binder is from 0.005 to 5% by weight based on the total amount of the premix. 9. The method of claim 8, wherein the amount of titanate binder is from 0.005 to 2.5% by weight based on the total amount of the premix. 10. The method of claim 1, wherein the vacuum is less than or equal to 0.1 Torr. (11) The method according to claim 1, wherein the inert atmosphere is a hydrogen or argon atmosphere. (12) The method according to claim 1, wherein the sintering temperature is 1040 to 1120°C. (13) A rare earth magnet with excellent magnetic performance manufactured by the method according to claim 1.