CN1036554C - Permanent magnets with good thermal stability - Google Patents

Abstract

A permanent magnet with good thermal stability is basically composed of components that can be expressed by the following general formula:

R[Fe _1-xyz Co _x B _y Ga _z ] _A

Wherein R can be only neodymium, or one or more rare earth elements mainly composed of neodymium, praseodymium or cerium, 0≤x≤0.7, 0.02≤y≤0.3, 0.001≤z≤0.15, 4.0≤A≤7.5.

The permanent magnet may also contain one or more additional elements selected from niobium, tungsten, vanadium, tantalum and molybdenum. The permanent magnet has a large coercive force and a high Curie temperature, and thus has good thermal stability.

Description

Permanent magnets with good thermal stability

The invention relates to a rare-earth permanent magnet material, in particular to a rare-earth iron-boron permanent magnet material with good thermal stability.

So far, the new formulation of the rare earth iron boron permanent magnet better than the rare earth cobalt permanent magnet material has been developed (Japanese patent publication 59-46008, 59-64733 and 59-89401 and M.Sagawa et al. in 1984 Article written by "Journal of Applied Physics" on page 2083 of Volume 55, Issue 6, "New permanent magnet materials with neodymium and iron as the main components"). According to these documents, for example, an alloy of Nd ₁₅ Fe ₇₇ B ₈ [Nd(Fe _0.91 B _0.09 ) _5.67 ] has such magnetic properties: [BH] maximum is close to 35 megagauss Oersted, iHc is close to 10 kilooersted . However, the Curie temperature of clay iron boron magnets is low, so their thermal stability is poor. In order to solve these problems, an attempt was made to increase the Curie temperature by adding cobalt (Japanese Patent Laid-Open No. 59-64733). Specifically, the Curie temperature of the rare-earth iron-boron permanent magnet is about 300°C, and the highest is 370°C (Japanese Patent Publication 59-46008), and replacing part of the iron in the rare-earth iron-boron magnet with cobalt can increase the Curie temperature to 400-800°C (Japanese Laid-Open Patent No. 59-64733). Adding cobalt at the same time reduces the coercive force iHc of the rare earth iron boron magnet.

In the past, some people tried to increase the coercive force by adding aluminum, titanium, vanadium, chromium, manganese, zinc, hafnium, niobium, tantalum, molybdenum, germanium, antimony, tin, bismuth, nickel, etc. It has been pointed out that aluminum is particularly effective in increasing the coercive force (Japanese Patent Laid-Open No. 59-89401). However, since these elements are all non-magnetic elements except nickel, adding a large amount of these elements will reduce the residual magnetic flux density Br, thereby reducing the maximum [BH].

In addition, it has been proposed to replace part of neodymium with heavy rare earth elements such as terbium, dysprosium and holmium to increase the coercive force while maintaining a high [BH]max (Japanese Patent Laid-Open Nos. 60-32306 and 60-34005). Replacing part of neodymium with heavy rare earth elements can increase the coercive force from about 9 thousand Oersteds to 12-18 thousand Oersteds at the maximum [BH] of about 30 megagauss Oersteds, but because heavy rare earth elements are extremely expensive , so replacing part of neodymium with such heavy rare earth elements will increase the cost of rare earth iron boron magnets, which is not what we want.

In addition, it has been proposed to add cobalt and aluminum to improve the thermal stability of rare earth iron boron magnets (T, Mizoguchi et al., "Applied Physics Letters" 1986, Vol. 48, p. 1309). Replacing part of iron with cobalt can increase the Curie temperature Tc, but at the same time reduce iHc, which is probably because Nd〔Fe, Co〕 ₂ ferromagnetic precipitation phase appears at the grain boundary, thereby forming the crystal nucleus formation area of the reverse domain. Adding aluminum and cobalt at the same time can form a non-magnetic Nd [Fe, Co, Al] ₂ phase, which has the effect of inhibiting the generation of the crystal nucleus formation region of the reverse magnetic domain. However, since the addition of aluminum greatly reduces the Curie temperature Tc, the thermal stability of rare earth iron boron magnets containing cobalt and aluminum inevitably deteriorates at temperatures as high as 100°C or above. In addition, the coercive force of this magnet is only about 9 kOe.

It is therefore an object of the present invention to provide a rare-earth iron-boron permanent magnet with a raised Curie temperature and sufficient coercive force and thus improved thermal stability.

The inventors and colleagues of the present invention have carried out in-depth research on the above purpose, and found that adding gallium, or adding cobalt and gallium together, can produce rare earth iron boron with high Curie temperature, sufficient coercive force, high thermal stability and low cost. magnet.

That is to say, the good permanent magnet of thermal stability of the present invention basically is made up of the following composition of its expression:

R〔Fe _1-xyz Co _{x By} Ga _z 〕A in which R is only neodymium, or one or more rare earth elements mainly composed of neodymium, praseodymium or cerium, 0≤X≤0.7, 0.02≤Y≤0.3, 0.001 ≤Z≤0.15, 4.0≤A≤7.5.

Figure 1 is the relationship curve of the irreversible flux loss of NdFeB, NdFeB and NdFeBGa magnets as a function of heating temperature.

Figure 2 is the relationship curve of the irreversible flux loss of NdFeCoB, NdFeCoB and NdFeCoBGa magnets as a function of heating temperature.

Figure 3 is the relationship curve of the irreversible flux loss of NdFeCoB, NdFeCoBGa and NdFeCoBGaW magnets as a function of heating temperature.

Fig. 4 is the relationship curve of the irreversible magnetic flux loss of Nd [Fe _0.85-x Co _0.06 B _0.08 Ga _x W _0.01 ] _5.4 as a function of heating temperature.

Figure 5 shows the magnets prepared by (a) rapid quenching→heat treatment→resin bonding, (b) rapid quenching→heat treatment→hot pressing, and (c) rapid quenching→HIP*→upset forging. The relationship curve of temperature change. Note: *HIP＝Isobaric hot pressing

Figure 6 compares the magnetic properties of NdFeCoB, NdFeCoBAl and NdFeCoBGa magnets.

Figure 7 is Nd [Fe _0.72 Co _0.2 B _0.08 ] _5.6 , Nd _0.8 Dy _0.2 [Fe _0.72 Co _0.2 B _0.08 ] _5.6 , Nd [Fe _0.67 Co _0.2 B _0.08 Al _0.05 ] _5.6 and Nd [Fe _0.67 Co _0.2 B _0.08 Ga _0.05 〕 _5.6 The relationship curve of the irreversible magnetic flux loss of the magnet as a function of the heating temperature.

Figure 8(a) to (d) are Nd [Fe _0.72 Co _0.2 B _0.08 ] _5.6 , Nd _0.8 Dy _0.2 [Fe _0.72 Co _0.2 B _0.08 ] _5.6 , Nd [Fe _0.67 Co _0.2 B _0.08 Al _0.05 ] _5.6 and Nd [ Fe _0.67 Co _0.2 B _0.08 Ga _0.05 〕 _5.6 The relationship curve of the open-loop magnetic flux of the magnets changing with the heating temperature.

Figure 9(a) to (d) are Nd[Fe _0.67-zu Co _0.25 B _0.08 G _z W _u ] _5.6 , Nd[Fe _0.67 Co _0.25 B _0.08 ) ₅₆ , Nd[Fe _0.65 Demagnetization curves of Co _0.25 B _0.08 Ga _0.02 ] _5.6 and Nd [Fe _0.635 Co _0.25 B _0.08 Ga _0.02 W _0.015 ] _5.6 magnets.

The reason why the present invention limits the composition range of each component in the magnet alloy will be discussed below.

When cobalt is added to the rare-earth iron-boron magnet, its Curie temperature is increased, but its crystal magnetic anisotropy constant is decreased, thereby reducing the coercive force. However, when cobalt and gallium are added at the same time, a magnet with a higher Curie temperature can be obtained, thereby increasing the coercive force. Adding elements such as aluminum and silicon to rare earth iron-cobalt-boron magnets can increase the coercive force, but gallium can be added to maximize the coercive force. While heavy rare earth elements such as terbium, dysprosium, and holmium are commonly used to increase coercivity, the use of gallium minimizes the use of expensive heavy rare earth elements, if any. Therefore, adding gallium or adding cobalt and gallium at the same time can make up for the disadvantage of the low Curie temperature of rare earth iron boron magnets, which will lead to poor thermal stability. magnet.

The amount of cobalt represented by "X" is 0-0.7. When the amount of cobalt exceeds 0.7, the residual magnetic flux density Br becomes too low. In order to fully increase the Curie temperature Tc, the lower limit of cobalt is preferably 0.01, and in order to better balance the magnetic properties of iHc and Br and Tc, the upper limit of cobalt is preferably 0.4. The most ideal amount of cobalt is 0.05-0.25.

The addition of gallium will significantly increase the coercive force. This increase appears to be due to an increase in the Curie temperature of the BCC phase in the magnet. The BCC phase is a polycrystalline phase having a body-centered cubic crystal structure surrounding the NdFeB magnet [Nd ₂ Fe ₁₄ B] main phase in a width of 100 to 5000 angstroms. The BCC phase is surrounded by a neodymium-rich phase (neodymium: 70-95 atomic percent, the rest is iron). The Curie temperature of this BCC phase corresponds to the temperature at which the coercive force of the magnet is lower than 50 Oersted, and greatly affects the temperature characteristics of the magnet. The addition of gallium can increase the Curie temperature of the BCC phase and effectively improve the temperature characteristics.

The amount of gallium represented by "Z" is 0.001-0.15. When the amount of gallium is less than 0.001, there is basically no effect on raising the Curie temperature of the magnet. On the other hand, when "Z" exceeds 0.15, the saturation magnetization and Curie temperature will be greatly reduced, resulting in an undesirable permanent magnet material. The more ideal amount of gallium is 0.002-0.10, and the most ideal amount of gallium is 0.005-0.05.

When the amount of boron represented by "Y" is less than 0.02, the Curie temperature is low and high coercive force cannot be obtained. On the other hand, when the boron amount "Y" is larger than 0.3, the saturation magnetization increases to form a phase undesirable for magnetic properties. Therefore, the amount of boron should be 0.02 to 0.3. The ideal range of "Y" is 0.03-0.20. The most ideal amount of boron is 0.04-0.15.

When "A" is less than 4, the saturation magnetization is low, and when "A" exceeds 7.5, a phase rich in iron and cobalt appears, so that the coercive force is greatly reduced. Therefore, "A" should be 4.0 to 7.5. The ideal "A" range is 4.5 to 7.0. The most ideal "A" range is 5.0 to 6.8.

The permanent magnets of the present invention may also contain additional elements, which are generally represented by "M" in the following formula:

R〔Fe _1-xyzu Co _{x By} Ga _{z Mu} 〕 _A wherein R can be neodymium alone, or one or more rare earth elements mainly composed of neodymium, praseodymium or cerium, and some of them can be replaced by dysprosium, terbium or holmium, M is one or more elements selected from niobium, tungsten, vanadium, tantalum or molybdenum, 0≤X≤0.7, 0.02≤Y≤0.3, 0.001≤Z≤0.15, 0.001≤u≤0.1, 4.0≤A≤7.5 .

Niobium, tungsten, vanadium, tantalum or molybdenum are added to prevent grain growth. The amount of these elements represented by "u" is 0.001 to 0.1. When "u" is less than 0.001, no sufficient effect can be obtained, and when "u" exceeds 0.1, the saturation magnetization is greatly reduced to give an undesirable permanent magnet.

Adding niobium does not reduce Br (residual magnetic flux density) as much as adding gallium, but slightly increases iHc. Niobium is effective in improving corrosion resistance, so niobium is a highly effective additive when highly heat resistant alloys may be exposed to higher temperatures. When the amount of niobium represented by "u" is less than 0.001, the effect of raising iHc sufficiently cannot be exerted, and the corrosion resistance of the magnet alloy is not high enough. On the other hand, when the amount of niobium exceeds 0.1, the Br and Curie temperature will drop significantly, which is not desirable. The ideal range of niobium is 0.002≤Z≤0.04.

Adding tungsten (w) can greatly improve the temperature characteristics. When the amount of tungsten ["u"] exceeds 0.1, the saturation magnetization and coercive force decrease greatly. When "u" is smaller than 0.001, sufficient effects cannot be obtained. The ideal amount of tungsten is 0.002-0.04.

As for the rare earth element "R", neodymium alone, or neodymium in combination with a light rare earth element such as praseodymium or cerium, or praseodymium plus cerium, may be used. When containing praseodymium and/or cerium, the ratio of praseodymium to neodymium can be 0:1～1:0, and the ratio of cerium to neodymium can be 0:1～0.3:0.7.

Neodymium can also be replaced by dysprosium, which slightly increases the Curie temperature and coercive force iHc. Therefore, adding dysprosium can effectively improve the thermal stability of the permanent magnet of the present invention. However, excessive dysprosium will lead to a decrease in the residual magnetic flux density Br. Therefore, the ratio of dysprosium to neodymium should be 0.03:0.97～0.4:0.6 according to the original ratio. The ideal atomic ratio is 0.05-0.25.

The permanent magnet of the present invention can be produced by powder metallurgy, rapid quenching or resin bonding. These methods are described below.

(1) powder metallurgy method

The magnet alloy is prepared by arc melting method or high frequency melting method. The purity of raw materials: 90% or more of rare earth elements, 95% or more of iron, 95% or more of cobalt, 90% or more of boron, 95% or more of gallium, M (niobium, tungsten, vanadium, tantalum, Molybdenum) (if any) is 95% or more. The boron raw material may be an iron-boron alloy, and the gallium raw material may be an iron-gallium alloy. In addition, the raw material of M (niobium, tungsten, vanadium, tantalum, molybdenum) can be iron-niobium alloy, iron-tungsten alloy, iron-vanadium alloy, iron-tantalum alloy or iron-molybdenum alloy. In view of the fact that iron-boron alloy and iron-gallium alloy inevitably contain Impurities such as aluminum and silicon, so the synergistic effect of elements such as gallium, aluminum and silicon can be used to obtain high coercive force.

The crushing process may include crushing and grinding processes. Crushing can be carried out by stamping mill, jaw crusher, brown mill, rolling mill, etc., and grinding can be carried out by jet mill, vibration mill, ball mill, etc. In any case, the pulverization process is best carried out in a non-oxidizing atmosphere to prevent oxidation of the alloy. The final particle size is preferably 2-5 microns [FSSS].

The resulting fine powder is pressed with a mold in a magnetic field. To make the alloy have anisotropic properties, it is essential that the C axes of the magnetic powder to be pressed should be arranged in the same direction. Sintering is carried out at 1050°C to 1150°C in an inert gas such as argon, helium, etc. or in vacuum or in hydrogen. Heat treatment is carried out on the sintered magnet alloy at 400 ℃ ~ 1000 ℃.

(2) Rapid quenching

The magnet alloy is prepared in the same manner as the powder metallurgy method (1). The resulting alloy melt is rapidly quenched with a single-roll or double-roll quenching device. That is, for example, an alloy melted by high frequency is sprayed through a nozzle onto a roll rotating at a high speed, thereby rapidly quenching it. The obtained flake product is heat-treated at 500-800°C. Materials made by this rapid quenching method can be used as three types of permanent magnets.

A) The resulting sheet-like product is pulverized to a particle size of 10 to 500 micrometers with a roller mill or the like. The powder is mixed with, for example, epoxy resin for molding, or nylon resin for injection molding. In order to improve the adhesion between the alloy powder and the resin, an appropriate coupling agent can be added to the alloy powder before blending. The resulting magnets are isotropic.

B) Use a hot press or isobaric hot press (HIP) to press the flake product to produce a loose isotropic magnet. The magnets thus prepared are isotropic.

c) The loose isotropic magnet obtained in (b) above was upset-forged to be flattened. Plastic deformation makes the magnet anisotropic, that is, its C axes are aligned in the same direction. The magnets thus prepared are anisotropic.

(3) Resin bonding method

The raw material can be the rare earth iron-cobalt-boron-gallium alloy obtained in the above (1), the sintered object obtained by crushing and sintering the above alloy, the rapidly quenched flakes obtained in the above (2), or the hot-pressed or upset forged flakes. loose product. These loose products are crushed into a particle size of 30-500 microns with jaw crusher, brown mill, roller mill, etc. The resulting fine powder is mixed with a resin for molding or injection molding. Applying a magnetic field during the molding process results in anisotropic magnets with their C-axes aligned in the same direction.

Now introduce the content of the present invention in further detail by following examples.

In the examples, the raw materials used were neodymium 99.9% pure, iron 99.9% pure, cobalt 99.9% pure, boron 99.5% pure, gallium 99.9999% pure, niobium 99.9% pure and tungsten 99.9% pure , all other elements used had a purity of 99.9% or greater.

example 1

Prepared by arc melting method, its composition is Nd [Fe _0.70 Co _0.2 B _0.07 M _0.03 ] _6.5 [M = boron, aluminum, silicon, phosphorus, titanium, vanadium, chromium, manganese, nickel, copper, gallium, germanium, zirconium, niobium , Molybdenum, silver, indium, antimony, tungsten] various alloys. The obtained ingot is coarsely crushed with a stamping mill and a roller rolling machine, and after being sieved into a particle size finer than 32 mesh, it is ground with a jet mill. The pulverization medium was nitrogen, thus giving a fine powder with a particle size [FSSS] of 3.5 microns. The resulting powder was pressed in a magnetic field of 15 kOe, the direction of the magnetic field being perpendicular to the direction of pressing. The pressing pressure is 2 tons/square centimeter. The resulting green body was sintered in vacuum at 1090° C. for 2 hours. After quenching, heat treatment is performed at 500-900°C. The results are shown in Table 1.

Of the 19 elements "M" studied, only gallium achieves an iHc of more than 10 kOersted. This shows that gallium is particularly effective in increasing the coercive force. Incidentally, although the coercive force was increased by adding aluminum, the coercive force was only 8.5 kOe.

Example 2

An alloy having the following composition was pulverized, pulverized, sintered and heat-treated in the same manner as in Example 1.

Table I

Magnetic properties of Nd(Fe _0.7 Co _0.2 B _0.07 M _0.03 ) _6.5 magnets

M B Al Si P Ti V CR M Ni Cu4πIS (Qian Gaus) 13.31 12.61 12.80 12.77 13.19 12.30 12.50 12.574πIR (Thousand Gaus) 12.80 12.45 12.65 13.05 12.34 12.78 12.32ihc (Ast) 2.6 8.57.0 0 4.8 4.9 5.1 5.3 4.1 3.0 (BH) maximum (Maggarta Oaster) 133.5 32.0 0 24.0 25.5 28.0 24.1 18.1TC (℃) 477 460 482 478 478 485 481

GA GE ZR NB Mo Aσ in SB W4πIS (Thousand Gauss) 12.60 12.72 12.30 13.03 13.10 13.22 12.05 12.954πir (Thousand Gauss) 12.50*10.5 12.9*****12.75ihc (Thousand Ost) 16.0*4.3 6.9***************************************** *6.0 (BH) the largest (Maggarta Oaster) 35.0*12.1 35.1*****32.2TC (℃) 468 479 466 477 4683 488 476 Note: TC: Curry temperature

* close to 0

Nd [Fe _0.9-x Co _x B _0.07 Ga _0.03 ] _5.8 (X=0, 0.05, 0.1, 0.15, 0.2, 0.25);

Nd [Fe _0.93-x Co _x B _0.07 ] _5.8 (X = 0, 0.05, 0.1, 0.15, 0.2, 0.25); and

Nd _0.9 Dy _0.1 [Fe _0.93-x Co _x B _0.07 ] _5.8 X=0, 0.05, 0.1, 0.15, 0.2, 0.25); and

The magnetic properties of the obtained magnets were measured, and the results are shown in Table 2, Table 3 and Table 4.

Table II

Magnetic properties of Nd〔Fe _0.9-x Co _x B _0.07 Ga _0.03 〕 _5.8 magnet

X 0.05 0.1 0.15 0.2 0.25 magnetic performance 4πIR (Qian Gaos) 12.6 12.55 12.43 12.31 12.2 12.09ihc (Thousand Oster) 20.6 19.6 18.3 17.9 17.8 16.5 (BH) maximum 37.0 36.2 35.1 34.3 33.2

Table 3

Magnetic properties of Nd〔Fe _0.93-x Co _x B _0.07 〕 _5.8 magnet

X 0.05 0.1 0.15 0.2 0.25 magnetic performance 4πIR (Qian Gaos) 13.4 13.32 13.21 13.09 13.0 12.88ihc (Thousand Ost) 9.0 8.8 8.0 7.5 7.1 (BH) 42.1 41.5 40.8 39.7 38.8

Table 4

Nd _0.9 Dy _0.1 〔Fe _0.93-x Co _x B _0.07 〕 Magnetic properties of _5.8 magnets

X 0.05 0.1 0.15 0.2 0.25 magnetic performance 4πIR (Qian Gaos) 12.62 12.51 12.38 12.19 12.11ihc (Thousand Ost) 15.6 15.0 14.1 13.4 12.3 11.6 (BH) maximum 38.2 37.5 35.8 35.0 34.3

Each sample with cobalt content of 0 and 0.2 was heated at various temperatures for 30 minutes, and then the change of its open-loop magnetic flux (irreversible magnetic flux loss) was measured to understand their thermal stability. The samples tested were those processed to give a permeability of -2. The sample was magnetized at a magnetic field strength of 25 kOe and its flux was first measured at 25°C. The sample was heated to 80°C, then cooled to 25°C, and the magnetic flux was measured again. This determines the irreversible flux loss at 80°C. Gradually increase the heating temperature to 200°C, increasing by 20°C in each step, and obtain the irreversible magnetic flux loss at each temperature in the same way. The results are shown in Figure 1 and Figure 2. It can be seen here that the addition of gallium increases the coercive force of the magnets, thereby greatly improving their thermal stability.

Example 3

Each magnet having the following composition is crushed, ground, sintered and heat-treated in the same manner as Example 1:

Nd [Fe _0.7 Co _0.2 B _0.08 Ga _0.02 ] _A [A=5.6, 5.8, 6.0, 6.2, 6.4, 6.6] and

Nd [Fe _0.92 B _0.08 ] _A [A=5.6, 5.6, 6.0, 6.2, 6.4, 6.6]

The magnetic properties of each of the magnets thus prepared were measured. The results are shown in Table 5 and Table 6.

Table 5

Magnetic properties of Nd〔Fe _0.7 Co _0.2 B _0.08 Ga _0.02 〕 _A magnet

A 5.6 5.8 6.0 6.2 6.4 6.6 Magnetic Performance 4πIR (Qian Gaos) 12.25 12.32 12.39 12.48 12.56 12.7ihc (Thousand Ost) 15.4 15.1 15.6 14.2 13.0 (BH) maximum 35.8 36.0 36.5 36.9 37.1 (Zhaoste)

Table 6

Magnetic properties of Nd〔Fe _0.92 B _0.08 〕 _A magnet

    A    5.6    5.8     6.0     6.2    6.4      6.6磁性能4πIr(千高斯)13.04  13.2    13.4    13.6    13.7    13.8iHc(千奥斯特)10.0   9.3     9.0     0       0       0(BH)最大     40.2   41.3    42.6    0       0       0(兆高斯奥斯特)

When A=6.2 or above, the iHc and [BH] of the NdFeB ternary alloy are almost zero at most. But even when A is 6.6, if cobalt and gallium are added, the coercive force will be high and the magnetic properties will be good. It can be explained theoretically that in the NdFeB ternary alloy, when A is 6.2 or above, the oxidation of neodymium reduces the neodymium-rich phase as a liquid phase during the sintering process, so the coercive force cannot be obtained. On the other hand, when both cobalt and gallium are added, the gallium as a liquid phase replaces the proven oxidized neodymium, giving it a high coercive force.

Example 4

Alloys having the following compositions were prepared by arc melting: Nd[Fe _0.82 Co _0.1 B _0.07 Ga _0.01 ] _6.5 and Nd [Fe _0.93 B _0.07 ] _6.5 . The resulting alloys are rapidly quenched from their melts by the single-roll method. The resulting sheet was heat-treated at 700° C. for 1 hour. The sample thus prepared was pulverized to about 100 microns with a roller mill. The resulting coarse powders of each composition were divided into two groups: (A) one group was blended with epoxy resin and then molded, and (B) the other group was hot-pressed. The magnetic properties of the respective magnets thus obtained are shown in Table 7.

Table 7

Magnetic properties of magnets prepared by rapid quenching method

Nd(Fe _0.82 Co _0.1 Bo _0.07 Ga _0.01 ) _6.5 Nd(Fe _0.93 B _0.07 ) _6.5 Magnetic properties (A) (B) (A) (B) 4πIr (kilogauss) 6.1 8.4 6.3 8.8iHc (kiloersted) 21.6 20.1 14.6 12.3 (BH) max 7.1 13.2 7.3 13.6 (megauss Oersted) irreversible magnetic flux loss* 1.3 1.8 4.3 5.1

Note*: Irreversible magnetic flux loss after heating at 100°C for 0.5 hours

(A) Bonded magnet

(B) Hot-pressed magnet

From the above data, it can be seen that when both cobalt and gallium are added, the iHc is as high as 20 kOe or more, resulting in a magnet with good thermal stability.

Example 5

An alloy having the following composition was prepared by arc melting: Nd[Fe _0.82 Co _0.1 B _0.07 Ga _0.01 ] _5.4 . The resulting alloy is rapidly quenched from its melt by the single-roll method. The samples were pressed with an isobaric hot press and flattened by upsetting. The resulting magnet had the following magnetic properties: 4πIr = 11.8 kGauss, iHc = 13.0 kOersted, [BH]max = 32.3 megagauss Oersted.

Example 6

Alloys having the following compositions were prepared by arc melting: Nd[Fe _0.12 Co _0.1 B _0.07 Ga _0.01 ) _5.4 and Nd[Fe _0.92 B _0.08 ] _5.4 . The resulting alloys were processed in two ways: (a) one of them was crushed to 50 microns or less, and (b) the other was rapidly quenched from its melt by the single-roll method, and the resulting flakes were subjected to a Hot pressing (HIP), followed by upsetting to flatten it, and crushing to 50 microns or less. These powders are mixed with epoxy resin, which is then placed in a magnetic field to make magnets. The magnetic properties of the obtained magnets are shown in Table 8. It should be pointed out that the coercive force of NdFeB ternary alloy is extremely low, while the magnet containing cobalt and gallium has sufficient coercive force.

Table 8

Magnetic Properties of Bonded Magnets

Nd(Fe _0.82 Co _0.1 B _0.07 Ga _0.01 〕 _5.4 Nd(Fe _0.92 B _0.08 〕 _5.4 Magnetic properties (A) (B) (A) (B) 4πIr (kilogauss) 8.2 9.3 8.6 9.6iHc (kiloersted) 5.0 7.6 0.8 2.3 (BH) max 13 18 3 10 (megauss Oersted)

Note: (A) ingot→crushing→resin bonding

(B) Ingot billet→quick quenching→HIP→upsetting→crushing→resin blending.

Example 7

An alloy having the following composition was made into an ingot by high frequency melting: (Nd _0.8 Dy _0.2 ) [Fe _0.835 Co _0.06 B _0.08 Nb _0.015 Ga _0.01 ] _5.5 . The obtained alloy ingot was coarsely pulverized by stamping and rolling mill, and then finely pulverized in nitrogen as a pulverizing medium to obtain a fine powder with a particle size (FSSS) of 3.5 microns. The fine powder was pressed in a 15 kOe magnetic field, the direction of the magnetic field being perpendicular to the direction of pressing. The pressing pressure is 2 tons/square centimeter. The resulting green body was sintered in vacuum at 1100° C. for 2 hours. A series of the resulting sintered alloys was heated at 900°C for 2 hours and then slowly cooled to room temperature at a rate of 1.5°C/min.

Cooling is followed by annealing at various temperatures between 540°C and 460°C. The magnetic properties of each heat-treated magnet were measured, and the results are shown in Table 9.

Table 9

BR BR BHC IHC [BH] Maximum annealing temperature (℃) (Gauss) (Ost) (Ost) (Maggarta) 540 10400 10000 26500 26.0560 10450 10010 26.2580 10400 10000 26.0600 10100 264620 10400 10400 10400 10100 26200 26.0640 10400 10100 25200 26.1

After the magnets were thermally demagnetized, they were treated to have a permeability Pc = -2, and then magnetized at 25 kOe. They were heated between 180°C and 280°C in increments of 20°C for 1 hour. The irreversible magnetic flux loss at each heating temperature was measured, and the results are shown in Table 10.

Table Ten

Irreversible magnetic flux loss (%, Pc=-2)

Annealing temperature (℃) 180 200 220 240 260 280

540 0.8 1.0 1.3 1.9 4.0 25.0

560 0.8 1.0 1.2 1.8 3.8 22.5

580 0.9 1.1 1.3 1.8 3.2 21.6

600 0.9 1.1 1.2 2.0 4.2 19.3

620 0.9 1.1 1.2 1.8 7.6 22.0

640 0.8 1.0 1.2 2.2 4.3 25.4

It can be seen from Table 10 that even when heated at 260°C, the irreversible magnetic flux loss is 5%, which shows that the magnets have good thermal stability.

For comparison, an alloy of [Nd _0.8 Dy _0.2 ][Fe _0.86 Co _0.06 B _0.08 ] _5.5 was prepared in the same manner as above. The annealing temperature is 600°C. The magnetic properties of the obtained magnets are as follows: Br is close to 11200 Gauss, bHC is close to 10700 Oe, iHc is close to 24000 Oe, and [BH] is close to 29.8 megagauss Oe. When Pc=-2, the irreversible magnetic flux loss due to heating is 1.0% at 180°C, 1.8% at 200°C, 5.7% at 220°C, and 23.0% at 240°C.

Therefore, it is clear that when niobium and gallium are added simultaneously, the heat resistance increases by about 40°C.

Example 8

Three kinds of alloys with the following expressions are melted, pulverized, and made into products in the same manner as in example 7:

[Nd _0.8 Dy _0.2 ] [Fe _0.92-x Co _x B _0.08 ] _5.5 , wherein X=0.06～0.12,

[Nd _0.8 Dy _0.2 ] [Fe _0.905-x Co _x B _0.08 Nb _0.015 ] _5.5 , where X=0.06～0.12,

[Nd _0.8 Dy _0.2 ] [Fe _0.895-x Co _x B _0.08 Nb _0.015 Ga _0.01 ] _5.5 , where X=0.06～0.12,

Each of the resulting green objects was sintered in vacuum at 1090°C for 1 hour, then heat-treated at 900°C for 2 hours, and then cooled to room temperature at a rate of 1°C/min. For annealing, it was reheated at 600° C. in an argon flow for 1 hour, and then rapidly cooled in water. The magnetic properties of each sample were measured, and the results are shown in Table 11 (A) to (C).

Table 11 (A)

〔Nd _0.8 Dy _0.2 〕〔Fe _0.92-x Co _x B _0.08 〕 _5.5

Br BR BHC IHC [BH] Maximum X (Gauss) (Ost) (Ost) (Ost) [Zhaoster] 0.06 11000 10500 24000 30.008 11050 10500 20000 30.10 11050 10450 17000 30.12 11000 10500 15000 000 000 30.0

Table 11 (B)

[Nd _0.8 Dy _0.2 ](Fe _0.905-x Co _x B _0.08 Nb _0.015 ) _5.5

Br BR BHC IHC [BH] Maximum X (Gauss) (Ost) (Ost) (Oster) [Zhaoster] 0.06 10800 10400 28.00.08 10500 10500 18.80.10 10800 10400 28.00.12 10900 10400 151000000 28.2

Table 11 (C)

(Nd _0.8 Dy _0.2 )(Fe _0.895-x Co _x B _0.08 Nb _0.015 Ga _0.01 ) _5.5

Br bHc iHc 〔BH〕Maximum

X (Gauss) (Oersted) (Oersted) 〔Megagauss Oersted〕

0.06 10450 10100 26400 26.4

0.08 10500 10200 25300 26.6

0.10 10550 10200 24000 26.7

0.12 10500 10200 22700 26.7

Table 12 (A) ~ (C) also lists the irreversible magnetic flux loss caused by heating. In any of these three alloys, the increase in cobalt content will reduce iHc and the maximum [BH] will remain roughly the same. The irreversible magnetic flux consumption becomes larger with the increase of cobalt content. The heat resistance is the highest when the amount of cobalt is 0.06. Comparing the three alloys, it can be seen that the alloy containing both gallium and niobium has the highest heat resistance.

Table 12 (A)

〔Nd _0.8 Dy _0.2 〕(Fe _0.92-x Co _x B _0.08 ) _5.5

Irreversible magnetic flux loss [%, Pc=-2]

x 160°C 200°C 220°C

0.06 0.12 3.3 9.6

0.08 0.08 3.9 10.3

0.10 8.2 28.5 35.5

0.12 9.5 30.1 37.1

Table 12 (B)

〔Nd _0.8 Dy _0.2 〕(Fe _0.905-x Co _x B _0.08 Nb _0.015 〕 _5.5

Irreversible magnetic flux loss [%.Pc=-2]

x 160°C 200°C 240°C 260°C

0.06 0.74 0.96 9.5 26.3

0.08 0.75 9.5 18.8 35.5

0.10 2.3 19.3 44.6 59.8

0.12 3.5 26.1 51.6 61.5

Table 12 (C) (Nd _0.8 Dy _0.2 ) [Fe _0.895-x Co _x B _0.08 Nb _0.015 Ga _0.01 ) _5.5

Irreversible magnetic flux loss [%.Pc=-2]

x 180°C 200°C 240°C 260°C 280°C

0.06 0.94 1.1 2.0 4.2 19.3

0.08 0.76 0.97 1.7 8.0 21.6

0.10 0.74 0.92 1.6 5.2 18.7

0.12 0.70 0.94 3.4 12.4 24.4

Example 9

In the same manner as in Example 7, various alloys having the following expressions were melted, pulverized and made into magnets:

[Nd _0.8 Dy _0.2 ] [Fe _0.86-u Co _0.06 B _0.08 Nb _u ] _5.5 , where u = 0-0.05. The resulting green body was sintered in vacuum at 1080° C. for 2 hours. The resulting sintered body was further heated at 900°C for 2 hours, and then cooled to room temperature at a cooling rate of 2°C/min. For annealing, they were heated at 600° C. for an additional 0.5 h in argon flow, followed by rapid cooling in water. The magnetic properties of each sample were measured, and the results are shown in Table 13.

Table 13

(Nd _0.8 Dy _0.2 )(Fe _0.86-u Co _0.06 B _0.08 Nb _u ) _5.5

Br bHc iHc 〔BH〕Maximum

u (Gauss) (Oersted) (Oersted) [megaussian Oersted]

0 11050 10700 22500 29.5

0.003 11050 10700 23100 29.2

0.006 11050 10600 23800 29.0

0.009 10850 10500 24300 28.2

0.012 10850 10500 24700 28.4

0.015 10850 10500 25000 28.3

0.020 10700 10400 26200 27.4

0.030 10500 10000 28000 26.1

0.040 10300 9900 ＞28000 25.3

0.050 10150 9700 ＞28000 24.0

Obviously adding niobium can make Br and 〔BH〕 decrease the most while increasing iHc. It can be seen from Table 14 that the irreversible magnetic flux loss decreases with the increase of iHc when heated at 220 °C.

Table 14

[Nd _0.8 Dy _0.2 )(Fe _0.86-u Co _0.06 B _0.08 Nb _u ) _5.5

u Irreversible magnetic flux loss when heated at 220°C (%, Pc=-2)

0 10.1

0.003 8.7

0.006 6.3

0.009 5.0

0.012 4.6

0.015 3.1

0.020 2.5

0.030 2.0

0.040 1.8

0.050 1.5

Example 10

An alloy having the following expression: [Nd _0.8 Dy _0.2 ] [Fe _0.8-z Co _0.06 B _0.08 Ga _z ] _5.5 was melted, pulverized and formed into a magnet in the same manner as in Example 7. After sintering, they were each heated at 900°C for 2 hours, then cooled to room temperature at a cooling rate of 1.5°C/min, annealed at 580°C for 1 hour in an argon flow, and then rapidly quenched in water. The obtained magnetic properties of each magnet are shown in Table 15, and their irreversible magnetic flux losses when heated at 220°C are shown in Table 16.

Table 15

[Nd _0.8 Dy _0.2 ] [Fe _0.86-z Co _0.06 B _0.08 Ga _z ] _5.5

Br BR BHC IHC [BH] Maximum Z (Gauss) (Ost) (Ost) [Zhaoster] 0 11050 10700 29.50.002 10900 10600 23500 28.01 106500 27.20.03 103000000> 28000 25.60.07 9500 9200 ＞ 28000 21.70.10 8900 8600> 28000 18.90.12 8500 8200> 28000 17.00.15 8000 7800> 28000 15.3

Table 16 [Nd _0.8 Dy _0.2 ] [Fe _0.86-z Co _0.06 B _0.08 Ga _z ] _5.5

Z Irreversible magnetic flux loss when heated at 220°C (%, Pc=-2)

0 10.1

0.002 7.5

0.01 2.7

0.03 0.7

0.07 0.5

0.10 0.3

0.12 0.1

0.15 0.1

It can be seen that the addition of gallium greatly reduces Br and 〔BH〕, and at the same time greatly increases iHc, thereby improving the heat resistance [thermal stability] of each magnet.

Example 11

In the same manner as Example 10, an alloy having the following chemical formula was melted, pulverized and made into a magnet: [Nd _d.9 Dy _0.1 ] [Fe _0.845-z Co _0.06 B _0.08 Nb _0.015 Ga _z ] _5.5 , wherein Z=0～0.06 . The measured magnetic properties are shown in Table 17, and the irreversible magnetic flux loss when heated at 200°C is shown in Table 18.

Table 17 [Nd _0.9 Dy _0.1 ) [Fe _0.845-z Co _0.06 B _0.08 Nb _0.015 Ga _z ] _5.5

Br HC IHC [BH] Z [Gauss] [Ost] [Asto] the largest [Milloster] 0 11850 11550 15200 34.01 11400 11000 19800 31.60.02 11100 24900 29.0.03 11100 10600 28000 28000 29.10.04 10800 10300 ＞28000 28.00.06 10550 10100 ＞28000 26.9

Table 18 [Nd _0.9 Dy _0.1 ] [Fe _0.845-z Co _0.06 B _0.08 Nb _0.015 Ga _z ] _5.5

Z Irreversible magnetic flux loss when heated at 200°C [%, Pc=-2]

0 38.1

0.01 20.3

0.02 4.5

0.0 3 1.8

0.04 1.2

0.05 0.7

It can be seen that the addition of Ga can improve the thermal stability of the magnet even with a small amount of Dy instead of Nd.

Example 12

Alloys prepared by arc melting and having the following compositions: Nd [Fe _0.86 Co _0.06 B _0.08 ] _5.6 , Nd [Fe _0.84 Co _0.06 B _0.08 Ga _0.02 ] _5.6 and Nd [Fe _0.825 Co _0.06 B _0.08 Ga _0.02 W _0.015 ] _5.6 . The obtained ingot is coarsely crushed with a stamping mill and a roller rolling machine, sieved to be finer than 32 mesh, and then finely ground with a jet mill. Nitrogen was used as the crushing medium, thus resulting in a fine powder of 3.5 micron particle size [FSSS]. The resulting powder was compacted in a magnetic field of 15 kOe, the direction of the magnetic field being perpendicular to the direction of compaction. The pressing pressure is 2 tons/square centimeter. The resulting green body was sintered in vacuum at 1080° C. Austria for 2 hours. After quenching, heat treatment was carried out at 500-900° C. for 1 hour, and the results are shown in Table 19.

Table 19

Magnetic properties of NdFeCoBGaW magnets

                                                                      

Composition (thousand Gauss) Oersted〕Gauss Oersted〕Nd〔Fe _0.86 Co _0.06 B _0.08 〕 _5.6 13.0 11.2 40.3Nd〔Fe _0.84 Co _0.06 B _0.08 Ga _0.02 〕 _5.6 12.4 17.3 36.4Nd〔Fe _0.825 Co _0.08 B ₀ Ga _0.02 W _0.015 〕 _5.6 12.1 18.7 35.3

Each sample was heated at various temperatures for 30 minutes, and then the change in open-loop magnetic flux was measured to understand its thermal stability. The samples tested were those processed to give a permeability coefficient [PC] of -2. The results are shown in Figure 3. It can be seen from Figure 3 that a magnet with high thermal stability can be obtained when cobalt, gallium and tungsten are added at the same time.

Example 13

In the same manner as Example 12, an alloy having the following composition was pulverized, ground and sintered:

Nd [Fe _0.85-z Co _0.06 B _0.08 Ga _z W _0.01 ] _5.4 [Z = 0, 0.01, 0.02, 0.03, 0.04, 0.05].

The magnetic properties of the obtained magnets are shown in Table XX.

The thermal stability of the Nd [Fe _0.85-z Co _0.06 B _{0.06 Gaz} W _0.01 ] _5.4 [Z = 0, 0.02, 0.04] sample was measured in the same manner as in Example 12. The results are shown in Fig. 4 .

Table 20 Nd [Fe _0.85-z Co _0.06 B _0.08 Ga _z W _0.01 ] _5.4 Magnetic properties of magnets Z 4πIr (kilogauss) iHc [kiloersted] [BH] max [megauss Oersted] 0 12.6 12.5 37.80.01 12.32 15.2 35.80.02 12.06 17.4 34.70.03 11.77 18.5 33.00.04 11.52 19.7 31.70.05 11.29 21.0 29.3

Example 14

An alloy having the following composition was prepared by arc melting; Nd [Fe _0.825 Co _0.06 B _0.08 Ga _0.02 W _0.015 ] _6.0 . The resulting alloy is rapidly quenched from its melt by the single-roll method. The resulting flake product is made loose in the following three ways:

(A) Heat treatment at 500-700°C, blend with epoxy resin, and then mold.

(B) heat treatment at 500-700°C, and then hot pressing.

(C) Perform isobaric hot pressing, and then upsetting to make it flat.

The magnetic properties of the obtained magnets are shown in Table 21.

Table 21 Magnetic properties of Nd(Fe _0.825 Co _0.06 B _0.08 Ga _0.02 W _0.015 ] _6.0 Magnets Method 4πIr〔kilogauss〕iHc〔kiloersted〕〔BH〕Maximum〔megauss Oersted〕(A) 6.0 22.6 7.1(B) 8.0 20.2 12.6(C) 12.4 15.9 36.0

The thermal stability of each sample was measured in the same manner as in Example 12, and the results are shown in FIG. 5 .

Example 15

An alloy having the following composition was prepared by arc melting: Nd[Fe _0.85 Co _0.04 B _0.08 Ga _0.02 W _0.01 ] _6.1 . The resulting alloy is rapidly quenched from its melt by the single-roll method. The sample thus prepared was pressed by isostatic hot pressing, and then flattened by heading. The loose samples were pulverized to less than 80 microns, blended with epoxy resin, and shaped in a magnetic field. The resulting magnets had the following magnetic properties: 4πIr = 8.6 kGauss iHc = 13.2 kOersteds, [BH] max = 16.0 megagauss Oersteds.

Example 16

Prepared by arc melting method, its composition formula is Nd _1-α Dy _α [Fe _0.72 Co _0.2 B _0.08 ] _5.6 [α=0, 0.04, 0.08, 0.12, 0.16, 0.2), Nd [Fe _0.72-Z Co _0.2 B _0.08 Al _Z ] _5.6 [Z=0, 0.01, 0.02, 0.03, 0.04, 0.05] and Nd [Fe _0.72-Z Co _0.2 B _0.08 Ga _Z ] _5.6 [Z=0, 0.01, 0.02, 0.03, 0.04, 0.05] alloy. The obtained ingot is coarsely crushed with a stamping mill and a roller rolling mill, sieved to be finer than 32 mesh, and then finely ground with a jet mill. Nitrogen gas was used as the pulverization medium, thus resulting in a fine powder with a particle size of 3.5 microns [FSSS]. The resulting powder was compacted in a magnetic field of 15 kOe, the direction of the magnetic field being perpendicular to the direction of compaction. The pressing pressure is 1.5 tons/square centimeter. The resulting green body was sintered in vacuum at 1040° C. for 2 hours. After quenching, heat treatment was performed at 600-700°C for 1 hour, and the results are shown in Fig. 6 . Magnets containing gallium have higher coercive force than those containing dysprosium or aluminum, and the maximum drop of 4πIr and [BH] is also smaller.

The composition is Nd [Fe _0.72 Co _0.2 B _0.08 ] _5.6 , Nd _0.8 Dy _0.2 [Fe _0.72 Co _0.2 B _0.08 ] _5.6 , Nd [Fe _0.67 Co _0.2 B _0.08 Al _0.05 ] _5.6 and Nd [Fe _0.67 Co _0.2 B _0.08 Ga _0.05 〕 _5.6 The magnets are processed so that they have the shape of permeability coefficient Pc=-2. After being magnetized, they are heated at various temperatures for 30 minutes, and then the changes of their open-loop magnetic flux are measured to understand their thermal stability. . The result is shown in Figure 7. It can be seen from the figure that the change of irreversible magnetic flux loss with temperature is related to the coercive force, and the addition of gallium can produce a magnet with good thermal stability. For example, the irreversible magnetic flux loss at 160°C is 5% or less.

Example 17

[A]Nd[Fe _0.72 Co _0.2 B _0.08 ] _5.6 , [B]Nd _0.8 Dy _0.2 [Fe _0.72 Co _0.2 B _0.08 ] _5.6 , [C]Nd[Fe _0.67 Co _0.2 B _0.08 Al _0.05 ] prepared from Example 16 _5.6 and 〔〕Nd〔Fe _0.67 Co _0.2 B _0.08 Ga _0.05 〕 _5.6 Take small pieces of several millimeters from each side of the magnet, and after magnetization, measure the change of their magnetic flux with temperature with a vibrating magnetometer. Measurements are performed without a magnetic field. The results are shown in Figure 8. The change of magnetic flux with temperature has two inflection points, one inflection point is on the low temperature side corresponding to the Curie temperature of the BCC phase, and the other inflection point is on the high temperature side corresponding to the Curie temperature of the main phase. Gallium-containing magnets have a lower Curie temperature in the main phase than magnets without additives. On the other hand, the former is higher than the latter in terms of the Curie temperature of the BCC phase. But the addition of aluminum greatly reduces the Curie temperature of the main phase and the BCC phase, making the thermal stability reach an undesired level.

Example 18

In the same manner as Example 16, an alloy having the following composition was pulverized, ground, sintered and heat-treated:

Nd [Fe _0.67 Co _0.25 B _0.08 ] _5.6 ,

Nd [Fe _0.65 Co _0.25 B _0.08 Ga _0.02 ] _5.6 and

Nd [Fe _0.635 Co _0.25 B _0.08 Ga _0.02 W _0.015 ] _5.6 .

The sintering temperatures were 1020°C, 1040°C, 1060°C and 1080°C, respectively. Their magnetic properties were measured, and the results are shown in Figure 9 (B) to (C). Figure 9 [A] compares the demagnetization curves of the above magnets whose composition formula can be summarized as follows: Nd [Fe _0.67-zu Co _0.25 B _0.08 G _z W _u ] _5.6 , where Z=0 or 0.02, u=0 or 0.015. It can be seen from Fig. 9 [B] and [C] that in the absence of tungsten, the higher the sintering temperature, the worse the perpendicularity of the resulting magnets, resulting in the growth of coarse grains with low coercive force. On the other hand, in the case of adding tungsten, as shown in Figure 9 [D], increasing the sintering temperature will not lead to the growth of coarse grains, so the perpendicularity is good. It can be seen from Figure 9 [A] that the addition of gallium and tungsten increases the coercive force of the magnet.

Example 19

In the same manner as Example 16, the composition will be Nd [Fe _0.69 Co _0.2 B _0.08 Ga _0.02 M _0.01 ] _5.6 (the

The alloy in which M is vanadium, niobium, tantalum, molybdenum or tungsten) is crushed, ground, sintered and heat treated. inferred

The magnetic properties of the magnets are shown in Table 22.

Table 22 Nd [Fe _0.69 Co _0.2 B _0.08 Ga _0.02 M _0.01 ] _5.6 [M: vanadium, niobium, tantalum, molybdenum, tungsten]

Magnetic properties of

                                                                      

Composition (thousand Gauss) Oersted] Gauss Oersted] Nd [Fe _0.69 Co _0.2 B _0.08 Ga _0.02 V _0.01 〕5.6 12.0 17.0 34.0Nd〔Fe _0.69 Co _0.2 B _0.08 Ga _0.02 Nb _0.01 〕5.6 12.0 16.0 33.9Nd〔 FE _0.69 CO _0.2 B _0.08 GA _0.02 TA _0.01 ] 5.6 11.9 16.5 33.0nd [FE _0.69 CO _{0.2 B 0.08} GA _0.02 MO _0.01 ] 5.6 12.1 15.0 34.9nd [Fe _0.69 CO _0.08 Ga _0.02 W _0.01 ] 5.6 11.8 17.5.5.5.5.5.

Example 20

An alloy having the composition [Nd _0.8 Dy _0.2 ][Fe _0.85-u Co _0.06 B _0.08 Ga _0.01 Mo _u ] _5.5 (where u = 0-0.03) was pulverized, pulverized, sintered and heat-treated in the same manner as in Example 16. The obtained magnet was heated at 260°C to measure its magnetic properties and irreversible magnetic flux loss [Pc=-2]. The results are shown in Table 23.

Table 23

〔Nd _0.8 Dy _0.2 〕〔Fe _0.85-u Co _0.06 B _0.08 Ga _0.01 Mo _u ) _5.5

Br BR BHC IHC [BH] The biggest irreversible loss U (Gauss) [Qian Ost] [Qian Ost] [Mazaos Oaster] consumption*[ %] 0 11.0 10.5 26.4 16.70.005 10.8 10.3 27.0 28.2 9.00 .010 10.6 10.2 28.5 27.0 4.0015 10.5 10.0 29.0 26.0 2.10.02 10.3 9.8> 30.0 25.2 1.00.03 9.8 9.2> 30.0 22.8 0.9 0.9

Note *Irreversible magnetic flux loss

Example 21

In the same manner as Example 16, the composition is Nd [Fe _0.855-u Co _0.06 B _0.075 Ga _0.01 V _u ] _5.5

(wherein u=0～0.02] carry out pulverization, pulverization, sintering and heat treatment. All magnets that will draw

Its magnetic properties and irreversible magnetic flux loss [Pc=-2] were measured by heating at 160°C.

The results are shown in Table 24.

Table 24

Nd〔Fe _0.855-u Co _0.06 B _0.075 Ga _0.01 V _u 〕 _5.5

Br BR BHC IHC [BH] The biggest irreversible loss U (Gauss) [Qian Ost] [Qian Ost] [Milloster] 〔[ %] 0 11.9 11.6 17.9 34.1 7.60.7 11.2 18.2 33.2 6.200 .01 11.6 11.0 18.3 32.4 7.90.015 11.5 10.9 19.2 31.9 4.20.020 11.4 10.8 20.5 31.2 2.1

Note: *Irreversible magnetic flux loss

Example 22

In the same manner as in Example 16, an alloy having the composition (Nd _0.9 Dy _0.1 ] [Fe _0.85-u Co _0.06 B _0.08 Ga _0.01 Ta _u ] _5.5 (where u = 0-0.03) was pulverized, ground, sintered and heat-treated. The obtained magnets were heated [Pc=-2] at 160°C to determine their magnetic properties and irreversible flux loss [Pc=-2]. The results are shown in Table 25.

Table 25 [Nd _0.9 Dy _0.1 ] [Fe _0.85-u Co _0.06 B _0.08 Ga _0.01 Ta _u ] _5.5

Br BR BHC IHC [BH] The biggest irreversible loss U (Gauss) [Qian Ost] [Qian Ost] [Milloster] 〔[ %] 0 11.8 11.3 16.5 33.5 8.005 11.6 11.5 32.4 4.100 .010  11.4    10.9           18.9          31.5             3.70.015  11.3    10.9           19.5          30.7             3.20.020  11.1    10.6           19.8          29.8             3.00.025  10.9    10.4           20.2          28.7             2.10.030  10.7    10.3           21.0          27.7             1.9

Note: *Irreversible magnetic flux loss

As mentioned in the above examples, adding gallium to NdFeB magnets or adding cobalt and gallium at the same time can increase the Curie temperature and coercive force of the magnet, thereby improving the thermal stability of the magnet. In addition, adding M (one or more of niobium, tungsten, vanadium, tantalum, and molybdenum) cobalt and gallium to the NdFeB magnet can further increase the Curie temperature and coercive force of the magnet.

The present invention has been described through the above examples, but it should be pointed out that these examples do not limit the present invention, and any modification can be carried out as long as it does not depart from the scope of the present invention specified by the appended claims of this specification.

Claims (6)

1. the sintered permanent magnets of a good thermal stability is characterized in that, this permanent magnet is grouped into by the one-tenth that available following general expression is represented basically: R (Fe _1-x-y-z-uCo _xB _yGa _zM _u) wherein R can be neodymium only, or one or more rare earth metals of mainly forming by neodymium, praseodymium or cerium, the available dysprosium of a part in these rare earth elements, terbium or holmium replace, M is one or more elements that are selected from niobium, tungsten, vanadium, tantalum and molybdenum, 0≤X≤0.7,0.02≤Y≤0.3,0.001≤Z≤0.15,0.001≤u≤0.1,4.0≤A≤7.5.

2. according to the sintered permanent magnets of claim 1 good thermal stability, it is characterized in that 0.01≤X≤0.4,0.03≤X≤0.2,0.002≤Z≤0.1,0.002≤u≤0.04,4.5≤A≤7.0.

3. according to the sintered permanent magnets of claim 1 good thermal stability, it is characterized in that R mainly is made up of neodymium and dysprosium, neodymium is 0.97: 0.03 to 0.6: 0.4 to the atomic ratio of dysprosium.

4. according to the sintered permanent magnets of claim 3 good thermal stability, it is characterized in that 0.01≤X≤0.4,0.03≤Y≤0.2,0.002≤Z≤0.1,0.002≤u≤0.04 and 4.5≤A≤7.0.

5. according to the permanent magnet of the sintering good thermal stability of claim 1 or 2 or 3, it is characterized in that M is a niobium.

6. according to the sintered permanent magnets of the good thermal stability of claim 4, it is characterized in that M is a niobium.

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