KR910001065B1 - Permanent magnet - Google Patents

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Description

Permanent magnet with excellent thermal stability

1 is a graph showing the change of irreversible loss of magnetic flux of Nd-Fe-B, Nd-Dy-Fe-B and Nd-Fe-B-Ga magnets with heating temperature.

2 is a graph showing the change of irreversible loss of magnetic flux of Nd-Fe-Co-B, Nd-Dy-Fe-Co-B and Nd-Fe-Co-B-Ga magnets with heating temperature.

3 is a graph showing the change of irreversible loss of magnetic flux of Nd-Fe-Co-B, Nd-Fe-Co-B-Ga and Nd-Fe-Co-B-Ga-W magnets with heating temperature.

4 is a graph showing the change of irreversible loss of magnetic flux of Nd (Fe _0.85-x Co _0.06 B _0.08 Ga _x W _0.01 ) 5.4 with heating temperature.

5 shows the change of irreversible loss of magnetic flux along with the heating temperature of the magnet produced by (a) quenching → heat treatment → resin bonding, (b) quenching → heat treatment → hot compression molding, and (c) quenching → HIP → upsetting. Graph shown.

6 is a graph comparing magnetic properties of Nd-Dy-Fe-Co-B, Nd-Fe-Co-B-Al, and Nd-Fe-Co-B-Ga magnets.

7 shows 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 Graph showing the change of irreversible loss of magnetic flux of magnet.

8a to 8 (d) show 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 with heating temperature. And Nd (Fe _0.67 Co _0.2 B _0.08 Al _0.05 ) _5.6 . A graph showing a change in open magnetic flux of a magnet.

9a to 9 (d) show Nd (Fe _0.67-zu Co _0.25 B _0.08 Ga _z W _u ) _5.6 , Nd (Fe _0.67 Co _0.25 B _0.08 ) _5.6 , Nd (Fe _0.65 Co _0.25 B) manufactured at various sintering temperatures. _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 Graph showing demagnetization curve of magnet.

The present invention relates to a rare earth permanent magnet material of the present invention, and more particularly, to an R-Fe-B permanent magnet material having excellent thermal stability.

R-Fe-B permanent magnet materials include R-Co permanent magnet materials (Japanese Laid-Open Patent Publications 59-46008, 59-64733 and 59-89401, and many of M. Sagawa's 1984 Japanese applied physics). "New materials for permanent magnets based on Nd and Fe" published in Vol. 55 have been developed as new compositions having higher magnetic properties. According to him, for example, the Nd ₁₅ Fe ₇₇ B ₈ [Nd (Fe _0.91 B _0.09 ) _5.67 ] alloy has a magnetic property of (BH) maximum of almost 35 MGOe and iHc of almost 10 KOe.

However, R-Fe-B magnets have low thermal stability due to low Curie temperature, and to solve this, there have been attempts to increase the Curie temperature by adding cobalt (Japanese Patent Laid-Open No. 59-64732). In particular, the R-Fe-B permanent magnet has a Curie temperature of about 300C and a maximum of 370C (JP-A-59-46008), whereas in the R-Fe-B magnet, a part of iron is replaced by cobalt to change the Curie temperature. Some have raised to 400-800 degreeC (Unexamined-Japanese-Patent No. 59-64733).

However, adding cobalt to the R-Fe-B magnet lowers the coercive force iHc.

Attempts have been made to improve the coercivity by addition of aluminum, titanium, vanadium, chromium, manganese, zinc, hafnium, niobium, tantalum, molybdenum, gallium, antimony, tin, bismuth, nickel and the like. What is found here is that aluminum is particularly effective in improving the coercive force (Japanese Laid-Open Patent Publication No. 59-89401). However, since the elements other than nickel are nonmagnetic, the addition of a large amount of the elements decreases the residual magnetic flux density Br and, in turn, decreases the (BH) maximum.

There have also been proposals to replace heavy rare earth elements, such as terbium, dysprosium and holmium, with some of the Nd to improve the coercivity and to keep the high (BH) maximum as it is (JP-A-60-32306 and 60-). 34005). By replacing a portion of Nd with heavy rare earth elements, the coercive force is increased from 9 KOe to 12-18 KOe for (BH) up to 30 MGOe. However, since the heavy rare earth elements are expensive, a large amount of replacement of the heavy rare earth elements to neodymium is not good because the unit cost of the R-Fe-B magnet becomes high.

Other attempts to improve the thermal stability of R-Fe-B magnets include the addition of cobalt and aluminum (Tee, Mizo Gucci's many 1986 applied physics books, 48). By replacing part of iron with cobalt, the free temperature Tc is high, but iHc is rather low because it is believed that ferromagnetic precipitation phases of Nd (Fe, Co) ₂ will appear at the interfacial phase forming the nucleation sites in the reverse region. The addition of a combination of aluminum and cobalt forms a nonmagnetic Nd (Fe, Co, Al) ₂ phase that suppresses the generation of nucleation sites in the inverse magnetic region, but the addition of aluminum significantly reduces the Curie temperature Tc. R-Fe-B magnets containing aluminum inevitably have poor thermal stability at high temperatures of 100 ° C. or higher. The magnet's coercive force iHc is only 9 KOe.

Accordingly, an object of the present invention is to provide an R-Fe-B magnet having an increased curie temperature, sufficient coercive force, and thus improved thermal stability.

As a result of an in-depth study of the above object, the present inventors added gallium or a combination of cobalt and gallium to the R-Fe-B magnet, the Curie temperature is increased, the coercive force is sufficient, and thus the thermal stability is also increased. In addition, I found out that it is advantageous in terms of unit price.

The permanent magnet excellent in thermal stability according to the present invention consists essentially of a composition represented by the following general formula.

R (Fe _1-zyz Co _x B _y Ga _z ) A In the general formula, R is neodymium alone or one or more of rare earth elements mainly composed of neodymium, praseodymium or cesium, and 0 ≦ x ≦ 0.7, 0.02 Y ≦ 0.3, 0.001 ≦ z ≦ 0.15, and 4.0 ≦ A ≦ 7.5.

The reason for limiting the components of the magnet alloy in the present invention is as follows.

When cobalt is added to the R-Fe-B magnet, the Curie temperature rises, but the crystal magnetic anisotropy constant decreases, thereby decreasing the coercive force. However, adding a combination of cobalt and gallium increases the Curie temperature and the coercivity. Coercivity is improved even if elements such as aluminum and silicon are added to the R-Fe-B magnet, but the maximum directivity of the coercivity can be achieved by addition of gallium. In addition, although heavy rare earth elements such as terbium, dysprosium, and holmium are usually added to improve coercivity, gallium can be used to minimize the use of expensive heavy rare earth elements. That is, the disadvantage of R-Fe-B magnet, which has low thermal stability due to low Curie temperature, is that the coercive force is higher by adding gallium or a combination of cobalt and gallium, and the Curie temperature is increased, so the thermal stability is more excellent. This is solved by providing an advantageous magnet in terms of surface area.

The amount of cobalt represented by "x" is 0 to 0.7. Above 0.7, the residual magnetic flux density Br of the final magnet becomes too low. The lower limit of cobalt for sufficiently improving the Curie temperature Tc is preferably 0.01, and the upper limit of cobalt for improving magnetic properties such as iHc, Br, and Tc is preferably 0.4. The most suitable amount of cobalt is 0.05 to 0.25.

The addition of gallium significantly improves the coercive force. This improvement is manifested by an increase in the Curie temperature on the BCC in the magnet. The BCC phase is a polycrystalline phase of a body-centered cubic crystal structure surrounding the main phase of an Nd-Fe-B magnet (Nd ₂ Fe ₁₄ B) with a width of 100 to 5000 GPa. This BCC phase is again surrounded by a niobium sub-image (Nd: 70 to 95 atomic%, balance: iron). Curie temperature on the BCC corresponds to the temperature at which the coercivity of the magnet is 50Oe or less, which greatly affects the temperature characteristics of the magnet. The addition of gallium increases the Curie temperature on the BCC phase and is effective in improving the temperature characteristics.

The amount of gallium represented by "z" is 0.01 to 0.15. Below 0.001, there is no substantial effect on improving the Curie temperature of the magnet. On the other hand, above 0.15, the saturation magnetization and Curie temperature are severely reduced, which is an undesirable permanent magnet material. Suitable amounts of gallium are 0.002 to 0.10 and most suitable amounts are 0.005 to 0.05.

When the amount of boron indicated by "y" is 0.02 or less, the Curie temperature is lowered and high coercive force cannot be obtained. On the other hand, above 0.3, the saturation magnetization is reduced to form a phase which is not desired for magnetic properties. Therefore, the amount of boron should be 0.02 to 0.3, suitable amount is 0.03 to 0.20, most suitable amount is 0.04 to 0.15.

If "A" is 4 or less, the saturation magnetization is low, and if it is 7.5 or more, iron and cobalt incubations appear and the coercive force is severely reduced. Therefore "A" should be 4.0 to 7.5, 4.5 to 7.0 is suitable, the most suitable range is 5.0 to 6.8.

The permanent magnet of the present invention further contains an additional element represented by "M" in the following general formula.

R (Fe _1-xyzu Co _z B _y Ga _z M _u ) A In the general formula, R is a rare earth composed mainly of neodymium, praseodymium, or cesium, which may be neodium alone or part of which may be replaced by dysprosium, tebium, or holmium One or more of the elements; M is one or more of the elements 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 and 4.0 ≦ A ≦ 7.5.

Niobium, tungsten, vanadium, tantalum or molybdenum are added to inhibit particle growth. The amount of the elements indicated by "u" is from 0.001 to 0.1. At 0.001 or less, the effect is insufficient. At 0.1 or more, the saturation magnetization is severely reduced, resulting in an undesirable permanent magnet.

The addition of niobium does not reduce Br as much as the addition of gallium and raises iHc slightly. Niobium is effective in improving corrosion resistance and is very effective as an additive in the case of high heat resistant alloys which are easily exposed to relatively high temperature. If the amount of niobium indicated by "u" is less than 0.001, not only can not expect a sufficient effect on the improvement of iHc, but also the corrosion resistance of a magnet alloy will become inadequate, whereas at 0.1 or more, Br and Curie temperature fall unexpectedly. A suitable range of niobium is 0.002 ≦ z ≦ 0.04.

The addition of tungsten contributes to the significant improvement in temperature characteristics. If the amount of tungsten (" u ") exceeds 0.1, the coercive force of saturation magnetization greatly decreases, and if less than 0.001, a sufficient effect is not obtained. Suitable amounts of tungsten are 0.002 to 0.04.

Regarding the rare earth element "R", it is neodymium alone or a combination of neodymium and light rare earth elements such as praseodymium, cerium or praseodymium and cerium. The ratio of praseodymium to niobium in containing praseodymium and / or cerium is 0: 1 to 1: 0, and the ratio of cerium to niobium is 0: 1 to 0.3: 0.7.

Neodymium can also be replaced by dysprosium to slightly increase the Curie temperature and improve the coercive force iHc. That is, the addition of dysprosium is effective to improve the thermal stability of the permanent magnet of the present invention. However, an excessive amount of dysprosium reduces the residual magnetic flux density Br, so the ratio of dysprosium to neodymium is in the atomic ratio of 0.03: 0.97 to 0.4: 0.6, and the suitable atomic ratio of dysprosium to neodymium is 0.05 to 0.25.

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

(1) powder metallurgy

The magnet alloy is obtained by arc melting or high frequency melting. The purity of the starting materials is at least 90% rare earth elements, at least 95% iron, at least 95% cobalt, at least 90% boron, at least 95% gallium, and at least 95% M (niobium, tungsten, vanadium, tantalum, molybdenum) if present. . The starting material of boron is ferroboron and the starting material of gallium is ferrogallium. Further, starting materials of M (niobium, tungsten, vanadium, tantalum, molybdenum) are ferroniobium, ferro tungsten, ferrovanadium, ferro tantalum or ferro molybdenum. Since ferroboron and ferrogalium contain inevitable impurities such as aluminum and silicon, high coercive force is obtained by synergistic action of elements such as gallium, aluminum and silicon.

Micronization consists of the stages of micronization and milling. The micronization is carried out with stamp mills, jaw crushers, brown mills, disc mills, etc., and milling is carried out with jet mills, vibration mills, ball mills, and the like. In any case, micronization should be carried out in a non-oxidizing atmosphere to prevent oxides of the alloy. Final particle size is suitably 2 to 5 μm (FSSS) as measured by Fischer Subsieve Sizer (FSSS).

The final fine powder is compression molded into a die in a magnetic field. This is essential for providing the alloy with anisotropy with the C-axis in which the magnetic powder to be compressed is arranged in the same direction. Sintering is performed at 1050-1150 degreeC by inert gas, such as argon, helium, or a vacuum or hydrogen atmosphere. The heat treatment for the sintered magnetic alloy is performed at 400 to 1000 ° C.

(2) quenching method

Magnetic alloys are produced in the same manner as the electrical powder metallurgy (1). The molten metal of the final alloy is quenched with a single roll or double roll quench system. That is, for example, the alloy melted by high frequency is injected into a roll rotating at high speed through a nozzle and quenched. The flake product thus formed is heat treated at 500 to 800 ° C. The material manufactured by such a quenching method is used for three types of permanent magnets.

(a) The final flake product is micronized to a particle size of 10 to 500 mu m with a disk mill or the like. This powder is mixed with an epoxy resin for die molding and a nylon resin for injection molding as an example. In order to improve the adhesion between the alloy powder and the resin, it is preferable to apply an appropriate binder to the alloy powder before mixing. This is an isotropic magnet.

(b) The flake product is compressed by hot compression molding or hot isostatic compression molding (HIP) to produce bulky isotropic magnets. This becomes an isotropic magnet.

(c) The bulky isotropic magnet obtained from electricity (b) is flattened by upsetting. Such plastic deformation causes the magnet to have anisotropy in which the C-axis is arranged in the same direction. This becomes an anisotropic magnet.

(3) resin bonding method

The starting material may be obtained by hot compression molding or upsetting the R-Fe-Co-B-Ga alloy obtained from the electricity (1), the sintered body obtained by micronization and sintering of the alloy, the quenched flakes obtained from the electricity (2), or It is a bulky product obtained. The fine powder obtained by finely pulverizing a bulky product to a particle size of 30 to 500 탆 with a jaw crusher, a brown mill, a disk mill or the like is combined with a resin and subjected to die molding or injection molding. When the magnetic field is applied during the molding operation, the C-axis becomes anisotropic magnets arranged in the same direction.

Hereinafter, the present invention will be described in more detail with examples.

The starting materials used in the examples are 99.9% pure neodymium, 99.9% pure iron, 99.9% pure cobalt, 99.5% pure boron, 99.9999% pure gallium, 99.9% pure niobium and 99.9% pure tungsten. The purity of the other elements used is 99.9% or higher.

Example 1

Composition is Nd (Fe _0.70 Co _0.2 B _0.07 M _0.03 ) _6.5 And antimony and tungsten) were prepared by arc melting. The ingot was roughly ground with a stamp mill and a disk mill, sieved finer than 32 mesh and then milled with a jet mill. The micronized medium was N ₂ gas and the particle size (FSSS) of the fine powder was 3.5 μm. This powder was compression molded in a 15 KOe magnetic field perpendicular to the compression direction. The pressure was 2 t / cm ² . The molded body was sintered at 1090 ° C. for 2 hours, heat treated at 500 to 900 ° C. for 1 hour, and then quenched. The results are shown in Table 1.

TABLE 1

Of the 19 elements "M" tested, only gallium had an iHc of more than 10 KOe, indicating that gallium is very effective at improving coercive force. In addition, the coercivity increases with the addition of aluminum, but this is as low as 8.5 KOe.

Example 2

The alloy having the following composition was ground, milled, sintered and heat treated in the same manner as in Example 1.

Nd (Fe _0.9-x Co _x B _0.07 Ga0.02) _5.8

Where x = 0, 0.15, 0.1, 0.15, 0.2, 0.25

Nd (Fe _0.9--x Co _x B _0.07 ) _5.8

Where x = 0, 0.05, 0.1, 0.15, 0.2, 0.25

Nd _0.9 Dy _0.1 (Fe _0.93-x Co _x B _{-.- 7} ) _5-8

Where x = 0, 0.05, 0.1, 0.15, 0.2, 0.25

The final magnet was tested for magnetic properties and the results are shown in Tables 2, 3 and 4.

TABLE 2

TABLE 3

TABLE 4

Samples with cobalt amounts of 0 and 0.2, respectively, were heated at various temperatures for 2 minutes and then measured for changes in open magnetic flux (irreversible loss of magnetic flux) to determine thermal stability. The sample tested was a permeability coefficient (P _C ) -2. The sample was magnetized at 25 KOe magnetic field strength, and the magnetic 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. Thus, irreversible loss of magnetic flux at 80 ° C was measured. The irreversible loss of the magnetic flux at each temperature was calculated | required in the same way by raising heating temperature to 200 degreeC by 20 degreeC. This result is shown in FIG. 1 and FIG. As can be seen from that, the coercive force of the magnet is increased due to the addition of potassium, and thus the thermal stability is greatly improved.

Example 3

Fine, milled, sintered and heat treated in the same manner as in Example 1 for the magnetic alloy having the following composition.

Nd (Fe _0.7 Co _0.2 B _0.08 G _a0.02 ) _A

Where A = 5.6, 5.8, 6.0, 6.2, 6.4, 6.6

Nd (Fe _0.92 B _0.08 ) _A

Where A = 5.6, 5.8, 6.0, 6.2, 6.4, 6.6

Magnetic properties of the alloys thus prepared were measured, and the results are shown in Tables 5 and 6.

TABLE 5

TABLE 6

In the Nd-Fe-B ternary alloy, the coercive force and the (BH) maximum were nearly zero when A was 6.2 or more. However, by adding cobalt and potassium, even when A was 6.6, the coercive force was increased to generate high magnetic properties. Therefore, in the Nd-Fe-B ternary alloy, when the A is 6.2 or more, the neodymium sub-phase which acts as a liquid phase in the sintering process is reduced by oxidation of neodymium so that it is not possible to obtain high coercive force. On the other hand, when both cobalt and gallium are added, gallium acts as a liquid instead of neodymium which is supposed to be oxidized, resulting in high coercive force.

Example 4

The _{alloys having the} composition of Nd (Fe _-.82 Co _-.i B _0.07 G _a0.01 ) _6.5 and Nd (Fe _0.93 B _0.07 ) _6.5 were arc-dissolved, and the molten metal was quenched by the single roll method, and the flaky phase The material was heat treated at 700 ° C. for 1 hour. The sample thus prepared was finely divided into 100 micrometers with a disc, and the coarse powder of each composition was separated into two groups, namely, ① epoxy resin mixed and molded into a die, and ② hot pressed. Magnetic properties of each of the final magnets were measured and listed in Table 7.

TABLE 7

As is clear from the above data, the addition of both cobalt and gallium increases the iHc to 20 KOe or more, resulting in excellent thermal stability of the magnet.

Example 5

The alloy whose composition is Nd (Fe _0.82 Co _0.1 B _0.07 G _a0.01 ) _5.4 was melt | dissolved, and the molten metal was quenched by the single roll method. Samples were flattened by compression and upset by HIP method. The magnetic properties of the final magnet were 4πIr = 11.8KG, iHc = 13.0 KOe, (BH) maximum = 32.3 MGOe.

Example 6

The alloys whose compositions were Nd (Fe _0.82 Co _0.1 B _0.07 G _a0.01 ) _4.4 and Nd (Fe _0.92 B _0.08 ) _4.4 were arc-dissolved and prepared. Two ways to get the final alloy. That is, ① finely divided to 50 μm or less and ② quench the molten metal by a single roll method, and hot-isostatic compression molding (HIP) the flaky product and flattening by upsetting, and then finely divided to 50 μm or less It was processed. This powder was mixed with the epoxy resin and magnetized in the magnetic field. The magnetic properties of the final magnets are listed in Table 8. As can be seen, the Nd-Fe-B ternary alloy had extremely low coercive force, while the coercive force was sufficient for magnets containing both cobalt and potassium.

TABLE 8

Example 7

An alloy having a composition of (Nd _0.8 Dy _0.2 ) (Fe _0.835 Co _0.06 B _0.015 G _a0.01 ) _5.5 was made of ingot by high frequency melting. The alloy ingot was roughly ground with a stamp mill and a disk mill, and then finely ground in a nitrogen atmosphere as a fine grinding medium to produce a fine powder having a particle size (FSSS) of 3.5 mu m. This powder was compression molded at a magnetic field of 15 KOe perpendicular to the compression direction. The pressure was 2 t / cm ² . The produced body was sintered under vacuum at 1100 ° C. for 2 hours and then cooled to room temperature. Many final sintered alloys were heated to 900 ° C. for 2 hours and then cooled to room temperature at 1.5 ° C./min.

After cooling, annealing was performed at various temperatures between 540 ° C and 640 ° C. Magnetic properties of the heat-treated alloys were measured and the results are shown in Table 9.

TABLE 9

After thermal demagnetization of the magnet, the permeability radix Pc had −2 and magnetized again to 25 KOe. The magnet was heated for 20 h between 180 and 280 ° C. for 20 hours and the irreversible loss of magnetic flux was measured at each heating temperature. The results are in Table 10.

TABLE 10

As can be seen from Table 10, the loss of baggavers of the magnetic flux is 5% or less even at 260 ° C. heating, which means that the magnet has excellent thermal stability.

For comparison, an alloy having a composition 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. Annealing temperature was 600 degreeC. The magnetic properties of the final magnet were Br = almost 11200G, bHc = almost 10700 Oe, iHc = almost 24000 Oe and (BH) max = almost 29.8 MGOe. In the case of Pc = -2, the irreversible loss of the magnetic flux by heating was 1.0% for 180 ° C heating, 1.8% for 200 ° C heating, 5.7% for 220 ° C heating, and 23.0% for 240 ° C heating.

Therefore, it is clear that the addition of both niobium and gallium increases the heat resistance by 40 ° C.

Example 8

General formula (Nd _0.8 Dy _0.2 ) (Fe _0.92-x Co _x B _0.08 ) _5.5, where x = 0.06 to 0.12, (Nd _0.8 Dy _0.2 ) (Fe _0.895-x CoxB _0.08 Nb _0.015 G _a0.01 ) _5.5, where x = 0.06 to 0.12, and (Nd _0.8 Dy _0.2 ) (Nd _0.895-x Co _x B _0.08 Nb _0.015 Ga _0.01 ) _5.5 , wherein three alloys represented by x = 0.06 to 0.12 were produced in the same manner as in Example 7. Prepared by dissolving and micronizing.

Each final body was sintered at 1090 ° C. under vacuum for 1 hour, then heat treated at 900 ° C. for 2 hours, and cooled to room temperature at a rate of 1 ° C./min. Again under an argon gas stream, annealing was performed at 600 DEG C for 1 hour, followed by water cooling. Magnetic properties were measured for each sample, and the results are shown in Tables 11A to 11C.

TABLE 11a

Table 11b

TABLE 11c

Tables 12a to 12c also show irreversible losses of magnetic flux due to heating. In any of the three types of alloys, iHc decreases as the cobalt content increases substantially without change to the (BH) maximum. The irreversible loss of magnetic flux increases with increasing cobalt content. When the cobalt content is 0.06, the heat resistance is the best. The comparison of the three alloys shows that the alloys containing both gallium and niobium have the highest heat resistance.

TABLE 12a

Table 12b

TABLE 12c

Example 9

Various alloys represented by the general formula (Nd _0.8 Dy _0.2 ) (Fe _0.86-u Co _0.06 B _0.08 Nb _u ) _5.5, where u = 0 to 0.05, were dissolved and finely prepared in the same manner as in Example 7. The final green body was sintered under vacuum at 1080 ° C. for 2 hours, and the sinter was further heated to 900 ° C. for 2 hours and cooled to room temperature at a cooling rate of 2 ° C./min. This was again annealed at 600 DEG C for 0.5 hour under argon gas stream, followed by water cooling. Magnetic properties were measured for each sample, and the results are shown in Table 13.

TABLE 13

As can be seen from the above table, the addition of niobium decreases the Br and (BH) maximums but increases iHc, and the irreversible loss of magnetic flux due to heating at 220 ° C. decreases with increasing iHc.

TABLE 14

Example 10

General formula (Nd _0.8 Dy _0.2 ) (Fe _0.86-z Co _0.06 B _0.08 Ga _z ) ⁼ _. ⁼ , Where an alloy represented by z = 0 to 0.15 was dissolved and finely prepared in the same manner as in Example 7. It was heated to 900 ° C. for 2 hours after sintering and then cooled to room temperature at a cooling rate of 1.5 ° C./min. This was again annealed at 580 ° C. for 1 hour under argon gas flow and water cooled. The magnetic properties of the final magnet are shown in Table 15, and the irreversible loss of the magnetic flux due to heating at 220 캜 is shown in Table 16.

TABLE 15

TABLE 16

Here, as can be seen, the addition of gallium greatly reduces the Br and (BH) maximums, but the iHc increases significantly, improving the magnet's heat resistance (thermal stability).

Example 11

_.9Dy_0.1)(Fe_0.845-zCo_0.06B_0.08Nb_0.015Ga_z)_5.5,여기서 z=0내지 0.06으로 표시되는 합금을 실시예 10과 동일한 방식으로 용해하고 미분하여 만들었다. 측정한 자기 성질은 표 17에, 220℃ 가열에 의한 자속의 비가역 손실은 표 18에 실었다.Regular diet (Nd

_.9 Dy _0.1 ) (Fe _0.845-z Co _0.06 B _0.08 Nb _0.015 Ga _z ) _5.5, where an alloy represented by z = 0 to 0.06 was dissolved and finely prepared in the same manner as in Example 10. The measured magnetic properties are shown in Table 17, and the irreversible loss of magnetic flux due to heating at 220 ° C is shown in Table 18.

TABLE 17

TABLE 18

Tables 17 and 18 show that even when a small amount of dysprosium is added to neodymium, the addition of gallium contributes to the improvement of the thermal safety of the magnet.

Example 12

The alloys of composition Nd (Fe _0.86 Co _0.06 B _0.08 ) _5.6, Nd (Fe _0.84 Co _0.06 B _8.08 Ga _0.02 ) _5.6 and Nd (Fe _0.825 Co _0.06 B _0.08 Ga _0.02 W _0.015 ) _5.6 are arc-dissolved, and the ingot is Rough milling with stamp mill and disk mill followed by sieving finer than 32 mesh with jet mill. The finely divided medium was N ₂ gas, and a fine powder having a particle size (FSSS) of 3.5 μm was obtained. The final powder was molded in a magnetic field of 15 KOe perpendicular to the compression direction, with a pressure of 2 t / cm ² . The living body was sintered under vacuum at 1080 DEG C for 2 hours, heat treated at 500 to 900 DEG C for 1 hour, and then quenched. The results are shown in Table 19.

TABLE 19

Each sample was heated at various temperatures for 30 minutes and then measured for changes in open magnetic flux to determine thermal safety. The specimens had a permeability coefficient (Pc) of -2. This result is shown in FIG. 3, as can be clearly seen from FIG. 3, the addition of cobalt, gallium and tungsten blends improves the thermal stability of the magnet.

Example 13

A powder having a composition of Nd (Fe _0.85-z Co _0.06 B _0.08 Ga _z W _0.01 ) _5.4, wherein z = 0, 0.01, 0.02, 0.03, 0.04, 0.05 was subjected to fine powder, milling, sintering and heat treatment in the same manner as in Example 12. did.

The magnetic properties of the final magnets are listed in Table 20.

TABLE 20

The thermal stability of the sample whose composition is Nd (Fe _8.85-z Co _0.06 B _0.08 Ga _z W _0.01 ) _5.4, where z = 0, 0.02, 0.04, was measured in the same manner as in Example 12. The results are shown in FIG.

Example 14

The flaky product obtained by arc-dissolving _{6.0 and} phosphorus alloys whose composition is Nd (Fe _0.825 Co _0.06 B _0.08 Ga _0.02 W _0.015 ) _6.0, and molten metal was quenched by the single roll method was cast by the following three methods.

(1) It heat-processed at 500-700 degreeC, mixed with epoxy resin, and die-molded.

(2) It heat-processed at 500-700 degreeC, and hot compression molding.

(3) Hot isostatic compression molding was performed and flattened by upsetting.

The magnetic properties of the final magnets are listed in Table 21.

TABLE 21

Each sample was measured for thermal stability in the same manner as in Example 12, and the results are shown in FIG.

Example 15

An alloy having a composition of Nd (Fe _0.85 Co _0.04 B _0.08 Ga _0.02 W _0.01 ) _6.1 was arc-dissolved, the sample obtained by quenching the molten metal by the single roll method was compressed with HIP, and then upset and flattened. The volume was finely divided to 80 µm or less, mixed with an epoxy resin, and then subjected to magnetic field. The magnetic properties of the magnet thus obtained were 4 ∏ Ir = 8.6 KG, iHC = 13.2 KOe and (BH) maximum = 16.0 MGOe.

Example 16

The composition is Nd _1-α Dy _α (Fe _0.72 Co _0.2 B ₈₀₈ ) _5.6 , where 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, where z = 0, 0.01, 0.02, 0.03, 0.04, 0.05, Nd (Fe _0.72-z Co _0.2 B _0.08 Ga _z ) 5.6, where an alloy of z = 0, 0.01, 0.02, 0.03, 0.04, 0.05 is arc-dissolved and the ingot Was roughly ground with a stamp mill and a disk mill, and then sieved finer than a 32 mesh with a jet mill. The finely divided medium was N ₂ gas and a fine powder having a particle size (FSSS) of 3.5 μm was obtained. The powder was compression molded at a pressure of 1.5 t / cm 2 at a magnetic field of 15 KOe perpendicular to the compression direction. The living body was sintered under vacuum at 1040 ° C. for 2 hours, heat treated at 600 to 700 ° C. for 1 hour and then quenched. The results are shown in FIG. As can be seen from this, gallium-containing magnets have a higher coercive force, and 4 ∏Ir and (BH) maximum decrease a little compared with dysprosium or aluminum-containing magnets.

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 _0.02 B _0.08 Al _0.05 ) _5.6 and Nd (Fe _0.67 Co _0.2 B _0.08 Ga _0.05 ) A magnet with _5.6 was formed into a shape with a permeability coefficient (Pc) of -2, magnetized, and heat treated at various temperatures for 30 minutes, and then the change in open magnetic flux was measured to determine thermal stability. The results are shown in Figure 7, where the irreversible loss of magnetic flux and the change in deck strength depend on the coercive force, and the addition of gallium improves the thermal stability of the magnet, i.e. below 5% I can see that.

Example 17

(1) Nd (FE _0.72 Co _0.2 B _0.08 ) _5.6 prepared in Example 16, (2) Nd _0.8 Dy _0.2 (Fe _0.72 Co _0.2 B _0.08 ) _5.6 , (3) Nd (Fe _0.67 Co _0.2 B _0.08 Al _0.05 ) ₅₀₆ and (4) Nd (Fe _0.67 Co _0.2 B _0.08 Ga _0.05 ) _5.6 Magnets were cut from each other by a few millimeters in small amounts and magnetized, and the change in magnetic flux and temperature was measured by a vibrating magnetic field. This measurement was performed without magnetic field, and the results are shown in FIG. The change between the magnetic flux and the temperature has two curved portions, that is, the low temperature side corresponding to the Curie temperature on the BCC and the high temperature side corresponding to the Curie temperature of the main phase. Magnets containing gallium have a lower Curie temperature in the main phase than those without a gallium, but are relatively high for the Curie temperature in the BCC phase. However, the addition of aluminum significantly reduces the Curie temperatures in the columnar and BCC phases, thus degrading thermal safety.

Example 18

The alloys of composition Nd (FE _0.67 Co _0.25 B _0.08 ), Nd (Fe _0.65 Co _0.25 B _0.03 Ga _0.02 ) _5.6 and Nd (Fe _0.635 Co _0.25 B _0.08 Ga _0.02 W _0.015 ) _5.5, phosphorus alloys were prepared in the same manner as in Example 16 Fine powder, milling, sintering and heat treatment. Sintering temperature was 1020 degreeC, 1040 degreeC, 1060 degreeC, and 1080 degreeC, respectively, and the magnetic property was measured. The results are shown in Figures 9b and 9 (c). Figure 9a shows a comparison of the demagnetization curves of the magnets with the general formula Nd (Fe _0.67-zu Co _0.25 B _0.08 Ga _z W _u ) _5.6, where z = 0 or 0.25, u = 0 or 0.051. As shown in Figs. 9B and 9 (c), when the tungsten is not contained, the higher the sintering temperature, the worse the angle formation of the magnets, and the coercive grains with lower coercivity grow. On the other hand, when tungsten is contained, as shown in FIG. 9A, a high sintering temperature does not induce coarse grain growth, resulting in good angular formation. Figure 9a shows the improvement of the coercive force of the magnet due to the mixing of gallium and tungsten.

Example 19

An alloy whose composition is Nd (Fe _0.69 Co _0.2 B _0.08 Ga _0.02 M _0.01 ) _5.6 , wherein M is vanadium, niobium, tantalum, molybdenum or tungsten, was ground, milled, sintered and heat treated in the same manner as in Example 16. The magnetic properties of the final magnets are listed in Table 22.

Table 22

Example 20

An alloy having a composition of (Nd _0.8 Dy _0.2 ) (Fe _0.85-u Co _0.06 B _0.08 Ga _0.01 Mo _u ) _5.5 was ground, milled, sintered and heat treated in the same manner as in Example 16. The final magnet was measured for magnetic properties and irreversible loss of magnetic flux at 260 ° C. (Pc = -2) and the results are shown in Table 23.

TABLE 23

Example 21

An alloy having a composition of Nd (Fe _0.855-u Co _0.06 B _0.075 Ga _0.01 V _u ) _5.5 was ground, milled, sintered and heat treated in the same manner as in Example 16. The final magnet was measured for magnetic properties and irreversible loss of magnetic flux (Pc = -2) at 160 ° C. and the results are shown in Table 24.

TABLE 24

Example 22

Composition (Nd _0.9 Dy _0.1 ) (Fe _0.85-U Co _0.06 B _0.08 Ga _0.01 Ta _u ) _{5.5 An} alloy with u = 0 to 0.03 was subjected to fine powder milling, sintering and heat treatment in the same manner as in Example 16. The final magnet was measured for magnetic properties and irreversible loss of magnetic flux at 160 ° C. (Pc = -2) and the results are shown in Table 25.

TABLE 25

As described above, the addition of gallium, or gallium and cobalt simultaneously, increases the Curie temperature and the coercive force of the Nd-Fe-B magnet, thereby providing excellent thermal stability. In addition, by adding M (niobium, tungsten, vanadium, tantalum, molybdenum, one or more) together with cobalt and gallium, the Curie temperature and coercive force could be further increased.

Although the invention has been described in detail with reference to the embodiments, the invention is not limited thereto, and any modifications may be made within the scope of the invention as defined in the appended claims.

Claims (5)

General formula R (Fe _1-xyzu Co _x B _y Ga _z M _u ) A, where R is neodymium alone or one or more of the rare earth elements composed mainly of neodymium, proseodymium or cesium Can be replaced with dysprosium, terbium, or holmium, M is one or more elements selected from niobium, tungsten, vanadium, tantalum and molybdenum, 0≤x≤0.7, 0.02≤y≤0.3, 0.001≤z≤ A thermally stable sintered permanent magnet having a composition of 0.15, 0.001 ≦ u ≦ 0.1 and 4.0 ≦ A ≦ 7.5. The sintered permanent magnet according to claim 1, wherein 0.01≤x≤0.4, 0.03≤y≤0.2, 0.02≤z≤0.1, 0.002≤u≤0.04 and 4.5≤A≤7.0. The sintered permanent magnet according to claim 1, wherein R mainly consists of neodymium and dysprosium, and an atomic ratio of neodymium to dysprosium is 0.97: 0.03 to 0.6: 0.4. 4. The sintered permanent magnet of claim 3, wherein 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. The sintered permanent magnet according to any one of claims 1 to 4, wherein M is niobium.

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