HK1070740B - R-t-b system rare earth permanent magnet - Google Patents

Description

R-T-B rare earth permanent magnet

Technical Field

The present invention relates to R-T-B (R is 1 or 2 or more of rare earth elements (although the rare earth elements are a concept including Y) and T (1 or 2 or more transition metal elements essential for Fe or Fe and Co) based rare earth permanent magnets, and particularly to a rare earth permanent magnet having high magnetization characteristics.

Background

Among rare earth permanent magnets, R-T-B based rare earth permanent magnets are used in various electric appliances because of their excellent ferromagnetic properties, abundant Nd as a main component, and relatively low cost.

Research and development have been mainstream so far for improving the magnetic properties of R-T-B based rare earth permanent magnets, specifically for improving the residual magnetic flux density, the coercive force, or the maximum energy product. However, research and development focusing on magnetization characteristics have been recently carried out. R-T-B rare earth permanent magnets require a higher magnetizing field than ferrite magnets. For example, when a ring-shaped R-T-B-based rare earth permanent magnet is used for a rotor of a motor, the ring-shaped R-T-B-based rare earth permanent magnet may be magnetized by using a winding for a wound motor after the R-T-B-based rare earth permanent magnet is assembled to the motor. When the motor is small, the wire diameter of the winding is made small to obtain a predetermined number of turns, and a large current cannot flow. Therefore, a sufficient magnetization magnetic field cannot be applied to the R-T-B based rare earth permanent magnet. Therefore, R-T-B based rare earth permanent magnets used for the above applications are required to have as high magnetization characteristics as possible at a low magnetization magnetic field.

For example, Japanese patent application laid-open No. 2002-356701 discloses a rare earth alloy sintered body having an average composition of a main phase of (LR) as an R-T-B based rare earth permanent magnet excellent in magnetization characteristics_1-xHR_x)₂T₁₄A (T is Fe or a mixture of Fe and at least one transition metal element other than Fe, A is boron or a mixture of boron and carbon, LR is at least one light rare earth element, HR is at least one heavy rare earth element, 0 < x < 1). The rare earth alloy sintered compact contains (LR)_1-pHR_p)₂T₁₄A (0. ltoreq. p < 1) with a composition of 1 st main phase and (LR)_1-qHR_q)₂T₁₄A (0. ltoreq. q < 1) is a crystal grain of at least one of the 2 nd main phases.

According to the technique disclosed in Japanese unexamined patent publication No. 2002-356701, the magnetization characteristics can be improved without lowering the magnetization characteristics. However, in order to obtain a magnetic susceptibility of about 50%, a magnetization magnetic field of about 0.8MA/m (10kOe) is required. Therefore, it is desired to obtain a magnetic susceptibility of about 50% with a lower magnetizing field.

Further, Japanese patent application laid-open No. 2003-217918 discloses a rare earth sintered magnet for the purpose of improving magnetization characteristics, which contains R (R is 1 or 2 or more of rare earth elements (however, the rare earth element is a concept containing Y) in weight%, and Nd is 50 atomic% or more of R): 25-35%, B: 0.8 to 1.5%, and if necessary, M (at least one selected from Ti, Cr, Ga, Mn, Co, Ni, Cu, Zn, Nb, and Al): 8% or less, and the balance of T (Fe or Fe and Co) and unavoidable impurities. The rare earth sintered magnet has a Fe content of 80 at% or more_ACo_1-AThe Fe phase (2) has a crystal structure in which the Fe phase (2) remains in a sintered body in a size of 0.01 to 300 [ mu ] m, and has a magnetic susceptibility Br (0.2MA/m)/Br (2.0MA/m) of 59% or more as measured by residual magnetic flux density and a magnetic susceptibility φ (0.3MA/m)/φ (4.0MA/m) of 4% or more as measured by magnetic flux.

However, in Japanese unexamined patent publication No. 2003-217918, the value of the magnetic susceptibility Br (0.2MA/m)/Br (2.0MA/m) as evaluated by the remanent flux density is 59% or more, and the value of the magnetic susceptibility φ (0.3MA/m)/φ (4.0MA/m) as evaluated by the magnetic flux density is 4% or more, it cannot be said that the magnetization characteristics are good.

On the other hand, according to the studies of the present inventors, an R-B-T-based rare earth permanent magnet having a higher magnetic susceptibility at a low magnetic field shows a tendency that a magnetization characteristic curve of the magnetic susceptibility varying with a magnetizing field shows a smooth slope. I.e. a larger magnetizing field is required before reaching a susceptibility in the vicinity of 100%, which is not ideal.

The present invention has been made in view of the above problems, and an object of the present invention is to provide: provided is an R-B-T system rare earth permanent magnet which can obtain a higher magnetic susceptibility with a low magnetic field and can exhibit a magnetization characteristic curve in which the magnetic susceptibility rises rapidly until the magnetic susceptibility reaches near 100%, for example, about 90%.

Disclosure of Invention

It is known that when a high coercive force is obtained in a conventional permanent magnet, the remanent magnetic flux density is lowered, whereas when a high remanent magnetic flux density is obtained, the coercive force is lowered. For example, the required characteristics can be obtained by adjusting the amount of Dy as a rare earth element. Specifically, the Dy amount is increased when a high coercive force is to be obtained, and the Dy amount is decreased when a high residual magnetic flux density is to be obtained, whereby the desired characteristics can be obtained. Further, it has been empirically found that a permanent magnet having a high coercive force can obtain high magnetization characteristics.

The present inventors have R₂T₁₄Phase B (R is 1 or 2 or more of rare earth elements (the rare earth elements areY-containing concept), T is 1 or 2 or more transition metal elements essential for Fe or Fe and Co) as a main phase, and a sintered body composed of a grain boundary phase containing more R than the main phase. As a result, it was found that excellent magnetization characteristics, which have not been obtained before, can be obtained by controlling the average crystal grain size and the oxygen content of the sintered body and further containing Zr and/or Nb.

This finding can also be applied to a permanent magnet of a low coercive force type (hereinafter referred to as "low coercive force type") and a permanent magnet of a high coercive force type (hereinafter referred to as "high coercive force type"). Hereinafter, the magnetization characteristics of the low coercive force type permanent magnet and the high coercive force type permanent magnet will be described in order. As described later, the high coercive force type permanent magnet has higher magnetization characteristics.

First, the low coercive force type permanent magnet of the present invention will be explained.

The R-T-B rare-earth permanent magnet of the present invention (hereinafter, the R-T-B rare-earth permanent magnet is simply referred to as "permanent magnet") exhibits a magnetization characteristic in which a total magnetic flux when an effective magnetic field of 240kA/m (3kOe) is applied (but the effective magnetic field is equal to the applied magnetic field — counter magnetic field) is f1, a total magnetic flux when an effective magnetic field of 800kA/m (dkoe) is applied is f2, and a total magnetic flux when an effective magnetic field of 2000kA/m (25kOe) is applied is f3, with Pc (permeability) of 2, and a magnetic susceptibility a (f 1/f3 × 100) of 40% or more and a magnetic susceptibility B (f 2/f3 × 100) of 90% or more (first permanent magnet). Here, Pc (magnetic permeability) is the reciprocal of the magnetic resistance.

According to the 1 st permanent magnet of the present invention, when Pc is 0.5, the magnetic susceptibility a is 30% or more and the magnetic susceptibility b is 80% or more; further, when Pc is 1, high magnetization characteristics can be realized, in which the magnetic susceptibility a is 35% or more and the magnetic susceptibility b is 90% or more.

The permanent magnet can ensure that the residual magnetic flux density (Br) is more than 1.35T and the maximum energy product ((BH) max) is 350kJ/m³The square ratio (Hk/HcJ) is 95% or more.

In order to obtain the above excellent magnetization characteristics, it is important that the oxygen content in the sintered body is 2000ppm or less, and further 1500ppm or less, and the grain size in the sintered body is 3.3 to 4.3 μm, in the first permanent magnet according to the present invention. In order to obtain the above excellent magnetization characteristics, it is important that Zr is dispersed in the sintered body.

According to the 1 st permanent magnet of the present invention, a magnet having R: 25 to 35 wt% (R is 1 or 2 or more of rare earth elements, and the rare earth element is a concept containing Y), B: 0.5 to 4.5 wt%, 1 or 2 of Al and Cu: 0.02 to 0.5 wt%, Zr: 0.03 to 0.25 wt%, Co: a permanent magnet comprising a sintered body having a composition of not more than 2 wt% (excluding 0) and the balance Fe is preferable.

The 1 st permanent magnet according to the present invention may contain 0.1 to 4.0 wt% of Dy as R.

The 1 st permanent magnet according to the present invention contains Zr dispersed at least in grain boundaries of the sintered body.

The 1 st permanent magnet according to the present invention relates to a low coercive force type permanent magnet having a coercive force (HcJ) of 1680kA/m (21kOe) or less.

As described above, according to the permanent magnet of the present invention having the feature 1, the magnetization characteristics can be improved even for the low coercive force type permanent magnet.

Next, a description will be given of a high coercive force type permanent magnet.

The high coercive force type permanent magnet of the present invention exhibits a magnetization characteristic (No. 2 permanent magnet) in which the total magnetic flux when an effective magnetic field of 240kA/m (3kOe) is applied (however, when the effective magnetic field is equal to the applied magnetic field — counter magnetic field) is F1, when an effective magnetic field of 400kA/m (5kOe) is applied is F2, and when an effective magnetic field of 2000kA/m (25kOe) is applied is F3, the magnetic susceptibility c (equal to F1/F3 × 100) is 60% or more, and the magnetic susceptibility d (equal to F2/F3 × 100) is 85% or more, respectively.

From the above, it is empirically known that a permanent magnet of a type having a high coercive force can obtain a high magnetization characteristic. Therefore, higher magnetization characteristics than those of the high coercive force type permanent magnet have not been desired. However, the present inventors have conducted various studies and have confirmed that, by containing a larger amount of heavy rare earth elements and further containing elements such as Nb in an R-T-B based rare earth permanent magnet of a type having a higher coercive force, it is possible to obtain excellent magnetization characteristics which have not been obtained before by controlling the average crystal grain size and oxygen content of a sintered body.

According to the 2 nd permanent magnet of the present invention, high magnetization characteristics in which the magnetic susceptibility c is 40% or more and the magnetic susceptibility d is 70% or more can be realized at 0.5 for Pc and the magnetic susceptibility c is 55% or more and the magnetic susceptibility d is 80% or more can be realized at 1 for Pc.

The permanent magnet can ensure that the residual magnetic flux density (Br) is more than 1.20T and the maximum energy product ((BH) max) is 240kJ/m³The square ratio (Hk/HcJ) is 90% or more.

In order to obtain the above excellent magnetization characteristics, it is important that the 2 nd permanent magnet of the present invention has an oxygen content of 2000ppm or less, further 1500ppm or less, and a grain size of 3.5 to 5.0 μm in the sintered body. In order to obtain the above excellent magnetization characteristics, it is important that Nb and/or Zr be dispersed in the sintered body.

According to the 2 nd permanent magnet of the present invention, a magnet having R: 25-35 wt%, B: 0.5 to 4.5 wt%, 1 or 2 of Al and Cu: 0.02 to 0.5 wt%, Nb: 0.2 to 1.5 wt% and Zr: 0.03 to 0.25 wt% of 1 or 2 species, Co: a permanent magnet comprising a sintered body having a composition of not more than 2 wt% (excluding 0) and the balance Fe is preferable.

According to the 2 nd permanent magnet of the present invention, since a high coercive force type permanent magnet is targeted, 4.0 to 12.0 wt% of Dy may be contained as R; the composition may further contain 1.0 to 6.0 wt% of Tb as R. Dy and Tb are effective elements for obtaining high coercive force. Dy and Tb may be contained alone or in combination. Therefore, the 2 nd permanent magnet can have a coercive force (HcJ) of 1680kA/m (21kOe) or more.

In the case where Nb is contained in the permanent magnet of the present invention, the Nb is dispersed in the main phase (R) in the sintered body₂T₁₄B) And in grain boundaries. When Zr is contained in the permanent magnet, the Zr is dispersed in grain boundaries in the sintered body.

The 1 st permanent magnet and the 2 nd permanent magnet according to the present invention can be used for any type of magnet. Particularly, when the magnet is used for a magnet magnetized in multiple poles, the effect can be remarkably exhibited.

In the 1 st permanent magnet and the 2 nd permanent magnet, 1 or more of Ti, V, Cr, Mn, Bi, Nb, Ta, Mo, W, Sb, Ge, Sn, Ni, Si, Hf, Ga, and the like may be added for the purpose of improving coercive force and temperature characteristics, improving production efficiency, reducing cost, and the like. Among them, Ga is effective for improving the magnetization characteristics, and is preferably added in a range of 0.02 to 1.5% by weight, and more preferably 0.1 to 1% by weight.

Further, in order to have high magnetic properties, it is preferable that the content of nitrogen in the sintered body is limited to 20 to 600ppm and the content of carbon is limited to 1500ppm or less.

Drawings

Fig. 1 is a graph showing the composition of the raw material alloy used in experimental example 1 and the composition of the sintered body obtained in experimental example 1.

Fig. 2 is a graph showing the magnetic properties and the like of the permanent magnets (samples 1 to 5) obtained in experimental example 1.

Fig. 3 is a graph showing the results of measuring the magnetic susceptibility (Pc ═ 2) for samples 1 to 5.

FIG. 4 is a graph showing the relationship (magnetization characteristic curve) between the magnetization magnetic field and the magnetic susceptibility for samples 1 to 5.

Fig. 5 is a graph showing values of magnetization magnetic fields required for obtaining magnetic susceptibility of 40%, 50%, 60%, 70%, 80%, 90%, and 95% in samples 1 to 5.

Fig. 6 is a graph showing the composition of the raw material alloy used in example 2 and the composition of the sintered body obtained in example 2.

Fig. 7 is a graph showing the magnetic properties and the like of the permanent magnets (samples 6 to 8) obtained in experimental example 2.

Fig. 8 is a graph showing the results of measuring magnetic susceptibility (Pc ═ 2) for samples 6 to 8.

Fig. 9 is a graph showing the relationship (magnetization characteristic curve) between the magnetization magnetic field and the magnetic susceptibility for samples 6 to 8.

Fig. 10 is a graph showing the composition of the raw material alloy used in experimental example 3 and the composition of the sintered body obtained in experimental example 3.

FIG. 11 is a graph showing the magnetic properties and the like of the permanent magnets (samples 9 to 11) obtained in Experimental example 3.

Fig. 12 is a graph showing the results of measuring the magnetic susceptibility (Pc ═ 2) for samples 9 to 11.

FIG. 13 is a graph showing the relationship between the magnetization magnetic field and the magnetic susceptibility (magnetization characteristic curve) for samples 9 to 11.

Fig. 14 is a graph showing the composition of the raw material alloy used in experimental example 4 and the composition of the sintered body obtained in experimental example 4.

FIG. 15 is a graph showing the magnetic properties and the like of the permanent magnets (samples 12 to 14) obtained in Experimental example 4.

Fig. 16 is a graph showing the results of measuring the magnetic susceptibility (Pc ═ 2) for samples 12 to 14.

Fig. 17 is a graph showing the relationship (magnetization characteristic curve) between the magnetization magnetic field and the magnetic susceptibility for samples 12 to 14.

FIG. 18 is a plan view and a magnetization pattern showing the shape of the test pieces prepared from samples 12 to 14.

FIG. 19 is a graph showing the relationship between the position of the one-dot chain line and the total magnetic flux (B) in the test piece of FIG. 18 at different magnetizing voltages.

Fig. 20 is a graph showing the magnetic properties and the like of the permanent magnet (sample 15) obtained in experimental example 5.

Fig. 21 is a graph showing the results of measuring the magnetic susceptibility for sample 15(Pc ═ 2.0), sample 16(Pc ═ 1.0), and sample 17(Pc ═ 0.5).

FIG. 22 is a graph showing the relationship between the magnetization magnetic field and the magnetic susceptibility (magnetization characteristic curve) for samples 15 to 17.

FIG. 23 is a graph showing the compositions of alloys used in obtaining permanent magnets (samples 18 to 23) in Experimental example 6.

FIG. 24 is a graph showing the magnetic properties and the like of samples 18 to 23.

Fig. 25 is a graph showing the results of measuring the magnetic susceptibility of samples 18 to 23(Pc ═ 2).

FIG. 26 is a graph showing the compositions of alloys used in obtaining permanent magnets (samples 24 to 28) in Experimental example 7.

FIG. 27 is a graph showing magnetic properties and the like of samples 24 to 28.

Fig. 28 is a graph showing the results of measuring the magnetic susceptibility of samples 24 to 28(Pc ═ 2).

FIG. 29 is a graph showing the compositions of alloys used in obtaining permanent magnets (samples 29 to 36) in Experimental example 8.

FIG. 30 is a graph showing the magnetic properties and the like of the samples 18 and 29 to 36.

Fig. 31 is a graph showing the results of measuring the magnetic susceptibility (Pc ═ 2) for samples 18 and 29 to 36.

FIG. 32 is a graph showing the compositions of alloys used in obtaining permanent magnets (samples 37 to 40) in Experimental example 9.

FIG. 33 is a graph showing magnetic characteristics and the like of samples 37 to 40.

Fig. 34 is a graph showing the results of measuring the magnetic susceptibility (Pc ═ 2) for samples 37 to 40.

FIG. 35 is a graph showing the relationship between the position of the one-dot chain line and the total magnetic flux (B) in the test piece of FIG. 18 at different magnetizing voltages.

FIG. 36 is a graph showing the compositions of alloys used in obtaining permanent magnets (samples 41 to 44) in Experimental example 10.

FIG. 37 is a graph showing magnetic characteristics and the like of samples 41 to 44.

Fig. 38 is a graph showing the results of measuring the magnetic susceptibility (Pc ═ 2) for samples 41 to 44.

Fig. 39 is a graph showing the results of measuring the magnetic susceptibility (Pc ═ 2) of samples 19, 45, and 46.

Detailed Description

Hereinafter, a permanent magnet and a method for manufacturing the same according to the present invention will be described.

As is known, the permanent magnet obtained according to the invention contains at least R₂T₁₄B crystal grains (wherein R is 1 or 2 or more of rare earth elements, and the rare earth elements are a concept containing Y), a main phase composed of T crystal grains of 1 or more transition metal elements mainly consisting of Fe or Fe and Co, and a grain boundary phase containing more R than the main phase.

< magnetization characteristics >

First, the magnetization characteristics of the permanent magnet according to the present invention will be described.

The 1 st permanent magnet according to the present invention of the low coercive force type described above has a magnetic susceptibility a (f 1/f3 × 100) of 40% or more and a magnetic susceptibility b (f 2/f3 × 100) of 90% or more.

Here, f1 is the total magnetic flux when an effective magnetic field of 240kA/m is applied (however, the effective magnetic field is an applied magnetic field — a counter magnetic field) with Pc (permeability) of 2, f2 is the total magnetic flux when an effective magnetic field of 800kA/m is applied, and f3 is the total magnetic flux when an effective magnetic field of 2000kA/m is applied.

Pc of the present invention is identified from FIGS. 5 to 4 on page 146 of "xi-Tu permanent magnet" (Biao Hao Fu Jian et al, Jian , published by Senebi). The magnetic susceptibility was measured as follows. After a closed magnetic circuit is formed by clamping the magnet to be evaluated on the pole shoe, the magnet is magnetized by passing a current. At this time, the applied magnetic field is an effective magnetic field. After magnetization the total magnetic flux was determined by a fluxmeter.

As described above, the magnetization characteristic described here is desirable to have a larger magnetic susceptibility in a low magnetic field and to allow a magnetization characteristic curve to exist on the low magnetic field side. However, it was not easy to satisfy both of them before. However, the present invention can provide a permanent magnet having a magnetization characteristic that has not been achieved before, in which a (f 1/f3 × 100) is 40% or more and a (f 2/f3 × l00) is 90% or more. Even in the range of 240kA/m to 800kA/m, the permanent magnet according to the present invention has excellent magnetic susceptibility as shown in examples described later.

In order to obtain the above magnetization characteristics, it is important that the average crystal grain diameter of the sintered body is within a limited range of 3.3 to 4.3 μm. As will be described later in example 1, when the average grain size is less than 3.3 μm or more than 4.3. mu.m, the magnetic susceptibility a and the magnetic susceptibility b cannot be obtained.

On the other hand, the 2 nd permanent magnet according to the present invention of the high coercive force type described above has a magnetic susceptibility c (═ F1/F3 × 100) of 60% or more and a magnetic susceptibility d (═ F2/F3 × 100) of 85% or more.

Here, F1 is the total magnetic flux when an effective magnetic field of 240kA/m is applied (however, the effective magnetic field is an applied magnetic field — a demagnetizing field) with Pc (permeability) of 2, F2 is the total magnetic flux when an effective magnetic field of 400kA/m is applied, and F3 is the total magnetic flux when an effective magnetic field of 2000kA/m is applied.

When the total magnetic flux amount when an effective magnetic field of 800kA/m is applied is F4, the magnetic susceptibility e (F4/F3 × 100) is 95% or more, and the magnetic susceptibility is extremely high. Pc, magnetic susceptibility, and total magnetic flux were measured in the same manner as in the case of the 1 st permanent magnet.

As described above, the magnetization characteristic described here is preferably such that the low magnetic field has a larger magnetic susceptibility (magnetic susceptibility is also referred to as "magnetizing susceptibility" or "magnetizing susceptibility") and the rise in magnetic susceptibility is steep. However, both have not been previously easy to satisfy. However, the 2 nd permanent magnet according to the present invention of the high coercive force type can obtain a permanent magnet having a magnetic susceptibility c (F1/F3 × 100) of 60% or more, a magnetic susceptibility d (F2/F3 × 100) of 85% or more, and a magnetic susceptibility e (F4/F3 × 100) of 95% or more, and having a high magnetic susceptibility and a rapid increase in magnetic susceptibility at a low magnetic field which has not been obtained before.

In order to obtain the above magnetization characteristics, it is important that the average crystal grain diameter of the sintered body is within a limited range of 3.5 to 5.0 μm. As will be described later in example 2, when the average grain size is less than 3.5 μm or more than 5.0. mu.m, the magnetic susceptibility c and the magnetic susceptibility d cannot be obtained.

In the case of using a low coercive force type permanent magnet or a high coercive force type permanent magnet, as a factor of the composition for obtaining the above magnetization characteristics, it is possible to limit the oxygen content in the sintered body and to contain Zr and/or Nb. This is described in the column of < chemical composition > described later.

< multipolar magnetized magnet >

As described above, the present invention is preferably applied to a magnet that performs multipolar magnetization. The magnets magnetized in multiple poles include radial anisotropic or polar anisotropic ring magnets used in motors, rectangular parallelepiped magnets used for driving a pickup head (pickup head) of a device such as a CD or a DVD, and sector magnets used for a VCM (voice coil motor). These multipolar magnetized magnets have a plurality of N · S polarities.

When the permanent magnet of the present invention is applied to the above multipolar magnetized magnet, the width of the neutral zone (neutral zone) can be made narrow. Therefore, the total magnetic flux increases, for example, a magnet for a motor, enabling the characteristics of the motor to be improved. The neutral region as used herein refers to a region where neither N nor S is magnetized at a boundary of polarity inversion when magnetization (also referred to as magnetization or magnetization) of the magnet is performed. Particularly, for a magnet having a small size and a magnet having a large number of poles, the ratio of the area occupied by the neutral zone is increased. Therefore, the width of the neutral region can be narrowed by performing multipolar magnetization of the permanent magnet having excellent magnetization characteristics of the present invention. This improves the characteristics of a motor using the magnet.

< chemical composition >

Next, an ideal chemical composition of the R-T-B based rare earth permanent magnet according to the present invention will be described. The chemical composition referred to herein means a final composition after sintering (sintered body composition).

The rare earth permanent magnet of the present invention contains 25 to 35% by weight of a rare earth element (R).

Here, R in the present invention is 1 or 2 or more species among La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu and Y. When the R content is less than 25 wt%, R which becomes the main phase of the R-T-B rare earth permanent magnet₂T₁₄B₁The generation of crystal grains is insufficient, alpha-Fe with soft magnetism is precipitated, and the coercive force is remarkably reduced; on the other hand, when the R amount exceeds 35% by weight, R is present as the main phase₂T₁₄B₁The volume ratio of crystal grains is reduced and the residual magnetic flux density is reduced. When the amount of R exceeds 35% by weight, R reacts with oxygen and the amount of oxygen contained increases. The consequent decrease in the R-rich phase, which is effective for the occurrence of coercivity, results in a decrease in coercivity. Therefore, the amount of R is determined to be 25 to 35% by weight. The preferable R content is 28 to 33 wt%, and the more preferable R content is 29 to 32 wt%.

Nd is a preferred rare earth element as a main component because it is abundant in resources and relatively inexpensive. Dy and Tb are effective for improving coercive force. Accordingly, it is preferable to select Nd and/or Dy as the main components of the rare earth elements, and the total amount of Nd, Dy and/or Tb is 25 to 35% by weight. Dy and Tb are preferably determined in the above ranges, with importance placed on the respective degrees of residual magnetic flux density and coercive force. In order to obtain a high residual magnetic flux density, Dy is preferably 0.1 to 4.0 wt%; on the other hand, when a high coercive force is desired, the Dy content is preferably 4.0 to 12.0 wt%. The Tb content is preferably 1.0 to 6.0% by weight. In addition, Tb is higher than Dy in the effect of enhancing coercive force. Tb has an effect of enhancing coercive force about 2 times as much as Dy when it is contained in the same amount.

As described above, the present invention is the feature 1 in that the low coercive force type permanent magnet also has excellent magnetization characteristics. Therefore, when the Dy content is 0.1 to 4.0 wt%, the effect of the feature 1 of the present invention can be sufficiently exhibited. Dy is added in an amount of 10 wt% or less to the entire rare earth elements, and in this case, the coercive force (HcJ) is 1680kA/m or less, and 1440kA/m or less.

On the other hand, the feature 2 of the present invention is that the permanent magnet of the high coercive force type also has excellent characteristics. Therefore, when Dy and/or Tb are/is in the above range, the effect of the feature 2 of the present invention can be fully exhibited. In this case, the coercive force (HcJ) is more than 1680kA/m, 1750kA/m or more, and further 2000kA/m or more.

The permanent magnet of the present invention contains 0.5 to 4.5% by weight of boron (B). When B is less than 0.5% by weight, a high coercive force cannot be obtained; however, when B exceeds 4.5 wt%, the residual magnetic flux density tends to decrease. Therefore, the upper limit is 4.5 wt%. The content of B is preferably 0.5 to 1.5% by weight, more preferably 0.8 to 1.2% by weight.

The permanent magnet of the present invention may contain Al and/or Cu in an amount of 0.02 to 0.5 wt%. When Al and/or Cu is contained in this range, the obtained permanent magnet can have a high coercive force and improved temperature characteristics. When Al is added, the Al content is preferably 0.03 to 0.3% by weight, and more preferably 0.05 to 0.25% by weight. When Cu is added, the amount of Cu is preferably 0.15 wt% or less (excluding 0), and more preferably 0.03 to 0.08 wt%.

It is important that the permanent magnet of the present invention contains 0.2 to 1.5 wt% of Nb and/or 0.03 to 0.25 wt% of Zr. In order to improve the magnetization characteristics of the permanent magnet, Zr is effective. Further, when the oxygen content is reduced in order to improve the magnetic properties of the permanent magnet, Zr exerts an effect of suppressing abnormal growth of crystal grains in the sintering process, and the structure of the sintered body is made uniform and fine. Therefore, the effect of Zr is remarkable when the oxygen content is low. The preferable content of Zr is 0.05 to 0.25 wt%, and the more preferable content is 0.1 to 0.2 wt%.

Similarly to Zr, Nb is effective for improving the magnetization characteristics of the permanent magnet. Further, Nb also exerts an effect of suppressing abnormal growth (growth) of crystal grains in the sintering process when the oxygen content is reduced in order to improve the magnetic properties of the permanent magnet, and makes the structure of the sintered body uniform and fine. Therefore, Nb is remarkably effective when the oxygen content is low, like Zr. The preferable content of Nb is 0.5 to 1.3 wt%, and the more preferable content is 0.5 to 1.2 wt%.

The oxygen content of the permanent magnet of the present invention is 2000ppm or less. When the oxygen content is large, the oxide phase of the nonmagnetic component increases, and the magnetic properties deteriorate. In the present invention, the oxygen content in the sintered body is set to 2000ppm or less, preferably 1500ppm or less, and more preferably 1000ppm or less. However, simply reducing the oxygen content results in an insufficient amount of oxide phase having the effect of suppressing grain growth. Because of this, abnormal growth of crystal grains is easily caused in the process of obtaining sufficient density rise at the time of sintering. In the present invention, Nb and/or Zr having an effect of suppressing abnormal grain growth is added in a predetermined amount while improving the magnetization characteristics.

The permanent magnet of the present invention contains Co in an amount of 2 wt% or less (excluding 0), preferably 0.1 to 1.0 wt%, more preferably 0.3 to 0.7 wt%. Co has an effect of improving the curie temperature and the corrosion resistance of the grain boundary phase.

< production method >

Next, a suitable method for manufacturing a permanent magnet according to the present invention will be described.

In this embodiment, the compound B is used₂T₁₄A method for producing a permanent magnet according to the present invention by a so-called hybrid method of producing an alloy mainly composed of a B grain phase (low R alloy) and an alloy containing more R than the low R alloy (high R alloy) will be described. However, it is a matter of course that the permanent magnet of the present invention can be produced by using a single raw material alloy.

First, a low R alloy and a high R alloy are obtained by strip casting (strip casting) in a vacuum or an inert gas, preferably in an Ar atmosphere. The low R alloy may contain Cu and Al in addition to rare earth elements, Fe, Co, and B. In addition, the high R alloy may contain Cu and Al in addition to the rare earth elements, Fe, Co, and B. In addition, when Zr is added, it is preferable that Zr is contained in the low R alloy.

After the low R alloy and the high R alloy are produced, the raw material alloys thereof may be pulverized separately or together. The pulverization step includes a coarse pulverization step and a fine pulverization step. First, the raw material alloys were coarsely pulverized to a particle size of about several hundred μm. The coarse pulverization is preferably carried out in an inert gas atmosphere by a masher, a jaw crusher, a Brownian pulverizer (ブラウンミル), or the like. In order to improve the coarse pulverization property, it is effective to perform the coarse pulverization after hydrogen is occluded.

After the coarse grinding step is completed, the process proceeds to a fine grinding step. The fine grinding is carried out by mainly using a jet mill to grind coarse powder having a particle size of about several hundred microns to an average particle size of 2.5 to 6 microns, preferably 3 to 5 microns. The jet mill is a method of ejecting a high-pressure inert gas (e.g., nitrogen gas) from a narrow nozzle to generate a high-speed gas flow, accelerating coarsely pulverized powder by the high-speed gas flow, and pulverizing the coarsely pulverized powder by causing collision between the coarsely pulverized powder and the target or the container wall.

The mixing of the 2 alloys is not limited basically, but when the low R alloy and the high R alloy are pulverized separately in the fine pulverization step, the low R alloy powder and the high R alloy powder that have been finely pulverized are mixed in a nitrogen atmosphere. The mixing ratio of the low R alloy powder to the high R alloy powder is about 80: 20-97: 3 in terms of weight ratio. Similarly, the same applies to the mixing ratio in the case where the low R alloy powder and the high R alloy powder are pulverized together. When finely pulverizing, a fine powder having a high orientation during molding can be obtained by adding about 0.01 to 0.3 wt% of a pulverizing aid such as zinc stearate.

Then, a mixed powder of the low R alloy powder and the high R alloy powder is filled in a mold surrounded by an electromagnet, and a magnetic field is applied to orient the crystal axis in the magnetic field for molding. The magnetic field is formed in a magnetic field of about 12 to 20kOe (960 to 1600kA/m) at a rate of 0.3 to 3.0t/cm²(30 to 300MPa) or so. Preferably, the magnetic field is 0.7 to 1.5t/cm in 960 to 1360kA/m²(70 to 150MPa) under a pressure of about 70 to 150 MPa.

After shaping in a magnetic field, the shaped bodies are sintered in a vacuum or in an inert gas atmosphere. Sintering at 1000-1100 deg.C for 1-5 hr. However, it is necessary to adjust the sintering temperature depending on various conditions such as composition, pulverization method, and difference in particle size and particle size distribution,

before the sintering step, the grinding aid, gas, and the like contained in the molded body may be removed.

After sintering, the resulting sintered body may be subjected to an aging treatment. This step is an important step for controlling the coercivity. In the case of aging treatment in 2 stages, it is effective to maintain the aging treatment at around 600 ℃ and around 800 ℃ for a predetermined time. The hybrid method is particularly effective because the coercive force increases when heat treatment is performed at around 800 ℃ after sintering. Further, since the heat treatment at around 600 ℃ greatly increases the coercive force, when the aging treatment is performed in 1 stage, the aging heat treatment at around 600 ℃ may be performed.

(examples)

Next, the present invention will be described in more detail with reference to specific examples. Example 1 is an experimental example of a low coercive force type permanent magnet, and example 2 is an experimental example of a high coercive force type permanent magnet.

[ 1 st embodiment ]

< Experimental example 1>

Raw material alloys (low R alloy and high R alloy) having the compositions shown in fig. 1 were produced by strip casting.

Each of the obtained raw material alloys was allowed to store hydrogen at room temperature, and then subjected to dehydrogenation at 600 ℃ for 1 hour in an Ar atmosphere, followed by hydrogen pulverization treatment.

In order to obtain high magnetic characteristics, the oxygen content of the sintered body was controlled to 1000ppm or less in experimental example 1, and therefore the protective atmosphere in each step from hydrogen pulverization (recovery after pulverization) to sintering (charging into a sintering furnace) was controlled to an oxygen concentration of less than 100ppm (this is true in experimental examples 2 to 11 below).

The 2-stage pulverization of the coarse pulverization and the fine pulverization is usually carried out, and the coarse pulverization step is omitted in experimental example 1 (this is also true in experimental examples 2 to 11 below).

The hydrogen-pulverized low R alloy and high R alloy were mixed at a ratio of 90: 10, and 0.1% oleamide was added as a pulverization aid. Then, the resulting mixture was finely pulverized by a jet mill to obtain 5 kinds of fine powders having an average particle diameter (D) of 3.82. mu.m, 4.00. mu.m, 4.15. mu.m, 4.29. mu.m, 4.64. mu.m, etc. The particle size was measured by a laser diffraction particle size distribution meter (Mastersizer manufactured by malvern instrument). Fig. 1 shows the final composition obtained by mixing the low R alloy and the high R alloy.

The obtained fine powder was subjected to pressure molding in a magnetic field of 1320kA/m (16.5kOe), to obtain a molded article. Density of the shaped bodyIs 4.2Mg/m³。

The obtained molded body was sintered at 1060 ℃ for 4 hours in vacuum and then quenched. The resulting sinter was then subjected to 2-stage aging treatment at 900 ℃ for 1 hour and 530 ℃ for 2.5 hours (both in an Ar atmosphere).

The magnetic properties of the obtained permanent magnet were measured by a B-H plotter, and the density, average crystal grain diameter, oxygen content, nitrogen content, and carbon content of the sintered body were also measured. The results are shown in FIG. 2. In fig. 2, d represents the average crystal grain diameter of the sintered body, ρ represents the density of the sintered body, Br represents the residual magnetic flux density, HcJ represents the coercive force, (BH) max represents the maximum energy product, and Hk/HcJ represents the squareness ratio. The squareness ratio (Hk/HcJ) is an index of magnet performance, and indicates how much the square of the hysteresis loop opens in quadrant 1. Hk is the external magnetic field strength at which the magnetic flux density in quadrant 2 of the hysteresis loop is 90% of the residual magnetic flux density. The average crystal grain size of the sintered body was evaluated by observing the polished surface of the sintered body with a simple polarizing microscope (BX 60M manufactured by Olympus Sangyo Co., Ltd. ) and using an image processing apparatus (IP-1000 manufactured by Asahi Kasei corporation ). By this evaluation, the area of the crystal grains is obtained, and thus it is converted into the diameter of the equivalent circle as the diameter of the crystal grains.

As shown in FIG. 2, it is understood that any of the permanent magnets of samples 1 to 5 has a residual magnetic flux density of 1.4T or more, a coercive force of 1000kA/m or more, and 400kJ/m³A higher maximum energy product near or above. It is also known that any permanent magnet has an oxygen content of 1000ppm or less, a nitrogen content of 500ppm or less, and a carbon content of 1000ppm or less, and the impurity content is at a low level.

Next, the magnetic susceptibility (Pc ═ 2) of the permanent magnets of samples 1 to 5 was measured. The results are shown in fig. 3 and 4. As shown in fig. 3 and 4, sample 1(3.2 μm) having the smallest average crystal grain size and sample 5(4.4 μm) having the largest average crystal grain size have low magnetic susceptibility at low magnetization magnetic field.

Fig. 5 shows values of magnetization magnetic fields required for obtaining magnetic susceptibility of samples 1 to 5 of 40%, 50%, 60%, 70%, 80%, 90%, and 95%. As shown in FIG. 5, samples 2 to 4 were able to obtain a magnetic susceptibility of 40% in a magnetic field of 240kA/m (3 kOe). In contrast, samples 1 and 5 required a magnetizing field of 320kA/m (4 kOe). Similarly, in samples 2 to 4, the magnetic susceptibility of 50%, 60%, 70%, 80%, 90%, and 95% can be obtained with a lower magnetizing field than in samples 1 and 5.

As is clear from the above, by setting the average crystal grain size of the sintered body to 3.3 to 4.3 μm, preferably 3.5 to 4.0 μm, a magnetic susceptibility of 40% or more can be obtained with a low magnetizing field of 240 kA/m. It is also found that by setting the average crystal grain size of the sintered body to 3.3 to 4.3 μm, it is sufficient to obtain a lower magnetizing field with 90% magnetic susceptibility. In other words, a higher magnetic susceptibility can be obtained with a low magnetizing field.

< Experimental example 2>

3 kinds of permanent magnets (samples 6 to 8) were obtained in the same manner as in experimental example 1, except that the raw material alloy having the composition shown in fig. 6 was used and the oxygen content in the pulverized gas (nitrogen gas) was controlled during the production of fine powder, so that the oxygen content in the final sintered body was changed. The magnetic properties and the like of the 3 types of permanent magnets obtained were measured in the same manner as in experimental example 1. The results are shown in FIG. 7. Ts in FIG. 7 is a sintering temperature, and the other symbols are the same as those in FIG. 2.

As shown in FIG. 7, it is understood that all of the permanent magnets of samples 6 to 8 have a residual magnetic flux density of 1.4T or more, a coercive force of about 1000kA/m, and 400kJ/m³Higher maximum energy product nearby.

Next, the magnetic susceptibility (Pc ═ 2) of the permanent magnets of samples 6 to 8 was measured. The results are shown in fig. 8 and 9. As shown in fig. 8 and 9, sample 6 having the lowest oxygen content of the sintered body of 580ppm had a high magnetic susceptibility at a low magnetizing field. That is, in sample 6, a magnetic field at 240kA/m (3kOe) can provide a magnetic susceptibility of 40% or more, a magnetic field at 400kA/m (5kOe) can provide a magnetic susceptibility of 70% or more, and a magnetic field at 800kA/m (10kOe) can provide a magnetic susceptibility of 95% or more. On the other hand, sample 7 requires a magnetic field of 400kA/m (5kOe) to obtain a magnetic susceptibility of about 60%, and sample 8 cannot obtain a magnetic susceptibility of 55% even when a magnetic field of 400kA/m (5kOe) is applied.

As described above, the magnetic susceptibility is related to the amount of oxygen contained in the permanent magnet. Further, the oxygen content is preferably 2000ppm or less, more preferably 1000ppm or less, from a low magnetization magnetic field to a high magnetization magnetic field in order to increase the magnetic susceptibility.

< Experimental example 3>

3 kinds of permanent magnets (samples 9 to 11) were obtained in the same manner as in example 1 except that the raw material alloy shown in FIG. 10 was used. The obtained permanent magnet was measured for magnetic properties and the like as in experimental example 1. The results are shown in FIG. 11. The reference numerals in fig. 11 are the same as those in fig. 7.

As shown in fig. 11, sample 9 containing no M element had a very low squareness ratio of 60.22%, and was not a practical permanent magnet; both of sample 10 containing Zr as the M element and sample 11 containing Ti had a residual magnetic flux density of 1.4T or more, a coercive force of around 1100kA/M, and 400kJ/M³Left and right of this higher maximum energy product.

The structure of sample 9 was observed, and abnormal growth of crystal grains reaching about 100 μm was observed in the sintered body of sample 9. This is because the oxygen content is as low as about 2000ppm, and the amount of oxide inhibiting the growth of crystal grains is reduced. It is presumed that the presence of such abnormally grown grains is a cause of a low squareness ratio.

The same observation of the tissue was also performed for samples 10 and 11. As a result, abnormally grown crystal grains as observed in sample 9 were not observed. It was confirmed that Zr in sample 10 or Ti in sample 11 was dispersed in the sintered body, specifically, in the grain boundary, which is understood that Zr or Ti forms a certain compound and the compound suppresses abnormal growth of the crystal grains.

Next, the permanent magnets of samples 9 to 11 were measured for magnetic susceptibility (Pc ═ 2). The results are shown in fig. 12 and 13. As shown in fig. 12 and 13, it is understood that sample 10 containing Zr as an M element has a higher magnetic susceptibility at a low magnetic susceptibility than sample 9 containing no M element and sample 11 containing Ti. That is, in sample 10, the magnetic susceptibility of more than 40% was obtained at a magnetization magnetic field of 240kA/m (3 kOe). In contrast, samples 9 and 11 only had a magnetic susceptibility of 30% or less.

As described above, Zr and Ti, which are M elements, are effective elements for improving magnetic properties, particularly squareness ratio (Hk/HcJ), by suppressing abnormal growth of crystal grains together, and Zr is effective elements for improving not only magnetic properties but also magnetization properties.

< Experimental example 4>

3 types of permanent magnets (sample 12, sample 13, and sample 14) were obtained in the same manner as in experimental example 1 except that the raw material alloy shown in fig. 14 was used. The magnetic properties and the average grain size of the sintered body were measured for samples 12 to 14 in the same manner as in example 1. The results are shown in FIG. 15.

As can be seen from fig. 15, samples 12 and 13 have almost the same remanence (Br). Further, sample 14 had a higher Dy content than those of samples 12 and 13, and thus had a high coercive force (HcJ) of 1300 kA/m. The magnetic susceptibility of samples 12 to 14 (Pc ═ 2) was measured in the same manner as in experimental example 1. The results are shown in fig. 16 and 17. As shown in FIGS. 16 and 17, sample 13 containing no Zr and having a high oxygen content exhibited a magnetic susceptibility of only about 24% at a magnetization field of 240 kA/m. In contrast, sample 12 and sample 14 containing Zr exhibited a magnetic susceptibility of 50% or more at a magnetizing field of 240 kA/m.

Further, a test piece (thickness: 2.1mm) having the shape shown in FIG. 18 was produced from sample 12 and sample 13, and was magnetized in a concave shape as shown in FIG. 18. The magnetization conditions were the following 4 conditions:

800μF×500V

800μF×800V

800μF×1100V

800μF×1500V

the total magnetic flux on the chain line of fig. 18 was measured for each magnetization condition. Fig. 19 is a graph showing the relationship of the position on the dotted line with respect to the total magnetic flux (B) at different magnetization voltages.

Sample 12 and sample 13 showed equivalent total magnetic flux (B) at a magnetization voltage near full magnetization of 1500V. However, sample 12 had a total magnetic flux (B) 1.3 times or more that of sample 13 at a magnetizing voltage of 500V. Similarly, sample 12 had a total magnetic flux (B) of 1.1 times or more that of sample 13 at a magnetizing voltage of 800V. When the magnetization voltage was 500V, the slope of the latter sample (sample 13) was smaller than that of the former sample (sample 12) when the curves of the samples 12 and 13 in the vicinity of the 3.5mm position where the polarity should be reversed were compared, indicating that the neutral zone occurred.

From the above results, by using the sample 12 excellent in magnetization characteristics, the width of the neutral region can be reduced. Therefore, the sample 12 having excellent magnetization characteristics can be used to provide excellent operating characteristics to the magnetizer.

< Experimental example 5>

A permanent magnet (sample 15) was produced in the same manner as in experimental example 1 using the raw material alloy having the composition shown in fig. 1. The obtained permanent magnet was measured for magnetic properties and the like in the same manner as in experimental example 1. The results are shown in FIG. 20.

Next, from this permanent magnet, samples were prepared in which Pc was 2.0 (sample 15), Pc was 1.0 (sample 16), and Pc was 0.5 (sample 17), and the magnetic susceptibility was measured in the same manner as in experimental example 1, and the results are shown in fig. 21 and 22.

As shown in fig. 21 and 22, the magnetic susceptibility tends to decrease with a decrease in Pc. At a magnetization magnetic field of 240kA/m, a magnetic susceptibility of Pc ═ 1.0 is shown at 35% or more, a magnetic susceptibility of Pc ═ 0.5 is shown at 30% or more, and a high magnetic susceptibility is shown at a low magnetic field. It is also known that a magnetic susceptibility of Pc ═ 1.0 is 90% or more and a magnetic susceptibility of Pc ═ 0.5 is 80% or more in a magnetic field of 800 kA/m.

[ example 2 ]

< Experimental example 6>

A raw material alloy having the composition shown in fig. 23 was produced by strip casting.

The obtained raw material alloy was subjected to hydrogen pulverization treatment under the same conditions as in experimental example 1.

To the hydrogen-pulverized alloy, 0.1% oleamide was added as a pulverization aid. Then, the resulting mixture was finely pulverized by a jet mill to obtain 6 kinds of fine powders having average particle diameters (d) of 3.3. mu.m, 3.7. mu.m, 4.1. mu.m, 4.4. mu.m, 4.8. mu.m, and 5.3. mu.m. The coarse grinding step was omitted as in experimental example 1. The particle size was measured in the same manner as in example 1.

The obtained fine powder was subjected to pressure molding in a magnetic field of 1320kA/m (16.5kOe), to obtain a molded article. The density of the shaped body was 4.2Mg/m³。

The obtained molded body was sintered at 1040 ℃ for 4 hours in vacuum and then quenched. The obtained sintered body was then subjected to 2-stage aging treatment at 800 ℃ for 1 hour and 530 ℃ for 2.5 hours (both in an Ar atmosphere).

The obtained permanent magnet was measured for magnetic properties and the like in the same manner as in experimental example 1. The results are shown in FIG. 24.

As shown in FIG. 24, it is understood that any of the permanent magnets of samples 18 to 23 has a residual magnetic flux density of 1.3T or more, a coercive force of 2000kA/m or more, and 340kJ/m³A maximum energy product near or above, and a square ratio (Hk/HcJ) of 90% or more. It is also known that the oxygen content of any permanent magnet is 1000ppm or less, the nitrogen content is 500ppm or less, the carbon content is 1000ppm or less, and the impurity content is at a very low level.

Next, the permanent magnets of samples 18 to 23 were measured for magnetic susceptibility (Pc ═ 2). The results are shown in FIG. 25. As shown in FIG. 25, it is understood that the permanent magnets of sample 18(3.3 μm) having the smallest average crystal grain size and sample 23(5.3 μm) having the largest average crystal grain size obtained less than 60% of the magnetic susceptibility at a magnetization field of 240 kA/m.

From the above, it was confirmed that a low magnetization magnetic field of 240kA/m can provide a magnetic susceptibility of 60% or more by setting the average crystal grain size of the sintered body to 3.5 to 5.0. mu.m, preferably 4.0 to 4.5. mu.m. Further, by setting the average crystal grain size of the sintered body to be in the range of 3.5 to 5.0. mu.m, a magnetic susceptibility of 85% or more can be obtained at a low magnetizing field of 400 kA/m. Further, it is understood that the permanent magnet according to the present invention has a magnetic susceptibility of 95% or more, which is obtained from a magnetizing field of 800kA/m, and the magnetic susceptibility rises rapidly.

< Experimental example 7>

5 kinds of permanent magnets (samples 24 to 28) were obtained in the same manner as in experimental example 6, except that the raw material alloy having the composition shown in fig. 26 was used and the oxygen content in the pulverized gas (nitrogen gas) during the production of fine powder was controlled to change the oxygen content of the final sintered body. The obtained permanent magnet was measured for magnetic properties and the like in the same manner as in experimental example 1, and the results thereof are shown in fig. 27.

As shown in FIG. 27, it is understood that any of samples 24 to 28 has a residual magnetic flux density of 1.3T or more, a coercive force of 2300kA/m or more, and 330kJ/m³The nearby maximum energy product.

Next, the magnetic susceptibility (Pc ═ 2) of the samples 24 to 28 was measured. The results are shown in FIG. 28. As shown in FIG. 28, it is understood that sample 24 having the oxygen content of the sintered body of 490ppm at the lowest is the highest in the magnetic susceptibility at a low magnetization field. In samples 24 to 27, a magnetic field at 240kA/m (3kOe) gave a magnetic susceptibility of 70% or more, a magnetic field at 400kA/m (5kOe) gave a magnetic susceptibility of 90% or more, and a magnetic field at 800kA/m (10kOe) gave a magnetic susceptibility of almost 100%. On the other hand, in sample 28, a magnetic susceptibility exceeding 60% cannot be obtained at a magnetization field of 240kA/m (3 kOe). Similarly, the magnetic susceptibility of the magnetizing field at 400kA/m (5kOe) was not 85%.

As described above, the magnetic susceptibility is related to the amount of oxygen contained in the permanent magnet. In order to increase the magnetic susceptibility from a low magnetization field to a high magnetization field, the oxygen content must be controlled to 2000ppm or less, preferably 1500ppm or less, and more preferably 1000ppm or less.

< Experimental example 8>

8 kinds of permanent magnets (samples 29 to 36) were obtained in the same manner as in example 1, except that the raw material alloy shown in FIG. 29 was used. The obtained permanent magnet was measured for magnetic properties and the like in the same manner as in experimental example 1, and the results are shown in fig. 30. Also, sample 18 of experimental example 6 is shown in fig. 30.

As shown in FIG. 30, the squareness ratio (Hk/HcJ) of sample 29 containing no M element was 93.6%, which was lower than that of the other samples. On the other hand, samples 18 and 30 to 36 containing the M element have a squareness ratio (Hk/HcJ) exceeding 95%, and particularly, sample 30 containing Nb, sample 34 containing Ga, and sample 36 containing Zr and Nb have a high squareness ratio (Hk/HcJ) and a high coercive force (HcJ).

The structure of the sample 29 was observed, and abnormally grown crystal grains of the sample 29 reaching about 100 μm were observed in the sintered body. This is because the oxygen content is as low as about 1000ppm, and the amount of oxide inhibiting the growth of crystal grains is reduced. It is presumed that the presence of such abnormally grown grains is a cause of a low squareness ratio.

The same observation of the structure was also carried out for samples 18, 30 to 36, but no abnormally grown crystal grains observed for the target sample 29 were observed. It was confirmed that Nb is dispersed in the main phase grains and the grain boundary phase in samples 18, 30 and 36, and Zr is dispersed in the grain boundary phase in samples 31 and 36, which can be interpreted as that Nb or Zr forms a compound that suppresses abnormal growth of the grains.

Next, the magnetic susceptibility (Pc ═ 2) of the permanent magnets of samples 18 and 29 to 36 was measured. The results are shown in FIG. 31. The results of sample 18 are also shown in FIG. 31. As shown in FIG. 31, while sample 29 containing no M element had a magnetic susceptibility of 50% or less at 240kA/M, samples 18 and 30 to 36 containing M element had a magnetic susceptibility of 60% or more at 240 kA/M. While sample 29 containing no M element had a magnetic susceptibility of 85% or less at a magnetic field of 400kA/M, samples 18 and 30 to 36 containing M element had a magnetic susceptibility of 85% or more at a magnetic field of 400 kA/M.

As is clear from the above, the M element is an element effective for improving magnetic properties, particularly squareness ratio (Hk/HcJ), and is also an element effective for improving magnetization properties by suppressing grain growth. In particular, Nb, Zr, and Ga are effective elements for increasing both magnetic properties and magnetization properties.

< Experimental example 9>

4 types of permanent magnets (samples 37 to 40) were obtained in the same manner as in example 6, except that the raw material alloy shown in FIG. 32 was used. For samples 37 to 40, magnetic properties, the average grain size of the sintered body, and the like were measured in the same manner as in example 6. The results are shown in FIG. 33.

As is clear from fig. 32 and 33, the coercive force (HcJ) increases and the remanent magnetic flux density (Br) decreases as the Dy content increases.

The magnetic susceptibility (Pc ═ 2) of samples 37 to 40 was measured in the same manner as in experimental example 6. The results are shown in FIG. 34. As shown in fig. 34, the magnetic susceptibility is improved with an increase in the Dy content. Particularly, the difference is significant in a magnetization magnetic field of 400kA/m or less.

Further, a test piece (thickness: 2.1mm) having the shape shown in FIG. 18 was produced using samples 37 and 40, and the piece was magnetized in a concave shape as shown in FIG. 18. The magnetization conditions were 4 conditions as follows:

800μF×350V

800μF×600V

800μF×900V

800μF×1500V

the total magnetic flux on the chain line of fig. 18 was measured for each magnetization condition. Fig. 35 is a graph showing the relationship of the position on the dotted line with respect to the total magnetic flux (B) at different magnetization voltages.

Sample 37 and sample 40 showed equivalent total magnetic flux (B) at a magnetization voltage near full magnetization of 1500V. However, sample 37 had a total magnetic flux (B) of 1.3 times or more that of sample 40 at a magnetizing voltage of 350V. Similarly, sample 37 had a total magnetic flux (B) of 1.1 times or more that of sample 40 at a magnetizing voltage of 600V. When the magnetization voltage was 350V, the slope of the sample 37 near the 3.5mm position where the polarity should be reversed was smaller than that of the sample 40, as shown by comparing the curves, indicating that the neutral zone occurred.

From the above results, by using a sample having excellent magnetization characteristics, the width of the neutral region can be reduced. Therefore, excellent operating characteristics can be given to the solenoid (activator).

< Experimental example 10>

4 types of permanent magnets (samples 41 to 44) were obtained in the same manner as in example 6, except that the raw material alloy shown in FIG. 36 was used. For samples 41 to 44, magnetic properties, the average grain size of the sintered body, and the like were measured in the same manner as in example 6. The results are shown in FIG. 37.

As shown in fig. 36 and 37, as the amount of Tb increases, the coercive force (HcJ) increases, but the remanence (Br) decreases. The magnetic susceptibility (Pc ═ 2) of the samples 41 to 44 was measured in the same manner as in experimental example 6. The results are shown in FIG. 38. As shown in fig. 38, the magnetic susceptibility increases with an increase in the amount of Tb. Particularly, the difference is significant when the magnetization magnetic field is 400kA/m or less. Further, as compared with experimental example 9, the same effect as Dy can be obtained with a smaller Tb content.

< Experimental example 11>

Further, as to sample 19 of experimental example 6, Pc ═ 1.0 (sample 45) and Pc ═ 0.5 (sample 46) were prepared, and the magnetic susceptibility was measured in the same manner as in experimental example 6. The results are shown in FIG. 39.

As shown in fig. 39, the magnetic susceptibility tends to decrease with decreasing Pc, and in a 240kA/m magnetization magnetic field, the magnetic susceptibility of Pc ═ 1.0 is 55% or more and the magnetic susceptibility of Pc ═ 0.5 is 40% or more, and a high magnetic susceptibility is exhibited in a low magnetization magnetic field. In a 400kA/m magnetization magnetic field, a magnetic susceptibility of Pc 1.0 is 80% or more, and a magnetic susceptibility of Pc 0.5 is 70% or more.

According to the method 1 of the present invention, a permanent magnet having an improved magnetic susceptibility at a low magnetization field of around 320kA/m (4kOe) and an improved magnetic susceptibility at a high magnetization field of 800kA/m (10kOe) or more can be obtained.

According to the method 2 of the present invention, a permanent magnet having an improved magnetic susceptibility at a low magnetization field of about 400kA/m (5kOe) and an improved magnetic susceptibility at a magnetization field of 800kA/m (10kOe) or more can be obtained.

Such a permanent magnet having excellent magnetization characteristics can be used in a multipolar magnetized magnet, and the width of the neutral region can be narrowed. The motor using such a ring magnet can maintain high rotation performance.

In addition, a magnet having a high magnetic susceptibility may actually generate a larger total magnetic flux than a magnet having a low magnetic susceptibility although it is made of a high-cost material and has high magnetic characteristics. Thus, the present invention can achieve the required total magnetic flux with a lower cost magnet. Further, the size of the magnet can be reduced.

Claims (23)

1. An R-T-B based rare earth permanent magnet characterized in that: the R-T-B based rare earth permanent magnet comprises a magnet having R₂T₁₄A main phase of a B phase and a sintered body of a grain boundary phase containing more R than the main phase, wherein R is 1 or 2 or more kinds of rare earth elements, T is 1 or 2 or more kinds of transition metal elements essential for Fe or Fe and Co, the rare earth elements are in the concept of containing Y, and the sintered body has a composition of R: 25-35 wt%, B: 0.5 to 4.5 wt%, 1 or 2 of Al and Cu: 0.02 to 0.5 wt%, average of the weight of the sintered bodyThe sintered body has a crystal grain diameter of 3.3 to 4.3 [ mu ] m, an oxygen content of 2000ppm or less, a total magnetic flux of f1 when an effective magnetic field of 240kA/m is applied at a permeability Pc of 2, a total magnetic flux of f2 when an effective magnetic field of 800kA/m is applied, and a total magnetic flux of f3 when an effective magnetic field of 2000kA/m is applied, wherein a magnetic susceptibility a is f1/f3 × 100 is 40% or more, and a magnetic susceptibility b is f2/f3 × 100 is 90% or more.

2. The R-T-B rare earth permanent magnet according to claim 1, wherein: the coercive force HcJ of the R-T-B rare earth permanent magnet is 1672kA/m or less.

3. The R-T-B rare earth permanent magnet according to claim 1, wherein: the R-T-B rare earth permanent magnet has a remanence Br of 1.35T or more and a maximum energy product (BH) max of 350kJ/m³The square ratio Hk/HcJ is more than 95%.

4. The R-T-B rare earth permanent magnet according to claim 1, wherein: the sintered body has an oxygen content of 1500ppm or less.

5. The R-T-B rare earth permanent magnet according to claim 1, wherein: zr is dispersed in the sintered body.

6. An R-T-B based rare earth permanent magnet characterized in that: the R-T-B based rare earth permanent magnet comprises a magnet having a magnetic composition comprising R: 25-35 wt%, B: 0.5 to 4.5 wt%, 1 or 2 of Al and Cu: 0.02 to 0.5 wt%, Zr: 0.03 to 0.25 wt%, Co: 2% by weight or less, excluding 0, and the balance Fe, wherein R is 1 or 2 or more of rare earth elements containing Y, the sintered body has an oxygen content of 2000ppm or less, and the sintered body has an average grain size of 3.3 to 4.3 μm.

7. The R-T-B rare earth permanent magnet according to claim 6, wherein: r is 0.1 to 4.0 wt% Dy.

8. The R-T-B rare earth permanent magnet according to claim 6, wherein: zr is dispersed in the grain boundaries in the sintered body.

9. The R-T-B rare earth permanent magnet according to claim 6, wherein: the R-T-B based rare earth permanent magnet is a magnet magnetized in multiple poles.

10. The R-T-B rare earth permanent magnet according to claim 6, wherein: the sintered body has a nitrogen content of 20 to 600ppm and a carbon content of 1500ppm or less.

11. An R-T-B based rare earth permanent magnet characterized in that: the R-T-B based rare earth permanent magnet comprises a magnet having R₂T₁₄A main phase of a B phase and a sintered body of a grain boundary phase containing more R than the main phase, wherein R is 1 or 2 or more kinds of rare earth elements, T is 1 or 2 or more kinds of transition metal elements essential for Fe or Fe and Co, the rare earth elements are in the concept of containing Y, and the sintered body has a composition of R: 25-35 wt%, B: 0.5 to 4.5 wt%, 1 or 2 of Al and Cu: 0.02 to 0.5 wt%, wherein the sintered body has an average crystal grain diameter of 3.5 to 5.0 μm, an oxygen content of 2000ppm or less, a total magnetic flux when an effective magnetic field of 240kA/m is applied at a permeability Pc of 2 is F1, a total magnetic flux when an effective magnetic field of 400kA/m is F2, and a total magnetic flux when an effective magnetic field of 2000kA/m is F3, and wherein a magnetic susceptibility c is F1/F3 x 100 is 60% or more, a magnetic susceptibility d is F2/F3 x 100 is 85% or more, and an effective magnetic field-applied diamagnetic field is applied.

12. The R-T-B rare earth permanent magnet according to claim 11, wherein: the coercive force HcJ of the R-T-B rare earth permanent magnet exceeds 1680 kA/m.

13. The R-T-B rare earth permanent magnet according to claim 11, wherein: the R-T-B rare earth permanent magnet has a remanence Br of 1.20T or more and a maximum energy product (BH) max of 240kJ/m³The square ratio Hk/HcJ is more than 90%.

14. The R-T-B rare earth permanent magnet according to claim 11, wherein: the sintered body has an oxygen content of 1500ppm or less.

15. The R-T-B rare earth permanent magnet according to claim 11, wherein: nb is dispersed in the sintered body.

16. An R-T-B based rare earth permanent magnet characterized in that: the R-T-B based rare earth permanent magnet comprises a magnet having a magnetic composition comprising R: 25-35 wt%, B: 0.5 to 4.5 wt%, 1 or 2 of Al and Cu: 0.02 to 0.5 wt%, Nb: 0.2 to 1.5 wt% and Zr: 0.03 to 0.25 wt% of 1 or 2 kinds of Co: 2% by weight or less, excluding 0, and the balance Fe, wherein R is 1 or 2 or more of rare earth elements, the rare earth elements are Y-containing elements, the content of oxygen in the sintered body is 2000ppm or less, and the average grain size of the sintered body is 3.5 to 5.0 [ mu ] m.

17. The R-T-B rare earth permanent magnet according to claim 16, wherein: r is 4.0 to 12.0 wt% Dy and/or 1.0 to 6.0 wt% Tb.

18. The R-T-B rare earth permanent magnet according to claim 16, wherein: nb is dispersed in the main phase and grain boundaries of the sintered body, and Zr is dispersed in the grain boundaries of the sintered body.

19. The R-T-B rare earth permanent magnet according to claim 16, wherein: the R-T-B based rare earth permanent magnet is a magnet magnetized in multiple poles.

20. The R-T-B rare earth permanent magnet according to claim 16, wherein: the sintered body has a nitrogen content of 20 to 600ppm and a carbon content of 1500ppm or less.

21. The R-T-B rare earth permanent magnet according to claim 16, wherein: the R-T-B based rare earth permanent magnet contains 0.02 to 1.5 wt% of Ga.

22. A multipolar magnetized magnet, characterized in that: the R-T-B based rare earth permanent magnet comprises a magnet having a magnetic composition comprising R: 25-35 wt%, B: 0.5 to 4.5 wt%, 1 or 2 of Al and Cu: 0.02 to 0.5 wt%, Zr: 0.03 to 0.25 wt%, Co: and a sintered body having a composition of 2 wt% or less, excluding 0, and the balance being Fe, wherein R represents 1 or 2 or more of rare earth elements containing Y, wherein R represents a concept of containing 0.1 to 4.0 wt% of Dy, and wherein when the total magnetic flux when an effective magnetic field of 240kA/m is applied with a permeability of Pc of 2, f1, the total magnetic flux when an effective magnetic field of 800kA/m is applied, f2, and the total magnetic flux when an effective magnetic field of 2000kA/m is applied, f3, the magnetic susceptibility a is f1/f3 × 100 is 40% or more, and the magnetic susceptibility b is f2/f3 × 100 is 90% or more, and the balance is Fe.

23. A multipolar magnetized magnet, characterized in that: the multipolar magnetized magnet is composed of a magnet having R: 25-35 wt%, B: 0.5 to 4.5 wt%, 1 or 2 of Al and Cu: 0.02 to 0.5 wt%, Nb: 0.2 to 1.5 wt% and Zr: 0.03 to 0.25 wt% of 1 or 2 kinds of Co: and a sintered body having a composition of 2 wt% or less, excluding 0, and the balance being Fe, wherein R represents 1 or 2 or more of rare earth elements containing Y, and wherein R represents 4.0 to 12.0 wt% of Dy and/or 1.0 to 6.0 wt% of Tb, and wherein when the total magnetic flux when an effective magnetic field of 240kA/m is applied at a permeability Pc of 2 is F1, the total magnetic flux when an effective magnetic field of 400kA/m is F2, and the total magnetic flux when an effective magnetic field of 2000kA/m is F3, the magnetic susceptibility c is F1/F3 × 100 is 60% or more, and the magnetic susceptibility d is F2/F3 × 100 is 85% or more, and the balance is Fe.