JPH04155902A - Permanent magnet and manufacture thereof - Google Patents

Abstract

PURPOSE:To realize an R-Fe-B permanent magnet which has a remarkably large coercive force and residual magnetic flux density and a great mechanical strength by maldistributing Dy and Tb near the grain boundary at the specified ratio and by holding the oxygen content down within the specified range. CONSTITUTION:The main ingredients of this magnet are R (R is one or more kinds of rare earth metal elements containing Y), T (T is Fe, Fe or/and Co) and B. The relation among the Tb content TbC and Dy content DyC, in the central part of a crystal grain and the Tb content TbB and Dy content DyB near the grain boundary of the crystal grain is shown by (TbB+DyB)-(TbC+ DyC)>=0.2(%). The oxygen content is 5000ppm or lower. The values of TbC and DyC and the values of TbB and DyB are found by cutting the magnet, polishing the cutting plane and then measuring the content of each element in the central part of the crystal grain and near the grain boundary inside the crystal grain about a square region of the side length 10mum or above in the cutting plane.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention provides R (R is one or more rare earth metal elements including Y), T (T is Fe, or Fe and CO). ) and B, and a method for manufacturing the same.

<Prior Art> As rare earth metal magnets with high performance, Sm--Co magnets with an energy product of 32 MGOe are mass-produced using powder metallurgy.

However, this method has the disadvantage that the cost of Sm and Co raw materials is high. Among rare earth metal elements, elements with small atomic weights, such as Ce, Pr, and Nd, are more abundant and cheaper than Sm. Further, Fe is cheaper than Co.

Therefore, in recent years, R-Fe-B magnets such as Nd-Fe-B magnets have been developed, and sintered magnets are disclosed in Japanese Patent Laid-Open No. 59-46008.

For magnets made by the sintering method, the conventional Sm-Co powder metallurgy process (melting → casting → ingot coarse grinding - thorough crushing - press - sintering - magnet) can be applied, and high magnetic properties can also be easily obtained. It is.

When an R-Fe-B magnet is manufactured by a sintering method, a raw material powder of an R-Fe-B alloy having the same composition as the magnet to be manufactured is usually molded and sintered.

The characteristics of an R-Fe-B magnet depend approximately on the R composition.

That is, the type of R and the content of R determine magnetic properties such as residual magnetic flux density and coercive force.

For example, when the main component of R is a light rare earth metal element such as Nd or Pr, (Nd.

Since the Pr)xFexE phase is the main component, a high residual magnetic flux density can be obtained. However, (Nd.

Pr)zFe++ A high coercive force cannot be obtained only with the B phase.

On the other hand, when part of Nd or Pr is replaced with a heavy rare earth metal element such as D y Ji') T b, a (D y, T b ) z F e l 4 B phase with a large anisotropic magnetic field HA appears. . Since magnetization reversal is difficult when the anisotropic magnetic field HA is large, the coercive force is improved by adding a heavy rare earth metal element.

However, since the (D y , T b ) 2F 614B phase has a low saturation magnetic flux density, the residual magnetic flux density decreases as the amount of the heavy rare earth metal element added increases.

Therefore, it has been difficult to achieve both high residual magnetic flux density and high coercive force.

Under these circumstances, a method has been proposed for obtaining high coercive force by mixing R-Fe-B alloy powder with heavy rare earth metal element oxide powder and sintering the mixture (Japanese Patent Application Laid-Open No. 1983-1999).
253805). The proposal of adding oxide powder and sintering is proposed by Appl, Phys, Lett, 48.
(8), 24 February 1986, 548-
550).

However, in the R-Fe-B permanent magnet described in JP-A-61-253805, the coercive force iHc is Dy
With the addition of oxides, the increase from 9.3kOe without additives to 21.2kOe
Although the residual magnetic flux density Br has decreased to 10.7 kG from 12.3 kG without additives, it has improved to kOe.

This decrease in r is considered to be because oxygen in the Dy oxide oxidizes Nd, forms a nonmagnetic phase in the magnet, and remains. The iH increases as the amount of Dy oxide added increases.
Although c improves, Br decreases.

In addition to these problems, in order to obtain high magnetic properties in R-Fe-B magnets, it is necessary to increase the ratio of the main phase of the RiFezBm structure. Although it is effective to reduce the ratio,
Reducing the ratio of rare earth-rich phases in the grain boundaries reduces the strength near the grain boundaries, which causes the problem of a decrease in the mechanical strength of the magnet, so it is possible to improve both magnetic properties and mechanical strength. It was difficult to do so.

<Problems to be Solved by the Invention> The present invention has been made in view of the above circumstances, and provides an R-Fe-B permanent magnet that has extremely high coercive force and residual magnetic flux density, and has high mechanical strength. The purpose is to provide a manufacturing method.

Means for Solving the Problems> Such objects are achieved by the present invention as described in (1) to (5) below.

(1) R (R is one or more rare earth metal elements including Y), T (T is Fe, or Fe and Co
s3 and B as the main components, the Tb content T b e and Dy in the central part of the crystal grains are
Content D y e and T near the grain boundaries of crystal grains
The relationship between b content Tb and Dy content Dy1l is (Tbs + DyB ) - (TbC + Dye ) ≧ 0
．． 2 (%) (however, TbC , D'Jc , T
bs and DyB are expressed in atomic percentages), and
A permanent magnet characterized by having an oxygen content of 5000 ppm or less.

(2) The permanent magnet according to (1) above, containing R: 12.5 to 15 at% and B: 5 to 8 at%.

(3) Let the coercive force iHc be X koe, and the residual magnetic flux density B
The permanent magnet according to (2) above, where Y≧−〇, lX+14.2, where r is YkG.

(4) A method for manufacturing a permanent magnet according to any one of (1) to 3) above, comprising: Rf (Rf is one or more rare earth metal elements, at least Nd and/or
or Pr), T and B as main components, and Ra (Ra is one of the rare earth metal elements).
A method for producing a permanent magnet, comprising the steps of molding and sintering a mixture with an additive powder whose main component is a metal (including at least Dy13 and/or Tb) and/or an Ra compound. .

(5) The additive powder is Ra dihydride and/or R
(a) The method for producing a permanent magnet as described in (4) above, which contains metal as a main component.

Effect〉 The permanent magnet of the present invention has R, T and B as main components.

Then, Tb content T b c in the central part of the crystal grain
and I) y content D y c, Tb content Tbs near the grain boundaries of crystal grains, and I) y content D y
The relationship with a is (Tbs + Dye) - (TbC
+Dyc)≧0.2(%), and the oxygen content is 5000 pp11 or less. In addition, TbC
, Dye, Tbs and Dys are values expressed in atomic percentages.

By unevenly distributing Tb and y in this way, the oxygen content in the magnet is suppressed within the above range, and R: 12.5 to 15.
% and B: 5 to 8 atomic %, the coercive force iHc is reduced to X kO
e and the residual magnetic flux density Br is YkG, a magnet with high magnetic properties that satisfies Y≧−〇, IX+14.2 can be obtained.

More specifically, iHc is 10 kOe or more, especially 12
A value of more than kOe was obtained, and Br was 12.8k.
A value of 13.6 kG or more can be obtained, especially 13.6 kG or more. Note that, normally, Y≦−〇, about lX+16.

The manufacturing method for making Tb and Dy unevenly distributed as described above is not particularly limited, but in the present invention, Rf (R
f is one or more rare earth metal elements, and at least N
d and/or Pr), T and B as main components, and Ra (Ra is one or more rare earth metal elements, and at least Dyj15 and/or
It is preferable to fabricate a permanent magnet by molding and sintering a mixture with an additive powder whose main components are metal S (or containing Tb) and/or an Ra compound.

Note that the Ra compound refers to Ra hydride, Ra oxide, R
One or more types selected from a carbide, Ra nitride, Ra halide, etc.

By such a manufacturing method, as described above, y, T
A unevenly distributed state of b can be easily obtained, and high productivity can be achieved.

When Ra hydride is used as the additive powder, hydrogen is removed from the Ra hydride during sintering to form Ra metal. Also, R
When using a oxide, Dy oxide and Tb oxide are reduced to a metallic state during sintering. Other Ra compounds also tend to metallize during sintering.

Then, the Ra metal in the additive powder turns into a liquid phase during sintering, and exists mainly near the grain boundaries of the crystal grains in the sintered magnet.

Therefore, near the grain boundaries, the anisotropic magnetic field H, is large and the (Dy, Tb) 2 Fe+4B phase, which is difficult to reverse magnetization, is the main phase.

And since the reversal of magnetization proceeds from near the grain boundaries,
A high coercive force can be obtained by unevenly distributing Dy and Tb near the grain boundaries.

On the other hand, in the vicinity of the center of the crystal grain, which is the main phase, the (Nd, Pr) x Fe14B phase with high saturation magnetization is the main phase, so a high residual magnetic flux density is obtained.

In the present invention, extremely high coercive force and extremely high residual magnetic flux density can be obtained by unevenly distributing Tb and D37 so that (T bs + Dys ) and (rbc + Dyc ) have the above relationship.

Furthermore, setting the oxygen content of the magnet to 5000 ppm or less can be achieved mainly by strictly controlling the oxygen content of the basic composition alloy powder, the oxygen content of the additive powder, and the amount of oxygen mixed in the manufacturing process. If the main component of the additive powder is Ra hydride and/or Ra metal,
Since there is no increase in the amount of oxygen caused by the added powder, it is extremely easy to suppress the oxygen content of the magnet to 5000 ppm or less. In addition, Ra hydride and/or Ra
If metal is used, other impurities such as carbon will not increase.

Furthermore, when Ra hydride and/or Ra metal is used, Dy
Since the amount of Dy and Tb added can be determined, the desired amount of Dy and Tb can be determined.
b can be added, and a magnet with extremely high magnetic properties can be manufactured.

Furthermore, since hydrogen in the Ra hydride does not remain in the magnet after sintering, the addition of the Ra hydride does not cause deterioration in characteristics.

Furthermore, rare earth metals can be easily crushed and made into fine particles by hydrogenation, and their oxidation resistance is significantly improved, making them easy to handle.Also, since they can be mixed with the basic composition alloy powder in a fine particle state, they have good dispersibility. The uneven distribution state as described above can be accurately and easily detected.

Furthermore, it is thought that Ra oxide is reduced by an oxidation-reduction reaction with the rare earth metal in the basic composition alloy powder and enters the vicinity of the grain boundaries, but such oxidation-reduction reaction is not completely completed. Since this may not be carried out, it is not always possible to utilize all of the Ra in the added oxide, and there is a possibility that characteristics corresponding to the amount of Ra added may not be obtained. However, when Ra metal or Ra hydride is added,
Since the entire amount added is effectively utilized, the characteristics as designed can be obtained.

In addition, the permanent magnet of the present invention has higher strength than Nd and Pr, has a higher concentration of y and Tb near the grain boundaries, and
Since the oxygen content is low, less rare earth metals are oxidized, resulting in high mechanical strength. Moreover, magnetic properties can be improved by unevenly distributing Dy and Tb, so even if the design emphasizes mechanical strength and increases the ratio of rare earth-rich phase at the grain boundaries, magnetic properties better than conventional ones can be obtained. It will be done.

<Specific configuration> Hereinafter, a specific configuration of the present invention will be explained in detail.

The permanent magnet of the present invention has R (R is one or more rare earth metal elements including Y), T (T is Fe, or Fe and CO), and B as main components.

The relationship between the Tb content T b c and Dy content Dy c in the central part of the crystal grain and the Tb content T b m and Dy content Dy near the grain boundary of the crystal grain is (TbB + Dym ) −(The + Dye
)≧0.2(%) and the oxygen content is 5000
ppm or less.

In addition, TbC, Dye%Tbs and Dy.

is a value expressed in atomic percentage.

Furthermore, T b c and D y c, and T b s and Dyl are measured as follows.

The magnet is cut, the cut surface is polished, and the content of each element in the center of the crystal grain and the content of each element near the grain boundary within the crystal grain are determined for a rectangular region with a side of at least 100 mm on this cut surface. Measure the content.

In the present invention, an annular region extending from the grain boundary to a distance of 1/20 of the average grain size is defined as the vicinity of the grain boundary of the crystal grain.
Further, the region excluding the annular region from the grain boundary to a distance of 115 times the average grain size, that is, the region inside the annular region is defined as the central portion of the crystal grain.

The element content may be analyzed using an electron beam probe microanalyzer (EPMA) or the like.

The measurement of the element content is performed in order from the crystal grains with the largest grain size in the rectangular region, and is terminated when the total area of the measured crystal grains exceeds 50% of the total area of the crystal grains in the region. . The reason why all of the crystal grains appearing in the cross section of the magnet are not measured is because among the crystal grains appearing in the cross section, those with small grain sizes are crystal grains whose central portions are not exposed.

If (Tbs +01m) - (TbC +Dyc) is less than the above range, it will not be possible to simultaneously achieve high coercive force and high residual magnetic flux density.

In addition, (TbB +01m) −(TbC +Dyc
) is 0.4% or more, especially 0.6% or more, higher magnetic properties can be obtained.

Also, (Tbs + D3's) - (TbC +
There is no particular limit to the upper limit of Dye), but it is usually about 6%.

In addition, TbC +Dyc is 0 to 6%, Tb @ +D
It is preferable that ys is 0.2 to 11.8%.

The ratio of Dy and Tb is arbitrary. Tb and Dy are unevenly distributed within the crystal grains as described above, but the rare earth metal elements as a whole are hardly unevenly distributed, and are distributed at an almost constant ratio within the crystal grains. are doing.

The crystal grain size of the permanent magnet of the present invention is usually 0.5 to 30μ
m, particularly about 1 to 20 μm.

The present invention can be applied without particular limitation to any R-Fe-B permanent magnet containing 8% carbon and B, but in order to obtain good magnetic properties, R: 12.5 to 15 atoms. % and B: 5 to 8 atomic %, and the balance is preferably T. With such a composition, a permanent magnet can be obtained in which Y≧−0, 1X+14.2, where iHc is X kOe and Br is YkG.

It also contains 12.5 to 14 atom% of R2 and 5 to 7 atom% of B, the balance is substantially T, and the oxygen content is 40 atom%.
By setting the composition to 00 pp or less, a permanent magnet with Y≧−0, lX+14.6 can be obtained.

Further, it contains R: 12.5 to 13.5 at% and B: 5 to 6.5 at%, the balance is substantially T, and the oxygen content is 35
By setting the composition to be 00 ppa+ or less, Y≧-〇, IX+14. A permanent magnet with s is obtained.

Although there is no particular lower limit to the oxygen content, the oxygen content is at least 1000 ppm or more, usually 2000 ppm or more, as oxygen contained in the raw material alloy or mixed in during the manufacturing process.

The rare earth metal element R contained in the permanent magnet of the present invention is at least one of Nd%Pr, Ho%Tb, and Dy.
species, or in addition, La%Sm, Ce, Gd%Er,
Eu, Pm.

Those containing one or more of Tm, Yb, and Y are preferred.

To explain R in detail, the total of Nd and Pr is 8 of the entire R.
It is preferably 0 atom % or more, particularly 85 to 98 atom %. Further, it is preferable that the total amount of Dy and Tb is 1 to 20 atomic %, particularly 2 to 15 atomic %, of the entire R.
By setting the composition within this range, even higher coercive force and residual magnetic flux density can be obtained. Note that the ratio between Nd and Pr and the ratio between Dy and Tb are arbitrary.

If the R content is less than the above range, the crystal structure after sintering becomes a cubic structure, making it difficult to obtain a high coercive force iHc.

When the R content exceeds the above range, the R-rich nonmagnetic phase increases and the residual magnetic flux density Br decreases.

Note that by using CO as a part of T, the temperature characteristics can be improved without impairing the magnetic characteristics. However, if Co exceeds 50% of T, the magnetic properties will deteriorate, so it is preferable that Co is 50% or less of T.

If the B content is less than the above range, a rhombohedral structure will be formed after sintering, resulting in insufficient iHc, and if it exceeds the above range, the B-rich nonmagnetic phase will increase, resulting in a decrease in Br.

In addition to R, T, and B, the permanent magnet may also contain Ni, Si, Cu, Ca, and the like as unavoidable impurities in an amount of 2% by weight or less of the total.

Furthermore, by replacing a part of B with one or more of P1S%N, productivity can be improved and costs can be reduced. In this case, the amount of substitution is preferably 0.4% by weight or less of the total weight.

In addition, in order to improve iHc, improve productivity, and reduce costs, AI2, Ti%V%Cr, and Mn.

B i, Nb%Ta%M0. W, Sb%Ge, Ga, S
One or more of n, Zr%Ni, Si%Hf, etc. may be added. In this case, the total amount added is preferably 5% by weight or less.

As a method for manufacturing the permanent magnet of the present invention, (TbB
+DVws)-(TbC+Dyc) can be within the above range, and there are no particular limitations as long as the oxygen content can be suppressed within the above range, but such an elemental distribution and oxygen content can be easily obtained, Moreover, since the productivity is extremely high, it is preferable to use the manufacturing method of the present invention described below.

In the manufacturing method of the present invention, a basic composition alloy powder mainly composed of Rf (Rf is one or more rare earth metal elements and includes at least Nd and/or Pr), T and B, and Ra (Ra is , one or more rare earth metal elements, including at least oxide, y and/or Tb)
A permanent magnet is manufactured by molding and sintering a mixture with an additive powder containing a metal and/or an Ra compound as a main component. Note that there are no particular restrictions on the Ra compound, but Ra
It is preferable to use one or more selected from hydrides, Ra oxides, Ra carbides, Ra nitrides, and Ra halides.

By using such a method and appropriately selecting the composition of the rare earth metal element Rf contained in the basic composition alloy powder and the composition of the rare earth metal element Ra contained in the additive powder, (
T b * 10゛D y a ) and (T he 10D
y e ) can have the above relationship.

The basic composition alloy powder contains at least Nd and/or Pr as rare earth metal elements.

The composition of the basic composition alloy powder may be determined so as to obtain the desired magnet composition when mixed with the additive powder, but in the present invention, the basic composition has a total of Nd and Pr of 90 atomic % or more of Rf. Preferably, alloy powder is used. N
When the sum of d and Pr is less than 90 atomic percent of Rf, it becomes difficult to obtain a high residual magnetic flux density.

In addition, in order to make the magnet composition after sintering within the above range, R: 10 to 14 atomic % and B: 5 to 8 atomic %, especially R: 10 to 13 atomic % and B: 5 to 8 atomic %. Preferably, a powder alloy with a basic composition containing 7 at.% is used.

The additive powder mixed with the basic composition alloy powder contains at least Dy and/or Tb as rare earth metal elements.

The rare earth metal element Ra contained in the additive powder is Tb and D
It is preferable that the total amount of y is 20 atomic % or more, particularly 50 atomic % or more. The total of Tb and Dy is 20 atomic% of Ra
If untreated, it will be difficult to obtain both high residual magnetic flux density and high coercive force.

In addition, examples of rare earth metal elements other than Tb and Dy that may be included in the additive powder include HOlPr and Nd. These rare earth metal elements have the effect of improving sinterability, and the coercive force is only slightly reduced by the inclusion of these elements.

The additive powder contains Ra metal and/or Ra compound as a main component, but in order to suppress the content of impurities such as oxygen, it is preferable to contain Ra hydride and/or Ra metal as main component.

In other words, even if oxygen is strictly blocked until the forming process, the basic composition alloy powder usually contains 20
Since it contains more than 00 ppm of oxygen, the Ra
When adding as an oxide, Dy and Tb cannot be added sufficiently in order to prevent the oxygen content from exceeding the above range.

The total content of Ra hydride and Ra metal in the additive powder is preferably 50% by weight or more, particularly 80% by weight or more, and most preferably 100% by weight. If the total content of Ra hydride and Ra metal is less than the above range, impurities due to the added powder will increase significantly, and especially when the added powder contains Ra oxide, the manufacturing process of the basic composition alloy powder, molding, baking, etc. It becomes necessary to extremely strictly cut off oxygen during the binding process, etc., leading to higher costs and lower productivity.

Further, as described above, when Ra hydride or Ra metal is used, unlike Ra oxide, the entire amount added is effectively utilized, so a magnet with characteristics corresponding to the amount of Ra added can be obtained.

However, oxygen and carbon have the effect of suppressing grain growth, and depending on the composition of the basic composition alloy powder, it may be preferable to contain a certain amount of oxygen and carbon. The content of oxygen and carbon may be adjusted by including Ra carbide. If oxygen and carbon are added in the form of Ra compounds, the amounts added can be accurately controlled.

In addition, as mentioned above, Ra hydride is Ra in a metallic state.
It is easier to powder than , and has high oxidation resistance.
Therefore, the additive powder preferably contains Ra hydride as a main component, and more preferably consists essentially only of Ra hydride.

The composition, structure, etc. of hydrides of rare earth metal elements are, for example, r
A. Pebler and W. E. Wallace
”Crystal 5structures of 5o
"use Lanthanide Hydrides",
J, Phys, Chell, 66 (196
2), p., 148 J, and the Ra hydride used in the present invention may be appropriately selected from these, but it is particularly preferable to use one mainly composed of trihydride.

Although there are no particular limitations on the method for producing Ra hydride, the hydride can be easily obtained by heating an Ra metal ingot or its powder in a hydrogen atmosphere. There are no particular restrictions on the conditions at this time, but the pressure is usually 0.1~
It is preferable that the atmospheric pressure is about 20 atm and about 100 to 800°C.

The average particle size of the particles constituting the basic composition alloy powder and the average particle size of the particles constituting the additive powder are usually 0.2 to 20
μm1 It is particularly preferable that it is about 1 to 10 μm.
Particles with a particle size less than the above range are active and therefore pose a risk of ignition due to oxidation, and if the particle size exceeds the above range, a high coercive force cannot be obtained.

The basic composition alloy powder is made from a cast ingot with a particle size of 10
It is produced by coarsely pulverizing it to about 0 μm and then finely pulverizing it to a particle size within the above range.

When using a hydride as the additive powder, hydrogenate an ingot, coarsely pulverized powder, or finely pulverized powder by the method described above,
Finally, the finely ground powder is mixed with the basic composition alloy powder.

Furthermore, when Ra metal is used as the additive powder, it is difficult to pulverize, so it is pulverized by an atomization method or the like and mixed with the basic composition alloy powder.

Incidentally, coarse pulverization may be carried out using a stamp mill or the like, and fine pulverization may be carried out using a jet mill or the like.

In addition to the method of mixing each finely pulverized powder, a method of mixing each coarsely pulverized powder and pulverizing the mixture may be used.

There is no particular restriction on the mixing ratio of the basic composition alloy powder and the additive powder, but if the addition amount is too small, the addition effect will be small, and if it is too large, the Br will decrease, so the additive powder should be 10% of the basic composition alloy powder. % by weight or less, especially 0.5-5% by weight
It is preferable that

After mixing the basic composition alloy powder and the additive powder, they are molded.

Preferably, shaping is carried out in a magnetic field. In this case, the magnetic field strength is 10 kOe or more, and the molding pressure is 1 to 5 t.
/c+s'' is preferable.

In addition, each process of crushing, mixing, and molding is performed using Ar gas, N
It is preferable that the process be carried out in a non-oxidizing gas atmosphere such as gas.

After shaping, it is sintered at 1000 to 1200°C for 0.5 to 24 hours and then rapidly cooled. The sintering atmosphere is vacuum or Ar.
An atmosphere of an inert gas such as gas is preferable.

After this, preferably in an inert gas atmosphere,
Aging treatment is performed at 00°C for 1 to 5 hours.

Note that the method for manufacturing the permanent magnet of the present invention is not limited to the method of the present invention as described above, and for example, a powder such as the basic composition alloy powder used in the above method, namely T
Tb, Dy,
Alternatively, a thin film of these alloys is formed by vapor deposition, etc.
A method of molding and sintering this powder can also be used.

Furthermore, for example, when sintering the compact of the above-mentioned basic composition alloy powder, Tb or Dy may be supplied in the form of a gas or liquid. If supplied in the form of a gas, Tb or Dy may be sintered in the vapor. Byo (, when supplying as a liquid, place T on the molded body)
When chips containing b and Dy are placed and sintered, the chips melt and penetrate into the molded body.

<Examples> Hereinafter, specific examples of the present invention will be shown and the present invention will be explained in further detail.

Permanent magnet samples shown in Table 1 below were produced by the method shown below.

First, a mixture of basic composition alloy powder and additive powder was prepared at 12k.
Molding was carried out at a pressure of 1.5 t/ca+'' in a magnetic field of Oe.

Table 1 shows the composition of the basic composition alloy powder, the composition of the additive powder, and the amount of the additive powder added to the basic composition alloy powder.

The hydride used as the additive powder was prepared by leaving a rare earth metal ingot at 400° C. for 3 hours in a hydrogen stream of 1 atm.

In samples No. 0.202 to 206.401.404 and 405, the coarsely ground powder of the basic composition alloy powder and the coarsely ground powder of the additive powder were mixed and then finely ground by a jet mill.

In addition, samples No. 102-105 and 302-3
In No. 06, the basic composition alloy powder and the additive powder, each finely pulverized by a jet mill, were mixed. The average particle size of the basic composition alloy powder is 4μm, and the average particle size of the additive powder is 2μm.
m or less.

The Dy metal used in sample No. 106 was a powder with an average particle size of 20 μm produced by an atomization method because it was difficult to finely pulverize it.

Next, the molded body was sintered in vacuum at 1075° C. for 12 hours, and then rapidly cooled.

The obtained sintered body was subjected to an aging treatment at 600° C. for 1 hour in an Ar atmosphere to obtain a permanent magnet sample.

Table 1 shows the total content of rare earth metal elements R in the magnet.

Note that all of Fe and B in the basic composition alloy powder were contained in the magnet sample after sintering.

From the permanent magnet sample prepared in this way, 15
Cut out a magnet piece of X10X20+IIm to use as a permanent magnet sample for measurement, and measure the residual magnetic flux density Br and coercive force iHc.
and (BH)wax were determined.

In addition, for each sample, Tb at the center of the grain
The content Tb, c and the Dy content D y e, and the Tb content T b a and D near the grain boundary of the crystal grain
The y content D y s was measured by EPMA, and (Tbs + Dym ) - (TbC +03
'c) was calculated.

The measurement was performed by cutting the sample and using the method described above. Note that the measurement area was a square area with one side of 200 μm.

FIG. 1 shows an EPMA photograph of a cross section of sample No. 202. The photograph on the right side of FIG. 1 represents the content distribution of Dy, and the photograph on the left side represents the distribution of Nd content. In Figure 1, the regions with high contents of each element are bright (photographed). The photograph on the right side of Figure 1 shows that the content of Dy is high near the grain boundaries, and the photograph on the side shows that the content of Dy is high near the grain boundaries. It can be seen that the Nd content is high in the center of the crystal grains.
Note that the distribution of the total content of Dy and Nd was almost constant within the crystal grains.

Further, as a result of observation using a scanning electron microscope, each of the above samples had crystal grains with an average grain size of about 10 to 15 μm.

Furthermore, the oxygen content of each sample was measured using a gas analyzer.

Moreover, for samples No. 401 to 405, the samples were processed into 5×10×25 mm and subjected to a bending strength test.

The results are shown in Table 1.

From the results of the above examples, the effects of the present invention are clear.

That is, (Tbs + Dys) - (TbC +
Dye ) is 0.2% or more and the oxygen content is 5000 ppm or less, both high iHc and high Br are obtained in the samples of the present invention.

In addition, when comparing samples with the same basic composition alloy powder composition but different additive powder compositions, it is found that N0.304 using hydride as the additive powder, N0.305 using hydride and oxide, and only oxide N0.30 using
Br and iHc are higher than 6.

Furthermore, No.401 has almost the same magnetic properties as No.0.401.
The bending strength is about twice as high as that of 402 (also, the R in the magnet is
N0.4 with almost the same content but no added powder
Compared to 03, it has higher magnetic properties and strength.

<Effects of the Invention> According to the present invention, by unevenly distributing Dy and Tb near the grain boundaries at a predetermined ratio and suppressing the oxygen content within a predetermined range, both coercive force and residual magnetic flux density can be significantly increased. Furthermore, an R-Fe-B permanent magnet with high mechanical strength is realized.

In the manufacturing method of the present invention, Dy and Tb are contained in the additive powder in a metallic state or as a compound such as a hydride or oxide, and this additive powder is mixed with the basic composition alloy powder and sintered. The uneven distribution of y and Tb as described above can be easily achieved.

In particular, when a hydride, metallic glue, y, or Tb is used, it is extremely easy to suppress the oxygen content of the magnet within a predetermined range.

Furthermore, since the hydride is easily pulverized, it can be finely pulverized and mixed with the basic composition alloy powder. Therefore, the added powder is well dispersed, and the uneven distribution of Dy'PTb can be accurately and easily achieved.

Moreover, since hydrides have good oxidation resistance, they are easy to handle.

[Brief explanation of the drawing]

FIG. 1 is a photograph substituted for a drawing showing a metal structure, and is an electron beam probe microanalyzer (EPMA) photograph of a cross section of a permanent magnet of the present invention.

Claims (5)

[Claims] (1) A permanent magnet mainly composed of R (R is one or more rare earth metal elements including Y), T (T is Fe, or Fe and Co), and B, a crystal The relationship between Tb content Tb_C and Dy content Dy_C in the center of the grain and Tb content Tb_B and Dy content Dy_B near the grain boundary of the grain is (Tb_B+Dy_B)-(Tb_C+Dy_C)≧0.
．． 2 (%) (however, Tb_C, Dy_C, Tb
_B and Dy_B are expressed in atomic percentages), and the oxygen content is 5000 ppm or less. (2) R: 12.5 to 15 atom% and B: 5 to 8 atomic% The permanent magnet according to claim 1, comprising: (3) Coercive force iHc is XkOe, residual magnetic flux density Br
The permanent magnet according to claim 2, wherein Y≧−0.1X+14.2, where YkG is YkG. (4) A method for manufacturing a permanent magnet according to any one of claims 1 to 3, comprising: Rf (Rf is one or more rare earth metal elements and includes at least Nd and/or Pr), T and B as a main component, and Ra (Ra is one or more rare earth metal elements, and at least Dy and/or
A method for manufacturing a permanent magnet, comprising the steps of molding and sintering a mixture with an additive powder whose main component is a metal (or containing Tb) and/or an Ra compound. (5) The additive powder is Ra dihydride and/or R
The method for producing a permanent magnet according to claim 4, wherein the main component is a metal.