JPH0832943B2 - Method for producing rare earth-B-Fe sintered magnet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention provides at least one of the rare earth elements including Y (hereinafter, referred to as R), B, and B, which are excellent in corrosion resistance and do not deteriorate magnetic properties at the same time. The present invention relates to a method for manufacturing a sintered magnet containing Fe as an essential component.

[Conventional technology]

In recent years, Nd-B-Fe-based permanent magnets have been discovered that have higher magnetic properties than conventional Sm-Co-based magnets and that do not necessarily include Sm and Co, which are expensive in terms of resources. This Nd-B-
In the method for producing an Fe-based permanent magnet, first, a raw material powder is melted and cast, the obtained alloy ingot is crushed, press-molded while applying a magnetic field if necessary, and further sintered.

However, this Nd-B-Fe-based permanent magnet has its excellent magnetic properties, but on the other hand, it has a drawback that it is very easily corroded and the magnetic properties are greatly deteriorated.

As a countermeasure for these, in JP-A-61-185910,
A method of forming a Zn thin film by diffusion on the surface of an RB-Fe based permanent magnet. In JP-A-61-270308, after removing the surface layer of the RB-Fe based permanent magnet, an Al thin film layer is formed. The method of deposition is shown.

[Problems to be solved by the invention]

However, the Nd-B-
The corrosion protection method for Fe-based permanent magnets involves applying a corrosion-resistant protective film such as Zn or Al to the surface of the permanent magnet, and requires a separate process from the magnet manufacturing process, which makes the process complicated. In addition, the cost increases. In addition, the above anticorrosion method,
It only protects the outside of the permanent magnet against corrosion, etc., and if the protective film peels or cracks, the corrosion penetrates from those places to the inside and the internal corrosion is There has been a problem that the magnetic characteristics cannot be prevented and the magnetic characteristics are deteriorated accordingly.

[Means for solving problems]

Then, the present inventors have proposed RB-Fe having excellent corrosion resistance.
As a result of conducting research to develop a system permanent magnet, RB-
Fe-based alloy powder, to which at least one of Ni, Co, Mn, Cr, Ti, V and Nb oxides was added in a total amount of 0.0005 to 2.5 wt% was molded and sintered, and if necessary, Corrosion resistance is improved by performing heat treatment with R-
They have found that a B-Fe based sintered magnet can be manufactured.

The present invention has been made based on such knowledge, and the method for producing an RB-Fe-based sintered magnet of the present invention will be described below in further detail.

(1) RB-Fe alloy powder having a constant composition is prepared. The RB-Fe alloy powder is prepared by, for example, a method of melting, casting, crushing an ingot, a method of melting and atomizing, or a reduction diffusion method using a rare earth oxide as a starting material.

At least one of oxides of Ni, Co, Mn, Cr, Ti, V and Nb is added to the RB-Fe alloy powder in a total amount of 0.0005 to 2.
5% by weight is blended. The reason for setting this range is 0.005
If it is less than 5% by weight, the effect of corrosion resistance is not sufficient.
This is because the magnetic properties become insufficient when the content exceeds the weight percentage.

(2) The mixed powder obtained by the above method is molded and compacted by a compression press or the like. The pressure at this time is 0.5-10t / c
molding pressure of m ² is good, the magnetic field at the time of molding as required (5K
By applying Oe or more, the magnetic characteristics are improved. The series of molding and consolidation may be wet or dry, and the atmosphere is more preferably a non-oxidizing atmosphere. For example, it may be performed in a vacuum, in an inert gas, or in a reducing gas. At the time of molding, if necessary, a molding aid (a binder, a lubricant, etc.) may be added. These include paraffin, brain damage,
Stearic acid, stearic acid amide, stearic acid salt and the like can be used, and the addition amount is preferably 0.001 to 2% by weight. If the amount of the molding aid is less than 0.001% by weight, the lubricity required for molding is insufficient, which is not preferable.
If the content is more than 10% by weight, the magnetic properties of the sintered body deteriorate significantly after sintering.

(3) The obtained compact is sintered at a temperature of 900 to 1200 ° C. Temperature: Residual magnetic flux density below 900 ° C (hereinafter referred to as Br)
Is not sufficient, and when the temperature exceeds 1200 ° C., Br and the squareness decrease, which is not preferable. Sintering is preferably performed in a non-oxidizing atmosphere to prevent oxidation. Ie a vacuum,
An atmosphere of an inert gas or a reducing gas is preferable. The temperature rising rate during sintering may be between 1 and 2000 ° C./min. When a molding aid is used, it is desirable in terms of magnetic properties that the temperature rising rate is reduced to about 1 to 1.5 ° C./min and the molding aid is removed during the temperature rise. This is because the holding time during sintering may be 0.5 to 20 hours, and if the time is shorter than 0.5 hours, the sintering density will vary, and if it is longer than 20 hours, problems such as oxidation will occur. Cooling rate after sintering is 1-2000 ℃ / m
However, if it is too early, cracks may occur in the sintered body, and if it is too slow, there is a problem in terms of industrial productivity, so the above range was set.

(4) After the above sintering, heat treatment is performed at a temperature of 400 to 700 ° C. to further improve the magnetic characteristics. The heat treatment is desirably in a non-oxidizing atmosphere as in sintering. The temperature rise rate of this heat treatment is 10 to 2000 ° C./min, and the above temperature: 400
Hold at ~ 700 ° C for 0.5-10 hours, cooling rate: 10-2000 ° C / mi
You can do it with n. The heat treatment may be basically performed in a pattern of raising, holding, and cooling, but the same effect can be obtained by repeating the pattern as needed or by changing the temperature stepwise.

Next, the component composition of the RB-Fe based sintered magnet applied to the present invention and the reason for the limitation will be described.

The magnet manufactured by the present invention contains R, B and Fe as essential elements. As R, Nd, Pr or a mixture thereof is preferable, and in addition, Tb, Dy, La, Ce, Ho, Er, Eu, Sm, Gd, Pm, Tm, Y
Rare earth elements such as b, Ln and Y may be contained, and the total amount is 8 to 30 element%. If it is less than 8 atom%, sufficient holding power (hereinafter referred to as iHc) cannot be obtained, and if it exceeds 30 atom%, Br
This is because the

B is 2 to 28 atomic%. Less than 2 atomic% is sufficient
This is because iHc cannot be obtained, and if it exceeds 28 atomic%, Br decreases, and excellent magnetic properties cannot be obtained.

R-B-Fe-based sintered magnets are produced using R, B, and Fe as essential elements, but the effect of the present invention is lost even if part of Fe is replaced with other elements or impurities are included. Not done.

That is, 50 atomic% or less of Co may be substituted for Fe. This is because high iHc cannot be obtained if Co exceeds 50 atomic%. As an element other than the above, one or more of the following specified atomic% or less elements (however, when two or more elements are contained, the total amount of elements is less than or equal to the maximum value of these elements) is replaced with Fe element. However, the effect of the present invention is not lost. These elements are listed below (unit: atomic%) Ti: 4.7, Ni: 8.0, Bi: 5.0, W: 8.8, Zr: 5.5, Ta: 10.5, Mo: 8.7, Ca: 8.0, Hf: 5.5, Ge: 6.0 , Nb: 12.5, Mg: 8.0, Cr: 8.5, Sn: 3.5, Al: 9.5, Sr: 7.5, Mn: 8.0, Sb: 2.5, V: 10.5, Be: 3.5, Ba: 2.5, Cu: 3.5, S : 2.5, P: 3.3, C: 4.0, O: 1.0 The cause of the improvement of the corrosion resistance by the oxide addition of the present invention is that the R-rich liquid phase generated during sintering
Some of these oxides are reduced, and these are precipitated in the grain boundaries in the metallic state, and these metals themselves are inherently corrosion resistant, so it is considered that they contribute to the improvement of the corrosion resistance of the magnet. To be

〔Example〕

Next, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. In this example, the determination of the state of rust on the surface of the sintered body was performed by cutting the sintered body subjected to the corrosion resistance test, and visually confirming that no rust was observed around the cut surface. When rust was observed, the sample was rated "rust", and when rust was observed around the cut surface and rust had penetrated into the interior, "significant rust" was determined.

(1) Examples 1 to 5 and Comparative Examples 1 to 3 15% Nd-8% B-remaining Fe (however,% is atomic%) were melted to obtain alloy ingots. The alloy ingot was crushed to obtain fine powder having an average particle diameter of 3.5 μm, and Cr ₂ O ₃ powder having an average particle diameter of 1.2 μm was blended as shown in Table 1 and mixed to obtain a raw material powder. The raw material powder obtained was molded in a magnetic field (14 KOe) at a molding pressure of 2 t / cm ² in the air, and the vertical length was 12 mm ×
Width: 10 mm x Height: 10 mm A molded body is created, and this molded body is heated in vacuum (10 ^-5 Torr) at a heating rate of 5 ° C / min and held at a temperature of 1100 ° C for 1 hour. After sintering under the conditions described above, it was cooled at a rate of 50 ° C / min.

Next, this sintered body was heated in Ar gas at a heating rate of 10 ° C /
After raising the temperature at min and maintaining the temperature at 620 ° C. for 2 hours, the temperature was lowered at a temperature of 100 ° C./min for heat treatment.

After measuring the magnetic properties of these heat-treated sintered bodies, a corrosion resistance test was conducted. Corrosion resistance test, in air, temperature: 60 ℃,
Humidity: 90%, left for 650 hours. After carrying out the above corrosion resistance test, the magnetic characteristics were measured again and the rust generation state was observed. The results are shown in Table 1.

(2) Examples 6 to 10 and Comparative Examples 4 to 6 13.5% Nd-1.5% Dy-8% B-remaining Fe (however,% is atomic%) were melted to obtain alloy ingots. This alloy ingot was crushed using a jaw crusher, a disc mill and a ball mill to obtain a fine powder with an average particle size of 3.2 μm. TiO ₂ powder having an average particle size of 1.5 μm was blended with this fine powder as shown in Table 2 and mixed to obtain a raw material powder. The raw material powder thus obtained is molded in a magnetic field (14 KOe) at a molding pressure of 1.5 t / cm ² to form a molded body of 12 mm in length × 100 mm in width × 10 mm in height. Medium (250 Torr), heating rate: 10
Temperature rises at ℃ / min, temperature: 1080 ℃, after sintering for 2 hours, 100
Cooled at a cooling rate of ° C / min. Then, this sintered body is Ar
Temperature rising rate in gas: 20 ℃ / min, temperature: 650 ℃,
After holding for 1.5 hours, it was cooled at a rate of 100 ° C./min to perform heat treatment.

After measuring the magnetic properties of these heat-treated TiO ₂ powder-containing sintered bodies, they were left in the atmosphere at a temperature of 60 ° C and a humidity of 90% for 650 hours to carry out a corrosion resistance test. The appearance of rust was visually observed, and the results are also shown in Table 2.

(3) Examples 11 to 16 and Comparative Examples 7 to 8 13.5 Nd used in the above Examples 6 to 10 and Comparative Examples 4 to 6
-1.5% Dy-8% B-remaining Fe (however,% is atomic%) alloy powder was mixed with MnO ₂ powder having an average particle diameter of 1.0 μm in a ratio shown in Table 3 and mixed to obtain a raw material powder. , This raw material powder was molded in a magnetic field (12KOe) at a molding pressure of 5t / cm ² , and vertical: 12mm ×
A compact having a width of 10 mm and a height of 10 mm was produced. These compacts were heated in decompressed Ar (250 Torr) at a rate of 15 ° C / min, and then sintered under the conditions of temperature: 1200 ° C and held for 2 hours.
Cooled at ° C / min.

Next, this sintered body is heated at 30 ° C./min and heated to 650
After maintaining at ℃ for 1.5 hours, it was cooled at 200 ℃ / min. After measuring the magnetic properties of the heat-treated sintered body, the temperature was set to 60.
A corrosion resistance test was conducted by leaving it for 650 hours in the atmosphere of 90 ° C. and humidity of 90%, the magnetic characteristics were measured again, and the rust generation state was visually observed. The results are shown in Table 3.

(4) Examples 17-22 and Comparative Examples 9-10 13.5 Nd used in the above Examples 6-10 and Comparative Examples 4-6
-1.5% Dy-8% B-remaining Fe (however,% is atomic%) alloy powder was mixed with Co ₂ O ₃ powder having an average particle diameter of 1.2 μm in a ratio shown in Table 4 and mixed to obtain a raw material. This raw material powder was compacted in a magnetic field (20KOe) at a compaction pressure of 10t / cm ² and a vertical length of 20
A molded body of mm × width: 20 mm × height: 15 mm was produced. These compacts were heated in Ar at a reduced pressure (250 Torr) at a heating rate of 20 ° C / min and sintered at a temperature of 900 ° C for 20 hours and then 500 ° C.
It cooled at the cooling rate of / min.

Next, this sintered body is heated to 500 ° C at a heating rate of 1000 ° C / min.
It was heated to, held for 7 hours, and then cooled at a rate of 500 ° C./min.

After measuring the magnetic properties of this heat-treated sintered body, temperature: 6
The corrosion resistance test was carried out by leaving it in the atmosphere of 0 ° C and humidity of 90% for 650 hours, the magnetic characteristics were measured again, and the rust generation was visually observed. The results are shown in Table 4. .

(5) Examples 23 to 29 and Comparative Examples 11 to 12 13.5 Nd used in the above Examples 6 to 10 and Comparative Examples 4 to 6
-1.5% Dy-8% B-remaining Fe (however,% is atomic%) alloy powder was mixed with NiO powder having an average particle diameter of 1.0 μm in a ratio shown in Table 5, and mixed to obtain a raw material powder, This raw material powder was compacted in a magnetic field (14KOe) at a compaction pressure of 15t / cm ² , and vertical length: 12mm
A molded product having a width of 10 mm and a height of 10 mm was prepared. These compacts were heated in vacuum (10 ⁻⁵ Torr) at 5 ° C./min, sintered at a temperature of 1080 ° C. for 1 hour, and cooled at 50 ° C./min.

Next, this sintered body was heated at a heating rate of 20 ° C./min, held at a temperature of 800 ° C. for 1 hour and at a temperature of 620 ° C. for 1.5 hours, then cooled at 100 ° C./min and heat treated. .

After measuring the magnetic properties of this heat-treated sintered body, leave it in the atmosphere of temperature: 60 ° C, humidity: 90% for 650 hours to perform a corrosion resistance test and measure the magnetic properties after the above corrosion resistance test. The state of rust generation was observed, and the results are shown in Table 5.

(6) Examples 30 to 35 and Comparative Examples 13 to 14 15% produced in the above Examples 1 to 5 and Comparative Examples 1 to 3
Nd-8% B-remaining Fe (however,% is atomic%) alloy powder was mixed with V ₂ O ₅ powder having an average particle diameter of 1.4 μm in a ratio shown in Table 6, and mixed to prepare a raw material. It was made into powder. This raw material powder was compacted in a magnetic field (20KOe) at a compacting pressure of 7t / cm ² , and the vertical length was 2
A molded body of 0 mm x width: 20 mm x height: 15 mm was produced. These compacts were heated in vacuum (10 ^-5 Torr) at a heating rate of 100 ° C / min, and sintered at a temperature of 1000 ° C for 10 hours, then 3
It was cooled at a cooling rate of 00 ° C / min.

Next, this sintered body is heated at a heating rate of 100 ° C./min,
Temperature: 550 ° C. After holding for 2 hours, it was cooled at a cooling rate of 300 ° C./min and heat treated.

The magnetic properties of this heat-treated sintered body were measured, and the sintered body was left in the atmosphere of temperature: 60 ° C, humidity: 90% for 650 hours to perform a corrosion resistance test, and then the magnetic properties were measured again. In addition, the generation of rust was visually observed and the results are shown in Table 6.

(7) Examples 36 to 41 and Comparative Examples 15 to 16 15% used in the above Examples 1 to 5 and Comparative Examples 1 to 3
Nd-8% B-remaining Fe (however,% is atomic%) alloy powder was mixed with Nb ₂ O ₃ powder having an average particle diameter of 1.2 μm in the proportions shown in Table 7, and mixed. The raw material powder was used. This raw material powder was molded in a magnetic field (5 KOe) at a molding pressure of 1 t / cm ² to prepare a compact having a length of 12 mm, a width of 10 mm, and a height of 10 mm. These compacts were heated in vacuum (10 ^-5 Torr) at a temperature rising rate of 3 ° C / min, and then sintered at a temperature of 1200 ° C for 0.5 hour and then cooled at a cooling rate of 5 ° C / min. Cooled.

This sintered body was heated at a heating rate of 20 ° C / min and a temperature of 45 ° C.
After holding at 0 ° C. for 2 hours, it was cooled at a cooling rate of 900 ° C./min and heat-treated.

After the above heat treatment, the magnetic properties of the sintered body are measured, and the sintered body is left in an atmosphere at a temperature of 60 ° C. and a humidity of 90% for 650 hours to perform a corrosion resistance test, and the magnetic characteristics after the corrosion resistance test are measured. Then, the occurrence of rust on the surface was observed and the results are shown in Table 7.

(8) Examples 42 to 54 and Comparative Examples 17 to 21 13.5 used in the above Examples 6 to 10 and Comparative Examples 4 to 6
Nd-1.5% Dy-8% B-remaining Fe (however,% is atomic%) alloy powder, Cr ₂ O ₃ (average particle size: 1.2 μm), NiO (average particle size: 1.0
μm), Co ₂ O ₃ (average particle size: 1.2 μm) MnO ₂ (average particle size: 1.
0 μm), TiO ₂ (average particle size: 1.5 μm), V ₂ O ₃ (average particle size:
Two or more kinds of oxide powders of 1.4 μm) and Nb ₂ O ₃ (average particle size: 1.2 μm) were blended and mixed at a ratio shown in Table 8 to obtain a raw material powder.

The above raw material powder is molded in a magnetic field (14 KOe) at a molding pressure of 1.5 t / cm ² to create a compact of vertical: 12 mm × width: 10 mm × height: 10 mm, and the compact is depressurized in Ar. The sample was heated at (250 Torr) at a heating rate of 10 ° C / min, sintered at a temperature of 1080 ° C for 2 hours, and cooled at a cooling rate of 100 ° C / min.

Then, this sintered body was heated in Ar gas at a heating rate of 20 ° C / mi.
Temperature is raised at n, temperature: 650 ℃, hold for 1.5 hours, then 100 ℃ /
Heat treatment was performed by cooling at a cooling rate of min. After measuring the magnetic properties of these heat-treated oxide-containing sintered bodies, the samples were left in the air at a temperature of 60 ° C. and a humidity of 90% for 650 hours, subjected to a corrosion resistance test, and subjected to the corrosion resistance test. ,
The magnetic characteristics were measured again, and the generation state of rust on the surface was visually observed. The results are shown in Table 8.

[Effect of the Invention] From the results of Tables 1 to 8 above, the sintered magnet produced by molding and sintering the RB-Fe alloy powder had rust on the surface after the corrosion resistance test, and the rust was generated. Penetrates into the interior to cause remarkable corrosion, and the deterioration of the magnetic properties after the corrosion resistance test is also remarkable.
-Sintered magnets are manufactured by using powder obtained by adding 0.0005 to 2.5% by weight of at least one of Ni, Co, Mn, Cr, Ti, V, and Nb oxides to B-Fe alloy powder in total. Then, it can be seen that a sintered magnet having excellent corrosion resistance can be manufactured, and further deterioration of the magnetic properties after the corrosion resistance test can be suppressed.

R in which the above oxides are added in total exceeding 2.5% by weight
The sintered magnet produced from the -B-Fe alloy powder does not show rust on the surface, but the magnetic properties of the produced sintered magnet itself are low, and the amount of addition of the oxide is 0.00
If less than 05% by weight of raw material powder is used, rust will occur on the surface of the sintered magnet and the magnetic properties after the corrosion resistance test will be significantly deteriorated.

As described above, R-B-Fe based sintering produced by using a raw material powder obtained by adding one or more of the above oxide powders in total to 0.0005 to 2.5% by weight to the R-B-Fe based alloy powder. Since the magnet has excellent corrosion resistance and the deterioration of magnetic properties is improved,
The RB-Fe-based sintered magnet manufactured by the manufacturing method of the present invention does not require surface treatment, and the magnetic characteristics of the sintered magnet are less deteriorated. This is an excellent industrial effect of preventing the above.

Claims (2)

[Claims] 1. R—B—Fe containing R (R is at least one of rare earth elements including Y), B and Fe as essential components.
A powder obtained by adding 0.0005 to 2.5% by weight of at least one of oxides of Ni, Co, Mn, Cr, Ti, V and Nb in total to a base alloy powder, and performing sintering. Rare earth
Manufacturing method of B-Fe system sintered magnet. 2. The rare earth-B-Fe system sintered magnet produced by the method for producing a rare earth-B-Fe system sintered magnet as described above, wherein the rare earth-B-Fe system sintered magnet is heat-treated.
Manufacturing method of B-Fe system sintered magnet.