JPH02298231A - Manufacture of rare earths-b-fe series sintered magnet having excellent corrosion resistance and magnetic characteristics - Google Patents

Abstract

PURPOSE:To obtain the sintered magnet having excellent corrosion resistance and magnetic characteristics by mixing alloy powder contg. rare earth elements, B and Fe as essential components with the hydride powder of specified elements, forming the mixed powder and thereafter sintering it in a nonoxidizing atmosphere. CONSTITUTION:The powder of a rare earths-B-Fe series alloy constituted of at least one kind among rare earth elements excluding Y such as Nd, Pr or their mixture, 8 to 30atom%, 2 to 28atom% B and the balance Fe is admixed with one or more kinds of hydride powder of elements such as Zr, Ta, Ti, Nb, Hf, V and Y in the total ratio of 0.0005 to 3wt.%. If required, a forming auxiliary such as paraffin is added to the mixed powder, which is subjected to press forming. The formed part is sintered at 900 to 1200 deg.C in vacuum or in the atmosphere of nonoxidizing gas such as inert gas, reducing gas or the like. The product is finally subjected to heat treatment at 400 to 700 deg.C, by which the sintered magnet having excellent corrosion resistance and magnetic characteristics can be manufactured.

Description

Detailed Description of the Invention [Industrial Field of Application] This invention provides at least 11Ei (hereinafter referred to as R) of rare earth elements other than Y, B and Fe, which have excellent corrosion resistance and excellent magnetic properties. The present invention relates to a method for producing a sintered magnet as an essential component.

[Conventional technology]

In recent years, Nd-B-Fe-based permanent magnets have been invented that have better magnetic properties than conventional 5s-Co-based magnets and do not necessarily contain SII or Co, which are expensive resources.

The method for manufacturing this Nd-B-Fe permanent magnet is to first melt and cast raw material powder, crush the obtained alloy ingot, press-form it while applying a magnetic field as necessary, and then sinter it. It is.

However, while this Nd-B-Fe based permanent magnet has excellent magnetic properties, it also has the drawback of being highly corroded and resulting in a large deterioration of magnetic properties.

As a countermeasure against these problems, JP-A-185910 discloses a method of diffusing and forming a Zn thin film on the surface of a rare earth-B-Fe based permanent magnet, and JP-A-81-270308 discloses a method of diffusing and forming a Zn thin film on the surface of a rare earth-B-Fe based permanent magnet. After removing the surface layer of the permanent magnet, a thin film layer of Al1 is applied, and in JP-A-83-77104, the surface of the rare earth-B-Fe permanent magnet is coated with epoxy resin or thermosetting acrylic resin. , methods of applying oxidation-resistant resins such as synthetic resins for coating such as alkyd resins, melamine resins, and silicone resins are disclosed.

[Problem to be solved by the invention]

However, the Nd-B-
All corrosion prevention methods for Fe-based permanent magnets involve applying a corrosion-resistant protective film such as Zn, 8Ω, or synthetic resin to the surface of the permanent magnet, which requires a process different from the magnet manufacturing process. This complicates the process and increases costs, and furthermore, the thickness of the synthetic resin protective film deteriorates the precision of the J method, especially for small magnet products. In any case, the above corrosion prevention method only protects the outside of the permanent magnet from corrosion, etc., and if the above protective film peels off or cracks occur, corrosion will occur from those places inside. Penetration caused the problem that internal corrosion could not be prevented and magnetic properties deteriorated accordingly.

[Means to solve the problem]

Therefore, the present inventors have developed a rare earth material -B- which has excellent corrosion resistance.
As a result of research to develop Fe-based sintered magnets, we found that R -B -Fe, which has at least one of the surface class elements other than Y (hereinafter referred to as R), B, and Fe, is an essential component.
alloy powder (hereinafter referred to as R-B-Fe alloy powder)
ni, zr, Ta.

TI, Nb, V, Hr, Y hydride powder 0561
A rare earth-B-Fe based sintered magnet having excellent corrosion resistance and magnetic properties can be obtained by mixing a species or two or more species in a total of 0.0005 to 3% by weight, molding the resulting mixed powder, and sintering it. We obtained the knowledge that it is possible to do this.

This invention has been made based on this knowledge, and includes Zr hydride powder, Ta hydride powder, Ti hydride powder, Nb hydride powder,
Corrosion resistance and This invention is characterized by a method for manufacturing rare earth-B-Fe sintered magnets with excellent magnetic properties.

The magnetic properties can be further improved by further heat-treating the rare earth-B-Fc-based sintered magnet obtained by sintering.

The mixed powder, molding method, sintering method, and heat treatment used in the method for producing a rare earth-B-Fe sintered magnet of the present invention will be described in detail below.

(1) Mixed Powder The above R-B-Fe alloy powder can be prepared by melting, casting and pulverizing an ingot, melting and atomizing, or reducing and atomizing using a rare earth oxide as a starting material. Either method may be used.

The above R is preferably Nd, Pr or a mixture thereof, and also Tb, La, CcrSm.

May contain rare earth elements such as Gd and Yb, with a total amount of 8~
It is preferable to set it to 30 atom%. This is because if it is less than 8 atomic %, sufficient coercive force cannot be obtained, and if it exceeds 30 atomic %, the residual magnetic flux density decreases.

The content of the upper 2s is preferably 2 to 28 at%.

If it is less than 2 atom%, sufficient coercive force cannot be obtained;
This is because if the value exceeds 1, the residual magnetic flux density decreases, and excellent magnetic properties cannot be obtained.

Zr hydride powder,
1f4 or two or more of Ta hydride powder, T1 hydride powder, Nb hydride powder, ■ hydride powder, Hf hydride powder and Y hydride powder in a total of 0.000
A mixed powder is prepared by mixing 5 to 3 parts by weight. As the hydride powder, a hydride powder having the following molecular formula can be used.

ZrH powder (x-1, 5-2), TaH powder (x = 1-2), TiH powder (x-0, 7-2), NbH powder (x-0, 8-2), VH powder (x = 0.8~2), HfH powder (x-1,7~2°), and YH powder (x
-1,8~3) The total amount of hydride mixed in the R-B-Fe alloy powder is preferably 0.0005 to 3% by weight. Total amount is 0
．． If the content is less than 0.005% by weight, the corrosion resistance effect will not be sufficiently exhibited, while if it exceeds 3% by weight, the magnetic properties will be insufficient.

(2) Molding method The mixed powder obtained by the above method is molded and compacted using a compression press or the like. The pressure at this time is 0.5 to 10t/c
- The molding pressure is good, and if necessary, the magnetic field (5
Magnetic properties are improved by applying KOe or more). The series of molding may be performed in a wet or dry manner, and the atmosphere is preferably a non-oxidizing atmosphere, for example, in a vacuum, an inert gas, or a reducing gas. During molding, molding aids (binder, lubricant, etc.) may be added if necessary. Paraffin, camphor, stearic acid, stearamide, stearate, etc. can be used as these, and the amount added is preferably 0.001 to 2% by weight.

If the amount of the forming aid added is less than 0.0% by weight, the lubricity required during molding will be insufficient, which is undesirable.On the other hand, if it exceeds 2% by weight, the magnetic properties of the sintered body will deteriorate after sintering. is remarkable.

(3) Sintering method The obtained molded body is sintered at a temperature of 900 to 1200°C. If the temperature is less than 900°C, the residual magnetic flux density will not be sufficient, and if the temperature exceeds 1200°C, the residual magnetic flux density and squareness will decrease, which is not preferable. Sintering is preferably performed in a non-oxidizing atmosphere to prevent oxidation. That is, a vacuum, an inert gas or a reducing gas atmosphere is preferable. The temperature increase rate during sintering may be between 1 and 2000"C/1lin.

In addition, if a molding aid is used, the temperature increase rate should be 1 to 1.5℃.
/1n, and removing the above-mentioned forming aid during temperature rise is preferable in terms of magnetic properties.

The holding time during sintering may be between 0.5 and 20 hours, and may be 0.5 to 20 hours.
．． This is because if the time is shorter than 5 hours, the sintered density will vary, and if the time is longer than 20 hours, problems such as coarsening of crystal grains will occur. The cooling rate after sintering was determined to be within the above range, since if it is too slow, there is a high possibility that cracks will occur in the sintered body, and if it is too slow, there will be problems in terms of industrial production efficiency.

(4) After sintering using a heat treatment method, in order to further improve magnetic properties,
Heat treatment is performed at a temperature of 400 to 700°C. As with sintering, the above heat treatment is preferably performed in a non-oxidizing atmosphere. This heat treatment is preferably carried out at a heating rate of 10 to 700°C, held at the above temperature of 40 to 700°C for 0.5 to 10 hours, and a cooling rate of 10 to 2000°C/1. The above heat treatment can basically be carried out in a pattern of increasing temperature, holding, and cooling, but similar effects can be obtained by repeating this process or changing the temperature stepwise as necessary.

Note that the R-B-Fo-based sintered magnet of this invention is produced by molding and sintering a mixed powder of R-B-Fe-based alloy powder and hydride powder, but the R-B-Fc of this invention Even if a part of the system sintered magnet is replaced with other elements or contains impurities, the effects of the present invention are not lost.

That is, Fe may be replaced with 50 atomic % or less of Co. This is because if Co exceeds 50 atomic %, bright iHc cannot be obtained. As elements other than the above, one or more of the following elements below the specified atomic % (however, if 2F!i or more is included, the total amount of elements is below the value of the maximum value among these elements) is replaced with Fe element However, the effect of this invention is not lost. These elements are shown below (unit: atomic %).

Tl: 4.7. Nl: 0.8.
Bl: 5.0°W: 8.11.
Zr: 5.5. Ta:40.5゜Mo:8
．． 7. Ca28.0, Hr:5.5゜Ge: G,
0. Nb: 12.5. Mg: 8.0°C
r: &, 5. Sn: 3.5. A,
l): 9.5°Sr: 7.5. Mn
: 8.0. Sb: 2.5°V: lO
,5,Be: 3.5. Ba: 2.5°Cu: 3.5. S: 2.5. P
: 3.3°C; 4.0. O: 1.
5. Ga: 6.0゜In general, the cause of corrosion in R-B-Fe sintered magnets is that the R-rich phase formed around the main phase is the phase that is most likely to be corroded. It is said that intergranular corrosion occurs inside the magnet, but when the hydride powder of this invention is added and mixed and sintered, the R-rich phase reacts with the hydride powder, making it difficult to corrode. The corrosion-resistant R-rich phase has the effect of suppressing the growth of crystal grains during the sintering process and increasing the density. Therefore, the R-B-Fe system has excellent corrosion resistance and magnetic properties. It is considered that a sintered magnet can be obtained.

〔Example〕

Next, the present invention will be explained in more detail based on examples.

First, an alloy ingot was prepared by melting 15%Nd-8%B-remaining Fe (where % is atomic%).
This alloy ingot was pulverized to prepare a fine powder with an average particle size of 3.5-.

On the other hand, as a hydride powder, ZrH2 powder with an average particle size of 1.3μ, average particle size:
1.5m T a H2 powder, average particle size: 1.3-T
iH2 powder, average particle size: 1.3 mm Nb H, powder, average particle size: 1.5 mm VH powder, average particle size: 1.3 mm Hf H2 powder, average particle size: 1.
A 1 μs YH3 powder was prepared, and these powders were blended and mixed in the proportions shown in Table 1 to obtain a raw material powder.

This raw material powder was molded in an Ar gas atmosphere at a pressure of 1.5 t.
/cd in a magnetic field (12KOe), length: 12mm
A molded body measuring 10 mm in width and 10 mm in height was produced. These molded bodies were heated at a temperature increase rate of 10°C/1 inch in a vacuum atmosphere of pressure crab I
A sintered body was produced by cooling at a cooling rate of / tg I n, and these sintered bodies were further heated at a heating rate of 5°C/sin in the same atmosphere as the sintering atmosphere described above, to a temperature of 262°C.
After holding at 0°C for 2 hours, a cooling heat treatment was performed at a cooling rate of 50°C/win to obtain the present invention R-B shown in Table 1.
-Fc-based sintered magnets 1 to 45 and comparative R-B-F (3
System sintered magnets 1 to 18 were produced.

R-B-Fc based sintered magnet 1 of the present invention immediately after being produced above
After measuring the magnetic properties (residual magnetic flux density: Br, coercive force: iHc and maximum energy product: BHmax) of ~45 and comparative R-B-Fc sintered magnets 1-17, these sintered magnets were heated at a temperature of 260℃. ℃, humidity = 90% atmosphere
A corrosion resistance test was conducted after being left for 000 hours, and the present R-B-Fe based sintered magnets 1 to 45 and comparative R
Magnetic properties of B-Fe sintered magnets 1 to 17 (residual flux density: B', coercive crab iHc and maximum energy product: BH
) was measured, and the occurrence of rust on the surface and inside of the sintered magnet after the above corrosion resistance test was also observed, and the results are shown in Table 1.

To determine the occurrence of the above-mentioned problems, cut a sintered magnet that has been subjected to a corrosion resistance test, and visually inspect it.If no rust is observed around the cut surface, it is considered "no rust," and if rust is observed around the cut surface, it is "rust-free." If rust was observed around the cut surface and the rust had penetrated into the interior, it was classified as "significantly rusted."

〔Effect of the invention〕

From the results in Table 1, it can be seen that in Comparative R-B-Fe sintered magnet 1 made from R-B-Fe alloy powder alone, rust occurred on the surface after the corrosion resistance test, and the rust penetrated into the interior. Although significant corrosion occurs and the magnetic properties deteriorate significantly after the corrosion resistance test, the above R
-B-Fc alloy powder contains Zr, Ta, Tl, Nb,
The R-B-Fe-based sintered magnet of the present invention, which is made from powder containing 18 or two or more of V, Hr, and Y hydride powders in a total amount of 0.0005 to 3% by weight, has corrosion resistance. It can be seen that the material has excellent magnetic properties, and no deterioration of the magnetic properties occurs in the corrosion resistance test.

Furthermore, a comparative R-B-Fe-based sintered magnet 3.5.7.9. was manufactured using the raw material powder to which the above-mentioned hydride was added in a total amount exceeding 3% by weight. II, +3°15, 17, and 18, no rust was observed on the surface, but the magnetic properties deteriorated.On the other hand, when the amount of hydride added was 0.0005
Comparative R-B-F made from raw powders of less than % by weight
It can be seen that the e-based sintered magnets 2.4.6.8°10, 12.14, and 16 all had rust on their surfaces, and their magnetic properties deteriorated significantly after the corrosion resistance test.

As mentioned above, a total of 0.0005 to 3 of one or more of the above hydride powders is added to the R-B-Fc alloy powder.
R-B-Fc manufactured using raw material powder added by weight%
The R-B-F series sintered magnet produced by the production method of the present invention has excellent corrosion resistance and improves deterioration of magnetic properties.
C-series sintered magnets do not require surface treatment, and the magnetic properties of the sintered magnets are less likely to deteriorate, so they have an excellent industrial effect of preventing deterioration in the performance of devices incorporating these magnets. It is.

Claims (1)

[Claims] (1) R-B whose essential components are at least one rare earth element other than Y (hereinafter referred to as R), B, and Fe.
-Fe-based alloy powder contains Zr, Ta, Ti, Nb, V, H
Corrosion resistance and magnetic properties characterized by molding and sintering a mixed powder obtained by mixing a total of 0.0005 to 3% by weight of one or more of r and Y hydride powders. A method for producing a rare earth-B-Fe based sintered magnet with excellent properties.