JP3009687B2 - Manufacturing method of high corrosion resistant sintered permanent magnet material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a sintered permanent magnet material having a composition with improved corrosion resistance of an Fe—BR based sintered permanent magnet material having high magnet properties. On the other hand, Cu, Al, halogen elements are essential elements, and halogen elements are added as halides to the alloy powder before and after the jet mill pulverization process to improve the corrosion resistance of the material itself in composition, and the corrosion resistance provided on the material surface The present invention relates to a method for manufacturing a highly corrosion-resistant Fe-BR-based sintered permanent magnet material which has improved peeling resistance of a film, and in particular, has prevented reduction in bending strength of a thin magnet material.

Conventional technology Permanent magnet materials are used in a variety of household electrical appliances, automobiles, communication devices, and peripherals for large computers.
It is one of the very important electric and electronic materials used in a wide range of fields.

With the recent demand for higher performance and smaller size of electric and electronic devices, higher performance is also required for permanent magnets. Conventionally, rare-earth cobalt magnets have been known as permanent magnets that meet such demands.However, rare-earth cobalt magnets are rare earths, are rarely contained in rare-earth ores, and are expensive.
In large amounts, and 50 to 60 wt% of Co.

The applicant has previously decided that Sm and Co, which are rare and expensive as resources, are not essential, and that as a rare earth element, a light rare earth element such as Nd or Pr contained in a rare earth ore is used as a central element, and iron and By using boron, we found the existence of a ternary compound containing iron, boron, and rare-earth R as essential elements with uniaxial magnetic anisotropy having excellent magnetic properties. We have proposed Fe-BR-based magnetic anisotropic sintered magnets having high permanent magnet properties that greatly exceed the energy product (Japanese Patent Publication No. 61-34242, Japanese Patent Application Laid-Open No. 59-1984).
-89401, JP-A-60-34005).

Fe-BR magnets are more likely to rust in humid environments than Sm-Co magnets, and are used after being subjected to various surface treatments to improve corrosion resistance in general applications for electronic equipment. There is a need to.

Until now, Ni plating (Japanese Patent Laid-Open No. 60-54)
No. 406, JP-A-63-254702), resin coating (JP-A-60-6
No. 3901), ion plating (JP-A-61-166116)
No.), electrodeposition coating (JP-A-61-130453, JP-A-63-1509)
No. 05, JP-A-63-217601) and various other methods have been proposed.

Problems to be Solved by the Invention However, these methods have also been variously improved,
In addition, there was a problem that the corrosion resistance was not sufficient and the device could not be used for a long time under severe environmental conditions.

This is not indispensable in any surface treatment, and there are minute holes and pinholes in the surface coating, from which water, water vapor, and oxygen enter the surface of the magnet,
Due to the formation of rare earth elements and iron rust.

That is, since rust is generated, the surface coating is torn or floated, resulting in peeling of the surface coating, deteriorating the properties of the magnet, or the peeled coating or rust impairing the function of the electronic device.

In a hot and humid environment, water molecules penetrate the coating, so that the Nd-rich grain boundary phase in the magnet turns into hydroxide and crystal grains are detached, and the volume expansion of the grain boundary phase accompanying hydroxylation occurs. For this reason, cracks are generated, corrosion proceeds one after another, and there is a problem that a thin magnet has a low bending strength and a low adhesion force of a coating film depending on the use.

As a method of improving the corrosion resistance of the Fe-BR based sintered magnet, it has been proposed to improve the corrosion resistance of the magnet material itself without depending on the surface treatment. For example, the use of a low B composition (No. 60, Autumn Meeting of the Japan Institute of Metals (October 1987))
4) Addition of Co and Al (JP-A-63-38555).

However, although the corrosion resistance is relatively improved as compared to before the composition change, there is no fundamental improvement such that the surface treatment becomes unnecessary. In addition, there were problems such as a decrease in iHc due to a change in the composition, and severer heat treatment conditions for obtaining good magnet properties.

In view of the present situation, the present invention solves the above-mentioned problems, that is, by improving the composition and manufacturing of Fe-BR-based sintered magnets, improving the corrosion resistance without deteriorating the properties of the magnets, Fe that can prevent peeling of the corrosion-resistant coating and decrease in adhesion, and in particular, can maintain stable corrosion resistance and magnet properties even when a thin magnet is exposed to a high-temperature and high-humidity environment for a long time.
An object of the present invention is to provide a method for producing a sintered BR permanent magnet material.

Means for Solving the Problems The inventors of the present invention have repeatedly studied the composition of Fe-BR-based permanent magnets with the aim of improving the corrosion resistance. By adding, for example, contained in the Nd-rich grain boundary precipitation phase in the sintered body, grain boundary preferential corrosion is prevented, and rust generation of the material itself is not significantly reduced as compared with those not containing this. The surface treatment enhances the adhesion of the corrosion-resistant coating and significantly improves the weather resistance. Even if the thin magnet is exposed to a high-temperature and high-humidity environment for a long time, stable corrosion resistance and magnet properties are maintained without a decrease in bending strength. Was found to be able to be maintained.

Further, the present inventors have repeatedly studied manufacturing improvements for the purpose of improving the corrosion resistance of the Fe-BR based permanent magnet, and as a result, pulverized the alloy powder having the above-described compositional improvement. Use of a jet mill in the process, that is, after adding a halogen element as a halide to the coarsely pulverized powder, finely pulverize with a jet mill, or finely pulverize with a jet mill, and then add the halogen element to the finely pulverized powder. It has been found that by adding as a halide, the halogen element together with Cu and Al tends to be contained in the R-rich grain boundary precipitation phase in the sintered body, and as a result, preferential grain boundary corrosion is prevented. Was completed.

That is, the present invention provides a rare earth element R of 13 at% to 16 at%, wherein R is one or two kinds of Pr and Nd, or one or two kinds of Dy and Tb in addition to the above-mentioned elements and unavoidable impurities. It is composed of other rare earths contained, when two or more kinds, satisfy 0.8 ≦ (Pr + Nd + Dy + Tb) /R≦1.0, B 6at% -9at%, Cu 0.01at% -0.5at%, Al 0.1at% -2at%, X 0.01 at% to 1.0 at%, where X is at least one of halogen elements F, Cl, Br and I, balance Fe and Co 71.5 at% to 81 at%, provided that 0 ≦ Co / (Fe + Co) ≦ 0.4 In producing a sintered permanent magnet material in which X together with Cu and Al is contained in the R-rich grain boundary precipitate phase in the sintered body, a step of coarsely pulverizing an alloy made of elements other than X, A step of finely pulverizing the obtained coarsely pulverized powder with a jet mill, and further pressing the obtained finely pulverized powder in a magnetic field, sintering, and heat treating. In the step of a method for producing a highly corrosion resistant sintered permanent magnetic material of adding X to the coarsely pulverized powder or pulverized powder as a halide.

BEST MODE FOR CARRYING OUT THE INVENTION Reasons for Limiting the Composition of Components In the present invention, it is usually sufficient to use any one of Pr and Nd as the rare earth R. May be used,
It may be composed of one or two of Dy and Td in addition to one or two of Pr and Nd, and another rare earth contained as an unavoidable impurity. In the case of two or more, 0.8 ≦ (Pr + Nd + Dy + Tb) / R It is only necessary to satisfy ≦ 1.0.

That is, in the present invention, R represents one or two of Nd and Pr.
A high coercive force is obtained only by the species, but if necessary, the Nd
+ Dy or Nd + Pr + Dy as described above,
By substituting with Tb, the effect of increasing the coercive force is further enhanced.

When R is less than 13 at%, 15 kOe which is a feature of the present invention is used.
If the above high coercive force cannot be obtained, and if it exceeds 16 at%, the residual magnetic flux density (Br) decreases and (BH) max of 20 MGOe or more cannot be obtained, so the range is 13 at% to 16 at%.

When R is in the range of 15 at% to 16 at%, a coercive force of 18 kOe or more can be obtained without lowering (BH) max, which is a particularly preferable range.

In the present invention, in order to obtain a maximum energy product of 20 MGOe or more and a coercive force of 15 kOe or more, B needs to be added in an amount of 6 at% or more. , 6 at% to 9 at%.

Cu has an effect of improving coercive force and an effect of improving corrosion resistance together with the following halogen elements. To obtain such an effect, addition of 0.01 at% or more is necessary. In order to reduce the squareness of the demagnetization curve, Cu is set in the range of 0.01 at% to 0.5 at%. In particular, the addition range of Cu for obtaining good demagnetization curve squareness is 0.02at%.
~ 0.09at%.

Al has an effect of improving coercive force and an effect of improving corrosion resistance together with the following halogen elements.
It is necessary to add 0.1 at% or more. However, if it exceeds 2 at%, not only does the maximum energy product decrease, but also the thermal stability significantly deteriorates due to a significant decrease in the Curie temperature. The range is from 0.1 at% to 2 at%.

The addition of the halogen element X, which is one of the features of the present invention, is contained in the R-rich grain boundary precipitation phase in the sintered body together with the Cu and Al, thereby preventing preferential grain boundary corrosion, that is, Cu, Al Further, R which coexists C, O ₂ and halogen element X
By dispersing the rich secondary phase around the main phase composed of R ₂ Fe ₁₄ B, the R-rich phase is not preferentially corroded.
R ₂ Fe ₁₄ B is also corroded at the same time, and intergranular corrosion such as dropping of crystal grains does not occur. Therefore, the adhesion of the corrosion-resistant coating by the surface treatment is improved, and the weather resistance is remarkably improved. Further, the expansion of the grain boundary precipitation phase due to the hydroxylation is suppressed, and the reduction in strength due to the occurrence of cracks is prevented.

In order to prevent the preferential corrosion of the grain boundary, a halogen element X
Must be contained in the R-rich grain boundary precipitation phase in the sintered body.

The halogen element X is at least one of F, Cl, Br and I, and it is necessary to add 0.01 at% or more to obtain the above effect. 0.01at%-1.0a
t% range.

In the permanent magnet of the present invention, the residual content of each of the above elements is
Fe occupies. That is, it is in the range of 71.5 at% to 81 at%. Also, part of Fe can be replaced by Co, and Co is Fe-BR
It has the effect of increasing the Curie temperature of the system-based permanent magnet, improving the temperature characteristics of the residual magnetic flux density, and improving the corrosion resistance.
(Fe + Co) ≦ 0.4 is preferable.

When the permanent magnet of the present invention is manufactured, O ₂ or C may be contained in the manufacturing process in some cases. That is, the raw material, dissolved, grinding, sintering, may be mixed from the process, such as heat treatment, O _2, the content of more than 2000ppm may have the effect of preventing grain boundary preferentially corroded as described above, the residual and more than 8000ppm Since the magnetic flux density decreases or the sintering temperature at which a high sintering density is obtained becomes narrower, and the productivity becomes worse, 2000 to 8000 ppm
Is preferred.

Also, C may be mixed from the raw material or added as a binder or a lubricant in order to improve the powder formability, but the content of 200 ppm or more has an effect of preventing grain boundary preferential corrosion as described above, High coercive force (iHc) above 2000ppm
Is not obtained, so the content is preferably 200 to 2000 ppm.

Manufacturing Method The permanent magnet having the above composition according to the present invention exhibits excellent corrosion resistance and magnet properties as a magnetic anisotropic sintered magnet by the method described below.

First, an alloy powder having a Fe-BR composition as a starting material is obtained.

After the usual alloy melting, for example, an alloy ingot obtained by cooling under conditions that do not become amorphous, such as casting, may be pulverized and classified into an alloy powder by classification, blending, or the like, or may be directly reduced from a rare earth oxide by a direct reduction method ( An alloy powder obtained according to JP-A-59-219404) can be used.

The average particle size of the alloy powder that has undergone the coarse pulverization and fine pulverization steps described below is in the range of 0.5 to 10 μm. In order to obtain excellent magnet properties, the average particle size is most preferably from 1.0 to 5 μm.

The coarse pulverization is performed by a jaw crusher, a stamp mill, a disk mill or the like. Milling is also a wet grinding grinding in a solvent, but can be either dry pulverization trituration with atmosphere dry such as N ₂ gas, the present invention is a powder particle size that can achieve a higher coercive force Pulverization by a jet mill that can obtain a uniform powder is used.

In particular, in the present invention, the halogen element X as a halide such as LiX is added to the coarsely pulverized alloy powder before the jet mill pulverization, or the finely pulverized alloy powder pulverized by the jet mill is used as a halide such as LiX. By adding and mixing the halogen element X in the form, it becomes easy to be contained in the R-rich grain boundary precipitation phase in the sintered body, and 80% or more of the halogen element X becomes the R-rich grain boundary precipitation in the sintered body. Contained in the phase to prevent grain boundary preferential corrosion.

The addition is LiX and LiF halogen element X, fluorides such as _{AlF 3, AlX 3, MAlX 3} (M is a metal element K, Ca, Co, Cr, etc.), Li ₂
May be carried out in the form of a halide such as MF _6, RCl ₂ with hygroscopic, RCl _3, CaCl _2, etc., it is not preferable because flowability becomes mass absorbs moisture lowers the humidity high plant environment, In particular, LiX has no hygroscopicity, and only Li disappears during the production process, so that it is preferable in industrial production.

As an example, the pulverizing step includes a coarse pulverizing step and a fine pulverizing step. X is LiF, AlF ₃ , Al
X ₃ , MAlX ₃ , Li ₂ MF _{6 and the} like are added, and in a pulverization step of pulverizing several μm by a jet mill, these additives are finely divided and can be uniformly dispersed in the R-rich phase.

After the above coarse pulverization, the halogen element X was added to LiX, A
_{lF 3, AlX 3, MAlX 3} , by mixing a powder such as Li ₂ MF ₆ can be uniformly dispersed in the R-rich phase.

Next, the alloy powder is molded, and the molding method can be performed in the same manner as a normal powder metallurgy method, and pressure molding is preferable.
In order to make the alloy anisotropic, for example, the alloy powder is pressed at a pressure of 0.5 to 3.0 ton / cm ^{2 in} a magnetic field of 5 kOe or more.

The sintering of the molded body may be performed at a predetermined temperature of 900 to 1200 ° C. in a normal reducing or non-oxidizing atmosphere.

For example, this compact is not placed in a vacuum of 10 ^-2 Torr or less,
Sintering is carried out in an atmosphere of an inert gas or a reducing gas having a purity of 1 to 76 Torr and a purity of 99% or more at a temperature of 900 to 1200 ° C. for 0.5 to 4 hours.

The sintering is performed by adjusting conditions such as temperature and time so as to obtain a predetermined crystal grain size and sintering density.

The density of the sintered body is preferably 95% or more of the theoretical density (ratio) in terms of magnetic properties, corrosion resistance and bending strength.
At 40-1160 ° C., a density of more than 7.2 g / cm ³ is obtained, which corresponds to more than 95% of the theoretical density. Furthermore, sintering at 1060 to 1120 ° C. reaches a theoretical density ratio of 99% or more, which is particularly preferable.

The obtained sintered body is heat-treated at 430 ° C. to 900 ° C. for 0.1 hour to 10 hours. Such heat treatment is performed, for example, in a vacuum or in an atmosphere of an inert gas or a reducing gas. Also,
It may be kept at a predetermined temperature, and if it is within such a temperature range, it may be gradually cooled, or may be kept at a temperature of 650 to 900 ° C. once for 5 minutes to 10 hours after sintering within the temperature range, A multi-stage aging treatment of two or more stages in which heat treatment is performed at a lower temperature than the upper stage is also effective.

The surface of the obtained magnet body is coated with a corrosion-resistant metal plating layer by an electroless plating method or an electrolytic plating method, or a resin layer or the like, and is further subjected to an aluminum chromate treatment to enhance the corrosion resistance. Layer treatment.

EXAMPLES Example 1 Nd _14.5 Dy _0.5 Fe _bal B ₇ Cu _0.03 was obtained by using commercially available ferrobon (equivalent to JIS G 2318 FBL1), pure Cu and pure Al as Nd, Dy, electrolytic iron and B having a purity of 97 wt%. An Al _0.2 alloy was melted by high frequency melting and then cast into a mold to obtain an ingot.

These ingots were coarsely pulverized with a motor grinder and finely pulverized in a N ₂ gas with a jet mill to obtain fine powder having an average particle size of 2.6 to 3.3 μm.

At this time, after the ingot was coarsely pulverized, 0.1% by weight of LiF was added to (A) (the present invention) and nothing was added to (B) (comparative example) using a jet mill.

This raw material powder was pressed under a magnetic field of 10 kOe at a pressure of 1.5 ton / cm ² , and the obtained green compact was sintered at 1080 ° C. for 3 hours and further subjected to a heat treatment at 600 ° C. for 1 hour. . afterwards,
A 0.2mm thin magnet was created by machining.

After the obtained thin magnet was coated with an epoxy resin to a thickness of 50 μm, the bending strength was measured, and after exposing to 80 ° C. and 90% RH for 1000 hours, the bending strength was measured. Table 1 shows the measurement results. The bending strength test is based on the following equation.

As is clear from Table 1, it is understood that the transverse rupture strength was significantly reduced when F was not added.

S = 3Pl / 2bt ² S = Bending force (kg / mm ² ), P = Forced force (k
g), t = magnet thickness (mm), b = width of magnet cross section (mm) l = distance between fulcrum points of magnet Example 2 Magnetization (A) (the present invention) in the same manner as in Example 1
And (B) (Comparative Example) were subjected to various surface treatments as shown in Table 2 and left at 80 ° C. × 90% RH for 1000 hours. Then, the adhesion of the corrosion-resistant film was checked by a grid test (JIS K5400). , ASTM D3359-
83), and the test results are shown in Table 2. The evaluation was evaluated as x when a slight defect occurred in the corrosion resistant film. The test specimen was 20 mm × 10 mm × 8 mm.

Example 3 In the same manner as in Example 1, Nd ₁₀ Pr _4.5 Dy _0.5 Fe _bal B ₇ Cu _0.06 Al _{0.05 to 2.5} X
_Magnets of 0 to _1.3 (0 when X is less than 0.01) were prepared. Incidentally, the halogen X was added to the coarsely pulverized powder in the form of KAlX _4. No. ^* is a comparative example.

0.2mm × 19mm × 10m from various halogen-added magnets
After forming a thin magnet having a thickness of 50 m and coating the surface with an epoxy resin having a thickness of 50 μm, the bending strength after exposure to 80 ° C. × 90 ° C. for 1000 hours was measured in the same manner as in Example 1. The results are shown in Table 3, where 20 kg / mm ² or more is indicated by ○, and less than 20 kg / mm ² is indicated by ×.

After coating the same size on a 20mm x 10mm x 8mm test piece, measure the magnet properties, and after PCT test, 60 hours or 80 ℃ x 90% RH for 1000 hours, check the adhesion of the corrosion resistant film The evaluation was based on an eye test (JIS K5400, ASTM D3359-83). The evaluation was evaluated as x when a slight defect occurred in the corrosion resistant film. Table 3 shows the results.

As shown in Table 3, in the example in which the halogen element X was not added (No. 6) and the example in which the addition amount of Al was small (No. 1), the film peeling resistance did not satisfy the desired characteristics.

In addition, in the example in which the halogen element X was added beyond the limited range (No. 9) and in the example in which the addition amount of Al was too large (No. 5), the magnetic properties were deteriorated.

Further, as in the example (No. 11) and the example (No. 14),
_{If the} amount of C and C is too large, the desired film peeling resistance can be obtained, but the magnetic properties (particularly iHc) are lowered.
Therefore, in order to obtain the effect of adding the halogen element X to be added together with Cu and Al, which is a feature of the present invention, O ₂ is 2,000 to 80.
Preferably, 200 ppm and 200 ppm of C are contained.

Effect of the Invention The sintered permanent magnet obtained by the present invention is obtained by adding a halogen element to a coarsely pulverized powder and then finely pulverizing with a jet mill, or finely pulverizing with a jet mill, and then adding a halogen to the finely pulverized powder. By adding the element as a halide, the halogen element is easily contained in the R-rich grain boundary precipitation phase in the sintered body together with Cu and Al,
As a result, grain boundary preferential corrosion is prevented. (1) The magnet was processed into a thin magnet having a thickness of 1 mm or less, exposed to a high-temperature, high-humidity environment after surface treatment with a known resin coating or metal film, etc. The reduction in bending strength at the time is improved.

(2) After surface treatment, after exposure to a high-temperature and high-humidity environment, a decrease in adhesion strength of a corrosion-resistant film such as a resin or a metal film is improved and excellent corrosion resistance is exhibited.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akira Makita 2-15-17 Egawa, Shimamoto-cho, Mishima-gun, Osaka Pref. Yamazaki Works, Sumitomo Special Metals Co., Ltd. (56) References JP-A-62-188746 (JP, A)

Claims (1)

(57) [Claims] 1. Rare earth R 13 at% to 16 at%, wherein R is one or two of Pr and Nd, or one or two of Dy and Tb in addition to the above elements and contained as unavoidable impurities 0.8 ≦ (Pr + Nd + Dy + Tb) /R≦1.0, B 6at% ~ 9at%, Cu 0.01at% ~ 0.5at%, Al 0.1at% ~ 2at%, X 0.01 at% to 1.0 at%, where X is at least one of halogen elements F, Cl, Br and I, balance Fe and Co 71.5 at% to 81 at%, provided that 0 ≦ Co / (Fe + Co) ≦ 0.4, A step of coarsely pulverizing an alloy consisting of elements other than X, in producing a sintered permanent magnet material containing X in the R-rich grain boundary precipitation phase in a sintered body together with Cu and Al, A step of finely pulverizing the obtained coarsely pulverized powder with a jet mill, and a step of subjecting the obtained finely pulverized powder to pressure molding, sintering and heat treatment in a magnetic field Oite method of the coarsely pulverized powder or highly corrosion resistant sintered permanent magnetic material to be added X to finely ground powder as halides.