JPH0422010B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Field The present invention relates to a cylindrical permanent magnet whose main components are R (R is at least one of rare earth elements including Y), B, and Fe, and which has a magnetic difference in the radial direction of the cylinder. The present invention relates to a cylindrical radially anisotropic permanent magnet body that has anisotropy and has excellent magnetic properties, oxidation resistance, and strength. Conventional technology In general, permanent magnets used in motors are isotropic cylindrical magnets for low output, and anisotropic arcuate magnets assembled into a cylindrical shape for high output. To simplify the assembly process of high-power magnets, integrally molded cylindrical permanent magnets are MO・6Fe ₂ O ₃
(M; Sr, Ba, Pb) hard ferrite is proposed. In addition, with the recent demand for smaller size and higher efficiency of electrical and electronic equipment, there is also a demand for smaller and lighter motors. However, the use of hard ferrite, which has low magnetism, limits the ability to reduce the size and weight of motors, and the application of rare earth Co magnets, which have the best magnetic properties, is currently being considered. However, this rare earth Co magnet contains 50~60wt% Co.
In addition, it is very expensive because it uses Sm, which is not contained in rare earth ores.Although it is manufactured using the normal sintering method, the strength of the sintered body is weak.
Due to problems such as easy breakage after sintering, it is difficult to manufacture an integrally molded cylindrical radially anisotropic permanent magnet body, which further increases the price and makes it difficult to apply it to make motors smaller and lighter. It was hot. To solve this problem, a bonding method has been proposed in which magnet powder is bonded and solidified with a resin or metal binder. Furthermore, rare earth Co magnets range from R ₁ Co ₅ to R ₂ Co ₁₇
The system has high performance and is resource-saving, but even if the bond method is used, the main components are expensive Sm and Co, making it very expensive. Problems to be Solved by the Invention The present inventor previously developed Fe-B as a new high-performance permanent magnet that does not necessarily contain expensive Sm or Co.
-Fe-B-R system based on R ternary compound (R is at least one rare earth element including Y)
Permanent magnets were proposed (Japanese Patent Application No. 145072/1983, Patent Application No. 166663/1983, Patent Application No. 200204/1983, Patent Application No. 1983)
−5813). They also proposed a resin magnet obtained by kneading Fe-BR alloy powder and a binder (Japanese Patent Application No. 171909/1982). In this Fe-BR-based permanent magnet, R is Nd or
Using resource-rich light rare earths, mainly Pr,
It is an excellent permanent magnet that has Fe, B, and R as its main components and can obtain an extremely high energy product of 25 MGOe or more. In these systems, B is not used as a type of amorphous promoting element as conventionally known, but as an essential element for forming the Fe--B--R ternary compound. However, the Fe-B-R permanent magnet body, which has the above-mentioned excellent magnetic properties, contains rare earth elements and iron, which tend to oxidize in the air and gradually produce stable oxides, so it cannot be used in magnetic circuits. When incorporated, oxides generated on the magnet surface cause
This caused a decrease in the output of the magnetic circuit and variations between the magnetic circuits, and there was also the problem of contamination of peripheral equipment due to shedding of surface oxide. The present invention provides an Fe-BR-based permanent magnet body that has excellent magnetic properties and can achieve miniaturization and weight reduction of the motor in an integrally molded cylindrical radially anisotropic permanent magnet body for such a motor. It is an object. Means for Solving the Problems The inventor conducted various studies to obtain a high-performance, compact, and lightweight magnetic circuit using this new permanent magnet, and found that the average particle size of sintered magnets was By filling the die molding space with magnet raw material powder of the desired composition of 0.5 to 50 μm, press-molding in a magnetic field while applying a magnetic field radially in the radial direction of the compact, then sintering, and further aging treatment.
Br 12kG or more, iHc 11kOe or more, (BH) max
It was discovered that a cylindrical radially anisotropic permanent magnet body having extremely excellent magnetic properties and strength of 35 MGOe or more and a bending strength of 25 Kg/mm ² or more can be obtained. In addition, by coating the surface of the cylindrical radially anisotropic Fe-B-R permanent magnet with an oxidation-resistant plating layer, resin layer, or chemical conversion coating layer, a strong and stable oxidation-resistant coating layer can be obtained. It was discovered that the formation of oxides on the surface can be suppressed for a long period of time, and that excellent oxidation resistance and strength can be obtained, especially by providing a metal plating such as Ni to the required thickness. That is, this invention provides R (where R is at least one kind of rare earth elements including Y) from 12 atomic % to 20 atomic %.
atomic%, B4 atomic% ~ 24 atomic%, Fe65 atomic% ~ 82
This permanent magnet is characterized by having atomic percent as a main component, having magnetic anisotropy radially in the radial direction of the cylindrical magnet, and having its surface coated with an oxidation-resistant film layer. Function The reasons for limiting the composition of the permanent magnet body according to the present invention will be explained below. Rare earth element R used in the permanent magnet body of this invention
is a rare earth element that includes yttrium (Y) and includes light rare earths and heavy rare earths, and at least one of these, preferably light rare earths such as Nd and Pr, or a mixture with Nd, Pr, etc. Use. In addition, it is usually sufficient to have one type of R, but in practice, a mixture of two or more types (Mitsushimetal, didymium, etc.) can be used for reasons such as availability, Sm, Y, La, Ce, Gd etc. are other R, especially
It can be used as a mixture with Nd, Pr, etc. Note that this R may not be a pure rare earth element,
It may contain impurities that are unavoidable during production within an industrially available range. R is an essential element in the new above-mentioned permanent magnet body, and if it is less than 12 atomic %, the crystal structure becomes a cubic structure that is the same as α-iron, so high magnetic properties, especially high coercive force, cannot be obtained. If it exceeds 20 atomic%, R
The rich nonmagnetic phase increases, the residual magnetic flux density (Br) decreases, and a permanent magnet with excellent characteristics cannot be obtained. Therefore, R should be in the range of 12 atomic % to 20 atomic %. Further, it is necessary that light rare earth metals account for 50% or more of R. Furthermore, replacing 1 to 30% of a part of R with one or more of the heavy rare earth elements Dy, Tb, Ho, Gd, Er, and Yb can improve the coercive force and the maximum energy product. B is an essential element in the new above-mentioned permanent magnet. If it is less than 4 at%, it will form a rhombohedral structure and a high coercive force (iHc) will not be obtained, and if it exceeds 24 at%, it will form a B-rich nonmagnetic phase. increases, and the residual magnetic flux density (Br) decreases, making it impossible to obtain an excellent permanent magnet. Therefore, B is in the range of 4 at.% to 24 at.%. Fe is an essential element in the new above-mentioned permanent magnet.If it is less than 65 at%, the residual magnetic flux density (Br) decreases, and if it exceeds 82 at%, high coercive force cannot be obtained. % to 82 atomic %. Further, in the permanent magnet body according to the present invention,
Substituting a portion of Fe with Co can improve the temperature characteristics of the resulting magnet without impairing its magnetic properties, but if the amount of Co substitution exceeds 50% of Fe,
On the contrary, it is not preferable because the magnetic properties deteriorate. Further, the permanent magnet according to the present invention has R, B,
In addition to Fe, the presence of unavoidable impurities in industrial production can be tolerated, but a portion of B can be replaced with 4.0 atomic % or less of C,
At least one of P below 3.5 atom%, S below 2.5 atom%, Cu below 3.5 atom%, total amount 4.0
By substituting atomic percent or less, it is possible to improve the manufacturability and reduce the cost of permanent magnets. In addition, at least one of the following additional elements is
It is added to R-B-Fe permanent magnets because it is effective in improving coercive force, etc., improving manufacturability, and reducing costs. However, addition to improve coercive force causes a decrease in residual magnetic flux density (Br), so it is desirable to add in a range that is equal to or higher than the residual magnetic flux density of conventional hard ferrite magnets. Al less than 9.5 atom%, Ti less than 4.5 atom%, V less than 9.5 atom%, Cr less than 8.5 atom%, Mn less than 8.0 atom%, Bi less than 5 atom%, Nb less than 12.5 atom%, 10.5 Ta less than 9.5 atom%, Mo less than 9.5 atom%, W less than 9.5 atom%, Sb less than 2.5 atom%, Ge less than 7 atom%, Sn less than 3.5 atom%, Zr less than 5.5 atom%, 5.5 atom Permanent magnet It becomes possible to increase the coercive force of the body. In the R-B-Fe permanent magnet of this invention,
It is essential that the main crystal phase be tetragonal, which is particularly effective in obtaining fine and uniform alloy powder and producing a sintered permanent magnet having excellent magnetic properties. In addition, the alloy for permanent magnets of the present invention has a main phase of a compound having a tetragonal crystal structure with a grain size in the range of 1 to 100 μm, and in particular, the volume ratio is 1% to 50%.
Containing a non-magnetic phase (excluding non-magnetic intermetallic compounds and oxide phases) is essential for producing a bonded magnet with excellent magnetic properties. Oxidation-resistant film layer When the oxidation-resistant film layer in this invention is a plating layer, it is plated with a metal or alloy having oxidation resistance such as Ni, Cu, or Zn, or a composite plating thereof with a thickness of 25 μm or less. The plating method is electroless plating or electrolytic plating,
Alternatively, a method using the above-mentioned plating in combination may be used.
Further, the oxidation-resistant plating layer in the present invention has no effect on the magnetic properties of the permanent magnet. In addition, if the thickness of the oxidation-resistant plating layer exceeds 25 μm, the strength of the plating film will deteriorate, it will be difficult to obtain dimensional accuracy of the product, and the plating process will take a long time. However, since this is not preferable in terms of cost, the thickness of the plating layer must be 25 μm or less. For example, in the case of composite plating such as Cu base, Ni plating, Ni electroless plating base, Ni electrolytic plating, etc., the thickness is 5 μm to 15 μm, in the case of Ni plating and Cu plating, the thickness is 5 μm to 15 μm, and the Zn plating is In case of
A plated layer with a thickness of 5 μm to 15 μm is most preferable from the viewpoint of not only oxidation resistance but also strength and cost. In addition, when the oxidation-resistant coating layer is an oxidation-resistant resin layer,
With a layer thickness of 25 μm or less, the resin may be a synthetic resin for coatings such as epoxy resin, thermosetting acrylic resin, alkyd resin, melamine resin, silicone resin, or a composite resin of these resins. For the purpose of improving membrane reinforcement, the above resins contain rust-preventing pigments such as zinc oxide, zinc chromate, red lead, etc. in an amount of 80% or less based on the amount of resin, and if benzotriazole is included, it is The content may be 1% or less. In addition, in the case of an oxidation-resistant coating layer consisting of an oxidation-resistant chemical conversion coating, a phosphate coating such as zinc phosphate or manganese phosphate or a chromate coating is preferable, and the surface of these chemical conversion coatings is further coated with a paint or resin layer. Good too. In this invention, the thickness of the chemical conversion coating is preferably 3 μm to 10 μm in the case of a phosphate film, and 2 μm to 5 μm in the case of a chromate film. Examples Examples according to the present invention will be shown below to clarify its effects. As a starting material, electrolytic iron with a purity of 99.9%, B19.4
Feroboron alloy with a purity of 99.7% or more, with the remainder consisting of Fe and impurities such as Al, Si, and C.
These were radio-frequency melted using Nd and then cast into water-cooled molds. Thereafter, the ingot was coarsely ground with a stamp mill to a throughput of 35 meshes, and then ground with a ball mill for 3 hours to obtain a fine powder with a particle size of 3 to 10 μm. This fine powder was inserted into a mold, oriented in a magnetic field of 10 kOe, and heated at a pressure of ² t/cm2.
It was molded into a cylindrical body with a height of 13 mm. The obtained compact was sintered at 1100°C for 1 hour in Ar, then allowed to cool, and further sintered in Ar.
A cylindrical radially anisotropic permanent magnet according to the present invention was produced by aging at 600°C for 2 hours. The component composition of the magnet at this time is 15Nd−8B−
It was 77Fe. Test pieces with dimensions of 13 mm x 8 mm x 6 mm were cut out from the obtained permanent magnet body, and each test piece was plated under the plating conditions shown in Table 1. The magnetic properties and oxidation resistance of each sample after plating were evaluated. , the adhesive strength was measured. The results are shown in Table 2. The oxidation resistance shown in Table 2 was evaluated based on the oxidation weight gain and oxide film thickness of the test piece when the test piece was left in an atmosphere of 60° C. and 90% humidity for 3 days.
Note that the oxide film thickness is expressed as the maximum thickness of the oxide film. In addition, the adhesive strength was determined by gluing the above-mentioned test piece after plating treatment to a holding plate with an adhesive called Araldite AW-106 (trade name), and then applying shear force to the test piece using an Amsler tester. The adhesive strength was measured. For comparison, Table 3 shows a non-plated sample with the same components as the example of the present invention as an oxidation test.
The oxidation weight gain and oxide film thickness of each sample after being left for 3 days were evaluated. As is clear from Tables 2 and 3, an oxide film was formed on the surface of the magnet alloy during the short-term oxidation test for the unplated sample, and as time progressed, the oxidation progressed internally, resulting in magnetic properties. In addition, as the oxide film increases due to oxidation of the magnet incorporated in the magnetic circuit, the space in the magnetic circuit becomes increasingly narrow, and eventually the space becomes 0. However, the permanent magnet according to the present invention has excellent oxidation resistance, and when incorporated into a magnetic circuit, it can stabilize output characteristics and improve reliability. It turns out that it is extremely effective.

【table】

【table】

[Table] Effects of the Invention The cylindrical radially anisotropic permanent magnet body according to the present invention has extremely excellent magnetic properties, and even if it is a sintered magnet, it has superior strength to the conventional rare earth Co sintered magnet. and further consists of the required composition.
By coating the surface of the Fe-BR-based cylindrical permanent magnet with an oxidation-resistant plating layer, a resin layer, or a chemical conversion coating layer, a strong and stable oxidation-resistant coating layer can be obtained, and the oxides generated on the surface. can be suppressed for a long time,
In particular, when plated with metal such as Ni to the required thickness, excellent oxidation resistance and strength can be obtained, making this cylindrical radially anisotropic permanent magnet ideal for downsizing and reducing the weight of motors.

Claims (1)

[Claims] 1 R (R is at least one rare earth element including Y) 12 atomic% to 20 atomic%, B4 atomic% to
The main components are 24 at%, Fe65 at% to 82 at%,
A permanent magnet body characterized by having magnetic anisotropy radially in the radial direction of the cylindrical magnet body and having an oxidation-resistant coating layer coated on the surface.