JPH0422007B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Field This invention relates to a permanent magnet whose main components are R (R is at least one rare earth element including Y), B, and Fe, and the surface of the R-Fe-B permanent magnet is acid-resistant. This invention relates to rare earth/iron/boron based permanent magnets that have improved oxidation resistance by sequentially coating with a chemical conversion film and a resin layer. BACKGROUND ART Permanent magnetic materials are one of the extremely important electrical and electronic materials used in a wide range of fields, from various household appliances to peripheral terminal equipment for large computers. The miniaturization of electrical and electronic equipment in recent years,
With the demand for higher efficiency, permanent magnet materials are required to have increasingly higher performance. Current typical permanent magnet materials are alnico, hard ferrite and rare earth cobalt magnets. As the cobalt raw material situation has become unstable in recent years, the demand for alnico magnets containing 20 to 30 wt% cobalt has decreased, and inexpensive hard ferrite, whose main component is iron oxide, has become the mainstream magnet material. Summer. On the other hand, rare earth cobalt magnets contain cobalt from 50 to
It is very expensive because it contains 60wt% and uses Sm, which is not included in rare earth ores.
Compared to other magnets, the magnetic properties are much higher,
It has come to be used mainly for small, high value-added magnetic circuits. Therefore, the present inventor first developed R as a new high-performance permanent magnet that does not necessarily contain expensive Sm or Co.
-Proposed a permanent magnet of Fe-B system (R is at least one rare earth element including Y) (Patent application 1983-
No. 145072). In this R-Fe-B permanent magnet, R is Nd or
Using resource-rich light rare earths, mainly Pr,
It is an excellent permanent magnet that has Fe as its main component and exhibits an extremely high energy product of over 25 MGOe. Problems to be Solved by the Invention However, the R-Fe-B permanent magnets having the above-mentioned excellent magnetic properties contain rare earth elements and iron, which tend to oxidize in the air and gradually form oxides. When an R-Fe-B permanent magnet is incorporated into a magnetic circuit, oxides generated on the magnet surface cause a decrease in the output of the magnetic circuit and variations between the magnetic circuits, and the surface oxide may fall off. There was a problem of contamination of peripheral equipment due to The object of the present invention is to provide a novel R-Fe-B permanent magnet with improved oxidation resistance and whose main components are rare earth elements, iron, and boron. Means for Solving the Problems This invention contains R (at least one rare earth element including Y) from 8 atomic% to 30 atomic%, B2 atomic% to 28 atomic%, and Fe42 atomic% to 90 atomic%. This is an R-Fe-B permanent magnet characterized in that the surface of a permanent magnet whose main component is a tetragonal phase is coated with an oxidation-resistant chemical coating and a resin layer in this order. Effect: In order to suppress oxides generated on the surface of an R-Fe-B permanent magnet, this invention provides a strong and stable oxidation-resistant chemical conversion coating on the surface, and then forms a resin layer in a laminated manner. . The oxidation-resistant chemical conversion coating in this invention is preferably a phosphate coating such as zinc phosphate or manganese phosphate, or a chromate coating. 3 μm to 10 μm from the surface, preferably 2 μm to 5 μm in the case of a chromate coating. The oxidation-resistant resin layer laminated on the surface of the oxidation-resistant chemical coating in this invention is made of synthetic resins for paints such as epoxy resins, thermosetting acrylic resins, alkyd resins, melamine resins, and silicone resins, or composite resins of these resins. In addition, for the purpose of rust prevention and improving paint film reinforcement, the above resin may contain rust preventive pigments such as zinc oxide, zinc chromate, red lead, or benzotriazole. It may be something you do. In this invention, the above-mentioned pigment contained in the oxidation-resistant resin may be contained in an amount of 80% or less based on the amount of the resin, and the amount of benzotriazole may be contained in an amount of 1% or less based on the amount of the resin. In addition, in this invention, as a coating method for the oxidation-resistant resin layer applied to the chemical conversion coating coated on the surface of the permanent magnet, general coating methods such as brush coating, spraying, dipping, and electrodeposition are used. This resin layer is applied by baking and then baked.
It is sufficient that the thickness is 5 μm or more; if it exceeds 25 μm, it becomes difficult to obtain dimensional accuracy of the product, so a thickness of 25 μm or less is preferable. Therefore, this invention mainly uses resource-rich light rare earths, mainly Nd and Pr, as R.
By using Fe, B, and R as the main components,
An excellent R-Fe-B permanent magnet having an extremely high energy product of 25 MGOe or more, high residual magnetic flux density, high coercive force, and high oxidation resistance can be obtained at a low cost. Reasons for limiting the composition The reasons for limiting the composition of the permanent magnet according to the present invention will be explained below. The rare earth element R used in the permanent magnet of this invention is
It is a rare earth element that includes yttrium Y, light rare earth elements, and heavy rare earth elements, and at least one of these elements, preferably a light rare earth element such as Nd or Pr, or a mixture with Nd, Pr, etc. is used. That is, R includes neodymium (Nd), praseodymium (Pr), lanthanum (La), cerium (Ce), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), and eurobium (Eu). , samarium (Sm), gadolinium (Gd), thulium (Tm), ytterbium (Yb), lutetium (Lu), and yttrium (Y). 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 new R-Fe-B permanent magnets, and if it is less than 8 atomic %, the crystal structure becomes cubic, which is the same structure as α-iron, resulting in high magnetic properties, especially high coercive force. If it exceeds 30 atomic %, the R-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 8 atomic % to 30 atomic %. B is an essential element in the new R-Fe-B permanent magnet, and if it is less than 2 atom%, it will form a rhombohedral structure and high coercive force (iHc) cannot be obtained;
If it exceeds Br, the amount of B-rich nonmagnetic phase increases and the residual magnetic flux density Br decreases, making it impossible to obtain an excellent permanent magnet. Therefore, B should be in the range of 2 atomic % to 28 atomic %. Fe is an essential element in new R-Fe-B permanent magnets, and if it is less than 42 at%, the residual magnetic flux density
If Br decreases and exceeds 90 atomic %, high coercive force cannot be obtained, so Fe is contained in a range of 42 atomic % to 90 atomic %. In addition, in the alloy for permanent magnets according to the present invention, replacing a portion of Fe with Co can improve the temperature characteristics without impairing the magnetic properties of the resulting magnet, but the amount of Co substitution is If it exceeds 50%, the magnetic properties will deteriorate, which is not preferable. 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 Fe or B can be replaced with 4.0 atomic% or less C, 3.5 atomic% or less P, 2.5 atomic% or less S, 3.5 atomic% or less At least one type of Cu,
By substituting a total amount of 4.0 at% or less,
It is possible to improve the manufacturability and lower the cost of permanent magnets. In addition, at least one of the following additional elements is
It is added to R-Fe-B 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 % or less of Hf.However, if two or more types are contained, the maximum content is less than the atomic percentage of the element having the maximum value among the added elements.
It becomes possible to increase the coercive force of permanent magnets. In the R-Fe-B permanent magnet of this invention,
It is essential that the main crystalline phase be tetragonal, which is effective in obtaining a fine and uniform alloy powder and producing a sintered permanent magnet with excellent magnetic properties. Further, the alloy for permanent magnets of the present invention is characterized by containing a non-magnetic phase (excluding oxide phase) of 1% to 50% by volume, and in the case of a sintered magnet, the particle size is 1 to 50%.
The main phase is a compound with a tetragonal crystal structure in the range of 100 μm. Furthermore, the R-Fe-B permanent magnet of the present invention can be press-molded in a magnetic field to obtain a magnetically anisotropic magnet, and press-molded in a no-magnetic field to obtain a magnetically isotropic magnet. Obtainable. Permanent Magnet Characteristics The R-Fe-B permanent magnet according to the present invention exhibits a coercive force iHc≧1kOe, a residual magnetic flux density Br≧4kG,
The maximum energy product (BH)max is equal to or higher than that of hard ferrite, and in the most preferable composition range, (BH)max≧10MGOe, and the maximum value is
Reach over 25MGOe. In addition, in the composition of the permanent magnet according to the present invention, when the main component of R is 50% or more of light rare earth metals, R12 atomic% to 20 atomic%, B4 atomic% to 24 atomic%, Fe65 atomic% to 82 atomic%. When the main component is Nd, sintered magnets exhibit the best magnetic properties, especially when the light rare earth metal is Nd.
(BH)max reaches its maximum value of 33MGOe or more. 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
%, the balance is Fe and Al5.3%, Si0.7%,
Feroboron alloy consisting of impurities such as C0.03%,
Nd with a purity of 99.7% or higher was used, and after being high-frequency melted, it was cast into a water-cooled copper mold. Note that the above composition is expressed in wt%. 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 molded under a pressure of 1.5 t/cm ² . The obtained compact was sintered at 1100°C for 1 hour in Ar, then allowed to cool, and then sintered in Ar for 600°C.
A permanent magnet according to the present invention was produced by subjecting it to an aging treatment at ℃ for 2 hours. The composition at this time is 14Nd−8.5B−77.5Fe
It was hot. A test piece was cut out from the obtained permanent magnet into a size of 15 mm x 10 mm x 6 mm, and as shown in Table 1, each test piece was degreased, pickled, and then subjected to phosphate treatment A, phosphate treatment B, and phosphate treatment under the following conditions. Perform lead chromate treatment C,
Thereafter, each test piece was treated with the paint and coating conditions shown in Table 1. The coating thickness, magnetic properties, oxidation resistance, adhesive strength, and dimensional accuracy of each test piece after resin coating were measured. The measurement results are shown in Table 2.

【table】

【table】

[Table] In the oxidation resistance test, the above specimen was heated at 60°C and 90°C.
The test piece was evaluated based on the oxidation weight increase when the test piece was left in an atmosphere with a humidity of 30% for 3 days. In the adhesive strength test, the above test piece, which has been treated with a coating film after chemical conversion treatment, is adhered to a holding plate using an adhesive called Araldite AW-106 (trade name), and then a shearing force is applied to the test piece using an Amsler tester. The adhesive strength per area was measured. Dimensional accuracy is measured by measuring the dimensions of the test piece after coating treatment, and is expressed as (maximum value) - (minimum value) = R. For comparison, a test piece with the same components as the example of the present invention was subjected to an oxidation test in the same atmosphere at 60°C and 90% humidity as above, without being subjected to chemical conversion treatment or lamination treatment of coating film treatment. The oxidation weight gain and oxide film thickness (maximum oxide film thickness value) of each sample when left for 1 day, 2 days, and 3 days were evaluated, and the results are shown in Table 3.

【table】

【table】

【table】

【table】

[Table] Effects of the invention As is clear from the examples, an oxide film was formed on the surface of the magnet alloy in the comparative untreated sample during the short-term oxidation test, and oxidation progressed inside as time progressed. As a result, it was confirmed that the magnetic properties had deteriorated. In addition, the increase in the oxide film due to oxidation of the comparative example magnet incorporated in the magnetic circuit is caused by
becomes narrower and narrower, and eventually the void becomes zero, resulting in a decrease in the output of the magnetic circuit and further causing difficulty in operation. On the other hand, the R-Fe-B permanent magnet according to the present invention has an oxidation-resistant chemical coating with high adhesive strength and a resin layer, so it has excellent oxidation resistance as shown in Table 2. it is obvious. Therefore,
When the R-Fe-B permanent magnet having an oxidation-resistant chemical conversion coating and a resin layer according to the present invention is incorporated into a magnetic circuit or the like, it is extremely effective in stabilizing output characteristics and improving reliability.

Claims (1)

[Claims] 1 R (wherein R is at least one rare earth element including Y) 8 to 30 atom%, B2 to 28 atom%, and Fe42 to 90 atom% as main components , A permanent magnet characterized in that the surface of a permanent magnet whose main phase is a tetragonal phase is coated with an oxidation-resistant chemical coating and a resin layer in sequence.