JPH04237103A - Manufacture of resin-coupled type magnet powder having excellent corrosion-resisting property - Google Patents

Abstract

PURPOSE:To prevent deterioration of magnetic characteristics, and to effectively improve corrosion-resisting property by stirring on heating the magnetic powder for magnet corrosion-resisting metal powder in chloride vapor, and the surface of the magnetic powder for magnet is coated with corrosion-resisting metal. CONSTITUTION:Magnetic powder for magnet is the magnetic powder of rare earth-iron-boron permanent magnet, and corrosion-resisting metal powder consists of Ni, Cr or mixed powder of Ni and Cr. By stirring up the above- mentioned magnetic powder for magnet and the corrosion-resisting metal powder in chloride vapor by applying heat, the surface of the magnetic powder for magnet can be coated with corrosion-resisting metal. Also, ammonium chloride, hydrogen chloride and the like can be favourably used for the aforesaid chloride vapor. A fluidized-layer system, a ball mill system and the like are used for agitation of the magnetic powder for magnet and the corrosion-resisting metal powder. Accordingly, a uniform film is formed on the surface of the magnetic powder as a whole. As a result, complete coating and surface treatment can be conducted, and sufficient oxidation-resisting property and corrosion-resisting property can be obtained.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to surface treatment for the purpose of imparting corrosion resistance to magnetic powder for resin-bonded magnets, for example, magnetic powder for magnets made of intermetallic compounds or alloys containing rare earth metals and transition metals as main components. It is related to.

0002

2. Description of the Related Art Permanent magnetic materials are widely used as one of the most important materials for electronic devices, ranging from large-scale nuclear fusion plasma devices and computer peripherals to home appliances. By the way, in recent years, with the increasing performance and miniaturization of electronic devices, permanent magnet materials are also required to have higher performance, and one of the most important evaluation items is the energy product. Permanent magnet materials made of intermetallic compounds or alloys as main components are attracting attention because of their high energy product, and among them, rare earth, iron, and boron-based permanent magnet materials are expected to have particularly high energy products and low raw material costs. ing.

However, although rare earth/iron/boron based permanent magnet materials have the advantage of high energy product, their main components are oxidation and
Because it contains large amounts of rare earth elements and iron that are easily corroded, it is used extensively because it may cause deterioration of magnet performance due to oxidation and corrosion on the surface, and contamination and failure of equipment due to peeled surface oxidation and corrosive substances. This has not yet been achieved. Therefore,
In order to improve the drawbacks of this rare earth/iron/boron based permanent magnet material, it is necessary to impart oxidation resistance by adding a fourth element (for example, Japanese Patent Application Laid-Open No. 61-217549), and to improve oxidation resistance on the surface of the permanent magnet. plating of metallic metals (for example, JP-A-60-5
4406), vapor deposition of metals and inorganic compounds (for example, JP-A-61-163266), diffusion coating of base metals (
JP-A-61-185910), silica glass coating (JP-A-63-9103), resin coating (JP-A-63-9103)
0-63902) and the like have been proposed. However, these methods all provide oxidation resistance to a sintered or cast magnet molded body, and cannot be used for the resin-bonded magnet that is the object of the present invention.

By the way, as mentioned above, casting and sintering methods have traditionally been used as methods for molding permanent magnets, but recently, molding is easier and complex shapes can be molded.
Moreover, the application of resin-bonded magnets, which can be easily made anisotropic, is expanding. This involves mixing raw material magnetic powder for permanent magnets with resin and processing the mixture into a desired shape using a pressure molding method such as injection molding, extrusion molding, or compression molding. When rare earth, iron, and boron based permanent magnet materials are applied to resin-bonded permanent magnets, oxidation and corrosion particles fall off from the magnet molded body due to oxidation and corrosion of the magnetic particles, making oxidation and corrosion resistance problems even more serious. It becomes serious.

Therefore, in order to improve the corrosion resistance of powder particles of rare earth elements, transition metals, and boron alloys in resin-bonded magnets, Japanese Patent Application Laid-Open No. 60-63902 introduces the particles into a plasma flame. , a method of forcibly oxidizing the surface has been proposed.

[0006]

[Problems to be Solved by the Invention] However, with conventional methods, (1) coating and surface treatment are incomplete and sufficient oxidation and corrosion resistance cannot be obtained; (2) coating and surface treatment processes are insufficient. Complicated and inefficient (3
Problems remained, including (4) insufficient durability of the coating and surface treatment, and (4) the volume fraction of the magnet decreased due to the coating and surface treatment, resulting in deterioration of magnetic properties.

[0007]Also, it is possible to apply a metal coating to the surface of the magnetic powder particles by plating, but (1) the coating layer has many defects and the required oxidation resistance and corrosion resistance cannot be obtained, making the coating thicker. (2) Plating bath management is complicated and productivity is poor.

The present invention advantageously solves the above-mentioned problems, and proposes a method for manufacturing magnetic powder for resin-bonded magnets that effectively improves corrosion resistance without causing deterioration of characteristics. The purpose is to

[0009]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides corrosion-resistant properties on the surface of magnetic powder for magnets by heating and stirring magnetic powder for magnets and corrosion-resistant metal powder in chloride vapor. This is a method for producing magnetic powder for a corrosion-resistant resin-bonded magnet, which is coated with a magnetic metal. The present invention is particularly effective for sintered magnets made of intermetallic compounds or alloys containing rare earth metals and transition metals as main components, and magnetic powder made of intermetallic compounds or alloys containing rare earth metals and transition metals as main components. Further, as the corrosion-resistant metal, Cr, Ni, Co, etc. are effective.

Further, as the chloride vapor, ammonium chloride, hydrogen chloride, etc. can be advantageously used. A fluidized bed method, a ball mill method, or the like can be used to stir the magnetic powder for the magnet and the corrosion-resistant metal powder.

[0011]

[Operation] In the present invention, magnetic powder is heated and stirred in chloride vapor together with a powder containing a corrosion-resistant metal. At this time, in the lower temperature part of the powder containing the magnetic powder and the corrosion-resistant metal, the magnetic powder-constituting metal and the corrosion-resistant metal are chlorinated to generate metal chloride vapor. In addition, at higher temperature areas, the aforementioned metal chloride vapor decomposes on the surface of the magnetic powder to form a metal coating containing a corrosion-resistant metal. In this way, the formation of a coating originates from temperature non-uniformity,
Since the entire powder containing the magnetic powder and the corrosion-resistant metal is stirred, a uniform coating is formed on the surface of the magnetic powder as a whole. Generally, it is sufficient that the above-mentioned temperature non-uniformity occurs naturally, but coating formation can also be promoted by intentionally providing a temperature distribution.

0012

[Examples] Examples and comparative examples of the present invention include Nd2
Magnetic powder obtained by melting a metal with a composition represented by Fe14B2, rapidly solidifying it, and pulverizing it is used as a raw material, and its properties are as follows.
A raw material mixed with 49 parts of magnetic powder and 1 part of epoxy resin powder,
After dry press molding at a press pressure of 6 ton/cm2, curing was performed at 170° C. for 1 hour in a nitrogen atmosphere to harden the epoxy resin, which was processed into a resin-bonded magnet and evaluated.

Example 1 Vaporized ammonium chloride was blown from the bottom of the processing container into which raw magnetic powder and metal Cr powder were mixed and charged, and the processing container was turned into a fluidized bed while the mixed powder of raw material magnetic powder and metal Cr powder was being fluidized. It was heated to 340°C and coated to a thickness of 800 Å. Example 2 A mixed powder of metallic Ni powder instead of the metallic Cr powder of Example 1 was heated to 300° C. while forming a fluidized bed and coated to a thickness of 500 Å.

Example 3 Vaporized ammonium chloride was introduced into a container of a rotary ball mill containing a mixture of raw material magnetic powder and metal Cr+Ni powder, and the container was opened while the mixed powder of raw material magnetic powder and metal powder was being mixed by rotation. It was heated to 350°C and coated to a thickness of 1000 Å. Example 4 A mixed powder of metal Cr powder was used in place of the metal powder Cr+Ni in Example 3. Other treatment conditions were the same as in Example 3.

Comparative Example 1 After degreasing raw magnetic powder with ethanol, it was immersed in a plating bath in which 3 parts of nickel chloride, 1 part of sodium hypophosphite, and 5 parts of ammonium chloride were dissolved in 100 parts of water, and heated to 90°C while stirring. Electroless nickel plating was performed while maintaining the temperature to a coating thickness of 800 Å. Comparative Example 2 Nickel electroless plating was performed under the same conditions as Comparative Example 1 until the thickness was 7500 Å.

The prepared samples were evaluated for energy product by measuring demagnetization curves, and were subjected to moisture resistance tests and salt spray tests. The humidity resistance test was performed by exposing the product to a constant temperature and humidity chamber at 80°C and 95% RH for 1000 hours, and evaluating the number of rust spots in 100 samples.The salt spray test was performed using 5% salt water at 35°C.
It was sprayed for 100 hours and evaluated by the number of rusted particles in 100 samples. The manufacturing conditions and evaluation results of Examples and Comparative Examples are shown in Tables 1 and 2.

According to the examples of the present invention, sufficient corrosion resistance can be obtained with a thin coating, whereas in the comparative examples, sufficient corrosion resistance cannot be obtained unless the coating thickness is increased to the extent that the energy product deteriorates. Not yet.

[0018]

By using the present invention, it is possible to obtain metal-coated magnetic powder used in resin-bonded magnets that exhibits sufficient corrosion resistance even with a thin coating thickness and has no deterioration in energy product. Furthermore, a corrosion-resistant metal can be coated by a simple method without using a treatment bath that is complicated to manage.

Claims (3)

[Claims] 1. A resin with excellent corrosion resistance, characterized in that the surface of the magnetic powder for a magnet is coated with a corrosion-resistant metal by heating and stirring the magnetic powder for a magnet and the corrosion-resistant metal powder in chloride vapor. A method for manufacturing magnetic powder for bonded magnets. 2. The method for producing magnetic powder for resin-bonded magnets with excellent corrosion resistance according to claim 1, wherein the magnetic powder for magnets is powder of rare earth, iron, and boron based permanent magnets. 3. The corrosion-resistant metal powder is made of Ni, Cr or N.
3. The method for producing magnetic powder for a resin-bonded magnet with excellent corrosion resistance according to claim 1 or 2, wherein the powder is a mixed powder of i and Cr.