JPS61253302A - Treatment of magnetic powder - Google Patents

Abstract

PURPOSE:To prevent the oxidation deterioration during the process for production and using of a magnet by bringing magnetic powder consisting of an intermetallic compd. with a specific phosphorus compd. and exposing the same to an oxygen-contg. atmosphere. CONSTITUTION:The magnetic powder consisting of the intermetallic compd. contg. a rare earth element such as Sm and ferrous metal a sesential constituting components is brought into contact with the phosphorus compd. of a phosphoric acid, etc. having active proton of <=4pKa. The powder is exposed to the atmosphere contg. oxygen such as air simultaneously or after the contact. The exposing time is usually several minutes to several hours. The powder is substantially kept free from oxidation during the process of production and use of the magnet when the rare earth magnet powder treated by the above- mentioned method is used. The safe and easy production of the rare earth plastic magnetic having a magnetic characteristic is thus made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for processing magnetic powder. Specifically, it is an intermetallic compound whose main constituents are rare earth metals and iron group metals, which have high crystal magnetic anisotropy and whose powder is useful as a raw material for rare earth plastic magnets, such as RCo 5 series, R
The present invention relates to a treatment method for preventing oxidative deterioration of powder of a 2Co17-based (R is a rare earth element) Nd-Fe-B-based intermetallic compound.

[Conventional technology]

Plastic magnets are generally manufactured by kneading magnetic powder in the range of 1 to 150 μs with liquid thermosetting resin or molten thermoplastic resin, and using ordinary plastic molding methods such as compression molding, injection molding, and extrusion molding. Ru. Unlike magnets made by sintering or casting, it is easy to mold.
It has the characteristics of elasticity and chemical resistance.

Ferrite has traditionally been used as a magnetic powder, but as stronger magnets are required, intermetallic compounds (hereinafter referred to as Attempts have been made to use fine powder of rare earth magnets (abbreviated as rare earth magnets) as magnetic powder.

[Problem that the invention seeks to solve]

When manufacturing plastic magnets, they are exposed to high temperatures when mixed with resin or during molding. Rare earth magnet powder, unlike ferrite, is very easily oxidized as described in, for example, JP-A-54-11iHe and JP-A-54-71031, so it is oxidized during the process of making plastic magnets, and as a result, However, there is a problem in that the magnetic properties of the resulting rare earth plastic magnet are significantly inferior. Furthermore, in extreme cases, oxidation may rapidly progress during production and ignition may occur, posing a safety problem.

Even if the product is manufactured using a method that is less likely to be exposed to high temperatures during manufacturing, such as compression molding, some products may be used near the heat-resistant temperature of the binder resin, and may deteriorate over time due to oxidation during use. However, there was a problem in that the magnetic properties deteriorated over time.

Many methods have been proposed for manufacturing high-performance rare earth plastic magnets, one of which is to coat magnetic powder with a phosphorus compound to reduce the surface friction coefficient of the powder and increase the density of the magnet and the orientation of the magnetic powder. There are methods to improve the performance of magnets using powder methods (for example, Japanese Patent Application Laid-Open No. 57-28
104), this method is characterized in that a phosphorus compound is used as a coating agent instead of conventionally used oil, paraffin, fluororesin, etc.

Phosphorus compounds used range widely, including compounds of the constituent elements of the magnetic powder and phosphorus, organic compounds containing phosphorus, and inorganic compounds, but specifically include manganese phosphates, zinc phosphates, iron phosphates, Zinc phosphate/manganese type, zinc phosphate O calcium type, etc. are listed. All of these are known as main components of a phosphate coating solution for steel sheets. That is, this method is an application of the phosphate film chemical conversion treatment method for ordinary steel sheets to magnetic powder.

The magnetic powder prepared by this method has a film formed on its surface derived from the main component of the phosphate film chemical solution, but its bulk specific gravity is small, and rare earth plastic magnets obtained using this powder as a raw material are The performance was insufficient (see Comparative Example 4!@).

Therefore, an object of the present invention is to provide a method for treating rare earth magnetic powder so as to prevent oxidative deterioration during the manufacturing process and during use of rare earth plastic magnets made from the rare earth magnetic powder.

[Means for solving problems]

The above object of the present invention is achieved by the following method for processing magnetic powder.

A magnetic powder made of an intermetallic compound whose main constituents are rare earth metals and iron group metals is brought into contact with a phosphorus compound having active protons having a pKa of 4 or less, or at the same time, the powder is placed in an oxygen-containing atmosphere. A method for processing magnetic powder, characterized by exposing it to magnetic powder.

In the present invention, fine powder of a rare earth magnet is brought into contact with a phosphorus compound having a proton having a pea of 4 or less, such as phosphoric acid, acidic phosphoric acid esters, dialkyldithiophosphoric acid, phosphorous acid, and acidic phosphite esters. let The method of contact is immersion in a solution of a phosphorus compound. Spray with a solution of phosphorus compounds. Alternatively, a method such as exposure to vapor of a phosphorus compound may be used. Note that the concentration of phosphorus compounds in the solution used for dipping or spraying is normal.

A range of 0.1 to 20 wt% is suitable. Further, the temperature during contact is in the range of room temperature to 100° C., and the contact time is usually in the range of several minutes to several hours.

In the present invention, the rare earth magnet powder is exposed to an oxygen-containing atmosphere, usually air, at the same time as or after the rare earth magnet powder is brought into contact with the phosphorus compound.

The exposure time can vary over a wide range depending on the composition of the rare earth magnet, the degree of growth of crystals, the particle size of the powder, the oxygen concentration of the atmosphere, the temperature, the type of phosphorus compound, and its concentration, but it usually ranges from several minutes to several hours. It is.

In addition, when contacting with a phosphorus compound and exposing it to an atmosphere containing oxygen at the same time, it is better to use the conditions of contact with the phosphorus compound, and when exposing to an atmosphere containing oxygen after contact, the temperature should be set at 50'' to 250℃, or higher. Preferably 50° to 200°C
It is appropriate to expose at a temperature of .

In the present invention, the particle size of the rare earth magnet powder is as follows:
Although it varies depending on the composition, use, etc., 1 to 150 μs, particularly 1 to 100 μs is appropriate.

〔Example〕

The method of the present invention will be explained in more detail with reference to Examples below.

Example 1 Sm 25.8%, Fe 14.7%, Cu 7.7%, Z
r 1.9% Ss+2Co17 magnetic powder (particle size 44 to 63 scales), the remainder of which is GO, was immersed in a 0.5 wt% phosphoric acid aqueous solution at room temperature for 30 minutes, washed with water, and then heated at 80°C for 30 minutes.
Exposure to air for 0 minutes.

97 parts by weight of this powder were mixed with 3 parts by weight of a mixture of epoxy resin and curing agent, compression molded, and then 130 parts by weight
After curing by heating at ℃ for 30 minutes, it was magnetized. The obtained magnet had a magnetic flux density of 0.90 KG after a temperature characteristic test for 800 hours in air at 140°C.

Example 2 The same operation as in Example 1 was performed except that a 5 wt % phosphorous acid methanol solution was used instead of the 0.5 wt % phosphoric acid aqueous solution. The magnetic flux density was 0.92KG.

Example 3 The same magnetic powder as in Example 1 was immersed in a methanol solution of 10 wt % acidic dimethyl phosphate at 50° C. in an air atmosphere for 2 hours, and then dried. 87 parts by weight of this powder was mixed with 3 parts by weight of a mixture of epoxy resin and curing agent, compression molded, heated at 130° C. for 30 minutes to cure, and then magnetized. The obtained magnet had a magnetic flux density of 0.89 KG after a temperature characteristic test for 800 hours in air at 140°C.

Comparative Example 1 The same operation as in Example 1 was performed except that no aeration treatment was performed. The magnetic flux density was 0.79KG.

Comparative Example 2 The same operation as in Example 1 was performed except that the sample was not immersed in the phosphoric acid aqueous solution. The Fi1 flux density was 0.75 KG.

Comparative Example 3 The same operation as in Example 1 was performed except that the sample was not immersed in an aqueous phosphoric acid solution and no aeration treatment was performed. Magnetic flux density is 0.75KG
Met.

Comparative Example 4 The magnetic powder used in Example 1 was replaced with Mn(H2POa)22.
0 parts by weight, Mn(NO3)2-ffH2O0.5 parts by weight, Fe(H2POa) 20.1 parts by weight, 83P04
A chemical conversion treatment was performed at 80° C. for 10 minutes using a phosphate film conversion solution consisting of 0.2 parts by weight and 17.2 parts by weight of H2O. The XRF analysis value of the obtained powder was Sm38998 (cps
), Ca211492 (cps), Fe10337 (
cps).

Mn3H85 (cps), P70881 (cps), and the bulk density was 1.771 g/crm3. This powder was molded, hardened and magnetized in the same manner as in Example 1, and the magnetic flux density after zero magnetization was 0.84 KG.

〔Effect of the invention〕

When rare earth magnet powders treated by the method of the present invention are used, they are substantially free from oxidation during the manufacturing process and during use, and therefore rare earth plastic magnets with high magnetic properties can be produced safely and easily.

Claims (1)

[Claims] 1. At the same time, contacting a magnetic powder made of an intermetallic compound whose main constituents are rare earth metals and iron group metals with a phosphorus compound having active protons having a pKa of 4 or less,
Alternatively, a method for processing magnetic powder, which comprises exposing it to an oxygen-containing atmosphere after contacting it.