JPS61208806A - Surface treating method and permanent magnet - Google Patents

Abstract

PURPOSE:To prevent the generating of rust by diffusing carbon on the surface of an R-B-Fe magnet. CONSTITUTION:An R-B-Fe magnet is heated and held in atmosphere which contains CO gas and small quantity of CH4 gas or C3H6 gas and further anhydrous NH3 gas as required, heated and held in atmosphere which contains NH3 gas by a method of carburizing the surface of the magnet or at 450-690 deg.C, and by a method of nitriding the surface of the magnet. The formation of a nitrided layer by the nitriding causes a nitride with these elements, and is effective at the point of preventing the generation of rust when containing Al, Cr, Ti, V and/or Mo.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and a magnet for preventing complex formation in R--B--Fe magnets.

[Conventional technology]

Conventional typical rare earth magnets are 1-5 series RCoz magnets (R
is a rare earth element such as Sm, Cm, Pr, etc.) Winter 12
-17 series R2 (Co Fe Cw M ) + y magnet (
MG;! TLZ + -J-1+ % JL
j HaA'l”l ”F'S *, h
x--he, ms S a-*, O
, Cμ, etc., to the surface, or actively forming a thin oxide film to reduce subsequent oxidation.

[Problem that the invention seeks to solve]

However, in recent years, RB Fe-based magnets have been developed (JP-A-59-46008, JP-A-59-222564).
However, this surface is very susceptible to oxidation (refer to the above publication), but surface treatment methods other than those conventionally known have become necessary.

[Problem to be solved by the invention]

That is, the surface of the R=B-Fe magnet is chemically unstable and more likely to rust than the conventional R-Co magnet. Therefore, an object of the present invention is to provide a surface treatment method that prevents complex formation on the surface of a magnet.

[Means for solving problems]

In order to achieve the above object, the present invention provides an R-B Fe-based magnet at 700 to 900°C in an atmosphere containing -anhydrous NHs gas and a small amount of CH gas or C3H1l gas, if necessary. A method of carburizing the surface of the magnet by heating and holding it in a surrounding environment, or at a temperature of 450 to 690°C,
This is a method in which the magnet surface is heated and maintained in an atmosphere containing NHS gas to nitride the magnet surface. The nitriding layer is formed by nitriding treatment of M, Cr, and Ti.

When it contains V, Mo, etc., it is accompanied by a titanide with these elements and is particularly effective in preventing rust.

〔Example〕

SaishitaThe present invention will be described in more detail with reference to Examples.

Example 1 Melting - Ingot - Powder - Molding - Sintering - Heat treatment - Driving -
34%Nd-1" by weight by a known method called surface treatment.
A sintered magnet of %B-remaining Ft was prepared.

After preparation, 1% NH, 4% CHa by volume at 850℃
.

5 in a gas atmosphere of 26% CO, 30% H2, and the remainder H2.
After carburizing for 0 minutes, it was further carburized in KR gas for 6 hours.
After treatment at 60° C.XIHυ, it was rapidly cooled and evaluated for magnetic properties and the presence or absence of complex formation. The results are shown in Table 1.

Table 1 An O mark indicates no rust formation, and an X mark indicates rust formation.

The presence or absence of complex formation was evaluated by visual observation after being left indoors (at room temperature) for 30 days.

Example 2 After creating a sintered magnet in the same manner as in Example 1, it was subjected to a nitriding treatment at 500°C for 50 minutes in an NHs gas atmosphere, followed by a treatment at 660°C and I Hv in A-gas, followed by rapid cooling and evaluation. Served. The results are shown in Table 1.

Comparative Example 1 As in Examples 1 and 2, a sintered magnet was prepared using a known method and then subjected to evaluation. In other words, as a raw material, pure 999% (
Using electrolytic iron (% by weight) and 99% B (199% Net), it was weighed and melted to obtain a final sintered body having a weight ratio of 33% Nd - t'% B - balance Fe.

and got an ingot. The alloy ingot was finely pulverized using a Jita crusher and a jet mill to obtain an average particle size of 3.5μ.
m powder was obtained. The obtained raw material was molded at a molding pressure of 4 t/cd to obtain a molded body. Note that during molding, a magnetic field of 10 KOg was applied parallel to the molding direction.

The obtained molded body was vacuumed (10-'T) at 1100°C for 1 hour.
After sintering in Aυ gas at 900°C
After holding v, slowly cool to room temperature, and then again to 660℃X I Hv
The mixture was then cooled to room temperature. After cooling, the surface is finished.

It was subjected to a thorough evaluation. The results are shown in Table 1.

〔Effect of the invention〕

As shown in Table 1, it has been found that by performing carburizing treatment or titanizing treatment, the magnetic properties are at almost the same level and rust formation can be prevented, and the industrial value of the present invention is extremely large.

Claims (1)

[Claims] 1. Carbon is added to the surface of an R-B-Fe magnet consisting of essential elements R (where R is at least one rare earth element including Y), B, and Fe containing unavoidable impurities. A surface treatment method characterized by carrying out a diffusion treatment. 2. A surface treatment method characterized by diffusing nitrogen onto the surface of an R-B-Fe magnet. 3. A permanent magnet characterized by being subjected to surface treatment according to items 1 and 2.