JPH01319909A - Manufacturing method of Fe-BR permanent magnet - Google Patents

Abstract

PURPOSE:To obtain an excellent Fe-B-R based permanent magnet by adding one-axis pressure and a current to the collected body of Fe-B-R based thin pieces in an unbalanced state, thereby obtaining a high density sintered body. CONSTITUTION:Fe-B-R based thin pieces (R represents one or two or more kinds of rare earth elements incorporating Y) in an unbalanced state which commonly have an R2Fe14B phase and an amorphous phase are filled in a cavity. One-axis pressure and a current are added, and Joule heat is generated at the contact interfaces between the thin pieces. Thus, atomic bonding at the contact interfaces is achieved. The Joule heat is absorbed into the inner part from the surface layer of each thin piece. Thus the surface layer of each thin piece is quickly cooled. In this way, a high density sintered body is obtained, and the excellent Fe-B-R based permanent magnet is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for producing Fe-B-R water-based magnets, and more specifically to R2 obtained by an ultra-quenching method.
A Fe-BR-based water magnet using Fe-BR-based flakes (where R is one or more rare earth elements including Y) as a starting material that shares an Fe++B phase and an amorphous phase. This relates to a manufacturing method.

Conventional technology R2Fe++ Nonequilibrium state F sharing B phase and amorphous phase
The e-BR-based flakes are obtained by freezing at least a portion of the e-BR-based flake from a high-temperature melt state in a melt state, for example, by ultra-quenching at 10'C/sec or higher. Therefore, it is essentially as thin as 20 to 30 μm (and approximately 20+ nm).
It can only be obtained in the form of the following pieces. Such R2Fe
Non-equilibrium state Fe-B-R sharing 1B phase and amorphous phase
As practical permanent magnets that require various shapes, thin flakes cannot be used directly as they are (they must be integrated by some means. Practical permanent magnets include resin magnets, hot-pressed magnets, etc.) There are known ways to do this.

Problems to be Solved by the Invention Non-equilibrium Fe that shares an R2FezB phase and an amorphous phase
The (BH)max of a -BR based thin piece, for example a Fe83NdI384 resin magnet with a relative density of 80%, is 8MGOe. In this case, it is difficult to significantly improve the magnetic properties, partly because it is difficult to increase the relative density to 80% or more. on the other hand,
For example, the relative density of p6a3Nd+384 is 98-99%, and the (BH) max of the hot-pressed magnet is 14MGO.
It becomes e. However, in this case, it is necessary to employ a relatively high optimal processing temperature of 600 to 900°C and a relatively high processing pressure of 1 to 3 ton/cnf.

In particular, since the processing temperature is in the generation and/or growth temperature range of the R2Fe+4B phase, it is necessary to accurately control the processing temperature and processing pressure in relation to time, and to ensure and maintain a chemically inert atmosphere. There are some difficulties that must be overcome.

Therefore, although hot-pressed magnets have better magnetic properties than resin magnets, it is difficult to manufacture practical magnets that require various shapes, and their industrial value has been poor.

Means for Solving the Problems The present invention fills a cavity with a non-equilibrium Fe-B-R flake that shares an R2Fe14B phase and an amorphous phase, applies uniaxial pressure and electric current, and Atomic bonding of the contact interface is achieved by generating Joule heat at the contact interface, and the surface layer of the flake is rapidly cooled by absorbing Joule heat from the flake surface layer into its interior.

Action resistance sintering acid discharge sintering is known as a method for sintering difficult-to-sinter materials. The present invention has found that it is extremely effective to apply this method to the sintering of non-equilibrium Fe--B--R flakes that share an R2Fe++B phase and an amorphous phase. The principle of this method is to sinter the thin film using Joule heat by momentarily passing a large current through the thin film itself.

Since the individual flakes generally have an oxide film with high electrical resistance, the aggregate of flakes has a large electrical resistance as a whole. The Joule heat per unit volume of the flake assembly is Q B = 12 ・RB (RB is the electrical resistance at the contact interface of the flake) and QC; 12 ・RC (RC is the electrical resistance inside the flake). RB is generally the Since the level is more than 100 times higher, assuming that a series circuit of RBRC is constructed, the Joule heat per unit volume Qs is more than 100 times as much as Qc, and the contact interface between the thin pieces is heated preferentially.

Then, the bonding at the partially formed contact points without an oxide film spreads rapidly and throughout. The characteristics of this method are that the thickness of the film with high electrical resistance is only a few tens of nanometers, and that it is heated by electricity, so that the non-equilibrium state in which the R2Fe+4B phase and the amorphous phase are shared does not shift due to the application of electricity at the m58C level. It is possible to sinter Fe-B-R flakes. Note that applying pressure to the flake aggregate during this energization to promote rearrangement of the flakes due to sintering and reducing pores improves the magnetic properties of the Fe-B-R permanent magnet according to the present invention. This is particularly important and a necessary condition.

Nonequilibrium state F sharing R2Fe+4B phase and amorphous phase
The composition of e-BR-based flakes is particularly (1) 12
~20 at.% Nd, 4-12 at.% B.

The balance is Fe and unavoidable impurities, c2) 12 to 20 at% Nd, 4 to 12 at% B, and 30 at% or less C
o (O atomic % is excluded <), the balance is Fe, and unavoidable impurities can be exemplified. Also R2Fez
The method for producing a non-equilibrium Fe-B-R flake that shares three phases and an amorphous phase is as follows: (1) A master alloy is produced by arc melting or high frequency melting. (2) Using the mother alloy as a melt, at least 10% of the mother alloy in the melt state is processed by an ultra-quenching method such as a single roll method, a twin roll method, or an ultrasonic gas atomization method.
At a cooling rate of '°C/sec or more, at least a part of the thin section is frozen in a melt state. (3) The thin piece is heated at a temperature of 600 to 950°C and Ar
The R2Fe+4B phase is kept in a high H atmosphere or in a vacuum.
This can be obtained by setting the crystal grain size to 40 to 400 nm to obtain the cj level.

Example The present invention will be explained below with reference to Examples.

Fee3Nd+384 by single roll method in Ar atmosphere
Ultra-quenched thin sections were obtained. By X-ray diffraction, this flake was found to be Nd2
Non-equilibrium state Fe-B sharing Fe+4B phase and amorphous phase
- It was found that it was a R type flake.

This thin piece was filled into a cylindrical cavity with a diameter of 5 mm, and uniaxial pressure and electric current were applied in the height direction of the cavity at room temperature. However, the pressure is 2 ton/cd, and the current is boosted and rectified to a predetermined DC voltage, and the capacitor group is charged and then discharged via a thyristor.
OA, 300m5ec, 2 cycles of electricity was applied.

FIG. 1 shows the flake texture of the sintered body. Also, Figure 2 (
a) and (b) show Nd2Fe+4B grains in the original flake and sintered body, respectively. As is clear from the figure, atomic bonds are formed at the contact interface of the flakes due to Joule heat, and the pressure applied at this stage promotes the rearrangement of the flakes during sintering, reducing the number of vacancies. It has a high density of 98.5%. Moreover, since the surface layer of the flake can be rapidly cooled by absorbing Joule heat from the surface layer of the flake into the interior of the flake, the transition to a non-equilibrium state and the generation and/or growth of Nd2Fe+4B phase crystal grains can be prevented before and after sintering. do not have.

The above sintered magnet has magnetic properties after pulse magnetization of 50KOe, Br8KG, Hcb6.8KOe, Hcj15KOe,
(BH) max 15 MGOe, ensuring high performance as a magnetically isotropic magnet.

Effects of the Invention The present invention is capable of increasing the density in a manufacturing method for producing practical magnets having various shapes from non-equilibrium Fe-B-R flakes that share an R2FezB phase and an amorphous phase. R
A hot press method in which temperature and pressure must be accurately controlled in relation to time in the generation and/or growth temperature range of the 2Fe14B phase, and a chemically inert atmosphere must be secured and maintained. The aim is to improve the

The present invention is to form a high-density sintered body by applying uniaxial pressure and electric current to an aggregate of non-equilibrium Fe-B-R flakes at room temperature or higher, even without any special atmosphere. It has high industrial value because it can

[Brief explanation of the drawing]

Figure 1 is a micrograph showing the texture of a non-equilibrium Fe-B-R flake sintered body, and Figure 2(a) is a micrograph showing the grain structure of R2Fe+4B crystal grains in the flake before sintering.
b) is a micrograph showing the grain structure of R2FezB crystal grains in the thin section after sintering. Name of agent: Patent attorney Toshio Nakao and one other person Figure 1

Claims (1)

[Claims] A cavity is filled with non-equilibrium Fe-B-R system flakes that share the R_2Fe_1_4B phase and the amorphous phase (where R is one or more rare earth elements including Y), and uniaxial pressure and current are applied. Fe-B which performs atomic bonding at the contact interface by generating Joule heat at the contact interface of the flake, and rapidly cools the flake surface layer by absorbing Joule heat from the flake surface layer into its interior. -R
A method of manufacturing permanent magnets.