JPH03202439A - Manufacture of magnetostrictive rod constituted of rare earth-iron alloy - Google Patents

Abstract

PURPOSE:To obtain the rod excellent in crystal orientational properties at a high solidifying velocity by subjecting a rare earth-iron alloy base metal charged to a cylindrical refractory on a water-cooled metallic mold in a vacuum chamber to arc melting and thereafter solidifying it by heat elimination from the above mold. CONSTITUTION:A rare earth-iron alloy base metal 26 is charged to the upper end part of a cylindrical refractory 24 in which both ends are opened and placed in a water-cooled metallic mold 22 at the bottom of a vacuum chamber 10. Next, the vacuum chamber 10 is evacuated and is thereafter introduced with an inert gas to melt a pure Ti ingot placed on the mold 22 by arc discharge formed between the ingot and a W electrode 16 and to remove O2 remaining in the chamber 10. After that, the electrode 16 is moved onto the refractory 24, and arc discharge is executed between the base metal 26 and the electrode 16, by which a molten body 28 of the base metal 26 can be obtd. in the refractory 24 and the temp. of the refractory 24 simultaneously rises. After that, when an electric current in the arc discharge is gradually reduced, by the heat radiated from the mold 22 and the remaining heat in the arc discharge and the refractory 24, a heat flow directed from the lower end to the upper end of in the refractory 24 is generated. Thus, the rod made of a rare earth-iron alloy in which crystals are oriented can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a magnetostrictive metal rod, and particularly to a method for manufacturing a magnetostrictive rod with high crystal orientation in a magnetostrictive material using a rare earth iron alloy.

[Prior Art] Magnetostriction refers to a phenomenon in which a magnetic material stretches or contracts when it is magnetized, and conversely, when a strain that causes a dimensional change is applied to the magnetic material, it causes the magnetic material to elongate or contract. This is essentially the same phenomenon as the stress magnetic phenomenon that causes magnetization. As devices that utilize this magnetostriction phenomenon, magnetostrictive sensors that detect stress and magnetostrictive oscillators that serve as electroacoustic transducers are known.

Desired magnetic properties for a magnetostrictive material are a large magnetostrictive constant and a large electromechanical coupling coefficient. The electromechanical coupling coefficient is an index that represents the conversion efficiency from electrical input energy to mechanical output energy and the conversion efficiency from mechanical input energy to electrical output energy.The larger the magnetostriction constant, the higher the magnetic permeability. The larger the value, the larger the value.

As a metal-based magnetostrictive material, Ni has the oldest history, and Ni-Co alloys are also known, but in recent years, ReFe, which is an intermetallic compound of rare earths Re and Fe,
A huge magnetostriction phenomenon has been discovered in materials, and materials with a saturation magnetostriction constant λS of 300×10−′ or more at room temperature have been developed.

“Problems to be Solved by the Invention” Furthermore, the magnetostriction constant λI0° of the ReFex alloy is extremely small compared to λ and can be almost ignored. For example, in DyFe2, it is 1^, 1/λtoo 1>600, and many Most of the magnetostriction of crystals is due to λ. Therefore, when manufacturing magnetostrictive rods from rare earth iron alloys, it is essential to improve the orientation of the crystals.

Furthermore, the crystal orientation in the rod axis direction not only increases the magnetostriction constant but also reduces internal loss at grain boundaries.

Conventionally, the Bridgman method and the zone melting method are known as methods for producing crystal-oriented rods, but both of these methods have extremely slow production rates and are not suitable for industrial production. The typical solidification rate required to ensure crystal orientation by these methods is:
The rate is several centimeters per hour, and cannot be applied to industrial production at all.

Furthermore, a drawback of these conventional methods is that since the molten alloy is held in a container such as a crucible for a long time until solidification is completed, contamination from the crucible is unavoidable. Even if a floating zone melting method without a container is used in the zone melting process and contamination from the container is avoided, this method still requires the preparation of rods of a certain diameter, and Contamination from the crucible is unavoidable when producing the rod, and the process is complicated, making it unsuitable for industrial production.

The present invention has been made in view of the above-mentioned problems when manufacturing magnetostrictive rods made of rare earth iron alloys, and includes:
It is an object of the present invention to provide a method for manufacturing a magnetostrictive rod that has excellent productivity, has little contamination from a container such as a crucible, and can obtain a magnetostrictive rod with excellent crystal orientation.

[Means for Solving the Problems] A method for manufacturing a magnetostrictive rod made of a rare earth iron alloy according to the present invention is to manufacture a magnetostrictive rod made of a rare earth iron alloy in a cylindrical refractory whose lower end is in contact with a water-cooled metal mold in a vacuum chamber filled with an inert gas. Alloy (ReFe
x; However, in the formula, Re is one or more rare earth metals, Fe is iron, and X is 1.5 to 2.0. ), arc melting the rare earth iron alloy from the upper part of the cylindrical refractory, and then solidifying the molten rare earth iron alloy from the lower end by removing heat from the water-cooled metal mold. .

The method of the invention is generally applicable to magnetostrictive alloys of iron and rare earth elements. The crystalline alloy compound has the general formula Re Fe 2 where rare earth (Re) includes any rare earth metal.

ReFe2 alloys have positive and negative magnetic anisotropy constants, so by selecting a rare earth iron alloy that combines two or more appropriate rare earth elements, the magnetostriction constant can be kept large and the magnetic anisotropy constant can be reduced. Efforts are being made to reduce the polarity. Of course, the present invention is also applicable to rare earth iron alloys containing two or more kinds of rare earth elements.

When preparing metals to produce alloys, the surfaces of the metals must be cleaned.Next, predetermined amounts of metal components are weighed and alloyed using conventional arc equipment. Weighings and proportions must be accurate to obtain the exact desired alloy composition.

The button-shaped or piece-shaped alloy thus prepared is completely homogenized by repeating arc melting and solidification.

Meanwhile, a cylindrical refractory is installed in a vacuum chamber filled with inert gas, with its lower end touching a water-cooled metal mold. Both ends of this cylindrical refractory are open. The materials of this cylindrical refractory are B N , Y 20 x, Cab, MgO
, Al2O3, 5iOz, etc., or ceramics containing these components sintered with an appropriate binder. It is desirable that the cylindrical refractory be sufficiently thick so that solidification does not occur from the wall surface of the refractory.In order to prevent solidification from the wall surface of the refractory, a heating element may be installed around the cylindrical refractory to heat it.

In addition, the shape of this cylindrical refractory must not have a height/inner diameter ratio that is too large, because if the ratio is too large, the heat energy from the arc, which will be described later, will not be sufficiently transmitted to the bottom of the cylindrical refractory. First, the proportion of unmelted alloy increases, resulting in a decrease in yield.

Next, the button-shaped or piece-shaped rare earth iron alloy formed by the above-described method is charged into the cylindrical refractory. The alloy is melted using an arc from the top of the cylindrical refractory. When the melting is completed and the arc is stopped, the molten body is heat removed from the water-cooled metal mold that is in contact with the bottom of the cylindrical refractory, and solidification progresses from the bottom to the top, resulting in an alloy rod with oriented crystals. I can do it.

[Function] According to the present invention, the rare earth iron alloy melted by arc discharge or the like within the cylindrical refractory is forcibly removed by the water-cooled metal mold provided in contact with the lower end of the cylindrical refractory. Therefore, the solidification rate is extremely high, and production efficiency is very high.Also, since the time from melting to solidification is very short, contamination from cylindrical refractories can be minimized, so there is virtually no contamination. It is so small that it can be ignored.

Furthermore, it is equipped with a cooling means for removing heat through a water-cooled metal mold provided in contact with the lower end of the cylindrical refractory and a heat retaining wall made of the cylindrical refractory, ensuring a downward heat removal path. This makes it possible to solidify the melt gradually from the bottom to the top. First, a solid-liquid interface is formed at the bottom of the cylindrical refractory, and as the downward heat flow continues, the interface gradually moves upward. This control of heat flow makes it possible to obtain the desired axial crystal orientation.

[Embodiments] Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of the device used in this example. An exhaust pipe 12 and an inert gas introduction pipe 1 are provided on the side of the vacuum chamber 10.
4 is attached, the exhaust pipe 12 is connected to a vacuum pump (not shown), and an inert gas is introduced from the inert gas introduction pipe 14. Also, vacuum chamber 1
A tungsten electrode 16 is suspended from the ceiling of 0, and one end of this tungsten electrode 16 is connected to an arc power source 18.

A copper water-cooled metal mold 22 containing a water-cooled pipe 20 is installed at the bottom of the vacuum chamber 10, and a cylindrical refractory 24 with both ends open is placed on top of the mold 22 with one open end in contact with the mold. The dimensions of this cylindrical refractory 24 are a hollow cylinder with an inner diameter of 20 vam, an outer diameter of 50 mm, and a height of 30 m5, and the material is 9.
It is 9% CaO.

In this cylindrical refractory 24, Tbo, 27DFo, t3Fe
The inside of the vacuum chamber 10 is connected to the exhaust pipe 12, and the inside of the vacuum chamber 10 is connected to the exhaust pipe 12. After evacuating to 10-5 Torr with a pump, 0.7 atm of Ar was introduced through the inert gas introduction pipe 14. Subsequently, the pure Ti lump previously placed in the water-cooled metal mold 22 in the vacuum chamber 10 was melted by an arc discharge formed between it and the tungsten electrode 16, and oxygen remaining in the vacuum chamber 10 was removed.

Thereafter, the tungsten electrode 16 is moved onto the cylindrical refractory 24, and the rare earth iron alloy base material 2 inside the cylindrical refractory 24 is moved.
Arc discharge was performed between 6 and the tungsten electrode 16. As a result, a molten body 28 of the rare earth iron alloy was obtained within the cylindrical refractory 24, and at the same time, heat was transmitted to the cylindrical refractory 24 and the temperature of the cylindrical refractory 24 rose.

After the melt 28 was obtained, the current of the arc discharge was gradually reduced. Through this operation, heat is removed from the water-cooled metal mold 22, arc discharge occurs, and residual heat from the cylindrical refractory 24 causes
A heated action occurred from the lower end of the cylindrical refractory ej24 toward the upper end. Therefore, the solidification interface progressed from the lower end to the upper end, and an alloy rod having a composition of Tb, 2°D Fa, ysF el and 1% with crystal orientation was obtained.

In this example, it took 0.1 hour to obtain a rare earth iron alloy magnetostrictive rod with a diameter of 20 mm and a height of 25 mm. Compared to the conventional zone melting method, which takes one hour to obtain a rare earth iron alloy magnetostrictive rod of the same composition and shape, this example can be manufactured in a shorter time of approximately 0.1 hour. It was confirmed that the method of the present invention has extremely high productivity.

In addition, as a result of magnetostriction measurement in a DC magnetic field with a strain gauge attached to the magnetostrictive rod obtained in this example, the saturation magnetostriction constant λS was 1400xlO-', and it has excellent magnetic properties as a magnetostrictive material. It has been found.

[Effects of the Invention] As explained above, the method for manufacturing a magnetostrictive rod made of a rare earth iron alloy according to the present invention includes a rare earth iron alloy base material charged into a cylindrical refractory placed on a water-cooled metal mold in a vacuum chamber. After arc melting, it solidifies by removing heat from a water-cooled metal mold, and the molten rare earth iron alloy is melted by a water-cooled metal mold installed in contact with the lower end of the cylindrical refractory. Because the heat is forcibly removed, the solidification rate is extremely high, and the production efficiency of magnetostrictive rods is very high.Also, by cooling the water-cooled metal mold, a solid-liquid interface is formed at the bottom of the cylindrical refractory, and the interface Since the heat flow gradually moves upward, controlling this heat flow makes it possible to obtain a desired axial crystal orientation, making it possible to manufacture a magnetostrictive rod with excellent magnetostrictive properties.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a melting apparatus used in the method of the present invention.

Claims (3)

[Claims] (1) In a vacuum chamber filled with inert gas, a rare earth iron alloy (Re
Fex; However, in the formula, Re is one or more rare earth metals, Fe is iron, and x is 1.5 to 2.0
It is. ), arc melting the rare earth iron alloy from the upper part of the cylindrical refractory, and then solidifying the molten rare earth iron alloy from the lower end by removing heat from the water-cooled metal mold. A method for manufacturing a magnetostrictive rod made of rare earth iron alloy. (2) BN, Y_2O_3, CaO,
A method for manufacturing a magnetostrictive rod made of a rare earth iron alloy according to claim 1, which uses ceramics containing MgO, Al_2O_3, and SiO_2. (3) The method for manufacturing a magnetostrictive rod made of a rare earth iron alloy according to claim 1, wherein the cylindrical refractory is heated by a heating element installed around the cylindrical refractory.