JPH0611888B2 - Manufacturing method of rare earth-iron giant magnetostrictive alloy ingot - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a rare earth-iron-based giant magnetostrictive alloy ingot, and a technique for inexpensively producing a material having high magnetostrictive characteristics with less impurities mixed therein. Regarding

[Conventional technology]

In the 1970s, the giant magnetostrictive alloy consisting of REFe ₂ intermetallic compound succeeded in raising the Curie point in the rare earth-iron alloy material to generate giant magnetostriction at room temperature, and became the spotlight as a practical material ( Unexplored processing technology, 198
May 6th, pp. 2 to 7), inventions relating to materials (Japanese Patent Publication No. 61-33892, Japanese Patent Publication No. 64-73050), and inventions relating to manufacturing methods (Japanese Patent Publication No. 62-1099).
46 and JP-A-63-242442) have been proposed.

Usually, the giant magnetostrictive alloy is used in a rod shape, but it is roughly classified into a single crystal type and a polycrystalline type.

As a manufacturing method, for the single crystal type, the zone melt method (Japanese Patent Laid-Open No. 62-109946) and the Bridgman method (CT Murray: Design News 16-6-88 (198) are used.
8) 140), etc., and for the polycrystalline type, powder sintering method (USP 4,152,178), casting method (Meru Teruo: Special Seminar "Giant Magnetostrictive Material and Its Application")
Ed., Advanced Machining Technology Promotion Association, (1988), 1).

In the present magnetostrictive material, it is desirable that the crystal be oriented in <111> from the viewpoint of magnetostrictive crystal anisotropy.
It is difficult to obtain an alignment material for the above, and the <112> orientation is practically used (JD Verhoeven and 3 others, Metallurgic
al Tra-ns. A18A [1987], 223). on the other hand,
In the powder sintering method, this powder is subjected to an orientation press in a magnetic field,
It can be oriented in <111>, but 100% orientation is difficult, and the characteristics are slightly inferior to those of the single crystal type using <112>.

As the casting method, an ordinary solidification method and a unidirectional solidification method can be considered. In the former, the crystal orientation is often random, and the performance is low. The latter exists as data so far, but the content of the manufacturing method and the crystal orientation are not mentioned. (Mr. Teruo, Mori: Giant Magnetostrictive Material and Its Applications).

The above is a performance evaluation based on the classification in the final process of production, but from the viewpoint of melting the alloy, the zone melt method, Bridgman method, and powder sintering method show the uniformity of the alloy components. In order to obtain, a step of uniform dissolution as a pretreatment (hereinafter,
Pre-dissolution) is essential.

This pre-melting step is generally performed by a usual high-frequency melting method, arc melting method, or the like, and is a treatment for forming a lump-shaped or rod-shaped uniform component distribution alloy required for the next step.

In the high frequency melting method, the rare earth element (RE) in the present material is extremely active, there is no suitable crucible material, and an industrial crucible material cannot avoid contamination by the crucible material, resulting in deterioration of properties, which is preferable. Absent. Therefore, the arc melting method of copper hearth is usually used as the premelting.

[Problems to be Solved by the Invention]

In any case, the zone melt method, the Bridgman method, or the powder sintering method is expensive in terms of cost since the materials are manufactured by the respective methods after the pre-melting treatment.

On the other hand, as a casting method, a high frequency melting method, an arc melting method and the like are conceivable. However, if the casting is simply performed, the characteristics can be obtained only in the range of 1 to 1/10 of the fraction of a single crystal.
In order to improve the material properties, it is necessary to align the crystal orientation by applying the unidirectional solidification method.

However, there are few examples in which the unidirectional solidification method is applied to this material, and although there is data, the manufacturing method and crystal orientation are not mentioned.

Generally, the application of the unidirectional solidification method to industrial materials is applied to turbine rotor blade materials, and P.I. D. Law (Powder do
The wn method) and the rapid solidification (HRS) method have been used (Yukiya Nakagawa et al. 2 people: The Japan Institute of Metals, 17 , [7] (197).
8), 589), a high-frequency heating furnace is a normal furnace, and contamination from the crucible material is considered, so it is difficult to apply to this material.

An object of the present invention is to solve the above-mentioned problems and to provide a method for efficiently producing a rare earth-iron based magnetostrictive alloy by a commercial scale directional solidification method.

[Means for Solving the Problems]

As a result of various studies by the present inventors in order to achieve the above object, the present invention has been completed based on the technical knowledge described below.

That is, the present invention uses a plasma arc torch as shown in FIG. 1 and a plasma arc melting furnace having a bottomless water-cooled copper mold provided below the plasma arc torch to continuously supply a rare earth-iron-based giant magnetostrictive alloy raw material. The composition is melted by a plasma flame to form a melted part on the upper part of the mold, and the solidified alloy is continuously drawn out from the lower part of the mold. The depth of the melted part is determined by the temperature gradient G of the liquid phase and the solidification rate. By adjusting the ratio G / R of R to be a certain value or more,
The ingot is manufactured by aligning the crystal directions in one direction.

[Action]

 The configuration and operation of the present invention will be described.

As a melting method for this material, an arc melting method or the like is preferable to the high frequency melting method in consideration of the reactivity in the crucible. That is, the consumable electrode type arc melting method, the non-consumable electrode type arc melting method, the plasma arc melting method, and the electron beam melting method are effective.

At the same time when these melting methods are applied, the solidification method is not the so-called button melting method of water-cooled copper molds that are often used in small-scale melting, but a continuous rod-shaped solidified material is drawn directly below the melting part. The so-called ingot lowering method (bottoming mold method, laminated solidification method) as shown in FIG. 1 is effective.

In the arc melting method and the beam melting method, the melting temperature is higher than that of the high frequency melting method (several thousands K to 10,000 K or more), and the thickness of the melting portion is thin. Is considerably larger than that of ordinary solidification, and the empirical rule that columnar crystals of unidirectional solidification can be obtained when G / R (R: solidification rate) is larger than a certain value can be easily satisfied. It was found that the crystal growth orientation was stable at <112>.

Among the various melting methods described above, the plasma arc melting method is particularly effective. That is, in the electron beam melting method, the atmospheric gas pressure is 10 ⁻³ to 10 ⁻⁸ Torr, and it is difficult to control the composition of an alloy material containing a high vapor pressure component.
The equipment is more expensive than plasma arc melting. In the consumable electrode type arc melting method, it is necessary to manufacture the present system alloy material rod electrode as a preliminary preparation, and in the non-consumable electrode type arc melting method, contamination by the electrode material (for example, W) is considered, which is not preferable.

〔Example〕

 An example of the present invention will be described.

Using a plasma arc melting furnace as shown in FIG.
A unidirectionally solidified sample of 0 mm and 120 mm1 was prepared.

Raw material _{Tb 0. 3 Dy 0. 7} Fe 1. 95 3N grade 87 in the target composition of
A wt% Tb-Fe master alloy, 3N grade 88 wt% Dy-Fe master alloy and electrolytic iron were crushed to -20 mesh to +100 mesh and mixed, and continuously charged from a feeder.

Melting was carried out using a plasma arc torch with a power output of 10 KW, and a 120 mm 1 × 30 mm rod was placed at 10 cm / hr-20
It was pulled down at a speed of 0 cm / hr. Coagulation rate R is 10-20
It is estimated to be 0 cm / hr. Solidification temperature (liquidus) is about 12
It is 50 ° C. and the melt temperature gradient G is 3000
G = (14
77-8477) / (0.5-1.5) ≈17000-
1000 ° C / cm, G / R = (17,000-100
It is considered that the range is 0) / (10 to 200) = 1700 to 5 hr ° C./cm.

The obtained sample was heat-treated at 1000 ° C. for 7 days (Ar atmosphere). FIG. 2 shows a photograph of a macrostructure of a cross section in the direction of the long axis of the sample. An X-ray diffraction image of the rod cross section is shown in Fig. 3 (a).

As a reference value, a commercially available single crystal rod (FSZM (Free stand
An X-ray diffraction image (FIG. 3 (c)) of a cross section of the zone melting method) and an X-ray diffraction image (FIG. 3 (b)) of the powder of the sample obtained in this example are also shown. . In this sample, the peak intensity on the (422) plane increases in the diffraction image of the rod cross section, and the <1
It can be seen that the orientation of 12> is increased.

The magnetostriction values of the sample of the present invention are shown in FIG. 4, and the catalog values of general arc-melted products and commercial products of the FSZM method are shown in FIG. 4 for comparison.

From these, arc melting, beam melting, and ingot lowering methods are effective as methods for producing a unidirectionally solidified magnetostrictive material having a magnetostriction value comparable to <112> single crystal material, and plasma arc melting and ingot lowering are particularly effective. It has become clear that a combination of methods is preferred.

Thereby, the unidirectionally solidified material can be manufactured more advantageously than the single crystal material in terms of cost.

〔The invention's effect〕

Since the present invention is configured as described above, it has the following effects and is extremely useful industrially.

1. There are few cavities and few cracks (things cast directly from the high frequency melting furnace, many cracks due to button melting of arc melting, large dimensions are difficult to recover, and magnetostriction characteristics are low).

2. Since the melting time is short and the drawing speed is considerably high, rapid production of alloy rods is possible and the productivity is good.

3. The atmospheric gas pressure is atmospheric pressure, and even if a substance having a high vapor pressure is used, it is stable without a large compositional change.

4. Inclusion of inclusions (oxides) in the alloy rod is not preferable, but in plasma arc melting, they float and are removed to the casting surface side by wiping of the plasma arc and do not mix into the alloy bulk.

5. Since the pre-melting step is unnecessary and the manufacturing can be performed in a single step, the cost can be reduced.

6. It can also be used as a raw material rod for the zone melt method.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view of an apparatus for carrying out the method of the present invention, FIG. 2 is a photograph showing a macroscopic metal structure of a longitudinal section of a magnetostrictive alloy rod obtained by the method of the present invention, and FIG. FIG. 4 is an explanatory diagram showing an analysis image, and FIG. 4 is an explanatory diagram showing magnetostrictive characteristic values.

Claims (2)

[Claims] 1. When producing a rare earth-iron-based giant magnetostrictive alloy ingot having a uniform crystal orientation, a plasma arc torch and a plasma arc melting furnace having a bottomless water-cooled mold provided below the plasma arc torch are continuously used. In the production of a rare earth-iron-based giant magnetostrictive alloy ingot, which comprises melting the supplied raw material mixture by a plasma flame to form a melted part in the upper part of the mold, and continuously drawing out the solidified alloy from the lower part of the mold. The depth of the melting portion is adjusted so that the ratio G / R of the temperature gradient G of the liquid phase to the solidification rate R becomes a certain value or more, a rare earth-iron-based giant magnetostrictive alloy ingot. A method of manufacturing. 2. The method for producing a rare earth-iron-based giant magnetostrictive alloy ingot according to claim 1, wherein the mold is a water-cooled copper mold.