JPH0741876A - Production of metal or metal alloy ingot by electron beam melting - Google Patents

Abstract

PURPOSE:To produce the ingot which is fine in crystal grains and has a uniform a granular crystalline structure having fine crystal grains by imparting ultrasonic vibrations to metal at the time of melting the metal by irradiation with an electron beam and pulling the molten metal as the ingot. CONSTITUTION:The ingot 9 of the metal to be melted is first arranged in a water-cooled crucible 1 of a bottomless type and a raw material electrode 7 consisting of the metal to be melted on its surface is heated and melted by irradiation with the electron beam 10 from an electron gun 2 to form a molten metal pool 11 in the upper part of the ingot 9. The ingot 9 is made successively longer by the solidification thereof and is pulled gradually from the crucible 1 by a pulling device 8. The ultrasonic vibrator transducer 4 as a raw material is mounted on the metallic electrode 7 in such a case and >=0.1kHz ultrasonic vibrations are applied to the molten metal layer 11, by which the ingot 9 having the fine and uniform granular crystals and excellent plastic workability is obtd. without forming the coarse and large columnar crystals at the time of solidifying the molten metal pool 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an ingot of a metal or a metal alloy by electron beam melting. More specifically, an ingot having a fine crystal grain and a homogeneous structure of a granular crystal is produced by an electronic method. A method of manufacturing by beam melting.

[0002]

2. Description of the Related Art The electron beam melting method melts a raw material electrode by colliding electrons accelerated in a vacuum with a metal or metal alloy, which is a raw material electrode, and converting the kinetic energy of the accelerated electrons into heat energy. This is one of the melting methods of casting into an ingot of the required shape.

A specific example of the electron beam melting method will be described with reference to FIG. In the figure, 1 is a water-cooled crucible, 2 is an electron gun, 7 is a raw material electrode, and 9 is an ingot. As shown in FIG. 2, a water-cooled crucible 1 installed in a melt chamber of an electron beam melting facility is irradiated with an electron beam 10 from a source electrode 7 in a horizontal direction or a vertical direction from an electron gun 2.
The molten metal 8 is dropped into the water-cooled crucible 1 and the melted raw material molten metal 8 is cast into the water-cooled crucible 1 and continuously solidified while being pulled out from below as an ingot 9. Continuous casting can be performed simultaneously. Since the electron beam melting method has an excellent purification effect, it is mainly a metal such as titanium or a refractory metal or a metal alloy (hereinafter abbreviated as “metal”).
It has been used in the production of ingots and has been attracting attention in recent years as a useful means for producing high-performance, high-quality functional materials due to its excellent cleansing effect.

However, when an ingot of a refractory metal having a melting point of 2000 ° C. or higher such as molybdenum or tungsten is manufactured by the electron beam melting method, the crystal grains become coarse during solidification, and coarse growth of columnar crystals occurs, which causes the ingot. It has already been found that it adversely affects the plastic workability in the subsequent steps such as forging and rolling. Such a phenomenon is due to the inherent physical properties of refractory metals (high melting point, latent heat of fusion, primary recrystallization, etc.), melting characteristics peculiar to electron beam melting (slow cooling rate, easy formation of columnar crystals) and their factors. This is due to the casting characteristics that are manifested by combining.

As a powerful means for solving the above problems,
The applicant of the present invention is a patent for a method of directly increasing the ultrasonic vibration energy to the molten metal, thereby promoting the generation of crystal nuclei and suppressing the coarsening of crystal grains to make the crystal grains finer, to break the columnar crystals or to form the granular crystals. Filed an application (Japanese Patent Application No. 5-9642, Japanese Patent Application 5)
-073684). Here, in order to introduce the ultrasonic vibration energy to the target location, an ultrasonic vibrator and a vibrating horn can be used. As a specific energy introduction method, the horn is fixed to the lower part of the ingot or the mold. A lower fixing method or the like can be adopted.

In the melting and casting methods other than the electron beam melting method, it is possible to apply ultrasonic vibration energy by the upper introduction method in which the horn is directly immersed in the molten metal, but the upper introduction method uses high temperature molten metal or electron beam irradiation. Since the horn melts, it cannot be used in the electron beam melting method. on the other hand,
The lower method is difficult to put into practical use due to many problems such as the distance from the horn to the surface of the molten metal is large and the ultrasonic wave transmission efficiency is poor, and the crucible is damaged by cavitation.

Therefore, an object of the present invention is to solve the above-mentioned problems in the electron beam melting method, and (a) to prevent the crystal grains from coarsening and to make them finer by promoting the generation of crystal nuclei. In the early stage of solidification where columnar crystals start to develop, the influence of heat removal from the mold is weakened, the solidification direction is randomized to destroy the columnar crystals and to form granular crystals.
As a result, the object is to establish an ultrasonic vibration energy applying means capable of stably producing a metal ingot excellent in plastic workability on an industrial scale.

[0008]

Means for Solving the Problems The inventors of the present invention have earnestly studied while carrying out a number of experiments using a raw material electrode as an ultrasonic vibration medium in order to achieve the above-mentioned object, and as a result, have obtained the following findings. I arrived. That is, in order to apply ultrasonic energy directly to the molten metal from the raw material electrode, the drip melting method is the most suitable among the electron beam melting methods, and here, based on the knowledge obtained in the production of metal ingots by the electron beam drip melting method, The invention was completed.

Therefore, in the method for producing a metal ingot by electron beam melting according to the present invention, at least one of the molten metal in the crucible and the tip of the electrode is irradiated with an electron beam and the raw material electrode immersed in the molten metal in the crucible is As a vibration medium, ultrasonic vibration is applied to the molten metal. That is, the vibration method is not the upper or lower introduction method as in the prior art, but ultrasonic waves are transmitted from the medium to the molten metal by using the raw material electrode itself as the vibration medium. As a result, ultrasonic waves destroy the columnar crystals by promoting the formation of crystal nuclei in the molten metal and further inhibiting the directional growth on the inner surface of the crucible. Further, in the present invention, the raw material electrode is immersed in the molten metal and melted by the heat of the molten metal. For this purpose, it is necessary to irradiate the molten metal with an electron beam to supply heat for melting or to melt the tip of the electrode itself with the electron beam. Further, in the initial stage of melting, the raw material electrode is irradiated with an electron beam to be melted as in the conventional drip-melt method, or a raw material mass previously inserted in the crucible is melted with an electron beam.

In the melting of the present invention, a further excellent effect can be obtained by applying ultrasonic vibration having a resonance frequency to the rod-shaped or plate-shaped raw material electrode. In this method, since the raw material electrode vibrates at its own resonance frequency, the molten metal is stirred and vibrated. For example, since the length of the rod resonating at 20 kHz is 130 mm, when ultrasonic vibration of 20 KHz is applied to the electrode having a length of 130 mm, the amplitude of ultrasonic waves of 20 kHz is increased, and the above-mentioned effect is further enhanced.

In the present invention, when the tip of the raw material electrode is irradiated with an electron beam, when the raw material electrode is tapered, the vibration effect given to the molten metal is reduced. Therefore, it is necessary to pay attention to the shape of the tip of the electrode.

Furthermore, the crucible is a water-cooled type having a bottom through hole, and continuous casting can be performed by continuously pulling out the ingot solidified in the crucible from the bottom through hole.

Further, in order to use the raw material electrode as an ultrasonic medium, the ultrasonic vibration horn and the oscillator may be connected to the raw material electrode by an appropriate method, but preferably, the ultrasonic vibration horn is connected to the end of the raw material electrode. It is most suitable to guide the raw material electrode into the crucible through a vibrator by a guide rod fixed to the raw material electrode. Furthermore, when the ultrasonic vibration frequency applied to the raw material electrode is 0.1 [kHz] or more, a remarkable effect can be obtained in the above-mentioned refinement of crystal grains and breakage of columnar crystals.
In addition, when the frequency (f) is changed according to the length (L) of the raw material electrode so that the relationship (c: constant) of L = 0.5cf-1 is kept constant, the melting process of the entire raw material electrode It is possible to obtain a resonance condition with and to manufacture an ingot having a uniform fine crystal structure. Hereinafter, the present invention will be described in more detail with reference to FIG.

FIG. 1 is an explanatory view of a main part of an electron beam melting apparatus applied to the production of metal according to the present invention. In FIG. 1, as in the conventional electron beam melting apparatus, an electron gun 2 and a water-cooled crucible 1 are arranged in a melt chamber (not shown), and a raw material electrode having an ultrasonic vibrator 4 and a vibration horn 5 fixed thereto. 7 is attached to the feeder 3 and is immersed in the molten metal in the vertical direction or at an inclination angle.

As shown in FIG. 1, a molten metal 1 in which a raw material electrode 7 attached to the tip of a water-cooled vibrating horn 5 is already formed
Ultrasonic vibrations are transmitted to the molten metal 11 while being immersed in 1. In this state, the raw material electrode 7 is caused to resonate with a vibrating medium,
By tracking the resonance frequency according to the amount of decrease in the length of the raw material electrode due to melting, the resonance can be continued during the period when the raw material electrode 7 is consumed.

When manufacturing a metal ingot with the above apparatus, first, an ingot 9 is produced with an electron beam 10.
A pool of molten metal 11 is formed on top. The raw material electrode 7 is gradually melted by the heat of the molten metal 11 or the irradiation heat of the electron beam, and the ingot 9 in which the solidification has progressed is pulled out from below the water-cooled crucible 1. At this time, since the length of the raw material electrode 7 becomes shorter as the melting progresses, the feeder 3 always maintains the contact state with the molten metal 11, and the oscillation frequency of ultrasonic vibration is varied so that the raw material electrode 7 always resonates. .

[0017]

As described above, according to the present invention, in order to produce a material required to have high performance and high quality, it is possible to obtain ultrasonic vibration energy from a molten raw material while melting the molten raw material with an electron beam. Excellent performance can be imparted by making the obtained ingot into a fine structure and granular crystals to form a uniform structure. Further, the performance can be further improved by causing the molten raw material to resonate with the ultrasonic vibration frequency (claim 2). By combining the electron beam melting method of the present invention and continuous casting, crystal grains of 10 mm or less can be obtained (claim 3). When a vibrator or the like is arranged at the end of the raw material electrode, an accurate resonance condition can be found in the case of longitudinal waves (claim 4). Further, a uniform ingot can be manufactured by changing the frequency according to the consumption length of the raw material electrode (claim 6).

[0018]

EXAMPLES Next, the effects of the present invention will be described more specifically by way of examples. Metal ingots were manufactured by the "invention method" and the "conventional electron beam melting method" using the apparatus shown in FIGS. Here, as a typical example, φ1 with an electron beam output of 100 [kw]
The production of a 20 mm molybdenum ingot will be described.

When the "conventional electron beam melting method" is carried out, the ultrasonic vibrator and the horn are not used as shown in FIG. 2, while the "invention method" is a furnace pressure of 1 × 10. -4 ~ 1
It was carried out by the following means within the range of × 10 -5 [mbar].
The raw material electrode attached to the feeder is melted from a length of 0.5 [m] to a length of 0.05 [m], and the frequency is also changed from 4 [kHz] to 45 [kHz] accordingly, and the resonance condition is changed. While keeping it, it was directly immersed in the molten metal to proceed with solidification.

Φ120 × 500 thus obtained
Looking at the macrostructure of an ingot of mmL of molybdenum, the average crystal grain size of the ingot obtained by the conventional electron beam melting method is 10 mm or more, and it is non-uniform and columnar crystals, whereas it is obtained by the method of the present invention. The average grain size of the resulting ingot was as fine as 10 mm or less, and the columnar crystals were completely broken into granular crystals and had a homogeneous structure. In addition, in one melting, the tip of the raw material electrode is left about 50 mm to complete the melting, then the vibrator 4 and the horn 7 are removed from the raw material electrode, attached to another electrode, reused, and repeated many times. It was

[0021]

Industrial Applicability As described above, according to the present invention, it is possible to stably mass-produce a metal or an ingot whose crystal grains are refined and crystallized and which has a uniform structure. This brings about a very useful effect.

[Brief description of drawings]

FIG. 1 is a principal part explanatory view of an example of an apparatus applied to manufacture a metal or a metal alloy according to the present invention.

FIG. 2 is a principal part explanatory view of an apparatus example applied to the production of a metal or a metal alloy by a conventional electron beam melting method.

[Explanation of symbols]

 1 Water-cooled Crucible 2 Electron Gun 3 Raw Material Electrode Feeder 4 Ultrasonic Transducer 5 Ultrasonic Vibrating Horn 6 Transducer Protective Case 7 Raw Material Electrode 8 Ingot Extractor 9 Ingot 10 Electron Beam 11 Molten Metal

Claims (6)

[Claims] 1. A method for producing a metal or metal alloy ingot by electron beam melting, wherein at least one of the molten metal in the crucible and the tip of the raw material electrode is irradiated with an electron beam and the raw material electrode immersed in the molten metal in the crucible is used. A method for producing a metal or metal alloy ingot by electron beam melting, characterized in that ultrasonic vibration is applied to the molten metal as a vibration medium. 2. The method for producing a metal or metal alloy ingot by electron beam melting according to claim 1, wherein ultrasonic vibration having a resonance frequency is applied to the raw material electrode. 3. The crucible is a water-cooled type having a bottom through hole, and the ingot solidified in the crucible is continuously pulled out from the bottom through hole. A method for producing a metal or metal alloy ingot by electron beam melting. 4. The raw material electrode is guided to the inside of the crucible by a guide rod fixed to the raw material electrode via an ultrasonic vibration horn and a vibrator at the end of the raw material electrode. A method for producing a metal or metal alloy ingot by electron beam melting according to any one of claims. 5. The method for producing a metal or metal alloy ingot by electron beam melting according to claim 1, wherein the ultrasonic vibration frequency applied to the raw material electrode is 0.1 [kHz] or higher. 6. The method for producing a metal or metal alloy ingot by electron beam melting according to claim 2, wherein the frequency is changed according to the length of the raw material electrode.