JPH06200334A - Equipment for the production of high-purity metals and alloys - Google Patents

Abstract

(57) [Summary] [Purpose] To generate an injection stream composed of a material with high purity. The present invention relates to an apparatus for producing high-purity metals and alloys. In this device, the electric slag remelting method is combined with the cooled induction crucible technology. This makes it possible to achieve surprising advantages, for example, considerable energy savings, reduced run times, and very high purity of the metal or alloy produced. In addition, inductive flow guidance systems, cold-flushed flow-through technology or ingot reactor equipment can be used.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to an apparatus for producing high purity metals and alloys in a cooled crucible consisting of one or several metal segments surrounded by an induction coil.

[0002]

2. Description of the Related Art Highly stressed parts, such as
Turbine buckets must be made of high purity material. If the material contains external substances, these inclusions, under high stress, become the starting point for ciliary cracks and the like, and eventually the entire part is destroyed.

In the conventional method of producing high purity metals or alloys, the starting material is remelted into an ingot by the vacuum induction melting (VIM) method. However, the purity of the ingot thus obtained is often still not sufficient. Furthermore, in principle, such ingots have a heterogeneous structure, which is due in particular to the fact that the solidification of the metal in a manner that determines the outer diameter of the ingot occurs from the outside to the inside. To obtain higher purity, the ingot is subjected to vacuum arc remelting (VAR) method. Here, the ingot has the shape of a cylindrical electrode connected to one pole of the voltage source, and the container for dropping material drops from the electrode is connected to the other pole of this voltage source. In this case, an arc is formed between the electrode and the ingot to be produced in the chill mold, and this arc will melt the ingot electrode from one end.

Another known method, namely electric slag remelting (= ESR, DE = Z: Korousic, B. et al: ESR Technology
of High Purity Copper Alloys, Metall, February 198
7, pp. 153-155), the voltage is VAR method (German Patent Application Publication No. 23497) in a similar manner.
21), even if it is applied as in
No arc is formed between the electrode and the molten material in the chill mold. Therefore, the electric current passing through the electrode immersed in the slag causes the slag to be heated by resistance heating, which melts the electrode material. The molten material penetrates into the slag. A metallurgical reaction occurs between the molten material and the slag surface, producing a high-purity molten metal under the slag. ES
The advantage of the R method is that it can be carried out at normal atmospheric pressure.

The workpiece itself, for example a turbine component, can be manufactured from the purified material by forging.
However, it is also possible to atomize the purified liquefied material to produce a powder, which is placed in a mold container and compressed by mechanical pressure.

In the VAR and ESR methods, the thermal energy required for melting is obtained by passing an electric current across the resistor.

On the other hand, in so-called induction heating, melting energy is introduced into the molten material by eddy currents.
This eddy current is generated by the AC magnetic field in the coil.
Here, the coil is arranged around a crucible containing the molten material (see DE 3026722).

The crucible must be wholly or at least partially transparent to the magnetic field so that the magnetic field can penetrate the molten material. When the crucible is made of ceramic, the magnetic field penetrates the molten material without problems, but in ceramic crucibles where the metal is melting, there is a problem. That is, the crucible has a high melting temperature and is capable of transmitting AC magnetic fields, while in some cases the crucible may react with the melt or a portion of the brittle ceramic crucible may peel off and become contained in the melt. It mixes with things. In contrast, metal crucibles have high toughness and do not react directly with the melt. These drawbacks are due to the fact that eddy currents are generated in the crucible, preventing the AC magnetic field from penetrating the molten material. In addition, the metal crucible has a relatively low melting temperature.

It is known to use metal crucibles for the induction melting of metals and alloys despite the above-mentioned negative properties (DEP 518 499, EP 0 276 544, DE-A-39).
40029, EP-A-0 480 845). Here, the wall of the crucible is divided into several segments, reducing the production of eddy currents with a shielding effect and allowing the induction heating of the molten material. On the other hand, the crucible segment is cooled with, for example, water so that it is not melted by the potentially high temperature of the molten material. By installing the crucible segments in a special way, the introduction of energy into the molten material can be optimized. Furthermore, it is also possible to keep the melt from the inner wall surface of the crucible, for example by the radiation pressure of the magnetic field emanating from the coil. In a cooled induction crucible, the melt is removed from the crucible by tilting the crucible after it has been formed. However, it is also known to provide an opening in the bottom of such a crucible and atomize the molten stream flowing out of this opening to produce a metal powder or a metal oxide powder (DE-A-40 11 392). ). To shape the injection flow, a conical or rotating hyperbolic funnel consisting of metallic fluid-cooled segments surrounded by induction coils is provided. Depending on the shape of the funnel, select the AC current frequency at which the induction coil operates and divide by the induction coil tooth pitch
By choosing the rate of total current per slot, the injection flow can be shaped and blocked.

[0010]

It is an object of the present invention to produce an injection stream of a material of higher purity than the material produced by the method described above.

[0011]

SUMMARY OF THE INVENTION The above-mentioned problems are solved by an apparatus in which at least one electrode made of a metal or an alloy is immersed in a liquid slag layer formed above in a crucible, and the electrode is connected to a power source. Is solved by using.

Further, the above apparatus according to the present invention is
There is the fact that it can operate in air or in an inert gas chamber or under excess pressure.

[0013]

An embodiment of the invention is shown in the accompanying drawings,
The details will be described below.

In the device 1 shown, the elements of the electric slag remelting process are combined with those of the induction crucible technology. Electrode 2
Is melted by an electric energy source 3, the first terminal 4 of which is connected to the electrode 2,
The electrode 5 is connected to the crucible 6. A starter plate (not shown) may be provided. The energy source 3 may be either a DC or AC power source. This crucible 6
Is a slotted crucible containing several vertically oriented fins, only some of which are shown at 7-13. The end of the electrode 2 is immersed in the liquid slag layer 14 and melted by the generation of high heat in the slag layer 14. The melted and purified molten material 15 collects under the slag layer 14. Until this point,
This is a conventional electric slag remelting method. In this known method, a pool of liquefied electrode material 15 occurs at a certain depth of the slag layer 14. Under this pool, the material solidifies again. The slowness of the ESR method generally does not allow the entire contents of the crucible 6 under the slag layer 4 to be kept in liquid form, possibly flowing out of the opening of the crucible 6 and being atomized. . The continuous progression of the melting process is achieved according to the invention by the crucible 6 being a cooled induction crucible. The crucible has, around its circumference, a water-cooled induction coil 16, which is connected via terminals 17, 18 to A
It is connected to the C current source 19. With the help of this induction coil, the molten material 15 can remain in the liquid state. An opening 20 is provided at the lower end of the crucible 6 and is closed by a stopper 21 made of the same material as the electrode 2 during a normal melting operation. This stopper 21
It is formed by cooling through the wall of the crucible 6 or is preset in place. If the melting energy supplied by the coil 16 is not sufficient, the solidified stopper continues upward as a solidified layer 22. The remaining melt 15 is kept in a liquid state by the inductive action of the coil 16 and produces an electric current. These currents are indicated by curved arrows 23-26, which are schematic representations of very complex current movements and are not an exact representation of the actual currents. However, in any case, when a slag current occurs, the inclusions and impurities still present in the slag reach the outside and are picked up by the slag layer and removed from the melt. Therefore, the remelted material is purified again.

The electrode 2 can be rotated with the help of a motor 36. The electrode 2 can also be vertically moved up and down by a lifting mechanism 27 attached to the device 29 so as to be movable on the vertical rail 28.

Once the melt 15 is sufficiently purified, it is removed from the crucible 6 and subjected to further processing. For this purpose, another induction coil 31 has a crucible 6
Is provided at the lower end 30 of the power source and receives power from an AC power source 37. When a current flows through this coil 31, the induced heat energy concentrates on the stopper 21 and melts it. After the stopper has melted, the liquid material 15 can flow downward from the crucible 6 through the opening 20,
Further processing produces metal and alloy powders. It is also possible to produce semi-finished products by continuous casting or bottom shrinking. The method can also be carried out continuously by melting the electrodes and allowing the material to flow out.

This further treatment is known per se (eg USP 4 762 553, USP 4869 469). Therefore, it may not need to be described further here. It should be appreciated that the known cold finger technique may be used to divert the stream, or an ingot reactor system may be used. The AC current of the current source 3, which is exactly what is used in the ESR method, can have a variable frequency. One electrode 2
Alternatively, two or more electrodes may be melted simultaneously. In the case of three electrodes, the current source 3 is preferably a three-phase power source.

To heat the melt 15, two separate AC current sources 19, 37 are shown in the figure. However, instead of two AC current sources, one is sufficient if one or the other winding can be switched.

The present invention is a cold finger technique (A. Gubchenko, Y. Norikov, A. Choud for discharging a stream).
hury, F. Hugo: Vacuum Induction and Induction Plasm
a Furnaces with Cold Crucible, Paper presented at
the Vacuum Metallurgy Conference, 1991, Pittsburgh
/ USA) or ingot reactor device (A.Choudhury: V
acuum Metallurgy, ASM International, 1990, pp. 13
6,137) is also advantageous.

The injection flow from crucible 6 can be transferred to a chill mold where it solidifies to form an ingot. It is also possible to use an injection flow from crucible 6 to fill the lost wax mold. Further, the injection flow can be atomized with an inert gas to produce fine metal powder. Furthermore, a continuous rope can be drawn from the tapered region of the crucible 6 to make its diameter variable. The induction coil 16 may be divided into two or more parts and these parts may be connected to the same or different voltages.

[0021]

The advantages achieved by the present invention are that the ESR electrode material can be purified by a slag reaction, the liquefied molten material by heating in an induction oven and concentrating the impurities of the skull on the potentially cold crucible surface. To purify. Furthermore, by combining the two technologies in one installation, one dissolution method compared to separate installations, significant energy savings, reduced operating times, and potentially higher purities are achieved. You can
These advantages add to the large spectrum in the final product. Furthermore, the method is suitable for almost any kind of atmosphere,
For example, it may be carried out in vacuum, in air, in an inert gas, and under excess pressure. Combined equipment may be provided with outlets that allow the realization of the most favorable process conditions for a particular end product.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional elevation view showing an embodiment of the device of the present invention.

[Explanation of symbols]

 1 Device of the Present Invention 2 Electrode 3 Electric Energy Source 4 First Terminal 5 Second Terminal 6 Crucible 7 Fin 14 Liquid Slag Layer 15 Molten Material 16 Induction Coil 17 Terminal 18 Terminal 19 Current Source 20 Opening 21 Stopper 22 Solidification Layer 23 Current 24 Current 25 Current 26 Current 27 Lifting mechanism 28 Vertical rail 31 Another induction coil 36 Motor 37 AC current source

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical indication C22B 9/187 F27B 14/06 7516-4K H05B 6/24 8915-3K (72) Inventor Norbert Ludwig Federal Republic of Germany D-8751 Niedernberg Nordling 5 A (72) Inventor Harald Scholz Federal Republic of Germany D-6458 Rodenbach-Albert-Einstein-Schutrasse 2 (72) Inventor Michael Hoffmann Federal Republic of Germany D-6450 Hanau 7 Von Aif-Strasse 11 (72) Inventor Franz Hugo Federal Republic of Germany D-8750 Asiafenburg Sonnenstraße 24

Claims (16)

[Claims] 1. An apparatus for producing high purity metals and alloys in a cooled crucible consisting of one or several metal segments surrounded by an induction coil, the crucible (6) comprising a liquid slag layer (14). And an electrode (2) made of a metal or an alloy is immersed in the liquid slag layer, the electrode (2) being connected to a voltage source (3). . 2. Device according to claim 1, characterized in that a metal plate is provided as counter electrode. 3. The device according to claim 1, wherein the slag layer (14) has two or more electrodes made of metal or alloy immersed therein, these electrodes being a power source (3).
A device, characterized in that one or several electrodes are connected to each other and act as counter electrodes. 4. Device according to claim 1, characterized in that the crucible (6) has an opening (20) in its bottom. 5. The device according to claim 1, wherein the crucible (6) tapers towards its bottom, the tapered region of the crucible being surrounded by an induction coil (31). A device characterized in that the coil is connected to an AC voltage source (37). 6. Device according to claim 1, characterized in that the electrode (2) can be rotated about its longitudinal axis by a drive (36). 7. Device according to claim 1, characterized in that the electrode (2) can be lowered by a drive (27). 8. The device according to claim 4, wherein the opening (2
0) stopper (21) made of the same material as the electrode (2)
A device characterized by being closed by. 9. Device according to claims 5 and 8, characterized in that the induction heating power of the induction coil (31) is high enough to melt the stopper (21). 10. The apparatus according to claim 1, wherein an ingot reactor device is arranged instead of the crucible bottom. 11. A device according to claim 1, characterized in that the injection flow moves from the crucible (6) to the chill mold, where it solidifies to form an ingot. 12. A device according to claim 1, characterized in that the injection flow from the crucible (6) is used to fill the lost wax mold. 13. A device according to claim 1, characterized in that the powder is formed by an injection flow from the crucible (6) by atomizing an inert gas. 14. Device according to claim 5, characterized in that a continuous rope is drawn from the tapered region of the crucible (6), the rope diameter being variable. 15. A device according to claim 1, characterized in that the process is carried out in vacuum, in air, in excess pressure or in an inert gas. 16. Device according to claim 1, characterized in that the induction coil (16) is segmented.