JPS60103136A - Metal refinement - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for refining metals. Electric slag remelting is a secondary melting or refining method. The primary produced ingot, known as a consumable electrode, is remelted and solidified again under precisely controlled conditions to improve the grain structure of the ingot so that the next melt lasts longer than can be obtained during f. Furthermore, inclusions and impurities forming inclusions are removed. Remelting is carried out by passing an electric current between the consumable electrode and the second electrode and by resistance heating.The consumable electrode is partially immersed in the slag layer, and the slag layer generates Joule heat for melting. A puddle of metal is formed on the underside of the slag. The slag provides a path for the electrical current. It also removes inclusions and inclusion-forming impurities from the melt.

Normally current flows through the slug between the consumable electrode and the input. Such an approach works very well when the ingot formed has a cross-section that is substantially the same or larger than one side of the melted electrode paste. However, such a method is undesirable if the cross-section of the ingot formed is smaller than the cross-section of the electrode to be melted, for example if the ingot formed is bar. If the cross section of the ingot is small, it is necessary to interrupt the current frequently. Interrupting the 11i current means intermittently cutting off the current path, and it is necessary to cut off the current using multiple qliding contacts to the ingot. The multi-contacts are formed in two
If the surface of the 1" cut is not smooth or clean, there will be a lot of lint and problems.

The path of current through the ingot tends to create another problem when the ingot formed is smaller than the electrode being melted. The high current required to melt the consumable electrodes resistively heats the ingot and slows solidification.

There was a desire to provide an alternative current path. An experiment was conducted in which a current was passed between the consumable electrode and the melt through the slag. This resulted in unstable operation of the furnace and damage to the crucible.

It was assumed that a layer of slag would solidify against the crucible wall and that this slag layer would promote arcing through the slag layer. The crucible was water cooled.

The present invention provides a current path that avoids arcing that occurs when current is passed between the consumable electrode and the second electrode, which has cooling means as an integral part. The invention also provides a method for passing molten metal through the slag, for example, when passing an electric current between two non-consumable electrodes, at least one of which has cooling means as an integral part, across the slag. Provides a current path that prevents arcing from occurring during injection. Passing current through at least one electrically conductive member interposed between the slag and the cooled electrode eliminates arcing that would otherwise occur when passing current through the slag and between the electrodes. The electrically conductive member 11 has a melting point higher than the LA degree of the slag. For this 7111, the temperature of the slag is the temperature at a location away from the wall of the crucible, and the fact is that there is a temperature gradient in the slag layer.

Electric slag remelting processes are disclosed in numerous references, including U.S. Pat. No. 4,108,255 and U.S. Pat. No. 4,145,563. Patent No. 4,108. ．． No. 255 and No. 4,145,565 do not disclose the current path e,1 of the present invention. Patent No. 4,108
．． The current path in the '255 patent is between the consumable electrode, the crucible, and the mandrel used to cast the cavity input. In Patent No. 4,145,563, the current path is lined with gold wire. However, the crucible liner is insulated from the crucible.

Many references disclose methods for purifying metals that are already molten. Included in these references is West German Patent Application No. WF No. 1,485,646. Similar to the references mentioned in the previous section, Patent No. 1,485,646 does not disclose the current path of the present invention. Patent Nos. 1, 48 and 646 IM describes that slag is electrically F from a crucible. A peripheral solidified slag shell 13 is noted. The electrically conductive members of the present invention do not require such insulation.

It is therefore an object of the present invention to provide a method for refining metals characterized by the use of improved current paths.

The front needle and other objects of the present invention are best understood from the following description, ie, the reference to the drawings herein.

The drawing is a schematic diagram of the components that form the current path.

The present invention provides a method for refining gold in a crucible containing a layer of molten slabs, in which the molten metal moves downward through a slag and resolidifies as an ingot at the bottom. The Ruslag is maintained in a molten state by passing a current between the first and second electrodes through the slag layer. The @2 electrode has liquid or gaseous cooling means as an integral part thereof. It is usually made from copper or copper alloys. Current is passed between the first and second electrodes through at least one electrically conductive member interposed between the slug and the second electrode. The first electrode gradually melts.
! I'l may be a consumable electrode partially immersed in the molten slag so that the drop of metal moves downwards from the molten slag. The second electrode is usually a melt electrode, but may also be a non-consumable '+'tt electrode partially immersed in a layer of molten slag. The current source may be direct current or alternating current, but alternating current is preferred.

The electrically conductive metal has a melting point higher than the temperature of the slag.

The shape, thickness and conductivity of the member are such that the surface portion of the member in contact with the slag has a temperature above the solidification temperature of the slag. A member having a relatively high thermal conductivity generally needs to be thicker than a similarly shaped member having a relatively low thermal conductivity. Generally, the member projects from the second electrode into the slug, but may also be embedded in the electrode. A metal with a high melting point such as tantalum is suitable as a material constituting the component. There is no critical minimum length for the member.

They are usually at least 3/16 inch (4,8 x 1
In most cases, two or more members will be provided, which may be interposed between the slug and the second electrode by any means known to those skilled in the art. Brazing is one special means of attaching parts.

Components forming a current path according to the invention are schematically shown in the drawing. Current flows between the consumable electrode 1 and the crucible 3 through the slag layer 5 and the electrically conductive member 7. The inject 9 and the molten metal reservoir #) 11 are also shown.

The following examples are illustrative of several aspects of the invention.

An attempt was made to flow the LP contact current between the consumable electrode and the tsuba through the slag layer, but this resulted in damage to the tsuba. This attempt was made using a research electric slag with a 6-hole furnace at normal current (1900 amperes) and voltage.
1 is made of nickel-based alloy and has a diameter of 6.5 inches (88.9 x
10-3 meters). The inuit was obtained with a diameter of 1 inch (25.4 x 10 -3 meters).

The inside diameter of the top is 5.25 inches (133,4
x 10-3 meters). Rutsuho inspected the product prior to testing to ensure that there were no defects or malfunctions. When inspected after the test, it was found that the crucible was severely etched, which appeared to be arc scars. The etching depth typically ranged from 1/64 inch (4 x 10'-' meters) to 1/16 inch (1,6 x 10'-3 meters).

The test lasted only 11] minutes. If the etching had penetrated the wall of the rutsuho, water would have gushed into the molten slag and caused an explosion. This is the extent of damage to Rutsuho.
U, it was almost impossible to conduct further experiments in the flow.

The 'ilf passage of the present invention was tested under exactly the same conditions as the trial described in the previous section. Four tantalum protrusions were soldered to the base. All its dimensions are 378 inches long (9,5X10-5 meters) and 5/8 inches diameter (
15.9 x 1o3 meters).

The test lasted 6.5 minutes. A current of 2000 amperes was applied. Upon inspection of the crucible, no damage was found.

The tantalum protrusions were slightly corroded.

Nine additional tests were performed on the same tantalum projections.

The same nickel-based alloy was used as the consumable electrode. The tantalum protrusions protected the crucible and did not cause any damage during the test.

It will be apparent to those skilled in the art that the novel principles of the invention disclosed herein, when taken in conjunction with the specific embodiments thereof, suggest various other modifications and applications of the same invention. Therefore, the principles of the invention should not be limited to the specific embodiments of the invention described herein, provided the scope of the appended claims is understood.

[Brief explanation of drawings]

The drawing shows a schematic diagram of the components forming the current path of the melting furnace. 1...Consumable electrode, 3...Rutsu, 5...Slag,
7...Tantalum electrode, 9...Impit, 11...
- Molten metal.

Claims (1)

[Claims] (1) A method for refining metal in a tank comprising a layer of molten slag, wherein the molten metal moves downward through the slag and solidifies again as an indentation at the bottom, and The slag is maintained in a molten state by passing a current between the first electrode and the second electrode through the slag layer, and the second
in which the electrode has cooling means as an integral part, at least one electrically conductive conductor interposed between the first electrode and the second electrode between the slug and the second electrode; passing an electric current through the electrically conductive member, the electrically conductive member having a melting point higher than the bulk temperature of the slag, and the portion of the surface of the electrically conductive member in contact with the slag reaching the freezing point of the slag. The above method characterized in that it has a higher temperature. 2. The method of claim 1, wherein the electrically conductive member projects into the slug. (3) The method according to claim 1, wherein the electrically conductive member is a high melting point metal. (4) The method according to claim 3, wherein the high melting point metal is tantalum. (5) The method of claim 1, wherein there are at least two electrically conductive members. (6) the electrically conductive member is at least 5716 inches (
2. A method according to claim 1, wherein the length is 4.8 x 10-3 meters). (7) the first electrode is a consumable electrode and features the electrode partially within the molten slag layer such that it gradually melts and metal droplets migrate downwardly from the molten slag layer; A method as claimed in claim 1. (8) The method of claim 1, wherein the second electrode is a liquid cooled electrode. (9) The method according to claim 1, wherein the second electrode is a crucible. aI The method of claim 1, wherein the second electrode is a non-consumable electrode partially immersed in the layer of molten slag. (11) The method according to claim 7, wherein the cross section of the ingot is smaller than the cross section of the consumable electrode. (121'*The method according to claim 1, wherein the second electrode is copper or a copper alloy.