SU1048810A1 - Plasma unit for melting and refining metal - Google Patents

Abstract

PLASMA INSTALLATION FOR MELTING AND REFINING OF METAL, containing melting chamber with drain. toe 5 plasma torch and underwater electrode, characterized in that, in order to increase the efficiency of the metal refining process, simplify the design, increase durability and reliability of operation, the installation is equipped with a submersible plasma tuyere located in the side wall of the melting chamber opposite the drain tip on the same level, and a reversing rotation mechanism that allows the melting chamber to be tilted up to 90, both towards the discharge nose and towards the plasma tuyere.

Description

The invention relates to metallurgy and foundry.

A known plasma plasma filling system, which is equipped with an intermediate funnel and a sealed chamber for the casting mold, is expanded; laid on the drain sock.

As a disadvantage of these furnaces, low efficiency should be noted. the process of refining, metal due to the low intensity of the melt mixing, the furnace designs are known for. :: smelting and refining of metal, in which metal is melted by a continuous arc, and its refining is carried out by mixing with a stream of exhaust gas entering the melt from the bottom cavity

4 electrodes.

Plasma furnaces of this type include a plasma torch embedded in the furnace shank, a bottom electrode and equipped with a recirculation loop connecting the working space of the furnace with the cavity of the bottom electrode. The furnace recirculation system consists of a gas cleaning system, an injector and a nozzle with a valve for gas discharge.

The disadvantages of such furnaces are

- the complexity and low reliability of the gas recirculation and purification system, the complexity of the system for controlling its consumption, and the low efficiency of the metal refining process.

3 (04

Also known is a Linde furnace, which includes a refractory lined melting chamber, a plasma torch, a bottom electrode, and coils for electro magnetic stirring of sid metal, mounted in the furnace bottom.

The disadvantages of such a furnace include the insufficient mixing efficiency of the melt, the complexity of the design.

The closest in technical essence and the achieved effect is a plasma furnace for melting and refining metals, containing a chamber with a drain toe, a plasma torch and a bottom electrode I

The disadvantages of this furnace are the large laboriousness of manufacturing inserts with a given porosity, their low durability and the associated frequent repairs of the bottom electrode and crucible lining, the difficulty of maintaining the melting temperature due to the purging of the metal with cold gases, the design complexity of the furnace blowing device and the low efficiency of the refining process melt.

The aim of the invention is to improve the efficiency of the metal refining process, simplifying the design, increasing the durability and reliability of the pWs.

The goal is achieved by the fact that a plasma unit for melting and refining metal, containing a melting chamber with a toe-loaded plasmatron and a bottom electrode, according to the invention, is equipped with a Plasma blowing lance located in the side steak of the melting chamber opposite the drain toe at the same level with it, and a reversing mechanism rotation, allowing the melting chamber to be tilted up to 90, both toward the toe side and towards the plasma tuyere.

FIG. depicts the proposed installation, general view; figure 2 is a view along arrow L of FIG. 1,

The plasma unit for melting and refining the metal includes a removable cover 1 with a plasma torch 2, a melting chamber 3, a bottom electrode 4 mounted in the bottom part of the melting chamber, a submersible-type plasma tuyere 5, which is installed in the side steak of the furnace opposite

Sock 6 and flush with it. The installation is equipped with a reversing turning mechanism 7, which is tightly connected to the furnace body. Plasma lance 5 is a type of indirect action plasma torch, in which two electrodes (cathode and anode) are mounted in one housing. Such plasmatrons are widely used, for example, in plasma spraying.

The proposed structure works as follows.

The setup 3 loads the mixture 3 into the melting chamber 3, covers with a lid 1, switches on the plasma torch 2 and melts the metal. When the melting is completed, the plasma torch 2 is turned off and the plasma lance is switched on 5. Simultaneously with the inclusion of the plasma lance, a reversible turning mechanism is turned on and the furnace is rotated 90 times to the side of the lance 5. After filling the overspot space with liquid metal, the refining of the furnace is made by blowing it ionized m gas that enters the melt through a plasma lance, where it is heated to high temperatures. The proposed design, along with the refining of the melt with high-temperature ionized gas, makes it possible to treat the powder-like reagents in the heated state by passing them through the torch tuyere 5.

At the end of the melt processing process, the plasma tuyere incorporates a reversible turning mechanism and tilts the furnace towards the drain tip b to drain the metal into the mold. At the time of discharge of the metal, the plasma lance is switched off. After the metal is released from the smelting chamber, the furnace returns to its original position and the process repeats.

Testing of the proposed construction of a plasma furnace for melting and refining metals was carried out in the smelting of structural steel 40X.

The design of the pilot plant included a water-cooled melting chamber, a removable lined crater with a plasma torch and a plasmatron moving mechanism. In the lower part of the smelting chamber, a bottom water cooled electrode was mounted. A plasma non-waterproof lance was permanently installed in the side wall of the melting chamber on the opposite side of the drain tip and at the same level with it. The installation of the tuyere was carried out in such a way that, after the charge was melted, it did not contact the melt. The plasma torch and the plasma tuyere were connected to the same BITP-602 power source and they worked from the same power source alternately. Rotation of the furnace by 90 ° towards the flame tuyere and towards the drain tip for pouring the metal into the mold was carried out manually using a gear. During the melting process, the current on the plasma torch was changed from 400 to 700 A. When the melt was blown with ionized gas, the current supplied to the plasma tuyere was constant and amounted to 600 A. As the working gas in the plasma torch and plasma tuyere, argon ..; The work of the pilot plant was concluded as follows. The furnace lid was opened with a plasma torch and the mixture was loaded into the crucible. Then the flap was closed, the plasma torch was turned on, and the bolts were melted. After the metal melted, the plasma torch was turned off and the plasma pump was switched on simultaneously. The furnace was turned 90. At the same time, the plasma lance and the underfurmenian space were filled with metal. The flow rate of argon entering the metal through the plasma lance was controlled by the intensity of the melting of the melt (which was controlled visually through the inspection hatch). The argon flow rate at a constant pressure of 2.5 atm was controlled with a PC-3 rotameter. The upper argo overpressure limit is limited by the required flow; the lower pressure limit must exceed yN, where the specific gravity of the melt, H is the height from the plasma tuyere nozzle to the metal mirror. With a smaller gas overpressure, the melt can penetrate into the working space of the plasma tuyere and the last out of order. The melt was blown with ionized argon through the plasma tuyere for 3–3.5 min, and the argon consumption was 0.60, 8 m / t metal. During the purge of argon melt its temperature in; embroidered at 10-15 C due to the heat introduced into the metal using a plasma tuyere. The proposed constructive. This solution allows not only to combine the processes of smelting and refining the metal, but also to carry out the refining of the melt without overheating it to high temperatures. As a result of this, along with an increase in quality. The capacity of the cast metal increases the productivity of the melting units. After refining the melt, the furnace is turned to the side of the drain sock and the metal is poured into the mold. When the plasma tuyere was released from the melt, it was turned off. At the end of the casting, the furnace was returned to its original position and the melting process was repeated. An experimental test showed that the reversing mechanism should ensure that the furnace turns 90 in both directions. When turning the stove towards the drain sock is less than .90 it is difficult to drink metal completely from the melting chamber. When the angle of rotation of the furnace is greater than 90 °, the metal droplets remaining on the hearth and the walls of the melting chamber may fall on the plasma torch nozzle and the cover, as a result of which the plasma torch goes out and its seal is broken. Turning the furnace towards the plasma tuyere less than 90 does not ensure effective mixing of the melt when it is blown with ionized gas through the bulk form. At an angle of rotation of more than 90 °, there is a danger of the melt reaching the plasmatron as a result of the metal being fused when it is refined with a plasma tuyere. Along with this, with a larger angle of rotation of the furnace towards the tuyere, the metal may fall into the plug-in connection / key and the melting chamber, this complicates their sealing during operation. The location of the plasma tuyere in the side wall of the melting chamber on the opposite side of the discharge nose and at the same level with it is optimal. When mounting the tuyere not against the drain sock, it is necessary to reduce the volume of the metal being smelted in order to eliminate melt emissions through the s-beer sock during its purging with an ionized gas. Installing the burglar below the level of the drain nose also requires a reduction in the volume of melted metal to avoid contact of the tuyere with the melt during smelting. Mounting the plasma tuyere above the level of the drain toe does not allow for the required intensification of the melt mixing process during purging. In order to intensify the process of melting the melt at a higher location of the tuyere, it is necessary to increase the angle of rotation of the furnace towards the tuyere, which causes the same undesirable phenomena that have been mentioned above. The proposed constructive solution allows to increase the duration of the blowdown devices, since the devices in such furnaces do not constantly contact the melt, but only for a short time during the refining of the metal. Tests of the proposed design showed that the plasma submerged lance in the refining process works reliably and efficiently. No cases of ousting of the tuyere were observed since switching it on and off, it was essential in the absence of contact of the plasma tuyere with the metal. Investigation of the quality of the injected metal showed that the content of oxygen in it is reduced by 15–20%, of hydrogen to 30%. The number of non-thallic inclusions decreases by 35-40%, and the density of the cast metal increases by 1.2-1.3% compared with the base object .; Plasma-induction melting technology was adopted as the base object for casting by melted models. and non-metallic inclusions in the metal, by 1.2-1.3% of the density of the cast products and more than twice the service life of the blowing devices for metal refining according to preliminary calculations will be about 60 thousand rubles. per year per furnace during smelting of complex alloyed steels.

Power source

40

Claims (1)

PLASMA INSTALLATION FOR Smelting and refining of metal, containing a melting chamber with a drain toe, a plasma torch and a hearth electrode, characterized in that, in order to increase the efficiency of the metal refining process, simplify the design, increase durability and reliability, the installation is equipped with a plasma immersion lance, located in the side wall of the melting chamber opposite the drain sock at the same level with it, and. ·, A reversible rotation mechanism, allowing you to tilt the melting chamber up to 90 ° both in the direction of the drain toe, and in the direction of the plasma lance.