RU2371652C1 - Electric furnace for preparation of alloys of nonferrous metals - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: electric furnace contains lined bath with side walls and bottom, contacting to melt, installed in bottom electric heating unit, consisting of refractory heat-conducting block and heating elements, and source of electric energy. Heating elements are implemented in the form of current-carrying electrodes, installed in lining of bottom, refractory heat-conducting block is implemented from electroconductive resistance material on the basis of carbon and is a part of lining of bottom of furnace, herewith top surface of refractory heat-conducting block is in contact to current-carrying cooled electrode through melt of metal, and its bottom surface - to other current-carrying electrode through source of electric energy.

EFFECT: increasing serviceability of electric fire ensured by increasing of reliability of electric heating unit and lining of bottom as a result of reduction of gradient of temperatures by thickness of refractory heat-conducting block.

2 cl, 2 tbl, 1 dwg

Description

The invention relates to the field of metallurgy and electrical technology, namely to electric furnaces used for the preparation of non-ferrous metal alloys.

In electric furnaces and similar installations intended for the preparation of alloys, there is a need for an electric heater - a source of thermal energy, which would provide thermal energy to the lower part of the molten liquid in the bath of an electric furnace and have a high degree of operational reliability.

Known arc electric furnaces with hearth electrodes (RF patent No. 2097947, publ. 11/27/97, Cl. H05B 7/20, 7/11, F27D 11/10, F27B 3/10), in which an electric source of thermal energy is used discharge, which is a burning electric arc.

In this type of electric furnace, the bulk of the thermal energy is released above the upper layers of the melt, due to which a temperature difference occurs between its upper and lower layers.

Tamman's electric furnace is also known, the principle of operation of an electric heater which is based on the release of thermal energy in a resistance electric heater, which is also an element of the enclosing structure (Zuev V.M. Heat treatment of metals / V.M. Zuev. M .: Higher school, 1976 p. 240, fig. 127).

In the preparation of electrically conductive melts, such as non-ferrous metal alloys, in such an electric furnace there is a need for electrical isolation of the electric heater from the melt. For this purpose, an intermediate electrical insulating layer is created between the electric heater and the electrically conductive alloy. This leads to a decrease in the reliability of the electric heater and its thermal efficiency.

Closest to the claimed electric furnace for the preparation of metal alloys is an electric furnace (Norwegian patent No. WO 9716051, publ. 1997.05.01, Cl. H05B 3/10, H05B 3/62) containing a lined bath with side walls and a hearth in contact with melt, an electric heater, consisting of a refractory heat-conducting block located in the hearth, in the openings of which are installed heating elements, as well as a source of electrical energy.

The disadvantage of this design is the installation of heating elements in the holes of the refractory heat-conducting block, which leads to an unacceptable temperature gradient in it, the formation of cracks and the subsequent passage of the melt to the heating elements. Replacing an electric heater significantly reduces the operational reliability of an electric furnace.

The problem solved by the invention is to increase the operational reliability of the electric furnace by increasing the reliability of the electric heater and the lining of the hearth as a result of a decrease in the temperature gradient across the thickness of the refractory heat-conducting block.

To solve the problem in the proposed electric furnace for the preparation of non-ferrous metal alloys, containing a lined bath with side walls and a hearth in contact with the melt, an electric heater installed in the hearth, including a refractory heat-conducting block and heating elements, and an electric energy source, according to the invention, the heating elements are made in the form of current-carrying electrodes installed in the lining of the hearth, the refractory heat-conducting block is made of electrically conductive A carbon-based resistive material is part of the lining of the furnace hearth, with the upper surface of the refractory heat-conducting block in contact with the current-carrying cooled electrode through the metal melt, and its lower surface with the other current-conducting electrode through the electric energy source. In this case, the electrode in contact with the melt can be made of a material that is the basis of the alloy being prepared.

In accordance with the proposed technical solution, a refractory heat-conducting block installed in the bottom is a source of thermal energy - an electric heater, capable of providing the required amount of thermal energy when an electric current flows through it to heat the metal melt. This is due to the implementation of the refractory heat-conducting block of an electrically conductive resistive material. At the same time, the block is simultaneously part of the lining of the hearth of the electric furnace.

For this purpose, the refractory heat-conducting block is located in the lining of the electric furnace so that one of its surfaces is electrically insulated from the melt and connected to one of the poles of the electric energy source through a current lead, and the other is in contact with the melt. The second pole of the electric energy source is connected to a current-conducting electrode in contact with the melt, which is made of material that is the basis of the alloy being prepared. With this arrangement of the refractory heat-conducting block, the most uniform release of thermal energy in it is ensured.

The drawing shows a cross section of the proposed electric furnace for the preparation of non-ferrous metal alloys, which includes: a lined bath 1, fenced from the sides by lined walls 2, a refractory heat-conducting block 3 located in the insulating lining of the hearth 4 so that the upper surface of the refractory heat-conducting block 3 it contacts through a metal melt with a current-supplying electrode 5, and the lower surface - with a current-conducting electrode 6. Using a current-supply 7 made of material with n With a specific electrical resistivity, the current-supplying electrode 6 is connected to the electric energy source 8. The second pole of the electric energy source 8 is connected to the cooled part of the current-supplying electrode 5 by means of the current-supplying 5. In the cooled part of the current-supplying electrode 5, a cavity 10 is provided for the cooling liquid entering it through the system cooling 11. The temperature of the current-supplying electrode 5 is maintained at the required level by the automatic control system 12, regulating her coolant flow rate. When you turn on the source of electrical energy 8 through the current leads 7, 9 begins to flow electric current. Part of the thermal energy is released in the current-supplying electrode 5. In order to ensure the required temperature conditions of the current-supplying electrode 5, a cooling fluid is passed through the cavity 10, due to which its shape and physical properties are maintained stable. In this case, the bulk of the thermal energy is released in the refractory heat-conducting block 3 and transferred to the melt, heating it to a predetermined temperature.

It is proposed to use carbon-based electrically conductive resistive materials with a high melting point as a material of a refractory heat-conducting block: silicon carbide, siliconized graphite (table 1). Table 1 shows the physical properties of electrically conductive resistive materials, confirming the possibility of their use as a material of a refractory heat-conducting block.

As applied to a specific performance example, to compare the relative operational reliability of electric heaters, structurally made in accordance with the proposed technical solution and prototype, their mathematical and physical models were created. The characteristics of electric heaters that determine their relative operational reliability were investigated on the models. At the same time, electrically conductive resistive materials were used for electric heaters, shown in table 1. The corresponding results are shown in table 2. From the characteristics given in table 2, it follows that the operational reliability of electric heaters made according to the proposed technical solution is significantly higher than that of the prototype.

Thus, the design of the electric furnace in accordance with the proposed technical solution and the results of studies on mathematical and physical models confirm that the operational reliability of the electric furnace can be significantly improved by increasing the reliability of the electric heater and the lining of the hearth.

Another advantage of the proposed technical solution is that it can be used in metallurgical equipment such as tray systems, ladles, refining plants, in the outlet openings and nozzles of metallurgical vessels, as well as in laboratory furnaces. In these cases, the dimensions and shape of the refractory heat-conducting block are selected depending on the specific requirements for the above equipment.

Table 1 No. Material Refractory
° C Electrical resistivity at (20 ÷ 1200) ° C, μOhm · m The temperature coefficient of linear expansion, 10 ^-6 ° C ^-1 The coefficient of thermal conductivity, W / (m · ° C) one Silicon Carbide, SiC 2200 10 ÷ 105 5.05 4 ÷ 35 2 Siliconized Graphite 1800 3 ÷ 2 4.2 20 ÷ 200

table 2 No. Material of refractory heat-conducting block Siliconized Graphite Silicon Carbide, SiC Technical solution Proposed Prototype Proposed Prototype one Total allocated power, W 14640 14640 14640 14640 2 The maximum temperature gradient, ° C / m 2600 4860 3092 6753 3 Heat resistance (comparative Good Good Satisfactory
naya Satisfactory
naya

Claims (2)

1. An electric furnace for the preparation of non-ferrous metal alloys, containing a lined bath with side walls and a hearth, in contact with the melt, an electric heater installed in the hearth, consisting of a refractory heat-conducting block and heating elements, and an electric energy source, characterized in that the heating elements are made in in the form of current-carrying electrodes installed in the lining of the hearth, the refractory heat-conducting block is made of an electrically conductive resistive material based on carbon and is part of the lining of the hearth of the furnace, the upper surface of the refractory heat-conducting block being in contact with the current-carrying cooled electrode through the molten metal, and its lower surface is in contact with another current-conducting electrode through the electric energy source. 2. The electric furnace according to claim 1, characterized in that the current-conducting cooled electrode in contact with the melt is made of material that is the basis of the alloy being prepared.