RU2191335C2 - Melting electric arc furnace - Google Patents

Abstract

FIELD: electrical engineering, namely electric arc furnaces for melting steels and alloys. SUBSTANCE: furnace includes bath, three-phase power transformer, three electrodes for melting metal. Working portions of said electrodes are arranged in cavity of furnace. Electrodes are connected to respective phases of secondary winding of transformer. Furnace is provided with source of direct electric current and three-phase group of inductance. There is bottom conductor in bath. One pole of additional source of direct current is connected to said bottom conductor in order to be connected with electrically conductive part of burden in bath; its other pole is connected to zero point of power transformer and(or) to zero points of three-phase group of inductance in order to provide simultaneous connection (through electric arcs) of bottom conductor, power transformer and furnace bath. EFFECT: accelerated melting of burden due to uniform supply of energy to bath, lowered specific consumption of electric energy for melting, free space under crown of furnace for heating up burden by means of exhaust gas. 4 dwg

Description

The invention relates to electrical engineering, to smelting arc furnaces and can be used for smelting steel and alloys
Known arc electric furnace containing a heating and melting source in the working space, in which the electrode is connected to a direct current power source and located in the central region above the furnace bath (Soyfer V.M., Kuznetsov L.N. Arc furnace in a steelmaking shop. - M .: Metallurgy, 1989, p. 179).

The disadvantages of such a furnace are:
- the concentration of energy supply in the Central region of the furnace, which leads to uneven heating of the surface of the bath;
- due to the fact that the current in such a furnace, ceteris paribus, is practically summed in one electrode, then, in comparison with a three-phase AC furnace, the DC furnace electrode has a significantly larger thickness, weight and other complicated parameters.

 Known arc electric furnace containing 3 electrodes in the working space of the furnace, connected to the secondary three-phase network of the power transformer, the furnace electrodes are spatially placed with a shift around the circumference (Nikolsky L.E. et al. Thermal work of arc steelmaking electric furnaces. - M .: Metallurgy, 1981 , p. 53).

The disadvantages of the furnace are:
- A large locality of the arc and the corresponding uneven supply of energy to the bath.

 - When melting in the initial stage of melting, there is a high probability of collapse of the charge and, accordingly, the occurrence of short circuits due to the formation of deep wells melt the mixture.

 - Increased energy consumption for smelting.

 - The structural complexity of placing additional electrodes to accelerate the heating and melting of charge materials of the “filling” of the smelting with the simultaneous location of the shaft for heating the charge with exhaust gases from the side of the furnace roof.

 The objective of the invention is the creation of a melting arc electric furnace, providing an extension of the area of energy supply, more uniform distribution over the area of the bath and increasing the stability of burning arcs in order to accelerate the melting of the charge and, accordingly, obtaining a reduced specific energy consumption for melting, as well as preservation, in the case of necessary, space in the roof of the furnace for the device shaft heating the mixture with exhaust gases in the smelting process.

 The problem is solved in that a melting arc furnace containing a bath, a three-phase power transformer, three electrodes for melting the metal, the working parts of which are located in the furnace space, connected in phase to the secondary windings of the power transformer, is equipped with a direct current source and a three-phase inductive resistance group, and the bathtub is made with a hearth conductor, while one pole of an additional DC source is connected to the hearth conductor for connection with a conductive h charge in the bath, and the other pole to the zero point of the power transformer and / or to the zero points of the three-phase inductive reactance group to ensure simultaneous connection through the electric arcs of the bottom conductor, power transformer and furnace bath.

 In the inventive melting arc electric furnace, alternating and direct currents are superimposed on each other in each phase in one arc discharge. When using three electrodes, the space in the upper part of the furnace is additionally saved for the device to mine and heat the mixture in it with exhaust gases generated during the melting of charge materials and gases from the use of alternative heat sources in the furnace.

With the simultaneous use of alternating and constant currents in one arc discharge, as the experience shows, in most current modes the cross section of the arc discharge increases and covers a large surface area of the heated metal, which contributes to the acceleration of smelting, reduction of specific energy consumption for melting
In FIG. 1 - 3 shows a schematic diagram of a melting arc electric furnace. In FIG. 1 - power electrodes of a three-phase network. To improve understanding of the drawings, the electrodes are arranged in a single line, although in fact they are arranged with a shift around the circumference. In FIG. 1a, 2 and 3, a top view of the arch is given, where the power electrodes are shown with a shift, the remaining projections are shown in a vertical section of the furnace.

 The notation in FIG. 1 - 3: 1 - oven, 2 - bath lining; 3 - alternating current source (power transformer); 4 - a direct current source; 5 - power electrodes; 6 - hearth conductor; 7 - inductive resistance group; 8 - arch of the furnace; 9 - "filling" of the mixture; 10 - secondary network of a power transformer; 11 - secondary windings of the power transformer; 12 - exhaust channel of the furnace; 13 is a top view of the arch.

 Ignition of the arcs is carried out according to the usual procedure from the power transformer 3. Then, a constant voltage from the DC source 4 is applied to the hearth conductor 6 and the zero point of the transformer 11. This mode is controlled in accordance with the specified technological mode of melting.

 When using carbon unalloyed charge 9, the electric arc melting furnace 3 can, together with the energy of electric arcs, work with fuel burners, with the injection of carbon materials, oxygen and foam slag. This oven can be used in a ladle furnace system.

 Thus, it is very important for the furnace to operate by supplying currents of arcs from above through three-phase power electrodes; no less important is the application of direct current to them, supplied to the discharge zone through a hearth conductor and charge. With this supply, an energetically saturated volume of space above the charge is formed and the area of energy input into the charge is expanded, the stability of arc burning increases, which, ultimately, leads to a significant decrease in the specific energy consumption for melting. Of no less importance is the fact that the upper part of the furnace roof is not deformed by the addition of additional electrodes.

Claims (1)

 A melting electric arc furnace containing a bath, a three-phase power transformer, three electrodes for melting metal, the working parts of which are located in the furnace space, connected in phase to the secondary windings of the power transformer, characterized in that it is equipped with a direct current source and a three-phase inductive resistance group, and a bath made with a hearth conductor, while one pole of an additional DC source is connected to a hearth conductor for connection with the conductive part of the charge bath and the other pole - to the zero point of the power transformer and / or to the zero point three-phase groups of the inductive reactance for providing simultaneous connection through electric arc hearth conductor of the power transformer and the furnace.

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