RU2227881C2 - Electric-arc melting furnace (versions) - Google Patents

Abstract

FIELD: metallurgy. SUBSTANCE: invention relates to electric-arc melting furnaces and at can be used for melting steels and alloys. Proposed electric-arc melting furnace has hearth conductor arranged under conducting part of charge bath opposite to electrodes connected to three-phase power transformer with organization of concentrated ionized space in limited volume under electrodes. EFFECT: provision of stable conditions of heating and melting of metal. 3 cl, 11 dwg

Description

The invention relates to electrical engineering, to smelting electric arc furnaces and can be used for smelting steel and alloys.

In modern designs of electric arc furnaces, the supply of electric energy to the furnace bath is mainly represented by two options: through a single-electrode and a three-electrode circuit. In the first case, the energy is concentrated in one spot under the arc, and the rest is transmitted by the column of the arc. In the second scheme, the spots under the arc are spaced into three sites.

In the submitted application, the following solutions are used as an analog and prototype: a melting electric arc furnace is known that contains a heating and melting source in the working space, in which the electrode is connected to a direct current power source and placed in the central region above the furnace bath (V.Soifer, Kuznetsov L.N. Arc furnace in a steelmaking workshop (Moscow: Metallurgy, 1989, p. 179).

The disadvantages of such a furnace are: the concentration of energy supply in the central region of the furnace bath, which leads to uneven heating of its surface; In large-capacity melting furnaces, there is an increase in the transverse dimensions of the electrode and, accordingly, there are known difficulties in their production.

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 in a circle (Nikolsky L.E. et al. Thermal work of arc steel-smelting electric furnaces. M .: Metallurgy, 1981 , p. 53).

The disadvantages of such a furnace are: the local action of electric arcs on the surface of the bath creates an uneven supply of energy from the current source; uneven supply of energy in the initial stage of melting leads to collapses of the charge and short circuits, which leads to an extension of the melting of the filling metal and an increase in the energy consumption for melting.

Another device of an electric arc melting furnace is also known, which contains two sources of electric energy, including supplying electric arcs with alternating current from a three-phase power transformer and from a direct current source, one pole of which is connected to a bushing conductor, and the other pole of this source is connected to the zero point of the secondary windings of a power transformer and / or a three-phase inductive reactance group or to zero points of both devices (Russian patent No. 2191335 of 03/13/2000, prototype).

This solution is not universal. It does not provide for the exact spatial reference of the supply of electric arcs in the melting furnace from two energy sources. At the same time, this solution is focused only on the connection of the secondary windings of the power transformer according to the "star" scheme. In practice, as you know, the secondary windings of a power transformer are often connected in a “triangle” pattern.

The task of the invention is to eliminate the disadvantages of the known solutions for the construction of electric arc melting furnaces.

The problem is solved in that an electric arc melting 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, and an additional DC source connected to one of its poles through a hearth conductor with the metal of the bath mixture, and the other pole of the DC source connected to the zero point of the secondary windings of the power transformer and / or three-phase groups e of inductive resistance or zero points of both devices, while a three-phase group of power electrodes is installed in the area opposite the hearth conductor located under the conductive part of the bath mixture, and the secondary windings of the power transformer and inductive resistances are connected in a star configuration, as well as an electric arc melting furnace, containing a bath, a three-phase power transformer, three electrodes for melting metal, the working parts of which are located in the space of the furnace, connected in phase to the secondary kam of the power transformer, and an additional DC source connected through one of its poles to the bath charge metal through the bottom conductor and the other pole of the DC source connected to the zero point of the three-phase group of inductances connected in the star circuit, characterized in that the secondary windings power transformer connected in a "triangle".

Due to the location of the electrodes connected to the power transformer, opposite the hearth conductor, exact spatial interconnection of power, electric arcs in the melting furnace from two energy sources is carried out and phase-by-phase equal conditions for the interaction of direct current with alternating current are created. High ionization of the sub-electrode space becomes a medium in which, due to the phase shift of the currents, the arc discharge moves between the electrodes and thereby increases the effective section of the conductive space under the electrodes. Under these conditions, the charge is melted over a larger area, which allows energy input through one well. In this case, collapses and short circuits are excluded, the melting time of the filling metal is reduced, energy and refractories are saved.

In industrial conditions, the connection of the secondary windings of a power transformer according to the "triangle" scheme is widely used. The high degree of ionization of the sub-electrode space makes it possible to connect the secondary windings of the power three-phase transformer using two “triangles” using two sources of energy, and connect one pole to the bottom conductor at the DC source, and connect the second to the zero point of the three-phase inductive resistance group performed according to the “ star". This solution reduces energy loss and simplifies furnace construction. Other operational and simple possibilities of operation of the furnace on combined currents, direct and alternating, are also opening up.

Figure 1 and 1A, 2 and 3 shows a diagram of an electric arc melting furnace, and figure 4 - its basic installation design. On figa and 4 - power electrodes to improve understanding of the drawings are aligned, although in fact they are located with a shift around the circumference. In figures 1, 2 and 3, a view of the arch is given from above, where the power electrodes are shown with a shift around the circumference, the rest of the projection is shown in a vertical section of the furnace.

Designations in the drawings: 1 - oven; 2 - lining of the bath; 3 - alternating current source (power transformer); 4 - a direct current source; 5 - power electrodes; 6 - hearth conductor; 7 - three-phase group of inductive resistance, connected according to the "star"; 8 - furnace arch; 9 - “filling” of the charge; 10 - secondary network of a power transformer; 11 - secondary windings of a power transformer connected by a star circuit; 12 - exhaust channel of the furnace; 13 is a top view of the arch of the furnace; 14 and 14a - the switch in the on and respectively off states at the entrance to the rectifying units; 15 and 15a, respectively, from the side of the primary windings 3 of the power transformer; 16 - connection of the secondary windings according to the "star" scheme; 17 - respectively, according to the “star” or “triangle” pattern.

The furnace operates as follows (Fig.1, 1 a, 2 and 3).

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

In Fig. 4 a, b, c, d, e, e, h, variants of the basic circuit in different designs are presented. They work taking into account the features embedded in them, without leaving the field of claims of the proposed solution. The schematic diagrams shown in figa, b, c work according to the same algorithms as the circuit in figure 1, 1 a, 2 and 3.

The circuits in this figure 4 are shown in working condition. The start-up of the circuits in Fig. 4 g, e does not differ from the start-up of the circuits of the options described above, only the furnace is operated at constant current using secondary windings 16 of the power transformer (Fig. 4 g) and the group of inductive resistances 7. In these embodiments, the primary windings 3 of the transformer are disconnected from the network.

The furnace circuit shown in FIG. 4 e also operates on direct current. It involves simultaneously the secondary power windings 16 of the transformer and the inductive reactance group 7.

The furnace depicted in FIG. 4z operates as a conventional alternating current furnace. The DC source 4 in this embodiment is disabled by the switching device (switch) 14a.

Installation versions of the basic circuit of an electric arc melting furnace (Fig. 4) open up the possibility of operating the furnace in a combined version, when direct and alternating currents are used in various ratios, including the predominance of direct or alternating current.

At the finishing stage of the melting, a large capacity in most cases is not required, therefore, the finish of the melting can be performed in the declared furnace both on constant-alternating, constant, and alternating currents. This confirms the wide possibilities of the claimed electric arc melting furnace.

For the stage of melting the charge materials, the furnace can be equipped with devices for supplying energy from alternative sources, it can operate on a “ladle furnace” and as a unit in which steel is melted with alloying and preliminary deoxidation of the metal in the bath and final - when the liquid melt is drained into the ladle . The smelting of metal in the inventive furnace can be performed according to other known technological schemes.

Thus, the inventive electric arc melting furnace is an effective universal melting unit for the smelting of steel and alloys.

Claims (2)

1. An electric arc melting furnace containing a bath, a three-phase power transformer, three electrodes for melting metal, the working parts of which are located in the space of the furnace, connected in phase to the secondary windings of the power transformer, and an additional DC source connected to one of its poles through a ground conductor with metal charge bath, and the other pole of the DC source connected to the zero point of the secondary windings of the power transformer and / or three-phase group of inductive resistance or evym points both devices, characterized in that the group of three-phase power electrodes installed in front of the hearth conductor disposed beneath the conductive portion of the charge bath, and the secondary winding of the power transformer and inductive reactances connected in a "star." 2. An electric arc melting furnace containing a bath, a three-phase power transformer, three electrodes for melting metal, the working parts of which are located in the space of the furnace, connected in phase to the secondary windings of the power transformer, and an additional DC source connected to one of its poles through a ground conductor with metal charge bath, and the other pole of the DC source is connected to the zero point of the three-phase group of inductive resistances connected according to the "star" scheme, characterized in that The original windings of the power transformer are connected in a “triangle” pattern.

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