RU2614862C2 - Method and device for out-of-furnace metal working in ladle - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: device for out-of-furnace liquid steel working in the steel-teeming ladle comprises an upper and at least one lower electrode, current distributor and inert gas supplyconduit pipe. The lower electrode is formed as a set of steel plates, non-conductive ceramic inserts are positioned between them, where holes are made for inert gas supply, providing the ability to periodically change the gas flow during the treatment cycle. The mentioned plates with inserts and channels for supplying an inert gas are enclosed in a shell connected with the base and with a cover attached to the bottom of the ladle through the embedded sectors and insulating gasket. Current distributor and conduit pipe are connected with the mentioned cover.

EFFECT: increased efficiency of out-of-furnace metal refining, expanded technological capabilities, increased durability, reliability and durability of the device.

6 cl, 5 dwg

Description

The present invention relates to the field of metallurgy, and specifically to out-of-furnace treatment of liquid steel in a steel pouring ladle.

A known method for the out-of-furnace treatment of liquid steel in a ladle-furnace assembly, comprising heating a metal with a DC arc using the upper electrode and the hearth electrode installed in the lower part of the ladle (G.N. Okorokov, A.I. Donets, Al.G. Shalimov and et al. “Heating became a direct current discharge in out-of-furnace processing plants,” steel “Steel”, No. 5, 1994, pp. 36-40).

A ladle-furnace assembly containing a lined bucket, top and bottom electrodes is also known there.

Under the action of the current flowing through the melt, conductive mixing of the bath occurs, which contributes to the production of a homogeneous metal. However, due to the insufficient intensity of mixing, the processing time is increased, and the required uniformity of the metal is not always and not fully achieved.

Of the known closest to the proposed technical essence and achievable results is a method of out-of-furnace treatment of liquid steel in a ladle-furnace assembly, comprising heating the metal with a DC arc using the upper electrode and the bottom electrode installed in the lower part of the bucket, as well as treating the metal with an inert gas blown into the melt through a lance built into the bottom of the side wall of the bucket (Protasov A.V., Bershitsky I.M. “Development and research of units for out-of-furnace steel processing with electric m heating of a DC arc metal "w-L" Electrometallurgy »№1, 2012, pp. 2-7, Fig. 3).

There is also known a device for out-of-furnace metal processing, containing a lined bucket, top and bottom electrodes, as well as a lance for injection into an inert gas melt.

Inert gas supply, in addition to electric arc heating, extends the technological capabilities of out-of-furnace processing due to the intensification of mixing and the additional effect of metal refining by inert gas bubbles.

However, the technological capabilities of the method are limited due to the uneven distribution of inert gas over the volume of the bath.

In addition, the reliability and durability of the device are insufficient due to overheating of the bottom electrodes and the weakening of the strength of the bucket due to the presence of additional holes. The low resistance of the electrodes is caused by the fact that a current of tens of kiloamps is supplied to the hearth electrodes made of steel with limited electrical and thermal conductivity. Moreover, their cooling is carried out only from the outer narrow end. As a result, the steel forming the current-carrying parts of the electrodes is melted, and the ceramic insulation is destroyed.

The technical result of the proposed technical solution is to increase the efficiency of out-of-furnace metal refining, to expand technological capabilities, increase the durability, reliability and durability of the device.

The technical result is achieved by the fact that in the method of out-of-furnace treatment of liquid steel in a ladle, comprising heating the metal with a DC arc using the upper and at least one lower electrode located in the bottom or at the bottom of the ladle wall, as well as treating the metal with an inert gas, blown into the melt in the lower part of the bath, inert gas is fed into the melt through holes made in the hearth electrode.

The inert gas flow rate during the treatment cycle is changed at least once from the minimum value determined from the condition for preventing metal from flowing into the holes in the bottom electrode to the maximum value determined from the condition for preventing breakdown on the surface of the bath.

In a device for out-of-furnace metal processing in a ladle containing an upper and at least one lower electrode, a current supply and a purge gas supply pipe, the lower electrode is provided with holes for supplying a purge gas.

The lower electrode can be made in the form of a set of steel plates, between which are located ceramic insulating inserts, in which openings are made for injecting gas.

Ceramic insulating inserts can be made of porous refractory with pores directed along the current-carrying plates.

One of the lower electrodes may be located in the bottom at the bottom of the bucket wall.

The current lead is made in the form of a hollow cable with a hole for supplying a purge gas.

Thanks to the blowing of the current-carrying elements by an adiabatically expanding purge gas, the working temperature of the lower electrode (lower electrodes) decreases and, thereby, its resistance is increased and it is possible to supply additional electric power, which contributes to an increase in the processing intensity.

The combination of the lower electrodes with the purge units can reduce the number of holes in the lower part of the bucket and, thereby, increase the reliability and safety of work.

Placing one of the lower blowing units in the lower part of the side wall of the bucket eliminates weakly mixed zones of the bath located near the bottom of the bucket.

The essence of the invention is illustrated by its example with reference to the accompanying drawings, where:

in FIG. 1 shows a diagram of a method,

in FIG. 2 - remote element I of FIG. one,

in FIG. 3 is the same as FIG. 1, option with lower electrodes in the bottom and wall of the bucket,

in FIG. 4 shows a view A of FIG. 2

in FIG. 5 a section BB in FIG. 2;

A method for the out-of-furnace treatment of liquid metal in a ladle involves heating a metal 1 located under a slag layer 2 in a ladle 3 using the upper 4 and two lower electrodes 5, and purging the bath with an inert gas 6 supplied through pipelines 7 through the lower electrodes.

A device for implementing the method is a steel pouring ladle 3, consisting of a casing 8 and a refractory lining 9, covered with a cover 10. In the bottom 11 of the ladle 3 lower electrodes 5 are placed, which are a set of current-carrying steel plates 12 with ceramic insulating inserts 13 in which holes are made 14 for inert gas passage. (Alternatively, one of the lower electrodes 5 can be placed in the wall of the bucket - Fig. 3). The insulating ceramic inserts 13 can also be made of a porous refractory with pores directed along the current-carrying plates 12. The plates 12 with the inserts 13 are enclosed in a shell 15 connected to the base 16 with channels 17 for supplying purge gas with a lid 18 fixed to the bottom of the bucket 11 through embedded sectors 19 and an insulating spacer 20. A pipe 7 and a cable 21 are connected to the cover 16 and are connected to the gas and electrical connectors 22, 23 with the supply unit 24 of the shop lines.

An example implementation of the method:

Smelting of steel 45 with a mass of 150 tons is subjected to processing. The technological process includes the supply of lime and fluorspar with guidance on the metal surface of highly basic refining slag, about 12 cm thick, electric arc heating, degassing and removal of non-metallic inclusions by purging the metal with an inert gas. During processing, the steel is subjected to conductive mixing due to the flow of current through the melt and gas-dynamic mixing due to the injection of inert gas. The inert gas flow rate during the treatment cycle is changed at least once from the minimum value determined from the condition for preventing metal from flowing into the holes in the bottom electrode to the maximum value determined from the condition for preventing breakdown on the surface of the bath.

The use of two or more lower electrodes when heating and blowing, with holes for blowing inert gas, and periodic changes in the parameters of the blast and the input power contribute to more efficient mixing of the bath. Inert gas injection cools the melt in the zone adjacent to the hearth electrodes, thereby increasing their service life.

Thus, the use of this technical solution allows you to:

- increase the intensity of out-of-furnace treatment of liquid metal,

- to increase the range of combinations of effects on liquid metal through alternating and variable modes of supply of purge gas and input of electricity into the liquid metal by its volume with different intensities in a dynamic mode with a more complete involvement in the processing of the entire volume of liquid metal in the ladle.

Compared with the closest analogues, the proposed technical solution provides more efficient metal refining while improving the operational properties of the equipment used.

Claims (6)

1. A method of out-of-furnace treatment of liquid steel in a ladle, comprising heating the metal with a DC arc using the upper and at least one lower electrode and treating the metal with an inert gas injected into the melt in the lower part of the metal bath, characterized in that the volume of liquid metal is mixed during processing by supplying an inert gas to the melt through holes made in the lower electrode, with a periodic change in gas flow during the processing cycle.   2. The method according to p. 1, characterized in that the inert gas flow rate during the treatment cycle is changed at least once from the minimum value determined from the condition for preventing metal from flowing into the holes in the lower electrode to the maximum value determined from the condition for preventing the breaker by bath surface. 3. A device for out-of-furnace metal processing in a ladle containing an upper and at least one lower electrode, a current supply and an inert gas supply pipe, characterized in that the lower electrode is made in the form of a set of steel plates, between which ceramic current-insulating inserts with holes for supply inert gas, wherein said plates with inserts and channels for supplying inert gas are enclosed in a shell connected to the base and to a lid fixed to the bottom of the bucket through embedded sectors and zoliruyuschuyu gasket, the current supply line and connected to said cover. 4. The device according to claim 3, characterized in that the ceramic insulating inserts are made of porous refractory with pores directed along the current-carrying plates. 5. The device according to p. 3, characterized in that one of the lower electrodes is located in the lower part of the wall of the bucket. 6. The device according to p. 3, characterized in that the current supply is combined with the inert gas supply pipe.

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