RU2291203C2 - Method of making vanadium-containing steel - Google Patents

Abstract

FIELD: ferrous metallurgy; methods of making vanadium-containing steel in electric arc melting furnaces.

SUBSTANCE: steel making process is carried out by series; mass of metal burden of the first heat in series exceeds mass of subsequent heats by 10-20% and mass of burden of the last heat in series is lesser than that of previous heat by 10-20%. Oxidizing process is carried out till concentration of carbon is not lower than 0.10% of low content in finished steel and at temperature which is below liquidus temperature by 180-240°C; at tapping the first melt and subsequent melts, furnace slag flux is cutout and at last heat of series, slag is subjected to deoxidation by coke powder, crushed ferro-silicon in the amount of 0.08-0.10% each and the last melt is tapped into ladle with furnace slag; at tapping all the melts into ladle , solid slag-forming additive is introduced into ladle after it has been filled by ¼ of its height; solid slag-forming additive contains lime and vanadium-containing converter slag at ratio of (1.2-1.9) : (0.5-0.9), respectively in the amount of 1.7-2.8 of mass of molten steel in ladle; if necessary, deoxidizing and alloying agent are added; slag-forming additive, deoxidizing and alloying agents are added before ladle is filled with steel to ¾ of its height. Proposed method ensures reduction of melting time by 18 min; reduction of power requirements by 15 kW/h/ton and reduction of consumption of electrodes by 0.18 kg/t.

EFFECT: enhanced efficiency; enhanced through extraction of vanadium.

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Description

The invention relates to ferrous metallurgy, in particular to methods for smelting vanadium-containing steel in electric arc furnaces.

Known methods for smelting vanadium-containing steels in electric arc furnaces, including charging the charge, conducting an oxidation period, conducting a reduction period, introducing vanadium-containing material, deoxidizing slag and metal in the furnace, releasing steel into the ladle and subsequent deoxidizing metal in the ladle, where vanadium-containing material is used vanadium slag, which is introduced into the furnace in the filling [1, 2, 3], in the filling and oxidation period [4], in the oxidation period, followed by the oxidation of slag and metal oven [5, 6], in the recovery period [7].

Significant disadvantages of these methods of smelting vanadium-containing steels are:

- long duration of smelting in connection with the alloying with vanadium in the furnace and the need for a recovery period and deoxidation of metal and slag in the furnace;

- high operating costs associated with a long melting period (consumption of electrodes, electricity, refractories);

- increased consumption of ferroalloys due to high waste associated with the deoxidation of steel in the furnace.

There is also a known method of producing vanadium alloyed steel, including steel smelting, pouring into a ladle, an additive in the ladder of slag converter, deoxidizing agents, alloying alloys, fluorspar, characterized in that in order to increase the absorption of vanadium, yield metal, reduce the consumption of manganese-containing ferroalloys, after with metal filling 1 / 7-1 / 6 of the bucket volume, aluminum slag from the production of secondary aluminum in a quantity of 0.1-0.3 kg / t of steel is planted under the stream, and when filling 1 / 6-1 / 5 of the bucket volume, converter vanadium slag is introduced [ 8].

Significant disadvantages of this method are:

1. Increased contamination of steel by non-metallic slag inclusions and an increase in the oxygen concentration in steel due to the preliminary deoxidation of steel by ferroalloys with the subsequent introduction of the required amount of converter vanadium slag.

2. The possibility of "slagging" of slag and metal, leading to a decrease in the extraction of vanadium from vanadium-containing slag due to the addition of vanadium-containing slag to the bucket with insufficient filling volumes (1 / 6-1 / 5 of the bucket volume).

3. A reduced level of physical and mechanical properties due to the significant concentration of oxygen in the steel and contamination of the steel by non-metallic inclusions of the endogenous type.

There is also known a prototype method for smelting vanadium-containing steel, including charging the mixture, melting, oxidizing the melt, alloying the steel by adding vanadium slag followed by reduction of vanadium from oxides using a reducing agent, and vanadium slag is added together with slag from aluminum remelting in a ratio of 2, 5: (1-1.5) after downloading the oxidizing slag [9].

Significant disadvantages of this method are:

1. Increased pollution of steel non-metallic alumina-containing inclusions in connection with the use of slag from remelting aluminum as a reducing agent.

2. Increased melting time due to the addition of vanadium slag to the furnace, and not to the ladle when melting is released.

3. A reduced level of physical and mechanical properties due to a significant degree of contamination of steel with alumina-containing inclusions.

The desired technical results of the invention are: reducing the duration of the smelting, reducing the consumption of electricity and electrodes, refractories and increasing through extraction of vanadium.

To this end, a method is proposed for smelting vanadium-containing steel, including feeding a metal charge consisting of scrap metal and molten iron into an electric arc furnace, melting, oxidizing period, deoxidation and alloying of steel, while the steel is smelted in batches, and the steel smelting of the first melting in the series is made by 10 -20% more mass of the metal charge of the subsequent melts, and the mass of the metal charge of the last heat in the series is reduced by 10-20% relative to the previous one, the oxidation period is carried out until carbon monoxide not lower than 0.10% of its lower content in finished steel and at a temperature above the liquidus temperature of 180-240 ° C, and when the first and subsequent melts are released, furnace slag is cut off, steel is deoxidized and alloyed in the ladle, and on the last in a series the melts deoxidize the slag in the furnace with coke powder, crushed ferrosilicon in the amount of 0.08-0.10% each, and release the last melt into the ladle with furnace slag, and when all the melts are discharged into the ladle after filling 1/4 of the ladle height, a solid slag-forming mixture consisting of lime and vanadium-containing converter slag at a ratio of respectively (1.2-1.9): (0.5-0.9) in an amount of 1.7-2.8% by weight of the molten steel in the ladle, and the necessary deoxidizers and alloying agents, in this case, the additive of the slag-forming mixture, deoxidizing agents and alloying materials is completed before filling 3/4 of the ladle height with steel.

The claimed limits are selected experimentally. The blending of the first smelting is 10-20% more than the weight of the metal filling plant (scrap metal and molten iron) provides a molten slag-steel residue passing from the smelting to the smelting, providing, firstly, when the scrap metal is poured into the furnace, it is protected from mechanical shocks and lining destruction, and secondly guaranteed cut-off of furnace slag. If the residue in the furnace is less than 10%, there is a chance that furnace slag will enter the ladle, and if the residue in the furnace is more than 20% by weight, the technical and economic indicators of smelting are reduced.

The carbon content was chosen based on the fact that when the carbon concentration is less than 0.10% below its lower content in the finished steel, the oxygen content in the steel increases and increased fumes of ferroalloys are noted.

The temperature is selected based on heat loss and casting conditions; at a temperature below 180 ° C below the liquidus temperature due to high heat losses in the ladle it is impossible to cast on a continuous casting machine; when liquidus is overheated at a temperature of 240 ° C, it is necessary to cool molten steel in the ladle to optimize the temperature-speed casting conditions. The deoxidation of slag by coke powder, crushed ferrosilicon in the last heat in the amount of 0.08-0.10% by weight of the metal filling provides the required level of oxygen in steel when deoxidized furnace slag gets into the ladle.

The ratio of lime and vanadium-containing converter slag is selected based on the degree of extraction of vanadium in steel. With a decrease in the ratio of lime less than 1.2 and vanadium-containing slag less than 0.5, the degree of vanadium extraction decreases to 40%, and with an increase in the ratio of lime more than 1.9 and vanadium-containing slag more than 0.9, the slag ratio increases, costs increase with an invariable degree of vanadium recovery .

The ratio and amount of the mixture is selected based on the optimal basicity of the slag contributing to the increase of manganese extraction, as well as the heat-insulating ability of the slag. When the amount of slag is less than 1.7% by mass, heat losses through the slag are large; when the amount of slag is more than 2.8% by mass, a significant amount of heat is needed to melt the slag-forming mixture.

The inventive method of smelting rail steel was implemented in the smelting of steel in electric arc furnaces DSP-100I7. Smelting was carried out according to the following scheme. The filling of the first heat in the series for metal filling was 10–20 tons more than subsequent fillings, and the last in the heat series was 10–20 tons less. The filling consisted of 80-90 tons of scrap metal and 3-8 tons of lime. Pouring cast iron in an amount of 30-40 tons was carried out from an iron bucket by means of a bridge crane with an open arch after the melting of the "wells" and partial upsetting of scrap metal in the furnace. Carbon oxidation was carried out in a furnace by blowing steel through a water-cooled arched lance, while the temperature in the furnace was 180–240 ° C above the liquidus line. At the last in a series of smelting, slag was additionally deoxidized with coke powder, crushed ferrosilicon of 80-100 kg each. When released into the ladle, a solid slag-forming mixture was planted, consisting of lime (1200 and 1900 kg) and vanadium-containing slag (500-900 kg), and the necessary deoxidizers and alloys. The experimental melts used vanadium-containing slag of the following chemical composition: 16.0-19.8% V ₂ O ₅ ; 12-14.5% SiO ₂ ; 2.0-2.8% CaO; P≤0.05%; 9.8-11.4% MnO. Parameters of experimental swimming trunks are given in the table.

The inventive method provides a reduction in the duration of smelting by an average of 18 minutes and an electric power consumption of 15 kW h / t, an electrode consumption of 0.18 kg / t, a refractory consumption of a furnace by 0.08 kg / t.

Information sources

1. A.S. 358374 C 21 C 5/52

2. A.S. 394437 C 21 C 5/52

3. A.S. 665003 C 21 C 5/52

4. A.S. 663728 C 21 C 5/52

5. A.S. 2133281 IPC ⁶ C 21 C 5/52

6. A.S. 1046294 C 21 C 5/52

7. A.S. 1014919 C 21 C 5/52

8. A.S. 1788750 C 21 C 7/00

9. A.S. 1014919 C 21 C 5/52

Table Parameters of experimental swimming trunks No. of swimming trunks No. in series and The recovery of vanadium,% Carbon concentration below the lower limit Oven temperature before release (higher liquidus) The mass of coke powder, crushed ferrosilicon,% Mixture (lime and vanadium-containing slag) The mass of solid slag-forming mixture,% Melting time, min Electric power consumption, kWh / t Electrode consumption kg / t Metal filling weight, t The recovery of vanadium,% one one 82 0.15 180 0.08: 0.08 1.2: 0.5 1.7 140 440 3.81 125 82 2 2 40 0.10 240 0.10: 0.10 1.0: 0.5 2.9 one hundred 410 3.81 109 40 3 3 88 0.10 180 0.10: 0.10 1.3: 0.8 2,8 90 410 3.81 105 88 four four 91 0.10 190 0.10: 0.10 1.5: 0.6 2.7 70 420 3.81 95 91 5 one 94 0.05 200 0.10: 0.10 1.9: 0.5 2.1 150 450 3.8 120 94 6 2 96 0.10 200 0.10: 0.10 1.8: 0.6 2,3 one hundred 420 3.8 105 96 7 3 89 0.10 210 0.10: 0.10 1.8: 0.9 2.1 90 425 3.8 106 89 8 four 92 0.10 220 0.10: 0.10 1.9: 0.9 1.9 90 435 3.8 107 92 9 5 92 0.05 180 0.10: 0.10 1.9: 0.8 1.8 85 425 3.8 110 92 10 6 95 0.09 190 0.10: 0.10 1.4: 0.9 1.8 85 425 3.8 109 95 eleven 7 88 0.06 180 0.10: 0.10 1.2: 0.6 2.1 65 410 3.8 91 88 12 one 94 0.09 220 0.10: 0.10 1.3: 0.8 2,5 150 440 3.81 120 94 13 2 90 0,07 220 0.10: 0.10 1.5: 0.8 2.7 75 430 3.81 110 90 fourteen 3 95 0.10 210 0.10: 0.10 1.6: 0.9 2.1 70 420 3.81 106 95 fifteen four 96 0.11 240 0.09: 0.09 2.0: 0.5 2.2 65 410 4.0 90 96

Claims (1)

A method of smelting vanadium-containing steel, including feeding a metal charge consisting of scrap metal and molten iron into an electric arc furnace, melting, oxidizing period, deoxidation and alloying of steel, characterized in that the steel is smelted in series, and the mass of the first melting metal is 10-20% more the mass of the metal charge of the next heat, and the mass of the metal of the last heat in the series is 10-20% less than the weight of the metal of the previous heat, the oxidation period is carried out until the concentration of carbon n e is lower than 0.10% of its lower content in finished steel and at a temperature above the liquidus temperature of 180-240 ° C, and when the first and subsequent melts are released, furnace slag is cut off and steel is deoxidized and alloyed in the ladle, and the last in a series of smelting is carried out deoxidation of slag in the furnace with coke powder, crushed ferrosilicon in the amount of 0.08-0.10% each, and the last melt is released into the ladle with furnace slag, and when all the heats are discharged into the ladle after filling 1/4 of the ladle height, a solid slag-forming mixture is planted consisting of lime and vanadium of converter-containing slag at a ratio of respectively (1.2-1.9) :( 0.5-0.9) in an amount of 1.7-2.8% by weight of the molten steel in the ladle, and the necessary deoxidizers and alloying agents, while the additive of the slag-forming mixture, deoxidizers and alloying is completed before filling 3/4 of the height of the bucket with steel.