SU1186652A1 - Method of steel melting in powerful arc furnaces - Google Patents

Abstract

A METHOD FOR MELTING STEEL IN HIGH-POWER OTHER FURNACES, including loading the metal charge, slag-forming materials and injecting gaseous oxygen directly into the slagging zone, differs by the fact that, in order to reduce the duration of the melting and improve the conditions for oxidative refining of the melt, the furnace melts on the furnace and reduces the duration of the smelting process and improves the conditions for the oxidizing refining of the melt and the melting of the melting furnace. lime in the amount of; 30-45 kg per 1 ton of steel together with cast iron shavings at a ratio of 0.2-0.5 kg of chuggun chips per 1 kg of lime and from the moment the furnace was turned on, oxygen was introduced at House 2-20 m / h and a 1 t of metal charge. (L eo a: a

Description

This invention relates to ferrous metallurgy, in particular to electric steel making. The purpose of the invention is to reduce the efficiency of smelting and improve the oxidative refining conditions of the melt. When smelting steel in high-power non-limes, loading lime in a hearth in one portion in an amount of 30-45 kg / t allows to obtain slag with basicity (CaO / SiO) at a level of 2.5-3.5 and sufficient, from the standpoint of ehreny, stabilization of combustion and shielding arcs, number. With a smaller amount of lime (30 kg / t), the amount and basicity of the slag formed are insufficient. for efficient operation: reduced arc stability and voltage utilization; The dephosphorizing capacity of such slag is insufficient to obtain a given phosphorus content in the metal. With a larger amount of lime (45 kg / t), the degree of its use decreases: it does not have time to dissolve in the slag during the smelting of the charge and mechanical removal occurs, moreover, with an increase in CaO in the slag of a certain level (60%), the slag thickens and the phosphorus ability decreases, the duration of melting and the power consumption increase. Loading cast iron chips together with lime at a ratio of 0.2-0.5 kg of chips per 1 kg of lime contributes to a more rapid slagging. The low melting point of iron shavings leads to the rapid formation of a melt; oxidation of iron impurities (Si, Mn, C) with the introduction of oxygen on the one hand leads to the rapid formation of slag and dissolution of lime in it, on the other - to an increase in temperature due to exothermic reactions of oxidation of iron impurities in the slag forming zone, which is especially important the initial period of melting of the charge. Oxidation of carbon with the addition of this causes foaming slag and stabilizes the burning of arcs. All this has a positive effect on. so far: stove operation times: shortening time and power consumption. When loading, together with lime, iron chips, with a ratio of less than 0.2 kg per 1 kg of lime, the rate of slag formation and dephosphorization of the metal sharply decreases, and the melting rate increases. Loading cast iron chips together with lime in an amount of more than 0.5 kg per 1 kg of lime is associated with certain difficulties, since the mass of the mixture (lime and cast iron chips) is large and it is not loaded on the hearth in one portion. This is possible, and when the mixture is loaded together with the metal, the efficiency of lime utilization decreases. The introduction of oxygen into the slagging zone (into the zone of loading the mixture of lime and cast iron chips) from the moment the furnace is turned on with a flow rate of 2–20 m / h per 1 ton of metal charge promotes the loosening of the mixture of lime and cast iron chips in the initial period of melting of the charge, thereby accelerating the slagging process , increases the content-; Kie in the slag FeO, contributes to the foaming of the slag and improve the conditions of burning arcs. When oxygen is introduced into the slagging zone after a certain time (5-15 minutes) after turning on the furnace, the slagging conditions deteriorate, since the wells are smelted in this case, when steel is smelted in a high-power furnace, the mixture is melted, the lime dissolves slowly the duration of the heat is increased. The introduction of oxygen during the period of the reduction of their intakes into the zone of direct slag formation with a flow rate of 2–20 m / h. on 1: t of metal charge provides optimal slag formation conditions. The minimum values refer to the beginning of the charge charge period (since the furnace was turned on), the maximum values by the end of the melting period and depend on the quality of the metal charge (oxidation, density, etc.) and the mass of slag-forming materials on the bottom. When oxygen consumption is less than 2 m / h per 1 ton of metal charge, the effect of loosening the mixture of lime and cast iron shavings is not achieved, the slag is not sufficiently oxidized and, consequently, the conditions of metal dephosphorization worsen. When oxygen consumption is more than 20 m / h per 1 ton metal charge increases the waste of elements, primarily iron: which reduces the yield of the metal. In addition, with such an oxygen consumption, due to the intensive mixing of the metal, there can be emissions from the working window threshold. The proposed method allows, under the conditions of steel smelting in high-power furnaces, to provide early slag formation, the formation during the smelting of the charge and slag in the amount of 60-80 kg / ton of steel with basicity (CaO / SiO) equal to 2.5-3.0, which stabilize the burning of long arcs, increase the voltage utilization ratio, and contribute to the success of the metal dephosphorization process by the end of the melting period. In this way.

The simple method of steel smelting in high-power furnaces can reduce the duration of smelting and improve the conditions for oxidative refining of the melt. The slag of the melting period can be used without renewal during the oxidation period (its phosphorus absorption capacity is high), which also contributes to a reduction in the duration of smelting and a decrease in power consumption.

Example. The steelmaking of ShKh15 according to the proposed method is carried out under test conditions in a 100-ton arc furnace with a transformer capacity of 63 MVA.

As in the experimental and comparative meltings, the metal stool consists of 25-30% of recycled scrap, 10% of iron shavings and 60-65% of imported scrap with the same bulk density. After the previous smelting has been completed, the lime kiln together with foreign chips is loaded in one portion with the help of a mash, together with foreign chips, the tube is laid to enter the oxygen and the metal portion of the solder is charged. Coke is used as a carburizer, which is charged to the furnace hearth. When conducting pilot melts, the amount of lime in the filling varies from 10 to 50 kg per ton of steel, and the ratio of cast iron chips

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- And lime - from 0.10 to 0.60. Oxygen is introduced directly into the slagging zone with an oxygen tube and through the lance from the moment the furnace is turned on after 2.5, 10 and 15 minutes 5 after switching on, changing its flow rate from 1-5 (at the beginning of melting) to 10-30 m / h per 1 t steel (at the end of melting).

Melting by known technology; 1lt with a load of lime on the hearth (10 kg per 1 ton of coal) and in the basement (15 kg per 1 ton), while before the basement iron ore (45 kg per 1 ton of steel) and oxygen are loaded into the furnace 10 minutes after it was turned on at a rate of 4-10 1 tonnes of steel was introduced into the furnace.

In tab. Figures 1 and 2 show the characteristics and technical and economic indicators of the experience of melting in comparison with melting according to the known technology. From these data, it can be seen that when steel is smelted according to the proposed method, a minimum duration of smelting increases, the power consumption increases and the conditions of oxidative refining, in particular, the melt dephosphorization, improve. So, in comparison with steel smelting according to the known technology, the duration of smelting is reduced by 35-44 minutes, the consumption of electric energy is reduced by 45-55 kWh / t, the phosphorus content in the metal at the charge melting is 0.009-0.0122%, which is twice lower than comparative fusion.

Table

0.15

15 min after power on

After 5 min

0.30 after power up

After 2 min

0.20 after switching on

0.35

From the moment you turn on the oven

After 2 min

0.50 after power on

1.5-10

46.0

1.6

15.2

2-10

50.0

16,0

1.6

2-15

60.0

2.5

16.4

2-20

76.0

3.2

18.0

4-20

85.0.

3.5

19.6

Continued table. I

Content in

it ke,%

Table 2.

Claims (1)

METHOD FOR Smelting steel in high-power other furnaces, including loading a metal charge, slag-forming materials and introducing gaseous oxygen directly into the slagging zone, distinguished by the fact that, in order to reduce the melting time and improve the conditions of oxidative refining of the melt, they are loaded onto the furnace hearth in one portion lime in an amount of: 30-45 kg per 1 ton of steel together with cast-iron shavings at a ratio of 0.2-0.5 kg of pig-iron shavings per 1 kg of lime and oxygen is introduced from the moment the furnace is turned on at a flow rate of 2-20 / H per 1 ton of the metal charge. 1 1186652 2