SU1254021A1 - Method of producing flux for steel production - Google Patents

Description

The invention relates to ferrous metallurgy, in particular, to methods for producing fluxes of special compositions for intensifying the process of slag formation during the conversion of cast iron.

The aim of the invention is the elimination of furnace formation in the furnace and more complete absorption of the flux in the steelmaking industry.

The proposed method of manufacturing a flux for steelmaking involves feeding into a kiln, together with limestone, a ferritic additive containing 1-3% silica with a Fe Oj / CaO 2-3 molar ratio in an amount of 20-30% of the total mass of feed material into the furnace. In this case, the temperature of the torch in the burning zone is maintained at 400–1500 ° C.

A proposed method for producing a flux consists in the joint calcination of limestone and a ferritic-based additive material containing 1-3% SiO in its composition.

The limited content of silica (1-3% SiO) eliminates its harmful effect on the impregnation of lime by iron oxides, since in this case the formation of a refractory dicalcium silicate (t 2130 C) is excluded, which covers the shell of lime and exerts a retarding effect on diffusion iron oxides inside the pieces. In addition, the presence of 2CaO-SiO contributes to the formation of wall accretions in the furnace. The lower limit of the SiO content in the ferritic additive (1%) is associated with a constant silica impurity in the limestone.

Ferritic additives can be prepared from a mixture of hematite ore and limestone roasting waste by mechanical mixing of the components. Some metallurgical wastes may be a finished ferritic additive. For example, Converter production sludges or smelting sludge sludge. The size of the ferritic mixture is in the range of 0.2-0 mm. Ferritic additive is fed to the feed end of the kiln in the low-temperature zone.

In the boot end of the tube furnace in the low-temperature zone due to heat waste and (1-gx; gases are consumed

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the evaporation of hygroscopic moisture of the material, the decomposition of Ca (OH), and at 560–600 С solid phase reactions between CaO and Fe begin to occur intensively (with the formation of low-melting monocarbon ferrite, and an excess of iron oxide contributes to the formation of eutectic between CaO-Fe 0 and Fe 0

To melt the ferritic additive, the temperature of the flame in the burning zone is maintained in the range of 1400-1500 ° C. Ferritic melt impregnates pieces of lime to a depth of 3-12 mm. The temperature of the flame below 1400 ° C leads to a decrease in the temperature of the lining heating, and the ferritic additives begin to freeze on it, forming a skull, which reduces the cross-sectional area of the furnace and adversely affects the gas dynamics during firing. The temperature of the flame above 1500 ° C leads to intensive heating of the lining and melting of the ferritic material in the burning zone, deep refractory of the refractory is carried out with iron oxides and collapse of the lining.

Due to the ferritic shell, the blackness of the material is increased, the heat exchange between the gas phase and the material is intensified, the firing time is reduced, and the productivity of the kiln is increased.

With a lime particle size of 20-40 mm and a content of 0-15% in it, the amount of ferritic additive supplied to the kiln should be 20-30% of the total weight of the feed material. The amount of the ferritic additive below 20% leads to the formation of a very thin crust on the lime pieces, and the effectiveness of such pieces has little effect on converter smelting. Excessive addition of a ferritic additive (more than 30%) 5 leads to an excess of iron-containing components, their separation and saturation.

The flux obtained during co-firing is a highly active slag-forming material. The ferritic crust has a strength that exceeds the strength of lime; during transport, much less dust is produced. Lime under the shell loses its tendency to hydration, while retaining a high reactivity, therefore, while reducing lime consumption

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smelting, its assimilation into the slag bath increases, and the slag’s refining capacity increases.

The experiments were carried out in lime kiln kilns for 50 hours. The mixture consisted of 70–80% limestone from the Zhirnovsky deposit and 20–30% finely ground ferrite additive. The composition of limestone, wt.%: FeO 0,77; SiO., 0.76; CaO 54.09; ppt 43. The composition of the ferritic additive, wt.%:, 00, with Ge Od / CaO 2-3; SiO 2.4.

For firing, a pipe burner was used in the pipe. The fuel was natural gas. The furnace lining in the preparatory zone is class B fire clay in the firing zone, hromo-magnesite. The firing temperature 1400-1500 C.

Due to the fact that the ferritic flu absorbs the heat of the gas-oxygen torch to a greater degree, it increases the number of revolutions of the tube furnace in order to avoid lime burn. As a result of impregnation of limestone during its burning, lime was obtained, impregnated with iron oxides from the surface, containing, in wt.%: CaO 72-80.5; MgO 4.4; SiO 5.3; Fe 0 9.6 - 14.0; ppt 0.2.

Fractional composition of the obtained product:

0 mm 10-5 mm 5-0 mm

65% 12.5% 22.5%

 the ferritic shell of the lime pieces was 3–12 mm.

 The results of the influence of the burning temperature, the amount of the iron-containing additive and the composition of the additive on the chemical composition of the burning products are presented in Table. one.

In order to study the slagging process, smelting was carried out with the converter poured on the 3rd and 6th minutes of purging.

The obtained results were compared with the indices of row heats, in which ordinary lime and fluorspar were used for slagging. Visual observations showed that the flushing of the hot-melted ferritic flux obtained by the proposed method proceeded smoothly without blowouts, the liquid Hbtfi homogen was running on the final rolls, and undisturbed lime was completely absent.

The improvement of slag formation is confirmed by the data obtained from the heaps.

The results of changes in the chemical composition of the slag during the purge are given in Table. 2

As can be seen from the table. 2, in the case of the use of ferritic flux, the basicity of the final slag grows faster than in row melts, which is due to the ferritic structure of the new Ash-forming.

The main indicators of the experimental data are given in table. 3, which shows that the use of ferritic flux as a whole has satisfactory characteristics in terms of the quality and temperature of the metal, and the consumption of materials. The optimal consumption of ferritic flux per tonne of liquid steel is in the range of 75-80 kg / t, spar - 1.0 kg / t.

The use of ferritic flux in the oxygen-converter process showed that the process of lime-iron slag induction during the bathing of the bath with oxygen improves, saving lime by 10-15% and spar by 50-80%.

As a result of using the ferrite flux obtained by the proposed technology in oxygen-converter smelting, an early pickup of active lime-ferrous slag is achieved, which makes it possible to intensify the refining processes and to obtain an economic effect for reducing the consumption of lime by 15%, due to its more complete absorption .

Known7 I

Received by

the proposed method 20

80.0 - 1.20 0.65 0.038 0.12 1680 0.027 0.01 10.2 3.2

90.0 3.20 0.68 0.043 0.12 1640 0.027 0.01 10.8 3.2

Compiled by K. Sorokin. Editor L. Povhan Tehred L. Kravchuk

Order 4689/30 Circulation 552Subscription

VNIISH1 USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, st. Project, 4

table 2

Table 3

Proof-reader I. Erdeyi

Claims (1)

METHOD FOR PRODUCING FLUX FOR STEEL Smelting, including firing c. a tubular furnace of a material consisting of limestone with a ferrite additive, and maintaining a predetermined torch temperature in the firing zone, characterized in that, in order to exclude stratification in the furnace and more fully assimilate flux in steelmaking, the ferrite additive contains 1-3% silica with the ratio iron oxide to calcium oxide in it, equal to 2-3, the amount of additive is 20-30% of the total mass of material loaded into the furnace, and the flame temperature in the firing zone is maintained equal to 1400-1500 ° C. ί