SU1371979A1 - Slag-forming mixture for steel-melting process - Google Patents

Abstract

The invention relates to the field of ferrous metallurgy, namely to steelmaking in aggregates with a base lining. The aim of the invention is to improve the quality of the metal, increase the durability of the refractory lining and the yield of liquid metal, as well as reduce the duration of melting. Slag-forming mixture for steelmaking contains, in wt.%: Dolomite 18-27, materials containing iron oxides (converter or scale, or sludge from open-hearth furnaces) 55-64, graphite 3-7 and main steelmaking slag 11-15. The use of the charge improves the quality of the metal by reducing, (sulfur content by 14-36%, phosphorus by 14-24% and non-metallic inclusions by 16-36Z, increase the resistance of the refractory lining by 5-9%, increase the yield of liquid metal by 2-4%. 4 tables. S cl

Description

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FIELD OF THE INVENTION The invention relates to ferrous metallurgy, namely to steelmaking in aggregates with main lining.

The purpose of the invention is to improve the quality of the metal, increase the durability of the refractory lining and the output of the liquid metal, as well as reduce the duration of melting.

Slag-forming mixture contains dolomite, a material containing iron oxides (converter of dust or scale, or sludge of open-hearth furnaces), graphite and the main recirculating slag at the next;% ratio of components, May,%:

Dolomite18-27

Material containing iron oxides (converter dust or scale, or sludge from open-hearth furnaces) 55-64 Graphite3-7

The main steelmaking slag 11-15 Improving the quality of the material is accomplished by reducing the concentration of harmful impurities (sulfur, phosphorus), gases and non-metallic inclusions by actively forming the uuia phase with optimal physicochemical properties and increasing the metal-slag contact surface. The optimal values of the physicochemical properties and composition of the slag, the high rate of its formation also determine the increase in the durability of the refractory lining, the yield of liquid metal, the reduction in the duration of melting. The cost reduction of steel became due to the removal of expensive and / - ficitous bauxite and fluorspar from the composition of the charge, reducing the consumption of lime (limestone).

The use of dolomite within the specified limits contributes to the formation of a furnace w-pack with optimal physicochemical properties. The input amount of this material contributes to obtaining low-melting slags with relatively low values of the initial melting temperature and viscosity, the depth of penetration of magnesian slags into the refractory pores less, The saturation interval of furnace furnace slag with magnesium oxide from the lining of the steelmaking unit is also reduced. Use of dolomite in coli9792

less than 18 wt.% leads to a decrease in the resistance of the refractory lining. An increase in the content of this material in the composition of the charge over 27 wt.% Is inexpedient, since the duration of the slag formation period is prolonged, the metal is re-oxidized, saturated with gases from the furnace space, slags are heterogeneous, refractory, highly viscous, low-reactive, which also reduces the quality its yield increases the duration of melting. Requirements for dolomite must comply with the EAST.

Intensification of the process of assimil - lime (limestone), dolomite and the formation of active

0 to harmful impurities of the slag phase with optimal values of physical characteristics (solidus temperature, viscosity), resulting in an increase in metal quality, lining resistance and shortening of the heat of melting, are achieved by the established limits of consumption of materials containing iron oxides (converter, dust or scale, or slime, etc.),

0 in the composition of the proposed slag-forming mixture. In addition, such materials are an additional source for increasing the yield of liquid metal. If materials are found to be less than 55% by weight, the rate of assimilation of lime (lime), dolomite and slag formation decreases. At the same time, the latter has high temperatures of the onset of melting, viscosity and degree of heterogeneity, which leads respectively to a decrease in the quality and yield of the liquid metal, an increase in the duration of melting. With a content of over 64 wt.%, The durability of the refractory lining decreases, the degree of oxidation of the metal and slag phases increases, which also adversely affects the quality of the alloyed steel.

The use of graphite in the composition of the mixture proposed is aimed at reducing the cooling effect of materials containing iron oxides and dolomite decomposing during the smelting process, and also serves as an active antioxidant. In addition, graphite will increase the resistance of the slag foam, which additionally prevents the metal from being saturated with gases.

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and during the electric arc process, shields the walls of the furnace from long arcs, increasing their service life. In the open-hearth process, foaming the spine improves its removal from the steelmaking bath, shortening the duration of the melt. Graphite increases the contact surface of the slag-metal phase, stabilizes the development of the slag-forming process along the path of refining the metal from sulfur, phosphorus gases and non-metallic inclusions, and increases the yield of the liquid metal due to the reduction of iron oxides. This also increases the durability of the lining, shortens the duration of smelting and expands the possibility of increasing the consumption of steel scrap when using the specified charge in the converter process. A graphite content of less than 3 wt.% Does not eliminate the cooling effect from the use of materials containing iron oxides and dolomite, the slagging process is delayed, the stability of the slag foam decreases, the degree of oxidation of the metal and slag increases. From here, the quality of steel inevitably decreases, the yield of liquid metal and the lining durability fall, the duration of smelting increases. The content of graphite over 7 wt.% Is inexpedient, since it leads to active foaming, the premature removal of slag from the furnace, the loss of charge materials and metal. According to physico-chemical parameters, graphite should comply with GOST standards.

The use of the main steelmaking slag (final converter, open-hearth, electric arc) increases the absorption of dolomite, the rate of formation of homogeneous highly active furnace slag, increases foaming of the latter, especially intensively in the presence of graphite, and, accordingly, the surface of its contact with the metal. The main steelmaking slag, being a carrier of corols and iron oxides, serves as an additional source for increasing the yield of liquid metal as a result of interaction with graphite. In addition, the use of steelmaking slag improves the conditions for the removal of furnace slag from the steelmaking bath in open-hearth and electric arc processes, which is

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to reduce the total duration of the heat. If the main steelmaking slag contains less than 11 wt.%, The rate of slag formation decreases, the contact surface of the slag-metal phase and, accordingly, the slag refining capacity, the degree of assimilation and extraction of iron from the slag decreases, the duration of smelting increases. The increase in the content of the main steelmaking slag (15% wt.%) Adversely affects the course of slag formation: vigorous foaming at an excessive amount of the furnace furnace slag, resulting in its early spontaneous download, which complicates the normal course of the process, increases losses metal and batch materials, additional costs are required to fix such furnace slag.

Example. Melting is carried out in the main electric arc furnace. The consumption of the slag-forming mixture is A- 6 kg / ton.

in tab. Figure 1 shows the variants of the quantitative composition of the slag-forming mixture that were used in the bottoms: the first and second variants of the bottoms correspond to the boundary contents of the components; option 3 - medium content; options A and 5 - different from the proposed composition; 6-9 - in the composition of the mixture is missing one of the components of the proposed mixture. In tab. Figures 2 and 3 present data on the chemical composition of materials containing iron oxides and basic steelmaking slags. As a known mixture using the composition, wt.%: Dolomite 20; converter dust 17.5; fluorite limestone to 15; bauxite 25; known to 22.5. Melting steel using the proposed mixture (Table A) improves the quality of the metal by reducing the sulfur concentration by 20–25 wt.%, Phosphorus by 16–20 wt.%, Hydrogen nd 19–26 wt.%, Non-metallic inclusions by 16– 21 wt.%, Oxygen at 32- 37 wt.%.

The durability of the refractory lining is estimated by the time of impregnation and dissolution of the refractory sample in the slag. Increase this

The coater, in contrast to the application of the known charge, is 9 min. The yield of liquid metal also increases due to a decrease in the amount of magnetic fraction in the slag by 2-3 wt.%. The shortening of the melting period in an electric arc furnace is 10-15 minutes. A significant role in achieving a positive effect from the use of the proposed mixture is given to the slag phase, the temperature of the initial melting point of which, compared to the use of the known mixture, is lower by 30–3.3 C, and the viscosity is 0.25–0.3 N-s / m In addition, the melting time of full-scale slag samples is reduced by 3-4 minutes. The latter confirms the position of a higher rate of formation of the slag phase in the proposed mixture.

In the case of using the charge with different component consumption limits (melting 4 and 5, Table 1), the goal is not achieved (Table 4): the quality of the metal deteriorates, the lining durability decreases and the yield of liquid metal increases, the duration of melting increases. The use of fluxing charge plates 4 and 5 does not ensure the formation of slags with optimal values of physicochemical characteristics: composition 4 — slags are excessively liquid-mobile, high

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the degree of oxidation of the slag metal phase; Composition 5 - heterogeneous, refractory, viscous slags, the surface of the contact of metal and slag is small (in comparison with melts 1-3).

When using mixtures for melts 6-9 (Table 1), the goal is not achieved.

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Claims (1)

Invention Formula Slag-forming mixture for the steelmaking process, including dolomit and material containing iron oxides (converter dust or scale, or psham open-hearth furnaces), in order to improve the quality of the metal, increase the durability of the refractory lining and the yield of liquid metal, reduce the duration of smelting, it additionally contains graphite and the main steelmaking slag with the following ratio of components, wt.%: Dolomit18-27 Material containing iron oxides (converter dust or dross or sludge Open-hearth furnaces) 55-64 Graphite .3-7 The main steel slag11-15 Table 1. 29 64 (T) but S ts yn) n