RU2729810C1 - Deoxidising mixture - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgical briquettes for steel making and deoxidation of final steel-smelting slags. Briquette contains as binding component organic material with amount of carbon in mechanical mixture by 1–10 % more than stoichiometric to available in slag metal oxides, iron and iron powder is wastes from steel and/or cast iron production, silicon wastes are wastes from silicon production in the following ratio, wt%: binding component 9–23, wastes from steel and/or cast iron production 10–25, wastes from silicon production – the rest.

EFFECT: invention enables to obtain briquette with high degree of deoxidation of treated slag and metal, with possibility of obtaining low content of iron oxides in slag and high quality of metal due to reduced oxidation thereof, note here that said briquette has low cost due to production wastes and is easily delivered to furnaces.

1 cl, 2 tbl

Description

The invention relates to the field of ferrous metallurgy, in particular to the production of high quality steel.

Known deoxidizer for steel in the form of metallic aluminum (Grigoryan V.A., Belyanchikov L.N., Stomakhin A.Ya. Theoretical foundations of electric arc-furnace processes. M .: Metallurgy, 1987. 272 S.).

Aluminum is most commonly used as a deoxidizing agent, as it is the most powerful deoxidizing agent. But the products of deoxidation are non-metallic inclusions in the form of Al ₂ O _{3 of a} hard and acute-angled shape, which has a harmful effect on steel, clogs the steel ladle outlet channel during the casting process, which can even lead to a stoppage of casting. In addition, aluminum does not contribute to the desulfurization of the steel and the reduction of iron oxides in the final slag.

Known steel deoxidizer containing aluminum as a low-melting matrix component, and an iron-based alloy - as a refractory shielding component with a ratio of mass fractions of the matrix and reinforcing components in the range 25/75 - 50/50, and the refractory component is used in the form of particles 0, 5-10.0 mm, and the refractory component in the form of a shot made of steel or cast iron (RF patent No. 2192495). The disadvantage of this invention is the presence of actually one deoxidizer - aluminum, which forms non-metallic inclusions in the form of Al ₂ O _{3 of a} solid and acute-angled shape, which has a harmful effect on steel, clogs the steel ladle outlet channel during the casting process, which can even lead to a stoppage of casting. In addition, aluminum does not contribute to the desulfurization of the steel and the reduction of iron oxides in the final slag. In addition, the presence of refractory elements will significantly increase the melting point of the deoxidizing agent, which will lead to a decrease in the deoxidizing ability of the mixture - the difficulty of removing iron oxides from the refined slag and the residual oxygen content in the steel being produced.

Known briquette for deoxidation of steel, obtained by pressing aluminum shavings with particles of the additive, characterized in that the additive used is a chloride-fluoride flux in an amount of 2-5 wt. %.

2. A briquette according to claim 1, characterized in that a chloride-fluoride flux is used containing NaCl-KCl-Na ₃ AlF ₆ at a component ratio, wt. %:

NaCl 40-45 CS1 40-45 Na ₃ AlF ₆ 10-20

(RF patent №2336313)

The disadvantage of this deoxidizer is a small amount of aluminum, the main deoxidizer, therefore, the claimed deoxidizer will not remove the required amount of iron and oxygen oxides, thereby reducing the quality of the steel produced.

The closest analogue to the claimed object in terms of the technical essence and the achieved result is a deoxidizer-modifier briquette for steel and cast iron, in the body of which aluminum powder and iron-containing crushed ligature of the FS 30, RZM 30 type are introduced as a binder, and is saturated as an active element discretely distributed ultrafine titanium nitride powder (BY 9521 $ U 2013.08.30).

The disadvantage of such a briquette is low strength due to the weak binder material - aluminum and the difficulty of briquetting, in addition, a small amount of aluminum, which will not facilitate the removal of the required amount of iron and oxygen oxides, thereby reducing the quality of the steel produced. The presence of an iron-containing material with a large amount of silicon in the form of FS 30 also does not contribute to the removal of iron oxides from the deoxidized slag.

The problem solved by the invention is to obtain a deoxidizing mixture in the form of a briquette with a high degree of deoxidation of the processed deoxidized slag, with the possibility of increased removal of iron oxides from it and a decrease in the oxygen content in the metal, which will lead to an increase in its quality.

The technical result, which ensures the solution of the problem, is achieved by the complete replacement of aluminum, rare-earth metals and titanium nitrides, steel or cast iron powder, which are expensive as binders, with waste from steel and / or cast iron production, instead of FS 30, with waste from silicon production containing from 18 to 38% aluminum oxides , as a binder to use coke residue, which promotes the reduction of iron oxides from the slag and the reduction of oxygen in the metal

The problem is solved by the fact that the known deoxidizing-modifying mixture for steel and cast iron in the form of a briquette, in the body of which aluminum powder and an iron-containing crushed master alloy of the FS 30, RZM 30 type are introduced as a binder, and as an active element it is saturated with discretely distributed ultrafine powder titanium nitride mixture, according to the invention, instead of the binder component, an organic material is introduced with the amount of carbon in the mechanical mixture more than 10% more than stoichiometric to the existing oxides, and instead of iron powder and cast iron, waste from steel and / or cast iron production in the ratio, wt. %:

Binder component 9-23; Waste from steel and / or pig iron production 10-25; Waste from silicon production rest.

The binder is an organic material with a total coke residue of 30-50% with the amount of carbon in the mechanical mixture and the binder 1-10% more than stoichiometrically required for the reduction of iron, silicon, aluminum and calcium oxides contained in the deoxidized slag.

Waste from steel and / or cast iron production resulting from mechanical processing of various parts, rolled products, etc., processed into a crushed product to a size of 1-2 mm.

Waste from silicon production (MKS) TU 24.10. 12-01-16174179-2017, has a chemical composition, wt. %: silicon not less than 65; aluminum 5.0; manganese 1.5; chrome 1.0; carbon 2.0; sulfur 0.1; phosphorus 0.1; oxides of aluminum, silicon, calcium, iron, manganese; moisture no more than 2.0. Available as powder or briquettes.

Prepare deoxidizing mixture as follows. Since all mixtures are in the form of powders, they are crushed to the required uniform condition, the required amount of each ingredient is measured, thoroughly mixed and pressed into pillow-shaped briquettes with a strength of 0.5 kN (50 kg) on a special press and placed in tared polypropylene bags , weighing 25-50 kg, which can be transported to the working platform of the melting unit.

The declared deoxidizing mixture is environmentally friendly, since it mainly consists of aluminum production waste, in which there are no harmful substances.

The introduction into the mixture of more than 29% of the binder component of organic material with the amount of carbon in the mechanical mixture more than 10% more than stoichiometric to the existing oxides, will lead to an increase in the strength of the briquette, it will be poorly distributed over the surface of the deoxidized slag and will not ensure the removal of iron oxides from it, and this will reduce the quality of the resulting steel. The introduction into the mixture of less than 9% of the binder component of organic material with the amount of carbon in the mechanical mixture is less than 1%, more than stoichiometric will lead to a violation of the strength of the briquette, its destruction during transportation, in addition, it will be poorly distributed over the surface of the deoxidized slag, which will lead to uneven removal iron oxides over the area of the slag, and since the deoxidation process is fast, the quality of the steel being smelted will deteriorate, there are no substances. In addition, the amount of carbon in organic material may not be sufficient to reduce iron oxides.

The introduction of more than 25% of waste from steel and / or cast iron production into the mixture will lead to an increase in the strength of the briquette and gravity, the briquette will settle on the hearth of the furnace and will not crumble and will not ensure the removal of iron oxides from the deoxidized slag, and this will reduce the quality of the resulting steel. The introduction of less than 10% of waste from steel and / or cast iron production into the mixture will lead to insufficient density of the briquette (2.23-2.25 g / cm ³ ) and it, burning on the surface of the deoxidized slag, will not provide the necessary removal of iron oxides from it , and this will reduce the quality of the smelted steel

The introduction of more than 81% of waste from silicon production into the mixture will lead to a sharp decrease in the basicity and deoxidizing ability of the claimed deoxidizing mixture, will not provide the necessary removal of iron oxides from it, and this will also reduce the quality of the steel being smelted. The introduction of less than 52% of waste from silicon production into the mixture will not reduce the oxidation of the slag (steel), especially since at this moment there will be a lack of carbon content in the deoxidizer (see above). These two elements only together and in larger quantities provide the required degree of slag deoxidation, i.e. removal of iron oxides from it will not be ensured, the quality of steel will decrease.

To substantiate the advantages of the claimed deoxidizing mixture for steel in comparison with the existing mixture, experimental melts were carried out.

Experimental compositions of the mixture were made in the slag-forming mixtures department of Shlakservice LLC, PJSC Magnitogorsk Iron and Steel Works, briquettes were made and packaged in polypropylene bags weighing 25 and 50 kg.

9 tests were carried out with different mixture compositions, of which:

Compositions No. 1-2 contain components in an amount that is beyond the minimum values of the claimed deoxidizing mixture;

Compositions 3-5 contain components taken in the claimed ratio;

Compositions No. 6-7 contain components in an amount exceeding the maximum declared values of the claimed deoxidizing mixture;

Formulations No. 8 - according to the prototype.

The tests of the declared deoxidizing mixture were carried out at PJSC "Magnitogorsk Iron and Steel Works" during the smelting of steel K 55, smelted in an arc furnace with a capacity of 6 tons. Bags with briquettes (by composition) were placed in special containers and brought to the working site of the furnace. During the deoxidizing smelting period, these bags were manually thrown into the open working window of the furnace onto the available slag (minimum amount). We closed, if possible, tightly available holes in the walls of the furnace. After 30 minutes, they looked at the color of the slag formed after the introduction of the deoxidizing mixture, if it became light, opened the working window of the furnace, let the slag into the slag, checked its chemical composition and the composition of the metal that was released into the ladle. We checked the content of iron oxides in the slag and the final oxygen content in the metal (checked the oxidation and, accordingly, the quality of the metal).

The compositions of the deoxidizing mixture and slags are shown in Table 1. The results of experimental heats are shown in Table 2.

The use of compositions No. 1 and 2 for the manufacture of a deoxidizing mixture is impractical, since this leads to a deterioration in the oxidation of the final slag, an increased content of iron oxides in the slag, and a small removal of the amount of sulfur.

For compositions No. 6 and 7, the same picture was observed: deterioration of the oxidation of the final slag, increased content of iron oxides in the slag, low removal of the amount of sulfur.

The analysis of the results of the studies showed that the composition of the declared deoxidizing mixture No. 3-5), in comparison with the prototype (No. 8), gave improved quality indicators, namely, good residual oxidizing ability of the slag, good indicators for the residual content of iron oxides in the final slag and a satisfactory reduction in the sulfur content of the metal.

Claims (2)

A deoxidizing mixture in the form of a briquette for steelmaking slag, containing a binder component, iron and cast iron powder and a silicon-containing material, characterized in that an organic material with a total coke residue of 30-50% is used as a binder component with the amount of carbon in the mixture by 1-10% more than the stoichiometric value required for the reduction of metal oxides contained in the slag, as a powder of iron and cast iron - waste from steel and / or cast iron production, and as a silicon-containing material - waste from silicon production, with a mixture ratio, wt%: Binder component 9-23 Waste from steel and / or pig iron production 10-25 Waste from silicon production rest

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