RU2139939C1 - Sponge iron - Google Patents

Abstract

FIELD: ferrous metallurgy; applicable in production of steel microalloyed with vanadium, and vanadium slag used in production of ferroalloys and alloying compositions. SUBSTANCE: sponge iron contains, wt.%: SiO₂ 4.4-5.4; Al₂O₃ 3.2-3.6; CaO 1.6-2.3; MgO 3.2-3.6; TiO₂ 3.3-3.7; N₂O₅ 0.7-0.9; P₂O₅ 0.010-0.015; S 0.004-0.015; iron oxides 3.2-7.9; C 2.0-3.5 the balance, metallic iron. Maintained in sponge iron is ratio Fe metallic/Fe total + 0.075C = 1.03-1.17. Said composition of sponge iron is characterized by high degree of metallization equalling 0.92-0.97, satisfactory metallurgical properties allowing use of it in electric furnace without preliminary pelletizing and high content of carbon that intensifies assimilation of vanadium in course of heat and results in quality vanadium slag suitable in smelting of ferroalloys. EFFECT: higher efficiency. 1 tbl

Description

 The invention relates to ferrous metallurgy and can be used for the production of steel, microalloyed with vanadium, and vanadium slag, which is further used for the production of ferroalloys and alloys.

The known composition of spongy iron used for the manufacture of high-strength castings and the production of phosphate slag, and containing 0.1 - 0.5% V ₂ O ₅ , 0.1 - 0.7% TiO ₂ , 1.0 - 5.0% P ₂ O ₅ , 0.5 - 5.0% C and 25.8 - 99.5 Fe _met (1).

 The disadvantage of this sponge iron is the insufficient content of vanadium oxides for the smelting of vanadium steel. In addition, the content of metallic iron varies over a wide range and the process of smelting steel from sponge iron with a low content of metallic iron is associated with a significant decrease in the productivity of the electric furnace.

The closest in technical essence and the achieved result is spongy iron, obtained from the non-fluxed pellets of the Kachkanarsky GOK, containing, by weight. %: 65.5 - 70.0 Fe _meth , 11.0 - 14.0 FeO, 1.4 - 2.0 C, 1.5-2.4 CaO, 2.8 - 3.2 MgO, 2, 4 - 2.6 TiO ₂ , 4.2 - 5.5 SiO ₂ , 2.8 - 3.2 Al ₂ O ₃ , 0.7 - 0.8 V ₂ O ₅ , 0.010-0.015 P ₂ O ₅ , 0.004-0.006 S, as well as iron oxides with the ratio of metallic iron to total iron Fe _met / Fe _total = 0.84 - 0.91 (2).

A disadvantage of the known sponge iron is a low metallization degree (Fe _met / Fe _total ), a low carbon content and a high amount of fine fractions of 5-0 mm, reaching 20%.

 An object of the invention is to increase the degree of metallization and yield of commercial products (class above 5 mm) and increase the degree of assimilation of iron and vanadium in the process of steelmaking in an electric furnace.

The problem is achieved in that in a spongy iron containing SiO ₂ , Al ₂ O ₃ , CaO, MgO, TiO ₂ , V ₂ O ₅ , P ₂ O ₅ , S, C, Fe _met and iron oxides, the ingredients are taken in the following ratio, wt.%:
SiO ₂ - 4.4-5.4
Al ₂ O ₃ - 3.2-3.6
CaO - 1.6-2.3
MgO - 3.2-3.6
TiO ₂ - 3.3 - 3.7
V ₂ O ₅ - 0.7 - 0.9
P ₂ O ₅ - 0.010-0.015
Fe oxides - 3.2-7.9
S - 0.004-0.015
C - 2.0 - 3.5
Fe _Met - Else
the ratio of Fe _met / Fe _total and the carbon content in the spongy iron are related by the following ratio of Fe _met / Fe _total + 0.057 C = 1.03 - 1.17.

The proposed sponge iron differs from the known formulations in the increased carbon content, as well as in a different amount of amphoteric oxides (TiO ₂ , Al ₂ O ₃ and MgO), the presence of which in the sponge iron is known. However, the proposed amount of these ingredients in the composition of spongy iron gives it properties that are not manifested in known solutions. Thus, an increased amount of refractory amphoteric oxides prevents the destruction of granules in low-temperature zones of reduction of higher iron oxides with the formation of a metal skeleton and, as a result, leads to an increase in the yield of the product and an increase in the degree of metallization. It is known that in the structure of metallized pellets, titanium oxides are represented by microinclusions up to 5 μm in size, uniformly distributed in the grains of reduced iron (2, p. 31), which react with carbon (3, p. 7 - 12). In this case, an increased content of TiO ₂ promotes the formation of titanium carbides in large quantities and an increase in the carbon content in the spongy iron. Thus, an increase in the content of titanium oxides to 3.7% will make it possible to obtain sponge iron with a carbon content increased to 3.5%. Another important aspect of the invention is the balanced content of metallic iron, oxides, vanadium and carbon oxides in the spongy gland. When the value of (Fe _meth / Fe _total + 0.057 C) = 1.03 - 1.17, the optimum degree of assimilation of vanadium in the process of melting sponge iron is reached, which is 85 - 90%, which will make it possible to obtain commercial vanadium slag. With a value of this ratio less than 1.03, the degree of assimilation of vanadium decreases and does not reach the desired 85-90%, and with an increase in the ratio of more than 1.17, the carbon content will exceed 3.5%, which will require additional purging of the melt with oxygen to bring the steel to the optimum chemical composition. In addition, the increased carbon content in the spongy iron will lead to the release of too much gas during the smelting process and the melt will spill out of the furnace.

The invention is illustrated by the following examples. For experimental verification of the claimed composition were made up of 14 mixtures. In accordance with the invention, the concentrate of the Gusevo-Gorsky deposit was used as the ore part, to which the concentrate of the Kachkanarsky deposit was added in an amount of 5-10%, which provides an increase in the content of aluminum, titanium and magnesium oxides in the mixture. The components were mixed, moistened to 8.5 - 9.0% and pelletized. The obtained pellets were fired at a temperature of 1350 - 1370 ^o C, adjusting the ratio of ore and slag minerals by oxidation of magnetite during heating and dissociation of hematite during firing. For comparison, pellets from Lebedinsky GOK concentrate were prepared. A less than 5 mm class was removed from the calcined pellets, and then they were loaded into the kiln of the Oskol Electro-Metallurgical Plant and metallized at a temperature of 900 ^o C with a reducing gas of the following composition, wt.%: H ₂ 57.4 - 68.4, CO 22.9 - 36.4, CO ₂ 2.0 - 2.5, CH ₄ 1.3 - 1.4, H ₂ O the rest. Pellets with the addition of Kachkanarsky GOK concentrate and pellets from Olenegorsky GOK concentrate were loaded into different pockets of one container and metallized together. The compositions of sponge iron and their properties (metallization degree - fm, x100%, yield - + 5 mm, porosity - P,% and compressive strength - G, kg / pellet) are given in the table. Example 1 shows the composition and properties of sponge iron, corresponding to the closest analogue and obtained in the furnace of the Beloretsk metallurgical plant. The composition and properties of sponge iron according to the invention are presented in examples 2-9, 11 and 13, and the composition and properties of sponge iron from Lebedinsky GOK concentrate are shown in examples 10, 12 and 14. A comparison of the properties of sponge iron according to the invention and the prototype (example 1) shows that the spongy iron according to the invention has a significantly greater porosity and metallization degree, as well as an increased yield of products that do not require briquetting before melting in an electric furnace. A comparison of the properties of the sponge iron according to the invention and the sponge iron from the Olenegorsk GOK concentrate shows that despite the increased porosity, degree of metallization, and compressive strength, the latter was less carbonized since practically does not contain titanium oxides, which reduces the degree of assimilation of vanadium in the process of electric melting and adversely affects the quality of commercial vanadium slag.

 The process of direct alloying of steel with vanadium-containing sponge iron at the Oskol Electro-Metallurgical Combine increases the through vanadium extraction coefficient (from ore to steel) to 60–63% against 30–32% according to the ore – ferrovanadium scheme. The use of the proposed sponge iron will provide an effect both in the production of low alloy steels and in the production of ferroalloys.

References
1. USSR author's certificate N 872559, C 21 B 13/00, 1981.

 2. Rovnushkin V.A. and others. "Coke-free processing of titanomagnetite ores", edited by Bratchikova SG, M., "Metallurgy", 1988. 247 p.

 3. Kiparisov S.S. and others, "Titanium carbide. Obtaining, properties, application", M., "Metallurgy", 1987, 216 S.

Claims (1)

Sponge iron for microalloying steel and producing vanadium slag containing SiO ₂ , Al ₂ O ₃ , CaO, MgO, TiO ₂ , V ₂ O ₅ , P ₂ O ₅ , S, C, Fe met and iron oxides, characterized in that the ingredients are taken in the following ratio, wt.%:
SiO ₂ - 4.4 - 5.4
Al ₂ O ₃ - 3.2 - 3.6
CaO - 1.6 - 2.3
MgO - 3.2 - 3.6
TiO ₂ - 3.3 - 3.6
V ₂ O ₅ - 0.7 - 0.9
P ₂ O ₅ - 0.010 - 0.015
Iron oxides - 3.2 - 7.9
S - 0.004 - 0.015
C - 2.0 - 3.5
Fe Met - Else
the ratio Fe met / Fe total and the carbon content in the spongy iron are interconnected by the ratio of Fe met / Fe total + 0.057С = 1.03 - 1.17.

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