RU2096491C1 - Steel foundry process - Google Patents

Abstract

FIELD: ferrous metallurgy. SUBSTANCE: process includes smelting steel in steel-smelting assembly, deoxidation, alloying, producing liquid metal containing silicon and aluminum reducing agents, adding oxide mixture containing calcium and manganese oxides in the ratio 0.6 to 1.2, keeping liquid material in ladle under slag with basicity corresponding to CaO/SiO₂ ratio from - 0.7 to 1.8 arising after manganese is reduced by silicon and aluminum dissolved in metal. EFFECT: enhanced efficiency of process. 2 cl

Description

 The invention relates to ferrous metallurgy and can be used in the smelting of alloy steels.

 A known method of alloying steel with manganese by introducing manganese ore and aluminum into the ladle and then mixing the steel with slag / 1 /.

The disadvantages of the method are:
high thermodynamic strength and low chemical activity of manganese oxides in manganese ore in the form of divalent manganese in silicates and aluminosilicates;
the use of aluminum for manganese reduction, which is reduced not only by aluminum manganese, which restores not only manganese, but also silicon from oxides, and its consumption does not exceed the stoichiometrically necessary for manganese reduction;
reduction product in slag are manganese aluminates to metal;
non-metallic inclusions of spinel type x are formed in the metal. MnO, Al ₂ O ₃ , which are poorly removed due to the high work of adhesion (W _adg ) at the boundary of a liquid metal non-metallic inclusion;
increases the total aluminum content in steel.

 The closest in technical essence is the method of alloying steel with manganese, including smelting, metal release into the ladle, alloying and inert gas purging, while after the metal is released into the ladle, the low-phosphorus manganese-containing slag of ferroalloy production, reducing agent and lime in the amount providing slag basicity 2.0 3.5. Oxygen is supplied to the bucket surface for 3 to 30 seconds. / 2 /.

The low-phosphorus manganese-containing slag contains significantly less phosphorus compared to manganese ores or their concentrates, but contains a high content of silica (23 35%). Manganese in the phosphoric slag is in the form of a chemically strong compound MnSiO ₃ rhodonite. The addition of lime helps to destroy chemical bonds in manganese silicate, its reduction with aluminum or silicon, and the formation of calcium silicates in the slag.

The disadvantage of this method is that to accelerate the melting of the mixture it is necessary to purge it with oxygen, as a result of which the destruction of chemical bonds in minerals occurs, additional heat of exometric oxidation reactions of the reducing agent is released. Along with Ca ₂ SiO ₄ , Ca ₃ SiO ₅ is formed in the slag, its melting point is increased, and the extraction of manganese is reduced due to its dissolution in Ca ₃ SiO ₅ .

The disadvantage of this method is that the lime is given in an amount that ensures the basicity of the slag 2 3.5, and oxygen is supplied to the metal surface for 3 30 s. At the indicated flow rate of lime mixed with manganese-containing slag before the reduction of manganese, solid solid solutions (Ca, MnO) with a high melting point of more than 1400 ^o C, as well as free lime, are formed along with calcium silicates. The mixture has a large melting range of liquidus solidus.

 The invention is aimed at reducing the consumption of materials, increasing the extraction of manganese and increasing its content in steel, as well as improving the quality of steel by reducing alumina.

To do this, in a known method for the production of steel, including its smelting in a steel-smelting unit, deoxidation, alloying and slag treatment, an oxide mixture containing manganese and calcium oxides at a ratio of CaO / Mn _X O is introduced into a molten metal containing reducing agents: silicon and aluminum _y 0.6: 1.2 and maintain it in a ladle under slag with a basicity of CaO / SiO ₂ = 0.7 1.8, formed after the reduction of manganese by silicon and aluminum dissolved in the metal.

To alloy steel, manganese ore is used, in which manganese is not in the form of oxides of divalent manganese, but in the form of oxides of three or tetravalent manganese, due to which it has a low melting point and high oxygen reactivity in the resulting oxide melt (d ₀ 2 ^- ) This is also achieved because the ore (and / or its concentrate) is mixed with lime at a ratio of oxides CaO / (Mn ₂ O ₃ + MnO ₂ ) = 0.6: 1.2, which provides the lowest melting point, is placed in the furnace before release or into the bucket, during the release, restore silicon with the formation of slag having a basicity of CaO / SiO ₂ = 0.70: 1.80, and maintain the steel under the slag in the bucket. Silicon metal reduction provides a reduction in the residual aluminum content and obtaining globular inclusions that are easily removed from steel and assimilated by calcium silicate slag.

 Slag with a basicity of 0.7 to 1.8 has a low melting point and viscosity and, along with the removal of non-metallic inclusions, can also reduce the sulfur content in the metal.

The ratio of manganese oxides and calcium oxides in the initial mixture is due to the fact that in the indicated ratio when using ore and a concentrate with different silica contents, manganese oxides are in the form of Mn ₂ O ₃ and MnO ₂ and the mixture has the lowest melting point. At a CaO / Mn _X O _y ratio of less than 0.6, the melting point increases due to the formation of divalent manganese oxides and solid solutions (Ca, Mn) O and spinels of the type (Ca, Mn) Mn ₂ O ₃ at a CaO / Mn _X O _y ratio more than 1.2 due to free CaO lime.

Example 1. In an electric arc furnace, the iron-carbon product was melted with deoxidation and alloying. The liquid metal containing the reducing agents: silicon and aluminum, was poured into the ladle at a temperature of 1700 ^o C without slag, during the release, a mixture of manganese ore (Mn 48.0% SiO ₂ 3.5% Fe 3.4% CaO 1 , 5% Al ₂ O ₃ 2.5% P 0.05%), and lime (CaO 90%) with a ratio of CaO / Mn _X O _y = 0.6 and ferrosilicon FS-65. After exposure, a metal was obtained with a manganese content of 0.7%, taking into account the extraction of residual manganese from the iron-carbon intermediate when it was discharged from the furnace 100% and slag with a basicity of CaO / SiO _{2 of} 0.7%. A chemical steel was obtained in the ladle, C 0.3; Mn 0.7; Si 0.2; Al 0.001; S 0.015.

Example 2. In an open-hearth furnace, the iron-carbon product was melted with deoxidation and alloying. A liquid metal containing reducing agents: silicon and aluminum, was poured into the ladle at a temperature of 1650 ^o C, at the same time introduced a mixture of manganese ore specified in example 1 and lime at a ratio of 1: 1. After aging, manganese was reduced by silicon dissolved in a liquid metal. After the reduction of manganese, a metal with a manganese content of 1.0% and a slag with a basicity of CaO / SiO ₂ = 1.4 were obtained.

Extraction of manganese from the oxide mixture was 93%
Got a mixture composition, C 0.35; Mn 1.0; Si 0.32; Al 0.002; S is 0.020.

Example 3. In an electric arc furnace, the iron-carbon product was melted with deoxidation and alloying. A liquid metal containing reducing agents: silicon and aluminum, was poured into a ladle at a temperature of 1670 ^o C without slag. At the time of production, manganese ore and lime were mixed into the ladle at a ratio of CaO / Mn _X O _y = 1.8 and FS-65 ferrosilicon and kept under slag in the ladle formed after reduction of manganese with a basicity of CaO / SiO ₂ = 1, 8.

 Got the composition of the steel, C 0.32; Mn 1.08; Si 0.28; Al 0.0025; S is 0.012.

The ratio CaO / Mn _X O _y from 0.6 to 1.2 gives a minimum melting point, so going beyond these limits increases the cost of thermal energy.

At a CaO / SiO ₂ ratio _of less than 0.7 less, an increase in manganese is not ensured, and at a CaO / SiO ₂ ratio _of more than 1.8, a homogeneous slag composition is formed.

 The proposed method of steel smelting in comparison with the known one allows to reduce the consumption of manganese-containing raw materials, lime, reducing agent per unit of recoverable manganese, respectively, to reduce the slag ratio, increase the extraction of manganese into metal, and reduce the content of alumina inclusions.

 The method also allows to increase the manganese content in steel and to expand the range of steels containing manganese, which can be smelted by the proposed method, without additional thermal energy costs.

Claims (2)

1. Method for the production of steel, including the smelting of metal in a steelmaking unit, deoxidation, alloying, obtaining a liquid metal containing silicon and aluminum reducing agents, introducing manganese and calcium oxides into a liquid metal, treating the liquid metal in the ladle with slag formed after the reduction of manganese with silicon and aluminum dissolved in a metal, characterized in that the oxides of manganese and calcium are introduced into the liquid metal in the form of an oxide mixture at a ratio of CaO / Mn _x O _{y of} 0.6 1.2, and the processing of slag is carried out by exposure to liquid metal under slag with a basicity of CaO / SiO ₂ 0.7 1.8.  2. The method according to claim 1, characterized in that with the oxide mixture in the liquid metal is additionally introduced a reducing agent containing silicon.