RU2296167C2 - Method of doping the steel by manganese - Google Patents

Abstract

FIELD: ferrous metallurgy; methods of doping the steel by manganese.

SUBSTANCE: the invention is pertaining to ferrous metallurgy, in particular, to doping the steel by manganese in the furnace and-or at the out-of-furnace treatment of the smelt with the manganese oxides mixtures. Conduct injection of manganese oxides and the reducing agent batchwise in the molten metal, and also add calcium oxides, then exercise the metal tapping in the ladle and its treatment in the ladle. At that the first batch of the manganese oxides introduce into the molten metal after the dross release on the mirror of the molten metal in the mixture with the reducing agent and which amount makes 40-60 % from the necessary amount, and the remaining part of the mixture is fed together with the lime during the metal tapping into the ladle. The invention allows to decrease consumption of the manganese-containing raw, lime and the reducing agent per a unit of the reduced manganese, to decrease the order of the dross, to increase extraction of manganese into the metal and to decrease the share of the nonmetallic impurities.

EFFECT: the invention ensures the decreased consumption of the manganese-containing raw, lime and the reducing agent per a unit of the reduced manganese, the decreased order of the dross, the increased extraction of manganese into the metal and the decreased share of the nonmetallic impurities.

4 cl, 2 ex, 3 tbl

Description

The invention relates to ferrous metallurgy, in particular to alloying steel with manganese by furnace and / or after-furnace treatment of the melt with oxide manganese mixtures.

Alloying steel with oxide mixtures is called direct alloying, i.e. alloying steel with manganese or other elements without the need for smelting standard ferroalloys (ferromanganese, silicomanganese and metallic manganese).

A known method of alloying steel with manganese, including smelting, discharging metal into a ladle, supplying alloying materials and purging metal with an inert gas, in which, after releasing metal into a ladle, a low-phosphorus manganese-containing ferroalloy slag is produced on the melt, a reducing agent and lime in an amount ensuring slag basicity 2, 0-3.5; however, it is allowed to supply oxygen to the bucket surface for 3-30 seconds (USSR AS No. 1044641, MKI C 21 C 7/00, 1983).

The disadvantages of the analogue are:

- low extraction of manganese from silicate manganese-containing slag;

- the need for overheating of the metal before being released into the ladle in order to melt the manganese-containing charge;

- unreasonably high basicity of the final slag;

- the need to purge the surface of the bucket with oxygen, which can lead to the oxidation of both the already reduced metal and the reducing metal itself.

A known method of steel production, 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 the liquid metal in the form of an oxide mixture with their ratio CaO / Mn _x O _y = 0, 6-1.2, with the processing of slag is carried out by exposure of molten metal under the slag with a basicity of CaO / SiO ₂ = 0.7-1.8 (RF patent No. 2096491, IPC C 21 C 7/00, 1997).

The disadvantages of the analogue are:

- the uncertainty in the ratio of calcium oxides to manganese oxides due to the fact that manganese has four compounds with oxygen (MnO, Mn ₃ O ₄ , Mn ₂ O ₃ , MnO ₂ );

- the ratio of CaO / SiO _{2 is} maintained in the range from 0.7 to 1.8, which is equivalent to working both on acidic slags and on basic slag with the same result - this contradicts the theory and cannot provide high manganese recovery in steel. Closest to the proposed method is the production of low-carbon structural steel according to the patent of the Russian Federation No. 2212453, IPC С 21 С 7/00, 2003, in which metal is smelted in a steel-smelting unit, deoxidation and alloying, introduction of manganese and calcium oxides into a liquid metal , the release of metal into the ladle, the processing of liquid metal in the ladle with slag formed after the reduction of manganese by aluminum, and the manganese oxides are introduced into the liquid metal in two portions, one of which is introduced into the steelmaking unit but with a carbon-containing reducing agent, taken in the ratio of (8.8–9.2) / 1, based on the preparation in the metal before releasing the manganese content in the amount of 0.1–0.2 required in the finished steel into the ladle, another portion of manganese oxides is introduced together with an aluminum-containing reducing agent, calcium oxides are introduced into the ladle in the form of a refining mixture with barium oxides at a ratio of 8.5-9.5, the ratio of manganese oxides fed to the ladle, the aluminum-containing reducing agent and the refining mixture being chosen equal to (70-75 ) :( 8-10) :( 17-20).

The disadvantages of this method of alloying steel with manganese are:

- the use of carbon as a reducing agent requires higher process temperatures;

- the difficulty of smelting due to the need to constantly conduct rapid analysis of the metal and slag for the content of the main elements (Mn and C in the metal and MnO and CaO in the slag);

- unreasonably low residual concentration of manganese in the metal when processing it in the furnace and the need to use furnace slag when processing metal in a ladle;

- low extraction of manganese in steel;

- unreasonably strong effect of a low consumption of BaO (0.52 kg / t) on the high sulfur absorption capacity of the slag.

The technical result to which the invention is directed is to simplify the technology of alloying steel with manganese, increase the extraction of manganese and improve the quality of the steel.

To achieve the named technical result, the proposed method introduces manganese oxides and a reducing agent in portions of the liquid metal as well as calcium oxides, releases the metal into the ladle and processes it in the ladle, the first portion of manganese oxides being introduced into the liquid metal after the slag is released onto the metal mirror mixed with a reducing agent, the amount of which is 40-60% of the required, and the rest of the mixture is set together with lime in the process of releasing the metal into the ladle. In addition, the claimed technical solution is additionally characterized by the following features:

- metals are used as reducing agents, the thermodynamic strength of the oxides of which is higher than that of manganese oxide;

- the silicon content in the steel before being released into the bucket is maintained 20-30% above its upper limit;

- as manganese use its compounds with oxygen with a manganese content of from 62.2 to 72.0%;

- after the release of the metal it is purged with an inert gas for 3-5 minutes.

Distinctive features of the proposed method are: feeding to the metal mirror a mixture containing manganese oxides with a reducing agent, and the fact that the rest of the mixture is set together with lime in the process of releasing the metal into the ladle.

Submission to the furnace of a mixture of manganese oxides with a reducing agent of less than 40% of the required amount leads to an increase in the amount of slag in the ladle and worsens its refining properties. If the amount of the mixture supplied to the electric furnace is more than 60%, this will increase the amount of slag and the loss of manganese in the form of kings.

Fluctuations in the manganese content in its compounds with oxygen from 62.2 to 72.0% are explained by the presence of several of its compounds in the mixture: MnO ₂ (62.2% Mn) and Mn ₃ O ₄ (72.0% Mn).

The practice of using inert gas as a source for averaging the chemical composition of the finished metal has established that this takes 3-5 minutes.

An example implementation of the method.

Example No. 1.

In a laboratory electric arc furnace with a transformer with a capacity of 100 kVA, experiments were carried out on the smelting of steels of three grades: 15G, 16G2, 20 (see table 1).

Table 1 steel grade C Si Mn S R Appointment no more 15G 0.12-0.19 0.17-0.37 0.7-1.0 0,035 0,035 TU14-143250-77 16G2 0.12-0.20 0.17-0.37 2.0-2.4 0,030 0,035 TU14-143250-77 twenty 0.17-0.24 0.17-0.37 0.35-0.65 0,040 0,035 TU14-143250-77

The choice of these grades of steel is due to the different content of manganese in them at a constant concentration of silicon. The volume of each heat is 10 kg of finished steel.

After the charge of the billet is melted and liquid metal is obtained, it is deoxidized, FS65 grade ferrosilicon, lime slag is induced, and 5 minutes after melting, the slag is discharged into the mold. The temperature of the steel in the furnace according to the optical pyrometer is 1590 ° C. Part of the mixture consisting of manganese oxides and a reducing agent (Si, Al, SiCa) is assigned to a liquid metal mirror. The choice of reducing agent is determined by the degree of oxidation of manganese. If the manganese-containing component of the mixture consists of manganese dioxide, then silicon ferrosilicon is used as a reducing agent, and they achieve that the silicon concentration in the metal at the end of smelting is 0.41-0.45%. If the oxidation state of manganese is lower, then aluminum or silicocalcium is used as a reducing agent. With this technique, they accelerate the assimilation of manganese due to the rapid passage of exothermic reactions. The temperature of the metal in the furnace is 10-15 ° C higher than before the introduction of the mixture. The resulting slag is released into the mold, and the metal into the heated ladle. The rest of the mixture consisting of manganese oxides, a reducing agent and lime is assigned to the metal stream during its release.

The experimental results are shown in table 2 and table 3.

table 2 steel grade Technological parameters The total weight of the mixture, kg The content of Mn,% KHO / me Additive to the oven Bucket Additive Purge time, min Weight, kg/% Composition, kg Weight, kg/% Composition, kg KHO Vos KHO Vos Lime 16G2 0.548 62.2 / 2.21 0.219 / 40 0.147 0,072 0.329 / 60 0.221 0.108 0.280 3.0 twenty 0.122 67.4 / 0.53 0,073 / 60 0,049 0.024 0,049 / 40 0,033 0.016 0,047 5,0 15G 0.176 72.0 / 0.94 0,088 / 50 0,067 0,021 0,088 / 50 0,067 0,021 0,023 4.0 The closest analogue The composition of the mixture specified in the furnace: manganese ore + coke in the ratio (8.8-9.2) / 1. Mixture consumption 70 kg / t. The composition of the mixture specified in the bucket: manganese ore (90 kg) + secondary aluminum (15 kg) + refining mixture (calcium oxide + barium oxide) in an amount of 30 kg / t. Table 3 Results obtained Extract Mn,
% Non-metallic inclusions Construction oxides Point oxides Sulfides 96.51 2.2 2.0 2.6 98.05 2.0 1,5 2.0 97.44 1.9 1.4 2.2 The closest analogue 85.0 3.0 2.6 1,1

Example No. 2.

In the foundry of the Obukhov Metallurgical Plant on the DSP-5 furnace, industrial melting of steel of grade 25L was carried out in accordance with the parameters declared in the present invention.

Steel composition,%: carbon - 0.22-0.3; manganese - 0.45-0.9; silicon - 0.2-0.52; phosphorus - 0.03; sulfur - 0.03.

In this example, as a manganese-containing raw material, a chemical concentrate (KHO) is used, which contains: MnO ₂ - 99.4%, SiO ₂ - 0.3%, CaO - 0.1%, P - 0.01%. The weight of the heat is 7300 kg.

A mixture containing chemical concentrate, FS65 ferrosilicon and lime is preliminarily prepared, some of which (50%) is set in the furnace on liquid metal free of slag; the second part (50%) - into the bucket as liquid metal is released there. The composition of the first part of the mixture: 53.8 kg KHO + 26.7 kg FS65 + 57.8 kg lime. The composition of the second part of the mixture: 53.8 kg KHO + 18.7 kg FS65 + 45.0 kg lime. The temperature of the metal at the outlet is 1570 ° C. The duration of the steel alloying process is 40 minutes.

The total duration of the heat, its individual periods does not change.

An analysis of the results of industrial testing of the technology of direct alloying of steel with manganese oxides showed that a chemical concentrate can be used instead of manganese ferroalloys. The degree of extraction of manganese from the mixture exceeds 90%. At the same time, melting technology was simplified due to the simplicity of preparation of mixtures and their compositions.

The proposed method of steel smelting, in comparison with the known one, allows to reduce the consumption of manganese-containing raw materials, lime and a reducing agent per unit of reduced manganese, respectively, to reduce the slag rate, increase the extraction of manganese into metal and reduce the content of non-metallic inclusions. The method also allows to increase the manganese content in steel and to expand the assortment of steels containing manganese, which can be smelted by the proposed method, without additional thermal energy costs.

The developed method can be implemented at Obukhov Special Steel CJSC, as well as at other plants smelting a similar range of steels.

Claims (4)

1. The method of alloying steel with manganese, including the introduction into the liquid metal of manganese oxides and a reducing agent in portions, as well as calcium oxides, the release of metal into the ladle and its processing in the ladle, characterized in that the first portion of manganese oxides is introduced into the liquid metal after the slag is released onto the mirror metal in a mixture with a reducing agent, the amount of which is 40-60% of the required, and the rest of the mixture is set together with lime during the release of metal into the ladle. 2. The method according to claim 1, characterized in that metals are used as reducing agents, the thermodynamic strength of the oxides of which is higher than that of manganese oxide. 3. The method according to claim 1, characterized in that the silicon content in the steel before being released into the ladle is maintained 20-30% higher than its upper limit for a given steel grade. 4. The method according to claim 1, characterized in that after the release of the metal it is purged with an inert gas for 3-5 minutes