RU2346989C2 - Method of production of steel in oxygen converter - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention refers to ferrous metallurgy, particularly to methods of production of steel in oxygen converters. The method consists in charging metal scrap, lime, products containing oxides of calcium, silicon, magnesium, aluminium and iron, then in pouring cast iron, and in bath lancing with a gaseous oxidiser. Additionally in course of bath lancing magnesia briquetted carbon and iron containing flux is added; its consumption is determined depending on weight of flux, on medium weight of liquid steel, on contents of silicon in cast iron, on weight of cast iron, on weight of slag-forming material, on required contents of magnesium oxide in slag and on contents of magnesium oxide in slag-forming material.

EFFECT: obtaining required contents of magnesium oxide in slag and increased durability of oxygen converters.

1 ex

Description

The invention relates to ferrous metallurgy, in particular to methods for the production of steel in converters

A known method of producing steel in a converter, including draining the final slag from the previous smelting into a mixer, provides complete immersion of scrap into slag, immersion of scrap metal in the form of a bag with a size of 400 × 800 × 1200 mm and a mass of 1200 kg, its exposure required to freeze on the calculated metal mass of slag, its extraction and filling of scrap metal together with slag into the converter, cast iron casting, slag-forming and purging the bath with oxygen (USSR, 1832725 class. С21С 5/28).

The disadvantages of this method include the low productivity of the technology of freezing slag on scrap, the need to use a mixer to store liquid slag, the impossibility of accurately dosing the ratios of scrap and slag, and accordingly the impossibility of accurately determining the amount of introduced components of the slag, in particular magnesium oxide, which leads to an excessive consumption of magnesium-containing components to obtain the desired content of magnesium oxide in the slag and, accordingly, to reduce the resistance of the converters.

Closest to the claimed is (RU, 2169197, class C21C 5/58, publ. 06/20/2001) a method of producing steel in an oxygen converter, comprising loading scrap metal, an iron-containing product for processing waste slag, lime, casting iron, blowing a bath with a gaseous oxidizing agent, and iron-containing the product consists of metal - 60% and slag - 40% of the components, the slag component contains oxides of calcium, silicon, magnesium, aluminum, manganese and iron, lime consumption is determined from the expression:

Q _reference = 12.5 + ([Si] _cast × 2.14 × Q _cast × B) × 0.01 × 0.1 × Q _sl , where

[Si] _Chug - the silicon content of the iron,%;

Q _Chug - flow of liquid iron, t;

In - the basicity of the slag required to obtain a lost steel grade;

Q _SL - consumption of iron-containing product for processing waste slag,

12.5, 2.14, 0.01, 0.1 - empirical coefficients obtained experimentally.

The known method does not provide the desired technical result for the following reasons.

The implementation of the method leads to a decrease in the resistance of the oxygen converter, an increase in the number of exogenous non-metallic inclusions, the yield of metal is reduced, and production is reduced.

The introduction of an iron-containing product for processing waste slag leads to a delay in the process of slag formation, decreases the content of magnesium oxide in the slag and, accordingly, the stability of the oxygen converter due to the unstable fractional composition, it is difficult to dissolve it in the converter bath, since at first a newly formed slag is frozen and only after reaching a certain temperature, its dissolution begins.

At the same time, the content of magnesium oxide in the iron-containing product of processing waste slag is unstable and can vary from 3 to 12%, which leads to inefficient use of the material and a decrease in the durability of the lining of the oxygen converter.

Signs of the closest analogue that coincide with the essential features of the claimed invention: loading scrap metal, lime, a product containing oxides of calcium, silicon, magnesium, aluminum and iron, cast iron casting, blowing the bath with a gaseous oxidizing agent.

The basis of the invention is the task of improving the method of steel production in an oxygen converter, in which the required content of magnesium oxide in the slag is obtained, at the lowest cost, the lining resistance of oxygen converters is increased, the number of exogenous non-metallic inclusions is reduced, the volume of production and yield of metal increases.

The expected technical result is obtaining the required content of magnesium oxide in the slag at the lowest cost, increasing the resistance of oxygen converters, reducing the number of exogenous non-metallic inclusions, improving the quality of steel, increasing the yield and increasing production.

To solve this problem, in a method comprising loading scrap metal, slag-forming material, flux, cast iron casting, purging the bath with a gaseous oxidizing agent, according to the invention, the mass of slag-forming material and the content of magnesium oxide in it are determined and briquetted magnesian carbon is charged as flux and iron-containing product with a flow rate determined from the expression:

G _fm = ((0,025 × G _v + 0,05 × Si × Q _{Chug Chug} + ΣG _i) × (MgO) _{SHL -ΣG i × (MgO) i)} / 80, where

Q _fm - mass flux of magnesia briquetted carbon and iron, t;

G _article - the average mass of liquid steel, t;

Si _Chug - the silicon content in the iron,%;

Q _Chug - weight iron, t;

G _i - mass of slag-forming material, t;

(MgO) _sl - the required content of magnesium oxide in the slag,%. (Mg0) i is the content of magnesium oxide in the slag-forming material,%.

0.025; 0.05; 80 - empirical coefficients obtained experimentally.

The technical result is achieved due to the fact that a flux — magnesia briquetted carbon and iron — is added as a product, depending on the silicon content in the cast iron, the mass of cast iron, the mass of slag-forming materials and the content of magnesium oxide in the slag-forming material.

The essence of the claimed technical solution consists in introducing into the converter bath a flux with a high content of magnesium oxide, which, thanks to the iron oxides and carbon it contains, quickly dissolves in the slag, practically does not affect the heat balance of the smelting and increases the concentration of magnesium oxide above the equilibrium value, thereby preventing the transfer of magnesium oxide from the converter lining to slag. Magnesia briquetted carbon and iron flux according to TU 0750-001-34533009-2007 contains not less than 70% MgO, not more than 5% SiO ₂ , Fe ₂ O ₃ 4.0-8.0%, C 4.0-8, 0% The calculation of the mass flow of slag-forming material is carried out depending on the mass of cast iron, its silicon content, and CaO content in lime

This method is illustrated by an example.

In a 370-ton top-purged oxygen converter, S235JR steel was smelted according to STO MMK 209-2006. The consumption of liquid pig iron is 307 tons, scrap 103 tons. The content in silicon iron is 0.55%, manganese 0.26%, sulfur 0.025% and phosphorus 0.051%. The temperature of cast iron is 1386 ° C. The required content of magnesium oxide in the slag is 13%. The estimated amount of flux of magnesia briquetted carbon and iron was determined according to the formula:

Q _fm = ((0.025 × 370 + 0.05 × 0.55 × 307 + 10.0 + 16.2) × 13- (10.0x5 + 16.2 × 28) / 80 = 1.08 t

Magnesia briquetted carbon- and iron-containing flux in the amount of 1 ton was transferred to the converter before cast iron pouring together with 1.4 ton of lime (5% magnesium oxide) and 8.8 ton of iron dolomite (28% magnesium oxide). Then they poured liquid cast iron and filled up scrap metal.

Purge was conducted through a six-nozzle lance with an oxygen flow rate of 1150-1200 m ³ / min. During the purge, 8.6 tons of lime and 7.4 tons of ferruginous dolomite were delivered. The consumption of oxygen for melting amounted to 21557 m ³ .

After the purge was completed, the temperature of the metal was measured, which amounted to 1667 ° С, and samples of metal and slag were taken. The chemical composition of the metal was determined by the spectral method, and slag was determined by the X-ray diffraction method. The metal contained: carbon 0.034%, manganese 0.05%, sulfur 0.026%, phosphorus 0.010%, slag 32.8% CaO, 13.62% SiO ₂ , 30.32% FeO, 13.1% MgO, 2, 2% Al ₂ O ₃ , 0.062% S and 0.75% P ₂ O ₅ .

Out-of-furnace melting processing was carried out at the ladle furnace.

The finished steel contained 0.15% carbon, 0.02% silicon, 0.50% manganese, 0.012% phosphorus and 0.010% sulfur.

The introduction of a flux with a high content of magnesium oxide into the converter bath allows one to obtain the required content of magnesium oxide in the slag, increase the resistance of oxygen converters, reduce the number of exogenous non-metallic inclusions, improve the quality of steel, yield and increase production.

Claims (1)

A method of producing steel in an oxygen converter, including loading scrap metal, slag-forming material, flux, cast iron casting, purging the bath with a gaseous oxidizing agent, characterized in that the mass of slag-forming material and the content of magnesium oxide are determined and briquetted magnesian carbon is charged as flux and iron-containing product with a flow rate determined from the expression:
G _fm = ((0,025 · G _v + 0,05 · Si · G _{Chug Chug} + ΣG _i) · (MgO) _{SHL -ΣG i · (MgO) i)} / 80
where G _fm - mass of briquetted magnesian carbon and iron flux, t;
G _article - the average mass of liquid steel, t;
Si _Chug - the silicon content in the iron,%;
_Chug G - mass of iron, t;
G _i - mass of slag-forming material, t;
(MgO) _sl - the required content of magnesium oxide in the slag,%;
(MgO) _i is the content of magnesium oxide in the slag-forming material,%;
0.025; 0.05; 80 - empirical coefficients obtained experimentally.