RU2322512C1 - Slag-forming solid mixture for steel refining - Google Patents

Abstract

FIELD: ferrous metallurgy, namely out-of-furnace treatment of metal by means of slag-forming solid mixtures.

SUBSTANCE: mixture for refining steel contains next relation of components, mass.%: lime, 77 - 89; alumo-concentrate of given type, 11 - 23.

EFFECT: reduced cost price of steel, less quantity of harmful outbursts to atmosphere, lowered contamination degree of steel with non-metallic inclusions, improved physical-mechanical properties of steel.

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Description

The invention relates to ferrous metallurgy, specifically to out-of-furnace metal processing by solid slag-forming mixtures.

Known [1] is a mixture for processing molten steel containing lime, fluorine-containing material, alumina-containing material, aluminum shot and lump aluminum, in which ferroalloy slag is contained as alumina and fluorine-containing materials in the following ratio of components, wt.%:

Lime 63 ÷ 72 Alumina Slag ferroalloy production 22 ÷ 26 Aluminum fraction 4 ÷ 7 Slug aluminum 2 ÷ 4

Significant disadvantages of this mixture are:

- high cost of aluminum-containing materials;

- a long process of slag formation and low refining ability of the formed furnace slag for non-metallic inclusions;

- high emissions of dusty alumina-containing materials (alumina-containing slag of ferroalloy production).

Also known is a solid slag-forming mixture for refining steel [2], containing lime, fluorspar, aluminum-containing material, and as an aluminum-containing material it contains dusty waste from the production of silumin AK-17 in the following ratio, wt.%:

Lime 72 ÷ 80 Fluorspar 17 ÷ 20 Dusty waste production of silumin AK-17 3 ÷ 7

Significant disadvantages of this mixture are:

- high alumina and fluoride emissions;

- increased steel contamination by exogenous inclusions of alumina-containing materials from the components of the mixture due to the high melting temperature of the mixture and erosion of the lining of the steel pouring ladle due to the use of fluorine-containing material (fluorspar);

- low level of physical and mechanical properties due to the high contamination of steel with non-metallic inclusions.

Known as a prototype mixture for processing liquid steel [3], containing lime, alumina and aluminum-containing materials, and as an alumina-containing material, it contains ferroalloy slag, and as an aluminum-containing material - dusty aluminum-containing silumin wastes at a ratio of components, wt. %:

Lime 66 ÷ 73 Alumina Slag ferroalloy production 24 ÷ 27 Dusty aluminum silumin production waste 5 ÷ 7

Significant disadvantages of this mixture are:

- high emissions of dusty alumina-containing and aluminum-containing materials;

- a high level of contamination of the smelted steel with non-metallic inclusions due to the high melting point of the mixture and the lengthy process of slag formation;

- reduced level of physico-mechanical properties of steel due to contamination of steel with aluminum-containing non-metallic inclusions.

The desired technical results of the invention are:

reducing the cost of steel produced, reducing harmful emissions into the atmosphere, reducing the level of pollution by non-metallic inclusions, increasing the level of physical and mechanical properties of steel.

For this purpose, a solid slag-forming mixture for refining steel is proposed, containing lime, alumina and aluminum-containing materials, characterized in that it contains aluminum concentrate AVK-50F as an alumina and aluminum-containing material in the following ratio, wt.%:

Lime - 77 ÷ 89 Aluminum concentrate - 11 ÷ 23

The claimed limits are selected experimentally.

The choice of the boundary parameters of lime is due to the fact that when the content of lime in the mixture is less than 77%, the basicity of the melt of the mixture decreases, the physicochemical and refining properties of the slag deteriorate, the level of contamination of steel with nonmetallic inclusions increases, and the physicomechanical properties of steel decrease.

With an increase in the lime content of more than 89%, heat losses sharply increase during slag formation, incomplete dissolution of lime is observed, thick non-reactive slag is formed, as a result of which the level of steel contamination with exogenous nonmetallic inclusions increases and the physical and mechanical properties of steel decrease.

The limits of changes in the content in the mixture of aluminum concentrate are determined by the fact that with an increase in the content above the declared upper limit (more than 23%) it is possible to obtain a higher aluminum content in the finished steel, while the physical and mechanical properties of the steel are reduced, the pollution of steel by non-metallic inclusions is increased, and steel casting is complicated by CCM as a result of tightening the pouring glasses.

When the aluminum content in the mixture is less than 11%, an unacceptably low aluminum content in the finished steel is obtained, which leads to a decrease in grain size and, as a result, a decrease in the physicomechanical properties of steel.

The inventive mixture was used in the processing of steel in the ladle during the release of heat from the furnace (with a flow rate of 4.5-13.5 kg / t of steel).

In experimental swimming trunks, an aluminum concentrate of the AVK-50F grade of the following chemical composition was used, wt.%: Al≥50; Mg <6; Al ₂ O ₃ ≤37.4; Cu≤3.8; Zn 3 3.3; Si≤5; Pb≤0.3; Sn≤0.2.

The material, along with metal-active aluminum, contains alumina (aluminum oxide), which contributes to the rapid formation of reactive slag with high refining ability. The material was used in the form of pillow-shaped briquettes with an average size of 50 × 50 × 30 mm, and the mechanical crush strength of the briquette was not less than 100 kg.

Lime fractions up to 80 mm with a CaO≥85% content were used.

Steel grades st 20, 15, 37G2S, 40X were smelted in an electric arc furnace type DSP 100N10, equipped with a bay window, the melting was produced with cut-off furnace slag, during the production the mixture was planted in the claimed limits.

The mixtures used are shown in table 1, the results of use are shown in table 2.

As a result of industrial use of the mixture, the following results were obtained:

- reduced the cost of smelted steel by 8 rubles / ton of steel;

- reduced dust content by an average of 2 mg / m ³ ;

- the level of contamination of steel with non-metallic inclusions is reduced (the length of the line of aluminum-containing inclusions is reduced by an average of 0.35 mm);

- yield strength and strength increased by an average of 3.4 MPa.

List of sources

1. RF patent No. 2039091, cl. C21C 7/064.

2. RF patent No. 2003702, cl. C21C 7/076.

3. RF patent No. 2003701, cl. C21C 7/076.

Table 1 The compositions of the inventive mixtures Component Mix Number one 2 3 four 5 6 7 8 9 10 Lime% 77 78 80 88 86 84 81 85 79 89 Aluminum concentrate,% 23 22 twenty 12 fourteen 16 19 fifteen 21 eleven

table 2 Mixture Test Results Mixture consumption, kg / t steel Mix Number one 2 3 four 5 6 7 8 9 10 prototype 4,5 8.9 6.5 10.0 12.0 6.1 11,4 12.8 13.0 13.5 15-17 Dustiness, mg / m ³ 17 17 16 fifteen fifteen fifteen fifteen fifteen 16 fifteen 19-20 Contamination level (line length of aluminum-containing inclusions, mm) 1,2 0.8 0.9 0.5 0.9 0.8 0.7 0.6 0.5 1,1 1.3-1.5

Claims (1)

Solid slag-forming mixture for steel refining containing lime, alumina and aluminum-containing material, characterized in that it contains aluminum concentrate AVK-50F as alumina and aluminum-containing material in the following ratio, wt.%: lime 77 ÷ 89 aluminum concentrate AVK-50F 11 ÷ 23