RU2296800C2 - Steel smelting flux and method of production of such flux - Google Patents

Abstract

FIELD: metallurgy; methods of production of steel smelting flux.

SUBSTANCE: proposed flux contains the following components, mass fraction-%: magnesium oxide base; calcium oxide, 3.0-12.0; iron oxides, 5.0-15.0; aluminum oxide, 0.2-2.5; silicon dioxide, 2.0-5.0. Components of burden containing natural magnesite, caustic magnesite and sideritic ore are mixed in revolving furnace at the following content of burden components, mass fraction-%: natural magnesite, 40-65; caustic magnesite, 20-55; sideritic ore, 5-15; components are roasted at temperature of 1550-1700°C for obtaining rolled product. Roasted material is cooled and is classified , thus obtaining finished product in form of fraction more than 4 mm and fraction less than 4 mm. Screenings of fraction less than 4 mm are used as main starting material by briquetting the lumpy flux.

EFFECT: high content of magnesium oxides; high rate of dissolving in slag melts.

8 cl, 3 tbl, 1 ex

Description

The invention relates to the field of metallurgy, in particular to fluxes of steelmaking.

Known slag-forming reagent containing more than 15% MgO, which is obtained from magnesite and dolomite with the addition of 5-20% Portland cement, followed by wetting with water in an amount of 4-30% and forming briquettes (US Patent No. 4451293, C 22 B 9/10, from May 29, 87).

The disadvantage of the slag-forming reagent is the low MgO content.

Known metallurgical flux (Application Germany No. 3444518, C 04 B 5/06, from 14.07.88,), consisting of natural magnesite fraction 15-0 mm

The disadvantage of this flux is its slow dissolution in the main converter slag due to the fact that it is practically a monomineral material containing MgCO ₃ , as well as the disadvantages of using this flux are the high energy costs associated with its dissolution due to high losses during calcination of magnesite (up to 50%).

The closest in technical essence is a flux of calc-magnesian composition, which contains, wt.%: 26.0-35.0 magnesium oxide; 0.3-7.0 alumina; 5.0-15.0 iron oxides; 0.5-7.0 silica and the rest is calcium oxide (RF Patent No. 2145357, C 21 C 5/36, dated 02.10.2000).

The disadvantage of the above lime-magnesia flux is the low MgO content, which leads to an increase in its one-time fraction supplied to the converter if it is necessary to increase magnesium oxide in the slag, and therefore to increase the amount of forming slag, and a corresponding increase in energy consumption for dissolving it in the slag.

The closest in technical essence to the claimed method is a method for producing lime-magnesia flux, comprising mixing the components of the raw material mixture by co-grinding and pelletizing the material by burning sludge in a rotary kiln. After cooling, two products are isolated from the calcined material, the target in the form of a fraction larger than 5 mm and the screening in the form of a fraction of less than 5 mm, which is returned back to the furnace for re-pelletizing (RF Patent No. 2151535, C 21 C 5/36, from 20.11.1999 g.).

The disadvantage of this method is the low strength of the cake, the finished product and the high energy costs associated with the return of the screening material back to the furnace for re-pelletizing.

The objective of the invention is to provide a steelmaking flux having a high MgO content, low apparent density, providing a sufficiently high dissolution rate of flux in slag melts of the main composition. The proposed production method allows the production of flux in the form of rounded granules and briquettes of the required size with high mechanical strength, providing reliable storage and transportation for a long time without destruction.

The solution to this problem is achieved by the fact that the known steelmaking flux containing oxides of calcium, iron, magnesium, aluminum and silica, according to the invention contains these components in the following ratio, wt.% On calcined substance:

magnesium oxide the basis calcium oxide 3.0-12.0 iron oxides 5.0-15.0 aluminium oxide 0.2-2.5 silica 2.0-5.0

The technical result of the method for producing steelmaking flux is achieved in that the mixing of the charge components, consisting of natural magnesite, caustic magnesite and siderite ore, is carried out directly in a rotary kiln with the following content of the charge components, wt. share,%:

natural magnesite 40-65 caustic magnesite 20-55 siderite ore 5-15

The raw material mixture is fired at a temperature of 1550-1700 ° C, providing a rounded product. The calcined material is cooled and classified to obtain the finished product in the form of a fraction of more than 4 mm and a screening fraction of less than 4 mm. Screening of calcined material fractions of less than 4 mm is used as the main starting material for the manufacture of coarse flux briquetting method. The mixture for the manufacture of briquetted flux contains in its composition a fraction of less than 4 mm and a ground component of the same composition with the following content of the components of the mixture, wt. share,%:

screening of burnt material 70-90 ground component 10-30 binder, in excess of 100% 0.5-8

finished briquettes are heat treated at a temperature of 160-230 ° C.

In addition, three more variants of the briquetted steelmaking flux mixture are proposed, which differ from the initial one in that the following are used as the ground component:

1. Caustic magnesite;

2. Ground mixture consisting of caustic magnesite and agglomerate of iron ore in a ratio of 50 ± 5 - 50 ± 5%;

3. The ground mixture consisting of sifting out the calcined material 4-0 mm and iron ore sinter in a ratio of 60 ± 5 - 40 ± 5% with the same content of components in the charge.

The main active ingredients of the flux are magnesium oxide and its compounds with iron oxides. They interact well with the components of steelmaking slag and dissolve in it. Flux magnesium oxide interacts with such slag components as FeO and SiO _{2, which are} aggressive with respect to refractory lining, and binds them into neutral compounds like merwinite, monticellite, ferrite and magnesium wustite. The last two are refractory compounds and, in interaction with the components of the slag, form a continuous series of solid solutions of ferrites and wustites of complex composition, in this regard, the viscosity of the slag increases, which positively affects the degree of impregnation of the lining with slag. Due to the general increase in MgO in the slag, the chemical gradient decreases for this component at the “refractory lining - slag” boundary and, ultimately, the dissolution rate of the periclase-containing lining of the melting furnace decreases. However, the creation of a viscous slag melt containing up to 10-12% MgO provides good adhesion to the lining. After the metal is drained, the prepared slag is applied to the converter lining by blowing it with high pressure nitrogen. On the surface of the lining, the slag crystallizes and forms a protective layer, the resistance of this layer reaches two heats. After washing off the protective layer, the operation for preparing and swelling the slag is repeated.

In the claimed methods for the production of flux in comparison with the prototype uses less costly redistribution of production:

- at the redistribution of the preparation of the raw mix excludes energy-intensive redistribution of the preparation of sludge;

- the return of the fine product of a fraction of less than 4 mm back to the furnace for re-firing is replaced by redistributing the briquetting of a specially prepared mixture,

- a method for the production of flux by briquetting a mixture, additionally containing caustic magnesite and / or its ground component with an iron ore sinter, makes it possible to produce a flux having a high dissolution rate in slag melts of the main composition.

The preparation of a flux of the indicated chemical composition with an apparent density of less than 3.0 g / cm ³ allows it to be dissolved in the main slag melts within no more than 10 minutes.

An analysis of the methods for producing steelmaking slag fluxes known in the technical and patent literature did not reveal the use of the claimed features that ensure the minimum energy consumption of pelletized flux that does not collapse during transportation and storage, which indicates that the claimed invention is not obvious.

An example of a specific implementation.

Natural magnesite with a particle size of less than 40 mm, caustic magnesite in the form of trapped dust from a rotary kiln and siderite ore in the ratio shown in table 1, is fed into a rotary kiln. The raw materials of the mixture, passing through the preparation and decarbonization zones of the furnace, are mixed, and the mixture enters the firing zone in a relatively uniform state. In the high temperature zone of the furnace due to the formation of fusible compounds, mainly calcium ferrites and the presence of caustic magnesite, the mixture is sintered to form pellets with sizes up to 40 mm. The raw material mixture was fired in the temperature range 1550-1700 ° C. The firing temperature below 1550 ° C leads to a significant decrease in the yield of the target lumpy product, and temperatures above 1700 ° C lead to an increase in non-productive fuel consumption.

The amount of rounded material and its apparent density are directly proportional to the amount of caustic dust supplied to the furnace. The calcined material was dispersed to obtain a finished product of a fraction of more than 4 mm and a screening product of a fraction of less than 4 mm. The yield of a fraction of less than 4 mm averaged 40%.

Utilization of fractions less than 4 mm was carried out by means of briquetting of semi-dry masses containing a ground component in the initial charge, and dry phenolic powder (TFP) with a solvent — ethylene glycol in the amount of 3.0% and 1.5%, respectively, over 100%, was used as a binder. After briquetting, the briquettes were heat treated at a temperature of 160-230 ° C. The selected temperature range allows you to get briquettes with the highest possible strength.

The compositions of the masses are presented in table 2.

The finished flux in the form of pellets and briquettes was tested for strength, shelf life and dissolution rate in molten converter slag at a temperature of 1610 ± 10 ° C. The initial converter slag, flux and final slag with the addition of 10% flux to it had the following chemical composition, wt. share in%:

MgO SiO ₂ Fe ₂ About ₃ Cao FeO Al ₂ O ₃ MnO Source slag 4.0 18.9 6.9 47.6 11.8 1.4 9,4 Flux 86.1 3.0 6.8 3.6 - 0.5 - Final slag 10.5 18.3 9,4 42.8 8.9 1.4 8.7

The absorption of MgO slag was 85% relative to the calculated value.

The test results are shown in table 3.

Analysis of the above results shows that the use of the inventive production methods allows to obtain a flux durable, not collapsing during transportation and storage, as well as having a low apparent density and, as a result, a relatively high dissolution rate in the steelmaking slag melt.

Table 1 Charge number The composition of the mixture, the content of components,% The chemical composition of the flux, wt. share,% Exit MgO Cao SiO ₂ Al ₂ About ₃ Fe ₂ About ₃ Δm _prk fr. less than 4 mm,% natural magnesite caustic magnesite siderite ore prototype - 30.3 50,5 4.6 4.6 10.0 0.1 17.6 one 65 twenty fifteen 77.6 5.31 4.10 1.94 10.9 0.16 41.5 2 40 fifty 10 83.8 3.36 3.20 1,52 8.31 0.12 29.8 3 fifty 45 5 87.3 3.38 2.99 0.95 5.16 0.32 36.1 table 2 Charge number screening of calcined material 4-0 mm The content of fractions,% The chemical composition of the briquetted flux, wt. share,% Ground component prepared from: 4-0 mm K.mag. K.mag. + agl. 4-0 + agl. MgO Cao SiO ₂ Al ₂ About ₃ Fe ₂ O ₃ Δm _prk 1a 85 fifteen - - - 83,4 4.23 3.41 1.48 7.42 0.1 2a 90 - 10 - - 84.8 4.05 3.29 0.76 6.65 0.81 3a 80 - - twenty - 76.5 3.67 3.93 2,34 12.60 3.30 4a 70 - - - thirty 74.8 3.81 4.21 2.42 14,4 0.36

Table 3 Experience Number The density is apparent. g / cm ³ Compressive strength, N / granule Destructive storage 30 days,% Flux dissolution time, min prototype 2.98 31.5 16,0 11,4 one 2.89 52.1 4.0 8.6 2 2.65 53.6 3.6 9,4 3 2.71 56.1 3.8 10.0 1a 2.41 51,4 2,8 9.6 2a 2,32 43,2 2.1 8.7 3a 2,38 41.1 2.6 8.6 4a 2.46 44.6 2.6 8.4

Claims (8)

1. Steelmaking flux containing oxides of magnesium, calcium, iron, aluminum and silicon dioxide, characterized in that it contains these oxides in the following ratio, wt.% Per calcined substance: Magnesium oxide The basis Calcium oxide 3.0-12.0 Iron oxides 5.0-15.0 Aluminium oxide 0.2-2.5 Silica 2.0-5.0 2. A method of producing a steelmaking flux, comprising mixing the raw materials of the charge, firing the mixture in a rotary kiln, isolating the target product from the calcined material in the form of a large fraction, characterized in that natural magnesite, caustic magnesite and siderite ore are used as components of the raw material charge, which mixed directly in a rotary kiln, with the following components, wt.%: Natural magnesite 40-65 Caustic Magnesite 20-55 Siderite ore 5-15 and burn it at a temperature of 1550-1700 ° C, providing a rounded product. 3. The method according to claim 2, characterized in that the calcined material is cooled and classified to obtain the finished product in the form of a fraction of more than 4 mm and a screening fraction of less than 4 mm. 4. The method according to claim 3, characterized in that the screening of the calcined material fractions of less than 4 mm is used as the main starting material for the manufacture of lump flux briquetting method. 5. The method according to claim 4, characterized in that the mixture for the manufacture of briquetted flux contains a fraction of less than 4 mm and a ground component of the same composition, with the following content of the components of the mixture, wt.%: Screening of burnt material 70-90 Ground component 10-30 Binder, in excess of 100% 0.5-8 finished briquettes are heat treated at 160-230 ° C. 6. The method according to claim 4, characterized in that the mixture for the manufacture of briquetted flux further comprises a ground component in the form of caustic magnesite. 7. The method according to claim 4, characterized in that the mixture for the production of briquetted flux further comprises a ground component in the form of a ground mixture consisting of caustic magnesite and iron ore agglomerate in the ratio (50 ± 5: 50 ± 5)%. 8. The method according to claim 4, characterized in that the mixture for the manufacture of briquetted flux further comprises a ground component in the form of a ground mixture consisting of screening the calcined material and iron ore sinter in a ratio of (60 ± 5: 40 ± 5)%.