RU2187563C2 - Method of preparation of charge material in form of briquettes for heat - Google Patents

Abstract

FIELD: metallurgy, particularly, preparation of charge materials for smelting of pig iron and steel. SUBSTANCE: method includes mixing of metal oxides with finely divided carbon-containing material and binder pressing and subsequent drying. Binder is used in form of mechanical mixture of sodium carbonate, dust from gas cleaning of electric arc furnace and manganese-containing materials, and sandy loam with their amounts of, wt.%: mixture 30; the balance, sandy loam. In this case, metal oxides are preliminarily ground. Carbon-containing material amounts up to 20-50% in terms of carbon from oxides weight. Finely ground metal oxides and binders are mixed, and obtained mixture is mixed with carbon-containing material uniformly moistened with aqueous solution of Na₂O*n*SiO₂ or sulfite-cellulose liquor. EFFECT: produced briquettes with high strength. 2 cl, 1 tbl

Description

 The invention relates to metallurgical production, namely to the preparation of charge materials for smelting cast iron and steel.

A known briquette for the production of cast iron and steel, which contains steel oxide, a carbon-containing material and a binder in the form of an alloy of oxides SiO ₂ , Na ₂ O, CaO and Al ₂ O ₃ , which is a small-component silicate glass. The basis of such a binder are oxides of silicon, aluminum and calcium [1].

 The disadvantage of this briquette is the high viscosity of the binder in the molten state and the low wettability of the surfaces of the solid phases of the briquette (particles of scale and carbon) inherent in glasses.

 This leads to a sufficiently large number of interconnected pores in the heated briquette, which contributes to a decrease in its strength, significant oxidation of carbon and, consequently, a decrease in the level of carburization of the metal by melting, which is especially undesirable when using briquettes in the production of cast iron. Another disadvantage of the briquette is: the absence of binder oxides in the composition, which increase the adhesion strength between iron oxides and the silica-based melt, the lack of technological regulations for the preparation of the briquetted mixture, which is important for ensuring the high-temperature strength of the briquette (the ability not to crumble until the metal recovery and carbonization processes are completed) ) and its density.

 The objective of the invention is the creation of a method of preparing the charge material for melting in the form of briquettes with increased values of strength and carburizing ability of the molten metal.

 The technical result of the invention is a method for preparing the charge material for melting in the form of briquettes with increased values of strength and carburizing ability of the molten metal.

 A method of preparing a charge material in the form of briquettes for melting involves mixing metal oxides with finely ground carbon-containing material and a binder, pressing and subsequent drying.

As a binder, a mechanical mixture is used, consisting of sodium carbonate, dust from gas cleaning of an electric arc furnace and manganese-containing materials, and sandy loam with their ratio, wt.%:
Mixture - 30
Sandy Loam - Else
In this case, the metal oxides are subjected to preliminary grinding, the amount of carbon-containing material is 20-50% by carbon of the mass of oxides. The metal oxides are crushed, the binder is finely ground, a mixture of oxides and binder is prepared and mixed with a carbon-containing material uniformly moistened with an aqueous solution of Na ₂ O • n • SiO ₂ or sulphite bard.

 The specified technical result is achieved by the influence of the following factors.

Firstly, the influence of the use of a binder consisting of a mechanical mixture containing sodium carbonate, dust from gas treatment of electric arc furnaces and manganese-containing materials, and sandy loam at a ratio, wt.%:
Mixture - 30
Sandy Loam - Else
In addition to oxides of silicon, aluminum and calcium, sandy loam contains potassium oxide, which reduces the surface tension of the silicate melt and improves its wetting ability. A positive effect of potassium oxide is to reduce the communicating porosity in the briquette, which reduces the oxidation of carbon in it by atmospheric oxygen, therefore, the degree of carburization of the melt increases.

 The addition of manganese-containing materials, for example, high-manganese slag or manganese ore, enriches the binder with manganese oxide, which increases the adhesion between the silicate-based binder and iron oxides, which leads to an increase in briquette strength.

 Secondly, the development of certain regulations of the technological process for preparing the briquetted mixture. The regulation consists of the following steps.

 1. The enveloping of ground metal oxides with a finely ground binder by mixing.

2. Wetting the crushed carbon-containing material with an aqueous solution of Na ₂ O • n • SiO ₂ (water glass) or sulphite bard by mixing.

3. Joint mixing of the mixtures obtained: metal oxides with a binder and a carbon-containing material moistened with an aqueous solution of Na ₂ O • n • SiO ₂ or sulphite bard.

 At the third stage of preparation of the mixture, the mixture of oxides with a binder adheres to carbon particles and carbon is isolated from oxides as a result of the formation of a boundary layer consisting of a binder and liquid glass.

After pressing the mixture, drying and heating the briquette in the temperature range 800-900 ^o With the binder is melted together with the dry residue of liquid glass, a fuzzy glassy film is formed, separating particles of carbon and oxides.

 It was experimentally established that the glassy film has a fairly high level of adhesive interaction with metal oxides, while there is practically no interaction between carbon and film. The continuous cellular film frame formed in the volume of the briquette provides briquette strength and gas tightness.

 With the simultaneous mixing of metal oxides, carbon-containing materials and a binder and wetting them with liquid glass (or bard), carbon prevents the formation of a continuous frame. As a result, the high temperature strength and gas tightness of the briquette are reduced.

As a criterion for assessing the high-temperature strength of the briquette, its strength after firing at 800-880 ^o C (the interval of the binder melting) and cooling in air is taken.

 The method of preparation of charge materials in a production environment is as follows. The mill scale is grinded, for example, in grinding runners or in a mill to a particle size of 0.3-1.5 mm and sieved through a sieve with a 2 mm mesh without residue. The carbon-containing material is ground to a polydisperse mixture with particle sizes of not more than 3 mm.

 The components of the binder are ground and sieved, for example, through a sieve 020 without residue. The starting components for the binder are a mechanical mixture consisting of sodium carbonate, dust from gas treatment of an electric arc furnace and manganese-containing materials, and sandy loam. To prepare the binder, use the ratio, wt.%: Mixture - 30, sandy loam - the rest.

 A binder is prepared by co-grinding the components, for example, in a mill.

 Having selected a part of each component by weight corresponding to a given percentage of briquetted mixture, they are thoroughly mixed, for example, in mixing runners in the following steps.

 1. The coating of crushed metal oxides with a binder by mixing.

2. Wetting the crushed carbon-containing material with an aqueous solution of Na ₂ O • n • SiO ₂ or sulphite bard by mixing.

3. Joint mixing of the mixtures obtained: metal oxides with a binder and a carbon-containing material moistened with an aqueous solution of Na ₂ O • n • SiO ₂ or sulphite bard.

The carbon-containing substance is taken in an amount of 20-50% by carbon of the mass of oxides, and the amount of a binder is 5-10% by weight of a mixture of oxides with a carbon-containing material. To give the briquette strength in the wet and dried state, an aqueous solution of Na ₂ O • n • SiO ₂ (GOST 13978-67) with a density of 1.3-1.5 g / cm ³ or sulphite bard with a density of 1.07-1 is added to the mixture 09 g / cm ³ in an amount of 7-10% in excess of 100% of the total weight of the mixture. Then, the resulting mass is pressed. Pressing is carried out at a specific pressure of 10-25 MPa on mechanical or hydraulic presses. The shape of the briquettes is arbitrary, the mass of briquettes is 0.2-3.5 kg. The briquettes are dried at a temperature of 200-250 ^o C in the dryer for 1.0-2.5 hours. After drying, the briquettes are ready for use as a mixture for steelmaking furnaces.

 The method has successfully passed industrial tests in the conditions of the Volgograd Metallurgical Plant "Red October".

 Example. Iron oxides of metallurgical production — steel oxide containing Fe total 72.5%, were used as metal oxides, and electrode combat was used as the carbon-containing material. The briquetting mixture was prepared in two ways.

1) Sequential mixing of the components according to the scheme:
scale + binder; carbon + water glass; joint mixing of the mixtures obtained - scale with a binder and carbon-containing substance with liquid glass.

 2) Simultaneous mixing of components: scale + carbon-containing material + binder + water glass.

The mixture was pressed at a specific pressure of 10 MPa to obtain cylindrical briquettes with a diameter and a height of 10 mm, dried at 250 ^o C, calcined at 860 ^o C and cooled in air.

 The briquettes obtained for both options for the preparation of the briquetted mixture, after drying and firing, were tested for compression and melted in alundum crucibles in a Tamman furnace. Compression tests did not reveal significant differences in the strength of briquettes made according to both options and subjected only to drying. Their strength is in the range of 4-5 MPa. However, after firing, the differences in strength and carburizing ability are obvious. The results of mechanical testing and conducting heats are given in the table. As you can see, the proposed method for the preparation of the charge material has an advantage compared with the known in terms of strength and carburizing ability.

Sources of information
RU 2083681. Briquette for the production of cast iron and steel. Ageev A.A. and others. Of. bull. "Inventions (applications and patents)", 1997, 19.

Claims (2)

1. The method of preparing the charge material in the form of briquettes for melting, comprising mixing metal oxides with finely ground carbon-containing material and a binder, pressing and subsequent drying, characterized in that the mechanical mixture consisting of sodium carbonate, dust from the gas treatment of an electric arc furnace is used as a binder and manganese-containing materials, and sandy loam at their ratio, wt.%:
Mixture - 30
Sandy Loam - Else
while the metal oxides are subjected to preliminary grinding, the amount of carbon-containing material is 20-50% by carbon of the mass of oxides. 2. The method according to claim 1, characterized in that the metal oxides are ground, the binder is finely ground, a mixture of oxides and a binder is prepared and mixed with a carbon-containing material uniformly moistened with an aqueous solution of Na ₂ O • n • SiO ₂ or sulphite bard.

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