RU2247158C1 - Method of extra-furnace alloying of iron-carbon alloys in ladle - Google Patents

Abstract

FIELD: ferrous metallurgy.

SUBSTANCE: proposed method includes tapping of iron-carbon melt from steel-making unit into ladle and feeding deoxidizing and alloying reagents into ladle in the course of tapping. Melt is alloyed by briquettes containing metallic silicon carbide in the amount of 5-80 mass-%, carbon material in the amount of 10-85 mass-% and the remainder being binder; after tapping, melt is deoxidized by aluminum and ferro-alloys are added for obtaining required chemical composition. Briquettes contain additionally substandard fines of ferro-manganese at ratio of silicon to manganese of 1:(2.2-3.7). Metallic silicon carbide is introduced into briquettes in form of sludges. Used as carbon material are heat-treated carbon-containing materials of electrode production process. Proposed method makes it possible to alloy iron-carbon alloys with silicon and carbon for obtaining high range of steel grades at reduced content of sulfur in melt.

EFFECT: enhanced efficiency; low cost of product.

4 cl, 2 tbl, 2 ex

Description

The invention relates to ferrous metallurgy, and in particular to methods of out-of-furnace treatment and alloying of melted iron-carbon alloys in a ladle using complex alloys.

The closest in technical essence is the method of out-of-furnace deoxidation of steel by silicon carbide of a fraction of 0.1-10 mm, containing 80-90% pure silicon carbide, 2-5 wt.% Free carbon, the rest is impurities, deoxidants are fed during the production process with a flow rate of 1- 5 kg / t of melt depending

After the release, deoxidizers are additionally supplied in the range of 0.2 -0.4 kg / t of melt and aluminum with a flow rate in the range of 0.1-1.5 kg / t of melt, while the deoxidizer is given according to

where Q ₁ - deoxidant consumption in the production process, kg / t;

Q ₂ - deoxidant consumption after release, kg / t;

C ₁ and C ₂ - carbon content in the melt at the beginning of production and the required carbon content in the finished steel, wt.%;

Si ₁ and Si ₂ - silicon content in the melt at the beginning of production and the necessary silicon content in the finished steel, wt.%;

K ₁ and K ₂ - empirical coefficients characterizing the physico-chemical laws during steel deoxidation, equal to 1.6-10.0 and 0.33-8.0, respectively, kg / t;

After that, the melt is alloyed with aluminum in the form of a wire rod with flow rates in the range of 0.3-0.7 kg / t of melt and purged with argon for 1-5 minutes at a rate of 0.5-2.0 l / min per ton of steel (Pat. Russia No. 2219249, C 21 C 7/00. Publish. 12.20.2003).

The disadvantage of this method is the inability to adjust the ratio of silicon / carbon in the smelting of calm or semi-quiet steels, which narrows the range of the range of smelted steel grades and makes it difficult to obtain a grade of silicon and carbon in the finished steel. In addition, silicon carbide according to patent No. 2219249 is used only as a deoxidizing agent, and not as a ligature.

The technical task of the claimed invention is to achieve complex alloying of iron-carbon alloys with silicon and carbon, providing the possibility of obtaining a wide range of assortment of smelted steel grades, as well as to reduce the sulfur content in the finished melt, reducing the cost of the finished product.

The technical result is achieved due to the fact that the method of out-of-furnace alloying of iron-carbon alloys in the ladle includes the release of the iron-carbon melt from the steelmaking unit into the ladle, feeding the deoxidizers and alloys into the ladle during the melt discharge, while the melt is alloyed with briquettes containing 5-80 wt% silicon carbide. %, carbon material 10-85 wt.%, a binder - the rest; and after the release, the melt is deoxidized with aluminum and adjusted in chemical composition with ferroalloys, the briquette additionally containing substandard fines of ferromanganese with a silicon to manganese ratio of 1: (2.2-3.7), and sludge is used as metallurgical silicon carbide, but carbon material use heat-treated carbon-containing electrode materials.

The briquette may additionally contain substandard trifle of ferromanganese with a ratio of silicon to manganese - 1: (2.2-3.7), and its sludge can be used as metallurgical silicon carbide. As a carbon-containing mixture can be used materials heat-treated carbon-containing electrode production.

The saturation of the iron-carbon alloy with silicon and carbon occurs due to the interaction of silicon carbide with the melt by the reaction

SiC _tv + Fe = [Si] _Fe + [C] _Fe

with the assimilation of silicon and carbon by molten metal.

The joint introduction of silicon and carbon in the compound, which is chemically inert, ensures the achievement of predetermined parameters in chemical composition.

The combination of carbon-containing materials with silicon carbide ensures the sufficiency of the carbonization process.

Silicon carbide (for example, metallurgical), TU 002222-162-99 is the product of a chemical-thermal reaction for the reduction of quartz sand with carbon black petroleum coke:

SiO ₂ + C = SiC + 2CO.

The process is carried out in self-propelled resistance furnaces according to the Acheson method. In contrast to abrasive silicon carbide (a-SiC), metallurgical is represented by a structural modification of b-SiC. To implement the technical solution for this application can be used any of these types of silicon carbide.

Upon receipt of a commercial product (grain and powders) from abrasive silicon carbide, the primary piece is crushed with further sieving on screens in fractions. At all stages of processing, dust collection is carried out by bag filters. The product deposited in the filter bags (sludge) is a finely divided material with particle sizes less than 0.05 mm and contains SiC 70-90%.

Carbon-containing materials according to TU 1914 - 01827208846 - 99 and / or TU 1914 - 00194042 - 026 - 01 as well as silicon carbide are products of chemical-thermal reactions of pure components, therefore they do not contain harmful impurities (sulfur, phosphorus, non-ferrous metals), which negatively affect steel quality. The cost of iron-carbon alloy is reduced due to the fact that carbon-containing materials and sludges of silicon carbide are secondary raw materials with valuable metallurgical properties at a relatively low price.

The low content of harmful impurities also allows you to save material and energy resources for their removal from the melt, which also reduces the cost of the product.

The limits for introducing a mechanical mixture of metallurgical silicon carbide and / or its sludge with carbon material (TU 1914 - 01827208846 - 99) and / or heat-treated carbon-containing material of the electrode production (TU 1914 - 00194042 - 026 - 01) are explained by the physicochemical laws of alloying calm and semi-quiet steel grades, as well as their final chemical composition, and are selected empirically.

At lower values, the steel will not be sufficiently deoxidized and will not correspond to the vintage chemical composition. It is not economically feasible to give a larger amount, which also will not provide the necessary steel composition and reduce the temperature of the melt.

The introduction of a mechanical mixture or briquettes within the specified limits reduces the oxidation of steel and allows you to get a fairly deoxidized metal (calm, semi-quiet) of a given chemical composition while saving aluminum.

The introduction of aluminum as a deoxidizing agent is explained by the physicochemical laws of steel deoxidation. At lower values, the steel will not be sufficiently deoxidized, boiling.

At high values, the steel will have excess aluminum and corundum (alpha - Al ₂ O ₃ ) non-metallic inclusions of the stroke type will form, and, as a result, a decrease in the physicomechanical properties of steel.

The use of the mixture in an unbricked form leads to the removal of material by convective flows and increases the consumption of material, which affects the cost of the final product.

The introduction of a mechanical mixture in the form of briquettes avoids the removal of fine fractions and more efficiently use the active components, strictly observing their predetermined ratios.

The limits of the content of components in the briquette are explained by the physicochemical laws of alloying iron-carbon melts and the chemical composition of steel.

EXAMPLE 1

Experimental swimming trunks were carried out on a 250-ton converter during the smelting of calm and semi-quiet steel grades. After melting, the metal from the converter containing С 0.04% Si 0.0015% was poured into the ladle. By filling 1/3 of the bucket, briquettes were introduced under a stream of metal. The briquettes were completed after the release of approximately 70% of the metal. Manganese metal refinement was carried out by giving ferromanganese FMN78 to the ladle. The final deoxidation of the metal was carried out with aluminum pig AB 87. The data of the experimental melts are shown in table 1.

Table 1 Indicators Steel alloying options in the bucket Half Steel Calm steel Beyond steel grade St6ps St3ps St5ps St3sp St4sp St2sp compositions * The content of silicon carbide, wt.% 5 25 40 45 65 80 3 85 The content of the carbon-containing electrode production material, wt.% 85 65 fifty 45 25 10 87 5 The increase in sulfur, wt.% 0.0041 0.0034 0.0022 0.0025 0.0018 0.0001 0.005 0.0001 The carbon content in the finished metal, wt.% 0.48 0.2 0.35 0.18 0.25 0.11 0.51 0.08 The silicon content in the finished metal, wt.% 0.16 0.15 0.12 0.13 0.3 0.21 0.09 0.37 *) the resulting alloys do not match the specified grade steels.

When the content of silicon carbide or its sludges in the composition of the briquette (may also be in the mixture) in the amount of 5-80 wt.%, The grade silicon content in the steel is ensured. At lower values, the silicon content will not match the vintage. At large values, an excess of silicon will appear, which does not correspond to the vintage, contributing to the formation of silicate non-metallic inclusions.

If the briquette contains carbon and / or material of heat-treated carbon-containing electrode production in the range of 10-85 wt.%, The required carbon content is provided. At lower values, the necessary decrease in the oxidation of steel will not be provided; at higher values, an excess of carbon will occur in excess of the required values.

Binder in quantity - the rest provides the necessary strength of briquettes during transportation and overloads. As a binder, you can use all known binders (cement, flour, water glass, briquettes, etc.).

The inventive briquettes allow alloying steel in the bucket, strictly observing the Si / C ratio. The ratio of the components of the briquette varies based on specific production conditions and the content of Si and C in the finished metal of a given brand,

EXAMPLE 2

Experimental swimming trunks were carried out on a 250-ton converter in the smelting of calm and semi-quiet steel grades. After melting, the metal from the converter containing C 0.04%, Si 0.0015%, Mn 0.065% was poured into the ladle. By filling 1/3 of the bucket, briquettes were introduced under a stream of metal, additionally containing fines of ferromanganese at a ratio of silicon to ferromanganese 1: (2.2-3.7). The briquettes were completed after the release of approximately 70% of the metal. Manganese was not further refined. The final deoxidation of the metal was carried out with aluminum pig AB 87. The data of the experimental melts are shown in table 2.

table 2 Indicators Steel alloying options in the bucket Half Steel Calm steel Outlawing compositions steel grade St6ps St2ps St3Gps St2sp St5sp St6sp The ratio of silicon / manganese in briquettes 1: 2.2 1: 3 1: 3,7 1: 2.2 1: 3 1: 3,7 1: 1.9 1: 4.0 The content of the carbon-containing electrode production material, wt.% 70 41 70 twenty 65 80 5 87 The carbon content in the finished metal, wt.% 0.4 0.11 0.21 0.1 0.35 0.45 0,07 0.55 The silicon content in the finished metal, wt.% 0.2 0.13 0.1 0.15 0.17 0.2 0.39 0,065 The manganese content in the finished metal, wt.% 0.6 0.35 0.95 0.4 0.55 0.75 0.83 0.2

The analysis of table 2 shows that when the ratio of the composition of the briquette of silicon to manganese 1: (2.2-3.7) ensures the optimal processability of the process and obtaining a given chemical composition of steel. The use of substandard trifles of ferromanganese in the briquette will reduce the cost of smelted steel.

The analysis of scientific, technical and patent literature shows the absence of coincidence of the distinguishing features of the proposed method in comparison with the known technical solutions in this field.

Claims (4)

1. The method of out-of-furnace alloying of iron-carbon alloys in the ladle, including the release of the iron-carbon melt from the steelmaking unit into the ladle, feeding the deoxidizers and alloying alloys into the ladle during the melt process, characterized in that the melt is alloyed with briquettes containing metallurgical silicon carbide 5-80 wt.%, carbon material 10-85 wt.%, the rest is binder, and after release, the melt is deoxidized with aluminum and adjusted by chemical composition with ferroalloys. 2. The method according to claim 1, characterized in that the briquette additionally contains substandard fines of ferromanganese with a ratio of silicon to manganese 1: (2.2-3.7). 3. The method according to claim 1, characterized in that the metallurgical silicon carbide is introduced into the composition of the briquette in the form of its sludge. 4. The method according to claim 1, characterized in that as the carbon material used materials are heat-treated carbon-containing electrode production.