WO2006001727A1 - Method for out-of-furnace iron-carbon steel alloying in a ladle - Google Patents

Abstract

The inventive method for out-of-furnace iron-carbon steel alloying in a ladle relates to ferrous metallurgy and consists in discharging an iron-carbon melt from a steelmaking vessel into a ladle, in adding deoxidising and alloying agents to the ladle during the melt discharge, wherein the melt is alloyed by briquettes containing 5-80 mass % silicon carbide, 10-85 mass % carbonaceous material, the rest being a binder, in deoxidising the discharged melt by aluminium and in obtaining the melt chemical composition by ferroalloys. The briquette also contains off-grade ferromanganese fines at a silicon-manganese ratio of 1:(2.2-3.7), a metallurgical silicon carbide is embodied in the form of the sludge thereof and the carbonaceous material is embodied in the form of heat-treated carbon-containing materials from electrode production.

Description

 METHOD OF EXTRACTIONAL ALLOYING OF IRON-CARBON ALLOYS IN THE BUCKET

Technical field

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

State of the art

The closest in technical essence is the method of out-of-furnace deoxidation of steel with silicon carbide fraction 0.1 ÷ 10 mm, containing 80-

90% pure silicon carbide, 2–5% of May. free carbon, the rest is impurities, - deoxidizers are supplied during the production process with a flow rate of 1 ÷ 5 kg / t of melt according to:

где Qi - расход раскислителя в процессе вылуска, кг/т; Q₂- расход раскислителя после выпуска, кг/т;After the release, deoxidizers are additionally supplied within 0.2 ÷ 0.4 kg / t of melt and aluminum with a flow rate in the range of Q, 1 ÷ 1, 5 kg / t of melt, while the deoxidizer is produced according to:

where Qi is the deoxidant consumption during the hatch 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,% May;

Si-i and Si ₂ - the silicon content in the melt at the beginning of production and the necessary silicon content in the finished steel,% May; K ₁ and K ₂ are empirical coefficients characterizing the physicochemical 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 0.3–0.7 kg / t of the melt and is purged with argon for 1–5 minutes with a flow rate of 0.5 ÷ 2.0 l / min per ton of steel. (Pat. Of Russia Na 2219249, C21C7 / 00. Publ. 20.12.2003.)

The disadvantage of this method is the impossibility of adjusting the silicon / carbon ratio in the smelting of mild 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 N22219249 is used only as a deoxidizing agent, and not as a ligature.

Disclosure of invention

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 reducing 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 silicon carbide 5 ÷ 80 wt. %, carbon material 10 ÷ 85 wt.%, the rest is binding, and after release, the melt is deoxidized with aluminum and adjusted by chemical composition with ferroalloys, and the briquette additionally contains substandard the smallest detail of ferromanganese at a silicon to manganese ratio of 1: (2.2–3.7), and its sludge is used as metallurgical silicon carbide, and heat-treated carbon-containing materials of electrode production are used as a carbon material.

The briquette may additionally contain substandard trifle of ferromanganese with a silicon to manganese ratio of 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] _Fθ + [c] _Fβ

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. Carbon-containing materials according to TU1914-01827208846-99 and / or

TU914-00194042-026-01, like silicon carbide, are the products of chemothermal reactions of pure components, therefore they do not contain harmful impurities (sulfur, phosphorus, non-ferrous metals), which negatively affect the quality of steel. Reducing the cost of iron - carbon alloy is due to the fact that carbon-containing materials and sludge 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 (TU1914-01827208846-99) and / or heat-treated carbon-containing material of the electrode production (TU1914-00194042-026-01) are explained by the physicochemical laws of alloying calm and semi-quiet steel grades, as well as their final chemical composition and empirically selected.

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 quite deoxidized metal (quiet, 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 - AI 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 the components in the briquette are explained by the physicochemical laws of alloying iron - carbon melts and the chemical composition of steel.

The best embodiments of the invention

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 bucket. The final deoxidation of the metal was carried out with pig aluminum AB 87. The data of the experimental melts are shown in table 1. Table 1

*) - the resulting alloys do not match the specified grade steels

If the briquette contains silicon carbide or its sludge (may also be in a mixture) in the amount of May 5 - 80. % provides grade silicon content in steel. 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 within May 10 - 85. % required content is provided carbon. 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.

The binder in quantity - the rest, provides the necessary strength of the 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 smelting was carried out on a 250-ton converter in the smelting of calm and semi-quiet steels. After melting, the metal from the converter containing С - 0.04% Si - 0.0015% Mn - 0.065% was poured into the ladle. After filling 1/3 of the bucket under a stream of metal, briquettes were added that additionally contained trifle of ferromanganese with 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 pig aluminum AB 87. The data of the experimental melts are shown in table 2.

table 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 trifle 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

CLAIM 1. A method for 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 silicon carbide 5 ÷ 80 wt.%.% , carbon material 10 ÷ 85 wt.%, the rest is binding, 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 further comprises 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 sludge is used as metallurgical silicon carbide; 4. The method according to p. T, characterized in that the materials used are carbon-treated materials containing carbon-containing electrode production.