RU2392333C1 - Method of low-carbon steel production - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method involves low-carbon semi-finished product in steel melting aggregate, product release to steel pouring ladle, preliminary deoxidation by feeding ferrosilicium in amount sufficient for recovery of at least half of oxygen content from low-carbon semi-finished product, final deoxidation by aluminium additive and reinforcement with manganese during release upon steel pouring ladle filling at least at 0.2 ladle height. Manganese reinforcement is performed by manganese-containing oxide material feed together with slag forming agent in amount sufficient to obtain basicity of 1.7-1.8.

EFFECT: increased degree of manganese and aluminium recovery without use of metal manganese.

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Description

The invention relates to ferrous metallurgy, specifically to the production of low carbon steel.

There is a known method of steel production, including steelmaking in a steelmaking unit, discharge into a steel-pouring ladle, metal purging after argon discharge in a stream, introduction of aluminum and specific consumption of 2.0 kg / t of metal and manganese metal with specific consumption of 1.71 kg / into the ladle t of metal (SU No. 1235924 A1, class C21C 7/00, publ. 06/07/1986).

This method solves the particular problem of reducing the time spent by the metal in the bucket, increasing the efficiency of out-of-furnace metal processing. At the same time, the useful use of aluminum for deoxidation of metal and residual aluminum in steel is at the level of 50%, and the assimilation of metal of manganese metal does not exceed 70%.

The closest analogue of the claimed invention in technical essence and the achieved result is a method of steel smelting for a sheet, including smelting a semi-product in a steelmaking unit, releasing non-deoxidized metal into a ladle, purging the metal in the ladle with inert gas until a temperature of 1585-1595 ° C, preliminary deoxidation with a carbon block with exposure to metal at a depth of 20-80% of its height for 2-5 minutes, without stopping purging, final deoxidation and alloying with manganese with aluminum and metal additives manganese in portions weighing 200-750 kg each, while the consumption of metallic manganese is 1-2.5 kg / t of steel, aluminum 1-2.5 kg / t of steel (SU No. 981385 A1, class C21C 7/00, publ. December 15, 1982).

The known method does not achieve the required technical result for the following reasons.

The supply of aluminum and metal manganese to a 300-ton steel ladle with costs of 450 kg and 750 kg, respectively, indicates that the useful use of aluminum for deoxidation and residual content in the metal does not exceed 40%, and the loss of manganese metal is more than 30%. In addition, the use of metallic manganese in the known method as a deoxidizing agent not only leads to irrational consumption, but also contributes to the deterioration of the quality of the finished metal due to its contamination with manganese oxides, which cannot be reduced simultaneously introduced by aluminum due to the low oxygen concentration in the formed non-metallic inclusions. The preliminary deoxidation of the undeoxidized intermediate with a carbon block followed by the addition of metallic manganese into it promotes the formation of manganese carbides Mn ₃ C, the most fragile microstructure that leads to destruction during stamping.

The basis of the invention is the task of improving the method of steel production by optimizing process parameters. The expected technical result is an increase in the degree of assimilation of manganese and aluminum with the exception of the use of metallic manganese.

The technical result is achieved in that in a method for producing low carbon steel, including smelting a low carbon intermediate in a steelmaking unit, releasing it into a steel pouring ladle, preliminary deoxidation, final deoxidation with aluminum additive and alloying with manganese, according to the invention, preliminary deoxidation is carried out by supplying ferrosilicon in an amount that does not allow removal less than half the oxygen content of the low-carbon intermediate, and the final deoxidation with aluminum Inium and doping with manganese are carried out during the production process by filling the steel pouring ladle by at least 0.2 of its height, while doping with manganese is carried out by supplying a single portion of manganese-containing oxide material together with slag-forming material in an amount providing a basicity of 1.7-1, 8.

When testing the production technology of low-carbon steel with the replacement of metallic manganese with oxide manganese-containing material, it was found that the most acceptable basicity of the slag formed during the reduction of manganese should be 1.4-1.5. Due to the fact that the low-carbon intermediate produced from the steelmaking unit contains a large amount of oxygen, it was experimentally found a solution by which, under the conditions of the proposed method, half of the oxygen contained in the low-carbon intermediate was reduced. The resulting silicon oxides are adsorbed by the slag, reducing its basicity from 1.7-1.8 to the desired 1.4-1.5. Therefore, effective preliminary deoxidation with ferrosilicon minimizes non-metallic inclusions, and also, due to the absence of carbon in the metal, prevents the formation of manganese carbides Mn ₃ C, which negatively affects the stamping of rolled products from low-carbon steel.

Since in the proposed method, manganese alloying is carried out by supplying a single portion of manganese-containing oxide material together with a slag-forming material, manganese is introduced into the metal by its reduction from oxides, thereby preventing the formation of manganese oxides, which also negatively affect the quality of the finished steel.

The final deoxidation with an aluminum additive, which is carried out during the production process simultaneously with alloying with manganese, provides an increase in the useful use of aluminum and manganese. Aluminum in the proposed method is not removed in the gas phase, since the amount of oxygen in the easily reducible manganese oxide contained in the slag is many times higher than the oxygen content in the low-carbon product, especially after preliminary deoxidation. Therefore, in the process of the interaction of aluminum with metal oxygen and slag, under-oxidized gaseous aluminum oxides are practically not formed, which cause aluminum to be removed into the gas phase. This leads to the rational use of aluminum and its small losses.

High extraction of manganese is ensured by technological methods that do not provide for the deoxidation of metal by manganese, and therefore, its additional consumption.

The absence of carbon and silicon in the reduced products in the proposed method ensures the complete exclusion of manganese metal as a deoxidizer and alloying material.

The supply of materials to the steel pouring ladle by filling it with metal of at least 0.2 of its height is due to the hydrodynamics of the liquid metal at the time of release. When the bucket is filled with metal up to 0.2 of its height, the metal is intensively mixed with the formation of vortex-like flows concentrating at the walls of the bucket. Therefore, the supply of materials during this period is accompanied by their intensive mixing with the metal melt, noticeability, a decrease in the melting rate and the deterioration of all technological parameters. By filling the bucket with metal at least 0.2 times its height, the surface of the liquid metal comes into a relatively calm state and the risk of involving the supplied materials in the volume of the molten metal is sharply reduced, which helps to increase technological parameters, in particular, to increase the extraction of manganese from oxide material and useful use aluminum.

Example.

In the production of 08Yu grade steel in a 160-ton oxygen converter, low-carbon intermediate was smelted, which at a temperature of 1650 ° C and chemical composition, wt.%: C 0,03; Mn 0.05; S 0.015; P 0.008 was discharged into the steel ladle. At the beginning of production, FS-65 ferrosilicon was added in a single portion with a specific consumption of 0.9 kg / t of low-carbon intermediate. To fill the steel pouring ladle, a manganese-containing oxide material containing 40.0% manganese was supplied to a height of 0.2 with a specific consumption of 6.2 kg / t low carbon intermediate, aluminum with a specific consumption of 1.3 kg / t low carbon intermediate and lime with a specific consumption 2.5 kg / t low carbon intermediate, providing a basicity of 1.75. The finished metal had the following chemical composition, wt.%: C 0.03; Mn 0.27; S 0.010; P 0.007; Al 0.040. Metallic manganese was not used. The manganese recovery was 94.3%; aluminum losses did not exceed 5.0%.

Using the proposed method for the production of low carbon steel provides an increase in the degree of assimilation of manganese and aluminum with the exception of the use of metallic manganese.

Claims (1)

A method of producing low carbon steel, including smelting a low carbon intermediate in a steelmaking unit, releasing it into a steel casting ladle, preliminary deoxidation, final deoxidation with an aluminum additive, and alloying with manganese, characterized in that the preliminary deoxidation is carried out by ferrosilicon supplied in an amount that ensures removal of at least half oxygen from the low-carbon intermediate, and the final deoxidation with aluminum additive and doping with manganese lead in the process of manufacture ladle filling not less than 0.2 of its height, wherein the doping is carried out with manganese serving single portion manganese oxide material with the slag forming material, the amount of which provides a slag basicity equal to 1.7-1.8.