RU2241045C1 - Method for steel smelting in basic oxygen furnace - Google Patents

Abstract

FIELD: iron metallurgy, in particular steel smelting in basic oxygen furnace with desired minimum content of non-iron additives.

SUBSTANCE: method includes charge of solid batch, casting of liquid iron, oxygen blasting of bath, and adding of slagging materials. Solid iron and light-gage cold rolled crop are used as the batch, consumption of which is determined from equations: Msi = 198,5-0,5 x Mli - 350 x Crdes - 200 x Nides-150 x Cudes, where Msi is solid iron mass, ton; Mli is liquid iron mass, ton; Crdes, Nides and Cudes are permissible content of corresponding elements in finished steel, %; 198.5, 0,5, 350, 200 and 150 are empirically determined coefficients; Ml = Mmch - Msi, where Ml is mass of light-gage cold rolled crop and Mmch is metal charge mass in cold oxygen furnace.

EFFECT: selection of optimum ratio between solid iron and light-gage cold rolled crop to produce permissible content of non-iron metals with reduced of costs, increased yield of product with desired quality, etc.

1 ex

Description

The invention relates to the field of ferrous metallurgy, namely to smelting steel with the required minimum content of impurities of non-ferrous metals.

A known method for the production of cold rolled steel for shadow masks and magnetic screens of color picture tubes, including loading 6-10 tons of lime on the bottom of the converter, pouring half a ladle of molten iron, loading metallized pellets and scrap, as the last one uses trimmed slabs and sheets of steel grades 08Yu, 08ps with a mass fraction of copper of not more than 0.08%, the supply of lime weighing 6-10 tons and pouring the rest of cast iron (Production of cold-rolled steel for shadow masks and magnetic screens of color picture tubes. Through technological instruction TI 106-PHL. 2.4.5-14-88. Novolipetsk Metallurgical Plant, Lipetsk, 1988, p.2).

The disadvantages of this method include the lack of information about the content of Cr, Ni, Cu in the edging of slabs and sheets, which does not allow to accurately determine the consumption of metallized pellets, which can guarantee a minimum content of non-ferrous metals in steel. At the same time, metallized pellets have a high cost and require special storage conditions, because have a tendency to spontaneous combustion.

The closest analogue of the claimed invention is a method of steelmaking in oxygen converters, which includes loading a solid charge, pouring molten iron, subsequent purging of the bath with oxygen, introducing slag-forming and solid oxidizing agents, and a semi-finished product for metallurgical processing consisting of an iron-carbon alloy and an oxide material is used as a solid charge , and scrap metal in the ratio (0.1-3.0): 1, while the semi-finished product is loaded in an amount of 25-300 kg per 1 ton of molten iron (see the description of the patent of the Russian Federation No. 207 5513, IPC 7 C 21 C 5/28, publ. 20.03.97, bull. No. 8).

Signs of the closest analogue, coinciding with the essential features of the claimed invention: loading a solid charge, pouring molten iron, subsequent purging of the bath with oxygen, the introduction of slag-forming.

The known method does not provide the desired technical result for the following reasons.

Found in the known method, a technique for reducing the content of non-ferrous metal impurities involves additional costs for the manufacture of semi-finished product.

In addition, iron ore pellets included in the semi-finished product worsen the heat balance of the smelting and lead to a decrease in yield.

The basis of the invention is the task of improving the method of steelmaking in an oxygen converter, in which, by choosing the ratio of scrap metal - hard cast iron, an acceptable content of non-ferrous metal impurities is provided at the lowest cost, increasing the yield.

The problem is solved in that in the method of steelmaking in an oxygen converter, which includes loading a solid charge, pouring molten iron, subsequent purging of the bath with oxygen, introducing slag-forming materials, solid iron and thin-sheet cold-rolled edging are used as a solid charge, the flow rate of which is determined respectively from the expressions

Mt. chug. = 198.5-0.5 × Mzhid. chug.-350 × Cr-demand-200 × Nitreb.-150 × Sutreb.,

where is Mt. - mass of solid iron, t;

Mzhid.chug. - mass of molten iron, t;

Sreb., Nitreb., Sutreb. - permissible element content in finished steel,%;

198.5; 0.5; 350; 200; 150 - empirical coefficients obtained experimentally,

Ml = Mmz-Mzhid.chug.-Mtv.chug.,

where ML is the mass of cold-rolled thin-sheet trim, t;

Mmz - the mass of the metal into an oxygen converter, t

The essence of the claimed technical solution consists in loading a solid charge, pouring liquid cast iron, then purging the bath with oxygen, introducing slag-forming materials, in order to obtain the required content of non-ferrous metal impurities and to increase the yield as solid charge, solid cast iron and cold-rolled thin-sheet trimmings are additionally used.

The choice of the optimal ratio of solid cast iron and cold-rolled thin-sheet trim allows you to get a valid content of non-ferrous metal impurities.

This method is illustrated by the following example.

Steel grade 08Y is smelted with the required content of chromium, nickel and copper not more than 0.02% of each element.

A converter with a capacity of 370 tons pours 315 tons of molten iron, the estimated amount of solid iron, determined by the formula

Mt. chug. = 198.5-0.5 × 315-350 × 0.02-200 × 0.02-150 × 0.02 = 25 t

then the estimated amount of cold rolled sheet metal trim of the rolling shops, determined by the formula

Ml = 400-315-25 = 60 t.

After purging, the metal contains 0.04% carbon, 0.003% silicon, 0.05% manganese, 0.011% sulfur, 0.007% phosphorus, 0.013% chromium, 0.011% nickel, 0.016% copper.

During the production of smelting, 468 kg of ferromanganese FMN70 and 30 kg of pig aluminum are seated in the intermediate, during out-of-furnace processing 684 kg of aluminum wire rod is introduced and the steel obtained is cast on a continuous casting machine.

Finished steel has the following chemical composition: 0.05% carbon, 0.01% silicon, 0.12% manganese, 0.008% sulfur, 0.009% phosphorus, 0.017% chromium, 0.015% nickel, 0.017% copper.

Thus, when smelting by the proposed method, the required content of non-ferrous metal impurities is achieved, the fulfillment of orders for the rental of the first surface finishing group for the production of automotive sheets is improved, production and profit are increased.

Claims (1)

The method of steelmaking in an oxygen converter, which includes loading a solid charge, pouring molten iron, then purging the bath with oxygen, introducing slag-forming materials, characterized in that solid iron is used as solid charge and cold-rolled sheet metal, the flow rate of which is determined, respectively, from the expressions Mt. chug = 198.5-0.5 · Mzhid. chug.-350 · Srtreb.-200 · Nitreb.-150 · Sutreb., where - Mt. chug - mass of solid iron, t; Mzhid.chug. - mass of molten iron, t; Sreb., Nitreb., Sutreb. - permissible element content in finished steel,%; 198.5; 0.5; 350; 200; 150 - empirical coefficients obtained experimentally, Ml = Mmz-Mzhid.chug.-Mtv.chug, where - Ml is the mass of cold-rolled thin-sheet trim, t; Mmz - the mass of the metal into an oxygen converter, t