RU2252264C1 - Method of production of reinforcing-bar steel - Google Patents

Abstract

FIELD: metallurgy; methods of production of low-carbon and medium-carbon steel for reinforcement of the reinforced concrete constructions.

SUBSTANCE: the invention is pertaining to metallurgy, in particular, to the methods of production of low-carbon and medium-carbon steel for reinforcement of the reinforced concrete constructions. The technical result is a reduction of a cost of aluminum used per a smelt and decreased costs of production of the reinforcing-bar steel at the expense of optimization of input of aluminum at deoxidation and alloying of the steels by aluminum just in the quantity necessary for prevention of their strain ageing. The method of production of the reinforcing-bar steels includes: smelting of the metal; its deoxidation and alloying by ferromanganese and ferrosilicon in a ladle, out-of-furnace metallothermy of steel, ladling of steel in ingots or by an installation of a continuous casting of ingots. After alloying by ferromanganese and ferrosilicon during the further out-of-furnace metallothermy of the steel conducted in the aggregate a furnace - a ladle enter aluminum. Contents of the residual aluminum in the steel adjust depending on the share of nitrogen so, that the contents of aluminum in 1.8-2.2 times exceeded the share of nitrogen. It is desirable to enter aluminum into the steel in the form of a wire or powder with a stream of a noble gas.

EFFECT: the invention ensures reduction of a cost of aluminum used per a smelt and decreased costs of production of the reinforcing-bar steel at the expense of optimization of input of aluminum at deoxidation and alloying of the steels by aluminum1.

2 cl, 1 ex

Description

The invention relates to metallurgy, in particular to a technology for the production of low- and medium-carbon steel grades for reinforcing reinforced concrete structures.

A known method for the production of steel in an arc furnace, including a series of operations, such as melting the mixture, purging with oxygen, removing oxidizing slag, adding ferroalloys to the bath surface to alloy steel, adding slag-forming agents and deoxidizing refining slag with powder deoxidizers (1).

The disadvantage of this method is the high waste of alloying elements and deoxidizers due to their reaction with residual oxidative slag, which cannot be completely removed, and with a metal having a high oxygen concentration.

A known method of preventing aging of steel by alloying it with aluminum. In this case, aluminum binds to nitrides and prevents the formation of iron nitrides, which are released along crystallographic planes and dislocations, which sharply reduces the level of mechanical properties. Moreover, the recommended aluminum content is 0.02 ... 0.04 (2).

Closest to the claimed invention is a method of smelting medium- and high-carbon low alloy steels, including decarburization of the metal to a carbon content below its grade in finished steel, the release of the metal and the introduction of carbon-containing materials, ferromanganese and alloying ferroalloys in order to obtain the alloy alloy of the required chemical composition , while the input of carbon-containing materials and ferromanganese is carried out simultaneously from the beginning of production to filling 0.25 ... 0.4 volume of the bucket , Then adding of the alloying ferroalloys, finishing it with a metal filling 0.5 ... 0.8 bucket volume (3). This invention is taken as a prototype.

Signs of the prototype, coinciding with the essential features of the claimed invention: metal smelting, deoxidation and alloying with ferroalloys in the ladle.

The disadvantage of this method is the lack of dependence of the additive in aluminum steel on the actual content of oxygen and nitrogen in the steel (see example 2). As a result, steel with a high nitrogen content is prone to aging. On the other hand, with a low nitrogen content in steel, the addition of aluminum is excessive, which is impractical from the point of view of the economy.

The task to which the invention is directed is to optimize the consumption of aluminum during deoxidation and alloying of steel with aluminum only in the amount necessary to prevent aging, which can significantly reduce the consumption of aluminum for smelting and thereby reduce the cost of production of reinforcing steel.

The problem is solved in that a method for the production of reinforcing steel is proposed, including smelting metal, deoxidation and alloying with ferromanganese and ferrosilicon in a ladle, out-of-furnace processing of steel, casting of steel into ingots or at a continuous casting plant, while after alloying with ferromanganese and ferrosilicon in the process of further after furnace treatment carried out in the ladle furnace unit, aluminum is introduced, and the content of residual aluminum in the steel is regulated depending on the nitrogen content in this way m, the aluminum content of 1.8-2.2 times the nitrogen content of aluminum is introduced into the mechanical metal in wire form or in powder form in an inert gas stream.

Despite the fact that the aluminum content in the reinforcing steel is not regulated, its introduction into the reinforcing steel is necessary for the binding of nitrogen to nitrides and, as a result, to prevent its aging.

The introduction of aluminum into a metal after alloying it with silicon and manganese is due to the fact that preliminary alloying of steel with manganese and silicon in an amount of 1% leads to a sharp decrease in the oxygen content in steel (to 0.003% at 1550 ° C). As a result, upon subsequent introduction of aluminum, only a small part of it is bound by oxygen, which can be neglected, and the bulk of aluminum remains in the liquid metal and interacts with nitrogen during cooling, forming aluminum nitrides.

The introduction of aluminum into steel in an amount less than 1.8 of the nitrogen content in the steel is not sufficient for the complete binding of nitrogen to nitrides. On the other hand, the introduction of aluminum into steel in an amount greater than 2.2 the nitrogen content in the steel is impractical for economic reasons, because is redundant.

Due to the fact that during out-of-furnace processing of steel, a slag layer is located in the ladle on the metal surface, aluminum is introduced into the metal either in the form of a wire using a tribamer, or it is blown into the metal in the form of a powder in an inert gas stream.

Execution example

In a 140-ton converter, a carbon intermediate weighing 135 tons was smelted and the metal was released into the ladle. In the ladle, the metal was deoxidized and alloyed with ferromanganese and ferrosilicon in the amount necessary to obtain the grade composition of 35GS steel. Then, on the ladle-furnace unit, the nitrogen content in steel was determined, which amounted to 0.008%, and then aluminum in the amount of 21.6 kg was added to the steel with a tribamer. The calculation of the required amount of aluminum was carried out as follows:

1. The required aluminum content in the steel is A = 2.0N, where N = 0.008%. Thus, A = 0.016%.

2. To introduce such an aluminum content into steel with a smelting mass of 135 tons, (0.016 / 100) × 135000 = 21.6 kg of aluminum will be required.

Next, the metal was poured into molds weighing 4.5 and 6.5 tons (combined composition) and rolled into reinforcement No. 12, followed by sampling for chemical analysis. The chemical analysis showed that the aluminum content in the steel is 0.016%, which is quite enough to bind all nitrogen to nitrides. Thus, the steel smelted by the proposed method has lower production costs compared with steel smelted by the technology of the prototype. The test results are shown in the table.

Table Options The known method The proposed method The characteristic of the metal in the converter Chemical composition, % carbon 0.08 0,07 manganese 0.15 0.16 nitrogen 0.005 0.005 Temperature ° C 1620 1620 Characterization of metal in a steel ladle carbon 0.33 0.34 manganese 0.90 0.91 silicon 0.75 0.75 aluminum 0,021 - nitrogen 0.008 0.008 Temperature ° C 1580 1580 Consumption of aluminum, g / t 510 - Characterization of metal in a steel casting ladle at AKOS carbon 0.33 0.34 manganese 0.90 0.91 silicon 0.75 0.75 aluminum 0.015 * 0.016 nitrogen 0.008 0.008 Consumption of aluminum, g / t - 230 The total consumption of aluminum for melting, kg 68.85 31.05 * decrease in aluminum content is associated with the surfacing and assimilation of oxides by slag

Sources of information

1. Kramarov A.D. Steel production in electric furnaces, M. Metallurgy, 1969, p.148-161.

2. Povolotsky D.Ya. Aluminum in structural steels, M. "Metallurgy", 1970, p.232.

3. Copyright certificate No. 1068493, cl. C 21 C 5/52, 05/10/82, adopted as a prototype.

Claims (2)

1. Method for the production of reinforcing steel, including smelting, deoxidation and alloying with ferromanganese and ferrosilicon in a ladle, out-of-furnace processing of steel, casting of steel into ingots or at a continuous casting plant, characterized in that after alloying with ferromanganese and ferrosilicon during further out-of-furnace treatment, conducted in the ladle furnace unit, aluminum is introduced, while the content of residual aluminum in the steel is controlled depending on the nitrogen content so that the aluminum content is 1.8-2.2 p the basics exceeded the nitrogen content. 2. The method according to claim 1, characterized in that the aluminum is introduced into the metal in the form of a wire or in the form of a powder in an inert gas stream.