RU2286393C1 - Method for reducing of steel in ladle - Google Patents

Abstract

FIELD: ferrous metallurgy, in particular, production of high quality low-carbon steel.

SUBSTANCE: method involves introducing into melt during discharging of said melt from processing unit into ladle of granulated or lumpy reducing agent having density lower than that of melt in ladle; introducing reducing agent into melt by concentrated high-speed pulsed flow providing penetration of reducing agent directly into melt. Reducing agent is introduced into melt flow by means of shot-blasting unit. Reducing agent used is granulated or lumpy aluminum with 0.5-12.0 mm sized granules or lumps. Method allows loss in burning of reducing agent to be decreased by twice.

EFFECT: decreased loss in burning of reducing agent, intensified penetration of reducing agent into melt and improved quality of metal.

5 cl, 1 ex

Description

The invention relates to the field of ferrous metallurgy, in particular to technological methods for the production of high-quality low-carbon steel.

An invariable and especially important process used in the production of high-quality steels is the process of deoxidation or removal of excess oxygen from a melt prepared for casting.

An increased or inadequate oxygen content in the hardened metal determines the continuation of the oxidation of residual carbon in it with the release of gaseous carbon monoxide, up to the end of crystallization of the ingot. At the same time, gas porosity is formed in the finished product, which violates its quality indicators and density.

The most commonly used deoxidation method in steelmaking is the deposition method. A feature of this method is the transfer of oxygen from a solution in the form of iron oxide into non-metallic compounds with elements that have more than iron, affinity for oxygen and less than iron oxide, and are soluble in metal. In this case, the resulting oxidation products are released from the metal into slag in the solid or liquid state.

In the practice of the production of specialized steels, precipitating deoxidation is carried out in a ladle or directly at an out-of-furnace treatment plant. Along with aluminum, sometimes silicon, manganese, magnesium, barium, calcium, complex alloys, aluminum and others are used as deoxidants and modifiers in steel production.

The most common method of introducing aluminum is the method of introducing aluminum into the bucket in the form of pieces or in ingots or pieces commensurate with them. With this input of the deoxidizing material, the degree of assimilation of the useful deoxidizing element by the melt is at an extremely low level (for example, for aluminum 5–20%) and is extremely unstable. The input method itself requires significant manual labor.

To reduce the burnout of deoxidizing agents, methods of introducing deoxidizing agents into the ladle in crushed lumpy or granular form are used.

The closest in technical essence and the achieved result is a method of steel deoxidation in a ladle, including the introduction of a granular or lump deoxidizer into the melt during its discharge from the technological unit into the ladle, having a density lower than the melt density in the ladle (Yu.F. Vyatkin, V.A. .Vikhrevchuk, VFPolyakov et al. Resource-saving technology for the deoxidation of steel by aluminum in a ladle. Chermetinformatsiya Bulletin, No. 6, 1990, pp. 53-55).

However, the known method has the following disadvantages: the introduced ground deoxidizer is fed to the melt mirror or the surface of the metal stream upon release, as a result of which most of it burns out due to atmospheric oxygen, without being able to dissolve in the metal, which leads to losses of the deoxidizer and reduces the quality of the metal.

The objective of the invention is to develop a deoxidation technology that improves the quality of the metal, reduce material loss.

The expected technical result is a decrease in deoxidant fumes, an increase in the assimilation stability, an increase in the quality of the metal.

The technical result is achieved by the fact that in the known method of steel deoxidation in a ladle, comprising introducing into the melt during the process of pouring it from the process unit into the ladle a granular or lump deoxidizer having a density lower than the density of the melt in the ladle, according to the invention, the deoxidizer is introduced into the melt in a concentrated high-speed stream with pulse providing penetration of the deoxidizer directly into the melt.

Other embodiments of the deoxidation process are possible, providing that

- the deoxidizer is injected into the jet of melt, drained into the ladle from the technological unit, using a shot blasting machine;

- as a deoxidizing agent, granular or lump aluminum is used with a granule or lump size of 0.5-12 mm, which can be introduced into a stream of melt being drained into a ladle from a technological unit using a shot blasting machine;

- the place of introduction of aluminum into the stream is set depending on its fractional composition, the finer the size of the granules, the closer the place of introduction of stream into the stream to the surface of the melt in the bucket to be filled.

In order to introduce the granules directly into the melt at the required flow rate, it is necessary to give the granules or pieces a speed that provides for this granule the equilibrium of the dynamic pressure of the high-speed flow and the static pressure inside the metal:

ω ² ρ _1/2 = l · ρ ₂ · g,

where ω is the flow rate of the reagent;

ρ ₁ and ρ ₂ is the flux density of the reagent and liquid steel;

g is the acceleration of gravity;

l is the immersion depth of the reagent in the melt.

The calculations show that to ensure the conditions for the introduction of granular aluminum with a fraction of 0.5-12 mm directly into the stream being drained from the steelmaking unit into the ladle, the deoxidizer must be supplied with a pulse (i) from 40 to 318.6 N ("N" - Newton, kg m / s ² ).

The information given does not exhaust all possible values of the flow momentum and is determined only for aluminum. One of the technical devices that allow the deoxidizer to be immersed in the melt, both in the stream and under the metal mirror in the bucket, is a shot blasting machine. Typically, such machines are equipped with metering devices and allow the blowing agent to be injected in portions of 50 to 200 kg.

Another feature of the invention is that the place of introduction of aluminum into the stream is set depending on its fractional composition, the finer the size of the granules, the closer the place of introduction of stream into the stream to the surface of the melt in the bucket to be filled. When a granule is less than 0.5 mm in size, the granules melt at the moment of contact with a stream of metal, which leads to a significant oxidation of the deoxidizer with atmospheric oxygen. The supply of a deoxidizing agent with a fraction of more than 12 mm leads to difficulties in the operation of the shot blasting machine for introducing a deoxidizing agent into the melt and also to additional deoxidant combustion in air. When the melt moves from a cut of the outlet or toe of the gutter, the metal is crushed, captures oxygen from the air during its movement, which leads to its intoxication. The mixing power of the jet is so great that if a fine fraction deoxidant is fed to the cut of the gutter, it practically does not enter the bucket, and therefore, when feeding the reagent into the jet for each reagent, it is necessary to determine the place of introduction into the jet at which the losses of the deoxidizing reagent are minimal.

Example No. 1

The method is implemented in the smelting of steel 20 in an arc furnace.

The metal was deoxidized with manganese and silicon. When releasing metal, aluminum was introduced into the bucket in the form of a fraction of a fraction of 6 mm in portions of 100 kg using a shot blasting machine with a capacity of 400 kg / min. Air pressure in the highway 5 atm. The transportation route was made of a metal pipe, which provided a flow of aluminum into the melt stream at a distance of about 1.5-2.0 m from it.

The melt was released from the furnace with a temperature of 1545 ° C. Aluminum was introduced based on the calculation of its introduction up to 1.5 kg per ton of steel with a pulse of 200 N.

When steel was deoxidized by the claimed method, the oxygen content in it was 0.005-0.006% with a residual aluminum content of 0.022%.

In the same steel melted by the prototype method, the oxygen content was 0.007-0.008%, with a residual aluminum content of 0.017%.

The application of the proposed invention allows to reduce the amount of deoxidizing agent by 2 times, increase its absorption and improve the quality of the metal.

Claims (5)

1. The method of deoxidation of steel in a ladle, comprising introducing into the jet of melt during its discharge from the technological unit into a ladle a granular or lump deoxidizer having a density lower than the density of the melt in the ladle, characterized in that the deoxidizer is introduced into the melt stream by a concentrated high-speed flow pulse, providing penetration of the deoxidizer directly into the melt. 2. The method according to claim 1, characterized in that the deoxidizer is injected into the jet of melt, drained into the ladle from the technological unit, using a shot blasting machine. 3. The method according to claim 1, characterized in that as a deoxidizer using granular or lump aluminum with a size of granules or pieces of 0.5-12 mm 4. The method according to claim 3, characterized in that the aluminum is injected into the stream of melt, drained into the ladle from the technological unit, using a shot blasting machine. 5. The method according to claim 4, characterized in that the place of introduction of aluminum into the stream is set depending on its fractional composition, the finer the size of the granules, the closer the place of introduction of the stream into the stream to the surface of the melt in the bucket to be filled.