BRPI0621816A2 - steel pan deoxidization method - Google Patents

Abstract

The invention relates to producing a high-quality low-carbon steel. The inventive ladle steel deoxidation method consists in introducing granulated or lump desoxidant, the density of which is less than the density of a melt in a ladle, in to a said melt. Said desoxidant is introduced during the melt pouring off a production unit into the ladle by means of a concentrated high-rate flow, the impulse of which allows the desoxidant to penetrate directly inside the melt. The desoxidant is introduced into the melt stream with the aid of a shotblast machine. The desoxidant is embodied in the form of a granulated or lump aluminium of a size ranging from 0,5 to 12,0 mm. The use of the invention makes it possible to reduce the desoxidant loss by two times, to increase the recovery thereof and to improve the metal quality.

Description

"STEEL COOKING DEOXIDATION METHOD"

The present invention relates to steelmaking, in particular technologies for producing high quality low carbon steel.

A common and especially important process used in the production of high quality steels is the process of deoxidizing or removing excess oxygen from a run prepared for pan loading.

A high or inadequate oxygen content of a solid metal predetermines the continuity of residual carbon oxidation processes accompanied by gaseous carbon oxide until ingot crystallization is complete. Additionally, a finished product has gas porosities that affect its quality and density.

Deposition is a deoxidation method most widely used in steelmaking. This method consists of transferring oxygen from a solution, where it is present as ferrous oxide, to non-metallic compounds with elements that have more affinity for oxygen than iron and less than oxide irons and which are soluble in metal. Oxidation products thus formed escape from the metal to the slag in a solid or liquid state.

In special steel production practices, deoxidization is performed in a pan, or directly in an off-kiln treatment facility. Sometimes silicon, manganese, magnesium, barium, calcium, complex alloys are used in addition to aluminum as deoxidizing agents and modifiers in steel making.

The most common method of adding aluminum is to feed it into a pan in the form of pellets or commensurable bars. When a deoxidizing material is added using this method, the degree of adoption of its useful element for a run is at an extremely low level (eg 5-20% for aluminum) and is highly unstable. The exact method of addition implies a significant amount of labor.

In order to reduce deoxidant losses, various methods are used to add agglomerated or granulated oxidants to a pan.

A method of deoxidizing steel in the pan including the

The addition of granular or agglomerated deoxidizer, whose density is lower than that of the liquid bath, in said liquid bath during its pan leakage in a production unit has been considered a prototype (Yu. F. Vyatkin, VA Vikhrevchuk, VF Polyakov et al. "A resource-saving technology of deoxidizing steel with aluminum in a ladder", "Chermetinformatsya Journal, No. 6, 1990, p. 53-55).

But the known method has the following disadvantages: A broken deoxidizer is introduced to the surface of the liquid bath or the surface of the metal jet during the leakage, as its main part is burned with oxygen from the air and cannot dissolve in the metal. This results in loss of deoxidizer and a lower quality metal.

The object of the invention is to provide a deoxidation method that enables to improve metal quality and reduce deoxidant loss.

An anticipated technical effect is less loss of deoxidizer, greater stability of its acceptance and better metal quality.

The stated technical effect can be achieved because of this in the known method of steel pan deoxidation, including the addition of a granulated or agglomerated deoxidizer whose density is less than the density of the liquid bath in the pan, a deoxidizer is introduced according to with the invention, in a liquid bath jet by means of a high speed concentrated stream whose momentum ensures penetration of said deoxidizer directly into the liquid bath. Other embodiments of the inventive deoxidation method are possible, consisting of the following:

- a deoxidizer is introduced into a liquid bath jet, which is poured into a pan in a production facility using a shot blasting machine;

Granulated or agglomerated aluminum is used as the deoxidizer, granules or agglomerates having a size of 0.5 to 12 mm, which can be introduced into the poured liquid bath jet in a production unit in a pan by a shot blasting machine. ;

- A place for introducing an aluminum stream into said jet is selected depending on its fractional composition, where the fewer granules, the closer is the place where the stream is introduced to the surface of the liquid bath in a pan being filled.

In order to introduce granules directly into a liquid bath of a required flow rate, such granules or agglomerates must be fed at a speed that ensures for a given granule the equilibrium condition between high velocity dynamic pressure and static pressure within the granule. metal.

<formula> formula see original document page 4 </formula>

Where

ω = chemical agent flow rate;

P1 and p2 = chemical agent flux density and liquid steel flux density, respectively;

g = acceleration of gravity;

1 - depth of penetration of the chemical agent in the liquid bath.

The calculations show that in order to ensure conditions for penetration of 0.5 - 12 mm granular aluminum directly into the pouring jet in a pan in a steel plant, said deoxidizer must be fed with a momentum (force impulse) from 40 to 318.6 N (from N means Newton equal to 0.102 kgf).

The data presented does not cover all possible values of the flow moment and is set for aluminum only. A shot blasting machine is a device that allows penetration of a deoxidizer into a liquid bath, either in a jet or under the metal surface in a pan. Such machines are usually provided with measuring devices and allow to feed a deoxidizer in batches of 50 to 200 kg.

Another feature of this invention is the fact that a place for

Introducing aluminum into the metal jet is determined based on its fractional composition, the smaller the granule size, the closer to the surface of the liquid bath in the pan being filled at the point of introduction. Granules smaller than 0.5 mm are fused at the time of contact with the metal jet, which leads to significant oxidation of a deoxidizer by air oxygen. When feeding a deoxidizer over 12 mm in size, certain problems arise in the operation of a shot blasting machine that make it difficult for the deoxidizer to enter a liquid bath and contribute to the combustion of the deoxidizer in the air. When a liquid bath leaks at the exit edge or lead edge, the metal separates and trap oxygen during air during movement, which leads to its loss by burning. The mixing power of the jet is so high that if a small size deoxidizer is fed to the conductor edge, it will practically not enter the pan and consequently, when a chemical agent is fed into a jet, a location should be determined. introduction of the chemical agent in which deoxidant loss is minimal.

Example 1

The inventive method was implemented to produce steel 20 in an arc furnace. The metal was deoxidized with manganese and silicon. During the casting of the metal in a pan, aluminum pellets with a size of 6 mm were introduced into 100 kg batches using a shot blasting machine with a productivity of 400 kg / machine. Air pressure on the track was 5 bar. The transport route was made of a metal tube, ensuring the introduction of an aluminum stream into the liquid bath jet at a distance of approximately 1.5 to 2.0 m.

The temperature of the liquid bath at the furnace outlet was 1,545 ° C. Aluminum was introduced at the moment of 200 N based on 1.5 kg of aluminum per ton of steel.

During deoxidation of steel according to the inventive method, its oxygen content was 0.005 - 0.006% and the residual aluminum content was 0.022%. Steel produced according to the prototype method has an oxygen content of 0.007 - 0.008% and a residual aluminum content of 0.017%.

When implemented, this invention allows to reduce deoxidant loss by two times, increases its acceptance and significantly improves the quality of the metal.

Claims (5)

Steel pan deoxidization method, comprising introducing a granulated or agglomerated deoxidizer into a liquid bath jet during its pouring into a pan in a production unit, wherein said deoxidizer has a density that is less than the density of the Said liquid bath in said pan, characterized in that a deoxidant is introduced into the jet of the liquid bath with a high velocity concentrated flow moment, which ensures the penetration of said deoxidizer directly into said liquid bath. Method according to claim 1, characterized in that a shot blasting machine is used to introduce the deoxidant into a poured liquid bath jet in a pan in a production unit. Method according to claim 1, characterized in that granulated or agglomerated aluminum of granule size or agglomerate of 0.5 mm to 12 mm is used as a deoxidizer. Method according to Claim 3, characterized in that a shot blasting machine is used to introduce aluminum into the poured liquid bath jet in a pan in a production unit. Method according to claim 4, characterized in that the place of introduction of the aluminum flux into a jet is selected based on its fractional composition, the smaller the granule size, the closer From the surface of the liquid bath in a pan being filled is the place of introduction of said flow into said jet.