RU2562848C1 - Method of steel deoxidation in ladle - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: granulated aluminium containing the deoxidant is supplied into the fusion flow by pulsing high-speed flow of carrier gas at the frequency 5-15 Hz, and the angle between conditional axes of the flow of steel and the flow of granules of aluminium is maintained within 15-30 degrees. During supply variation of angle of flow of granules amounts 2-4 degrees.

EFFECT: invention allows to optimise conditions of adding of granules as far as the flow of aluminium granules is completely absorbed by metal flow without recoiling and a passing the flow through, with aluminium waste decrease.

3 cl, 1 dwg

Description

The invention relates to the field of ferrous metallurgy, in particular to a method for reducing the primary oxidation of a metal by aluminum at the beginning of its release from a steelmaking unit into a steel-pouring ladle.

The method used to reduce the primary oxidation of metal at the outlet by adding pig iron secondary aluminum to the ladle has a serious drawback due to the fact that, due to its lower density, aluminum floats to the surface of the metal in the ladle and is oxidized due to atmospheric oxygen (20-30% carbon waste) and slag oxides in which aluminum robs oxygen (carbon monoxide 50-60%). Only about 20% of aluminum is consumed for metal deoxidation. The high burnout of aluminum in this case forces an increase in its consumption, increasing the cost of steel and worsening its quality. Absorption of aluminum is extremely unstable, so it is difficult to achieve the necessary degree of deoxidation of steel, which also leads to the need to supply excess aluminum to the output. Dosing the amount of aluminum fed into the ladle at the outlet (at least with an accuracy of 1 kg) is impossible, since the weight of one ingot is 17-20 kg, which also leads to an overrun.

To reduce the burning of aluminum and its overspending, methods of entering it under the melt level using rods, flux-cored wire (the most common) and aluminum bullets fired into the melt by a pneumatic machine gun are known [1]. These methods can be used on out-of-furnace steel processing units, and their application at the beginning of production is inefficient and for several reasons is impossible.

A known method of deoxidation of metal in a ladle, including entering into the melt during its discharge from the technological unit into a ladle of granular or lump aluminum [2]. However, in this case, there is a high aluminum fumes due to air oxygen and slag oxides.

The closest in technical essence and the achieved result is a method of steel deoxidation in a ladle (prototype) [3], which includes introducing into the melt stream during the process of pouring it from the technological unit into the aluminum granule bucket 0.5-12 mm in size by a concentrated high-speed flow pulse generated carrier gas using a shot blasting machine. The granules begin to deoxidize the metal even in the stream and falling under the metal level in the bucket (due to the small size) manage to be absorbed by the melt before it even emerges to the surface. At the same time, the gas flow rate must ensure that the deoxidizer penetrates directly into the melt so that the granules do not bounce off the denser metal in the stream and do not pierce the stream through, which invariably leads to loss of aluminum.

However, the practice [4] of mastering this method showed that it is very difficult to adjust the speed of the granules and gas, to find the optimal place and angle of introduction of the granules into the metal jet in order to avoid loss of granules: part of the granules flies away from the metal stream, and part pierces it through, worsening the deoxidation efficiency and increasing fumes of aluminum.

The technical result of the claimed invention is to optimize the conditions for introducing a deoxidizer into the melt, providing more efficient deoxidation, coagulation and evacuation of deoxidation products.

This result is achieved by the fact that in the known method of steel deoxidation in a ladle, including introducing into the stream of metal during its discharge from the steelmaking unit into the steel-pouring ladle an aluminum-containing deoxidizer with a high-speed carrier gas stream, according to the invention, the deoxidizer is fed into the melt stream with a pulsating high-speed carrier gas stream with a frequency of 5-15 Hz, while the angle between the conventional axes of the metal stream and the flow of granules is maintained within 15-30 degrees.

In addition, in one embodiment of the method, the deoxidizer is injected into the stream of the melt being drained into the bucket using a pneumatic conveying system.

At the same time, when applying, the change in the flow angle of the deoxidizing stream is 2-4 degrees.

The proposed method is carried out using a pneumatic conveying installation with a flexible granule line. During the movement of the fluidized flow of granules along the main with narrowing - at the exit from the fluidization vessel to the stationary granule line and with expansion - at the exit from the spear of the granule line pulsations with an infrasonic frequency of 0.5-1.5 Hz arise. At the exit of the spear, the flow of granules is unstable. This is also indicated by the intense vibrations of the flex. Pulsates both the speed and density of the portions of the granules. Therefore, a dense stream of granules moving at high speed flushes the melt stream through it, during its discharge into the bucket, and a discharged portion of granules moving at low speed bounces off of it.

With an average output velocity of the carrier gas of 60 m / s and granules of 45 m / s, velocity pulsations can be ± 15%, which in absolute value for carrier gas will be 60 ± 9 m / s, and for granules 45 ± 6.7 m /from.

The invention allows to increase the assimilation of granular aluminum by a metal stream by imparting pulsations to the stream of aluminum granules with a frequency of up to 15 Hz. For this, a pellet flow interrupter with a frequency of 5-15 Hz is installed at the outlet of the fluidization vessel (the pulsations of 0.5-1.5 Hz completely disappear). The decrease in ripple amplitude is inversely proportional to the increase in frequency.

The drawing graphically shows a decrease in the amplitude of the pulsation of the gas stream with increasing frequency. That is, giving the carrier gas stream with pulsation granules with a frequency of 5-15 Hz reduces their amplitude and stabilizes the flow. This allows you to adjust the interaction of the melt jet, in the process of its discharge from the steelmaking unit into the ladle, with the flow of aluminum granules from the spear of the granule conduit, as a result of which almost complete assimilation of the granules by the metal will be ensured (they do not bounce from the metal jet and do not flash it through).

This method of supplying granular aluminum allows you to guaranteedly reduce its consumption by 15-25% compared with the prototype.

In addition, flow pulsations can significantly accelerate mass transfer processes between the deoxidizer and the metallurgical melt. Subsequent experience in metallurgy has shown that the use of pulsations of reacting media makes it possible to selectively control the progress of metallurgical processes. The proposed method of deoxidation with a pulsation frequency of 5-15 Hz will accelerate how the deoxidation process itself will contribute to more efficient coagulation of deoxidation products and faster evacuation of them from metal, thereby improving the quality of products.

The angle between the axis of the jet of metal flowing into the bucket and the axis of the flow of aluminum granules also contributes to the efficiency of deoxidation. In order for the kinetic energies of the metal stream and the flow of granules to contribute to a better absorption of the deoxidizer, it is necessary to have a minimum angle of introduction of the stream. Experience has shown that it is impossible to put a spear of a granular conduit on a chipboard and on converters so that this angle is less than 15 degrees. When the angle reaches more than 30 degrees, there is a likelihood of flashing the metal stream with granules. Therefore, for this method, it is most rational to vary this angle in the range of 15-30 degrees.

If the spear of the granular conduit is attached to the steel structures of the steelmaking unit not rigidly, but by means of elastic gaskets, then the spear will begin to vibrate at a frequency of 5-15 Hz, while the change in the flow angle will be 2-4 degrees, also contributing to an increase in the efficiency of the deoxidation process due to a more uniform distribution granules in the volume of a jet of molten metal.

An example of a specific implementation of the proposed method.

When steel is smelted in a 100-ton chipboard, the release lasts 5 minutes. With the beginning of the release, deoxidizer granules are fed into a stream of metal with a temperature of 1600-1650 ° C in a carrier gas stream with pulsations of a frequency of 5-15 Hz, while the consumption of deoxidizing granules is up to 100-500 kg / min, and the exposure duration is 0.8- 1.0 min The deoxidizer is introduced along the jet at an angle of 15-30 degrees.

To implement the proposed method, a pneumatic conveying installation with flexible sections of the granule line is used, the spear of which is attached to the steel structures of the steelmaking unit not rigidly, but by means of elastic gaskets and provides a change in the direction of flow of the granules by 2-4 degrees.

The carrier gas used is compressed air, nitrogen or argon. After that, silicomanganese is fed, followed by ferrosilicon.

If pig aluminum is used for deoxidation, then its consumption will be 1.5-1.6 kg / t, if the prototype method is 1.15-1.25 kg / t, and the proposed method will reduce it to less than 1, 0 kg / t The size of the used aluminum granules is 0.5-12 mm.

In addition to reducing the cost of production, its quality will increase by reducing its contamination with aluminous inclusions, which are stress concentrators.

In view of the foregoing, the claimed technical solution meets the criterion of ″ novelty ″.

Sources of information taken into account

1. V.I. Zhuchkov, O.Yu. Sheshukov, E.Yu. Lozova, L.A. Marshuk. Modern methods for introducing modifiers into molten iron and steel - Sat. reports of the Foundry consultation No. 1 “Modification as an effective method for improving the quality of cast irons and steels” - Chelyabinsk: Chelyabinsk Press House, 2006 - p.52.

2. Yu.F. Vyatkin, V.A. Vikhrevchuk, V.F. Polyakov et al. Resource-saving deoxidation technology for steel in aluminum in a ladle. Bulletin "Chermetinformation", No. 6. 1990. S. 53-55.

3. Pat. RF N 2286393, IPC C21C 7/06 (2006.01), publ. 10/27/2006.

4. Schumacher EE, Semenyak M.Yu., Smokty VV, and others. Assessment of existing methods of deoxidation by aluminum at the outlet from the steelmaking unit. Steel. M :. 2012. No7. S.23-26.

Claims (3)

1. A method of deoxidizing steel in a ladle, including introducing into the stream of metal during its discharge from the steelmaking unit into the steel pouring ladle a granular aluminum-containing deoxidizer with a high-speed carrier gas stream, characterized in that the granular aluminum-containing deoxidant is fed into the melt stream with a pulsating high-speed carrier gas stream a frequency of 5-15 Hz, while the angle between the conventional axes of the steel stream and the flow of aluminum granules is set within 15-30 degrees. 2. The method according to p. 1, characterized in that the deoxidizer is injected into the stream of the melt poured into the bucket using a pneumatic conveying system. 3. The method according to p. 1, characterized in that when applying, the change in the angle of the flow of granules is 2-4 degrees.

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