EP1541699A1 - Method for feeling steel - Google Patents

Abstract

Said invention relates to methods for the out-of-furnace processing of metal for the iron and steel industry. Said invention makes it possible to expand an active zone of coverage of metal volume by gas or a gas-powder mixture, thereby reducing the time required for obtaining a homogenised composition of metal without increasing the quantity of supplied gas, i.e. to solve the problem of the intensified steel feeling by gas or gas-powder bubbling. The inventive method for feeling steel consists in blowing steel from the bottom by gas or a gas-powder mixture through at least two designed blowdown devices diametrically arranged on the opposite sides of a ladle. The bubbling is carried out alternatively through the devices arranged on the opposite sides of the ladle, a pressure for preventing the flowing of metal in the device which is not used at given moment being maintained therein. The alternative operational time of the blowdown devices is increased proportionally to the increase of steel in the ladle, the volume of supplied gas being unchangeable when the gas or gas-powder mixture supply is switched from one blowdown device to another.

Description

The invention relates to methods for the treatment of liquid metal in a pan outside the furnace in black metallurgy.

It is known that in the treatment of steel outside the furnace Inert gas and technological powder in the melt either through in the Melt submerged blow molds or by special in the pan bottom arranged plugs are supplied.

The intensification of the stirring process of the metal, which is a reduction The steelworking time has an important meaning in the process treating metal outside the oven in a pan. The Homogenization of the melt accelerates the processes of calming and the disposal of non-metallic inclusions, as well as desulphurisation and Dephosphorization of the steel, which is the achievement of the objectives of ladle metallurgy guaranteed.

A method is known for intensifying the stirring of metal in a pan by increasing the gas flow rate for blowing. in the known method leads the gas through a blow mold of the type "hollow Stopper rod "and to avoid splashing of metal at elevated Gas supply is used a disc-shaped front part (screen) on the Stopper rod (see, e.g., Stahl, No. 12, 1999, pp. 17-19).

The main disadvantage of the method is the attempt to complete the task of Intensify the stirring of the metal by increasing the gas supply to solve. Moreover, in this case, most of the metal in the pan is not from the stirring comprises, in particular not in their soil zones. All in all reduces the above mentioned the effectiveness of the known method in the Solution of the task.

Also known is a method for stirring steel in a pan, including the introduction of a soluble gas into the steel, which is at Vacuum treatment in the form of the smallest on the melt surface Floating bubbles in the steel (as well as in soda water) separates (see For example, "Steelmaking on the Threshold of the Third Millennium", Annex 7 to the Journal "News of Black Metallurgy Abroad", 2000, p. 25).

The main disadvantage of the known method lies in its obvious More expensive, u.a. because of the need for a recirculating vacuum treatment (NK-PERM process of the company "Nippon Kokan").

Also known is a method of stirring steel in a pan its stirring by means of electromagnetic forces (see, e.g. "Injection Metallurgy", edited by Sidorenko M.B., Moscow, "Metallurgy", 1986, p. 90).

The main drawback of this process is the high cost of used equipment with a relatively low stirring effect.

Also known is a method for stirring steel in a pan, comprising blowing the steel from below by means of a gas or gas-powder mixture through arranged in the lower part of the molten bath Blowing devices, of which at least one is offset from the middle of the pan (See, for example, the indicated source "Injection Metallurgy", pp. 142-143 and Fig. 12). Although in the practice of the known method, the supply of Gas or gas-powder mixture through special plugs in the bottom of the pan is preferred, its implementation concludes the supply of the specified Components by a submerged tuyere (tuyeres) is not enough.

This known method for stirring metal in a pan by the supply of gas or a gas-powder mixture comes the essential Characteristics closest to the method according to the invention and will therefore accepted as the closest prior art.

The known method has a significant disadvantage: in the course of Blowing the steel by means of the gas / gas powder mixture is the Metal stirred unevenly over the pan volume. Especially the im Entry path of the gas / gas powder mixture in the steel areas (most active zone) of the liquid metal become an intense stirring motion subjected. When approaching the gas / gas powder mixture to the Surface of the metal in the pan widen these areas, flow through (reducing speed) the upper layers of the Melting bath and sink from the surface as weakened descending Streams down. Of course, this portrayed image reduces that Movement of stirred metal efficiency of stirring of steel because it the entire volume of metal in the pan and especially the bottom zones of the Melting bath detected very slowly. Altogether the posed task of the Acceleration of the homogenization of the metal composition is not achieved. The known process requires increased use of gas and in particular in time, which in the current technological manufacturing process of steel in the essential is not sufficiently available.

The inventive method for stirring metal in a pan does not have the mentioned disadvantages. In this method, the active zone the detection of the metal volume by the gas / gas powder mixture significantly widened. This leads to the reduction of the time to reach a homogenized metal composition without increasing the supplied Amount of gas, i. the technical task of intensifying the stirring of steel in a pan by blowing a gas / gas powder mixture solved.

The technical results mentioned are achieved in that A method of stirring steel in a pan, comprising blowing of the steel from below by means of a gas / gas powder mixture through at least two provided blowing devices, which are diametrically are arranged opposite sides of the pan, according to the invention the blowing through alternately first by one of the blowing devices, the on one side of the pan, and then the other Blowing device, which is located on the other side of the pan, takes place. there one stops in the blowing device, which does not blow through at the moment, a pressure which precludes the inflow of metal into this device. The Period of the operation change between the blowing devices is increased with the increase in steel mass in the pan. The volume of the supplied Gas is at the switching of the supply of gas or gas-powder mixture from one blowing device to the other left unchanged.

The inventive method for stirring metal in a pan by blowing of gas or a gas-powder mixture is on hand explained in more detail of schematic drawings.

In Fig. 1, a pan is shown with metal, in the two Blowing devices are provided as a plug in the pan bottom. In Fig. 2 is an analogue pan with two blowing devices in the form of tuyeres shown. In Fig. 3, the view in the direction of arrow A gem. Fig. 1 shown. Fig. 4 shows the view in the direction of arrow A gem. Fig. 2. Here the pan has at least two blowing devices.

The ladle 1 is filled with the liquid steel 2. in the The bottom of the ladle (Fig. 1) are on diametrically opposite sides of the pan 1 (Fig. 3) at least two blowing devices 3 are provided. The number of these Devices can be higher, but must be straight. In the pan 1 can on blow molds 4 arranged diametrically opposite sides of the pan 1 be provided. The number of blow molds may be higher but must be even. The Gas or gas powder mixture 5 is the pan by plugging in each case Pan base (Fig. 1) or tuyeres 4 (Fig. 2). The gas or the Gas-powder mixture can be fed to the pan separately. In this Case increases the number of devices 3 (blow molding 4) to the next even number. In Fig. 1 - 4 are the main currents of the metal, in the supply of the gas or gas-powder mixture on one side of the Form pan, shown with thin lines 6. Those streams which are form when switching the blowing devices are with the dotted lines. 7 shown. Increasing the number of plugs 1 (blowing nozzles 4) does not change the nature or effect of the proposed method increases but additionally the intensification of the stirring of the steel, i. increases the Effectiveness (but at the same time complicates the construction).

The method of stirring steel in a pan is as follows carried out.

In the pan 1, the steel 2 is poured. The for the doping, Desulfurization and dephosphorization of the steel necessary elements become by known methods or as a powder by the described Devices 3 (or 4), or by both methods simultaneously in the steel introduced.

The supply of the gas (gas-powder mixture) 5 through the plug 3 (the Blow mold 4), for example, in Fig. 1 - 4 left, is turned on. One uses inert gas, for example argon. The result is formed in the Melt the main currents, which are represented by the lines 6. In this time is in the stopper 3 (in the tuyere 4) on the opposite Side of the pan held a gas pressure, which is the inflow of steel into these excludes. After a certain time (period) the direction of the Main flows of the metal in the pan bath by supply of the gas (gas-powder mixture) 5 through the plug 3 (blow mold 4), on the opposite Side of the pan is arranged (in Fig. 1 - 4 right), in the opposite Changed direction. The main streams of the metal in the molten bath begin in this way to move, as shown by the dotted line 7 in Fig. 1 - 4. By the periodic change of the direction of movement of the metal streams 6 → 7 → 6 etc., the stirring of the metal is substantially intensified. As a result, will in the course of a shorter time a homogenized steel composition in the Pan, i. the task is solved.

The period of change of direction of supply of gas (gas-powder mixture) is practically determined. However, the periodicity of the specified change with the increase of the steel mass in the pan, because only in this case, the metal streams 6 and 7 have the desired shape (shown in Fig. 1 and 2) and the change of direction of the supply of the gas (Gas-powder mixture) minimally affects their mutual damping.

There is a period of change of direction for the given ones Conditions of operation of the pan is optimal. A reduction in duration this period is not recommended because zones are more incomplete Homogenization of the melt in the steel volume form. An increase in the Duration of this period is permissible and is governed by the general technological The rhythm of steelmaking is determined.

example 1

A "cold model" of a pan 1 had the one shown in Fig. 1 Dimensions. In the pan was tap water 2 up to the height of 430 mm filled. The pan was equipped with three platinum electrodes: one in the bottom Part of the pan (distance from the water level 370 mm), one in the middle part of the Pan (distance from the water level 220 mm) and one in the upper part of the pan (Distance from the water level 60 mm), the advance in the areas tap water - 0.1 wt.% Aqueous KCl solution were calibrated. All three electrodes were 55 mm away from the inner wall of the pan model. There was also one portable electrode provided with the addition of the homogenization of the Solution in the centers of the pan model, in the bottom part, at the Water surface, as well as in the joints of the floor and the walls of the pan was evaluated.

A 20% KCI concentrate was prepared and in a thin Rubber balloon on the bottom of the pan model in the area near the Pan wall, which was located 90 ° from the devices 3, lowered. Of the Balloon was cut up. It was by the 20% KCl concentrate after its uniform distribution over the body of water a concentration of 0, 1% KCl set in the water, on which the electrodes were calibrated. The Use of the balloon has a minimal disruptive effect on the balloon Water bath guaranteed.

The gas (air) was absorbed by the devices in the soil in an amount supplied from 6 l / min. For a larger air supply was the Bubble-forming regime of blow-through disturbed.

Under the specified conditions and blowing air through a device 3 without change of direction was after 84 min. A homogeneous 0.1 wt.% KCl solution in the water of the pan. The solution was on all additionally measured sites over the entire solution mass practically equal.

Example 2

Under the conditions given in Example 1 was a alternating air supply with a period of 30 sec. performed. In which Change in direction was the amount of air supplied at 6 l / min. held. After 35 min, the pan model became a homogeneous solution with the above Receive concentration, i. the stirring time was 2.4 times compared to Example 1 reduced.

Example 3

Under the conditions given in Examples 1 and 2 was a alternating air supply with a period of 20 sec. performed. To 60 min. was in the pan a homogeneous solution with the above concentration obtained, i. the stirring time was reduced 1.4 times compared to Example 1. At the end of the 60-minute stirring, there were zones in the water volume larger and smaller concentrations than 0.1% KCl detected in water were not registered by the main electrodes.

Example 4

Under the conditions given in Examples 1 and 2 was a alternating air supply with a period of 10 sec. performed. After 84 - 87 min. was in the pan a homogeneous solution with the above concentration obtained, i. the stirring time became practical in comparison with Example 1 maintained. At the end of the stirring were in the water volume zones with larger and smaller concentrations than 0, 1% KCl detected in water, the were not registered by the main electrodes.

Example 5

Under the conditions given in Examples 1 and 2 was a alternating air supply with a period of 40 sec. performed. To 55 min. was in the pan a homogeneous solution with the above concentration obtained, i. the stirring time was reduced 1.5 times compared to Example 1. The water volume lacked zones with a KCI concentration that differed from the Concentration of 0.1 wt.% KCl difference.

Example 6

Under the conditions given in Examples 1 and 2 was a alternating air supply with a period of 50 sec. performed. To 60 min. was in the pan a homogeneous solution with the above concentration obtained, i. the stirring time was reduced 1.4 times compared to Example 1. The water volume lacked zones with a KCI concentration that differed from the Concentration of 0.1 wt.% KCI distinguished.

The inventive method for stirring steel in a pan allows a substantial intensification by a simple process management the stirring of the steel (a reduction in the time to carry out) without a loss of stirring quality.

Claims (3)

A method of stirring steel in a pan, comprising blowing the steel from below by means of a gas or gas-powder mixture through at least two provided blowing devices arranged on diametrically opposite sides of the pan, characterized in that the blowing through alternately first one of the blowing devices, which is arranged on one side of the pan, and thereafter by the other blowing device, which is located on the other side of the pan, wherein one holds in the blowing device, which is not currently blown through, a pressure, the excludes the inflow of metal into this device. Method for stirring steel in a ladle according to claim 1, characterized in that the period of change of operation of the blowing devices is increased with increasing steel mass in the ladle. A method of stirring steel in a ladle according to claim 1, characterized in that the volume of the gas supplied is left unchanged when switching the supply of the gas or gas-powder mixture from one blowing device to the other.

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