RU2002815C1 - Method of treating steel in casting ladle - Google Patents

Description

chenp their speed in a given volume of the cavity of a vertical cylinder.

Maintaining the temperature of the inner surface of the lining 20-70 ° C higher than the melting temperature of the additives provides optimal conditions for the melting of dust (fraction up to 2 mm) deposited on the surface of the cylinder cavity and its free flowing in liquid form directly to the molten steel. These conditions include the rate of particle melting, fluidity during runoff, and minimal heat consumption.

When the indicated temperature is exceeded by 20 ° C, the above conditions are met for particles with a fraction of up to 2 mm. When this temperature drop decreases below 20 ° С, for example, when the difference is 15 ° С, the aggregate state of large particles is still in a solid (more precisely softened) form and the viscosity of the flowing melt increases

While maintaining the temperature drop of 70 ° C, the heat load in the cylinder cavity reaches the limit value for the lining resistance. Further temperature exceeding above 70 ° C requires either expensive materials, such as zirconium, or the use of a water-cooled frame (for example, a hollow or tubular structure), This provides a significant waste of heat. Keeping the exhaust duct clean above the metal mirror increases the throughput of the evolved gases. In order to additionally isolate them at a given degree of melt mixing over a pure metal mirror, it is advisable to maintain controlled rarefaction without increasing the oxidizing potential in this zone. This technical result is achieved by forced exhaustion of gases from a pure metal mirror, for example, by burning fuel in a cylinder cavity in a tangential manner, i.e. fuel with an oxidizing agent is introduced potentially on the surface of the inner lining of the cylinder.

With this (tangential) input of the energy source, which is the fuel-oil mixture supplied under pressure by burners, a reduced pressure is created in the cylinder cavity, which facilitates boiling of the deoxidized steel, which decreases when atmospheric pressure is restored. When a slight vacuum is created, boiling resumes and increases with increasing vacuum. Boiling is caused by the release of gases dissolved in the metal, i.e. by changing the vacuum above the metal surface, a controlled degassing process can be carried out. Thus, due to a decrease in the partial pressure of hydrogen and nitrogen, these gases are released from the liquid metal both by desorption from the surface and diffusion of dissolved gases

0 into the surface layer, and by diffusion into pop-up bubbles of carbon monoxide and desorption into the gas phase. By facilitating the release of gas bubbles, high chemical homogeneity is achieved, temperature is equalized in the volume of the steel, and, consequently, the uniformity of its mechanical properties is increased. Putting alloying elements into such (previously deoxidized) metal

0 provides during processing the production of cleaner steel in the content of non-metallic inclusions. The introduction of a small amount of nitride-forming elements into such a metal eliminates the harmful effect of nitrogen at its high content. The purity of the treated steel and the uniformity of the chemical composition ensures the stability of the metal properties not only within the limits of the ingot and smelting, but also of the entire steel produced by any method of smelting, while it becomes possible to increase the performance of steelmaking units, reduce the consumption of alloying elements, reduce the number of deoxidizing

5 It should also be noted that such steel processing requires minimal capital and energy costs for its implementation and does not complicate the technology of its production in existing steelmaking workshops.

0 Thus, the processing of steel in a casting ladle with a partially immersed hollow cylinder and purging by maintaining the internal surface of the cylinder at a temperature level not lower than

5, the melting temperature of additives, by exceeding the melting temperature of additives by 20-70 ° C and by maintaining a controlled vacuum above the liquid metal in the cylinder, increases the processing efficiency by eliminating the possibility of formation of deposits in the gas discharge zone, and reduction of dust extraction during the loading of additives and droplet liquid steel, increasing the degree of degassing of the melt,

5 heating the seated materials and reducing the suction of cold air, reducing heat loss through the cylinder cavity. As a result of the above, the quality of the treated steel and the efficiency of the processing process increase.

for the descent (input) of ferroalloys and deoxidizers, and for the removal of gases from the melt, and this in turn reduces the degree of interaction of the additives with the melt and increases the pressure above the metal mirror in the cylinder, which degrades the metal degassing in the ladle. In addition, the introduction of cold additives into the melt increases the heat loss of the metal during its refinement, which in turn leads to a decrease in the temperature of the metal in the casting ladle, and this increases the melting time in the furnace and leads to an additional consumption of refractories and an increase in energy consumption.

The objective of the invention is to improve the quality of steel by increasing the efficiency of processing it in the casting ladle during its refinement.

The technical result is achieved in that the inner surface of the cylinder liner outside the zone of molten metal is maintained at a temperature level not lower than the melting point of the ferroalloys.

In addition, the result is achieved by the fact that the temperature of the inner surface of the lining outside the zone of molten metal is maintained at 20-70 ° C higher than the melting temperature of the ferroalloys, as well as by the fact that vacuum is maintained in the cylinder cavity above the metal mirror.

The method of processing steel in a casting ladle is illustrated in the drawing.

According to the proposed method, a casting ladle 1 with steel discharged from the furnace is installed under a vertical lifting and lowering lined hollow cylinder 2 with an inner diameter of 600-1200 mm and a height of 1800-2200 mm, which is immersed with the lower part in the melt 200-400 mm, the metal mirror in the bucket outside the lined hollow cylinder is protected from oxidation by slag, and inside the cylinder is left clean, where ferroalloys with alloying elements and deoxidants are introduced, which are introduced into the cylinder from above in the form of lumpy (crushed) material s and mix them with the melt by blowing through a movable purge immerse lance 3 located coaxially to the cylinder and the bucket,

Argon or nitrogen are used as the gas for purging the melt. The lower section of the lance is in the volume of metal at a distance of 500-1000 mm from the bottom of the bucket.

For purging the melt, it is possible to use various porous inserts (plugs) installed in the bottom

casting bucket. Depending on the bucket capacity, the specific gas flow rate is 0.015-0.6 m / t. The blowing time for homogenizing the metal in the bucket volume is 3-5 minutes, for stirring in order to refine the liquid steel 5-10 minutes. During the expiration in the melt, the gas jets decompose into small bubbles and are carried out through the metal, which is unprotected by slag, into in this case through the cavity of a vertical immersion cylinder. The rate of gas evolution from the liquid metal will increase when creating a vacuum above

a mirror of metal. To refine steel in a ladle into pure metal through a cylinder cavity, ferroalloys with alloying elements, for example FeCr, SiMn, FeSi, are placed on top and deoxidizers are mixed with

melt during the purge process. The intensity of the bubbling in the melt and the evolution of gases from the melt increases. At the same time, the internal surface roughness of the cylinder liner outside the zone (above the boundary) of the molten metal is maintained at a temperature not lower than the maximum melting temperature of the loaded materials (additives), for example, ferroalloys, by its additional

heated by burners. In this case, the dust particles (the finely dispersed fraction of additives) melt and when they fall on the surface of the lining, together with droplets of entrained metal, they will flow into the melt in liquid form, while their settling on the lining ceases, which eliminates the formation of suction.

For forced and economical

the process of melting particles on the surface of the lining is practically sufficient to maintain its temperature above the melting temperature of the maximum temperature of the added additives. Maintaining such a temperature level ensures that the droplets of metal deposited on the lining from its surface back into the molten metal, keeping the lining clean, from which there are no conditions for the formation of accretions. Thus, there are no obstacles (hydraulic resistance) from the accretions on the path of the additives, which improves the quality of finishing steel (from the point of view of normal input

additives) and uniformity of removal of exhaust gases. This eliminates air leakage to the mirror of a pure metal, and the temperature potential of injected additives increases due to the countercurrent effect of high-temperature gases and increases the example of a specific embodiment under the conditions of the electric furnace melting shop of the Orsk-Khalilovsky steel mill.

Initial data:

1. The object of processing is a steel-pouring ladle with a capacity of 130 tons.

2. Geometric parameters of a hollow cylinder, mm:

Height 1800

Diameter int. 1150

Outside Diameter 1650

3. Depth of immersion of the cylinder in the melt 200-300 mm;

4. Lining characteristic - high alumina with A120z content above 75%.

5. Installation of the cylinder - on the lid of the steel-pouring ladle, aligned with it.

6. Heating cylinder -3 pcs, gas-air burners.

7. The consumption of natural gas on the burner 30-50 m3 / h.

8. Installation of burners - on the lateral surface of the cylinder, tangentially to it, at a distance of 1100 mm from the lower end of the cylinder.

9.Characteristic of additives loaded into the stele-filling bucket - lump FeCr; SlMn; FeSi and other fractions up to 2 mm 10-15% Lpl “1540 ° С.

10.Characteristic of the processed steel - calm crack-proof grades of type 40X.

Comparison of the method under consideration was carried out in comparison with the solution taken as a prototype and used in the camera installation of steel refining ESPTsOKhMK.

When comparing samples taken from 10 swimming trunks of the compared solutions, the following average practical results were obtained (see Tables 1 and 2).

(56) 1. Vlasov N.N., King V.V., Rad B.C. Ferrous metal casting. Handbook, Moscow: Metallurgists, 1987, p. 88, fig. 56 a.

2. There, fig. 56 b

3. There, p. 89, fig. 57.

4.Novik L.M. Out-of-furnace vacuum metallurgical steel. M .: Nauka, 1986, p. 79, fig. 49.

5.Knuppel G. Deoxidation and szkumna-on steel processing. M: Metallurgists, 1984, p. 354, fig. 342.

Table 1

Test result

Marriage of the first redistribution (cracks, flaws),%

Volume of metal with oxide inclusions 5 or more points,% Nitrogen content in the metal,% Hydrogen content, ml / 100 g Me Steel processing cost, r / t

Prototype

Sentence

0.64

6.4

, 0093

4.93

1.5

0.48

41

0.0071

2.57

1.1

table 2

Cap

1aris dm