SU929713A1 - Method for treating molten steel - Google Patents

Description

The invention relates to ferrous metallurgy, and more specifically to the technology of processing liquid steel. A known method of treating a molten metal is one in which the melt is blown by an inert gas through a tuyere located above or near the melt surface, while the inert gas is fed under a pressure of 1-10 atm 1. The disadvantage of the known method is that so high pressure of the inert gas, effective mixing of the metal, its degassing and refining from non-metallic inclusions is not achieved. The closest technical feasibility and the achieved result is the method of processing liquid steel, which consists in introducing into the steel through a purge lance a carrier gas of a pore-sludge reagent in the amount of 20-150 g / t of steel per minute, containing 15-100% alkaline earth metal, the depth of the tuyere is 60-85% of the height of the liquid metaste p. 12. A disadvantage of the known method is the low use of alkaline earth metal and the increased consumption of such metal due to insufficient height of mercury. As a result, the limited time of interaction between the dust and gas jet and the metal. The aim of the invention is to increase the degree of refining of the metal and reduce the consumption of powdered reagent. The goal is achieved by the fact that in the method of steel processing, which includes the introduction of a powdery reagent in the amount of 20-150 g / t of steel per minute, containing 15,100% alkali metal, into the steel through the purge tuyere into steel, before blowing it into powdery reagents for 10 -15 s is supplied with a carrier gas when the blowing lance is immersed in liquid steel to a depth of 86-95% of the height of the metal column. Increasing the depth of the alkaline-earth metal input leads to an increase in the coactant time of the reagent with the steel. In this case, more favorable conditions are created for the interaction of the alkaline earth metal with the liquid steel and the degree of its assimilation increases. As a consequence, increasing the depth of the input alkaline earth metal leads to a decrease in its consumption with the same effect processing. The intermittent introduction of powdered reagent into the carrier gas contributes to a further decrease in its consumption, since during the period between the introduction of the previous and subsequent portions of porous gas, the desulfurization reactions are more fully completed due to the further redistribution of the reaction product between the metal and slag. The essence of the method for treating molten steel is as follows. Metal treatment with the reagent is carried out in a ladle after deoxidation of steel by known methods. Deoxidation of the steel is carried out, for example, with silicon, manganese, aluminum or a circular deoxidizer. Before the tuyere begins to sink, gas begins to be supplied through it, then. the lance is introduced into the molten steel to a depth of 86 to 95% of the height of the metal column. After immersing the tuyere at a predetermined depth, the carrier gas is continued to be supplied for 10–15 s, after which the powder-like suspension is purged with powder. Powdered reagent can be injected intermittently with a time interval between the end of the previous and the beginning of the subsequent entry equal to 0.5-1.5 min, and with decreasing its consumption with an intensity of 1-5% per minute to a value equal to 50-90% of its consumption at the start of the purge. The inclusion and cessation of the powder supply can also be carried out when the tuyere is positioned above the metal level. Materials containing alkaline earth and rare earth metals, such as silicocalcium, magnesium, calcium carbide, calcium oxide and magnesium, REM silicides, etc., can be used as a powder reagent. Alkaline earth and rare earth reagents can be mixed with components that increase the efficiency of their effect on the metal. or improve slag formation, concomitant metal processing reagent. Such components may be. For example, aluminum, fluorspar, etc. Before blowing, the metal can be treated with liquid synthetic slag or slag-forming mixtures. The minimum value of the immersion depth of the tuyere in meta) w (86%) is justified by the fact that, starting from this depth, the most optimal conditions (minimum in time) are created for processing the entire volume of the metal of the ladle. The maximum depth of immersion of the tuyere into the metal (95%) is limited to a value that, if exceeded, can lead to the danger of mechanical damage to the bottom of the bucket by a gas jet with solid powder reagent. The minimum (10 s) and maximum (50 s) times for delivery of the carrier gas after the tuyere has been immersed to a predetermined depth are justified by the need to obtain a steady state gas supply in the system, which, due to the compressibility of the gas, has considerable inertia when blowing metal in the drums (small to 100 t) and (large 100-350 t) capacity, respectively. The minimum (0.5 min) and maximum vl, 5 min) time intervals between the moments of entering portions of powdered reagent are selected based on the need to complete the redistribution of the reaction products between the metal and slag with the duration of the powder purge cycle up to 3 min and 4-8 min, respectively . Increasing the use of the reagent also contributes to reducing its consumption by the end of the purge to 50-90% of its original value due to a decrease in temperature during the purge and, as a consequence, an increase in the refining ability of calcium. At the same time, a decrease in the consumption of the reagent below 50% of its initial value leads to a significant reduction in the duration of the purge of the metal, and an increase in its more than 90% causes a significant decrease in the efficiency of this technological procedure. The minimum (1% per minute) and maximum (5% per minute) intensity values for reducing the consumption of powdered reagent are respectively for hot (with temperatures over 1610 ° C) and cold (with temperatures below 1650 ° C) metal. . Example. In a laboratory electric arc furnace, the metal is charged with a charge of 1.5 tons. After the metal has been deoxidized with ferromanganese, ferrosilicon and aluminum, it is rinsed with a powdery reagent, silicocalcium grade SK-30. The basic chemical composition of all the experimental heats is approximately the same and the average content of elements is% 0.1 carbon, 1.5 manganese, o, oz aluminum. As a criterion of the degree of metal treatment with the reagent, the magnitude of the change in the sulfur content in it as a result of blowing is used. In tab. 1 shows the results obtained by purging the test bottoms with the powdered reagent of the proposed method, in comparison with the data of the melts treated by a known method.

As can be seen from the table. 1 according to the proposed method, the degree of desulfurization of the metal is much higher than when processed in a known manner.

In tab. 2 shows the results obtained with the intermittent introduction of powdered reagent into the metal of the experimental heats.

With this technology, a further reduction in the consumption of alkaline earth metal is achieved (as compared with the known method - by 64-210 g / t, with a single blowdown at 24-70 g / t).

In tab. 3 shows the results of metal processing with a decrease in reagent consumption by the end of the purge. Period duration

the supply of pure carrier gas at the start of the purge time is 25 seconds in all heats.

Gradually controlled (as the metal is being purged) the input of the reagent allows reducing the total consumption of calcium.

Thus, when processing liquid steel according to the proposed method, the efficiency of the process increases by increasing the degree of refining the metal and reducing the consumption of reagent.

The introduction of such a method of its processing into the practice of steel production will make it possible to obtain high-quality steel with a small cost and consumption of technological additives, which will help reduce the cost of the metal

Table 1

Proposed 1

15

840

300

20

20

500

50

200

5 6

840,800

7 8

500 200

0.040

0,002

0.042

80.036 0.003

0.033

0.022

0.029 0.007

0.040

0.027

0.013

8570,041 0,0130,028

7580.036. 0,0100,026

0.015

0.029 0.014

80.039 0.031 0.008

one

table 2

Table 3

Claims (3)

Claim 1. The method of processing liquid steel, which consists in introducing through a blowing mold into steel a carrier gas of a powdered reagent in an amount of 20-150 g / t of steel per min, containing 15-100% alkaline earth metal, characterized in that, in order to increase the degree of refining metal and reducing the consumption of powdered reagent, before purging with powdered reagents for 10-15 seconds, the carrier gas is supplied while the purge lance is immersed to a depth of 86-95% of the height of the metal column, and then the powder is purged at the same depth different reagent. 2. The method of pop. 1, characterized in that the powdered reagent is administered intermittently with an interval of time between 40 ‘the end of the previous and the beginning of the subsequent input equal to 0.5-1.5 minutes. - '3. The method according to claims 1 and 2, characterized in that the consumption of the powdered reagent is reduced with an intensity of 1 - 5% 45 per minute to a value equal to 50-90% of its consumption at the beginning of purging.