RU2441924C1 - Steel circulation degassing method - Google Patents

Abstract

FIELD: metallurgy. SUBSTANCE: invention relates to the area of iron-and-steel industry and may be used for steel ladle refining by steel circulation degassing. The method comprises the vacuum chamber inlet pipe dipping into a ladle with metal, pressure decrease above metal, introduction of argon into metal via the sucking pipe and into the vacuum chamber by horizontal jet, in peripheral direction, the argon consumption ratio in the sucking pipe and in the vacuum chamber within (1:1)-(2:1). Argon shall be introduced with sonic velocity, its content [C] in the metal being in the range of 0.040-0.0.001%. Argon shall be introduced into metal in the vacuum chamber by two dimensional jet, the jet being 0.5-1 mm and the length of 6-14 mm as it approaches the metal. ^ EFFECT: stable production of extra-low carbon content and gas content (hydrogen and nitrogen); energy carrier consumption reduction for steel degassing. ^ 4 cl, 4 ex, 6 dwg

Description

The invention relates to ferrous metallurgy and can be used for out-of-furnace steel refining by circulating evacuation.

A known method of circulating evacuation of steel, including the supply of a transporting gas (argon) to the suction pipe, in which the flow of gas (argon) for ladles with a capacity of 100-400 tons (the most common in high-performance oxygen-converter and electric steel-making shops) is taken in the range from 400 l / min up to 1200 l / min, which corresponds to a specific consumption of argon (3-4) · 10 ^-3 m ³ / (min · t) [Morozov A.N. Out-of-furnace degassing of steel. / A.N. Morozov, M.M. Strekalovsky, G.I. Chernov, Ya.E. Katsnelson. - M .: Metallurgy, 1975. - S.143-154].

The closest in technical essence and the achieved effect to the proposed method is a method of circulating evacuation of steel, comprising introducing argon into the metal in the suction pipe and in the vacuum chamber with horizontal jets in the radial direction with a ratio of argon flow rates through the suction pipe and vacuum chamber within (1: 1 ) - (2: 1) respectively. Argon is introduced into the metal in a vacuum chamber through 16 lances with a diameter of 3 mm. The vacuum treatment parameters are: bucket capacity (smelting mass) 250 t, suction speed 1,500 kg / h, argon consumption through the nozzle is from 240 to 300 m ³ / h (16-20) · 10 ^-3 m ³ / (min · t), the argon consumption in the vacuum chamber is from 120 to 300 m ³ / h (8-20) · 10 ^-3 m ³ / (min · t) [Steel production with ultra-low contents of carbon and nitrogen at the Nippon Kokan plant In Fukuyama. // News of ferrous metallurgy abroad. 1996. No2. S.37-39].

The disadvantage of this method is the high specific consumption of argon, which requires the use of vacuum pumps of increased productivity - 6 kg / (h · t) (1500 kg / h: 250 t) compared with the usual capacity (about 3 kg / (h · t)) . This is due to an increase in the cost of argon, steam production and water treatment.

The problem to which the invention is directed is to reduce the consumption of energy carriers (argon, steam, water) for evacuation of steel with guaranteed receipt of ultra-low contents of carbon and gases (hydrogen, nitrogen).

The technical result of the invention is to reduce the total consumption of argon introduced into the vacuum chamber and reduce the required performance of the vacuum pump (relative to the prototype) with guaranteed production of ultra-low contents of carbon and gases.

This problem is solved by the fact that in the method of circulating evacuation of steel, which includes lowering the nozzles of the vacuum chamber into the ladle with metal, reducing the pressure above the metal, introducing argon into the suction nozzle and into the vacuum chamber by horizontal jets in the radial direction with the ratio of argon flow rates through the suction nozzle and vacuum the chamber in the range of (1: 1) - (2: 1), respectively, according to the invention, argon is introduced at a sound velocity of expiration to the content of [C] in the metal in the range of 0.040-0.001%.

In addition, argon in a vacuum chamber is introduced into the metal with flat jets with a width of 0.5-1 mm and a length of 6-14 mm when they enter the metal.

In addition, the total consumption of argon in a vacuum chamber is (5-7.9) · 10 ^-3 m ³ / (t · min).

In addition, argon in a vacuum chamber is introduced into the metal by pulsating jets.

It is known that the removal of carbon and dissolved gas from a metal is well described by a first-order kinetic equation:

,

,

where C, C ₀ - current and initial concentration of carbon or gas;

F / V _m is the specific metal-gas phase interface.

Argon flushing with flat jets in the reduced mode under conditions of reduced residual pressure leads to the creation of high-speed jets, crushing in the metal volume into many small bubbles, increasing the F / V _m value many times and thereby the speed and efficiency of decarburization and degassing.

In addition, metal acceleration occurs in the near-jet space. The presence of a velocity gradient in the metal volume leads to the formation of zones of reduced pressure with the release of dissolved gas bubbles in them, i.e. the so-called phenomenon of gas cavitation occurs, which, as you know, occurs with a certain ratio

(обычно = 0,3-1,0),

(usually = 0.3-1.0)

where ρ, V is the density and velocity of the melt;

Δр is the difference between the total and partial pressure of the gas at a given point.

Thus, along with argon bubbles in the metal volume in the vacuum chamber, bubbles of evolved gas (CO, H ₂ , N ₂ ) also appear and are located. These bubbles are thermodynamically unstable at atmospheric pressure, under conditions of reduced pressure, especially in a vacuum chamber, grow vigorously, increasing even more the effect of metal refining.

The upper values of the specific argon flow rate range are selected from the conditions for preventing metal emissions into the vacuum conduit of the installation, and the lower ones are for conditions when purging with argon at a sound speed, which ensures the occurrence of gas cavitation.

The use of a pulsating argon flow allows one to further intensify the mixing of the metal and the mass transfer process in the metal volume to the metal – inert gas interface and increase the contact surface of the metal and gas without increasing the inert gas consumption.

The invention allows guaranteed to receive the content of ultra-low carbon (less than 0.002-0.003%) and gas (hydrogen (no more than 2.1 cm ³ / 100g), nitrogen (less than 0.003-0.004% when using a batch of pure nitride elements, such as titanium et al.) for evacuating the non-deoxidized steel and low concentrations of gases (hydrogen is not more than 1 cm ^3/100 g and nitrogen (less than 0.004%) even killed steel during evacuation.

Thus, the proposed method allows guaranteed to obtain ultra-low content of carbon and harmful gases without increasing current costs and commissioning additional capacities for the production of steam and prepared water.

An example implementation of the proposed method is illustrated in figures 1-5.

Figure 1 shows the circulation vacuum.

Figure 2 presents a section aa of a circulation vacuum degasser.

Figure 3 presents a section bB of the circulation vacuum.

Figure 4 presents a view In a circulating vacuum.

Figures 5 and 6 show the comparative number of gas bubbles formed when argon is introduced into the metal by flat jets (Fig. 5) and conventional (round) jets (Fig. 6).

Positions (figures 1-6) are indicated: 1 - bucket, 2 - vacuum chamber, 3 - suction pipe, 4 - drain pipe, 5 - molten metal, 6 - tuyere for introducing an argon stream.

The method is carried out in a manner.

The bucket 1 is installed under the vacuum chamber 2 of the RH installation, the bucket has two nozzles, one of which is suction 3 and the other is drain 4. The argon is blown into the lower part of the suction nozzle 3 and into the vacuum chamber 2. Then the RH-installation is lowered by nozzles 3 and 4 into the metal 5 in the bucket 1, the vacuum pump is turned on, and the molten metal 5, due to the pressure difference between the vacuum chamber 2 and the atmosphere, rises along both nozzles 3, 4 to a barometric height in the vacuum chamber. Argon jets introduced through tuyeres 6 with sound velocities give rise to a huge additional reaction surface, intensifying and deepening the decarburization and degassing of molten metal 5. From drain pipe 4, the degassed metal, falling back into ladle 1, mixes with the molten metal 5 located in it. reducing carbon and gas content. At the end of the metal circulation process, the pump is turned off, the RH installation is raised and the argon supply is stopped.

Example 1

In the production of IF-type steel, it is required to have an extremely low level of interstitial atoms, especially [C] ≤0.003% and [N] ≤0.0035%. When smelted in an oxygen converter, the iron-carbon unoxidized intermediate is discharged into the ladle. At the release, exactly the required amount of carbon is added for preliminary deoxidation, setting the contents of [C] = 0.02-0.04% and [O] = 0.04-0.05% before vacuuming on the RH-unit. Next, the metal bucket is fed to the RH installation. Before the start of evacuation (in 0.5-1 minute), argon is fed into the suction pipe and into the vacuum chamber with a flow rate that excludes the entry of metal into the tuyeres. Then the RH installation is lowered by nozzles into the metal in the bucket. After reaching R _ost = 300 mm RT.article argon is introduced into the nozzle and into the vacuum chamber at a sound speed with a flow ratio of 1: 1 in the nozzle and in the vacuum chamber and vacuum at P _ost ≤1 mm Hg. within 15-20 minutes Then, 4–5 min before the end, the argon flow rate is reduced to the usual level and the required amount of aluminum, titanium, and niobium is introduced into the metal to bind C, O, S, N. 5-7 minutes after this, the pump is stopped. RH-installation is raised and the flow of argon is stopped.

Example 2

An iron-carbon intermediate with [C] = 0.04% is released from the oxygen converter, the metal is fed to the RH unit. Argon is introduced into the nozzle and into the vacuum chamber with flat jets in an amount excluding the entry of metal into the flat tuyeres. The RH installation is lowered into the metal in the bucket and the argon consumption in the nozzle and in the vacuum chamber is increased to 5 · 10 ^-3 m ³ / (t · min). Argon is introduced by flat horizontal jets of size 0.51 mm × 6 mm with sound speed. Then, upon reaching [C] = 0.002-0.001%, the argon consumption is reduced to the usual level (4.0-4.5) · 10 ^-3 m ³ / (t · min), deoxidants are added (aluminum, titanium, niobium) and vacuum another 5-7 minutes After that, the pump is turned off, the RH installation is raised and the argon supply is stopped.

Example 3

The iron-carbon intermediate is discharged from the oxygen converter at [C] = 0.02-0.04%, corrected [O] by planting carbon in the bucket to [O] = 0.04-0.05%, and fed to the RH unit. Then argon is fed into the nozzle and into the vacuum chamber, the RH installation is lowered, the vacuum pump is turned on, and argon is fed at a sound speed with 1 mm × 14 mm flat jets with a flow rate of 7.9 · 10 ^-3 m ³ / (t · min) the nozzle and into the vacuum chamber, respectively, in the interval [C] = 0.040-0.001%. Upon reaching [C] = 0.002-0.001%, the argon input intensity is reduced to normal (4.0-4.5) · 10 ^-3 m ³ / (t · min), aluminum, titanium, niobium are added and vacuum is applied for another 6-8 min Then the pump is turned off, the RH-installation is raised and the flow of argon is stopped.

Example 4

It is carried out as in example 1, but argon is introduced into the vacuum chamber by pulsating jets.

The invention allows guaranteed to obtain ultra-low content of carbon and gases (hydrogen, nitrogen) while reducing energy consumption for evacuation of steel.

Claims (4)

1. A method of circulating evacuation of steel, including lowering the nozzles of the vacuum chamber into a ladle with metal, reducing the pressure above the metal, decarburizing the metal by introducing argon into the metal into the suction nozzle and into the vacuum chamber by horizontal jets in the radial direction with the ratio of argon consumption in the suction nozzle and vacuum the chamber within (1: 1) - (2: 1), characterized in that the input of argon jets into the metal is carried out with a sound velocity of expiration to the content of [C] in the metal 0,040-0,001%. 2. The method according to claim 1, characterized in that the argon in the vacuum chamber is introduced into the metal with flat jets with a width of 0.5-1 mm and a length of 6-14 mm when they enter the metal. 3. The method according to claim 1, characterized in that the total consumption of argon in a vacuum chamber is (5-7.9) · 10 ^-3 m ³ / (t · min). 4. The method according to claim 1, characterized in that argon in a vacuum chamber is introduced into the metal by pulsating jets.

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