JPH09280751A - Electric furnace bottom gas-blowing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent nonferrous metals such as lead and the like contained in a molten steel from intruding through a gas blowing hole as much as possible and facilitate to exclude the non-ferrous metals by raising gas pressure even if the nonferrous metals have entered by forming the gas blowing hole in a funnel like shape or an umbrella like shape. SOLUTION: A gas blowing hole 10 is formed in a funnel like or umbrella like shape. The gas blowing hole 10 having such a funnel like or umbrella like shape can blow gas at a higher speed at an upper side of an outer peripheral portion of the blowing hole than at a lower side so that molten lead having a tendency to adhere onto a top side of an outer peripheral portion of the blowing hole is scattered into outside stumping material and becomes easy to be absorbed. On the other hand, droplet molten lead adhering on a lower side of the outer peripheral portion of the blowing hole is difficult to be scattered but easy to move into the stumping material in vicinity due to vibration of a whole furnace body or vibration during gas blowing operation, and therefore the molten lead generally becomes difficult to adhere onto the peripheral portion of the hole. By raising blow gas pressure the lead intruding into the hole can be easily excluded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for introducing a stirring gas into a molten metal from the bottom of an electric furnace, and particularly to prevent intrusion of a low melting point metal such as lead contained in the molten metal. The present invention relates to an electric furnace bottom gas blowing device capable of discharging invaded metal.

[0002]

2. Description of the Related Art In an electric arc melting furnace, when refining the molten steel in the furnace, it has been conventional to stir the molten steel with a gas for the purpose of homogenizing the molten steel, promoting a metallurgical reaction, and the like. In steelmaking by an electric furnace, it is well known that the molten steel is stirred by introducing an inert gas into the molten steel from a gas injection port on the hearth or the bottom of the furnace to remove impurities and accelerate the metallurgical reaction.

FIG. 3 is a diagram for explaining such a gas blowing device. FIG. 3A is a cross-sectional view of the bottom of the electric furnace. An irregular shaped refractory 2 having air permeability and a refractory 3 having no air permeability are applied to the bottom of the electric furnace body 7 to form a hearth. However, a plurality of gas blowing elements 1 are embedded in the amorphous refractory 2. Gas blowing element 1
As shown in FIGS. 3 (b) and 3 (c), is a distribution device 6 in which a small-diameter gas blow-out hole is formed in a steel annular pipe of about 25 A in a diagonally downward direction, and a furnace connected to the annular pipe. A gas introducing pipe 5 extending to the outside and a distributor 6
A tarai-shaped or cylindrical container 4 is arranged around the container to prevent leakage of blown-out gas such as nitrogen gas and argon gas, and ensure stable supply. Such a gas blowing element is usually installed at 3 to 4 places in the hearth part, and gas is blown into the furnace through a special stamp material capable of securing and maintaining a gas passage for a long time.

[0004]

By the way, as shown in FIG. 4, the tubular pipe constituting the distributor 6 of the gas blowing element 1 has, for example, 6 gas outlet holes 8.
The holes are narrowed downward at a pitch of about 0 mm. Non-ferrous metals such as lead are contained as impurity components in the molten steel in the electric furnace, of which metal with a higher specific gravity than iron moves through the hearth refractory and moves to the iron skin side of the electric furnace hearth. However, at this time, when it comes into contact with the pipe constituting the distributor 6, the droplets adhere to the surface thereof. The deposited non-ferrous metal droplets usually move to the lower iron-clad refractory and are absorbed by the vibration during operation of the electric furnace, and then move to the iron-clad side. The lead 9 in the form of droplets attached to the vicinity of the gas blowing hole 8 hangs down as shown by the arrow in the figure, and enters the inside from the gas blowing hole 8. The cause of this is breathing when gas is blown out (pressure fluctuation when gas is blown out). Capillary phenomenon Pressure inside the distribution device due to gas blowout (about 2 Kg /
cm ² ) decrease is considered.

The droplet-shaped lead 9 thus infiltrated is cooled by the gas inside the distribution device 6 and solidified, which is accumulated and gradually increases in the direction of the gas introduction pipe 5, and finally the gas introduction pipe 5 is closed. In some cases, it may block and make gas injection impossible. Due to these reasons, the service life of gas blowing devices is generally about 1.5 in Europe.
In Japan, the actual situation is about 0.5 years (20 CH / day) in Japan, and there has been a demand for extending its life.

The present invention has been made in view of the above circumstances, and prevents the non-ferrous metal such as lead from entering the inside of the gas blowing apparatus and facilitates the discharge of the non-ferrous metal such as lead that has entered. It is an object to provide a gas blowing device.

[0007]

DISCLOSURE OF THE INVENTION The present invention provides a device for agitating molten steel by ejecting gas from a blow-out hole of an annular pipe embedded in a breathable amorphous refractory at the bottom of an electric furnace. By making it funnel-shaped or umbrella-shaped,
It is characterized in that non-ferrous metals such as lead contained in the molten steel are prevented from entering as much as possible through the gas blowing holes, and even if they enter, they can be easily discharged by increasing the gas pressure.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. The gas blowing device of the present invention basically has the same configuration as that described with reference to FIG. 3, and only the structure of the gas blowing hole is different, so the description of the same components will be omitted below, and the structure of the gas blowing hole will be omitted. Only explained. FIG. 1 is a diagram for explaining a distributor of the present invention, and FIG. 2 is a diagram for explaining gas blowing holes in the present invention. As shown in FIG. 1, the gas blowing holes 10 are alternately provided in a circumferential direction with a downward angle θ of about 45 ° at a pitch of about 60 mm. Of course, they may be provided not toward the circumferential direction but toward the same side as shown in FIG. The dispersibility of gas is better when they are provided alternately in the circumferential direction. If the gas blow-out hole is facing upward, it is easy for molten lead, etc. to enter, so θ
Is preferably smaller than 90 °, and the angle θ is preferably about 30 ° to 60 ° in order to enhance the effect that the downwardly jetted gas rises in the gas permeable stamp material and stirs the molten steel.

As shown in FIG. 2, the gas blowing hole 10 of the present invention is characterized by having a funnel shape (or an umbrella shape). In this way, if the blowing hole is funnel-shaped,
The flow velocity of the gas blown out at the upper side of the outer edge of the blowout port is higher than that at the lower side, and even if molten lead is attached to the upper portion of the outer edge of the blowout port, it is easily scattered and absorbed in the stamp material on the outside. On the other hand, the liquid molten lead attached to the lower part of the outer edge of the blowout port is hard to scatter, but it is easy for the molten lead to move to the surrounding stamp material due to the vibration of the entire furnace body or the vibration during the gas blowing, so the molten lead as a whole is around the hole periphery. It becomes difficult to adhere to. Also,
Even if they adhere, the distance of the inner surface of the hole until they reach the inside of the pipe increases, so that it is less affected by the fluctuation of the gas pressure when the gas is blown out, and the molten lead is less likely to enter. Further, since the pore diameter becomes large, the capillarity phenomenon is less likely to occur, and the contact resistance of the droplets adhering to the inner surface of the pore is reduced accordingly, so that the release gas pressure is increased and molten lead that has entered the pore is easily It becomes possible to discharge.

Since the surrounding stamp material is coarse particles of 3 to 8 mm, it is necessary to make the diameter of the bottom of the funnel-shaped hole smaller than this. If the hole diameter at the bottom is reduced, not only coarse particles but also molten non-ferrous metal can be made difficult to enter. However, if the pore size is made smaller, more pressure must be applied in order to eject the required amount of gas, and increasing the pressure is not preferable because there is a risk of splashing of molten steel, and in order to avoid increasing the pressure. Since many blow holes must be narrowed, the bottom hole diameter is preferably about 1 mmφ. The gas blowing hole 10 preferably has not only the funnel-shaped portion 10a but also the straight portion 10b (FIG. 2). Considering the strength of the hole, the straight portion 10b is about 1/5 of the pipe wall thickness. Is preferably left. The angle α of the funnel-shaped portion is 9
The angle is preferably 0 ° to 120 °. When the angle is 90 ° or less, the distance between the gas blowing hole and the outer peripheral portion of the funnel becomes short, and the effect is small. If the angle is 120 ° or more, it becomes difficult to balance the diameter of the gas outlet with the depth of the funnel-shaped portion. In order to smoothly discharge the gas, it is necessary that the total area of the cross section of the gas blowing hole and the cross-sectional area of the gas introduction pipe are approximately the same.

[0011]

As described above, according to the present invention, the non-ferrous metal such as molten lead is less likely to enter the gas blowing device, and even if the non-ferrous metal enters, it is easy to discharge the non-ferrous metal. It is possible to extend it significantly compared to that of
Therefore, the repair interval becomes long, the operating efficiency can be improved, and the steelmaking cost can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a gas distribution device of the present invention.

FIG. 2 is a diagram illustrating a gas blowing hole of the present invention.

FIG. 3 is a diagram illustrating a conventional gas blowing device.

FIG. 4 is a diagram illustrating a conventional gas distribution device.

FIG. 5 is a view showing a gas blowing hole.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Element for blowing gas, 2 ... Irregular refractory material having air permeability, 3 ... Refractory material having no air permeability, 4 ... Container, 5 ...
Gas introducing pipe, 6 ... Distributor, 7 ... Electric furnace body, 8 ... Gas blowing hole, 9 ... Molten lead attached, 10 ... Gas blowing hole, 10a ... Funnel-shaped portion, 10b ... Straight portion.

Claims (2)

[Claims] 1. An annular pipe embedded in a breathable amorphous refractory at the bottom of an electric furnace and having a plurality of gas blowing holes narrowed obliquely downward for blowing gas from the furnace bottom to stir molten steel. A gas blowing device comprising a gas introduction pipe connected to the annular pipe from outside the furnace, wherein the gas blowing holes of the annular pipe are funnel-shaped or umbrella-shaped . 2. The electric furnace bottom gas blowing device according to claim 1, wherein the funnel-shaped or umbrella-shaped gas blowing hole includes a funnel-shaped portion and a straight portion.