JPH06192718A - Method for blowing in oxygen or oxygen-containing gas without wearing lance - Google Patents

Abstract

PURPOSE:To improve the utilizing efficiency of oxygen-containing gas, to suppress the spattering of molten metal and slag and to prevent the wearing of the lance by regulating blowing direction and blowing velocity, etc., of the lance for oxygen-containing gas from the upper part. CONSTITUTION:In a DC electric furnace 1 arranged with an upper electrode 6 and a furnace bottom electrode 7 in the furnace body 4, the lance 10 for blowing in oxygen and a lance 11 for blowing in powdery material are inserted from an operating hole 9, and by blowing in the oxygen or the oxygen- containing gas and the powdery material for refining into the molten metal 8 from the upper part, the refining is executed. Then, the height (h) from the surface of the molten metal 8 to the blowing out position of the lance 10 for blowing in oxygen is set at 300-700mm and the angle theta in the blowing out direction is made >=30 deg.. Further, the ratio L/H of L by equation VaXd=0.73X (L/sintheta<1.54>)<1/2>X(h+L/ sin theta<1.54>) (wherein, Va: gas flowing velocity Nm/sec, d: throat diameter of a widened end nozzle mm, L: recessed depth of the molten metal by blowing in mm) the ratio of the L and depth H of the molten metal 8 is made 0.4-0.7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric furnace used for melting a metal material, refining a molten metal, etc., in which oxygen is blown into the molten metal from above at supersonic speed, and powder is added as needed. The present invention relates to a method for blowing oxygen or an oxygen-containing gas that does not exhaust the blowing lance.

[0002]

2. Description of the Related Art As an electric furnace used for melting metal materials, refining molten metal, etc., it is attached to electrodes placed above the metal materials charged in the furnace and furnace walls such as the bottom and side walls of the furnace. A DC electric furnace that melts metal materials and smelts molten metal by passing an electric current between the electrodes and the three electrodes that are placed above the metallic materials charged in the furnace. An alternating current electric furnace for melting a metal material and refining a molten metal is known.

In this type of electric furnace, in order to promote the melting of metal materials and the refining of molten metal, the operation of blowing oxygen and powder into the molten metal in the furnace is generally performed using a pipe. There is.

Conventionally, an operator has carried out a work of holding a pipe for blowing oxygen and powder and blowing it into a furnace. For example, as shown in Japanese Utility Model Laid-Open No. 2-38457, the pipe is mounted on a self-propelled carriage. A device has been proposed which is mounted on a machine to hold a pipe for mechanically blowing oxygen and powder and sends it into the furnace, which reduces the heavy work of the worker and the work in a high temperature environment.

On the other hand, in a converter for refining molten metal, for example, as shown in Japanese Patent Application Laid-Open No. 1-219116, a non-consumable lance water-cooled from above is used for refining into the furnace. It is blowing.

[0006]

However, for example, in the method disclosed in Japanese Utility Model Laid-Open No. 2-38457, an ordinary pipe is used as a pipe for blowing oxygen and powder, and the flow velocity at the pipe outlet is , The speed of sound is not exceeded, and oxygen and powder do not penetrate sufficiently into the molten metal.

Therefore, in order to improve the utilization efficiency of oxygen and powder, it is necessary to immerse the pipe in the molten metal for use, and the pipe is gradually consumed, and the pipe is supplied to the self-propelled carriage by an operator. Need to do. Such complicated work occurs, and the cost of the consumed pipe becomes enormous.

On the other hand, in a converter for refining molten metal, a non-consumable lance is put into practical use because the lance cooled with water is blown into the furnace from the upper part. Since the height from the surface to the opening is 10 m or more, the scattering of molten metal and slag does not pose a problem.

However, in the electric furnace, the height to the furnace lid is about 2 m, so that the non-consumable lance that is practically used in the converter cannot be applied as it is, and in the electric furnace, Considering that it is used to accelerate the melting of metallic materials, the lance is charged from the work port, which is very different from the way it is used in the converter. It is difficult to apply to an electric furnace.

The object of the present invention is to enjoy the advantages of abolishing the conventional complicated work and reducing the cost of the consumable pipe, and also dramatically improving the utilization efficiency of oxygen or oxygen-containing gas and carbon powder, and An object of the present invention is to provide a method for injecting oxygen or an oxygen-containing gas that does not consume a lance and can be operated safely with minimal scattering of slag.

[0011]

A method of blowing oxygen or an oxygen-containing gas which does not consume a lance according to the present invention is a method of blowing oxygen or an oxygen-containing gas into a molten metal from above, in which the surface of the molten metal is blown. Height h to the blowing position of the oxygen or oxygen-containing gas lance is 300 m
In the range of m to 700 mm, the angle θ between the surface of the molten metal and the blowing direction of the lance for oxygen-containing gas is 30 degrees or more, and the dent of the molten metal due to blowing at the blowing point using the following calculation formula It is characterized by blowing so that the ratio of the depth L and the bath depth of the molten metal is in the range of 0.4 to 0.7.

[0012]

[Equation 2]

[0013]

The supersonic jet can be obtained by using the divergent nozzle used in the lance of the converter. Considering only the reaction, the greater the dent of the molten metal due to the supersonic jet of oxygen, the higher the utilization efficiency of oxygen,
Moreover, the stirring of the molten metal bath becomes vigorous, and the larger the dent of the molten metal, the better.

However, if the dent depth L of the molten metal becomes too deep, it reaches the furnace bottom and the refractory at the furnace bottom is eroded, which causes a problem. The relationship is shown in FIG. As can be seen in this figure, as the depth of the molten metal (L) / the depth of the molten metal bath (H) increases, the wear of the refractory on the furnace bottom increases, and L / H exceeds 0.7 in particular. And the wear of the refractory on the bottom of the furnace becomes significantly large. Therefore, by setting L / H to 0.7 or less, it is possible to suppress the wear of the refractory material on the furnace bottom due to the blowing of the supersonic jet.

Further, when oxygen and powder are blown into the furnace by a conventional pipe, the depth of immersion of the pipe into the molten metal is
Since the pipe will be melted, the bath depth of molten metal will be 0.3 at most.
Approximately 0.4, and the advantage of the non-consumable lance is L / L in order to eliminate pipe cost, abolish complicated work such as pipe supply, and improve the utilization efficiency of oxygen and powder.
H must be 0.4 or more, so that the ratio of the depth of the molten metal indentation to the depth of the molten metal bath is 0.4 to 0.
A range of about 7 is appropriate.

On the other hand, depending on the blowing conditions, the molten metal or the slag may be severely scattered, which not only deteriorates the yield but also hinders the operation. The scattering of the molten metal or slag mainly occurs in the furnace wall (horizontal) direction and the upward direction of the blowing direction. The angle θ between the surface of the molten metal and the blowing direction of the oxygen lance (hereinafter, referred to as the blowing angle) is dominant in the scattering of the molten metal or slag in the furnace wall (horizontal) direction of the blowing direction. The relationship is shown in FIG.
As can be seen from this figure, as the blowing angle θ becomes smaller, the molten metal is more scattered to the furnace wall side, the wear of the furnace wall becomes more severe, and the refractory or However, the wear of the water cooling box is significantly increased.

The upward splash of molten metal or slag is
The height h from the surface of the molten metal to the blowing position of the divergent nozzle of the oxygen lance (hereinafter referred to as the blowing height) is dominant, and the relationship is shown in FIG. When the lance is brought closer to the bath surface at the same gas flow rate, the scattering height gradually increases, but the dent of the molten metal until the scattering height reaches a peak at a certain lance height is a smooth concave shape.

When the lance is further brought closer to the bath surface, the flying height decreases, but after the flying height reaches the peak, the smooth concave shape of the dent portion of the molten metal collapses and the dent appears. This is because bubbles are entrained in the part and the kinetic energy of the gas is efficiently transmitted to the molten metal side.

That is, the ratio of the kinetic energy of the gas that contributes to the stirring of the molten metal increases due to the change in the shape of the recessed portion, and the energy spent for scattering the molten metal and the like decreases relatively.

When blowing into an electric furnace with a height of about 2 m to the furnace lid, as shown in this figure, the scattering height is about 2 m.
In the following, the lance height needs to be 700 mm or less in order to cause the inclusion of bubbles in the dent portion. This makes it possible to suppress the scattering of the molten metal or the slag and enhance the stirring of the molten metal.

Further, by setting the blowing height h to be 700 mm or less, the nozzle blowing position is immersed in the formed slag. Therefore, when the slag is forming, scattering of molten metal is captured by the slag. , The effect of reducing is also derived.

On the other hand, the required height for preventing large lumps of molten metal from being blown into the lance constantly is about 3
If it is less than this height, it will damage the lance itself and shorten the life of the lance, and the frequency of repairing the tip of the lance or replacing the lance itself will increase. Because the merit of abolishing complicated work, which is one of the above, cannot be fully enjoyed,
The blowing height must be 300 mm or more.

In a blowing method in which oxygen or an oxygen-containing gas is blown into the molten metal from above without consuming the lance,
The height h from the surface of the molten metal to the blowing position of the oxygen lance is in the range of 300 mm to 700 mm, and the angle θ formed by the blowing directions of the molten metal and the oxygen lance is 30.
By blowing at a ratio of the dent depth L of the molten metal due to the blowing at the blowing point to the bath depth of the molten metal in the range of 0.4 to 0.7 This is an epoch-making operation that can enjoy the advantages of eliminating unnecessary work and eliminating the cost of consumable pipes, dramatically improving the utilization efficiency of oxygen or oxygen-containing gas, and minimizing the scattering of molten metal and slag. It is possible to provide a method of blowing oxygen or an oxygen-containing gas that does not consume the lance.

[0024]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view of a DC electric furnace to which the present invention is applied, and FIG. 2 is a diagram showing the relationship between the depth of molten metal indentation (L) / the depth of molten metal bath (H) and the wear index of the furnace bottom refractory due to blowing. FIG. 3 is a diagram showing the relationship between the angle θ formed between the surface of the molten metal and the blowing direction of the oxygen lance and the wear index of the furnace wall.

The DC electric furnace 1 shown in FIG. 1 comprises a furnace body 4 covered with a refractory 2 and a water-cooled box 3, and a furnace lid 5 arranged above the furnace body 4, and is elevated from the center of the furnace lid 5. Due to the direct current supplied to the free upper electrode 6 and the bottom electrode 7 arranged at the bottom of the furnace, the molten metal 8 of scrap mainly charged in the direct current electric furnace and the tip of the upper electrode 6 The scrap is melted or the molten metal 8 is heated by an arc formed between them. In order to assist the heating and refining of the molten metal 8, an oxygen blowing lance 10 water-cooled from a working port 9 provided in the furnace body 4 and a water-cooling lance 10 disposed below the oxygen blowing lance 10 are provided. A powder blowing lance 11 is placed in the furnace. The lances 10 and 11 can be adjusted in position in the furnace or retracted from the furnace by a driving device (not shown).

By using a divergent nozzle for the oxygen blowing lance 10, a supersonic jet can be obtained. Considering only the reaction, the greater the dent of the molten metal 8 due to the supersonic jet of oxygen, the higher the utilization efficiency of oxygen, and the more vigorous the stirring of the molten metal 8, the better the dent of the molten metal 8 becomes. .

However, the dent depth L of the molten metal 8
When the depth becomes too deep, it reaches the bottom of the furnace, and the refractory 2 on the bottom of the furnace is eroded, which causes a problem. The relationship is shown in FIG. As can be seen from this figure, the wear of the refractory 2 on the bottom of the furnace increases as the L / H increases, and particularly when the L / H exceeds 0.7, the wear of the refractory 2 on the bottom of the furnace significantly increases. For this reason,
By setting L / H to 0.7 or less, it is possible to suppress the wear of the refractory 2 on the furnace bottom due to the injection of a supersonic jet.

Further, when oxygen and powder are blown into the furnace by a conventional pipe, the depth of immersion of the pipe in the molten metal is 0.3 to the bath depth of the molten metal at most, because the pipe is melted and damaged.
It is about 0.4, and the advantage of non-consumable lance is L / H in order to eliminate pipe cost, abolish complicated work such as pipe supply, and improve the utilization efficiency of oxygen and powder.
Must be 0.4 or more, and therefore the molten metal 8
The ratio of the dent depth L and the bath depth H of the molten metal 8 is appropriately in the range of 0.4 to 0.7.

On the other hand, depending on the blowing conditions, the molten metal 8 or the slag becomes more severely scattered, which not only deteriorates the yield but also hinders the operation. Molten metal 8
Alternatively, the slag scattering mainly occurs in the furnace wall (horizontal) direction and the upward direction of the blowing direction. The angle θ between the surface of the molten metal 8 and the blowing direction of the oxygen blowing lance 10 (hereinafter referred to as the blowing angle) governs the scattering of the molten metal 8 or slag in the furnace wall (horizontal) direction of the blowing direction. The relationship is shown in FIG. As can be seen from this figure, the blowing angle θ
As the value becomes smaller, the amount of molten metal scattered to the furnace wall side increases and the furnace wall wears more severely.
If it is less than 0 degree, the wear of the refractory on the furnace wall or the water cooling box 3 becomes significantly large.

The upward scattering of the molten metal 8 or slag is dominated by the height h from the surface of the molten metal 8 to the blowing position of the divergent nozzle of the oxygen lance (hereinafter referred to as the blowing height). The relationship is shown in FIG. The flying height gradually increases as the lance is brought closer to the bath surface at the same gas flow rate, but the flying height has a peak at a certain lance height, and when the lance is brought closer to the bath surface, the flying height becomes higher. It is decreasing.

The dent of the molten metal 8 until the height of the scattering reaches a peak is a smooth concave shape. When the lance is brought closer to the bath surface, the flying height decreases, but after the flying height reaches the peak, the smooth concave shape of the dented portion of the molten metal 8 collapses and the dented portion appears. This is because bubbles are entrained and the kinetic energy of the gas is efficiently transmitted to the molten metal 8 side.

That is, the change in the shape of the dent portion increases the ratio of the kinetic energy of the gas that contributes to the stirring of the molten metal 8 and the energy consumed for scattering the molten metal 8 and the like relatively decreases. is there.

In order to have a flying height of about 2 m or less and to generate bubbles in the dented portion, it is necessary to set the blowing height to 700 mm or less. This can prevent the molten metal or the slag from scattering and enhance the stirring of the molten metal.

Further, by setting the blowing height h to be 700 mm or less, the blowing position of the nozzle is soaked in the formed slag. Therefore, when the slag is forming, the scattering of the molten metal is captured by the slag. , The effect of reducing is also derived.

On the other hand, the required height is about 300 mm so that large lumps of the molten metal 8 due to blowing do not steadily scatter on the lance. If the height is higher than this height, the lance itself may be damaged. You can use Lance without.

[0036]

As described above, the method of blowing oxygen or oxygen-containing gas which does not consume the lance of the present invention is
In the blowing method of blowing oxygen or an oxygen-containing gas into the molten metal 8 from above, the height h from the surface of the molten metal to the blowing position of the oxygen blowing lance 9 is 300 mm.
To 700 mm and the angle θ between the surface of the molten metal 8 and the blowing direction of the oxygen blowing lance 9 is 30.
Blow at a ratio of the dent depth L of the molten metal 8 due to the blowing at the blowing point to the bath depth of the molten metal in the range of 0.4 to 0.7 The oxygen and powder blowing pipe which was a product can be changed to a non-consumable type, the cost of the consumable pipe can be eliminated, and complicated work such as the supply work of the pipe to the truck etc. can be eliminated.

Further, the scattering of the molten metal 8 and slag is minimized to suppress the wear of the furnace wall, the steady scattering of a large mass of the molten metal to the lance is suppressed, and the damage to the lance itself is suppressed. Furthermore, since oxygen and carbon powder can be blown deeply into the molten metal, the utilization efficiency of oxygen and carbon powder can be dramatically improved, and safe operation can be achieved, not only automation of work but also improvement of productivity and energy cost. It greatly contributes to the reduction of, and its effect is extremely large.

[Brief description of drawings]

FIG. 1 is a sectional view of a DC electric furnace to which the present invention is applied.

FIG. 2 is a diagram showing the relationship between the dent depth (L) of the blown molten metal / the bath depth (H) of the molten metal and the wear index of the furnace bottom refractory.

FIG. 3 is a diagram showing the relationship between the angle θ formed between the surface of the molten metal and the blowing direction of the oxygen lance and the wear index of the furnace wall.

FIG. 4 is a relationship diagram of a height h from the surface of the molten metal to a blowing position of an oxygen lance and a scattering height of the molten metal.

[Explanation of symbols]

 1 DC Electric Furnace 2 Refractory 3 Water Cooling Box 4 Furnace Body 5 Furnace Lid 6 Upper Electrode 7 Furnace Bottom Electrode 8 Molten Metal 9 Working Port 10 Oxygen Blowing Lance 11 Powder Blowing Lance

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroki Hidaka 46-59 Nakahara, Tobata-ku, Kitakyushu City, Fukuoka Prefecture 46-59 Nippon Steel Corporation Machinery & Plant Division

Claims (1)

[Claims] 1. A blowing method of blowing oxygen or an oxygen-containing gas from above into a molten metal, wherein a height h from a surface of the molten metal to a blowing position of a lance for oxygen or an oxygen-containing gas is in a range of 300 mm to 700 mm. And the angle θ formed between the surface of the molten metal and the blowing direction of the oxygen-containing gas lance is 30 degrees or more, and the dent depth L of the molten metal and the molten metal due to the blowing at the blowing point are calculated using the following formula. The method for injecting oxygen or oxygen-containing gas that does not consume the lance, characterized in that the ratio with the bath depth is in the range of 0.4 to 0.7. [Equation 1]