JPS5952923B2 - Secondary refining equipment for molten steel, etc. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a secondary refining apparatus for refining molten steel, etc., for refining molten steel, etc., tapped into a ladle or the like from a converter or the like outside the furnace.

Conventionally, molten steel that has been primarily refined in a converter or electric furnace is tapped from the furnace into a ladle, where alloys and deoxidizing agents are added to the molten steel to remove impurities such as oxygen. Secondary refining is performed outside the furnace to adjust the composition of steel to obtain the desired composition.

Various methods have been proposed as secondary refining methods. For example, in addition to using a vacuum degassing device to prevent molten steel from being oxidized by the atmosphere during processing, it also actively removes gases that are impurities in molten steel. There are vacuum degassing methods that perform simultaneous removal, and molten steel stirring methods that simply use gas to stir molten steel without using a vacuum degassing device.

Particularly representative of the latter molten steel stirring method is the so-called inert gas stirring method in which an inert gas is blown into the molten steel and the molten steel is stirred using floating blades of gas bubbles.

This technology of stirring molten steel using inert gas does not require any special equipment, just using a gas blowing nozzle or porous plug, and the processing method is simple. It has many characteristics as a technology.

However, the stirring force is weak, and due to the principle of stirring, the interface between the slag and molten steel is most strongly stirred. It is difficult to prevent this from occurring.

Another problem is that the oxygen concentration at the end of the treatment does not drop sufficiently due to oxygen flowing in from the slag.

Furthermore, when the blowing gas flow rate is increased to strengthen the stirring power, the slag layer on the surface of the molten steel bath at the gas bubble release position is removed to the surrounding area, and the molten steel comes into direct contact with the atmosphere, causing the molten steel to be heated by the oxygen in the atmosphere. It has the disadvantage of being oxidized and reducing refining efficiency.

In response to this, a device as shown in FIG. 1 has recently been proposed which improves on the drawback □ of the above-mentioned molten steel stirring method.

In this device, a porous plug 31 is attached to the bottom of a ladle 1, and an inert gas introduced from a pipe 32 is blown into the molten metal 34 in the ladle 1 as bubbles 33 through the porous plug 31. 35 is vertically inserted into the molten metal in the ladle 1 from above through the slag layer 3 so that the lower end of the cylinder 35 is immersed in the molten metal 34, exposing the molten metal surface without the slag layer inside this cylinder. This device allows the blown gas to escape from the exposed molten metal surface in the cylinder 35 into the atmosphere.

According to this device, mixing and agitation between the two phases that occur when the blown gas bubbles pass through the interface between the slag and the molten steel can be prevented, so that reactions between the two phases can be effectively prevented.

Further, since the gas phase in the cylinder in contact with the molten steel bath becomes a non-oxidizing atmosphere due to the dissipation of the blown gas from the molten steel, reactions between the atmosphere and the molten steel can be prevented.

However, although the device shown in Figure 1 has an excellent function in preventing reactions between molten steel and slag or molten steel and the atmosphere, it has no effect on improving stirring power compared to conventional technology. However, since the immersed refractory cylinder attenuates the kinetic energy of the upward flow of molten steel caused by gas bubbles, it causes problems such as a decrease in stirring power, and it is difficult to add alloying agents during processing, and in this respect, it is difficult to add alloying agents. It has the disadvantage that it is inferior to standard vacuum degassing equipment.

The present invention is applicable to secondary refining in which the purpose is not to degas H, N, etc. in molten steel, but to promote deoxidation reaction and equalize alloy component concentration and temperature by stirring the molten steel. We provide secondary refining equipment that can prevent reactions between molten steel and slag or molten steel and the atmosphere, has a sufficiently low oxygen concentration after treatment, is excellent in deoxidation treatment, has a high yield of additive alloys, and is easy to adjust components. The purpose is to

This invention fluctuates the gas pressure in the immersion tube and cylinder immersed in the ladle, thereby causing the ladle self-melting steel to flow into the cylinder (lifted by vacuum suction) or flow out (drop). This is a device for stirring self-molten steel in a ladle, and at the same time directly injecting an alloying agent into the molten steel.

FIG. 2 of the drawings shows the device of the present invention, and the reference numeral 1 in the drawing shows the device of the present invention.
2 indicates a ladle, 2 indicates molten steel in the ladle, and 1.3 indicates molten steel slag.

The molten steel stirring technique involves immersing a gas injection immersion pipe 4 into the molten steel 2 in the ladle to a predetermined depth, and injecting inert gas or the like to stir the molten steel.

In the case of the present invention, a cylinder consisting of three parts: a lower cylinder 5, a middle cylinder 6, and an upper cylinder 7 are concentrically connected to the upper part of the immersion tube 4 to form a main body.

The cylinder, except for the upper cylinder 7, is lined with refractory material and has a flange 5a.

Each can be divided via 6a.

By having a structure that can be divided in this way, the deposited metal grows inside the cylinder due to splashes, etc., and flows into the pressurized gas pipe and alloying agent injection shoe 1, which will be described later, which are open facing the inside of the cylinder. When a situation arises that causes a blockage,
This has the advantage of simplifying maintenance and partial replacement work.

On the other hand, the upper cylinder 7 is cut off from the mountain cylinder 6, and inside thereof there is a pressurized gas pipe 8. A reduced pressure gas pipe 9 is housed therein.

The lower ends of these gas pipes 8° 9 project into the middle cylinder 6 and are arranged so as to face the molten steel 2.

Incidentally, these gas pipes 8 and 9 are connected to the original piping outside the cylinder via extendable hoses 10 and 11, respectively, so as to absorb the vertical movement of the cylinder.

Further, a part of a multi-stage alloying agent cutting device capable of shielding the internal pressure at each stage is disposed inside the upper cylinder.

This alloy agent cutting device is composed of a chute and a hopper, which are arranged in multiple stages in series, and dampers 21 and 22 are provided at the hopper outlet of each stage to open and close by operating cylinders 19 and 20. , made it possible to shield.

The reason why each stage is shielded in this way is because the pressure inside the cylinder is adjusted in order to stir the molten steel 2 in the ladle 1, so when adding the alloying agent, there is no direct connection between the inside and outside of the cylinder. Due to the need to prevent and demarcate the upper hopper of atmospheric pressure.

The alloying agent cutting device shown in the drawing is one embodiment, and has a charging chute 13 whose lower end protrudes into the cylinder as the lowest part, and a lower hopper 14 and a relay shoe 1 extending upward.
~15, this is an example in which the upper hopper 161, the introduction chute 17, and the cutting chute 18 are connected.

In short, by opening and closing the dampers 21 and 22, the alloying agent is introduced into the ladle self-melting steel 2 while being isolated from the atmosphere.

Pressurized gas pipe 8 and depressurized gas pipe 9 protruding into the cylinder mentioned above
, and the opening direction of the lower end of the charging chute 13 are respectively oriented parallel to the cylindrical axis direction.

This is mainly due to the fact that the alloying agent is poured directly into the molten steel 2, since the cylinder has a small diameter, so it tends to collide with the inner wall of the cylinder, potentially damaging the refractory layer. It is effective for

However, in order to avoid damaging the alloying agent even if it collides with the inner wall of the cylinder, for example, if the particles are fine, the opening direction of the input chute must be the same as the axial direction of the cylinder. There isn't.

Furthermore, the above restriction is also removed when the cylinder is used obliquely with respect to gravity.

The upper part of the cylinder is attached to an elevating bowl 24 that moves up and down along a pole 23 by a drive device (not shown), and can be immersed in molten steel or taken out of the ladle 1.

Next, the operation of this prime device will be explained.

Gas flow control valves 25, 26 and electromagnetic valves 27, 28 are installed in the middle of two lines of piping arranged in the upper part of the cylinder: a pressurized gas pipe 8 containing high-pressure inert gas, and a depressurized gas pipe 9. These are opened and closed via a controller 30 that responds to instructions from a pressure detector 29 attached to a cylinder.
By controlling the pressure inside the cylinder, molten steel is stirred by flowing into and out of the cylinder.

On the other hand, the alloying agent is added as follows.

A predetermined amount of alloying agent is cut out from the bunker into a cutting chute 18, passed through an introduction chute 17, and stored in an upper hopper 16.

At this time, the damper 22 at the bottom of the upper hopper 16 is closed and is shielded from the subsequent feeding path.

Next, the damper 22 is opened and the alloying agent is introduced into the lower hopper 14 through the relay chute 15.

At this time, the damper 21 at the lower end of the lower hopper 14 is closed and completely isolated from the interior of the inner cylinder and dipping tube 4.

After closing the damper 22, the damper 21 connected to the charging chute 13 is opened to discharge the alloying agent into the cylinder.

The alloying agent is added by repeating this operation.

The invention as described above has the following excellent effects firstly.

(1) Inside the ladle: The interface between the molten steel and the slag layer covering the steel bath surface is not stirred.

This prevents the molten steel from reacting with the highly oxidized slag that is unavoidably injected into the ladle at the same time as the molten steel from the converter, reducing oxidation loss of the alloy during processing and reducing the oxygen concentration after processing. descend.

(2) The molten steel comes into direct contact with the gas phase only at the bath surface inside the cylinder, and by creating an inert gas atmosphere inside the cylinder, oxidation of the molten steel by the atmosphere can be prevented.

(3) By changing the period and magnitude of the pressure fluctuation of the gas phase inside the cylinder, any desired stirring force can be obtained, and by changing the depth of immersion in the cylinder, the molten steel can be particularly stirred to a desired depth in the ladle. Can be stirred vigorously.

(4) Since there are no mechanically moving parts and the device is simple, the device construction cost is low and the processing cost is also low.

(5) Since there are no mechanically moving parts, it is easy to control the cycle of inflow and outflow of molten steel, and high-speed operation is easily possible by reducing the cycle to several seconds or less to increase the stirring force.

(6) Since it does not require a high vacuum of several mmFf or less like a normal vacuum degassing device, there is no need to use large-scale equipment, and pressurization and depressurization operations can be easily performed without time delay with a simple device. This makes it possible to increase the flow velocity of the molten steel flowing out from the cylinder, which serves as the stirring force for the molten steel in the ladle, by a pressurizing operation that is particularly industrially easy.

Secondly, the device of the present invention is equipped with an alloying agent cutting device and is configured to be able to adjust the pressure during the process of adding the alloying agent, so it is easy to supply the alloying agent into the ladle where the pressure fluctuates rapidly. It is.

Thirdly, making the cylinder divisible has an effect in terms of repair time and cost.

Fourthly, since the opening direction of the alloying agent injection chute is set in the direction of the tube axis of the cylinder, the cylinder is not damaged when the alloying agent is introduced, and the life can be improved.

[Brief explanation of the drawing]

FIG. 1 of the drawings is a sectional view showing an example of a conventional inert gas stirring device, FIG. 2 is a sectional view of the device of the present invention, and FIG. 3 is a route diagram of a pressure control system. 1... Ladle, 2... Molten steel, 3...
...Slag, 4...Dipping tube, 5...Lower cylinder, 6...Middle cylinder, 7...Upper cylinder, 8... - Pressurized gas pipe, 9... Decompression gas pipe, 10.11... Hose, 13...
...Input chute, 14...Lower hopper, 1
5...Relay chute, 16...Upper hopper, 17...Introduction chute, 18...
... Cutting chute, 19, 20... Cylinder, 21, 22... Damper, 23...
・Paul, 24... Lifting bowl, 25, 26...
... Gas flow control valve, 27.28 ... Solenoid valve, 29 ... Pressure detection valve, 30 ... Controller.

Claims (1)

[Claims] 1 In a device that stirs the molten metal in the container by inserting and immersing the immersion tube into a container holding molten metal, and varying the gas pressure inside the immersion tube to lift or drop the molten metal into the tube, the upper part of the immersion tube Connect a cylinder that can be divided into
A depressurized gas pipe and a pressurized gas pipe are arranged in the upper part of the cylinder, and an alloying agent cutting device consisting of a chute and a hopper that can shut off each stage via a damper is arranged. Secondary refining equipment.