JP7647787B2 - Vacuum degassing device and method for preventing deformation of lower tank - Google Patents

Description

The present invention relates to a vacuum degassing device and a method for preventing deformation of the lower tank.

In the secondary refining of molten steel in the steelmaking process, the RH (Ruhrstahl-Heraeus) process is a typical secondary refining method, and a vacuum degassing apparatus with two immersion tubes (also called an RH vacuum degassing apparatus) is used as a device for carrying out this RH process. In the RH process, two immersion tubes installed at the bottom of the vacuum degassing apparatus are immersed in the molten steel for processing. For this reason, in the past, in order to safely cool the immersion tubes, which are the parts that come into direct contact with the molten steel, cooling methods that devise a cooling liquid circulation method have been used (see, for example, Patent Document 1). In addition, there are also examples in which a double-layered heat shield is installed on the immersion tube to reduce the amount of cooling required for the flange part of the immersion tube and the return tube (see Patent Document 2).

JP 2014-218711 A Japanese Utility Model Publication No. 60-56756

The methods described in Patent Document 1 and Patent Document 2 can cool the immersion tube that comes into direct contact with the molten steel, but cannot prevent thermal deformation of the lower tank. In addition, applying the method described in Patent Document 1 to the lower tank requires providing a cooling pipe in the lower tank as well, which complicates the equipment, and when applying the method to existing equipment, significant modifications to the equipment, including the cooling pipes, are required.

Therefore, the present invention has been made with a focus on the above-mentioned problems, and aims to provide a vacuum degassing device and a method for preventing deformation of the lower tank that can prevent thermal deformation of the lower tank in a simple manner.

(1) According to one aspect of the present invention, there is provided a vacuum degassing apparatus having a lower tank with two reflux pipes, the lower tank having a heat shield disposed below the bottom surface of the main body of the lower tank and between the two reflux pipes.

(2) In the vacuum degassing apparatus described above in (1), the heat insulating plate is configured to be removable.
(3) In the vacuum degassing apparatus described in (1) or (2) above, the lower tank further includes a cooling means for cooling the heat insulating plate.

(4) In the vacuum gas system described in any one of (1) to (3) above, the length of the heat shield in the depth direction perpendicular to the lateral direction in which the two return pipes are arranged when viewed from the bottom is equal to or greater than 1/2 the diameter of the return pipes.

(5) According to one aspect of the present invention, there is provided a method for preventing deformation of a lower vessel having two reflux pipes in a vacuum degassing apparatus, the method comprising providing a heat shield below the bottom surface of the main body of the lower vessel and between the two reflux pipes.

According to one aspect of the present invention, a vacuum degassing device and a method for preventing deformation of a lower tank are provided that can prevent thermal deformation of the lower tank in a simple manner.

1 is a front cross-sectional view showing a vacuum degassing apparatus according to an embodiment of the present invention. FIG. 4 is a front cross-sectional view showing the lower tank. FIG. 1A and 1B are schematic diagrams showing a lower tank, in which (A) is a plan view and (B) is a side view. FIG. 13 is a bottom view showing a modified example of the lower tank. FIG. 11 is a front cross-sectional view showing a modified example of the lower tank.

In the following detailed description, an embodiment of the present invention will be described with reference to the drawings. In the description of the drawings, identical or similar parts are given the same or similar reference numerals, and duplicate explanations will be omitted. The drawings are schematic and may differ from the actual product. In addition, the embodiments shown below are examples of devices and methods for embodying the technical concept of the present invention, and the technical concept of the present invention does not specify the materials, structure, arrangement, etc. of the components as described below. The technical concept of the present invention may be modified in various ways within the technical scope defined by the claims.

<Configuration of Vacuum Degassing Apparatus>
A vacuum degassing apparatus 1 according to an embodiment of the present invention will be described. As shown in Fig. 1, the vacuum degassing apparatus 1 is an apparatus that performs a degassing refining process using the RH method, which is one of the secondary refining processes, on molten steel 3 contained in a ladle 2, and is also called an RH vacuum degassing apparatus. The ladle 2 also contains slag 4 floating on the bath surface of the molten steel 3. The vacuum degassing apparatus 1 includes a vacuum chamber 5 consisting of an upper chamber 6 and a lower chamber 7, two immersion tubes 8, a duct 9, a raw material inlet 10, and a top blowing lance 11.

The upper vessel 6 and the lower vessel 7 are vessels connected vertically. A duct 9 is connected to the top of the upper vessel 6, and the vacuum vessel 5 is evacuated through the duct 9. The top blowing lance 11 is a lance that blows oxygen gas and a flux into the molten steel 3 in the vacuum vessel 5. The raw material inlet 10 adds auxiliary raw materials such as alloys and fluxes to the molten steel 3 in the vacuum vessel 5. The two immersion tubes 8 are cylindrical members whose lower parts are covered with refractory material and are immersed in the molten steel 3, and are respectively connected to the two reflux pipes 71 of the lower vessel 7. The immersion tubes 8 are also configured to be able to blow in reflux gas (also called reflux gas).

In such a vacuum degassing apparatus 1, two immersion tubes 8 are immersed in the molten steel 3 contained in the ladle 2, and the air in the vacuum chamber 5 is exhausted through a duct 9 by an exhaust system (not shown), thereby sucking the molten steel 3 into the vacuum chamber 5. Then, reflux gas is blown in from one of the immersion tubes 8, causing the molten steel 3 to reflux through the two reflux tubes 71, thereby carrying out the degassing process. In addition, auxiliary materials are added and oxygen gas is blown from the top blowing lance 11, as necessary.

(Configuration of the lower tank)
As shown in Fig. 2, the lower vessel 7 is covered with an iron shell on the outside and is provided with a refractory material on the inside. As shown in Figs. 1 to 4, the lower vessel 7 has a cylindrical main body 70 with a bottom, two reflux pipes 71, a heat shield 72, a support member 73, and a cooling means 74. In the following description, a direction parallel to the vertical direction when the lower vessel 7 is installed in the vacuum degassing apparatus 1 (e.g., the vertical direction in Figs. 1 and 2) is referred to as the vertical direction, a direction parallel to the horizontal direction in which the two reflux pipes 71 are arranged (e.g., the left-right direction in Figs. 1 to 3) is referred to as the horizontal direction x, and a direction parallel to the horizontal direction and perpendicular to the horizontal direction x (e.g., the vertical direction in Fig. 3) is referred to as the depth direction y.

The two return pipes 71 are cylindrical members to which the two immersion pipes 8 are respectively connected, and as shown in FIG. 3, they penetrate the bottom of the main body 70 in the vertical direction and are spaced a predetermined distance apart in the horizontal direction. Note that in FIG. 3, the flanges of the return pipes 71 for connecting to the immersion pipes 8 are omitted.

The heat shield 72 is a plate-like member provided below the bottom surface of the main body 70, and two pieces are provided separately in the depth direction. The heat shield 72 is arranged in the center (center of the bottom surface) of the main body 70 when viewed from the bottom, and is provided between the two reflux pipes 71. When the heat shield 72 is installed in the lower tank 7, the part where it overlaps with the reflux pipe 71 (the lateral end at the center of the depth direction) is cut out in an arc shape, and the radius of this arc is approximately the same as the radius of the outer circumference of the reflux pipe 71. The heat shield 72 is provided at a predetermined distance from the bottom surface of the main body 70. This distance is not particularly limited, but is appropriately set according to the equipment specifications so that the heat insulating effect of the air layer between the bottom surface of the main body 70 and the heat shield 72 is sufficiently obtained as described below, and thermal deformation of the heat shield 72 is suppressed. Furthermore, the material of the heat shield 72 is not particularly limited as long as it provides the above-mentioned heat insulating effect and sufficiently suppresses deformation, and may be, for example, iron, refractory material, ceramics, etc. From the viewpoint of the cooling effect described below, it is preferable that the heat shield 72 is made of iron. Also, by making the heat shield 72 out of iron, it is possible to prevent deterioration of the heat shield 72 during use and damage due to insufficient strength, etc.

The size of the heat shield 72 is not particularly limited, but in order to prevent thermal deformation of the lower tank 7 due to the heat insulating effect described below, it is preferable that the shape dimensions of the heat shield 72 when viewed from the bottom are as follows. It is preferable that the horizontal length Lx (see FIG. 3) of the heat shield 72 is equal to or greater than the distance a between the two reflux pipes 71, or equal to or greater than the diameter (outer diameter) D of the reflux pipe 71. It is also preferable that the depth direction length Ly of the heat shield 72 is equal to or greater than 1/2 of the diameter D, and more preferably equal to or greater than the diameter D. It is also preferable that the heat shield 72 is disposed on both sides in the depth direction y of the line P connecting the centers of the two reflux pipes 71. Furthermore, the shape is not limited to a square, and may be other shapes.

The support member 73 is a member that supports the heat shield 72, and is, for example, a rail on which the heat shield 72 can be installed. The support member 73 may be provided by being fixed to the bottom surface of the main body 70, or may be provided by being fixed to another structure. In this embodiment, as an example, the support member 73 is a rail that supports both lateral ends of the heat shield 72 and the depth end on the center side of the bottom surface. The heat shield 72 is installed by being placed on the rail, which is the support member 73, and is configured to be removable.

The cooling means 74 is a mechanism for cooling the heat shield 72, and in the present embodiment, as an example, it is a nozzle that cools the heat shield 72 by injecting air. The cooling means 74 is provided so that the direction of air injection is approximately horizontal, and the injected air hits the heat shield 72. The cooling means 74 is not particularly limited as long as it can cool the heat shield 72 and does not react with the molten steel 3 or the slag 4, but it is preferable that it is an air-cooled means in consideration of cost and ease of installation. In addition, by using the air-cooled means as the cooling means 74, it is possible to apply the cooling means 74 to existing equipment without the need for large-scale modifications, compared to the case where a mist cooling pipe is used as the cooling means. In addition, when a mist cooling pipe is used as the cooling means 74, it is difficult to install and remove it, and there is a possibility of a steam explosion when a water leak occurs due to equipment failure, etc., but by using the air-cooled means 74, such problems are also eliminated.

In the vacuum degassing apparatus 1 according to this embodiment, an air layer is formed between the bottom surface of the main body 70 of the lower vessel 7 and the heat shield 72. The insulating effect of this air layer suppresses heating of the bottom surface of the main body 70 due to radiant heat from the molten steel 3, thereby preventing thermal deformation of the main body 70 of the lower vessel 7. Furthermore, since the vacuum degassing apparatus 1 according to this embodiment has a cooling means 74 for cooling the heat shield 72, the insulating effect is further improved and deformation of the heat shield 72 can also be suppressed.

In addition, in the vacuum degassing apparatus 1 according to this embodiment, the heat shield 72 is formed in a rectangular shape with an arc-shaped cutout at the portion where it overlaps with the reflux pipe 71, thereby making it possible to reduce the gap between the heat shield 72 and the immersion pipe 71 and blocking radiant heat from this gap. As a result, thermal deformation of the lower tank 7 can be suppressed more effectively than when the gap between the heat shield 72 and the immersion pipe 71 is large, for example when the cutout portion is rectangular.

Furthermore, the vacuum degassing apparatus 1 according to this embodiment can reduce the number of parts used to suspend the heat shield 72 and simplify the configuration compared to when a large heat shield is installed under the lower tank using bolts and hooks. Therefore, even when removing the heat shield 72 due to splashing during operation, the removal can be easily performed without causing removal problems.

<Modification>
Although the present invention has been described above with reference to specific embodiments, it is not intended that the invention be limited by these descriptions. By referring to the description of the present invention, other embodiments of the present invention including various modifications in addition to the disclosed embodiments will be apparent to those skilled in the art. Therefore, it should be understood that the embodiments of the invention described in the claims also include embodiments including these modifications described in this specification, either alone or in combination.

For example, in the above embodiment, the heat shield 72 has a rectangular shape with the horizontal end at the center of the depth direction cut out into a fan shape when viewed from the bottom, but the present invention is not limited to such an example. The heat shield 72 may be provided below the center of the bottom surface of the main body 70, and may have a different shape and dimensions from those of the above embodiment. In addition, in the above embodiment, two heat shields 72 are provided side by side in the depth direction, but the present invention is not limited to such an example. The heat shield 72 may be a single plate as long as there is no interference with the reflux pipe 71. The heat shield 72 may also be further divided. As an example, Figures 5 and 6 show a case where the heat shield 72 is made of four plates. In the example shown in Figures 5 and 6, the heat shield 72 is divided into two in the depth direction and the horizontal direction, and when four plates are provided, it has the same shape as the heat shield 72 in the above embodiment. By increasing the number of heat shields 72, the installation of the heat shield 72 becomes easier. Furthermore, if there is a structure to which the support member 73 can be fixed at the center in the horizontal direction, the support member 73 can be easily installed at the center in the horizontal direction.

The present invention also provides a method for preventing deformation of the lower tank 7 having two reflux pipes 71 of the vacuum degassing device 1, in which a heat shield 72 is provided as in the above embodiment.

Reference Signs List 1 Vacuum degassing device 2 Ladle 3 Molten steel 4 Slag 5 Vacuum tank 6 Upper tank 7 Lower tank 70 Main body 71 Reflux pipe 72 Heat shield 73 Support member 74 Cooling means 8 Submerged tube 9 Duct 10 Raw material inlet 11 Top blowing lance

Claims (5)

A vacuum degassing apparatus having a lower vessel with two reflux pipes,
The lower vessel is a vacuum degassing apparatus having a heat shield divided into multiple parts that is disposed below the bottom surface of the lower vessel and between the two return pipes, and a support member that is fixed to the bottom surface of the lower vessel and on which both ends of the heat shield in the direction in which at least the two return pipes are aligned are placed . The vacuum degassing device of claim 1, wherein the heat shield is removable. The vacuum degassing device according to claim 1 or 2, wherein the lower tank further includes a cooling means for cooling the heat shield. The vacuum degassing device according to claim 1 or 2, wherein the length of the heat shield in the depth direction perpendicular to the lateral direction in which the two reflux tubes are arranged in a bottom view is at least half the diameter of the reflux tubes. A method for preventing deformation of a lower vessel having two reflux pipes of a vacuum degassing apparatus, comprising the steps of:
A method for preventing deformation of a lower tank, comprising providing a heat shield divided into multiple pieces below the bottom surface of the main body of the lower tank and between the two return pipes, and providing a support member in the lower tank that is fixed to the bottom surface of the lower tank and on which both ends of the heat shield in at least the direction in which the two return pipes are aligned are placed .

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