JPH0776717A - Water-cooling ladle cover in ladle for refining metal - Google Patents

Abstract

PURPOSE:To prevent the excess heat conduction and to improve the water- cooling effect by efficiently and surely executing the formation of a heat insulating layer around heat conductive pipes in a water-cooling structure utilizing splash stuck by spattering to a water-cooling ladle cover. CONSTITUTION:The water-cooling ladle cover 10 in the ladle for refining the metal is formed as hat-shape by winding the heat conductive pipe 11 so as to abut on mutual pipes. The heat conductive pipe 11A positioned at the inside of an opening part of the ladle in the heat conductive pipes at the lowermost step contacting with the opening edge of the ladle 6, is arranged by projecting in the center axial direction in the opening part at the radius of the heat conductive pipe to the heat conductive pipe 11B just above the upper step.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to hot metal and molten steel under reduced pressure,
The present invention relates to a ladle lid having a water-cooling structure which is provided in a refining device for refining molten metal such as various other alloys, or a metal refining ladle used in a metal melting and refining device, etc.

[0002]

2. Description of the Related Art In a refining device or a metal melting and refining device for refining molten metal of ordinary steel, special steel, stainless steel, and molten steel, and alloys such as nickel alloys and chrome alloys under vacuum or reduced pressure. Is, for example, a metal refining ladle (hereinafter sometimes simply referred to as a ladle) in which the molten metal is injected and held in advance is installed at a predetermined position in the vacuum container, and then the decompression device outside the vacuum container is installed. To depressurize the inside of the vacuum vessel, and remove the molten metal held inside the ladle from the bottom of the ladle by introducing an inert gas such as argon gas supplied from the gas supply device outside the vacuum vessel. Oxygen gas is blown into the molten metal from the oxygen top blowing lance that can be moved up and down through the vacuum container and the ladle lid of the ladle while being stirred by being blown through the gas blowing nozzle provided in Refining is carried out such that the top-blown blowing.

Such an apparatus is capable of preferentially advancing the decarburization reaction to produce ultra-low carbon steel and alloys, degassing unnecessary gas in the molten metal, stirring the molten metal, and melting the molten metal. In recent years, many have been installed and used in order to effectively increase the amount and adjust the component composition.

In a refining apparatus for refining molten metal of this kind under reduced pressure, a ladle for refining metal is often used, and in particular, it is placed on a circular opening edge of the ladle so as to be openable and closable inside the ladle. The ladle lid that encloses the molten metal as much as possible is an indispensable member. This is because it is necessary for the following reasons.

There are cases in which the molten metal in the ladle has slag (layer) and cases in which it does not, but refining with the required metallurgical reactions under suitable temperature control by suppressing the temperature drop of this molten metal. In order to save energy especially when expensive electric energy is used as a heat source, the molten metal in the ladle, etc. The radiant heat radiated from the inside to the inner wall of the vacuum container and the seal is blocked, and the vacuum container is made highly airtight.
In order to extend the service life of the vacuum vessel and its decompression equipment, maintain light maintenance, and reduce the power required for the decompression equipment, the ladle outside the ladle due to bumping of the molten metal that occurs when the pressure inside the vacuum vessel is reduced That is, in order to prevent the outflow of the molten metal into the vacuum vessel, bumping of the molten metal described above, stirring of the molten metal by ladle bottom blowing of inert gas and blowing of oxygen gas from an oxygen top blowing lance, To prevent splashes caused by splashing and adhering to the circular opening edge of the ladle itself, the outer pig skin, and the inner wall and seal of the vacuum container outside the ladle, the ladle itself caused by the above items and paragraphs, This is to reduce the work of cleaning and repairing the inside of the vacuum container and the seal portion thereof, and to prevent the production yield of the refined molten metal from decreasing due to the above and items.

Conventionally, in a ladle used for refining a molten metal under such a reduced pressure, a ladle lid which is openably and closably mounted on the circular opening edge of the ladle is, for example, Japanese Patent Laid-Open Publication No. 56-146753, JP-A-2-205
As disclosed in Japanese Patent No. 619, a refractory structure having a refractory arranged along the inside of a steel frame and an iron skin forming a skeleton and an outer shell has been used. This ladle lid is placed directly above the ladle that holds a large amount of molten metal at a very high temperature of 1700 ° C or higher, for example, ensuring safety at the operating site and improving operability and workability. Therefore, uncooled ones are usually used, and they have the following problems.

(A) Under severe conditions of use, the refractory structure is easily deformed, and the refractory is worn, damaged, and easily dropped from this structure.

(B) For the reasons described above and paragraphs,
The molten metal spillage and splash adhere to the ladle lid and enlarge it, making it impossible to place or repeatedly use.

(C) Splash is adhered to the opening for raising and lowering the oxygen top blowing lance of oxygen gas, which is provided in advance in the refractory structure, the insertion port of the hopper duct for supplying iron alloy, etc., and the gas vent port. As it enlarges, it blocks each of these openings, making it difficult or impossible to operate.

(D) Due to the reasons (a) to (c) above, frequent inspections, repairs and repairs must be performed.

(E) Due to the reasons (a) and (d) above, the useful life of the ladle lid is shortened (for example, 100
It is uneconomical because it increases the service life of heat) and cost.

Therefore, recently, such a ladle lid has a refractory structure (body) having various problems described in the above items (a) to (e), and is referred to the above item (c). A metal pipe (steel pipe) that allows cooling water to pass through the ladle lid, except for the openings provided in the ladle lid in advance.
A water-cooled structure having a concentric circular shape or a zigzag spiral shape closely wound in an attached state, that is, the entire structure is wound in a hat shape has been tried.

[0013]

This ladle lid having a water cooling structure generally achieves the original functions (roles and purposes) of the ladle lid described in the above items 1 to 3, and the above (a) to (e). )
The problems of the conventional refractory structure described in Section 1 are solved and the service life is extended, which is advantageous in terms of refining operation, workability, maintenance, cost, etc. Since the energy loss carried away from the molten metal inside the ladle due to the heat removal effect of the cooling water to be watered increases, as described in the above paragraphs and paragraphs, while suppressing the temperature drop of the molten metal and slag to save energy, above all It is disadvantageous and problematic in terms of refining and producing good quality molten metal under suitable temperature control.

In other words, the energy corresponding to this energy loss has to be supplemented by appropriate means separately, resulting in cost increase and change in operation and working conditions, extension of the operation and working time, and the like. The problem remains that the advantage of water cooling cannot be utilized.

Therefore, an object of the present invention is to enable efficient and reliable formation of a heat insulating layer around a heat transfer tube in a water-cooling structure utilizing the attachment of splashes scattered as described above, and cooling water. Achieving the original function of the ladle lid described in the above items (1) and (a) by appropriately increasing the water cooling effect while preventing excessive heat removal by
It is an object of the present invention to provide a water-cooled ladle lid capable of comprehensively satisfying the problems of the conventional refractory structure described in (e).

[0016]

According to the present invention, in a water cooling ladle lid which is openably and closably mounted on a circular opening edge of a ladle used for metal refining, the water cooling ladle lid is Above the circular opening of the pan, heat transfer pipes made of steel pipe are wound so that the pipes are installed as much as possible, and formed into a hat shape, while cooling water is passed through this heat transfer pipe group. Of the group of heat transfer tubes arranged in series in the horizontal direction at the bottom of the ladle in contact with the circular opening edge of the ladle, the heat transfer tube located inside the circular opening of the ladle is the heat transfer tube immediately above it. And a water cooling ladle lid of a ladle for metal refining, which is arranged so as to project in the central axis direction within the circular opening of the ladle over the radius of the heat transfer tube.

Further, according to the present invention, when the heat transfer tube made of steel has a small diameter, a predetermined number of heat transfer tubes are further added in addition to the heat transfer tube located inside the circular opening of the ladle, and the series is arranged in series in the horizontal direction. It is characterized in that it is arranged so as to project.

Further, according to the present invention, the heat transfer tube has a tube diameter capable of passing a cooling water at a flow rate sufficient to withstand the radiant heat emitted from the molten metal and / or the slag layer held inside the ladle. Characterize.

[0019]

According to the present invention, the heat transfer tube located in the innermost circular opening of the ladle in the group of heat transfer tubes arranged in series in the horizontal direction at the lowermost stage in contact with the circular opening end edge of the ladle is With respect to the heat transfer tube immediately above it, the heat transfer tube is arranged so as to protrude in the direction of the central axis within the circular opening of the ladle, the radius of the heat transfer tube or more. Moreover, when this heat transfer tube has a small diameter, a predetermined number of heat transfer tubes are additionally provided in addition to the heat transfer tubes located inside the circular opening of the ladle, and the heat transfer tubes are arranged so as to project in series in the horizontal direction. In such a water-cooled ladle lid, in order to reduce and control the heat energy that is originally carried away by the cooling water, the size and shape of the water-cooling structure, including the diameter and material of the heat transfer tubes (Surface area, sealing of each opening, etc.)
There is a countermeasure technology to mitigate and adjust the heat conduction by the structure including, the temperature and temperature control of cooling water and the flow rate and flow rate control, and by lining a heat-insulating refractory on the surface of the heat transfer tube group. Such countermeasure technology is not basic and complicated, and it is not always satisfactory in terms of accuracy and reliability, and it is not economical because maintenance costs, refractory costs, and construction costs are too high. .

According to the present invention, as a result of various investigations and experiments conducted to solve the actual situation of the ladle lid having such a water cooling structure and the above-mentioned problems of the present invention, when refining the molten metal as described above. Focusing on the splash splash that inevitably occurs, we considered using the splash splash positively.

That is, when the molten metal is smelted as described above, the splash splash is unavoidably generated, and if this is attached to the surface of the heat transfer tube group on the inner surface of the water-cooled structure, the actual situation can be easily and economically. And the problem can be solved. However, it is not effective if the material intended to be a fireproof material having a heat insulating property or the material intended to have a thicker heat transfer tube is easily peeled off and dropped.

In consideration of such a point, the present invention relates to a heat transfer tube group which is wound in a concentric circular shape or a spiral shape so that the tubes are installed as closely as possible, and has a circular opening edge of a ladle. The heat transfer tube located in the innermost circular opening of this ladle, out of the heat transfer tube group arranged in series in the horizontal direction of the lowest step in contact with, is at least as large as the radius of the heat transfer tube with respect to the heat transfer tube immediately above it. , It is configured so as to project in the central axis direction inside the circular opening of this ladle, so that the splash scattered on the heat transfer tubes located inside the circular opening of the ladle is easily peeled off. It is possible to place it on the heat transfer tubes one by one so that they will not drop and to make the splash group grow up to the heat transfer tubes in the upper stage one after another, and the necessary amount of splash layer is placed around each heat transfer tube. Form and heat by this While mitigating the electrically adjusted to minimize the energy loss as described above, is the is possible to solve the problem of circumstances and the present invention ladle lid of the water-cooling structure.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A ladle lid of a refining ladle in a vacuum refining apparatus will be described in detail below as an embodiment according to the present invention with reference to the drawings. 1 is an enlarged cross-sectional view of a heat transfer tube group in the ladle lid 10 of the embodiment of the present invention, FIG. 2 is a cross-sectional front view of the heat transfer tube group of the hat-shaped ladle lid 10, FIG.
Similarly, it is a partially omitted plan view. FIG. 4 is a schematic vertical sectional view of a vacuum refining apparatus as an embodiment of the present invention.
The vacuum refining apparatus 1 includes a vacuum container system including a vacuum container 1a and a vacuum container lid 1b which can be opened and closed via a seal portion 2, and an exhaust system including an exhaust gas duct 4 and an exhaust device 5 connected to the vacuum container system. , A gas supply system comprising a gas supply device 3 for supplying an inert gas such as argon gas through a gas injection nozzle 3a arranged at the bottom of the ladle 6 for stirring molten metal or slag, It is formed by a ladle 6 placed at a predetermined position in the vacuum container 1a for accommodating the molten metal.

The vacuum container lid 1b has an oxygen top blowing lance 7.
Is provided so as to be vertically movable up and down, and hoppers 8a and 8b for supplying alloy iron and flux for increasing the amount of molten metal and adjusting the component composition are attached.
During the vacuum refining operation of the molten metal, the exhaust system is driven to maintain the inside of the vessel 1 at a predetermined depressurized state, and the gas supply system is operated to inactivate the molten metal from the gas injection nozzle at the bottom of the ladle 6. Oxygen is blown from the lance 7 onto the molten metal in the ladle 6 while blowing gas and stirring.

The ladle 6 is a ladle body 9 having a circular opening.
And the ladle lid 10. The lid 10 is placed on the edge of the circular opening of the main body 9 so as to be openable and closable, and the molten metal held inside the main body 9 is sealed as much as possible to suppress the temperature drop and the molten metal. It is designed so as to prevent the outflow of the splashes to the outside of the main body 9 and the splash of splashes to the outside of the main body 9. The ladle lid 10 is provided with an opening / closing opening 10a for the oxygen top blowing lance 7, an insertion opening 10b for supplying hoppers (ducts) 8a, 8b for supplying iron alloy, and a gas vent. Also, the ladle lid 10 is
This is a water-cooled hat-shaped lid, and a heat transfer tube 11 made of a steel tube is densely attached to the inner surface side of an iron shell, which is an outer shell, so that there is no gap as much as possible. As the heat transfer tube 11, a steel tube bent in an arc shape is used, and it is arranged in multiple rows concentric with the central axis O of the main body 9 and the lid 10 over the entire surface of the lid 10 that requires cooling, and adjacent tubes The ends are folded together and connected by a pipe 12 to form a fluid conduit which is generally concentric or zigzag spiral, for example. In the embodiment shown in FIGS. 2 and 3, the fluid pipelines formed by the heat transfer tubes are distinguished by the upper, middle, and lower stages of the pipelines, and the cooling water is circulated to the respective pipelines. It has become so.

Of the three stages of flow pipes, the pipe line having the largest spiral diameter in the lower stage has its lowermost portion in the same horizontal plane along the edge of the lid 10, as shown in an enlarged view in FIG. A heat transfer tube 1 which is in the shape of a plurality of arcs arranged in series and in close contact with each other, and is located inside the circular opening of the ladle body 9 most.
1A is provided so as to project in the direction of the central axis O in the circular opening of the ladle body 9 with respect to the heat transfer tube 11B immediately above. In the example shown in FIG. 1, the heat transfer tube 1 immediately above the first and second heat transfer tubes 11A and 11C in the lowest stage
1B is arranged so as to rest on the valley portion. The innermost heat transfer tube 11A and the heat transfer tube 11B immediately above the innermost heat transfer tube 11B have a spiral diameter (circumferential diameter) of the heat transfer tube 11B.
In contrast to that of A, the relationship in which it is larger than 1/2 of the direct line of the heat transfer tube 11, that is, the relationship in which the heat transfer tube 11A projects in the central axis direction by a radius of the tube or more with respect to the heat transfer tube 11B immediately above it. Is arranged so that In addition, when the heat transfer tube 11 made of this steel tube has a small diameter, in addition to the heat transfer tube 11A located inside the circular opening of the ladle body 9 at the most, a predetermined required number of heat transfer tubes 1
1D, ... May be added and the elements may be arranged so as to project in series in the horizontal direction in the central axis direction. In addition, each heat transfer tube 11
Is affixed to the adjacent pipes 11 by brazing and welding the adjacent pipes 11 except for the above-mentioned required openings 10a and 10b so as not to generate a void as much as possible.

The ladle lid 10 of the above-described embodiment is installed and used so as to close the circular opening at the upper end of the ladle body 9 as much as possible. During the vacuum refining process, the splashes, which are scattered during the oxygen blowing, adhere to the inner surface of the ladle lid 10. The attached splash is removed from the surface of the heat transfer tube 11 and cooled to shrink. In this case, the heat transfer tube 11A and the heat transfer tube 11
Since the diameter of B in the circumferential direction is different and the former is smaller, the splash that is placed on the heat transfer tube 11A and adhered between both tubes 11A and 11B does not separate from the heat transfer tube even when cooled and contracted.
Also, it will not drop easily and will be stable in that position. This state is shown by the shaded area B in FIG. Then, once it remains in this portion, the hatched areas B and C shown in FIG. As a result, most of the cooling tubes 1 except the heat transfer tube 11 near the top are
Splash adheres to the inner surface of the first group. However, the attached splash acts to reduce (reduce) the heat conduction of the heat transfer tubes 11 when the thickness reaches a certain value, and reduces the cooling ability of the splash surface (inner exposed surface). Splash growth does not occur. As a result, the heat conduction on the surface of the heat transfer tube 11 group is reduced, as in the case where a refractory is additionally provided, so that the temperature decrease of the molten metal can be suppressed and maintained at a high temperature state.

Table 1 shows various values when actually measured using the ladle lid 10 according to the embodiment of the present invention. In addition, in the same table, refractory 1 shown in FIG. 5 as a comparative example.
3 also shows the results when the conventional lid 10 having a structure in which 3 is attached to the heat transfer tube 11 is used.

[0029]

[Table 1]

As is clear from Table 1, in the embodiment of the present invention, a splash having a thickness of 23 mm was deposited when 10 heats were used, and the splash deposit thickness was increased as 20,30 heats and heats numbers were overlapped.
However, it was found that the growth of the splash adhered at 30 heats almost stopped, and it remained at a constant thickness,
Further, it is also clear that the temperature difference is almost the same as 4 ° C. as compared with the comparative example, that is, the heat removal amount is small.

In this embodiment, the heat transfer tube 11 arranged in series at the lowermost stage in contact with the ladle body 9 has a maximum spiral diameter of about 3300 mm, and the heat transfer tube 11 has a tube diameter (outer diameter) of 76.3 mm. Ladle 6 by using the steel pipe of
It is possible to circulate and circulate the cooling water in an amount sufficient to withstand the radiant heat from the hot metal and the molten steel surface inside, and it is possible to prolong the service life of the heat transfer tube. Further, the ladle lid according to the present invention is not limited to a vacuum refining furnace, but can be applied to an electric furnace, a metal melting and refining furnace such as a converter.

[0032]

As described above in detail, the water cooling ladle lid of the metal refining ladle according to the present invention is formed by winding a heat transfer tube made of a steel pipe into a hat shape. The heat transfer tube group corresponding to the eaves (overhanging eaves) surrounding the is arranged under a specific condition. With such a configuration, the splash generated from the molten metal and the slag held inside the ladle is positively utilized, the adhesion of this splash is ensured, and the splash layer after that is surely attached. Growth to a predetermined thickness can be promoted and maintained in a stable and strong state.

Therefore, the problems of the conventional ladle lid having the refractory structure described in the above items (a) to (e) can be solved, and the excessive cooling in the normal water cooling structure can be avoided. This has the remarkable effect of extending the service life of the ladle lid itself by 2 to 4 times as long as the conventional one while preventing the temperature drop of the molten metal and slag inside the ladle. Moreover, while achieving the original functions (roles and purposes) of the ladle lid described in the above items to (1) comprehensively and achieving the object of the present invention, stable operation over a long period of time can be performed with energy saving and economic efficiency. The industrial value of the water cooling ladle lid according to the present invention is very large.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view of a heat transfer tube group in a ladle lid 10 according to an embodiment of the present invention.

FIG. 2 is a cross-sectional front view of a heat transfer tube group of the ladle lid 10 formed in the hat shape shown in FIG.

3 is a partially omitted plan view of the heat transfer tube group of the ladle lid 10 shown in FIG. 1. FIG.

FIG. 4 is a schematic vertical sectional view of a vacuum refining apparatus.

FIG. 5 is a schematic sectional view of a ladle lid of a comparative example.

[Explanation of symbols]

 6 Ladle 7 Oxygen top blowing lance 9 Ladle body 10 Ladle lid 11 Heat transfer tube 11A Bottom heat transfer tube 11B Second step heat transfer tube 12 Folded tube

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Makoto Sudo 4976 Nomura Minami-cho, Shinnanyo-shi, Yamaguchi Prefecture Shunan Steel Works (72) Inventor Isao Ueki 4976 Nomura-minami-cho, Shinnanyo-shi, Yamaguchi Nisshin Shunan Steel Works, Ltd.

Claims (3)

[Claims] 1. A water-cooled ladle lid that is openably and closably mounted on the circular opening edge of a ladle used for metal refining, wherein the water-cooled ladle lid is a steel pipe in the sky above the circular opening of the ladle. A heat transfer tube consisting of is formed into a hat shape by winding the tubes so that they are installed as closely as possible, and while cooling water is passed through this heat transfer tube group, the heat transfer tube that comes into contact with the circular opening edge of the ladle Of the group of heat transfer tubes arranged in series in the horizontal direction in the lower stage, the heat transfer tube located at the innermost circular opening of the ladle has a radius of the heat transfer tube equal to or more than the radius of the heat transfer tube immediately above the heat transfer tube immediately above. A water-cooled ladle lid for a metal refining ladle, which is arranged so as to project in the central axis direction inside the circular opening of the pot. 2. When the heat transfer tube made of steel has a small diameter, a predetermined number of heat transfer tubes are further added in addition to the heat transfer tube located inside the circular opening of the ladle so as to project in series in the horizontal direction. The ladle lid of the ladle for metal refining according to claim 1, wherein the ladle lid is provided. 3. The heat transfer tube has a tube diameter capable of passing cooling water at a flow rate that can sufficiently withstand the radiant heat emitted from the molten metal and / or the slag layer held inside the ladle. The ladle lid of the ladle for metal refining according to claim 1 or 2.