JPH0629454B2 - Immersion tube cooling method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for efficiently cooling a dip pipe such as a molten steel degassing facility, especially a core metal.

(Prior Art) For example, as shown in the immersion pipe 3 of the batch type molten steel vacuum degassing apparatus of FIG. 8, the immersion pipe conventionally used for the treatment of desulfurization and degassing of molten iron is the inner and outer surfaces of the core metal 4 in the longitudinal direction. It is general that refractories 5 and 6 are applied to the above.

However, the core metal 4 of the dip tube 3 is to fix the surrounding refractories 5 and 6 and stabilize it as a structure.

By the way, as for the relationship between the number of processing charges of the batch type molten steel vacuum degassing apparatus 1 and the temperature of the core metal 4, as shown in FIG. 9 as an example, the temperature of the core metal 4 gradually rises as the number of processing charges increases. . Moreover, as melting damage of the surrounding refractories 5 and 6 progresses, the temperature repeats a vertical amplitude during processing and during non-processing.

Further, the linear expansion of the cored bar 4 due to the temperature rise of the cored bar 4 is larger than the linear expansion of the surrounding refractory material, and the temperature amplitude during the treatment and the non-treatment which occurs with the progress of the melting loss of the refractory material. Was the rate-determining factor for the life of the refractory of the immersion pipe, which caused cracks in the refractory construction boundary due to the difference in linear expansion between the core metal 4 and the refractories 5 and 6, and significantly promoted wear due to permeation of slag / molten steel.

On the other hand, Fig. 10 [Mechanical Engineering Handbook (Mechanical Materials) Revision 5
Edition, published by the Japan Society of Mechanical Engineers in 1968], in the case of ordinary steel, when the temperature exceeds 500 ° C, the mechanical strength remarkably decreases. Creep due to the applied weight is also considered to be one of the causes of the deterioration of non-object life.

In this way, the extension of the cored bar 4 due to the rise in temperature causes cracks to occur at the construction boundaries of the immersion pipe refractories 5 and 6, and molten steel and slag infiltrate from the relevant part, so that local melting loss of the refractories 5 and 6 is caused. It is necessary to replace the new immersion pipe 3 with a new one before the end of the immersion pipe life due to uniform melting of the refractory substances 5 and 6, which increases the treatment cost of molten steel and repairs the refractory substances 5 and 6. The increase in time leads to a decrease in processing time.

A cooling method aimed at solving the above-mentioned problems and suppressing the thermal expansion of the immersion pipe cored bar 4 has been studied in the past. For example, JP-A-58-9 proposed by the present inventors.
As shown in Japanese Patent No. 6813, the cored bar 4 has a jacket structure or a joined body of cooling pipes, or a cooling pipe is wound around an existing cored bar, and a gas-water mixed fluid is sent into the cooling pipe or the jacket. A method of evaporating inside the cooling pipe or jacket to cool the core bar, or a double cylinder gap of the core bar having a double cylindrical structure of an inner cylindrical iron plate and an outer cylindrical iron plate as disclosed in JP-A-59-1617. There is a structure of an immersion pipe in which a coolant supply branch pipe is arranged at a constant interval so as to abut the inner cylindrical iron plate and the outer cylindrical iron plate, and the core metal 4 is cooled efficiently and uniformly.

However, even in this method, the cooling surface is limited to the surface of the cored bar, and only cooling by convective heat transfer on the surface of the cored bar is performed. Moreover, since the core metal 4 is a structure for reinforcing the refractory material of the dipping pipe 3, it is necessary to use a thick plate material, and a projection for promoting convective heat transfer on the surface of the core metal or a fin for increasing the cooling area. It is difficult to attach such a structure because of its structure or cost.

(Problems to be Solved by the Invention) The present invention is the reason why the refractory life is shortened due to thermal expansion due to insufficient cooling of the immersion pipe core bar, which is a drawback of the conventional method as described above, or the core bar is a thick plate material. Therefore, a cooling method of an immersion pipe that easily solves the problem that it is difficult to attach protrusions, fins, etc. for promoting heat transfer, and effective heat removal cooling cannot be performed due to high manufacturing cost, etc. To provide.

(Means for Solving Problems) The present invention provides a method of supplying a gas fluid to a gap of a submerged pipe core bar composed of an outer peripheral cylindrical iron plate and an inner peripheral cylindrical iron plate for cooling, in which a metal plate is interposed in the gap. It is a method for cooling an immersion pipe, which is characterized by being inserted.

Hereinafter, a method for cooling a dip tube according to the present invention will be described based on an embodiment shown in the drawings.

FIG. 1 is a sectional view of an immersion pipe showing an embodiment of the cooling method according to the present invention, in which a steel plate 9 is placed in the gap between the outer cylindrical iron plate 7 and the inner cylindrical iron plate 8 of the immersion pipe core metal 4 having a double cylindrical structure. It is a front sectional view of the immersion pipe 3 which is charged and cooled by air.

FIG. 2 (a) is a horizontal cross-sectional view of the cored bar 4 in FIG. 1. For example, a metal plate such as a steel plate or a copper plate or a solid plate having a high emissivity (hereinafter collectively referred to as a metal plate 9) is externally arranged. It is inserted in the gap between the cylindrical iron plate 7 and the inner cylindrical iron plate 8 and between the cooling air supply pipes 10.

Since the charged metal plate 9 is not a structure of the cored bar 4, it may be a thin metal plate, and the cored bar 4 or the cooling air supply pipe 10 may be used.
It is not necessary to fix it to the base, and it is sufficient to insert it in the gap of the double cylindrical structure.

2 (b) is a vertical cross-sectional view of the core metal 4 portion of FIG. 1, in which the cooling air discharged from the cooling air supply pipe 10 passes through the core metal internal cooling air flow passage 11 and the external cylindrical iron plate. Heat is discharged from the exhaust port 12 by convective heat transfer from the surfaces of the internal cylindrical iron plate 7 and the inner cylindrical iron plate 8 and the charged metal plate 9.

The cooling mechanism of the cored bar 4 composed of the outer cylindrical iron plate 7 and the inner cylindrical iron plate 8 when the metal plate 9 is charged is shown in FIGS. 3 (a) and 3 (b) in comparison with the conventional method.

FIG. 3 (a) is a schematic view of the temperature distribution of the outer cylindrical iron plate 7, the inner cylindrical iron plate 8 and the cooling air when air cooling is performed by the conventional method in a cored bar having a double cylindrical structure. The gold 4 has a heat quantity Q ₀ on the surface of the core metal due to convective heat transfer to the cooling air.
Is removed from the heat.

FIG. 3 (b) shows the temperature of the outer cylindrical iron plate 7, the inner cylindrical iron plate 8, the inserted metal plate 9 and the cooling air in the case of air cooling to which the cooling method according to the present invention is applied in the cored bar having the double cylindrical structure. FIG. 4 is a schematic diagram of distribution, in which a heat quantity Q _{2 is} transferred from the high-temperature core metal 4 to the inserted metal plate 9 by radiant heat transfer, and the heat quantity Q ₂
Is removed by convective heat transfer to the cooling air on the surface of the inserted metal plate 9. Of course, even on the surface of the core metal, the heat quantity Q ₁ is removed by convective heat transfer to the cooling air. Therefore, on the surface of the core metal, both direct convective heat transfer to the cooling air and radiant heat transfer to the inserted metal plate 9 are performed. The heat is removed, and a larger amount of heat (Q ₁ + Q ₂ ) can be removed as compared with the amount of heat Q ₀ of the conventional method.

In addition, the installation method of the insertion metal plate 9 in the gap of the cored bar 4 of the double cylindrical structure composed of the outer cylindrical iron plate 7 and the inner cylindrical iron plate 8 is as follows.
A cutting plate may be simply inserted between the cooling air supply pipes 10, but in order to prevent the cooling air flow from being interrupted, it is preferable that the inserted metal plate 9 does not come into contact with the core metal 4. As shown in FIG. 5, a protrusion 13 is partially provided as a spacer, or a method of improving the heat removal effect, a method of forming a metal plate 9 in a bellows shape as shown in FIG. As shown in the figure, a method of charging the steel plate 9 in the direction of the diagonal line of the cooling air flow passage 11 surrounded by the outer cylindrical iron plate 7, the inner cylindrical iron plate 8 and the cooling air supply pipe 10 while winding the cooling air supply pipe 10 is used. You can get it. Although air was used in this method for cooling, a gas fluid such as Ar or N ₂ may be used, and the solid charged in the gap of the cored bar is not limited to the metal plate 9 and may be any solid. The one having a high emissivity is preferable.

(Example) Hereinafter, one example of the immersion pipe cooling method of the present invention will be described.

Example 1 The cooling method of the present invention was applied to the air cooling of a submerged pipe core metal of a batch type molten steel vacuum degassing treatment facility having a treatment capacity of 300 Ton / ch.

Compressed air is used as the cooling air at 300 Nm ³ / Hr, the mounting pitch of the cooling air supply pipe is 200 mm, and the cooling air supply pipe is 10 A.
20 SGP steel pipes were attached, and as shown in FIG. 1, a steel plate having a thickness of 0.2 mm was placed in the gap between the cores having a double cylindrical structure.

In this case, the core metal temperature is about 1,000 to 1,200 ° C when not cooled, and is about 700 to 800 ° C in the conventional cooling method, but can be lowered to about 500 to 600 ° C by applying the present invention. It was possible to extend the life of the immersion pipe from about 500 to 600 times to about 650 to 700 times.

Example 2 In Example 1, protrusions 13 having a height of about 3 mm were provided at a pitch of 20 mm on the charged steel plate to promote convective heat transfer, and the protrusions 13 were charged into the gap of the double cylindrical structure cored bar.

(Fig. 4 shows a schematic view of the steel plate.) In this case, heat removal from the surface of the charged steel plate is further increased as compared with Example 1 due to convective heat transfer, that is, heat removal from the surface of the core metal is increased. , The core metal temperature dropped to about 450-550 ℃.

The immersion tube life was about 650 to 700 times, which was not much different from that of Example 1, but due to the improved cooling capacity of the core metal, sufficient cooling capacity was obtained even if the compressed air for cooling was reduced to 200 Nm ³ / Hr. Therefore, the cost of compressed air can be reduced.

(Effects of the Invention) As described above, in air cooling of a cored bar having a double-cylindrical structure, by charging a solid material such as a steel plate into the gap of the cored bar, the surface of the cored bar is changed into a charged steel plate or a solid material. Radiant heat transfer to the cooling steel, and convection heat transfer from the surface of the charged steel plate solids, etc. by cooling air improves the cooling capacity, greatly extending the life of the immersion pipe core and reducing the cost of cooling air. Became.

[Brief description of drawings]

FIG. 1 is a sectional view of an immersion pipe showing an embodiment of the present invention. 2 (a) and 2 (b) are respectively B- of the horizontal sectional view of FIG.
The partial sectional view of B ', and the vertical sectional view of a core metal part. FIG. 3 (a) is a schematic diagram of the temperature distribution of the core metal and cooling air when air cooling is performed by the conventional method. FIG. 3 (b) is a schematic view of the temperature distribution of the core metal and the cooling air when the present invention is applied to FIG. 3 (a). FIG. 4 is a schematic diagram of a charged steel plate provided with protrusions for promoting convective heat transfer. FIG. 5 is a schematic view of a charging steel plate provided with protrusions as spacers. FIG. 6 is a partial horizontal cross-sectional view of the cored bar when a bellows-shaped steel plate is inserted. FIG. 7 is a partial horizontal cross-sectional view of a cored bar when a steel plate is inserted while being wound around a cooling air supply pipe in a diagonal direction of a cooling air flow path. FIG. 8 (a) is a front sectional view of a batch type molten steel vacuum degassing apparatus. FIG. 8 (b) is a sectional view taken along the line AA ′ of FIG. 8 (a). FIG. 9 is a graph showing the relationship between the number of processing charges of the batch type molten steel vacuum degassing apparatus and the temperature of the core metal. FIG. 10 is a graph showing the relationship between the mechanical strength of ordinary steel and temperature. 1 ... Vacuum degassing device, 2 ... vacuum tank 3 ... immersion tube, 4 ... core metal 5,6 ... refractory, 7 ... external cylindrical iron plate 8 ... internal cylindrical iron plate, 9 ... metal plate 10 ... Air supply pipe, 11 ... Air flow path

Claims (1)

[Claims] 1. A method of supplying a gas fluid to a gap of a dipping pipe core bar composed of an outer peripheral cylindrical iron plate and an inner peripheral cylindrical iron plate immersed in molten steel and covered with a refractory to cool the metal. A cooling method for an immersion pipe, characterized in that a plate is inserted.