JPS61253318A - Method for cooling immersion pipe - Google Patents

Abstract

PURPOSE:To enhance the cooling power of a cooling fluid and to prolong the life of the mandrel of an immersion pipe by arranging metallic plates in the gap in the mandrel having a double-walled cylindrical structure and by feeding the cooling fluid. CONSTITUTION:Metallic plates such as steel plates 9 are arranged among parts of a cooling air feeding pipe 10 in the gap between the outer and inner cylindrical iron plates 7, 8 of the mandrel 4 of an immersion pipe 3 for a molten pig iron degassing equipment or the like. Cooling air absorbs heat from the surfaces of the iron plates 7, 8 and the metallic plates 9 during passing through the air path and the air is exhausted from the exhaust port. By this cooling method, the temp. of the mandrel can be lowered to about 500-600 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for efficiently cooling a immersion tube, particularly a core metal, in a hot metal degassing treatment facility or the like.

(Prior Art) For example, as shown in the immersion tube 3 of a batch-type molten steel vacuum degassing apparatus in FIG. Refractories 5.6 and 5.6 are generally installed.

The main role of the core metal 4 of the immersion tube 3 is to fix the surrounding refractory material 5.6 and stabilize the structure.

By the way, the relationship between the number of processed charges and the temperature of the core metal 4 in the batch-type molten steel vacuum degassing apparatus l is shown as an example in FIG. 9. As the number of processed charges increases, the temperature of the core metal 4 gradually increases. do. Moreover, as the melting loss of the surrounding refractories 5.6 progresses, the temperature begins to repeat vertical swings between the treatment and non-treatment states.In addition, as the temperature of the core metal 4 increases, the linear expansion of the core metal 4 increases. , the linear expansion of the surrounding refractories is also large, and the temperature amplitude during treatment and non-treatment, which occurs as the refractory erosion progresses, is due to the linear expansion difference between the core metal 4 and the refractories 5 and 6. This caused cracks to occur at the boundaries of the refractory construction, which caused significant wear and tear due to penetration of slag and molten steel, and became a limiting factor in the lifespan of the immersion pipe refractories.

On the other hand, as shown in Figure 10 [from Mechanical Engineering Handbook (Mechanical Materials Edition) Revised 5th Edition, published by the Japan Society of Mechanical Engineers, 1968], in the case of ordinary steel, the mechanical strength significantly decreases when the temperature exceeds 500°C. In addition to the linear expansion of the core metal 4, creep due to its own weight applied to the core metal 4 when not treated is also considered to be one of the factors that deteriorates the life of the refractory. In this way, the elongation of the core metal 4 due to a rise in temperature is Cracks occur at the construction boundaries of refractories 5 and 6, and molten steel and slag infiltrate into the area, which promotes localized erosion of refractories 5 and 6. It is necessary to replace the immersion tube 3 with a new one before the life of the immersion tube ends, resulting in an increase in processing costs for hot metal, molten steel, etc., and a decrease in processing time due to an increase in the time required to repair the refractories 5 and 6.

Cooling methods aimed at solving the above-mentioned problems and suppressing the thermal expansion of the immersion tube core metal 4 have been studied in the past.
As shown in Japanese Patent Publication No. 96813, the core metal 4 has a jacket structure or a joint of cooling pipes, or a cooling pipe is wrapped around an existing core metal and a steam/water mixed fluid is sent into the cooling pipe or jacket. A method of cooling the core metal by evaporation inside the cooling pipe, jacket, or JP-A-59-
Refrigerant supply branch pipes are arranged at regular intervals in the double cylindrical gap of the core metal, which has a double cylindrical structure of an inner cylindrical iron plate and an outer cylindrical iron plate, so as to come into contact with the inner cylindrical iron plate and the outer cylindrical iron plate, as in Publication No. 1617, There is a dipping tube structure that cools the core bar 4 efficiently and uniformly.

However, even with this method, the cooling surface is limited to the surface of the core metal, and cooling is performed only by convection heat transfer on the surface of the core metal.Moreover, since the core metal 4 is a structure for reinforcing the refractory material of the immersion tube 3, the thick plate However, it is difficult to attach protrusions to promote convection heat transfer or fins to increase the cooling area on the surface of the core metal due to structural or cost considerations.

(Problems to be Solved by the Invention) The present invention solves the drawbacks of the conventional method as described above, such as a reduction in the life of the refractory due to thermal expansion due to insufficient cooling of the core metal of the immersion tube, or a problem in which the core metal is thick. This is an immersion tube that easily solves the problem that mounting protrusions, fins, etc. that promote heat transfer is difficult to process, and that effective heat removal cooling is not possible due to high manufacturing costs. The objective is to provide a cooling method for

(Means for solving problems) The present invention includes an outer cylindrical iron plate and an inner cylindrical iron plate.

A method for cooling an immersion tube by supplying a gas fluid to a gap in a core metal of the immersion tube, which is characterized in that a metal plate is inserted into the gap.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for cooling a immersion tube according to the present invention will be described below based on an embodiment shown in the drawings.

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

FIG. 2(a) is a horizontal cross-sectional view of the core metal 4 shown in FIG. 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 pipe 10.

The loaded metal plate 9 is not a structure of the core metal 4, so it can be a thin metal plate, and moreover, it is not a structure of the core metal 4 or the cooling air supply pipe 10.
There is no need to fix it to the cylindrical structure, just insert it into the gap in the double cylindrical structure.

FIG. 2(b) is a vertical cross-sectional view of the four parts of the core metal shown in FIG. Heat is transferred from the surfaces of the iron plate 7, the inner cylindrical iron plate 8, and the charged metal plate 9 by convection heat transfer, and is discharged from the exhaust port 12.

The cooling mechanism of the core metal 4 consisting 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. (a) is a schematic diagram 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 using the conventional method in a core metal having a double cylindrical structure. 4, the amount of heat Qo is removed by convection heat transfer to the cooling air on the surface of the core metal.

FIG. 3(b) shows the outer cylindrical iron plate 7, the inner cylindrical iron plate 8, the interposed 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 a core metal having a double cylindrical structure. This is a schematic diagram of temperature distribution. A quantity of heat Q2 is transferred from the high-temperature core metal 4 to the interposed metal plate 9 by radiation heat transfer, and the heat quantity Q2 is transferred by convection to the cooling air on the surface of the interposed metal plate 9. Heat is removed by heat transfer. Of course, the amount of heat Q1 is also removed from the core metal surface by convection heat transfer to the cooling air, so on the core metal surface, both direct convection heat transfer to the cooling air and radiant heat transfer to the interposed metal plate 9 occur. A larger amount of heat (Q1+Q2) can be removed compared to the amount of heat removed Qo in the conventional method.

The method for installing the insertion metal plate 9 in the gap between the core metal 4 having a double cylindrical structure consisting of the outer cylindrical iron plate 7 and the inner cylindrical iron plate 8 is as follows.
It is possible to simply insert a cutting plate between the cooling air supply pipes 10, but in order not to obstruct the cooling air flow, it is preferable that the inserted metal plate 9 does not come into contact with the core metal 4. As shown in Fig. 5, the protrusions 13 are partially provided as spacers, or the heat removal effect is increased, as shown in Fig. 6, the metal plate 9 is made into a bulky shape, or as shown in Fig. As shown in Fig. 7, a steel plate 9 is inserted in the diagonal direction of a cooling air flow path 11 surrounded by an outer cylindrical iron plate 7, an inner cylindrical iron plate 8, and a cooling air supply pipe 10 while winding the cooling air supply pipe IO. etc. may also be used. Although air is used for cooling, gaseous fluids such as Ar and N2 may also be used.Furthermore, the solid to be charged into the gap between the core metals is not limited to the metal plate 9, but any solid material may be used, and it is preferable. should have a high emissivity.

(Example) An example of the immersion tube cooling method of the present invention will be described below.

Example 1 The cooling method of the present invention was applied to air cooling of a immersion tube core in a batch type molten steel vacuum degassing facility with a processing capacity of 80 Q Ton/ch.

Compressed air of 800 Nm3/Hr is used for the cooling air, the installation pitch of the cooling air supply pipes is 200mm, and 20 IOA SEP steel pipes are installed as the cooling air supply pipes.

As shown in Fig. 1, a thickness of 0.0 mm is placed in the gap between the double cylindrical core metals.
A 2 mm steel plate was charged.

In this case, the core metal temperature is Looo-1,200 when not cooled.
It is around 700-800'C with conventional cooling methods.
By applying the present invention, the number of
It can be lowered to about 0℃, compared to conventional 500~6℃.
The lifespan of the immersion tube was 650-70 times.
Example 2 In Example 1, protrusions 13 with a height of approximately 8 mm were provided at a pitch of 20 mm to promote convection heat transfer on the charged steel plate.
It was inserted into the gap between the double cylindrical core metal.

(Figure 4 shows a schematic diagram of the steel plate.) In this case, the heat removal due to convection heat transfer on the surface of the charged steel plate becomes even greater than in Example 1, that is, the heat removal from the core metal surface increases. , the core metal temperature decreased to about 450 to 550°C.

The life of the immersion tube was about 650 to 700 times, which was not much different from 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 lowered to 200 Nm3/Hr. This has made it possible to reduce the cost of compressed air.

(Effects of the Invention) As described above, in air cooling of a core metal having a double cylindrical structure, by charging a solid object such as a steel plate into the gap between the core metals, it is possible to Cooling air is generated by radiant heat transfer to the object. Cooling capacity is increased by convection heat transfer from the surface of the charged steel sheet solid object, etc., significantly extending the life of the core metal of the immersion tube and reducing the cost of cooling air. devaluation became possible.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a dip tube showing an embodiment of the present invention. vertical cross section. Figure 3 (ω is a schematic diagram of the temperature distribution of the core metal and cooling air when air cooling is performed using the conventional method. Figure 3 (b) is a diagram of the core when the present invention is applied to Figure 3 (a). A schematic diagram of the temperature distribution of gold and cooling air. Figure 4 is a schematic diagram of a charged steel plate with protrusions to promote convective heat transfer. Figure 5 is a schematic diagram of a charged steel plate with protrusions as spacers. Fig. 6 is a partial horizontal cross-sectional view of the core metal part when a steel plate with a shabby shape is charged. Fig. 7 is a partial horizontal sectional view of the core metal part when a steel plate with a shabby shape is charged. Fig. 7 shows a case where the steel plate is charged while being wound around the cooling air supply pipe in the diagonal direction of the 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 partial horizontal sectional view of the core metal part in the case of FIG. 8(a). A' sectional view. Figure 9 is a graph showing the relationship between the processing number and the number of yarns in a batch-type molten steel vacuum degassing equipment and the temperature of the core metal. Figure 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 material
7... External cylindrical iron plate 8... Internal cylindrical iron plate
9...Metal plate 10...Air supply pipe 11
... Air flow path tm Fig. 2 (V Fig. 3 (a) Fig. 5 Fig. 4 Fig. 6 Fig. 7 VB 1^ Fig. 9 μm1 Churn J # (Duck

Claims (1)

[Claims] A method for cooling an immersion tube by supplying a gas fluid to the gap between an outer cylindrical iron plate and an inner cylindrical iron plate, the method comprising inserting a metal plate into the gap. .