JPS59130664A - Cooler for continuous casting billet - Google Patents

Abstract

PURPOSE:To spray water over a wide range with a small amt. of air by connecting a branch in the upper direction of a liquid header pipe, and disposing an externally mixing type gas ejecting part for forming a liquid-gas mixture in the outlet part thereof. CONSTITUTION:The top end of a water branch 4 disposed in the upper part of a water header 2 is extended to the outside of an air header 3 and air is discharged from the header 3 to the outside from an air branch 5. The number of the branches 5 is 2 per one water branch in this case but is permitted to use >=3 depending upon the condition of use. Then the flow of the water and the flow of the air from the two directions collide roughly simultaneously against each other in the front end part 6 of the branch 4 and the branch 5, and the water is atomized by the energy of the air; at the same time, the water drops atomized by the colliding film of the air formed by the two streams of the air flow spread. A prescribed spraying angle is obtainable by selecting adequately the angle 9 at which the flow of the water and the flow of the air collide against each other between 0-60 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for cooling slabs in continuous steel casting, and more particularly, to a two-fluid spray cooling nozzle for ensuring a wide liquid (generally [water]) amount control range. It is.

In continuous casting equipment, it is an important element in the cooling conditions performed in the secondary cooling area, and the quality of continuously cast slabs is greatly influenced by the quality of the cooling conditions.

For continuous casting of steel, molten steel is cooled in a water-cooled mold, and 10 to 2
After forming a solidified shell, high-pressure energy is applied to the surface of the slab, which is still in the state of molten steel, at a surface temperature of about 1200℃, or air energy VC is applied!
A spray of cooling water is sprayed to completely solidify the inside of the slab. During this cooling process, the slab is leveled until it is completely solidified.
It is necessary to withstand VC. The relationship between the secondary cooling conditions and the quality of the slab will be explained in detail below using FIG. 1.

If the secondary cooling is insufficient, the strength of the solidified shell will be insufficient, and the solidified shell of the slab will bulge between the rolls due to the static pressure of the molten steel. It is well known that this phenomenon is one of the major causes of metallurgical defects, such as central segregation and internal cracks.To prevent this, it is necessary to provide a certain amount of water to the slab. There is a casting speed depending on the amount of water.

Restricted by steel type, composition, casting conditions, etc.

Furthermore, surface cracks, which are one of the defects in continuously cast slabs,
Secondary cooling conditions have a major influence. This surface split'rLvc
On the other hand, the metallurgical strength properties of the material are 700℃
The influence of the embrittlement region that exists near 950°C cannot be ignored. Therefore, when casting boron-containing steel, etc., which is highly susceptible to transverse cracking, in order to prevent transverse cracking on the surface of the slab, the surface temperature of the slab near the straightening part of the curved continuous casting machine must be adjusted to the above-mentioned embrittlement level. It is necessary to avoid the high temperature side of the region, and it is necessary to aim for low water flow and slow cooling. As a secondary cooling nozzle for such parts, it is necessary to have a very low water flow control range. The cooling pattern at this time is the curve ◯ in Figure 1.

On the other hand, when applying continuous casting technology to high-grade steels, especially steels for low-temperature toughness, it is necessary to maintain the cooling rate above a certain level and to refine the TiN using a VJ. It is necessary to have a control range for the amount of water. The cooling pattern at this time is curve I in FIG. Continuous casting machines that produce a wide variety of high-grade steels are shown in Figure 1 depending on the type of steel being cast. : Cooling pattern must be changed. Therefore, for this type of secondary cooling,
Low water flow 1, 2'/sin m' (olo 'A = book)
There is a need for a two-fluid spray cooling nozzle that uses both gas and liquid and can control a wide water flow range from 120'/m=m'(10'1m1n lines) to a high water flow rate.

In contrast, most of the current two-fluid spray cooling nozzles are internally mixed in structure, as shown in Figure 2.
For example, "Tetsu to Hagane JVOT, 68 (1982) p. 1782) This type of nozzle has the disadvantage that the low water volume side cannot be controlled or water does not come out due to the balance between air pressure and water pressure. (“Tetsu to Hagane J
VOL 65 (1979, p. 608) Conventional external mixing type two-fluid jet M cooling nozzles are capable of controlling the amount of water over a relatively wide range, but the spray angle is small and it is difficult to atomize a certain amount of water [H It has the disadvantage of requiring a large amount of air.

For example, the internal mixing type spray angle can vary from 100° to 120°.
In contrast, the r5t and mist angle of conventional external mixing types are about several tens of degrees.Therefore, when conventional internal mixing type two-fluid spray nozzles are used in such continuous casting machines for high-grade steel, The amount of water cannot be controlled, resulting in non-uniform cooling, and when conventional external mixing type two-fluid spray nozzles are used, non-uniform temperature distribution occurs due to non-uniform cooling in the lateral direction of the slab, and a large amount of pressure and air is required. Requires cost.

In order to solve these problems, the present invention relates to an external mixing type two-fluid spray nozzle that has a large spray angle and a wide water volume control range, and includes a liquid branch pipe upward from the liquid goo pipe. In addition, an external mixing type gas ejection part for generating a liquid/gas mixture is arranged near the outlet of the liquid branch pipe, and the flow rate characteristics of water and air can be controlled without mutual interference. This external mixing type two-fluid spray nozzle is characterized in that the spray angle can be freely secured from a wide-angle force to a narrow-angle angle.

Examples of the present invention are shown below in Figs. 4, 5, 7, and 8.
This will be explained in detail using figures. In addition, in the present invention,
Although the types of liquid and gas are not limited, they will be described as water and air, respectively, for convenience.

FIG. 4 is an overall view showing an example of the device of the present invention, FIG. 6 is a comparative example for the present invention, FIGS. 7(a) to (d) are cross-sectional views of the embodiment of the present invention, and FIG. It is a figure showing the spraying situation of the present invention, where ■ is a slab, 2 is a water hole, 3 is an air hole, 4 is a water drain pipe, and 5 is an air branch pipe. The supplied P water is first distributed almost uniformly to each drain pipe by the water header 2. At this time, as shown in Figure 5(a), the water header
Since the water drain pipe 4 is extended upward from 2, the inside of the water header is filled with water even when the amount of water is low, so it exhibits a sufficient header effect and distributes water evenly. can. 1. For example, if the outlet of the drain pipe is located next to or at the bottom of the water rug, the minimum amount of water that can be distributed evenly is 117'; By this, the lower limit water amount is O, l 1-
A = Can be enlarged under the main ball. The water is evenly distributed in the water header, flows through the drain pipe, and exits the nozzle.

Furthermore, if the water header 2 and the water drain pipe 4 are connected, depending on the conditions of use, it may be no problem to do it as shown in Fig. 5 (b) or U (C), and the point is that the It is only necessary that the drain pipe 4 is disposed in the upper direction, and thereby the effects of the present invention can be exhibited. There is also no particular restriction on the number of drain pipes per water header, and the size of the cast slab is 7.
It can be determined as appropriate depending on the width or thickness.

Next, the structure of the nozzle portion and the atomization mechanism will be explained. In the comparative example shown in Fig. 6, the tip of the water branch pipe 4 is located inside the air header 3. This has the disadvantage of causing breathing (pulsating state) and uneven water volume, making it impossible to control. In order to solve this drawback, an embodiment of a nozzle characterized in that the tip of the branch pipe 4 is extended outside the air header 3 is shown in FIG. 7(a).

In this case, since air pressure does not act on the water outlet, no breathing phenomenon occurs even at low water volumes, and sufficient atomization can be achieved over a wide range of water volumes. However, even in the case of this shaped nozzle, the shortcoming of the external mixing two-fluid nozzle, which is the small spray angle, has not yet been improved.

This is an example in which further improvements have been added to the embodiments shown in FIGS. 7(b) to 7(d) in order to expand the @ fog angle. In this case, air is supplied from the air header 3 and discharged from the air branch pipe 5 to the outside of the system. The number of air branch pipes 5 is basically two per drain pipe, but depending on usage conditions, three or more may be effective.

At the tip 6 of the drain pipe 4 and the air branch pipe 5, the water flow and the air flow from two directions collide almost identically, and the water is atomized by the energy of the air, and the two air flows are The atomized water droplets spread due to the air collision film formed by this. At this time, the collision angle between the water flow and the air flow is 9
A predetermined spray angle 8 (FIG. 8) can be obtained by appropriately selecting the angle between 06 and 60 degrees.

The relationship between the collision angle 9 and the spray angle 8 is shown in FIG.

For example, if a wide spray angle is desired and the impingement angle is selected to be 60°, the spray angle will reach 140° and the spray cooling area 7 will be 600 mm. However, increasing the collision angle even further is not good because the spray spreads too much and the ratio of the effective amount of water to the amount of supplied water decreases.

In addition, air header, water header, and air branch pipe.

Although the shape of the water drain pipe has been described as a cylindrical shape in this description, as long as each required cross-sectional area is ensured, any shape other than a circle, such as an oval or a corner, is acceptable and can be applied to the present invention.

11. The relationship between the sizes of the air branch pipe and the drain pipe is as follows:
In order to achieve good spraying over the entire range of spray spread, the following equation must be satisfied between the diameter of the air branch pipe or, in the case of an oval shape, the major axis and the diameter d of the drain pipe.

D〉d・・・・・・・・・・・・・・・(1)
As explained above, in the nozzle of the present invention, since the air flow and the water flow collide at a certain angle at the tip, the energy of the air works effectively to atomize water without wasting it, as shown in Figure 9. Furthermore, the amount of air required for the good atomization range according to the present invention is very small compared to conventional internal mixing type spray nozzles. Furthermore, since it is basically an external mixing type, the air jetting characteristics and the water jetting characteristics do not interfere with each other, and control in actual use is easy.

As mentioned above, by using the two-fluid spray cooling nozzle of the present invention for secondary cooling in continuous casting, it is possible to uniformly spray cool the slab with a relatively small amount of air, and to prevent the occurrence of cavities and surface cracks. It is possible to prevent this, and depending on the type of steel, strong cooling is also possible, making it possible to manufacture a wide variety of high-quality steels with the same continuous casting machine.

[Brief explanation of the drawing]

Figure 1 shows typical cooling patterns for strong cooling and slow cooling in continuous casting, Figure 2 shows an example of a conventional internal mixing spray nozzle, and Figure 3 shows a conventional external mixing spray nozzle. FIG. 4 is a diagram showing an example of a mixing type spray nozzle, FIG. 4 is an overall view showing an example of the device of the present invention, FIG. 5 is a sectional view showing the relationship between the water rudder and the tree branch pipe in the present invention, and FIG. 7 is a cross-sectional view of a spray nozzle showing an example of the present invention, FIG. 8 is a diagram showing a spraying situation of the present invention, and FIG. 9 is a diagram showing an existing nozzle and a nozzle of the present invention. FIG. 10 is a diagram showing the relationship between the amount of water and the amount of air, and FIG. 10 is a diagram showing the impact angle, the spray angle, and the effective ratio of the impact angle and water. ■ = Slab, 2: Water header, 3: Air header, 4: Tree branch pipe, 5: Air branch pipe, 6: Collision area of water and air, 7: Spray cooling area, 8: Spray angle, 9: The angle of collision between water and air. Patent Applicant Representative Patent Attorney Hano (1 person) Fig. 1 Pole 2 [・J 366- Fig. 3 Fig. 4 [4 Fig. 5 Fig. 6 Fig. 8 Fig. 7 (b) (a) Figure 9 This issue (Richishima book) Figure 10 insert ↑ Chromaticity 368

Claims (1)

[Claims] (]) A liquid branch pipe is connected and arranged above the liquid header pipe, and an external mixing type gas jetting part for generating a liquid/gas mixture is arranged near the outlet of the liquid branch pipe. A cooling device for continuous casting slabs, characterized by the following. (2) In the external mixing type gas ejection part for generating a liquid/gas mixture, a liquid branch pipe passes through the gas header, and the liquid is atomized by the gas supplied from the ladder to the gas at the exit of the liquid branch pipe. 2. The cooling device according to claim 1, comprising an external mixing type two-fluid spray nozzle that can control liquid flow rate characteristics and gas flow rate characteristics without interfering with each other. (3) The external mixing type gas ejection part for generating a liquid/gas mixture should be installed at an appropriate angle in the range of 00 force 1 to 6o0 with respect to the direction in which the liquid flows immediately after the liquid exits the liquid branch pipe (diameter d) K. External mixing type 2 is characterized in that gas flows collide from gas branch pipes in two or more opposing directions (the diameter is larger than the liquid branch pipe diameter d), and the spray angle can be arbitrarily maintained from wide angle force to narrow angle. A cooling device according to claim 1, comprising a fluid spray nozzle.