JPH0810906A - Cooling structure of continuous casting mold - Google Patents

Abstract

(57) [Summary] [Object] To provide a cooling structure capable of easily performing extremely uniform heat removal and cooling on a slab in a continuous casting mold. [Structure] The mold tube 8A and a frame plate 9 located outside thereof form a cooling water passage 10. A lower water supply tank for supplying cooling water to the cooling water passage 10 is provided below the cooling water passage 10, and an upper drainage tank 17 for draining the cooling water from the cooling water passage 10 is provided above the cooling water passage 10. The lower water supply tank is provided with a water supply nozzle whose water supply direction is a tangential direction of the lower water supply tank to form a swirl water supply tank 18 which imparts a swirl flow to the supplied cooling water. A rectifying plate 20 is provided in the swirling water tank 18 in the circumferential direction. [Effect] The cooling water flow velocity can be made uniform over the circumferential direction of the cooling water passage, and hence the cooling capacity can be made uniform. Rhombic deformation and surface cracks can be greatly reduced, and the quality of the slab and the yield are significantly improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling structure for a continuous casting mold in which the effect of preventing rhombus deformation and surface cracking of a slab is enhanced.

[0002]

2. Description of the Related Art When performing continuous casting, the molten steel poured into a continuous casting mold is cooled and solidified by heat removal through a mold tube, and sent out as a high temperature cast piece. Figure 10
[Fig. 4] is a diagram explaining a solidified shell generation / growth process at this time. That is, the molten steel 4 injected into the mold tube 8A is the same as the mold tube 8A and the mold tube 8A.
Heat is removed and cooled by the cooling water flowing through the cooling water passage 10 formed by the frame plate 9 located outside A. Then, the solidified shell 12 is generated and grows at a portion in contact with the inner wall of the mold tube 8A. At this time, if the cooling capacity becomes uneven in the circumferential direction of the mold tube 8A, the thickness of the solidified shell 12 becomes uneven over the circumferential direction of the slab, which causes rhombus deformation and surface cracking of the slab.

In order to prevent such rhombic deformation and surface cracks, it is essential that the solidified shell 12 be uniformly grown in the circumferential direction of the slab, and the cooling capacity of the mold tube 8A is made uniform in the circumferential direction. There is a need. The cooling capacity via the mold tube 8A generally depends on the flow rate of the cooling water flowing on the back surface of the mold tube 8A, and this cooling water flow rate is determined by the pressure at the inlet of the cooling water passage 10. Therefore, in order to make the cooling capacity of the molded tube 8A uniform in the circumferential direction, it is necessary to make the pressure at the inlet of the cooling water passage 10 uniform.

In order to prevent rhombus deformation and surface cracking of the cast slab, the pressure at the inlet of the cooling water passage 10 is set to the mold tube 8.
Conventionally, as a method of making the water uniform in the circumferential direction of A, a plurality of cooling water supply nozzles are installed or the capacity of the lower water supply tank 16 is increased.

[0005]

However, increasing the number of cooling water supply nozzles and increasing the capacity of the lower water supply tank 16 is naturally limited in terms of equipment, and the pressure at the inlet of the cooling water passage 10 is limited. There is a problem in that the flow rate of the cooling water flowing on the back surface of the mold tube 8A cannot be made uniform due to insufficient uniformity.

[0006]

According to the present invention, there is provided a cooling water channel constituted by a mold tube and a frame plate located outside the mold tube, a lower water tank for supplying the cooling water to the cooling water channel, and the cooling water is drained. In a cooling structure for a continuous casting mold composed of an upper drain tank, a swirl feed for supplying swirl flow to the cooling water by providing a water supply nozzle in the lower water tank with a water supply direction directed to a tangential direction of the lower water tank. This is a cooling structure for a continuous casting mold, which is characterized by being used as a water tank.
It is preferable to provide a straightening vane continuous in the circumferential direction of the swirl water supply tank and having a narrow slit on the upper surface or the lower surface at a position radially from the inner wall of the swirl water supply tank.

[0007]

The present invention applies the phenomenon represented by Bernoulli's equation. As can be seen from Bernoulli's equation, a fluid with a certain potential moves while converting the kinetic energy and pressure energy of the fluid itself into each other. That is, the pressure energy in the circumferential direction of the mold is also made uniform by first making the kinetic energy of the fluid flowing from the water supply pipe uniform by the swirling flow in the circumferential direction of the mold. After that, the motion vector of the fluid is converted in the narrow gap of the straightening vanes, and the cooling water is made to flow along the casting direction of the mold. Allows heat removal and cooling of the slab.

[0008]

[Example] When using a continuous casting machine with an arc radius of 7 m, billet casting with a slab size of 150 x 150 mm and a casting speed of 1.5 m / min, a conventional mold and a mold according to the present invention flow velocity in a cooling water passage. A comparison test was conducted on the uniformity and the occurrence rate of rhombus deformation.

FIG. 1 shows an example of a mold having a cooling structure of the present invention, and FIG. 4 shows a conventional mold of a comparative example. As shown in FIG. 3, in the mold of the example, a swirl water supply tank 18 having an outer diameter of φ496 and an inner diameter of φ390 was provided with two water supply nozzles 19 oriented in the tangential direction in two symmetrical directions. Also, the current plate 2 having a thickness of 9 mm
Sheets are provided on the inside and outside, the inner straightening plate is a square shape of 210 mm square and has a slit around the entire circumference on the lower side of the swirling water tank 18, and the outer straightening plate is a circular shape with an inner diameter of 382 mm and is swirling It was arranged so as to have a slit over the entire circumference on the upper side of. The gaps between the slits were all about 10 mm.

FIGS. 7 and 8 show the cooling water flow velocity in the cooling water passage located on the back surface of the four faces of the mold tube of the mold of the example and the mold of the comparative example. As is clear from FIG. 8, in the mold of the comparative example, a variation of about 0.5 m / s is seen in the flow velocity in the cooling water passage, but as shown in FIG. It is about 0.1 m / s, and the uniformity of the flow velocity in the cooling water passage is significantly improved. Further, FIG. 9 shows a cumulative generation ratio of rhombus deformation angles in the mold of the comparative example and the mold of the example. As is clear from FIG. 9, the diamond-shaped deformation occurrence ratio in the mold of the example was significantly improved as compared with the mold of the comparative example, and surface cracks and the like were prevented, and the slab quality could be satisfactorily cast.

[0011]

In the mold adopting the cooling structure of the present invention, by uniformizing the feed water pressure utilizing the swirling flow, the cooling water flow velocity is made uniform over the circumferential direction of the cooling water passage located on the back surface of the mold tube. , The slab can be cooled uniformly,
Rhombic deformation of the slab and surface cracking can be greatly reduced as compared with the conventional mold. As a result, there is a remarkable improvement effect in terms of the quality and yield of the slab. In addition, since the cooling water can be made uniform with a simple and compact structure, there is no restriction due to the facility connection, and the mold can be installed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a mold adopting a cooling structure of the present invention.

FIG. 2 is a sectional view taken along line DD of FIG.

FIG. 3 is a sectional view taken along line EE of FIG.

FIG. 4 is a cross-sectional view showing a conventional mold.

5 is a sectional view taken along line FF of FIG.

6 is a sectional view taken along line GG of FIG.

FIG. 7 is a cooling water channel 4 of a mold adopting the cooling structure of the present invention.
It is a figure which shows the cooling water flow velocity which flows along a surface.

FIG. 8 is a diagram showing a flow velocity of cooling water flowing through the surface of the cooling water passage of the conventional mold.

FIG. 9 is a diagram comparing the occurrence ratios of rhombus deformation angles in the example and the comparative example.

FIG. 10 is a partial cross-sectional view showing a conventional continuous casting apparatus centering on a continuous casting mold.

[Explanation of symbols]

 2 Tundish 4 Molten steel 8 Mold 8A Mold tube 9 Frame plate 10 Cooling channel 12 Solidification shell 14 Cast slab 16 Lower water tank 17 Upper drain tank 18 Swirling water tank 19 Water supply nozzle 20 Rectification plate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Makoto Takahashi 46-59 Nakahara, Tobata-ku, Kitakyushu City Nippon Steel Corporation Machinery & Plant Division (72) Inventor Hisaki Sato 46-59 Nakahara, Tobata-ku, Kitakyushu City Nippon Steel Co., Ltd. Machinery & Plant Division (72) Inventor Kiyoshi Kimishima 46-59 Nakahara, Tobata-ku, Kitakyushu City Nippon Steel Co., Ltd. Machinery & Plant Division

Claims (2)

[Claims] 1. A cooling water channel composed of a mold tube and a frame plate located outside the mold tube, a lower water tank for supplying cooling water to the cooling water channel, and an upper drain tank for draining the cooling water. In the cooling structure for a continuous casting mold, the lower water tank is provided with a water supply nozzle in which a water supply direction is directed in a tangential direction of the lower water tank, and a swirling water tank for imparting a swirl flow to the supplied cooling water is provided. Cooling structure for continuous casting mold. 2. The straightening plate having a narrow slit that is continuous in the circumferential direction of the swirl water supply tank and is provided on the upper surface or the lower surface at a position radially from the inner wall of the swirl water supply tank. Cooling structure for continuous casting mold.