JPS61209748A - Mold for continuous casting - Google Patents

Abstract

PURPOSE:To improve the cooling effect of copper plates and to improve remarkably production efficiency by forming the cooling slits and molten metal level measuring slits provided on the rear of a surface in contact with a molten metal to the same depth and specifying the shape of each slit part. CONSTITUTION:The cooling slits 28 formed on the same shape (width X depth Xbase shape) are provided to cooling water paths of copper plates 11 for continuous casting over the entire length from the bottom to top end thereof and the molten metal level measuring slits 30 are provided to molten metal level measuring parts 22, 24. The slits 28 and the slits 30 are formed to the same depth and the base of each molten metal level measuring slit is curved to decrease the concentration of thermal stress. Each slit 30 is made wider than the width of the slits 28 and the ratio thereof is preferably made 1:1.4-1:4. The production efficiency is thus remarkably improved.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides continuous casting molds, particularly high-speed casting molds that have recently attracted attention, molds with electromagnetic brakes, and other new technologies. The present invention relates to a continuous casting mold suitable for mold cooling, which places a large heat load on the continuous casting mold.

(Prior art) As shown schematically in Fig. 1, a continuous casting mold has a mold lO
The copper plate 11 constituting the molten metal 12 is constantly cooled by cooling water from the back side of the surface 13 in contact with the molten metal 12.

The cooling water rises through the cooling waterway 18 from the water supply port 16, while absorbing heat from the molten metal from the back surface of the copper plate 11.
and is ejected from the device. At this time, in order to increase the heat exchange efficiency in the cooling channel 18, a large number of vertically long slits (grooves) (see Fig. 2) are provided on the copper plate side of the cooling channel. Furthermore, a gamma ray source 2 for detecting the level of the hot water inside the mold.
2 and a scintillation section 24 are provided near the mold, and for this purpose, the copper plate 11 has a slit 30 for measuring the level of the hot water (see Fig. 2) in addition to the above-mentioned cooling slit.
In Figure 0, which is provided in the same manner, the T-ray transmission area is indicated by a chain line. In this way, the T-rays from the γ-ray source 22 are transmitted to the scintillation section 2 provided on the opposite side.
4 and measure the T-ray transmittance at that time to measure the hot water level. Therefore, the copper plate 11 in front of the scintillation part 24 has a deep slit (that is, the thickness of the copper plate is thinner) and a wider slit compared to other cooling slits for transmitting T-rays. It is provided. In FIG. 1, the configuration of this portion is represented by a staircase portion 25. Reference numeral 26 indicates a mold back frame.

FIG. 2 shows a cross section of a part of the mold copper plate at this time, in which both a cooling slit 28 and a molten metal level measuring slit 30 are provided.

By the way, conventionally, as shown in FIG. 2, the cooling slit 28 for cooling the copper plate itself and the slit 30 for measuring the hot water level for T-ray transmission (hereinafter also referred to as "γ-ray source slit") are completely different. It has been designed to perform 100% of each function. Therefore, in order to improve measurement accuracy, the γ-ray source slit was cut into the copper plate portion corresponding to the measurement range as thin as possible. Therefore, since the inside of the gamma ray source slit is wide and deep, the water flowing there rapidly slows down at the aforementioned step section 25, and generally the flow rate of the water flowing through the cooling slit section is 20 to 3
It is about 0%.

As a result, the capacity within the rllA source slit is greatly reduced, which appears as local deformation of the copper plate.

Moreover, stress concentration caused by differences in slit shape, cross section, etc. acted, causing cracks to occur.

(Problems to be Solved by the Invention) In recent years, molds for high-speed casting, molds with electromagnetic stirring devices, molds with electromagnetic brakes (EMBr), etc. have become widely used, but these methods In these cases, rapid cooling or large amounts of heat must be removed in a short period of time, and the molded copper plates used in these applications have a higher heat load than ordinary molded copper plates, so conventional copper plate cooling methods Cracks from the bottom of the γ-ray source slit or local deformation near the molten steel meniscus, that is, local deformation in an area up to about 100 mm from the top of the γ-ray source slit, occur in a short period of time, shortening the life of the copper plate, and at the same time, This caused production problems due to replacement.

Thus, an object of the present invention is to provide a continuous casting mold with extremely high cooling capacity, and furthermore, to completely eliminate cracks and deformation during high-speed casting, electromagnetic stirring casting, and electromagnetic brake casting as described above. (The purpose is to provide a continuous casting mold with a long life that does not occur.

(Means for Solving the Problems) The present inventors have made various studies to achieve the above-mentioned objective, and in order to solve such problems, they focused on the flow velocity flowing inside the γ-ray source slit. In this case, we found that it is necessary to satisfy the following conditions.

(2) It is necessary to maintain a flow velocity of 6 s/g+in or higher in the Tγ ray source slit, and to have a groove shape that does not allow the flow velocity to change midway.

(2) The groove shape is such that the flow velocity in the T gamma ray source slit is higher than the flow velocity in the cooling slit other than the gamma ray source slit portion.

(2) Shape the slit to avoid concentration of thermal stress in the Tγ-ray source slit and to prevent stagnation of the cooling water flow.

Therefore, as a result of pursuing a slit shape that satisfies these conditions, we conducted a preliminary experiment to examine the flow velocity resistance and cooling effect by making each slit shape the same shape through the lower and upper ends of the mold. Approximately 76℃ at surface temperature
It was found that the overall lifespan was 2 to 3 times better, and further improvements were made to arrive at the present invention.

That is, the gist of the present invention is to provide a continuous casting mold consisting of a mold copper plate having a cooling slit and a slit for measuring the level of the molten metal on the back side of the surface in contact with the molten metal. The depth of the slit for level measurement, that is, the depth in the direction toward the surface in contact with the molten metal described above, is the same, and the bottom corner of each slit is formed in a cross-sectional shape with rounding. The cross-sectional shape is the same up to the upper end, and more preferably, the ratio of the width of the cooling slit to the width of the slit for measuring the hot water level is 1:
This is a continuous casting mold characterized by having a tit of 1.4 to 1.4.

The fact that the corners of the bottom of each slit are rounded means that the bottom shape in the cross section of each slit is a curved surface and does not have a straight part.This is to avoid concentration of thermal stress and to improve cooling. This is to avoid disturbing the flow of water.

However, as will be described later, the maximum value of the radius of curvature at that time is set to 5R (where R is the slit width), and when exceeding this value, the center portion of the bottom may be a flat surface.

Generally, there is one slit for measuring the hot water level, but it is better to provide as many cooling slits as possible to enhance the cooling effect, and usually about three slits are provided for every 4.5 to 6.5 c+s. The ratio of the width of the slit for measuring the hot water level to the width of each cooling slit is 1.4:1 to 4:
1, but this is because if the slit for measuring the level of the hot water level is narrower than this, the amount of gamma rays transmitted will not be sufficient. This is because it occurs.

Next, the present invention will be further explained with reference to the drawings. FIG. 3 shows a cross section of each slit employed in the present invention.
As shown in Figure 3, over the entire length of the mold from the bottom end to the top end,
A cooling slit 28 and a hot water level measuring slit 30 having the same shape (width x depth x bottom shape) are provided on the copper plate 11.

By adopting such a shape, cross-sectional changes in the middle of the cooling slit, especially the slit for measuring the hot water level, are eliminated, and a decrease in the flow rate of the cooling water flowing therethrough and stagnation of the flow in the shape-changing portion are eliminated.

Note that the bottom surfaces of the cooling slit 28 and the slit 30 for measuring the level of the hot water level are configured with curved surfaces, but this is not particularly necessary in order to maintain a constant flow of cooling water. This is done to minimize thermal stress concentration by eliminating changes as much as possible.

As already mentioned, it is preferable that the slit 30 for measuring the hot water level be made wider than the width of the other cooling slits 28, and that the ratio is i:t, 4 to 1:4. The range is a range where the amount of γ-ray transmission and the cooling effect of this part are balanced.

Note that if the γ-ray source slit and other cooling slits are the same, the flow velocity is the same. By the way, when the mold shown in Figure 1 is used, the comparison of the flow velocity when the width ratio of the gamma ray source slit and the other cooling slit is 2:1 is shown in Table 1 below. The reason why the flow rate is faster in the source slit is because it is wider than the other slits, so there is less water resistance.

By making each first surface the same and making the remaining thickness of the copper plate the same, r
This will lower the allowable stress of the copper plate in the llAR section, and by rounding the bottom of the γ-ray source slit (however, if it exceeds R5, the flat surface + corner part R5) can avoid stress concentration. It can prevent cracks and deformation. Further, in this case, there is no disturbance in the flow of cooling water, and the water flow resistance is minimized.

Next, we looked at how the mold surface temperature changes when the casting speed is changed in the same way as the shape of each slit changes. The results are summarized in Table 2 below. In Table 0, points A and B refer to the temperatures measured at points A and B in FIGS. 2 and 3.

Table 2 As described above, according to the present invention, by passing each slit in the same shape from the lower end of the mold to the upper end, the flow velocity from the inlet of each slit to the outlet of the slit becomes constant.
.

Therefore, the flow velocity in the T-ray source (including the vicinity of the top of the mold) was greatly improved, and the copper plate cooling effect was improved.

As a result, there is no local deformation of the T-ray source, and the lifespan of the copper plate is two to three times longer than that of the conventional one.

Furthermore, since the cooling efficiency has been improved, it is no longer necessary to change the material of the copper plate to a high-strength, high-grade product depending on the casting speed.Therefore, the cost of the copper plate can be reduced, for example, by 30 to 40%.

Furthermore, by improving the shape of each slit in the copper plate according to the present invention, the stress concentration on the γ-ray source slit was constantly reduced, and no cracks were generated. This elimination of cracks is thought to be due to the synergistic effect of the cooling effect and the cross-sectional shape.

(Effects of the invention) According to the present invention, the actual operational benefits are as follows: ■ The number of mold replacements is reduced, and production efficiency is greatly improved; ■ The number of mold replacements is reduced. It is possible to significantly reduce maintenance costs; and ■ benefits such as improved quality and highly efficient energy recovery can be achieved through stable operation.

[Brief explanation of drawings]

FIG. 1 is a schematic longitudinal cross-sectional view of a continuous casting mold; FIG. 2 is a partial cross-sectional view of a conventional mold copper plate; and FIG. 3 is a partial cross-sectional view of a mold copper plate according to the present invention. It is. 10: n-type 11: #l; 4 plates 12:
Molten metal 13: Surface 16: Water supply port 18: Cooling channel 20: Drain port 22: γ-ray source 24: Scintillation section

Claims (2)

[Claims] (1) A mold for continuous casting consisting of a copper plate with a cooling slit and a slit for measuring the level of the molten metal on the back side of the surface in contact with the molten metal, the depth of the cooling slit and the slit for measuring the level of the molten metal A mold for continuous casting, characterized in that each slit has the same cross-sectional shape with rounded bottom corners, and has the same cross-sectional shape from the lower end of the mold to the upper end of the mold. (2) The mold for continuous casting according to claim 1, wherein the ratio of the width of the cooling slit to the width of the slit for measuring the level of hot water is 1:1.4 to 1:4. .