JP2011125883A - Slab cooling method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a slab cooling method and device, for effectively cooling a high temperature slab after continuous casting, without generating warpage. <P>SOLUTION: Cooling water feed nozzles 3a, 3b of water-spraying and cooling the side faces in the longitudinal direction of stacked slabs 1 are arranged on both the sides of a slab placing stand 2 to be stacked with a plurality of high temperature slabs after continuous casting. The intervals between the tips of cooling water feed nozzles 3a, 3b and the side face in the longitudinal of each slab are controlled to 1,500 to 2,000 mm, and the area of ≥80% in the side face in the longitudinal direction of the slab 1 is water-sprayed and cooled at the water quality density of 2-5 L/min/t. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a slab cooling method and a slab cooling device capable of efficiently cooling while suppressing generation of warpage in a state where a plurality of steel pieces (hereinafter referred to as slabs) after continuous casting are stacked. It is.

  The continuously cast slab is transported to the next hot rolling step and subjected to a predetermined treatment. From the viewpoint of production management, it is widely cooled to the room temperature before the predetermined treatment. It has been broken. For this cooling, a method of water-cooling in a state where a plurality of slabs are stacked is widely performed due to the limitation of the yard space. On the other hand, depending on the method of water cooling, there is a problem that deformation of the slab occurs.

  The cause of the deformation will be described with reference to the drawings. In cooling billets, as shown in FIG. 3, a method of injecting cooling water to the end face in the longitudinal direction is widely used for stacked slabs. After contact, it may fall along the cooling surface and accumulate between the stacked slabs as shown in FIG. 1 or between the bottom slab and the pedestal. In the staying part, as shown in FIG. 2, the steel slab is rapidly cooled, so that the temperature difference between the upper and lower surfaces of the steel slab increases, and the amount of thermal expansion (thermal stress) on the lower surface and the amount of thermal expansion on the upper surface are increased. As a result, the slab deforms. In particular, in the lowermost slab, the cooling of the lower surface proceeds by the water staying on the cradle, and the slab is deformed into a convex shape. In addition to this thermal expansion effect, due to the slab's own weight, upward downward warping (hereinafter referred to as “upward warping”) expands with the progress of cooling due to the vertically downward force acting on the end of the steel piece in the longitudinal direction.

  In particular, when an upper warp occurs in the bottom slabs stacked, the slabs stacked on the slabs deform in a shape that conforms to the shape of the bottom slab, and the stacked slabs are chained upward. It becomes a shape. Such a slab in which warpage has occurred becomes a factor causing various obstacles in the subsequent hot rolling process.

  For cooling the high-temperature slab after continuous casting, for example, there is a method disclosed in the following patent document.

  In Patent Document 1, after cooling in the air until the surface temperature of the side surface of the continuously cast steel slab is 600 ° C. or lower, the steel slab is laminated to a height of 1 m or more, A method of spraying and cooling both longitudinal sides of the steel slab located in the lower part except for a range of at least 0.3 m downward from the upper surface is disclosed. There is a high possibility that cooling water stays in the gap between the lower surface and the ground and cools the lower surface of the steel slab, and as described above, warping occurs from the bottom steel slab.

In addition, when water spray cooling is not performed until the surface temperature becomes 600 ° C. or less, a space such as a yard is required until the slab temperature decreases from casting to 600 ° C., and the cooling time to room temperature becomes longer. , Production efficiency decreases.

Japanese Patent No. 4089664

  This invention is made | formed in view of this point, and it aims at providing the slab cooling method and apparatus which can cool the high temperature slab after continuous casting effectively, without generating a curvature. Is.

  In order to achieve the above-mentioned object, the inventors have conducted extensive research, and as a result, cooling water was stacked by cooling the slab with the amount of cooling water sprayed in the longitudinal direction of the high-temperature slab and the injection distance within a predetermined range. It has been found that cooling water can be uniformly cooled without accumulating cooling water between the bottom slab and the ground.

The present invention has been made on the basis of the above findings, and has the following gist.
(1) The distance between the tip of the cooling water supply nozzle and the side surface in the longitudinal direction of the slab is 1500 mm or more and 2000 mm or less, and the water amount density is 2 L / min / t or more and 5 L / min / t or less, and the area is 80% or more of the longitudinal side surface. Method and apparatus for cooling a high-temperature slab for water spray cooling.
(2) In the invention of (1), the cooling water supply nozzle is a conical nozzle having an injection angle of 40 ° or more.

  According to the cooling method and the cooling device of the high-temperature slab of the present invention, after laminating a plurality of high-temperature slabs after continuous casting, the water density and the cooling range of the cooling water to be sprinkled are optimized when the water is cooled. Therefore, it is possible to prevent the slab from warping and cool the slab efficiently without taking any special measures.

It is the schematic which showed the retention state of the cooling water. It is a figure showing the temperature fall by cooling water retention. It is the schematic (front view) which showed the water spray cooling method of this invention. It is the schematic (side view) which showed the water spray cooling method of this invention.

  In the present invention, as described above, after laminating the slabs after continuous casting, both end surfaces in the longitudinal direction of the slabs are end surfaces in the longitudinal direction at a water density of 2 L / min / t or more and 5 L / min / t or less. This is a cooling method for a slab in which an area of 80% or more is sprayed and cooled. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an outline of the configuration of the cooling device according to the present embodiment.

  As shown in FIG. 3, in the vicinity of both sides in the longitudinal direction of the slab table 2 on which a plurality of stacked high-temperature slabs 1 are installed, water is sprayed toward the side surfaces of the stacked slabs 1. A cooling device 3 is provided. From the cooling nozzles 3a and 3b, cooling water is sprayed so as to cover 80% or more of both end faces of the stacked high-temperature slabs 1. The amount of cooling water to be injected (water density) is 2 L / min / t or more and 5 L / min / t or less with respect to the total weight (t: ton) of the stacked slabs. The distance L between the tips of the supply nozzles 3a and 3b and the end face of the slab 1 to be cooled is 1500 mm or more and 2000 mm or less. As shown in FIG. 4, a large number of cooling nozzles 3a and 3b are installed in the longitudinal direction so as to minimize the surface area of the slab that is not sprinkled.

  Generally, as the amount of cooling water increases, the time required to cool the high-temperature slab to room temperature can be shortened. However, as described above, between the slabs in which the cooling water is stacked and between the bottom slab and the ground or slab stand. When it accumulates in the gap between the two, deformation due to the temperature difference between the upper and lower surfaces of the slab occurs. For this reason, it is important to instantly vaporize the water after cooling and suppress the cooling water pool by the diffusion effect of the outside air.

  From the above viewpoint, the amount of the cooling water to be injected is 5 L / min / t or less with respect to the total weight of the stacked slabs, and the end surfaces of the cooling water supply nozzles 3a and 3b and the end surface of the slab 1 that performs cooling. The distance L must be 1500 mm or more. However, if the amount of the cooling water to be injected is too small, it takes a long time for cooling. Therefore, in order to cool to the target temperature in a predetermined time, it is set to 2 L / min / t or more. The water cooling time is within 10 hours, and the temperature is less than 100 ° C.

  On the other hand, if the cooling water injection distance is increased, the cooling water may not sufficiently reach the slab 1 due to scattering by the wind and the like, and therefore the distance between the tips of the cooling water supply nozzles 3a and 3b and the end surface of the slab 1 that performs cooling. L is 2000 mm or less.

  Further, it is desirable that the time for cooling the high-temperature slab to room temperature is shorter from the viewpoint of production control. Therefore, in ensuring cooling efficiency, water is sprayed over an area of 80% or more of the end surface in the slab longitudinal direction.

  The cooling water supply nozzles 3a and 3b are preferably conical nozzles having an injection angle of the cooling water jet 4 of 40 ° or more. This is because, when the area of 80% or more of the end face of the slab 1 is covered with cooling water, the number of nozzles to be installed can be reduced for securing the water spray area, and the capital investment can be suppressed. Further, since the cooling water is jetted in the form of finer droplets, it is easily vaporized by contact with the high temperature slab, and is effective in preventing the generation of stagnant water.

Table 1 shows the test results confirming the effect of the slab cooling method according to the present invention.

  In Table 1, Test 1 to Test 8 show examples of the present invention, and Test 9 to Test 14 show comparative examples. As test conditions, the influence of the water density for cooling the slab and the influence of the slab and the cooling water supply nozzle tip distance were evaluated.

The slab temperature at the start of cooling was used based on the temperature at the center of the slab longitudinal direction.
Since a conveyance time is required from the end of continuous casting to the start of the test, cooling was performed from a temperature of about 700 ° C.

Since the size of the slab to be cooled varies, it is shown in Table 1 as an average size.
The number of stages is 7 stages.

  Tests 1 to 8 are sprinkling cooling within 10 hours, which is the target cooling time, and the end surface temperature in the longitudinal direction can be lower than the target 100 ° C., and the deformation amount (warpage) of the slab at the end of cooling is The allowable amount of less than 70 mm was achieved. Test 9 is a case where the water density is less than 2 L / min / t, and the amount of warpage achieved the target, but the required cooling time failed to achieve the target.

Tests 12 to 14 were cases where the amount of cooling water was greater than 5 L / min / t, and the cooling time was shortened, but the amount of warpage was greater than the allowable amount, and the objective could not be achieved. In Tests 10 and 11, the cooling water injection distances are 2100 mm and 1400 mm, respectively. In Test 10, the water cooling time cannot be within the target, and in Test 11, the amount of warpage is less than the regulation value. It became bigger.

1 stacked slabs 11 to 17 slabs 2 slab table 3 cooling device 3a cooling water supply nozzle 3b cooling water supply nozzle 4 cooling water jet
L Slab longitudinal direction end surface and cooling water nozzle tip distance

Claims (4)

  A method for cooling a high-temperature slab after continuous casting, wherein a plurality of stacked slabs in a stacked state are provided with a cooling water supply nozzle on the longitudinal side surface, and the tip of the cooling water supply nozzle and the slab longitudinal side surface The slab cooling method is characterized by spraying and cooling an area of 80% or more of the side surface in the longitudinal direction at a water density of 2 L / min / t or more and 5 L / min / t or less with an interval of 1500 mm to 2000 mm.   2. The slab cooling method according to claim 1, wherein a conical nozzle having an injection angle of 40 ° or more is used as the cooling water supply nozzle.   A slab cooling device in which a cooling water supply nozzle for sprinkling and cooling the longitudinal side surface of a slab is disposed on both sides of a slab placing table on which a plurality of high-temperature slabs after continuous casting are stacked. The distance between the tip and the side surface in the longitudinal direction of the slab is 1500 mm or more and 2000 mm or less, and the water density of 2 L / min / t or more and 5 L / min / t or less is used for water-cooling the area of 80% or more of the longitudinal side surface. A slab cooling device characterized by that.   The slab cooling device according to claim 3, wherein the cooling water supply nozzle is a conical nozzle having an injection angle of 40 ° or more.

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