JP3890773B2 - Slab cooling method and equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and equipment for cooling a slab of 250 mm square or less, generally called a billet, and is particularly suitable for suppressing and preventing warpage in the cooling process.
[0002]
[Prior art]
For example, a slab (bloom) of 500 mm square or less cast by a continuous casting machine is generally transported to a rolling mill as it is, or rolled after being cooled in a cooling bed and then transported. are categorized.
[0003]
[Problems to be solved by the invention]
However, a slab generally called a billet of 250 mm square or less has a problem that warpage tends to occur during the cooling process. In particular, when the slabs in the middle of cooling are brought into contact with each other and carried out, the outermost slab has a large warp. It was known that this warpage seems to be affected by temperature, but in order to cool all the slabs so that they do not warp, the slabs must be placed sufficiently apart from each other. A vast cooling floor is required.
[0004]
An object of the present invention is to provide a cooling method and equipment for a slab that can suppress and prevent plastic deformation such as warpage of a slab of 250 mm square or less.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, the method for cooling a slab according to claim 1 of the present invention is a method for cooling a slab of 250 mm square or less, and when the slabs are brought into contact with each other during unloading, the slab The surface temperature is cooled to 600 ° C. or lower.
[0006]
Moreover, the cooling method of the slab which concerns on Claim 2 among this invention is a method of cooling a slab of 250 mm square or less, Comprising: At the time of conveyance, adjacent slabs are spaced apart by 500 mm or more and conveyed. It is characterized by this.
[0007]
Further, the slab cooling facility according to claim 3 of the present invention is a facility for cooling a slab of 250 mm square or less, and requires a time required for the slab surface temperature to be 600 ° C. or less. It is provided with the piece conveyance path | route and the thermometer which detects slab surface temperature.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the method for cooling a slab and its equipment according to the present invention will be described in detail with reference to the drawings.
[0009]
FIG. 1 is an explanatory diagram of a continuous casting machine and its payout portion according to this embodiment. In this figure, in order to facilitate understanding, the continuous casting machine to the payout yard are shown in a front view, and the payout yard is shown in a plan view, and the two are joined and displayed. The molten steel supplied from the ladle 1 to the tundish 2 is cast in a mold 3 and sent out as a slab 4, changed in posture to horizontal transfer by a bending roller 5, then cut by a cutting machine 6 and cast into a slab 7. become. This is stamped by a stamping machine 8, bent by a bending straightening machine 9, and carried out through a dispensing yard 10. Although this continuous casting machine can also produce various slabs 7 according to the size of the mold 3, only a slab of 250 mm square or less called the billet will be described here.
[0010]
The slabs carried out from the payout yard are placed on a trailer side by side in contact with each other as shown in FIG. 2, for example. Then, during unloading, warping occurs in the endmost slabs arranged, that is, the outer slabs. This warpage occurs because the outer side of the outer slab is in contact with the atmosphere, and the opposite side, that is, the inner side, is still in contact with the hot slab, that is, the hot piece. Appears as warp due to plastic deformation.
[0011]
Therefore, when this thermoplastic deformation was investigated from both the temperature difference between the outer side surface and the inner side surface of the outer slab and the average temperature of the slab, it was found that plastic deformation occurred in the shaded area in FIG. It was. Next, how is the coordinate point between the temperature difference between the outer surface and the inner surface of the outer slab, which changes with time, and the average temperature of the slab, depending on the temperature immediately before contact, that is, the initial contact temperature. As a result of investigation, for example, when the contact initial temperature is 800 ° C., the temperature difference-average temperature coordinate enters the thermoplastic deformation region, but does not enter when the contact initial temperature is 600 ° C. That is, if the initial contact average surface temperature is 600 ° C. or less, even if the slabs are brought into contact with each other, warpage due to thermoplastic deformation does not occur or can be suppressed to a small level.
[0012]
Using this result, the elapsed time from the meniscus required for the average slab surface temperature to be 600 ° C. or less was investigated. As shown in FIG. It was found that the surface temperature was 600 ° C. or lower. In other words, if a path that takes 40 minutes or more from the meniscus to the carry-out is configured, the average surface temperature of the slabs that come into contact with the carry-out is 600 ° C. or less. Even so, the outer slab is not warped.
[0013]
However, the present inventors also paid attention to the point that no condition is required if the slabs are not in contact with each other, and similarly investigated the thermal influence from adjacent slabs. FIG. 5a shows the relationship between the slab (billet) interval expressed by the distance between the centers of 150 mm square slabs and the temperature difference between the outside and the inside of the adjacent slabs, and FIG. 5b shows the slab (billet) interval. The relationship with the warpage amount is shown respectively. Since it was found that the temperature difference and the warp amount are substantially proportional, it can be seen that the temperature difference and the warp amount are inversely proportional to the slab (billet) interval. Here, since the thermoplastic deformation expressed by the amount of warpage is a problem, paying attention to this point, if the slab (billet) interval represented by the center-to-center distance is 500 mm or more, preferably 650 mm or more, the amount of warpage is 25 mm or less. It turns out that there is no problem as a product.
[0014]
As described above, in this embodiment, the payout yard is configured as shown in FIG. That is, the line from the front side of the transfer line to the carry-out is the main, and the cooling bed at the back of the transfer line is reserved. The spare cooling floor is the second storage bank 13, the main line having the same depth (11 m) is the first storage bank 11, and the distance between the adjacent slabs is 900 mm at the center distance. The residence time in the storage bank 11 was 7 minutes. Since the required time from the meniscus to the first storage bank 11 is 20 minutes, a walking beam type new storage bank 12 having a depth of 10 m is provided on the main line following the first storage bank 11. The distance between the slabs was set to 660 mm in the center-to-center distance, and the required conveyance time was set to 14 minutes. As a result, the total required time from the meniscus to unloading is 40 minutes, and the average surface temperature of the slab is 600 ° C. or less. By configuring the slab conveyance line in this way, in this embodiment, it is possible to suppress and prevent warpage of a slab of 250 mm square or less.
[0015]
In the present embodiment, the interval between the slabs is fixed, but the slab average surface temperature only needs to be 600 ° C. or less before the slabs are brought into contact with each other during unloading. Since the distance between the centers should be 500 mm or more, the slab surface temperature in the discharge yard was detected with a thermometer, and the final slab average surface temperature was detected to be 600 ° C. or less. The slab interval may be adjusted according to the slab surface temperature.
[0016]
【The invention's effect】
As described above, according to the method for cooling a slab of the present invention, when cooling slabs of 250 mm square or less, when bringing the slabs into contact with each other during unloading, the slab surface temperature is cooled to 600 ° C. or less. In addition, it is possible to suppress and prevent plastic deformation such as warpage due to a temperature difference of the slabs by transporting adjacent slabs at a distance of 500 mm or more at the center distance during transportation.
[0017]
Further, according to the slab cooling equipment of the present invention, a slab conveying path that requires a time required for the slab surface temperature to be 600 ° C. or lower when cooling a slab of 250 mm square or less, and the slab By providing a thermometer that detects the surface temperature, a time required for the temperature to be 600 ° C. or less by the time of unloading is obtained according to the surface temperature of the slab, By doing so, it is possible to suppress and prevent plastic deformation such as warpage due to a temperature difference of the slab.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a continuous casting machine in which a slab cooling method and apparatus according to the present invention are implemented.
FIG. 2 is an explanatory diagram of slab warpage that occurs during unloading.
FIG. 3 is an explanatory diagram showing a relationship between a surface temperature difference and an average surface temperature in an outer slab.
FIG. 4 is an explanatory diagram showing the relationship between the elapsed time from the meniscus and the average surface temperature of the slab.
FIG. 5 is an explanatory diagram showing a relationship between a slab interval, a temperature difference, and a warp amount.
6 is a detailed explanatory diagram of the payout yard in FIG. 1. FIG.
[Explanation of symbols]
1 ladle 2 tundish 3 mold 4 slab 5 bending roll 6 cutting machine 7 slab (billet)
8 is a stamping machine 9 is a bending straightening machine 10 is a payout yard 11 is a first storage bank 12 is a new storage bank 13 is a second storage bank

Claims (3)

A method for cooling a slab of 250 mm square or less, wherein the slab surface temperature is cooled to 600 ° C. or lower when the slabs are brought into contact with each other during unloading. A method for cooling a slab of 250 mm square or less, wherein adjacent slabs are transported at a distance of 500 mm or more at a center-to-center distance during transport. A facility for cooling a slab of 250 mm square or less, comprising a slab conveying path that requires a time required for the slab surface temperature to be 600 ° C. or less, and a thermometer that detects the slab surface temperature. A slab cooling facility characterized by that.

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