JPH0910823A - Method for controlling flow rate of continuous cooling device for plate - Google Patents

Abstract

PURPOSE: To prevent the shape of a plate from becoming bad caused by the occurrence of the uneven cooling, due to an uneven injection state in the case of slow cooling while throttling the cooling water quantity of a continuous cooling device injecting cooling water from the upside and the downside of a plate 1 running horizontally and continuously. CONSTITUTION: In a limit flow rate or below in which the flow rate of upper nozzles 3 becomes uneven, by making the flow rate of either the upper nozzles 3 or lower nozzles 4 zero, or by fixing the flow rate of the upper nozzles 3 to the limit flow rate and by adjusting only the flow rate of the lower nozzles 4, the control range of the flow rate is enlarged downward, and even and slow cooling is achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling medium in a continuous steel plate cooling apparatus for cooling a plate by continuously running a high temperature plate, particularly a thin steel plate horizontally, and injecting a cooling medium from a large number of nozzles on the upper and lower surfaces thereof. Flow rate control method.

[0002]

2. Description of the Related Art As a device that has been widely used for the purpose of continuously cooling a thin steel plate, a high-temperature plate is continuously run horizontally and a cooling medium is sprayed on its upper and lower surfaces from a number of nozzles to cool it. There is technology. Although water is generally used as the cooling medium in many cases, a two-fluid nozzle that mixes water and air and ejects the mixture is often used.

An example of such a device is schematically shown in FIG. This will be described below according to this example. The steel plate 1 that continuously travels on the transport roll 5 passes through the inside of the cooling device main body 2, and is cooled by jetting cooling water from the upper nozzle 3 and the lower nozzle 4.
The cooling water is boosted from the water storage tank 6 by the pump 7 and is sent to the upper nozzle 3 and the lower nozzle 4 by the supply pipe 8 and the steel plate 1
Injected to. A heat exchanger is provided in the middle of the pipe 8 to cool the water. The water after jetting is returned pipe 10, filter 1
It is returned to the water storage tank 6 through 1 and is recycled.

In the conventional water amount control, a flow rate adjusting valve 12 is provided in the middle of the supply pipe 8, the temperature of the steel plate on the outlet side of the cooling device is detected by the plate thermometer 13, and the total water amount required by the control device 14 is calculated. Calculate and control the regulating valve 12. The water distribution above and below is normally adjusted to be 1: 1 by the manual valve 15 or a fixed orifice, and it is not necessary to operate this during operation. Even when air is mixed, the amount of air is generally kept constant and the amount of water is controlled as described above.

[0005]

A problem of the conventional flow rate control method in cooling a plate is that if the cooling water amount is small, the cooling becomes non-uniform. That is,
Since the nozzle tip opening of the upper nozzle is downward, there is a limit point, that is, a limit flow rate, at which it becomes difficult to uniformly jet from a large number of nozzles when the amount of water decreases. If the amount of water in the upper nozzle is reduced below this limit flow rate, a non-uniform jetting state occurs, resulting in uneven cooling and poor plate shape.

Therefore, in such a cooling device, the flow rate cannot be reduced to less than twice the limit flow rate, and it is difficult to perform slow cooling. It is an object of the present invention to provide a flow rate control method for a continuous steel plate cooling device capable of uniformly and accurately cooling the entire surface of a plate when performing such slow cooling.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, in which a hot plate is continuously run horizontally and a cooling medium is jetted from a large number of nozzles on the upper and lower surfaces thereof. When cooling the plate, determine the limit flow rate at which the flow rate of the upper nozzle becomes non-uniform, and set the flow rate of either the upper or lower nozzle to 0 in the region where the total required upper and lower nozzle flow rate is less than twice the limit flow rate. A flow control method for a steel plate continuous cooling device is provided.

Further, in this case, instead of setting the flow rate of one of the upper and lower nozzles to 0, the flow rate of the upper nozzle is fixed to the limit flow rate, and only the flow rate of the lower nozzle is adjusted. A method for controlling a flow rate of an apparatus is provided.

[0009]

The present invention corresponds to the case of gentle cooling when the cooling medium is supplied from the upper and lower nozzles to cool from both sides of the plate. Since the upper nozzle has a downward opening, the cooling medium flows nonuniformly on the plate surface at a small flow rate. The flow rate at the critical point where such non-uniformity occurs is defined as the critical flow rate. The case where the required flow rate of the cooling medium to be supplied from the upper and lower nozzles is not more than twice the limit flow rate is the required control region of the present invention. In this region, in the first aspect of the present invention, control is performed so that either the upper or lower flow rate becomes zero. Further, in the second aspect of the present invention, the flow rate of the upper nozzle is fixed to the limit flow rate, and only the flow rate of the lower nozzle is adjusted. In this way, the accurate flow rate control range of the cooling device is expanded to the small flow rate side to achieve uniform slow cooling. When the plate to be cooled is thick, there is a problem that a temperature difference occurs between the front and back of the plate in single-sided cooling, but the temperature difference between the front and back of the thin plate is so small that it can be ignored.

When the present invention is adopted, if the upper nozzle flow rate is set to 0, the lower nozzle does not have a limit flow rate like the upper nozzle, so that the flow controllable range is expanded downward to a very small flow rate. can do. Even if the flow rate of the lower nozzle is set to 0 in consideration of the heat resistance of the upper nozzle, it is possible to perform the flow rate control that achieves uniform cooling up to about half of the conventional total flow rate of the upper and lower sides. This will be described below for the cooling system of FIG. 6 with reference to FIGS. 2 to 4, the horizontal axis represents the total required flow rate Qt, and the vertical axis represents the flow rate Qu of the upper nozzle and the flow rate Qb of the lower nozzle.

(A) FIG. 2 shows a case where the flow rate Qu of the upper nozzle is Qu = 0. If Qu = 0 in a region where the total flow rate Qt of the upper nozzle flow rate Qu and the lower nozzle flow rate Qb is less than or equal to twice the limit flow rate Qg, Qb can be adjusted as shown by the broken line in FIG. it can. (B) FIG. 3 shows a case where the flow rate Qb of the lower nozzle is Qb = 0. If Qb = 0 in a region where the total flow rate Qt of the upper nozzle flow rate Qu and the lower nozzle flow rate Qb is less than or equal to twice the limit flow rate Qg, Qa can be adjusted as shown by the solid line in FIG. Therefore, the flow rate can be adjusted until the flow rate Qu of the upper nozzle reaches the limit flow rate Qg.

(C) FIG. 4 shows a case where the flow rate Qu of the upper nozzle is fixed to the nozzle limit flow rate Qg, where Qt is Qg.
Qu is fixed to Qg in a region of 2 times or less, and only Qb is adjusted.

[0013]

FIG. 1 is a flowchart showing an embodiment of the present invention. In this embodiment, a water and air two-fluid nozzle was used instead of the conventional device configuration described in FIG. Air is guided from the blower 16 through the duct 17 to the nozzle header. The nozzle header forms a double pipe, and the nozzle is configured to supply and jet water to the center of the air hole.

In this device configuration, a shutoff valve 18 is added to the upper nozzle side of the pipe branched from the water supply pipe 8 to the upper and lower nozzles. The limit point at which uniform injection of the upper nozzle in the cooling zone having a length of about 2 m, that is, the limit flow rate Qg was experimentally found to be about 5 m ³ / h. The shutoff valve 18 is closed in a region of twice the limit water amount or less. The upper and lower total flow rate (twice the limit flow rate, that is, 2Qg) at the limit point for performing control to close the shutoff valve was set to 2Qg = 2 × 5 = 10 m ³ / h. Also, to prevent hunting of control, about 10
% Dead zone was set and controlled.

As a result, before the control method was adopted, when the amount of water was reduced, the injection of the upper nozzle became non-uniform and the plate shape was disturbed, but this phenomenon disappeared. If the shutoff valve 18 is provided on the lower nozzle side of the pipe branched into the upper and lower nozzles, the control range is slightly narrowed, but the upper nozzle is preferentially ejected, which is useful for protecting the upper nozzle, which is disadvantageous in heat resistance. Is.

Next, another embodiment will be described with reference to FIG. Although the overall configuration of the device is omitted, it is the same as in FIG. The flow rate adjusting valves 12 in FIG. 6 were branched for the upper and lower nozzles of the water supply pipe 8 and then attached one by one. Then, when the required water amount Qt becomes equal to or less than twice the limit water amount Qg, the flow rate Qu of the upper nozzle is fixed to Qg, and the flow rate Qb of the lower nozzle is adjusted to Qb = Qt−Qg.

[0017]

EFFECTS OF THE INVENTION According to the present invention, the practical effect is large such that the lower limit of the flow rate control range can be expanded without a large amount of device modification work and cost, and delicate slow cooling can be performed, resulting in a reduction in shape defects. .

[Brief description of the drawings]

FIG. 1 is a flow sheet showing a device configuration of a cooling device according to an embodiment.

FIG. 2 is a graph illustrating the operation of the present invention.

FIG. 3 is a graph illustrating the operation of the present invention.

FIG. 4 is a graph illustrating the operation of the present invention.

FIG. 5 is a flow sheet of another embodiment.

FIG. 6 is a flow sheet showing a conventional example.

[Explanation of symbols]

 1 Steel Plate 2 Cooling Device 3 Upper Nozzle 4 Lower Nozzle 5 Conveying Roll 6 Water Storage Tank 7 Water Supply Pump 8 Water Supply Piping 10 Water Return Piping 11 Filter 12 Flow Control Valve 13 Plate Thermometer 14 Controller 15 Manual Valve 16 Blower 17 Duct 18 Shutoff valve

Claims (2)

[Claims] 1. When a high-temperature plate is continuously run horizontally and a cooling medium is sprayed on the upper and lower surfaces of the plate by cooling medium to cool the plate, the limit flow rate at which the flow rate of the upper nozzle becomes non-uniform is determined. A flow rate control method for a continuous steel plate cooling device, wherein the flow rate of any one of the upper and lower nozzles is set to 0 in a region where the required total flow rate of the upper and lower nozzles is not more than twice the limit flow rate. 2. The steel sheet according to claim 1, wherein the flow rate of the upper nozzle is fixed to a limit flow rate and only the flow rate of the lower nozzle is adjusted, instead of setting the flow rate of either the upper or lower nozzle to zero. Flow control method for continuous cooling device.