JPH01143712A - Method for cooling steel sheet - Google Patents

Abstract

PURPOSE:To prevent a front end of a steel sheet from supercooling and to homogenize the material of the steel sheet and to improve the flatness thereof by injecting cooling water in a lower part after the front end of the steel sheet passes through on the cooling water header in the lower part. CONSTITUTION:The front end of the steel sheet is detected by a sensor 6 and thereafter the front end position of the steel sheet is calculated by a pulse transmitter connected to a table roll 1 to detect the extent of movement of the steel sheet and a computing element to compute the carrying distance of the steel sheet. At the same time, the front position of the steel sheet certifies by a current director of a driving motor for a dewatering squeezing roll 2 that the front end position of the steel sheet has passed through the dewatering squeezing roll 2 and the front end position is calculated from the position of the dewatering squeezing roll 2. When the front position calculated of the steel sheet has passed through on a lower cooling water heater 3 having a solenoid valve 4 opening and closing the lower cooling channel, the solenoid valve 4 is opened to inject the cooling water from the cooling water header 3. Hereby, the front end of the steel sheet does not scoop the lower cooling water to prevent the front end of the steel sheet from supercooling.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for cooling a steel plate that can prevent the tip of the steel plate from being overcooled in equipment for cooling the steel plate after hot rolling. It is.

"Prior art" In conventional thick steel plate online cooling equipment, a method was adopted in which cooling water was jetted over the entire area of the cooling equipment and cooled by passing through the thick steel plate.However, in such a method, The cooling water from the upper header applied to the center of the steel plate flows to the front and rear ends of the steel plate, and the temperature at the front and rear ends of the steel plate being carried into the cooling equipment is originally lower than that at the center. There was a problem in that the steel plate could not be cooled uniformly, and the mechanical test values of the steel plate after cooling were different between the center and the leading and trailing edges, and the flatness of the leading and trailing edges could not be achieved.These problems have been resolved. For example, there is a technique disclosed in Japanese Unexamined Patent Publication No. 56-86622.This technique attempts to obtain a uniform cooling effect by applying cooling water at different times at the front and rear ends and at the center. This is an effective means to prevent supercooling of the leading and trailing edges caused by cooling water flowing from the upper part of the steel plate.

[Problems to be Solved by the Invention] However, the supercooling of the tip of the steel plate is not only caused by the flow of upper cooling water as described above, but also by the lower cooling water spouted to the upper part in a space where there is no steel plate. Another cause is the so-called "scoop water," in which water rides on the upper surface of the steel plate tip and cools the steel plate. FIG. 4 is a diagram showing the generation of "scooped water", and shows a situation in which the cooling water injected from the lower cooling header 3a in front of the tip of the steel plate 7 is on the upper surface of the tip of the steel plate 7. The above method has a problem in that it cannot be an effective means for overcooling caused by this "scooping water". The present invention was made in view of the above circumstances, and it is an object of the present invention to provide a method that prevents supercooling caused by "scooping water" and enables uniform cooling of a steel plate.

[Means for solving the problem] The above problem is solved by starting water flow through the cooling header after the tip of the steel plate passes through the ladder position to the lower cooling.

In order to accurately grasp the position of the tip of the steel plate in the cooling equipment, the position of the tip of the steel plate is detected by a position detector, and also by detecting changes in the load current of the draining roller provided in the cooling equipment. detecting the movement distance of the steel plate above the conveyance roller by a conveyance distance detector;
The position of the tip of the steel plate is sequentially calculated from these values.

[Operation] Since the lower cooling water is injected after the tip of the steel plate passes over the lower cooling water header, the tip of the steel plate does not scoop up the lower cooling water, and the tip of the steel plate is prevented from overcooling. Moreover, the upper surface of the tip of the steel plate is prevented from being further supercooled than the lower surface.

[Embodiment of the Invention] An embodiment of the invention will be described in detail below with reference to the drawings. FIG. 1 is a configuration diagram showing an apparatus used for accelerated cooling of a steel plate according to the present invention. A is a quenching zone, which is a device used when manufacturing Gyleft quench material. B is an Enoki refrigerating zone, which is a device used when producing accelerated cooling material. 1 is a table roll, 2 is a draining squeeze roll, 3 is a lower cooling water header, 4 is a solenoid valve that opens and closes the lower cooling water channel, 5 is an upper cooling water header, and 6 is a sensor that detects the tip of the steel plate. In addition, there is a pulse transmitter (not shown) that detects the transport distance from the sensor 6 that detects the tip of the steel plate, a calculator (not shown) that calculates the transport distance of the steel plate, and the load on the drive motor of the draining squeeze roll 2. It has a current detector (not shown). When manufacturing Gyleft quench material, water is passed through all the lower cooling water headers 3 and upper cooling water headers 5 of the rapid cooling zone A and the slow cooling zone B to cool the steel plate. When producing an accelerated coolant, water is not passed through the quenching zone A, but only through the quenching zone B.

The operation of the lower cooling water header 3 and the upper cooling water header 5 at this time will be described in detail. The steel plate is conveyed from left to right in FIG. The tip of the steel plate is detected by a sensor 6 that detects the tip of the steel plate, and then a pulse transmitter (not shown) connected to the rotating shaft of the table roll 1 that detects the amount of movement of the steel plate and the conveyance distance of the steel plate are calculated. Arithmetic unit (not shown)
Calculate the position of the tip of the steel plate. At the same time, a load current detector for the drive motor of the draining squeeze roll 2 (not shown)
After confirming that the tip position of the steel plate has passed the drain squeeze roll 2, the tip position of the steel plate is calculated from the position of the drain squeeze roll 2 using the same method as described above. When the calculated tip position of the steel plate passes over the lower cooling water header 3 having the solenoid valve 4 that opens and closes the lower cooling water channel, the solenoid valve 4 that opens and closes the lower cooling water channel is opened and the lower cooling water header 3 is moved from the lower cooling water header 3. Spray cooling water. That is,
As shown in FIG. 2, for the lower header 3a, cooling water is not injected before the tip of the steel plate 2 passes the position of the lower header 3a, and as shown in FIG.
The cooling water should be injected after passing the position.

[Effects of the Invention] As explained above, in the present invention, the lower cooling water is injected after the tip of the steel plate passes over the lower cooling water header, so the tip of the steel plate does not scoop up the lower cooling water, and the steel plate Overcooling of the tip is prevented. Moreover, the upper surface of the tip of the steel plate is prevented from being further supercooled than the lower surface. As a result, the material of the steel plate becomes uniform,
This has the effect of improving the flatness of the leading and trailing ends.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a device used for accelerated cooling of a steel plate according to an embodiment of the present invention, Fig. 2 is a diagram showing the situation before the tip of the steel plate passes through the target lower cooling header, and Fig. 3 4 is a diagram showing the situation after the tip of the steel plate passes through the target lower cooling header, and FIG. 4 is a diagram showing the situation in which "scoop water" is generated by the conventional steel plate cooling method. 1...Table roll, 2...Drain squeeze roll,
3... Ladder to lower cooling water, 4... Solenoid valve to open and close lower cooling water channel, 5... Ladder to upper cooling water, 6...
- Sensor that detects the tip of the steel plate, 7... steel plate.

Claims (1)

[Claims] While conveying the hot rolled steel plate on conveyor rollers,
In a method of cooling with cooling water from an upper and lower cooling header or a lower cooling header having injection nozzles provided between conveyor rollers in cooling equipment, the tip position of the steel plate is detected by a position detector, and Detection is made by detecting a change in the load current of the provided draining squeeze roll, the distance traveled by the steel plate above the conveyance roller is detected by a conveyance distance detector, and the position of the tip of the steel plate is sequentially calculated from these values. A method for cooling a steel plate, characterized in that water flow through the lower cooling header is started after the tip of the steel plate passes through the lower cooling header position.