JPH082460B2 - Steel plate cooling method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a steel sheet cooling method capable of preventing the tip of the steel sheet from being overcooled in a facility for cooling the steel sheet after hot rolling. Is.

"Prior Art" In the conventional thick steel plate online cooling equipment, a method of cooling a thick steel plate while cooling water is being sprayed over the entire cooling equipment has been adopted. The cooling water from the upper header applied to the central part of the steel plate flows to the front and rear ends of the steel plate, and the temperature of the front and rear ends of the steel plate that is originally carried into the cooling equipment is lower than that of the central part. There was a problem that it was not possible to uniformly cool, and the mechanical test values of the steel sheet after cooling differed between the central part and the front and rear ends, and the flatness at the front and rear ends did not appear. For example, there is a technique disclosed in Japanese Patent Laid-Open No. 56-86622. With this technique, it is possible to obtain a uniform cooling effect by changing the time of applying cooling water at the front and rear end portions and the central portion. something like There is an effective means for subcooling the leading and trailing portions that occur by the cooling water from the steel plate top.

[Problems to be Solved by the Invention] However, the fact that the tip of the steel plate is overcooled is not only caused by the flow of the upper cooling water as described above, but also the lower cooling that is jetted to the upper part in the space without the steel plate. The so-called "scooping water", in which water rides on the top surface of the steel plate tip to cool the steel plate, is also a cause. FIG. 4 is a diagram showing the generation of “scooping water”, showing a state in which the cooling water sprayed from the lower cooling header 3 a in front of the tip of the steel plate 7 is on the top surface of the tip of the steel plate 7. The above-mentioned method has a problem that it cannot be an effective means for supercooling by "scoop water". The present invention has been made in view of such circumstances, and an object thereof is to provide a method capable of preventing supercooling by "scooping water" and capable of uniformly cooling a steel sheet.

[Means for Solving the Problems] The above problems are solved by starting the passage of water through the cooling header after the leading end position of the steel sheet has passed the lower cooling header position.

In order to accurately grasp the tip position of the steel plate in the cooling equipment, it is also possible to detect the tip position of the steel sheet by a position detector and also detect the change in the load current of the draining roller provided in the cooling equipment. The moving distance of the steel plate on the carrying roller is detected by a carrying distance detector, and the tip position of the steel plate is sequentially calculated from these values.

[Operation] Since the lower cooling water is sprayed after the tip of the steel sheet passes over the lower cooling water header, the tip of the steel sheet does not scoop up the lower cooling water, and the tip of the steel sheet is prevented from being overcooled. Moreover, the upper surface of the tip of the steel plate is prevented from being further cooled as compared with the lower surface.

[Embodiment of the Invention] An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing an apparatus used for accelerated cooling of a steel sheet according to the present invention. A is a quenching zone and is an apparatus used when manufacturing a direct quench material. B is a slow cooling zone and is an apparatus used when manufacturing the 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 for opening and closing a lower cooling water channel, 5 is an upper cooling water header, and 6 is a sensor for detecting the tip of a steel plate. In addition, a pulse transmitter (not shown) that detects the conveying distance from the sensor 6 that detects the tip of the steel plate, a calculator (not shown) that calculates the conveying distance of the steel plate, and the load on the drive motor for the draining diaphragm roll 2 It has a current detector (not shown). When manufacturing the direct quench material, all the lower cooling water header 3 and the upper cooling water header 5 in the quenching zone A and the cooling zone B are passed to cool the steel sheet. When manufacturing the accelerated cooling material, water is not passed through the quenching zone A but only through the slow cooling 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 sheet is conveyed from left to right in FIG. The front end of the steel plate is detected by the sensor 6 for detecting the front end of the steel plate, and then the pulse transmitter (not shown) connected to the rotary shaft of the table roll 1 for detecting the moving amount of the steel plate and the transport distance of the steel plate are calculated. The tip position of the steel plate is calculated by a calculator (not shown). At the same time, it is confirmed by the load current detector (not shown) of the drive motor of the drainage squeeze roll 2 that the tip position of the steel plate has passed through the drainage squeeze roll 2, and the position of the drainage squeeze roll 2 is determined by the same method as described above. The tip position of the steel plate is calculated by calculating from. When the calculated tip position of the steel plate passes over the lower cooling water header 3 having the solenoid valve 4 for opening and closing the lower cooling water channel, the solenoid valve 4 for opening and closing the lower cooling water channel is opened and Inject cooling water. That is, as shown in FIG. 2, as for the lower header 3a, cooling water is not jetted before the tip of the steel plate 2 passes through the position of the lower header 3a, and the position of the lower header 3a as shown in FIG. After passing through, the cooling water is sprayed.

[Effects of the Invention] As described above, in the present invention, since the lower cooling water is jetted 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 is prevented from being overcooled. Moreover, the upper surface of the tip of the steel plate is prevented from being further cooled as compared with the lower surface. As a result, the material of the steel sheet becomes uniform, and the flatness of the front and rear ends is improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an apparatus used for accelerated cooling of a steel sheet according to an embodiment of the present invention, FIG. 2 is a diagram showing a state before the tip of the steel sheet passes through a target lower cooling header, FIG. 3 FIG. 4 is a diagram showing a situation after the tip of the steel plate has passed through the target lower cooling header, and FIG. 4 is a diagram showing a situation in which “scooping water” is generated by the conventional cooling method of the steel plate. 1 ... Table roll, 2 ... Draining roll, 3 ...
… Lower cooling water header, 4 …… Solenoid valve that opens and closes the lower cooling water channel, 5 …… Upper cooling water header, 6 …… Sensor that detects the tip of the steel plate, 7 …… Steel plate.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 62-21413 (JP, A)

Claims (1)

[Claims] 1. A steel sheet after hot rolling is cooled by cooling water from upper and lower portions having a jet nozzle provided between the conveying rollers in a cooling facility or a lower cooling header while being conveyed on the conveying rollers. In the method, the tip position of the steel plate is detected by a position detector and the change is detected by detecting a change in the load current of the draining squeeze roll provided in the cooling equipment, and the movement of the steel plate on the transport roller is performed. The distance is detected by the transport distance detector, the tip position of the steel sheet is sequentially calculated from these values, and the water passage of the lower cooling header is started after the position of the tip portion of the steel sheet has passed the lower cooling header position. A method for cooling a steel sheet, comprising: