JPS61162222A - Method for water cooling steel plate in control rolling - Google Patents

Abstract

PURPOSE:To uniformly cool effectively a steel plate on a table roller by controlling the rotating direction and speed of the table roller according to the positive and negative and value of the random function generated on each optional time from a computor. CONSTITUTION:The temp. of a rolled steel plate 2 is measured by a radiation type thermometer 18 and in case of this measured value being higher than the temp. of rolling re-start, the steel plate 2 is fed to a water cooling zone 4. Simultaneously with starting a water cooling on receipt of the signal of an inlet side position detector 6 a computor 10 generates a random function every three seconds and rotates normally and reversely the table roller 5 according to the speed corresponding to the value of function. The temp. is measured after cooling for the set time by the thermometer 8 and the rolling is re-started if reaching the prescribed temp. The steel plate excellent in the plate thickness accuracy is obtainable because of the generation of a shower mark and roll mark being able to be prevented by cooling like this.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a hot rolling method, particularly a method for cooling a steel plate in controlled rolling. It's about how to do it.

(Prior art) In recent years, in hot rolling of thick plates, in order to improve the toughness of the steel, after a predetermined number of rolling passes, the steel plate 2 coming out of the rolling mill 1 is heated by a large number of water-cooling jets, as shown in FIG. A rolling method has been developed in which the rolled material is passed through a water cooling zone 4 in which a nozzle 3 is arranged, cooled to a scheduled rolling restart temperature as shown in FIG. 2, and then rolled again to perform a combination of controlled rolling and controlled cooling. There is. In this controlled rolling method, the steel plate is rolled every predetermined number of rolling passes.
Generally, the temperature of the hot-rolled steel sheet is adjusted to the rolling restart temperature by sending the hot-rolled steel sheet into the water-cooling zone 4 and cooling it with water.

(Problem to be Solved by the Invention) Conventionally, during water cooling in a water cooling zone, the steel plate 2 is reciprocated by table rollers 5 in the water cooling zone 4 in order to avoid local cooling of the steel plate. In the conventional method, the steel plate 2 is fed to the exit end of the water cooling zone 4, and a reversal signal is sent to the table roller 55 using a position detection signal from the position detector 7 installed at the exit end 4a, and the table roller is reversed. By returning the steel plate to the inlet side, the temperature of the steel plate is adjusted to the rolling restart temperature while reciprocating. However, according to this method of operating the table roller, the steel plate moves from left to right as shown by arrow A in FIG.
) J: After the sea urchin is stopped once, it is fed backwards from right to left as shown by arrow B in FIG. 3 (0). In the conventional method of stopping the table roller 5 once at a fixed position corresponding to the exit position detector 7 and then reversing it, a large amount of heat is removed from the table roller 5 when the table roller 5 is once stopped. Since stopping during reversal is repeated at the same position, heat is removed at a certain position repeatedly, and as a result,
As shown in FIG. 4, when a roller mark C is formed on a steel plate, a shower mark is also formed on the upper surface of the steel plate for the same reason. The pitch of these marks is as short as 700 ft 1 m, and when the rotation speed of the rolling mill drive motor is increased, the response of automatic plate thickness control (AGC) cannot keep up, resulting in thickness deviation in the longitudinal direction of the steel plate, which is a major problem. It becomes.

(Means for solving the problem) The present invention has been made in view of these circumstances.
In order to eliminate the formation of marks such as table marks and shower marks due to local supercooling fII (blown heat) that occurs during water cooling in controlled rolling, the rotation direction of the table from arbitrary time t to [+Δ[ is given by a random function. The purpose is to rotate the table roller 5 forward and reverse at random time intervals and speeds, thereby preventing the formation of the above-mentioned marks.

Therefore, in the present invention, there is provided a method in which, in controlled rolling, a steel plate is moved in a water-cooling zone from a double roller and water-cooled until the temperature of the steel plate reaches the rolling restart temperature, which is calculated randomly from a computer at any given time. A function is generated, and the rotation direction and speed of the table roller are controlled depending on whether the function is positive or negative and the value thereof.

According to the present invention, the rotational direction and speed of the table roller supporting the steel plate in the water cooling zone are controlled by the positive/negative value and value of a random function generated at predetermined time intervals from an 81 calculator. Random functions are generally expressed as y-γnd(x), and random functions that are generated sequentially have no correlation. Therefore, the table roller 5 is reversed regardless of the position of the steel plate 2 in the water cooling zone 4, and the stopping position of the steel plate when the retaple roller is reversed changes variously, thereby stopping the reverse □ rotation. At times, the portions of the steel plate that are strongly subjected to heat extraction by the table rollers and the cooling water shower change in various ways, and are no longer locally strongly cooled. Therefore, table roller marks and cooling water shower marks can be prevented from occurring, and sheet thickness deviations in the longitudinal direction of the steel sheet can be prevented from occurring.

(Example) Examples of the present invention will be described in detail below based on the accompanying drawings.

FIG. 1 shows an example in which the present invention is applied to thick plate rolling.

In the figure, 1 is a thick plate hot rolling mill, 2 is a hot rolled steel plate, 8 is a radiation type thermometer, and an entry side position detector 6 is installed on the inlet side of the water cooling zone 4 of the water cooling device, which is sufficiently longer than the length of the steel plate. 9 is a motor for driving the table roller 5, and 10 is configured to transmit a water cooling start signal to the water cooling device when the entry side position detector 6 changes from ON to OFF.
is a random function (y-γnd(x
)), and when the generated random function is positive, a forward rotation signal is sent to the motor 9, and when it is negative, a reverse rotation signal is sent to the motor 9.

Further, the calculator 10 indicates that, for example, when the steel plate 2 being cooled protrudes from the exit side of the water cooling zone 4 due to more positive random functions being generated than negative random functions,
The output side position detector 7 sends a protrusion signal to the computer 10,
As a result, the computer 10 sends a reverse rotation signal to the motor 9,
In the opposite case, the entry side position detector 6 operates in a similar manner to maintain the steel plate 2 within the cooling zone 4.

Next, the effect will be explained.

The temperature of the steel plate 2 which has now been rolled for n passes is measured by a radiation thermometer 8, and when this measured value is higher than the rolling restart temperature, the steel plate 2 is fed into the water cooling zone 4.

The water cooling zone 4 receives the F signal from the inlet position detector 6 from ON to ○, and starts water cooling, and the computer 10 turns from ON to OFF.
Receive the signal and generate a random function (y-γnd(x)) by 2
Random 4 that occurs every second and corresponds to the value of the function y
At the r value of 11 degrees, the daple roller 5 is rotated forward or reverse depending on whether the function y is positive or negative.

In this way, the steel plate 2 is controlled by the position detectors 6 and 7 on both sides so that it does not protrude from the water cooling zone 4, and is reciprocated into the water cooling zone 4 and water cooled for a preset time of -1.

After cooling for a set time, the steel plate is taken out of the water cooling zone 4 and the plate temperature is measured using a thermometer 8. If the plate temperature has cooled to the rolling restart temperature, rolling is resumed. On the other hand, if the temperature of the plate is still higher than the rolling restart temperature, the water cooling operation described above is repeated to cool the plate to the rolling restart temperature.

Next, the results of water cooling using the method of the present invention will be described.

A slab with dimensions of 240 x 2000 x 3500 mm was rolled from a heating furnace extraction temperature of 1150°C and rolled for 16 passes to a plate thickness of 16 mm. The temperature at that time was 940°C, but the rolling restart temperature was 840°C, so this steel plate was sent to the water cooling zone and water cooled by controlling the double row □ by the method of the present invention. No marks were found, product dimensions 8X 3000x4
When the plate thickness in the longitudinal direction of the plate was measured when the product was rolled to 8000 mm, the plate thickness deviation was at most 80 μm.

On the other hand, when a steel plate under the same rolling conditions as above was cooled using conventional force, the shower mark and roll mark were 75.
When the plate thickness was measured in the longitudinal direction of the plate at a pitch of 0 mm, there was a thickness deviation of 150 to 250 μm at a pitch of about 15 m.

(Effects of the Invention) According to the present invention, shower marks and roll marks can be prevented, and a steel plate with excellent plate thickness accuracy can be obtained.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an embodiment of the present invention applied to thick plate rolling, Fig. 2 is a diagram showing controlled rolling, Fig. 3 is an explanatory diagram showing roll marks on a steel plate, and Fig. 4 is a diagram showing an example of applying the present invention to thick plate rolling. , is a perspective view of a steel plate with shower marks. 1... Rolling mill 2... Steel plate 3... Water-cooled diene 1 to nozzle 4... Water-cooled zone 5... Table roller 6.
...Enter side position detector 7...Output side position detector 8...
Thermometer 9... Drive motor 10... Computer patent applicant Kawasaki Steel Corporation cc3, Oυ % deafness

Claims (1)

[Claims] 1. In controlled rolling, a method in which a steel plate is cooled by water while moving it in a water-cooling zone using table rollers until the temperature of the steel plate reaches the rolling restart temperature, a random function is generated every arbitrary time from a computer, and this function is A water cooling method for a steel plate in controlled rolling, characterized in that the rotation direction and speed of the table roller are controlled according to positive/negative values and values.