JP3633539B2 - Steel plate cooling method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for cooling a steel plate, and in particular, in cooling a high-temperature steel plate with cooling water in a hot rolling process, the accuracy of the water cooling end temperature can be improved and the non-uniform temperature in the plate can be reduced. It relates to a cooling method.
[0002]
[Prior art]
It is usually performed to manufacture a steel sheet having desired characteristics by cooling a high-temperature steel sheet before hot rolling or during hot rolling using cooling water and rolling at a predetermined temperature, such as controlled rolling. ing. At that time, the residual cooling water staying on the upper surface of the high-temperature steel sheet after the water cooling ends causes a decrease in temperature controllability due to supercooling, uneven material due to temperature unevenness, and poor steel plate shape due to vertical temperature difference. Sometimes. For this reason, drainage of residual cooling water staying on the upper surface of the high-temperature steel sheet has been conventionally performed.
[0003]
As techniques for draining the upper surface of the high-temperature steel sheet, the following techniques are disclosed in Japanese Patent Publication No. 59-13573, Japanese Patent Laid-Open No. 9-141322, and Japanese Patent Laid-Open No. 11-123439.
[0004]
Prior art 1 disclosed in Japanese Patent Publication No. 59-13573 discloses cooling of a hot-rolled steel material that cools the hot-rolled steel material by injecting a coolant from a plurality of cooling banks into the hot-rolled steel material fed from a finish rolling mill. In the apparatus, a draining nozzle for ejecting a high-pressure fluid toward the hot-rolled steel material is provided between the plurality of cooling banks, so that the downstream side is not affected by the cooling liquid upstream from the nozzle. The nozzle is arranged.
[0005]
Prior art 2 disclosed in Japanese Patent Application Laid-Open No. 9-141322 is a residual cooling in which a mixture of water and air is injected from a draining nozzle during hot-run cooling of a hot sheet continuous rolling line and stays on the steel strip. It is characterized by eliminating water.
[0006]
Prior art 3 disclosed in Japanese Patent Application Laid-Open No. 11-123439 is a draining spray device used for the purpose of eliminating residual cooling water staying on a steel plate conveyed from a line table. A header is provided so as to cross the line table, and a plurality of side spray nozzles for injecting high-pressure water onto the steel sheet toward the outside in a direction perpendicular to the line from the line table are arranged in the water supply header. Is.
[0007]
[Problems to be solved by the invention]
However, each of the above-mentioned prior arts 1 to 3 is a technique for draining the residual cooling water staying on the upper surface of the passing high-temperature steel sheet, and is not suitable for removing the remaining cooling water on the upper surface of the steel sheet that is stopped. .
[0008]
Therefore, when the steel sheet is stopped, for example, it remains in the water cooling device even after the water cooling is finished, the conventional technology cannot sufficiently eliminate the residual cooling water on the upper surface of the steel sheet. The problem of the non-uniformity of the material resulting from a fall, temperature nonuniformity, and the steel plate shape defect resulting from a temperature difference between the upper and lower sides still occurs. Also, because it is difficult to accurately measure the steel plate temperature at the end of the water cooling due to the residual cooling water, the water cooling becomes insufficient due to concern about overcooling by the residual cooling water, and re-cooling is necessary. The efficiency may be reduced.
[0009]
Accordingly, an object of the present invention is to suppress the local cooling by the residual cooling water staying on the upper surface of the steel plate that is stopped or oscillated at a certain place, and the water cooling end temperature It is an object of the present invention to provide a method for cooling a steel sheet that can improve the accuracy of the steel sheet and reduce non-uniform temperature inside the sheet.
[0010]
[Means for Solving the Problems]
This invention relates to a step of measuring the temperature of a steel plate before the start of water cooling when cooling a hot steel plate to the target cooling temperature using cooling water, and water cooling conditions based on the measured temperature before the start of water cooling and the target cooling temperature. A plurality of nozzles immediately after completion of the step of water-cooling a steel plate that is stopped or oscillated at a certain location according to the determined water-cooling conditions, and the step of water-cooling the steel plate. Residual cooling water that stays on the upper surface of the steel sheet by injecting a fluid from one edge side of the steel sheet that is stopped or oscillated at a certain location from the draining nozzle group that has been retained toward the upper surface of the steel sheet A method for cooling a steel sheet, comprising: a step of removing, and a step of measuring a temperature of the steel plate after completion of the step of removing residual cooling water.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a steel plate cooling method according to the present invention will be described with reference to the drawings.
[0012]
FIG. 1 is an explanatory view showing an embodiment of a steel sheet cooling method according to the present invention, FIG. 2 is a plan view showing a water draining state by a water draining nozzle group in the present invention, and FIG. is there. In the following description, air will be described as an example of the draining fluid to be sprayed onto the steel sheet, but a fluid other than air, for example, an inert gas may be used.
[0013]
In FIG. 1 to FIG. 3, 1 is a rolling line, 2 is a roughing mill provided in the rolling line 1, 3 is a finishing mill provided in the rolling line 1 downstream of the roughing mill 2, and 4 is rough rolling. It is a water cooling device provided along the rolling line 1 between the mill 2 and the finishing mill 3. The water cooling device 4 is divided into a plurality of blocks (4 blocks, 4A to 4D in this example) along the rolling line 1, and toward the steel plate 5 on the rolling line 1 that has been roughly rolled by the roughing mill 2. Cooling water is injected to cool the steel plate 4 to a predetermined temperature. For example, when water-cooling one steel plate, water-cooling is performed using the water-cooling blocks 4A and 4B, and when water-cooling two steel plates along the rolling line, one steel plate is used using the water-cooling blocks 4A and 4B. Water cooling is performed, and the other steel plate is water cooled using the water cooling blocks 4C and 4D.
[0014]
Reference numeral 6 denotes a draining nozzle group for removing residual cooling water staying on the steel plate 5, and is installed on one side of the rolling line 1 orthogonal to the rolling line 1. As shown in FIG. 2, the draining nozzle group 6 has a plurality of air injection nozzles 7 and is divided into a plurality of blocks (in this example, 4 blocks, 6A to 6D) corresponding to each block of the water cooling device 4. In addition, air is supplied from the air receiver 8 through the header pipe 9.
[0015]
Reference numeral 10 denotes a thermometer, which measures the temperature of the steel plate before the start of water cooling. 11A and 11B are also thermometers. The thermometer 11A measures the temperature after the water cooling of the steel plates cooled by the water cooling blocks 4A and 4B, and 11B after the water cooling of the steel plates cooled by the water cooling blocks 4C and 4D. Measure the temperature. A water cooling control unit 12 controls a series of water cooling operations. Reference numeral 13 denotes a thermometer installed on the front surface of the finish rolling mill 3 for confirming the steel plate temperature before the start of finish rolling in control rolling or the like.
[0016]
The steel sheet is cooled as follows.
[0017]
The steel plate 5 roughly rolled by the rough rolling machine 2 moves on the rolling line 1 toward the water cooling device 4, and the temperature of the steel plate before the start of water cooling is measured by the thermometer 10. The water cooling control device 12 measures the temperature before the start of water cooling measured by the thermometer 10 and the target cooling temperature at the end of water cooling determined to be a predetermined finish rolling start temperature in anticipation of a temperature drop due to air cooling after the end of water cooling. The water cooling conditions such as the amount of cooling water and the water cooling time of the water cooling device 4 are determined based on the material and dimensions of the steel plate. Alternatively, the water cooling condition may be preliminarily determined by predicting the temperature before the water cooling start before the measurement with the thermometer 10, and the water cooling condition may be finally determined based on the measurement result of the temperature before the water cooling start with the thermometer 10. And if the steel plate 5 stops in the water cooling device 4, according to the instruction | indication of the water cooling control apparatus 12, a cooling water will be injected toward the steel plate 5 from the water cooling device 4 according to the above-mentioned water cooling conditions. Immediately after the predetermined water cooling time is over and the injection of cooling water from the water cooling device 4 is stopped, the water cooling control device 12 immediately instructs the water draining nozzle group 6 from one edge side of the steel plate 5 to the upper surface of the steel plate 5. Air is jetted all at once. Thereby, the residual cooling water staying on the steel plate 5 is excluded from the upper surface of the steel plate 5. Then, the temperature of the steel sheet after completion of water cooling is measured by the thermometer 11A, and it is checked by the water cooling control device 12 whether or not the water cooling end temperature is the target cooling temperature. In addition, when cooling by putting two steel materials in a water cooling device, the water cooling end temperature of one steel plate is measured by the thermometer 11A, and the water cooling end temperature of the other steel plate is measured by the thermometer 11B. Then, after confirming that the steel plate temperature has reached the target cooling temperature, the steel plate 5 is conveyed toward the finishing mill 3. It is finally confirmed by the thermometer 13 that the temperature before the start of finish rolling is a predetermined temperature, and the finish mill 3 is rolled.
[0018]
Thus, immediately after the water cooling of the steel plate 5 is finished, the residual cooling water staying on the upper surface of the steel plate 5 is excluded from the upper surface of the steel plate 5, so that local cooling by the residual cooling water is eliminated, and the supercooling, temperature Generation of unevenness or shape defects can be prevented.
[0019]
Further, since the residual cooling water staying on the upper surface of the steel plate 5 is eliminated, the temperature of the steel plate at the end of the water cooling can be accurately measured by the thermometers 11A and 11B, so whether or not the end of the water cooling is the target cooling temperature. Can be confirmed accurately. Then, by feeding back the information to the determination of the water cooling condition for the next steel sheet, it becomes possible to determine the water cooling condition and implement it with higher accuracy. As a result, the accuracy of the water cooling end temperature is improved, the variation in material can be reduced, the frequency of recooling is reduced, and the production efficiency can be improved. Incidentally, the implementation result that the frequency of recooling was reduced to ½ of the conventional one by applying the present invention has been obtained.
[0020]
Conventionally, since the temperature of the steel sheet at the end of water cooling cannot be measured with high accuracy, it has been found that re-cooling is necessary only by measuring the temperature on the front surface of the finishing mill, and in that case, the steel sheet must be sent back to the water cooling device. However, since the temperature of the steel sheet at the end of water cooling can be accurately measured in the water cooling device, even if re-cooling is necessary, it is sufficient to restart the water cooling in the water cooling device without any extra time loss due to reverse feeding. be able to.
[0021]
The draining nozzle group 6 may be installed in parallel to the upper surface of the steel plate 5, but when the air injection angle from the nozzle 7 is zero, the flow velocity is greatly reduced, so as shown in FIG. It is preferable to incline downward by an angle (θ) with respect to the upper surface of the steel plate 5 on the rolling line (conveying roller). Further, the draining nozzle group 6 may be constituted by a slit nozzle parallel to the rolling line 1 in addition to the plural nozzles 7.
[0022]
In order to drain the residual cooling water staying on the upper surface of the steel sheet more reliably, the flow rate of air sprayed from the drain nozzle group toward the steel sheet is set at 3 m / mm at a position 1 mm away from the upper surface of the steel sheet at a temperature of 400 ° C. or higher. What is necessary is just to adjust to sec or more. This is because, in a steel plate having a temperature of 400 ° C. or higher, the residual cooling water on the upper surface of the steel plate is in a film boiling state, so that water can be drained even with a slight air flow rate.
[0023]
【Example】
Examples of the steel sheet cooling method according to the present invention will be described below.
[0024]
As shown in FIG. 1, in a thick plate factory in which a rolling line 1 includes two rolling mills, a rough rolling mill 2 and a finishing rolling mill 3, a water cooling device 4 is provided between the rough rolling mill 2 and the finishing rolling mill 3. A draining nozzle group 6 is installed. A thermometer 10 for measuring the steel plate temperature before the start of water cooling, thermometers 11A and 11B for measuring the steel plate temperature after the end of water cooling, and a thermometer 13 for measuring the steel plate temperature before the start of finish rolling are installed. The water cooling operation is controlled by the water cooling control device 12.
[0025]
The length of the water cooling device 4 is 20 m, and is installed from the position 10 m downstream of the rough rolling mill 2. The distance between the roughing mill 2 and the finishing mill 3 is 50 m. The water cooling device 4 is divided into four first, second, third and fourth blocks 4A, 4B, 4C and 4D from the upstream side every 5 m. The draining nozzle group 6 is also divided into four first, second, third and fourth blocks 6A, 6B, 6C and 6D from the upstream side. The air injection nozzles 7 of each block have a diameter of 7 mm, and are installed on the one side of the rolling line 1 at a spacing of 500 mm, 10 blocks per block, 40 blocks in total, each from the air receiver 8 to the header. Air is supplied through the tube 9. The horizontal distance between the nozzle 7 and the transport roller was 200 mm, the vertical distance was 250 mm, and the inclination angle (θ) was 2 degrees.
[0026]
And the dimension after the rough rolling of the high temperature steel plate 5 used in the examples is about 80 mm in thickness, about 4.5 m in width, and about 7.5 m in length, and the surface average temperature before the start of water cooling is that of the thermometer 10. The measurement was 910 ° C. The target cooling temperature was 830 ° C.
[0027]
After the water cooling control device 12 determines the water cooling conditions based on the above steel plate dimensions, the surface average temperature before the start of water cooling, the target cooling temperature, etc., the steel plate 5 is placed in the first and second blocks 4A, 4B of the cooling device 4. It carried in and water-cooled according to water-cooling conditions. Immediately after the end of water cooling, air was sprayed from the nozzles 7 of the first and second blocks 6A and 6B of the draining nozzle group 6 toward the upper surface of the steel plate 5 at a spray pressure of 0.5 MPa. During water cooling and draining, the steel plate 5 was oscillated in the direction of the rolling line 1 with a stroke of 600 mm.
[0028]
The distance from the tip of the nozzle 7 to the edge of the steel plate 5 on the opposite side is about 5 m, and the flow velocity of the jet air at the position of 1 mm from the top surface of the steel plate 5 that was carried out during non-rolling is an average by pitot tube measurement. It was 7.2 m / sec.
[0029]
As a result of water cooling of the steel plate 5 in this manner, the residual cooling water staying on the upper surface of the steel plate 5 was almost swept away from the upper surface of the steel plate about 8 seconds after the draining. In the measurement with the thermometer 11A, the surface average temperature of the steel sheet 5 after the water cooling was 828 ° C., and the temperature variation was within 15 ° C.
[0030]
And after confirming that the steel plate temperature before finish rolling was a predetermined temperature with the thermometer 13, as a result of finishing rolling with the finish rolling mill 3, both the shape and the material were good.
[0031]
【The invention's effect】
According to this invention, after cooling the steel plate by injecting the cooling water from the cooling device toward the steel plate on the rolling line, immediately, the fluid is simultaneously delivered from the draining nozzle group having a plurality of nozzles toward the upper surface of the steel plate. By spraying, the residual cooling water staying on the upper surface of the steel sheet is drained all at once, so that local cooling by the residual cooling water is prevented, so that the temperature controllability is improved and the temperature unevenness is suppressed. Can be made uniform. In addition, since the remaining residual cooling water is eliminated, the temperature of the steel sheet after the water cooling can be accurately measured, so it is possible to accurately check whether or not the target cooling temperature is reached, and the variation in material can be reduced. At the same time, a reduction in production efficiency due to recooling can be prevented.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an embodiment of the present invention.
FIG. 2 is a plan view showing a water draining state by a water draining nozzle group in the present invention.
3 is a view in the direction of arrow A in FIG. 2;
[Explanation of symbols]
1: Rolling line 2: Rough rolling mill 3: Finishing rolling mill 4: Cooling devices 4A to 4D: Cooling device block 5: Steel plate 6: Draining nozzle group 6A to 6D: Draining nozzle group block 7: Air injection nozzle 8: Air receiver 9: Header pipe 10: Thermometer 11A, 11B: Thermometer 12: Water cooling controller 13: Thermometer

Claims (1)

A step of measuring the temperature of the steel plate before the start of water cooling when cooling the hot steel plate to the target cooling temperature using cooling water, and a step of determining the water cooling condition based on the measured temperature before starting the water cooling and the target cooling temperature. And a step of water-cooling a steel plate that is stopped or oscillated at a certain location according to the determined water-cooling conditions, and a draining nozzle group having a plurality of nozzles immediately after the step of water-cooling the steel plate From the one edge side of the steel plate that is stopped or is oscillating at a certain place, jetting fluid toward the upper surface of the steel plate and eliminating the residual cooling water that remains on the upper surface of the steel plate; And a step of measuring the temperature of the steel plate after completion of the step of removing residual cooling water.

Images