JPH0450369B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for cooling hot steel plates in a hot rolling line or a heat treatment line for steel plates.

(Prior art) Conventionally, when cooling such hot steel plates,
Depending on the purpose, methods are adopted, such as spraying cooling water, using slits or pipe laminators, installing an immersion weir on the line and passing the hot steel plate through cooling water, and using close spray nozzles. ing.

However, methods that spray cooling water, use slits or pipe lamina, or install a weir in the line and pass hot steel plates through cooling water have a narrow range of control over the cooling capacity. Due to the structure of the equipment used for this purpose, there are many drawbacks such as the tendency for the shape of the steel plate to deteriorate, so it is only used for some special purposes.

On the other hand, the method using close spray nozzles has a wide range of control over the cooling capacity, and as shown in Japanese Patent Publication No. 47-46641, the deterioration of the shape of the steel plate has been considerably improved. This method has been widely adopted in recent years.

However, with this cooling method, there is a difference in the phenomenon of stagnation of the cooling water injected from the spray nozzle onto the steel plate, which is the material to be cooled, between the front and rear ends of the steel plate and the center of the steel plate. The tip and rear ends have the disadvantage that the temperature of the steel plate is lower than that of the center and that warping is likely to occur.

This phenomenon will be explained based on FIG. When the heated steel plate 1 enters the cooling device, the water jetted from the lower spray nozzle 4b arranged between each roll of the conveyor roll 2 collides with the lower surface of the steel plate 1 and immediately falls, but each of the presser rolls 3 After the water jetted from the upper spray nozzle 4a arranged between the rolls collides with the upper surface of the steel plate 1, it remains on the steel plate as surface water.
Since the water on the plate between the respective rolls of the presser roll 3 only falls from both ends of the steel plate, the amount of water on the plate remains in the center of the steel plate in the state shown as 5a. On the other hand, in the case of the tip or rear end of the steel plate 1, since it falls from the tip or rear end at the same time from both side edges of the steel plate, residual plate water 5b remains at the tip or rear end of the steel plate. The amount is smaller compared to the central portion.

Fig. 2 shows the height H of the remaining amount of water on the plate and the steel plate 1 of the spray water sprayed from the upper spray nozzle 4a.
The relationship with surface impact pressure is shown. It can be seen from the figure that the collision pressure is greatly influenced by the water height H above the plate. This means that the impact pressure of the spray water will be lower at the tip or rear end of the steel plate where the residual height H of the plate water 5b is low and at the center where the residual height H of the plate water 5a is high, as shown in Fig. 1. This shows that this causes a difference in the cooling capacity of each part of the steel plate.

That is, the front or rear end of the steel plate is cooled more rapidly than the center. The remaining height H of the plate water 5, which affects the cooling ability of the spray water, is:
Since it changes depending on the amount of spray water used Q, the width of the steel plate, and the roll pitch P, these are the factors that ultimately change the cooling capacity of this type of steel plate cooling device.

(Objective of the Invention) An object of the present invention is to provide a cooling method for uniformizing the temperature in the longitudinal direction of a steel plate and obtaining a well-shaped steel plate by paying attention to the above-mentioned phenomenon.

(Structure of the Invention) The present invention tracks and manages the position of a hot steel plate in a hot steel plate cooling device, and uses the tracking information to control the opening/closing timing of a cutoff valve disposed in a header to spray liquid at a position where the tip or rear end of the hot steel plate has reached. The injection is controlled by controlling the time required for opening and closing.

(Example) An example of the present invention will be described in detail below with reference to the drawings. FIG. 3 is an overall configuration diagram of a cooling device suitable for carrying out the method of the present invention, FIG. 4 is a diagram of a cooling liquid supply system between rolls, FIG. 5 is an explanatory diagram of the open and closed states of the header shutoff valve, and FIG. The figure shows an example of the configuration of the cooling calculation control device, and FIG. 7 is a time chart for explaining the shutoff valve control.

Reference numeral 6 indicates the entire cooling device, which is installed in a hot steel plate conveyance line, and includes a conveyance roll 2, a presser roll 3, a spray nozzle 4, a header 7, and a cutoff valve 1.
0, a flow rate control valve 11 and a flow rate measuring device 12. Reference numeral 8 indicates a steel plate entry detector provided on the entry side of the hot steel plate 1 of the cooling device 6, and 9a and 9b indicate thermometers for detecting the temperature of the steel plate installed on the entry and exit sides of the cooling device, respectively. It is.

The shutoff valve 10 is shown in detail in FIG.
The shutoff valve is placed in the middle of the coolant supply pipe to the header 7 arranged above and below between the rolls 2 and 3, and is brought into the closed state shown in FIG. It operates from the open state shown in FIG. 5b, and from the open state to the closed state.

FIG. 6 is a block diagram showing a cooling calculation and control device for controlling the opening and closing operations of the cutoff valve 10. In the same figure, 13 indicates the steel type and thickness of the hot steel plate;
A cooling control mechanism that controls the cooling capacity of the entire cooling device by calculating the amount of cooling liquid, the speed of sheet passing through the cooling device, the number of coolant supply headers, etc. based on the plate width, plate length, temperature distribution before starting cooling in the longitudinal direction, etc. It is. Reference numeral 14 denotes a cutoff valve control calculation mechanism that calculates the opening/closing operation locations of the cutoff valve 10, the required opening/closing time of the cutoff valve 10, the opening/closing timing, etc. based on the commands from the cooling control mechanism 13. 1
6 is the plate length information given from the cooling control mechanism 13, the steel plate tracking start signal obtained by the steel plate detector 8, and the conveying table passing speed information obtained by the rotation speed detector provided on the conveying roller table in the cooling device. This is a steel plate position tracking management mechanism that manages the positions of the leading and trailing ends of the steel plate 1 from time to time. 15 is the cutoff valve control calculation mechanism 14
and a cutoff valve on/off timing control mechanism that controls the opening and closing of a specific cutoff valve 10 instructed by the command of the steel plate position tracking management mechanism 16 at the instructed timing and required time, and 17 is the cutoff valve 1
This is a shutoff valve operation performance management mechanism that detects an operation performance of 0 and feeds it back to the cooling control mechanism 13.

The operation of each cutoff valve 10 is performed based on a predetermined program based on the calculation results of the cooling control mechanism 13 and the cutoff valve control calculation mechanism 14.

FIG. 7 shows a time chart of opening/closing control in the case of five shutoff valves A, B, C, D, and E. In the figure, the upper view shows the passing time of the steel plate at each header position, and the lower view shows the open/closed state of each cutoff valve corresponding to each passing time. The vertical axis L indicates the distance from the entrance side of the cooling device 6 shown in FIG. 3, and the horizontal axis indicates the elapsed time T after the steel plate 1 enters. The header shutoff valves A and B installed at L ₁ and L ₂ are
It is used to block the front and rear ends of the steel plate, and the control timing is Tt ₁ + ΔTt ₁ and Tt ₂ at the steel plate tip.
+ΔTt ₂ , the rear end of the steel plate is Tb ₁ −ΔTb ₁ and Tb ₂ −
_ΔTb2 . In addition, the cutoff valve C of the header provided at a distance L ₃ is used to shut off only the tip of the steel plate, and the control timing is Tt ₃ +ΔTt ₃ , and the distance L ₄
The cutoff valve D of the header installed in the header is used to shut off only the rear end of the steel plate, and the control timing is Tb ₄ −
ΔTb is ₄ . Furthermore, the header's shutoff valve E provided at a distance _L5 is not used to shut off the front and rear ends, and is always open while the steel plate 1 is in the cooling device 6.

The entry of the hot steel plate 1 into the cooling device 6 is detected by a signal from the steel plate entry detector 8, and the steel plate position tracking management mechanism 16 grasps the steel plate tip and rear end positions from time to time, and the cutoff valve on/off timing control mechanism 1
The signal is input to 5.

Next, a method of controlling the shutoff valve will be explained.

First, at the stage when the rear end of the preceding steel plate passes through the cooling device 6, the cooling control mechanism 13 determines the amount of cooling liquid and the number of cooling liquid supply headers for the next steel plate 1, and the shutoff valve 10 is opened (in the open state). 5b), the amount of cooling liquid supplied to each header is adjusted by the flow rate control valve 11 and the flow rate measuring device 12. Next, flow control valve 1
1, and when the next steel plate 1 enters the cooling device 6, the temperature distribution in the longitudinal direction on the entrance side is measured using the thermometer 9a, and the steel plate threading speed, opening/closing operation shutoff valve,
and determine the opening/closing timing and the required opening/closing time of the shutoff valve. The required opening/closing time can be changed arbitrarily, and FIG. 8 shows an example of the relationship between the shutoff valve opening/closing operation time and the flow rate. Regarding the water hammer phenomenon, which is a concern at this time, since the opening and closing timings of the shutoff valves that perform the opening and closing operations are different, the effect on the overall system is small and there is no problem.

In making the above determination, for example, as shown in FIG. 9a, the cutoff valve opening/closing location, opening/closing timing, and required opening/closing time are controlled based on the temperature distribution in the inlet longitudinal direction of the leading and trailing ends of the steel plate, as shown in FIG. 9a. The injection of the coolant was controlled as shown in b, and the temperature distribution at the leading and trailing ends of the steel plate after cooling was as shown in Fig. 9c.
Inject the liquid uniformly in the longitudinal direction or by delaying the valve opening/closing timing as shown by the dotted line in b above,
As shown in FIG. 9(d), it is possible to freely control the temperature distribution to obtain the optimum temperature distribution to obtain a good shape.

Next, when the tip of the steel plate reaches the installation position L ₁ of the header 7 having the cutoff valve A, in order to cut off the coolant from the tip of the steel plate by a distance V・ΔTt ₁ with the cutoff valve A,
Shutoff valve A is operated from closed to open using the relationship Tt ₁ +ΔTt ₁ . Next, when the tip of the steel plate reaches the installation positions L ₂ and L ₃ of the header with the shutoff valves B and C,
As in the case of the above-mentioned shutoff valve A, the time Tt ₂ +ΔTt ₂ and
Shutoff valves B and C are opened from closed at Tt ₃ +ΔTt ₃ .

Furthermore, as the steel plate progresses and the rear end of the steel plate reaches around the position _L1 of the header having the shutoff valve A, the time Tb ₁ - ΔTt ₁ is required to cut off the coolant by a distance V・ΔTb ₁ from the rear end of the steel plate. Activate shutoff valve A to change it from open to closed. Similarly, installation positions L ₂ and L ₄ of headers with shutoff valves B and D at the rear end of the steel plate
Once near the time Tb ₂ − ΔTb ₂ and Tb ₄
-Control the shutoff valves B and D from open to closed at ΔTb ₄ . Finally, at the time Tb ₀ when the rear end of the steel plate is extracted from the cooling device 6, the shutoff valves A, B, and D remain closed.
from closed to open.

In the above explanation, there is no distinction made between the shutoff valves A to E for use on the top surface of steel plates and those for the bottom surface of the steel plate, but for example, in cases where it is not possible to expect an effect by shutting off only the top surface due to thick material, etc., or by providing both the top and bottom, the entire shutoff can be achieved. It is also possible to install both the upper and lower valves to reduce the number of valves.

Moreover, the shutoff valves may not be provided between all the rolls in the cooling device, but may be provided at certain intervals, or may be provided in specific zones.

As the coolant, water or water to which a rust preventive agent is added is used.

In addition, the combination of shutoff of the coolant at the tip and rear end of the steel plate of the shutoff valves A, B, C, D, and E and the shutoff distance ΔT・V depend on the size of the heated steel plate, cooling pattern, temperature pattern before cooling, etc. After cooling, the longitudinal temperature deviation and shape of the steel sheet are controlled to be optimal.

(Effects of the Invention) The effects of the present invention are listed below.

(1) Uniform cooling can be achieved over the entire length of the steel plate.

(2) Through (1) above, a steel plate with uniform overall length can be obtained.

(3) According to (1) above, a steel plate with good shape can be obtained over the entire length of the steel plate.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of a conventional type of close spray type cooling device, Fig. 2 is a diagram showing the relationship between water height above the plate and spray impingement pressure, and Fig. 3 is an overall configuration diagram of a cooling device suitable for the method of the present invention. Fig. 4 is a diagram of the cooling liquid supply system between the rolls, Fig. 5 a and b are explanatory diagrams of the open and closed states of the cutoff valve, Fig. 6 is a block diagram showing an example of the configuration of the cooling calculation control device, and Fig. 7 9 is a time chart for explaining the shutoff valve opening/closing control, FIG. 8 is an explanatory diagram showing the shutoff valve opening/closing operation time, and FIGS. 9a to 9d are explanatory diagrams showing an example of control for obtaining an arbitrary temperature distribution by the shutoff valve opening/closing control. DESCRIPTION OF SYMBOLS 1... Hot steel plate, 2... Conveyance roll, 3... Opposing presser roll, 4... Spray nozzle, 5... Board water, 6...
Cooling device, 7... Header, 8... Steel plate entry detector,
9... Steel plate thermometer, 10... Shutoff valve, 11... Flow rate control valve, 12... Flow rate measuring device, 13... Cooling control mechanism,
14...Shutoff valve control calculation mechanism, 15...Shutoff valve on/off timing control mechanism, 16...Steel plate position tracking management mechanism, 17...Shutoff valve operation performance management mechanism.

Claims (1)

[Claims] 1. In a method of injecting and cooling a hot steel sheet while pressing it from above and below with a plurality of rolls, a cutoff valve that can arbitrarily control the opening/closing time is provided in the header placed above and/or below between each roll, and A means for detecting the passing position of the hot steel plate, a means for detecting the longitudinal temperature profile before the start of cooling, and a cooling calculation control means are provided, and the tip and/or
Alternatively, a method for cooling a hot steel plate characterized by controlling the opening and closing of a cutoff valve of a header corresponding to a position through which the rear end portion is going to pass.