JPS63126611A - Cooling device for hot rolled sheet steel - Google Patents

Abstract

PURPOSE:To enlarge the range of a cooling capacity and to quicken control by providing plural feed water pipings, arranging a flow regulating valve and three-way valve on each feed water piping as well and controlling the flow regulating valve and three-way valve with their opening and closing via a cooling state detector. CONSTITUTION:The feed water pipings 12A, 12B feeding a cooling water of different temp. each other are provided on a cooling device 10, connection pipings 13A, 13B are arranged to the respective piping as well and the piping 13A, 13B are linked with a single nozzle header 14 by shunting them. In this case flow regulating valves 15A, 15B and threeway valves 16A, 16B are respectively arranged on the connection pipings 13A, 13B from the upper stream side in order and the valves 15A, 15B, 16A, 16B are respectively controlled quickly by the cooling state control device 18 connected to the temp. sensor 17 of a hot-run table. With this method the range of the cooling capacity from rapid cooling till slow cooling is enlarged and the control is quickened.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a cooling device for hot rolled steel sheets.

[Prior Art] Various cooling devices are currently in use as cooling devices for hot-rolled steel sheets on hot run tables from the end of hot rolling to winding. The characteristics required of such a cooling device include the following.

■A single cooling device can provide a wide range of cooling capabilities from rapid cooling to slow cooling.

■Achieving stable cooling performance.

■It is possible to quickly and stably turn on/off the cooling water supply (high-speed response) by turning on/off the water stop valve, etc.

All of the above characteristics are achieved by being able to significantly control the material of the steel plate, achieving uniformity of the material in the longitudinal and width directions, and reducing equipment costs.
It has a great advantage in that hot-rolled steel sheets can be manufactured with high efficiency.

[Problems to be Solved by the Invention] However, there is no conventional cooling device that satisfies each of the characteristics (1) to (4) above.

That is, "Ishikawajima Harima Techniques Vol. 21 No. 4 No. 293-288", "Mitsubishi Heavy Industries Techniques Vol. 20 No. 3 No. 35"
As described in "Pages 2 to 357," in the slit laminar flow, which is said to have a large cooling capacity, the water film breaks if the amount of water corresponding to the thickness of the slit is not supplied. Even if we try to reduce the amount of water to reduce the capacity, there is a limit. In other words, it is not suitable for heating or cooling.

In addition, for both pipe laminar flow and slit laminar flow, a method has been proposed as a control method to improve high-speed response, in which water ejected from a nozzle is blocked by a gutter and drained out of the cooling area. This is a control in which the amount of cooling water is set to O or 100%, and fine control of the cooling capacity is completely impossible.

It is qualitatively known at manufacturing sites that the cooling capacity fluctuates due to changes in water temperature, but although this is a factor that causes errors in the cooling state, it is not a factor that can control the cooling state. There wasn't. That is, even if the water temperature is actively controlled, it is difficult to change the water temperature quickly using conventional methods.

An object of the present invention is to stably and quickly control a wide range of cooling capabilities from rapid cooling to warm cooling.

[Means for Solving the Problems] The hot-rolled steel plate cooling device according to the present invention has two or more water supply pipes that supply cooling water, and the continuous pipes connected to each of the water supply pipes are made to merge with each other. connect to a single cooling nozzle header, provide a flow control valve on the upstream side of each connection pipe, provide a three-way valve on the downstream side of each connection pipe, and connect the first port of the three-way valve to the flow control valve side. The second boat of the three-way valve is connected to the cooling nozzle header side, and the third boat of the three-way valve is connected to the drainage system and is equipped with a cooling state detection device that detects the cooling state of the W4 plate cooling zone. The cooling state control device is configured to include a cooling state control device that controls opening and closing of the flow control valve and/or the three-way valve based on the detection result of the state detection device.

[Operation] According to the present invention, the control operation of the cooling state control device based on the cooling state detection device causes various combinations of the open/closed states of the flow rate adjustment valve and the open/closed states of the three-way valve, thereby controlling the amount of water spouted by the cooling nozzle header and the water temperature. can be rapidly and stably changed over a wide range. Thereby, a wide range of cooling balances from rapid cooling to warm cooling can be stably and quickly controlled.

[Example] Fig. 1 is a schematic diagram showing a cooling device according to an embodiment of the present invention, Fig. 2 is a schematic diagram showing the cooling piping system of Fig. 1, and Fig. 3 is a modification of the cooling piping system. Figure 4 is a diagram showing the relationship between water volume density and temperature drop (cooling capacity) for slit laminar flow and pipe laminar flow, and Figure 5 is a diagram showing the relationship between water temperature and heat transfer coefficient (cooling capacity) for slit laminar flow. Noh)
Figure 6 is a diagram showing the lower limit water amount at which a stable water film can be obtained in slit laminar flow, and Figure 7 is a diagram showing the change in water amount and temperature drop (cooling capacity) due to the implementation of the present invention. A diagram showing the relationship, FIG. 8 is a schematic diagram showing a conventional cooling piping system.

In Figures 1 and 2, 10 is a cooling device, 11 is a steel plate transported through a steel plate cooling zone, 12A and 12B are water supply pipes, 13A and 13B are connection pipes, 14 is a cooling nozzle header, and 15A and 15B are flow rates. Control valves 16A and 16B are three-way valves, 17 is a temperature sensor (cooling state detection device), and 18 is a cooling state control device.

That is, the cooling device 10 has two water supply pipes 12A and 12B that supply cooling water of mutually different water temperatures, and a connecting pipe 13 that is connected to each of the water supply pipes 12A and 12B.
A, 13B are merged with each other and connected to a single cooling nozzle header 14, and flow regulating valves 15A, 15B are provided on the upstream side of each connecting pipe 13A, 13B, and each connecting pipe 13A, 1
Three-way valves 16A and 16B are provided on the downstream side of 3B, and three-way valve 1
The first ports of 6A and 16B are flow control valves 15A and 15B.
The second boat of the three-way valve L6A, 16B is connected to the side of the cooling nozzle header 14, and the second boat of the three-way valve L6A, 16B is connected to the side of the cooling nozzle header 14,
The third boat of B is connected to the drainage system. The cooling device 10 also includes a temperature sensor 17 that detects the cooling state of the steel plate 11 conveyed through the steel plate cooling zone.
Based on the detection results of the flow rate fil valves 15A, 15B.
and/or a cooling state control device 18 that controls opening and closing of the three-way valves 16A and 16B.

Note that the cooling device 10 may have three cooling piping systems shown in FIG. 3 instead of the two cooling piping systems shown in FIG. 2. In the cooling piping system shown in Figure 2, water supply piping 12C1 connection piping 13C1 flow rate adjustment pipe 15
A C1 three-way valve 16C is added.

That is, the cooling device 10 has each flow control valve 15A, 15
By opening and closing the three-way valves 16A, 16B, and 16C, the amount and temperature of water supplied to the nozzle header 14 can be independently varied.

For example, if responsiveness is particularly important, in FIG. 2, the water amount Q1 in the pipe 12A. If the flow control valves 15A and 15B are preset so that the water amount is Q2 in the pipe 12B,
By combining the opening and closing of the three-way valves 16A and 16B, four levels of cooling performance, 0, Ql, Q2, and Ql + Q2, can be selected for lockstitching.

If the response of the three-way valves 16A and 16B is fast, the cooling capacity can be changed quickly.

In addition, in FIG. 3, the pipe 12A has a water temperature of T1. Water amount Q
l, the pipe 12B has a water temperature of T2. Water amount Q2. The water temperature of the pipe 12C is T3. If you preset the water amount to Q3,
Similarly, it is possible to control the cooling capacity in 23 ways, and by changing the preset water volume and water temperature, it is possible to virtually continuously control the cooling capacity over an extremely wide range with the same cooling device. .

In addition, in the present invention, high-temperature water and low-temperature water are supplied through independent water supply piping systems, and the amount of water in each water supply piping is made variable using individual flow control valves, so as long as the original water supply is stable, conventional It becomes possible to perform control using water temperature as a control factor, which has been considered as a disturbance and not considered as a control factor.

Also, as a matter of course, the more water supply piping systems (12A, 12B, 12C, etc.) as described above, the more extensive control of the cooling capacity becomes possible. There is a limit because it increases the size and cost.

In addition, since the cooling capacity is changed depending on the water temperature and water volume, there are no particular restrictions on the type of nozzle, such as slit laminar nozzles,
No matter what type of nozzle, such as a pipe laminar nozzle, a wide cooling capacity control range can be obtained.

It is also clear that by dividing the water supply system of each cooling device at each position on the hot run table, more fine control of the steel plate material becomes possible. However, it is not necessarily necessary to provide such a complicated cooling mechanism for all cooling devices on a hot run table that is longer than 100 m. It is considered that it is sufficient to apply the cooling mechanism of

As a comparative example, FIG. 8 shows a cooling piping system conventionally used in many hot rolling mills.

In addition, Figure 4 shows the influence of the water volume density per nozzle unit width on the cooling capacity (evaluated by the amount of temperature drop from the start to the end of cooling), regardless of whether a pipe laminar nozzle or a slit laminar nozzle is used. The cooling capacity can be changed by changing the water density. This also applies to existing sprays, mist cooling, etc. However, in the case of slit laminar flow, there is a lower limit for a single slit thickness due to the unstable phenomenon described below.

Figure 5 also shows the case where the water temperature is changed using a slit laminar nozzle (the water density is constant at 0.5 m37 min I).
It shows the change in cooling capacity (heat transfer coefficient) of The cooling capacity increases greatly as the water temperature decreases, and this tendency is more pronounced when the steel plate surface temperature is low.

Further, FIG. 6 shows the lower limit water amount at which a stable water film can be obtained when a slit laminar nozzle is used. According to this, in a normal nozzle with a constant slit thickness, the lower limit of the amount of water is limited in terms of the stability of the water film. It was also confirmed that if the amount of water is extremely increased with the same slit thickness, the flow velocity becomes extremely high, leading to a decrease in cooling performance mainly due to wood scattering. Therefore, under conditions where a normal nozzle with a constant slit thickness is used, it is quite difficult to control the cooling capacity only by increasing or decreasing the amount of water, which is also disadvantageous in terms of cooling efficiency.

Next, in the present invention, when water is supplied through two or more different water supply pipes, a water temperature difference that should be set between the pipes will be explained. Experimental studies were conducted by setting the above water temperature difference under various conditions. The evaluation of the cooling capacity control range was performed using high-temperature water A (T
I), under the conditions of low temperature water B (T2), the total water density Q,
The cooling rate (V) was set at a constant value of 8+w3/min, and the ratio R (Vmax/Vsin) of the maximum value V+max and the minimum value Vsin of the cooling rate (V) from 800°C to 500°C was used. Therefore, the larger R is, the wider the cooling rate control range is, which is advantageous. As a result, as shown in Table 1, a wide cooling capacity control range can be obtained when there is no water temperature difference of at least 20'O. It was acknowledged that this could not be done. Further, it is desirable that the difference in water temperature between high temperature water and low temperature water be large.

Next, regarding control in the present invention, in the manufacturing process, the steel plate temperature is usually measured at the inlet and outlet sides of the cooling device. However, in the conventional system, dynamic cooling control based on such data cannot be performed mainly due to the narrow variable range of cooling capacity and poor response. However, according to the present invention, an extremely wide cooling control range can be obtained by changing the water temperature and water amount simultaneously or separately, and the cooling capacity can be finely adjusted. thing)
In the present invention, water is supplied at an appropriate temperature and amount to each of the plurality of pipes according to the expected temperature fluctuations, and a three-way valve is used to prevent sudden temperature fluctuations. For gentle temperature fluctuations, it is appropriate to use a flow control valve to control the temperature, but it goes without saying that control becomes easier if the response speed of the flow control valve is sufficiently fast. In line with the actual manufacturing process, if the plate thicknesses differ significantly between the coils or the target temperatures differ, the flow control valve opening degree is mainly set to 311. Furthermore, it is considered appropriate to respond to variations in the cooling pattern at the leading end, rear end, etc. within the same coil by opening and closing a three-way valve.

Hereinafter, specific implementation results of the present invention will be explained.

Example 1 In a cooling piping system as shown in FIGS. 1 and 2, the water supply pipe 12A is Q, 2m" 7 minutes, and the water supply pipe 12B is 0.
Provide water supply of 4 m3/min, and open three-way valves 16A and 16B.
An experiment was conducted in which the amount of water at the nozzle exit side was changed by switching between steps ① to ②. That is, in step ■, both three-way valves 16A and 16B are fully closed, and in step ■
Now, open the three-way valve 16A, close the three-way valve 18B, and step ■
Now, close the three-way valve 16A, open the three-way valve 16B, and step
In this case, both valves 16A and 16B were opened. Each step ■
The time required for ~■ is 0.5S or less, and the water amount changes extremely quickly to 0, 0.2, 0.4, 0. f1m3/min. Under these conditions, when the steel plate temperature drop due to passing through the cooling zone is viewed as cooling capacity, the temperature drop varied in the range of 10°C to 150°C for these four levels.

Example 2 In a cooling piping system as shown in Figs. 1 and 2, water at a temperature of 20°C is supplied to the water supply pipe 12A and water at a temperature of 80°C is supplied to the water supply pipe 12B', and the water temperature is O~0.8m3. The cooling capacity was evaluated by varying the amount of water within a range of 1/min layer and determining the amount of temperature drop from the steel plate temperature difference before and after the cooling zone. A slit laminar nozzle with a slit thickness of 5 mm was used as the nozzle.

The results are shown in Figure 7, with the total amount of water taken on the horizontal axis.
The vertical axis represents the amount of temperature drop. By arbitrarily changing the water volume ratio of the water supply pipes 12A and 12B, it is possible to change the cooling capacity over a wide range within the hatching range.In particular, under the condition of one pipe, there is a lower limit water volume due to wood membrane breakage, so only rapid cooling is required. It is recognized that heating and cooling becomes easy without any problems.

Changing the water temperature at the nozzle requires operating a flow control valve, but it can still be changed in just a few seconds. When changing the amount of water by opening and closing a three-way valve, the change can be made with a delay time of about 1 to 2 seconds. Therefore, it has sufficient responsiveness as an actual cooling device.

Example 3 Next, the first example (simulation results) of feedback control and feedforward control will be described.
As shown in the figure, a temperature sensor 17 is installed on the hot run table following the rolling mill, and the cooling state control device 18 sequentially calculates the deviation between the preset target temperature and the actual temperature, and uses the deviation to adjust the temperature of the predetermined valve. It controls the opening/closing or the degree of opening, and is a control that feeds back forward from the temperature sensor 17 and feeds forward to the rear. A comparison was made between a conventional control method in which only the water amount is controlled by opening and closing a valve, and a method in which both the water amount and water temperature are controlled as in the present invention. A hot-rolled steel plate with a thickness of 4.5 mm was rolled on an actual machine, the temperature at the entrance of the finishing mill was set at 100°C, the target temperature at the temperature sensor position was set at 850°C, and a steady state was achieved while performing feedback control and feedforward control. , the rolling speed was sequentially increased and then decreased. In the conventional method, the temperature control accuracy is ±50° C., whereas in the method of the present invention, the temperature control accuracy is ±5° C., making it clear that higher precision control is possible.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to stably and quickly control a wide range of cooling capabilities from rapid cooling to warm cooling.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a cooling device according to an embodiment of the present invention, FIG. 2 is a schematic diagram showing the cooling piping system of FIG. 1, and FIG. 3 is a schematic diagram showing a modification of the cooling piping system. Figure 4 is a diagram showing the relationship between water volume density and temperature drop (cooling capacity) for slit laminar flow and vibrating laminar flow, and Figure 5 is a diagram showing the relationship between water temperature and heat transfer coefficient (cooling capacity) for slit laminar flow.
Figure 6 is a diagram showing the lower limit water amount at which a stable water film can be obtained in slit laminar flow, and Figure 7 is a diagram showing the change in water amount and temperature drop (cooling capacity) due to the implementation of the present invention. A diagram showing the relationship, FIG. 8 is a schematic diagram showing a conventional cooling piping system. io...cooling device, ■! ...Steel plate, 12A, 12B
, 12C... Water supply piping, 13A, 13B, 13C...
・Connection piping, 14...Cooling nozzle header, 15A, 1
5B, 15C...flow control valve, 18A, 16B, 16
C... Three-way valve, 17... Temperature sensor (cooling state detection device), 18... Cooling state quantity g4 device. Agent Patent Attorney Osamu Shiokawa 1 Figure 1 Figure 2 Figure 3 Figure 4 Water volume '1m (TrL3./m+n-m) Figure 6
' Slit thickness (mTn)

Claims (1)

[Claims] (1) It has two or more water supply pipes that supply cooling water, the connecting pipes connected to each water supply pipe are merged with each other and connected to a single cooling nozzle header, and the flow rate is on the upstream side of each connecting pipe. A control valve is provided, a three-way valve is provided on the downstream side of each connecting pipe, the first port of the three-way valve is connected to the flow rate control valve side, the second port of the three-way valve is connected to the cooling nozzle header side, and the three-way valve is connected to the flow rate control valve side. The third port of the valve is connected to the drainage system and is equipped with a cooling state detection device that detects the cooling state of the steel plate cooling zone, and opens and closes the flow control valve and/or the three-way valve based on the detection result of the cooling state detection device. 1. A cooling device for hot-rolled steel sheets, characterized by comprising a cooling state control device for controlling the cooling state.