JP3096366B2 - Metal strip cooling system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for cooling a metal strip such as a steel strip.

[0002]

2. Description of the Related Art Conventionally, a steel strip passed by immersion in a zinc bath is heated at a predetermined temperature, thereby forming an alloy layer of steel and zinc with an appropriate thickness, and then cooling water is applied. It is necessary to spray and stop the progress of alloying to an arbitrary degree. When the alloy layer is thin, the plating layer tends to peel off. As the alloy layer becomes thicker, it becomes brittle, and the plating layer on the surface peels off in a powdery state, causing a phenomenon called powdering. Therefore, accurate temperature control of the steel strip during cooling is required.

Conventionally, a driver changes the number of nozzles for injecting cooling water while monitoring the temperature of the steel strip after passing through the nozzle for injecting cooling water. It is clear that the steel strip temperature cannot be controlled quickly and accurately. When the thickness of the steel strip is changed and the cooling load fluctuates significantly,
Precise temperature control of the steel strip is not possible.

Another prior art for solving such a problem is shown in FIG. After the galvanization, the steel strip 1 is heated and travels upward in FIG. This steel strip 1 has a cooling zone 2
Is cooled by the cooling water injected from the nozzle 4 in the housing 3. Cooling water is supplied to the nozzle 4 from a pipe 5 via a flow control valve 6. The temperature detecting means 7 disposed on the outlet side of the cooling zone 2 detects the temperature of the steel strip 1 and gives a signal representing the detected temperature to the temperature controller 8. The signal representing the target temperature from the reference temperature 9 is given, and the signal representing the flow rate of the cooling water corresponding to the difference between the actual detected temperature and the target temperature is given to the flow controller 10. The flow controller 10 is provided with a signal representing the actual temperature detected by the flow meter 11 interposed in the pipe 5, and thus the flow rate provided by the temperature controller 8 and the flow rate detected by the flow meter 11 The flow controller 10 controls the opening degree of the flow control valve 6 so that is equal. The flow control valve 6 has its valve body displaced to a position corresponding to a signal from the flow controller 10 by a motor or an air cylinder or the like, thereby changing the flow path cross-sectional area, and thus controlling the flow rate of the cooling water.

[0005]

The prior art shown in FIG. 9 has a structure in which the valve body of the flow control valve 6 is driven to be displaced to a position corresponding to the flow rate.
The time required for the flow rate control is long, and therefore, it is impossible to cool the steel strip 1 running at a high speed with sufficient responsiveness to perform accurate temperature control.

Further, in the prior art shown in FIG.
Since the flow rate of the cooling water supplied to the nozzle 4 is adjusted by the single flow control valve 6, the range in which the flow rate can be controlled,
That is, the rangeability is relatively small, so that a wide flow control range required when there is excessive cooling load fluctuation may not be obtained.

An object of the present invention is to provide a metal strip cooling apparatus capable of accurately cooling a metal strip cooling temperature with high responsiveness and capable of coping with a large cooling load fluctuation. It is to be.

[0008]

SUMMARY OF THE INVENTION The present invention is directed to a plurality of nozzles, which are sequentially arranged in the running direction of a metal strip and inject cooling fluid to the running metal strip, a cooling fluid source, and each of the nozzles. A plurality of on-off valves for supplying / cutting off a cooling fluid from a cooling fluid source for each stage; and a means for detecting the temperature of the metal strip, which is provided downstream of the last stage nozzle in the traveling direction, Means for setting a predetermined temperature, and selectively opening and closing the on-off valve for each stage of the nozzle in response to each output of the temperature detecting means and the temperature setting means so that the detected temperature becomes a predetermined temperature. Control means for controlling, wherein the control means calculates a flow rate of a cooling fluid to be injected from a nozzle corresponding to a difference between the detected temperature and the set temperature, and an output of the first calculation means Responsive to the flow rate of the nozzle corresponding to the flow rate And a third calculating means for calculating and calculating a difference between the flow rate calculated by the first calculating means and the flow rate of the cooling fluid injected from the determined number of nozzles. An integrating means responsive to the output of the third calculating means for integrating the difference in the flow rate with the passage of time; A metal comprising: a correcting means for correcting the number of stages determined by the second calculating means when the flow rate becomes equal to or more than a flow rate; and a driving means for opening an on-off valve corresponding to the nozzle of the number of stages corrected by the correcting means. It is a cooling device for the belt.

[0009]

Further, the present invention is characterized in that the first and second calculating means perform a calculating operation at every predetermined control cycle.

Further, according to the present invention, a plating bath in which a metal band is immersed and plated, and a metal band plated through the plating bath is heated further upstream than the nozzle at the most upstream stage in the traveling direction. And means for alloying.

[0012]

According to the present invention, nozzles for injecting a cooling fluid such as cooling water are sequentially provided for each stage in the traveling direction of the metal strip.
A plurality of stages are arranged, and for each stage, cooling fluid is supplied from a cooling fluid source via an on-off valve, and this on-off valve is not a flow control valve described in connection with the above-mentioned prior art, but is fully open or It has a configuration that performs a fully closed operation, and thus such an opening and closing operation is at a high speed. Therefore, the on-off valve of each stage of the nozzle can be selectively opened and closed so that the difference between the detected temperature of the metal band detected by the temperature detecting means and the temperature set by the temperature setting means becomes zero, In this way, the number of nozzles digitally discretized according to the temperature difference was determined and the cooling fluid was jetted to the metal band,
The temperature of the metal strip after cooling can be maintained at the set temperature at high speed and accurately. Further, the opening / closing valve is provided at each stage of the nozzle as described above, and by increasing the number of stages of such a nozzle, it becomes possible to respond to a great change in cooling load with high responsiveness. .

[0013] Further, in accordance with the difference between the detected temperature of the metal strip and the set temperature by the first calculating means, the flow rate of the cooling fluid necessary for making the difference zero is calculated by the first calculating means. The number of nozzles corresponding to the flow rate of the cooling fluid calculated by the first calculating means is calculated and determined by the second calculating means, and the number of stages determined by calculating by the second calculating means is The correction means corrects the flow rate of the cooling fluid calculated by the first calculating means by opening the opening / closing valve corresponding to the number of nozzles corrected by the correcting means by the driving means. And calculating the difference between the flow rate of the cooling fluid ejected from the nozzles of the number of stages determined and calculated by the second calculation means by the third calculation means,
The difference in the flow rate is integrated over time by the integrating means, and the integrated value is equal to or greater than the injection flow rate of the nozzle of the single stage,
Or, when it becomes the following, that is, when the absolute value of the integral value is equal to or more than the injection flow rate of the nozzle of a single stage, the number of stages is corrected by the above-described correction means, so that the metal band after cooling is The outlet side temperature can be maintained at the set temperature with high accuracy.

Further, according to the present invention, the first and second arithmetic means are provided with a predetermined control cycle, for example, 0.1
By performing the calculation operation every second, the temperature control of the steel strip in each control cycle can be performed with high accuracy.

Further according to the present invention, such a cooling device for a metal strip controls the alloying of the metal strip by immersing the metal strip in a plating bath of zinc or the like and then passing the metal strip in a heating zone and a soaking zone. In order to perform, it can be suitably implemented.

[0016]

FIG. 1 is a system diagram showing an entire configuration of an embodiment of the present invention. The cooling device for the steel strip 12, which is a metal strip according to the invention, is implemented in connection with the cooling strip 13.

FIG. 2 is a system diagram showing an alloying furnace 14 and the like in which such a cooling zone 13 is used. Steel strip 12
The molten zinc 15 is wound around a sink roll 13 in a molten zinc pot 16 in which the molten steel is stored, whereby the steel strip 12 is galvanized, and the thickness of the plating layer is reduced by a compressed air jet nozzle 17. Adjusted. The steel strip thus plated is supplied to the heating zone 18 of the alloying furnace 14.
, And soaked in the soaking zone 19, further cooled in the cooling zone 13 thereabove, and supplied through the roll 20. The speed of the steel strip 12 is a high speed, for example, 200 m / min at the maximum. The alloying furnace 14 has a height of, for example, 60 m, of which the cooling zone 13 has a height of, for example, 2 to 3 m.
With a height of

FIG. 3 is a graph showing the temperature of the steel strip 12 in the pot 16 and the alloying furnace 14. Alloying furnace 1
4, the zone W of the heating zone 18, the soaking zone 19 and the cooling zone 13
In 1, heated to, for example, 500-550 ° C.
An alloy layer of zinc and steel is formed with an appropriate thickness. The present invention is implemented so that the range W1 in which such alloying is performed can be appropriately set and the quality of the galvanized steel strip can be improved.

Referring again to FIG. 1, the housing 21 of the cooling zone 13 is divided into upper and lower cooling spaces 23, 2 by a partition wall 22.
In the upper cooling space 23, a plurality of (four in this embodiment) nozzles 2 are sequentially arranged in the running direction of the steel strip 12.
5 to 28 are arranged from the upstream side (the lower part in FIG. 1) to the downstream side (the upper part in FIG. 1) of the steel strip 12. To each of the nozzles 25 to 28, cooling water, which is a cooling fluid, is pumped from a cooling water source 29 through a pipe 30 and further through opening / closing valves 31 to 34 of each stage. The on-off valves 31 to 34 are fully opened and fully closed to supply / cut off the cooling water to the nozzles 25 to 28.
The lower cooling space 24 also has the same configuration as the upper cooling space 23, and the corresponding parts are indicated by the same numerals with the suffix a. Thus, the upper and lower cooling spaces 2
A plurality of nozzles 25-28, 25a-
By providing the cooling space 28a, each cooling space 23, 2
Maintenance can be facilitated by arbitrarily switching between use and non-use of 4.

Temperature detecting means 3 for detecting the temperature of steel strip 12
5 is provided at the final stage, that is, further downstream (in the upper part of FIG. 1) in the traveling direction than the nozzle 28 on the downstream side in the traveling direction. The output of the temperature detecting means 35 is given to a temperature controller 36. Temperature setting means 3 for setting a target value of the temperature
The output of 7 is also provided to a temperature controller 36. The temperature controller 36 calculates and calculates a signal representing a temperature difference between the detected temperature and the set temperature, and supplies the calculated signal to the flow controller 39 via the switch 38 from the line 73. The flow controller 39 supplies a signal representing the flow rate of the cooling water to be injected from the nozzles 25 to 28 corresponding to the temperature difference between the detected temperature and the set temperature to the electric circuit 41 from the line 40. The output of the cooling water flow meter 76 is also supplied to the flow controller 39, and the control operation is confirmed.

Referring to FIG. 4, the output of line 39 of flow controller 39 is the flow rate of the cooling water for making the temperature difference between the detected temperature and the set temperature zero. Indicated at 42. The electric circuit 41 selectively controls the opening and closing of the on-off valves 31 to 34 as indicated by the staircase waveform 43 in response to the signal indicating the flow rate of the cooling water indicated by such a straight line 42. Such on-off valves 31 to
In practice, the opening / closing control of the valve 34 causes the output of the flow controller 39 via the line 40 to have a hysteresis in response to an increase and a decrease as shown in FIG. 5, thereby causing chattering of the on-off valves 31 to 34. prevent.

In this way, as shown in FIG. 6, the electric circuit 41 sets the on-off valves 31 to 34 to a predetermined control cycle T1.
Perform each time. For example, T1 may be 0.1 sec.

In the above-described embodiment, the configuration relating to the cooling space 23 has been mainly described.
The configuration is also the same, and the same reference numerals are given the suffix a as shown in FIG. 1 as described above. The present invention
It can be implemented not only in connection with the alloying furnace 14 after the plating of the steel strip, but also in other fields for cooling the metal strip.

FIG. 7 is a block diagram showing a specific configuration of the electric circuit 41. A signal representing the flow rate of the cooling fluid derived from the flow controller 39 to the line 40 is calculated by the arithmetic means 45.
Given to. The calculation means 45 calculates and determines the number of stages of the nozzles 25 to 28 corresponding to the flow rate indicated by the signal of the line 40 according to the graph 43, as shown in FIG. When the flow rate represented by the signal of the line 40 is 0 to F1, the on-off valves 31 to 34 of each stage of the nozzles 25 to 28 are provided.
Are all closed, and in the range of the flow rates F1 and F2, 1
Two on-off valves, for example, 31 open, two on-off valves, for example, 31 and 32 open in the range of flow rates F2 to F3, and three on-off valves, for example, 31 to 3 for flow rates F3 to F4.
3 is opened, and all the on-off valves 31 are in the range of flow rates F4 to F5.
~ 34 are determined to open. A signal indicating the number of the on-off valves 31 to 34 to be opened is supplied from the line 46 to the stage number correcting means 47, and the number of the stages is corrected. The representative signal is provided to the drive means 49 via line 48. The drive means 49 selects the number of stages to be used, that is, the open / close valves 31 to 34 to be opened, and controls the open / close of the open / close valves 31 to 34. A signal indicating the number of stages derived from the stage number correcting means 47 to the line 48, that is, the number of the on-off valves 31 to 34 to be opened is supplied to the cooling water flow rate calculation circuit 51 from the line 50. As shown in FIG. 8, the cooling water flow rate calculation circuit 51
Cooling water flow rates F11, F12,
The signals representing F13 and F14 are calculated and derived to a line 52. The subtraction circuit 53 is connected to the line 40 from the flow controller 39.
Is subtracted from the signal representing the flow rate of the cooling fluid derived from the cooling water flow rate calculation circuit 51 via the line 52 from the signal representing the flow rate of the cooling fluid.
4, a signal representing the flow rate difference indicated by the reference sign ΔF in FIG. 4 is derived. Such a cooling water flow rate calculation circuit 5
1 and the subtraction circuit 53 constitute an operation means 55.

A signal representing the flow rate difference ΔF derived from the line 54 is supplied to an integrating means 56, and the flow rate difference ΔF is integrated with time. This integral value is a positive or negative value. The temperature controller 36, the flow controller 39, and the calculation means 45 perform a sampling operation for each control cycle T1, and repeat the calculation operation. The reset circuit 75 causes the integrating means 56 to perform a reset operation at the above-described times t1 and t2 in FIG. 6 within each control cycle T1, and resets the integrated value to zero.

The output of the integrating means 56 is supplied to an adding circuit 57, the signal from the line 58 is added, and the output of the adding circuit 57 is derived to the first judging means 59. The judgment means 59 subtracts the value Q57 given from the addition circuit 57 from the cooling water injection flow rate ΔQ1 by the nozzle of the single stage of the nozzles 25 to 28 to perform the calculation of Expression 1, thereby obtaining the value QI. . Whether or not this value QI is positive is calculated as shown in Expression 2.

QI = Q57−ΔQ1 (1) QI> 0 (2) When Expression 2 is satisfied, a signal is derived to the line 60, and the command circuit 61 sends the nozzles 25 to 28 to the stage number correction means 41.
Among them, a command signal for further opening the one-stage on-off valves 31 to 34 is generated and given to the correction means 47. As a result, the correction means 47 corrects the line 48 by adding 1 to the number of stages represented by the electric signal from the line 46. Thus, among the current on-off valves 31 to 34, those that are closed are further opened by one step by the driving means 49. The signal on the line 60 is supplied from the OR gate 62 to the reset circuit 75 to reset the integrating means 56.
Signal conducts the switch 63, and outputs a signal representing the value QI from the signal generation circuit 64 to the switch 6
The signal is supplied to the adder circuit 57 from the line 58 via 3. Nozzles 25-28, 25a-28a, and on-off valves 31-
34, 31a to 34a have the same configuration.

When the judging means 59 judges that the above equation 2 is not satisfied, the following second judging means 65
Then, the value QD is calculated based on Equation 3.

QD = Q57−ΔQ2 (3) Here, ΔQ2 is a cooling water injection flow rate that decreases when one of the single-stage on-off valves 31 to 34 of the nozzles 25 to 28 is closed. And ΔQ1 = ΔQ2. This value QD
Is determined by the determining means 65 so that the equation 4 is satisfied, that is, whether the value QD is negative. If the value QD is negative, a signal indicating this is derived to the line 66, and the command circuit 67
Derives a command signal for closing one of the one-stage on-off valves among the on-off valves 31 to 34 that are currently open, and gives the command signal to the correcting means 47.

QD <0 (4) As a result, the correcting means 47 subtracts 1 from the number of the on-off valves 31 to 34 to be in the open state represented by the electric signal from the line 46 and gives the result to the line 48, As a result, the driving means 49 closes one of the open / close valves 31 to 34 and stops one stage of the nozzles 25 to 28 for injecting the cooling water. At the same time, the electric signal on the line 66 is supplied from the OR gate 62 to the reset circuit 75,
Is reset, and the signal on the line 66 closes the switch 68, so that the signal representing the value QD from the signal generating circuit 64 is supplied from the conducting switch 68 to the adding circuit 57 via the line 58. When the above expressions 2 and 4 do not hold in the judgment means 59 and 65, the switch 69 is turned on and the signal generation circuit 64 is turned on.
Is provided from line 58 to summing circuit 57.

The present invention can be implemented not only in the alloying furnace 14 but also in other fields.

[0032]

As described above, according to the present invention, a cooling fluid is jetted by sequentially arranging a plurality of nozzles in the running direction of a steel strip or the like in the direction of travel of the metal strip. A cooling fluid is supplied from a fluid source via an opening / closing valve for each stage, and the temperature is set by a temperature detecting unit provided on a downstream side in the traveling direction of the metal band from a nozzle of the final stage, and set by a temperature setting unit. The opening / closing valve of each stage of the nozzle is selectively opened / closed by the control means so that the difference from the set temperature becomes zero, and the opening / closing operation of the opening / closing valve is described in relation to the above-mentioned prior art. Since the speed is sufficiently high as compared with the flow control operation speed of the flow control valve, it is possible to accurately bring the metal strip to a desired set temperature and achieve cooling with high responsiveness.

Even if the cooling load fluctuates excessively due to a change in the thickness of the metal band or the like, it can be dealt with by controlling the number of spray stages by the control means. Further, the nozzles in each stage may have the same configuration, and the configuration of the control means can be simplified, and the implementation is easy.

Further, the control means calculates the flow rate of the cooling fluid to be jetted from the nozzles so that the difference between the detected temperature and the set temperature becomes zero by the first calculation means, and determines the number of nozzle stages corresponding to this flow rate. Determined by the second calculating means,
The difference between the flow rate calculated by the first calculation means and the flow rate ejected from the nozzles of the number of stages determined by the second calculation means is determined by the third calculation means, and the difference between the flow rates is calculated as the time elapses. When the absolute value of the integrated value is equal to or greater than the injection flow rate of the single-stage nozzle, the number of stages determined by the second calculating means is corrected, and the opening and closing of the on-off valve is controlled based on the correction result. As a result, accurate temperature control is possible and microscopic flow rate fluctuations
Adverse effects on temperature are practically neglected, and accurate metal strip cooling temperatures can be achieved as described above, and accurate temperature control is possible without necessarily providing a large number of nozzle stages. The effect is achieved.

Further, according to the present invention, the calculation of the flow rate and the number of stages by the first and second calculation means is performed at predetermined control intervals, for example, every 0.1 sec. Accurate control of the cooling temperature is possible, and the cooling of the metal strip can be performed using as many nozzles as possible, for example, without cooling using only a small number of nozzles. The use efficiency of the device is good.

According to the present invention, such a cooling apparatus for a metal strip according to the present invention immerses the metal strip in a plating bath of zinc or the like, passes the plating, and then heats the coating in a heating zone or a soaking zone. It is then possible to carry out the invention with cooling and thus to produce a metal strip having a high quality alloyed plating layer.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an entire configuration of an embodiment of the present invention.

FIG. 2 shows an alloying furnace 14 with a metal strip 13 according to the invention.
FIG. 2 is a system diagram showing a configuration of a molten zinc pot 16 and the like.

FIG. 3 is a graph showing temperature distributions in a molten zinc pot 16 and an alloying furnace 14.

FIG. 4 is a diagram for explaining the principle of the electric circuit 41 shown in FIG.

FIG. 5 is a diagram for explaining an operation performed by an electric circuit 41 to prevent chattering of the on-off valves 31 to 34.

FIG. 6 shows opening / closing valves 31 to 34 every predetermined control cycle T1.
FIG. 4 is a diagram for explaining an operation in which opening and closing are controlled.

FIG. 7 is a block diagram showing a specific configuration of an electric circuit 41.

FIG. 8 is a graph for explaining the operation of the arithmetic circuit 51;

FIG. 9 is a system diagram of the prior art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 Steel strip 13 Cooling zone 14 Alloying furnace 15 Hot-dip zinc 18 Heating zone 19 Uniform tropical zone 21 Housing 23, 24 Cooling space 25-28, 25a-28a Nozzle 29 Cooling water source 31-34, 31a-34a On-off valve 35 Temperature detecting means 36 temperature controller 37 temperature setting means 39 flow controller 41 electric circuit 45 calculating means 47 stage number correcting means 49 driving means 51 calculating circuit 53 subtracting circuit 55 calculating means 56 integrating means 57 adding circuit 59, 65 judging means 61 one step increasing command Signal generation circuit 64 Signal generation circuit 67 One-stage subtraction command signal generation circuit 75 Reset circuit

Continued on the front page (72) Inventor Katsuyuki Takezaki 5 Ishizu Nishimachi, Sakai City, Osaka Nisshin Steel Co., Ltd. Inside the Sakai Works (72) Inventor Kazuhiro Majima 5 Ishizu Nishimachi, Sakai City, Osaka Nissin Steel Co., Ltd. Inside the Sakai Plant (72) Inventor Hiroyuki Suzuki 4-2-1, Honmachi, Chuo-ku, Osaka-shi Toshiba Kansai Branch (72) Inventor Hozumi Akita 4-2-1, Honmachi, Chuo-ku, Osaka-shi Toshiba Kansai Branch (56) References JP-A-57-98633 (JP, A) JP-B-61-3379 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) C21D 9/573 101 C21D 1/00 123 C21D 11/00 101 C23C 2/00-2/40

Claims (3)

(57) [Claims] 1. A metal strip is sequentially arranged in a traveling direction of a metal strip,
A multi-stage nozzle for injecting a cooling fluid into a traveling metal strip, a cooling fluid source, and supplying / supplying a cooling fluid from the cooling fluid source to each stage of the nozzle.
A plurality of on-off valves to be shut off, and provided on the downstream side in the traveling direction from the last stage nozzle,
Means for detecting the temperature of the metal strip, means for setting a predetermined temperature, in response to each output of the temperature detecting means and the temperature setting means, so that the detected temperature becomes a predetermined set temperature, Control means for selectively controlling the on / off valve of each stage of the nozzle to open and close, wherein the control means calculates a flow rate of the cooling fluid to be injected from the nozzle corresponding to a difference between the detected temperature and the set temperature. A first calculating means for calculating the number of nozzles corresponding to the flow rate in response to an output of the first calculating means; and a flow rate calculated by the first calculating means and the determination. A third calculating means for calculating and calculating a difference between the flow rate of the cooling fluid ejected from the nozzles of the determined number of stages, and an integral responsive to an output of the third calculating means for integrating the difference in the flow rate with the passage of time. Means and the output of the integrating means. And correcting means for correcting the number of stages determined by the second calculating means when the absolute value of the integral value is equal to or greater than the injection flow rate of the nozzle of the single stage; and nozzles of the number of stages corrected by the correcting means. Drive means for opening a corresponding on-off valve. 2. The method according to claim 1, wherein the first and second calculating means perform a calculating operation at every predetermined control cycle.
The cooling device for a metal strip according to claim 1. 3. A plating bath for immersing and plating a metal strip, and an alloy which is heated by passing through the plating bath to form an alloy on the upstream side of the nozzle at the most upstream stage in the running direction. 3. A cooling device for a metal strip according to claim 1, wherein means for converting the metal strip is disposed.