KR100508510B1 - Method for controlling thickness of tandem cold mill - Google Patents

Abstract

The present invention relates to a method for precisely controlling the thickness of a continuous cold rolling mill, and the present invention relates to a method for precisely controlling the thickness of a continuous cold rolling mill, wherein each plate thickness detection value of two thickness meters (302,303) provided in the final stand (301) ( A first step of judging whether the difference between A and B is smaller than a set value and determining whether there is an error in the detected value of the thickness meter; In the case where there is an error in the detected value in the first step, the theoretical thickness t of the product is calculated by using the plate speed and the plate thickness of the front end stand of the final stand and the plate speed of the final stand. A second step of determining which of the two thickness meters (302, 303) is a thickness meter which is a detected value error by using? A third step of determining a measurement mode by setting a thickness meter which is the detected value error identified in the second step as a slave and another error-free thickness meter as a master; A fourth step of detecting a thickness corresponding to the measurement mode determined in the third step, and feedback-controlling the speed of the main motor 308 of the final stand 301 so that the predetermined order thickness and the detected thickness are the same. According to the present invention, in the continuous cold rolling operation by comparing the two measured values from the two thickness meters to use the thickness control more accurate thickness information, the rolling operator is not recognized in the continuous cold rolling operation It is possible to automatically prevent the occurrence of a large amount of thickness defect due to an abnormal thickness gauge.

Description

Precise thickness control method of continuous cold rolling mill {METHOD FOR CONTROLLING THICKNESS OF TANDEM COLD MILL}

The present invention relates to a method for precisely controlling the thickness of a continuous cold rolling mill, and in particular, by comparing two measurement values from two thickness meters in a continuous cold rolling operation, by using the more accurate thickness information to control the thickness of the continuous cold rolling. The present invention relates to a method for precisely controlling the thickness of a continuous cold rolling mill, which can automatically prevent a large amount of thickness defects caused by an abnormal thickness gauge that a rolling operator cannot recognize in an operation.

1 is a conventional continuous cold rolling line 110 configuration diagram, referring to Figure 1, this continuous cold rolling line facility is a cold rolling material for the hot rolled coil 101 to the reel to release for continuous operation Pay off reel 102, the welder 103 for butt welding the trailing end of the trailing hot rolled coil to the trailing end of the preceding coil, and the hot rolled coil in operation to adjust the storage volume of the entry and exit of the rolling process. Looper (Looper 104,107) to balance work speed, hydrochloric acid tank 105 to remove scale layer formed on hot rolled coil surface, and Side Trimmer, 106 to cut coil width to demand width ), Continuous cold rolling mill (Tandem Mill, 108) for cold rolling hot rolled coils to meet the required thickness of the material to be demanded, and tension reel (109) for winding the cold rolled products back into coil form. Consists of

2 is a configuration diagram of a thickness detection and control device of a conventional continuous cold rolling mill. Referring to FIG. The rolling operation starts by being strongly driven into the roll bite by the strong frictional force between the roll 203 and the lower work roll 204. In the same manner, the second stand 205, the third stand 206, and the last stand 4 Rolling is performed according to a predetermined reduction ratio for each stand while sequentially passing through the stands 207, thereby obtaining a product 208 having a final thickness required by the demand.

In such a conventional continuous cold rolling mill thickness detection and control device, the rolling thickness control is automatically performed according to the reduction rate per stand set by the reduction calculation model, the thickness is controlled in the first stand 202 In the process, the thickness signal detected by the X-ray-thickness meter 209 installed in front of the first stand 202 is converted into an electrical signal by a signal converter, and then transmitted to a programmable logic controller (PLC). If the detected value is thicker than the information thickness of the material, this signal is self-edited and calculated by PLC to give the hydraulic increase command to the push up cylinder (210) to match the information thickness. The thickness control to close is performed. At this time, the case where the detected value is thinner than the information thickness of the material is similarly controlled, and the control method is the same for the other stands.

There is also a method of controlling the thickness by controlling the roll speed by controlling the rotation speed of the main motors (222 to 225) of each stand without using such a hydraulic pressure reduction, which is based on the law of volume invariant before and after rolling, The thickness control is performed by adjusting the roll speed of each stand while calculating and comparing the mass value multiplied by the plate speed and the thickness value measured by the thickness meters (209, 211 to 214) and the tachometers (215 to 218) installed separately. Do it.

This conventional thickness control method is called AGC (Automatic Gauge Control), and all the rolling mills control the thickness by this method.

The thickness of the product is detected by a value detected by the first detection and control X-ray thickness meter 214 installed at the rear of the fourth stand 207, which is the final stand, and the detected value is equal to the actual thickness. In order to know whether the value is expressed, in view of the characteristics of the continuous line, one coil per thermal coil was measured with a micrometer at a separate inspection site, and the consistency of the product thickness was checked while preventing productivity from being measured for thickness.

3 is a flow chart of the production of a conventional continuous cold rolling mill. Referring to FIG. 3, when cold rolling of the continuous cold rolling mill 108 proceeds, the plate thickness is measured at # 4 thickness meter 214 behind the stand 207. It will be detected (401). The detected thickness detection value is displayed as an analog value on a control panel installed in the cold rolling mill cab to provide the driver with detection information detected by the thickness meter (402). . The cold rolling mill operator will continue rolling based on the displayed thickness information, and the local operator outside the cab will be able to determine whether the thickness of the product being produced is suitable for the order thickness. In the absence of this, the thickness of the product is measured manually by one time per 10 coils (404) using a micrometer provided at the site.

In this way, if the measured product thickness performance falls within the order thickness ordered by the demand (405), the operator considers that the thickness information is intact and includes the previously measured nine coils. When the coil is manufactured as a genuine product and the micrometer actual thickness is out of the ordered thickness range required by the demand, the defective coil and the nine coils previously worked are subjected to defects due to poor thickness. (407).

FIG. 4 is a flow chart of a thickness defective product in a conventional thickness system. Referring to FIG. 4, the plate thickness detection 408 value of the thickness gauge 4 of the stand 301 measuring the thickness of the final product is measured as a rolling operation is performed. Detection errors of the X-ray thickness meter itself increase, such as heat generation and deterioration, X-ray tube voltage change, and X-ray projection amount change (409). In this case, on the control panel of the cab where the driver of the cold rolling mill can obtain thickness information, the thickness information that is incorrectly read due to the detection error of the thickness meter is displayed (410).

However, the cold rolling mill operator believes that the display value is correct because no thickness information is provided other than the thickness information displayed on the control panel during the rolling mill operation. Therefore, it is necessary for the operator to recognize the actual thickness of the rolled product. It becomes impossible (411).

In this case, the AGC system, which is an automatic thickness control system of the cold rolling mill, incorrectly recognizes wrongly detected thickness information as the correct thickness information and sets it as a control target to perform thickness control (412). Due to such incorrect thickness information, the actual thickness of the product is out of the allowable thickness of the order thickness (413) to produce a product of poor thickness (414). Eventually, even if such a thickness defect occurs, the cold rolling mill worker will continue to perform the normal rolling operation while recognizing the product with the actual thickness as genuine (415).

Due to this series of processes, the thickness defects generated in actual operations are over 1,000 tons per year, and moreover, the problem is that if the local worker does not measure the thickness of the product by micrometer, it is not necessary for the operator to know the mass. There was a problem that a thickness defect of the.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and therefore, an object of the present invention is a theoretical product obtained by the law of invariant volume before and after rolling the detection value by two X-ray thickness meters installed behind the final stand of the continuous cold rolling mill. By comparing the thickness with the real time in threefold, it automatically selects the thickness meter without error and applies it to the thickness control of the rolling mill, eliminating the process of measuring the product thickness micrometer by the inaccurate and heavy workload. In view of the above, there is provided a method of precisely controlling the thickness of a continuous cold rolling mill to prevent the occurrence of a large amount of product length thickness defects that are generated in a state in which a rolling worker or a product inspector does not know.

As a technical means for achieving the above object of the present invention, the method of the present invention is a method for precisely controlling the thickness of a continuous cold rolling mill, wherein the difference between the plate thickness detection values of two thickness meters installed on the final stand is greater than the set value. A first step of determining whether there is an error in the detected value of the thickness meter by judging whether it is small; In the case where there is an error in the detected value in the first step, the product theoretical thickness is calculated using the sheet speed and plate thickness of the front end stand of the final stand, and the plate speed of the final stand, and the two A second step of determining which thickness gauge is a detected value error in the thickness gauge; A third step of determining a measurement mode by setting a thickness meter which is the detected value error identified in the second step as a slave and another error-free thickness meter as a master; And a fourth step of detecting a thickness corresponding to the measurement mode determined in the third step and feedback-controlling the speed of the main motor of the final stand such that the predetermined order thickness and the detected thickness are the same.

Hereinafter, an apparatus for precisely controlling thickness of a continuous cold rolling mill according to the present invention will be described in detail with reference to the accompanying drawings. In the drawings referred to in the present invention, components having substantially the same configuration and function will use the same reference numerals.

5 is a configuration diagram of a precise precision control device of the continuous cold rolling mill for carrying out the present invention. Referring to FIG. 5, the precision precision control device of the continuous cold rolling mill for carrying out the present invention is the fourth stand (the final stand) 301) # 4-1 thickness meter 302 installed at the rear, # 4-2 thickness meter of the # 4-2 thickness meter 303 and # 3 gamma ray thickness meter installed at the rear of the # 3 stand 305 A sensor unit 309 consisting of a 304, a # 3 tachometer 306 and a # 4 tachometer 307 installed at the rear of the stand 3 and 4, respectively, and the sensor unit 309. PLC unit 310 which performs feedback control on the speed of the main motor 308 of the final stand 301 according to the determination result determined by the detection value and the set value of the PLC unit 310. Actuator unit 311 including the No. 4 stand main motor 308 to perform the actual control according to the product of ().

The PLC unit 310 determines whether the difference between the plate thickness detection values A and B of the two thickness meters 302 and 303 installed on the final stand 301 is smaller than the set value, thereby detecting the thickness value of the thickness meter. Is determined, and if there is an error in the detected value, the product theoretical thickness (t) is calculated by using the plate speed and plate thickness of the front end stand of the final stand and the plate speed of the final stand. The thickness t is used to determine which of the two thickness meters 302 and 303 is a detection value error, and the thickness meter which is the detected detection value error is set as a slave and another thickness meter without an error is set as a master. It is configured to determine the measurement mode, detect the thickness corresponding to the determined measurement mode, and feedback control the speed of the main motor 308 of the final stand 301 so that the estimated order thickness and the detected thickness are the same.

6 is a flowchart showing a method for precisely controlling the thickness of a continuous cold rolling mill according to the present invention.

Operation according to the present invention configured as described above will be described in detail below based on the accompanying drawings.

5 and 6, the difference between the plate thickness detection values A and B of the two thickness meters 302 and 303 installed in the final stand 301 will be explained. It is determined whether there is an error in the detected value of the thickness meter by determining whether it is smaller than the set value, which will be described in detail below.

That is, the conventional thickness gauge # 4-1 thickness meter 302 detects the product thickness value A as before (501) and the newly added # 4-2 thickness meter 303 detects the product thickness value B at the same time. (502). The two thickness values detected in this way are converted into electrical signals by the converter and transmitted to the PLC. In PLC, the absolute difference between the two thickness detection values is larger than 0.4% of the order thickness. It is determined (503). That is, the following equation (1) is used to determine whether the detection error occurs in the thickness detection # 4-1, # 4-2 thickness gauge.

[│ A-B│ / Order system] x 100] 0.4

As a result of this determination, if the absolute value of the difference between the two thickness detection values is less than 0.4% of the order thickness, both thickness meters can be judged that the product thickness value is normally detected without an error, and thus the product is normally produced. 504, on the other hand, if it is greater than or equal to, it is determined that one of the two thickness gauges is indicative of a detection error (although it is not known which thickness meter) and compared with the calculated product theoretical thickness 505.

Then, in the second step (505-509), if there is an error in the detected value in the first step, the product theoretical thickness (using the sheet speed and plate thickness of the front end stand of the final stand and the plate speed of the final stand) t) is calculated, and the theoretical thickness t is used to determine which of the two thickness meters 302 and 303 is a detection value error, which will be described in detail below.

In other words, the calculation of the theoretical thickness t of the product (505) is shown in Equation 2 as the plate velocity values (a) 506 and # 4 plate detected by the # 3 tachometer 306 by the law of volume invariant before and after rolling. It is obtained by mass flow calculation of the plate velocity values (b) 507 detected by the speed gauge 307 and the plate thickness values (c) 508 detected by the # 3 gamma ray thickness meter 304. The equation for calculating the theoretical thickness of the product using this volume invariant law is shown in Equation 2 below.

a x c = b x t

t = (a x c) / b

Therefore, if the thickness detection value of the # 4-1 and # 4-2 equipment exceeds the maximum measurement error of 0.4% by the calculation result of (503), it is determined which of the two thickness meters is causing the two detection error. As shown in Equation 3, the absolute value of the value obtained by subtracting the product theory thickness t calculated from the thickness value A detected by the # 4-1 thickness meter 302 and the # 4-2 thickness meter 303 If the difference between the absolute value of the value obtained by subtracting the product theory thickness t from the detected thickness value B is greater than 0, it can be determined that a detection error of the # 4-1 thickness meter 302 has occurred ( 509).

│A-t│- │B-t│ 0

Next, in the third step (510-513) to determine the measurement mode by setting the thickness meter, which is the detection value error identified in the second step as a slave, and another error-free thickness meter as the master, it will be described in detail Is as follows.

It is determined whether the # 4-1 thickness meter 302 is a master thickness meter which is used for thickness control or a slave thickness meter which is a detection thickness meter added for thickness verification (510). ).

That is, if # 4-1 thickness meter 302 is set as the master thickness meter, PLC recognizes the wrong thickness detection value that caused the detection error as the correct product thickness value and enters the wrong thickness control. Due to the continuous thickness defects in the PLC, the mode of the thickness gauge is automatically changed from On-Line to # 4-1 Thickness gauge 302 to Slave thickness gauge and # 4-2 Thickness gauge. 303 is converted into a master thickness meter (511).

Conversely, the product theory thickness t from the absolute value of the product value calculated by the thickness value A detected by the # 4-1 thickness meter 302 minus the thickness value B detected by the # 4-2 thickness meter 303. If the difference between the absolute values of the subtracted values is less than 0, the # 4-2 thickness meter 303 may determine that the thickness error has occurred (509), and the # 4-1 thickness meter 302 is set as the master thickness meter (512). ), The thickness meter mode is automatically changed to # 4-1 thickness meter 302 as the master thickness meter and # 4-2 thickness meter 303 as the slave thickness meter so that the thickness meter where the detection error occurs is controlled by the product thickness. (513).

Finally, in the fourth step 514-522, the main motor 308 of the final stand 301 is detected so that the thickness corresponding to the measurement mode determined in the third step is detected and the ordered thickness is equal to the detected thickness. To control the speed of feedback

In the above process, when the mode of the thickness meter is automatically changed or when the detection error does not occur in the master thickness meter in use and the automatic mode change of the thickness meter is not necessary, the detection error occurrence check of the thickness meter is checked. When the # 4-2 thickness meter 303 is the master thickness meter, the demand is subtracted from the order thickness to reduce the product thickness value detected by the # 4-2 thickness meter 303 to increase the degree of thickness control. If not less than zero (514) or not equal (= large) (515), the actual product thickness is thinner than the order thickness.

Therefore, if the PI generated by Mass Flow AGC causes the control signal to slow down by rotating the current value of main motor 308 in stand 301, the gear box is slowed down. The rotational force is transmitted to the roll through the spindle and spindle, and the rotation speed of the roll is reduced (516), and the length of the plate exiting to the roll exit per unit time is reduced. Will increase.

If the order thickness and the product thickness are not the same at this time, the main motor of the # 4 stand continues to decelerate until the two thicknesses are the same (517).

If the order thickness is smaller than the # 4-2 thickness detection value, since the actual thickness is thicker than the order thickness, the number of revolutions of the main motor 308 of the # 4 stand 301 and the main motor 308 is determined by the mass flow age. It increases until the thickness is the same (518) and becomes the same (519) to perform normal product production (504).

As mentioned above, even when the # 4-2 thickness meter 302 is set as the master thickness meter by the on-line mode conversion of the thickness meter, when the detection error is generated by Equation 3 above, Mr. Chun changes the thickness meter online mode to reset the # 4-1 thickness meter to the master and the error-produced # 4-2 thickness meter to the slave (513). In this way, if the order thickness is smaller than the detected value of the # 4-1 thickness meter 302 after the thickness meter mode is reset (520), the number 4 stands 301 for the thinner product thickness of the main motor 308 By increasing the current value of (521) and accelerating until the actual thickness is equal to the order thickness (522), the product is produced (504).

If the order thickness is equal to the detected value of the # 4-1 thickness meter 302 (523), the product is produced. If the thickness is large, the actual thickness is thinner than the order thickness. The current value of 308 is decreased to decelerate until the actual thickness is equal to the order thickness (524), and then to become the same (525) to produce the product (504).

As described above, the present invention additionally installs a thickness meter for detection and control at the back of stand No. 4 (301) to fundamentally solve the occurrence of thickness defects. It automatically divides even what is measured correctly and automatically connects the target thickness to the automatic thickness control system. This prevents thickness defects caused by abnormal thickness gauge detection.

The following shows an application example of the present disease.

First, the application example 1 is for the case where the ultra-low carbon steel cold rolling operation is performed with an order thickness of 0.513 mm and a master thickness gauge # 4-1.

In the conventional case, the thickness control system detects that 0.54mm is the actual thickness because the # 4 thickness meter detects with a detection value of 0.514 and misunderstands 0.516mm due to the disturbance. Control is made to make the plate thickness thinner. In this way, the actual plate thickness is thinner, but the thickness meter continuously detects the product thickness as 0.516mm and transmits it to the control system because of the error that occurs, and eventually the plate thickness becomes thinner, causing thickness defects. It is triggered.

However, in the case of the present invention, the # 4-1 thickness meter detection value 0.514mm, the # 4-2 thickness meter detection value 0.512mm, the # 3 thickness meter detection value 0.521mm, the # 3 tachometer detection value 349mpm, the # 4 tachometer If an error occurs when the # 4-1 thickness meter incorrectly recognizes the product thickness as 0.516 mm and detects it due to distortion, it detects "[│ (0.516-0.512) │ / 0.513] x 100 = 0.8> 0.4% "This is more than 0.4%, which is the maximum measurement error of the two thickness meters, so we can confirm the occurrence of errors in the thickness meter.

The product theoretical thickness is calculated by the law of volume invariance, "0.521 x 349 = product theory thickness (t) x 355, ∴ t = 0.512 mm", and to check the error-producing thickness meter "│0.516-0.512│- | 0.512-0.512 | = 0.004 mm> 0 ".

Therefore, the # 4-1 thickness meter set as the master thickness meter is confirmed as the thickness meter that has a detection error, and the thickness mode is automatically changed during on-line, but the # 4-2 thickness meter is reset to the master thickness meter to resume normal production. The # 4-1 thickness meter is reset to the slave thickness meter after zeroing, and then reinserted to perform detection.

Next, Application Example 2 is for the case of performing a semi-low-cold cold rolling operation with a thickness of 0.703mm order, the thickness of the master thickness gauge # 4-2.

In the conventional case, when the # 4-2 thickness meter detects with a detection value of 0.704 mm and an error that is incorrectly recognized as 0.701 mm is caused by the disturbance, the thickness control system recognizes that 0.701 mm is the actual thickness. The thickness control is made to make the plate thickness thicker. In this way, the actual plate thickness is increased, but the thickness meter continuously detects the product thickness as 0.701mm and transmits it to the control system due to the error that occurs, and eventually the plate thickness becomes thicker, causing thickness defects. It will cause breakage.

However, in the present invention, # 4-1 thickness gauge detection value 0.704mm, # 4-2 thickness gauge detection value 0.705mm, # 3 thickness gauge detection value 0.717mm, # 3 tachometer detection value 873mpm, # 4 tachometer When detecting with the detection value of 890mpm and an error that # 4-2 thickness meter misidentifies the product thickness as 0.701mm and detects it due to distortion, "[│ (0.704-0.701) │ / 0.703] x 100 = 0.43> 0.4% "This is more than 0.4%, which is the maximum measurement error of the two thickness meters, so we can confirm the occurrence of errors in the thickness meter. In other words, when calculating the theoretical thickness of the product, it is "0.717 x 873 = product theory thickness (t) x 890 ∴ t = 0.703 mm" by the law of volume invariance, and it is "0.704-0.703│- | 0.701-0.703 | =-0.001 mm <0 ".

Therefore, the # 4-2 thickness meter set as the master thickness meter is confirmed as the thickness meter in which a detection error has occurred, and the thickness mode is automatically changed during on-line, but the # 4-1 thickness meter is reset to the master thickness meter to resume normal production. The # 4-2 thickness meter is reset to the slave thickness meter after zeroing, and then reinserted to perform detection.

According to the present invention as described above, in the case of continuous cold rolling operation, the effect that can automatically prevent the occurrence of a large amount of thickness defects generated in the absence of recognition by the rolling operator and the product inspector due to the detection error of the final product thickness gauge There is.

The above description is only a description of one embodiment of the present invention, the present invention is capable of various changes and modifications within the scope of the configuration.

1 is a configuration diagram of a conventional continuous cold rolling line facility.

2 is a block diagram of a thickness detection and control device of a conventional continuous cold rolling mill.

3 is a flow chart of the production of a conventional continuous cold rolling mill.

Figure 4 is a flow chart of the thickness bad product generation of the conventional thickness system.

5 is a configuration diagram of a thickness precision control device of a continuous cold rolling mill for carrying out the present invention.

6 is a flowchart showing a method for precisely controlling the thickness of a continuous cold rolling mill according to the present invention.

Explanation of symbols on main parts of drawing

101: hot rolled coil 102: Pay Off Reel

103: welder 104,107: looper

105: hydrochloric acid tank 106: side trimmer

108: Tandem Cold Mill 109: Tension Reel

110: continuous cold rolling line 301: stand No. 4

302: # 4-1 thickness meter (# 4-1 x-ray) 303: # 4-2 thickness meter (# 4-2 x-ray)

304: Thickness No. 3 (# 3 Gamma Ray) 305: No. 3 Stand

306: No.3 (# 3) Speedometer 307: No.4 (# 4) Speedometer

308: 4 main motor main stand 309: Sensor unit

310: Processor part (PLC part) 311: Actuator part

Claims (3)

In the precision control method of the thickness of the continuous cold rolling mill, A first step of determining whether there is an error in the detected value of the thickness meter by determining whether a difference between the plate thickness detection values A and B of the two thickness meters 302 and 303 provided in the final stand 301 is smaller than the set value; In the case where there is an error in the detected value in the first step, the theoretical thickness t of the product is calculated by using the plate speed and the plate thickness of the front end stand of the final stand and the plate speed of the final stand. A second step of determining which of the two thickness meters (302, 303) is a thickness meter which is a detected value error by using? A third step of determining a measurement mode by setting a thickness meter which is the detected value error identified in the second step as a slave and another error-free thickness meter as a master; A fourth step of detecting a thickness corresponding to the measurement mode determined in the third step, and feedback-controlling the speed of the main motor 308 of the final stand 301 so that the predetermined order thickness and the detected thickness are the same. Precision control method of the thickness of the continuous cold rolling mill characterized in that. The method of claim 1, wherein in the first step Using the plate thickness detection values A and B of the two thickness meters 302 and 303 of the final stand 301, it is determined whether the value obtained by dividing the difference by the order thickness falls within the maximum detection error of the two thickness meters. Thickness precision control method of continuous cold rolling mill characterized by the above-mentioned. The method of claim 1, wherein in the second step The theoretical thickness t of the product is "t = (axc) / b" (a: plate speed value detected by the # 3 tachometer 306, b: plate speed value detected by the # 4 tachometer 307 , c: plate thickness value detected by the # 3 gamma ray thickness meter 304, Then, the determination is the absolute value (| At |) of the value obtained by subtracting the product theory thickness (t) calculated from the thickness value (A) detected by the # 4-1 thickness meter 302 and the # 4-2 thickness meter (303). ) Is compared to the difference (| At |-| Bt |) of the absolute value (| Bt |) of the value obtained by subtracting the product theory thickness (t) from the detected thickness value (B) of the continuous cold rolling mill. Thickness precision control method.