KR20100037380A - Apparatus and method for controlling pinch roll - Google Patents

Abstract

PURPOSE: A pinch roll control device and a control method thereof are provided to prevent operation from being stopped or production throughput from being lowered by minimizing strip thickness change due to a pinch roll mark. CONSTITUTION: A pinch roll control device comprises a strip skew detector, a pinch roll load standard value output unit, a pinch roll stress controller, and a pinch roll gap controller. The strip skew detector detects the skew measurement value of the strip(S30). The pinch roll load standard value output unit outputs pinch roll standards load as a final standard load within a standards load maximum/minimum range(S51). According to the final standard load, the pinch roll stress controller calculates the pinch roll gap standard value(S52). According to the pinch roll gap standard value, the pinch roll gap controller controls the pinch roll gap.

Description

Pinch roll control device and control method {APPARATUS AND METHOD FOR CONTROLLING PINCH ROLL}

The present invention relates to a pinch roll control device, and more particularly, to pinch roll gap is automatically controlled to an appropriate level according to the amount of meandering of the strip to prevent strip meandering and to prevent pinch roll marks from occurring on the strip. It relates to a pinch roll control device and a control method.

In general, a twin roll type sheet casting process supplies molten steel to a space formed by a pair of casting rolls being cooled and a pair of edge dams in contact with the casting roll side to rotate the casting rolls in a direction facing the casting rolls. The solidification shell (Shell) formed by rapid solidification at the surface of the casting roll by the heat outflow into the roll is coalesced at the proximal point between the casting rolls to form a cast steel to produce a hot rolled steel sheet of 2 ~ 6mm thickness directly from molten steel, It is a new steel processing process that has been in the spotlight in many respects, such as reducing facility investment costs and energy consumption, thereby lowering manufacturing costs and reducing pollution gas emissions.

In the steel sheet manufacturing process including the twin-roll thin sheet casting process, the cast slab formed through the casting machine in order to improve the surface quality of the steel sheet, to refine the structure and to ensure the dimensional quality at a rolling rate of 30% or more in the rolling mill installed on the back of the casting machine The rolling is started, and the process is performed so that the thickness of the strip may approach the target thickness by gradually reducing the roll gap of the rolling mill after rolling is started and the cast steel passes through the rolling mill. A pinch roll is provided at the inlet side of the rolling mill for the purpose of stably carrying out such a rolling process. The pinch roll maintains a constant tension of the strip and performs tension and meander control to prevent the meandering of the strip. have.

On the other hand, in recent years, as the demand for high quality steel sheet surface increases, controlling the roll gap of the rolling mill as well as the pinch roll gap that affects the surface quality of the strip so that the tension and meander control of the strip is achieved at an appropriate level. It is required.

Conventionally, the pinch roll load is calculated in operation in consideration of the tension of the strip, the pinch roll and the friction coefficient between the strips, and the like to prevent slippage between the strip and the pinch roll. However, when the operation is carried out by maintaining the pinch roll load initially set as described above, as shown in Figure 1, the pinch roll mark (PR Mark) is generated in the steel sheet and the thickness of the steel sheet by the generated pinch roll mark The problem of fluctuation occurs. Such pinch roll marks are easily generated even at low pinch roll loads due to the high temperature of the cast steel at 1200 ° C or higher, and the variation in the thickness of the steel plate caused by the pinch roll marks may cause meandering during cold rolling. In addition, as shown in FIG. 2, when winding up, a specific part of the coil is generated to generate a build up, which causes a problem of deteriorating productivity due to a decrease in work speed.

If the pinch roll load is less than the proper level, pinch rolls or rolling mills may cause slippage between the strips and the rolls, causing meandering problems, and vibration and scratches, resulting in lower work efficiency and product quality. Adversely affects. In addition, since the pinch roll gap must be largely adjusted for meandering control, a problem of lowering responsiveness and reducing workability occurs. On the contrary, when the pinch roll load is increased to prevent the occurrence of strip meandering, the frequency of pinch roll marks is increased to cause problems such as the buildup phenomenon as described above.

Therefore, in order to prevent the pinch roll mark generation of the strip, it is required to minimize the load of the pinch roll within the limit as long as the problem of meandering of the strip does not occur, but the conventional pinch roll control method is insufficient in preparation for this. .

The present invention was created in order to solve the problems of the prior art as described above, by automatically setting the minimum pinch roll load within the limit of the slip between the strip and the pinch roll and the meander control state during operation An object of the present invention is to provide a pinch roll control device and a control method for minimizing variation in strip thickness due to a roll mark.

The pinch roll control apparatus of the present invention for solving the above problems is provided with a strip meander detector which is provided adjacent to the pinch roll to detect the meandering measurement amount of the strip; The pinch roll reference load is calculated from the strip meander measurement information transmitted from the strip meander detector, and the pinch roll reference load is compared with the set threshold range, and the pinch roll reference load is within the limits of the maximum and minimum limits. A pinch roll load reference value calculation unit for calculating a final reference load as a reference value; A pinch roll load controller that calculates a pinch roll gap reference value according to a final set reference load calculated by the pinch roll load reference value calculation unit; And a pinch roll gap controller that controls the pinch roll gap to be adjusted according to the pinch roll gap reference value calculated by the pinch roll load controller.

At this time, the pinch roll control device further comprises a strip thickness detector which is provided on the exit side of the rolling mill for detecting the thickness of the strip, the pinch roll load reference value calculation unit is the threshold of the thickness of the strip transmitted from the strip thickness detector When it is determined that the value is reached, the strip meander detector is characterized by controlling to detect the strip meander measurement.

The pinch roll control device may further include a servo valve and a roll gap adjusting cylinder for adjusting the gap of the pinch roll, and the pinch roll gap controller controls the pinch roll gap by controlling the servo valve and the roll gap adjusting cylinder. It features.

According to another aspect for solving the above problems, the pinch roll control method of the present invention includes a meander detection step of detecting the meandering measurement amount of the strip adjacent to the pinch roll; A reference load comparison step of determining whether to fall within a critical range by calculating a pinch roll reference load according to the strip meander measurement amount detected in the meander detection step; A pinch roll gap reference value calculating step of calculating a pinch roll gap reference value by calculating the pinch roll reference load as a final setting reference load when it is determined that the pinch roll reference load calculated in the reference load comparison step falls within a critical range; And a pinch roll gap control step of controlling the pinch roll gap according to the pinch roll gap reference value calculated in the pinch roll gap reference value calculation step.

At this time, the pinch roll control method further comprises a strip thickness comparison step of detecting the strip thickness of the rolling mill exit side and compare with the threshold value, and the strip thickness detected in the strip thickness comparison step has reached the threshold value If it is determined that the meander detection step is performed, and if it is determined that the strip thickness detected in the strip thickness comparison step does not reach a threshold value, the pinch roll gap is controlled by maintaining the set pinch roll reference load. do.

In addition, when it is determined that the pinch roll reference load is greater than the upper limit threshold in the reference load comparison step, the pinch roll gap is controlled by calculating the maximum limit of the reference load as the final reference reference load, and the pinch roll reference load in the reference load comparison step. When it is determined that the value is smaller than the lower limit threshold, the pinch roll gap is controlled by calculating the minimum limit value of the reference load as the final reference reference load.

At this time, in the reference load comparison step, the pinch roll reference load is calculated according to the strip meander measurement amount, when the strip meander measurement amount is smaller than the set reference meander amount, an amount proportional to the difference between the strip meander measurement amount and the reference meander amount. The pinch roll reference load is calculated so that the pinch roll reference load is reduced, and when the strip meander measurement amount is larger than the set reference meander amount, the pinch roll reference load is calculated so as to increase by an amount proportional to the difference between the strip meander measurement amount and the reference meander amount. ,

Preferably, in the reference load comparison step, the pinch roll reference load may be calculated according to the strip meander measurement amount according to the following formula.

[Equation]

Str_m = | Str_a | -A

F_cal = F_set + Ki * ∫Str_m dt

Here, | Str_a | is an absolute meandering measurand of the strip, A is a reference meandering amount, Str_m is a strip meandering amount, F_set is an initially set pinch roll reference load, Ki is an integral gain, and F_cal is a pinch roll reference load.

According to the pinch roll control device and control method of the present invention, it is possible to prevent the pinch roll mark from being generated on the strip by setting the minimum pinch roll load that does not cause slippage and meander control between strip and pinch roll during operation. Of course, by minimizing the variation in strip thickness due to the pinch roll mark, it is possible to prevent an operation interruption and a decrease in production speed due to trouble during cold rolling, which is a post-process. In addition, by controlling the gap of the pinch roll to an appropriate level, it is possible to prevent defects such as vibration and scratches from occurring, thereby improving the quality of the steel sheet produced.

Hereinafter, with reference to the accompanying drawings will be described in detail the pinch roll control device and control method of the present invention.

1 is a block diagram of a pinch roll control apparatus according to an embodiment of the present invention.

Referring to Figure 1, the pinch roll control device of the present invention is a strip thickness detector (8), strip meander detector (5), pinch roll load reference value calculation unit 9, pinch roll load controller 10 and And a pinch roll gap controller 11.

Both side ends of the pinch rolls 4a and 4b are provided with servo valves 3a and 3b and roll gap adjusting cylinders 2a and 2b for adjusting the pinch roll gap, and the strip thickness detector 8 has a backup roll 6a. And 6b) and on the exit side of the rolling mill composed of work rolls 7a and 7b.

The strip thickness detector 8 detects the thickness of the strip 1 rolled by a rolling mill and transmits the detected strip thickness information to the pinch roll load reference value calculation unit.

The strip meander detector 5 is provided at the exit side of the pinch rolls 4a and 4b and detects the meandering measurand of the strip, and then transmits the strip meander measurement information to the pinch roll load reference value calculating section 9. Play a role.

The pinch roll load reference value calculation unit 9 determines whether the thickness of the strip has reached a set threshold value from the strip thickness information transmitted from the strip thickness detector 8, and the thickness of the strip 1 is from the target thickness. When it is determined that the error reaches within the error range (for example, 50㎛) serves to calculate the pinch roll reference load from the strip meander measurement information transmitted from the strip meander detector (5). In this case, the meandering measurement amount of the meandering strip is measured by the meandering strip detector 5 so that the meandering measurement amount is transmitted according to the control command signal of the pinch roll load reference value calculating section 9.

At this time, the pinch roll load reference value calculation unit 9 calculates the pinch roll reference load so that when the strip meander measurement amount is smaller than the set reference meander amount, the pinch roll load reference amount is reduced by an amount proportional to the difference between the strip meander measurement amount and the reference meander amount. If the strip meander measurement amount is larger than the set reference meander amount, the pinch roll reference load is calculated to increase by an amount proportional to the difference between the strip meander measurement amount and the reference meander amount.

In other words, when the strip meander measurement amount is smaller than the reference meander amount, the strip meander is being controlled to an appropriate level, which means that the pinch roll reference load is excessively set, and thus the pinch roll mark is likely to occur on the strip. Therefore, in this case, in order to minimize the pinch roll reference load within the limit to prevent strip meandering, the pinch roll reference load is reduced to be smaller than the initially set pinch roll reference load by an amount proportional to the difference between the strip measurand and the reference meander amount. By calculating, pinch roll marks can be prevented from occurring on the strip.

On the contrary, when the strip meander measurement amount is larger than the reference meandering amount, the pinch roll reference load is set less so that the pinch roll mark is less likely to occur on the strip, but it means that strip meandering occurs. Strip meandering can be stopped by calculating the pinch roll reference load so that the pinch roll reference load is increased by an amount proportional to the difference value.

The pinch roll load reference value calculator 9 calculates the pinch roll reference load and then compares the calculated pinch roll reference load with a set threshold range. At this time, if it is determined that the pinch roll reference load falls within the set threshold range, the pinch roll reference load is calculated as the final set reference load. If it is determined that the pinch roll reference load is greater than the upper limit threshold, the maximum limit value of the set reference load is calculated as the final setting reference load, and if it is determined that the pinch roll reference load is smaller than the lower limit threshold value, the set reference load minimum limit value is calculated. Calculate the final reference load.

The pinch roll load controller 10 calculates a pinch roll gap reference value for maintaining the final set reference load transmitted from the pinch roll load reference value calculation unit 9, and transmits the pinch roll gap reference value to the pinch roll gap controller 11. Perform.

The pinch roll gap controller 11 controls the servo valves 3a and 3b and the roll gap adjusting cylinders 2a and 2b to follow the pinch roll gap reference value transmitted from the pinch roll load controller 10 to control the pinch roll gap. It plays a role of controlling.

5 is a flowchart illustrating a pinch roll control method according to an embodiment of the present invention.

Hereinafter, the pinch roll control method of the present invention will be described in detail with reference to FIG. 5.

In the pinch roll control method of the present invention, as shown in Figure 5, strip thickness comparison step (S10), meander detection step (S30), reference load comparison step (S40), pinch roll gap reference value calculation step (S50), And a pinch roll gap control step (S60).

First, when rolling is started, the strip thickness detector 8 provided at the exit side of the rolling mill detects the thickness of the strip (S11), and transmits the detected strip thickness information to the pinch roll load reference value calculation unit 9. do.

The pinch roll load reference value calculating unit 9 performs a step of determining whether the thickness of the strip reaches a predetermined threshold value from the transmitted strip thickness information (S12). At this time, if it is determined that the thickness of the strip does not reach the threshold value, after performing the step of controlling the pinch roll gap to maintain the initially set pinch roll reference load (S20), the strip thickness again reaches the threshold value It is determined whether or not to perform (S10).

If it is determined in the strip thickness comparison step S10 that the thickness of the strip reaches a threshold value, the meander measurement of the strip 1 is performed in the strip meander detector 5 provided at the exit side of the pinch rolls 4a and 4b. Detecting the amount, and transmitting the detected meander measurement information to the pinch roll load reference value calculation unit 9 (S30).

The pinch roll load reference value calculating unit 9 calculates the pinch roll reference load according to the strip meander measurement information detected and transmitted by the strip meander detector 5 (S41). More specifically, first, the meandering amount Str_a of the strip detected by the strip meandering detector 5 deviates from the reference meandering amount A according to Equation 1 below. Calculate

[Equation 1]

Str_m = | Str_a | -A (| Str_a | is the absolute value of strip meander)

Here, the reference meandering amount (A) is preferably set to an appropriate level required according to the working environment, such as the width, thickness, working speed of the strip.

Thereafter, in the pinch roll load reference value calculation unit 9, the pinch roll reference load F_cal is calculated using the calculated strip meandering amount Str_m according to Equation 2 below.

[Equation 2]

F_cal = F_set + Ki * ∫Str_m dt

Here, F_set is an initial pinch roll reference load and Ki is an integral gain.

When the pinch roll reference load is calculated as described above, a step of determining whether the calculated pinch roll reference load falls within a critical range is performed (S42).

At this time, when it is determined that the calculated pinch roll reference load falls within the critical range, the pinch roll load reference value calculation unit 9 applies the calculated pinch roll reference load as the final setting reference load (S51).

If it is determined that the pinch roll reference load calculated in the reference load comparison step (S40) is out of the upper limit threshold range, the pinch roll load reference value calculation unit 9 applies the maximum limit of the reference load as the final setting reference load, and calculates When it is determined that the pinch roll reference load is out of the lower limit threshold range, the minimum limit value of the reference load is applied as the final reference reference load (S70).

That is, the pinch roll load reference value calculation unit 9 applies the pinch roll reference load as the final setting reference load within the minimum and maximum limit values of the reference load by the following equation (3).

[Equation 3]

If F_cal> F_max, then F_lst = F_max

If F_cal <F_min, then F_lst = F_min

If F_min ≤ F_cal ≤ F_max, then F_lst = F_cal

Here, F_max is the maximum limit of the reference load, F_min is the minimum limit of the reference load, F_lst means the final reference reference load.

In this way, the final setting reference load is set within the minimum and maximum limits to prevent the pinch roll gap from being drastically adjusted.

The pinch roll load controller 10 calculates the pinch roll gap reference value according to the final set reference load calculated by the pinch roll load reference value calculation unit 9 (S52).

Thereafter, the pinch roll gap controller 11 adjusts the servo valves 3a and 3b and the roll gap adjustment cylinders 2a and 2b according to the pinch roll gap reference values calculated by the pinch roll load controller 10 to adjust the pinch roll gap. A control step is performed (S60).

By repeating the steps (S30 ~ S70), the pinch roll reference load is minimized within the limit that strip meandering does not occur according to the meander measurement amount of the strip in real time, thereby preventing the pinch roll mark from occurring on the strip. It becomes possible.

EXAMPLE

A 2.8 mm thick rolled material was rolled at a rolling speed of 60 mpm to obtain a strip having a thickness of 2.0 mm and a width of 1300 mm, and the thickness deviation of the strip was measured. In the exemplary embodiment, after the rolling starts and the thickness of the strip starts to decrease, the strip measurand is detected from the time when the thickness of the strip starts to reach the target thickness (2.0 mm) and within 50 µm, that is, 2.05 (mm). The pinch roll reference load was calculated and the reference meandering capacity (A) was set to 5 mm. The reference load maximum limit value (F_max) was set to the initial reference reference load, and the reference load minimum limit value (F_min) was 1.6 tons.

As a comparative example, the same material was rolled under the same conditions, but the pinch roll control method of the present invention was not performed. The result of measuring the strip thickness deviation at this time is shown in FIG. 3.

When the pinch roll gap is controlled to an appropriate level by the pinch roll control method of the present invention, as shown in the graph of FIG. 6, the strip thickness deviation is within about 20 to 30 μm over the width direction, whereas in the comparative example, As shown in the graph of FIG. 3, the strip thickness deviation is formed in a large width of about 40 to 60 μm, and shows a large thickness variation of about 15 μm locally, whereby the pinch roll control method of the present invention is used. It can be seen that there is an excellent effect in minimizing the thickness variation caused by the pinch roll mark.

1 is a view showing that a pinch roll mark is generated in a conventional steel sheet coil.

2 is a view showing that the build-up occurs in the conventional steel sheet coil.

Figure 3 is a graph showing that thickness variation occurs in the strip by a conventional pinch roll control method.

Figure 4 is a block diagram of a pinch roll control apparatus according to an embodiment of the present invention.

5 is a flowchart for explaining a pinch roll control method according to an embodiment of the present invention.

Figure 6 is a graph showing that the strip thickness deviation is reduced by the pinch roll control method of the present invention.

♧ description of symbols for the main parts of the drawing

1: strip 2a, 2b: roll gap adjustment cylinder

3a, 3b: Servo valve 4a, 4b: Pinch roll

5: strip meander detector 6a, 6b: backup roll

7a, 7b: work roll 8: strip thickness detector

9: pinch roll load reference value calculation unit 10: pinch roll load controller

11: pinch roll gap controller

Claims (8)

A strip meander detector provided adjacent to the pinch roll to detect a meander measurement of the strip; The pinch roll reference load is calculated from the strip meander measurement information transmitted from the strip meander detector, and the pinch roll reference load is compared with the set threshold range, and the pinch roll reference load is within the limits of the maximum and minimum limits. A pinch roll load reference value calculation unit for calculating a final reference load as a reference value; A pinch roll load controller that calculates a pinch roll gap reference value according to a final set reference load calculated by the pinch roll load reference value calculation unit; And A pinch roll gap controller configured to control the pinch roll gap to be adjusted according to the pinch roll gap reference value calculated by the pinch roll load controller. The method according to claim 1, The pinch roll control device further comprises a strip thickness detector provided on the exit side of the rolling mill to detect the thickness of the strip, The pinch roll control reference value calculating unit may control the pinch roll control unit to detect a strip meander measurement amount when the strip meander detector determines that the thickness of the strip transmitted from the strip thickness detector reaches a predetermined threshold value. Chi. The method according to claim 1 or 2, The pinch roll control device further comprises a servo valve and a roll gap adjusting cylinder for adjusting the gap of the pinch roll, The pinch roll gap controller controls the pinch roll gap by controlling the servo valve and the roll gap adjusting cylinder. A meandering detecting step of detecting a meandering measurement amount of the strip adjacent to the pinch roll; A reference load comparison step of determining whether to fall within a critical range by calculating a pinch roll reference load according to the strip meander measurement amount detected in the meander detection step; A pinch roll gap reference value calculating step of calculating a pinch roll gap reference value by calculating the pinch roll reference load as a final setting reference load when it is determined that the pinch roll reference load calculated in the reference load comparison step falls within a critical range; And And a pinch roll gap control step of controlling the pinch roll gap according to the pinch roll gap reference value calculated in the pinch roll gap reference value calculation step. The method according to claim 4, The pinch roll control method further comprises a strip thickness comparison step of detecting the strip thickness of the rolling mill exit side and compare with the threshold value, If it is determined that the strip thickness detected in the strip thickness comparison step reaches a threshold value, the meander detection step is performed; And if it is determined that the strip thickness detected in the strip thickness comparison step does not reach a threshold value, the pinch roll gap is controlled by maintaining the initially set pinch roll reference load. The method according to claim 4, If it is determined that the pinch roll reference load is greater than the upper limit threshold in the reference load comparison step, the pinch roll gap is controlled by calculating the maximum limit of the reference load as the final reference reference load. In the reference load comparison step, if the pinch roll reference load is determined to be smaller than the lower limit threshold, the pinch roll control method characterized in that to control the pinch roll gap by calculating the minimum reference load minimum limit value as the final set reference load. The method according to any one of claims 4 to 6, wherein the pinch roll reference load is calculated according to the strip meander measurement in the reference load comparison step. If the strip meandering amount is smaller than the set reference meandering amount, the pinch roll reference load is calculated to decrease by an amount proportional to the difference between the strip meandering measurand and the reference meandering amount, A pinch roll control method for calculating a pinch roll reference load so that when the strip meander measurement amount is larger than the set reference meander amount, the pinch roll reference load is calculated to increase by an amount proportional to the difference between the strip meander measurement amount and the reference meander amount. The method according to any one of claims 4 to 6, The pinch roll control method for calculating the pinch roll reference load according to the strip meander measurement in the reference load comparison step is performed according to the following formula. [Equation] Str_m = | Str_a | -A F_cal = F_set + Ki * ∫Str_m dt Here, | Str_a | is an absolute meandering measurand of the strip, A is a reference meandering amount, Str_m is a strip meandering amount, F_set is an initially set pinch roll reference load, Ki is an integral gain, and F_cal is a pinch roll reference load.

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