KR100780420B1 - Determination method for reduction rate pattern to improve the strip crown - Google Patents

Abstract

The present invention predicts the final stand plate profile by the initial rolling reduction ratio, and compares the calculated plate crown amount obtained by the result with the target plate crown amount, and the rolling load distribution ratio for each stand until the calculated crown amount converges within the target crown amount. By repeating the above process by adjustment, the present invention relates to a reduction rate pattern determination method for determining a reduction rate pattern.

According to the present invention, a first step of predicting the plate profile value at the final stand exit; A second step of calculating a plate crown amount using the predicted plate profile value; If the difference between the calculated crown amount and the target crown amount is smaller than the reference value, the current reduction ratio pattern is regarded as a completed reduction ratio pattern, and a third rolling state amount (rolling speed, rolling load, roll gap, etc.) is calculated. step; If the difference between the calculated crown amount and the target crown amount is not smaller than the reference value, the rolling load distribution ratio for each stand is changed to a new state amount, the exit thickness for each stand is recalculated, and the new rolling reduction rate is calculated again. Provided is a method for determining a reduction ratio pattern, wherein the stand exit plate profile is predicted again.

Rolling, stand, rolling load, rolling reduction, crown

Description

Determination method for reduction rate pattern to improve the strip crown             

1 is a flow chart showing the process of this conventional stand thickness determination method,

2 is a flowchart illustrating a process of a method for determining a reduction ratio pattern for obtaining a good plate crown according to an embodiment of the present invention.

3 is a flowchart illustrating a process of performing a plate profile prediction calculation illustrated in FIG. 2;

4 is a flowchart illustrating a process of calculating an initial rolling state amount such as a rolling speed, a rolling load, and a roll gap based on the finally obtained rolling reduction rate.

The present invention relates to a method for determining a reduction ratio pattern capable of obtaining a good plate crown, and more particularly, to predict the final stand plate profile at an initial reduction ratio, and to calculate a target plate crown amount obtained by the target plate. It relates to a reduction ratio pattern determination method for determining the reduction ratio pattern by repeating the above process by adjusting the rolling load distribution ratio for each stand until the calculated crown amount converges within the target crown amount as compared to the crown amount.

In order to roll to match the target thickness for the entry material during continuous cold rolling and hot rolling, the rolling rate, tension and rolling speed of each stand of the next rolled material are calculated in advance while the current rolled material is being rolled. Just before the material enters the rolling mill, it is changed from the current setting amount to the setting amount for the next material rolling.

At this time, the rolling reduction pattern for each stand is the most important factor for determining the shape (crown) of the plate at the final stand exit side. Therefore, known techniques proposed to obtain a good plate shape include the following methods.

First, predictive rolling in order to maintain the rolling load of the final stand, which is a basic condition for obtaining a good shape of the rolled plate, and a method of setting rolling conditions for providing uniform roughness and good plate shape of the steel sheet in the final stand. There is a method of determining the final stand side plate thickness so that the load coincides with the target rolling load and determining the thickness (rolling reduction rate) of each stand based on this (Japanese Patent Application Laid-open No .: 60-54215).

However, these methods have a limitation in obtaining a good plate shape only by the concept that the shape of the plate is made good by maintaining the rolling load conditions of the final stand constant because the stand controlling the plate shape is the final stand. Therefore, the plate profile at the final stand according to the reduction ratio pattern is confirmed by direct prediction (simulation), and is constant when the target plate crown (thickness at the center portion and 25 mm from the edge portion) is not obtained. By changing the rolling reduction pattern by the rule, it is repeated until the target plate crown is obtained to determine the final rolling reduction pattern. Thus, there is a need for a new reduction ratio setting method capable of obtaining a better plate shape.

An object of the present invention for solving the problems of the prior art as described above is to predict the final stand plate profile at the initial reduction ratio, and the calculated plate crown amount obtained by the result compared with the target plate crown amount to calculate the target crown amount By repeating the above process by adjusting the rolling load distribution ratio for each stand until it converges within the crown amount, it is to provide a method for determining the reduction ratio pattern.

In order to achieve the above object, according to the present invention, in the method of determining the reduction ratio pattern for improving the crown of the plate in the continuous cold rolling and hot rolling process, the reduction ratio for each stand obtained in the initial rolling set amount calculation is calculated A first step of predicting a plate profile value at the final stand exit; A second step of determining whether a difference between the calculated crown amount and the target crown amount is smaller than a reference value by calculating the plate crown amount using the predicted plate profile value; If the difference between the calculated crown amount and the target crown amount is smaller than the reference value, the current reduction ratio pattern is regarded as a completed reduction ratio pattern, and a third rolling state amount (rolling speed, rolling load, roll gap, etc.) is calculated. step; If the difference between the calculated crown amount and the target crown amount is not smaller than the reference value, the rolling load distribution ratio for each stand is changed to a new state amount, the exit thickness for each stand is recalculated, and the new rolling reduction rate is calculated again. A fourth step of proceeding to the second step after predicting the stand exit plate profile again; It provides a reduction rate pattern determination method comprising a.

Hereinafter, a method of determining a reduction ratio pattern for improving a crown of a plate according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

In general, the shape of the hot rolled sheet is a major factor in determining the shape of the cold rolled sheet, and is a major factor in determining the cold rolling workability, and the shape of the cold rolled sheet is a major management index directly related to the quality required by the consumer.

During the rolling of the current coil, the host computer receives the information of the coil to be rolled next, and the various rolling state quantities required for the next coil rolling, that is, rolling reduction, tension, rolling speed, rolling load, motor power and roll gap. Calculate and calculate the required rolling speed and roll gap using the programmable logic controller (PLC) before the coil enters the mill stand.                     

In the process of calculating the initial rolling set amount, in the present site, the part about the shape of the plate is not particularly considered except that the rolling load acting on the final stand is set smaller than the shear stand. In addition, in the known technique (Japanese Patent Application Laid-Open No. 60-54215), in order to keep the rolling load of the final stand which is the basic condition for obtaining a good plate shape in the process of calculating the initial rolling state amount, The method of determining the thickness (rolling reduction rate) of each stand so as to match the target rolling load is used.

Figure 1 is a flow chart showing the process of this conventional stand thickness determination method.

보다 작은지 여부를 판단하여, 작으면, 스텝 S105에서, 최종 설정량을 계산한 후, 종료한다. 이때, 최종 설정량 계산을 후술하는 도 4에 도시된 계산 플로우(Flow)를 이용하게 된다.First, in step S101, a reduction ratio is calculated. At this time, the normal reduction ratio is read from a previously stored setting table. Next, after calculating a rolling load in step S102, the final stand rolling load is compared in step S103. In step S104, the difference between the calculated (predicted) rolling load and the target rolling load is a reference value.

It is judged whether or not it is smaller, and if it is small, in step S105, the final set amount is calculated and then ends. In this case, a calculation flow shown in FIG. 4, which will describe the final set amount calculation, will be used.

On the other hand, if it is not small as a result of the determination in step S104, after returning to each stand reduction rate in step S106, the process returns to step S102.

However, the conventional stand thickness determination method described above is a concept that the shape of the plate can be made good by keeping the rolling load conditions of the final stand constant since the stand controlling the plate shape is the final stand. Since the profile (plate width direction thickness distribution) according to the reduction ratio pattern for each stand is accumulated, and the final plate profile is determined at the exit of the final stand, it is difficult to obtain a good plate shape only by considering a constant rolling load at the final stand.

Therefore, when the method proposed in the present invention to solve the above problems, it is as follows.

2 is a flowchart illustrating a process of a method of determining a reduction ratio pattern for obtaining a good plate crown according to an embodiment of the present invention.

First, in step S201, the rolling reduction pattern for each stand obtained in the initial rolling set amount calculation (generally, most of them are read from a setting table) is calculated, and then in step S202, the plate profile at the final stand exit side is calculated. Forecast by the program. At this time, the plate profile calculation follows the method shown in FIG.

보다 작은지 여부를 판단한다.Subsequently, in step S203, the plate crown amount (center thickness-25 mm point thickness from the plate end) is calculated using the obtained plate profile, and in step S204, the difference between the calculated crown amount and the target crown amount is a reference value.

Determine if smaller than

If the determination result in step S204 is small, that is, the calculated plate crown amount is smaller than the target plate crown amount, in step S205, the rolling reduction pattern at this time is regarded as a completed rolling reduction pattern, and the final rolling state amount (rolling Speed, rolling load, roll gap, etc.) are calculated, and the initial rolling setting state quantity calculation is completed. At this time, the final rolling state amount calculation follows the method shown in FIG.                     

On the other hand, if it is not small as a result of the determination in step S204, in step S206 to step S208, the rolling load distribution ratio for each stand is changed to calculate a new state quantity, that is, each stand exit thickness and speed. Use this to recalculate the new rolling rate and use it to re-predict the final stand exit plate profile. Then, the plate crown amount is calculated using the obtained plate profile and compared with the target crown amount.

On the other hand, when the calculation crown is larger than the target crown, the process is repeated until it is within the target crown.

 Next, a detailed method for each step used in the present invention will be described. FIG. 3 is a flowchart illustrating a process of performing the plate profile prediction calculation shown in FIG. 2.

First, in step S301, the contact pressure distribution between each roll is calculated, where each roll means a work roll, an intermediate roll, an intermediate roll, and a reinforcement roll. Subsequently, in step S302 and step S303, the deflection amount of each roll is calculated using the contact pressure distribution between the rolls, and the elastic deformation amount (flat deformation amount) generated on the surface of the work roll by the force the work roll receives from the strip when rolling is calculated. do. Then, in step S304, the sum of the calculated deflection amount of the work roll and the flat deformation amount is obtained, and in steps S305 and S306, when the sum is twice, the width direction roll gap in consideration of the deformation amount of the roll when rolling The distribution is obtained, and this roll gap distribution eventually becomes the profile (width thickness distribution) of the plate.

On the other hand, the formula used in the above process is a well-known formula through the literature so it will be omitted here (see 壓延 and 壓延).

The method for deriving a new reduction ratio pattern by adjusting the rolling load distribution ratio for each stand is as follows. The rule to be satisfied in adjusting the rolling load ratio to derive a new state quantity is basically satisfying the rolling load distribution ratio, and the mass flow of the rolled material for each stand must be the same, and at the same time, considering the elastic deformation of the rolling mill, The thickness calculation formula must be satisfied. This part is explained by the formula.

는 동력 배분율이고,

는 전 압연 하중이며, i는 스탠드를 나타낸다.here,

Is the power distribution ratio,

Is the total rolling load, and i represents the stand.

는 모터 드루핑(Drooping)이며, G는 모터 토크이고, V는 스트립 속도이며, h는 스트립 두께이고, U는 스트립을 통과한 매스의 양을 나타낸다. Where f is the advance rate,

Is motor drooping, G is motor torque, V is strip speed, h is strip thickness, and U is the amount of mass that has passed through the strip.

는 롤 갭이고, P는 압연 하중이며, K는 압연기 강성이고,

는 초기 롤 갭 보정치를 의미한다.here,

Is roll gap, P is rolling load, K is rolling mill stiffness,

Denotes an initial roll gap correction value.

Equation 1 is a formula for obtaining a rolling load distribution ratio, Equation 2 is a mass flow formula, and Equation 3 is a gauge-meter formula.

Each rolling amount (rolling load (P), advance rate (f), etc.) constituting the above [Equation 1] to [Equation 3] is composed of a complex formula again, these formulas (1) ~ (3 Substituting and substituting in) yields a complex nonlinear polynomial equation. Therefore, Newton's iterative method, which is a numerical method, is frequently used to solve the nonlinear polynomial equations. In order to use this, each equation is changed to Newton's differential equation form as follows. At this time, Equation 4 corresponds to Equation 1, and Equation 5 corresponds to Equation 2.

는 열연판 소재 두께가 압연 하중 변화에 미치는 영향 계수이 고,

는 각 스탠드 입측 두께가 압연 하중 변화에 미치는 영향 계수이며, '프라임(')'이 붙은 상태량은 새로 도출되는 상태량을 의미한다.here,

Is the coefficient of influence of the thickness of the hot rolled sheet on the rolling load change,

Is the coefficient of influence of each stand side thickness on the rolling load change, and the state amount with 'prime' means a newly derived state amount.

는 열연판 소재 두께가 선진율에 미치는 영향 계수이고,

는 열연판 소재 두께가 모터 토크에 미치는 영향 계수이며,

는 각 스탠드 입측 두께가 선진율에 미치는 영향 계수를 나타낸다.here

Is the coefficient of influence of the thickness of the hot rolled sheet material on the advancement rate,

Is the coefficient of influence of the thickness of the hot rolled sheet material on the motor torque,

Represents the coefficient of influence of each stand side thickness on the advance rate.

When the above-described equations (3) to (5) are changed and solved, new state quantities (each stand exit thickness and rolling speed) can be obtained.

4 is a flowchart illustrating a process of calculating an initial rolling state amount such as a rolling speed, a rolling load, and a roll gap based on the finally obtained rolling reduction rate.

First, in step S401 to step S405, the reduction ratio, tension, sheet speed, advance rate and roll speed are calculated, and in step S406, the speed is checked.                     

As a result of the determination in step S406, if the speed does not exceed the reference value, the deformation resistance, the rolling load, the motor torque, and the motor power are calculated in steps S407 to S410. On the other hand, if the speed exceeds the reference value as a result of the determination in step S406, the flow returns to step S403.

Next, in step S411, if power is checked and power does not exceed a reference value, in step S413, a roll gap is calculated and it completes. On the other hand, if the power exceeds the reference value, the speed is changed in step S412, and then the flow returns to the step S403.

While the invention has been described above based on the preferred embodiments thereof, these embodiments are intended to illustrate rather than limit the invention. It will be apparent to those skilled in the art that various changes, modifications, or adjustments to the above embodiments can be made without departing from the spirit of the invention. Therefore, the protection scope of the present invention will be limited by the appended claims, and should be construed as including all such changes, modifications or adjustments.

According to the present invention as described above, the final stand plate profile is predicted at the initial reduction ratio, and the calculated plate crown amount obtained by the result is compared with the target plate crown amount until the calculated crown amount converges within the target crown amount. By repeating the above process by adjusting the rolling load distribution ratio for each stand, if the reduction ratio pattern is determined, there is an effect that a fairly good plate crown can be obtained as compared with the method of maintaining the existing final stand rolling load constant.

Claims (3)

In the method of determining the rolling reduction pattern for improving the crown of the plate in the continuous cold rolling and hot rolling process, A first step of calculating a rolling reduction pattern for each stand obtained in the initial rolling set amount calculation, and then predicting a plate profile value at the final stand exiting side; A second step of determining whether a difference between the calculated crown amount and the target crown amount is smaller than a reference value by calculating the plate crown amount using the predicted plate profile value; If the difference between the calculated crown amount and the target crown amount is smaller than the reference value, the current reduction ratio pattern is regarded as a completed reduction ratio pattern, and a third rolling state amount (rolling speed, rolling load, roll gap, etc.) is calculated. step; If the difference between the calculated crown amount and the target crown amount is not smaller than the reference value, the rolling load distribution ratio for each stand is changed to a new state amount, the exit thickness for each stand is recalculated, and the new rolling reduction rate is calculated again. A fourth step of proceeding to the second step after predicting the stand exit plate profile again; Reduction rate pattern determination method comprising a. The method of claim 1, The plate profile prediction method, Calculating a contact roll distribution between each roll; Calculating a deflection amount of each roll by using the contact pressure distribution between the rolls, and calculating an elastic deformation amount (flat deformation amount) generated on the surface of the work roll by a force received by the work roll from the strip when rolling; A sub-step of obtaining the widthwise roll gap distribution in consideration of the deformation amount of the roll during rolling by calculating the sum of the calculated deflection amount and the flat deformation amount of the work roll, and taking the double of the sum; Reduction rate pattern determination method comprising a. The method according to claim 1 or 2, The method of changing the rolling load distribution ratio is to satisfy the rolling load distribution ratio, while equalizing the inflow / outflow amount of the rolled material for each stand, and considering the elastic deformation of the rolling mill.

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