KR20040019732A - Method for setting up the rolling load to acquire the constant elongation percentage in the skin pass mill, apparatus thereof - Google Patents

Abstract

PURPOSE: A method and a system for setting roll force for securing certain elongation from skin pass mill are provided to differently set elongation for respective conditions by correcting a difference part between actually measure elongation values and a predicted elongation value. CONSTITUTION: The system for setting roll force for securing certain elongation from skin pass mill(1) comprises a PLG (pulse logic generator)(7) for calculating an elongation value by measuring the number of revolutions of skin pass rolling rolls and measuring actual production speed of strip and a strip speed difference between the front and rear of skin pass mill; a controlling computer(6) for calculating a set load value of the skin pass rolling rolls by receiving the measured elongation values and operation conditions from the PLG; and push-up cylinders(4a,4b) and position sensors(5a,5b) installed on a lower surface of back up roll of skin pass mill to change load of the skin pass rolling rolls according to the set load value calculated in the controlling computer, wherein the controlling computer is connected to the position sensors through signal lines(8).

Description

TECHNICAL FOR SETTING UP THE ROLLING LOAD TO ACQUIRE THE CONSTANT ELONGATION PERCENTAGE IN THE SKIN PASS MILL, APPARATUS THEREOF}

The present invention relates to a rolling load setting method and a device for securing a constant elongation in a rough rolling mill, and more particularly, according to the physical properties of the material and the load and production speed of the rolling roll in a skin pass mill. The present invention relates to a rolling load setting method and apparatus for securing a constant elongation in a rough rolling mill for securing a constant elongation by setting elongation varying according to the rolling position of a rolling coil differently for each condition.

In general, the production method used in skin pass rolling includes a roll force mode control method and an elongation percentage mode control method according to a process variable control object.

The roll force mode control method is a method of operating with constant tension and roll load according to the initial set value. The elongation of the produced product is severely changed. If the welding point or coil split is necessary, the operation speed should be changed from high speed to low speed. At this time, the yield point of the material changes according to the speed change.

However, since the roll load is kept constant, more stretching occurs when the low speed operating condition is the high speed operating condition.

In the case of the elongation control method, in order to keep the tension constant and maintain a constant elongation, the roll gap is adjusted by changing the roll gap.

In other words, the control is performed as a method of compensating for the error by comparing the set value of the elongation with the measured value.

However, in the normal speed section, it is easy to control, but if there is a large speed change in a short time, the controller cannot follow, and excessive roll gap change leaves a roll mark on the plate surface.

In addition, in the temper mill, the shape must be corrected in addition to securing the elongation, but when the roll load is excessively changed, the shape control may not work properly.

In order to solve the above problems, the present invention is distributed differently according to the material properties of the material and the load and the production speed of the rolling roll, and corrected the difference between the measured elongation and the estimated elongation of the elongation which varies depending on the rolling position of the rolling coil. The purpose of the present invention is to provide a method of securing a constant elongation rate in a rough rolling mill set differently for each condition.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a conceptual diagram showing a schematic configuration of a temper rolling facility and a location of installing a PLG constituting the present invention;

Figure 2 is a conceptual diagram showing the distribution of the region of the rolling roll and the strip to be rolled in temper rolling;

3 is a conceptual diagram showing the parameter definition for each region of the rolling roll and the strip to be rolled in temper rolling;

Figure 4 is a block diagram showing a rolling load setting device for securing a constant elongation in the temper rolling mill according to the present invention;

5 is an elongation distribution and rolling load distribution according to speed for a product produced in roll force mode;

6 is a yield stress distribution diagram of the rolled material according to the tensile speed;

7 is a flowchart illustrating a rolling load setting method for securing a constant elongation in a temper rolling mill according to the present invention.

♣ Explanation of symbols for main part of drawing ♣

7: PLG 1: Temper rolling mill 4A, 4B: Push-up cylinder 5A, 5B: Position sensor

6: computer for control 8: signal line

In order to achieve the above object, the present invention includes a PLG for measuring the number of revolutions of the tempered rolling rolls, and calculating the elongation value by measuring the actual production speed of the strip and the speed difference of the strip at the front and rear ends of the temper rolling mill; A control computer for receiving an elongation value and operating conditions measured from the PLG to calculate a load set value of the temper roll; In order to change the load of the temper rolling roll according to the load setting value calculated from the control computer, a constant elongation is secured in the temper mill comprising a push-up cylinder and a piston sensor installed on the lower surface of the backing roll of the temper rolling mill. It provides a rolling load setting device for.

In addition, the present invention comprises the steps of being instructed by the host computer, the steel grade, sheet thickness, sheet width, target elongation and operating speed which is the operating conditions determined according to the production coil; Determining a roll force setting value as a load prediction model according to the indicated operating conditions, the operating speed, and the yield strength of the material; Transferring a roll force value set by the load prediction model to a push-up cylinder of a temper mill and applying it to a rolling roll; PLG measures and calculates a change in elongation according to a roll force value applied to the temper roll; If the calculated elongation value and the set elongation value is within the tolerance, the rolling load for securing a constant elongation in the temper mill, characterized in that it is configured to keep the same roll force until the operation speed is changed. It provides a setting method.

Hereinafter, the theoretical background of the roll force mode to which the present invention is applied will be described by deriving a formula.

The present invention accommodates the advantages of the conventional roll force mode control method and the elongation control method, it is possible to produce a plate with a constant elongation by automatically setting the precise prediction of the roll load and the operating conditions setting method.

FIG. 2 is a conceptual diagram illustrating a distribution of regions of a rolling roll and a strip to be rolled in temper rolling, and FIG. 3 is a conceptual diagram illustrating parameter definition of regions of a rolling roll and a strip to be rolled in temper rolling.

First, for a roll force prediction model used in temper rolling (hereinafter, referred to as 'SPM'), the roll gap region is divided into seven different regions as shown in FIG. 2.

It goes through the elastic and plastic zones while passing through the roll gap, and is divided into the case where slip is present between the roll and the strip and the case where it is not. In each zone, different boundary conditions and equations are set according to the set assumptions. This is true.

The governing equations for the strip can be expressed as follows when neglecting the force balance and the strip width change.

------------------------------------------------(One )

In addition, in the case of low stretching such as SPM, the contact between strip and roll can be assumed as Hertzian Contact. In this case, the following relationship is established between roll pressure and roll deformation.

------------------------------------------(2)

Where 2Δb is the strip thickness reduction and P ₀ is the maximum Hertzian pressure value.

In addition, P ₀ can be expressed as P0 = E ^* a ₀ / 2R, and can be expressed as follows without dimensioning.

-------------------------------------------------- ------ (3)

Wherein a ^{U = μ · E * · r} / Y s.

As shown in FIG. 3, the exit contact length, a _2, is closely related to the entrance contact length a ₀ , where x = a ₂ at p = 0, Δb = Δb ₂ = rb ₀ Therefore, the following equation holds.

------------------------------------------(4)

Where r is the total rolling reduction of the strip, where r = (b ₀ -b ₂ ) / b ₀ = Δb ₂ / b ₀ .

Next, the equations for each region assumed in the roll gap will be described.

1) Area A

The region A is a section in which elastic deformation occurs, and it is assumed that there is little change in thickness. Since Δb ≒ 0 in Equation (2), the following equation holds.

---------------------------------------------- (5)

In addition, since the shear stress (q) = q, the following equation is established.

----------------------------------------------- (6)

Since db / dx = 0 in this region, the longitudinal stress, sigma _x is obtained by integrating Equation (1) as follows.

------------------------------- (7)

2) area B

Region B is a section in which plastic deformation occurs. When a force exceeding the yield stress of the material is applied in the area A, it is changed to the area B. The yield and slip conditions are as follows.

-------------------------------------------------- ----(8)

-------------------------------------------------- --- (9)

According to Equations (2), (8), (9) and Equation (1) which is an equilibrium equation, the pressure gradient, -dσ _x / dx, is expressed as follows.

-------------------------------------------------- ----------------- (10)

At this time, the pressure distribution, -σ _x can be obtained by integrating Equation (10). The integral performs numerical integration by Runge-Kutta method, and when σ _x is obtained, equations (8) and (9) are obtained. By substituting, σ _x and q can be obtained.

The strip thickness distribution is derived as follows from the obtained −σ _x and Equation (2).

---------------------------- (11)

3) zone C

In this region, it is assumed that there is no slip between the strip and the strip as the plastic deformation region. That is, the following equation can be derived from Δb = Δb1 and equation (2).

----------------------------- (12)

The longitudinal stress, sigma _x can be obtained using the above equation (12) and the yield condition equation.

-------------------------------------------------- ---- (13)

Shear stress, q can be derived as follows using the equations (1), (12), (13) and assuming db / dx = 0.

---------------------------------------- (14)

4) Zone D

In this area, there is no slip between the strip and the roll and it is assumed that it is an elastic deformation area. The detailed derivation process for this region is omitted and the resulting equation for stress distribution is described as follows.

-------------------------------------------------- ----------------- (15)

Where L ₄ and L ₅ are unknown and the remaining variables are

-------------------------- (16)

Shear stress, q is derived from Equations (15) and (1) as follows.

------------------------- (17)

5) Zone E

The strip behavior in the region E occurs in elastic deformation and moves faster than the work roll.

The vertical pressure on the strip, -σ _x and the shear stress, q, have the following relationship:

-------------------------------------------------- -(18)

Using equation (18) to determine the longitudinal stress, σ _x , assuming db / dx = 0, and integrating equation (1), the following results can be obtained.

------------------------------- (19)

6) Zone F

In this region, the strip undergoes plastic deformation and moves faster than the work roll speed. After a rather complicated process, we can derive the differential equation as follows: -σ _x can be determined by numerical integration.

-------------------------------------------------- ----------------- (20)

7) Zone G

In this area, the strip is elastic unloading and moves faster than the work roll. The following equations can be obtained from equation (2) and Δb = rb ₀ .

------------------------------------- (A29)

σx can be obtained by integrating Equation (1) with the condition that b = b ₂ = (1-r) b ₀ .

-------------------------------------------------- ---------------- (A30)

Where L ₇ is any integral constant.

In each of the above areas, the roll force prediction model used in the rough rolling (SPM) was derived according to the set assumptions, and the present invention can be variously applied according to the roll force prediction model.

1 is a conceptual diagram showing the schematic configuration of the temper rolling equipment and the installation location of the PLG constituting the present invention, Figure 4 is a configuration diagram showing a rolling load setting device for securing a constant elongation in the temper rolling mill according to the present invention to be.

In order to apply the above-described roll force prediction model, as shown in FIG. 1, a PLG (Pulse Logic Generator) 7 for measuring elongation before and after temper rolling, and a temper mill 1 as shown in FIG. 4. Receives a set value of push-up cylinders (4a, 4b) and position sensors (5a, 5b) and measured elongation values and operating conditions for changing the roll load of It is composed of a control computer (6) for calculating a, and is connected to the position sensors (5A, 5B) and the signal line (8).

Here, PLG (7) is a device for measuring the actual rotational speed of the plate by measuring the number of roll revolutions, is installed in the front and rear ends of the SPM (1) is a device for measuring the strip plate speed difference and calculates the elongation value from it.

5 is an elongation distribution and a rolling load distribution according to the speed for the product produced in the roll force mode, Figure 6 is a yield stress distribution of the rolled material according to the tensile speed, Figure 7 according to the present invention A flowchart of a rolling load setting method for securing a constant elongation in a rough rolling mill.

Operation and method of operation of the present invention is shown in the flow chart shown in FIG.

First, the steel grade, sheet thickness, sheet width, and target elongation, etc., determined by the production coil are instructed by the host computer.The previous coil and the boundary part have a welding point, so operate at a low speed when passing through this part. After this, high speed operation is performed.

In other words, the operation speed can be divided into a low speed section, a speed transition section from a low speed to a high speed section, and a high speed section. The value of the physical properties of the material used for the load prediction is a function of the operating speed, so the yield point for each speed should be obtained through the tensile test.

6 shows an example of the material property value test result according to the speed as an example of the material property value. Once the velocity is determined, the roll force setup value is determined by estimating the yield strength of the material from the corresponding steel grade and material property equation.

The setting method currently used is not the setting method based on the dynamic calculation but adopts the table method based on the performance of the operation, and the setting value also uses only one initial value regardless of the speed.

Therefore, it is not possible to reflect the change of material properties according to the change of operation speed or the manufacturing position of the coil.

As an example, FIG. 5 shows an elongation distribution of a product produced by a roll force mode, and it can be seen that elongation is greatly changed according to an operation speed and a coil position.

The roll force value set by the above-described load prediction model is transmitted to the push-up cylinders 4a and 4b of the SPM 1 and realized through the roll position movement.

That is, the elongation is changed according to the roll force changed as described above, and this value can be confirmed by the elongation value calculated from the PLG 7 again.

At this time, if the set value and measured value of elongation are within tolerance, it keeps the same roll force until the operation speed is changed.

If the tolerance is exceeded, the deformation resistance formula of the material is re-calibrated by reflecting the difference in elongation in the material property value, and the roll force value is reset, and the speed corresponds to the final speed in the speed transition section where the speed changes rapidly. The roll force value is calculated based on the property value.

In the case of the conventional elongation control method, the elongation change according to the speed change is controlled by the fine adjustment of the roll force, so it takes a long time and the control performance drops a lot, and the roll mark due to the excessive roll force change There was a problem that (Roll / Mark) occurs.

In this method, the predictive control is possible, and the method of correcting the difference between the measured elongation and the predicted elongation can solve all the problems caused by the speed change or the material property by the coil position.

As described above, according to the present invention, it is possible to easily cope with such a change in the operation speed during the tempered rolling operation, and to control the constant elongation through the whole rolling area of the coil, because the control system of the present invention can prevent the disturbance. At the same time, there is no sudden roll force change, and there is an advantage that it can be controlled without affecting the shape control performance even when controlling the vendor for shape correction.

Claims (3)

PLG for measuring the rotational speed of the tempered rolling rolls and calculating the elongation value by measuring the actual production speed of the strip and the speed difference of the strips at the front and rear ends of the temper rolling mill; A control computer for receiving an elongation value and operating conditions measured from the PLG to calculate a load set value of the temper roll; In order to change the load of the temper rolling roll according to the load setting value calculated from the control computer, a constant elongation is secured in the temper mill comprising a push-up cylinder and a piston sensor installed on the lower surface of the backing roll of the temper rolling mill. Rolling load setting device. Receiving instructions from the host computer for steel grade, sheet thickness, sheet width, target elongation and operating speed, which are operating conditions determined according to the production coil; Determining a roll force setting value as a load prediction model according to the indicated operating conditions, the operating speed, and the yield strength of the material; Transferring a roll force value set by the load prediction model to a push-up cylinder of a temper mill and applying it to a rolling roll; PLG measures and calculates a change in elongation according to a roll force value applied to the temper roll; If the calculated elongation value and the set elongation value is within the tolerance, the rolling load for securing a constant elongation in the temper mill, characterized in that it is configured to keep the same roll force until the operation speed is changed. How to set up. The method of claim 2, When the measured elongation value and the set elongation value exceeds the tolerance, the deformation resistance formula of the material is recalibrated by reflecting the difference in elongation to the material property value, and then the roll force value is reset. Rolling load setting method for securing a constant elongation in the temper mill.