KR100711407B1 - Method for adjusting the roll gap of single stand reversing mill - Google Patents

Abstract

An object of the present invention is to provide a method for precisely and automatically setting the roll gap in consideration of the deformation of the parts generated during the thick plate rolling process using a one-stand reversible rolling mill, the wear of the roll and the thermal crown.

The roll gap setting method of the one-stand reversible rolling mill according to the present invention for this purpose, the mill housing calculated by using the current roll gap (RG), the rolling load, the width of the strip and the thickness of the entry and exit side, the process conditions such as the bender force Apply the deformation amount (δ _h ) and roll deformation amount (δ _RD ) to the equation below to calculate the strip exit thickness estimate (h), compare this estimate with the actual measured strip exit thickness, and compare the constant α from the difference between the predicted and measured values: The value is determined, but each time the strip passes through the rolling roll, a new difference between the predicted value and the measured value is calculated, and the difference is compensated for by the constant α, and the roll gap is reset based on the calculated value.

Roll, mill, roll gap, load, crown, wear, deformation

Description

1 Method for adjusting the roll gap of single stand reversing mill}

1 is a schematic view showing a conventional one-stand reversible rolling mill,

Figure 2 is a diagram showing the change in the roll gap by the force applied to the roll in the relationship with the strip during the rolling process,

FIG. 3 is a diagram showing a result of conducting a kissing test for deriving a housing constant.

4 is a view showing the deformation analysis results of the work roll according to the change in the bender force;

5 is a view showing the deformation analysis results of the backup roll according to the change in the bender force;

6 is a view showing a result of calculating the load distribution between the work roll and the backup roll according to the change in the bender force;

7 is a view showing the calculation result of the flat deformation of the work roll according to the change in the bender force;

8 is a view comparing the error value of the estimated thickness of the strip exit according to the conventional roll gap setting method and the roll gap setting method according to the present invention.

<Description of the symbols for the main parts of the drawings>

1: strip 10: working roll

20: backup roll

The present invention relates to a roll gap setting method of a rolling mill, and in particular, in order to accurately set the roll gap in consideration of the effects of deformation, roll wear, and thermal crown, etc., generated during the rolling of a heavy plate using a one-stand reversible rolling mill. It is about how to.

In general, during the rolling process, the roll is not a rigid body but acts as an elastic body that deforms under force, and the gap between the rolls changes with time due to wear and heat deformation.

That is, as can be seen in Figures 1 and 2, in the case of rolling the strip 1 using a rolling mill provided with two work rolls 10 and two backup rolls 20, in particular, the work roll 10 Is subjected to a force F acting in a direction perpendicular to the direction in which the strip 1 travels, resulting in deformation and change in roll gap. S ₀ in FIG. 2 is the initial roll gap (ie zero), H is the initial thickness of the strip, h is the thickness after strip rolling.

 Therefore, in order to obtain a desired plate thickness in rolling, in particular in the rolling of a thick plate, it is necessary to precisely set the roll gap in consideration of the degree of deformation experienced by each part during the rolling process.

In the related art, an equation such as Equation 1 below was used to set a roll gap.

h: exit thickness of the strip

M: Mill modulus according to plate width and load

RF: Rolling force

S ₀ : Zero

S: Pressed position

O _f : Manual adjustment

However, as described above, the roll gap determination using the above formula is not a method configured in consideration of the deformation degree of each part during the rolling process and the effect of the deformation degree on the roll gap, but using a single slope (1 / M) Corresponds to how to determine. In fact, the roll gap is set by inputting the value of 1 / M and each process value obtained from the graph shown in FIG. 3 into [Equation 1] to estimate the exit thickness of the strip. Manually adjust the error by substituting the manual adjustment value accordingly. In this case, the manual adjustment value is a value that uses the result data of a similar operation previously or the driver corrects the difference between the expected value and the actual value whenever an error occurs.

Therefore, in the case of the conventional roll gap setting method, the accuracy is lowered and the manual intervention of the driver is frequently required, resulting in a low automation rate.

The present invention has been proposed to solve this problem to provide a roll gap setting method for precisely setting the roll gap in consideration of the effects of deformation, roll wear and thermal crown generated during the rolling process. .

With reference to the accompanying drawings, a roll gap setting method of a one-stand reversible rolling mill according to the present invention for achieving the above object will be described.

In the roll gap setting method according to the present invention, a prediction model as shown in Equation 2 is basically used.

RG: roll gap

δ _h : Mill housing deformation (may include deformation of screws, nuts, bearings, and other areas subject to force)

δ _RD : Roll deformation amount. here,

δ _RD = δ _WP : + δ _WB : + δ _BR = f (load, strip width, input / output side thickness, bender force)

δ _WP : Flat deformation (or local deformation) between work roll and strip

δ _WB : Flat deformation (or local deformation) between work roll and backup roll

δ _BR : bending deformation of the backup roll

That is, the exit thickness prediction of the strip according to the present invention mainly inputs process conditions such as rolling load, strip width and input / output side thickness, and bender force (the sensor will need to be installed to measure these values, of course). It is divided into a part (δ _RD ) for calculating the roll deformation and a part (δ _wear -δ _thermal ) for calculating and reflecting the wear and heat crown values of the roll. At this time, the part that calculates the roll deformation can be calculated regardless of the temporal situation through the dynamic calculation using the rolling load value as the input value, but the part determined by the heat crown and wear should be calculated strictly using the mathematical model. Such a predictive model is subject to error. (However, if the prediction model for the part determined by the heat crown and wear is accurate, the strip exit thickness prediction and the roll gap resetting may be performed according to [Equation 1].)

Therefore, in the present invention, after processing the portion (δ _wear -δ _thermal ) determined by the heat crown and wear in Equation 2 as a constant α, the strip exit thickness estimated and calculated from the equation and the actual value The measured strip exit thickness is compared to determine a constant value from the difference between the predicted value and the measured value, and each time the strip passes through the rolling roll, the difference between the predicted value and the measured value is calculated and the difference compensated for the constant α as the thickness correction value. Method can be used. In this case, the compensation for the constant α value is most simply to compensate for the difference between the measured thickness value and the predicted value of the strip as α, and moreover, by giving weight to the values used during the passage of all strips and all strips. You can decide. This can prevent the possibility of error due to abnormal measured values.

The constant treatment of (δ _wear -δ _thermal ) as above is based on the fact that the deformation values due to heat crown and wear do not change significantly with each strip pass. same.

On the other hand, RG refers to the current roll gap setting state, so it is not a problem since the roll gap is a measurable value at any time, and the mill housing deformation amount (δh) is after kissing the upper and lower work rolls 10, ie, contacting them. The total deformation amount can be calculated from the force applied at this time and the position change of the rolling mill hydraulic cylinder, and then calculated by subtracting the bending and local flat deformation amount of the roll as the housing deformation amount.

The roll gap is set in such a manner that when the measured thickness value with respect to the expected thickness of the exit thickness of the strip is changed using the above model, the change value is compensated for the constant α and a new roll gap is set.

4 to 7 are diagrams showing the results of the roll deformation and load calculation required for the use of the above equation, Figures 4 and 5 are the results of the calculation of the deformation amount of the work roll and the backup roll by the external force, respectively, Figure 6 is a strip It is a result of calculating the load value distributed between the work roll and the backup roll by the force transmitted from the work roll to the work roll, and FIG. 7 shows the work roll flat deformation amount by the force transmitted from the strip to the work roll. In the drawings, WR denotes a work roll and BUR denotes a backup roll. Since calculation of such a numerical value uses a conventional well-known technique, it is not demonstrated in detail here.

8 is a result data comparing the strip exit thickness error in the case of using the manual roll gap setting method by the conventional driver and the strip exit thickness error in the case of using [Equation 3]. The average error absolute value is 0.077 mm in the conventional case and is similar to each other as 0.07 according to the present invention, and the standard deviation is 0.079 mm in the conventional case and is similar to each other as 0.080 mm according to the present invention. Considering that the conventional method requires the driver to directly intervene, the accuracy of the exit thickness estimate of the strip must be high. According to the present invention, it is possible to set a roll gap with a similar or higher accuracy than the conventional method without frequent driver intervention. Can be.

As can be seen, the conventional method measures the mill constant M value by roll kissing and reflects it in the model, but the manual intervention of the driver is not possible because it cannot actively cope with the roll deformation that depends on the thickness, width and steel type of the actual strip. Although it is frequently and inconsistent, the present invention uses the method of calculating the roll bending and the flat strain by the mechanical model and correcting it using some difference value (predicted value-actual value), so that the automation is possible and the accuracy is very high. Is effective.

Claims (2)

The mill housing deformation amount (δ _h ) and the roll deformation amount (δ _RD ) calculated using the current roll gap (RG), the rolling load, the width and the thickness of the strip and the side thickness of the strip, the bender force, and the like are calculated by the following equation. To calculate the strip exit thickness estimate (h), Comparing this estimated value with the actual measured strip exit thickness, a constant α value is determined from the difference between the predicted value and the measured value, and each time the strip passes through the rolling roll, a new difference between the predicted value and the measured value is calculated to compensate for the constant α. And resetting the roll gap on the basis of the roll gap setting method.

RG: roll gap; δ _h : mill housing deformation; δ _RD : roll deformation, where δ _RD = δ _WP : + δ _WB : + δ _BR , δ _WP : flat deformation between work roll and strip, δ _WB : flat deformation between work roll and backup roll, δ _BR : Bending deformation amount of the backup roll. Mill housing deformation amount (δ _h ) and roll deformation amount (δ _RD ) calculated using current roll gap RG, rolling load, strip width and exit side thickness, bender force, etc., and normal prediction It is characterized by calculating the strip exit thickness estimate (h) by applying the deformation of the roll (δ _wear -δ _thermal ) of the roll calculated using the model to the following equation, and resetting the roll gap based on this: Roll gap setting method of 1 stand reversible rolling mill.

RG: roll gap; δ _h : mill housing deformation; δ _RD : roll deformation, where δ _RD = δ _WP : + δ _WB : + δ _BR , δ _WP : flat deformation between work roll and strip, δ _WB : flat deformation between work roll and backup roll, δ _BR : bending deformation amount of the backup roll; δ _wear : roll deformation due to wear, δ _thermalr : Roll deformation by heat.

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