JPH1110213A - Method for preventing overload in driving system for rolling mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for realizing the prevention of an overload in the driving system for a rolling mill by a simple method in the calculation for setting each pass of a rolling schedule, which is technique applied to the rolling mill in which the upper and lower rolls of the rolling mill are rotated at different speeds and related to a method for preventing an overload in the driving system such as a spindle of the rolling mill. SOLUTION: The estimating calculation of TAF which is the ratio of a max. torque at the time of biting in rolling which acts on the driving system of the rolling mill to a stational torque at the time of rolling is executed from the set value of a roll different speed are which is the ratio of the number of revolution of an upper roll to the number of revolution of a lower roll. The estimated value of the max. torque at the time of biting in rolling which is calculated based on this estimating-calculated TAF is compared with the value of the allowable torque of the rolling mill driving system and the rolling is executed by adjusting the set value of the roll different speed rate so that the estimated value of the max. torque at the time of biting in rolling is not higher than the value of the allowable torque.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique applied to a rolling mill in which upper and lower rolls of a rolling mill rotate at different speeds, and relates to a rolling method for preventing a drive system such as a rolling mill spindle from being overloaded.

[0002]

2. Description of the Related Art In recent years, in the rolling of a thick plate or the like, the upper and lower rolls of a rolling mill are used in each rolling pass in order to prevent the leading end of a rolled material from sticking to a rolling mill or a table roll due to a warpage or a downward warpage. The warpage is corrected by rolling at a different speed. However, the implementation of the different speed rotation causes imbalance in the spindle peak torque conventionally applied uniformly to the upper and lower spindles. The rotation speed of the upper roll and the lower roll, that is, the ratio of the rotation speeds of the upper spindle and the lower spindle, is referred to as a different speed ratio. FIGS. 3A and 3B schematically show how the peak torque is generated when the different speed ratio between the upper spindle and the lower spindle is zero (that is, the same speed).

FIG. 3A shows an upper spindle, and FIG. 3B shows a lower spindle. The horizontal axis in the figure is a time axis, which indicates the time immediately before the rolled material comes off, with the timing of biting the rolled material being zero. The vertical axis indicates the torque. As shown in the figure, when the different speed ratio is zero, the upper and lower spindles show the same behavior, and the peak torque immediately
Tmax appears and thereafter converges to the steady torque Ts. On the other hand, FIGS. 3C and 3D show cases where the speed of the upper spindle is higher than that of the case of the different speed rolling. In this case, as shown, the peak torque Tmax at the upper spindle (c) is much larger than the peak torque Tmax at the lower spindle (d). Conversely, when the speed of the lower spindle is high, it is clear that the peak torque Tmax of the lower spindle becomes larger, and the illustration is omitted here.

That is, in the case of variable speed rolling, an excessive peak torque is generated by a roll having a higher roll speed. This makes the estimation of the peak torque more difficult, and makes it more difficult to prevent the rolling mill from overloading. The ratio between the larger peak torque Tmax and the steady torque Ts is called TAF. Here, for convenience of the following description, this TAF is defined in advance as TAF = Tmax / Ts (1).

[0005] Conventionally, in rolling a thick plate or the like, a pass schedule is calculated before rolling, and a spindle peak torque of a rolling mill is predicted therein. This is because if the spindle peak torque is too large, the drive system such as the spindle and the spindle coupling will be damaged and a large secondary disaster will occur. Therefore, it is attempted to prevent the damage accident by predicting the spindle peak torque. Things.

[0006] Generally, the prediction of the spindle peak torque of a rolling mill is performed as follows: Tg = f (T, Δt, R, W, N, kf,... Etc.) (2) This is performed based on a given prediction formula. here,
T is the temperature of the rolled material, Δt is the rolling reduction, R is the radius of the work roll, W is the width of the rolled material, N is the number of rotations of the work roll, and kf is the deformation resistance.

However, since it is difficult to accurately give each parameter of the equation (2) such as the temperature T of the rolled material, the error of the spindle peak torque value predicted by the peak torque prediction equation (2) is determined. Is generally large. Therefore, in consideration of safety, the allowable value of the predicted torque was set to a low value, and the failure of the drive system equipment due to the generation of excessive torque was prevented.

For the purpose of improving the accuracy of predicting the spindle peak torque, Japanese Patent Application Laid-Open No. 62-3815 discloses
It is proposed to measure the actual spindle torque value in each rolling pass, calculate the deviation between the measurement result and the predicted value based on equation (2), and correct the torque predicted value in the next pass based on the deviation. ing.

[0009]

However, in this method, since an actual measured value of the spindle torque is obtained, it is necessary to attach a torque measuring device to the rotating spindle.
The control system becomes very complicated. In addition, since the method is to correct the prediction of the next pass based on the measurement results, there is a problem that the most important predicted value of the first pass of the rolling cannot be corrected. Furthermore, recalculation is performed for each pass, and setting is performed again based on the recalculation, so that a load is placed on the control computer, and in some cases, the control system is not updated in order to perform them in a short time until the next pass. Must not be.

However, the application of the above-mentioned conventional peak torque prediction formula was impossible because the error was large. On the other hand, the steady torque in each pass of the rolling schedule can be calculated and set relatively easily by determining each rolling condition in advance. Further, the present inventors have found that there is a strong correlation between the TAF and the abnormal speed based on operational experience and experiments.

An object of the present invention is to provide a method for realizing prevention of overload of a rolling mill drive system by a simple method in each pass setting calculation of a rolling schedule based on these findings.

[0012]

SUMMARY OF THE INVENTION The present invention relates to a method for preventing overload of a drive system of a rolling mill capable of changing the number of rotations of upper and lower rolls. It is the ratio between the maximum torque during rolling engagement and the steady torque during rolling that acts on the rolling mill drive system from the speed factor set value.
The TAF is estimated and calculated, and the estimated maximum torque during rolling engagement calculated based on the estimated and calculated TAF is compared with the allowable torque value of the rolling mill drive system. An object of the present invention is to solve the above-mentioned problem by a method for preventing a drive system overload of a rolling mill, wherein the rolling is performed by adjusting the roll differential speed set value so as to be equal to or less than a torque value.

[0013]

FIG. 2 shows an example of the relationship between the abnormal speed ratio and TAF. FIG. 2 shows a fitting curve obtained by plotting each experimental data with the abscissa representing the different speed ratio Δu (%) and the ordinate representing TAF, and fitting the correlation curve thereof. The initial setting value of the different speed ratio is determined empirically from the thickness of the steel grade so as to minimize the warpage, and is usually set to a common value in all the passes.

Here, a feature of the present invention is to prevent the drive system overload of the rolling mill by correcting and determining the abnormal speed according to the processing flow shown in FIG. 1 based on the relationship shown in FIG. Hereinafter, the details will be described step by step based on the flow of FIG. Although FIG. 1 shows only one pass, the steady-state torque Ts in all passes is actually determined based on the rolling schedule, and the different speed ratio is determined in all passes based on the determined torque.

First, an allowable stress value σlim of a driving system such as a rolling mill spindle is determined in advance based on an analysis method such as a finite element method. Similarly, the calculated maximum stress σm for the calculated maximum torque Tc is also obtained, and the process proceeds to the following steps. (Step 0) Each rolling condition is set, and the different speed ratio Δu is set. (Step 1) A steady torque Ts is obtained based on each rolling condition. (Step 2) Based on FIG. 2, TA
Estimate F. (Step 3) Peak torque from TAF and steady torque Ts
Calculate Tmax.

Tmax = TAF × Ts (3) (Step 4) Generated stress σx at peak torque Tmax
Is obtained from the ratio between the calculated maximum torque Tc and the calculated maximum stress σm by σx = σm × Tmax / Tc (4), and the generated stress σx is estimated and calculated. (Step 5) Next, the generated stress σx and the allowable stress value σli
Compare with m.

If σlim <σx, go to (Step 6) If σlim ≧ σx, go to (Step 7) (Step 6) Decrease the different speed ratio by a constant value a and return to (Step 2). (That is, the calculation of Δu = Δu−a is performed.) (Step 7) The differential speed Δu is finally determined.

Through the above steps, the abnormal speed ratio Δu is corrected and finally determined. In each rolling pass, it is possible to reduce the overload on the drive system by performing the rolling with correction based on the different speed ratio Δu determined above. In addition, it is clear that the present rolling mill drive system overload prevention method can be applied to any rolling mill, such as a rough rolling mill in a hot rolling line, which sets a pass schedule and rotates the upper and lower rolls at different speeds. It is.

[0019]

EXAMPLE The present invention was applied to a thick steel plate having a thickness of 9 mm, a width of 4600 mm and a total number of rolling passes of 21 passes, and rolling was performed. For the first pass in this case, the setting of the different speed ratio based on the above flow is shown as an example. The allowable stress value σlim of the mill drive system (spindle) is 15 kg / mm ² . In addition, the first-pass steady torque Ts was set to 220 t-m based on the above rolling conditions.
The default rate is 30%.

In step 2, TAF is 2.9 from FIG.
Becomes Therefore, in step 3, Tmax becomes Tmax = 2.9 × 220 = 638 tm. The ratio of σm / Tc is determined to be 0.0279 by another calculation, and from step 4, σx is determined as σx = 0.0279 × 638 = 17.8 kg / mm ² . However, in step 5, since this value exceeds the value of σlim (15 kg / mm ² ), the process proceeds to step 6, where Δu = 0.30−0.02 = 0.28 = 28% is given.

Next, a loop process is performed one after another at a different speed ratio of 28% so as to calculate by looping the steps after step 2, and finally a different speed ratio of 24% (TAF = 24%, Tmax = 528)
tm), σx = 14.8Kg / mm ² and σlim = 15Kg / mm
^{As the result} is below ² , the speed difference 24% is finally determined in step 7. As a result of preventing overloading based on the method exemplified above, the downtime of more than 10 hours (due to replacement work due to breakage of spindle coupling etc.), which has occurred once every two years, has been reduced. I was able to do nothing.

[0022]

According to the present invention, it is possible to prevent the overload of the rolling mill drive system while performing the warpage control by the variable speed rolling, thereby preventing the occurrence of downtime due to the drive system trouble.

[Brief description of the drawings]

FIG. 1 is a flowchart of a rolling mill drive system overload prevention method to which the present invention is applied.

FIG. 2 is a diagram showing a relationship between an abnormal speed ratio and TAF.

FIG. 3 is a schematic diagram showing generation of steady torque and peak torque in a spindle.

Claims (1)

[Claims] In a method for preventing overload of a drive system of a rolling mill capable of rolling by changing the number of rotations of upper and lower rolls of a rolling mill, rolling is performed from a set value of a roll differential speed which is a ratio of an upper roll rotation speed to a lower roll rotation speed. The TAF, which is the ratio between the maximum torque at the time of rolling engagement and the steady torque during rolling, acting on the mill drive system is estimated and calculated. The drive system of the rolling mill, wherein the rolling torque is adjusted by adjusting the set value of the roll different speed ratio such that the estimated value of the maximum torque at the time of rolling engagement is equal to or less than the allowable torque value. Overload prevention method.