RU2148447C1 - Strip rolling method - Google Patents

Abstract

FIELD: rolled stock production, possibly thick strip rolling process and equipment. SUBSTANCE: method comprises steps of correcting rolling modes according to results of measuring characteristics of deformation state; in first pass predicting rolling effort during stable stage of non-stable rolling period; increasing the last due to small initial value Vo of rolling speed; in order to achieve increased rolling speed, measuring current value P_r(X) of rolling effort and comparing it with reference value P_v; when value P_r(X) achieves P_v calculating two threshold values P1 and P2; comparing P_r with received values P1 and P2 and correcting rolling modes 1) when P_v is less than P1 by applying signal for reversing rolls, 2) when P1 is higher than P2 or equal to it by applying signal for accelerating rolls, 3) when P_v is less than P1 and P1 is less than P2 also applying signal for accelerating rolls and changing rolling speed in first pass; predicting rolling effort in next pass on base of effort values received in previous pass according to condition of equal values of specific pressure; carrying out correction process by changing reduction schedule or deformation speed. EFFECT: reliable protection of rolling mill against technological overloads.

Description

 The invention relates to the field of rolling production and can be used for rolling thick strips, while ensuring protection of the mill stand from technological overloads.

 A known method of rolling, in which to protect the working stand from technological overload using mechanical destructible devices [1].

 This method is associated with production losses due to the need to restore a mechanical device, installation, emergency situations.

 A known method of rolling strips, in which the rolling mode is adjusted based on the results of measuring the strain resistance [2].

 This method allows you to control the rolling mode, improve the accuracy of the rolled strips, stabilize the rolling process, but does not allow to predict the rolling force in the first pass and prevent the technological overload of the stand.

 In addition, if forecasting the rolling forces according to the results of measurements of the cutting forces, then large errors in the forecast results are possible, since the deformation conditions when cutting the strip and its deformation by the rolls differ significantly.

 The problem solved by the proposed invention is to provide the ability to protect the working stand from technological overload by adjusting the rolling conditions.

 This problem is solved as follows.

где P_д - допустимое усилие прокатки;
l - длина очага деформации;
X - текущая координата,
где X=0 соответствует моменту касания валков полосой.In the known method of rolling strips, including adjusting the rolling modes according to the results of measuring the characteristics of the deformation conditions, according to the invention in the first pass, the rolling force at the steady-state rolling stage is predicted during the non-stationary stage, the time of which is increased due to the small constant initial rolling speed V ₀ , for which they measure the current value of the rolling force P _CR (X) and compare it with the control value P _to , which is determined from the condition P _to ≥ Kε _p ,
where ε _p is the sensitivity threshold of the measuring tool;
K is the conversion coefficient;
and after reaching P _CR (X) the values of P _to calculate P ₁ and P ₂ based on the condition

where P _d - allowable rolling force;
l is the length of the deformation zone;
X is the current coordinate
where X = 0 corresponds to the moment when the rolls touch the strip.

- параметр очага деформации;
V_max - максимальная скорость прокатки;
α - коэффициент скоростного упрочения металла;
и сравнивают P_к с полученными значениями, а затем ведут корректировку режимов прокатки следующим образом: в случае P_к > P₁, подают сигнал на реверс валков, в случае P₁ > P₂ подают сигнал на ускорение валков, а при P₁ < P₂ также подают сигнал на ускорение валков и изменяют скорость прокатки в первом проходе, вычисляя ее по формуле

при этом в последующих проходах усилие прокатки прогнозируют на основе значений усилий, полученных в предыдущих проходах, исходя из равенства удельных давлений, а корректировку ведут путем изменения режима обжатия.

- parameter of the deformation zone;
V _max - maximum rolling speed;
α is the coefficient of speed hardening of the metal;
and comparing P _k with the received values, and then conduct the adjustment roll modes as follows: if P _in> P _1, is fed a signal to roll reverse, in the case of P _1> P ₂ fed signal to the acceleration rolls, and when P ₁ <P ₂ also give a signal to accelerate the rolls and change the rolling speed in the first pass, calculating it according to the formula

in the subsequent passes, the rolling force is predicted based on the values of the forces obtained in the previous passes, based on the equality of specific pressures, and the adjustment is carried out by changing the compression mode.

 The method is implemented as follows.

In the first pass, the rolling process starts at a low speed equal to V ₀ , with V ₀ ≤ V _max , where V _max is the specified maximum speed in the pass.

After the metal is captured by the rolls, the value of the path traveled by the rolls is monitored, i.e. the current coordinate X, and the measured rolling force P _CR (X).

The control value P _{k is} preliminarily determined from the condition P _k ≥ Kε _p ,
where ε _p is the sensitivity threshold of the measuring tool;
K is the conversion coefficient.

 This value is a condition that the control value of the rolling force does not belong to the region of nonlinearity of the pulp dose.

где α - коэффициент скоростного упрочения металла,
P_д - допустимое усилие прокатки,
l - длина очага деформации,
X - текущая координата, где X=0 соответствует моменту касания валков полосой,

- параметр очага информации.Upon reaching P _CR (X) the control value of P _to determine the value of the allowable rolling force P ₁ in the X coordinate and the possible force P ₂ in the same coordinate, if the rolling speed instantly increased from V ₀ to V _max according to the formulas:

where α is the coefficient of speed hardening of the metal,
P _d - allowable rolling force,
l is the length of the deformation zone,
X is the current coordinate, where X = 0 corresponds to the moment the strips touch the strips,

- parameter of the source of information.

путем замены P_ст на P_д, которая получена в свою очередь из обработки экспериментальных данных по изменению усилия прокатки в нестационарных стадиях деформации, когда формируется сначала очаг деформации, а затем его передние и задние внешние зоны.The indicated dependence (1) is obtained from the empirical formula:

by replacing P _st with P _d , which is obtained in turn from processing experimental data on the change in rolling force in the unsteady stages of deformation, when the deformation center is formed first, and then its front and rear outer zones.

 Formula (2) takes into account the speed hardening of metal according to the method of V.I. Zyuzin.

Then, the obtained values of P _k , P ₁ , P _{2 are} compared and the rolling mode is adjusted.

In the case of P ₁ <P _k, even at a low rolling speed, overload should be expected, therefore, a signal is fed to the rolls reverse.

In the case of P ₁ > P _1, one should not expect overload even at a given rolling speed V _max , therefore a signal is sent to accelerate the work rolls.

а затем подаются сигналы на ускорение рабочих валков и на изменение уставки на максимальную скорость в первом проходе. После реализации процесса прокатки данного сляба значения V_max восстанавливаются.At P _to <P ₁ ≤ P ₂ there are certain reserves for increasing the rolling speed, but at V = V _{max the} stand overload should be expected, therefore, for the first pass, a new maximum speed is calculated by the formula:

and then signals are sent to accelerate the work rolls and to change the setpoint to maximum speed in the first pass. After the implementation of the rolling process of this slab, the values of V _{max are} restored.

где F_кi, F_кi-1 - величины контактных площадей в i и i-1 проходах, а корректировку ведут путем изменения режимов обжатия.In subsequent passes, the rolling force is predicted based on the values of the forces obtained in the previous passes based on the assumption of the equality of specific pressures:

where F _ki , F _ki-1 are the values of the contact areas in i and i-1 passes, and the correction is carried out by changing the compression regimes.

 An example of a specific implementation in the first pass in the roughing stand of the plate mill "2800", having a diameter of 1300 mm work rolls. Allowable rolling force 25 MN, control force 5 MN.

 Consider the case of rolling a slab 300 x 2650 x 1100 mm.

 The calculated absolute compression value is 15 mm.

Suppose that the cage staff mixed up the steel grade and instead of carbon steel filed alloyed. We begin the rolling process with V ₀ = 0.25 m / s, and the set maximum speed V _max = 1.5 m / s.

 The coefficient of speed hardening is assumed to be 0.143.

 Let us also assume that the control value of the rolling force is achieved at: X (a) = 18 mm, X (b) = 25 mm and X (c) = 40 mm.

т. е. P₁ < P_к и даже при заниженной скорости прокатки следует ожидать превышения допустимого значения усилия, поэтому подается сигнал на реверс валков.In case a, the calculation of P ₁ gives a value of 4.16 MN:

i.e., P ₁ <P _k, and even at a lower rolling speed, one should expect exceeding the allowable force value, therefore a signal is sent to the rolls reverse.

а

т. е. P_к < P₁ < P₂, поэтому следует вычислить новую максимальную скорость,

и после чего следует подать сигнал на ускорение рабочих валков до скорости 0,338 м/с.In case B:

a

i.e., P _k <P ₁ <P ₂ , so you should calculate the new maximum speed,

and then you should give a signal to accelerate the work rolls to a speed of 0.338 m / s.

Так как P₁ > P₂ (7,24 МН > 6,46 МН), то подается сигнал на ускорение рабочих валков.In case of C:

Since P ₁ > P ₂ (7.24 MN> 6.46 MN), a signal is sent to accelerate the work rolls.

 In the second and subsequent passes, rolling is carried out as follows.

 Suppose that in the first pass, the maximum rolling forces fixed during rolling of a slab of 300 x 2650 x 1100 mm are 20 MN and 24 MN.

 The absolute reduction in the first pass was 15 mm.

 According to the compression program in the second pass, compression of 20 mm is supposed.

 The case when the force of 20 MN is recorded in the first pass.

Так как прогнозируемое усилие прокатки меньше допустимого, то режим прокатки не изменяется.

Since the predicted rolling force is less than permissible, the rolling mode does not change.

 Case 24 MN.

Прогнозируемое усилие прокатки больше допустимого, режим прокатки во втором проходе корректируется.

The predicted rolling force is greater than the allowable one, the rolling mode in the second pass is adjusted.

Sources of information
1. Patent of Russia N 2021860, MKI B 21 V 33/00.

 2. USSR author's certificate N 1592070, MKI V 21 V 37/10, (prototype).

Claims (1)

A method of rolling strips, mainly thick, comprising adjusting the rolling modes according to the results of measuring the characteristics of the deformation conditions, characterized in that in the first pass the rolling force is predicted at a steady rolling stage in a non-stationary stage, which is increased due to the low initial rolling speed V _about , for which measure the current value of the rolling force P _CR (X) and compare it with the control value P _to , which is determined from the condition
P _to ≥ Kε _p ,
where ε _p is the sensitivity threshold of the measuring tool;
K is the conversion coefficient,
and after reaching P _CR (X) the values of P _to calculate P ₁ and P ₂ based on the condition

where P _d - allowable rolling force;
l is the length of the deformation zone,
X is the current coordinate, where X = 0 corresponds to the moment the strips touch the strips;

- parameter of the deformation zone,
V _max - maximum rolling speed;
α is the coefficient of speed hardening of the metal,
and comparing P _k with the received values, and then conduct the adjustment roll modes as follows: if P _in> P ₁ is fed a signal to reverse the rolls, if P ₁ ≥ P ₂ fed signal to the acceleration rolls, and at P _to <P ₁ <P ₂ also give a signal to accelerate the rolls and change the maximum rolling speed in the first pass, calculating it according to the formula

in the subsequent pass, the rolling force is predicted based on the value of the force obtained in the previous pass, based on the equality of specific pressures, and the adjustment is carried out by changing the compression mode or strain rates.