RU2494828C1 - Method of automatic strip tension adjustment at continuous mill roughing stands - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to metallurgy, particularly, to rolling with minimum tension or rolling underthrust at hot wide-strip rolling mill roughing stands. Strip tension is adjusted for every group consisting of vertical and horizontal stands at free metal rolling at vertical stand. Prior to metal pickup by horizontal stand rolls, measured and memorised are mean free rolling current of vertical stand motor to maintain horizontal stand roll drive rpm in compliance with enclosed relationship. After horizontal stand roll metal pickup, motor static load current stabilisation is performed by feeding correction signal defined by enclosed ratio. Adaptive correction of rpm by memorised last rpm setting is effected also for vertical stand roll electric drive.

EFFECT: accurate sizes of strip due to elimination of mutual influence of vertical and horizontal stands in combined rolling.

2 dwg

Description

The invention relates to automation of rolling production and can be used to provide rolling with a minimum tension or support of rolling in a continuous subgroup of roughing stands of a broadband hot rolling mill.

There is a method of automatically adjusting the tension of rolled products with minimal tension or back-up of long metal, which includes determining and storing the current of the electric motor of the previous stand of the inter-span gap, measuring the current of the same electric motor after the metal enters the next stand of the inter-span gap, comparing these currents and correcting the speed of the previous stand according to the signal, proportional to the difference of these currents (the method is implemented by the device, see AS No. 1397110, B21B 37/52).

The disadvantage of this method is that the tension is controlled and regulated only in one inter-stand space, while the disturbances caused by fluctuations in the speed of the stands during their regulation have a significant effect on the rolling mode in the entire group of stands, i.e. in other interstitial spaces. In addition, the method does not take into account the influence on the mechanical and electrical equipment of dynamic loads that occur during the capture of metal by rolls, and also does not provide for an adaptive change in the current setting when rolling subsequent strips of a given batch or when switching to a new batch of metal.

The closest analogue to the claimed object is a method for automatically adjusting the strip tension in the rough group of stands of a continuous rolling mill, including setting free speeds and their ratios for the previous and subsequent stands of the inter-stand gap for free rolling mode, measuring and memorizing the motor current of the previous stand in free rolling mode, measurement of the static load currents of engines of the previous and subsequent stands of the inter-span gap while metal is in them depending on the ratio of these signals, proportional-integral control of the speed of the previous stand, transmission of the output total signal to the control system of the previous inter-stand gap, adaptive correction of the speed setting of the previous stand according to the last stored speed for optimal reception of the next workpiece (the method is implemented by the device, see AS No. 1708462, B21B 37/52).

The known method has the following disadvantages.

When the strip is rolled together in vertical and horizontal rolls of the roughing group, there is no plastic deformation of the metal in the inter-stand space under the action of compressive or tensile forces. In this case, the horizontal and vertical rolls turn out to be rigidly connected through the rolled metal, their linear speeds are forcibly aligned, and there are no corrective connections with the linear speeds of the rolls. The correction of the speed of the rolls of the previous horizontal stands, proposed in the known method, when the joint rolling of metal in a vertical and horizontal stands ceases to act. This is because the vertical stand, due to an inconsistent speed reference, does not allow matching the speeds of the interconnected horizontal stands. As a result of this, uncontrolled deviations of tension arise both in the inter-stand spaces between the cage groups and in the gap between the vertical and horizontal cages of one group. The level of tension in the interstand spaces of a continuous subgroup of the roughing group of stands should be maintained at a constant level close to zero. The occurrence of backwater leads to emergency conditions, therefore, is unacceptable. Since the main task of regulating the tension in the draft group is the formation of the strip width, uncontrolled changes in tension lead to deviations in the geometric dimensions of the section (width and thickness) of the strip, which lead to deviations of these parameters along the length of the strip and, as a result, lower quality of the products.

In addition, in the known method does not take into account the magnitude of the static subsidence of the speed of the electric drive of the vertical rolls, as a result of which, at the moment of capture of the metal by the rolls of the horizontal stand, a mismatch of the speeds of the horizontal and vertical rolls appears. The capture in conditions of mismatch of the speeds of the rolls is accompanied by the impact of the roll on the rolls, which leads to the emergence of dynamic loads that destroy the mechanical and electrical equipment of the mill, and accordingly reduce its reliability and durability. Dynamic shocks also occur when a strip enters a vertical stand due to a mismatch in the speed of its rolls and the speed at which the strip exits the previous horizontal stand.

The technical result of the invention is to increase the accuracy of the dimensions of the strip section by eliminating the mutual influence of vertical and horizontal stands in the process of joint rolling.

The technical result is achieved by the fact that in the known method, including the free rolling mode, setting the speeds and their ratios for the previous and subsequent stands of the interstand space, measuring and storing the current of the motor of the previous stand in free rolling mode, measuring the static load currents of the engines of the previous and subsequent stands of the interstand the gap while the metal is in them, depending on the ratio of these signals, proportional-integral speed control the main stand, transmitting the output total signal to the control system of the previous interstand space, adaptive correction of the speed setting of the previous stand according to the last stored speed for optimal reception of the next workpiece, according to the invention additionally for each group consisting of vertical and horizontal stands, in the free rolling mode of metal in a vertical stand, before the metal is captured by the rolls of a horizontal stand, the average value of the free rolling current of the engine is measured and stored rtikalnoy stand, horizontal stand speed drive roll support according to the relationship

, $${\omega }_G={\omega }_{\mathrm{AT}}\frac{D_{\mathrm{AT}}}{D_G}\cdot \frac{\mathrm{one}}{\cos {\alpha }_G}$$

,

where ω _G , ω _B are the speeds of horizontal and vertical rolls, respectively;

D _G , D _In - the diameters of horizontal and vertical rolls;

α _G - angle of metal capture by rolls of a horizontal stand;

after the metal is captured by the rolls of the horizontal stand, during the joint rolling of metal in the vertical and horizontal stands, the static load current of the vertical stand motor is stabilized by applying a correction signal determined by the integral dependence

, $$U_{\mathrm{TO}\mathrm{AT}}=\frac{\mathrm{one}}{T_{\mathrm{AND}}R}\left(I_{\mathrm{AT}\mathrm{from}\mathrm{about}\mathrm{at}m.}-I_{\mathrm{AT}\mathrm{from}\mathrm{at}.\mathrm{from}Red.}\right)$$

,

where I _Vsovm. - the current value of the static current of the vertical stand motor during joint rolling;

I _Sun. - the stored average value of the static current of the vertical stand motor during free rolling;

T _And - integration constant,

and adaptive correction of the speed setpoint according to the last stored speed is also carried out for the electric drive of the vertical stand rolls.

Distinctive features of the proposed method are:

- measuring and storing the average value of the free rolling current of the vertical stand engine;

- during joint rolling of metal in a vertical and horizontal stands, stabilization of the static load current of the vertical stand engine by applying an integral corrective action, determined by the difference between the static currents of separate and joint rolling in a horizontal stand (I _Vsovm -I _{Vsv .} );

- setting the speed of the electric drive of the horizontal stand before the strip is captured by the rolls, calculated taking into account the speed of the electric drive of the vertical stand, the ratio of the diameters of the rolls of the vertical and horizontal stands, as well as the angle of metal capture by the rolls of the horizontal stand;

- adaptive correction of the speed setting of the electric drive rolls of the vertical stand according to the last stored speed during joint rolling.

Measurement and storage of the free rolling current of the engine is known and used in the method adopted for the prototype.

However, in the known method, an uncontrolled (random) current value is stored, which during rolling in the draft group varies over a wide range. So, when rolling glide marks, current deviations can vary in the range of several tens of percent of the steady rolling current. In addition, significant current overshoot occurs in the dynamic strip capture mode. Therefore, storing a random current value can lead to significant tension control errors. More accurate results can be obtained by the proposed calculation and storing the average value of the free rolling current of the vertical stand engine.

The stabilization of the current of the static load of the engine during joint rolling is also used in the method adopted for the prototype.

However, in the known method, this operation relates to the electric drive of the previous horizontal stand. The influence of vertical stands on the rolling process in the roughing group is not controlled and therefore not stabilized. This causes uncontrolled changes in tension or the occurrence of backwater in the inter-cleft spaces, which is unacceptable under the conditions of joint rolling.

Setting the speed of the electric drive of the horizontal stand before the strip is captured by the rolls, calculated taking into account the speed of the electric drive of the vertical stand, the ratio of the diameters of the rolls of the vertical and horizontal stands, as well as the angle of metal capture by the rolls of the horizontal stand, provides the most accurate ratio of the speeds of the rolls of the vertical and horizontal stands before capturing the horizontal stand, which provides a reduction in dynamic loads of mechanical and electrical equipment.

Adaptive correction of the speed setting of the electric drive of the rolls of the vertical stand according to the last stored speed during joint rolling is known and is also used in the method adopted for the prototype.

However, the speed correction is carried out in the electric drives of the previous horizontal stands, the speed correction of the electric drives of the vertical stands is not provided, and therefore the vertical stands are not prepared for rolling the following bands based on the rolling parameters of the previous ones.

In General, the distinguishing features of the proposed method can eliminate the mutual influence of the vertical and horizontal stands during joint rolling. This is ensured by the corrective effect on the speed of the vertical stand, which varies according to the integral law. In addition, dynamic shocks are reduced when the strip is gripped by a horizontal stand due to a more precise setting of the speed of its electric drive, calculated taking into account the speed of the electric drive of the vertical stand, the ratio of the diameters of the rolls of the vertical and horizontal stands, as well as the angle of metal capture by the rolls of the horizontal stand. As a result, the accuracy of maintaining a tension close to zero is increased, the occurrence of backwater is eliminated, thereby increasing the accuracy of the geometric dimensions along the strip section, and accordingly, the quality of the products is improved.

The invention is illustrated by drawings, where:

figure 1 presents a diagram of the joint rolling of metal in horizontal and vertical stands;

figure 2 presents a diagram of a device that implements a method for automatically controlling the tension of the strip in the rough group of stands of a continuous rolling mill.

Figure 1 and figure 2 presents the horizontal rolls 1, 2 of the previous and subsequent along the rolling horizontal stands and vertical rolls 3, interconnected through rolled metal 4.

The device (figure 2) that implements the inventive method for automatically controlling the tension of the strip in the rough group of stands of a continuous rolling mill, contains pushing devices 5, 6 rolls 1, 2 of the corresponding horizontal stands equipped with sensors of the gap 7, 8. The output of the gap sensor 8 of the subsequent stand 2 connected to the first input of the computing device 9, the second and third inputs of which are connected to the outputs of the static current sensor 10 and the speed sensor 11 of the electric drive 12 of the vertical rolls 3. The fifth and sixth inputs of the computing devices 9 are connected to the outputs of the static current sensor 13 and speed sensor 14 of the electric drive 15 of the horizontal rolls 2. Similarly, the seventh and eighth inputs of the computing device 9 are connected to the outputs of the static current sensor 16 and the speed sensor 17 of the electric drive 18 of the rolls 1 of the previous horizontal stand. The outputs of the computing device 9 are connected to the first inputs of the control units 19, 20, 21, which are connected by their outputs to the control inputs of the electric drives 12, 15, 18, respectively. The second inputs of the control units 19, 20, 21 are connected to the outputs of the speed setting unit 22 of the electric drives.

A method for automatically controlling the rolling process in a continuous group of stands is as follows.

When capturing metal 4 (Fig. 1) by vertical rolls 3, the following operations are carried out: measure the clearance N _{H of} horizontal rolls 2; calculate the cosine of the angle of capture cos α _G metal horizontal rolls 2 according to

$$\cos {\alpha }_G=\mathrm{one}-\frac{H_{\mathrm{one}}-H_2}{D_G},\left(\mathrm{one}\right)$$

summarize the values of the static current I _{V of the} electric drive of the vertical stand and consider the number of terms N in the sum. When separately rolling metal 4 in the vertical 3 and horizontal 2 rolls of the subsequent stand, the speed ω _{G2 of the} horizontal rolls is regulated as a function

$${\omega }_{G2}={\omega }_{\mathrm{AT}}\frac{D_{\mathrm{AT}}}{D_G}\cdot \frac{\mathrm{one}}{\cos {\alpha }_G},\left(2\right)$$

obtained from the condition of joint rolling without tension:

V _α = V _B = V _Г2 · cosα _Г ;

where V _α is the horizontal component of the linear velocity V _{Г2 of the} horizontal rolls 2 at the capture point of metal 4;

V _In - peripheral (linear) speed of the vertical rolls 3;

H ₁ , H ₂ - the thickness of the metal at the inlet and outlet of the horizontal stand.

In this case, by the time of the capture of the metal 4 by horizontal rolls 2, the horizontal component V _{α of the} linear velocity V _{Г2 of the} horizontal rolls 2 becomes equal to the linear velocity V _M2 (Fig. 1) of the metal 4 emerging from the vertical rolls 3 (take V _M2 = V _В ). This ensures the capture of metal by rolls 2 of a horizontal stand with minimal dynamic loads.

When the metal 4 is captured by horizontal rolls 2, they stop summing the static current values I _{V of the} electric drive of the vertical stand 3 and count the number of terms N in the sum, calculate and store the average value of I _All-medium. static current electric drive vertical stand 3 to capture metal rolls 2 horizontal stand:

$$I_{\mathrm{AT}\mathrm{from}\mathrm{at}.\mathrm{from}Red.}=\frac{{\displaystyle \sum I_{\mathrm{AT}}}}{N}\left(3\right)$$

and switch from controlling the speed ω _{G2 of the} horizontal rolls 2 to the regulation of the static current I _{V of the} electric drive of the vertical rolls 3. When the metal 4 is rolled together in the vertical 3 and horizontal 2 rolls, the static current I _{B of the} electric drive of the vertical rolls 3 is regulated, while the value of the correction signal U _KV (figure 2) is calculated by the formula

$$U_{\mathrm{TO}\mathrm{AT}}=\frac{\mathrm{one}}{T_{\mathrm{AND}}R}\left(I_{\mathrm{AT}\mathrm{from}\mathrm{about}\mathrm{at}m.}-I_{\mathrm{AT}\mathrm{from}\mathrm{at}.\mathrm{from}Red.}\right).\left(\mathrm{four}\right)$$

When the metal 4 is ejected from the vertical rolls 3, they switch from regulating the static current to controlling the speed ω _{G2 of the} horizontal rolls 2. At the same time, the parameters of joint rolling are remembered for adaptive correction of the speed setting of the electric drive of the vertical stand rolls during rolling of the next strip. This provides minimal correction of the speed of the rolls of the vertical stand, as a result of which the gripping conditions are improved and dynamic loads are reduced.

Similarly, when the metal is captured by the rolls of the subsequent horizontal stand 2, the speed of the rolls of the previous horizontal stand 1 is corrected.

When the metal 4 is captured by horizontal rollers 2, they switch from controlling the speed ω _Г1 to regulating the static current I _{Г1 of the} electric drive of the horizontal rolls 1 of the previous stand. When metal 4 is rolled together in horizontal rolls 1 and 2, the static current I _{G1 of the} electric drive of horizontal rolls 1 is regulated, while the value of the correction signal U _{KG1 is} calculated by the formula (according to the method adopted for the prototype — according to the proportional-integral law):

$$U_{\mathrm{TO}G\mathrm{one}}=\left(K+\frac{\mathrm{one}}{T_{\mathrm{AND}}R}\right)\left(I_{G\mathrm{one}\mathrm{from}\mathrm{about}\mathrm{at}m.}-I_{G\mathrm{one}\mathrm{from}\mathrm{at}.\mathrm{from}Red.}\right),\left(5\right)$$

where I _G1sv.red. - the average current value of the electric drive rolls 1 of the previous horizontal stand before the capture of metal by the rolls 2 of the subsequent horizontal stand;

I _G1sovm. - the current value of the static current of the electric horizontal rolls 1 during joint rolling;

K is the coefficient of the proportional part of the proportional-integral controller.

When the metal 4 leaves the horizontal rolls 1 of the previous stand, they switch from controlling the static current to controlling the speed ω _{G1 of the} rolls. The joint rolling parameters for adaptive speed correction during the capture of the next lane are remembered.

The device (figure 2) that implements the inventive method, works as follows.

At the moment of capture of the metal 4 by vertical rollers 3, the computing device 9 in accordance with the dependence (1) calculates the cosine of the angle of capture of the metal 4 by horizontal rollers 2 of the subsequent stand. In the period before the metal is captured by horizontal rolls 2 from the output of the computing device 9, a control signal U _{КГ2 of the} speed ω _{Г2 of the} horizontal rolls 2 is supplied to the input of the control unit 20, which ensures its regulation according to expression (2). Corrective signals U _КГ1 on the first horizontal and vertical U _КВ stands are absent. In the same period, the computing device 9 sums up the values of the static current I _V.

When capturing metal 4 by horizontal rolls 2, the computing device 9 calculates and stores the average value of I _Vsv.red. static current I _V , depending on (3), disables the correction signal U _КГ2 for speed ω _{Г2 of} horizontal rolls 2 from the input of the control unit 20. Simultaneously, from the second and third outputs of the computing device 9, correction signals U _КВ , U _{КГ1 are supplied} to the inputs of the control units 19 and 21 electric drives 12, 18 vertical and previous horizontal stands, respectively. These signals are calculated according to dependences (4) and (5) for static currents I _{V of} electric drives of vertical and horizontal I _G1 rolls. During the period of joint rolling of metal 4 in the vertical 3 and horizontal 2 stands, the computing device 9 automatically regulates the static currents I _B and I _{G1 of the} electric drives of vertical 3 and horizontal rolls.

The implementation of the proposed method due to additional automatic correction of the speed of the vertical stand allows to exclude its influence on the coordination of speeds of the previous and subsequent stands of the inter-stand gap. This ensures the equality of speeds during joint rolling

V _M1 = V _M2 = V _α ,

which will provide increased accuracy of tension control and the elimination of backwater.

As a result of increasing the accuracy of tension control, it is possible to increase the accuracy of geometric dimensions (width and thickness) along the strip section, their deviations along the strip length are reduced, and the quality of the products is accordingly improved. In addition, by matching the speeds of the vertical and horizontal stands before the metal is captured by the rolls of the horizontal stand and adaptive correction of the speed of the vertical stand, shocks are eliminated and the dynamic loads of mechanical and electrical equipment are reduced. This provides increased reliability and durability of the unit as a whole, as well as reduced downtime due to equipment breakdowns.

Claims (1)

A method for automatically controlling the strip tension in the rough group of stands of a continuous rolling mill, including setting free speeds and their ratios for the previous and subsequent stands of the inter-stand gap for the free rolling mode, measuring and storing the current of the motor of the previous stand in free rolling mode, measuring the static currents of the engines of the previous and the subsequent stand of the inter-cleft gap while the metal is in them, depending on the ratio of these signals is proportional flax-integral control of the speed of the previous stand, transfer of the output total signal to the control system of the previous inter-stand gap, adaptive correction of the speed setting of the previous stand according to the last stored speed for optimal reception of the next workpiece, characterized in that it is additional for each group consisting of vertical and horizontal cages, in the mode of free rolling of metal in a vertical cage, before the metal is captured by the rolls of the horizontal cage, the average its current value of free rolling of the vertical stand engine, the speed of the electric roll rolls of the horizontal stand is maintained according to the dependence
$${\omega }_G={\omega }_{\mathrm{AT}}\frac{D_{\mathrm{AT}}}{D_G}\cdot \frac{\mathrm{one}}{\cos {\alpha }_G},$$

where ω _G , ω _In - peripheral speeds of horizontal and vertical rolls, respectively;
D _G , D _In - the diameters of horizontal and vertical rolls;
α _G - angle of metal capture by rolls of a horizontal stand;
after the metal is captured by the rolls of the horizontal stand, during the joint rolling of metal in the vertical and horizontal stands, the static load current of the vertical stand motor is stabilized by applying a correction signal determined by the integral dependence
$$U_{\mathrm{TO}\mathrm{AT}}=\frac{\mathrm{one}}{T_{\mathrm{AND}}R}\left(I_{\mathrm{AT}\mathrm{from}\mathrm{about}\mathrm{at}m}-I_{\mathrm{AT}\mathrm{from}\mathrm{at}.\mathrm{from}Red}\right),$$

where I _Vsovm - the current value of the static current of the vertical stand engine during joint rolling,
I _VSV.red - the stored average value of the static current of the vertical stand motor during free rolling,
$$\frac{\mathrm{one}}{p}$$

- time integration operator,
T _And - integration constant,
and adaptive correction of the speed setpoint according to the last stored speed is also carried out for the electric drive of the vertical stand rolls.

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