RU2189875C2 - Device for automatic control of strip flatness - Google Patents

Abstract

FIELD: rolling process; automated control systems for sheet mills. SUBSTANCE: proposed device includes meter for measuring lack of flatness, rolling force and speed meters, hydraulic bend system and mill cooling systems, unit for calculation of difference between mill shapes, forces and speed of rolling at jstand (j=1,..., n-1) and at last stand (n-stand) of mill and units for calculation of hydraulic bend and delivery of cooling fluid for j-stand and last stand)nstand) of mill. Novelty of invention consists in availability of meter for measuring thickness of semi-finished rolled stock in width placed before first stand of mill and arithmetical unit for determination of local increased thickness on semi-finished rolled stock and noting their location and differential lubrication system over length of roll bodies in first stand of mill. EFFECT: stabilized rolling process in first stands of mill; increased ingot-to product yield; enhanced flatness of cold-rolled strips due to avoidance of lack of flatness in first stand of continuous rolling mill. 4 dwg

Description

 The invention relates to rolling production and can be used in automated quality management systems of rolled strips on continuous sheet mills.

 Known devices for regulating the flatness of strips, containing a sectional meter measuring the distribution of tension across the width of the strip, blocks for calculating the adjusting settings of hydraulic bending and zone cooling, as well as systems that perform this regulation ([1], Devidson R. "Automatic flatness control". Iron and Steel Engineer , 1986, 10, pp. 44-48. [2], Caristedt AG, Keijser O. "Modern approach to flatness measurement and control in cold rolling", Iron and Steel Engineer, 1991, 4, pp. 34-37).

 The purpose of these devices is to regulate the flatness of the strips at the exit of the last stand of a continuous sheet mill, i.e. obtaining cold rolled strips with a given distribution of specific tensions along the width of the strip. However, the solution to the problem of obtaining a flat strip also depends on the stability of the rolling process in the first stands of the continuous mill, which is determined by the distribution of specific tension across the strip width, i.e. depends on the effectiveness of controlling the means of regulating flatness (PSA) of the first stands.

 Closest to the proposed device in technical essence is a device for automatically controlling the flatness of the strips in the first stands of the mill, which contains a non-flatness meter, measuring forces and speeds of rolling, hydraulic bending and cooling systems of rolling rolls, a unit for calculating the differences between the values of machine profiling, efforts and rolling speeds in the j-th (j = 1, ... n-1) and last (n-th) mill stands, as well as the blocks for calculating the hydraulic bending adjustment settings and coolant supply for the jth mill and the last (n-th) mill stand ([3], USSR Copyright Certificate 1705072, class B21B37 / 00, 1992).

 The known device, adopted as a prototype, allows you to effectively manage the PSA in the first stands of the mill in order to create the optimal distribution of specific tension across the strip width from the point of view of stability of the rolling process and provides strips at the output of the last mill stand with a given diagram of specific tension across its width.

 This device works on the principle of program control and closed control by deviation. The latter causes transport lag in the management of the PSA of the mill stands, which leads to an increase in the proportion of metal rejection by non-flatness. In particular, if a local thickening is present on the tackle, then local non-flatness is formed in the first mill stands in the strip. Taking into account the fact that the rolling speed on modern continuous mills is high enough (~ 20-30 m / s) and for the reconfiguration of the differentiated coolant supply to the rolls (the most effective SRP channel for eliminating local non-flatness), it takes a certain time in the stands, then some part of the strip from the first stands with local non-flatness passes the last stand without regulation ([4], Bozhkov AI, Nastich VP Flatness of rolled sheets. - M.: INTERMET ENGINEERING, 1998. - 264 p.). This is a disadvantage of the device in question.

 It is possible to reduce the number of rolled strips with local non-flatness by determining local thickenings on the tackle at the entrance to the mill and creating conditions for minimizing compression of thickened sections in each stand. The first is achieved by installing a thickness gauge along the width of the tack at the entrance to the first stand, the second by increasing the coolant supply to the roll section corresponding to local thickening in the strip, and reducing the lubricant supply to the same roll section.

 The essence of the proposed device lies in the fact that it contains a process automation unit, force and rolling speed meters, a non-flatness meter, a unit for setting hydraulic bending and cooling rolls of the last mill stand, a unit for calculating the differences between the values of machine profiling, forces and rolling speeds in the jth (j = 1, ... n-1) and the last (n-th) mill stands, the unit for calculating the hydraulic bending adjustment settings and coolant supply for the jth mill, the hydraulic bending and cooling system of the rolling rolls, is connected s with process automation unit j-th (j = 1, ... n-1), the mill stand, the video device tracking system for the rolling process. At the same time, it is equipped with a tread thickness gauge installed in front of the first stand of the rolling mill, the output of which is connected to the input of the arithmetic unit for determining local thickenings on the tack and storing their location. The output of this unit is connected to the input of the technological automation unit, designed to signal the cooling system of the rolling rolls for maximum supply of coolant and the differential supply system of lubricant along the length of the roll barrel to minimize the supply of lubricant to sections of rolls corresponding to sections of the strip with local thickenings. The system of differential supply of lubricant along the length of the roll barrel is available in the first stands of the mill.

 Comparative analysis with the prototype shows that the inventive device is characterized by the presence of new devices and units: a tackle thickness gauge in width, an arithmetic unit and a system for differential supply of lubricant along the length of the roll barrel.

 Figure 1 presents the connection diagram of the proposed device with the rest of the elements of the rolling mill systems.

 The device for automatically adjusting the flatness of the strips contains measuring instruments of rolling force 1 and speed 2, the outputs of which are connected to the inputs 3.1, 3.2, 3.3, 3.4 of the first arithmetic unit 3, the output of which is connected to the input 4.1 of the second arithmetic unit 4, the inputs 4.2, 4.3 of which are connected to the outputs block 5 forming the settings of the hydraulic bending and cooling of the rolls in the last stand. The output of the non-flatness meter 6 is connected to the input of block 5 and the input 4.4 of the second arithmetic block 4. The output of the rolled thickness gauge 7 across the first stand of the cold rolling mill is connected to the input of the third arithmetic block 8. The outputs of arithmetic blocks 4 and 8 are connected to the input unit 9 of technological automation, controlling the hydraulic bending 10, the cooling system 11 and the differential supply system of lubricant 12 along the length of the rolls of the jth mill stand, and the video device 13.

 The inputs 3.5, 3.6, 3.7, 3.8, 3.9 of the first arithmetic unit 3, 4.5, 4.6, 4.7, 4.8, 4.9, 4.10, 4.11, 4.12, 4.13 of the second arithmetic unit 4 and 8.1 of the third arithmetic unit 8 are connected to the interface of the computer-aided technological automation.

Figure 2 shows the block diagram of the first arithmetic unit for calculating the differences between the values of machine profiling, efforts and rolling speeds of the jth and nth mill stands. Measuring instruments of efforts (P _j , P _n ) and speeds (V _j , V _n ) rolling for the j-th and n-th stands, respectively, are presented in the form of sensors 3.1-3.4. The outputs of the sensors 3.3-3.4 are connected to the inputs of the inverters 15 and 16, the outputs of which are connected to the first inputs of the adders 23 and 24, the second inputs of which are connected to the outputs of the sensors 3.1-3.2. The input of the inverter 14 is connected to the channel of the interface, which gives signals about the values of the machine profiling of the work rolls of the nth stand (D _n ). The output of the inverter 14 is connected to the first input of the adder 22, the second input of which is connected to the channel of the interface, which gives signals about the values of machine profiling of the work rolls of the j-th stand (D _j ). The outputs of the adders 22, 23 and 24 are connected to the first inputs of the multipliers 17, 18, 19, the second inputs of which are connected to the interface channels, which give signals about the values of the transmission coefficients from the effects of machine profiling (K _Dj ), effort (K _Pj ) and speed ( K _Vj ) rolling the j-th stand on the uneven tension and the shape of the strip. The outputs of the multipliers 18 and 19 are connected to the inputs of the inverters 20 and 21, the outputs of which are connected to the first inputs of the adders 25 and 26, where the second input of the adder 25 is connected to the output of the multiplier 17, and the second input of the adder 26 is connected to the output of the adder 25. The output channel of the first arithmetic block is the output of the adder 26.

 In FIG. 3 is a block diagram of a second arithmetic unit for calculating the hydraulic bending adjustment settings and coolant supply for the jth mill stand.

The output of the first arithmetic unit is connected to the input of the inverter 33, the output of which is connected to the first input of the adder 39, the second input of which is connected to the input of the sensor 4.4 of the flatness meter 6, installed at the output of the last stand of the mill, which gives signals about the uneven tension across the strip width (δσ _n ) The output of the adder 39 is connected to the first input of the divider 32, the second input of which is connected to the interface channel, which gives signals about the value of the transmission coefficient from the effects of hydraulic bending (K _Fj ), the roll system of the jth stand on the tension unevenness and the shape of the strip. The first input of the divider 29 and the first input of the divider 31 are connected with the same channel of the interface. The second input of the divider 29 is connected to the output of the adder 38, the first input of which is connected to the channel of the interface, which gives signals about the value of the uneven tension along the strip width in the jth mill stand (δσ _{ass j} ). The second input of the adder 38 is connected to the inverter 30, the input of which is connected to the channel of the interface, which gives signals about the value of the uneven tension across the width of the strip in the n-th stand of the mill (δσ _{back n} ). The second input of the divider 31 is connected to the interface channel, which gives a signal about the value of the transmission coefficient from the effects of cooling (K _Qj ) of the roll system of the jth stand on the uneven tension and the shape of the strip. The first input of the multiplier 28 is connected to the first output of the unit for setting the hydraulic bending settings (F _gn ) for cooling (δQ _n ) of the rolls and the nth stand, which generates a signal δQ _n . The second input of the multiplier 28 is connected to the output of the divider 27, the inputs of which are connected to the interface channels, and which give signals about the values of the transmission coefficients from the effects of cooling (K _Qj ) and hydraulic bending (F _gn ) of the roll system of the nth stand on the tension unevenness and strip shape . The outputs of the multiplier 28 and dividers 29, 32 are connected to the first inputs of the adders 40, 41, 42. The second input of the adder 40 is connected to the second output of the unit for setting the hydraulic bending and cooling rolls in the n-th stand, which gives the signal F _gn . The output of the adder 41 is connected to the second input of the adder 42, the output of which is connected to the first input of the divider 34, the second input of which is connected to the channel of the interface, which gives a signal about the value of the change in band stiffness behind the jth stand (Δg _j ). The output of the divider 34 is connected to the first input of the multiplier 35 and to the first input of the multiplier 36, the second input of which is connected to the output of the multiplier 37, the first input of which is connected to the output of the divider 31. The second inputs of the multipliers 35 and 37 are connected to the interface channels that give signals about the values weight coefficients of the settings of hydraulic bending (K ₁ ) and cooling rolls (K ₂ ) in the j-th stand. The outputs of the multipliers 35 and 36 are the outputs of the second arithmetic unit and are connected to the inputs of the technological automation unit 9.

 Figure 4 presents a block diagram of a third arithmetic unit for determining local thickenings on the roll and remembering their location.

From the tackle thickness meter over width 7, the discrete values of the thickness H _i (i = 1, .., N is the specified number of measurements on the bandwidth) are fed to the inputs of the adders 43 and the inputs of the inverters 45. The outputs of the adders 43 are connected to the inputs of the dividers 44, the outputs which are connected to the first inputs of the adders 46, the second inputs of which are connected to the outputs of the inverters 45. The outputs of the adders 46 are connected to the first inputs of the comparison units 47, the second inputs of which are connected to the channel 8.1 interface, which gives signals about the threshold value of the difference in the thickness of the tack (ΔH _back ) . The outputs of the comparison units 47 are connected to the inputs of the storage units 48, in which the numbers of i sections along the width of the tack having a local thickening are fixed. The outputs of the storage units 48 are the outputs of the third arithmetic unit and are connected to the inputs of the technological automation unit 9.

The current values of the control channels for stabilizing the rolling process and regulating the shape of the strip from the outputs of the multipliers 35, 36 are expressed as a percentage of their maximum values, and the distribution of tensions along the width of the strip is described by a parabola and, for simplicity, is specified through the unevenness
δσ _j = δσ _{cr j} -δσ _{cf j} , j = 1, ..., n, (1)
where σ _cr , σ _cf are specific stresses at the edge and middle of the strip (in practice, the distribution of tension along the strip width has the most diverse character and can be specified either in tabular form or by polynomials of various orders).

Weighting factors K ₁ and K ₂ are related by
K ₁ = 1-K ₂ , (2)
and the transmission coefficients K _Dj , K _pj , K _vj , K _Fj , K _Qj , K _Dn , K _Fn , K _Qn and the coefficient of change of the stiffness of the strip Δg _{j are} calculated by a known method.

 The device for automatically regulating the flatness of the strips is as follows.

The current values of the force and rolling speed, measured in the last (n-th) mill stand by sensors 3.3 and 3.4 (figure 2), are fed to the inputs of inverters 15 and 16, respectively, of the first arithmetic unit. The signal corresponding to the set value of the machine profiling of the work rolls and the last mill stand, which is summed in the adder 22 with the signal corresponding to the set value of the machine profile of the work rolls of the controlled (jth) mill stand, is input to the inverter 14. The current values of the force and rolling speed, measured in a controlled stand by sensors 3.1 and 3.2, are summed with the output signals of inverters 15 and 16, respectively. The signals from the outputs of the adders 22, 23 and 24 are fed to the first inputs of the multipliers 17, 18 and 19, the second inputs of which give signals corresponding to the given values of the transmission coefficients K _Dj , K _Pj , K _Vj for the uneven tension in the controlled stand before the machine profiling , effort and rolling speed. For the cold rolling mill "2030" of OJSC "NLMK" empirical dependencies of transmission coefficients were obtained:
K _Dj = 120h _j +0.000182 B,
K _pj = 0.09-0.00545h _j -0.0000273 V, (3)
j = 1, ..., n,
K _vj = 0.05-0.00364h _j -0.0000182 V,
where h _j , B is the thickness and width of the strip at the exit of the jth stand, mm.

The multiplied signals K _pj , and from the output of the adder in the multiplier K _vj and from the output of the adder in the multiplier are inverted in the inverters. In the adder, the signals from the output of the multiplier and the output of the inverter are added and the resulting signal is fed to the input of the adder, where it is summed with the signal from the inverter and the resulting signal from the output of the adder is fed to the inverter of the second arithmetic unit. The current values of the unevenness of the strip tension, measured by the sensor at the exit of the mill at different sections of the strip width, either at fixed intervals of time or at a fixed number of revolutions of the measuring roller (for example, when using a stressometric roller), are fed to the input of the adder, where they are summed with the output signal inverter. The resulting signal from the adder is fed to the input of the divider, where it is divided by the set signal corresponding to the transfer coefficient K _Fj , the uneven tension in the controlled stand from the action of coolant supply, and the divider, where the resultant signal from the output of the adder is divided into it, the inputs of which are supplied signal of a given value of uneven tension on δσ bandwidth _{backside j} stand in a controlled inverter and inverting the signal of a given value of uneven tension across the strip width δσ _{backside n} in the last stand.

For the cold rolling mill “2030” of OJSC “NLMK” empirical dependences of transmission coefficients K _Qj and K _Fj were obtained:
K _Qj = 0.073h _j +0.000114 V,
K _Fj = 0.236h _j +0.000182 V, (4)
j = 1, ..., n.

(порог сравнения)

где k=1,2...,М - количество участков полосы, для которых вычисляется порог сравнения: М=N/3; m=1,4,7,10,...,N-2.The signals about the given values of the transmission coefficients for the tension unevenness in the nth stand from the hydraulic bending force K _Fn , and from the action of the coolant supply K _Qn , are fed to the inputs of the divider, from the output of which the signal K _Qn / K _Fn goes to the first input of the multiplier, to the second the input of which from the block of settings of the hydraulic bending and cooling of the rolls for the last stand of the mill gives a signal to change the setpoint for the coolant flow rate δQ _n Q in the last stand of the mill. The signal received at the output of the multiplier is fed to the input of the adder, where it is summed with the output signal about the value of the hydraulic bending force in the last stand F _gn from the unit for setting the hydraulic bending and cooling rolls settings. The resulting signal from the output of the adder is summed with the output signal of the divider in the adder, the output of which the resulting signal is summed in the adder with the output signal of the divider. The resulting signal from the output of the adder is fed to the input of the divider, which is divided into a signal about the set (or calculated (3)) value of the change in the stiffness of the strip at the output of the controlled stand. The signal from the output of the divider is fed to the input of the multiplier, where it is multiplied with a signal about a given value of the weight coefficient K ₂ . From the output of the multiplier and the output of the divider, the signals are fed to the inputs of the multiplier. Simultaneously with the output of the divider, the signal is fed to the input of the multiplier and multiplied with the signal about the specified value of the weight coefficient K ₁ . The obtained control signals from the outputs of the multipliers are fed to the input of the technological automation unit, which in turn gives control signals F _gj and δQ _j to the actuating mechanisms of regulation by hydraulic bending systems and coolant supply to the jth stand. The signals from the meter thickness of the rolled along the width 7, installed at the input of the first stand, enter the arithmetic unit 8 for determining local thickenings on the roll and remembering their location (figure 4). All discrete values of the thickness of the tackle along the width H _i (i = 1, .., N is the given number of measurements on the width) are divided into groups of three values. In the adder 43 they are summed, and the output value from it in the divider 44 is divided into three, thus the value

(comparison threshold)

where k = 1,2 ..., M is the number of strip sections for which the comparison threshold is calculated: M = N / 3; m = 1,4,7,10, ..., N-2.

поступающего из блока 44

В блоке 47 происходит сравнение ΔH_фi с заданным значением ΔH_зад, которое вводится оператором или выбирается автоматически в зависимости от толщины подката. Если ΔH_фi≤ΔH_зад, то локальное утолщение отсутствует и изменения в регулирование процесса не вносятся; если ΔH_фi>ΔH_зад, то на i-ом участке ширины полосы присутствует локальное утолщение, а значение индекса i запоминается в блоке 48. Из этого блока сигнал об индексе i подается в блок технологической автоматики 9, откуда поступает сигнал в систему охлаждения прокатных валков, в которой производится перераспределение подачи охлаждающей жидкости таким образом, чтобы на участок валков, соответствующий участку полосы с дефектом, подавалось максимальное количество охлаждающей жидкости. Аналогичный сигнал подается в систему дифференцированной подачи смазки по длине бочки валков, в которой производится перераспределение подачи смазки, и на этот участок подается минимальное количество смазки. При выборе значений уставок отдельных каналов регулирования в первую очередь используют систему охлаждения валков, гидроизгиб используют для оперативного регулирования формы полосы в случаях резкого изменения характера распределения натяжения по ширине полосы (смена типоразмера, изменение режима прокатки и т. д.) и снижают до минимума по мере стабилизации теплового профиля валков. Такая альтернатива достигается с помощью весовых коэффициентов К₁ и К₂, связанных зависимостью (1), которые могут принимать значения в диапазоне 0-1, тем самым изменяя вес канала регулирования (F_rjδQ_j соответственно) в общей системе регулирования.The invertible thickness values from the inverters 45 enter the adders 46, where the difference between the actual thickness values H _i and the comparison threshold is calculated

coming from block 44

In block 47, a comparison is made of ΔH _phi with a predetermined value of ΔH _ass , which is entered by the operator or is selected automatically depending on the thickness of the tack. If ΔH _phi ≤ΔH _ass , then there is no local thickening and changes to the regulation of the process are not made; if ΔH _phi > ΔH is the _back , then on the i-th section of the bandwidth there is a local thickening, and the value of the index i is stored in block 48. From this block, the signal about the index i is fed to the technological automation unit 9, from where the signal comes to the cooling system of the rolling rolls , in which the coolant supply is redistributed so that the maximum amount of coolant is supplied to the roll section corresponding to the defective strip section. A similar signal is fed into the differential lubrication supply system along the length of the roll barrel, in which the lubricant is redistributed, and a minimal amount of lubricant is supplied to this section. When choosing the settings of individual control channels, the roll cooling system is primarily used, hydraulic bending is used to quickly control the shape of the strip in cases of a sharp change in the nature of the distribution of tension across the strip width (change of size, change in rolling mode, etc.) and reduce to a minimum as the thermal profile of the rolls stabilizes. Such an alternative is achieved using weights K ₁ and K ₂ connected by dependence (1), which can take values in the range 0-1, thereby changing the weight of the control channel (F _rj δQ _j, respectively) in the general control system.

 Using the proposed device, in comparison with the known one, it is possible not only to stabilize the rolling process due to preliminary compression of the strip edges in the first mill stands, taking into account changes in its rigidity at each compression step, to increase the yield due to a decrease in the probability of strip breakage in the inter-stand spaces due to cracks on its edges, to improve the geometric characteristics of rolled products through the rational use of flatness control systems for the strip, but also create conditions for poppy imalnogo reduce compression tackle thickened portion and passing it through the mill without additional stretching, which leads to prevention of local flatness on cold rolled strip.

Sources of information
1. Devidson R. "Automatic flatness control". Iron and Steel Engineer, 1986, 10, pp. 44-48.

 2. Caristedt A.G., Keijser O. "Modern approach to flatness measurement and control in cold rolling". Iron and Steel Hngineer, 1991, 4, pp. 34-37.

 3. Copyright certificate of the USSR 1705072, cl. B 21 B 37/00, 1992.

 4. Bozhkov A.I., Nastich V.P. Flatness of sheet metal. - M.: INTERMET ENGINEERING, 1998 .-- 264 p.

Claims (1)

 A device for automatically controlling the flatness of strips on an n-stand rolling mill, comprising a technological automation unit, force and rolling speed meters, a unit for setting hydraulic bending and cooling rolls of the last mill stand, the input of which is connected to the output of a non-flatness meter installed behind the last stand, a hydraulic bending system and cooling rolls connected to the technological automation unit of the j-th (j = 1,..., n-1) mill stand, calculation unit for adjusting the settings of the hydraulic bending and lubricants o-cooling fluid for the j-th stand, the unit for calculating the differences between the values of machine profiling, efforts and rolling speeds of the j-th and last n-th stands of the mill, the first and second inputs of which are connected to the outputs of the meters of force and rolling speed in the j-th stands, the third and fourth inputs are connected to the outputs of the force and rolling speed meters in the nth stand, the first input of the unit for calculating the hydraulic bending adjustment settings and the supply of cutting fluid for the jth mill stand is connected to the output of the unit for calculating the differences between the values of tank profiling, efforts and rolling speeds of the jth and last nth stands of the mill, the second and third inputs are with the outputs of the unit for setting the hydraulic bending and cooling rolls in the last stand, the fourth input with the output of the flatness meter, and the output with the inputs of the block technological automation and video devices for monitoring the rolling process, characterized in that it is equipped with a tread thickness gauge installed in front of the first stand of the rolling mill, the output of which is connected to the input of the arithmetic unit o determination of local thickenings on the roll and storing their location, the output of which is connected to the input of the technological automation unit, designed to signal the cooling system of the rolling rolls for maximum coolant supply and the differential feed lubrication system along the length of the roll barrel for minimal supply of lubricant to the roll sections, bands corresponding to sections with local thickenings.

Images