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WO2010146615A1 - Method for dynamically controlling flatness in steel strip rolling - Google Patents

Method for dynamically controlling flatness in steel strip rolling Download PDF

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Publication number
WO2010146615A1
WO2010146615A1 PCT/IT2010/000270 IT2010000270W WO2010146615A1 WO 2010146615 A1 WO2010146615 A1 WO 2010146615A1 IT 2010000270 W IT2010000270 W IT 2010000270W WO 2010146615 A1 WO2010146615 A1 WO 2010146615A1
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WO
WIPO (PCT)
Prior art keywords
rolling
flatness
lower limit
dynamically controlling
steel strip
Prior art date
Application number
PCT/IT2010/000270
Other languages
French (fr)
Other versions
WO2010146615A8 (en
Inventor
Constantino Di Pietro
Luca Onofri
Original Assignee
Thyssenkrupp Acciai Speciali Terni S.P.A.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Thyssenkrupp Acciai Speciali Terni S.P.A. filed Critical Thyssenkrupp Acciai Speciali Terni S.P.A.
Publication of WO2010146615A1 publication Critical patent/WO2010146615A1/en
Publication of WO2010146615A8 publication Critical patent/WO2010146615A8/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
    • B21B37/28—Control of flatness or profile during rolling of strip, sheets or plates
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B2265/00—Forming parameters
    • B21B2265/02—Tension
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B2265/00—Forming parameters
    • B21B2265/12—Rolling load or rolling pressure; roll force
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B2265/00—Forming parameters
    • B21B2265/14—Reduction rate
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B2275/00—Mill drive parameters
    • B21B2275/02—Speed
    • B21B2275/04—Roll speed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
    • B21B37/28—Control of flatness or profile during rolling of strip, sheets or plates
    • B21B37/30—Control of flatness or profile during rolling of strip, sheets or plates using roll camber control

Definitions

  • the present invention refers to a method for dynamically controlling flatness in steel strip rolling.
  • the invention refers to a method for dynamically controlling flatness in the rolling of a steel strip in cold rolling stands, by means of a human- machine interface and control algorithms.
  • the rolling is one of the most important industrial production process that permits to obtain planar products destined to very different industrial sectors such as the household appliance and the automobile ones.
  • the main objectives of the rolling mill process are:
  • the rolling stand i.e. the plant by which the rolling process is performed, is a set substantially constituted) by rolls and their supports (cage), motor and relevant transmission members.
  • the main parts of a rolltng,mill stand are: - working rolls, which are directly in contact with the rolled product, intermediate rolls,; as support of the working rolls, which are intended to reduce:the deflection under load, " - cage, designed to contain the stand components and oppose the
  • the rolling mill can work; on-line, so as to produce a subsequent and progressive reduction of the rolled product thickness and length, or, in case of reversible rolling mill, following a forward and reverse pass.
  • the rolling mill process can be realized as hot or cold rolling.
  • the hot rolling exploits the higf) material plasticity at high temperature and allows to obtain large deformations in case of reduced loads on rolling rolls.
  • the cold rolling mill allows to have a good surface finishing and it is realized by means of limited deformations and high loads on rolling rolls.
  • the strip is subjected tq the simultaneous traction and compression actions, for the reason that the rolling rolls cause a crushing and a partial stretching and, above all, keep the strip in tension (what doesn't happen in the case of hot rolli/ig).
  • the rolling is a working by plastic deformation, where the material in course of manufacture reaches the desired width and thickness, increasing its length.
  • the compression action of the rolls on the material in course of manufacture is rarely perfectly uniform along the total cross section and so the material undergoes a not uniform elongation in the rolling direction that produces different length increments in the fibers that constitute the material.
  • defects can be of different type as a function of several elements, such as: the geometry of the inlet material to be rolled , the rolls form, the forces distribution during the contact between rolls and material, the action of different devices tending to modify the form of rolling space. So, in the rolling mill process, to guarantee high quality and productivity, the objective is to have a strip which is as much as possible flat.
  • the flatness defects are quantified by an index named l-unit. Considering the strip as a set of adjacent fibers, the application of different forces on each longitudinal fiber will cause different increments of their length.
  • the l-unit is obtained by the comparison between two fibers lengths during the rolling of the plate.
  • a fiber generally the central one, is taken as reference whereas the remaining ones are compared with it.
  • the l-unit parameter (I) is given by the following expression:
  • measurement approaches based on radiation principle, are utilized.
  • Such devices are based on] stationary meters, scanning meters that detect the plate thickness while it moves at right angle with respect to the rolling direction and profile calculation units .
  • optical measurement such as: laser localization, optical and passive triangulation, holographic interferometry, speckle topography.
  • a flatness target is initially defined and fixed, i.e. a theoretic curve that represents the tensions distribution on the cross section of an optimal strip. This curve has the task of guaranteeing stable rolling condition and/or a strip form adapted to the downstream rolling process . and/or performances in agreement with the customer demand.
  • the flatness measurement system provides the real strip flatness curve: the flatness control system, thusj modifies during the rolling process the set of the different devices equipping the rolling mill and acting on the rolling space form in order to make a coincidence between real measured flatness curve and the theoretical one.
  • the rolling pass exhibits phases of acceleration, running speed, strip deceleration. These phases imply significant changes of the rolling parameters and consequently of the rolling space geometry.
  • the changes are: the rolling force: the different speeds affect the lubrication conditions and consequently the strip-roll damping coefficient with resultant effects on the rolling loads size: low rolling speed increases rolling forces tend to increase and the strip edges tend to be hyper-rolled and lengthened, therefore not respecting the fixed reference values, temperature: the different rolling speeds generate different material deformation rates, to which heat generation corresponds; this implies that the rolling rolls temperature and, so, their thermal expansion change accordingly to different speeds, contact arc: due to the flattening of the working roll, the flattening resulting to be smaller at high speed, the strip-roll contact arc results to be shorter at high speeds.
  • a method for dynamically controlling flatness in steel strip rolling as a function of: steel type, - thickness reduction rate, rolling steps number, comprising the following operations: measurements of instantaneous rolling parameters PLI, selected in the group comprising: speed and/or eventually acceleration as speed derivation and/or possibly separation force and/or possibly reel drawing,
  • the dynamically controlling flatness method of the present invention provides a calculation algorithm of the dynamic flatness curve.
  • this calculation algorithm consists in a polynomial function that, in particular, can be of eighth degree.
  • This polynomial function is expressed by means of the following relation:
  • a A , A , A are functions of: 2, 4 6 8
  • the material type, - the thickness reduction rate being, in the case in which the instantaneous rolling parameter includes only the speed
  • A c2 * [200 / (lower limit - upper limit)] * PU - [100 * (lower limit + upper limit) / (lower limit - upper limit)] / 100
  • A c4 * [200 / (lower limit - upper limit)] * PU - [100 * (lower limit + upper 4 limit) / (lower limit - upper limit)] / 100
  • A c6 * [200 / (lower limit - upper limit)] * PLI - [100 * (lower limit + upper 6 limit) / (lower limit - upper limit)] / 100
  • A c8 * [200 / (lower limit - upper limit)] * PLI - [100 * (lower limit + upper 8 limit) / (lower limit - upper limit)] / 100
  • c2, c4, c6 and c8 are functions of the steel type, thickness reduction rate, rolling steps number, with values in the range of -50 to +50 and wherein the speed admissible values are in the range of 0-800 m/min, the separation force values find between 2000 and 20000 KN and the reel drawing values are in the range of 100 to 700 KN.
  • the instantaneous rolling parameters PU can be used: - in case of alternative, in reciprocal substitution , in combination, by means of weighted mean summation with a weight percentage for the speed equal to 60%, for the acceleration equal to 30%, for the separation force equal to 5% and for the reel drawing equal to 5% in the change of the target flatness curve.
  • the proposed method provides that, as a function of the instantaneous rolling parameters (speed, acceleration, forces, pulling,%) measurements during the working, during running and in particular during the transition phases, dynamic flatness target curves are elaborated by means of a eighth degree polynomial.
  • the instantaneous rolling parameters include only the speed. So far, a general description of the present invention has been given. Invention embodiments will be described with the help of the figures and of the examples so as to better understand objectives, features, advantages and application modes.
  • Figure 1 shows some type of flatness defects.
  • Figure 2 represent the block diagram of a well-known flatness control method.
  • Figure 3 shows the block diagram of the method according to present invention.
  • Figure 4 shows the functional diagram of the method according to the present invention, where the mill stand and the coiler/uncoiler are respectively indicated with I and 2.
  • an austenitic steel 304 has been rolled with a Sendzimir rolling stand.
  • the initial thickness of the product in course of manufacture has been reduced by 70% by means of 9 passes.
  • the strip instant speeds have been continuously measured and the acceleration has been measured as speed derivate.
  • a rolling speed measured during the fifth pass has been of 400m/min and the speed value range has been of 200-800 m/min.
  • the values range of the separation force i.e. the force that is realized between roll and working material, has been of 3000-7000 KN.
  • the coiler/uncoiler drawing reel values range has been of 100-450 KN.
  • the utilized values of the c2, c4, c6, c8 coefficients have been respectively 10, 0, 0, 50.
  • corrective actions have been carried out on the flatness profile by means of both an automatic control system and the driving of specific actuators (such as first intermediate rolls and eccentric saddles).
  • a flatness index I has been detected which corresponds to a low presence of defects, i.e. a I value between 0 and 5 l-unit.
  • a ferritic steel 430 has been rolled with a Sendzimir rolling stand.
  • the initial thickness of the product in working has been reduced by 70% by means of 8 passes.
  • a rolling speed measured during the third pass has been of 300m/min and the speed value range has been of 200-800 m/min.
  • the values range of the separation force i.e. the force that is realized between roll and working material, has been of 2000-5000 KN.
  • the coiler/uncoiler drawing reel values range has been of 100-450 KN.
  • the utilized values of the c2, c4, c6, c8 coefficients have been respectively 5, 0, 0, 30.
  • a flatness index I has been detected which corresponds to a low presence of defects, i.e. a I value between 0 and 5 l-unit.
  • a austenitic steel 304 has been rolled with a Sendzimir rolling stand.
  • the initial thickness of the product in working has been reduced by 70% by means of 9 passes.
  • a rolling speed measured during the second pass has been of 60m/min and the speed value range has been of 10-800 m/min.
  • the values range of the separation force i.e. the force that is realized between roll and working material, has been of 3000-7000 KN.
  • the coiler/uncoiler drawing reel values range has been of 100-450 KN.
  • Example 4 an austenitic steer 304 has been rolled with a not reversible rolling stand having two cages.
  • the 1 initial thickness of the product in course of manufacture has been reduced by 40%.
  • the strip instant speeds have been continuously measured and the acceleration has been measured as speed derivate.
  • a rolling speed measured during the second reduction has been of 50m/min and the speed value range has been of 0-120 m/min.
  • the values range of the separation force, force that is realized between roll and working material, has been of 10000-20000 KN.
  • the coiler/uncoiler drawing reel values range has been of 100-700 KN.
  • a flatness index I has been detected which corresponds to a low presence of defects, i.e. a I value between 0 and 5 l-unit.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Metal Rolling (AREA)
  • Coating With Molten Metal (AREA)
  • Laminated Bodies (AREA)

Abstract

The present invention refers to a method for dynamically controlling flatness in steel strip rolling, in function of: steel type, - thickness reduction rate, rolling steps number, comprising the following operations: measurements of instantaneous rolling parameters PLI, selected in the group comprising: speed and/or possibly acceleration as speed derivation and/or possibly separation force and/or possibly reel drawing, computerized elaboration suitable to evaluate on input the mentioned instantaneous rolling parameters, activation of a flatness control system. Figure 4 shows the functional diagram of the invention.

Description

Method for dynamically controlling flatness in steel strip rolling
Description
The present invention refers to a method for dynamically controlling flatness in steel strip rolling.
In particular, the invention refers to a method for dynamically controlling flatness in the rolling of a steel strip in cold rolling stands, by means of a human- machine interface and control algorithms.
As well known, the rolling is one of the most important industrial production process that permits to obtain planar products destined to very different industrial sectors such as the household appliance and the automobile ones.
The main objectives of the rolling mill process are:
- to give desired sizes, forms and surface finishing to the material, - to improve mechanical characteristics.
The rolling stand, i.e. the plant by which the rolling process is performed, is a set substantially constituted) by rolls and their supports (cage), motor and relevant transmission members.
The main parts of a rolltng,mill stand are: - working rolls, which are directly in contact with the rolled product, intermediate rolls,; as support of the working rolls, which are intended to reduce:the deflection under load, " - cage, designed to contain the stand components and oppose the
. rolling load, T guide train, to provide the rotation of the rolls at desired speed and torque, - - - actuators, to provide for the working rolls distance regulation, regulation mechanism of the pass line, to regulate the pass line height, . ; - flatness and profile actuators, to provide rolls regulation and achieve the expected rolled strip flatness and profile. The rolling mill can work; on-line, so as to produce a subsequent and progressive reduction of the rolled product thickness and length, or, in case of reversible rolling mill, following a forward and reverse pass. The rolling mill process can be realized as hot or cold rolling.
The hot rolling exploits the higf) material plasticity at high temperature and allows to obtain large deformations in case of reduced loads on rolling rolls. The cold rolling mill allows to have a good surface finishing and it is realized by means of limited deformations and high loads on rolling rolls. In this type of rolling, the strip is subjected tq the simultaneous traction and compression actions, for the reason that the rolling rolls cause a crushing and a partial stretching and, above all, keep the strip in tension (what doesn't happen in the case of hot rolli/ig).
The rolling is a working by plastic deformation, where the material in course of manufacture reaches the desired width and thickness, increasing its length.
The two principal problems that are faced during the rolling mill, in order to be able to realize high quality products with high productivity, are connected to the thickness and the flatness of the obtained product. The compression action of the rolls on the material in course of manufacture is rarely perfectly uniform along the total cross section and so the material undergoes a not uniform elongation in the rolling direction that produces different length increments in the fibers that constitute the material.
These length differences generate tensions inside the strips, that, in case they overcome the material stability limits, cause flatness defects.
These defects can be of different type as a function of several elements, such as: the geometry of the inlet material to be rolled , the rolls form, the forces distribution during the contact between rolls and material, the action of different devices tending to modify the form of rolling space. So, in the rolling mill process, to guarantee high quality and productivity, the objective is to have a strip which is as much as possible flat.
Flatness defects can cause even break of the material in course of manufacture, Le: when the u ndulations are such that the strip in course of manufacture is thickened under the rolling rolls, and consequently considerable idle plant problems are caused.
The flatness defects are quantified by an index named l-unit. Considering the strip as a set of adjacent fibers, the application of different forces on each longitudinal fiber will cause different increments of their length.
The l-unit is obtained by the comparison between two fibers lengths during the rolling of the plate. A fiber, generally the central one, is taken as reference whereas the remaining ones are compared with it.
The l-unit parameter (I) is given by the following expression:
I'= ΔL/Lx lθ5
where ΔL/L = plate sinuosity, L = plate length
In the steel-production, normally the following range of the flatness index are considered: low presence of defects 0<l<5 l-unit normal presence of defects 5<l<50 l-unit high presence of defects 50<l
To have information about the flatness, since it is not possible to measure the flatness itself directly during the rolling mill process, in particular during the cold rolling mill process, being applied in this phase a tension to the product in course of manufacture, different methods are today utilized that furnish indirect indications of the flatness.
For example, measurement approaches, based on radiation principle, are utilized. Such devices are based on] stationary meters, scanning meters that detect the plate thickness while it moves at right angle with respect to the rolling direction and profile calculation units .
It has been utilized measurement approaches based on the tension (stress-meters), that forecast an external tension applied to the product in course of manufacture, able to evaluates tension variations along the plate width and provide flatness indications, as described in WO2006132585 that refers to both a method and a device for the optimization of the flatness control in the rolling of a strip.
Moreover/ additional approaches exist, which are based on optical measurement such as: laser localization, optical and passive triangulation, holographic interferometry, speckle topography.
As a function of the'mentioned flatness measurements, corrective actions of the flatness control will be activated on the rolling mill, with the consequent activation of the flatness actuators. By means of the flatness control it is possible to reduce the discrepancy between what demanded and what is possible to obtain as a function of the rolling operative parameters- Today, in order to solve problems connected to the strip flatness, a flatness target is initially defined and fixed, i.e. a theoretic curve that represents the tensions distribution on the cross section of an optimal strip. This curve has the task of guaranteeing stable rolling condition and/or a strip form adapted to the downstream rolling process . and/or performances in agreement with the customer demand.
;The flatness measurement system provides the real strip flatness curve: the flatness control system, thusj modifies during the rolling process the set of the different devices equipping the rolling mill and acting on the rolling space form in order to make a coincidence between real measured flatness curve and the theoretical one.
Nevertheless, the systems nowadays in use, do not provide a dynamic solution but only a static solution fixed at the beginning of the manufacture (single pass) and followed during the whole working period (single pass), whilst the process conditions of the pass itself are not constant, with consequent variation of the. rolling space.
The rolling pass exhibits phases of acceleration, running speed, strip deceleration. These phases imply significant changes of the rolling parameters and consequently of the rolling space geometry. The changes are: the rolling force: the different speeds affect the lubrication conditions and consequently the strip-roll damping coefficient with resultant effects on the rolling loads size: low rolling speed increases rolling forces tend to increase and the strip edges tend to be hyper-rolled and lengthened, therefore not respecting the fixed reference values, temperature: the different rolling speeds generate different material deformation rates, to which heat generation corresponds; this implies that the rolling rolls temperature and, so, their thermal expansion change accordingly to different speeds, contact arc: due to the flattening of the working roll, the flattening resulting to be smaller at high speed, the strip-roll contact arc results to be shorter at high speeds.
It is felt, therefore, the necessity of providing a solution to the flatness problem, in the different working phases, as a function of the transition or running situation, giving a dynamic flatness profile.
In particular, the problem to avoid the following disadvantages is felt: incorrect flatness measurements done by the measurement equipments, - incorrect evaluations at low speed due to the low flatness control capacity due to the limited movement of the intermediate rolls, occurrence of uncontrolled flatness defects and of such size that determines hindrance and strip tears with rolls damage and production loss. The present invention allows to overcomes the previously mentioned disadvantages.
In fact, it is objective of the present invention a method for dynamically controlling flatness in steel strip rolling, as a function of: steel type, - thickness reduction rate, rolling steps number, comprising the following operations: measurements of instantaneous rolling parameters PLI, selected in the group comprising: speed and/or eventually acceleration as speed derivation and/or possibly separation force and/or possibly reel drawing,
- computerized elaboration suitable to evaluate on input the mentioned instantaneous rolling parameters, - activation of a flatness control system.
The dynamically controlling flatness method of the present invention provides a calculation algorithm of the dynamic flatness curve. In an embodiment of this invention this calculation algorithm consists in a polynomial function that, in particular, can be of eighth degree. This polynomial function is expressed by means of the following relation:
2 4 6 8 y(i) = A x(i) + A x(i) + A x(i) + A x(i) 2 4 6 8
wherein:
i: is a point on the strip transverse axis y(i): is the ordinate position of the i point on the strip transverse axis x(i): is the abscissa position of the i point on the strip transverse axis in correspondence to y(i) A A , A , A are functions of: 2, 4 6 8
- the real value of the instantaneous rolling parameters PLI,
- the admissible lower and upper limits of the instantaneous rolling parameters PLI,
- the material type, - the thickness reduction rate being, in the case in which the instantaneous rolling parameter includes only the speed,
A = c2 * [200 / (lower limit - upper limit)] * PU - [100 * (lower limit + upper limit) / (lower limit - upper limit)] / 100
A = c4 * [200 / (lower limit - upper limit)] * PU - [100 * (lower limit + upper 4 limit) / (lower limit - upper limit)] / 100
A = c6 * [200 / (lower limit - upper limit)] * PLI - [100 * (lower limit + upper 6 limit) / (lower limit - upper limit)] / 100 A = c8 * [200 / (lower limit - upper limit)] * PLI - [100 * (lower limit + upper 8 limit) / (lower limit - upper limit)] / 100
wherein c2, c4, c6 and c8 are functions of the steel type, thickness reduction rate, rolling steps number, with values in the range of -50 to +50 and wherein the speed admissible values are in the range of 0-800 m/min, the separation force values find between 2000 and 20000 KN and the reel drawing values are in the range of 100 to 700 KN.
The instantaneous rolling parameters PU can be used: - in case of alternative, in reciprocal substitution , in combination, by means of weighted mean summation with a weight percentage for the speed equal to 60%, for the acceleration equal to 30%, for the separation force equal to 5% and for the reel drawing equal to 5% in the change of the target flatness curve.
In this embodiment, the proposed method provides that, as a function of the instantaneous rolling parameters (speed, acceleration, forces, pulling,...) measurements during the working, during running and in particular during the transition phases, dynamic flatness target curves are elaborated by means of a eighth degree polynomial.
These curves are sent to the flatness control system that, comparing the dynamic flatness target curve (polynomial) and the measured flatness curve (by means of conventional flatness measurement devices), carries out the correction of the flatness defects. The flatness control system, in order to follow the instant target curve provided by the proposed system, effects the modifications by means of flatness control actuators action (intermediate rolls, side eccentric saddle, etc.).
In a variation of the so far described invention embodiment, the instantaneous rolling parameters include only the speed. So far, a general description of the present invention has been given. Invention embodiments will be described with the help of the figures and of the examples so as to better understand objectives, features, advantages and application modes.
Figure 1 shows some type of flatness defects. Figure 2 represent the block diagram of a well-known flatness control method.
Figure 3 shows the block diagram of the method according to present invention. Figure 4 shows the functional diagram of the method according to the present invention, where the mill stand and the coiler/uncoiler are respectively indicated with I and 2.
Example 1
According to the present example, an austenitic steel 304 has been rolled with a Sendzimir rolling stand.
The initial thickness of the product in course of manufacture has been reduced by 70% by means of 9 passes. During the single rolling pass the strip instant speeds have been continuously measured and the acceleration has been measured as speed derivate.
A rolling speed measured during the fifth pass has been of 400m/min and the speed value range has been of 200-800 m/min. The values range of the separation force, i.e. the force that is realized between roll and working material, has been of 3000-7000 KN.
The coiler/uncoiler drawing reel values range has been of 100-450 KN. The utilized values of the c2, c4, c6, c8 coefficients have been respectively 10, 0, 0, 50. On the basis of the measurements conducted by means of the indications given by the dynamic flatness curve according to the present invention, corrective actions have been carried out on the flatness profile by means of both an automatic control system and the driving of specific actuators (such as first intermediate rolls and eccentric saddles). In the reference example a flatness index I has been detected which corresponds to a low presence of defects, i.e. a I value between 0 and 5 l-unit.
Example 2
In this example, a ferritic steel 430 has been rolled with a Sendzimir rolling stand.
The initial thickness of the product in working has been reduced by 70% by means of 8 passes.
During the single rolling pass the strip instant speeds have been continuously measured and the acceleration has been measured as speed derivate.
A rolling speed measured during the third pass has been of 300m/min and the speed value range has been of 200-800 m/min.
The values range of the separation force, i.e. the force that is realized between roll and working material, has been of 2000-5000 KN. The coiler/uncoiler drawing reel values range has been of 100-450 KN. The utilized values of the c2, c4, c6, c8 coefficients have been respectively 5, 0, 0, 30.
On the basis of the measurements conducted by means of the indications given by the dynamic flatness curve according to the present invention, corrective actions have been carried out on the flatness profile by means of both an automatic control system and the driving of specific actuators (such as first intermediate rolls and eccentric saddles).
In the reference example a flatness index I has been detected which corresponds to a low presence of defects, i.e. a I value between 0 and 5 l-unit.
Example 3
According to the present example, a austenitic steel 304 has been rolled with a Sendzimir rolling stand.
The initial thickness of the product in working has been reduced by 70% by means of 9 passes.
During the single rolling pass the strip instant speeds have been continuously measured and the acceleration has been measured as speed derivate!
A rolling speed measured during the second pass has been of 60m/min and the speed value range has been of 10-800 m/min.
The values range of the separation force, i.e. the force that is realized between roll and working material, has been of 3000-7000 KN.
The coiler/uncoiler drawing reel values range has been of 100-450 KN.
The utilized values of the c2, c4, c6, c8 coefficients have been respectively 10, 0, 0, 50.
On the basis of the measurements conducted by means of the indications given by the dynamic flatness curve according to the present invention, corrective actions have been carried out on the flatness profile by means of both an automatic control system and the driving of specific actuators (such as first intermediate rolls and eccentric saddles).
In the reference example it has been detected a flatness index I corresponding to a low presence of defects, i.e. a I value between 0 and 5 l-unit.
Example 4 According to the present realization example, an austenitic steer 304 has been rolled with a not reversible rolling stand having two cages.
The1 initial thickness of the product in course of manufacture has been reduced by 40%. During the single rolling pass, the strip instant speeds have been continuously measured and the acceleration has been measured as speed derivate.
A rolling speed measured during the second reduction has been of 50m/min and the speed value range has been of 0-120 m/min.
The values range of the separation force, force that is realized between roll and working material, has been of 10000-20000 KN.
The coiler/uncoiler drawing reel values range has been of 100-700 KN.
The utilized values of the c2, c4, c6, c8 coefficients have been respectively 10, 0, 0, 50.
On the basis of the measures conducted by means of the indications given by the dynamic flatness curve according to the present invention, corrective actions have been carried out on the flatness profile by means of both an automatic control system and the driving of specific actuators (such as first intermediate rolls and eccentric saddles).
In the reference example a flatness index I has been detected which corresponds to a low presence of defects, i.e. a I value between 0 and 5 l-unit.

Claims

Claims
1. Method for dynamically controlling flatness in steel strip rolling, in function of: steel type, - thickness reduction rate, rolling steps number, comprising the following operations: measurements of instantaneous rolling parameters PLI, selected in the group comprising: speed and/or possibly acceleration as speed derivation and/or possibly separation force and/or possibly reel drawing, computerized elaboration suitable to evaluate on input the mentioned instantaneous rolling parameters, activation of a flatness control system.
2. Method for dynamically controlling flatness in steel strip rolling, according to claim 1, wherein said computerized elaboration includes a dynamic flatness curve calculation algorithm.
3. Method for dynamically controlling flatness in steel strip rolling, according to claim 2, wherein said calculation algorithm is a polynomial function.
4. Method for dynamically controlling flatness in steel strip rolling, according to claim 3, wherein said polynomial function is of eighth degree.
5. Method for dynamically controlling flatness in steel strip rolling, according to claim 4, wherein said polynomial function is expressed by means of the following relation:
2 4 6 8 y(i) = A x(i) + A .x(i) + A_ x(i) + A| x(i) 2 4 6 8 wherein: i: is a point on the strip transverse axis y(i): is the ordinate position of the i point on the strip transverse axis x(i): is the abscissa position of the i point on the strip transverse axis in correspondence with y(i)
A A , A , A are functions of: 2 4 6 8 the real value of the instantaneous rolling parameters PLI, the admissible lower and upper limits of the instantaneous rolling parameters PLI, - the material type, the thickness reduction rate being, A = c2 * [200 / (lower limit - upper limit)] * PU - [100 * (lower limit + upper limit) / (lower limit - upper limitjjl/ 100
A = c4 * [200 / (lower limit - upper limit)] * PLI - [100 * (lower limit + upper 4 limit) / (lower limit - upper limit)] / 100 A = c6 * [200 / (lower limit - upper limit)] * PLI - [100 * (lower limit + upper 6 limit) / (lower limit - upper limit)] / 100
A = c8 * [200 / (lower limit - upper limit)] * PLI - [100 * (lower limit + upper 8 limit) / (lower limit - upper limit)] / 100 wherein c2, c4, c6 and c8 are functions of the steel type, thickness reduction rate, rolling pass numbers, with values in the range of -50 to +50.
6. Method for dynamically controlling flatness in steel strip rolling, according to claim 5, wherein said instant rolling parameters PLI, are utilized: in case of alternative, in reciprocal substitution , in combination, by means of weighted mean summation with a weight percentage for the speed equal to 60%, for the acceleration equal to 30%, for the separation force equal to 5% and for the reel drawing equal to 5% in the change of the target flatness curve.
7. Method for dynamically controlling flatness in steel strip rolling, according to any claim 4-6, wherein the speed values are in the range of 0 to 800 m/min.
8. Method for dynamically controlling flatness in steel strip rolling, according to any claim 4-7, wherein the separation forces values are in the range of 2000 to 20000KN.
9. Method for dynamically controlling flatness in steel strip rolling, according to any claim 4-8, wherein the reel drawing values are in the range of 100 to 700
KN.
10. Method for dynamically controlling flatness in steel strip rolling, according to any claim 5-7, wherein the instant rolling parameters include only the speed.
PCT/IT2010/000270 2009-06-17 2010-06-17 Method for dynamically controlling flatness in steel strip rolling WO2010146615A1 (en)

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ITRM2009A000306A IT1394608B1 (en) 2009-06-17 2009-06-17 METHOD FOR DYNAMIC CONTROL OF FLATNESS IN THE LAMINATION OF A STEEL TAPE.

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CN105436211A (en) * 2015-12-17 2016-03-30 太原重工股份有限公司 Shape closed-loop feedback control method for single-stand reversing six-roller rolling unit
CN110232232A (en) * 2019-05-31 2019-09-13 宝钢湛江钢铁有限公司 One kind being suitable for continuous annealing incoming profile aim curve optimal setting
CN110851994A (en) * 2019-11-21 2020-02-28 燕山大学 Online shape target curve adjusting method for cold-rolled strip
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CN116343360A (en) * 2023-03-28 2023-06-27 东北大学 Continuous prediction method for longitudinal thickness of cold-rolled strip steel based on data driving
CN116881613A (en) * 2023-09-05 2023-10-13 东北大学 Setting method of high-order item plate-shaped target curve based on flatness

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US10661322B2 (en) 2013-03-25 2020-05-26 Abb Schweiz Ag Method and control system for tuning flatness control in a mill
CN105436211A (en) * 2015-12-17 2016-03-30 太原重工股份有限公司 Shape closed-loop feedback control method for single-stand reversing six-roller rolling unit
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CN116343360A (en) * 2023-03-28 2023-06-27 东北大学 Continuous prediction method for longitudinal thickness of cold-rolled strip steel based on data driving
CN116881613A (en) * 2023-09-05 2023-10-13 东北大学 Setting method of high-order item plate-shaped target curve based on flatness
CN116881613B (en) * 2023-09-05 2023-12-01 东北大学 Setting method of high-order item plate-shaped target curve based on flatness

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