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
  • B21B37/16—Control of thickness, width, diameter or other transverse dimensions
  • B21B37/18—Automatic gauge control
• • 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
  • B21B37/16—Control of thickness, width, diameter or other transverse dimensions
  • B21B37/165—Control of thickness, width, diameter or other transverse dimensions responsive mainly to the measured thickness of the product
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B15/00—Arrangements for performing additional metal-working operations specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
  • B21B2015/0057—Coiling the rolled product
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B2261/00—Product parameters
  • B21B2261/02—Transverse dimensions
  • B21B2261/04—Thickness, gauge
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B38/00—Methods or devices for measuring, detecting or monitoring specially adapted for metal-rolling mills, e.g. position detection, inspection of the product
  • B21B38/04—Methods or devices for measuring, detecting or monitoring specially adapted for metal-rolling mills, e.g. position detection, inspection of the product for measuring thickness, width, diameter or other transverse dimensions of the product

Definitions

• the invention relates to a method and a device for correcting the thickness of a metallic strip during rolling with a roll stand with adjusting elements for regulating the thickness of the metallic strip and at least one take-up reel.
• the rolled metallic strips are wound as a bundle on a winding reel after passing through a roll stand.
• An important quality feature of the rolled strip rolled as a bundle is, among other things, the thickness of the strip and its fluctuations.
• the thickness of the metallic strip has been determined using a radiometric measuring method and the control elements of the roll stand have been controlled depending on this value.
• the radiometric measuring method the radiation transmitted by the metallic band of an emitter arranged on the other side of the metallic band is measured with the aid of a detector arranged on one side of the metallic band. The radiation measured by the detector is dependent on the absorption in the metallic band, which is determined in particular by the thickness of the metallic band.
• the deviation of the radiometrically determined strip thickness A setpoint of the thickness of the strip is used as an input variable for controlling actuating elements of the roll stand to influence the thickness of the metallic strip.
• the radiometric thickness measurement value depends on other influencing factors, for example the alloy composition of the strip, the air density and air temperature in the measuring path, for example when blowing off or extracting heated air, the proportion of coolant and lubricant mist in the measuring path and the temperature of the rolling stock and the like System components for determining the thickness. It is therefore absolutely necessary to determine the influencing variables and standardize the radiometric measuring method to the additional influencing variables.
• a disadvantage of the previously known method for correcting the strip thickness of a metallic strip during rolling is that the influencing variables cannot be determined and the radiometric measuring method cannot be standardized to these influencing variables under rolling conditions.
• To correct the alloy-dependent absorption behavior of the metallic strip it is necessary to measure the alloy composition on a cast sample using spark spectrometry and use it to calculate an absorption index for the alloy, which is taken into account in the radiometric measurement process.
• Variations in sampling and measurement uncertainties in spark spectrometry mean that the radiometrically determined thickness is provided with a confidence interval that must be taken into account depending on the product requirements.
• the electrical zero point of the detector signal is used with the radiator diaphragm closed, on the other hand, in the case of full irradiation, i.e. without a sample in the measurement path, a compensation factor is determined which takes into account the absorption conditions in the measurement section at this time. This happens automatically during the change of the bundle or every time the emitter aperture is opened without the material to be measured. With the help of the measurement of the temperature change and an empirical weighting factor determined from this, the temperature change in the measuring path with rolling stock is inferred. It is not possible to record the integral temperature profile in the measuring path, which shows strong variations during rolling due to the hot rolled strip. The integral temperature profile can therefore not be taken into account in the radiometric thickness determination.
• control standards i.e. metallic sheets, the absorption properties of which do not change except due to temperature changes.
• the absorption curve stored in the measuring system can be corrected by checking the thickness measurement values of these control standards.
• this adjustment can also only be carried out when the rolling process is interrupted.
• the present invention is based on the object of providing a method and a device for correcting the thickness of a metallic strip during rolling with a roll stand, which or the manufacture of rolled strips with a guaranteed reduced thickness tolerance.
• the previously derived and demonstrated object is achieved in terms of method in that an average strip thickness of a strip section is determined from at least one strip length measurement and the measurement of the associated rotation of the winding reel, and the adjusting elements of the roll stand are at least dependent on the determined average strip thickness of the band section can be controlled.
• This takes advantage of the fact that the average layer spacing of the tape on the take-up reel is linked to the measured tape length and take-up reel turn, from which the average tape thickness can be determined using a fill factor.
• the required measurements of the strip length and the take-up reel rotation are almost independent of the influencing variables of the radiometric thickness measurement, so that a measured value of the average strip thickness of a strip section is available that is independent of the ambient conditions of the roll stand. It has been shown that a sufficiently precise value for the average strip thickness can be determined even after short strip lengths.
• the strip thickness is also measured radiometrically and the adjusting elements of the roll stand are controlled as a function of a radiometric strip thickness corrected with the mean strip thickness
• This provides an input variable for controlling the strip thickness when rolling a metallic strip, which on the one hand enables the control elements to be influenced almost instantaneously and on the other hand can be corrected independently of the typical influencing variables of the radiometric determination of the strip thickness during the rolling process.
• the strip length is measured using the laser Doppler velocimetry method.
• the laser Doppler velocimetry method (LDV method) is a standard method for measuring flow velocities. The principle is to detect and evaluate the scattered light from a particle, which is one generated by a laser source Crossed interference fringing system. The frequency of the received signal is then proportional to the particle speed. If the interference fringe system is imaged on the rolled strip, the speed of the rolled strip can be determined very precisely by means of scattered light evaluation. This provides a highly accurate tape length measurement for determining the average tape thickness of a tape section.
• the number of revolutions of the take-up reel is measured using high-resolution incremental encoders on the take-up reel axis or take-up reel motor axis, the number of revolutions of the take-up reel required to determine the average strip thickness can be determined in a simple manner with sufficient accuracy.
• the method according to the invention has an advantageous embodiment in that a plurality of values for the average strip thickness of the same strip section are determined by selecting a plurality of different starting points and strip lengths to be measured for determining the average strip thickness.
• This measure makes it possible to carry out a statistical evaluation of the values of the average strip thickness of a strip section and to reduce the measurement error when determining the average strip thickness of a strip section, so that the strip thickness tolerances of the rolled strip can be further reduced.
• the influence of the reeling process on the filling factor can, according to a further developed embodiment of the method according to the invention, be taken into account in that the values for the average strip thickness of the same strip section are additionally smoothed with variable weighting depending on the current coil diameter of the strip on the reel. This can prevent fluctuations in the coil diameter from having a greater impact on the determination of the average strip thickness, particularly at the start of the reeling process.
• the process reliability in determining the average strip thickness can be further increased by carrying out at least one further, redundant strip length measurement in accordance with an advantageous embodiment of the method according to the invention.
• the system automatically switches to a further, redundant strip length measurement, it can be ensured that the dynamic thickness correction can be carried out continuously, even if a strip length measurement system fails. The rolling process therefore does not have to be interrupted.
• the derived and demonstrated object is achieved with a device for correcting the thickness of a metallic strip during rolling with at least one roll stand with adjusting elements for regulating the thickness of the strip, at least one take-up reel and means for Measurement of the strip length and the extent of the associated rotation of the take-up reel are solved in that means are provided for controlling the adjusting elements of the roll stand as a function of an average strip thickness determined from the measured strip length and the associated rotation of the take-up reel.
• this measure enables the strip thickness of a metallic strip to be measured and adjusted almost independently of the ambient conditions of the roll stand during rolling.
• an input variable for controlling the adjusting elements is available immediately after the strip is rolled, if additional means for radiometric thickness determination of the metallic strip are provided between the roll stand and the reel.
• additional means for radiometric thickness determination of the metallic strip are provided between the roll stand and the reel.
• the device according to the invention has an advantageous embodiment in that means for redundant tape length measurement are provided. On the one hand, this can increase the process reliability during rolling in relation to the failure of a strip length measuring system, and on the other hand, the respective strip length measurement can be checked by the redundant strip length measurement, so that its accuracy can be increased. In addition, the accuracy of the tape length measurement can be further increased by providing a laser Doppler velocimetry system for tape length measurement in accordance with a further developed embodiment of the device according to the invention.
• Fig. 2a in a schematic representation, the method used in the first embodiment Determination of the average strip thickness from a strip length measurement
• Fig. 2b in a sectional view of a take-up reel with several layers of a metallic tape
• Fig. 3 in a block diagram the control of a next embodiment of a device for correcting the thickness of a metallic strip during rolling.
• FIG. 1 of a device for correcting the thickness of a metallic strip 1 during rolling has a rolling stand 2 with adjusting elements (not shown) for regulating the thickness of the strip 1, a deflection roller 3 and a take-up reel 4.
• an LDV system 5 for measuring the strip length an incremental encoder 6 on the take-up reel axis 7 and a radiator 8 and a detector 9 for radiometric determination of the strip thickness are shown.
• the metallic strip 1 after it has left the roll stand 2 is deflected via a deflection roller 3 and wound up on the reel 4.
• An average strip thickness can be calculated from the number of revolutions of the take-up reel 4 and the associated strip length.
• FIG. 2a shows the basic sequence of the method for determining the average strip thickness of a metallic strip 1 with the aid of an LDV system 5 and a take-up reel 4.
• the LDV system 5 measures the length of the strip when winding the strip 1 onto it Take-up reel 4, the first layer of tape 1 taking up a radius r which is fixed by take-up reel 4.
• FIG. 2b shows a sectional view of a take-up reel 4 with several layers of a metallic strip 1 wound on it.
• the mean layer spacing h of the wound strip 1 results from the difference in radii of the radii r m and r n and the number of layers wound between the radii, the corresponding number of revolutions of the take-up reel 4. The following therefore applies to the average layer spacing h between any two take-up radii r m and r n :
• L n is the length running from an arbitrary starting point
• n is the associated number of revolutions of the take-up reel 4
• L m is a fixed length from the same starting point
• m is the associated number of revolutions of the take-up reel 4 to the fixed length L m .
• the deflection roller 3 can in principle also be used to measure the band lengths L n or L m , but a contactless and slip-free measurement with the LDV system 5 is preferable, since this enables a much more precise band length measurement becomes.
• High-resolution incremental encoders 6, which are arranged on the take-up reel 7, provide the associated number n or m of revolutions of the take-up reel. With these measured values is first a Average layer spacing h is calculated according to the above formula, so that the average strip thickness of a strip section can be calculated from h using a fill factor.
• the calculation of the average strip thickness takes place according to an adjustable strip length with the aid of the computer 10, which on the one hand displays the measured average strip thickness on the display 11 and on the other hand forwards the value for dynamic thickness correction to a first comparison device 12.
• the comparison device 12 the value of the average strip thickness is compared with the target thickness 13 of the strip 1 and the difference is passed on to a next comparison device 14 as a dynamic thickness deviation.
• the value of the dynamic thickness deviation is added to the radiometric band thickness 15 determined with the aid of the radiator 8 and the detector 9, and another as a dynamically corrected actual thickness 16 in the comparison device 14
• Comparator 17 supplied. This now determines the controlled variable for the control of the actuating elements 18 from the deviation of the dynamically corrected actual thickness 16 from the target thickness 13.
• the value of the dynamic thickness correction can be sufficient during the rolling process after short strip lengths, for example after a wound strip length of approx. 50 m can be determined exactly. Although this does not apply to the beginning of the rolling process, since in this case the fluctuations due to the winding process are still too large, there is a possibility of correcting the radiometrically determined strip thickness 15 in the further course of the rolling process, which is independent of the influencing variables of the radiometric strip thickness measurements , By excluding these influencing factors, the Control of the control elements of the rolling stand 18 can be carried out much more precisely, which leads to a significant reduction in the strip thickness tolerances.
• 3 shows the block diagram of the control of a corresponding exemplary embodiment of a device for correcting the thickness of a metallic strip during rolling.
• the parameters, sizes and conditions mentioned below are only to be regarded as an example configuration of the control, which can vary depending on the rolling stock to be produced ,
• the block diagram shown in FIG. 3 initially has a logic AND gate 19 with 6 inputs 20, 21, 22, 23, 24, 25 and an output 26.
• the inputs 20 to 24 can be used, for example, to determine whether the laser is functional, whether the nominal thickness is more than 0.8 mm, whether data on the alloy of the alloy is stored in a table, whether manual or automatic mode is selected and whether the Belt speed is greater than 100 m / min, for example, queried and used to activate the thickness correction. Additional conditions can be taken into account via additional inputs on the AND gate 19.
• the input 25 of the AND gate 19 is connected to the output of a logical OR gate 27, which in turn has two inputs 28 and 29, which are connected to the output of the comparison elements 30 and 31, respectively are.
• the comparator 30 the actual value of the strip length 32 is compared with a starting value of the strip length 35 calculated from the target thickness 33 via a functional element 34, and an output signal is switched to the OR gate 27 as soon as the actual value of the strip length 32 is above a certain starting value of the strip length 35 lies.
• the comparator 31 compares the absolute value of the difference 39 between the nominal thickness 33 and the mean strip thickness 37 determined with the LDV method with the value 33 dependent on the nominal thickness 33 using the difference element 36. If the absolute deviation is less than, for example, 1% of the target thickness, the output of the comparison element 31 is switched on and a signal is present at the input 29 of the OR element 27.
• the deviation of the average strip thickness 37 from the target thickness 33 is less than 1% of the target thickness or the actual value of the strip length 32 is greater than a start value of the strip length 35, then a signal is present at the input 25 of the AND element 19. If the inputs 20 to 25 of the AND element 19 are connected, the output 41 of the logic circuit is set to “auto correction switched on” via the output 26 of the AND element 19 with the aid of the setting element 40 of the PID element 43.
• the PID element 43 determines the dynamic thickness correction 44 of the radiometrically measured actual thickness 46 from the control deviation in the form of the difference 39 between the nominal thickness 33 and the mean band thickness 37 determined with the LDV method
• the regulation of the PID element 43 can, however, be prevented by a comparison element 46 connected to the PID element 43, provided that the control deviation 39 is, for example, less than 1% of the target thickness 33.
• the dynamic thickness correction 44 is now added to the measured actual thickness 45 in the adder 47 and is applied as a corrected actual thickness 48 to the input 49 of a switch 50.
• the output 51 of the switch 50 is in turn connected directly to an input, not shown, for the control of the control elements of the roll stand.
• the switch 50 connects the input 49 to the output 51 and the actuating elements of the roll stands are controlled with the corrected actual thickness 48 In the control of the control elements, not shown, the value output via the output 51 is compared again with the target thickness 33 and the control elements of the roll stand 2 are controlled accordingly.
• the switch 50 it is possible to use the switch 50 to manually switch the control of the actuating elements to the actual thickness 46 by connecting the output 51 of the switch 50 to the input 52 of the switch 50.
• an automatic switchover to the control with the actual thickness 46 can also take place, namely when the reset element 54 is used to reset the output 41 via the OR element 53.
• the input 55 of the OR link 53 which checks the operating state of the emitter in the run-out, or the input 56 of the OR link 53, which monitors the falling below a minimum value for the belt speed, a signal.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Control Of Metal Rolling (AREA)
• Length Measuring Devices By Optical Means (AREA)
• Particle Accelerators (AREA)
• Details Of Television Scanning (AREA)
• Surface Acoustic Wave Elements And Circuit Networks Thereof (AREA)
• Length-Measuring Devices Using Wave Or Particle Radiation (AREA)
• Winding, Rewinding, Material Storage Devices (AREA)
• Measuring And Recording Apparatus For Diagnosis (AREA)
• Metal Rolling (AREA)

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