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
  • B21B37/30—Control of flatness or profile during rolling of strip, sheets or plates using roll camber control
  • B21B37/32—Control of flatness or profile during rolling of strip, sheets or plates using roll camber control by cooling, heating or lubricating the rolls

Definitions

• the invention relates to a method for influencing relevant quality parameters of a rolled strip according to the preamble of claim 1 and a device for influencing relevant quality parameters of a rolled strip according to the preamble of claim 8.
• Hot rolling stock with temperatures between 800 - 1200 ° C causes the work rolls to heat up noticeably and the resulting thermal expansion.
• the result is the so-called thermal crowning of the work rolls, which has a direct influence on the thickness, thickness cross profile and flatness of the strip.
• the geometry of the strip cross-section is influenced by the geometry of the rolls in a roll stand, that is, the crowning of the rolls. It is known to control the thermal crown by means of appropriate actuators such as adjustment, bending force, etc. to compensate.
• This method comes e.g. B. in so-called CVC or taper rollers to wear.
• CVC rollers can only be preset in the unloaded state. Therefore, they are used only for the default.
• this process is extremely complex and costly and leads to a reduction in the service life of a roll stand.
• the object of the invention is to provide a method which allows the geometry of a rolled strip to be influenced in a simpler manner.
• the invention has for its object to provide a device that allows the To influence the geometry of a rolled strip in a simpler way.
• the object is achieved according to the invention by a method according to claim 1 or by a device according to claim 8.
• the relevant quality parameters of a rolled strip are influenced in a roll stand with rolls by adjusting the crowning of the rolls, i. H. the surface geometry of the rolls in the longitudinal direction of the rolls, the crowning of the rolls being set by adjustable cooling of the rolls or their surface in the longitudinal direction of the rolls, and the setting of the cooling of the rolls by means of a controller depending on an actual value of the crowning and a predetermined value Setpoint of crowning is done.
• the control algorithm of the controller is preferably a fuzzy logic algorithm.
• a forward-looking control takes place with a view of the next rolled strip or advantageously of the next strips in analogy to the method disclosed in DE 196 18 995 A1 and in the corresponding US Pat. No. 5,855,131 A.
• This is very advantageous because the thermal crowning reacts only sluggishly to the environment (water cooling) (controlled system with delay).
• the setting of the thermal crowning is carried out in such a way that sufficient reserves of other (delay-free) manipulated variables regarding profile and flatness remain available.
• the appropriate controller setpoints are provided by an associated pass schedule calculation.
• FIG. 1 shows a first embodiment of the device according to the invention
• FIG. 3 shows a first embodiment of the controller used in the device according to FIG. 1,
• FIG. 4 shows a second embodiment of the controller used in the device according to FIG.
• reference numeral 2 denotes a controlled system, ie a cooling device and the rolls of a roll stand, in which the cooling of the rolls is set according to a value k, which is the output variable of a controller 1.
• the controller 1 calculates the quantity k as a function of the difference between the setpoint p so ⁇ (z, t) and an estimated value P ⁇ St (z, t) of the crowning of the rollers.
• the estimated value p lst (z, t) of the thermal crowning is determined using a roller model 3 as a function of the value k.
• the values p so ⁇ (z, t), P ⁇ st (zt), p (z, t) and k are generally not scalars, but vectors. They advantageously designate a thickness distribution with respect to Psoii (z, t), p ls (z, t) and p (z, t) and with respect to k a coolant distribution in the longitudinal direction of the rolls. It is particularly advantageous to represent the thickness distribution and the coolant distribution not by individual support points, but by polynomials and their parameters. This is illustrated in FIG. 2.
• the coolant distribution dependent on the value k is determined, for example, by three parameters V ⁇ r V 2 and V 3 (volume flows of the Cooling water) is reproduced which form the output variables of the Reg- "coupler 1 and supplied to the rolling model 3.
• V ⁇ r V 2 and V 3 volume flows of the Cooling water
• an approximated actual value a 'of the crowning is determined, which on the one hand is used for other applications in the system and on the other hand is fed back to a comparator 6 connected upstream of the controller 1.
• controller setpoint In addition to the set parameters for the current band, the controller setpoint also still includes the set parameters for the next band or for the next bands.
• the shape of the thermal crown of the work rolls is to be influenced with the aid of targeted cooling strategies. It has been shown that the thermal expansion in the middle of the roller is not relevant, since this can be compensated for by the adjustment of the rollers.
• the thermal crowning related to the center of the roll is therefore defined as:
• Quality criterion can e.g. B. be the quadratic quality index:
• the roller temperature model calculates the thermal expansion of the roller as a function of its axial position by solving the three-dimensional Fourier 1 heat conduction equation, taking into account the boundary conditions on all surfaces of the roller.
• the assumption is made that the thermal expansion is almost independent of the circumferential direction, since the areas in which azimuthal influences play a role are due to the roll rotation only in a thin layer below the roll surface. This assumption can be confirmed by three-dimensional numerical reference calculations.
• ⁇ ( ⁇ , z, t) ⁇ c ( ⁇ , z, t) (4)
• the heat flows through the pins should also not be taken into account here, since they only have a long-term influence on the thermal deformation of the roll in the area of the belt contact and therefore have no effect on the quality of a roll crown control.
• the distribution of the heat transfer coefficient of the water is determined by the distribution of the specific volume flow of the cooling water at the roll surface over a generally non-linear characteristic.
• This characteristic curve can also be subject to other influences such as the surface temperature of the roller and must be suitably modeled.
• the distribution of the volume flow must be determined using a suitable model from the geometrical arrangements of the roller, chilled beams and nozzles in the roll stand and the N independent supply volume flows in the individual cooling circuits V_ (t):
• v ( ⁇ , z, t) F v ( ⁇ , z, V ⁇ (t), V 2 (t), V N (t))
• the specific heat flow from the roll gap qg ( ⁇ , z, t) is calculated using a suitable roll gap model.
• a fuzzy controller the mode of operation of which is shown in FIG. 3, has proven to be particularly suitable for such a complex set of rules.
• fuzzy controller has to be adapted to every problem, cannot be applied to strategically different cooling concepts in the same way and the adjustment effort with increasing number of independent cooling circuits (greater than 3) due to the exponentially increasing number of rules grows.
• the controller can therefore be designed as an energy balance controller based on the following assumptions: •
• the volume flows can be gradually adjusted from the current operating point.
• the step size can be specified, but it is a maximum of the positioning range of the valves in the sampling interval.
• the current thermal expansion of the roller and its surface temperature distribution are available either in the form of measured values or in the form of calculated values from an observer.
• the thermal expansion at an axial position is proportional to the mean temperature averaged in the circumferential and radial directions at the axial position:
• T 0 is the reference temperature
• ß is the coefficient of thermal expansion. This relationship can be shown by neglecting mechanical stresses.
• the associated, expected profiles standardized to the band are approximately calculated with an energy approach, which is described further below.
• the volume flows can be changed continuously in both directions, this results in 3 N combinations. If the cooling circuits can only be switched on or off, 2 N combinations result.
• the combination that minimizes the (square) error area between the expected thermal crowning and the target crowning in the next time step is used as the manipulated variable for the volume flows.
• This method corresponds to a method of the steepest zero-order descent since no sensitivities have to be calculated here.
• the process can be transferred to other cooling concepts.
• the computing effort increases exponentially with the number of independently controllable cooling circuits.
• the descent according to the sensitivities according to the individual volume flows is also conceivable.
• a sensitivity model had to exist which either calculated the sensitivity of the boundary conditions from the changes in the volume flows of the individual cooling circuits directly or estimated them by small deflections.
• Tr, ⁇ , z, t temperature distribution in the roller T c coolant temperature
• T (z, t) radially and azimuthally averaged temperature T 0 reference temperature for the thermal expansion E (z, tJ thermal energy of a disc at the position

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Control Of Metal Rolling (AREA)
• Metal Rolling (AREA)

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• 1999
  • 1999-12-10 DE DE19959553A patent/DE19959553A1/de not_active Ceased
• 2000
  • 2000-06-15 AT AT00949106T patent/ATE249291T1/de active
  • 2000-06-15 DE DE50003655T patent/DE50003655D1/de not_active Revoked
  • 2000-06-15 EP EP00949106A patent/EP1185385B1/fr not_active Revoked
  • 2000-06-15 WO PCT/DE2000/001960 patent/WO2000078475A1/fr active IP Right Grant
• 2001
  • 2001-12-17 US US10/015,562 patent/US6697699B2/en not_active Expired - Fee Related

Non-Patent Citations (1)

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