Cooling of a metal strip using a position-controlled valve device

Abstract

To cool a metal strip (1), liquid coolant (5) is supplied to the strip by a supply device (9) from a feed line (10). A valve (13) in the feed line (10) sets the valve (13) to a respective opening position (s) for adjusting the coolant flow (F) to the metal strip (1) per unit of time. An upstream condition detection device (14) upstream of the valve device (13) in the feed line (10) detects an upstream condition (ZV) of the coolant (5). A control unit (6) determines a set point (s*) for an opening position (s) of the valve device (13) corresponding to the set point (F*) for the coolant flow (F) based on a set point (F*) for the coolant flow (F*), the upstream condition (ZV) of the coolant (5) and a valve characteristic (C) of the valve device (13). The valve characteristic (C) follows a characteristic curve (K) of the coolant flow (F) as a function of the opening position (s) of the valve device (13), relative to a reference condition (ZR) of the coolant (5) upstream of the valve device (13) in the feed line (10). The control unit (6) sets the opening position (s) of the valve device (13) according to the set point (s*) that has been determined.

Claims

1. An operating method using a cooling device for cooling a metal strip by means of a liquid coolant; wherein the cooling device includes an application device configured for applying coolant to the metal strip, and a valve device arranged in a feed line for the coolant, the valve device having a plurality of open positions, and the valve device exhibiting a characteristic coolant flow (K): 1) at a given pressure that is applied to the coolant in the feed line upstream of the valve device, and 2) at an open position from among the plurality of open positions, the characteristic coolant flow having a unique value at a given pressure that is applied to the coolant in the feedline upstream of the valve device and an open position from among the plurality of open positions, and wherein the cooling device is configured to receive a set point value (F*) for a desired coolant flow (F) to flow out of the valve device that is applied per unit of time to the metal strip by the application device; the method comprising: feeding the coolant to the application device by the feed line for feeding the coolant; receiving by a control device that controls the cooling device the set point value (F*) for a desired coolant flow (F) to flow out of the valve device that is applied per unit of time to the metal strip by the application device; detecting by a pressure detection device an upstream condition (ZV) of the coolant in the feed line upstream of the valve device, the upstream condition (ZV) being an upstream feed-line pressure (pV) applied to the coolant in the feed line upstream of the valve device; determining by the control device of the cooling device a setpoint value (s*) for the open position from among the plurality of open positions of the valve device that would result in the desired coolant flow from the valve device, based on the set point valve (F*) for the desired coolant flow (F) to flow out of the valve device, and the characteristic coolant flow (K) of the valve device at the detected upstream condition (ZV) of the coolant; and opening the valve device to an open position from among the plurality of open positions that corresponds to the determined setpoint value (s*) to obtain the desired coolant flow (F) to flow out of the valve device.

2. The operating method as claimed in claim 1, further comprising: detecting a downstream condition (ZH) of the coolant in the feed line between the valve device and the application device or in the application device; and correcting the characteristic line (K) of the valve device based on the upstream condition (ZV) of the coolant, the downstream condition (ZH) of the coolant and the open position of the valve device.

3. The operating method as claimed in claim 2, wherein the downstream condition (ZH) of the coolant comprises a downstream feed-line pressure (pH) that is applied to the coolant in the feed line between the valve device and the application device or in the application device.

4. The operating method as claimed in claim 1, wherein the upstream feed-line pressure (pV) of the coolant in the feed line upstream of the valve device lies between 1.5 bar and 5.0 bar.

5. The operating method as claimed in claim 1, wherein the upstream feed-line pressure (pV) of the coolant in the feed line upstream of the valve device lies between 2.0 bar and 3.0 bar.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a handling line for a metal strip,

(2) FIG. 2 shows a cooling device and

(3) FIG. 3 shows a valve characteristic.

DESCRIPTION OF AN EMBODIMENT

(4) According to FIG. 1, a handling line for a metal strip 1 has at least one rolling stand 2usually a number of rolling stands 2 in tandem arrangementand a coiling device 3. In the rolling stands 2, the metal strip 1 is rolled. Then, the metal strip 1 is coiled by the coiling device 3. Between the rolling stands 2 and/or between the last rolling stand 2 and the coiling device 3, cooling devices 4 may be arranged.

(5) The cooling devices 4 cool the metal strip 1 with a liquid coolant 5. The liquid coolant 5 is generally water, or at least contains water as a main constituent.

(6) The handling line is controlled by a control device 6. The control device 6 may comprise a number of subunits, which respectively control part of the handling line.

(7) The present invention depends on the control device 6 to control at least one of the cooling devices 4. Therefore, just one of the cooling devices 4 is discussed below in conjunction with FIGS. 2 and 3as representative of all the cooling devices 4.

(8) As indicated by the abbreviation C, the control device 6 is formed as a software-programmable control device. It is programmed with a computer program 7 stored on a machine readable, non-transitory storage medium of a computer program product. The computer program 7 comprises machine code 8, which can be executed directly by the control device 6. The processing of the machine code 8 by the control device 6 brings about the internal functionality of the control device 6, which is explained more specifically below in conjunction with the overall functioning mode of the cooling device 4 considered.

(9) According to FIG. 2, the cooling device 4 has an application device 9. The application device 9 is used to apply the coolant 5 to the metal strip 1. The application device 9 may for example be formed as an upper spray bar, by means of which the coolant 5 is applied to the metal strip 1 from above. Alternatively, the application device 9 may for example be formed as a lower spray bar, by means of which the coolant 5 is applied to the metal strip 1 from below. Other refinements are also possible.

(10) The coolant 5 is fed to the application device 9 by a feed line 10 from a reservoir 11. A pump 12 is arranged in the feed line 10. The pump 12 applies the coolant 5 is applied with a pressure pV, hereinafter referred to as the upstream feed-line pressure pV. A valve device 13 is also arranged in the feed line 10. between the pump 12 and the application device 9.

(11) The valve device 13 is formed as a servo valve. By appropriate setting of the valve device 13 to a respective opening position s, thereforesee FIG. 3a coolant flow F that is applied per unit of time to the metal strip 1 by the application device 9 can be set. It is possible that the opening position s, and consequently also the coolant flow F, can be set steplessly between 0 and a maximum flow, in a way corresponding to the solid line in FIG. 3. Alternatively, it is possible that the opening position s, and consequently also the coolant flow F, can be set in a number of steps, in a way corresponding to the small dots in FIG. 3. The number of steps is in this case at least three. For example, it may be 7 (=2.sup.31), 15 (=2.sup.41) or generally 2.sup.n1 (n=5, 6, . . . ). In any event, the coolant flow F can be set by the valve device 13 to a number of values other than 0.

(12) The dependence of the coolant flow F on the opening position s that is represented in FIG. 3, as an example, corresponds to a characteristic line K of the coolant flow F as a function of the opening position s of the valve device 13. The characteristic line K only applies whenever the coolant 5 has the reference condition ZR in the feed line 10 upstream of the valve device 13. The reference condition ZR preferably comprises at least one reference pressure that is applied to the coolant 5 in the feed line 10 upstream of the valve device 13.

(13) The characteristic line K represents within the scope of the present invention the relevant part of a valve characteristic C of the valve device 13. If appropriate, the valve characteristic C may additionally comprise further parameters of the valve device 13. Examples of such parameters are delay times that may occur when changing the opening position s (step-response). However, this is of secondary importance within the scope of the present invention.

(14) In the feed line 10, an upstream condition detection device 14 is arranged upstream of the valve device 13. The upstream condition detection device 14 is operable to detect an upstream condition ZV of the coolant 5 that the coolant 5 actually has in the feed line 10 upstream of the valve device 13. The upstream condition ZV preferably comprises at least the upstream feed-line pressure pV that is (actually) applied to the coolant 5 in the feed line 10 upstream of the valve device 13.

(15) According to FIG. 2, the control device 6 is fed a setpoint value F* for the coolant flow F and the upstream condition ZV. Furthermore, the valve characteristic C of the valve device 13 is also known to the control device 6. The control device 6 is therefore capable of determining on the basis of the setpoint value F* for the coolant flow F, the upstream condition ZV of the coolant 5 and the valve characteristic C of the valve device 13, in particular the characteristic line K, a setpoint value s* for the opening position s of the valve device 13. The determined setpoint value s* for the opening position s of the valve device 13 corresponds to the predetermined setpoint value F* for the coolant flow F. The control device 6 sets the opening position s of the valve device 13 in a way corresponding to the determined setpoint value s*. The control device 6 can alternatively set the valve device 13 in an open-loop or closed-loop controlled manner.

(16) In a preferred refinement of the present invention, according to FIG. 2, a downstream condition detection device 15 is arranged in the feed line 10 between the valve device 13 and the application device 9. The downstream condition detection device 15 detects a downstream condition ZH of the coolant 5 that the coolant 5 has in the feed line 10 between the valve device 13 and the application device 9. Alternatively, the downstream condition detection device 15 may be arranged in the application device 9 itself. In this case, the downstream condition detection device 15 detects a downstream condition ZH of the coolant 5 that the coolant 5 has in the application device 9 itself. The downstream condition ZH is likewise fed to the control device 6. The control device 6 is therefore capable of correcting the characteristic line K of the valve device 13 on the basis of the upstream condition ZV of the coolant 5, the downstream condition ZH of the coolant 5 and the opening position s of the valve device 13. The downstream condition ZH may in particularby analogy with the upstream condition ZVcomprise a downstream feed-line pressure pH that is applied to the coolant 5 in the feed line 10 between the valve device 13 and the application device 9 or in the application device 9 itself.

(17) For correcting the characteristic line K, the characteristic line K is preferably parameterized. For example, interpolation points for which the associated coolant flow F is predefined may be predetermined. In this case, an interpolation takes place between the interpolation points. If a deviation of the downstream condition ZH from an expected downstream condition occurs for an opening position s of the valve device 13 that lies between two interpolation points, the coolant flows F defined for the two interpolation points may for example be corrected in a weighted manner in a way corresponding to the distances of the opening position s from the two interpolation points. The weighting is in this case all the greater the smaller the distance of the opening position s from the respective interpolation point.

(18) It is possible that the upstream feed-line pressure pV that the coolant 5 has in the feed line 10 upstream of the valve device 13 is relatively low, for example lies at about 0.2 bar to 0.3 bar. Preferably, however, the upstream feed-line pressure pV lies between 1.5 bar and 5.0 bar. In particular, it may lie between 2.0 bar and 3.0 bar.

(19) The present invention has many advantages. In particular, the coolant flow F can be set precisely and reproducibly in an easy and low-cost way, while overshooting can be avoided.

(20) Although the invention has been illustrated more specifically and discussed in detail by the preferred exemplary embodiment, the invention is not restricted by the examples disclosed and other variations may be derived therefrom by a person skilled in the art without departing from the scope of protection of the invention.

LIST OF DESIGNATIONS

(21) 1 Metal strip 2 Rolling stands 3 Coiling device 4 Cooling devices 5 Coolant 6 Control device 7 Computer program 8 Machine code 9 Application device 10 Feed line 11 Reservoir 12 Pumps 13 Valve device 14 Upstream condition detection device 15 Downstream condition detection device C Valve characteristic F Coolant flow F* Setpoint value for the coolant flow K Characteristic line pH Downstream feed-line pressure pV Upstream feed-like pressure s Opening position s* Setpoint value for the opening position ZH Downstream condition ZR Reference condition ZV Upstream condition