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. A handling line having a cooling device for cooling a metal strip with a liquid coolant, comprising: an application device configured for applying coolant to the metal strip; a feed line for the coolant; a valve device arranged in the 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; a pressure detection device that detects 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; and a control device that 1) receives 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, 2) is configured to determine 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 3) sets the open position of the valve to an open position from among the plurality of open positions that corresponds to the determined setpoint value (s*).

2. The handling line of claim 1, further comprising a detector that detects a downstream condition (ZH) of the coolant in the feed line downstream of the valve device, wherein the control device is configured to correct 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 handling line of claim 2, wherein the detector that detects the downstream condition is located between the valve device and the application device.

4. The handling line of claim 2, wherein the detector that detects the downstream condition is in the application device.

5. The handling line of claim 2, wherein the downstream condition (ZH) of the coolant comprises a downstream feed-line pressure (pH) that is applied to the coolant downstream of the valve device.

6. The handling line of claim 5, wherein the downstream feed-line pressure (pH) is detected in the feed line between the valve device and the application device.

7. The handling line of claim 5, wherein the downstream feed-line pressure (pH) is detected in the application device.

8. The handling line of claim 1, wherein the application device is an upper spray bar.

9. The handling line of claim 1, wherein the application device is a lower spray bar.

10. The handling line of claim 1, further comprising a reservoir connected to the feed line and a pump in the feed line upstream of the valve device.

11. The handling line of claim 1, wherein the valve device is a servo valve.

12. The handling line of claim 1, further comprising a rolling stand for rolling the metal strip located upstream or downstream of the cooling device.

13. The handling line of claim 1, further comprising a coiling device downstream of the cooling device.

14. The handling line of claim 1, further comprising a detector that detects a downstream condition (ZH) of the coolant in the feed line downstream of the valve device, wherein the control device is configured to parameterize the characteristic line (K) to correct 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.

15. The handling line of claim 14, wherein the control device corrects the characteristic line (K) by predetermining interpolation points for which the associated coolant flow (F) is predefined, interpolating between the interpolation points, and correcting the coolant flow between the interpolation points when a deviation of the downstream condition (ZH) from an expected downstream condition occurs for the set open position of the valve device.

16. The handling line of claim 15, wherein the coolant flows (F) defined for the two interpolation points is corrected in a weighted manner that corresponds to distances of the set open position from the interpolation points.

17. The handling line of claim 16, wherein the weighting is greater when the distance of the set open position from the respective interpolation point is smaller.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] FIG. 1 shows a handling line for a metal strip,

[0049] FIG. 2 shows a cooling device and

[0050] FIG. 3 shows a valve characteristic.

DESCRIPTION OF AN EMBODIMENT

[0051] 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. 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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 2n1 (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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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

[0067] 1 Metal strip [0068] 2 Rolling stands [0069] 3 Coiling device [0070] 4 Cooling devices [0071] 5 Coolant [0072] 6 Control device [0073] 7 Computer program [0074] 8 Machine code [0075] 9 Application device [0076] 10 Feed line [0077] 11 Reservoir [0078] 12 Pumps [0079] 13 Valve device [0080] 14 Upstream condition detection device [0081] 15 Downstream condition detection device [0082] C Valve characteristic [0083] F Coolant flow [0084] F* Setpoint value for the coolant flow [0085] K Characteristic line [0086] pH Downstream feed-line pressure [0087] pV Upstream feed-like pressure [0088] s Opening position [0089] s* Setpoint value for the opening position [0090] ZH Downstream condition [0091] ZR Reference condition [0092] ZV Upstream condition