A Device and Method for Descaling Rolling Stock

Abstract

A nozzle head for descaling rolling stock, said rolling stock moving relative to said nozzle head, is adapted to be mounted for rotation about an axis of rotation relative to a surface of said rolling stock. Said nozzle head comprises a plurality of nozzles adapted to spray a liquid on said rolling stock, wherein said nozzles are positioned at different radial distances from said axis of rotation.

Claims

1-15. (canceled)

16. A nozzle head for descaling rolling stock moving relative to said nozzle head; wherein said nozzle head is adapted to be mounted for rotation about an axis of rotation relative to a surface of said rolling stock; wherein said nozzle head comprises a plurality of nozzles adapted to spray a liquid on said rolling stock; and wherein said nozzle head comprises a first group of at least two of said nozzles positioned at a first radial distance from said axis of rotation, and a second group of at least one of said nozzles positioned at a second radial distance from said axis of rotation, wherein said second radial distance is smaller than said first radial distance.

17. The nozzle head according to claim 1, wherein said second radial distance is at most 0.9 times said first radial distance, and in particular at most 0.8 times said first radial distance.

18. The nozzle head according to claim 1, wherein said nozzles are arranged along circles or ellipses with different radii.

19. The nozzle head according to claim 1, wherein said nozzles are radially inclined outwardly.

20. The nozzle head according to claim 1, further comprising at least a first nozzle positioned at a first radial distance from said axis of rotation, said first nozzle being radially inclined outwardly at a first outward inclination angle, and a second nozzle positioned at a second radial distance from said axis of rotation, said second nozzle being radially inclined outwardly at a second outward inclination angle, wherein said second radial distance is smaller than said first radial distance and wherein said second outward inclination angle is different from said first outward inclination angle.

21. The nozzle head according to claim 1, wherein said nozzles are inclined in a circumferential direction of said nozzle head, in particular in a direction of rotation of said nozzle head or against a direction of rotation of said nozzle head.

22. The nozzle head according to claim 1, further comprising at least a first nozzle positioned at a first radial distance from said axis of rotation, said first nozzle being inclined in a circumferential direction at a first circumferential inclination angle, and a second nozzle positioned at a second radial distance from said axis of rotation, said second nozzle being inclined in a circumferential direction at a second circumferential inclination angle, wherein said second radial distance is smaller than said first radial distance and wherein said second circumferential inclination angle is different from said first circumferential inclination angle.

23. The nozzle head according to claim 1, further comprising at least a first nozzle positioned at a first radial distance from said axis of rotation, said first nozzle having a first orifice size, and a second nozzle positioned at a second radial distance from said axis of rotation, said second nozzle having a second orifice size, wherein said second radial distance is smaller than said first radial distance, and wherein said second orifice size is different from said first orifice size, in particular smaller or larger than said first orifice size.

24. A device for descaling rolling stock, the device comprising a plurality of nozzle heads, each of the plurality of nozzle heads being adapted to be mounted for rotation about an axis of rotation relative to a surface of said rolling stock; wherein each said nozzle head comprises a plurality of nozzles adapted to spray a liquid on said rolling stock; and wherein each said nozzle head comprises a first group of at least two of said nozzles positioned at a first radial distance from said axis of rotation, and a second group of at least one of said nozzles positioned at a second radial distance from said axis of rotation, wherein said second radial distance is smaller than said first radial distance; wherein the plurality of nozzle heads is arranged vertically and/or horizontally across a width of said rolling stock, and/or arranged circularly across said rolling stock.

25. The device according to claim 24, wherein the plurality of nozzle heads includes a first nozzle head and a second nozzle head, in particular arranged in a row across a width of said rolling stock; wherein said first nozzle head is mounted for rotation about a first axis of rotation relative to a surface of said rolling stock; wherein said first nozzle head comprises a first plurality of nozzles adapted to spray said liquid on said rolling stock; wherein said first plurality of nozzles comprises a first group of at least one nozzle positioned at a first radius, and a second group of at least one nozzle positioned at a second radius, wherein said second radius is smaller than said first radius; wherein said second nozzle head is mounted for rotation about a second axis of rotation relative to a surface of said rolling stock; wherein said second nozzle head comprises a second plurality of nozzles adapted to spray said liquid on said rolling stock; wherein said second plurality of nozzles comprises a first group of at least one nozzle positioned at a first radius, and a second group of at least one nozzle positioned at a second radius, wherein said second radius is smaller than said first radius; wherein said first nozzle head is positioned closer to a boundary or an edge of said rolling stock than said second nozzle head; wherein said first group of nozzles of said first nozzle head comprises fewer nozzles than said first group of nozzles of said second nozzle head; and/or wherein said first group of nozzles of said first nozzle head comprises nozzles of smaller orifice size than said first group of nozzles of said second nozzle head.

26. A method for descaling rolling stock, comprising: rotating a nozzle head about an axis of rotation relative to a surface of said rolling stock, said nozzle head comprising a plurality of nozzles; and spraying a pressurized liquid on said rolling stock from said nozzles; wherein said nozzle head comprises a first group of at least two of said nozzles positioned at a first radial distance from said axis of rotation, and a second group of at least one of said nozzles positioned at a second radial distance from said axis of rotation, wherein said second radial distance is smaller than said first radial distance.

27. The method according to claim 26, wherein said rolling stock is a heated or non-heated stock of metal, in particular a non-ferrous metal.

28. The method according to claim 26, wherein said plurality of nozzles comprises at least a first nozzle positioned at a first radial distance from said axis of rotation, and a second nozzle positioned at a second radial distance from said axis of rotation, wherein said second radial distance is smaller than said first radial distance, and said method comprises a step of spraying a different amount of liquid from said second nozzle than from said first nozzle, in particular a different amount of liquid per rotation of said nozzle head.

29. A computer program comprising computer-readable instructions, wherein said instructions, when read on said computer, are adapted to implement on a device for descaling rolling stock functionally connected to said computer a method according to claim 26.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0097] The features and numerous advantages of the device and method for descaling rolling stock will become best apparent from a detailed description of embodiments with reference to the drawings, in which:

[0098] FIG. 1 is a top plan view of a spray pattern according to the state of the art;

[0099] FIG. 2 is a schematic view of a descaling apparatus in which a device and method according to the present invention may be employed;

[0100] FIG. 3 is a schematic perspective view of a descaling device according to an embodiment of the invention;

[0101] FIG. 4 is a schematic perspective view of a nozzle head with nozzles at different radial distances according to an embodiment of the invention;

[0102] FIG. 5 is a schematic lower plan view of a nozzle head that illustrates the position of nozzles on different circles according to an embodiment of the invention;

[0103] FIG. 6 is a schematic illustration of the relation between the radial distance and the jet opening angle of neighboring nozzles according to an embodiment;

[0104] FIG. 7 schematically illustrates a spray pattern that can be obtained with a nozzle head according to an embodiment of the invention; and

[0105] FIG. 8 is a flow diagram that illustrates a method according to an embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[0106] Embodiments of the invention will now be described for the example of the descaling of a hot rolled stock of thin steel by spraying it with water under high pressure. However, the present invention is versatile, and can be applied for the descaling of a large variety of materials, including the hot or cold descaling of ferrous or non-ferrous metals.

[0107] FIG. 2 is a schematic illustration of a rolling mill 10 for producing a wide steel strip. The steel is annealed in an annealing furnace 12 and enters a roughing mill section as a rolled stock 14 which is transported along the direction F (indicated by an arrow) by means of a roller train comprising driven rollers 16.

[0108] The rolling mill 10 comprises a plurality of roughing mills along the path of the rolling stock 14. FIG. 2 shows two vertical roughing mills 18, 18′ sandwiching a horizontal roughing mill 20 along the direction of travel F of the rolling stock 14. However, this is merely an example, and in practical applications the rolling mill 10 may comprise a larger number of vertical and horizontal roughing mills and/or finishing mills to shape the rolling stock 14.

[0109] As can be further taken from FIG. 1, two descaling devices 22, 22′ are positioned in between the roughing mills 18, 20 and 20, 18, respectively. These descaling devices 22, 22′ are adapted to spray water under high pressure on all four sides of the rolling stock 14 so as to remove scale layers from the lower and upper surfaces and the side surfaces of the rolling stock 14. For instance, for a rolling stock 14 of a width of 900 mm and moving at a velocity of approximately 1 meters per second in the direction of arrow F, the descaling devices 22, 22′ may operate at a pressure of approximately 1000 to 1200 bar and a flow rate of approximately 300 to 6,000 liters of water per minute each. The descaling of rounds, bars, pipes (inside and outside), forging blocks and other stock may employ similar parameters.

[0110] FIG. 3 illustrates the set-up and design of the descaling device 22 in additional detail. The descaling device 22′ can be largely identical.

[0111] The descaling device 22 comprises a plurality of nozzle heads 24 arranged in a linear array across the width of the rolling stock 14. FIG. 3 shows an array of five nozzle heads 24 on a upper side of the rolling stock 14, and four nozzle heads 24 at a lower side thereof. However, the number of nozzle heads 24 in any given descaling device 22 may vary depending on the size and width and shape of the rolling stock 14, its material composition and the operating parameters. In some examples, the descaling device 22 may spray on all four sides of the rolling stock 14, i.e., on the upper and lower surface sides as well as on the side surfaces of the rolling stock 14.

[0112] Each of the nozzle heads 24 is mounted to rotate around a central axis of rotation Z. For ease of presentation, only one axis Z is depicted in FIG. 3. However, each of the nozzle heads 24 similarly have their own axis of rotation, generally all in parallel, and are driven to rotate about their respective axis of rotation Z by means of a drive unit. The drive unit is not shown in FIG. 3 for ease of presentation, but will be explained below with reference to FIG. 4. The drive unit may comprise a hydraulic, pneumatic or electric drive motor. Each of the nozzle heads 24 may be provided with their own drive unit. Alternatively, a single integrated drive unit can be employed for a plurality of nozzle heads 24.

[0113] In some examples, the drive unit may comprise an electric motor adapted to rotate the nozzle heads 24 relative to the surface of the rolling stock 14 at a number of revolutions of from 200 to 1,200 rpm.

[0114] As can be further taken from FIG. 3, each of the nozzle heads 24 are connected via tubing 26 to a pressure generating supply unit 28 that is adapted to supply the nozzle heads 24 with a liquid to be sprayed on the rolling stock 14. For instance, the supply unit 28 may receive the liquid from a liquid reservoir 30 and may comprise a plurality of centrifugal pumps or displacement pumps 32 driven by respective motors 34 and adapted to supply pressurized liquid to said nozzle heads 24 via check valves 36 and the tubing 26.

[0115] FIG. 4 is a schematic perspective illustration of a nozzle head 24 in greater detail.

[0116] As can be taken from FIG. 4, the nozzle head 24 is generally cylindrical in shape, and is mounted rotatably relative to the tubing 26 and surface of the rolling stock 14 about its central cylindrical axis Z. FIG. 4 also shows a drive unit 38, such as an electrical motor or hydraulically motor or pneumatic motor that drives the nozzle head 24 to rotate about the axis of rotation Z.

[0117] As can be further taken from FIG. 4, the nozzle head 24 comprises a plurality of nozzles mounted at a lower side surface of the nozzle head 24 and adapted to rotate with the nozzle head 24 and to spray the liquid provided through the tubing 26 on the surface of the rolling stock 14. Some of these nozzles are indicated by reference numerals 40e to 40d, wherein the nozzles 40a and 40b are positioned at a first radial distance from the cylindrical axis Z, and the nozzles 40c and 40d are located at a second radial distance from the cylindrical axis Z that is smaller than the first radial distance. FIG. 4 also illustrates the corresponding spray patterns 42a to 42d of the respective nozzles 40a to 40d on the surface of the rolling stock 14.

[0118] Some or all of the nozzles 40a to 40d can be tilted slightly outwardly, for instance at an outward inclination angle in the range of approximately 10°.

[0119] Moreover, each of the nozzles 40a to 40d may be inclined in a forward circumferential direction, i.e. in a direction of rotation of the spray head 24. For instance, a circumferential inclination angle of the nozzles may be in the range of approximately 20°.

[0120] Once the nozzle head 24 rotates and the nozzles 40a to 40d spray the liquid under the outward inclination angle and forward inclination angle onto the surface of the rolling stock 14, scale layers that may form on the surface of the rolling stock 14 during the milling, or in between milling steps, are efficiently and thoroughly removed.

[0121] The design and inner workings of the nozzle head 14 may be generally similar to those described in U.S. Pat. No. 5,502,881 and US 2007/0277358 A1, and full reference is made to these documents.

[0122] However, unlike in the prior art, the nozzles are not all arranged at an outmost circumference of the nozzle head 24. Rather, the nozzles are positioned at different radial distances from the axis of rotation Z, as will now be described in further detail with reference to FIG. 5.

[0123] FIG. 5 is a schematic lower plan view of a nozzle head 24 according to an embodiment and illustrates how a plurality of nozzles 40a to 40e are positioned on the nozzle head 24.

[0124] As can be taken from FIG. 5, the nozzles 40a to 40e of the nozzle head 24 can be arranged along three concentric circles 44.sub.1, 44.sub.2, 44.sub.3 with different radii r.sub.1, r.sub.2, r.sub.3, wherein the center of the circles 44.sub.1, 44.sub.2, 44.sub.3 corresponds to the axis of rotation Z. The radii r.sub.1, r.sub.2, r.sub.3 hence represent the radial distance of the respective nozzles 40a to 40e arranged on the respective circles 44.sub.1, 44.sub.2, 44.sub.3. In the configuration of FIG. 5, the second (middle) circle 44.sub.2 is smaller than the first (outmost) circle 44.sub.1, with a radius r.sub.2=0.7×r.sub.1. The third (innermost) circle 44.sub.3 is the smallest, with a radius r.sub.3=0.7×r.sub.2.

[0125] In general, each of the respective circles 44.sub.1, 44.sub.2, 44.sub.3 may comprise any number of nozzles. In some examples, any of the circles 44.sub.1, 44.sub.2, 44.sub.3 comprises at least two nozzles.

[0126] In some examples, the number of nozzles per circle 44.sub.1, 44.sub.2, 44.sub.3 may be at most six.

[0127] In the example of FIG. 5, two nozzles 40a, 40b are positioned diametrically opposite on the outermost circle 44.sub.1 at a radial distance r.sub.1 from the axis of rotation Z. Two nozzles 40c, 40d are positioned diametrically opposite on the middle circle 44.sub.2 at a radial distance r.sub.2 from the axis of rotation Z. In the configuration of FIG. 5, the pair of nozzles 40c, 40d are rotated with respect to the pair of nozzles 40a, 40b by 90° in a circumferential direction (direction of rotation). A single nozzle 40e is positioned on the innermost circle 44.sub.3 at a radial distance r.sub.3 from the axis of rotation Z. In other examples, the innermost circle 44.sub.3 comprises two nozzles that are positioned diametrically opposite, similarly to the outermost circle 44.sub.1 and the middle circle 44.sub.2.

[0128] A radial distance R between nozzles on different radii may be chosen depending on the height H of the nozzles above the rolling stock 14 and depending on the jet opening angle α of the nozzles so that the spray patterns of the neighboring nozzles touch or slightly overlap when impinging on the stock 14.

[0129] A corresponding configuration for neighboring nozzles 40b, 40c is shown in FIG. 6, where R=r.sub.1−r.sub.2. Similar considerations apply in case R=r.sub.2−r.sub.3. Based on geometric considerations, we have

[00001]$\tan \frac{\alpha }{2}=\frac{R}{2\times H}$

[0130] As can be taken from this relation, the jet opening angle α, the radial distance R between neighboring nozzles and the height H of the nozzles above the surface of the rolling stock 14 may be interdependent.

[0131] The distribution of nozzles 40a to 40e at varying radial distances from the axis of rotation Z leads to a more homogeneous, more uniform spray pattern across the surface of the rolling stock 14. A corresponding spray pattern 46 is shown schematically in FIG. 7. As can be taken from a comparison of FIG. 7 with FIG. 1, the nozzle head 24 according to the invention helps to avoid the formation of strips 104, 104′ in the spray pattern. As a result, the surface of the rolling stock 14 may be descaled more thoroughly, and more uniformly. Moreover, a given level of desired descaling can be achieved with a smaller amount of liquid, and hence at lower cost.

[0132] The examples of FIGS. 4 and 5 show five nozzles 40a to 40e arranged on three different circles 44.sub.1, 44.sub.2, 44.sub.3. However, this is just an example, and a larger or smaller number of nozzles arranged on a larger or smaller number of circles may be employed.

[0133] Moreover, the nozzles 40a to 40e need not necessarily be arranged pairwise or in circles, but could be distributed differently at different radial distances from the axis of rotation Z on the lower side of the nozzle head 24.

[0134] The outward inclination angle and circumferential inclination angle of the nozzles 40a to 40e may be chosen identically or differently for each of the nozzles 40a to 40e.

[0135] Similarly, an orifice size, such as an orifice diameter, of the nozzles 40a to 40e may vary, depending on a distance of the respective nozzle from the axis of rotation Z. For instance, the outermost nozzles 40a, 40b on the circle 44.sub.1 may have orifices of larger size than the innermost nozzle 40e on the circle 44.sub.3, and hence may spray more liquid per rotation, in accordance with the larger surface area of the rolling stock 14 across which they sweep.

[0136] In case several nozzle heads 24 are arranged in a row or otherwise across a width of the rolling stock 14, as illustrated in FIG. 3, all the nozzle heads 24 may be identical, and may correspond to the nozzle head 24 described above with reference to FIGS. 4 and 5.

[0137] However, in other embodiments, the configuration and position of the nozzles may differ depending on the position of the nozzle head 24 in the descaling device 22. For instance, a nozzle head at the edge or boundary of the rolling stock 14 could have a smaller number of nozzles, or nozzles with a smaller orifice size on the outermost circle. In an embodiment, such a nozzle head could correspond to the nozzle head shown in FIG. 5, but with the nozzle 40b removed.

[0138] In general, the number of nozzle heads, the number of nozzles on the different radii of the nozzle heads, as well as the distance between neighboring nozzle heads, the height H of the nozzles above the surface of the rolling stock and the fluid pressure can be chosen depending on the type and surface properties of the rolling stock, so to achieve a desired impingement.

[0139] A method according to an embodiment of the invention is schematically illustrated in the flow diagram of FIG. 8.

[0140] In a first step S10, the nozzle head 24 is rotated about an axis of rotation Z relative to a surface of the rolling stock 14. Said nozzle head 24 comprises a plurality of nozzles 40a to 40e.

[0141] In a second step S12, a pressurized liquid, such as water, is sprayed on said surface of said rolling stock 14 from said nozzles 40a to 40e, wherein said nozzles 40a to 40e are positioned at different radial distances r.sub.1, r.sub.2, r.sub.3 from said axis of rotation Z.

[0142] The embodiments described above and the Figures merely serve to illustrate the invention, but should not be construed to imply any limitation. The scope of the invention is determined by the appended claims.

REFERENCE SIGNS

[0143] 10 rolling mill [0144] 12 annealing furnace [0145] 14 rolling stock [0146] 16 roller train [0147] 18, 18′ vertical roughing mills [0148] 20 horizontal roughing mill [0149] 22, 22′ descaling devices [0150] 24 nozzle heads [0151] 26 tubing [0152] 28 supply unit [0153] 30 liquid reservoir [0154] 32 centrifugal pumps [0155] 34 motors of centrifugal pumps [0156] 36 check valves [0157] 38 drive unit [0158] 40a-40e nozzles of nozzle head 24 [0159] 42a-42d spray patterns of nozzles 40a-40d [0160] 44.sub.1, 44.sub.2, 44.sub.3 circles of nozzle head 24 [0161] 46 spray pattern [0162] 100 rolling stock [0163] 102 spiral spray pattern [0164] 104, 104′ strips in spiral spray pattern 102