Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B39/00—Arrangements for moving, supporting, or positioning work, or controlling its movement, combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
  • B21B39/02—Feeding or supporting work; Braking or tensioning arrangements, e.g. threading arrangements
  • B21B39/12—Arrangement or installation of roller tables in relation to a roll stand
• • 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
  • B21B38/02—Methods or devices for measuring, detecting or monitoring specially adapted for metal-rolling mills, e.g. position detection, inspection of the product for measuring flatness or profile of strips

Definitions

• the invention relates to the hot rolling of thin strip, i.e. metal strip of a thickness of less than 1 ⁇ 1.5 mm.
• thin strip i.e. metal strip of a thickness of less than 1 ⁇ 1.5 mm.
• Hot working requires, however, particular measures: for instance the speed of output of the strip must in certain cases be kept below predetermined limits because otherwise the head of the strip might be lifted as a result of air resistance.
• the strip advances too rapidly in the output section of the rolling mill (i.e. the part of the mill which is downstream the last rolling stand), there is a risk that its head might strike the guide rolls on which it is moving: following such impacts, it would be deflected upwards so that a part of the strip would be raised from the roll train as a result of air resistance, thereby making its control and subsequent winding on the reel problematic.
• a continuous rolling technique (also called “endless”), in which a single initial strip is cut at the end of rolling, into sections of predetermined length which are then wound as respective coils.
• the strip is obtained from a bar of multiple weight than that of the final coils to be produced, which may in turn be obtained either by joining smaller bars using conventional roughing plants or by thin slab casting.
• This special equipment generally entails some increase in costs, such that plants for the endless rolling of thin strip can be considered rather expensive. Another factor also needs to be considered.
• the technical problem underlying this invention is therefore that of providing a hot rolling mill with structural and operational features suitable to overcome the limits of the state of the art described above.
• the invention aims to provide a rolling mill for hot working of thin strip, in which the strip is fed in a controlled manner in order to avoid any risk of its lifting in the case of high speeds; a rolling mill of this type is therefore an alternative to rolling mills of endless type and is able to produce successive batches of strip without the drawbacks described above.
• Fig. 1 is a simplified side view of the output section of the rolling mill according to the invention
• Fig. 2 shows the possible positions of a tensiometric roller in the output section of the preceding figure
• Fig. 3 shows a detail of Fig. 2 on an enlarged scale.
• reference 1 indicates overall the output section of a rolling mill according to the invention, upstream and downstream of which there are disposed finishing stands 2 (known per se) for the final rolling of a strip N.
• the section 1 comprises a series of driven rollers 3 adapted to feed the strip, and a station 4 for the detection of its geometrical characteristics (thickness, shape, width) upstream and downstream of which there are located generators of air jets 5, 6, which will be better described below.
• a cooling station 8 Downstream the first drive unit 7 there is provided a cooling station 8 which, in accordance with a preferred embodiment of the invention, is of the ultra- fast cooling type or UFC; this kind of station, indeed, is able to remove large quantities of heat by supplying relevant flows of cooling fluid and are generally used in the rolling of large thickness plates, in order to improve their mechanical properties (likewise a hardening treatment).
• the position of the reel could however be different from that described above; for instance it could also be disposed lower with respect to the horizontal feeding direction of the strip, as shown by the dashed line in Fig. 1.
• the reel 10 comprises a spindle 11 wherein the strips arriving one after the other are wound and around which pressure rolls 12 are arranged in a known manner; between the second drive unit 9 and the reel 10 there are disposed guides
• the generators of air jets 5, 6, may take the form of fans or compressors appropriately provided with air supply ducts, or of nozzles supplied with compressed air from the distribution network of the industrial plant in which the rolling mill is located.
• the task of these generators is to exert a pressure on the upper surface of the strip N being fed along the output section of the rolling mill 1, in order to keep it flattened against the rollers way formed by the rollers 3; the air velocity thus has a vertical downwardly facing component (with reference to the drawings).
• the blown air may also have a horizontal velocity component parallel to the surface of the strip and greater than the feeding speed of the latter: the generators 5 and 6 thus direct the air jets in an inclined manner with respect to the strip in order to obtain the effects referred before.
• the rolling mill in which the output section 1 described above is located operates as follows; it should be stressed that the rolling mill structure upstream of this section has not been considered in detail here, since it is of secondary importance for the purposes of understanding the present invention.
• the movement of the strip N is thus controlled by the air in order to enable its correct engagement with the first drive unit 7, which helps to feed it in a guided manner; in this respect it should be noted that these units are provided with guide members (not shown) adapted to guide the free end of the strip towards the rolls. It should also be noted that at this stage water is sprayed on the strip in the cooling station 8, thereby helping to hold it pressed against the motor-driven rollers 3 up to the second drive unit 9.
• This unit 9 then deflects the direction of feed of the strip N towards the reel 10; this result is obtained by means of the inclination of its rolls as shown in the drawings, which deflect the strip who is then conveyed by the guides 13 towards the spindle 11 and the pressure rollers 12 so that it can be wound in a manner similar to that normally used in the art.
• the wound strip is then removed from the spindle and the reel is ready to receive a new strip as it arrives; it should be noted in this respect that in the rolling mill of the invention there is a dead time between a strip and the next one, during which the last coil wound can be removed. This is due to the fact that in the case of rolling mills wherein the initial bars are obtained by continuous casting, the operating times required for the formation of each of them are long enough to enable the strip obtained from the previous bar to reach the winding reel.
• the strip is controlled aerodynamically in the output section 1, by exerting a pressure on it that avoid separation thereof from the roller way; this solution is very efficient and operationally flexible and can be applied in the case of high strip speeds (the speed of the air flow can be adjusted at will to increase or decrease the pressure on the strip).
• the aerodynamic control of the strip according to the teaching of the present invention can therefore be advantageously used in new rolling mill plant and in existing plants as well.
• the air jets may be readily adjusted to improve the control of the strip; for instance, it is possible to adjust the pressure exerted by the air in the direction of the width of the strip so as to curve its section and make it more resistant to longitudinal bending and less sensitive to the destabilising phenomena described above.
• a velocity component of the air parallel to that of feeding the strip is created in this way; as this component is greater than the feeding speed of the strip, it prevents the latter from being lifted since it forces the fore head thereof downwards when it is deflected upwards by the impacts with the rolls 3.
• the horizontal velocity component also makes it possible to avoid exerting an excessive pressure on the strip perpendicular thereto.
• these strips are thin and can therefore be readily deformed, particularly by bending. As a consequence it would be more difficult for the strip to slide along the rolls and its head would be more likely to impact against these rolls.
• FIGs. 2 and 3 An example of this is shown in Figs. 2 and 3, wherein the first one shows a number of positions in which it is possible to locate a device for measuring planarity 20 with a tensiometric roller 21 along the output section of Fig. 1, while the second shows a particular embodiment of this roller in greater detail.
• tensiometric rollers are already known in the field of rolling where they are used to measure the planarity of strips, i.e. the presence of undulations in their configuration due to differing deformation between their edge and their centre.
• tensiometric rollers are rollers split longitudinally into cylindrical sections, adjacent to one another and idle with respect to a same axis transverse to the strip; the tensiometric roller is brought into contact with the strip by urging it against the strip and slightly deflecting its run.
• the friction of the strip on the various cylindrical sections making up the roller causes a different rotation between one section and another when there are undulations in the strip that locally alter the strip-roller friction conditions.
• tensiometric rollers are usually disposed between the final rolling stands (i.e., with reference to Fig. 1, between the stands 2 shown therein); this means, however, that the planarity measurement carried out does not take account of the deformation due to the final stand, which must be evaluated using theoretical models and algorithms with all the limitations arising therefrom.
• This device may preferably be disposed immediately after the final rolling stand 2 or immediately before the second drive unit 9, as shown in Fig. 2 in which the tensiometric roller is shown respectively by 21 ' in the former case and by 21" in the latter case.
• the above-mentioned device is formed by the tensiometric roller 21 and by a returning roller 22 which is disposed on the opposite side of the former with respect to the strip N, in a position facing the adjacent motor-driven roll 3. In the rest position, both rollers 21 and 22 are spaced from the strip; when the planarity measurement is to be carried out the tensiometric roller 21 is urged upwards and the returning roller 22 downwards so as to bring the strip immediately back into the normal plane of feed.
• the tensiometric roller 21 provides the desired measurement according to its normal operation.
• FIG. 3 A possible embodiment of the device 20 is shown on an enlarged scale in Fig. 3, where reference is made to its position immediately downstream of the final stand 2.
• the tensiometric roller 21 is mounted together with a roller 3' of the type of those fomring the rollers way 3, on a frame 23 that can oscillate with respect to a fixed axis 24 under the action of a hydraulic jack 25.
• the roller 3' When it is not necessary to measure the planarity of the strip, the roller 3' is in the position aligned with the other adjacent rollers 3 (as shown in dashed lines in Fig. 3) and the strip slides on it while the tensiometric roller is distanced; vice versa, when this measurement is to be carried out the tensiometric roller 21 is raised causing the frame 23 to oscillate, and at the same time distancing the roller 3'.
• the returning roller 22 is mounted on an arm 28 that also oscillates with respect to a base 29 secured to the bearing structure S of the rolling stand 2.
• planarity measurement device as designed above has the advantage of limiting the wear of the tensiometric roller, thereby ensuring that the measurements provided are reliable; it will be appreciated that this device may also be subject to many variants. It should be borne in mind in this respect that it would be possible to locate a planarity measurement device immediately after the second drive unit 9, as an alternative to the previous two positions; in this case the device 20 could be subject to further modifications linked to the different position of the tensiometric roller with respect to the strip, i.e. above rather than below it (see Fig. 3 in which the tensiometric roller is shown by 21 '"), and to the absence of the rollers 3 of the strip rollers way.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Metal Rolling (AREA)
• Winding, Rewinding, Material Storage Devices (AREA)
• Laminated Bodies (AREA)

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• 1999
  • 1999-01-11 IT IT1999MI000021A patent/IT1306927B1/it active
• 2000
  • 2000-01-07 ES ES00901321T patent/ES2218105T3/es not_active Expired - Lifetime
  • 2000-01-07 WO PCT/IT2000/000006 patent/WO2000041823A1/fr active IP Right Grant
  • 2000-01-07 AT AT00901321T patent/ATE262384T1/de not_active IP Right Cessation
  • 2000-01-07 DE DE60009212T patent/DE60009212T2/de not_active Expired - Lifetime
  • 2000-01-07 EP EP00901321A patent/EP1062061B1/fr not_active Expired - Lifetime

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