Abstract:
A shape detection device is incorporated as part of a hot strip reversing mill. The shape detection device is a shape detector roll adapted to contact the metal strip. The shape detector roll is used to provide data to an automated shape control and steering system. Preferably, the hot strip reversing mill includes a pair of hot reversing stands and a pair of coiler furnaces positioned on opposite sides of the pair of mill stands.

Description:
This is a continuation-in-part of U.S. patent application Ser. No. 08/639,724 filed on Apr. 29, 1996, now U.S. Pat. No. 5,901,591. 
    
    
     BACKGROUND 
     1. Field of Invention 
     The present invention relates to shape detection methods and apparatuses for a hot strip mill and, more particularly, to a shape detection device and method used in conjunction with a hot strip reversing mill. 
     2. Background Art 
     During the hot rolling of metal strip, such as steel, the rolling process can cause undesirable shape defects in the profile and flatness along the width of the metal strip. This generally results from internal stress differentials within the strip which appear during reduction in a hot strip reversing mill having coiler furnaces on opposite sides. As the need for improved shape is ever present from a mill, techniques are required to ensure the desired shape is achieved during the reduction of the metal strip. 
     These shape defects can be greatly minimized and often avoided by applying shape control techniques in controlling the rolls of the mill. Shape control techniques include adjustments at the reversing stand of roll bending, screw-down positions, roll shifting and roll cooling. Also, it is important to control the steering of the metal strip between the rolls at the reversing stand to keep the metal strip tracking on mill center. 
     In order to apply the shape control techniques, the operator must be able to detect when the process is causing the shape defects or when the metal strip tracks off mill center. Currently, the operator visually checks for defects caused by the process and ensures that the metal strip is tracking on mill center. The operator then must adjust the mill manually using the shape control techniques to correct for defects and adjust steering of the metal strip if the metal strip is off mill center. 
     Pressure transducers and load cells have been used on each side of the reversing stands to detect force differentials between the stand sides to indicate the metal strip is tracking off mill center. The use of pressure transducers or load cells can be unreliable because strip geometry, temperature changes in the metal or hardness of the metal can also cause force differentials that can be detected by the pressure transducers or the load cells. 
     Today, automated shape control systems using computer technology can control shape of the metal strip with the use of shape detectors. Shape detectors or shape feedback devices detect shape defects throughout the metal strip. The shape control system uses the data from the detector for monitoring and continuously correcting the flatness of the metal strip. The automated shape control system relieves the operator from visually checking for defects and manually making changes to the process. Such systems and shape detectors are described in U.S. Pat. Nos. 3,459,019; 3,688,571; 4,289,005; 4,356,714; 4,428,244; 4,512,170; 4,700,557; 4,809,527; 4,809,528; 4,860,212; 4,964,289; 5,089,776; 5,231,858; 5,267,170; 5,285,684; and 5,400,258. 
     Shape detectors can be a contact or non-contact shape metering device as discussed in the above-mentioned patents. Each type of shape metering device has the main purpose of detecting shape defects in the metal strip and has been used in cold strip mills and in the finishing train of hot strip mills. Some types of shaper Bring devices can also be used to detect metal strip position and, therefore, can also be used for automatic steering control. One problem that arises is that shape detectors must be incorporated into the design of existing mills. Currently for Steckel and other hot strip reversing mills, an operator still checks for shape defects visually and makes manual adjustments to the mill. Visual detection by an operator is still employed because the mills already in operation are generally restricted to the space available to add a contact or non-contact shape metering device. Although overall space is still a concern with new mills, a new mill can be designed to accommodate shape detectors. 
     Objects of the present invention are to overcome the drawbacks of the prior art designs and to provide a hot strip reversing mill design which incorporates shape detectors in the most efficient and cost-effective manner. 
     SUMMARY OF THE INVENTION 
     The objects of the present invention are satisfied by providing a hot strip reversing mill having at least one hot reversing stand, a pair of coilers on either side of the hot reversing stand and at least one shape detector roll adapted to engage the strip worked on by the hot reversing mill. In one embodiment of the present invention, two hot reversing stands are provided which operate in tandem. A shape detector roll may be positioned between the two hot reversing stands. One embodiment of the present invention additionally includes two sets of pinch rolls between the pair of hot reversing stands and respective coiler furnaces. The present invention provides that shape detector rolls may be provided as one of the rolls of each set of the pinch rolls. These and other objects of the present invention will be clarified in the description of the preferred embodiment taken together with the attached figures, wherein like reference numerals represent like elements throughout. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a twin stand hot strip reversing mill according to the present invention; 
     FIG. 2 illustrates a shape detector roll utilized in the hot strip reversing mill according to the present invention; and 
     FIG. 3 is a schematic view of an automated shape control system utilized in the hot strip reversing mill according to the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a twin stand hot strip reversing mill  10  according to the present invention. The mill  10  includes a pair of four-high hot reversing mill stands  12  and  14 , each having a pair of backup rolls and a pair of work rolls. A coiler furnace  16  is positioned upstream of the mill stand  12  and a coiler furnace  18  is positioned downstream of the mill stand  14 . Each coiler furnace  16  and  18  includes a drum about which the product being rolled is coiled once it has been reduced to a thickness capable of being coiled. It is preferred that the mill stands  12  and  14  are designed to operate in tandem. Similar twin stand hot strip reversing mills are described in commonly assigned U.S. Pat. No. 5,511,303; U.S. patent application Ser. No. 08/371,137; and U.S patent application Ser. No. 08/669,999, which are incorporated herein by reference. 
     The mill  10  includes a pinch roll and shear assembly  20  positioned between the coiler furnace  16  and mill stand  12  and a pinch roll and shear assembly  22  positioned between the mill stand  14  and the coiler furnace  18 . The construction of a pinch roll and shear combination is described in commonly assigned U.S. Pat. No. 5,285,670. The pinch rolls of each pinch roll and shear assembly  20  and  22  include a movable top roll  24  and a bottom roll  26 . Generally, the top roll  24  is vertically movable relative to the bottom roll  26  between an advanced position where both the top roll  24  and the bottom roll  26  engage the strip and a retracted position where the top roll  24  serves as a deflector roll for the adjacent coiler furnace  16  or  18 . The relative movement between the top roll  24  and the bottom roll  26  may be reversed depending upon the position of the adjacent coiler furnace  16  or  18  relative to a pass line of the mill  10 . For example, the bottom roll  26  would move vertically relative to the top roll  24  and act as a deflector roll in a retracted position where the adjacent coiler furnace  16  or  18  is below the pass line of the mill  10 . In the arrangement shown in FIG. 1, the top roll  24  may be formed as a segmented detector roll to function as a shape metering roll as described in parent application Ser. No. 08/639,724, which is incorporated herein by reference. In the retracted position, the segmented detector roll will be a deflector roll for the strip at the entrance of the adjacent coiler furnace  16  or  18 . 
     The mill  10  additionally includes a pair of centering guides  28  and  30  utilized to help maintain the strip in the appropriate centered position. Centering guide  28  is positioned between the pinch roll and shear assembly  20  and the mill stand  12 , and centering guide  30  is positioned between the mill stand  14  and the pinch roll and shear assembly  22 . The mill  10  additionally includes a vertical edger  32  positioned between the mill stand  14  and the centering guide  30 . The vertical edger  32  is not positioned between the mill stands  12  and  14  in the mill  10  of the present invention to allow for appropriate positioning of a shape detector between the mill stands  12  and  14  as will be described below. 
     The present invention provides a shape detector roll  34  positioned between the mill stands  12  and  14 . The shape detector roll  34  is movable by hydraulic cylinder  35  to engage the strip being reduced on the mill  10 . Through engagement of the strip, the shape detector roll  34  can supply tension to the strip and detect the shape of the worked strip. The shape detector roll  34  is preferably a segmented roll as illustrated in FIG.  2 . As shown in FIG. 2, the shape detector roll  34  is formed as a segmented roll made up of a plurality of segments  36  with each segment  36  including a detector  38  such as a load cell or strain gauge to detect strain forces as well as the location of the metal strip in relation to the mill center. The shape detector roll  34  has substantially the same construction as top roll  24  when a shapemetering roll is incorporated into the pinch roll and shear assembly  20  or  22 . 
     The operation of an automatic control system  40  is schematically illustrated in FIG.  3 . Each detector  38  provides data to a shape control system  42  of the automatic control system  40  which will monitor and continuously correct the profile and flatness of the metal strip. A steering control system  44  can also be included as part of the automatic control system  40  to continuously monitor the tracking of the metal strip along the mill center and correct the steering of the metal strip to ensure that the metal strip drags on mill center. The automatic control system  40  automatically adjusts the mill  10  in a conventional manner. Specifically, the automatic control system  40  may adjust any one or more of roll bending, screw-down positions, roll shifting, steering of the metal strip as well as other control functions of the mill  10  in order to correct defects that occur during the rolling of the metal strip. 
     As discussed above, in the mill  10  according to the present invention, it is anticipated that in addition to the shape detector roll  34  that the top roll  24  of one or both of the pinch roll and shear assemblies  20  and  22  may be formed as a shape detector roll. Each additional shape detector roll would also be coupled to the automatic control system  40  substantially in the same manner as disclosed in FIG.  3 . However, it is anticipated that in certain applications only the shape detector roll  34  between the mill stands  12  and  14  will be necessary, and the top roll  24  of each pinch roll and shear assembly  20  and  22  may be formed as a conventional roll. 
     The present invention additionally contemplates utilizing individual shape detector rolls between each mill stand  12  and  14  and the associated coiler furnaces  16  and  18  which are not associated with a set of pinch rolls. These shape detector rolls would act as deflector rolls for the adjacent coiler furnace  16  or  18 . In the mill configuration shown in FIG. 1, a shape detector roll acting as a deflector roll would be positioned between each respective mill stand  12  or  14  and the associated coiler furnace  16  or  18  essentially where top roll  24  is positioned (in FIG. 1) but would not be associated with a pinch roll and shear assembly  20  or  22 . The shape detector roll forming the deflector roll will be on the same side of the pass line as the adjacent coiler furnace  16  or  18 . The construction and control for this shape detector roll would be the same as described above for the shape detector roll  34 . This modification will be relevant in mill designs where a pinch roll assembly is positioned such that neither of its rolls could serve as a deflector roll for an adjacent coiler furnace. 
     It will be obvious to those of ordinary skill in the art that various modifications may be made to the present invention without departing from the spirit and scope of the present invention. Consequently, the scope of the present invention is intended to be defined by the attached claims.