Abstract:
A high-precision rolling mill with the flexture of the roll being controlled two-dimensionally which mainly comprises a mill stand, roll systems and roll supports. To minimize the flexural deformation of the rolls during rolling, the inventive rolling mill is also provided with a two-dimensional supporting system which is commonly composed of the mill stand, the roll supports and intermediate supporting means between the mill stand and the roll supports. The intermediate supporting device comprises pressing devices and horizontal pads, as well as vertical pad sets. The configuration of rolling mill results in the great reduction of the flexure, thus reducing the thickness error of cross-section of rolled plate and strip.

Description:
FIELD OF THE INVENTION 
     The invention generally relates to a rolling mill for producing plate and strip, and in particular to a rolling mill in which a roll&#39;s flexure is controlled in two-dimensional directions, thereby the rolled plate and strip have very high thickness precision in cross section. 
     BACKGROUND OF THE INVENTION 
     Generally, there are a variety of kinds of rolling mills for rolling plate and strip, and they are classified according to the number of rolls into the two-high mill, the four-high mill and the cluster mill, but the most commonly used rolling mills are the four-high mill, the HC mill and the cluster mill and so on. For two-high type, four-high type mills, there exist many disadvantages, the main disadvantage is that: when a rolled piece passes the mill stand, since the pressing devices are located at the necks of the rolls, the rolls are caused to have larger bending deformation, and the deformations of the rolls will result in the thickness error in the cross section of the rolled piece (rolled plate and strip), thus seriously affecting the quality of the rolled piece. To solve the above problem, the method of increasing the diameter of the rolls has to be adopted, and for a four-high mill, also the method of increasing the diameter of the supporting rolls has to be adopted. However, as the diameter of the rolls increases, it is certain to cause the rolling forces to abruptly increase, and the change of the rolling forces in turn causes an increase of the bending deformation of the rolls. 
     The cluster mills include integral housing type mills and open type mills (as shown in FIGS. 1,  2 ), Japanese Patent 54-1259 discloses a cluster mill which adopts a tower-like roll system. Of course, such rolling mills all have the advantage of high rigidity, but in a cluster mill, the portions of the mill stand which contact the supporting rolls still have bending deformation under rolling forces, thus causing the flexural deformation of the working rolls and affecting the uniformity of the thickness of rolled piece as a result. 
     The solution to the problem of the roll&#39;s flexural deformation to reduce or eliminate the effect of the roll&#39;s flexural deformation on the thickness of rolled piece consists in the control of the shape of the clearance between the working rolls to make the flexural deformation of the working rolls not to be affected by the change of rolling forces. A Chinese Patent (application number 89101393, issuance number CN 1013250B) discloses “A rolling mill with rolls of small flexure and high rigidity”. To achieve above object, according to the patent, the supporting rolls at the outmost layer of the tower-like roll system are supported on the roll supports in the form of a mufti-section beam; rolling forces acting on the working rolls are transmitted respectively to the upper and lower roll supports via the roll systems; the vertical component of the force borne by the roll supports are transmitted to the mill stand via the downward acting or upward devices or similar elements such as pads; the number of the downward acting or upward acting devices is at least two, and the positions of the downward acting or upward acting devices are in the middle region of the axis of the working roll on the roll supports. It can be seen, the solution of that patent can make the flexural deformation of the roll supports in the vertical plane substantially not to vary with the rolling forces, thus effectively reducing the thickness error in the cross-section of the rolled piece. However, for the cluster mills with a tower-like roll system, the force transmitted from the working rolls to the intermediate rolls has vertical and horizontal components, therefore the peripheral supporting rolls also bear significant horizontal component force. For the rolling mill disclosed in Chinese Patent No. 89101393, the horizontal component force causes the roll supports to have horizontal flexural deformation, thus causing the intermediate rolls as well as the working rolls to have larger flexural deformation. 
     As stated above, for solving the problem of flexural deformation of the working rolls of a cluster mill, it is not only necessary to reduce the flexural deformation produced by the vertical component force, but also that produced by the horizontal component force, that is, it is obliged to solve the problem of deformation in two-dimensional directions, so that a working roll can be held straight and the thickness precision in the cross-section of the rolled piece is increased. 
     SUMMARY OF THE INVENTION 
     Therefore, the invention is aimed to solve the problem of the two-dimensional flexural deformation of the rolls, namely, the invention can reduce not only the flexural deformation in vertical direction, but also that in horizontal direction. Accordingly, the object of the invention is to provide a high-precision rolling mill, as compared with the prior art, when the rolling mill of the invention is subjected to the rolling force, the flexural deformation of the rolls can be greatly reduced, resulting in the reduction of the thickness error in the cross-section of the rolled piece and the increase of the dimension accuracy of the rolled piece. 
     To achieve the above-mentioned object, the embodiment of the invention is as follows: the rolling mill for rolling plate and strip comprises a mill stand, an upper and a lower roll systems and an upper and a lower roll supports. The mill stand is of a frame shape and is able to bear rolling forces, and all parts and components of the rolling mill, such as the roll systems, are incorporated in the frame. The roll system is so arranged as to be of a tower-like configuration. The roll system is composed of three parts, a working roll, supporting rolls and intermediate rolls; the upper and lower supporting rolls disposed at the outmost layer of the roll system are respectively supported on the upper and lower roll supports in the form of a mufti-section beam, and the upper roll support can be moved up and down if necessary to adjust the magnitude of the clearance between the rolls. The rolling mill is characterized in that the mill stand, the roll supports and the intermediate supporting means between the frame and the roll supports commonly compose a two-dimensional supporting system. The intermediate supporting means is disposed on at least one of the upper and lower roll supports and is arranged in the region of the middle part of the roll body axis of the working roll with its length being not longer than the length of the roll body of the working roll. The intermediate supporting means includes pressing devices and horizontal pads; there are at least two pressing devices disposed above the upper roll support and placed in the mill stand, the lower roll support is supported by horizontal pads, and both the pressing devices and the horizontal pads are arranged in the region of the middle part of the roll body axis of the working roll on the roll support. In the invention there are also disposed upper and lower vertical pad sets along a horizontal direction, which are respectively positioned between the two side walls of the upper and lower roll supports and supported on the side walls of the mill stand, and the upper and lower vertical pad sets are respectively composed of two wedge-shaped menders to prevent the flexural deformation due to the horizontal component force. The shape of the mill stand is mated with that of the roll supports. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The embodiments of the invention will be described in detail in connection with accompanying drawings, and the object of the invention will become more apparent from the following description: 
     FIG. 1 is a schematic view of a conventional rolling mill; 
     FIG. 2 is a schematic view of a conventional open type cluster mill; 
     FIG. 3 is a schematic view of a conventional cluster mill disclosed in a Japanese Patent; 
     FIG. 4 is a front sectional view of the first embodiment of the rolling mill in accordance with the invention; 
     FIG. 5 is a sectional view of the first embodiment of the invention taken along line A—A in FIG. 4; 
     FIG. 6 is a sectional view of the first embodiment of the invention taken along line B—B in FIG. 4; 
     FIG. 7 is a sectional view of the first embodiment of the invention taken along line C—C in FIG. 4; 
     FIG. 8 is a front sectional view of the second embodiment of the rolling mill in accordance with the invention; 
     FIG. 9 is a sectional view of the second embodiment of the invention taken along line D—D in FIG. 8; 
     FIG. 10 is a front sectional view of the third embodiment of the invention. 
     FIG. 11 is a sectional view of the third embodiment taken along line E—E in FIG.  10 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1-3 are schematic views showing the commonly used conventional rolling mills. Due to their structure, it is inevitable for the rolls to deflect during rolling, and this will directly affect the quality of the rolled piece. Therefore, the surface precision of rolled piece, especially the thickness precision of plate, can not meet the requirements. 
     FIGS. 4-7 show the first embodiment of the high-precision rolling mill with flexures being controlled two-dimensionally in accordance with the invention. As can be seen in FIG. 4, a two-dimensional supporting system comprises a frame  10 , roll supports  4 ,  5 , and intermediate supporting means provided between the frame and the roll supports. In the frame  10  there are provided the main parts and components such as upper and lower roll systems, upper and lower roll supports, and etc. The frame  10  can be formed into an integral one, or can be formed by several parts connected together by means of welding or other connecting methods. The upper and lower roll systems are respectively composed of a working roll  1 , intermediate rolls  2  and supporting rolls  3  which form a tower-like roll system together. The rolled piece is designated by  12 . The supporting rolls  3  at the outmost layer of the roll system are supported in the form of a mufti-section beam, generally two or more section beam (refer to FIG.  5 ), on the upper and lower roll supports  4  and  5 . In the intermediate supporting means, the pressing devices  6  are provided between the upper roll support  4  and the upper inner wall of the frame  10 , the devices  6  are installed on the roll support  4  and located at the middle region of the axis of the working roll, generally located within the length of the roll body of the working roll. The pressing devices  6  can move up and down, causing the upper roll support  4  to move up and down in the integral frame  10  to adjust the clearance between the rolls. For carrying out automatic control, the pressing devices can also be equipped with an automatic sheet thickness controlling device (not shown in the figures) so as to accurately detect the magnitude of the rolling force and the clearance between the rolls. Therefore, the production can be automated to obtain high precision products. 
     Between the lower roll support  5  and the lower inner wall of the frame  10  there are disposed horizontal pads  7  (FIG.  4 ), the horizontal pads are placed under the roll support and located at the middle region of the axis of the working roll, generally located within the length of the roll body of the working roll. Obviously, the lower roll support  5  is supported by the horizontal pads  7 . The horizontal pads  7  can be of different sizes, namely, the thickness of the horizontal pads can form a thickness series. The adjustment of the rolling line can be realized by using horizontal pads  7  with different thickness. And also, the horizontal pads  7  can be replaced by a hydraulic device or a screw device. 
     Referring to FIGS. 4,  6  and  7 , it can be clearly seen from FIG. 4 that, besides being supported vertically by the pressing devices  6 , the upper roll support  4  is supported horizontally by two pairs of upper vertical pad sets  8 ,  8 . which are disposed between the inner side wall of the frame  10  and the upper roll support  4 . The upper vertical pad sets  8 ,  8  are respectively on the left side and the right side of the upper roll support  4 , and located at the middle region of the axis of the working roll, being within the length of the roll body. The upper vertical pad sets  8  each is composed of two mating wedge-shaped members with opposite inclinations (refer to FIG.  6 ). Similarly, the lower roll support  5  is not only supported vertically by the horizontal pads  7 , but also supported horizontally by lower vertical pad sets  9 ,  9  which are disposed between the inner side walls of the frame  10  and the lower roll support  5 . The lower vertical pad sets  9 ,  9  are respectively on the left side and the right side of the lower roll support  5 , and located at the middle region of the axis of the working roll, being within the length of the roll body. The lower vertical pad set  9  is also composed of mating wedge-shaped members (see FIG.  7 ). The lower roll support  5 , together with the horizontal pads  7  and the lower vertical pad sets  9 , is supported on the frame  10 , and the upper roll support  4 , together with the upper vertical pad sets  8  and the pressing devices  6 , is supported on the frame  10 . 
     Due to the above-mentioned structure of the rolling mill of the invention, the flexures of the rolls are substantially reduced. This is because that the frame, the roll supports and the intermediate supporting means between the frame and the roll supports of the rolling mill form a two-dimensional supporting system together, namely providing support in both vertical and horizontal directions, and specifically, the upper and lower roll supports, the supporting rolls, intermediate rolls and working rolls are all supported in both horizontal and vertical directions. The rolling forces borne by the working rolls are transmitted to the supporting rolls through the working rolls and the intermediate rolls. The supporting rolls comprise several backing bearings mounted on an axle (refer to FIG.  5 ). Therefore, the outer ring of the bearings rotates when the rolling force is transmitted to the outer ring, and the rolling force is then transmitted to the upper roll support through the bearings. The vertical component force finally reaches the upper inner wall of the frame via the pressing devices, and the horizontal component force reaches the side walls of the frame via the vertical pad sets. Similarly, the rolling force borne by the working roll is transmitted to the lower roll support via the intermediate rolls and the supporting rolls, with the vertical component force being transmitted to the lower inner wall of the frame via the horizontal pads  7  and the horizontal component force being transmitted to the side walls of the frame via the vertical pad sets  9 . The pressing devices, the horizontal pads and the vertical pad sets on the force transmitting path are all located at the middle region of the axis of the working roll, being within the length of the roll body. 
     Therefore, the rolling mill of the invention guarantees the proper shape, namely, the linearity of the generating line of the working roll not only in the vertical plane but also in the horizontal plane, as a result, the flexural deformation of the working roll basically does not vary with the rolling force. Therefore, the roll&#39;s flexural deformation is significantly reduced, resulting in the reduction of the error in thickness of the rolled strips. 
     The adjustment of the clearance between the rolls is accomplished by moving the upper roll support  4  up and down in the windows of the frame  10 , the upper roll support is driven by the pressing devices. 
     The rolling mill of the embodiment can be placed upside down, and accordingly the pressing devices become upward acting devices. Such a modification may have the same effects. 
     The hydraulic pressing devices can also be replaced by a screw device. 
     FIGS. 8-9 show the second embodiment of the invention. The rolling mill also comprise a two-dimensional supporting system composed of a mill stand, roll supports and intermediate supporting means between the mill stand and the roll supports. The particular components comprise the frame  10 , the upper roll support  24 , the lower roll support  25 , pads  21  and the roll systems, each of the roll systems includes a working roll  1 , intermediate rolls  2  and supporting rolls  3 . As in the first embodiment, the roll system also forms a tower-like roll system, and the supporting rolls  3  at the outmost layer are also respectively supported on the roll supports  24  and  25  in the form of multi-section beams. The second embodiment differs from the first embodiment in that: in the intermediate supporting means, there are provided pressing devices  26 ,  27  in place of the pressing devices  6  and the upper vertical pad sets  8  in the first embodiment, and lower pads  21  in place of the horizontal pads  7  and lower vertical pad sets  9 . This will be specifically described in the following. 
     Referring to FIG. 8, it can be seen from the figure that the lower roll support  25  is supported on the frame  10  through two pads  21  which are arranged obliquely between the frame  10  and the lower roll support  25 , the outer side walls of the upper and lower roll supports respectively have an oblique surface formed thereon, the oblique surface inclines inwardly and meets the respective top surface. The upper roll support  24  is supported on the frame  10  through the pressing devices  26 ,  27  which, as shown in the figure, are obviously composed of screws  27  and pads  26 . The pressing devices are disposed symmetrically on the roll support  24  (refer to FIG.  9 ). Each pad  26 , when viewed from the front, has an oblique surface which match one of the oblique surfaces on the upper roll support  24 . The threads on a pair of screws  27  are used for adjustment, it can be seen from the figure that they can move the upper roll support  24  up and down, thus causing the roll system to move up and down to adjust the clearance between the rolls. When the rolling resultant force including horizontal and vertical component forces acts on the upper roll support  24 , the force is transmitted to the screw-pad sets  26 ,  27  and finally reaches the frame  10 ; the shape of the frame  10  should match with that of the roll supports  25 ,  24 . Since the upper roll support  24  and the lower roll support  25  have oblique supporting surfaces, the frame  10  can bear the horizontal force and the vertical force. The pressing devices  26 ,  27  and the pads  21  on the force transmitting path are all located in the middle region of the axis of the working roll, being within the length of the roll body of the working roll, therefore, the flexural deformations of the frame in both directions can be converted into the quasi-rigid displacement of the components from the roll supports up to the working rolls. As a result, the two dimensional supporting system reduces the flexural deformation of the working rolls. FIG. 9 is a sectional view taken along line D—D in FIG.  8 . The structure of the second embodiment and the shapes of the various components are clearly shown in FIG.  8  and FIG.  9 . In addition, the number of the pressing devices can be more than two. 
     The rolling mill of the embodiment can be placed upside down, and the same effects can be obtained. 
     The screw device in the embodiment can be replaced by hydraulic cylinders or the like. 
     FIGS. 10 and 11 are schematic views of the third embodiment. It can be seen from the figures that the lower roll support  35  and lower pads  31  have the same structures as those in the second embodiment. The difference between them lies in the arrangement of the pressing devices  36 ,  37 . The pressing devices  36 ,  37  are installed obliquely with respect to the central axis of the frame  10  at the upper surface of the frame  10  and are arranged oppositely, thus causing the arrangement of the whole rolling mill to be more rational. 
     In the third embodiment, the transmission of the rolling forces borne by the rolling mill and the force-bearing members of the vertical and horizontal component forces are the same as those in the second embodiment, and the principles and functions of the two-dimensional supporting system to reduce the flexural deformation of the working rolls are also substantially the same, and this will not be repeatedly described herein. 
     Compared with the prior art, the invention has the following advantages: 
     Since the rolling mill of the invention has an integral frame the shape of which corresponds to the shape of the roll supports and the frame is of very high rigidity; the pads between the roll supports and the frame or the clearance adjusting devices are located in the middle region of the axis of the working roll within the range of length of the roll body of the working roll, and composes a two-dimensional supporting system, thus, the shape of the generating line of the working rolls is guaranteed not only in the vertical plane but also in the horizontal plane. As a result, the bending deformation of the working rolls basically does not vary with the rolling force, resulting in the remarkable reduction of the thickness error of the rolled strips. 
     The rolling mill of the invention can simplify the design of the roll shape (cambering) and the control of the roll shape during rolling. The bending deformations of the working rolls of the inventive rolling mill occurred in horizontal and vertical directions do not vary with the rolling forces. Since among the various factors associated with the cambering such as the bending deformation, flattening deformation, heat expansion and wear etc., the most important one—bending deformation—can be left out of consideration and the heat expansion and wear are also slowly changing factors, the design of the roll shape and the control of the roll shape during rolling can be greatly simplified. In addition, the “roll pass” formed by the bending deformations of the two working rolls in a conventional rolling mill is eliminated, thus facilitating the transverse flow of the metal and being advantageous to roll high-precision strips with wedge-shaped blanks, and the phenomenon of the “edge attenuation” of strips is greatly improved. 
     In the above mentioned embodiments of the invention, the number of the rolls in the roll system is  12 , but the roll systems may have different number of rolls. In addition, the different roll supports can mate with each other, and can also mate with the roll supports or the roll systems in a conventional rolling mill. 
     The invention is not limited to cold rolling mills, and is also applicable to hot-rolling mills for rolling strips. 
     Although the preferred embodiments of the invention have been described, to persons skilled in the art, various modifications can be made to the invention without going beyond the scope of the attached claims of the invention.