Plant and method for producing flat rolled products

Abstract

Rolling method to produce a metal strip (P) in coil-to-coil, semi-endless or endless mode, in a rolling plant ( 10 ) comprising: a continuous casting device ( 11 ) to produce slabs; a furnace ( 16 ) configured to maintain the slabs at a certain temperature and/or to heat the slabs; at least one roughing stand ( 25 ) to reduce the thickness of the slabs and obtain an intermediate rolled product; a plurality of finishing stands ( 31 ) to reduce the thickness of the intermediate rolled product and obtain the strip (P); a rapid heating device ( 28 ) interposed between the at least one roughing stand ( 25 ) and the plurality of finishing stands ( 31 ) to heat the intermediate rolled product in each operating mode, so that the temperature of the strip (P) in correspondence with the outlet of the last finishing stand ( 31 ) is comprised between 830° C. and 860° C.

1 . Rolling method to produce a metal strip having a final thickness comprised between 0.6 mm and 25 mm, in a rolling plant configured to operate in an operating mode selected from a group comprising coil-to-coil mode, semi-endless mode and endless mode, and which comprises at least:
 a continuous casting device configured to produce thin slabs, having an initial thickness comprised between 50 mm and 160 mm;   a furnace configured to maintain said slabs at a certain temperature and/or to heat said slabs;   at least one roughing stand configured to reduce the thickness of at least one of said slabs in order to produce an intermediate rolled product, and a plurality of finishing stands configured to reduce the thickness of said intermediate rolled product in order to obtain said metal strip;   a rapid heating device, consisting of selectively activatable elements, which is interposed between said at least one roughing stand and said plurality of finishing stands and is configured to heat said intermediate rolled product;   and being wherein said rapid heating device is always kept active in the coil-to-coil or semi-endless mode to produce a strip having a final thickness smaller than 4.0 mm to heat said intermediate rolled product so that the temperature of said metal strip in correspondence with the outlet of the last finishing stand is comprised between 830° C. and 860° C.   
     
     
         2 . Method as in  claim 1 , and in which said operating mode is said coil-to-coil mode or said semi-endless mode, wherein a rolling speed (V L ) of said intermediate rolled product in correspondence with said plurality of finishing stands is lower than or equal to about 12 m/s. 
     
     
         3 . Method as in  claim 2 , wherein said rolling speed (V L ) is substantially constant. 
     
     
         4 . Method as in  claim 2 , wherein for the same final thickness (SF), said rolling speed (V L ) is substantially the same between said coil-to-coil mode and said semi-endless mode. 
     
     
         5 . Method as in  claim 2 , wherein said rolling speed is adjusted to an optimal value (V L-OPT ) corresponding to the speed that minimizes the operating costs (C OPEX ) of said plant, wherein said operating costs (C OPEX ) of said plant are calculated as C OPEX (V L , SF)=C HI (V L , SF)+C RI (V L , SF), wherein C HI (V L , SF) is the operating cost for the electrical power supply of said rapid heating device and C RI (V L , SF) is the operating cost represented by the risk of blockage of said intermediate rolled product and by the poor quality of the strip that would be obtained without reaching said temperature comprised between about 830° C. and about 860° C. in correspondence with the outlet of the last finishing stand. 
     
     
         6 . Rolling plant to produce a metal strip having a final thickness (SF) comprised between 0.6 mm and 25 mm, configured to operate in an operating mode selected in a group comprising coil-to-coil mode, semi-endless mode and endless mode, and which comprises at least:
 a continuous casting device configured to produce thin slabs, that is, having an initial thickness comprised between 50 mm and 160 mm;   a first selectively activatable cutting device configured to cut said slabs produced by said continuous casting device;   a furnace configured to maintain said slabs at a certain temperature and/or to heat said slabs;   at least one roughing stand configured to reduce the thickness of at least one of said slabs in order to produce an intermediate rolled product, and a plurality of finishing stands configured to reduce the thickness of said intermediate rolled product in order to obtain said metal strip;   a rapid heating device, consisting of selectively activatable elements, which is interposed between said at least one roughing stand and said plurality of finishing stands and is configured to heat said intermediate rolled product;   a second selectively activatable cutting device configured to cut said metal strip according to a predefined length;   the plant also comprising a management and control unit configured to command the functioning of said cutting devices so as to define said operating mode, wherein the management and control unit is also configured to always keep said rapid heating device active in the coil-to-coil or semi-endless mode in order to produce a strip having a final thickness smaller than about 4.0 mm.   
     
     
         7 . Plant as in  claim 6 , wherein said management and control unit is also configured to set a rolling speed (V L ) of said plurality of finishing stands to a value lower than about 12 m/s in the coil-to-coil or semi-endless operating mode.