Process and system for manufacturing metal strips and sheets without discontinuity between continuous casting and rolling

Abstract

A process and system for manufacturing metal strips of 0.14-20 mm thickness and metal sheets of 10-100 mm thickness from slabs of thickness between 30 and 300 mm by continuous casting of the bow type. The slab upon casting is fed without discontinuity directly to the rolling step after heating in an induction furnace without any intermediate product. The rolled flat product is withdrawn as sheet upon controlled cooling, by means of cutting and withdrawal device or wound on a reel to form a coil of a continuous strip severable by cutting device downstream of a cooling system. Surface cooling devices can be provided between rolling stands. The feed speed from continuous casting to the end of rolling is increasing step by step in relation to the thickness reductions and the quality of the end product, with regulation in cascade to the downstream direction.

1 . A plant for manufacturing metal strips with thickness in the range between 0.14 and 20 mm and metal sheets with thickness in the range between 10 and 100 mm from a continuous casting, the plant comprising a mould and subsequent bow caster with means for liquid core reduction starting from slabs ( 1 ) of thickness between 30 and 300 mm and width between 600 and 4000 mm, wherein said mould has a ratio≧1.1 between its surface S M  at a meniscus, subtracting an area S T  interested by the submerged nozzle, and a cross-section area Sb of the slab ( 1 ) at an outlet of continuous casting, there being provided a secondary cooling system for obtaining, at the outlet of continuous casting, a slab having an inverted temperature gradient and a cross-section with an average surface temperature of the slab<1150° C. and with an average core temperature>1350° C., as well as a finishing mill ( 11 ) directly connected with the continuous casting at a maximum distance of 50 m, the plant further comprising an induction heating furnace ( 12 ) between the continuous casting outlet and a rolling-mill ( 11 ) and at an outlet of the rolling mill ( 11 ), either a cutting device ( 14 ) of coils, wound on an end reel ( 15 ), after a final cooling system ( 13 ), or a cutting device ( 14 ′) for the withdrawal of sheets ( 10 ) also cooled by said cooling system ( 13 ). 
     
     
         2 . The plant according to  claim 1 , wherein said in line rolling mill ( 11 ) is comprised of at least one stand, up to a maximum of twenty stands, wherein power required for a first five stands is determined as a function of the slab thickness at the casting outlet (SpB), multiplying such a value by increasing factors from 20 for the first stand to 100 for the last one in relation with a width of 1600 mm, while for greater widths by increasing these multiplying factors proportionally to the ratio between the actual width and 1600 mm. 
     
     
         3 . The plant according to  claim 2 , further comprising a surface cooling system ( 13 ′) based on pressurized water, including between at least two adjacent rolling stands opposite nozzles facing the slab ( 1 ). 
     
     
         4 . The plant according to  claim 3 , wherein the water pressure in the casting secondary cooling is between 10 and 40 bar and the distance of the cooling nozzles from the slab ( 1 ) is≦150 mm. 
     
     
         5 . The plant according to  claim 2 , further comprising rolls for the rolling-mill stands ( 11 ) with a diameter in a range between 300 and 800 mm. 
     
     
         6 . The plant according to  claim 2 , wherein said device ( 14 ′) for cutting and withdrawal of the sheets ( 20 ) is downstream of said cooling device ( 13 ′) intermediate between the stands, and upstream of said cooling system ( 13 ), downstream of which there is provided a shear ( 14 ) for cutting the rolled strip at the end of winding of which coil ( 15 ). 
     
     
         7 . The plant according to  claim 2 , further comprising a surface cooling system ( 13 ′) based on pressurized water, including between at least two adjacent rolling stands opposite nozzles facing the slab ( 1 ).