Ultra-thin slab or thick-strip casting

Abstract

A system of twin-roll casting an ultra-thin slab or thick-strip of metal with a liquid core still present inside the hollow shell of the casting as it exits the nip of the opposing counter rotating casting rolls. The wide sides of the cast shell are formed against a recessed casting surface on each roll and the narrow end walls of the shell are formed against the tapered ends of the recessed area so one half of the narrow end wall is formed on each roll and the two halves are joined together at the nip to form the full perimeter of the metal casting. A liquid-cooled copper mold liner provides continued support to each of the four sides of the casting below the twin-rolls and contact with those chilled copper mold liners continues to remove heat from the liquid core of the casting enabling the shell to continue growing in thickness. As the casting exits the mold it will be of adequate thickness to pass through opposing pairs of support rolls below the mold without bulging where water sprays can provide the additional cooling needed for final and complete solidification. A variation of this system uses one or more separating dams to cast different metals or different alloys of the same metal to integrally cast a dual-layer or multi-layer ultra-thin slab or thick strip of metal with a thin metal layer on one or both of the wide and narrow end casting surfaces.

1 . A twin roll continuous casting system, comprising:
 first and second casting rolls; and   a recessed roller surface on at least one of the first and second casting rolls for forming at least a portion of a casting shell.   
     
     
         2 . A twin roll continuous casting system according to  claim 1 , wherein a portion of the recessed roller surface is constructed and arranged to facilitate narrow end solidification of a casting shell. 
     
     
         3 . A twin roll continuous casting system according to  claim 1 , wherein both the first and second casting rolls have a recessed roller surface. 
     
     
         4 . A twin roll continuous casting system according to  claim 3 , wherein the recess defined in the first casting roll has a first maximum depth and the recess defined in the second casting roll has a second maximum depth, and wherein the first maximum depth is substantially the same as a second maximum depth. 
     
     
         5 . A twin roll continuous casting system according to  claim 3 , wherein the recess defined in the first casting roll is substantially symmetrical with respect to the recess that is defined in the second casting roll. 
     
     
         6 . A twin roll continuous casting system according to  claim 1 , wherein the recessed roller surface is constructed and arranged to form a wide side of a casting shell. 
     
     
         7 . A twin roll continuous casting system according to  claim 1 , wherein the recessed roller surface has a maximum depth, and wherein the maximum depth is substantially equal to about 50% of a design casting thickness. 
     
     
         8 . A twin roll continuous casting system according to  claim 1 , wherein the recessed roller surface includes a recessed casting surface and a narrow end casting surface, and wherein a recess angle defined between the recessed casting surface and the narrow end casting surface is substantially within a range that is about 90° to 130°. 
     
     
         9 . A twin roll continuous casting system according to  claim 8 , wherein the recess angle is substantially within a range of about 100° to 120°. 
     
     
         10 . A twin roll continuous casting system according to  claim 1 , wherein the recessed roller surface includes a recessed casting surface and a first narrow end casting surface, and wherein a corner defined between the two casting surfaces is concavely radiused. 
     
     
         11 . A twin roll continuous casting system according to  claim 10 , wherein the recessed roller surface includes a second narrow end casting surface, and wherein the second narrow end casting surface is substantially symmetrical in shape to the first narrow end casting surface. 
     
     
         12 . A twin roll continuous casting system according to  claim 10 , wherein the concavely radiused corner defines an average radius of curvature, and wherein a ratio of the average radius of curvature to a design casting thickness is substantially no more than about 0.5 or less. 
     
     
         13 . A twin roll continuous casting system according to  claim 12 , wherein the ratio of the average radius of curvature to the design casting thickness is substantially within a range of about 0.1 to about 0.33. 
     
     
         14 . A twin roll continuous casting system according to  claim 13 , wherein the ratio of the average radius of curvature to the design casting thickness is substantially within a range of about 0.2 to about 0.3. 
     
     
         15 . A twin roll continuous casting system according to  claim 1 , further comprising support structure positioned beneath the casting rolls for supporting the casting shell. 
     
     
         16 . A twin roll continuous casting system according to  claim 15 , wherein the support structure is constructed and arranged to support substantially an entire perimeter of the casting shell as viewed in transverse cross-section. 
     
     
         17 . A method of continuously casting a metal material, comprising steps of:
 providing a molten metal material; and   cooling the molten metal material into a solid casting using a casting roller that has a recess defined therein.   
     
     
         18 . A method of continuously casting a metal material according to  claim 17 , wherein the speed of casting is substantially between about 6 meters per minute to about 100 meters per minute. 
     
     
         19 . A method of continuously casting a metal material according to  claim 18 , wherein said speed of casting is substantially between about 8 meters per minute and 80 meters per minute. 
     
     
         20 . A twin roll continuous casting system, comprising:
 first and second casting rolls that are constructed and arranged to form a casting shell; and   support structure positioned beneath the casting rolls for supporting substantially an entire perimeter of the casting shell as viewed in transverse cross-section.   
     
     
         21 . A twin roll continuous casting system according to  claim 20 , wherein said support structure comprises copper. 
     
     
         22 . A twin roll continuous casting system according to  claim 20 , wherein said support structure is liquid cooled. 
     
     
         23 . A twin roll continuous casting system according to  claim 20 , wherein the support structure is constructed and arranged to facilitate continued solidification of the casting shell. 
     
     
         24 . A twin roll continuous casting system according to  claim 20 , wherein the support structure includes a hard surface coating to minimize wear, the hard surface coating having a hardness that is substantially within a range of about 250 to about 1200 Vickers. 
     
     
         25 . A twin roll continuous casting system according to  claim 20 , wherein the support structure includes a first support surface for supporting a narrow end of the casting shell, and wherein the first support surface is tapered at an upper portion thereof. 
     
     
         26 . A twin roll continuous casting system according to  claim 25 , wherein portions of the first support surface beneath the upper portion are substantially flat. 
     
     
         27 . A twin roll continuous casting system, comprising:
 a cavity that is constructed and arranged to hold a liquid metal pool;   first and second casting rolls;   at least two separating dams positioned axially within the cavity for separating the cavity into at least three separate metal pools;   wherein different materials may be cast simultaneously in at least three layers into a single casting shell.   
     
     
         28 . A twin roll continuous casting system according to  claim 27 , wherein at least one of the at least three metal pools includes a surface cladding material. 
     
     
         29 . A twin roll continuous casting system according to  claim 27 , wherein a thickness ratio between about 1:1:1 to as high as 1:40:1. 
     
     
         30 . A method of continuously casting a material, comprising steps of:
 providing at least three different pools of molten material within a cavity; and   fabricating a multi-layer casting shell using first and second casting rolls simultaneously using material from each of the at least three different pools of molten material.   
     
     
         31 . A method of continuously casting material according to  claim 30 , wherein the step of fabricating a multilayer casting shell includes fabricating at least one cladding layer from a cladding material. 
     
     
         32 . A method of continuously casting material according to  claim 31 , wherein the cladding material is selected from a group consisting of stainless steel, zinc and copper. 
     
     
         33 . A twin roll continuous casting system, comprising:
 a cavity that is constructed and arranged to hold a liquid metal pool;   at least one separating dam positioned within the cavity for separating the cavity into at least two separate metal pools of different materials; and   first and second casting rolls for receiving material from the at least two separate metal pools and casting at least a first layer having a first thickness and a second layer having a second thickness into a single casting shell, and wherein a ratio of the first and second thicknesses is substantially within a range of about 1:2 to about 1:40.   
     
     
         34 . A twin roll continuous casting system according to  claim 33 , wherein a thickness ratio between two of the layers is substantially within a range of about 1:3 to about 1:35. 
     
     
         35 . A twin roll continuous casting system according to  claim 34 , wherein a thickness ratio between two of the layers is and most preferably substantially within a range of about 1:4 to about 1:30.