Patent Publication Number: US-8113267-B2

Title: Twin-roll casting machine

Description:
TECHNICAL FIELD 
     The present invention relates to a twin-roll casting machine. 
     BACKGROUND ART 
     Known as one of techniques for directly producing a strip from molten metal is twin-roll continuous casting in which molten metal is supplied to between a pair of rotated rolls so as to deliver solidified metal in the form of strip. 
       FIGS. 1-3  show an example of a conventional twin-roll casting machine with a pair of chilled rolls  1   a  and  1   b  horizontally juxtaposed and a pair of side weirs  2   a  and  2   b  associated with the rolls  1   a  and  1   b.    
     The rolls  1   a  and  1   b  are constructed such that cooling water passes through insides of the rolls, a nip G between the rolls being controllable to be increased or decreased depending upon thickness of a strip  3  to be produced. 
     Velocity and direction of rotation of the rolls  1   a  and  1   b  are set such that the outer peripheries of the respective rolls move from above towards the nip G at the same velocity. 
     The one and the other side weirs  2   a  and  2   b  surface-contact one and the other ends of the rolls  1   a  and  1   b , respectively. Nozzle pieces  4   a  and  4   b  for supply of molten metal are arranged in a space defined by the rolls  1   a  and  1   b  and side weirs  2   a  and  2   b  so as to be positioned just above the nip G (see, for example, Patent Literature 1). 
     The one and the other nozzle pieces  4   a  and  4   b  are supported to have a constant gap against the one and the other side weirs  2   a  and  2   b , respectively. 
     Each of the nozzle pieces  4   a  and  4   b  has a top with an elongated nozzle trough  6  for reception of molten metal  5 , and longitudinal side walls each with a plurality of openings  7  at portions of the walls adjacent to lower ends of the walls so as to supply the molten metal  5  from the nozzle trough  6  to between the rolls  1   a  and  1   b , the openings  7  being spaced apart from each other axially of the roll  1   a ,  1   b . Pouring of the molten metal  5  into the respective nozzle troughs  6  provides a molten metal pool  8  above the nip G and in contact with outer peripheries of the rolls  1   a  and  1   b.    
     As shown by arrows in  FIG. 2(   a ), with respect to each of the nozzle pieces  4   a  and  4   b , the openings  7  are formed symmetrically at the portions adjacent to the one and the other rolls  1   a  and  1   b , respectively. 
     In the above-mentioned twin-roll casting machine, the molten metal pool  8  is formed and the rolls  1   a  and  1   b  are rotated with the cooling water passing through and cooling the rolls  1   a  and  1   b , so that molten metal  5  is solidified on the outer peripheries of the rolls  1   a  and  1   b  into solidified shells  9  so as to deliver downward the strip  3  from the nip G. 
     In this case, loads are applied to necks of the respective rolls  1   a  and  1   b  in directions toward each other so as to make the produced strip  3  to have a targeted thickness.
     [Patent Literature 1] JP 2000-202590A   

     SUMMARY OF INVENTION 
     Technical Problems 
     However, with respect to each of the nozzle pieces  4   a  and  4   b , symmetrical formation of the openings  7  at the portions adjacent to the one and the other rolls  1   a  and  1   b  brings about the molten metal  5  in the pool  8  flowing faster at the portions adjacent to the openings  7  than at the other portions, so that the molten metal  5  is difficult to cool on the outer peripheries of the rolls  1   a  and  1   b  adjacent to the openings  7 . 
     Thus, as shown in  FIG. 2(   b ), solidification of the shells  9  progresses (with thickness increased) on the outer peripheries of the rolls  1   a  and  1   b  at portions away from the openings  7  while solidification of the shells  9  is hard to progress on the outer peripheries of the rolls  1   a  and  1  at portions adjacent to the openings  7 . 
     As a result, the strip  3  to be delivered from the rolls  1   a  and  1   b  is formed with ridges of the shells  9  with progressed solidification being brought together while unsolidified regions  10  remain at valleys between the adjacent ridges axially of the rolls  1   a  and  1   b  as shown in  FIG. 2(   c ). 
     Thus, as shown in  FIG. 2(   d ), the strip  3  completely contracted due to solidification has irregularities in crosswise thickness distribution with disadvantageous result that cracks may be produced. 
     The invention was made in view of the above and has its object to provide a twin-roll casting machine capable of suppressing irregularities in crosswise thickness distribution of a strip. 
     Solution to Problems 
     In order to attain the above object, in a first aspect of the invention, provided are a pair of chilled rolls, a pair of side weirs and a nozzle piece arranged in a space defined by said rolls and said side weirs, said nozzle piece being formed with a plurality of molten-metal delivery openings spaced apart from each other axially of the rolls at portions of the nozzle piece adjacent to one and the other rolls, respectively, said openings adjacent to the one roll being in antiphase to those adjacent to the other roll. 
     In a second aspect of the invention, provided are a pair of chilled rolls, a pair of side weirs and first and second nozzle pieces arranged in tandem axially of the rolls and in a space defined by said rolls and said side weirs, each of said first and second nozzle pieces being formed with a plurality of molten-metal delivery openings spaced apart from each other axially of the rolls at portions of the nozzle piece adjacent to one and the other of the rolls, respectively, said openings adjacent to the one roll being in antiphase to those adjacent to the other roll. 
     In a third aspect of the invention, the first nozzle piece is set to have smaller and greater molten-metal delivery ranges axially along the one and the other rolls, respectively, and the second nozzle piece is set to have greater and smaller molten-metal delivery ranges axially along the one and the other rolls, respectively. 
     In a fourth aspect of the invention, each of the openings has cross section elongated axially of the rolls. 
     Advantageous Effects of Invention 
     According to a twin-roll casting machine of the invention, the following excellent effects and advantages can be obtained. 
     (1) The openings of the nozzle piece adjacent to the one roll are in antiphase to those adjacent to the other roll, so that the solidified shells on the outer peripheries of the one and the other rolls can be brought together with ridges and valleys of the solidified shell on the outer periphery of the one roll being confronted to valleys and ridges of the solidified shell on the outer periphery of the other roll, respectively.
 
(2) Thus, the strip delivered from the rolls has tendency of being equalized with no irregularities in crosswise thickness distribution, cracks being prevented from being produced.
 
(3) When the first and second nozzle pieces are arranged in tandem and the first nozzle piece is set to have the smaller and larger molten-metal delivery ranges axially along the one and the other rolls, respectively, and the second nozzle piece is set to have the larger and smaller molten-metal delivery ranges axially along the one and the other rolls, respectively, then a ridge of the solidified shell on the outer periphery of the one roll at axially intermediate portion thereof is not confronted to a ridge of the solidified shell on the outer periphery of the other roll at axially intermediate portion thereof with an advantageous result that the strip delivered by the rolls has further equalized crosswise thickness distribution.
 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic view showing an example of a conventional twin-roll casting machine laterally of chilled rolls; 
         FIG. 2  is schematic views showing relationship between the nozzle pieces and cross-sectional shape of the strip in  FIG. 1 ; 
         FIG. 3  is a schematic perspective view showing the twin-roll casting machine in  FIG. 1 ; 
         FIG. 4  is schematic views showing relationship between the nozzle pieces and cross-sectional shape of the strip in an embodiment of a twin-roll casting machine according to the invention; 
         FIG. 5  is a partial plan view showing an example of a specific shape of the nozzle pieces in  FIG. 4 ; 
         FIG. 6  is a view looking in direction of arrows VI in  FIG. 5 ; 
         FIG. 7  is a view looking in direction of arrows VII in  FIG. 6 ; and 
         FIG. 8  is a schematic view showing nozzle pieces in a further embodiment of a twin-roll casting machine according to the invention. 
     
    
    
     REFERENCE SIGNS LIST 
     
         
           1   a  chilled roll 
           1   b  chilled roll 
           2   a  side weir 
           2   a  side weir 
           5  molten metal 
           11   a  nozzle piece 
           11   b  nozzle piece 
           13  opening 
       
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the invention will be described in conjunction with the drawings. 
       FIGS. 4-7  show an embodiment of a twin-roll casting machine according to the invention with a pair of chilled rolls  1   a  and  1   b  horizontally juxtaposed, a pair of side weirs  2   a  and  2   b  associated with the rolls  1   a  and  1   b , and nozzle pieces  11   a  and  11   b.    
     One  11   a  of the nozzle pieces is positioned just above the nip G and is supported to have a constant gap against one  2   a  of the side weirs, the other nozzle piece  11   b  being positioned just above the nip G and being supported to have a constant gas against the other side weir  2   b.    
     Each of the nozzle pieces  11   a  and  11   b  has a top with an elongated nozzle trough  12  for reception of molten metal  5 , a plurality of openings  13  being on an inner bottom of the nozzle trough  12  and pass downwardly through the bottom, the openings  13  being dividedly arranged adjacent to the one and the other rolls  1   a  and  1   b , respectively, and spaced apart from each other axially of the rolls  1   a  and  1   b.    
     As shown by arrows in  FIG. 4(   a ), with respect to each of the nozzle pieces  11   a  and  11   b , the openings  13  are formed alternately (in antiphase) at portions adjacent to the one and the other rolls  1   a  and  1   b.    
     As shown in  FIG. 5 , the openings  13  are substantially formed to be oval in cross section extending axially of the rolls  1   a  and  1   b.    
     A bottom of each of the nozzle pieces  11   a  and  11   b  has guides  14  which laterally guide the molten metal  5  flowing out from the respective openings  13  to outer peripheries of the rolls  1   a  and  1   b , respectively, the guides extending throughout each of the nozzle pieces  11   a  and  11   b  (see  FIGS. 6 and 7 ), so that pouring of the molten metal  5  into the nozzle troughs  12  brings about the molten metal pool  8  in contact with the outer peripheries of the rolls  1   a  and  1   b.    
     In the above-mentioned twin-roll casting machine, the molten metal pool  8  is formed and the rolls  1   a  and  1   b  are rotated with the cooling water passing through and cooling the rolls  1   a  and  1   b , so that the molten metal  5  is solidified on the outer peripheries of the rolls  1   a  and  1   b  into solidified shell  9  so as to deliver downward the strip  3  from the nip G. 
     In this case, as shown in  FIG. 4(   a ), with respect to each of the nozzle pieces  11   a  and  11   b , the openings  13  formed adjacent to the one roll  1   a  are in antiphase to those adjacent to the other roll  1   b  so that the solidified shells  9  on the outer peripheries of the one and the other rolls  1   a  and  1   b  are brought together as shown in  FIG. 4(   c ) with ridges of the shell  9  with progressed solidification on the outer periphery of the one roll  1   a  being confronted to valleys of the shell  9  with unprogressed solidification on the outer periphery of the other roll  1   b  and similarly with valleys of the shell  9  on the outer periphery of the one roll  1   a  being confronted to ridges of the shell  9  on the outer periphery of the other roll  1   b , as shown in  FIG. 4(   b ). 
     Thus, the unsolidified regions  10  between both the solidified shells  9  are decreased in comparison with those of the prior art shown in  FIG. 2(   c ). The strip  3  completely contracted due to solidification has tendency of being equalized with no irregularities in crosswise thickness distribution as shown in  FIG. 4(   d ), cracks being prevented from being produced. 
       FIG. 8  shows a further embodiment of a twin-roll casting machine according to the invention in which parts similar to those in  FIGS. 4-7  are represented by the same reference numerals. 
     In this twin-roll casting machine, a pair of nozzle pieces  11   a  and  11   b  have opposed ends slanted to chilled rolls  1   a  and  1   b , so that the nozzle piece  11   a  is shorter in length adjacent to the one roll  1   a  and is longer in length adjacent to the other roll  1   b  and the nozzle piece  11   b  is longer in length adjacent to the one roll  1   a  and is shorter in length adjacent to the other roll  1   b.    
     As shown by arrows, with respect to each of the nozzle pieces  11   a  and  11   b , the openings  13  are formed alternately (in antiphase) at portions adjacent to the one and the other rolls  1   a  and  1   b.    
     Number of the openings  13  on the nozzle piece  11   a  adjacent to the roll  1   a  is less than that adjacent to the roll  1   b ; number of the openings  13  on the nozzle piece  11   b  adjacent to the roll  1   b  is less than that adjacent to the roll  1   a.    
     In other words, the nozzle piece  11   a  is set to have smaller and greater molten-metal delivery ranges axially along the one and the other rolls  1   a  and  1   b , respectively. The nozzle piece  11   b  is set to have greater and smaller molten-metal delivery ranges axially along the one and the other rolls  1   a  and  1   b , respectively. As a result, a gap S 1  between the nozzle pieces  11   a  and  11   b  on the side of the one roll  1   a  is not confronted to a gap S 2  between the nozzle pieces  11   a  and  11   b  on the side of the other roll  1   b  diametrically of the rolls  1   a  and  1   b.    
     Thus, a ridge of the solidified shell on the outer periphery of the one roll  1   a  at axially intermediate portion thereof is not confronted to a ridge of the solidified shell  9  on the outer periphery of the other roll  1   b  at axially intermediate portion thereof with an advantageous result that the strip  3  delivered by the roll  1   a  has further equalized crosswise thickness distribution (see  FIG. 4  with respect to strip  3  and the solidified shells  9 ). 
     It is to be understood that a twin-roll casting machine of the invention is not limited to the above embodiments and that various changes and modifications may be made without departing from the scope of the invention. 
     INDUSTRIAL APPLICABILITY 
     A twin-roll casting machine of the invention may be applied to production of strips of steel and other various metals.