Abstract:
An improved sliding chain-type ingot mold for a continuous casting plant, including two pairs of chains arranged in a closed ring system and configured to rotate in opposite directions, each pair including at least one of molding elements and shell-type elements which forms a closed mold, the two pairs of chains being arranged to wind up on respective sprockets, one pair having a first set of the at least one of molding elements and shell-type elements configured to interlock with a second set of the at least one of molding elements and shell-type elements on the other pair to form a cavity for receiving a molten material, external pressurizing rollers configured to act on the first and second sets of the plurality of at least one of molding elements and shell-type elements to detach and approach with each other, and fixed contrasting elements fixedly positioned to counteract the pressurizing rollers.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of Ser. No. 09/178,429, filed on Oct. 26, 1998 and now issued as U.S. Pat. No. 6,192,972. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention refers to an improved sliding chain-type ingot mold for a continuous casting plant. 
     2. Description of the Background 
     The production of billets and ingots by a continuous casting process formerly utilized stationary mold or shell-type elements in which the steel coming from the ladle and basket was introduced. These plants have at in any case always suffered from considerable drawbacks, both from the viewpoint of productivity and of the difficulty of cooling the mold or shell-type elements. 
     It is in fact precisely the stationary structure of these mold or shell-type elements, being among other things of a limited longitudinal size, as well as the difficulties of maintaining contact between the solidified crust and the stationary structure, which allow only modest casting speeds, with a resulting slow and difficult heat dissipation from the mold or shell-type elements. 
     A solution was found in the production of trays capable of feeding several casting lines in parallel, all equipped with stationary mold or shell-type elements of the limited size mentioned above. However, even this solution involves some drawbacks, as any increase of the casting lines also causes an increase and a multiplication of the maintenance requirements and some heat dissipation problems. 
     Consequently, some plants have been developed which utilize a multiple number of mold or shell-type elements in motion, being firmly attached to two chains or crawler tracks arranged in a closed ring. These two chains arranged in a closed ring are over a straight portion of their path made to interface with each other, so as to generate a closed molding path to which the liquid metal coming from the trays can be directly fed. 
     Thanks to the lengthening of the longitudinal size of the closed mold, this system allows considerably boosting the casting speed, so as to attain the same productivity of three or four of the parallel lines described above. This also achieves the notable advantage of making it possible to operate directly in line with a subsequent rolling train or similar. 
     This type of continuous casting process, simply known as a sliding chain-type ingot mold, provides in particular, as mentioned, for two chains arranged in a closed ring, each carrying a multiple number of molding elements. 
     The molding elements can be made to interface with each other, so as to form a closed mold in the straight portion of the chain. In particular, in order to achieve this, a chain carries molding elements that are in one of their terminal portions capable of interlocking with the terminal portion of the molding elements carried by another chain. This produces a length of continuous cavity, formed in its interior by the interfacing and associated molds, in which the molten metal coming from the trays is cast. 
     Even this sliding chain-type ingot mold presents drawbacks and problems due to the deformations generated by the internal heat transmitted directly to the molten metal. 
     The deformations mainly cause a detachment of the two portions of the mold interfacing and associated with each other to form the cavity, with a resulting leakage of molten metal. 
     This also leads to a considerable reduction of the heat transmission, which overheats the copper structures designed to cool the interfacing molts, even up to the point of melting them. 
     Moreover, it is precisely because of these stresses that a deformation of the two interfacing molds occurs, causing slippages which lead to a rapid wastage of the same. 
     SUMMARY OF THE INVENTION 
     The main purpose of this invention is to solve the technical problems affecting the mentioned known art in an extremely simple, economical and particularly functional manner, while also eliminating the drawbacks outlined above. 
     Another purpose is to reduce to a minimum the wear of the parts involved and in reciprocal contact during the continuous casting process. 
     In view of these purposes and in accordance with the invention, it was conceived to produce an ingot mold of a sliding chain-type, capable of being employed in a continuous casting process, having the characteristics outlined in the attached claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The structural and functional characteristics of this invention and its advantages with respect to the known art will become even clearer and more evident from an analysis of the following description, with reference to the enclosed drawings showing examples of an ingot mold according to this invention. In the drawings: 
     FIG. 1 is a view of part of a vertical, continuous casting plant equipped with a sliding chain-type ingot mold according to the invention; 
     FIG. 2 is a view of part of a horizontal continuous casting plant equipped with a sliding chain-type ingot mold according to the invention; 
     FIG. 3 is an enlarged raised side view of a detail of the two plants shown in FIG.  1  and/or  2 , taken next to the end of the straight portion, before the gap between the molding elements interfacing with each other; 
     FIG. 4 is an enlarged transversal cross-section, taken along the line IV—IV of FIG.  1  and/or  2 ; 
     FIGS. 5 and 6 are enlarged transversal cross sections, taken along the line V—V of FIG.  1  and/or  2 , showing the chain and the relative molding elements in two different positions of forward motion; 
     FIGS. 7 and 8 are two simplified cross sections of a second embodiment of the molding elements, capable of being positioned on the opposing chains of the ingot mold of this invention; 
     FIGS. 9 and 10 are two simplified cross sections of a third embodiment of the molding elements of the ingot mold of this invention, similar to that shown in FIGS. 7 and 8; and 
     FIGS. 11 and 12 are two simplified cross sections of a fourth embodiment of the molding elements, capable of being positioned on the opposing chains of the ingot mold of this invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The FIGS. 1 and 2 show two continuous casting plants, one of a vertical and the other of a horizontal type, both equipped with a sliding chain-type ingot mold according to this invention. 
     The figures show a basket  10  feeding a dragging chain-type ingot mold, indicated in its overall form by  11 . 
     The ingot mold  11  comprises two pairs of chains  12  and  13 , both arranged in a closed ring, rotating in opposite directions and carrying a multiple number of molding or shell-type elements  14  and  15 . 
     The molding or shell-type elements  14  and  15 , forming two half-molds, can be made to interface with each other so as to form a closed mold. In particular, the two half molds are capable, when engaged with each other, of forming a cavity for the casting of metal. 
     The ingot mold  11  is in fact designed so that the two pairs of chains  12  and  13  are made to wind up on sprockets  16  and  17  which, in addition to causing the chains&#39; forward motion, also define a straight portion of the ingot mold in which the two opposing half molds engage with each other so as to interlock and form a continuous cavity. 
     In order to achieve this, a pair of chains  13  carries some molding elements  15  fitted in a terminal portion with external surfaces  19  capable of inserting and engaging themselves in corresponding internal surfaces  18  of a terminal portion of the half-mold elements  14  carried by the other pair of chains  12 . This produces a length of continuous cavity, formed internally by the half molds  14  and  15  interfacing and associating with each other, into which the molten metal coming from the tray  10  is directly cast. 
     The molding elements  14  and  15 , as shown in the cross sections of FIGS. 4-6, both comprise a base portion  20  and  21 , each of which is projecting some leg-shaped walls  22 ,  24  and  23 ,  25 , capable of forming a more or less pronounced, essentially U-shaped section. 
     The pair of chains  13  is arranged to the sides of the base portion  21 , just as the pair of chains  12  is arranged to the sides of the base portion  20 . 
     In this second case it is also worth noting that the base portion carries two lateral extensions  26 , fitted with a hollow seat  27  housing a rod which also passes through a hole  29  in the base portion  20 . 
     This arrangement produces a connecting element designed to maintain a firm bond between the two portions  14   a  and  14   b , which constitute each molding element  14  of the embodiment shown. It can in particular be noted that these two portions  14   a  and  14   b  are coupled along opposing, rounded and complementary surfaces  30 , around which the two portions  14   a  and  14   b  of the molding element  14  may oscillate in the way of a spherical coupling working in combination with an underlying barrel-shaped roller  39 . 
     This oscillation is also possible because the two extremities of the rod  28  are fitted, between the locking nuts  31  and the hollow seats  27 , with elastic elements such as cup-type springs or Belleville springs  32 . 
     This arrangement guarantees contact but allows a slight reciprocal rotation. It is worth noting that the two molding elements  14  and  15  offer a symmetric shape with respect to an axis of symmetry  38  perpendicular to the two base portions  20  and  21 . 
     The upper surfaces of the two lateral extensions  26  of the base portion  20  are further equipped with two cam-shaped surfaces  33 . These cam-shaped surfaces are capable of contacting and interacting with some engaging elements constituted by a pair of rollers  34  in a fixed frame  35  at the extreme end of the straight portion of the ingot mold. The cam-shaped surfaces  33  are arranged along the longitudinal direction of motion of the two pairs of chains, and increase in height in the direction of their forward motion. 
     The straight portion of the ingot mold may provide for some rollers  36 , which are always firmly attached to the fixed frame  35 . These rollers  36 , which are positioned from opposite sides on the external surfaces of the leg-shaped walls  22 ,  24  of the molding elements  14 , form a lateral guide, thanks also to the presence of springs  37  capable of modulating their lateral pushing action. 
     Of course both sets of multiple molding elements  14  and  15  are equipped with their relative cooling facilities (not shown) as well as with some guiding elements along their entire path. 
     The operation of an arrangement according to this invention is as follows. 
     Some drive units, not shown, rotate the two pairs of chains  12  and  13  along with their respective molding elements  14  and  15 . 
     When the liquid metal feed is started from the tray  10 , this metal enters between the molding elements  14  and  15 , which are associated to engage with each other and form a continuous cavity in motion along the straight portion of the two pairs of chains  12  and  13 . 
     During the motion of the two pairs of chains  12  and  13  along with their relative molding elements  14  and  15  closed between them, the cavity is kept in a continuous and uniform condition also thanks to the presence of the rollers  36  acting on the external surfaces of the leg-shaped walls  22 ,  24  of the molding elements  14 . 
     This produces a composite and continuous forward motion nearly up to the end of the straight portion, where each of the engaged molding elements  14  and  15  comes to be opened by the deviation of the two pairs of chains to which the molding elements are firmly attached. 
     It is in this phase that the cam surfaces  33  placed on the extensions  26  of the base portion  20  of each molding element  14  come to interact with the engaging elements constituted by the rollers  34 . Since the cam-shaped surfaces  33  are rising in height in the direction of their forward motion, this generates, as shown in FIG. 6, a reciprocal rotation between the two portions  14   a  and  14   b  of the molding element  14 . The entire process is obviously made possible, as shown above, by the presence of the two rounded surfaces  30  and the springs  32  placed on the extremities of the rod  28  and the underlying barrel-shaped roller that acts to counter the rotation. 
     This slight rotation causes a detachment between the internal surfaces  18  of the molding element  14  and the external surfaces  19  of the molding element  15  that facilitates their detachment. 
     This rotation also helps to prevent friction between the mentioned surfaces, and any undesirable deformations on the two molding elements. 
     This solves the problems of the known continuous casting plants, while eliminating the wear which boosts the number of repairs and the operating costs of the ingot mold. 
     FIGS. 7 and 8 show a simplified alternative first embodiment of molding elements capable of being positioned on the pairs of chains while using various means of engagement. 
     In this embodiment the molding elements are generally produced, as shown before, one in a single piece and the other in two pieces. In this embodiment equal elements are designated by the same reference numbers as formerly used, preceded by the number “ 1 ”. 
     Each lower molding element  114  is in fact produced in, two portions, indicated by  114   a  and  114   b , and presents an asymmetrical shape with respect to an axis  138  set perpendicular to two base portions  120  and  121 . 
     FIG. 7 shows a first transversal cross section where it can be seen that in the molding element  114  the base portion  120  constitutes the first portion  114   a , which is fitted on one side with a pointed leg-type wall  122 . The other side carries a rounded surface  130  facing a complementary rounded surface  130  of the second portion  114   b . This second portion  114   b  extends on the other side into a vertical leg-type wall  124 , similar to the previous walls  24 , but arranged to the side of the upper base portion  121 . 
     The molding section  115  is simply constituted by a molding element rather similar to the molding element  114 , but is rotated in its arrangement by 180° with respect to the mentioned axis  138  of the mold, and produced from a single piece. 
     The internal surfaces of the leg-shaped wall  124  of the upper molding element  115  are set against the external surfaces  118  of the pointed leg-shaped wall  122  of the lower molding element  114 , and the same applies on the other side to the same leg-shaped walls  124  and  122 . It can be noted that the three pressurizing rollers  136  form lateral guides and a fixed lower roller  140 . 
     A second cross section in FIG. 8 shows that there are two fixed upper and lower rollers  139  acting to counter the motion. There are also two upper and lower pressurizing rollers  134  which act on the cam-shaped surfaces  133  extending from the free extremities of the portion  114   b  of the lower molding element  114  and from the leg-shaped wall  124  of the upper molding element  115 . The pressurizing rollers  134  act as external engaging elements. 
     This arrangement of the rollers promotes the detachment between the two molding elements  114  and  115 , for example by forcibly oscillating the portion  114   b  around the rounded surfaces  130  and the upper molding element with respect to the fixed upper roller  139 . 
     An arrangement based on an inclined rod  127  passing through some hollow seats  127  produces a connecting element designed to keep the two portions  114   a  and  114   b  tied up to each other even during the oscillation. 
     Two further cross sections in FIGS. 9 and 10 offer a simplified view of an alternative embodiment very similar to the one shown in FIGS. 7 and 8. 
     In this embodiment the molding elements  114  and  115  are both produced from a single piece, and there is no pair of rounded surfaces  130 . 
     In this manner both the lower molding element  114  and the upper molding element  115  oscillate with respect to the two fixed lower and upper rollers  139 , whenever the two upper and lower pressurizing rollers  134  act on the cam-type surface  133 , if available, or by shifting the pressurizing rollers  134  with the aid of an appropriate actuator. 
     In a simplified manner, FIGS. 11 and 12 finally show a fourth alternative embodiment of some molding elements capable of being positioned on the pairs of chains. 
     Even in this embodiment, both molding elements are produced from a single piece, and equal elements are indicated by the same reference numbers preceded by the number “2”. 
     A lower molding element  214  is produced from a single piece and presents an asymmetrical shape with respect to an axis  238  perpendicular to the two base portions  220  and  221 . The upper molding element  215  is simply constituted by a molding element entirely similar to the lower molding element  214 , but rotated in its arrangement by 180° with respect to the axis  238 . 
     In the section shown in FIG. 11 it can be seen that the molding elements  114  and  115  have somewhat different forms of the leg-shaped walls  222  and  224  extending from the base portions  220  and  221 , but the situation is entirely equivalent. 
     Even in this case there are three pressurizing rollers  236  forming lateral guides, and a fixed lower supporting roller  240 . 
     A second cross section in FIG. 12 shows that there are two fixed lateral rollers  239  acting to counter the motion, and two further pressurizing rollers  234  acting on the opposing lateral cam-shaped surfaces  233  of the two molding elements  214  and  215 , again if available, or being shifted by appropriate actuators not shown here. The pressurizing rollers  234  act as external engaging elements. 
     It is precisely this arrangement of rollers that promotes the detachment between the two molding elements  214  and  215 , for instance by oscillating the molding elements with respect to the relative fixed roller  239 . 
     This produces the same technical solutions which are the object of this invention. 
     It is obviously evident that there may be different arrangements of rollers and that the cam-shaped surfaces may be fixed to interact with the rollers, without abandoning the scope of protection of this invention. 
     This accomplishes the purpose mentioned in the introductory description. The embodiments may naturally differ from those shown for purely exemplifying and non-limiting purposes in the drawings, just as there can be different elements of reciprocal engagement capable of generating the forcible separation of the molding elements while eliminating harmful friction. 
     The scope of protection of the invention is in any case circumscribed by the enclosed claims.