Continuous casting device

Abstract: A continuous casting device includes a pair of cooling rolls (1, 2) that rotate in the opposite directions to each other; a pair of side weirs (11) whose inner surface (11a) covers the end surfaces (1a, 2a) of the cooling rolls (1, 2), and whose circular surface (12b) covers the peripheral surfaces (1b, 2b) of the cooling rolls (1, 2) in which at least one of the side weirs (11) is movable in an axial direction of the cooling rolls (1, 2). The continuous casting device also includes electromagnets for forming a magnetic flux in a direction parallel with a contact surface of the side weirs (11) with the molten metal (4) along the peripheral surfaces (1b, 2b) of the cooling rolls (1, 2) at the portions opposite to the peripheral surfaces (1b, 2b) of the cooling rolls (1, 2) of the side weirs (11).

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting device in which a molten metal is supplied between two rolls that rotate to manufacture a band-like plate continuously. 2. Description of the Related Art Figs. 12 and 13 show one example of a conventional continuous casting device in which a molten metal is supplied between two rolls that rotate to manufacture a band-like plate continuously. Fig. 12 is a schematic front view showing the conventional continuous casting device whereas Fig. 13 is a plan view thereof. As shown in Figs. 12 and 13, the continuous casting device is mainly made up of a pair of rolls 1 and 2 which are disposed horizontally in parallel with each other, and a pair of weirs 5 for accumulating a molten metal 4 (hereinafter a steel is referred to as a molten steel as an example) supplied from a supply nozzle 3 in a valley-shaped space which is defined by those cooling rolls 1 and 2. The weirs 5 are located in such a state as to cover an end surface of one cooling roll 1 or 2 and to cover the peripheral surface of the other cooling roll 2 or 1. Each of the weirs 5 is equipped with a heater 6 for heating and controlling a temperature. The cooling rolls 1 and 2 are driven by drive means not shown in such a manner that the respective opposed outer peripheral surfaces of those cooling rolls 1 and 2 rotate downward. In the continuous casting device thus organized, when the cooling rolls 1 and 2 are activated, and the molten steel 4 is supplied from the nozzle 3 to the valley-shaped space defined between the cooling rolls 1 and 2, then the molten steel 4 is solidified on the outer peripheral surface of the cooling rolls 1 and 2 to thereby generate a solidified shell. The solidified shell is guided downward with the rotation of the cooling rolls 1 and 2 and is then pressed by the cooling rolls 1 and 2 on the close contact portion thereof, to thereby form a single band-like plate (steel plate) 4a. The band-like plate 4a is extruded continuously. With a change in the position of at least one weir 5 in an axial direction of the cooling rolls 1 and 2, the width of the band-like plate 4a to be cast can be changed. The continuous casting device thus organized is disclosed, for example, in Japanese Patent Unexamined Publication No. Sho 63-180348. By the way, in the above-mentioned continuous casting device, a leakage of the molten steel 4 from the ends of the' cooling rolls 1 and 2 is merely mechanically restrained by pushing the arc-shaped surface of the weirs 5 against the peripheral surfaces of the cooling rolls 1 and 2. In other words, the weirs 5 and the molten steel 4 are in contact with each other, and because the solidification of the molten steel 4 is developed in particular along the vicinity of the portion where the peripheral surfaces of the cooling rolls 1, 2 and the weirs 5 are in contact with the molten steel 4, a defect occurs on the end portions of the cast plate, and also there arise such problem that the rolls are deformed by the abrasion of the roll surface, and the sealing performance of the molten steel 4 is lowered by the abrasion of the weir material and so on. Another type of the system for sealing the ends of the cooling rolls 1 and 2 is a system for shutting the molten steel using a.c. magnetic field, as disclosed in Japanese Patent Unexamined Publication No. Hei 6-99251, Japanese Patent Unexamined Publication No. Hei 3-35851. The system disclosed in Japanese Patent Unexamined Publication No. Hei 6-99251 is made up of a pair of side weirs disposed between a pair of cooling rolls and having a wall portion made up of electrically conductive segments, cores (ferromagnetic substance) disposed above and below those side weirs, induction coils wound around the cores and so on. Upon applying a.c. current to the induction coils, an a.c. magnetic field is developed vertically in the induction coils. The magnetic field makes an induction current flow in the electrically conductive segments, to thereby develop a magnetic field due to the induction current. As a result, a magnetic flux is concentrated between the molten steel which is disposed between the cool rolls and the induction segments as a composite magnetic field consisting of the vertical magnetic field and the magnetic field caused by the induction current. Hence, the strong magnetic field and the induction current that flows in the molten steel allow the Lorentz's force to be exerted on the molten steel in a direction of going away from the induction segments, to thereby restrain the leakage of the molten steel from the ends of the cooling rolls. However, the system disclosed in Japanese Patent Unexamined Publication No. Hei 6-99251 requires that the induction current is allowed to flow in the induction segments except that the current flows into the induction coils, to thereby increase the loss of the Joule's heat. Also, because the system has a structure in which the leakage of the molten steel is prevented by the overall surfaces of the weirs, an excessive electric power is consumed in order to seal a portion other than the portion where the cooling rolls are in contact with the weirs which is the most important to seal. The system disclosed in Japanese Patent Unexamined Publication No. Hei 3-35851 has weirs which are situated between a pair of rolls and made up of a circular conductor, a refractory material and a heater for heating the weirs. In the weirs, upon applying an a.c. current to the electric conductor, an a.c. magnetic field is so developed as to surround the electric conductor. Hence, the magnetic field and the induction current that flows in the molten steel allow the Lorentz's force to be exerted on the molten steel in a direction of going away from the electric conductor, to thereby restrain the leakage of the molten steel from the ends of the cooling roll ends. However, in the system disclosed in Japanese Patent Unexamined Publication No. Hei 3-35851, the magnetic field is spread over the periphery of the electric conductor, and a leakage magnetic flux is large, thereby being incapable of applying an effective magnetic field. A prior art continuous casting device with the features of the preamble portion of claim 1 is described in DE 43 07 850 Cl. This device has only a single electric conductor extending along the entire sealing surface around the circumferences of the cooling rolls and the top section of a V-shaped gap between the cooling rolls. It furthermore has a magnetic return path arranged near the conductor and adapted in its shape to the cross-sectional shape of the gap between the pair of cooling rolls. SUMMARY OF THE INVENTION An object of the present invention is to solve the above mentioned problems with the conventional continuous casting devices. In order to solve this object the present invention provides a continuous casting device with the features set out in claim 1. According to the thus organized continuous casting device of the present invention, the directions of the magnetic fluxes in the molten metal are identical with each other so that the magnetic fluxes do not interfere with each other. Therefore, the magnetic fluxes are not weakened even at the portions close to the cooling rolls, to thereby enhance the effect of preventing the leakage of the molten metal. In the continuous casting device in accordance with the present invention, said electric conductors disposed in said side weirs can be located in such a manner that the directions of the currents in said electric conductor at the sides facing with said molten metal along the peripheral surfaces of the respective cooling rolls at the portions where said pair of cooling rolls are closest to each other are identical with each other. In this case, said electric conductors provided in said side weirs may be connected to a single a.c. power supply. Also, in forming circuits that allow the currents to flow in opposite direction to each other, said electric conductor is turned back at a portion nearest to said pair of cooling rolls into a V-shape. This is preferable in that the length of said cooling electric conductor can be prevented from being lengthened, the impedance of said cooling electric conductor can be kept small, and the capacity of the power supply can be reduced in order to produce the Loventz's force of the same level. Furthermore, in arranging said electric conductors opposed to the end surface of said cooling roll, said ferromagnetic substances are arranged in a U-shape and opened at the end surface sides of said cooling rolls, to surround said electric conductor into which a current flows in one direction. Also, in arranging said electric conductors opposed to the peripheral surfaces of said cooling rolls, said ferromagnetic substance is arranged in an L-shape and opened at the peripheral surface sides of said cooling rolls and said molten metal side, to surround said electric conductor into which a current flows in one direction, and said electric conductor into which a current flows in the other direction is arranged at an opposite side of said electric conductor into which a current flows in one direction with respect to said ferromagnetic substance. This is preferable in that the side weirs are made in parallel with each other so that the magnetic flux can be concentrated on the molten steel. As a result, the Lorentz's force is more effectively exerted in a direction of making the molten steel away from the electromagnet portion, to thereby increase the sealing effect. Also, a layer-shaped heat resisting material is disposed between the elctric conductor and the molten metal. This is preferable in that heat is isolated between the electric conductor and the molten metal, thereby being capable of preventing a temperature from rising. The above and other objects and features of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic front view showing a continuous casting device in accordance with an embodiment of the present invention; Fig. 2 is a front view showing the continuous casting device of Fig. 1; Fig. 3 is an enlarged view showing the continuous casting device taken along a line B-B of Fig. 1; Fig. 4 is an enlarged view showing the continuous casting device taken along a line C-C of Fig. 1; Fig. 5 is an explanatory diagram showing an example of the connection of a cooling electric conductor to an a.c. power supply; Fig. 6 is an explanatory diagram showing an example of the connection of a cooling electric conductor to an a.c. power supply; Fig. 7 is an explanatory diagram showing an example of the connection of a cooling electric conductor to an a. c. power supply; Fig. 8 is a schematic front view showing a continuous casting device in accordance with another embodiment of the present invention; Fig. 9 is a schematic front view showing a continuous casting device in accordance with yet still another embodiment of the present invention; Fig. 10 is an explanatory diagram showing an example of the connection of a cooling electric conductor to an a.c. power supply; Fig. 11 is an explanatory diagram showing the state of a magnetic flux in the case where the currents flowing into the adjacent portion and the second adjacent portion of the cooling electric conductor are identical in the directions with each other and in the case where the currents flowing into the adjacent portion and the second adjacent portion of the cooling electric conductor are different in their directions from each other; Fig. 12 is a schematic front view showing one example of a conventional continuous casting device; and Fig. 13 is a plan view showing the conventional continuous casting device of Fig. 12. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Now, a description will be given in more detail of embodiments of the present invention with reference to the accompanying drawings. A continuous casting device in accordance with an embodiment of the present invention is shown in Figs. 1 to 11. It should be noted that the same parts as those shown in Figs. 12 and 13 are designated by the same symbols, and the duplicated description will be omitted. Fig. 1 is a schematic front view showing a continuous casting device in accordance with an embodiment of the present invention, Fig. 2 is a plan view thereof, Fig. 3 is an enlarged sectional view taken along a line B-B in Fig. 1, and Fig. 4 is an enlarged sectional view taken along a line C-C in Fig. 1. In Figs. 1 and 2, reference numerals 1 and 2 denote a pair of cooling rolls which are opposed to each other, which are designed in such a manner that their surfaces opposed to each other are moved downward while being rotatably driven. A molten metal supply nozzle 3 is confronted by a valley-shaped space defined between those cooling rolls 1 and 2 so that a molten steel supplied from the supply nozzle 3 is accumulated in the valley-shaped space defined between the cooling rolls 1 and 2. A pair of side weirs 31 are disposed which have an inner surface 31a with which an end surface 1a or 2a of one cooling roll 1 or 2 is covered, and a circular surface 31b with which a peripheral surface 2b or 1b of the other cooling roll 2 or 1 is covered. Those side weirs 31 are made of a heat resistant insulating material such as ceramics. A heater 12 for heating is disposed within each side weir 31. Hereinafter, the description of the side weirs 31 is conducted on the side weir 31 on the lower side of Fig. 2, but the side weir 31 on the upper side of Fig. 2 is identical in structure with that on the lower side thereof except that the locations of the cooling rolls 1 and 2 which are opposed to each other are different therebetween. A cooling electric conductor 32 is located within each side weir 31. The cooling electric conductor 32 is arranged along the vicinity of a circular portion which is in contact with the cooling rolls 1, 2, the side weirs 31 and the molten steel 4. For example, the cooling electric conductor 32 is disposed inside of the side weir 31 in such a manner that the circular surface 31b side of the side weir 31 is situated along the peripheral surface 2b of the cooling roll 2 and also along the molten steel 4 side, as shown in Fig. 1. The cooling electric conductor 32 is connected with a single a.c. power supply 14. Each of ferromagnetic substances 33 is so disposed as to surround each cooling electric conductor 32, which forms an electromagnet in cooperation with a ferromagnetic substance 33 disposed so as to surround the cooling electric conductor 32. As shown in Fig. 1, the cooling electric conductor 32 is made up of a first separated portion 32a (indicated by a solid line in the figure), a first adjacent portion 32b (indicated by a dotted line in the figure), a second separated portion 32c (indicated by the solid line in the figure) and a second adjacent portion 32d (indicated by the dotted line in the figure). The first separated portion 32a extends from an a.c. power supply 14 to the vicinity of the lower end along the peripheral surface 1b of the cooling roll 1 at the right side in the figure and is positioned at a portion separated from the molten steel 4. The first adjacent portion 32b is contiguous to the separated portion 32a, is folded back at a portion close to the lower end, extends to the vicinity of the upper portion along the peripheral surface 2b of the cooling roll 2, and is positioned at a portion adjacent to the molten steel 4. The second separated portion 32c is contiguous to the adjacent portion 32b, is folded back at a portion close to the upper end portion, extends to the vicinity of the lower portion along the peripheral surface 2b of the cooling roll 2, and is positioned at a portion separated from the molten steel 4. The second adjacent portion 32d is contiguous to the second separated portion 32c, is folded back at a portion close to the lower end, extends to the vicinity of the upper portion along the peripheral surface 1b of the cooling roll 1, and is positioned at a portion adjacent to the molten steel 4. In other words, the cooling electric conductor 32 is folded back at a portion closest to the cooling rolls 1 and 2 into a V-shape. It should be noted that Fig. 1 shows a state in which the first separated portion 32a, the first adjacent portion 32b, the second separated portion 32c and the second adjacent portion 32d are shifted from each other for convenience of description, however, in fact, those respective portions are overlapped with each other in a front view. The first separated portion 32a and the second separated portion 32c of the cooling electric conductor 32, and the first adjacent portion 32b and the second adjacent portion 32d thereof are grouped by the identical current flowing direction in the cooling electric conductor 32, respectively, (for example, a current flows downward in the first separated portion 32a and the second separated portion 32c whereas a current flows upward in the first adjacent portion 32b and the second adjacent portion 32d), and in the cooling electric conductors 32 of each group are formed circuits into which currents flow in the directions opposite to each other. A ferromagnetic substance 33 is disposed between the cooling electric conductors 32 in each group, that is, between the first separated portion 32a and the second adjacent portion 32d and between the second separated portion 32c and the first adjacent portion 32b, respectively. Now, a description will be given of an arrangement state of the cooling electric conductors 32 and the ferromagnetic substances 33 with reference to Figs. 3 and 4. Fig. 3 shows a state in which the end surface 1a of the cooling roll 1 is covered with the inner surface 31a of the side weir 31, whereas Fig. 4 shows a state in which the peripheral surface 2b of the cooling roll 2 is covered with the circular surface 31b of the side weir 31. As shown in Fig. 3, at a portion where the end surface 1a of the cooling roll 1 is covered with the side weir 31, there is disposed a U-shaped ferromagnetic substance 33 which is opened at the end surface 1a side of the cooling roll 1, that is, the molten steel 4 side. Four second adjacent portions 32d of the cooling electric conductor 32 are disposed inside of the ferromagnetic substance 33 in a state where they are surrounded by the ferromagnetic substance 33. Those four second adjacent portions 32d are arranged at two stages in such a manner that two adjacent portions 32d are in parallel with each other at each stage. Four first separated portions 32a of the cooling electric conductor 32 are disposed on the back surface side of the ferromagnetic substance 33, and the four separated portions 32a are aligned. The four first separated portions 32a and the four second adjacent portions 32d are electrically insulated from each other by an insulator 39. A heat resisting material 34 is disposed between the second adjacent portions 32d of the cooling electric conductor 32 and the molten steel 4 in the form of layers. The heat resisting material 34 is made up of the combination of layers which are thick at the side of the molten steel 4 and become thinned toward an opposite side of the molten steel 4 (for example, layers of 2.0 mm, 1.0 mm and 0.5 mm in thickness in state order from the molten steel 4 side). The heat resisting material 34 insulates heat between the cooling electric conductor 32 and the molten steel 4. An insulating material 35 is disposed around an electromagnet which is formed of the cooling electric conductor 32 and the ferromagnetic substance 33, and also an electromagnetic sealing material 36 is disposed around the insulating material 35. In this manner, the outside of the electromagnet is surrounded by the electromagnetic sealing material 36, to thereby prevent the magnetic flux 37 from being leaked to the outside. It should be noted that, in Fig. 3, reference numeral 38 denotes a cooling water within the cooling electric conductor (conduit) 32, reference numerals 41a and 41b denote heat resisting materials', and reference numeral 40 denotes a support material for the heater 12. As shown in Fig. 4, at a portion where the peripheral surface 2b of the cooling roll 2 is covered with the side weir 31, the ferromagnetic substance 33 is disposed in an L-shape both ends of which are directed to the molten steel 4 side and the peripheral surface 2b side of the cooling roll 2, respectively. Four first adjacent portions 32b of the cooling electric conductor 32 are disposed inside of the ferromagnetic substance 33 in'a state where they are surrounded by the ferromagnetic substance 33. Those four first adjacent portions 32b are arranged at two stages in such a manner that two first adjacent portions 32b are in parallel with each other at each stage. Four second separated portions 32c of the cooling electric conductor 32 are disposed on the back surface side of the ferromagnetic substance 33, and four first separated portions 32a are arranged in two lines apart from each other. The four second separated portions 32c and the four first adjacent portions 32b are electrically insulated from each other by an insulator 39. The heat resisting material 34 which is made up of the combination of layers as in the above-mentioned manner is disposed between the first adjacent portions 32b of the cooling electric conductor 32 and the molten steel 4. The heat resisting material 34 insulates heat between the cooling electric conductor 32 and the molten steel 4. An electromagnet, which is formed of the cooling electric conductor 32 and the ferromagnetic substance 33, around which a heat resisting material fiber 42 is wound in multilayer and is fixedly tied, to thereby ensure the electrical insulating property and the heat insulating property of the electromagnet at a side that faces with the peripheral surface 2b of the cooling roll 2. Also, the outside of the electromagnet is surrounded by an electromagnetic sealing material 36, to thereby prevent the magnetic flux 37 from being leaked to the exterior. In this example, examples of connecting the cooling electric conductor 32 thus organized to the a.c. power supply 14 will be described with reference to Figs. 5, 6 and 7. In Fig. 5, the cooling electric conductor 32 disposed in one side weir 31 (lower side of Fig. 2) and the cooling electric conductor 32 disposed in the other side weir 31 (upper side of Fig. 2) are connected to two a.c. power supplies 14, respectively. Then, the cooling electric conductor 32 of one side weir 31 is so designed as to be connectable to the a.c. power supply 14 of the other side weir 31 by a switch S. In Fig. 6, the cooling electric conductor 32 disposed in one side weir 31 and the cooling electric conductor 32 disposed in the other side weir 31 are disposed in parallel with each other and connected to one a.c. power supply 14. In Fig. 7, the cooling electric conductor 32 disposed in one side weir 31 and the cooling electric conductor 32 disposed in the other side weir 31 are disposed in series and connected to one a.c. power supply 14. A description will be given of the modification of the embodiment of the present invention with reference to Figs. 8 and 9. Fig. 8 is a schematic front view showing a continuous casting device in accordance with the modification of the embodiment of the present invention, and Fig. 9 is a plan view thereof. It should be noted that components identical with those shown in Figs. 1 to 7, 12 and 13 are represented by the same symbols, and the duplicated description will be omitted. In Figs. 8 and 9, reference numerals 1 and 2 denote a pair of cooling rolls which are opposed to each other, which are designed in such a manner that their surfaces opposed to each other are moved downward while being rotatably driven. A molten metal supply nozzle 3 is confronted by a valley-shaped space defined between those cooling rolls 1 and 2 so that a molten steel supplied from the supply nozzle 3 is accumulated in the valley-shaped space defined between the cooling rolls 1 and 2. There are provided a pair of side weirs 51 that cover the end surfaces 1a and 2a of the cooling rolls 1 and 2 in such a manner that the cooling rolls 1 and 2 are not moved in an axial direction. In this example, unlike the preceding example (refer to Fig. 1 and others), the width of the band-like plate cannot be arbitrarily changed. Those side weirs 51 are made of a heat resistant insulating material such as ceramics as in the above-mentioned example, and a heater 12 for heating is disposed within each side weir 51. Both the adjacent portions 32b and 32d of the cooling electric conductor 32 are surrounded by the U-shaped ferromagnetic substances 33 (refer to Fig. 3). An arranging state of the cooling electric conductor 32 in the side weirs 51 is shown in Fig. 10. As shown in the figure, the state in which the cooling electric conductor 32 is arranged is identical with that of the cooling electric conductor 32 in the side weir 31 shown in Fig. 6. Also, a state of connecting to the a.c. power supply 14 can be also applied with the example of Fig. 5 or 6. In the continuous casting device thus organized, the inner side surface 31a of one side weir 31 is in contact with the end surface 1a or 2a of the cooling roll 1 or 2, and the circular surface 31b of the side weir 31 is in contact with the peripheral surface 2b or 1b of the other cooling roll 2 or 1, when the continuous casting device starts to operate. Also, in the continuous casting device shown in Figs. 8 and 9, the side weirs 51 are in contact.with the end surface of the cooling rolls 1 and 2. In this state, the molten steel 4 is supplied from the supply nozzle 3 in such a manner that the molten steel 4 is accumulated in the valley-shaped space between the cooling rolls 1 and 2 up to a given level. When the molten steel 4 is accumulated therein up to the given level, the operation of the continuous casting device is started, and a predetermined interval is held between the side weirs 31 and the cooling rolls 1, 2. Upon the application of an a.c. current (frequency of about 0.5 to 10. kHz, 1 to 2 kHz in practical use) to the cooling electric conductors 32, a magnetic flux 37 is developed around the first adjacent portion 32b and the second adjacent portion 32d of the cooling electric conductor 32, as shown in Figs. 3 and 4. The magnetic flux 37 allows an induction current to flow in the molten steel 4, and the interaction of the induction current and the magnetic flux 37 allows a magnetic pressure (the Lorentz's Force) 43 to be exerted in a direction of pushing back the molten steel 4. Then, as shown in Fig. 1 and others, since the cooling electric conductor 32 is formed in a V-shape by folding back the cooling electric conductor 32 at portions closest to the cooling rolls 1 and 2, the length of the cooling electric conductor 32 is prevented from being lengthened more than a required length, the impedance of the cooling electric conductor 32 is kept small, and the capacity of the power supply is reduced in order to produce the Lorentz's force of the same level. Also, the cooling electric conductor 32 is classified into groups where the direction of a current flowing into the cooling electric conductor 32 is identical with each other, and the currents flowing in the same direction are allowed to flow in the group adjacent to the molten steel 4, that is, in the first adjacent portion 32b and the second adjacent portion 32d, whereby the direction of magnetic flux in the molten steel 4 becomes identical, to thereby eliminate the mutual interference. In particular, the magnetic fluxes are not weakened at the portions close to the cooling rolls 1 and 2. Figs. 11(a) and 11(b) show a state of the magnetic flux in the case where the directions of current flowing into the first adjacent portion 32b and the second adjacent portion 32d of the cooling electric conductor 32 are identical with each other, and a state of the magnetic flux in the case where they are different from each other. As shown in Fig. 11(a), in the case where the directions of current flowing into the first adjacent portion 32b and the second adjacent portion 32d are different from each other, the magnetic flux developed around the first adjacent portion 32b and the magnetic flux developed around the second adjacent portion 32d are opposite in direction to each other in the molten steel 4. For that reason, in particular, at a portion where the cooling rolls 1 and 2 are close to each other such that both the magnetic fluxes overlap with each other (a portion where the first adjacent portion 32b and the second adjacent portion 32d are close to each other), the magnetic fluxes interfere with each other so as to'be weakened. On the contrary, as shown in Fig. 11(b), in the case where the directions of current flowing into the first adjacent portion 32b and the second adjacent portion 32d are identical with each other, the magnetic flux developed around the first adjacent portion 32b and the magnetic flux developed around the second adjacent portion 32d are identical in the direction with each other in the molten steel 4. For that reason, even at a portion where the cooling rolls 1 and 2 are close to each other such that both the magnetic fluxes overlap with each other, the magnetic flux is not weakened. The lower portion where the cooling rolls 1 and 2 are close to each other is larger in a force that allows the molten steel 4 to be leaked out to the outside than the upper portion where the cooling rolls 1 and 2 are apart from each other. For that reason, in order to push back the molten steel 4, the lower side requires more Lorentz's force than that of the upper side. Hence, as described above, the magnetic fluxes are prevented from being weakened at the portions where the cooling rolls 1 and 2 are close to each other to prevent the Lorentz's force from being lowered at the close portion, thereby being capable of more surely sealing the molten steel 4. Also, as shown in Fig. 3, at a portion where the side weir 31 cover the end surface 1a of the cooling roll 1, since the U-shaped ferromagnetic substance 33 is arranged in such a manner that it surrounds the second adjacent portion 32d of the cooling electric conductor 32, the magnetic flux 37 can be concentrated on the molten steel 4 in parallel with the side weir 31. As a result, the Lorentz's force 43 is more effectively exerted in a direction along which the molten steel 4 is away from the electromagnetic portion to increase the sealing effect. Furthermore, because a closed magnetic path is formed by the U-shaped ferromagnetic substance 33, the molten steel 4 and the cooling roll 1 (electromagnetic steel plate of the end surfaces), the molten steel side portion of the magnetic flux 37 extends from the molten steel 4 to the cooling roll 1 so as to pass through a boundary between the molten steel 4 and the outer periphery 1b of the cooling roll 1. For that reason, the Lorentz's force 43 is effectively exerted on the contact portion of the molten steel 4 with the outer periphery 1b of the cooling roll 1 which is important in sealing of the molten steel 4. Also, at the portion where the peripheral surface 2b of the cooling roll 2 is covered with the side weir 31, because a closed magnetic path is formed by the L-shaped ferromagnetic substance 33, the molten steel 4 and the cooling roll 2 (due to the action as the ferromagnetic substance of nickel plating), the magnetic flux 37 can be concentrated on the molten steel 4 in parallel with the side weirs 31, and the molten steel side portion of the magnetic flux 37 extends from the molten steel 4 to the cooling roll 2 so as to pass through a boundary between the molten steel 4 and the peripheral surface 2b of the cooling roll 2. For that reason, the Lorentz's force 43 is effectively exerted on the contact portion of the molten steel 4 with the outer periphery 2b of the cooling roll 2 which is important in sealing of the molten steel 4. Also, as shown in Figs. 3 and 4, since a layer-shaped heat insulating material 34 is disposed between the cooling electric conductor 32 and the molten steel 4, a heat is insulated between the cooling electric conductor 32 and the molten steel 4, to thereby prevent the temperature of the cooling electric conductor 32 from rising. Further, as shown in Fig. 5, in the case where both-sided cooling electric conductors 32 are connected to two a.c. power supplies 14, respectively, even though one of those a.c. power supplies 14 is suspended, the other a.c. power supply 14 serves as backup with closing the switch S, to thereby enhance the reliability of the device.

Claims: A continuous casting device, comprising a pair of cooling rolls (1,2) that are adapted to rotate in the opposite directions to each other; a pair of side weirs (31;51), one of which surrounds the peripheral surface (1b,2b) or the end surface (1a,2a) of one of said cooling rolls (1,2) and the other of which surrounds the end surface (1a,2a) or the peripheral surface (1b, 2b) of the other of said cooling rolls (1,2); electric conductors (32) for forming a magnetic flux (37) in a direction parallel with a contact surface of said side weirs (31;51) with a molten metal (4) along the peripheral surfaces (1b,2b) of said cooling rolls (1,2), said electric conductors (32) are disposed in the vicinity of a portion of said side weirs (31;51) along the peripheral surfaces (1b,2b) of said cooling rolls (1,2); and a ferromagnetic substance (33) provided between the electric conductors (32); characterized in that the electric conductors (32) of each side weir are formed in a loop comprising a plurality of contiguous folded segments (32a,32c;32b,32d) disposed in the vicinity of the portion of the respective side weir (31;51) along the peripheral surfaces (1b,2b) of said cooling rolls (1,2), the segments (32a,32c;32b,32d) are arranged in groups of segments in which the direction of the currents in the conductor segments (32a,32c;32b,32d) is identical, one group (32b,32d) is arranged adjacent to the molten metal (4) and another group (32a,32c) is arranged separated from the molten metal (4), the current direction in the segments in the group (32b,32d) that is arranged adjacent to the molten metal (4) is opposite to the direction of flow of the molten metal (4), and said ferromagnetic substance (33) is provided between the conductor segments (32b,32d) that are arranged adjacent to the molten metal (4) and the conductor segments (32a,32c) that are arranged separated from the molten metal (4). A continuous casting device as claimed in claim 1, characterized in that said conductor segments (32a,32c;32b,32d) disposed on said side weirs (31;51) are arranged so that the directions of the currents in said conductor segments (32a,32c;32b,32d) at the sides' facing said molten metal (4) along the peripheral surfaces of the respective cooling rolls (1,2) at the portions where said pair of cooling rolls (1,2) are closest to each other are identical with each other. A continuous casting device as claimed in claim 2, characterized in that said electric conductors (32) provided in said side weirs (31;51) are connected to a single a.c. power supply (14). A continuous casting device as claimed in claim 1, wherein, in forming circuits in which currents flow in opposite directions to each other, said electric conductors (32) are turned back at a portion nearest to said pair of cooling rolls (1,2) into a V-shape. A continuous casting device as claimed in claim 4, characterized in that , when said electric conductors (32) are arranged opposed to the end surfaces of said cooling rolls (1,2), said ferromagnetic substances (33) are arranged in a U-shape and opened at the end surface sides (1a,2a) of said cooling rolls (1,2), to surround said conductor segments (32b,32d) that are arranged adjacent to the molten metal (4), and, when said electric conductors (32) are arranged opposed to the peripheral surfaces (1b,2b) of said cooling rolls (1,2), said ferromagnetic substance (33) is arranged in an L-shape and opened at the peripheral surface sides (1b,2b) of said cooling rolls (1,2) and said molten metal (4) side, to surround said conductor segments (32b,32d) that are arranged adjacent to the molten metal (4), and said conductor segments (32a,32c) that are arranged separated from the molten metal (4) are arranged at an opposite side of said conductor segments (32b,32d) that are arranged adjacent to the molten metal (4) with respect to said ferromagnetic substance (33). A continuous casting device as claimed in any one of claims 1 to 5, characterized in that a layer-shaped heat resisting material (34) is disposed between said electric conductors (32) and said molten metal (4).

Inventors: AOI TATSUFUMI, KAWADA NORIYUKI, NAKAJIMA HIROSHI, NAKASHIMA MOTOMI, UNOKI KENICHI, WAKIYAMA YOUICHI, AOI, TATSUFUMI, KAWADA, NORIYUKI, NAKAJIMA, HIROSHI, NAKASHIMA, MOTOMI, UNOKI, KENICHI, WAKIYAMA, YOUICHI, Aoi, Tatsufumi, c/o Hiroshima Res. &amp; Dev. Ctr., Kawada, Noriyuki, c/o Hiroshima Res. &amp; Dev. Ctr., Nakajima, Hiroshi, c/o Hiroshima Res. &amp; Dev. Ctr., Nakashima, Motomi, c/o Hiroshima Res. &amp; Dev. Ctr., Unoki, Kenichi, c/o Hiroshima Res. &amp; Dev. Ctr., Wakiyama, Youichi, c/o Hiroshima Machinery Works
Applicants: MITSUBISHI HEAVY IND LTD, MITSUBISHI JUKOGYO KABUSHIKI KAISHA
Application year: 1996
Main classification: B22D11
IPC codes: B22D11