Casting nozzle

Abstract

A casting nozzle suited to manufacture a casting material of pure magnesium or magnesium alloy is provided. A nozzle is utilized to manufacture a casting material by supplying molten metal to a portion between rolls which become a casting die, and arranged so that a pouring port is located between a pair of rolls opposed to other. This nozzle includes a main body formed of oxide material such as alumina, and a coating layer which is provided on the inner surface of the main body which comes into contact the molten metal, and formed of material that does not include oxygen substantially. Since the main body does not come into direct contact with the molten metal due to the coating layer, it is possible to prevent oxygen included in the main body from reacting with the molten metal. Further, in the nozzle, a casting die contact portion which comes into contact with the rollers is formed of thermal insulation material, whereby it is prevented that the molten metal in the nozzle is cooled through the casting die contact portion by the rollers.

Claims

1. A casting nozzle which supplies molten metal of pure magnesium or magnesium alloy into a twin roll movable casting die, the casting nozzle comprising: a nozzle main body formed of a thermal insulation material, and a molten metal contact portion on the nozzle main body formed of a layer of low oxygen material, wherein the thermal insulation material is composed of an oxide material having mainly aluminum oxide or calcium silicate with a thermal conductivity of 1.00 W/mK at 600 C. or less, and wherein the molten metal contact portion terminates inside the nozzle main body at a distance of 0.3 mm to 40 mm from a mouth of a pouring port of the casting nozzle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1(A) is a schematic constitutional view showing a state where continuous cast is performed by a twin-roll casting method using a nozzle of the invention, FIG. 1(B) is a sectional view showing a schematic constitution of the nozzle of the invention, and FIG. 1(C) is a front view of the nozzle of the invention, viewed from a pouring port side.

(2) FIG. 2 is a graph showing a temperature distribution of a molten metal from a pouring basin to a portion between rolls.

(3) FIG. 3 is a sectional view showing other embodiments of the nozzle of the invention, in which (A) shows an example in which forming material of a nozzle is different from that of the nozzle shown in FIGS. 1, (B) and (C) show examples in which a main body is formed of two kinds of materials that are different from each other, and (D) and (E) show examples in which a reinforcement member is provided.

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS

(4) 1, 1A, 1B, 1C, 1D, 1E, N Nozzle

(5) 1a, 1Aa, 1Ba, 1Ca, 1Da, 1Ea Main body

(6) 1b, 1c Pouring port side main body

(7) 1bb, 1cc Pouring basin side main body

(8) 2 Casting die contact portion

(9) 3, 3A, 3B, 3C, 3D, 3E Coating layer

(10) 4, 4A, 4B, 4C, 4D, 4E Pouring port

(11) 5, 6 Reinforcement member

(12) 10 Roll

(13) 11 Water path

(14) 20 Pouring basin

(15) 21 Supporter

(16) 22 Transporting conduit

(17) 100 Casting material

(18) 200 Gate

BEST MODE FOR CARRYING OUT THE INVENTION

(19) Embodiments of the invention will be described below.

(20) FIG. 1(A) is a diagram which explains a state where continuous cast is performed by a twin-roll casting method using a casting nozzle of the invention, FIG. 1(B) is a sectional view showing a schematic constitution of the nozzle of the invention, and FIG. 1(C) is a front view of the nozzle of the invention in a state where a gate is arranged, viewed from a pouring port side. A nozzle 1 of the invention is a member utilized as a transporting path for molten metal of pure magnesium or magnesium alloy, which supplies the molten metal which has been molten in a melting furnace (not shown) through a pouring basin to a movable casting die. Particularly, the nozzle 1 is a nozzle used in continuous cast (twin-roll casting method) using a twin roll movable casting die composed of a pair of rolls 10.

(21) The nozzle 1 includes a cylindrical main body 1a, and its inner side becomes a transporting path of molten metal. One end side of the main body 1a having an opening part is tapered off, and the opening part on this tapered side is utilized as a pouring port 4 from which the molten metal is supplied to the casting die. The pouring port 4, as shown in FIG. 1(C), has the rectangular shape in which a long diameter (width) is larger than a short diameter (thickness). In the example shown in FIG. 1(C), in order to manufacture a casting material having a desired size, gates 200 are arranged on both sides of the pouring port 4. The width and thickness of the pouring port 4 are appropriately selected according to the width and thickness of the desired casting material. The other end side of the main body 1a is fixed to a pouring basin 20 which stores temporarily the molten metal from the melting furnace (not shown). In this example, in the nozzle 1, at the periphery on the pouring basin side, a stainless supporter (reinforcement member) 21 is arranged thereby to heighten rigidity of the nozzle 1. To the pouring basin 20, a transporting conduit 22 is connected, and the molten metal from the melting furnace is supplied through the transporting conduit 22 to the pouring basin 20. Then, the molten metal is transported from the pouring basin 20 to the nozzle 1, and supplied from the nozzle 1 to a portion between the rolls 10. Each roll 10 is a cylindrical body, and the rolls 10 are arranged opposed to each other with the predetermined space, and rotate in opposite directions to each other as shown by arrows in FIG. 1(A). The space between the rolls 10 is appropriately selected according to the thickness of the desired casting material. The width (length in the axial direction) of the roll 10 is appropriately selected according to the width of the desired casting material. In case that the width of the roll 10 is larger than the width of the desired casting material, gates (not shown) are appropriately provided to obtain the casting material having the desired width. Inside the roll 10, a water path 11 is provided, and water is permitted to flow therein at any time. The surface of the roll 10 is cooled by this water. Namely, the roll 10 has a so-called cooled water structure. In order to cause the pouring port 4 to be located between the rolls 10, and to make the space between the pouring 4 and the rollers 10 substantially zero, the nozzle 1 is arranged so that the peripheral side of the pouring port 4 comes into contact with the rolls 10. In the nozzle 1, a portion which comes into contact with the roll 10 becomes a casting die contact portion 2.

(22) By utilizing the above nozzle 1 and rolls 10, a casting material 100 is obtained from the molten metal of the pure magnesium or the magnesium alloy. Specifically, the molten metal which has been molten in the melting furnace is supplied from the melting furnace through the transporting conduit 22 and the pouring basin 20 to the nozzle 1, and further supplied from the pouring port 4 of the nozzle 1 to the portion between the rolls 10. The temperature of the molten metal, while the molten metal is transported in the nozzle 1, starts to lower gradually. When the molten metal is supplied between the rolls 10, it is rapidly cooled and solidified by the contact with the rolls 10, and thereafter discharged by rotation of the rolls 10 as the casting material 100. By thus supplying the molten metal between the rolls 10 continuously, the long casting material 100 is obtained. In this example, a sheet-shaped casting material 100 is manufactured.

(23) This nozzle 1 is characterized by including, on the inner surface of the nozzle 1 which comes into contact with the molten metal, a coating layer 3 formed of material that does not include substantially oxygen, in, order to prevent reaction between the molten metal of pure magnesium or the molten metal of magnesium alloy and the nozzle forming material. In this example, the main body 1a of the nozzle 1 is formed of thermal insulating material composed of oxide material such as aluminum or silica. When such the nozzle 1 comes into contact with the molten metal having Mg as a main component, there is fear that the oxygen in the thermal insulation material reacts with Mg in the molten metal and the nozzle 1 is damaged thereby to disenable cast. Therefore, on the inner surface of the nozzle 1, which comes into contact with the molten metal, the coating layer 3 is provided. In this example, the coating layer 3 is formed on the entirety of the inner surface of the nozzle 1. Further, in this example, the coating layer 3 is formed by applying graphite powers.

(24) In the nozzle of the invention thus including the coating layer formed of the material (the material that does not include oxygen substantially in this example) that is lower in oxygen density than oxide material, the main body formed of the oxide material does not come directly into contact with the molten metal of pure magnesium or magnesium alloy that is easy to react with oxygen, and it is possible to prevent effectively the molten metal and the nozzle from reacting with each other. Further, in the nozzle of the invention, since the contact portion with the roller (casting die contact portion) is formed of the thermal insulation material, heat of the molten metal in the nozzle is difficult to be transmitted to the rollers through the casting die contact portion. Therefore, in the nozzle of the invention, it is possible to suppress the molten metal in the nozzle from being cooled through the casting die contact portion by the rollers, so that a disadvantage that the molten metal is cooled and solidified in the nozzle thereby to enable cast is difficult to be produced. Therefore, by utilizing the nozzle of the invention, the casting material can be stably manufactured. Further, in this example, since the nozzle is supported by the supporter, it is possible to prevent the nozzle main body from being distorted due to weight of the molten metal or weight of the nozzle itself.

EXAMINATION EXAMPLE 1

(25) A nozzle having a coating layer on the inner surface of a nozzle main body as shown in FIG. 1 is manufactured, and pure magnesium or magnesium alloy is cast by means of a twin roll movable casting die shown in FIG. 1. As a comparative example, utilizing a nozzle having no coating layer, pure magnesium or magnesium alloy is cast similarly.

(26) In this examination, as the nozzle main body, a casting nozzle by ZIRCAR, which has aluminum oxide and silicon oxide as main components, is worked and used (full length: 100 mm, thickness of leading end: 1.8 mm, width: 250 mm, sectional area on pouring basin side: 2500 mm.sup.2, long diameter: 250 mm, short diameter: 10 mm, sectional area of pouring port: 1250 mm.sup.2, long diameter: 250 mm, short diameter: 5 mm). Further, in the nozzle having the coating layer, the coating layer is formed on the entirety of the inner surface of the nozzle main body. In formation of the coating layer, a boron nitride spray in which boron nitride powder is mixed in solvent (ethanol), and a graphite spray in which graphite powder is mixed in solvent (ethanol) are used. After the powder is applied by one of their sprays, the powder is applied by the other spray to laminate the powdery layers. Thereafter, the laminated layers are sintered at temperature of 300 C. This lamination coating step and the sintering step are repeated five times thereby to obtain a coating layer having thickness of about 0.35 mm.

(27) In this examination, using a twin-roll casting machine of roll diameter 1000 mmwidth 500 mm, a sheet-shaped casting material of thickness 5 mmwidth 250 mm is manufactured. The width of the casting material, as shown in FIG. 1(C), by providing appropriately gates 200, is adjusted so as to become the desired width. In the nozzle, one end side having a pouring port is arranged between rolls, and the other end side is fixed to a pouring basin. Further, in this examination, there are used molten metals of pure magnesium (composed of 99.9 mass % or more Mg and impurity), AZ31 corresponding alloy (including 3.0% Al, 1.0% Zn and 0.15% Mn in mass %, and others of Mg and impurity) and AZ91 corresponding alloy (including 9.0% Al, 0.7% Zn and 0.32% Mn in mass %, and others of Mg and impurity).

(28) In result, in case that the nozzle having the coating layer is utilized, the molten metal did not react with the nozzle during casting, and a pure magnesium casting material and a magnesium alloy casting material can be obtained. To the contrary, in case that the nozzle having no coating layer is utilized, the nozzle reacted severely with the molten metal (Mg) in the casting time and is damaged, so that a casting material cannot be obtained. Further, in each nozzle, at the periphery on the pouring basin side, a stainless supporter is arranged. In this example, two stainless plates each having 0.2 mm thickness and 240 mm width are prepared, and arranged so as to put the pouring basin side of the nozzle between. Further, before the molten metal is transported, when a check near the pouring port of the nozzle is made, there is no partially distorted portion in each nozzle.

(29) Further, temperature distribution of the molten metal is investigated from the inside of the pouring basin to the portion between the rolls. As the molten metal, pure magnesium (melting point Tm: about 650 C.) is utilized. The temperature of the molten metal in the pouring basin is adjusted to about 710 C. The temperature of the molten metal is investigated by arranging temperature sensors in measurement points. A graph in FIG. 2 shows a result of this investigation. Further, as a comparative example, using a graphite nozzle manufactured in the similar shape, in a state where one end side of the nozzle where a pouring port is provided is similarly located between rolls and the other end side thereof is fixed to a pouring basin, the temperature distribution of the molten metal is investigated. This result is also shown in the graph of FIG. 2. In FIG. 2, the same parts as those in FIG. 1 are denoted by the same reference numerals and symbols.

(30) In case that the nozzle of the invention having the coating layer on the inner surface of the main body is used, the temperature of the molten metal which is about 710 C. in the pouring basin, as shown by a solid line A in FIG. 2, became lower while the molten metal passed through the inside of the nozzle N after coming out from the pouring basin 20, approximated the melting point Tm near the pouring port 4, lowered sharply when the molten metal came out from the pouring port 4 and came into contact with the rolls 10, and became lower than the melting point. Further, after this nozzle is used for two hours, when the temperature distribution of the molten metal is similarly investigated, as shown by a dashed line A, the temperature distribution is nearly the same as that shown by the solid line A. From this result, it is confirmed that by utilizing the nozzle of the invention, a casting material could be stably obtained in use for a long period.

(31) To the contrary, in case that the graphite nozzle is utilized, the temperature of the molten metal which is about 710 C. in the pouring basin 20, as shown by a dashed line a, became lower than the melting point Tm in the nozzle and the molten metal is solidified, so that the molten metal cannot be cast. It is thought that this is because the graphite is better in thermal conductivity than the thermal insulation material used in the nozzle of the invention and the graphite nozzle is cooled in contact with the rolls, whereby the molten metal in the nozzle is also cooled and the temperature of the molten metal lowers. Therefore, in order to enable the cast, it is necessary to make the temperature of the molten metal in the pouring basin 20 higher than the melting point Tm by 100 C. When the temperature distribution is investigated in this state, the temperature of the molten metal which is Tm+100 C. in the pouring basin 20, as shown by a dashed line a, became lower while the molten metal passed through the inside of the nozzle N after coming out from the pouring basin 20, approximated the melting point Tm near the pouring port 4, lowered sharply when the molten metal came out from the pouring port 4 and came into contact with the rolls 10, and became lower than the melting point. From this result, it is confirmed that: in case that the graphite nozzle is utilized, the temperature of the molten metal is increased thereby to enable the cast without reaction between the molten metal and the nozzle, as in the nozzle of the invention. However, after this nozzle is used for ten minutes, when the temperature of the molten metal is similarly investigated, the temperature of the molten metal, as shown by a dashed line a, did not lower to an approximation of the melting point Tm even near the pouring port 4, a difference between the temperature near the pouring port 4 and the temperature at the contact portion of the molten metal with the rolls 10 became large, and defects such as casting wrinkles are produced on the surface of the obtained casting material. It is thought that this is because the nozzle is kept warm by the molten metal since the graphite is good in thermal conductivity as described above, whereby the temperature of the nozzle increases and the temperature of the molten metal is difficult to lower. Therefore, in case that the graphite nozzle is utilized, it is necessary to make the temperature of the molten metal higher; and when the casting material is manufactured for a long period, it is necessary to cool the nozzle appropriately. Accordingly, utilizing the nozzle of the invention enables the casting material to be manufactured with better productivity.

EXAMINATION EXAMPLE 2

(32) Regarding the nozzle having the coating layer used in the examination example 1, nozzles which are different in coating layer forming area are manufactured. In this examination, plural nozzles each of which has the coating layer on the pouring basin on the inner surface of the nozzle, and no coating layer on the pouring port side thereof are manufactured. Specifically, by gradually backing the coating layer forming area on the inner surface of the nozzle from the pouring port side of the nozzle, nozzles which are different in size (length) from the pouring port side to the coating layer forming area are manufactured. The nozzle provided with a portion having the coating layer and a portion having no coating layer is obtained by previously masking the portion having no coating layer, and forming a coating layer on a portion except the masking portion. In this examination, by performing masking with different distances from the pouring port, the forming area of the coating layer is changed, whereby the plural nozzles which are different in size from the pouring port side to the coating layer forming area are manufactured. In the thus obtained each nozzle which had the coating layer on the pouring basin and no coating layer on the pouring port side, a temperature sensor (thermocouple) is buried in a boundary between the coating layer forming portion and the coating layer not-forming portion, and temperature distribution in each nozzle is investigated. As molten metal, pure magnesium, AZ31 corresponding alloy, and AZ91 corresponding alloy similar to those in the examination example 1 are used.

(33) In result, in any molten metal of pure magnesium and magnesium alloy, in a portion where the temperature of the molten metal in the nozzle is higher than a melting point (liquidus temperature) by about 13 to 15 C., sharp reaction is produced, and the whole of the nozzle is damaged. From this result, it is conformed that: when the coating layer is provided on a portion where the temperature of the molten metal in the nozzle becomes at least a melting point+Tm C., and particularly on the pouring basin side area, it is possible to prevent a disadvantage that cast became impossible due to reaction between the nozzle formed of high oxygen material and the molten metal, or the nozzle is damaged.

EXAMINATION EXAMPLE 3

(34) A nozzle having a coating layer on the whole of the inner surface of a nozzle main body, which is used in the examination example 1, and a nozzle having a coating layer on a portion except the vicinity of a pouring port are manufactured. Using the twin roll casting die shown in FIG. 1, pure magnesium and magnesium alloy are cast. The nozzle having no coating layer near the pouring port is obtained by masking the area which is 30 mm distant from the pouring port, and forming a coating layer on a portion except this masking portion. The coating layer is formed similarly to in the examination example 1. In this example, a 200 kg casting sheet of thickness 4.5 mmwidth 200 mm is manufactured. The thickness of the casting sheet is changed by adjusting the distance between the rollers. Further, the width of the casting sheet is adjusted by appropriately providing gates. As molten metal, similarly to in the examination example 1, pure magnesium, AZ31 corresponding alloy, and AZ91 corresponding alloy are used.

(35) In result, in any nozzle, a 200 Kg casting sheet could be manufactured without any problems. Particularly, in the nozzle having no costing layer near the pouring port, the sectional area of the pouring port is not reduced by the coating layer, and the sectional area of the pouring port is larger than that in the nozzle having the coating layer also near the pouring port. Therefore, without increasing supply-pressure of the molten metal, a casting material that is good in surface properties could be obtained. To the contrary, in the nozzle having the coating layer on the whole of the inner surface of the nozzle, the short diameter of the pouring port is reduced by the coating layer (thickness 3.5 mm) by about 0.7 to 0.8 mm. Therefore, in order to reduce deterioration of the surface properties caused by decrease in sectional area of the pouring port, it is necessary to perform such an operation as to increase the pouring pressure of the molten metal.

EXAMINATION EXAMPLE 4

(36) Various nozzles as shown in FIG. 3 are manufactured, and magnesium and magnesium alloy are cast, using the twin roll movable casting die shown in FIG. 1. In this examination, a 100 kg casting sheet of thickness 5 mmwidth 250 mm is manufactured, using a similar twin-roll casting machine of roll diameter 1000 mmwidth 500 mm to that in the examination example. As molten metal, similarly to in the examination example 1, pure magnesium, AZ31 corresponding alloy, and AZ91 corresponding alloy are used.

(37) In a nozzle 1A shown in FIG. 3(A), a main body 1Aa is formed of calcium silicate (which has a density of 0.78 g/cc and has thermal conductivity of 0.19 W/mK at 600 C.), and a coating layer 3A is provided on the whole of the inner surface of the main body 1Aa. The coating layer 3A, using a spray in which mixed powder of boron nitride and graphite is mixed in solvent (ethanol), by repeating ten times an operation of applying the powder on the inner surface of the main body 1Aa, and thereafter sintering the applied powder at 160 C. temperature, is formed with about 0.2 mm thickness. A pouring port 4A for which the coating layer 3A is provided has the rectangular shape of longer diameter 250 mm and short diameter 5 mm.

(38) Further, in a nozzle 1A shown in FIG. 3(A), a main body 1Aa is formed of calcium silicate (which has a density of 0.83 g/cc and has thermal conductivity of 0.145 W/mK at 600 C.), and a coating layer 3A is provided on the whole of the inner surface of the main body 1Aa. The coating layer 3A, using a spray in which mixed powder of boron nitride and graphite is mixed in solvent (ethanol), by repeating ten times an operation of applying the powder on the inner surface of the main body 1Aa, and thereafter sintering the applied powder at 160 C. temperature, is formed with about 0.2 mm thickness. A pouring port 4A for which the coating layer 3A is provided has the rectangular shape of longer diameter 250 mm and short diameter 5 mm.

(39) Still further, in a nozzle 1A shown in FIG. 3(A), a main body 1Aa is formed of Al.sub.2O.sub.3 (which has a density of 0.190.26 g/cc and has thermal conductivity of 0.11 W/mK at 600 C.), and a coating layer 3A is provided on the whole of the inner surface of the main body 1Aa. The coating layer 3A, using a spray in which mixed powder of boron nitride and graphite is mixed in solvent (ethanol), by repeating ten times an operation of applying the powder on the inner surface of the main body 1Aa, and thereafter sintering the applied powder at 160 C. temperature, is formed with about 0.2 mm thickness. A pouring port 4A for which the coating layer 3A is provided has the rectangular shape of longer diameter 250 mm and short diameter 5 mm.

(40) Still further, in a nozzle 1A shown in FIG. 3(A), a main body 1Aa is formed of SiO.sub.2 (which has a density of 0.46 g/cc and has thermal conductivity of 0.16 W/mK at 600 C.), and a coating layer 3A is provided on the whole of the inner surface of the main body 1Aa. The coating layer 3A, using a spray in which mixed powder of boron nitride and graphite is mixed in solvent (ethanol), by repeating ten times an operation of applying the powder on the inner surface of the main body 1Aa, and thereafter sintering the applied powder at 160 C. temperature, is formed with about 0.2 mm thickness. A pouring port 4A for which the coating layer 3A is provided has the rectangular shape of longer diameter 250 mm and short diameter 5 mm.

(41) Still further, in a nozzle 1A shown in FIG. 3(A), a main body 1Aa is formed of SiO.sub.2 (which has a density of 0.69 g/cc and has thermal conductivity of 0.38 W/mK at 600 C.), and a coating layer 3A is provided on the whole of the inner surface of the main body 1Aa. The coating layer 3A, using a spray in which mixed powder of boron nitride and graphite is mixed in solvent (ethanol), by repeating ten times an operation of applying the powder on the inner surface of the main body 1Aa, and thereafter sintering the applied powder at 160 C. temperature, is formed with about 0.2 mm thickness. A pouring port 4A for which the coating layer 3A is provided has the rectangular shape of longer diameter 250 mm and short diameter 5 mm.

(42) Still further, in a nozzle 1A shown in FIG. 3(A), a main body 1Aa is formed of SiO.sub.2 (which has a density of 1.10 g/cc and has thermal conductivity of 1.00 W/mK at 600 C.), and a coating layer 3A is provided on the whole of the inner surface of the main body 1Aa. The coating layer 3A, using a spray in which mixed powder of boron nitride and graphite is mixed in solvent (ethanol), by repeating ten times an operation of applying the powder on the inner surface of the main body 1Aa, and thereafter sintering the applied powder at 160 C. temperature, is formed with about 0.2 mm thickness. A pouring port 4A for which the coating layer 3A is provided has the rectangular shape of longer diameter 250 mm and short diameter 5 mm.

(43) In a nozzle 1B shown in FIG. 3(B), a pouring port side of a main body 1Ba is different in forming material from a pouring basin side thereof. A pouring port side main body 1b is formed of aluminum sintering compact, and a pouring basin side main body 1bb is formed of graphite. On the inner surface of this main body 1Ba, a coating layer 3B is provided at a portion except the vicinity of a pouring port 4B (except area which is 0.3 mm distant from the pouring port). The coating layer 3B, preparing a boron nitride spray in which boron nitride powder is mixed in solvent (ethanol), and a graphite spray in which graphite powder is mixed in solvent (ethanol), by repeating ten times an operation of laminating the powders on the inner surface of the main body 1Ba (except the vicinity of pouring port where masking is applied), using alternately the both sprays, and thereafter sintering the laminated powders at 300 C. temperature, is formed with about 0.4 mm thickness. A pouring port 4B has the rectangular shape of longer diameter 250 mm and short diameter 5.4 mm.

(44) In a nozzle 1C shown in FIG. 3(C), similarly to in the nozzle 1B, a pouring port side of a main body 1Ca is different in forming material from a pouring basin side thereof. A pouring port side main body 1c is formed of boron nitride sintering compact, and a pouring basin side main body 1cc is formed of graphite. On the inner surface of this main body 1Ca, a coating layer 3C is provided partially on the inner surface of the pouring port side main body 1c, and not is provided in an area which is 40 mm distant from the pouring port, and on the inner surface of the pouring basin side main body 1cc formed of graphite. The coating layer 3C, using a spray in which mixed powder of boron nitride, carbon and graphite is mixed in solvent (ethanol), by repeating eight times an operation of applying the powders onto the inner surface of the main body 1Ca (except the vicinity of pouring port where masking is applied, and the pouring basin side main body), and thereafter sintering the applied powders at 160 C. temperature, is formed with about 0.4 mm thickness. A pouring port 4C has the rectangular shape of longer diameter 250 mm and short diameter 5.4 mm.

(45) In a nozzle 1D shown in FIG. 3(D), a main body 1Da is formed of Isowool Board (of which main components are alumina and silica) by ISOLITE, and a coating layer 3D is provided on the whole of the inner surface of the main body 1Da. The coating layer 3D, using a spray in which boron nitride powder is mixed in solvent (ethanol), by repeating five times an operation of applying the powder on the inner surface of the main body 1Da, and thereafter sintering the applied powder at 160 C. temperature, is formed with about 0.25 mm thickness. A pouring port 4D for which the coating layer 3D is provided has the rectangular shape of longer diameter 250 mm and short diameter 4.9 mm. This nozzle 1D contains plural stainless bars inserted into the main body 1Da as reinforcement members 5. In this example, particularly, the reinforcement members 5 are arranged on the pouring basin side. By thus arranging the reinforcement members 5, the nozzle 1D can prevent the main body 1Da from being deformed by weight of molten metal.

(46) In a nozzle 1E shown in FIG. 3(E), a main body 1Ea is formed of a calcium silicate board, and a coating layer 3E is provide only on the pouring basin side of the inner surface of the main body 1Ea but is not provided on the pouring port side (in an area which is 75 mm distant from a pouring port 4E). Namely, in this nozzle 1E, the coating layer 3E is provided only on a portion of the inner surface which comes into contact with molten metal of which the temperature is Tm+10 C. or more. The coating layer 3E, using a spray in which graphite powder is mixed in solvent (ethanol), by repeating eight times an operation of applying the powder on the inner surface of the main body 1Ea (except the area on the pouring port side to which masking has been applied), and thereafter sintering the applied powder at 300 C. temperature, is formed with about 0.4 mm thickness. The pouring port 4E has the rectangular shape of longer diameter 250 mm and short diameter 5.4 mm. This nozzle 1E, similarly to the nozzle 1D, has reinforcement members 6 arranged on the pouring basin side of the main body 1Ea. In the nozzle 1E, stainless plates are arranged as the reinforcement member 6 on the peripheral surface of the main body 1Ea. In this example, particularly, the reinforcement members 6 are arranged on the pouring basin side. By thus arranging the reinforcement members 6, the nozzle 1E can prevent the main body 1Ea from being deformed by weight of the molten metal.

(47) When cast is performed using the above nozzles, in any nozzles, without any problems, a casting sheet of 100 Kg is manufactured. At this time, in the nozzles 1B, 1C and 1E each of which has no coating layer near the pouring port, since the sectional area of the pouring port is not reduced by the coating layer, the casting material which is good in surface properties could be obtained without increasing the supply-pressure of the molten metal. In the nozzles 1A and 1D each of which has the coating layer on the whole of the inner surface of the nozzle, though the area of the pouring port is reduced by the coating layer, the casting material which is good in surface properties could be obtained by performing such an operation as to increase the pouring pressure of the molten metal.

(48) Further, in the nozzles 1B and 1C where a part of each nozzle main body is formed of graphite that is good in thermal conductivity, the heater or the like could be arranged at the periphery of the pouring basin side main body formed of graphite to heat the molten metal, whereby lowering of the melting temperature in the nozzle could be reduced. Further, when a wear-resistant member is arranged on the movable casting die contact side of the nozzle, the nozzle damage caused by slide with the movable casting die could be reduced.

(49) Although the invention has been described in detail and with reference to specified embodiments, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.

INDUSTRIAL APPLICABILITY

(50) The casting nozzle of the invention, when continuous cast of magnesium or magnesium alloy is performed, can be preferably utilized as a molten metal transporting member which supplies molten metal from a melting furnace to a movable casting die.