BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an exchangeable continuous casting nozzle used for a slide nozzle device which pours molten metal such as molten steel into a casting mold, while controllably feeding the molten metal from a container such as a ladle and a tundish in a metal casting field. 
     2. Description of the Related Art 
     The slide nozzle device pours molten metal into a casting mold from a container for molten metal, e.g. a tundish. A conventional slide nozzle device is generally shown in FIG. 4. A conventional slide nozzle device attached to a bottom wall of the tundish comprises an upper nozzle  1  disposed on a bottom wall of the tundish, an upper fixed plate  2  supporting the upper nozzle  1  from below, a lower fixed plate  3 , and a sliding plate  4  disposed between the upper fixed plate  2  and the lower fixed plate  3  and operated by a sliding means  5  to turn on/turn off the molten metal. 
     The slide nozzle device further comprises a collector nozzle  6  connected to the lower fixed plate  3  and an immersion nozzle  10  extending into a casting mold, and surrounded by a metal mantle  12 , and a frame  18  uniting the above plates and nozzles in a body. These nozzles are made of various refractory materials. Further, a fixing flange  14  is fastened, through a metal supporting bar  13 , to a metal casing  15  that surrounds the lower fixed plate  3 . Fixing flange  14  unites the lower fixed plate  3 , the collector nozzle  6 , and the immersion nozzle  10  in a body. Arms  16  disposed beneath the frame  18  mounting the sliding means  5  fix the lower fixed plate  3 , the collector nozzle  6 , and the immersion nozzle  10 , all of which are united in the frame  18 . 
     The molten metal in the container passes through a through hole  1 A of the upper nozzle  1 , a through hole  2 A of the upper fixed plate  2 , a through hole  4 A of the sliding plate  4 , a through hole  3 A of the lower fixed plate  3 , a through hole  6 A of the collector nozzle  6 , and a through hole  10 A of the immersion nozzle  10 , and then it is poured into the casting mold (not shown). 
     The conventional slide nozzle device has a problem that the air is entrapped into the through holes through seams between the lower fixed plate  3  and the collector nozzle  6 , and between the collector nozzle  6  and the immersion nozzle  10 , thereby causing the molten metal to be oxidized, which deteriorates the quality of the molten metal. 
     The reasons for the above problem are given in details as follows: 
     (1) Mortar disposed in the seam between the collector nozzle  6  and the immersion nozzle  10  deteriorates in plasticity due to heat of the molten metal passing through the through holes inside the nozzles. 
     (2) The metal supporting bar  13  fastening the fixing flange  14  is subjected to thermal expansion, thereby decreasing the fastening force of fastening the lower fixed plate  3 , the collector nozzle  6 , and the immersion nozzle  10 . 
     (3) The fastening force due to the metal supporting bar  13  and the bending moment caused at replacing the nozzle, etc., causes the mating faces of the collector nozzle  6  and the immersion nozzle  10  to be broken. Furthermore, the slide nozzle device has other problems related to the time required to unite the collector nozzle  6  and the immersion nozzle  10 , and to the economical efficiency such as the manufacturing cost. 
     Therefore, in order to solve the above-mentioned problems, a Japanese Provisional Patent Publication (Kokai) No. 6-13457 has disclosed, as shown in FIG. 5, an integral nozzle  30  in which the lower fixed plate, the collector nozzle and the immersion nozzle are integrated with one another in a body. The integral nozzle  30  comprises a tube body  32  made of a refractory material and a flange portion  33  contacting to the sliding plate. An upper part of an inner circumferential portion of the tube body  32  and an upper face of the flange portion  33  are formed with an insert portion  34  made of a wear-resistant and greater hardness refractory material, and then the flange portion  33  is surrounded by a metal casing  35 . 
     This integral nozzle eliminates the need for using mortar in the seam between the collector nozzle and the immersed nozzle, etc., which solves the problem of oxidizing the molten metal due to lowering of the sealing property. Further, a metal mantle, bolts and nuts required to unite the collector nozzle and the immersion nozzle can be eliminated, which brings about the resolution of the problems related to the manufacturing cost and time. 
     However, the existent continuous casting nozzles are clogged during long time use, which requires a frequent replacement of the nozzle. Further, the replacement must be carried out quickly in order to increase the efficiency, which causes the bending stress to be applied in a direction to replace the nozzle. 
     In the integral nozzle  30  disclosed in Japanese Provisional Patent Publication (Kokai) No. 6-13457, since the whole integral nozzle  30  is made of a refractory material, the performance of the sealing property is improved and further the total length of the nozzle is increased. However, it has other problems related to not only the transportation and the handling, but also occurrence of the breakage due to the weak strength against the bending stress in a direction to replace the nozzle. Moreover, the above-mentioned nozzle should be replaced more frequently, which requires quickness of the replacing work, improvement of the safety, and easiness of replacing the nozzle. 
     It is therefore an object of the invention to provide a continuous casting nozzle used for a slide nozzle device, which is capable of being easily transported and being quickly and safely replaced, and further is not easily damaged on handling, particularly, on replacing. 
     SUMMARY OF THE INVENTION 
     To attain the above object, the inventor has paid a keen attention to reinforcing of a continuous casting nozzle, conjunction between a metal casing portion surrounding a flange portion and a metal skirt portion surrounding a tube body, and thereby have invented the following: 
     The present invention provides an exchangeable continuous casting nozzle to be used in a slide nozzle device, comprising: 
     (a) a nozzle including a flange portion made of a refractory material having a through hole for receiving molten metal flowing out of the upper nozzle, and a tube body of a refractory material, continuing from the flange portion and having another through hole continuing from the through hole, and 
     (b) a metal protecting body including a metal casing portion surrounding the flange portion, a metal skirt portion surrounding an upper portion of the tube body, and metal reinforcing portions disposed around a junction between the metal casing portion and the metal skirt portion in parallel with a direction to detach/attach the nozzle for reinforcing. 
     The exchangeable continuous casting nozzle has the metal reinforcing portions on the connecting portion of the metal casing portion and the metal skirt portion in parallel with the nozzle attaching/detaching direction; therefore, quick replacement of the integral nozzle prevents the nozzle from being broken at a connecting at portion between the flange portion and the tube body. 
     Preferably, the metal reinforcing portion comprises a reinforcing portion shaped like a half rectangular in horizontal section, fixed to the metal casing portion and the metal skirt portion from the outside. 
     This metal reinforcing portion is simple in contour, which ensures easy working and a sufficient strength of the metal reinforcing portion. 
     Preferably, the metal reinforcing portion comprises a reinforcing portion having a curved portion which is identical in curvature with the metal skirt portion, and a plate-like portion connected to the curved portion, the reinforcing portion being fixed to the metal casing portion and the metal skirt portion from the outside. 
     This metal reinforcing portion is complicated in contour; however, preliminarily preparing parts enables the parts to be easily welded, and so on. 
     Preferably, the metal reinforcing portion comprises a reinforcing portion having a curved portion which is shaped like a circle or polygon in horizontal section, and a bar-like member, the reinforcing portion being fixed to the metal casing portion and the metal skirt portion from the outside. 
     This metal reinforcing portion is simple in contour, which ensures easy working and a sufficient strength of the metal reinforcing portion. 
     Preferably, the metal reinforcing portion comprises a reinforcing portion shaped like a crescent in horizontal section, fixed to the metal casing portion and the metal skirt portion from the outside. 
     This metal reinforcing portion is complicated in contour; however, preliminarily preparing parts enables the parts to be easily welded, and so on. 
     Preferably, the metal reinforcing portion comprises a reinforcing portion shaped like a triangle in vertical section, fixed to the metal casing portion and the metal skirt portion from the outside. 
     This metal reinforcing portion is simple in contour, which ensures easy working and a sufficient strength of the metal reinforcing portion. 
     Preferably, the metal reinforcing portion comprises a reinforcing portion shaped like a deformed pentagon in vertical section, fixed to the metal casing portion and the metal skirt portion from the outside. 
     This metal reinforcing portion is simple in contour, which also ensures easy working and a sufficient strength of the metal reinforcing portion. 
     More preferably, the flange portion comprises at least two refractory material layers of a lower layer and an upper layer, the lower layer being made of the same refractory material as the tube body, and the upper layer being made of a refractory material which is greater in hardness than the tube body. 
     It is preferable that an upper face of the flange portion contacts to the lower fixed plate or the sliding plate which is greater in hardness, and that it is greater in hardness than the tube body so as not to be eroded by the flowing molten metal. 
     Further preferably, the flange portion is preferably made of three refractory layers of a lower layer, an intermediate layer, and an upper layer, the lower layer being made of the same material as the tube body which is less in hardness, and then the intermediate layer and the upper layer are made of materials which become greater in hardness in order than the tube body. 
     The intermediate layer has an intermediate hardness between those of the tube body and the upper layer, which prevents the lower layer and the upper layer from being separated due to the difference between the thermal expansion thereof. 
     Further advantages of the invention will be apparent from the following description of the preferred embodiments of the invention as illustrated in the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional drawing of a slide nozzle device using an exchangeable continuous casting nozzle according to the present invention; 
     FIG. 2 a  is a sectional drawing of a head portion of an exchangeable continuous casting nozzle according to the present invention, 
     FIG. 2 b  is a drawing of the nozzle of FIG. 2 a  as viewed from below, 
     FIGS. 2 c,    2   d ,  2   e ,  2   f ,  2   g , and  2   h  are perspective views showing various embodiments of a metal reinforcing portion; 
     FIGS. 3 a,    3   b ,  3   c ,  3   d ,  3   e , and  3   f  are sectional drawings showing various embodiments of a slide nozzle device using an exchangeable continuous casting nozzle according to the present invention; 
     FIG. 4 is a sectional drawing of a slide nozzle device ; and 
     FIG. 5 is a sectional drawing of a conventional casting nozzle. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The invention will now be described in detail with reference to the drawings showing respective embodiments. 
     An embodiment of the invention will now be described with reference to FIG.  1 . There is shown in FIG. 1 an example of a tundish as a container for molten metal and also a slide nozzle device  100  connected to an upper nozzle  1  which is embedded in a bottom brick of the tundish. The slide nozzle device  100  comprises an upper fixed plate  2 , a sliding plate  4 , and a frame  18  accommodating the upper fixed plate  2  and the sliding plate  4 . The frame  18  is provided with a sliding means  5  for sliding the sliding plate  4 , and an arm  16  for pressing the upper fixed plate  2  and the sliding plate  4  accommodated in the frame  18 , and a flange portion  22  of an exchangeable integral nozzle  10  from below. 
     The arm  16  receives a reactive force of a spring fixed to the frame  18 , and presses a supporting member  23  for supporting the flange portion  22  of the exchangeable integral nozzle  10 , and the like. The flange portion  22  of the integral nozzle  10  and an upper part of the tube body continuing from the flange portion  22  are surrounded by a metal casing portion  26 A and a metal skirt portion  26 B. The metal casing portion  26 A and the metal skirt portion  26 B protect the integral nozzle  10 , thereby enables the integral nozzle  10  to be protected from damage when attached to or detached from the supporting member  23  of the slide nozzle device  100 . As the supporting member  23  comprises two rails disposed parallel to each other and the nozzle  10  can be inserted into the slide nozzle device  100  in the direction perpendicular of this drawing, the metal casing portion  26 A and the metal skirt portion  26 B are reinforced by metal reinforcing portions  20  not shown in this figure. However, it is described in FIG. 2 a  and FIG. 2 b.    
     FIG. 2 a  is a sectional drawing of a head portion of a continuous casting nozzle according to the invention, and FIG. 2 b  is a view of the nozzle of FIG. 2 a  as viewed from below. FIGS. 2 c  to  2   g  are perspective views showing various embodiments of a metal reinforcing portion. 
     In FIG. 2 a  and FIG. 2 b , the flange portion  22  is surrounded by the metal casing portion  26 A, and an upper part of the tube body continuing from the flange portion  22  is protected by the metal skirt portion  26 B. The metal casing portion  26 A and the metal skirt portion  26 B are integrally made of an iron plate of 1 to 3 mm thickness. Therefore, moving the integral nozzle  10  in an attaching/detaching direction to attach to or detach from the integral nozzle  10  causes a connecting portion of the flange portion  22  and the tube portion to be damaged due to a large bending moment caused by the exchange of the integral nozzle  10 . 
     Therefore, a pair of the metal reinforcing portions  20  are, as shown in FIG. 2 b , disposed on both sides of the connecting portion of the metal casing portion  26 A and the metal skirt portion  26 B with respect to the nozzle attaching/detaching direction. FIG. 2 c  shows a reinforcing portion  20  shaped like a half rectangular in horizontal section, fixed to the metal casing portion  26 A and the metal skirt portion  26 B from the outside. This half rectangular-shaped reinforcing portion  20  is simple in contour, which ensures easy working and a sufficient strength of the metal reinforcing portion. In this embodiment, the metal casing portion  26 A, the metal skirt portion  26 B and the metal reinforcing portion  20  constitute a metal protection body  26 . 
     A metal reinforcing portion  20  shown in FIG. 2 d  comprises a reinforcing portion having a curved portion which is identical in curvature with the metal skirt portion  26 B, and a plate-like portion fixed to the curved portion, the reinforcing portion being fixed to the metal casing portion  26 A and the metal skirt portion  26 B from the outside. 
     This metal reinforcing portion  20  is complicated in contour; however, preliminarily preparing parts enables the parts to be easily welded, and so on. 
     A metal reinforcing portion shown in FIG. 2 e  comprises a reinforcing portion  20  having a curved portion which is shaped like a circle or polygon in horizontal section, and a bar-like member, the reinforcing portion being fixed to the metal casing portion  26 A and the metal skirt portion  26 B from the outside. 
     This metal reinforcing portion  20  is simple in contour; however, it can be easily made by welding, and so on. 
     A metal reinforcing portion  20  shown in FIG. 2 f  comprises a reinforcing portion shaped like a crescent in horizontal section, fixed to the metal casing portion  26 A and the metal skirt portion  26 B from the outside. 
     This metal reinforcing portion  20  is complicated in contour; however, preliminarily preparing parts enables the parts to be easily welded, and so on. 
     An metal reinforcing portion  20  shown in FIG. 2 g  comprises a reinforcing portion shaped like a triangle in vertical section, fixed to the metal casing portion  26 A and the metal skirt portion  26 B from the outside. This metal reinforcing portion  20  is simple in contour; however, it can be easily made by welding, and so on. 
     A metal reinforcing portion  20  shown in FIG. 2 h  comprises a deformed pentagon in vertical section, fixed to the metal casing portion  26 A and the metal skirt portion  26 B from the outside. This metal reinforcing portion  20  is simple in contour; however, it can be easily made by welding, and so on. 
     The reinforcing portion can be constructed by selecting not only one type but also two or more types as illustrated from FIGS. 2 c  to  2   h  so long as the portion can be inserted into the supporting member  23 . For example the half rectangular member (FIG. 2 c ) can be more reinforced by combination of the triangle (FIG. 2 g ) or the deformed pentagon (FIG. 2 h ). The material of the metal protecting body  26 , which should not be particularly limited by this specific description, is preferably made of usual steel plate which is inexpensive, and capable of being easily welded. The exchangeable integral casting nozzle  10  should be provided with at least a pair of the metal reinforcing portions  20  on the connecting portion of the metal casing portion  26 A and the metal skirt portion  26 B in parallel with the nozzle attaching/detaching direction; therefore, quick replacement of the nozzle  10  prevents the nozzle from being broken at an intermediate portion between the flange portion  22  and the tube body. 
     Then, a pair of the metal reinforcing portions  20  are arranged in parallel with the nozzle attaching/detaching direction, which effectively reduces the bending stress applied to the metal skirt portion  26 B, and enables the nozzle  10  to be replaced quickly and smoothly according to the shape of the casting mold. The above-mentioned metal reinforcing portions  20  basically reinforces the resistance against the bending stress of the nozzle  10  with respect to the nozzle attaching/detaching direction of the nozzle  10 , and also prevents the exchangeable nozzle  10  to be wrongly inserted into the slide nozzle device  100 . As the exchangeable nozzle  10  is inserted perpendicularly to the sheet of FIG. 1 for exchange, it is interfered with the supporting members  23  made of two rails arranged parallel with each other, which prevents the nozzle  10  to be inserted into the slide nozzle device  100  in the wrong direction. 
     FIGS. 3 a  to  3   f  are sectional views showing various combination of parts of the slide nozzle device  100  using the exchangeable nozzle  10  according to the invention. FIG. 3 a  shows an embodiment of the slide nozzle device  100  corresponding to that of FIG. 1, in which the flange portion  22  of the nozzle  10  directly contacts to the sliding plate  4 . FIG. 3 b  shows an embodiment the slide nozzle device  100  in which the nozzle  10  directly contacts to the upper fixed plate  2  because the molten metal pouring is controlled by the tundish stopper  40 . FIG. 3 c  shows an embodiment of the slide nozzle device  100  in which the flange portion  22  contacts to a protrusion of the lower fixed plate  3 . FIG. 3 d  shows an embodiment of the slide nozzle device  100  in which the nozzle  10  contacts to the lower fixed plate  3  from below. FIG. 3 e  shows an embodiment of the side nozzle device  100  which is substantially identical with that of FIG. 3 b . FIG. 3 f  shows an embodiment of the side nozzle device  100  in which the flange portion  22  has a recess portion fitted to a protrusion of the lower fixed plate  4 . 
     Particularly in the embodiment of FIG. 1, i.e. FIG. 3 a  among the above-mentioned embodiments, the flange portion  22  is made of preferably at least two layers comprising an upper layer ( 22 A) and a lower layer  22 C as suggested in FIG. 2 a  (the intermediate layer  22 B should be ignored). The lower layer  22 C is made of a refractory material which is substantially identical with that of the tube body, and the upper layer ( 22 A) is made of material which are greater in hardness and in anti-wearing property than the refractory material of the tube body. This prevents the upper face of the flange body  22  from being eroded by the molten metal flowing down, although the upper face of the flange body  22  contacts to the lower fixed plate  3  or the sliding plate  4  which is greater in hardness. 
     The flange portion  22  can be made of three refractory layers of an upper layer  22 A, an intermediate layer and a lower layer  22 C as shown in FIG. 2 a . The lower layer  22 C is made of the same material as that of the tube body which is less in hardness, and then the intermediate layer  22 B and the upper layer  22 A are made of materials which becomes greater in hardness in order than the tube body. This prevents the tube body of a less hardness and the upper layer of a greater hardness from being separated due to the difference of the heat expansion therebetween. 
     The tube body is preferably made of a refractory material having erosion resistance, i.e. aluminum-graphite brick mainly made of alumina of about 45 wt %, graphite, and silica, e.g. aluminum-graphite material mainly made of alumina of about 45 wt %, silica of about 25 wt %, and graphite of about 30 wt %. The same is true for the material of the lower layer  22 C of the flange portion  22 . 
     The intermediate layer  22 B is preferably made of refractory material having alumina of over about 50 wt %, e.g. aluminum-graphite material mainly made of alumina of about 63 wt %, silicon carbide (SiC) of about 5 wt %, and graphite of about 32 wt %. The upper layer  22 A is preferably made of refractory material of a greater hardness, e.g. alumina of about 60 wt %, silicon carbide of about 10 wt %, and graphite of about 20 wt %. 
     In addition, preferably, the inner wall of the nozzle on which the molten metal, particularly the molten steel, flows is preferably made of a material having a high erosion resistance. Further, a part and the vicinity of the outer face of the nozzle contacting to casting mold powder is preferably coated by a material having a high erosion resistance to the casting mold powder, e.g. zirconia refractory material including zirconia of about 75 wt %, and graphite of 20 wt %. 
     The above-mentioned nozzle is manufactured by a conventional method of forming the nozzle as one body preferably by cold hydrostatic pressure forming method, and then sintering it. 
     While the above is a description of various embodiments of the present invention, the scope of the present invention should not be limited by the specific structures disclosed, and should include any other embodiments and equivalent which those skilled in the art can easily employ. 
     The exchangeable continuous casting nozzle according to the invention is reinforced by metal protecting bodies each comprising a metal reinforcing portion for a metal casing portion and a metal skirt portion. Therefore, it is possible to prevents the nozzle from being broken, and to quickly and safely move and replace the nozzle. 
     Further, disposing the metal protecting portions in parallel with a nozzle attaching/detaching direction, thereby making the direction of the bending stress applied to the nozzle parallel to the nozzle moving direction, which effectively decreases the bending stress, and further enables the nozzle to be attached to or detached from a container, or the like. This enables the nozzle to be quickly replaced in various casting work. 
     Moreover, the metal reinforcing portion has also an effect to prevent the nozzle from being wrongly inserted into a slide nozzle device. The metal reinforcing portion is shaped into a contour of the metal casing portion and the metal skirt portion, or such a contour as to be suited to the frequencies of the nozzle replacement, which results in reinforcement of conjunction between the metal casing portion and the metal skirt portion.
An exchangeable continuous casting nozzle used for a slide nozzle device connected to an upper nozzle disposed on a bottom portion of a container for molten metal, comprises a nozzle including a flange portion made of a refractory material having a through hole for receiving molten metal flowing out of the upper nozzle, and a tube body of a refractory material having another through hole following the through hole, and a metal protecting body including a metal casing portion surrounding the flange portion, a metal skirt portion surrounding an upper portion of the tube body following the flange portion, and metal reinforcing portions disposed on the slide nozzle device in parallel with a direction to detach/attach the nozzle, for reinforcing junction between the metal casing portion and the metal skirt.