Abstract:
A tubular refractory channel ( 2 ) that can be inserted as a flowthrough for liquid metal into a thermally insulating outer lining ( 10 ) and can be connected with the outer lining ( 10 ) by a refractory mortar layer ( 9 ). In order to prevent liquid metal from penetrating into the mortar layer ( 9 ), even if the mortar layer contracts, the outer lining ( 10 ) overlaps the metal inflow-side of a front face ( 4 ) of the channel ( 2 ).

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a tubular refractory channel, in particular a refractory nozzle, serving as a flowthrough for liquid metals, in particular liquid steel, with the channel being insertable into a thermally insulating outer lining and the channel and the outer lining being, if appropriate, connectable with a refractory mortar layer. 
     The invention relates furthermore to a method for packing joints between two refractory parts, in particular rotationally symmetrical parts, disposed one within the other which can be connected with a refractory mortar or cement, against the penetration of liquid metal, in particular liquid steel. 
     2. Description of Related Art 
     DE 196 51 534 A1 describes such a device. A refractory pouring sleeve as a wear part is slid into an insulating intermediate sleeve. A cement layer is provided in the joint between the sleeves. The pouring sleeve is heated inductively to casting temperatures. Thereby the cement layer is also brought nearly to casting temperatures. The result can be contraction, which leads to the fact that after a certain degree of wear, liquid metal can enter the space between the sleeves. This is undesirable. In particular, in the case of inductive heating of the pouring sleeves, liquid metal itself which has penetrated into the joint becomes coupled to the electromagnetic field of the inductor whereby it is additionally heated and liquified so that the danger exists that the cemented joint is under strong corrosive stress, wears prematurely and, consequently, further liquid metal can penetrate into the joint. Furthermore, the danger exists of a breakthrough of liquid metal at the other end of the joint. The liquid metal that has penetrated into the joint, incidentally, shields at least partially the pouring sleeve against the electromagnetic field of the inductor such that its intended heating is impaired. 
     SUMMARY OF THE INVENTION 
     It is the task of the present invention to propose a channel and a joint packing of the above described type in which liquid metal is prevented from penetrating into the joint. 
     The above object is achieved according to the invention by constructing the thermally insulating outer lining so that it overlaps the front face at the metal inflow-side of the tubular channel in the axial and radial direction so that the front face, on the one hand, is protected and, on the other hand, the joint between channel and outer lining, which can be filled with a refractory mortar, is not accessible in the aural direction of the main flow of the liquid metal such that no significant quantities of the liquid metal can penetrate into the joint. 
     In a preferred embodiment of the invention, the joint between the channel and the outer lining in the region of the front face of the channel is at least singly bent at an angle in the manner of a labyrinth in the approximately radial and approximately axial direction of the channel. This lengthens the joint and makes the penetration of liquid metal difficult in particular if it is filled with mortar or cement since the liquid metal would have to enter into the joint against the direction of the main flow, which is not to be anticipated. 
     In a preferred embodiment of the invention, a refractory cord and/or a refractory textile tape is wound around the channel. The mortar volume in the joint becomes smaller corresponding to the volume of the cord and/or the textile tape such that the contraction of the mortar has a lesser effect. A material can be used for the cord and/or the textile tape, which contracts significantly less than mortar and, unlike mortar, does not become hard and brittle by sintering but rather retains a certain elasticity by fissuring throughout. The cord and/or the textile tape preferably comprises substantially carbon. 
     A method of the above-described type is distinguished thereby in that onto the outer diameter of a second refractory part (channel) slidable into a first refractory part (outer lining) an encircling refractory cord or an encircling refractory textile tape is applied and that subsequently the two parts are slid one above the other in a mortar and/or cement bed potentially placed between them such that the first refractory part overlaps, as a thermally insulating outer lining at the side at which the metal flows in, the front face of the second refractory part (channel). 
     Therewith a simple method is created with which the joint is packed such that even if the mortar or cement contracts, virtually no liquid metal penetrates into it. 
     Further advantageous embodiments of the invention are evident in the appended claims and the following description of an exemplary embodiment. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The FIGURE depicts in partial section a melt vessel connected to a chill mold. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A chill mold  1  includes a sleeve in the form of a tubular, rotationally symmetrical, refractory channel  2  which comprises a material capable of being inductively coupled. The channel  2  has a conical outer surface  3  and a front face  4  at the inflow side of the channel  2 . 
     An inductor  7  is installed in a wall  5  of a metallurgical melt vessel  6  (tundish). The inductor  7  is supported in a sleeve brick  8 . An outer lining  10 , formed by a rotationally symmetrical, refractory formed part is fastened in the sleeve brick  8  by means of mortar layer  9 . The outer lining is external with respect to the channel  2 . The outer surface  3  of the channel  2  and the outer lining  10  are formed so as to have a conical shape in order to facilitate sliding one into the other. The melt vessel  6  is lined on the inside with a wear layer  11  that also overlaps the outer lining  10  at the inflow side of the channel  2 . 
     Between the outer lining  10  and the channel  2  is a joint  12 . The outer lining  10  forms a region  13  that encompasses the outer surface  3  of channel  2 , and a region  14  that overlaps the front face  4  of channel  2 . Consequently, the joint  12  forms a zone  15  between the region  13  and the outer surface  3  and a zone  16  between the region  14  and the front face  4 . Zone  16  is thus bent at an angle in an approximately radial direction and an approximately axial direction, and thus, the zone  16  is in the form of a labyrinth. The zone is moved out of the main effective region of the inductor  7 . 
     In the region  14  of the outer lining  10 , overlapping front face  4 , there is an annular projection  17  directed in the main flow direction A of the melt. On the front face  4  of channel  2  there is an annular projection  18  extending in a direction opposite or against the main flow direction A. Also, the projection  18  is disposed radially outside of the projection  17  with respect to the throughlet cross section. Thereby, the joint  12  is bent at an angle in zone  16  in the form of a labyrinth, with one labyrinth course  16 ′ in the proximity of the throughflow cross section being directed against the direction of the main flow A. 
     During operation the liquid metal flows in the main flow direction A from the melt vessel  6  into the chill mold  1 . The throughflow cross section D 1  for the metal melt in region  14  of the outer lining  10  is approximately equal to that of the throughflow cross section D 2  in the main flow direction A of the channel  2  in the proximity of the front face  4 . As shown in the FIGURE, the throughflow cross section D 1  is slightly larger than the throughflow cross section D 2 . The throughflow cross section D 2  of channel  2  can expand toward the chill mold  1 . 
     A mortar and/or cement layer can be provided in joint  12 , and such layer, which additionally serves for packing joint  12 . The joint  12  may also preferably be provided with not only mortar or cement, but a refractory cord  21  and/or a refractory textile tape, preferably substantially comprising carbon. 
     As shown in the FIGURE, the refractory cord and/or the refractory textile tape can be wound spirally or helically on the outer surface  3  and, potentially, additionally on the front face  4  of channel  2 . In order to improve the seating and retention of the cord and/or the textile tape on the outer surface  3  or the front face  4 , prefabricated grooves  19 , extending spirally or helically, can be formed on the outer surface  3  and/or on the front face  4 . Instead of the grooves, or in addition, the outer surface  3  and/or the front face  4  can also be roughened as indicated by reference numeral  20 . 
     In order to carry out simply the desired packing of the joint  12 , the cord and/or the textile tape is wound onto the exposed outer surface  3  of channel  2  and potentially the front face  4  before the melt vessel  6  is moved to the chill mold  1 . Subsequently a mortar and/or cement bed is placed on the outer surface  3  and/or into the outer lining fastened on the melt vessel  6 . Subsequently the melt vessel  6  with the outer lining  10  is slid over channel  2  of the chill mold  1 . Thereby, region  14  of the outer lining  10  then overlaps the front face  4 . 
     However, it is also possible to connect the outer lining  10  and the channel  2  directly with one another if, based on their production and during their connection, the two refractory parts can be joined with narrow tolerances. 
     If during a subsequent operation the melt flows from the melt vessel  6  in the main flow direction A through the throughflow cross sections D 1  and D 2  into the chill mold  1 , when the inductor  7  is switched on, no significant quantities of melt will penetrate into joint  12 , especially in zone  15 . The penetration of melt into zone  15  is prevented due to the overlap of the front face  4  and the resulting labyrinth form, as well as potentially the mortar or cement layer and the cord or the textile tape, respectively.