Abstract:
A container for molten metal has at least one opening in which a refractory nozzle brick is mounted. A refractory purge plug or a refractory sleeve defining an outlet opening is inserted in the nozzle brick opening. A defined gap is formed between the nozzle brick opening and the purge plug or the sleeve and is filled with a refractory mass, this mass consisting of a material which can be easily bored or milled out of the mass for the purpose of replacing the purge plug or the sleeve. In this manner, laborious cleaning steps can be avoided and the nozzle brick no longer risks being damaged.

Description:
FIELD OF THE INVENTION 
     The invention relates to a method for mounting and removing a refractory purge plug or a refractory sleeve in or from a refractory nozzle brick mounted in a container for molten metal, and a container for molten metal for implementation of the method. 
     BACKGROUND OF THE INVENTION 
     Till now conical refractory purge plugs (purge sleeves), by means of which gas is introduced into the molten metal, or conical refractory sleeves, which respectively form an outlet opening, are generally inserted into correspondingly formed nozzle brick openings. They are separated from the latter by narrow mortar joints (approximately 1 to 3 mm wide). When the worn purge plugs or sleeves break loose, which happens due to pulling, chiselling out using pneumatic hammers, burning out, squeezing out etc., these parts are time and again destroyed, the remains being left hanging in the respective nozzle brick opening. These remains, as well as mortar remains and any steel tongues, must be removed, which is very labour-intensive. When they break loose, and during the cleaning steps, damage to or destruction of the nozzle brick can occur. 
     Generally time-consuming nozzle brick repairs are necessary after every purge plug or sleeve change. The cleaning steps on the hot, refractory parts are dangerous and constitute heavy labour. When applying the mortar to the purge plug or to the sleeve an uneven mortar thickness can occur, or during the manually implemented mounting of the purge plug or the sleeve the mortar can become uneven in some places or even be totally stripped off locally. This leads to known problems such as premature wear in the region of the joints, the penetration of steel into the joint and even the risk of breaking through. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     The object that forms the basis of the present invention is to provide an inexpensive method for the mounting and removal of a refractory purge plug or a refractory sleeve and a container for molten metal in and out of a refractory nozzle brick mounted in the container with which changing of the purge plug or the sleeve is considerably facilitated and the risk of damage to the perforated brick caused by the change is largely eliminated. 
     This object is achieved according to the invention by a method in which a new purge plug or a new sleeve is introduced into the nozzle brick opening and positioned and fixed in the nozzle brick opening, and thereafter, a gap between the nozzle brick opening and the purge plug or the sleeve is filled with a refractory mass, and by a container including a refractory nozzle brick mounted in a container opening, and comprising a refractory purge plug inserted into a nozzle brick opening defined by the refractory nozzle brick or a refractory sleeve forming an outlet opening, and a refractory mass arranged in a gap defined between the nozzle brick opening and the purge plug or the sleeve and which is made of a material such that it is removable for the purpose of changing the purge plug or the sleeve, and wherein the purge plug or the sleeve has a cylindrical outer surface. 
     Preferred further configurations of the container according to the invention and of the method according to the invention form the subject matter of the dependent claims. 
     Since in order to remove a worn purge plug or a worn sleeve manually implemented breaking loose, which constitutes dangerous heavy work, is no longer required, but rather these parts can easily be detached with the aid of suitable tools (drilling or milling tools), not only are the laborious cleaning steps dispensed with, but also the risk of the nozzle brick being damaged. Dispensing with the laborious cleaning and repair steps constitutes an enormous saving in time, and in addition operational safety is increased. 
     Moreover, the change can be automated. The problems associated with so-called mortar joints (premature wear in the joint region, the penetration of steel into the joints or even the risk of breaking through) also cease to exist. Any premature wear of the nozzle brick can be automatically restored when the purge plug or the sleeve is changed (the refractory mass filling a gap between the nozzle brick opening and the purge plug or the sleeve is also distributed over the worn regions of the nozzle brick). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following the invention is described in greater detail by means of the drawings. These show as follows: 
         FIG. 1  shows part of a container for molten metal with a refractory nozzle brick inserted into an opening and a refractory purge plug to be replaced, mounted in the nozzle brick; 
         FIG. 2  shows the part of the container according to  FIG. 1  with a new refractory purge plug; 
         FIG. 3  is an illustration corresponding to  FIG. 1  with a different variation of a refractory purge plug; 
         FIG. 4  shows part of a container for molten metal with a nozzle brick inserted into an opening and a refractory sleeve forming an outlet opening mounted in the nozzle brick and which is to be replaced; and 
         FIG. 5  shows a further embodiment of the nozzle brick and the new refractory sleeve mounted in said nozzle brick and forming an outlet opening. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In  FIGS. 1 and 2  part of a container  1  for molten metal, for example a so-called ladle for molten steel, is shown, only an outer steel jacket  2  and a refractory lining  3  of the container being visible. A refractory nozzle brick  5 , which has a cylindrical nozzle brick opening  6 , is inserted into an opening  4  of the container  1 . 
     According to  FIGS. 1 and 2  a refractory purge plug  10 , which according to the invention consists of two coaxial parts  11 ,  12  produced (pre-assembled) as one piece is inserted into the nozzle brick opening  6 . The inner part  11  with a gas connection  13 , which corresponds to a conventional purge plug, as used for introducing gas into the molten metal, has a conical outer surface  11   a , the outer part  12  a corresponding conical inner surface  12   a . The outer part  12 , which here actually adopts the function of a conventional nozzle brick, has a cylindrical outer surface  12   b . According to the invention, between this outer surface  12   b  and the cylindrical nozzle brick opening  6  there is an annular gap  15  which is filled with a refractory mass. The width of the gap is preferably 10 to 50 mm. 
     The removal of a worn purge plug is no longer implemented by means of breaking loose or chiselling out, burning out, squeezing out, pushing etc., but rather according to the invention the refractory mass is drilled out of the gap  15 , and the purge plug  10  is thus released. With an annular gap  15 , for this purpose conventional drills  16 , e.g. core drills, can be used, as indicated in  FIG. 1 . By means of the drilling process one obtains a clean surface on the nozzle brick  5  and a precise geometric shape. The laborious cleaning and repair steps are dispensed with. 
     After the worn purge plug has been drilled out, a new purge plug  10  is introduced through an opening  4   a  in the bottom of the container  1  into the nozzle brick opening  6  by means of an appropriate apparatus (e.g. lifting tool, push rod, robot etc.) and positioned and fixed here. The mechanical placement allows precise centring here. The positioning of the new purge plug  10  in the nozzle brick opening  6  can be supported, for example, by laser measurement and/or optical methods. 
     As indicated in  FIG. 2 , a base plate  17  is then placed on the container  1 , and the gap  15  is filled with the refractory mass, this being implemented preferably by means of a pump, by pouring, spraying or pushing in. In  FIG. 2  the feed  18  for the refractory mass is indicated. If the nozzle brick  5  already has worn regions, no repair to the nozzle brick is required since the pumped mass is distributed evenly within the annular gap  15  and also over the worn regions of the nozzle brick  5 . 
       FIG. 3  shows a purge plug  10 ′ mounted in a nozzle brick  5 ′ which has a cylindrical outer surface  10   a . Between this outer surface  10   a  and a cylindrical nozzle brick opening  6 ′ of the nozzle brick  5 ′ there is in turn a gap  15 ′ that can be filled with a refractory mass. The mounting and removal of the purge plug  10 ′ takes place in the same way as described above. In  FIG. 3  a drilling tool  16 ′ is in turn indicated with which the refractory mass can be drilled out in order to remove the purge plug  10 ′ from the annular gap  15 ′. 
     The cylindrical configuration of the outer surface of the purge plug on the one hand and of the nozzle brick opening on the other hand, which produces an annular gap, is advantageous by not absolutely necessary. The gap could by all means taper conically or extend vertically, or have a rectangular horizontal cross-section, in which case one would then use milling tools such as e.g. end mills instead of drilling tools  16 ,  16 ′ according to  FIGS. 1 and 3  in order to remove the refractory mass. 
     In the same way as the purge plugs, according to the invention refractory sleeves which form an outlet opening can be mounted in corresponding openings of the containers for molten metal or in the nozzle bricks used here. These are sleeves adjacent to which respectively is the uppermost closure plate of a slide closure with which the outlet opening can be kept closed or open. 
       FIG. 4  shows a nozzle brick  25  with a nozzle brick opening  26  mounted in an opening  24  of the container  1  for molten metal. A refractory sleeve  30 , which has an outlet opening  31 , is inserted into the nozzle brick opening  26 . Between the nozzle brick opening  26  and a cylindrical part  26   a  of the latter and a cylindrical outer surface  30   a  of the sleeve  30  there is an annular gap  35  which is filled with a refractory mass. The nozzle brick opening  26  has an upper, conically extending part  26   b  which encloses a space  32  with an extended diameter in comparison to the sleeve  30  and its outlet opening  31 . 
     With a variation shown in  FIG. 5 , this space  32 ′ is provided in the sleeve  30 ′, and the conically extending part  31   a ′ is allocated to the outlet opening  31 ′. Between the cylindrical outer surface  30   a ′ of the sleeve  30 ′ and the cylindrical nozzle brick opening  26 ′ there is in turn an annular gap  35 ′ which is filled with a refractory mass. A base plate  17 ′ is placed on the container  2 . 
     Similarly to the purge plug  10  according to  FIGS. 1 and 2  the sleeve could also consist of two coaxial parts produced (pre-assembled) as one piece, the inner of which would have a conical external shape, and the outer of which would have a corresponding conical internal shape. The outer part would then adopt the function of a conventional nozzle brick. The nozzle brick  5 ;  5 ′;  25 ;  25 ′ mounted in the container forms a framing brick which guarantees the stability of the system. 
     The mounting and removal of the sleeves  30  and  30 ′ according to  FIGS. 4 and 5  takes place in a similar way to the mounting and removal of the purge plugs  10  and  10 ′ according to  FIGS. 1 to 3  already described. The refractory mass is advantageously removed from an annular gap with a drilling tool  36  in order to withdraw a worn sleeve (see  FIG. 4 ). If the gap is not shaped annularly (e.g. has a rectangular horizontal cross-section), the mass is milled out. The filling of the gap around the new sleeve positioned in the nozzle brick opening is in turn preferably implemented by means of a pump, by pouring, spraying or pushing in (see feed  38  in  FIG. 5 ). 
     Since manually implemented breaking loose, which constitutes dangerous heavy labour, is no longer necessary in order to remove a worn purge plug or a worn sleeve, but rather these parts can easily be detached with the aid of suitable tools (drilling or milling tools), not only can the laborious cleaning steps be dispensed with, but also the risk that the nozzle brick will be damaged. Dispensing with the laborious cleaning and repair steps also means a huge saving in time. Operational safety is increased. Moreover, the change can be automated. The problems associated with so-called mortar joints (premature wear in the joint region, penetration of steel into the joints or even the risk of breaking through) also cease to exist. Any premature wear of the nozzle brick can be automatically restored when the purge plug or the sleeve is changed (the refractory mass filling the gap between the nozzle brick opening and the purge plug or the sleeve is also distributed over the worn regions of the nozzle brick). 
     Removal of the refractory mass can also be implemented by burning with at least one or more lances instead of using a drill, a milling tool or the like. The refractory mass is chosen in this case such that it can be burnt out relatively easily and even in an automated manner.