Patent Publication Number: US-2009230159-A1

Title: Method for pouring off melt from a tiltable metallurgical vessel and installation for carrying out the method

Description:
The invention relates to a method for pouring off melt, in particular slag and/or steel melt, from a tiltable metallurgical vessel, in particular a steelworks converter, into a receiving vessel, in particular a ladle or a slag pot, and also to an installation for automatically carrying out the method. 
     A method of this type is known from WO 03/004198 A2. This involves pouring off steel melt into a receiving vessel brought into position underneath a tap hole of a steelworks converter, allowance being made for numerous parameters relevant to the tapping, such as for example the tilting angle of the steelworks converter, the state of the lining of the tap hole, the state of the lining of the steelworks converter, the volume of the charge, the tapping time, the chemical compositions of the steel and the slag, the temperature of the same, etc., and the tilting angle of the steelworks converter being set in dependence on these parameters. Independently of this, the receiving vessel is located vertically underneath the tap hole of the converter. The levels of the melt bath of the converter and of the receiving vessel are constantly observed. 
     For pouring off melts into a casting mold, it is known (DE 26 31 015 A1) to set the tilting angle of a tiltable pouring ladle in dependence on the position of the casting mold, the casting stream leaving the mouth of the pouring ladle and always maintaining its position, i.e. its position in space. The casting mold is provided with a melt level measuring device, so that overflowing of the casting mold can be avoided. 
     A casting machine with an inductively heatable tiltable melt furnace is known from EP 0 240 128 B1, the melt furnace being tiltable and a casting mold which enters the melt and takes up the melt being submersible in the melt, or the tilting angle of the melt furnace being adjustable, for the purpose of keeping the degree of submersion, and consequently the degree of filling, of the casting mold constant, in dependence on the height of the melt bath level. 
     It is known from DE 35 32 763 A1 to pour off melt from a tiltable pouring ladle into a casting mold brought into position directly in relation to the pouring ladle, the melt bath level in the casting mold being observed and the tilting angle of the pouring ladle being controlled in dependence on it. A casting machine of a similar configuration is known from DE 12 35 520 A1. 
     The invention addresses the problem of further developing a method of the type described at the beginning to the extent that the pouring off can be carried out in a fully automated manner, a casting stream that changes as the tilting of the metallurgical vessel progresses being transferred optimally into the receiving vessel. 
     This problem is solved according to the invention by the combination of the following features:
         establishing the tilting position of the metallurgical vessel in which the melt to be poured off leaves the metallurgical vessel in the form of a casting stream,   determining the position of the casting stream produced by the established tilting position of the metallurgical vessel,   bringing the receiving vessel into position for receiving the casting stream produced by the metallurgical vessel in accordance with the established tilting position and, after the pouring off has begun,   adjusting the receiving vessel in accordance with the casting stream as it changes in dependence on the tilting angle of the metallurgical vessel, which changes as the pouring off progresses.       

     The height of the bath level in the metallurgical vessel can be determined directly or indirectly; directly by means of a bath level measuring device and indirectly by the height of the bath level in the metallurgical vessel being established before establishing the tilting position, by calculation on the basis of the internal volume of the metallurgical vessel and the weight of the melt or the melts, in the latter case the internal volume of the metallurgical vessel preferably being measured by means of a laser scanner before the filling of the metallurgical vessel. 
     If the measuring of the bath level in the metallurgical vessel is performed by means of a bath level measuring device, the angle between a measuring beam of the measuring device and the bath level and the distance of the bath level from the measuring device are measured. 
     A method for tapping steel from a steelworks converter is characterized in that, for pouring off steel melt from a steelworks converter, the bath level of the slag melt is ascertained, the tilting position of the metallurgical vessel for pouring off the steel melt being determined with allowance for the bath level of the slag melt in such a way that the bath level of the slag melt for the tilting position of the steelworks converter is at a safe distance from the converter mouth of the steelworks converter when the steel melt is tapped. 
     The metallurgical vessel is preferably tilted continuously during the pouring off of melt. 
     If the tilting of the metallurgical vessel is performed very slowly, the metallurgical vessel can also be tilted step by step to avoid overheating of the drive motors. 
     The individual steps to be carried out when pouring off are expediently carried out in an automated manner with the aid of a computer control, as is the righting of the metallurgical vessel after pouring. 
     For the adding of an additive into the receiving vessel, an adding chute is provided, and is adjusted in accordance with the casting stream as it changes in dependence on the tilting angle of the metallurgical vessel, which changes as the pouring off progresses, and/or in accordance with the adjusted receiving vessel. 
     An installation for carrying out the method according to the invention is characterized by the combination of the following features:
         a metallurgical vessel, equipped with a position measuring device for measuring the tilting angle and an associated control for tilting the metallurgical vessel,   a receiving vessel, which can be made to travel in the direction of the tilting plane of the metallurgical vessel, with a position measuring device and an associated control for the traveling of the receiving vessel,   a measuring device for directly or indirectly, preferably continuously, recording the bath level of the melt in the metallurgical vessel, and optionally by a   device for detecting the end of tapping, the beginning of slag tapping and residual steel.       

     For the adding of an additive, an adding chute is provided, and is equipped with a position measuring device for measuring the position and an associated control for positioning the adding chute in dependence on the position of the casting stream and/or the position of the receiving vessel. 
     If the recording of the bath level is performed indirectly, a weighing device for the receiving vessel is provided. 
    
    
     
       The invention is explained in more detail below on the basis of an exemplary embodiment, which is represented in the drawing.  FIGS. 1 to 4  show in a schematic representation different tilting positions of a steelworks converter during the pouring off of steel melt and the subsequent pouring off of slag melt. 
     
    
    
     A steelworks converter  1  is fixed in a customary way in a baling ring  2 , which baling ring  2  can be tilted by way of two lifting lugs  4 , lying diametrically opposite each other and defining a pivot axis  3 , in bearings arranged on the foundation, to be precise by means of an electric drive that is not represented any more specifically. 
     Underneath the steelworks converter  1 , a ladle carriage  5  for receiving steel melt  6  in a ladle  7  and furthermore a slag carriage  8  for receiving slag melt  9  in a slag pot  10  can be made to travel in the plane of symmetry/tilting of the steelworks converter  1 , to be precise likewise in each case by means of an electric drive. 
     Provided to the side of the steelworks converter  1 , to be precise likewise in the plane of symmetry/tilting, is a melt bath level measuring device  11  provided with a cooling system. This measuring device  11  is aimed at the interior of the steelworks converter  1 , and the height  12  of the melt bath level can be determined as soon as the converter mouth  13  of the steelworks converter  1  is directed toward the measuring device  11  during the tilting of the steelworks converter  1 , to be precise by measuring the angle  14  between a measuring beam  15  of the measuring device  11  and the bath level  16  and measuring the distance of the bath level  16  from the measuring device  11 . The measuring device  11  may, for example, operate by means of a laser beam or else by means of radar. 
     The tilting position of the steelworks converter  1  can be established by means of a position measuring device that is usually present in steelworks. In the same way, the positions of the receiving vessels that can be made to travel underneath the steelworks converter, that is to say the ladle  7  and the slag pot  10 , can also be established by means of customary position measuring devices that are not represented any more specifically. Both the tilt drive of the steelworks converter  1  and the travel drive of the ladle carriage  5  and of the slag carriage  8  are equipped with controls for exact positioning. 
     Instead of the measuring device  11 , the actual bath level  16  in dependence on the tilting angle of the steelworks converter  1  at any one time can also be calculated on the basis of the actual geometry of the converter at the time (meaning here the state of the lining) and the size of the charge. For this, the actual amount of poured-off steel melt  6  at any one time is continuously recorded during the tapping by means of weighing devices for weighing the total weight of the receiving vessels  7 . On the basis of the calculated converter content and the given geometry of the converter, the actual bath level  16  at any one time can consequently be calculated. 
     The automatic pouring-off operation proceeds as follows: it is started by the operator. The steelworks converter  1  is automatically tilted in the direction for pouring off steel melt  6 , the actual bath level  16  at any one time being continuously recorded, to be precise by one of the two methods described above, either from the distance of the bath level  16  from the measuring device  11  and the angle  14  that the bath level  16  forms with the measuring beam  15  of the measuring device  11 , or by volume and weight measurements. 
     A maximum possible bath level  16  is dictated by the lowest edge  13 ′ of the converter mouth  13 . A table with the data for the maximum bath level  16  in dependence on the tilting angle of the steelworks converter  1  is stored in the control system and can be adapted installation-specifically in the course of commissioning. In order to avoid melt being tipped out via the converter mouth  13 , the maximum possible bath level is reduced by an adjustable value and it is stipulated for the pouring-off control system as a setpoint bath level value. That is to say, in other words, a safe distance of the bath level  16  from the lowest edge  13 ′ of the converter mouth  13  is maintained. 
     The actual data obtained at a given time are used to calculate the tilting position of the steelworks converter  1  in which steel melt  6  to be poured off leaves the tap hole  17  in the form of a casting stream  18 . This provides a specific position of the casting stream  18 , which is produced by the established tilting position and this position instigates the bringing into position of the receiving vessel  7  for receiving the steel melt  6  to be precise under computer control. The steelworks converter  1  is then tilted into the position for beginning tapping (cf.  FIG. 1 ); in the case of the exemplary embodiment represented, the tilting angle is 51°. 
     For continuous pouring off of the steel melt  6 , the steelworks converter  1  is then tilted further under computer control and the receiving vessel, i.e. the ladle  7 , is adjusted under computer control in accordance with the changing casting stream  18 , the position of the casting stream  18  being calculated in accordance with the tilting angle of the steelworks converter  1 , likewise under computer control, to be precise until the pouring off of the steel melt  6  is ended. This is illustrated in  FIG. 2  for the case of the exemplary embodiment represented; the tilting angle of the steelworks converter is 96.7°. 
     At the end of the pouring off of the steel melt  6 , the tap hole  17  is closed, for example by a closure device with a closure body, which can be brought from a standby position into a closing position, as described in EP 1 054 068 A2. 
     The relationship between the tilting angle of the steelworks converter  1  and the position of the casting stream  18  or the position of the ladle carriage  5  is stored as a fixed parameter in the automation system and is adapted installation-specifically. 
     During the pouring off of the steel melt  6 , additive can be introduced into the ladle  7  by means of an adding chute  19  in dependence on the converter tilting angle of the steelworks converter  1  or in dependence on the position of the ladle carriage  5 . The position of the adding chute  19  is likewise recorded by means of a continuous position measuring system and automatically positioned in accordance with the position of the receiving vessel  7 . The start of adding additives either takes place automatically or is initiated by the operator. 
     This is followed by the pouring off of the slag melt  9  via the converter mouth  13 , to be precise likewise automatically. It is started by the operator, after which the steelworks converter  1  is automatically tilted in the direction of slag tapping. When the position for the beginning of slag tapping is reached (cf.  FIG. 3 , tilting angle −100°), the steelworks converter  1  is tilted further at minimal speed until slag melt  9  flows via the crucible mouth into the slag pot  10 , which has previously been brought into position. During this operation too, the slag carriage  8  is automatically positioned in dependence on the converter tilting angle. The relationship between the tilting angle and the slag carriage  8  is likewise stored as a fixed parameter in the automation system and is likewise adapted installation-specifically. A slag detection system detects the flowing out of the slag melt  9 . 
     From this point in time, the tapping control system takes over the control of the pouring-off operation. The steelworks converter  1  is then tilted further, continuously or step by step, in accordance with the plan stored in the automation system, until residual steel is detected by the slag detection system or the maximum pouring-off tilting angle (cf.  FIG. 4 , tilting angle −150°) is reached. After reaching the maximum tilting angle or when residual steel is detected, the steelworks converter is automatically righted again.