Abstract:
A method and system for dispensing an additive wire involves use of a lance for delivering the additive wire and determination of location data with respect to a surface of a metallurgical melt into which the lance is placed.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application No. 61/668,954, filed Jul. 6, 2012, which is incorporated herein by reference it its entirety for all purposes. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a method and system for metal production. 
     BACKGROUND OF THE INVENTION 
     In the production of steel, a ferrous melt is typically produced in a suitable furnace and then tapped into a ladle where it is treated with one or more ingredients for refining or alloying purposes. It is well known to add calcium to the molten ferrous material at this point as a refining agent for oxide inclusion flotation, oxide inclusion morphology modification, desulfurization, etc. Unfortunately, the low density (relative to steel), volatility and reactivity of calcium severely complicate the task of providing a satisfactory process for its addition to the molten material in the ladle. 
     A variety of techniques have been employed for the addition of calcium to the molten material in a steelmaking ladle. Bulk addition of calcium-containing particulate materials is unsatisfactory because these materials rapidly rise to the surface of the melt without spending a sufficient residence time therein. Efforts to increase residence time by pouring the particulate material directly into the tapping stream from the furnace give rise to excessive reaction of the calcium with atmospheric oxygen. Introductions of calcium-containing materials by plunging or the injection of clad projectiles into the melt generally provide adequate residence times but are complicated, expensive and time-consuming procedures. It has also been proposed to inject calcium-containing powders into a melt by inert gas injection through a refractory lance. Since sizable flows of gas are required to propel the powder into the molten ferrous material, a high level of turbulence is generated at the surface of the melt as the gas is released, thereby causing an excessive exposure of the molten ferrous material to oxygen and nitrogen in the atmosphere. Furthermore, after leaving the lance, the calcium tends to rise rapidly through the melt in the inert gas plume surrounding the lance or in upwelling molten material adjacent the plume. Thus, calcium residence time in the bath is unacceptably low. 
     In an attempt to overcome the above-mentioned problems, calcium has also been added to melts in steelmaking ladles in the form of a calcium metal-containing wire (clad or unclad) continuously fed through the upper surface of the melt. A major advantage of wire feeding is that large flows of gas are not needed, as in powder injection, to propel the calcium-containing material into the molten ferrous material. However, the high volatility of calcium hinders the attainment of an efficient utilization of the calcium added in surface wire feeding. 
     U.S. Pat. No. 4,512,800 discloses an apparatus and method for treating molten ferrous material with processing additives in wire form such as calcium containing wires directly into a quantity of molten material using a heat-resistant lance having an outlet disposable beneath the surface of the molten material. In such a lance apparatus, the wire is fed into a passage going through the lance and an inert gas is concurrently injected into the passage together with the wire to prevent clogging of the lance by solidification of molten material while agitating the molten material by gas bubble agitation. 
     There is a continuing need for an effective and efficient method and system for dispensing an additive into molten metal. 
     SUMMARY OF THE INVENTION 
     Briefly and in general terms, the present invention is directed to a method and system for dispensing an additive into a molten metal. 
     In aspects of the present invention, a method comprises positioning an outlet of a lance below a surface of a metallurgical melt, the positioning including determining location data relative to the surface of the metallurgical melt, and dispensing an additive wire out of the outlet while the outlet is below the surface of the metallurgical melt. 
     In aspects of the present invention, a system comprises a wire feeding apparatus, and a lance configured to receive a metallurgical wire from the wire feeding apparatus and to dispense the metallurgical wire from an outlet of the lance, the lance further configured to dispense the metallurgical wire below a surface of a metallurgical melt. The system further comprises a distance measuring device configured to determine location data relative to the surface of a metallurgical melt, and a displacing assembly configured to move the lance in accordance with the location data. 
     Any one or a combination of two or more of the following can be appended to the above aspects to form additional aspects of the invention. 
     The metallurgical melt includes a slag layer and a molten metal below the slag layer, and the positioning includes maintaining the outlet below an interface between the slag layer and the molten metal. 
     The positioning includes maintaining the outlet at a predetermined depth below the interface based on the determined location data relative to the surface of the metallurgical melt. 
     The determining of the location data includes emitting a laser beam toward the surface of the metallurgical melt. 
     The determining of the location data is performed by a distance measuring assembly, and the positioning of the outlet of the lance includes sending a signal from the distance measuring assembly to a displacing assembly configured to move the lance. 
     The positioning of the outlet of the lance includes moving the lance in response to the signal from the distance measuring assembly. 
     The positioning of the outlet of the lance is performed in accordance with information from an encoder configured to track movement of the lance and in accordance with the location data. 
     The positioning of the outlet of a lance includes moving the lance together with a wire straightener. 
     An encoder is configured to track movement of the lance or movement of a position actuator of the displacing assembly. 
     The displacing assembly is configured to move the lance in accordance with information from the encoder and in accordance with the location data. 
     The distance measuring device is configured to emit a laser beam. 
     The displacing assembly includes an electric motor and a motor control, and the motor control is configured to control the motor in accordance with the location data. 
     The displacing assembly includes a hydraulic pump and a hydraulic control, and the hydraulic control is configured to control the hydraulic pump in accordance with the location data. 
     The displacing assembly is configured to move the wire feeding apparatus together with the lance in accordance with the location data. 
     The wire feeding apparatus includes a wire straightener. 
     The displacing assembly is configured to maintain the outlet of the lance at a predetermined depth in the metallurgical melt based on the location data. 
     The displacing assembly is configured to maintain the outlet of the lance at the predetermined depth from an interface between a slag layer and a molten metal of the metallurgical melt. 
     The features and advantages of the invention will be more readily understood from the following detailed description which should be read in conjunction with the accompanying drawings. 
     INCORPORATION BY REFERENCE 
     All publications and patent applications mentioned in the present specification are herein incorporated by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. To the extent there are any inconsistent usages of words and/or phrases between an incorporated publication or patent and the present specification, these words and/or phrases will have a meaning that is consistent with the manner in which they are used in the present specification. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of an embodiment of the shallow metallurgical wire injection and depth control system of the present invention and a cross-sectional side view of a metallurgical vessel showing metal and slag in the vessel; 
         FIG. 2  is a side view of an embodiment of the shallow metallurgical wire injection and depth control system of the present invention and a cross-sectional side view of a metallurgical vessel showing metal and slag in the vessel; and 
         FIG. 3  is a perspective view of front and rear support pieces of a structure for supporting a wire feeding apparatus and a lance. 
     
    
    
     All drawings are schematic illustrations and the structures rendered therein are not intended to be in scale. It should be understood that the invention is not limited to the precise arrangements and instrumentalities shown, but is limited only by the scope of the claims. 
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Referring now in more detail to the exemplary drawings for purposes of illustrating embodiments of the invention, wherein like reference numerals designate corresponding or like elements among the several views, there is shown in  FIG. 1  a system that includes wire feeding apparatus  10  for shallow metallurgical wire injection, and depth control lance  12  for feeding an additive wire into a quantity of molten metal below the surface of the molten metal. Lance  12  comprises inlet  14 , outlet  16 , and passage  18  provided between inlet  14  and outlet  16  for additive wire  20  being fed through lance  12 . 
     Wire feeding apparatus  10  includes laser device  22  (also referred to as a distance measuring device). Laser device  22  can include a laser emitter  23  or laser range finder. Laser device  22  outputs laser beam  24  to scan distance  37  from laser device  22  to top surface  26  of slag layer  27  in metallurgical vessel  30 . 
     Laser device  22  can have a cooling means  32  for cooling a laser emitter and associated equipment of laser device  22 . Any one or a combination of range and position data from laser device  22  is sent to laser scanning unit  34 . Laser scanning unit  34  can be a laptop computer or personal computer tower. Laser scanning unit  34  is configured to calculate the distance and/or position from top surface  26  of slag layer  27  to laser device  22 . Since lance  12  is configured to be displaced along a predetermined path and the position of laser device  22  relative to lance  12  is known via encoder  44 , laser scanning unit  34  can send a signal to motor control  35  (also referred to as a controller) to raise or lower lance  12  to desired penetration depth  36  into steel melt  28 .  FIG. 1  shows encoder  44  in communication with motor control  35 . Thus it will be appreciated that raising and lowering of lance  12  can be performed in accordance with information from encoder  44  and laser device  22 . Using the present invention, lance  12  will penetrate to the same range of predetermined depth  36 , for example 12 to 24 inches (30 to 61 cm), into steel melt  28  during the feeding of metallurgical wire  20 . It will be appreciated that other numerical values and ranges for predetermined depth  36  may be used. 
     In some embodiments, it is desired to maintain tip  46  of lance  12  at a shallow predetermined depth, 12 to 24 inches for example, in the metal or steel melt  28 . In some embodiments, tip  46  of lance  12  is placed in a position which is 12 to 24 inches (30 to 61 cm) below top  29  of steel melt  28 . Top  29  of the steel melt  28  is below slag layer  27 . Top  29  is referred to as interface  29  between slag layer  27  and steel melt  28 . 
     Slag layer  27  may contain lime, silica, or other material. Slag layer  27  may be added to molten metal  28  in metallurgical vessel  30  prior to dispensing of additive wire  20  into molten metal  28 . 
     Wire feeding apparatus  10  can have a means for displacing lance  12  along the front of structural member  40  such as motor driven chain  42  operatively coupled to motor  43 , as shown in  FIG. 1  or a hydraulically driven unit such as a telescoping unit ( FIG. 2 ) which can be driven in the extending and contracting positions. 
     Motor control  35  is configured to control the operation of motor  43  which displaces lance  12  along a predetermined path. Motor  34  is also referred to as a position actuator and can be an electric motor for example. Encoder  44 , which can be an analog device for example, is configured to track the movement of lance  12  in both movement directions  47  relative to laser device  22  and/or relative to vessel  30 . Encoder  44  is configured to sense and keep track of back and forth movements of motor  43  or lance  12 . 
     In some embodiments, wire feeding apparatus  10  includes any one or both of wire straightener  48  and cone  50  to assist in the feeding of metallurgical wire  20  into wire feeding apparatus  10 . 
     In some embodiments, wire feeding apparatus  10  includes proximity switch  52  configured to be activated by sensor  54  when lance  12  is in a particular designated position on wire feeding apparatus  10 . 
     The position of lance  12  can be driven by motor  43  configured to drive chain  42 . 
     In some embodiments, wire feeding apparatus  10  includes block device  56  to prevent lance  12  from being positioned too far down in metallurgical melt  27 ,  28 . Metallurgical melt refers to molten metal  28  and any slag layer  27 . 
     In  FIG. 1 , laser device  22  is mounted on structural support  40  which supports wire feeding apparatus  10 . Laser device  22  can include moveable cover piece  58  to protect laser optics and any heat-sensitive parts of laser device  22  from heat radiated from metallurgical melt  27 ,  28 . Laser device  22  can determine distance  37  of up to 40 meters from laser device  22  to a target, such as top surface  26  of slag layer  27 . A suitable laser device, such as a laser emitter or laser range finder and laser scanning unit, is available from the Ferrotron Division of Minteq International Inc. of Duisburg, Germany. 
       FIG. 2  shows another embodiment of the invention in which a system includes wire feeding apparatus  10  for shallow metallurgical wire injection, and depth control lance  12  for feeding additive wire  20  into a quantity of molten metal  28  below the surface of the molten metal surface. Lance  12  comprises inlet  14 , outlet  16 , and passage  18  provided between inlet  14  and outlet  16  for additive wire  20  being fed through lance  12 . Laser device  22  (also referred to as a distance measuring device) can be a laser emitter or laser range finder. Laser device  22  can be mounted at a location in the production facility which has a view of slag layer  27  in metallurgical vessel  30 . Laser device  22  emits laser beam  24  to scan the position and/or distance from laser device  22  to top surface  26  of slag layer  27  in metallurgical vessel  30 . The position and/or distance is referred to herein as location data of the laser device  22  relative to top surface  26  of slag layer  27 . The location data from laser device  22  is sent to laser scanning unit  34  configured to calculate distance  37  from laser device  22  to top surface  26  of slag layer  27 . Laser scanning unit  34  can be, for example, a laptop computer or personal computer tower. Because lance  12  is displaced along a predetermined path and the location of laser device  22  is known in the coordinate system of lance  12 , laser scanning unit  34  can send a signal to hydraulic control  35  to raise or lower lance  12  such that lance tip  46  is at desired depth  36  in steel melt  28  based on distance  37  from laser device  22  to slag layer  27 . 
     Encoder  44  can provide the location of laser device  22  within the coordinate system of lance  12 .  FIG. 2  shows encoder  44  in communication with hydraulic control  35 . Thus it will be appreciated that moving lance  12  in directions  47  can be controlled by hydraulic control  35  in accordance with information from encoder  44  and laser device  22 . 
     The depth control system, which comprises laser device  22 , laser scanning unit  34 , hydraulic control  35 , and encoder  44 , can operate as a feedback control loop. During operation as a feedback control loop, the position of lance  12  is adjusted automatically by the depth control system to maintain desired depth  36  while the level of interface  29  fluctuates, such as may occur during a change in the amount of molten metal  28  in vessel  30 . 
     Wire feeding apparatus  10  can have a displacing means for displacing lance  12  along the front of structural member  40 . The displacing means or displacing assembly includes hydraulic control  35  (also referred to as a controller) configured to control operation of pump  43  (also referred to as a position actuator). Pump  43  is configured to extend and contract telescoping hydraulic cylinders  60  which displace lance  12  along a predetermined path. Encoder  44  is configured to track the movement of lance  12  in both directions  47  along the predetermined path. Encoder  44  can be an analog device. 
     In some embodiments, tip  46  of lance  12  is placed in a position which is 12 to 24 inches (30 to 61 cm) from interface  29  between steel melt  28  and slag layer  27 . Wire feeding apparatus  10  can have a wire straightener  48  and/or cone to assist in feeding of metallurgical wire  20  into wire feeding apparatus  10 . 
     In some embodiments, it is desired to maintain tip  46  of lance  12  at shallow predetermined depth  36  in the metal or steel melt  28 , preferably 12 to 24 inches (30 to 61 cm) deep. It will be appreciated that other numerical values and ranges for predetermined depth  36  may be used. 
     Wire feeding apparatus  10  can have proximity switch  52  configured to be activated by a sensor on lance  12  when lance  12  is in a particular designated position. 
     The position of lance  12  can be driven by telescoping hydraulic cylinders  60  configured to drive carriage  62  on wire feeding apparatus  10  in both the up and down movements  47 . 
     In  FIG. 2 , laser device  22  is mounted on structure  70  in a metallurgical production facility. Lance  12  is movable relative to structure  70 . Laser device  22  is configured to determine distance  37  from a target, such as top surface  26  of slag layer  27 , to laser device  22 . Distance  37  can be in the range of 20 to 40 meters. A suitable laser device  22 , such as a laser emitter or laser range finder and laser scanning unit, is available from the Ferrotron Division of Minteq International Inc. of Duisburg, Germany. 
     As shown in  FIGS. 2 and 3 , carriage  62  can have wheels  72  ( FIG. 2 ) which ride in grooves  74  ( FIG. 3 ). Lance fitting  76  can connect lance  12  to wire straightener  48 . Wire feeding apparatus  10  can have an inert gas which is injected into lance  12  to prevent solidification of steel around lance  12  and assist which mixing of the metallurgical additive from metallurgical wire  20  with the steel or melt. Wire straightener  48  can have motor  78  which drives gears in gear box  80 . 
     In  FIGS. 1 and 2 , lance  12  is made of heat resistant material. Lance  12  is configured to resist degradation and corrosion when exposed to molten metal  28 , such as molten steel. In some embodiments, lance  12  includes a ceramic refractory casing made of alumina or any other refractory material such as those used to cover the interior of kilns and the like. 
     In some embodiments, metallurgical wire  20  is a calcium-containing wire. Examples of calcium-containing wire include a tubular sheath of iron or steel having a central core filled with calcium. 
       FIGS. 1 and 2  show a schematic communication line between scanning unit  34  and distance measuring device  22 , a schematic communication line between controller  35  and position actuator  43 , a schematic communication line between controller  35  and encoder  44 , and a schematic communication line between scanning unit  34  and controller  35 . The schematic connection lines represent any form of communication. For example, the communication lines can represent physical wires, or wireless communication, or a combination thereof. 
     In  FIGS. 1 and 2 , wire straightener  48  can include a plurality of rollers between which metallurgical wire  20  is passed and straightened in preparation for delivery through passage  18  of lance  12 . Rollers may be coupled to the gears in gear box  80  ( FIG. 2 ) which are driven by motor  78 . Wire straightener  48  is attached to lance  12 . The means for displacing the lance causes lance  12  and wire straightener  48  to move together. In  FIG. 1 , activation of motor  43  causes chain  42  to raise or lower lance  12  together with wire straightener  48 . In  FIG. 2 , lance  12  and wire straightener  42  are attached to carriage  62  so that activation of pump  43  causes hydraulic cylinders  60  to raise or lower lance  12  together with wire straightener  48 . In other embodiments, lance  12  and wire straightener  48  do not move together. 
     In  FIGS. 1 and 2 , a displacing assembly comprises position actuator  43  (an electric motor or a hydraulic pump, for example) and controller  35  (a motor control or a hydraulic control, for example). A distance measuring assembly comprises distance measuring device  22  (a laser device, for example) and scanning unit  34  (a laser scanning unit, for example). Other types of distance measuring devices are within the scope of the present invention. For example, an acoustic distance measuring device and associated acoustic scanning unit can be used instead of laser device  22  and laser scanning unit  34 . 
     It will be appreciated that the displacing assembly of  FIG. 1  can be used in combination with the distance measuring assembly of  FIG. 2 , and the displacing assembly of  FIG. 2  can be used in combination with the distance measuring assembly of  FIG. 1 . 
     While several particular forms of the invention have been illustrated and described, it will also be apparent that various modifications can be made without departing from the scope of the invention. It is also contemplated that various combinations or subcombinations of the specific features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the invention. All variations of the features of the invention described above are considered to be within the scope of the appended claims. It is not intended that the invention be limited, except as by the appended claims.