Abstract:
An apparatus and associated method for manipulating an electrode comprising a stub, an electrode, and a yoke. The stub is affixed to and protrudes from the electrode, and has a first opening. The yoke is sized to receive at least a portion of the stub, and has a second opening positioned for alignment with the first opening of the stub and receipt of a locking member extending through the first opening and the second opening. The apparatus may include a current conducting tube. The elongated yoke may extend around at least a portion of the stub to be removably pinned thereto. The current conducting tube may extend around the elongated yoke to be in electrical contact with the stub.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of application Ser. No. 09/330,950, filed Jun. 11, 1999 now U.S. Pat. No. 6,273,179. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is directed, generally, to continuous metal casting, and more particularly to a method and apparatus for electrode or metal ingot casting. 
     2. Description of the Invention Background 
     Over the years, a variety of methods and improvements have been developed for casting metal electrodes and ingots. An electrode essentially comprises a solid cast metal block that is formed to be remelted and cast into an ingot, or into a certain geometric form. To accomplish the remelting of the electrode, an appropriate amount of electrical current is applied to the electrode utilizing known techniques and process controls. Thus, an electrode is essentially an intermediate product used in metal casting processes and an ingot is a finished product that is usually subsequently subject to mechanical deformation, such as forging or rolling. 
     Metal electrodes may be formed utilizing a variety of casting processes. For example, electrodes may be continuously casted in a vertically oriented process wherein the electrode is cast into a stationary mold from plasma arc, electron beam, vacuum induction, skull induction, skull or ac furnaces. 
     FIGS. 1-4 illustrate the conventional dovetail assembly and electrode forming process in vertical continuous casting. Conventional continuous casting of steel and titanium electrode melting in electron beam, plasma arc or skull furnaces typically uses a supporting mechanism, such as a cylindrical block  2 , that is machined to include a dovetail  3 . The cylindrical block  2  is detachably engaged to side wall  4  to form a vertical continuous casting vessel  5 . 
     During vertical continuous casting, molten metal is introduced into, and fills, the vessel  5 . Because the cylindrical block  2  is made from a conductive metal, the cylindrical block  2  conducts heat away from the molten mass, and thereby encourages solidification near the bottom of the vessel  5 . As is common in continuous casting, the cylindrical block  2  is detached from the side wall  4  and is mechanically moved downward to grow the electrode column length. As the cylindrical block  2  moves downward, molten metal is continually added into the vessel  5  to maintain the liquid level of the molten metal at the top of the side wall  4 . Typically, a heat source is used near the top of the vessel  5  to provide additional heat in this area for maintaining the molten mass in the molten state and preventing premature solidification. The dovetail  3  locks the electrode to the cylindrical block  2 , as the block  2  moves downward. Through this process, for example, an electrode of approximately 15,000-25,000 pounds may be produced. The electrode is then laterally removed from the dovetail  3  and released from the cylindrical block for further processing. 
     As the cylindrical block  2  moves downward, however, streaks of molten metal may run down along the surface of the electrode and form icicle-like formations or “rundowns” over the sides of the dovetail  3 . These “rundowns” can act as a latch that prevents removal of the electrode from the cylindrical block  2 . Accordingly, these “rundowns” must be chiseled from the dovetail  3  so that the electrode can be withdrawn from the block  2 . 
     Furthermore, such process generally provides a cast electrode that has a relatively uneven surface that is not well suited for uniform adhesion to other flat surfaces, such as a conducting solid cylinder which is used to introduce current into the electrode during the re-melting process. Thus, during subsequent vacuum arc or electroslag re-melting, introduction of current into or through the cast surface on many occasions causes arcing that results in damage to the re-melting equipment. A massive plunge/stub must be welded to one end of the electrode. The plunge/stub has a smooth surface and is used both to support the electrode weight and to introduce current into it. FIG. 4 illustrates the conventional electrode assembly wherein an electrode  6  is welded to the solid conducting stub  7  for subsequent re-melting of the electrode through the application of a current thereto through the conducting stub  7 . 
     The need to mechanically remove the “rundowns” from the cylindrical block and the additional welding processes add a significant amount of time and cost to the continuous casting process. Accordingly, a continuous casting locking mechanism and electrode assembly is needed that eliminates these additional process steps to increase manufacturing time and efficiency. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention addresses the above-mentioned needs by providing an apparatus for manipulating an electrode and associated method. 
     In one form of the invention, the apparatus comprises a stub, an electrode, and a yoke. The stub is affixed to and protrudes from the electrode, and has a first opening. The yoke is sized to receive at least a portion of the stub, and has a second opening positioned for alignment with the first opening of the stub and receipt of a locking member extending through the first opening and the second opening. 
     In another embodiment, the apparatus of the present invention comprises a stub, an electrode, a yoke, and a current conducting tube. The stub protrudes from the electrode and is affixed thereto. The elongated yoke extends around at least a portion of the stub and is removably pinned thereto. The current conducting tube extends around the elongated yoke and is in electrical contact with the stub. 
     The present invention also provides a method for manipulating and applying an electrical current to an electrode. A stub having a first opening is affixed to the electrode. A yoke is removably attached to the stub such that a second opening of the yoke and the first opening of the stub may receive a locking member when the first opening and the second opening are aligned. An electricity conducting path is established between the stub and a source of electricity. 
     The present invention also provides a method for manipulating an electrode. A stub is affixed to the electrode. An elongated yoke is extended around at least a portion of the stub, and removably pinned thereto. A current conducting tube is extended around the elongated yoke such that the current conducting tube is in electrical contact with the stub. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     The characteristics and advantages of the present invention may be better understood by reference to the accompanying drawings, wherein like reference numerals designate like elements and in which: 
     FIG. 1 is a top view of a prior art electrode support mechanism and dovetail; 
     FIG. 2 is a cross-sectional view of the prior art support mechanism and dovetail of FIG. 1 taken along line II—II in FIG. 1; 
     FIG. 3 is a cross-sectional view of the of an electrode formed in a convention mold incorporating the support mechanism and dovetail of FIG. 1; 
     FIG. 4 is a cross-sectional view of prior art electrode assembly; 
     FIG. 5 is an exploded cross-sectional view of one embodiment of the present invention illustrating the locking assembly of the present invention; 
     FIG. 6 is a cross-sectional view of the locking assembly of the present invention; 
     FIG. 6A is another cross-sectional view of the locking assembly and mold showing molten material being introduced into the mold to form an electrode; 
     FIG. 7 is an exploded cross-sectional view of one embodiment of the electrode assembly of the present invention; 
     FIG. 8 is an exploded cross-sectional view of the assembly of FIG. 7 rotated 90 degrees; 
     FIG. 9 is a top plan view illustrating the shoes of the present invention; 
     FIG. 10 is a cross-sectional view of the electrode assembly of FIG. 7 ready for attachment to a furnace ram; and 
     FIG. 11 is a cross-sectional view illustrating the electrode assembly of FIG. 10 attached to a furnace ram. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     It is to be understood that the Figures and descriptions of the present invention have been simplified to illustrate elements that are relevant for a clear understanding of the present invention, while eliminating, for purposes of clarity, other elements. Those of ordinary skill in the art will recognize that other elements may be desirable in order to implement the present invention. However, because such elements are well known in the art, and because they do not facilitate a better understanding of the present invention, a discussion of such elements is not provided herein. 
     In the present Detailed Description of The Invention, the invention will be illustrated in the form of a metal electrode or ingot assembly having a particular configuration. To the extent that this configuration gives size and structural shape to the electrode assembly, it should be understood that the invention is not limited to embodiment in such form and may have application in whatever size, shape, and configuration of electrode assembly desired. Thus, while the present invention is capable of embodiment in many different forms, this detailed description and the accompanying drawings disclose only specific forms as examples of the invention. Those having ordinary skill in the relevant art will be able to adapt the invention to application in other forms not specifically presented herein based upon the present description. 
     Also, the present invention and devices to which it may be attached may be described herein in a normal operating position, and terms such as upper, lower, front, back, horizontal, proximal, distal, etc., may be used with reference to the normal operating position of the referenced device or element. It will be understood, however, that the apparatus of the invention may be manufactured, stored, transported, used, and sold in orientations other than those described. 
     The terms “ingot” and “electrode,” as used herein, describe essentially the same solid cast metal block. However, United States import classification characterizes an “electrode” of metal as an intermediate product, which will be further re-melted and cast into an “ingot,” or into a part of certain geometry. The term “ingot” typically refers to finished products that are subject to mechanical deformation such as forging or rolling. For clarity, however, the term “electrode” will be used throughout the present detailed description to describe either the unfinished or finished solid cast metal block of the present invention. 
     The present invention is generally directed to application in vertical continuous electrode casting into a stationary mold from plasma arc, electron beam, vacuum induction, skull induction, skull or arc furnace, and the like, and to static electrode casting into a stationary mold with a stationary electrode. The electrode of the present invention may be used in an electrode assembly for engagement with a furnace ram for further re-melting. One skilled in the art will appreciate, however, that the present invention may be incorporated into other continuous metal casting processes not particularly identified herein. 
     Turning now to the drawings, FIGS. 5 and 6 are cross-sectional views of one form of the electrode locking assembly  8  of the present invention comprising a sacrificial stub  12 , a mold  14 , and a locking member  16  for forming an electrode  10  (FIG.  7 ). 
     The stub  12  may be a solid metallic block formed by any means known in the art such as, for example, by casting of machining. The stub  12  may be any shape, such as, for example, a cylindrical block having a circular cross-section taken along the x-axis and a rectangular cross-section taken along the y-axis, as illustrated. The stub  12  may have a slight offset  13  that separates a top portion  15  from an inset portion  17 . The material that forms the stub  12  should be compatible with the metal that forms the electrode  10 . For example, for an electrode fabricated from a titanium alloy, the stub  12  may comprise the same titanium alloy. The stub  12  includes a first transverse opening  18  passing through the inset portion  17 . The first opening  18  may be machine-drilled or cast. When the stub  12  is a cylindrical block, the first opening  18  may be a radial opening passing through the stub&#39;s center. 
     The mold  14  may be an open ended vertical continuous casting vessel for forming the electrode  10 . The mold  14  includes a bottom block portion  20  and side walls  22 . The bottom block  20  is a support member for the forming electrode  10  and may be formed of any heat conductive material that conducts heat away from the molten metal, while also preventing the fusion of molten metal thereto. Some metals that may comprise the bottom block  20  are, for example, copper, gold, or silver. The bottom block  20  may be any shaped block such as, for example, a cylindrical block and cooperates with the side walls  22  to initially form a mold cavity  21  within the mold  14 . The bottom block  20  includes a recessed portion  24  having a counterbored portion  25 . The recessed portion  24  and the counterbore  25  are typically centrally positioned from the outer edge of the bottom block  20 . The recessed portion  24  may be any shape or configuration that mates with the shape or configuration of the stub  12 , such as, for example, a cylindrical recess, and may be sized slightly larger than the inset portion  17  of the stub  12  so that the inset portion  17  can be received therein. The bottom block  20  includes a second opening  26  passing through the recessed portion  24 . The second opening  26  may be any shape or configuration, and may be, for example, a radial cylindrical opening passing through the diameter of the bottom block  24  when the bottom block  20  is a cylindrical block. The second opening  26  is configured such that when the stub  12  is received into the recessed portion  24  of the support mold  14 , the second opening  26  may be positioned in alignment with the first opening  18  of the stub  12 . 
     The locking member  16  may be a solid metal member having a length approximately, but not necessarily, equal to the width of the bottom block  20  of the mold  14 . The locking member  16  may be a rod, plate, pin, bar, screw, bolt, clasp, clip, or other fastener that is sized to be received into the first opening  18  of the stub  12  and the second opening  26  of the mold  14  to lock the stub  12  to the mold  14 . The locking member  16  may be any metal or metal alloy suitable for use with the stub  12 , such as, for example, titanium, mild carbon steel, or hardened carbon steel. 
     It is contemplated that the components that form the electrode locking assembly  8  may have dissimilar shapes. For example, it is contemplated that the bottom block  20  may have a recessed portion  24  having a rectangular cross-section and the stub  12  may be a cylinder having a circular cross-section. Likewise, the first and second openings  18 ,  26 , respectively, may have a rectangular cross-section and the locking member  16  may be cylindrical rod having a circular cross-section. If the components have dissimilar shapes, an adapter or the like (not shown) may be used between components to limit their movement and provide a secure fit therebetween. 
     It is also contemplated that the stub  12  and the bottom block  20  of the mold  14  may have more than one opening passing therethrough to provide additional locking strength therebetween. If additional openings are present, each opening in the stub  12  will typically have a corresponding opening to, and be in alignment with, an opening in the bottom block  20  for receipt of a corresponding locking member  16 . 
     To form the electrode  10  of the present invention, the stub  12  is lowered into the recessed portion  24  of the mold  14  and positioned such that the first opening  18  in the stub  12  corresponds to, and is in relative alignment with, the second opening  26  in the bottom block  20 . The stub  12  is secured to the mold  14  by inserting the locking member  16  through the second opening  26  and the first opening  18 , thereby locking the stub  12  to the mold  14 . See FIG.  6 . Molten metal  19  is then introduced from a source  11  into the mold  14  and around the stub  12 . See FIG.  6 A. The heat from the molten metal  19  liquefies at least a part  15 ′ of the top portion  15  of the stub  12  so that the metal that forms the top of the stub  12  mixes and integrates with the incoming molten metal  19 . Alternatively, at least a part of the top portion  15  may be melted with a suitable heat source such as an electron beam gun, plasma torch or electric arc, prior to the molten metal  19  being introduced and mixed with the stub  12 . The bottom block  20  of the mold  14  conducts heat away from the molten mass, and thereby encourages solidification. Accordingly, solidification of the molten mass begins from the bottom of the mold  14  while more molten metal  19  is introduced into the mold  14  over the solidifying mass to build the electrode  10 . As is common in electrode formation, following cooling and solidification of the molten metal  19  at the bottom block  20  of the mold  14 , the detachable bottom block  20  slowly moves downward (represented by arrow “A” in FIG. 6A) while molten metal  19  is continually added at the top of the mold  14  to maintain the liquid level of the molten metal  19  at the top of the side walls  22 . The skilled artisan will appreciate that the bottom block  20  may be moved downward by hydraulic or mechanical means. Typically, a plasma torch  23  or other suitable heat source is used near the top of the mold  14  and provides addition heat in this area to maintain the molten mass in the molten state to prevent premature solidification. As the bottom block  20  moves downward, the locking member  16  prevents the stub  12  from disengaging from the recessed portion  24 . Accordingly, the stub  12  “pulls” the forming electrode  10  downward. Through this process, the electrode  10  is grown to the desired size, typically between 15,000-25,000 pounds. Following formation of the electrode  10 , the locking member  16  is removed from the first opening  18  and the second opening  26 , allowing removal of the electrode  10  having the integrated stub  12  from the mold  14 . Such removal of the locking member or members  16  may be accomplished by a secondary locking member and hammer (not shown). The electrode  10  may then be inverted onto a suitable turntable or other suitable support structure for incorporation into the electrode assembly  30 , described below. 
     FIGS. 7-9 illustrate the electrode  10  and integrated stub  12  of the present invention incorporated into the electrode assembly  30  which may be used to facilitate the manipulation of the electrode  10  for further processing applications. The electrode assembly  30  may include the electrode  10  and integrated stub  12 , a yoke  32 , a fastening member  38 , a shoe  40 , a current conducting tube  42 , and a ejector member  46 . 
     The yoke  32  may be a solid metal shaft having a top portion  32 ′ and a bottom portion  32 ″. The yoke  32  may be formed of any metal capable of withstanding the high melting temperatures associated with continuous casting, such as mild carbon steel, hardened carbon steel, or a more heat resistant material such as a nickel based superalloy, such as, for example, Allvac Alloy 718, manufactured by Teledyne Allvac, Monroe, N.C. The yoke  32  may comprise a one piece machined plate, or a two-piece component joined by any known means in the art, such as, for example, by welding. The top portion  32 ′ may include an orifice  33 ′ for receiving a securing member, such as, for example, a detachable pin member  33  for attachment to a ram of a conventional furnace as described below. The pin  33  may be formed of any metal sufficient to support the weight of the electrode  10 , such as, for example, hardened carbon. steel. The bottom portion  32 ″ includes a C-shaped bracket  34  sized to receive the top and side portions of the stub  12  while exposing the stub ends  37 . The bracket  34  may have leg members  35 , as illustrated. In this form, the bracket  34  and leg members  35  are sized to receive the stub  12  with a small gap therebetween. Bracket openings  36  pass through the leg members  35  and, in the final assembly, correspond to, and are in alignment with, the first opening  18  for attachment to the stub  12 . 
     The fastening member  38  may be a solid metal member having a length approximately, but not necessarily, equal to the width of the bracket  34 . The fastening member  38  may be a rod, plate, pin, bar, screw, bolt, clasp, clip, or other fastener that is sized to be received into the openings  36  in the leg members  35  and the first opening  18  to secure the yoke  32  to the stub  12 . The fastening member  38  may be made of any heat resistant material known in the art that withstands the relatively high temperatures associated with continuous casting, such as, for example, mild carbon steel, hardened carbon steel, or a more heat resistant material such as a nickel based superalloy, such as, for example, Allvac Alloy 718. 
     The shoe  40  is an electrical conductor that is placed around the ends  37  of the stub  12  exposed by the bracket  34  and forms an electrical contact between the stub  12  and the conducting tube  42 . The. shoe  40  may be any conductive metal such as, for example copper. The shoe  40  may be any shape or configuration that fits over the ends  37  of the stub  12 , such as, for example, a two-piece cylinder that has a recess therein for receiving the stub ends  37 . When positioned over the stub ends  37 , the shoe  40 , generally, should not contact the leg members  35  of the yoke  32 . In the final assembly, the shoe is held in place over the stub  12  by the current conductive tube  42 . See FIGS. 10 and 11. It is contemplated that any number of shoes  40  may be used. 
     The current conducting tube  42  is a hollow conductive member having a top and bottom portion. The bottom portion includes an inner beveled recess  43  sized to receive the shoes  40  and for making electrical contact therewith. The inner recess  43  may be any shape or configuration, such as, for example, cylindrical, that provides good contact with the shoe  40 . When the conducting tube  42  is positioned over the yoke  32 , the inner recess  43  receives and makes contact with the shoe  40  as the yoke  32  centrally extends through the hollow portion of the conducting tube  42 . The top portion of the conducting tube  42  includes a beveled outer recess  44  that makes contact with the furnace ram, described below. The conducting tube  42  may be formed of any conductive material known in the art that can withstand the compressive forces of the furnace ram and the expansive forces of the shoe  40  such as, for example, mild carbon steel, hardened carbon steel, or titanium. 
     The ejector member  46  may be any spacing member known in the art for forcing the electrode assembly  30  from the furnace ram after the electrode is re-melted, described below. The ejector member  46  may be, for example, a C-shaped ring extending around the yoke  32  and positioned between the top of the conducting tube  42  and the pin  33  (FIGS.  10  and  11 ). The ejector member  46  may be formed of any material capable of withstanding the force needed to separate the electrode assembly  30  from the furnace ram, such as, for example, mild carbon steel, hardened carbon steel, and titanium. 
     It is contemplated that all of the components of the electrode assembly  30  need not have the same shape or configuration to provide good electrical contact or to securely fasten the assembly. For example, it is contemplated that the bracket  34  may have a rectangular cross-section and the stub  12  may be a cylinder having a circular cross-section. Likewise, the inner recess  43  may have a rectangular cross-section and the shoe  40  may be a cylinder having a circular cross-section. If the components have dissimilar shapes or configurations, an adapter or the like (not shown) may be used between components to limit their movement and provide a secure fit therebetween. 
     It is also contemplated that the stub  12  and the leg members  35  may have more than one opening passing therethrough to facilitate the use of additional locking members for additional locking strength. If additional openings are present, each opening in the stub  12  will typically have a corresponding opening to, and be in alignment with, an opening in the leg members  35  for receipt of fastening member  38 . 
     FIGS. 10 and 11, illustrate the electrode assembly  30  attached to a ram  48  of a conventional vacuum arc re-melt (VAR) furnace. The yoke  32  is lowered onto the stub  12  and the fastening member  38  is inserted through opening  36  in the leg members  35  and the first opening  18  of the stub  12 . The shoe  40  is placed around the stub  12  and the current conducting tube  42  is lowered onto the yoke  32  exposing pin  33  out of the top of the conducting tube  42 . The ejector member  46  is placed between the top of the conducting tube  42  and the pin  33 . As is well known in the art, legs  52  of the furnace ram  48  are pulled over the pin  33 , while tubular member  54  is moved upward by a hydraulic cylinder (not shown) to pull the electrode assembly  30  into the furnace ram  48 , preventing further upward movement of the electrode assembly. In operation, when a crane grasps the top of the yoke  32 , the electrode assembly  30  self-centers under the weight of the electrode  10 . The assembly  30  is then placed into a vacuum arc remelting furnace, electroslag remelting furnace, or other type furnace whereby current passes through the electrode  10  for re-melting. The majority of the current travels from the furnace ram  48 , into the beveled outer recess  44  of the conducting tube  42 , down the conducting tube  42 , into the shoe  40 , into the stub  12 , and into the electrode  10 . After the re-melting operation is complete, the electrode assembly  30  is detached from the furnace ram  48 . The ejector member  46  forces the release of the conducting tube  42  from the furnace ram  48  before the shoe  40  releases from the conducting tube  42  to eject the electrode assembly  30  from the furnace ram  48  upon completion of the re-melting process. The electrode assembly  30  may then be disassembled in reverse order. 
     Those of ordinary skill in the art will readily appreciate that re-melting the electrode  10  at high electrical currents may cause overheating of the electrode assembly components. The actual sustainable current limits depends on a number of factors, including the nature of the metal being re-melted, the electrode weight, the cooling effect on the mold, and the gas or vacuum environment and on the overall heat transfer balance in the system. The material selection for each component affects the load carrying capability at elevated temperatures as well as the interaction with electromagnetic fields. 
     The present invention provides an efficient and cost effective electrode assembly for vertical continuous casting processes. The locking assembly  8  allows for easy release of the sacrificial stub  12  from the mold  14 . During conventional continuous electrode casting into a stationary mold, the streaks of molten metal run down along the surface of the electrode and form “icicles” or “rundowns” that act to latch the formed electrode to the dovetail. These “rundowns” must be mechanically removed or broken in order to release the electrode from the dovetail. The sacrificial stub  12  of the present invention does not have any surfaces at an angle to the casting axis. Accordingly, any “rundowns” need not be removed in order to release the electrode  10  from the mold  14 . As a result, the present invention eliminates the need for mechanically removing (chiseling) the solidified streaks of metal on the sides of the electrode, and effectively replaces the traditional dovetail mechanism. 
     Moreover, the stub  12  may include a smooth machined surface that provides good electrical contact for conducting high re-melting current. Because the stub  12  has a smooth outer surface, the stub  12 , in combination with the electrode assembly  30  herein disclosed, can be used to introduce current into the electrode. The opening  18  in the stub  12  allows a load needed for maintaining the tight contact of the current conducting surfaces to be applied. The opening  18  also allows easy gripping and positioning of the electrode  10  in a re-melting furnace. If properly machined from the electrode  10  after re-melting, the stub  12  can be reused. 
     The present invention provides excellent co-axiality between the stub  12  and the electrode  10 , particularly when compared to the co-axiality achieved by conventionally welding a stub to a pre-cast electrode. The interface area between the stub  12  and the electrode  10  of the present invention is of the same quality as the electrode  10 , whereas conventional welding (either through metal inert gas (MIG) welding to the cold electrode in air or in a dedicated chamber) produces a weld area that may absorb oxygen or nitrogen from the environment and form potentially deleterious nitride or oxide particles. 
     Although the foregoing description has necessarily presented a limited number of embodiments of the invention, those of ordinary skill in the relevant art will appreciate that various changes in the configurations, details, materials, and arrangement of the elements that have been herein described and illustrated in order to explain the nature of the invention may be made by those skilled in the art, and all such modifications will remain within the principle and scope of the invention as expressed herein in the appended claims. In addition, although the foregoing detailed description has been directed to embodiments of the continuous casting of metal electrodes in the form of vertical continuous casting in a stationary mold, it will be understood that the present invention has broader applicability and may be used in connection with continuous casting of electrodes for use in additional applications. All such additional applications of the invention remain within the principle and scope of the invention as embodied in the appended claims.