Abstract:
An apparatus and process are provided for supporting a billet inside an induction coil while the billet is being heated by electric induction. Two or more rails of a heat resistant ceramic material provide a curvilinear surface on which the billet can slide into and out of the coil and sit on during the heating process. Rail position adjustment means may be provided for moving the rails to accommodate billets of various sizes.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/538,132 filed Jan. 21, 2004, hereby incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to a billet support system for supporting a billet while it is heated by electric induction.  
       BACKGROUND OF THE INVENTION  
       [0003]     A billet composed of an electrically conductive material can be heated by electric induction. The billet is placed inside a solenoidal coil and ac current supplied to the coil establishes a magnetic field that penetrates the billet. The field induces eddy current in the billet that heats the billet. Generally there are three methods of placing a billet inside the coil. In the first method the coil is seated in a container that is placed within the coil. The container may be an open boat-shaped structure formed from a non-magnetic material such as a stainless steel. In the second method the billet is pushed into the coil by an appropriate mechanical system and seated on billet support members. In the third method the billet is externally supported while a portion (such as the center or an end) of the billet is inductively heated; this method is not applicable to billet support when the billet length is shorter than the coil. In all methods a thermal insulating material generally surrounds the billet within the coil to assist in retention of the induced heat. This thermal insulating material generally takes the form of an open cylinder formed from a suitable refractory. Known billet support systems comprise two or more water-cooled rods disposed longitudinally along the interior wall of the thermal insulating material. The rods are composed of non-magnetic material such as a stainless steel. The billet is pushed into the coil and seated on the rods. The rods are cooled by flowing a cooling medium, such as water, through passages within the rods. Cooling is required since a significant amount of heat induced in the billets can be transferred by conduction to the rods. Further the rods may be electrically conductive and experience some induced heating from the generated magnetic field. Over time the rod material wears away and portions of the internal cooling passages leak water, which can cause electrical short circuits in the induction coil. Further the necessity of making water connections to the rods inhibits repositioning of the rods to better accommodate billets of varying sizes. Therefore there is the need for a billet support system that does not require water or other internal cooling systems and can be easily adjusted to handle multiple sizes of billets.  
       BRIEF SUMMARY OF THE INVENTION  
       [0004]     In one aspect, the present invention is an apparatus for, and method of, supporting a billet within an induction coil. The billet support system comprises two or more rails having a curvilinear surface upon which the billet sits in the coil. In some examples of the invention, the rails are longitudinally disposed within a thermal insulating element. In some examples of the invention, the rails are formed from a heat-resistant ceramic and are individually adjustable about the thermal insulating element to accommodate billets of varying dimensions.  
         [0005]     Other aspects of the invention are set forth in this specification. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]     For the purpose of illustrating the invention, there is shown in the drawings a form that is presently preferred; it being understood, however, that this invention is not limited to the precise arrangements and instrumentalities shown.  
         [0007]      FIG. 1 ( a ) is a side elevational view of one example of the billet support system of the present invention wherein adjusting elements of each support rail are independent from each other.  
         [0008]      FIG. 1 ( b ) is a cross sectional view through line A-A in  FIG. 1 ( a ).  
         [0009]      FIG. 2 ( a ) is a side elevational view of another example of the billet support system of the present invention wherein adjusting elements of each support rail utilize common elements.  
         [0010]      FIG. 2 ( b ) is a cross sectional view through line B-B in  FIG. 2 ( a ).  
         [0011]      FIG. 3  is a side elevational view of another example of the billet support system of the present invention wherein the support rails provide sufficient curvilinear billet seating surfaces for varying sizes of billets without adjustment of the support rails.  
         [0012]      FIG. 4 ( a ) is a side elevational view of another example of the billet support system of the present invention wherein the support system also serves as a thermal insulating structure.  
         [0013]      FIG. 4 ( b ) is a cross sectional view through line C-C in  FIG. 4 ( a ).  
         [0014]      FIG. 5 ( a ) is a side elevational view of another example of the billet support system of the present invention wherein support rails are radially disposed around the opening for a billet.  
         [0015]      FIG. 5 ( b ) is a cross sectional view through line D-D in  FIG. 5 ( a ). 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]     There is shown in  FIG. 1 ( a ) and  FIG. 1 ( b ) one example of the billet support system of the present invention. Thermal insulation  14  is generally cylindrical in shape and is inserted within solenoidal induction coil  12 . In this non-limiting example of the invention three rails  16  are longitudinally disposed along the interior wall of thermal insulation  14 .  
         [0017]     Each rail comprises a heat resistant material, such as a ceramic based on silicon (Si), aluminum (Al), oxygen and nitrogen (generally known as a “sialon” ceramic). See U.S. Pat. No. 4,113,503 for one example of a sialon ceramic. Each rail is generally cylindrical in shape; however the shape of the rail is not limited to cylindrical shapes. In general the rail is shaped to provide a curvilinear seating surface for a billet. A hole is provided at each end of a rail. Each side support member  18  includes an appropriately shaped dowel to fit in the hole. Joining member  20  can be a threaded rod that protrudes at each end through a hole in each of the side support members as shown for one of the three rails in  FIG. 1 ( b ). Fasteners  22  rigidly hold together the rectangular-shaped frame structure formed by rail  16 , two side members  18  and joining member  20 . In this example of the invention billet  90  is pushed into the open cylinder formed by thermal insulation  14  to make contact with and slide along portions of the curvilinear surfaces of the three rails. Generally coil  12  will be much closer to the billet than diagrammatically shown in  FIG. 1 ( a ) and  FIG. 1 ( b ). Side members  18  may be extended so that joining member  20  is disposed external to coil  12 . Alternatively joining member  20  may be replaced by independent fasteners associated with each side member to hold a rail in place.  
         [0018]      FIG. 2 ( a ) and  FIG. 2 ( b ) illustrate another example of the billet support system of the present invention wherein arc-shaped joining member  24  provides a means for adjusting the locations of rails  16   a  about the inner wall of the thermal insulation. In this non-limiting example an arc-shaped opening in member  24  provides the adjusting means. The opening may be appropriately notched or marked for set alternative rail positions to accommodate billets of various sizes. Side members  18  for each rail are joined together as shown in  FIG. 2 ( a ) which, in this example, is similar to the method used in  FIG. 1 ( a ) except for the inclusion of arc-shaped joining members  24 . In alternative examples of the invention each side member, in lieu of the hole through which joining member  20  passes, may have a post passing though the arc-shaped opening in adjacent joining member  24  which is used to fasten the side member to joining member  24 . For example the post may be threaded and fastened about joining member  24  with a bolt. In this particular example of the invention the rails are generally hemispherical in cross section and modified with a base curvature to conform to the curvature of the inside wall of the thermal insulation.  
         [0019]      FIG. 3  illustrates another example of the billet support system of the present invention. In this example rails  16   b  are two in number and generally semielliptical in cross section and modified with a base curvature to conform to the curvature of the inside wall of the open cylinder. The broad cross sectional curvilinear billet seating surface afforded by generally semielliptical rails  16   b  provides a billet support means that can accommodate a variety of sizes of billets (e.g. billets  90 ,  90   a  and  90   b  with perimeters shown in  FIG. 3 ) without adjusting the positions of rails  16   b . In this example rails  16   b  may be permanently attached to the thermal insulation, integrally cast with the thermal insulation or imbedded in the thermal insulation. In other examples of the invention rails  16   b  may be provided with position adjusting members as illustrated in  FIG. 1 ( a ) or  FIG. 2 ( a ).  
         [0020]      FIG. 4 ( a ) and  FIG. 4 ( b ) illustrate another example of the billet support system of the present invention wherein the function of billet support is provided by a generally cylindrically-shaped element  26  into which a billet is insert at entrance end  26   a . In this example the entrance end is beveled or otherwise shaped to prevent jamming the billet against the end of element  26  as it is pushed into the element. Further the interior bottom wall of element  26  may deviate from true cylindrical to provide a better seating surface for the billet as shown in  FIG. 4 ( a ). In this example of the invention element  26  can serve both as the means for seating the billet inside the coil and as thermal insulating means.  
         [0021]      FIG. 5 ( a ) and  FIG. 5 ( b ) illustrate another example of the billet support system of the present invention wherein a plurality of rails  16   c  are radially disposed around the opening in which a billet is placed. In this arrangement of the invention rails  16   c  may be fastened about thermal insulation  14  as described above or partially embedded into the thermal insulation as shown in the figures. The exposed curvilinear surfaces of the lower rails provide a surface for seating a billet in and sliding a billet through the coil. The exposed curvilinear surfaces of the other rails provide a means for preventing a billet from jamming into the interior wall of the insulation as it is pushed through the coil. For example, as shown in  FIG. 5 ( b ) while billet  90  has substantially vertical end surfaces, billet  91 , which will push billet  90  out of the coil as billet  91  is pushed into the coil has a leading end surface that is skewed from the vertical. In such situations the leading end of billet  90  will have a tendency to jam against the upper interior wall of the thermal insulation. The exposed curvilinear surfaces of rails  16   c  embedded in the upper wall will provide a low friction surface upon which billet  90  will continue to slide out of the coil rather than jam in the coil.  
         [0022]     In the above examples of the invention cylindrically-shaped thermal insulation  14  may be replaced by any other structure suitable for mounting of the rails, or mounting structure, when rail mounting is required within the induction coil. That is the rail mounting structure may be separate from the thermal insulation if used. Generally the thermal insulation comprises a substantially non-magnetic material.  
         [0023]     The foregoing examples do not limit the scope of the disclosed invention. The scope of the disclosed invention is further set forth in the appended claims.