Abstract:
A method for hearthless processing of a solid metallic material consisting essentially of titanium or other metal or alloy thereof which includes providing a solid metal block having a processing surface and a base surface and consisting essentially of titanium or a metal, forming a pool of molten metal on the processing surface of the solid metal block provided in step, adding the metallic material to be processed to the pool of molten metal formed in step, and melting the metallic material to be processed, and removing metallic material melted in step from the pool of molten metal.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to specialized metallurgical processes and more particularly to plasma arc cold hearth refining (PACHR) and electron beam cold hearth refining (EBCHR) of titanium or other metals and alloys thereof. 
     2. Background Information 
     The prior art discloses a number of processes for the plasma arc cold hearth refining (PACHR) and electron beam cold hearth refining (EBCHR) of titanium and other metals and alloys thereof. 
     U.S. Pat. No. 5,224,534 to Shimizu, et al., for example, discloses a method of producing a titanium or other metal or titanium or other alloy material by EBCHR which comprises melting the said metallic material and casting a meltable electrode, characterized in that the electrode produced by EBCHR is made by enveloping the said metallic material melted with an enclosure formed from a metallic material having a higher thermal conductivity than said particular metal. The evaporation loss of the alloy element of the said particular metal is compensated by adjusting the input chemistry of the solid particular metal. Titanium sponge or titanium scrap may be produced into a slab with a square cross section and then directly rolling the slab without subjecting the slab to forging before the rolling. 
     U.S. Pat. No. 6,019,812 to Volas, et al. discloses a PACHR process which provides an ingot of improved properties and including a PACHR furnace operated inside a chamber containing an inert gas, such as helium, 1.1 atm pressure levels. Raw material metals for a desired titanium or titanium alloy composition are supplied to a melting hearth located inside the chamber and heated by a plasma torch which utilizes an inert gas. The plasma arc melts the raw material metal thereby forming a molten pool of metal that is directed to at least one refining hearth. Plasma torches located in the refining hearths maintain the metal in a molten state as it passes through the cold hearth to allow impurities present in the metal to be refined therefrom. After passing through the refining hearths, the molten metal is poured into an ingot mold while still under 1.1 atm inert gas pressure. The molten material is then allowed to cool and solidify into a continuously cast ingot. The thus formed ingot is then subjected to hot working and fabrication operations. 
     In conventional plasma arc cold hearth refining (PACHR) and electron beam cold hearth refining (EBCHR) of metals such as titanium alloys and superalloys and other metals and their alloys, a water cooled copper hearth is supplied with raw materials in the forms of loose lumps and pieces or premelted fabricated solid bars. This material is melted and refined by plasma arc or electron beam. A solid skull will form when molten metal contacts with the bottom and side wall surfaces of the water cooled copper hearth. A molten metal pool will then form on top of the solid skull. The refined molten metal is poured from the hearth into a cylindrical or rectangular mold to form a continuously cast cylindrical ingot or rectangular slab. 
     The use of a water cooled copper hearth in a conventional cold hearth furnace (PACHR or EBCHR) has a number of limitations. 
     One such limitation is that the water cooled hearth removes a significant amount of heat from the molten metal. As a result, high power input from plasma (PACHR) or electron beam (EBCHR) is needed to maintain a desired melting rate and molten metal superheat. Consequently, the thermal efficiency of many prior art systems is low. 
     Another disadvantage of the prior art methods is that it is necessary to control the heat transfer rate at the bottom and sidewall surfaces of the solid skull. In practice it is found that it is difficult and expensive to effect such control of the heat transfer rate at the bottom and side wall surfaces of the solid skull. 
     Another disadvantage of the prior art methods is that the water cooled copper hearth, which is used in such methods, is a complex and expensive equipment. 
     Another disadvantage of the prior art methods is that during operation, the water cooled copper hearth experiences very high temperature gradient which results in high level of thermal stresses. Consequently, the hearth may crack and need expensive repair work. In addition, furnace downtime will also significantly reduce the metal throughput rate. 
     A still further disadvantage of the method of the prior art is that the setup and exchange of the water cooled copper hearth is a time-consuming work, which reduces overall productivity of the furnace. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention for titanium or other metals or their alloys to provide a simple and inexpensive means of controlling heat transfer rates in a plasma arc cold hearth refining (PACHR) or electron beam cold hearth refining (EBCHR) and allows for simple and inexpensive means of water cooling associated apparatus. 
     It is another object of the present invention to provide a method of plasma arc cold hearth refining (PACHR) and electron beam cold hearth refining (EBCHR) of titanium and other metals or their alloys which substantially avoid high levels of thermal stress and resulting cracking in associated apparatus. 
     It is still a further object of the present invention to provide a method for plasma arc cold hearth refining (PACHR) and electron beam cold hearth refining (EBCHR) of titanium and other metals and their alloys which can be accomplished with apparatus which is easily inexpensively and quickly set up and assembled to allow practice of the method. 
     The present invention comprises a method of hearthless block melting (HLBM) and an apparatus for accomplishing this method. 
     First a solid metal block having an upper processing surface and a base surface is provided which consists essentially of titanium or other metal or alloy which is to be processed. A plasma arc or electron beam is then used to form a pool of molten metal on the upper processing surface of the metal block. The titanium or other metal or alloy to be processed is then added to the pool of molten metal and is melted. The titanium or other metal or alloy melted in this way is then removed from the pool of molten metal and is poured into an ingot mold to form a cylindrical ingot or rectangular slab. 
     HLBM uses a solid metal block as the molten metal container. The chemical composition of the block is similar to the ingot/slab to be produced. The equipment that is used to replace the water cooled copper hearth includes a water cooled copper base plate, a reusable block sitting on the base plate, and a water cooled copper pour-lip attached to the block. At the start of the operation, the block is first melted by the plasma arc or electron beam to form a molten pool. The raw material is then added at the one end of the block without the pour-lip. The overflow molten metal is poured into the ingot casting mold through the attached pour-lip. The shape of the block is not limited to rectangular. It can be “C” shaped, “T” shaped, “L” shaped, or small ended rectangular or hexagonal shaped. There is no limitation to the number of plasma torches or electron beam guns to be used for the furnace. 
     The heat transfer rate between the bottom of the block and the base plate can be reduced to maintain a deeper and bigger molten pool in the block. The block bottom to base plate heat transfer rate can be reduced by either insulating the block bottom or machining out a certain groove pattern at the block bottom to reduce the contacting area between the block bottom surface and the base plate. The insulating material can be any metallic as well as non-metallic foil, sheet, plate, and block. The total surface area of the machined groove pattern can be adjusted to change the block/base plate interface heat transfer rate. For plasma arc cold hearth refining (PACHR), helium gas jet can be introduced to selectively cool the block side walls and prevent molten metal flow out from block side walls . A metal shield guide can be used to protect the helium gas pipeline from the plasma or electron beam heat or overflow molten metal. The block can be clamped with the base plate to maintain a close contact and consistent heat transfer rate between the block bottom.surface and the base plate. At the start of the operation, a solid block of metal with the similar chemical composition of the molten metal to be produced is put into the pour-lip. During the melting operation, the top portion of the solid block will be melted away to allow the molten metal to flow through. The bottom portion of the block will stay solid to prevent molten metal having a direct contact with the water cooled copper base plate and losing superheat. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The preferred embodiment of the invention, illustrative of the best mode in which applicant contemplated applying the principles, is set forth in the following description and is shown in the drawings and is particularly and distinctly pointed out and set forth in the appended claims. 
     FIG. 1 a  is a schematic vertical cross sectional view of the apparatus used in the practice of a method representing a preferred embodiment of the present invention; 
     FIG. 1 b  is a schematic vertical cross sectional view of the apparatus used in the practice of a method representing an alternate preferred embodiment of the present invention; 
     FIG. 2 a  is a horizontal cross sectional view of the solid block and casting mold used in an alternate preferred embodiment of the present invention; 
     FIG. 2 b  is a horizontal cross sectional view of another solid block and casting mold used in another preferred embodiment of the present invention; 
     FIG. 2 c  is a horizontal cross sectional solid block and casting mold used in another preferred embodiment of the present invention; 
     FIG. 2 d  is a horizontal cross sectional solid block and casting mold used in another preferred embodiment of the present invention; 
     FIG. 3 a  is a vertical cross sectional view of the solid block and base plate used in another preferred embodiment of the method of the present invention; 
     FIG. 3 b  is a horizontal view of the block bottom surface from  3   b - 3   b  in FIG. 3 a;    
     FIG. 3 c  is a horizontal view of the block bottom surface similar to the one shown in FIG. 3 b  showing another preferred embodiment of the present invention; 
     FIG. 3 d  is a horizontal view similar of the block bottom surface to the one shown in FIG. 3 b  showing another preferred embodiment of the method of the present invention; 
     FIG. 3 e  is a vertical cross sectional view of the solid block and base plate used in another preferred embodiment of the present invention; 
     FIG. 4 a  is a schematic side elevational and partial vertical cross sectional view of a solid phase block, base plate and ingot mold used in another preferred embodiment of the method of the present invention; 
     FIG. 4 b  is vertical cross sectional end view of the solid phase block and base plate shown in FIG. 4 a ; 
     FIG. 5 a  is a schematic vertical cross sectional end view of a solid block illustrating a first step in another preferred embodiment of the method of the present invention; 
     FIG. 5 b  is a schematic vertical cross sectional end view similar to FIG. 5 a  a second step in another preferred embodiment of the method of the present invention; and 
     FIG. 5 c  is a schematic horizontal cross sectional view of the block shown in FIG. 5 b  along with the ingot mold. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1 a , there is a rhomboid shaped solid block of titanium  10  which has a base surface  12 , a top processing surface  14 , a pair of lateral surfaces as at surface  16 , a rear surface  18 , and a front surface  20 . On the top processing surface  14 , there is a pool of molten titanium  22  which is produced by melting solid titanium by means of a plasma torch or alternatively an electron beam gun  24 . There is also a second plasma torch or alternatively an electron beam gun  26 . The apparatus also includes an input ramp  28 , by means of which solid phase titanium input material  30  enters the pool of molten titanium  22 . The apparatus also includes an output lip  32  which is water cooled by means of water tubes as at tube  34 . Adjacent the output lip  32  there is a water cooled copper mold  36  which is cooled by means of water tubes as at tube  38 . The second plasma torch or electron beam gun  26  is positioned over the mold  36 . The mold  36  has a mold interior  40  which includes a solid titanium ingot  42  and an ingot molten pool of titanium  44 . Solid phase block  10  rests on an upper base plate  46  which is cooled by means of water tubes as at tube  48 . It will be seen that plasma torch or electron beam gun  24  is positioned over processing surface  14  of the block of titanium  10 . The plasma torch or electron beam gun  26  is positioned over the mold  36 . It will be understood that ordinarily if a plasma torch is used to cover the processing surface  14  of the block of titanium, that a plasma torch will be positioned over the mold  36 . If an electron beam generator is positioned over the processing surface  14 , then an electron beam generator will be positioned over the mold  36 . A suitable plasma torch is commercially available from Retech located at Ukiah, Calif. under model no. RP-75T. A suitable electron beam gun is commercially available from Retech located at Ukiah, Calif. under model no. Bakish E480-30-MOD-100-33. It will also be understood that the pool of molten titanium  22  may be initially formed by melting a portion of the block of titanium on the processing surface  14 . Alternatively, the pool of molten titanium  22  may be initially formed by filing a recess on the processing surface  14  with separately melted titanium. 
     Referring to FIG. 1 b , there is a rhomboid shaped solid block of titanium  310  which has a base surface  312 , a top processing surface  314 , a pair of lateral surfaces as at surface  316 , a rear surface  318 , and a front surface  320 . On the top processing surface  314 , there is a pool of molten titanium  322  which is produced by melting solid titanium by means of a plasma torch or alternatively an electron beam gun  324 . There is also a second plasma torch or alternatively an electron beam gun  326 . The apparatus also includes a titanium bar  328  to be melted by means of which droplets of liquid phase titanium input material  330  resulting from the melting of bar  328  enter the pool of molten titanium  322 . The apparatus also includes an output lip  332  which is water cooled by means of water tubes as at tube  334 . Adjacent the output lip  332  there is a water cooled copper mold  336  which is cooled by means of water tubes as at tube  338 . The second plasma torch or electron beam gun  326  is positioned over the mold  336 . The mold  336  has a mold interior  340  which includes a solid titanium ingot  342  and an ingot molten pool of titanium  344 . Solid block  310  rests on an upper base plate  346  which is cooled by means of water tubes as at tube  348 . It will be seen that plasma torch or electron beam gun  324  is positioned over processing surface  314  of the block of titanium  310 . The plasma torch or electron beam generator  326  is positioned over the mold  336 . 
     Referring to FIG. 2 a , in an alternate embodiment of the invention, the solid block of titanium  50  is what will be referred to as being generally “C” shaped. This block has a first section  52  and a spaced parallel second section  54 . A perpendicular section  56  connects the first section  52  and second section  54 . On the upper surface of the block, there is a molten metal pool  58 . On the first section  52  there is an input material  60  into the molten metal pool  58 . On the second section  54 , there is a pour lip  62  from which molten metal is poured into a casting mold  64  to form an ingot  66 . 
     Referring to FIG. 2 b , in another embodiment there is a solid block of titanium  68 . This block has a rear section  70  and a front section  72  which is perpendicular to the rear section. On the top surface of the block  68 , there is a molten metal pool  74  which at its rear has input material  76  and at its opposed side there is a pour lip  78  from which metal enters an adjacent casting mold  80  to form an ingot  82 . Such a shape of the block in which the front section  72  is medially positioned relative to the end section is referred to herein as “T” shaped. 
     Referring to FIG. 2 c , another embodiment is a hexagonal shaped, solid metal block  84 . This block has front sloped shoulders  86  and  88  and a restricted front side  90 . On its upper surface it has a molten metal pool  92  with input material  94  adjacent its rear side. There is a pour lip  96  which is adjacent a casting mold  98  in which an ingot  100  is formed. 
     Referring to FIG. 2 d , in another embodiment similar to the above described “T” shaped block there is a solid block of titanium  468 . On the top surface of the block  468  there is a molten metal pool  474  which at its rear side  470  has input material  476  and at its opposed side there is a pour lip  478  from which metal enters an adjacent casting mold  480  to form an ingot  482 . Such a shape of the block in which the front section  472  is medially positioned relative to the end section is referred to herein as “L” shaped. 
     Referring to FIGS. 3 a  and  3   b , in another embodiment, there is a solid block of metal  102  which has a base surface  104  and a top processing surface  106 . On the top processing surface  106  there is a pool of molten metal  108 . Beneath the base surface  104  there is a water cooled copper base plate  110  with a plurality of cooling water tubes as at tube  112 . On the base surface  104  of the solid block  102 , there are a plurality of machined grooves as at groove  114  and  116 . Between the grooves as at grooves  114  and  116 , there are a plurality of plate contact projections as at  118  and  120 . It would be appreciated that the heat transfer between block  102  and base plate  110  may be adjusted by means of the number, size and pattern of the machined grooves as at groove  114  and  116 . 
     Referring to FIG. 3 c , an embodiment which is similar to the embodiment shown in FIGS. 3 a  and  3   b  except for the pattern of grooves on the base plate is shown. In this embodiment, there are three traverse grooves  514 ,  516  and  518  and two longitudinal grooves  520  and  521 . This pattern of transverse and longitudinal grooves forms a pattern of solid areas as at areas  523 ,  525  and  527 . 
     Referring to FIG. 3 d , another embodiment which is similar to the embodiment shown in FIGS. 3 a  and  3   b  except for the pattern of the grooves is shown. There are two concentric continuous grooves  614  and  616 . This pattern of concentric grooves form a patter of concentric solid areas  618 ,  620  and  621 . 
     Referring to FIG. 3 e , in another embodiment, there is a solid block of metal  702  which has a base surface  704  and a top processing surface  706 . On the top processing surface  706  there is a pool of molten metal  708 . Beneath the base surface  704  there is an insulating sheet  710  which can be made from various materials such as metal sheet, non-metallic fibers, and ceramic plate. Beneath the insulating sheet  710  there is a water cooled copper base plate  712  with a plurality of cooling water tubes as at the tube  714 . 
     Referring to FIGS. 4 a  and  4   b , in another embodiment, there is a solid block of titanium  122  which has a base surface  124  and top processing surface  126 . This block also has lateral surfaces  128  and  130  and a front side  132  and a rear side  134 . On the top processing surface  126 , there is a molten metal pool  136  with a water cooled output lip  138  which is cooled by means of cooling water tubes as at tube  140 . Adjacent the output lip  138 , there is a water cooled mold  142  which includes cooling water tubes as at tube  144  and which has a mold interior  146  in which there is formed a solid ingot  148  beneath an ingot molten metal pool  150 . The base surface  124  of the solid block  122  has a plurality of machined grooves as at grooves  152  and  154  and the base surface  124  is superimposed on a water cooled copper base plate  156  which has a plurality of water tubes as at tube  158 . Superimposed on the water cooled copper base plate  156  is a block side plate  160  which is fixed to the water cooled copper base plate  156  by means of clamp  162 . For plasma arc cold hearth cold hearth refining (PACHR) adjacent the lateral surfaces  128  and  130  and the rear side  134  of the solid block, there is a helium gas pipeline  164  with holes for helium release on the inner and upper side as at holes  166  and  168 . Such holes produce helium gas jets  170 ,  172 ,  174 , and  176 . Above the helium gas pipeline  164 , there is a shield  178 . 
     Referring to FIG. 5 a , the apparatus used in a preferred embodiment of the method of the present invention is shown before melting. Referring to FIGS. 5 b  and  5   c , this apparatus is shown during melting. This apparatus has a solid titanium block  180  with a top surface  182  and a base surface  184 . The block  180  also has a rear end  186  and front end  188 . Surfaces  190  and  192  and a pour lip  194  which is water cooled by cooling watertubes as at tube  196 . Before melting in the pour lip  194  there is solid phase metal  198  as is shown in FIG. 5 a . FIGS. 5 b  and  5   c  shows the block with a molten metal pool  200 , and molten metal flow  202  through the pour lip  194 . Adjacent the pour lip  194  there is a solid skull  204 . Adjacent pour lip  194  there is a mold  206  with an ingot  208 . 
     The method and apparatus described above may be used for the hearthless melting of superalloys including nickel based, iron based and cobalt based superalloys. The method and apparatus described above may also be used for the hearthless melting of molybdenum, tantalum, hafnium and zirconium as well as alloys of the aforesaid metals. 
     The method of the present invention is further described with reference to the following examples. 
     EXAMPLE 1 
     A Ti-6Al4V titanium alloy block having dimensions of 14″×7″×3″ and a weight of 48 lbs. was heated on its upper surface by means of a 150 kW helium plasma torch to a temperature above the Ti-6Al1-4V melting point for a period of 10 minutes until a molten pool of the capacity of approximately 100 cu. in. was formed. Ti-6Al1-4V sponge compacts having approximate dimensions of 4″×3″×2″ were added to the pool at a rate of 0.75 lbs./min. Molten metal was discharged from a pour lip into an ingot at a rate of 0.75 lbs./min. 
     EXAMPLE 2 
     A Ti-6Al1-4V titanium alloy block having dimensions of 14″×7″×3″ and a weight of 48 lbs. is heated on its upper surface by means of a 150 kW helium plasma torch to a temperature above the Ti-6A1-4V melting point for a period of 10 minutes until a molten pool of the capacity of approximately 100 cu. in. is formed. A Ti-6Al-4V feeder bar is positioned at a distance of 4″ above the molten pool so that one end was directly above the pool. The end directly above the pool is heated with the same 150 kW helium plasma torch to above the Ti-6Al-4V melting point. Droplets of molten metals having an approximate weight of 0.75 lbs./min. are allowed to fall directly into the molten pool so that they remain in the liquid phase during the entire fall period. Molten metal is discharged from a pour lip into an ingot at a rate of 0.75 lbs./min. 
     EXAMPLE 3 
     A Ti-6Al-4V titanium alloy block having dimensions of 14″×9″×4″ and a weight of 82 lbs. and which had 0.05″ wide by {fraction (1/16)}″ deep grooves machined evenly spaced on its bottom surface to reduce the surface area by 50% was heated on its upper surface by means of a 150 kW helium plasma torch to a temperature above the Ti-6Al-4V melting point for a period of 10 minutes until a molten pool of the capacity of approximately 170 cu. in. was formed. Titanium sponge compacts having approximate dimensions of 4″×3″×2″ were added to the pool at a rate of 1.1 lbs./min. Molten metal was discharged form a pour lip into an ingot at a rate of 1.1 lbs./min. 
     EXAMPLE 4 
     A Ti-6Al-4V titanium alloy block having dimensions of 14″×9″×4″ and a weight of 82 lbs. and which has 0.05″ wide by {fraction (1/16)}″ deep grooves machined evenly spaced on its bottom surface to reduce the surface area by 50% is heated on its upper surface by means of a 150 kW helium plasma torch to a temperature above the Ti-6Al-4V melting point for a period of 10 minutes until a molten pool of the capacity of approximately 170 cu. in. is formed. A line is transporting helium gas under a pressure of 55 psi is peripherally positioned around the block and helium gas is discharged onto the block in 30 equally spaced jets at a distance of from 0.1 inches at a rate of 10 cu. ft./min. Titanium sponge compacts having approximate dimensions of 4″×3″×2″ are added to the pool at a rate of 1.1 lbs./min. Molten metal is discharged form a pour lip into an ingot at a rate of 1.1 lbs./min. 
     EXAMPLE 5 
     A IN718 nickel based superalloy block having dimensions of 14″×7″×3″ and a weight of 94 lbs. is heated on its upper surface by means of a 150 kW helium plasma torch to a temperature above the IN718 melting point for a period of 10 minutes until a molten pool of the capacity of approximately 100 cu. in. is formed. IN718 scraps are added to the pool at a rate of 0.51 lbs./min. Molten metal is discharged from a pour lip into an ingot at a rate of 0.51 lbs./min. 
     EXAMPLE 6 
     A molybdenum alloy block having dimensions of 14″×7″×3″ and a weight of 108 lbs. is heated on its upper surface by means of a 150 kW helium plasma torch to a temperature above the molybdenum alloy melting point for a period of 10 minutes until a molten pool of the capacity of approximately 100 cu. in. is formed. Molybdenum alloy scraps are added to the pool at a rate of 0.41 lbs./min. Molten metal is discharged from a pour lip into an ingot at a rate of 0.41 lbs./min. 
     EXAMPLE 7 
     A tantalum alloy block having dimensions of 14″×7″×3″ and a weight of 176 lbs. is heated on its upper surface by means of a 150 kW helium plasma torch to a temperature above the tantalum alloy melting point for a period of 10 minutes until a molten pool of the capacity of approximately 100 cu. in. is formed. Tantalum alloy scraps are added to the pool at a rate of 0.41 lbs./min. Molten metal is discharged from a pour lip into an ingot at a rate of 0.41 lbs./min. 
     EXAMPLE 8 
     A hafnium alloy block having dimensions of 14″×7″×3″ and a weight of 141 lbs. is heated on its upper surface by means of a 150 kW helium plasma torch to a temperature above the hafnium alloy melting point for a period of 10 minutes until a molten pool of the capacity of approximately 100 cu. in. is formed. Hafnium alloy scraps are added to the pool at a rate of 0.58 lbs./min. Molten metal is discharged from a pour lip into an ingot at a rate of 0.58 lbs./min. 
     EXAMPLE 9 
     A zirconium alloy block having dimensions of 14″×7″×3″ and a weight of 69 lbs. is heated on its upper surface by means of a 150 kW helium plasma torch to a temperature above the zirconium alloy melting point for a period of 10 minutes until a molten pool of the capacity of approximately 100 cu. in. is formed. Zirconium alloy scraps are added to the pool at a rate of 0.88 lbs./min. Molten metal is discharged from a pour lip into an ingot at a rate of 0.88 lbs./min. 
     EXAMPLE 10 
     A Ti-6Al-4V alloy having dimensions of 14″×7″×3″ and a weight of 48 lbs. is heated on its upper surface by means of a 150 kW electron beam gun to a temperature above the Ti-6Al-4V melting point for a period of 10 minutes until a molten pool of the capacity of approximately 100 cu. in. is formed. Ti-6Al-4V sponge compacts having approximate dimensions of 4″×3″×2″ is added to the pool at a rate of 0.75 lbs./min. Molten metal is discharged from a pour lip into an ingot at a rate of 0.75 lbs./min. 
     EXAMPLE 11 
     A iron based superalloy having dimensions of 14″×7″×3″ and a weight of 83 lbs. is heated on its upper surface by means of a 150 kW electron beam gun to a temperature above the iron based superalloy melting point for a period of 10 minutes until a molten pool of the capacity of approximately 100 cu. in. is formed. A 5″ diameter iron based superalloy feeder bar is positioned at a distance of 4″ above the molten pool so that one end is directly above the pool. The end directly above the pool is heated with the same 150 kW electron beam gun to above the iron based superalloy melting point. Droplets of molten metals having an approximate weight of 0.58 lbs./min. are allowed to fall directly into the molten pool so that they remain in the liquid phase during the entire fall period. Molten metal is discharged from a pour lip into an ingot at a rate of 0.58 lbs./min. 
     EXAMPLE 12 
     A cobalt based superalloy having dimensions of 14″×7″×3″ and a weight of 78 lbs. is heated on its upper surface by means of a 150 kW electron beam gun to a temperature above the cobalt based superalloy melting point for a period of 10 minutes until a molten pool of the capacity of approximately 100 cu. in. is formed. A 5″ diameter cobalt based superalloy feeder bar is positioned at a distance of 4″ above the molten pool so that one end is directly above the pool. The end directly above the pool is heated with the same 150 kW electron beam gun to above the cobalt based superalloy melting point. Droplets of molten metals having an approximate weight of 0.53 lbs./min. are allowed to fall directly into the molten pool so that they remain in the liquid phase during the entire fall period. Molten metal is discharged from a pour lip into an ingot at a rate of 0.53 lbs./min. 
     The term “block” as used herein means a mass of titanium or other metal or an alloy thereof which is of any regular or irregular shape and which may have either planar or irregular surfaces and which may have interior cavities. 
     The term “processing surface” as it is used herein means any surface on a block of metal which is in the horizontal plane or which has some other angular orientation which would allow the formation of a liquid pool therein. 
     It will also be appreciated by those skilled in the art that, while the processing surface on which the pool of molten metal is formed on the block will ordinarily be an upper surface, it would be possible, within the scope of this invention, to use other surfaces on a block as such a processing surface on which the pool of molten titanium may be formed. Non-limiting examples of surfaces which may be the processing surface other than as the top surface of a block would include a sloped lateral surface or an interior surface in a cavity in the block. 
     The terms “solid” or “solid block” as used herein refer to metal which is in the solid state of matter. Any block having interior cavities or bores or which may otherwise be described as hollow will still be considered to be “solid” as long as the block is comprised of metal in its solid phase. 
     The term “alloy” as used herein means any material comprising either two or more metals or one or more metals and a nonmetal. This term is further intended to encompass both compounds and mixtures. The term is also intended to encompass solid solutions in which two or more components of a crystalline material are mixed so that ions, atoms or molecules of one component replaces some of the ions, atoms or molecules of the other component in its normal crystal lattice, or in which such ions, atoms or molecules of one component occupy interstitial positions in the normal crystal lattice of the other component. 
     The term “superalloy” as used herein means any alloy based on a Group VIII element (per usual United States convention or Groups 8-10 under IUPAC 1980 Recommendation) and which may ordinarily comprise various combinations of nickel, iron, cobalt and chromium as well as lesser amounts of tungsten, titanium, niobium, tantalum or hafnium and which is resistant to mechanical stresses and chemical degradation after extended exposure above 1200° F. and more preferably above 2000° F. 
     It will be appreciated that a method and apparatus for efficiently melting and processing titanium and other metals and their alloys has been described. 
     It will be appreciated that a method and apparatus has also been described which allows for efficient heat transfer during melting and processing of titanium and other metals and their alloys. 
     It will also be appreciated that a method and apparatus has been described which allows for efficient cooling of the block sidewall during melting and processing of titanium and other metals and their alloys by plasma arc cold hearth refining (PACHR). 
     It will also be appreciated that a method and apparatus has been described which avoids very high temperature gradients and thermal stresses and cracking in the water cooled copper hearth during the melting and processing of titanium and other metals and their alloys. 
     It will finally be appreciated that a method and apparatus has been described for the melting and processing of titanium and other metals and their alloys which allows for a quick, easy and inexpensive apparatus set up and assembly for such procedures. 
     Accordingly, the improved METHOD OF MELTING TITANIUM AND OTHER METALS AND ALLOYS BY PLASMA ARC OR ELECTRON BEAM is simplified, provides an effective, safe, inexpensive, and efficient method and device which achieves all the enumerated objectives, provides for eliminating difficulties encountered with prior methods and devices, and solves problems and obtains new results in the art. 
     In the foregoing description, certain terms have been used for brevity, clearness, and understanding; but no unnecessary limitations are to be implied therefrom beyond the requirement of the prior art, because such terms are used for descriptive purposes and are intended to be broadly construed. 
     Moreover, the description and illustration of the invention is by way of example, and the scope of the invention is not limited to the exact details shown or described. 
     Having now described the features, discoveries, and principles of the invention, the manner in which the METHOD OF MELTING TITANIUM AND OTHER METALS AND ALLOYS BY PLASMA ARC OR ELECTRON BEAM is practiced, constructed and used, the characteristics of the method and construction, and the advantageous new and useful results obtained; the new and useful steps, structures, devices, elements, arrangements, parts, and combinations are set forth in the appended claims.