Apparatus for molding metals

Abstract

An apparatus for molding a metal material. The apparatus includes a vessel with portions defining a passageway through the vessel. An inlet is located toward one end and a member or agitation means is located within the passageway. A plurality of heaters are located a length of the vessel. The first of the heaters is located immediately downstream of the inlet and is a low frequency induction coil heater whereby the temperature gradient through the vessel's sidewall is minimized.

1  An apparatus for molding a metal material comprising: 
 a barrel having portions defining a passageway through said barrel, said barrel also including portions defining an inlet into said passageway;  
 a member located within said passageway; and  
 a plurality of heaters located along a length of said barrel, a first one of said heaters being located as a first one of said plurality of heaters downstream of said inlet, said first one of said plurality of heaters being a low frequency induction coil heater.  
 
     
     
         2 . The apparatus of  claim 1  wherein said first one of said plurality of heaters is located within seven (7) inches of said inlet.  
     
     
         3 . The apparatus of  claim 1  further comprising a second one of said plurality of heaters, said second one being located immediately downstream of said first one of said plurality of heaters, said second one being a low frequency induction coil heater.  
     
     
         4 . The apparatus of  claim 3  wherein said first and second ones of said heaters have different coil spacing from each other.  
     
     
         5 . The apparatus of  claim 3  wherein said first and second ones of said heaters are spaced less than six (6) inches apart.  
     
     
         6 . The apparatus of  claim 1  wherein said one of said plurality of heaters has an operating frequency of less than 1000 Hz.  
     
     
         7 . The apparatus of  claim 1  wherein said one of said plurality of heaters has an operating frequency in the range of greater than 0 to 400 Hz.  
     
     
         8 . The apparatus of  claim 1  wherein said one of said plurality of heaters has an operating frequency of about 60 Hz.  
     
     
         9 . The apparatus of  claim 3  wherein said first and second ones of said plurality of heaters have an operating frequency of in the range of greater than 0 to 1000 Hz.  
     
     
         10 . The apparatus of  claim 3  wherein said first and second ones of said plurality of heaters has an operating frequency of about 60 Hz.  
     
     
         11 . The apparatus of  claim 3  wherein said first and second ones of said plurality of heaters are operated by separate power sources.  
     
     
         12 . The apparatus of  claim 1  wherein said vessel is constructed of a non-magnetic material.  
     
     
         13 . The apparatus of  claim 1  wherein said vessel is a barrel.  
     
     
         14 . The apparatus of  claim 1  wherein said member is a rotatable screw.  
     
     
         15 . The apparatus of  claim 1  wherein said vessel is constructed of a material having a high electrical resistivity.  
     
     
         16 . The apparatus of  claim 1  wherein said member is magnetic.  
     
     
         17 . The apparatus of  claim 1  wherein said vessel is constructed of a Ni-base, Fe—Ni base or austenitic stainless steel.  
     
     
         18 . The apparatus of  claim 3  wherein said first one of said heaters has a lower operating frequency than said second one of said heaters.  
     
     
         19 . The apparatus of  claim 1  wherein said barrel further includes a liner of non-magnetic alloy increasing corrosion and wear resistance of said barrel.  
     
     
         20 . The apparatus of  claim 1  wherein all of said plurality of heaters are low frequency induction heaters.  
     
     
         21 . The apparatus of  claim 1  wherein at least one of said plurality of heaters has a variable operating frequency, said frequency being variable during operation of said apparatus.  
     
     
         22 . The apparatus of  claim 1  wherein power to at least one of said plurality of heaters is controlled by a closed loop feedback control having a sensor.  
     
     
         23 . The apparatus of  claim 1  wherein at least two of said plurality of heaters have different operating frequencies.  
     
     
         24 . The apparatus of  claim 1  further comprising a power source providing power at a low frequency to at least one of said plurality of heaters.  
     
     
         25 . The apparatus of  claim 24  wherein said power source includes phase control.  
     
     
         26 . The apparatus of  claim 24  wherein said power source includes pulse width modulation control.  
     
     
         27 . The apparatus of  claim 24  wherein said power source includes an inverter from a three phase rectifier.  
     
     
         28 . The apparatus of  claim 27  wherein said rectifier includes pulse width modulation control.  
     
     
         29 . The apparatus of  claim 1  wherein said heaters deliver a first power level to said member and a second power level to said barrel.  
     
     
         30 . An apparatus for molding a metal material comprising: 
 a barrel having portions defining a passageway through said barrel, said barrel also including portions defining an inlet into said passageway;    a rotatable member located within said passageway; and    a plurality of low frequency induction heaters located along a length of said barrel and including a first and a second heater positioned successively downstream of said inlet, said first heater having a power density greater than a power density of said second heater.    
     
     
         31 . A method of heating a metal material for subsequent molding comprising the steps of: 
 introducing the metal material into a vessel;    directly heating a member located within the vessel;    introducing the metal material about the member;    heating the metal material by extracting heat from the member to the metal material to achieve a temperature for molding; and    maintaining a temperature gradient of less than 100° C. through a wall thickness section of the vessel.    
     
     
         32 . The method of  claim 31  further comprising the step at least partially directly heating the metal material.  
     
     
         33 . The method of  claim 31  wherein said directly heating step includes the step of low frequency inductive heating of the vessel.  
     
     
         34 . The method of  claim 31  wherein said directly heating step includes the step of low frequency inductive heating of the member.  
     
     
         35 . The method of  claim 31  wherein said heating the metal material step includes the step of low frequency inductive heating of the metal material.  
     
     
         36 . The method of  claim 31  wherein said heating step and said directly heating step include the step of low frequency inductive heating of the vessel, member and metal material.  
     
     
         37 . The method of  claim 31  further comprises the step of heating the metal material to a temperature above its solidus temperature, but not exceeding its liquidus temperature.  
     
     
         38 . The method of  claim 31  further comprising the step of stirring the metal material to decrease particle size and increase roundness of said solid phase in the metal material.  
     
     
         39 . The method of  claim 31  further comprising the step of heating the metal material to a temperature above its liquidus temperature.  
     
     
         40 . The method of  claim 31  further comprising the step of preheating the member and vessel.  
     
     
         41 . The method of  claim 40  wherein said preheating step includes the step of axially retracting the member within the vessel.  
     
     
         42 . The method of  claim 41  wherein said preheating step includes the step of low frequency inductive heating of the member.  
     
     
         43 . The method of  claim 40  wherein said preheating step includes the step of inductively heating the member.  
     
     
         44 . The method of  claim 31  wherein said maintaining step maintains a temperature gradient of less than 50° C. through a wall thickness section of the vessel.  
     
     
         45 . The method of  claim 31  wherein said maintaining step maintains a temperature gradient of about 25° C. through a wall thickness section of the vessel.