Heated trough for molten aluminum

Abstract

A method of heating molten aluminum flowing in a heated trough member comprising the steps of providing a source of molten aluminum and providing a rough member comprised of a first side and a second side, the first and the second sides having outside surfaces, the sides formed from a ceramic material resistant to attack by molten aluminum. The first side and second side have heating element receptacles provided therein with protection tubes provided in the receptacles. The protection tubes are comprised of a refractory selected from the group consisting of mullite, boron nitride, silicon nitride, silicon carbide, graphite, silicon aluminum oxynitride or a metal selected from Kovar® and titanium. Electric heating elements are positioned in the tubes. Molten aluminum is flowed along the trough member from the source and electric power is passed to the heating elements to heat the molten aluminum as it flows along the trough member.

What is claimed is:  
     
         1 . A method of heating molten aluminum flowing in a heated trough member from a molten aluminum source to a processing operation, the method 
 (a) providing a source of molten aluminum;    (b) providing a tough member comprised of a first side and a second side, said first and said second sides having outside surfaces, said sides formed from a ceramic material resistant to attack by molten aluminum, said first side and second side having: 
 (i) heating element receptacles provided therein;  
 (ii) electric heating elements positioned in at least one side;  
   (c) flowing molten aluminum along said trough member from said source; and    (d) passing electric power to said heating elements and heating said molten aluminum as it flows along said trough member.    
     
     
         2 . The method in accordance with  claim 1  wherein said trough member is substantially U-shaped.  
     
     
         3 . The method in accordance with  claim 1  wherein said first and second sides are joined to a bottom side to form said trough member.  
     
     
         4 . The method in accordance with  claim 1  wherein said trough member has a ceramic bottom sealed to said ceramic material comprising said sides for containing said molten aluminum flowing through said trough.  
     
     
         5 . The method in accordance with  claim 1  wherein said material is selected from the group consisting of silicon carbide, silicon nitride, magnesium oxide, spinel, carbon and mixtures thereof.  
     
     
         6 . The method in accordance with  claim 1  wherein said receptacles contain a contact medium for improved conduction of heat from said heating elements to said ceramic material, the contact medium selected from the group consisting of powdered material, low melting metal and a glass material.  
     
     
         7 . The method in accordance with  claim 1  wherein said contact medium is an amalgam.  
     
     
         8 . The method in accordance with  claim 1  wherein said receptacles contain protection tubes comprised of a material selected from the group consisting of mullite, boron nitride, silicon nitride, silicon carbide, graphite, silicon aluminum oxynitride or a metal selected from the group consisting of Kovar® and titanium.  
     
     
         9 . The method in accordance with  claim 1  wherein said first and second sides are comprised of: 
 (a) a metal layer disposed on said outside surfaces; and  
 (b) an insulation layer positioned between said metal layer and said first and second sides of ceramic material.  
 
     
     
         10 . The method in accordance with  claim 1  wherein said ceramic material contains copper medium for improved heat transfer.  
     
     
         11 . The method in accordance with  claim 1  wherein said first side and said second side have a heat-reflective layer disposed on said outside surfaces.  
     
     
         12 . A method of heating molten metal flowing in a heated trough member from a molten metal source to a processing operation, the method comprising the steps of: 
 (a) providing a source of molten metal;    (b) providing a trough member comprised of a first side and a second side, said first and said second sides having outside surfaces, said sides formed from a ceramic material resistant to attack by molten metal, said first side and second side having: 
 (i) heating element receptacles provided therein;  
 (ii) protection tubes provided in said receptacles, said protection tubes comprised of a refractory selected from the group consisting of mullite, boron nitride, silicon nitride, silicon carbide, graphite, silicon aluminum oxynitride or a metal selected from Kovar® and titanium; and  
 (iii) electric heating elements positioned in said tubes;  
   (c) flowing molten metal along said trough member from said source; and    (d) passing electric power to said heating elements and heating said molten metal as it flows along said trough member.    
     
     
         13 . A method of heating molten aluminum flowing in a heated trough member comprising the steps of: 
 (a) providing a source of molten aluminum;    (b) providing a trough member comprised of a bottom, a first side and a second side, said first and said second sides having outside surfaces, said sides joined to said bottom to form said tough member, said sides and bottom formed from a ceramic material resistant to attack by molten aluminum, said ceramic material comprised of a material selected from the group consisting of silicon carbide, silicon nitride, magnesium oxide, spinel, carbon and mixtures thereof, said first side and second side having: 
 (i) heating element receptacles provided in said first side and said second side;  
 (ii) refractory tubes provided in said receptacles, said refractory tubes comprised of a refractory selected from the group consisting of mullite, boron nitride, silicon nitride, silicon carbide, graphite and silicon aluminum oxynitride; and  
 (iii) electric heating elements positioned in said refractory tubes;  
   (c) flowing molten aluminum along said trough member from said source; and    (d) passing power to said heating elements and heating said molten aluminum as it flows along said trough member.    
     
     
         14 . The method in accordance with  claim 13  wherein said contact medium is an amalgam.  
     
     
         15 . The method in accordance with  claim 13  wherein said tubes are comprised of mullite.  
     
     
         16 . The method in accordance with  claim 13  wherein said ceramic material contains copper medium for improved heat transfer.  
     
     
         17 . The method in accordance with  claim 13  wherein said first side and said second side have a heat-reflective layer disposed on said outside surfaces.  
     
     
         18 . An improved trough member for flowing molten aluminum from a molten metal source to a processing operation and for adding heat to said molten metal flowing in said through member, said trough comprised of: 
 (a) a bottom and side comprised of a ceramic material resistant to attack by said molten metal, said bottom and sides joined together to form said trough member;    (b) a series of heating element receptacles provided in said ceramic material comprising said sides, said receptacles having refractory tubes disposed in said receptacles, said refractory tube comprised of a refractory selected from the group consisting of mullite, boron nitride, silicon nitride, silicon carbide, graphite and silicon aluminum oxynitride, zirconium, stabilized zirconium and mixtures thereof; and    (c) electric heating elements provided in said refractory tubes for transferring heat to molten metal flowing in said trough member.    
     
     
         19 . The trough member in accordance with  claim 18  wherein said ceramic material is comprised of silicon carbide, silicon nitride, magnesium oxide, spinel, carbon and mixtures thereof.  
     
     
         20 . The trough member in accordance with  claim 18  wherein said ceramic material contains copper fibers for improved heat transfer.  
     
     
         21 . The trough member in accordance with  claim 18  wherein said receptacles contain a contact medium for improved heat transfer selected from the group consisting of powdered material, low melting metal and an amalgam.  
     
     
         22 . The trough member in accordance with  claim 18  wherein said sides have an outside surface having a heat-reflective layer disposed on said outside surface to reflective heat inwardly to said trough.  
     
     
         23 . The trough member in accordance with  claim 18  wherein said electric heating elements are electrically connected in a series circuit.  
     
     
         24 . The trough member in accordance with  claim 18  wherein said electric heating elements are controlled as part of a closed loop control system.  
     
     
         25 . The trough member in accordance with  claim 18  wherein said electrical power input to said heaters is modulated by a controller.  
     
     
         26 . An improved trough member for flowing molten aluminum from a molten aluminum source to a processing operation and for adding heat to said molten aluminum flowing in said trough member, said trough comprised of: 
 (a) a bottom and side comprised of a ceramic material resistant to attack by said molten aluminum, said bottom and sides joined together to from said trough member having an outside surface;    (b) a layer of insulation provided on said outside surface;    (c) a series of heating element receptacles provided in said ceramic material comprising said sides, said receptacles having refractory tubes disposed in said receptacles, said refractory tube comprised of a refractory selected from the group consisting of mullite, boron nitride, silicon nitride, silicon carbide, graphite and silicon aluminum oxynitride, zirconium, stabilized zirconium and mixtures thereof;    (d) electric heating elements provided in said refractory tubes for transferring heat to molten aluminum flowing in said trough member; and    (e) a controller in communication with said heating to modulate electrical power input to said heating elements.