Method for purifying high-purity aluminium by directional solidification and smelting furnace therefor

Abstract

Provided is a method for preparing high-purity aluminum by directional solidification, comprising the steps of: providing 4N to 5N aluminum as raw material, heating the same to a temperature of 670° C. to 730° C., maintaining the temperature for 7 minutes to 80 minutes, cooling the bottom of chamber ( 3 ) to allow the aluminum liquid crystallizing in a direction from the bottom to top of the chamber ( 3 ) for 1 hour to 8 hours to obtain a crystalline ingot, during the crystallization process of a finished product of crystalline ingot, stifling and heating the aluminum liquid, maintaining a particular temperature gradient of the aluminum liquid, and removing a portion of the crystalline ingot from one end of the ingot, the remaining portion being the high-purity aluminum. Also provided is a smelting furnace, comprising a shell ( 1 ), a heating device ( 2 ), a chamber ( 3 ), a temperature measurement device, a stirring device and a cooling device ( 6 ).

1 . A method for preparing high-purity aluminum by directional solidification, characterized in that it comprises the following steps:
 step one, providing 4N to 5N aluminum as raw material, and cleaning the surface of the aluminum raw material;   step two, feeding the aluminum raw material from the step one into a chamber of a smelting furnace wherein the aluminum raw material is heated to a temperature of 670° to 730° C., so that the aluminum raw material is completely melted to form an aluminum liquid;   step three, maintaining the aluminum liquid from step two at the temperature of 670° C. to 730° for 7 minutes to 80 minutes;   step four, cooling the bottom of the chamber to allow the aluminum liquid crystallizing in a direction from the bottom to top of the chamber for 1 hour to 8 hours to obtain a crystalline ingot, from which a finished crystalline ingot product is to be prepared by removing of a portion of the ingot from the ingot end where the crystallization is lastly completed, and wherein at least during the crystallization process for forming the ingot part which corresponds to the finished crystalline ingot product, a mechanical stirring and/or electromagnetic stirring is applied to the aluminum liquid, and at the same time the aluminum liquid is heated, maintaining the temperature of the crystal plane of the aluminum liquid at 655° C. to 665° C. and the temperature of the liquid surface of the aluminum liquid at 695° to 705°, and temperature of the aluminum liquid increasing gradually from the crystal plane to the liquid surface;   step five, removing a portion of the crystalline ingot from the ingot end where the crystallization is lastly completed, wherein the ingot portion to be removed depends on the desired purity of the crystalline ingot product to be obtained and ranges from 15% to 70% of the thickness of the entire crystalline ingot, the remaining portion of the crystalline ingot being the finished crystalline ingot product, i.e. a high-purity aluminum product with the desired purity.   
     
     
         2 . The method for preparing high-purity aluminum by directional solidification as claimed in  claim 1 , characterized in that in step one, cleaning the surface of the aluminum raw material includes:
 the surface of the aluminum raw material being cleaned by a physical cleaning process, and then   a chemical cleaning process being applied to remove the oxide film from the surface of the aluminum raw material.   
     
     
         3 . The method for preparing high-purity aluminum by directional solidification as claimed in  claim 1  or  claim 2 , characterized in that, in step four,
 a mechanical stirring is applied to the aluminum liquid by a dried and preheated stirring blade, and the distance between the stirring blade and the crystal plane is 10 mm to 50 mm; and/or 
 an electromagnetic stirring is applied to the aluminum liquid wherein the distance between the layer stirred by electromagnetic stirring and the crystal plane is 10 mm to 50 mm. 
 
     
     
         4 . A smelting furnace useful for implementing the method for preparing high-purity aluminum by directional solidification as claimed in any one of  claims 1  to  3 , characterized in that it comprises a shell, a heating device, a chamber, a temperature measurement device, a stirring device and a cooling device: wherein,
 the chamber is installed in the shell: 
 the heating device is arranged between the shell and the chamber, and when one heating device is presented, it is arranged in a position at the upper part of the chamber, when a plurality of heating devices are presented, they are arranged at an interval in a direction from the upper to the lower part of the chamber; 
 the cooling device is arranged under the chamber at the bottom of the furnace; 
 the stirring device comprises a mechanical stirring device and/or an electromagnetic stirring device; and 
 the temperature measurement device comprises a hearth temperature sensoring device and a chamber temperature sensoring device, the hearth temperature sensoring device is arranged between the cooling device and the shell, and the chamber temperature sensoring device is used for measuring the chamber temperature at different positions along the height direction of the chamber. 
 
     
     
         5 . The smelting furnace useful for implementing the method for preparing high-purity aluminum by directional solidification as claimed in  claim 4 , characterized in that the stirring device comprises a mechanical stirring device; wherein,
 the stirring blade of the mechanical stirring device is arranged in the lower part of the mechanical stirring device, and is able to ascend or descend along the height direction of the stirring device.   
     
     
         6 . The smelting furnace useful for implementing the method for preparing high-purity aluminum by directional solidification as claimed in  claim 4  or  claim 5 , characterized in that the stirring device comprises an electromagnetic stirring device, which is arranged between the shell and the heating device, and is arranged in a dislocation manner with the heating device along the height direction of the smelting furnace. 
     
     
         7 . The smelting furnace useful for implementing the method for preparing high-purity aluminum by directional solidification as claimed  claim 4  or  claim 5 , characterized in that a thermal insulation layer is arranged inside the shell and outside the heating device. 
     
     
         8 . The smelting furnace useful for implementing the method for preparing high-purity aluminum by directional solidification as claimed in  claim 7 , characterized in that the stirring device comprises an electromagnetic stirring device, the electromagnetic stirring device which is arranged between the thermal insulation layer and the heating device and is arranged in a dislocation manner with the heating device along the height direction of the smelting furnace. 
     
     
         9 . The smelting furnace useful for implementing the method for preparing high-purity aluminum by directional solidification as claimed in  claim 4  or  claim 5 , characterized in that the chamber temperature sensoring device comprises several temperature sensors distributed at the outside of the chamber along the height direction of the chamber. 
     
     
         10 . The smelting furnace useful for implementing the method for preparing high-purity aluminum by directional solidification as claimed in  claim 4  or  claim 5 , characterized in that the heating device is an electric heating device.