Method and apparatus for manufacturing billets for thixocasting

Abstract

Provided are a method and apparatus for continuously manufacturing quality billets for thixocasting that have a fine, uniform, spherical particle structure, in a short time, with improvements in energy efficiency and mechanical properties, cost reduction, convenience of casting, and shorter manufacturing time. The method involves applying an electric field to a domain of a sleeve defined by first and second plungers inserted through each end of the sleeve and loading a molten metal into the domain of the sleeve to form a semi-solid metallic slurry, moving the first plunger toward the second plunger to compress the semi-solid metallic slurry and form a billet via cooling, and shifting the billet toward the second plunger to discharge the billet from the sleeve.

What is claimed is:  
     
         1 . A method of manufacturing billets for thixocasting, the method comprising: 
 (a) applying an electric field to a domain of a sleeve defined by first and second plungers inserted through each end of the sleeve and loading a molten metal into the domain of the sleeve to form a semi-solid metallic slurry;    (b) moving the first plunger toward the second plunger to compress the semi-solid metallic slurry and form a billet via cooling; and    (c) shifting the billet toward the second plunger to discharge the billet from the sleeve.    
     
     
         2 . The method of  claim 1 , after step (b), comprising (c) shifting the billet toward the second plunger and moving the first plunger backward to allow for a domain between the billet and the first plunger that is the same in size as the domain initially defined between the first and second plungers and repeating steps (a) and (b) to continuously form another billet, wherein step (c) is repeated to continuously form a number of billets.  
     
     
         3 . The method of  claim 1 , wherein applying the electromagnetic field to the domain is performed prior to loading the molten metal into the sleeve.  
     
     
         4 . The method of  claim 1 , wherein applying the electromagnetic field to the domain is performed at the start of loading the molten metal into the sleeve.  
     
     
         5 . The method of  claim 1 , wherein applying the electromagnetic field to the domain is performed in the middle of loading the molten metal into the sleeve.  
     
     
         6 . The method of  claim 1 , wherein applying the electromagnetic field to the sleeve is sustained until the molten metal in the domain of the sleeve has a solid fraction of 0.001-0.7.  
     
     
         7 . The method of  claim 6 , wherein applying the electromagnetic field to the sleeve is sustained until the molten metal in the domain of the sleeve has a solid fraction of 0.001-0.4.  
     
     
         8 . The method of  claim 7 , wherein applying the electromagnetic field to the sleeve is sustained until the molten metal in the domain of the sleeve has a solid fraction of 0.001-0.1.  
     
     
         9 . The method of  claim 1 , further comprising cooling the molten metal after loading into the domain under the electromagnetic field.  
     
     
         10 . The method of  claim 9 , wherein cooling the molten metal is sustained until the molten metal in the domain has a solid fraction of 0.1-0.7.  
     
     
         11 . The method of  claim 9 , wherein cooling the molten metal is performed at a rate of 0.2-5.0/sec.  
     
     
         12 . The method of  claim 9 , wherein cooling the molten metal is performed at a rate of 0.2-2.0/sec.  
     
     
         13 . An apparatus for manufacturing billets for thixocasting, the apparatus comprising: 
 a stirring unit which includes a space and applies an electromagnetic field to the space;    a sleeve which extends across the space of the stirring unit and includes a domain into which a molten metal is loaded;    a first plunger which is inserted through an end of the sleeve to form a sidewall of the domain of the sleeve and is moved to compress a semi-solid slurry manufactured in the domain; and    a second plunger which is inserted through the other end of the sleeve to form the other sidewall of the domain of the sleeve and which is kept in place when the first plunger is moved to compress the slurry and is moved backward after a billet having a predetermined size has been formed as a result of the compression.    
     
     
         14 . The apparatus of  claim 13 , wherein the sleeve comprises a billet discharge hole in its lower surface a predetermined distance away from the domain toward the second plunger.  
     
     
         15 . The apparatus of  claim 13 , wherein the stirring unit applies the electromagnetic field prior to loading the molten metal into the sleeve.  
     
     
         16 . The apparatus of  claim 13 , wherein the stirring unit applies the electromagnetic field at the start of loading the molten metal into the sleeve.  
     
     
         17 . The apparatus of  claim 13 , wherein the stirring unit applies the electromagnetic field in the middle of loading the molten metal into the sleeve.  
     
     
         18 . The apparatus of  claim 13 , wherein the stirring unit applies the electromagnetic file until the molten metal in the sleeve has a solid fraction of 0.001-0.7.  
     
     
         19 . The apparatus of  claim 18 , wherein the stirring unit applies the electromagnetic field until the molten metal in the sleeve has a solid fraction of 0.001-0.4.  
     
     
         20 . The apparatus of  claim 19 , wherein the stirring unit applies the electromagnetic field until the molten metal in the sleeve has a solid fraction of 0.001-0.1.  
     
     
         21 . The apparatus of  claim 13 , wherein the sleeve comprises a temperature control element.  
     
     
         22 . The apparatus of  claim 21 , wherein the temperature control element comprises at least one of a cooler and an electrical heater.  
     
     
         23 . The apparatus of  claim 21 , wherein the temperature control element cools the molten metal in the sleeve to reach a solid fraction of 0.1-0.7.  
     
     
         24 . The apparatus of  claim 21 , wherein the temperature control element cools the molten metal in the sleeve at a rate of 0.2-5.0/sec.  
     
     
         25 . The apparatus of  claim 24 , wherein the temperature control element controls the molten metal in the sleeve at a rate of 0.2-2.0/sec.