Patent ID: 7811356
Filing Date: 2010-10-12
Classification: C01B,C22B,Y02P

Abstract:
1. A method for purifying a metal, comprising: a first step of holding a first molten metal containing impurities in a first crucible; a second step of immersing a first cooling body in the first molten metal held in the first crucible while letting a cooling fluid flow in the interior of the cooling body to crystallize a first purified metal on a surface of the cooling body; a third step of taking out the first cooling body with the first purified metal crystallized thereon from the first molten metal; a fourth step of holding in a second crucible a second molten metal having an impurity concentration less than that of the first molten metal of the first step; a fifth step of melting the first purified metal crystallized in the second step to form a molten first purified metal and holding the molten first purified metal in said second crucible together with the second molten metal held in the fourth step; a sixth step of immersing a second cooling body in the second molten metal held in the fifth step while letting a cooling fluid flow in the interior of the cooling body to crystallize a second purified metal on a surface of the cooling body; and a seventh step of taking out the second cooling body with the second purified metal crystallized thereon in the sixth step from the second molten metal; wherein the sixth and seventh steps are carried out a plurality of times, with repetition of the first through fifth steps a plurality of times, by adding and melting in the first crucible an impurity-containing metal of an amount equal to the amount of the first purified metal crystallized in the first through fifth steps: wherein said impurities comprise iron, aluminum, calcium and phosphorus, and wherein said iron, aluminum, calcium and phosphorus is reduced to a level of 0.1 ppmw or less.