Method for vacuum-refining and purifying magnesium metal

The invention provides a method for vacuum-refining and purifying magnesium metal. The method comprises the following steps: placing crude magnesium into a vacuum furnace; starting a vacuumizing system; after pressure in the vacuum furnace is less than 300Pa, starting to increase temperature; when temperature is increased to 700-1300 DEG C, controlling the pressure in the vacuum furnace within 5-100Pa and keeping the temperature for 10-180 minutes; and meanwhile, controlling the temperature of a refrigeration area within 300-800 DEG C; and after ending the temperature preservation and the temperature in the vacuum furnace is less than 200 DEG C, closing the vacuumizing system, thereby obtaining a distilled residual and obtaining massive or strip magnesium metal in the refrigeration area. The method provided by the invention has the advantages of simple process, low cost, easiness in operation and wide application scope; the separation of magnesium metal, magnesium oxide and carbon in a magnesium metal condensate prepared according to a carbon thermal reduction method is effectively realized; the magnesium metal condensate with higher purity is obtained; and the whole reaction process is performed in vacuum and is free from environmental pollution.