Impurity removal
Common metal impurities are nickel, titanium, chromium, iron, aluminum, silicon, copper, manganese, zinc, sodium, etc. Non-metallic impurities include chloride, oxide and nitride. These impurities have a bad influence on the performance of metallic magnesium. Impurities such as iron, nickel and chloride will deteriorate the corrosion resistance of magnesium. Non-metallic impurities such as CaO, SiO2, Fe2O3, MgO and magnesium and zinc present in magnesium , Aluminum, silicon and other metal impurities make magnesium brittle. When magnesium is used as a reducing agent, these impurities will reduce the quality of the reduced metal. Therefore, no matter whether the crude magnesium produced by molten salt electrolysis or thermal reduction is produced, it must be refined to remove impurities before it can be cast into a commercial magnesium ingot.
Method of refining magnesium
Depending on the quality requirements of magnesium, different refining methods can be used. Magnesium refining methods mainly include magnesium flux refining, magnesium sedimentation refining, magnesium vacuum distillation refining, and magnesium addition refractory metal refining, etc. The first two methods mainly remove impurities such as non-metal oxides and iron from crude magnesium. The latter two methods mainly remove metallic impurities and are used to produce high-purity magnesium. The refined magnesium produced by magnesium refining is commonly referred to as commercial magnesium [.
Thermal reduction magnesium smelting
Product reduction of magnesium by thermal reduction process refers to a method of smelting magnesium that uses a reducing agent to reduce magnesium oxide to metallic magnesium at high temperature. During the Second World War, due to the sudden increase in the demand for magnesium, the magnesium produced by the molten salt electrolysis method could no longer meet the demand, so the thermal reduction method of magnesium smelting developed into an important method of metal magnesium production.
Thermal reduction magnesium smelting methods include Pijiang magnesium smelting, semi-continuous silicon thermal magnesium smelting, Bolzano magnesium smelting, carbothermal magnesium smelting, and carbide thermal magnesium smelting, etc.