HIGHLY-INERT MOLD SHELL FOR CASTING, PREPARATION METHOD THEREFOR, AND METHOD FOR IMPROVING PRECISION OF MAGNESIUM ALLOY CASTING

A highly-inert mold shell for casting, comprising a surface layer for being in contact with a magnesium alloy pouring fluid. The surface layer contains an inorganic compound, and the inorganic compound is selected from at least one of boron anhydride, borax, potassium fluoride, and sodium fluoride. Taking the total amount of raw material of the surface layer as a reference, the content of the inorganic compound accounts for 10-40 wt%. A method for preparing the described mold shell, a method for improving the precision of a magnesium alloy casting, and a use of applying the described mold shell in improving the precision of a magnesium alloy casting. After pouring, the mold shell is heated, and the temperature rises. The specific inorganic compound is capable of melting and expanding, forming a molten state, and can fill a gap in the surface layer of the mold shell, plugging the gap in the surface layer. In an optional embodiment, a one-layer film can also be formed, thereby isolating magnesium from the mold