Thermit welding flux for high hardness steel rail and welding method thereof

The invention discloses a thermit welding flux for a high hardness steel rail and a welding method thereof. The thermit welding flux consists of aluminum powder, ferric oxide and alloy additives, wherein the aluminum power is pure aluminum powder, the content of active aluminum is more than 98 percent, and the granularity is between 30 and 60 meshes; the ferric oxide is formed by oxidation in the process of heating a rolled steel material, and the granularity of the ferric oxide is between 18 and 80 meshes; and other alloy additives comprise iron shots, silicon iron, ferromanganese, ferrochrome, ferrovanadium, ferromolybdenum and rare-earth alloy. The method for performing thermit welding on the high hardness steel rail by using the thermit welding flux comprises the following steps of: (a) filling the thermit welding flux in a reaction crucible, and igniting the welding flux to initiate a thermit reaction; (b) casting thermit molten steel generated in the reaction into a closed cavity formed by a sand mould