Method for preparing shell of titanium alloy investment casting with long and narrow through hole

The invention provides a method for preparing a shell of a titanium alloy investment casting with a long and narrow through hole. The method comprises the following steps of preparing a wax mold in which a through hole is formed; coating the surface of the wax mold with a refractory coating A; coating the outer surface of the refractory coating A with a refractory coating B; enabling a core rod to be inserted into the through hole, the two ends of the core rod to extend out of the hole opening of the through hole, and then the gap between the core rod and the through hole to be filled with mixed slurry; coating the outer surface of the refractory coating B and the outer surface of the core rod with a refractory coating C; heating to remove the wax mold, and roasting to consolidate the refractory coating A, the refractory coating B, the refractory coating C, the mixed slurry and the core rod to form the shell. According to the technical solution, the core rod is made of the titanium alloy material, deformation