Defect repair method for thin-wall cylindrical titanium alloy casting with large opening in cylinder wall

The invention discloses a defect repair method for a thin-wall cylindrical titanium alloy casting with a large opening in the cylinder wall and relates to the technical field of metal material welding. The cross section of the large opening is rectangular, and the length direction of the rectangle is identical to that of the titanium alloy casting. The method comprises the following steps that first, the position of a casting defect is determined, the casting defect and the surrounding oxidation layer are removed, and a reinforcing rib assembly is fixed to the titanium alloy casting; then, thecasting defect is pre-heated, repairing welding is performed by adopting a fusion welding method, and after repairing welding is ended, the repairing welding quality is inspected; after inspection isqualified, the titanium alloy casting is placed in a thermal treatment furnace for vacuum thermal treatment, and the thermal treatment temperature is 650-800 DEG C; and finally, the reinforcing rib assembly is cut off from th