Method of forming casting with flow passage, and casting formed by the same

A method of forming a casting with a flow passage, comprising:

• forming a core obtained by filling a tubular pipe with a filler;
• inserting the core into a mold having a cavity corresponding to a shape of the casting to be formed;
• performing a casting process by injecting a molten metal into the cavity;
• and
• removing the filler from the core,
• wherein the casting process is performed through a high-pressure casting process,
• wherein the forming the core comprises:
• filling the tubular pipe with the filler;
• and
• drawing and extruding the tubular pipe filled with the filler.