Casting process

A casting process comprising placing a breakable core into a cavity in a mold and pouring a molten metal into said cavity under a pressure by means of a plunger, wherein the speed of displacement of said plunger is controlled at three states of first, second and third velocities, said second velocity being higher than said first velocity and said third velocity being lower than said second velocity, and wherein the pressure applied to the molten metal by said plunger after its complete displacement at said third velocity is controlled to a primary pressure and a secondary pressure higher than said primary pressure, so that a solidified film of molten metal is formed on the surface of said core to surround said core under said primary pressure and the molten metal is completely solidified under the secondary pressure, the magnitude of said primary pressure and its time of application being related to the breakable core to achieve the formation of said solidified film of molten metal on the surface of said core and enable said core to resist the subsequent application of the higher secondary pressure and prevent breakage of the core.