The lower mold which forms the external side of the vehicle wheel is water-cooled by water-cooling pipes. The rib-forming portions of the upper mold which forms the internal side of the vehicle wheel are forcibly air-cooled by the air passages provided along the rib-forming portions. Since water-cooling has better cooling capacity than air-cooling, the molten material inside the cavity between the lower mold and the upper mold is solidified from the external side thereof, and no defects such as shrinkage cavities occur on the external side thereof. When the internal side is solidified, the rib portions are solidified not much later than the other portion of the internal side, thereby shortening the casting cycle time. The split molds which form the cavity for forming therein the rim portion of the vehicle wheel are opened earlier than the upper mold, at the time when the surface layer portion of the molten material in the cavity has been solidified. If the split molds are kept clamped, the clearance to be generated between the split molds and the molten material upon contraction thereof due to solidification, restricts the heat dissipation from the molten material to the split molds, resulting in retarded solidification. To the contrary, early opening of the split molds leads to accelerated solidification of the molten material due to cooling of the rim portion by the atmosphere.
A pressure die-casting apparatus D for a vehicle wheel including a lateral die 30 slidably displaced and a molten metal feeding port 312 of said lateral die 30 of which center axis extends vertically relative to the slidable surface of said lateral die 30, characterized in that a strainer receiving chamber 72 is disposed at the contact surface between said molten metal feeding port 312 and said lateral die 30, and a trainer R is received in said strainer receiving chamber 72.
A mold for casting a vehicle wheel includes a movable top core which cooperates with a base member to define a mold cavity. The mold also includes a plurality of movable segments mounted upon the top core. The movable segments define a central gate which communicates with the mold cavity. The central gate receives a charge of molten metal and feeds the charge into the mold cavity. A porous filter is disposed within the gate.
