Aluminum alloy pattern ring low-pressure cast outer mold structure and low-pressure casting method

The invention discloses an aluminum alloy pattern ring low-pressure cast outer mold structure which comprises an outer mold body which is in a conical shape overall and is provided with a cavity inside; a position in the outer mold body, which is close to the bottom, is provided with a cooling liquid runner; the cooling liquid runner circumferentially goes around the outer mold body for a round, and a partition board is arranged in the cooling liquid runner; and both sides of the partition board are respectively provided with a water inlet nozzle and a water outlet nozzle of the cooling liquid runner. The invention solves the defects of shrinkage, porosity and the like which occur below a casting; and because the clotting time of the lower part of the casting is shortened, the shrinkage rates of the calibers at the upper and the lower parts are nearly the same, thereby facilitating the accurate setting of casting process parameters, and improving the dimensional precision of the casting.