Pattern for the lost foam casting process including a pouring-basin-foming portion, a sprue-forming portion, a runner-forming portion, a gate-forming portion, and a riser-forming portion. The sprue-forming portion forms an inverted conical sprue having a blade-lightener therein for quickly filling, and substantially simultaneously firing, the gates. A glue joint may be used between the pouring- basin-forming portion and the sprue-forming portion to increase the residence time of the melt in the pouring basin. The runners formed by the pattern each have an inline riser through which melt flows during pouring and in which melt is stored to feed the casting with melt during shrinkage of the casting A sand dam surrounds the mouth of each gate and traps particulates from a liquid styrene layer that precedes the melt front in the riser.

Pattern for the lost foam casting process including a pouring-basin-forming portion, a sprue-forming portion, a runner-forming portion, a gate-forming portion, and an inline-riser-forming portion. The runners formed by the pattern each have an inline riser through which melt flows between an inlet to and outlet from the riser during pouring, and in which melt is stored to feed the casting with melt during cooling/shrinkage of the casting. A sand dam surrounds the mouth of each gate and traps particulates from a liquid styrene layer that precedes the melt front in the riser.

A method for casting of metal articles using external pressure and having particular application to lost foam casting of metal articles. A polymeric foam pattern having a configuration corresponding to an article to be cast is placed in an outer flask and the pattern is connected through a polymeric foam gating system to a pouring cup located at the upper end of the flask. The pouring cup has a volume equal to 5% to 75% of the combined volume of the gating system and the pattern. A finely divided inert material, such as sand, is placed in the flask surrounding the pattern and fills the internal cavities within the pattern. The flask containing the pattern is then positioned in an outer pressure vessel having a removable lid and a molten metal is fed into the pouring cup. The lid on the pressure vessel is closed and an external gaseous pressure is applied to the molten metal in the pouring cup as the molten metal feeds through the gating system to the pattern and progressively decomposes the polymeric foam material. The gaseous products of decomposition passing into the interstices of the sand and the molten metal filling the void created by decomposition of the foam. By applying pressure to the molten metal during filling, the molten metal front is more stable and fewer casting defects arise.

A sprue structure is specifically designed to facilitate the rapid filling of molded polystyrene patterns with molten metal. It comprises a down sprue and parallel columnar members that are connected to the down sprue. The flow of molten metal is initially downward through the first columnar member and then it reverses direction to flow upwardly through second and third columnar members so that the patterns to be cast receive molten metal as it travels upwardly through the second and third columnar members. This decreases the amount of pyrolyzation products that could otherwise flow through in-gates and into the patterns to be cast.

An apparatus and method to delay the application of pressure on a molten metal front to equalize a pressure gradient present at the molten metal front during pressurized lost foam casting processes, or other pressurized casting processes. A pressure equalization member is placed over a pouring cup to divert the direct application of pressure to molten metal present in the pouring cup. The pressure equalization member allows for increased pressurization rates in such processes, facilitating interdendritic feeding while reducing microporosity and metal penetration defects.