Image Number 3 for United States Patent #6253828.
For the production of precision cast objects a gas change method is used. A melting crucible (1) and a casting mold (2) with at least partially porous walls are disposed in a gastight receptacle (5). The casting mold (2) with the mold cavity (3) is evacuated before the pouring-in process and subsequently flushed with a light gas, for example helium. After the mold cavity (3) is filled, the surface level (18) of the melt in the casting mold (2) is acted upon by a second heavy gas, for example argon, and subjected to excess pressure. A better degree of filling of the mold cavity (3) and an improved structure of the cast object results.