Riser pattern mfr. - using core made of material removable by melting, shrinking, or vaporising

摘要

The core is surrounded by a shell made of gas permeable material with the heat insulating and/or exothermically reacting properties. A pneumatic core is formed as an integral part in the shell. A zirconium sand layer is pref. introduced into the cavity to act as a knock-off core. This provides a ready means of removing the core, independent of the degree of permeability of the shell.