Method and apparatus for centrifugal casting

A method for the centrifugal casting of metal articles, said method comprising the steps of

• providing a rotary mold assembly having a cylindrical mold having an inner mold surface with a longitudinal length and a generally open axial end, said mold having at least one air inlet for directing air to said mold surface and at least one air outlet for discharging air from said mold surface, said air outlet being spaced radially outward with respect to said air inlet,
• providing an air permeable primary lining on said inner mold surface, said primary lining being in communication with said air inlet and said air outlet,
• providing an air impermeable mold facing layer on said air permeable lining, wherein said air impermeable mold facing layer is formed by introducing a predetermined amount of particles of a dry, binderless milled second refractory material onto said primary lining while continuously rotating said cylindrical mold at a sufficient speed to distribute said refractory material along said primary lining and form a layer of said refractory material on said primary lining, and contacting said layer of said second refractory material with a plowing material with a plowing tool while continuously rotating said cylindrical mold to physically redistribute, compact and densify said particles of said layer of said second refractory material and to form said air impervious mold facing layer to predetermined dimensions, and further shaping said mold lining with a contouring tool,
• rotating said mold at a speed sufficient to cast a molten metal against said inner surface of said mold and to draw air in said air inlet through said air permeable mold facing layer on said mold surface and to discharge air through said air outlet, and
• introducing a molten metal onto said air impermeable mold facing layer and molding said metal.

A method of casting a metal article comprising the steps of:

• rotating a rotary mold having an inner mold surface with a longitudinal length and a generally open axial end,
• introducing an amount of particles of a dry, binderless milled refractory material into said rotating mold and distributing said refractory material by centrifugal force against said inner mold surface to form a loose layer of refractory material,
• positioning a plowing tool in said mold, said plowing tool having a working surface with a leading edge and a trailing edge with respect to a direction of rotation of said mold,
• moving said plowing tool to a first position where said working surface of said plowing tool penetrates and plows said loose layer toward said mold surface, where said working surface is at an angle such that said trailing edge penetrates said loose layer to a depth greater than said leading edge to compact and densify a bottom portion of said layer of refractory material and form a compacted densified air impervious layer having a thickness,
• gradually moving said plowing tool away from said mold surface to a second position spaced outwardly from said first position to increase the thickness of said compacted densified layer to compact and densify the entire depth of said layer of refractory layer to form a compacted and densified air impervious layer,
• contacting said air impervious layer with a contouring tool and contouring said air impervious layer by removing a portion of said refractory material from said air impervious layer, and
• introducing a molten metal onto said air impervious layer and molding said metal article.