Casting of metal objects

A method of producing a metal casting in a mould assembly, comprising:

• filling liquid metal from a liquid metal source upwardly through at least one primary inlet into a mould cavity defined by a mould assembly, said mould assembly having at least one thermal extraction member comprising at least one large surface area region of a high thermally conductive material, said thermal extraction member being positioned in a lower part of said mould cavity;
• after filling said mould cavity with said liquid metal, transferring said mould assembly to a cooling station;
• solidifying said metal in said mould cavity, said thermal extraction member remaining in said lower part of said mould cavity during said solidifying to cause rapid and positive extraction of heat from said metal during said solidifying, such that positive heat extraction from said metal is maintained substantially for the duration of said solidifying to thereby achieve directional solidification throughout substantially all of the metal.

A method of producing a metal casting in a mould assembly comprising mould segments defining a mould cavity having at least one primary inlet below the top of the mould cavity for receiving liquid metal from a liquid metal source, said mould assembly having at least one thermal extraction member being at least one large surface area region of a high thermally conductive material positioned to cause rapid and positive extraction of heat from a solidifying casting in said mould assembly and a sealing means for sealing said mould cavity from the liquid metal source, said method comprising the steps of filling liquid metal from the liquid metal source into said mould assembly, sealing and isolating said mould assembly from said liquid metal source, removing heat from said thermal extraction member after sealing said mould cavity such that a shell of metal adjacent the thermal extraction member is solidified, and transferring at least the mould segments and metal contained therein to a cooling station, wherein said mould assembly is arranged such that positive heat extraction from said casting is maintained substantially for the duration of solidification of liquid metal in the casting to thereby achieve directional solidification throughout substantially all of the casting.