Rapid extrusion of hot-short-sensitive alloys

A method for extruding products from an elevated temperature billet of hot-short-sensitive metal alloy at higher than conventional rates and/or at lower extrusion pressures than for single dies while maintaining a good surface finish, comprising

• (a) extruding a primary extrusion product from the billet through a primary reduction die having an extended land and producing an elevated in situ pressure on the primary extrusion product within the primary die,
• (b) cooling at least an outer surface portion of the primary extrusion product over substantially the entire extended land to reduce or maintain a temperature therein below the solidus temperature at the in situ pressure of the lowest-melting phase prior to a second reduction,
• (c) extruding the cooled primary extrusion product through a secondary die and maintaining the temperature of at least a substantial portion of the primary extrusion product above the recrystallization temperature and producing a back pressure contributing to the in situ pressure on the metal alloy in the primary reduction die sufficient to keep the primary extrusion product in contact with the extended primary die land and to reduce the tensile stresses therein, and
• (d) cooling the extruded product in the secondary extrusion die such that the temperature of at least an outer surface portion thereof is below the solidus temperature at atmospheric pressure of the lowest-melting phase after the second reduction.

A method for extruding products from an elevated-temperature billet of hot-short-sensitive metal alloy at higher than conventional rates and/or at lower extrusion pressures than for single dies while maintaining a good surface finish, comprising

• (a) extruding a primary extrusion product from the billet through a primary reduction die having an extended land,
• (b) cooling at least an outer surface region of the primary extrusion product over substantially the entire extended land to reduce or maintain the temperature thereof below the solidus temperature at atmospheric pressure of the lowest-melting phase prior to a second reduction,
• (c) extruding the cooled primary extrusion product through a secondary reduction die and maintaining the temperature of at least a substantial portion of the primary extrusion product above the recrystallization temperature and producing a back pressure on the metal alloy in the primary reduction die sufficient to keep the primary extrusion product in contact with the extended primary die land and to reduce tensile stresses therein, and
• (d) cooling an outer surface portion of the extruded product in the secondary die below the solidus temperature at atmospheric pressure of the lowest-melting phase while maintaining an interior portion thereof above the solidus temperature.