Heat treatment and extrusion of aluminum alloy

Claim 1

THE PROCESS THAT COMPRISES HEATING AN EXTRUSION BILLET FORMED OF PRECIPITATION HARDENABLE ALUMINUM ALLOY CONTAINING MAGNESIUM AND SILICON AS ITS PRIMARY HARDENING CONSTITUENTS, MAINTAINING SAID BILLET AT A TEMPERATURE FOR A PERIOD SUFFICIENT TO PLACE MOST OF SAID HARDENING CONSTITUENTS IN SOLUTION, THEN COOLING SAID BILLET FROM SAID TEMPERATURE DOWN TO ABOUT 800*F., FURTHER COOLING THE BILLET AT AN AVERAGE RATE OF AT LEAST ABOUT 300*F. PER HOUR FROM ABOUT 800*F. TO ABOUT 400*F., WHEREBY SAID BILLET IS CAPABLE OF EXTRUSION AT A TEMPERATURE BELOW ABOUT 875* F. AND AT RATES OF SPEED AND WITH RESULTANT MECHANICAL PROPERTIES COMPARABLE TO THOSE OF AN EXTRUSION FORMED FROM A BILLET SLOWLY COOLED FROM 800*F. TO 400 DEGREES F. AND SUBSEQUENTLY EXTRUDED AT AT TEMPERATURE IN EXCESS OF ABOUT 875*F., SUBSEQUENTLY REHEATING SAID BILLET TO EXTRUSION TEMPERATURE, AND THEN EXTRUDING THE MATERIAL OF SAID HEATED BILLET TO A PREDETERMINED SHAPE.