Method For Producing High Strength Aluminum Alloy Extruded Material With High SCC Resistance

Abstract

A method includes: casting a billet using an aluminum alloy comprising, by mass: 6.0 to 8.0% of Zn, 1.5 to 2.8% of Mg, 0.10 to 0.50% of Cu, 0.10 to 0.50% of Zr, 0.005 to 0.05% of Ti, 0.10 to 0.40% of Mn, 0.05% or less of Cr, with a total of Mn+Cr+Zr being 0.10 to 0.50%, and a balance of Al and inevitable impurities; subjecting the resulting casted billet to homogenization treatment at 470 to 560° C. for 1 to 14 hours, followed by cooling at a cooling rate of 50° C./hr or higher; and subjecting the billet to extrusion process, immediately followed by air cooling until the temperature of an extruded material drops to 300 to 480° C., and further cooling to 200° C. or less at a cooling rate within a range of 150 to 950° C./min, and thereafter subjecting the extruded material to artificial aging treatment.

1 . A method for producing a high strength aluminum alloy extruded material with high SCC resistance, the method comprising:
 casting a billet using an aluminum alloy comprising, by mass: 6.0 to 8.0% of Zn, 1.5 to 2.8% of Mg, 0.10 to 0.50% of Cu, 0.10 to 0.50% of Zr, 0.005 to 0.05% of Ti, 0.10to 0.40% of Mn, 0.05% or less of Cr, with a total of Mn+Cr+Zr being 0.10 to 0.50%, and a balance of Al and inevitable impurities;   subjecting the resulting casted billet to homogenization treatment at 470 to 560° C. for 1 to 14 hours, followed by cooling at a cooling rate of 50° C./hr or higher; and   subjecting the billet to extrusion process, immediately followed by air cooling until the temperature of an extruded material drops to 300 to 480° C., and further cooling to 200° C. or less at a cooling rate within a range of 150 to 950° C./min, and thereafter subjecting the extruded material to artificial aging treatment.   
     
     
         2 . The method for producing a high strength aluminum alloy extruded material with high SCC resistance according to  claim 1 , wherein the artificial aging treatment comprises:
 a first stage at 80 to 130° C. for 2 to 8 hours, and a second stage at 130 to 160° C. for 2 to 16 hours, and   wherein the extruded material has a 0.2% proof strength of 460 MPa or more and high SCC resistance.