Aluminum alloy for small-bore hollow shape use excellent in extrudability and intergranular corrosion resistance and method of production of same

Abstract

Provided as an aluminum alloy for finely hollow shapes is an aluminum alloy that is reduced in the content of Cu, which is problematic with respect to intergranular corrosion resistance, and that can be kept having a noble self-potential and has excellent extrudability. The alloy has a chemical composition which contains 0.05-0.15 mass % Fe, up to 0.10 mass % Si, 0.03-0.07 mass % Cu, 0.30-0.55 mass % Mn, 0.03-0.06 mass % Cr, and 0.08-0.12 mass % Ti and which optionally further contains up to 0.08 mass % V so as to satisfy the relationship Ti+V=0.08 to 0.2 mass %. Also provided is a process for producing a finely hollow aluminum alloy shape.

1 . An aluminum alloy for small-bore hollow shape use which is excellent in extrudability and intergranular corrosion resistance which has a chemical composition which contains Fe: 0.05 to 0.15 mass %, Si: 0.10 mass % or less, Cu: 0.03 to 0.07 mass %, Mn: 0.30 to 0.55 mass %, Cr: 0.03 to 0.06 mass %, and Ti: 0.08 to 0.12 mass % and has a balance of Al and unavoidable impurities. 
     
     
         2 . The aluminum alloy for small-bore hollow shape use which is excellent in extrudability and intergranular corrosion resistance as set forth in  claim 1 , further containing V: 0.08% mass % or less in a relationship giving Ti+V: 0.08 to 0.2 mass %. 
     
     
         3 . A method of production of an aluminum alloy for small-bore hollow shape use which is excellent in extrudability and intergranular corrosion resistance comprising homogenization by heating a DC cast billet of an aluminum alloy which has a chemical composition as set forth in  claim 1  at a speed of 80° C./hour or less to 550 to 590° C., holding it there for 0.5 to 6 hours then holding it at 450 to 350° C. in range for 0.5 to 1 hour or cooling by a cooling speed of 50° C./hour down to 200° C. or less. 
     
     
         4 . A method of production of a small-bore hollow shape made of an aluminum alloy which is excellent in intergranular corrosion resistance comprising homogenization by heating a DC cast billet of an aluminum alloy which has a chemical composition as set forth in  claim 1  at a speed of 80° C./hour or less to 550 to 590° C., holding it there for 0.5 to 6 hours then holding it at 450 to 350° C. in range for 0.5 to 1 hour or cooling by a cooling speed of 50° C./hour down to 200° C. or less, reheating the billet to 450 to 550° C., then extruding it to a desired shape by a working degree of an extrusion ratio of 30 to 1000.