High-strength aluminum alloy extruded product exhibiting excellent corrosion resistance and method of manufacturing same

• US 8,298,357 B2
• Filed: 03/02/2011
• Issued: 10/30/2012
• Est. Priority Date: 04/07/2003
• Status: Active Grant

• Current Assignee: The Society of Japanese Aerospace Companies, Sumitomo Light Metal Industries Limited (UACJ Corporation)
• Original Assignee: The Society of Japanese Aerospace Companies, Sumitomo Light Metal Industries Limited (UACJ Corporation)
• Inventors: Sano, Hideo, Yoshino, Yasuaki
• Primary Examiner(s): Wyszomierski, George
• Assistant Examiner(s): MORILLO, JANELL COMBS
• Application Number:
  US12/932,634
• Publication Number:
  US 20110155291A1
• Time in Patent Office: 608 Days
• Field of Search: 148/690, 148/689, 722/64, 72265-269
• US Class Current: 148/690
• CPC Class Codes: B21C 23/002 Extruding materials of special alloys so far as the composition of the alloy requires or permits special extruding methods of sequences
• CPC Class Codes: B21C 23/08 Making wire, bars, tubes
• CPC Class Codes: B21C 25/02 Dies
• CPC Class Codes: B21C 25/025 Selection of materials therefor
• CPC Class Codes: C22C 21/14 with silicon
• CPC Class Codes: C22C 21/16 with magnesium

Abstract

The present invention provides a high-strength aluminum alloy extruded product exhibiting excellent corrosion resistance and secondary workability and suitably used as a structural material for transportation equipment such as automobiles, railroad vehicles, and aircrafts, and a method of manufacturing the same. The aluminum alloy extruded product has a composition containing 0.6 to 1.2% of Si, 0.8 to 1.3% of Mg, and 1.3 to 2.1% of Cu while satisfying the following conditional expressions (1), (2), (3) and (4),
3%≦Si %+Mg %+Cu %≦4%  (1)
Mg %≦1.7×Si %  (2)
Mg %+Si %≦2.7%  (3)
Cu %/2≦Mg %≦(Cu %/2)+0.6%  (4)
and further containing 0.04 to 0.35% of Cr, and 0.05% or less of Mn as an impurity, with the balance being aluminum and unavoidable impurities. The cross section of the extruded product has a recrystallized structure with an average grain size of 500 μm or less.

Claims

1. A method of manufacturing an aluminum alloy extruded product, comprising the steps of:

extruding a billet of an aluminum alloy having a composition comprising, in mass %, 0.6-1.2% Si, 0.8-1.3% Mg, 1.3-2.1% Cu, 0.04-0.35% Cr and no more than than 0.05% Mn as an impurity, with the balance being aluminum and unavoidable impurities and the following (1)-(4) relationships being satisfied,

3%≦

Si %+Mg %+Cu %≦

4% 

 

(1)

Mg %≦

1.7×

Si % 

 

(2)

Mg %+Si %≦

2.7% 

 

(3)

Cu %/2≦

Mg %≦

(Cu %/2)+0.6% 

 

(4)

into a hollow product by using a porthole die having a ratio, D/W, of chamber depth D to bridge width W of 0.5 or more while setting a ratio of a flow speed of the aluminum alloy in a non-joining section to a flow speed of the aluminum alloy in a joining section in a chamber, where the billet reunites after entering a port section of the die in divided flows and subsequently encircling a mandrel, at 1.5 or less, to obtain a hollow extruded product having a cross-sectional structure which has a recrystallization microstructure with a grain size of no more than 500 μ

m and, in which, a surface defect is not observed after the hollow extruded product is subjected to a solution heat treatment by heating to 530°

C. at a temperature rise rate of 10°

C./sec, water quenching within 10 seconds after completion of the solution heat treatment, aged at 180°

C. for 10 hours and subjected to 90°

bending.

2. The method of claim l, additionally comprising the steps of homogenizing the billet at a temperature equal to or higher than 500°

C. and lower than the melting point of the aluminum alloy and heating the homogenized billet to a temperature equal to or higher than 470°

C. and lower than the melting point of the aluminum alloy and extruding the billet.

4. The method of claim 2, additionally comprising a quenching step of maintaining a surface temperature of the extruded product immediately after extrusion at 450°

C. or higher and then cooling the extruded product to 100°

C. or lower at a cooling rate of 10°

C./sec or more or subjecting the extruded product to a solution heat treatment at a temperature of 480 to 580°

C. at a temperature rise rate of 5°

C./sec or more and then a quenching step of cooling the extruded product to 100°

C. or lower at a cooling rate of 10°

C./sec or more and a tempering step of heating the extruded product at 170 to 200°

C. for 2 to 24 hours.

3. The method of claim l, additionally comprising a quenching step of maintaining a surface temperature of the extruded product immediately after extrusion at 450°

C. or higher and then cooling the extruded product to 100°

C. or lower at a cooling rate of 10°

C./sec or more or subjecting the extruded product to a solution heat treatment at a temperature of 480 to 580°

C. at a temperature rise rate of 5°

C./sec or more and then a quenching step of cooling the extruded product to 100°

C. or lower at a cooling rate of 10°

C./sec or more and a tempering step of heating the extruded product at 170 to 200°

C. for 2 to 24 hours.