Aluminum Alloy Forging Member and Process for Producing the Same

• US 20090000705A1
• Filed: 03/23/2007
• Published: 01/01/2009
• Est. Priority Date: 03/31/2006
• Status: Active Grant

• Current Assignee: Klaus Schmidt
• Original Assignee: Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel Limited)
• Inventors: Inagaki, Yoshiya, Nakai, Manabu, Fukuda, Atsumi
• Granted Patent: US 8,152,940 B2
• Time in Patent Office: Days
• US Class Current: 148/550
• CPC Class Codes: B21K 1/12 of specially-shaped cross-section
• CPC Class Codes: C22C 21/02 with silicon as the next major constituent
• CPC Class Codes: C22C 21/06 with magnesium as the next major constituent
• CPC Class Codes: C22F 1/00 Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working apparatus for mechanical working of metal B21, B23, B24
• CPC Class Codes: C22F 1/05 of alloys of the Al-Si-Mg type, i.e. containing silicon and magnesium in approximately equal proportions

Abstract

The present invention provides an aluminum alloy forging material having enhanced strength, toughness, and corrosion resistance, and a method of producing the material. An aluminum alloy forging material 1 produced with specified components under specified conditions has an arm portion 2 including a relatively narrow and thick peripheral rib 3 and a thin and relatively wide central web 4 having a thickness of 10 mm or less and having a substantially H-shaped sectional form. In a width-direction section of a maximum stress producing site of the rib 3a, the density of crystals observed in the structure of a sectional portion 7 where the maximum stress is produced, the spacing of grain boundary precipitates and the size and density of dispersed particles observed in the structure of a sectional portion 8 including a parting line, the recrystallization ratio observed in each of the sectional portions 7 and 8 of the rib, and the recrystallization ratio observed in a sectional portion 9 of the web 4a adjacent to the sectional structure of the rib 3a in the width direction are defined for enhancing the strength, toughness, and corrosion resistance of the aluminum alloy forging material.

Claims

1. An aluminum alloy forging material comprising an arm portion composed of, by % by mass, 0.5 to 1.25% of Mg, 0.4 to 1.4% of Si, 0.01 to 0.7% of Cu, 0.05 to 0.4% of Fe, 0.001 to 1.0% of Mn, 0.01 to 0.35% of Cr, 0.005 to 0.1% of Ti, Zr controlled to less than 0.15%, and the balance composed of Al and inevitable impurities, the material having a substantially H-shaped width-direction sectional form including a relatively narrow and thick peripheral rib and a relatively wide central web, wherein in a width-direction sectional structure in a maximum stress producing site of the rib, the density of crystals observed in the sectional structure in the maximum stress producing site is 1.5% or less in terms of an average area ratio, and the average spacing between grain boundary precipitates observed in the sectional structure including a parting line, which is produced in forging, is 0.7 μ

m or more.

2. The aluminum alloy forging material according to claim 1, wherein in the width-direction sectional structure in the maximum stress producing site of the rib, the size of dispersed particles observed in the sectional structure in the maximum stress producing site is 1200 Å

or less in terms of an average diameter, the density of the dispersed particles is 4% or more in terms of an average area ratio, the area ratio of recrystallized grains observed in the sectional structure of the rib is 10% or less in terms of an average area ratio, and the area ratio of recrystallized grains observed in a sectional structure of the web adjacent to the sectional structure of the rib in the width direction thereof is 20% or less in terms of an average area ratio.

3. The aluminum forging material according to claim 1, wherein the average area ratio of the crystals observed in the sectional structure of the maximum stress producing site is 1.0% or less, and the average spacing between the grain boundary precipitates observed in the sectional structure including the parting line, which is produced in forging, is 1.6 μ

m or more.

4. The aluminum alloy forging material according to claim 1, wherein the composition contains, by % by mass, 0.7 to 1.25% of Mg, 0.8 to 1.3% of Si, 0.1 to 0.6% of Cu, 0.1 to 0.4% of Fe, 0.2 to 0.6% of Mn, 0.1 to 0.3% of Cr, 0.01 to 0.1% of Ti, Zr controlled to less than 0.15%, and the balance composed of Al and inevitable impurities.

5. The aluminum alloy forging material according to claim 1, wherein the composition contains, by % by mass, 0.9 to 1.1% of Mg, 0.9 to 1.1% of Si, 0.3 to 0.5% of Cu, 0.1 to 0.4% of Fe, 0.2 to 0.6% of Mn, 0.1 to 0.2% of Cr, 0.01 to 0.1% of Ti, Zr controlled to less than 0.15%, and the balance composed of Al and inevitable impurities.

6. The aluminum alloy forging material according to claim 1, wherein the thickness of the web is as small as 10 mm or less.

7. A method for producing the aluminum alloy forging material according to claim 1 comprising:

casting at an average cooling rate of 100°

C./s or more an aluminum alloy melt having a composition containing, by % by mass, 0.5 to 1.25% of Mg, 0.4 to 1.4% of Si, 0.01 to 0.7% of Cu, 0.05 to 0.4% of Fe, 0.001 to 1.0% of Mn, 0.01 to 0.35% of Cr, 0.005 to 0.1% of Ti, Zr controlled to less than 0.15%, and the balance composed of Al and inevitable impurities, or the above-described preferred composition;

homogenizing heat-treating the cast ingot by heating in a temperature range of 460°

C. to 570°

C. at a heating rate of 10 to 1500°

C./hr and maintaining the ingot in the temperature range for 2 hours or more;

cooling the ingot to room temperature at a cooling rate of 40°

C./hr or more;

reheating the ingot to a hot-forging start temperature;

performing hot die-forging to form an aluminum alloy forging material including an arm portion which has a substantially H-shaped width-direction sectional form and which includes a relatively narrow and thick peripheral rib and a relatively wide central web, the forging finish temperature being 350°

C. or more;

performing solution treatment by maintaining the material in the temperature range of 530°

C. to 570°

C. for 20 minutes to 8 hours;

hardening the material at an average cooling rate in the range of 200 to 300°

C./s; and

performing artificial age hardening.