Metal treatment – Stock – Aluminum base
Reexamination Certificate
2002-05-16
2004-04-27
Wyszomierski, George (Department: 1742)
Metal treatment
Stock
Aluminum base
C420S532000, C420S535000, C420S553000
Reexamination Certificate
active
06726785
ABSTRACT:
FIELD
The present invention relates to an aluminum alloy sheet material and a method for producing the same.
BACKGROUND
Wrought materials using an aluminum alloy are used in many fields by taking advantage of its lighter weight as compared with steel materials. For example, in recent years, automobiles are desired to be light weight for reducing the amount of exhaust gases (to prevent environmental pollution) and for improving fuel efficiencies, considering the effect on global environments. For attaining the above objective, use of an aluminum alloy is being investigated. It is thought that sheet materials using an aluminum alloy are able to be applied for various sheet members, such as outer materials including a hood and a door, or inner materials of automobiles, and that they can greatly contribute for making the body of the automobile lightweight.
Aluminum alloys of 5000-series and 6000-series are representative materials that have been conventionally used for such the aluminum alloy sheet material for automobiles. However, there are such problems for applying these alloy sheet materials for the automobile that they are a little inferior in mechanical strength to steel materials even by taking hardening after baking into consideration, that cracks are liable to occur in forming with a press and the like due to inferior formability to other materials including steel materials, and that the material is broken at a bending portion formed by hem-bending to bend the periphery of the sheet material when it is used as an outer material. Since impurity contents of these alloys are strictly prescribed, a virgin ingot of aluminum and mother alloys containing various kinds of additive elements should be blended as raw materials for producing the sheet material. Accordingly, it is difficult to use aluminum alloy scraps or secondary ingots and the like that are supplied from markets and contain a rather large amount of impurities, for applying to these sheet materials by re-melting them as they are, rendering them difficult for recycling.
SUMMARY
The present invention is an aluminum alloy sheet material, which comprises 2.6% by mass or more and less than 3.5% by mass of Si (% by mass is simply denoted by % hereinafter), 0.05 to 0.5% of Mg, 0.5% or more and less than 1.2% of Cu, 0.6 to 1.5% of Mn, 0.5 to 1.6% of Zn, and 0.3 to 2.0% of Fe, and which comprises, if necessary, at least one selected from the group consisting of 0.01 to 0.2% of Cr, 0.01 to 0.2% of Zr, 0.01 to 0.2% of V, and 0.01 to 0.2% of Ti, with the balance of Al and unavoidable impurities.
Further, the present invention is a method for producing an aluminum alloy sheet material, which method comprises:
melting and casting an aluminum alloy which comprises 2.6% or more and less than 3.5% of Si, 0.05 to 0.5% of Mg, 0.5% or more and less than 1.2% of Cu, 0.6 to 1.5% of Mn, 0.5 to 1.6% of Zn, and 0.3 to 2.0% of Fe, and which comprises, if necessary, at least one selected from the group consisting of 0.01 to 0.2% of Cr, 0.01 to 0.2% of Zr, 0.01 to 0.2% of V, and 0.01 to 0.2% of Ti, with the balance of Al and unavoidable impurities;
hot-rolling the cast aluminum alloy after applying homogenizing treatment;
cold-rolling the rolled aluminum alloy, to form a sheet thereof with a prescribed thickness; and
subjecting the sheet to heat-treatment by holding the sheet at a temperature of 450° C. or more for a time period of 120 seconds or less, and cooling to a temperature of 100° C. or less at a cooling speed of 100° C./min or more;
wherein, with respect to the aluminum alloy sheet material, tensile strength and 0.2% proof stress, when they are represented by T (MPa) and Y (MPa), respectively, satisfy conditions as shown by the following formula:
T
2
/Y
≧350.
Further, the present invention is a method for producing an aluminum alloy sheet material, which method comprises:
melting and casting an aluminum alloy which comprises 2.6% or more and less than 3.5% of Si, 0.05 to 0.5% of Mg, 0.5% or more and less than 1.2% of Cu, 0.6 to 1.5% of Mn, 0.5 to 1.6% of Zn, and 0.3 to 2.0% of Fe, and which comprises, if necessary, at least one selected from the group consisting of 0.01 to 0.2% of Cr, 0.01 to 0.2% of Zr, 0.01 to 0.2% of V, and 0.01 to 0.2% of Ti, with the balance of Al and unavoidable impurities;
hot-rolling the cast aluminum alloy after applying homogenizing treatment;
cold-rolling the rolled aluminum alloy, to form a sheet thereof with a prescribed thickness; and
subjecting the sheet to heat-treatment by holding the sheet at a temperature of 300° C. or more and 420° C. or less for a time period of 30 minutes or more, and cooling to room temperature at a cooling rate of 60° C./min or less;
wherein, with respect to the aluminum alloy sheet material, 0.2% proof stress is 100 MPa or less.
Further, the present invention is a method for producing an aluminum alloy sheet material, which method comprises:
melting and casting an aluminum alloy which comprises 2.6% or more and less than 3.5% of Si, 0.05 to 0.5% of Mg, 0.5% or more and less than 1.2% of Cu, 0.6 to 1.5% of Mn, 0.5 to 1.6% of Zn, and 0.3 to 2.0% of Fe, and which comprises, if necessary, at least one selected from the group consisting of 0.01 to 0.2% of Cr, 0.01 to 0.2% of Zr, 0.01 to 0.2% of V, and 0.01 to 0.2% of Ti, with the balance of Al and unavoidable impurities,
wherein a cooling rate for solidifying a molten liquid is adjusted to 50° C./sec or more by continuous cast-rolling, in the melting and casting step.
Other and further features and advantages of the invention will appear more fully from the following description.
DETAILED DESCRIPTION
According to the present invention, there is provided the following means:
(1) An aluminum alloy sheet material, comprising 2.6% or more and less than 3.5% of Si, 0.05 to 0.5% of Mg, 0.5% or more and less than 1.2% of Cu, 0.6 to 1.5% of Mn, 0.5 to 1.6% of Zn, and 0.3 to 2.0% of Fe, with the balance of Al and unavoidable impurities;
(2) The aluminum alloy sheet material described in item (1), further containing a component originating from scraps of an aluminum alloy in at least a part of the sheet material;
(3) The aluminum alloy sheet material described in item (1) or (2), wherein concentrations of Si, Mn and Fe, when they are represented by A%, B% and C%, respectively, satisfy conditions as shown by the following formula:
(0.015×
A+
0.15×
B+
0.03×
C
)≦0.445, and
wherein a density of precipitates with an average diameter of 100 &mgr;m or more is 2 precipitates/cm
2
or less;
(4) The aluminum alloy sheet material described in item (1), (2) or (3), wherein tensile strength and 0.2% proof stress, when they are represented by T (MPa) and Y (MPa), respectively, satisfy conditions as shown by the following formula:
T
2
/Y
≧350;
(5) The aluminum alloy sheet material described in item (1), (2) or (3), wherein 0.2% proof stress is 100 MPa or less;
(6) The aluminum alloy sheet material described in item (1), (2) or (3), wherein 0.2% proof stress after baking of a coating is higher by 30 MPa or more than 0.2% proof stress before baking;
(7) A method for producing the aluminum alloy sheet material described in item (4), comprising:
melting and casting an aluminum alloy which comprises 2.6% or more and less than 3.5% of Si, 0.05 to 0.5% of Mg, 0.5% or more and less than 1.2% of Cu, 0.6 to 1.5% of Mn, 0.5 to 1.6% of Zn, and 0.3 to 2.0% of Fe, with the balance of Al and unavoidable impurities;
hot-rolling the cast aluminum alloy after applying homogenizing treatment;
cold-rolling the rolled aluminum alloy, to form a sheet thereof with a prescribed thickness; and
subjecting the sheet to heat-treatment by holding the sheet at a temperature of 450° C. or more for a time period of 120 seconds or less, and cooling to a temperature of 100° C. or less at a cooling speed of 100° C./min or more;
(8) A method for producing the aluminum alloy sheet material described in (5) comprising:
melting and casting an aluminum alloy which comprises 2.6% or more and less than 3.5% of Si, 0.05 to 0.5% of Mg, 0.5% or more and less
Bekki Yoichiro
Hayashi Noboru
Kuroki Morio
Oyama Koji
Combs Morillo Janelle
Knobbe Martens Olson & Bear LLP
The Furukawa Electric Co. Ltd.
Wyszomierski George
LandOfFree
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