Metal treatment – Stock – Aluminum base
Reexamination Certificate
2000-02-16
2001-12-04
Wyszomierski, George (Department: 1742)
Metal treatment
Stock
Aluminum base
C420S532000
Reexamination Certificate
active
06325870
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an aluminum sheet material having excellent mechanical strength, press formability, bending property, and weldability; and, more particularly, to an aluminum sheet material for automobiles that can be produced at low cost by making use of recovered aluminum materials, such as recycled aluminum casting scraps of automobiles, recycled aluminum can scraps, recycled aluminum sash scraps, and the like, as raw materials, and a method of producing the same.
BACKGROUND ART
Conventionally, cold-rolled steel sheets have been mainly used for automotive body panels. In recent years, however, there has been a strong demand for reducing the weight of automobile bodies, from the viewpoint of improving mileage, and the use of aluminum sheets or plates instead of steel sheet has been studied. Further, aluminum sheets are now actually being utilized for part of automobile bodies. Excellent press formability, high mechanical strength, good corrosion resistance, and the like are required for the aluminum sheets as a material of automotive body panels. An Al—Mg—Si alloy (6000-group alloy), such as 6061-alloy and the like, has been conventionally used as an aluminum alloy for a material to meet such demands as described above.
However, there have been problems that sufficient weldability cannot be obtained by the aforementioned 6000-group alloy, the cost of the aforementioned 6000-group alloy is higher than that of steel sheet, and the like.
An object of the present invention is to provide an aluminum sheet material whose weldability is improved while ensuring mechanical strength and bending property required for a material for automobile body panels.
Another object of the present invention is to provide an aluminum sheet material possessing such characteristics required for a material for automobile body panels, which can be produced at low cost by making use of recycled aluminum materials.
DISCLOSURE OF INVENTION
The present inventors have studied in earnest taking the aforementioned problems into consideration. Consequently, the present inventors found that an aluminum sheet material having the following specific composition could solve the aforementioned problems. The present invention was attained based on that finding.
(1) An aluminum sheet material for automobiles, which comprises 3.5 to 5 wt % of Si, 0.3 to 1.5 wt % of Mg, 0.4 to 1.5 wt % of Zn, 0.4 to 1.5 wt % of Cu, 0.4 to 1.5 wt % of Fe, and 0.6 to 1 wt % of Mn, and comprises one or more members selected from the group of 0.01 to 0.2 wt % of Cr, 0.01 to 0.2 wt % of Ti, 0.01 to 0.2 wt % of Zr, and 0.01 to 0.2 wt % of V, with the balance of aluminum and unavoidable impurities.
(2) A method of producing an aluminum sheet material for automobiles that is the aluminum sheet material for automobiles as stated in the above (1), wherein at least one member selected from the group of automobile aluminum parts scraps containing 2.5 wt % or above of Si, aluminum can scraps containing 1 wt % or above of Mg, or aluminum sash scraps containing 0.2 wt % or above of Mg, is used as at least a part of aluminum alloy casting ingot.
(3) The method of producing an aluminum sheet material for automobiles as stated in the above (2), wherein the recycled scraps can be used up to maximum 100% as raw materials for the aluminum alloy casting ingot.
(4) An aluminum sheet material for automobiles, which has an aluminum alloy composition comprising between more than 2.6 wt % and 5 wt % of Si, 0.2 to 1.0 wt % of Mg, 0.2 to 1.5 wt % of Zn, 0.2 to 1.5 wt % of Cu, 0.2 to 1.5 wt % of Fe, and between 0.05 and less than 0.6 wt % of Mn, and comprising one or more members selected from the group of 0.01 to 0.2 wt % of Cr, 0.01 to 0.2 wt % of Ti, 0.01 to 0.2 wt % of Zr, and 0.01 to 0.2 wt % of V, with the balance of aluminum and unavoidable impurities.
(5) A method of producing an aluminum sheet material for automobiles that is the aluminum sheet material for automobiles as stated in the above (4), wherein automobile aluminum parts scraps are used for at least a part of raw materials of a casting ingot for the aluminum alloy, in the production of the aluminum sheet material for automobiles.
(6) The method of producing an aluminum sheet material for automobiles that is the aluminum sheet material for automobiles as stated in the above (1) or (4), wherein reduction from a casting ingot to a final product is 98% or above, in the production of the aluminum sheet material for automobiles.
BEST MODE FOR CARRYING OUT THE INVENTION
A first embodiment of the aluminum sheet material for automobiles of the present invention is an aluminum sheet material for automobiles, characterized by comprising 3.5 to 5 wt % of Si, 0.3 to 1.5 wt % of Mg, 0.4 to 1.5 wt % of Zn, 0.4 to 1.5 wt % of Cu, 0.4 to 1.5 wt % of Fe, and 0.6 to 1 wt % of Mn, and further comprising one or more members selected from the group of 0.01 to 0.2 wt % of Cr, 0.01 to 0.2 wt % of Ti, 0.01 to 0.2 wt % of Zr, and 0.01 to 0.2 wt % of V, with the balance of aluminum and unavoidable impurities.
The aluminum sheet material of the first embodiment is described more in detail.
Si content is generally 3.5 to 5 wt %. Si improves the mechanical strength of Al sheet material and ensures the required elongation. If the Si content is too low, such effects will be insufficient. Further, if the Si content is too high, elongation lowers, and further the bending property also lowers.
Mg content is generally 0.3 to 1.5 wt %, preferably 0.3 to 0.8 wt %. Mg forms an intermetallic compound with the above-mentioned Si and improves mechanical strength by deposition of Mg
2
Si. If the Mg content is too low, such effects are insufficient, and when too high, elongation lowers.
Zn content is generally 0.4 to 1.5 wt %, preferably 0.4 to 1.2 wt %. Zn lowers the melting point of Al sheet material of the present invention and improves spot weldability, simultaneously improving surface treatment property, thereby improving the degreasing property and the chemical conversion property. When the Zn content is too low, the chemical conversion property is poor, and when too high, corrosion resistance deteriorates.
Cu content is generally 0.4 to 1.5 wt %, preferably 0.4 to 1.2 wt %. Cu lowers the electric conductivity and the melting point of Al sheet material, and improves spot weldability. Further it contributes to improving impact absorption energy, because of enhancement of the mechanical strength of Al sheet material. When the Cu content is too low, such effects are insufficient, and when too high, elongation lowers.
Fe content is generally 0.4 to 1.5 wt %, preferably 0.4 to 1.2 wt %. Fe contributes to improving toughness and impact absorption energy, because of grain refining. When the Fe content is too low, such effects are insufficient, and when too high, surface appearance deteriorates, because of a large crystallized phase.
Mn content is generally 0.6 to 1.0 wt %, preferably 0.6 to 0.8 wt %. Mn lowers the electric conductivity of Al sheet material, and enhances the mechanical strength thereof. When the Mn content is too low, such effects are insufficient, and when too high, elongation and bending property lower.
Further, an element selected from the group of Cr, Ti, Zr, and V improves the bending property and toughness of Al sheet material of the first embodiment, by grain refining, thereby improving press formability and energy absorptivity. Cr content is generally 0.01 to 0.2 wt %, preferably 0.01 to 0.1 wt %; Ti content is generally 0.01 to 0.2 wt %, preferably 0.01 to 0.1 wt %; Zr content is generally 0.01 to 0.2 wt %, preferably 0.01 to 0.1 wt %, and V content is generally 0.01 to 0.2 wt %, preferably 0.01 to 0.1 wt %.
A second embodiment of the present invention is an aluminum sheet material for automobiles, characterized by having an aluminum alloy composition comprising, as essential elements, between more than 2.6 wt % and 5 wt % of Si, 0.2 to 1.0 wt % of Mg, 0.2 to 1.5 wt % of Zn, 0.2 to 1.5 wt % of Cu, 0.2 to 1.5 wt % of Fe, and between 0.05 and less than 0.6 wt % of Mn, and further comprisi
Bekki Yoichiro
Hayashi Noboru
Kashiwazaki Kazuhisa
Birch & Stewart Kolasch & Birch, LLP
Combs-Morillo Janelle
The Furukawa Electric Co. Ltd.
Wyszomierski George
LandOfFree
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