Aluminum alloy sheet

Inactive Publication Date: 2017-12-07
KOBE STEEL LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention relates to a method of improving the properties of a 6000-series aluminum alloy sheet used for automotic outer panels. The method involves controlling the production conditions of the sheet to balance the formation of solid solution and precipitation of pan-tempered treatment (PTT) compounds containing sulfur and phosphorus. This results in a sheet that has improved formability, has lowered strength, and enhances the room-temperature aging response. Additionally, the method facilitates the formation of large boundaries between the pan-tempered treatment compounds and the aluminum matrix to improve filiform corrosion resistance. Overall, the present invention provides an efficient way to produce an aluminum alloy sheet that combines excellent formability, BH response, and filiform corrosion resistance.

Problems solved by technology

There has hence been a problem in that they, when held at room temperature after a solution quenching treatment, undergo age hardening and increase in strength, thereby deteriorating in formability into panels.
Moreover, in the case where such room-temperature aging is great, there is also a problem that the BH response deteriorates and the heating during an artificial aging (hardening) treatment at a relatively low temperature, such as a paint baking treatment of the panel after being formed, does not improve the proof stress to such a degree that the panel comes to have the required strength.

Method used

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Examples

Experimental program
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examples

[0090]Examples of the present invention are explained. 6000-series aluminum alloy sheets were individually produced so as to differ in the average number density of Sn compounds having the specific composition and size and in the amount of the boundaries between the Sn compounds and the aluminum matrix, by changing the soaking treatment conditions or process annealing conditions. These sheets were held at room temperature for 30 days after the production, and then evaluated for strength, BH response (bake hardenability), hem workability, and filiform corrosion resistance. The results thereof are shown in Table 2.

[0091]Specific conditions used for producing the aluminum alloy sheets were as follows. Slabs of aluminum alloys respectively having the compositions shown in Table 1 were commonly produced through casting by the DC casting method. Here, the average rate of cooling from the liquidus temperature to the solidus temperature in the casting was set at 50° C. / min in common with al...

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Abstract

The present invention relates to an Al—Mg—Si sheet which contains, in terms of mass %, 0.3-1.0% Mg, 0.5-1.5% Si, 0.005-0.2% Sn, 0.02-1.0% Fe, and 0.02-0.6% Mn, with the remainder comprising Al and unavoidable impurities, characterized by having a structure wherein compounds that are detected with an SEM having a magnification of 500 diameters and are identified with an X-ray spectrometer include Sn compounds which contain Mn and Fe and which have an Sn content of 1.0 mass % or higher and a diameter of 0.3-20 μm in terms of equivalent circular diameter, the average number density of the Sn compounds being 500-3,000 / mm2, and wherein the length of the boundary between each Sn compound and the aluminum matrix is in the range of 3-20 / mm on average in terms of value obtained by dividing the total peripheral length of the Sn compound grain by the area thereof determined with the SEM. This aluminum alloy sheet satisfies the formability after natural aging at room temperature and bake hardenability which are required of automotive outer panels, and has excellent filiform rust resistance.

Description

TECHNICAL FIELD[0001]The present invention relates to an Al—Mg—Si alloy sheet, and especially relates to an aluminum alloy sheet excellent in formability, BH response and corrosion resistance. The term “aluminum alloy sheet” used in the present invention means an aluminum alloy sheet that is a rolled sheet, such as a hot-rolled sheet or cold-rolled sheet, and that has undergone refining, such as a solution heat treatment and a quenching treatment, and has not undergone a bake hardening treatment. Hereinafter, aluminum is referred to also as Al.Background Art[0002]In recent years, the social request for weight reduction in vehicles including automobiles is increasing more and more due to considerations to the global environment or the like. In order to meet the request, aluminum alloy materials which are excellent in terms of formability and bake hardenability and are more lightweight are coming to be increasingly used as materials for automotive panels, in particular, large body pan...

Claims

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Application Information

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IPC IPC(8): C22C21/02C22F1/05
CPCC22F1/05C22C21/02C22C21/06C22F1/00C22C21/08
InventorSHISHIDO, HISAOMATSUMOTO, KATSUSHIARUGA, YASUHIROTAKADA, SATORUOZAWA, TAKAHIROTATSUMI, AKIHIKO
OwnerKOBE STEEL LTD