Formable aluminum alloy sheet

Abstract

The present invention provides an aluminum alloy sheet for forming which is a high-Mg-content Al—Mg alloy sheet reduced in β-phase precipitation and improved in press formability. This aluminum alloy sheet for forming comprises an Al—Mg alloy containing 6.0-15.0 mass % Mg. In each of square regions, each side of which has the dimension of the whole sheet width (W), that are set in a surface of the alloy sheet, the concentration of Mg is measured at width-direction measurement points, Px, set at given intervals a and b respectively in the sheet-width direction and the sheet-length direction, and the average of the values of Mg concentration measured at the plurality of width-direction measurement points (Px) is taken as a width-direction average Mg concentration (Co). The concentration of Mg is measured at a plurality of thickness-direction measurement points (Py) set at a given interval in the sheet-thickness direction throughout the whole sheet thickness with respect to the plurality of width-direction measurement points (Px), and the average of the values of Mg concentration measured at the plurality of thickness-direction measurement points (Py) is taken as a thickness-direction average Mg concentration (Ci). The absolute value of the degree of regional Mg segregation (X) defined by the difference (Ci−Co) between the thickness-direction average Mg concentration (Ci) and the width-direction average Mg concentration (Co) is 0.5 mass % or less at most and is 0.1 mass % or less on average.

Description

TECHNICAL FIELD [0001]The present invention relates to a formable aluminum alloy sheet which is an Al—Mg alloy sheet containing Mg in a high content and has satisfactory formability.BACKGROUND ART [0002]As is well known, a variety of aluminum alloy sheets has been generally widely used in transportation machines such as automobiles, ships, aircraft, and vehicles; machines; electric products; construction materials; structures; optical appliances; and members or parts of wares, according to properties of respective alloy categories. Such aluminum alloy sheets often formed typically through stamping into the members and parts for use in these applications. Of aluminum alloys, Al—Mg alloys being in good balance between strength and ductility are advantageous for satisfactory formability. The Al—Mg alloys are represented by alloys prescribed in Japanese Industrial Standards (JIS) A 5052 and A 5182. These Al—Mg alloy sheets, however, have inferior ductility and thereby have inferior form...

AI Technical Summary

Benefits of technology

The present invention provides a formable aluminum alloy sheet that has controlled amounts of Mg, β phases, and other elements such as Fe, Si, Ti, B, Mn, Cr, Zr, V, Cu, and Zn. This results in better stamping performance, with reduced Mg segregation and improved performance. Controlled content of Mg and other elements can lead to even better results.

Problems solved by technology

These Al—Mg alloy sheets, however, have inferior ductility and thereby have inferior formability to customary cold-rolled steel sheets.

However, a sheet of such a high-Mg-content Al—Mg alloy is hardly industrially manufactured by a common manufacturing method of casting a material into an ingot typically through direct chill (DC) casting, soaking the ingot, and hot-rolling the soaked ingot.

This is because Mg is segregated in the ingot upon casting and causes the Al—Mg alloy to have significantly reduced ductility and to be liable to suffer from cracking upon common hot rolling process.

However, it is also difficult to manufacture the high-Mg-content Al—Mg alloy sheet through such low-temperature hot rolling.

This is because the high-Mg-content Al—Mg alloy material has remarkably high resistance to deformation upon the low-temperature rolling, and this extremely restricts sizes of products to be manufactured in view of performance of current rolling mills.

However, the material Al—Mg alloy, if containing the third element in a high content, tends to suffer from coarse intermetallic compounds and causes the aluminum alloy sheet to have low ductility.

Increase in Mg content therefore has a ceiling according to this technique, and it is difficult to allow an Al—Mg alloy to contain Mg in a content of more than 8 percent by mass.

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