DE112011102796T5 - Formable aluminum alloy sheet - Google Patents

Abstract

The present invention provides an aluminum alloy sheet for forming, which is a high Mg content Al-Mg alloy sheet having a reduced β-phase precipitate and improved press formability. This aluminum alloy sheet for forming comprises an Al-Mg alloy comprising 6.0 to 15.0 mass% of Mg. In each of square areas, each side of which has the dimensions of the total sheet width (W) set in a surface of the alloy sheet, the concentration of Mg is measured at widthwise measuring points Px at predetermined intervals a and b in the width direction of the sheet and the longitudinal direction of the sheet are set, and the average of the values of the Mg concentration measured at the plurality of widthwise measuring points (Px) is used as the average Mg concentration in the width direction (Co). The concentration of Mg is measured at a plurality of measuring points in the thickness direction (Py) set at a predetermined interval in the thickness direction of the sheet over the entire sheet thickness with respect to the plurality of measuring points in the width direction (Px), and the average of Values of the Mg concentration measured at the plurality of measuring points in the thickness direction (Py) are used as the average Mg concentration in the thickness direction (Ci). The absolute value of the degree of regional Mg segregation (X) defined by the difference (Ci-Co) between the average Mg concentration in the thickness direction (Ci) and the average Mg concentration in the width direction (Co) is at most 0 , 5 mass% or less and on average 0.1 mass% or less.

Description

Technical area

The present invention relates to a workable aluminum alloy sheet which is an Al-Mg alloy sheet having a high Mg content and a satisfactory workability.

State of the art

It is known that various aluminum alloy sheets in transport machines, such. As automobiles, ships, aircraft and vehicles, machinery, electrical products, construction materials, structures, optical devices and elements or parts of goods according to the characteristics of respective alloy categories are widely used. Such aluminum alloy sheets are often typically formed by stamping to the elements and parts for use in these applications. Of aluminum alloys, Al-Mg alloys, which have a good balance of strength and ductility, are advantageous for satisfactory formability. The Al-Mg alloys are represented by alloys that are in Japanese Industrial Standards (JIS) A 5052 and A 5182 are described. However, these Al-Mg alloy sheets have poor ductility and thereby poor formability as compared with cold-rolled steel sheets. To overcome these disadvantages, chemical compositions of Al-Mg alloy sheets and the optimization of their production conditions have been studied.

Typically, an Al-Mg alloy, if it has an increased Mg content of more than 6 mass%, preferably more than 8 mass%, may have a better strength-ductility balance. However, a sheet of such Mg-containing Al-Mg alloy can hardly be industrially produced by a usual manufacturing method of casting a material into a billet, typically by direct-cooling (DC) casting, soaking the billet, and hot-rolling the warmed block getting produced. This is because Mg undergoes segregation during casting in the block and results in the Al-Mg alloy having significantly reduced ductility and tending to crack in conventional hot rolling processes.

One possible solution for avoiding the temperature range at which cracking occurs is hot rolling at a low temperature. However, it is also difficult to produce the high Mg Al-Mg alloy sheet by such low-temperature hot rolling. This is because the high Mg content Al-Mg alloy material in low temperature rolling has a considerable resistance to deformation, and this extremely limits the sizes of products to be manufactured in view of the performance of current rolling mills strong. Regardless of this, a technique of adding a third element, such as. As Fe or Si, proposed so that an Al-Mg alloy may contain Mg in a higher content. However, the material of the Al-Mg alloy, when it has a high content of the third element, tends to have coarse intermetallic compounds and causes the aluminum alloy sheet to have a low ductility. Therefore, the increase of the Mg content has an upper limit according to this technique, and there are problems when an Al-Mg alloy contains Mg in a content of more than 8 mass%.

As possible solutions to these problems, various techniques have been proposed for making high Mg content Al-Mg alloy sheets by a continuous two-roll casting or other continuous casting process.

For example, Patent Document (PTL) 1 describes an aluminum alloy sheet for automobiles, which is manufactured by a continuous two-roll casting and which is a high-Mg Al-Mg alloy sheet having a Mg content of 6 to 10 mass% Al-Mg intermetallic compounds have an average size of 10 μm or less.

PTL 2 describes an aluminum alloy sheet for automobile body panels made by continuous casting, which is an Al-Mg alloy sheet having a Mg content of 2.5 to 8 mass%. The aluminum alloy sheet contains Al-Mg intermetallic compounds having sizes of 10 μm or more in a number density of 300 / mm ² or less, and has an average grain size of 10 to 70 μm.

PTL 3 describes an Al-Mg alloy sheet produced by a continuous two-roll casting and having an Mg content of 8 to 14 mass%. When Mg concentrations in the thickness direction of the Al-Mg alloy sheet are measured and averaged to obtain an average, absolute values of differences (deviation widths) between the average Mg concentration and the respective Mg concentrations have a maximum of 4 mass% or less and an average of 0.8 mass% or less. This can inhibit the precipitation of Al-Mg intermetallic compounds.

documents list

Patent documents

• PTL 1: Japanese Unexamined Patent Application Publication (JP-A) No. H 07-252571
• PTL 2: JP-A No. H 08-165538
• PTL 3: JP-A No. 2007-77485

Summary of the invention

Technical problem

Intermetallic Al-Mg compounds which are precipitated during casting often cause breakage during stamping, as described in PTL 1 and PTL 2. The downsizing of Al-Mg intermetallic compounds (also referred to as "β-phase (s)") or the reduction in the amounts of coarse β-phase is therefore to increase the punching capability of an Al-Mg alloy sheet effective with high Mg content. According to the techniques described in PTL 1 and PTL 2, Al-Mg intermetallic compounds precipitated in casting are suppressed by performing cooling at a high speed (at a high casting speed) in the casting step. However, with increasing Mg content in an Al-Mg alloy sheet, it becomes difficult to reduce the β phase to an extent such that the punching ability is not adversely affected when only adjusting the cooling rate is used in the casting step becomes.

In the technique described in PTL 3, setting of soaking and finish annealing conditions is used to reduce the amount of Mg segregation (Mg concentration distribution) in the thickness direction of the sheet, so that the precipitation of Al-Mg intermetallic compounds (β Phase) caused by segregation of Mg (nonuniformity of Mg concentration) is suppressed. However, such a high Mg content Al-Mg alloy sheet produced by a usual continuous two-roll casting method has the disadvantage of Mg segregation also in a widthwise direction. For this reason, it is disadvantageously difficult to reduce the β-phase of the high Mg content Al-Mg alloy sheet to an extent such that the punching ability is not adversely affected if only the reduction of the degree the Mg segregation in the thickness direction is used.

Accordingly, there is a need for a technique for suppressing β phases of a high Mg content Al-Mg alloy sheet to such an extent that the punching ability is not adversely affected instead of or in addition to the setting of the cooling rate in a casting step and / or to reduce the extent of Mg segregation in the thickness direction by adjusting conditions for soaking and finish annealing after the casting step.

The present invention has been made to solve such problems, and an object of the present invention is to provide a workable aluminum alloy sheet which is a high Mg Al alloy sheet having, to a lesser extent, precipitation of Has β-phase in the interior and which has a better pressing or punching capacity (press or stamping formability).

the solution of the problem

To solve the problem, the present invention provides a deformable aluminum alloy sheet containing Mg in a content of 6.0 mass% or more and 15.0 mass% or less and further containing Al and impurities. The aluminum alloy sheet has a average Mg concentration in the width direction of Co, wherein the average Mg concentration in the width direction (Co) is an average of Mg concentrations, at a plurality of measuring points in the width direction, at predetermined intervals in a width direction and in a longitudinal direction, respectively of the sheet are arranged in a square area set on a surface of the deformable aluminum alloy sheet, each side of the square area having the dimension of a complete sheet width. The aluminum alloy sheet has average Mg concentrations in the thickness direction of Ci for the plurality of respective measurement points in the width direction, wherein the average Mg concentrations in the thickness direction (Ci) are each an average of Mg concentrations measured at a plurality of measurement points in the thickness direction which are arranged in a thickness direction of the sheet at a predetermined distance in the entire sheet thickness. The aluminum alloy sheet has regional Mg segregation degrees of X defined as the difference (Ci - Co) between each of the average Mg concentrations in the thickness direction (Ci) and the average Mg concentration in the width direction (Co), the absolute values of have regional Mg degrees of segregation (X) a maximum of 0.5 mass% or less and an average of 0.1 mass% or less.

The deformable aluminum alloy sheet having the above configuration has regional Mg segregation degrees (X) having a maximum and an average set to predetermined dimensions or less, with the regional Mg segregation degrees (X) each being a difference between each of the average Mg concentrations in the thickness direction (Ci) and the average Mg concentration in the width direction (Co) are defined. The workable aluminum alloy sheet is thereby less subject to Mg segregation in the entire sheet, particularly both in the thickness direction and in the width direction, and has less precipitation of β phases in the interior thereof as well as lower non-uniform strain and stress concentration upon forming.

In a preferred embodiment of the present invention, the aluminum alloy sheet has Mg concentrations in the thickness direction of Ct, wherein the Mg concentrations in the thickness direction in a thickness direction at a predetermined distance over the entire sheet thickness for at least one of the measuring points in the width direction in the determination of the regional Mg Degrees of solubility (X) are measured, and the aluminum alloy sheet has Mg segregation degrees in the thickness direction of Y in addition to the regional Mg segregation degrees (X), each as the difference (Ct-Ci) between each of the Mg concentrations in the thickness direction (Ct ) and an average Mg concentration in the thickness direction (Ci) corresponding to the at least one widthwise measuring point, wherein the absolute values of the Mg segregation degrees in the thickness direction (Y) are a maximum of 4 mass% or less and an average of 0.8 mass% or less.

The deformable aluminum alloy sheet, when having the above-mentioned configuration, has Mg segregation degrees in the thickness direction (Y) having a maximum and an average set at certain levels or less, in addition to the regional Mg segregation degrees (X) , The Mg segregation degrees in the thickness direction (Y) are respectively defined as the difference between each of the Mg concentrations in the thickness direction (Ct) and the average Mg concentration in the thickness direction (Ci). As a result, the deformable aluminum alloy sheet undergoes even less segregation of Mg and has less precipitation of β-phase in the interior thereof as well as lower nonuniform deformation and stress concentration during forming.

In another preferred embodiment of the present invention, the aluminum alloy formable sheet has Mg in a content of more than 8 mass% and less than or equal to 14 mass%.

The deformable aluminum alloy sheet, when having the above configuration, has a content of Mg within the specified range, and thereby can have higher strength and better ductility and less precipitation of β-phase inside thereof.

In a further preferred embodiment of the deformable aluminum alloy sheet according to the invention, the impurities comprise at least one element selected from the group consisting of Fe in a content of 1.0 mass% or less, Si in a content of 0.5 mass% or less, Ti in one Content of 0.1 mass% or less, B in a content of 0.05 mass% or less, Mn in a content of 0.3 mass% or less, Cr in a content of 0.3 mass% or less, Zr in a content of 0.3 mass% or less, V in a content of 0, 3 wt% or less, Cu is in a content of 1.0 mass% or less and Zn is in a content of 1.0 mass% or less.

The deformable aluminum alloy sheet, when having the above configuration, is adjusted in Fe and Si content as impurities, and therefore, less precipitates of intermetallic compounds in the interior thereof and better fracture toughness, and better pressability. Have punching capacity. The intermetallic compounds here are Al-Mg- (Fe, Si) and other Al-Mg intermetallic compounds, as well as intermetallic compounds other than Al-Mg intermetallic compounds, such as Al-Mg compounds. B. intermetallic Al-Fe and Al-Si compounds. This aluminum alloy sheet is also adjusted in content of Ti, B, Mn, Cr, Zr, V, Cu and Zn, which act as impurities, and can be protected from the adverse effects on the pressing capability.

Advantageous Effects of the Invention

The deformable aluminum alloy sheet according to the present invention has lower Mg segregation and less resulting formation of β phases and can have excellent punching ability. The deformable aluminum alloy sheet may have an even better punching capability when the Mg content is set within a narrower range, or at least one member selected from Fe, Si, Ti, B, Mn, Cr, in addition to Mg. Zr, V, Cu and Zn, in a set content.

Brief description of the drawings

1 FIG. 12 shows a plurality of measurement points for Mg concentrations to be used in determining the Mg segregation degrees of a recoverable aluminum alloy sheet according to the present invention, wherein the view (a) is a plan view and the view (b) is a cross-sectional view along the line AA in the view (a) is.

2 FIG. 10 is a cross-sectional view schematically illustrating a structure of a continuous strip caster for use in producing a deformable aluminum alloy sheet according to the present invention. FIG.

3 FIG. 10 is a cross-sectional view schematically illustrating a continuous strip caster for use in producing a deformable aluminum alloy sheet according to the present invention. FIG.

4 Fig. 12 is a graph illustrating calculation results of regional Mg degrees of segregation in a malleable aluminum alloy sheet satisfying conditions set forth in the present invention.

5 Fig. 12 is a graph illustrating calculation results of regional Mg degrees of segregation in a workable aluminum alloy sheet which does not satisfy conditions set forth in the present invention.

6 FIG. 12 is a graph illustrating calculation results of Mg segregation degrees in the thickness direction in the deformable aluminum alloy sheet satisfying conditions set forth in the present invention.

7 FIG. 12 is a graph illustrating calculation results of Mg segregation degrees in the thickness direction in the aluminum alloy forming sheet that does not satisfy conditions set forth in the present invention.

Description of embodiments

Formable aluminum alloy sheets according to embodiments of the present invention will be illustrated in detail below.

A deformable aluminum alloy sheet according to an embodiment of the present invention (hereinafter also referred to simply as an "aluminum alloy sheet") is an aluminum alloy sheet having Mg at a high content and regional Mg degrees of segregation X based on are set to predetermined values or less, the regional Mg segregation degrees X being respectively defined by an average Mg concentration in the width direction Co and an average Mg concentration in the thickness direction Ci.

First, the chemical composition of the aluminum alloy sheet according to the present embodiment is illustrated with respect to the significance of respective alloying elements and reasons why the contents are determined.

The aluminum alloy sheet according to the present embodiment comprises an aluminum alloy containing Mg in a content of 6.0 mass% or more and 15.0 mass% or less, and further contains Al and impurities, that is, Al. H. an Al-Mg alloy with a high Mg content. In a preferred embodiment, the aluminum alloy sheet comprises a high Mg Al-Mg alloy containing as an element other than Mg and as an impurity at least one element selected from the group consisting of Fe in a content of 1.0 mass% or less, Si in a content of 0.5 mass% or less, Ti in a content of 0.1 mass% or less, B in a content of 0.05 mass% or less, Mn in a content of 0.3 mass% or less, Cr in a content of 0.3 mass% or less, Zr in a content of 0.3 mass% or less, V in a content of 0.3 mass% or less, Cu in a content of 1.0 mass% or less, and Zn in a content of 1.0 mass% or less.

mg

The element magnesium (Mg) is an important alloying element for increasing the strength and ductility of the aluminum alloy sheet. An aluminum alloy sheet containing Mg in a content of less than 6.0 mass% may be insufficient in strength and ductility, and may not have properties of a high Mg content Al-Mg alloy, resulting in insufficient molding. Punching capacity leads. In contrast, an aluminum alloy sheet containing Mg at a content of more than 15.0 mass% may be difficult to have an Mg segregation, that is, an Mg segregation. H. the regional Mg degrees of segregation, which is within the specified range, even if its production process and conditions are adjusted. An aluminum alloy sheet having regional Mg degrees of segregation which are not set within the given ranges may have precipitation of larger amounts of β phases, thereby having markedly poor punching capability, undergoing greater strain hardening, and thereby becoming insufficient Has cold rolling properties. To avoid this, the aluminum alloy sheet has an Mg content of 6.0 mass% or more and 15.0 mass% or less, and preferably more than 8 mass% and less than or equal to 14 mass%.

Fe and Si

The amounts of the elements iron (Fe) and silicon (Si) should be minimized. Fe and Si are referred to as Al-Mg intermetallic compounds which typically contain Al-Mg (Fe, Si) and as intermetallic compounds other than Al-Mg intermetallic compounds such as Al-Mg compounds. B. intermetallic Al-Fe and Al-Si compounds excreted. When the aluminum alloy sheet has an Fe content of more than 1.0 mass% or an Si content of more than 0.5 mass%, it may have an excretion of such intermetallic compounds in excessively large amounts and thereby have significantly deteriorated fracture toughness and formability, which leads to a significantly poor pressing or punching capacity. To avoid this, the aluminum alloy sheet has an Fe content of 1.0 mass% or less, and preferably 0.5 mass% or less, and an Si content of 0.5 mass% or less, and preferably 0.3 mass% or less.

Ti, B, Mn, Cr, Zr, V, Cu and Zn

Titanium (Ti) and boron (B) have the effect of allowing a cast strip (ingot) to have a finer structure. Manganese (Mn), chromium (Cr), zirconium (Zr) and vanadium (V) have the effect of allowing a rolled sheet to have a finer structure, and copper (Cu) and zinc (Zn) also have the effect of to allow a sheet to have a higher strength. To show these effects, one or more of these elements may be contained within a range that does not adversely affect the pressing capability exhibited by the alloy sheet of the present invention. Preferred contents of these elements that are acceptable are 0.1 mass% or less of Ti, 0.05 mass% or less B, 0.3 mass% or less Mn, 0.3 mass% or less Cr, 0.3 mass% or less Zr, 0.3 mass% or less V, 1.0 mass% or less Cu and 1.0 mass% or less Zn.

Next, referring to the 1 the average Mg concentration in the width direction Co, the average Mg concentrations in the thickness direction Ci, and the regional Mg segregation degrees X of the aluminum alloy sheet are described in detail, wherein the regional Mg segregation degrees X are represented by the average Mg concentration in the width direction Co and the average Mg Concentrations in the thickness direction Ci are defined.

Average Mg concentration in the width direction Co

With reference to 1 (a) For example, the average Mg concentration in the width direction Co can be determined in the following manner. First, a square area, each side of which has the dimension of the entire sheet width W, on a surface of an aluminum alloy sheet 60 established. A plurality of measuring points in the width direction Px are set at a predetermined distance "a" in a width direction and at a predetermined distance "b" in a longitudinal direction in the square area, namely, an area formed by sides of the entire sheet width W and sides of the sheet length L is surrounded with the same dimension as the entire sheet width W. Mg concentrations become at the plurality of measuring points in the width direction Px in the surface of the aluminum alloy sheet 60 measured. The average of the measured Mg concentrations is defined as the average Mg concentration in the width direction Co serving as an index of the amount of Mg segregation on the surface in the width direction of the aluminum alloy sheet 60 serves. The Mg concentrations can be determined by preparing an electron probe X-ray microanalyzer (EPMA) capable of linear analysis and scanning the aluminum alloy sheet 60 in the width direction using the EPMA.

The reproducibility in measuring the amount of Mg segregation in the width direction of the aluminum alloy sheet 60 For example, by setting a square area, each side of which has the dimension of the entire sheet width W, on a surface of the aluminum alloy sheet 60 and measuring the Mg concentrations in the region on the surface of the aluminum alloy sheet 60 to be obtained. The measuring points in the width direction Px are preferably set in the range in a number (number of points) of 5 or more in the width direction, excluding the sheet edges, and 5 or more in the longitudinal direction, ie, 25 in total or more. The distance "a" in the width direction and the distance "b" in the longitudinal direction of the sheet can be set so that the number of measuring points in the width direction Px is set to 25 or more. In a more preferred embodiment, the distance "b" in the longitudinal direction may be set to be 0.5 to 2 times the distance "a" in the width direction.

Average Mg concentration in the thickness direction Ci

With reference to the 1 (b) For example, the average Mg concentrations in the thickness direction Ci are calculated in the following manner. First, a plurality of measurement points in the thickness direction Py at a predetermined distance "c" in a thickness direction through the entire sheet thickness T are set. They are set for all measurement points in the width direction Px in the range. Mg concentrations (ie, the below-mentioned Mg concentrations in the thickness direction Ct) at respective sheet depth positions are measured for each measuring point in the thickness direction Py. The average of the measured Mg concentrations is defined as the average Mg concentration in the thickness direction Ci, which is an index of the degree of Mg segregation in the thickness direction (depth direction) of the aluminum alloy sheet 60 serves. The Mg concentrations can be measured with an EPMA as indicated above. Specifically, the Mg concentrations at the respective thickness positions can be measured by the total sheet thickness T in the area by scanning, in the thickness direction, cross sections of the aluminum alloy sheet cut in the width direction.

The distance "c" in the thickness direction of the sheet is preferably set to 0.2 mm or less to the reproducibility of the amount of Mg segregation in the thickness direction of the aluminum alloy sheet 60 sure. An original measurement point of the measurement points in the thickness direction Py is the corresponding measurement point in the width direction Px at which the Mg concentration has already been measured.

Regional Mg Segregation X

The regional Mg degrees of segregation X are each defined as the difference (Ci - Co) between each of the average Mg concentrations in the thickness direction (Ci) and the average Mg concentration in the width direction (Co) and serve as an index of the extent of Mg segregation in the entire aluminum alloy sheet 60 in both the thickness direction and the width direction. In the aluminum alloy sheet according to the invention 60 Absolute values of regional Mg degrees of segregation X have a maximum of 0.5 mass% or less and an average of 0.1 mass% or less. The average Mg concentration in the width direction Co, the average Mg concentrations in the thickness direction Ci, and the regional Mg segregation degrees X can be determined by the chemical composition of the aluminum alloy sheet 60 and its manufacturing conditions mentioned below, typically by the cooling conditions at the time of casting, the thickness or the amount of removal (removal of material) of a cast strip, the heat soaking conditions and the finish annealing conditions.

When the regional Mg segregation degrees X have a large positive maximum and / or a large positive average, there is a tendency for β phases to be precipitated due to Mg segregation. Such β phases cause breakage and, as they increase, affect the strength and elongation of the aluminum alloy sheet disadvantageously, resulting in insufficient workability. If the regional Mg Segregation Xs have a large negative maximum and / or a large negative average, the aluminum alloy sheet may have a large number of localized regions with significantly low Mg concentrations. The areas with significantly low Mg concentrations have low strengths. Therefore, only the regions of low Mg concentrations preferentially deform in the case of tensile deformation during forming, resulting in nonuniform deformation. This can lead to a local or partial concentration of stress during forming and may result in the aluminum alloy sheet having insufficient workability, particularly due to poor elongation.

For these reasons, an aluminum alloy sheet 60 have an insufficient formability if it has a maximum of more than 0.5 mass% and / or an average of more than 0.1 mass%, as absolute values, of the regional Mg Segregation X, ie if it is not one of the conditions or both which are defined in the present invention, is sufficient.

The aluminum alloy sheet according to the invention 60 In addition to the regional degrees of Mg segregation X, it is preferably set to predetermined levels or less with respect to the Mg segregation degrees in the thickness direction Y. The Mg segregation degrees in the thickness direction Y are respectively defined by a Mg concentration in the thickness direction Ct and an average Mg concentration in the thickness direction Ci.

Mg concentrations in the thickness direction Ct and average Mg concentration in the thickness direction Ci

The Mg concentrations in the thickness direction Ct are Mg concentrations which are at the plurality of measurement points Py in the thickness direction Py, which are in the 1 (b) are measured, as described above. The average Mg concentration in the thickness direction Ci is an average of the measured Mg concentrations in the thickness direction Ct.

The Mg concentrations in the thickness direction Ct and the average Mg concentration in the thickness direction Ci are Mg concentrations in the thickness direction of the sheet measured for at least one measuring point in the width direction Px in the region measured as in the determination of the regional Mg Degrees of thinning X. The Mg concentrations in the thickness direction Ct are preferably determined by measuring the Mg concentrations for a measuring point in the widthwise direction Px in the middle part of the sheet width, and more preferably by measuring the Mg concentrations for three measuring points in the width direction Px, including a measuring point in the middle part and two near both ends of the sheet width, and forming the average of the measured values.

Mg segregation degrees in the thickness direction Y

The Mg segregation degrees in the thickness direction Y are respectively defined as the difference (Ct-Ci) between a Mg concentration in the thickness direction (Ct) and the average Mg concentration in the thickness direction (Ci) and serve as an index of the extent of Mg segregation in the thickness direction of the aluminum alloy sheet 60 , The Mg segregation degrees in the thickness direction Y, when used in combination with the regional Mg segregation degrees X, can satisfactorily increase the extent of Mg segregation in the entire aluminum alloy sheet 60 play. In the aluminum alloy sheet according to the invention 60 For example, the absolute values of the Mg segregation degrees in the thickness direction Y preferably have a maximum of 4 mass% or less and an average of 0.8 mass% or less. The Mg concentrations in the thickness direction Ct, the average Mg concentrations in the thickness direction Ci and the Mg segregation degrees in the thickness direction Y can be determined by the chemical composition of the aluminum alloy sheet 60 and its production conditions, typically by the cooling conditions during casting, the thickness or rate of removal (removal of material) of the cast strip, the heat soak conditions, and the finish annealing conditions.

When the Mg segregation degrees in the thickness direction Y have a large positive maximum and / or a large positive average, there is a tendency that β-phases are precipitated due to Mg segregation. Such β phases cause breakage and, as they increase, affect the strength and elongation of the aluminum alloy sheet disadvantageously, resulting in insufficient workability. When the Mg segregation degrees in the thickness direction Y have a large negative maximum and / or a large negative average, the aluminum alloy sheet may have a large number of local areas with significantly low Mg concentrations. The areas with significantly low Mg concentrations have low strengths. Therefore, only the regions of low Mg concentrations preferentially deform in the case of tensile deformation during forming, resulting in nonuniform deformation. This can lead to a local or partial concentration of stress during forming and may result in the aluminum alloy sheet having insufficient workability, particularly due to poor elongation.

For these reasons, an aluminum alloy sheet 60 have insufficient formability when the absolute values of the Mg segregation degrees in the thickness direction Y have a maximum of more than 4 mass% and / or an average of more than 0.8 mass%. In particular, an aluminum alloy sheet 60 which does not satisfy a specific condition or both specific conditions, have insufficient workability.

Average grain size

The aluminum alloy sheet of the present invention preferably has an average grain size of 100 μm or less in the surface thereof.

The aluminum alloy sheet, if it has fine grains having an average grain size of 100 μm or less in the surface thereof, may have better punching ability. The aluminum alloy sheet, when it has coarse grains having an average grain size of more than 100 μm, may tend to have insufficient punching capability, resulting in defects such as e.g. B. cracking and orange peel surfaces during forming leads. In contrast, the aluminum alloy sheet, if it comprises excessively fine grains having an excessively small average grain size, may optionally have flow pattern (SS) marks on pressing, which marks particularly occur in 5xxx aluminum alloy sheets , To avoid this, the aluminum alloy sheet preferably has an average grain size of 20 μm or more.

As used herein, the term "grain size" refers to the largest dimension of a grain in the longitudinal direction. The grain size is measured in the L direction according to a line cutting method by mechanically polishing the aluminum alloy sheet to 0.05 to 0.1 mm, electrolytically etching the surface of the polished sheet, and examining the etched surface with an optical microscope at 100 times magnification. In this measurement, a measurement line is set to have a length of 0.95 mm. Three lines are defined per field of view and a total of five fields of view are examined. Consequently, the total measuring line length is 0.95 mm by 15 mm.

Next, a method for producing the aluminum alloy sheet will be illustrated.

The aluminum alloy sheet of the present invention can be produced by a melt-casting step, a soaking step, a cold-rolling step and a finish-annealing step. The respective steps are illustrated below.

<Melting-casting step>

The melt-casting step is a step of melting a high-Mg Al-Mg alloy having the above-mentioned chemical composition so as to obtain a molten metal and making a cast strip from the molten metal a continuous strip casting process. The continuous strip casting method is preferably a continuous casting method using a fixed graphite mold.

The continuous casting process, which uses a fixed graphite mold, is similar to that described in U.S. Pat 2 shown continuous strip caster 10 carried out. First, a molten metal 2 that in a holding furnace 1 is stored, through an inlet 1a in a continuous form 3 (fixed graphite form 4 poured). Next is the molten metal 2 in the fixed graphite form 4 that with a water cooling jacket 5 is cooled, solidified. This results in a cast band 6 with a small thickness. The manufactured cast tape 6 of rolls 7 to a subsequent step. In this casting method, cooling is used at a higher speed as in the DC casting process, thereby providing a finer cast structure and contributing to better punching capability. Moreover, with this casting method, a cast strip having a relatively small thickness of about 5 mm can be obtained, and there is a requirement of pre-hot rolling, finish hot rolling and other steps after casting with conventional DC blocks having thicknesses of 200 to 600 mm be carried out, eliminated.

cooling rate

In the continuous casting process using a fixed graphite mold, cooling may be carried out at a rate of 15 ° C / s, provided that the cast strip 6 has a thickness of 5 to 20 mm. Cooling, when carried out at excessively low speed, can cause the aluminum alloy sheet to have a high degree of Mg segregation and this can affect the control of Mg segregation levels within the ranges specified in the present invention. so that the excretion of β-phase induced by Mg segregation is not suppressed. In this connection, the regional Mg degrees of segregation X and the Mg degrees of segregation in the thickness direction Y are hereinafter also referred to as "Mg segregation degrees". In addition, β-phases generally tend to be coarse and to be excreted in large quantities. This can very likely lead to the aluminum alloy sheet having a significantly poor punching capability.

It is difficult to measure the cooling rate directly. The cooling rate can therefore be calculated from a dendrite arm spacing (secondary dendrite arm spacing: DAS) of the cast strip 6 after casting, are determined by a known method, typically a method disclosed in U.S. Pat The Japan Institute of Light Metals (ed.): "Measuring method of dendritic arming and cooling rate of aluminum alloy", published on August 20, 1988 , is described. In particular, the cooling rate may be determined by measuring an average distance "d" of adjacent secondary dendrite arms (secondary arms) in the cast structure of the cast strip 6 according to the intersection method (in three or more fields of view at ten or more points of intersection). The cooling rate is then determined according to the following expression: d = 62 × C -0.337, where d is the secondary dendrite arm spacing (mm) and C is the cooling rate (° C / s). The cooling rate can therefore also be referred to as the solidification rate.

casting temperature

In the continuous casting process, which uses a fixed graphite mold, casting of the molten metal may occur 2 in the fixed graphite mold 4 at a temperature higher than the liquidus temperature by 50 ° C or more and 250 ° C or less, and preferably at a temperature higher than the liquidus temperature by 100 ° C or more and 150 ° C or less. Casting, when carried out at a temperature below the temperature which is 50 ° C higher than the liquidus temperature (liquidus temperature + 50 ° C), may cause solidification of the molten metal within the mold, so that cracking of the cast Bands is caused. Casting, when carried out at a temperature above the temperature which is higher by 250 ° C than the liquidus temperature (liquidus temperature + 250 ° C), may cause slow cooling after casting at a low speed, and may cause a higher Mail to Mg segregation cause. This can be the setting or control of the Mg segregation levels within the impede the precipitation of β-phase precipitation and cause deterioration of formability due to high degrees of Mg segregation.

stripping

In the continuous casting process using a fixed graphite mold, the cast strip can 6 for stabilizing the casting by periodically rotating the rolls 7 be returned in a direction opposite to the casting direction. The rollers 7 transport the cast strip 6 in the casting direction in a forward operation. The recycling may be performed with a path length of 0.5 mm or more and 5 mm or less, and preferably 1 mm or more and 3 mm or less. The castability is more stabilized when the cast strip is held for a hold time of 1 second or shorter before being returned.

When recycling is performed with a path length greater than 5 mm, a segregated layer having a high Mg concentration can be formed in a surface of the cast strip 6 is generated, penetrate into the tape, so that a tearing of the cast strip is caused at this point, causing a breakage. If the recycle is done with a path length of less than 0.5 mm, a solid-liquid coexistence zone can not be compressed and left tear-sensitive, and this can lead to the cast strip 6 in a region comprising the solid-liquid coexistence zone. To avoid this, the recirculation may be performed with a path length of 0.5 mm or more and 5 mm or less.

Average casting speed

The pouring of the molten metal 2 in the fixed graphite mold 4 in the continuous casting method using the fixed graphite mold, it can be carried out at an average casting speed of 100 mm / min or more and 500 mm / min or less, and preferably 250 mm / min or more and 350 mm / min or less. The casting, when carried out at an average casting speed of less than 100 mm / min, can rapidly solidify the molten metal 2 near the inlet 1a cause the peel resistance of the section as it is pulled off by the rollers 7 is increased and the resulting band 6 can tear. Casting, when carried out at an average casting speed of more than 500 mm / min., May result in molten metal due to insufficient cooling in the vicinity of an outlet 4a for the cast band emerges.

Thickness of the cast strip

The cast band 6 that has been continuously cast according to the continuous casting method using a fixed graphite mold may have a thickness in the range of 5 mm or more and 20 mm or less. If a cast band 6 should be formed with a thickness of less than 5 mm, the molten metal 2 near the inlet 1a solidify quickly so that the peel resistance in the area when peeled off by the rollers 7 is increased and the resulting band 6 can be sensitive to a tearing. If a cast band 6 may be formed with a thickness of more than 20 mm, the cooling in the casting takes place, if appropriate, very slowly with an extremely low cooling rate, so that the extent of Mg segregation is increased. This may impair the control of Mg segregation levels within the ranges specified in the present invention and impair the suppression of excretion of β phases induced by large Mg segregation levels. In addition, β-phases generally tend to be coarse and to be excreted in large quantities. This can very likely lead to the aluminum alloy sheet having a significantly poor punching capability.

wear

In the continuous casting method using a fixed graphite mold, it is preferable to use ablation in which both sides of the produced cast strip 6 to a predetermined extent or machined or peeled since it is likely that there will be Mg segregation in the surfaces of the cast strip 6 takes place. The ablation removes Mg segregation areas on both sides of the band, and thereby the Mg segregation levels within of the ranges set in the present invention. The depth of the Mg segregation regions corresponds to the length of the backward path length, and the ablation can be performed by an amount corresponding to the backward path length at peeling.

The continuous strip casting method has been exemplified above by the continuous casting method using a fixed graphite mold as an example, but the method is not limited thereto. The continuous strip casting method may be any method as long as it can adjust the Mg segregation degrees of the aluminum alloy sheet within the ranges specified in the present invention, and it may be e.g. B. is a continuous two-roll casting process.

The continuous two-roll casting process can be used with a continuous strip caster 100 be performed as they are in the 3 is illustrated. First, a molten metal 300 from a holding furnace 200 through a molten metal feed nozzle 400 in a nip between a pair of rotating water-cooled copper molds (twin rolls 500 ) poured and solidified. The solidified metal is rolled immediately after solidification and in the nip between the twin rolls 500 quenched and thereby results in a cast band 600 with a small thickness. Examples of the continuous two-roll casting method are a Hunter method and a continuous casting method between cylinders (3C). With the continuous two-roll casting process, a sheet (strip) having a relatively small thickness of 1 to 13 mm can be obtained and eliminates the need for steps such as steps. For example, a pre-hot rolling and a finish hot rolling after casting, which are carried out in the production of conventional direct cooling (DC) blocks (with thicknesses of 200 to 600 mm).

<Durchwärmschritt>

The soaking step is a step in which the cast strip 6 produced in the previous step is subjected to a predetermined soaking. The soaking is performed at a temperature of 400 ° C or above and the liquidus temperature or below for a required period of time. When the cast strip 6 produced by the continuous strip casting method is thoroughly heated in a continuous heat treatment furnace, the heat treatment (heat soaking) is performed for a period of about one second (1 second) or shorter. The soaking reduces the extent of Mg segregation, and the aluminum alloy sheet may have Mg degrees of segregation set within the ranges specified in the present invention.

There is a sufficient possibility of producing intermetallic Al-Mg compounds (β-phases) both in the temperature increase and in the cooling of the cast strip 6 in the soaking when the rate of temperature rise and / or the rate of cooling is or are excessively low. Such β-phases are likely to be generated at temperatures of the central part of the cast strip from 200 ° C to 400 ° C during the temperature rise and at temperatures from the soak temperature down to 100 ° C during cooling. In order to suppress generation of β phases, heating up to the soaking temperature is preferably performed at an average rate of temperature rise of 5 ° C / sec or more at temperatures of the central part of the cast strip from 200 ° C to 400 ° C, and cooling from the soaking temperature is preferably carried out at an average cooling rate of 5 ° C / sec or more at temperatures of the central part of the cast strip from the soaking temperature down to 100 ° C.

<Cold rolling step>

The cold rolling step is a step of cold rolling the warmed cast strip 6 to a thickness of a sheet product of typically 0.1 mm or more and 13 mm or less. The cold rolling converts the cast structure into a deformation structure. Accordingly, an intermediate annealing is performed at half of the cold rolling, so that a cold rolling reduction in finish cold rolling of 60% or less is provided when the cast strip 6 has a large thickness before cold rolling. The degree of conversion to a deformation structure as a result of cold rolling may also vary depending on the cold rolling reduction in cold rolling. For this reason, the cast structure may remain for the control of the metallic texture, but such a cast residue structure is acceptable within a range that does not adversely affect the formability and the mechanical properties.

<Fertigglühschritt>

The finish annealing step is a step in which the cold rolled sheet produced in the previous step is subjected to predetermined finish annealing. In the finish annealing step, the cold-rolled sheet is finish-annealed at a temperature of 400 ° C or above and below the liquidus temperature (° C). Finished annealing reduces the extent of Mg segregation, allows the aluminum alloy sheet to have Mg segregation levels within ranges specified in the present invention, and protects the aluminum alloy sheet from excretion of β phases and insufficient press or anneal Punching capacity, each due to Mg segregation.

Finished annealing performed at a temperature below 400 ° C is very likely to provide no solution effects, and may not effectively reduce the extent of Mg segregation. In order to avoid this, the finish annealing is preferably carried out at a temperature of 450 ° C or above. After the final annealing, the sheet is preferably cooled at a maximum cooling rate of 10 ° C / s or more at temperatures of 500 ° C down to 300 ° C. Cooling after finish annealing, when performed at a low average cooling rate of less than 10 ° C / sec, on the contrary, can increase the extent of Mg segregation during the cooling process. In this case, the resulting aluminum alloy sheet may not have Mg degrees of segregation set within the ranges used in the present invention. And may optionally have a precipitation of β phases as well as a reduced punching capability due to large degrees of Mg segregation. The average cooling rate is preferably 15 ° C / sec or more.

EXAMPLES

Next, some working examples of the present invention will be illustrated below.

Molten metals of Al-Mg alloys having chemical compositions as given in Table 1 (Examples A, B, C, D and E and Comparative Examples F and G) were prepared under conditions as shown in Table 2, cast to give cast strips of thicknesses as shown in Table 2. The casting was carried out by the continuous casting method using a fixed graphite mold or the continuous two-roll casting method as mentioned above. The respective cast strips were selectively subjected to abrasion and soaking under the conditions as shown in Table 2 and then cold rolled to obtain cold rolled sheets having a thickness of 1.0 mm or 11.0 mm without hot rolling. During the cold rolling, no intermediate annealing was performed. Next, the respective cold-rolled sheets were finish-annealed in a continuous annealing furnace at temperatures and cooling conditions as shown in Table 2 for a holding time at the annealing temperature of one second or shorter, whereby aluminum alloy sheets for forming as Examples Nos. 1 to 5 and Comparative Examples Nos. 6 to 20 were obtained. The aluminum alloy sheet for forming as Comparative Example No. 6 was produced by a two-roll continuous casting method described in PTL3.

The continuous casting method using a fixed graphite mold was carried out at a backward path length of 3 mm, an average casting speed of 300 mm / min and a casting temperature higher by 140 ° C than the liquidus temperature. The continuous two-roll casting process was performed with a peripheral speed of the twin rolls of 70 m / min and a casting temperature for casting the molten metal into a nip between the twin rolls which was 20 ° C higher than the liquidus temperature. This procedure was performed without lubrication of the surfaces of the twin rolls.

The liquidus temperatures of the respective alloys were measured with the software Thermo-Calc Ver. R (A1-DATA Ver.6) for the thermodynamic calculation.

The resulting workable aluminum alloy sheets (Examples Nos. 1 to 5 and Comparative Examples Nos. 6 to 22) were subjected to calculation and evaluation of regional Mg segregation X and Mg segregation degrees in the thickness direction Y according to the following methods. The results are shown in Table 2.

4 shows the calculated regional Mg Segregation X of Example Nos. 1 and 5 shows the calculated regional Mg segregation X of Comparative Example No. 6. 6 shows the calculated Mg segregation degrees in the thickness direction Y of Example 1 and FIG 7 shows the calculated Mg segregation degrees in the thickness direction Y of Comparative Example No. 16.

Calculation and assessment of regional Mg Segregation X

First, a square area having a dimension of one side of 100 mm was set on a surface of a sample of a workable aluminum alloy sheet. Next, in the area, five points excluding the sheet edges were set in the width direction at a pitch of 16.6 mm (pitch "a"), and five pitches in the longitudinal direction at a pitch of 25 mm (pitch "b"). ). Thus, a total of 25 measurement points in the width direction Px (Nos. 1 to 25) were set (cf. 1 (a) ). Mg concentrations in the surface of the aluminum alloy sheet were measured at the respective measuring points, and the average was formed so that an average Mg concentration in the width direction Co was obtained.

Next, a plurality of measuring points in the thickness direction Py in the thickness direction were set at a pitch of 0.01 mm (pitch "c") for each of the measuring points in the width direction Px (Nos. 1 to 25 (see FIGS 1 (b) ). Mg concentrations of the aluminum alloy sheet were measured at the respective measuring points (predetermined thickness positions (predetermined depth positions)), and the average was formed so that an average Mg concentration in the thickness direction Ci was obtained.

For each of the measuring points in the width direction Px (Nos. 1 to 25), a regional Mg segregation degree X was calculated from the average Mg concentration in the thickness direction Ci and the average Mg concentration in the width direction Co, with the regional Mg segregation degree X as the difference between these (Ci - Co) is defined (see the 4 and 5 ). Mg concentrations were measured with an EPMA (JXA-8800RL, electron probe X-ray microanalyzer from JEOL Ltd.).

The regional Mg degrees of segregation X were evaluated in the following manner. A sample having a maximum of absolute values of regional Mg segregation X of 0.5 mass% or less was evaluated as satisfactory (o) and a sample having a maximum of more than 0.5 mass% was judged unsatisfactory (x) , A sample having an average of absolute values of the regional Mg degrees of segregation X of 0.1 mass% or less was judged to be satisfactory (○), and a sample having an average of more than 0.1 mass% was evaluated as unsatisfactory (x ).

Calculation and evaluation of Mg segregation degrees in thickness direction Y

One (# 13) of the widthwise measuring points (Nos. 1 to 25) was selected, and the Mg concentrations measured at that point (No.13) in the thickness direction (at the plurality of measuring points in the thickness direction Py) were measured. were defined as Mg concentrations in the thickness direction Ct. The Mg segregation degrees in the thickness direction Y were respectively calculated as the difference (Ct-Ci) between each of the Mg concentrations in the thickness direction Ct and the average Mg concentration in the thickness direction Ci calculated as an average of Mg concentrations corresponding to the respective ones (Thickness direction) measurement points have been measured, calculated. The measuring points in the thickness direction Py, when positioned at a depth of 0.01 mm or 1.0 mm, are positioned in the surfaces of the alloy sheet (see FIGS 6 and 7 ).

The Mg segregation degrees in the thickness direction Y were evaluated in the following manner. A sample having a maximum of absolute values of Mg segregation degrees in the thickness direction Y of 4 mass% or less was judged to be satisfactory (o) and a sample having a maximum of more than 4 mass% was judged unsatisfactory (x). A sample having an average of absolute values of Mg segregation degrees in the thickness direction Y of 0.8 mass% or less was judged to be satisfactory (○), and a sample having an average of more than 0.8 mass% was rated unsatisfactory (x ).

Average grain size

Average grain sizes of the formed aluminum alloy formable sheets (Examples Nos. 1 to 5 and Comparative Examples 6 to 22) were measured according to the above-mentioned measuring method.

Examples Nos. 1 to 5 and Comparative Examples Nos. 6 to 10, 12 to 17 and 19 to 22 had average grain sizes in the range of 30 to 60 μm. Comparative Examples Nos. 11 and 18 had average grain sizes of more than 100 μm.

Evaluation of pressing or punching capacity

The pressability of the aluminum alloy formable sheets produced (Examples Nos. 1 to 5 and Comparative Examples Nos. 6 to 22) was evaluated according to the following method. The results are shown in Table 2.

Test specimens were taken from the alloy sheets and subjected to tensile tests to measure the tensile strength (TS (MPa)) and the total elongation (EL (%)). The punching ability was evaluated based on a strength-ductility balance defined as the product of TS and EL (TS × EL). A sample having a strength-ductility balance of 11,000 or more was judged to be acceptable (o), and a sample having a ductility-toughness balance of less than 11,000 was judged unacceptable (x).

Tabelle 2 (Teil 1)

Tabelle 2 (Teil 2)

Tabelle 2 (Teil 3)

The specimens were taken from each alloy sheet at arbitrary five points in the longitudinal direction at a pitch of 100 mm or more. From the measured tensile strengths and elongations of the five specimens per sample, the average was formed, respectively, so that a TS and an EL of the specimen were obtained. The tensile tests were done according to JIS Z 2201 under the use of JIS No. 5 specimens carried out. The test specimens were produced so that their longitudinal directions corresponded to the rolling direction of the alloy sheet sample. The tensile tests were performed at a constant crosshead speed of 5 mm / min until the test specimen broke. Table 1

Table 2 (part 1)

Table 2 (part 2)

Table 2 (part 3)

The results in Tables 1 and 2 show that Examples Nos. 1 to 5 satisfying the conditions set forth in the present invention with respect to the pressing ability of Comparative Examples Nos. 6 to 22 satisfies the conditions are not sufficient in the present invention are superior.

In particular, in Comparative Example No. 6, which was the alloy sheet described in PTL 3, the Mg segregation degrees (Mg regional segregation degrees) were not within the ranges specified in the present invention, and it had a poor pressing - or punching on. Comparative Examples Nos. 7 and 14 had Mg degrees of segregation which were within the ranges specified in the present invention, but they had Mg contents lower than the lower limit, thereby having poor strength-ductility balance showed and showed a poor pressing or punching capacity. Comparative Examples Nos. 8 and 15 had Mg contents above the upper limit, thereby exhibiting large degrees of Mg segregation and exhibiting a poor pressing ability. Comparative Examples Nos. 9, 10, 16 and 17 were not subjected to soaking, whereby they had large degrees of Mg segregation and exhibited a poor pressing ability. Comparative Examples Nos. 11 and 18 were cooled by casting at a low cooling rate, thereby exhibiting high degrees of Mg segregation and exhibiting poor punching performance. Comparative Examples Nos. 12 and 19 were subjected to finish annealing performed at a low temperature, thereby exhibiting high degrees of Mg segregation and exhibiting poor pressability. Comparative Examples 13 and 20 were subjected to finish annealing performed at a low cooling rate, thereby exhibiting high degrees of Mg segregation and exhibiting poor punching performance. Comparative Example 21 was subjected to abrasion of 1.75 mm from both sides of a cast strip, and the cast strip was produced by the continuous two-roll casting method. This comparative example did not have Mg segregation degrees (regional Mg segregation degrees) within the ranges as set forth in the present invention and showed a poor pressing ability. Comparative Example 22 was not subjected to abrasion of 1.75 mm from either side of a cast strip, wherein the cast strip was produced by the continuous casting process using a fixed graphite mold, whereby it had high degrees of Mg segregation and a poor compression set. or punching capacity showed.

While the present invention has been described with reference to embodiments and examples thereof, it should be noted that the invention is not limited to such specific embodiments thereof and various modifications and changes may be made therein without departing from the spirit and scope of the invention as they are hereinafter, to depart. The present application is based on Japanese Patent Application No. 2010-187756 , filed on Aug. 25, 2010, the entire contents of which are incorporated herein by reference.

LIST OF REFERENCE NUMBERS

a, b, c

distance

L

plate length

W

sheet width

T

sheet thickness

px

Measuring point in width direction

Py

Measuring point in thickness direction

1

Holding furnace

1a

inlet

2

Molten metal

3

continuous casting mold

4

fixed graphite mold

4a

Outlet for cast strip

5

Water jacket

6

Cast band

7

roller

10

Continuous strip caster

100

Continuous strip caster

200

Holding furnace

300

Molten metal

400

Feed nozzle for molten metal

500

double roll

600

Cast band

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• JP 07-252571 A [0009]
• JP 08-165538A [0009]
• JP 2007-77485 A [0009]
• JP 2010-187756 [0092]

Cited non-patent literature

• Japanese Industrial Standards (JIS) A 5052 [0002]
• A 5182 [0002]
• The Japan Institute of Light Metals (ed.): "Measuring method of dendritic arming and cooling rate of aluminum alloy" published on August 20, 1988 [0059]
• JIS Z 2201 [0089]
• JIS No. 5 Specimens [0089]

Claims (4)

A convertible aluminum alloy sheet comprising Mg in a content of 6.0 mass% or more and 15.0 mass% or less and further comprising Al and impurities wherein the aluminum alloy sheet has an average Mg concentration in the width direction of Co, wherein the average Mg concentration in the width direction (Co) is an average of Mg concentrations measured at a plurality of measuring points in the width direction, wherein the plurality of measuring points in Widthwise direction at predetermined intervals in a width direction or in a longitudinal direction of the sheet is arranged in a square area set on a surface of the deformable aluminum alloy sheet, each side of the square area having the dimension of a complete sheet width, wherein the aluminum alloy sheet has average Mg concentrations in the thickness direction of Ci for the plurality of respective width-direction measuring points, wherein the average Mg concentrations in the thickness direction (Ci) are each an average of Mg concentrations measured at a plurality of measuring points in the thickness direction be arranged in a thickness direction of the sheet at a predetermined distance over the entire sheet thickness, and wherein the aluminum alloy sheet has regional Mg segregation degrees of X defined respectively as the difference (Ci - Co) between each of the average Mg concentrations in the thickness direction (Ci) and the average Mg concentration in the width direction (Co), the absolute values of have regional Mg degrees of segregation (X) a maximum of 0.5 mass% or less and an average of 0.1 mass% or less. Formable aluminum alloy sheet according to claim 1, wherein the aluminum alloy sheet has Mg concentrations in the thickness direction of Ct, wherein the Mg concentrations in the thickness direction in a thickness direction of the sheet at a predetermined distance over the entire sheet thickness for at least one of the widthwise measuring points in determining the regional Mg segregation degrees (X) be measured, and wherein the aluminum alloy sheet has, in addition to the regional Mg degrees of segregation, (X) Mg segregation degrees in the thickness direction of Y, each as the difference (Ct - Ci) between each of the Mg concentrations in the thickness direction (Ct) and the average Mg concentration in the thickness direction (Ci) corresponding to the at least one width-direction measuring point, wherein the absolute values of the Mg segregation degrees in the thickness direction (Y) have a maximum of 4 mass% or less and an average of 0.8 mass% or less. A malleable aluminum alloy sheet according to claim 1 or 2, wherein Mg is contained in a content of more than 8 mass% and less than or equal to 14 mass%. A malleable aluminum alloy sheet according to claim 1 or 2, wherein said impurities comprise at least one member selected from the group consisting of Fe in a content of 1.0 mass% or less, Si in a content of 0.5 mass% or less, Ti in one Content of 0.1 mass% or less, B in a content of 0.05 mass% or less, Mn in a content of 0.3 mass% or less, Cr in a content of 0.3 mass% or less, Zr in a content of 0.3 mass% or less, V in a content of 0.3 mass% or less, Cu in a content of 1.0 mass% or less, and Zn in a content of 1.0 mass% or less.

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