ALUMINUM MATERIAL WITH HIGH FORMABILITY

Abstract

An aluminum material, which is composed of crystal grains having different crystal orientations, in which the crystal grains comprise Cube-oriented crystal grains, Brass-oriented crystal grains and Copper-oriented crystal grains with a balance of crystal grains of other orientations, and in which the proportion of the Cube-oriented crystal grains is from 0.3 to 0.7, the proportion of the Brass-oriented crystal grains is from 0.1 to 0.5, the proportion of the Copper-oriented crystal grains is 0.2 or less, and the total proportion of these orientations is from 0.4 to 1.0; and a car component using the same.

Description

TECHNICAL FIELD

The present invention relates to an aluminum material. In particular, the present invention relates to an aluminum material excellent in the high degree of hem-bendability required in assembling car body panels, car parts, machine parts or the like, and excellent in sheet formability properties such as press formability for forming a body or casing.

BACKGROUND ART

In cars, advances are being made in the use of aluminum for body panels. A 6000-series (Al—Mg—Si base) aluminum alloy excellent in bake hardenability (property of exhibiting precipitation hardening under heating during paint-baking) that achieves high strength through painting with baking has been often used for outer panels, while a 5000-series (Al—Mg base) aluminum alloy excellent in draw formability has been used for inner panels.

While the outer panel made of the 6000-series aluminum alloy is required to be excellent in bendability, namely in workability in the hem-bending usually used to caulk it with an inner panel, the 6000-series (Al—Mg—Si base) aluminum alloy plate is in fact poor in hem-bendability. A particular problem is that a panel that has been subjected to solution treatment at a high temperature for enhancing its bake-hardenability is extremely poor in hem-bendability.

In addition, an outer panel of the 6000-series aluminum alloy is required to have excellent workability in press forming, which is a panel forming method that minimizes restraints on car design decisions. However, this aluminum alloy is inferior to conventional steel sheets and 5000-series aluminum alloy sheets in press formability, and improvement in this regard is desired for unification of used materials to facilitate recycling of the car parts.

Under such circumstances, the methods that have been proposed include a method for controlling surface hardness of the aluminum alloy sheet for improving bendability (for example, see Patent Document 1), a method for controlling the sizes of crystal grains and precipitates (for example, see Patent Documents 2 and 3), a method for controlling crystal orientation on the surface of the aluminum alloy sheet (for example, see Patent Documents 4 and 5), a method for controlling crystal orientation in the entire aluminum alloy sheet (for example, see Patent Document 6), and a method for controlling bendability by controlling the crystal orientation to a given depth from the surface of the aluminum alloy (for example, see Patent Document 7).

Proposed methods for improving sheet formability include a method for improving press formability by controlling Lankford values in the directions of 0°, 45° and 90°, respectively, relative to the direction of rolling of the aluminum alloy sheet (for example, see Patent Documents 8 and 9), and a method for improving press formability and bendability by controlling the relation between the tensile strength and proof stress and by controlling the crystal grain size on the surface of the aluminum alloy sheet and precipitation free zone (PFZ) (for example, see Patent Document 10).

It is known that design of the relation between the crystal orientation of crystal grains and quality of sheet can be optimized based on the results obtained from single crystal oriented materials in Cube orientation, Brass orientation and Copper orientation (for example, see Non-Patent Document 1). Moreover, there are known to be difference in the deformability of unidirectionally grain oriented materials in deep drawing, which is one of sheet forming methods (for example, see Non-Patent Document 2).

For precise processing of the body shape, the material used in car body panels is required to have a high level of compatibility between heavy bending, such as hem-bending, necessary for assembling the body, and sheet formability, typically press formability. However, it has been difficult to improve both hem-bendability and formability of aluminum alloy sheet to a level equal to that of conventional steel bodies, although improvement of only hem-bendability has been possible. To the contrary, an attempt to improve the level of sheet formability has the effect of degrading the level of hem-bendability. Realization of a high level of sheet formability has been difficult even by a method for enhancing press formability and bendability in the relation between the tensile strength and proof stress and by controlling the crystal grain size on the surface of the aluminum alloy sheet and precipitation free zone (PFZ).

[Patent Document 1] JP-A-2003-129201

[Patent Document 2] JP-A-2003-221637

[Patent Document 3] JP-A-2003-268472

[Patent Document 4] JP-A-2003-226926

[Patent Document 5] JP-A-2003-226927

[Patent Document 6] JP-A-2003-268475

[Patent Document 7] JP-A-2004-27253

[Patent Document 8] JP-A-2002-146462

[Patent Document 9] JP-A-2004-10982

[Patent Document 10] JP-A-2003-105473

[Non-Patent Document 1] Eiji Nakamachi and Yoshiki Hamada: Plasticity and Processing, 39-446 (1998), 252

[Non-Patent Document 2] Hideo Morimoto and Eiji Nakamachi: Furukawa Electric Review 103 (1999), 7

DISCLOSURE OF INVENTION

Under these circumstances, the inventors of the present invention investigated the effect of distribution of crystal grain orientation on hem-bendability and sheet formability, and accomplished this invention which achieves a high level of compatibility between hem-bendability and sheet formability.

It is an object of the present invention to provide an aluminum material in which hem-bendability and sheet formability are compatible at a high level.

Specifically, the present invention provides an aluminum material excellent in both characteristics of rigorous bending formability, such as hem-bending, and of sheet formability, such as press forming, by controlling the proportion of Cube orientation, Brass orientation and Copper orientation of the crystal orientations exhibited by crystal grains comprising the aluminum material.

The texture of the rolled sheet is usually expressed by the relation between the rolled surface and roll direction ((ABC) and <DEF>) of the sheet material (in which A, B, C, D, E and F each represent an integer). The distribution of crystal orientation of the texture of the sheet material refers to the proportion of the crystal orientation peculiar to each sheet material relative to random orientation.

The Cube orientation, Brass orientation and Copper orientation were evaluated in the present invention. The Cube orientation represents (100)<001> orientation of the crystal, Brass orientation represents (011)<211> orientation of the crystal, and Copper orientation represents (112)<111> orientation of the crystal. There may be deviation between the orientation of the actual sheet material and the ideal orientation of the Cube orientation, Brass orientation or Copper orientation. Therefore, crystal orientation within a deviation of ±5° from the ideal orientation of each crystal was deemed to be included in the Cube orientation, Brass orientation or Copper orientation based on the ideal orientation of crystals in the Cube orientation, Brass orientation and Copper orientation.

The present invention provides the following means:

(1) An aluminum material, which is composed of crystal grains having different crystal orientations,
wherein the crystal grains comprise Cube-oriented crystal grains, Brass-oriented crystal grains and Copper-oriented crystal grains with a balance of crystal grains of other orientations, and
wherein the proportion of the Cube-oriented crystal grains is from 0.3 to 0.7, the proportion of the Brass-oriented crystal grains is from 0.1 to 0.5, the proportion of the Copper-oriented crystal grains is 0.2 or less, and the total proportion of these orientations is from 0.4 to 1.0;
(2) An aluminum material, which is composed of crystal grains having different crystal orientations,
wherein the crystal grains comprise Cube-oriented crystal grains, Brass-oriented crystal grains and Copper-oriented crystal grains with a balance of crystal grains of other orientations, and
wherein the proportion of the Cube-oriented crystal grains is from 0.4 to 0.6, the proportion of the Brass-oriented crystal grains is from 0.2 to 0.4, the proportion of the Copper-oriented crystal grains is from 0.05 to 0.1, and the total proportion of these orientations is from 0.65 to 0.9;
(3) An aluminum material, which is composed of crystal grains having different crystal orientations and excellent in sheet formability,
wherein the crystal grains comprise Brass-oriented crystal grains and Copper-oriented crystal grains with a balance of crystal grains of other orientations, and wherein the proportion of the Brass-oriented crystal grains is from 0.2 to 0.4, the proportion of the Copper-oriented crystal grains is from 0.05 to 0.1, and the total proportion of these orientations being from 0.25 to 0.5;
(4) The aluminum material as described in the above item (1) or (2), wherein the aluminum material has sheet formability that does not sustain cracks on a punch-stretched surface stretched at a stretch height of 30 mm, and has hem-bendability in a range within which cracks do not occur on a bent surface at a bent radius/thickness ratio of 0.5 or less;
(5) The aluminum material as described in the above item (1) or (2), wherein the aluminum material has sheet formability that does not sustain cracks on a punch-stretched surface stretched at a punch-stretch height of 50 mm, and has hem-bendability in a range within which cracks do not occur on a bent surface at a bent radius/thickness ratio of 0.25 or less;
(6) The aluminum material as described in any one of the above items (1) to (5), wherein the aluminum material is an aluminum alloy comprising from 0.25 to 1.0 mass % of Mg and from 0.5 to 1.3 mass % of Si with a balance of Al and inevitable impurities;
(7) The aluminum material as described in any one of the above items (1) to (5), wherein the aluminum material is an aluminum alloy comprising from 0.25 to 1.0 mass % of Mg, from 0.5 to 1.3 mass % of Si, 1 mass % or less of each of Cu, Zn and Mn, 0.40 mass % or less of Fe and 0.1 mass % or less of each of Ti and Cr with a balance of Al and inevitable impurities;
(8) The aluminum material as described in any one of the above items (1) to (5), wherein the aluminum material is an aluminum alloy comprising from 0.40 to 1.0 mass % of Mg, from 0.5 to 1.3 mass % of Si, 1 mass % or less of each of Cu and Mn, 0.3 mass % or less of Zn, 0.20 mass % or less of Fe and 0.1 mass % or less of each of Ti and Cr with a balance of Al and inevitable impurities;
(9) The aluminum material as described in any one of the above items (1) to (5), wherein the aluminum material is an aluminum alloy comprising from 0.25 to 1.0 mass % of Mg, from 0.5 to 1.3 mass % of Si, 1 mass % or less of each of Cu, Zn and Mn, 0.40 mass % or less of Fe, and 0.1 mass % of each of Ti and Cr, and further comprises 0.20 mass % or less of each of V and Zr, with a balance of Al and inevitable impurities;
(10) The aluminum material as described in any one of the above items (1) to (5), wherein the aluminum material is an aluminum alloy comprising 0.40 to 1.0 mass % of Mg, from 0.5 to 1.3 mass % of Si, 1 mass % or less of each of Cu and Mn, 0.3 mass % or less of Zn, 0.20 mass % or less of Fe, and 0.1 mass % or less of each of Ti and Cr, and further comprises 0.1 mass % or less of each of V and Zr, with a balance of Al and inevitable impurities;
(11) A car component using the aluminum material as described in the above item (4) or (5); and
(12) A car component using the aluminum material as described in any one of the above items (6) to (10).

Other and further features and advantages of the invention will appear more fully from the following description, appropriately referring to the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1(a) to 1(c) views schematically illustrating the method of hem-bendability testing carried out in Example 1, wherein FIG. 1(a) shows setting of a test sample, FIG. 1(b) shows forced penetration with a punch, and FIG. 1(c) shows contact bending (clamping) with a vice.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described in detail below.

The present inventors provide materials that satisfy the requirements of both rigorous bending such as hem-bending and sheet forming such as body panel forming at a high level as a result of being optimally controlled in the proportions among three orientations, namely, the Cube orientation, Brass orientation and Copper orientation, exhibited by crystal grains constituting the aluminum material. For example, good bendability and sheet formability are exhibited in an aluminum material with the proportion of the Cube orientation crystal grains from 0.3 to 0.7, the proportion of the Brass-oriented crystal grains from 0.1 to 0.5, the proportion of the Copper-oriented crystal grains of 0.2 or less, and the total proportion of the crystal grain orientations of the Cube orientation, Brass orientation and Copper orientation from 0.4 to 1.0.

The relation between the proportion of crystal grains constituting the aluminum material and both characteristics will be described below.

First, it is known that the crystal orientation density of crystal grains of the Cube orientation markedly affect hem-bending, and it is also known that hem-bending improves as the crystal grain orientation density becomes higher than the crystal orientation density of random orientation crystal grains. In the present invention, it is also preferable for the proportion of crystal grains of the Cube orientation to be increased for improving hem-bending. However, the increase of the proportion of the Cube-oriented crystal grains may result in large impairment of sheet formability.

Accordingly, through various studies, it was concluded in the present invention that the range of the proportion of the Cube-oriented crystal grains is preferably from 0.3 to 0.7, more preferably from 0.4 to 0.6. Practically sufficient hem-bendability can be achieved in the lower limit region of this range, while sheet formability sufficient for press forming a body panel into the outer shape of the car can be maintained at the upper limit region.

Second, a high proportion of Brass-oriented crystal grains enables good sheet formability, contrary to the case where the proportion of the Cube-oriented crystal grains is high. However, the effect of the Brass-oriented crystal grains on hem-bendability was not known, and the effect of the proportion thereof was also unclear.

Accordingly, the effect of the proportion of the Brass-oriented crystal grains on hem-bending and sheet forming was carefully investigated in the present invention, and the range of the proportion of the Brass-oriented crystal grains was defined as from 0.1 to 0.5, preferably from 0.2 to 0.4. High levels of both hem-bendability and sheet formability can be achieved by adjusting the proportion of the Brass-oriented crystal grains in the range from 0.1 to 0.5 within the range of the proportion of the Cube-oriented crystal grains. A material outside the above-mentioned range may be excellent in one or the other of hem-bendability and sheet formability or may be poor in both properties.

Third, the proportion of the Copper-oriented crystal grains is 0.2 or less, preferably from 0.05 to 0.15, and more preferably from 0.05 to 0.1. The ratio was restricted as described above because, while the Copper-oriented crystal grains are known to have the same effect as that of the Brass-oriented crystal grains for sheet formability, it was found in the present invention that an additional effect of increasing the levels of both hem-bendability and sheet formability is achieved by permitting the Copper-oriented crystal grains to exist in the above-mentioned proportion. Therefore, the Copper-oriented crystal grains are presumed to serve as buffer materials between the Cube-oriented crystal grains and Brass-oriented crystal grains.

The method for calculating the proportion of crystal orientations will be described below.

An aluminum sheet material to be subjected to measurements, or an aluminum sheet material with a predetermined thickness (for example, 1 mm), was prepared. After degreasing the surface with an oil cleaning agent such as acetone, the surface oxide layer was removed with an oxide layer removing agent (for example, aqua regia for aluminum alloy) suitable for the quality of the aluminum sheet material. The aluminum sheet was mirror-finished by electropolishing, and the portion near the surface layer of the aluminum sheet was used as a test sample for the measurement of the crystal orientation.

Then, the crystal orientation of the crystal grains of the test sample was measured by electron backscatter diffraction pattern method (abbreviated as EBSP hereinafter).

The test sample was measured using a thermionic emission scanning electron microscope. The crystal orientations of the crystal grains within a unit area were measured, and proportions of the number of crystal grains of the Cube orientation, Brass orientation and Copper orientation, respectively, were determined assuming the number of the total crystal grains in the unit area to be 1. The ratio of each orientation to the total of all orientations was defined as the proportion of that orientation. For example, when the total number of crystal grains in a 1.0 mm square is 100 and the total number of the crystal grains of the Cube orientation, Brass orientation and Copper orientation is 100 (no crystal grains of other crystal orientations), the sum of the proportions (total proportion) of the Cube orientation, Brass orientation and Copper orientation is 1.

The aluminum material according to the present invention exhibits good bendability and sheet formability in the proportion of the crystal orientations when the crystal structure has a face-centered cubic structure. While examples of material of the face-centered cubic structure include Al alloys, Cu alloys, Ni alloys, Ag alloys and Au alloys, particularly pronounced effects are manifested in the Al alloy.

An Al—Mg—Si alloy comprising from 0.25 to 1.0 mass % of Mg and from 0.5 to 1.3 mass % of Si with a balance of Al and inevitable impurities is preferable as the Al alloy for obtaining a large effect.

Si and Mg contained in the Al—Mg—Si alloy as an essential element are precipitated as a Mg₂Si compound. The Si and Mg serve for improving the strength. When the content of Si is too small, the effect is not sufficiently exhibited while, when the content of Si is too large, bendability may be markedly decreased due to natural aging. On the other hand, a large amount of coarse Mg₂Si compounds may be precipitated when the content of Mg is too large. Consequently, the amount of solid solution is so greatly decreased that lowering of bendability and bake-hardenability may occur. For example, it is preferable to adjust the lower limit of the content of Mg to 0.40 mass % or more for increasing the strength of the sheet material a little higher.

Cu, Zn, Mn, Cr and Ti may be added to the alloy in addition to Mg and Si. Addition of Cu enhances the strength, ductility, degreasing ability and chemical conversion performance; addition of Zn enhances the degreasing ability and chemical conversion performance; and addition of Mn, Ti and Cr serves for facilitating refining of crystal grains to improve bendability. However, corrosion resistance and ductility may be reduced when these elements are added in excess.

While there are no practical problems when Cu and Zn each are added in the range of 1 mass % or less, the upper limit of addition may be appropriately determined to a level of 1 mass % or less in terms of a balance between the strength, ductility, degreasing ability and chemical conversion performance, and corrosion resistance and ductility. Zn is preferably added in an amount of 0.3 mass % or less for enhancing corrosion resistance of the sheet.

With respect to the amounts of addition of Mn, Cr, and Ti, that facilitate refining of crystal grains and improve bendability, the amount of addition of Mn is preferably 1 mass % or less, and the amounts of addition of Ti and Cr are preferably 0.1 mass % or less.

Fe contained as an impurity in addition to the above-mentioned elements forms precipitates that are harder than the Mg₂Si compound, and promotes propagation of cracks by forming large strain around the precipitate. Accordingly, the amount of Fe is preferably 0.40 mass % or less, more preferably 0.20 mass % or less. V and Zr may be optionally added in a range of 0.20 mass % or less in order to refine the crystal grains. While the amounts of addition of V and Zr do not affect hem-bendability and sheet formability such as press formability in the range of addition amount of 0.20 mass % or less, the amount of addition is preferably 0.1 mass % or less in terms of corrosion resistance and ductility.

According to the present invention, it is possible to provide an aluminum material excellent in the high level of hem-bendability required in assembling car body panels, car parts machine parts and the like, and in sheet formability properties such as press formability for forming the bodies and casings.

The present invention will be described in more detail based on examples given below, but the invention is not meant to be limited by these.

EXAMPLES

Example 1

An Al alloy comprising 0.5 mass % of Mg, 0.9 mass % of Si, 0.06 mass % of Mn, 0.07 mass % of Fe, 0.10 mass % of Cu and 0.005 mass % or less each of Zn, Ti and Cr with a balance of Al were melted and cast into an ingot with a thickness of 500 mm by a conventional method. After homogenizing the ingot at 540° C. for 6 hours, it was hot-rolled under conditions of an initiation temperature of 500° C. and termination temperature of 200° C. to obtain a hot-rolled plate with a thickness of 10 mm. Then, the hot-rolled plate was cold-rolled to a predetermined thickness so that a raw finish sheet with a thickness of 1 mm would be obtained by finish cold roll reduction ratio of 20%, 30%, 50%, 70% or 90%. A raw finish sheet with a thickness of 1 mm was directly obtained from the hot-roll plate with a thickness of 10 mm with respect to a sample having the finish cold roll reduction ratio of 90%.

The cold-rolled sheet with a predetermined thickness was then annealed at 325° C. for 2 hours, and a raw finish sheet with a thickness of 1 mm was prepared by applying finish cold rolling. A test sample was prepared by subjecting the raw finish plate to solution heat treatment at 500° C. using a continuous annealing furnace and to stabilization treatment at 100° C. for 24 hours.

The occupancy ratio of the crystal orientation was measured by the above-mentioned method, and the results are shown in Table 1.

Test sample No. 1 described in Table 1 was subjected to finish roll at a finish cold roll reduction ratio of 20%; the finish cold roll reduction ratios were 30% for sample No. 2, 50% for sample No. 3, 70% for sample No. 4, 80% for sample No. 5, 10% for sample No. 10 and 90% for sample No. 11.

The proportion of each crystal orientation includes the crystal orientation within a deviation of ±5° from each ideal orientation of the Cube orientation, Brass orientation and Copper orientation.

The test sample prepared was subjected to a 180° bending test and a punch stretchability test, and hem-bendability and sheet formability were evaluated.

With respect to hem-bendability, a 180° bending test was used by sequentially subjecting the test sample to pre-impartment of strain as shown in FIG. 1(a), forced penetration with a punch at a bend angle of 170° as shown FIG. 1(b), and clamping with a vice as shown in FIG. 1(c). The curvature R of the tip of the punch 1 was changed to 0.25, 0.5, 0.75 and 1.0 mm, and hem-bendability test was repeated five times for every curvature R of the tip. The minimum curvature of the tip that caused no surface roughness and cracks was described in the column of hem-bendability in Table 1. Accordingly, the smaller is the curvature of the tip that caused no surface roughness and cracks, the more excellent is hem-bendability.

With respect to punch-stretch moldability, the test sample was cut into a specimen of 300 mm square, and a lubricating oil was coated on both surfaces of the specimen. Then, a stretch testing was conducted five times at a punch-stretch height of 50 mm using a ball-head punch with a diameter of 100 mm to evaluate punch stretchability.

The test samples showing no incidence of cracks for all the specimens were evaluated as “∘”, the test samples showing cracks in one specimen in all the test specimens were evaluated as “Δ”, and the test samples showing cracks in two or more specimens in all the test specimens were evaluated as “x” in Table 1.

The strength, 0.2% proof stress and elongation were from 230 to 240 MPa, from 130 to 140 MPa and 30% or more, respectively, except the test sample subjected to finish cold roll reduction ratio of 90%. While the test sample subjected to finish cold roll ratio of 90% showed approximately the same strength and 0.2% proof stress with those of the above other test materials, its elongation was as low as 17%.

	TABLE 1
	Test	Workability in hem-		Proportion of crystal orientation
	sample	bending (Curvature	Sheet	Cube	Brass	Copper	Total
Classification	No.	of tip) (mm)	formability	orientation	orientation	orientation	proportion
This	1	0.5	∘	0.3	0.5	0.15	0.95
invention	2	0.5	∘	0.4	0.4	0.10	0.90
	3	0.25	∘	0.5	0.25	0.07	0.82
	4	0.25	∘	0.6	0.2	0.05	0.85
	5	0.25	∘	0.7	0.1	0.05	0.85
Comparative	10	1.0	Δ	0.25	0.55	0.1	0.90
example	11	0.25	x	0.95	—	—	0.95

As shown in Table 1, hem-bendability and sheet formability were good in the test sample Nos. 1 to 5 having crystal orientation within the range of the present invention. However, the test sample No. 10 having a low proportion of the Cube orientation and high proportion of the Brass orientation was poor in both characteristics. With respect to the test sample No. 11 in which almost all the crystal grains showed the Cube orientation, although it was excellent in hem-bendability, sheet formability was poor. In other words, Table 1 shows that an excellent material satisfying the above item (8) can be obtained.

An excellent material satisfying the above item (6) can be obtained by manufacturing a material by adding only 0.5 mass % of Mg and 0.9 mass % of Si with a balance of Al and inevitable impurities by the same process as in Example 1. When test samples were manufactured by the same process as in Example 1 using a material in which only the amount of addition of Fe was changed to 0.25 mass % and a material in which the amounts of addition of Fe and Cu were changed to 0.25 mass % and 0.15 mass %, respectively, excellent results satisfying the above item (7) were obtained in both materials. When test samples were manufactured by the same process as in Example 1 using a material prepared by adding 0.15 mass % each of V and Zr and a material prepared by adding 0.08 mass % each of V and Zr in the material in Example 1, excellent results satisfying the above item (9) or item (10) were obtained in both materials.

INDUSTRIAL APPLICABILITY

Since the aluminum material of the present invention is excellent in hem-bendability and sheet formability, it can be advantageously used for car body panels, car parts and machine parts.

Having described our invention as related to the present embodiments, it is our intention that the invention not be limited by any of the details of the description, unless otherwise specified, but rather be construed broadly within its spirit and scope as set out in the accompanying claims.

Claims

1. An aluminum material, which is composed of crystal grains having different crystal orientations,

wherein the crystal grains comprise Cube-oriented crystal grains, Brass-oriented crystal grains and Copper-oriented crystal grains with a balance of crystal grains of other orientations;

wherein, among the orientations of crystal grains, the proportion of the Cube-oriented crystal grains is from 0.3 to 0.5, the proportion of the Brass-oriented crystal grains is from 0.25 to 0.5, the proportion of the Copper-oriented crystal grains is from 0.07 to 0.15, and the total proportion of these orientations is from 0.82 to 0.95 with the balance of crystal grains of other orientations;

wherein the aluminium material has sheet formability that does not sustain cracks on a punch-stretched surface stretched at a punch-stretch height of 50 mm, and has hem-bendability in a range within which cracks do not occur on a bent surface at a bent radius/thickness ratio of 0.5 or less; and

wherein the aluminum material is an aluminum alloy comprising from 0.25 to 1.0 mass % of Mg and from 0.5 to 1.3 mass % of Si with a balance of Al and inevitable impurities.

2. The aluminum material according to claim 1, which further comprises 0.1 mass % or less of Cu, 0.06 mass % or less of Mn, and 0.20 mass % or less of Fe.

3. The aluminum material according to claim 1, which further comprises 0.20 mass % or less of each of V and Zr.

4. The aluminum material according to claim 2, which further comprises 0.20 mass % or less of each V and Zr.

5. A car component using the aluminum material according to claim 1.

6. A car component using the aluminum material according to claim 2.

7. A car component using the aluminum material according to claims 3.

8-43. (canceled)