JP2001207232A - Energy absorptive member made of aluminum alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an energy absorptive member made of an aluminum alloy light in weight, high in energy absorptivity, having required strength or the like and suitable as a shock absorptive member for an automobile or the like. SOLUTION: In this energy absorptive member made of the aluminum alloy, when the breading extention of the gage length of 5 mm in the extruding direction of an aluminum alloy extruded material is defined as α(%) and 0.2% yield strength is defined as σ (MPs), α>=24 and (α×σ)>=6,000 are satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an energy absorbing member made of extruded aluminum alloy. More specifically, the present invention relates to an energy-absorbing member suitable as a frame member for a vehicle body side member for reducing impact on occupants at the time of a collision of a transportation device, particularly an automobile.

[0002]

2. Description of the Related Art In recent years, in transport equipment such as automobiles, protection of occupants from the impact at the time of collision has been increasingly emphasized.
Structures and equipment to protect occupants in the event of a collision are being mandated. Specifically, in the front engine part and the rear trunk part of the car, structures and means have been studied in which structural members such as side members plastically deform in an accordion-like manner in the event of a collision and absorb energy at the time of the collision. I have. Conventionally, a cold-rolled steel plate has been used as a structural material that absorbs energy at the time of such a collision, and is assembled by press forming and spread welding. However, in recent years, the weight of the vehicle has been required to be reduced in light of environmental issues and improvement of athletic performance, and application of an aluminum material which is lighter than a steel plate is being studied. As an aluminum material suitable for this purpose, an extruded material that can easily produce a structural material having a complicated shape and is expected to be lighter than a plate material is expected. Material properties required for such an energy absorbing member include:
It is possible to perform hollow extrusion, to have the strength required as a structural material, to have a large amount of energy absorption at the time of collision, and to be capable of welding.

[0003]

An energy absorbing member made of an aluminum alloy is disclosed in Japanese Unexamined Patent Publication No. 7-118782.
In Japanese Patent Application Laid-Open No. H11-163, the one in which the elongation at break and the local elongation are specified within a predetermined range has been proposed, but the energy absorption member, which is the most important characteristic, is not always sufficient. In addition, among the conventional aluminum alloy extruded materials, Al-Mg-
Although there are Si-based alloys and Al-Zn-Mg-based alloys, these have a problem that energy absorption is not sufficient only by conventional extrusion. Accordingly, an object of the present invention is to provide an energy absorbing member made of an aluminum alloy, which is lightweight, has high energy absorption, has required strength and the like, and is suitable as a shock absorbing member for automobiles and the like. I do.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the energy absorption and material properties of extruded aluminum alloys, and have found that conventional JIS 13B, JIS 5
It is impossible to correctly evaluate the energy absorption by combining only the elongation at break and the local elongation of the tensile test specimen. The energy absorption is correlated with the elongation at break at the gauge length of 5 mm and the 0.2% proof stress value. Have been found, and based on this finding, the present invention has been accomplished. That is, in the present invention, the elongation at break of 5 mm in gauge length in the extrusion direction of the extruded aluminum alloy is α (%), and the 0.2% proof stress is σ.
(MPa), α ≧ 24 and (α × σ) ≧
An object of the present invention is to provide an aluminum alloy energy absorbing member satisfying 6000. In addition,
In the present invention, the values of α and σ are values obtained by performing a tensile test on a JIS No. 13B test piece at a tensile speed of 5 mm / min. In the extrusion direction, the elongation at break α at a gauge length of 5 mm is defined as a line at 5 mm intervals perpendicular to the extrusion direction in a parallel portion of the test piece, and the tensile test is performed. It is a value (%) indicating the ratio of elongation to the original 5 mm measured.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The energy absorbing member of the present invention is made of an extruded aluminum alloy. It is only necessary to have the values of α and σ described later, and the composition of the aluminum alloy can be various, but from the point of relatively high strength and elongation, an Al-Mg-Si-based or Al-Zn-Mg-based alloy is used. It can be preferably used.

The extruded aluminum alloy used for the energy absorbing member of the present invention has a gauge length of 5 mm in the extrusion direction.
Has the following values with respect to the elongation at break α (%) and the 0.2% proof stress value σ (MPa). Α of the extruded aluminum alloy used in the present invention is 24% or more, preferably 30% or more. If the value of α is too small, the members will not be evenly collapsed in an accordion shape when subjected to an impact, and the desired energy absorption will not be obtained. Also, the value of the product of α and σ (α
× σ) is an aluminum alloy extruded material of 6000 or more, preferably 6500 or more. If the value of (α × σ) is too small, the amount of energy absorbed by plastic deformation of the material is small, and the member cannot be made an energy absorbing member. The energy absorption of the energy absorbing member of the present invention is the energy absorption in a compression test, which is usually 10 k
g · m or more, preferably 12 kg · m or more.

[0007] By adjusting the composition of the aluminum alloy or adjusting the heat treatment conditions as necessary, an aluminum alloy extruded material having the above α and σ values can be obtained. The method of adjustment differs depending on the composition of the alloy to be used. For example, when the value of α is too small, adjustment by heat treatment is performed. Also, (α × σ)
Is too small, it can be adjusted by adding an element for improving the strength, changing the aging conditions, and the like. By using the aluminum alloy extruded material adjusted to the values of α and σ as described above, it is possible to obtain an energy absorbing member in which a decrease in energy absorption amount is prevented while maintaining characteristics such as necessary strength. .

The shape and size of the energy absorbing member of the present invention are not particularly limited, and can be appropriately used as a member requiring energy absorption such as collision. Specifically, for example, in an automobile or the like, it is suitable as a member for reducing an impact on an occupant at the time of a collision. Examples of such a member include a frame member for a side member and a bumper beam member.

[0009]

Next, the present invention will be described in more detail based on examples and comparative examples. Examples 1 to 9 and Comparative Examples 1 to 4 An alloy having a composition shown in Table 1 below was melted and cast in a billet having a diameter of 220 mm, and homogenized at 470 to 580 ° C. for 2 to 8 hours. It was extruded in a square shape having a square shape with a side of 100 mm and a thickness of 2.5 mm. further,
As shown in Table 2 below, immediately after the extrusion, air-cooled with a fan,
Thereafter, an aged T5 tempered material (described as “air cooling” in Table 2) and a T6 tempered material that was kept at a temperature of 470 to 520 ° C. for 40 minutes, then water-cooled, and further aged were treated (“Table 2” in Table 2). Described as “water-cooled”), and the following tests were performed.

Tensile Test The above material was cut into a JIS No. 13B test piece, and a scribe line perpendicular to the extrusion direction was inserted into a parallel portion of the test piece at intervals of 5 mm, and a test was performed at a tensile speed of 5 mm / min. Parallel part 5mm
Elongation after fracture α (%), 0.2% proof stress σ (MP
a) and tensile strength (MPa) were measured, and the results are shown in Table 2. In addition, if the tensile strength is 150 MPa or more, it can be used as a structural member of an automobile. Compression test As shown in FIG. 1, 10 mm /
Load at a compression speed of 1 min.
The amount of energy absorption was determined from the load applied up to 00 mm and the amount of deformation. FIG. 2 shows a measurement example of the displacement load curve at the time of the compression test. Table 2 shows the obtained energy absorption amounts.

[0011]

[Table 1]

[0012]

[Table 2]

As is evident from Table 2, in Examples 1 to 9 of the present invention, a large amount of energy absorption was obtained while maintaining the required strength, whereas α <2
Comparative Examples 1 to 4% and / or (α × σ) <6000
In No. 4, a material having a sufficient energy absorption was not obtained.

[0014]

The energy-absorbing member of the present invention is made of a lightweight aluminum alloy and has a high energy-absorbing property while satisfying the strength required as a structural material. Therefore, the present invention is extremely useful as a shock absorbing member for an automobile or the like.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a compression test method in an example.

FIG. 2 is a measurement example of a displacement load curve in a compression test in Examples.

Claims (1)

[Claims] 1. The extrusion direction of an aluminum alloy extruded material,
Assuming that the elongation at break at a gauge length of 5 mm is α (%) and the 0.2% proof stress is σ (MPa), α ≧ 24 and (α ×
σ) ≧ 6000 is satisfied, the energy absorbing member made of an aluminum alloy.