JPH05247575A - Automobile shock absorbing member made of aluminum alloy - Google Patents

Abstract

PURPOSE:To improve bending strength and energy absorbing property by allowing a recrystallization layer of specific thickness to exist on the external surface of an extruded Al alloy material. CONSTITUTION:A recrystallization layer is provided, to >=70mum thickness, to the external surface of an extruded Al alloy material. As the extruded material, an Al alloy having a composition consisting of, by weight, 0.5-1.7% Si, 0.5-1.5% Mg, one or >=2 kinds selected from 0.05-0.25% Zr, 0.2-0.6% Mn, 0.05-0.3% Cr, and 0.1-1.0% Cu, and the balance Al with inevitable impurities is preferred. By this method, the breakage of the extruded material can be practically prevented, and an automobile shock absorbing member made of Al alloy improved in the amount of energy absorption at the time of collision can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shock absorbing reinforcing member for an automobile, for example, an aluminum alloy automobile shock absorbing member used for a side beam and a bumper beam for reinforcing a door for side collision protection.

[0002]

2. Description of the Related Art Although steel is usually used as a reinforcing member for automobiles, the application of aluminum alloys has been studied in recent years to meet the demand for weight reduction. These reinforcing members are required to withstand an impact load at the time of a vehicle collision and to have a high energy absorption amount.

[0003]

However, in the conventional aluminum alloy, both strength against load and energy absorption ability cannot be satisfied because of insufficient strength and elongation of the material.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide an aluminum alloy automobile shock absorbing member having high load resistance, that is, high bending strength and high energy absorbing ability. ..

[0005]

The aluminum alloy automobile shock absorbing member according to the present invention is made of an aluminum alloy extruded material, and a recrystallized layer having a thickness of 70 μm or more is present on the outer surface of the extruded material. It is characterized by

In this case, the extruded material contains 0.5 to 1.7% by weight of Si and 0.5 to 1.5% by weight of Mg, and Zr; 0.05 to 0.25% by weight, Mn;
Whether to use an aluminum alloy containing 0.6% by weight, Cr; 0.05 to 0.3% by weight, and Cu; 0.1 to 1.0% by weight, and the balance being Al and inevitable impurities. Or 0.5 to 1.5 wt% Mg
And Zr; 0.05 to 0.25 wt%, V; 0.03 to 0.15 wt%, Mn; 0.2 to 0.6 wt%, Cr; 0.05 to 0.3 wt% and Cu; 0.05.
It is preferable to use an aluminum alloy which contains one or more elements selected from 0.6 to 0.6% by weight, with the balance being Al and inevitable impurities.

[0007]

The inventors of the present invention have conducted earnest research to develop an aluminum alloy that eliminates the above-mentioned drawbacks of the prior art. As a result, the reinforcing member is made of an aluminum alloy extruded material, and The present inventors have found that it is effective to form a recrystallized layer having a thickness of 70 μm or more on the surface, and completed the present invention.

The structure of the extruded aluminum alloy material generally includes a fibrous crystal form composed of sub-crystal grains and a crystal form composed of recrystallized grains. The elongation is higher than that of the fibrous structure.
Therefore, when the recrystallized layer is applied to the surface of the extruded material where a tensile force is generated by the bending load with an appropriate thickness (70 μm or more), there is an effect that it becomes difficult to break. As a result, the aluminum alloy provided with this recrystallized layer becomes a member having a high energy absorption amount at the time of collision.

Next, the reasons for adding the respective components and the reasons for limiting the composition of the aluminum alloy according to claims 2 and 3 will be described. In order to have a bending strength equal to that of steel materials currently used as reinforcing members for automobiles and lighter than the steel materials, the strength of the aluminum alloy needs to be a certain value or more. Therefore, the range of each component of the aluminum material is determined from the viewpoint of obtaining the material strength equal to or higher than the certain value.

First, the reason for limiting the component range of the aluminum alloy according to claim 2 will be described. The second aspect of the present invention is a 6000 series aluminum alloy.

When the content of Si and Mg in the Si, Mg aluminum alloy is increased, the strength is improved, but when the content is too large, the extrudability of the aluminum alloy is reduced. To obtain the required strength, S
i must be 0.5% by weight or more and Mg must be 0.5% by weight or more.
Also, in order to maintain a constant extrudability, the upper limit of Si is 1.
7% by weight, the upper limit of Mg is 1.5% by weight.

Zr, Mn, Cr Zr, Mn, Cr all have the same action. That is, Zr, Mn, and Cr enhance the strength of aluminum alloy crystal grains by forming them into fibrous shapes. When the content of these elements is high, a fibrous structure is formed over the entire thickness of the extruded material, a recrystallized layer is not provided on the surface, the surface elongation is decreased, and the extrudability is decreased.

Zr, Mn, and Cr determine the lower limit of the content as the amount necessary to obtain the required strength, and to add the recrystallized layer and maintain the extrudability, the upper limit of the addition amount thereof is required. Limit the value.

When Zr is less than 0.05% by weight, the recrystallized layer becomes too much and the strength is lowered. When Zr exceeds 0.25% by weight, the recrystallized layer is not sufficiently applied or the extrudability deteriorates. Therefore, the amount of Zr is 0.05 to 0.25% by weight. For the same reason, the content of Mn is 0.2 to 0.6% by weight, Cr
Is 0.05 to 0.3% by weight.

Cu Cu has the function of increasing the strength of the aluminum alloy.
However, if the Cu content is excessive, the extrudability and the corrosion resistance deteriorate. Cu content is 0.1% by weight to maintain strength
The above is necessary. When Cu is contained alone, 0.3 wt% or more is necessary. On the other hand, when the Cu content exceeds 1.0% by weight, extrudability and corrosion resistance are deteriorated. Therefore, Cu
The content is 0.1 to 1.0% by weight.

Next, the reasons for adding the components and limiting the composition of the aluminum alloy according to the third aspect will be described.

Mg, Zn Mg, Zn are elements necessary for maintaining the strength of the aluminum alloy. If Mg is less than 0.5% by weight and Zn is less than 4% by weight, the desired strength cannot be obtained. Also, Mg is 1.
If the content of 5% by weight and Zn exceeds 7% by weight, the extrudability of the aluminum alloy is reduced and the elongation is also reduced, so that the required characteristic values cannot be obtained. For the above reasons, the Mg content is 0.
The Zn content is 5 to 1.5% by weight, and the Zn content is 4 to 7% by weight.

Zr, V, Mn, Cr Zr, V, Mn, Cr enhance the strength of the aluminum alloy. The ranges of the contents of these elements are determined for the same reasons as the reasons for limiting the composition of these components in the aluminum alloy described in claim 2. That is, the lower limit of the content of these elements is determined as the amount necessary to obtain the required strength, and the upper limit of the addition amount is limited in order to impart a recrystallized layer and maintain extrudability. To do. Therefore, the contents of these elements are specified in the following ranges.

Zr: 0.05 to 0.25% by weight, V: 0.03 to 0.15
% By weight, Mn: 0.2 to 0.6% by weight, Cr: 0.05 to 0.3% by weight.

Cu Cu is added to improve the strength and stress corrosion cracking resistance of the aluminum alloy. If the Cu content is less than 0.05% by weight, the effect is small. On the other hand, when the Cu content is 0.6% by weight or more, general corrosion resistance and extrudability deteriorate. Therefore, the content of Cu is set to 0.05 to 0.6% by weight.

In the aluminum alloy described in claim 2, the essential additive elements are Mg and Si, and in the aluminum alloy described in claim 3, the essential additive elements are Mg and Zn. The additional elements other than this are selectively added.

[0022] Ti in both alloy systems, for finer ingot tissue may contain 0.005 to 0.05% by weight of Ti.

[0023]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

Aluminum alloys having the components shown in Tables 1 and 2 below were melted by a conventional method and cast into an ingot having a diameter of 200 mm. Table 1 shows examples and comparative examples of the aluminum alloy described in claim 2, and Table 2 shows examples and comparative examples of the aluminum alloy described in claim 3.

[0025]

[Table 1]

[0026]

[Table 2]

Then, after subjecting each ingot to a required homogenizing treatment, it was extruded into a reinforcing member having a shape shown in FIG. While supporting this extruded material at its both ends as shown in FIG.
A bending test was performed by applying a load P to the central portion, and the maximum load at break and the displacement until break were examined.

FIG. 3 shows an example of curves of bending load and displacement. The energy absorption amount is indicated by the area of the hatched area in FIG. In this bending test, if the extruded profile breaks,
The load and displacement curves are as shown in Fig. 3B.
The load drops sharply and the amount of energy absorbed is small. Generally, a material having a high maximum load and a long displacement before breaking has a large amount of energy absorption and is suitable as a shock absorbing member. The results of this bending test are shown in Tables 3 and 4 below, corresponding to the alloys in Tables 1 and 2, respectively.

[0029]

[Table 3]

[0030]

[Table 4]

However, the extrudability was evaluated as superiority or inferiority at the maximum speed in the range where cracking occurs when extruding at a high speed, but this cracking does not occur. The standard is that the maximum extrusion speed is 10 m.
/ Min or more, ◯ indicates a maximum extrusion speed of 5 to 9 m / min, and × indicates a maximum extrusion speed of 2 m / min. The maximum bending load is
Under the conditions of this bending test, if it is 800 kg or more, it can be made lighter than steel material, so the maximum strength is 800 to 1100 k
The case of g is indicated by ○, and the case of 1100 kg or more is indicated by ◎. Furthermore,
Displacement until breakage is ◎ for 350 mm or more, 350 to 250 mm
The case is shown by ○, and the case of 200 mm or less is shown by ×.

As a result, as is clear from Tables 3 and 4, the thickness of the recrystallized layer was 70 μm in the case of the examples of the present invention.
Since it is m or more, it has excellent extrudability, high bending strength, large displacement until breakage, and excellent energy absorption capability. On the other hand, in the case of the comparative example in which the thickness of the recrystallized layer did not reach 70 μm or the recrystallized layer did not exist at all, either characteristic was low and the comprehensive evaluation was poor.

[0033]

As described in detail above, according to the present invention, since the recrystallized layer having a thickness of 70 μm or more is formed on the surface of the extruded material of aluminum alloy, the bending strength is high and the energy absorption ability is high. A highly lightweight automobile shock absorbing member can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing a part of the shape of a shock absorbing member according to an example and a comparative example of the present invention.

FIG. 2 is a perspective view showing a bending test method.

[Figure 3]

Claims (4)

[Claims] 1. An extruded material of an aluminum alloy,
An aluminum alloy automobile shock absorbing member, wherein a recrystallized layer having a thickness of 70 μm or more is present on the outer surface of this extruded material. 2. The extruded material comprises 0.5 to 1.7% by weight of Si.
And 0.5 to 1.5% by weight of Mg, and Zr;
05 to 0.25% by weight, Mn; 0.2 to 0.6% by weight, Cr;
5. An aluminum alloy containing one or more elements selected from 05 to 0.3% by weight and Cu; 0.1 to 1.0% by weight, and the balance being Al and an unavoidable impurity aluminum alloy. The automobile shock absorbing member made of the aluminum alloy according to [4]. 3. The extruded material comprises 0.5 to 1.5% by weight of Mg.
And Zr; 0.05 to 0.25 wt%, V; 0.03 to 0.15 wt%, Mn; 0.2 to 0.6 wt%, Cr; 0.05 to 0.3 wt% and Cu; 0.05.
The aluminum alloy shock absorber for automobiles according to claim 1, wherein the aluminum alloy contains one or more elements selected from 0.6 to 0.6% by weight, and the balance is Al and an aluminum alloy which is an unavoidable impurity. Element. 4. The aluminum alloy automobile shock absorbing member according to claim 1, wherein the extruded material contains 0.005 to 0.05% by weight of Ti.