JP3525979B2 - High strength aluminum alloy extruded material with excellent bending workability - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-strength aluminum alloy extruded material having excellent bending workability, which is suitable for automobile members and construction members such as frames and fuel tank brackets that require small bending work.

[0002]

2. Description of the Related Art Aluminum alloys have the advantages of being lighter in weight and less rusty than iron. Further, since the extruded material has an advantage that it can be extruded in an arbitrary cross-sectional shape, it has come to be widely used for housing sashes, automobile parts and the like. Among these automobile parts, for example, a frame material needs to be bent from an aluminum alloy extruded material into a desired shape, and in particular, there is a processed portion having a small bending radius in the body design, and it is required to reduce the weight by using a high-strength material. ing. Further, the fuel tank bracket needs to have a bending radius that matches the shape of the fuel tank, and therefore processing and weight reduction with a small bending radius are required to maximize the tank capacity. However, when working with a small bending radius, cracks are likely to occur during bending, and the extruded material tends to be thinned for weight reduction, so bending is becoming more difficult.

[0003]

As a method of performing bending with a small radius, there is a method of reducing the strength of the material and increasing the elongation to bend in order to suppress cracking during processing. In this case, However, there is a drawback in that the thickness must be increased in order to compensate for the decrease in strength and the weight is increased. In the rotary pull bending, there is a method of applying an axial force to reduce the strain on the outside of the bending, but in this case, there is a problem that wrinkles increase on the inside of the bending. When the strength of the material is increased by artificial aging or the like, the elongation is reduced accordingly and the bending radius may exceed the working limit. In such a case, a method in which bending is performed in the T1 tempered state and then the strength is increased by artificial aging is effective, but there is a drawback that the handling property for artificially aging the bending material is deteriorated. .

The present invention has been made in view of the above problems, and has a high strength and an excellent bending workability, and is a high-strength aluminum alloy extruded material suitable for a vehicle frame or a fuel tank bracket of a truck. The purpose is to provide.

[0005]

The aluminum alloy extruded material excellent in bending workability according to the present invention has a bending work with R / H of 2 or less (where R: bending inner diameter (radius), H: bending of cross section). Aluminum alloy extruded material that has a radial height (unit: mm), and a proof stress of 20 kgf / m
The elongation is 15% or more at m ² or more, and the plastic neutral axis Y in the cross section is (7H−R) / 10 or more from the inner side of bending , (8H
-R) / 10 or less. The plastic neutral axis means the center position of the cross-sectional area of the profile, that is, the position that divides the cross-sectional area into two equal parts, and the bending inner diameter means the distance from the center of bending to the bend inside of the profile. An aluminum alloy particularly suitable for this aluminum alloy extruded material is 0.5 to 1.5 wt% Si, 0.4 to 0.8 wt% Mg,
0.35 to 0.7 wt% Cu, 0.15 to 0.5
% Of Mn, 0.07 to 0.2% by weight of Zr and 0.001 to 0.05% by weight of Ti as main components, and 0.07 to 0.2% by weight of Cr as necessary. Then
The balance has a composition of Al and inevitable impurities.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The aluminum alloy extruded material according to the present invention is used for frame materials, fuel tank brackets, etc., which is equivalent to T63 temper of 6063 alloy or T4 of 6061 alloy.
The yield strength was 20 kgf / mm ² or more, which was equivalent to tempering. When bending with a small bending radius of R / H of 2 or less, cracking occurs if the elongation of the material is less than 15%,
Elongation is 15% or more.

Explaining the reason why the cross-sectional shape of the extruded material is limited, when the aluminum alloy extruded material having the above mechanical properties is used, the plastic neutral axis Y of the extruded material cross section is less than (7H-R) / 10 from the bending inner side. If so, cracks are likely to occur during bending, and in order to suppress the cracks, the core must be pulled (the core 1 is lowered to the right in FIG. 2) to allow the wrinkles. If the plastic neutral axis Y exceeds (8H-R) / 10 from the inside of the bend, cracking can be suppressed but wrinkles become large. Therefore, the plastic neutral axis Y of the cross section of the extruded material is (7H-R) / 10 or more, (8H
-R) / 10 or less.

In the aluminum alloy extruded material, as one of the measures for ensuring that the plastic neutral axis Y satisfies the above-mentioned range, for example, as shown in FIG. Connected surfaces Wa, W
An extruded material having a hollow cross-sectional shape of b and Wc and having a shape in which a part of the parallel surface is trapezoidally protruded inside the hollow portion can be mentioned. At this time, particularly when the width-thickness ratio of the hollow cross section is 15 or less, it is effective in suppressing the generation of wrinkles. In the above extruded material, the width-thickness ratio of the hollow cross section means that the length of the parallel portion of the protrusion is B (B ₁ , B ₂ ),
When the wall thickness is b (b ₁ , b ₂ ), it is defined as B / b. In the case of having a plurality of hollow cross-sections as shown in FIG. 5B, the width-thickness ratio B / b (B ₁ / b ₁ ,
The larger value of B ₂ / b ₂ ) may be set to 15 or less.

As the extruded material to which the present invention is applied, in addition to the cross-sectional shapes shown in FIG. 5 and Examples 1 to 3 below, cross-sections such as a day shape, an eye shape, a square shape, and a trapezoid shape can be used. Examples thereof include a hollow shape or a shape having a hollow portion, or a shape having a U-shaped cross section.

Next, the reason for adding each component and the reason for limiting the composition of the extruded aluminum alloy material according to the present invention will be described. With this composition, the aluminum alloy extruded material has the above-mentioned mechanical properties of high strength and high elongation and is excellent in bending workability. (Si) Si has the effect of increasing the strength of the aluminum alloy together with Mg. Further, Si also has the effect of improving the elongation characteristics of the aluminum alloy. However, if the Si content is less than 0.5% by weight, the effect of improving the strength cannot be sufficiently obtained. Also, the Si content is 1.5% by weight.
If it exceeds, strength is saturated and corrosion resistance is also reduced.
Therefore, the Si content is 0.5 to 1.5% by weight.

(Mg) Mg is a main element that enhances the strength of the aluminum alloy. However, the Mg content is 0.4
If it is less than wt%, the effect of improving the strength cannot be sufficiently obtained. Further, when the Mg content exceeds 0.8% by weight, the strength increases, but the elongation property deteriorates and the workability deteriorates. Therefore, the Mg content is 0.4 to 0.
8% by weight.

(Cu) Cu has the effects of increasing the strength of the aluminum alloy and improving the elongation characteristics. However, if the Cu content is less than 0.35% by weight, the strength and elongation cannot be sufficiently improved. However, Cu
If the content exceeds 0.7% by weight, the strength increases but the corrosion resistance deteriorates. Therefore, the Cu content is 0.1 to 0.7% by weight.

(Ti) Ti has the effect of refining the crystal grains in the aluminum alloy ingot. However, if the Ti content is less than 0.001% by weight, the effect cannot be sufficiently obtained. Further, when the Ti content exceeds 0.05% by weight, the effect of refining the crystal grains is saturated, and the addition of more than that is wasted. Therefore, the Ti content is 0.00
1 to 0.05% by weight.

(Mn, Cr, Zr) Mn, Cr and Zr
All have the effect of refining the crystal grains. But M
n content is less than 0.15% by weight, Zr content is 0.07
If the content is less than 10% by weight and the Cr content is less than 0.07% by weight, the respective effects are not sufficient, the Mn content exceeds 0.5% by weight, the Zr content exceeds 0.2% by weight, and Cr If the content exceeds 0.2% by weight, the effect of addition is saturated. Therefore, the Mn content is 0.15 to 0.5% by weight, the Zr content is 0.07 to 0.2% by weight, and the Cr content is 0.07 to 0.2% by weight. Note that Cr is a selective element and may be added as necessary.

[0015]

EXAMPLES Next, examples of the present invention will be described in comparison with comparative examples. (Example 1) First, an aluminum alloy ingot (diameter: 155 mm) having the composition shown in Table 1 was melted by a usual method. Incidentally, Comparative Example 6 is equivalent to 6N01, and Comparative Example 7 is 606.
3 and Comparative Example 8 are 6061 equivalent aluminum alloys, and Comparative Examples 9 and 10 are the same aluminum alloys as Invention Example 1. Then, at a temperature of 520 ° C., 4
Homogenization treatment was performed. After that, the extrusion temperature is 500
Each ingot was extruded at a temperature of ℃ and an extrusion speed of 10 m / min, and immediately cooled with water. All of the cross sections are square and the external dimensions are 40 mm × 40 mm (H = 40 mm).
As shown in (a), (b) and (c), the plastic neutral axis in the cross section was changed by the thickness distribution. As shown in Table 2 below, Invention Examples 1 and 2 and Comparative Examples 1 to 8 are cross-sections C, Comparative Example 9 is cross-section A, and Comparative Example 10 is cross-section B.

[0016]

[Table 1]

Next, each extruded material is cut into a predetermined length, and 17
An artificial aging treatment was performed at a temperature of 5 ° C. for 6 hours to obtain a test material. The yield strength σ0.2 and the breaking elongation δ of these test materials are J
It measured according to the metal material test method prescribed | regulated to JISZ2241 using the IS5 test piece. Table 2 shows the results and the evaluation (evaluation 1) of the mechanical properties.

Further, a bending test was conducted for each of the test materials of the invention example and the comparative example, with the arrow side in FIG.
A draw bender is used for the bending test. As shown in the schematic view of FIG. 2, the core 1 is inserted inside each test material 10, and the clamp die 2, pressure die 3, wiper die (wrinkle prevention metal )
Bending was performed by using No. 4 and the bending die 5, and at this time, the bending inner diameter of the bender was 70 mm (R = 70 mm), and the presence or absence of cracks and the wrinkle height during 90 ° bending were measured. Under the bending conditions of this example, the plastic neutral axis Y is 2 from the inside of the bend.
The case of 1 ≦ Y ≦ 25 is within the specified range of the present invention. Table 2 shows the results of this bending test and the evaluation of bending workability (evaluation 2). Here, the case where cracks occurred or the case where the wrinkle height exceeded 2 mm was marked with X, and the case where no crack occurred and the wrinkle height was 2 mm or less was marked with O. Furthermore, comprehensive evaluation (Both evaluation 1 and evaluation 2 are evaluated as ○,
Any one of which is evaluated as x) is shown at the end of Table 2.

[0019]

[Table 2]

As is clear from Table 2, all of the invention examples had good strength, elongation and bending workability, and none of the comparative examples had satisfactory bending workability and mechanical properties.

(Example 2) Aluminum alloys having compositions of invention examples 1 and 2 and comparative examples 1 to 10 shown in Table 1 were extruded, and as shown in FIG. 3, a cross section composed of both flanges and two webs. A shaped material (H = 50 mm) was obtained. At that time, as shown in FIGS. 3D, 3E and 3F, the thickness of one flange was changed to change the plastic neutral axis. As shown in Table 3 below, Invention Examples 1 and 2 and Comparative Examples 1 to 8 are cross-sections, Comparative Example 9 is cross-section D, and Comparative Example 10 is cross-section E. The process before and after extrusion was the same as that of Example 1 including the artificial aging treatment.

For this test material, the mechanical characteristics are considered to be the same as in Table 2 of Example 1, so the measurement test was omitted.
Only a bending test was performed. In the bending test, as in Example 1, the inside of the bend was set to 70 mm (R = 70 mm) using the bend bender with the arrow side in FIG. 3 being the bending inside, and the presence or absence of cracks and the wrinkle height during 90 ° bending were measured. . Under the bending processing conditions of this example, when the plastic neutral axis Y is 28 ≦ Y ≦ 33 from the inside of the bending, it is within the specified range of the present invention. Table 3 shows the results of this bending test and evaluation of bending workability (evaluation 2). The evaluation criteria are the same as in Table 2 of Example 1.
(In addition, in Table 3, the mechanical properties and the evaluation (evaluation 1) obtained in the measurement test of Example 1 are also shown.) Furthermore, the comprehensive evaluation (the evaluation criteria are the same as those in Example 1) is shown in Table 3.
Showed at the end of.

[0023]

[Table 3]

As is apparent from Table 3, all of the invention examples had good strength, elongation and bending workability, and none of the comparative examples had satisfactory bending workability and mechanical properties.

(Example 3) An aluminum alloy having the composition of Inventive Example 1 in Table 1 was extruded, and as shown in FIG. 4, a cross-sectional shape member (H = 50) composed of both flanges and two webs.
mm) was obtained. However, one of them (FIG. 4H) changed the plastic neutral axis by making the center of one flange project trapezoidal inside the hollow portion. The process before and after extrusion was the same as that of Example 1 including the artificial aging treatment. For this test material, the bending test was performed using a draw bender with the arrow side in FIG.
The bending inner diameter was 70 mm (R = 70 mm), and the presence or absence of cracks and the wrinkle height during 90 ° bending were measured. Under the bending processing conditions of this example, when the plastic neutral axis Y is 28 ≦ Y ≦ 33 from the inside of the bending, it is within the specified range of the present invention.

The plastic neutral axis Y and the width-thickness ratio B / b of this test material
Table 4 shows the value of and the bending test result. As is clear from Table 4, the cross-section C (invention example) has the plastic neutral axis and the width-thickness ratio satisfying the requirements of the present invention, has no cracks, has a small wrinkle height of 2 mm or less, and is excellent in bending workability. Was there. However, in each of the comparative examples, cracking occurred and bending workability was poor.

[0027]

[Table 4]

[0028]

According to the present invention, it is possible to obtain an aluminum alloy extruded material satisfying predetermined mechanical properties and at the same time excellent in bending workability. This aluminum alloy extruded material shows excellent bending workability even in bending with a small radius of R / H of 2 or less, and has a small bending radius such as a vehicle frame or a fuel tank bracket for a truck. Suitable for

[Brief description of drawings]

FIG. 1 is an explanatory view of a cross-sectional shape of a test material used in an example.

FIG. 2 is a simple explanatory view of the bending method used in the examples.

FIG. 3 is an explanatory view of a cross-sectional shape of a test material used in Examples.

FIG. 4 is an explanatory view of a cross-sectional shape of a test material used in Examples.

FIG. 5 is a schematic sectional view showing a preferred embodiment of the present invention.

[Explanation of symbols]

1 core 2 clamp type 5 Bending type

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) B21D 7/00 C22C 21/00 C22F 1/04

Claims (9)

(57) [Claims] 1. A bending process in which R / H is 2 or less (however, R:
Bending an inner diameter, H: the cross section of the bending radius direction of the height, a both units an aluminum alloy extruded material is subjected to a mm), yield strength has elongation of 15% or more at 20 kgf / mm ² or more, the bending inward And the surface on the outside of the bend are parallel,
And the surface on the outside of bending is thicker than the surface on the inside of bending
The plastic neutral axis Y in the cross section from the inside of the bend (7H
A high-strength aluminum alloy extruded material excellent in bending workability, characterized by being in the range of -R) / 10 or more and (8H-R) / 10 or less. 2. A bending process in which R / H is 2 or less (however, R:
Bending inner diameter, H: height of cross section in bending radius direction, both are single
The position is mm)
Yield strength of 20 kgf / mm ² or more and elongation of 15% or more
Yes, a hollow cross-sectional shape by a plurality of surfaces that leads to their two parallel opposed faces, and have a part of the surface of bending on the inside of the plane parallel is projected into the hollow portion inside in a trapezoidal shape, The plastic neutral axis Y in the cross section is from the inside of the bend
Range of (7H-R) / 10 or more and (8H-R) / 10 or less
A high-strength aluminum alloy extruded material with excellent bending workability, which is characterized by being inside the enclosure . 3. The high-strength aluminum alloy extruded material excellent in bending workability according to claim 2, wherein the width-thickness ratio of the hollow cross-section is 15 or less. 4. A bending process in which R / H is 2 or less (however, R:
Bending inner diameter, H: height of the cross-section in the bending radius direction, each of which is in mm) is an aluminum alloy extruded material,
The yield strength of the unprocessed part is 20 kgf / mm ² or more and the elongation is 15
% Or more, and the surface inside and outside the bend in the cross section
Are parallel to each other, and the outside surface of the bend is thicker than the inside surface
The plastic neutral axis Y in the cross section is large (7
A high-strength aluminum alloy extruded material having excellent bending workability, which is in the range of (HR) / 10 or more and (8HR) / 10 or less. 5. A bending process in which R / H is 2 or less (however, R:
Bending inner diameter, H: height of cross section in bending radius direction, both are single
An aluminum alloy extruded material having a unit of mm),
The yield strength of the unprocessed part is 20 kgf / mm ² or more and the elongation is 15
% Or more Yes, a hollow cross-sectional shape by a plurality of surfaces that leads to their two parallel opposed faces, and have some of the bent inner surface of the parallel plane is projected into the hollow portion inside the trapezoidal , The plastic neutral axis Y in the cross section is
Range of (7H-R) / 10 or more and (8H-R) / 10 or less
A high-strength aluminum alloy extruded material with excellent bending workability , characterized by being inside the enclosure . 6. The high-strength aluminum alloy extruded material having excellent bending workability according to claim 5, wherein the width-thickness ratio of the hollow cross-section is 15 or less. 7. 0.5 to 1.5% by weight of Si, 0.4
To 0.8 wt% Mg, 0.35 to 0.7 wt% Cu, 0.15 to 0.5 wt% Mn, 0.07 to 0.2 wt% Zr and 0.001 to 0. 0.05% by weight
Ti as the main component, and if necessary 0.07 to 0.2
The high-strength aluminum alloy extruded material excellent in bendability according to any one of claims 1 to 6, which has a composition containing Cr by weight and the balance being Al and inevitable impurities. 8. A vehicle frame material comprising the aluminum alloy extruded material according to any one of claims 4 to 7 as a part of constituent elements. 9. A fuel tank bracket material for a truck, comprising the aluminum alloy extruded material according to any one of claims 4 to 7 as a part of constituent elements.