JP2002173728A - Al-Mg BASED ALUMINUM ALLOY HOLLOW EXTRUSION MATERIAL FOR BULGING - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aluminum alloy hollow extrusion material for bulging suitable to forming for the frames, joints or the like of automobiles, rolling stocks or building members. SOLUTION: The Al-Mg based aluminum alloy extrusion material contains, by mass, 1.5 to 5.0% Mg and 0.005 to 0.2% Ti. Provided that its total elongation is defined as δT, and uniform elongation as δU, δT is controlled to >=15%, and δU/δT to >=0.75.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy hollow extruded material having excellent bulge formability suitable for forming a frame or a joint portion of an automobile, a railway car or a building member.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of environmental problems such as global warming and destruction of the ozone layer, in order to suppress an increase in carbon dioxide gas in the atmosphere, lightening of automobiles and introduction of electric automobiles have been in earnest. Is being considered. As part of this reduction in weight, the replacement of materials, that is, the use of aluminum alloy materials instead of steel plates that have been mainly used in conventional structural materials for automobiles is increasing. Also in electric vehicles, there is a strong need to reduce the weight of the vehicle body to compensate for the increase in weight for loading batteries. Furthermore, the use of aluminum alloy materials has attracted attention, as extruded materials that provide a constant, but free cross-sectional shape in the longitudinal direction can expand the degree of freedom of design and improve the formability by obtaining a cross-sectional shape close to the final shape. For example, Japanese Patent Application Laid-Open No. 2000-177621 describes that an aluminum alloy extruded material is used for manufacturing a suspension subframe.

On the other hand, bulge forming has attracted attention as a method for forming parts having complicated shapes such as a joint member used for joining frames to each other at the time of assembling a vehicle body and a suspension subframe. It is known to use a suspension bulge formed by bulging. In addition, Japanese Patent Laid-Open No. 5-2
Japanese Patent No. 12464 describes that a 5000 series (Al-Mg based) aluminum alloy plate is hydraulically formed.

[0004]

In the case of Al-Mg based aluminum alloys, an annealing material (O material), which is generally advantageous in terms of formability, has been used as a material for bulging. However, when the overhang height of the bulge molding was high, a crack was formed at the top of the overhang portion, and the overhang molding could not be performed greatly. The present invention has been made in view of such problems with respect to bulge forming of an Al-Mg-based aluminum alloy, and is excellent in bulge formability (particularly, overhang height), and is suitable for a frame of an automobile, a railway vehicle, or a building member. Another object of the present invention is to provide an Al-Mg-based aluminum alloy hollow extruded material suitable for forming a joining member and the like.

[0005]

Means for Solving the Problems The inventors of the present invention conducted various experimental studies to develop an Al-Mg-based aluminum alloy hollow extruded material having excellent bulge formability. In the case where excellent bulge formability is not obtained, it is further found that when the ratio of uniform elongation to elongation at break shows a predetermined value or more, excellent bulge formability can be obtained, and it is possible to obtain the present invention based on it. did it.

That is, the Al-Mg-based aluminum alloy hollow extruded material according to the present invention contains 1.5 to 5.0% of Mg and 0.005 to 0.2% of Ti, and has a total elongation of δ _T. An Al—Mg-based aluminum alloy hollow extruded material for bulge forming, wherein δ _T is 15% or more and δ _U / δ _T is 0.75 or more, when uniform elongation is δ _U. . In the present invention, bulge molding refers to expanding a part of a member by using fluid pressure (sometimes called hydroforming) and expanding a part of the member by applying a negative pressure to the outside of the member. Means to put out.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The Al-Mg-based aluminum alloy contains, if necessary, one or more of Mn, Cr, Zr and V as additional elements other than the above, and further contains Fe as an unavoidable impurity. , And other elements. Hereinafter, the reason for adding each component in the aluminum alloy hollow extruded material according to the present invention will be described. Mg Mg forms a solid solution in the aluminum matrix and improves the alloy strength. Strength required for structural members such as automobile frames or joint members (proof strength σ0.2 ≧ 50MPa)
In order to obtain Mg, it is necessary to add 1.5% or more of Mg. However, if added in excess of 5.0%, the amount of solid solution becomes excessive, and δ _U / δ _T becomes less than 0.75, so that excellent bulge formability cannot be obtained. Therefore, the Mg content is 1.
5 to 5.0%. A more desirable range is 2.0-4.
0%.

[0008] Ti Ti improves the alloy strength by refining the crystal grains during casting. To achieve this effect, Ti
It is necessary that the added amount be 0.005% or more. Further, when less than 0.005%, it is difficult to crystal grains get larger [delta] _T and [delta] _U / [delta] _T coarse. on the other hand,
If the amount of Ti exceeds 0.2%, the above effect is saturated, and further, a coarse intermetallic compound is crystallized to obtain a predetermined alloy strength,
[delta] _T and [delta] _U / [delta] _T can not be obtained. Therefore, the content of Ti is set to 0.005 to 0.2%, more preferably 0.01 to 0.1%, and still more preferably 0.01 to 0.1%.
05%.

Mn, Cr, Zr, V One or more of these elements may be used, if necessary, in order to control the structure in the manufacturing process, that is, to prevent crystal grains from coarsening and improve stress corrosion cracking resistance. Is added. 0.05%, 0.05%, 0.05%, 0.01 respectively
% Or less, the effect is not obtained.
3% saturated, the effect exceeds 0.3%, also coarse intermetallic compound is crystallized predetermined alloy strength, [delta] _T and [delta]
_U / δ _T cannot be obtained.

Inevitable impurities Fe is the most inevitable impurity contained in aluminum ingots. If it exceeds 0.5% in the alloy, coarse intermetallic compounds are crystallized during casting, and the mechanical properties of the alloy are reduced. Impair the nature. Therefore, the content of Fe is restricted to 0.5% or less. Further, when casting an aluminum alloy, impurities are mixed from various routes such as a base metal, an intermediate alloy of an additional element, and a compound. The elements to be mixed are various,
Of impurities other than Si, 0.4% or less of Si and 0.2% of Cu
% Or less, Zn is 0.2%, and other impurities are 0.1% by itself.
If it is not more than 05% and the total amount is not more than 0.15%, it hardly affects the properties of the alloy. Therefore, these impurities are set to the above numerical values or less. In addition, B among impurities is mixed into the alloy in an amount of about 1/5 of the Ti content with the addition of Ti, but a more preferable range is 0.02% or less, and further preferably 0.01% or less.

Further, the Al—Mg based aluminum having the above composition
Δ_TIs not less than 15% and δ_U
/ Δ_TIs excellent in bulge formability when is more than 0.75
About the uniform elongation δ_UIs large,
The deformation of the overhang during bulge forming is not localized,
Can withstand more intense machining due to mechanical deformation and dispersion of strain
It is supposed to be. On the other hand, conventionally used for bulge molding
O material was changed to δ as shown in the examples described later._TIs large
Even δ_U/ Δ_TIs relatively small, and the overhang is locally deformed
It is probable that the cracks were concentrated. Of the above composition
In the extruded Al-Mg aluminum alloy, δ_TPassing
And δ_U/ Δ _TThe material satisfying the above conditions is, for example, H11
It can be obtained from two materials (see JIS H0001). After extrusion
A tretch (correction) may be performed. δ_TAnd δ_U/ Δ_T
Collects a tensile test specimen specified in JIS from the extruded material,
It can be determined by conducting a tensile test.

The Al-Mg-based aluminum alloy hollow extruded material according to the present invention can be produced by various extrusion methods, but indirect extrusion produces coarse recrystallized grains on the surface of the extruded material rather than direct extrusion. Is desirable in the sense of preventing
Further, the mandrel method is more preferable than the port hole method from the viewpoint of ensuring the uniformity of the structure in the cross section (there is no welded portion).

[0013]

Next, an embodiment of the present invention will be described. First, aluminum alloy ingots having the compositions shown in Table 1 below were melted by a usual method, and these ingots were subjected to 520 ° C. × 4
hr, an extrusion process was performed at an extrusion temperature of 520 ° C. and an extrusion speed of 5 m / min. 1 to
About 8, the outer diameter is 38.5 mm and the wall thickness is 1.5 mm
No. round pipe, No. 9 has an outer diameter of 47.0 mm,
A round pipe having a thickness of 1.5 mm was obtained. The material was cooled by air cooling with a fan (cooling rate: about 100 ° C./min) immediately after extrusion. No. Nos. 1 to 5 are left as they are. 6 ~
No. 8 was annealed at 380 ° C. × 2 hr after stretching. 9 was drawn to an outer diameter of 38.5 mm,
The thickness was 1.5 mm (H34), and each was used as a test material.

[0014]

[Table 1]

[0015] For this test materials, to create a JIS12A No. 5 test pieces were a tensile test according to JISZ2241, the tensile strength .sigma.B, the [delta] _T (elongation to fracture) strength σ0.2 and total elongation determined Was. Further tensile tests obtained in stress - based on strain diagram, calculated elongation to the point showing the maximum stress as the uniform elongation [delta] _U, the ratio to the total elongation of the uniform elongation [delta] _{U /} [delta]
_T was calculated. Table 2 shows the results. Further, this test material was cut into a length of 177 mm, and a bulge forming test was performed. FIG. 1 is a schematic view showing a bulge forming test method. Each test material (pipe) 5 is set on a lower die 1, mandrels 2 and 3 are inserted into end surfaces of the pipes, and then an upper die 4 is tightened. At the same time as applying pressure to the inside of the pipe by passing water 6 through the holes 2a and 3a inside the pipe 3, the mandrel 2 and 3 were moved to compress the pipe in the longitudinal direction, thereby forming a T-shape. The internal pressure (water pressure) was set to 14.7 MPa, the mandrel compression amount was set to 85 mm (42.5 mm on one side), and the overhang height (see FIG. 2) was set to 70 mm. The bulge formability was evaluated based on the presence or absence of cracks (cracks) generated on the surface of the overhang head. The results are shown in Table 2 below. Here, no cracking was evaluated as ○, and cracking was evaluated as x.

[0016]

[Table 2]

As shown in Table 2, the component composition, δ
The value of _T and [delta] _U / [delta] _T satisfies the provisions of the present invention No. 1
No. 3 to No. 3 have good bulge formability and have a proof stress σ 0.2
Also satisfies the required strength as a structural member. On the other hand, No. 2 having a large amount of Mg No. 4 has a small value of δ _U / δ _T , is inferior in bulge formability, and has a small amount of Mg. No. 5 has insufficient proof stress.
In addition, No. 3 having a small value of δ _U / δ _T was used. 6-7 and total elongation δ
No. _T less than 15%. No. 9 is inferior in bulge formability.
In addition, the extruded material according to the present invention also has good mouth-opening workability such as bending of an end portion and hemming workability.

[0018]

As described above, as described above, Al-
In the case of Mg-based aluminum alloy hollow extruded material, the total elongation δ
_By setting _T and the ratio δ _U / δ _T of the uniform elongation to the total elongation to a predetermined value or more, excellent bulge formability can be obtained. This Al-Mg-Si-based aluminum alloy hollow extruded material is suitable as a bulge forming material for frames and joining members of automobiles, railway vehicles, ships or building members.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a bulge forming test method according to an example.

FIG. 2 is an explanatory diagram of an overhang height by a bulge forming test of an example.

[Explanation of symbols]

 1 Lower mold 2, 3 Mandrel 4 Upper mold 5 Test material (pipe)

Claims (1)

[Claims] 1. Al containing 1.5 to 5.0% (mass%, hereinafter the same) of Mg and 0.005 to 0.2% of Ti.
Consists -Mg series aluminum alloy hollow extruded material, the total elongation [delta] _T, when the uniform elongation was [delta] _U, wherein the [delta] _T is at least 15%, and [delta] _U / [delta] _T is 0.75 or more Al-Mg based aluminum alloy hollow extruded material for bulge forming.