JP2002097540A - Hollow member of aluminum alloy superior in hydroforming property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hollow member of an aluminum alloy which is suitable for forming a frame member or a bonding member of an automobile, a vehicle or a building, and is superior in a hydroforming property. SOLUTION: The hollow member of the aluminum alloy comprises a composition of 0.5-1.4% Si, 0.30-0.75% Mg, 0.1-0.4% Fe, 0.005-0.1% Ti, 0.0001-0.004% B, 0.02-0.20% Mn and 0.05-0.25% V so as to satisfy 0.12%<=Mn+V<=0.30%, and 0.03-0.4% Cu, and one or two kinds of 0.02-0.05% Cr and 0.02-0.05% Zr as needed, and Al and inevitable impurities as the balance. It further comprises a crystal grain structure which satisfies a condition of (Dl+Dt)/2<=100 μm and Dl/Dt<=2.0, wherein Dl is an average crystal grain size in the longitudinal direction of the hollow member, and Dt is an average crystal grain size in the short transverse direction of the hollow member.

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 member excellent in hydroforming properties suitable for forming a frame, a joint member, or the like of an automobile, a vehicle, or a building member.

[0002]

2. Description of the Related Art In recent years, due to environmental problems such as global warming, there has been a strong demand for reducing the weight of automobiles in order to reduce exhaust gas and improve fuel efficiency. As a method of reducing the weight of the car body,
The most effective method is to replace a steel sheet, which has been mainly used in the past, with an aluminum material, and the use of aluminum alloy materials, especially extruded or drawn aluminum alloy materials, which can integrally form structures having complicated shapes, is increasing. I have.
For example, a hollow member obtained by extruding or further drawing an aluminum alloy ingot is integrally formed into a predetermined shape, and these are joined to form a vehicle body skeleton. It is commercialized in. As a processing technique for integrally molding these aluminum alloy extruded hollow members into a predetermined shape, a hydroforming technique has recently attracted attention. Hydroforming is a processing method mainly including pipe expansion molding by hydraulic pressure in a pipe material mold, and can freely change the cross-sectional shape of the same member. In this processing method, for example, prior to hydroforming, it is also generally practiced to form and bend a tube into a complex cross-sectional shape using a movable die in preforming. In addition, in the hydraulic forming, in many cases, the inflow of the material into the deformed portion is promoted by pushing in the tube axis direction.

[0003] As an aluminum alloy hollow member for performing such hydroforming, at present there are 60 members.
Al-M such as 63 alloy, 6N01 alloy, 6061 alloy
A hollow member obtained by extruding a g-Si alloy is mainly used (for example, see Japanese Patent Application Laid-Open No. 10-4).
No. 6280). After the hollow member is processed into a predetermined cross-sectional shape by preforming, hydroforming is performed. In addition, taking advantage of the characteristics of the extruded shape that can be formed into a free cross-sectional shape, a hollow shape that has been extruded into a predetermined cross-sectional shape other than a tubular shape in advance is used as a raw material, and directly from this shape or an appropriate preliminary molding is performed. After that, hydroforming has been performed.

[0004]

However, Al-Mg
-Si-based alloys, for example, 6063 alloy, 6N01 alloy,
In the 6061 alloy and the like, the high-strength T5 or T6 material is inferior in hydroforming properties, so that it was necessary to use an O material having a high pipe expansion ratio. However,
In the case of molding using O material, heat treatment including solution heat treatment, quenching, and aging must be performed after molding in order to obtain the necessary strength for parts, and deformation due to thermal stress and quenching distortion is inevitable. There was a problem. Further, when the O material is used as it is in order to avoid the decrease in accuracy, it is necessary to increase the plate thickness because the strength is low, and there is a problem that the weight reduction effect by the aluminum alloy is reduced. The present invention has been made in view of such a problem, and an object of the present invention is to provide an aluminum alloy hollow member having both strength required for a part and good hydroforming properties.

[0005]

SUMMARY OF THE INVENTION From the above viewpoint, the present inventors have studied to obtain a hollow member having sufficient strength and excellent hydroforming properties of a molded part obtained by hydroforming. As a result, all of the hollow members made of an Al alloy having the component composition and the crystal grain structure described in the following (a) to (c) have excellent hydroforming properties, and furthermore, these hollow members are subjected to artificial aging treatment. Thus, a research result was obtained that mechanical strength of 160 MPa or more was obtained. (A) In mass% (% indicates mass%), Si:
0.5 to 1.4%, Mg: 0.30 to 0.75%, F
e: 0.1 to 0.4%, Ti: 0.005 to 0.1%,
B: contains 0.0001 to 0.004%, the balance being Al
Mn and V are further added to an Al alloy having a composition consisting of
0.05 to 0.25% (however, 0.12% ≦ Mn + V
≦ 0.3%), the average crystal grain size in the length direction of the hollow member is Dl, and the average crystal grain size in the thickness direction of the hollow member is Dt.
+ Dt) / 2 ≦ 100 μm and a hollow member made of an Al alloy having a crystal grain structure satisfying the conditions of Dl / Dt ≦ 2.0. (B) In addition to the Al alloy described in (A), Cu:
A hollow member made of an Al alloy containing 0.03 to 0.4%, (c) an Al alloy according to the above (a) or (b),
Further, Cr: 0.02 to 0.05%, Zr: 0.02 to
A hollow member made of an Al alloy containing one or two of 0.05%,

The present invention has been made based on the above research results, and (1) Si: 0.5 to 1.4.
%, Mg: 0.30 to 0.75%, Fe: 0.1 to 0.1%.
4%, Ti: 0.005 to 0.1%, B: 0.0001
０．００0.004%, and further, Mn and V
n: 0.02 to 0.20%, V: 0.05 to 0.25
%, 0.12% ≦ Mn + V ≦ 0.30%, the balance being Al and unavoidable impurities, Dl as the average crystal grain size in the longitudinal direction of the hollow member, and Dt as the hollow member. The average crystal grain size in the thickness direction of (Dl +
(Dt) / 2 ≦ 100 μm, D1 / Dt ≦ 2.0, an aluminum alloy hollow member excellent in hydroformability, made of an Al alloy having a crystal grain structure, and (2) Si: 0.5 to 1 0.4%, Mg: 0.30
0.75%, Fe: 0.1 to 0.4%, Ti: 0.00
5 to 0.1%, B: 0.0001 to 0.004%, C
u: 0.03 to 0.4%, and Mn and V are further changed to Mn: 0.02 to 0.20%, V: 0.05 to
0.25%, 0.12% ≦ Mn + V ≦ 0.30%, the balance being composed of Al and unavoidable impurities, and Dl containing an average crystal grain size in the longitudinal direction of the hollow member,
When Dt is the average crystal grain size in the thickness direction of the hollow member,
(Dl + Dt) / 2 ≦ 100 μm, Dl / Dt ≦ 2.0
(3) an aluminum alloy hollow member having an excellent hydroforming property made of an Al alloy having a crystal grain structure satisfying the following conditions: (3) an Al alloy having the composition described in the above (1) or (2), further comprising Cr: 0 .02-0.05
%, Zr: 0.02 to 0.05% of an aluminum alloy hollow member having an excellent hydroforming property and made of an Al alloy having a composition containing one or two of them.

The aluminum alloy hollow member having excellent hydroforming properties according to the above (1), (2) or (3) is obtained by DC casting a billet having the component composition as described in the above (1), (2) or (3). The billet is prepared by the following method, and the billet is subjected to a homogenizing heat treatment.
It is produced by extruding at a temperature in the range of 450 to 550 ° C., immediately followed by water cooling or water cooling followed by drawing. Here, the drawing process is a cold process for obtaining a predetermined dimensional accuracy by reducing the cross section of the extruded material through a die. In the aluminum alloy hollow member thus obtained, assuming that the average crystal grain size in the length direction of the hollow member is Dl and the average crystal grain size in the thickness direction of the hollow member is Dt, (Dl + Dt) / 2 ≦ 10.
0 μm, and has a grain structure satisfying the condition of Dl / Dt ≦ 2.0.

When the hollow member according to any one of the above (1) to (3) is subjected to artificial aging treatment at a temperature of 150 to 210 ° C. for 1 to 24 hours, a hydroforming having a yield strength of 160 MPa or more is performed. An aluminum alloy hollow member having excellent properties can be obtained.

The reason why the component composition and crystal grain size of the aluminum alloy constituting the hollow member are limited as described above will be described. A. Component Composition (a) Si, Mg These components have the effect of improving the strength by precipitating as fine Mg ₂ Si compounds, but the content of either Si or Mg is less than 0.5%. Mg: 0.3
%, The amount of precipitates formed is so small that the desired strength cannot be ensured. On the other hand, if the content exceeds 1.4% Si and 0.75% Mg, hydroforming occurs. This is not preferred because the properties, bending workability, and extrusion or drawing workability are reduced.
Therefore, Si: 0.5 to 1.4%, Mg: 0.30
０．７0.75%. More preferable ranges of Si and Mg are: Si: 0.7 to 1.2%, Mg: 0.40 to 0.1%.
60%.

(B) Fe The Fe component forms an intermetallic compound with Al, which serves as a nucleation site for recrystallization, and makes the extruded structure a fine equiaxed grain structure. As a result, hydroforming properties and It has an effect of improving bending workability, but if its content is less than 0.1%, the desired effect cannot be obtained.
Addition of more than 0.4% is not preferred because recrystallization at the time of extrusion is suppressed and elongated grains and a fibrous structure appear, and hydroforming properties deteriorate. Therefore, the addition amount of Fe is set to 0.1 to 0.4%.

(C) Ti, B These components are added because they have the effect of refining the cast structure and preventing casting cracks. However, even if the content of either Ti or B is less than 0.005%, B: 0.000
If it is less than 1%, the desired effect cannot be obtained. On the other hand, if any of the contents of Ti and B exceeds 0.1% of Ti and 0.004% of B, a huge intermetallic compound is formed. As a result, the toughness is lowered, and the hydroforming property and the bending workability are lowered, which is not preferable.
Therefore, the contents of Ti and B are respectively set to Ti:
0.005 to 0.1%, B: 0.0001 to 0.004
%.

(D) Mn, V These components together form an intermetallic compound with Al, and these serve as nucleation sites for recrystallization to make the extruded structure a fine equiaxed grain structure. Hydroformability and bendability are improved, and the effect is particularly enhanced by adding these components in combination. However, when the content of Mn and V is less than 0.02%,
V: If less than 0.05%, the desired effect cannot be obtained, while
Content of Mn and V is Mn: 0.20%, V: 0.2
If it exceeds 5%, recrystallization at the time of extrusion is suppressed, and a fibrous structure appears, which is undesirable because hydroforming properties and bending workability deteriorate. Therefore, the contents of Mn and V are respectively Mn: 0.02 to
0.20%, V: 0.05 to 0.25%. Mn
And V need to be added in combination, and the amount added at that time is such that the sum of Mn and V is 0.12% ≦ Mn + V ≦
More preferably, the condition of 0.30% is satisfied. Therefore, the added amount of Mn and V is Mn: 0.02 to 0.2.
0%, V: 0.05 to 0.25% and 0.12% ≦ M
n + V ≦ 0.30%.

(E) Cu Cu is added as needed because it has the effect of improving the strength of the hollow member by forming a solid solution in the base material. If the Cu content is less than 0.03%, a desired Cu content is obtained. The effect of improving the strength cannot be obtained. On the other hand, if the content exceeds 0.4%, the corrosion resistance decreases, which is not preferable. Therefore, Cu:
0.03 to 0.4%.

(C) Cr, Zr These components together form an intermetallic compound with Al, these serve as nucleation sites for recrystallization, and the extruded structure has a fine equiaxed grain structure, and the hydroforming property And Cr is added as necessary to improve the bending workability. However, if Cr: less than 0.02% and Zr: less than 0.02%, the desired effects cannot be obtained. On the other hand, Cr: 0.05%, Z
When r exceeds 0.05%, recrystallization at the time of extrusion is suppressed, and elongated grains and a fibrous structure appear, and hydroforming properties and bending workability are undesirably deteriorated. Therefore, the contents of Cr and Zr are respectively Cr: 0.02 to 0.05% and Zr: 0.
It was set to 02-0.05%.

B. Structure (f) Average Particle Size and Shape of Crystal Grains The hollow member is manufactured by extrusion or further drawing, and the structure of the obtained hollow member is preferably as fine as the crystal grains are. Assuming that the average crystal grain size in the direction of direction is Dl and the average crystal grain size in the thickness direction of the hollow member is Dt, (Dl + Dt) / 2 ≦ 10
The thickness must be 0 μm, and in order to further enhance the hydroforming property, it is preferable to use relatively spherical crystal grains without a fibrous structure. Therefore, the crystal grain of the Al alloy constituting the hollow member of the present invention is (Dl + Dt) / 2 ≦ 1
It was determined to be within a range of 00 μm and D1 / Dt ≦ 2.0.

C. Mechanical properties Aluminum alloy hollow members for hydroforming require strength, and have a proof strength of 160M.
It must be Pa or more.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Having the compositions shown in Tables 1 and 2,
An Al alloy billet having a diameter of 204 mm is melted, and the billet is subjected to a homogenization treatment at a temperature of 545 ° C. for 4 hours, and then an extruder of 1650 tons is used. : 5m / min
The aluminum alloy hollow member of the present invention having a wall thickness of 2.7 mm and an outer diameter of 43 mm is subjected to an artificial aging treatment at 160 ° C. for 4 to 8 hours. Hereinafter, hollow members of the present invention 1 to 16, comparative aluminum alloy hollow members 1 to 4 (hereinafter, comparative hollow members), and conventional aluminum alloy hollow members (hereinafter, conventional hollow members) 1 to 2 were produced.

[0018]

[Table 1]

[0019]

[Table 2]

The hollow member 1 of the present invention thus obtained
-16, comparative hollow members 1-4 and conventional hollow members 1-2
Observing the microstructure of the cross section of the above, if the average crystal grain size in the length direction of the hollow member is Dl and the average crystal grain size in the thickness direction of the hollow member is Dt, the values of (Dl + Dt) / 2 and Dl / Dt And the results are shown in Table 3.

Further, tensile test pieces were cut out from the hollow members 1 to 16 of the present invention, the comparative hollow members 1 to 4 and the conventional hollow members 1 and 2, and the proof stress was measured using the tensile test pieces. Are shown in Table 3. Further, the hollow members 1 to 16 of the present invention, the comparative hollow members 1 to 4 and the conventional hollow members 1 to 2 are expanded by applying an internal pressure and being pushed in the axial direction, thereby expanding the pipe at the breaking position when the breaking occurs. The perimeter was determined, and the rate of change of the perimeter until fracture was 18% or more was indicated by ○, and less than 18% was indicated by x, and the hydroforming properties were evaluated. The results are shown in Table 3.

[0022]

[Table 3]

[0023]

According to the results shown in Tables 1 to 3, the hollow members 1 to 16 of the present invention have an excellent expansion ratio as compared with the conventional hollow members 1 and 2 and the comparative hollow members 1 to 4. It turns out that it is excellent in forming property.

As described above, since the aluminum alloy hollow member of the present invention is excellent in hydroforming properties, various parts having excellent strength can be produced with high accuracy, and the improvement of the weight reduction of automobiles is greatly achieved. It can contribute and bring about excellent industrial effects.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hisao Tanigawa 2-3-3 Shiba, Minato-ku, Tokyo Inside Mitsubishi Aluminum Co., Ltd. (72) Inventor Shigeyuki Nakagawa 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Automobile Stock Within the company (72) Inventor Satoshi Majima 2 Nihonsan Motor Co., Ltd., 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa

Claims (3)

[Claims] 1. In mass% (% means mass%) Si: 0.5 to 1.4%, Mg: 0.30 to 0.75%, Fe: 0.1 to 0.4%, Ti: 0.005 to 0.1%, B: 0.0001 to 0.004%, and Mn and V are further defined as: Mn: 0.02 to 0.20%, V: 0.05 to 0.25%, 0.12% ≦ Mn + V ≦ 0.30%, with the balance being Al and unavoidable impurities, and Dl containing the average crystal grain size in the length direction of the hollow member, When Dt is the average crystal grain size in the thickness direction of the hollow member, (Dl + Dt) / 2 ≦ 100 μm, Dl / Dt ≦
An aluminum alloy hollow member excellent in hydroformability, comprising an Al alloy having a crystal grain structure satisfying the condition of 2.0. 2. Si: 0.5 to 1.4%, Mg: 0.30 to 0.75%, Fe: 0.1 to 0.4%, Ti: 0.005 to 0.1%, B : 0.0001 to 0.004%, Cu: 0.03 to 0.4%, and further, Mn and V: Mn: 0.02 to 0.20%, V: 0.05 to 0 .25%, 0.12% ≦ Mn + V ≦ 0.30%, the balance being Al and inevitable impurities, and Dl being the average crystal grain length in the longitudinal direction of the hollow member, Dt Is the average crystal grain size in the thickness direction of the hollow member, (Dl + Dt) / 2 ≦ 100 μm, Dl / Dt ≦
An aluminum alloy hollow member excellent in hydroformability, comprising an Al alloy having a crystal grain structure satisfying the condition of 2.0. 3. Al having the composition according to claim 1 or 2.
Cr: 0.02 to 0.05%, Zr:
An aluminum alloy hollow member excellent in hydroforming properties, comprising an Al alloy having a composition containing one or two of 0.02 to 0.05%.