JP4296584B2 - Aluminum alloy hollow member with excellent hydroforming properties - Google Patents

Description

【００１９】
【表２】

【００２０】
このようにして得られた本発明中空部材１〜１６、比較中空部材１〜４および従来中空部材１〜２の断面のミクロ組織を観察し、中空部材の長さ方向における平均結晶粒径をＤｌ、中空部材の厚さ方向における平均結晶粒径をＤｔとすると、（Ｄｌ＋Ｄｔ）／２およびＤｌ／Ｄｔの値を求め、その結果を表３に示した。
【００２１】
さらに、本発明中空部材１〜１６、比較中空部材１〜４および従来中空部材１〜２から引張り試験片を切り出して作製し、この引張り試験片を用いて耐力を測定し、その結果を表３に示した。
さらに、本発明中空部材１〜１６、比較中空部材１〜４および従来中空部材１〜２に内圧を負荷すると共に軸方向に押し込みを行なうことにより拡管し、破断が生じたときの破断位置での周長を求め、破断までの周長変化率が１８％以上を○、１８％未満が×で示し、ハイドロフォーミング性を評価し、その結果を表３に示した。
【００２２】
【表３】

【００２３】
【発明の効果】
表１〜３に示される結果から、本発明中空部材１〜１６は従来中空部材１〜２および比較中空部材１〜４に比べて、拡管率が優れているところから、ハイドロフォーミング性に優れていることが分かる。
【００２４】
前述のように、この発明のアルミニウム合金中空部材は、ハイドロフォーミング性に優れているところから、強度の優れた各種部品を精度よく作製することができ、自動車の軽量化の向上に大いに寄与することができ、産業上優れた効果をもたらすものである。[0001]
[Industrial application fields]
The present invention relates to an aluminum alloy hollow member excellent in hydroforming properties suitable for molding a frame, a joining member, or the like of an automobile, a vehicle, or a building member.
[0002]
[Prior art]
In recent years, due to environmental problems such as global warming, there is a strong demand for weight reduction of automobiles in order to reduce exhaust gas and improve fuel efficiency. The most effective method for reducing the weight of the vehicle body is to replace the steel material, which has been mainly used in the past, with aluminum, so that aluminum alloy materials, especially aluminum alloy extruded materials that can be used to integrally form structures with complex shapes, are most effective. Or the use of drawing material is increasing. 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 together to form a car body skeleton, and an aluminum space frame car body is assembled with an outer panel panel. Has been commercialized.
As a processing technique for integrally forming these aluminum alloy extruded hollow members into a predetermined shape, a hydroforming technique has recently attracted attention. Hydroforming is a processing method that mainly consists of pipe expansion molding by hydraulic pressure in the mold of the pipe material, and the sectional shape of the same member can be freely changed. In this processing method, for example, prior to hydraulic forming, forming and bending into a complex cross-sectional shape using a movable mold of a pipe material is generally performed in preforming. Further, in the hydraulic forming, in many cases, material inflow to the deformed portion is promoted by pushing in the tube axis direction.
[0003]
Currently, hollow members obtained by extruding Al—Mg—Si alloys such as 6063 alloy, 6N01 alloy, and 6061 alloy are mainly used as aluminum alloy hollow members for performing such hydroforming. (For example, refer to JP-A-10-46280). Hydroforming is performed after processing this hollow member into a predetermined cross-sectional shape by preforming. In addition, taking advantage of the features of extruded shapes that can be molded into a free cross-sectional shape, a hollow shape material that has been previously extruded into a predetermined cross-sectional shape other than a tubular shape is used as a raw material. After performing, hydroforming is performed.
[0004]
[Problems to be solved by the invention]
By the way, in the Al-Mg-Si alloy, for example, 6063 alloy, 6N01 alloy, 6061 alloy, etc., high strength T5 or T6 material is inferior in hydroforming property, so it is necessary to use O material with high tube expansion rate. was there.
However, when molding using O material, in order to obtain the required strength of the part, it must be subjected to heat treatment consisting of solution treatment, quenching, and aging after molding, and deformation due to thermal stress and quenching strain can be avoided. There was a problem of wanting.
Further, when the O material is used as it is in order to avoid this decrease in accuracy, it is necessary to increase the plate thickness because the strength is low, and there is a problem that the lightening effect by the aluminum alloy is reduced.
The present invention has been made in view of such problems, 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]
[Means for Solving the Problems]
From the viewpoints described above, the present inventors have conducted research to obtain a hollow member having sufficient strength of a molded part obtained by hydroforming and excellent hydroforming properties. The hollow members made of an Al alloy having the component composition and the crystal grain structure described in (iii) to (c) are all excellent in hydroforming properties, and are further subjected to artificial aging treatment to have mechanical strength of 160 MPa or more. The result of the research that it has become.
(B) In mass% (hereinafter,% indicates 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 the remaining Al alloy having a composition composed of Al and inevitable impurities, Mn and V are further changed to Mn: 0.00. 02 to 0.2%, V: 0.05 to 0.25% (provided that 0.12% ≦ Mn + V ≦ 0.3%), and average crystal in the length direction of the hollow member When the grain size is Dl and the average crystal grain size in the thickness direction of the hollow member is Dt, it is made of an Al alloy having a crystal grain structure that satisfies the conditions of (Dl + Dt) / 2 ≦ 100 μm and Dl / Dt ≦ 2.0. Hollow member,
(B) A hollow member made of an Al alloy containing Cu: 0.03 to 0.4% in addition to the Al alloy described in (a) above,
(C) The Al alloy described in (i) or (b) further contains one or two of Cr: 0.02 to 0.05% and Zr: 0.02 to 0.05%. A hollow member made of an Al alloy,
[0006]
This invention was made based on the above research results,
(1) Si: 0.5-1.4%, Mg: 0.30-0.75%, Fe: 0.1-0.4%, Ti: 0.005-0.1%, B: 0 0.0001% to 0.004%, 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. %, With the remainder consisting of Al and inevitable impurities, and Dl as the average crystal grain size in the length direction of the hollow member, and Dt as the average crystal grain size in the thickness direction of the hollow member, (Dl + Dt) / 2 ≦ 100 μm, aluminum alloy hollow member excellent in hydroforming property made of an Al alloy having a crystal grain structure that satisfies the conditions of Dl / Dt ≦ 2.0,
(2) Si: 0.5-1.4%, Mg: 0.30-0.75%, Fe: 0.1-0.4%, Ti: 0.005-0.1%, B: 0 0.0001 to 0.004%, Cu: 0.03 to 0.4%, 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%, with the remainder comprising Al and inevitable impurities, Dl is the average crystal grain size in the length direction of the hollow member, and Dt is the thickness of the hollow member An aluminum alloy hollow member having an excellent hydroforming property made of an Al alloy having a crystal grain structure satisfying the conditions of (Dl + Dt) / 2 ≦ 100 μm and Dl / Dt ≦ 2.0 as the average crystal grain size in the vertical direction ,
(3) In addition to the Al alloy having the composition described in (1) or (2) above, one or two of Cr: 0.02 to 0.05% and Zr: 0.02 to 0.05% The aluminum alloy hollow member having an excellent hydroforming property, which is made of an Al alloy having a composition containing the above, has a feature.
[0007]
The aluminum alloy hollow member excellent in hydroforming properties described in (1), (2) or (3) is prepared by billet having the component composition described in (1), (2) or (3) by DC casting. Then, the billet is subjected to a homogenization heat treatment, and the billet subjected to the homogenization heat treatment is extruded at a temperature in the range of 450 to 550 ° C., and immediately thereafter water-cooled or water-cooled and further drawn. 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. The aluminum alloy hollow member thus obtained has (Dl + Dt) / 2 ≦ 100 μm, where Dl is the average crystal grain size in the length direction of the hollow member and Dt is the average crystal grain size in the thickness direction of the hollow member. And a grain structure satisfying the condition of Dl / Dt ≦ 2.0.
[0008]
When the hollow member according to any one of (1) to (3) is subjected to artificial aging treatment at a temperature of 150 to 210 ° C. for 1 to 24 hours, the hydroforming property having a yield strength of 160 MPa or more is excellent. An aluminum alloy hollow member is obtained.
[0009]
The reason why the component composition and the 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 a fine Mg ₂ Si compound, but even if the content of either Si or Mg is Si: less than 0.5%, Mg: less than 0.3% In this case, the amount of precipitates to be generated is reduced and the desired strength cannot be ensured. On the other hand, when the content exceeds Si: 1.4% and Mg: 0.75%, hydroforming properties, bending This is not preferable because processability and extrusion or drawing processability are lowered. Therefore, it was set to Si: 0.5 to 1.4% and Mg: 0.30 to 0.75%. More preferable ranges of Si and Mg are Si: 0.7 to 1.2% and Mg: 0.40 to 0.60%.
[0010]
(B) Fe
The Fe component forms an intermetallic compound with Al. These serve as nucleation sites for recrystallization, and the extruded structure becomes a fine equiaxed grain structure. As a result, hydroforming and bending workability are improved. However, if the content is less than 0.1%, the desired effect cannot be obtained. On the other hand, if the content exceeds 0.4%, recrystallization during extrusion is suppressed, and elongated grains and fibrous structures are formed. It appears, and the hydroforming property deteriorates, which is not preferable. Therefore, the addition amount of Fe is set to 0.1 to 0.4%.
[0011]
(C) Ti, B
These components are added because they have the effect of refining the cast structure and preventing casting cracks, but even if the content of either Ti or B is Ti: less than 0.005%, B: less than 0.0001% On the other hand, if any content of Ti and B exceeds Ti: 0.1% and B: 0.004%, a huge intermetallic compound is produced and toughness is not obtained. Is lowered, and hydroforming property and bending workability are lowered. Therefore, the contents of Ti and B are set to Ti: 0.005 to 0.1% and B: 0.0001 to 0.004%, respectively.
[0012]
(D) Mn, V
Both of these components form an intermetallic compound with Al, and these serve as nucleation sites for recrystallization, making the extruded structure a fine equiaxed grain structure, thereby improving hydroforming and bending workability. In particular, by adding these components in combination, the effect is further increased. However, if the contents of Mn and V are Mn: less than 0.02% and V: less than 0.05%, the desired effect cannot be obtained. On the other hand, if the contents of Mn and V exceed Mn: 0.20% and V: 0.25%, recrystallization during extrusion is suppressed, and a fibrous structure appears, resulting in hydroforming properties and bending. Since workability deteriorates, it is not preferable. Therefore, the contents of Mn and V were determined to be Mn: 0.02 to 0.20% and V: 0.05 to 0.25%, respectively. It is necessary to add Mn and V in combination, and it is more preferable that the amount of addition at that time satisfies the condition that the sum of Mn and V is 0.12% ≦ Mn + V ≦ 0.30%. Therefore, the addition amounts of Mn and V were determined as Mn: 0.02 to 0.20%, V: 0.05 to 0.25%, and 0.12% ≦ Mn + V ≦ 0.30%.
[0013]
(E) Cu
Since Cu has the effect of improving the strength of the hollow member by dissolving in the substrate, it is added as necessary. However, if the content is less than 0.03%, the desired strength improvement effect cannot be obtained. On the other hand, if the content exceeds 0.4%, the corrosion resistance decreases, which is not preferable. Therefore, it was determined that Cu: 0.03 to 0.4%.
[0014]
(C) Cr, Zr
These components together form an intermetallic compound with Al, which becomes a nucleation site for recrystallization, makes the extruded structure a fine equiaxed grain structure, and improves hydroforming and bending workability. However, if Cr: less than 0.02% and Zr: less than 0.02%, the desired effect cannot be obtained, while if Cr: 0.05% and Zr: 0.05% are exceeded, respectively. Further, since recrystallization during extrusion is suppressed and elongated grains and fibrous structures appear, hydroforming properties and bending workability deteriorate, which is not preferable. Therefore, the contents of Cr and Zr were set to Cr: 0.02 to 0.05% and Zr: 0.02 to 0.05%, respectively.
[0015]
B. Structure (f) Average particle diameter 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, and the length of the hollow member When the average crystal grain size in the direction is Dl and the average crystal grain size in the thickness direction of the hollow member is Dt, it is necessary to set (Dl + Dt) / 2 ≦ 100 μm. A relatively spherical crystal grain is preferably used. Therefore, the crystal grains of the Al alloy constituting the hollow member of the present invention are determined so as to be within the range of (Dl + Dt) / 2 ≦ 100 μm and Dl / Dt ≦ 2.0.
[0016]
C. Mechanical properties An aluminum alloy hollow member for hydroforming requires strength from 160 MPa or more because strength is required.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
An Al alloy billet having the composition shown in Tables 1 and 2 and having a diameter of 204 mm was melted, subjected to homogenization treatment at a temperature of 545 ° C. for 4 hours, and then extruded at 1650 tons. Extrusion temperature: 500 ° C., extrusion speed: 5 m / min using a machine, then immediately water-cooled, and then subjected to artificial aging treatment at 160 ° C. for 4 to 8 hours to achieve a wall thickness of 2.7 mm , Outer diameter: 43 mm of the present invention Al alloy hollow member (hereinafter referred to as the present hollow member) 1 to 16, comparative Al alloy hollow member (hereinafter referred to as the comparative hollow member) 1 to 4 and conventional Al alloy hollow member 1-2 were produced (hereinafter referred to as conventional hollow members).
[0018]
[Table 1]

[0019]
[Table 2]

[0020]
The microstructures of the cross sections of 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 thus obtained were observed, and the average crystal grain size in the length direction of the hollow member was determined as Dl. Assuming that the average crystal grain size in the thickness direction of the hollow member is Dt, the values of (Dl + Dt) / 2 and Dl / Dt were obtained, and the results are shown in Table 3.
[0021]
Further, tensile test pieces were cut out from the present invention hollow members 1 to 16, comparative hollow members 1 to 4 and conventional hollow members 1 to 2, and the yield strength was measured using the tensile test pieces. It was shown to.
Furthermore, the present invention hollow members 1 to 16, the comparative hollow members 1 to 4 and the conventional hollow members 1 to 2 are expanded with an internal pressure while being pushed in the axial direction, and at the break position when the break occurs. The circumference was determined, and the rate of change in circumference until breakage was 18% or more, and less than 18% was indicated by x. Hydroforming properties were evaluated, and the results are shown in Table 3.
[0022]
[Table 3]

[0023]
【The invention's effect】
From the results shown in Tables 1 to 3, the hollow members 1 to 16 of the present invention are superior in hydroforming properties because the tube expansion rate is superior to the conventional hollow members 1 and 2 and the comparative hollow members 1 to 4. I understand that.
[0024]
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 contribute greatly to the reduction in weight of automobiles. It is possible to produce an excellent industrial effect.

Claims (3)

In mass% (% indicates 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%,
In addition, Mn and V,
Mn: 0.02 to 0.20%,
V: 0.05-0.25%,
0.12% ≦ Mn + V ≦ 0.30%,
A composition comprising the remainder of Al and inevitable impurities, and
When Dl is the average crystal grain size in the length direction of the hollow member and Dt is the average crystal grain size in the thickness direction of the hollow member, the conditions of (Dl + Dt) / 2 ≦ 100 μm and Dl / Dt ≦ 2.0 are satisfied. An aluminum alloy hollow member excellent in hydroforming properties, characterized by comprising an Al alloy having a crystal grain structure. 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: 0.03-0.4%,
In addition, Mn and V,
Mn: 0.02 to 0.20%,
V: 0.05-0.25%,
0.12% ≦ Mn + V ≦ 0.30%,
A composition comprising the remainder of Al and inevitable impurities, and
When Dl is the average crystal grain size in the length direction of the hollow member and Dt is the average crystal grain size in the thickness direction of the hollow member, the conditions of (Dl + Dt) / 2 ≦ 100 μm and Dl / Dt ≦ 2.0 are satisfied. An aluminum alloy hollow member excellent in hydroforming properties, characterized by comprising an Al alloy having a crystal grain structure. The Al alloy having the composition according to claim 1 or 2 further has a composition containing one or two of Cr: 0.02 to 0.05% and Zr: 0.02 to 0.05%. An aluminum alloy hollow member excellent in hydroforming properties, characterized by comprising an Al alloy.