JPH10306338A - Hollow extruded material of al-cu-mg-si alloy, excellent in strength and corrosion resistance, and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hollow extruded material of Al-Cu-Mg-Si type aluminum alloy useful as a structural body for transport equipment, such as automobile, excellent in strength and corrosion resistance, and capable of manufacture on an actual machine base. SOLUTION: This extruded material has a composition which consists of, by weight, 0.5-1.5% Si, 0.9-1.6% Mg, 1.2-2.5% Cu, further 0.02-0.4% Cr, and the balance Al with inevitable impurities and in which conditional inequalities 3<=Si%+Mg%+Cu%<=4, Mg%<=1.7×Si%, Mg%+Si%<=2.7, 2<=Si%+Cu%<=3.5, and Cu%/2<=Mg%<=(Cu%/2)+0.6 are satisfied and the content of Mn as an impurity is limited to <=0.05%. Moreover, when a tensile test is carried out, in a direction perpendicular to the direction of extrusion, with respect to the deposit of a hollow cross section formed by mean of extrusion in which hot extrusion is performed to form a hollow cross section by using a porthole die or a spider die, breakage occurs in the part other than the deposit and the strength of the deposit is higher than that of the material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Al-Cu-Mg-Si alloy hollow extruded material having excellent strength and corrosion resistance, and particularly to Al-Cu-Mg which is suitably used as a structure of transportation equipment.
TECHNICAL FIELD The present invention relates to a -Si alloy hollow extruded material and a method for producing the same.

[0002]

2. Description of the Related Art Performances required for structures of automobiles and other transportation equipment include 1) strength, 2) corrosion resistance, and 3) fracture mechanics (e.g., fatigue crack propagation, fracture toughness, etc.).
Recent development trends of materials include not only strength, but also comprehensive evaluations from material production to assembly and operation of members.

As a high-strength aluminum alloy, Al-Cu-Mg (2000) or Al-Zn-
Mg-Cu-based (7000-based) aluminum alloys are known, but these alloys are excellent in strength but not necessarily sufficient in workability and corrosion resistance. In addition, extrudability is poor, and hot cracking occurs during extrusion, so that the extrusion speed must be set to, for example, 1 m / min or less, which causes an increase in manufacturing cost. Also, when extruding into a hollow shape using a porthole die or a spider die, the extrudability is further deteriorated, and it is difficult to extrude with a real extruder having a low extrusion pressure, and therefore a combination of solid shapes is used to form a hollow shape. The range of application is limited, for example, in the form of a structural material.

[0004] On the other hand, Al-Mg-Si (6000) aluminum alloys are generally inferior in strength to the above-mentioned high-strength aluminum alloys, but are superior in corrosion resistance and extrudability, and have a high speed. It is possible to reduce the production cost, and it is also common to extrude into a hollow shape using a porthole die or a spider die. From this, in order to obtain a high-strength aluminum alloy with the same extrudability as the 6000 series alloy, we will improve the strength characteristics of the 6000 series aluminum alloy to obtain the same strength as the 2000 series and 7000 series alloys Attempts have been made to obtain higher strength than the conventional 6061 alloy 6013 alloy, 6056 alloy,
Alloys such as 6082 have been developed.

[0005] The structures of transportation equipment such as automobiles, vehicles, and aircrafts are required to have excellent strength properties, but they are exposed to severe corrosive environments during use, and therefore have excellent corrosion resistance. It must not cause fatigue failure in the environment. Therefore, it is necessary that the structural body material has these characteristics in a well-balanced manner. In addition, with respect to these characteristics, even a slight difference may have considerable importance due to the advancement of technology, and if any of the characteristics is slightly inferior, a comprehensive evaluation as a material cannot be obtained. From such a viewpoint, when the above-mentioned 6000 series aluminum alloy is viewed, particularly when it is applied as a material for a structure for transportation equipment, it cannot be said that it has necessarily satisfactory performance.

One of the inventors, in cooperation with the inventor other than the inventor of the present invention, firstly, in order to improve the properties of the 6000 series aluminum alloy, Si: 0.5-1.5%, Mg: 0.9-1.5%.
%, Cu: 1.2 to 2.4%, conditional expression, 3 ≦ Si% + Mg%
+ Cu% ≦ 4, Mg% ≦ 1.7 × Si%, Cu% / 2 ≦ Mg
%, (Cu% / 2) +0.6 Si, Mg and C
u, further contains Cr: 0.02 to 0.4%, and Mn as an impurity is limited to 0.05% or less, and has a composition consisting of aluminum and unavoidable impurities. A high-strength aluminum alloy with good corrosion resistance was proposed. (Japanese Unexamined Patent Publication No. 8-269608)

[0007]

SUMMARY OF THE INVENTION The present invention relates to an experiment on the extrusion characteristics of the high strength aluminum alloy proposed above.
As a result of the examination, by further specifying the component composition of the aluminum alloy, and preferably by applying specific extrusion conditions, it is possible to easily manufacture a hollow extruded material that was difficult with the 2000 series alloy and the 7000 series alloy. It has been made based on the finding that
It has the same strength as the 00 series alloy and the 7000 series alloy, has the same corrosion resistance as the 6000 series alloy, and has excellent strength and corrosion resistance that enables stable production at actual machine base and actual production base speeds. An object of the present invention is to provide an Al-Cu-Mg-Si alloy hollow extruded material and a method for producing the same.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an Al-Cu-M having excellent strength and corrosion resistance.
The g-Si alloy hollow material has a Si content of 0.5 to 1.5% and a Mg content of 0.9.
-1.6%, Cu: 1.2-2.5%, conditional expression, 3 ≦ Si% +
Mg% + Cu% ≦ 4, Mg% ≦ 1.7 × Si%, Mg% +
Si% ≦ 2.7, 2 ≦ Si% + Cu% ≦ 3.5, Cu% / 2 ≦
It contains Si, Mg, and Cu satisfying Mg% ≦ (Cu% / 2) +0.6, further contains Cr: 0.02 to 0.4%, and Mn as an impurity is limited to 0.05% or less. An extruded material having a hollow cross-section having an unavoidable impurity composition, which breaks at a portion other than the welded portion when a tensile test is performed on a welded portion in the hollow cross-section formed by extrusion in a direction perpendicular to the extrusion direction. The first feature is that the above aluminum alloy further comprises Zn: 0.03
A second feature is that it contains 2.0%.

According to the present invention, Al- is excellent in strength and corrosion resistance.
The method for producing a hollow extruded material of a Cu—Mg—Si alloy is as follows.
After homogenizing at a temperature lower than the melting point, if the billet temperature during extrusion is T (° C.) and the extrusion speed is V (m / min), the billet temperature T during extrusion is in the range of 350 to 550 ° C. Hot extrusion is performed on a hollow section using a porthole die or a spider die at an extrusion speed satisfying the conditions of V ≦ (1/12) × T−31 and V ≦ − (1/9) × T + 60. The first feature is that after hot extrusion, a solution treatment is performed by heating and holding at a temperature rising rate of 5 ° C / s or more to a temperature range of 500 to 580 ° C, and then cooling at 10 ° C / s or more. After quenching to cool to a temperature of 100 ° C or less at a speed, 170-200
A second feature is that a heat treatment is performed at 2 ° C. for 2 to 24 hours.

After the billet of the aluminum alloy having the above composition is homogenized at a temperature of 500 ° C. or more and less than the melting point, the billet temperature during extrusion is T (° C.), and the extrusion speed is V (m / min). The billet temperature T at the time of extrusion was 350
Hollow cross section using a porthole die or a spider die at an extrusion speed satisfying the conditions of V ≦ (1/12) × T−31 and V ≦ − (1/9) × T + 60 in a temperature range of up to 550 ° C. After hot-extrusion molding, the extruded material immediately after extrusion is quenched at a cooling rate of 10 ° C / s or more to a temperature of 100 ° C or less, and then heat-treated at 170 to 200 ° C for 2 to 24 hours. This is the third feature.

The significance of the addition of each component in the aluminum alloy of the present invention and the reason for the limitation will be described. Si coexists with Mg to form a fine intermetallic compound Mg ₂ Si to increase the strength of the alloy. If the content of Si is less than 0.5%, sufficient strength cannot be obtained, and if the content exceeds 1.5%, the corrosion resistance of the alloy decreases. Therefore, the content range of Si is 0.5 to 1.
5% is preferred. More preferably, it is in the range of 0.7 to 1.2%.

Mg coexists with Si to precipitate Mg ₂ Si, and coexists with Cu to finely precipitate the compound CuMgAl ₂ to improve the strength of the alloy. If the content of Mg is less than 0.9%, a sufficient effect cannot be obtained, and if it exceeds 1.6%, the corrosion resistance decreases. Therefore, the content range of Mg is 0.
9-1.6% is preferred. More preferably, it is in the range of 1.0 to 1.2%.

Cu, like Si and Mg, is an element that contributes to improving the strength of the alloy. If the content is less than 1.2%, the effect is not sufficient. If the content exceeds 2.5%, the corrosion resistance of the alloy is reduced, the deformation resistance at the time of extrusion is increased, and compaction tends to occur in hollow extrusion. Therefore, the content range of Cu is 1.2 to
2.5% is preferred. More preferably, it is in the range of 1.5 to 2.0%. Cr contributes to improving the formability by making the structure of the alloy finer and improving the corrosion resistance. A preferable content range is 0.02 to 0.4%. If the content is less than 0.02%, the effect is not sufficient. If the content exceeds 0.4%, a coarse intermetallic compound is easily formed and the moldability is reduced.

Mn refines the crystal grains to improve the alloy strength, but forms an Mn-based intermetallic compound.
In the present invention, Mn is 0.05% or less, preferably 0.02%
It is important to limit the content to 0.01% or less, more preferably.

According to the present invention, as described above, Si, Mg, C
u as an essential component, and for these components, a conditional expression, 3 ≦ Si% + Mg% + Cu% ≦
4, Mg% ≦ 1.7 × Si%, Mg% + Si% ≦ 2.7, 2
≦ Si% + Cu% ≦ 3.5, Cu% / 2 ≦ Mg% ≦ (Cu%
/ 2) +0.6 is an essential requirement. Under these conditions, an intermetallic compound that gives the alloy strength and extrudability that enables the production of hollow extruded materials without lowering the corrosion resistance of the alloy material. Is obtained. Si, M
If the total content of g and Cu is less than 3%, it is difficult to obtain a desirable dispersion of the compound, and if it exceeds 4%, the corrosion resistance of the alloy is deteriorated. Further, the quantitative relationship between Mg and Si is expressed as Mg% ≦ 1.7 × Si
%, Mg% + Si% ≦ 2.7, the quantitative relationship between Si and Cu is 2
≦ Si% + Cu% ≦ 3.5, the quantitative relationship between Mg and Cu is Cu
% / 2 ≦ Mg ≦ (Cu% / 2) +0.6,
The production amount and distribution state of the intermetallic compound are controlled, so that the alloy can be provided with well-balanced strength characteristics, extrudability, and corrosion resistance.

[0016] Zn added as a selective component forms an intermetallic compound, which refines the crystal grain size of the alloy and improves the strength of the alloy. Preferred addition amount is 0.03 to 2.0
%. If the amount of Zn is less than the lower limit, the effect is small, and if the amount exceeds the upper limit, the formation of coarse intermetallic compounds increases, and the moldability and corrosion resistance deteriorate. In the present invention, 0.005 to 0.1% of Ti and 1 to 50ppm of B are added to refine the casting structure to prevent ingot cracking and improve the formability, similarly to a normal aluminum alloy. Does not affect the properties of the present invention.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION A preferred method for producing an aluminum alloy hollow extruded material of the present invention will be described. A molten aluminum alloy having the above composition is formed by, for example, semi-continuous casting, and the obtained extruded billet is heated to 500 ° C. Homogenize at a temperature not less than the melting point. If the homogenization treatment temperature is lower than 500 ° C., ingot segregation is not sufficiently removed, and M
The solid solution of the g ₂ Si compound and Cu becomes insufficient, and the strength and elongation decrease.

Next, the billet temperature T (° C.) at the time of extrusion is
At 350 to 550 ° C, V ≦ (1/12) × T−31 and V ≦ −
Hot extrusion molding is performed on a hollow section using a porthole die or a spider die at an extrusion speed that satisfies the condition of (1/9) × T + 60 (V: extrusion speed (m / min)). If the extrusion speed does not satisfy the above conditions, the extruder reaches the pressure limit and is likely to be clogged or the extruded material is easily cracked.

After hot extrusion, at a heating rate of 5 ° C./s or more
A solution treatment is carried out by heating and holding in a temperature range of 500 to 580 ° C, followed by a quenching process of cooling at a cooling rate of 10 ° C / s or more to a temperature of 100 ° C or less, ~twenty four
heat treatment of h. 5 ° C heating rate during solution treatment
If it is less than / s, the crystal grains are likely to be coarse and the elongation after T6 treatment is reduced. If the holding temperature is less than 500 ° C., the solid solution of the precipitate is insufficient, and the strength and elongation are reduced. If the temperature exceeds 580 ° C, elongation decreases due to local eutectic melting. If the cooling rate during the quenching treatment is less than 10 ° C./s, the compound precipitates in an undesired distribution state and the ductility is reduced, thereby impairing the corrosion resistance, strength and elongation.

Although the aluminum alloy material of the present invention has excellent elongation even after quenching and aging at room temperature (T4 tempering), it is preferable to perform tensile straightening after quenching,
Heat treatment at 170-200 ° C for 2-24h. Heat treatment temperature is 1
If the temperature is lower than 70 ° C., heat treatment for a long time is required to obtain the desired performance, which is not preferable for industrial production. Heat treatment at a temperature exceeding 200 ° C. lowers the strength. If the heat treatment time is less than 2 hours, sufficient strength cannot be obtained, and if it exceeds 24 hours, the strength starts to decrease.

In the present invention, after the billet of the aluminum alloy having the above composition is homogenized at a temperature of 500 ° C. or more and less than the melting point, the billet temperature T at the time of extrusion is determined.
(° C) is a temperature in the range of 350 to 550 ° C, and V ≦ (1/12) ×
At a extrusion speed (m / min) that satisfies the condition of T-31 and V ≦-(1/9) × T + 60, it is hot-extruded into a hollow section using a porthole die or a spider die, and applied with a die quench. The present invention can also be carried out by performing a quenching treatment of cooling the hollow extruded material immediately after extrusion to a temperature of 100 ° C. or less at a cooling rate of 10 ° C./s or more and then performing a heat treatment at 170 to 200 ° C. for 2 to 24 hours. A hollow extruded material having the desired properties can be obtained.

[0022]

Hereinafter, examples of the present invention will be described in comparison with comparative examples. Example 1 A billet (diameter: 254 mm) of an aluminum alloy shown in Table 1 was produced by semi-continuous casting, and the billet was homogenized at 525 ° C. for 8 hours.
° C, extrusion speed of 3m / min, hot extrusion molding into a hollow cross-sectional shape using a porthole die (maximum load during extrusion is 26
MN, extrusion ratio 55). The shape of the extruded cross section was a “Japanese” cross section, width 140 mm, height 75 mm, wall thickness 2 mm, the inside dimensions of the two hollows were 67 mm wide × 71 mm high, and the R of the corner was 2 mm. . In this hollow extruded material,
The central portion of each wall of the two rectangular tubular hollow portions (4
Places).

Next, the hollow extruded material was subjected to a solution treatment at a temperature of 530 ° C. for 10 minutes, followed by a quenching treatment by water cooling, and a further 180 ° C.
For 6 hours to obtain a T6 tempered material.
The resulting hollow extrusions, tensile test performed Tensile Properties (Tensile Strength (sigma _B), yield strength (sigma _{0. 2),} elongation ([delta])) was measured and subjected to intergranular corrosion testing. JISW 1 for intergranular corrosion test
After washing the hollow extruded material according to 103, 57 g of NaCl and 30%
After immersion for 6 hours in a test solution at 30 ° C. adjusted to 1 liter with H ₂ O ₂ with water, the corrosion loss was measured. Table 2 shows the test results.

As shown in Table 2, all the test materials according to the present invention show excellent tensile performance and corrosion resistance. No welding line was observed at the welded portion (each wall of the rectangular tubular hollow portion) in the hollow cross section, indicating a good welded state. A tensile test was performed on the welded portion in a direction perpendicular to the extrusion direction, but no breakage occurred at the welded portion, and the welded portion had excellent strength higher than the strength of the material.

[0025]

[Table 1]

[0026]

[Table 2]

Comparative Example 1 According to the same steps and conditions as in Example 1, after homogenization treatment, a 2024 alloy, a 2014 alloy and 70
Hot extrusion into a hollow cross-sectional shape was performed for 75 alloy,
Clogging occurred and a hollow extruded material could not be obtained.

Comparative Example 2 A hollow extruded material was manufactured from an aluminum alloy having the composition shown in Table 3 according to the same process and conditions as in Example 1, and a tensile test and an intergranular corrosion test were performed in the same manner as in Example 1. .
Table 4 shows the results. In Table 3, those outside the conditions of the present invention are underlined.

[0029]

[Table 3] << Table Note >> Alloy No.5 is Si + Mg + Cu> 4, Alloy No.6 is Si + Mg + Cu
<3 Alloy No.7 is Mg> 1.7 × Si, Alloy No.8 is Cu / 2 <Mg, Alloy N
o.9 is Mg> (Cu / 2) +0.6

[0030]

[Table 4]

As can be seen from Table 4, those which deviate from the limits and the conditional expressions of the alloy composition of the present invention are inferior in strength, formability or corrosion resistance. Alloy No.5 is Si, M
Since the total amount of g and Cu exceeds 4, the corrosion resistance is poor.
Alloy material No. 6 has low strength because the total amount of Si, Mg and Cu is less than 3. Alloy material No. 7 does not satisfy the relational expression between Mg and Si, and alloy materials Nos. 8 and 9 do not satisfy the relational expression between Mg and Cu, so that the corrosion resistance is poor. Test material No.10 is Cu
Since the alloy material No. 11 has a small amount and the Mn amount exceeds the limit value, and the test material No. 12 contains a large amount of Zn, all of them have poor corrosion resistance.

[0032]

As described above, according to the present invention, the strength,
Al-Cu which has excellent corrosion resistance and can be manufactured on a real machine basis
Abstract: Provided is a hollow extruded material of an Mg-Si-based aluminum alloy and a method for producing the same. This hollow extruded material is useful as a structure of a transportation device such as an automobile.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C22F 1/00 640 C22F 1/00 640A 683 683 691 691B 691C 691A 692 692A 692B 694 694B (72) Inventor Tadashi Minoda Minato-ku, Tokyo 5-11-3 Shimbashi Sumitomo Light Metal Industry Co., Ltd.

Claims (5)

[Claims] (1) Si: 0.5 to 1.5% by weight (the same applies hereinafter)
%, Mg: 0.9 to 1.6%, Cu: 1.2 to 2.5%,
≦ Si% + Mg% + Cu% ≦ 4, Mg% ≦ 1.7 × Si
%, Mg% + Si% ≦ 2.7, 2 ≦ Si% + Cu% ≦ 3.5
, Cu% / 2 ≦ Mg% ≦ (Cu% / 2) +0.6, and further contains Cr: 0.02 to 0.2%.
Extruded material with a hollow cross-section containing 4% and having an Mn content as an impurity of 0.05% or less, and having a balance of aluminum and unavoidable impurities. Al-Cu-Mg excellent in strength and corrosion resistance characterized in that when subjected to a tensile test in the direction perpendicular to the extrusion direction, it breaks at parts other than the welded part
-Si-based alloy hollow extruded material. 2. An aluminum alloy further comprising Zn: 0.03
The Al-Cu-Mg-Si alloy hollow extruded material according to claim 1, wherein the Al-Cu-Mg-Si alloy is excellent in strength and corrosion resistance. 3. A billet of an aluminum alloy having a composition according to claim 1 or 2 is homogenized at a temperature of 500 ° C. or more and less than a melting point, and then the billet temperature during extrusion is set to T.
(° C.), when the extrusion speed is V (m / min), V ≦ (1/1) when the billet temperature T during the extrusion is in the range of 350 to 550 ° C.
2) Strength characterized by performing hot extrusion molding on a hollow section using a porthole die or spider die at an extrusion speed satisfying the conditions of × T-31 and V ≦-(1/9) × T + 60. And a method for producing an Al-Cu-Mg-Si alloy hollow extruded material having excellent corrosion resistance. 4. After the hot extrusion, a solution treatment is performed in which the solution is heated and held in a temperature range of 500 to 580 ° C. at a rate of 5 ° C./s or more, and then cooled at a rate of 10 ° C./s or more. After quenching to cool down to below
The method for producing an Al-Cu-Mg-Si alloy hollow extruded material having excellent strength and corrosion resistance according to claim 3, wherein the heat treatment is performed for 24 hours. 5. A billet of an aluminum alloy having the composition described in claim 1 or 2 is homogenized at a temperature of 500 ° C. or more and less than a melting point, and then the billet temperature during extrusion is set to T.
(° C.), when the extrusion speed is V (m / min), V ≦ (1/1) when the billet temperature T during the extrusion is in the range of 350 to 550 ° C.
2) Hot extrusion molding into a hollow section using a porthole die or a spider die at an extrusion speed that satisfies the conditions of × T-31 and V ≦ − (1/9) × T + 60. Al with excellent strength and corrosion resistance characterized by performing a quenching treatment at a cooling rate of 10 ° C / s or more to a temperature of 100 ° C or less, and then performing a heat treatment at 170 to 200 ° C for 2 to 24 hours.
-A method for producing a Cu-Mg-Si alloy hollow extruded material.