JP2002241880A - Aluminum alloy extrusion profile material having excellent bending workability and production method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an Al-Mg-Si based alloy extrusion shape material which has excellent bending workability in a T5 material or a T6 material. SOLUTION: The aluminum alloy extrusion profile material has a composition containing, by weight, 0.40 to 0.75% Si and 0.65 to 1.0% Mg so as to satisfy -0.05%<=(Si-Mg/1.73)<=0.20, and further containing 0.02 to <0.05% Mn and 0.02 to <0.05% Zr, and also containing 0.05 to 0.4% Cu, and further containing 0.1 to 0.4% Fe, 0.005 to 0.1% Ti and 0.0001 to 0.004% B, and the balance Al with inevitable impurities. The profile material has a crystal grain structure in which the average grain size in the cross section in the extruding direction of the crystal grains is <=100 μm, and also, the ratio between the length in the extruding direction of the crystal grains and the length in the thickness direction is <=2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extruded aluminum alloy material having excellent extrudability, mechanical properties, bending workability and corrosion resistance and suitable for use as a frame material or a bumper reinforcing material of an automobile, and a method for producing the same. It is about.

[0002]

2. Description of the Related Art An Al-Mg-Si alloy is excellent in extrudability, so that it is easy to produce a thin-walled hollow material. In addition, it has moderate mechanical properties and good corrosion resistance as a structural material. Therefore, it is widely used as a frame material for automobiles and a reinforcing material for bumpers. And a typical alloy is JIS6N01 alloy.

[0003]

The above 6N0
In the case of alloy 1 or the like, high strength T5 material or T6
Since the material is inferior in bending workability, it was necessary to use T4 material. However, when bending is performed using T4 material, aging treatment must be performed after processing in order to obtain the necessary strength for the part, and a user without a heat treatment furnace cannot be manufactured, In addition, there is a problem that a reduction in productivity due to a reduction in the amount of processing per operation and a reduction in dimensional accuracy due to thermal deformation are unavoidable. The present invention
In view of the above problems, an Al alloy extruded material excellent in bending workability with T5 or T6 material, and an Al material capable of efficiently producing the extruded material.
An object of the present invention is to provide a method for manufacturing an extruded alloy material.

[0004]

The present inventors have made intensive studies to achieve the above object, and as a result, have found that Al-Mg-Si
In the system alloy, the excess Si is controlled from the balance composition of Mg ₂ Si, and the size and shape of the crystal grains are controlled by adding a small amount of Mn and Zr in combination. It has been found that the bending workability of the T5 material or the T6 material is improved by suppressing the precipitation of Si particles on the crystal grain boundaries during the cooling process by setting the value to the value or more, and the present invention has been accomplished. That is, the aluminum alloy extruded material of the present invention is Si: 0.4% by weight.
0-0.75%, Mg: 0.65-1.0%, and-
0.05 ≦ (Si—Mg / 1.73) ≦ 0.20, Mn is 0.02% or more and less than 0.05%, and Zr is 0.02% or more and less than 0.05%. And Cu: 0.05 to 0.4%, and Fe: 0.
1 to 0.4%, Ti: 0.005% to 0.1%, B:
The composition contains 0.0001 to 0.004%, the balance being Al and unavoidable impurities, the average grain size in the cross section of the crystal grains in the extrusion direction is 100 μm or less, and the length and thickness direction of the crystal grains in the extrusion direction Characterized by having a grain structure having a ratio to the length of 2 or less.

The method for producing an extruded aluminum alloy according to the present invention is characterized in that, in terms of% by weight, Si: 0.40 to 0.75% and Mg: 0.
65-1.0%, and -0.05 ≦ (Si-Mg /
1.73) ≦ 0.20, Mn in an amount of 0.02% to less than 0.05%, Zr in an amount of 0.02% to less than 0.05%, and Cu: 0.05 ~ 0.4%
, Fe: 0.1 to 0.4%, and Ti: 0.
005% to 0.1%, B: 0.0001 to 0.004%
Is heated to a temperature of 460 ° C. to 560 ° C. and then extruded, and an average cooling from 500 ° C. to 200 ° C. on the side coming out of the extruder. The speed is set to 50 ° C./sec or more.

[0006] The extruded aluminum alloy material of the present invention is preferably used as a frame material for automobiles or a bumper reinforcing material having a high demand for bending workability. is not.

Next, the reason why the composition of the Al alloy constituting the Al alloy hollow material of the present invention is limited as described above will be described. A. Component composition (a) Si and Mg: These components contain fine Mg
₂ has the effect of improving the strength by precipitating as a Si compound, but the Si:
If the content is less than 0.40% and the content of Mg is less than 0.65%, the amount of precipitates formed is so small that the desired strength cannot be secured, while the content of these components is Si: 0.75%.
% And Mg: more than 1.0%, the bending workability is reduced. Further, -0.05 ≦ (Si-Mg /
When 1.73) ≦ 0.20, the extrudability is not significantly impaired, and the strength is increased. However, −0.05 ≦ ((Si content) − (Mg content) /
When the amount is less than the amount satisfying the relationship of 1.73), the effect cannot be sufficiently obtained. On the other hand, ((Si content) − (Mg content))
If the amount satisfies the relationship of (/1.73)≦0.20, the Si particles will precipitate at the crystal grain boundaries during the cooling process and the aging treatment after the extrusion, and the bending workability will deteriorate. (B) Cu: Cu improves the strength by dissolving in the ground, but if its content is less than 0.05%, its effect is not sufficient, while if it exceeds 0.4%, the corrosion resistance of the Al alloy is reduced. (C) Mn, Zr: These components form an intermetallic compound with Al, and the intermetallic compound serves as a nucleation site for recrystallization, and the metal structure of the extruded Al alloy material is formed into fine granular crystal grains. This has the effect of forming a structure consisting of: as a result, the bending workability is improved. However, Mn and Zr
If the lower limit is less than the respective lower limit, the above effect is not sufficiently obtained.On the other hand, if the upper limit is exceeded, an elongated grain structure or a partial fiber structure elongated in the extrusion direction appears, and the bending workability deteriorates. . (D) Ti, B: These components have a function of refining the cast structure and preventing casting cracks. However, in any of the contents of Ti and B, Ti: less than 0.005%, and B: 0. If the content is less than 0001%, the desired effect cannot be obtained. On the other hand, if the content of either Ti or B exceeds 0.1% Ti and 0.004% B, a huge metal Intermetallic compounds are formed to reduce toughness and bending workability. (E) In addition, Cr content is 0.01% as a component composition.
It is preferable to regulate as follows. Cr is important in controlling the grain structure of the extruded Al alloy.
When the content of Cr exceeds 0.01%, an extruded grain structure is formed in a part of the grain structure of the extruded Al alloy, so that the bending workability is significantly deteriorated. It should be noted that, in such a case where the extended grain structure or the fibrous structure is formed only in a part of the grain structure, bending workability is higher than that in which the grain structure is constituted only by the extended grain structure or the fibrous structure. Is inferior.

B. Next, the reasons for limiting the metallographic structure will be described. The Al alloy extruded profile of the present invention is manufactured by extrusion, and its metal structure is a structure composed of granular crystal grains, and the average crystal grain size is 100 μm or less, and the aspect ratio of the crystal grains, ie, Al Excellent bending workability can be obtained when the ratio of the length in the extrusion direction to the length in the thickness direction of the crystal grains constituting the extruded alloy material is 2 or less, but the average crystal grain size is 10%.
If it exceeds 0 μm, or if it has an elongated grain structure in which the aspect ratio of crystal grains exceeds 2, or if it has a partially fibrous structure in the thickness direction, the bending workability will deteriorate.

C. Manufacturing Conditions The reason why the extrusion processing temperature is limited to the temperature range of 460 ° C. to 560 ° C. is that if the extrusion processing is performed at a temperature lower than 460 ° C., the temperature is too low, so that the solute atoms cannot be sufficiently dissolved to obtain a desired strength. You can't get it. On the other hand, 56
Extrusion at a temperature exceeding 0 ° C. causes defects such as cracks due to local melting. If the cooling rate after extrusion is less than 50 ° C./sec, Si particles precipitate at the crystal grain boundaries during cooling, and the bending workability deteriorates.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a partial cross-sectional configuration diagram schematically illustrating a configuration of a portion including an extrusion die of an extruder according to the present invention. In this figure, the Al charged in the extruder 1
The alloy billet 2 is processed into a predetermined shape by being extruded through an extrusion die 3. Further, a cooling means 4 for cooling the Al alloy material is provided on the outlet side of the extrusion die 3.

The Al alloy extruded material of the present invention is prepared by smelting an Al alloy billet having the above-described composition by a conventional method, holding the billet at about 500 to 600 ° C., and homogenizing the billet. After heating to about 560 ° C., the extruder 1 is extruded into a predetermined shape using the extruder 1 shown in FIG. 1, and cooled at 50 ° C./sec or more by the cooling means 4 provided at the exit side of the extrusion die 3 of the extruder 1. Manufactured with rapid cooling at speed. The cooling means 4 shown in FIG. 1 can be applied without any problem as long as it is a cooling method capable of rapidly cooling the Al alloy material discharged from the extrusion die 3 such as water cooling or liquid nitrogen injection. Can be.

[0012]

The present invention will be described in more detail with reference to the following examples. (Examples 1 to 4) First, as an extruded aluminum alloy material satisfying the requirements of the present invention, an alloy billet having a composition shown in Table 1 and having a diameter of 204 mm was melted by a conventional method. After a homogenization treatment of holding at 545 ° C. for 4 hours, an extrusion temperature of 500 using an extruder of 1650 tons.
° C, extrusion speed: 5 m / min, cooling: 150 ° C / sec (water cooling)
Extrusion processing is performed under the conditions of
3.5 m thick having desired strength (proof strength of 220 MPa or more) by applying artificial aging treatment for 4 to 8 hours
m, an Al alloy extruded profile having a cross section of 70 mm × 80 mm was produced.

(Comparative Examples 1 to 6) Next, in order to compare the alloy composition, the crystal grain size, and the aspect ratio of the crystal grain size according to the difference in aspect ratio, Table 1 was used under the same conditions as those in Examples 1 to 4 above. The aluminum alloy extruded profiles of Comparative Examples 1 to 6 were prepared from alloy billets having the composition shown in Table 1. Comparative Example 1 is a 6063 alloy, Comparative Example 2 is a 6N01 alloy, and Comparative Example 3 is a 6061 alloy.

(Comparative Examples 7 to 9) Next, in order to compare the production conditions, the aluminum alloy extruded members of Comparative Examples 7 to 9 were prepared from alloy billets having the same composition as in Example 1 shown in Table 1. Was prepared. However, the manufacturing conditions other than the following conditions were the same as those in Example 1.

[0015]

[Table 1]

Next, the Al of the above Examples and Comparative Examples
For the extruded alloy material, microstructure observation, proof stress measurement by a tensile test, and bending workability evaluation were performed. The bending workability was evaluated by a U-shaped bending test. This U-shaped bending test uses a punch having a bending radius (tip radius) of 11 mm, and bends the test piece along the tip of the punch to determine whether or not cracks occur on the outer surface of the bending tip of the test piece. Was evaluated. The results are shown in Tables 2 and 3. From the results shown in Table 2, A of Examples 1-4 satisfying the requirements of the present invention
All alloy materials have a fine equiaxed grain structure and a proof stress of 22
It was confirmed that it had desired strength of 0 MPa or more and excellent bending workability. On the other hand, it was confirmed that all of the Al alloy materials of Comparative Examples 1 to 6 which did not satisfy the requirements of the present invention were inferior in bending workability. Further, the extruded Al alloys of Comparative Examples 7 to 9 which do not satisfy the requirements of the method for producing an extruded Al alloy of the present invention were all inferior in bending workability.

[0017]

[Table 2]

[Table 3]

[0018]

As described in detail above, according to the present invention, Si: 0.40 to 0.75% by weight, Mg:
0.65 to 1.0%, and -0.05 ≦ (Si-Mg
/1.73)≦0.20 and Mn
0.02% to less than 0.05%, Zr 0.02% to less than 0.05%, and Cu: 0.05 to 0.4%
%, Fe: 0.1 to 0.4%, Ti:
0.005% to 0.1%, B: 0.0001 to 0.00
4%, the balance being Al and unavoidable impurities, and the average grain size of the crystal grains in the cross section in the extrusion direction is 100.
μm or less, and the ratio of the length of the crystal grains in the extrusion direction to the length in the thickness direction has a grain structure of 2 or less. Can be provided.

Next, according to the method for producing an extruded aluminum alloy material of the present invention, the temperature of 500 ° C. in the cooling step on the die exit side is obtained.
By cooling at a rate of 50 ° C./sec or more from 200 ° C. to 200 ° C., an extruded Al alloy having excellent bending workability can be efficiently and stably manufactured.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional configuration diagram of an extruder according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 extruder 2 Al alloy billet 3 extrusion die 4 cooling means

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Claims (2)

[Claims] 1. 0.40 to 0.75% by weight of Si,
Mg: 0.65 to 1.0%, and -0.05 ≦ (Si
-Mg / 1.73) ≦ 0.20, Mn is 0.02% or more and less than 0.05%, and Zr is 0.02% or less.
Contains 2% or more and less than 0.05%, and Cu: 0.05 to
0.4%, Fe: 0.1-0.4%, T
i: 0.005% to 0.1%, B: 0.0001 to 0.
004%, the balance being Al and unavoidable impurities, and the average grain size of the crystal grains in the cross section in the extrusion direction is 1
An extruded aluminum alloy material excellent in bending workability, characterized by having a crystal grain structure of not more than 00 μm and having a ratio of the length of the crystal grains in the extrusion direction to the length in the thickness direction of 2 or less. 2. 0.4% to 0.75% by weight of Si;
Mg: 0.65 to 1.0%, and -0.05 ≦ (Si
-Mg / 1.73) ≦ 0.20, Mn is 0.02% or more and less than 0.05%, and Zr is 0.02% or less.
Contains 2% or more and less than 0.05%, and Cu: 0.05 to
0.4%, Fe: 0.1-0.4%, T
i: 0.005% to 0.1%, B: 0.0001 to 0.
An aluminum alloy ingot containing 004% and the remainder consisting of Al and unavoidable impurities is heated to a temperature of 460 ° C. to 560 ° C., extruded, and extruded from 500 ° C. to 2 °
A method for producing an extruded aluminum alloy material, wherein the average cooling rate to 00 ° C. is 50 ° C./sec or more.