JP2001115227A - High strength aluminum alloy extruded material excellent in surface characteristic, and two-wheeler frame using the extruded material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high strength aluminum alloy extruded material excellent in surface characteristic and suitably used for two-wheeler frame. SOLUTION: The high strength aluminum alloy extruded material excellent in surface characteristic has a composition which consists of, by weight, >5.0-6.5% Zn, 1.5-2.0% Mh, 0.05-0.25% Cu, >0.20-0.40% Mn, 0.05-0.25% Zr, <=10.30% Fe, <=0.20% Si, 0.01-0.1% Ti and the balance Al with inevitable impurities and in which the contents of the above Fe, Si, Mn and Zn satisfy inequalities (Fe+Si)/Mn>=1.0... (1) and (Fe/Si)+Zn>=6.2... (2).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-strength aluminum alloy extruded material having excellent surface properties and a motorcycle frame using the extruded material.

[0002]

2. Description of the Related Art For a frame for a motorcycle such as a motorcycle or a bicycle, a lightweight aluminum alloy extruded material is used for the purpose of environmental protection and improvement of operation functions, and the extruded material is assembled to the frame by welding. When decorativeness is required, the extruded material is subjected to an alumite treatment. For this reason, the aluminum alloy has mechanical properties and stress corrosion cracking resistance required for a motorcycle frame, and has excellent extrudability, weldability, and alumite treatment properties.
Zn-Mg based JIS7N01 alloy, JIS7003 alloy and the like are used.

[0003]

However, these alloys are recrystallized during or immediately after the extrusion, and a coarse-grained structure (coarse recrystallized structure) appears on the surface, and the surface properties are deteriorated. As a result, there is a problem that the surface is roughened at the time of bending and the alumite treatment property (brightness) is reduced. The present invention has been made in view of such a situation, and the object is to provide excellent mechanical properties, extrudability, stress corrosion cracking resistance, and weldability required for a motorcycle frame. It is an object of the present invention to provide a high-strength aluminum alloy extruded material, and a motorcycle frame using the extruded material.

[0004]

According to the first aspect of the present invention,
More than 5.0 wt% Zn and 6.5 wt% or less, 1.5 wt% Mg
~ 2.0wt%, Cu is 0.05wt% ~ 0.25wt%, M
n is more than 0.20 wt% and 0.40 wt% or less, and Zr is 0.0
5 wt% to 0.25 wt%, Fe 0.30 wt% or less, Si
0.20 wt% or less, Ti 0.01 wt% to 0.1 wt%
Contained, with the balance being Al and unavoidable impurities, and the contents of Fe, Si, Mn, and Zn are as follows (1) and (2):
It is a high-strength aluminum alloy extruded material excellent in surface properties characterized by satisfying the formula. (Fe + Si) /Mn≧1.0 (1) (Fe / Si) + Zn ≧ 6.2 (2)

According to a second aspect of the present invention, there is provided a motorcycle frame using the high-strength aluminum alloy extruded material according to the first aspect.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The alloy components of the extruded aluminum alloy according to the present invention will be described below. Zn contributes to improvement in strength. The reason for defining the Zn content to be more than 5.0 wt% and 6.5 wt% or less is that the effect is not sufficiently obtained at 5.0 wt% or less, and stress corrosion cracking is liable to occur at more than 6.5 wt%. That's why.

[0007] Mg coexists with Zn and contributes to strength improvement. The reason for limiting the Mg content to 1.5 wt% to 2.0 wt% is that if the content is less than 1.5 wt%, the effect is not sufficiently obtained, and if the content exceeds 2.0 wt%, the extrudability and stress corrosion cracking resistance are increased. This is because the property is reduced. A particularly desirable content is from 1.55 wt% to 1.8 wt%.

[0008] Cu improves stress corrosion cracking resistance. C
The reason why the content of u is defined as 0.05 wt% to 0.25 wt% is that if the content is less than 0.05 wt%, the effect cannot be sufficiently obtained, and if it exceeds 0.25 wt%, fine cracks are easily generated at the time of welding. It is because it becomes. A particularly desirable content is 0.10 wt.
% To 0.20 wt%.

Mn promotes solid solution hardening or precipitation hardening and contributes to strength improvement. The reason that the content of Mn is specified to be more than 0.20 wt% and not more than 0.40 wt% is that the effect is not sufficiently obtained when the content is 0.20 wt% or less, and when the content exceeds 0.40 wt%, the extrudability deteriorates. This may cause defects. Particularly desirable content is more than 0.20 wt% and 0.28
wt% or less.

[0010] Zr suppresses recrystallization during or immediately after extrusion, thereby preventing generation of a coarse-grained structure. That is, Zr
The addition stabilizes the fibrous structure. When the coarse-grained structure is generated, the surface of the bent portion is roughened, and the alumite processability is reduced. The content of Zr is 0.05wt% ~ 0.25wt
The reason for specifying the percentage is that if the content is less than 0.05% by weight, the effect cannot be sufficiently obtained, and if the content exceeds 0.25% by weight, coarse crystals are formed, and the effect cannot be sufficiently obtained. .

[0011] Ti makes the structure finer and reduces the surface roughness, thereby preventing rough skin. Ti content of 0.01 wt%
The reason for defining the content to be 0.1 wt% is that if the content is less than 0.01 wt%, the effect cannot be sufficiently obtained, and if the content exceeds 0.1 wt%, coarse crystals are formed and the surface roughness becomes large.

Fe and S contained as unavoidable impurities
i increases the surface roughness of the extruded material to reduce the alumite treatment property. Therefore, the content of Fe is 0.30% by weight or less,
Is specified to be 0.20 wt% or less.

The surface roughness is determined by adding the amounts of Mn and Zn to the sum or ratio of the contents of Fe and Si (Fe / S
It can be further reduced by adjusting to satisfy the following equations (1) and (2) in accordance with i). [(Fe + Si) / Mn] ≧ 1.0 (1) [(Fe / Si) + Zn] ≧ 6.2 (2) where Fe, Si, Mn, and Zn in the above formula are (Wt%). The above (1), (2)
The formula was derived by the present inventors through various studies on improving the surface properties of the extruded aluminum alloy.

Since Cr contained as an unavoidable impurity increases the quenching sensitivity and lowers the strength, it is desirable to suppress the Cr content to 0.04 wt% or less, and particularly to 0.02 wt% or less.

The extruded material of the present invention can be used for a bumper beam of an automobile, a bumper reinforcement, a side door beam,
It can be suitably used for a space frame or the like.

[0016]

The present invention will be described below in detail with reference to examples. (Example 1) An aluminum alloy having a composition within the specified value of the present invention shown in Table 1 was melted and cast by a conventional method to a diameter of 145 mm.
And then homogenized by heating at 470 ° C. for 6 hours, and extruding at an extrusion temperature of 460 to 500 ° C. and an extrusion speed of 6 m / min.
A square tube having a thickness of 5 mm and a thickness of 3 mm was manufactured.

(Comparative Example 1) The square tube was manufactured in the same manner as in Example 1 except that an aluminum alloy having a composition outside the specified range of the present invention shown in Table 1 was used.

Specimens were cut out from each of the square tubes produced in Example 1 and Comparative Example 1, and the specimens were allowed to stand at room temperature for 3 days (natural aging).
Heated at 0 ° C. for 8 hours and aged in two stages. (1) Mechanical properties, (2) Stress corrosion cracking resistance (SC
C), (3) surface properties, and (4) extrusion processability were evaluated. Table 2 shows the results.

(1) As for mechanical properties, a tensile test was conducted according to JIS-H
The evaluation was carried out in accordance with 4100. (2) Stress corrosion cracking resistance was evaluated by examining the state of cracking when a test specimen loaded with 0.2% strain was immersed in a dichromic acid solution for 360 minutes.も の indicates that no stress corrosion cracking occurred, and x indicates that occurred. (3) The surface properties were evaluated by bending the test piece at 160R and observing the surface roughness of the bent portion.た indicates that the skin was not rough, and X indicates that the skin was rough. (4) The extrudability was evaluated by observing the surface of the extruded material (square tube).な い indicates no defect, and X indicates a defect.

[0020]

[Table 1]

[0021]

[Table 2]

As is clear from Table 2, N of the present invention example
o. 1 to 6 are mechanical properties (tensile strength, proof stress, elongation), stress corrosion cracking resistance (SCC), surface properties,
The extrudability was good and overall excellent. On the other hand, in Comparative Example No. No. 7 is inferior in mechanical properties due to small amounts of Mn, Mg and Zn. No. 8 is inferior in extrudability due to a large amount of Mn. No. 9 was inferior in stress corrosion cracking resistance due to a small amount of Cu. No. 10 is [(Fe
+ Si) / Mn] is less than 1.0. 11 is [(Fe / S
i) + Zn] was less than 6.2, and the surface properties were lowered in each case.

Each of the test pieces obtained in Example 1 was subjected to an alumite treatment, and all of the test pieces were finished to have a bright and beautiful surface. Further welding tests were performed, but the welds were all sound.

[0024]

As described above, the aluminum alloy extruded material of the present invention is made of Zn, Mg, Cu, Mn, Zr, T
i is contained in a predetermined amount to maintain the mechanical properties, extrudability, weldability, and stress corrosion cracking resistance, and to regulate the contents of the impurity elements Fe and Si to a predetermined value or less.
e + Si) /Mn≧1.0, (Fe / Si) + Zn ≧
By satisfying the two expressions of 6.2, the surface properties of the extruded material are improved, and the extruded material can be suitably used for a motorcycle frame or the like, and has a remarkable industrial effect.

Claims (2)

[Claims] 1. The method according to claim 1, wherein Zn is contained in an amount exceeding 5.0 wt% and not more than 6.5 wt%.
g from 1.5 wt% to 2.0 wt%, Cu from 0.05 wt%
0.25 wt%, Mn is more than 0.20 wt% and 0.40 wt% or less, Zr is 0.05 wt% to 0.25 wt%, and Fe is 0.3
0 wt% or less, Si is 0.20 wt% or less, Ti is 0.01
wt.-0.1 wt.%, the balance being Al and unavoidable impurities, and the contents of Fe, Si, Mn, and Zn satisfy the following formulas (1) and (2). High strength aluminum alloy extruded material with excellent properties. (Fe + Si) /Mn≧1.0 (1) (Fe / Si) + Zn ≧ 6.2 (2) 2. A frame for a motorcycle, wherein the extruded high-strength aluminum alloy according to claim 1 is used.