JP4036325B2 - Aluminum alloy extruded material excellent in impact fracture resistance and vehicle member using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to an aluminum alloy extruded material effective for achieving aluminum in parts that require high impact fracture resistance, such as vehicle suspension parts, and a high impact fracture resistant member using the same.
[0002]
[Prior art]
For the purpose of reducing the weight of the vehicle, the use of aluminum as a suspension component has been studied. For example, in the configuration example of the vehicle suspension component shown in FIG. 4, the lower arm 8 and the upper arm 6 are solid components. There are used aluminum alloy castings and forgings (JP 2001-73056 A, JP 2001-162318 A). In addition, 7 is a knuckle.
On the other hand, the parts of the brackets 1 are hollow parts, and if a member is obtained with an aluminum alloy extruded material, the machining of the hollow part processing and the flatness of the mounting surface can be reduced, and the weight can be reduced. Low cost is expected.
However, since vehicle suspension parts are parts that directly receive and absorb impact during travel, they are required to have not only high strength but also high impact fracture resistance.
Conventionally, cast iron members have been generally employed because an aluminum alloy extruded material that can satisfy the required quality of such high strength and high impact fracture resistance has not been obtained.
[0003]
[Problems to be solved by the invention]
In view of the above circumstances, an object of the present invention is to provide an aluminum alloy extruded material excellent in strength and impact fracture resistance, a vehicle component using the aluminum alloy extruded material, and the like.
[0004]
[Means for Solving the Problems]
The technical gist of the invention of claim 1 is that Si: 0.5 to 0.9 mass%, preferably 0.6 to 0.8 mass%, Mg: 0.75 to 1.15 mass%, preferably 0.00. 85 to 1.05 mass%, Cu: 0.10 to 0.35 mass%, preferably 0.15 to 0.30 mass%, Mn: 0.02 to 0.20 mass%, preferably 0.02 to 0.02. 10% by mass, Cr: 0.1 to 0.3% by mass, preferably 0.1 to 0.2 % by mass , Ti: 0.02% by mass and Fe: 0.30 to 0.45% by mass ( The component is adjusted so that it is preferably in the range of 0.30 to 0.40% by mass (excluding 0.30) except for 0.30, and the balance is Al and inevitable impurities. An aluminum alloy extruded material excellent in destructibility was obtained.
[0005]
In a conventional aluminum alloy extruded material, in order to obtain high strength while considering extrusion processability, the component ratio of Mg and Si is adjusted, and while considering corrosion resistance such as local corrosion and stress corrosion cracking, Cu For the purpose of adjusting the components and further improving the strength by refining the recrystallized grains, a small amount of Ti component or the like was adjusted.
However, with such an alloy composition, a spherical crystal structure is formed, and when an impact force is applied, fracture propagation propagates along this spherical grain boundary, and sufficient toughness, Charpy characteristics, etc. are not obtained. On the other hand, in the invention of claim 1, the Fe component is 0.30 to 0.45 mass% (excluding 0.30) while suppressing recrystallization during extrusion of the aluminum alloy with the Mn and Cr components. ) , Preferably a stable fibrous structure (fiber structure) is obtained by adjusting the amount in the range of 0.30 to 0.40 mass% (excluding 0.30) .
That is, conventionally, the Fe component is treated as an impurity, and when casting a billet for extrusion processing, a huge intermetallic compound may be crystallized, which may impair the mechanical properties as an aluminum alloy. In order to suppress the mixing of Fe components.
On the other hand, the applicant of the present application has found that a stable fibrous structure can be obtained by appropriately adjusting the Fe component range by a combination of Mn, Cr components and the like.
[0006]
Si component is 0.5 to 0.9% by mass, preferably 0.6 to 0.8% by mass, and Mg component is 0.75 to 1.15% by mass, preferably 0.85 to 1.05% by mass. The adjustment to the range is intended to improve the tensile strength and the yield strength by precipitation of Mg ₂ Si particles while considering the extrusion processability.
Note that it is preferable to adjust the component slightly Si-rich with respect to the theoretical ratio of Mg ₂ Si.
[0007]
If Cu component is added excessively, it causes local corrosion and causes stress corrosion cracking resistance. Therefore, considering these, 0.10 to 0.35% by mass, preferably 0 Adjusted to the range of .15 to 0.30 mass%.
[0008]
When Mn and Cr components are excessive, not only the extrudability is lowered, but also the toughness is lowered. Therefore, the Fe component is 0.30 to 0.45% by mass (except 0.30) , preferably 0.30. In the range of ~ 0.40% by mass (excluding 0.30) , the Mn component is 0.02 to 0.20% by mass, preferably 0.02 to 0% as the range for stabilizing the fibrous structure most effectively. .10 mass%, Cr component 0.1 to 0.3 mass%, preferably 0.1 to 0.2 mass%.
[0009]
The technical gist of the invention according to claim 2 is to provide an extrusion method for effectively expressing the physical properties of the extruded material having the above alloy composition with high productivity.
Si: 0.5 to 0.9% by mass, preferably 0.6 to 0.8% by mass, Mg: 0.75 to 1.15% by mass, preferably 0.85 to 1.05% by mass, Cu: 0.0. 10 to 0.35% by mass, preferably 0.15 to 0.30% by mass, Mn: 0.02 to 0.20% by mass, preferably 0.02 to 0.10% by mass, Cr: 0.1 to 0. 3% by mass, preferably 0.1 to 0.2 % by mass , Ti: 0.02% by mass and Fe: 0.30 to 0.45% by mass (excluding 0.30), preferably 0.30 The components were adjusted so as to be in the range of 0.40% by mass (excluding 0.30), and the balance was extruded using an aluminum alloy composed of Al and inevitable impurities. Immediately thereafter, the average cooling rate was 500 ° C./min. The technical point of view is to cool it as described above and then perform artificial aging treatment.
Here, “immediately after extrusion” means in a range where the temperature of the extruded material does not become about 500 ° C. or less after extrusion.
The cooling rate refers to the rate until the extruded material reaches about 200 ° C. or less.
Thus, rapid cooling immediately after extrusion has the effect of suppressing the progress of recrystallization of the aluminum alloy and forming a stable fibrous structure.
[0010]
The metal structure of the aluminum alloy extruded material thus obtained will be described.
As shown in FIG. 5 (a), the structure in the extrusion direction of the extruded material using a conventional aluminum alloy is a granular structure, and cracks are easy to propagate along the grain boundary. The cross-sectional metal structure in the extrusion direction of the obtained aluminum alloy extruded material was a fibrous structure as shown in FIG.
As a result, an aluminum alloy extruded material having high strength and high impact fracture resistance was obtained as described above.
[0011]
The novel aluminum alloy extruded material according to claim 1 or claim 2 is excellent in toughness, particularly has a high Charpy impact value, and can be applied to various members, parts and the like that require impact fracture resistance.
Among them, vehicle suspension parts and the like are required to have an impact fracture resistance that can withstand a large running impact. Therefore, it is only possible to apply a new aluminum alloy extruded material according to the present invention to aluminize with an extruded material. become.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
In order to obtain the component composition of Examples 1 to 3 shown in FIG. 1 (Table 1) and the composition of Comparative Example 1 (corresponding to JIS A6N01) and Comparative Example 2 (corresponding to JIS A6061), an aluminum alloy billet (diameter 204 mm) ) Was cast by a conventional method and homogenized at about 560 ° C. for 6 hours.
This billet was preheated to about 520 ° C., extruded at an extrusion speed of about 5 m / min, and continuously water-cooled at a speed of 500 to 600 ° C./min.
Then, after cutting to a predetermined length, the bracket member was obtained by artificial aging at 185 ° C. for about 6 hours.
[0013]
A test piece was cut out from each of the above test materials, and the following tests and evaluations were performed.
Tensile strength, 0.2% proof stress, and elongation were measured in accordance with JISZ2241 after cutting out JISZ2201 and 14A test pieces.
The Charpy impact value was measured in accordance with JISZ2242 by cutting out a JISZ2202 and V-notch No. 4 test piece.
The evaluation of the fibrous structure was performed by polishing the cross section in the extrusion direction and measuring the area ratio of the fibrous structure by observation with a 25 × optical microscope.
[0014]
The results are shown in FIG. 2 (Table 2).
The “extrusion direction” in the item column means that the test piece was cut out and evaluated in the extrusion direction, and “vertical direction” means that the test piece was cut out and evaluated in a direction perpendicular to the extrusion direction.
Comparative Example 1 corresponding to the JIS A6N01 alloy had a grain structure almost entirely and had low tensile strength, proof stress, etc., but also had a low Charpy impact value.
Comparative Example 2 corresponding to JIS A6061 alloy showed values close to those of Examples 1 to 3 according to the present invention, but the ratio of the fibrous structure was as low as 37% and the Charpy impact value was low.
On the other hand, in the aluminum alloy extruded materials shown in Examples, the ratio of the fibrous structure was high and the Charpy impact value was high.
[0015]
For example, the bracket 1 which is a suspension part shown in FIG. 4 has a bush inserted inside the hollow portion, and the bush is steel from which the rubber member 2, the steel cylindrical member 3, the rubber mount member 4 and the shaft are inserted and connected from the outside. It is composed of a cylindrical member 5.
In addition, 1b is a bracket attachment surface and 1a is an attachment hole.
In terms of the function of the product, tensile strength of 300 MPa or more, proof stress of 270 MPa or more, elongation of 13% or more, Charpy impact value, extrusion direction of 25 J / cm ₂ and vertical direction of 17 J / cm ₂ or more are required. ing.
Moreover, as a result of comparing the corrosion resistance with the JIS A6061 alloy (Comparative Example 2) and the salt spray test, there is no difference. As a result of the vehicle salt damage running test using the sample of Example 3, harmful corrosion and stress corrosion cracking are I was not able to admit.
[0016]
【The invention's effect】
In the present invention, by adjusting the combination of the Si component and the Mg component and the Cu component, the Fe component, which has been conventionally referred to as an impurity, is adjusted to a predetermined range while ensuring the tensile strength and the proof stress value. Thus, an aluminum alloy extruded material having excellent impact fracture resistance can be obtained by suppressing recrystallization with the Mn component and the Cr component.
In this case, by rapidly cooling immediately after extrusion, recrystallization is suppressed and a more stable fibrous structure is obtained.
In addition, by applying this extruded material, for example, as shown in FIG. 4, it is easy to ensure the flatness of the mounting surface 1b, and the impact fracture resistance of a bracket or the like with high accuracy of the hollow shape and almost no machining is required. A member is obtained.
[Brief description of the drawings]
FIG. 1 shows an example of an alloy composition (material component) of an aluminum alloy according to the present invention.
FIG. 2 shows a test evaluation result of the extruded material.
FIG. 3 shows a configuration example of a suspension component.
FIG. 4 shows a structural example of a bracket.
FIG. 5 shows a schematic diagram of a metal structure.
[Explanation of symbols]
1 Bracket 1a Bracket mounting hole 1b Bracket mounting surface

Claims (2)

Si: 0.5 to 0.9% by mass, Mg: 0.75 to 1.15% by mass, Cu: 0.10 to 0.35% by mass, Mn: 0.02 to 0.20% by mass, Cr: 0.1 to 0.3% by mass, Ti: 0.02% by mass , Fe: 0.30 to 0.45% by mass (excluding 0.30) Is an aluminum alloy extrudate excellent in impact fracture resistance, characterized in that is an inevitable impurity with Al. Si: 0.5 to 0.9 mass%, Mg: 0.75 to 1.15 mass%, Cu: 0.10 to 0.35 mass%, Mn: 0.02 to 0.20 mass%, Cr: 0.1 to 0.3% by mass, Ti: 0.02% by mass , Fe: 0.30 to 0.45% by mass (excluding 0.30) Is obtained by extruding using an aluminum alloy consisting of Al and inevitable impurities, immediately after cooling at an average cooling rate of 500 ° C./min or more, and then performing an artificial aging treatment. Aluminum alloy extruded material with excellent destructibility.

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