JPH09194977A - High strength aluminum alloy excellent in machinability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high strength aluminum alloy excellent in corrosion resistance, anodizing treatment property, and recyclability as well as in machinability. SOLUTION: This aluminum alloy has a composition consisting of, by mass, 1.5-12.0% Si, 3.5-6.0% Cu, 0.4-1.0% Mg, and the balance Al with inevitable impurities. Further, if necessary, this aluminum alloy can contain, other than the above alloying elements, either of the following (1), (2), and (3): (1) either or both of 0.5-1.5mass% Mn and 0.01-0.1mass% Ti; (2) one or more kinds among, by mass, 0.5-1.0% Fe, 0.1-0.5% Cr, and 0.1-0.5% Zr; (3) free combination of the elements enumerated in the above (1) and (2).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a high-strength aluminum alloy having excellent machinability.

[0002]

2. Description of the Related Art Among aluminum alloys, heat treatment type alloys centering on 2000 series Al-Cu alloys have high mechanical properties and have been used as various structural materials for aircrafts. As a general processing method for this type of alloy, cutting or drilling is often performed.
Alloys and 2024 alloys, etc., have poor machinability because the chips generated during cutting are difficult to divide, and it has been difficult to employ them in machine parts for complex cutting and drilling.

On the other hand, in order to improve the machinability of this type of aluminum alloy, conventionally, for example, AA2011 alloy (Cu: 5.0 to 6.0 mass%, Pb: 0.2 to 0.6) was used.
%, Bi: 0.2 to 0.6% by mass, balance Al), and low-melting-point metals such as Pb, Bi, and Sn were added.
These low-melting-point metals hardly form a solid solution in aluminum and exist in granular form in the aluminum alloy.The low-melting-point metal particles are melted by the heat generated during the cutting process to cut the chips and cut the aluminum alloy. Improve.

[0004]

However, although aluminum alloys containing these low melting point metals have improved machinability, they cannot be said to have sufficient corrosion resistance, and low melting point metals have the drawback of causing thermal embrittlement. It was necessary to pay sufficient attention to the environment. In addition, aluminum alloys containing low-melting metals, when recycled as scrap for melting,
There is also a problem that it can be diverted only to a relatively small alloy type that requires Pb, Bi, etc., and the diverted range is narrowed, which is disadvantageous in recyclability. Mechanical parts may be anodized on the surface in order to improve corrosion resistance, wear resistance or decorative effect. However, in the case of an aluminum alloy containing Pb or Bi, a part where Pb or Bi is exposed on the surface is exposed. However, there is a problem in that an oxide film is not formed, and only an alumite film that is inhomogeneous and has no gloss is obtained.

The present invention has been made in view of the above problems of the prior art, and is to obtain a high-strength aluminum alloy having mechanical properties and corrosion resistance equivalent to those of the conventional 2014 alloy and 2024 alloy, and having excellent machinability. With the goal. At the same time, it is an object to obtain a high-strength aluminum alloy having high recyclability and capable of forming a uniform and glossy alumite coating and having excellent machinability.

[0006]

As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention have found that Pb was added to a highly machinable aluminum alloy such as AA2011 alloy for the purpose of improving machinability. It was found that the above object can be achieved by using Si and Mg or the like instead of adding a low melting point metal such as Si, Bi and Sn, and based on the findings, the present invention has been completed. That is, the high-strength aluminum alloy having excellent machinability according to the present invention has a Si: 1.5-
12.0% by mass, Cu: 3.5 to 6.0% by mass, Mg:
Each of them contains 0.4 to 1.0% by mass, and the balance is Al and unavoidable impurities. Further, the high-strength aluminum alloy excellent in machinability according to the present invention, if necessary, contains Mn: 0.5 to 1.5 mass% or T in addition to the above alloy elements.
i: 0.01 to 0.1% by mass, either or both, or Fe: 0.5 to 1.0% by mass, C
r: 0.1 to 0.5% by mass, Zr: 0.1 to 0.5% by mass, and at least one of them is contained, or the above elements are freely combined and contained. To do. The aluminum alloy for alumite treatment according to the present invention specifies the use of the above-mentioned high-strength aluminum alloy having excellent machinability for alumite treatment.

The above-mentioned high-strength aluminum alloy having excellent machinability has excellent mechanical properties, but is inferior in machinability and cannot be applied to many machine parts.
Compared with the alloy and 2024 alloy, it is a heat-treatable aluminum alloy that has the same mechanical properties and corrosion resistance and has significantly improved machinability, and is an alloy that enables complex cutting. Further, the cutting ability of the cutting chips is good, and troubles such as winding of the cutting chips around the tool due to long cutting chips do not occur. Also,
Since no low-melting point metal such as Pb or Bi is added for improving the machinability, it has higher corrosion resistance and higher alumite processability than the AA2011 alloy, does not cause thermal embrittlement, and does not impair recyclability. Incidentally, the aluminum alloy, in accordance with a conventional method, for example, subjected to melting, casting, homogenization treatment, then extrusion processing, solution treatment, quenching, aging treatment to give a predetermined strength, then cutting Can be used for

Next, the reason for adding each element and the reason for limiting the amount added in the aluminum alloy will be described.

Si: 1.5 to 12.0 mass% Si forms a Si-based compound in the aluminum structure, improves cutting of chips and improves machinability. This is S
This is because the i-based compound becomes a starting point of strain propagation. The lower limit of Si addition is 1.5%, which is the solid solubility limit in aluminum.
It is necessary to exceed 2.0%, and in order to clarify the effect of Si, addition of 2.0% or more is desirable. On the other hand, the upper limit of addition of Si must be less than 12.0% of the eutectic point in order to prevent the deterioration of extrudability and the embrittlement of the extruded material due to the formation of coarse primary crystal Si and the increase in deformation resistance. 6% or less, which is particularly favorable for extrusion productivity.

Cu: 3.5 to 6.0% by Mass Cu enhances strength by heat treatment and enhances strain hardening ability to promote cutting of chips. If the Cu content is less than 3.5%, its effect is poor, while if it is added in excess of 6.0%, the corrosion resistance decreases and the extrudability also decreases. Particularly, from the viewpoint of securing strength and good corrosion resistance and extrudability, 3.8% or more and 5.5% or less are desired.

Mg: 0.4 to 1.0% by mass Mg coexists with Si and becomes Mg ₂ Si during heat treatment to be precipitated, which has the effect of increasing strength. If the Mg content is less than 0.4%, the effect cannot be obtained, while 1.0%
If it is added over the range, the extrudability decreases. In particular, from the viewpoint of securing strength and good extrudability, 0.6% or more, 0.
8% or less is desired.

Mn: 0.5 to 1.5% by mass Mn has the effect of forming a solid solution to increase the strength of the material, and also has the effect of promoting cutting of chips in order to improve the strain hardening ability. However, if the Mn content is less than 0.5%, a sufficient effect cannot be obtained, while if it is added over 1.5%, the extrudability deteriorates. Particularly, from the viewpoint of securing strength and good extrudability, 0.7% or more and 1.3% or less are desired.

Ti: 0.01-0.1 mass% Ti refines the cast structure and stabilizes the mechanical properties.
However, if the Ti content is less than 0.01%, the effect cannot be obtained, while if added over 0.1%, the effect is saturated.

Fe: 0.5 to 1.0% by mass, Cr: 0.
1 to 0.5% by mass, Zr: 0.1 to 0.5% by mass Fe, Cr, and Zr each form a compound with Al,
Improves machinability by becoming the starting point for cutting chips. If the content is less than the lower limit, the effect is not sufficient, while
If it exceeds the upper limit, a coarse compound is formed and the extrudability deteriorates.

As the inevitable impurities of the aluminum alloy, Pb, Bi, and Sn are each allowed to be 0.05 mass% or less in accordance with the chemical composition defined in JIS H4040. If a large amount of these components is contained, the corrosion resistance and the alumite processability of the aluminum alloy are deteriorated, but within the above range, these properties are not affected. Also, other unavoidable impurities are individually allowed to be 0.05% by mass or less.

[0016]

EXAMPLES Examples of the present invention will be specifically described below in comparison with comparative examples. An alloy having the chemical composition shown in Table 1 and Table 2 was melted, an extruded billet having a diameter of 160 mm was prepared by semi-continuous casting, homogenized and heat-treated at 470 ° C. for 4 hours, and then extruded at a temperature of 400 ° C. to a diameter of 60 mm. Extrusion,
This was solution treated at 500 ° C. for 1 hour, quenched in water, and then subjected to natural aging. Using this as a test material, the mechanical properties, machinability, corrosion resistance and alumite treatment property of each were measured in the following manner. In addition, in order to check the extrudability, the extrusion load is fixed (600 tons) in the above extrusion, and the extrusion speed (speed at which the extruded material comes out) is measured, and the extrudability of each extruded material is evaluated as follows. did.

[0017]

[Table 1]

[0018]

[Table 2]

Mechanical properties: JIS4 sampled in the extrusion direction
Tensile strength, proof stress, and elongation were measured using the No. test piece according to the metal material test method specified in JISZ2241. Machinability; using a commercially available high-speed steel 4 mm diameter drill, cutting at a rotation speed of 1500 mm / min and a feed of 300 mm / min, and observing the occurrence of wrapping around the drill, as well as chip cutting property. For inspection, the weight per 100 chips was measured. Corrosion resistance: A 72-hour CASS test (adding 100 ppm of cupric chloride to 5% saline and spraying a solution adjusted to pH = 3 with acetic acid at 50 ° C.) to measure weight reduction per unit area . Alumite treatment property: The polished sample surface was subjected to sulfuric acid alumite treatment to make the thickness of the oxide film 10 μm and the surface gloss was observed. Extrudability: ◎ (excellent) when the value of the extrusion speed is greater than 5 m / min, ○ (useable) when the value is 2 to 5 m / min,
When it was less than 2 m / min, it was evaluated as x (not usable).

The test results are shown in Tables 3 and 4.
Alloys 1 to 14 corresponding to the examples of the present invention all showed excellent machinability and corrosion resistance, and this was confirmed to be alloy 24 of the comparative example.
(Corresponding to conventional 2014 alloy) and alloy 25 (conventional 2
(Compared to 024 alloy), it has remarkably excellent machinability, has the same mechanical properties, and has the same or excellent corrosion resistance. Further, the extruded material has no peeling or seizure marks, has a good surface property, and has an extrudability within a range in which it can be sufficiently used.

[0021]

[Table 3]

[0022]

[Table 4]

On the other hand, the alloys 15 to 26 of the comparative examples are alloys whose compositions are out of the range of the present invention, and some properties are inferior to those of the example alloys 1 to 14. That is,
Alloy 16 is inferior in machinability due to insufficient Si content (inferior cutting ability of cutting chips and winding of cutting chips).
5, 17, 19, 21 to 23 are Si, Mg, and
Since Cu, Fe, Cr and Zr are excessive, the extrudability is poor and the alloy 19 is also poor in corrosion resistance. Also, conventional alloys 24, 25
Is poor in machinability, and alloy 26 containing Pb and Bi (corresponding to the conventional AA2011 alloy) has improved machinability but poor corrosion resistance and alumite treatment.

[0024]

INDUSTRIAL APPLICABILITY As described above, the aluminum alloy according to the present invention is a heat-treatable alloy which has remarkably excellent machinability, mechanical properties, and corrosion resistance as compared with 2014 alloy and 2024 alloy. Further, since troubles such as long wrapping of chips do not occur, and the machinability is improved without using Pb and Bi unlike the conventional AA2011 alloy, thermal embrittlement due to the low melting point metal also occurs. Since it is not obtained, it has excellent anodizing property and high recyclability.
The industrial value is extremely high as a high-strength aluminum alloy that can be applied to each application in which the 011 alloy has been used.

Claims (6)

[Claims] 1. Si: 1.5 to 12.0 mass%, Cu:
A high-strength aluminum alloy having excellent machinability, which contains 3.5 to 6.0% by mass and Mg: 0.4 to 1.0% by mass with the balance being Al and inevitable impurities. 2. Si: 1.5 to 12.0 mass%, Cu:
3.5-6.0 mass%, Mg: 0.4-1.0 mass%,
Mn: A high-strength aluminum alloy containing 0.5 to 1.5% by mass, the balance being Al and unavoidable impurities, and having excellent machinability. 3. Si: 1.5 to 12.0 mass%, Cu:
3.5-6.0 mass%, Mg: 0.4-1.0 mass%,
Ti: A high-strength aluminum alloy having excellent machinability, which contains 0.01 to 0.1 mass% of each, and the balance of Al and unavoidable impurities. 4. Si: 1.5 to 12.0 mass%, Cu:
3.5-6.0 mass%, Mg: 0.4-1.0 mass%,
Mn: 0.5 to 1.5 mass%, Ti: 0.01 to 0.1
A high-strength aluminum alloy having excellent machinability, characterized in that it contains each mass% and the balance is Al and unavoidable impurities. 5. Further, Fe: 0.5 to 1.0% by mass,
Cr: 0.1 to 0.5% by mass, Zr: 0.1 to 0.5% by mass, and one or more of them are contained. High-strength aluminum alloy with excellent machinability. 6. An aluminum alloy for alumite treatment, which has the chemical composition according to any one of claims 1 to 5.