JP2001240931A - Aluminum alloy excellent in machinability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aluminum alloy provided with mechanical properties and corrosion resistance equal to those of the conventional AA2011 alloy and excellent in machinability without being incorporated with Pb. SOLUTION: This aluminum alloy has a composition containing, by mass, 4.8 to 5.9% Cu, 0.3 to 1.0% Bi, 0.3 to 1.0% Sn and 0.005 to 0.05% Ti, furthermore containing, at need, 0.4 to 1.0% Mg or one or more kinds selected from 0.05 to 0.5% Mn, 0.05 to 0.5% Cr and 0.05 to 0.5% Zr, and the balance Al with impurities. The alloy is subjected to solution-quqenching treatment and aging treatment after hot working such as extrusion and rolling and is subjected machining.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy having excellent machinability.

[0002]

2. Description of the Related Art Among aluminum alloys, heat-treatable alloys, especially 2000-series Al-Cu alloys, have high mechanical properties and have been used as various structural materials for aircraft and the like. As a general processing method of this type of alloy, cutting or drilling is often performed after extrusion. For example, 2014 alloy and 2024 alloy are difficult to cut off chips generated during cutting, so that the cutting property is low. And it was difficult to adopt it for machine parts for complicated cutting and drilling.

On the other hand, in order to improve the machinability of an aluminum alloy extruded material of this type, conventionally, for example, AA201
1 alloy (Cu: 5.0-6.0%, Pb: 0.2-0.0%)
6%, Bi: 0.2-0.6%, balance Al)
Low melting point metals such as Pb and Bi were added. These low-melting-point metals hardly form a solid solution in aluminum, but exist in a granular form in an aluminum alloy, and the low-melting-point metal particles are melted by the heat generated during cutting to separate chips (melt embrittlement), Improves the machinability of extruded aluminum alloy.

[0004]

However, in response to the recent increase in demand for global environmental protection, there has been an increasing movement to regulate the use of harmful components such as Pb. Pb accumulates when ingested by the human body and causes Pb addiction such as neuropathy and anemia. In Japan, the Ministry of International Trade and Industry set the "Guidelines for Waste Management and Recycling by Item" in 1997, and set numerical targets for reducing Pb usage for automobiles and motorcycles. In response, automakers have formulated voluntary action plans. On the other hand, in the EU, there are “Directive on Packaging and Packaging Waste” and “Proposed EU Directive on End-of-Life Vehicles”, and Pb, Cd, H
g, stipulates to reduce the amount of hexavalent Cr used.

The present invention has been made in view of such circumstances, and an object of the present invention is to obtain an aluminum alloy which does not contain Pb, has the same mechanical properties and corrosion resistance as a conventional AA2011 alloy, and is excellent in machinability. Aim.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, Pb added to a high machinability aluminum alloy such as AA2011 alloy for the purpose of improving the machinability. It has been found that the above object can be achieved by adding Sn and Bi simultaneously instead of adding, and the present invention has been completed based on the findings. That is, the aluminum alloy excellent in machinability according to the present invention is Cu: 4.8 to 5.9%, Bi: 0.3 to
1.0%, Sn: 0.3 to 1.0%, Ti: 0.005
０．０５0.05%, with the balance being Al and impurities, characterized by having been subjected to solution treatment / hardening treatment and aging treatment after hot working. In addition, the aluminum alloy having excellent machinability according to the present invention may further include M
g: 0.4 to 1.0%, or / and Mn: 0. 1%.
05-0.5%, Cr: 0.05-0.5%, Zr:
Contains at least one of 0.05 to 0.5%. In the above aluminum alloy, the total content of Bi and Sn is desirably 0.6 to 1.4%.

The above-mentioned aluminum alloy has good chip breaking properties, and does not cause trouble such as winding of chips around a tool due to long chips. Further, since Pb is not added for improving the machinability, the environment is considered in comparison with the AA2011 alloy. The aluminum alloy is melted, cast, and homogenized according to a conventional method, and then subjected to hot working such as extrusion or rolling to obtain an extruded or rolled material (such as a bar material). After being subjected to solution treatment, quenching and aging treatment to give a predetermined strength, it is subjected to cutting.

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

Cu: 4.8 to 5.9% Cu enhances the strength by heat treatment and promotes chip breaking to improve strain hardening ability. If the Cu content is less than 4.8%, the effect is poor. On the other hand, if the Cu content exceeds 5.9%, the corrosion resistance decreases and the hot workability (extrudability, etc.) also decreases. It is desirably 5.5% or less, particularly from 5% or more and 5.4% or less, from the viewpoint of securing strength and good corrosion resistance and hot workability.

Bi: 0.3 to 1.0% Sn: 0.3 to 1.0% By adding Bi and Sn simultaneously, B having a low melting point can be obtained.
The fine particles of the i-Sn alloy are dispersed in the aluminum alloy, so that the chip is melted and embrittled by the cutting heat, so that excellent chip breaking properties are obtained. As the content of Bi and Sn is closer to the eutectic composition (Bi: Sn = 57: 43), the melting point of the dispersed particles can be reduced, and the efficiency of melt embrittlement of chips increases. On the other hand, the melting point of the dispersed particles increases as the Bi and Sn contents deviate from the eutectic composition even if Bi alone or Sn alone or simultaneously added, and the melting embrittlement efficiency of the chips by the cutting heat is low. , Resulting in poor chip breaking performance. Moreover, when Bi and Sn are added alone, they segregate at the crystal grain boundaries, and the elongation is reduced. Furthermore, Bi and Sn
When the content is small, the effect of improving the machinability is small, and when the content is large, elongation and corrosion resistance are reduced. From the above points, Bi and Sn are added at the same time, and their contents are both 0.3 to 1.0%. The total content is desirably 0.6-1.4%.

Ti: 0.005 to 0.05% Ti refines a cast structure and stabilizes mechanical properties.
However, if the Ti content is less than 0.005%, the effect cannot be obtained, while if the content exceeds 0.05%, the effect is saturated. Mg: 0.4 to 1.0% Mg is Al ₂ CuMg due to coexistence with Cu and Al.
And has the effect of increasing the strength, further promoting the strain hardening ability and increasing the chip breaking ability. If the Mg content is less than 0.4%, the effect cannot be obtained.
If added in excess of, the hot workability (extrudability, etc.) will be reduced. In particular, from the viewpoint of securing strength and good hot workability, the content is preferably 0.6% or more and 0.8% or less when added.

Mn: 0.05-0.5% Cr: 0.05-0.5% Zr: 0.05-0.5% Mn, Cr and Zr each form a compound with Al,
In order to improve the machinability as a starting point of chip breaking, one or more kinds are appropriately added. If the added amount is less than 0.05%, the effect is not sufficient, while if it exceeds 0.5%, a coarse compound is formed and the hot workability (extrudability, etc.) is reduced.

[0013] Among the impurities, Fe and Si are impurities contained in the aluminum alloy in a large amount, and when present in the aluminum alloy in excess of 0.35% and 0.2%, respectively, crystallize a coarse intermetallic compound, Impairs the mechanical properties of the alloy. Therefore, the contents of Fe and Si are 0.35% and 0.2%, respectively.
% Or less. Further, when casting an aluminum alloy, impurities are mixed from various routes such as a base metal and an intermediate alloy of an additive element. There are various elements to be mixed, but impurities other than Fe alone have 0.05% or less, and if the total amount is 0.15% or less, it hardly affects the characteristics of the aluminum alloy. Therefore, these impurities alone are 0.0%
5% or less, and the total amount is 0.15% or less. In addition, B among impurities is mixed into the alloy in an amount of about 1/5 of the Ti content with the addition of Ti, but a more preferable range is 0.02% or less, and further preferably 0.01% or less. .

[0014]

EXAMPLES Examples of the present invention will be specifically described below in comparison with comparative examples. An extruded billet having a diameter of 160 mm was prepared by melting an alloy having the chemical composition shown in Table 1 and semi-continuous casting, and subjected to a homogenizing heat treatment at 470 ° C. for 4 hours.
Extruded to a diameter of 46 mm at an extrusion temperature of 400 ° C.
After solution treatment at 20 ° C. for 1 hour and quenching in water,
An artificial aging treatment was performed at 5 ° C. for 9 hours. Using this as a test material, the mechanical properties, machinability, and corrosion resistance of each were measured in the following manner. In order to check the extrudability, in the above extrusion, the extrusion load was kept constant (600 tons), the extrusion speed (speed at which the extruded material came out) was measured, and the extrudability of each extruded material was evaluated in the following manner. did.

[0015]

[Table 1]

Mechanical properties: JIS4 sampled in the extrusion direction
The 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 4 mm diameter drill made of high-speed steel, cutting was performed under the conditions of a rotation speed of 1500 mm / min and a feed of 300 mm / min, observing the occurrence of wrapping around the drill, and checking the chip breaking ability. In order to investigate, the number of chips per 100 g of chips was measured. Corrosion resistance; 200 hours SST test (salt spray test method)
Was carried out in accordance with the provisions of JISZ1271, and the weight loss per unit area was measured. Extrudability: when the value of the extrusion speed is more than 5 m / min, ◎ (excellent), when 2 to 5 m / min, ○ (usable),
When it was smaller than 2 m / min, it was evaluated as x (not usable).

Table 2 shows the results of these tests. All of the alloys 1 to 5 corresponding to the examples of the present invention show excellent mechanical properties, machinability and corrosion resistance. In addition, the extruded material has no surface peeling or burning marks, has good surface properties, and has excellent extrudability. On the other hand, the alloys 6 to 13 of the comparative examples are alloys whose compositions are out of the range of the present invention, and all have inferior characteristics to those of the alloys of the examples 1 to 5. That is, alloy 6 has poor extrudability and corrosion resistance due to excessive Cu content, alloy 7 has poor cutability due to insufficient Cu content, and alloy 8 has poor Cu content.
Is too low in elongation and corrosion resistance due to excessive Bi and Sn contents, alloy 9 is inferior in machinability due to insufficient Bi and Sn contents, alloy 10 has no Sn addition and alloy 11
No addition of Bi makes the alloy less inferior in machinability, and alloy 12 has too much Bi and alloy 13 has too much Sn to have low elongation and poor retirement.

[0018]

[Table 2]

[0019]

As described above, according to the present invention, a predetermined amount of Cu
By simultaneously adding Bi and Sn to an aluminum alloy containing, it is possible to improve the machinability without using Pb unlike the conventional AA2011 alloy, and to respond to the recent demand for global environmental protection. Can be.

Claims (4)

[Claims] 1. Cu: 4.8-5.9% (mass%, the same applies hereinafter), Bi: 0.3-1.0%, Sn: 0.3-1.
0%, Ti: 0.005 to 0.05%, with the balance being Al and impurities, which have been subjected to solution treatment, quenching treatment and aging treatment after hot working, and have excellent machinability. Aluminum alloy. 2. The aluminum alloy having excellent machinability according to claim 1, further comprising Mg: 0.4 to 1.0%. 3. Mn: 0.05-0.5%, C
The aluminum alloy having excellent machinability according to claim 1 or 2, wherein the aluminum alloy contains at least one of r: 0.05 to 0.5% and Zr: 0.05 to 0.5%. . 4. The total content of Bi and Sn is from 0.6 to 1.
The aluminum alloy excellent in machinability according to any one of claims 1 to 3, which is 4%.