JP2002206132A - Aluminum alloy extrusion material having excellent machinability and production method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aluminum alloy extrusion material which has excellent machinability. SOLUTION: The aluminum alloy extrusion material has a composition containing, by mass, 1.5 to 12% Si and 0.5 to 6% Mg, if required, containing at least one kind selected from the group consisting of 0.5 to 2% Mn, 0.15 to 3% Cu and 0.04 to 0.35% Cr, and further containing 0.01 to 0.1% Ti, and the balance Al with inevitable impurities. The average particle size of the crystallized particles of Si and Si based compounds is 2 to 20 μm, and the area ratio thereof is 2 to 12%. The extrusion material can be obtained by dissolving the alloy to obtain an ingot in which DAS(dendrite arm spacing) is 10 to 50 μm, subjecting the ingot to soaking treatment at 450 to 520 deg.C, and thereafter performing extrusion molding thereto.

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 machinability, which is suitable for a machine part or the like which frequently uses a cutting process in a manufacturing process.

[0002]

2. Description of the Related Art Among aluminum alloys, non-heat-treatable alloys, mainly 3000-series Al-Mn alloys, have moderate mechanical properties, excellent corrosion resistance and cold forgeability, and can be formed at low cost. Since it is possible, it is often used for machine parts and the like. At that time, it is generally commercialized by cold forging, followed by cutting and drilling. However, this type of alloy has difficulty in cutting chips generated at the time of cutting and is inferior in machinability, so that it has been difficult to employ it in machine parts that require complicated cutting and drilling.

[0003] Among aluminum alloys, non-heat-treated alloys, mainly 5000-series Al-Mg-based alloys, have moderate mechanical properties (slightly higher in strength level than 3000 series), corrosion resistance and cold working. It has excellent performance and can be processed at low cost, so it has many uses for optical devices and other mechanical parts such as cameras and microscope tubes. In that case, cutting and drilling are generally performed after cold forging. Has been commercialized. However, this type of alloy is inferior in machinability due to the difficulty in cutting chips generated during cutting, and it has been difficult to employ it in machine parts that require complicated cutting and drilling.

On the other hand, a conventional high machinability aluminum alloy is an AA6262 alloy (Si: 0.4
0.8 to 1.2 mass%, Mg: 0.8 to 1.2 mass%, Cu:
0.15 to 0.4% by mass, Pb: 0.4 to 0.7% by mass, Bi: 0.4 to 0.7% by mass, the balance being Al). It contains a low melting point metal such as Bi or Sn (see JP-A-54-143714 and JP-A-3-39442). These low-melting-point metals hardly form a solid solution in aluminum, but micro-segregate in the form of particles in an aluminum alloy. Improve the performance.

[0005] The above-mentioned AA6262 alloy is a mechanical part that is frequently used for cutting, especially drilling in the manufacturing process.
For example, a heat-treated aluminum alloy conventionally used as a material for a housing of an anti-skid brake system of an automobile, such as Pb, Bi,
It is expected that the effect of improving the machinability by the addition of a low melting point metal such as Sn can be obtained not only in the above-mentioned heat-treated alloy but also in the non-heat-treated alloy (for example, Japanese Patent Application Laid-Open No. Hei 3-3).
No. 9442).

[0006]

However, aluminum alloys to which these low-melting-point metals have been added improve machinability, but on the other hand, have low corrosion resistance, and low-melting-point metals also have the disadvantage of causing thermal embrittlement. Had to pay close attention to Furthermore, when the alloy is recycled as scrap, it can be diverted to only a relatively small number of alloy types that require Pb, Bi, etc., which is disadvantageous in terms of recyclability because the diverted range is narrowed.

[0007] Further, in order to enhance corrosion resistance, abrasion resistance or decorative effect, mechanical parts may be subjected to alumite treatment on the surface. In the case of an aluminum alloy to which Pb or Bi is added, Pb or Bi is added to the surface. There is a problem that an oxide film is not formed at an exposed portion, and only an alumite film having a non-uniform and low gloss can be obtained.

[0008] A non-heat-treated aluminum alloy having improved machinability without containing such a low melting point metal is disclosed in Japanese Patent Application Laid-Open No. Sho 60-1.
No. 84658, Pb, Bi,
The machinability was not sufficient as compared with an aluminum alloy containing a low melting point metal such as Sn.

The present invention has been made in view of the above-mentioned problems of the prior art, and is intended to obtain an extruded aluminum alloy having excellent machinability, and to provide a uniform alumite film having excellent corrosion resistance, recyclability and recyclability. It is an object to obtain an extruded aluminum alloy that can be formed.

[0010]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, low melting point metals such as Pb, Bi, Sn and the like which have been conventionally added for the purpose of improving machinability. Was added, and instead, it was found that the machinability could be improved by dispersing the second phase hard particles having an appropriate particle size in the matrix at a certain area ratio. It was completed.

The extruded aluminum alloy having excellent machinability according to the present invention has an average particle size of the second phase hard particles of 2 to 20.
μm, and the area ratio is 2 to 12%. The second phase hard particles are preferably a Si-based compound that is crystallized when the molten aluminum alloy solidifies.

When the second phase hard particles are a Si compound, the preferred composition of the aluminum alloy is Si: 1.5
-12%, Mg: 0.5-6%. More specifically, Si: 1.5 to 12%, Mg: 0.5 to 6
%, An aluminum alloy consisting of the balance of Al and inevitable impurities, Mn: 0.5 to 2%, Cu: 0.1
Aluminum alloy containing at least one of 5 to 3% and Cr: 0.04 to 0.35%, in addition to these components,
Furthermore, an aluminum alloy containing 0.01 to 0.1% of Ti can be mentioned.

Further, in order to obtain the second phase hard particles having a predetermined average particle size and area ratio by using the aluminum alloy, the aluminum alloy is cast to form an ingot having a DAS (dendritic arm spacing) of 10 to 50 μm. After soaking at 450 to 520 ° C., extrusion molding may be performed.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The extruded aluminum alloy of the present invention has an average particle size of 2 to 20 μm and an area ratio of 2 to 12%.
By dispersing the second phase hard particles in the matrix, the hard particles stop the slip of the crystals generated in the chips during cutting, and the slip lines accumulate here to create minute cavities. It is considered to be an excellent cutting property because it serves as a starting point for cutting chips. As such second phase hard particles,
It is preferable that the material is at least harder than the aluminum alloy base material and has low interface consistency with the base material.
Crystallized or precipitated particles of Ni-based compounds, Fe-based compounds, and the like, in addition to the system-based compounds. Among them, Si and Si-based compounds are most preferable in consideration of hardness and consistency.

Here, the average particle diameter of the second phase hard particles is 2 to 2.
When the average particle diameter is smaller than 2 μm, the accumulation of slip lines is less likely to occur and the number of starting points of division is reduced, resulting in inferior machinability. On the other hand, when the average particle diameter exceeds 20 μm, This is because extrudability deteriorates, tool wear during cutting becomes severe, and material elongation becomes poor. Further, the area ratio of the second phase hard particles is 2 to 1
The reason why the area ratio is set to 2% is that if the area ratio is less than 2%, there are few starting points of the division and the machinability is poor, while the area ratio is 12%.
%, The extrudability deteriorates, tool wear during cutting becomes severe, and the elongation of the material becomes poor. The average particle size of the second phase hard particles is preferably 3 to 10 μm, more preferably 4 to 6 μm, and the area ratio is preferably 5 to 10%, more preferably 5 to 7%.

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

Si: 1.5 to 12.0% Si forms a Si-based compound in the aluminum structure, improves the cutting performance of the chips, and improves the cutting performance. This is because the Si-based compound serves as a starting point for cutting chips. The lower limit of Si addition must exceed the solid solubility limit of 1.5% in aluminum, and in order to clarify the effect of Si, the addition of 2.0% or more is desirable. That is, from the viewpoint of obtaining excellent machinability, Si is 2.0%.
It is better to be 12.0%. On the other hand, the upper limit of the addition of Si is required to be 12.0% or less of the eutectic point in order to prevent extrudability from being lowered or embrittlement of the extruded material due to generation of coarse primary crystal Si and increase in deformation resistance. There is. In particular, the extrudability is desirably 6% or less.

Mg: 0.5-6.0% Mg has the effect of improving the chip hardening ability in order to improve the strain hardening ability, and has the effect of forming a solid solution to increase the strength of the material.
If the Mg content is less than 0.5%, the effect cannot be sufficiently obtained, and if the Mg content exceeds 6.0%, the deformation resistance increases and the extrudability decreases. From the viewpoint of securing strength and good extrudability, it is preferably about 1.0% or more and 3.0% or less. However, from the viewpoint of exclusively suppressing deformation resistance during extrusion and improving extrudability. , Less than 1.0%, particularly 0.9% or less, a remarkable effect can be obtained. Therefore, in that case, Mg is 0.5 to 1.0%, or 0.5 to 1.0%.
It may be 0.9%.

Mn: 0.5 to 2.0% Mn has the effect of forming a solid solution to increase the strength of the material, and has the effect of promoting chip breaking to improve strain hardening ability. However, if the Mn content is less than 0.5%, a sufficient effect cannot be obtained, while if it exceeds 2.0%, the extrudability decreases. In particular, from the viewpoint of securing strength and good extrudability, 0.7% or more and 1.5% or less are desired.

Cu: 0.15 to 3.0% Cu forms a solid solution to increase the strength of the material, and has the effect of promoting cutting of chips to improve strain hardening ability.
It is added instead of or together with Mn. But C
When the u content is less than 0.15%, the effect is poor. On the other hand, when the u content exceeds 3.0%, the corrosion resistance decreases and the extrudability also decreases. In particular, from the viewpoint of securing strength and good corrosion resistance and extrudability, 0.3% or more and 0.8% or less are desired.

Cr: 0.04 to 0.35%, Cr forms a compound with Al, and serves as a starting point of chip cutting to improve machinability. However, if the content is less than 0.04%, the effect is not sufficient, while if it exceeds 0.35%, a coarse compound is formed and the extrudability is reduced.

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

As the inevitable impurities of the aluminum alloy, Pb, Bi, and Sn are each allowed to be 0.05% by mass or less in accordance with the chemical components specified in JIS H4040. If these low melting point metals are contained in a large amount, the corrosion resistance of the aluminum alloy is degraded, but within this range, the properties are not affected. Also, other unavoidable impurities are individually allowed to be 0.05% by mass or less.

In order to obtain the above-described distribution of the second phase hard particles in the extruded Al—Si—Mg alloy,
An ingot having a DAS of 50 μm or less was obtained, and
It is necessary to soak at 0 ° C. This ingot is used as a material for cutting after extrusion. Depending on its composition or as necessary, it is subjected to quenching-aging treatment immediately after extrusion or to reheating to form a solution-quenching-aging treatment. And then subjected to a cutting process, or a forging process followed by a cutting process.

The DAS is adjusted by the solidification rate in the casting step. If it is larger than 50 μm, the average particle size of the Si-based compound after soaking is larger than 20 μm, and if smaller than 10 μm, the average particle size is 2 μm or more. It becomes difficult. If the soaking temperature is higher than 520 ° C., the average particle size grows larger than 20 μm, and if it is lower than 450 ° C., the deformation resistance becomes large and the extrudability becomes poor. The time of the soaking is about 1 to 24 hours. When the time is shorter than 1 hour, there is no effect, and when the time is longer than 24 hours, the effect is saturated.

[0026]

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 was melted and semi-continuously cast to 160 mm under various cooling conditions.
Extruded billets having a diameter were produced, and each was subjected to a homogenizing heat treatment at a soaking temperature shown in Table 1 for 12 hours. D of this extruded billet
After each measurement of AS, at an extrusion temperature of 500 ° C., 60 mm
Immediately after water-cooling, subjected to aging treatment at 170 ° C for 6 hours to obtain a test material, the average particle size of each Si-based compound particle and its area ratio, machinability, tool wear, and mechanical properties Was measured in the following manner. However, Comparative Example 11
Was not measured because it could not be extruded.

[0027]

[Table 1]

Average particle size and area ratio: The average particle size and the area ratio of the Si-based compound particles were determined using an image analyzer (Luzex, trade name, manufactured by Nireco Co., Ltd.) based on a 400-fold optical microscope photograph. Was. Machinability: Using a commercially available high-speed steel 10 mm diameter drill,
Cutting was performed under the conditions of a rotation speed of 1500 mm / min and a feed speed of 300 mm / min, and the weight per 100 chips was measured.
Those having 5 g or less were evaluated as ○, and those exceeding 0.5 g were evaluated as x. Tool wear: Under the same conditions as above, 50 holes having a depth of 20 mm were drilled in a test material having a thickness of 30 mm, and those having an R _max of the inner surface of the 50th hole of 6.3 μm or less were ○ and 6.3 μm. Those exceeding were evaluated as ×. Mechanical properties: Using a JIS No. 4 test piece sampled in the extrusion direction, the tensile strength (σ _B ), proof stress (σ _0.2 ), and elongation (δ) are measured according to the metal material test method specified in JIS Z2241. did.

The test results are shown in Table 1.
Test Nos. 1 to 4 are those in which the composition and manufacturing conditions satisfy the requirements of the present invention, Test Nos. 5 to 7 are those in which only the manufacturing conditions satisfy the requirements of the present invention, and Test Nos. 8 to 11 are those in which only the composition specifies the present invention. It satisfies. As shown in Table 1, Invention Examples 1 to 4 in which the composition and the average particle size and the area ratio of the second phase hard particles (Si-based compound) satisfy the requirements of the present invention have excellent machinability and low tool wear. On the other hand, Comparative Example 5 with a small amount of Si has a small average particle size and poor machinability. Comparative Examples 6 and 7, which have a large amount of Si, have a large average particle size, large tool wear, and poor material elongation. Even if the composition satisfies the requirements of the present invention, DAS
Comparative Example 8 having a small average particle diameter of the second phase hard particles was small and inferior in machinability, and Comparative Example 9 having a large DAS was large in the average particle diameter and large in tool wear and inferior elongation. Comparative Example 10 having a high soaking temperature has a large average particle size, large tool wear, and poor elongation.

[0030]

As described above, the extruded aluminum alloy according to the present invention is excellent in machinability and mechanical properties even though low melting point metals such as Pb and Bi are not used. And, since there is no trouble such as wrapping of chips around the tool due to long chips and little tool wear, it is particularly suitable as a material for machine parts created by unmanned operation using automatic machine tools, In addition, thermal embrittlement due to low melting point metal cannot occur, and there is no difficulty in recyclability,
The industrial value is extremely large. Further, since the extruded aluminum alloy according to the present invention has improved machinability without adding Pb or Bi, it is possible to form a uniform and glossy alumite film having excellent alumite treatment property.

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Claims (9)

[Claims] An average particle diameter of the second phase hard particles is 2 to 20 μm.
m, an extruded aluminum alloy excellent in machinability, having an area ratio of 2 to 12%. 2. The extruded aluminum alloy according to claim 1, wherein the second phase hard particles are Si and a Si-based compound. 3. The extruded aluminum alloy according to claim 1, wherein the second phase hard particles are crystallized particles. 4. The aluminum alloy extruded material according to claim 1, which contains 1.5 to 12% of Si (mass%, the same applies hereinafter) and 0.5 to 6% of Mg. 5. Si: 1.5-12%, Mg: 0.5-
The aluminum alloy extruded material according to claim 4, containing 6%, and the balance being Al and unavoidable impurities. 6. Mn: 0.5 to 2%, Cu:
The aluminum alloy extruded material according to claim 4 or 5, containing at least one of 0.15 to 3% and Cr: 0.04 to 0.35%. 7. The extruded aluminum alloy material according to claim 4, further comprising Ti: 0.01 to 0.1%. 8. Si: 1.5-12%, Mg: 0.5-
An aluminum alloy containing 6% is cast to obtain an ingot having a DAS (dendritic arm spacing) of 10 to 50 μm, which is heat-treated at 450 to 520 ° C., and then extruded. Manufacturing method of extruded aluminum alloy. 9. Si: 1.5 to 6%, Mg: 0.5 to 3
% DAS is 10-5
A method for producing an extruded aluminum alloy having excellent machinability, comprising obtaining an ingot of 0 μm, soaking at 450 to 520 ° C., and extruding the ingot.