WO2013114582A1

WO2013114582A1 - Aluminum alloy having excellent wear resistance, extrudability, and forging workability

Info

Publication number: WO2013114582A1
Application number: PCT/JP2012/052215
Authority: WO
Inventors: 謙介森
Original assignee: 古河スカイ株式会社
Priority date: 2012-02-01
Filing date: 2012-02-01
Publication date: 2013-08-08
Also published as: EP2811041A4; CN104160049A; CN104160049B; EP2811041B1; EP2811041A1

Abstract

Provided is an aluminum alloy with which not only is improved productivity in terms of extrudability and forging performance realized, but also the necessary properties are satisfied, by optimization of the amount of elements contained in the aluminum alloy. Provided is an aluminum alloy, characterized by comprising 5.5 to 7.0% of Si, 1.0 to 2.0% of Cu, 0.4 to 0.8% of Mg, 0.05 to 0.15% of Cr, 0.05 to 0.25% of Ni, and further, 0.01 to 0.05% of Sr as desired, with the balance being Al and inevitable impurities, wherein when the eutectic Si size at the center in the cross section perpendicular to the lengthwise direction of the extruded material is Sc and the eutectic Si size of the surface layer side is Ss, Sc - Ss < 15 µm² and the number of particles having a eutectic Si size of 20 µm² or less is 1,000 to 3,000 particles/mm².

Description

Aluminum alloy with excellent wear resistance, extrudability, and forgeability

The present invention relates to an aluminum alloy having excellent wear resistance, extrudability, and forgeability that is used as a component such as a compressor in automobiles and home appliances.

Some aluminum alloys used for compressors in automobiles and home appliances are required to have wear resistance. For example, an aluminum alloy used in a compressor is an Al—Si alloy added with 10 mass% (hereinafter “%”) or more of Si for the purpose of improving wear resistance and reducing the coefficient of thermal expansion. Patent Document 1 describes a sliding aluminum alloy having excellent fatigue resistance and non-seizure properties. In this aluminum alloy, Si is added in an amount of 1 to 15% as an essential element because it contributes to non-seizure and wear resistance. However, it is described that when the addition amount of Si exceeds 15%, the aluminum alloy becomes brittle.

JP 03-006345 A

Since aluminum alloys used for the compressors and the like are required to have excellent wear resistance, expansion coefficient, etc., a large amount of Si is added. However, such an aluminum alloy has improved wear resistance, expansion coefficient, and the like, but there are concerns such as deterioration of workability such as extrudability and deterioration of surface properties. This is because an aluminum alloy tends to become difficult to process as the component concentration of each composition added increases. In particular, Si added to improve wear resistance decreases productivity in the processing steps in the extrusion process and the forging process. As a matter of fact, such an aluminum alloy often has an excessive specification having such characteristics more than necessary with respect to wear resistance, expansion coefficient, and the like required for a member to be used. That is, since these aluminum alloys do not necessarily have extremely excellent wear resistance and the like, it is preferable from the viewpoint of productivity that necessary characteristics such as wear resistance are controlled to an optimum state depending on the application.
Therefore, an aluminum alloy having an excellent cost effect can be obtained without reducing productivity by harmonizing required characteristics and productivity as required.
Therefore, the development of a balanced aluminum alloy capable of obtaining necessary characteristics while suppressing the deterioration of productivity as much as possible has become an issue.

In view of the above circumstances, an object of the present invention is to provide an aluminum alloy that is capable of producing a forged product that is excellent in extrudability and forgeability in an Al-Si alloy and that maintains wear resistance. And

As a result of intensive studies, the present inventors have obtained knowledge that an aluminum alloy harmonized with necessary characteristics and productivity can be obtained by adjusting the addition amount of each composition and controlling the eutectic Si size. That is, it has been found that the object of the present invention can be achieved by the following means.

That is, according to the present invention, Si is 5.5 to 7.0 mass% (hereinafter referred to as%), Cu is 1.0 to 2.0%, Mg is 0.4 to 0.8%, Cr 0.05 to 0.15%, Ni is 0.05 to 0.25%, the balance is made of Al and unavoidable impurities, and the eutectic Si size in the center in the cross section perpendicular to the longitudinal direction of the extruded material is Sc, when the eutectic Si size on the surface layer side is Ss, Sc—Ss ≦ 15 μm ² , and the number of grains having an eutectic Si size of 20 μm ² or less is 1000 to 3000 / mm ^2. An aluminum alloy having excellent wear resistance, extrudability, and forgeability is provided.

Preferably, an aluminum alloy excellent in wear resistance, extrudability, and forgeability that further contains 0.01 to 0.05% of Sr is provided.

According to the present invention, by appropriately controlling each composition and eutectic Si size of an aluminum alloy, it is possible to produce extrudates and forgings that are excellent in extrudability and forgeability and that have maintained wear resistance. An aluminum alloy material that can be provided can be provided.

It is a figure which forges the extruded product manufactured by extrusion.

Hereinafter, embodiments of the present invention will be described.
First, each additive element in the aluminum alloy of the present invention will be described.

Si contributes to wear by generating a Si compound. Si is an element that forms Mg ₂ Si together with Mg and contributes to strength. When the amount of Si added is less than 5.5%, the effects of strength and wear resistance are weak. If it exceeds 7.0%, the surface properties deteriorate and the extrudability decreases.

Cu contributes to strength improvement. If the added amount of Cu is less than 1.0%, the effect of improving the strength is small, and if it exceeds 2.0%, the extrusion processability and corrosion resistance deteriorate. *

Mg forms Mg ₂ Si together with Si and contributes to strength improvement. If the added amount of Mg is less than 0.4%, the effect is small. When it exceeds 0.8%, the extrusion processability is lowered. Preferably, Mg is 0.55 to 0.65%.

Cr is effective for crystal grain refinement and contributes to strength improvement. When the amount of Cr added is less than 0.05%, the effect is small. If it exceeds 0.15%, the effect does not change greatly. Preferably, Cr is 0.07 to 0.10%.

Ni is effective in improving heat resistance and wear resistance, and contributes to improvement in strength. If the added amount of Ni is less than 0.05%, the effect is small. If it exceeds 0.25%, the effect does not change greatly. Moreover, extrudability is deteriorated. Preferably, Ni is 0.07 to 0.13%.

Sr is an element that contributes to improvement of mechanical properties when added. Sr is used for improving the crystallized Si, and when added, the crystallized Si becomes a fine form. The amount of Sr added is preferably 0.01 to 0.05%. If the amount of Sr added is less than 0.01%, the effect is small. If it exceeds 0.05%, the effect does not change greatly.

When Fe and Mn are added, other elements and compounds are formed and the effect obtained from each additive element is reduced. Therefore, the amount is 0.5% or less in the aluminum alloy of the present invention.

In addition, the aluminum alloy of the present invention comprises unavoidable impurities and Al in addition to the above elements. For example, a small amount of Ti, Zr, and Zn may be included as long as the effects of the invention are not impaired. The range which is not impaired means 0.05% or less.

Since eutectic Si affects the surface properties and wear resistance, the uniformity of these properties is determined by the size and distribution of eutectic Si in the extruded and forged materials. In other words, the aluminum alloy of the present invention is excellent in extrudability and forgeability by controlling the content of each composition such as Si, and further, by controlling the size and distribution of eutectic Si, the characteristics depending on the surface properties and parts. Variation of the is prevented. Therefore, it is possible to obtain an extruded material and a forged material, which have been imparted with characteristics uniformly according to the present invention, with high productivity.
By controlling Ss and Sc so that Sc—Ss ≦ 15 μm ² , the surface property of the extruded material is good, and variations in the wear resistance characteristics of the extruded surface layer side portion and the central portion can be suppressed. Regarding the eutectic Si size, Ss is the eutectic Si size when the central side is observed with a field of view 100 times larger than that of an optical microscope on the basis of a depth of 50 μm from the surface layer in a cross section perpendicular to the longitudinal direction of the extruded material. is there. Ss is the maximum when four points are measured at intervals of a central angle of 90 degrees in the same field of view. Sc is the eutectic Si size obtained by observing the central part of the cross section of the extruded material with a field of view of 100 times the optical microscope. The eutectic Si size in the present invention refers to the crystal area of eutectic Si.
Furthermore, when the eutectic Si size in the extruded material is 20 μm ² or less, the surface roughness can be suppressed. In order to obtain wear resistance, the number of eutectic Si grains is 1000 to 3000 / mm ² . When the number of grains of eutectic Si having a size of 20 μm ² or less is less than 1000 / mm ² , the effect of wear resistance after forging is small. When the number of eutectic Si grains exceeds 3000 / mm ² , extrudability and forgeability are hindered.

In addition, there is no limitation in particular about the manufacturing conditions and tempering of the aluminum alloy in this invention, What is necessary is just to select tempering according to a use on normal manufacturing conditions.
When using an extruded product as a forged product, the hardness of the material affects the workability in the forging process. Therefore, the tempering of the extruded product of the present invention is preferably F, T1, or O, and more preferably tempering.
Further, the tempering after forging may be selected according to the required characteristics, but is preferably T6 in the present invention.

The present invention will be described in detail based on examples, but the present invention is not limited thereto.
First, heating was performed in a range of 700 ° C. to 740 ° C., an alloy having the composition shown in Table 1 was melted, and cast as a molten aluminum alloy using a mold. The amount of cooling water was controlled to be 70 to 100 L / min.
After obtaining an ingot having a diameter of 220 mm, the ingot was subjected to homogenization treatment by heating at 490 ° C. for 4 hours. An extruded round bar with a diameter of 30 mm was produced from this ingot by one-hole extrusion at 500 ° C.

The extruded material of the sample was observed at the center side in a field of view 100 times that of an optical microscope with a depth of 50 μm from the surface layer as a reference in a cross section perpendicular to the longitudinal direction. In the same field of view, four points were measured at intervals of a central angle of 90 degrees, and the maximum eutectic Si size (Ss) was measured. In addition, the eutectic Si size (Sc) was observed at the center of the cross section of the extruded material with a field of view of 100 times the optical microscope. The eutectic Si grain size and number were analyzed by software “image analysis software A image-kun” manufactured by Asahi Kasei Engineering Corporation. As for the surface properties, a sample that did not get caught when the surface was stroked with an HB pencil was judged as “good”, and a sample that got caught was judged as “failed”. The results are shown in Table 2. What was a predetermined value was acceptable, and those outside the predetermined value were unacceptable.

Next, the extruded round bar was annealed at 400 ° C. for 5 hours to obtain an O material. In the forging evaluation, it was confirmed that the eutectic Si size and number were within the scope of the invention.
Next, the extruded round bar was cut into a length of 100 mm in the longitudinal direction, and upsetting forging with a processing rate of 80% was performed. The forged product was subjected to solution treatment at 520 ° C. for 2 hours and immediately quenched with hot water at 50 ° C. Further, an artificial aging treatment was performed at 180 ° C. for 10 hours to obtain a tempering of T6.
Here, the upsetting forging rate is a value calculated by (r1-r2) / r1 × 100 in FIG.

The test alloy forged product thus obtained was subjected to a tensile test, an appearance after upset forging, and a wear test. The results are shown in Table 3.
(1) Appearance after upset forging Observe the appearance after 80% upset forging, and pass (= “○” notation) if no cracks are seen, and reject (= “×”) that show cracks. Notation).
(2) Tensile test Tensile test pieces were sampled so that the longitudinal direction of the extruded bar was the length direction of the test piece, and a JIS No. 4 test piece was prepared and tested. As an evaluation, a tensile strength (TS) of 300 MPa or more is regarded as acceptable, and a value less than this is regarded as unacceptable.
(3) Wear test The specific wear amount was evaluated by the Ogoshi type wear test. As test conditions, the lubricating oil was gear oil (75W-90), the mating material was SCM415, the friction distance was 1200 m, and the load was 19 kgf. As the evaluation of the friction test, a specific wear amount of 5.0 × 10 ⁻⁹ or less was accepted, and a specific wear amount exceeding this was rejected.

From Tables 1 and 2, the extruded materials 1 to 10 of the present invention had good surface properties, and Comparative Examples 11 to 17 had poor surface properties.
Inventive Examples 1 to 10 have good surface properties because the compositions are within a preferable range. That is, since the surface was smooth, it was manufactured with good extrudability and high productivity.
The extruded materials of Comparative Examples 11 to 14, 16 and 17 are out of the preferred range, and thus are extruded materials having poor surface processability and poor extrusion processability.
The extruded material of Comparative Example 11 has a high Si content and a large Sc—Ss value. Therefore, it is an extruded material with poor surface processability and extrusion processability.
The extruded material of Comparative Example 12 has a low Si content and a large Sc-Ss value. Therefore, it is an extruded material with poor surface processability and extrusion processability.
The extruded material of Comparative Example 13 has a low content of Si and Cu. Therefore, it is an extruded material with poor surface processability and extrusion processability.
The extruded material of Comparative Example 14 has a high content of Si, Cu, Mg, and Cr. Therefore, it is an extruded material with poor surface processability and extrusion processability.
In the extruded material of Comparative Example 16, Sr is outside the preferred range, and the number of eutectic Si sizes is 20 μm ² or less. Therefore, it is an extruded material with poor surface processability and extrusion processability.
The extruded material of Comparative Example 17 has a high Si content, a low Mg content, and a high Sc—Ss value in the composition. Therefore, it is an extruded material with poor surface processability and extrusion processability.
The extruded material of Comparative Example 15 is an extruded material having a composition within the range, but having a high Sc—Ss value, and having poor surface processability and an extrudability.

From Table 3, the inventive examples 1 to 10 were all good in appearance after upset forging, the tensile test and the specific wear amount, and the comparative examples 11 to 17 were not good.
The forged materials of Invention Examples 1 to 10 have good tensile tests and specific wear. Moreover, since it is excellent in forging workability, the appearance after upsetting forging is good.
Since the forged material of Comparative Example 11 has a high Si content in the composition, cracks are seen in the appearance after upsetting forging. In other words, the forging processability is poor and it is not good as a forging material.
The forged material of Comparative Example 12 is low in tensile strength and low in wear resistance because of its low Si content in the composition. Also, from Table 2, since the number of eutectic Si sizes of the extruded material is less than 20 μm ² , the wear resistance is inferior.
The forged material of Comparative Example 13 is low in the tensile strength and inferior in wear resistance because of the low content of Si and Cu in the composition.
Since the forged material of Comparative Example 14 has a high content of Si, Cu, Mg, and Cr in the composition, cracks are seen in the appearance after upsetting forging. In other words, the forging processability is poor and it is not good as a forging material.
The forged material of Comparative Example 15 has a composition within the range, and the appearance after upset forging, the tensile test, and the specific wear amount are all good, but the extruded material of Comparative Example 15 has poor extrudability from Table 2. Productivity is not good. Therefore, in Comparative Example 15, the productivity of the forging material is poor.
The forged material of Comparative Example 16 has a high content of Si, Cu and Sr in the composition, and from Table 2, since the eutectic Si size of the extruded material is a large number of 20 μm ² or less, the appearance after upsetting forging Cracks are seen. In other words, the forging processability is poor and it is not good as a forging material.
Since the forged material of Comparative Example 17 has a high Si content and a low Mg content in the composition, cracks are seen in the appearance after upset forging. In other words, the forging processability is poor and it is not good as a forging material.

1 Extruded rod after cutting (before forging)
2 Forging machine r1 Material height before upset forging r2 Material height after upset forging 3 Rotating ring 4 Evaluation material (aluminum alloy)

Claims

Si is 5.5 to 7.0 mass% (hereinafter referred to as%), Cu is 1.0 to 2.0%, Mg is 0.4 to 0.8%, and Cr is 0.05 to 0.15. %, Ni is 0.05 to 0.25%, the balance is made of Al and inevitable impurities, and the eutectic Si size at the center in the cross section perpendicular to the longitudinal direction of the extruded material is Sc, and the eutectic at the surface layer side. Sc—Ss ≦ 15 μm 2 when the Si size is Ss, and the number of grains having an eutectic Si size of 20 μm 2 or less is 1000 to 3000 pieces / mm 2 . Aluminum alloy with excellent forgeability.
The aluminum alloy according to claim 1, further comprising 0.01 to 0.05% of Sr.