CN104160049B - Mar proof, extrudability, the aluminium alloy of forging excellent processability - Google Patents

Abstract

The present invention provides a kind of aluminium alloy, and it is by the amount of element optimization contained in enabling aluminum alloy to, and not only makes extrudability, the such productivity ratio of forging property be improved, and meet necessary characteristic.A kind of aluminium alloy is provided, it is characterized in that, containing Si5.5～7.0%, Cu1.0～2.0%, Mg0.4～0.8%, Cr0.05～0.15%, Ni0.05～0.25% and according to desired Sr0.01～0.05%, surplus is made up of Al and inevitable impurity, on the cross section vertical with the length direction of extruded material, the eutectic Si size of central part is set to Sc, the eutectic Si size of top layer sidepiece is set to Sc Ss≤15 μm during Ss², and eutectic Si size is 20 μm²Following grain number is 1000～3000/mm²。

Description

Aluminum alloy with excellent wear resistance, extrudability, and forging workability

technical field

The present invention relates to an aluminum alloy excellent in wear resistance, extrudability, and forgeability used as components such as compressors in automobiles, home appliances, and the like.

Background technique

Aluminum alloys used for compressors and the like in automobiles, home appliances, and the like are required to have wear resistance and the like. For example, an aluminum alloy used in a compressor is an Al-Si alloy to which 10% by mass (hereinafter simply referred to as %) or more of Si is added in order to improve wear resistance and reduce thermal expansion coefficient. Patent Document 1 describes an aluminum alloy for sliding that is excellent in fatigue resistance and non-sintering properties. In this aluminum alloy, Si is added in an amount of 1 to 15% as an essential element contributing to non-sinterability and wear resistance. However, it is described that when the amount of Si added exceeds 15%, the aluminum alloy becomes embrittled.

[Prior Art Literature]

【Patent Literature】

[Patent Document 1] Japanese Patent Application Laid-Open No. 03-006345

Contents of the invention

【Problems to be solved by the invention】

The aluminum alloys used in compressors and the like are required to be excellent in wear resistance, expansion coefficient, etc., and therefore, a large amount of Si is added. However, although such an aluminum alloy has improved wear resistance, expansion coefficient, etc., there is a possibility that processability such as extrudability may decrease, and surface properties may deteriorate. This is because the aluminum alloy tends to be difficult to process as the concentration of each component added increases. In particular, Si added to improve wear resistance reduces productivity in the processing steps in the extrusion process and the forging process. In fact, such aluminum alloys often have excessive specifications that are more than necessary in terms of wear resistance, expansion coefficient, and the like required for components used. That is, these aluminum alloys do not necessarily need to be remarkably excellent in wear resistance and the like. Therefore, from the viewpoint of productivity, it is preferable to control the necessary properties such as wear resistance to an optimum state according to the application.

Therefore, an aluminum alloy having an excellent effect in terms of cost can be obtained without lowering productivity by reconciling properties required as needed with productivity.

Therefore, it is an issue to develop an aluminum alloy that maintains a balance between the reduction in productivity during production as much as possible and the obtained aluminum alloy having necessary properties.

In view of the above circumstances, an object of the present invention is to provide an aluminum alloy that can be used for producing forgings that is excellent in extrudability and forging workability among Al-Si-based alloys and that maintains wear resistance.

【Methods used to solve the problem】

As a result of intensive studies, the present inventors obtained the insight that an aluminum alloy in which necessary characteristics and productivity are balanced can be obtained by adjusting the addition amount of each component and controlling the size of eutectic Si. That is, it was found that the object of the present invention described above is achieved by the following means.

That is, according to the present invention, there is provided an aluminum alloy excellent in wear resistance, extrudability, and forgeability, characterized in that it contains Si5.5-7.0% by mass (hereinafter referred to as %), Cu1.0-2.0 %, Mg0.4～0.8%, Cr0.05～0.15%, Ni0.05～0.25%, and the balance is composed of Al and unavoidable impurities. When the eutectic Si size is Sc and the eutectic Si size at the surface side is Ss, Sc-Ss≤15 μm ² , and the number of eutectic Si particles with a eutectic Si size of 20 μm ² or less is 1000 to 3000/mm ² .

It is preferable to provide an aluminum alloy excellent in wear resistance, extrudability, and forgeability, which further contains 0.01 to 0.05% of Sr.

【Invention effect】

The present invention can provide an aluminum alloy material for producing extruded materials and forged materials that is excellent in extrudability and forging processability and maintains wear resistance by appropriately controlling the various compositions of the aluminum alloy and the size of the eutectic Si.

Description of drawings

[ Fig. 1 ] is a diagram of forging an extruded product produced by extrusion.

detailed description

Embodiments of the present invention will be described below.

First, each additional element in the aluminum alloy of the present invention will be described.

Si contributes to abrasiveness by forming a Si compound. In addition, Si forms Mg ₂ Si together with Mg, and Si is an element contributing to strength. When the amount of Si added is less than 5.5%, the effects of strength and wear resistance are weak. When it exceeds 7.0%, surface properties will deteriorate and extrudability will fall.

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

Mg forms Mg ₂ Si together with Si and contributes to an increase in strength. When the added amount of Mg is less than 0.4%, the effect is small. When exceeding 0.8%, extrusion processability will fall. Preferably, Mg is 0.55 to 0.65%.

Cr is effective for miniaturization of crystal grains and contributes to improvement of strength. When the amount of Cr added is less than 0.05%, this effect is small. After exceeding 0.15%, the effect does not change significantly. Cr is preferably 0.07 to 0.10%.

Ni is effective for improving heat resistance and wear resistance, and also contributes to improving strength. When the amount of Ni added is less than 0.05%, the effect is small. When it exceeds 0.25%, the effect does not change greatly, and extrudability deteriorates. Ni is preferably 0.07 to 0.13%.

The addition of Sr contributes to the improvement of mechanical properties. Sr is used for improvement treatment of crystallized Si, and by adding Sr, crystallized Si becomes a fine form. The added amount of Sr is preferably 0.01 to 0.05%. When the added amount of Sr is less than 0.01%, the effect is small. When it exceeds 0.05%, the effect does not change significantly.

When Fe and Mn are added, they will form compounds with other elements, and the effect of each added element will be reduced. Therefore, the aluminum alloy in the present invention is 0.5% or less.

In addition, the aluminum alloy of the present invention contains unavoidable impurities and Al in addition to the above elements. For example, Ti, Zr, and Zn may be contained in small amounts within the range that does not impair the effects of the invention. The range that does not impair the effect of the invention means 0.05% or less.

Since eutectic Si affects surface properties and wear resistance, the uniformity of these properties is determined by the size and distribution of eutectic Si in extruded materials and forged materials. That is, the aluminum alloy of the present invention obtains excellent extrudability and forgeability by controlling the content of various components such as Si, and in addition, by controlling the size and distribution of eutectic Si, it prevents defects caused by surface properties and parts. Deviations in characteristics. Thus, according to the present invention, extruded materials and forged materials with uniform properties can be obtained with high productivity.

By controlling Ss and Sc so that Sc-Ss≦15 μm ² , the surface properties of the extruded material can be improved, and uneven distribution of wear resistance properties between the side and center of the extruded surface layer can be suppressed. Regarding the size of the eutectic Si, Ss refers to the size of the eutectic Si when the central side is observed in the field of view of 100 times of an optical microscope at a depth of 50 μm from the surface layer on a cross-section perpendicular to the longitudinal direction of the extruded material. Ss is measured at 4 locations at intervals of 90 degrees at the central angle in the same field of view, and the largest value among them shall prevail. Sc refers to the size of the eutectic Si at the center of the cross-section of the extruded material observed in a 100-fold field of view of an optical microscope. The eutectic Si size in the present invention refers to the crystal area of eutectic Si.

In addition, by setting the size of the eutectic Si in the extruded material to 20 μm ² or less, surface roughness can be suppressed. In addition, in order to obtain wear resistance, the number of eutectic Si grains is 1000 to 3000 grains/mm ² . When the number of eutectic Si grains with a size of 20 μm ² or less is less than 1000/mm ² , the effect on wear resistance after forging is small. When the number of eutectic Si particles exceeds 3000/mm ² , extrudability and forging workability are hindered.

It should be noted that neither the production conditions nor the tempering of the aluminum alloy in the present invention are particularly limited, and the tempering may be selected according to the application under normal production conditions.

When an extruded product is used as a forged product, the workability in the forging process affects the hardness of the material. Therefore, the tempering of the extruded product of the present invention is preferably F, T1, O, and the more preferable tempering is O.

In addition, the quenching and tempering after forging may be selected according to the required characteristics, but T6 is preferable in the present invention.

【Example】

The present invention will be described in detail based on examples, but the present invention is not limited thereto.

First, by heating in the range of 700°C to 740°C, the alloys having the compositions shown in Table 1 were melted to obtain molten aluminum alloys, which were cast using metal molds. Control so that the amount of cooling water reaches 70 to 100 L/min.

After obtaining an ingot with a diameter of 220 mm, the ingot was subjected to a homogenization treatment by heating at 490° C. for 4 hours. This ingot was extruded through one hole at 500° C. to obtain an extruded round rod with a diameter of 30 mm.

The extruded material of this sample was observed on the central side with a 100-fold field of view of an optical microscope based on a depth of 50 μm from the surface layer on a cross-section perpendicular to the longitudinal direction. Four locations were measured at intervals of 90 degrees at a central angle in the same field of view, and the largest eutectic Si size (Ss) was measured. In addition, the eutectic Si size (Sc) was observed in the field of view of 100 times of an optical microscope at the central portion of the cross section of the extruded material. In addition, the size and number of eutectic Si grains were analyzed by the software "image analysis software A like-kun" manufactured by Asahi Kasei Engineering Co., Ltd. Regarding the surface properties, when the surface was scratched with an HB pencil, the case where there was no scratch was set as pass "◯", and the case where scratch was set as fail "x". The results are shown in Table 2. If it reaches the specified value, it is acceptable, and if it is outside the specified value, it is unqualified.

Next, the extruded round rod was annealed at 400° C. for 5 hours to obtain an O material. In the forging evaluation, it was confirmed that the size and number of eutectic Si were within the range of the invention.

Next, this extruded round bar was cut to a length of 100 mm in the longitudinal direction, and subjected to upset forging with a working ratio of 80%. After the forged product was subjected to solution treatment at 520°C for 2 hours, it was immediately quenched with warm water at 50°C. Then artificial aging treatment was carried out at 180° C. for 10 hours to obtain T6 tempering.

Here, the machining rate of upset is a value calculated by (r1-r2)/r1×100 in FIG. 1 .

Tensile tests, appearance observations after upset forging, and wear tests were performed on the above-mentioned test alloy forged products thus obtained. The results are shown in Table 3.

(1) Appearance after forging

The appearance after 80% upset was observed, and when no cracks were observed, it was judged to be acceptable (=marked with “◯”), and when cracks were observed, it was judged to be unacceptable (=marked with “×”).

(2) Tensile test

The tensile test pieces were collected so that the longitudinal direction of the extruded rod was the longitudinal direction of the test piece, and JIS No. 4 test pieces were prepared and tested. As an evaluation, a tensile strength (TS) of 300 MPa or more was regarded as acceptable, and a value lower than this value was regarded as unacceptable.

(3) Wear test

The specific wear amount was evaluated by a Ohkoshi wear test. Here, as test conditions, the lubricating oil is gear oil (75W-90), the object material is SCM415, the friction distance is 1200m, and the load is 19kgf. As an evaluation of the friction test, a specific wear amount of 5.0×10 ^-9 or less was regarded as acceptable, and a value exceeding this value was regarded as unacceptable.

【Table 1】

【Table 2】

【table 3】

According to Table 1 and Table 2, the surface properties of the extruded materials 1 to 10 of the examples of the present invention are good, and the surface properties of the extruded materials of Comparative Examples 11 to 17 are poor.

In Examples 1 to 10 of the present invention, since the compositions were within the preferable range, the surface properties were good. That is, since the surface is smooth, extrudability is good, and it can manufacture with high productivity.

Since the extruded materials of Comparative Examples 11 to 14, 16 and 17 had compositions outside the preferred range, these extruded materials may be scratched in terms of surface properties, and extrusion processability was poor.

The extruded material of Comparative Example 11 had a large Si content and a large value of Sc—Ss. Therefore, the extruded material may be scratched in terms of surface properties, and extrusion processability is poor.

The extruded material of Comparative Example 12 had a small Si content and a large value of Sc—Ss. Therefore, the extruded material may be scratched in terms of surface properties, and extrusion processability is poor.

The extruded material of Comparative Example 13 contained little Si and Cu. Therefore, the extruded material may be scratched in terms of surface properties, and extrusion processability is poor.

The extruded material of Comparative Example 14 contained many Si, Cu, Mg, and Cr contents. Therefore, the extruded material may be scratched in terms of surface properties, and extrusion processability is poor.

In the extruded material of Comparative Example 16, Sr was out of the preferred range, and the number of eutectic Si with a size of 20 μm ² or less was large. Therefore, the extruded material may be scratched in terms of surface properties, and extrusion processability is poor.

The extruded material of Comparative Example 17 had a composition with a large Si content, a small Mg content, and a large value of Sc—Ss. Therefore, the extruded material may be scratched in terms of surface properties, and extrusion processability is poor.

The composition of the extruded material of Comparative Example 15 was within the range, but the value of Sc-Ss was large, so the extruded material may be scratched in terms of surface properties, and the extrusion processability was poor.

According to Table 3, the appearance after upset forging, tensile strength, and specific wear amount of Examples 1 to 10 of the present invention are all good, while Comparative Examples 11 to 17 are not good.

The forged materials of Examples 1 to 10 of the present invention were superior in tensile strength and specific wear. In addition, forging workability is excellent, so the appearance after upset forging is good.

The forged material of Comparative Example 11 had a large Si content in the composition, so cracks were observed in the appearance after upset forging. That is, the forging workability is poor, and it is not good as a forging material.

In the forged material of Comparative Example 12, the Si content in the composition was small, so the tensile strength deteriorated and the wear resistance deteriorated. Also, according to Table 2, the number of extruded materials having a eutectic Si size of 20 μm ² or less was small, and thus the abrasion resistance deteriorated.

In the forged material of Comparative Example 13, the content of Si and Cu in the composition was small, so the tensile strength deteriorated and the wear resistance deteriorated. The forged material of Comparative Example 14 contained many Si, Cu, Mg, and Cr contents in the composition, so cracks were observed in the appearance after upset forging. That is, the forging workability is poor, and it is not good as a forging material.

The composition of the forged material of Comparative Example 15 was within the range, and the appearance after upset forging, tensile strength, and specific wear amount were all good. However, according to Table 2, the extrusion processability of the extruded material of Comparative Example 15 was poor, and the productivity was not good. Therefore, the productivity of the forged material of Comparative Example 15 was poor.

The forged material of Comparative Example 16 has a large content of Si, Cu, and Sr in the composition. In addition, according to Table ² , there are many extruded materials whose eutectic Si size is 20 μm or less. to the crack. That is, the forging workability is poor, and it is not good as a forging material.

The forged material of Comparative Example 17 has a composition with a large Si content and a small Mg content, so cracks were observed in the appearance after upset forging. That is, the forging workability is poor, and it is not good as a forging material.

【Description of symbols】

1 extruded rod finished cutting (before forging)

2 forging machine

r1 material height before upset forging

r2 material height after upset forging

3 swivel ring

4 Evaluation material (aluminum alloy)

Claims (2)

1. An aluminum alloy excellent in wear resistance, extrudability, and forgeability, characterized in that it contains 5.5 to 7.0 mass % of Si, 1.0 to 2.0 mass % of Cu, 0.4 to 0.8 mass % of Mg, and 0.05 to 0.05 mass % of Cr 0.15% by mass, 0.05 to 0.25% by mass of Ni, and the balance is composed of Al and unavoidable impurities. The crystal area of the eutectic Si in the center of the section of the extruded material observed in the field of view of 100 times the optical microscope is set to Sc is the value of eutectic Si measured at 90-degree intervals at central angles in the same field of view of 100 times the optical microscope on the basis of a depth of 50 μm from the surface layer on a cross-section perpendicular to the longitudinal direction of the extruded material. When Ss is the largest value of the crystal area, Sc-Ss≦15 μm ² , and the number of eutectic Si grains with a crystal area of 20 μm ² or less is 1000 to 3000/mm ² . 2. The aluminum alloy according to claim 1, further comprising 0.01 to 0.05% of Sr.