JPH09279319A - Production of aluminum alloy for compressor parts, excellent in machinability, wear resistance and toughness - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an Al alloy for compressor parts, excellent in machinability, wear resistance, and toughness. SOLUTION: An aluminum alloy, having a composition which consists of 6.5-7.5% Si, 1.5-4.5% Cu, 0.2-0.8% Mg, 0.1-0.8% Mn, 0.05-0.25% Sb, and the balance Al with impurities and in which Fe content is controlled to <0.25%, is cast into an ingot of 300-600mm outside diameter by a water cooled type semi-continuous casting process so that a cast structure, in which the average grain length of eutectic Si is regulated to 3-5μm and eutectic Si of η5μm length comprises >=75% in the whole eutectic Si, is obtained. After homogenizing treatment, the ingot is formed into extruded material of 10-130mm outside diameter by means of extrusion at >=50% reduction of area, followed by hot forging. The resultant forging is subjected to solution heat treatment at >=500 deg.C and then to water quenching and tempering treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an aluminum alloy for compressor parts which has excellent wear resistance and toughness.

[0002]

2. Description of the Related Art Compressor parts for vehicles, households, industrial use, etc. are required to have not only wear resistance but also excellent toughness in order to withstand safety and severe use. Although an A4032 alloy (Al-Si eutectic alloy) has been used as a material for such parts, the A4032 alloy has low strength and elongation and is poor in toughness. Therefore, JP-A-60-1
Japanese Patent No. 97838 proposes an alloy in which alloy elements such as Cu, Mg, Fe and Mn are adjusted.

[0003]

The T6 treated material of A4032 alloy or Al-Si eutectic alloy in which elements such as Cu, Mg, Fe and Mn are adjusted has a high strength of 38 to 39 kgf /. The toughness is inferior because the elongation is only about mm ² and the elongation is about 8 to 10%. In addition, hypoeutectic Al-
Although the Si alloy has both improved strength and elongation and improved toughness, it does not have sufficient properties required for compressor parts. The present invention has been completed as a result of investigations and studies to satisfy the required characteristics as a compressor part, and by adjusting the size and distribution of eutectic Si in the cast structure, wear resistance and machinability are improved. Excellent, tensile strength after T6 treatment of hot forged material is 43kgf / mm ²
Above, elongation 15% or more, notch toughness 13kgf / m
It is an object of the present invention to provide a method for manufacturing an aluminum alloy compressor part having excellent mechanical properties and toughness of at least m ² .

[0004]

In order to achieve the object, the manufacturing method of the present invention has the following characteristics: Si: 6.5-7.5% by weight,
Cu: 1.5-4.5 wt%, Mg: 0.2-0.8 wt%, Mn: 0.1-0.8 wt%, Sb: 0.05-
An aluminum alloy having a composition of 0.25% by weight, the balance being Al and impurities, and having an Fe content regulated to less than 0.25% by weight was melted and the average particle length of eutectic Si was 3
An outer diameter of 3 μm so that a eutectic Si having a length of 5 μm or less and having a length of 5 μm or less accounts for 75% or more of the entire eutectic Si.
An ingot having a diameter of 0 to 600 mm is cast by a water-cooled semi-continuous casting method, and after homogenizing the ingot, an extruded material having an outer diameter of 10 to 130 mm is manufactured by an extrusion process with a surface reduction rate of 50% or more, The extruded material is hot forged, and the forged material is subjected to solution treatment at a temperature of 500 ° C. or higher, followed by water quenching and tempering. The aluminum alloy used is
Further, Ti: 0.1 wt% or less, or Ti: 0.1 wt% or less and B: 0.02 wt% or less can be included.

[0005]

The present inventors have found that when a molten alloy obtained by adding Sb to a hypoeutectic Al-Si alloy in which alloy elements and their contents are specified is cast by a water-cooled semi-continuous casting method, It has been found that eutectic Si is sufficiently miniaturized also in billets. The ingot in which the eutectic Si is refined in this way is
Since the eutectic Si is not excessively refined as compared with the cast body in which the eutectic Si is refined by the quenching method and the plastically worked body thereof, wear resistance is secured.

The alloy components and contents of the aluminum alloy used in the present invention will be described. Si: 6.5 to 7.5 wt% It is an alloying element effective in forming eutectic Si and imparting wear resistance. The effect of improving wear resistance becomes remarkable when Si is contained in an amount of 6.5% by weight or more. However, when a large amount of Si exceeding 7.5% by weight is contained, the elongation is remarkably reduced and the toughness is impaired. Cu: 1.5 to 4.5 wt% An alloying element that improves the strength and elongation after T6 treatment,
When the content is 1.5% by weight or more, the effect of Cu becomes remarkable.
However, if the Cu content exceeds 4.5% by weight, the elongation decreases and the corrosion resistance deteriorates.

Mg: 0.2 to 0.8% by weight It is an alloy component that gives strength by forming a precipitate of Mg ₂ Si, and the content of 0.2% by weight or more makes the strength improving effect remarkable. . However, when a large amount of Mg exceeding 0.8% by weight is contained, the elongation decreases, and the plastic workability such as casting and extrudability deteriorates. Mn: 0.1 to 0.8% by weight The Al-Si-Fe-based crystallized product generated by the presence of Fe is changed to a fine rounded Al-Si-Mn (Fe) -based crystallized product to improve toughness. At the same time, the crystallized substances have the effect of imparting wear resistance. Such an effect becomes prominent when the Mn content is 0.1% by weight or more. But,
When a large amount of Mn exceeding 0.8% by weight is contained, the toughness is rather lowered.

Sb: 0.05 to 0.25% by weight It is an effective alloying element that refines eutectic Si and improves machinability, toughness and plastic workability. The action and effect of Sb is
It is remarkably exhibited at a content of 0.05% by weight or more. However, when the Sb content exceeds 0.25% by weight, Mg ₃ S
The crystallization of the b compound lowers the toughness and also lowers the strength improving action of Mg. The effect of adding Sb is N
It cannot be obtained with other eutectic Si refiners such as a and Sr. This is presumed to be due to the following reasons. That is, S
When b is added, eutectic Si is finely and uniformly distributed. On the other hand, when Na or Sr is added, the degree of refinement of the eutectic Si differs depending on the location of the cast body, and a fine portion and a finer portion are produced. Therefore, when such a cast body is extruded to form an extruded rod, it is considered that a fine portion and a finer portion remarkably appear, and a difference in the structure causes a difference in characteristics. Further, when Na and Sr are added, gas absorption on the surface of the molten metal is severe, and undesired phenomena such as impossibility of casting due to blockage of dip tube during water-cooled semi-continuous casting occur. On the other hand, Sb
When it contains, since it is not necessary to solidify the molten metal at a particularly high speed, a billet having a large diameter is obtained, and as a result, the extrusion productivity is improved. Specifically, diameter 300-60
With a 0 mm billet, eutectic Si can be uniformly and appropriately refined. Even with such a large-diameter billet, that is, even in the case of casting in which the cooling condition is close to mild cooling, eutectic Si with a controlled grain size is crystallized, and the average grain length of eutectic Si is 3 or less. ~
A cast structure in which the eutectic Si having a length of 5 μm or less and having a length of 5 μm or more accounts for 75% or more of the entire eutectic Si is obtained.

Ti: 0.1% by weight or less, B: 0.0
2% by weight or less Ti and B are alloy elements added as necessary,
It acts to prevent casting cracking. However, if Ti in excess of 0.1 wt% or B in excess of 0.02 wt% is added, an intermetallic compound of Ti or B is produced, which deteriorates workability in the subsequent extrusion / forging process. The aluminum alloy used in the present invention may contain impurities mixed in from the recycled material or the like in the melting process. Fe is a typical example of such impurities. Fe has the effect of forming fine crystallized substances in the presence of Mn to improve wear resistance, but when the content increases, a large amount of Al-Fe-Mn-Si-based crystallized substances are generated and the toughness is increased. Is damaged. for that reason,
The Fe content is regulated to less than 0.25% by weight, preferably less than 0.1% by weight by adjusting the blending amount of the recycled material and the like. Zn, Cr, and the like other than Fe also cause a decrease in toughness, so it is preferable to regulate each to 0.05 wt% or less.

Cast structure: average grain length of eutectic Si is 3 to
Eutectic Si having a length of 5 μm or less and 5 μm or less is 75% or more of the entire eutectic Si. The average particle length and area ratio of the eutectic Si are factors that affect the physical properties of the aluminum alloy material. From the numerous experiments by the present inventors, in the alloy system specified in the present invention,
The eutectic Si having an average particle length of 3 to 5 μm and a length of 5 μm or less is 75% or more of the whole eutectic Si,
It was found from a number of experiments by the present inventors that it is necessary to satisfy the physical properties required for a compressor part manufactured by extrusion after casting and forging. If the average particle length of eutectic Si is 5 μm or more, the machinability and toughness of the alloy material are deteriorated. On the contrary, the average particle length of eutectic Si is 3
If it is smaller than μm, the eutectic Si is excessively divided and finely divided by the plastic working in the subsequent step, and the required wear resistance cannot be obtained. If the amount of eutectic Si having a length of more than 5 μm exceeds 25% of the total amount of eutectic Si in terms of area ratio, the elongation and toughness of the alloy material deteriorate. The average particle length and area ratio of eutectic Si can be measured by an image analysis method.

Water-Cooling Semi-Continuous Casting Method In order to obtain an ingot having the above-mentioned casting structure, a water-cooling semi-continuous casting method using a water-cooled mold is used to obtain an outer diameter of 300 to 600 mm.
Cast billets. When the outer diameter of the billet is less than 300 mm, the effect of the mass effect is small, and the eutectic Si is excessively refined as in the case of rapid cooling. Therefore, the eutectic Si becomes too fine in the subsequent extrusion / forging, and the required wear resistance cannot be obtained. On the contrary, when a billet having an outer diameter of more than 600 mm is cast, the mass effect is so great that the billet is cast in a slowly cooled state, so that the grain structure and the eutectic Si become a coarse cast structure, leading to deterioration in toughness.

Extrusion: Area reduction of 50% or more, outer diameter 10
Extruded material of ˜130 mm An ingot having a controlled casting structure is manufactured into an extruded material having an outer diameter of 10 to 130 mm by an extrusion process with a surface reduction rate of 50% or more. Examples of the extruded material include solid material and shaped material. The eutectic Si is divided by extrusion, but the outer diameter is 10 mm
If the extrusion processing is carried out at a high processing rate up to that, the eutectic Si obtained at the time of casting will be excessively divided by the plastic working to become finer and wear resistance will be deteriorated. On the contrary, when extruded material larger than 130 mm, eutectic Si produced by plastic working
The cutting and miniaturization do not proceed easily and machinability and toughness decrease. Similarly, in extrusion processing with a surface reduction ratio of less than 50%, the eutectic Si is not easily divided and refined, and the machinability and toughness deteriorate. Heat treatment Extruded material should be 500 ° C or higher, preferably 5 after hot forging.
Solution treatment is performed at a temperature of 10 to 530 ° C., and then water quenching and tempering treatments are performed to give required strength.

[0013]

EXAMPLE An aluminum alloy having the composition shown in Table 1 was melted by a conventional method and then cast into a billet having an outer diameter of 325 mm by a water-cooled semi-continuous casting method using a water-cooled mold.
The obtained billet was homogenized at 510 ° C. for 6 hours, and an extruded rod having an outer diameter of 45 mm was manufactured by an indirect extruder.

[0014]

When the material numbers 2 and 4 after extrusion were observed under a microscope, they had the structures shown in FIGS. 1 and 2, respectively. In Document No. 4 containing Sb, as shown in FIG. 2, the eutectic Si (black dots) had a finely and uniformly distributed structure. On the other hand, in sample No. 2 in which Sb was not added, as shown in FIG. 1, a portion in which the eutectic Si could not be divided and remained in a relatively large state was observed. Material number 2
When the cut surfaces of Nos. 4 and 4 were observed in the enlarged visual field of the optical microscope, they had the structures shown in FIGS. 3 and 4, respectively. S
In Material No. 4 in which eutectic Si was finely and uniformly distributed by adding b, as shown in FIG. 4, the scratches on the cut surface were small. From this, it is understood that Material No. 4 has excellent machinability. On the other hand, in sample No. 2, large flaws were generated on the cutting surface as seen in FIG.

Next, the average grain length of eutectic Si in the cast material and the amount of eutectic Si having a grain length of 5 μm or less were measured by an image analysis method. The average particle length of eutectic Si was the average value of the maximum particle lengths. Further, an extruded material having a diameter of 45 mm was cut into a predetermined length and subjected to compression hot casting at a temperature of 400 ° C. and a surface reduction rate of 50%. T6 treatment for forged products (510 ° C x 4 hours solution treatment → water quenching → 170 ° C x 10 hours tempering treatment)
After applying, the mechanical properties, notch toughness, and wear resistance were measured. The notch toughness was measured by making a notch with an angle of 45 degrees perpendicular to the axial direction and applying a static tensile load. As for wear resistance, using Ogoshi type wear resistance tester, load 21 kg, rotary wear FC28, wear speed 1 to 3 m / sec, wear distance 60
It was measured under the condition of 0 m.

[0017]

As can be seen from the results in Table 2, according to the present invention, the average grain length of eutectic Si in the cast structure is small, and a large amount of eutectic Si having a grain length of 5 μm or less is present. As a result, a product having excellent mechanical properties after T6 treatment, having a tensile strength of 43 kgf / mm ² or more, an elongation of 15% or more, and a notch toughness of 13 kgf / mm ² or more, can be obtained. On the other hand, the comparative examples of sample numbers 1, 2, 7, and 8 and the A4032 alloy are inferior in any of the properties and do not satisfy the properties required for the compressor part.

[0019]

As described above, in the present invention, the hypereutectic Al-Si alloy having the specified component and content is cast by the water-cooled semi-continuous casting method, and the average particle of eutectic Si is obtained. The eutectic Si having a length of 3 to 5 μm and a length of 5 μm or less is adjusted to have a cast structure in which it is 75% or more of the whole eutectic Si.
When an ingot with this casting structure is extruded and hot forged into the final product compressor parts, eutectic Si is appropriately divided and refined by plastic deformation during extrusion and forging, contributing to wear resistance. It is possible to improve the toughness while ensuring the action of eutectic Si. Also, because of the excellent forgeability due to the above-mentioned casting structure, cracks do not occur even if plastic working with a high degree of working is performed, it can be effectively used as a forging material, and machinability is also Since it is good, processing with high dimensional accuracy is possible. In this way, a compressor component having high toughness and wear resistance and excellent safety is manufactured.

[Brief description of drawings]

FIG. 1 is a photomicrograph showing the metallographic structure of an ingot containing no Sb.

FIG. 2 is a photomicrograph showing the metallographic structure of an ingot to which Sb has been added according to the present invention.

FIG. 3 is a micrograph showing a metal structure of a cutting surface of an ingot containing no Sb, which is observed in an enlarged view of an optical microscope.

FIG. 4 is a micrograph showing a metal structure when a cutting surface of an ingot to which Sb is added according to the present invention is observed in an enlarged view field of an optical microscope.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location C22F 1/00 612 8719-4K C22F 1/00 612 630 8719-4K 630B 8719-4K 630D 631 8719- 4K 631Z 683 8719-4K 683 691 8719-4K 691B 694 8719-4K 694A (72) Inventor Shigeyuki Kobayashi 2-20 Higashishinagawa, Shinagawa-ku, Tokyo Inside Japan Light Metal Co., Ltd.

Claims (2)

[Claims] 1. Si: 6.5 to 7.5% by weight, Cu:
1.5-4.5% by weight, Mg: 0.2-0.8% by weight,
Mn: 0.1 to 0.8 wt%, Sb: 0.05 to 0.2
5% by weight, with the balance being Al and impurities,
An aluminum alloy whose Fe content is regulated to less than 0.25% by weight is melted, and the average particle length of eutectic Si is 3 to 5 μm.
m, the eutectic Si having a length of 5 μm or less is 75
%, The outer diameter of 300-
A 600 mm ingot is cast by a water-cooled semi-continuous casting method, and after homogenizing the ingot, an extruded material having an outer diameter of 10 to 130 mm is manufactured by an extrusion process with a surface reduction rate of 50% or more. Material is hot forged, and the forged material is subjected to solution treatment at a temperature of 500 ° C. or higher, followed by water quenching and tempering treatment, and a method for producing an aluminum alloy for compressor parts having excellent wear resistance and toughness. . 2. Further, Ti: 0.1% by weight or less or Ti:
The method for producing an aluminum alloy for a compressor part according to claim 1, wherein an aluminum alloy containing 0.1% by weight or less and B: 0.02% by weight or less is used.