JP6738212B2 - Aluminum alloy forged product and manufacturing method thereof - Google Patents

Description

The present invention relates to an aluminum alloy forged product having excellent strength at high temperatures and a method for manufacturing the same, and in particular, a large thermal load such as an engine piston of an internal combustion engine, abrasion resistance, and seizure resistance are required. The present invention relates to an aluminum alloy forged product suitable as a sliding member and a manufacturing method thereof.

Since an engine piston of an internal combustion engine is a member that slides at high temperatures, it is required to have excellent wear resistance, sufficiently high temperature strength, and seizure resistance.

In addition, as automobile parts, in response to the recent demand for improvement in fuel consumption in the automobile industry, it has become necessary to achieve weight reduction and high functionality. Therefore, a lightweight aluminum alloy material has been attracting attention as a sliding member for automobile engine pistons and the like, instead of conventional steel materials and cast iron materials.

Among various aluminum alloys, the eutectic or hypereutectic Al—Si alloy contains Si in an amount of about 10% by mass or more. Since this eutectic or hypereutectic Al-Si alloy has a small coefficient of thermal expansion and excellent wear resistance, it is used as a material for sliding members such as engine pistons for automobiles.

However, since an Al-Si alloy containing a large amount of Si is manufactured by a casting method, it is difficult to completely eliminate casting defects, and primary crystal Si may coarsely crystallize or segregate. Therefore, there is a problem that strength and toughness are reduced. Further, since this kind of Al-Si alloy is limited in the kind and addition amount of alloy elements, there is a limit to further improving the performance of this Al-Si alloy.

Under such circumstances, attention has been paid to aluminum alloy powder materials that can be used even in a high temperature atmosphere. As the aluminum alloy powder, one or two of Si: 15.0 to 25.0% and Fe: 5.9% to 15.0% or Mn: 7.1 to 15.0% by weight is used. There is known an aluminum alloy powder containing a heavy metal of some kind, the balance being Al containing unavoidable impurities, and having Si crystal grains having a size of 15 μm or less (see Patent Document 1).

JP-A-63-266005

By the way, in recent years, in order to improve the combustion efficiency and output of the internal combustion engine, the combustion temperature of the internal combustion engine is increasing. Along with this, for example, sliding members such as automobile engine pistons are also required to have sufficiently large strength in a temperature range higher than conventional ones. It was not possible to meet such a demand.

The present invention has been made in view of the above technical background, and provides an aluminum alloy forged product having high forging strength that is easily deformed, has excellent forgeability such as no cracking, and has high high-temperature strength, and a manufacturing method thereof. The purpose is to

In order to achieve the above object, the present invention provides the following means.

[1] Si: 10.0 mass% to 19.0 mass%, Mn: 3.0 mass% to 10.0 mass%, Cu: 0.5 mass% to 10.0 mass%, Mg: 0.2 An aluminum alloy atomized powder forged product containing 1% by mass to 3.0% by mass and the balance being Al and inevitable impurities,
The cross-sectional structure structure of the forged product includes a θ phase of CuAl ₂ , and an average circle equivalent diameter of the θ phase is in a range of 0.66 μm to 1.66 μm.

[2] The forged product contains an Al-Mn-Si based intermetallic compound, and in the cross-sectional structure structure of the forged product, the average equivalent circle diameter of the Al-Mn-Si based intermetallic compound is 0.04 μm to 0. The aluminum alloy forged product according to the above 1, which is in a range of 24 μm.

[3] The forged aluminum alloy further contains 0.01 or more of one or more elements selected from the group consisting of Ti, Zr, V, W, Cr, Co, Mo, Ta, Hf, and Nb. The aluminum alloy forged product according to the above item 1 or 2, which contains mass% to 5.0 mass%.

[4] Si: 10.0 mass% to 19.0 mass%, Mn: 3.0 mass% to 10.0 mass%, Cu: 0.5 mass% to 10.0 mass%, Mg: 0.2 A powdering step of obtaining an aluminum alloy powder by rapidly solidifying a molten metal of an aluminum alloy containing mass% to 3.0 mass% and the balance consisting of Al and unavoidable impurities by atomization to obtain an aluminum alloy powder;
A molding step of compression molding the aluminum alloy powder to obtain a green compact,
An extrusion step of hot extruding the green compact to obtain an extruded material;
A forging step, in which the extruded material is hot forged to obtain a forged product having a θ phase with a sectional structure structure of CuAl ₂ and an average circle equivalent diameter of the θ phase of 0.66 μm to 1.66 μm. A method for manufacturing an aluminum alloy forged product, comprising:

[5] The forged product contains an Al-Mn-Si-based intermetallic compound, and the average equivalent circle diameter of the Al-Mn-Si-based intermetallic compound is 0.04 μm to 0 in the sectional structure structure of the forged product. The method for producing an aluminum alloy forged product according to the above item 4, which has a range of 24 μm.

[6] The molten aluminum alloy further contains one or more elements selected from the group consisting of Ti, Zr, V, W, Cr, Co, Mo, Ta, Hf, and Nb in 0.01 or more. The method for manufacturing an aluminum alloy forged product according to claim 4 or 5, wherein the forged aluminum alloy contains 5 to 5.0% by mass.

According to the invention of [1], there is provided an aluminum alloy forged product which has excellent forgeability such that it is easily forged and deformed and does not crack, and has high high-temperature strength. Therefore, this forged product is suitable as, for example, a sliding member such as an automobile engine piston.

According to the invention of [2], an aluminum alloy forged product having higher strength at high temperature is provided.

According to the invention of [3], there is provided an aluminum alloy forged product having further increased high temperature strength.

According to the invention of [4], it is possible to manufacture an aluminum alloy forged product which has excellent forgeability such that it is easily deformed by forging, does not crack, and has high high-temperature strength. Therefore, the obtained forged product is suitable as a sliding member such as an automobile engine piston, for example.

According to the invention of [5], an aluminum alloy forged product having higher strength at high temperature can be manufactured.

According to the invention of [6], it is possible to manufacture an aluminum alloy forged product having further increased high temperature strength.

It is a perspective view showing an example of an extruded material before forging. It is a perspective view showing an example of a forged product concerning the present invention.

The aluminum alloy forged product according to the present invention has Si: 10.0% by mass to 19.0% by mass, Mn: 3.0% by mass to 10.0% by mass, Cu: 0.5% by mass to 10.0% by mass. %, Mg: 0.2% by mass to 3.0% by mass, the balance being an aluminum alloy atomized powder forged product consisting of Al (aluminum) and inevitable impurities, and the cross-sectional structure structure of the forged product is CuAl. _Two θ phases are provided, and the average equivalent circle diameter of the θ phases is in the range of 0.66 μm to 1.66 μm.

The forged product having the above configuration is an aluminum alloy atomized powder forged product, and the forged product is fine and uniform structure obtained by using the atomized powder, and compared with the alloy obtained by the casting method, It is possible to improve properties such as wear resistance and low coefficient of thermal expansion. Furthermore, the forged product having the above-mentioned structure has a cross-sectional structure structure that includes the θ phase of CuAl ₂ and the average circle equivalent diameter of the θ phase is in the range of 0.66 μm to 1.66 μm, so that it is easy to forge and deform. It has excellent forgeability such as no cracking, and high strength at high temperature.

If the average circle-equivalent diameter of the θ phase is smaller than 0.66 μm, a large high temperature strength cannot be obtained. Further, when the average circle equivalent diameter of the θ phase is larger than 1.66 μm, the dispersion hardening ability is lowered and, for example, the strength (high temperature strength) in the operating temperature range of the sliding member cannot be sufficiently obtained. Among them, the average circle equivalent diameter of the θ phase is preferably 0.86 μm to 1.46 μm.

The aluminum alloy forged product has an Al-Mn-Si based intermetallic compound, and in the cross-sectional structure structure of the forged product, the average circle equivalent diameter of the Al-Mn-Si based intermetallic compound is 0.04 μm to 0. A structure having a range of 24 μm is preferable. If the average circle equivalent diameter is smaller than 0.04 μm, a large high temperature strength cannot be obtained. Further, if the average equivalent circle diameter is larger than 0.24 μm, the dispersion hardening ability is lowered and, for example, the strength in the operating temperature range of the sliding member (high temperature strength) cannot be obtained sufficiently.

The circle-equivalent diameter of the θ phase is a value converted as a diameter of a circle having the same area as the area of the θ phase (CuAl ₂ ) in the SEM photograph (image). The equivalent circle diameter of the compound is a value converted as the diameter of a circle having the same area as the area of the Al-Mn-Si based intermetallic compound in the SEM photograph (image).

Next, a method for manufacturing an aluminum alloy forged product according to the present invention will be described. Si: 10.0 mass% to 19.0 mass%, Mn: 3.0 mass% to 10.0 mass%, Cu: 0.5 mass% to 10.0 mass%, Mg: 0.2 mass% to A molten aluminum alloy containing 3.0% by mass and the balance of Al and unavoidable impurities is rapidly solidified by an atomizing method and powdered to obtain an aluminum alloy powder (powdering step).

The molten aluminum alloy having the above specific composition is prepared by a usual melting method. The obtained molten aluminum alloy is pulverized by an atomizing method. The atomization method is a method in which fine droplets of molten aluminum alloy are misted and sprayed by a gas flow of nitrogen gas or the like from a spray nozzle, and the fine droplets are rapidly cooled and solidified to obtain fine aluminum alloy powder. The cooling rate is preferably 10 ³ to 10 ⁵ °C/sec. It is preferable to obtain an aluminum alloy powder having a size of 30 μm to 70 μm. It is preferable to classify the obtained aluminum alloy powder using a sieve, and it is more preferable to obtain an aluminum alloy powder having a particle size of 150 μm or less.

Next, the aluminum alloy powder obtained in the powderizing step is compression molded to obtain a green compact (compression molding step). As an example, an aluminum alloy powder heated to 250° C. to 300° C. is filled in a mold heated to 230° C. to 270° C., and compression-molded into a predetermined shape to obtain a green compact. The pressure for the compression molding is not particularly limited, but normally, it is preferably set to 0.5 tons/cm ^{2 to} 3.0 tons/cm ² . Further, it is preferable to use a green compact having a relative density of 60% to 90%. The shape of the green compact is not particularly limited, but in consideration of the next extrusion step, it is preferably a cylindrical shape or a disk shape.

Next, the green compact obtained in the compression molding step is hot extruded to obtain an extruded material (extrusion step). If necessary, the green compact is subjected to mechanical processing such as chamfering, then degassed, heated, and then subjected to an extrusion step. The heating temperature of the green compact before extrusion is preferably 300°C to 450°C. At the time of extrusion, for example, a green compact is inserted into an extrusion container, a pressing force is applied by an extrusion ram, and the extrusion die is extruded into, for example, a round bar shape. At this time, it is desirable to preheat the extrusion container to 300°C to 400°C. By thus extruding hot, the plastic deformation of the green compact progresses, and an extruded body in which aluminum alloy powders (particles) are bonded and integrated is obtained. At the time of the extrusion, the extrusion pressure is preferably set to 10 MPa to 25 MPa.

Next, the extruded material obtained in the extruding step is hot forged to have a θ phase of CuAl _{2 in} cross-sectional structure, and the average circle equivalent diameter of the θ phase is 0.66 μm to 1.66 μm. A forged product can be obtained (forging process). For example, a round bar-shaped extruded material is cut into a predetermined length as needed, and then hot forged. This hot forging is preferably a closed forging or a semi-closed forging so that the forged material (forged product) has a shape close to the product shape (for example, engine piston shape), but the product (forged product) Free forging may be used depending on the shape. The hot forging temperature is preferably set to 300°C to 450°C.

The forged material may be cut or surface-polished to be a product (forged product) such as a sliding member such as an automobile engine piston, but may be subjected to the following heat treatment. ..

A solution treatment is applied to the forged material. This solution treatment is a treatment for supersaturating Cu, Mg, etc., and the heating temperature of the solution treatment is preferably 480°C to 500°C.

After the solution treatment, quenching is performed by water quenching or the like to obtain a material (supersaturated solid solution) in which Cu, Mg, etc. are supersaturated in a solid state beyond the solid solution limit at room temperature. The quenching temperature is preferably 0°C to 50°C.

After the quenching treatment, an aging treatment is performed. By this aging treatment, an intermetallic compound containing Cu, Mg or the like can be finely precipitated to improve the strength and wear resistance of the forged product. The aging treatment is preferably performed at a temperature of 180°C to 280°C for 1 hour to 4 hours.

By subjecting the forged product after the aging treatment to mechanical processing such as cutting or surface polishing, products (forged products) such as sliding members such as engine pistons for automobiles can be obtained.

The composition of the aluminum alloy in the forged product and the method for manufacturing the forged product of the present invention will be described below. The aluminum alloy has Si: 10.0% by mass to 19.0% by mass, Mn: 3.0% by mass to 10.0% by mass, Cu: 0.5% by mass to 10.0% by mass, Mg:0. It is an aluminum alloy containing 0.2 mass% to 3.0 mass% and the balance being Al and inevitable impurities.

The Si content in the aluminum alloy is in the range of 10.0% by mass to 19.0% by mass. If the Si content is less than 10.0% by mass, the amount of Si crystallized substances is reduced, resulting in deterioration of wear resistance and strength. If the Si content exceeds 19.0% by mass, coarse primary crystals are produced. Si crystallizes and causes a decrease in strength, and also causes embrittlement of the material, resulting in a decrease in forgeability. Among them, the Si content in the aluminum alloy is preferably 12% by mass to 16% by mass, and it is possible to surely achieve both high temperature strength and excellent forgeability.

The Mn content in the aluminum alloy is in the range of 3.0% by mass to 10.0% by mass. If the Mn content is less than 3.0% by mass, the dispersion strengthening by the Al-Mn-Si based intermetallic compound cannot be sufficiently obtained. Further, when the Mn content exceeds 10.0 mass %, the hardness and wear resistance are rather lowered, and the material tends to become brittle in the molded body. Above all, the Mn content in the aluminum alloy is preferably 6.0% by mass to 8.0% by mass.

The Cu content in the aluminum alloy is in the range of 0.5% by mass to 10.0% by mass. Cu is an essential element for improving room temperature strength and high temperature strength. When the Cu content is less than 0.5% by mass, the amount of solid solution is reduced and the effect of improving the strength is reduced, and the effect of improving the strength by the dispersion strengthening by the crystallized CuAl ₂ phase is also small. When the Cu content exceeds 10.0 mass %, the extrudability may be deteriorated, and the θ phase (CuAl ₂ ) may be coarsely precipitated or crystallized at the grain boundaries to reduce the elongation at break.

The Mg content in the aluminum alloy is in the range of 0.2% by mass to 3.0% by mass. Like Cu, Mg is an essential element for improving room temperature strength and high temperature strength. If the Mg content is less than 0.2% by mass, the effect of improving strength is small. Moreover, when the Mg content exceeds 3.0 mass %, the extrusion processability deteriorates.

In the forged product and the method for manufacturing the forged product of the present invention, the aluminum alloy is further one or two selected from the group consisting of Ti, Zr, V, W, Cr, Co, Mo, Ta, Hf and Nb. You may make it the structure which contains each said element 0.01 mass%-5.0 mass %. In this case, an aluminum alloy forged product having further increased high temperature strength can be obtained.

Next, specific examples of the present invention will be described, but the present invention is not particularly limited to these examples.

<Example 1>
An aluminum alloy containing Si: 15.8% by mass, Mn: 6.83% by mass, Cu: 3.14% by mass, Mg: 1.11% by mass, the balance being Al and inevitable impurities was heated to 1000 After obtaining the aluminum alloy melt at ℃, atomize the aluminum alloy melt with gas, rapidly solidify it into powder, classify with a 100 mesh screen, and obtain an aluminum alloy powder that has passed through a 100 mesh screen. ..

Next, the obtained aluminum alloy powder was preheated to a temperature of 280° C., and the preheated aluminum alloy powder was filled in a mold heated and held at the same temperature of 280° C., and a pressure of 1.5 ton/cm ² was applied. By compression molding, a cylindrical green compact (molded body) having a diameter of 210 mm and a length of 250 mm was obtained. Next, the obtained green compact was face-milled with a lathe to a diameter of 203 mm to obtain a green compact billet.

Next, the obtained billet is heated to 350° C., the heated billet is inserted into an extrusion container having an inner diameter of 210 mm which is heated and held at 350° C., and the extrusion ratio is 7.8 by an indirect extrusion method using a die having an inner diameter of 75 mm. Was extruded to obtain an extruded material 10. The obtained extruded material was cut into a length of 30 mm, then heated to 450° C. and hot free forged to obtain an aluminum alloy forged product 20 having a diameter of 107.5 mm and a length of 15 mm. 1 shows the extruded material 10 before forging, and FIG. 2 shows the forged product 20 after forging.

<Comparative Example 1>
As an aluminum alloy for forming a molten aluminum alloy, Si: 15.6 mass%, Mn: 6.72 mass%, Cu: 3.09 mass%, Mg: 1.06 mass% are contained, and the balance is Al. An aluminum alloy forged product was obtained in the same manner as in Example 1 except that an aluminum alloy containing unavoidable impurities was used, the temperature of the molten aluminum alloy was set to 900° C., and a 170-mesh sieve was used as the sieve.

<Comparative example 2>
As an aluminum alloy for forming a molten aluminum alloy, Si: 15.6 mass%, Mn: 6.78 mass%, Cu: 3.12 mass%, Mg: 1.11 mass% are contained, and the balance is Al. An aluminum alloy forged product was obtained in the same manner as in Example 1 except that an aluminum alloy containing unavoidable impurities was used and the temperature of the molten aluminum alloy was set to 1100°C.

<Comparative example 3>
As an aluminum alloy for forming a molten aluminum alloy, Si: 15.6 mass%, Mn: 6.78 mass%, Cu: 3.12 mass%, Mg: 1.11 mass% are contained, and the balance is Al. An aluminum alloy forged product was obtained in the same manner as in Example 1 except that an aluminum alloy containing unavoidable impurities was used, the temperature of the molten aluminum alloy was 1100° C., and a 50-mesh sieve was used as the sieve.

<Comparative example 4>
As an aluminum alloy for forming a molten aluminum alloy, Si: 15.6 mass%, Mn: 6.72 mass%, Cu: 3.09 mass%, Mg: 1.06 mass% are contained, and the balance is Al. An aluminum alloy forged product was obtained in the same manner as in Example 1 except that an aluminum alloy containing unavoidable impurities was used and the temperature of the molten aluminum alloy was set to 900°C.

Each forged aluminum alloy product obtained as described above was evaluated based on the following evaluation method. The results are shown in Table 1.

<High temperature tensile strength evaluation method>
The obtained forged product was heated to 490° C., held for 3 hours, and then quenched in water at 20° C. Then, as an aging treatment, it was heated at 220° C. for 1 hour to obtain a T7-treated product. The T7 treated product is processed into a tensile test piece having a gauge length of 20 mm and a parallel part diameter of 4 mm, and a high temperature tensile strength test (tensile strength at 300° C.) of the tensile test piece is performed. did. The high temperature tensile test was performed at 300° C. after holding the high temperature tensile test piece at 300° C. for 100 hours. It evaluated based on the following judgment criteria. In Example 1, the tensile strength at 300° C. was 160 MPa, and the evaluation was ⊚ (a large high temperature tensile strength is obtained).
(Criteria)
"A"... Tensile strength at 300°C is 160 MPa or more "O"... Tensile strength at 300°C is 155 MPa or more and less than 160 MPa "△"... Tensile strength at 300°C is 150 MPa or more and less than 155 MPa "X"... At 300°C Has a tensile strength of less than 150 MPa.

<Method of evaluating structure of forged products>
The obtained forged product was heated to 490° C., held for 3 hours, and then quenched in water at 20° C. Then, as an aging treatment, it was heated at 220° C. for 1 hour to obtain a T7-treated product. A tissue observation sample having a size of 10 mm×10 mm×10 mm was cut out from the T7-treated product. After embedding the obtained structure observation sample in resin, the surface was mirror-finished by physical polishing, and the structure was observed using a FE-SEM (Field Emission Scanning Electron Microscope; JEOL JSM-7000F) on a cross section perpendicular to the upsetting direction. (The backscattered electron image was observed). Image analysis of the obtained backscattered electron image (×10 k) was performed. The target of the image analysis is the θ phase (CuAl ₂ phase) and the Al-Mn-Si based intermetallic compound, and for any of the objects, the circle equivalent diameters of arbitrary 3 fields of view (3 places) in the electron microscope image are taken. Each was calculated|required and the average value was calculated and the "mean circle equivalent diameter" was calculated|required. That is, the average equivalent circle diameter of the θ phase (CuAl ₂ phase) and the average equivalent circle diameter of the Al—Mn—Si intermetallic compound were determined (see Table 1).

As is clear from Table 1, the aluminum alloy forged product of Example 1 according to the present invention had high high-temperature tensile strength (tensile strength at 300°C).

On the other hand, in the aluminum alloy forged products of Comparative Examples 1 to 4 which deviate from the specified range of the present invention, the high temperature tensile strength (tensile strength at 300°C) was insufficient.

Since the aluminum alloy forged product according to the present invention and the aluminum alloy forged product manufactured by the manufacturing method of the present invention have excellent forgeability and excellent strength at high temperature, sliding of engine pistons for automobiles, etc. It is suitable as a member, but is not particularly limited to such use.

10... Extruded material 20... Aluminum alloy forged product

Claims (2)

Si: 10.0 mass% to 19.0 mass%, Mn: 3.0 mass% to 10.0 mass%, Cu: 0.5 mass% to 10.0 mass%, Mg: 0.2 mass% to An aluminum alloy atomized powder forged product containing 3.0% by mass, the balance being Al and inevitable impurities,
The cross-sectional structure structure of the forged product includes a θ phase of CuAl ₂ , and an average circle equivalent diameter of the θ phase is in a range of 0.66 μm to 1.66 μm. The forged product contains an Al-Mn-Si-based intermetallic compound, and the average equivalent circle diameter of the Al-Mn-Si-based intermetallic compound is 0.04 μm to 0.24 μm in the cross-sectional structure structure of the forged product. The aluminum alloy forged product according to claim 1, which is in a range.

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