JP2010018854A - Lightweight and high strength aluminum alloy excellent in heat resistance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide lightweight and high strength aluminum alloy excellent in heat resistance at a temperature of near 300°C. <P>SOLUTION: The aluminum alloy is composed of 2.5-3.3% Cu, 1.5-2.2% Mg, 0.2-0.4% Si, 0.5-1.1% Fe, 0.8-1.3% Ni, 0.40-0.70% Mn, 0.10-0.20% Zr, 0.10-0.60% Sc, 0.005-0.15% Ti and the balance Al with impurities, and has a density of less than 2.80 g/cm<SP>3</SP>. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a lightweight and high-strength aluminum alloy having excellent heat resistance suitable for automobile parts and the like, and a method for producing the same.

In recent years, from the viewpoint of protecting the global environment, there has been a demand for reduction in CO ₂ emissions and improvement in fuel consumption of internal combustion engines by reducing the weight of automobiles. With the progress of weight reduction of automobile parts by the application of aluminum materials, parts for internal combustion engines such as engine parts are increasingly demanded for aluminum alloys having higher strength at room temperature and higher temperature than before.

  Conventionally, A2618 alloy known as a heat-resistant aluminum alloy and its improved alloy (see Patent Document 1) have been used for engine parts, but the A2618 alloy and its improved alloy are resistant to temperatures near 150 ° C. Although it is a lightweight alloy having properties, the strength tends to decrease at a high temperature of 200 ° C. or higher. Therefore, in a component whose temperature rises to a high temperature of about 300 ° C., in order to ensure the strength as the component, Designs to increase the diameter have been made.

A2219, etc., is an aluminum alloy with excellent high-temperature strength at around 300 ° C., but the strength at room temperature is lower than that of the A2618-based alloy, and since the amount of Cu added is large, the density becomes 2.80 g / cm ³ or more. There is a disadvantage that there is little lightening effect.
Japanese Patent No. 3354972

  The present invention has been made to solve the above-mentioned conventional problems in heat-resistant aluminum alloys, and the object thereof is an aluminum alloy having excellent heat resistance at a temperature around 300 ° C., light weight and high strength, and It is in providing the manufacturing method.

The lightweight and high-strength aluminum alloy excellent in heat resistance according to claim 1 for achieving the above object is Cu: 2.5 to 3.3%, Mg: 1.5 to 2.2%, Si: 0 0.2 to 0.4%, Fe: 0.5 to 1.1%, Ni: 0.8 to 1.3%, Mn: 0.40 to 0.70%, Zr: 0.10 to 0.20 %, Sc: 0.10 to 0.60%, Ti: 0.005 to 0.15%, the balance is Al and impurities, and the density (g / cm ³ ) is less than 2.80. And

  The lightweight and high-strength aluminum alloy having excellent heat resistance according to claim 2 is characterized in that, in claim 1, the content ratio of Cu and Mg (Cu% / Mg%) is in the range of 1.1 to 2.2. And

  The lightweight and high-strength aluminum alloy excellent in heat resistance according to claim 3 is characterized in that, in claim 1 or claim 2, the altitude after being held at 300 ° C. for 100 hours is 25 HRB or more.

  The method for producing a lightweight, high-strength aluminum alloy having excellent heat resistance according to claim 4 is a method of homogenizing the ingot of the aluminum alloy having the composition according to claim 1 or 2 and performing one or more hot The material is processed to produce a hot-worked material, and then subjected to a solution treatment in a temperature range 1 to 5 ° C. lower than the measured eutectic melting start temperature of the hot-worked material, and an artificial aging treatment is performed. Features.

  ADVANTAGE OF THE INVENTION According to this invention, the aluminum alloy which was excellent in heat resistance in the temperature of about 300 degreeC, and was lightweight and provided with high intensity | strength and its manufacturing method are provided.

  The significance of the alloy component of the aluminum alloy according to the present invention and the reason for its limitation will be described. Cu is an element contributing to strength improvement, and the preferred content is in the range of 2.5 to 3.3%. If it is less than 2.5%, the effect of improving the strength is small, and if it exceeds 3.3%, the melting point is greatly lowered, so the solution treatment temperature must be lowered, and therefore the degree of supersaturation in the matrix after solution treatment Becomes smaller and the strength cannot be improved.

  Mg functions together with Cu to increase strength. Preferable content is in the range of 1.5 to 2.2%, and if it is less than 1.5%, the effect is small, and if it exceeds 2.2%, the deformation resistance is high in hot working such as extrusion, so that productivity is high. Is inferior.

The content ratio of Cu and Mg (Cu% / Mg%) is preferably in the range of 1.1 to 2.2. When the content ratio (Cu% / Mg%) is less than 1.1, the GPB zone which is the main strengthening phase and Since the formation of the S ′ phase is small, the strength tends to decrease, and when the content ratio (Cu% / Mg%) exceeds 2.2, Al ₂ Cu and Al ₂ MgCu are formed, and Al, Al ₂ Cu, and Since eutectic melting of Al ₂ MgCu occurs at 508 ° C., solution treatment must be performed at a temperature lower than this temperature, and strength reduction is likely to occur because solution treatment is not sufficiently performed.

  Si precipitates a finely dispersed phase of an Al—Mn—Si based compound together with Mn, enhances the pinning effect of dislocation, prevents coarsening of recrystallized grains during solution treatment, and increases strength. The preferable content is in the range of 0.2 to 0.4%. If the content is less than 0.2%, the effect is small. If the content exceeds 0.4%, a compound of Mg and Si is formed and the heat resistance is lowered.

  Fe is an element that forms a compound with Ni and improves heat resistance. The preferable content of Fe is in the range of 0.5 to 1.1%, and if the content is less than 0.5%, the effect is small, and if the content exceeds 1.1%, an Al—Fe system dispersed in the matrix phase, Since an Fe-based compound such as an Al-Fe-Cu-based compound is generated, the effect becomes small.

  Ni is an element that forms a compound with Fe and improves heat resistance. A preferable content of Ni is in the range of 0.8 to 1.3%, and if the content is less than 0.8%, the effect is small. If the content exceeds 1.3%, an Al—Ni-based material that disperses in the parent phase, Al— Since the Ni-based intermetallic compound such as Ni-Cu is generated, the effect is reduced.

  Mn precipitates and disperses a fine Al—Mn—Si compound together with Si, thereby suppressing recrystallization that occurs during solution treatment of the alloy and improving the strength. The preferable content range is 0.4 to 0.7%, and if the content is less than 0.4%, the effect is small. If the content exceeds 0.7%, the crystal is not precipitated finely, and a large crystallized product is easily generated. Get smaller.

Zr suppresses recrystallization that occurs during the solution treatment and increases the strength due to fine dispersion of the Al ₃ Zr compound. The preferable content range is 0.10 to 0.20%, and if the content is less than 0.10%, the effect is small, and if it exceeds 0.20%, the effect is small because a large crystallized product is easily generated without being finely precipitated. Become.

Sc suppresses recrystallization that occurs during the solution treatment by fine dispersion of the Al ₃ Sc compound, and contributes to precipitation hardening at around 300 ° C., thereby improving heat resistance. The preferable content range is 0.10 to 0.60%, and if it is less than 0.10, the effect is small, and if it exceeds 0.60%, it does not precipitate finely and a large crystallized product is likely to be generated, so the effect is small. .

As a result of tests and studies by the inventors, in general 2000 series alloys, fine precipitation strengthening phases of Al and Cu or Al, Mg and Cu such as θ ′ phase and S ′ phase are coarse during holding at 300 ° C. However, when Sc is added in an amount of 0.10 to 0.60%, an Al ₃ Sc compound having an L12 crystal structure consistent with aluminum precipitates during holding at 300 ° C. to increase the strength. Therefore, it was found that the softening due to holding at high temperature was suppressed as a whole material, and it became clear that the effect of Sc was particularly high in the range of the content of other elements in the alloy of the present invention.

  Ti is added to stabilize the fine grain structure and to obtain heat resistance. The preferable content range is 0.005 to 0.15%, and if it is less than 0.005%, the effect is small, and if it exceeds 0.15%, it does not precipitate finely and is likely to generate a giant crystallized product. Therefore, the effect becomes small.

  Even if Cr and Zn are each contained in the range of 0.10% or less in the aluminum alloy of the present invention, the characteristics of the present invention are not adversely affected.

The density of the aluminum alloy of the present invention is preferably less than 2.80 g / cm ³ . The density of the alloy can be calculated from the density of each element and the mixing ratio. The density of most aluminum alloys currently mass-produced is less than 2.80 g / cm ³ but has low heat resistance. An alloy to which a large amount of Cu alloy is added, such as A2219 alloy, is excellent in heat resistance, but since the density of the contained element Cu is large, the density of the alloy increases and the effect of weight reduction decreases. Even a heat-resistant alloy needs to be lightweight, so the density is less than 2.80 g / cm ³ .

The manufacturing method of the aluminum alloy of this invention is demonstrated.
The aluminum alloy having the above composition is melted and cast by a conventional method, and the ingot (billet) is homogenized and then hot-worked to produce a hot-worked material. The hot working is preferably extrusion or forging. Since hot crystals such as extrusion and forging form sub-crystal grains of 10 μm or less and increase the strength, it is more preferable to perform one or more hot workings in order to obtain high strength.

  As the manufacturing process, if it is an extruded material, for example, casting, homogenization treatment, extrusion, solution treatment, aging process, if it is a forging material, for example, casting, homogenization treatment, extrusion, forging, solution treatment The aging process is performed. The manufacturing process is selected according to the application. Further, the tempering may be selected according to the use, but T6, T7, and T8 tempering are preferable in order to obtain high strength.

  In order to obtain higher strength, the hot work material is measured for eutectic melting start temperature with a differential scanning calorimeter, heated to a temperature range 1 to 5 ° C. lower than the measured eutectic melting start temperature, It is preferable to perform a solution treatment that is held at a temperature of 0.5 to 5 hours, and then perform an artificial aging treatment that is held at a temperature of 150 to 220 ° C. for 3 to 30 hours.

  Examples of the present invention will be described below in comparison with comparative examples, and the effects of the present invention will be demonstrated based on the examples. In addition, these Examples show one embodiment of this invention, and this invention is not limited to these.

Example 1
A billet (diameter 90 mm) of aluminum alloys (A1 to A18) having the composition and density shown in Table 1 was homogenized (470 ° C. × 25 h) and then hot extruded at 450 ° C. to obtain For the extruded material (extruded shape: round bar with a diameter of 15 mm), the starting temperature of the eutectic melting temperature is obtained using a differential scanning calorimeter, and solution treatment is performed at a temperature 3 ° C. lower than that temperature, followed by quenching in the usual manner Then, an artificial aging treatment of 190 ° C. × 20 h was performed to obtain a T6 tempered extruded material.

  Using the obtained extruded material as a test material, a tensile test based on JIS Z 2241 (the test piece is a test piece according to JIS Z 2201, Remark 2 of the metal material tensile test piece No. 4 test piece) is performed at room temperature. The tensile strength was evaluated. Further, for the purpose of evaluating heat resistance, Rockwell hardness (HRB) was measured at room temperature according to JIS Z 2245 for a test material that was heat-treated at 300 ° C. for 100 hours. The tensile strength was 500 MPa or more, and the hardness after heat treatment for 100 hours at 300 ° C. was determined to pass 25 HRB or more. The evaluation results are shown in Table 2.

As can be seen from Table 2, all of the test materials 1 to 18 according to the present invention have a tensile strength of 500 MPa or more and a hardness after heat treatment of holding at 300 ° C. for 100 hours satisfies 25 HRB or more. It was strong and heat resistant. Further, the density of each of the test materials 1 to 18 was less than 2.80 g / cm ³ and had light weight.

Comparative Example 1
Billets (90 mm in diameter) of aluminum alloys (B1-19) having the component composition and density shown in Table 3 were processed in the same manner as in Example 1 to obtain T6 tempered extruded materials, and the obtained extruded materials were used as test materials. As in Example 1, the tensile strength was evaluated, and the Rockwell hardness (HRB) was measured at room temperature for the test material that was heat-treated at 300 ° C. for 100 hours. 4 shows. In Table 3, those outside the conditions of the present invention are underlined.

  As shown in Table 4, since the test materials 19 and 20 have a small amount of Cu, the test material 21 has a small amount of Mg, and the test material 23 has a small Si content. Since it was outside the scope of the invention, the test materials 31 and 32 were low in tensile strength because the Zr amount was outside the scope of the present invention.

  Although the test material 22 was satisfactory in material properties, it had a problem in productivity due to poor hot workability (extrusibility) due to a large amount of Mg. Since the test material 24 has a large amount of Si, the test materials 25 and 26 have an Fe content outside the range of the present invention, and the test materials 27 and 28 have a Ni content outside the range of the present invention. Since Nos. 33 and 34 were out of the scope of the present invention, the test materials 35 and 36 were inferior in heat resistance because the Ti quantity was outside the range of the present invention. The test material 37 has a problem in that the alloy composition satisfies the conditions of the present invention, but the density is large.

Claims (4)

Cu: 2.5-3.3% (mass%, the same applies hereinafter), Mg: 1.5-2.2%, Si: 0.2-0.4%, Fe: 0.5-1.1% , Ni: 0.8 to 1.3%, Mn: 0.40 to 0.70%, Zr: 0.10 to 0.20%, Sc: 0.10 to 0.60%, Ti: 0.005 A lightweight, high-strength aluminum alloy excellent in heat resistance, characterized by comprising ~ 0.15%, consisting of the balance Al and inevitable impurities, and having a density (g / cm ³ ) of less than 2.80. The lightweight and high-strength aluminum alloy excellent in heat resistance according to claim 1, wherein the content ratio of Cu and Mg (Cu% / Mg%) is in the range of 1.1 to 2.2. The lightweight, high-strength aluminum alloy having excellent heat resistance according to claim 1 or 2, wherein the hardness after holding at 300 ° C for 100 hours is 25 HRB or more. After homogenizing the ingot of the aluminum alloy having the composition according to claim 1 or 2, a hot work material is produced by performing at least one hot work, and then the hot work measured. A method for producing a lightweight, high-strength aluminum alloy excellent in heat resistance, characterized by subjecting a solution treatment in a temperature range 1 to 5 ° C. lower than the eutectic melting start temperature of the material and performing an artificial aging treatment.