Aluminum alloy forging material and method for manufacturing same

Abstract

Provided is an aluminum alloy forging material having high proof stress and capable of further improving creep characteristics. An aluminum alloy forging material according to the present invention contains 0.10 mass% to 0.25 mass% of Si, 0.9 mass% to 1.3 mass% of Fe, 1.9 mass% to 2.7 mass% of Cu, 1.3 mass% to 1.8 mass% of Mg, 0.90 mass% to 1.20 mass% of Ni, 0.01 mass% to 0.10 mass% of Ti, and 0.10 mass% or less of Zn, with the remainder being Al and inevitable impurities. Further, the proof stress in a tensile test at 180°C is 220 MPa or greater and, in a DSC curve obtained by differential scanning calorimetry, the S' phase formation peak area appearing in a temperature range of 200°C to 400°C is 1.8 J / g or greater.

Description

Aluminum alloy forgings and their manufacturing method

[0001] The present invention relates to an aluminum alloy forging and a method for producing the same.

[0002] Generally, many rotating and linear components, such as engine, compressor, and turbocharger impellers, are used continuously at high temperatures, so the aluminum alloy forgings used for these components must have particularly good creep properties.

[0003] For example, Patent Document 1 discloses an aluminum alloy forging containing 0.10 to 0.25 mass% Si, 0.9 to 1.3 mass% Fe, 1.9 to 2.7 mass% Cu, 1.3 to 1.8 mass% Mg, 0.10 mass% or less Zn, 0.9 to 1.2 mass% Ni, 0.01 to 0.1 mass% Ti, and the balance being Al and unavoidable impurities. The aluminum alloy forging also specifies a total content of Fe and Ni of 2.2 mass% or less, a total content of Mn, Cr, and Zr of 0.20 mass% or less, an average circle-equivalent diameter of the intermetallic compounds of 4.5 μm or less, and a variation in the distance between the intermetallic compounds in the ST direction of 2.3 or less.

[0004] Japanese Patent Application Publication No. 2021-134414

[0005] However, rotating parts and linear motion parts are required to have improved resistance to higher rotation speeds and higher temperatures, and accordingly, the aluminum alloy forgings used as raw materials are required to have both better creep properties and high yield strength.

[0006] In recent years, achieving carbon neutrality has become an issue for society as a whole, and the manufacturing of forging materials also requires CO ２ In other words, if the heat treatment temperature and the heat treatment time can be reduced under various heat treatment conditions in the manufacturing process of forged materials, the CO ２ Emission reductions can be achieved.

[0007] The present invention has been made in consideration of the above problems, and aims to provide an aluminum alloy forging material that has high yield strength and can further improve creep properties. The present invention also aims to reduce the manufacturing cost in the manufacturing process of the aluminum alloy forging material and to reduce CO ２ The present invention aims to provide a method for manufacturing aluminum alloy forgings that can suppress emissions and reduce the impact on global warming.

[0008] The above object can be achieved by the following aluminum alloy forging material (1) according to the present invention.

[0009] (1) An aluminum alloy forging containing Si: 0.10% by mass or more and 0.25% by mass or less, Fe: 0.9% by mass or more and 1.3% by mass or less, Cu: 1.9% by mass or more and 2.7% by mass or less, Mg: 1.3% by mass or more and 1.8% by mass or less, Ni: 0.90% by mass or more and 1.20% by mass or less, Ti: 0.01% by mass or more and 0.10% by mass or less, Zn: 0.10% by mass or less, and the balance being Al and unavoidable impurities, characterized in that the aluminum alloy forging has a yield strength of 220 MPa or more in a tensile test at 180°C, and an S' phase formation peak area appearing in a temperature range of 200°C to 400°C in a DSC curve obtained by differential scanning calorimetry is 1.8 J / g or more.

[0010] The above object can also be achieved by the following method for producing an aluminum alloy forging according to the present invention (2).

[0011] (2) A method for producing the aluminum alloy forging according to (1), comprising: a casting step of casting an aluminum alloy ingot containing Si: 0.10% by mass to 0.25% by mass, Fe: 0.9% by mass to 1.3% by mass, Cu: 1.9% by mass to 2.7% by mass, Mg: 1.3% by mass to 1.8% by mass, Ni: 0.90% by mass to 1.20% by mass, Ti: 0.01% by mass to 0.10% by mass, Zn: 0.10% by mass or less, with the balance being Al and unavoidable impurities; a homogenization-quenching step of subjecting the aluminum alloy ingot to a homogenization heat treatment, hot forging, solution treatment, and quenching treatment; and an artificial aging treatment step of subjecting the quenched material after quenching to an artificial aging treatment. The method for producing an aluminum alloy forging is characterized in that the heating temperature in the artificial aging treatment step is 170°C or higher and 220°C or lower, and the heating time is less than 22 hours.

[0012] According to the present invention, it is possible to provide an aluminum alloy forging material that has high yield strength and can further improve creep properties.

[0013] Furthermore, according to the present invention, in the manufacturing process of aluminum alloy forgings, it is possible to reduce manufacturing costs and CO ２ It is possible to provide a method for manufacturing aluminum alloy forgings that can suppress emissions and reduce the impact on global warming.

[0014] Fig. 1 is a graph showing a DSC curve, with the vertical axis representing DSC (mW / mg) and the horizontal axis representing temperature T (°C). Fig. 2 is a schematic diagram showing the locations of samples taken in this example. Fig. 3A is a plan view showing the area from which test specimens were taken from the obtained aluminum alloy forging. Fig. 3B is a side view of the aluminum alloy forging shown in Fig. 3A. Fig. 4 is a graph showing the relationship between creep rupture time and S' phase formation peak area, with the vertical axis representing creep rupture time t and the horizontal axis representing S' phase formation peak area.

[0015] The present inventors have conducted extensive research into the relationship between aging conditions and creep properties in order to further improve the creep properties of aluminum alloy forgings. As a result, the present inventors have found that sub-aging, compared to typical peak aging, can improve creep properties. The present inventors have also found that there is a correlation between the area of ​​a peak appearing in a predetermined region in a DSC curve obtained by differential scanning calorimetry for aluminum alloy forgings and creep properties. The present invention has been made based on these findings. Hereinafter, aluminum alloy forgings according to embodiments of the present invention will be described in detail.

[0016] [Aluminum Alloy Forging] The aluminum alloy forging according to this embodiment contains the following specific elements in predetermined content ranges. Specifically, AA2618 aluminum alloy, which has excellent high-temperature properties, can be used as the material for the aluminum alloy forging according to this embodiment. The elements contained in the aluminum alloy forging and the reasons for limiting their contents will be described in detail below. In the following description, the aluminum alloy forging may be simply referred to as the forging.

[0017] (Si: 0.10% by mass or more and 0.25% by mass or less) Si, together with Mn, precipitates fine dispersed phases such as Al-Mn-Si compounds, enhances the dislocation pinning effect, and suppresses coarsening of recrystallized grains during solution treatment, thereby improving the strength of the aluminum alloy forging. If the Si content in the forging is less than 0.10% by mass, the strength-improving effect cannot be fully achieved. Therefore, the Si content in the forging is set to 0.10% by mass or more, preferably 0.13% by mass or more, and more preferably 0.15% by mass or more, based on the total mass of the forging.

[0018] On the other hand, if the Si content in the forged material exceeds 0.25% by mass, compounds of Mg and Si are formed, resulting in a decrease in heat resistance. Therefore, the Si content in the forged material is set to 0.25% by mass or less, preferably 0.23% by mass or less, and more preferably 0.21% by mass or less, based on the total mass of the forged material.

[0019] (Fe: 0.9% by mass or more and 1.3% by mass or less) Fe forms Fe-Ni compounds together with Ni, and has the effect of improving the heat resistance of aluminum alloy forgings. If the Fe content in the forgings is less than 0.9% by mass, the effect of improving the heat resistance of the forgings cannot be sufficiently obtained. Therefore, the Fe content in the forgings is set to 0.9% by mass or more, and preferably 1.0% by mass or more, based on the total mass of the forgings.

[0020] On the other hand, if the Fe content in the forged material exceeds 1.3 mass%, Fe-based compounds such as Al-Fe and Al-Fe-Cu compounds are significantly formed and dispersed in the matrix, reducing the effect of improving heat resistance. Therefore, the Fe content in the forged material is set to 1.3 mass% or less, and preferably 1.2 mass% or less, based on the total mass of the forged material.

[0021] (Cu: 1.9% by mass or more and 2.7% by mass or less) Cu has the effect of improving the strength of aluminum alloy forgings at room temperature and high temperatures. Specifically, by including Cu in the forgings at a predetermined content, both solid solution strengthening and precipitation strengthening effects are obtained, thereby ensuring the high-temperature yield strength and heat resistance required in this embodiment. More specifically, Cu combines with Al and Mg during high-temperature artificial aging treatment to precipitate G.P.B. zones and S' phases finely and densely, thereby improving the strength of the forgings after artificial aging treatment. The S' phase will be described later.

[0022] If the Cu content in the forged material is less than 1.9% by mass, the effect of improving the strength of the forged material cannot be sufficiently obtained. Therefore, the Cu content in the forged material is set to 1.9% by mass or more, preferably 2.0% by mass or more, and more preferably 2.1% by mass or more, based on the total mass of the forged material. On the other hand, if the Cu content in the forged material exceeds 2.7% by mass, the eutectic melting start temperature decreases, and the solution treatment temperature must be lowered. This reduces the amount of Cu dissolved in the matrix, making it impossible to obtain the effect of improving the strength of the forged material. Therefore, the Cu content in the forged material is set to 2.7% by mass or less, preferably 2.6% by mass or less, and more preferably 2.5% by mass or less, based on the total mass of the forged material.

[0023] (Mg: 1.3% by mass or more and 1.8% by mass or less) Mg, in combination with Cu, has the effect of improving the strength of an aluminum alloy forging at room temperature and at high temperatures. Specifically, by including a predetermined amount of Mg in the forging, both solid solution strengthening and precipitation strengthening effects can be obtained, thereby ensuring the high-temperature yield strength and heat resistance required in this embodiment. More specifically, Mg combines with Al and Cu during high-temperature artificial aging treatment to precipitate G.P.B. zones, S' phases, and the like, finely and densely, thereby improving the strength of the forging after artificial aging treatment.

[0024] If the Mg content in the forged material is less than 1.3 mass%, the effect of improving the strength of the forged material cannot be sufficiently obtained. Therefore, the Mg content in the forged material is set to 1.3 mass% or more, preferably 1.4 mass% or more, and more preferably 1.5 mass% or more, based on the total mass of the forged material. On the other hand, if the Mg content in the forged material exceeds 1.8 mass%, the deformation resistance of the material increases during hot working such as forging, and productivity decreases. Therefore, the Mg content in the forged material is set to 1.8 mass% or less, preferably 1.7 mass% or less, and more preferably 1.6 mass% or less, based on the total mass of the forged material.

[0025] (Ni: 0.90% by mass or more and 1.20% by mass or less) Ni forms Fe-Ni compounds together with Fe, and has the effect of improving the heat resistance of aluminum alloy forgings. If the Ni content in the forgings is less than 0.90% by mass, the effect of improving heat resistance cannot be sufficiently obtained. Therefore, the Ni content in the forgings is set to 0.90% by mass or more, preferably 0.95% by mass or more, and more preferably 1.00% by mass or more, based on the total mass of the forgings.

[0026] On the other hand, if the Ni content in the forged material exceeds 1.20 mass%, Ni-based compounds such as Al-Ni and Al-Ni-Cu compounds are formed dispersed in the matrix, reducing the effect of improving heat resistance. Furthermore, coarse Fe-Ni and other intermetallic compounds are formed, making cracks more likely to occur during hot working such as forging, reducing productivity. Therefore, the Ni content in the forged material should be 1.20 mass% or less, preferably 1.18 mass% or less, and more preferably 1.10 mass% or less, based on the total mass of the forged material.

[0027] (Ti: 0.01% by mass or more and 0.10% by mass or less) Ti is a component contained in the forged material to stably obtain a fine crystal grain structure. If the Ti content in the forged material is less than 0.01% by mass, the effect of stabilizing the fine crystal grain structure cannot be sufficiently obtained. Therefore, the Ti content in the forged material is set to 0.01% by mass or more, and preferably 0.04% by mass or more, based on the total mass of the forged material.

[0028] On the other hand, if the Ti content in the forged material exceeds 0.10 mass%, large Al-Ti compounds are formed during casting, resulting in a decrease in strength. Therefore, the Ti content in the forged material is set to 0.10 mass% or less, and preferably 0.09 mass% or less, based on the total mass of the forged material.

[0029] (Zn: 0.10% by mass or less) Zn is an element that is often contained in forged materials as an unavoidable impurity. Zn is also an element that has the effect of improving the room-temperature and high-temperature strength of aluminum alloy forged materials through solid-solution strengthening and precipitation strengthening. However, since the effect of improving the room-temperature and high-temperature strength of aluminum alloy forged materials can be sufficiently obtained by Cu and Mg, Zn does not necessarily need to be contained in the forged material.

[0030] Furthermore, if the Zn content in the forged material exceeds 0.10 mass%, the corrosion resistance of the forged material decreases. Therefore, the Zn content in the forged material is set to 0.10 mass% or less, preferably 0.09 mass% or less, more preferably 0.08 mass% or less, and even more preferably 0.05 mass% or less, based on the total mass of the forged material.

[0031] (Balance: Al and inevitable impurities) The balance of the aluminum alloy forging according to this embodiment is Al and inevitable impurities. The inevitable impurities are inevitably contained due to the raw materials used in actual operation. In addition to the above-mentioned Zn, examples of inevitable impurities include Mn, Cr, Zr, and V. Of these inevitable impurities, V is preferably 0.05 mass% or less with respect to the total mass of the forging. Furthermore, the total content of Mn, Cr, and Zr is preferably 0.20 mass% or less, and more preferably 0.15 mass% or less with respect to the total mass of the forging. Note that, as long as the V content and the total content of Mn, Cr, and Zr do not exceed the upper limit values ​​described in this embodiment, the effects of the present invention are not hindered not only when they are contained as inevitable impurities, but also when they are actively contained.

[0032] (0.2% yield strength in tensile test at 180°C: 220 MPa or more) The aluminum alloy forging according to this embodiment aims to achieve even better creep properties than conventional forgings. For example, in the aluminum alloy forging described in Patent Document 1, the creep properties (time until fracture of a test specimen) at a temperature of 180°C and a load stress of 220 MPa are at most 284.6 hours. Therefore, in this embodiment, creep properties better than those of conventional products, i.e., the desired creep properties, are set to 290 hours or more. To achieve this creep property, the forging needs to have a 0.2% yield strength of 220 MPa or more when subjected to a tensile test at 180°C. Therefore, the aluminum alloy forging should have a 0.2% yield strength of 220 MPa or more in a tensile test at 180°C, preferably 250 MPa or more, and more preferably 280 MPa or more. The 0.2% proof stress in a tensile test at 180°C can be measured, for example, in accordance with "High temperature tensile test method for steel materials and heat-resistant alloys" in JIS G0567:2020 using a flanged test piece described in Appendix A.

[0033] (S' phase formation peak area: 1.8 J / g or more) Generally, when differential scanning calorimetry (DSC) is performed on an aluminum alloy material, an upwardly convex exothermic peak is obtained due to the precipitation phenomenon of precipitates of several nm. It is also known that a downwardly convex endothermic peak is obtained due to solid solution (dissolution) ((Reference 1) Akikazu Maezono, Light Metals, Vol. 51, No. 9, (2001), 464-476., (Reference 2) Taichi Suzuki, Hideaki Yata, Hideo Yoshida, Light Metals, Vol. 68, No. 7, (2018), 333-338.).

[0034] 1 is a graph showing a DSC curve with the vertical axis representing DSC (mW / mg) and the horizontal axis representing temperature T (°C). The analytical conditions for the graph in FIG. 1 are as follows: Apparatus used: Therma plus EVO2 high-sensitivity differential scanning calorimeter DSC8231 (manufactured by Rigaku Corporation) Heat flux type DSC apparatus (JIS K 0129:2005) Measurement conditions: Temperature increase from room temperature (approximately 25°C) to 530°C in a nitrogen gas atmosphere at a temperature increase rate of 10°C / min Sample: Approximately 20 mg used Reference sample: Al ２ O ３ powder

[0035] As shown in Figure 1, in the aluminum alloy forging according to this embodiment, DSC measurement reveals an exothermic peak C for S' phase formation within the temperature range of 200 to 400°C. The S' phase is an intermediate layer (metastable phase) that is thought to precipitate after the G.P.B. zone, and has a lath-like morphology and an orthorhombic structure with a = 4.0 Å, b = 9.2 Å, and c = 7.1 Å, with the precipitation plane in the {210} <100> direction. The parent phase is a compound that is partially coherent to semicoherent and easily nucleates on dislocation loops. This S' phase is a precipitate phase that contributes to improving strength, and although no clear chemical formula has been reported, the stable S phase is CuMgAl ２ In this embodiment, the area of ​​the S' phase formation peak that appears in the temperature range of 200°C or higher and 400°C or lower in the DSC curve obtained by DSC is specified.

[0036] The S' phase formation peak area will be further explained using Figure 1. The peak (S' phase formation peak) appearing in the temperature range of 200°C or higher and 400°C or lower is defined as exothermic peak C, and the peak adjacent to exothermic peak C via endothermic peak B on the lower temperature side is defined as exothermic peak A. In this specification, the area per unit heating rate (°C / s) of the shaded region surrounded by exothermic peak C and an auxiliary line drawn through the apex of exothermic peak A and parallel to the x-axis is defined as the "S' phase formation peak area."

[0037] If the S' phase formation peak area in the forged material is less than 1.8 (J / g), the desired creep properties cannot be obtained. Therefore, the S' phase formation peak area is set to 1.8 (J / g) or more. On the other hand, although there is no particular upper limit for the S' phase formation peak area, when a sample as quenched (before the artificial aging treatment described below) is measured, which may have the largest S' phase formation peak area, it is 7.4 (J / g). Therefore, it is preferable that the S' phase formation peak area in the forged material be 7.4 (J / g) or less.

[0038] Next, a method for producing an aluminum alloy forging according to an embodiment of the present invention will be described.

[0039] [Method for Manufacturing Aluminum Alloy Forgings] The method for manufacturing an aluminum alloy forging according to this embodiment includes a casting step of casting an aluminum alloy ingot having a predetermined composition, a homogenization-quenching step of subjecting the resulting aluminum alloy ingot to a homogenization heat treatment, hot forging, solution treatment, and quenching, and an artificial aging treatment step of subjecting the quenched material to an artificial aging treatment. Each step will be described in more detail below.

[0040] <Casting Process> The casting process is a process of casting a molten metal melted to a predetermined composition to produce an aluminum alloy ingot. The aluminum alloy ingot contains Si, Fe, Cu, Mg, Ni, and Ti in predetermined contents, with a Zn content of a predetermined value or less, and the balance consisting of Al and unavoidable impurities. The contents of each element in the aluminum alloy ingot and the reasons for limiting the numerical values ​​are the same as those for each element in the aluminum alloy forging, and are as described above. The casting method and the shape of the ingot are not particularly limited, and conventional methods and shapes can be used.

[0041] <Homogenization-Quenching Process> Next, the aluminum alloy ingot obtained by the casting process is subjected to homogenization heat treatment, hot forging, solution treatment, and quenching. The temperature rise rate and holding temperature of the homogenization heat treatment are not particularly limited, and general conditions can be used. The temperature rise rate of the homogenization heat treatment can be, for example, 5°C / min or less, and the holding temperature can be, for example, 450 to 550°C. The start temperature and end temperature of the hot forging are also not particularly limited, and general conditions can be used. The start temperature of the hot forging can be, for example, 350 to 500°C, and the end temperature can be, for example, 300 to 500°C. The holding temperature, holding time, and heating rate of the solution treatment are also not particularly limited, and general conditions can be used. The holding temperature of the solution treatment can be, for example, 520 to 570°C, the holding time can be, for example, 20 minutes to 20 hours, and the heating rate can be, for example, 100°C / hour or more. Quenching is a treatment process in which the material after solution treatment is cooled by immersing it in water or hot water, and the cooling rate is not particularly limited, and general conditions can be used. The cooling rate in quenching can be, for example, 40°C / second or more.

[0042] <Artificial Aging Treatment Step> The artificial aging treatment step is a step of performing artificial aging treatment on the quenched material obtained by the quenching step. As described above, in this embodiment, the creep properties of the forged material are improved by setting the artificial aging treatment step conditions to sub-aging. In other words, it is important to select heat treatment conditions before peak aging. The sub-aging conditions are determined by appropriately selecting the balance between heating temperature and heating time. For example, a general heating temperature range can be applied, and a heating time shorter than the general heating time can be selected.

[0043] If the heating temperature in the artificial aging treatment step is less than 170°C, the forged material cannot be sufficiently hardened. Therefore, the heating temperature in the artificial aging treatment step is set to 170°C or higher, preferably 180°C or higher, and more preferably 190°C or higher. On the other hand, if the heating temperature in the artificial aging treatment step exceeds 220°C, the condition for under-aging is not met, making it difficult to improve creep properties. Therefore, the heating temperature in the artificial aging treatment step is set to 220°C or lower, preferably 210°C or lower, and more preferably 200°C or lower.

[0044] If the heating time in the artificial aging treatment step is 22 hours or more, the condition for under-aging will be exceeded, making it difficult to improve creep properties. Therefore, the heating time in the artificial aging treatment step is set to less than 22 hours.

[0045] The present embodiment will be described in more detail below with reference to examples, but the present invention is not limited to these examples, and modifications can be made within the scope of the spirit of the present invention, and all such modifications are included in the technical scope of the present invention.

[0046] <Production of Aluminum Alloy Forgings> (Casting Process) FIG. 2 is a schematic diagram showing the location of samples taken in this example. An iron mold 11 having a cylindrical shape with a bottom and a smaller diameter at the bottom than at the opening was prepared. Molten aluminum alloy having a predetermined composition was poured into this mold 11 to produce an ingot 12 by metal mold casting. The mass of the resulting ingot 12 was approximately 5.5 kg. Next, the ingot 12 removed from the mold 11 was cut and machined to produce a cylindrical sample 13 from approximately the center of the ingot 12. The size of the sample 13 was 100 mm in diameter and 120 mm in height. Note that in this example, the mass of the ingot 12 was approximately 5.5 kg. However, the ingot is not limited to this size. For example, an ingot weighing 2 tons or more can also be used to produce an aluminum alloy forging under similar conditions described below.

[0047] (Homogenization-quenching process) Sample 13 was then placed in an air furnace and subjected to homogenization heat treatment at a temperature of 520°C for 20 hours, after which it was cooled to room temperature. Sample 13 was then placed in an air furnace again and heated to 300-340°C, after which it was removed from the furnace and hot forged using a hydraulic forging press. The hot-forged material was then placed in an air furnace and subjected to solution treatment at a temperature of 530°C for 6 hours, after which it was quenched in boiling water to obtain a quenched material.

[0048] (Artificial Aging Treatment Step) The quenched material after the homogenization-quenching step was then placed in an air furnace and artificially aged at a temperature of 197°C for the time shown below to obtain T61-treated aluminum alloy forgings. In this example, the artificial aging treatment time for Inventive Example No. 1 was 16 hours, which was a treatment condition resulting in under-aging. The artificial aging treatment time for Comparative Example No. 1 was 22 hours, which was a treatment condition resulting in peak aging. The artificial aging treatment time for Comparative Example No. 2 was 36 hours, which was a treatment condition resulting in over-aging.

[0049] Fig. 3A is a plan view showing a region from which test specimens were taken from the obtained aluminum alloy forging, and Fig. 3B is a side view of the aluminum alloy forging shown in Fig. 3A. The disk-shaped aluminum alloy forging 21 had a diameter of 200 mm in the rolling direction (L direction) and a thickness of 30 mm in the plate thickness direction (ST direction). In Figs. 3A and 3B, the hatched areas indicate a region 22 from which test specimens were taken. Specifically, test specimens for tensile tests and creep tests were taken from the center of the plate thickness of the aluminum alloy forging 21 and from a region 22 extending radially from near the center of the disk shape.

[0050] <Evaluation of Aluminum Alloy Forgings> Measurement by DSC, tensile tests, and creep tests were carried out using test specimens taken from the obtained aluminum alloy forgings 21. In addition, the electrical conductivity of the obtained aluminum alloy forgings 21 was measured.

[0051] (Calculation of S' Phase Formation Peak Area) A sample for DSC measurement was taken from the chuck of a tensile test specimen taken from the aluminum alloy forging 21, and DSC measurement was performed. Then, the S' phase formation peak area that appeared in the temperature range of 200 to 400 ° C was calculated. The measurement conditions were as follows. - Apparatus used: Therma plus EVO2 high-sensitivity differential scanning calorimeter DSC8231 (manufactured by Rigaku Corporation) - Heat flux type DSC apparatus (JIS K 0129: 2005) - Measurement conditions: From room temperature (approximately 25 ° C) to 530 ° C, in a nitrogen gas atmosphere, at a heating rate of 10 ° C / min - Sample: Approximately 20 mg used - Reference sample (reference): Al ２ O ３ powder

[0052] (Tensile test) In accordance with JIS G 0567:2020 "High temperature tensile test method for steel materials and heat-resistant alloys," a tensile test was carried out at 180°C using a flanged test piece described in Appendix A, and the tensile strength, 0.2% yield strength, and elongation after fracture were measured.

[0053] (Creep test) In accordance with JIS Z 2271:2010 "Methods for creep and creep rupture testing of metallic materials," creep rupture times were measured at a temperature of 180°C under a load of 220 MPa. A creep rupture time of 290 hours or more was judged to be good (◯) in the creep test. A creep rupture time of less than 290 hours was judged to be poor (×) in the creep test.

[0054] (Measurement of Electrical Conductivity) The obtained aluminum alloy forging 21 was cut at an arbitrary position, and the exposed cross section was mechanically polished to #2000, and the electrical conductivity of the obtained surface was measured. The electrical conductivity was measured at room temperature (about 25°C) by pressing the probe tip of a conductivity meter against the sample. Note that, as long as the measurement surface is relatively smooth, the electrical conductivity can be measured as any desired polishing roughness. The devices used to measure the electrical conductivity are as follows: - Device used: Conductivity meter SIGMASCOPE SMP350 (manufactured by Fischer Instruments Inc.) - Applicable standards: ASTM E1004, etc.

[0055] The contents of each component contained in the aluminum alloy forgings and the heating conditions in the artificial aging treatment step are shown in Table 1 below, and the measurement results of each test are shown in Table 2 below.

[0056]

[0057]

[0058] Figure 4 is a graph showing the relationship between creep rupture time and S' phase formation peak area, with the vertical axis representing creep rupture time t and the horizontal axis representing S' phase formation peak area. As shown in Tables 1 and 2 and Figure 4, Inventive Example No. 1 has forged materials containing components within the ranges specified by the present invention, and the heating temperature and time in the artificial aging treatment step were appropriately controlled, resulting in under-aging. Therefore, the S' phase formation peak area was 1.8 J / g or more, the 0.2% proof stress at a high temperature of 180°C was 220 (MPa), and the creep rupture time was 290 hours or more. Furthermore, since the heating time in the artificial aging treatment step can be set shorter than conventional methods, manufacturing costs can be reduced and CO ２ This has reduced emissions and reduced the impact on global warming.

[0059] On the other hand, in Comparative Examples Nos. 1 and 2, the heating conditions in the artificial aging treatment step were conditions that resulted in peak aging or overaging, and therefore the desired creep properties could not be obtained.

[0060] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. Furthermore, the components of the above-described embodiments may be combined in any manner without departing from the spirit of the invention.

[0061] This application is based on a Japanese patent application (Patent Application No. 2024-061714) filed on April 5, 2024, the contents of which are incorporated herein by reference.

[0062] 11 Mold 12 Ingot 13 Sample 21 Aluminum alloy forging

Claims

1. An aluminum alloy forging containing Si: 0.10% by mass or more and 0.25% by mass or less, Fe: 0.9% by mass or more and 1.3% by mass or less, Cu: 1.9% by mass or more and 2.7% by mass or less, Mg: 1.3% by mass or more and 1.8% by mass or less, Ni: 0.90% by mass or more and 1.20% by mass or less, Ti: 0.01% by mass or more and 0.10% by mass or less, Zn: 0.10% by mass or less, the balance being Al and unavoidable impurities, characterized in that the aluminum alloy forging has a yield strength of 220 MPa or more in a tensile test at 180°C, and an S' phase formation peak area appearing in the temperature range of 200°C to 400°C in a DSC curve obtained by differential scanning calorimetry is 1.8 J / g or more.

2. A method for producing the aluminum alloy forgings according to claim 1, comprising: a casting step of casting an aluminum alloy ingot containing Si: 0.10% by mass to 0.25% by mass, Fe: 0.9% by mass to 1.3% by mass, Cu: 1.9% by mass to 2.7% by mass, Mg: 1.3% by mass to 1.8% by mass, Ni: 0.90% by mass to 1.20% by mass, Ti: 0.01% by mass to 0.10% by mass, Zn: 0.10% by mass or less, the balance being Al and unavoidable impurities; a homogenization-quenching step of subjecting the aluminum alloy ingot to a homogenization heat treatment, hot forging, solution treatment and quenching treatment; and an artificial aging treatment step of subjecting the quenched material after quenching to an artificial aging treatment. The method for producing an aluminum alloy forging is characterized in that the heating temperature in the artificial aging treatment step is 170°C or higher and 220°C or lower, and the heating time is less than 22 hours.

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