Forged aluminum alloy product, preparation method thereof and aluminum alloy forged piston

Abstract

The invention discloses a forged aluminum alloy product and a preparation method thereof and an aluminum alloy forged piston, a cast ingot with the radial size of 50-150mm is obtained by at least controlling the continuous casting speed to be more than 200mm / min and the overall cooling rate of the cast ingot to be greater than or equal to 15 DEG C / s, and then soaking treatment, cooling and forging are sequentially performed; in the product, after T6 heat treatment, the residual as-cast structure is below 10%, the sub-grain size is less than 30 microns, the area percentage of the sub-grain structure is more than 60%, the average size of eutectic silicon is below 5 microns, the roundness is more than 0.6, the average size of dispersion particles is 0.1-2 microns, and the number density is 105-1011 particles / cm < 2 >; according to the preparation method, ingot casting extrusion and related procedures which are necessary in the conventional process can be omitted, the preparation process is greatly shortened, the strength, plasticity and other performance are also remarkably improved, and the preparation method can be used for the aluminum alloy forged piston.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloys, and in particular to a forged aluminum alloy product and a preparation method thereof, and an aluminum alloy forged piston. Background Art

[0002] Aluminum alloy forged piston alloy has the advantages of light weight, high strength, high wear resistance, high heat resistance, excellent volume stability, etc., and has broad application prospects in the fields of automobiles, ships, aviation, etc. This type of alloy has excellent casting properties, and the billet is used to manufacture pistons and other parts working at high temperatures after forging or extrusion. However, if the eutectic structure and coarse solidified phase in this type of alloy billet are not refined, the matrix material will be severely split, causing the material strength and plasticity to deteriorate. At present, the conventional forging piston process is: first prepare ordinary alloy ingots, extrude them after equalization, then saw and cut the extruded bars into forging billets, and finally forge the billets into pistons and perform heat treatment. However, in practice, this process still has the following shortcomings: 1. During the casting process, modifiers and refiners are usually added to refine α-Al and fully modify the eutectic silicon structure. However, in practice, the eutectic structure still often has large pieces of primary silicon structure and needle-like eutectic silicon, which can seriously split the matrix material and cause the material strength and toughness to deteriorate. For example, the mechanical properties of pistons made of conventional 4032 aluminum alloy are yield strength of 290MPa, tensile strength of 330MPa and elongation of 3%. The performance is slightly lacking and it is difficult to meet the increasing demand;

[0003] 2. The conventional casting + extrusion + forging process has a long process flow. The entire forming process involves ingot casting, ingot soaking, soaking ingot cooling, ingot heating before extrusion, ingot extrusion, extrusion bar cooling, extrusion bar cutting and heating, bar forging and other processes. On the one hand, the entire forming process involves multiple steps, with a long production cycle and is time-consuming and labor-intensive. On the other hand, there are considerable challenges in accurately controlling all of these processes, especially since the bars generate large reservoir energy during the extrusion process. If the forming process control in the extrusion and forging steps is not proper, coarse grains due to extrusion and forging are very likely to occur.

[0004] Therefore, it is urgent to develop a solution related to aluminum alloy forged pistons to avoid the occurrence of the above-mentioned defects to the greatest extent. Summary of the invention

[0005] The object of the present invention is to overcome one or more deficiencies in the prior art and to provide an improved method for preparing forged aluminum alloy products. This method allows the present invention to omit a large number of cumbersome steps such as "heating before ingot extrusion, ingot extrusion, extruded bar cooling, extruded bar cutting and heating" when preparing forged aluminum alloy products, greatly simplifying the production process and reducing production costs, while also being able to have excellent mechanical properties.

[0006] The present invention also provides a forged aluminum alloy product prepared by the above method, which can be an aluminum alloy forged piston or other parts working at high temperature.

[0007] To achieve the above object, a technical solution adopted by the present invention is: a method for preparing a forged aluminum alloy product, the method comprising:

[0008] (1) forming an aluminum alloy melt, and casting the aluminum alloy melt in a continuous casting process at a casting speed of greater than or equal to 200 mm / min and an overall cooling rate of the ingot greater than or equal to 15° C. / s to obtain an ingot with a radial dimension of 50-150 mm;

[0009] (2) performing homogenization treatment, cooling and forging on the ingot obtained by casting in sequence;

[0010] The forged aluminum alloy product is controlled to have a residual cast structure of less than 10% after T6 heat treatment, a subgrain size of less than 30 μm, an area percentage of subgrain structure greater than 60%, an average size of eutectic silicon less than 5 μm, a roundness greater than 0.6, an average size of dispersed particles of 0.1-2 μm, and a number density of 10 5 -10 11 Pieces / cm 2 .

[0011] According to the present invention, the method of the present invention can omit the extrusion process and related pre- and post-processes in the existing conventional preparation of aluminum alloy forged pistons, greatly simplifying the process and shortening the production cycle. Therefore, the method for preparing forged aluminum alloy products described in the present invention does not include the extrusion process of the ingot, the heating process before extrusion, the cooling process after extrusion, and the cutting and heating process of the extruded rod.

[0012] According to some preferred aspects of the present invention, the method comprises: obtaining an ingot after the casting, cutting the ingot into a forging blank, and then sequentially performing the homogenization treatment, the cooling and the forging;

[0013] Wherein, the time for transferring the forging blank after the homogenization treatment to the cooling place for water quenching is controlled within 10 seconds.

[0014] According to some preferred aspects of the present invention, during the forging process, the process time of transferring the cooled material to be forged to the forging equipment is controlled within 10 seconds, the temperature is raised to 450-480°C at a heating rate of 5°C / s or more, the temperature difference between the core and the edge of the material to be forged is controlled to be less than 5°C, hydraulic die forging is used for forging, the forging speed is 1-10mm / s, and the overall forming strain rate is controlled to be 1s -1 Within.

[0015] According to some preferred aspects of the present invention, during the forging process, the forging process is controlled according to formula (1) and the forging structure is controlled;

[0016] P = α1 × (σ 2 / G)(1), where P is the reservoir energy, α1 is the material coefficient, σ is the material flow stress, and G is the alloy shear modulus;

[0017] The forged sample is tested by using formula (1). When P meets the expected value, the corresponding forging speed and strain rate are determined; when P exceeds the expected value, the forging speed and strain rate are adjusted.

[0018] According to some preferred aspects of the present invention, the casting speed is greater than or equal to 250 mm / min. Further, the casting speed includes but is not limited to 250-350 mm / min.

[0019] According to some preferred aspects of the present invention, the overall cooling rate of the ingot is greater than or equal to 20°C / s. Further, the overall cooling rate of the ingot includes but is not limited to 20-40°C / s.

[0020] According to some preferred aspects of the present invention, during the casting process, the difference between the cooling rates at R / 2 and the core of the ingot is controlled not to exceed 2°C / s, where R is the distance from the center of a radial cross section of the ingot to its surface.

[0021] According to the present invention, after the casting, in the cast structure of the obtained ingot, the primary α-Al is fine equiaxed crystals with a size less than 100 μm, the eutectic silicon deformation grade is greater than level 4 (American Foundry Association aluminum-silicon alloy modification grade-1984), and the solidified second phase size is less than 20 μm.

[0022] According to the present invention, after the homogenization treatment, in the organizational structure, the average size of the eutectic silicon is less than 5 μm, and the roundness is greater than 0.6.

[0023] According to some preferred aspects of the present invention, the homogenization treatment comprises: treating at 400-480° C. for 5-12 hours.

[0024] According to some preferred aspects of the present invention, the cooling rate is controlled to be greater than or equal to 10° C. / s.

[0025] According to some preferred aspects of the present invention, the T6 heat treatment comprises the following steps performed in sequence:

[0026] Treat at 500-530℃ for 5-12h;

[0027] Treat at 150-170°C for 2-18h.

[0028] In some embodiments of the present invention, the method further comprises: after T6 heat treatment, transferring to a quenching water tank, the transfer time is controlled within 15s, and the quenching cooling rate is greater than 20°C / s

[0029] In some embodiments of the present invention, after T6 heat treatment, the forged aluminum alloy product has a yield strength greater than or equal to 330 MPa, a tensile strength greater than or equal to 390 MPa, and an elongation greater than or equal to 6% at room temperature.

[0030] In some embodiments of the present invention, after T6 heat treatment, the linear expansion coefficient of the forged aluminum alloy product at room temperature is 19×10 -6 -24×10 -6 / ℃.

[0031] According to some preferred aspects of the present invention, the aluminum alloy melt comprises:

[0032] 8.0 wt. % to 13.0 wt. % Si;

[0033] 0.1 wt.% to 1.0 wt.% Mg;

[0034] 0.5 wt. % to 4.0 wt. % Cu;

[0035] 0.1 wt.% to 3.0 wt.% Ni;

[0036] 0.01 wt.% to 1.0 wt.% of M1 and 0.02 wt.% to 1.0 wt.% of M2, wherein the M1 comprises Nb and Sr, and the M2 comprises Zr, Er and Mo;

[0037] and inevitable impurities, and the Al content is adjusted so that the total amount of the aluminum alloy melt is 100wt.%.

[0038] In some embodiments of the present invention, the M1 further comprises Ti and / or B.

[0039] According to some preferred aspects of the present invention, in the M1, the ratio of the content of Nb to the content of Sr is 1-10:1.

[0040] In some embodiments of the present invention, the M2 further comprises a combination of one or more selected from V, Mn and Cr.

[0041] According to some preferred aspects of the present invention, in the M2, the ratio of the content of Zr, the content of Er and the content of Mo is 1-2:1-4:1.

[0042] In some embodiments of the present invention, the aluminum alloy melt comprises:

[0043] 8.0 wt. % to 13.0 wt. % Si;

[0044] 0.1 wt.% to 1.0 wt.% Mg;

[0045] 0.5 wt. % to 4.0 wt. % Cu;

[0046] 0.1 wt.% to 3.0 wt.% Ni;

[0047] 0.01 wt.% to 1.0 wt.% of M1 and 0.02 wt.% to 1.0 wt.% of M2;

[0048] M1 contains 0.01 wt.% to 0.6 wt.% Nb, 0.01 wt.% to 0.05 wt.% Sr, 0.05 wt.% to 0.3 wt.% Ti, 0.05 wt.% to 0.3 wt.% B;

[0049] M2 contains 0.1 wt.% to 0.2 wt.% Zr, 0.1 wt.% to 0.4 wt.% Er, 0.1 wt.% to 0.2 wt.% Mo, 0.1 wt.% to 0.6 wt.% V, 0.1 wt.% to 0.2 wt.% Mn, 0.1 wt.% to 0.6 wt.% Cr;

[0050] and inevitable impurities, and the Al content is adjusted so that the total amount of the aluminum alloy melt is 100wt.%.

[0051] In some embodiments of the present invention, the dispersed particles include Al3X dispersed particles and selective Al6X dispersed particles, where X is selected from one, two, three or more of M2. For example, the dispersed particles include Al3Zr dispersed particles, Al3Er dispersed particles, Al3Mo dispersed particles, Al6Mn dispersed particles, and the like.

[0052] Another technical solution provided by the present invention is a forged aluminum alloy product, wherein the forged aluminum alloy product is made by the method for preparing a forged aluminum alloy product as described above.

[0053] Another technical solution provided by the present invention is: an aluminum alloy forged piston, and the preparation process of the aluminum alloy forged piston includes the method for preparing a forged aluminum alloy product described above.

[0054] Another technical solution provided by the present invention is an aluminum alloy, comprising:

[0055] 8.0 wt. % to 13.0 wt. % Si;

[0056] 0.1 wt.% to 1.0 wt.% Mg;

[0057] 0.5 wt. % to 4.0 wt. % Cu;

[0058] 0.1 wt.% to 3.0 wt.% Ni;

[0059] 0.01 wt.% to 1.0 wt.% of M1 and 0.02 wt.% to 1.0 wt.% of M2, wherein the M1 comprises Nb and Sr, and the M2 comprises Zr, Er and Mo;

[0060] and inevitable impurities, and the Al content is adjusted so that the total amount of the aluminum alloy melt is 100wt.%.

[0061] In some embodiments of the present invention, the total content of unavoidable impurities is less than or equal to 0.25 wt.%, preferably less than 0.15 wt.%.

[0062] Another technical solution provided by the present invention is a method for preparing the aluminum alloy described above, the method comprising:

[0063] The other components of the aluminum alloy except M1 and M2 are mixed and melted, and the first refining is carried out, and the slag is removed. Then, M1 and M2 are added, mixed and melted, and the second refining is carried out, and the slag is removed and allowed to stand.

[0064] In some embodiments of the present invention, the other components of the aluminum alloy except M1 and M2 are mixed and melted at 770-800°C, and a furnace sample is taken after the added charge is completely melted and the composition is uniform, and the sampling temperature is 745-755°C; after the furnace analysis is qualified, when the melt temperature is 740-750°C, Ar gas is used for the first refining, and the refining time is 15-20min. After refining, the slag is removed again, and M1 and M2 elements are added after slag removal at a temperature of 735-745°C. After complete melting, the melt is stirred evenly, and when the melt temperature is 740-750°C, Ar gas refining is performed for the second time on the melt, and the refining time is 15-20min. After refining, the slag on the surface of the melt is removed, and the melt is allowed to stand after slag removal for secondary component sampling, and casting is prepared when the composition meets the requirements.

[0065] In the present invention, “above” and “below” indicating a numerical range include the number itself. For example, “above 0.5” means greater than or equal to 0.5; and “below 0.4” means less than or equal to 0.4.

[0066] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0067] Based on the defects of the existing manufacturing of pistons and other parts working at high temperatures, such as insufficient mechanical (mechanical) properties and complex forming processes, the present invention innovatively provides an improved method for preparing forged aluminum alloy products. The method controls the continuous casting speed to be above 200 mm / min and the overall cooling rate of the ingot to be greater than or equal to 15°C / s to obtain an ingot with a radial size of 50-150 mm. Combined with the addition of M1 elements containing Nb and Sr, it is achieved that α-Al can be refined and the eutectic structure can be fully modified; and further adding M2 elements containing Zr, Er and Mo can achieve the formation of M2 supersaturated solid solution (which can subsequently form high density dispersed phase), and can also prevent or eliminate the generation of coarse M2-containing coarse flaky second phase; in particular, the aforementioned process and composition adjustment and control enable the preparation process of the forged aluminum alloy product of the present invention to directly skip the "heating before ingot extrusion, ingot extrusion, extruded bar cooling, extruded bar cutting and heating" and other processes that must be carried out in the conventional preparation process, thereby greatly shortening the preparation process, and the volume proportion of forging structure subgrains and the distribution density of dispersed strengthening phases in the forged aluminum alloy product of the present invention are also greatly improved, and the mechanical (mechanical) properties such as strength and plasticity are also significantly improved, and the piston field installation operation test of more than 10,000 hours under various working conditions has been passed. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 The eutectic structure diagram of the edge of the ingot prepared in Example 1 of the present invention;

[0069] Figure 2 The eutectic structure diagram of the core of the ingot prepared in Example 1 of the present invention;

[0070] Figure 3 This is a eutectic structure diagram of the ingot after the homogenization treatment prepared in Example 1 of the present invention;

[0071] Figure 4 This is a subgrain structure diagram of the aluminum alloy forged piston prepared in Example 1 of the present invention;

[0072] Figure 5 This is a microstructure diagram of the ingot grains prepared in Comparative Example 1 of the present invention;

[0073] Figure 6 This is the organization diagram of the ingot grains prepared in Comparative Example 2 of the present invention;

[0074] Figure 7 This is a microstructure diagram of the ingot grains prepared in Comparative Example 3 of the present invention;

[0075] Figure 8 This is the dispersed precipitation phase diagram of the aluminum alloy forged piston prepared in Comparative Example 4 of the present invention. DETAILED DESCRIPTION

[0076] At present, with the increasingly higher requirements for piston performance, it is generally believed that a certain amount of transition elements can be added to enhance the comprehensive performance of the alloy. However, in practice, it is found that the added transition elements are very likely to form a coarse second phase containing transition elements in the core of the ingot. These coarse second phases containing transition elements are mostly lamellar and needle-shaped structures, which will have a serious splitting effect on the matrix and are prone to stress concentration, becoming a crack source, which in turn reduces the mechanical properties of the alloy, especially the negative performance of strength and plasticity is more prominent, which runs counter to the original purpose of adding transition elements.

[0077] After a lot of practical research, the inventors of the present invention believe that it is caused by the influence of the casting rate and the cooling rate in the casting process. When the casting rate and the cooling rate are low to a certain extent, it is easy for the transition elements to appear in the form of coarse flake and needle-shaped second phases containing transition elements during the alloy processing, and it also has a negative effect on the effectiveness of the modifier and refiner, which can easily lead to poor modification and refinement effects on the core of the ingot. Even if excessive modifiers and refiners are added, it is difficult to refine α-Al and fully modify the eutectic silicon structure. This poorly modified eutectic structure often has large pieces of primary silicon structure and needle-shaped eutectic silicon, which can seriously split the matrix material, causing the material strength and toughness to deteriorate.

[0078] Based on the above research findings, the present invention innovatively provides a method for preparing forged aluminum alloy products, which obtains an ingot with a radial size of 50-150 mm by controlling the casting speed to at least 200 mm / min and the overall cooling rate of the ingot to be greater than or equal to 15°C / s, and then the ingot obtained by casting is subjected to homogenization treatment, cooling and forging in sequence. Furthermore, combined with the addition of M1 elements containing Nb and Sr, and M2 elements containing Zr, Er and Mo. The results show that in the prepared forged aluminum alloy product, after T6 heat treatment, the residual cast structure is less than 10%, the subgrain size is less than 30μm, the area percentage of the subgrain structure is greater than 60%, the average size of eutectic silicon is less than 5μm, the roundness is greater than 0.6, the average size of the dispersed particles is 0.1-2μm, and the number density is 10 5 -10 11 Pieces / cm 2 .

[0079] At the same time, surprisingly, the above-mentioned improved method of the present invention can also omit the processes such as "heating before ingot extrusion, ingot extrusion, extruded rod cooling, extruded rod cutting and heating" that must be carried out in the conventional preparation process, thereby greatly shortening the preparation process.

[0080] Furthermore, the preparation method of the forged aluminum alloy product comprises:

[0081] (a) The ingredients are prepared according to the standard composition in Table 1, and the other ingredients in the aluminum alloy except M1 and M2 are mixed and melted at 770-800°C. After the added charge is completely melted and the composition is uniform, a furnace sample is taken, and the sampling temperature is 745-755°C; after the furnace analysis is qualified, when the melt temperature is 740-750°C, Ar gas is used for the first refining, and the refining time is 15-20min. After refining, the slag is removed again, and M1 and M2 elements are added after the slag is removed, and the temperature is 735-745°C. After the melt is completely melted, the melt is stirred uniformly, and when the melt temperature is 740-750°C, Ar gas refining is performed for the second time, and the refining time is 15-20min. After refining, the slag on the surface of the melt is removed, and the melt is allowed to stand after slag removal, and secondary component sampling is performed. When the composition meets the requirements, the aluminum alloy melt is obtained, and casting is prepared;

[0082] The wrought aluminum alloy product or its intermediate aluminum alloy (eg, ingot, aluminum alloy melt, etc.) described in the present invention may have the element composition shown in Table 1.

[0083] Table 1

[0084]

[0085]

[0086] (b) casting the aluminum alloy melt in a continuous casting process at a casting speed of greater than or equal to 200 mm / min and an overall cooling rate of the ingot greater than or equal to 15° C. / s, wherein the radial dimension of the cast ingot is 70-150 mm; wherein the cooling water flow rate is adjusted to control the overall cooling rate of the ingot and the difference between the cooling rate at R / 2 of the ingot and the core, and the casting temperature is 735-750° C.;

[0087] (c) sawing the ingot into forging blanks of preset specifications and sending them into a soaking furnace for soaking treatment, wherein the soaking treatment process is 400-480° C. for 5-12 hours;

[0088] After the homogenization treatment, the forging blank is immediately water quenched, and the cooling rate is greater than or equal to 10°C / s, and the time for transferring the homogenization treatment forging blank to the cooling place for water quenching is controlled to be within 10s;

[0089] Forging is performed, the process time of transferring the cooled material to be forged to the forging equipment is controlled within 10 seconds, the temperature is raised to 450-480°C at a heating rate of 5°C / s or more, the temperature difference between the core and the edge of the material to be forged is controlled to be less than 5°C, hydraulic die forging is used for forging, the forging speed is 1-10mm / s, and the overall forming strain rate is controlled to be 1s -1 within;

[0090] During the forging process, the forging process is controlled according to formula (1) and the forging structure is controlled; P = α1×(σ 2 / G)(1), where P is reservoir energy, α1 is material coefficient, σ is material rheological stress, and G is material shear modulus; the forged sample is tested by formula (1), and when P meets the expected value, the corresponding forging speed and strain rate are determined; when P exceeds the expected value, the forging speed and strain rate are adjusted;

[0091] Perform T6 heat treatment: 500-530℃×5-12h+150-170℃×2-18h; after T6 heat treatment, transfer to quenching water tank, the transfer time is controlled within 10, and the quenching cooling rate is greater than 50℃ / s.

[0092] The above scheme is further described below in conjunction with specific embodiments; it should be understood that these embodiments are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following embodiments; the implementation conditions adopted in the embodiments can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions in conventional experiments.

[0093] Unless otherwise specified in the following examples, all raw materials are commercially available or prepared by conventional methods in the art.

[0094] Example 1-2

[0095] This example provides a forged aluminum alloy product and a preparation method thereof. The forged aluminum alloy product of this example is an aluminum alloy forged piston having the element composition shown in Table 2.

[0096] Table 2

[0097]

[0098] The preparation method comprises:

[0099] (a) The ingredients are prepared according to the standard composition in Table 2, and the other ingredients in the aluminum alloy except M1 and M2 are mixed and melted at 785±5℃. After the added charge is completely melted and the composition is uniform, the furnace front sample is taken, and the sampling temperature is 750±5℃; after the furnace front analysis is qualified, when the melt temperature is 745±5℃, Ar gas is used for the first refining, and the refining time is 20min. After refining, the slag is removed again, and M1 and M2 elements are added after the slag is removed. The temperature is 740±5℃. After the melt is completely melted, the melt is stirred evenly. When the melt temperature is 745±5℃, Ar gas refining is performed for the second time. The refining time is 20min. After refining, the slag on the surface of the melt is removed, and the melt is allowed to stand after slag removal. Secondary component sampling is performed. When the composition meets the requirements, the aluminum alloy melt is obtained and casting is prepared;

[0100] (b) The aluminum alloy melt is cast in a continuous casting process at a casting speed of 200 mm / min and an overall cooling rate of 15° C. / s, and the radial dimension of the cast ingot is 70 mm (see the eutectic structure diagram of the ingot at the edge). Figure 1 As shown, the eutectic structure diagram in the core is shown in Figure 2 The cooling water flow rate is adjusted to control the difference between the cooling rate of the whole ingot and the cooling rate at R / 2 and the core of the ingot to be 1.5°C / s, and the casting temperature is 740±5°C;

[0101] (c) The ingot is sawn into forging billets of 100 mm × 50 mm in size and sent to a soaking furnace for soaking treatment. The soaking treatment process is to treat at 500 ° C for 6 hours (see the eutectic structure diagram of the ingot after soaking treatment). Figure 3 shown);

[0102] After the homogenization treatment, the forging blank is immediately water quenched at a cooling rate of 10°C / s, and the time for transferring the homogenization treated forging blank to the cooling place for water quenching is controlled to be 8s;

[0103] Forging is performed, the process time of transferring the cooled material to be forged to the forging equipment is controlled to be 8s, the temperature is raised to 460°C at a heating rate of 5°C / s, the temperature difference between the core and the edge of the material to be forged is controlled to be less than 5°C, hydraulic die forging is used for forging, the forging speed is 2mm / s, and the overall forming strain rate is controlled to be 1s -1 within;

[0104] Perform T6 heat treatment: 530℃×8h+160℃×8h; after T6 heat treatment, transfer to quenching water tank, transfer time is controlled to 8s, quenching cooling rate is 50℃ / s, and obtain aluminum alloy forged piston (the subgrain structure diagram of aluminum alloy forged piston is shown in Figure 4 shown).

[0105] Example 3

[0106] The method is basically the same as Example 1, except that the aluminum alloy melt is cast in a continuous casting process at a casting speed of 220 mm / min and an overall cooling rate of the ingot of 18° C. / s.

[0107] Example 4

[0108] The method is basically the same as Example 1, except that the aluminum alloy melt is cast in a continuous casting process at a casting speed of 300 mm / min and an overall cooling rate of the ingot of 35° C. / s.

[0109] Comparative Example 1

[0110] The same as Example 1, the only difference is that the casting speed is 60 mm / min, and the overall cooling rate of the ingot is 5°C / s. Figure 5 shown.

[0111] Comparative Example 2

[0112] The same as Example 1, the only difference is that the ingot size is 250mm in diameter. The grain structure diagram of the ingot prepared in this example is shown in Figure 6 shown.

[0113] Comparative Example 3

[0114] The method is basically the same as Example 1, except that only Nb is added to M1 (the content of Nb is equal to the total amount of M1 in Example 1), and only Zr is added to M2 (the content of Zr is equal to the total amount of M2 in Example 1). The microstructure of the ingot grains prepared in this example is shown in Figure 7 shown.

[0115] Comparative Example 4

[0116] The same as Example 1, the only difference is that no M2 element is added. The dispersion precipitation phase diagram of the aluminum alloy forged piston prepared in this example is shown in Figure 8 shown.

[0117] Performance Testing

[0118] The organizational characteristics and room temperature tensile properties of the aluminum alloy forged pistons obtained in the above embodiments and comparative examples are shown in Tables 3 and 4, wherein Table 3 is the statistical results of the organizational characteristics of each aluminum alloy forged piston, and Table 4 is the statistical results of the room temperature mechanical properties (test standard: GB / T 16865-2013) of each aluminum alloy forged piston.

[0119] Table 3

[0120]

[0121] Table 4

[0122]

[0123] At the same time, the linear expansion coefficient of Example 1 was measured to be 20.3×10 -6 / ℃, the linear expansion coefficient of Example 2 is 20.1×10 -6 / ℃.

[0124] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

[0125] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

Claims

1. A method for preparing a forged aluminum alloy product, characterized in that: The method for preparing a forged aluminum alloy product comprises: (1) forming an aluminum alloy melt, and casting the aluminum alloy melt in a continuous casting process at a casting speed of greater than or equal to 200 mm / min and an overall cooling rate of the ingot greater than or equal to 15° C. / s to obtain an ingot with a radial dimension of 50-150 mm; (2) performing homogenization treatment, cooling and forging on the ingot obtained by casting in sequence; The forged aluminum alloy product is controlled to have a residual cast structure of less than 10% after T6 heat treatment, a subgrain size of less than 30 μm, an area percentage of subgrain structure greater than 60%, an average size of eutectic silicon less than 5 μm, a roundness greater than 0.6, an average size of dispersed particles of 0.1-2 μm, and a number density of 10 5 -10 11 Pieces / cm 2 .

2. The method for preparing a forged aluminum alloy product according to claim 1, characterized in that: The method comprises: obtaining an ingot after the casting, cutting the ingot into forging blanks, and then sequentially performing the homogenization treatment, the cooling and the forging; Wherein, the time for transferring the forging blank after the homogenization treatment to the cooling place for water quenching is controlled within 10 seconds.

3. The method for preparing a forged aluminum alloy product according to claim 1, characterized in that: During the forging process, the time for transferring the cooled material to be forged to the forging equipment is controlled within 10 seconds, the temperature is raised to 450-480°C at a heating rate of 5°C / s or more, the temperature difference between the core and the edge of the material to be forged is controlled to be less than 5°C, hydraulic die forging is used for forging, the forging speed is 1-10mm / s, and the overall forming strain rate is controlled to be 1s -1 Within.

4. The method for preparing a forged aluminum alloy product according to claim 1, characterized in that: During the forging process, the forging process is controlled according to formula (1) and the forging structure is controlled; P = α1 × (σ 2 / G)(1), where P is the reservoir energy, α1 is the material coefficient, σ is the material flow stress, and G is the alloy shear modulus; The forged sample is tested by using formula (1). When P meets the expected value, the corresponding forging speed and strain rate are determined; when P exceeds the expected value, the forging speed and strain rate are adjusted.

5. The method for preparing a forged aluminum alloy product according to claim 1, characterized in that: The casting speed is greater than or equal to 250 mm / min, and the overall cooling rate of the ingot is greater than or equal to 20°C / s; and / or, during the casting process, the difference between the cooling rate at R / 2 of the ingot and the core is controlled not to exceed 2°C / s, where R is the distance from the center of the radial cross section of the ingot to its surface.

6. The method for preparing a forged aluminum alloy product according to claim 1, characterized in that: After the casting, in the cast structure of the obtained ingot, the primary α-Al is fine equiaxed crystals with a size less than 100μm, the deformation grade of eutectic silicon is greater than level 4, and the size of the solidified second phase is less than 20μm; and / or, after the homogenization treatment, in the organizational structure, the average size of eutectic silicon is less than 5μm and the roundness is greater than 0.

6.

7. The method for preparing a forged aluminum alloy product according to claim 1, characterized in that: The homogenization treatment includes: treating at 400-480° C. for 5-12 hours; and / or controlling the cooling rate of the cooling to be greater than or equal to 10° C. / s.

8. The method for preparing a forged aluminum alloy product according to claim 1, characterized in that: The T6 heat treatment includes the following steps performed in sequence: Treat at 500-530℃ for 5-12h; Treat at 150-170°C for 2-18h; And / or, the method further comprises: after the T6 heat treatment, transferring to a quenching water tank, wherein the transfer time is controlled within 15 seconds, and the quenching cooling rate is greater than 20°C / s.

9. The method for preparing a forged aluminum alloy product according to claim 1, characterized in that: After T6 heat treatment, the yield strength of the forged aluminum alloy product at room temperature is greater than or equal to 330 MPa, the tensile strength is greater than or equal to 390 MPa, and the elongation is greater than or equal to 6%; and / or, after T6 heat treatment, at room temperature, the linear expansion coefficient of the forged aluminum alloy product is 19×10 -6 -24×10 -6 / ℃.

10. The method for preparing a forged aluminum alloy product according to claim 1, characterized in that: The method for preparing a forged aluminum alloy product does not include the extrusion process of the ingot, the heating process before extrusion, the cooling process after extrusion, and the cutting and heating processes of the extruded bar.

11. The method for preparing a forged aluminum alloy product according to claim 1, characterized in that: The aluminum alloy melt comprises: 8.0 wt.% to 13.0 wt.% Si; 0.1 wt.% to 1.0 wt.% Mg; 0.5 wt. % to 4.0 wt. % Cu; 0.1 wt.% to 3.0 wt.% Ni; 0.01 wt.% to 1.0 wt.% of M1 and 0.02 wt.% to 1.0 wt.% of M2, wherein the M1 comprises Nb and Sr, and the M2 comprises Zr, Er and Mo; and inevitable impurities, and the Al content is adjusted so that the total amount of the aluminum alloy melt is 100wt.%.

12. The method for preparing a forged aluminum alloy product according to claim 11, characterized in that: The M1 further comprises Ti and / or B, and in the M1, the ratio of the Nb content to the Sr content is 1-10:1; and / or, the M2 further comprises a combination of one or more selected from V, Mn and Cr, and in the M2, the ratio of the Zr content, the Er content and the Mo content is 1-2:1-4:

1.

13. The method for preparing a forged aluminum alloy product according to claim 11 or 12, characterized in that: The dispersed particles include Al3X dispersed particles and selective Al6X dispersed particles, and X is selected from one, two, three or more of M2.

14. A forged aluminum alloy product, characterized in that The forged aluminum alloy product is made by the method for preparing a forged aluminum alloy product according to any one of claims 1 to 13.

15. An aluminum alloy forged piston, characterized in that: The process for preparing the aluminum alloy forged piston comprises adopting the method for preparing a forged aluminum alloy product as described in any one of claims 1 to 13.

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