Large high-strength heat-resistant aluminum alloy wheel hub forgings and methods for making same

Abstract

The present application belongs to the technical field of aluminum alloy material structure manufacturing, and relates to a large high-strength heat-resistant aluminum alloy hub forge and a preparation method thereof. The method is suitable for preparing a large hub with a diameter (Φ500mm~Φ800mm) x depth (200mm~400mm) x outer wall thickness (20mm~50mm). Compared with a conventional hub, the present application obtains a preparation method suitable for Al-Cu-Mg-Ag alloy large hub forgings by optimizing alloy components, combining extrusion + forging compound breaking down, medium-temperature die forging, deep cryogenic treatment and other processes, so that the large hub forgings have excellent high-strength heat-resistant performance. The room temperature yield strength is higher than 450MPa, the tensile strength is higher than 500MPa, and the elongation is higher than 8%. The 150℃ high-temperature tensile yield strength is higher than 400MPa, the tensile strength is higher than 450MPa, and the elongation is higher than 10%. The 200℃ high-temperature tensile yield strength is higher than 350MPa, the tensile strength is higher than 400MPa, and the elongation is higher than 12%.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy structural component manufacturing technology, specifically relating to a large high-strength heat-resistant aluminum alloy wheel hub forging and its preparation method, especially the preparation of large wheel hub forgings with a diameter exceeding 20 inches. Background Technology

[0002] Aluminum alloy wheels are widely used in the transportation industry due to their advantages such as lightweight, high strength, and corrosion resistance. With the development of the transportation industry and the increasing demand for load-bearing capacity, challenges have been placed on the load-bearing capacity and heat resistance of wheels, making the enlargement of wheel components inevitable. Existing literature mainly focuses on the manufacturing processes of small-sized forgings with wheel diameters ranging from 17 inches (431.8 mm) to 20 inches (508 mm), while there are few reports on manufacturing methods for large wheel forgings with diameters exceeding 20 inches (508 mm). This invention combines extrusion and forging to provide a method for manufacturing large aluminum alloy wheel forgings, applicable to heavy-duty freight vehicles, large aircraft, and other large transportation vehicles.

[0003] During the high-speed braking process of a car or aircraft, the service temperature of the wheel hub can rise to 150℃~200℃ due to heat transfer from the brake disc and tires. Therefore, wheel hub forgings need to have certain heat resistance to maintain high strength at 150℃~200℃. Currently, among heat-resistant aluminum alloys, automotive wheel hubs mainly use 6061 aluminum alloy, while aircraft wheel hubs mainly use 2014 aluminum alloy. 6061 aluminum alloy has relatively low strength, with a peak-aged room temperature tensile strength not exceeding 400MPa. 2014 aluminum alloy has higher strength, with a tensile strength reaching 450MPa, but its heat resistance is limited.

[0004] Currently, the common method in the manufacturing process of aluminum alloy wheels is to directly perform isothermal forging on homogenized ingots. This method has high production efficiency, but the strength of the forgings obtained is relatively low. Especially for large structural parts, the larger billet size will result in poorer deformation uniformity, making it difficult to obtain high strength.

[0005] Al-Cu-Mg-Ag alloys have become a research hotspot in recent years, proving their excellent heat resistance. The addition of Ag leads to the formation of finer, more dispersed Ω-phase within the alloy, which stabilizes the matrix precipitates. These Ω-phase precipitates are relatively stable at high temperatures, contributing to the alloy's high-temperature strength. However, there are currently no reports on large-scale structural forgings made from Al-Cu-Mg-Ag alloys, and no engineering applications have been reported. Summary of the Invention

[0006] The purpose of this invention is to provide a large, high-strength, heat-resistant aluminum alloy wheel hub forging and its preparation method. Based on Al-Cu-Mg-Ag alloy, a large Al-Cu-Mg-Ag wheel hub forging suitable for engineering is successfully prepared by synergistic development of optimized billet opening process and heat treatment process.

[0007] To solve this technical problem, the technical solution of the present invention is as follows:

[0008] On the one hand, a method for preparing a large, high-strength, heat-resistant aluminum alloy wheel forging is provided, comprising the following steps:

[0009] (1) Prepare aluminum alloy round ingots with ingot size Φ600~Φ1000mm and composition as follows: Cu 5.0~5.4wt.%, Mg 1.0~1.5wt.%, Ag 0.6~1.0wt.%, Mn 0.5~0.8wt.%, Be 0.1~0.2wt.%, Zr 0.1~0.2wt.%, Si≤0.10wt.%, Fe≤0.10wt.%, balance is Al and unavoidable impurities;

[0010] (2) After homogenization treatment of round ingots at 480±10℃ / 6~10h+510±10℃ / 24h~28h, extrusion billeting and free forging billeting are carried out. The extrusion heating temperature is 400℃~420℃ and the extrusion ratio is controlled at 4~7. The free forging billet heating temperature is 350℃~400℃ and the final forging temperature is not lower than 350℃. Further, the extrusion heating temperature is more preferably 400℃~410℃ and the free forging billet heating temperature is more preferably 360℃~380℃.

[0011] (3) After the billet is cut into sections, it is made into a blank. The blank is then isothermally forged according to the actual wheel hub shape. The blank heating temperature is 350℃~400℃, and the final forging temperature of the forging is not lower than 350℃.

[0012] (4) The hub is solution hardened at a temperature of 510±10℃ and the solution time is determined according to the thickness of the forging section. After solution hardening, it is water-cooled and quenched at room temperature.

[0013] (5) After quenching, the forging is slowly cooled to -150℃~-200℃ and then cryogenically treated for 2~4h. After being quickly taken out, it is rapidly heated to 175℃±5℃ at a heating rate of 20℃~30℃ / min for aging treatment for 12h~16h.

[0014] Furthermore, the composition of the aluminum alloy round ingot is as follows: Cu 5.2-5.4 wt.%, Mg 1.1-1.4 wt.%, Ag 0.7-0.9 wt.%, Mn 0.6-0.7 wt.%, Be 0.1-0.2 wt.%, Zr 0.1-0.2 wt.%, Si≤0.10 wt.%, Fe≤0.10 wt.%, with the balance being Al and unavoidable impurities.

[0015] Specifically, in step (2), the free forging process involves three forging operations, specifically two upsetting and one drawing. This invention's preparation method comprehensively considers both extrusion and billet-making processes. When the extrusion ratio is 4-7 and the forging operation is three times, the wheel hub achieves optimal matching of room temperature and high temperature tensile properties.

[0016] Specifically, the cooling rate in step (5) slow cooling treatment is 2℃~4℃ / min.

[0017] Preferably, the extrusion speed in step (2) is 10-20 mm / s.

[0018] Specifically, in step (4), the relationship between the solution treatment time and the thickness of the forging section is as follows: the maximum thickness of the section is D mm, and the solution treatment time is 3D min.

[0019] Preferably, the transfer time in step (5) is no more than 5 minutes.

[0020] Based on the ingot size of Φ600~Φ1000mm in step (1), and matching the process parameters in the preparation method of this invention, a large-scale forged wheel hub was obtained: a large forged wheel hub with a diameter (Φ500~Φ800mm) × depth (200mm~400mm) × outer wall thickness (20mm~50mm) can be prepared.

[0021] On the other hand, a large, high-strength, heat-resistant aluminum alloy wheel hub is provided, which is prepared according to the above method. The prepared wheel hub forging has a room temperature yield strength higher than 450 MPa, a tensile strength higher than 500 MPa, and an elongation higher than 8% along the main grain deformation direction. Under high-temperature tensile testing at 150°C, the yield strength is higher than 400 MPa, the tensile strength is higher than 450 MPa, and the elongation is higher than 10%. Under high-temperature tensile testing at 200°C, the yield strength is higher than 350 MPa, the tensile strength is higher than 400 MPa, and the elongation is higher than 12%.

[0022] The beneficial effects of this invention are:

[0023] Regarding alloy composition optimization, firstly, for wrought aluminum alloys, the limiting solubility of Cu in aluminum alloys is approximately 5.5%, and further increasing the Cu content will not further improve strength. Therefore, to obtain higher mechanical properties and for cost considerations, the Cu content is controlled within the range of 5.0% to 5.4%. Secondly, increasing the content of Mg and Ag elements in synergy is beneficial to improving high-temperature strength. When the Mg content is low, increasing the Ag content is not beneficial to performance; both Mg and Ag need to be increased simultaneously. However, Ag is expensive, and its addition as an alloying element is generally no more than 1%. At the same time, excessively high Mg content will compete with Cu to form AlCuMg precipitates, which will reduce the content of the Ω phase. Therefore, the Mg content is controlled within the range of 1.0% to 1.5%. Finally, Zr and Be elements are added in combination, mainly to increase the recrystallization temperature and improve thermal stability. Be is added in the form of an Al-Be master alloy, and the microalloying of Be elements has a certain improvement on the high-temperature resistance of the aluminum alloy.

[0024] The extrusion process employs a moderate extrusion ratio and speed to achieve a suitable degree of deformation in the billet, facilitating subsequent free forging and die forging.

[0025] Pre-forging the ingot into a blank can improve the strength of the forging. Forging blanking methods can be divided into free forging blanking and extrusion blanking. Free forging blanking usually requires multiple upsetting and drawing processes, resulting in a blank with relatively low deformable microstructure content but good plasticity, which is beneficial for subsequent deformation. Extrusion blanking results in a blank with higher deformable microstructure content, higher strength but lower plasticity.

[0026] To address the shortcomings of existing processes, this invention utilizes a combination of extrusion and free forging for billet preparation. An optimal billet preparation process path was determined through experiments, and the billet was then die-forged to produce large Al-Cu-Mg-Ag wheel hub forgings that exhibit both tensile strength and plasticity at both room temperature and high temperature. The medium-temperature forging temperature (350℃~400℃) is lower than the recrystallization temperature. Combined with a suitable deformation process, this minimizes recrystallization during deformation, preserving the alloy's deformed structure and substructure as much as possible, thereby improving room temperature and high temperature tensile properties. Simultaneously, an appropriate solution treatment time allows the second phase to dissolve back and retains the deformed structure of the alloy matrix. Since large forgings generate significant residual stress during forging, which is detrimental to subsequent finishing, the forgings after solution treatment must undergo cryogenic treatment. This involves slow cooling to -150℃~-200℃ followed by holding for 2~4 hours to reduce residual stress and stabilize dimensions and alloy substructure, while preventing the generation of new internal stresses due to rapid cooling. After cryogenic treatment, rapid heating to the aging temperature further releases the internal stresses. Finally, peak aging was used to achieve high room temperature and high temperature mechanical properties in the alloy.

[0027] Specifically:

[0028] During the billet preparation process, the extrusion ratio used in extrusion billet preparation is 4-7. When the extrusion ratio is too small, the degree of deformation is small, making it difficult to achieve the purpose of forming a deformed structure. When the extrusion ratio is too large, the billet forms a strong deformed structure, resulting in excessive material strengthening, which is not conducive to subsequent die forging deformation and is prone to cracking during the forging process. The extrusion ratio should be matched with the subsequent forging process. Free forging, after process verification, adopts a 2-upset-1-drawing method. After extrusion billet preparation, the blank undergoes 2 upset-1-drawing free forging to obtain a moderate degree of deformation, and the resulting blank combines the characteristics of extrusion and free forging products. Both free forging and die forging processes use medium-temperature forging, with the forging temperature heated to 350℃-400℃. The purpose is to deform the forging while minimizing recrystallization. Since the forging needs to be repeatedly hammered during the forging process, the forging temperature may rise further. When high-temperature forging (400℃-480℃) is used, if the temperature rises further during deformation, dynamic recrystallization is very likely to occur, resulting in a decrease in the strength of the finished forging. Low-temperature forging (300℃~350℃) results in billets with excessive deformation resistance, making them difficult to form. A final forging temperature of at least 350℃ allows for dynamic recovery of the forging, preserving the deformed structure and reducing subsequent recrystallization. After forming, the forging undergoes solution quenching followed by cryogenic treatment. Slow cooling at 2℃~4℃ / min to -150℃~-200℃ and rapid heating at 20℃~30℃ / min to the aging temperature effectively reduces internal stress while stabilizing dimensions and substructure. A peak aging regime of 175℃±5℃ / 12h~16h is used to achieve high strength.

[0029] After combining the above processes, the prepared large heat-resistant aluminum alloy wheel hubs with a diameter of (Φ500mm~Φ800mm) × (200mm~400mm) depth × (20mm~50mm) outer wall thickness combine high strength and plasticity with a high yield. Their room temperature yield strength is higher than 450MPa, tensile strength is higher than 500MPa, and elongation is higher than 8%. At 150℃, the high-temperature tensile yield strength is higher than 400MPa, tensile strength is higher than 450MPa, and elongation is higher than 10%. At 200℃, the high-temperature tensile yield strength is higher than 350MPa, tensile strength is higher than 400MPa, and elongation is higher than 12%. Attached Figure Description

[0030] To more clearly illustrate the technical solutions implemented in this invention, the accompanying drawings used in the embodiments of this invention will be briefly explained below. Obviously, the drawings described below are merely some embodiments of this invention. Those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0031] Figure 1The process flow for manufacturing large, high-strength, heat-resistant aluminum alloy wheel forgings;

[0032] Figure 2 This is a schematic diagram of the cross-section of the obtained wheel hub forging. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] The features of various aspects of the embodiments of the present invention will now be described in detail. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can also be practiced without these specific details. The following description of the embodiments is merely intended to provide a better understanding of the invention by illustrating examples. The invention is not limited to any specific setups and methods provided below, but covers all improvements, substitutions, etc., to product structures and methods without departing from the spirit of the invention.

[0035] In the various figures and the following description, well-known structures and techniques are not shown in order to avoid unnecessary obscuring of the invention. The description is given below in conjunction with the preparation of large-size wheel hub forgings of different dimensions.

[0036] Example 1:

[0037] The steps to manufacture a wheel hub with a diameter of 550mm × depth of 250mm × wall thickness are as follows:

[0038] (1) Prepare qualified Φ650mm aluminum alloy round ingots with the following composition: Cu 5.2wt.%, Mg 1.2wt.%, Ag 0.8wt.%, Mn 0.6wt.%, Zr 0.1wt.%, Be 0.15wt.%, Si≤0.10wt.%, Fe≤0.10wt.%, with the balance being Al and unavoidable impurities.

[0039] (2) After homogenizing the round ingot at 480℃ / 6h+510℃ / 24h, it was extruded and billeted. The extrusion heating temperature was 420℃, the extrusion speed was 10mm / s, and the extrusion ratio was 4.7, to produce Φ300mm round bars.

[0040] (3) After the Φ300mm round bar is cut into segments, it is forged freely. The free forging method is 2 upsetting and 1 drawing. The free forging heating temperature is 400℃ and the final forging temperature is 360℃.

[0041] (4) The billet after the blanking is subjected to isothermal die forging. The heating temperature of the forging billet is 380℃, the heating temperature of the die is 380℃, and the final forging temperature is 355℃.

[0042] (5) The wheel hub is solution hardened, and then water hardened at room temperature after solution hardening at 520℃ for 75 min.

[0043] (6) After quenching, the forging is cooled to -180℃ at 2℃ / min for 2 hours and then heated to 175℃ at a heating rate of 25℃ / min.

[0044] (7) The wheel hub forging is subjected to aging treatment at 175℃ / 12h.

[0045] Example 2

[0046] The steps for manufacturing a wheel hub with a diameter of 750mm × depth of 400mm × wall thickness of 50mm are as follows:

[0047] (1) Prepare qualified aluminum alloy round ingots with an ingot size of Φ1000mm. The composition of the ingots is Cu 5.4wt.%, Mg 1.3wt.%, Ag 0.9wt.%, Mn 0.7wt.%, Zr 0.1wt.%, Be 0.13wt.%, Si≤0.10wt.%, Fe≤0.10wt.%, with the balance being Al and unavoidable impurities.

[0048] (2) After homogenization treatment of the round ingot at 480℃ / 10h+510℃ / 28h, it is extruded and billeted. The extrusion heating temperature is 400℃, the extrusion speed is 20mm / s, the extrusion ratio is 6.25, and a Φ400mm round bar is made.

[0049] (3) After the Φ400mm round bar is cut into segments, it is for free forging. The free forging method is 2 upsetting and 1 drawing. The free forging heating temperature is 380℃ and the final forging temperature is 354℃.

[0050] (4) The billet after the blanking is subjected to isothermal die forging. The heating temperature of the forging billet is 390℃, the heating temperature of the die is 390℃, and the final forging temperature is 363℃.

[0051] (5) The wheel hub is solution hardened at 520℃ for 150 min and then water hardened at room temperature.

[0052] (6) After quenching, the forging is cooled to -180℃ at 2℃ / min for 4 hours and then heated to 175℃ at a heating rate of 25℃ / min.

[0053] (7) The wheel hub forging is subjected to aging treatment at 175℃ / 16h.

[0054] Comparative Examples 1 to 14:

[0055] The wheel hub with a diameter of 550mm × 250mm × 25mm was prepared. Except for the blanking process, the rest of the process was the same as in Example 1.

[0056] (1) Prepare qualified aluminum alloy round ingots with an ingot size of Φ650mm. The composition of the ingots is Cu 5.2wt.%, Mg 1.2wt.%, Ag 0.8wt.%, Mn 0.6wt.%, Zr 0.1wt.%, Be 0.15wt.%, Si≤0.10wt.%, Fe≤0.10wt.%, with the balance being Al and unavoidable impurities.

[0057] (2) After homogenization treatment of the round ingot at 480℃ / 6+510℃ / 24h, the billet is opened. The extrusion heating temperature is 420℃, the extrusion speed is 10mm / s, the free forging heating temperature is 380℃, and the final forging temperature is not lower than 350℃. The extrusion ratio and billet opening method are shown in Table 1.

[0058] (3) The blank after the billet is forged by die forging. The die forging process is the same as in Example 1.

[0059] (4) The wheel hub is solution hardened, and then water hardened at room temperature after solution hardening at 520℃ for 75 min.

[0060] (5) After quenching, the forging is cooled to -180℃ at 2℃ / min for 2 hours and then heated to 175℃ at a heating rate of 25℃ / min.

[0061] (6) The wheel hub forging is subjected to aging treatment at 175℃ / 12h.

[0062] Comparative Examples 15 to 28:

[0063] The wheel hub with a diameter of 750mm × 400mm × 50mm was prepared. Except for the blanking process, the rest of the process was the same as in Example 2.

[0064] (1) Prepare qualified aluminum alloy round ingots with an ingot size of Φ1000mm. The composition of the ingots is Cu 5.4wt.%, Mg 1.3wt.%, Ag 0.9wt.%, Mn 0.7wt.%, Zr 0.1wt.%, Be 0.13wt.%, Si≤0.10wt.%, Fe≤0.10wt.%, with the balance being Al and unavoidable impurities.

[0065] (2) After homogenization treatment of the round ingot at 480℃ / 10h + 510℃ / 28h, it is extruded and billeted. The extrusion heating temperature is 400℃, the extrusion speed is 20mm / s, the free forging heating temperature is 380℃, and the final forging temperature is not lower than 350℃. The extrusion ratio and billeting method are shown in Table 2.

[0066] (3) The blank after the billet is forged by die forging. The die forging process is the same as in Example 2.

[0067] (4) The wheel hub is solution hardened at 520℃ for 150 min and then water hardened at room temperature.

[0068] (5) After quenching, the forging is cooled to -180℃ at 2℃ / min for 4 hours and then heated to 175℃ at a heating rate of 25℃ / min.

[0069] (6) The wheel hub forging is subjected to aging treatment at 175℃ / 16h.

[0070] Comparative Examples 29 to 36:

[0071] The wheel hub with a diameter of 750mm × 400mm × 50mm was prepared. Except for the alloy composition, the other processes were the same as in Example 2.

[0072] (1) Prepare qualified aluminum alloy round ingots with an ingot size of Φ1000mm and their composition as shown in Table 3.

[0073] (2) After homogenization treatment of the round ingot at 480℃ / 10h+510℃ / 28h, it is extruded and billeted. The extrusion heating temperature is 400℃, the extrusion speed is 20mm / s, the extrusion ratio is 6.25, and a Φ400mm round bar is made.

[0074] (3) After the Φ400mm round bar is cut into segments, it is forged freely. The free forging method is 2 upsetting and 1 drawing. The free forging heating temperature is 380℃, and the final forging temperature is not lower than 350℃.

[0075] (4) The billet after the blanking is subjected to isothermal die forging. The heating temperature of the forging billet is 390℃, the heating temperature of the die is 390℃, and the final forging temperature is not lower than 350℃.

[0076] (5) The wheel hub is solution hardened at 520℃ for 150 min and then water hardened at room temperature.

[0077] (6) After quenching, the forging is cooled to -180℃ at 2℃ / min for 4 hours and then heated to 175℃ at a heating rate of 25℃ / min.

[0078] (7) The wheel hub forging is subjected to aging treatment at 175℃ / 16h.

[0079] Table 1: Comparison data between Example 1 and Comparative Examples 1-14

[0080]

[0081]

[0082] Table 2: Comparison data between Example 2 and Comparative Examples 15-28

[0083]

[0084] Table 3: Comparison of components between Example 2 and Comparative Examples 29-36

[0085] Serial Number Alloy composition Remark Example 2 Al-5.4Cu-1.3Mg-0.9Ag-0.7Mn-0.1Zr-0.13Be / Comparative Example 29 Al-4.3Cu-1.3Mg-0.9Ag-0.7Mn-0.1Zr-0.13Be Different Cu contents Comparative Example 30 Al-5.4Cu-0.8Mg-0.9Ag-0.7Mn-0.1Zr-0.13Be Different Mg contents Comparative Example 31 Al-5.4Cu-1.7Mg-0.9Ag-0.7Mn-0.1Zr-0.13Be Different Mg contents Comparative Example 32 Al-5.4Cu-1.3Mg-0.4Ag-0.7Mn-0.1Zr-0.13Be Different Ag contents Comparative Example 33 Al-5.4Cu-0.5Mg-1.0Ag-0.7Mn-0.1Zr-0.13Be Different Mg and Ag contents Comparative Example 34 Al-5.4Cu-1.0Mg-0.5Ag-0.7Mn-0.1Zr-0.13Be Different Mg and Ag contents Comparative Example 35 Al-5.4Cu-1.3Mg-0.9Ag-0.7Mn Different Zr and Be contents Comparative Example 36 Al-5.4Cu-1.3Mg-0.9Ag-0.7Mn-0.13Zr Different Be content

[0086] Table 4 Comparison of mechanical properties between Example 1 and Comparative Examples 1-14

[0087]

[0088] Table 5 Comparison of mechanical properties between Example 2 and Comparative Examples 15-28

[0089]

[0090] Table 6 Comparison of mechanical properties between Example 2 and Comparative Examples 29-36

[0091]

[0092]

[0093] Table 4 shows a comparison of the room temperature and high temperature mechanical properties of the process routes of Example 1 and Comparative Examples 1-14; Table 5 shows a comparison of the room temperature and high temperature mechanical properties of Example 2 and Comparative Examples 15-28; and Table 6 shows a comparison of the room temperature and high temperature mechanical properties of different components of Example 2 and Comparative Examples 29-36.

[0094] As can be seen from Examples 1 and Comparative Examples 1-14, compared with extrusion-only and forging-only processes, the extrusion + forging composite blanking process significantly improves the room temperature and high temperature strength of the wheel hub. Examples 1 and Comparative Examples 1-8 show that when the extrusion ratio is the same in the composite blanking process, increasing the number of forging blanks can significantly increase the wheel hub strength. When the extrusion ratio is 2, the degree of extrusion deformation is relatively small. After 1-5 forging blanks, the strength is high but still has room for improvement. When the extrusion ratio is 4.7, the degree of extrusion deformation is moderate. Combined with 1-5 forging blanks, the strength at various temperatures can reach a high level. However, the number of subsequent forging blanks should not be too high. When the number of forging blanks is 5, the strength decreases because excessive deformation easily leads to energy accumulation and recrystallization in the alloy, which in turn reduces the strength. Considering both strength and plasticity matching, the optimal number of forging blanks after extrusion is 3. When the extrusion ratio is 8, the deformation of the billet after extrusion is too large, and the plasticity is significantly reduced. It is very easy to crack during the subsequent forging and upsetting process. Therefore, a large extrusion ratio should not be used in the extrusion + forging composite billet opening process.

[0095] As can be seen from Examples 2 and Comparative Examples 15-28, when manufacturing larger wheel hub forgings, a larger extrusion ratio should be used in the extrusion + forging composite blanking process to improve the degree of deformation. When the extrusion ratio is 6.25, the optimal mechanical properties can be obtained by combining three forging blanking processes. However, when the extrusion ratio is 8, although the wheel hub obtains higher strength, the elongation is lower.

[0096] Therefore, taking into account both extrusion and forging processes, the wheel hub can achieve the optimal match between room temperature tensile and high temperature tensile properties when the extrusion ratio is 4 to 7 and the forging number is 3.

[0097] As shown in Example 2 and Comparative Example 29, the tensile properties of the forgings significantly decreased when the Cu content decreased to 4.3 wt%. As shown in Example 2 and Comparative Examples 30 and 31, both room temperature and high temperature tensile properties decreased when the Mg content decreased to 0.8 wt%. However, when the Mg content reached 1.7 wt%, the room temperature strength was higher, while the high temperature strength decreased. This is because excessive Mg competes with Cu to form the AlCuMg phase, reducing the content of the Ω phase. The high-temperature strengthening effect of the AlCuMg phase is weaker than that of the Ω phase, thus reducing the high-temperature performance of the forging. As shown in Example 2 and Comparative Example 32, both room temperature and high temperature strength decreased significantly when the Ag content decreased to 0.4 wt%. The heat resistance of forgings mainly depends on Ag, therefore its content should not be too low. As shown in Example 2 and Comparative Examples 33 and 34, both room temperature and high temperature strength of the forgings were lower when the Mg content was low and the Ag content was high. Increasing both the Mg and Ag contents simultaneously resulted in more ideal room temperature and high temperature strength for the forging. As can be seen from Example 2 and Comparative Examples 35 and 36, the strength of the forgings is low without the addition of Zr and Be. The performance of the alloy is improved when 0.1 wt% Zr is added alone, and the high-temperature performance of the alloy is further improved when 0.13 wt% Be is added. The combined addition of Zr and Be can enable the forgings to obtain ideal room temperature and high-temperature properties.

[0098] The large, high-strength, heat-resistant aluminum alloy wheel forgings obtained by this invention exhibit a room temperature yield strength higher than 450 MPa, a tensile strength higher than 500 MPa, and an elongation higher than 8%. At 150°C, the tensile yield strength is higher than 400 MPa, the tensile strength is higher than 450 MPa, and the elongation is higher than 10%. At 200°C, the tensile yield strength is higher than 350 MPa, the tensile strength is higher than 400 MPa, and the elongation is higher than 12%.

[0099] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a large, high-strength, heat-resistant aluminum alloy wheel hub forging, characterized in that: Includes the following steps: (1) Prepare aluminum alloy round ingots with dimensions of Φ600~Φ1000mm and composition of: Cu 5.0~5.4wt.%, Mg 1.0~1.5wt.%, Ag 0.6~1.0wt.%, Mn 0.5~0.8wt.%, Be 0.1~0.2wt.%, Zr 0.1~0.2wt.%, Si≤0.10wt.%, Fe≤0.10wt.%, with the balance being Al and unavoidable impurities; (2) After homogenization treatment of round ingots at 480±10℃ / 6~10h+510±10℃ / 24h~28h, extrusion billeting and free forging billeting are carried out. The extrusion heating temperature is 400℃~420℃ and the extrusion ratio is controlled at 4~7. The free forging billet heating temperature is 350℃~400℃ and the final forging temperature is not lower than 350℃. (3) After the billet is cut into sections, it is made into a blank. The blank is then isothermally forged according to the actual wheel hub shape. The blank heating temperature is 350℃~400℃, and the final forging temperature of the forging is not lower than 350℃. (4) The hub is solution hardened at a temperature of 510±10℃ and the solution time is determined according to the thickness of the forging section. After solution hardening, it is water-cooled and quenched at room temperature. (5) After quenching, the forging is slowly cooled to -150℃~-200℃ and then cryogenically treated for 2~4h. After being quickly taken out, it is rapidly heated to 175℃±5℃ for aging treatment for 12h~16h.

2. The preparation method according to claim 1, characterized in that: The aluminum alloy round ingot composition in step (1) is: Cu 5.2-5.4 wt.%, Mg 1.1-1.4 wt.%, Ag 0.7-0.9 wt.%, Mn 0.6-0.7 wt.%, Be 0.1-0.2 wt.%, Zr 0.1-0.2 wt.%, Si≤0.10 wt.%, Fe≤0.10 wt.%, with the balance being Al and unavoidable impurities.

3. The preparation method according to claim 1, characterized in that: In step (2), the free forging process involves three forging operations, specifically two upsetting and one drawing.

4. The preparation method according to claim 1, characterized in that: In step (2), the extrusion speed is 10-20 mm / s.

5. The preparation method according to claim 1, characterized in that: The relationship between solution treatment time and forging section thickness in step (4): If the maximum section thickness is D mm, then the solution treatment time is 3D min.

6. The preparation method according to claim 1, characterized in that: In step (5), the cooling rate during the slow cooling process is 2℃~4℃ / min.

7. The preparation method according to claim 1, characterized in that: In step (5), the rapid heating rate is 20℃~30℃ / min.

8. The preparation method according to claim 1, characterized in that: In step (5), the transfer time should be no more than 5 min to 10 min.

9. The preparation method according to claim 1, characterized in that: Used to manufacture large forged wheel hubs with diameter (Φ500~Φ800mm) × depth (200mm~400mm) × outer wall thickness (20mm~50mm).

10. A large, high-strength, heat-resistant aluminum alloy wheel hub, characterized in that: The wheel hub is prepared according to any one of claims 1 to 9; the prepared wheel hub forging has a room temperature yield strength higher than 450 MPa, a tensile strength higher than 500 MPa, and an elongation higher than 8% along the main grain deformation direction; when stretched at 150°C, the yield strength is higher than 400 MPa, the tensile strength is higher than 450 MPa, and the elongation is higher than 10%; when stretched at 200°C, the yield strength is higher than 350 MPa, the tensile strength is higher than 400 MPa, and the elongation is higher than 12%.

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