7-series aluminum alloy forged in short process and application of 7-series aluminum alloy

Abstract

The invention relates to the technical field of aluminum alloy material processing, and discloses a 7-series aluminum alloy subjected to short-process forging processing and application thereof, and the 7-series aluminum alloy comprises the following chemical components in percentage by weight: 7.0%-7.5% of Zn, 2.2%-2.5% of Mg, less than or equal to 0.20% of Fe, 0.3%-0.5% of Cu, 0.3%-0.5% of Mn, 0.1%-0.3% of Cr, 0.1%-0.2% of Zr, 0.05%-0.15% of Y, 0.1%-0.2% of La and the balance of Al. The novel production process of homogenizing, high-temperature forging, product cooling and artificial aging is adopted in 7-series aluminum alloy forging, the process of aluminum bar cooling and reheating after homogenizing in a traditional production process and the processes of extrusion forming, off-line solid solution and temperature rising before product forging are greatly simplified, energy consumption is remarkably reduced, and the production cost is reduced. And the production efficiency is improved. The prepared 7-series aluminum alloy has the characteristic of ultrahigh strength, the strength can be improved by 40% or above, the product weight can be greatly reduced, lightweight design is effectively achieved, and the overall performance of automobile chassis parts is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloy material processing, and in particular to a 7 series aluminum alloy processed by a short-process forging process and applications thereof. Background Art

[0002] With the rapid development of the automotive industry and the increasing demand for lightweight components, aluminum alloys are gaining widespread application in automotive parts due to their advantages, such as lightweight, high strength, and excellent corrosion resistance. In particular, aluminum alloy forgings have gradually replaced traditional steel components in chassis components, such as axles and chassis structures. However, the currently commonly used 6-series aluminum alloy still has certain limitations in meeting the high-strength requirements of modern automotive chassis components.

[0003] The traditional 6-series aluminum alloy chassis components, such as steering knuckles and suspension arms, have a complex production process, typically involving multiple steps, including aluminum bar casting, homogenization, cooling, heating, extrusion, sawing, heating, forging, cooling, offline solutionizing, and artificial aging. This production process is not only time-consuming but also energy-intensive, resulting in high production costs. Furthermore, due to the high solution temperature of 6-series aluminum alloys, problems such as coarse grains and deformation are prone to occur during the forging process, impacting the fatigue resistance and quality of the final product.

[0004] In order to solve the above problems, the industry has been exploring new aluminum alloy materials and forging processes. 7 series aluminum alloy has become a research hotspot due to its ultra-high strength and low quenching sensitivity. However, the 7 series aluminum alloy has poor formability, large springback, and large forming load, making it difficult to obtain complex-shaped structural parts through traditional cold forming processes. Although hot forming processes can improve the forming properties of 7 series aluminum alloys to a certain extent, there are still problems such as complex procedures and high costs. Therefore, it is of great significance to develop a new 7 series aluminum alloy preparation method that can simplify the production process, reduce energy consumption, and improve product quality. Summary of the Invention

[0005] The purpose of the present invention is to provide an ultra-high-strength 7-series aluminum alloy for short-process forging of automobile chassis components and a production process thereof, thereby providing at least a beneficial option or creating conditions for solving one or more technical problems existing in the prior art, such as the complex production process, high energy consumption, high cost and unsatisfactory product quality of automobile chassis components.

[0006] To achieve the above objectives, the present invention adopts the following technical solutions.

[0007] A 7 series aluminum alloy processed by short-process forging has the following chemical composition by weight: Zn 7.0%-7.5%, Mg 2.2%-2.5%, Fe≤0.20%, Cu 0.3%-0.5%, Mn 0.3%-0.5%, Cr 0.1%-0.3%, Zr 0.1%-0.2%, Y 0.05%-0.15%, La 0.1%-0.2%, and the balance is Al.

[0008] The short-process forging process includes the following steps: 1) Homogenization: The aluminum rod is processed in two continuous homogenization furnaces in sequence. The temperature of the first continuous homogenization furnace is set at 440-460℃ and the holding time is 2-3 hours; the temperature of the second continuous homogenization furnace is set at 520-540℃ and the holding time is 1-2 hours; 2) High-temperature forging: Continuous forging is carried out at a temperature of 480-520℃; 3) Product cooling: The forged product is cooled at a cooling rate of ≥100℃ / minute; 4) Aging treatment: The cooled product is sent to a continuous aging furnace for pre-aging treatment at a pre-aging temperature of 80℃-120℃ and a holding time in the furnace of 2 hours-6 hours; the pre-aging product is artificially aged at a temperature of 120℃-150℃ and a holding time of 14 hours-22 hours.

[0009] More preferably, the chemical composition of the 7 series aluminum alloy is as follows by weight: Zn 7.2%, Mg 2.3%, Cu 0.4%, Mn 0.4%, Cr 0.2%, Zr 0.15%, Y 0.1%, La 0.15%, Fe 0.15%, and the balance is Al.

[0010] More preferably, the chemical composition of the 7 series aluminum alloy is as follows by weight: Zn 7.4%, Mg 2.4%, Cu 0.35%, Mn 0.35%, Cr 0.15%, Zr 0.12%, Y 0.08%, La 0.12%, Fe 0.18%, and the balance is Al.

[0011] More preferably, the forging process also includes aluminum rod casting and sawing steps: aluminum alloy raw materials are configured according to the raw material ratio and melt-cast to obtain aluminum rods with a diameter of 50-150 mm and a length of 6000-7000 mm, and then the aluminum rods are sawed into short rods with a length of 200-500 mm.

[0012] More preferably, the flatness of the sawing surface during sawing is ≤0.5 mm.

[0013] More preferably, the forging process further comprises a surface processing step: performing surface CNC processing on the product after aging treatment.

[0014] More preferably, the forging process further comprises a surface treatment step: treating the product surface by adopting an anodic oxidation or coating surface treatment process.

[0015] More preferably, the tensile strength of the 7 series aluminum alloy is ≥600 MPa, and the grain size of all grains after CNC machining on the product surface is between 3-10 μm.

[0016] On the other hand, the present invention also provides the use of the 7 series aluminum alloy processed by the short process forging as described above in the manufacture of automobile chassis parts.

[0017] On the other hand, the present invention also provides the use of the short-process forging 7 series aluminum alloy as described above in automobile chassis security components.

[0018] The present invention adopts the above technical solution to have at least the following beneficial effects.

[0019] 1. The 7 series aluminum alloy forging process of the present invention adopts a new production process of homogenization - high-temperature forging - product cooling - artificial aging, which greatly simplifies the process of cooling and reheating the aluminum rod after homogenization in the traditional production process, as well as the process of extrusion molding, offline solid solution and heating before product forging, significantly reducing energy consumption and improving production efficiency.

[0020] 2. The present invention uses two continuous homogenizing furnaces to set different temperatures for insulation treatment. The first furnace uses 440℃-460℃ for insulation to ensure that the strengthening phase elements inside the material are completely dissolved. The second furnace uses 520℃-540℃ for insulation to ensure that most of the second phase is dissolved into the matrix, which effectively avoids the problems of overburning caused by the second high-temperature homogenization and premature precipitation of the second phase due to excessive temperature loss during the forging process, resulting in a decrease in strength.

[0021] 3. Since the 7 series alloy designed in the present invention has a relatively low quenching sensitivity, the temperature at the time of forging is controlled to be higher than 450°C, which can ensure the strength of the material after artificial aging and significantly improve the fatigue resistance and quality of the product.

[0022] 4. The 7 series aluminum alloy prepared by the present invention has ultra-high strength characteristics, the strength can be increased by more than 40%, and the product weight can be greatly reduced, effectively realizing lightweight design and significantly improving the overall performance of automobile chassis components.

[0023] 5. By utilizing the alloy formula and short-process forging process of the present invention, the comprehensive cost of a single product can be reduced by more than 30% compared with the traditional process, which significantly reduces the production cost and at the same time brings better lightweight effect to the vehicle, with important economic benefits and practical value.

[0024] Some other beneficial effects of the present invention will become more apparent from the following description or will be understood in practice. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0026] A 7-series aluminum alloy processed by a short-process forging process has the following chemical composition by weight: Zn 7.0%-7.5%, Mg 2.2%-2.5%, Fe≤0.20%, Cu 0.3%-0.5%, Mn 0.3%-0.5%, Cr 0.1%-0.3%, Zr 0.1%-0.2%, Y 0.05%-0.15%, La 0.1%-0.2%, and the balance is Al. The addition of Zn, Mg, and Cu primarily enhances alloy strength. The composite addition of Mn, Cr, Y, La, and Zr forms a large number of micron- or submicron-sized second-phase particles, forming heterogeneous nuclei and refining the aluminum alloy grains. Furthermore, these numerous fine, dispersed particles can be evenly distributed in the aluminum matrix, pinning dislocations and effectively hindering grain boundary migration. This stabilizes the aluminum alloy's substructure, inhibiting the growth of recrystallized grains and preventing grain growth during forging that affects performance. At the same time, the Y element can effectively reduce the size of the precipitated phase and increase the density of the precipitated phase, thereby improving the mechanical properties of the material.

[0027] The production process of the 7 series aluminum alloy includes the following steps: 1) aluminum bar casting: aluminum alloy raw materials are configured according to the raw material ratio, and aluminum bars with a diameter of 50-150 mm and a length of 6000-7000 mm are obtained by a conventional aluminum bar casting process; 2) sawing: the aluminum bars are sawn into short bars with a length of 200-500 mm, and the quality of the sawn surface is ensured during sawing; 3) short bar homogenization: the short bars are sequentially processed through two continuous homogenization furnaces, the first furnace is set at a temperature of 440-460°C and the holding time is 2-3 hours to ensure that the strengthening phase elements inside the material are completely dissolved; the second furnace is set at a temperature of 520-540°C and the holding time is 1-2 hours to ensure that most of the second phase is dissolved into the matrix and the deformation resistance during the forging process is reduced; 4) high temperature forging: a hot forging process is adopted and the short bars are continuously processed at a temperature of 480-520°C. Continue forging, and keep the contact tooling of the forging equipment at a high temperature to prevent the material from losing temperature; 5) Product cooling: Place the forged product on a cooling table and use air cooling with a cooling rate of ≥100℃ / minute; 6) Continuous furnace pre-aging: Send the cooled product to a continuous aging furnace for pre-aging treatment. The aging temperature is 80℃-120℃, and the storage time in the furnace is 2 hours-6 hours; 7) Box furnace aging: The pre-aged product is framed and the entire frame is sent to a box-type aging furnace for artificial aging treatment. The aging temperature is 120℃-150℃, and the holding time is 14 hours-22 hours; 8) Surface processing: The surface of the aged product is CNC processed to achieve the product size required by the component; 9) Surface treatment: Use surface treatment processes such as anodizing and coating to improve the corrosion resistance of the product.

[0028] Through the above-mentioned process parameter optimization, the 7-series aluminum alloy prepared by the present invention has the following characteristics: 1) compared with traditional 6-series chassis components, the product strength can be increased by more than 40%, with a tensile strength of ≥600MPa; 2) the product weight can be reduced by more than 30%; 3) after CNC machining on the product surface, the grain size of all grains can be controlled within 3-10μm, and the fatigue resistance is excellent.

[0029] The 7 series aluminum alloy of the present invention can be widely used in automobile chassis parts, such as axles, chassis components and other security parts, and has good practical value and economic benefits. Example 1

[0030] A 7 series aluminum alloy processed by short process forging has the following alloy compositions by weight: Zn 7.2%, Mg 2.3%, Cu 0.4%, Mn 0.4%, Cr 0.2%, Zr 0.15%, Y 0.1%, La 0.15%, Fe 0.15%, and the balance Al.

[0031] The production process of the 7 series aluminum alloy by the above-mentioned short-process forging is as follows: 1) Aluminum bar casting: Aluminum alloy raw materials are configured according to the raw material ratio and cast to obtain aluminum bars with a diameter of 120 mm and a length of 6500 mm.

[0032] 2) Sawing: The aluminum rod obtained in step 1) is sawn into 300 mm short rods, and the flatness of the sawn surface is ≤ 0.5 mm.

[0033] 3) Short rod homogenization: Two-stage homogenization is adopted. The holding temperature of the first continuous homogenizing furnace is 450℃ and the homogenization time is 2.5 hours; the holding temperature of the second continuous homogenizing furnace is 530℃ and the homogenization time is 1.5 hours.

[0034] 4) High temperature forging: Keep the aluminum bar above 500℃ before entering the die forging, preheat the die to 400℃, and control the temperature at 480℃-490℃ after forging.

[0035] 5) Product cooling: After forging is completed, it is air-cooled at a rate of 120°C / minute. After it drops to room temperature, it is immediately transferred to the aging furnace.

[0036] 6) Aging treatment: The cooled product is sent to a continuous aging furnace for pre-aging treatment at an aging temperature of 100°C and a holding time of 4 hours. The pre-aging product is framed and the entire frame is sent to a box-type aging furnace for artificial aging treatment at an aging temperature of 140°C and a holding time of 18 hours.

[0037] 7) Surface treatment: sandblasting anodizing, film thickness 15μm.

[0038] The 7 series aluminum alloy prepared in this embodiment has the following mechanical properties: tensile strength 620 MPa, yield strength 580 MPa, elongation 14%, and grain size 5-8 μm. Example 2

[0039] A 7 series aluminum alloy processed by short process forging has the following alloy compositions by weight: Zn 7.4%, Mg 2.4%, Cu 0.35%, Mn 0.35%, Cr 0.15%, Zr 0.12%, Y 0.08%, La 0.12%, Fe 0.18%, and the balance Al.

[0040] The production process of the 7 series aluminum alloy by the above-mentioned short-process forging is as follows: 1) Aluminum bar casting: Aluminum alloy raw materials are configured according to the raw material ratio and cast to obtain aluminum bars with a diameter of 80 mm and a length of 7000 mm.

[0041] 2) Sawing: The aluminum rod obtained in step 1) is sawn into 250 mm short rods, and the flatness of the sawn surface is ≤ 0.5 mm.

[0042] 3) Short rod homogenization: Two-stage homogenization is adopted. The holding temperature of the first continuous homogenizing furnace is 445℃ and the homogenization time is 3.0 hours; the holding temperature of the second continuous homogenizing furnace is 525℃ and the homogenization time is 2.0 hours.

[0043] 4) High temperature forging: Keep the aluminum bar above 500℃ before entering the die forging, preheat the die to 400℃, and control the temperature at 480℃-490℃ after forging.

[0044] 5) Product cooling: After forging is completed, it is air-cooled at a rate of 120°C / minute. After it drops to room temperature, it is immediately transferred to the aging furnace.

[0045] 6) Aging treatment: The cooled product is sent to a continuous aging furnace for pre-aging treatment at an aging temperature of 85°C and a holding time of 6 hours. The pre-aging product is framed and the entire frame is sent to a box-type aging furnace for artificial aging treatment at an aging temperature of 130°C and a holding time of 22 hours.

[0046] 7) Surface treatment: sandblasting anodizing, film thickness 15μm.

[0047] The 7 series aluminum alloy prepared in this embodiment has the following mechanical properties: tensile strength 635 MPa, yield strength 595 MPa, elongation 13%, and grain size 4-7 μm. Example 3

[0048] A 7 series aluminum alloy processed by short process forging has the following alloy compositions by weight: Zn 7.0%, Mg 2.2%, Cu 0.5%, Mn 0.5%, Cr 0.3%, Zr 0.2%, Y 0.15%, La 0.2%, Fe 0.12%, and the balance Al.

[0049] The production process of the 7 series aluminum alloy by the above-mentioned short-process forging is as follows: 1) Aluminum bar casting: Aluminum alloy raw materials are configured according to the raw material ratio and cast to obtain aluminum bars with a diameter of 60 mm and a length of 6000 mm.

[0050] 2) Sawing: The aluminum rod obtained in step 1) is sawn into 500 mm short rods, and the flatness of the sawn surface is ≤ 0.5 mm.

[0051] 3) Short rod homogenization: Two-stage homogenization is adopted. The holding temperature of the first continuous homogenizing furnace is 460℃ and the homogenization time is 2.0 hours; the holding temperature of the second continuous homogenizing furnace is 540℃ and the homogenization time is 1.0 hour.

[0052] 4) High temperature forging: Keep the aluminum bar above 500℃ before entering the die forging, preheat the die to 400℃, and control the temperature at 480℃-490℃ after forging.

[0053] 5) Product cooling: After forging is completed, it is air-cooled at a rate of 120°C / minute. After it drops to room temperature, it is immediately transferred to the aging furnace.

[0054] 6) Aging treatment: The cooled product is sent to a continuous aging furnace for pre-aging treatment at an aging temperature of 120°C and a holding time of 2 hours. The pre-aging product is framed and the entire frame is sent to a box-type aging furnace for artificial aging treatment at an aging temperature of 150°C and a holding time of 14 hours.

[0055] 7) Surface treatment: Sandblasting anodizing film, film thickness 15μm.

[0056] The 7 series aluminum alloy prepared in this embodiment has the following mechanical properties: tensile strength 650 MPa, yield strength 610 MPa, elongation 12%, and grain size 3-6 μm.

[0057] Comparative Example 1.

[0058] A 7 series aluminum alloy processed by short process forging has the following alloy compositions by weight: Zn 7.2%, Mg 2.3%, Cu 0.4%, Mn 0.4%, Cr 0.2%, Zr 0.15%, Y 0.1%, La 0.15%, Fe 0.15%, and the balance Al.

[0059] The production process of the 7 series aluminum alloy by the above-mentioned short-process forging is as follows: 1) Aluminum bar casting: Aluminum alloy raw materials are configured according to the raw material ratio and cast to obtain aluminum bars with a diameter of 120 mm and a length of 6500 mm.

[0060] 2) Sawing: The aluminum rod obtained in step 1) is sawn into 300 mm short rods, and the flatness of the sawn surface is ≤ 0.5 mm.

[0061] 3) Short rod homogenization: The holding temperature of the continuous homogenizing furnace is 530℃ and the homogenization time is 1.5 hours.

[0062] 4) High temperature forging: Keep the aluminum bar above 500℃ before entering the die forging, preheat the die to 400℃, and control the temperature at 480℃-490℃ after forging.

[0063] 5) Product cooling: After forging is completed, it is air-cooled at a rate of 120°C / minute. After it drops to room temperature, it is immediately transferred to the aging furnace.

[0064] 6) Aging treatment: The cooled product is sent to a continuous aging furnace for pre-aging treatment at an aging temperature of 100°C and a holding time of 4 hours. The pre-aging product is framed and the entire frame is sent to a box-type aging furnace for artificial aging treatment at an aging temperature of 140°C and a holding time of 18 hours.

[0065] 7) Surface treatment: sandblasting anodizing, film thickness 15μm.

[0066] The 7 series aluminum alloy prepared in this comparative example has the following mechanical properties: tensile strength 580 MPa, yield strength 550 MPa, elongation 7%, and grain size 5-8 μm.

[0067] This comparative example shows that the lack of a first-stage low-temperature aging process will lead to a decrease in mechanical properties, which may be due to internal overburning.

[0068] Comparative Example 2.

[0069] A 7 series aluminum alloy processed by short process forging has the following alloy compositions by weight: Zn 7.2%, Mg 2.3%, Cu 0.4%, Mn 0.4%, Cr 0.2%, Zr 0.15%, Y 0.1%, La 0.15%, Fe 0.15%, and the balance Al.

[0070] The production process of the 7 series aluminum alloy by the above-mentioned short-process forging is as follows: 1) Aluminum bar casting: Aluminum alloy raw materials are configured according to the raw material ratio and cast to obtain aluminum bars with a diameter of 120 mm and a length of 6500 mm.

[0071] 2) Sawing: The aluminum rod obtained in step 1) is sawn into 300 mm short rods, and the flatness of the sawn surface is ≤ 0.5 mm.

[0072] 3) Short rod homogenization: The holding temperature of the continuous homogenizing furnace is 450℃ and the homogenization time is 2.5 hours.

[0073] 4) High temperature forging: Keep the aluminum bar above 500℃ before entering the die forging, preheat the die to 400℃, and control the temperature at 480℃-490℃ after forging.

[0074] 5) Product cooling: After forging is completed, it is air-cooled at a rate of 120°C / minute. After it drops to room temperature, it is immediately transferred to the aging furnace.

[0075] 6) Aging treatment: The cooled product is sent to a continuous aging furnace for pre-aging treatment at an aging temperature of 100°C and a holding time of 4 hours. The pre-aging product is framed and the entire frame is sent to a box-type aging furnace for artificial aging treatment at an aging temperature of 140°C and a holding time of 18 hours.

[0076] 7) Surface treatment: sandblasting anodizing, film thickness 15μm.

[0077] The 7 series aluminum alloy prepared in this comparative example has the following mechanical properties: tensile strength 550 MPa, yield strength 500 MPa, elongation 12%, and grain size 4-8 μm.

[0078] This comparative example shows that the lack of homogenization in the high-temperature section will lead to a decrease in mechanical properties. This may be because the lack of homogenization in the high-temperature section leads to segregation in the forging temperature, and the precipitation of strengthening phase elements during the forging process affects the solid solution effect.

[0079] Comparative Example 3.

[0080] A 7 series aluminum alloy processed by short process forging has the following alloy compositions by weight: Zn 7.2%, Mg 2.3%, Cu 0.4%, Mn 0.4%, Cr 0.2%, Zr 0.15%, Y 0.1%, La 0.15%, Fe 0.15%, and the balance Al.

[0081] The production process of the 7 series aluminum alloy by the above-mentioned short-process forging is as follows: 1) Aluminum bar casting: Aluminum alloy raw materials are configured according to the raw material ratio and cast to obtain aluminum bars with a diameter of 120 mm and a length of 6500 mm.

[0082] 2) Sawing: The aluminum rod obtained in step 1) is sawn into 300 mm short rods, and the flatness of the sawn surface is ≤ 0.5 mm.

[0083] 3) Short rod homogenization: Two-stage homogenization is adopted. The holding temperature of the first continuous homogenizing furnace is 450℃ and the homogenization time is 2.5 hours; the holding temperature of the second continuous homogenizing furnace is 530℃ and the homogenization time is 1.5 hours.

[0084] 4) High temperature forging: Keep the aluminum bar above 500℃ before entering the die forging, preheat the die to 350℃, and control the temperature at 430℃-450℃ after forging.

[0085] 5) Product cooling: After forging is completed, it is air-cooled at a rate of 120°C / minute. After it drops to room temperature, it is immediately transferred to the aging furnace.

[0086] 6) Aging treatment: The cooled product is sent to a continuous aging furnace for pre-aging treatment at an aging temperature of 100°C and a holding time of 4 hours. The pre-aging product is framed and the entire frame is sent to a box-type aging furnace for artificial aging treatment at an aging temperature of 140°C and a holding time of 18 hours.

[0087] 7) Surface treatment: sandblasting anodizing, film thickness 15μm.

[0088] The 7 series aluminum alloy prepared in this embodiment has the following mechanical properties: tensile strength 590 MPa, yield strength 540 MPa, elongation 15%, and grain size 5-8 μm.

[0089] This comparative example shows that lowering the preheating temperature of the forging die will lead to a decrease in product strength. This may be because lowering the preheating temperature of the forging die will lead to a drop in temperature after forging, resulting in a decrease in the solid solution effect and affecting the subsequent product strength.

[0090] Comparative Example 4.

[0091] A 7 series aluminum alloy processed by short process forging has the following alloy compositions by weight: Zn 7.2%, Mg 2.3%, Cu 0.4%, Mn 0.2%, Y 0.3%, La 0.3%, Fe 0.15%, and the balance Al.

[0092] The production process of the 7 series aluminum alloy by the above-mentioned short-process forging is as follows: 1) Aluminum bar casting: Aluminum alloy raw materials are configured according to the raw material ratio and cast to obtain aluminum bars with a diameter of 120 mm and a length of 6500 mm.

[0093] 2) Sawing: The aluminum rod obtained in step 1) is sawn into 300 mm short rods, and the flatness of the sawn surface is ≤ 0.5 mm.

[0094] 3) Short rod homogenization: Two-stage homogenization is adopted. The holding temperature of the first continuous homogenizing furnace is 450℃ and the homogenization time is 2.5 hours; the holding temperature of the second continuous homogenizing furnace is 530℃ and the homogenization time is 1.5 hours.

[0095] 4) High temperature forging: Keep the aluminum bar above 500℃ before entering the die forging, preheat the die to 400℃, and control the temperature at 480℃-490℃ after forging.

[0096] 5) Product cooling: After forging is completed, it is air-cooled at a rate of 120°C / minute. After it drops to room temperature, it is immediately transferred to the aging furnace.

[0097] 6) Aging treatment: The cooled product is sent to a continuous aging furnace for pre-aging treatment at an aging temperature of 100°C and a holding time of 4 hours. The pre-aging product is framed and the entire frame is sent to a box-type aging furnace for artificial aging treatment at an aging temperature of 140°C and a holding time of 18 hours.

[0098] 7) Surface treatment: sandblasting anodizing, film thickness 15μm.

[0099] The 7 series aluminum alloy prepared in this embodiment has the following mechanical properties: tensile strength 580 MPa, yield strength 540 MPa, elongation 10%, and grain size 13-20 μm.

[0100] This comparative example shows that reducing the Mn content and removing the Cr and Zr elements results in decreased mechanical properties and elongation, and increased grain size. This is likely due to the high-temperature forging process, which can lead to grain growth and reduced mechanical properties and elongation.

[0101] Comparative Example 5.

[0102] A 7 series aluminum alloy processed by short process forging has the following alloy compositions by weight: Zn 7.2%, Mg 2.3%, Cu 0.4%, Mn 0.4%, Cr 0.3%, Zr 0.3%, Fe 0.15%, and the balance Al.

[0103] The production process of the 7 series aluminum alloy by the above-mentioned short-process forging is as follows: 1) Aluminum bar casting: Aluminum alloy raw materials are configured according to the raw material ratio and cast to obtain aluminum bars with a diameter of 120 mm and a length of 6500 mm.

[0104] 2) Sawing: The aluminum rod obtained in step 1) is sawn into 300 mm short rods, and the flatness of the sawn surface is ≤ 0.5 mm.

[0105] 3) Short rod homogenization: Two-stage homogenization is adopted. The holding temperature of the first continuous homogenizing furnace is 450℃ and the homogenization time is 2.5 hours; the holding temperature of the second continuous homogenizing furnace is 530℃ and the homogenization time is 1.5 hours.

[0106] 4) High temperature forging: Keep the aluminum bar above 500℃ before entering the die forging, preheat the die to 400℃, and control the temperature at 480℃-490℃ after forging.

[0107] 5) Product cooling: After forging is completed, it is air-cooled at a rate of 120°C / minute. After it drops to room temperature, it is immediately transferred to the aging furnace.

[0108] 6) Aging treatment: The cooled product is sent to a continuous aging furnace for pre-aging treatment at an aging temperature of 100°C and a holding time of 4 hours. The pre-aging product is framed and the entire frame is sent to a box-type aging furnace for artificial aging treatment at an aging temperature of 140°C and a holding time of 18 hours.

[0109] 7) Surface treatment: sandblasting anodizing, film thickness 15μm.

[0110] The 7 series aluminum alloy prepared in this embodiment has the following mechanical properties: tensile strength 560 MPa, yield strength 520 MPa, elongation 12%, and grain size 11-16 μm.

[0111] This comparative example shows that omitting the addition of Y and La significantly reduces the material's strength after aging and increases the grain size. This is likely because omitting the addition of Y and La results in poor grain refinement and a decrease in the density of aging precipitates, significantly reducing the material's strength after aging.

[0112] It should be noted that the various technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the various technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0113] The above embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art could make numerous modifications and improvements without departing from the scope of the present invention, all of which fall within the scope of protection of the present invention. Any portions not described in the specific embodiments represent prior art or common knowledge.

[0114] It should also be noted that, in the description of the present invention, the detailed description of the preferred embodiment of the present invention and the included embodiments can more easily understand the content of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those of ordinary skill in the art to which the present invention belongs. In the event of a conflict, the definitions in this specification shall prevail.

[0115] As used herein, the term "prepared from" is used synonymously with "comprising." As used herein, the terms "comprising," "including," "having," "containing," or any other variations thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0116] In the present invention, when amount, concentration or other value or parameter is expressed as a range, preferred range or a series of upper preferred values ​​and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, regardless of whether the range is disclosed separately. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted as including a range of "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5" etc. When a numerical range is described in the present invention, unless otherwise stated, the range is intended to include its end value and all integers and fractions within the range.

[0117] In addition, the indefinite articles "a" and "an" before the elements or components of the present invention do not limit the quantity requirements (i.e., the number of occurrences) of the elements or components. Therefore, "a" or "an" should be interpreted as including one or at least one, and elements or components in the singular also include plural forms, unless the number clearly refers to the singular form.

Claims

1. A 7 series aluminum alloy processed by short process forging, characterized in that: The chemical composition of the 7 series aluminum alloy is as follows by weight: Zn 7.0%-7.5%, Mg 2.2%-2.5%, Fe≤0.20%, Cu 0.3%-0.5%, Mn 0.3%-0.5%, Cr0.1%-0.3%, Zr 0.1%-0.2%, Y 0.05%-0.15%, La 0.1%-0.2%, and the balance is Al; The forging process includes the following steps: 1) Homogenization: The aluminum bars are processed in two continuous homogenization furnaces in sequence. The temperature of the first continuous homogenization furnace is set at 440-460℃ and the holding time is 2-3 hours; the temperature of the second continuous homogenization furnace is set at 520-540℃ and the holding time is 1-2 hours. 2) High-temperature forging: Continuous forging is carried out at a temperature of 480-520℃. 3) Product cooling: The forged products are cooled at a cooling rate of ≥100℃ / minute. 4) Aging treatment: The cooled products are sent to a continuous aging furnace for pre-aging treatment at a pre-aging temperature of 80℃-120℃ and a holding time in the furnace of 2 hours-6 hours. The pre-aging products are then artificially aged at a temperature of 120℃-150℃ and a holding time of 14 hours-22 hours.

2. The 7 series aluminum alloy processed by short process forging according to claim 1, characterized in that: The chemical composition of the 7 series aluminum alloy is as follows by weight: Zn 7.2%, Mg 2.3%, Cu 0.4%, Mn 0.4%, Cr 0.2%, Zr 0.15%, Y 0.1%, La 0.15%, Fe 0.15%, and the balance is Al.

3. The 7 series aluminum alloy processed by short process forging according to claim 1, characterized in that: The chemical composition of the 7 series aluminum alloy is as follows by weight: Zn 7.4%, Mg 2.4%, Cu 0.35%, Mn 0.35%, Cr 0.15%, Zr 0.12%, Y 0.08%, La 0.12%, Fe 0.18%, and the balance is Al.

4. The 7 series aluminum alloy processed by short process forging according to claim 1, characterized in that: The forging process also includes aluminum rod casting and sawing steps: aluminum alloy raw materials are prepared according to the raw material ratio and melt-cast to obtain aluminum rods with a diameter of 50-150 mm and a length of 6000-7000 mm, and then the aluminum rods are sawed into short rods with a length of 200-500 mm.

5. The 7 series aluminum alloy processed by short process forging according to claim 4, characterized in that: The flatness of the sawing surface during sawing is ≤0.5mm.

6. The 7 series aluminum alloy processed by short process forging according to claim 1, characterized in that: The forging process also includes a surface processing step: performing CNC processing on the surface of the product after aging treatment.

7. The 7 series aluminum alloy processed by short process forging according to claim 1, characterized in that: The forging process also includes a surface treatment step: treating the product surface by adopting an anodic oxidation or coating surface treatment process.

8. The 7 series aluminum alloy processed by short process forging according to claim 1, characterized in that: The tensile strength of the 7 series aluminum alloy is ≥600 MPa, and the grain size of all grains on the product surface after CNC processing is between 3-10 μm.

9. Use of the 7 series aluminum alloy processed by short-process forging according to any one of claims 1 to 8 in the manufacture of automobile chassis parts.

10. Use of the 7 series aluminum alloy processed by short-process forging as claimed in any one of claims 1 to 8 in automobile chassis security parts.