A method of producing a 6xxx aluminum alloy automotive forging

Abstract

The application relates to a production method of a 6xxx aluminum alloy vehicle forging, belonging to the field of aluminum alloy material processing, and the production process is as follows: smelting, casting, extruding special-shaped rods, homogenizing heat treatment, sawing and forging, solid solution treatment and aging treatment; the biggest difference between the method and a traditional production process is that the order of extruding and homogenizing heat treatment is different; the preparation process of a forging blank is different; meanwhile, the method is suitable for the production of all 6xxx aluminum alloy vehicle forgings; the application further provides a high-strength and high-toughness 6xxx aluminum alloy material, and the alloy components are as follows: (0.9-1.1 wt.%) Mg, (1.1-1.3 wt.%) Si, (0.5-0.7 wt.%) Cu, (0.5-0.7 wt.%) Mn, (0.1-0.3 wt.%) Cr, (less than 0.5 wt.%) Fe, and the balance is composed of Al and inevitable impurity elements.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy material processing, and specifically relates to a method for producing 6xxx aluminum alloy automotive forgings. Background Technology

[0002] The largest application market for aluminum alloy forgings is in automotive chassis components, including critical safety parts such as control arms, steering knuckles, subframes, and connecting rods. Since the automotive chassis serves as the assembly that supports and mounts various vehicle components, chassis parts are essential structural safety components, requiring good strength, rigidity, fatigue resistance, and overall performance. Currently, aluminum alloy forgings for automotive applications are mostly made from 6082 or 6061 aluminum alloys, and their manufacturing process is as follows: Figure 1 As shown. The aluminum alloy automotive forgings prepared using this process currently face the following problems: ① Low material performance. With the increasing demands for lightweight automobiles, the performance of existing aluminum alloy materials, such as 6061 or 6082 aluminum alloys, cannot meet the requirements. Furthermore, the service requirements necessitate an Fe content of less than 0.15 wt.%, leading to increased material costs and limiting the use of recycled aluminum; ② Prone to coarse grains and low fatigue resistance. Under the existing process, the alloy accumulates a large amount of deformation energy after extrusion. During subsequent forging, some parts of the components further store deformation energy. Therefore, during alloy solution treatment, this accumulated deformation energy becomes the driving force for recrystallization and coarse recrystallization, resulting in coarse grain structures in the final forging microstructure. These coarse grain structures can lead to fatigue fracture during the service life of automotive forgings, posing a safety hazard; ③ Long process flow and high cost. In the preparation of automotive forgings, the homogenization process is the most time-consuming and energy-intensive, resulting in high equipment occupancy. Additionally, the forging blank preparation process mainly involves roll forging, bending, and preforming, which are lengthy and complex, requiring significant manpower and resources.

[0003] Currently, some companies have their own solutions to the problems mentioned above.

[0004] (1) Addressing the issue of low material performance. The commonly used 6082 and 6061 aluminum alloys have relatively low performance. Some companies have developed many high-strength and high-toughness aluminum alloys, such as Kobe Steel [US 8372220], Kenlun Aluminium [WO2016071257A1], and Aluminum Corporation of China [CN102337434B]. These alloys can achieve a yield strength greater than 380 MPa and an elongation greater than 10%. They all employ the following alloying strategy: increasing the Mg and Si content and adding Cu to change the type and quantity of strengthening phases, while simultaneously increasing the Mn and Cr content to increase the number of dispersed phases and effectively suppress coarse recrystallization. However, there are no reports on alloying strategies related to the tolerance of Fe element in aluminum alloy automotive forgings using recycled aluminum.

[0005] (2) Regarding the problem of coarse grain formation and low fatigue resistance: To effectively suppress coarse grain formation, the main method is to perform high-temperature, long-term heating before forging to effectively eliminate the deformation energy stored during the extrusion process. The main problem with this method is that it increases equipment downtime and consumes more energy.

[0006] (3) Regarding the issues of long process flow and high cost. This is currently the biggest problem facing aluminum alloy automotive forgings, which greatly limits their application range and can only be used in high-end models. To solve this problem, some companies have eliminated the extrusion process and adopted direct forging from cast ingots. However, this process requires a large amount of deformation to eliminate the casting structure, making the blank preparation process more complicated. In addition, the performance of forgings obtained by direct forging from cast ingots is lower than that of forgings obtained by traditional processes. Therefore, this process often uses highly alloyed 6xxx aluminum alloys. Summary of the Invention

[0007] To address the aforementioned problems, one objective of this invention is to provide a method for producing 6xxx aluminum alloy automotive forgings. A key feature of this method is its applicability to the production of all 6xxx aluminum alloy automotive forgings, wherein "all 6xxx aluminum alloys" include conventional 6xxx aluminum alloy materials, high-strength and high-toughness 6xxx aluminum alloy materials, and 6xxx aluminum alloy materials with high Fe content tolerance.

[0008] Another object of the present invention is to provide a method for producing 6xxx aluminum alloy automotive forgings with high Fe content tolerance.

[0009] The high-strength and high-toughness 6xxx aluminum alloy material described above has the following properties: yield strength greater than 400MPa, elongation greater than 10%, and fatigue strength greater than 140MPa.

[0010] The high-strength and high-toughness 6xxx aluminum alloy material has the following specific alloy composition: (0.9–1.1 wt.%) Mg, (1.1–1.3 wt.%) Si, (0.5–0.7 wt.%) Cu, (0.5–0.7 wt%) Mn, (0.1–0.3 wt%) Cr, (less than 0.5 wt%) Fe, with the balance consisting of Al and unavoidable impurity elements. It also satisfies the condition Cu(wt.%) - [Si(wt.%) - Mg(wt.%)] = 0.4 wt.%.

[0011] Mg, Si, and Cu elements are primarily used to form nano-strengthening phases during the aging process. The strength design of 6xxx aluminum alloys is based on controlling the content and ratio of Mg and Si to maximize the amount of the Mg2Si phase. Specifically, a Mg / Si atomic ratio of 2 (mass ratio of 1.73) maximizes the Mg2Si content. However, the β” phase precipitated during aging does not follow this ratio. To maximize the amount of strengthening phases, Si is usually used in excess to achieve higher strength. Additionally, adding Cu to 6xxx aluminum alloys can form the Q phase with Mg and Si, as seen in 6061 aluminum alloys. This changes the type of strengthening phase from Mg2Si to a combination of Mg2Si and Q phases, thereby increasing the alloy strength. Therefore, Mg, Si, and Cu are typically used as the main alloying elements to achieve higher strength in 6xxx aluminum alloys, and higher content generally results in higher strength. However, due to limitations in the solid solubility of alloying elements... Excessive alloy element content can lead to the formation of excessive coarse second phases at grain boundaries, reducing the material's toughness and fatigue resistance. This invention proposes an alloy composition of (0.9–1.1 wt.%) Mg, (1.1–1.3 wt.%) Si, and (0.5–0.7 wt.%) Cu, while simultaneously satisfying Cu(wt.%) - [Si(wt.%) - Mg(wt.%)] = 0.4 wt.%. Under this alloy composition, the strengthening phases are a large amount of Q phase and a small amount of Mg₂Si, and these are present in the largest quantities, resulting in the optimal alloy performance.

[0012] Mn and Cr are primarily used as submicron dispersed phases during homogenization. Mn, Cr, Al, Fe, and Si mainly form α-Al(FeMn)Si and Cr-containing phases during homogenization. These phases effectively pin dislocations during subsequent alloy deformation, inhibiting recrystallization and coarse recrystallization; the higher their content, the better the dislocation pinning effect. However, due to the limitations of solid solubility of alloying elements, excessively high content can lead to the formation of excessive coarse second phases at grain boundaries, reducing the material's toughness and fatigue resistance. This invention proposes a Mn content of (0.5–0.7 wt%) Mn and (0.1–0.3 wt%) Cr. With this alloy composition, the number of dispersed phases obtained after homogenization is maximized, resulting in a high proportion of subgrains and no coarse grains in the product.

[0013] A short-process production method for 6xxx aluminum alloy automotive forgings specifically includes the following steps: melting, casting, extrusion of shaped bars, homogenization heat treatment, sawing and forging, solution treatment and aging treatment, etc. Figure 2 As shown. Specifically includes:

[0014] a. smelting

[0015] The raw materials are melted into an alloy liquid, refined in a furnace, and then left to stand.

[0016] b. Casting

[0017] Using conventional ladle refining and filtration methods, the treated molten alloy is poured into the runner and then refined in an external degassing box before filtration. The alloy is then cast using conventional semi-continuous casting methods, employing techniques such as DC casting or electromagnetic casting to produce round casting bars.

[0018] c. Extruded profiled rods

[0019] The method for producing aluminum alloy automotive forgings of this invention has certain differences in extrusion process parameters compared to conventional 6xxx aluminum alloys, specifically as follows: ① Extrusion method. Both forward and reverse extrusion can be used, with reverse extrusion being preferred. This is because forward extrusion results in greater shear deformation on the surface, easily producing coarse grains. Furthermore, the irregularly shaped extruded bars provided by this invention cannot be peeled off, so these coarse grains must be pushed into the flash during forging, leading to low material utilization. Reverse extrusion, on the other hand, results in uniform internal and external deformation during the extrusion process, minimizing the problem of coarse grains on the surface, thus making it the preferred method. ② Extrusion ratio: The method of this invention requires a relatively large and moderate extrusion ratio, ideally between 30 and 70. If the extrusion ratio is too small, the second phase at the grain boundaries will not be sufficiently broken down, resulting in coarse second phases in the forging and reducing the toughness and fatigue resistance of the forging. If the extrusion ratio is too large, the deformation energy stored in the material during extrusion will be too large, leading to excessively large recrystallized grains after homogenization, resulting in a coarse forging structure and reducing the toughness and fatigue resistance of the forging. ③ Extrusion process. Traditional extrusion processes for 6xxx aluminum alloys used in automobiles require high-temperature (above 500℃) and medium-speed (2-3 mm / s) online water quenching. The purpose is to ensure the extrusion temperature is as close as possible to the alloy's solid solution line to achieve maximum elemental solidification. Water quenching also ensures no strengthening phase precipitation occurs during cooling. The starting point of this invention differs from the traditional approach, primarily aiming to obtain irregular cross-sections and, after subsequent homogenization heat treatment, to produce forged billets with finer fibrous or recrystallized structures. Therefore, the extrusion process employed in this invention is as follows: extrusion temperature 400-480℃, extrusion speed 3.5-6 mm / s, extrusion ratio 30-70, and online air or water quenching. This is because excessively high extrusion temperatures and speeds would lead to dynamic recrystallization, resulting in coarser structures. Furthermore, excessively low rheological stress in the aluminum matrix would prevent the hard particles of the second phase from easily breaking down and flowing with the matrix. If the extrusion temperature is too low, the extrusion bar will have too much deformation energy stored in it, which will lead to coarse recrystallization (secondary recrystallization) during the subsequent homogenization process, resulting in coarse grains.

[0020] d. Homogenization heat treatment

[0021] The purpose of homogenization heat treatment is to reduce microsegregation, minimize or eliminate the second phase at grain boundaries, and control the precipitation of dispersed phases. This invention provides two homogenization heat treatment processes.

[0022] Homogenization heat treatment process - 1. A three-step process of heating-isothermal-cooling is adopted. This process is mainly used in this field for 6xxx aluminum alloys that do not contain Mn, and is a conventional method in this field. However, the homogenization heat treatment method for producing aluminum alloy automotive forgings based on this invention differs significantly from the traditional method. This is mainly because the traditional process is based on the as-cast structure, while the process of this invention is based on the extruded structure. Therefore, for the three-step process of heating-holding-cooling, this invention requires a shorter homogenization time, but the cooling rate needs to be faster. Specifically, the temperature is raised to 550-570°C at a rate of 1-5°C / min, held for 4-6 hours, cooled to 350°C at a rate of not less than 8°C / min, and then cooled to room temperature at a rate of not less than 4°C / min. The reason for this is that after extrusion, the grain and second phase sizes become smaller, and the element diffusion time is shortened. Therefore, the homogenization holding time is shorter than that of the traditional process. At the same time, the homogenized material is directly used as the forging blank. Therefore, it is necessary to ensure that the second phase at the grain boundaries in the blank is as small as possible. Thus, a high cooling rate must be used above 350°C during the cooling process to ensure that the second phase (Mg2Si phase or Q phase) precipitates little or no at the grain boundaries.

[0023] Homogenization Heat Treatment Process - 2. A two-stage homogenization heat treatment process is adopted, namely, five steps: heating-low temperature isothermal-heating-high temperature isothermal-cooling. This process is suitable for 6xxx aluminum alloys containing Mn. For 6xxx aluminum alloys containing Mn, a low temperature treatment stage is added. The purpose is as follows: Mn is added to 6xxx aluminum alloys to precipitate the α-Al(FeMn)Si phase during the homogenization process. The formation of this phase is a nucleation and growth process. That is, during the homogenization heating process, the transition phase u nucleates on the β' phase, and the u phase is rich in Mn and Cr elements. Then, the α dispersed phase heterogeneously nucleates on the u phase. Therefore, it is necessary to increase the amount of β' phase to achieve the increase of α dispersed phase. Therefore, this invention adds a low temperature isothermal stage to precipitate a large amount of β' phase. The two-stage homogenization heat treatment process proposed in this invention is as follows: heating to 300-355°C at a rate not exceeding 3°C / min, holding at that temperature for 6-8 hours, heating to 550-570°C at a rate not exceeding 3°C / min, holding at that temperature for 4-6 hours, cooling to 350°C at a rate not less than 8°C / min, and then cooling to room temperature at a rate not less than 4°C / min.

[0024] e. Sawing and Forging

[0025] The extruded bar after homogenization heat treatment is sliced ​​along the extrusion direction, and the slice thickness meets the forging requirements.

[0026] f. Solution treatment and aging treatment

[0027] The forgings were subjected to T6 heat treatment using a solution treatment and aging process.

[0028] The production process for aluminum alloy automotive forgings provided by this invention differs significantly from traditional processes in that: ① the order of extrusion and homogenization heat treatment is different. Traditional processes involve homogenization heat treatment followed by extrusion into round bars to provide billets for subsequent processing. However, because the material stores a large amount of deformation energy during extrusion, this energy further accumulates during subsequent forging, leading to coarse grains during solution heat treatment and a significant reduction in fatigue resistance. Therefore, high-temperature, long-duration annealing is typically required before forging. This results in high-temperature, long-duration heating before and after extrusion, leading to high equipment occupancy, high energy consumption, and high costs. This invention reverses the extrusion and homogenization heat treatment processes, which has the advantage of reducing the second phase (such as...) at the grain boundaries in the ingot during extrusion. Figure 3 As shown, it is broken under high temperature and high pressure, and its size is significantly reduced (e.g.) Figure 4 As shown), the time required for subsequent homogenization heat treatment is also significantly reduced (e.g. Figure 5 (As shown), and it does not require high-temperature, long-duration annealing before forging, significantly reducing energy consumption and costs in the production process. ② The preparation process of the forging blank is different. Aluminum alloy automotive forgings are usually more complex in shape, such as... Figure 6 As shown. Traditional forging blank preparation mainly involves steps such as roll forging, bending, and pre-forming, which are lengthy, complex, and labor-intensive. This invention provides a method for preparing forging blanks, specifically as follows: extruding the blank into a profile, and then slicing it (e.g....) Figure 7 As shown), directly precision forged into automotive forgings (such as...). Figure 8 (As shown).

[0029] In summary, the production method for aluminum alloy automotive forgings provided by this invention has advantages such as short process, energy efficiency, low cost, and high cost.

[0030] This invention also provides a method for producing high Fe-tolerance 6xxx aluminum alloy automotive forgings.

[0031] The alloys used in aluminum alloy automotive forgings have strict requirements for Fe content, typically less than 0.15 wt.%. This is because an increase in Fe content results in a large number of coarse Fe-containing second phases at the grain boundaries of the forgings, severely reducing their toughness and fatigue resistance. Under these conditions, the types and proportions of recycled aluminum used in the production process are limited, leading to increased material costs and carbon emissions for automotive forgings. The automotive forging production method provided by this invention can effectively accommodate 6xxx aluminum alloys with high Fe content, specifically as follows: Direct extrusion of the cast ingot, using a relatively large extrusion ratio (30-70), allows the Fe-containing second phase at the grain boundaries in the cast ingot to be broken and dispersed under high temperature and high pressure. During the subsequent homogenization heat treatment, the broken second phase dissolves and spheroidizes, resulting in fine and uniform second phases in the final forging, minimizing the loss of toughness and fatigue resistance.

[0032] The beneficial effects of this invention are:

[0033] This invention provides a high-strength and high-toughness 6xxx aluminum alloy material with a yield strength greater than 400 MPa, elongation greater than 10%, and fatigue strength greater than 140 MPa, suitable for hot working methods such as forging and extrusion. This invention also provides a method for producing aluminum alloy automotive forgings and a method adapted for producing 6xxx aluminum alloy forgings with high Fe content. The method for producing aluminum alloy automotive forgings provided by this invention has advantages such as short process, energy efficiency, low cost, and effective compatibility with 6xxx aluminum alloys with high Fe content. Attached Figure Description

[0034] Figure 1 Traditional aluminum alloy automotive forging production process;

[0035] Figure 2 The production process of aluminum alloy automotive forgings according to the present invention;

[0036] Figure 3 The microstructure of the alloy casting rod proposed in this invention;

[0037] Figure 4 The microstructure of the alloy after extrusion proposed in this invention;

[0038] Figure 5 The microstructure of the alloy after homogenization proposed in this invention;

[0039] Figure 6 Aluminum alloy automotive control arm forgings;

[0040] Figure 7 The extruded blank provided by this invention;

[0041] Figure 8 The aluminum alloy automotive forgings prepared by the process provided by this invention. Detailed Implementation

[0042] The following is a detailed description of a high-strength and high-toughness 6xxx aluminum alloy material and a method for producing 6xxx aluminum alloy automotive forgings according to the present invention.

[0043] An alloying method for a high-strength and high-toughness 6xxx aluminum alloy is applicable not only to the manufacturing method of this invention but also to other hot working methods such as forging and extrusion. The specific alloy composition includes: (0.9–1.1 wt.%) Mg, (1.1–1.3 wt.%) Si, (0.5–0.7 wt.%) Cu, (0.5–0.7 wt.%) Mn, (0.1–0.3 wt.%) Cr, (less than 0.5 wt%) Fe, with the balance consisting of Al and unavoidable impurity elements. The following condition must be met: Cu(wt.%) - [Si(wt.%) - Mg(wt.%)] = 0.4 wt.%. The specific functions of each component are as follows:

[0044] a. The roles of Mg, Si, and Cu

[0045] Mg, Si, and Cu elements are mainly used to form nano-reinforcing phases during the aging process, including β” and Q’ phases. The β” phase is composed of Mg and Si, while the Q’ phase is composed of Mg, Si, and Cu. Increasing the content of Mg, Si, and Cu increases the number of reinforcing phases; however, excessive amounts will result in an excessive number of grain boundary second phases in the final product, leading to a decrease in toughness and fatigue resistance. Furthermore, the relationship between the contents of Mg, Si, and Cu can effectively control the composition of the β” and Q’ phases. Therefore, this invention explicitly specifies the relationship between the contents of Mg, Si, and Cu as: Cu(wt.%) - [Si(wt.%) - Mg(wt.%)] = 0.4wt.%. Under this relationship, the reinforcing phase composition consists of a large amount of Q’ phase and a small amount of β” phase, with the highest quantity, resulting in the optimal performance of the alloy.

[0046] b. The role of Mn and Cr

[0047] Mn and Cr are mainly used as submicron dispersed phases during homogenization. Mn, Cr, Al, Fe, and Si primarily contribute to the α-Al(FeMn)Si phase and Cr-containing phase during homogenization. These phases effectively pin dislocations during subsequent alloy deformation, inhibiting recrystallization and coarse recrystallization. Higher content of these phases results in better dislocation pinning. However, due to limitations in the solid solubility of alloying elements, excessively high content can lead to the formation of excessive coarse second phases at grain boundaries, reducing the material's toughness and fatigue resistance. This invention proposes a Mn content of (0.5–0.7 wt%) Mn and (0.1–0.3 wt%) Cr. With this alloy composition, the most abundant dispersed phases are obtained after homogenization, resulting in a high proportion of subgrains and no coarse grains in the product.

[0048] A method for producing 6xxx aluminum alloy automotive forgings

[0049] This method is applicable to the production of all 6xxx aluminum alloy automotive forgings, and its specific processes are as follows: melting, casting, extrusion of shaped bars, homogenization heat treatment, sawing and forging, solution treatment and aging treatment. Specifically, it includes:

[0050] a. smelting

[0051] Using conventional smelting methods in this field, raw materials (primary aluminum or liquid aluminum, recycled aluminum, various raw materials) are melted into an alloy liquid, refined in a furnace, and then left to stand.

[0052] b. Casting

[0053] Using conventional ladle refining and filtration methods in this field, the treated molten alloy is poured into the flow channel and then refined with nitrogen or argon in an external degassing box (at least two rotors), followed by filtration (using a two-stage filter box, deep bed, or tubular filter).

[0054] Round casting rods are manufactured using conventional semi-continuous casting methods in this field, followed by pouring at 720-680℃, and employing techniques such as DC casting or electromagnetic casting.

[0055] c. Extruded profiled rods

[0056] The method for producing aluminum alloy automotive forgings according to this invention requires extrusion process parameters that differ significantly from those for conventional 6xxx aluminum alloys, specifically as follows: ① Extrusion method: Both forward and reverse extrusion are possible, with reverse extrusion being preferred. ② Extrusion ratio: Based on the method of this invention, a relatively large and moderate extrusion ratio is required, set at 30–70. ③ Extrusion process: The process used is an extrusion temperature of 400–480℃, an extrusion speed of 3.5–6 mm / s, and online air quenching or water quenching.

[0057] d. Homogenization heat treatment

[0058] This invention provides two homogenization heat treatment processes.

[0059] Homogenization heat treatment process - 1. The conventional method in this field is adopted, namely, three steps of heating-holding-cooling. Specifically, the temperature is raised to 550-570°C at a heating rate of 1-5°C / min, held at that temperature for 4-6 hours, cooled to 350°C at a rate of not less than 8°C / min, and then cooled to room temperature at a rate of not less than 4°C / min.

[0060] Homogenization heat treatment process - 2. A two-stage homogenization heat treatment process is adopted, namely, five steps: heating-low temperature isothermal-heating-high temperature isothermal-cooling. Specifically, the temperature is raised to 300-355℃ at a rate not exceeding 3℃ / min and held for 6-8 hours. Then, the temperature is raised to 550-570℃ at a rate not exceeding 3℃ / min and held for 4-6 hours. Finally, the temperature is cooled to 350℃ at a rate not less than 8℃ / min and then cooled to room temperature at a rate not less than 4℃ / min.

[0061] e. Sawing and Forging

[0062] This invention involves slicing a heat-treated, homogenized extrusion bar along the extrusion direction, with the slice thickness meeting forging requirements. Forging is performed using conventional forging methods in the art. Since the shape of the extrusion bar slices is similar to the shape of the forging, precision forging is sufficient compared to traditional forging methods.

[0063] f. Solution treatment and aging treatment

[0064] The forgings were subjected to T6 heat treatment using conventional solution treatment and aging methods in this field.

[0065] A high Fe tolerance 6xxx aluminum alloying scheme

[0066] This method is applicable to all 6xxx aluminum alloys used for forging, but its production method is only applicable to the method provided by this invention. The Fe content is preferably within the tolerance range of 0.5 wt.%. The forging production method of this invention allows the Fe-containing second phase at the grain boundaries in the cast ingot to be broken and dispersed under high temperature and pressure during extrusion. In the subsequent homogenization heat treatment, the broken second phase dissolves and spheroidizes, resulting in a fine and uniform second phase in the final forging, minimizing the loss of toughness and fatigue performance. When the Fe content exceeds 0.5 wt.%, it becomes more difficult to control the Fe-containing second phase in the product using this method, leading to a greater loss of toughness and fatigue performance in the forging.

[0067] Example 1

[0068] A method for producing 6xxx aluminum alloy automotive forgings includes the following operations:

[0069] The high-strength and high-toughness 6xxx aluminum alloys and their compositions listed in Table 1 were used. The alloys provided in this invention were compared with these alloys, differing only in whether they satisfied the relationship Cu(wt.%) - [Si(wt.%) - Mg(wt.%)] = 0.4wt.%. Those not satisfying this relationship were considered as the comparison alloy group. These alloys were then used to obtain ingots with a diameter of 512mm through DC casting. Following an extrusion ratio of 30.3, an extrusion temperature of 400℃, an extrusion speed of 6mm / s, and online water quenching, they were forward extruded into shaped extruded bars (cross-section as shown). Figure 7 (As shown), then the temperature is increased to 350°C at a rate of 3°C / min, held for 8 hours, then increased to 560°C at a rate of 3°C / min, held for 4 hours, cooled to 350°C at a rate of 8°C / min, and then cooled to room temperature at a rate of 4°C / min for homogenization heat treatment (homogenization heat treatment process-2 of this invention). After slicing, the slices are heated to 450°C and held for 15 minutes before forging into automotive control arm forgings (such as...). Figure 8 (As shown), the forging is finally subjected to T6 heat treatment.

[0070] The properties of the obtained alloy automotive forgings are listed in Table 2.

[0071] Table 1. Composition (wt.%) of the high-strength and high-toughness 6xxx aluminum alloy of the present invention and comparative alloys.

[0072]

[0073] Table 2 Mechanical and fatigue properties of the high-strength and tough 6xxx aluminum alloy and comparative alloys of the present invention.

[0074]

[0075] Example 2

[0076] A method for producing 6061 aluminum alloy automotive forgings with different Fe contents includes the following operations:

[0077] The 6061 aluminum alloy materials with different Fe contents listed in Table 3 were used. Taking automotive multi-link forgings as the product, the production process was as follows: After obtaining ingots with a diameter of 358 mm by DC casting, these alloys were reverse extruded into shaped extruded bars by an extrusion ratio of 48.2, an extrusion temperature of 450℃, an extrusion speed of 4.5 mm / s, and an online water quenching process. Then, the bars were heated to 560℃ at a rate of 3℃ / min, held for 6 hours, cooled to 350℃ at a rate of 8℃ / min, and then cooled to room temperature at a rate of 4℃ / min for homogenization heat treatment (homogenization heat treatment process-1 of this invention). The bars were then sliced, heated to 480℃ and held for 15 min, and then forged into automotive control arm forgings. Finally, the forgings were subjected to T6 heat treatment.

[0078] The properties of various alloy automotive forgings obtained under different process conditions are listed in Table 4.

[0079] Table 3. Composition of 6061 aluminum alloy with different Fe contents (wt.%)

[0080]

[0081]

[0082] Table 4 Mechanical and fatigue properties of 6061 aluminum alloys with different Fe contents

[0083]

[0084] The traditional generation methods described in Table 4 are based on... Figure 1The production process is as follows: After obtaining 300mm diameter ingots by DC casting, these alloys are heated to 560℃ at a rate of 3℃ / min, held for 9 hours, and then cooled to room temperature at a rate of 2-3℃ / min for homogenization heat treatment. Then, they are forward extruded into 60mm diameter round bars by an extrusion ratio of 25, an extrusion temperature of 500℃, an extrusion speed of 3mm / s, and online water quenching. The bars are then sawn into short bars of fixed length, heated to 480℃ and held for 25 minutes, and then rolled, bent, pre-formed and precision forged into automotive control arm forgings. Finally, the forgings are subjected to T6 heat treatment.

[0085] Example 3

[0086] A method for producing 6082 aluminum alloy automotive forgings with different Fe contents includes the following operations:

[0087] The 6082 aluminum alloy materials with different Fe contents listed in Table 5 were used. Taking automotive multi-link forgings as the product, the production process was as follows: These alloys were obtained as 425mm diameter ingots through DC casting, then reverse-extruded into shaped extruded bars using an extrusion ratio of 69.1, an extrusion temperature of 450℃, an extrusion speed of 3.5mm / s, and online gas quenching. The bars were then heated to 350℃ at a rate of 3℃ / min, held for 8 hours, then heated to 570℃ at a rate of 3℃ / min, held for 6 hours, cooled to 350℃ at a rate of 8℃ / min, and then cooled to room temperature at a rate of 4℃ / min for homogenization heat treatment (homogenization heat treatment process-2 of this invention). After slicing, the slices were heated to 490℃ and held for 15 minutes before forging into automotive control arm forgings (such as…). Figure 7 (As shown), the forging is finally subjected to T6 heat treatment.

[0088] The properties of various alloy automotive forgings obtained under different process conditions are listed in Table 6.

[0089] Table 5. Composition of 6082 aluminum alloy with different Fe contents (wt.%)

[0090]

[0091] Table 6 Mechanical and fatigue properties of 6082 aluminum alloys with different Fe contents

[0092]

[0093] The traditional generation methods described in Table 6 are based on Figure 1The production process is as follows: After obtaining 300mm diameter ingots by DC casting, these alloys are heated to 560℃ at 3℃ / min, held for 9 hours, and cooled to room temperature at a rate of 2-3℃ / min for homogenization heat treatment. Then, they are forward extruded into 60mm diameter round bars by extrusion at an extrusion ratio of 25, an extrusion temperature of 500℃, an extrusion speed of 3mm / s, and online water quenching. The bars are then sawn into short bars of fixed length, heated to 480℃ and held for 25 minutes, and then rolled, bent, pre-formed and precision forged into automotive control arm forgings. Finally, the forgings are subjected to T6 heat treatment.

Claims

1. A method for producing 6xxx aluminum alloy automotive forgings, characterized in that, The production process includes: smelting, casting, extrusion of shaped bars, homogenization heat treatment, sawing and forging, solution treatment and aging treatment; The process for extruding profiled bars is as follows: extrusion ratio of 30~70, extrusion temperature of 400~480℃, extrusion speed of 3.5~6mm / s, and online air quenching or water quenching. The homogenization heat treatment process for 6xxx aluminum alloys containing Mn is as follows: heat to 300~355℃ at a rate not exceeding 3℃ / min, hold for 6~8 hours, heat to 550~570℃ at a rate not exceeding 3℃ / min, hold for 4~6 hours, cool to 350℃ at a rate not less than 8℃ / min, and then cool to room temperature at a rate not less than 4℃ / min.

2. The method for producing 6xxx aluminum alloy automotive forgings according to claim 1, characterized in that, The extrusion method for extruding shaped bars is either forward extrusion or reverse extrusion.

3. The method for producing 6xxx aluminum alloy automotive forgings according to claim 1, characterized in that, The homogenization heat treatment process for 6xxx aluminum alloys without Mn is as follows: heat to 550~570℃ at a heating rate of 1~5℃ / min, hold for 4~6 hours, cool to 350℃ at a rate of not less than 8℃ / min, and then cool to room temperature at a rate of not less than 4℃ / min.

4. The method for producing 6xxx aluminum alloy automotive forgings according to claim 1, characterized in that, The tolerance for Fe content in 6xxx aluminum alloy for automotive forgings is 0.5 wt.%.

5. The method for producing 6xxx aluminum alloy automotive forgings according to claim 1, characterized in that, The 6xxx aluminum alloy is a high-strength and high-toughness 6xxx aluminum alloy material, and its alloy composition is as follows: Mg: 0.9~1.1wt.%, Si: 1.1~1.3wt.%, Cu: 0.5~0.7wt.%, Mn: 0.5~0.7wt%, Cr: 0.1~0.3wt%, Fe: less than 0.5wt.%, with the balance consisting of Al and unavoidable impurity elements, and the composition satisfies the condition Cu(wt.%)-[Si(wt.%)-Mg(wt.%)]=0.4wt.%.

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