Control method for forging 6-series aluminum alloy hub coarse grains and application

Abstract

The invention provides a control method for forging 6-series aluminum alloy hub coarse grains and application. Comprising the following steps that S1, an aluminum alloy material subjected to pre-deformation and homogenization treatment is heated to 400-500 DEG C, and heat preservation is conducted; s2, preheating a forging die to 350-460 DEG C, and locally cooling the surface of a die cavity of a part, used for forming the hub, in the die, the temperature of the surface of the die cavity is 50-100 DEG C lower than that of the other parts of the die; the parts for forming the hub comprise the die cavity parts corresponding to corner areas at the joints of the spokes and the rim and the die cavity parts corresponding to spoke plate thickness transition areas between the adjacent spokes; and S3, the heated aluminum alloy material is placed in the die treated in the step S2 to be forged and formed. The technical problems that in the production process of an existing 6xxx series aluminum alloy forged hub, coarse grains are likely to appear, and then the mechanical property of a product is uneven, the fatigue life is shortened, and the yield is low are solved.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy forging technology, specifically to a method and application for controlling coarse grains in forged 6-series aluminum alloy wheels. Background Technology

[0002] 6xxx series aluminum alloys use magnesium (Mg) and silicon (Si) as the main alloying elements, and... 6xxx series aluminum alloys are a class of heat-treatable strengthened aluminum alloys, with the 6xxx phase being the primary strengthening phase. Due to their high strength, excellent corrosion resistance, and good formability, these alloys are widely used in automotive lightweighting, particularly in the manufacture of forged aluminum alloy wheels. However, because aluminum alloy forgings typically have complex structures, the uneven strain distribution in different areas during forging leads to significant differences in strain across different parts, resulting in inhomogeneous grain structure. In certain localized areas, abnormal grain growth, known as "coarse grains," easily occurs, where individual grains are significantly larger than the average grain size. The formation of coarse grains mainly stems from the inconsistent grain boundary migration rates during heat treatment above the recrystallization temperature after large plastic deformation, causing some grains to preferentially and rapidly grow. This structural defect significantly reduces the mechanical properties and fatigue life of the wheel, severely impacting product safety and service reliability, and has become a key technical bottleneck restricting the high-performance application of 6xxx series aluminum alloy wheels. Currently, the conventional production process for forged aluminum alloy wheels generally includes: aluminum bar blanking - aluminum bar preheating - die preheating - forging - spinning forming - heat treatment (solution + aging) - machining, ultimately obtaining a finished wheel that meets dimensional and performance requirements. However, this traditional process lacks targeted control methods for local temperature control during forging, making it difficult to effectively suppress the formation of coarse grains. There is an urgent need to develop a process method that can precisely control the grain structure in key areas of the wheel to improve the overall product performance and yield. Summary of the Invention

[0003] To achieve the above objectives, the present invention provides a method for controlling the coarse grains of forged 6-series aluminum alloy wheels, comprising the following steps: S1. Extrude the aluminum alloy billet at 450~470℃, homogenize it at 550~570℃, and then heat it to 400~500℃ and hold it. S2. Preheat the forging die to 420-460°C, and locally cool the surface of the die cavity used for forming the wheel hub, so that the temperature of the die cavity surface is 50°C-100°C lower than that of the rest of the die: Parts used for forming wheel hubs: mold cavity parts corresponding to the corner area where the spokes and rim connect, and mold cavity parts corresponding to the thickness transition area of ​​the spokes between adjacent spokes; S3. Place the heated aluminum alloy material into the mold processed in step S2 for forging.

[0004] This invention involves extruding aluminum alloy billets at 450–470°C, homogenizing them at 550–570°C, and then heating them to 400–500°C for holding (S1). This effectively eliminates segregation in the as-cast structure, promotes the dispersed distribution of strengthening phases, and yields a fine and uniform initial grain structure. Simultaneously, before forging, the die is preheated to 420–460°C, and local cooling is implemented on the die cavity surface corresponding to key areas prone to strain concentration, such as the corner area between the spokes and the rim, and the transition area between the thickness of adjacent spokes. This local cooling is 50–100°C lower than the rest of the die (S2). This allows for precise control of the local thermal state during the forging process, suppressing abnormal recrystallization and grain coarsening induced by high temperature and large deformation in high-strain areas, and avoiding cracking due to decreased material plasticity caused by excessive cooling. Finally, forging is completed under this synergistic process (S3), resulting in a wheel hub without coarse-grained structures in key areas and with significantly improved mechanical properties.

[0005] In some embodiments, the extrusion molding temperature is 450–470°C. The extrusion molding temperature can be, for example, any value between 450°C, 455°C, 460°C, 465°C, 470°C, or 450–470°C.

[0006] In some embodiments, the homogenization treatment temperature is 550–570°C. The homogenization treatment temperature can be, for example, 550°C, 555°C, 560°C, 565°C, 570°C, or any value between 550 and 570°C.

[0007] In some embodiments, the billet heating and holding temperature is 400–500°C. The heating and holding temperature can be, for example, 400°C, 420°C, 450°C, 480°C, 500°C, or any value between 400°C and 500°C.

[0008] In some embodiments, the preheating temperature of the forging die is 420–460°C. The die preheating temperature can be, for example, any value between 420°C, 430°C, 440°C, 450°C, 460°C, or 420–460°C.

[0009] In some embodiments, the temperature difference after local cooling of the mold cavity surface is 50–100°C. The temperature difference can be, for example, any value between 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, or 50–100°C.

[0010] According to an embodiment of the present invention, the local cooling method includes at least one of air cooling and water mist spraying cooling.

[0011] According to an embodiment of the present invention, in step S1, the deformation amount of the extrusion forming is 10~20%.

[0012] In some embodiments, the deformation amount of the extrusion molding is 10% to 20%. The deformation amount can be, for example, any value between 10%, 12%, 15%, 18%, 20%, or 10% to 20%.

[0013] According to an embodiment of the present invention, the deformation amount of the extrusion forming in step S1 is controlled at 10% to 20%, which provides favorable conditions for the formation of fine and dispersed recrystallized grains in the subsequent homogenization process; at the same time, this deformation range avoids excessive local temperature rise or uneven structure due to excessive deformation, and also prevents insufficient deformation from failing to fully improve the original structure defects.

[0014] According to an embodiment of the present invention, in step S1, the homogenization process takes 4 to 8 hours.

[0015] According to an embodiment of the present invention, the aluminum alloy material comprises, by mass percentage: Si: 0.5-0.6%, Fe: 0.1-0.3%, Cu: 0.15-0.4%, Mn≤0.15%, Mg: 0.8-1.1%, Cr: 0.05-0.1%, Zn≤0.2%, Ti: ≤0.05%.

[0016] Under the above conditions, the deep synergy with pre-deformation, homogenization treatment, and local cooling processes in key parts of the mold achieves high strength while also possessing excellent microstructure uniformity and performance stability.

[0017] According to an embodiment of the present invention, the aluminum alloy material comprises, by mass percentage: Si: 0.5-0.6%, Mn: 0.1-0.15%, Ti: 0.04-0.05%.

[0018] In some embodiments, the Si content in the aluminum alloy material is 0.5% to 0.6% by mass percentage. The Si content can be, for example, any value between 0.50%, 0.52%, 0.55%, 0.58%, 0.60%, or 0.5% to 0.6%.

[0019] In some embodiments, the Fe content in the aluminum alloy material is 0.1% to 0.3% by mass percentage. The Fe content can be, for example, any value between 0.10%, 0.15%, 0.20%, 0.25%, 0.30%, or 0.1% to 0.3%.

[0020] In some embodiments, the Cu content in the aluminum alloy material is 0.15% to 0.4% by mass percentage. The Cu content can be, for example, any value between 0.15%, 0.20%, 0.25%, 0.30%, 0.35%, 0.40%, or 0.15% to 0.4%.

[0021] In some embodiments, the Mn content in the aluminum alloy material, by mass percentage, does not exceed 0.15% (i.e., ≤0.15%). The Mn content can be, for example, 0.05%, 0.08%, 0.10%, 0.12%, 0.15%, or any value between 0 and 0.15%.

[0022] In some embodiments, the Mg content in the aluminum alloy material is 0.8% to 1.1% by mass percentage. The Mg content can be, for example, any value between 0.80%, 0.85%, 0.90%, 0.95%, 1.00%, 1.05%, 1.10%, or 0.8% to 1.1%.

[0023] In some embodiments, the Cr content in the aluminum alloy material is 0.05% to 0.1% by mass. The Cr content can be, for example, any value between 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, or 0.05% to 0.1%.

[0024] In some embodiments, the Zn content in the aluminum alloy material, by mass percentage, does not exceed 0.2% (i.e., ≤0.2%). The Zn content can be, for example, any value between 0.05%, 0.10%, 0.15%, 0.20%, or 0 to 0.2%.

[0025] In some embodiments, the Ti content in the aluminum alloy material, by mass percentage, does not exceed 0.05% (i.e., ≤0.05%). The Ti content can be, for example, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, or any value between 0 and 0.05%.

[0026] According to an embodiment of the present invention, the forging process further includes spinning, heat treatment, and machining.

[0027] According to an embodiment of the present invention, the heat treatment step includes solution treatment followed by artificial aging.

[0028] According to an embodiment of the present invention, the solution temperature is 500~520°C; The aging temperature is 160℃~170℃.

[0029] This invention also proposes the application of the aforementioned method for controlling coarse grains in forged 6-series aluminum alloy wheels in the field of automotive parts. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0031] Figure 1 The red circle shown indicates a common coarse grain location in the spoke window of a forged wheel; Figure 2 The image shown is a 50x magnification mosaic of the metallographic structure obtained by a conventional mold before cooling. Figure 3 The image shown is a metallographic structure obtained by refrigerating a conventional mold, magnified 100 times. Figure 4 The image shown is a 50x magnified composite of the metallographic structure obtained by mold cooling in Embodiment 1 of the present invention. Figure 5 The image shown is a metallographic structure obtained by mold cooling in Embodiment 1 of the present invention, magnified 100 times. The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0032] 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 a part of the embodiments of the present invention, and not all of them. 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.

[0033] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0034] The forging die described in this invention is a conventional wheel forging die used in the field. Its overall structure, cavity configuration, and forming method are consistent with existing 6-series aluminum alloy wheel forging dies, and it does not rely on special structures or dedicated die designs. The technical effect of this invention does not come from changes in the die structure itself, but is achieved by implementing local temperature control on forming areas prone to strain concentration, such as the corner area connecting the wheel spoke and the rim, and the thickness transition area between adjacent spokes, under existing general die conditions.

[0035] To further illustrate the present invention, the following examples are provided: Example 1 A method for controlling localized coarse grains in forged 6-series aluminum alloy wheels comprises the following steps: A1. Cut the aluminum alloy round bar into blanks and saw it to the specified dimensions to prepare raw materials for forging; A1a, Pre-deformation treatment: The aluminum alloy round bar after A1 blanking is preheated to 450℃ for single-pass deformation using extrusion, with the deformation amount controlled at 10%; A1b, Homogenization heat treatment: The aluminum alloy round bar after A1a deformation is held at 550℃ for 4 hours, and then cooled to room temperature in the furnace; A2. Place the aluminum alloy material treated with A1b into a gas furnace and heat it to reach the forging temperature of 400℃. A3. Place the forging die in the mold furnace and heat it to the required temperature of 350℃, and ensure good lubrication; A4. Place the heated mold into a 6000-ton forging press to prepare for forging; A5. Cool the localized areas of the mold where coarse grains are prone to appear, reducing the temperature of the localized areas by approximately 50°C, while leaving the remaining areas uncooled. A6. Place the aluminum alloy material processed in A2 into the mold in A5 for forging. Control the forging temperature at 420℃ and the forging rate at 9mm / s to ensure that the total deformation is >50% to form the wheel hub blank. A6.5 Immediately after forging, water quench: After forging in A6, immediately remove the wheel blank from the mold and water quench it. Use room temperature water for cooling at a rate of 50℃ / s and continue cooling to 100℃. Then continue with step A7. A7. Place the forging blank treated with A6.5 into a vertical spinning machine, and spin the blank rim into shape using 3 spinning wheels; A8. Place the wheel hub from A7 into a heat treatment furnace for heat treatment strengthening. The solution treatment process is 510℃ for 3 hours, and the aging process is 185℃ for 8 hours. A9. The heat-treated wheel hub prototype in A8 is machined on a lathe to carve out the designed shape.

[0036] In the above embodiments, the 6-series aluminum alloy is 6061 aluminum alloy, prepared according to the following weight fraction: Si: 0.5%, Fe: 0.1%, Cu: 0.4%, Mn: 0.15%, Mg: 0.8%, Cr: 0.05%, Zn: 0.1%, Ti: 0.05%, with the balance being Al.

[0037] Example 2 A method for controlling localized coarse grains in forged 6-series aluminum alloy wheels comprises the following steps: A1. Cut the aluminum alloy round bar into blanks and saw it to the specified dimensions to prepare raw materials for forging; A1a, Pre-deformation treatment: The aluminum alloy round bar after A1 blanking is preheated to 450℃ for single-pass deformation using extrusion, with the deformation amount controlled at 10%; A1b, Homogenization heat treatment: The aluminum alloy round bar after A1a deformation is held at 550℃ for 4 hours, and then cooled to room temperature in the furnace; A2. Place the aluminum alloy material treated with A1b into a gas furnace and heat it to reach the forging temperature of 400℃. A3. Place the forging die in the mold furnace and heat it to the required temperature of 360℃, and ensure proper lubrication; A4. Place the heated mold into a 6000-ton forging press to prepare for forging; A5. Cool the localized areas of the mold where coarse grains are prone to appear, reducing the temperature of the localized areas by approximately 60°C, while leaving the remaining areas uncooled. A6. Place the aluminum alloy material processed in A2 into the mold in A5 for forging. Control the forging temperature at 420℃ and the forging rate at 9mm / s to ensure that the total deformation is >50% to form the wheel hub blank. A6.5 Immediately after forging, water quench: After forging in A6, immediately remove the wheel blank from the mold and water quench it. Use room temperature water for cooling at a rate of 55℃ / s and continue cooling to 90℃. Then continue with step A7. A7. Place the forging blank treated with A6.5 into a vertical spinning machine, and spin the blank rim into shape using 3 spinning wheels; A8. Place the wheel hub from A7 into a heat treatment furnace for heat treatment strengthening. The solution treatment process is 510℃×3h, and the aging process is 185℃×8h. A9. The heat-treated wheel hub prototype in A8 is machined on a lathe to carve out the designed shape.

[0038] In the above embodiments, the 6-series aluminum alloy is 6061 aluminum alloy, prepared according to the following weight fraction: Si: 0.55%, Fe: 0.2%, Cu: 0.25%, Mn: 0.12%, Mg: 1.05%, Cr: 0.08%, Zn: 0.1%, Ti: 0.045%, with Al as the balance.

[0039] In this embodiment, firstly, in the alloy composition design, by precisely controlling the Cr content within the range of 0.08–0.10%, Mn within 0.10–0.15%, and Ti within 0.04–0.05%, and adjusting the Mg / Si ratio, the key phase can be directionally precipitated during subsequent heat treatment under the above composition. Furthermore, through a pretreatment process (S1), extrusion pre-deformation is performed at 450°C, breaking up the casting dendrites and coarse primary phases, shortening the diffusion paths of elements such as Cr, Mn, and Ti, and creating nucleation conditions for the efficient and uniform precipitation of dispersed phases in the subsequent homogenization treatment. The subsequent homogenization treatment is closely coupled with the composition design: without specific components, pretreatment cannot form a sufficient amount of thermally stable phase; without pretreatment, the component potential cannot be fully activated, resulting in a sparse and inefficient pinning network. Finally, in the forging process, the localized cooling process of the die cools key areas on the die corresponding to the spoke-rim corner and the thickness transition zone of the spokes, making their surface temperature 50–100°C lower than that of the die body. This significantly reduces the actual deformation temperature of the aluminum alloy in this area. At this point, the highly thermally stable dispersed phase prepared in the first two steps and the low-temperature environment produce a crucial synergistic amplification effect: the low temperature itself directly inhibits the thermodynamic driving force of atomic diffusion and grain boundary migration, reducing the tendency for recrystallization; more importantly, under low-temperature conditions, the grain boundary migration ability is severely limited, while the pinning effect of the highly thermally stable dispersed phase is persistent. It is completely maintained or even relatively enhanced at low temperatures. Localized cooling not only creates a ring unfavorable to grain growth but also allows the alloy's internal pinning network to work together to freeze the grain boundaries in strain-concentrated areas.

[0040] Comparative Example 1 A method for controlling localized coarse grains in forged 6-series aluminum alloy wheels comprises the following steps: A1. Cutting to length: Cut the aluminum alloy round bar into blanks and saw it to the specified dimensions to prepare raw materials for forging; A2. Aluminum bar preheating: Place the aluminum alloy material prepared in S1 into a gas furnace and heat it to reach the temperature of 400℃ required for forging. A3. Mold preheating: Place the forging mold in the mold furnace and heat it to the required temperature of 350℃, and ensure good lubrication; A4. Loading the mold: Place the heated mold from S3 into the 6000-ton forging press to prepare for forging; A5. Forging and forming: The aluminum alloy material prepared in S2 is placed into the mold in S3 for forging to form the blank of the wheel hub; A6. Spinning: The forging blank in S5 is placed into a vertical spinning machine, and the blank rim is spun into shape by 3 spinning wheels; A7. Heat treatment: The wheel hub in S6 is placed in a heat treatment furnace for heat treatment strengthening. The solution treatment process is 510℃×3h, and the aging process is 185℃×8h. A8. Machining: The wheel hub prototype after heat treatment in S7 is machined on a lathe to carve out the designed shape.

[0041] Comparative Example 2 The difference between this comparative example and Example 1 is that the local cooling temperature of the mold is 40°C, while the other conditions are the same.

[0042] Comparative Example 3 The difference between this comparative example and Example 1 is that the local cooling temperature of the mold is 110°C, while the other conditions are the same.

[0043] Comparative Example 4 A method for controlling localized coarse grains in forged 6-series aluminum alloy wheels comprises the following steps: A1. Cut the aluminum alloy round bar into blanks and saw it to the specified dimensions to prepare raw materials for forging; A2. Aluminum bar preheating: Place the aluminum alloy material prepared in S1 into a gas furnace and heat it to reach the temperature of 400℃ required for forging. A3. Place the forging die in the mold furnace and heat it to the required temperature of 350℃, and ensure good lubrication; A4. Place the heated mold into a 6000-ton forging press to prepare for forging; A5. Cool the localized areas of the mold where coarse grains are prone to appear, reducing the temperature of the localized areas by about 30°C, while leaving the other areas uncooled. A6. Place the prepared aluminum alloy material into the mold of S5 for forging to form the blank of the wheel hub. A7. Place the forging blank into a vertical spinning machine and spin the blank rim into shape using 3 spinning wheels; A8. The wheel hub is placed in a heat treatment furnace for heat treatment strengthening. The solution treatment process is 510℃×3h, and the aging process is 185℃×8h. A9. The heat-treated wheel hub prototype is machined on a lathe to carve out the designed shape. In the above embodiment, the 6-series aluminum alloy is 6061 aluminum alloy, prepared according to the following weight fraction: Si: 0.5%, Fe: 0.1%, Cu: 0.4%, Mn≤0.15%, Mg: 0.8%, Cr: 0.05%, Zn≤0.2%, Ti: ≤0.05%, with the balance being Al.

[0044] Comparative Example 5 A method for controlling localized coarse grains in forged 6-series aluminum alloy wheels includes the following steps: A1. Cut the aluminum alloy round bar into blanks and saw it to the specified dimensions to prepare raw materials for forging; A2. Place the prepared aluminum alloy material into a gas furnace and heat it to reach the forging temperature of 400℃. A3. Place the forging die in the mold furnace and heat it to the required temperature of 350℃, and ensure good lubrication; A4. Place the heated mold into a 6000-ton forging press to prepare for forging; A5. Cool the localized areas of the mold where coarse grains are prone to appear, reducing the temperature of the localized areas to 110℃, while leaving the other areas uncooled. A6. Place the prepared aluminum alloy material into the mold of S5 for forging to form the blank of the wheel hub. A7. Place the forging blank into a vertical spinning machine and spin the blank rim into shape using 3 spinning wheels; A8. The wheel hub is placed in a heat treatment furnace for heat treatment strengthening. The solution treatment process is 510℃×5h, and the aging process is 185℃×8h. A9. The heat-treated wheel hub prototype is machined on a lathe to carve out the designed shape.

[0045] In the above embodiments, the 6-series aluminum alloy is 6061 aluminum alloy, prepared according to the following weight fraction: Si: 0.5%, Fe: 0.1%, Cu: 0.4%, Mn: 0.15%, Mg: 0.8%, Cr: 0.05%, Zn: 0.1%, Ti: 0.05%, with the balance being Al.

[0046] Table 1 Comparison of local coarse-grained microstructure of wheel hubs in the examples and comparative examples. Table 2 Performance Comparison of Examples and Comparative Examples This invention provides a method for controlling localized coarse grains in forged 6-series aluminum alloy wheel hubs, which offers significant technical advantages and practical application effects compared to traditional forging processes. As shown in Table 1, after adopting the method of this invention, the grain size in key areas prone to coarse grains, such as wheel hub corners, is significantly refined, coarse grain regions are essentially eliminated, and the grain structure is highly uniform. Simultaneously, the tensile strength of the product is improved, fatigue life is increased, and early failure caused by microstructure inhomogeneity is effectively prevented, significantly enhancing the service reliability of the wheel hub under high stress and cyclic load conditions. Furthermore, by implementing localized cooling (e.g., air cooling or water mist cooling) of the mold in areas prone to coarse grains at 50–100°C, not only is the material flow and recrystallization behavior optimized, but the thermal load in these areas is also significantly reduced, minimizing thermal corrosion and thermal fatigue damage, and extending the mold's service life. In summary, this invention has outstanding advantages in improving product quality, performance stability, and production economy.

[0047] As can be seen from the data comparison in Table 2, the yield strength of Example 2 reached 345 MPa and the tensile strength reached 378 MPa. At the same time, the synergistic effect of alloy composition optimization, pre-deformation, homogenization treatment and local cooling of mold resulted in a hardness range of 116-118 HBW for Example 2, with a fluctuation range of only 2 HBW, showing excellent microstructure uniformity.

[0048] like Figure 1 As shown, the red circle indicates the typical locations where coarse grains are most likely to appear in the spoke window of a forged aluminum alloy wheel. These locations are mainly concentrated in the corner area where the spoke connects to the rim and in the thickness transition zone between adjacent spokes. During the forging process, these areas experience strain concentration due to geometric abrupt changes. In addition, the uniform temperature of traditional dies and the resulting localized high temperatures promote abnormal growth of dynamically recrystallized grains, thus forming a coarse-grained structure and becoming weak points in performance. Figure 2 and Figure 3 The metallographic structure obtained using the conventional process (i.e., Comparative Example 1) is shown: obvious coarse equiaxed crystals are visible in the areas corresponding to the red circles, with uneven grain size and grain diameters exceeding 100 μm in some areas, confirming the existence of coarse grain defects.

[0049] In comparison, Figure 4 and Figure 5 As in Example 1, the process steps of Example 1 of the present invention are adopted, and the entire spoke window area has a uniform structure with no obvious coarse grain aggregation; Figure 5 Further analysis revealed that the grains were small, equiaxed, and densely distributed, with an average grain size significantly smaller than that of traditional processes. This fully demonstrates that local cooling effectively suppressed recrystallization and coarsening behavior in the high-strain region.

[0050] The above technical solutions of the present invention are merely preferred embodiments and do not limit the patent scope of the present invention. All equivalent structural transformations made under the technical concept of the present invention using the contents of the specification and drawings of the present invention, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method of controlling coarse grain in a forged 6-series aluminum alloy wheel, characterized by, Includes the following steps: S1. Extrude the aluminum alloy billet at 450~470℃, homogenize it at 550~570℃, and then heat it to 400~500℃ and hold it. S2. Preheat the forging die to 350-460°C, and locally cool the surface of the die cavity used for forming the wheel hub, so that the temperature of the die cavity surface is 50-100°C lower than that of the rest of the die: The parts used for forming wheel hubs include: the mold cavity corresponding to the corner area where the spokes and rim connect, and the mold cavity corresponding to the thickness transition area of ​​the spokes between adjacent spokes; S3. Place the heated aluminum alloy material into the mold processed in step S2 for forging.

2. The method of controlling coarse grain of a wrought 6-series aluminum alloy wheel hub according to claim 1, characterized by, The local cooling method includes at least one of air cooling and water mist spraying.

3. The method for controlling coarse grains in forged 6-series aluminum alloy wheels according to claim 1, characterized in that, In step S1, the deformation amount of the extrusion forming is 10~20%.

4. The method for controlling coarse grains in forged 6-series aluminum alloy wheels according to claim 1, characterized in that, In step S1, the homogenization process takes 4 to 8 hours.

5. The method for controlling coarse grains in forged 6-series aluminum alloy wheels according to claim 1, characterized in that, The aluminum alloy material comprises, by mass percentage: Si: 0.5-0.6%, Fe: 0.1-0.3%, Cu: 0.15-0.4%, Mn≤0.15%, Mg: 0.8-1.1%, Cr: 0.05-0.1%, Zn≤0.2%, Ti: ≤0.05%.

6. The method for controlling coarse grains in forged 6-series aluminum alloy wheels according to claim 5, characterized in that, The aluminum alloy material comprises, by mass percentage: Si: 0.5-0.6%, Mn: 0.1-0.15%, Ti: 0.04-0.05%.

7. The method for controlling coarse grains in forged 6-series aluminum alloy wheels according to claim 1, characterized in that, The forging process also includes spinning, heat treatment, and machining.

8. The method for controlling coarse grains in forged 6-series aluminum alloy wheels according to claim 7, characterized in that, The heat treatment steps include solution treatment followed by artificial aging.

9. The method for controlling coarse grains in forged 6-series aluminum alloy wheels according to claim 7, characterized in that, The solution temperature is 500~520℃; The artificial aging temperature is 160℃~170℃.

10. The application of the method for controlling coarse grains in forged 6-series aluminum alloy wheels according to any one of claims 1 to 9 in the field of automotive parts.

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