6061 aluminum alloy forged wheel and preparation method

Abstract

The invention provides a 6061 aluminum alloy forged wheel and a preparation method, belonging to the technical field of aluminum alloy processing. The aluminum alloy material composition design of the 6061 aluminum alloy forged wheel is Si0.7-0.8%, Mg0.8-1.2%, Cu0.30-0.35%, Mn0.08-0.12%, Cr0.15-0.25%, Ti0.020-0.030%, Zr 0.003-0.006%, Fe<0.2%, Na<0.0005%, Ca<0.0005%, Pb<0.005% and the balance Al according to mass percentage. The preparation method includes heating of ingot billet, low-temperature preform forging, medium-temperature preforming forging, high-temperature final forging, low-temperature shaping, cold spinning and low-temperature aging. The variable temperature forging control method of the invention controls the recrystallization volume fraction, and the method can meet the performance requirements of the wheel and realize the lightweight, high strength and good fatigue resistance of the material. The preparation process has a smooth connection, the process window is operational and implementable, the product performance is stable, and the process is short, low-carbon, environmentally friendly, and energy-saving.

Description

Technical Field

[0001] The invention relates to a 6061 aluminum alloy forged wheel and a preparation method thereof, and belongs to the technical field of aluminum alloy processing. Background Art

[0002] The wheel is a key component for lightweighting of automobiles and an important safety component. During service, the wheel must have high strength to support the weight of the entire vehicle on the one hand, and on the other hand, it will be subjected to radial and bending stresses and requires sufficient fatigue resistance.

[0003] The main method for making high-end aluminum alloy wheels is forging, and then machining to produce finished wheels. At present, the internal structure of conventional forged aluminum alloy wheels is mainly recrystallized structure. The temperature of the forging process is maintained by the initial temperature of the billet. As the number of forgings increases, the temperature of the forgings decreases successively. During the forging process, as the temperature decreases and the number of deformation passes increases, the internal structure of the forging cannot be controlled. The anisotropy of the internal structure of the forgings increases. In addition, when a fault occurs during the forging process, the internal structure of the forging will experience secondary recrystallization. The abnormal growth of grains leads to the appearance of coarse grains, and the mechanical properties of the material drop sharply. It is not easy to find it later, resulting in fatigue cracks during the service life of the wheel, which reduces the service life of the wheel. In particular, there are too many recrystallized structures in the wheel mounting plate, which reduces the fatigue life of the material. The wheel is very easy to crack when it is subjected to the impact of alternating loads during use. Summary of the invention

[0004] The present invention aims to provide a 6061 aluminum alloy forged wheel and a preparation method thereof, so that the wheel has higher strength and fatigue performance, the structure is stable during the forging process, and the recrystallization fraction can be controlled.

[0005] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0006] A 6061 aluminum alloy forged wheel is forged from an aluminum alloy material. The aluminum alloy material composition is designed according to mass percentage: Si0.7-0.8%, Mg0.8-1.2%, Cu0.30-0.35%, Mn0.08-0.12%, Cr0.15-0.25%, Ti0.020-0.030%, Zr 0.003-0.006%, Fe<0.2%, Na<0.0005%, Ca<0.0005%, Pb<0.005% and the balance Al.

[0007] The preferred embodiment of the 6061 aluminum alloy forged wheel has a ratio of Mg to Si of 1.4-1.6, and Mn+Cr of 0.25-0.35%. The alloying elements Mn+Cr can better suppress the recrystallization fraction of the material during the subsequent thermal deformation process. Controlling the ratio can better control the internal structure of the material, so that it can find a better balance with the forging recovery structure.

[0008] A preparation method of a 6061 aluminum alloy forged wheel comprises the following steps: heating an ingot blank, forging a low-temperature preform, forging a medium-temperature preforming, forging a high-temperature final forging, shaping at a low temperature, cold spinning and aging at a low temperature. The heating temperature of the ingot blank is 410-430°C, the forging temperature of the low-temperature preform is 380-410°C, the forging ratio is 2-3, the forging temperature of the medium-temperature preforming is 500-510°C, the forging ratio is 1-2, the high-temperature final forging temperature is 530-540°C, the forging ratio is 4-5, the shaping temperature of the low temperature is 150-200°C, the cold spinning is carried out at room temperature, the spinning deformation is 40%-50%, the aging temperature of the low temperature is 183°C and the time is 7-8 hours.

[0009] A preferred method for preparing a 6061 aluminum alloy forged wheel, wherein the blank after low temperature forging and medium temperature forging needs to be uniformly coated with graphite, the thickness of the coating graphite is about 20-30um, and the heating time is 20min; the blank after low temperature forging needs to be uniformly coated with graphite, the purpose of which is to quickly heat the blank to 500-510°C when heated, and its internal structure is transformed from a recovery structure to a recrystallized structure, because its forging ratio is low and the recrystallized structure fraction is 30%, and its material internal structure is a mixed structure of recovery + recrystallized structure; the blank after medium temperature forging needs to be uniformly coated with graphite, and quickly heated to 530-540°C for 30min, the purpose of which is to change the temperature of the blank to 500-510°C when heated, and the internal structure of the blank is transformed from a recovery structure to a recrystallized structure, because its forging ratio is low and the recrystallized structure fraction is 30%, and the internal structure of the material is a mixed structure of recovery + recrystallized structure; the blank after medium temperature forging needs to be uniformly coated with graphite, and quickly heated to 530-540°C for 30min, the purpose of which is to change the temperature of the blank to 500-510°C when heated, and the internal structure of the blank is transformed to a recrystallized structure during forging. During the forging process, the temperature needs to be close to the solid solution temperature so that the Mg2Si in the material composition can be dissolved back, and the forging ratio is controlled at 4-5, so that part of the recovery structure is transformed into a recrystallized structure again, the recrystallization fraction is 50%, and the rest is a recovery structure. The recovery structure has high tensile strength and yield strength, but the material elongation is reduced, the recrystallized structure has medium tensile strength and yield strength, but the material elongation is increased. After variable temperature forging, the internal structure of the forging can be adjusted to 50% recrystallized structure and 50% recovery structure, while ensuring high tensile strength and yield strength while having good plasticity and elongation, so that the material structure is balanced and the fatigue life and load-bearing capacity of the wheel are improved.

[0010] A preferred method for preparing a 6061 aluminum alloy forged wheel, wherein the low-temperature shaping temperature is 150-200°C, at which the deformation of the forging does not change, and the forging is punched and expanded at an expansion angle of 20° to facilitate subsequent spinning.

[0011] A preferred method for preparing a 6061 aluminum alloy forged wheel, wherein the sample is subjected to a force of 1 to 2 T / cm during low temperature preform 2 , forging shear speed 22mm / sec, forging die temperature 420℃, the die has heating and heat preservation device, the distance between the upper die and the lower die is 10~15mm, the pressure is maintained for 3s, and the sample is subjected to 2~3T / cm during medium temperature pre-forging 2 , forging shear speed 8mm / sec, forging die temperature 480℃, the die has heating and heat preservation device, the distance between the upper die and the lower die is 5-8mm, the pressure is maintained for 3s, and the sample is subjected to 4-5T / cm during high temperature final forging 2 Forging shear speed is 5mm / sec, forging die temperature is 520℃, the die has a heat preservation device, punching pressure is 50T, and stroke is 180-260mm.

[0012] A preferred method for preparing a 6061 aluminum alloy forged wheel, wherein the high temperature final forging is 530-540°C. After the final forging, a manipulator needs to place the forging in a water tank within 15 seconds to cool it to room temperature. The outlet water temperature of the forging blank is 30-60°C to form a supersaturated solid solution. This step can replace the solution treatment of the conventional process and save the solution treatment process.

[0013] A preferred method for preparing a 6061 aluminum alloy forged wheel, wherein the rim is formed by cold spinning, the spinning positioning surface is first accurately positioned at the center of a mold, the mold speed is 450 r / min, the feed speed of the spinning start point is 200-400 mm / s, the feed speed of the rim deep groove position is 500-700 mm / s, the spinning wheel speed is 300-500 r / min, the spinning tail top stroke is 600 mm, and the spinning mold core runout after mold closing is less than 0.1 mm.

[0014] A preferred method for preparing a 6061 aluminum alloy forged wheel comprises an aging treatment of keeping the wheel at 183° C. for 7-8 hours and naturally cooling the wheel after leaving the furnace.

[0015] The advantages of the present invention are:

[0016] The preparation method of the present application controls the chemical composition of the blank, regulates the forging temperature and forging ratio, and finally obtains an aluminum alloy material with excellent microstructure. The material can meet the performance requirements of the wheel pair and can completely replace other materials to achieve lightweight, high strength and good fatigue resistance. In addition, the short process of the present application can reduce the solid solution process, save energy and reduce carbon emissions. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 The as-cast macrostructure of the alloy provided in this application;

[0019] Figure 2 The metallographic structure of the low-temperature preform provided in this application;

[0020] Figure 3 The metallographic structure after high temperature final forging and quenching provided in this application;

[0021] Figure 4 The metallographic structure after spinning provided for this application;

[0022] Figure 5 Provide a schematic diagram of the forging temperature gradient for this application;

[0023] Figure 6 A schematic diagram of the forging deformation gradient is provided for this application. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0025] The invention provides a 6061 aluminum alloy forged wheel, which is forged from an aluminum alloy material. The aluminum alloy material composition is designed to be Si0.7-0.8%, Mg0.8-1.2%, Cu0.30-0.35%, Mn0.08-0.12%, Cr0.15-0.25%, Ti0.020-0.030%, Zr 0.003-0.006%, Fe<0.2%, Na<0.0005%, Ca<0.0005%, Pb<0.005% and the balance Al according to mass percentage. The ratio of Mg to Si in the composition is 1.4-1.6, and Mn+Cr is 0.25-0.35%.

[0026] The present invention also provides a method for preparing a 6061 aluminum alloy forged wheel, which comprises the following steps:

[0027] S1. Composition design of cast rods:

[0028] The aluminum alloy material composition is designed according to the mass percentage of Si0.7-0.8%, Mg0.8-1.2%, Cu0.30-0.35%, Mn0.08-0.12%, Cr0.15-0.25%, Ti0.020-0.030%, Zr 0.003-0.006%, Fe<0.2%, Na<0.0005%, Ca<0.0005%, Pb<0.005% and the balance of Al;

[0029] Mg and Si elements: The content of Mg and Si elements affects the alloy properties in the quenched and aged states. As the content increases, the tensile strength of the alloy increases and the elongation decreases. In addition to the influence of the total content of Mg and Si, when the total content is constant, the alloy properties are different with different ratios of Mg and Si content; when the Si content is excessive, as the proportion of Si content increases, the tensile strength of the alloy increases, but the corrosion resistance decreases; when the Mg content is high, as the Mg content increases, the tensile strength of the alloy increases, and the corrosion resistance of the alloy is poor at this time; when Mg / Si is 1.4-1.6, the alloy has higher tensile strength and better corrosion resistance, and can be effectively dissolved back during high-temperature final forging. The low-magnification structure of the cast rod is as follows: Figure 1 ;

[0030] S2. Casting rod heating:

[0031] The heating temperature of the cast rod is 410-430℃ and kept warm for 2.5-3 hours; in order to better heat evenly, the cast rods should be evenly spaced when heated and fed, and the spacing between each cast rod after sawing should be more than 200mm. The heating temperature of the cast rod is medium-low temperature. The purpose is to provide the temperature required for the low-temperature preform. The aluminum rod is heated at this temperature for 2.5 hours, which does not destroy the original internal structure and can reduce the material's resistance to plastic deformation;

[0032] S3. Low temperature preform forging:

[0033] The low-temperature preform forging temperature is 380-410℃, and the forging ratio is 2-3;

[0034] The aluminum bar is deformed at 380-410℃. Under the appropriate forging deformation, the casting structure can be better destroyed and the internal structure of the material can be fibrotic. Due to the low temperature, the internal structure of the material does not recrystallize during the forging process. The internal structure of the material is mainly recovery structure, which provides a good metallographic structure for the next medium-temperature forging. It should be pointed out that the forging deformation is an important parameter for controlling the material structure. The forging deformation is controlled at 2-3, the mold temperature is heated and maintained at about 400℃, and there is a heating and heat preservation device around the mold. The sample is subjected to a force of 1-2T / cm during low-temperature prefabrication. 2 , forging shear speed 22mm / sec, the distance between the upper die and the lower die is 10-15mm, and the pressure is maintained for 3s. The metallographic structure of the low-temperature preform is as follows Figure 2;

[0035] S4, medium temperature preforming forging:

[0036] The medium temperature preforming forging temperature is 500-510℃, and the forging ratio is 1-2;

[0037] The blank after low temperature forging needs to be coated with graphite evenly. The purpose is to quickly heat the blank to 500-510℃ when heated. The thickness of the coating graphite is about 20-30um, the heating time is about 20min, the forging ratio is 1-2, and its internal structure is transformed from recovery structure to recrystallization structure. Because of its low forging ratio, the recrystallization structure fraction is 30%, and the internal structure of the material is a mixed structure of recovery + recrystallization structure. During medium temperature pre-forging, the sample is subjected to a force of 2-3T / cm 2 , forging shear speed 8mm / sec, forging die temperature 480℃, the die has heating and heat preservation device, the distance between upper die and lower die is 5-8mm, pressure is maintained for 3s;

[0038] S5, high temperature final forging:

[0039] The high temperature final forging temperature is about 530-540℃, and the forging ratio is 4-5;

[0040] Just like low temperature forging requires heating, the blank after medium temperature forging needs to be evenly coated with graphite and quickly heated to 530-540℃ for 30min. The purpose is to approach the solid solution temperature during the forging process so that the Mg2Si in the material composition can be dissolved back. After high temperature forging, the blank needs to be quickly cooled to 30-40℃ within 15s to form a supersaturated solid solution, which is convenient for uniform precipitation in the subsequent aging process for aging strengthening. The forging ratio is controlled at 4-5, so that part of the recovery structure is transformed into a recrystallized structure again. The fraction is 50%, and the rest is recovery structure. The recovery structure has high tensile strength and yield strength, but the material elongation is reduced. The recrystallized structure has medium tensile strength and yield strength, but the material elongation is increased. After temperature-variable forging, the internal structure of the forging can be adjusted to 50% recrystallized structure and 50% recovery structure. While ensuring high tensile strength and yield strength, it also has good plasticity and elongation, so that the material structure is balanced, and the fatigue life and load of the wheel are improved. During high-temperature final forging, the sample is subjected to a force of 4-5T / cm 2 Forging shear speed 5mm / sec Forging die temperature 520℃ The die has a heat preservation device, the distance between the upper die and the lower die is 2mm and the pressure is maintained for 3s. The metallographic structure of the high temperature forging is as follows Figure 3 ;

[0041] S6, low temperature shaping:

[0042] The low-temperature shaping temperature is 150-200°C. At this temperature, the deformation of the forging does not change. It is only punched and expanded at an angle of 20° to facilitate subsequent spinning.

[0043] S7, cold spinning:

[0044] The rim is formed by cold spinning. First, the spinning positioning surface is accurately positioned to the center of the mold. The mold speed is 450r / min, the feed speed of the starting point is 200-400mm / s, the feed speed of the rim deep groove position is 500-700mm / s, the spinning wheel speed is 300-500r / min, the spinning tail stroke is 600mm, and the spinning mold core runout is <0.1mm after mold closing;

[0045] The main purpose of this design is to further refine the forging structure, especially the wheel rim, through the method of work hardening to improve the performance of the material. Experiments have shown that the grain structure of the forgings that have obtained a supersaturated solid solution is significantly refined by spinning. In order to obtain the supersaturated solid solution S4, water cooling is performed immediately after high-temperature final forging. The structure after spinning is shown in Figure 4 ;

[0046] S8, aging treatment:

[0047] Aging treatment is to keep the temperature at 183℃ for 7-8h, and then cool naturally after leaving the furnace;

[0048] The aging process is the process of precipitation of the second phase from the supersaturated solid solution. It is also a kind of solid-state phase transition. The transformation is completed by the nucleation and growth of the new phase. This nucleation and growth depends first on the change of the free energy of the system. The aging precipitation sequence of 6061 alloy is: supersaturated solid solution (SSSS) → solute atom segregation zone (GP) → β″ → β′ → β(Mg2Si). Spinning cold deformation introduces more dislocations and improves deformation energy storage. During low-temperature aging, the aluminum matrix recovers and subgrains appear, which makes it have higher tensile strength and yield strength. The grain boundaries are serrated, which improves stability. The aging process also eliminates the residual stress generated during high-temperature thermal deformation, thereby improving the fatigue resistance of the material.

[0049] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0050] Example 1

[0051] The present embodiment provides an aluminum alloy forged wheel, whose chemical composition, measured by mass percentage, includes: Si 0.75%, Mg 1.05%, Cu 0.30%, Mn 0.08%, Cr 0.25%, Ti 0.025%, Zr 0.005%, Fe 0.08% and the balance Al.

[0052] The preparation method thereof comprises the following steps:

[0053] (1) Ingot sawing: Cut the long ingot into short ingots with a cutting length of 300 mm;

[0054] (2) Heating of cast ingot: heating furnace temperature is 420°C, heating time is 2.5h;

[0055] (3) Low temperature preform: The aluminum bar is forged at a temperature of 410-420°C, a deformation of 2 at a forging ratio, a forging speed of 20-25 mm / sec, the forging die temperature is maintained at about 400°C, and the forging temperature after forging is 400-410°C;

[0056] (4) Forgings are evenly sprayed with graphite, with a graphite coverage thickness of 20-30um;

[0057] (5) After the graphite coating, the forging was heated in a gas furnace set at 505°C for 25 minutes;

[0058] (6) Medium temperature pre-forging: The preform forging temperature is about 500℃, forging is carried out at a forging ratio of 1.5, the forging speed is 10mm / sec, the forging die temperature is maintained at 480℃, and the forging temperature after forging is 490℃;

[0059] (7) The forgings after pre-forging are evenly sprayed with graphite, with a graphite coverage thickness of 35um;

[0060] (8) The preformed forging is heated in a gas-fired heating furnace set at 535° C. for 35 minutes;

[0061] (9) High temperature final forging, the pre-forging temperature is 530℃, forging is carried out at a forging ratio of 4, the forging speed is 5mm / sec, the forging die temperature is maintained at 490℃, the forging temperature after forging is 535-540℃, and it is immediately taken out and kept in water at 40℃ for 200S;

[0062] (10) After the forging is heated to 150°C, it is expanded and shaped;

[0063] (11) After the forging is shaped, it is cooled to room temperature and then the rim is spun. The spinning deformation is 40%, the spinning spindle speed is 450r / min, and the spinning wheel feed speed is F=500mm / min. The end diameter of the spinning die runs out by 0.1mm;

[0064] (12) Aging treatment: The aging treatment is carried out at 183°C for 8 hours, followed by natural cooling after being taken out of the furnace.

[0065] Example 2

[0066] The present embodiment provides an aluminum alloy forged wheel, the chemical composition of which, by mass percentage, includes: Si 0.8%, Mg 1.2%, Cu 0.25%, Mn 0.10%, Cr 0.3%, Ti 0.030%, Zr 0.006%, Fe 0.10% and the balance Al.

[0067] The rest of the contents are in accordance with Example 1.

[0068] Example 3

[0069] Except for the following parameters which are different from those in Example 1, the other contents are the same as those in Example 1.

[0070] The heating temperature of the cast rod is 400℃, the preform forging ratio is 2.5, the medium temperature pre-forging ratio is 1, and the high temperature final forging ratio is 3.

[0071] Example 4

[0072] Except for the following parameters which are different from those in Example 1, the other contents are the same as those in Example 1.

[0073] The post-heating temperature of the preform is 490℃, the heating temperature of the medium-temperature preforming is 520℃, and the post-forging temperature is 525℃.

[0074] Comparative Example 1

[0075] This comparative example provides a 6061 aluminum alloy forged wheel, the chemical composition of which is shown in the following table:

[0076] Si% Fe% Cu% Mn% Mg% Cr％ Zn% Ga% Ti% Ca% Na% B％ Al％ 0.70 0.2 0.3 0.08 1.2 0.15 ≤0.05 ≤0.05 ≤0.05 ≤0.05 ≤0.05 ≤0.05 margin

[0077] From the table, we can conclude that the ratio of Mg to Si is 1.71, and Mn + Cr is 0.23%;

[0078] The preparation method thereof comprises the following steps:

[0079] (1) Casting the melt into round ingots: Casting into ingots according to the composition in the above table, the diameter of the ingot is 254 mm;

[0080] (2) Homogenization treatment: 525°C for 16 hours, followed by water spraying for cooling after homogenization;

[0081] (3) Ingot sawing: Cut the long ingot into short ingots with a cutting length of 400 mm;

[0082] (4) Heating of cast ingot: heating furnace temperature is 480°C, heating time is 3h;

[0083] (5) Forging: Forging is performed multiple times into the final forging. The process parameters are the same as the mainstream process parameters in the current industry. The forging is lubricated with oil-based lubricants. The forging process temperature is between 420-450°C.

[0084] (6) Solution quenching: The solution temperature is 530°C, the time is 3 h, the quenching water transfer time is 15 s, and the temperature of the forging billet after leaving the water is 35°C.

[0085] (7) Aging treatment: Aging treatment is carried out at 170°C for 8.5 hours, followed by air cooling after being taken out of the furnace.

[0086] Table 1. Performance test results of Examples 1-4 and Comparative Example 1

[0087] Example Yield Strength tensile strength Elongation fatigue Example 1 370 390 13 2 million Example 2 385 400 12 2 million Example 3 365 380 14 2.2 million Example 4 370 395 12 1.8 million Comparative Example 1 310 350 16 750,000

[0088] It can be seen from the above table that Examples 1-4 provided in the present application all have higher tensile strength, yield strength and fatigue performance, and the performance is better than that of the comparative example.

[0089] In summary, the preparation method and implementation of the aluminum alloy variable temperature forging controlled recrystallization volume fraction wheel provided in the present application have stable product performance, save the solid solution process and the process flow is low-carbon and environmentally friendly.

[0090] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a 6061 aluminum alloy forged wheel, wherein the 6061 aluminum alloy forged wheel is forged from an aluminum alloy material, and the aluminum alloy material composition is designed according to mass percentage of Si 0.7-0.8%, Mg 0.8-1.2%, Cu 0.30-0.35%, Mn 0.08-0.12%, Cr 0.15-0.25%, Ti 0.020-0.030%, Zr 0.003-0.006%, Fe <0.2%, Na <0.0005%, Ca <0.0005%, Pb <0.005% and the balance Al, characterized in that: The preparation method of 6061 aluminum alloy forged wheel includes ingot blank heating, low temperature preform forging, medium temperature preforming forging, high temperature final forging, low temperature shaping, cold spinning and low temperature aging. The ingot blank heating temperature is 410-430℃, the low temperature preform forging temperature is 380-410℃, the forging ratio is 2-3, the medium temperature preforming forging temperature is 500-510℃, the forging ratio is 1-2, the high temperature final forging temperature is 530-540℃, the forging ratio is 4-5, the low temperature shaping temperature is 150-200℃, the cold spinning is carried out at room temperature, the spinning deformation is 40%-50%, the low temperature aging temperature is 183℃, and the time is 7-8 hours; after the forging is final forged, the manipulator needs to place the forging in a water tank within 15S to cool it down to room temperature, and the water outlet temperature of the forging blank is 30~60℃.

2. The method for preparing a 6061 aluminum alloy forged wheel according to claim 1, characterized in that: The ratio of Mg to Si in the composition is 1.4-1.6, and Mn+Cr is 0.25-0.35%.

3. The method for preparing a 6061 aluminum alloy forged wheel according to claim 1, characterized in that: Forgings after low-temperature preform forging and medium-temperature preforming forging require uniform coating graphite with a thickness of 20-30um.

4. The method for preparing a 6061 aluminum alloy forged wheel according to claim 1 is characterized in that: the low-temperature shaping temperature is 150-200°C, at which the deformation of the forging does not change, and the forging is punched and expanded, and the expansion angle is 20°.

5. The method for preparing a 6061 aluminum alloy forged wheel according to claim 4, characterized in that: When the forging is preformed at low temperature, the force is 1~2 T / cm 2 , forging shear speed 22mm / sec, forging die temperature 420℃, forging die with heating and heat preservation device, distance between upper die and lower die is 10~15mm, pressure holding 3s, forging force 2~3 T / cm during medium temperature preforming forging 2 , forging shear speed 8mm / sec, forging die temperature 480℃, forging die with heating and heat preservation device, distance between upper die and lower die is 5~8mm, pressure holding 3s, forging force 4~5T / cm during high temperature final forging 2 , forging shear speed 5mm / sec, forging die temperature 520℃, forging die has insulation device, punching pressure 50T, stroke 180~260mm.

6. The method for preparing a 6061 aluminum alloy forged wheel according to claim 1 is characterized in that: the wheel rim is formed by cold spinning, the spinning positioning surface is first accurately positioned at the center of the mold, the mold speed is 450r / min, the feed speed of the starting point is 200-400mm / s, the feed speed of the rim deep groove position is 500-700mm / s, the spinning wheel speed is 300-500r / min, the spinning tail top stroke is 600mm, and the spinning mold core runout after mold closing is less than 0.1mm.

7. The method for preparing a 6061 aluminum alloy forged wheel according to claim 1, characterized in that: the aging treatment is performed at 183°C, the temperature is kept for 7-8 hours, and the wheel is naturally cooled after being taken out of the furnace.

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