A method of swage forming an aluminum alloy flange

Abstract

The present application relates to the technical field of die forging, and particularly relates to a die forging forming method of an aluminum alloy flange, which comprises the following steps: freely forging raw materials to obtain an initial blank; obtaining a target forging ratio according to the size of the initial blank and the target size of a final forging piece; performing primary die forging to obtain a pre-forging piece with a flange structure formed, wherein a first strain rate is obtained by real-time detection of the leading edge travel speed of the flange structure to adjust the downward speed of the forging press; performing secondary die forging to make the flange structure radially expand and form a central blind hole, and obtaining a final forging piece, wherein the leading edge travel speed of the flange is detected within a time window to obtain a second strain rate to adjust the downward pressure of the forging press; and sequentially performing solid solution heat treatment and aging heat treatment on the final forging piece to obtain a heat-treated forging piece. The die forging method adopted in the present application is used for forging a 6082 aluminum alloy large flange forging piece, and the flange forging piece has excellent mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of die forging technology, and in particular to a die forging method for aluminum alloy flanges. Background Technology

[0002] 6082 aluminum alloy is an aluminum-magnesium-silicon heat-treatable alloy with medium strength, widely used in mechanical structural parts, shipbuilding, aerospace equipment, and construction. It is suitable for processing into bars, plates, and tubes. Its main characteristics include good formability, weldability, and corrosion resistance. It retains its workability after annealing, and its mechanical properties can be significantly improved through quenching and artificial aging. Currently, the production of 6082 aluminum alloy in China is only at the level of a few leading companies, with overall industry output remaining low. Furthermore, forging methods are mostly based on isothermal forging combined with die forging, which places high demands on production lines and results in very high production costs for companies. At the same time, there is limited experience in producing large forgings, and the forging process is still not fully mature, leading to less than ideal mechanical properties in the finished products.

[0003] Chinese Patent Publication No. CN111020249A discloses a forging process for high-strength aluminum alloy fittings. This technical solution uses aluminum ingots made of 6082 aluminum-magnesium-silicon alloy. The molten aluminum is cast into a mold cavity using a low-pressure casting process, where air pressure is introduced into the furnace to obtain a casting blank. The die-cast blank is then placed in a precision forging mold cavity for forging, directly causing plastic deformation and increasing density. Finally, heat treatment and machining are performed to obtain the desired fitting forging. However, this high-strength aluminum alloy fitting forging process has the following problems: the die forging process places high demands on the production line and is not suitable for large forgings; furthermore, the mechanical properties of the finished product are not ideal. Summary of the Invention

[0004] Therefore, the present invention provides a die forging method for aluminum alloy flanges to overcome the problems of complex and costly isothermal die forging process for large 6082 aluminum alloy flanges in the prior art, as well as insufficient strength uniformity and microstructure stability.

[0005] To achieve the above objectives, the present invention provides a die forging method for aluminum alloy flanges, comprising:

[0006] Step S1: Obtain cylindrical aluminum alloy raw material, heat the raw material to the forging temperature and then perform upsetting and rounding treatment, return the upsetting and rounded hot part to the furnace for reheating to obtain the initial billet, wherein the aluminum alloy raw material is 6082 aluminum alloy;

[0007] Step S2: Based on the dimensions of the initial billet and the target dimensions of the final forging, obtain the target forging ratio;

[0008] Step S3: The initial billet is placed in an annular die, and a pre-forged flange structure is obtained by initial die forging using a forging press. The travel speed of the leading edge of the flange structure is detected in real time to obtain the first strain rate. Based on the first strain rate and the first strain rate reference value, the adjustment amount of the basic pressing speed is determined. Based on the target forging ratio and the adjustment amount of the basic pressing speed, the pressing speed of the forging during the initial die forging is adjusted.

[0009] Step S4: A punch is placed at the center of the upper surface of the pre-forged part, and a secondary die forging is performed by a forging press to radially expand the flange structure and form a central blind hole, thereby obtaining the final forging. The secondary die forging is performed based on the adjusted pressing speed, and the travel speed of the leading edge of the flange edge is detected within a time window to obtain a second strain rate. The pressing pressure of the forging press during the secondary die forging process is adjusted according to the second strain rate and the second strain rate reference value. The duration of the time window is determined based on the adjusted pressing speed and the target size of the flange structure.

[0010] Step S5: The final forging is subjected to solution heat treatment and aging heat treatment in sequence to obtain a heat-treated forging;

[0011] Step S6: Detect the axial hardness distribution of the flange structure of the heat-treated forging to obtain the hardness uniformity, and adjust the first strain rate reference value in the initial die forging process according to the hardness uniformity.

[0012] Further, step S3 includes:

[0013] Step S31: The initial billet is continuously pressed down by a forging press to perform the first die forging.

[0014] Step S32: During the initial die forging process, the forward speed of the flange structure of the initial billet is continuously acquired from a lateral perspective during the forging process, and the first strain rate is calculated.

[0015] Step S33: Determine the adjustment amount of the foundation compression rate based on the first strain rate;

[0016] Step S34: Correct the basic pressing speed adjustment amount according to the target forging ratio to obtain the corrected pressing speed adjustment amount, and adjust the pressing speed of the forging press based on the corrected pressing speed adjustment amount.

[0017] Step S35: When the forging press reaches the preset pressing height, the initial die forging ends, and the pre-forged part is obtained.

[0018] Further, step S4 includes:

[0019] Step S41: A punch is provided at the center position of the upper surface of the pre-forged part;

[0020] Step S42: Continue pressing the punch down at the adjusted pressing speed;

[0021] Step S43: Within the time window, continuously acquire the average leading edge travel speed of the flange structure during the forging process of the pre-forging part from a lateral perspective, and calculate the second strain rate.

[0022] Step S44: Determine the degree of fluidity deviation based on the second strain rate. If the degree of fluidity deviation is greater than or equal to the allowable threshold, adjust the output pressure of the forging press.

[0023] Step S45: When the forging press reaches the preset pressing height, the secondary die forging ends, and the final forging is obtained.

[0024] Further, in step S33, the adjustment amount of the foundation pressing speed is determined based on the first deviation value calculated from the first strain rate and the first strain rate reference value. When the first deviation value is positive, the pressing speed is reduced by a first proportional coefficient, and when the first deviation value is negative, the pressing speed is increased by a second proportional coefficient.

[0025] Furthermore, in step S34,

[0026] The correction amount of the basic pressing speed adjustment is positively correlated with the target forging ratio.

[0027] Further, step S44 includes:

[0028] Step S441: Obtain the second deviation value based on the difference between the second strain rate and the second strain rate reference value;

[0029] Step S442: Calculate the degree of liquidity deviation based on the second deviation value;

[0030] Step S443: Compare the degree of fluidity deviation with the allowable threshold. If the degree of fluidity deviation is greater than or equal to the allowable threshold, adjust the output pressure of the forging press. If the degree of fluidity deviation is less than the allowable threshold, maintain the output pressure of the forging press.

[0031] Furthermore, in step S443, the adjustment amount of the output pressure of the forging press is determined according to the degree of fluidity deviation, wherein the adjustment amount of the output pressure is positively correlated with the degree of fluidity deviation.

[0032] Furthermore, the duration of the time window is negatively correlated with the adjusted pressing speed, and the duration of the time window is positively correlated with the target size of the flange structure.

[0033] Furthermore, the duration of the time window is determined by multiplying the ratio of the target outer diameter of the flange to the adjusted pressing speed with the time window coefficient.

[0034] Furthermore, it also includes:

[0035] Step S7: The heat-treated forging is subjected to dimensional inspection, rough machining, flaw detection, physical and chemical testing, and finish machining in sequence to obtain the finished aluminum alloy flange.

[0036] Compared with the prior art, the beneficial effects of the present invention are that by controlling the deformation dynamics parameters and dislocation structure evolution process of die forging in stages, the present invention enables 6082 aluminum alloy to form an optimized subgrain structure and dislocation density ratio in dynamic recovery, providing a uniform nucleation substrate for aging precipitates, and significantly improving the strength uniformity and structural stability of large flange forgings.

[0037] Furthermore, this invention effectively suppresses material flow inhomogeneity through real-time strain rate feedback and forging ratio correction mechanisms during the initial forging stage. Based on the dynamic adjustment of the pressing speed at the flange leading edge velocity, combined with feedforward compensation of the target forging ratio, it overcomes the differences in hardening effects of high dislocation density materials, stabilizing the dislocation multiplication rate within the optimized range that promotes precipitate nucleation.

[0038] Furthermore, this invention accurately captures the material flow state through an adaptive time window design in the final forging stage, dynamically determines the observation period based on the pressing speed and flange size, eliminates monitoring errors caused by stress relaxation hysteresis in large-sized components, and ensures the reliability of the assessment of dislocation reorganization dynamic equilibrium.

[0039] Furthermore, this invention optimizes the subgrain boundary formation quality through bidirectional pressure compensation for fluidity deviation. When there is a positive deviation, the pressure is increased to promote dislocation cross-slip and avoid depleted regions, while when there is a negative deviation, the pressure is reduced to suppress excessive dislocation entanglement, so that the subgrain integral number and dislocation density are synergistically matched to the β" phase precipitation requirements.

[0040] Furthermore, this invention achieves efficient coupling of strengthening mechanisms through the synergy of initial forging speed control and final forging pressure adjustment. Initial forging ensures orderly dislocation proliferation to enhance solid solution effect, while final forging optimizes dislocation spatial configuration to improve precipitation efficiency. By combining subgrain boundary strengthening and grain boundary strengthening, highly uniform mechanical properties are obtained. Attached Figure Description

[0041] Figure 1 This is a flowchart of the die forging method for aluminum alloy flanges according to an embodiment of the present invention;

[0042] Figure 2 This is a flowchart of step S3 of the die forging method for aluminum alloy flanges according to an embodiment of the present invention;

[0043] Figure 3 This is a flowchart of step S4 of the die forging method for aluminum alloy flanges according to an embodiment of the present invention;

[0044] Figure 4 This is a schematic diagram of the initial die forging of the aluminum alloy flange according to an embodiment of the present invention;

[0045] Figure 5 This is a schematic diagram of the secondary die forging process in the die forging method for aluminum alloy flanges according to an embodiment of the present invention;

[0046] Figure 6 This is a dimensional drawing of the final forging of the aluminum alloy flange using a die forging method according to an embodiment of the present invention.

[0047] Figure 7 This is a parameter diagram of the solution heat treatment and aging heat treatment of the die forging method for aluminum alloy flanges according to an embodiment of the present invention.

[0048] In the figure, 11-initial billet; 12-pre-forging part; 13-final forging part; 21-die body; 22-die base; 23-demolding bottom block; 31-upper anvil; 32-lower round anvil; 4-punch. Detailed Implementation

[0049] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0050] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0051] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0052] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0053] This invention provides a die-forging method for aluminum alloy flanges applied to the forging of 6082 aluminum alloy. Due to the significant dynamic recovery characteristics and moderate strain rate sensitivity of 6082 aluminum alloy, its hardenability differs from that of 2xxx series high-strength aluminum alloys and its hot cracking tendency is relatively high. Furthermore, the strong dependence of its precipitated phase nuclei on dislocation structures is significantly different from that of conventional aluminum alloys. Conventional isothermal forging processes struggle to balance dislocation multiplication and dynamic recovery, easily leading to uneven β" phase precipitation. Additionally, isothermal forging processes are costly and complex. Therefore, this embodiment provides a die-forging method for 6082 aluminum alloy flanges; please refer to [link to relevant documentation]. Figure 1 As shown, it is a flowchart of the die forging method for aluminum alloy flanges according to an embodiment of the present invention, including:

[0054] Step S1: Obtain cylindrical aluminum alloy raw material, heat the raw material to the forging temperature and then perform upsetting and rounding treatment, return the upsetting and rounded hot part to the furnace for reheating to obtain initial billet 11, wherein the aluminum alloy raw material is 6082 aluminum alloy;

[0055] In this embodiment of the invention, the heating temperature is 460℃, the heat preservation coefficient is 1.5min / mm, and the heat preservation time for hot parts to return to the furnace is halved.

[0056] Step S2: Based on the dimensions of the initial billet 11 and the target dimensions of the final forging 13, the target forging ratio is obtained;

[0057] In this embodiment of the invention, the formula for calculating the forging ratio is specifically the ratio of the cross-sectional area of ​​the initial billet 11 to the cross-sectional area of ​​the final forging 13, which is dimensionless and denoted as R; wherein, the cross-sectional area of ​​the final forging 13 is the surface area of ​​the flange structure.

[0058] It is understandable that the cross-sectional area of ​​the initial billet 11 in the formula is taken as the measured value after being heated in the furnace, and the cross-sectional area of ​​the final forging 13 is determined according to the product design drawings; preferably, the forging ratio is in the range of 3.2 to 4.5, which is determined based on the dynamic recrystallization critical strain experiment of 6082 aluminum alloy, and will not be elaborated here.

[0059] Understandably, the target forging ratio plays a corrective role as a benchmark parameter in process control. During the plastic deformation of aluminum alloys, the forging ratio directly reflects the degree of macroscopic strain in the material. This strain degree is quantitatively correlated with the dislocation density and subgrain structure development within the deformation zone. According to the metallurgical strengthening mechanism, a specific range of dislocation density can provide effective nucleation sites for aging precipitates, while the subgrain structure can suppress precipitate coarsening. By controlling the forging ratio within the optimal range, the dislocation density and subgrain integral number of the deformed microstructure can reach a synergistic state, at which point the nucleation rate and size distribution of precipitates reach a better balance. This microstructure state is conducive to the formation of dispersed strengthening phases during subsequent heat treatment, thereby improving the strength stability of the material. In subsequent forging process control, using the target forging ratio as a correction benchmark allows for adaptive adjustment of process parameters for different deformation conditions, improving material flow uniformity and reducing microstructure and property fluctuations caused by local strain differences.

[0060] Step S3: The initial billet 11 is placed in an annular die, and a pre-forged part 12 of the flange structure is obtained by the first die forging through a forging press. The traveling speed of the leading edge of the flange structure is detected in real time to obtain the first strain rate. Based on the first strain rate and the first strain rate reference value, the adjustment amount of the basic pressing speed is determined. Based on the target forging ratio and the adjustment amount of the basic pressing speed, the pressing speed of the forging is adjusted during the first die forging.

[0061] Please continue reading. Figure 2 and Figure 4 As shown, this is a flowchart of step S3 of the die-forging method for aluminum alloy flanges according to an embodiment of the present invention, and a schematic diagram of the initial die-forging of the die-forging method for aluminum alloy flanges according to an embodiment of the present invention; specifically, step S3 includes:

[0062] Step S31: The initial billet 11 is continuously pressed down by a forging press to perform the first die forging.

[0063] In this embodiment of the invention, the forging press is a forging hydraulic press with a maximum nominal pressure of 6000T; the annular die is placed on the upper surface of the lower anvil 32 of the forging hydraulic press, the initial blank 11 is placed in the annular die, and the upper anvil is placed on the upper surface of the initial blank 11. The upper anvil is continuously pressed down by the forging press to perform the initial die forging; wherein, the annular die includes a die body 21 arranged sequentially from top to bottom, and a die base 22 welded and fixed to the die body 21. The die base 22 has a stepped demolding block 23 for demolding at its center.

[0064] Step S32: During the initial die forging process, the forward speed of the flange structure of the initial billet 11 during the forging process is continuously acquired from a lateral perspective, and the first strain rate is calculated.

[0065] In this embodiment of the invention, an industrial camera is used to continuously acquire the radial expansion of the outer edge of the flange per unit time during the forging process of the initial blank 11 from a side view.

[0066] In this embodiment of the invention, the first strain rate is the radial expansion of the outer edge of the flange structure within the sampling time divided by the product of the initial blank's radial outer diameter and the sampling time. The specific formula for calculating the first strain rate is as follows:

[0067] ,

[0068] Where s1 is the first strain rate, in seconds. -1 △t is the sampling time of the industrial camera, in seconds (s), preferably △t is 0.1s; △L is the radial expansion of the outer edge of the flange structure within the time △t, in millimeters (mm); L0 is the radial outer diameter of the initial blank 11, in millimeters (mm).

[0069] Step S33: Determine the adjustment amount of the foundation compression rate based on the first strain rate;

[0070] Specifically, in step S33, the adjustment amount of the foundation pressing speed is determined based on the first deviation value calculated from the first strain rate and the first strain rate reference value. When the first deviation value is positive, the pressing speed is reduced by a first proportional coefficient, and when the first deviation value is negative, the pressing speed is increased by a second proportional coefficient.

[0071] In this embodiment of the invention, the first deviation value is the difference between the first strain rate and the first strain rate reference value, divided by the first strain rate reference value. The specific formula for calculating the first deviation value is as follows:

[0072] ,

[0073] Where d1 is the first deviation value, which is dimensionless; s r1 This is the first strain rate reference value, in seconds. -1 The value range is 0.8s. -1 ~1.2s -1 Preferably, s r1 Take 0.8s -1 .

[0074] The specific formula for calculating the adjustment amount of the base compression speed is as follows:

[0075] ,

[0076] Wherein, △V bV0 is the base pressing speed adjustment amount, in mm / s; V0 is the current pressing speed, in mm / s; k1 is the first proportional coefficient, with a value range of 0.4 to 0.6, preferably 0.4; k2 is the second proportional coefficient, with a value range of 0.2 to 0.4, preferably 0.35.

[0077] It is understandable that the difference in the values ​​of the proportional coefficients k1 and k2 for adjusting the compression speed stems from the asymmetric nature of the aluminum alloy's strain rate sensitivity, with k1 > k2 reflecting a more significant material hardening effect during high-speed deformation; the speed adjustment amount ΔV b The unit is consistent with V0 (mm / s), and the adjusted speed must meet the equipment safety limit (usually ≤100mm / s).

[0078] Understandably, since the flange area bears the maximum shear stress and has clearly defined deformation constraints during die forging, its strain rate changes can sensitively reflect the material flow resistance state. When the measured strain rate is higher than the reference value, it indicates that the material flow is too fast and easily leads to local thinning. In this case, proportionally reducing the pressing speed can increase the dislocation cross-slip time and promote the orderly arrangement of dislocations to form subgrain boundaries. When the strain rate is lower than the reference value, the dislocation multiplication rate is increased by accelerating the speed to avoid excessive consumption of deformation energy during dynamic recovery. This speed regulation based on strain rate feedback essentially controls the dislocation dynamics to match the substructure development rate with the nucleation requirements of the precipitated phase, thereby obtaining a strengthening phase with a more concentrated size distribution in the subsequent aging treatment, ultimately improving the uniformity of the mechanical properties of the forging.

[0079] Step S34: Correct the basic pressing speed adjustment amount according to the target forging ratio to obtain the corrected pressing speed adjustment amount, and adjust the pressing speed of the forging press based on the corrected pressing speed adjustment amount.

[0080] Specifically, in step S34,

[0081] The correction amount of the basic pressing speed adjustment is positively correlated with the target forging ratio.

[0082] In this embodiment of the invention, the calculation formula for the adjusted downward pressing speed is as follows:

[0083] ,

[0084] Wherein, △V is the adjustment amount of the basic pressing speed, in mm / s; β is the forging ratio correction coefficient, dimensionless, which is based on the forging ratio test calibration of 6082 aluminum alloy series, and will not be elaborated here. The value range is 0.08 to 0.15, preferably β is 0.08; R is the target forging ratio, dimensionless.

[0085] Understandably, the target forging ratio is determined at the initial stage of the process, and its value characterizes the overall deformation design value of the forging from the initial billet 11 to the final formed. This preset macroscopic deformation amount is directly related to the initial configuration state of the dislocation structure inside the material. A higher forging ratio means that the design requires greater plastic deformation, thus pre-setting a more significant work hardening potential. When adjusting the speed during the actual forging process, if this preset hardening potential is ignored, the same adjustment amount will produce different responses under different forging ratio conditions. By introducing a correction coefficient that is positively correlated with the target forging ratio, it is essentially to pre-compensate for the expected changes in material flow resistance based on the overall deformation design scale, so that the speed adjustment amount remains moderately sensitive under low forging ratio conditions and enhances the control force under high forging ratio conditions.

[0086] This invention effectively overcomes the control lag caused by differences in material hardening state through a feedforward correction mechanism based on a preset forging ratio, ensuring that the dislocation multiplication rate is always within the kinetic window for optimizing the nucleation phase.

[0087] Step S35: When the forging press reaches the preset pressing height, the initial die forging ends, and the pre-forged part 12 is obtained.

[0088] Step S4: A punch 4 is placed at the center of the upper surface of the pre-forged part 12, and a secondary die forging is performed by a forging press to radially expand the flange structure and form a central blind hole, resulting in the final forging part 13. The secondary die forging is performed based on the adjusted pressing speed, and the forward travel speed of the flange edge is detected within a time window to obtain a second strain rate. The pressing pressure of the forging press during the secondary die forging process is adjusted according to the second strain rate and the second strain rate reference value. The duration of the time window is determined based on the adjusted pressing speed and the target size of the flange structure.

[0089] Please continue reading. Figure 3 and Figure 5 As shown, this is a flowchart of step S4 of the die-forging method for aluminum alloy flanges according to an embodiment of the present invention, and a schematic diagram of the secondary die-forging of the die-forging method for aluminum alloy flanges according to an embodiment of the present invention; specifically, step S4 includes:

[0090] Step S41: A punch 4 is provided at the center position of the upper surface of the pre-forged part 12;

[0091] Step S42: Continue pressing down the punch 4 at the adjusted pressing speed;

[0092] In this embodiment of the invention, after a punch 4 is set at the center of the upper surface of the pre-forged part 12, an upper anvil is placed on the upper surface of the punch 4, and the upper anvil is continuously pressed down by a forging press to perform secondary die forging.

[0093] Step S43: Within the time window, continuously acquire the average leading edge travel speed of the flange structure of the pre-forged part 12 during the forging process from a lateral perspective, and calculate the second strain rate.

[0094] In this embodiment of the invention, the second strain rate is the average radial expansion of the outer edge of the flange structure within each sampling duration in the time window, divided by the product of the radial outer diameter of the flange structure of the pre-forged part and the sampling time. The specific formula for calculating the second strain rate is as follows:

[0095] ,

[0096] Where s2 is the second strain rate, in seconds. -1 , △L p L1 is the average radial expansion of the outer edge of the flange structure within each Δt time interval in the time window, in millimeters (mm); L1 is the radial outer diameter of the flange structure of the pre-forged part 12, in millimeters (mm).

[0097] The time window is a continuous period from the instant the punch 4 contacts the upper surface of the pre-forging 12 until the duration of the time window has elapsed. The second strain rate measured during this period can characterize the dynamic equilibrium state of dislocation reorganization.

[0098] Specifically, the duration of the time window is negatively correlated with the adjusted pressing speed, and the duration of the time window is positively correlated with the target size of the flange structure.

[0099] Specifically, the duration of the time window is determined by multiplying the ratio of the flange target outer diameter to the adjusted pressing speed with a time window coefficient.

[0100] In this embodiment of the invention, the duration of the time window is the ratio of the target outer diameter of the flange to the adjusted pressing speed, multiplied by a time window coefficient. The specific formula for calculating the duration of the time window is as follows:

[0101] ,

[0102] Among them, T w The duration of the time window is in seconds (s); D is the target outer diameter of the flange, in millimeters (mm); V a The adjusted downward pressure velocity is expressed in mm / s; m is the time window coefficient, which is dimensionless and ranges from 0.5 to 0.8. Preferably, m is 0.6, which is determined by flow stability testing, and will not be elaborated further here.

[0103] Understandably, during the final forging process where punching and diameter expansion occur simultaneously, the material flow state exhibits inertial characteristics due to historical deformation, requiring a sufficiently long observation period to accurately assess the control effect. The negative correlation between the time window and the pressing speed essentially reflects the dynamic response characteristics under different process rhythms. In high-speed forging, material flow changes rapidly, and shortening the window allows for timely capture of state changes, while low-speed forging requires extending the window to accumulate effective data. Conversely, the positive correlation between the window and flange size stems from the inherently higher requirements for deformation coordination in large-sized components; larger deformation areas require longer stress wave transmission periods to establish a stable flow field.

[0104] This dynamic window design effectively overcomes the phase lag problem caused by the traditional fixed sampling period when evaluating material flowability, ensuring that the detected second strain rate truly reflects the dynamic equilibrium state of dislocation reorganization.

[0105] Step S44: Determine the degree of fluidity deviation based on the second strain rate. If the degree of fluidity deviation is greater than or equal to the allowable threshold, adjust the output pressure of the forging press.

[0106] Specifically, step S44 includes:

[0107] Step S441: Obtain the second deviation value based on the difference between the second strain rate and the second strain rate reference value;

[0108] In this embodiment of the invention, the second deviation value is the difference between the second strain rate and the second strain rate reference value, divided by the second strain rate reference value. The specific formula for calculating the second deviation value is as follows:

[0109] ,

[0110] Where d2 is the second deviation value, which is dimensionless; s r2 This is the second strain rate reference value, in seconds. -1 The value range is 0.9s. -1 ~1.1s -1 Preferably, s r2 Take 0.9s -1 .

[0111] Step S442: Calculate the degree of liquidity deviation based on the second deviation value;

[0112] In this embodiment of the invention, the degree of fluidity deviation is the product of the absolute value of the material sensitivity coefficient and the second deviation value. The specific formula for calculating the degree of fluidity deviation is as follows:

[0113] ,

[0114] Wherein, λ is the degree of fluidity deviation, dimensionless; α is the material sensitivity coefficient, dimensionless, with a value range of 0.15 to 0.25, preferably α is 0.2, which is based on the rheological curve calibration of several aluminum alloys, which will not be elaborated here.

[0115] Step S443: Compare the degree of fluidity deviation with the allowable threshold. If the degree of fluidity deviation is greater than or equal to the allowable threshold, adjust the output pressure of the forging press. If the degree of fluidity deviation is less than the allowable threshold, maintain the output pressure of the forging press.

[0116] Specifically, in step S443, the adjustment amount of the output pressure of the forging press is determined according to the degree of fluidity deviation, wherein the adjustment amount of the output pressure is positively correlated with the degree of fluidity deviation.

[0117] In this embodiment of the invention, the formula for calculating the adjustment amount of the output pressure is as follows:

[0118] ,

[0119] Where ΔP is the adjustment amount of the output pressure, in tons (T); f is the pressure adjustment coefficient, dimensionless, ranging from 1.0 to 1.5, preferably f is 1.2; λ t To allow a threshold, dimensionless, preferably, λ t Take 0.08; P0 is the current output pressure, in tons (T).

[0120] Understandably, the pressure adjustment mechanism in this step optimizes precipitation strengthening by regulating the dislocation reorganization process. Its technical principle is based on the unique multiphase strengthening mechanism of 6xxx series aluminum alloys. The essence of pressure adjustment in the final forging stage is to control the spatial configuration of the dislocation network. When a positive strain rate deviation is detected, the pressurization operation increases hydrostatic pressure to promote dislocation cross-slip, avoiding insufficient nucleation sites for precipitates due to dislocation depletion. Conversely, when there is a negative deviation, the pressure reduction decreases shear stress to suppress excessive dislocation entanglement and prevent abnormal coarsening of precipitates caused by high dislocation density. This bidirectional regulation enables sub-... When the crystal integral number and dislocation density reach an optimal balance, the increased dislocation density provides more nucleation sites for the β" phase, prompting the precipitates to refine to the optimal size of 6nm to 9nm. At the same time, the orderly distribution of subgrain boundaries forms dislocation walls that hinder the excessive growth of the precipitates. Compared to the single objective of controlling the dislocation multiplication rate and preventing shear defects by adjusting the speed in the initial forging stage, the final forging pressure adjustment focuses more on building an ideal substructure template at the end of high-temperature deformation, so that the β" phase can form a uniformly distributed needle-like precipitate along the zone axis during subsequent aging treatment, fundamentally improving the yield strength of the forging.

[0121] Step S45: When the forging press reaches the preset pressing height, the secondary die forging ends, and the final forging 13 is obtained.

[0122] Step S5: The final forging 13 is subjected to solution heat treatment and aging heat treatment in sequence to obtain a heat-treated forging;

[0123] In this embodiment of the invention, the final forging 13 is removed from the annular mold by pushing the demolding bottom block 23; the placement of the final forging 13 is changed from horizontal to vertical by using a tooling bracket to increase the overall contact area between the final forging 13 and water, thereby providing a cooling effect without affecting the overall furnace loading; an external thermocouple is required during heat treatment.

[0124] In one specific embodiment, the final forging 13 is subjected to solution heat treatment at a temperature of 530±5℃ for 5 to 5.5 hours, followed by water cooling. Then, the final forging 13 is subjected to solution heat treatment and aging heat treatment at a temperature of 173±5℃ for 13 to 13.5 hours, followed by air cooling.

[0125] Step S6: Detect the axial hardness distribution of the flange structure of the heat-treated forging to obtain the hardness uniformity, and adjust the first variable rate reference value in the initial die forging process according to the hardness uniformity.

[0126] In this embodiment of the invention, hardness uniformity is the difference between the maximum and minimum measured hardness values, divided by the average measured hardness values. The specific formula for calculating hardness uniformity is as follows:

[0127] ,

[0128] Among them, H u For hardness uniformity, dimensionless; H max This represents the maximum measured hardness value, expressed in HB; H min This represents the minimum measured hardness value, expressed in HB; H v This is the average value of the measured hardness values, in HB, which is the sum of all measured hardness values ​​divided by the total number of measured hardness values.

[0129] In practice, an HB hardness tester is used to uniformly set test points on the upper surface of the flange structure of the heat-treated forging, with the center of the blind hole as the center. The test direction is perpendicular to the upper surface of the flange structure, and the total number of measured hardness values ​​is taken as 4 to 10.

[0130] In this embodiment of the invention, the adjustment formula for the first variable rate reference value is specifically as follows:

[0131] ,

[0132] Among them, s k This is the adjusted first variable speed reference value, in seconds. -1μ is the feedback coefficient, dimensionless, with a value range of 1 to 1.5, preferably μ is 1.5; H0 is the hardness uniformity threshold, in HB, with a value range of 0.05 to 0.8, preferably H0 is 0.05.

[0133] Among them, the adjusted first variable rate reference value s k It still meets the 0.8s requirement. -1 ≤s k ≤1.2s -1 .

[0134] In the subsequent die forging process, the adjusted first variable rate reference value is adopted.

[0135] It is understandable that the axial hardness uniformity of forgings after heat treatment essentially reflects the consistency of precipitate distribution. The nucleation density of precipitates directly depends on the uniformity of the dislocation network formed during the initial forging stage. When insufficient hardness uniformity is detected, it indicates regional differences in dislocation density. High-hardness areas correspond to dense precipitates due to high dislocation density, while low-hardness areas result in sparse precipitates due to dislocation scarcity. By increasing the baseline value of the initial forging strain rate through negative feedback, the baseline value of the dislocation multiplication rate is essentially increased overall, prompting the material to form a high dislocation density state over a larger area, thereby increasing the nucleation sites for precipitates across the entire region. At the same time, increasing the baseline value can suppress dislocation density troughs caused by local flow hysteresis and reduce the dislocation density range between regions. This closed-loop control makes the spatial distribution of the dislocation network more uniform in subsequent forging, ultimately ensuring that the precipitates are uniformly dispersed along the grain interior during aging treatment, fundamentally improving the consistency of the axial mechanical properties of the flange.

[0136] Step S7: The heat-treated forging is subjected to dimensional inspection, rough machining, flaw detection, physical and chemical testing, fine machining, and final inspection in sequence to obtain the finished aluminum alloy flange.

[0137] In this embodiment of the invention, after rough machining to ensure a surface roughness of Ra6.3, ultrasonic testing is performed; after sampling, physical and chemical tests are conducted, followed by fine machining and final testing to obtain the finished aluminum alloy flange.

[0138] Please see Figure 6 and Figure 7 As shown, these are, respectively, the dimensional diagram of the final forging of the aluminum alloy flange using the die forging method according to an embodiment of the present invention, and the parameter diagram of the solution heat treatment and aging heat treatment of the aluminum alloy flange using the die forging method according to an embodiment of the present invention.

[0139] Example 1:

[0140] Using raw material 6082 from Suzhou Jiaohang Zhongxin New Materials Co., Ltd. (compliant with EN 573-3-2019+A2-2023 standards), the blank weight was 310kg, with dimensions of Φ458mm×700mm. Heated to 460℃ (holding coefficient 1.5min / mm), it was freely forged and upset to a height of 282mm, then rolled to a diameter of 720mm. The furnace holding time was halved to obtain the initial blank. The target forging ratio R was calculated to be 4.23.

[0141] The initial billet was placed in a ring mold and forged using a hydraulic press at an initial pressing speed of 80 mm / s. An industrial camera (Δt = 0.1 s) was used to monitor the flange leading edge speed in real time, and the first strain rate was calculated. The first strain rate was 1.05 s. -1 At that time, the pressing speed was adjusted from 80mm / s to 66.62mm / s.

[0142] A punch was placed in the center of the pre-forged part and pressed down at 66.62 mm / s. The calculated time window was 9.8 s. The fluidity deviation measured within the time window was 0.071, which did not trigger pressure adjustment.

[0143] The final forging is subjected to solution heat treatment and aging heat treatment in sequence to obtain a heat-treated forging. The hardness of the axial normal surface of the heat-treated forging is tested (9 test points are selected uniformly in a ring), and the hardness uniformity Hu is calculated to be 0.48, which does not trigger the adjustment of the first strain rate reference value.

[0144] Example 2:

[0145] Step S34 is modified to directly use the basic pressing speed adjustment amount without forging ratio correction, and the rest is exactly the same as in Example 1.

[0146] Example 3:

[0147] Step S43 is modified to use a fixed time window of 5 seconds, and the rest is exactly the same as in Example 1.

[0148] Example 4:

[0149] Step S44 is modified to maintain the output pressure unchanged and cancel the threshold judgment, and the rest is exactly the same as in Example 1.

[0150] Tensile tests were performed on Examples 1 to 4 according to EN ISO 6892-1:2019, and the experimental results are shown in Table 1.

[0151] Table 1 Performance test results of each embodiment

[0152] ;

[0153] It can be seen that in Example 2, the absence of forging ratio correction led to inaccurate material flow control, widening the difference between high and low dislocation density regions, and uneven distribution of precipitate nucleation sites, resulting in a simultaneous decrease in strength and hardness. In Example 3, the use of a fixed time window caused misjudgment of dislocation recombination state, and the lag in pressure compensation resulted in incomplete subgrain boundary formation, an increase in dislocation entanglement regions, and a significant deterioration in elongation. In Example 4, the lack of a pressure compensation mechanism prevented the correction of abnormal material flow, and the coexistence of dislocation-poor and entanglement regions led to increased dispersion in precipitate size, resulting in a comprehensive decline in overall mechanical properties. These three examples together demonstrate that the synergistic effect of forging ratio feedforward compensation, dynamic window monitoring, and bidirectional pressure control can ensure the uniformity of dislocation density spatial distribution in die forging and optimize the precipitate nucleation substrate.

[0154] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

Claims

1. A method for forging an aluminum alloy flange using a die, characterized in that, include: Step S1: Obtain cylindrical aluminum alloy raw material, heat the raw material to the forging temperature and then perform upsetting and rounding treatment, return the upsetting and rounded hot part to the furnace for reheating to obtain the initial billet, wherein the aluminum alloy raw material is 6082 aluminum alloy; Step S2: Based on the dimensions of the initial billet and the target dimensions of the final forging, obtain the target forging ratio; Step S3: The initial billet is placed in an annular die, and a pre-forged flange structure is obtained by initial die forging using a forging press. The travel speed of the leading edge of the flange structure is detected in real time to obtain the first strain rate. Based on the first strain rate and the first strain rate reference value, the adjustment amount of the basic pressing speed is determined. Based on the target forging ratio and the adjustment amount of the basic pressing speed, the pressing speed of the forging during the initial die forging is adjusted. Step S4: A punch is placed at the center of the upper surface of the pre-forged part, and a secondary die forging is performed by a forging press to radially expand the flange structure and form a central blind hole, thereby obtaining the final forging. The secondary die forging is performed based on the adjusted pressing speed, and the travel speed of the leading edge of the flange edge is detected within a time window to obtain a second strain rate. The pressing pressure of the forging press during the secondary die forging process is adjusted according to the second strain rate and the second strain rate reference value. The duration of the time window is determined based on the adjusted pressing speed and the target size of the flange structure. Step S5: The final forging is subjected to solution heat treatment and aging heat treatment in sequence to obtain a heat-treated forging; Step S6: Detect the axial hardness distribution of the flange structure of the heat-treated forging to obtain the hardness uniformity, and adjust the first strain rate reference value in the initial die forging process according to the hardness uniformity.

2. The die forging method for aluminum alloy flanges according to claim 1, characterized in that, Step S3 includes: Step S31: The initial billet is continuously pressed down by a forging press to perform the first die forging. Step S32: During the initial die forging process, the forward speed of the flange structure of the initial billet is continuously acquired from a lateral perspective during the forging process, and the first strain rate is calculated. Step S33: Determine the adjustment amount of the foundation compression rate based on the first strain rate; Step S34: Correct the basic pressing speed adjustment amount according to the target forging ratio to obtain the corrected pressing speed adjustment amount, and adjust the pressing speed of the forging press based on the corrected pressing speed adjustment amount. Step S35: When the forging press reaches the preset pressing height, the initial die forging ends, and the pre-forged part is obtained.

3. The die forging method for aluminum alloy flanges according to claim 2, characterized in that, Step S4 includes: Step S41: A punch is provided at the center position of the upper surface of the pre-forged part; Step S42: Continue pressing the punch down at the adjusted pressing speed; Step S43: Within the time window, continuously acquire the average leading edge travel speed of the flange structure during the forging process of the pre-forging part from a lateral perspective, and calculate the second strain rate. Step S44: Determine the degree of fluidity deviation based on the second strain rate. If the degree of fluidity deviation is greater than or equal to the allowable threshold, adjust the output pressure of the forging press. Step S45: When the forging press reaches the preset pressing height, the secondary die forging ends, and the final forging is obtained.

4. The die forging method for aluminum alloy flanges according to claim 2, characterized in that, In step S33, the adjustment amount of the foundation pressing speed is determined based on the first deviation value calculated from the first strain rate and the first strain rate reference value. When the first deviation value is positive, the pressing speed is reduced by a first proportional coefficient, and when the first deviation value is negative, the pressing speed is increased by a second proportional coefficient.

5. The die forging method for aluminum alloy flanges according to claim 2, characterized in that, In step S34, The correction amount of the basic pressing speed adjustment is positively correlated with the target forging ratio.

6. The die forging method for aluminum alloy flanges according to claim 3, characterized in that, Step S44 includes: Step S441: Obtain the second deviation value based on the difference between the second strain rate and the second strain rate reference value; Step S442: Calculate the degree of liquidity deviation based on the second deviation value; Step S443: Compare the degree of fluidity deviation with the allowable threshold. If the degree of fluidity deviation is greater than or equal to the allowable threshold, adjust the output pressure of the forging press. If the degree of fluidity deviation is less than the allowable threshold, maintain the output pressure of the forging press.

7. The die forging method for aluminum alloy flanges according to claim 6, characterized in that, In step S443, the adjustment amount of the output pressure of the forging press is determined according to the degree of fluidity deviation, wherein the adjustment amount of the output pressure is positively correlated with the degree of fluidity deviation.

8. The die forging method for aluminum alloy flanges according to claim 1, characterized in that, The duration of the time window is negatively correlated with the adjusted pressing speed, and the duration of the time window is positively correlated with the target size of the flange structure.

9. The die forging method for aluminum alloy flanges according to claim 8, characterized in that, The duration of the time window is determined by multiplying the ratio of the target outer diameter of the flange to the adjusted pressing speed with the time window coefficient.

10. The die forging method for aluminum alloy flanges according to claim 1, characterized in that, Also includes: Step S7: The heat-treated forging is subjected to dimensional inspection, rough machining, flaw detection, physical and chemical testing, and finish machining in sequence to obtain the finished aluminum alloy flange.

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