Frame rib type aluminum alloy die forging low residual stress design method

Abstract

The invention provides a low residual stress design method for a frame rib type aluminum alloy die forging. According to the low-residual-stress design method for the frame rib type aluminum alloy die forging disclosed by the invention, by supplementing the machining allowance of the part, the quenching residual stress under different characteristic structure parameters and the distribution condition of the residual stress after different cold pressing deformation parameters are analyzed on the basis of simulation, so that the cold pressing blank molded surface optimization design is realized; according to the method, the residual stress of a core body of the frame and rib type aluminum alloy die forging is controlled to be below a first preset value, then hot forging simulation is carried out based on a cold-pressed blank molded surface, a hot-forged blank molded surface is designed based on equipment tonnage, material mold filling and streamline optimization, and finally the required frame and rib type aluminum alloy die forging can be obtained.

Description

Technical Field

[0001] The present invention relates to the field of complex workpiece processing, and in particular to a low residual stress design method for a frame-rib type aluminum alloy die forging. Background Art

[0002] Aluminum alloy, a material with low density and high specific strength, is widely used in aircraft as the primary load-bearing components. These large-sized aluminum alloy integral frame-rib parts, comprised of ribs and webs, are typically machined from aluminum alloy die forgings to ensure their overall mechanical properties, particularly their fatigue resistance through the thickness.

[0003] However, due to the complex structure and large size of large-size aluminum alloy integral frame rib parts, the residual stress distribution inside the large-size aluminum alloy integral frame rib parts is uneven and the stress level is high. In addition, the residual stress of the large-size aluminum alloy integral frame rib parts will be further released during the machining process, resulting in the geometric size of the large-size aluminum alloy integral frame rib parts being out of tolerance. When the deviation is too large, it will directly lead to the scrapping of the large-size aluminum alloy integral frame rib parts. When the deviation is small, it usually leads to the large-size aluminum alloy integral frame rib parts being assembled with stress, seriously affecting the life of the aircraft. Summary of the Invention

[0004] In view of this, an embodiment of the present invention provides a low residual stress design method for frame-rib type aluminum alloy die forgings to solve the problem of geometric size deviation of existing large-size aluminum alloy integral frame-rib type parts due to uneven internal residual stress distribution and high stress level.

[0005] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0006] A low residual stress design method for a frame-rib type aluminum alloy die forging, comprising:

[0007] S1. Add machining allowance to each part of the frame-rib aluminum alloy die forging in the simulation software;

[0008] S2. Analyze the residual stresses in various parts of the frame-rib aluminum alloy die forging after quenching and cold pressing in simulation software;

[0009] S3. If the residual stress of the frame-rib type aluminum alloy die forging is less than the first preset value, and the residual stress differences corresponding to all parts of the frame-rib type aluminum alloy die forging are less than the second preset value, determining the cold-pressed profile of the frame-rib type aluminum alloy die forging; otherwise, adjusting the supplementary machining allowances of various parts of the frame-rib type aluminum alloy die forging in the simulation software, and executing S2;

[0010] S4. Analyzing in simulation software whether structural defects occur in a frame-rib aluminum alloy die forging after hot forging under a preset strategy, wherein the preset strategy includes a forging temperature setting, a forming speed setting, a forming tonnage setting, and a molded surface obtained by forging;

[0011] S5. If no structural defects occur in any part of the frame-rib type aluminum alloy die forging, determine the various surface parameters of the frame-rib type aluminum alloy die forging, where the structural defects include structural permeation; otherwise, adjust the preset strategy and execute S4.

[0012] Preferably, S2 includes:

[0013] S21. Analyze the residual stresses of various parts of the frame-rib aluminum alloy die forging after quenching in simulation software;

[0014] S22. If the residual stress of the frame-rib type aluminum alloy die forging is less than the third preset value, and the residual stress differences corresponding to all parts of the frame-rib type aluminum alloy die forging are less than the fourth preset value, determining the cold-pressed profile of the frame-rib type aluminum alloy die forging; otherwise, adjusting the supplementary machining allowances of various parts of the frame-rib type aluminum alloy die forging in the simulation software, and executing S21;

[0015] S23. Analyze the residual stress of various parts of the frame-rib aluminum alloy die forging after cold pressing in the simulation software.

[0016] Preferably, the supplementary machining allowances of various parts of the frame-rib type aluminum alloy die forging are adjusted in the simulation software, including:

[0017] The fillet angle and the height of the short rib of the frame-rib aluminum alloy die forging are adjusted in the simulation software.

[0018] Preferably, adjusting the fillet angle and the height of the short rib of the frame-rib type aluminum alloy die forging in the simulation software includes:

[0019] In the simulation software, the fillet angle of the frame-rib aluminum alloy die forging is adjusted within a preset angle range;

[0020] In the simulation software, the height of the short ribs of the frame-rib type aluminum alloy die forgings is adjusted within a preset height range.

[0021] Preferably, before executing S23, the method further includes:

[0022] The cold pressing deformation range of the web of the frame-rib type aluminum alloy die forging is set to 0.5%-1%, and the cold pressing deformation range of the rib is set to 1%-2.5%.

[0023] Preferably, S4 includes:

[0024] S41. Design the structural parameters, forming speed, and hot forging temperature of the frame-rib aluminum alloy die forging in simulation software;

[0025] S42. Analyze forging forming force;

[0026] S43. Design the pre-forging times and pre-forging die profile based on the forming force;

[0027] S44. Analyze the forming force and structural streamline of the frame-rib type aluminum alloy die forgings at different forging stages in the simulation software, and determine whether structural defects occur in the frame-rib type aluminum alloy die forgings.

[0028] Preferably, after S5, the method further includes:

[0029] S6. Determining a slab of the frame-rib type aluminum alloy die forging based on various profile parameters of the frame-rib type aluminum alloy die forging;

[0030] S7. Hot forging and cold pressing are performed on the slab of the frame rib type aluminum alloy die forging.

[0031] Preferably, S7 includes:

[0032] S71, placing the slab into a furnace at a preset temperature for heat treatment;

[0033] S72, hot forging the slab based on the forming speed;

[0034] S73, placing the slab into the furnace, and allowing the slab to cool to below the target temperature as the furnace temperature decreases;

[0035] S74, placing the slab in a room temperature environment to cool;

[0036] S75, machining the slab to obtain a frame-ribbed aluminum alloy die forging;

[0037] S76. Insulating the frame-ribbed aluminum alloy die forgings;

[0038] S77, quenching the frame rib type aluminum alloy die forging;

[0039] S78. Cold press the frame rib type aluminum alloy die forgings.

[0040] Preferably, after S7, the method further includes:

[0041] S8. Detect residual stress of frame rib type aluminum alloy die forgings.

[0042] Based on the low residual stress design method of a frame rib type aluminum alloy die forging provided by the present invention, by supplementing the machining allowance of each part of the frame rib type aluminum alloy die forging in the simulation software, and analyzing the residual stress of each part of the frame rib type aluminum alloy die forging after quenching and cold pressing in the simulation software, if the residual stress of the frame rib type aluminum alloy die forging is less than a first preset value, and the residual stress difference corresponding to all parts of the frame rib type aluminum alloy die forging is less than a second preset value, the cold pressing profile of the frame rib type aluminum alloy die forging is determined; otherwise, the residual stress difference of each part of the frame rib type aluminum alloy die forging is analyzed in the simulation software. The supplementary machining allowance is adjusted, and the residual stress of each part of the frame-rib type aluminum alloy die forging after quenching and cold pressing is analyzed in the simulation software; then, the simulation software is analyzed whether the frame-rib type aluminum alloy die forging has structural defects after hot forging under the preset strategy; if no structural defects occur in various parts of the frame-rib type aluminum alloy die forging, the various surface parameters of the frame-rib type aluminum alloy die forging are determined, wherein the structural defects include structural permeation; otherwise, the preset strategy is adjusted, and the simulation software is analyzed whether the frame-rib type aluminum alloy die forging has structural defects after hot forging under the preset strategy. Through the above-mentioned disclosed low residual stress design method for frame-rib type aluminum alloy die forgings, by supplementing the part processing allowance, the quenching residual stress under different characteristic structural parameters and the distribution of residual stress after different cold pressing deformation parameters are analyzed based on simulation, and then the cold-pressed billet profile is optimized to control the residual stress of the core body of the frame-rib type aluminum alloy die forging to below a first preset value. Then, hot forging simulation is carried out based on the cold-pressed billet profile, and the hot forging billet profile is optimized and designed based on the equipment tonnage, material filling and streamline. Finally, the required frame-rib type aluminum alloy die forging can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0044] Figure 1 A schematic flow chart of a low residual stress design method for a frame-rib aluminum alloy die forging provided in an embodiment of the present invention;

[0045] Figure 2 A schematic diagram of a specific execution flow for analyzing the residual stresses of various parts of the frame-rib aluminum alloy die forging after quenching and cold pressing in simulation software provided by an embodiment of the present invention;

[0046] Figure 3 A schematic structural diagram of a frame-ribbed aluminum alloy die forging provided in an embodiment of the present invention;

[0047] Figure 4 A schematic diagram of a process for analyzing in simulation software whether a frame-rib aluminum alloy die forging has structural defects after hot forging under a preset strategy, provided in an embodiment of the present invention;

[0048] Figure 5 A schematic flow chart of another method for designing low residual stress of a frame-rib aluminum alloy die forging provided by an embodiment of the present invention;

[0049] Figure 6 A schematic flow chart of another method for designing low residual stress of a frame-rib aluminum alloy die forging provided by an embodiment of the present invention;

[0050] Figure 7 A schematic diagram of the process of hot forging and cold pressing a slab of a frame-rib type aluminum alloy die forging provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0051] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0052] In this application, the terms "comprises," "comprising," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not preclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0053] The embodiment of the present invention provides a method for designing low residual stress of frame rib type aluminum alloy die forgings, see Figure 1 The low residual stress design method of frame rib type aluminum alloy die forgings includes at least the following steps:

[0054] S1. Add processing allowance to each part of the frame-rib type aluminum alloy die forging in the simulation software.

[0055] It should be noted that by adding machining allowances to various parts of the frame-rib aluminum alloy die forging in the simulation software, the outer shape of the frame-rib aluminum alloy die forging can be formed, which is convenient for subsequent forging simulation.

[0056] refer to Figure 3The various parts of the conventional frame-rib type aluminum alloy die forging of the present application include the web thickness 1, the rib top 2, the rib thickness 3, the fillet of the rib bottom 4, the fillet of the rib top 5, and the rib draft angle 6. In the simulation software, the processing allowance is added to the various parts of the frame-rib type aluminum alloy die forging, such as increasing the single-side thickness of the web by 15mm-25mm, increasing the top of the rib by 5mm-10mm, increasing the single-side thickness of the rib by rib height h / 8mm-rib height h / 3mm, increasing the fillet of the top of the rib to R5-R30, the fillet of the top of the rib to R5-R10, and the draft angle of the rib to 5deg-10deg.

[0057] S2. Analyze the residual stress of various parts of the frame-rib aluminum alloy die forging after quenching and cold pressing in the simulation software.

[0058] It should be noted that by analyzing the residual stresses of various parts of the frame-rib type aluminum alloy die forging after quenching and cold pressing, the processing deformation caused by the release of residual stress during the machining of the frame-rib type aluminum alloy die can be effectively reduced. Therefore, it is necessary to ensure that the residual stress of the frame-rib type aluminum alloy die forging is less than the first preset value, and the residual stress differences corresponding to all parts of the frame-rib type aluminum alloy die forging are less than the second preset value.

[0059] It should also be noted that the first preset value and the second preset value need to be set according to frame-rib type aluminum alloy die forgings of different sizes, and this application does not make specific limitations.

[0060] Preferably, the first preset value is 250 MPa and the second preset value is 50 MPa.

[0061] S3. Determine whether the residual stress of the frame-rib type aluminum alloy die forging is less than a first preset value, and whether the residual stress differences corresponding to all parts of the frame-rib type aluminum alloy die forging are less than a second preset value. If the residual stress of the frame-rib type aluminum alloy die forging is less than the first preset value, and the residual stress differences corresponding to all parts of the frame-rib type aluminum alloy die forging are less than the second preset value, execute step S31; otherwise, adjust the supplementary machining allowances of various parts of the frame-rib type aluminum alloy die forging in the simulation software, and execute S2.

[0062] S31. Determine the cold-pressed profile of the frame-ribbed aluminum alloy die forging.

[0063] S4. Analyze in the simulation software whether structural defects occur in the frame-rib type aluminum alloy die forging after hot forging under the preset strategy. If no structural defects occur in all parts of the frame-rib type aluminum alloy die forging, execute step S5; otherwise, adjust the preset strategy and execute S4, wherein the preset strategy includes forging temperature setting, forming speed setting, forming tonnage setting and the mold surface obtained by forging, and structural defects include structural permeation.

[0064] It should be noted that by analyzing whether structural defects occur in the frame-rib type aluminum alloy die forging after hot forging under a preset strategy, it can be determined whether the profile of the frame-rib type aluminum alloy die forging is the desired profile.

[0065] Specifically, refer to Figure 4 , analyzing in simulation software whether structural defects occur in frame-rib aluminum alloy die forgings after hot forging under a preset strategy specifically includes the following steps:

[0066] S41. Design the structural parameters, forming speed and hot forging temperature of frame-rib aluminum alloy die forgings in simulation software.

[0067] S42. Analyze forging forming forces.

[0068] S43. Based on the forming force, design the pre-forging times and the pre-forging die profile.

[0069] S44. Analyze the forming force and structural streamline of the frame-rib type aluminum alloy die forgings at different forging stages in the simulation software, and determine whether structural defects occur in the frame-rib type aluminum alloy die forgings.

[0070] It should be noted that in order to meet the external dimensions and mechanical properties of parts, the preparation of frame-rib aluminum alloy die forgings also needs to consider the control of formability and organizational streamlines. When the surface after cold pressing optimization is not completely suitable for hot forging, although the thinning of the cross-section thickness and the reduction of the fillet size are beneficial to reducing the residual stress of the parts, the filling process is difficult during hot forging, and the equipment tonnage is required to be high, which is prone to organizational defects such as through-flow. Therefore, it is necessary to first design the structural parameters, forming speed and hot forging temperature of the frame-rib aluminum alloy die forging in the simulation software, and then analyze the forging forming force. Based on the forming force, design the pre-forging number and pre-forging die surface, and finally analyze the forming force and organizational streamline of the frame-rib aluminum alloy die forging at different forging stages in the simulation software, and determine whether the frame-rib aluminum alloy die forging has organizational defects.

[0071] S5. Determine the various surface parameters of the frame-rib type aluminum alloy die forging.

[0072] It should be noted that the surface of the frame-rib type aluminum alloy die forging after cold pressing optimization is not completely suitable for hot forging. Although the thinning of the cross-section thickness and the reduction of the fillet size are beneficial to reducing the residual stress of the parts, the filling of the mold is difficult during the hot forging process, and the equipment tonnage is required to be high, and it is easy to produce structural defects such as through-flow. Therefore, it is necessary to judge whether all parts of the frame-rib type aluminum alloy die forging have no structural defects. If all parts of the frame-rib type aluminum alloy die forging have no structural defects, determine the various surface parameters of the frame-rib type aluminum alloy die forging. Otherwise, adjust the preset strategy, that is, adjust the forging temperature setting, forming speed setting, forming tonnage setting and the surface obtained by forging, until all parts of the frame-rib type aluminum alloy die forging have no structural defects.

[0073] For easier understanding, an example is given below.

[0074] For example: the hot forging temperature is set to 377℃, the forming speed is 30mm / s, the forming tonnage of the formed part is 63.8MN, and the internal temperature of the material is lower than 420℃.

[0075] Through simulation, it is shown that the fillet produces through-flow. Therefore, the fillet size is adjusted, that is, the fillet angle is set to R10 to R25. When the fillet angle of the frame-rib type aluminum alloy die forging is R20, through-flow will not occur in the frame-rib type aluminum alloy die forging. Therefore, it can be determined that the hot forging forming strategy is single forming. Considering the safety margin, the forming speed is 20 mm / s and the fillet angle is R20.

[0076] The embodiment of the present invention supplements machining allowances for various parts of a frame-rib type aluminum alloy die forging in simulation software, and analyzes the residual stresses of various parts of the frame-rib type aluminum alloy die forging after quenching and cold pressing in the simulation software. If the residual stress of the frame-rib type aluminum alloy die forging is less than a first preset value, and the residual stress differences corresponding to all parts of the frame-rib type aluminum alloy die forging are less than a second preset value, the cold pressing profile of the frame-rib type aluminum alloy die forging is determined; otherwise, the supplemented machining allowances for various parts of the frame-rib type aluminum alloy die forging are adjusted in the simulation software. The residual stresses of various parts of the frame-rib type aluminum alloy die forging after quenching and cold pressing are analyzed in the simulation software; then, the frame-rib type aluminum alloy die forging is analyzed in the simulation software whether structural defects occur after hot forging under the preset strategy; if no structural defects occur in various parts of the frame-rib type aluminum alloy die forging, the various surface parameters of the frame-rib type aluminum alloy die forging are determined, where structural defects include structural permeation; otherwise, the preset strategy is adjusted, and the simulation software is analyzed whether structural defects occur after hot forging under the preset strategy. Through the above-mentioned disclosed low residual stress design method for frame-rib type aluminum alloy die forgings, by supplementing the part processing allowance, the quenching residual stress under different characteristic structural parameters and the distribution of residual stress after different cold pressing deformation parameters are analyzed based on simulation, and then the cold-pressed billet profile is optimized to control the residual stress of the core body of the frame-rib type aluminum alloy die forging to below a first preset value. Then, hot forging simulation is carried out based on the cold-pressed billet profile, and the hot forging billet profile is optimized and designed based on the equipment tonnage, material filling and streamline. Finally, the required frame-rib type aluminum alloy die forging can be obtained.

[0077] Specifically, refer to Figure 2 When executing step S2, the specific execution steps of step S2 include the following steps:

[0078] S21. Analyze the residual stress of various parts of the frame-rib aluminum alloy die forging after quenching in the simulation software.

[0079] S22. Determine whether the residual stress of the frame-rib type aluminum alloy die forging is less than the third preset value, and the residual stress differences corresponding to all parts of the frame-rib type aluminum alloy die forging are less than the fourth preset value. If the residual stress of the frame-rib type aluminum alloy die forging is less than the third preset value, and the residual stress differences corresponding to all parts of the frame-rib type aluminum alloy die forging are less than the fourth preset value, execute step S23; otherwise, adjust the supplementary machining allowances of various parts of the frame-rib type aluminum alloy die forging in the simulation software, and execute S21.

[0080] It should be noted that, since the residual stress of the frame rib type aluminum alloy die forging is less than the third preset value, and the residual stress difference corresponding to all parts of the frame rib type aluminum alloy die forging is less than the fourth preset value, it means that the supplementary processing allowance of various parts of the frame rib type aluminum alloy die forging meets the stress requirement after quenching. Therefore, the cold pressed surface of the frame rib type aluminum alloy die forging can be determined; and when the residual stress of the frame rib type aluminum alloy die forging is not less than the third preset value, and / or the residual stress difference corresponding to all parts of the frame rib type aluminum alloy die forging is not less than the fourth preset value, it means that the supplementary processing allowance of various parts of the frame rib type aluminum alloy die forging does not meet the stress requirement after quenching. Therefore, the supplementary processing allowance of various parts of the frame rib type aluminum alloy die forging is adjusted in the simulation software, and step S21 needs to be executed again.

[0081] Specifically, the adjustment of the supplementary machining allowances of various parts of the frame-rib aluminum alloy die forging in the simulation software includes:

[0082] The fillet angle and the height of the short rib of the frame-rib aluminum alloy die forging are adjusted in the simulation software.

[0083] It should be noted that, since the thickness of the web and ribs is limited by the processing allowance, this application mainly adjusts the fillet of the bottom of the rib and the height of the short rib.

[0084] It is worth noting that when adjusting the angle of the fillet and the height of the short ribs of the frame-rib type aluminum alloy die forging, the present application adjusts the angle of the fillet of the frame-rib type aluminum alloy die forging within a preset angle range, such as adjusting within the range of R5-R25, and adjusts the height of the short ribs of the frame-rib type aluminum alloy die forging within a preset height range, such as adjusting within the range of 1-mm20mm.

[0085] S23. Determine the cold pressing profile of the frame-rib type aluminum alloy die forging, and analyze the residual stress of various parts of the frame-rib type aluminum alloy die forging after cold pressing in simulation software.

[0086] It should be noted that, since the residual stress control of frame rib type aluminum alloy die forgings can be considered from two aspects, namely, on the one hand, it is necessary to consider reducing the residual stress formed after quenching by optimizing the mold surface design in the quenching stage, and on the other hand, it is necessary to consider reducing the residual stress of the frame rib type aluminum alloy die forgings in the core part of the frame rib type aluminum alloy die forgings that is effectively transmitted by cold pressing deformation by optimizing the structure and cold pressing parameters in the cold pressing stage, therefore, the embodiment of the present application first analyzes the residual stress of each part of the frame rib type aluminum alloy die forgings after quenching in the simulation software, and then determines that the residual stress of the frame rib type aluminum alloy die forgings is less than the third preset value, and the residual stress corresponding to all parts of the frame rib type aluminum alloy die forgings is less than the third preset value. The residual stress difference is less than the fourth preset value. If the residual stress of the frame rib type aluminum alloy die forging is less than the third preset value, and the residual stress difference corresponding to all parts of the frame rib type aluminum alloy die forging is less than the fourth preset value, the cold pressed surface of the frame rib type aluminum alloy die forging is determined, and finally the residual stress of each part of the frame rib type aluminum alloy die forging after cold pressing is analyzed in the simulation software; otherwise, the supplementary processing allowance of each part of the frame rib type aluminum alloy die forging is adjusted in the simulation software, and the residual stress of each part of the frame rib type aluminum alloy die forging after quenching is analyzed in the simulation software. By optimizing in the above manner, the surface of the frame rib type aluminum alloy die forging can be effectively optimized.

[0087] Furthermore, before executing S23, that is, before analyzing the residual stress of each part of the frame-rib type aluminum alloy die forging after cold pressing in the simulation software, the following steps are also included:

[0088] The cold pressing deformation range of the web of the frame-rib type aluminum alloy die forging is set to 0.5%-1%, and the cold pressing deformation range of the rib is set to 1%-2.5%.

[0089] It should be noted that by setting the cold deformation range of the web of the frame-rib aluminum alloy die forging to 0.5%-1% and the cold deformation range of the rib to 1%-2.5%, and by selecting a value within the range of 0.5%-1% for the web and 1%-2.5% for the rib forging, the distribution of residual stress in various parts of the frame-rib aluminum alloy die forging and after cold pressing can be analyzed. When the lowest rib fillet is R15, the short rib is 10mm higher than the web, the cold deformation of the web is 0.6%, and the cold deformation of the rib is 2.0%, the residual stress level is the lowest, reaching 121MPa, which is less than 150MPa. The residual stress nonuniformity of the frame-rib aluminum alloy die forging is less than 50MPa, indicating that the supplementary machining allowance of various parts of the frame-rib aluminum alloy die forging is the required value.

[0090] It should also be noted that if the residual stress of the frame-rib type aluminum alloy die forging is not less than the first preset value, and / or the residual stress difference corresponding to all parts of the frame-rib type aluminum alloy die forging is not less than the second preset value, the cold pressing deformation of the web can be adjusted within 0.5%-1% and / or the cold pressing deformation of the rib can be adjusted within the range of 1%-2.5%.

[0091] Further, refer to Figure 5 After executing step S5, the following steps are further included:

[0092] S6. Determine the slab of the frame-rib type aluminum alloy die forging based on various surface parameters of the frame-rib type aluminum alloy die forging.

[0093] S7. Hot forging and cold pressing are performed on the slab of the frame rib type aluminum alloy die forging.

[0094] It should be noted that, since the surface of the frame-rib type aluminum alloy die forging obtained by simulation optimization of the simulation software is optimal, the slab of the frame-rib type aluminum alloy die forging is first determined based on the various surface parameters of the frame-rib type aluminum alloy die forging, and then the slab of the frame-rib type aluminum alloy die forging is hot forged and cold pressed to obtain a frame-rib type aluminum alloy die forging with low residual stress.

[0095] When executing step S7, refer to Figure 7 The specific execution steps of step S7 include:

[0096] S71. Place the slab into a furnace at a preset temperature for heat treatment.

[0097] It should be noted that when placing the slab into a furnace at a preset temperature for heat treatment, a certain temperature and holding time need to be set.

[0098] S72. Hot forging the slab based on the forming speed.

[0099] It should be noted that before hot forging, the hot forging die needs to be placed in a furnace for insulation, and the temperature is set to the required temperature. After insulation for a period of time, the die is installed first, and then hot forging begins.

[0100] It is worth noting that after the frame-rib type aluminum alloy die forgings are placed in the die, the temperature of the frame-rib type aluminum alloy die forgings needs to be tested. When the temperature of the frame-rib type aluminum alloy die forgings is lower than the required temperature, the die needs to be placed in a furnace to continue to keep warm.

[0101] S73, placing the slab into the furnace, and allowing the slab to cool down to below the target temperature as the furnace temperature decreases.

[0102] S74. Place the slab in a room temperature environment to cool.

[0103] S75. Machining the slab to obtain a frame-rib-shaped aluminum alloy die forging.

[0104] It should be noted that since the fillet is adjusted during the design of the hot forging surface, in order to facilitate the subsequent cold pressing to eliminate the residual stress, the slab is machined according to the tree after residual stress optimization to obtain a frame-ribbed aluminum alloy die forging.

[0105] S76. Insulate frame-rib type aluminum alloy die forgings.

[0106] S77. Quench the frame-rib type aluminum alloy die forgings.

[0107] S78. Cold press the frame rib type aluminum alloy die forgings.

[0108] It should be noted that steps S71 to S78 are the preparation process of frame-rib type aluminum alloy die forgings, which is the existing technology, and the specific parameters such as temperature, holding time, quenching method, quenching time, cooling time, cold pressing parameters and cold pressing time can be set by technical personnel in this field according to needs.

[0109] Further, refer to Figure 6 After executing step S7, the method further includes the following steps:

[0110] S8. Detect residual stress of frame rib type aluminum alloy die forgings.

[0111] It should be noted that by detecting the residual stress of the frame-rib type aluminum alloy die forging, it can be determined whether the prepared frame-rib type aluminum alloy die forging is the desired low residual stress part.

[0112] To facilitate understanding of steps S7 and S8, the specific execution process of hot forging and cold pressing of a slab of a frame-rib type aluminum alloy die forging is described by way of example.

[0113] Place the slab in a soaking furnace for heat treatment, set the temperature to 377°C, and keep it warm for 8 hours; then place the hot forging die in the furnace for insulation, set the temperature to 350°C, and keep it warm for 10 hours; then install the die, and start hot forging after installation. After the frame-rib type aluminum alloy die forging is placed on the die, test the temperature of the frame-rib type aluminum alloy die forging. If the temperature of the frame-rib type aluminum alloy die forging is less than 360°C, it needs to be placed in a soaking furnace to continue insulation; then set the forming speed to 20mm / s and start forging; after forging is completed, measure the temperature of the frame-rib type aluminum alloy die forging and record it. The temperature of the frame-rib type aluminum alloy die forging needs to be higher than 360°C, and place the frame-rib type aluminum alloy die forging in the soaking furnace, cool it down to below 200°C with the furnace, and place it in the air to cool to room temperature.

[0114] Because the corner radius was adjusted during the hot forging surface design, the frame-rib aluminum alloy die forgings were machined based on the optimized residual stress model to facilitate the elimination of residual stresses during subsequent cold pressing. The solidification furnace was heated to 477°C. Once at temperature, the frame-rib aluminum alloy die forgings were placed in the solidification furnace and held for 8 hours. Simultaneously, the cold pressing die was installed. When the solidification furnace holding time expired, the forgings were quenched in water at 60°C for 15 minutes, with a quenching transfer time of less than 15 seconds. The quenching medium was water at 60°C. After 15 minutes, the forgings were removed from the water and transferred to the cold pressing die for cold pressing. The aging furnace was heated to 120°C. Once at temperature, the cold-pressed frame-rib aluminum alloy die forgings were placed in the aging furnace. The transfer time from quenching to aging was less than 2 hours. The aging furnace was held at 120°C for 8 hours, then heated to 175°C and held for 6 hours.

[0115] Finally, through experiments, it was measured that the yield strength of the frame-ribbed aluminum alloy die forging was 410MPa, the tensile strength was 498MPa, and the fracture toughness was 28MPa•m1 / 2, which met the material performance index requirements. Combined with the small hole method and ultrasonic residual stress test, the residual stress in the core of the material was 102MPa, and the unevenness at the bottom of the rib was about 45MPa. After the part was processed, the geometric deviation was 0.17mm, which met the part requirements.

[0116] The present invention proposes a low residual stress design method for frame-rib type aluminum alloy die forgings, which solves the problems of large residual stress level, uneven stress distribution and serious part tolerance after machining in large-sized integral frame-rib type die forgings.

[0117] First, the part processing allowance is supplemented. Based on the simulation analysis of the quenching residual stress under different characteristic structural parameters and the distribution of residual stress after different cold pressing deformation parameters, the cold pressing billet profile is optimized to control the core residual stress of the forging (i.e., frame-rib type aluminum alloy die forging) to below 150 MPa.

[0118] Then, hot forging simulation is carried out based on the cold-pressed billet profile, and the hot forging billet profile is optimized and designed based on equipment tonnage, material filling and streamline.

[0119] Finally, based on the optimization results, billet processing, hot forging, cold quenching, machining, solution quenching heat treatment, cold pressing, and aging heat treatment are carried out in sequence to complete the preparation of the forgings.

[0120] Through the above-mentioned disclosed low residual stress design method for frame-rib type aluminum alloy die forgings, residual stress control is taken as the design goal of the forgings, and quenching residual stress control and cold pressing residual stress reduction are achieved through optimization of characteristic structure and cold pressing parameters. The maximum value of the body residual stress of the frame-rib type aluminum alloy die forgings is controlled below 150 MPa, and the unevenness is controlled below 50 MPa, effectively reducing the processing deformation caused by residual stress release during the machining of frame-rib type parts.

[0121] On the other hand, the hot forging surface takes filling and streamline control into consideration, and the connection between the hot forging and cold pressing surfaces is achieved through machining. Therefore, the synergistic optimization of the residual stress, shape and material mechanical properties of the frame-rib aluminum alloy die forgings can be achieved.

[0122] The low residual stress design method for frame-rib aluminum alloy die forgings disclosed in the present invention has the following advantages over the prior art:

[0123] 1. Prior art aluminum alloy forging designs only consider formability and streamline control, eliminating quenching residual stresses through a 1% to 2% cold pressing. However, for large-scale, integral frame-ribbed die forgings, the complex surface structure results in high residual stress non-uniformity and numerous cold pressing deformation dead zones, leading to significant deformation during machining due to residual stress release. The present invention, however, prioritizes residual stress control and fully considers both the formation and elimination of residual stresses. This reduces the core residual stress to below 150 MPa and the non-uniformity to below 50 MPa, effectively avoiding machining deformation.

[0124] 2. Integral frame-rib die forgings are usually used as the main load-bearing parts of aircraft, and have high requirements for the material properties and geometric accuracy of the parts. Therefore, on the one hand, it is necessary to optimize the design of the material organization streamlines and deformation of the forging surface during the hot forging process to ensure material properties. On the other hand, it is also necessary to optimize the design of the cold-pressed surface to reduce residual stress and thus improve geometric accuracy. However, the optimization results of the cold-pressed surface are not conducive to the hot forging of the forging. In order to achieve coordinated control of the material properties and geometric accuracy of the parts, this patent innovatively proposes to process them into cold-pressed optimized surfaces after hot forging, which not only ensures the control of residual stress by cold pressing, but also guarantees the mechanical properties of the forging.

[0125] Each embodiment in this specification is described in a progressive manner. The same or similar parts between the embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple. For relevant parts, refer to the partial description of the method embodiment. The system and system embodiments described above are merely schematic. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. A person of ordinary skill in the art can understand and implement it without making any creative efforts.

[0126] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the above description has generally described the components and steps of each example according to their functions. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present invention.

[0127] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A low residual stress design method for frame-rib type aluminum alloy die forgings, characterized in that: include: S1. Add machining allowance to each part of the frame-rib aluminum alloy die forging in the simulation software; S2. Analyzing the residual stresses of various parts of the frame-rib aluminum alloy die forging after quenching and cold pressing in simulation software; S3. If the residual stress of the frame-rib type aluminum alloy die forging is less than a first preset value, and the residual stress differences corresponding to all parts of the frame-rib type aluminum alloy die forging are less than a second preset value, determining a cold-pressed profile of the frame-rib type aluminum alloy die forging; otherwise, adjusting the supplementary machining allowances of various parts of the frame-rib type aluminum alloy die forging in the simulation software, and executing S2; S4. Analyzing in simulation software whether structural defects occur in the frame-rib aluminum alloy die forging after hot forging under a preset strategy, wherein the preset strategy includes a forging temperature setting, a forming speed setting, a forming tonnage setting, and a molded surface obtained by forging; S5. If no tissue defects occur in all parts of the frame-rib type aluminum alloy die forging, determine various surface parameters of the frame-rib type aluminum alloy die forging, wherein the tissue defects include tissue permeation; otherwise, adjust the preset strategy and execute S4.

2. The low residual stress design method for frame-rib type aluminum alloy die forgings according to claim 1 is characterized in that: Said S2 comprises: S21. Analyzing the residual stress of various parts of the frame-rib aluminum alloy die forging after quenching in simulation software; S22. If the residual stress of the frame-rib type aluminum alloy die forging is less than the third preset value, and the residual stress differences corresponding to all parts of the frame-rib type aluminum alloy die forging are less than the fourth preset value, determining the cold-pressed profile of the frame-rib type aluminum alloy die forging; otherwise, adjusting the supplementary machining allowances of various parts of the frame-rib type aluminum alloy die forging in the simulation software, and executing S21; S23. Analyze the residual stress of various parts of the frame-rib type aluminum alloy die forging after cold pressing in simulation software.

3. The low residual stress design method for frame-rib type aluminum alloy die forgings according to claim 2, characterized in that: The adjustment of the supplementary machining allowances of various parts of the frame-rib aluminum alloy die forging in the simulation software includes: The fillet angle and the height of the short rib of the frame-rib aluminum alloy die forging are adjusted in the simulation software.

4. The low residual stress design method for frame-rib type aluminum alloy die forgings according to claim 3, characterized in that: The adjusting of the fillet angle and the height of the short rib of the frame-rib type aluminum alloy die forging in the simulation software includes: In the simulation software, the fillet angle of the frame-rib aluminum alloy die forging is adjusted within a preset angle range; In the simulation software, the height of the short ribs of the frame-rib type aluminum alloy die forgings is adjusted within a preset height range.

5. The low residual stress design method for frame-rib type aluminum alloy die forgings according to claim 2, characterized in that: Before executing S23, the following steps are also included: The cold pressing deformation range of the web of the frame-rib type aluminum alloy die forging is set to 0.5%-1%, and the cold pressing deformation range of the rib is set to 1%-2.5%.

6. The low residual stress design method for frame-rib type aluminum alloy die forgings according to claim 1, characterized in that: Said S4 comprises: S41. Design the structural parameters, forming speed, and hot forging temperature of the frame-rib aluminum alloy die forging in simulation software; S42. Analyze forging forming force; S43. Designing the number of pre-forging times and the profile of the pre-forging die based on the forming force; S44. Analyze the forming force and structural streamline of the frame-rib type aluminum alloy die forgings at different forging stages in the simulation software, and determine whether structural defects occur in the frame-rib type aluminum alloy die forgings.

7. The low residual stress design method for frame-rib type aluminum alloy die forgings according to claim 1, characterized in that: After S5, the following is also included: S6. Determining a slab of the frame-rib type aluminum alloy die forging based on various profile parameters of the frame-rib type aluminum alloy die forging; S7. Hot forging and cold pressing are performed on the slab of the frame rib type aluminum alloy die forging.

8. The low residual stress design method for frame-rib type aluminum alloy die forgings according to claim 7, characterized in that: The S7 includes: S71, placing the slab into a furnace at a preset temperature for heat treatment; S72, hot forging the slab based on the forming speed; S73, placing the slab into the furnace, and allowing the slab to cool to below the target temperature as the furnace temperature decreases; S74, placing the slab in a room temperature environment to cool; S75, machining the slab to obtain a frame-ribbed aluminum alloy die forging; S76. Insulating the frame-ribbed aluminum alloy die forgings; S77, quenching the frame rib type aluminum alloy die forging; S78. Cold press the frame rib type aluminum alloy die forgings.

9. The low residual stress design method for frame-rib type aluminum alloy die forgings according to claim 7, characterized in that: After S7, the following steps are also included: S8. Detect residual stress of frame rib type aluminum alloy die forgings.

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