Forming method of aluminum alloy structure with double convex hulls and large drawing ratio

Abstract

The invention discloses a forming method for a double-convex-hull and large-drawing-ratio aluminum alloy configuration, and relates to the field of aluminum alloy configuration machining, the method is used for forming through a first mold and a second mold, and the method comprises the following steps that S1, blanking is conducted; s2, first forming is conducted, specifically, a first die is adopted for conducting punch forming on the blank, the height of a convex hull after punching is not larger than 31 mm, and the diameter of a hull opening exceeds the design size; s3, annealing is conducted; s4, secondary forming is conducted, specifically, a second die is adopted for conducting punch forming on the blank, the height of each convex hull ranges from 37 mm to 39 mm after punch stretching, and a reinforcing rib is punched between every two convex hulls; s5, solution treatment; s6, third-time shape correction is conducted, specifically, within 15 min after solution treatment, the reinforcing ribs and the convex hulls are punched to the designed height through the second die; s7, natural aging; and S8, machining is conducted. According to the method, the material cracking risk can be effectively reduced, large-draw-ratio non-cracking forming of the part is achieved, and high-quality part forming is completed.

Description

Technical Field

[0001] The present invention relates to the field of processing of aluminum alloy configurations, and in particular to a forming method for an aluminum alloy configuration with double convex hulls and a large drawing ratio. Background Art

[0002] The initial state of the material of part 1 is 2024 - O, and the final delivery state is T42; the properties of 2024 material are tensile strength σb MPa ≥ 425, yield strength σs MPa ≥ 275, and elongation rate of 12%; this material has good formability in the annealed and newly quenched states. The blank thickness for manufacturing part 1 is 1 mm. After part 1 is manufactured, part 1 is a double convex hull 11 structure with an outer dimension of 390 mm in length, 290 mm in width, and 41 mm in height; among them, the height of convex hull 11 is 41 mm, and convex hull 11 and the bottom flange surface 13 are rounded at a radius of 6 mm, that is, the size of the flange opening 14 is 93 mm. There are 3 stiffeners 12 with a height of 8 mm (actually equivalent to a semi - cylindrical groove) connected between the two convex hulls 11, and an open strip window in each convex hull 11; the bottom flange surface 13 of part 1 has multiple pre - holes, and the specific structure is as Figures 1 - 3 shown.

[0003] Manufacturing part 1 has the following difficulties: 1. The strength of 2024 aluminum alloy is relatively high, but its plasticity is relatively poor; during the forming process, especially for operations such as bending and stretching of complex shapes, the material is prone to defects such as cracking and wrinkling; 2. Part 1 has a double convex hull 11 structure with a large drawing ratio, and it is difficult to form in one step; when forming the stiffener 12 and convex hull 11 in one step, it will crack at about 33 mm of the drawing height of part 1 and convex hull 11; when only forming convex hull 11 without stiffener 12, it will also crack at about 35 mm of the drawing height; 3. There are 3 stiffeners 12 connected between the two convex hulls 11, and the transition radius between the convex hull 11, stiffener 12 and the bottom flange surface 13 is relatively small, which seriously affects the flow of the material during the forming process, making it extremely difficult to feed the material during the forming process of part 1 and prone to cracking.

[0004] Therefore, for the processing of this part, a new forming method is needed. Summary of the Invention

[0005] The purpose of the present invention is: aiming at the above - mentioned problems, to provide a forming method for an aluminum alloy configuration with double convex hulls and a large drawing ratio, which can effectively reduce the risk of material cracking, and achieve crack - free forming of the part with a large drawing ratio, and complete high - quality part forming.

[0006] The technical solution adopted by the present invention is as follows: A forming method for an aluminum alloy configuration with double convex hulls and a large drawing ratio, which uses a first mold and a second mold for forming. The first mold has two convex hull punches with a radius greater than the radius of the convex hulls, and the center distance between the two convex hull punches matches the center distance of the two convex hulls to be processed on the part; the size of the second mold matches the design size of the part; the method includes the following steps: S1: Blanking, cutting the blank so that the blank can meet the requirement of machining at least one part; S2: First forming, using the first mold to stamp and form the blank. After stamping, the height of the convex hull does not exceed 31 mm, and the diameter at the mouth of the package exceeds the design size; S3: Annealing, annealing the blank after the first forming; S4: Second forming, using the second mold to stamp and form the blank. After stamping and stretching, the height of the convex hull is between 37 mm and 39 mm, and a reinforcing rib is stamped between the two convex hulls; S5: Solution treatment, performing solution treatment on the blank after the second forming; S6: Third sizing, within 15 minutes after the solution treatment, using the second mold to stamp the reinforcing rib and the convex hull to the design height; S7: Natural aging, natural aging is not less than 96 h after the third sizing; S8: Machining, machining the outer shape, size and openings of the part to complete the preparation of the part.

[0007] Further, in step S1, laser blanking is used for blanking, and the blanking size meets the requirement of machining one part with one blank; after blanking, the blank is cleaned to remove the surface burrs and edge ablation layers on the cutting surface, and the surface defects of the blank are polished.

[0008] Further, in step S2, the radius of the convex hull mold on the first mold is 50 mm, the height of the convex hull mold is 31 mm, and the transition radius is 11 mm.

[0009] Further, in step S3, the annealing temperature is 405°C - 415°C, the holding time is 60 min - 65 min. After the holding is completed, it is furnace-cooled to 260°C at a cooling rate not greater than 28°C / h, and then taken out of the furnace and air-cooled to room temperature.

[0010] Further, in step S4, the height of the convex hull after stamping is 38 mm.

[0011] Further, in step S5, during the solution treatment process, the heating temperature is 490°C - 498°C, the holding time is 30 - 35 min. After the holding is completed, it is taken out of the furnace and quenched in water, and the quenching transfer time ≤ 10 s.

[0012] Further, the water temperature during water quenching is 20°C - 30°C.

[0013] Further, in step S7, the natural aging duration is 96h, and the ambient temperature is 20°C - 25°C.

[0014] Further, after step S8, the parts need to be cleaned after machining to remove burrs.

[0015] Further, after cleaning the parts, the parts are subjected to fluorescence inspection and final dimensional inspection. After passing the inspection, the parts are packaged with neutral kraft paper.

[0016] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are as follows: 1. By adding an annealing process after the first forming, the present invention eliminates cold work hardening, obtains the highest plasticity of the material, and reduces the cracking risk from the aspect of material properties. 2. The present invention uses 2 sets of molds and forms to the designed height through 3 times of stamping, and solves the problem of part forming cracking from the process method. 3. The present invention solves the problem of difficult material feeding by first forming double convex hulls and then forming 3 reinforcing ribs, increasing the transition R during the first forming, and finally shaping in place. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be described by way of examples with reference to the accompanying drawings, where: Figure 1 is a schematic structural diagram of the part disclosed by the present invention; Figure 2 is a schematic dimensional diagram of the front view of the part; Figure 3 is Figure 2 the sectional view dimensional diagram in the A - A direction of Figure 4 is a schematic dimensional diagram of the part after the first forming; Markings in the figure: 1 - part; 11 - convex hull; 12 - reinforcing rib; 13 - bottom flange surface; 14 - bag mouth. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] As Figures 1 - 4 shown, a forming method for an aluminum alloy configuration with double convex hulls and a large drawing ratio is used to produce the part 1 described in the production background technology, and its specific design dimensions are as follows: Part 1 has a double convex hull 11 structure with a thickness of 1 mm, an outer dimension of 390 mm in length, 290 mm in width, and 41 mm in height. Among them, the height of the convex hull 11 is 41 mm, and the convex hull 11 and the bottom flange surface 13 are transitioned by a fillet with a radius of 6 mm, that is, the size of the mouth 14 is 93.23 mm. There are 3 stiffening ribs 12 with a height of 8 mm (actually equivalent to a semi-cylindrical groove in shape) connected between the two convex hulls 11, and there are open strip windows in each convex hull 11. The bottom flange surface 13 of Part 1 has multiple pre-holes.

[0019] This method uses two molds, namely the first mold and the second mold. Both the first mold and the second mold have two convex hull punches. For the convenience of description and distinction, the convex hull punch on the first mold is called the convex hull punch one, and the convex hull punch on the second mold is called the convex hull punch two.

[0020] Among them, the radius of the convex hull punch one is 50 mm, and the height is 31 mm. There is a fillet with a radius of 11 mm between the convex hull punch one and the bottom surface of the first mold. When using the first mold for stamping, considering the thickness of Part 1 is 1 mm, on the convex side of the convex hull 11, it can achieve a fillet corner transition between the convex hull 11 and the bottom flange surface 13 with a radius of 10 mm. The center distance between the two convex hull punches one matches the center distance of the two convex hulls 11 to be processed on Part 1. The size of the second mold matches the design size of Part 1, that is, the radius of the convex hull punch two is 41 mm, and the height is also 41 mm. There is a fillet with a radius of 7 mm between the convex hull punch two and the bottom surface of the second mold. Similarly, considering the thickness of Part 1 is 1 mm, on the convex side of the convex hull 11, it can achieve a fillet corner transition between the convex hull 11 and the bottom flange surface 13 with a radius of 6 mm. The center distance between the two convex hull punches two matches the center distance of the two convex hulls 11 to be processed on Part 1, and there is a stiffening rib punch between the two convex hull punches in the second mold, and the height of the stiffening rib punch is 8 mm.

[0021] The specific steps of this method are as follows: S1: Blanking. The material is cut into a rectangular blank by laser cutting, and the blanking size can meet the requirement of processing 1 Part 1 from 1 blank. After blanking, the blank is cleaned to remove the burrs on the cutting surface and the edge ablation layer, and the surface defects of the blank are polished.

[0022] S2: First forming. The first mold is used to stamp and form the blank. After stamping, the height of the convex hull 11 is 31 mm, and the width at the mouth 14 exceeds the design size (93.23 mm), that is, the width at the mouth 14 is 106.23 mm. The mouth 14 and the bottom surface of the blank are transitioned by a fillet with a radius of 10 mm. The formation of this fillet benefits from the fillet with a radius of 11 mm between the convex hull punch one and the bottom surface of the first mold.

[0023] Regarding step S2, it should be noted that by performing the first stamping forming with a convex die of a larger diameter, sufficient material can be brought in to generate stretching, achieving the purpose of pre-bending, and reducing the defects such as cracking and wrinkling of the material caused by the large amount of stretched material and large bending amplitude during the second stamping forming; the large-sized mouth 14 enables the material at the position of the mouth 14 to be drawn towards the middle rather than being stretched into the convex hull 11 during the second forming, greatly reducing the possibility of cracking of the material at the position of the mouth 14 and overcoming the problem of difficult material feeding. Moreover, increasing the transitional R effectively solves the problem of material feeding during subsequent sizing.

[0024] S3: Annealing, annealing the blank after the first forming; the annealing temperature is 405°C - 415°C, the holding time is 60 min - 65 min. After the holding is completed, it is furnace-cooled to 260°C at a cooling rate of 28°C / h and then air-cooled to room temperature. It should be noted that part 1 should be heated up with the furnace, and the holding time starts when the thermocouple with the lowest temperature reaches the lower limit of the holding temperature tolerance. Regarding step S3, setting the annealing after the first forming in step S2 can effectively eliminate cold work hardening and obtain the highest plastic properties of the material, reducing the cracking risk from the aspect of material properties.

[0025] S4: Second forming, using the second die to stamp and form the blank. After stamping and stretching, the height of the convex hull 11 is between 37 mm and 39 mm, and a reinforcing rib 12 is stamped between the two convex hulls 11; preferably, the height of the convex hull 11 is 38 mm.

[0026] It should be noted that the design dimensions are not reached during the second forming process of step S4. The purpose is to avoid the difficulty of subsequent sizing to the design dimensions due to the existence of the thermal deformation amount of part 1 during the subsequent solution treatment. That is, if the design dimensions are directly reached during the second forming, problems such as the height of the convex hull 11 exceeding the design dimensions are likely to occur after thermal deformation, making it difficult to restore to the design dimensions. Therefore, the design dimensions are not reached during the second forming process of step S4, providing a margin for the thermal deformation amount of part 1 during the solution treatment and facilitating subsequent continued stamping and stretching to the design dimensions.

[0027] S5: Solution treatment, performing solution treatment on the blank after the second forming; during the solution treatment process, the heating temperature is 490°C - 498°C, the holding time is 30 - 35 min. After the holding is completed, it is quenched in water after taking out of the furnace, and the quenching transfer time ≤ 10 s.

[0028] In this step S5, solution treatment mainly dissolves the strengthening phases in the alloy to form a supersaturated solid solution. At this temperature, for the 2024 aluminum alloy, the strengthening phases in the alloy can be effectively dissolved, while avoiding grain boundary melting and the risk of overburning. After the heat preservation is completed, water quenching is carried out. The water quenching can achieve a cooling rate of 200°C / s to avoid the precipitation of coarse phases. The water temperature for water quenching needs to be controlled at 20°C - 30°C. At this temperature, it ensures sufficient water quenching cooling and also avoids deformation caused by rapid temperature drop. The transfer time for water quenching does not exceed 10 s, which meets the standard specified in the aviation standard AMS2772E.

[0029] S6: The third sizing is actually to use the second mold for the third forming, that is, to stamp the reinforcing rib 12 and the boss 11 to the designed height using the second mold. It should be noted that when performing the third sizing, it needs to be completed within 15 minutes after the solution treatment, that is, before the solute atoms (such as Cu / Mg) precipitate to form the strengthening phase (GP zone). During this time period, the material has good plasticity and the strengthening phase has not formed, so the material is not easily cracked during the third sizing.

[0030] S7: Natural aging. After the third sizing, the natural aging is not less than 96 h, and optionally it is 96 h. This meets the law of the strength change of the 2024 aluminum alloy with time.

[0031] It should be noted that the environmental temperature for natural aging is 20°C - 25°C. At this temperature, it ensures the precipitation rate of solute atoms and also avoids uneven performance caused by too fast precipitation.

[0032] S8: After the natural aging is completed, the part 1 is machined, that is, the outer shape, size, and openings of the part 1 are machined so that the size and outer shape of the part 1 both meet the design of the part 1. After machining, the part 1 needs to be cleaned to remove burrs. After cleaning the part 1, the part 1 is subjected to fluorescent inspection and final dimension inspection. After passing the inspection, the part 1 is packaged with neutral kraft paper, thus completing the processing and preparation of the part 1.

[0033] It should be noted that fluorescent inspection is mainly to detect whether cracks are generated. For the part 1 produced by this method, hard block inspection is carried out. There are no cracks on all parts 1, which can effectively reduce the risk of material cracking and achieve crack-free forming with a large tensile ratio of the part 1, completing the high-quality forming of the part 1. Packaging the part 1 with neutral kraft paper is to avoid the reaction between the part 1 and the packaging. The requirement is that there is no bare surface, and at the same time, bubble pads are used for protection to ensure the basic dimensions of the part 1 during storage and transportation.

[0034] The present invention is not limited to the foregoing specific embodiments. The present invention extends to any new feature or any new combination disclosed in this specification, as well as to any new method or process step or any new combination disclosed.

Claims

1. A forming method for an aluminum alloy configuration with double convex hulls and a large drawing ratio, characterized in that: Forming is carried out using a first mold and a second mold. The first mold has two boss punches with a radius greater than the radius of the bosses (11). The center distance between the two boss punches matches the center distance of the two bosses (11) to be processed on the part (1). The size of the second mold matches the designed size of the part (1). The following steps are included: S1: Blanking. Cut the blank so that the blank can be used to process at least one part (1). S2: First forming. Use the first mold to stamp and form the blank. After stamping, the height of the boss (11) does not exceed 31 mm, and the diameter at the mouth of the boss (14) exceeds the designed size. S3: Annealing. Anneal the blank after the first forming. S4: Second forming. Use the second mold to stamp and form the blank. After stamping, the height of the boss (11) is between 37 mm and 39 mm, and a reinforcing rib (12) is stamped between the two bosses (11). S5: Solution treatment. Carry out solution treatment on the blank after the second forming. S6: Third sizing. Within 15 minutes after the solution treatment, use the second mold to stamp the reinforcing rib (12) and the boss (11) to the designed height. S7: Natural aging. The natural aging time after the third sizing is not less than 96 h. S8: Machining. Machine the outer shape, size, and openings of the part (1) to complete the preparation of the part (1).

2. The molding method according to claim 1, wherein: In step S1, laser blanking is used for blanking. The blanking size is such that one blank can be used to process one part (1). After blanking, the blank should be cleaned to remove the surface burrs and edge ablation layers on the cutting surface, and the surface defects of the blank should be polished.

3. The forming method according to claim 1, characterized in that: In step S2, the radius of the boss (11) mold on the first mold is 50 mm, the height of the boss (11) mold is 31 mm, and the transition radius is 11 mm.

4. The molding method according to claim 1, wherein: In step S3, the annealing temperature is 405°C - 415°C, the holding time is 60 min - 65 min. After the holding is completed, cool it in the furnace at a cooling rate not greater than 28°C / h to 260°C, and then take it out of the furnace and air-cool it to room temperature.

5. The molding method according to claim 1, wherein: In step S4, the height of the boss (11) after stamping is 38 mm.

6. The forming method according to claim 1, wherein: In step S5, during the solution treatment process, the heating temperature is 490°C - 498°C, the holding time is 30 - 35 min. After the holding is completed, take it out of the furnace and quench it in water. The quenching transfer time ≤ 10 s.

7. The forming method according to claim 6, wherein: The water temperature during water quenching is 20°C - 30°C.

8. The molding method according to claim 1, wherein: In step S7, the natural aging duration is 96 h, and the ambient temperature is 20°C - 25°C.

9. The shaping method according to claim 1, wherein: After step S8, the part (1) needs to be cleaned after machining to remove burrs.

10. The molding method according to claim 9, wherein: After cleaning the part (1), conduct fluorescent inspection and final dimensional inspection on the part (1). After passing the inspection, package the part (1) with neutral kraft paper.

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