Deep drawing and flanging method for aluminum alloy large deep-diameter rotary body top cover part

Abstract

The application discloses a deep-diameter rotary body top cover part deep drawing and flanging and hole forming method, three rubber pads with diameters gradually increasing are arranged at the center position of the inner surface of the top cover, the rubber pad S, the rubber pad M and the rubber pad L, the rubber pad S is arranged at the uppermost position and is in contact with a convex die to perform initial deep drawing. The application effectively avoids uneven material deformation and rupture at the round corner during the deep drawing forming process of the top cover part, thereby solving the problem of excessively high local area thinning rate and part rupture, and the part forming qualified rate is 100%.

Description

Technical Field

[0001] This invention belongs to the field of metal material processing technology, and relates to a method for deep drawing and forming of flanged protrusions in aluminum alloy large aspect ratio rotary body top cover parts. Background Technology

[0002] In the aerospace field, top cover components are mostly made of aluminum alloy sheets, and the top cover and the bottom ring together form the tank bottom. To meet the requirements of "low cost, high reliability, and high thrust" for modern large liquid-fueled launch vehicles, the structural dimensions of current tank components tend to be "large and deep." The structure of the top cover component is also different, with the difference being its higher overall height and a larger ratio of height to diameter at the large end. In this invention, this feature is named the large depth-to-diameter ratio.

[0003] The novel structural features of the top cover component have brought new challenges to its forming process. The large aspect ratio of the top cover results in significant sheet deformation during forming, leading to hardening and decreased plasticity. From a microscopic perspective, a large number of dislocations and microcracks have accumulated within the grains at this stage. Furthermore, the large aspect ratio of the top cover component itself, a rotating body structure, makes material feeding and flow difficult during deep drawing. These factors combined result in excessive thinning or even breakage at the die fillet corners during aluminum alloy top cover forming, leading to the inability to form parts that meet design requirements and a low yield rate. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies, such as difficulty in material flow, high thinning rate, cracking at rounded corners, and low yield, and to provide a method for deep drawing and flanging forming of aluminum alloy large aspect ratio rotating body top cover parts.

[0005] To achieve the above objectives, the present invention employs the following technical solutions:

[0006] A method for deep drawing and flanging punch forming of aluminum alloy large aspect ratio rotating body top cover parts includes the following steps:

[0007] S1. Three rubber pads with diameters ranging from small to large are set at the center of the inner surface of the top cover: rubber pad S, rubber pad M, and rubber pad L. Rubber pad S is placed on the topmost side and contacts the punch to perform initial deep drawing.

[0008] S2. When the real-time hydraulic pressure reaches a preset fixed value A, remove the rubber pad S. Continue to draw the remaining rubber pads M and L until the hydraulic pressure reaches A. Remove the hole rubber pad M. Continue to draw the remaining rubber pad L until the pressure reaches A. Remove the rubber pad L and continue to draw until the pressure reaches A. Clean the semi-finished parts and perform stress-relief annealing.

[0009] S3. Continue to add rubber pads S, M, and L, and draw the mold until the pressure is A. Remove rubber pad S, and continue to draw the remaining rubber pads M and L until the pressure is A. Remove the hole rubber pad M, and continue to draw the remaining rubber pad L until the pressure is A. Remove rubber pad L, and continue to draw the mold until the closing height of the pressure mold is 20-30mm, at which point the hydraulic pressure does not exceed A. Clean the semi-finished parts and perform stress-relieving annealing.

[0010] S4. Open the initial hole and grind it, then form the convex hole by flanging in two passes.

[0011] As a preferred embodiment, the large end diameter of the top cover part is Φ1000~2000mm, the height is 330~400mm, and the wall thickness is 8~13mm.

[0012] As a preferred embodiment, the diameter of the flange hole at the small end of the top cover part is Φ500~600mm, and the straight line height of the flange is 20~40mm.

[0013] As a preferred embodiment, the diameter of the rubber pad S is smaller than the inner diameter of the final flange hole, which is Φ400~500mm, and the thickness is 20~40mm; the diameter of the rubber pad M is Φ500~650mm; and the diameter of the rubber pad L is Φ650~800mm.

[0014] As a preferred embodiment, the real-time pressure to A indicates that the drawing die punch has contacted the part and completed the deformation amount of one pass.

[0015] As a preferred embodiment, the real-time pressure A is 10–20 MPa.

[0016] As a preferred embodiment, in steps S2 and S3, the annealing temperature of the stress annealing process is 300–420°C, and the holding time is 35–55 min.

[0017] As a preferred embodiment, in step S4, the initial hole diameter is Φ380~450mm.

[0018] As a preferred method, in step S4, after opening the initial hole, the cross-section and the drawn rounded corners are polished smooth.

[0019] In a further preferred embodiment, the punch and the die are arranged opposite to each other, a pressure ring is provided on the outer side of the punch, a flip-hole punch is provided at one end of the punch, and a punch is provided inside the punch.

[0020] In the initial forming stage of this invention, in order to increase the deformation area of ​​the raw material (sheet metal) and allow the material to flow over a larger range, circular rubber pads with diameters ranging from small to large are added above the sheet metal. The material is drawn to a set pressure value and then drawn to a stop. After annealing, the above operation is repeated to achieve a state that is close to the initial hole of the mold. After annealing, the initial hole is opened, that is, the initial hole for the flange is opened on the formed convex bulge. Finally, under the action of the convex hole mold, the convex hole is continued in multiple passes until the final size requirement is met.

[0021] The present invention has the following advantages:

[0022] This invention effectively avoids uneven material deformation and cracking at rounded corners during the deep drawing process of top cover parts, thus solving the problem of excessive thinning rate in local areas leading to part cracking, and achieving a 100% part forming qualification rate. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the top cover component structure;

[0024] Figure 2 This is a schematic diagram of a deep drawing die structure;

[0025] Figure 3 A schematic diagram (cross-section) of the semi-finished part before the initial hole is drilled;

[0026] Figure 4 This is a cross-sectional view of the top cover component.

[0027] In the diagram: 1—punch, 2—ejector pin, 3—punch, 4—die, 5—blade ring, 6—flipping punch. Detailed Implementation

[0028] The present invention will now be described in detail with reference to the accompanying drawings.

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0030] Example:

[0031] This example provides a method for deep drawing and flanging punch forming of an aluminum alloy large aspect ratio rotating body top cover. By utilizing a rubber pad to increase the deformation zone of the sheet metal, the material flows more smoothly, resulting in more uniform deformation and preventing cracking during forming, thus increasing the part yield to 100%. In this example, the material is annealed 2A14 aluminum alloy with a thickness of 9.5mm. The part has a major diameter of Φ1380mm, a minor diameter of Φ580mm, and a total height of 380mm. The specific implementation steps are as follows:

[0032] Step 1: Design the drawing die and flanging die based on the shape of the part and the flow characteristics of its curved surface. The die structure in this example is as follows: Figure 2As shown. The mold includes a punch 1, a punch 3, a die 4, a blank holder 5, and a flanging punch 6. The mold can form deep drawing and flanging processes; during deep drawing, the flanging punch is removed; during the flanging process, the flanging punch 6 is connected to the punch 3, and the flanging punch 6 moves downward with the punch 3 to perform flanging. The punch's main function is positioning; it is installed at the center of the punch 2. During deep drawing, the punch 3 presses down, driving the punch 1 downward. When it contacts the sheet metal, it leaves a mark at the center of the sheet metal, which serves as the center for the subsequent flanging hole. The punch and die surfaces are offset according to the theoretical ellipsoidal surface of the part to ensure a gap of 9.5mm between the material thickness and the blank holder 5. The blank holder 5 is fitted with the corresponding blank holder surface to ensure that it does not affect material flow during subsequent deep drawing, ensuring a gap of 9.5 + 0.3 + 0.1mm.

[0033] Step 2: Determine the blank size using simulation. To ensure smoother material flow, select the lower limit of the size, that is, as small as possible while still meeting the part dimensions. In this example, the blank size is Φ1480.

[0034] Step 3: Place the sheet metal on die 4, and place rubber pads S, M, and L on top of the sheet metal for deep drawing. In this example, the dimensions of rubber pads S, M, and L are Φ450, Φ600, and Φ700, respectively, and the thickness of each is 30mm. When the hydraulic pressure reaches 15MPa, stop deep drawing, remove rubber pad S, and continue deep drawing until the hydraulic pressure reaches 15MPa. Remove rubber pad M, and continue deep drawing at the same hydraulic pressure, then remove rubber pad L. Note that 15MPa indicates that the part has undergone a certain degree of deformation at this point; clean the part and anneal it.

[0035] Step 4: Continue deep drawing, repeating Step 3 until the mold closing height reaches 20mm (note: maintain hydraulic pressure not exceeding 15MPa). Clean the parts and anneal them. A schematic diagram of the semi-finished parts is shown below. Figure 3 As shown;

[0036] Step 5: Open the initial hole. In this example, the initial hole size is Φ410, and the area around the opening is polished smooth.

[0037] Step 6: Replace and install the punching mold to perform the punching process to prevent breakage. Punch the holes in two passes. After punching is completed, remove the excess material by machining and polish the parts until smooth.

[0038] In summary, the forming method provided by this invention not only promotes more uniform material flow in the sheet metal deformation area, effectively solving the problem of excessive thinning leading to cracking during the forming process, but also ensures that the thickness of the product part meets the part design requirements. The part structure determines that its thinnest area is near the small-end opening; therefore, the thickness measurement range is as follows... Figure 4 As shown, the thickness from end B to C is 50mm. The specific thickness values ​​are shown in Table 1 below.

[0039] Table 1. Measurement Table of Flanged Hole Thickness of Top Cover

[0040]

[0041] This invention is not limited to the specific embodiments described above. The invention extends to any new feature or combination disclosed in this specification, as well as any new method or process step or combination disclosed herein.

Claims

1. A method for deep drawing and flanging punch forming of aluminum alloy large aspect ratio rotating body top cover parts, characterized in that, Includes the following steps: S1. Three rubber pads with diameters ranging from small to large are set at the center of the inner surface of the top cover part: rubber pad S, rubber pad M, and rubber pad L. Rubber pad S is placed on the topmost part and contacts the punch to perform initial deep drawing. S2. When the hydraulic pressure reaches a preset fixed value A, remove the rubber pad S. Continue to draw the remaining rubber pads M and L until the hydraulic pressure reaches A. Remove the rubber pad M and continue to draw the remaining rubber pad L until the hydraulic pressure reaches A. Remove the rubber pad L and continue to draw the remaining rubber pad until the hydraulic pressure reaches A. Clean the semi-finished parts and perform stress-relief annealing. S3. Continue to add rubber pads S, M, and L, and draw the mold until the hydraulic pressure reaches A. Remove rubber pad S, and continue to draw the remaining rubber pads M and L until the hydraulic pressure reaches A. Remove rubber pad M, and continue to draw the remaining rubber pad L until the hydraulic pressure reaches A. Remove rubber pad L, and continue to draw the mold until the mold closing height is 20-30mm, at which point the hydraulic pressure does not exceed A. Clean the semi-finished parts and perform stress-relief annealing. S4. Open the initial hole and grind it, then form the convex hole by flanging in two passes.

2. The method for deep drawing and flanging punch forming of aluminum alloy large aspect ratio rotating body top cover parts according to claim 1, characterized in that: The large end diameter of the top cover part is Φ1000~2000mm, the height is 330~400mm, and the wall thickness is 8~13mm.

3. The method for deep drawing and flanging punch forming of aluminum alloy large aspect ratio rotating body top cover parts according to claim 1, characterized in that: The diameter of the flanged hole at the small end of the top cover part is Φ500~600mm, and the straight line height of the flange is 20~40mm.

4. The method for deep drawing and flanging punch forming of aluminum alloy large aspect ratio rotating body top cover parts according to claim 1, characterized in that: The diameter of the rubber pad S is smaller than the diameter of the small end flange hole, ranging from Φ400 to 500 mm, and the thickness is 20 to 40 mm; the diameter of the rubber pad M ranges from Φ500 to 650 mm; and the diameter of the rubber pad L ranges from Φ650 to 800 mm.

5. The method for deep drawing and flanging punch forming of aluminum alloy large aspect ratio rotating body top cover parts according to claim 1, characterized in that: The hydraulic pressure to A indicates that the punch has contacted the top cover part and completed the deformation of one pass.

6. The method for deep drawing and flanging punch forming of aluminum alloy large aspect ratio rotating body top cover parts according to claim 1, characterized in that: The value of A is 10–20 MPa.

7. The method for deep drawing and flanging punch forming of aluminum alloy large aspect ratio rotating body top cover parts according to claim 1, characterized in that: In steps S2 and S3, the annealing temperature of the stress-relief annealing process is 300–420°C, and the holding time is 35–55 min.

8. The method for deep drawing and flanging punch forming of aluminum alloy large aspect ratio rotating body top cover parts according to claim 1, characterized in that: In step S4, the initial hole diameter is Φ380~450mm.

9. The method for deep drawing and flanging punch forming of aluminum alloy large aspect ratio rotating body top cover parts according to claim 1, characterized in that: In step S4, after the initial hole is opened, the cross-section and the drawn rounded corners are polished smooth.

10. The method for deep drawing and flanging punch forming of aluminum alloy large aspect ratio rotating body top cover parts according to any one of claims 1-9, characterized in that: The punch and die are arranged opposite to each other, and a pressure ring is provided on the outer side of the punch.

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