Liquid die forging method for large thin-wall aluminum alloy box

Abstract

The invention discloses a liquid die forging method for a large thin-wall aluminum alloy box. The liquid die forging method comprises the following steps that S1, a die is closed; s2, molten metal is poured; s3, pressurizing and mold filling are conducted, specifically, a pressure head is started, and meanwhile molten metal in all pressure chambers is pushed to rapidly enter a box part mold cavity to fill the box part mold cavity; s4, pressurizing, solidifying and feeding; s5, the male die retreats to the set position and is separated from the box part, the blank pressing die retreats to the set position, and the workpiece is ejected out; and S6, after the workpiece is cooled to the room temperature, a material cake and an overflow discharging system at the bottom of the box body are removed, and a large thin-wall aluminum alloy box body part blank can be obtained. Large thin-wall box parts can be produced, the molten metal filling distance is remarkably shortened, the mold filling capacity is remarkably improved, and complete forming can be achieved even if the wall thickness is very small.

Description

Technical Field

[0001] The invention relates to a cable connector and a production process, and in particular to a liquid die forging method for a large thin-walled aluminum alloy box. Background Art

[0002] Large thin-walled box parts have important applications in the lightweighting of automobiles, aerospace, and rail transportation. Such parts cannot be forged due to their small wall thickness and multiple ribs. If integral die-casting is used, the required die-casting machine capacity is tens of thousands of tons, which is currently unprecedented. Sand casting is difficult to form completely, with a high scrap rate and low performance. Low-pressure casting can form, but the performance is low and the forming defects lead to a high scrap rate. The current mainstream technology is to use profiles or sheets for stamping and welding. This method has low production efficiency, and the welds cause "weak points" in the parts.

[0003] Liquid die forging is a method for high-performance forming of structural parts. In the prior art, the wall thickness of liquid die forgings is generally not less than 5mm, and the liquid forging pressure is not less than 80MPa. The prior art is for single weights of more than 30Kg, wall thickness less than 5mm, and projected area greater than 1m 2 It is very difficult to forge large structural parts by liquid die forging: (1) The pouring volume is large, which requires a large diameter pressure chamber. When the pressure chamber exceeds 150mm, the pressure head will expand by up to mm due to heat, which will destroy the matching relationship between the pressure head and the pressure chamber, causing aluminum leakage or jamming, making production impossible; (2) The wall thickness is small, and defects such as cold shut and flow marks are difficult to avoid. In order to solve this problem, the existing technology has improved by increasing the pressure, but due to the small wall thickness, the pressure transfer process is greatly attenuated, and the problem of incomplete forming still exists; (3) The projected area of ​​the workpiece is large, and the required clamping force of the liquid forging machine is huge. For example, a rectangular part with a contour of 1.5×1.0 meters has a projected area of ​​1.5m 2 According to the general requirement of the prior art, the specific pressure is 100MPa, and the clamping force is greater than 15,000 tons. Such a large liquid die forging machine is still blank in the world, so it is necessary to improve the liquid die forging method to solve the difficulty of integral forming of large thin-walled aluminum alloy parts. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects in the prior art that circuit boards require auxiliary fixtures and have more process flows, and to provide a liquid die forging method for large thin-walled aluminum alloy boxes, which can produce large thin-walled box parts, significantly shorten the metal liquid filling distance, and significantly improve the filling capacity, so that even if the wall thickness is very small, it can be completely formed.

[0005] To achieve the above object, the present invention provides a liquid die forging method for a large thin-walled aluminum alloy box, comprising the following steps:

[0006] S1, closed mold: the mold includes an upper edge of the box body formed by the close contact between the edge pressing mold and the male mold, and a closed box body mold cavity formed by the male mold and the female mold;

[0007] S2. Pouring molten metal: Pour molten metal with a temperature 80-120°C higher than the liquidus temperature into each pressure chamber at the same time to a fixed amount, and let it stand to discharge slag and gas;

[0008] S3, pressurized filling: start the pressure head and push the metal liquid in each pressure chamber to quickly enter the mold cavity of the box part to fill it;

[0009] S4, pressurized solidification and shrinkage compensation: Continue to increase the pressure through the pressure head to make the molten metal flow to fill the mold and shrinkage compensation. After a certain period of filling, the punch moves downward to compress the high-temperature molten metal below it to achieve pressure shrinkage compensation and plastic deformation. After completion, the punch is depressurized until the pressure head is depressurized after complete solidification and forming;

[0010] S5, the punch returns to the set position, separates from the box body, and the blank holder returns to the set position to eject the workpiece;

[0011] S6. After the workpiece is cooled to room temperature, the cake (process waste) at the bottom of the box and the overflow system are removed to obtain a large thin-walled aluminum alloy box blank.

[0012] Furthermore, in step S1, the edge pressing die is mounted outside the male die, and a gap between the two is 0.08-0.15 mm.

[0013] Furthermore, in step S1, the upper edge of the box body is moved downward synchronously by the edge holding die and the male die, so that the edge holding die is in close contact with the top surface of the female die, and after being pressurized to a set pressure, the pressure is maintained at rest;

[0014] The box body mold cavity is a closed mold cavity formed by the male mold and the female mold after the male mold is continuously pressed down to a setting position, wherein a distance is formed between the bottom surface of the male mold and the bottom surface of the female mold.

[0015] Furthermore, the distance between the bottom surface of the punch and the bottom surface of the die is the sum of the wall thickness of the box body, the machining allowance and the linear shrinkage plus 0.5 mm;

[0016] Furthermore, in step S2, at least two pressure chambers are included, the interior of each pressure chamber is cylindrical and is equipped with a pressure head that matches with the pressure chamber to block the lower opening and can move vertically;

[0017] The diameter of the pressure chamber is 100-260 mm, and is located at the plane of the bottom surface of the box body. The center distance is controlled within the range of 200-1000 mm.

[0018] Furthermore, the standing time in step S2 is 1 to 5 seconds.

[0019] Furthermore, the movement speed of the pressure head in step S3 is 100-1000 mm / s.

[0020] Furthermore, in step S4, the pressure head pressurizes the pressure chamber to a pressure F 1 Then continue to maintain the pressure F 1 Maintain pressure. 1 After a few seconds, the molten metal solidifies and takes shape, and the pressure head can be relieved;

[0021] Maintain pressure at the pressure head t 2 After seconds, the punch continues to pressurize the box body mold cavity to pressure F 2 Then continue to maintain the pressure F 2 Maintain pressure until t 3 The pressure can be relieved in seconds;

[0022] Among them, the above t 1 ≥t 2 +t 3 .

[0023] Furthermore, at the pressure F 1 Under the action of the pressure chamber, the metal liquid generates a pressure P 1 , at pressure F 2 Under the action of 2 ;

[0024] Among them, the above P 1 ≤P 2 .

[0025] Furthermore, the pressure P 1 and pressure P 2 Both are 20-120MPa.

[0026] Preferably, the pressure P 1 and pressure P 2 Both are 20-80MP.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) It is capable of producing large thin-walled box parts with a minimum wall thickness of 2 mm. Due to the use of a double pressure chamber, the metal liquid filling distance is significantly shortened and the filling capacity is significantly improved. Even if the wall thickness is very small, it can be fully formed.

[0029] (2) There are no pore defects, and the speed at which the pressure head pushes the molten metal into the mold cavity can be precisely controlled, so that the mold can be fully filled without entraining air;

[0030] (3) There is no shrinkage defect. Since the punch is compressed by pressure, it is equivalent to a compression deformation of the box body, which can achieve rheological compensation, so there is no shrinkage defect;

[0031] (4) The process yield rate is as high as over 90%. Since the material cake is only 20-30 mm thick and the process waste material is small, the process yield rate can be increased by 30-40 percentage points compared with the existing technology of die casting and liquid die forging.

[0032] (5) The mechanical properties are uniform and high. Due to the use of pressure crystallization technology, the workpiece has fine structure and excellent mechanical properties.

[0033] (6) It has a wide range of applications and can be used to form various large thin-walled box-type parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 It is a flow chart of a liquid die forging method for a large thin-walled aluminum alloy box provided by the present invention;

[0036] Figure 2 It is a structural schematic diagram of the mold provided by the present invention;

[0037] Figure 3 It is a structural exploded view of the mold provided by the present invention after casting is completed.

[0038] Included in the figure are:

[0039] 1. Bending die; 2. Punch; 3. Concave die; 4. Cavity; 5. Liquid metal; 6. Pressing chamber; 61. Press head. DETAILED DESCRIPTION

[0040] The technical scheme in this embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in this embodiment of the present invention. Obviously, the described embodiment is one embodiment of the present invention, not all embodiments of the present invention. Based on this embodiment of the present invention, all other embodiments of the present invention obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] Please refer to Figures 1 to 3 The present invention provides a liquid die forging method for a large thin-walled aluminum alloy box, comprising the following steps:

[0042] S1. Closed mold: The mold includes: a press mold 1, a male mold 2 and a female mold 3. The press mold 1 is mounted outside the male mold 2, and the gap between the two is 0.08-0.15 mm. The outer contour of the male mold 2 is consistent with the inner contour of the box body, and its lower plane matches the shape of the inner bottom surface of the box body to form the inner cavity of the box body; the female mold 3, whose mold cavity 4 is consistent with the outer shape of the box body, is used to form the outer shape of the box body, and the inner bottom surface of the cavity of the female mold 3 is consistent with the outer bottom surface of the box body;

[0043] The mold is started, and the blank holder 1 and the punch 2 move downward synchronously, so that the blank holder 1 is in close contact with the top surface of the die 3, and after the pressure is applied to a set pressure, the pressure is kept static to form the upper edge of the box body. This pressure value can be determined according to the actual molten metal 5 and is not specifically limited;

[0044] A closed mold cavity 4 is formed by continuously pressing the punch 2 down to the set position and then forming it with the die 3, wherein a distance is formed between the bottom surfaces of the punch 2 and the die 3. The distance between the bottom surfaces of the punch 2 and the die 3 is the sum of the wall thickness of the box part, the machining allowance and the linear shrinkage plus 0.5 mm. Setting a 0.5 mm allowance helps to ensure the fit between the punch 2 and the die 3 during the mold forming process and reduce product dimensional errors caused by mold deformation, temperature changes and other factors.

[0045] S2, pouring molten metal 5: In this embodiment, at least two pressure chambers 6 are included, and the pressure chambers 6 are installed below the die 3 and communicated with the die cavity 4 of the die 3. The interior of the pressure chambers 6 is cylindrical and is equipped with a pressure head 61 that matches it to block its lower mouth, and can move vertically. The diameter of the pressure chambers 6 is 100-180 mm, and they are all located on the plane of the bottom surface of the box body. The center distance is controlled within the range of 200-1000 mm. The number of pressure chambers 6 can be determined according to specific needs. For example, it can also be set to three or even more. It only needs to set the position of the controller so that the three pressure chambers 6 can evenly input the molten metal 5.

[0046] The metal liquid 5 with a temperature higher than the liquidus temperature by 80-120°C and a qualified composition is poured into each pressing chamber 6 at the same time to a certain amount, and then left to stand for 1-5 seconds for slag removal and exhaust;

[0047] S3, pressurized filling: start the pressure head 61, and at the same time push the metal liquid 5 in each pressure chamber 6 to quickly enter the box part mold cavity 4 to fill it. The movement speed of the pressure head 61 is 100-1000mm / s.

[0048] S4, pressurized solidification and shrinkage compensation: the pressure head 61 pressurizes the pressure chamber 6 to the pressure F1 and continues to maintain the pressure F1 to make the molten metal 5 flow, fill the mold and shrink. After the pressure is maintained for t1 seconds, the molten metal 5 solidifies and forms, and the pressure head 61 can release the pressure. After the pressure head 61 fills the mold and maintains the pressure for t2 seconds, the punch 2 moves downward to compress the high-temperature molten metal 5 below it. The punch 2 continuously pressurizes the box mold cavity 4 to the pressure F2 and continues to maintain the pressure F 2 Maintain pressure until t 3 After 10 seconds, pressure compensation and plastic deformation are realized, and after completion, the punch 2 is depressurized. 1 ≥t 2 +t 3 ;

[0049] At pressure F 1 Under the action of the pressure chamber 6, the metal liquid 5 generates a pressure P 1 , at pressure F 2 Under the action of 2 , pressure P 1 and pressure P 2 are controlled between 20-80MPa, and P 1 ≤P 2 .

[0050] S5, the punch 2 returns to the set position and is separated from the box body, and the blank holder 1 returns to the set position to eject the workpiece;

[0051] S6. After the workpiece is cooled to room temperature, remove the cake (process waste) at the bottom of the box and the overflow system to obtain a large thin-walled aluminum alloy box blank.

[0052] Example 1

[0053] In this embodiment, the molding of a new energy battery base is taken as an example. The wall thickness of the box body is 4±0.1mm, the machining allowance is 1mm, and the linear shrinkage is 0.04mm. In this embodiment, in step S1, the distance between the bottom surface of the punch 2 and the bottom surface of the die 3 is set to 4+1+0.04+0.5=5.54mm. In step S4, the pressure head 61 is pressurized to the set pressure F 1 =400 tons and continue to pressurize until the pressure is maintained for the set time t 1 = Release the pressure after 85 seconds. Maintain the pressure at the lower pressure head 61t 2 = After 15 seconds, the punch 2 is pressurized to the set pressure F 2 =6000 tons and continue to pressurize until the pressure is maintained for the set time t 3 = Pressure relief after 68 seconds; t 1 ≥t 2 +t 3 , F 1The pressure P generated by the metal liquid 5 in the pressure chamber 6 1 =20MPa, at F 2 Under the action of 2 =50MPa, and the rest is processed in the same manner as the normal steps of the present invention. The final size of the battery base after processing is 4.05mm in wall thickness, which is within the required range. In addition, the organizational properties of the thick-walled part and the thin-walled part are respectively 50µm for the secondary dendrite arm spacing at 15mm thick part, 305MPa for strength, and 7.5% for elongation; and 42µm for the secondary dendrite arm spacing at 4.1mm thin wall thickness, 315MPa for strength, and 8.1% for elongation, which are basically consistent with each other, and effectively solve the problem of wall thickness effect of solidification of large workpieces in the prior art, in which the strength decays by about 10% and the elongation decays by about 25% for every 10mm wall thickness difference.

[0054] Example 2

[0055] This embodiment takes a large thin-walled box body as an example, the main body wall thickness is 2mm, the length is 1650mm, the width is 920mm, the processing allowance is 1.5mm, and the linear shrinkage is 0.05mm. Therefore, the distance between the bottom surface of the punch 2 and the bottom surface of the die 3 is set to 2+1.5+0.05+0.5=4.05mm; in this embodiment, three pressure chambers 6 are set with a diameter of 180mm, and the lower pressure head 61 is pressurized to the set pressure F 1 = 150 tons and continue to pressurize until the pressure is maintained for the set time t 1 =13 seconds later, the pressure is released. Maintain the pressure at the lower pressure head 61t 2 = After 8 seconds, the punch 2 is pressurized to the set pressure F 2 = 12000 tons and continue to pressurize until the pressure is maintained for the set time t 3 = Pressure relief after 4 seconds; t 1 ≥t 2 +t 3 ,F 1 The pressure P generated by the metal liquid 5 in the pressure chamber 6 1 =60MPa, at F 2 Under the action of 2=80MPa, to achieve pressure solidification, pressure compensation and plastic deformation, and other settings remain unchanged; this pressure difference ensures that there will be no aluminum drilling during filling, and the later high pressure makes the inside of the box body dense, and a certain amount of plastic deformation occurs, and the organizational properties of the core and the outer surface are basically the same (the secondary dendrite arm spacing at the core with a wall thickness of 15mm is 43µm, the strength is 302MPa, and the elongation is 7.8%; the secondary dendrite arm spacing at the thin wall of 2mm is 38µm, the strength is 320MPa, and the elongation is 8.8%), which effectively solves the wall thickness effect problem of the existing technology in the solidification of large workpieces, in which the strength decays by about 10% and the elongation decays by about 25% for every 10mm wall thickness difference.

[0056] Example 3

[0057] A large thin-walled box body has a wall thickness of 3.5mm, a length of 1400mm, a width of 810mm, a processing allowance of 1mm, and a linear shrinkage of 0.03mm. Therefore, the distance between the bottom surface of the punch 2 and the bottom surface of the die 3 is set to 3.5+1+0.03+0.5=5.03mm. The diameters of the two pressure chambers 6 are both 160mm, and the lower pressure head 61 is pressurized to the set pressure F 1 =40 tons and continue to pressurize until the pressure is maintained for the set time t 1 =15 seconds before the pressure is released. After the pressure head 61 maintains pressure for t2 = 10 seconds, the punch 2 increases the pressure to the set pressure F 2 =9100 tons and continue to pressurize until the pressure is maintained for the set time t 3 = pressure relief after 5 seconds; t 1 ≥t 2 +t3, F 1 The pressure P generated by the metal liquid 5 in the pressure chamber 6 1 =20MPa, at F 2 Under the action of 2 =80MPa, to achieve pressure solidification and pressure compensation, and other settings remain unchanged; it ensures that the interior of the box is dense and undergoes certain plastic deformation, and the organizational properties of the core and the outer surface are basically consistent. Specifically, the secondary dendrite arm spacing at 30mm in the core of the wall thickness of this embodiment is 52µm, the strength is 301MPa, and the elongation is 6.8%; the secondary dendrite arm spacing at 4.0mm in the thin wall is 38µm, the strength is 318MPa, and the elongation is 8.5%, which effectively solves the wall thickness effect problem of the prior art in which the strength decays by about 10% and the elongation decays by about 25% for every 10mm wall thickness difference.

[0058] Comparative Example 1

[0059] The difference between this embodiment and embodiment 1 is that the distance between the bottom surface of the punch 2 and the bottom surface of the die 3 is set to 4.9 mm, which does not meet the requirement that the distance between the bottom surface of the punch 2 and the bottom surface of the die 3 = the wall thickness of the box body + processing allowance + linear shrinkage + 0.5 mm. As a result, the final battery base has a size of 3.85 mm after processing, which is out of tolerance, and has obvious internal shrinkage defects and cannot be formed, so it is scrapped.

[0060] Comparative Example 2

[0061] The difference between this embodiment and embodiment 1 is that the distance between the bottom surface of the punch 2 and the bottom surface of the die 3 is set to 5 mm, which does not meet the requirement that the distance between the bottom surface of the punch 2 and the bottom surface of the die 3 = the wall thickness of the box body + processing allowance + linear shrinkage + 0.5 mm. As a result, the wall thickness of the battery base finally formed after processing is 4.2 mm, which is out of tolerance and scrapped.

[0062] Comparative Example 3

[0063] The difference between this embodiment and embodiment 1 is that the distance between the bottom surface of the punch 2 and the bottom surface of the die 3 is set to 6.2 mm. The requirement that the distance between the bottom surface of the punch 2 and the bottom surface of the die 3 = the wall thickness of the box body + processing allowance + linear shrinkage + 0.5 mm is not met. As a result, the rear wall of the battery base formed in the end is 5.20 mm, which is obviously too thick, resulting in an increase in the amount of processing and an increase in cost.

[0064] Comparative Example 4

[0065] The difference between this embodiment and embodiment 1 is that the distance between the bottom surface of the punch 2 and the bottom surface of the die 3 is set to 7 mm. The requirement that the distance between the bottom surface of the punch 2 and the bottom surface of the die 3 = the wall thickness of the box body + processing allowance + linear shrinkage + 0.5 mm is not met. As a result, the rear wall of the battery base finally formed is 5.5 mm, which is obviously too thick, resulting in an increase in the amount of processing and an increase in cost.

[0066] Comparative Example 5

[0067] The difference between this embodiment and embodiment 1 is that the wall thickness of the box body is 4±0.10mm, the processing allowance is 1.5mm, and the linear shrinkage is 0.05mm. Therefore, the distance between the bottom surface of the punch 2 and the bottom surface of the die 3 is set to 6.55mm. As a result, the rear wall of the battery base finally formed is 5.7mm. Obviously, it is too thick, which increases the amount after processing and increases the cost.

[0068] Comparative Example 6

[0069] The difference between this comparative example and Example 2 is that the pressure head 61 increases the pressure to the set pressure F 1 = 150 tons and continue to pressurize until the pressure is maintained for the set time t 1 =13 seconds later, the pressure is released. Maintain the pressure at the lower pressure head 61t 2After 8 seconds, the punch 2 is pressurized to the set pressure F 2 = 12000 tons and continues to be pressurized until the pressure is maintained for the set duration t 3 The pressure is released after 4 seconds; t 1 ≥t 2 +t 3 , F 1 Under the action of, the pressure P generated by the molten metal 5 in the pressure chamber 6 1 = 10 MPa, under F 2 Under the action of, the pressure P is generated inside the molten metal 5 in the mold cavity 4 2 = 80 MPa, when P1 is lower than 20 MPa, the phenomenon of incomplete forming occurs; when it is higher than 80 MPa, the equipment tonnage increases significantly and the cost rises.

[0070] Comparative Example 7

[0071] The difference between this comparative example and Example 2 is that, F 1 Under the action of, the pressure P generated by the molten metal 5 in the pressure chamber 6 1 = 80 MPa, under F 2 Under the action of, the pressure P is generated inside the molten metal 5 in the mold cavity 4 2 = 60 MPa, at this time P2 < P1, then insufficient feeding occurs, there are shrinkage defects inside, and the product is scrapped.

[0072] Comparative Example 8

[0073] The difference between this comparative example and Example 2 is that, F 1 Under the action of, the pressure P generated by the molten metal 5 in the pressure chamber 6 1 = 60 MPa, under F 2 Under the action of, the pressure P is generated inside the molten metal 5 in the mold cavity 4 2 = 90 MPa, at this time P2 is less than 20 MPa, insufficient feeding and plastic deformation cannot occur, the structure coarsens, and the performance decreases; if P2 is greater than 80 MPa, the equipment tonnage increases significantly and the mold life also decreases significantly, increasing the product cost.

[0074]

[0075] From Examples 1-3, the wall thickness tolerance of the new energy battery base in Example 1 is considered to be qualified within the range of the required wall thickness ±0.1mm, and the wall thickness tolerance of the large thin-walled box parts in Examples 2 and 3 is considered to be visibly qualified within the range of the required wall thickness ±0.1mm. From the above table, it can be determined that when the distance between the bottom surface of the punch 2 and the bottom surface of the die 3 is strictly controlled according to the formula that the distance between the bottom surface of the punch 2 and the bottom surface of the die 3 is the sum of the wall thickness of the box part, the machining allowance and the linear shrinkage plus 0.5mm, the wall thickness of the finished products of Examples 1-3 of the present invention are all within the qualified tolerance range, thereby ensuring the qualified rate of the wall thickness after machining and improving the forming quality.

[0076] Referring to Example 1 and Comparative Examples 1-5, under other identical conditions, in Comparative Examples 1 and 2, when the distance between the bottom surface of the punch 2 and the bottom surface of the die 3 is less than the sum of the wall thickness of the box body, the machining allowance and the linear shrinkage plus 0.5 mm, the distance between the bottom surface of the punch 2 and the bottom surface of the die 3 is strictly controlled, and the molded wall thicknesses are 3.85 mm and 4.2 mm, respectively, which are obviously lower than the qualified tolerance of 4±0.1 mm, and are scrapped due to excessive tolerance; at the same time, in Comparative Examples 3-5, the distance between the bottom surface of the punch 2 and the bottom surface of the die 3 is greater than the sum of the wall thickness of the box body, the machining allowance and the linear shrinkage plus 0.5 mm, and the wall thickness of the molded product is too thick, resulting in an increase in the amount after processing and an increase in cost.

[0077] Referring to Example 2 and Comparative Examples 6-9, when the pressure P1 in Comparative Example 6 is less than 20-80 MPa, the molding porosity will be 5% (the qualified product needs a porosity of less than 2%), and the shrinkage defect rate will be 20% (the qualified product shrinkage defect rate is 0%), resulting in incomplete molding and scrapping; in Comparative Example 7, P 1 >P 2 When the shrinkage is insufficient, there are shrinkage defects inside, and the product is scrapped; in Comparative Example 8, P 2 Less than 20MPa, it cannot fully compensate for the condensation plastic deformation, the structure is coarsened, the performance is reduced, P 2 When the pressure is greater than 80MPa, the equipment tonnage increases significantly, the mold life also decreases significantly, and the product cost increases.

[0078] Therefore, through the above comparison, it can be known that by controlling the holding time of the pressure head 61 and the pressurization and holding time of the punch 2, the metal liquid 5 in the pressure chamber 6 and the metal liquid 5 in the mold cavity 4 form a pressure difference of pressure P1 and P2 within the setting range, thereby realizing pressure solidification and pressure compensation, ensuring that the interior of the box body is dense and undergoes certain plastic deformation, and the organizational properties of the core and the outer surface are basically consistent, effectively solving the wall thickness effect of solidification of large workpieces.

[0079] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A liquid die forging method for a large thin-walled aluminum alloy box, characterized in that: The steps include: S1, closed mold: the mold comprises an upper edge of the box body formed by the close contact between the edge holding mold (1) and the male mold (2), and a closed box body mold cavity (4) formed by the male mold (2) and the female mold (3); S2, pouring molten metal (5): pouring molten metal (5) having a temperature higher than the liquidus temperature by 80-120°C into each pressure chamber (6) at the same time to a fixed amount, and leaving it to stand for slag removal and exhaust; S3, pressurized filling: start the pressure head (61), and simultaneously push the metal liquid (5) in each pressure chamber (6) to quickly enter the box part mold cavity (4) to fill it; S4, pressurized solidification and shrinkage compensation: the pressure head (61) is continuously pressurized to make the molten metal (5) flow to fill the mold and shrinkage compensation. After a certain period of filling, the punch (2) moves downward to compress the molten metal (5) below it to achieve pressure shrinkage compensation and plastic deformation. After completion, the punch (2) is depressurized until the solidification is complete and the pressure head (61) is depressurized. S5, the punch (2) returns to the set position and is separated from the box body, and the blank holder (1) returns to the set position to eject the workpiece; S6. After the workpiece is cooled to room temperature, the cake and overflow system at the bottom of the box are removed to obtain a large thin-walled aluminum alloy box blank.

2. A liquid die forging method for a large thin-walled aluminum alloy box according to claim 1, characterized in that: In the step S1, the edge pressing die (1) is mounted outside the punch die (2), and the gap between the two is 0.08-0.15 mm.

3. A liquid die forging method for a large thin-walled aluminum alloy box according to claim 2, characterized in that: In the step S1, the upper edge of the box body is moved downward synchronously by the edge pressing die (1) and the punch die (2), so that the edge pressing die (1) is in close contact with the top surface of the die (3), and after the pressure is applied to a set pressure, the pressure is maintained at rest; The box body mold cavity (4) is a closed mold cavity (4) formed by the male mold (2) being continuously pressed down to a set position and then formed with the female mold (3), wherein a distance is formed between the bottom surface of the male mold (2) and the bottom surface of the female mold (3).

4. A liquid die forging method for a large thin-walled aluminum alloy box according to claim 3, characterized in that: The distance between the bottom surface of the punch (2) and the bottom surface of the die (3) is the sum of the wall thickness of the box body, the machining allowance and the linear shrinkage plus 0.5 mm.

5. The liquid die forging method for a large thin-walled aluminum alloy box according to claim 1, characterized in that: In the step S2, at least two pressure chambers (6) are included, the interior of each pressure chamber (6) is cylindrical and is equipped with a pressure head (61) that matches the pressure head to block the lower opening and move vertically; The diameter of the pressure chamber (6) is 100-260 mm, and is located at the plane of the bottom surface of the box body, and the center distance is controlled within the range of 200-1000 mm.

6. A liquid die forging method for a large thin-walled aluminum alloy box according to claim 5, characterized in that: The standing time in step S2 is 1 to 5 seconds.

7. The liquid die forging method for a large thin-walled aluminum alloy box according to claim 1, characterized in that: The movement speed of the pressure head (61) in step S3 is 100-1000 mm / s.

8. The liquid die forging method for a large thin-walled aluminum alloy box according to claim 1, characterized in that: In the step S4, the pressure head (61) increases the pressure of the pressure chamber (6) to a pressure F1 and continues to maintain the pressure F1 for t1 seconds, and after the metal liquid (5) solidifies and forms, the pressure head (61) can release the pressure; After the pressure head (61) maintains pressure for t2 seconds, the punch (2) continuously pressurizes the box body mold cavity (4) to a pressure F2 and continues to maintain the pressure F2 for pressure maintenance. After the pressure is maintained for t3 seconds, the pressure can be released. Among them, the above-mentioned t1≥t2+t3.

9. A liquid die forging method for a large thin-walled aluminum alloy box according to claim 8, characterized in that: Under the action of the pressure F1, the metal liquid (5) in the pressure chamber (6) generates a pressure P1, and under the action of the pressure F2, a pressure P2 is generated inside the metal liquid (5) in the mold cavity (4); Among them, the above-mentioned P1≤P2.

10. A liquid die forging method for a large thin-walled aluminum alloy box according to claim 9, characterized in that: The pressure P1 and the pressure P2 are both 20-120 MPa.

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