A large thin-walled aluminum alloy box liquid die forging method

Abstract

The application discloses a large thin-wall aluminum alloy box body liquid die forging method, which comprises the following steps: S1, closing a die; S2, pouring metal liquid; S3, pressurizing and filling: starting a pressure head, and simultaneously pushing the metal liquid in each pressure chamber to quickly enter a box body part mold cavity, so that the box body part mold cavity is filled; S4, pressurizing and solidifying and feeding; S5, the male die is retreated to a set position and is separated from the box body part, the edge die is retreated to a set position, and the workpiece is ejected; and S6, after the workpiece is cooled to room temperature, a cake at the bottom of the box body and a discharge overflow system are removed, so that a large thin-wall aluminum alloy box body part blank can be obtained. The application can produce a large thin-wall box body part, the metal liquid filling distance is obviously shortened, the filling capacity is obviously improved, and even when the wall thickness is very small, the box body part can be completely formed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of liquid die forging of aluminum alloy parts, in particular to a liquid die forging method for large thin-walled aluminum alloy box bodies. BACKGROUND

[0002] Large thin-walled box body parts have important applications in the lightweight of automobiles, aerospace and rail transportation. Because of the small wall thickness and multiple ribs, such parts cannot be forged into shape. If overall die casting is used, the required die casting machine capacity reaches tens of thousands of tons, and there is no precedent at present. If sand casting is used, it is difficult to form completely, the scrap rate is high, and the performance is low. If low-pressure casting is used, it can be formed, but the performance is low and the forming defects lead to a high scrap rate. The existing mainstream technology is to use profile or sheet stamping and welding to form, which 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 forged parts is generally not less than 5 mm, and the liquid forging specific pressure is not less than 80 MPa. It is very difficult for the prior art to perform overall liquid die forging on large structural parts with a single weight of more than 30 Kg, a wall thickness of less than 5 mm, and a projection area of more than 1 m 2 : (1) Large pouring volume is required for a large-diameter pressure chamber. When the pressure chamber is more than 150 mm, the thermal expansion of the pressure head can reach mm level, which damages the matching relationship between the pressure head and the pressure chamber, causing aluminum leakage or jamming, and making it impossible to produce; (2) Small wall thickness makes it difficult to avoid defects such as cold separation and flow marks. In order to solve this problem, the prior art improves the pressure, but due to the small wall thickness, the pressure transmission process decays greatly, and the complete forming problem still exists; (3) Large projection area of the workpiece requires a huge locking force of the liquid forging machine. For example, a rectangular part with an outline of 1.5 x 1.0 meters has a projection area of 1.5 m 2 . According to the general requirement of the prior art, the locking force is more than 15,000 tons at a specific pressure of 100 MPa. 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 overall forming of large thin-walled aluminum alloy parts. SUMMARY

[0004] The purpose of the present application is to overcome the defects in the prior art liquid die forging process, and to provide a liquid die forging method for large thin-walled aluminum alloy box bodies, which can produce large thin-walled box body parts, significantly shorten the metal liquid filling distance, significantly improve the filling capacity, and completely form even if the wall thickness is very small.

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

[0006] S1, closing the mold: the mold includes the upper edge of the box formed by the close contact of the blanking die and the punch, and the closed box part mold cavity formed by the punch and the recess die;

[0007] S2, pouring the metal liquid: pour the metal liquid with a temperature of 80-120℃ higher than the liquidus temperature into each compression chamber at the same time to a certain amount, and stand still to remove slag and exhaust;

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

[0009] S4, pressurized solidification and feeding: continue to increase the pressure through the pressure head to make the metal liquid flow and fill, and after a certain time of filling, the punch moves downward to compress the high-temperature metal liquid below it, realizing pressure feeding and plastic deformation, and after completion, the punch is relieved, and the pressure head is relieved until complete solidification and forming;

[0010] S5, the punch retreats to the set position and separates from the box part, and the blanking die retreats to the set position and ejects the workpiece;

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

[0012] Further, in step S1, the blanking die is fitted outside the punch, and the gap between the two is 0.08-0.15mm.

[0013] Further, in step S1, the upper edge of the box is formed by the synchronous downward movement of the blanking die and the punch, so that the blanking die is in close contact with the top surface of the recess die, and is pressurized to a set pressure and then stands still;

[0014] The box part mold cavity is a closed mold cavity formed by the continuous downward movement of the punch to the set position and the recess die, wherein the distance between the bottom surface of the punch and the bottom surface of the recess die is formed.

[0015] Further, the distance between the bottom surface of the punch and the bottom surface of the recess die is the sum of the wall thickness of the box part, the processing allowance and the linear shrinkage plus 0.5mm;

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

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

[0018] Further, the standing time in step S2 is 1-5s.

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

[0020] Further, in step S4, the pressure head pressurizes the pressure chamber to pressure F1 and continues to maintain the pressure F1 to keep pressure, and after keeping pressure for t1 seconds, the metal liquid is solidified and formed, and the pressure head can be depressurized.

[0021] After the pressure head keeps pressure for t2 seconds, the punch continuously pressurizes the mold cavity of the box part to pressure F2 and continues to maintain the pressure F2 to keep pressure, and after keeping pressure for t3 seconds, the pressure can be released.

[0022] Wherein, t1≥t2+t3.

[0023] Further, under the action of the pressure F1, the metal liquid in the pressure chamber generates a pressure P1, and under the action of the pressure F2, the metal liquid inside the mold cavity generates a pressure P2.

[0024] Wherein, P1≤P2.

[0025] Further, the pressure P1 and the pressure P2 are both 20-120 MPa.

[0026] Preferably, the pressure P1 and the pressure P2 are both 20-80 MP.

[0027] Compared with the prior art, the beneficial effects of the present application are:

[0028] (1) Large thin-walled box parts can be produced, with the smallest wall thickness being 2 mm. Since a double pressure chamber is used, the metal liquid filling distance is significantly shortened, the filling capacity is significantly improved, and even if the wall thickness is very small, complete forming can be achieved.

[0029] (2) There is no porosity defect, the speed of the pressure head pushing the metal liquid into the mold cavity can be accurately controlled, and complete filling can be achieved without gas entrapment.

[0030] (3) There is no shrinkage defect. Due to the compression of the punch, the box part is compressed and deformed, and rheological shrinkage can be achieved, so there is no shrinkage defect.

[0031] (4) The process yield is as high as 90% or more. Since the cake is only 20-30 mm thick, the process scrap is small, and the process yield 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. Since the pressure crystallization technology is used, the workpiece structure is fine and the mechanical properties are excellent.

[0033] (6) Wide application range, can be used to form various large thin-walled box parts. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings described below are only some embodiments of the present application, and the other drawings can be obtained by those skilled in the art without creative effort based on these drawings.

[0035] Fig. 1 is a flow chart of a large thin-walled aluminum alloy box liquid die forging method provided by the present application;

[0036] Fig. 2 is a structural schematic diagram of a mold provided by the present application;

[0037] Fig. 3 is a structural exploded view of the mold provided by the present application.

[0038] In the drawings, there are:

[0039] 1, a blank holder die; 2, a punch; 3, a die; 4, a die cavity; 5, a metal liquid; 6, a pressing chamber; 61, a pressing head. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only one of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative effort belong to the scope of protection of the present application.

[0041] Please refer to Figs. 1 to 3 The present application provides a large thin-walled aluminum alloy box liquid die forging method, which comprises the following steps:

[0042] S1, closing the mold: the mold comprises a blank holder die 1, a punch 2 and a die 3, the blank holder die 1 is sleeved outside the punch 2, and the gap between the two is 0.08-0.15 mm; the outer contour of the punch 2 is consistent with the inner contour of the box part, and the lower plane thereof matches the shape of the inner bottom surface of the box part to form the inner cavity of the box part; the die cavity 4 of the die 3 is consistent with the shape of the box part to form the shape of the box part, and the inner bottom surface of the die cavity of the die 3 is consistent with the shape of the outer bottom surface of the box part;

[0043] Start the mold, and move the blank holder die 1 and the punch 2 downward synchronously to make the blank holder die 1 tightly contact with the top surface of the die 3, and then press to the set pressure, and then stop and keep pressure, so as to form the upper edge of the box, and the pressure value can be determined according to the actual metal liquid 5, and is not specifically limited;

[0044] After the punch 2 is continuously pressed to the set position to form a closed mold cavity 4 with the concave die 3, a distance is formed between the bottom surface of the punch 2 and the bottom surface of the concave die 3, the distance between the bottom surface of the punch 2 and the bottom surface of the concave die 3 is the sum of the wall thickness of the box part, the machining allowance and the linear shrinkage plus 0.5 mm, the setting of the 0.5 mm allowance helps to ensure the matching degree between the punch 2 and the concave die 3 during the mold forming process, and reduces the product size error caused by factors such as mold deformation and temperature change.

[0045] S2, pouring metal liquid 5: in this embodiment, at least two compression chambers 6 are included, the compression chambers 6 are installed below the concave die 3 and communicate with the mold cavity 4 of the concave die 3, the inside of the compression chamber 6 is cylindrical and is installed with a compression head 61 matched therewith to block the lower opening thereof and can move vertically, the diameter of the compression chamber 6 is 100-180 mm, is located at the plane of the bottom surface of the box part, the center distance is controlled within the range of 200-1000 mm, and the number of the compression chamber 6 can be determined according to specific needs, for example, it can also be set to three or even more, only the position set by the controller is needed to make the three compression chambers 6 uniformly input the metal liquid 5;

[0046] The metal liquid 5 with a temperature higher than the liquidus temperature by 80-120℃ and qualified composition is poured into each compression chamber 6 to a certain amount at the same time, and is placed for 1-5s for deslagging and degassing;

[0047] S3, pressure filling: the compression head 61 is started, and the metal liquid 5 in each compression chamber 6 is pushed to quickly enter the box part mold cavity 4, so as to fill it, and the movement speed of the compression head 61 is 100-1000mm / s.

[0048] S4, pressure solidification and feeding: the compression head 61 pressurizes the compression chamber 6 to the pressure F1 and continues to maintain the pressure F1 for pressure keeping, so as to make the metal liquid 5 flow and fill, and feed, after t1 seconds of pressure keeping, the metal liquid 5 is solidified and formed, the compression head 61 can be depressurized, after t2 seconds of filling and pressure keeping of the compression head 61, the punch 2 moves downward to compress the high-temperature metal liquid 5 below it, the punch 2 continuously pressurizes the box part mold cavity 4 to the pressure F2 and continues to maintain the pressure F2 for pressure keeping, and after t3 seconds of pressure keeping, pressure feeding and plastic deformation are realized, and after completion, the punch 2 is depressurized, wherein t1≥t2+t3.

[0049] The metal liquid 5 in the compression chamber 6 generates the pressure P1 under the action of the pressure F1, and the metal liquid 5 in the mold cavity 4 generates the pressure P2 under the action of the pressure F2, the pressure P1 and the pressure P2 are both controlled within 20-80MPa, and P1≤P2.

[0050] S5, the punch 2 retreats to the set position and is separated from the box part, the edge clamp die 1 retreats to the set position, and the workpiece is ejected;

[0051] S6, after the workpiece is cooled to room temperature, the cake (process excess material) at the bottom of the box and the exhaust system are removed, and a large thin-walled aluminum alloy box body part blank can be obtained.

[0052] Example 1

[0053] In this embodiment, the molded new energy battery base is taken as an example, the wall thickness of the box body part is 4±0.1 mm, the machining allowance is 1 mm, and the linear shrinkage is 0.04 mm. In step S1, the distance between the bottom surface of the convex die 2 and the bottom surface of the concave die 3 is set to 4+1+0.04+0.5=5.54 mm. In step S4, the lower head 61 is pressurized to a set pressure F1=400 tons and continues to be pressurized until the pressure is maintained for a set time t1=85 seconds and then the pressure is released. After the lower head 61 is pressurized for t2=15 seconds, the convex die 2 is pressurized to a set pressure F2=6000 tons and continues to be pressurized until the pressure is maintained for a set time t3=68 seconds and then the pressure is released; t1≥t2+t3. The metal liquid 5 in the pressure chamber 6 generates a pressure P1=20 MPa under the action of F1. The metal liquid 5 inside the mold cavity 4 generates a pressure P2=50 MPa under the action of F2. Other normal steps of the present application are processed, and finally the size of the shaped battery base after machining is wall thickness 4.05 mm, which is within the required range. In addition, the microstructure and properties of the thick wall part and the thin wall part are as follows: the secondary dendrite arm spacing at the thick wall part with a thickness of 15 mm is 50 μm, the strength is 305 MPa, and the elongation is 7.5%; the secondary dendrite arm spacing at the thin wall part with a thickness of 4.1 mm is 42 μm, the strength is 315 MPa, and the elongation is 8.1%. Both are basically the same, effectively solving the wall thickness effect problem of the existing technology that the wall thickness difference is every 10 mm, the strength attenuation is about 10%, and the elongation attenuation is about 25% for large workpieces.

[0054] Example 2

[0055] The present embodiment takes a certain large thin-walled box body as an example, the main body wall thickness is 2 mm, the length is 1650 mm, the width is 920 mm, the machining allowance is 1.5 mm, and the linear shrinkage is 0.05 mm, so the distance between the convex die 2 bottom surface and the concave die 3 bottom surface is set to 2+1.5+0.05+0.5=4.05 mm; the present embodiment sets three pressure chambers 6, each with a diameter of 180 mm, the lower pressure head 61 is pressurized to a set pressure F1=150 tons and continuously pressurized until the pressure is maintained for a set time t1=13 seconds and then released. After the lower pressure head 61 is pressurized for t2=8 seconds, the convex die 2 is pressurized to a set pressure F2=12000 tons and continuously pressurized until the pressure is maintained for a set time t3=4 seconds and then released; t1≥t2+t3, the metal liquid 5 in the pressure chamber 6 generates a pressure P1=60 MPa under the action of F1, and the metal liquid 5 inside the mold cavity 4 generates a pressure P2=80 MPa under the action of F2, realizing pressure solidification and pressure feeding and plastic deformation, and other settings remain unchanged; this pressure difference ensures that there will be no drilling of aluminum during filling, and through the later high pressure, the inside of the box body is made dense, and a certain plastic deformation occurs, and the core and the outer surface have basically the same organizational performance (the secondary dendrite arm spacing at the core of the wall thickness of 15 mm is 43 μm, the strength is 302 MPa, and the elongation is 7.8%; the secondary dendrite arm spacing at the thin wall of 2 mm is 38 μm, the strength is 320 MPa, and the elongation is 8.8%), effectively solving the wall thickness effect problem of the solidification of large workpieces in the prior art, which is that the wall thickness difference is every 10 mm, the strength attenuation is about 10%, and the elongation attenuation is about 25%.

[0056] Embodiment 3

[0057] A large thin-walled box part, wall thickness 3.5mm, length 1400mm, width 810mm, machining allowance 1mm, linear shrinkage 0.03mm, so the distance between the bottom surface of the male die 2 and the bottom surface of the female die 3 is set to 3.5+1+0.03+0.5=5.03mm. The diameters of the two compression chambers 6 are both 160mm, the lower press head 61 is pressurized to a set pressure F1=40 tons and continuously pressurized, and after pressure maintaining for a set time t1=15 seconds, it is depressurized. After the lower press head 61 is pressure maintained for t2=10 seconds, the male die 2 is pressurized to a set pressure F2=9100 tons and continuously pressurized, and after pressure maintaining for a set time t3=5 seconds, it is depressurized; t1≥t2+t3, the metal liquid 5 in the compression chamber 6 generates a pressure P1=20MPa under the action of F1, and the metal liquid 5 in the cavity 4 generates a pressure P2=80MPa under the action of F2, realizing pressure solidification and pressure feeding, and other settings remain unchanged; ensuring that the box part is compact inside and undergoes certain plastic deformation, and the core and the outer surface have basically the same microstructure and performance, specifically, the secondary dendrite arm spacing at the core 30mm 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 the thin wall 4.0mm is 38μm, the strength is 318MPa, and the elongation is 8.5%, effectively solving the wall thickness effect problem of large workpiece solidification in the prior art, that is, the wall thickness difference is every 10mm, the strength attenuation is about 10%, and the elongation attenuation is about 25%.

[0058] Comparative Example 1

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

[0060] Comparative Example 2

[0061] The difference between this embodiment and Example 1 is that the distance between the bottom surface of the male die 2 and the bottom surface of the female die 3 is set to 5mm, which does not meet the requirement that the distance between the bottom surface of the male die 2 and the bottom surface of the female die 3 = box part wall thickness + machining allowance + linear shrinkage + 0.5mm, as a result, the final formed battery base after machining has a wall thickness size of 4.2mm, which is out of tolerance and is 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 member + the machining allowance + the wire shrinkage + 0.5 mm is not met. As a result, the rear wall of the finally formed battery base is 5.20 mm, which is obviously too thick to increase the amount after machining and increase the 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 member + the machining allowance + the wire shrinkage + 0.5 mm is not met. As a result, the rear wall of the finally formed battery base is 5.5 mm, which is obviously too thick to increase the amount after machining and increase the cost.

[0066] Comparative Example 5

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

[0068] Comparative Example 6

[0069] The difference between this comparative example and embodiment 2 is that the lower head 61 is pressurized to a set pressure F1 = 150 tons and continues to be pressurized until the pressure is maintained for a set time t1 = 13 seconds and then the pressure is released. After the lower head 61 is maintained at pressure for a time t2 = 8 seconds, the punch 2 is pressurized to a set pressure F2 = 12000 tons and continues to be pressurized until the pressure is maintained for a set time t3 = 4 seconds and then the pressure is released; t1 ≥ t2 + t3, the pressure P1 = 10 MPa generated by the molten metal 5 in the pressure chamber 6 under the action of F1, and the pressure P2 = 80 MPa generated inside the molten metal 5 in the mold cavity 4 under the action of F2, P1 is lower than 20 MPa, and the phenomenon of incomplete forming occurs; higher than 80 MPa, the device tonnage increases significantly, and the cost increases.

[0070] Comparative Example 7

[0071] The difference between this comparative example and embodiment 2 is that the pressure P1 = 80 MPa generated by the molten metal 5 in the pressure chamber 6 under the action of F1, and the pressure P2 = 60 MPa generated inside the molten metal 5 in the mold cavity 4 under the action of F2, at this time P2 < P1, then the insufficient feeding occurs, there are shrinkage defects inside, and the product is scrapped.

[0072] Comparative Example 8

[0073] The difference between the present comparative example and example 2 is that the pressure P1 generated by the molten metal 5 in the pressure chamber 6 under the action of F1 is 60 MPa, and the pressure P2 generated inside the molten metal 5 in the mold cavity 4 under the action of F2 is 90 MPa, at this time P2 is less than 20 MPa, which cannot fully compensate for the plastic deformation, the organization is coarsened, and the performance is reduced; if P2 is greater than 80 MPa, the equipment tonnage increases significantly, the mold life also decreases significantly, and the product cost increases.

[0074]

[0075]

[0076] From examples 1-3, the wall thickness tolerance of the new energy battery base formed in example 1 is considered to be qualified within the range of the required wall thickness ±0.1 mm, and the wall thickness tolerance of the large thin-walled box part formed in examples 2 and 3 is considered to be qualified within the range of the required wall thickness ±0.1 mm. From the above table, it can be determined that when the distance between the bottom surface of the convex mold 2 and the bottom surface of the concave mold 3 is strictly controlled to be the sum of the wall thickness of the box part, the machining allowance and the linear shrinkage plus 0.5 mm, the wall thickness of the products of examples 1-3 of the present application is within the qualified tolerance range, which ensures the qualified rate of the wall thickness after processing and forming, and improves the quality of the forming.

[0077] Referring to examples 1 and comparative examples 1-5, in other same cases, in comparative examples 1 and 2, the distance between the bottom surface of the convex mold 2 and the bottom surface of the concave mold 3 is less than the sum of the wall thickness of the box part, the machining allowance and the linear shrinkage plus 0.5 mm, and the distance between the bottom surface of the convex mold 2 and the bottom surface of the concave mold 3 is strictly controlled, the formed wall thickness is 3.85 mm and 4.2 mm respectively, which is obviously lower than the qualified tolerance 4 ±0.1mm , and is out of tolerance and scrapped; at the same time, in comparative examples 3-5, the distance between the bottom surface of the convex mold 2 and the bottom surface of the concave mold 3 is greater than the sum of the wall thickness of the box part, the machining allowance and the linear shrinkage plus 0.5 mm, and the wall thickness of the product after forming is too thick, which causes the amount to increase after processing and the cost to increase.

[0078] Referring to examples 2 and comparative examples 6-9, in comparative example 6, the value of the pressure P1 is less than 20-80 MPa, which will cause the forming porosity to be 5% (the qualified product requires the porosity to be less than 2%), the shrinkage defect rate to be 20% (the qualified shrinkage defect rate is 0%), which leads to incomplete forming and scrapping; in comparative example 7, P1>P2, which causes insufficient compensation and internal shrinkage defects, and the product is scrapped; in comparative example 8, P2 is less than 20 MPa, which cannot fully compensate for the plastic deformation, the organization is coarsened, and the performance is reduced; P2 is greater than 80 MPa, which significantly increases the equipment tonnage, significantly reduces the mold life, and increases the product cost.

[0079] Therefore, through the above comparison, it can be known that by controlling the pressure maintaining time of the pressure head 61 and the pressure maintaining time of the male die 2, the pressure difference between the metal liquid 5 in the pressure chamber 6 and the metal liquid 5 in the mold cavity 4 is formed within the setting range of the pressure P1 and P2, the pressure solidification and the pressure feeding are realized, the inside of the box body part is ensured to be compact and a certain plastic deformation occurs, the tissue performance of the core part and the outer surface is basically consistent, and the wall thickness effect of the solidification of the large workpiece is effectively solved.

[0080] The above embodiment is the preferred embodiment of the present application, but the embodiment of the present application is not limited by the above embodiment, and any change, modification, replacement, combination, simplification made without departing from the spirit and principle of the present application should be an equivalent replacement mode, which is included in the protection scope of the present application.

Claims

1. A method of liquid die casting a large thin-walled aluminum alloy case, characterized by, It comprises the following steps: S1, closing the mold: the mold comprises the upper edge of the box formed by the close contact of the blanking die (1) and the punch (2), and the closed box part mold cavity (4) formed by the punch (2) and the concave die (3), the closed mold cavity (4) is formed by the punch (2) continuously pressed to the set position and the concave die (3), wherein the distance between the bottom surface of the punch (2) and the bottom surface of the concave die (3) is the sum of the wall thickness of the box part, the machining allowance and the linear shrinkage plus 0.5mm; S2, pouring metal liquid (5): including at least two compression chambers (6), the inside of the compression chamber (6) is cylindrical and is equipped with a compression head (61) matched with it to block its lower opening and make vertical movement; the diameter of the compression chamber (6) is 100~260mm, which is located at the plane of the bottom surface of the box part, the center distance is controlled within the range of 200~1000mm, and the metal liquid (5) with a temperature higher than the liquidus temperature by 80~120℃ is poured into each compression chamber (6) at the same time to a certain amount and is left to remove slag and exhaust; S3, pressurized filling: start the compression head (61) and push the metal liquid (5) in each compression chamber (6) to quickly enter the box part mold cavity (4) to fill it, the movement speed of the compression head (61) in step S3 is 100~1000mm / s; S4, pressurized solidification and feeding: continue to increase the pressure through the compression head (61) to make the metal liquid (5) flow and fill, and after a certain time of filling, the punch (2) moves downward to compress the metal liquid (5) below it to realize pressure feeding and plastic deformation, after completion, the punch (2) is depressurized, and after complete solidification and forming, the compression head (61) is depressurized, the compression head (61) is pressurized to a pressure F1 and continues to maintain the pressure F1 for pressure holding, after t1 seconds of pressure holding, the metal liquid (5) is solidified and formed, and the compression head (61) can be depressurized; After t2 seconds of pressure holding of the compression head (61), the punch (2) continuously pressurizes the box part mold cavity (4) to a pressure F2 and continues to maintain the pressure F2 for pressure holding, and after t3 seconds of pressure holding, it can be depressurized; Wherein, t1≥t2+t3; Under the action of the pressure F1, the metal liquid (5) in the compression chamber (6) generates a pressure P1, and under the action of the pressure F2, the metal liquid (5) inside the box part mold cavity (4) generates a pressure P2; Wherein, P1≤P2; S5, the punch (2) retreats to the set position and is separated from the box part, the blanking die (1) retreats to the set position, and the workpiece is ejected; S6, after the workpiece is cooled to room temperature, the cake on the bottom of the box and the overflow system are removed, and a large thin-walled aluminum alloy box part blank is obtained.

2. A method of liquid die casting a large thin-walled aluminum alloy box body according to claim 1, characterized in that: In step S1, the blanking die (1) is sleeved outside the punch (2), and the gap between the two is 0.08~0.15mm.

3. A method of liquid die casting a large thin-walled aluminum alloy box body according to claim 2, characterized in that: In step S1, the upper edge of the box is moved downward synchronously by the blanking die (1) and the punch (2), so that the blanking die (1) is in close contact with the top surface of the concave die (3), and is pressurized to a set pressure and then is stationary for pressure holding.

4. A method of liquid die casting a large thin-walled aluminum alloy box body according to claim 1, characterized in that: The standing time in the step S2 is 1-5s.

5. A method of liquid die casting a large thin-walled aluminum alloy box body according to claim 1, characterized in that: The pressure P1 and the pressure P2 are both 20-120MPa.

Images