Thin-walled high-performance double-frame auxiliary frame and liquid die forging method thereof

Abstract

This invention discloses a thin-walled, high-performance double-frame subframe and its liquid forging method, relating to the field of automotive manufacturing technology. The subframe includes a left longitudinal beam, a right longitudinal beam, a front crossbeam, a rear crossbeam, and a central crossbeam. The liquid forging method arranges two gating systems within the subframe cavity. Each gating system consists of a runner, a main runner, and branch runners radiating from the main runner. The cross-sectional area of ​​the main runner and branch runners gradually decreases from the runner towards the gate along the direction of molten metal flow. During the liquid forging pressurization stage, the extrusion pressure gradually increases as the cross-sectional area decreases. The liquid forging machine drives two barrels and the runner to seal against the corresponding feed inlets and independently controls the two extrusion hammers. The central axis of the runner is located within the symmetrical center plane of the subframe to shorten the molten metal flow distance from each gate to the far end of the mold filling. This method can reduce the weight of the risers and runners, shorten the filling distance, reduce the risk of cold shuts and performance degradation, and improve the density and consistency of the casting.

Description

Technical Field

[0001] This invention relates to the field of automobile manufacturing technology, and in particular to a thin-walled, high-performance double-frame subframe and its liquid forging method. Background Technology

[0002] With the application and promotion of new energy vehicles, OEMs are increasingly demanding lightweighting of vehicles in order to improve the driving range of their models and reduce the load of power batteries. As a large and key structural component of the unsprung part of the vehicle chassis, the lightweighting of the subframe has a particularly significant impact on the improvement of the overall vehicle's driving range.

[0003] Currently, lightweight solutions for subframes mainly employ low-pressure casting of aluminum alloys or welding of castings with extruded profiles. However, due to the low-pressure filling and solidification characteristics of low-pressure casting, the main body wall thickness in automotive subframe applications is generally >4mm. Furthermore, the multi-liter nozzles, large risers, and internal runner feeding characteristics of low-pressure casting add extra weight to the subframe, hindering further weight reduction. For example, Chinese invention patent application CN114985684A discloses a design method for a low-pressure casting gating system with an overflow slag pot. This invention uses a multi-liter nozzle layout and large riser feeding, and the gating channels all employ a thick structure. This design significantly reduces material utilization in subframe manufacturing. The thick residual bosses of the risers increase the weight of the subframe body and the difficulty of subsequent CNC machining, further increasing the manufacturing cost of the subframe. Furthermore, Chinese invention patent application CN117483711A discloses a liquid forging method for subframes. This method employs a single-shank horizontal extrusion technique, which involves a long filling process on the upper side of the subframe, resulting in significant instantaneous extrusion pressure. This can lead to casting shrinkage defects at the far end of the filling process, and a substantial decrease in the mechanical properties of the parts, ultimately increasing the risk of subframe fracture failure. Therefore, current liquid forging methods for subframes still have shortcomings and urgently require further improvement. Summary of the Invention

[0004] The purpose of this invention is to provide a thin-walled, high-performance double-frame subframe and its liquid forging method, in order to solve the problems mentioned above.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, this application provides a thin-walled, high-performance double-frame subframe, the subframe comprising a left longitudinal beam, a right longitudinal beam, a front crossbeam, a rear crossbeam, and a middle crossbeam located in the middle, all connected in a surrounding manner. The first part of the subframe forms the front frame, and the second part forms the rear frame. The structure of the subframe is an integral hollow structure or an open cross-section structure composed of the combination of the front frame and the rear frame. The wall thickness of the main body of the subframe is 3-4 mm to achieve weight reduction.

[0006] In a possible implementation manner, the subframe is in a double-frame structure shaped like a "day" character in a planar projection.

[0007] In a second aspect, the present application provides a liquid forging method for the thin-walled high-performance double-frame structure subframe provided in the first aspect. The liquid forging method includes the following steps: S1. Obtain a mold for forming the double-frame structure subframe. The mold has a double-frame structure subframe cavity and is provided with a first feeding port and a second feeding port; two pouring systems connected to the first feeding port and the second feeding port are arranged in the mold. Each pouring system is composed of a handle, a main runner connected to the handle, and a sub-runner that diverges from the main runner and is connected to different regions of the subframe cavity; S2. Make the cross-sectional areas of the main runner and the sub-runner gradually decrease along the metal liquid flow direction from the handle to the gate, so that the cross-sectional area of the runner at the gate is smaller than that at the handle, so that the extrusion pressure in the liquid forging pressurization stage gradually increases from the handle to the gate as the cross-sectional area decreases; S3. Make the central axis of each handle be located within the symmetric center plane of the subframe, or the central axes of each handle be mirror-symmetrically arranged with respect to the symmetric center plane of the subframe, and make each pouring system be arranged at intervals in the plane of the subframe to shorten the metal liquid flow distance from each gate to the filling far end; S4. Inject metal liquid into each barrel, and an extrusion hammer head for pushing the metal liquid in the barrel is arranged at the bottom of the barrel; the liquid forging machine drives the two barrels and the two handles to move to the first feeding port and the second feeding port of the mold and press tightly against the corresponding feeding ports to form a seal; S5. The liquid forging machine controls each extrusion hammer head independently, and respectively sets the opening time and running speed of each extrusion hammer head, so that the metal liquid in the two barrels pushes the metal liquid to move upward at a uniform speed of <0.6 m / s to expel the residual air in the barrels, and the upper end surfaces of the metal liquid in the barrels are kept at the same height for filling; S6. The liquid forging machine continues to independently control the movement of each extrusion hammer head, so that the metal liquid fills the mold runner at a speed of <1.5 m / s, and makes the metal liquid levels in the runners of each pouring system be kept flush or controlled to be flush, so that the air in the cavity is discharged upward in an orderly manner from the low position; S7. During the filling process, first make the molten metal in the low-position pouring system smoothly fill the lower die part of the subframe cavity, and make the two streams of molten metal continue to fill after converging at the high parting line position of the subframe cavity, so as to reduce the gas entrapment caused by the confluence and prevent the product from having porosity or lack of material defects. S8. The two extrusion hammers continue to move upward to apply pressure, pushing the converged molten metal to fill the subframe cavity to complete the filling; when the filling of the subframe cavity is ≥ 70%, the filling speed is allowed to be increased, but the speed is less than 2 m / s and laminar flow filling is maintained. S9. When the molten metal surface is still 5 mm - 15 mm away from completely filling the cavity, switch the two extrusion hammers to the high-pressure liquid forging mode and apply mechanical pressure to each handle. S10. Maintain the mechanical pressure of the two extrusion hammers until the molten metal in the subframe and each pouring system solidifies, and then relieve the pressure, open the mold and take out the subframe blank.

[0008] In a possible implementation manner, in step S1, the subframe is a double-frame structure in the shape of "day", and the two pouring systems are respectively arranged in the geometric center regions of the front frame and the rear frame of the subframe.

[0009] In a possible implementation manner, when the central axis of each handle is located in the symmetry center plane of the subframe, the central projections of the two handles are located on the same symmetry center line, so that the filling distances of the molten metal on both sides of the subframe are the same, thus enabling synchronous filling on both sides.

[0010] In a possible implementation manner, the mold is provided with an exhaust groove structure at the outer frame parting line of the subframe; in step S4, both of the two handles adopt vertical pouring, so that the molten metal moves in a laminar flow against gravity in the two handles, so as to improve the exhaust effect and reduce the risk of gas entrainment.

[0011] In a possible implementation manner, the two barrels are arranged on the moving mechanism of the liquid die forging machine, so that the center distance between each handle and each handle is adjustable, and the adjustable range of the center distance is 300 mm - 800 mm, and the central axes of the two handles are always located in the symmetry center plane of the subframe or symmetric about the symmetry center plane during the adjustment process.

[0012] In a possible implementation manner, in step S5, the liquid die forging machine adopts an independent control mode for each extrusion hammer, at least including respectively controlling the start time, running speed and pressurizing pressure of the two extrusion hammers.

[0013] In one possible implementation, in step S1, each of the main channels is distributed to the left and right longitudinal beams respectively, and the two branch channels are respectively connected to the corresponding areas of the front crossbeam, the middle crossbeam and the rear crossbeam. The channel structure is symmetrical from left to right, so that the molten metal remains stable during the filling process of the subframe and avoids air entrapment or uneven performance.

[0014] In one possible implementation, in step S2, the main channel and the branch channel gradually thin from the sprue to the gate along the flow direction of the molten metal. The gate thickness is 5mm to 25mm, and the ratio of the gate thickness to the initial thickness of the channel is 1.5 to 5. The gate thickness is set at 1.5 to 3.5 times the wall thickness of the corresponding gate position and does not exceed 25mm.

[0015] In one possible implementation, the two barrels are mounted on a moving mechanism on a liquid forging machine. The liquid forging machine adjusts the position of the two barrels by controlling the moving mechanism, so that the center distance between each barrel is adjustable within the range of 300mm to 800mm. During the adjustment process, the central axis of each barrel is kept within the symmetrical center plane of the subframe.

[0016] In one possible implementation, in step S3, the position of the material handle of one of the two casting systems can be set in the adjacent area of ​​the outer side of the front crossbeam or the outer side of the rear crossbeam, and the center of the material handle is located in the symmetrical center plane of the subframe or its projection is located on the symmetrical center line, and the two side diversion channels connected to it are arranged in a fan shape. Alternatively, the two gating systems can be arranged in the adjacent areas on the outer side of the left longitudinal beam and the outer side of the right longitudinal beam of the subframe, respectively.

[0017] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: (1) The present invention adopts the central stub extrusion filling method, and the outer side of the product adopts a small slag bag for slag collection and venting. This significantly reduces the number of gates and runners in low pressure casting, eliminates the riser structure, effectively improves the utilization rate of raw materials, and thus reduces the manufacturing cost of the subframe. (2) The subframe of the present invention is manufactured using liquid forging technology with double casting stalks. Compared with the maximum filling distance of about 700mm to 1000mm on the double frame subframe in liquid forging with single casting stalks, this solution can shorten the maximum filling distance to about 350mm to 500mm. This can greatly shorten the casting filling distance and solve the defects of incomplete filling or cold shut in the mold cavity. At the same time, the distance of liquid forging pressure holding is shortened, which is more conducive to ensuring the consistency of the mechanical properties of the product body and suppressing the performance degradation caused by excessive distance.

[0018] (3) The present invention makes the cross-sectional area of ​​the main channel and the branch channel gradually decrease from the sprue to the gate along the flow direction of the molten metal. The gradually thinning channel structure is conducive to increasing the extrusion pressure at the gate, so that the subframe can obtain greater extrusion and feeding pressure, thereby making the internal structure more compact. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the subframe structure in this invention; Figure 2 This is a schematic diagram of the mold for the subframe in this invention; Figure 3 This is a schematic diagram of the extrusion hammer head in this invention; Figure 4 This is a schematic diagram of the open-type subframe in this invention; Figure 5 This is a schematic diagram of a second embodiment of the subframe in the present invention; Figure 6 This is a schematic diagram of the third embodiment of the subframe in this invention.

[0020] In the figure: (1) left longitudinal beam, (2) right longitudinal beam, (3) front crossbeam, (4) middle crossbeam, (5) rear crossbeam, (7) subframe, (7-1) front frame, (7-2) rear frame; (8) first casting system, (8-1) first material handle, (8-2) first main channel, (8-3) first branch channel, (9) exhaust groove; (10) second casting system, (10-1) second material handle, (10-2) second main channel, (10-3) second branch channel, (11) first material cylinder, (12) first extrusion hammer, (13) second material cylinder, (14) second extrusion hammer; (16-1) third material handle, (16-2) first flow channel, (16-3) second flow channel, (17) U-shaped section, (17-1) reinforcing rib. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0022] In related technologies, the existing low-pressure casting process for subframes has the following problems: low-pressure casting uses pneumatic filling and holding pressure, with a pressure generally between 0.06 and 0.15 MPa. The relatively low filling pressure reduces the flow distance of the molten metal in the mold cavity, making low-pressure casting unsuitable for manufacturing subframe products with a wall thickness of less than 4 mm. Furthermore, the pressure is often affected by insufficient furnace sealing performance, resulting in large pressure fluctuations, which in turn leads to uneven product performance and non-density within the product. To address the problems of low-pressure casting, this invention uses a liquid forging process for thin-walled, high-performance double-frame subframes and manufactures a thin-walled, high-performance double-frame subframe.

[0023] As Figures 1-6 , a thin-walled high-performance double-frame structure subframe, wherein the structure of the subframe 7 may include a left longitudinal beam 1, a right longitudinal beam 2, a front cross beam 3, a rear cross beam 5 connected in an enclosing manner, and a middle cross beam 4 provided in the middle. The front cross beam 3 is connected to the rear cross beam 5 through the left longitudinal beam 1 and the right longitudinal beam 2. The middle cross beam 4 is provided between the front cross beam 3 and the rear cross beam 5. That is, the first part of the subframe 7 constitutes the front frame 7-1, and the second part constitutes the rear frame 7-2. The subframe (7) is in a double-frame structure of a "day" shape in a planar projection. In addition, the structure of the subframe 7 may be an integral hollow structure formed by combining the above-mentioned front frame 7-1 and rear frame 7-2, or an open-section structure.

[0024] On the other hand, the present invention also provides a liquid die forging method for a thin-walled high-performance double-frame structure subframe. The liquid die forging method includes the following steps: S1. Obtain a mold for forming the double-frame structure subframe 7. The liquid die forging method of the double-frame "day" shape subframe 7 adopts a double-gating system, that is, a first gating system 8 and a second gating system 10. The mold has a cavity of the double-frame structure subframe 7 and is provided with a first feeding port and a second feeding port; a first gating system 8 and a second gating system 10 are provided in the mold and are connected to the first feeding port and the second feeding port; each gating system is composed of a sprue, a main runner connected to the sprue, and a sub-runner that diverges from the main runner and is connected to different regions of the cavity of the subframe 7; The first gating system 8 is composed of a first sprue 8-1, a first main runner 8-2, and a first sub-runner 8-3; the first main runner 8-2 is connected to the first sprue 8-1 together, and the first sub-runner 8-3 diverges from the first main runner 8-2 and is connected to different regions of the cavity of the subframe 7; The second gating system 10 is composed of a second sprue 10-1, a second main runner 10-2, and a second sub-runner 10-3; the second main runner 10-2 is connected to the second sprue 10-1 together, and the second sub-runner 10-3 diverges from the second main runner 10-2 and is connected to different regions of the cavity of the subframe 7; The main channel and branch channels of the first gating system 8 and the second gating system 10 together form a dendritic bionic distribution channel structure. This channel structure is arranged symmetrically from left to right with the center of the first material handle 8-1 and the second material handle 10-1 as the reference, and connects the first material handle 8-1, the second material handle 10-1 and the sub-frame 7 body respectively. This allows the molten aluminum alloy to flow smoothly from the first material handle 8-1 and the second material handle 10-1 into the channel, avoiding turbulent flow and air entrapment during the flow process. The forward structure also helps to reduce the casting pressure and speed loss of the molten metal. The dendritic bionic distribution channel structure, with the thick main channel directly connecting the material handle and the part, makes the molten metal filling time shorter and the pressure loss lower. The dendritic branch channel structure is arranged forward along the direction of the molten metal flow channel, which greatly reduces the speed loss of the molten metal flow and allows the branch channel to maintain a high extrusion pressure. In step S1, the two gating systems are respectively arranged in the geometric center areas of the front frame 7-1 and the rear frame 7-2 of the subframe 7; that is, the first gating system 8 is arranged in the geometric center area of ​​the front frame 7-1 of the subframe 7, and the second gating system 10 is arranged in the geometric center area of ​​the rear frame 7-2. The mold features an venting groove 9 structure at the parting line of the subframe 7 outer frame. Existing low-pressure casting technology for subframes employs multiple sets of risers and large riser feeding methods, with the number of risers reaching 6 to 10 sets. Consequently, its material utilization rate is generally less than 50%. The liquid forging method of this invention achieves a material utilization rate of 60% to 70%, effectively saving casting costs. Furthermore, the gate of this invention is concentrated on the inner side of the subframe 7 frame, which can be quickly removed by punching or laser cutting, significantly improving manufacturing efficiency compared to the sawing removal required in low-pressure casting.

[0025] S2. The cross-sectional area of ​​the main runner and branch runners gradually decreases from the sprue to the gate along the direction of molten metal flow, making the runner cross-section at the gate smaller than that at the sprue; that is, the cross-sectional area of ​​the first main runner 8-2 and the first branch runner 8-3 gradually decreases from the first sprue 8-1 to the gate along the direction of molten metal flow, and the cross-sectional area of ​​the second main runner 10-2 and the second branch runner 10-3 gradually decreases from the second sprue 10-1 to the gate along the direction of molten metal flow. The gate thickness is 5mm to 25mm, and the ratio of the gate thickness to the initial runner thickness is 1.5 to 5. The gate thickness is set at 1.5 to 3.5 times the wall thickness at the corresponding gate position and does not exceed 25mm, so that the extrusion pressure during the liquid forging pressurization stage increases with the cross-sectional area. The area decreases while gradually increasing from the first sprue 8-1 / second sprue 10-1 towards the gate, thereby providing higher extrusion and feeding pressure for the casting. Specifically, this design helps the molten metal to maintain laminar flow during filling and avoids air entrapment, and makes the gate solidify later than the part body, so that the liquid forging extrusion pressure is continuously transmitted to the subframe 7 body for feeding. However, when the gate thickness exceeds 25mm, the runner thickness will increase simultaneously, which will significantly reduce the material utilization rate and increase the manufacturing cost. In addition, unlike the constant cross-section runner design of low pressure casting, the gradually thinning runner structure adopted in this invention helps to increase the extrusion pressure at the gate, so that the subframe 7 obtains greater extrusion and feeding pressure and thus makes the internal structure more compact.

[0026] S3. Ensure that the central axis of each sprue is located within the symmetry center plane of the subframe 7, and that the center projections of the two sprues are located on the same symmetry center line, so that the metal liquid filling distance on both sides of the subframe 7 is the same, thereby enabling synchronous filling on both sides; or, the central axis of each sprue is arranged in a mirror image symmetrical about the symmetry center plane of the subframe 7, and each gating system is arranged at intervals in the plane of the subframe 7. That is, the central axes of the first sprue 8-1 and the second sprue 10-1 are located within the symmetry center plane of the subframe 7. In other words, the central axes of the first sprue 8-1 and the second sprue 10-1 are arranged in a mirror image symmetrical about the symmetry center plane of the subframe 7, and the first gating system 8 and the second gating system 10 are arranged at intervals in the plane of the subframe 7, so as to shorten the metal liquid flow distance from their respective gates to the far end of the filling, so that the filling distance on both sides of the subframe 7 is the same or approximately the same, thereby enabling synchronous filling on the left and right sides, which is beneficial for controlling the synchronous filling of the metal liquid in the mold cavity to ensure consistent performance on the left and right sides of the subframe product.

[0027] S4. Molten metal is injected into each barrel, and a pressing hammer for pushing the molten metal inside the barrel is provided at the bottom of the barrel; the liquid forging machine drives the two barrels and two material handles to move to the first and second feed ports of the mold, and they are pressed tightly against the corresponding feed ports to form a seal. That is, molten metal is injected into the first barrel 11 and the second barrel 13. The bottom of the first barrel 11 is provided with a first pressing hammer 12 for pushing the molten metal inside the first barrel 11, and the bottom of the second barrel 13 is provided with a second pressing hammer 14 for pushing the molten metal inside the second barrel 13; the liquid forging machine drives the first barrel 11 and the first material handle 8-1 to move to the first feed port of the mold, and they are pressed tightly against the corresponding feed port to form a seal. The liquid forging machine drives the second barrel 13 and the second material handle 10-1 to move to the second feed port of the mold, and they are pressed tightly against the corresponding feed port to form a seal.

[0028] S5. The liquid forging machine independently controls each extrusion hammer, setting the opening time and running speed of each extrusion hammer. That is, the liquid forging machine independently controls the first extrusion hammer 12 and the second extrusion hammer 14, setting the opening time and running speed of the first extrusion hammer 12 and the second extrusion hammer 14 respectively, so that the molten metal in the first barrel 11 and the second barrel 13 moves upward at a uniform speed of <0.6m / s to remove residual air in the barrel, and the upper end surfaces of the molten metal in the first barrel 11 and the second barrel 13 are kept at the same height for filling.

[0029] S6. The liquid forging machine continues to independently control the movement of each extrusion hammer. Specifically, the liquid forging machine continues to independently control the movement of the first extrusion hammer 12 and the second extrusion hammer 14, causing the molten metal to fill the mold runner at a speed of <1.5 m / s. This process requires controlling the speed of the first extrusion hammer 12 and the second extrusion hammer 14 to maintain the molten metal in a laminar flow state, preventing tumbling and air entrapment in the runner. Furthermore, the molten metal levels of the first gating system 8 and the second gating system 10 within the runner are kept flush or controlled to be flush, meaning the lower runner completes filling first, followed by the higher runner, allowing air in the cavity to be discharged in an orderly manner from lower to higher positions. A multi-stage speed control strategy is employed during the filling stage to maintain the molten metal in a laminar flow state, shortening the filling time while avoiding air entrapment defects during filling.

[0030] S7. During the filling process, the molten metal from the low-position gating system is first used to smoothly fill the lower mold part of the sub-frame 7 cavity, and the two streams of molten metal are made to merge at the high parting line of the sub-frame 7 cavity and continue filling, so as to reduce the defects of air entrapment or material shortage in the product caused by the convergence of air.

[0031] S8. The two extrusion hammers continue to move upward to apply pressure, that is, the first extrusion hammer 12 and the second extrusion hammer 14 continue to move upward to apply pressure, pushing the merged molten metal to fill the cavity of the subframe 7 to complete the filling. When the cavity of the subframe 7 is filled to ≥70%, the filling speed is allowed to be increased, but the speed is less than 2m / s and laminar flow filling is maintained. This design helps to shorten the filling time of the subframe 7 and reduce the risk of cold shut or material shortage at the far end of the filling.

[0032] S9. When the molten metal level is 5mm to 15mm away from completely filling the cavity, switch the two extrusion hammers to the high-pressure liquid forging mode and apply mechanical pressure to each shank; that is, switch the first extrusion hammer 12 and the second extrusion hammer 14 to the high-pressure liquid forging mode and apply mechanical pressure to the first shank 8-1 and the second shank 10-1. Specifically, when the subframe 7 is a hollow structure with a core, the applied mechanical pressure is 20MPa to 80MPa; when the subframe 7 is an open structure, the applied mechanical pressure is 80MPa to 150MPa. This design can compensate for the response delay characteristics of the hydraulic system, achieve synchronous hammer pressure building and mold filling, extend the high-pressure action time on the product, and allow more molten metal in the first shank 8-1 and the second shank 10-1 to continuously fill the solidification shrinkage area of ​​the subframe 7 through the unsolidified flow channels, thereby making the subframe 7 casting more dense and reducing casting shrinkage defects.

[0033] S10. Maintain the mechanical pressure of the two extrusion hammers until the molten metal in the subframe 7 and each gating system solidifies, that is, maintain the mechanical pressure of the first extrusion hammer 12 and the second extrusion hammer 14 until the molten metal in the subframe 7 and the first gating system 8 and the second gating system 10 solidifies. Then, release the pressure, open the mold and take out the subframe 7 blank, thereby completing the blank forming preparation of the whole state forged subframe.

[0034] In this embodiment, the liquid forging technology used is different from the sequential solidification mode of low-pressure casting in the prior art. The solidification process of the liquid forging subframe casting is simultaneous solidification in the die cavity area, which greatly shortens the holding pressure time of casting, doubles the production efficiency of the subframe compared with low-pressure casting, and thus reduces the manufacturing cost of the subframe. Compared with the existing low-pressure casting technology that uses 5-10 sets of multiple liquid inlet ports, the casting material utilization rate is less than 50%. In this invention, the first sprue 8-1 and the second sprue 10-1 at the central position are used for extrusion filling. Small slag pockets are used for slag collection and exhaust on the outer side of the product. Compared with low-pressure casting, the number of gates and runners is greatly reduced, and the riser structure is cancelled, which can increase the material utilization rate to more than 60%, effectively improving the utilization rate of raw materials and thus reducing the manufacturing cost of the subframe. The centers of the vertical first sprue 8-1 and the second sprue 10-1 are respectively located at the geometric centers of the front and rear frames. In addition, the vertical structure design can enable the molten metal to achieve counter-gravity laminar flow filling from the bottom end to the upper side of the part, avoiding gas entrainment during filling. Compared with the prior art, the double-sprue structure adopted in this invention can shorten the filling distance of the molten metal in the casting process by half, effectively solving the problem that the filling distance of the molten metal is too long during the casting of the "day"-shaped double-frame subframe 7, resulting in incomplete filling or cold lap defects in the subframe blank, that is, solving the problem of attenuation of the mechanical properties of the product and the generation of casting defects due to the attenuation of the extrusion pressure at the far end of filling, enabling the subframe to obtain better quality performance; specifically, in this invention, the filling distance of the molten metal from the upper gate to the farthest end of the double-frame subframe is about 700 mm - 1000 mm, and cold lap or performance attenuation at the far end of filling is likely to occur. The double-sprue liquid forging technology in the subframe 7 of this invention can shorten this farthest filling distance to 350 mm - 500 mm, solving the cold lap and performance attenuation problems of the prior art, making the filling distances of the molten metal on the left and right sides of the product the same, and thus making the performances on the left and right sides of the product consistent.

[0035] For the liquid forging process used in this invention, both the filling and holding pressure processes are controlled by a hydraulic system. The maximum hammer head pressure can reach 150 MPa, which can meet the casting forming of the subframe with a main wall thickness of 3 - 4 mm, facilitating further reduction of the weight of the subframe based on low-pressure casting and achieving a better lightweight effect; at the same time, applying a high holding pressure can continuously compensate for shrinkage in the thick and large areas of the subframe, enabling the subframe product to obtain a denser structure and solving the problem of easy generation of casting shrinkage porosity defects in the low-pressure casting process.

[0036] In some embodiments, there are differences in the front and rear frame dimensions and weights of the "day"-shaped double-frame subframe 7. Therefore, the diameter specifications of the first handle 8-1 and the second handle 10-1 of the present invention can adopt unequal diameter specifications. According to the specifications of the subframe 7, the weight of the poured aluminum alloy metal liquid in a single barrel is 10 kg to 30 kg. Therefore, the diameter specifications of the first handle 8-1 and the second handle 10-1 can be designed within the range of 100 mm to 165 mm. The diameter specification is selected to be the smallest specification diameter that meets the pouring capacity, so as to minimize the weight of the pouring system and achieve the optimal material utilization.

[0037] In some embodiments, such as Figure 3 shown, there may be a height difference between the first handle 8-1 and the second handle 10-1 to match diverse subframe structures and expand the application scope of the present invention; this height difference can be achieved by adjusting the lengths of the first barrel 11 and the second barrel 13, and the height difference value can be designed according to the height difference value of the parting surface of the front and rear frames of the subframe 7.

[0038] In some embodiments, such as Figure 3 shown. In step S4, both handles adopt vertical pouring, that is, both the first handle 8-1 and the second handle 10-1 adopt vertical pouring, so that the metal liquid moves in a laminar flow against gravity in the first handle 8-1 and the second handle 10-1, which is beneficial to exhausting the air in the mold cavity and avoiding the occurrence of porosity defects in the product; in addition, the vertical pouring method enables more precise control of the speed of the metal liquid in the mold cavity, avoiding the entrained air caused by the disordered flow velocity of the metal liquid at the lower side of the handle due to gravity during the horizontal pouring in the prior art; that is, it can improve the exhaust effect and reduce the risk of entrained air.

[0039] In some embodiments, such as Figure 3 shown. The two barrels are arranged on the moving mechanism of the liquid forging machine, so that the center distance between each handle and each handle is adjustable. That is, the first barrel 11 and the second barrel 13 are arranged on the moving mechanism of the liquid forging machine. The liquid forging machine controls the moving mechanism to adjust the positions of the first barrel 11 and the second barrel 13 respectively, so that the center distance between the first handle 8-1 and the second handle 10-1 is adjustable, and the adjustable range of the center distance is 300 mm to 800 mm, and the central axes of the two handles are always located within the symmetric center plane of the subframe 7 or symmetric about the symmetric center plane during the adjustment process.

[0040] The adjustment method for the first material shank 8-1 and the second material shank 10-1 is as follows: The first material cylinder 11 and the second material cylinder 13 on the liquid forging machine are designed as independently moving and controlled modules. That is, the first material cylinder 11 and the second material cylinder 13 are mounted on the moving mechanism of the liquid forging machine. The moving mechanism can be controlled separately by software programs, thereby adjusting the position of the first material cylinder 11 and the second material cylinder 13 and thus their spacing. The spacing between the first material cylinder 11 and the second material cylinder 13 of this invention is adjustable within the range of 300mm to 1000mm. The dual material shanks are compatible with different diameter specifications. The appropriate stalk diameter is selected based on the amount of molten metal used in the filling area of ​​each stalk. The stalk diameter can be selected from 100mm to 165mm, and the length of the stalk can be adjusted to maintain the optimal utilization rate of molten metal. This design is more suitable for manufacturing subframes of various specifications with double frame structures, resulting in higher material utilization in casting. To ensure the balanced performance of the liquid forged subframe, the spacing adjustment must ensure that the centers of the first stalk 11 and the second stalk 13 are always on the symmetrical center plane of the subframe 7. This design facilitates the matching of various specifications of subframe structures and improves the versatility of this patented product.

[0041] In some embodiments, in step S5, the liquid forging machine adopts an independent control method for each extrusion hammer, that is, the liquid forging machine adopts an independent control method for the first extrusion hammer 12 and the second extrusion hammer 14, which includes controlling the start time, running speed and pressure of the first extrusion hammer 12 and the second extrusion hammer 14 respectively. The start time, running speed and pressure of the first extrusion hammer 12 and the second extrusion hammer 14 can be independently controlled according to the casting process requirements, which can meet the complex subframe part forming process requirements.

[0042] In some embodiments, such as Figure 2 As shown. In step S1, each main flow channel is distributed to the left longitudinal beam 1 and the right longitudinal beam 2 respectively, and the two branch channels are connected to the corresponding areas of the front crossbeam 3, the middle crossbeam 4 and the rear crossbeam 5 respectively. That is, the first main flow channel 8-2 and the second main flow channel 10-2 are distributed to the left longitudinal beam 1 and the right longitudinal beam 2 respectively, and the first branch flow channel 8-3 and the second branch flow channel 10-3 are connected to the corresponding areas of the front crossbeam 3, the middle crossbeam 4 and the rear crossbeam 5 respectively. Moreover, the flow channel structure is symmetrical from left to right, so that the molten metal remains stable during the filling process of the subframe 7, avoiding air entrapment or uneven performance.

[0043] In some embodiments, the first flow channel 8-3 and the second flow channel 10-3 are respectively connected to the thick-walled structure of the subframe 7. This design can achieve limited filling of the thick-walled area and is more conducive to replenishing the thick structural area with molten metal through continuous liquid forging extrusion pressure, avoiding casting shrinkage and porosity defects in the thick area.

[0044] In some embodiments, such as Figure 4 As shown. In step S9, the double-sprue liquid forging method of the present invention is also applicable to the open-type subframe 7 structure; its open-type structure is that the main body has a "U" shaped cross section 17, so that the open side of the subframe faces the ground after it is installed in the vehicle, so as to avoid the accumulation of liquid or impurities on the subframe during vehicle use, which would cause abnormal noise and corrosion; multi-directional reinforcing ribs 17-1 are designed in the "U" shaped cross section to improve the cross-sectional stiffness of the subframe; the subframe 7 with an open-type structure can be subjected to twice the mechanical extrusion pressure compared to the hollow structure during liquid forging, which is beneficial for the subframe body to obtain higher mechanical properties.

[0045] In some embodiments, such as Figure 5 As shown. In step S3, if the material handle cannot be arranged at its geometric center due to structural limitations, either the current frame 7-1 or the rear frame 7-2 can move at least one material handle from the first casting system 8 and the second casting system 10 outward.

[0046] Specifically, such as Figure 5 As shown. The sprue of one of the two gating systems can be positioned in the adjacent area outside the front crossbeam 3 or the rear crossbeam 5, with the center of the sprue located within the symmetrical center plane of the subframe 7 or its projection located on the symmetrical center line, and the two side distribution channels connected to it arranged in a fan shape. That is, the sprue of one of the first gating system 8 and the second gating system 10 can be positioned in the adjacent area outside the front crossbeam 3 or the rear crossbeam 5, such as... Figure 5 As shown, the material handle here is represented by the third material handle 16-1. The center of the third material handle 16-1 is located in the symmetry center plane of the subframe 7 or its projection is located on the symmetry center line. The first flow channel 16-2 and the second flow channel 16-3 connected to its two sides are arranged in a fan shape, so that the molten metal can be distributed to the two sides for filling.

[0047] In another embodiment, such as Figure 6 As shown, the two gating systems are respectively arranged in the adjacent areas outside the left longitudinal beam 1 and the right longitudinal beam 2 of the subframe 7. That is, the first gating system 8 and the second gating system 10 are respectively arranged in the adjacent areas outside the left longitudinal beam 1 and the right longitudinal beam 2, and are mirror-symmetrical about the left and right symmetrical planes. The number and position of the first runner 8-3 or the second runner 10-3 can be adjusted according to the specific subframe 7 product. This change in feature does not change the essential structure of the liquid forging gating system of the present invention. Through the above-mentioned outward arrangement, without changing the partitioned liquid supply nature of the dual gating system, it can be adapted to the double-frame subframe structure with small front and rear frames or limited central area, thereby expanding the applicability of the method of the present invention.

[0048] In the description of this invention, it should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0049] Furthermore, in the description of this invention, the terms "upper," "lower," "front," "rear," "left," "right," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0050] On the other hand, it should be noted that, unless otherwise explicitly specified and limited, the terms "set up," "located in," "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

Claims

1. A thin-walled, high-performance double-frame subframe, characterized in that, The subframe (7) includes a left longitudinal beam (1), a right longitudinal beam (2), a front crossbeam (3), a rear crossbeam (5) that are enclosed and connected, and a middle crossbeam (4) provided in the middle; The first part of the subframe (7) forms a front frame (7-1), and the second part forms a rear frame (7-2). The structure of the subframe (7) is an integral hollow structure or an open cross-section structure composed of the combination of the front frame (7-1) and the rear frame (7-2); The subframe (7) is formed by molding casting with a high oil pressure of 60 MPa to 150 MPa, and the main wall thickness of the subframe (7) can reach 3 to 4 mm.

2. The thin-walled high-performance double-frame subframe according to claim 1, characterized in that, The subframe (7) is in a "day"-shaped double-frame structure in the plane projection.

3. A liquid forging method for a thin-walled, high-performance double-frame subframe as described in claim 1 or 2, characterized in that, The liquid die forging method includes the following steps: S1. Obtain a mold for forming the double-frame structure subframe (7). The mold has a cavity of the double-frame structure subframe (7) and is provided with a first feeding port and a second feeding port; two gating systems are arranged in the mold and are connected to the first feeding port and the second feeding port. Each gating system is composed of a sprue, a main runner connected to the sprue, and a sub-runner that diverges from the main runner and is connected to different regions of the subframe (7) cavity; S2. Make the cross-sectional areas of the main runner and the sub-runner gradually decrease along the flowing direction of the molten metal from the sprue to the gate, so that the cross-sectional area of the runner at the gate is smaller than that at the sprue; S3. Make the central axis of each sprue be located in the symmetry center plane of the subframe (7), or the central axes of each sprue be arranged symmetrically with respect to the symmetry center plane of the subframe (7), and make each gating system be arranged at intervals in the plane of the subframe (7); S4. Inject molten metal into each barrel, and an extrusion hammer head for pushing the molten metal in the barrel is provided at the bottom of the barrel; Driven by a liquid die forging machine, two barrels and two sprues are moved to the first feeding port and the second feeding port of the mold and are tightly attached to the corresponding feeding ports to form a seal; S5. The liquid die forging machine independently controls each extrusion hammer head, and respectively sets the opening time and running speed of each extrusion hammer head, so that the molten metal in the two barrels pushes the molten metal to move upward at a uniform speed of <0.6 m / s to expel the residual air in the barrels, and the upper end surfaces of the molten metal in the barrels are kept at the same height for filling; S6. The liquid die forging machine continues to independently control the movement of each extrusion hammer head, so that the molten metal fills the mold runner at a speed of <1.5 m / s, and makes the height of the molten metal surface in the runner of each gating system be kept flush or controlled to be flush; S7. During the filling process, first make the molten metal of the low-position gating system smoothly fill the lower die part of the subframe (7) cavity, and make the two-way molten metal converge at the high parting line position of the subframe (7) cavity and then continue to fill; S8. The two extrusion hammer heads continue to move upward to apply pressure, and push the converged molten metal to fill the subframe (7) cavity to complete the filling; when the filling of the subframe (7) cavity is ≥70%, it is allowed to increase the filling speed, but the speed is less than 2 m / s and laminar flow filling is maintained; S9. When the molten metal level is 5mm to 15mm away from completely filling the cavity, switch the two extrusion hammers to the high-pressure liquid forging mode and apply mechanical pressure to each spool. S10. Maintain the mechanical pressure of the two extrusion hammers until the subframe (7) and the molten metal in each gating system solidify, then depressurize, open the mold and remove the subframe (7) blank.

4. The liquid forging method for the thin-walled high-performance double-frame subframe according to claim 3, characterized in that, In step S1, the two casting systems are respectively arranged in the geometric center areas of the front frame (7-1) and the rear frame (7-2) of the subframe (7).

5. The liquid forging method for the thin-walled high-performance double-frame subframe according to claim 4, characterized in that, When the central axis of each of the material stalks is located in the symmetrical center plane of the subframe (7), the central projections of the two material stalks are located on the same symmetrical center line, so that the metal liquid filling distance on both sides of the subframe (7) is the same, thereby enabling synchronous filling on both sides.

6. The liquid forging method for the thin-walled high-performance double-frame subframe according to claim 3, characterized in that, The mold has an exhaust groove structure at the parting line of the outer frame of the subframe (7); in step S4, both material handles are vertically poured, so that the molten metal moves in the two material handles in a laminar flow against gravity, so as to improve the exhaust effect and reduce the risk of air entrapment.

7. The liquid forging method for the thin-walled high-performance double-frame subframe according to claim 3, characterized in that, The two material cylinders are mounted on the moving mechanism of the liquid forging machine, so that the center distance between each material shank is adjustable, and the adjustable range of the center distance is 300mm to 800mm. During the adjustment process, the central axis of the two material shanks is always located in the symmetrical center plane of the subframe (7) or symmetrical about the symmetrical center plane.

8. The liquid forging method for the thin-walled high-performance double-frame subframe according to claim 3, characterized in that, In step S5, the liquid forging machine adopts an independent control method for each extrusion hammer, which includes controlling the start time, running speed and pressure of each extrusion hammer separately.

9. The liquid forging method for the thin-walled high-performance double-frame subframe according to claim 3, characterized in that, In step S1, each of the main channels is distributed to the left longitudinal beam (1) and the right longitudinal beam (2) respectively. The two branch channels are connected to the corresponding areas of the front crossbeam (3), the middle crossbeam (4) and the rear crossbeam (5) respectively. The channel structure is symmetrical from left to right, so that the molten metal remains stable during the filling process of the subframe (7) and avoids air entrapment or uneven performance.

10. The liquid forging method for the thin-walled high-performance double-frame subframe according to claim 3, characterized in that, In step S2, the main channel and the branch channel gradually thin from the sprue to the gate along the flow direction of the molten metal. The gate thickness is 5mm to 25mm, and the ratio of the gate thickness to the initial thickness of the channel is 1.5 to 5. The gate thickness is set at 1.5 to 3.5 times the wall thickness of the corresponding gate position and does not exceed 25mm.

11. The liquid forging method for the thin-walled high-performance double-frame subframe according to claim 3, characterized in that, The two material cylinders are mounted on the moving mechanism of the liquid forging machine. The liquid forging machine adjusts the position of the two material cylinders by controlling the moving mechanism, so that the center distance between each material shank is adjustable within the range of 300mm to 800mm. During the adjustment process, the central axis of each material shank is kept within the symmetrical center plane of the subframe (7).

12. The liquid forging method for the thin-walled high-performance double-frame subframe according to claim 3, characterized in that, In step S3; The position of the material handle of one of the two casting systems can be set in the adjacent area outside the front crossbeam (3) or the rear crossbeam (5), and the center of the material handle is located in the symmetrical center plane of the subframe (7) or its projection is located on the symmetrical center line, and the two side flow channels connected to it are arranged in a fan shape. Alternatively, the two gating systems can be arranged in the adjacent areas outside the left longitudinal beam (1) and the right longitudinal beam (2) of the subframe (7), respectively.

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