Die-casting die for aluminum alloy connecting support of new energy automobile

Abstract

The invention relates to a die-casting die, in particular to a die-casting die for an aluminum alloy connecting support of a new energy automobile, and aims to overcome the defects of unbalanced mold filling speed, shrinkage porosity, cold shut and the like in local positions in the mold filling process of an initially designed die-casting die. Optimized measures are as follows: the branch runners, close to the rib parts, of the fastening parts are in arc transition connection with the transverse runner, so that the jet flow tendency of molten metal in the branch runners when the molten metal enters a cavity is reduced, and negative-pressure air suction or air entrapment is prevented; the sectional areas of the branch pouring gate and the inner pouring gate are increased, and the mold filling speed of the rib part and the fastening part is increased; the auxiliary overflow groove is formed in the middle position, close to the flow gate, of the fastening part and used for discharging gas close to the local position of the flow gate, generation of air holes is reduced, and therefore liquid phase islands at the corners of the fastening part are prevented from being formed.

Description

Technical Field

[0001] The present invention relates to the field of die-casting dies, and in particular to a die-casting die for an aluminum alloy connecting bracket of a new energy vehicle. Background Art In the manufacturing process of new energy vehicles, it is often necessary to connect the motor of the car with other power components to improve system efficiency and realize complex functions. This aluminum alloy connecting bracket part used for the assembly of new energy vehicle motors and other power components is made of A356.2 aluminum alloy and mass-produced by cold chamber high-pressure casting. The material has the advantages of good fluidity, low specific gravity and good corrosion resistance, and has good properties such as no tendency to thermal cracking during die-casting production, small linear shrinkage, and good air tightness. The connecting bracket product weighs 2.75Kg, the product volume is 1013.38cm3, the average wall thickness is 3.5mm, the product size is 319mm×209mm, and the die-casting mold material of the connecting bracket part is SKA61. In order to realize the function of connecting the electric motor of new energy vehicles with various power components of different shapes, the inner surface structure of the connecting bracket is designed with many uneven frames and thin-walled connecting ribs. This uneven frame and rib structure causes uneven filling speed and flow rate of various parts during aluminum alloy die casting, which is prone to local defects such as pores, cold shuts and lack of materials, especially in the parts that need machining. The initially designed pouring system uses multiple sub-runners and inner gates with equal cross-sectional areas to pour the casting cavity, and each sub-runner intersects with the cross runner vertically. Multiple overflow troughs are also set to stabilize the flow state of the molten metal, and to accommodate impurities and improve the exhaust effect. MAGMASOFT software was used to simulate the temperature change, filling speed, air pressure change and shrinkage defect prediction of the die-casting filling process of the bracket. The results showed that the filling speed was uneven and the filling completion time was not synchronized during the filling process; in the early stage of filling, the heat conduction speed between the aluminum liquid and the mold was not synchronized, and there was a certain difference in the temperature change rate; the air pressure at the intersection of the fastening part cavity and the rib part cavity was higher, and there was a small amount of aluminum liquid encapsulated in the inner gate; there were liquid phase islands at the four corners of the fastening part to form heat nodes, which would cause shrinkage defects after solidification, and would affect the connection between the motor and other power components after molding. Summary of the invention

[0002] The present invention aims to solve the above technical problems, optimize and balance the filling flow and speed, so that the filling of the rib cavity, the fastening cavity and the frame cavity can be completed synchronously, and the difference in temperature change speed can be reduced.

[0003] The technical solution adopted by the present invention is a die-casting mold for an aluminum alloy connecting bracket for new energy vehicles, including an upper mold, a lower mold, a pouring system and an overflow system, wherein the upper mold can be separated and buckled relative to the lower mold, and a casting cavity is formed when the upper mold and the lower mold are buckled; the casting cavity includes a rib cavity, a fastening cavity and a frame cavity, and the complexity is that the frame cavity is larger than the fastening cavity and larger than the rib cavity; the pouring system includes a straight runner, a cross runner, a branch runner and an inner gate; one end of the straight runner is connected to the gate, and the other end is connected to the cross runner, and a plurality of branch runners are vertically connected to the cross runner, and each branch runner is It is connected to the casting cavity through corresponding inner gates; wherein the number of branch runners connected to the frame cavity is greater than the number of branch runners connected to the fastening cavity, and the number of branch runners connected to the fastening cavity is greater than the number of branch runners connected to the rib cavity; the overflow system includes multiple overflow grooves, which are respectively connected to the casting cavity; wherein the number of overflow grooves connected to the fastening cavity is greater than the number of overflow grooves connected to the frame cavity, and the number of overflow grooves connected to the frame cavity is greater than the number of overflow grooves connected to the rib cavity; the inner gate cross-sectional area of ​​the fastening cavity close to the rib cavity is greater than the inner gate cross-sectional area of ​​the rib cavity.

[0004] Increasing the cross-sectional area of ​​the inner gate of the fastening part cavity close to the rib part cavity can increase the filling flow of the rib part cavity and the fastening part cavity, speed up the filling speed, and balance it with the filling of the frame cavity to prevent uneven filling speed and the intersection of aluminum liquids with different speeds and temperatures to form defects such as air inclusion, laminar flow and flow lines. In the initial design, due to the small cross-sectional area of ​​the inner gate, the flow rate and air pressure increased, resulting in insufficient time for the heat conduction between the aluminum liquid and the mold to be fully exchanged, resulting in asynchronous heat conduction speed. Therefore, on the other hand, increasing the cross-sectional area of ​​the inner gate can reduce the flow rate and air pressure of the inner gate, so that the heat conduction between the aluminum liquid and the mold can be fully exchanged.

[0005] Furthermore, an inclined connection is provided between the branch runner and the cross runner in the fastening portion cavity close to the rib portion cavity.

[0006] Changing the angle between the runner and the cross runner will affect the flow speed and pressure distribution of the aluminum liquid in the cross runner. By increasing the angle, the flow speed of the aluminum liquid can be controlled to a certain extent, reducing the jetting tendency of the aluminum liquid when entering the cavity, avoiding turbulence and air holes caused by excessive speed, and can also help maintain appropriate static pressure to ensure that the metal liquid can smoothly fill the cavity. The runner is fed in an inclined shape, which can also prevent negative pressure suction or air entrapment.

[0007] Furthermore, an auxiliary overflow groove is provided at a middle position of the fastening portion close to the inner gate.

[0008] Due to the thick wall thickness of the fastening part, it is easy to generate hot spots at the uneven wall thickness position, and the gating system cannot effectively compensate for shrinkage, resulting in reduced density of local crystal structure, shrinkage defects and shrinkage holes during solidification. An auxiliary overflow groove is set in the middle of the fastening part near the inner gate to remove the gas near the inner gate, which can reduce the generation of pores and help solve the problem of liquid phase islands formed at the corners of the fastening part.

[0009] Furthermore, the inclination angle between the runner and the cross runner of the fastening portion cavity close to the rib portion cavity is 110° to 165°.

[0010] The purpose of setting the sub-runner to be inclined and intersecting with the cross runner is to control the flow speed of the aluminum liquid, reduce the jetting tendency of the aluminum liquid when entering the cavity, avoid turbulence and air holes caused by too fast speed, and prevent negative pressure air suction or air entrapment. If the inclination angle is less than 110°, it will not play the above role. If the inclination angle is greater than 165°, the molten metal may encounter more resistance during the flow process, thereby reducing fluidity, affecting the smooth filling of the cavity by the aluminum liquid, and may cause defects such as underfilling or cold shut in the casting. In addition, if the inclination angle is too large, it may affect the flow state of the molten metal in the cross runner, thereby affecting the temperature distribution, resulting in inconsistent cooling speeds in different parts of the casting, causing stress concentration, and even leading to the formation of cracks.

[0011] Furthermore, the inner gate is in a flat bell-mouth shape.

[0012] The flat bell-shaped ingate design can reduce the temperature difference to a certain extent, which is beneficial for preventing cracks near the ingate. In addition, the flat bell-shaped shape helps to reduce the turbulence of the fluid and improve the filling consistency, which is crucial to ensure the quality of the casting.

[0013] Furthermore, the number of branch runners connected to the rib portion is 1 to 2, the number of branch runners connected to the fastening portion is 2 to 4, and the number of branch runners connected to the frame portion is 3 to 5.

[0014] Because the complexity of the frame part of the target casting is greater than that of the fastening part, and the complexity of the fastening part is greater than that of the rib part, the frame part has the largest number of branch runners, followed by the fastening part, and the least is the rib part. Combined with the design of parameters such as cavity filling time, inner gate cross-sectional area, and filling pressure, the number of branch runners connected to the rib part is set to 1-2, the number of branch runners connected to the fastening part is 2-4, and the number of branch runners connected to the frame part is 3-5, so that the filling speeds of the rib part, fastening part, and frame part are balanced, and the filling completion time can be synchronized.

[0015] Furthermore, the number of overflow grooves connected to the rib portion is 1 to 2, the number of overflow grooves connected to the fastening portion is 4 to 6, and the number of overflow grooves connected to the frame portion is 3 to 5.

[0016] The rib part is a thin-walled frame connecting rib, and the required aluminum liquid flow is less, so 1 to 2 overflow grooves can meet the requirements; the frame part has a more complex structure, but its wall thickness is more uniform, so 3 to 5 overflow grooves are set; for the fastening part, although its structure is not as complex as the frame part, its wall thickness is uneven, and the thickness of the part connected with the rib part and the frame part is larger, which is prone to shrinkage holes and shrinkage defects during solidification. The fastening part needs to be machined after die-casting, and has high requirements on the dimensional accuracy and internal structure density of the parts. Therefore, 4 to 6 overflow grooves are set in the fastening part to stabilize the flow state of the molten metal, and to accommodate impurities and improve the exhaust effect, thereby improving the die-casting quality of this part.

[0017] Furthermore, the rib portion cavity has a thin-walled portion, and an overflow groove is connected to the thin-walled portion.

[0018] Due to the narrow cavity in the thin-walled area, the phenomenon of "air trapped in dead corners" may occur due to poor filling during filling. Therefore, an overflow groove is also set here to avoid this situation.

[0019] Furthermore, the overflow trough includes a main body, a connecting part and an exhaust channel, wherein the connecting part connects the main body with the casting cavity, and one end of the exhaust channel is connected to the main body and the other end passes through the upper mold.

[0020] The condensed molten metal at the front end of the injection cavity and the gas involved in the molten metal during the filling process enter the main part of the overflow tank through the connecting part, ensuring the flow state of the aluminum liquid and ensuring that the molten metal can smoothly fill the cavity. The main part contains the condensed molten metal, and the gas is discharged from the mold through the exhaust channel.

[0021] Furthermore, the rib portion cavity is a thin-walled frame connecting rib, the fastening portion cavity has a thicker wall thickness, the frame portion cavity has a more uniform wall thickness, and the thickness of the rib portion cavity and the fastening portion cavity is greater than the thickness of the frame portion cavity.

[0022] The structural characteristics of the casting cavity have a crucial impact on the design of the mold. The thin-walled structure of the rib cavity has a small amount of aluminum liquid flow during filling, which is prone to spraying, air entrainment and cold shut defects. It is necessary to balance the filling pressure and reasonably set the overflow groove. The wall thickness of the fastening cavity is thicker, and the heat is not easy to dissipate. At the same time, it cannot be effectively compensated for shrinkage, which may lead to a decrease in the density of the local crystal structure, and shrinkage defects and shrinkage holes during solidification. Therefore, it is necessary to adjust the filling speed and pressure to achieve more uniform pouring and reduce the generation of liquid phase islands, or increase the ventilation system to reduce the generation of pores to avoid the formation of liquid phase islands. The wall thickness of the frame cavity is relatively uniform, and the thickness is less than that of the fastening cavity and the rib cavity. It solidifies faster, but due to the difference in filling flow and speed, the local position where the aluminum liquid of the frame cavity and the solid cavity meet is prone to defects such as pores, cold shuts and deformation, thereby affecting the dimensional accuracy and ultimately affecting the realization of the connection and installation function. Therefore, it is necessary to balance the filling speed and pressure of the frame cavity, the fastening cavity and the rib cavity.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: by increasing the cross-sectional area of ​​the inner gate of the fastening part cavity close to the rib part cavity, increasing the filling flow of the rib part cavity and the fastening part cavity, accelerating the filling speed, and achieving balance with the filling of the frame part cavity, the defects such as air inclusion, laminar flow and flow lines formed by the intersection of aluminum liquids of different speeds and temperatures due to the uneven filling speed are reduced. At the same time, the cross-sectional area of ​​the inner gate is increased, the flow rate and air pressure of the inner gate are reduced, and the heat conduction between the aluminum liquid and the mold is fully exchanged, solving the problems of the asynchronous heat conduction speed between the aluminum liquid and the mold, the difference in the temperature change speed, and the uneven distribution of temperature gradients in various parts of the filling process. Accelerating the filling speed of the inner gate can also enable the aluminum liquid to evenly fill the cavity, reduce the generation of pores and defects in the fastening part, and also play a certain role in avoiding the formation of liquid phase islands in the fastening part cavity. The gate of the fastening part cavity near the rib part cavity is changed to an inclined pouring design, which reduces the tendency of the molten metal from the gate to spray when entering the cavity, lengthens the stroke, and feeds in an inclined manner, which can also prevent negative pressure suction or air entrapment. An auxiliary overflow groove is set in the middle position of the fastening part cavity near the gate to reduce the generation of air holes in the corners of the fastening part, thereby avoiding the formation of liquid phase islands there. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A three-dimensional diagram of the aluminum alloy connecting bracket.

[0025] Figure 2(a) is a schematic diagram of the initial design cavity, pouring system and overflow system.

[0026] Figure 2(b) is a schematic diagram of the structure of the initial design cavity.

[0027] Figure 2(c) is a schematic diagram of the structure of the initial design connecting bracket casting system.

[0028] FIG3( a ) is a simulation diagram of aluminum liquid filling 20%.

[0029] FIG3( b ) is a simulation diagram of the aluminum liquid filling 60%.

[0030] FIG3( c ) is a simulation diagram of the aluminum liquid filling 85%.

[0031] FIG3( d ) is a simulation diagram of 95% aluminum liquid filling.

[0032] Figure 4(a) is a simulation diagram of the air pressure change and air entrainment defect during the filling process.

[0033] Figure 4(b) is a simulation diagram for prediction of thermal shrinkage defects.

[0034] Figure 5 This is a three-dimensional diagram of the upper mold.

[0035] Figure 6 This is a three-dimensional view of the lower mold.

[0036] Figure 7 Schematic diagram of the connection between the optimized cavity, gating system and overflow system.

[0037] Figure 8 Schematic diagram of the optimized cavity structure.

[0038] Fig. 9 This is a schematic diagram of the structure of the optimized pouring system.

[0039] Fig.10 Simulation-generated PQ after modification of the second ingate cross-sectional area 2 Relationship curve.

[0040] Figure 11(a) shows the simulation of the gas pressure at the intersection of the molten metal before optimization.

[0041] Figure 11(b) shows the simulation of the gas pressure at the intersection of the metal liquid after optimization.

[0042] Fig.12 This is a simulation diagram of the temperature changes of the molten metal and mold during the filling process. DETAILED DESCRIPTION

[0043] The drawings of the present invention are only for illustrative purposes and should not be construed as limiting the present invention. In order to better illustrate the following embodiments, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product; it is understandable to those skilled in the art that some well-known structures and their descriptions in the drawings may be omitted.

[0044] like Figure 1As shown, the target casting is an aluminum alloy connecting bracket 1 for new energy vehicles, including a rib portion 11, a fastening portion 12 and a frame portion 13. The rib portion 11 is a thin-walled frame connecting rib. The metal liquid flow rate is relatively small during die casting, which is prone to spraying, air entrainment and cold shut defects. It is necessary to balance the filling pressure and reasonably set the overflow groove. The fastening portion 12 is a connecting and fastening assembly part that connects other parts. After die casting, it is necessary to perform machining. Therefore, the dimensional accuracy and internal structure density of the parts in this part are relatively high, and the internal structure of the casting must be dense and free of pores. The wall thickness of the frame portion 13 is relatively uniform and easy to solidify quickly, but due to the difference in filling flow and speed, the local position where it intersects with the solid part is prone to defects such as pores, cold shut and deformation. The thickness of the rib portion 11 and the fastening portion 12 is greater than the thickness of the frame portion 13.

[0045] According to the structural characteristics and quality requirements of the target castings, the preliminary pouring system, overflow system and mold preheating temperature were designed according to the selected die-casting machine equipment parameters such as pressure, speed and barrel diameter. The process parameters are shown in Table 1. Table 1 Initial parameters of the numerical simulation of low-pressure casting of bracket Parameter name Numeric Parameter name Numeric Die casting machine tonnage 800t Cavity filling time 0.032s Casting pressure 650bar Gate speed 56m / s Injection stroke 530mm Initial mold temperature 185° Minimum punch speed 0.2m / s Ingate cross-sectional area adjustment range <![CDATA[2.0cm 2 -5.5cm 2 ]]> Punch maximum speed 3.5m / s Aluminum liquid temperature 660° Punch diameter 50mm Maximum filling pressure 63.5Mpa

[0046] According to the basic principle that the location of the inner gate should make the metal liquid fill the cavity as short as possible and prevent the metal liquid from losing too much heat during the filling process and causing die-casting defects such as cold shut or pattern, the initial design of the inner gate adopts multiple short-flow sub-gates as shown in Figure 2(a) to feed the material simultaneously. The cross-sectional shape and size of each sub-gate are similar, in order to make the metal liquid fill evenly and smoothly, which is conducive to exhaust and transmission of static pressure. At the same time, for the flat and dispersed shape of the connecting bracket, the differentiated structures of the rib part, the fastening part, and the frame part may hinder the balanced filling of the aluminum liquid. During the filling, the intersection of several metal liquid flows will also produce eddy currents and air rolls due to collision. At the same time, the difference in solidification timing caused by uneven wall thickness will also cause die-casting defects such as cold shut and deformation. Therefore, multiple overflow grooves are designed to stabilize the flow state of the metal liquid, and play a role in accommodating impurities and improving the exhaust effect. Among them, for the thin wall of the frame of the rib part, in order to avoid the "dead corner trapped air" phenomenon caused by poor filling here, an overflow groove is specially set here.

[0047] As shown in Figures 2(a), 2(b) and 2c, a die-casting mold for an aluminum alloy connecting bracket for new energy vehicles includes an upper mold 6, a lower mold 7, a pouring system 3 and an overflow system 4. The upper mold 6 can be engaged and separated relative to the lower mold 7. When the upper mold 6 and the lower mold 7 are engaged, the upper mold 6 and the lower mold 7 can form a casting cavity 2.

[0048] The casting cavity 2 includes a rib portion cavity 21 , a fastening portion cavity 22 and a frame portion cavity 23 .

[0049] The pouring system 3 includes a sprue 31, a runner 32, a branch runner 33 and an inner gate 34. One end of the sprue 31 is connected to the main gate, and the other end is connected to a first runner 321 and a second runner 322. The first runner 321 and the second runner 322 are respectively located on both sides of the sprue 31. The first runner 321 is sequentially connected to a first branch runner 331, a second runner 332a and a third runner 333, and the second runner 322 is sequentially connected to a fourth runner 334, a fifth runner 335 and a sixth runner 336. The first branch runner 331, the second runner 332a, the third runner 333, the fourth runner 334, the fifth runner 335 and the sixth runner 336 are respectively perpendicularly intersected with the first runner 321 and the second runner 322. The cross-sectional shapes and sizes of the first branch runner 331, the second branch runner 332a, the third branch runner 333, the fourth branch runner 334, the fifth branch runner 335 and the sixth branch runner are similar. The first branch runner 331 is connected to the rib cavity 21 through the first ingates 341, the second branch runner 332a and the third branch runner 333 are connected to the fastening cavity 22 through the second ingates 342a and the third ingates 343 respectively, the fourth branch runner 334, the fifth branch runner 335 and the sixth branch runner 336 are connected to the frame cavity 23 through the fourth ingates 344, the fifth ingates 345 and the sixth ingates 346 respectively, and the cross-sectional areas of the first ingates 341, the second ingates 342a and the sixth ingates 343 are 2.25 cm 2 The cross-sectional areas of the third ingates 343, the fourth ingates 344 and the fifth ingates 345 are all 3.35 cm 2 .

[0050] The overflow system includes multiple overflow grooves 4, which are respectively connected to the casting cavity 2, wherein there is one overflow groove 4 connected to the rib portion cavity 21, which is arranged at the thin-wall position of the rib portion cavity 21, there are four overflow grooves 4 connected to the fastening portion cavity 22, and there are three overflow grooves 4 connected to the frame portion cavity 23.

[0051] According to the die-casting structural characteristics and quality requirements of the connecting bracket parts, MAGMASOFT software was used to simulate the temperature change, filling speed, air pressure change and shrinkage defect prediction of the bracket die-casting filling process.

[0052] like Figure 3(a) , 3(b), 3(c) and 3(d) show the simulation of each stage of aluminum liquid filling. Through simulation comparison, it can be seen that there is an imbalance in the filling speed and cooling and solidification order of each process area during the solidification process of the bracket casting. From the temperature change simulation results, it can be seen that in the initial filling stage of aluminum liquid in Figure 3(a), the heat conduction speed between the aluminum liquid and the mold is not synchronized, and there is a certain difference in the temperature change speed. As shown in Figure 3(b), the filling completion time of the rib cavity, the fastening cavity, and the frame cavity is not synchronized. When the first completed frame cavity is basically full, the rib cavity and the fastening cavity are still nearly one-fifth unfilled. As shown in the simulation results of Figures 3(c) and (d), air suffocation is formed in the fastening cavity near the rib cavity. At the same time, the temperature gradient distribution of each part of the filling process is very uneven, which is prone to shrinkage, shrinkage and cold shut defects. The reason may be that the uneven filling speed causes the aluminum liquid in different areas to cool at different speeds, thereby forming different temperature gradients.

[0053] For the situation shown in Figure 3(a), the cross-sectional area of ​​the gate at that position and the angle between the gate and the cross runner can be increased to reduce the aluminum liquid flow rate of the gate and the gate, so that the heat conduction between the aluminum liquid and the mold can be fully exchanged. For the situations shown in Figures 3(b), 3(c) and 3(d), it is also necessary to increase the cross-sectional area of ​​the gate at the corresponding position, increase the filling flow rate and filling speed, so that the filling flow rate and speed of the rib cavity, the fastening cavity and the frame cavity are balanced. For the situation where the temperature gradient of each part of the filling process is unevenly distributed, the cross-sectional area of ​​the gate at the corresponding position can be increased and the filling speed at the corresponding position can be adjusted so that the aluminum liquid in each part of the casting cavity can fill the mold evenly to reduce the formation of temperature gradient.

[0054] The air pressure simulation shown in Figure 4(a) shows that the air pressure value is higher at the intersection of the rib part and the fastening part. There is air pocket in the machined area of ​​the fastening part. There is a possibility of internal air holes after machining. At the same time, there is a small amount of air inclusion in the molten aluminum at the inner gate position.

[0055] The reason is that the feed flow and speed of the six ingates are not balanced. When the aluminum liquid from different ingates meet at the final filling position of the casting at different speeds and temperatures, defects such as air inclusion, laminar flow and flow lines are easily formed at the intersection of the metal liquid. The cross-sectional area of ​​the ingates at the corresponding positions can be increased to increase the filling flow and filling speed, so that the filling flow and speed of the rib cavity, the fastening cavity and the frame cavity are balanced, and the speed difference and temperature difference when the aluminum liquid meets can be reduced.

[0056] The defect prediction simulation in Figure 4(b) shows that there are liquid islands at the four corners of the fastening part to form heat nodes, and shrinkage defects will appear after solidification. The reason is that the wall thickness of the fastening part is relatively thick, which makes the wall thickness thicker at the four corners of the fastening part, resulting in heat not being easy to dissipate, making this area the last part to solidify. In this case, the surrounding metal has solidified to form a relatively closed space, so that this part of the molten metal cannot be effectively compensated for shrinkage, thus forming liquid islands. The pouring speed and pressure can be adjusted to achieve more uniform pouring and reduce the generation of liquid islands. The ventilation system can also be increased to reduce the generation of pores to avoid the formation of liquid islands.

[0057] Based on the above simulation results and analysis, the root cause of the above defects is the unbalanced filling flow and speed of the rib cavity, the fastening cavity and the frame cavity. The aluminum liquid that enters the cavity earlier has different temperatures and speeds from the aluminum liquid that enters the cavity later. After they meet, defects such as air inclusion, laminar flow and flow lines are formed. Therefore, the pouring system and the overflow system should be changed to balance the relationship between the local filling flow and filling pressure of the casting, balance the filling speed of the rib, fastening and frame, and synchronize the solidification and cooling time. At the same time, the exhaust system can be added to reduce the generation of pores and avoid the formation of hot nodes at the corners of the fastening part.

[0058] Therefore, the present invention provides a die-casting mold for an aluminum alloy connecting bracket for new energy vehicles, including an upper mold 6, a lower mold 7, a pouring system 3 and an overflow system 4. The upper mold 6 can be buckled and separated relative to the lower mold 7. When the upper mold 6 and the lower mold 7 are buckled, the upper mold 6 and the lower mold 7 can form a casting cavity 2.

[0059] The casting cavity 2 includes a rib portion cavity 21 , a fastening portion cavity 22 and a frame portion cavity 23 .

[0060] The pouring system 3 includes a sprue 31, a runner 32, a branch runner 33 and an inner gate 34. One end of the sprue 31 is connected to the main gate, and the other end is connected to a first runner 321 and a second runner 322. The first runner 321 and the second runner 322 are respectively located on both sides of the sprue 31. The first runner 321 is sequentially connected to a first branch runner 331, a second branch runner 332a and a third branch runner 333, and the second runner 322 is sequentially connected to a fourth branch runner 334, a fifth branch runner 335 and a sixth branch runner 336. The first branch runner 331, the third branch runner 333, the fourth branch runner 334, the fifth branch runner 335, and the sixth branch runner 336 intersect the first horizontal runner 321 and the second horizontal runner 322 perpendicularly, respectively, and the second branch runner 332 intersects the first horizontal runner 321 obliquely, and the inclination angle is 110° to 165°. The cross-sectional areas of the first branch runner 331, the second branch runner 332, the third branch runner 333, the fourth branch runner 334, the fifth branch runner 335, and the sixth branch runner 336 are equal. The first branch runner 331 is connected to the rib portion cavity 21 through the first ingates 341, the second branch runner 332 and the third branch runner 333 are connected to the fastening portion cavity 22 through the second ingates 342 and the third ingates 343 respectively, the fourth branch runner 334, the fifth branch runner 335 and the sixth branch runner 336 are connected to the frame portion cavity 23 through the fourth ingates 344, the fifth ingates 345 and the sixth ingates 346 respectively, and the cross-sectional area of ​​the second ingates 342, the third ingates 343, the fourth ingates 344 and the fifth ingates 345 is 3.35 cm 2 The cross-sectional area of ​​the first gate 341 and the sixth gate 346 are both 2.25 cm 2 .

[0061] The overflow system includes multiple overflow grooves 4, which are respectively connected to the casting cavity 2, wherein there is one overflow groove 4 connected to the rib cavity 21, which is arranged at the thin-wall position of the rib cavity 21, and there are four overflow grooves 4 connected to the fastening cavity 22. An auxiliary overflow groove 5 is also arranged between the second inner gate 342 and the third inner gate 343, and there are three overflow grooves 4 connected to the frame cavity 23.

[0062] As shown in the figure, the overflow groove 4 includes a connecting portion 41, a main portion 42 and an exhaust channel 43. The connecting portion 41 connects the main portion 42 with the casting cavity 2. One end of the exhaust channel 43 is connected to the main portion 43 and the other end leads to the outside of the mold.

[0063] During die casting, aluminum liquid is injected from the gate and enters the cavity through the sprue, cross runner, branch runner and inner gate in sequence. The condensed aluminum liquid that enters earlier and the gas and impurities in the cavity enter the main part through the connecting part of the overflow groove to stabilize the flow state of the aluminum liquid. The main part accommodates the condensed aluminum liquid and impurities, and the exhaust channel discharges the gas out of the mold.

[0064] MAGMASOFT software generates PQ based on the equipment and ingate design. 2 The relationship curve helps designers verify the process area where the relationship between filling pressure and flow is ideal, so as to test and judge the rationality of the design of the size of the gate. Enter different gate design related parameters in the software, and the software will automatically calculate the corresponding PQ 2 Relationship curve, check PQ 2 The relationship between the process adaptation window and whether it is within the optimal process parameter combination range in the gray area.

[0065] like Fig.10 As shown in the figure, the cross-sectional area of ​​the optimized second gate is input, and the PQ generated by the simulation is 2 The process curve is in the optimal region, which proves that the optimization scheme of changing the cross-sectional area of ​​the second gate is feasible. 2 The relationship curve diagram is shown in Figure 2. The parameters such as the maximum filling pressure, cavity filling time and initial mold temperature of the initial process are also adjusted and optimized accordingly. The specific parameter improvements are shown in Table 2. Table 2 Comparison of initial process and optimized solution parameters Initial parameter name Numeric Optimization scheme parameter name Numeric Initial mold temperature 180° Initial mold temperature 190° Cavity filling time 0.031s Cavity filling time 0.035s Ingate cross-sectional area <![CDATA[2.25cm 2 ]]> Ingate cross-sectional area <![CDATA[3.35cm 2 ]]> Maximum filling pressure 62.5Mpa Maximum filling pressure 64.6Mpa

[0066] In order to verify whether each area of ​​the casting has a balanced filling pressure and flow rate, MAGMASOFT software is used again to simulate and verify the optimized solution. At the same time, the optimized solution is simulated and analyzed for the filling process pressure and solidification temperature, and the pressure and temperature comparison simulation curve from liquid phase to solid phase of the optimized part die casting process is obtained.

[0067] like Figure 11(a) , 11(b) As shown in the figure, from the comparison of the air pressure simulation at the intersection of the aluminum liquid filling ends before and after optimization, it can be seen that the initial design air pressure value is high, reaching 3567Mbar, while the air pressure value after optimization is reduced to 2302Mbar; this shows that the risk of gas inclusion tendency at this metal liquid intersection position is greatly reduced.

[0068] By selecting analog sensors placed at locations where shrinkage may occur during prediction, MAGMASOFT software can also generate heat exchange and temperature change curves between the molten metal and the mold at key locations to check whether the temperature curve of the solidification process is smooth. Figure 8As shown in the figure, the heat conduction temperature curve between the local mold and the molten metal of the optimized casting decreases gently, proving that the casting has obtained a reasonable cooling and solidification rate in the process from liquid phase to solid phase; and avoiding defects such as shrinkage caused by excessive temperature gradient between the casting and the mold.

[0069] It can be seen from the optimized simulation results that the optimized technical solution reduces the air pressure at the intersection of the aluminum liquid filling end, avoiding defects such as shrinkage caused by excessive temperature gradient between the casting and the mold.

[0070] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the technical solution of the present invention, and are not intended to limit the specific implementation methods of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the claims of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A die-casting mold for an aluminum alloy connecting bracket for a new energy vehicle, comprising an upper mold, a lower mold, a pouring system and an overflow system, wherein the upper mold can be separated and buckled relative to the lower mold, and a casting cavity is formed when the upper mold and the lower mold are buckled; The casting cavity includes a rib cavity, a fastening cavity and a frame cavity, and the complexity is that the frame cavity is larger than the fastening cavity and larger than the rib cavity; The pouring system includes a sprue, a runner, a branch runner and an ingate; one end of the sprue is connected to the gate and the other end is connected to the runner, and the runner is vertically connected to multiple branch runners, each of which is connected to the casting cavity through a corresponding ingate; The number of branch runners connected to the frame cavity is greater than the number of branch runners connected to the fastening cavity, and the number of branch runners connected to the fastening cavity is greater than the number of branch runners connected to the rib cavity; The overflow system includes a plurality of overflow grooves, which are respectively connected to the casting cavity; wherein the number of overflow grooves connected to the fastening part cavity is greater than the number of overflow grooves connected to the frame part cavity, and the number of overflow grooves connected to the frame part cavity is greater than the number of overflow grooves connected to the rib part cavity; It is characterized in that The cross-sectional area of ​​the ingate of the fastening portion cavity close to the rib portion cavity is larger than the cross-sectional area of ​​the ingate of the rib portion cavity.

2. The die-casting mold of the aluminum alloy connecting bracket for new energy vehicles according to claim 1, characterized in that: The gate is arranged in a sloping connection between the branch gate and the cross gate of the fastening part cavity close to the rib part cavity.

3. The die-casting mold of the aluminum alloy connecting bracket for new energy vehicles according to claim 1, characterized in that: An auxiliary overflow groove is arranged at a middle position of the fastening portion cavity close to the inner gate.

4. The die-casting mold of the aluminum alloy connecting bracket for new energy vehicles according to claim 2, characterized in that: The inclination angle between the branch runner and the cross runner of the fastening part cavity close to the rib part cavity is 110° to 165°.

5. The die-casting mold of the aluminum alloy connecting bracket for new energy vehicles according to claim 1, characterized in that: The inner gate is in a flat bell-mouth shape.

6. The die-casting mold of the aluminum alloy connecting bracket for new energy vehicles according to claim 1, characterized in that: The number of branch runners connected to the rib cavity is 1 to 2, the number of branch runners connected to the fastening cavity is 2 to 4, and the number of branch runners connected to the frame cavity is 3 to 5.

7. The die-casting mold of the aluminum alloy connecting bracket for new energy vehicles according to claim 1, characterized in that: The number of overflow grooves connected to the rib part cavity is 1 to 2, the number of overflow grooves connected to the fastening part cavity is 4 to 6, and the number of overflow grooves connected to the frame part cavity is 3 to 5.

8. The die-casting mold of the aluminum alloy connecting bracket for new energy vehicles according to claim 1, characterized in that: The rib portion cavity has a thin wall portion, and an overflow groove is connected to the thin wall portion.

9. The die-casting mold of the aluminum alloy connecting bracket for new energy vehicles according to claim 1, characterized in that: The overflow trough comprises a main body, a connecting part and an exhaust channel. The connecting part connects the main body with the casting cavity. One end of the exhaust channel is connected to the main body, and the other end passes through the upper mold.

10. The die-casting mold of the aluminum alloy connecting bracket for new energy vehicles according to claim 1, characterized in that: The rib cavity is a thin-walled frame connecting rib, the fastening cavity has a thicker wall thickness, the frame cavity has a more uniform wall thickness, and the thickness of the rib cavity and the fastening cavity is greater than the thickness of the frame cavity.

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