A large thin-walled automobile middle fixed support die-casting mold gating system and a working method thereof

Abstract

The present application relates to a support gating technology field, specifically relates to a large thin-walled automobile middle fixed support die-casting mould gating system and working method thereof, the system comprises: outer gating system, the outer gating system includes the main cross gate, branch cross gate and inner gate which are communicated, the main cross gate is U-shaped, the cross-sectional area of the main cross gate gradually decreases from the metal liquid input end of the main cross gate to the metal liquid output end of the main cross gate, and the branch cross gate is arranged on the main cross gate;Inner gate system, the inner gate system is arranged in the hollow area of the casting cavity, and the inner gate system includes I-shaped inner gate and Y-shaped inner gate, and the inner gate system is in the form of a thin sheet bridge;Ladle system, the ladle system is communicated with the casting cavity through the overflow port, and the ladle system includes the slag discharge groove and the overflow groove which are connected in sequence;Exhaust groove, the exhaust groove is communicated with the ladle system.The present application carries out zoned feeding and internal flow guide for thin-walled parts, and realizes uniform filling of the casting.

Description

Technical Field

[0001] This invention relates to the field of bracket casting technology, specifically to a casting system for a large thin-walled automotive mid-section fixed bracket die-casting mold and its working method. Background Technology

[0002] As a crucial component of automotive interiors, the dashboard has a complex structure, typically integrating a central control display screen, audio system, and other multimedia equipment, and is connected to the vehicle body via a fixed bracket. The central fixed bracket, serving as the primary mounting carrier for the dashboard, requires careful consideration in its structural strength, assembly feasibility, and resistance to deformation. Die casting is a highly efficient technology for producing metal parts, injecting molten metal at high pressure into a mold cavity, where it cools to form the desired part. Aluminum alloys, due to their lightweight, high strength, and excellent casting properties, are a commonly used material for automotive fixed brackets. During die casting, the design of the gating and venting systems directly impacts the quality of the casting. The gating system, including the sprue, runner, and ingate, controls the flow direction, speed, and filling sequence of the molten metal, ensuring a dense internal structure and a defect-free surface. The venting system removes gases and impurities from the mold cavity through overflow channels and venting channels, preventing defects such as porosity and cold shuts. Die-cast aluminum alloys have good fluidity but a fast solidification rate; therefore, a well-designed gating and venting system is necessary to balance the filling speed and temperature distribution, ensuring the molding quality of large, thin-walled parts.

[0003] In existing technologies, the dimensions of conventional die-cast aluminum alloy products are typically controlled within 400mm, with a wall thickness of around 4mm. However, the central fixed bracket involved in this application has a length of 808mm and an average wall thickness of only 2.3mm, classifying it as an ultra-large thin-walled die-casting part. Such products face numerous challenges during the forming process: First, the aluminum melt suffers significant heat loss during long-distance flow, easily leading to insufficient filling at the end, resulting in undercasting or cold shut defects. Second, the thin-walled structure exhibits uneven temperature distribution during cooling, easily causing warping deformation exceeding the allowable deformation tolerance of 2.0mm, affecting assembly accuracy. Furthermore, the presence of porosity or shrinkage cavities at the mounting points and machined surfaces significantly reduces structural strength. Existing gating and venting system designs are typically designed for small to medium-sized castings and are insufficiently adaptable to large, thin-walled parts. For example, traditional ingate designs struggle to ensure continuous filling of the molten metal during long flows, leading to cold shuts or porosity in isolated boss areas. Simultaneously, the layout of overflow channels and venting channels fails to effectively balance cavity pressure, exacerbating warping deformation problems. Furthermore, the turbulence of molten metal during die casting can easily trap gas, further deteriorating the quality of the casting. Therefore, it is urgent to optimize the design of the gating system to solve the forming defects and deformation problems of large, thin-walled die castings. Summary of the Invention

[0004] To address the aforementioned technical problems of incomplete filling, cold shuts, porosity, and severe warping deformation in large thin-walled aluminum alloy die castings due to their long process flow, thin wall thickness, and complex structure, this invention provides a gating system and its working method for a large thin-walled automotive center fixed bracket die casting mold. This invention primarily utilizes a double-sided feeding U-shaped external gating system, an internal Y / I-shaped internal gating system, an n-shaped slag trap system, and a damping corrugated plate vacuum exhaust system. These features enable rapid, sequential, and uniform filling of the mold cavity with molten metal, efficient removal of gas and impurities, and significant balancing of the mold's temperature and pressure fields. Ultimately, this achieves the technical effect of stably producing high-quality large thin-walled die castings with dense internal structure, precise dimensions, and controllable deformation.

[0005] The technical means employed in this invention are as follows: A die-casting mold gating system for a large thin-walled automotive mid-section fixed bracket includes: An external gating system is used to introduce molten metal into the casting cavity. The external gating system includes a main gating, a branch gating, and an ingate that are connected to each other. The main gating is U-shaped and its cross-sectional area gradually decreases from the molten metal inlet end to the molten metal outlet end. The branch gating is located on the main gating. An ingate system is provided in the hollow area of ​​the casting cavity to guide the flow of molten metal inside the hollow area. The ingate system includes an I-type ingate and a Y-type ingate, and the ingate system is in the form of a thin sheet-like connecting bridge. A slag bag system, wherein the slag bag system is connected to the casting cavity through an overflow port, and the slag bag system includes a slag discharge trough and an overflow trough connected in sequence; An exhaust channel is connected to the slag bag system and is used to extract gas from the slag bag system and the casting cavity. A vacuum system, which is connected to the exhaust duct.

[0006] Furthermore, the main horizontal runner is U-shaped, the cross-section of the main horizontal runner is trapezoidal, and the width and thickness of the main horizontal runner gradually decrease from the molten metal inlet end to the molten metal outlet end of the main horizontal runner.

[0007] Furthermore, a first branch horizontal runner and a second branch horizontal runner are provided at the corner of the main horizontal runner. The extension direction of the first branch horizontal runner near the molten metal input end of the main horizontal runner is at an angle of 20~40° with the horizontal direction, and the extension direction of the second branch horizontal runner near the molten metal output end of the main horizontal runner is at an angle of 35~55° with the horizontal direction. A third branch horizontal runner is provided at the end of the main horizontal runner, and the extension direction of the third branch horizontal runner is at an angle of 30~50° with the tangent direction at the end of the U-shaped main horizontal runner.

[0008] Furthermore, the cross-sectional shape of the ingate is rectangular, and the formula for calculating the total area of ​​the ingate in the gating system of the large thin-walled automotive mid-section fixed bracket die-casting mold is as follows:

[0009] in, A 内浇口 This represents the total area of ​​the ingate. G The sum of the mass of the casting, the slag catcher system, the ingate system, and the venting channels. ρ The density of aluminum alloy, v 内 For the filling speed of aluminum alloy, t The filling time for the molten metal.

[0010] Furthermore, the Y-shaped ingate is connected to the inner wall of the main runner facing the casting cavity. The Y-shaped ingate includes an inlet, an inner runner, and an outlet. The inner runner forms a diversion section near the outlet, which divides the molten metal into two streams and guides them to the outlet. The included angle of the inner runner near the inlet is 55~66°. The diversion section adopts a transition between a circular arc and a straight line segment. The type I inlet gate is located between the end of the main horizontal gating and the slag bag system. The inlet of the type I inlet gate is rectangular, and the length-to-width ratio of the rectangle is greater than 7.

[0011] Furthermore, the inlet end of the slag discharge trough is connected to the casting cavity, the outlet end of the slag discharge trough is connected to the inlet end of the overflow trough, and the outlet end of the overflow trough is connected to the vacuum system. The overflow trough includes a single-inlet overflow trough, a double-inlet overflow trough, a forward and reverse bidirectional overflow trough, and a series overflow trough. The dual-inlet overflow channel is located in the molten metal confluence area at the bottom of the casting cavity, and the dual-inlet overflow channel is connected to the casting cavity through two independent overflow channels. The bidirectional overflow channel is located at the bottom of the hollowed-out area of ​​the casting cavity, and the bidirectional overflow channel simultaneously receives both forward-flowing and reverse-flowing molten metal. The series overflow channels are located at the end of the casting cavity. The series overflow channels are a first overflow channel and a second overflow channel connected in sequence. The size of the first overflow channel is larger than that of the second overflow channel.

[0012] Furthermore, the exhaust groove is a damping corrugated plate structure, and the exhaust groove is provided with multi-stage corrugated teeth. The gas flow path is a tortuous path along the gap of the corrugated teeth, and the exhaust gap of the exhaust groove gradually decreases from the input end to the output end.

[0013] This invention also includes a method for operating a large thin-walled automotive mid-section fixed bracket die-casting mold gating system, based on the aforementioned large thin-walled automotive mid-section fixed bracket die-casting mold gating system, comprising the following steps: Close the mold and preheat it to bring the mold cavity temperature to the predetermined range; Start the vacuum system connected to the exhaust groove to pre-evacuate the cavity and gating system; The die-casting machine performs injection, and the molten metal sequentially passes through the sprue, main runner, branch runner and ingate of the external gating system and enters the casting cavity. Some of the molten metal is supplemented and locally fed through the hollow area inside the cavity by the ingate system. During the filling process, the gas, cold material and molten metal containing impurities in the mold cavity are pushed into the slag packing system, and the gas is continuously extracted by the vacuum system through the exhaust groove. After filling, pressure is maintained, and then the casting cools and solidifies in the mold cavity; Open the mold and eject the casting with the outer sprue, inner sprue bridge and slag pocket.

[0014] Compared with the prior art, the present invention has the following advantages: 1. The dual-sided feeding U-shaped external gating system and multi-point coordinated internal gating system provided by the present invention achieve rapid, uniform and sequential filling of the casting by dividing the large thin-walled parts into short-distance feeding zones and internal directional flow, effectively eliminating cold shuts and undercast defects caused by excessively long process flow.

[0015] 2. The n-type slag bag layout and damping corrugated plate vacuum exhaust system provided by the present invention achieves efficient separation and active removal of gas and impurities in the mold cavity through graded slag collection and stepped speed reduction exhaust, which significantly improves the internal density of the casting and the quality of key mounting surfaces.

[0016] 3. The collaborative design scheme of the four systems of external gating, internal gating, slag bag and vacuum provided by the present invention achieves dynamic balance of mold temperature field and pressure field through structural complementarity and process parameter linkage, and controls the overall warpage deformation of large thin-walled die castings within 1.5mm, which meets the requirements of high-precision assembly.

[0017] Based on the above reasons, this invention can be widely applied in fields such as support systems and water supply systems. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of the die-casting mold gating system for the large thin-walled automobile mid-section fixed bracket of the present invention.

[0020] Figure 2 This is a schematic diagram of the external gating system of the present invention.

[0021] Figure 3 This is a schematic diagram of the Y-shaped inlet gating system of the present invention.

[0022] Figure 4 This is a schematic diagram of the structure of the Type I ingate of the present invention.

[0023] Figure 5 This is a schematic diagram of the slag packaging system of the present invention.

[0024] Figure 6 This is a front view of the dual-inlet overflow channel of the present invention.

[0025] Figure 7 This is a cross-sectional view of the dual-inlet overflow channel of the present invention.

[0026] Figure 8 This is a cross-sectional view of the series overflow channel of the present invention.

[0027] Figure 9 This is a front view of the exhaust channel of the present invention.

[0028] Figure 10 This is a cross-sectional view of the exhaust channel of the present invention.

[0029] Figure 11 This is a schematic diagram of the central fixing bracket of the present invention.

[0030] Figure 12 This is a schematic diagram of the isolated thin-walled trapezoidal column in region A7 of this invention.

[0031] Figure 13 This is a schematic diagram of the filling end in an embodiment of the present invention.

[0032] Figure 14 This is a schematic diagram of the partitioning of the slag bag system in an embodiment of the present invention.

[0033] Figure 15 This is a diagram illustrating the effect of numerical simulation filling in an embodiment of the present invention.

[0034] Figure 16 This is a diagram showing the sensor locations of the casting system during numerical simulation in an embodiment of the present invention.

[0035] Figure 17 The velocity-time curves at points S2 and S4 in the numerical simulation of this invention are shown in the embodiment of the invention.

[0036] Figure 18 The velocity-time curves at points S12 and S13 in the numerical simulation of this invention are shown in the embodiment of the invention.

[0037] Figure 19 This is a partial numerical simulation effect diagram of the filling time at 0.540 seconds in an embodiment of the present invention.

[0038] Figure 20 This is a diagram showing the positions of points S5, S6, and S7 during the numerical simulation in this embodiment of the invention.

[0039] Figure 21 The graph shows the velocity-time curves of points S5, S6, and S7 during the numerical simulation in this embodiment of the invention.

[0040] Figure 22 This is a numerical simulation diagram of the filling effect of the Type I inlet runner at 0.658 seconds in an embodiment of the present invention.

[0041] Figure 23 This is a diagram showing the positions of points S8 and S9 during the numerical simulation in this embodiment of the invention.

[0042] Figure 24 This is a velocity-time curve of points S8 and S9 during the numerical simulation in this embodiment of the invention. Figure 25 This is a numerical simulation diagram of the filling effect of the dual-inlet slag bag at 0.658 seconds in an embodiment of the present invention.

[0043] Figure 26 This is a numerical simulation diagram of the bidirectional slag pack filling effect at 0.658 seconds in an embodiment of the present invention.

[0044] Figure 27 This is a numerical simulation diagram of the bidirectional slag pack filling effect at 0.661 seconds in an embodiment of the present invention.

[0045] Figure 28 This is a numerical simulation diagram of the slag bag filling effect at 0.669 seconds in an embodiment of the present invention.

[0046] Figure 29 This is a photograph of a product with a gating system in the stationary mold direction.

[0047] Figure 30 This is a physical image of a product with a gating and drainage system, showing the moving mold direction.

[0048] Figure 31This is a physical image of the product in static orientation.

[0049] Figure 32 This is a physical image of the product in motion.

[0050] In the diagram: 1. Casting cake; 2. Main runner; 21. Branch runner; 22. Ingate; 31. Type I ingate; 32. Type Y ingate; 4. Slag bag system; 41. Double inlet overflow channel; 42. Bidirectional overflow channel; 43. Series overflow channel; 5. Venting channel; 6. Casting cavity. Detailed Implementation

[0051] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0052] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0053] Example 1 In the filling process of die-cast aluminum alloys, the fundamental conservation laws of fluid mechanics and thermodynamics play a crucial role.

[0054] Law of Conservation of Mass – Continuity Equation: Formula Expression – For incompressible fluids (liquid aluminum alloys can be approximated as incompressible during short-time filling), the continuity equation can be expressed as:

[0055] Among them, v x Let v be the velocity component of the fluid in the x-direction. y Let v be the velocity component of the fluid in the y-direction. zLet v be the velocity component of the fluid in the z-direction. The continuity equation can be used to adjust the flow velocity v of the molten metal, avoiding turbulence or splashing caused by excessive flow velocity. For thin gates, the flow velocity can be increased to quickly fill complex cavities. During the filling process, abrupt changes in cross-section will cause a sudden change in flow velocity, which may induce eddies and thus entrain gas, forming pores.

[0056] The law of conservation of energy—Bernoulli's equation: Bernoulli's equation is based on the law of conservation of energy and describes that in an ideal fluid (inviscid and incompressible) in steady flow (the flow velocity does not change with time), the sum of pressure energy, kinetic energy and potential energy (potential energy) at any cross section of the fluid is a constant.

[0057] Considering the conversion of pressure energy, kinetic energy, and potential energy in a fluid, Bernoulli's equation is: p / ρg+v 2 / 2g+h=C Where p is the fluid pressure, ρ is the density of the aluminum alloy, v is the flow velocity, g is the acceleration due to gravity, and h is the fluid height.

[0058] Since molten aluminum alloys are viscous (resulting in energy loss) and phase transformation (solidification) may occur during die casting, it is necessary to introduce energy loss terms (such as friction loss and local resistance) to modify Bernoulli's equation.

[0059] Where p1 is the pressure of the molten aluminum alloy at flow section 1, p2 is the pressure of the molten aluminum alloy at flow section 2, h1 is the height of flow section 1, h2 is the height of flow section 2, and Δh f v1 represents the total energy loss per unit weight of fluid (including frictional resistance, local resistance, and other energy losses) during the flow of molten aluminum alloy from section 1 to section 2. v2 represents the flow velocity of molten aluminum alloy at section 1 and v1 represents the flow velocity of molten aluminum alloy at section 2.

[0060] In a die-casting mold, when molten metal enters the cavity from the pressure chamber through the runner, the pressure is converted into kinetic energy. The pressure at the gate decreases but the flow rate increases. The energy loss is compensated by the injection pressure of the die-casting machine to ensure complete filling.

[0061] The law of conservation of momentum—the Navier-Stokes equations (NS equations): Considering the viscous forces and external forces acting on the fluid, the three-dimensional NS equations are as follows:

[0062] Where v is the velocity vector, t is time, µ is the fluid dynamic viscosity, g is the gravitational acceleration, ρ is the density of the aluminum alloy, and p is the fluid pressure. The Hamiltonian operator (also known as the gradient operator) is a differential operator in vector calculus.

[0063] Flow state judgment - Reynolds number (Re): Turbulence is easily formed when the die casting filling speed is high. The inertial term in the NS equation dominates, which may lead to metal splashing and oxide inclusions. Turbulence needs to be reduced by process parameters (such as injection speed and gating radius).

[0064] The Reynolds number is used to determine the fluid flow state (laminar or turbulent):

[0065] in, Re ρ is the Reynolds number, L is the characteristic length (e.g., runner diameter), v is the velocity vector, µ is the hydrodynamic viscosity, and ρ is the aluminum alloy density.

[0066] When filling aluminum alloys in die casting, the Reynolds number is typically greater than 2300 (the critical value for turbulence), leading to unstable flow. Reducing the flow velocity (v) or decreasing the characteristic length (L, such as refining the gating system) can lower the Reynolds number and reduce turbulence-induced defects.

[0067] The central fixing bracket in this embodiment has a length of 808mm, which is significantly larger than the conventional 400mm size of die-cast aluminum alloy products. Furthermore, its average thickness of 2.3mm is less than the conventional 4mm thickness of die-cast aluminum alloy. This product is a thin-walled, large-scale aluminum alloy die-casting part. Such die-casting parts are difficult to form and prone to defects such as under-casting and cold shuts. Additionally, due to factors such as temperature imbalance, the part is prone to warping and significant deformation. The overall deformation exceeds the specified maximum deformation of 2.0mm, resulting in a large number of scraps. Moreover, to meet strength requirements, this project requires that the installation area and machined surfaces be free of defects such as porosity, shrinkage cavities, and shrinkage porosity.

[0068] During die casting, the molten aluminum reaches a gate temperature of approximately 670°C in the mold. After pressure holding, the mold opens, and the temperature of the casting after removal is approximately 180°C. Based on experience with similar products, the perimeter of this project will warp and deform, with a maximum deformation exceeding 4mm. The bolt holes and clips will not meet the requirements for ensuring a close fit between the perimeter and the car body when installing automotive interior parts. Furthermore, due to the thin walls and extremely large length of this product, significant heat loss occurs during the aluminum flow, leading to defects such as cold shuts, porosity, and undercasting at the four isolated bosses.

[0069] like Figure 1 As shown, this embodiment provides a gating system for a large thin-walled automotive mid-section fixed bracket die-casting mold, comprising: The external gating system is used to introduce molten metal into the casting cavity. The external gating system includes a main gating, a branch gating, and an ingate that are connected. The main gating is U-shaped and its cross-sectional area gradually decreases from the molten metal inlet end to the molten metal outlet end. The branch gating is located on the main gating.

[0070] Specifically, it features a double-sided inlet U-shaped external gating system with a total of 20 internal gating gates and a total cross-sectional area of ​​1643 mm². 2 The average flow velocity of the ingate is about 50 m / s. Based on the product structure characteristics of the fixed support of the large thin-walled casting, the acceleration ratio is 12.5. The ingate is divided into three areas: bottom, main body and top. The high-speed filling time of the bottom ingate is 0.645s-0.647s, and the high-speed filling time of the top gate is 0.648s-0.647s. The diameter of the injection cylinder (injection piston) is 150mm. The cross-sectional area of ​​the main runner gradually decreases from bottom to top, and there are a total of 18 branch runners.

[0071] The ingate system is located in the hollowed-out area of ​​the casting cavity and is used to guide the flow of molten metal inside the hollowed-out area. The ingate system includes I-type ingate and Y-type ingate, and the ingate system is in the form of thin sheet-like bridges.

[0072] Y-type and I-type ingate designs; the thickness of the inlet of the Y-type ingate is 2.2mm, and the cross-sectional area of ​​the inlet is 98.4 × 2.2 = 216.48mm². 2 The inner horizontal runner is 3.5mm thick and has a cross-sectional area of ​​244.3mm². 2 The thickness of the discharge port is 1.5mm, and the cross-sectional area of ​​the discharge port is 25.5mm². 2 The acceleration ratio is 216.48 / (25.5×2)=4.24; the through-type I-shaped inlet is a narrow rectangle, 15mm wide and 2.2mm thick, with an inner horizontal runner of 33mm. 2 The discharge port thickness is 1.6mm, and the cross-sectional area is 15 × 1.6 = 24mm². 2 .

[0073] The slag bag system is connected to the casting cavity through an overflow port. The slag bag system includes a slag discharge trough and an overflow trough connected in sequence.

[0074] The n-type slag pot system consists of 27 slag pots arranged in an n-shape, with a total mass of 3.4 kg, approximately 100% of the casting mass. The overall slag pot system is divided into three parallel layers: the bottom slag pot, the middle slag pot, and the top slag pot.

[0075] The overflow trough includes: a dual-inlet slag bag design; a dual-overflow slag bag design; and a bidirectional slag bag design.

[0076] The venting channel is connected to the slag bag system and is used to extract gas from the slag bag system and the casting cavity.

[0077] The vacuum exhaust channel is designed with a three-section design (0.8-0.6-0.4mm) to ensure a stepped reduction in the flow rate of the molten aluminum. A 23×4mm blocking block is also included to further reduce the turbulent flow of the molten aluminum. The calculated minimum exhaust cross-sectional area is 147.2 mm². 2 105mm larger than theoretically required 2 .

[0078] Vacuum system, which is connected to the exhaust duct.

[0079] Furthermore, the main horizontal runner is U-shaped and has a trapezoidal cross-section. The width and thickness of the main horizontal runner gradually decrease from the molten metal inlet end to the molten metal outlet end.

[0080] According to the Navier-Stokes equation, in the die-casting process, when the molten metal fills the cavity at high speed, near the wall surface... The dominant viscous force will reduce the flow rate of the molten metal (forming a boundary layer). If the flow is too fast, it may also cause a local temperature drop and viscosity increase due to viscous dissipation, affecting the filling quality.

[0081] The large, thin-walled part involved in this embodiment has a module of 1.25mm (the ratio of the casting's volume to its surface area is 1111240 / 884724 = 1.25mm), which is slightly higher than half of the average wall thickness of 2.3mm. During the process of the molten aluminum flowing through the ingate at a high temperature of around 650°C, it undergoes intense heat exchange with the low-temperature mold wall (around 200°C), rapidly reducing the filling temperature. At the same time, the viscosity increases, and the flow rate decreases, which will lead to defects such as incomplete filling, undercasting, and product deformation.

[0082] According to the Navier-Stokes equations, a reasonable temperature field needs to be designed around the casting. In addition to using heat transfer oil to heat the die-casting mold, increasing the temperature field of the gating system to maintain a stable mass is one of the effective ways to solve this problem.

[0083] Because this large, thin-walled casting is highly susceptible to cold shuts and undercast defects, the molten aluminum needs to be filled with a high flow rate and a short cavity flow. To achieve these technical requirements, the overall design of the external gating system is as follows: the casting is placed vertically, and multiple gates fill the mold from both sides of the long side, i.e., a double-sided U-shaped horizontal gating system, symmetrical on both sides with the casting cake as the center. A typical aluminum alloy die-casting gating system accounts for 30% of the casting's mass. However, in this embodiment, due to the large, thin-walled casting with deformation and porosity requirements, the total mass of the gating system and sprue is 6604g, equivalent to 220% of the casting's mass.

[0084] The clamping force is calculated using the formula: F = P·A, where F is the clamping force, P is the injection ratio for large thin-walled castings (chosen as 80 MPa in this embodiment), and A is the total projected area of ​​the casting and gating system (2800 cm² in this embodiment). 2 .

[0085] Based on the PQ drawing design calculations, a 2500T die-casting machine with a pressure chamber diameter of φ150mm is proposed. The calculated molten cup filling degree is 31.98%. The horizontal runner has a trapezoidal cross-section, with the cross-sectional area decreasing sequentially along the aluminum melt flow direction. Figure 2 EE section 1375mm 2 FF section 1286mm 2 GG section 992mm 2 HH section 437mm 2 JJ section 228mm 2 The width of the cross-section of the gating system gradually decreases, and its trapezoidal thickness also gradually decreases.

[0086] The ingate is a very important part of die casting mold design. Its position, shape and size determine the quality of the part. The casting has a longitudinal length of 808mm and an outer circumference of more than 2200mm, and 20 ingates are designed.

[0087] like Figure 2 The grid diagram of the central fixed bracket product shows that the large thin-walled central fixed bracket has hollowed-out areas in F8, F6 and F3. The hollowed-out areas of this part are reflected in the mold as the gap between the moving mold and the stationary mold is zero. That is, the moving mold and the stationary mold are locally ground together in this part. These areas will hinder the flow of aluminum liquid. The gengate design is divided into bottom, middle, and top areas. The bottom area, near the molten aluminum, has three gengates with lengths of 66.0mm, 59.2mm, and 52.3mm, respectively, and two gengates on each side with widths of 34.9mm and 37.9mm. The middle area has four gengates on each side, for a total of eight gengates with lengths of 52.0mm, 53.4mm, 35.4mm, and 35.3mm. The top area has two branch gengates on each side (35.1mm and 73.6mm), and an additional small branch gengate with a width of 17.4mm on the left side, for a total of 20 gengates. This number of gengates is significantly greater than the 1-5 gengates typically found in die casting. The increased number of gengates leads to mutual compression and collision of the molten aluminum during filling, easily causing turbulence and air entrapment defects. Therefore, the rational layout of the gengate positions and shapes is a key challenge of this project.

[0088] Furthermore, a first branch horizontal runner and a second branch horizontal runner are provided at the corner of the main horizontal runner. The extension direction of the first branch horizontal runner near the molten metal input end of the main horizontal runner is at an angle of 20~40° with the horizontal direction, and the extension direction of the second branch horizontal runner near the molten metal output end of the main horizontal runner is at an angle of 35~55° with the horizontal direction. A third branch horizontal runner is provided at the end of the main horizontal runner, and the extension direction of the third branch horizontal runner is at an angle of 30~50° with the tangent direction at the end of the U-shaped main horizontal runner.

[0089] In a preferred embodiment, 18 branch runners are arranged between the main runner and the ingate. The branch runners guide the flow of molten aluminum based on the main runner. One of the bottom branch runners is inclined upward at 45° and the other is inclined downward at 30°. The top pouring end branch runner is bent inward at 40°.

[0090] The ingate has a rectangular cross-sectional shape. Based on the product's modulus of 1.25mm (the ratio of casting volume to surface area is 1111240 / 884724 = 1.25mm) and the characteristic of large, thin-walled castings with an average wall thickness of 2.3mm, and considering factors such as the ingate's requirement to avoid damaging the part, the gate thickness is designed to be 1.8mm. The formula for calculating the total area of ​​the ingate in the gating system of the die-casting mold for a large, thin-walled automotive center fixed bracket is as follows:

[0091] in, A 内浇口 This represents the total area of ​​the ingate. G The sum of the mass of the casting, the slag bag system, the ingate system, and the venting channel (mass of the gating system 3003 (casting mass) + 4688 (venting system mass) = 7691 (grams)). ρ The density of aluminum alloy is 2.7 g / cm³. 3 ), v 内 The filling speed of the aluminum alloy (the recommended filling speed for aluminum alloy is 40-60 m / s, with the larger value being 50 m / s). t The recommended filling time for molten metal is 0.03-0.05s (0.03-0.05s for large thin-walled aluminum alloys, taking the smaller value of 0.035s).

[0092] The total cross-sectional area of ​​the ingate is calculated to be 1627 mm². 2 .

[0093] Check the area of ​​the ingate: Total gate length: 2×(34.9+37.9)+(66.0+59.2+52.3)+2×(52.0+53.4+35.4+35.3)+2×(35.1+73.6)+17.4=913.1mm A of the actual in-core gating area 内浇口 =913.1mm × 1.8 = 1643mm 2 A of the actual in-core gating area 内浇口 1643mm 2 The theoretical total cross-sectional area is approximately 1627 mm². 2 .

[0094] An ingate is a gating system located in a hollowed-out area inside a casting, where both the inlet and outlet are directly connected to the casting. For example, in... Figure 2 The F8 and F1 hollow areas are equipped with ingates. In this embodiment, the purpose of the ingate design is to improve the local filling capacity while balancing temperature and feeding. The ingate design also follows the basic laws of conservation of mass, energy, and momentum (NS law). The casting ingate system includes a sprue, an ingate runner, and a discharge port. Structurally, it differs from the external gating system in that the ingate runner is generally a thin, sheet-like connecting bridge, while the external gating runner has a large cross-sectional dimension that gradually decreases in thickness.

[0095] like Figure 3 As shown, the Y-shaped ingate is connected to the inner wall of the main runner facing the casting cavity. The Y-shaped ingate includes a feed inlet, an inner runner, and a discharge outlet. The inner runner forms a diversion section near the discharge outlet, which divides the molten metal into two streams and guides them to the discharge outlet. The included angle of the inner runner near the feed inlet is 55~66°. The diversion section uses a transition between a circular arc and a straight line segment.

[0096] This large thin-walled central fixed bracket Figure 11 The A7 and J7 areas of the part are characterized by isolated, thin-walled trapezoidal pillars, the source of which is the molten aluminum used in their formation. Figure 2 The gating system has two branch gates, B7 and E7, such as... Figure 12 On the other hand, the trapezoidal column is hollow on the side corresponding to the gate, which means that the moving mold and the stationary mold fit together without gaps on the mold. Therefore, the molten aluminum must bypass the hollow area to fill the isolated thin-walled trapezoidal column.

[0097] To solve the above problems, this large thin-walled support is designed with a diversion-type Y-shaped inlet in the bottom area of ​​the filling, that is, a Y-shaped thin-walled connecting bridge is designed in the hollow part shown in the figure below.

[0098] As a preferred embodiment, the cross-sectional area of ​​the Y-shaped ingate gradually decreases from the inlet to the outlet according to the flow direction of the molten aluminum. The horizontal inclination angles on the left and right sides of the bottom of the Y-shape are 55° and 66° respectively. The middle part of the Y-shape is designed with R22.5 and R16.7 connected to the tangent of the straight segment. The top left side of the Y-shape is designed with a large arc R93.5 and the right side is designed with R84.6 tangent to the ingate. The molten aluminum is split at the intersection of the two large arcs at the top, and the flow direction points to the trapezoidal columns on the left and right sides respectively.

[0099] The inlet of this Y-type split-flow inlet gate is a long and narrow rectangle. The thickness of the inlet is limited to 2.2 mm due to the wall thickness of the part. The cross-sectional area of ​​the inlet is 98.7 × 2.2 = 217.14 mm². 2 The thickness of the inner horizontal runner gradually transitions from 2.2mm at the inlet to 3.5mm at a 5.2-degree angle. The cross-sectional area of ​​the inner horizontal runner is 69.8 × 3.5 = 244.3 mm². 2 The thickness of the discharge port is designed to be 1.5mm, and the cross-sectional area of ​​the discharge ports on both the left and right sides is 16.7 × 1.5 = 25.05mm². 2 It can be seen that the acceleration ratio in this Y-type secondary gating system is 217.14 / (25.05×2)=4.34. On the other hand, the molten aluminum alloy flows in a narrow region during die casting, resulting in intense heat exchange between the molten metal and the mold (interfacial heat transfer coefficient can reach 3000W / (m²)). 2 As the temperature in the mold decreases (K), the viscosity coefficient increases, the flow resistance increases, and the filling speed decreases. Therefore, a heating system needs to be designed in this area, typically using heat-conducting oil flowing at 200-220℃.

[0100] like Figure 4 As shown, the Type I ingate is located between the end of the main horizontal gating and the slag bag system. The inlet of the Type I ingate is rectangular, and the length-to-width ratio of the rectangle is greater than 7.

[0101] like Figure 13 Due to the long flow path, large and thin-walled components, rapid cooling, and low pressure transmission efficiency at the end of the filling process, quality defects such as cold shuts are prone to occur in this area. Cold shut defects appear as irregular, wavy, shallow grooves on the surface, are dark in color, lack metallic luster, and have a rough feel. Slow filling speeds lead to rapid heat dissipation from thin-walled parts, causing premature solidification of the molten metal at the leading edge, forming cold shut lines. Low mold temperatures, especially at the end of the mold, further accelerate molten metal cooling and weaken the interfacial bonding strength.

[0102] To solve the above problems, this large thin-walled support is designed with a through-type I-shaped ingate in the bottom area of ​​the filling, that is, an ingate in the hollow part.

[0103] The through-type I-shaped inlet is a narrow rectangle, 15mm wide and 2.2mm thick, with the inner horizontal runner gradually transitioning to 3mm. The cross-sectional area is 15 × 2.2 = 33mm². 2 The discharge port thickness is 1.6mm, and the cross-sectional area is 15 × 1.6 = 24mm². 2 As can be seen, the acceleration ratio in this through-type I-shaped ingate is 33 / 24=1.38, and the total length of the ingate is 29.2mm.

[0104] like Figure 5 As shown, the inlet end of the slag discharge trough is connected to the casting cavity, the outlet end of the slag discharge trough is connected to the inlet end of the overflow trough, and the outlet end of the overflow trough is connected to the vacuum system. The overflow trough includes a single-port overflow trough, a double-inlet overflow trough, a forward and reverse bidirectional overflow trough, and a series overflow trough.

[0105] The overflow system is a key component of die-casting mold design. It primarily functions to remove slag and vent through a slag sack (overflow channel) and a venting channel. Its design volume (mass) is typically 10-30% of the casting volume. In this embodiment, the central fixed support is a large, thin-walled component with a large projected area, rapid filling speed, and uneven temperature distribution. Besides slag removal, the slag sack design must also balance the mold temperature. In this embodiment, the overflow system weighs approximately 3.4 kg and has an overall n-shape. The total mass of the slag sack exceeds the 3.03 kg mass of the mold itself, approximately 110% of the casting volume. This liquid aluminum alloy cools from 640°C in the cavity to 200°C at the mold opening temperature, undergoing three stages: liquid cooling, crystallization cooling, and solid cooling. This releases a significant amount of heat to balance the mold temperature. The total heat released is Q = Q1 + Q2 + Q3, where: Liquid cooling (Q1): Cooling of liquid aluminum alloy from casting temperature T1℃ to liquidus temperature TL Sensible heat release Q1 = CL × m × (T1) TL) Crystallization and solidification (Q2): Aluminum alloy releases latent heat of crystallization Latent heat of crystallization Q2=m×L Solid-state cooling (Q3): The solid aluminum alloy is cooled from the solidus line TS to the mold opening temperature T2℃. Sensible heat release Q3 = CS × m × (TS) T2) Table 1 shows the values ​​and explanations for each parameter.

[0106] Table 1

[0107] Specific numerical calculations: Liquid cooling stage Q1: Q1 = 1.12 × 3.4 × (640) 585) = 1.12 × 3.4 × 55 = 212.32 kJ Crystallization and solidification stage Q2: Q2 = m·L = 3.4 × 390 = 1326 kJ Solid-state cooling phase Q3: Q3 = 0.90 × 3.4 × (525) 200) = 0.90 × 3.4 × 325 = 994.5 kJ Q=Q1+Q2+Q3=212+1326+994=2532kJ like Figure 14 Overall, the slag bag system design is divided into three areas: bottom, middle and top. The layout of its position is based on the end of the slag discharge and exhaust, and the determination of its volume takes into account factors such as heat balance and supplementary shrinkage.

[0108] The bottom area (C8-G10 area) has a total of 8 slag bags, 3 on each of the left and right sides, and 2 slag bags in the hollowed-out middle part.

[0109] The dual-inlet overflow channel is located in the molten metal confluence area at the bottom of the casting cavity, and the dual-inlet overflow channel is connected to the casting cavity through two independent overflow channels.

[0110] like Figure 6 and Figure 7 As shown, the bottom slag pot system features a large-capacity dual-inlet slag discharge channel on each of its left and right sides. The total volume of the slag pot is 77.5×36.4×20mm, with a dual-inlet spacing of 27.9mm. The inlet thickness is 1.2mm, which is 2 / 3 of the 1.8mm thickness of the ingate. Multiple streams of molten aluminum converge in this area, making it difficult to precisely control the slag discharge end. Designing a dual-inlet overflow channel in this area can create a more uniform flow field within the mold, allowing impurities such as gas and slag generated during molten metal filling to be discharged more efficiently through two channels, reducing defects such as porosity and inclusions inside the casting.

[0111] The bidirectional overflow channel is located at the bottom of the hollowed-out part of the casting cavity, and the bidirectional overflow channel receives both forward-flowing and reverse-flowing molten metal.

[0112] Area F9 corresponds to a partial hollowing out of the casting, with a hollowing-out size of 138×123mm. The surrounding temperature is low, which can easily cause cold shuts. At the same time, the molten aluminum with slag inclusions at the front end can easily be drawn into the casting, causing slag inclusion defects. The bidirectional overflow channel is located in the middle of the rectangular frame. The forward slag pool at the bottom collects the slag from the front end of the positive filling process, while the reverse slag pool is where the two streams of molten aluminum converge at the bottom of the frame, collecting slag in opposite directions.

[0113] like Figure 8As shown, the series overflow channels are located at the end of the casting cavity. The series overflow channels are a first overflow channel and a second overflow channel connected in sequence. The size of the first overflow channel is larger than that of the second overflow channel.

[0114] There are a total of 9 slag bags in the central area (C5-G7 area), with 3 slag bags on each side symmetrically arranged to form a vacuum exhaust channel, and 3 slag bags in the hollowed-out middle section.

[0115] Five slag bags on each of the left and right sides of the top area (C3-G4 area) converge into a vacuum exhaust channel.

[0116] The top slag collection system is located at the end of the aluminum molten metal filling process. Rapid deceleration to prevent flash and reduce impact on the vacuum system are crucial factors in this area. However, a single slag collection pot and overflow trough have limitations in capturing molten slag, oxide scale, and gases. Connecting two overflow troughs in series increases the space for impurities and gases, enabling more efficient collection of molten slag, oxide scale, and other impurities and gases generated in the mold cavity.

[0117] like Figure 9 As shown, the exhaust groove is a damping corrugated plate structure. The exhaust groove is equipped with multi-stage corrugated teeth. The gas flow path is a tortuous path along the tooth gap of the corrugated teeth. The exhaust gap of the exhaust groove gradually decreases from the input end to the output end.

[0118] The n-type slag bag system converges at the end to four corrugated venting plates. Each corrugated venting plate contains 10 corrugated teeth. The first and second teeth have a venting gap of 0.8 mm, the third and fourth teeth have a venting gap of 0.6 mm, and the fifth to twelfth teeth have a venting gap of 0.4 mm. This design structure ensures that the high-speed molten aluminum is rapidly cooled in the first four teeth and stops flowing at most in the sixth tooth, ensuring that the aluminum alloy cannot enter the vacuum pipeline behind the venting plate.

[0119] Meanwhile, a 23×4mm hollowed-out narrow groove is designed near the inlet of the corrugated plate. In the mold, this is reflected as a harmonious blend between movement and stillness, with a gap of 0mm. The purpose is to prevent the regular and smooth flow of the high-speed aluminum liquid when it is filled to this part, to slow down the decrease in flow rate at the end, and to shorten the filling distance.

[0120] This system also includes a vacuum system with a pumping capacity of 76m³. 3 / hour, which translates to 21.11 liters / second. The cross-sectional area of ​​the vacuum exhaust channel is designed to meet the rated pumping flow rate of the vacuum system.

[0121] The air extraction flow rate is calculated using the following formula: Q'=A×V Where Q' is the vacuum pump flow rate (21.11 L / s), V is the airflow velocity (200 m / s), and A is the minimum cross-sectional area of ​​the exhaust duct (105 mm²). 2 ).

[0122] Verification: The cross-sectional area of ​​the exhaust duct bottleneck is 92 × 0.4 = 36.8 mm. 2 The total length of the four exhaust channels is 36.8 × 4 = 147.2 mm. 2 147.2mm 2 >105mm 2 Therefore, the exhaust capacity requirement is met.

[0123] This embodiment verifies the effectiveness of its application through flow field simulation using AnyCasting casting software. AnyCasting is an advanced casting simulation software system developed by AnyCasting Corporation of South Korea. It is a simulation system specifically developed for various casting processes, capable of simulating and analyzing the filling, heat conduction, and solidification processes of casting. With AnyCasting 6.0, defects such as incomplete filling, porosity, shrinkage cavities, cold shuts, inclusions, and deformation can be accurately predicted to guide the design of gating systems, cooling systems, and molds; optimize casting process parameters; reduce the number of trial moldings, lower casting costs; and improve product quality and market competitiveness. In the anyPRE module, a total of 11.42 million hexahedral variable meshes are created. The basic process settings are: primary injection speed 0.2 m / s, secondary injection speed 4 m / s, chamber length 900 mm, chamber diameter 150 mm, and cake thickness 35 mm. The software calculations show that the low-speed zone length is 7.6 mm and the high-speed zone length is 159 mm.

[0124] The solution method uses SOR iteration, with a convergence criterion of 0.01 and a relaxation factor of 1.8. The output conditions for the end of the simulation are 100% filling and 100% solidification, with 2% intervals between 90% and 100% filling and 2% intervals between solidification fractions between 0% and 26% filling.

[0125] like Figure 15 As shown, Figure 15 (a) to (f) show the effects of filling times of 0.6042 seconds, 0.6445 seconds, 0.6512 seconds, 0.6580 seconds, 0.6647 seconds, and 0.6714 seconds, respectively. From the filling sequence diagram (abcdef), it can be seen that the U-shaped filling on both sides is basically symmetrical. The low-speed filling of molten aluminum has already submerged the bottom gate. At approximately 0.65 seconds, rapid high-speed injection filling occurs. At 0.6512 seconds, the molten aluminum enters the top cavity through the top ingate. At this point, most of the middle and lower cavity areas are filled. At 0.6580 seconds, the overall filling is 97%. All the feed inlets converge at the top area, and at 0.6647 seconds, the overall filling is 98%. The filling of the casting cavity is basically complete, and the molten aluminum, including oxide inclusions, continues towards the slag pocket and venting channel.

[0126] Numerical simulations show that the gating system does not exhibit significant air entrapment or eddies during the filling process. The high-speed flow of the molten aluminum basically meets the requirements for sequential filling, with a high-speed filling time of approximately 35 milliseconds. The flow field and temperature field layout are reasonable and meet the requirements for casting manufacturing.

[0127] In the instrument setting module of the simulation analysis process, this embodiment sets one simulated sensor at the gating position to simulate and detect the flow state of molten aluminum at key points. Sensors S1, S2, S3, S4, S10, S11, S12, S13, S14, and S15 are simulated sensors at the U-shaped gating gate, such as... Figure 16 As shown.

[0128] from Figure 17 It can be seen that at 0.645 seconds of injection, the inner gates of S2 and S4 simultaneously inject at high speed, oscillate twice at a speed of 5 milliseconds, reach a relatively stable speed of about 50 m / s, then slowly decrease to 40 m / s, and stop high-speed injection at 0.678 seconds.

[0129] from Figure 18 It can be seen that the inner gates of S12 and S13 are injected at high speed in about 0.65 seconds, with the speed steadily increasing from 50m / s to 60m / s, 70m / s and 80m / s, and the high-speed injection stops in 0.678 seconds.

[0130] from Figure 19 The local numerical simulation cloud map at 0.540 seconds of filling time shows that the Y-shaped ingates on the left and right sides play a major role in filling the isolated thin-walled trapezoidal column, while the outer gates B7 and E7 tangentially impact the root of the moving mold trapezoidal column, which is a secondary and necessary supplement.

[0131] Figure 20 and Figure 21 Numerical simulation of the gate position shows that, affected by the speed of the bottom external gate, the speed at the inlet S5 of the inlet gate is stable at about 20 m / s, and accelerates to 50 m / s or 40 m / s after passing through the narrow outlet.

[0132] The Y-shaped ingate with split flow plays a major role in the isolated thin-walled trapezoidal pillars on both sides of the filling mold, while the outer sprue B7 E7 tangentially impacts the root of the trapezoidal pillars of the moving mold, serving as a secondary and necessary supplement.

[0133] from Figure 22 The local numerical simulation cloud map at 0.660 seconds of filling time shows that the streamlined aluminum liquid effectively replenishes the mass of the end filling through the through-type I-shaped ingate, and also balances the temperature field at the end.

[0134] like Figure 23 and 24Numerical simulations show that the aluminum molten metal filling velocity at this location is complex due to the influence of multiple runners. At the inlet S9, high-speed filling occurs at 0.658 seconds. Due to the mixing of multiple aluminum streams at this location, there is a brief fluctuation at 40 m / s, reaching a maximum speed of 70 m / s at 0.664 seconds, before rapidly decreasing to 30-40 m / s and fluctuating multiple times, again due to the superposition effect of subsequent multiple aluminum streams. At the outlet S8, the velocity is shown to lag behind S9 by 2 milliseconds, reaching a maximum speed of 60 m / s at 0.660 seconds. Due to the narrow inlet runner and obstructed flow, the velocity drops sharply, stabilizing at 60 m / s with the replenishment of subsequent aluminum streams. It is evident that the velocity at S8 consistently lags behind the inlet velocity at S9 by several milliseconds, and is higher than the inlet velocity during the stable phase. This simulation result is roughly consistent with the calculated velocity.

[0135] Depend on Figure 25 It is known that during the filling process of 0.658 seconds, two streams of molten aluminum are simultaneously ejected through the inlet, impacting the opposite slag pot mold wall, and converging downwards and outwards in a swirling motion, resulting in numerous slag inclusions and gas accumulation inside the slag pot. In this complex structure casting system of this embodiment, the two inlets correspond to different areas of molten metal flow, ensuring that impurities in each part can be effectively collected. X-ray inspection of this part reveals numerous pores and slag inclusion defects inside.

[0136] like Figure 26 and 27 As shown, the forward and reverse slag baffles are located in the middle of the rectangular frame. The forward slag baffle at the bottom collects the slag from the front of the forward-filling process, while the reverse slag baffle is where the two streams of molten aluminum converge at the bottom of the frame, collecting slag in opposite directions. The main function of the forward slag baffle is slag discharge, with an inlet thickness of 1-3mm. The main function of the reverse slag baffle is gas collection, with an inlet thickness of 0.5-1.5mm. Both slag baffles also help to balance the temperature in this area.

[0137] like Figure 28 As shown, the defective aluminum liquid at the front end first tilts into a large slag pot with a depth of 20mm and a width of 60mm. In the large slag pot, some of the slag is stored in a vortex. Then it enters a small slag pot with a depth of 11mm and a width of 11mm to further reduce the slag discharge speed, thereby reducing the probability of defects such as porosity and slag inclusions in the casting and preventing defects such as flash and burrs.

[0138] After passing through the first overflow trough, some of the gas and impurities are trapped, and the remainder enters the second overflow trough. Through two interceptions, impurities and gas in the cavity can be removed more thoroughly, greatly improving the internal and surface quality of the casting.

[0139] Figures 29-32 The images shown are physical photos of the product in this embodiment and physical photos of the product generated from this embodiment.

[0140] Example 2 This embodiment includes a working method for a die-casting mold gating system for a large thin-walled automotive mid-section fixed bracket, based on the die-casting mold gating system for a large thin-walled automotive mid-section fixed bracket in Embodiment 1, and includes the following steps: S1. Close the mold and preheat it to bring the mold cavity temperature to the predetermined range.

[0141] S2. Start the vacuum system connected to the venting groove to pre-vacuum the cavity and gating system.

[0142] S3. The die-casting machine performs injection, and the molten metal enters the casting cavity through the sprue, main runner, branch runner and ingate of the external gating system in sequence. Some of the molten metal is supplemented and locally fed through the hollow area inside the cavity by the ingate system.

[0143] S4. During the filling process, the gas, cold material and molten metal containing impurities in the mold cavity are pushed into the slag packing system, and the gas is continuously extracted by the vacuum system through the exhaust channel.

[0144] S5. After filling, pressure is maintained, and then the casting cools and solidifies in the mold cavity.

[0145] S6. Open the mold and eject the casting with the outer sprue, inner sprue bridge and slag pocket.

[0146] Through theoretical calculations, numerical simulation analysis, and practical verification, the central fixed bracket of the large thin-walled aluminum alloy part adopts a double-sided feeding U-shaped external gating system with a total of 20 internal gates; the simultaneous design of Y-type and I-type internal gating systems, as well as the corrugated plate venting system, can meet the requirements of casting, venting, and overflow, and mass-produce qualified parts.

[0147] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A gating system for a die-casting mold of a large thin-walled automotive mid-section fixed bracket, characterized in that, include: An external gating system is used to introduce molten metal into the casting cavity. The external gating system includes a main gating, a branch gating, and an ingate that are connected to each other. The main gating is U-shaped and its cross-sectional area gradually decreases from the molten metal inlet end to the molten metal outlet end. The branch gating is located on the main gating. An ingate system is provided in the hollow area of ​​the casting cavity to guide the flow of molten metal inside the hollow area. The ingate system includes an I-type ingate and a Y-type ingate, and the ingate system is in the form of a thin sheet-like connecting bridge. A slag bag system, wherein the slag bag system is connected to the casting cavity through an overflow port, and the slag bag system includes a slag discharge trough and an overflow trough connected in sequence; An exhaust channel is connected to the slag bag system and is used to extract gas from the slag bag system and the casting cavity. A vacuum system, which is connected to the exhaust duct.

2. The casting and gating system for the large thin-walled automotive mid-section fixed bracket die-casting mold according to claim 1, characterized in that, The main horizontal runner is U-shaped and has a trapezoidal cross-section. The width and thickness of the main horizontal runner gradually decrease from the molten metal inlet end to the molten metal outlet end.

3. The large thin-walled automobile mid-section fixed bracket die-casting mold gating system according to claim 1, characterized in that, At the corner of the main horizontal runner, there are a first branch horizontal runner and a second branch horizontal runner. The extension direction of the first branch horizontal runner near the molten metal input end of the main horizontal runner is at an angle of 20~40° with the horizontal direction. The extension direction of the second branch horizontal runner near the molten metal output end of the main horizontal runner is at an angle of 35~55° with the horizontal direction. At the end of the main horizontal runner, there is a third branch horizontal runner. The extension direction of the third branch horizontal runner is at an angle of 30~50° with the tangent direction at the end of the U-shaped main horizontal runner.

4. The large thin-walled automobile mid-section fixed bracket die-casting mold gating system according to claim 1, characterized in that, The cross-sectional shape of the ingate is rectangular, and the formula for calculating the total area of ​​the ingate in the gating system of the large thin-walled automotive mid-section fixed bracket die-casting mold is as follows: in, A 内浇口 This represents the total area of ​​the ingate. G The sum of the mass of the casting, the slag catcher system, the ingate system, and the venting channels. ρ The density of aluminum alloy, v 内 For the filling speed of aluminum alloy, t The filling time for the molten metal.

5. The casting and gating system for a large thin-walled automotive mid-section fixed bracket according to claim 1, characterized in that, The Y-shaped ingate is connected to the inner wall of the main runner facing the casting cavity. The Y-shaped ingate includes an inlet, an inner runner, and an outlet. The inner runner forms a diversion section near the outlet, which divides the molten metal into two streams and guides them to the outlet. The included angle of the inner runner near the inlet is 55~66°. The diversion section adopts a transition between a circular arc and a straight line segment. The type I inlet gate is located between the end of the main horizontal gating and the slag bag system. The inlet of the type I inlet gate is rectangular, and the length-to-width ratio of the rectangle is greater than 7.

6. The large thin-walled automobile mid-section fixed bracket die-casting mold gating system according to claim 1, characterized in that, The inlet end of the slag discharge trough is connected to the casting cavity, the outlet end of the slag discharge trough is connected to the inlet end of the overflow trough, and the outlet end of the overflow trough is connected to the vacuum system. The overflow trough includes a single-inlet overflow trough, a double-inlet overflow trough, a forward and reverse bidirectional overflow trough, and a series overflow trough. The dual-inlet overflow channel is located in the molten metal confluence area at the bottom of the casting cavity, and the dual-inlet overflow channel is connected to the casting cavity through two independent overflow channels. The bidirectional overflow channel is located at the bottom of the hollowed-out area of ​​the casting cavity, and the bidirectional overflow channel simultaneously receives both forward-flowing and reverse-flowing molten metal. The series overflow channels are located at the end of the casting cavity. The series overflow channels are a first overflow channel and a second overflow channel connected in sequence. The size of the first overflow channel is larger than that of the second overflow channel.

7. The large thin-walled automobile mid-section fixed bracket die-casting mold gating system according to claim 1, characterized in that, The exhaust groove is a damping corrugated plate structure, and the exhaust groove is provided with multi-stage corrugated teeth. The gas flow path is a tortuous path along the gap of the corrugated teeth, and the exhaust gap of the exhaust groove gradually decreases from the input end to the output end.

8. A method for operating a gating system for a die-casting mold of a large thin-walled automotive mid-section fixed bracket, implemented based on the gating system for a die-casting mold of a large thin-walled automotive mid-section fixed bracket as described in any one of claims 1-7, characterized in that... Includes the following steps: Close the mold and preheat it to bring the mold cavity temperature to the predetermined range; Start the vacuum system connected to the exhaust groove to pre-evacuate the cavity and gating system; The die-casting machine performs injection, and the molten metal sequentially passes through the sprue, main runner, branch runner and ingate of the external gating system and enters the casting cavity. Some of the molten metal is supplemented and locally fed through the hollow area inside the cavity by the ingate system. During the filling process, the gas, cold material and molten metal containing impurities in the mold cavity are pushed into the slag packing system, and the gas is continuously extracted by the vacuum system through the exhaust groove. After filling, pressure is maintained, and then the casting cools and solidifies in the mold cavity; Open the mold and eject the casting with the outer sprue, inner sprue bridge and slag pocket.

Images