Vacuum die casting method for spacer bar aluminum alloy

Abstract

The application provides a vacuum die casting method of an aluminum alloy for a spacer rod, which comprises the following steps: firstly, designing a structure section of a spacer rod rib plate as a double T section structure; secondly, adopting a three-plate mold matched with the double T section structure, arranging supporting columns in a stress area of the three-plate mold, and arranging a pouring system, a vacuum exhaust system, a temperature control system and a demolding system on the three-plate mold; then, providing a pressure injection force and a pressure injection speed not less than a set value through a die casting machine, cooperating with a point gate and a circular runner of the pouring system to pour a heat treatment free aluminum alloy melt into the three-plate mold, and synchronously starting the vacuum exhaust system and the temperature control system; finally, after the melt is cooled and solidified, a demolding system is started to synchronously eject, and a high strength and toughness spacer rod product is obtained. Through the double T section structure of the spacer rod rib plate and the optimized design of the mold, high quality die casting of the extra high voltage transmission spacer rod is realized.

Description

Technical Field

[0001] This invention belongs to the field of ultra-high voltage power transmission spacer manufacturing technology, specifically relating to a vacuum die casting method for aluminum alloy spacers. Background Technology

[0002] With the development of the power industry, ultra-high voltage (UHV) power transmission technology has become crucial for ensuring large-scale, long-distance power transmission. UHV transmission spacers, as important protective hardware for ensuring the safety of split conductors, are critical to the stable operation of transmission lines. To meet the requirements of high efficiency and stability in power transmission, while also considering lightweight design, specific materials and manufacturing processes are needed to produce spacers.

[0003] Currently, ultra-high voltage (UHV) transmission spacer bars are typically manufactured from aluminum alloy using a vacuum die-casting process. This process allows for a lightweight, thin-walled structural design while ensuring the spacer bars possess excellent mechanical properties, such as tensile strength ≥285MPa and elongation ≥8%. During die-casting, L-shaped, T-shaped, or cross-shaped rib structures are commonly used, relying on high-pressure die-casting (HPDC) or basic vacuum die-casting technology. However, in actual production, a balance must be struck between high-speed incomplete filling and rapid solidification to prevent defects.

[0004] Existing technologies for die-casting ultra-high voltage transmission spacer bars have many problems. For example, the cross-shaped stiffeners form hot spots due to metal concentration, and the maximum temperature difference during cooling and solidification can reach 31.33℃, which easily leads to defects such as microscopic porosity and air bubbles; ordinary gating systems have large pressure losses, and the runners are not high-gloss polished, making it easy to entrap air and resulting in poor filling uniformity; the mold rigidity is insufficient, and whether it is a non-three-plate mold structure or an unreasonable arrangement of support columns, the mold is prone to elastic deformation under high-pressure injection, affecting dimensional accuracy. Summary of the Invention

[0005] In view of this, the present invention provides a vacuum die-casting method for aluminum alloy spacer bars, aiming to achieve high-quality die casting of UHV transmission spacer bars by optimizing the stiffener structure, improving the gating system, and rationally designing the mold structure.

[0006] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0007] In a first aspect, the present invention provides a vacuum die-casting method for spacer bars made of aluminum alloy, comprising the following steps:

[0008] The structural cross-section of the spacer slab is designed as a double T-section structure; the double T-section structure is composed of two independent T-shaped stiffening slabs arranged side by side;

[0009] A three-plate mold adapted to the double T-section structure is adopted, and support columns are arranged in the stress area of ​​the three-plate mold. A gating system, a vacuum exhaust system, a temperature control system and a demolding system are configured on the three-plate mold. The gating system adopts a circular runner and a point gate, and the inner surface of the circular runner is treated with high-gloss polishing.

[0010] The die-casting machine provides an injection force and injection speed not less than the set value. In conjunction with the gating system's point gate and circular runner, the heat-free aluminum alloy molten liquid is injected into the three-plate mold to fill the cavity. Simultaneously, the vacuum exhaust system is activated to evacuate the gas inside the three-plate mold, and the temperature control system is activated to maintain the preset working temperature of the three-plate mold.

[0011] After the melt cools and solidifies, the demolding system is activated to eject the high-strength and tough spacer bar product.

[0012] Furthermore, in the double T-section structure, the thickness of the vertical stiffener of each T-shaped stiffener is the same as the wall thickness of the spacer base, the thickness of the horizontal stiffener ranges from 2.5 to 3.0 mm, the spacing between the two T-shaped stiffeners ranges from 8 to 12 mm, and the radius of the stiffener root is rounded to R2.0 to R2.5 mm.

[0013] Furthermore, after high-gloss polishing, the surface roughness Ra of the circular flow channel meets the requirement of Ra≥0.4μm.

[0014] Furthermore, the circular flow channel adopts a natural balance layout.

[0015] Furthermore, the length of the spot gate is 1-2mm, and the cross-sectional area of ​​the spot gate meets the requirement that the filling speed of the heat-free aluminum alloy melt is not less than 80m / s.

[0016] Furthermore, the support columns are evenly distributed along the stress concentration area of ​​the cavity of the three-plate mold.

[0017] Furthermore, the vacuum exhaust system includes a vacuum valve and multiple exhaust grooves located on the parting surface, slider, and ejector pin of the three-plate mold, with the depth of the exhaust grooves ranging from 0.08 to 0.15 mm.

[0018] The vacuum exhaust system is linked to the exhaust groove via a vacuum valve and is used to evacuate the cavity to a preset value before heat-free aluminum alloy molten fluid injection.

[0019] Furthermore, the injection speed provided by the die-casting machine is no less than 8m / s.

[0020] Furthermore, the demolding system includes ejection components and a linkage control mechanism;

[0021] The ejector components are flat ejector pins or top plates. Multiple ejector components are evenly arranged along the wall thickness of the spacer bar and below the stiffener plate, and are ejected synchronously through a linkage control mechanism.

[0022] Furthermore, the heat-free aluminum alloy is an Al-Si-Mg alloy.

[0023] In summary, this invention provides a vacuum die-casting method for spacer bars made of aluminum alloy. The method first involves designing the cross-section of the spacer bar stiffeners as a double-T section structure, consisting of two independent T-shaped stiffeners arranged side-by-side. Secondly, a three-plate mold adapted to the double-T section structure is used, with support columns arranged in the stress-bearing area of ​​the mold. A gating system, a vacuum exhaust system, a temperature control system, and a demolding system are also configured on the three-plate mold. The gating system employs a circular runner and a point gate, with the inner surface of the circular runner treated with high-gloss polishing. Then, a die-casting machine provides an injection force and injection speed not less than a set value, which, in conjunction with the point gate and circular runner of the gating system, injects heat-free aluminum alloy molten metal into the three-plate mold to fill the cavity. Simultaneously, the vacuum exhaust system is activated to evacuate the gas from the cavity of the three-plate mold, and the temperature control system is activated to maintain the preset working temperature of the three-plate mold. Finally, after the molten metal cools and solidifies, the demolding system is activated to eject the molten metal synchronously, resulting in a high-strength and tough spacer bar product. This invention solves the problems of hot spot defects, uneven filling and insufficient mold rigidity in the prior art by setting the spacer bar stiffener plate as a double T-shaped cross section structure, using an appropriate three-plate mold and arranging support columns in the stress area, and configuring a gating system with circular high-gloss polished runners and point gates, thus realizing high-quality die casting of UHV transmission spacer bars. Attached Figure Description

[0024] 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 only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 A flowchart of a vacuum die-casting method for spacer bars made of aluminum alloy is provided as an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of an existing spacer frame.

[0027] Figure 3 A schematic diagram of the cross-sectional structure of an existing spacer frame;

[0028] Figure 4 A schematic diagram of partial structural optimization of the spacer frame provided in an embodiment of the present invention;

[0029] Figure 5 A schematic diagram of the double-T structure of the spacer frame provided in an embodiment of the present invention;

[0030] Figure 6 The figure shows the simulation analysis results of the cooling and solidification of the cross-shaped cross-section stiffener provided in the embodiment of the present invention;

[0031] Figure 7 A diagram showing the cooling and solidification time of a cross-shaped cross-section stiffener provided in an embodiment of the present invention;

[0032] Figure 8 The figure shows the simulation calculation results of the cooling and solidification of the double T-section stiffener provided in the embodiment of the present invention;

[0033] Figure 9 A diagram showing the cooling and solidification time of the double T-section stiffener and its surrounding area provided in an embodiment of the present invention;

[0034] Figure 10 A schematic diagram of the vacuum die-casting principle provided for an embodiment of the present invention. Detailed Implementation

[0035] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0036] Please see Figure 1 This embodiment provides a vacuum die-casting method for spacer bars made of aluminum alloy, including the following steps:

[0037] S1: The structural cross section of the spacer slab is designed as a double T-section structure; the double T-section structure is composed of two independent T-shaped stiffeners arranged side by side.

[0038] It should be noted that the double T-section structure is a composite section structure formed by two independent T-shaped stiffeners (each T-shaped stiffener contains a basic structure in which vertical and horizontal stiffeners are connected vertically) arranged side by side. It is a stress-bearing and heat-dissipating structure of the spacer bar stiffener.

[0039] In one feasible implementation, this step can be achieved by obtaining the design parameters of the spacer frame width, drawing two independent T-shaped stiffeners using structural design software, and then ensuring that the two stiffeners are side by side and the spacing matches the frame width, thereby determining the spacer frame structure.

[0040] S2: A three-plate mold adapted to the double T-section structure is adopted, and support columns are arranged in the stress area of ​​the three-plate mold. A gating system, a vacuum exhaust system, a temperature control system and a demolding system are configured on the three-plate mold. The gating system adopts a circular runner and a point gate, and the inner surface of the circular runner is treated with high-gloss polishing.

[0041] It should be noted that the three-plate mold is a type of die-casting mold, consisting of three core templates: a fixed mold, a moving mold, and a stripper plate. It is suitable for the molding and demolding of complex die-cast parts and has better parting and feeding control capabilities compared to the two-plate mold.

[0042] Support columns are reinforcing components inside the mold, arranged in the stress area of ​​the three-plate mold, which can enhance the rigidity of the mold.

[0043] A circular runner is a molten liquid transport channel with a circular cross-section in a gating system, and its inner surface requires high-gloss polishing. High-gloss polishing refers to mechanically grinding to make the inner surface of the runner smooth and burr-free, which can reduce molten liquid flow resistance and prevent air entrapment.

[0044] The point gate is the feeding structure of the gating system, which works in conjunction with the circular runner to inject molten liquid.

[0045] The vacuum exhaust system is an auxiliary system for die casting, used to extract gas from the mold cavity and reduce porosity defects.

[0046] The temperature control system is a mold temperature control system used to maintain a stable mold temperature and ensure that the melt solidifies evenly.

[0047] The demolding system is a device for ejecting finished products, used to achieve synchronous ejection, thereby avoiding deformation caused by uneven stress on the finished products.

[0048] In one feasible implementation, the fixed mold, moving mold, and stripper plate structure of the three-plate mold are designed based on the dimensions and contours of the double T-shaped cross-section structure. Support columns are arranged and fixed in the stress concentration area of ​​the mold. A gating system with circular runners and point gates is machined and the inner surface of the circular runners is high-gloss polished. The vacuum exhaust system, temperature control system, and demolding system are assembled sequentially at the corresponding positions of the three-plate mold according to conventional logic to ensure that each system is firmly installed and functions without interference.

[0049] S3: The die-casting machine provides an injection force and injection speed not less than the set value. In conjunction with the gating system's point gate and circular runner, the heat-free aluminum alloy molten liquid is injected into the three-plate mold to fill the cavity. Simultaneously, the vacuum exhaust system is activated to evacuate the gas inside the three-plate mold, and the temperature control system is activated to maintain the preset working temperature of the three-plate mold.

[0050] It should be noted that a die-casting machine is a die-casting device that provides high-pressure thrust and high-speed conveying capabilities to drive molten metal to fill the mold cavity. Injection force is the force exerted by the die-casting machine to propel the molten metal into the mold cavity, and it is a key parameter ensuring dense filling of the molten metal. Injection speed is the flow rate of the molten metal through the runner and gate under the drive of the die-casting machine, and it directly affects the integrity of the filling process.

[0051] Heat-free aluminum alloy melt is a molten aluminum alloy raw material that can meet the requirements of high strength and toughness without subsequent solution treatment and aging treatment.

[0052] The cavity is a hollow spacer in the mold that has the same shape as the finished spacer bar, and it is the carrier for the solidification and forming of the molten metal.

[0053] The preset working temperature is the optimal working temperature of the mold determined based on the characteristics of the aluminum alloy material and the structure of the casting, and is used to maintain molding stability.

[0054] In one feasible implementation, heat-free aluminum alloy ingots are placed into a furnace, heated to a molten state, and kept at a constant temperature to homogenize and remove oxide scale. The die-casting machine is started, and the injection force and injection speed are set to a value not less than the preset value according to the filling requirements. The three-plate mold is preheated to the preset working temperature and kept stable through the temperature control system. The molten liquid is poured into the die-casting machine barrel. After the vacuum exhaust system is started to evacuate the gas in the cavity, the die-casting machine pushes the molten liquid through the gating system to inject it into the cavity until it is full. During the die-casting process, the mold temperature is adjusted in real time through the temperature control system.

[0055] S4: After the melt cools and solidifies, start the demolding system to eject it synchronously, and obtain the high-strength and tough spacer bar finished product.

[0056] It should be noted that synchronous ejection refers to a demolding method that drives multiple ejection components to operate simultaneously, so that the finished product is subjected to uniform force.

[0057] High-strength and tough spacer bars are finished products that meet the requirements for ultra-high voltage power transmission and possess excellent tensile strength and toughness.

[0058] In one feasible implementation, the cooling time is set according to the complexity of the spacer bar structure. After the molten liquid is completely solidified by the change in mold temperature or the die-casting cycle, the demolding system is activated and the ejector component is driven by the linkage mechanism to eject synchronously. The finished product is then removed manually or mechanically, completing the entire molding process.

[0059] This embodiment provides a vacuum die-casting method for aluminum alloy spacer bars. Based on the die-casting principle of liquid metal filling and cooling solidification, this method designs the ribs with a double-T cross-section structure to disperse metal accumulation areas, optimize heat conduction paths, and create structural conditions for uniform cooling of the molten metal. This fundamentally solves the microscopic porosity and air pocket problems caused by heat nodes formed by metal concentration in traditional ribs. A three-plate mold adapted to the double-T structure is used with supporting columns to improve mold rigidity, resist elastic deformation during high-pressure injection, and ensure dimensional accuracy. A gating system consisting of circular runners and point gates reduces molten metal flow resistance and heat loss. A vacuum exhaust system extracts gas from the cavity, reducing porosity and incomplete filling defects. A high-pressure, high-speed injection force from the die-casting machine propels the molten metal to quickly fill the cavity. A temperature control system maintains the preset working temperature of the mold, ensuring uniform solidification of the molten metal. Finally, synchronous ejection prevents deformation of the finished product, achieving high-quality die-casting of ultra-high voltage power transmission spacer bars.

[0060] In one embodiment of the present invention, in the double T-section structure, the thickness of the vertical rib of each T-shaped rib is the same as the wall thickness of the spacer bar foundation, the thickness of the horizontal rib is in the range of 2.5-3.0mm, the spacing between the two T-shaped ribs is in the range of 8-12mm, and the radius of the rib root is processed with a radius of R2.0-R2.5mm.

[0061] The following combination Figure 2-9 The optimization of the stiffener section structure in this embodiment, namely the design of changing the cross-shaped section structure to a double-T section structure, will be further introduced.

[0062] The die-cast structure of spacer bar frames is characterized by thin-walled plates and stiffening plates. From a structural cross-section perspective, it mainly includes L-type, T-type, and cross-type sections, such as... Figure 2 As shown.

[0063] Due to the thermal defects present in the cruciform stiffeners, the spacer frame structure can be designed using a thin-walled reinforcement method. Based on the material and forming process, the optimal wall thickness design parameters and the structural dimensional details of the target product are determined. The basic wall thickness design is 3.5mm. Figure 3 As shown.

[0064] The original cross-shaped stiffener is split into two independent T-shaped stiffeners (double T-shaped). The vertical stiffener thickness of each T-shaped stiffener is t=3.5mm (consistent with the wall thickness of the frame foundation), and the horizontal stiffener thickness is t=2.5-3.0mm. The distance between the two T-shaped stiffeners is tx=10mm (which can be adjusted within the range of 8-12mm according to the width of the frame). The root of the stiffener is set with a radius of R2.0-R2.5mm to eliminate stress concentration.

[0065] The purpose of modifying stiffeners is to avoid overlapping. For example, the cooling and solidification effect of cross-shaped stiffeners is worse than that of other structural stiffeners. Avoiding cross-shaped stiffeners can reduce the material cooling rate of the local structure and increase the risk of porosity and breakage. For the original cross-shaped stiffener design, it can be decomposed into two T-shaped structures, or a double-T structure. Please refer to [link / reference]. Figure 4 and Figure 5 ,in, Figure 4 This demonstrates a local structural optimization of the spacer frame, specifically the rib section shown in the circle, where structural optimization can be performed. By symmetrically shifting the upper and lower T-shaped structures left and right along the original centerline of the cross-shaped rib, a double-T structure is obtained. The double-T structure is shown below. Figure 5 As shown.

[0066] The cooling-solidification simulation results of the cruciform cross-section structure are as follows: Figure 6 As shown. Selecting a typical local structure, observation points were chosen at the top (point-1) and the roots on both sides (Point-2 and Point-3) of the cruciform cross-section stiffener. The simulation calculations of cooling and solidification time and the maximum temperature difference are shown below. Figure 7 As shown.

[0067] from Figure 7 It can be seen that during the cooling and solidification time of the cross-shaped stiffener, the temperature at all three detection points dropped below 450℃ within 4.5 seconds. During the filling process, in the first 2 seconds, the temperature at the top of the upper stiffener (Point-1) and the temperatures at its roots (Point-2 and Point-3) changed at approximately the same rate. After the molten aluminum alloy was deposited on the mold, the temperature at the top of the upper stiffener (Point-1) and the temperatures at its roots (Point-2 and Point-3) decreased at a faster rate, reaching the maximum difference (31.33℃) at 351 seconds. However, after 4.2 seconds, the temperature changes at the three nodes converged, with the temperature difference less than 10℃. During the subsequent cooling process, the temperatures at the observation points tended to be the same.

[0068] Based on the principle of effective thin-wall cooling, the original cruciform cross-section stiffener was replaced with a double-T cross-section stiffener. Simulations were performed using the same process, and the simulation results for cooling and solidification are as follows: Figure 8 As shown. The results of cooling and solidification time and maximum temperature difference for the double-T section stiffener are as follows. Figure 9 As shown.

[0069] Selecting a typical local structure, observation points are chosen at the top (point-1) of the double T-section stiffener, between two adjacent stiffeners (Point-2), and at the bottom (Point-3) of the lower stiffener. The simulation calculations of cooling solidification time and maximum temperature difference are as follows: Figure 9As shown.

[0070] from Figure 9 It can be seen that the cooling and solidification time of the double-T cross-section stiffener is 4.5 seconds, and the temperature at all three detection points drops below 450℃. During the filling process, in the first 2 seconds, the temperature changes of the upper stiffener (Point-1), the area between two adjacent stiffeners (Point-2), and the outer side of the lower stiffener (Point-3) of the double-T cross-section stiffener are basically the same over time. However, after the aluminum alloy melt is applied to the mold, the temperature drop rate of the upper stiffener (Point-1) and the area between two adjacent stiffeners (Point-2) is similar, but lags behind that of the bottom plate (Point-3) on the outer side of the stiffener, reaching the maximum difference at 3.38 seconds. The maximum temperature difference between the top of the double-T cross-section stiffener (Point-1), the area between two adjacent stiffeners (Point-2), and the outer side of the lower stiffener (Point-3) is 19.7℃. However, after 3.8 seconds, the temperature changes of the three nodes become closer, and the temperature difference reaches the minimum value of 2.47℃ after 4.26 seconds.

[0071] Therefore, the comparison of cooling and solidification effects before and after local structural optimization is as follows:

[0072] (1) Cross-shaped (Type-C) cross section stiffener

[0073] Structural features: The stiffeners are in a cross shape with a central intersection point (usually a hot spot) where metal is concentrated.

[0074] Cooling characteristics: Heat is relatively concentrated, especially in the root area where the ribs meet. The cooling paths interfere with each other, which can easily lead to a large temperature gradient.

[0075] (2) Double-T section stiffener

[0076] Structural features: It consists of two independent T-shaped stiffeners arranged side by side, which avoids serious accumulation of metal in the center and makes the roots of the stiffeners more dispersed.

[0077] Cooling characteristics: It follows the principle of thin-walled cooling effectiveness, increases the heat dissipation area, improves the heat conduction path, and reduces the thermal stagnation effect.

[0078] Table 1 shows a comparison of the calculation results for the cooling and solidification of the stiffeners in the two structures.

[0079] Table 1 Comparison of cooling and solidification parameters for the two structures

[0080]

[0081] It is evident that optimizing the cross-section to a double-T cross-section significantly improves the cooling and solidification effect.

[0082] Reduced heat concentration effect: The double-T structure effectively disperses metal accumulation and avoids severe heat knots formed by cross intersections.

[0083] More uniform temperature field: The maximum temperature difference is reduced by 37%, significantly reducing the risk of thermal cracking and residual stress caused by excessive temperature difference.

[0084] Better synchronous solidification: The temperature of each part tends to be consistent in a shorter time, which is conducive to the sequential solidification of the casting and improves the internal quality.

[0085] In summary, the double-T cross-section structure is superior to the traditional cross-section structure in terms of cooling uniformity and reduction of casting defects.

[0086] The design of the die-casting mold of the present invention will be described below with reference to some embodiments.

[0087] The gating system is crucial to the design of thin-walled die-casting molds and directly determines the success or failure of die casting. Therefore, in one embodiment of the present invention, the length of the gating point is 1-2 mm, and the cross-sectional area of ​​the gating point meets the requirement that the filling speed of the heat-free aluminum alloy melt is not less than 80 m / s.

[0088] First, the advantages of using a pin point gate are ease of removal, automatic breakage, and minimal gate mark, making it suitable for specimens with high subsequent requirements. Second, it results in low pressure loss. When passing through a small-section gate, the flow rate increases dramatically, generating extremely high shear rates, effectively reducing the apparent viscosity of the molten metal, making it flow like water, and greatly improving filling capacity. The pin point gate offers flexible placement, allowing for selection of the most ideal location in the cavity to achieve the optimal filling pattern.

[0089] Thin-walled parts require extremely high filling speeds (typically >80m / s, or even higher). The gate cross-sectional area should be small to achieve high-speed filling. A smaller value can be used in the initial design, gradually increasing to the optimal value through trial molding. The gate length should be as short as possible (typically 1-2mm) to reduce pressure loss and heat dissipation.

[0090] In other embodiments of the present invention, the circular flow channel, after being treated with high-gloss polishing, has a surface roughness Ra that meets the requirement of Ra≥0.4μm. The circular flow channel adopts a natural balance layout.

[0091] Circular runners are used because they have the smallest specific surface area, resulting in less heat loss and lower resistance. To prevent premature solidification of the molten metal, the runner dimensions should be larger than those of conventional die castings. The purpose is to act as an accumulator, providing sufficient high-temperature molten metal for subsequent flow through the gating gate. The runners must be highly polished to reduce flow resistance and prevent air entrapment.

[0092] For multi-cavity molds, a natural balance (geometric balance) runner layout must be adopted to ensure that the molten metal reaches the gates of all cavities simultaneously, ensuring that the filling conditions of each cavity are consistent, so that the test piece data can be compared.

[0093] In one embodiment of the present invention, the support columns are uniformly arranged along the stress concentration area of ​​the cavity of the three-plate mold.

[0094] Three-plate molds have complex structures and numerous plates, requiring extremely high rigidity and strength to prevent elastic deformation under high-pressure injection, which could affect dimensional accuracy or even cause flash. Therefore, the mold plate thickness must be sufficient, and the support pillars must be properly positioned in areas of high stress.

[0095] In addition, for the guiding system of a three-plate mold, extended guide pins and bushings can be used to ensure accurate positioning between the mold plates during mold opening and closing, especially when the stripper plate moves, thus avoiding friction and damage. Interlocking or side locks can also be considered to further improve mold closing accuracy.

[0096] For the forming core and cavity materials of three-plate molds, high-quality mold steels with high thermal conductivity, high thermal fatigue strength, and high toughness, such as DIEVAR and H13 (ESR electroslag remelted high-quality material), can be used, offering advantages in overall performance. High-thermal-conductivity copper alloy mold steels (such as the Ampco series) are used for difficult-to-cool localized areas, such as the core, significantly improving cooling efficiency. The cavity surface needs to be highly polished, or even mirror-polished, to reduce flow resistance and facilitate demolding.

[0097] In one embodiment of the present invention, the vacuum exhaust system includes a vacuum valve and multiple exhaust grooves disposed on the parting surface, slider and ejector pin of the three-plate mold, the depth of the exhaust grooves being 0.08-0.15mm; the vacuum exhaust system is linked with the vacuum valve and the exhaust grooves to draw the vacuum degree of the cavity to a preset value before heat treatment-free aluminum alloy melt injection.

[0098] For thin-walled specimens with extremely high requirements, a vacuum system is necessary. Evacuating the air from the cavity instantaneously before injection can significantly reduce porosity, lower filling resistance, and substantially improve filling capacity and specimen yield. When considering thin-walled filling, the smooth venting of gas from the cavity is crucial; otherwise, defects such as porosity and incomplete filling are easily generated. Vent depth must be very thin, approximately 0.08-0.15 mm. Too deep will cause molten metal blockage, while too shallow will result in poor venting. Vents must be located at the end of the molten metal filling process or in the last filled area. Furthermore, as many vents as possible should be provided to increase the total venting area. Multiple vents can be considered on the parting surface, slide block, and ejector pins. The ends of the vents should have sufficient space to open to the atmosphere or be connected to a vacuum valve.

[0099] Although thin-walled parts require less material, overflow channels are still necessary. Their primary purpose is not to store cold material, but rather to guide and vent air, acting as a trap at the end of the filling process to hold the cold molten metal mixed with gas. The overflow channels should be equipped with venting needles or venting blocks to ensure effective venting.

[0100] Furthermore, a temperature control system is crucial for maintaining mold thermal balance and ensuring stable production of high-quality test pieces. For a temperature control system, a dense and uniform cooling channel layout can be implemented. Thin-walled parts have short cycle times and concentrated heat, requiring efficient cooling. Multiple series or parallel fine cooling channels should be used, positioned as close as possible to the cavity surface (typically within 15-20 mm) to ensure uniform cavity temperature. Precise control should be achieved using a mold temperature controller; a dual-channel controller is recommended to control the temperature of the moving and stationary molds separately, optimizing filling and shrinkage conditions. During the initial mold start-up phase, or when producing certain temperature-sensitive alloys (such as magnesium alloys), heating rods may be necessary to preheat the mold and quickly bring it to its optimal operating temperature range.

[0101] In one embodiment of the present invention, the demolding system includes an ejection component and a linkage control mechanism;

[0102] The ejector components are flat ejector pins or top plates. Multiple ejector components are evenly arranged along the wall thickness of the spacer bar and below the stiffener plate, and are ejected synchronously through a linkage control mechanism.

[0103] Thin-walled specimens have low strength and are easily deformed. The ejection system must be numerous, evenly distributed, and operate synchronously. Flat ejector pins or large-area ejector sleeves are preferred to reduce the ejection force per unit area and avoid puncture or deformation during ejection. Ejector pins should be placed at thicker sections of the specimen wall or in locations with higher strength (such as below stiffeners).

[0104] In one embodiment of the present invention, the die-casting machine provides an injection speed of not less than 8 m / s, an injection force of not less than 120 MPa, and a pressure build-up time of not more than 50 ms.

[0105] The mold design must be matched with the performance of the selected die-casting machine:

[0106] High injection speed: The die casting machine must be able to provide extremely high and stable high injection speed (>8m / s, or even more than 10m / s).

[0107] Pressure build-up time: extremely short, ensuring that pressure is effectively transferred to the cavity before the molten metal solidifies.

[0108] Closed-loop real-time control: The die-casting machine should be able to monitor and control the injection curve in real time to ensure the process stability of each injection, which is crucial for obtaining repeatable specimen data.

[0109] In one embodiment of the present invention, the heat-free aluminum alloy is an Al-Si-Mg alloy.

[0110] As can be seen from the above embodiments, the key design points of the three-plate mold for thin-walled die casting specimens are shown in Table 2.

[0111] Table 2 Key Design Considerations for Three-Plate Molds for Thin-Walled Die Casting Specimens

[0112]

[0113] Please see Figure 10 , Figure 10 The principle of vacuum die casting is illustrated: The die casting machine first propels the heat-free aluminum alloy molten liquid for low-speed injection. After reaching the starting point, the vacuum valve opens and the vacuum exhaust system starts. Through linkage with the vacuum tank, the gas in the cavity of the three-plate mold (die casting mold) adapted to the double T-shaped structure is evacuated. Then the main valve opens and the die casting machine enters the high-speed injection stage. At the same time, the vacuum feedback maintains the vacuum environment of the cavity. The molten liquid is injected into the cavity through the high-gloss polished circular flow channel and the point gate. During this process, the vacuum system continuously removes the gas in the cavity, reducing defects such as porosity. Finally, the molten liquid fills the cavity and completes the filling, ensuring the high-quality die casting of the UHV transmission spacer bar.

[0114] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0115] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0116] In the embodiments disclosed in this application, it should be understood that the disclosed devices / terminal equipment and methods can be implemented in other ways. For example, the device / terminal equipment embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual coupling or direct coupling or communication connection may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0117] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. 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 of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A vacuum die-casting method for spacer bars made of aluminum alloy, characterized in that, Includes the following steps: The cross-section of the spacer slab is designed as a double-T cross-section structure; the double-T cross-section structure is composed of two independent T-shaped stiffening slabs arranged side by side; A three-plate mold adapted to the double T-section structure is adopted, and support columns are arranged in the stress area of ​​the three-plate mold. A gating system, a vacuum exhaust system, a temperature control system and a demolding system are configured on the three-plate mold. The gating system adopts a circular runner and a point gate, and the inner surface of the circular runner is treated with high gloss polishing. The die-casting machine provides an injection force and injection speed not less than the set value. In conjunction with the gating system's point gate and circular runner, the heat-free aluminum alloy molten liquid is injected into the three-plate mold to fill the cavity. Simultaneously, the vacuum exhaust system is activated to evacuate the gas inside the three-plate mold, and the temperature control system is activated to maintain the preset working temperature of the three-plate mold. After the molten metal cools and solidifies, the demolding system is activated to eject the metal synchronously, resulting in a high-strength and tough spacer bar product. In the double T-section structure, the thickness of the vertical ribs of each T-shaped rib is the same as the wall thickness of the spacer base, the thickness of the horizontal ribs ranges from 2.5 to 3.0 mm, the spacing between the two T-shaped ribs ranges from 8 to 12 mm, and the radius of the rib root is rounded to R2.0 to R2.5 mm.

2. The vacuum die-casting method for spacer bars made of aluminum alloy according to claim 1, characterized in that, After being treated with high-gloss polishing, the surface roughness Ra of the circular flow channel meets the requirement of Ra=0.4μm.

3. The vacuum die-casting method for spacer bars made of aluminum alloy according to claim 2, characterized in that, The circular flow channel adopts a natural balance layout.

4. The vacuum die-casting method for spacer bars made of aluminum alloy according to claim 2, characterized in that, The length of the point gate is 1-2mm, and the cross-sectional area of ​​the point gate meets the requirement that the filling speed of the heat-free aluminum alloy melt is not less than 80m / s.

5. The vacuum die-casting method for spacer bars made of aluminum alloy according to claim 1, characterized in that, The support columns are evenly arranged along the stress concentration area of ​​the cavity of the three-plate mold.

6. The vacuum die-casting method for spacer bars made of aluminum alloy according to claim 1, characterized in that, The vacuum exhaust system includes a vacuum valve and multiple exhaust grooves located on the parting surface, slider, and ejector pin of the three-plate mold. The depth of the exhaust grooves ranges from 0.08 to 0.15 mm. The vacuum exhaust system is connected to the exhaust groove through the vacuum valve and is used to evacuate the vacuum level of the cavity to a preset value before heat-free aluminum alloy melt injection.

7. The vacuum die-casting method for spacer bars made of aluminum alloy according to claim 1, characterized in that, The die-casting machine provides an injection speed of no less than 8 m / s.

8. The vacuum die-casting method for spacer bars made of aluminum alloy according to claim 1, characterized in that, The demolding system includes an ejection component and a linkage control mechanism; The ejector component is a flat ejector pin or a top plate. Multiple ejector components are evenly arranged along the wall thickness of the spacer bar and below the stiffener plate, and are ejected synchronously through the linkage control mechanism.

9. The vacuum die-casting method for spacer bars made of aluminum alloy according to claim 1, characterized in that, The heat-free aluminum alloy is an Al-Si-Mg alloy.

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