Die-casting die and aluminum alloy vacuum die-casting system and method

Abstract

The invention relates to the technical field of aluminum alloy die-casting, in particular to a die-casting die and an aluminum alloy vacuum die-casting system and method. The die-casting die comprises a movable die, a fixed die and a fixed die insert, a cavity is formed after the movable die and the fixed die are assembled, the fixed die insert is located in the cavity and fixedly arranged on the fixed die, and the cavity is communicated with at least four vacuumizing channels; the fixed mold insert is provided with a working medium inlet, a working medium outlet and at least three stages of flow dividing pipelines, the flow dividing pipelines of the next stage are communicated with the flow dividing pipelines of the previous stage, the number of flow channels of the flow dividing pipelines of the next stage is n times that of the flow channels of the flow dividing pipelines of the previous stage, and n is a natural number larger than or equal to 2. According to the scheme provided by the invention, through the hierarchical multiplication design of the at least three stages of shunting pipelines and the synergistic effect of the four vacuumizing channels, uniform distribution and efficient exhaust of the working medium are realized, the temperature control precision and the cavity vacuum degree are remarkably improved, and the defect rates of air holes, shrinkage cavities and the like of the die casting are effectively reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aluminum alloy die casting, in particular to a die casting mold, an aluminum alloy vacuum die casting system and method. BACKGROUND

[0002] Die casting is a metal casting process characterized by the use of high pressure to fill mold cavities with molten metal, suitable for mass production of light metal castings, and is the most efficient process among various casting processes. The die casting mold is the core equipment of the metal pressure casting process, and the molten metal is pressed into the mold cavity at high speed under high pressure to achieve near-net forming of complex parts. As a key functional component of the mold, the insert is usually embedded in the vulnerable part of the mold cavity or core, the heat concentration area or the complex structure requiring special cooling, to improve the mold life, optimize the temperature field distribution and reduce the manufacturing cost. However, the water channel design of the traditional fixed mold insert usually adopts a single-stage runner structure, which is limited by the insufficient fit between the linear runner and the cavity, and there are problems of insufficient length coverage in the longitudinal heat exchange direction and significant heat conduction gradient, resulting in significant differences in cooling rate in different depth areas of the cavity. At the same time, in terms of horizontal heat exchange distribution, the single-stage runner is difficult to achieve uniform distribution of the working medium, which causes unbalanced temperature field distribution in different areas of the cavity surface, easily leading to shrinkage, deformation and other defects of the casting due to uneven cooling, and is difficult to meet the high precision requirements of the mold thermal equilibrium state for complex structure die castings. SUMMARY

[0003] To overcome the problems in the related art, the present application provides a die casting mold, an aluminum alloy vacuum die casting system and method, which realizes uniform distribution and efficient exhaust of the working medium through the hierarchical multiplication design of at least three-stage shunt pipelines and the synergistic effect of four vacuum extraction channels, significantly improves the temperature control precision and the cavity vacuum degree, and effectively reduces the defect rate of die castings such as porosity and shrinkage.

[0004] The first aspect of the present application provides a die casting mold, comprising a movable mold, a fixed mold and a fixed mold insert, the movable mold and the fixed mold form a cavity after closing, the fixed mold insert is located in the cavity and is fixedly arranged on the fixed mold, and the cavity is communicated with at least four vacuum extraction channels. The fixed mold insert has a working medium inlet, a working medium outlet and a multi-stage shunt pipeline, the multi-stage shunt pipeline has at least three stages, the lower stage shunt pipeline is communicated with the upper stage shunt pipeline, and the number of flow channels of the lower stage shunt pipeline is n times the number of flow channels of the upper stage shunt pipeline, the first stage shunt pipeline of the multi-stage shunt pipeline is communicated with the working medium inlet, and the last stage shunt pipeline of the multi-stage shunt pipeline is communicated with the working medium outlet, wherein n is a natural number greater than or equal to 2.

[0005] In some embodiments, the cross-sectional area of the working medium inlet is greater than the total cross-sectional area of the first stage shunt pipeline, and the cross-sectional area of a single flow channel in the upper stage shunt pipeline is greater than the total cross-sectional area of each flow channel in the lower stage shunt pipeline connected thereto.

[0006] In some embodiments, the ratio of the cross-sectional area of the working medium inlet to the total cross-sectional area of the first stage shunt pipeline is 1:(0.85-0.95); and the ratio of the cross-sectional area of a single flow channel in the upper stage shunt pipeline to the total cross-sectional area of each flow channel in the lower stage shunt pipeline connected thereto is 1:(0.85-0.95). The inner wall roughness Ra of the flow channel is ≤2 μm.

[0007] In some embodiments, the fixed mold insert is further provided with a plurality of micro flow channels communicating with the cavity.

[0008] In some embodiments, a base is further included, the material of the base is the same as that of the fixed mold insert, and the fixed mold insert is integrally formed on the base by 3D printing.

[0009] Compared with the prior art, the die casting mold provided by the present application, through the hierarchical multiplication design of at least three stages of shunt pipelines and the synergistic effect of at least four vacuum extraction channels, firstly, the flow channel network extends from the superficial layer of the cavity to the deep cavity structure, solving the problem of insufficient longitudinal coverage of the flow channel in the prior art, and realizing the improvement of the heat exchange area of the high heat load area and the optimization of the longitudinal and transverse heat exchange coverage of the die casting mold; secondly, through the gradient optimization of the cross-sectional area of the working medium inlet and each stage of flow channels and the control of the inner wall roughness, the control accuracy of the cavity temperature is significantly improved, and the defects such as shrinkage cavity and deformation caused by local hot spots are avoided; finally, the four vacuum extraction channels are arranged at intervals along the flow direction of the aluminum liquid, and the macroscopic and capillary action composite exhaust is formed by cooperating with the micro flow channels, which can effectively reduce the porosity of the die casting.

[0010] The second aspect of the present application provides an aluminum alloy vacuum die casting system, comprising an aluminum liquid generating device, a die casting machine, a spraying device, a vacuum device, and the die casting mold described above. The aluminum liquid generating device is used for melting aluminum alloy, and the die casting machine is communicated with the aluminum liquid generating device and injects the aluminum liquid into the mold. The spraying device is used for spraying release agent on the surface of the cavity of the die casting mold. The vacuum device is communicated with the vacuum extraction channels of the die casting mold.

[0011] In some embodiments, a detection device, a cooling device, a slag removal package device, a material cake removal device, a straightening device, a character and code engraving device, a part taking machine, and a conveying line are further included. The part taking machine is used for sequentially conveying the die casting parts in the die casting mold to the detection device, the cooling device, the slag removal package device, the material cake removal device, the straightening device, the character and code engraving device, and the conveying line. The detection device is used for detecting the integrity of the die casting; The cooling device is used for cooling the die casting; The slag pocket removing device is used for removing the slag pocket of the die casting; The sprue removing device is used for removing the sprue of the die casting; The straightening device is used for straightening the die casting; The lettering code device is used for lettering code on the die casting; The conveying line is used for transferring the die casting.

[0012] Compared with the prior art, the aluminum alloy vacuum die casting system provided by the application integrates the mold insert with multiple-stage shunt pipelines and exhaust setting, combines the vacuum device, the spraying device and the automatic processing unit, realizes the full-process integrated control of the aluminum alloy die casting from the aluminum liquid preparation to the post-processing of the die casting, and significantly improves the production efficiency and the quality level of the product.

[0013] The third aspect of the application provides an aluminum alloy vacuum die casting method, comprising the following steps: S1, melting aluminum alloy raw materials by using an aluminum liquid generating device, and controlling the melting temperature at 680-730 DEG C, and then adding a solid metal modifier to the molten aluminum liquid for refining; S2, preheating the die casting mold to 120-220 DEG C, and then spraying a release agent on the surface of the cavity of the die casting mold by using a spraying device; S3, vacuumizing the cavity, and conveying the refined aluminum liquid to a die casting machine, and injecting the aluminum liquid into the cavity by the die casting machine at a die casting pressure of 40-80 MPa and a die casting speed of 4-6 m / s, and pressure-cooling for 15-25 s; S4, opening the mold, and cooling for 6-16 s by spraying cooling water, and taking out the die casting by a taking machine; S5, sequentially detecting the integrity, cooling, removing the slag pocket, removing the sprue, straightening and lettering code processing of the die casting.

[0014] In some embodiments, in the step of vacuumizing the cavity, the vacuum degree of the cavity is controlled to be ≤100 mbar.

[0015] In some embodiments, the ratio of the sprue area of the die casting mold to the area of the injection punch of the die casting machine is 1:(6-16); and the filling degree of the compression chamber of the die casting machine is 30%-50%.

[0016] Compared with the prior art, the aluminum alloy vacuum die casting method provided by the application realizes the purpose of optimizing the aluminum liquid filling and solidification process by accurately controlling the melting temperature, the die casting parameters and the vacuum degree of the cavity, and matching the structural characteristics of the die casting mold, effectively reduces the internal defects of the die casting, and further improves the mechanical properties and the production stability of the die casting. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and other objects, features and advantages of the present application will become more apparent through a more detailed description of exemplary embodiments of the present application in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the present application.

[0018] Figure 1 This is the structural intention of the multi-stage diversion pipeline shown in the embodiment of the present application; Figure 2 Schematic diagram of the structure of the fixed mold insert shown in the embodiment of the present application; Figure 3 Schematic diagram of the structure of the microfluidic channel shown in the embodiment of the present application; Figure 4 Schematic diagram of the cooperation between the base and the fixed mold insert shown in the embodiment of the present application; Figure 5 Schematic diagram of the structure of the aluminum alloy vacuum die-casting system shown in the embodiment of the present application; Figure 6 is an X-ray image of the die casting obtained in Example 1 of the present application; Figure 7 is an X-ray image of the die casting obtained in Comparative Example 1 of the present application; Figure 8 Schematic diagram of the finished die-casting obtained in Example 1 of the present application; Figure 9 Schematic diagram of the finished die-casting obtained in Example 1 of the present application.

[0019] Reference numerals: 1. Die-casting mold; 10. Fixed mold insert; 100. Working fluid inlet; 101. Working fluid outlet; 102. Multi-stage diversion pipeline; 103. Microchannel; 20. Base; 2. Aluminum liquid generating device; 3. Die-casting machine; 4. Spraying device; 5. Detection device; 6. Cooling device; 7. Slag removal device; 8. Cake removal device; 9. Correction device; 11. Code engraving device; 12. Pick-up machine; 13. Conveyor line. DETAILED DESCRIPTION

[0020] The preferred embodiments of the present application will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present application are shown in the accompanying drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. Instead, these embodiments are provided to make the present application more thorough and complete, and to fully convey the scope of the present application to those skilled in the art.

[0021] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting thereof. As used in this application and the appended claims, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term "and / or," as used herein, refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0022] In the prior art, the waterway design of the insert is usually a single-flow channel structure. Due to the limitation of the structure of the die casting mold 1, it is difficult to achieve the mechanical thermal balance state of the cooling effect of the insert. This is because the linear structure of the flow channel and the cavity have poor fit, the heat distribution is significantly different, and then the casting has shrinkage, deformation and other defects due to uneven cooling. To solve the above problems, the embodiments of the present application provide a die casting mold, an aluminum alloy vacuum die casting system and method. Through the level multiplication design of at least three shunt pipelines and the synergistic effect of four vacuum extraction channels, uniform distribution and efficient exhaust of working medium are realized, the temperature control precision and the cavity vacuum degree are significantly improved, and the defect rate of die castings such as porosity and shrinkage is effectively reduced.

[0023] The technical solutions of the embodiments of the present application are described in detail below with reference to the drawings.

[0024] Figures 1 to 2 An embodiment of the present application is shown in the figure, Figure 2 An embodiment of the present application is shown in the figure. Referring to Figures 1 to 2 The die casting mold 1 provided by the present application comprises a movable mold, a fixed mold and a fixed mold insert 10. The movable mold and the fixed mold form a cavity after closing. The fixed mold insert 10 is located in the cavity and is fixed to the fixed mold. The cavity is connected to at least four vacuum extraction channels; The fixed mold insert 10 has a working medium inlet 100, a working medium outlet 101 and a multi-stage shunt pipeline 102. The multi-stage shunt pipeline 102 has at least three stages. The flow channel of the lower stage is in communication with the flow channel of the upper stage, and the number of flow channels of the lower stage is n times the number of flow channels of the upper stage. The first stage of the multi-stage shunt pipeline 102 is connected to the working medium inlet 100, and the last stage of the multi-stage shunt pipeline 102 is connected to the working medium outlet 101, wherein n is a natural number greater than or equal to 2. The fixed mold insert 10 realizes fine distribution of working medium shunt through the level multiplication design of at least three shunt pipelines and the number of flow channels of the lower stage being more than twice the number of flow channels of the upper stage, significantly improves the temperature control precision of the mold cavity, especially adapts to the multi-region temperature coordination demand of complex die casting mold 1, and reduces the shrinkage, deformation and other defects of the casting due to uneven cooling.

[0025] Specifically, the movable die and the fixed die are made of H13 hot work die steel, and the cavity surface is treated by nitriding. Those skilled in the art can determine the specific structure shape of the cavity according to the structure of the die casting. The fixed die is provided with an inlet, and the position of the inlet corresponds to the rear wall of the die casting. Four air extraction channels are arranged along the direction of the flow of the molten aluminum, and the diameter of the air extraction channel can be 8-12 mm, which is connected to the four air extraction ports of the vacuum device. A one-way valve can be arranged at the entrance of the channel to prevent the backflow of the molten aluminum. The fixed die insert 10 is embedded and fixed on the fixed die, forming part of the cavity, cooperating with the multi-stage shunt pipeline 103 to realize cavity forming, precise temperature control and exhaust. In specific implementation, the size and number of the fixed die insert 10 can be set according to the projection area of the die casting and the surface structure of the die casting. At the same time, the fixed die and the movable die are prearranged with oil or water interfaces, which are connected to the multi-stage shunt pipeline 102 of the fixed die insert 10 and the external cooling device, such as a cooling water circulation device, to realize regional temperature control.

[0026] In this embodiment, the regional temperature control means that the vacuum extraction is performed from the pressure chamber of the die casting machine. When the punch of the die casting machine is pressed in the pressure chamber to seal the pressure chamber, the pressure chamber is first subjected to vacuum extraction to suck the fumes in the pressure chamber at the first time. The vacuum extraction of the cavity can be divided into three stages, for example, the part near the inlet is one stage, the middle part of the cavity is two stages, and the end of the cavity is three stages. After the molten aluminum enters the cavity from the pressure chamber, the three-stage extraction process is performed in sequence. That is, when the molten aluminum fills 1 / 3 of the cavity, the first stage extraction is started, when it fills 2 / 3 of the cavity, the second stage extraction is started, and when it is completely filled, the third stage extraction is started. The duration of each stage can be 0.1-0.2s.

[0027] In this embodiment, the multi-stage shunt pipeline 102 of the fixed die insert 10 includes three-stage shunt pipelines, and each stage is composed of a flow channel. The first-stage shunt pipeline includes two first-stage flow channels, and the number of the first-stage flow channels is twice the number of the working fluid inlets 100. After the cooling working fluid enters the working fluid inlet 100, it is shunted through the first-stage shunt pipeline, thereby expanding the flow coverage area of the cooling working fluid in the fixed die insert 10. The number of flow channels of the second-stage shunt pipeline is twice the number of flow channels of the first-stage shunt pipeline, and the number of flow channels of the third-stage shunt pipeline is twice the number of flow channels of the previous stage. The flow channels of the third-stage shunt pipeline converge to the working fluid outlet 101. Through the network distribution structure of the multi-stage shunt pipeline 102, the cooling working fluid can form a fine flow channel network through step-by-step shunting, for example, the first-stage shunt pipeline covers the superficial layer region of the cavity, the second-stage extends to the middle layer heat load area, and the third-stage extends to the deep cavity structure of the cavity. Through the step-by-step extension of the flow channel length, the problem of insufficient longitudinal coverage of the traditional single flow channel can be solved, so as to optimize the longitudinal heat exchange and transverse heat exchange coverage of the die casting mold 1, improve the convective heat transfer efficiency and reduce the temperature gradient of the cavity surface, and improve the heat exchange efficiency of the die casting.

[0028] It can be understood that the 3D printing involved in the present application belongs to the mature application of the prior art, and the specific implementation method of the printing mold insert 10 will not be described here.

[0029] To facilitate understanding of the inventive concept of the present application, the hierarchical differentiation trigger condition of the multi-stage shunt pipeline 102 is explained in detail below. The hierarchical differentiation trigger condition can be specifically divided into heat concentration area-based, cavity profile feature-based, and fluid mechanics property-based. In terms of the hierarchical differentiation relationship between the heat concentration area-based and the multi-stage shunt pipeline 102, when there is a local high-heat area (such as a part with a wall thickness greater than or equal to 5 mm, a corner, or a thermal node) covered by the length of a certain stage shunt pipeline, the hierarchical differentiation will be triggered to increase the cooling waterway density, thereby reducing the local hot spot effect. For example, if the unit volume heat capacity of the area increases due to the increase in wall thickness, which is greater than 450 J / (kg·℃), the flow channel of the upper stage shunt pipeline should be differentiated into two lower stage shunt pipelines, so that the distance between the waterway and the cavity surface is controlled to be 1.5 to 2.5 times the flow channel diameter (for example, when the flow channel diameter is 4 mm, the distance is 6 to 10 mm), thereby improving the local heat exchange efficiency. In addition, when the simulation test shows that the temperature difference in the area is greater than 20℃, the certain stage shunt pipeline corresponding to the area can be expanded to the next stage by increasing the flow channel level (such as from the second stage to the third stage) to shorten the heat conduction path, expand the coverage area of the next stage flow channel, and achieve the purpose of improving the local heat exchange efficiency of the area.

[0030] In terms of the hierarchical differentiation relationship between the cavity profile feature-based and the multi-stage shunt pipeline 102, if the flow channel path of the current level encounters a cavity profile mutation (such as a curved surface turning, concave-convex structure), it can be differentiated into a lower stage shunt pipeline at this time to fit the complex shape. For example, at the corner with a curvature radius less than 10 mm, the next stage shunt pipeline needs to extend along the curvature direction, using a combination of arc and tangent paths to ensure that the distance deviation between the flow channel center line and the cavity surface is less than or equal to 0.5 mm; further, for deep cavity structures with a depth greater than 30 mm, the first stage shunt pipeline is differentiated into at least two secondary flow channels at the cavity opening position to ensure that the average distance between the flow channels of each stage shunt pipeline and the die casting is approximately the same.

[0031] In terms of the hierarchical differentiation relationship between the fluid mechanics characteristics and the multi-stage shunt pipeline 102, the hierarchical differentiation of the flow channel needs to meet the requirements of flow distribution and pressure balance. For example, the cross-sectional area of the upper level flow channel needs to be 1.05 to 1.2 times the sum of the cross-sectional areas of all flow channels of the lower level (for example, when the sum of the cross-sectional areas of the flow channels of the first stage shunt pipeline is 314 mm², the sum of the cross-sectional areas of the flow channels of the lower level shunt pipeline can be selected within the range of 266 to 298 mm²), so as to increase the flow rate of the flow channels of the lower level shunt pipeline and enhance the heat exchange effect on the die casting. In addition, the corresponding hierarchical differentiation can also be carried out according to the pressure loss. When the total flow channel length exceeds a certain limit value or the pressure loss along the way exceeds a limit value, for example, the total flow channel length is 600 mm (i.e. the designed length from the working medium inlet 100 to the working medium outlet 101), the single-path flow channel length is controlled to be within 200 mm through three-stage differentiation, so that the inlet pressure of the last stage flow channel is greater than or equal to 0.3 MPa, and the turbulent flow state is maintained.

[0032] Through the above technical solution, the mold insert 10 realizes accurate temperature control of the longitudinal depth and transverse area of the cavity to meet the high-precision molding requirements of complex structure parts.

[0033] In actual application, due to the friction between the cooling medium and the inner wall of the flow channel, the cooling medium will have a pressure loss along the way. To solve this technical problem and improve the flow rate of the fluid after hierarchical differentiation, on the basis of the above specific embodiments, the cross-sectional area of the working medium inlet 100 is greater than the total cross-sectional area of the first stage shunt pipeline, and the cross-sectional area of a single flow channel in the upper level shunt pipeline is greater than the total cross-sectional area of the flow channels of the lower level shunt pipeline connected thereto.

[0034] Specifically, after the cooling medium enters from the working medium inlet 100, the flow rate of the cooling medium can be considered as a constant value, and then enters the flow channel of the first stage shunt pipeline. Since the cross-sectional area of the first stage shunt pipeline is smaller than that of the working medium inlet 100, the cooling medium is accelerated after entering the flow channel of the first stage shunt pipeline, which can eliminate the friction effect of the inner wall of the flow channel and ensure the uniformity of the flow rate. The total cross-sectional area of the upper level shunt pipeline is greater than that of the lower level, so that the pressure gradient of the cooling medium is gentle during the hierarchical shunting process, and the uniformity of the flow rate is improved. Through the adjustment of the cross-sectional area at each level, the flow resistance of the cooling medium in the flow channel is optimized, the flow difference between the flow channels is reduced, and the temperature distribution uniformity of the mold cavity is improved, so as to solve the problem in the prior art that the flow rate is concentrated in the flow channel close to the inlet and the flow rate is insufficient in the distal flow channel. The design that the total cross-sectional area of the upper level is greater than that of the lower level can avoid local vortex and pressure loss caused by sudden expansion of the flow channel during the shunting process of the cooling medium, ensure that the working medium flows through the flow channels at a stable flow rate, and improve the convective heat transfer coefficient.

[0035] In practical application, due to the friction between the cooling medium and the inner wall of the flow channel, the cooling medium will have a pressure loss along the way. To solve this technical problem and improve the flow rate of the fluid after multiple hierarchical differentiation, in the above embodiment, the cross-sectional area of the working medium inlet 100 is greater than the total cross-sectional area of the first stage shunt pipeline, and the cross-sectional area of each flow channel in the upper stage shunt pipeline is greater than the total cross-sectional area of each flow channel in the lower stage shunt pipeline connected thereto. Specifically, after the cooling medium enters from the working medium inlet 100, the flow rate of the cooling medium can be considered as a constant value, and then enters the flow channel of the first stage shunt pipeline. Since the cross-sectional area of the first stage shunt pipeline is smaller than that of the working medium inlet 100, the cooling medium is accelerated after entering the flow channel of the first stage shunt pipeline, which can eliminate the friction effect of the inner wall of the flow channel and ensure the uniformity of the flow rate. The total cross-sectional area of the upper stage shunt pipeline is greater than that of the lower stage, so that the pressure gradient of the cooling medium is gentle during the hierarchical shunt process, and the uniformity of the flow rate is improved. By adjusting the cross-sectional area step by step, the flow resistance of the cooling medium in the flow channel is optimized, the flow difference of each flow channel is reduced, and the temperature distribution uniformity of the mold cavity is improved, so as to solve the problem that in the prior art, the flow rate of the flow channel near the inlet is concentrated, and the flow rate of the distal flow channel is insufficient. The design that the total cross-sectional area of the upper stage is greater than that of the lower stage can avoid local vortex and pressure loss caused by sudden expansion of the flow channel during the shunt process, ensure that the working medium flows through each stage flow channel at a stable flow rate, and improve the convective heat transfer coefficient.

[0036] Further, the ratio of the cross-sectional area of the working medium inlet 100 to the total cross-sectional area of the first stage shunt pipeline is 1:(0.85~0.95); the ratio of the cross-sectional area of a single flow channel in the upper stage shunt pipeline to the total cross-sectional area of each flow channel in the lower stage shunt pipeline connected thereto is 1:(0.85~0.95); The roughness Ra of the inner wall of the flow channel is ≤2μm.

[0037] For ease of understanding, the cross-sectional area of the working medium inlet 100 is defined as A0, and the total cross-sectional area of all flow channels of the first stage shunt pipeline is defined as A1. According to the fluid continuity equation (Q=A×v, Q is the volume flow rate, and v is the flow rate), when A0>A1total, the flow rate of the working medium will be moderately increased after entering the first stage shunt pipeline from the inlet, which can avoid the decrease of convective heat transfer efficiency caused by too low flow rate. The ratio is limited to 0.85~0.95 in this application, which can avoid local pressure loss caused by sudden decrease of cross-sectional area. Through simulation verification, the total pressure loss is <3% under this ratio, which meets the conventional power demand of the die casting mold 1 cooling system. Exemplarily, when the total cross-sectional area of the first stage shunt pipeline is 100mm 2 , the total cross-sectional area of the second stage is controlled in the range of 85mm 2 to 95mm 2The combination of differential cross-sectional area and flow channel number can dynamically allocate the cooling working medium to the high, medium and low heat load areas of the cavity. For example, in the high heat load area, the next level flow channel adopts a small cross-sectional area and a large number of flow channels to improve the heat exchange efficiency per unit area. In the low heat load area, the next level flow channel adopts a large cross-sectional area and a small number of flow channels to reduce the flow resistance. Under this setting, the application realizes the smooth transition of the working medium flow rate and pressure in the multi-stage shunt pipeline 102, solves the flow distribution imbalance problem caused by improper cross-sectional area design of the traditional flow channel, significantly improves the uniformity of the mold cavity surface temperature, and effectively suppresses the generation of casting shrinkage and deformation.

[0038] The inner wall of each flow channel of the multi-stage shunt pipeline 102 is treated by abrasive polishing and chemical polishing, and the surface roughness is controlled within the range of Ra≤2μm. In the specific implementation, alumina or diamond abrasive can be used to grind the inner wall of the flow channel step by step, and then an acidic polishing solution is used to further reduce the microscopic unevenness. After the flow channel is polished, the frictional resistance of the working medium flowing through the flow channel can be reduced, thereby suppressing the energy loss during the flow of the working medium, ensuring the flow balance of each flow channel in the multi-stage shunt pipeline 102, improving the temperature control accuracy of the mold cavity, and reducing the risk of defects caused by uneven cooling of the casting.

[0039] In this embodiment, by means of the number doubling design of the multi-stage shunt pipeline (i.e. the number of the next level flow channels is n times that of the previous level, and n≥2), combined with the flow channel cross-sectional area gradient optimization (i.e. the cross-sectional area of the previous level flow channel is 1.05 to 1.2 times the total cross-sectional area of the next level), the Reynolds number (Re) of the working medium flow is significantly improved. According to the principle of fluid mechanics, when the number of flow channels increases from the traditional design to 14 (2 in the first stage, 4 in the second stage, and 8 in the third stage) of the application, considering the change ratio of the collective cross-sectional area, the flow rate will increase and the Reynolds number will increase from the laminar state to the turbulent state under the condition that the total flow rate remains unchanged. In the turbulent state, the disturbance and mixing effect of the working medium through the inner wall of the flow channel are enhanced, the convective heat transfer coefficient is improved, and the control of the uniformity of the mold cavity surface temperature is realized. Further, the fixed mold insert 10 is also provided with a plurality of micro-flow channels 103 communicating with the cavity.

[0040] Referring to Figure 3, the micro flow channel 103 is an additional structure of the fixed mold insert 10, and cooperates with the multi-stage shunt pipeline 102 to form an integrated design of die casting cooling and exhaust. The diameter of the micro flow channel 103 can be 0.2-0.5mm, and in specific implementation, it can be adjusted according to the type of die casting alloy. For example, in aluminum alloy die casting, the diameter of the micro flow channel 103 can be 0.3-0.5mm, and for magnesium alloy, it can be 0.2-0.35mm; the cross-sectional shape of the micro flow channel 103 is circular or waist-shaped, and in a preferred embodiment, the micro flow channel 103 with a waist-shaped cross-section is selected to reduce 3D printing support. The micro flow channel 103 is arranged along the surface of the fixed mold insert 10 in contact with the cavity of the die casting mold 1, and is specifically distributed in the gas aggregation area (such as the cavity corner and deep cavity), the high heat load area at the end of the multi-stage shunt pipeline 102, and the predicted position of the fusion mark of the die casting. The number of micro flow channels 103 can be freely set according to the volume of the cavity, and a plurality of micro flow channels 103 are arranged in an array or a radial manner, with a spacing of 5-8mm between adjacent micro flow channels 103 to ensure that the exhaust covers no dead angle. One end of the micro flow channel 103 communicates with the inside of the cavity (the inlet), and the other end extends to the non-adhesion surface of the fixed mold insert 10 (the outlet); the outlet end is provided with an exhaust hole with an enlarged diameter to facilitate external connection of a vacuum exhaust device. The micro flow channel 103, the fixed mold insert 10 and the multi-stage shunt pipeline 102 are formed by the same 3D printing process, and in order to reduce the roughness of the inner wall of the micro flow channel 103 and thus save the polishing step of the micro flow channel 103, SLM technology can be used for 3D printing.

[0041] The exhaust principle of the micro flow channel 103 provided in the present application is that during the die casting process, the air, volatiles and organic combustion gases in the cavity are quickly discharged through the capillary channel formed by the micro flow channel 103 under the combined action of the metal liquid filling pressure and the external vacuum degree. Tests have shown that after the micro flow channel 103 is provided, the porosity of the die casting can be effectively reduced.

[0042] Through the above technical solution, combined with the high-precision forming capability of 3D printing, efficient exhaust of gas during die casting can be achieved, and the porosity defect rate of the die casting can be effectively reduced; at the same time, through collaborative optimization with the cooling system, the uniformity of the cavity temperature field is ensured, and finally the mechanical properties and surface quality of the die casting are improved.

[0043] When the fixed mold insert 10 is applied in large aluminum alloy die castings, since the mass of the aluminum alloy die casting may exceed 100kg, the spatial volume of the cavity is relatively large after volume conversion, and the fixed mold insert 10 used in cooperation also has a relatively large volume. If the entire fixed mold insert 10 is 3D printed, the cost will be too high. Therefore, in order to reduce production costs, on the basis of the above specific embodiments, please refer to Figure 4 , the die casting mold 1 further comprises a base 20, the base 20 and the fixed mold insert 10 are made of the same material, and the fixed mold insert 10 is formed on the base 20 by 3D printing.

[0044] In the forming process of large aluminum alloy die castings, due to the large size and complex structure of the castings, the following technical problems exist: 1. The forming quality of the castings is unstable, and defects such as pores, cold shuts, etc. are prone to occur; 2. The internal organization of the castings is uneven, affecting the mechanical properties; 3. The production efficiency of large castings is low, and the cost is high. These problems are mainly caused by the poor fluidity of molten metal, uneven cooling, and difficulty in controlling the mold temperature during the forming process of large castings. To solve the above problems, please refer to Figure 5 The application also provides an aluminum alloy vacuum die casting system, comprising an aluminum liquid generating device 2, a die casting machine 3, a spraying device 4, a vacuum device, and the above-mentioned die casting mold 1. The aluminum liquid generating device 2 is used for melting aluminum alloy, and the die casting machine 3 is in communication with the aluminum liquid generating device 2 and injects aluminum liquid into the mold. The spraying device 4 is used for spraying release agent on the surface of the cavity of the die casting mold 1. The vacuum device is in communication with the vacuum channel of the die casting mold 1.

[0045] Further, the aluminum alloy vacuum die casting system further comprises a detection device 5, a cooling device 6, a slag pocket removing device 7, a sprue removing device 8, a straightening device 9, a character and code marking device 11, a part taking machine 12 and a conveying line 13. The part taking machine 12 is used to sequentially convey the die castings in the die casting mold 1 to the detection device 5, the cooling device 6, the slag pocket removing device 7, the sprue removing device 8, the straightening device 9, the character and code marking device 11 and the conveying line 13. The detection device 5 is used to detect the integrity of the die castings. The cooling device 6 is used to cool the die castings. The slag pocket removing device 7 is used to remove the slag pocket of the die castings. The sprue removing device 8 is used to remove the sprue of the die castings. The straightening device 9 is used for the straightening of the die castings. The character and code marking device 11 is used for marking characters and codes on the die castings. The conveying line 13 is used for transferring the die castings.

[0046] Specifically, the sprue is arranged at the thick wall of the die casting, the thickness of the sprue is 3-5mm, and the projection area of the die casting is greater than 0.8m 2 , greater than 0.8m 2The projection area of the die-casting machine 3 ensures the large size of the castings, and the multi-channel vacuum pumping technology can effectively reduce the pores in the castings, improve the density and mechanical properties of the castings. At the same time, the die-casting machine 3 adopts a multi-section pouring mode, the die-casting pressure is 40-80 MPa, and the die-casting speed is 4-6 m / s, the high-pressure die-casting process can improve the filling speed and compaction effect of the molten metal, which is beneficial to improve the density and surface quality of the castings. And the die-casting chamber filling degree is controlled at 30%-50%, reasonable control of the die-casting chamber filling degree and temperature can optimize the metal flow and cooling in the die-casting process, further improve the casting quality and production efficiency. The die-casting chamber is controlled by oil temperature, and the temperature is 120-250℃. The pouring gate is set at the thick wall and multi-section pouring is adopted, which can improve the fluidity of the molten metal and reduce the turbulence in the pouring process, thereby reducing the generation of pores and cold shuts and other defects.

[0047] In the present embodiment, the number of the taking-out machines is two, one of which is used to place the die-castings on the conveying line 13, and the other one completes the rest of the interval work.

[0048] In the specific implementation, the aluminum alloy vacuum die-casting system adopts a programmable logic controller to realize automatic control of the whole process, and each device exchanges data through a network. The molten aluminum generating device is provided with a built-in temperature sensor for monitoring the temperature of the molten aluminum. When the temperature of the molten aluminum reaches the interval of 680-730℃, the device automatically delivers a certain amount of molten aluminum to the die-casting chamber of the die-casting machine through a pneumatic valve. During the vacuum treatment, the vacuum degree rapidly decreases to ≤50 mbar before the injection, maintains ≤80 mbar when the molten aluminum fills 1 / 3 of the mold cavity, and rises to ≤100 mbar after the filling is completed, so as to avoid backflow of the molten aluminum. The vacuum device specifically adopts a Roots-rotary vane composite vacuum pump set. The taking-out machine specifically adopts a six-axis robot, which positions the die-castings through a visual recognition system, and then transfers the die-castings to each post-processing device in sequence according to a preset path. The detection device adopts a combination scheme of X-ray real-time imaging detection and three-dimensional scanning, which can identify pore defects with a minimum diameter of 0.1 mm. The cooling device adopts a spray and air cooling composite cooling scheme, the nozzle diameter of the spray is 0.5 mm, the spray pressure can be set to 0.4-0.6 MPa, the air volume is 1500 m 3 / h, so as to control the time for cooling the die-castings from 300℃ to 80℃ within the interval of 60-90 s. The lettering device adopts a fiber laser marking machine, the marking depth is 0.05-0.1 mm, the minimum line width of the characters is 0.15 mm, and the dynamic generation and marking of information such as two-dimensional code, production date, batch number, etc. are supported.

[0049] The present application also proposes an aluminum alloy vacuum die-casting method, which comprises the following steps: S1, melt aluminum alloy raw materials by using molten aluminum generating device 2, the melting temperature is controlled at 680~730℃, then add solid metal modifier to the molten aluminum for refining, the solid metal modifier is added with 0.2% of Al-5Ti-1B modifier in the mass of molten aluminum, the stirring speed is 500r / min, and the holding time is 15min. The molten aluminum refining process can improve the quality of the molten aluminum, remove impurities and gas, and refine the grain structure. By adding the metal modifier and stirring, the modifier can be uniformly distributed in the molten aluminum, improving its effect, improving the mechanical properties and surface quality of the final die casting, and reducing the generation of defects such as pores. In the refining process, high-purity nitrogen is simultaneously introduced, the flow rate is 10~15L / min, and the bubble diameter is ≤1mm. The inclusions are removed by bubble flotation method.

[0050] S2, preheat the die casting mold 1 to 120~220℃, then spray the mold release agent on the surface of the die casting mold 1 through the spraying device 4. Spraying the mold release agent can prevent the molten aluminum from directly contacting the mold surface, reduce the adhesion of the molten aluminum to the mold, and facilitate the demolding of the casting. At the same time, the mold release agent can also play a role in heat insulation and lubrication, which helps to improve the surface quality of the casting and prolong the service life of the mold, thereby having a positive effect on the microstructure of the die casting.

[0051] S3, vacuumize the cavity, and deliver the refined molten aluminum to the die casting machine 3. The die casting machine 3 injects the molten aluminum into the cavity at a die casting pressure of 40~80MPa and a die casting speed of 4~6m / s, and keeps pressure cooling for 15~25s. During die casting, the injection punch first advances slowly at 0~2m / s to avoid air entrainment of the molten aluminum; before the molten aluminum contacts the cavity wall, it is erected at 4~6m / s to ensure the integrity of the filling. After die casting, pressure holding is performed, and the pressure is kept at 80MPa for 5s, then reduced to 40MPa and kept for 20s to match the solidification shrinkage characteristics of the casting. During die casting, the temperature gradient on the surface of the cavity is ≤15℃ through dynamic adjustment of the working fluid flow of the multi-stage shunt pipeline. At the same time, the mold temperature is controlled by water cooling of the fixed mold and the movable mold.

[0052] S4, open the mold, cool for 6~16s by cooling water spraying, and take out the die casting by the take-out machine 12. Cooling by cooling water spraying immediately after opening the mold can accelerate the cooling process of the die casting, help to control the cooling rate and temperature distribution of the die casting, improve the strength and hardness of the die casting. At the same time, it also reduces the deformation of the casting at high temperature, improves the dimensional accuracy, shortens the production cycle, and improves the production efficiency.

[0053] S5, the die casting is sequentially subjected to integrity detection, cooling, slag pocket removal, gate removal, shape correction and character code marking. The die casting is subjected to quality detection, among which the integrity detection can timely find and remove unqualified products, thereby improving product quality. The additional cooling process can further control the cooling rate of the die casting, thereby affecting the final mechanical properties. The slag pocket and cake removal can improve the appearance and functionality of the die casting. The shape correction process can correct the deformation possibly caused by uneven cooling, thereby improving the dimensional accuracy of the die casting. The character code marking is helpful for product traceability and management, and is completed by an automatic device, thereby ensuring the consistency and efficiency of the processing process.

[0054] Further, the cavity is vacuumized, and the vacuum degree of the cavity is controlled to be ≤100 mbar. In the embodiment, the micro flow channel and the four main vacuumizing channels realize high-efficiency exhaust through the synergistic effect of capillary effect and negative pressure suction. The fluid mechanics mechanism is based on the coupling of Bernoulli equation and Laplace capillary pressure formula. The pressure gradient difference between the micro flow channel and the main channel is superimposed with the capillary pressure difference, so that the exhaust efficiency is greatly improved compared with the traditional single-channel design, the vacuum degree of the cavity is further reduced, and the porosity defect rate of the die casting is further reduced.

[0055] Further, the ratio of the runner area of the die casting mold 1 to the area of the injection punch of the die casting machine 3 is 1:(6-16); and the filling degree of the pressure chamber of the die casting machine 3 is 30%-50%.

[0056] The embodiments of the present application will be described below in conjunction with examples. It should be understood that the examples are only used to illustrate the present application and are not intended to limit the scope of the present application Example 1 1. The temperature of the aluminum liquid in the holding furnace is 700°C.

[0057] 2. The solid metal modifier is put into the liquid metal raw material in the holding furnace, and the rotation mechanism is used to stir the liquid metal raw material.

[0058] 3. The die casting mold 1 is fixed on the movable and fixed mold plates of the die casting machine 3, the die casting mold 1 is preheated to 200°C, and a layer of release agent is uniformly sprayed on the inner surface of the mold cavity.

[0059] 4. The spraying direction of the first spraying device is adjusted so that the spraying path can fully cover the die casting mold 1 placed in the fixed mold cavity, and the second spraying device is adjusted so that the spraying path can fully cover the die casting mold 1 placed in the movable mold cavity.

[0060] 5. The molten aluminum liquid in the holding furnace is transported to the raw material conveying device on the die casting machine 3, and high-pressure die casting is performed. The casting pressure of the system is 60 MPa, the die casting speed is 5 m / s, and the cooling time is 20 s.

[0061] 6. After the die casting operation, the mold is opened, the cooling water spray cools for 10s, and the take-out machine 12 takes out the die casting located in the die casting mold 1.

[0062] 7. The take-out machine 12 transports the die casting to the detection equipment for integrity detection of the casting.

[0063] 8. The take-out machine 12 transports the die casting to the cooling device 6 for cooling of the casting, and the cooling time of the casting is 16s.

[0064] 9. The take-out machine 12 transports the die casting to the slag pocket removal device 7 for slag pocket removal of the casting.

[0065] 10. The take-out machine 12 transports the die casting to the sprue removal device 8 for sprue removal of the casting.

[0066] 11. The take-out machine 12 takes out the die casting from the sprue removal device 8 and transports it to the straightening equipment for straightening of the casting.

[0067] 12. The take-out machine 12 transports the die casting to the lettering device 11 for lettering.

[0068] 13. The take-out machine 12 transports the die casting to the conveying line 13, and the die casting enters the next process.

[0069] Example 2 The difference from Example 1 is that the fixed mold insert 10 of Example 2 does not perform polishing treatment on the multi-stage flow pipeline 102, and the remaining conditions are the same as those of Example 1.

[0070] Example 3 The difference from Example 1 is that the flow capacity of the fixed mold insert 10 of Example 3 is half of that of Example 1, and the remaining conditions are the same as those of Example 1.

[0071] Comparative Example 1 The difference from Example 1 is that the fixed mold insert 10 is not used in Comparative Example 1, and the remaining conditions are the same as those of Example 1.

[0072] Comparative Example 2 The difference from Example 1 is that the fixed mold insert 10 used in the comparative example has a single water channel structure.

[0073] According to GB / T 15114-2023, the quality of Examples 1-3 and Comparative Examples 1-2 is detected, and the test results are shown in Table 1: Table 1: Test results of each example and comparative example

[0074] As Figures 6~9As shown, the application realizes all-around optimization of the aluminum alloy vacuum die casting technology by the structure of the die casting die and application of the die casting die to an aluminum alloy vacuum die casting system. The multi-stage shunt pipeline and micro-flow channel combination design breaks through the bottleneck of traditional single-flow channel cooling unevenness, the die temperature control precision is improved by 30%, and the casting defect rate is reduced by 40%. Meanwhile, the die casting system of the application integrates the automatic post-processing of the aluminum alloy die casting, realizes the full-process closed-loop control from the aluminum liquid preparation to the finished product output, improves the production efficiency, and reduces the labor cost.

[0075] The above has described various embodiments of the application, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes are obvious to those skilled in the art without departing from the scope and spirit of the described embodiments. The selection of the terms used herein is intended to best explain the principles, practical application, or improvement of the technology in the market of the embodiments, or to enable other ordinary skilled persons in the art to understand the embodiments disclosed herein.

Claims

1. A die-casting mold, characterized in that: The invention comprises a movable mold, a fixed mold and a fixed mold insert (10), wherein the movable mold and the fixed mold are combined to form a mold cavity, the fixed mold insert (10) is located in the mold cavity and is fixed on the fixed mold, and the mold cavity is connected to at least four vacuum channels; The fixed mold insert (10) has a working medium inlet (100), a working medium outlet (101) and a multi-stage diversion pipeline (102). The multi-stage diversion pipeline (102) has at least three stages, the diversion pipeline of the next stage is connected to the diversion pipeline of the previous stage, and the number of flow channels of the diversion pipeline of the next stage is n times the number of flow channels of the diversion pipeline of the previous stage. The first stage diversion pipeline of the multi-stage diversion pipeline (102) is connected to the working medium inlet (100), and the last stage diversion pipeline of the multi-stage diversion pipeline (102) is connected to the working medium outlet (101), wherein n is a natural number ≥2.

2. The die-casting mold according to claim 1, characterized in that The cross-sectional area of ​​the working medium inlet (100) is larger than the total cross-sectional area of ​​the first-stage diversion pipeline, and the cross-sectional area of ​​a single flow channel in the upper-stage diversion pipeline is larger than the total cross-sectional area of ​​each flow channel in the lower-stage diversion pipeline connected thereto.

3. The die-casting mold according to claim 2, characterized in that: The ratio of the cross-sectional area of ​​the working medium inlet (100) to the total cross-sectional area of ​​the first-stage diversion pipeline is 1:(0.85-0.95); the ratio of the cross-sectional area of ​​a single flow channel in the upper-stage diversion pipeline to the total cross-sectional area of ​​each flow channel in the next-stage diversion pipeline connected thereto is 1:(0.85-0.95); The inner wall roughness of the flow channel is Ra≤2μm.

4. The die-casting mold according to claim 1, characterized in that The fixed mold insert (10) is also provided with a plurality of micro-channels (103) communicating with the mold cavity.

5. The die-casting mold according to claim 1, characterized in that: It also includes a base (20), the material of the base (20) is the same as that of the fixed mold insert (10), and the fixed mold insert (10) is integrally formed on the base (20) by 3D printing.

6. An aluminum alloy vacuum die-casting system, characterized in that: It comprises an aluminum liquid generating device (2), a die-casting machine (3), a spray device (4), a vacuum device, and a die-casting mold (1) according to any one of claims 1 to 5; The aluminum liquid generating device (2) is used to melt aluminum alloy, and the die-casting machine (3) is connected to the aluminum liquid generating device (2) and injects the aluminum liquid into the mold; The spray device (4) is used to spray a mold release agent on the cavity surface of the die-casting mold (1); The vacuum device is connected to the vacuum channel of the die-casting mold (1).

7. The aluminum alloy vacuum die-casting system according to claim 6, characterized in that: It also includes a detection device (5), a cooling device (6), a slag bag removal device (7), a cake removal device (8), a correction device (9), a code engraving device (11), a piece removal machine (12) and a conveying line (13); The piece removal machine (12) is used to sequentially transport the die-casting in the die-casting mold (1) to the detection device (5), the cooling device (6), the slag removal device (7), the cake removal device (8), the correction device (9), the lettering code device (11) and the conveying line (13); The detection device (5) is used to detect the integrity of the die casting; The cooling device (6) is used to cool the die casting; The slag removal device (7) is used to remove slag from the die casting; The cake removal device (8) is used to remove the gate of the die casting; The orthopedic device (9) is used for orthopedic treatment of die-cast parts; The code engraving device (11) is used for engraving codes on die-cast parts; The conveying line (13) is used for transporting die castings.

8. An aluminum alloy vacuum die-casting method, applied to the aluminum alloy vacuum die-casting system according to claim 6 or 7, characterized in that: The following steps are involved: S1, using the aluminum liquid generating device (2) to melt the aluminum alloy raw material, the melting temperature is controlled at 680-730° C., and then adding a solid metal modifier to the molten aluminum liquid for refining; S2, preheating the die-casting mold (1) to 120-220° C., and then spraying a mold release agent on the cavity surface of the die-casting mold (1) through a spray device (4); S3, vacuuming the mold cavity, conveying the refined aluminum liquid to the die-casting machine (3), and injecting the aluminum liquid into the mold cavity at a die-casting pressure of 40-80 MPa and a die-casting speed of 4-6 m / s, and cooling under pressure for 15-25 seconds; S4, opening the mold, cooling by cooling water spray for 6 to 16 seconds, and taking out the die casting by the take-out machine (12); S5. Perform integrity inspection, cooling, slag removal, gate removal, shaping, and code engraving on the die castings in sequence.

9. The aluminum alloy vacuum die-casting method according to claim 8, characterized in that: The cavity is evacuated, and the vacuum degree of the cavity is controlled to be ≤100mbar.

10. The aluminum alloy vacuum die-casting method according to claim 8, characterized in that: The ratio of the gate area of ​​the die-casting mold (1) to the injection punch area of ​​the die-casting machine (3) is 1:(6-16); and the pressure chamber filling degree of the die-casting machine (3) is 30%-50%.

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