A runner structure for die casting and a die casting method

Abstract

This invention relates to an ingate structure for die casting, comprising a gating body, a filtering unit, and a collecting unit, wherein the thickness of the gating body is [missing information]. h 1 = k × w A filtering unit is located at the front end of the gating system to prevent the pre-crystallized structure from flowing to the rear end of the gating system. A collecting unit is located at the front end of the gating system and upstream of the filtering unit to collect the pre-crystallized structure deposited due to the obstruction by the filtering unit. A die-casting method employs the above-mentioned ingate structure and a three-stage injection velocity. This invention can intercept and remove most of the coarse pre-crystallized dendrites; increase flow resistance, generating a high-shear flow field that forcibly mechanically breaks up residual pre-crystallization, achieving secondary homogenization of the structure; significantly reduce defects such as porosity and shrinkage caused by pre-crystallized structure in the casting body, improve the uniformity of the structure, enhance the internal quality and mechanical properties of the casting, increase the casting yield, and reduce production costs.

Description

Technical Field

[0001] This invention belongs to the field of die casting technology, specifically relating to an ingate structure and die casting method for die casting. Background Technology

[0002] Die casting technology, due to its advantages such as high production efficiency, high product dimensional accuracy, and low surface roughness, has been widely used in the production and manufacturing of automotive parts. With the rapid development of new energy vehicles, the performance requirements for die-cast aluminum alloy materials are becoming increasingly stringent. However, during the die casting process, due to the low speed of the pressure chamber, the alloy liquid preferentially nucleates and grows in the pressure chamber, resulting in the formation of coarse pre-crystallized structures in the microstructure. This causes inhomogeneity in the alloy's microstructure, which affects the alloy's fluidity and solidification shrinkage capacity, easily forming defects such as porosity, and cracks are prone to initiation at these locations, thus affecting the alloy's mechanical properties.

[0003] Currently, the main measures taken to reduce the hazards of pre-crystallized structures include: 1. Adding grain refiners: Adding grain refiners can round out coarse pre-crystallized structures. However, adding grain refiners can only improve the morphology of pre-crystallized structures and cannot effectively refine them. This has a limited effect on improving the mechanical properties of the alloy. Moreover, the grain refiners currently on the market contain expensive chemical elements such as Ti, Zr, Nd, and V, which greatly increases production costs.

[0004] See the patent with publication number CN116287883A, which discloses a die-casting aluminum-silicon alloy and a die-casting method for refining the pre-crystallized structure. The method involves adding commonly used refining elements such as Ti, Zr, Nd, and V to the alloy melt to refine the coarse pre-crystallized structure. However, these elements are expensive and tend to form coarse aluminum intermetallic compounds after entering the aluminum melt, resulting in an insignificant refining effect and harming the mechanical properties of the alloy.

[0005] 2. Optimize die casting process parameters: such as increasing the pouring temperature, increasing the injection speed, reducing the residence time of the alloy liquid in the pressure chamber and the cooling rate, etc. However, increasing the pouring temperature will lead to a coarse overall alloy structure, which is not conducive to improving mechanical properties. Process parameters such as injection speed need to work together, and there are many influencing factors, making process parameter control difficult.

[0006] 3. Optimize the gating system design: Based on the theory of molten alloy stopping flow under die casting conditions, namely the principle of pre-crystallized structure blocking the ingate, it is known that during the filling process, the pre-crystallized structure stays in the flow and forms a dendritic skeleton network. Under certain pressure conditions, the molten alloy continues to flow through the gaps in the dendritic skeleton network. Numerous studies have shown that the amount of pre-crystallized structure inside the casting is less the further away from the gate. Therefore, by reasonably optimizing the gating system design, the shear force generated by the molten alloy during the flow process can be used to break up the pre-crystallized structure, and the pre-crystallized structure can also be collected. This can greatly reduce the amount of pre-crystallized structure entering the mold cavity, improve the fluidity of the molten alloy, make the product structure more uniform, and reduce internal defects in the product.

[0007] The main purpose of existing ingates is to guide the molten metal, allowing it to enter the mold cavity smoothly and quickly, ensuring successful alloy filling. Although the cross-sectional area of ​​an ingate is generally smaller than that of a runner, increasing the shear force of the molten metal to some extent, the overall cross-sectional area of ​​the ingate is still relatively large to prevent pre-crystallized structures from clogging it. This limits its ability to break up pre-crystallized structures and effectively controls their entry into the mold cavity. Furthermore, to prevent pre-crystallized structures from clogging the ingate, the ingate height is still set relatively high, increasing the amount of molten metal used and raising production costs. In addition, for some castings with simpler structures, the molten metal flows directly into the gate after passing through the runner without an ingate transition. This abrupt change in the runner cross-sectional area can easily cause turbulence and air entrapment in the molten metal, leading to defects.

[0008] The patent with publication number CN110216263A discloses a flow channel for crushing and collecting pre-crystallized structures in a pressure chamber. It employs a bent structure to crush the pre-crystallized structure and a buffer bag to collect it. However, the sprue is located at the initial position of alloy flow, where the amount of pre-crystallized structure is the largest, and the pressure from the punch is significant. The amount of pre-crystallized structure collected is limited. When the molten alloy flows past the bent position, some pre-crystallized structure will break, but the flow rate at this position is low, resulting in less shear force and an unsatisfactory crushing effect. Furthermore, as the molten alloy continues to flow, the broken pre-crystallized structure will aggregate and grow, ultimately resulting in many large pre-crystallized structures still entering the mold cavity. Therefore, this patent has a probabilistic problem with pre-crystallization crushing, leading to low crushing efficiency. Additionally, the significant effect of the punch pressure at the sprue requires adjustment of die-casting process parameters, resulting in a narrow process window and significant operational difficulty. Summary of the Invention

[0009] One objective of this invention is to provide an ingate structure for die casting, particularly an ingate that effectively reduces the entry of coarse pre-crystallized structures from the pressure chamber into the casting cavity. This structure can effectively intercept and reduce the migration of coarse pre-crystallized structures from the pressure chamber into the casting cavity, thereby promoting a more uniform casting structure, significantly reducing the frequency of internal defects, and ultimately achieving a comprehensive improvement in the overall mechanical properties of the casting.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows: An ingate structure for die casting, comprising: The thickness of the gating body is: h 1 = k × w ,in: w For the thickness of the casting, k The coefficient is , and k =0.6-1; Filtering unit: The filtering unit is located at the front end of the gating body and is used to prevent the pre-crystallized structure from flowing to the rear end of the gating body; Collection unit: The collection unit is located at the front end of the main body of the gating system and upstream of the filter unit, and is used to collect the pre-crystallized structure deposited due to obstruction by the filter unit.

[0011] Preferably, in the above technical solution, the filtering unit includes a filtering channel, which divides the main body of the gating system into multiple gating segments, and the multiple gating segments are parallel to each other. The filtering channel is connected between the gating segments, and the filtering channel is perpendicular to or nearly perpendicular to the gating segments.

[0012] More preferably, the number of filter channels is m, the number of gating segments is m+1, and m≥1.

[0013] More preferably, the number m of the filter channels is 1 to 3, such as 1, 2, or 3.

[0014] More preferably, when multiple filter channels are provided, the multiple filter channels extend in the same direction so that the flow direction of the internal molten metal is consistent.

[0015] More preferably, the filter channel includes a first filter channel, and the length of the first filter channel is... h 2 ≥2 h 1 .

[0016] More preferably, the filter channel includes a first filter channel and a second filter channel, wherein the length of the first filter channel is... h 2 ≥2 h 1 The length of the second filter channel h 3 ≥2 h 1 .

[0017] More preferably, the gating system and the filter channel are integrally formed.

[0018] Preferably, in the above technical solution, the collection unit is disposed on at least one side of the filter unit, and the collection unit includes a collection channel and a collection trough. One end of the collection channel is connected to the main body of the pouring channel, and the other end of the collection channel is connected to the collection trough.

[0019] More preferably, the collection channel is perpendicular to the main body of the pouring channel.

[0020] More preferably, the cross-section of the collection trough is square.

[0021] Another object of the present invention is to provide a die casting method that, in conjunction with the aforementioned ingate structure, further improves the efficiency of pre-crystallized microstructure.

[0022] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A die casting method includes: preparing a die casting mold, wherein the mold cavity has the die casting ingate structure; injecting molten metal at an initial injection speed; switching to a secondary injection speed when the molten metal enters the ingate; and switching to a tertiary injection speed when the molten metal enters the ingate, until the molten metal fills the cavity of the die casting mold, wherein the initial injection speed is less than the secondary injection speed, and the secondary injection speed is less than the tertiary injection speed.

[0023] Preferably, the initial die-casting speed of the above technical solution is 0.15-0.3 m / s, such as 0.15 m / s, 0.2 m / s, 0.25 m / s, or 0.3 m / s; the secondary injection speed is 1.5 m / s-2.5 m / s, such as 1.5 m / s, 2.0 m / s, or 2.5 m / s; and the tertiary injection speed is 3 m / s-4.5 m / s, such as 3 m / s, 3.5 m / s, 3.8 m / s, 4 m / s, or 4.5 m / s.

[0024] More preferably, the initial die-casting speed is 0.15-0.2 m / s, the secondary injection speed is 2 m / s-2.5 m / s, and the tertiary injection speed is 3 m / s-3.8 m / s.

[0025] Preferably, the method further includes preheating the die-casting mold at a temperature of 180℃-250℃ and preparing a melt with a pouring temperature of 700℃-730℃.

[0026] The design principle of this invention is as follows: Precrystallized structures are formed when the molten metal, during its residence in the pressure chamber and in the slow injection stage, comes into contact with the cooler inner wall of the pressure chamber and the punch. This causes the melt to lose superheat, leading to premature nucleation and even growth. During the fast injection stage, the molten metal fills the mold cavity. The distribution pattern of precrystallized structures in castings is as follows: the greater the distance from the gate, the less precrystallized structure is present inside the casting. This is mainly because as the punch moves, it continuously peels away the solidified shell layer on the pressure chamber wall and causes it to accumulate at the front end of the punch. Therefore, the closer the melt is to the punch, the more precrystallized structure it contains, while the small amount of precrystallized structure that fails to accumulate near the punch is displaced by the flow of molten metal. Since the flow is concentrated near the gating, it can be inferred that the melt containing a small amount of pre-crystallized structure flows into the gating first. Furthermore, the melt containing a large amount of pre-crystallized structure, due to its higher density than normal aluminum melt, tends to deposit the pre-crystallized structure inside the gating as it flows, forming a dendritic framework network. The melt continues to flow through the gaps in this network. Additionally, the filling speed and shear rate are lower in castings far from the gating, preventing the pre-crystallized structure carried into the mold cavity by the fluid from advancing further. This results in a phenomenon where the amount of pre-crystallized structure decreases with increasing distance from the gating; that is, the pre-crystallized structure gradually decreases as the flow distance increases. Therefore, these phenomena indicate that for high-pressure die casting, the gating acts as a natural "sieve" for filtering pre-crystallized structure.

[0027] Due to its inherently small cross-sectional area, the ingate naturally creates a relatively high-pressure, high-shear-rate flow field environment, which has a significant obstacle and breakage potential for pre-crystallization. In addition, the typical multi-channel design can initially divert the pre-crystallization from the pressure chamber. By systematically improving the ingate structure, the melt flow state can be controlled more efficiently, thereby preventing coarse pre-crystallization from entering the cavity to the greatest extent.

[0028] This invention maximizes the performance of die casting by improving and optimizing the structure of the ingate and taking advantage of its natural advantages such as high flow rate and high shear rate.

[0029] First, the cross-sectional area of ​​the main body of the gating system of the present invention is much smaller than that of the traditional ingate. By reducing the thickness of the main body of the gating system, the cross-sectional area of ​​the ingate is further reduced, the shear rate of the alloy liquid is increased, and the flow resistance of the pre-crystallized structure is increased. This can effectively prevent the coarse pre-crystallized structure from flowing with the mainstream, reduce the entry of the pre-crystallized structure into the casting body, effectively break and disperse the pre-crystallized structure, inhibit the formation of new large-sized pre-crystallized structures, and significantly improve the surface and internal quality of the casting. While ensuring the smooth and rapid filling of the alloy liquid, it also reduces the generation of air entrapment.

[0030] Secondly, the present invention has a pre-crystallization filtration unit and a collection unit at the front end of the main body, which can effectively prevent the pre-crystallization from continuing to flow. When the alloy liquid flows through the filtration unit, the coarse pre-crystallized structure will continuously deposit at the bottom of the filtration unit and finally be collected by the collection unit. The pre-crystallized grains in the mainstream are screened and filtered, which can prevent the pre-crystallized structure from blocking the small ingate and ingating in advance and improve the fluidity of the alloy.

[0031] The single or continuous stepped structure also extends the length of the ingate, which is conducive to the accumulation and deposition of pre-crystallized structures in the alloy liquid in the ingate, reducing the amount of pre-crystallized material entering the casting cavity.

[0032] This invention utilizes a unified approach by thinning and extending the ingate structure, along with the auxiliary installation of a pre-crystallization filtration unit and a collection unit. This combined effect leverages the high-pressure fluid's high-shear refining properties while simultaneously addressing the issue of pre-crystallization blockage caused by a smaller ingate. This minimizes the intrusion of pre-crystallized material into the casting body, thereby improving the uniformity of the casting and ultimately enhancing its quality.

[0033] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: 1. This invention can deposit coarse pre-crystallized structures in the runner, intercept and remove most of the coarse pre-crystallized dendrites; increase flow resistance, generate a high shear flow field, and force mechanically break up the remaining pre-crystallized structures, transforming them from highly harmful coarse dendrites into fine, near-spherical particles, thus achieving secondary homogenization of the structure. 2. This invention can significantly reduce defects such as porosity and shrinkage caused by pre-crystallized structure in the casting body, improve the uniformity of structure, enhance the internal quality and mechanical properties of the casting, increase the casting yield, and reduce production costs. 3. This invention can be applied to existing molds, requiring only simple processing of existing molds. It is easy to operate and has low processing costs. It is applicable to a variety of alloys such as aluminum, magnesium and zinc in high-end high-pressure die castings and has a wide range of applications. It does not require the introduction of new chemical elements (refining elements), and provides a physical method for actively screening pre-crystallized structures, reducing the generation of new impurities and making it easy to control the chemical composition of the melt. Attached Figure Description

[0034] Appendix Figure 1 This is a schematic diagram of the inlet gating structure using a single stepped filter unit in this embodiment; Appendix Figure 2 For the appendix Figure 1 Schematic diagram of the AA section; Appendix Figure 3 For the appendix Figure 1 Schematic diagram of the BB section; Appendix Figure 4 This is a schematic diagram of the inner gating structure of the continuous stepped filter unit used in this embodiment; Appendix Figure 5 For the appendix Figure 4 Schematic diagram of the AA section; Appendix Figure 6 For the appendix Figure 4 Schematic diagram of the BB section; Appendix Figure 7 This is a diagram of a die-casting sample plate. Appendix Figure 8 This is a schematic diagram of a traditional ingate structure; Appendix Figure 9 For the appendix Figure 8 Schematic diagram of the AA section; Appendix Figure 10 For the appendix Figure 8 Schematic diagram of the BB section; Appendix Figure 11 Metallographic photograph of Al8SiMgMnCr alloy near the gate using a conventional ingate structure; Appendix Figure 12 Metallographic photograph of Al8SiMgMnCr alloy near the gate using the ingate structure of this embodiment; Appendix Figure 13 This is a schematic diagram of the stress-strain curves of tensile specimens near the gate of a conventional ingate and an ingate structure in this embodiment.

[0035] In the attached diagrams above: 1. Main body of the gating system; 10. Sections of the gating system; 2. Filter unit; 20. Filter channel; 200. First filter channel; 201. Second filter channel; 3. Collection unit; 30. Collection channel; 31. Collection slot. Detailed Implementation

[0036] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0038] Example 1: like Figures 1-6 The diagram shows an inner gating structure for die casting, including a gating body 1, a filtering unit 2, and a collecting unit 3. The structure of each unit is described in detail below.

[0039] The main body of the gating system 1 adopts a thin gating system with a small cross-sectional area, ensuring that the thickness of the main body of the gating system 1 is [missing information]. h1 = k × w ,in: w For the thickness of the casting, k The coefficient is , and k =0.6-1, preferably, k =0.6-0.8, such as 0.6~0.65, 0.65~0.7, 0.7~0.75, 0.75~0.8, etc., that is, the thickness of the main body 1 of the gating system is only 60%-100% of the thickness of the casting. On the one hand, by reducing the thickness of the main body 1 of the gating system, the cross-sectional area of ​​the main body 1 of the gating system is reduced, a high shear flow field is generated, and shear stress sufficient to overcome the interdendritic bonding force is applied to the pre-crystallized structure, breaking the pre-crystallized structure and realizing the secondary refinement of the structure, transforming it from coarse dendrites with stress concentration effect into finer near-spherical particles with less harm; on the other hand, by reducing the thickness of the main body 1 of the gating system, the flow resistance is increased, which hinders the continued flow of the pre-crystallized structure and reduces the probability that it will fill the key area of ​​the casting body with the mainstream, which can effectively reduce the total weight of the poured alloy liquid, improve the casting yield, and reduce production costs.

[0040] The filter unit 2 is located at the front end of the gating body 1 to prevent the pre-crystallized structure from flowing to the rear end of the gating body 1, thus preventing the gating body 1 from being thinned and causing it to become blocked prematurely.

[0041] In this embodiment, the filter unit 2 includes a filter channel 20, which divides the gating body 1 into multiple gating segments 10. These segments 10 are parallel to each other. The filter channel 20 connects the segments 10 and is perpendicular or nearly perpendicular to the segments 10. "Nearly perpendicular" can generally be considered as an angle of approximately ±85°. That is, the filter channel 20 and the gating segments 10 form an inner gating structure resembling a single step or a series of steps. Furthermore, the gating body 1 and the filter channel 20 can be integrally formed.

[0042] The quantity relationship between the filter channels 20 and the gating segments 10 satisfies the following: the number of filter channels 20 is m, the number of gating segments 10 is m+1, and m≥1. Preferably, the number of filter channels 20 m is 1~3, such as 1, 2, or 3. That is, the number of filter channels 20 should not exceed 3. In order to ensure smooth filling, the length of the gating body 1 can be appropriately extended. When multiple filter channels 20 are provided, the extension direction of multiple filter channels 20 is consistent so that the flow direction of the molten metal inside is consistent. On the one hand, by setting the filter unit 2, the flow direction of the melt can be changed from the original direction to a near-vertical direction. Since the density of the pre-crystallized structure is greater than that of the aluminum melt, its inertia is greater and it is difficult to follow the mainstream to complete the change, thus depositing and accumulating in the bottom area of ​​the back flow surface of the filter unit 2. On the other hand, by setting the filter unit 2, the length of the ingate structure is extended to a certain extent. As the flow distance increases, the amount of pre-crystallized structure gradually decreases. Extending the ingate structure allows the pre-crystallized structure to be deposited in the gating body 1 better, reducing the amount of pre-crystallized structure in the cavity.

[0043] In one implementation of this embodiment: as Figures 1-3 As shown: the main body 1 of the gating system has a rectangular cross-section, and the filter channel 20 includes a first filter channel 200, the length of which is... h 2 ≥2 h 1 At this point, a filter channel 20 is connected between the two gating segments 10, forming a single stepped inlet gating structure.

[0044] In another implementation of this embodiment: as Figures 4-6 As shown: The main body 1 of the gating system has a rectangular cross-section. The filter channel 20 includes a first filter channel 200 and a second filter channel 201. The length of the first filter channel is... h 2 ≥2 h 1 The length of the second filter channel h 3 ≥2 h 1At this time, the two filter channels 20 are connected between the three gating segments 10, forming a continuous stepped inner gating structure.

[0045] The collecting unit 3 is located at the front end of the gating body 1 and upstream of the filtering unit 2, and is used to collect pre-crystallized structures that have been deposited and accumulated due to obstruction by the filtering unit 2. The collecting unit 3 is located on at least one side of the filtering unit 2, preferably on both sides of the filtering unit 2. The collecting unit 3 collects a large amount of coarse pre-crystallized structures and works in conjunction with the filtering unit 2 to screen and filter the pre-crystallized structures in the melt, greatly reducing the possibility of pre-crystallized structures entering the mold cavity. This ensures that a large number of pre-crystallized dendrites in the gating body 1 are filtered and collected, eliminating concerns that the reduction in the size of the gating body 1 will cause premature blockage of the gating body 1 by pre-crystallization, thus guaranteeing the fluidity of the alloy liquid.

[0046] In this embodiment: the collection unit 3 includes a collection channel 30 and a collection trough 31. The collection channel 30 is perpendicular to the front end of the gating body 1 and is located upstream of the inlet of the filter channel 20. One end of the collection channel 30 is connected to the gating body 1, and the other end of the collection channel 30 is connected to the collection trough 31. The cross-section of the collection trough 31 is square. Compared with a structure with a circular cross-section, the pre-crystallized structure will not experience backflow.

[0047] This embodiment achieves automatic filtering of pre-crystallization using the ingate by reducing the thickness of the gating body 1 and coordinating the addition of a pre-crystallization filtering unit 2 and a collection unit 3 on the gating body 1. This maximizes the control of the flow state of the pre-crystallized structure, reduces the amount of pre-crystallized structure entering the casting body, and makes the casting structure uniform and improves its mechanical properties.

[0048] Example 2: A die-casting method includes: preparing a die-casting mold, wherein the mold cavity has an ingate structure as described in Example 1; installing the die-casting mold on a corresponding die-casting machine; preheating the mold by a die-casting mold temperature controller, wherein the mold preheating temperature is 180℃-250℃; and melting the melt to be cast using conventional alloy melting steps, wherein the melt pouring temperature is 700℃-730℃.

[0049] The molten metal is injected using an initial injection speed of 0.15-0.3 m / s, preferably 0.15-0.2 m / s. This is a slow injection speed, designed to prevent tumbling and surging of the molten metal and reduce air entrapment. When the molten metal enters the ingate, i.e., the entrance to the ingate structure, the injection speed is switched to a secondary injection speed of 1.5 m / s-2.5 m / s, preferably 2 m / s-2.5 m / s. Since the ingate structure in Example 1 uses a relatively thin main body and has one or more filter units, resulting in significant resistance, the injection speed is appropriately increased. Increasing the injection speed allows the melt to gain sufficient kinetic energy to move forward. Simultaneously, the melt also gains greater shear force, enabling better fragmentation of the pre-crystallized structure and reducing pressure on the pre-crystallized filtration and collection structure. This, combined with controlled injection speed, further enhances the effectiveness of the ingate structure and improves the efficiency of filtering the pre-crystallized structure. When the molten alloy flows to the ingate, i.e., the outlet of the ingate structure, the three-stage injection speed is switched. The three-stage injection speed is 3m / s-4.5m / s, preferably 3m / s-3.8m / s, allowing the melt to quickly fill the mold cavity. The casting pressure is generally 30MPa-50MPa.

[0050] The following describes in detail the preparation of the sample plate using the die-casting method of this embodiment.

[0051] This embodiment prepares a sample plate with an average thickness of 3 mm, including: Prepare a die-casting mold, and ensure that the internal gating structure of the mold cavity meets the following parameters: The main body of the gating system 1 satisfies: h 1 =0.8×3mm=2.4mm; Filter channel 20 only has the first filter channel 200, and the first filter channel 200 satisfies h 2 =2× h 1 =4.8mm.

[0052] The die-casting mold is installed on a die-casting machine with a clamping force of 400T. The mold is preheated by a die-casting mold temperature controller at a temperature of 200℃. Al8SiMgMnCr is prepared by weighing Al10Si master alloy, pure Mg ingot, Al10Mn master alloy, and Al10Cr master alloy in proportion. The mixture is then melted at 720℃. The melt is subjected to modification, refinement, and refining treatments in sequence to obtain the melt to be pressed. The pouring temperature is 700℃.

[0053] A three-stage injection speed is adopted. The initial injection speed is 0.2 m / s, which is the slow injection speed. When the molten alloy flows to the ingate, the second-stage injection speed is switched to the medium injection speed of 2.5 m / s. When the molten alloy flows to the ingate, the third-stage injection speed is switched to the fast injection speed of 3.8 m / s, and the casting pressure is 40 MPa.

[0054] The prepared test plate is as follows Figure 7 As shown.

[0055] Comparative example: like Figure 8 As shown: A traditional ingate structure is used, such as... Figure 9 As shown: Traditional ingates are thick runners with a gradually decreasing longitudinal cross-section, and the average thickness of the ingate is about 6mm. Figure 10 As shown: The cross-section of a traditional ingate is a trapezoidal structure that is wider at the top and narrower at the bottom.

[0056] The die-casting mold is installed on a die-casting machine with a clamping force of 400T. The mold is preheated by a die-casting mold temperature controller at a temperature of 200℃. Al8SiMgMnCr is prepared by weighing Al10Si master alloy, pure Mg ingot, Al10Mn master alloy, and Al10Cr master alloy in proportion. The mixture is then melted at 720℃. The melt is subjected to modification, refinement, and refining treatments in sequence to obtain the melt to be pressed. The pouring temperature is 700℃.

[0057] Injection is performed using an initial slow injection speed of 0.1-0.2 m / s. When the molten alloy flows to the inner gate, the injection speed is switched to a fast injection speed of 2.5-3 m / s.

[0058] like Figure 11 , 12 As shown: The number of coarse pre-crystallized structures in the near-gate metallographic photographs of Al8SiMgMnCr alloy cast using the ingate structure of this embodiment is significantly less than that in the near-gate metallographic photographs of alloys cast using the conventional ingate structure, and the segregation of eutectic Si is also significantly reduced.

[0059] like Figure 13 As shown: The mechanical properties of the Al8SiMgMnCr alloy near-gate specimen prepared using the traditional ingate structure are: tensile strength of 245 MPa, yield strength of 120 MPa, and elongation of about 5%; the mechanical properties of the Al8SiMgMnCr alloy near-gate specimen prepared using the ingate structure of this embodiment are: tensile strength of 269 MPa, yield strength of 129 MPa, and elongation of 8.4%.

[0060] The above data demonstrates that the ingate structure of this embodiment, through thinning and extending the ingate size, coordinating with a newly designed pre-crystallized filter unit, and supplemented by an upstream collection unit, works synergistically and in conjunction with a two-stage injection speed. Compared to traditional ingate structures, the tensile strength of the sample plate prepared by this structure is increased by more than 20 MPa, the yield strength by nearly 10 MPa, and the elongation by more than 3%. This effectively reduces the entry of coarse pre-crystallized structures from the pressure chamber into the mold cavity, reduces the number of coarse pre-crystallized structures inside the casting, and effectively improves the overall mechanical properties of the casting.

[0061] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. An ingate structure for die casting, characterized in that: include: The thickness of the gating body is: h 1 = k × w ,in: w For the thickness of the casting, k The coefficient is , and k =0.6-1; Filtering unit: The filtering unit is located at the front end of the gating body and is used to prevent the pre-crystallized structure from flowing to the rear end of the gating body; Collection unit: The collection unit is located at the front end of the main body of the gating system and upstream of the filter unit, and is used to collect the pre-crystallized structure deposited due to obstruction by the filter unit.

2. The die-casting ingate structure according to claim 1, characterized in that: The filtering unit includes a filtering channel that divides the main body of the gating system into multiple gating segments, and the multiple gating segments are parallel to each other. The filtering channel is connected between the gating segments and is perpendicular to or nearly perpendicular to the gating segments.

3. The die-casting ingate structure according to claim 2, characterized in that: The number of filter channels is m, the number of gating segments is m+1, and m≥1.

4. The die-casting ingate structure according to claim 3, characterized in that: The number m of the filter channels is 1 to 3.

5. The die-casting ingate structure according to claim 2, characterized in that: When multiple filter channels are provided, the extension direction of the multiple filter channels is consistent so that the flow direction of the molten metal inside them is consistent.

6. The die-casting ingate structure according to claim 2, characterized in that: The filter channel includes a first filter channel, the length of which is... h 2 ≥2 h 1 .

7. The die-casting ingate structure according to claim 2, characterized in that: The filter channel includes a first filter channel and a second filter channel, wherein the length of the first filter channel is... h 2 ≥2 h 1 The length of the second filter channel h 3 ≥2 h 1 .

8. The die-casting ingate structure according to claim 1, characterized in that: The collection unit is disposed on at least one side of the filter unit. The collection unit includes a collection channel and a collection trough. One end of the collection channel is connected to the main body of the pouring channel, and the other end of the collection channel is connected to the collection trough. The collection channel is perpendicular to the main body of the pouring channel; The cross-section of the collection tank is square.

9. A die-casting method, characterized in that: include: Prepare a die-casting mold, wherein the mold cavity has the die-casting ingate structure as described in any one of claims 1 to 8. The initial injection speed is used to inject the melt. When the melt enters the ingate, the injection speed is switched to the secondary injection speed. When the melt enters the ingate, the injection speed is switched to the tertiary injection speed until the melt fills the cavity of the die-casting mold. The initial injection speed is less than the secondary injection speed, and the secondary injection speed is less than the tertiary injection speed.

10. The die-casting method according to claim 9, characterized in that: The initial die-casting speed is 0.15-0.3 m / s, the secondary injection speed is 1.5 m / s-2.5 m / s, and the tertiary injection speed is 3 m / s-4.5 m / s.

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