An integrated salt core forming process for a cast aluminum alloy structural component of a vehicle caliper

Abstract

This invention relates to the field of aluminum alloy casting technology, and discloses an integrated salt core forming process for casting aluminum alloy structural parts for automotive calipers. The process includes obtaining molten aluminum alloy; preparing a full-salt-based core using salt raw materials; preheating the full-salt-based core, upper mold assembly, and lower mold assembly; progressively increasing the heating temperature of the full-salt-based core; placing the full-salt-based core into a casting cavity and pouring in molten aluminum alloy; removing the intermediate wedge block and fixing block after casting; separating the mold and removing the casting for cooling; and finishing and cleaning the casting before heat treatment. This invention reduces assembly process complexity and improves core structure forming accuracy by preparing an integrated full-salt-based core; improves structural strength through progressive heating of the full-salt-based core; and allows for quick and non-destructive removal of the casting by sequentially removing the intermediate wedge block, fixing block, and upper cover plate, avoiding mold damage, enabling reuse of the upper mold assembly, and reducing forming process complexity and cost.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy casting technology, specifically to an integrated salt core forming process for cast aluminum alloy structural parts for automotive calipers. Background Technology

[0002] As a key component of the vehicle braking system, automotive calipers face increasingly complex structures and demanding performance requirements as the industry develops. Fixed automotive calipers have a precise internal structure, typically including a cylinder space for piston movement and internal hydraulic passages connecting the two cylinders. These internal hydraulic passages need to be integrally formed during the casting process to ensure smooth brake fluid transmission under pressure, thereby preventing leakage and guaranteeing rapid braking response. Currently, automotive caliper production primarily utilizes gravity casting. In traditional techniques, the forming of internal hydraulic passages and cylinder space mainly relies on sand cores, such as using coated sand to pre-form the caliper's internal cavities. However, sand core forming processes have significant drawbacks in practical applications: poor surface quality: due to the large particle size and limited compactness of the sand core material itself, the cast hydraulic passages have a high surface roughness, increasing fluid flow resistance.

[0003] To address these issues, the industry has begun exploring solutions using salt cores instead of sand cores. For example, CN117680618A discloses a salt core forming process for caliper oil passages, utilizing the low gas emission and small particle size of the salt core material to reduce the surface roughness of the inner wall of the oil passages and improve the internal quality of the casting. While the application of salt cores improves surface precision and cleaning efficiency, challenges remain in the casting of high-performance integrated calipers: low structural integration: existing salt core structures often require multiple pieces to be assembled, which not only increases the assembly complexity of the core structure but also makes it difficult to guarantee high-precision positioning, easily leading to assembly errors; contradiction between positioning and demolding: as the internal oil passages of calipers become more complex and integrated, the stable positioning of large-size integrated salt cores within the mold becomes extremely difficult. During the casting process, the molten aluminum will scour and buoyant the complex salt core structure. Traditional mold structures often lead to difficulties in demolding after casting when fixing such salt cores, and forced demolding can easily cause physical damage to the precision integrated casting, increasing the complexity of the forming process and production costs. Therefore, how to design a caliper casting process that can achieve high-precision integrated molding, ensure stable positioning, and achieve non-destructive demolding is a technical problem that urgently needs to be solved in the current automotive brake component manufacturing field. Summary of the Invention

[0004] This invention addresses the challenge of designing a caliper casting process that achieves both high-precision integrated molding and stable positioning with non-destructive demolding. It provides an integrated salt-core molding process for aluminum alloy structural parts used in automotive caliper casting. The specific technical solution is as follows:

[0005] An integrated salt-core forming process for cast aluminum alloy structural parts of automotive calipers includes: heating aluminum alloy raw materials to obtain molten aluminum alloy; integrally preparing a full-salt-based core using salt raw materials, the full-salt-based core including a lower cylinder and oil passages located at both ends of the lower cylinder, with both ends of the oil passages intersecting with both ends of the lower cylinder; preheating the full-salt-based core, upper mold assembly, and lower mold assembly; and gradually increasing the heating temperature and holding it during the heating process, with the heating temperature range being 350℃-550℃, the heating time being 85min-100min, and the holding time being 10min-15min. The process of increasing the heating temperature includes: setting a three-stage heating temperature increase; setting the heating time according to the increase in heating temperature so that the heating rate decreases step by step; placing the preheated full-base core into the casting cavity formed by the merging of the upper mold assembly and the lower mold assembly, and pouring molten aluminum alloy from the lower mold assembly; the upper mold assembly includes an upper fixing component, which includes a separable intermediate wedge block and a fixing block; after casting and molding, the intermediate wedge block and the fixing block are removed in sequence, and the upper mold assembly and the lower mold assembly are separated to remove the casting for cooling; the cooled casting is trimmed and cleaned, and then heat-treated to complete the casting production.

[0006] Preferably, in step two, the all-basic core further includes several piston ends respectively disposed on both sides of the lower cylinder, the piston ends intersecting with the two ends of the oil passage to form an annular oil passage.

[0007] Preferably, the oil passage includes a beveled section intersecting the piston end, an arc-shaped section connected to the beveled section, and a bend section connected to the arc-shaped section, wherein the bend section has a U-shaped structure.

[0008] Preferably, the piston end includes an intermediate post communicating with the lower cylinder body. The end of the intermediate post near the lower cylinder body forms an annular rib, and the end of the intermediate post away from the lower cylinder body forms a connecting rib. The connecting rib communicates with both ends of the inclined section. The connecting ribs on the same side of the lower cylinder body are all connected through the connecting post to form an annular oil passage that connects the oil passage, the connecting rib, and the connecting post.

[0009] Preferably, the bottom of the fixing block is formed with a number of semi-circular holes, the bottom side of the middle wedge block is the bottom end face of the semi-circular hole to form a semi-circular groove, and the annular ribs are fitted into the semi-circular grooves to form a positioning structure.

[0010] Preferably, in step three, the upper mold assembly further includes an upper cover plate, the upper cover plate forming a through hole to embed the fixing block, the middle wedge block being embedded between the fixing blocks through a concave-convex structure, the side of the fixing block away from the middle wedge block forming a convex edge to connect with the upper cover plate, and the top of the middle wedge block forming a bolt connection structure with the tops of the fixing blocks on both sides.

[0011] When the fixing block and the intermediate wedge block are fixed in the through hole of the upper cover plate, the bottom of the upper mold assembly forms the upper half of the casting cavity, and the top of the lower mold assembly forms the lower half of the casting cavity.

[0012] Preferably, in step three, the lower mold assembly includes:

[0013] The lower base plate is connected to the upper cover plate, and the connection between the lower base plate and the upper cover plate forms a casting cavity to contain the molten aluminum alloy;

[0014] A pouring channel is formed on the top surface of the bottom plate, and the pouring channel forms an injection port on the side of the bottom plate.

[0015] Preferably, in step four, the cooling temperature range of the casting is 320℃-420℃, and the cooling time range is 200s-420s.

[0016] Preferably, in step five, the heat treatment includes:

[0017] The casting is subjected to solution treatment at a heating temperature of 530℃-550℃ and held for 5 hours-8.5 hours.

[0018] Control the solution transfer time to be less than or equal to 30 seconds;

[0019] The castings are subjected to aging treatment at a temperature of 170℃-200℃ for 3-6 hours.

[0020] As can be seen from the above technical solution, the present invention has the following beneficial effects:

[0021] This invention reduces the complexity of the core assembly process by preparing an integral all-salt-based core, while improving the molding accuracy of the core structure. Secondly, the all-salt-based core is fixed and positioned by independently removable fixing blocks and intermediate wedge blocks, which are combined with the lower mold assembly to form a casting cavity for pouring molten aluminum alloy. This allows the casting to be quickly and non-destructively removed by sequentially removing the intermediate wedge block, fixing block, and upper cover plate, avoiding damage to the mold for demolding. This enables the upper mold assembly to be reused, reducing the complexity of the molding process and lowering production costs. Attached Figure Description

[0022] Figure 1 This is a flowchart of an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the structure of a fully basic core;

[0024] Figure 3 This is a schematic diagram of the combined upper and lower mold components;

[0025] Figure 4 This is a structural schematic diagram of the upper fixing component;

[0026] Figure 5 This is a schematic diagram of the casting structure;

[0027] Figure 6 a and Figure 6 b shows the temperature field distribution of the casting from different perspectives after casting, obtained through CAE simulation analysis;

[0028] Figure 7 a and Figure 7 b is a diagram of air entrapment distribution obtained from CAE simulation analysis of the casting from different perspectives after casting is completed;

[0029] Figure 8 a and Figure 8 b is a diagram showing the distribution of oxide slag from different angles after casting, obtained through CAE simulation analysis.

[0030] In the diagram: 1. Upper mold assembly; 11. Upper fixing component; 111. Middle wedge block; 112. Fixing block; 113. Protruding edge; 114. Semicircular groove; 115. Bolt fixing component; 12. Upper cover plate; 2. Full-salt core; 21. Lower cylinder body; 22. Piston end; 221. Middle column; 222. Annular rib; 223. Connecting rib; 224. Connecting column; 23. Oil passage; 231. Inclined section; 232. Arc section; 233. Bend section; 3. Lower mold assembly; 31. Lower base plate; 32. Gating channel; 33. Injection port. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] In the description of the embodiments of the present invention, it should be noted that the terms "inner", "outer", "upper", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and 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 limiting the present invention.

[0033] like Figure 5 As shown, the casting in this embodiment is a U-shaped structure with an open end at the top for embedding the brake pad and a piston end 22 on its sidewall for embedding the piston to brake the brake pad.

[0034] like Figure 1As shown, this embodiment is an integrated salt core forming process for cast aluminum alloy structural parts of automotive calipers. Its features include: Step 1: Heating the aluminum alloy raw material to obtain molten aluminum alloy. Specifically, a furnace or heating container is used to heat the aluminum alloy, whose melting point is typically 480℃-660℃, melting it and maintaining the molten aluminum alloy to facilitate subsequent casting.

[0035] like Figure 2 As shown, step two: use salt raw materials to prepare a full salt-based core 2. The full salt-based core 2 includes a lower cylinder 21 and oil passages 23 set at both ends of the lower cylinder 21. Both ends of the oil passages 23 intersect with both ends of the lower cylinder 21 respectively. The full salt-based core 2, the upper mold assembly 1 and the lower mold assembly 3 are preheated.

[0036] Specifically, a one-piece all-basic core 2 is prepared using a salt-based composite material. This core includes a lower cylinder 21 corresponding to the caliper cylinder position, with oil passages 23 formed at both ends along its length. The two ends of the oil passages 23 are connected to the two ends of the lower cylinder 21, forming a one-piece structure. This avoids the need for assembling multiple sand cores, eliminating assembly errors. Furthermore, during the pouring of molten aluminum alloy, the oil passages 23 do not have stepped cross-sections, improving the fluidity of the molten aluminum alloy. Simultaneously, it reduces the hydraulic resistance of the caliper oil passages 23, increasing the caliper's braking response time. This avoids the impact of errors during the assembly of separate structures on the structural accuracy of the casting. It also completely eliminates the seam burrs formed at the joints of traditional multi-sand cores, a significant safety hazard in internal oil circuits. Consequently, when the molten aluminum alloy cools and contracts, the stress distribution is more uniform, preventing micro-cracks at oil circuit bends or joints, improving the caliper's fatigue life, and ultimately resulting in a high-precision, high-quality, and long-life caliper.

[0037] Secondly, a heating device is used to raise the temperature of the all-salt-based core 2 to near the temperature of the aluminum alloy liquid. This prevents the low-temperature all-salt-based core 2 from generating huge thermal stress under the impact of the high-temperature aluminum alloy liquid, which could lead to cracking or even bursting. By preheating the all-salt-based core 2, the temperature difference between the all-salt-based core 2 and the aluminum alloy liquid can be significantly reduced, allowing the all-salt-based core 2 to be heated gently and evenly when in contact with the aluminum alloy liquid, effectively eliminating thermal shock and preventing cracking.

[0038] like Figure 3 and Figure 4As shown, step three involves placing the preheated full-base core 2 into the casting cavity formed by the merging of the upper mold assembly 1 and the lower mold assembly 3, and then pouring molten aluminum alloy from the lower mold assembly 3. The upper mold assembly 1 includes an upper fixing member 11, which includes a separable intermediate wedge block 111 and a fixing block 112. Specifically, after the upper mold assembly 1 and the lower mold assembly 3 are merged, their interiors merge to form a casting cavity to hold the preheated full-base core 2. The opening end of the casting cavity is formed at the lower mold assembly 3 to prevent the full-base core 2 from being impacted by gravity during the injection of molten aluminum alloy, thereby preventing deformation of the casting. Secondly, the upper fixing member 11 corresponds to the open end of the caliper. It includes a middle wedge block 111 located in the middle position and fixing blocks 112 located on both sides of the middle wedge block 111. A sliding concave-convex structure is formed between the middle wedge block 111 and the fixing blocks 112, so that after the fixing blocks 112 are fixed relative to the full salt core 2, the middle wedge block 111 is embedded in the slide rail formed by the concave structure of the fixing blocks 112. It slides along the slide rail so that the two become one, and both are located at the top of the full salt core 2 for positioning and fixing, thereby forming the open end of the casting.

[0039] Secondly, in step four: after casting, the intermediate wedge block 111 and the fixing block 112 are removed sequentially to separate the upper mold assembly 1 and the lower mold assembly 3, allowing the casting to be removed for cooling. Specifically, the upper mold assembly 1 includes an upper cover plate 12 bolted to the lower mold assembly 3. The upper cover plate 12 is bolted to the fixing block 112. After the aluminum alloy liquid is poured into the casting cavity, it undergoes initial cooling to form a blank. Then, the intermediate wedge block 111 is moved away from the fixing block 112 along the slide rail, the fixing block 112 is separated from the upper cover plate 12, and the upper cover plate 12 is separated from the lower mold assembly 3. The upper mold assembly 1 and the lower mold assembly 3 are then separated in multiple steps, thus completely and without damage separating the upper mold assembly 1 from the casting, improving production quality, avoiding subsequent repairs, and reducing the complexity of the molding process.

[0040] Secondly, step five: trim and clean the cooled casting, and perform heat treatment on the casting to complete the casting production. Specifically, this embodiment can simultaneously cast two castings. After removing the castings, the riser and gating channel 32 are cut off to obtain two independent castings. Then, both are deburred and shot-blasted. After that, the castings are heat-treated to improve their structural strength and toughness, thereby meeting the strength requirements of automotive calipers. Then, the oil passages 23 inside the castings are flushed to remove all the residue of the full-base core 2 inside, thereby obtaining the finished automotive caliper.

[0041] Further, in step two, the heating temperature is gradually increased and held during the heating of the full-base core 2. The heating temperature range is 350℃-550℃, the heating time is 85min-100min, and the holding time is 10min-15min. The gradual increase in heating temperature includes: setting three stages of temperature increase; and setting the heating time according to the increase in heating temperature so that the heating rate gradually decreases. Specifically, a common heating device (such as an oven) is used to preheat the full-base core 2 using a gradual heating method. A preferred embodiment of the gradual increase in heating temperature is as follows: in the first stage, the full-base core 2 is heated to 400℃ for 25min; in the second stage, the full-base core 2 is heated to 500℃ for 25min; and in the third stage, the full-base core 2 is heated to 550℃ for 25min. In the first stage, the temperature is increased from room temperature to 400℃, and the heating rate is... The heating rate is greater than 4℃ / min in the first stage, 4℃ / min in the second stage, and 2℃ / min in the third stage. The heating rate decreases progressively in each of the three stages, resulting in a rapid initial temperature rise in the full-salt-based core 2, followed by a gradual horizontalization. This allows for rapid preheating in the early stages, reducing preheating time, and gradually releasing internal stress, preventing cracks due to excessive stress, improving heating uniformity, and further enhancing structural strength to avoid damage during aluminum alloy pouring. Secondly, after preheating the full-salt-based core 2, it is kept at 550℃ in an insulated chamber for 15 minutes to prevent a temperature drop during subsequent aluminum alloy pouring and reduce thermal stress.

[0042] Furthermore, in step two, the all-salt-based core 2 also includes several piston ends 22 respectively disposed on both sides of the lower cylinder 21. The piston ends 22 intersect with both ends of the oil passage 23 to form an annular oil passage. Specifically, piston ends 22 are formed on both sides of the lower cylinder 21 along its length. The piston ends 22 correspond to the piston parts of the automotive caliper and are connected to the oil passage 23, allowing hydraulic oil to enter the piston ends 22 through the oil passage 23 to drive the piston movement of the automotive caliper. Secondly, the all-salt-based core 2 includes four piston ends 22. The piston ends 22 on the same side are connected, and the piston ends 22 on different sides are connected through the oil passage 23, ensuring that all four piston ends 22 are connected. This allows the hydraulic oil to apply pressure to the pistons evenly through the oil passage 23, enabling the four pistons to brake the brake discs evenly and improving the braking effect. Among them, since the all-salt core 2 is an integral structure, and the oil passage 23 and piston end 22 are an integral structure, the connection between the two is smooth, avoiding the undulations at the connection between the oil passage 23 and piston end 22 which are spliced ​​later, thus slowing down the flow speed of hydraulic oil at this point, increasing its flow resistance, and reducing the piston response time.

[0043] Furthermore, the oil passage 23 includes a beveled section 231 intersecting the piston end 22, an arc-shaped section 232 connected to the beveled section 231, and a bent section 233 connected to the arc-shaped section 232. The bent section 233 has a U-shaped structure. Specifically, the oil passages 23 on the same side of the lower cylinder block 21 are all three-section structures. The first section consists of two beveled sections 231 that are directly connected to the piston end 22. The beveled sections 231 are inclined upwards (vertically). Figure 2 (The direction of the top surface of the cylinder 21 is perpendicular to the middle), and the other end of both is connected to the arc section 232. The arc section 232 forms a downward curved arc. The other end of the two arc sections 232 is connected to one end of the bent pipe section 233. The bent pipe section 233 has a U-shaped structure, which reverses the flow direction of hydraulic oil in the oil passage 23, so that the oil passage 23 can connect to the piston end 22 on different sides.

[0044] Furthermore, the piston end 22 includes an intermediate post 221 that communicates with the lower cylinder 21. The end of the intermediate post 221 near the lower cylinder 21 forms an annular rib 222, and the end of the intermediate post 221 away from the lower cylinder 21 forms a connecting rib 223. The connecting rib 223 communicates with both ends of the inclined section 231. The connecting ribs 223 on the same side of the lower cylinder 21 are all connected through the connecting post 224 to form an annular oil passage that connects the oil passage 23, the connecting rib 223, and the connecting post 224.

[0045] Specifically, two intermediate pillars 221 are formed at both ends of the lower cylinder 21 in the vertical length direction. The intermediate pillars 221 at the same end are parallel to each other, and the axes of the intermediate pillars 221 at different ends coincide. The axes of the intermediate pillars 221 are perpendicular to the two end faces of the lower cylinder 21 in the vertical length direction to form a cavity for placing the piston rings of the car caliper, and the piston rings move along the axis direction perpendicular to the intermediate pillars 221. Secondly, an annular rib 222 is formed at the intersection of the intermediate column 221 and the lower cylinder 21. Its diameter is larger than that of the intermediate column 221, thus forming a semi-annular groove in the casting. The intermediate column 221 is connected to the inclined section 231 of the oil passage 23 through the connecting rib 223. The diameter of the connecting rib 223 is larger than that of the intermediate column 221, forming an annular groove in the casting. This connects the oil passage of the casting formed by the oil passage 23 and the cavity formed by the intermediate column 221. At the same time, the connecting rib 223 on the same side is connected through the connecting column 224. Thus, the annular groove of the casting is connected through the oil passage formed by the connecting column 224. This connects the oil passage 23, the connecting rib 223 and the connecting column 224 of the all-salt core 2. Thus, the casting forms an annular oil passage by the oil passage 23, the connecting rib 223 and the connecting column 224, thereby improving the uniformity of hydraulic oil distribution.

[0046] Furthermore, the bottom of the fixing block 112 is formed with several semi-circular holes, and the bottom side of the middle wedge block 111 is the bottom end face of the semi-circular holes to form a semi-circular groove 114. The annular rib 222 is fitted into the semi-circular groove 114 to form a positioning structure. Specifically, the fixing blocks 112 are located on both sides of the middle wedge block 111, and their bottoms are formed with two semi-circular holes respectively. After the fixing blocks 112 and the middle wedge block 111 are engaged, the middle wedge block 111 can act as the bottom of the semi-circular hole, making it a semi-circular groove 114. Secondly, after the all-salt-based core 2 is placed into the casting cavity formed by the combined upper mold assembly 1 and lower mold assembly 3, the fixing block 112 and the intermediate wedge block 111 are respectively combined with the all-salt-based core 2. The annular ribs 222 of the all-salt-based core 2 are fitted into the semi-circular grooves 114 one by one, forming a positioning structure for the all-salt-based core 2. This prevents the all-salt-based core 2 from shifting position during the pouring of aluminum alloy liquid, improving the structural accuracy of the casting. At the same time, the all-salt-based core 2 is an integral structure, further avoiding the appearance of steps on the splicing surface due to splicing, thus improving the structural quality of the casting. Secondly, the bottoms of the fixing block 112 and the intermediate wedge block 111 are flush with the top of the lower cylinder 21, preventing the aluminum alloy liquid from entering the interior of the lower cylinder 21 through the top, which would affect the casting quality and cause waste of aluminum alloy liquid.

[0047] Furthermore, in step three, the upper mold assembly 1 also includes an upper cover plate 12, which forms a through hole to embed the fixing block 112. The middle wedge block 111 is embedded between the fixing blocks 112 through a concave-convex structure. The side of the fixing block 112 away from the middle wedge block 111 forms a protruding edge 113 to connect with the upper cover plate 12. The top of the middle wedge block 111 and the tops of the fixing blocks 112 on both sides form a bolt connection structure. When the fixing block 112 and the middle wedge block 111 are fixed in the through hole of the upper cover plate 12, the bottom of the upper mold assembly 1 forms the upper half of the casting cavity, and the top of the lower mold assembly 3 forms the lower half of the casting cavity.

[0048] Specifically, the fixing block 112 has a 7-shaped structure with a protruding edge 113 on one side of its top. This protruding edge 113 is bolted to the upper cover plate 12 for fixation, making the fixing block 112 a detachable fixing structure relative to the upper cover plate 12, which facilitates the removal of the casting after pouring. Secondly, a U-shaped groove is formed on the other side of the fixing block 112, and T-shaped grooves are formed on both sides of the middle wedge block 111 to embed into the U-shaped groove of the fixing block 112, forming a concave-convex structure. This allows the middle wedge block 111 to be embedded in the groove and connected to the fixing block 112 through the groove. Furthermore, threaded holes are formed on the top of both the middle wedge block 111 and the fixing block 112. When the middle wedge block 111 moves into place along the groove of the fixing block 112, bolts and connecting plates are used to fix the tops of the two together to form a bolted connection structure, thereby providing stable positioning for the all-salt core 2 and avoiding the impact of thermal expansion and contraction on the positioning accuracy of the all-salt core 2. First, the upper cover plate 12 and the lower mold assembly 3 are fixedly connected by bolts. Then, the fixing block 112 is embedded into the upper cover plate 12. Next, the middle wedge block 111 is embedded into the gap between the fixing blocks 112. Finally, the fixing block 112, the middle wedge block 111 and the upper cover plate 12 are locked and fixed by bolts and connecting plates.

[0049] Secondly, the fixed upper cover plate 12, fixing block 112, and intermediate wedge block 111 form a complete upper mold assembly 1, which can be disassembled into multiple parts. The upper mold assembly 1 is made of metal, and the bottom of the complete upper mold assembly 1 forms the upper half of the casting cavity. When the aluminum alloy liquid is poured into it, the fixing block 112 and intermediate wedge block 111 correspond to the opening end of the casting, that is, the opening end of the car caliper that is inserted into the brake disc. The cavity between the upper cover plate 12 and the sides of the fixing block 112 and intermediate wedge block 111 corresponds to the side wall of the upper half of the casting, that is, the side wall of the upper half of the car caliper. When removing the casting, only the intermediate wedge block 111, fixing block 112 and upper cover plate 12 need to be removed in sequence to remove it without affecting the casting. This allows the upper mold assembly 1 to be reused, reducing molding costs and reducing the complexity of the molding process.

[0050] Furthermore, in step three, the lower mold assembly 3 includes: a lower base plate 31 connected to the upper cover plate 12, the lower base plate 31 and the upper cover plate 12 being connected to form a casting cavity to contain molten aluminum alloy; a pouring channel 32 formed on the top surface of the lower base plate 31, the pouring channel 32 forming an injection port 33 on the side of the lower base plate 31.

[0051] Specifically, the top of the lower base plate 31 and the bottom of the upper cover plate 12 each form a partial casting cavity. After the upper cover plate 12, lower base plate 31, fixing block 112, and intermediate wedge block 111 are fixed, the casting cavity is spliced ​​into one piece to hold the all-salt-based core 2 and the aluminum alloy liquid. Next, the side of the lower base plate 31 forms an injection port 33 for the aluminum alloy liquid. The injection port 33 is connected to the pouring channel 32, which is connected to the casting cavity. This allows the aluminum alloy liquid to enter the casting cavity sequentially through the injection port 33 and the pouring channel 32, thereby encapsulating the preheated all-salt-based core 2 to form the casting.

[0052] Furthermore, in step four, the cooling temperature range of the casting is 320℃-420℃, and the cooling time range is 200s-420s.

[0053] Specifically, the casting is placed in a low-temperature environment for cooling treatment. The temperature of the low-temperature environment can be adapted to different cooling temperatures depending on the volume, wall thickness and weight of the casting, such as 320℃ and 400℃. In this embodiment, 400℃ is preferred, which can shorten the cooling and forming time of the casting and also avoid the casting cooling too quickly and affecting the forming quality of the automotive caliper. When the low-temperature environment is below 320℃, the casting cools too quickly and causes stress concentration. When the low-temperature environment is above 420℃, the cooling and forming time of the casting is too long and affects the forming efficiency. Secondly, the cooling time of the casting in a low-temperature environment varies depending on the volume, wall thickness, and weight of the casting, such as 200s and 300s. In this embodiment, 300s is preferred, which can ensure that the casting is completely cooled, ensure structural strength, and shorten the casting cooling and forming time, thereby improving forming efficiency. When the cooling time is less than 200s, there is an incomplete cooling inside the casting. When it is processed in the next step, its interior is cooled at room temperature, causing stress concentration inside. When the cooling time is greater than 420s, the forming time becomes too long and the forming efficiency decreases.

[0054] Furthermore, in step five, the heat treatment includes: performing a solution treatment on the casting at a heating temperature of 530℃-550℃ and holding it for 5 hours-8.5 hours; controlling the solution transfer time to be less than or equal to 30 seconds; and performing an aging treatment on the casting at an aging temperature of 170℃-200℃ and holding it for 3 hours-6 hours.

[0055] Specifically, heat treatment includes solution treatment and aging treatment. Solution treatment, to obtain a homogeneous supersaturated solid solution, involves placing the cleaned aluminum alloy casting into a heat treatment furnace, heating it to 530℃-550℃, and holding it for 5-8.5 hours. This allows the casting to obtain a supersaturated solid solution, improving its mechanical properties. The heating temperatures are 530℃, 540℃, and 550℃, with a preferred holding time of 7 hours. Next, the casting is removed from the solution treatment furnace, with the transfer time controlled within 30 seconds to ensure optimal performance, preferably within 15 seconds. This prevents premature precipitation of alloying elements due to air cooling during transfer, which could disrupt the supersaturated solid solution state and impair subsequent aging strengthening and final toughness. Secondly, the casting undergoes aging treatment to induce the precipitation of fine strengthening phases from the supersaturated solid solution, thereby achieving strengthening. Specifically, the transferred casting is placed in an aging furnace and heated to 170℃-200℃, preferably 180℃, and held for 3-6 hours, preferably 5 hours. Compared to the conventional aging treatment temperature of 160℃-175℃ and holding time of 6-7.5 hours, this significantly improves the diffusion ability of alloying elements, promoting the precipitation of strengthening phases at a faster rate and with smaller sizes. This more dispersed distribution of strengthening phases more effectively hinders casting deformation, thus enhancing the casting's strength. Higher yield strength, tensile strength, and hardness are achieved. For castings with large wall thickness variations, such as calipers, higher aging temperatures can effectively ensure heat transfer to the core of the casting, making precipitation strengthening more synchronous and uniform across the entire casting cross-section, avoiding the problem of lower performance in the core due to insufficient temperature. Secondly, while increasing the aging temperature may slightly reduce toughness, by shortening the holding time to 3-6 hours, coarsening of the strengthening phase (over-aging) caused by prolonged holding is avoided, thus balancing the improvement of strength and the guarantee of toughness, meeting the impact resistance requirements of automotive calipers.

[0056] Figure 6 a and Figure 6 b shows two angle views of the casting cavity. Figure 6 a and Figure 6 In section b, the colors represent the surface temperature of the casting in the casting cavity 9.941 seconds after pouring. The pouring temperature of the aluminum alloy liquid is 740℃, and the liquidus temperature is 570℃. The liquidus temperature refers to the lowest temperature at which the aluminum alloy is completely melted into a liquid state. In this embodiment, the overall temperature field is higher than the liquidus temperature, and the aluminum alloy liquid temperature is reasonably designed to avoid local cooling and forming of the aluminum alloy liquid during the pouring process.

[0057] Figure 7 a and Figure 7 b shows two angle views of the casting cavity. Figure 7 a and Figure 7The colors in b represent the gas volume ratio of the unit grid after 9.941 seconds following pouring. During the pouring process, the gas in the casting cavity flows to the outside, resulting in no porosity after the casting cools down, especially at the connection of the two ends of the oil passage, thus improving the structural strength of the casting.

[0058] Figure 8 a and Figure 8 b shows two angle views of the casting cavity. Figure 8 a and Figure 8 In figure b, the colors represent the concentration of oxide slag after 9.941 seconds following pouring. This indicates the risk index of oxide slag formation. The higher the value, the darker the color. Darker colors indicate a higher risk of oxide slag formation. The darker areas in the figure are distributed in the pouring channel to prevent oxide slag from forming inside the casting.

[0059] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0060] The technologies, shapes, and structures not described in detail in this invention are all known technologies.

Claims

1. A one-piece salt core forming process for cast aluminum alloy structural parts of automotive calipers, characterized in that, include: S1: Heat aluminum alloy raw materials to obtain molten aluminum alloy; S2: A full-salt-based core (2) is prepared using salt raw materials. The full-salt-based core (2) includes a lower cylinder (21) and oil passages (23) located at both ends of the lower cylinder (21). Both ends of the oil passages (23) intersect with both ends of the lower cylinder (21). The full-salt-based core (2), the upper mold assembly (1), and the lower mold assembly (3) are preheated. During the heating of the full-salt-based core (2), the heating temperature is increased stepwise and heat preservation is performed. The heating temperature range is 350℃-550℃, the heating time is 85min-100min, and the heat preservation time is 10min-15min. The stepwise increase in heating temperature includes: setting three stages of increasing heating temperature; and setting the heating time according to the increase in heating temperature so that the heating rate decreases stepwise. S3: The preheated full-salt core (2) is placed into the casting cavity formed by the upper mold assembly (1) and the lower mold assembly (3), and the aluminum alloy liquid is poured from the lower mold assembly (3). The upper mold assembly (1) includes an upper fixing member (11), which includes a middle wedge block (111) and a fixing block (112) that can be separated from each other. S4: After casting, the middle wedge block (111) and the fixing block (112) are removed in sequence, and the upper mold assembly (1) and the lower mold assembly (3) are separated to remove the casting for cooling. S5: Trim and clean the cooled castings, and perform heat treatment on the castings to complete the casting production.

2. The integrated salt core molding process according to claim 1, characterized in that, In step two, the all-salt core (2) also includes several piston ends (22) respectively disposed on both sides of the lower cylinder (21), the piston ends (22) intersecting with the two ends of the oil passage (23) to form an annular oil passage.

3. The integrated salt core molding process according to claim 2, characterized in that, The oil passage (23) includes a beveled section (231) that intersects with the piston end (22), an arc-shaped section (232) connected to the beveled section (231), and a bent section (233) connected to the arc-shaped section (232). The bent section (233) has a U-shaped structure.

4. The integrated salt core molding process according to claim 3, characterized in that, The piston end (22) includes an intermediate post (221) that communicates with the lower cylinder (21). The end of the intermediate post (221) near the lower cylinder (21) forms an annular rib (222), and the end of the intermediate post (221) away from the lower cylinder (21) forms a connecting rib (223). The connecting rib (223) communicates with both ends of the inclined section (231). The connecting ribs (223) on the same side of the lower cylinder (21) are all connected through the connecting post (224) to form the annular oil passage that connects the oil passage (23), the connecting rib (223), and the connecting post (224).

5. The integrated salt core molding process according to claim 4, characterized in that, The bottom of the fixing block (112) is formed with a number of semi-circular holes. The bottom side of the middle wedge block (111) is the bottom end face of the semi-circular holes to form a semi-circular groove (114). The annular rib (222) is fitted into the semi-circular groove (114) to form a positioning structure.

6. The integrated salt core molding process according to claim 1, characterized in that, In step three, the upper mold assembly (1) further includes an upper cover plate (12), the upper cover plate (12) forms a through hole to embed the fixing block (112), the middle wedge block (111) is embedded between the fixing blocks (112) through a concave-convex structure, the side of the fixing block (112) away from the middle wedge block (111) forms a convex edge (113) to connect with the upper cover plate (12), and the top of the middle wedge block (111) and the tops of the fixing blocks (112) on both sides form a bolt connection structure; When the fixing block (112) and the intermediate wedge block (111) are fixed in the through hole of the upper cover plate (12), the bottom of the upper mold assembly (1) forms the upper half of the casting cavity, and the top of the lower mold assembly (3) forms the lower half of the casting cavity.

7. The integrated salt core molding process according to claim 6, characterized in that, In step three, the lower mold assembly (3) includes: A lower base plate (31) connected to the upper cover plate (12) forms the casting cavity to accommodate the molten aluminum alloy. A pouring channel (32) is formed on the top surface of the lower base plate (31), and an injection port (33) is formed on the side of the lower base plate (31).

8. The integrated salt core molding process according to claim 1, characterized in that, In step four, the cooling temperature range of the casting is 320℃-420℃, and the cooling time range is 200s-420s.

9. The integrated salt core molding process according to claim 1, characterized in that, Step five, the heat treatment includes: The casting is subjected to solution treatment at a heating temperature of 530℃-550℃ and held for 5 hours-8.5 hours. Control the solution transfer time to be less than or equal to 30 seconds; The casting is subjected to aging treatment at a temperature of 170℃-200℃ for 3-6 hours.

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