Casting method of automobile calipers

Abstract

The invention relates to a casting method of automobile calipers, and belongs to the technical field of casting. The casting method comprises the steps that the sand core assembly is manufactured, the salt core is manufactured, the mold is preheated, and paint is sprayed to the surface of the forming cavity of the mold. And the upper sand core is buckled to the lower sand core to fix the salt core to form a combined core, and the combined core is put into a lower mold device of a casting mold to be subjected to mold closing. Injecting an aluminum alloy solution, and cooling to form a casting; the casting is taken out of the casting mold, and a sand shaking process and dead head removal are carried out; the salt core in the caliper blank is washed, and an oil liquid channel is formed; and the caliper blank is subjected to heat treatment, and production of the automobile calipers is completed. The combined core is formed by the sand core assembly and the salt core, the high-temperature structural stability of the sand core assembly is achieved, the effect that the salt core forms a smooth wall face at the position of the built-in oil way of the caliper blank can also be achieved, the salt core at the position of the built-in oil way is easy to clean and free of sand grain residues, and the oil way communication consistency is high.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of casting, in particular to a casting method of automobile caliper. BACKGROUND

[0002] With the development of automobile industry, the caliper assembly as an important part of the braking system in the vehicle, especially in some high-power vehicles, is fixed automobile caliper. The fixed automobile caliper is arranged with multiple pistons on both sides of the brake disc. During operation, brake fluid is distributed to both sides of the piston through the pipeline on the caliper body, the piston pushes the brake pad to tighten the brake disc, so as to achieve the effect of immediate braking. The existing automobile caliper adopts gravity casting mold processing, wherein the built-in oil passage and cylinder space of the automobile caliper are formed by sand core.

[0003] The fixed automobile caliper has a built-in oil passage for the movement of pistons on both sides. The built-in oil passage needs to be integrally formed during the casting of the automobile caliper. However, the built-in oil passage of the automobile caliper processed by the sand core casting process not only has large surface roughness, but also has great difficulty in cleaning the sand core corresponding to the built-in oil passage area. If the sand particles in the built-in oil passage area fall off and enter the piston, there is a risk of damage to the caliper assembly, and therefore improvement is needed. SUMMARY

[0004] To overcome the problems in the related art, the present application provides a casting method of automobile caliper to solve the technical problems of large roughness of the built-in oil passage of the sand core casting, great difficulty in cleaning, and sand particle residue.

[0005] According to a first aspect of the present application, a casting method of automobile caliper is provided, which comprises: making a sand core assembly, the sand core assembly comprising a lower sand core and an upper sand core that are complementarily matched; making a salt core, the salt core comprising a cylinder part and an oil passage pipe distributed at both ends of the cylinder part, the oil passage pipe being curved in a columnar shape, and both ends of the oil passage pipe intersecting both sides of the cylinder part, respectively; preheating the mold and spraying paint on the surface of the forming cavity of the mold; making a combined core, taking the salt core out of the heating equipment at a holding temperature, embedding the cylinder part into the lower sand core, and fastening the upper sand core to the lower sand core to fix the cylinder part, the oil passage pipe being taken out from both ends of the combined core, and both sides of the cylinder part exceeding the sand core assembly; placing the combined core into the lower mold device of the casting mold and closing the mold, wherein both ends of the salt core and the oil passage pipe are suspended in the forming cavity of the casting mold; cooling the aluminum alloy solution to form a cast; The cast is taken out of the casting mold, and the shakeout process and riser removal are performed to obtain a caliper blank; The salt core in the caliper blank is washed to form an oil passage; The caliper blank is heat treated to complete the production of the automobile caliper.

[0006] In an embodiment, the cylinder part includes two parallel intermediate columns and at least two connecting rods connecting the two intermediate columns; The intermediate column includes an intermediate rod and a shaped end at both ends of the intermediate rod, the diameter of the shaped end is larger than the diameter of the intermediate rod, part of the shaped end is embedded in the sand core assembly, and the end of the shaped end exceeds the sand core assembly, and the oil passage pipe intersects the end of the shaped end.

[0007] In an embodiment, the end of the shaped end has a radially protruding annular rib, the oil passage pipe intersects the annular rib, and the connecting rod connects the annular rib.

[0008] In an embodiment, the projection of the oil passage pipe on the plane where the two intermediate columns are located is in the shape of U, and at least part of the oil passage pipe is bent relative to the plane where the two intermediate columns are located.

[0009] In an embodiment, the salt core is made, including: The salt core is heated, the heating temperature ranges from 400 degrees Celsius to 520 degrees Celsius, and is maintained for 2.5-3.5 hours; The salt core is cooled to a holding temperature and is held, wherein the thermal expansion coefficient of the salt core at the holding temperature and the thermal expansion coefficient of the sand core at normal temperature are substantially the same.

[0010] In an embodiment, the lower sand core includes a lower mating surface, a lower fitting part, and a lower positioning groove recessed from the lower mating surface, the upper sand core includes an upper mating surface, an upper fitting part, and an upper positioning groove recessed from the upper mating surface, the lower mating surface and the upper mating surface are attached to each other, the lower fitting part and the upper fitting part are at least two protrusions and grooves that are complementarily fitted, and the lower positioning groove and the upper positioning groove define the cylinder part.

[0011] In an embodiment, the aluminum alloy solution is injected and then cooled to form a cast, including: The lower mold device is provided with at least one forming groove and pouring channels on both sides of the forming groove, the pouring channels are provided with three intermediate molten pools and injection ports corresponding to each intermediate molten pool along the flow direction, the injection ports are arranged towards the sand core assembly and are misaligned with the cylinder part.

[0012] In an embodiment, the injection of the aluminum alloy solution is followed by cooling to form a casting, including: The cooling mechanism is started to control the mold temperature at 360-400°C; The mold is controlled to maintain pressure for 350-370 seconds.

[0013] In an embodiment, the heat treatment of the caliper blank includes: The caliper blank is solution treated at a temperature of 530-550°C for 5-8.5 hours; The solution transfer time is controlled to be less than or equal to 30 seconds; The caliper blank is aged at a temperature of 160-175°C for 6-7.5 hours.

[0014] In an embodiment, the flushing of the salt core in the caliper blank includes: The flushing medium is aligned to flush the salt core in the caliper blank; The salt core in the caliper blank is dissolved, and the caliper blank forms corresponding oil passage and cylinder space.

[0015] The technical solution provided by the embodiments of the present application can include the following beneficial effects: The sand core assembly and the salt core form a combined core, which has both the high-temperature structural stability of the sand core assembly and the effect of forming a smooth wall surface at the built-in oil passage of the casting by the salt core, and the salt core at the built-in oil passage also has the advantages of easy cleaning and no sand particle residue. The cylinder part of the salt core is supported and limited by the sand core assembly, which reduces the volume of the corresponding area of the salt core, thereby reducing the high-temperature deformation amount of the salt core, and also enables the combined core to have a convenient assembly structure. The salt core corresponds to the cylinder space and the built-in oil passage of the casting, and the oil passage has high consistency in communication. BRIEF DESCRIPTION OF DRAWINGS

[0016] The accompanying drawings, which are incorporated into and form a part of the specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the application.

[0017] Figure 1 is a flowchart showing a casting method according to an embodiment.

[0018] Figure 2 is a structural schematic diagram of a combined core according to an embodiment.

[0019] Figure 3 is an exploded structural schematic diagram of a combined core according to an embodiment.

[0020] Figure 4 is a structural schematic diagram of a salt core according to an embodiment.

[0021] Figure 5is a schematic diagram of a main structure of a salt core according to an embodiment.

[0022] Figure 6 is a schematic diagram of a combined core in a lower mold device according to an embodiment.

[0023] In the figure, the sand core assembly 10; the lower sand core 11; the lower mating surface 111; the lower positioning groove 112; the lower fitting part 113; the upper sand core 12; the upper mating surface 121; the upper positioning groove 122; the top recess 123; the triangular protrusion 124; the salt core 20; the oil channel pipe 21; the arc-shaped area 211; the bevel area 212; the curved pipe area 213; the middle column 22; the middle rod 221; the forming end 222; the annular protruding rib 2221; the connecting rod 23; the middle rod 231; the cylinder part 24; the lower mold device 30; the pouring channel 31; the middle melt pool 311; the injection inlet 312; the forming groove 32; the lateral channel 33; the side melt pool 331. DETAILED DESCRIPTION

[0024] In the drawings of the embodiments of the present application, the same or similar reference numerals correspond to the same or similar components; in the description of the present application, it should be understood that if the terms "upper", "lower", "left", "right", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore the terms describing the positional relationship in the drawings are only used for exemplary illustration and cannot be understood as a limitation on the present application, for those skilled in the art, the specific meanings of the above terms can be understood according to the specific circumstances.

[0025] As shown in Figures 1 to 3 The present application provides a casting method of an automobile caliper, the casting method comprising the following steps: S101, a sand core assembly 10 is made, the sand core assembly 10 comprising a lower sand core 11 and an upper sand core 12 that are complementary to each other. The lower sand core 11 and the upper sand core 12 are two independent sand core structural members, a positioning cavity is formed at the folding and mating part of the lower sand core 11 and the upper sand core 12, and the outer peripheral wall of the sand core assembly 10 corresponds to the recessed area of the automobile caliper, which is hereinafter referred to as the mounting cavity. Optionally, the sand core assembly 10 is made of coated sand.

[0026] S102, a salt core 20 is made, the salt core 20 comprising a cylinder part 24 and oil channel pipes 21 distributed at both ends of the cylinder part 24, the oil channel pipes 21 being curved in a curve column shape, and the two ends of the oil channel pipes 21 intersecting with the two sides of the cylinder part 24 respectively. The salt core 20 is used for forming the cylinder space of the casting and the built-in oil channel for the flow of brake oil, wherein the cylinder part 24 is used for forming the corresponding cylinder space, and the oil channel pipes 21 are used for forming the corresponding built-in oil channel.

[0027] After the salt core 20 and the sand core assembly 10 are completed, the salt core 20 and the sand core assembly 10 are assembled to form a combined core.

[0028] S103, preheating the mold and spraying paint on the surface of the forming cavity of the mold. The mold is heated to be at a suitable casting temperature. Optionally, the preheating of the mold can be performed by flame baking or using the waste heat of the mold production or by a heating coil.

[0029] S104, making the combined core. The salt core 20 is taken out from the heating device at the holding temperature, the cylinder part 24 is embedded into the lower sand core 11, and the upper sand core 12 is buckled to the lower sand core 11 to fix the cylinder part 24. The oil passage pipe 21 is passed out from both ends of the combined core, and the two sides of the cylinder part 24 exceed the sand core assembly 10. The salt core 20 needs to be stored in the heating device before casting processing. The heating device heats the salt core 20, so that the thermal expansion coefficient of the salt core 20 and the thermal expansion coefficient of the sand core assembly 10 are basically the same or close to each other. During the casting process, the salt core 20 and the sand core assembly 10 expand consistently when the metal liquid is poured, so as to improve the forming quality.

[0030] The lower sand core 11 is placed on the workbench, and the salt core 20 is matched and placed in the lower sand core 11. Then, the upper sand core 12 is buckled to the lower sand core 11. The joint part of the lower sand core 11 and the upper sand core 12 forms a concave positioning cavity, and the cylinder part 24 is embedded and fixed in the positioning cavity. The cylinder part 24 of the salt core 20 is clamped and supported by the sand core assembly 10, the volume of the salt core 20 exposed outside the sand core assembly 10 is reduced, so as to reduce the high-temperature deformation amount of the salt core 20, and the combined core has a convenient assembly structure.

[0031] S105, the combined core is put into the lower mold device 30 of the casting mold, and the two ends of the salt core 20 and the oil passage pipe 21 are suspended in the forming cavity of the casting mold. Specifically, the lower mold device 30 has a forming groove 32, the lower sand core 11 is put into the forming groove 32, and the combined core is connected to the lower mold device 30. The space between the combined core and the forming cavity can be filled with the metal liquid, and the metal liquid forms a solid structure part corresponding to the casting.

[0032] S106, after the aluminum alloy solution is injected, the combined core is cooled to form a casting. The part of the salt core 20 exceeding the sand core assembly 10 is suspended, the metal liquid fills the space in the forming cavity, and the combined core is wrapped by the metal liquid. The metal liquid is cooled to form a casting. Preferably, the mold is a gravity casting mold, so as to reduce the impact of the metal liquid on the combined core, reduce the deformation amount of the combined core, and especially reduce the deformation amount of the salt core 20.

[0033] S107, the castings are taken out from the casting mold, and the sand shake process and the riser removal are performed to obtain the caliper blank. After the mold is opened, the castings are taken out, and the castings are shaken by the sand shake equipment to remove the coated sand corresponding to the sand core assembly 10. The salt core 20 in the middle part is broken or punched to hollow the corresponding combined core part of the casting. Then, the handle part corresponding to the riser and the pouring channel 31 is cut off, so that the corresponding caliper blank is reserved.

[0034] S108, the remaining salt core 20 in the caliper blank is flushed to form the oil passage. The caliper blank is flushed by the flushing equipment, specifically, the flushing equipment flushes the salt core 20 part located in the caliper blank, wherein the flushing equipment flushes the salt core 20 corresponding to the built-in oil way, and the salt core 20 in the caliper blank is dissolved during the flushing process, so that the built-in oil way is penetrated, and the built-in oil way prepared by the salt core 20 has high smoothness and does not leave sand.

[0035] S109, the caliper blank is heat treated to complete the production of the automobile caliper.

[0036] The sand core assembly 10 and the salt core 20 form a combined core, which has high temperature structural stability of the sand core assembly 10, and can have the effect of forming a smooth wall surface of the salt core 20 at the built-in oil way of the caliper blank, and the salt core 20 also has easy cleaning and no sand residue at the built-in oil way.

[0037] As shown in Figures 2 to 4 In an embodiment, the cylinder part 24 includes two parallel intermediate columns 22 and at least two connecting rods 23 connecting the two intermediate columns 22. The intermediate column 22 corresponds to the piston mounting part of the shaped automobile caliper, and the connecting rod 23 connects the intermediate column 22 to form a structure similar to a "mouth" character, a "day" character or a "eye" character.

[0038] In order to facilitate the preparation of the salt core 20, the salt core 20 and the sand core assembly 10 are assembled together. The intermediate column 22 includes an intermediate rod 221 and shaped ends 222 located at both ends of the intermediate rod 221, and the diameter of the shaped end 222 is greater than that of the intermediate rod 221. The shaped end 222 corresponds to the mounting part of the shaped piston, and the intermediate rod 221 connects the two shaped ends 222 into one body and fits into the positioning cavity defined in the sand core assembly 10 to constitute the peripheral positioning of the intermediate column 22. Part of the shaped end 222 is embedded in the sand core assembly 10 to constitute the axial positioning. Therefore, the intermediate column 22 can realize axial and circumferential positioning, and the sand core assembly 10 and the salt core 20 have high assembly precision. The shaped end 222 is embedded in the sand core assembly 10 to form a closely contacted bonding surface, avoid the entry of molten metal, and can form the side wall of the recessed area of the automobile caliper.

[0039] The end of the forming end 222 extends beyond the sand core assembly 10, and the oil passage 21 intersects at the end of the forming end 222. After casting is completed, the end of the forming end 222 is located inside the casting. After the casting completes the sandblasting process, part of the forming end 222 and the oil passage 21 are located inside the casting and need to be flushed and dissolved by flushing equipment to obtain a smoother wall surface and reduce the flow resistance of the oil.

[0040] Optionally, the connecting rod 23 includes a mid-position rod 231 located between the two intermediate columns 22, and the mid-position rod 231 may be configured as a flat rod.

[0041] In a preferred embodiment, the end of the forming end 222 has a radially protruding annular rib 2221, the oil passage pipe 21 intersects the annular rib 2221, and the connecting rod 23 connects to the annular rib 2221. The annular rib 2221 has an annular structure, and the connecting rod 23 intersects with the annular rib 2221. Correspondingly, there will be a corresponding annular groove and connecting channel in the casting to facilitate the flow of oil.

[0042] More preferably, each end of the molding end 222 has two annular ribs 2221, one of which is fitted and connected to the sand core assembly 10, and the other is suspended and connected to the annular rib 2221 and the connecting rod 23 respectively to form a continuous channel structure. Correspondingly, the pistons on both sides of the car caliper are connected through the channel structure.

[0043] like Figures 3 to 5 As shown, in one embodiment, the projection of the oil passage 21 onto the plane containing the two intermediate pillars 22 is U-shaped, and at least a portion of the oil passage 21 is bent relative to the plane containing the two intermediate pillars 22. The intermediate pillars 22 are arranged in parallel, and the plane containing the intermediate pillars 22 is referred to as the reference plane. The projection of the oil passage 21 onto the reference plane is U-shaped, thereby connecting the two ends of the intermediate pillars 22, so that the final internal oil passage of the casting can form a continuous oil passage connecting both sides. That is, an approximately annular flow oil passage is formed inside the casting.

[0044] In a direction perpendicular to the reference plane, the oil pipe 21 is bent and inclined relative to the reference plane to improve the structural strength and bending and torsional strength of the oil pipe 21, thereby maintaining the structural stability of the oil pipe 21. For example, on the midpoint perpendicular to the reference plane, the oil pipe 21 has an approximately V-shaped or C-shaped structure.

[0045] In one specific embodiment, the oil passage 21 includes a U-shaped bend 213, arc-shaped areas 211 distributed at both ends of the bend 213, and a beveled area 212 bending from the arc-shaped areas 211. The beveled areas 212 intersect at the forming end 222. The extending direction of the beveled areas 212 is inclined relative to the plane where the two intermediate pillars 22 are located. The bend 213 intersects the plane where the two intermediate pillars 22 are located. The projections of the bend 213, arc-shaped areas 211, and beveled areas 212 onto the reference plane are approximately U-shaped. On the midpoint plane perpendicular to the reference plane, the oil passage 21 has an approximately V-shaped structure.

[0046] In a further preferred embodiment, the inclined side region 212 is inclined downward toward the reference plane, the end of the bend region 213 protrudes upward toward the reference plane, and the arc region 211 is an arc-shaped surface to connect the inclined side region 212 and the bend region 213, which has high bending and torsional strength and high structural stability.

[0047] In one embodiment, the salt core 20 is fabricated in step S102, which includes the following steps: like Figures 1 to 3 As shown, the salt core 20 is heated to a temperature range of 400°C to 520°C and held for 2.5 to 3.5 hours. Heating the salt core 20 allows it to be adapted for aluminum alloy casting mold production. The heating temperature can be adjusted according to the salt core 20; for example, it can be set to 400°C, 420°C, 460°C, or 520°C. The salt core 20 is held at the corresponding temperature for the corresponding duration to improve its structural stability.

[0048] After the salt core 20 is heated, before it is combined with the sand core assembly 10 and placed into the mold, the salt core 20 needs to be preheated or kept at a certain temperature to improve the fluidity of the molten metal around the salt core 20. Specifically, the salt core 20 is cooled to a holding temperature and then held at that temperature. The coefficient of thermal expansion of the salt core 20 at the holding temperature is essentially the same as that of the sand core at room temperature.

[0049] In this step, the holding temperature of the salt core 20 can be adjusted to match the expansion coefficient of the sand core assembly 10, so that the expansion coefficients of the combined cores are basically the same, thereby maintaining the expansion consistency of the combined cores and improving casting accuracy. Furthermore, the high holding temperature of the salt core 20 can also maintain the stability of the molten metal flow around the combined core. For example, if the sand core assembly 10 uses conventional coated sand material, the holding temperature of the salt core 20 can be configured to 100 degrees Celsius-120 degrees Celsius.

[0050] In step S101, the sand core assembly 10 is made, and the sand core assembly 10 clamps and fixes the salt core 20. In an embodiment, the lower sand core 11 includes a lower matching surface 111, a lower fitting part 113, and a lower positioning groove 112 recessed from the lower matching surface 111, and the upper sand core 12 includes an upper matching surface 121, an upper fitting part, and an upper positioning groove 122 recessed from the upper matching surface 121, and the lower matching surface 111 and the upper matching surface 121 are matched with each other.

[0051] The lower sand core 11 and the upper sand core 12 are block structures, and the outer surfaces of the lower sand core 11 and the upper sand core 12 correspond to the cavity walls of the formed installation cavity. The lower fitting part 113 and the upper fitting part are at least two complementary fitting bosses and grooves, so that the fitting positions of the lower sand core 11 and the upper sand core 12 are accurate, and the assembly precision and consistency of the two are high. For example, the lower fitting part 113 is two lower fitting counterbores, and the lower positioning groove 112 is located between the two fitting counterbores. The upper fitting part is two protruding fitting bosses, and the fitting bosses and the fitting counterbores are inserted and fitted. The lower fitting part 113 and the upper fitting part can not only complementarily fit and position, but also increase the strength of the lower positioning groove 112 and the upper positioning groove 122 for limiting the cylinder part 24.

[0052] Further preferably, the top of the upper sand core 12 includes a lower recessed top groove 123 and two protruding triangular protrusions 124 from the top, and the two protruding triangular protrusions 124 are located on one side of the top groove 123. The top groove 123 can be matched with the upper die device of the mold for positioning, and can reduce the thickness of the top of the upper sand core 12. The protrusions on both sides of the top groove 123 have different heights, which can change the flowing direction of the metal liquid in the cavity, and the metal liquid wraps the salt core 20 from both sides to both sides of the forming cavity, so as to reduce the impact of the metal liquid on the salt core 20.

[0053] In step S106, after the aluminum alloy solution is injected, the mold is cooled to form a casting. The mold includes the lower die device 30 and the upper die device, and the upper die device and the lower die device 30 are matched and fitted.

[0054] The lower die device 30 is provided with at least one forming groove 32, and the forming groove 32 is a groove structure, and the groove wall of the forming groove 32 is basically the same as the outer peripheral wall shape of the automobile caliper. The combined core is put into the forming groove 32, and the lower sand core 11 and the lower die device 30 are assembled and connected. The upper die device and the upper sand core 12 are matched and positioned, so as to be connected and positioned. The oil passage pipe 21 of the salt core 20 is located in the forming cavity and is suspended, and both ends of the oil passage pipe 21 are formed in the interior of the casting after the metal liquid is poured.

[0055] As Figures 1 to 3 , Figure 6As shown, the lower mold device 30 is provided with pouring channels 31 and lateral channels 33 on both sides of the forming groove 32, which can guide the metal liquid into the forming cavity. The pouring channels 31 and the lateral channels 33 are connected with the injection ports 312 to form an annular flow channel structure. The pouring channels 31 and the lateral channels 33 inject metal liquid from opposite sides, which can improve the filling efficiency of the metal liquid, especially in the gravity casting mold with multiple injection positions, which can improve the metal liquid flowability and reduce the impact force on the combined core, thereby reducing the problem of deformation of the combined core due to impact.

[0056] As preferred, the lower mold device 30 is configured with a double-cavity structure, which can produce two automobile calipers at the same time. The lateral channels 33 are provided with two, and the pouring channels 31 are located in the middle position to deliver metal liquid to the two forming cavities.

[0057] Specifically, the pouring channels 31 are provided with three intermediate molten pools 311 and corresponding injection ports 312 at intervals along the flow direction, and the injection ports 312 are arranged towards the sand core assembly 10 and are staggered with the cylinder part 24. The intermediate molten pool 311 is a concave molten pool structure, and the depth of the intermediate molten pool 311 is greater than that of the flow channel, so that the metal liquid can be buffered at the intermediate molten pool 311 and the shrinkage amount during the cooling process of the casting in the forming cavity can be compensated.

[0058] The three intermediate molten pools 311 correspond to the three injection ports 312 respectively, and the direction of the injection port 312 is towards the sand core assembly 10 and avoids directly impacting the salt core 20, thereby reducing the expansion amount of the salt core 20 and improving the stability of the casting forming.

[0059] The lateral channels 33 and the pouring channels 31 are distributed on both sides of the forming cavity, thereby filling the same forming cavity from both sides. Not only the filling time is short, but also the impact force on the combined core is reduced. The impact forces on both sides of the combined core are in opposite directions, and part of the impact force is offset, thereby reducing the deformation of the combined core.

[0060] The lateral channels 33 are provided with three side molten pools 331 and corresponding side injection ports at intervals, and the side injection ports are arranged towards the sand core assembly 10 and are staggered with the cylinder part 24. The structure and principle of the lateral channels 33 and the pouring channels 31 are similar, and the side molten pool 331 can compensate the cold shrinkage of the automobile caliper part. The solidification time of the side molten pool 331 is longer than that of the forming cavity, which can improve the forming quality of the automobile caliper. The lateral channels 33 and the pouring channels 31 have the functions of flow channel and molten pool compensation, which greatly improve the forming effect of the automobile caliper.

[0061] As shown in FIG. 4, the pouring channels 31 and the lateral channels 33 are connected with the injection ports 312 to form an annular flow channel structure. The pouring channels 31 and the lateral channels 33 inject metal liquid from opposite sides, which can improve the filling efficiency of the metal liquid, especially in the gravity casting mold with multiple injection positions, which can improve the metal liquid flowability and reduce the impact force on the combined core, thereby reducing the problem of deformation of the combined core due to impact. Figures 1 to 3Further, the upper die device is provided with a riser corresponding to the side melt pool 331 and the middle melt pool 311 to further prolong the metal liquid cooling time of the corresponding area.

[0062] After the aluminum alloy solution is injected in step S106, the cooling forming into a casting is performed, specifically including the following cooling steps: The cooling mechanism is started to control the mold temperature at 360-400℃; The mold is controlled to keep pressure for 350-370 seconds.

[0063] The metal liquid is injected into the forming cavity from the side channel 33 and the pouring channel 31 respectively, and the filling is completed. The mold is cooled by the cooling mechanism, so that the metal liquid cooling forming time can be shortened, and the forming quality of the automobile caliper can be avoided from being affected by too fast cooling. The volume and weight of the automobile caliper can be adapted to different pressure keeping time and mold temperature. The mold temperature can be controlled at one of 360℃, 380℃, 390℃ and 400℃, and the mold pressure keeping time is controlled at one of 350 seconds, 355 seconds, 360 seconds, 365 seconds and 370 seconds, so that the automobile caliper has stable forming quality.

[0064] The heat dissipation speed and temperature of the thick-walled aluminum alloy casting of the automobile caliper can avoid slow solidification caused by high temperature, and prevent internal porosity caused by low temperature. The appropriate pressure keeping time ensures that the middle melt pool 311 part can continue to supplement the shrinkage before the metal liquid completely solidifies.

[0065] After the mold is opened, the casting is taken out and the sand shaking process is performed, so that the part corresponding to the sand core assembly 10 on the casting is removed. Further, part of the salt core 20 can be removed by vibration fracture or by flushing medium to remove the part corresponding to the cylinder part 24.

[0066] Then, the excess material handle and riser of the casting are removed, and the caliper blank is obtained.

[0067] Further, the salt core 20 in the caliper blank is flushed, including the following steps: The flushing medium flushes the salt core 20 in the caliper blank, and the salt core 20 in the caliper blank is dissolved. The caliper blank forms corresponding oil passage and cylinder space. The salt core 20 can be dissolved in the flushing medium, so as to leave the oil passage and the cylinder space in the caliper blank. The cylinder space is used for installing the piston, and the oil passage is used for flowing fluid, so as to realize smooth oil flow space.

[0068] The forming end 222 corresponds to the cylinder space, the connecting rod 23 and the oil passage pipe 21 correspond to the hole-shaped oil passage inside the forming caliper blank, the forming end 222 corresponds to the forming counterbore-shaped cylinder space, and the oil passage and the cylinder space form a fluid flow path similar to a ring shape, thereby being capable of driving the movement of the piston installed in the cylinder space.

[0069] After the caliper blank is cleaned, deburring is performed, and then the caliper blank is subjected to heat treatment, and the heat treatment step includes: The caliper blank is subjected to solid solution treatment, the heating temperature is 530-550 DEG C, and the holding time is 5-8.5 hours; the solid solution treatment can make the caliper blank obtain a supersaturated solid solution, thereby improving the mechanical properties of the material. The heating temperature is 530 DEG C, 540 DEG C, or 550 DEG C, and the holding time can be set to 5 hours, 6 hours, 6.5 hours, 7 hours, 8 hours, or 8.5 hours.

[0070] The solid solution transfer time is controlled to be less than or equal to 30 seconds; the caliper blank is taken out of the solid solution treatment furnace, and the solid solution transfer time is controlled to be within 30 seconds, so that the performance of the caliper blank reaches the best. For example, the solid solution transfer time is set to 20 seconds, 23 seconds, 25 seconds, 28 seconds, 30 seconds, etc. Controlling the solid solution transfer time minimizes the cooling delay after solid solution, avoids the alloying elements from precipitating in advance due to temperature drop during the transfer process, destroys the "supersaturated solid solution" state, and ensures the subsequent aging strengthening effect.

[0071] The caliper blank is subjected to aging treatment, the aging treatment temperature is 160-175 DEG C, and the holding time is 6-7.5 hours. The aging treatment temperature of the caliper blank is set to 160 DEG C, 163 DEG C, 168 DEG C, 170 DEG C, 172 DEG C, or 175 DEG C, which can reach the best performance state of the corresponding aluminum alloy casting, high material hardness and strength. Under the corresponding aging treatment temperature, it can be maintained for 6 hours, 6.5 hours, 6.8 hours, 7 hours, 7.2 hours, or 7.5 hours, which can not only ensure the precipitation of the strengthening phase, but also avoid the reduction of production efficiency caused by long aging, and significantly improve the hardness, elastic modulus and strength of the caliper blank. Compared with low-temperature aging, the aging time can be shortened by 30%-50%. The aging treatment process scheme is suitable for automobile caliper thick-walled structural parts and aluminum alloy castings with medium and high strength requirements. For example, for a 2024 aluminum alloy thick-walled casting, the tensile strength after the process treatment is 420-460 MPa, the yield strength is 320-360 MPa, the hardness (HV) is 125-135, and the elongation is 8%-10%.

[0072] It is to be understood that the application is not limited to the precise construction herein disclosed and shown in the drawings, and that various changes in shape, size and arrangements of parts can be made without departing from the scope of the application. It is intended that the application cover any adaptations, shapes, uses or modifications of the application including such departures from the present disclosure as come within the generic principles of the application and fall within the scope of the application.

Claims

1. A casting method of an automobile caliper, characterized by, The casting method comprises: manufacturing a sand core assembly, the sand core assembly comprising a lower sand core and an upper sand core which are complementarily matched; manufacturing a salt core, the salt core comprising a cylinder part and oil passage pipes which are distributed at two ends of the cylinder part, the oil passage pipes being curved in a curve column shape, and the two ends of the oil passage pipes intersecting with two sides of the cylinder part respectively; preheating a mold and spraying paint on a forming cavity surface of the mold; manufacturing a combined core, the salt core being taken out from a heating device at a holding temperature, the cylinder part being embedded in the lower sand core, the upper sand core being buckled to the lower sand core to fix the cylinder part, the oil passage pipes being penetrated from two ends of the combined core, and two sides of the cylinder part exceeding the sand core assembly; placing the combined core into a lower mold device of a casting mold and closing the mold, wherein the two ends of the salt core and the oil passage pipes are suspended in a forming cavity of the casting mold; injecting an aluminum alloy solution and cooling to form a casting; taking the casting out of the casting mold, performing sand shaking process and removing risers to obtain a caliper blank; flushing the salt core in the caliper blank to form oil liquid passages; performing heat treatment on the caliper blank to complete production of an automobile caliper.

2. The casting method according to claim 1, characterized by, The cylinder part comprises two intermediate columns which are arranged in parallel and at least two connecting rods which connect the two intermediate columns; The intermediate column comprises an intermediate rod and forming ends which are located at two ends of the intermediate rod, the forming ends have diameters which are greater than that of the intermediate rod, part of the forming ends are embedded in the sand core assembly, and the ends of the forming ends exceed the sand core assembly, and the oil passage pipes intersect with the ends of the forming ends.

3. The casting method according to claim 2, characterized in that, The ends of the forming ends have radially protruding annular ribs, the oil passage pipes intersect with the annular ribs, and the connecting rods connect the annular ribs.

4. The casting method according to claim 2, characterized by The projection of the oil passage pipes on the plane where the two intermediate columns are located is in a U shape, and at least part of the oil passage pipes are curved relative to the plane where the two intermediate columns are located.

5. The casting method according to claim 1, characterized by, The manufacturing of the salt core comprises: heating the salt core, the heating temperature ranges from 400 degrees Celsius to 520 degrees Celsius, and the heating is maintained for 2.5 hours to 3.5 hours; cooling the salt core to a holding temperature and performing holding, wherein the thermal expansion coefficient of the salt core at the holding temperature and the thermal expansion coefficient of the sand core at normal temperature are substantially the same.

6. The casting method according to claim 1, characterized by, The lower sand core comprises a lower matching surface, a lower embedded part and a lower positioning groove which is recessed from the lower matching surface, the upper sand core comprises an upper matching surface, an upper embedded part and an upper positioning groove which is recessed from the upper matching surface, the lower matching surface and the upper matching surface are matched with each other, the lower embedded part and the upper embedded part are at least two bosses and grooves which are complementarily embedded, and the lower positioning groove and the upper positioning groove define the cylinder part.

7. The casting method according to claim 1, characterized by, The injection of the aluminum alloy solution and the cooling to form the casting comprise: The lower mold device is provided with at least one forming groove and pouring channels which are located at two sides of the forming groove, the pouring channels are provided with three intermediate molten pools and injection ports which correspond to each intermediate molten pool and are arranged at intervals along a flowing direction, and the injection ports are arranged in a direction towards the sand core assembly and are arranged in a staggered manner with the cylinder part.

8. The casting method according to claim 7, characterized in that, The injection of the aluminum alloy solution and the cooling to form the casting comprise: controlling the mold temperature to be at 360 degrees Celsius to 400 degrees Celsius by starting a cooling mechanism; controlling the mold to maintain pressure for 350 seconds to 370 seconds.

9. The casting method according to claim 1, characterized by, The heat treatment of the caliper blank includes: solid solution treatment of the caliper blank, heating temperature is 530-550 ℃, holding time is 5-8.5 hours; controlling the solid solution transfer time to be less than or equal to 30 seconds; aging treatment of the caliper blank, aging treatment temperature is 160-175 ℃, holding time is 6-7.5 hours.

10. The casting method according to claim 1, characterized by, The flushing of the salt core in the caliper blank includes: flushing the salt core in the caliper blank by the flushing medium; dissolving the salt core in the caliper blank, and forming corresponding oil passage and cylinder space in the caliper blank.

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