Casting method of hub connecting frame for electric wheel

Abstract

The invention relates to a casting method of a hub connecting frame for an electric wheel, and belongs to the technical field of casting. Comprising the steps that a hub connecting frame pouring sand mold is manufactured; the method comprises the following steps: firstly, designing a hub connecting frame mold comprising a pouring system, and placing an exothermic riser and / or a chilling block on the mold corresponding to the hot spot position of the hub connecting frame; then a combined hub connecting frame pouring sand mold is manufactured through a sand mixer; then component proportioning and component smelting of the pouring liquid are carried out; the smelted pouring liquid is subjected to a spheroidizing inoculation reaction, after the spheroidizing inoculation reaction is completed, the temperature is controlled, pouring is conducted on the manufactured pouring sand mold, and stream secondary inoculation is adopted in the pouring process; and after pouring is completed, post-treatment is conducted on the hub connecting frame casting. By arranging the process feeding channel, designing a reasonable pouring system and controlling the casting solidification sequence, the problems that magnetic traces on the surface of the hub connecting frame exceed the standard and key parts are subjected to shrinkage porosity are solved, hub connecting frame castings with excellent quality and good performance can be obtained, and the yield of hub connecting frames for electric wheels is increased.

Description

Technical Field

[0001] The invention relates to the technical field of casting, and in particular to a method for casting a hub connecting frame for an electric wheel. Background Art

[0002] In the production operations of large open-pit coal mines, electric drive dump trucks have surpassed mechanical trucks to become the main transportation equipment due to their strong reliability and advancement, and have broad application prospects in the field of open-pit coal mines. The electric wheel is the core structure of the electric drive dump truck, integrating the wheel hub motor, brake, reducer and load-bearing device. It eliminates the clutch, transmission, differential and other components, and has a compact structure, large load bearing and high output torque. Due to the harsh environment and complex road conditions in the open-pit coal mine area, electric drive dump trucks are constantly subjected to impact during operation. The wheel hub connecting frame is a key component of the electric wheel. It is circumferentially constrained and axially limited with the inner gear ring of the brake, and is fixedly connected to the inner side of the wheel hub. It bears a large load and torque during the braking and transmission process of the truck. Therefore, the internal and surface quality requirements of the wheel hub connecting frame are relatively high. Technical requirements: The surface magnetic particle inspection level and ultrasonic inspection level of the wheel hub connecting frame product shall not exceed the second level specified in the national standard. The hub connector has a complex structure and uneven wall thickness, with the thickest part being 143mm and the thinnest part being only 13mm. The local heat node is large, the shrinkage compensation process is difficult, and shrinkage defects are easily formed. In order to prevent the hub connector from failing under the impact of load, the hub connector requires excellent comprehensive mechanical properties, not only high strength, but also high plasticity. Therefore, the hub connector casting is difficult to produce, has a low yield rate, and is costly.

[0003] In the prior art, CN106042777 B discloses a casting process for a rear axle hub connector, which uses a pressure casting method. Although a casting with high density and stable structural strength is obtained, it is unable to eliminate shrinkage defects and cannot fundamentally solve the problem of internal defects in the casting. In addition, the mold used in pressure casting is more prone to mold quality problems, and the structural design is relatively complex, which is not conducive to the assembly, maintenance and repair of the mold, and the investment cost of the mold is relatively high. Therefore, a casting method for a hub connector for an electric wheel is urgently needed to solve the problems of high production difficulty, low yield and high production cost in the casting of the hub connector in the prior art. Summary of the invention

[0004] The object of the present invention is to provide a method for casting a hub connecting frame for an electric wheel, so as to solve the problems raised in the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for casting a hub connecting frame for an electric wheel, comprising the following casting steps: S1. Making a casting sand mold for a wheel hub connection frame; firstly, designing a wheel hub connection frame mold including a casting system, and setting a heating riser and / or a chiller on the mold corresponding to the hot node position of the wheel hub connection frame; then, making a combined wheel hub connection frame casting sand mold by a sand mixer; S2, proportioning the casting liquid components and melting the components; S3, subjecting the smelted pouring liquid in S2 to a spheroidizing inoculation reaction, and after the spheroidizing inoculation reaction is completed, the temperature is controlled to be poured into the pouring sand mold prepared in S1, and secondary inoculation is adopted during the pouring process; S4. After the pouring is completed, the hub connecting frame casting is post-processed.

[0006] Preferably, in S1, a wheel hub connecting frame casting sand mold is manufactured, firstly, a wheel hub connecting frame mold including a casting system is designed, and a heating and heat-insulating riser and / or a chiller are arranged on the mold corresponding to the position of the thick and hot section of the wheel hub connecting frame; then, a combined wheel hub connecting frame casting sand mold is manufactured by a sand mixer, specifically: S10, firstly designing a combined hub connection frame mold including a casting system according to the hot node position of the hub connection frame, wherein the combined hub connection frame mold includes a plurality of sub-molds; using a sand mixer to make a plurality of sub-hub connection frame casting sand molds in a one-mold-one production method, wherein the joints between the sub-hub connection frame casting sand molds constitute the parting surface of the hub connection frame; S11. A plurality of sub-wheel hub connecting frame casting sand molds are made by a sand mixer in a one-mold-one production mode. During the production, a casting system, a gas outlet rod, a chiller and / or a heating riser are placed on the sub-mold according to the casting process, and then a sand box is placed on the mold plate, and sand is mixed by a sand mixer to form a resin sand mixture. Then, the mixture is evenly filled into the sand box, and after the mixture is flush with the surface of the sand box, the sand is stopped, and the mixture is left to stand for 15 min to 20 min. After the sand mold is hardened, the sand box is lifted by a crane to separate the sand mold from the sub-mold to obtain a sub-wheel hub connecting frame casting sand mold. S12, flow coating the casting molding part of the sub-wheel hub connecting frame casting sand mold obtained in S11, and after the coating is dried, clean the sub-wheel hub connecting frame casting sand mold cavity, place a filter component in the pouring channel of the pouring system, then fasten all the sub-wheel hub connecting frame casting sand molds with fasteners to form a wheel hub connecting frame casting sand mold assembly, then connect the pouring system with the wheel hub connecting frame casting sand mold assembly cavity, and finally paste a pouring cup at the pouring gate of the pouring system to form a combined wheel hub connecting frame casting sand mold.

[0007] Preferably, the combined hub connecting frame mold comprises two sub-molds; two sub-hub connecting frame casting sand molds are made by a sand mixer in a one-mold-one production method, and the two sub-hub connecting frame casting sand molds form a combined hub connecting frame casting sand mold radially up and down, and a horizontally arranged hub connecting frame casting cavity is formed inside, and the parting surface of the combined hub connecting frame casting sand mold is the bottom end of the first step of the end face of the hub connecting frame.

[0008] Preferably, the resin-sand mixture includes resin, hardener, curing agent and sand, and the addition ratio of resin and sand is resin / sand = 0.95wt.%~1.1wt.%; the addition ratio of curing agent and resin is curing agent / resin = 30wt.%~60wt.%; the resin is furan resin, the curing agent is benzenesulfonic acid curing agent, the sand is regenerated sand, and the regenerated sand is silica sand, the angular coefficient of which is ≤1.2, and the particle size is 40 / 70 mesh.

[0009] Preferably, the pouring system is a center-casting pouring system with a semi-open and semi-closed structure. The pouring system is provided with a sprue, a cross runner and an ingode. There are several ingodes, which are evenly spaced along the circumference of the pouring cavity, and the connecting end of the ingode and the pouring cavity is arranged in a trumpet shape; the sprue and the ingode are connected by several cross runners; the ratio of the cross-sectional areas of the sprue, the cross runner and the ingode is 1.1-1.3:1.4-1.6:1.

[0010] Preferably, the filter assembly comprises a ceramic bowl and a foam ceramic filter; the ceramic bowl is placed at the bottom of the sprue of the pouring system, and the foam ceramic filter is horizontally arranged at the ingrate of the ingrate.

[0011] Preferably, when placing the chill and / or heating riser in S11, at the hot node position above the parting surface of the hub connecting frame, a heating and insulating riser is installed on the sub-mold; at the hot node position below the parting surface of the hub connecting frame, a combination of heating and insulating risers and chills are installed on the sub-mold; at the intersection of the step structure of the hub connecting frame, the chill is installed along the step structure; the size of the heating and insulating riser is matched to the thickness of the casting at the installation position; the shape of the chill is matched to the shape of the hot node of the casting.

[0012] Preferably, the casting liquid composition ratio is C: 3.3-3.8%, Si: 2.0-2.4%, Mn: 0.2-0.5%; S: 0.06-0.11%, Cu: 0.4-0.7%, Mg: 0.03-0.05%, and the balance is iron and inevitable impurities; during smelting, all components are melted and the temperature is raised to 1540-1580°C for smelting, and then the temperature is lowered to 1480-1540°C for iron tapping.

[0013] Preferably, before pouring in S3, the smelted casting liquid is poured into a casting ladle, a sandwich structure is adopted in the groove of the casting ladle, and the spheroidizer, inoculant and silicon steel sheet are filled from bottom to top; when pouring, the casting liquid temperature is controlled at 1340-1360°C, and the casting is performed towards the pouring port of the assembled casting sand mold. During the pouring process, an inoculant with a particle size of 0.2-0.7 mm is used for secondary inoculation; the amount of inoculant added is 0.1-0.4% by mass of the total amount of the casting liquid.

[0014] Preferably, in S4, after pouring is completed, the casting is cooled for at least 12 h, the casting is unpacked and taken out, the runner and riser are removed, the casting surface is polished, and then heat treatment is performed. Beneficial Effects

[0015] The invention adopts a casting method of gravity casting of resin sand mold modeling, thereby solving the problems that pressure casting molds are prone to mold quality problems, are difficult to assemble, maintain and repair, and have high mold investment costs.

[0016] The present invention adopts a semi-open and semi-closed pouring system, and reasonably designs the cross-sectional area ratio of the sprue, the runner and the ingates. The ingates are designed to be in a trumpet shape to avoid molten iron splashing. A ceramic bowl is placed at the bottom of the sprue to prevent the molten iron from impacting the casting mold. A foam ceramic filter is placed horizontally at the inner intersection to filter the oxide slag, thereby solving the problem of magnetic trace accumulation on the surface of the hub connecting frame, and thus meeting the requirement that the magnetic particle flaw detection level of the casting is not less than level 2.

[0017] The present invention uses the bottom end of the first step of the end face of the hub connecting frame as the parting surface to form a combined hub connecting frame casting sand mold. When making the casting sand mold, a heating riser and / or a chill is placed according to the position of the hot node of the casting to achieve shrinkage compensation through the riser. The chill changes the solidification sequence of the casting and solves the shrinkage problem inside the casting.

[0018] At the intersection of the step structure of the casting, a chill is set along the shape of the step structure of the casting to change the solidification sequence of the hub connecting frame, achieve local sequential solidification, solve the internal shrinkage of the casting, and meet the requirements of ultrasonic flaw detection level 2 and above.

[0019] The present invention solves the problem of poor comprehensive mechanical properties of strength and plasticity of wheel hub connecting frame castings after heat treatment by preparing reasonable casting liquid components. After testing and verification, a wheel hub connecting frame with strength>700 Mpa and plasticity≥3% mechanical properties can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic structural diagram of a hub connecting frame of an embodiment; Figure 2 for Figure 1Sectional view at AA; Figure 3 A schematic structural diagram of a hub connecting frame mold according to an embodiment (1); Figure 4 for Figure 3 Sectional view at AA in the figure; Figure 5 FIG. 2 is a schematic structural diagram of a hub connecting frame mold according to an embodiment of the present invention. FIG. DETAILED DESCRIPTION

[0021] The technical solution of the present invention is described in detail below with reference to the accompanying drawings, but the protection scope of the present invention is not limited to the embodiments.

[0022] The schematic diagram of the hub connecting frame casting structure of the present invention is as follows Figure 1-Figure 2 As shown in the figure, structures 1, 2, 3, 4, 5, 6, 7, 8 and 9 are the mounting bosses of the hub connecting frame, which are connected to the hub by bolts during the assembly process to achieve the fixed connection between the hub connecting frame and the hub. Structures 10 and 11 are the end faces of the hub connecting frame. During the assembly process, the axial positioning is achieved by connecting the bolts and extending into the block of the brake inner gear ring. The wall thickness of structures 10 and 11 is more than 70 mm, and isolated heat nodes are easily formed in thick and large parts. The heat node here is large and difficult to shrink. Structures 12 and 13 are the sealing mating surfaces between the hub connecting frame and the brake end cover, and structures 15 and 16 are the sealing mating surfaces between the hub connecting frame and the rear seat of the frame. In order to ensure the sealing performance of the sealing mating surface, the tissue density of the sealing mating surface is extremely high, and magnetic marks are not allowed to appear during magnetic particle inspection. Structure 14 is the side wall of the central hole of the hub connector, where the central sleeve passes through. The surface quality and internal quality requirements are very high. During magnetic particle testing, magnetic marks are not allowed, and during ultrasonic testing, defects exceeding level 1 are not allowed. Structure 17 is the thin-walled area of ​​the hub connector, where solidification is preferentially performed during solidification, and isolated hot spots are easily formed. The hot spots are located at the stepped inner hole wall of the hub connector, where risers cannot be placed, and process shrinkage compensation is difficult. Placing cold iron is prone to carbide and hard spots, which causes the hub connector to be easily worn during use and causes the hub connector to fail.

[0023] Example 1: Please refer to Figure 1-Figure 5 In order to cast a wheel hub connecting frame that meets the requirements, this embodiment provides a method for casting a wheel hub connecting frame for an electric wheel, comprising the following casting steps: S1. Making a casting sand mold for a wheel hub connection frame; firstly, designing a wheel hub connection frame mold including a casting system, and setting a heating riser and / or a chiller on the mold corresponding to the hot node position of the wheel hub connection frame; then, making a combined wheel hub connection frame casting sand mold by a sand mixer; S2. The casting liquid components are proportioned and the components are smelted. The casting liquid components of this embodiment are proportioned as follows: C: 3.5%, Si: 2.2%, Mn: 0.3% by mass; S: 0.11%, Cu: 0.5%, Mg: 0.04%, and the remainder is iron and inevitable impurities. During smelting, all components are melted and then the temperature is raised to 1530-1570°C for smelting. The molten iron is calmed, melted and cooled to 1510°C for tapping.

[0024] S3. The smelted casting liquid in S2 is subjected to spheroidizing inoculation reaction. Before pouring, the smelted molten iron is first poured into a casting ladle. The groove of the casting ladle adopts a sandwich structure, and is filled with spheroidizing agent, inoculant and covered with silicon steel sheets from bottom to top. After the spheroidizing inoculation reaction is complete, the molten iron temperature is controlled at 1370°C and poured into the pouring port of the assembled casting sand mold. During the pouring process, an inoculant with a particle size of 0.2-0.7mm is used for secondary inoculation. The mass percentage of the inoculant added in the total amount of molten iron is 0.25%.

[0025] S4. After pouring, unpack after cooling for more than 12 hours, remove the runner and riser, and perform tempering and normalizing after grinding.

[0026] In this embodiment, when making the combined hub connecting frame casting sand mold in S1, specifically: S10, firstly designing a combined hub connecting frame mold including a casting system according to the hot node position of the hub connecting frame, the combined hub connecting frame mold including two sub-molds; using a sand mixer to make two sub-hub connecting frame casting sand molds in a one-mold-one-piece production method, the two sub-hub connecting frame casting sand molds form a combined hub connecting frame casting sand mold along the axial direction up and down, the inside of which constitutes a horizontally arranged hub connecting frame casting cavity, and the parting surface of the combined hub connecting frame casting sand mold is the bottom end of the first step of the end face of the hub connecting frame; S11. When making the casting sand mold of the sub-wheel hub connecting frame by a sand mixer, according to the casting process, a casting system, an air outlet rod, a cold iron and / or a heating riser are placed on the sub-mold, and then the sand box is placed on the mold plate, and the sand is mixed by a sand mixer to form a resin sand mixture. Among them, the resin sand mixture of this embodiment includes resin, hardener, curing agent and sand, and the addition ratio of resin and sand is resin / sand = 1wt.%; the addition ratio of curing agent and resin is curing agent / resin = 30wt.%; the resin adopts furan resin, the curing agent adopts benzenesulfonic acid curing agent, the sand is regenerated sand, and the regenerated sand adopts silica sand, whose angular coefficient is ≤1.2 and the particle size is 40 / 70 mesh. Then the mixture is evenly filled in the sand box. After the mixture is flush with the surface of the sand box, stop putting sand, and let it stand for 20 minutes. After the sand mold is hardened, the sand box is lifted by a crane to separate the sand mold from the sub-mold to obtain the casting sand mold of the sub-wheel hub connecting frame; S12, flow coating the casting molding part of the sub-wheel hub connecting frame casting sand mold obtained in S11, and after the coating is dried, clean the sub-wheel hub connecting frame casting sand mold cavity with an air gun, place a filter component in the pouring channel of the pouring system, then fasten all the sub-wheel hub connecting frame casting sand molds with fasteners to form a wheel hub connecting frame casting sand mold assembly, finally connect the pouring system with the wheel hub connecting frame casting sand mold assembly cavity, and stick a pouring cup at the pouring gate of the pouring system to form a combined wheel hub connecting frame casting sand mold.

[0027] In S12 of this embodiment, according to the casting process, the pouring system of this embodiment is a center pouring system, which adopts a semi-open and semi-closed structure. The pouring system is provided with a straight runner 27, a cross runner 26 and an ingode 25. The number of the ingodes 25 is three. The three ingodes are evenly spaced along the circumference of the central hole cavity of the hub connecting frame, and the connecting end of the ingode and the pouring cavity is set to a trumpet shape; the straight runner and the ingode are connected through three cross runners respectively; the ratio of the cross-sectional area of ​​the straight runner, the cross runner and the ingode is 1.1-1.3:1.4-1.6:1. The filter assembly of this embodiment includes a ceramic bowl and a foam ceramic filter; the ceramic bowl is placed at the bottom of the straight runner of the pouring system, and the foam ceramic filter is horizontally arranged at the ingode of the ingode. The size of the foam ceramic filter is 100 mm×100 mm×22 mm, and the porosity is 10ppi.

[0028] In this embodiment, when the cold iron and / or the heating riser are placed in S11, the thick and large heat node position on the upper part of the hub connecting frame parting surface is as follows: Figure 2 The structures 10 and 11 in the embodiment are provided with a heat-generating and heat-insulating riser on the sub-mold, that is, Figure 3 The structure 20 in the embodiment is used to perform liquid shrinkage compensation during the solidification process. At the hot spot position below the parting surface of the hub connecting frame, as shown in FIG. Figure 2 Structures 18 and 19 in Figure 1 The middle structure 1 to structure 9, i.e. the hub connecting frame shell, adopts a method of installing a heating and heat-insulating riser and a cold iron on the mold, wherein the heating and heat-insulating riser is placed at the structure 18 and the structure 19, i.e. Figure 3 In the structure 21, an arc-shaped cold iron is placed between the three heat-generating and heat-insulating risers, that is, Figure 4 In structure 22, the arc-shaped chiller is installed at the bottom of the hub connector housing. The arc-shaped chiller has a height of 80-90 mm and a thickness of 100-120 mm, which can accelerate the solidification of thick and large hot spots. The mounting boss of the hub connector, the side wall of the central hole of the hub connector, and the thin-walled area of ​​the hub connector are respectively stepped structures. Since it is impossible to place a riser for shrinkage compensation, this embodiment places a chiller at such a hot spot position to make the hot spot solidify first, thereby changing the solidification order of the casting and eliminating shrinkage defects in thick and large parts of the casting. According to Figure 3The cold iron of the hub connecting frame mounting boss is structure 23, and the step-shaped structure between the side wall of the central hole of the hub connecting frame and the thin-walled area of ​​the hub connecting frame is provided with three cold irons, namely Figure 4 The structure 24 in the embodiment of the present invention is characterized in that the three cold irons form an annular cold iron that matches the shape of the step-shaped structure. At the same time, the three annular cold irons are just in contact with the three heat-generating and heat-insulating risers of the thick and large hot section on the upper part of the wheel hub connecting frame parting surface, that is, Figure 3 The structure 20 in the casting interacts with each other, and the hot node here solidifies first through the annular chiller, which changes the solidification sequence of the casting, forms local sequential solidification, and eliminates the shrinkage defects in the thick and large parts here.

[0029] Example 2: The main difference between Example 2 and Example 1 is that in S1, when Example 2 uses a sand mixer to mix sand to form a resin-sand mixture, the resin addition ratio is resin / sand = 0.9wt.%, and the curing agent addition ratio is curing agent / resin = 35wt.%. The sand mixer is turned on, and the mixture of resin, hardener, curing agent, and sand is evenly filled into the sand box. After the mixture is flush with the sand box, stop adding sand and let it stand for 15 minutes. After the sand mold is hardened, the sand box is lifted by a crane to separate the sand mold from the mold.

[0030] In S2, the casting liquid components are proportioned and the components are smelted; the casting liquid components of this embodiment are proportioned as follows: by mass percentage, C: 3.6%, Si: 2.4%, Mn: 0.4%; S: 0.08%, Cu: 0.6%, Mg: 0.04%, and the remainder is iron and inevitable impurities. During smelting, all components are melted and then the temperature is raised to 1530-1570°C for smelting, and the molten iron is calmed, melted and cooled to 1500°C for tapping.

[0031] In S3, before pouring, the smelted molten iron is first poured into a casting ladle. The groove of the casting ladle adopts a sandwich structure, and is filled with spheroidizer, inoculant and covered with silicon steel sheets from bottom to top. After the spheroidizing and inoculation reactions are complete, the molten iron temperature is controlled at 1370°C and poured into the pouring port of the assembled casting sand mold. During the pouring process, an inoculant with a particle size of 0.2-0.7mm is used for secondary inoculation. The mass percentage of the inoculant added in the total amount of molten iron is 0.2%.

[0032] Example 3: The main difference between Example 3 and Example 1 is that in S1, when Example 3 uses a sand mixer to mix sand to prepare a resin-sand mixture, the ratio of resin added is resin / sand = 1.1wt.%, and the ratio of curing agent added is curing agent / resin = 30wt.%. The sand mixer is turned on, and the mixture of resin, hardener, curing agent, and sand is evenly filled into the sand box. After the mixture is flush with the sand box, stop adding sand, let it stand for 25 minutes, and after the sand mold is hardened, lift the sand box with a crane to separate the sand mold from the mold.

[0033] In S2, the casting liquid components are proportioned and the components are smelted; the casting liquid components of this embodiment are proportioned as follows: by mass percentage, C: 3.7%, Si: 2.1%, Mn: 0.4%, S: 0.08%, Cu: 0.7%, Mg: 0.04%, and the remainder is iron and inevitable impurities. During smelting, all components are melted and then the temperature is continued to rise to 1530-1570°C for smelting, and the molten iron is calmed, melted and cooled to 1520°C for tapping.

[0034] In S3, before pouring, the smelted molten iron is first poured into a casting ladle. The groove of the casting ladle adopts a sandwich structure, and is filled with spheroidizer, inoculant and covered with silicon steel sheets from bottom to top. After the spheroidizing and inoculation reactions are complete, the molten iron temperature is controlled at 1370°C and poured into the pouring port of the assembled casting sand mold. During the pouring process, an inoculant with a particle size of 0.2-0.6 mm is used for secondary inoculation. The mass percentage of the inoculant added in the total amount of molten iron is 0.27%.

[0035] Finally, the wheel hub adapters obtained in Example 1, Example 2 and Example 3 were subjected to mechanical property tests to obtain the test results shown in the following table. From the data in the table, it can be seen that the casting method adopted by the present invention obtains a wheel hub adapter casting with excellent internal quality and good performance.

[0036] Serial number Rm R A% HBW Example 1 892 566 3 297 Example 2 880 552 4 285 Example 3 887 556 3 290 As above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the present invention itself. Various changes in form and details may be made without departing from the spirit and scope of the present invention as defined in the appended claims. The specific component ratios used in the embodiments are only used as embodiments to illustrate the technical effects of the present invention. The ratio values ​​in the embodiments can be the numerical ranges in the claims or specific values, but they must be within the ranges defined in the claims. Moreover, the embodiments are only used as examples and are not limitations on the claims.

Claims

1. A method for casting a hub connecting frame for an electric wheel, characterized in that: The casting steps include: S1. Making a casting sand mold for a wheel hub connection frame; firstly, designing a wheel hub connection frame mold including a casting system, placing a heating riser and / or a chiller on the mold corresponding to the hot node position of the wheel hub connection frame; then, making a combined wheel hub connection frame casting sand mold by a sand mixer; S2, proportioning the casting liquid components and melting the components; S3, subjecting the smelted pouring liquid in S2 to a spheroidizing inoculation reaction, and after the spheroidizing inoculation reaction is completed, the temperature is controlled to be poured into the pouring sand mold prepared in S1, and secondary inoculation is adopted during the pouring process; S4. After the pouring is completed, the hub connecting frame casting is post-processed.

2. The method for casting a hub connecting frame for an electric wheel according to claim 1, characterized in that: In S1, a wheel hub connecting frame casting sand mold is manufactured. First, a wheel hub connecting frame mold including a casting system is designed, and a heating and heat-insulating riser and / or a chiller are placed on the mold corresponding to the thick and hot section of the wheel hub connecting frame. Then, a combined wheel hub connecting frame casting sand mold is manufactured by a sand mixer, specifically: S10, firstly designing a combined hub connecting frame mold including a casting system according to the hot node position of the hub connecting frame, wherein the combined hub connecting frame mold includes a plurality of sub-molds; using a sand mixer to make a plurality of sub-hub connecting frame casting sand molds in a one-mold-one production manner, wherein the joints between the sub-hub connecting frame casting sand molds constitute the parting surface of the hub connecting frame; S11. A plurality of sub-wheel hub connecting frame casting sand molds are made by a sand mixer in a one-mold-one production mode. During the production, a casting system, a gas outlet rod, a chiller and / or a heating riser are placed on the sub-mold according to the casting process, and then a sand box is placed on the mold plate, and sand is mixed by a sand mixer to form a resin sand mixture. Then, the mixture is evenly filled into the sand box, and after the mixture is flush with the surface of the sand box, the sand is stopped, and the mixture is left to stand for 15 min to 20 min. After the sand mold is hardened, the sand box is lifted by a crane to separate the sand mold from the sub-mold to obtain a sub-wheel hub connecting frame casting sand mold. S12, coating the casting molding parts of the sub-wheel hub connecting frame casting sand mold obtained in S11 with paint, and after the paint is dried, cleaning the molding cavity, placing a filter assembly in the pouring channel of the pouring system, and then fastening all the sub-wheel hub connecting frame casting sand molds with fasteners to form a wheel hub connecting frame casting sand mold assembly, and then connecting the pouring system with the wheel hub connecting frame casting sand mold assembly cavity, and finally pasting a pouring cup at the pouring gate of the pouring system to form a combined wheel hub connecting frame casting sand mold.

3. The method for casting a hub connecting frame for an electric wheel according to claim 2, characterized in that: The combined hub connecting frame mold comprises two sub-molds; two sub-hub connecting frame casting sand molds are made into one-mold-one-piece production mode by a sand mixer; the two sub-hub connecting frame casting sand molds form a combined hub connecting frame casting sand mold along the axial direction up and down, and a horizontally arranged hub connecting frame casting cavity is formed inside; and the parting surface of the combined hub connecting frame casting sand mold is the bottom end of the first step of the end face of the hub connecting frame.

4. The method for casting a hub connecting frame for an electric wheel according to claim 2, characterized in that: The resin-sand mixture includes resin, hardener, curing agent and sand, wherein the resin and sand are added in a ratio of resin / sand = 0.95wt.%~1.1wt.%; the curing agent and resin are added in a ratio of curing agent / resin = 30wt.%~60wt.%; the resin is furan resin, the curing agent is benzenesulfonic acid curing agent, the sand is regenerated sand, and the regenerated sand is silica sand, whose angular coefficient is ≤1.2 and particle size is 40 / 70 mesh.

5. The method for casting a hub connecting frame for an electric wheel according to claim 2, characterized in that: The pouring system is a center pouring system with a semi-open and semi-closed structure. The pouring system is provided with a straight runner, a cross runner and an ingode. The number of the ingodes is several, and the several ingodes are evenly spaced along the circumference of the pouring cavity, and the connecting end of the ingode and the pouring cavity is set to a trumpet shape; the straight runner and the ingode are connected by several cross runners; the ratio of the cross-sectional area of ​​the straight runner, the cross runner and the ingode is 1.1-1.3:1.4-1.6:

1.

6. The method for casting a hub connecting frame for an electric wheel according to claim 5, characterized in that: The filter assembly comprises a ceramic bowl and a foam ceramic filter; the ceramic bowl is placed at the bottom of the sprue of the pouring system, and the foam ceramic filter is horizontally arranged at the ingrate of the ingrate.

7. The method for casting a hub connecting frame for an electric wheel according to claim 3, characterized in that: When placing the chill and / or the heating riser in S11, at the hot node position above the parting surface of the hub connecting frame, a heating and insulating riser is installed on the sub-mold; at the hot node position below the parting surface of the hub connecting frame, a heating and insulating riser and a chill are installed on the sub-mold in combination; the size of the heating and insulating riser is adapted to the thickness of the casting at the installation position; the shape of the chill is adapted to the shape of the hot node of the casting.

8. The method for casting a hub connecting frame for an electric wheel according to claim 1, characterized in that: The casting liquid composition ratio is C: 3.3-3.8%, Si: 2.0-2.4%, Mn: 0.2-0.5%; S: 0.06-0.11%, Cu: 0.4-0.7%, Mg: 0.03-0.05%, and the balance is iron and inevitable impurities; during smelting, all components are melted and then the temperature is raised to 1540-1580° C. for smelting, and then the temperature is lowered to 1480-1540° C. for iron tapping.

9. The method for casting a hub connecting frame for an electric wheel according to claim 1, characterized in that: Before pouring in S3, the smelted pouring liquid is poured into a pouring ladle. The groove of the pouring ladle adopts a sandwich structure, and is filled with spheroidizer, inoculant and covered with silicon steel sheets from bottom to top. During pouring, the pouring liquid temperature is controlled at 1340-1360°C, and pouring is performed into the pouring port of the assembled casting sand mold. During the pouring process, an inoculant with a particle size of 0.2-0.7 mm is used for secondary inoculation. The amount of the inoculant added is 0.1-0.4% by mass of the total amount of the pouring liquid.

10. The method for casting a hub connecting frame for an electric wheel according to claim 1, characterized in that: In S4, after pouring is completed, the casting is cooled for at least 12 h, unpacked and taken out, and then the runner and riser are removed, and the casting surface is polished and heat treated.

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