Method for casting nodular cast iron motor shell for urban rail driving device

Abstract

The invention relates to a method for casting a nodular cast iron motor shell for an urban rail driving device, and belongs to the technical field of casting. Comprising the following steps: manufacturing a motor shell casting sand mold; the method comprises the following steps: firstly, designing a motor shell mold comprising a pouring system, and arranging an exothermic riser and / or a chilling block on the mold corresponding to a hot spot position of a motor shell; then, a motor shell pouring sand mold is manufactured through a mechanical core manufacturing method and a manual core manufacturing method; 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, motor shell casting post-processing is carried out. By adopting a filtering type pouring process, arranging a process feeding channel and adopting a reasonable smelting process, the problems that rays and magnetic powder in a key area of the motor shell exceed the standard, and local hot spot feeding is difficult are solved, a casting made of a high-strength and high-toughness material is obtained, and the yield of the motor shell is increased.

Description

Technical Field

[0001] The invention relates to the technical field of casting, and in particular to a method for casting a ductile iron motor housing for an urban rail drive device. Background Art

[0002] At present, my country's new urbanization process has entered a new stage of high-quality and in-depth development. Using central cities to drive the construction of modern metropolitan areas and urban clusters and deepen regional coordinated development will be the focus of urban development in a certain period of time in the future. As the size and scale of regional central cities continue to expand, urban rail will play an important role as a key mode of transportation to balance the even development of urban blocks.

[0003] As a key component of the urban rail drive system, the motor housing plays a fixed bearing role for the motor and bears certain alternating loads. Therefore, the motor housing has high requirements for surface and internal defects. Figure 1 The motor housing shown is connected to the main body of the drive device through the upper mounting bracket of structure 1, which plays a role in fixing the motor and bears a certain alternating load. It is a key part. The structure here is narrow and has a certain inclination angle. The size of the riser and the shrinkage capacity of the riser are limited. Structure 2 is the main structure of the motor housing, with a wall thickness of 11mm, to realize motor loading. Structure 3 is a junction box to realize the connection between the motor and the power circuit. Structure 4 and structure 5 are the lower mounting brackets of the motor housing, which play a role in assisting the fixing of the motor and bear a certain stress. It is a key part. Structure 6 is a heat dissipation window, which plays a role in cooling the motor during operation. The structure here is more complex, easy to stick to sand, and difficult to polish. Structure 7 is a safety bracket, which plays a certain protective role on the motor housing. When making the motor housing, it is necessary to meet the surface magnetic particle inspection level to meet the requirements of level 2 and above, and the radiographic inspection must meet the requirements of level 2 and above for key parts and level 3 for non-key parts. The main body of the motor housing is a thin-walled barrel-shaped structure with a large difference in wall thickness. There are isolated heat nodes at the contact points between the inner ring ribs and the barrel wall, the contact points between the upper and lower mounting brackets and the barrel wall, the contact points between the safety bracket and the barrel wall, and the contact points between the terminal box and the barrel wall, making the process design difficult. At the same time, in order to ensure the safe operation of the motor during use, the heat dissipation window of the motor housing is a thin-walled complex structure, which is prone to sand sticking problems. Sand mold design needs to give priority to this area. In addition, since the motor housing needs to withstand certain alternating loads during operation, the motor housing requires not only high strength but also good toughness. Combining the above requirements and its own structural characteristics, the casting and production of ductile iron motor housings for urban rail drive devices is difficult, the product qualification rate is low, the production cost is high, and it is difficult to meet the quality requirements of mass production and supply.

[0004] In the known literature ("Analysis of Defects in Cast Steel Motor Casing and Research on Process Optimization"), a production process for cast steel motor casings was introduced in the 2017 China Excellent Master's Thesis Collection, but its focus is on the product material, and there is almost no mention of cast iron motor casings. Therefore, a casting method for ductile iron motor casings for urban rail drive devices is urgently needed to solve the problems of high production difficulty, low yield and high production cost in the prior art when casting ductile iron motor casings for urban rail drive devices. Summary of the invention

[0005] The object of the present invention is to provide a method for casting a ductile iron motor housing for an urban rail drive device, so as to solve the problems raised in the above-mentioned background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for casting a ductile iron motor housing for an urban rail drive device, comprising the following casting steps: S1, making a motor housing casting sand mold; first designing a motor housing 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 motor housing; then using mechanical core making and manual core making methods to make a combined motor housing casting sand mold; 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 pouring is completed, the motor housing casting is post-processed.

[0007] Preferably, in S1, a motor housing casting sand mold is manufactured; first, a motor housing mold including a casting system is designed, and a heating riser and / or a chiller are arranged on the mold corresponding to the hot node position of the motor housing; then, a mechanical core making method and a manual core making method are used to manufacture a combined motor housing casting sand mold, specifically: S10, firstly designing a combined motor housing mold including a casting system according to the position of the hot node of the motor housing, wherein the combined motor housing mold includes a plurality of sub-molds; and making a plurality of sub-motor housing casting sand molds according to a one-mold-one-piece production method; S11. When a plurality of sub-motor housing casting sand molds are made according to a one-mold-for-one production method, the motor housing mold is divided into a key part sub-mold and a non-key part sub-mold according to the motor housing casting process; the key part sub-mold is used to make a key part motor housing casting sand mold by a mechanical core making method, and the non-key part sub-mold is used to make a non-key part motor housing casting sand mold by a manual core making method. When making the core, a chill and / or a heating riser are installed on the sub-mold, and the key part motor housing casting sand mold and the non-key part motor housing casting sand mold constitute the sub-motor housing casting sand mold; S12, applying coating to the casting molding parts of the sub-motor housing casting sand mold obtained in S11, and after the coating is dried, cleaning the mold cavity, placing a filter component in the pouring channel of the pouring system, and then fastening all the sub-motor housing casting sand molds with fasteners to form a motor housing casting sand mold assembly, and finally connecting the pouring system with the motor housing casting sand mold assembly, and pasting a pouring cup at the pouring gate of the pouring system to form a combined motor housing casting sand mold.

[0008] Preferably, the mechanical core making method adopts coated sand core making, by heating the key part sub-mold to 220℃~270℃, filling the coated sand grains into the mold through the sand shooting port, keeping warm for 150S~180S, opening the mold, and taking out the coated sand core; the manual core making method is to place the non-key part sub-mold including the pouring system in a sand box, inject the molding sand into the sand box from the sand shooting port of the sand shooting machine, and then let it stand and solidify for 12-15 minutes, open the mold, and take out the sand mold; the motor housing is horizontally arranged in the combined motor housing casting sand mold, and the heat dissipation window surface of the motor housing is placed vertically; the parting method of the motor housing adopts a horizontal parting structure, the parting surface is the central plane of the motor housing, and the lower mounting bracket of the motor housing is located at the upper part of the parting surface, and the upper mounting bracket is located at the lower part of the parting surface.

[0009] Preferably, the molding sand used in the manual core making method is silica sand with a particle size of 40 / 70 mesh, a strength of 0.5-1Mpa, and a gas generation amount of 10-12ml / g.

[0010] Preferably, the pouring system adopts an intermediate injection pouring method, and the pouring system is provided with a straight runner, a horizontal runner and an ingrate, and the ratio of the cross-sectional areas of the straight runner, the horizontal runner and the ingrate is 1.3-1.4:1.6-1.8:1.

[0011] Preferably, the filter assembly comprises a foam ceramic filter screen; the foam ceramic filter screen is horizontally arranged at the bottom of the sprue.

[0012] Preferably, when installing the cold iron and / or the heating riser in S11, at the hot node position above the parting surface of the motor housing, a heating and insulating riser is installed on the sub-mold; at the hot node position below the parting surface of the motor housing, a combination of a heating and insulating riser and a cold iron is installed on the sub-mold.

[0013] Preferably, the casting liquid composition ratio is C: 3.45-3.7%, Si: 2.1-2.3%, Mn: 0.2-0.3%; S: <0.2%, the balance is iron and inevitable impurities; during smelting, all components are melted and then heated to 1540-1580°C for smelting, and then cooled to 1480-1540°C for tapping.

[0014] Preferably, before pouring in S3, the smelted molten iron is poured into a pouring ladle. A dam-type structure is adopted in the groove of the pouring ladle, and spheroidizing agent, inoculant and silicon steel sheet are filled from bottom to top. After the spheroidizing and inoculation reaction is complete, the temperature of the molten iron is controlled at 1390-1410°C and the molten iron is poured into the assembled pouring cup. The molten iron enters the mold cavity from the pouring cup. 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 0.1-0.4%.

[0015] Preferably, in S4, after pouring is completed, the casting is opened after cooling for more than 6 hours, the pouring port and the riser are removed, and the casting is surface polished and then subjected to stress relief annealing. Beneficial Effects

[0016] The present invention designs a motor housing mold including a pouring system to form a combined motor housing pouring sand mold, and uses the motor housing parting surface as the interface. A heating riser and / or cold iron process design is adopted at key positions at the upper and lower parts of the parting surface, thereby overcoming the problem of difficulty in compensating for liquid shrinkage during solidification due to limited structure and size of heating risers at key positions, thereby achieving internal defect radiation level meeting the requirements of level 2 and above in the key area.

[0017] The present invention manufactures a casting sand mold for a sub-motor housing by combining mechanical core making with manual core making, so as to realize different casting requirements according to different parts of the casting, such as the upper mounting bracket, the lower mounting bracket, and the heat dissipation window of the motor housing are key parts with high casting requirements, so the mechanical core making method is selected to manufacture the casting sand mold, while the motor housing body, the junction box, and the safety support are non-key parts with relatively low casting requirements, so the manual core making method can be selected to manufacture the casting sand mold to reduce the production cost of the casting sand mold. The casting system of the casting sand mold of the present invention is supplemented with a foam ceramic filter to filter the secondary oxidation slag, thereby realizing that the surface magnetic particle flaw detection meets the requirements of level 2 and above.

[0018] The present invention adopts an intermediate injection type filtering pouring system and sets a reasonable cross-sectional area ratio of a sprue, a cross runner and an inner runner, thereby achieving a process yield rate of motor housing castings of ≥80%.

[0019] The present invention overcomes the problem of high strength and low toughness of the motor housing material by adopting a reasonable material ratio and smelting process, thereby realizing a high-strength and tough cast iron production technology with a strength of more than 400Mpa and an elongation of ≥18%. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of the structure of a motor housing in an embodiment; Figure 2 A schematic structural diagram of a motor housing mold according to an embodiment (1); Figure 3 Schematic diagram of the structure of the motor housing mold of the embodiment (2). 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] Example 1: Please refer to Figure 1-Figure 3 In order to cast a motor housing that meets the requirements, this embodiment provides a method for casting a ductile iron motor housing for an urban rail drive device, comprising the following casting steps: S1, making a motor housing casting sand mold; first designing a motor housing 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 motor housing; then using mechanical core making and manual core making methods to make a combined motor housing casting sand mold; S2, carry out the proportioning of the pouring liquid components and carry out component smelting; the mass percentage of the pouring liquid components of this embodiment is C: 3.6%, Si: 2.2%, Mn: 0.25%; S: 0.11%, the balance is iron and inevitable impurities, and after all the components are melted, continue to heat up to 1540-1580 ° C for smelting, wait for the molten iron to be calmed and melted, and cool down to 1520 ° C for iron tapping; S3, the smelted casting liquid in S2 is subjected to spheroidizing inoculation reaction, firstly, the smelted molten iron is poured into a casting ladle, the bottom of the casting ladle adopts a dam structure, and the spheroidizing agent, the inoculant and the silicon steel sheet are filled from bottom to top, after the spheroidizing inoculation reaction is complete, the molten iron temperature is controlled at 1410°C and the molten iron is poured into the assembled casting sand mold through the pouring cup, and the inoculant with a particle size of 0.2-0.7mm is used for secondary inoculation during the pouring process, and the mass percentage of the inoculant added in the total amount of molten iron is 0.2%; S4. After pouring, unpack after cooling for more than 6 hours, remove the gate and riser, and perform stress relief annealing after grinding.

[0023] In this embodiment, when manufacturing the combined motor housing casting sand mold in S1, specifically: S10, firstly designing a combined motor housing mold including a casting system according to the position of the hot node of the motor housing, the combined motor housing mold including a motor housing body sub-mold, an upper mounting bracket sub-mold, a lower mounting bracket sub-mold, a junction box mold, a heat dissipation window mold and a safety bracket mold; making a plurality of sub-motor housing casting sand molds according to a one-mold-for-one production method; S11. When a plurality of sub-motor housing casting sand molds are made according to the one-mold-for-one production method, the motor housing mold is divided into key part sub-molds and non-key part sub-molds according to the motor housing casting process; the key part motor housing casting sand mold is made by mechanical core making method using the key part sub-mold, and the non-key part motor housing casting sand mold is made by manual core making method using the non-key part sub-mold, when core making, cold iron and / or heating riser are installed on the sub-mold, and the key part motor housing casting sand mold and the non-key part motor housing casting sand mold constitute the sub-motor housing casting sand mold; wherein, the upper mounting bracket, the lower mounting bracket and the heat dissipation window of the motor housing are respectively key parts, and the sub-motor housing casting sand mold is made by mechanical core making method, while the junction box, the motor housing body and the safety bracket of the motor housing are non-key parts, and are made by manual core making method. The motor housing casting of this embodiment is mainly based on the motor housing body, and other components are arranged on the motor housing body. Therefore, the motor housing body casting sand mold can be used as the outer mold, and then other components are first combined into a combined mud core, and then formed into a motor housing casting sand mold assembly with the outer mold, and finally the casting system is installed. The mechanical core making method of the present embodiment adopts coated sand core making, by heating the key part sub-mold to 250℃~270℃, filling the coated sand grains into the mold through the sand shooting port, keeping warm for 150S~180S, opening the mold, and taking out the coated sand core; the manual core making method is to place the non-key part sub-mold containing the pouring system in a sand box, by shooting the molding sand into the sand box from the sand shooting port of the sand shooting machine, and then standing and curing for 12-15min, opening the mold, and taking out the sand mold; the motor housing is horizontally arranged in the combined motor housing casting sand mold, and the heat dissipation window surface of the motor housing is placed vertically; the parting method of the motor housing adopts a horizontal parting structure, the parting surface is the central plane of the motor housing, and the lower mounting bracket of the motor housing is located at the upper part of the parting surface, and the upper mounting bracket is located at the lower part of the parting surface; the molding sand and the coated sand of the motor housing of the present embodiment are both made of silica sand, with a particle size of 40 / 70 mesh, a strength of 0.5-1Mpa, and a gas emission of 10~12ml / g; S12, applying coating to the casting molding parts of the sub-motor housing casting sand mold obtained in S11, and after the coating is dried, cleaning the mold cavity, placing a filter component in the pouring channel of the pouring system, and then fastening all the sub-motor housing casting sand molds with fasteners to form a motor housing casting sand mold assembly, and finally connecting the pouring system with the motor housing casting sand mold assembly, and pasting a pouring cup at the pouring gate of the pouring system to form a combined motor housing casting sand mold.

[0024] The pouring system of this embodiment adopts the middle injection pouring method, and the pouring system is provided with a straight runner, i.e. Figure 2 In structure 6, the runner is Figure 2 Structure 2 and the gate in Figure 2 Structure 3 in Figure 2 The ratio of the cross-sectional area of ​​the sprue, runner and ingates in structure 6 is 1.1-1.2:1.2-1.3:1. The filter assembly of this embodiment includes a foam ceramic filter screen, that is, Figure 3 In the structure 1, the foam ceramic filter is horizontally arranged at the bottom of the sprue.

[0025] In this embodiment, when the cold iron and / or the heating riser are installed in S11, at the hot spot position above the parting surface of the motor housing, as shown in FIG. Figure 1 Structures 4 and 5 in the figure are the lower mounting brackets of the motor housing. A heating riser is installed on the sub-mold to perform liquid shrinkage compensation during the solidification process. At the hot spot below the parting surface of the motor housing, as shown in FIG. Figure 1 The structure 1 in the figure is the upper mounting bracket of the motor housing, which adopts the method of installing a heating riser and a chiller on the sub-mold to reduce the modulus of the hot section, increase the shrinkage feeding capacity of the riser, and solve the shrinkage problem of the thick and large hot section. Figure 3 The size of the structure 4 in the embodiment is adapted to the size of the casting at the hot node position. Figure 2 The size of structure 5 is 30 mm.

[0026] Example 2: The main difference between Example 2 and Example 1 is that in S11, the mechanical core making method adopts coated sand core making, by heating the key part sub-mold to 220℃~250℃, filling the coated sand grains into the mold through the sand shooting port, keeping warm for 150S~180S, opening the mold, and taking out the coated sand core; the manual core making method is to place the non-key part sub-mold including the pouring system in a sand box, by shooting the molding sand into the sand box from the sand shooting port of the sand shooting machine, and then letting it stand and solidify for 12-15 minutes, opening the mold, and taking out the sand mold.

[0027] In S2, the casting liquid components are proportioned and the components are smelted; the casting liquid components proportioned in this embodiment are: C: 3.55%, Si: 2.11%, Mn: 0.28%; S: 0.11%, the remainder is iron and inevitable impurities. After all the components are melted, the temperature is continued to be raised to 1540-1580°C for smelting, and the molten iron is cooled to 1510°C for tapping.

[0028] In S3, before pouring, the smelted molten iron is first poured into a pouring ladle. The bottom of the pouring ladle adopts a dam-type structure, and is filled with spheroidizer, inoculant and covered with silicon steel sheets from bottom to top. After the spheroidizing and inoculating reactions are complete, the molten iron temperature is controlled at 1400°C and the molten iron is poured into the assembled sand mold through the pouring cup. 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 0.15%.

[0029] Example 3: The main difference between Example 3 and Example 1 is that in S11, the mechanical core making method adopts coated sand core making, by heating the key part sub-mold to 220℃~250℃, filling the coated sand grains into the mold through the sand shooting port, keeping warm for 150S~180S, opening the mold, and taking out the coated sand core; the manual core making method is to place the non-key part sub-mold including the pouring system in a sand box, inject the molding sand into the sand box from the sand shooting port of the sand shooting machine, and then let it stand and solidify for 12-15 minutes, open the mold, and take out the sand 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: C: 3.6%, Si: 2.2%, Mn: 0.28%; S: 0.11%, and the remainder is iron and inevitable impurities. After all the components are melted, the temperature is continued to be raised to 1540-1580°C for smelting. After the molten iron is calmed and melted, the temperature is lowered to 1500°C for tapping.

[0031] In S3, before pouring, the smelted molten iron is first poured into a pouring ladle. The bottom of the pouring ladle adopts a dam-type 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 1390°C and the molten iron is poured into the assembled sand mold through a pouring cup. 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 0.1%.

[0032] Finally, the motor housings 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 connector casting with excellent internal quality and good performance.

[0033] Serial number Rm R A% HBW Example 1 408 284 26 133 Example 2 405 280 23 134 Example 3 403 281 21 134 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. A prior art test comparison group can be added, but the inventor is required to provide reaction conditions, reaction process and mechanical property test data as in the examples.

Claims

1. A method for casting a ductile iron motor housing for an urban rail drive device, characterized in that: The casting steps include: S1, making a motor housing casting sand mold; first designing a motor housing 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 motor housing; then using mechanical core making and manual core making methods to make a combined motor housing casting sand mold; 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 pouring is completed, the motor housing casting is post-processed.

2. The method for casting a ductile iron motor housing for an urban rail drive device according to claim 1, characterized in that: In S1, a motor housing casting sand mold is manufactured; first, a motor housing mold including a casting system is designed, and a heating riser and / or a chiller are arranged on the mold corresponding to the hot node position of the motor housing; then, a mechanical core making method and a manual core making method are used to manufacture a combined motor housing casting sand mold, specifically: S10, firstly designing a combined motor housing mold including a casting system according to the position of the hot node of the motor housing, wherein the combined motor housing mold includes a plurality of sub-molds; and making a plurality of sub-motor housing casting sand molds according to a one-mold-one-piece production method; S11, when a plurality of sub-motor housing casting sand molds are made according to a one-mold-for-one production method, the motor housing mold is divided into a key part sub-mold and a non-key part sub-mold according to the motor housing casting process, the key part sub-mold is used to make a key part motor housing casting sand mold by a mechanical core making method, and the non-key part sub-mold is used to make a non-key part motor housing casting sand mold by a manual core making method. When making the core, a chill and / or a heating riser are installed on the sub-mold, and the key part motor housing casting sand mold and the non-key part motor housing casting sand mold constitute the sub-motor housing casting sand mold; S12, applying coating to the casting molding parts of the sub-motor housing casting sand mold obtained in S11, and after the coating is dried, cleaning the mold cavity, placing a filter component in the pouring channel of the pouring system, and then fastening all the sub-motor housing casting sand molds with fasteners to form a motor housing casting sand mold assembly, and finally connecting the pouring system with the motor housing casting sand mold assembly, and pasting a pouring cup at the pouring gate of the pouring system to form a combined motor housing casting sand mold.

3. The method for casting a ductile iron motor housing for an urban rail drive device according to claim 2, characterized in that: The mechanical core making method adopts coated sand core making, heats the key part sub-mold to 220°C-270°C, fills the coated sand grains into the mold through the sand shooting port, keeps warm for 150S-180S, opens the mold, and takes out the coated sand core; the manual core making method places the non-key part sub-mold including the pouring system in a sand box, injects the molding sand into the sand box through the sand shooting port of the sand shooting machine, and then stands and solidifies for 12-15 minutes, opens the mold, and takes out the sand mold; the motor housing is horizontally arranged in the combined motor housing pouring sand mold, and the heat dissipation window surface of the motor housing is placed vertically; the parting method of the motor housing adopts a horizontal parting structure, the parting surface is the central plane of the motor housing, and the lower mounting bracket of the motor housing is located at the upper part of the parting surface, and the upper mounting bracket is located at the lower part of the parting surface.

4. The method for casting a ductile iron motor housing for an urban rail drive device according to claim 2, characterized in that: The molding sand used in the manual core making method is silica sand with a particle size of 40 / 70 mesh, a strength of 0.5-1Mpa, and a gas generation amount of 10-12ml / g.

5. The method for casting a ductile iron motor housing for an urban rail drive device according to claim 2, characterized in that: The pouring system adopts an intermediate injection pouring method, and the pouring system is provided with a straight runner, a horizontal runner and an ingrate, and the ratio of the cross-sectional areas of the straight runner, the horizontal runner and the ingrate is 1.3-1.4:1.6-1.8:

1.

6. The method for casting a ductile iron motor housing for an urban rail drive device according to claim 5, characterized in that: The filter assembly comprises a foam ceramic filter screen; the foam ceramic filter screen is horizontally arranged at the bottom of the sprue.

7. The method for casting a ductile iron motor housing for an urban rail drive device according to claim 3, characterized in that: When installing the chill and / or the heat-generating riser in S11, at the hot joint position above the motor housing parting surface, a heat-generating heat-insulating riser is installed on the sub-mold; at the hot joint position below the motor housing parting surface, a combination of a heat-generating heat-insulating riser and a chill is installed on the sub-mold.

8. The method for casting a ductile iron motor housing for an urban rail drive device according to claim 1, characterized in that: The casting liquid composition ratio is C: 3.45-3.7%, Si: 2.1-2.3%, Mn: 0.2-0.3%; S: <0.2%, the balance is iron and inevitable impurities; during smelting, all components are melted and then heated to 1540-1580°C for smelting, and then cooled to 1480-1540°C for iron tapping.

9. The method for casting a ductile iron motor housing for an urban rail drive device according to claim 1, characterized in that: Before pouring in S3, pour the smelted molten iron into the pouring ladle. The groove of the pouring ladle adopts a dam-type 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 1390-1410°C and poured into the assembled pouring cup. The molten iron enters the mold cavity from the pouring cup. 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 0.1-0.4%.

10. The method for casting a ductile iron motor housing for an urban rail drive device according to claim 1, characterized in that: In S4, after pouring is completed, the casting is unpacked after cooling for more than 6 hours, the pouring port and riser are removed, and the casting is surface polished and then stress relief annealing is performed.

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