A forming process for inner shielding cover of water pump assembly

Abstract

The present invention provides a forming process for an inner shielding cover of a water pump assembly, comprising the following steps: step 10, multi-step stretching of a stainless steel blank to form a cover cylinder and a flange plane located at the bottom opening of the cover cylinder; step 20, reverse stretching of the cover cylinder to form a rivet shaft; and stretching of the flange plane to form a preformed flange surface; step 30, multi-step reverse stretching of the rivet shaft to form a rivet shaft hole, and shaping of the cover cylinder, the rivet shaft and the rivet shaft hole; step 40, multi-step stretching of the preformed flange surface to form a multi-step flange surface; shaping and trimming of the multi-step flange surface to obtain a finished product. The present invention provides a forming process for an inner shielding cover of a water pump assembly, using stainless steel material, with a continuous process, without the need for annealing treatment, and the stainless steel material is not easily strongly magnetized during the forming process, so that the finished product has a better shielding effect.

Description

Technical Field

[0001] The invention belongs to the technical field of molding technology, and specifically relates to a molding process for an inner shielding cover shell of a water pump assembly. Background Art

[0002] The water pump assembly on new energy vehicles is equipped with a shielding cover. Due to the complex shape of the product and the requirement for non-magnetic or weak magnetic properties to achieve a shielding effect, the existing shielding covers are mostly injection molded. However, there is a high water pressure in the water pump, and there is a large temperature difference between the cold and hot water flows during the circulation process. Plastic products are prone to deformation and aging inside the assembly, with a short service life and potential safety hazards.

[0003] Stainless steel has good corrosion resistance, high temperature stability and excellent mechanical properties, and can be used in water pump assemblies. However, stainless steel has high yield strength, high hardness and significant cold work hardening effect. For small thin-material stretching parts with complex shapes such as shielding shells, multiple positive and negative stretching is required, and the process difficulty is very high during the material stretching and forming process. Because the material undergoes cold work hardening after multiple stretching, it is also necessary to anneal the stretched semi-finished products in the middle to eliminate internal stress and improve the toughness and elongation of the material before subsequent production. It is impossible to achieve a continuous process, with a low degree of automation and low production efficiency. The semi-finished products need to be cleaned of oil stains before annealing, otherwise it will affect the appearance of the product (there will be defects such as yellowing, blackening and dents on the product appearance), and the process is cumbersome. At the same time, annealing will cause deformation of stress release products and cannot guarantee product accuracy. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a forming process for a shielding cover shell inside a water pump assembly, which adopts stainless steel material, has a continuous process, does not require annealing treatment, and the stainless steel material is not easily strongly magnetized during the forming process, so that the finished product has a better shielding effect.

[0005] In order to solve the above technical problems, the present invention provides a forming process of an inner shielding shell of a water pump assembly, comprising the following steps:

[0006] Step 10, performing multi-step stretching on the stainless steel blank to form a cover cylinder and a flange plane located at the bottom of the cover cylinder, so that the error between the diameter of the cover cylinder and the preset cover diameter is within a preset error range;

[0007] Step 20, reversely stretching the cover cylinder to form a pre-stocked material to form a riveting shaft; and stretching the flange plane to form a pre-formed flange surface;

[0008] Step 30, performing multiple steps of reverse stretching on the rivet shaft to form a rivet shaft hole, and shaping the rivet shaft and the rivet shaft hole so that an error between an outer diameter of the rivet shaft and a preset outer diameter of the rivet shaft is within a preset error range, and an error between an inner diameter of the rivet shaft hole and a preset inner diameter of the rivet shaft hole is within a preset error range;

[0009] Step 40, performing multi-step stretching on the preformed flange surface to form a multi-step flange surface; and performing shaping and trimming on the multi-step flange surface to obtain a finished product.

[0010] As a further improvement of the present invention, the stainless steel blank is made of stainless steel material with a nickel content of not less than 12%.

[0011] As a further improvement of the present invention, in step 10, the stainless steel blank is first stretched to form a cylinder, and the top end surface of the cylinder is a plane; then the cylinder is subjected to at least two enhanced stretchings to gradually reduce the diameter of the cylinder and increase the height of the cylinder to form a cover cylinder; at the same time, the plane area around the bottom opening of the cylinder is gradually increased to form a flange plane; so that the error between the diameter of the cover cylinder and the preset cylinder diameter is within a preset error range; during multiple enhanced stretching processes, the top end surface of the cylinder is always a plane.

[0012] As a further improvement of the present invention, in step 10, each time the stretching is enhanced, a 120° inclined pressure ring is formed between the top edges of the concave and convex dies.

[0013] As a further improvement of the present invention, the step 20 specifically includes:

[0014] Step 201, reversely stretching the top surface of the housing cylinder to form a material storage cylinder with an opening facing upward in the housing cylinder;

[0015] Step 202, further strengthening and stretching the stock column, reducing the stock column diameter, and increasing the stock column height; at the same time, stretching the flange plane to form a preformed flange surface;

[0016] Step 203, the stock column is stretched again to reduce the diameter of the stock column and increase the height of the stock column to form a riveted shaft.

[0017] As a further improvement of the present invention, the preformed flange surface has a step.

[0018] As a further improvement of the present invention, the step 30 specifically includes:

[0019] Step 301, reversely stretching the rivet shaft to form a rivet shaft hole;

[0020] Step 302, reducing the inner diameter of the rivet shaft hole so that the error between the inner diameter of the rivet shaft hole and the preset inner diameter of the rivet shaft hole is within a preset error range;

[0021] Step 303, keeping the inner diameter of the rivet shaft hole unchanged, reducing the outer diameter of the rivet shaft, so that the error between the outer diameter of the rivet shaft and a preset outer diameter of the rivet shaft is within a preset error range;

[0022] Step 304, shaping the rivet shaft and the rivet shaft hole at the same time.

[0023] As a further improvement of the present invention, in step 302, a two-step stretching process is used to gradually reduce the inner diameter of the rivet shaft hole.

[0024] As a further improvement of the present invention, in step 303, a two-step stretching process is adopted to gradually reduce the outer diameter of the riveting shaft.

[0025] As a further improvement of the present invention, in step 40, when stretching to form a step, the step R angle is first made greater than a preset angle, and the step height is greater than a preset height, and then the step height is compressed to reduce the step R angle, and the error between the step R angle and the preset angle is within a preset error range.

[0026] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0027] The forming process of the inner shielding cover of the water pump assembly provided in the embodiment of the present invention adopts a stainless steel blank; firstly, the cover cylinder is stretched to form the cover cylinder, and the cover cylinder is stretched into place to meet the requirements of the finished product; then the cover cylinder is reversely stretched to form a rivet shaft, and the material is pre-stored to form the rivet shaft hole, and the flange plane is stretched at the same time to form a pre-formed flange surface; then multi-step stretching is performed to form the rivet shaft hole, and the outer diameter of the rivet shaft and the inner diameter of the rivet shaft hole meet the requirements of the finished product; finally, the pre-formed flange surface is stretched to form a multi-step flange surface, and the finished product is obtained after shaping and trimming. The forming process of the inner shielding cover of the water pump assembly of this embodiment adopts a stainless steel blank to repeatedly stretch and form the finished product in both positive and negative directions. Compared with plastic products, there is no hidden danger of aging and deformation, and the service life is improved. The forming process of the inner shielding cover of the water pump assembly of this embodiment is to stretch the rivet shaft only after the cover cylinder is stretched into place. Compared with forming the rivet shaft shape before the cover cylinder is stretched into place, it is avoided that the material in the rivet shaft hole is affected and flows out in the reverse direction when the cover cylinder is stretched again later, resulting in the failure of the rivet shaft hole forming. The forming process of the inner shielding shell of the water pump assembly of this embodiment stretches the flange surface while stretching to form the riveted shaft, and forms a preformed flange surface as early as possible when the material has good plasticity, which is conducive to the forming of the flange surface; moreover, the preformed flange surface can prevent the influence of the subsequent stretching process on the flange surface material during the forming process, forming a barrier effect, allowing the flange surface material to maintain relatively good plasticity and flatness, which is conducive to the subsequent multi-step flange surface forming. The forming process of the inner shielding shell of the water pump assembly of this embodiment uses stainless steel material, the process is continuous, no annealing treatment is required, and the stainless steel material is not easily strongly magnetized during the forming process, so that the finished product has a good shielding effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a flow chart of a molding process of an inner shielding cover of a water pump assembly according to an embodiment of the present invention;

[0029] Figure 2 is a process flow chart of step 10 in the method of an embodiment of the present invention;

[0030] Figure 3 is a process flow chart of step 20 in the method of an embodiment of the present invention;

[0031] Figure 4 is a process flow chart of step 30 in the method of an embodiment of the present invention;

[0032] Figure 5 This is a schematic diagram of the structure of a finished product prepared by the method of an embodiment of the present invention;

[0033] Figure 6 It is the process flow chart of Comparative Example 1;

[0034] Figure 7 This is the process flow chart of Comparative Example 2.

[0035] The figure includes: a housing cylinder 1, a flange plane 2, a rivet shaft 3, a preformed flange surface 4, a rivet shaft hole 5, and a multi-step flange surface 6. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is described in detail below with reference to the accompanying drawings.

[0037] The embodiment of the present invention provides a forming process of an inner shielding shell of a water pump assembly, such as Figure 1 As shown, the following steps are included:

[0038] Step 10, the stainless steel blank is subjected to multi-step stretching, such as Figure 2 As shown, a housing cylinder 1 and a flange plane 2 located around the bottom opening of the housing cylinder are formed. The error between the diameter of the housing cylinder and the preset housing diameter is within the preset error range. After step 10, the diameter of the housing cylinder meets the finished product requirements.

[0039] Step 20, such as Figure 3 As shown, the housing cylinder 1 is reversely stretched to form a pre-stocked material to form a riveting shaft 2. The flange plane 2 is stretched to form a preformed flange surface 4.

[0040] Step 30, such as Figure 4 As shown, the rivet shaft 2 is subjected to multi-step reverse stretching to form a rivet shaft hole 5, and the rivet shaft and the rivet shaft hole are shaped so that the error between the outer diameter of the rivet shaft and the preset outer diameter of the rivet shaft is within the preset error range, and the error between the inner diameter of the rivet shaft hole and the preset inner diameter of the rivet shaft hole is within the preset error range. After step 30, the outer diameter of the rivet shaft and the inner diameter of the rivet shaft hole both meet the requirements of the finished product.

[0041] Step 40, the preformed flange surface 4 is subjected to multi-step stretching to form a multi-step flange surface 5. The multi-step flange surface is shaped and trimmed to obtain Figure 5 Finished product shown.

[0042] As a preferred example, the stainless steel blank uses a stainless steel material with a nickel content of not less than 12%. This embodiment takes into account that although stainless steel materials are usually non-magnetic or weakly magnetic, multiple stretching and forming will cause the metallographic structure of the material to undergo phase change and generate magnetism. Therefore, this embodiment selects a stainless steel material with a nickel content of not less than 12%, which can significantly reduce the tendency of phase change. At the same time, the forming process of the present application is used, so that the stainless steel material is not easily strongly magnetized, and the finished product has a good shielding effect.

[0043] As a preferred example, Figure 2As shown, in step 10, the stainless steel blank is first stretched to form a cylinder, and the top surface of the cylinder is a plane. Then the cylinder is subjected to at least two enhanced stretchings to gradually reduce the diameter of the cylinder and increase the height of the cylinder to form a cover cylinder 1. While stretching the cylinder, the plane area around the bottom opening of the cylinder is gradually increased to form a flange plane 2. The error between the diameter of the cover cylinder and the preset cylinder diameter is within a preset error range. During the multiple enhanced stretching processes, the top surface of the cylinder is always a plane. Among them, the stainless steel blank is preferably round, which is convenient for stretching to form a cylinder, is more conducive to the flow of the material, and reduces the thinning of the material during the stretching process.

[0044] In this embodiment, after the cylinder is formed, in the subsequent strengthening and stretching process, only the cylinder diameter is reduced and the cylinder height is gradually stretched, and the top surface of the cylinder always remains flat. The top surface material of the cover cylinder has not participated in the stretching, so this part of the material has good original plasticity and will be better stored in the rivet shaft in the subsequent stretching process of forming the rivet shaft, effectively achieving the effect of pre-storage. Moreover, the top surface material of the cover cylinder is not affected by the tension, and the metallographic structure of the top surface material does not change, reducing the risk of magnetization.

[0045] Preferably, in step 10, each time the stretching is strengthened, a 120° bevel pressure ring is formed between the top edges of the concave and convex molds. In this embodiment, the bevel pressure ring can effectively and evenly press the top surface of the cylinder along the 120° bevel to stretch the cylinder side wall, ensuring smooth material flow, uniform material thinning, smooth side wall, and wrinkle-free, while helping the top surface material not to be affected by the tension, ensuring that the metallographic structure of the top surface material does not change.

[0046] As a preferred example, Figure 3 As shown, step 20 specifically includes:

[0047] Step 201, reversely stretching the top end surface of the casing column 1 to form a material storage column with an opening facing upward in the casing column.

[0048] Step 202, the stock column is further stretched to reduce the stock column diameter and increase the stock column height. At the same time, the flange plane 1 is stretched to form a preformed flange surface 4 with steps.

[0049] Step 203 , the stock column is stretched again to reduce the diameter of the stock column and increase the height of the stock column to form a riveting shaft 3 .

[0050] This embodiment only uses three steps of reverse stretching forming process to form the riveting shaft, pre-store materials, reduce the stretching of materials, reduce the influence of cold work hardening effect, and make the materials maintain good plasticity. While performing reverse strengthening stretching in the second step, the flange plane is stretched as early as possible to form a preformed flange surface. Since the material has good plasticity at this time, it is more conducive to forming flange surface steps. Moreover, the flange surface step can prevent the influence of other stretching process forming processes on the flange surface material, play a barrier role, and keep the flange surface material relatively good plasticity and flatness, which is conducive to the subsequent multi-step flange surface forming.

[0051] Preferably, the preformed flange surface 4 has a step. Only one step is formed, the shape is simple, which is conducive to the subsequent shaping of the preformed flange surface during the shaping of the riveting shaft, and is convenient for stripping after forming, and the step is not easy to deform.

[0052] As a preferred example, Figure 4 As shown, step 30 specifically includes:

[0053] Step 301 , reversely stretching the rivet shaft 3 to form a rivet shaft hole 5 .

[0054] Step 302 , reducing the inner diameter of the rivet shaft hole 5 so that the error between the inner diameter of the rivet shaft hole and a preset inner diameter of the rivet shaft hole is within a preset error range.

[0055] Step 303 , reducing the outer diameter of the rivet shaft 3 so that the error between the outer diameter of the rivet shaft 3 and a preset outer diameter of the rivet shaft is within a preset error range.

[0056] Step 304, shaping the rivet shaft 3 and the rivet shaft hole 5 at the same time.

[0057] In this embodiment, reverse stretching is first performed to allow the material at the height of the rivet shaft 3 to flow into the rivet shaft hole, and then the inner diameter of the rivet shaft hole is gradually stretched and reduced until the inner diameter of the rivet shaft hole meets the requirements of the finished product. Then, the inner diameter of the rivet shaft hole is kept unchanged, and the outer diameter of the rivet shaft is gradually stretched and reduced, and finally the whole is shaped. This embodiment uses fewer stretching processes to form a complex and high-dimensional precision rivet shaft hole in a smaller space in the housing column. This embodiment uses separate stretching of the rivet shaft hole and the rivet shaft inside and outside, which is conducive to the flow of materials, reduces the influence of mutual pulling when the materials are stretched, ensures that the local material wall thickness meets the requirements, and reduces the risk of product cracking.

[0058] Preferably, in step 302, a two-step stretching process is used to gradually reduce the inner diameter of the rivet shaft hole. Figure 4 As shown in FIG. 3 , the inner diameter of the rivet shaft hole is reduced from 6.4 mm to 5.0 mm and then to 4.0 mm. In step 303, a two-step stretching process is used to gradually reduce the outer diameter of the rivet shaft. While the outer diameter of the rivet shaft is reduced by stretching in the second step, the rivet shaft hole is also reshaped. For example, Figure 4As shown in the figure, the outer diameter of the rivet shaft is reduced from 13.0mm to 11.0mm and then to 8.9mm, and the inner diameter of the rivet shaft hole is reduced to 3.97mm after plastic shaping. By gradually reducing the inner diameter of the rivet shaft hole and the outer diameter of the rivet shaft through multi-step stretching, the local material can be effectively prevented from becoming thinner and easy to break.

[0059] Preferably, in step 304, while shaping the rivet shaft 3 and the rivet shaft hole 5, the R angles of the housing cylinder 1 and the preformed flange surface 4 are also shaped. Since the preformed flange surface 4 has only one step, compared with multiple steps, the simple shape is conducive to the shaping of the R angle, otherwise the height difference during shaping may cause the shaping to be incomplete.

[0060] Considering that the finished product requires the flange surface step R angle to be small (the R angle is the transition point between the horizontal and vertical surfaces of the step), and after several previous stretchings, the flange surface will have stretch wrinkles and the material will be hardened by cold work. During the process of forming the step, stress concentration will occur at the R angle, which is prone to cracking at the R angle. In step 40 of this embodiment, when stretching to form the step, the step R angle is first made greater than the preset angle, and the step height is greater than the preset height, and then the step height is compressed to reduce the step R angle to within the preset error range. This embodiment uses the method of increasing the forming R angle and then gradually shaping, compressing the height during the shaping process, so that the material flows to the R angle and reduces the R angle, effectively avoiding cracking at the R angle during step forming.

[0061] Two comparative examples are provided below.

[0062] Comparative Example 1

[0063] like Figure 6 As shown, the first to fourth processes first form the cover cylinder, but when the cover cylinder has not been stretched into place, the fifth process is used to start forming the rivet shaft shape. When the cover cylinder is subsequently stretched again, the material in the rivet shaft hole is affected by the stretching of the cover cylinder and flows out in the reverse direction, resulting in the failure of the rivet shaft hole to stretch.

[0064] Comparative Example 2

[0065] like Figure 7 As shown, the 1st to 5th processes use a spherical stretching process to form the cover, so that the top material initially participates in the stretching forming. After the material is stretched and reversed, the material of the rivet shaft hole is cold-work hardened and strongly magnetized. The 6th to 12th processes perform a spherical reverse stretching process to form the rivet shaft. The 12th to 20th processes perform a reverse stretching process on the rivet shaft again to form the rivet shaft hole. In order to prevent the rivet shaft hole from cracking in the 18th process, it is necessary to perform annealing treatment in the 17th process before subsequent re-forming. Comparative Example 1 uses a total of 29 processes.

[0066] The forming process of the inner shielding cover of the water pump assembly of this embodiment uses a stainless steel blank to repeatedly stretch and form the finished product. Compared with plastic products, there is no hidden danger of aging and deformation, and the service life is increased.

[0067] The molding process of the inner shielding cover of the water pump assembly of this embodiment uses stainless steel material with a nickel content of not less than 12%, which can significantly reduce the tendency of phase change. At the same time, the molding process of this application is used to make the stainless steel material less likely to be strongly magnetized, and the finished product has a better shielding effect.

[0068] In the forming process of the shielding case of the water pump assembly of this embodiment, when forming the case cylinder, the material of the top surface is ensured not to participate in the stretching, so that this part of the material maintains good original plasticity and is better stored in the rivet shaft during the subsequent stretching process of forming the rivet shaft, effectively achieving the effect of pre-storing the material. Moreover, the metallographic structure of the top surface material does not change, reducing the risk of being magnetized.

[0069] The forming process of the shielding cover shell inside the water pump assembly of this embodiment is to stretch the rivet shaft only after the cover column is stretched into place. Compared with forming the rivet shaft shape before the cover column is stretched into place, this avoids the material in the rivet shaft hole being affected and flowing out in reverse when the cover column is stretched again at a later time, resulting in failure of the rivet shaft hole forming.

[0070] The forming process of the inner shielding shell of the water pump assembly of this embodiment only uses a three-step reverse stretching forming process to form a riveted shaft, pre-store materials, reduce the stretching of the material, reduce the influence of the cold work hardening effect, and keep the material in good plasticity. While stretching to form the riveted shaft, the flange surface is stretched, and a preformed flange surface is formed as early as possible when the material has good plasticity, which is conducive to the forming of the flange surface; moreover, the preformed flange surface can prevent the influence of the subsequent stretching process on the flange surface material, forming a barrier effect, so that the flange surface material maintains relatively good plasticity and flatness, which is conducive to the subsequent multi-step flange surface forming.

[0071] The forming process of the inner shielding shell of the water pump assembly of this embodiment uses fewer stretching steps to form a complex rivet shaft hole with high dimensional accuracy in a small space in the shell column. The rivet shaft hole and the rivet shaft are stretched separately inside and outside, which is conducive to the flow of materials, reduces the influence of mutual pulling when the materials are stretched, ensures that the local material wall thickness meets the requirements, and reduces the risk of product cracking.

[0072] The forming process of the inner shielding cover of the water pump assembly of this embodiment is continuous and does not require annealing. Multi-station transfer equipment can be used to achieve local forming of the product at each station, thereby realizing batch automated production, improving production efficiency, stabilizing the production process, and achieving high product dimensional accuracy.

[0073] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A forming process for an inner shielding shell of a water pump assembly, characterized in that: The following steps are involved: Step 10, performing multi-step stretching on the stainless steel blank to form a cover cylinder and a flange plane located at the bottom of the cover cylinder, so that the error between the diameter of the cover cylinder and the preset cover diameter is within a preset error range; Step 20, reversely stretching the cover cylinder to form a pre-stocked material to form a riveting shaft; and stretching the flange plane to form a pre-formed flange surface; Step 30, performing multiple steps of reverse stretching on the rivet shaft to form a rivet shaft hole, and shaping the rivet shaft and the rivet shaft hole so that an error between an outer diameter of the rivet shaft and a preset outer diameter of the rivet shaft is within a preset error range, and an error between an inner diameter of the rivet shaft hole and a preset inner diameter of the rivet shaft hole is within a preset error range; Step 40, performing multi-step stretching on the preformed flange surface to form a multi-step flange surface; The multi-step flange surface is shaped and trimmed to obtain a finished product; In the step 10, the stainless steel blank is first stretched to form a cylinder, and the top surface of the cylinder is a plane; then the cylinder is subjected to at least two times of strengthening stretching, the cylinder diameter is gradually reduced, and the cylinder height is increased to form a cover cylinder; at the same time, the plane area of ​​the bottom opening of the cylinder is gradually increased to form a flange plane; so that the error between the diameter of the cover cylinder and the preset cylinder diameter is within the preset error range; during the multiple strengthening stretching processes, the top surface of the cylinder is always a plane; in the step 10, each time the strengthening stretching is performed, a 120° inclined pressure ring is formed between the top edges of the concave and convex dies; The step 20 specifically includes: Step 201, reversely stretching the top surface of the housing cylinder to form a material storage cylinder with an opening facing upward in the housing cylinder; Step 202, further strengthening and stretching the stock column, reducing the stock column diameter, and increasing the stock column height; at the same time, stretching the flange plane to form a preformed flange surface; Step 203, the stock column is stretched again to reduce the diameter of the stock column and increase the height of the stock column to form a riveted shaft.

2. The forming process of the inner shielding shell of the water pump assembly according to claim 1 is characterized in that: The stainless steel blank is made of stainless steel material with a nickel content of not less than 12%.

3. The forming process of the inner shielding shell of the water pump assembly according to claim 1 is characterized in that: The preformed flange surface has a step.

4. The forming process of the inner shielding shell of the water pump assembly according to claim 1 is characterized in that: The step 30 specifically includes: Step 301, reversely stretching the rivet shaft to form a rivet shaft hole; Step 302, reducing the inner diameter of the rivet shaft hole so that the error between the inner diameter of the rivet shaft hole and the preset inner diameter of the rivet shaft hole is within a preset error range; Step 303, keeping the inner diameter of the rivet shaft hole unchanged, reducing the outer diameter of the rivet shaft, so that the error between the outer diameter of the rivet shaft and a preset outer diameter of the rivet shaft is within a preset error range; Step 304, shaping the rivet shaft and the rivet shaft hole at the same time.

5. The forming process of the inner shielding shell of the water pump assembly according to claim 4 is characterized in that: In step 302, a two-step stretching process is used to gradually reduce the inner diameter of the rivet shaft hole.

6. The forming process of the inner shielding shell of the water pump assembly according to claim 4 is characterized in that: In step 303, a two-step stretching process is used to gradually reduce the outer diameter of the riveting shaft.

7. The forming process of the inner shielding shell of the water pump assembly according to claim 1 is characterized in that: In step 40, when stretching to form a step, the step R angle is first made greater than a preset angle and the step height is greater than a preset height, and then the step height is compressed to reduce the step R angle, and the error between the step R angle and the preset angle is within a preset error range.

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