Phosphoric acid pump shaft structure

Abstract

The utility model relates to a kind of phosphoric acid acid delivery pump pump shaft structure, including shaft body, the shaft body is sequentially provided with shaft head, shaft middle section, shaft body and shaft tail along the axial direction;The outer circumferential surface of shaft head is equipped with external thread section, and the shaft head end portion is provided with the central positioning hole extending along the axial direction;The outer circumferential surface of shaft middle section is sequentially provided with chromium plating and oxide film layer, and the outer diameter of shaft middle section is less than the outer diameter of shaft body;The connecting place of shaft head and shaft middle section, shaft middle section and shaft body, shaft body and shaft tail is equipped with transition arc;The shaft tail is equipped with the keyway that penetrates along radial direction;The inside of shaft body is equipped with the weight-reducing cavity extending along the axial direction, the opening end of the weight-reducing cavity is located at the end of shaft tail away from shaft body, and the inner wall of weight-reducing cavity is equipped with helical reinforcing rib.The utility model aims at solving the problems that the existing phosphoric acid acid delivery pump pump shaft is easy to be corroded in strong corrosive medium, the stress concentration at the connecting place of shaft section is easy to be broken, and the overall weight and mechanical properties are unbalanced.

Description

Technical Field

[0001] This utility model belongs to the technical field of corrosion-resistant acid pump shafts, and relates to a pump shaft structure for a phosphoric acid pump. Background Technology

[0002] Phosphoric acid, a highly corrosive inorganic acid, is a key raw material in chemical, metallurgical, and pharmaceutical industries. Its transportation relies on specialized phosphoric acid pumps, and the pump shaft, as the core transmission component of these pumps, directly bears the functions of transmitting impeller rotational torque and bearing medium pressure. Its performance stability determines the operating efficiency and safety of the entire transportation system. Currently, phosphoric acid pump shafts are mostly made of metal and must simultaneously meet three core requirements: resistance to phosphoric acid corrosion, resistance to high-frequency torque impact, and lightweight and energy saving. This is a key technical node in the design of phosphoric acid transportation equipment, and its structural rationality and performance have become core factors restricting the service life and operational reliability of phosphoric acid pumps.

[0003] In actual production and use, existing phosphoric acid pump shafts generally suffer from three major problems: First, rapid corrosion failure. Phosphoric acid not only chemically corrodes the surface of the pump shaft, but also causes erosion and wear due to the flow of the medium. This leads to the easy peeling and penetration of traditional single anti-corrosion coatings on the surface of the pump shaft, such as ordinary paint coatings or single metal plating. Surface rust and dimensional accuracy deteriorate in a short period of time, eventually leading to sealing failure or transmission jamming. Second, stress concentration and easy breakage. Due to functional requirements, the pump shaft needs to be designed with shaft sections of different diameters, such as the shaft head, shaft middle section, and shaft tail. Existing structures often use right-angle transitions or small-radius arc transitions, resulting in stress concentration areas at the shaft section connections. Under high-speed rotation and periodic torque impact, fatigue cracks are easily generated, and in severe cases, the pump shaft breaks, causing production stoppage losses. Third, imbalance between weight and mechanical properties. In order to improve strength, some designs use solid shafts, resulting in excessive pump shaft weight, which not only increases motor energy consumption but also aggravates bearing wear. On the other hand, some lightweight designs achieve this by reducing the shaft diameter, but at the expense of structural strength, making them unable to withstand the medium pressure and torque load during phosphoric acid transportation.

[0004] Search results show that current solutions to acid pump shaft problems mainly focus on two aspects: corrosion prevention and structural optimization. For example, patent publication number CN218207174U, entitled "A Centrifugal Corrosion-Resistant Acid Pump Shaft," discloses the application of an anti-corrosion coating on the outer periphery of the pump shaft body and sealing shaft section, and the optimization of the sealing structure through a spring-loaded pressure ring. The principle is to use the coating to isolate the corrosive medium, while the pressure ring compensates for the wear of the sealing gasket. The advantage of this solution is that it achieves a preliminary combination of sealing and corrosion prevention, and has high assembly convenience. However, the disadvantage is that it only uses a single anti-corrosion coating, does not specify the coating type and process, cannot cope with the strong corrosive properties of phosphoric acid, and does not solve the problems of stress concentration and weight imbalance in the shaft section. Long-term use is prone to coating peeling and shaft breakage. Utility Model Content

[0005] This invention provides a pump shaft structure for a phosphoric acid pump, which solves the problems of easy corrosion of existing phosphoric acid pump shafts in highly corrosive media, stress concentration and easy breakage at shaft connection points, and imbalance between overall weight and mechanical properties.

[0006] To solve the above problems, the technical solution adopted by the utility model is as follows: A phosphoric acid pump shaft structure includes a shaft body, which has a shaft head, a shaft middle section, a shaft body, and a shaft tail arranged sequentially along the axial direction. The shaft head has an external thread section on its outer circumferential surface, and a central positioning hole extending along the axial direction is opened at the end of the shaft head. The shaft middle section has a chromium plating layer and an oxide film layer arranged sequentially on its outer circumferential surface, and the outer diameter of the shaft middle section is smaller than the outer diameter of the shaft body. The connection between the shaft head and the shaft middle section, the shaft middle section and the shaft body, and the shaft body and the shaft tail are all provided with transition arcs. The shaft tail has a radially penetrating keyway. The shaft body has an axially extending weight-reducing cavity inside, the opening end of which is located at the end of the shaft tail away from the shaft body, and the inner wall of the weight-reducing cavity is provided with spiral reinforcing ribs.

[0007] The principle and advantages of this scheme are as follows: The shaft body is divided into functional zones along the axial direction: shaft head, shaft middle section, shaft body, and shaft tail. Each zone is specifically designed to meet operational requirements. The external thread section of the shaft head is used to achieve a reliable connection with the impeller and coupling, and the central positioning hole ensures assembly coaxiality and precise torque transmission. The shaft middle section, as the core area directly in contact with the phosphoric acid medium, adopts a composite protective structure of chromium plating and oxide film. The physical barrier of the chromium plating and the chemical inertness of the oxide film form a double protection to block the penetration of corrosive media. At the same time, the outer diameter of the shaft middle section is smaller than that of the shaft body, and with the transition arc at the connection of each shaft section, a gradual transition of shaft diameter is achieved, dispersing stress concentration under rotation and load. The shaft body has a weight-reducing cavity extending axially. While reducing material usage to achieve lightweighting, the spiral reinforcing ribs on the inner wall of the cavity form a continuous support structure to compensate for the weakening of the shaft body strength by the cavity, ensuring that the torsional and bending resistance meets the requirements of the working conditions. The radial keyway at the shaft tail achieves a stable connection with the power components. The overall structure, through the synergistic effect of each functional module, simultaneously solves the three major problems of corrosion, stress concentration, and imbalance between weight and strength.

[0008] Compared to existing technologies, which often employ a single coating or material upgrade, this solution utilizes a composite structure of chromium plating and oxide film, forming a dual protective barrier. Actual testing shows a continuous operating life of over 3 years in 80℃, 50% phosphoric acid medium, twice that of existing single-coated pump shafts, at only half the cost of a 316L stainless steel pump shaft. This resolves the contradiction between poor corrosion resistance and high cost in existing technologies. Furthermore, existing shaft connections often use right angles or fixed-radius arc transitions, easily leading to stress concentration and fracture. This solution, through a full-section arc transition design and a gradual diameter change between the shaft midsection and body, reduces the stress concentration coefficient by over 60%, lowering the pump shaft fracture rate and eliminating the risk of fracture under high-speed, high-torque conditions. Finally, existing technologies either use solid shafts or unreinforced weight-reduction holes. This solution combines a weight-reduction cavity with spiral reinforcing ribs, reducing shaft weight while increasing torsional strength compared to solid shafts, achieving an optimization of lightweight and high strength.

[0009] Furthermore, the external thread section is a trapezoidal thread with a major diameter of 38mm and a pitch of 3mm. The thread surface is coated with a polytetrafluoroethylene (PTFE) coating with a thickness of 0.02-0.05mm. Compared with ordinary triangular threads, trapezoidal threads have a larger tooth angle and a wider bearing surface, which can effectively disperse the force on the threaded pair when the pump shaft rotates, avoiding thread stripping or breakage caused by local stress concentration. This is suitable for the high-strength connection requirements of the phosphoric acid pump shaft, impeller, and coupling. The 38mm major diameter and 3mm pitch size combination ensures the tightness of the connection while reducing the difficulty of thread processing, facilitating precise positioning and locking during assembly. The PTFE coating has excellent chemical inertness, which can isolate the corrosion of the thread surface by the phosphoric acid medium, preventing the thread from getting stuck or seizing due to corrosion. At the same time, its extremely low coefficient of friction can reduce wear during assembly and disassembly, extending the service life of the thread. The 0.02-0.05mm coating thickness can ensure the protective effect without affecting the thread's fit accuracy, ensuring the stability and reliability of the connection structure.

[0010] Furthermore, the surface roughness of the deep hole wall of the central positioning hole is... Furthermore, the orifice is equipped with a 15° guide chamfer. The low-roughness of the orifice wall can significantly reduce the contact gap with mating parts such as locating pins and locking bushings, reduce vibration deviation when the pump shaft rotates at high speed, and reduce wear on mating surfaces, thereby improving positioning accuracy and connection stability. This makes it suitable for the stringent coaxiality requirements of phosphoric acid pumps. The 15° guide chamfer also provides precise guidance, guiding the mating parts to be inserted into the orifice quickly and smoothly, avoiding collision damage caused by misalignment during assembly, improving assembly efficiency, and dispersing stress concentration at the edge of the orifice. This prevents fatigue cracks during long-term use and extends the service life of the shaft head structure. The overall design takes into account ease of assembly, operational reliability, and structural protection.

[0011] Furthermore, the chromium plating layer has a thickness of 0.08-0.12 mm, and the oxide film layer is formed through anodizing. The membrane, with a thickness of 0.015-0.025 mm, features a sealed surface. The chromium plating, with its high hardness and density, resists media erosion and forms a physical barrier layer. A thickness of 0.08-0.12 mm ensures protective durability while avoiding the risk of plating peeling due to excessive thickness. The outer Al2O3 oxide film exhibits excellent chemical stability, forming a composite structure with the chromium plating. Its precise thickness of 0.015-0.025 mm balances protective effectiveness with film toughness. The sealed surface treatment of the oxide film blocks micropores, preventing phosphoric acid from penetrating to the substrate and completely eliminating the risk of localized corrosion. The synergistic effect of these three elements significantly improves the corrosion resistance of the pump shaft's midsection and maintains surface hardness to resist particle wear, making it suitable for the complex operating conditions in phosphoric acid transportation.

[0012] Furthermore, the radius of the transition arc is R2-R5mm, wherein the radius of the transition arc at the connection between the middle section of the shaft and the shaft body is larger than the radius of the transition arc at the connection between the shaft head and the middle section of the shaft. The radius of R2-R5mm can effectively avoid stress concentration caused by abrupt changes in size at the shaft section connection, preventing cracks or fractures under high-speed rotation and media impact. The differentiated radius designed according to the stress difference of the shaft section further precisely adapts to the working conditions of each part. The middle section of the shaft is the core stress area of ​​the pump shaft, bearing the torque and media pressure transmitted by the impeller. A larger radius transition arc can more fully disperse the concentrated stress in this area, reducing the risk of fatigue damage. The shaft head mainly undertakes the assembly and connection function, and the stress is relatively mild. A smaller radius arc can meet the stress dispersion requirements and save axial space, ensuring assembly compactness.

[0013] Furthermore, the keyway is a through-slot structure with a width tolerance of H9 and a depth tolerance of JS9. The surface roughness of both sides of the keyway is Ra3.2μm. The through-slot structure ensures full-length contact between the key and the slot, improving torque transmission efficiency and preventing deformation of the key or slot due to excessive local stress. The combination of the H9 width tolerance and the JS9 depth tolerance ensures precise fit between the key and the slot while providing reasonable clearance for assembly, avoiding assembly difficulties or loosening due to dimensional deviations. This adapts to the key connection requirements of different batches of couplings or impellers. The Ra3.2μm surface roughness reduces friction and wear between the key and the slot sides, lowers vibration noise during operation, and avoids stress concentration points formed on rough surfaces, preventing cracks under long-term alternating loads. The overall design balances the reliability of torque transmission, ease of assembly, and structural durability, making it suitable for the high-torque, high-vibration operating conditions of phosphoric acid pumps.

[0014] Furthermore, the length of the weight-reducing cavity is 2 / 5 to 3 / 5 of the total length of the shaft body, and the maximum inner diameter of the cavity is 1 / 3 to 1 / 2 of the outer diameter of the shaft body. The cavity and shaft body are coaxially aligned. This 2 / 5 to 3 / 5 length ratio reduces the overall weight of the pump shaft, decreasing inertial forces and energy consumption during rotation, while preventing the cavity from weakening the strength of the middle section of the shaft due to excessive length. The 1 / 3 to 1 / 2 inner diameter ratio ensures both weight reduction and sufficient wall thickness to maintain the shaft's torsional and bending resistance, preventing deformation during high-speed rotation. The coaxial alignment ensures that the center of gravity of the cavity and shaft body coincides, eliminating additional vibrations caused by eccentricity and reducing wear on bearings and other related components. These three factors work synergistically to ensure that the pump shaft, while reducing weight and energy consumption, still meets the high torque and high stability requirements of the phosphoric acid pump.

[0015] Furthermore, the pitch of the spiral reinforcing rib is 1.5-2 times the cavity diameter, and the rib thickness is 0.8-1.2mm. The reinforcing rib and the inner wall of the weight-reducing cavity are integrally formed. The pitch of 1.5-2 times the cavity diameter allows the reinforcing rib to be evenly distributed on the inner wall of the cavity, forming a continuous spiral support structure, effectively dispersing the radial force and torque during shaft rotation and avoiding local stress concentration. The rib thickness of 0.8-1.2mm minimizes the increase in weight while providing sufficient structural strength to compensate for the weakening of the shaft by the cavity, ensuring that the pump shaft's torsional and bending resistance is no less than that of a solid shaft. The integral forming process eliminates connection gaps, avoiding the risk of loosening or breakage that may occur with assembled reinforcing ribs, and improving the overall structural integrity.

[0016] Furthermore, a connecting arc is provided between the end of the external thread section near the middle section of the shaft and the outer circumferential surface of the shaft head. The radius of the connecting arc is R1.5-R4mm. This connecting arc replaces the traditional relief groove or right-angle transition, which can effectively eliminate stress concentration at the connection between the thread root and the outer circumferential surface of the shaft head. This avoids crack initiation or fracture caused by local stress superposition when the pump shaft rotates at high speed to transmit torque, and is especially suitable for the high-load operation of phosphoric acid pumps. The radius range of R1.5-R4mm can ensure stress dispersion effect. If the radius is too small, the stress dispersion will be insufficient. If the radius is too large, it will occupy axial space. It can also be adapted to the overall structure of the shaft head and does not affect the assembly and locking function of the external thread. At the same time, the arc transition can avoid the risk of wear and corrosion caused by sharp edges during assembly or media flushing, and extend the service life of the thread section and the shaft head. The overall design takes into account structural strength, assembly practicality and protection performance, and improves the operational reliability of the pump shaft. Furthermore, the shaft body is made of 2Cr13 stainless steel through quenching and tempering, with a hardness of 220-250 HBW after tempering. Both the head and tail ends of the shaft are provided with 30° anti-collision chamfers. After quenching and tempering, a uniform tempered sorbite structure is formed. The hardness of 220-250 HBW ensures the required torsional strength and toughness of the pump shaft, preventing deformation or breakage during high-speed rotation and torque transmission, while also taking into account the convenience of machining and adapting to the forming requirements of complex shaft structure. The 30° anti-collision chamfers can effectively eliminate the sharp edges and corners at the head and tail ends of the shaft, avoiding edge and corner damage caused by collisions during assembly and transportation, reducing stress concentration points to reduce the risk of fatigue cracks, and guiding the quick alignment with mating parts such as impellers and couplings during assembly, improving assembly efficiency. At the same time, it prevents sharp edges and corners from scratching seals or operators. The overall design takes into account the mechanical performance, protection, and practicality of the pump shaft. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of this utility model.

[0018] Figure 2 This is a cross-sectional view of the present invention. Detailed Implementation

[0019] The reference numerals in the accompanying drawings include: 1. Shaft body; 2. Center positioning hole; 3. External thread section; 4. Chamfer; 5. Chromium plating; 6. Oxide film layer; 7. Connecting arc; 8. Shaft middle section; 9. Shaft head; 10. Shaft tail; 11. Keyway; 12. Transition arc. Example 1 like Figure 1-2 As shown, a pump shaft structure for a phosphoric acid pump includes a shaft body 1. The shaft body 1 is made of 2Cr13 stainless steel and is heat-treated. After heat treatment, the hardness is controlled at 220-250 HBW to ensure that the shaft body has both good torsional strength and machinability. The shaft body 1 is integrally formed along the axial direction with a shaft head 9, a shaft middle section 8, a shaft body, and a shaft tail 10. Each functional section is coaxially arranged to ensure dynamic balance performance during rotation.

[0020] The outer circumferential surface of the shaft head 9 is machined with a trapezoidal external thread section 3, with a major diameter of 38mm and a pitch of 3mm. The thread surface is coated with a 0.02-0.05mm thick polytetrafluoroethylene coating to improve corrosion resistance and assembly smoothness. A connecting arc 7 with a radius of R1.5-R4mm is provided between the end of the external thread section 3 near the middle section 8 of the shaft and the outer circumferential surface of the shaft head 9 to eliminate stress concentration at the thread root. A central locating hole 2 extending axially is provided at the end of the shaft head 9. The wall roughness of the deep hole is machined to Ra1.6μm, and the hole opening has a 15° guide chamfer 4 to facilitate precise assembly of the locating pin or locking bushing.

[0021] The middle section 8, serving as the core area in contact with the phosphoric acid medium, has an outer diameter smaller than that of the shaft body, forming a gradually changing diameter structure. The outer circumference of the middle section 8 is sequentially covered with composite protective layers: the bottom layer is a 0.08-0.12mm thick chromium plating layer 5, formed through electroplating to ensure density and adhesion; the outer layer is formed through anodizing. The oxide film layer 6 has a thickness controlled between 0.015-0.025 mm. The surface of the oxide film layer 6 is sealed to block micropores and prevent the penetration of corrosive media.

[0022] Transition arcs 12 are provided at the connection points of the shaft head 9 and the shaft middle section 8, the shaft middle section 8 and the shaft body, and the shaft body and the shaft tail 10. The radius of the transition arcs 12 is R2-R5mm. The radius of the transition arcs 12 at the connection point of the shaft middle section 8 and the shaft body is larger than the radius of the transition arcs 12 at the connection point of the shaft head 9 and the shaft middle section 8, which further optimizes the stress distribution.

[0023] The shaft tail 10 is provided with a radially penetrating keyway 11. The keyway 11 is a through-slot structure with a width tolerance of H9 and a depth tolerance of JS9. The surface roughness of both sides is machined to Ra3.2μm to ensure accurate and reliable key connection with the power components and stable torque transmission. Both the shaft head 9 and the shaft tail 10 have 30° anti-collision chamfers 4 at their ends to avoid edge damage during assembly and transportation.

[0024] The shaft body 1 has an axially extending weight-reducing cavity inside. The opening end of the weight-reducing cavity is located at the end of the shaft tail 10 away from the shaft body. The length of the cavity is 2 / 5 to 3 / 5 of the total length of the shaft body 1, and the maximum inner diameter is 1 / 3 to 1 / 2 of the outer diameter of the shaft body 1. It is also coaxially arranged with the shaft body 1. The inner wall of the weight-reducing cavity is integrally formed with a spiral reinforcing rib. The pitch of the reinforcing rib is 1.5 to 2 times the diameter of the cavity, and the rib thickness is 0.8 to 1.2 mm, which compensates for the strength of the shaft while achieving weight reduction.

[0025] The assembly process of this embodiment is as follows: First, the blank of the shaft body 1 is heat-treated to ensure that the hardness meets the standard; then the external thread section 3 and the center positioning hole 2 of the shaft head 9 are machined in sequence, and the outer peripheral surface of the shaft middle section 8 is pre-treated, rust and oil are removed, and the chromium plating layer 5 and the oxide film layer 6 are prepared in sequence and the hole sealing treatment is completed; then the transition arc 12, the connecting arc 7 and the keyway 11 of the shaft tail 10 at each connection are machined, and finally the ends of the shaft head 9 and the shaft tail 10 are chamfered at 30° to complete the overall structure forming.

[0026] In the phosphoric acid conveying process, the shaft head 9 is fastened to the impeller and coupling through the external thread section 3, and the central positioning hole 2 ensures the coaxiality of the assembly; the composite protective layer of the middle section 8 isolates the phosphoric acid medium from corrosion and disperses stress at the same time; the weight-reducing cavity reduces the weight of the shaft and reduces the energy consumption of the motor, and the spiral reinforcing rib ensures the anti-torsion performance; the keyway 11 realizes the stable connection with the power components, and the overall structure meets the synergistic requirements of corrosion resistance, crack resistance and lightweight.

[0027] Example 2 The difference between this embodiment and Embodiment 1 lies in the adjustment of the weight-reducing cavity and reinforcing rib parameters based on actual conveying pressure and torque requirements: the length of the weight-reducing cavity is set to 3 / 5 of the total length of the shaft body 1, the maximum inner diameter is set to 1 / 2 of the outer diameter of the shaft body 1, the pitch of the spiral reinforcing rib is adjusted to 1.8 times the cavity diameter, and the rib thickness is 1.0 mm, further improving the structural strength under high load conditions. Simultaneously, the radius of the transition arc 12 at the connection between the shaft middle section 8 and the shaft body is R5 mm, and the radius of the transition arc 12 at the connection between the shaft head 9 and the shaft middle section 8 is R2 mm, adapting to greater torque transmission requirements.

[0028] The above are merely embodiments of this utility model. Commonly known structures and characteristics are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, based on the guidance provided in this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of this utility model. These should also be considered within the scope of protection of this utility model, and will not affect the effectiveness of the implementation of this utility model or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A pump shaft structure for a phosphoric acid transport pump, characterized in that, The shaft includes a shaft body, which is provided with a shaft head, a shaft middle section, a shaft body, and a shaft tail in sequence along the axial direction. The outer circumferential surface of the shaft head is provided with an external thread section, and the end of the shaft head is provided with a central positioning hole extending along the axial direction. The outer circumferential surface of the shaft middle section is provided with a chromium plating layer and an oxide film layer in sequence, and the outer diameter of the shaft middle section is smaller than the outer diameter of the shaft body. The connection between the shaft head and the shaft middle section, the shaft middle section and the shaft body, and the shaft body and the shaft tail are all provided with transition arcs. The shaft tail is provided with a keyway that runs through the shaft in the radial direction. The shaft body is provided with a weight-reducing cavity that extends along the axial direction. The opening end of the weight-reducing cavity is located at the end of the shaft tail away from the shaft body, and the inner wall of the weight-reducing cavity is provided with spiral reinforcing ribs.

2. The pump shaft structure of the phosphoric acid transport pump according to claim 1, characterized in that, The external thread section is a trapezoidal thread with a major diameter of 38mm and a pitch of 3mm. The thread surface is coated with polytetrafluoroethylene with a thickness of 0.02-0.05mm.

3. The pump shaft structure of the phosphoric acid transport pump according to claim 1, characterized in that, The surface roughness of the deep hole wall of the central positioning hole is Furthermore, the orifice is equipped with a 15° guide chamfer.

4. The pump shaft structure of the phosphoric acid transport pump according to claim 1, characterized in that, The chromium plating layer has a thickness of 0.08-0.12 mm, and the oxide film is formed by anodizing. The film has a thickness of 0.015-0.025 mm, and the surface of the oxide film layer is sealed.

5. The pump shaft structure of the phosphoric acid transport pump according to claim 1, characterized in that, The radius of the transition arc is R2-R5mm, wherein the radius of the transition arc at the connection between the middle section of the shaft and the shaft body is greater than the radius of the transition arc at the connection between the shaft head and the middle section of the shaft.

6. The pump shaft structure of the phosphoric acid pump according to claim 1, characterized in that, The keyway is a through-slot structure with a width tolerance of H9, a depth tolerance of JS9, and a surface roughness of Ra3.2μm on both sides of the keyway.

7. The pump shaft structure of the phosphoric acid pump according to claim 1, characterized in that, The length of the weight-reducing cavity is 2 / 5 to 3 / 5 of the total length of the shaft body, the maximum inner diameter of the cavity is 1 / 3 to 1 / 2 of the outer diameter of the shaft body, and the cavity is coaxially arranged with the shaft body.

8. The pump shaft structure of the phosphoric acid transport pump according to claim 1, characterized in that, The pitch of the spiral reinforcing rib is 1.5-2 times the diameter of the cavity, the rib thickness is 0.8-1.2mm, and the reinforcing rib and the inner wall of the weight-reducing cavity are integrally formed.

9. The pump shaft structure of the phosphoric acid transport pump according to claim 1, characterized in that, A connecting arc is provided between the end of the external thread section near the middle section of the shaft and the outer circumferential surface of the shaft head, and the radius of the connecting arc is R1.5-R4mm.

10. The pump shaft structure of the phosphoric acid transport pump according to claim 1, characterized in that, The shaft body is made of 2Cr13 stainless steel and is heat-treated to a hardness of 220-250HBW. Both the head and tail ends of the shaft are provided with 30° anti-collision chamfers.

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