Equipment and method for uniformly spraying axial paint film of steel pipe

Abstract

The invention discloses equipment and a method for uniformly spraying a steel pipe axial paint film, and relates to the technical field of steel pipe spraying. The device comprises a square pipe frame and a steel pipe fitting penetrating through the square pipe frame, and the two sides of the steel pipe fitting are driven by supporting rotating pieces to rotate. A first pushing frame and a second pushing frame which can be adjusted in position through an expansion piece are arranged in the square pipe frame, distance measuring probes are embedded in the pushing frames, and the first pushing frame is further provided with an electric heating module. The interior of the square pipe frame is divided into a spraying cavity, a drying area and a detection area, and a spraying assembly, an air exhaust assembly, an infrared paint film thickness gauge and the like are arranged in the spraying cavity, the drying area and the detection area respectively. According to the method, uniform coating of a paint film is achieved through steel pipe rotation, pushing frame positioning, gradient spraying, drying temperature control, thickness detection and dynamic paint make-up. The paint flow influence is counteracted to a certain extent, the detection accuracy is improved, the uniformity of the axial paint film of the steel pipe is ensured, and the product quality is improved.

Description

Technical Field

[0001] This invention relates to the field of steel pipe spraying technology, and in particular to a uniform axial paint film spraying device and method for steel pipes. Background Technology

[0002] In the steel pipe manufacturing and processing industry, applying paint film to the surface of steel pipes is a crucial process for improving their corrosion resistance, aesthetics, and service life. The uniformity of the paint film directly determines the protective performance and product quality of the steel pipe. However, existing axial paint film spraying technology for steel pipes still faces many problems in practical applications, making it difficult to meet the demands of high-precision, high-quality production. These problems are mainly reflected in the following aspects:

[0003] In existing spraying methods, the nozzles usually use indiscriminate spraying. However, the paint has fluidity. During the rotation of the steel pipe, under the combined effects of gravity and rotational inertia, the freshly sprayed paint will spread irregularly to specific areas on the surface of the steel pipe (such as below or behind in the direction of rotation), resulting in deviations in the paint film thickness at different positions along the axial direction of the steel pipe, making it difficult to achieve uniform coverage.

[0004] In existing technologies, paint film thickness is either measured uniformly after spraying or measured during spraying, but both methods have significant drawbacks. Freshly sprayed paint is in a colloidal state, and its physical properties (such as thickness and shape) differ considerably from its dried and formed state. Therefore, the paint film thickness measured at this stage does not reflect the true parameters of the final formed film. If touch-up painting is performed directly based on this inaccurate measurement result, the resulting paint film thickness will deviate significantly from the expected standard, failing to achieve the desired uniformity.

[0005] In summary, how to solve the defects such as uneven paint film thickness and poor coordination between inspection and subsequent touch-up during the steel pipe spraying process, and improve the quality and efficiency of steel pipe spraying, has become a technical problem that needs to be solved. Summary of the Invention

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0007] This invention provides a uniform axial paint coating device for steel pipes, comprising a square tube frame and steel pipes penetrating the square tube frame. Supporting rotating components are arranged at both ends of the steel pipes to support and drive their rotation. A first pusher is movably mounted at the bottom of the inner circumference of the square tube frame, and a second pusher is movably mounted at the top of the inner circumference. Both the first and second pushers are embedded with ranging probes that probe towards the steel pipes. Multiple electric heating modules are also evenly distributed on the top surface of the first pusher.

[0008] A lower expansion joint is fixedly installed on the bottom surface of the square tube frame, and the lower expansion joint is driven and connected to the first pusher. An upper expansion joint is fixedly installed on the top surface of the square tube frame, and the upper expansion joint is driven and connected to the second pusher. A spraying chamber, a drying area, and a testing area are provided between the square tube frame and its inner steel pipe components. The spraying area is located on one side of the line connecting the first and second pushers, and the drying area and testing area are located on the other side of the line connecting the first and second pushers.

[0009] A spraying assembly, which sprays paint horizontally towards the spraying chamber, is fixedly installed on one side of the square tube frame. The spraying assembly includes multiple nozzles. A horizontal expansion joint and an extraction assembly are fixedly installed on the other side of the square tube frame. A temperature probe is installed at the output end of the horizontal expansion joint. The drying zone is located between the heating module and the extraction assembly, and the detection zone is located between the extraction assembly and the second pusher. An infrared paint film thickness gauge facing the steel pipe is also fixedly installed at the top of the detection zone, along with a radial expansion joint that moves the infrared paint film thickness gauge.

[0010] As a preferred technical solution of the spraying equipment of the present invention: the first pusher is provided with a lower inclined surface facing the spraying component, and the second pusher is provided with an upper inclined surface facing the spraying component.

[0011] As a preferred technical solution of the spraying equipment of the present invention: the rotation axis of the supporting rotating component is located at the center of the cross-section of the square tube frame.

[0012] As a preferred technical solution of the spraying equipment of the present invention: the supporting rotating component is equipped with an angle encoding module for monitoring the rotation angle of the steel pipe component.

[0013] As a preferred technical solution of the spraying equipment of the present invention: a horizontal frame extending toward the drying zone is provided on the upper side of the first pusher, and multiple electric heating modules are embedded on the top surface of the horizontal frame. The multiple electric heating modules are distributed at the same horizontal height and all output heat vertically upward.

[0014] As a preferred technical solution of the spraying equipment of the present invention: the air extraction component includes an air extraction pump, the air extraction pipe of the air extraction pump is inserted into the inner circumference of the square tube frame, and the air intake end of the air extraction pipe is equipped with a wide-mouth air inlet hood that is inclined towards the outer surface of the steel pipe.

[0015] As a preferred technical solution of the spraying equipment of the present invention: the detection direction of the infrared paint film thickness gauge is directed towards the axis of the supporting rotating part.

[0016] This invention provides a method for uniformly spraying a paint film along the axial direction onto a steel pipe, comprising the following:

[0017] S1. The steel pipe fitting is inserted into the square tube frame, and the supporting rotating component is inserted into the two ends of the steel pipe fitting to form a positioning support. The supporting rotating component begins to drive the steel pipe fitting to rotate.

[0018] S2. During the rotation of the steel pipe fitting, the distance measuring probes on the first and second push frames continuously detect the distance to the outer ring surface of the steel pipe fitting. The lower expansion joint drives the first push frame to move, and the upper expansion joint drives the second push frame to move, until the distance between the distance measuring probes on both push frames and the outer ring surface of the steel pipe fitting reaches the system's preset gap dimension D. min .

[0019] S3. Based on the distance information of the outer ring surface of the steel pipe obtained by the ranging probe, the transverse expansion joint drives the temperature probe to move towards the steel pipe, so that the distance between the temperature probe and the outer ring surface of the steel pipe is adjusted to the preset gap size D. w .

[0020] S4. The radial expansion joint moves the infrared paint film thickness gauge, adjusting the distance between the infrared paint film thickness gauge and the outer ring surface of the steel pipe to the preset gap dimension D. r .

[0021] S5. The supporting rotating component drives the steel pipe to maintain its rotation state, and the spraying component sprays paint on the outer ring surface of the steel pipe. The spray nozzle works according to the preset spray volume configuration so that the paint initially covers the surface of the steel pipe.

[0022] S6. The steel pipe is rotated to the drying zone, where the heating module releases heat to dry the paint film. Simultaneously, a temperature probe monitors the drying zone temperature in real time, and the extraction assembly adjusts its extraction power based on the monitored temperature.

[0023] S7. The steel pipe is rotated to the inspection area, and the infrared paint film thickness gauge detects the thickness of the dried paint film, obtains the paint film thickness data at each position in real time, and compares it with the standard thickness preset by the system.

[0024] S8. When the paint film thickness at any position M is insufficient, the system calculates the difference between the thickness at position M and the standard thickness and matches the nozzle with the corresponding spray volume.

[0025] When the steel pipe is rotated to the spray range of the nozzle corresponding to position M, touch-up paint is applied through the nozzle to compensate for the thickness difference.

[0026] S9. After the touch-up painting is completed, the steel pipe fittings continue to be rotated, dried, and inspected to ensure the uniformity of the paint film.

[0027] As a preferred technical solution of the spraying method of the present invention: when the spraying assembly sprays paint on the outer ring surface of the steel pipe, the spraying volume of the spraying assembly nozzle increases sequentially from top to bottom.

[0028] As a preferred embodiment of the spraying method of this invention: the heating power of the electric heating module is positively correlated with the distance from the outer surface of the steel pipe. After entering the drying zone, the temperature probe detects the temperature T within the drying zone, and the air extraction assembly adjusts the air extraction power P according to the temperature T detected by the temperature probe. The air extraction power P is positively correlated with the temperature T.

[0029] Compared with existing technologies, the beneficial effects of this invention are:

[0030] 1. This invention addresses the problem of paint flowing downwards due to gravity and rotational inertia. The spray volume of the spraying assembly increases sequentially from top to bottom, which can offset the thickness deviation caused by the flow, making the axial distribution of the initially sprayed paint film more uniform. Furthermore, combined with the precise detection of the dried paint film by an infrared paint film thickness gauge and the dynamic paint replenishment mechanism based on the detection results, it can accurately compensate for the insufficient thickness in certain areas, further ensuring the uniformity of the paint film.

[0031] 2. This invention employs a "dry first, then test" process, avoiding testing errors caused by the significant difference in physical properties between the freshly sprayed paint surface (which is in a colloidal state) and the dried, formed paint. This ensures that the detected paint film thickness is closer to the actual parameters after final molding. Furthermore, the heating modules are distributed at the same horizontal height and all vertically upwards, outputting heat. Simultaneously, the heating power of the heating modules is positively correlated with the distance from the outer surface of the steel pipe, guaranteeing uniform heating of the outer surface and preventing localized overheating or underheating.

[0032] 3. In this invention, a temperature probe monitors the temperature of the drying zone in real time. The air extraction component adjusts its extraction power based on the monitored temperature, and the extraction power is positively correlated with the temperature. The drying temperature is controlled by air circulation to prevent localized overheating that could lead to paint film cracking or insufficient drying. Simultaneously, the wide-mouth air inlet hood of the air extraction component increases the airflow cross-sectional area and reduces the airflow rate, preventing airflow interference with the undried paint film. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the overall structure of the spraying equipment of the present invention.

[0034] Figure 2 for Figure 1 A magnified structural diagram of part A in the middle.

[0035] Figure 3 This is a schematic diagram of the spraying equipment of the present invention during operation.

[0036] Figure 4 for Figure 3 A magnified structural diagram of section B in the middle.

[0037] Figure 5 for Figure 3 A magnified structural diagram of part C in the middle.

[0038] Wherein: 1-square tube frame, 101-spraying chamber, 102-drying area, 103-inspection area; 2-spraying assembly, 201-spray head; 3-steel pipe fitting; 4-support rotating component; 5-first push frame, 501-lower inclined plate, 502-horizontal frame; 6-second push frame, 601-upper inclined plate; 7-lower expansion joint; 8-upper expansion joint; 9-distance measuring probe; 10-electric heating module; 11-horizontal expansion joint; 12-temperature probe; 13-air pump; 14-air extraction pipe; 15-wide-mouth air inlet hood; 16-infrared paint film thickness gauge; 17-radial expansion joint. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0040] Example 1, combined with appendix Figures 1 to 5 This equipment integrates spraying, drying, testing, and touch-up functions to achieve uniform axial paint coating on steel pipes. Its core structure and function are as follows:

[0041] The square tube frame 1 serves as the mounting frame for the entire equipment, providing fixed support for all components. Its interior is divided into a spraying chamber 101, a drying area 102, and a testing area 103, forming an orderly workflow channel. The steel pipe 3 runs through the interior of the square tube frame 1, and its rotation enables full-circumferential spraying of the outer surface.

[0042] The rotating support 4 is installed on both ends of the steel pipe 3. The rotation axis of the rotating support 4 is located at the center of the cross-section of the square tube frame 1 to ensure the stability of the axis when the steel pipe 3 rotates. The outer end of the rotating support 4 is connected to a drive motor, which is connected to a horizontal movement and lifting device. The rotating support 4 is forced to abut against the inner wall of the steel pipe 3 through the support contact block at the end of the telescopic mechanism, driving the steel pipe 3 to rotate synchronously.

[0043] The rotating support 4 is equipped with an angle encoding module: it monitors the rotation angle of the steel pipe 3 in real time, providing an angle reference for accurate positioning during subsequent paint touch-up, ensuring that the paint touch-up position corresponds exactly to the detected thickness position.

[0044] The first pusher 5 and the second pusher 6 are located at the bottom and top of the inner circumference of the square tube frame 1, respectively. The lower expansion joint 7 and the upper expansion joint 8 drive the first pusher 5 and the second pusher 6 to move up and down, respectively. By adjusting the distance between the pusher and the steel pipe component 3, precise positioning is achieved in conjunction with the ranging probe 9. The ranging probe 9 is embedded in the first pusher 5 and the second pusher 6. The ranging probe 9 continuously detects the distance to the outer ring surface of the steel pipe component 3, providing data for adjusting the pusher position and ensuring that the gap between the pusher and the steel pipe component 3 reaches the preset value D. min .

[0045] The lower inclined surface 501 (set on the first pusher 5) and the upper inclined surface 601 (set on the second pusher 6): When the pusher is close to the steel pipe 3, the two inclined surfaces can block the excess paint sprayed by the spraying component 2, prevent the paint from entering the drying area 102 and the detection area 103, and prevent the paint from contaminating or corroding the heating and detection components (such as the electric heating module 10 and the infrared paint film thickness gauge 16).

[0046] The electric heating modules 10 are evenly distributed on the top horizontal frame 502 of the first pusher 5. The electric heating modules 10 provide heat to the drying zone 102. They are distributed at the same horizontal height and heat vertically upwards to ensure that the outer surface of the steel pipe 3 is heated evenly.

[0047] The spraying assembly 2 is fixed to one side of the square tube frame 1. The spraying assembly 2 includes multiple nozzles 201 that spray paint horizontally toward the spraying chamber 101. Its core design is "the spray volume of the nozzles increases sequentially from top to bottom": because the paint tends to flow downwards due to gravity and the rotational inertia of the steel pipe, the increased spray volume of the lower nozzles can offset the uneven thickness caused by the flow, ensuring a more uniform axial distribution of the paint film during the initial spraying.

[0048] The drying zone 102 is located between the electric heating module 10 and the air extraction component. The paint film is dried by heating through the electric heating module 10, avoiding thickness deviation caused by the flow of undried paint.

[0049] The horizontal expansion joint 11 drives the temperature probe 12 to approach the steel pipe fitting 3, stabilizing the distance between it and the outer circumference of the steel pipe fitting 3 at a preset value D. w This ensures accurate temperature detection. Temperature probe 12 monitors the temperature of drying zone 102 in real time, providing a basis for adjusting the exhaust power.

[0050] The air extraction assembly includes an air pump 13, an air extraction pipe 14, and a wide-mouth air inlet hood 15. The air extraction pipe 14 is inserted into the square tube frame 1, and the wide-mouth air inlet hood 15 is tilted towards the outer surface of the steel pipe fitting 3, which increases the airflow cross-sectional area and reduces the airflow rate, thus preventing airflow from interfering with the undried paint film. The air extraction power P of the air pump 13 is positively correlated with the drying zone temperature T (the higher the temperature, the greater the air extraction power). By adjusting the airflow, the drying temperature is controlled to prevent local overheating that could lead to paint film cracking or insufficient drying.

[0051] The detection area 103 is located between the air extraction component and the second pusher 6. It is used to detect the thickness of the dried paint film to avoid detection errors caused by the difference between the undried paint film (colloidal state) and the dried state.

[0052] The infrared paint film thickness gauge 16 is fixed on the top of the detection area 103. The infrared paint film thickness gauge 16 adopts non-contact measurement, which will not damage the paint film surface. It can achieve micron-level precision detection and acquire paint film thickness data in real time. Its detection direction is aligned with the axis of the supporting rotating part 4 to ensure that the thickness measurement point is always the radially aligned point of the steel pipe part 3, thereby improving the detection accuracy.

[0053] The radial expansion joint 17 is fixed to the underside of the top plate of the square tube frame 1 via an angle-adjustable bracket. The radial expansion joint 17 drives the infrared paint film thickness gauge 16 to move, adjusting the distance between it and the outer ring surface of the steel pipe 3 to the preset value D. r This ensures that the thickness gauge operates within the optimal detection distance.

[0054] Example 2: The method for uniform axial paint film spraying of steel pipes according to this application, based on the structural characteristics of the equipment and the synergistic effect of each component, has the following specific process:

[0055] I. Steel pipe introduction and rotary start

[0056] Steel pipe positioning support: The steel pipe fitting 3 is inserted into the square tube frame 1, and the support rotating part 4 is inserted into the two ends of the steel pipe fitting 3. The support contact block at the end of the telescopic mechanism presses against the inner wall of the steel pipe fitting 3 to form a positioning support.

[0057] The rotating support 4 is connected to the drive motor, which drives the steel pipe 3 to rotate synchronously. The angle encoding module monitors the rotation angle of the steel pipe 3 in real time, providing a reference for subsequent positioning.

[0058] II. Equipment Position Calibration

[0059] Pusher position adjustment: During the rotation of the steel pipe 3, the distance measuring probes 9 on the first pusher 5 and the second pusher 6 continuously detect the distance to the outer ring surface of the steel pipe 3.

[0060] The lower expansion joint 7 drives the first pusher 5 to move upward, and the upper expansion joint 8 drives the second pusher 6 to move downward, until the distance between the ranging probe 9 on both pushers and the outer ring surface of the steel pipe 3 reaches the system's preset gap dimension D. min .(like Figure 2 , Figure 3 The minimum distance detected by the ranging probe 9 to the outer ring surface of the steel pipe 3 was originally D. x After the initial detection of the steel pipe component 3 is completed, the first pusher 5 moves upward until the minimum distance between the ranging probe 9 and the outer ring surface of the steel pipe component 3 reaches D. min At this time, the lower inclined surface 501 and the upper inclined surface 601 of the pusher can block the excess paint sprayed by the spraying component 2, so as to avoid contaminating the drying area 102 and the testing area 103.

[0061] Temperature probe positioning: Based on the distance information of the outer ring surface of the steel pipe fitting 3 obtained by the ranging probe 9, the transverse expansion joint 11 drives the temperature probe 12 to move towards the steel pipe fitting 3, so that the distance between the temperature probe 12 and the outer ring surface of the steel pipe fitting 3 is adjusted to the preset gap size D. w This ensures accurate temperature detection.

[0062] Thickness gauge position calibration: The radial expansion joint 17 moves the infrared paint film thickness gauge 16, adjusting the distance between it and the outer ring surface of the steel pipe 3 to the preset gap size D. r (The small gap between the temperature probe 12, the infrared paint film thickness gauge 16 and the outer ring surface of the steel pipe fitting 3 makes the detection accuracy higher. For example, it can shorten the air travel and reduce interference.)

[0063] The infrared paint film thickness gauge 16 is aligned with the axis of the supporting rotating part 4 to ensure that the detection point is the radially aligned point of the steel pipe, thereby improving the detection accuracy.

[0064] III. Preliminary Spraying Operation

[0065] The supporting rotating component 4 drives the steel pipe component 3 to maintain its rotation, and the multiple nozzles 201 of the spraying assembly 2 spray paint onto the outer ring surface of the steel pipe component 3 in the direction of the spraying chamber 101. The key design is that the spray volume of the nozzles increases sequentially from top to bottom, so that the paint initially and evenly covers the surface of the steel pipe component 3.

[0066] Design Considerations: If the upper nozzle 201 sprays a large volume, the paint on the outer ring surface of the steel pipe 3 will flow due to high potential energy and rotational potential energy. This invention replaces this with a lower nozzle 201 that sprays a large volume. When the paint sprayed from the lower nozzle 201 reaches the outer surface of the steel pipe 3, it quickly reaches the drying zone 102, and the paint film rapidly bonds with the outer ring surface of the steel pipe 3, shortening the time of negative impact from unstable paint on the outer ring surface of the steel pipe 3.

[0067] IV. Paint Film Drying Treatment

[0068] Heating in the drying zone: The steel pipe 3 rotates to the drying zone 102 (located between the heating module 10 and the exhaust assembly). Multiple heating modules 10 on the crossbeam 502 of the first pusher 5 release heat (the heating modules 10 are distributed at the same horizontal height and heat vertically upwards to ensure uniform heating). Furthermore, the heating power of the heating module 10 is positively correlated with the distance from the outer surface of the steel pipe 3 (the greater the distance, the greater the power, ensuring uniform heating at different locations).

[0069] Temperature and air extraction control: Temperature probe 12 monitors the temperature T of drying zone 102 in real time. The air extraction assembly (including air pump 13, wide-mouth air inlet hood 15, and air extraction pipe 14) adjusts the air extraction power P according to the temperature T, and P is positively correlated with T (the higher the temperature, the greater the air extraction power).

[0070] The wide-mouth air intake hood 15 increases the airflow cross-sectional area and reduces the airflow rate to avoid interfering with the undried paint film. It controls the drying temperature through air circulation to prevent local overheating or insufficient drying.

[0071] V. Coating film thickness testing

[0072] The steel pipe component 3 rotates to the detection area 103 (located between the air extraction assembly and the second pusher 6), and the infrared paint film thickness gauge 16 detects the thickness of the dried paint film: utilizing its high precision and fast response, it acquires paint film thickness data at various locations in real time. The detected data is compared with the system's preset standard thickness to identify locations with insufficient thickness.

[0073] The infrared paint film thickness gauge 16 adopts non-contact measurement: it will not cause damage or contamination to the paint film surface, and is suitable for paint films of various shapes and textures, especially soft, fragile or inconvenient paint films.

[0074] The infrared paint film thickness gauge 16 features high precision and fast response, enabling measurements at the micron level or even higher, meeting the requirements for precise control of paint film thickness. It can perform measurements in real time, obtaining results quickly, making it suitable for high-speed production lines or scenarios requiring rapid inspection.

[0075] VI. Touch-up painting adjustments (if necessary)

[0076] Difference calculation and nozzle matching: When the paint film thickness at any position M is insufficient, the system calculates the difference between the thickness at that position and the standard thickness, and matches the nozzle 201 with the corresponding spray volume according to the difference (because the spray volume of nozzle 201 increases from top to bottom, the larger the difference, the lower the nozzle is matched).

[0077] Precise paint touch-up: Based on the rotation angle of the steel pipe 3 monitored by the angle coding module, when the position M rotates to the spray range of the matching nozzle, the nozzle 201 starts the paint touch-up to make up for the thickness difference.

[0078] This operation does not require deliberate control of the spray volume of the nozzle 201. The spray volume of the nozzle 201 is preset and fixed. It is only necessary to match the correspondence between the amount of paint to be repaired and the spray volume. This matching relationship is also very simple. The larger the difference ε of the amount of paint to be repaired, the lower the nozzle 201 should be for repairing the paint.

[0079] VII. Final Processing and Export

[0080] After the touch-up painting is completed, the steel pipe 3 continues to rotate, passing through the drying zone 102 and the inspection zone 103 repeatedly to ensure that the paint film after touch-up is dry and of uniform thickness. After confirming that the paint film in all positions meets the standards, the support rotating part 4 is released, and the steel pipe 3 is exported from the square tube frame 1, completing the entire spraying process.

[0081] This invention avoids detection errors caused by differences in the state of undried paint films by "drying first and then testing". Combined with the design of the spray volume gradient of the nozzle, the dynamic paint replenishment mechanism and the precise temperature control, it achieves uniform control of the axial paint film of the steel pipe.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A uniform axial paint film spraying device for steel pipes, characterized in that: It includes a square tube frame (1) and a steel pipe (3) that passes through the square tube frame (1). The two ends of the steel pipe (3) are equipped with support rotating parts (4) that support and drive the steel pipe (3) to rotate. The square tube frame (1) has a first pusher (5) movably installed at the bottom of the inner circumference and a second pusher (6) movably installed at the top of the inner circumference. Both the first pusher (5) and the second pusher (6) are equipped with a ranging probe (9) that is directed toward the steel pipe fitting (3). The top surface of the first pusher (5) is also evenly distributed with multiple electric heating modules (10). The bottom surface of the square tube frame (1) is fixedly equipped with a lower telescopic device (7), which is driven and connected to the first push frame (5). The top surface of the square tube frame (1) is fixedly equipped with an upper telescopic device (8), which is driven and connected to the second push frame (6). The square tube frame (1) and its inner steel pipe fittings (3) are provided with a spraying chamber (101), a drying area (102), and a testing area (103). The spraying chamber (101) is located on one side of the line connecting the first pusher (5) and the second pusher (6), and the drying area (102) and the testing area (103) are located on the other side of the line connecting the first pusher (5) and the second pusher (6). The square tube frame (1) is fixedly installed on one side with a spraying assembly (2) that sprays paint horizontally toward the spraying chamber (101). The spraying assembly (2) includes multiple nozzles (201). A horizontal expansion joint (11) and an air extraction assembly are fixedly installed on the other side of the square tube frame (1). A temperature probe (12) is installed at the output end of the horizontal expansion joint (11). The drying zone (102) is located between the electric heating module (10) and the air extraction assembly. The detection zone (103) is located between the air extraction assembly and the second pusher (6). An infrared paint film thickness gauge (16) facing the steel pipe fitting (3) and a radial expansion joint (17) that drives the infrared paint film thickness gauge (16) to move are also fixedly configured on the top of the detection zone (103).

2. The axial uniform paint film spraying equipment for steel pipes according to claim 1, characterized in that: The first pusher (5) is provided with a lower stop slope (501) facing the spraying assembly (2), and the second pusher (6) is provided with an upper stop slope (601) facing the spraying assembly (2).

3. The axial uniform paint film spraying equipment for steel pipes according to claim 1, characterized in that: The rotation axis of the supporting rotating component (4) is located at the center of the cross section of the square tube frame (1).

4. The axial uniform paint film spraying equipment for steel pipes according to claim 1, characterized in that: The supporting rotating component (4) is equipped with an angle encoding module for monitoring the rotation angle of the steel pipe component (3).

5. The axial uniform paint film spraying equipment for steel pipes according to claim 1, characterized in that: The first pusher (5) has a horizontal frame (502) extending toward the drying zone (102) on its upper side. Multiple electric heating modules (10) are embedded on the top surface of the horizontal frame (502). The multiple electric heating modules (10) are distributed at the same horizontal height and all output heat vertically upward.

6. The axial uniform paint film spraying equipment for steel pipes according to claim 1, characterized in that: The air extraction assembly includes an air pump (13), the air extraction pipe (14) of the air pump (13) is inserted into the inner circumference of the square tube frame (1), and the air intake end of the air extraction pipe (14) is equipped with a wide-mouth air inlet hood (15) that is inclined toward the outer surface of the steel pipe fitting (3).

7. The axial uniform paint film spraying equipment for steel pipes according to claim 1, characterized in that: The infrared paint film thickness gauge (16) is directed towards the axis of the supporting rotating part (4).

8. A method for uniformly spraying a paint film axially onto a steel pipe, characterized in that, The steel pipe axial paint film uniform spraying equipment according to any one of claims 1 to 7 includes the following: S1. The steel pipe fitting (3) is inserted into the square tube frame (1), and the supporting rotating part (4) is inserted into the two ends of the steel pipe fitting (3) and forms a positioning support for it. The supporting rotating part (4) begins to drive the steel pipe fitting (3) to rotate. S2. During the rotation of the steel pipe fitting (3), the ranging probes (9) on the first pusher (5) and the second pusher (6) continuously detect the distance to the outer ring surface of the steel pipe fitting (3); The lower telescopic device (7) drives the first pusher (5) to move, and the upper telescopic device (8) drives the second pusher (6) to move, until the distance between the ranging probe (9) on both pushers and the outer ring surface of the steel pipe (3) reaches the system's preset gap size D. min ; S3. Based on the distance information of the outer ring surface of the steel pipe fitting (3) obtained by the ranging probe (9), the transverse expansion joint (11) drives the temperature probe (12) to move towards the steel pipe fitting (3), so that the distance between the temperature probe (12) and the outer ring surface of the steel pipe fitting (3) is adjusted to the preset gap size D. w ; S4. The radial expansion joint (17) moves the infrared paint film thickness gauge (16) to adjust the distance between the infrared paint film thickness gauge (16) and the outer ring surface of the steel pipe (3) to the preset gap size D. r ; S5. The supporting rotating component (4) drives the steel pipe component (3) to maintain rotation. The spraying component (2) sprays paint on the outer ring surface of the steel pipe component (3). The spray nozzle works according to the preset spray volume configuration, so that the paint initially covers the surface of the steel pipe component (3). S6. The steel pipe fitting (3) is rotated to the drying zone (102), and the electric heating module (10) releases heat to dry the paint film; Meanwhile, the temperature probe (12) monitors the temperature of the drying zone (102) in real time, and the air extraction component adjusts the air extraction power according to the monitored temperature. S7. The steel pipe fitting (3) is rotated to the detection area (103), and the infrared paint film thickness gauge (16) detects the thickness of the dried paint film, obtains the paint film thickness data at each position in real time, and compares it with the standard thickness preset by the system. S8. When the paint film thickness at any position M is insufficient, the system calculates the difference between the thickness at position M and the standard thickness and matches the nozzle with the corresponding spray volume. When the steel pipe fitting (3) is rotated to the spray range of the spray nozzle corresponding to position M, the paint is touched up through the nozzle to make up for the thickness difference; S9. After the touch-up painting operation is completed, the steel pipe fitting (3) continues to be rotated, dried and inspected to ensure the uniformity of the paint film.

9. A method for uniformly spraying a steel pipe axial paint film according to claim 8, characterized in that: When the spraying assembly (2) sprays paint on the outer ring surface of the steel pipe (3), the spray volume of the nozzle (201) of the spraying assembly (2) increases from top to bottom.

10. A method for uniformly spraying a steel pipe axial paint film according to claim 8, characterized in that: The heating power of the electric heating module (10) is positively correlated with the distance from the outer surface of the steel pipe fitting (3); After entering the drying zone (102), the temperature probe (12) detects the temperature T in the drying zone (102). The air extraction component adjusts the air extraction power P according to the temperature T detected by the temperature probe (12). The air extraction power P is positively correlated with the temperature T.

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