A steel pipe inner wall heating and coating machine and a coating method

Abstract

The application provides a steel pipe inner wall heating spraying machine and a spraying method, wherein the spraying machine comprises a base, a moving device, a spraying device and a heating device; the moving device drives the steel pipe to reciprocate along the length direction of the base; the spraying device comprises a spraying rod and a spraying head; the spraying rod is located in the steel pipe; one end of the spraying rod is connected with the base, and the opposite end is provided with the spraying head; the heating device is located in the steel pipe and is arranged at the end of the spraying rod close to the spraying head; the two ends of the steel pipe are respectively provided with a first flange and a second flange; the flange end face heating inductor and the flange end face powder spraying machine are arranged at the end faces of the first flange and the second flange; and the bottom of the flange end face heating inductor and the flange end face powder spraying machine is connected with the moving device. The flange heating and spraying are respectively completed by the flange end face heating inductor and the flange end face powder spraying machine, and the spraying of the inner wall of the steel pipe and the flange end is synchronously performed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steel pipe spraying, in particular to a steel pipe inner wall heating and coating machine and a coating method. BACKGROUND

[0002] The steel pipe spraying process is to preheat the steel pipe to a certain temperature, then coat a layer of plastic (nylon) powder on the inner wall of the steel pipe, and the powder is then melted and adhered to the pipe wall. After cooling, a solid protective film is formed to improve the corrosion resistance and wear resistance of the steel pipe.

[0003] The traditional process is to heat the entire steel pipe to a certain temperature, then coat a layer of plastic (nylon) powder, and the powder is then melted and adhered to the pipe wall. This process requires the entire steel pipe to be heated, and the heating device is relatively large. When spraying plastic (nylon) powder, the entire pipe needs to be sprayed. When processing long pipes, a powder spraying device equal to the length of the pipe is needed. Within the range of the equal length of the pipe, plastic nylon powder needs to be sprayed simultaneously, and uniformity of the powder spraying needs to be ensured. The processing difficulty is greater, and the longer the pipe, the greater the difficulty. For steel pipes with flanges at both ends, the heating method is also to heat the entire pipe, but two sets of end face powder spraying devices are needed to spray the flanges of the pipe. The coating of the pipe flange must be done at the same time as the inner wall, which also increases the processing difficulty.

[0004] Patent No. CN101773891A discloses a metal pipe inner wall spraying device, which cannot be used for spraying steel pipes with flanges at both ends. Therefore, a spraying device suitable for steel pipes with flanges at both ends is needed. SUMMARY

[0005] In view of the above, the present application provides a coating device and method suitable for steel pipes with flanges at both ends.

[0006] The technical solution of the present application is as follows: On the one hand, the present application provides a steel pipe inner wall heating and coating machine, which comprises a base, a moving device, a spraying device and a heating device. The steel pipe is connected with the moving device, the moving device is slidingly connected with the base, the length direction of the steel pipe is the same as that of the base, and the moving device drives the steel pipe to move back and forth along the length direction of the base. The spraying device comprises a spray rod and a spray head. The spray rod is located inside the steel pipe, one end of the spray rod is connected with the base, and the opposite end is provided with a spray head. The heating device is located inside the steel pipe and is arranged at one end of the spray rod close to the spray head.

[0007] On the basis of the above technical solution, preferably, the first flange and the second flange are respectively arranged at both ends of the steel pipe, flange end face heating inductors and end face powder spraying machines are arranged at the end faces of the first flange and the second flange, and the bottom of the flange end face heating inductors and the end face powder spraying machines are connected with the moving device.

[0008] On the basis of the above technical scheme, preferably, the flange end face heating inductor comprises an end face heating inductor and a support seat, the support seat is connected with the moving device, the support seat is provided with a first sliding rail and a second sliding rail, the first sliding rail is parallel to the length direction of the steel pipe, the second sliding rail is perpendicular to the first sliding rail, the end face heating inductor is slidingly connected with the first sliding rail, and the first sliding rail is slidingly connected with the second sliding rail through a sliding block.

[0009] On the basis of the above technical scheme, preferably, the heating device comprises a heating box and an inner hole heating inductor, the heating box is arranged at one end of the base, one end of the spray rod is connected with the heating box, the other end of the spray rod is provided with the inner hole heating inductor, the flange close to the heating box is a first flange, and the flange away from the heating box is a second flange.

[0010] On the basis of the above technical scheme, preferably, the spraying device further comprises a spray pipe and a powder spraying box, the spray pipe is arranged in the spray rod, one end of the spray pipe is communicated with the spray head, and the other end is communicated with the powder spraying box.

[0011] On the basis of the above technical scheme, preferably, the length of the spray rod is greater than the length of the steel pipe.

[0012] On the basis of the above technical scheme, preferably, the spraying device further comprises a powder guiding box and a powder collector, the powder guiding box is two, and is arranged at the bottom of the first flange and the second flange respectively, and the powder guiding box is communicated with the powder collector through a pipeline; the powder guiding box is connected with the moving device.

[0013] On the basis of the above technical scheme, preferably, the moving device and the steel pipe are provided with a roller assembly for rotating the steel pipe along the axis thereof.

[0014] On the basis of the above technical scheme, preferably, the roller assembly comprises a support piece, a support roller and a driving device, the support piece is in a V-shaped structure, and there are two, the bottom of each support piece is connected with the moving device and is arranged at the bottom of the steel pipe in a spaced manner, and the two ends of each support piece are rotatably provided with a support roller; the driving device is connected with at least one support roller and drives the support roller to rotate so as to drive the steel pipe to rotate.

[0015] On the basis of the above technical scheme, preferably, the spraying device further comprises a pressing piece, a pressing roller and a fixing frame, the fixing frame is connected with the moving device, the pressing piece is slidingly connected with the fixing frame in an up-down direction, the pressing piece is in an inverted V-shaped structure, the pressing roller is rotatably arranged at the two ends of the pressing piece and presses the top of the steel pipe, and the rotation shaft of the pressing roller is parallel to the central axis of the steel pipe.

[0016] On the basis of the above technical scheme, preferably, the spraying device further comprises a pressing piece, a pressing roller and a fixing frame, the fixing frame is connected with the moving device, the pressing piece is slidingly connected with the fixing frame in an up-down direction, the pressing piece is in an inverted V-shaped structure, the pressing roller is rotatably arranged at the two ends of the pressing piece and presses the top of the steel pipe, and the rotation shaft of the pressing roller is parallel to the central axis of the steel pipe.

[0017] S1, the pressing wheel compacts the steel pipe, the moving device drives the steel pipe to move to the direction of the heating box, until the nozzle is 200mm away from the second flange end face, reaches the waiting station;

[0018] S2, the first driving device drives the roller to rotate, and drives the steel pipe to rotate; the end face heating inductor located at the second flange end face moves to the direction of the steel pipe, and after approaching the steel pipe, the second flange end face is heated; after the heating is completed, the end face heating inductor retreats;

[0019] S3, the moving device drives the steel pipe to continue to move to the direction of the heating box, so that the inner hole heating inductor reaches the end face of the second flange, and the inner hole of the end face of the second flange is heated;

[0020] S4, after the heating is completed, the moving device drives the steel pipe to move away from the direction of the heating box, reaches the waiting station, and at this time, the powder spraying machine located at the end face of the second flange starts to spray powder;

[0021] S5, after the powder spraying of the second flange is completed, the moving device drives the steel pipe to move to the direction of the heating box, the inner hole heating inductor reaches the end face of the second flange, and the inner wall of the steel pipe is heated; during the heating process, the moving device continues to drive the steel pipe to move away from the direction of the heating box, and at the same time, the nozzle sprays the inside of the steel pipe;

[0022] S6, when the inner hole heating inductor reaches the end face of the first flange, the inner hole heating inductor stops heating, and the nozzle stops spraying powder; the end face heating inductor located at the end face of the first flange moves to the direction of the steel pipe, and after approaching the steel pipe, the end face of the first flange is heated; after the heating is completed, the end face heating inductor retreats; the powder spraying machine located at the end face of the first flange starts to spray powder;

[0023] S7, after the powder spraying is completed, the roller stops rotating, and the pressing wheel retreats and leaves the steel pipe.

[0024] The steel pipe inner wall heating and coating machine and the coating method have the following beneficial effects relative to the prior art:

[0025] (1) The flange heating and spraying of the present application are completed by the flange end face heating inductor and the end face powder spraying machine respectively, so that the spraying of the inner wall of the steel pipe and the end face of the flange is carried out synchronously.

[0026] (2) The spraying machine of the present application can realize heating and spraying simultaneously, which ensures the uniformity of powder spraying.

[0027] (3) The present application improves the stability of the steel pipe during movement through the cooperation of the supporting roller and the pressing wheel.

[0028] (4) The stability of the spraying device and the heating device is improved by setting the guide cylinder. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced. Obviously, the accompanying drawings in the following description only represent some of the embodiments of the present application, and all of the other drawings can be obtained by those of ordinary skill in the art without any creative effort based on these drawings.

[0030] Figure 1 It is a perspective view of the steel pipe inner wall heating and spraying machine of the present application;

[0031] Figure 2 It is Figure 1 An enlarged view of part A;

[0032] Figure 3 It is an internal structure diagram of the spraying device of the steel pipe inner wall heating and spraying machine of the present application;

[0033] Figure 4 It is a front view of the steel pipe inner wall heating and spraying machine of the present application

[0034] Figure 5 It is a left view of the steel pipe inner wall heating and spraying machine of the present application.

[0035] In the figure, 1 is a base, 2 is a moving device, 3 is a spraying device, 4 is a heating device, 5 is a steel pipe, 31 is a spraying rod, 32 is a spraying head, 51 is a first flange, 52 is a second flange, 6 is a flange end face heating inductor, 7 is an end face powder spraying machine, 61 is an end face heating inductor, 62 is a support seat, 8 is a first sliding rail, 9 is a second sliding rail, 10 is a sliding block, 41 is a heating box, 42 is an inner hole heating inductor, 33 is a spraying pipe, 34 is a powder spraying box, 11 is a powder guide box, 12 is a powder collector, 13 is a roller assembly, 131 is a support piece, 132 is a support roller, 133 is a driving device, 14 is a pressing piece, 15 is a pressing roller, 16 is a fixing frame, 17 is a first motor, 18 is a second motor, 611 is a heating plate, 71 is a powder spraying pipe, 19 is a third motor, and 20 is a guide cylinder. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments only represent some of the embodiments of the present application, and all of the other embodiments obtained by those of ordinary skill in the art without any creative effort based on these embodiments belong to the scope of protection of the present application.

[0037] As Figure 1 shown, in combination with Figures 2-5The steel pipe inner wall heating and coating machine tool comprises a base 1, a moving device 2, a spraying device 3 and a heating device 4, the moving device 2 is a moving trolley, a steel pipe 5 is detachably connected with the moving device 2, the base 1 is provided with a sliding rail, the moving device 2 is slidingly connected with the base 1, the length directions of the steel pipe 5 and the base 1 are the same, and the moving device 2 drives the steel pipe 5 to reciprocally move along the length direction of the base 1.

[0038] The spraying device 3 comprises a spraying rod 31, a spraying head 32, a spraying pipe 33 and a powder spraying box 34, the spraying rod 31 is located in the steel pipe 5, one end of the spraying rod 31 is connected with the base 1, and the opposite end is provided with the spraying head 32; the spraying pipe 33 is arranged in the spraying rod 31, one end of the spraying pipe 33 is communicated with the spraying head 32, and the other end is communicated with the powder spraying box 34; the heating device 4 is located in the steel pipe 5 and arranged at one end of the spraying rod 31 close to the spraying head 32. The lengths of the spraying rod 31 and the spraying pipe 33 are greater than the length of the steel pipe 5, and the length of the spraying rod 31 is greater than the length of the spraying pipe 33, so that the inner wall of the steel pipe 5 can be sprayed.

[0039] In the specific embodiment, a guide cylinder 20 is further included, the guide cylinder 20 is connected with one end of the spraying rod 31 close to the spraying head 32, and the guide cylinder 20 is embedded in the steel pipe 5, there is a gap between the guide cylinder 20 and the steel pipe 5, so that the guide cylinder 20 can smoothly pass through the inside of the steel pipe 5 during the movement of the steel pipe 5. The heating device 4 is located at one end of the guide cylinder 20 away from the spraying head 32.

[0040] First and second flanges 51 and 52 are arranged at two ends of the steel pipe 5 respectively, flange end face heating inductors 6 and end face powder spraying machines 7 are arranged at the end faces of the first and second flanges 51 and 52, the bottom of the flange end face heating inductor 6 is connected with the moving device 2, the end face powder spraying machine 7 is detachably connected with the flange end face heating inductor 6, and the heating inductor 6 and the end face powder spraying machine 7 move together with the steel pipe 5 when the moving device 2 drives the steel pipe 5 to move.

[0041] The flange end face heating inductor 6 comprises an end face heating inductor 61 and a support seat 62, the support seat 62 is detachably connected with the moving device 2, the support seat 62 is provided with horizontal first and second sliding rails 8 and 9, the first sliding rail 8 is parallel to the length direction of the steel pipe 5, the second sliding rail 9 is perpendicular to the first sliding rail 8, the end face heating inductor 61 is slidingly connected with the first sliding rail 8, the first sliding rail 8 is slidingly connected with the second sliding rail 9 through a sliding block 10, and the end face powder spraying machine 7 is detachably connected with the support seat 62.

[0042] In the specific embodiment, first and second motors 17 and 18 are further included, the first and second motors 17 and 18 are linear motors, and are connected with the support seat 62, the first motor 17 drives the end face heating inductor 61 to reciprocally move along the first sliding rail 8, and the second motor 18 drives the end face heating inductor 61 to reciprocally move along the second sliding rail 9.

[0043] In a specific embodiment, the end face heating sensor 61 includes a heating plate 611. The plane of the heating plate 611 is parallel to the plane of the end face of the first flange 51 or the second flange 52, and the end face of the first flange 51 or the second flange 52 is heated by the heating plate 611.

[0044] In a specific embodiment, the end face powder spraying machine 7 includes a powder spraying pipe 71. The length direction of the powder spraying pipe 71 is parallel to the plane where the end face of the first flange 51 or the second flange 52 is located, and the opening of the powder spraying pipe 71 is close to the end face of the first flange 51 or the second flange 52.

[0045] In a specific embodiment, the heating device 4 includes a heating box 41 and an inner hole heating sensor 42. The heating box 41 is disposed at one end of the base 1, one end of the spray bar 31 is connected to the heating box 41, and the other end of the spray bar 31 is provided with the inner hole heating sensor 42. The inner hole heating sensor 42 is annular and disposed inside the guide cylinder 20, located on the side of the nozzle 32 near the heating box 41. The flange near the heating box 41 is the first flange 51, and the flange away from the heating box 41 is the second flange 52.

[0046] In a specific embodiment, the top of the nozzle 32 is provided with a baffle to facilitate the uniform spraying of powder onto the inner wall of the pipe 5.

[0047] In a specific embodiment, the device further includes a powder guiding box 11 and a powder collector 12. There are two powder guiding boxes 11, which are respectively disposed at the bottom of the first flange 51 and the second flange 52. The powder guiding boxes 11 are connected to the powder collector 12 through pipes. The powder guiding boxes 11 are connected to the moving device 2. The powder collector 12 is equipped with a negative pressure suction head. Powder falling from the powder guiding boxes 11 is sucked into the powder collector 12 through the negative pressure suction head.

[0048] In a specific embodiment, a roller 13 assembly is provided between the moving device 2 and the steel pipe 5 to make the steel pipe 5 rotate along its axis.

[0049] In a specific embodiment, the roller assembly 13 includes a support member 131, support rollers 132, and a drive device 133. The support member 131 has a V-shaped structure and there are two of them. The bottom of both support members 131 is connected to the moving device 2 and is spaced apart at the bottom of the steel pipe 5. Each support member 131 has a support roller 132 rotatably mounted at both ends. The drive device 133 is connected to at least one support roller 132 and drives the support roller 132 to rotate, thereby driving the steel pipe 5 to rotate. The axis of rotation of the support roller 132 is parallel to the central axis of the steel pipe 5. The support rollers 132 are located on both sides of the bottom of the steel pipe 5, serving to support and drive the steel pipe 5 to roll.

[0050] In the specific embodiment, the pressing member 14, the pressing wheel 15 and the fixing frame 16 are further included, the fixing frame 16 is connected with the moving device 2, the pressing member 14 is connected with the fixing frame 16 in a sliding mode, the pressing member 14 is in an inverted V shape, the pressing wheel 15 is arranged at the two ends of the pressing member 14 and the top of the steel pipe 5 in a rotating mode, and the rotating shaft of the pressing wheel 15 is parallel to the central axis of the steel pipe 5.

[0051] In the specific embodiment, the third motor 19 for driving the pressing wheel 15 to slide on the fixing frame 16 is further included, the third motor 19 is connected with the fixing frame 16, and the driving end of the third motor 19 is connected with the pressing wheel 15.

[0052] A method for heating and coating the inner wall of a steel pipe, comprising the following steps:

[0053] S1, the pressing wheel 15 presses the steel pipe 5, the moving device 2 drives the steel pipe 5 to move towards the heating box 41 until the distance between the nozzle 32 and the end face of the second flange 52 is 200 mm, and the waiting station is reached; the second flange 52 is prevented from being sprayed when the second flange 52 is heated and sprayed;

[0054] S2, the driving device 133 drives the supporting roller 132 to rotate, thereby driving the steel pipe 5 to rotate; the end face heating inductor 61 located at the end face of the second flange 52 moves towards the steel pipe 5, and after approaching the steel pipe 5, the end face of the second flange 52 is heated; after the heating is completed, the end face heating inductor 61 retreats;

[0055] S3, the moving device 2 drives the steel pipe 5 to continue to move towards the heating box 41, so that the inner hole heating inductor 42 reaches the end face of the second flange 52, and the end face inner hole of the second flange 52 is heated;

[0056] S4, after the heating is completed, the moving device 2 drives the steel pipe 5 to move away from the heating box 41, and reaches the waiting station; at this time, the powder spraying machine 7 located at the end face of the second flange 52 starts to spray powder;

[0057] S5, after the powder spraying of the second flange 52 is completed, the moving device 2 drives the steel pipe 5 to move towards the heating box 41, the inner hole heating inductor 42 reaches the end face of the second flange 52, and the inner wall of the steel pipe 5 is heated; during the heating process, the moving device 2 continues to drive the steel pipe 5 to move away from the heating box 41, and at the same time, the nozzle 32 sprays the inside of the steel pipe 5;

[0058] S6, when the inner hole heating inductor 42 reaches the end face of the first flange 51, the inner hole heating inductor 42 stops heating, and the nozzle 32 stops spraying; the end face heating inductor 61 located at the end face of the first flange 51 moves towards the steel pipe 5, and after approaching the steel pipe 5, the end face of the first flange 51 is heated; after the heating is completed, the end face heating inductor 61 retreats; the powder spraying machine 7 located at the end face of the first flange 51 starts to spray powder;

[0059] S7, after the end of the powder spraying, the supporting roller 132 stops rotating, the pressing wheel 15 retreats and leaves the steel pipe.

[0060] The present application first heats and sprays the second flange 52 of the end face of the steel pipe 5, then the driving device 133 drives the steel pipe 5 to rotate while the moving device 2 drives the steel pipe 5 to move towards the first flange 51, thereby completing the heating and spraying of the inner wall of the steel pipe 5 and the first flange 51. The coating of the first flange 51 and the second flange 52 is completed by the end face heating inductor 61 and the end face powder spraying machine 7, and the coating of the inner wall of the steel pipe 5 is completed by the inner hole heating inductor 42 and the spraying head 32 located on the spraying rod 31.

[0061] By arranging the inner hole heating inductor 42 outside the spraying rod 31, the heating and spraying can be simultaneously performed.

[0062] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A steel pipe inner wall heating coating machine tool, comprising a base (1), a moving device (2), a spraying device (3) and a heating device (4), a steel pipe (5) is connected with the moving device (2), the moving device (2) is slidingly connected with the base (1), the length direction of the steel pipe (5) is the same as that of the base (1), the moving device (2) drives the steel pipe (5) to reciprocate along the length direction of the base (1); the spraying device (3) comprises a spraying rod (31) and a spraying head (32), the spraying rod (31) is located inside the steel pipe (5), one end of the spraying rod (31) is connected with the base (1), and the opposite end is provided with the spraying head (32); the heating device (4) is located inside the steel pipe (5) and is arranged at one end of the spraying rod (31) close to the spraying head (32); characterized in that: first and second flanges (51) and (52) are respectively arranged at two ends of the steel pipe (5), flange end face heating inductors (6) and end face powder spraying machines (7) are arranged at end faces of the first and second flanges (51) and (52), and bottoms of the flange end face heating inductors (6) and the end face powder spraying machines (7) are connected with the moving device (2); the flange end face heating inductor (6) comprises an end face heating inductor (61) and a supporting seat (62), the supporting seat (62) is connected with the moving device (2), first and second sliding rails (8) and (9) are arranged on the supporting seat (62), the first sliding rail (8) is parallel to the length direction of the steel pipe (5), the second sliding rail (9) is perpendicular to the first sliding rail (8), the end face heating inductor (61) is slidingly connected with the first sliding rail (8), and the first sliding rail (8) is slidingly connected with the second sliding rail (9) through a sliding block (10); a roller assembly (13) for rotating the steel pipe (5) along its axis is arranged between the moving device (2) and the steel pipe (5).

2. A machine for applying a coating to the inside of a steel tube as claimed in claim 1, characterized in that: the heating device (4) comprises a heating box (41) and an inner hole heating inductor (42), the heating box (41) is arranged at one end of the base (1), one end of the spraying rod (31) is connected with the heating box (41), the other end of the spraying rod (31) is provided with the inner hole heating inductor (42), and the inner hole heating inductor (42) is located at a side of the spraying head (32) close to the spraying rod (31); the flange close to the heating box (41) is the first flange (51), and the flange away from the heating box (41) is the second flange (52).

3. A machine for applying a coating to the inside of a steel tube as claimed in claim 2, characterised in that: the spraying device (3) further comprises a spraying pipe (33) and a powder spraying box (34), the spraying pipe (33) is arranged inside the spraying rod (31), one end of the spraying pipe (33) is communicated with the spraying head (32), and the other end is communicated with the powder spraying box (34).

4. A machine for applying a coating to the inside of a steel tube as claimed in claim 3, characterised in that: the length of the spraying rod (31) is greater than that of the steel pipe (5).

5. A machine for applying a coating to the inside of a steel tube as claimed in claim 3, characterized in that: a powder guide box (11) and a powder collector (12) are further included, two powder guide boxes (11) are arranged at bottoms of the first and second flanges (51) and (52), respectively, and the powder guide boxes (11) are communicated with the powder collector (12) through pipelines; and the powder guide boxes (11) are connected with the moving device (2).

6. A machine for applying a coating to the inside of a steel tube as claimed in claim 5, characterised in that: The roller assembly (13) comprises support pieces (131) and support rollers (132) and driving devices (133), the support pieces (131) are V-shaped structures, and there are two, the bottoms of the two support pieces (131) are connected with the moving device (2), and are arranged at intervals at the bottom of the steel pipe (5), and the two ends of each support piece (131) are rotatably provided with a support roller (132); the driving device (133) is connected with at least one support roller (132), and drives the support roller (132) to rotate, so as to drive the steel pipe (5) to rotate.

7. A machine for applying a coating to the inside of a steel tube as claimed in claim 6, characterised in that: Further comprising a pressing piece (14), a pressing roller (15) and a fixing frame (16), the fixing frame (16) is connected with the moving device (2), the pressing piece (14) is slidably connected with the fixing frame (16) in up and down directions, the pressing piece (14) is inverted V-shaped, the pressing roller (15) is rotatably arranged at the two ends of the pressing piece (14), and presses the top of the steel pipe (5), and the rotation shaft of the pressing roller (15) is parallel to the central axis of the steel pipe (5).

8. A method of applying a heat coating to the inner wall of a steel pipe, characterized by: The steel pipe inner wall heating and coating machine tool is used for coating, and the coating method comprises the following steps: S1, the pressing roller (15) presses the steel pipe (5), the moving device (2) drives the steel pipe (5) to move towards the heating box (41), until the distance between the nozzle (32) and the end face of the second flange (52) is 200mm, and the waiting station is reached; S2, the driving device (133) drives the support roller (132) to rotate, and drives the steel pipe (5) to rotate; the end face heating inductor (61) located at the end face of the second flange (52) moves towards the steel pipe (5), and after approaching the steel pipe (5), the end face of the second flange (52) is heated; after heating, the end face heating inductor (61) retreats; S3, the moving device (2) drives the steel pipe (5) to continue to move towards the heating box (41), so that the inner hole heating inductor (42) reaches the end face of the second flange (52), and the end face inner hole of the second flange (52) is heated; S4, after heating, the moving device (2) drives the steel pipe (5) to move away from the heating box (41), and reaches the waiting station, at this time, the powder spraying machine (7) located at the end face of the second flange (52) starts to spray powder; S5, after the powder spraying of the second flange (52) is completed, the moving device (2) drives the steel pipe (5) to move towards the heating box (41), the inner hole heating inductor (42) reaches the end face of the second flange (52), and the inner wall of the steel pipe (5) is heated, in the heating process, the moving device (2) continues to drive the steel pipe (5) to move away from the heating box (41), and at the same time, the nozzle (32) sprays the inside of the steel pipe (5); S6, when the inner hole heating inductor (42) reaches the end face of the first flange (51), the inner hole heating inductor (42) stops heating, and the nozzle (32) stops spraying powder; the end face heating inductor (61) located at the end face of the first flange (51) moves towards the steel pipe (5), and heats the end face of the first flange (51) after approaching the steel pipe (5); after heating is completed, the end face heating inductor (61) retreats; the end face powder spraying machine (7) located at the end face of the first flange (51) starts to spray powder; S7, after the powder spraying is completed, the supporting roller (132) stops rotating, and the pressing roller (15) retreats and leaves the steel pipe (5).

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