Pipe fitting bending machining process

Abstract

The invention discloses a pipe fitting bending machining process which comprises the following steps: S1, pretreatment and fixed-length cutting: a metal pipe is subjected to surface purification treatment, and the surface purification treatment at least comprises chemical degreasing and rust removal, so that a clean metal surface is obtained; precisely cutting the metal pipe according to a preset pipe bending length to form a straight pipe section; s2, outer surface cleaning and drying are conducted, specifically, a cleaning mechanism is adopted for cleaning the outer surface of the straight pipe section, the straight pipe section is horizontally conveyed in the radial direction of the straight pipe section, and in the process, the straight pipe section is driven to rotate around the axis of the straight pipe section in a contact mode; and S3, local preheating and bending are conducted, specifically, the straight pipe sections meeting the standard are subjected to local induction heating in the preset bending area, and the straight pipe sections are fed into a pipe bending machine in the hot state to be bent and formed.

Description

Technical Field

[0001] This invention relates to the field of pipe fitting processing technology, and more specifically, to a pipe bending processing technology. Background Technology

[0002] In the field of pipe fittings processing, pipe bends are key components in pipeline systems that change the flow direction, and their quality directly affects the safety, sealing, and service life of the entire system. Traditional pipe bending processes typically include basic steps such as material preparation, bending, and straightening. In actual processing, the pipe surface often has oil, oxides, or rust. If cleaning is not thorough, defects can easily occur during subsequent bending or coating processes, affecting the forming quality and coating adhesion. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a pipe bending process.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] This invention discloses a pipe bending process, comprising the following steps:

[0006] S1. Pre-treatment and fixed-length cutting: The metal pipe is surface-cleaned, including at least chemical degreasing and rust removal, to obtain a clean metal surface; the metal pipe is precisely cut according to the preset bending length to form straight pipe sections.

[0007] S2. External Surface Cleaning and Drying: A cleaning mechanism is used to clean the external surface of the straight pipe section. The straight pipe section is transported horizontally along its radial direction and driven to rotate around its own axis through contact. Simultaneously, the nozzles of the cleaning mechanism move synchronously with the straight pipe section and perform at least two stages of fluid spraying treatment on the outer surface of the rotating straight pipe section. The first stage uses cleaning fluid to remove microscopic oil and impurities, and the second stage uses clean water to rinse away residual cleaning fluid. After cleaning, the straight pipe section is subjected to hot air drying treatment, and its surface cleanliness and dryness are monitored online to ensure that the straight pipe section meets the standards for entering the bending process.

[0008] S3. Local preheating and bending: For straight pipe sections that meet the standards, local induction heating is performed in the predetermined bending area; then, while heated, the pipe is immediately fed into a pipe bending machine for bending and forming to produce a bent pipe blank.

[0009] S4. Stabilization treatment: Low-temperature stress-relieving annealing is performed on the bent tube blank after bending to eliminate or significantly reduce the residual stress introduced by the bending process and stabilize its geometry and metal microstructure.

[0010] S5. Finishing and Inspection: Heat-treated bends undergo internal and external surface treatment. The external surface is shot-blasted or sandblasted to enhance cleanliness and coating adhesion. The internal surface is flushed with high-pressure fluid. The bends that have undergone internal and external surface treatment are inspected for quality, and defective products are rejected.

[0011] Furthermore, in step S1, the chemical degreasing uses an alkaline degreasing agent, and the rust removal uses an acidic cleaning agent or an environmentally friendly neutral rust remover. After rust removal, water washing and passivation treatment are performed to form a temporary protective film on the pipe surface.

[0012] Furthermore, in step S2, the fluid sprayed from the nozzles of the cleaning mechanism is distributed in a fan shape, with 10%-20% overlap between the spray areas of adjacent nozzles. The spray direction is set along the axial direction of the straight pipe section, that is, the fan-shaped surface is perpendicular to the axial direction of the straight pipe section. The synchronous moving speed deviation between the nozzles and the conveyor belt does not exceed ±0.05m / min, ensuring that the fluid continuously covers the outer surface of the rotating straight pipe section, eliminating any cleaning dead corners.

[0013] Furthermore, in the hot air drying process in step S2, the hot air temperature is controlled between 60°C and 120°C, and the drying time is between 2 and 8 minutes, to ensure that the inner and outer surfaces of the pipe are fully dried and no significant temperature rise stress is generated.

[0014] Furthermore, the low-temperature stress-relief annealing treatment in step S4 is carried out in a controlled atmosphere furnace or a vacuum furnace, with an annealing temperature of 300℃-450℃ and a holding time of 45-120 minutes, followed by slow cooling to below 150℃ at a rate of no more than 50℃ / hour before being removed from the furnace.

[0015] Furthermore, when performing shot blasting on the outer surface of the bent pipe, stainless steel shot or cast steel grit is used as the abrasive. After shot blasting, the surface cleanliness reaches Sa2.5 or above, and the surface roughness Ra value is 6.3μm-12.5μm.

[0016] Furthermore, quality inspection includes dimensional accuracy verification, measurement of wall thickness reduction rate in curved areas, endoscopic internal visualization inspection, and pressure testing.

[0017] Furthermore, it also includes step S6, anti-corrosion coating: electrostatic spraying of epoxy resin, polyethylene or fluorocarbon coating on the qualified bend, followed by heating and curing in a curing oven to form a continuous and dense anti-corrosion coating.

[0018] Furthermore, before electrostatic spraying, the outer surface of the bent pipe is pretreated with phosphating or silanizing to further enhance the adhesion between the coating and the metal substrate.

[0019] The beneficial effects of this invention are: the cleaning method of synchronous movement of rotary conveyor and nozzle achieves full coverage cleaning of the outer surface of the pipe fittings; the two-stage spraying effectively removes impurities from the surface of the pipe fittings and avoids cleaning fluid residue, thus preparing for subsequent processing. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of one structure of the cleaning mechanism in this embodiment;

[0021] Figure 2 for Figure 1 Enlarged view of point A in the middle;

[0022] Figure 3 This is a top view of the conveyor belt in this embodiment;

[0023] Figure 4 This is a bottom view of the conveyor belt in this embodiment.

[0024] Reference numerals: 1. Cleaning tank; 2. Conveyor belt; 3. Support base; 4. Connecting rod; 5. Support wheel; 6. Pressure plate; 7. Inlet surface; 8. Trigger 1; 9. Screw motor; 10. Screw; 11. Screw slider; 12. Discharge tank; 13. Nozzle; 14. Storage tank 1; 15. Storage tank 2; 16. Three-way valve; 17. Supply tank; 18. Supply pump; 19. Cable chain; 20. Trigger 2; 21. Connecting block; 22. Fixing rod; 23. Support ball bearing; 24. Limiting block; 25. Inlet tank; 26. Guide block; 27. Guide rod. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] A pipe bending process includes the following steps:

[0027] Step S1, Pre-treatment and Fixed-Length Cutting: Apply a 5%-10% alkaline degreaser to the metal pipe and chemically degrease it for 10-15 minutes at 50℃-60℃. Then treat it with a 10%-15% acidic cleaner or environmentally friendly neutral rust remover for 5-8 minutes. After rust removal, wash with water and passivate. Cut the metal pipe precisely according to the preset bending length, with the cutting tolerance controlled within ±0.1mm, to form straight pipe sections.

[0028] Step S2, External Surface Cleaning and Drying: The straight pipe section is cleaned using a cleaning mechanism. The straight pipe section is conveyed horizontally along its radial direction at a speed of 0.2-0.5 m / min. Under the action of the support base and pressure plate, the straight pipe section rotates around its own axis at a speed of 2-5 r / min. The outer surface of the rotating straight pipe section is sprayed with a nozzle spray pressure of 0.2-0.5 MPa. The spray fluid is distributed in a 60°-90° fan shape, with 10%-20% overlap between the spray areas of adjacent nozzles. In the first stage, cleaning fluid is sprayed for 3-5 minutes to remove microscopic oil and impurities. In the second stage, clean water is sprayed for 2-3 minutes to remove residual cleaning fluid. After cleaning, the pipe section is dried with hot air at 60℃-120℃ for 2-8 minutes to ensure that the residual oil on the surface of the straight pipe section is ≤5 mg / m² and free of visible impurities, meeting the requirements of the bending process.

[0029] Step S3, Local Preheating and Bending: Local induction heating is applied to the predetermined bending area of ​​the straight pipe section at a heating rate of 10-30℃ / s, raising the material temperature to 60%-85% of its recrystallization temperature and maintaining it within this temperature range for 1-3 minutes. The pipe is then fed into a pipe bending machine and bent according to preset parameters such as the radius of curvature and bending angle to produce a bent pipe blank.

[0030] Step S4, Stabilization Treatment: The bent tube blank is subjected to low-temperature stress-relieving annealing in a controlled atmosphere furnace or vacuum furnace. The annealing temperature is 300℃-450℃, and the holding time is 45-120 minutes. Then, it is slowly cooled to below 150℃ at a rate of no more than 50℃ / hour before being taken out of the furnace. This process ensures that the residual stress inside the bent tube is eliminated by ≥80%, stabilizing its geometry and metal microstructure.

[0031] Step S5, Finishing and Inspection: The outer surface of the heat-treated bend is shot-blasted with stainless steel shot or cast steel grit with a particle size of 0.2-1.0 mm at a pressure of 0.3-0.6 MPa. After shot blasting, the surface cleanliness reaches Sa2.5 or higher, and the surface roughness Ra value is 6.3μm-12.5μm. The inner surface is flushed with high-pressure fluid at 0.8-1.2 MPa.

[0032] A comprehensive quality inspection is conducted on the bent pipe, including dimensional accuracy verification, wall thickness reduction rate measurement in the bending area, endoscopic internal visualization inspection, and pressure testing, and defective products are rejected during the inspection.

[0033] Step S6, Anti-corrosion coating: After phosphating or silanizing pretreatment of the outer surface of the inspected and qualified bend, electrostatic spraying is performed using epoxy resin, polyethylene or fluorocarbon coating, with a coating thickness of 0.1-0.2mm, and curing is carried out at 120℃-180℃ for 20-40 minutes.

[0034] like Figures 1-4 As shown, the cleaning mechanism includes a cleaning tank 1 and a conveyor belt 2. The left and right ends of the cleaning tank 1 are respectively provided with a feed opening and a discharge opening. There are two conveyor belts 2, located on the front and rear sides of the cleaning tank 1 respectively. Part of the conveyor belt 2 is located inside the cleaning tank 1. The conveyor belt 2 passes through the feed opening and discharge opening of the cleaning tank 1. Several support wheels 5 are rotatably provided on the front and rear side walls of the cleaning tank 1. The support wheels 5 support the upper part of the conveyor belt 2.

[0035] Several sets of support members are installed on the conveyor belt 2. The support members are evenly distributed on the conveyor belt 2, and the distance between two sets of support members is the same. Each support member includes several support seats 3, and a connecting rod 4 connects two corresponding support seats 3. The connecting rod 4 is used to keep the position of the support seat 3 stable and prevent the support seat 3 from tilting during the conveying process, which would cause the straight pipe section to fall off the support seat 3.

[0036] The upper part of the support base 3 has an arc-shaped groove that matches the size of the straight pipe section. The two ends of the straight pipe section can be placed in the arc-shaped grooves of the front and rear support bases 3 respectively, and the straight pipe section can rotate within the arc-shaped grooves of the support base 3. Support balls 23 can be installed in the arc-shaped grooves to support the straight pipe section and reduce friction between the straight pipe section and the arc-shaped grooves of the support base 3.

[0037] A fixing rod 22 is connected to the outer side of the conveyor belt 2, and a connecting block 21 is connected to the outer side of the support base 3. The fixing rod 22 passes through the connecting block 21, and the connecting block 21 is fixedly connected to the fixing rod 22. When the conveyor belt 2 is horizontal, the bottom of the support base 3 can abut against the surface of the conveyor belt 2, thus keeping the support base 3 horizontal. When the conveyor belt 2 bends, the bottom of the support base 3 can separate from the surface of the conveyor belt 2, without affecting the bending of the conveyor belt 2.

[0038] A pressure plate 6 is installed on the front wall of the cleaning tank 1, with its length aligned with the conveying direction of the conveyor belt 2. A straight pipe section on the support 3 contacts the lower surface of the pressure plate 6. During the conveying process, the straight pipe section rotates due to friction with the pressure plate 6, allowing the liquid sprayed from the upper nozzle 13 to cover the entire outer circumference of the straight pipe section, thus cleaning the entire section.

[0039] An inlet surface 7 is provided on the lower left side of the pressure plate 6. The height of the left end of the inlet surface 7 is lower than that of the right end, which makes it easier for the straight pipe section to enter under the pressure plate 6.

[0040] A lead screw motor 9 is installed inside the cleaning tank 1. The lead screw motor 9 drives a lead screw 10, and a lead screw slider 11 is installed on the lead screw 10. A liquid outlet tank 12 is installed below the lead screw slider 11, and several rows of nozzles 13 are installed below the liquid outlet tank 12. The number of rows of nozzles 13 is the same as the number of support bases 3. The single row of nozzles 13 is arranged roughly along the axial direction of the straight pipe section, with two nozzles 13 staggered from each other. The liquid sprayed from the nozzles 13 is fan-shaped, which extends along the axial direction of the straight pipe section. The liquid sprayed from two adjacent nozzles 13 overlaps to ensure that the entire surface of the straight pipe section is covered.

[0041] The cleaning tank 1 is equipped with a liquid supply tank 17, and a liquid supply pump 18 is installed on the side of the liquid supply tank 17. An inlet tank 25 is installed on the top of the outlet tank 12, and a pipe connects the liquid supply pump 18 and the inlet tank 25. A cable chain 19 is also included, positioned between the liquid supply pump 18 and the inlet tank 25, with the pipe housed within the cable chain 19. The cable chain 19 protects the pipe from damage due to bending.

[0042] Several triggers 8 are installed on the rear wall of the cleaning tank 1. The spacing between the triggers 8 is the same as the spacing between the connecting rods 4. The triggers 8 are connected to the lead screw motor 9 and the liquid supply pump 18. The initial position of the outlet tank 12 is set so that the position of the nozzle 13 corresponds to the position of the first three triggers 8. When the number of triggers 8 is triggered is the same as the number of support seats 3 in the support, it indicates that the straight pipe section on the support has reached below the pressure plate 6, and the cleaning operation begins. The lead screw motor 9 drives the outlet tank 12 to move with the conveyor belt 2 at the same speed as the conveyor belt 2, so that the nozzle 13 is positioned above the straight pipe section. At the same time, the liquid supply pump 18 is started, pumping liquid into the outlet tank 12, so that the liquid is sprayed out from the nozzle 13 and sprayed onto the straight pipe section at the lower angle.

[0043] When the trigger number 8 below the pressure plate 6 is less than the number of support seats 3 in the support components, it indicates that one of the straight pipe sections has left below the pressure plate 6, and the cleaning operation ends. The liquid supply pump 18 stops, and at the same time, the lead screw motor 9 drives the liquid outlet tank 12 to move in the opposite direction to the movement direction of the conveyor belt 2 to reset. The reset of the liquid outlet tank 12 must occur before the next set of support components enters below the pressure plate 6 to ensure that the next cleaning operation can proceed normally.

[0044] The upper part of the cleaning tank 1 is also equipped with a first liquid storage tank 14 and a second liquid storage tank 15. The supply tank 17 is connected to the first liquid storage tank 14 and the second liquid storage tank 15 via a three-way valve 16. A second trigger 20 is installed on the side wall of the cleaning tank 1, located on the movement path of the lead screw slider 11, and approximately in the middle of the movement path. The second trigger 20 is signal-connected to the three-way valve 16. The first liquid storage tank 14 and the second liquid storage tank 15 can store cleaning fluid and clean water, respectively. When the outlet tank 12 moves, causing the lead screw slider 11 to trigger the second trigger 20, the three-way valve 16 changes its connection state, switching the connection between the first liquid storage tank 14 and the supply tank 17 to the connection between the second liquid storage tank 15 and the supply tank 17, changing the supply from cleaning fluid to clean water.

[0045] A guide rod 27 is installed on the side wall of the cleaning tank 1 opposite to the side wall where the lead screw motor 9 is installed. A guide block 26 is installed on the liquid outlet tank 12, and the guide block 26 is fitted onto the guide rod 27. The guide block 26 can slide along the guide rod 27, thereby supporting and guiding the liquid outlet tank 12 and ensuring the smooth movement of the liquid outlet tank 12.

[0046] Two limiting blocks 24 are also installed on the side wall of the cleaning tank 1. The two limiting blocks 24 can limit the movement of the liquid outlet tank 12 to prevent the liquid outlet tank 12 from exceeding the maximum movement position.

[0047] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A pipe bending process, characterized in that, S1. Pre-treatment and fixed-length cutting: The metal pipe is surface-cleaned, including at least chemical degreasing and rust removal, to obtain a clean metal surface; the metal pipe is precisely cut according to the preset bending length to form straight pipe sections. S2. External Surface Cleaning and Drying: A cleaning mechanism is used to clean the external surface of the straight pipe section. The straight pipe section is transported horizontally along its radial direction and driven to rotate around its own axis through contact. Simultaneously, the nozzles of the cleaning mechanism move synchronously with the straight pipe section and perform at least two stages of fluid spraying treatment on the outer surface of the rotating straight pipe section. The first stage uses cleaning fluid to remove microscopic oil and impurities, and the second stage uses clean water to rinse away residual cleaning fluid. After cleaning, the straight pipe section is subjected to hot air drying treatment, and its surface cleanliness and dryness are monitored online to ensure that the straight pipe section meets the standards for entering the bending process. S3. Local preheating and bending: For straight pipe sections that meet the standards, local induction heating is performed in the predetermined bending area; then, while heated, the pipe is immediately fed into a pipe bending machine for bending and forming to produce a bent pipe blank. S4. Stabilization treatment: Low-temperature stress-relieving annealing is performed on the bent tube blank after bending to eliminate or significantly reduce the residual stress introduced by the bending process and stabilize its geometry and metal microstructure. S5. Finishing and Inspection: Heat-treated bends are treated with internal and external surfaces. The external surface is shot-blasted or sandblasted to enhance cleanliness and coating adhesion. The internal surface is flushed with high-pressure fluid. The bent pipes that have undergone internal and external surface treatment are subjected to quality inspection, and unqualified products are rejected.

2. The pipe bending process according to claim 1, characterized in that, In step S1, chemical degreasing uses an alkaline degreasing agent, and rust removal uses an acidic cleaning agent or an environmentally friendly neutral rust remover. After rust removal, water washing and passivation treatment are performed.

3. The pipe bending process according to claim 1, characterized in that, In step S2, the fluid sprayed from the nozzles of the cleaning mechanism is distributed in a fan shape, with 10%-20% overlap between the spray areas of adjacent nozzles, and the synchronous moving speed deviation between the nozzles and the conveyor belt does not exceed ±0.05m / min.

4. The pipe bending process according to claim 3, characterized in that, In step S2, the hot air drying process involves controlling the hot air temperature between 60°C and 120°C and the drying time between 2 and 8 minutes to ensure that the inner and outer surfaces of the pipe are fully dried without generating significant temperature rise stress.

5. The pipe bending process according to claim 1, characterized in that, The low-temperature stress-relief annealing in step S4 is carried out in a controlled atmosphere furnace or a vacuum furnace. The annealing temperature is 300℃-450℃, the holding time is 45-120 minutes, and then it is slowly cooled to below 150℃ at a rate of no more than 50℃ / hour before being taken out of the furnace.

6. The pipe bending process according to claim 1, characterized in that, In step S5, when the outer surface of the bent pipe is shot blasted, the abrasive used is stainless steel shot or cast steel sand. After shot blasting, the surface cleanliness reaches Sa2.5 or above, and the surface roughness Ra value is 6.3μm-12.5μm.

7. The pipe bending process according to claim 1, characterized in that, Quality inspection includes dimensional accuracy verification, measurement of wall thickness reduction rate in curved areas, endoscopic internal visualization inspection, and pressure testing.

8. The pipe bending process according to claim 1, characterized in that, It also includes step S6, anti-corrosion coating: electrostatic spraying of epoxy resin, polyethylene or fluorocarbon coating on the qualified bend, followed by heating and curing in a curing oven to form an anti-corrosion coating.

9. The pipe bending process according to claim 8, characterized in that, Before electrostatic spraying, the outer surface of the bent pipe is pretreated with phosphating or silanization.

Images