Spiral welded pipes are also a type of welded pipe equipment. Their strength is generally higher than that of straight seam welded pipes. They can use narrower billets to produce welded pipes with larger diameters, and can also use billets of the same width to produce welded pipes with different diameters. However, compared with straight seam pipes of the same length, the weld length increases by 30~100%, and the production speed is lower. Therefore, most smaller-diameter welded pipes use straight seam welding, while large-diameter welded pipes mostly use spiral welding.
First, the production process of spiral steel pipes: spiral seam steel pipes are made of strip steel coils as raw materials, extruded at room temperature, and welded by automatic double-wire double-sided submerged arc welding.
1. The raw materials are strip steel coils, welding wires, and fluxes. They must undergo strict physical and chemical inspections before being put into use.
2. The head and tail of the strip steel are butt-jointed, and single-wire or double-wire submerged arc welding is used. After the steel pipe is rolled into a steel pipe, automatic submerged arc welding is used for repair welding.
3. Before forming, the strip steel is leveled, trimmed, planed, surface cleaned, conveyed, and pre-bent.
4. The electric contact pressure gauge is used to control the pressure of the oil cylinder on both sides of the conveyor to ensure the smooth transportation of the strip.
5. External or internal control roller forming is adopted.
6. The weld gap control device is used to ensure that the weld gap meets the welding requirements. The pipe diameter, misalignment, and weld gap are strictly controlled.
7. Both internal and external welding are performed by single-wire or double-wire submerged arc welding with the American Lincoln electric welder to obtain stable welding specifications.
8. The welded welds are inspected by online continuous ultrasonic automatic flaw detectors to ensure 100% non-destructive testing coverage of spiral welds. If there are defects, the alarm will be automatically sounded and the mark will be sprayed. The production workers will adjust the process parameters at any time and eliminate the defects in time.
9. The steel pipe is cut into single pieces by an air plasma cutting machine.
10. After cutting into single steel pipes, the first three steel pipes of each batch shall be strictly inspected to check the mechanical properties, chemical composition, fusion status, surface quality of the steel pipes, and non-destructive testing of the welds. Only after ensuring that the pipe-making process is qualified can it be officially put into production.
11. The parts with continuous ultrasonic flaw detection marks on the welds shall be manually ultrasonically and X-rayed for review. If there are defects, they shall be repaired and then subjected to non-destructive testing again until it is confirmed that the defects have been eliminated.
12. The pipes where the strip butt welds and the T-joints intersect with the spiral welds are all inspected by X-ray television or film.
13. Each steel pipe is subjected to a hydrostatic pressure test, and the pressure is radially sealed. The test pressure and time are strictly controlled by the steel pipe water pressure microcomputer detection device. The test parameters are automatically printed and recorded.
14. The pipe ends are machined to accurately control the end face verticality, groove angle, and blunt edge.
Second, anti-corrosion spiral welded pipe technology: Since the individual mass of spiral welded pipes is relatively large, they must be stacked outdoors, but it is difficult to avoid being exposed to the sun and rain, so the problem of rust has always plagued the storage time and conditions of spiral welded pipes. Therefore, we must provide a comprehensive answer to the anti-rust knowledge of spiral welded pipes.
1. Mainly use tools such as wire brushes to grind the surface of steel. Cleaning and preheating spiral welded pipes can remove loose or raised oxide scales, rust, welding slag, etc. Manual tools can achieve Sa2-level rust removal, and power tools can achieve Sa3-level rust removal. If the steel surface is firmly attached to the oxide scale, the tool rust removal effect is not ideal, and the anchor pattern depth required for anti-corrosion construction cannot be achieved.
2. Pickling uses solvents and emulsions to clean the surface of welded steel pipes (welded pipes) for low-pressure fluid transportation to remove oil, grease, dust, lubricants, and similar organic matter, but it cannot remove rust, oxide scale, welding flux, etc. on the surface of steel, so it is only used as an auxiliary means in anti-corrosion production.
3. Generally, chemical and electrolytic methods are used for pickling. Pipeline anti-corrosion only uses chemical pickling, which can remove scale, rust, and old coatings. Sometimes it can be used as a re-treatment after sandblasting. Although chemical cleaning can achieve a certain degree of cleanliness and roughness on the surface, its anchor pattern is shallow and it is easy to pollute the stacking environment of spiral welded pipes.
4. When cleaning rusty pipe fittings with reasonable means, ensure that the pipe fittings serve production for a long time and create more production benefits.
Post time: Jan-14-2025