The advantages of thick-walled straight seam steel pipes lie in the fact that the online heat treatment process of the weld seam eliminates welding stress, refines the microstructure grains in the heat-affected zone, and improves physical and mechanical properties. Developed Western countries emphasize the application of HFW/ERW welded steel pipes. For example, Greece and Japan respectively produce HFW ф610mm×25.4mmX60 and X65 grade welded steel pipes to replace seamless steel pipes and thick-walled straight seam steel pipes. There is a misconception in China that HFW/ERW welded steel pipes can be used for diameters below ф406mm, while thick-walled straight seam steel pipes must be used for diameters above ф406mm. This has led to the development of HFW/ERW units towards producing thick-walled straight seam steel pipe products.
The future structural adjustment direction for high-frequency straight seam steel pipes is to move towards high-grade, large-wall-thickness product series. The typical process is the “F.F.X forming + hot tension reduction + full-pipe heat treatment” model to meet the market demands of oil and gas pipelines, subsea pipelines, and oil well pipes. High-frequency straight seam steel pipe heat treatment can also be used to develop structural pipes, boiler tubes, and marine pipelines for thick-walled straight seam steel pipes. High-frequency straight seam steel pipe manufacturers should also pursue product diversification, producing precision pipes for automobiles, light industry, chemicals, textiles, food, medical applications, medium and low-pressure boilers, household appliances, construction, and containers.
First, the basic procedures for daily maintenance of thick-walled straight seam steel pipes using a cantilever crane.
1. When hoisting thick-walled straight seam steel pipes, the wire rope must not be pulled at an angle to prevent it from derailing.
2. During operation, pay attention to ensuring the safety of personnel and equipment.
3. Regularly check the switches at the front and rear of the trolley, and ensure the switches at the maximum lifting limit of the hook are functioning properly and sensitively.
4. Lubricate the gears, sprockets, chains, ropes, and other lubrication points of the thick-walled straight seam steel pipes on schedule.
5. Operators of the cantilever crane must closely coordinate with the hoisting personnel and follow the hoisting instructions.
6. The hook must be fully loaded with the coil.
7. The wire rope should be replaced when 10% of its strands are broken. 8. Regularly check whether the lifting hook and brake are functioning properly and sensitively.
Second, the production process of thick-walled straight seam steel pipes.
The production process of large-diameter thick-walled straight seam steel pipes is automatic submerged arc welding. The process steps are: 1. Pre-bending, 2. Pre-welding, 3. Internal and external welding, 4. Rounding and straightening, 5. End treatment. Large-diameter thick-walled straight seam steel pipes are becoming increasingly important in the steel pipe application industry. The main application areas for large-diameter thick-walled straight seam steel pipes include water conservancy projects, steel structures, power industry, chemical industry, urban planning and construction, irrigation, long-distance oil and gas pipelines, bridge piling, and submarine oil pipelines.
1. Flaw Inspection of Thick-Walled Straight Seam Steel Pipe Plates: Before the steel plates used to manufacture large-diameter thick-walled straight seam welded steel pipes are put into production, the first step is to conduct a preliminary inspection of the steel plates.
2. Steel Plate Milling: A milling machine developed and researched in-house is used to mill the steel plates, creating a V-shaped bevel.
3. JCOE Forming: An imported JCO forming machine is used to repeatedly and progressively press the steel plate to form a “J” shape. The other end of the steel plate is then formed into a “C” shape using the same process, ultimately creating an open “O” shape.
4. Opening Pre-Welding: The opened thick-walled, straight seam steel pipe blank undergoes pre-welding, using a shallow, layered welding method.
5. Pre-welding followed by internal welding: Foreign double-sided automatic submerged arc welding machines perform submerged arc automatic welding on the inner weld seam of the thick-walled straight seam steel pipe.
b. External welding: Double-sided automatic submerged arc welding machines perform submerged arc automatic welding on the outer weld seam of the thick-walled straight seam steel pipe.
6. Cold expansion (reduction) diameter: Precision expansion of the thick-walled straight seam steel pipe improves the dimensional accuracy and reduces internal stress.
7. Non-destructive testing (NDT) on the industrial television production line for thick-walled straight seam steel pipes: 100% rigorous inspection is performed on the inner and outer weld seams of the straight seam welded steel pipe and adjacent base material. Working speed: 2.5 meters/minute.
8. Product hydrostatic testing: Each steel pipe is inspected on a hydrostatic testing machine to ensure the test pressure.
9. End treatment: Qualified thick-walled straight seam steel pipes are processed to meet the required pipe end shape.
10. Steel pipe corrosion protection: Thick-walled straight seam steel pipes undergo anti-corrosion coating and related work according to the contract process.
Post time: Dec-12-2025