What are the main production processes for straight seam steel pipes?
The production processes for straight seam steel pipes include high-frequency resistance welding (ERW), submerged arc welding (SAW), laser welding, etc. The ERW process heats the edge through high-frequency current and pressurizes welding, which is efficient and low-cost; the SAW process is suitable for thick-walled pipes, and the weld quality is more stable; laser welding has high precision but expensive equipment. Different processes are selected according to pipe diameter, wall thickness and application scenarios. Cold forming and hot forming will also affect the final performance.
What is the difference between high-frequency resistance welding (ERW) and submerged arc welding (SAW)?
ERW instantly heats the edge of the steel pipe through high-frequency current, without welding wire, and is suitable for thin-walled pipes and small and medium diameters; SAW uses arc and flux to weld in layers, which is suitable for thick-walled and large-diameter pipes. ERW has high production efficiency, but the weld may have unfused defects; SAW welds have better toughness, but higher energy consumption. Both have their own focuses in the fields of oil pipelines and construction.
How to control precision during the forming process of straight seam steel pipes?
The CNC roller adjustment unit is used to ensure uniform bending of the plate and strip, and the laser diameter gauge monitors the pipe diameter deviation in real time. The bevel angle of the edge needs to be controlled during the forming stage (usually 30°-35°), and the roundness is calibrated by the sizing machine after welding. The automated control system can reduce human errors, and the tolerance is usually controlled within ±0.5%.
What is the role of weld heat treatment?
Heat treatment (such as normalizing and tempering) can eliminate welding residual stress, refine the grain structure, and improve toughness and corrosion resistance. For example, API 5L standard requires normalizing for steel grades above X80. The heat treatment temperature needs to be precisely controlled at 30-50℃ above the Ac3 line to avoid overheating or underheating.
How to deal with internal and external burrs of straight seam steel pipes?
Remove external burrs with a scraper immediately after welding, and remove internal burrs with high-pressure gas or rotating tools. Burr residues can cause stress concentration or corrosion hazards, and require 100% inspection. Electrolytic polishing is used to further smooth the weld in some high-end applications.
