ERW steel pipe, or Electric Resistance Welded Steel Pipe, utilizes the skin effect and proximity effect of high-frequency current to heat and fuse the edges of hot-rolled coils formed by a shaping machine. Subsequently, pressure is applied through welding with pressing and extrusion rollers to achieve production. ERW exhibits characteristics such as high efficiency, cost-effectiveness, material conservation, and easy automation, making it extensively employed in industrial sectors like aviation, aerospace, energy, electronics, automobiles, and light industry. It holds a crucial role in the welding process.
Electric resistance welded steel pipes come in two forms: AC welded steel pipes and DC welded steel pipes. AC welding is further categorized into low frequency welding, medium frequency welding, super medium frequency welding, and high-frequency welding based on frequency. High-frequency welding is predominantly used for producing thin-walled or standard-walled steel pipes, with subdivisions such as contact welding and induction welding. DC welding is generally applied to small-diameter steel pipes.
In summary, high-frequency welded pipes are a subset of ERW welded pipes, produced through the high-frequency welding process. ERW straight seam welded pipes demonstrate advanced product performance, superior quality, and relatively economical features, particularly in the realm of oil and gas storage and transportation.
Definition Of SAW Steel Pipe:
SAW steel pipe, or Submerged Arc Welding Steel Pipe, encompasses two main types: Longitudinal Submerged Arc Welding Steel Pipe (LSAW steel pipe) and Spiral Submerged Arc Welding Steel Pipe (SSAW steel pipe). The SAW manufacturing process involves submerged arc welding of steel, creating high current density that prevents rapid heat loss from the flux layer, concentrating it in the welding region. The commonly used standard for SAW pipes is API 5L. SAW pipes are known for their high-quality welds, high production efficiency, and are widely applied in pressure vessels, pipe manufacturing, beams, low-pressure fluid systems, and steelworks.
Comparison Between ERW Steel Pipe And SAW Steel Pipe:
Manufacturing Method:
ERW Steel Pipe: Uses two copper electrodes to apply pressure and current during welding. The electrodes rotate as the material passes between them, allowing for continuous long welds.
SAW Steel Pipe: Utilizes submerged arc welding, with a welding arc submerged in flux. Continuous solid filler wire is input, and the pipe is double-welded, first from the inside and then from the outside.
Surface Quality:
ERW pipes have a flat, smooth welding seam, superior to the weld reinforcement found internally and externally in most SAW pipes (LSAW, SSAW).
Weld Defects:
ERW pipes exhibit fewer weld defects compared to SAW pipes due to the solvent deposited in SAW, resulting in more defects.
Residual Stress Ratio:
The residual stress ratio in ERW is lower than in SAW steel pipes. ERW pipes undergo more comprehensive deformation, resulting in smaller residual stress.
Overall Performance And Durability:
ERW pipes have similar overall performance to SAW pipes, but in case of defects, ERW pipes can be welded and repaired, ensuring greater durability compared to SAW pipes, which may crack or corrode.
SAW Welded Steel Pipe Manufacturing Process:
Single-Seam SAW: Involves submerged arc welding with a welding arc submerged in flux. Continuous solid filler wire is added from the outside. The pipe is double-welded, first from the inside and then from the outside.
Double Seam SAW: The first two halves are connected by tack welding (fit-up), creating two opposite weld seams welded from inside and outside.
Spiral SAW: The steel plate forms a spiral loop and is welded from inside and outside, allowing for a wide range of diameters. SSAW steel pipes are used for low-pressure services, while LSAW steel pipes are used for medium to high-pressure services, with SSAW being less costly than LSAW.
