Stålrør

Stålrør, or steel pipes, are cylindrical hollow sections produced from steel for conveying fluids or gases and for use as structural elements. They come in two broad forms: seamless pipes, produced by piercing and elongating a solid billet, and welded pipes, formed by rolling a plate or coil and welding the seam. Welded pipes can be further categorized as electric resistance welded (ERW), submerged arc welded (SAW), or longitudinally (LSAW) or helically welded (SSAW) depending on the seam orientation and welding method. Stålrør cover a range of materials, from carbon and low-alloy steels to stainless steels and specialty alloys, with the choice depending on strength, temperature, corrosion resistance, and service conditions. Some pipes are lined or coated internally or externally to improve durability and reduce friction.

Production and finishing: Manufacturing involves forming, welding or piercing, sizing, heat treatment, and surface finishing. Internal and external coatings, such as epoxy or polyethylene, may be applied for corrosion protection or flow optimization. Tolerances and surface quality are controlled by international standards, and pipes are tested by hydrostatic pressure and nondestructive methods before certification.

Applications: Stålrør are central to oil and gas transmission pipelines, water and wastewater distribution, chemical processing, and various industrial and construction projects. They also serve as structural members in buildings, bridges, and mechanical systems, where diameters and wall thicknesses are chosen to meet load and safety requirements.

Standards and terminology: Steel pipes are produced to international standards issued by organizations such as ASTM, API, and EN. Common examples include ASTM A53 and A106 for carbon steel pipes, API 5L for line pipe, and EN 10217-1 for welded steel tubes. The exact specification depends on intended use, diameter, wall thickness, and material.