Steel pipe

Steel pipes are hollow‑section steel products whose length significantly exceeds their diameter or perimeter. Based on cross‑sectional shape, they are classified into round, square, rectangular, and special‑shaped pipes; based on material, into carbon structural steel pipes, low‑alloy structural steel pipes, alloy steel pipes, and composite steel pipes; and based on application, into pipes for conveying pipelines, engineering structures, thermal equipment, the petrochemical industry, mechanical manufacturing, geological drilling, high‑pressure equipment, and more. According to manufacturing process, they are divided into seamless steel pipes and welded steel pipes; seamless pipes further subdivide into hot‑rolled and cold‑rolled (drawn) types, while welded pipes are categorized into straight‑seam welded pipes and spiral‑seam welded pipes.
Steel pipes are not only used for conveying fluids and powdered solids, exchanging heat, and fabricating machine parts and pressure vessels; they also constitute an economical type of steel. Employing steel pipes to construct structural trusses, columns, and mechanical supports can reduce weight and save 20% to 40% of metal, while enabling factory‑based, mechanized construction. Moreover, using steel pipes in the construction of highway bridges not only conserves steel and simplifies installation but also significantly decreases the surface area requiring protective coatings, thereby lowering both capital and maintenance costs.