Steel pipes have a hollow cross-section, and their length is much greater than that of steel with a diameter or circumference. Divided into circular, square, rectangular, and irregular steel pipes according to their cross-sectional shapes; Divided by material into carbon structural steel pipes, low alloy structural steel pipes, alloy steel pipes, and composite steel pipes; Classified by purpose, it is used for conveying pipelines, engineering structures, thermal equipment, petrochemical industry, mechanical manufacturing, geological drilling, and steel pipes for high-pressure equipment; According to production processes, seamless steel pipes are divided into seamless steel pipes and welded steel pipes. Seamless steel pipes are further divided into hot-rolled and cold-rolled (drawn) types, and welded steel pipes are further divided into straight seam welded steel pipes and spiral seam welded steel pipes.
Steel pipes are not only used for conveying fluids and powdered solids, exchanging heat energy, manufacturing mechanical parts and containers, but they are also an economical type of steel. Using steel pipes to manufacture building structural grids, pillars, and mechanical supports can reduce weight, save metal by 20-40%, and achieve factory mechanized construction. Using steel pipes to manufacture highway bridges not only saves steel and simplifies construction, but also greatly reduces the area of protective coatings, saving investment and maintenance costs.