A hollow-section steel pipe whose length is much greater than its diameter or circumference. According to the cross-sectional shape, it can be divided into round, square, rectangular and special-shaped steel pipes; according to the material, it can be divided into carbon structural steel pipes, low-alloy structural steel pipes, alloy steel pipes, and composite steel pipes. According to the application, it is divided into steel pipes for pipelines, steel pipes for engineering structures, steel pipes for thermal equipment, steel pipes for petrochemical industries, steel pipes for machinery manufacturing, steel pipes for geological drilling and steel pipes for high-pressure equipment. According to the production process, it is divided into seamless steel pipes and welded steel pipes, of which seamless steel pipes are further divided into hot rolling and cold rolling (drawing), 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 also an economical steel. Using steel pipes to make building structural grids, columns and mechanical supports can reduce weight, save 20-40% of metal, and realize mechanized construction in factories. Using steel pipes to make highway bridges can not only save steel and simplify construction, but also greatly reduce the area of ​​protective coatings, saving investment and maintenance costs.

The production method of steel pipe:

Steel pipes are divided into seamless steel pipes and welded steel pipes. The production process of seamless steel pipe is to thread a solid billet or ingot into a hollow capillary tube and then roll it into a steel pipe of the desired size. Different piercing and rolling methods constitute different methods of producing seamless steel pipes. The production process of welded steel pipe is to bend the tube blank (steel plate or strip) into a tubular shape, and then weld the gap into a steel pipe. Different methods of forming and welding are used to constitute different methods of producing welded steel pipes.

Seamless steel pipes are mainly produced by hot rolling. The extrusion method is mainly used to produce low plasticity high alloy steel pipes or special-shaped steel pipes and composite metal pipes that are difficult to perforate. Heat pipes can be continuously processed into small diameter thin-walled steel pipes by cold rolling and cold drawing. The steel pipe welding process is simple, the production efficiency is high, the cost is low, and the product variety is expanding.