Steel pipes are steels with a hollow cross-section whose length is much greater than the diameter or circumference. According to the cross-sectional shape, it is divided into circular, square, rectangular and special-shaped steel pipes; according to the material, it is divided into carbon steel pipes, low-alloy structural steel pipes, alloy steel pipes and composite steel pipes; Steel pipes for thermal equipment, petrochemical industry, machinery manufacturing, geological drilling, high-pressure equipment, etc. http://www.tszxsteel.com/steel-pipe/carbon-steel-pipe/