Square tube is a hollow square cross section light thin wall steel tube, also known as refrigeration bending steel profiles.Good comprehensive mechanical performance, weld ability, cold and hot working performance and corrosion resistance are good, good low temperature toughness.The purpose of the square tube construction, machinery manufacturing, steel construction projects, shipbuilding, solar power stents, steel structure engineering, power engineering, power plants, agricultural and chemical machinery, glass curtain wall, automobile chassis, airport, the boiler construction, highway railings, housing construction, pressure vessel, oil tank, bridge, power station equipment, lifting transportation machinery and other high load of welded structure, etc.