As the name suggests, square pipe is a kind of square pipe type. Many materials can form square pipe body. It is used for what purpose and where. Most square pipes are steel pipes, which are unpacked, leveled, crimped and welded to form round pipes, which are rolled into square pipes, and then cut to the required length. Generally, there are 50 square tubes in each package. In terms of spot, most of them are in large specifications, ranging from 10 * 10 * 0.8-1.5 ~ ~ 500 * 500 * 10-25mm. Square tubes are divided into hot-rolled seamless square tubes, cold drawn seamless square tubes, extruded seamless square tubes and welded square tubes according to the production process. Square tubes are divided into ordinary carbon steel square tubes and low alloy square tubes according to material. The welded square tubes are divided into: (a) according to the process - arc welded square tubes, resistance welded square tubes (high frequency and low frequency), gas welded square tubes and furnace welded square tubes（ b) According to the weld - straight welded square pipe and spiral welded square pipe. Ordinary carbon steel is divided into: Q195, Q215, Q235, SS400, 20# steel, 45# steel, etc; Low alloy steels are divided into Q345, 16Mn, Q390, St52-3, etc. Square pipes are divided into hot-dip galvanized square pipes, electro galvanized square pipes, oiled square pipes and pickled square pipes according to surface treatment. Square tubes are classified according to section shape: (1) simple section square tubes -- square tubes and rectangular tubes（ 2) Square tubes with complex section -- flower shaped square tubes, open square tubes, corrugated square tubes and special-shaped square tubes. Square tubes are classified according to wall thickness - super thick wall square tubes, thick wall square tubes and thin wall square tubes. Square tubes are divided into national standard square tubes, Japanese standard square tubes, British standard square tubes, American standard square tubes, European standard square tubes and non-standard square tubes according to production standards. Square pipes are divided into hot-dip galvanized square pipes, electro galvanized square pipes, oiled square pipes, pickled square pipes, etc. according to surface treatment. Square tube is a kind of light thin-walled steel tube with hollow square section, also known as steel cold-formed profile. It is a section steel with square section shape and size, which is made of Q235 hot-rolled or cold-rolled strip or coil as the base material, cold bending and high-frequency welding. In addition to wall thickness thickening, the corner size and edge flatness of hot-rolled extra thick wall square pipe reach or even exceed the level of resistance welding cold formed square pipe. Good comprehensive mechanical properties, weldability, cold and hot workability and corrosion resistance, and good low temperature toughness. The purpose of square tube includes construction, machinery manufacturing, steel construction and other projects, shipbuilding, solar power generation support, steel structure engineering, electric power engineering, power plant, agricultural and chemical machinery, glass curtain wall, automobile chassis, airport, boiler construction, highway railing, house construction, pressure vessel, oil storage tank, bridge, power plant equipment, Hoisting and transportation machinery and other welded structural parts with high load.