The square pipe is a hollow square section light thin-walled steel pipe. It is a section steel with a square cross-section shape and size made of Q235 hot-rolled or cold-rolled strip or coil as the base material, which is formed by cold bending and then welded by high-frequency welding. It has good comprehensive mechanical properties, weldability, cold and hot work ability and corrosion resistance, and has good low temperature toughness. Square pipe and rectangular pipe is equal and unequal length of the steel pipe. Is made of steel after the process of rolling. Generally the strip is unpacked, flattened, curled, welded to form a round pipe, and then rolled into a square pipe and then cut into the required length.