Rectangular tube is a hollow square section of light thin-walled steel pipe, also known as steel refrigeration bending profile. It is Q235 hot-rolled or cold-rolled strip or coil for the base material by cold bending processing and then by high-frequency welding made of square cross-sectional shape size of the section of steel. Hot-rolled extra-thick wall square tube in addition to wall thickness thickening outside the case, the corner size and side straightness are up to or even exceed the level of resistance welding cold forming square tube.It is Q235 hot-rolled or cold-rolled strip or coil for the base material by cold bending process forming and then by high-frequency welding made of square cross-sectional shape size of the steel. Hot rolled extra thick wall square tube in addition to wall thickness thickening outside the case, its corner size and side straightness are reached or even exceeded the level of resistance welding cold forming square tube.Rectangular tube classification: steel pipe is divided into seamless steel pipe and welded steel pipe (seam pipe) hot rolled seamless square tube, cold drawn seamless square tube, extruded seamless square tube, welded square tube.