Hollow section is cold formed and shaped at ambient temperature from steel strip or steel coil, both edges of which are continuously welded by electric resistance process. According to the shape, the hollow section can be divided into circular, square and rectangular. The general applications of hollow section are for building, structural, columns, beams, fence, construction machinery, agricultural equipment, machinery frames, furniture parts, rack, pallet, water line pipe, torque tube and fire protection pipes, etc.
The specification of circular hollow section (CHS) is out diameter from 21.3mm to 609.mm The specification of square hollow section (SHS) is from 20X20mm to 800X800mm and for rectangular hollow section (RHS) is always from 20X40mm to 600x800mm. The wall thickness of hollow section is decided by the steel strip or steel coil, mainly from 0.5mm to 20mm. The unit length can be cut into single random length, double random length and fixed length between 5.8 to12.2 meters. For the packaging issue, it can be packed in loose or in bundle in hexagonal with or without plastic wrap with two nylon rope at the two ends. Normal corrosion methods are light oiled coated and black lacquer painted on the pipe external body.
Besides hollow section can be also pre-galvanized steel pipe and hot dipped galvanized steel pipe. Pre-galvanized hollow section pipes are produced directly by galvanized steel coil and thickness of the zinc is 30 GSM to 120 GSM. Hot dipped galvanized hollow section pipes are bare pipes dipped with zinc and its zinc thickness can reach 200 GSM to 500 GSM. And hot dipped galvanized steel pipe are also with plain ends, bevelled ends, grooved ends, NPT or BSP thread ends with or without hot dipped galvanized coupling.
Main executive standards of hollow section are ASTM A500, ASTM A53, ASTM A795, BS 1387, ISO 65, AS 1163, EN 10219, EN10217, JIS G 3444, JIS G3452, JIS G3466, GB/T 6728, etc.