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 production processes.
The welded square tube is further divided into
1. Classified by process - electric arc welding square tube, resistance welding square tube (high frequency, low frequency), gas welding square tube, furnace welding square tube
2. Divided by weld seam - straight seam welded square pipe, spiral welded square pipe.