Classification of rectangular pipes: steel pipes are divided into seamless steel pipes and welded steel pipes (seamed pipes), hot-rolled seamless square pipes, cold-drawn seamless square pipes, extruded seamless square pipes, and welded square pipes.
The welded square tube is divided into:
1. According to the process - arc welded square tube, resistance welded square tube (high frequency, low frequency), gas welded square tube, furnace welded square tube;
2. According to the welding seam - straight seam welded square tube, spiral welded square tube.
