... , JIS, etcGradeMild Steel: Q195, Q215, Q235, SS400,20#, 45#, etcLow Alloy: Q345, 16Mn, Q390, ST52-3, etcSide Length12-110mmWall Thickness0.8 ... sqaure tubeBy Processarc welding sqaure tubeERW sqaure tube(high-frequency, low frequency) gas welding sqaure tubefurnace welded square tubeBy Weld straight ...