... 3.Wall Thickness:0.8-9mm 4.Length:5.8-12m Basic Information:Square tube is the tube that have equal side length. The steel ... strip welded round tube and then rolled into the square tube. ... StandedAISI, ASTM, BS, DIN, GB, JIS, etcGradeMild Steel: Q195, Q215, Q235, SS400,20#, 45#, etcLow Alloy: Q345, 16Mn, Q390, ST52-3 ...