Material: Q195 - Q235 Sizes: 15x15mm to 400x400mm Thickness:0.8-25mm Steel Grade: 10#-45#, ST35-ST52, Q195-Q345 Welded square steel pipe:1)standard:ASTM-A53A,BS1387-85,GB/T3091-20012)material:Q195-Q2353)Dia:20*20-500*500mm4)length:as customers' requirement5)Application:construction structure,machinery,container,hall struction,offshore oil field,airport structure,shipbuilding,automotive parts and ...