... 2. Advanced Roller Extrusion equipment line. 3.CE,ISO Hollow Square Steel Tube 1. STANDARD:GB/T3094-2000, GB/T6728-2002, ... steel.3. SURFACE:Bared, Galvanized, Oiled, Color Paint, 3PE; Or Other Anti-corrosive Treatment.4. TECHINQUE:Hot rolled, Cold rolled, ERW, High ... in this area.We engaged in research square and rectangular steel tube at the beginning of company established, now our technology ...