... .Manufacturer in Tianjin q235 2.5 inch SCH40 Black Carbon Steel Circular Hollow Section Pipe 1)Standard: ASTM A53 ... both standard and non-standard steel hollow box, including square steel pipe and rectangular steel pipes , which can be black steel pipe or galvanized steel pipes. ... Longitude Welding pipes(ERW) ,SSAW ,seamless steel pipes,steel strips,H&I Steel and pipe fittings,on which we have stable ...