1 high tention and good quality 2 black carbon steel pipe manufacture 3 widely use in many ways ... 4 GB,JIS,ISO,ASTM,BS,DIN the black carbon steel pipe is widely use in conveyor belt transmission ... ,Q195L,Q235 Q460 Q345 and so on Surfacelightly oil , include black, bright and pre-galvanized End cleanThickness toleranceto your standard or ...