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,machine ... there and have a trip. you know the rectangular steel pipe is world wide use in construction,goods shelf ... at sightProductivity20000 ton per monthMOQ10 ton per size black carbon steel pipe