... 4 GB,JIS,ISO,ASTM,BS,DIN the black carbon steel pipe is widely use in conveyor belt transmission,machine rotary ... trip. you know the rectangular steel pipe is world wide use in construction,goods shelf,steel sheds,truck manufactruing,road construction,fence ... trip. you know the rectangular steel pipe is world wide use in construction,goods shelf,steel sheds,truck manufactruing,road construction,fence ...