Hot Rolled Black Pipe is a tubular product intended primarily for such purposes as the conveying of water, fuel, gas, air, steam, etc. It has also been found to be a convenient form for use as structural members such as columns and railings.
As distinguished from tubing, pipe is commonly produced in greater quantities and in relatively few standard sizes. It is generally made to less exacting specifications for dimensions, finish, chemical composition, and mechanical properties than tubing.
Sizes and wall thicknesses of pipe were originally standardized to permit threading the end for joining lengths with couplings or other connectors. It is also connected without screw threads where lengths are joined together, or fittings attached, by welding or other means.