Black pipe fitting

Black pipe is a common type of steel pipe.

Cold rolled steel, when heated to annealing temperature, turns black on the surface due to contact with air at high temperatures, and is referred to as black annealed steel. Its surface has not been brightened, hence the black color. The physical properties become softer, making it easier to weld and form into steel pipes. The common hardness is 57HRB, and it can be annealed to different hardness levels as required.