Abstract: A thin wall mild carbon steel pipe for pumping concrete has a wall which has an internal diameter of five inches and a wall thickness in the range of 0.170 to 0.200. The composition of the pipe wall by weight is in percentages ranges of 0.27 to 0.34 carbon, 0.30 to 0.60 manganese, less than 0.30 silicon with only traces of phosphorus and sulfur. The pipe has an inner hardened wall portion of RC reading of about 60 and of a thickness in the range of 0.04 to 0.06 inches and a gradual transition in hardness therefrom to an outer ductile wall reading of about 30 RC. The unhardened mild carbon steel pipe is processed by progressively and successively heating axially annular portions of the pipe to a hardening temperature of 1650.degree. F. A quenching brine solution at a temperature below 50.degree. F. is immediately sprayed at a high velocity onto the progressively heated surface to reduce the temperature of the inner wall essentially instantaneously to the temperature of the brine solution.