Since the mid-1950’s, a number of failures and leaks in cathodically protected line pipe have initiated in localized hard spots in the pipe wall formed by inadvertent quenching of localized areas of the pipe skelp on the runout table immediately after the final hot-rolling pass in the steel mill. Analysis of these failures indicated that cracks ultimately resulting in the ruptures or leaks, had initiated by hydrogen stress cracking (HSC).
During 1969, preliminary studies were conducted to determine (1) the feasibility of using localized tempering treatments to soften hard spots in line ...
During 1969, preliminary studies were conducted to determine (1) the feasibility of using localized tempering treatments to soften hard spots in line pipe to a level at which they would be insensitive to HSC under normal gas- transmission-pipeline operating conditions and (2) the influence of such treatments on the mechanical properties of the cold- expanded pipe steel. These studies indicated that tempering for 30 minutes at temperatures up to 1000 F did not reduce the yield strength of the X-52 base steel below those of untempered pipe. This effort evaluates tempering temperatures on the mechanical properties of X-52, X-60, and X-65 pipe.