A Study of Stress Corrosion Phenomena Resulting from Transportation of Anhydrous Ammonia in Quenched-and-Tempered Steel Cargo Tanks.

摘要

The primary causative agent of stress-corrosion cracking (SCC) of quenched-and-tempered steels exposed to liquid ammonia is oxygen contamination. Under certain conditions carbon dioxide and water may also act as causative agents. Water in concentrations of 2000ppm or greater inhibits SCC. Methane and nitrogen also exhibit inhibitory effects. As produced liquid ammonia contains sufficient oxygen to cause cracking in many cases. The slow-strain-rate method is an accelerated test which produces stress-corrosion fractures with characteristics identical to those of service failures. A statistically determined discriminant function, D sub P,may be used to predict the SCC behavior of production ammonias. Another discriminant function, D sub L,is more applicable for high-purity,methane-and water-free ammonias.