2024 Volume 73 Issue 3 Pages 57-60
To grasp the long-term liquid ammonia SCC（Stress Corrosion Cracking）-resistance of surface softened clad steel plates applied to liquid ammonia tanks, the results of open inspections of two tanks were analyzed, and it turned out that: （1） Of the two TS610 MPa grade surface softened clad steel plates tanks that have been in use for 29 years, one tank has had no cracks, and the other tank had a cumulative total of six crack incidents. This number of crack incidents is remarkably smaller than the conventional TS610 MPa grade steel plates tank, and the long-term liquid ammonia SCC-resistance of surface softened clad steel plates was confirmed. （2） The cracks that occurred in the surface softened clad steel plates tanks were limited to the welded parts, and this phenomenon was the same as that of TS440 MPa SLA325A （JIS G 3126: Carbon steel plates for pressure vessels for low temperature service）, which has track records of application and operation to liquid ammonia tanks.
