The recent progress in steel plates for low temperature storage tank such as LNG, LPG ones are described in this paper.
First, general safety criteria for storage tankage is introduced with the rational basis from the point of fracture mechanics consideration. Then, actual properties of the steels and their weldments for these storage tanks, that is, 9% Ni steel for LNG storage tank and Low temperature AI killed or low Ni type steels for LPG one. Attention is focused in low temperature toughness both in base metal and their welds, and metallurgical and also fracture mechanics background for attaining required toughness or degree of fracture safety level is especially high-lighted. Finally, the safety level of each steels are categorized according to the fracture safety criteria.