This part of ISO 21028 specifies the toughness requirements of metallic materials for use at temperatures between − 20 °C and − 80 °C to ensure their suitability for cryogenic vessels. It is applicable to fine-grain and low-alloyed steels with specified yield strength = 460 N/mm2, aluminium and aluminium alloys, copper and copper alloys and austenitic stainless steels.