Increasing the Cryogenic Toughness of Steels

Grain-refining heat treatments increase toughness without substantial strength loss. Five alloys selected for study, all at or near technological limit. Results showed clearly grain sizes of these alloys refined by such heat treatments and grain refinement results in large improvement in toughness without substantial loss in strength. Best improvements seen in HP-9-4-20 Steel, at low-strength end of technological limit, and in Maraging 200, at high-strength end. These alloys, in grain refined condition, considered for model applications in high-Reynolds-number cryogenic wind tunnels.