低炭素オーステナイト系ステンレス鋼の極低温での機械的性質に及ぼす時効の影響

抄録

Mechanical properties of SUS 304L and 316L aged at 700°C;×75hr were investigated at the temperatures below the ambient temperature, especially at 4K. Cr rich carbides, M₂₃C₆, precipitated at grain boundaries and Cr depleted zones were formed during aging though both steels had low content of carbon. 4K tensile properties, notch strength, Charpy absorbed energy and fracture toughness of aged steels were all inferior to those of solutioned ones. Tensile properties showed the smallest degradation while fracture toughness showed the largest. It is evident that the grain boundary precipitation results in degradation of 4K mechanical properties. The degree of degradation corresponds to an extent of tri-axiality of stress which constrained plastic deformation.