Effects of Cold-rolling and Ni-equivalent on Mechanical Properties of Austenitic Stainless Steels at Cryogenic Temperatures

Abstract

Austenitic stainless steels, especially SUS304L and 316L, are candidate structural materials for cryogenic use. However, there are not enough data on Charpy absorbed energy at 4K nor reports on effects of coldrolling and Ni-equivalent on the tensile properties and absorbed energy for these steels. In this study, tensile and Charpy impact tests of cold-rolled SUS304L, SUS310S and SUS316L were carried out at 293 K, 77K and 4K. Microstructure and texture of the steels were also studied. Effects of cold-rolling and Ni-equivalent on low temperature mechanical properties of these stainless steels has been discussed. Results are summarized as follows;
1) 0.2% proof stress and ultimate tensile strength increased as the reduction of cold-rolling increased. In the 40% cold-rolled steels, there were little difference in the proof stress between the steels investigated. As the Ni-equivalent increased, the proof stress increased and tensile strength decreased at low temperatures.
2) The notch-to-unnotched ratio of tensile strengths increased as the cold-rolling reduction and Ni-equivalent increased.
3) As the cold-rolling reduction increased, the absorbed energy decreased. The absorbed energy in 40% cold-rolled steels at 4K was 40-100J.