Abstract
Though the ultimate strength and the proof stress of austenitic stainless steel increased by lowering the temperature, the tensile ductility and the toughness were reduced. However, the steels containing a small amount of ferrite still had a relatively high toughness at a temperature as low as −196°C. Scanning microscope examination of the broken tensile and impact test pieces showed that a quasi-cleavage type of fracture appeared at lower tempratures. It is considered that the quasicleavage type fracture is related to the area of ferrite and the stability of the austenite.
