Cold resistance of new cast Cr – Mn – Ni – Mo – N steel. Part 3. Stability of austenite during cooling and deformation

The work continues a series of two articles devoted to the study of cold resistance of new cast Cr – Mn – Ni – Mo – N steel including compa­rison with cold resistance of traditional Cr – Ni cast steel 12Kh18N10Т–CC (CC – centrifugally cast) published earlier in this journal. The mecha­nical properties of cast steels 05Kh21AG15N8MFL and 12Kh18N10Т–CC were studied in tensile tests at low temperatures. In particular, microstructures, engineering tensile curves at different temperatures were considered, microhardness measurements were carried out, and fractographic studies were conducted. The authors compared the results with the calculated and experimental estimates of austenite stability of the studied steels during cooling and deformation, with the results of impact bending tests. Using various methods that complement each other, it was revealed that under simultaneous static and impact loading: new austenitic cast steel alloyed with nitrogen retains austenite stability; in 12Kh18N10Т–CC steel, deformation-induced martensite is formed both under tension and under impact bending. The effect of deformation-induced martensite formation in this steel on the temperature dependence of mechanical properties was estimated. The research results were considered taking into account the available literary data including those on the mechanisms of deformation-induced martensite formation in metastable austenitic steels, the effect on the amount of deformation-induced martensite and the type of martensite depending on a decrease in test temperature, deformation rates under tension and impact bending, the relationship between the appearance of deformation-induced martensite and its type with the stacking fault energy level, the effect of deformation-induced martensite on mechanical properties during static and dynamic tests.