Chromium-manganese steels for the cryogenic technique

With a view of developing chromium-manganese steels with stable austenite for cryogenic technique, a study was made of the effect of manganese in amounts from 13 to 30% in steels with 10 and 12% Cr upon their strength, plasticity and resilience and of the effect of tempering (700 deg C) upon the above characteristics at +20, -196 and -253 deg C. Optimum compositions of these alloys were found without nitrogen and with nitrogen. Grade 03Kh13N3AP9 and 03Kh13N5AP9 steels were developed from the grade 03Kh13P9 steel by additionally alloying it with nitrogen and nickel. The metallographic and X-ray structure investigations of the above grades of steels subjected to no deformation and after failure at 20, -196 and -253 deg C have shown a close relationship of physicochemical properties with the phase transformations during cooling and deformation. It is found that the transition of the metal from brittle to resilient state at cryogenic temperatures occurs as austenite is stabilized in Cr-Ni and Cr-Mn steels through a rise in the contents of respectively Ni and Mn over predetermined ranges for each of them, Cr content remaining unchanged