[en] The effect of thermal and strengthening shock-wave treatment on the structure and physico-mechanical properties of the Kh12G14N5M steel has been studied. γ → α transformations don't take place in this steel under heating and cooling from 1200 up to -196 deg C and after cold plastic deformation with 50% reduction. After long-term (up to 5000 h) holding at 550-700 deg C carbide, nitride or intermetallic phase precipitation in the structure of this steel is not observed. Shock-wave treatment of steel leads to its considerable strengthening when satisfactory plasticity and impact strength conserving, that is due to structure formation with high density of uniformly distributed dislocations and twins. The Kh12G14N5M steel is on a par with the used Cr-Ni steels of 03Kh16N8M3 and 08Kh18N9 types in terms of long-term strength at 550-700 deg C and 200 MPa