The role and the relevance of creating diagrams of isothermal and thermo-kinetic transformation of supercooled austenite during the design of technological regimes of steel heat treatment have been investigated. It is shown that the studies of institutes and industrial enterprises of the Northwestern region of the country are of great importance for metallurgy. We have proved the need for a thorough examination of the transformation of supercooled austenite, and also systematized and generalized experimental data on the diagrams almost for all groups of steels and titanium alloys. Specific examples of the necessity of thermo-kinetic steel transformation diagrams for critical production tasks are given.