Systematic studies of the influence and interrelation of the temperature and physicotechnological factors on the crystallization and formation of structural zones in steel castings are carried out. Therefore, research aimed at determining the boundaries of the optimal influence of the thermal and technological factors on the processes of crystallization and structural formation of steels is important for further use of the regularities of the formation of structural zones in castings to optimize their macro- and microstructures and physical and mechanical properties. Changing the temperature–time conditions of crystallization and post-crystallization cooling allows for regulating the processes of forming the structure of steel castings. The phase-structural state and properties of steel in different structural zones of castings depend not only on the technological parameters of casting and crystallization, but can also be intentionally modified by regulating the conditions of solidification and structure formation. The study investigates the patterns of forming the main macrostructural zones across the section of castings of carbon hypoeutectoid steels and the quantitative changes of their length depending on the thermokinetic conditions of crystallization.