STRUCTURAL CHANGES IN STRUCTURAL STEELS DURING THERMAL CYCLING

Introduction: During experimental studies of structural steels responsible for the reliability of metal structures used, for example, in hoisting and transporting machinery, we established a correlation between the magnetic parameter Hp and characteristic changes in the metal microstructure during thermal cycling. It is shown that the Нр parameter depends on the initial structural state of steel, the amount and mass fraction of alloying elements, and the number of heating/cooling cycles. Methods: We found that an increase in the number of heating/cooling cycles and the amount of alloying elements, as well as preliminary cold plastic deformation with stage-by-stage control of structural changes using passive magnetic flux leakage testing results in a finer-grained structure, which was confirmed by metallographic analysis. Results: The paper considers specifics of structural changes in steels with different initial structures during thermal cycling. It is shown that the final grain size depends on the number of treatment cycles, the amount of alloying elements, and the initial microstructure. It is the fine-grain structure that improves the most important performance characteristics of steels: strength, cyclic strength, and cold brittleness.