Correlation of fracture toughness with microstructural parameters and standard mechanical properties of high-strength medium-alloy steel

Fracture toughness of rolled plates of high-strength medium-alloy steel with a martensitic or martensitic- bainite microstructure can vary widely depending on the parameters of their microstructure, which depends on the specific chemical composition, rolling parameters, quenching and tempering. In previous works, the authors studied the metal of various experimental smelts. The studied materials were significantly different in the size of structural components separated by large-angle boundaries (hereditary austenitic grain, martensite packages, and bainite crystallites). The continuation of these studies is the analysis of the relationship between the fracture toughness of a metal of one smelt and the general quenching parameters and, as a consequence, with the same parameters of the microstructure formed during quenching, but with different tempering parameters. A general structural state parameter based on the obtained data, and correlated with fracture toughness is proposed.