Study of factors governing steel toughness after high-temperature thermomechanical treatment

Formation during HTTT of recrystallized austenite grains may lead to a sharp reduction in fracture toughness K_Ic with unchanged values of strength and ductility. A reduction in fracture toughness may be overcome by steel purification.Temperature-time schedules for deformation with HTTT should provide austenite grain refinement, a specific austenite dislocation structure, and a reduction in the level of internal residual microstresses. However, toughness properties of steel after HTTT depend to a considerable degree on the concentration and distribution of harmful impurities forming segregations along austenite grain boundaries. Grain-boundary embrittlement as a result of enrichment in harmful impurities may reduce the structural strength of steel after HTTT. Formation during HTTT of recrystallized austenite grains may lead to a sharp reduction in fracture toughness K_Ic with unchanged values of strength and ductility. A reduction in fracture toughness may be overcome by steel purification. Temperature-time schedules for deformation with HTTT should provide austenite grain refinement, a specific austenite dislocation structure, and a reduction in the level of internal residual microstresses. However, toughness properties of steel after HTTT depend to a considerable degree on the concentration and distribution of harmful impurities forming segregations along austenite grain boundaries. Grain-boundary embrittlement as a result of enrichment in harmful impurities may reduce the structural strength of steel after HTTT.