The Study On Dynamic Fracture Toughness Of 12Cr1MoV Steel

In this paper, the changing law of the impact toughness of 12Cr1MoV steel versus holding time is studied at 540℃ by instrumented Charpy impact test. The results illustrate that the upper shelf, lower shelf and the ductile-to-brittle transition temperature of the impact energy change with the prolong of holding time. When the holding time is less than 500h, the ductile-to-brittle transition temperature rises and the brittleness magnifies. When the holding time is 500h, the ductile-to-brittle transition is highest and the brittleness is the largest. When the holding time is more than 500h, the ductile-to-brittle transition temperature drops, the brittleness declines and the toughness recovers voluntarily.In this paper, on the Hopkinson measure equipment, the dynamic fracture toughness of 12Cr1MoV steel studied at 500h is obtained. The curve has obvious the ductile-to-brittle transition trend for all range of temperature from ductile fracture at upper shelf to brittle fracture at lower shelf. The tendency of the curve of K1d—T is the same as that of the curve of CVN—T. But, The curve of K1d—T of 12Cr1MoV steel is closer to high temperature.With the testing results obtained from the instrumented impact tests and the experiential formulas, the dynamic fracture toughness values of 12Cr1MoV steel versus temperature and time at different isothermal holding time. The results illustrate that the curve of K1d—T of 12Cr1MoV steel is closer to high temperature than the curve of CVN—T at all range of holding time; and under the same temperature and different isothermal holding time, the curve of K1d—T is consistent with the kinetics curve of non-equilibrium segregation. The experiential formulas that is used in estimation has important using value.