High temperature fracture mechanism of a new type Cr-Mo-V hot-working die steel
The high-temperature fracture behavior of a new type Cr-Mo-V steel was studied through high-temperature tensile tests,and the microstructure evolution and carbide distribution characteristics in the thermal-mechanical coupling zone(fracture zone)and thermal stress zone(clamping zone)of the experimental steel at different tensile temperatures(25-700 ℃)were studied.The relationship between the types,distribution and size of the carbides in the steel and the high-temperature fracture behavior was analyzed.The evolution mechanism of microstructure near cracks in the new type Cr-Mo-V hot-working die steel during high-temperature deformation was clarified.The results show that as the tensile temperature increases,the tensile strength and yield strength of the experimental steel decrease,while the elongation and reduction of area increase.The fracture mode changes from brittle fracture to ductile fracture,and the transition temperature from brittle fracture to ductile fracture is about 400℃.During the high-temperature deformation,the dislocation density of the experimental steel decreases,and the tempered martensite undergoes decomposition,recovery,recrystallization and grain growth.M7C3 and M23C6 carbides precipitate and grow along the grain boundaries,and a small amount of fine granular MC carbides are dispersed in the grain.Due to the external force acting on the deformation zone,the temperature of the deformation zone will be higher than the tensile temperature,which provides thermodynamic conditions for the dissolution of small carbides near the fracture and the growth of large-sized carbides,leading to a decrease in small-sized carbides and an increase in large-sized carbides in the thermal-mechanical coupling zone.
Cr-Mo-V steelhot working die steelhigh-temperature tensilemicrostructure evolutioncarbides
NETL
NSTL
万方数据
