Abstract:
The fatigue crack growth properties and tensile properties of three casing-drilling steels with different microstructures were conducted by scanning electron microscope, fatigue test machine, and universal test machine. The quantitative relationship of different parameters was built. The results show that the tempered martensite steel possessed significantly higher tensile strength and yield strength than ferrite-bainite-tempered martensite steel and pearlite-ferrite steel. Pearlite-ferrite steel had the maximum Paris constant
m and minimum Paris constant
C. Tempered martensite steel had minimum Paris constant
m and the maximum Paris constant
C. For steels with the same or similar chemical composition, Paris constant
m decreased evidently with the increase of yield strength and Paris constant
C decreased significantly with the increase of elongation. For different steels, Paris constant
C increased with the decrease of paris constant
m. The materials composition should be modified to obtain excellent combination properties when the tensile properties were improved to the critical value by means of heat treatment.