Tensile and V-Notched Charpy Bending Behaviors of Pressurized Carbon Steels

Effects of carbon content and morphology of pearlite on the decrease of yield stress caused by a pressurization under hydrostatic pressure of 980 MPa were experimentally examined using two carbon steels, S15C with 0.14%C and S45C with 0.44%C. In addition to the above, an effect of the pressurization on ductile-to-brittle transition behaviors observed in Charpy impact test was also described. The present findings are summarized as follows.(1) The initial yield stress of S15C was decreased by the pressurization, while the stress of S45C was never affected. The decrease of the yield stress found in the former steel was 29 MPa in both cases of lammelar pearlite and spheroidal one.(2) The transition temperature of S15C subjected to the pressurization became lower by 7 to 10 K, being about 0.3 K/MPa in reduction of the temperature per unit decrease of the yield stress. On the contrary, the transition temperature of S45C was not affected even after pressurized, since its yield stress was not changed.(3) By spheroidization of pearlite, the transition temperature was lowered remarkably in S15C, but it was not varied in the other steel.