819 高強度鋼の動的環境ぜい化き裂進展と昇温脱離水素分析(GS-3 動的特性)

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The influences of dynamic loading conditions on the environmentally induced cracking under dynamic loading were investigated in two kinds of 1500 Mpa grade high-strength steels, a vanadium-added steel (V content: 0.3 %: 15LA steel) and a vanadium-free steel (V-free steel). The corrosive environment used was a 3% NaCl+3g/L NH_4SCN solution at 25℃. The tests were conducted at the cathodically charged condition with a constant cathodic current density of 3 mA/cm^2. The threshold stress intensity of the static SCC, KISCC, obtained in the 15LA steel was lower than that in the V-free steel, with higher crack growth rate. The threshold stress intensity factor of dynamic SCC under a small vibratory loads superimposed on a sustained load, KDSCC value became lower than those of the K_<lSCC>, in particular T-L specimen. The crack growth rate of both steels under low-frequency varying load at a stress ratio R of 0.1 and a stress cycle frequency of 0.1 Hz was enhanced compared with that in dry air due to cyclic stress corrosion cracking, with lower threshold than K_<ISCC>. The hydrogen evolution rate obtained by gas chromatograph with heating system was increased by the cathodic charging, with a lower temperature peak. The noticeable difference in the hydrogen evolution behavior between the two steels was that the hydrogen evolution rate increased over 80℃ in 15LA steel, but did not in the Vfree steel.
2004-03-17