抄録
The relationship between the degree of the effect of synthetic sea water in the freely corrosive condition on fatigue crack growth rate (FCGR) and alloying elements has been examined by the multiple regression analysis using 32 kinds of 980-1176 MPa grade steels which were quenched from 850°C and were tempered at 615°C. The maximum value of the ratio of FCGR in sea water at 0.167 Hz to that in air was used as the degree of the effect of sea water on FCGR. The stress ratio of 0.10 was used. The following results are obtained.
1) FCGR of the steel containing more than 1% Cr or containing more than 0.8% Mo is relatively high in sea water because cracks propagate through grain boundaries. However, the addition of less than 1% Cr or of less than 0.8% Mo has no influence on FCGR in sea water.
2) The addition of Si has detrimental influence and the addition of Cu, Mn or Al has beneficial influence on FCGR in sea water.
