关键词: 低合金钢, 低温疲劳, 疲劳裂纹扩展, 韧脆转变

Abstract: 　　Low temperature fatigue crack growth (FCG) behaviour of a low carbon low alloy steel (16Mn) is investigated under hot-rolled and high temperature-normalized conditions and a general expression for the low temperature FCG rates is offered. By means of this expression, much money will be saved because the FCG rates can be predicted from the tensile properties without additional empirical modification and low temperature fatigue test, if the endurance limit and FCG threshold at room temperature are predetermined. The results indicate that the upper bound temperature, below which the thermal component of fracture toughness equals to zero, may be defined as the ductile-brittle transition temperature of FCG mechanism, TFDBT Above TFDBT the FCG rates decrease with decreasing temperature but blow TFDBT the trend is reversed due to the change of the FCG mechanism in the intermediate region (da/dN≈10-8～10-8m·cycle-1) from the ductile striation into microcleavage.

Key words: Crack growth, Ductile-brittle transition, Fatigue at low temperatures, Low alloy steel