Prediction of Ar₃ during Very Slow Cooling in Low Alloy Steels

摘要

Considering the partition behavior of substitutional alloying elements, a computing method is developed to predict the starting temperature of proeutectoid ferrite transformation (Ar_(3)) in low alloy steels during cooling. The paraequilibrium γ /(α +γ ) phase boundary temperature (denoted Para Ae_(3)) and local equilibrium partition to no-partition transition temperature are calculated using Thermo-Calc software in Fe-C-M _(1), Fe-C-M _(1)-M _(2) and Fe-C-M _(1)-M _(2)-M _(3) (M _(1), M _(2) and M _(3) denote substitutional alloying elements) low alloy steels. Compared with Ar_(3) taken from published CCT diagrams, it is found that the transition temperature from partitioned to no-partitioned growth agrees relatively well with Ar_(3) when the cooling rate is less than 1°C/min.