Prediction of Ar_3 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 λ/(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℃/ min.