Abstract
The meta-stable lines in Fe-C diagram which are important for the theory of heat treatment of steels have been computed from free energies of ferrite, austenite, and cementite. The results obtained are given in Tables 1, 2, 3 and Fig. 2. The characteristics of the lines are as follows:-
(i) CSB line (γ-side line of A3) has the characteristics not so much different from those supposed hitherto.
(ii) On GPA line (α-side line of A3), the Concentration does not vary with the decrease of temperature below 6000. This suggests that the line may have no direct relation to Ar'' line.
(iii) GC line on which the free energies for α and γ are equal, is nearly parallel to Ar'' line.
(iv) LSM line (γ_??_α Fe3C) is nearly parallel to Ar' line.
