The iron–carbon eutectoid occurs at 723°C and 0.83 wt% C. Ferrite has 0.022 wt% C and cementite 6.67 wt% C. A 0.7 wt% C steel is cooled from 950°C below 723°C. Find the eutectoid-ferrite fraction (two decimals).
The fraction of austenite transforming into pearlite is $(0.700-0.022)/(0.830-0.022)=0.839109$. Ferrite fraction within pearlite is $(6.67-0.83)/(6.67-0.022)=0.878460$. Their product is 0.73713, so the eutectoid ferrite fraction is **0.74**. Pro-eutectoid ferrite is excluded.