Question

The complete transformation of austenite takes place during cooling from liquid state at:

• A. Just below 723 °C
• B. Just below 910 °C
• C. Just above 723 °C
• D. Just above 910 °C

Hint:

For low-carbon steels, the austenite phase transforms completely below 723°C during cooling.

Answer 1

The Correct Option is A

1. Understanding Austenite:
Austenite is a phase of steel in which the iron atoms are in a face-centered cubic (FCC) arrangement. It forms when the steel is heated above the critical temperature. 2. Transformation of Austenite:
The transformation of austenite to other phases, such as ferrite or pearlite, occurs when the temperature drops below a specific threshold. This transformation happens at 723°C for carbon steels. 3. Why Just Below 723°C:
Below 723°C, the austenite starts to decompose, and this is the temperature where the transformation is considered complete in common low-carbon steels.
Option 2 (Just below 910°C): This temperature corresponds to a higher phase transformation, like the austenite to cementite transformation in higher carbon steels. 4. Conclusion:
The complete transformation of austenite occurs just below 723°C, where the phase transformation to ferrite and pearlite completes.