Mechanical Engineering - Engineering Materials - Discussion

The correct answer is: 30° C to 50° C below upper critical temperature.

Full annealing in hyper-eutectoid steel involves heating the steel to a temperature below the upper critical temperature (Acm) to achieve a fully pearlitic microstructure. The typical temperature range for full annealing is 30° C to 50° C below the upper critical temperature.

Here's a brief explanation of the temperature ranges:
- Upper critical temperature (Acm): The temperature above which austenite forms.
- Lower critical temperature (Ar1): The temperature below which pearlite forms.

The correct temperature range for full annealing is below the upper critical temperature to prevent the formation of austenite and ensure a fully pearlitic microstructure.

The other options are not accurate:
- 30° C to 50° C above upper critical temperature: This would result in austenite formation, not full annealing.
- 30° C to 50° C above lower critical temperature: This would result in a mixture of pearlite and ferrite, not full annealing.
- 30° C to 50° C below lower critical temperature: This would result in a fully ferritic microstructure, not full annealing.

For full annealing;

Hypoeutectoid steel - 30 to 50°C above the upper critical temperature.
Hypereutectoid steel - 30 to 50°C above the lower critical temperature.

Both A and C are correct.

Thank you @Debajit.

Thanks @Debajit.