What is the transformational temperature of pure iron?

The transformational temperature of pure iron, specifically the A3 temperature or the eutectoid transformation point for iron, is 912° C. At this temperature, the structure of pure iron changes from a body-centered cubic (BCC) structure known as ferrite to a face-centered cubic (FCC) structure known as austenite. Understanding this transformation is crucial because it has significant implications for the properties of steel and the heat treatment processes that are used in metallurgy.

When the temperature reaches 912° C, iron can hold more carbon in solution than at lower temperatures, influencing its hardness, ductility, and overall mechanical properties. This temperature is critical for welding and forging processes, as it affects how iron and steel will behave under different conditions. Knowledge of such transformational temperatures allows welders and metallurgists to select appropriate techniques to control the microstructure and properties of alloyed steels effectively. The other options provided do not accurately reflect this A3 transformation temperature for pure iron, thus reinforcing the significance of understanding the correct transformational points in metallurgical processes.