What is the approximate temperature increase during the normalizing process compared to the upper transition temperature?

During the normalizing process, steel is typically heated to a temperature above its critical range to allow for a complete transformation of the microstructure. The upper transition temperature, often referred to as the upper critical temperature, is the temperature at which austenite begins to form as the steel is heated.

The approximate temperature increase during normalizing is generally around 55 degrees Celsius more than this upper transition temperature. This increase is essential as it ensures that the steel is fully austenitized, which contributes to refined grain structure upon cooling. A temperature increase of this magnitude helps facilitate uniformity in properties and enhances the material's overall mechanical characteristics, such as strength and toughness.

The other options do not align with the typical temperature ranges encountered in the normalizing process and do not provide sufficient heating above the upper transition temperature to achieve the desired microstructural changes.