ANS:B - remove internal stresses

When a metal undergoes various manufacturing processes such as casting, forging, welding, or machining, internal stresses can develop within the material due to non-uniform cooling, phase transformations, plastic deformation, or thermal gradients. These internal stresses can be detrimental to the mechanical properties and performance of the metal, potentially leading to dimensional instability, distortion, or even premature failure. The process of normalizing is specifically designed to address these internal stresses by subjecting the metal to controlled heating and cooling cycles. During normalizing:

1. Heating: The metal is heated to a temperature above its critical range, typically between 30°C to 50°C (86°F to 122°F) above the upper critical temperature for ferrous metals. This temperature allows for the transformation of the microstructure, including the dissolution of certain phases and the formation of a more uniform grain structure.
2. Holding: The metal is held at the elevated temperature for a sufficient period to ensure that the entire cross-section reaches thermal equilibrium. This allows for the redistribution of atoms and the relaxation of internal stresses within the metal.
3. Cooling: The metal is then allowed to cool in still air, resulting in the formation of a refined microstructure with a more uniform grain size and distribution. As the metal cools, the internal stresses are relieved, reducing the likelihood of distortion or cracking.

By removing internal stresses through normalizing, the mechanical properties of the metal can be improved, resulting in greater dimensional stability, enhanced toughness, and improved resistance to fatigue and fracture. Additionally, normalizing can help prepare the metal for subsequent machining, heat treatment, or other manufacturing processes, ensuring consistent and reliable performance in service.