ANS:C - stress-relieving

Stress relieving is a heat treatment process used to reduce internal residual stresses in a material, such as metal. These residual stresses can be generated during manufacturing processes like casting, forging, welding, or cold working (such as cold heading, which is used in the production of steel balls). Stress relieving aims to minimize or eliminate these stresses to improve the dimensional stability, reduce the risk of distortion or cracking, and enhance the mechanical properties of the material. Here's how stress relieving typically works:

1. Heating: The material, in this case, the steel balls, is heated to a specific temperature range, typically below the transformation temperature of the material. The exact temperature depends on factors such as the material composition, the severity of the residual stresses, and the desired outcome of the process.
2. Holding: Once the material reaches the desired temperature, it is held at that temperature for a certain period. This allows the internal stresses within the material to redistribute and relax gradually.
3. Cooling: After the material has been held at the specified temperature for the required duration, it is then cooled down slowly. The slow cooling rate helps prevent the reintroduction of significant residual stresses.

By subjecting the material to stress relieving, any internal stresses induced during manufacturing or processing are reduced or eliminated. This process can improve the dimensional stability of the material, reduce the risk of distortion or cracking, and enhance its mechanical properties, such as toughness and fatigue resistance. Stress relieving is often a critical step in the manufacturing process of components where dimensional stability and mechanical integrity are essential, such as in precision engineering, automotive, aerospace, and construction industries.