Which type of discontinuity is identified as a finishing processing discontinuity?

The type of discontinuity identified as a finishing processing discontinuity is a heat-treat crack. These cracks occur as a result of residual stresses introduced during heat treatment processes, such as quenching, where the material undergoes significant changes in temperature that can lead to cracking. This type of discontinuity is particularly relevant during the final stages of processing when the material is expected to meet strict tolerances and performance characteristics.

Heat-treat cracks are vital to be aware of in the finishing stages because they can severely affect the mechanical properties and reliability of the component. They result from the material being overly hardened or improperly cooled, leading to internal stresses that exceed the material's tensile strength.

The other types of discontinuities mentioned, such as internal forging bursts, casting defects, and porosity, occur at different stages of material processing and are typically related to the initial shaping or molding phases rather than the finishing stages. Recognizing the specific nature of heat-treat cracks as a finishing processing discontinuity helps emphasize the importance of meticulous monitoring and control during heat treatment in manufacturing processes.