Transformation-induced Residual Stresses

Residual stress which is an important consideration in the heat treatment of steel, and the development of a compressive residual stresses is discussed. The magnitude of the residual stress often depends on the microstructural gradient, defined as the transition from a fully martensitic to pearlitic microstructure. A residual compressive stress is developed in the outer surface while a compensating tensile stress is developed in the interior as the lengths of the bars shown are stretched and compressed to equal lengths. A high residual stress develops when the transition from martensite to pearlite is sharp, whereas a gradual change in the microstructure minimizes the residual stress, because each layer in the microstructure is only incrementally different. The maximum residual stress can be maintained by tempering temperatures minimum to 300°F