Residual stresses can be created in a number of ways, ranging from
ingot processing in the mill to the manufacture of the finished product.
Sources include rolling, casting, forging, bending, quenching, grinding,
and welding. In the stress-relief process, steel is heated to approximately
595
C (1105
F), ensuring that the entire part is heated uniformly, then
cooled slowly back to room temperature. The procedure is called stressrelief
annealing, or simply stress relieving. Care must be taken to ensure
uniform cooling, especially when a part has varying section sizes. If the
cooling rate is not constant and uniform, new residual stresses, equal to
or greater than existing originally, can be the result. Residual stresses in
ferritic steel cause significant reduction in resistance to brittle fracture. If
a steel, such as austenitic stainless steel, is not prone to brittle fracture,
residual stresses can cause stress-corrosion cracking (SCC). Warping is
the common problem.