Residual Stress States in Cementite and Ferrite in a Combined Cold Drawing Process of AISI 1045 Steel Using Neutron Diffraction and Synchrotron Radiation

The evaluation and control of residual stress states in manufacturing processes such as cold drawing can be difficult, especially in multi-phase materials. Diffraction methods are ideal for characterizing residual stresses in individual phases provided these phases scatter neutrons or X-rays well enough to obtain a good signal. Residual stresses determination problems in drawn components have been reported. Main constraints are measurements in the primary ferrite phase only. The presence of cementite in carbon steel is often neglected. A problem that has not yet been extensively investigated is how residual stresses in the ferrite and cementite phases develop in subsequent steps of material processing such as cold drawing. In this work a combined straightening and bar drawing process of AISI 1045 round bars from coils of a hot-rolled material was investigated. A careful characterization of the material, including residual stress states in the ferrite (α−Fe) and cementite (Fe3C) phases, using neutron diffraction and synchrotron diffraction was performed for each of the different manufacturing steps. The drawing and polishing and straightening (P.S.) parameters by crossed rolls were changed to evaluate their influence on the α−Fe and Fe3C residual stress distributions. After the drawing process, residual stresses in the cementite phase are highly tensile, as already reported, however it can be shown that after polishing and straightening steps residual stresses in the cementite phase decrease and residual stress distributions also depend on the tool angle used.