Residual Stress Analysis of Cold-drawn Pearlite Steel Wire Using White Synchrotron Radiation

Abstract

Measurement of the residual stresses in cold-drawn pearlitic steel wire was conducted using an energy dispersive X-ray diffraction technique. The residual stresses of the ferrite and cementite phases were determined for different crystal orientations and large residual stresses were found to exist in the colddrawn pearlitic steel wire. The residual stresses in the ferrite phase were compressive in the axial direction but nearly zero in the hoop and radial directions. In addition, the residual stresses of the reflection indices for the ferrite phase were similar to one another. For the cementite phase, while tensile residual stress existed in the axial direction, compressive residual stress existed in the hoop and radial directions. These stresses in the ferrite phase in the axial direction and cementite phase in all directions decreased along the radial positions. A residual stress state model was proposed on the basis of the aligned lamellar structure along the drawing direction; the model explains the effect of the lamellar direction on residual stress. Reanalysis of the wire sample using the proposed model provided residual strains and stresses in the lamellar direction that were different from the average values estimated using the simple stress analysis method.KEY WORDS: pearlitic steel; residual stress; energy dispersive X-ray diffraction; orientation of texture. steels using in situ measurement during tensile tests. 2-5,8)These analytical techniques have provided new information on the residual stresses in steel wires. For instance, Perez et al. revealed the existence of residual stresses in the ferrite and cementite phases in steel wire using neutron and synchrotron radiation, 9) whereas Kriška et al. focused on the evolution of macro and phase residual stresses in the ferrite phase. 10) However, few studies take the microstructure of the steel wires into account. Therefore, further studies are required to understand the details of residual stress states in cold-drawn pearlitic steel and the mechanisms of their generation.In this study, measurement of the residual stresses in a steel wire was performed using white synchrotron radiation to investigate the residual stresses of both ferrite and cementite phases, and they were measured along different crystal orientations. In addition, a simple model that considered the aligned lamellar structure along the drawing direction of the steel wire was proposed for understanding residual strains and stresses in detail and their generation mechanism. ExperimentalResidual stresses in a steel wire were measured. The chemical composition was 0.73% C, 0.19% Si, 0.5% Mn, 0.021% P, and 0.007% S in mass percentage. Initially, the

Correlation between Microstructural Evolution and Mechanical Properties of 2000 MPa Cold-Drawn Pearlitic Steel Wires during Galvanizing Simulated Annealing

“…The larger surface deformations during the cold-drawing process caused the profound microstructural difference between the surface and the center of the cold-drawn steel wires. Furthermore, the surface layer was heated significantly during the annealing process, thus resulting in large residual stresses [21,22]. Therefore, the evolution of residual stress states is another possible factor for the microstructural difference between the surface and the center of the cold-drawn steel wires.…”