Ref.: MmeCa09-009
Apresentador: João Rodrigues Barros Neto
Autores (Instituição): Leão, P.B.(Universidade Federal do Ceará); Barros Neto, J.R.(UNIVERSIDADE FEDERAL DO PIAUI); Lima, T.N.(Universidade Federal de Sergipe); Ramirez, A.J.(Ohio State University); de Abreu, H.F.(Universidade Federal Ceará);
Resumo:
Tensile armor layers on flexible pipes are usually composed of pearlitic steel in a rectangular wire shape. In this context, the manufacturing route of the flat pearlitic wires is: hot-rolling ? patenting treatment ? cold forming ? wire coiling ? stress relief ? re-winding wire process ? helical torsion around the pipe. To evaluate the effect of helical torsion angle on the deformation of pearlitic steel, rectangular-shaped wires in full lamellar and partially spheroidized pearlitic microstructures were submitted to a lab-simulated helical torsion. Based on this, the flat pearlitic steel samples were helically twisted in a lather machine with a cylindrical shaft. This procedure was performed with three wound angles (0, 20, and 60°) about the longitudinal axis of the shaft. In this way, microhardness maps were built from the cross-section of the helically twisted samples. Also, secondary electron imaging and electron backscattered diffraction were performed on the longitudinal section (lateral surface) of the lab-processed samples. Based on this, the employment of helical torsion in rectangular pearlitic steel wires resulted in a heterogeneous distribution of local hardness throughout the wires’ cross-section due to the combined effect of bending (mainly normal) and shear components. Under the low angle of helical torsion, the lamellar pearlitic microstructure was more resistant against normal bending strain than the partially spheroidized pearlitic condition, which promoted a more minor divergence in hardness distribution. The pearlitic blocks were mostly bowed in the helically twisted lamellar pearlitic wire under a low wound angle, demonstrating the predominant effect of shear deformation. Increasing the wound angle of helical torsion made it possible to realize a significant influence on the normal bending deformation and, consequently, a rise in the microhardness average in both evaluated conditions, which suggests that the normal bending component is the dominant hardener factor during helical torsion operation.