E Brandaleze and M Romanyuk
Universidad Tecnol├?┬│gica Nacional, Argentina
Posters & Accepted Abstracts: J Material Sci Eng
Steel wires, under severe cold drawing deformation, develop high strength. High carbon steel (C>0.80%) has a great demand in the steel market because of the extremely high strength (5-6 GPa). For this reason, it is relevant to increase the knowledge on the structural evolution and deformation mechanisms involved during wiredrawing process due to their critical applications, among which we can mention wires for: Bridges, cranes and tire cord. The mechanical behaviour aptitude is determined by torsion test. When the fracture surface is flat, the wire is apt. On the opposite, an irregular fracture surface (delamination) means poor mechanical properties. This paper presents a comparative study on steel wires (0.80% C) that presented normal behaviour and delamination problem during torsion test, in order to compare the structural evolution at high deformation. The deformation mechanisms and cementite stability was analyzed. The microstructural study was carried out applying light and Scanning Electron Microscopy (SEM). Finally, the structural information was correlated with results of Differential Scanning Calorimetry (DSC) and thermodynamic properties obtained by Fact Sage simulation. The structural study verified the presence of curling phenomenon in both steels products. It was possible to verify differences (~26%) in the interlaminar spacing (├?┬╗) of the pearlite between wires that present normal and delaminated behaviour under torsion test. The ductility loss (in the delaminated wire) is promoted by multiple causes: Higher interlaminar spacing, high nitrogen content in the product and the presence of dynamic strain aging, which is promoted by cementite destabilization and the formation of ├?┬Á carbide.
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