Loading...
Influence of processing and composition on the strength and torsional ductility of high strength steel wire
Ciganik, Christina
Ciganik, Christina
Citations
Altmetric:
Advisor
Editor
Date
Date Issued
2017
Date Submitted
Collections
Research Projects
Organizational Units
Journal Issue
Embargo Expires
Abstract
High strength drawn pearlitic steel wires are commonly used with a galvanized coating in applications such as bridge cable, mooring cable, and hoisting rope, where high tensile strengths and good ductilities are desirable parameters. If the torsional ductility is insufficient, galvanized wires can split longitudinally along the wire axis during loading, also known as delamination. The occurrence and possible origins of delamination have been extensively researched, but no single mechanism has been identified as the primary cause of its initiation. The purpose of this study was to explore relationships between steel chemical composition and processing, microstructure, tensile properties, and the propensity to delaminate during torsion. Wires were produced with different carbon and silicon concentrations, and processing variations included Stelmor cooling, intermediate lead patenting, and post-drawing hot-dip galvanizing. Aging heat treatments and tensile prestrains were applied to as-received wires to investigate the effects of thermal and mechanical processing on torsional ductility. The lead patenting process resulted in a wire with greater tensile strength and torsional ductility as well as a smaller ILS than Stelmor cooled wires; a greater change in UTS was observed in the lead patented condition compared to Stelmor cooled wires with increased aging time or temperature. Additions of carbon and silicon to the 0.92 C-0.2 Si base steel composition increased tensile strength and reduced ILS, but led to a reduced torsional ductility when compared to the low carbon, low silicon alloy. Modifying galvanized wires through tensile prestraining improved torsional ductility, presumably through effects on residual stresses and mobile dislocation density and/or dislocation distribution. Experimental aging treatments revealed the spheroidized microstructure did not control delamination behavior; instead, dislocation recovery and carbon-dislocation interactions within the ferrite induced by aging controlled delamination behavior in heat treated wires. From comparisons of lead patented and Stelmor cooled wire microstructures and properties, features such as bent cementite lamellae and “thick” ferrite regions are concluded to play a more critical role than ILS in delamination occurrence.
Associated Publications
Rights
Copyright of the original work is retained by the author.