Novel Degradation Mechanism of a Structural Wire Rope During Its Life Cycle

Abstract

High-carbon steel wire ropes are used for various high-load-bearing applications. They achieve tensile strength of the order of 2 GPa owing to a combination of fine pearlitic microstructure and work hardening during the drawing process. Despite these high strength levels, they can fail during service due to either manufacturing defects or service abuse. In this study, failure analysis of main hoist steel wire rope used in a basic oxygen furnace (BOF) was carried out. Several locations of the wire rope showed unprecedented microstructural degradation. The presence of surface martensite with transverse cracks was observed in severely abraded wires. Some locations of the rope revealed fusion of adjacent wires with increased interlamellar spacing of pearlite and formation of divorced pearlite in heat-affected and fusion zones, respectively. A significant variation in hardness across the wire rope was noted due to these in-service microstructural changes. Such macroscopic and microstructural deterioration has not been reported in open literature. Detailed failure analysis of the wire rope along with a novel theory explaining the mechanisms of such microstructural degradation is presented herein. This study confirms that the wire rope suffered premature damage due to improper lubrication during service that led to direct metal-to-metal contact, associated friction, abrasion, and fusion of wires. Excessive friction and abrasion of wires subsequently led to fatigue of some of the wires, as manifested by square or crown breaks and striation marks.