Metallurgical Investigation of Failed Locked Coil Track Ropes Used in a Mining Conveyor
- PDF / 1,142,670 Bytes
- 9 Pages / 595.276 x 790.866 pts Page_size
- 31 Downloads / 179 Views
CASE HISTORY—PEER-REVIEWED
Metallurgical Investigation of Failed Locked Coil Track Ropes Used in a Mining Conveyor S. K. Dhua Æ C. D. Singh Æ Amitava Ray
Submitted: 24 September 2007 / in revised form: 13 August 2008 / Published online: 17 September 2008 ASM International 2008
Abstract A locked coil track rope (LCTR) is essentially composed of wires (round and rail-shaped) laid helically in different layers. These wire ropes are sometimes used in conveyors carrying empty and loaded buckets in mining areas. During service, such wire ropes may fail prematurely due to disintegration/failure of individual groups of wires. To understand the genesis of LCTR wire failures, a detailed metallurgical investigation of failed rope wires was made and included visual examination, optical microscopy, scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). Two types of failed wires were investigated; one is from a 40 mm diameter locked coil track rope and the other from a 53 mm locked coil track rope. Optical microscopy of failed round wires in the 53 mm diameter rope clearly revealed fully decarburized layers at the surface and a few grain-boundary cracks. From the location of the failure, it was clear that apart from static tensile loads, the wire ropes had been subjected to bending and unbending loads near the saddle, as fully loaded or empty buckets traveled access the conveyor. The SEM studies confirmed that the fracture had been caused by initiation of fatigue cracks in the decarburized zone under conditions of repeated bending and unbending stresses superimposed on the static tensile load.
S. K. Dhua (&) C. D. Singh A. Ray R&D Centre for Iron & Steel, Steel Authority of India Limited, Doranda, Ranchi 834002, India e-mail: [email protected]; [email protected] C. D. Singh e-mail: [email protected] A. Ray e-mail: [email protected]
Keywords Failure analysis Wire ropes Decarburization Scanning electron microscopy
Introduction Steel wires, produced from controlled cooled or patented wire rods by single or multipass cold drawing, have many engineering applications including the manufacture of springs, needles, wire ropes, screws, and so forth. In rope manufacturing, steel wires are laid helically in different layers to make strands. The strands are laid helically to make a rope. Although steel wires are produced with various carbon contents, generally high-carbon steel wires are used for rope manufacturing because of their high strength. The strength of a wire rope is dependent on the strength of the individual wire components and their arrangement. The internal fretting of the wires, rope stiffness, and tendency to untwist will largely depend on the geometrical arrangement of the wires in a rope [1, 2]. The tensile strength of individual rope wires is largely dependent on three factors: composition, patenting methods, and amount of cold work [1]. Generally high-carbon steel wires (C * 0.45–0.85 wt.%) are used for rope making because of their high strength [1, 2]. Qualities of the wire ro
Data Loading...
