Metallurgical Investigation of a Prematurely Failed Concentric Reducer Tube Used in a Hot-Rolling Mill |
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Authors: | C D Singh S K Dhua M Kumar A K Jha T Mrinal K Sharma R R Abhyuday Y Kumar |
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Affiliation: | (1) R&D Centre for Iron & Steel, Steel Authority of India Limited, Doranda, Ranchi, 834002, India;(2) Department of Metallurgical Engineering, BIT Sindri, Dhanbad, 828123, India |
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Abstract: | A concentric reducer tube, which was a part of the top exit roughing hydraulic descaler in a hot strip mill failed prematurely
under working pressure. A detailed metallurgical investigation comprising physical examination, optical microscopy, scanning
electron microscopy, and electron probe microanalysis was carried out to find out the genesis of the failure. Physical examination
revealed cracks located symmetrically around the circumference of the tube that ran along its full length, up to the weld
beads at both ends. Optical microscopy of etched samples revealed a banded ferrite-pearlite structure and the existence of
forging folds near the change-in-section(160° fillets). Cracks were found to initiate from these forging folds. No structural
abnormalities were found in the weld beads and heat-affected zones. |
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Keywords: | Concentric reducer tube Failure analysis Banded structure Forging folds |
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