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Title: Detection and prevention of sticker wrench marks on batch annealed steel strip
Author: Stuckey, C. D.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 1997
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Sticker wrench marks are a surface defect which affects steel strip produced by the batch annealing route. The defect has a three stage formation mechanism; interlap diffusion bonding (sticking) which alters the pay-off geometry during uncoiling (wrenching), leading the Luders band formation (marking). It is estimated that sticker wrench marks cost British Steel Strip Products £1.73 million per annum in rejections for surface quality. The objectives of the project were to improve the understanding of the formation mechanism, seeking to identify procedures to detect and prevent the formation of wrench marks. Three main areas of work undertaken were interlap pressure prediction, wrench detection and wrench prevention. The calculation of the interlap pressure formed during coiling and in the cooling cycle of annealing was carried out using published algorithms. The results were used to justify modifications to the coiling tension pattern on the five stand mill and to introduce a retarded cool to the annealing cycle. Wrench detection involved the detection and analysis of noise emitted during uncoiling at the temper mill. The noise was found to contain characteristic frequency peaks, which were related to the breaking of the interlap bonds. The frequency of the spectral signatures is related to the dimensions of the defect and to strip gauge, uncoiling speed and, to a lesser extent, uncoiling tension. The intensity of the signatures was found to be related to the strength of the interlap bonds. Using these conclusions, an integrated signal processing and archiving system was designed which could determine the likelihood of a coil to form wrench marks. A method to control the pay-off geometry of the strip using electro-magnets was developed. The device, consisting of a magnet, stablising arm and positioning system, is placed over the pay-off point of the coil. Trials carried out on a narrow strip mill showed an alteration of the pay-off geometry to the desired tangential case, which should eliminate stick wrench marking.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (D.Eng.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available