Effect of upstream process on the quality of pipe and tubular products

Posted on 04 April 2012

>      Torsion testing is used on site as valid means for assessing a finished drawn product, available ductility, effect of work hardening and presence of surface defects. Upstream causes of this failure are bleed surface defects on the billet, Pinhole and cracks in the billet, scrappy surfaces and rolling laps and seams.Downstream monitoring and process control including : Dump Testing of wire rod, Eddy current monitoring in WR manufacturing and Billet inspection (spot grinding & shot blasting)

>   'Encast' Surface casting defects cause breaks in wire forming. Upstream causes resulting in this defects are : mould oscillation (negative strip action), mould level fluctuation and turbulence at the meniscus and slag rim,expansion and contraction of the shell in the mould. Eddy current inability to detect encast defects during hot rolling of the billet into wire rod.

>   Fracture in wire drawing product result from rolled in extraneous matter is caused by upstream factors i.e, Submerged Entry Nozzle failures, Mould flux and inclusions, scrappy surface billets and billet reconditioning (grit blasting). Monitoring of such material in rolling of wire rod can be done by Eddy current and Dump Testing.

Source: Dr Joon Sik Park , POSCO Korea

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