PACROLP, the prediction and avoidance of cracking in long product hot rolling
There is a need for EU steel producers to gain a scientific understanding across the board of the damage mechanisms inducing ductility break-ups at both the surface and sub-surface of deforming stock during hot rolling, for a range of free machining (FCS) and heat treatable (HT) steels. These steels, especially as-cast FCS steels, have inherent low ductility, which is conducive to corner cracking. The main objective of this multi-partner project was to develop a physical understanding of the causes and mechanisms of crack initiation and growth at high temperature and the relatively high strain rate during rolling of low ductility steel long products. This objective was achieved using a combination of innovative laboratory mechanical and pilot rolling tests, material constitutive modelling, microstructural characterisation, and online defect assessment and detection methods. Key beneficial or detrimental microstructural and geometrical parameters have been identified covering 'hook type' oscillation marks, cortical zone, mean local area fraction of MnS, Mn/S ratio, cohesive strength of inclusion/matrix, matrix hardening rate, initial solidification structure and surface state (oxidation/embrittlement). The project outcome concluded on the relevance of large and/or closely spaced MnS inclusions at early stages of void nucleation while small particles (including clustering) will mainly control the fracture event. Likewise, the influence of process parameters, such as reheating time, temperature-strain rate and tensile triaxiality-strain relationships, amongst other a-dimensional parameters, have been identified and accounted for in a range of material models. The project concludes with practical rolling recommendations and innovative concepts for future work.
Bibliographic Reference: EUR 23890- EN (2009), 149 pp., Euro: 20
Availability: http://bookshop.europa.eu/is-bin/INTERSHOP.enfinity/WFS/EU-Bookshop-Site/en_GB/-/EUR/ViewPublication-Start?PublicationKey=KINA23890 (Catalogue Number: KI-NA-23890-EN-S)
ISBN: ISBN: 978-92-79-11983-5
Record Number: 200910493 / Last updated on: 2009-12-11
Original language: en
Available languages: en