Influence of tramp elements (P, Cu, S, Sn) on the Mannesmann effect in the transversal hot rolling of engineering steels (MANNESTRAMP)

The main aim of the project was the analysis of the influence of some tramp elements on the susceptibility of engineering steels to axial crack generation during cross wedge rolling (CWR). Therefore, during the first half of the project, nine experimental heats with different levels of tramp elements were manufactured and all of them metallurgical and mechanically characterised. Hot torsion and tensile tests were also carried out, but no clear effect of tramp elements was determined in the experimental phase. CWR trials with some industrial heats and the development of the numerical model started to be carried out. During the second part of the project, the numerical model has been optimized following the law of “Norton-Hoff” for two different steel grades, C70S6 and 16MnCr5 at different temperatures. Subsequently, its validation in the CWR industrial trials has been carried out. Otherwise, to evaluate the influence of the chemical composition and the content and distribution of inclusions, all the manufactured industrial heats (C70S6, 16MnCr5, 30MnSiV6, 20MoCrS4, 20MnCr5 and 100Cr6) have been metallurgical and mechanically characterised and forgeability tests have been carried out. As it was expected, it has been confirmed the important influence of the MnS in the generation of internal cracks, which explains the high tendency of the C70S6 and the low tendency of 100Cr6 to the generation of internal cracks during the CWR trials. Finally, it has been possible to reproduce in a laboratory test a stress field similar to a hot cross rolling process, generating internal cracks by Mannesmann effect