from the conferences organized by TANGER Ltd.
The work roll surface in hot rolling mills suffers combined heat and mechanical load. The surface degradation leads to the formation of crack networks. The current research describes a thermal fatigue similar to the governing degradation mechanism, which causes the cracks formation perpendicular to surface. This paper describes the additional effect of cyclic thermal loads - the cause of parallel-to-surface cracks formation within long and thin carbides which is prone to forming inside HiCr steel. The cracks formation is investigated by both a thermal and a structure FEA. These analyses are conducted with a special finite element model which has a steel microstructure. The model is exposed to a thermal load at the end of the rolling gap. The result - the heterogeneous thermal field is applied like a BC for the structure analysis. The results are presented by a histogram of relative frequency of the first principal stress value, for each microstructure portion separately. The distribution of the first principal stress within the matrix shows a compressive stress state, which was anticipated. The distribution of the first principal stress within the carbide portion shows a tensile stress state, which was unexpected. This unexpected behavior is explained by a different thermal expansion coefficient of each portion of the microstructure. The matrix with a higher thermal expansion coefficient expands more rapidly than carbides which are pressed from a surrounding matrix which forces them to lengthen, and which, in turn, cause tensile stress within carbides. Based on the comparison with a microstructure typical to HiCr iron, the recommendation for a more durable and resistant microstructure structure are stated and explained.
Keywords: work rolls, hot rolling, microstructure, matrix, carbides, crack, formation, thermal fatigue© This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.