Evolution of microstructure, temperature and stress in a high speed steel work roll during hot rolling: Experiment and modelling
The present study aimed to investigate the microstructure, temperature and thermal stress evolution in a high speed steel (HSS) work roll under service conditions during the early stage of hot rolling. Microstructural observations revealed the formation of micro-voids at the work roll surface due to spalling of carbides at grain boundaries, which can act as initiation sites of cracks during further cyclic heating and cooling. A transient thermo-mechanical model predicted a maximum surface temperature of 580 °C during the first rolling revolution and a stable maximum temperature of about 630 °C with further rolling revolutions, and the results will be used as reference temperatures in future study on high temperature oxidation and wear mechanisms of HSS work roll materials under practical service conditions. No tensile thermal stress at the surface was observed during the early stage of the hot rolling process, which is significantly influenced by the work roll body temperature. The residual stress at work roll surface was compressive with magnitude of about 200 MPa as measured by X-ray diffraction technique.