An investigation into the tribological behaviour of a work roll material at high temperature

The tribological behaviour of work roll materials is always a key issue during the hot rolling of metals where high pressure and high temperature are applied to the strip. In this paper, the oxidation behaviour of a high speed steel roll material is investigated by a Gleeble 3500 thermal–mechanical simulator at 700 °C for different oxidation periods in dry air as well as in a moist atmosphere. The surface characteristics after oxidation are characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis. The results indicate that the humid atmosphere has a significant effect on the surface morphology of the oxide scale. A simulation of the hot rolling process is also conducted on a mini rolling mill which is incorporated within the Gleeble 3500 simulator. Two types of roller surfaces are investigated, one is a virgin surface and the other a pre-oxidized surface with 7 μm thick oxide scale. The experimental results show that the two types of roller surface exhibit quite different tribological behaviour in terms of friction and surface roughness. The rolling force and friction of pre-oxidized rolls are higher than that of virgin surface rolls for different thickness reductions and temperatures.