Oxidation Behaviour of Steel During hot Rolling by Using TiO2-Containing Water-Based Nanolubricant

The formation and performance of oxide scale on a low-alloy steel were investigated during hot rolling at 850 and 950 degrees C under various lubrication conditions, including benchmarks (dry condition and water) and water-based nanolubricants containing various concentrations of nano-TiO2 from 1.0 to 8.0 wt%. The results showed that the addition of nano-TiO2 particles in the lubricant significantly reduced the thickness of oxide scale and surface oxide roughness. The reduction reached the maximum when the concentration of TiO2 was 4.0 wt%. Detailed oxide phase characterisation and oxide component fraction determination revealed that hot rolling destroyed the conventional multi-layer oxide scale and promoted magnetite and haematite formation because of easy access of oxygen from the deformed structure. The effect of TiO2 was explained by the decrease in the rolling force, which led to a higher fraction of dense retaining wustite and therefore reduced the extent of further oxidation. Increasing temperature did not change the trend of lubrication effect but raised the rate of steel oxidation in general.