The influence of water-based nanolubrication on mill load and friction during hot rolling of 304 stainless steel

Using pure water in comparison to water-based lubricant containing 4% TiO2 nanoparticles (NPs), the hot rolling tests of 304 stainless steel were carried out at a rolling temperature of 1050 °C under varying rolling reductions and speeds. The effects of lubrication on rolling force, torque, power and contact friction were systematically investigated. The coefficient of friction (COF) during steady-state hot steel rolling was inversely calculated using a developed flow stress model. The COF models including the effects of rolling reduction and speed were proposed via multiple linear regression. The results indicated that the use of the nanolubricant enabled a reduction of rolling force up to 6.1% and decreases in rolling torque and power up to 21.6%, compared to that of water condition. The results obtained from the linear regression agreed well with those from the inverse calculation, suggesting the developed COF models had high accuracy. The lubrication mechanisms were derived from a boundary lubrication regime, owing to ball bearing and mending effects of TiO2 NPs, and formation of thin lubricant film under high rolling pressure.